IMT Institutional Repository: No conditions. Results ordered -Date Deposited.
2020-06-05T13:38:44Z
EPrints
http://eprints.imtlucca.it/images/logowhite.png
http://eprints.imtlucca.it/
2018-03-06T13:40:51Z
2018-03-06T13:40:51Z
http://eprints.imtlucca.it/id/eprint/3966
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3966
2018-03-06T13:40:51Z
I caratteri distintivi e le possibili classificazioni dei gruppi aziendali
Nicola Lattanzi
nicola.lattanzi@imtlucca.it
2018-03-06T13:39:09Z
2018-03-06T13:39:09Z
http://eprints.imtlucca.it/id/eprint/3965
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3965
2018-03-06T13:39:09Z
L'analisi del bilancio consolidato nell'ottica esterna
Nicola Lattanzi
nicola.lattanzi@imtlucca.it
2018-03-06T13:27:27Z
2018-03-06T13:27:27Z
http://eprints.imtlucca.it/id/eprint/3964
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3964
2018-03-06T13:27:27Z
Gli attori aziendali
Il capitolo affronta il tema della "variabile comportamentale" in termini di comportamento e motivazioni all'interno dei sistemi di pianificazione e controllo soffermandosi sopratutto sul ruolo e la funzione del controller e del planner.
Nicola Lattanzi
nicola.lattanzi@imtlucca.it
2018-01-24T12:15:04Z
2018-01-24T12:15:04Z
http://eprints.imtlucca.it/id/eprint/3886
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3886
2018-01-24T12:15:04Z
Single-valuedness of the demand correspondence and strict convexity of preferences: An equivalence result
If preferences are rational and continuous, then strict convexity implies that the demand correspondence is single-valued (e.g. Barten and Böhm, 1982, lemma 7.3). We show that if, in addition, preferences are strictly monotone then the converse is also true, namely single-valuedness of the demand correspondence implies strict convexity of preferences.
Ennio Bilancini
ennio.bilancini@imtlucca.it
Leonardo Boncinelli
2018-01-24T12:12:28Z
2018-01-24T12:12:28Z
http://eprints.imtlucca.it/id/eprint/3885
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3885
2018-01-24T12:12:28Z
If not only GDP, what else? Using relational goods to predict the trends of subjective well-being
In the last decade, a lively interdisciplinary discussion has grown around the evidence that, in the long-run, people’s subjective well-being is not significantly correlated with income growth. In other words, GDP growth does not predict the long run growth of subjective well-being. In this paper, we argue that there exists a different predictor of subjective well-being that works pretty well: sociability, i.e. the quality and quantity of social relationships (also referred to as relational goods). More precisely, we illustrate the role of sociability as a predictor of well-being, presenting the available evidence at both the within-country and the worldwide level. In particular, we discuss recent evidence from US cross-sectional data (General Social Survey, 1975–2004), cross-country time series (World Value Survey 1980–2005), and German panel data (German Socio-Economic Panel, 1996–2007). We conclude by indicating the most relevant open issues and suggesting future lines of research.
Stefano Bartolini
Ennio Bilancini
ennio.bilancini@imtlucca.it
2018-01-24T12:09:40Z
2018-01-24T12:09:40Z
http://eprints.imtlucca.it/id/eprint/3884
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3884
2018-01-24T12:09:40Z
Preferences and normal goods: An easy-to-check necessary and sufficient condition
We provide a necessary and sufficient condition for goods to be normal when utility functions are differentiable and strongly quasi-concave. Our condition is equivalent to the condition proposed by Alarie et al. (1990), but it is easier to check: it only requires to compute the minors associated with the border column (or row) of the bordered Hessian matrix of the utility function.
Ennio Bilancini
ennio.bilancini@imtlucca.it
Leonardo Boncinelli
2016-09-12T11:53:14Z
2016-09-13T06:34:44Z
http://eprints.imtlucca.it/id/eprint/3534
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3534
2016-09-12T11:53:14Z
Effects of visual experience on the human MT+ functional connectivity networks: an fMRI study of motion perception in sighted and congenitally blind individuals
Human middle temporal complex (hMT+) responds also to the perception of non-visual motion in both sighted and early blind individuals, indicating a supramodal organization. Visual experience, however, leads to a segregation of hMT+ into a more anterior subregion, involved in the supramodal representation of motion, and a posterior subregion that processes visual motion only. In contrast, in congenitally blind subjects tactile motion activates the full extent of hMT+. Here, we used fMRI to investigate brain areas functionally connected with the two hMT+ subregions (seeds) during visual and tactile motion in sighted and blind individuals. A common functional connectivity network for motion processing, including bilateral ventral and dorsal extrastriate, inferior frontal, middle and inferior temporal areas, correlated with the two hMT+ seeds both in sighted and blind individuals during either visual or tactile motion, independently from the sensory modality through which the information was acquired. Moreover, ventral premotor, somatosensory, and posterior parietal areas correlated only with the anterior but not with the posterior portion of hMT+ in sighted subjects, and with both hMT+ seeds in blind subjects. Furthermore, a correlation between middle temporal and occipital areas with primary somatosensory seeds was demonstrated across conditions in both sighted and blind individuals, suggesting a cortico-cortical pathway that conveys non-visual information from somatosensory cortex, through posterior parietal regions, to ventral extrastriate cortex. These findings expand our knowledge about the development of the functional organization within hMT+ by showing that distinct patterns of brain functional correlations originate from the anterior and posterior hMT+ subregions as a result of visual experience.
Pietro Pietrini
pietro.pietrini@imtlucca.it
James V. Haxby
Nicola Vanello
Claudio Gentili
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Lorenzo Sani
2016-09-12T11:28:13Z
2016-09-12T11:28:13Z
http://eprints.imtlucca.it/id/eprint/3532
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3532
2016-09-12T11:28:13Z
Early dysfunction of perceptual processes in developmental dyslexia
Objective: Single-letter reading is an early predictor of later reading success and identifies adult dyslexics [1]. This work investigates the differences between healthy and dyslexic children in brain activity during single-letter reading.
Methods: Event-related potentials (ERPs) were recorded from 45 healthy and 45 dyslexic children (age range 8–10 years) during self-paced letter recognition (SPLR), i.e. active reading aloud of letters presented at a self-determined pace. Standardized Low Resolution Electromagnetic Tomography (sLORETA) [2] was applied to individual ERPs and unpaired voxel-by-voxel t-test analysis (P < 0.05) was performed to compare the sLORETA maps between groups of subjects corresponding with the latency of the main grand average peaks.
Results: At middle latencies, dyslexics were characterized by a greater activation in the right middle-inferior frontal, insular and superior temporal regions and by impaired engagement of the left middle parietal lobe as compared to the healthy controls. At middle-long latencies, a significantly reduced activation in the left occipital gyrus was observed in dyslexic children compared to controls.
Conclusions: Distributed source imaging applied to ERPs describes the spatiotemporal dynamics of cerebral reading functions and allows inference regarding at which stage of the reading process the activation of the involved brain regions is disrupted in impaired readers. The existence of specific compensatory mechanisms may explain why dyslexic children who are characterized by impaired activation of left parietal and occipital regions show a significantly greater involvement of right temporal–parietal regions and premature engagement of right middle–inferior frontal regions as compared to controls.
Giuseppe A. Chiarenza
Silvia Casarotto
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Lorenzo Sani
Pietro Pietrini
pietro.pietrini@imtlucca.it
2016-09-12T09:25:16Z
2016-09-12T09:25:16Z
http://eprints.imtlucca.it/id/eprint/3529
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3529
2016-09-12T09:25:16Z
Is social phobia a “mis-communication” disorder? Brain functional connectivity during face perception differs between patients with social phobia and healthy control subjects
Recently, a differential recruitment of brain areas throughout the distributed neural system for face perception has been found in social phobic patients as compared to healthy control subjects. These functional abnormalities in social phobic patients extend beyond emotion-related brain areas, such as the amygdala, to include cortical networks that modulate attention and process other facial features, and they are also associated with an alteration of the task-related activation/deactivation trade-off. Functional connectivity is becoming a powerful tool to examine how components of large-scale distributed neural systems are coupled together while performing a specific function. This study was designed to determine whether functional connectivity networks among brain regions within the distributed system for face perception also would differ between social phobic patients and healthy controls. Data were obtained from eight social phobic patients and seven healthy controls by using functional magnetic resonance imaging. Our findings indicated that social phobic patients and healthy controls have different patterns of functional connectivity across brain regions within both the core and the extended systems for face perception and the default mode network. To our knowledge, this is the first study that shows that functional connectivity during brain response to socially relevant stimuli differs between social phobic patients and healthy controls. These results expand our previous findings and indicate that brain functional changes in social phobic patients are not restricted to a single specific brain structure, but rather involve a mis-communication among different sensory and emotional processing brain areas.
Mario Guazzelli
Pietro Pietrini
pietro.pietrini@imtlucca.it
Maria Ida Gobbini
Claudio Gentili
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Sabrina Danti
2016-03-22T10:19:53Z
2016-04-06T07:46:17Z
http://eprints.imtlucca.it/id/eprint/3293
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3293
2016-03-22T10:19:53Z
Polymeric supports in polysulfone functionalized by Molecular Imprinting Technology for protein recognition
Niccoletta Barbani
Caterina Cristallini
Elisabetta Rosellini
Giulio D. Guerra
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Paolo Giusti
2016-03-22T10:13:06Z
2016-03-22T10:13:06Z
http://eprints.imtlucca.it/id/eprint/3292
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3292
2016-03-22T10:13:06Z
Molecularly imprinted scaffolds for tissue growth technology
Niccoletta Barbani
Elisabetta Rosellini
Caterina Cristallini
G. Ciardelli
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Paolo Giusti
2016-03-22T10:11:52Z
2016-03-22T10:11:52Z
http://eprints.imtlucca.it/id/eprint/3291
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3291
2016-03-22T10:11:52Z
Synthesis and characterization of a novel pH-sensitive nanocarrier for targeted drug delivery
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Davide Silvestri
Caterina Cristallini
Niccoletta Barbani
2016-03-22T10:11:08Z
2016-03-22T10:11:08Z
http://eprints.imtlucca.it/id/eprint/3290
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3290
2016-03-22T10:11:08Z
Modelling drug delivery from stents through a finite element analysis
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Davide Silvestri
Caterina Cristallini
2016-03-22T09:49:02Z
2016-03-22T09:49:02Z
http://eprints.imtlucca.it/id/eprint/3285
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3285
2016-03-22T09:49:02Z
Design, fabrication and preliminary characterization of a bioartificial scaffold for tissue engineering
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Niccoletta Barbani
Caterina Cristallini
2016-03-22T08:54:27Z
2016-04-06T07:43:25Z
http://eprints.imtlucca.it/id/eprint/3269
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3269
2016-03-22T08:54:27Z
Poly(vinyl alcohol)-chitosan blends modified by means of a dehydrothermal treatment
Giulio D. Guerra
Niccoletta Barbani
Caterina Cristallini
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Elisabetta Rosellini
Davide Silvestri
2016-03-22T08:52:26Z
2016-03-22T08:52:26Z
http://eprints.imtlucca.it/id/eprint/3268
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3268
2016-03-22T08:52:26Z
Single and simultaneous release of drugs with different hydrophilicity from acrylic matrices
The aim of the work was the study of the simultaneous release of two
drugs with different hydrophilicity degrees from acrylic matrices. Newlysynthesized
acrylic matrices, paclitaxel (hydrophobic) and folic acid (hydrophilic)
were employed.
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Davide Silvestri
Caterina Cristallini
Paolo Giusti
2016-03-21T11:22:41Z
2016-04-05T12:18:04Z
http://eprints.imtlucca.it/id/eprint/3261
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3261
2016-03-21T11:22:41Z
Combined drug release from biodegradable bilayer coating for endovascular stents
In this work, the characterization of a biodegradable bilayer system, used as controlled and combined drug delivery platform, is reported. For this aim, a bilayer system, composed of poly(lactic-co-glycolic acid) and poly(3-hydroxybutyric-co-3-hydroxyvaleric acid), was investigated under physicochemical and functional aspects by evaluating polymer/polymer and polymer/stent material interactions, the kinetic of in vitro degradation, and drug release properties, comparing results with the monolayer reference systems. Obtained results showed that the bilayer system allowed increasing the total amount of eluted Tacrolimus and Paclitaxel drugs with respect to the monolayer systems in the considered testing period and conditions. This evidence was associated to a faster degradation of the tested copolymers in the bilayered configuration, excluding a synergic effect of two drugs on delivery performance. In addition, a macromolecular relaxation process was identified to govern the PLX release from poly(lactic-co-glycolic acid), whereas a pure Fickian diffusion occurred in the delivery of Tacrolimus from poly(3-hydroxybutyric-co-3-hydroxyvaleric acid). © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Davide Silvestri
Caterina Cristallini
M. Guadagni
G. Crifaci
Paolo Giusti
2016-03-21T11:11:45Z
2016-04-06T07:43:08Z
http://eprints.imtlucca.it/id/eprint/3260
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3260
2016-03-21T11:11:45Z
Biodegradable bioartificial materials made by chitosan and poly(vinyl alcohol). Part III: Materials toughened by means of a dehydrothermal treatment
The bioartificial chitosan–poly(vinyl alcohol) blends were toughened by means of a dehydrothermal treatment (DHT), to facilitate the formation of hydrogen bonds between the macromolecules. The materials were characterized by stress–strain test, contact angle measurement, spotlight Fourier transform infrared spectroscopy and chemical imaging, weight loss in water, swelling in water vapor saturated atmosphere, Alamar blue test to evaluate the indirect cytotoxicity, and the diffusive permeation, through membranes made with the blends, of D(+)glucose, vitamin B12, and bovine serum albumin. The results were compared with those of the blends crosslinked by glutaraldehyde (GTA). The Young's modulus ranges between 10.56 and 16.12 MPa, and it is higher for the blends subjected to DHT than for those crosslinked by GTA, a fact explainable by the elasticity of the latter, due to the flexible bridges connecting the different chains. The contact angles indicate a scarce wettability, and then a scarce hydrophilicity, which is confirmed by the chemical imaging of the surfaces, made in the total reflection (microATR) mode, of the films toughened by DHT: the ν(OH) band in the 4000–3000 cm-1 is nearly absent in all the regions of the maps. Moreover, the correlation maps indicate a homogeneous distribution of the two components within the blends. The weight loss in water is generally less than 15%, and increases with the content of the ionizable macromolecule chitosan in the blends, a trend shown also by the swelling after exposure to water vapors. Alamar blue test shows that none of the eluates, after being in contact with the materials up to seven days, appears cytotoxic toward murine fibroblasts. As concerning the diffusive permeation, it appears good for D(+)glucose, quite good for vitamin B12, and scarce for bovine serum albumin. In conclusion, the chitosan–poly(vinyl alcohol) blends studied appear to be suitable for their use as biomaterials.
Read More: http://www.worldscientific.com/doi/abs/10.4015/S1016237210002250
Davide Silvestri
Niccoletta Barbani
Giulio D. Guerra
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
Caterina Cristallini
2016-03-21T10:50:38Z
2016-03-21T10:50:38Z
http://eprints.imtlucca.it/id/eprint/3258
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3258
2016-03-21T10:50:38Z
Relevance of Mesh Dimension Optimization, Geometry Simplification and Discretization Accuracy in the Study of Mechanical Behaviour of Bare Metal Stents
In this paper, a set of analyses on the deployment of coronary stents by using a nonlinear finite element method is proposed. The author proposes a convergence test able to select the appropriate mesh dimension and a methodology to perform the simplification of structures composed of cyclically repeated units to reduce the number of degree of freedom and the analysis run time. A systematic study, based on the analysis of seven meshes for each model, is performed, gradually reducing the element dimension. In addition, geometric models are simplified considering symmetries; adequate boundary conditions are applied and verified based on the results obtained from analysis of the whole model.
Mariacristina Gagliardi
mariacristina.gagliardi@imtlucca.it
2016-03-08T08:55:40Z
2016-09-14T10:21:17Z
http://eprints.imtlucca.it/id/eprint/3183
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3183
2016-03-08T08:55:40Z
Introduzione. I beni culturali e la globalizzazione
Lorenzo Casini
lorenzo.casini@imtlucca.it
2016-01-15T10:33:58Z
2016-09-14T10:21:17Z
http://eprints.imtlucca.it/id/eprint/3012
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3012
2016-01-15T10:33:58Z
«Italian Hours»: the globalization of cultural property law
Cultural property offers a significant yet ambiguous example of the development of global regulatory regimes beyond the State. On the one hand, traditional international law instruments do not seem to ensure an adequate level of protection for cultural heritage; securing such protection requires procedures, norms and standards produced by global institutions, both public (such as UNESCO) and private (such as the International Council of Museums (ICOM)). On the other hand, a comprehensive global regulatory regime to complement the law of cultural property is still to be achieved. Instead, more regimes are being established, depending on the kind of properties and on the public interest at stake, although the complex of cultural property regimes appears to operate largely in isolation. Moreover, the huge cultural bias which dominates the debate about cultural property can accentuate the «clash of civilizations» and the cultural bias that already underlie the debate about global governance.
The analysis of the relationship between globalization and cultural property allows us to shed light on broader global governance trends affecting areas such as the role of States in global regimes, the development of public-private partnerships, and the proliferation of global norms and procedures. Cultural property, however, keeps its specificity and peculiarities, and this helps highlight the points of weakness and of strength in the adoption of administrative law techniques at the global level.
Lorenzo Casini
lorenzo.casini@imtlucca.it
2016-01-15T09:52:15Z
2016-09-14T10:21:17Z
http://eprints.imtlucca.it/id/eprint/3010
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3010
2016-01-15T09:52:15Z
Gli istituti di partecipazione in Europa
Lorenzo Casini
lorenzo.casini@imtlucca.it
2016-01-15T09:19:59Z
2016-09-14T10:21:17Z
http://eprints.imtlucca.it/id/eprint/3009
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3009
2016-01-15T09:19:59Z
The making of a Lex Sportiva: the court of arbitration for sport “The Provider”
The purpose of this paper is to examine the structure and functions of the Court of Arbitration for
Sport (CAS), in order to highlight a number of problems concerning judicial activities at the
global level more generally. Section 1 will outline CAS’ organization and functions, from its
inception to the present date. In particular, this section will show how the history of the CAS is
reminiscent of a famous German novel based on a biblical saga, “Joseph and his brothers” by
Thomas Mann: the CAS was originally the “favorite son” of the Olympic movement’s founding
fathers; it subsequently became the target of its envious “brothers” - i.e. the International
Federations and other sporting arbitration institutions - which viewed the CAS as a dangerous
enemy; ultimately, the CAS defeated its opponents, gained independence and brought normative
harmonization, thereby becoming “the Provider” of global sports law. Section 2 will focus on the
role of CAS in making a lex sportiva, and it will take into account three different functions: the
development of common legal principles; the interpretation of global norms and the influence on
sports law-making; and the harmonization of global sports law. Section 3 will consider the
relationships between the CAS and public authorities (both public administrations and domestic
courts), in order to verify the extent to which the CAS and its judicial system are self-contained
and autonomous from States. Lastly, section 4 will address the importance of creating bodies like
CAS in the global arena, and it will identify the main challenges raised by this form of
transnational judicial activity. The analysis of CAS and its role as “law-maker”, in fact, allows us
to shed light on broader global governance trends affecting areas such as the institutional design
of global regimes, with specific regard to the separation of powers and the emergence of judicial activities.
Lorenzo Casini
lorenzo.casini@imtlucca.it
2016-01-15T09:04:58Z
2016-09-14T10:21:17Z
http://eprints.imtlucca.it/id/eprint/3008
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3008
2016-01-15T09:04:58Z
Il mito di Sisifo ovvero la quarta riorganizzazione del Ministero per i beni e le attività culturali
Lorenzo Casini
lorenzo.casini@imtlucca.it
2016-01-13T12:08:39Z
2016-09-14T10:21:17Z
http://eprints.imtlucca.it/id/eprint/2983
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2983
2016-01-13T12:08:39Z
Il diritto globale dello sport
La dimensione globale dello sport è divenuta ormai dominante: vi sono norme e procedure sopranazionali, un'organizzazione mondiale, nuove forme di cooperazione tra Stati e organismi privati, giudici internazionali. Quali sono la natura e i caratteri del nuovo diritto globale dello sport? Quali principi e istituti di diritto pubblico vi trovano applicazione? Quali sono le peculiarità di questo "sistema amministrativo globale" e che cosa lo accomuna ad altri regimi ultrastatali?
Lorenzo Casini
lorenzo.casini@imtlucca.it
2015-11-18T13:29:55Z
2016-04-06T09:04:39Z
http://eprints.imtlucca.it/id/eprint/2925
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2925
2015-11-18T13:29:55Z
Modello animale per lo studio degli effetti metabolici indesiderati della terapia antiretrovirale HAART: variazioni della colesterolemia
L. Rossi
Gabriella Cavallini
R. Marotta
I. Olivieri
R. Pardelli
Ettore Bergamini
Maria Rita Metelli
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-18T11:43:01Z
2015-11-18T11:43:01Z
http://eprints.imtlucca.it/id/eprint/2924
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2924
2015-11-18T11:43:01Z
Verso un'etica... molecolare?
Pietro Pietrini
pietro.pietrini@imtlucca.it
Silvia Pellegrini
2015-11-18T11:23:28Z
2016-09-12T11:46:49Z
http://eprints.imtlucca.it/id/eprint/2923
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2923
2015-11-18T11:23:28Z
A MR Compatible Sensing Glove for Brain Studies
Nicola Vanello
Valentina Hartwig
Mario Tesconi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Giuseppe Zupone
Alessandro Tognetti
Daniela Bonino
Enzo Pasquale Scilingo
Fabrizio Cutolo
Giulio Giovannetti
Pietro Pietrini
pietro.pietrini@imtlucca.it
Danilo De Rossi
Luigi Landini
2015-11-18T11:19:55Z
2016-09-13T09:54:19Z
http://eprints.imtlucca.it/id/eprint/2922
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2922
2015-11-18T11:19:55Z
Cholinergic Effects in Visual Areas during Object and Spatial Working Memory Encoding: an fMRI study
Giacomo Handjaras
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
James V. Haxby
Pietro Pietrini
pietro.pietrini@imtlucca.it
Maura L. Furey
2015-11-18T11:14:36Z
2015-11-18T11:14:36Z
http://eprints.imtlucca.it/id/eprint/2921
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2921
2015-11-18T11:14:36Z
How neuroscience and behavioral genetics improve psychiatric assessment: Report on a violent murder case
Despite the advances in the understanding of neural and genetic foundations of violence, the investigation of the biological bases of a mental disorder is rarely included in psychiatric evaluation of mental insanity. Here we report on a case in which cognitive neuroscience and behavioral genetics methods were applied to a psychiatric forensic evaluation conducted on a young woman, J.F., tried for a violent and impulsive murder. The defendant had a history of multidrug and alcohol abuse and non-forensic clinical evaluation concluded for a diagnosis of borderline personality disorder. We analyzed the defendant’s brain structure in order to underlie possible brain structural abnormalities associated with pathological impulsivity. Voxel-Based Morphometry indexed a reduced gray matter volume in the left prefrontal cortex, in a region specifically associated with response inhibition. Furthermore, J.F.’s DNA was genotyped in order to identify genetic polymorphisms associated with various forms of violence and impulsive behaviour. Five polymorphisms that are known to be associated with impulsivity, violence, and other severe psychiatric illnesses were identified in J.F.’s DNA. Taken together, these data provided evidence for the biological correlates of a mental disorder characterized by high impulsivity and aggressive tendencies. Our claim is that the use of neuroscience and behavioral genetics do not change the rationale underlying the determination of criminal liability, which must be based on a causal link between the mental disorder and the crime. Rather, their use is crucial in providing objective data on the biological bases of a defendant’s mental disorder.
Davide Rigoni
Silvia Pellegrini
Veronica Mariotti
Arianna Cozza
Andrea Mechelli
Santo Davide Ferrara
Pietro Pietrini
pietro.pietrini@imtlucca.it
Giuseppe Sartori
2015-11-16T15:47:37Z
2015-11-16T15:47:37Z
http://eprints.imtlucca.it/id/eprint/2905
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2905
2015-11-16T15:47:37Z
Nonlinear matter spectra in coupled quintessence
We consider cosmologies in which a dark-energy scalar field interacts with cold dark matter. The growth of perturbations is followed beyond the linear level by means of the time-renormalization-group method, which is extended to describe a multicomponent matter sector. Even in the absence of the extra interaction, a scale-dependent bias is generated as a consequence of the different initial conditions for baryons and dark matter after decoupling. The effect is enhanced significantly by the extra coupling and can be at the 2%–3% level in the range of scales of baryonic acoustic oscillations. We compare our results with N-body simulations, finding very good agreement.
Fabio Saracco
fabio.saracco@imtlucca.it
M. Pietroni
N. Tetradis
V. Pettorino
G. Robbers
2015-11-05T10:51:18Z
2015-11-05T10:51:18Z
http://eprints.imtlucca.it/id/eprint/2808
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2808
2015-11-05T10:51:18Z
A study on wear resistance and microcrack of the Ti3Al/TiAl + TiC ceramic layer deposited by laser cladding on Ti–6Al–4V alloy
Laser cladding of the Al + TiC alloy powder on Ti–6Al–4V alloy can form the Ti3Al/TiAl + TiC ceramic layer. In this study, TiC particle-dispersed Ti3Al/TiAl matrix ceramic layer on the Ti–6Al–4V alloy by laser cladding has been researched by means of X-ray diffraction, scanning electron microscope, electron probe micro-analyzer, energy dispersive spectrometer. The main difference from the earlier reports is that Ti3Al/TiAl has been chosen as the matrix of the composite coating. The wear resistance of the Al + 30 wt. TiC and the Al + 40 wt. TiC cladding layer was approximately 2 times greater than that of the Ti–6Al–4V substrate due to the reinforcement of the Ti3Al/TiAl + TiC hard phases. However, when the TiC mass percent was above 40 wt., the thermal stress value was greater than the materials yield strength limit in the ceramic layer, the microcrack was present and its wear resistance decreased.
Jianing Li
Chuanzhong Chen
Tiziano Squartini
tiziano.squartini@imtlucca.it
Qingshan He
2015-03-26T11:36:44Z
2015-03-26T11:36:44Z
http://eprints.imtlucca.it/id/eprint/2439
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2439
2015-03-26T11:36:44Z
Set-membership EIV identification through LMI relaxation techniques
In this paper the Set-membership Error-In-Variables (EIV) identification problem is considered, that is the identification of linear dynamic systems when both the output and the input measurements are corrupted by bounded noise. A new approach for the computation of the Parameters Uncertainty Intervals (PUIs) is discussed. First the problem is formulated in terms of non-convex semi-algebraic optimization. Then, a Linear-Matrix-Inequalities relaxation technique is presented to compute parameters bounds by means of convex optimization. Finally, convergence properties and computational complexity of the given algorithms are discussed. Advantages of the proposed technique with respect to previously published ones are discussed both theoretically and by means of a simulated example.
Vito Cerone
Dario Piga
dario.piga@imtlucca.it
Diego Regruto
2015-02-09T09:45:25Z
2015-02-09T09:45:25Z
http://eprints.imtlucca.it/id/eprint/2576
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2576
2015-02-09T09:45:25Z
Performance prediction of service-oriented systems with layered queueing networks
We present a method for the prediction of the performance of a service-oriented architecture during its early stage of development. The system under scrutiny is modelled with the UML and two profiles: UML4SOA for specifying the functional behaviour, and MARTE for the non-functional performance-related characterisation. By means of a case study, we show how such a model can be interpreted as a layered queueing network. This target technique has the advantage to employ as constituent blocks entities, such as threads and processors, which arise very frequently in real deployment scenarios. Furthermore, the analytical methods for the solution of the performance model scale very well with increasing problem sizes, making it possible to efficiently evaluate the behaviour of large-scale systems.
Mirco Tribastone
mirco.tribastone@imtlucca.it
Philip Mayer
Martin Wirsing
2015-02-09T09:41:12Z
2015-02-09T09:41:12Z
http://eprints.imtlucca.it/id/eprint/2575
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2575
2015-02-09T09:41:12Z
Hybrid semantics for PEPA
In order to circumvent the problem of state-space explosion of large-scale Markovian models, the stochastic process algebra PEPA has been given a fluid semantics based on ordinary differential equations, treating all entities as continuous. However, low numbers of instances and/or relatively slow dynamics may make such approximation too coarse for some parts of the system. To deal with such situations, we propose an hybrid semantics lying between these two extremes, treating parts of the system as discrete and stochastic and others as continuous and deterministic. The underlying mathematical object for the quantitative evaluation is a stochastic hybrid automaton. A case study of a client/server system with breakdowns and repairs is used to discuss the accuracy and the cost of this hybrid analysis.
Luca Bortolussi
Vashti Galpin
Jane Hillston
Mirco Tribastone
mirco.tribastone@imtlucca.it
2015-02-09T09:31:35Z
2015-02-09T09:31:35Z
http://eprints.imtlucca.it/id/eprint/2574
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2574
2015-02-09T09:31:35Z
Scalable differential analysis of large process algebra models
This tutorial is concerned with the performance evaluation of hardware/software systems using ordinary differential equations which approximate large-scale continuous-time Markov processes derived from models described with the stochastic process algebra PEPA. The tutorial is divided into three parts. The first part illustrates the main theoretical results. The second part gives an overview of a software tool-the PEPA Eclipse Plug-in-which supports the differential analysis of PEPA. In the last part, this approach is related to other efficient analysis techniques in the literature. In particular, a comparison against layered queues is presented.
Mirco Tribastone
mirco.tribastone@imtlucca.it
2015-02-09T09:22:38Z
2015-02-09T09:22:38Z
http://eprints.imtlucca.it/id/eprint/2573
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2573
2015-02-09T09:22:38Z
Relating layered queueing networks and process algebra models
This paper presents a process-algebraic interpretation of the Layered Queueing Network model. The semantics of layered multi-class servers, resource contention, multiplicity of threads and processors are mapped into a model described in the stochastic process algebra PEPA. The accuracy of the translation is validated through a case study of a distributed computer system and the numerical results are used to discuss the relative strengths and weaknesses of the different forms of analysis available in both approaches, i.e., simulation, mean-value analysis, and differential approximation.
Mirco Tribastone
mirco.tribastone@imtlucca.it
2015-02-06T11:16:22Z
2015-02-06T11:16:22Z
http://eprints.imtlucca.it/id/eprint/2557
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2557
2015-02-06T11:16:22Z
Process-algebraic modelling of priority queueing networks
We consider a closed multiclass queueing network model in which each class receives a different
priority level and jobs with lower priority are served only if there are no higher-priority jobs in the
queue. Such systems do not enjoy a product form solution, thus their analysis is typically carried out
through approximate mean value analysis (AMVA) techniques. We formalise the problem in PEPA in
a way amenable to differential analysis. Experimental results show that our approach is competitive
with simulation and AMVA methods.
Giuliano Casale
Mirco Tribastone
mirco.tribastone@imtlucca.it
2015-01-20T15:10:55Z
2015-01-20T15:10:55Z
http://eprints.imtlucca.it/id/eprint/2531
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2531
2015-01-20T15:10:55Z
Micro-polar and second order homogenization of periodic masonry
Micro-polar and second order homogenization periodic elastic masonry are implemented for include geometric and material length scales in the constitutive equation. By the solution of the RVE equilibrium problems with properly prescribed boundary conditions the orthotropic elastic moduli of the higher order continua are obtained on the basis on the enhanced Hill-Mandel condition. A shear layer problem is analysed and the results from heterogeneous models are compared with those ones by the homogenization procedures; the second-order homogenization appears to provide better results in comparison to the micro-polar homogenization.
Andrea Bacigalupo
andrea.bacigalupo@imtlucca.it
Luigi Gambarotta
2015-01-20T14:44:16Z
2015-01-20T14:44:16Z
http://eprints.imtlucca.it/id/eprint/2530
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2530
2015-01-20T14:44:16Z
Second-order computational homogenization of heterogeneous materials with periodic microstructure
A procedure for second-order computational homogenization of heterogeneous materials is derived from the unit cell homogenization, in which an appropriate representation of the micro-displacement field is assumed as the superposition of a local macroscopic displacement field, expressed in a polynomial form related to the macro-displacement field, and an unknown micro-fluctuation field accounting for the effects of the heterogeneities. This second contribution is represented as the superposition of two unknown functions each of which related to the first-order and to the second-order strain, respectively. This kinematical micro-macro framework guarantees that the micro-displacement field is continuous across the interfaces between adjacent unit cells and implies a computationally efficient procedure that applies in two steps. The first step corresponds to the standard homogenization, while the second step is based on the results of the first step and completes the second-order homogenization. Two multi-phase composites, a three-phase and a laminated composite, are analysed in the examples to assess the reliability of the homogenization techniques. The computational homogenization is carried out by a FE analysis of the unit cell; the overall elastic moduli and the characteristic lengths of the second-order equivalent continuum model are obtained. Finally, the simple shear of a constrained heterogeneous two-dimensional strip made up of the composites considered is analysed by considering a heterogeneous continuum and a homogenized second-order continuum; the corresponding results are compared and discussed in order to identify the validity limits of the proposed technique.
Andrea Bacigalupo
andrea.bacigalupo@imtlucca.it
Luigi Gambarotta
2015-01-20T10:31:38Z
2015-01-20T10:31:38Z
http://eprints.imtlucca.it/id/eprint/2522
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2522
2015-01-20T10:31:38Z
Homogenization of Periodic Masonry
Andrea Bacigalupo
andrea.bacigalupo@imtlucca.it
Luigi Gambarotta
2015-01-19T13:21:07Z
2015-01-19T13:21:07Z
http://eprints.imtlucca.it/id/eprint/2502
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2502
2015-01-19T13:21:07Z
Second-order-enhanced computational homogenization for heterogeneous materials with periodic-microstructures
Andrea Bacigalupo
andrea.bacigalupo@imtlucca.it
Luigi Gambarotta
2015-01-19T13:06:58Z
2015-01-19T13:21:40Z
http://eprints.imtlucca.it/id/eprint/2501
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2501
2015-01-19T13:06:58Z
Omogeneizzazione non locale di mezzi eterogenei a microstruttura periodica
Andrea Bacigalupo
andrea.bacigalupo@imtlucca.it
2015-01-15T13:06:00Z
2015-01-15T13:06:00Z
http://eprints.imtlucca.it/id/eprint/2488
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2488
2015-01-15T13:06:00Z
Reversing higher-order pi
The notion of reversible computation is attracting increasing interest because of its applications in diverse fields, in particular the study of programming abstractions for reliable systems. In this paper, we continue the study undertaken by Danos and Krivine on reversible CCS by defining a reversible higher-order π-calculus (HOπ). We prove that reversibility in our calculus is causally consistent and that one can encode faithfully reversible HOπ into a variant of HOπ.
Ivan Lanese
Claudio Antares Mezzina
claudio.mezzina@imtlucca.it
Jean-Bernard Stefani
2015-01-12T14:32:40Z
2015-01-12T14:32:40Z
http://eprints.imtlucca.it/id/eprint/2464
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2464
2015-01-12T14:32:40Z
Improved parameter bounds for set-membership EIV problems
In this paper, we consider the set-membership error-in-variables identification problem, that is the identification of linear dynamic systems when output and input measurements are corrupted by bounded noise. A new approach for the computation of parameters uncertainty intervals is presented. First, the problem is formulated in terms of nonconvex optimization. Then, a relaxation procedure is proposed to compute parameter bounds by means of semidefinite programming techniques. Finally, accuracy of the estimate and computational complexity of the proposed algorithm are discussed. Advantages of the proposed technique with respect to previously published ones are discussed both theoretically and by means of a simulated example
Vito Cerone
Dario Piga
dario.piga@imtlucca.it
Diego Regruto
2015-01-12T14:29:10Z
2015-01-12T14:29:10Z
http://eprints.imtlucca.it/id/eprint/2463
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2463
2015-01-12T14:29:10Z
High-Altitude wind power generation
The paper presents the innovative technology of high-altitude wind power generation, indicated as Kitenergy, which exploits the automatic flight of tethered airfoils (e.g., power kites) to extract energy from wind blowing between 200 and 800 m above the ground. The key points of this technology are described and the design of large scale plants is investigated, in order to show that it has the potential to overcome the limits of the actual wind turbines and to provide large quantities of renewable energy, with competitive cost with respect to fossil sources. Such claims are supported by the results obtained so far in the Kitenergy project, undergoing at Politecnico di Torino, Italy, including numerical simulations, prototype experiments, and wind data analyses.
Lorenzo Fagiano
Mario Milanese
Dario Piga
dario.piga@imtlucca.it
2015-01-12T11:47:05Z
2015-01-12T11:47:05Z
http://eprints.imtlucca.it/id/eprint/2457
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2457
2015-01-12T11:47:05Z
Bounded error identification of Hammerstein Systems with backlash
Actuators and sensors commonly used in control systems may exhibit a variety of nonlinear behaviours that may be responsible for undesirable phenomena such as delays and oscillations, which may severely limit both the static and the dynamic performance of the system under control (see, e.g., [22]). In particular, one of the most relevant nonlinearities affecting the performance of industrial machines is the backlash (see Figure 22.1), which commonly occurs in mechanical, hydraulic and magnetic components like bearings, gears and impact dampers (see, e.g., [17]). This nonlinearity, which can be classified as dynamic (i.e., with memory) and hard (i.e. non-differentiable), may arise from unavoidable manufacturing tolerances or sometimes may be deliberately incorporated into the system in order to describe lubrication and thermal expansion effects [3]. The interested reader is referred to [22] for real-life examples of systems with either input or output backlash nonlinearities.
Vito Cerone
Dario Piga
dario.piga@imtlucca.it
Diego Regruto
2015-01-09T10:00:06Z
2015-01-09T10:00:06Z
http://eprints.imtlucca.it/id/eprint/2440
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2440
2015-01-09T10:00:06Z
Bounding the parameters of linear systems with stability constraints
Identification of linear systems, a priori known to be stable, from input output measurements corrupted by bounded noise is considered in the paper. A formal definition of the feasible parameter set is provided, taking explicitly into account prior information on system stability. On the basis of a detailed analysis of the geometrical structure of the feasible set, convex relaxation techniques are presented to solve nonconvex optimization problems arising in the computation of parameters uncertainty intervals. Properties of the computed relaxed bounds are discussed. A simulated example is presented to show the effectiveness of the proposed technique.
Vito Cerone
Dario Piga
dario.piga@imtlucca.it
Diego Regruto
2015-01-08T14:09:38Z
2015-01-08T14:09:38Z
http://eprints.imtlucca.it/id/eprint/2438
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2438
2015-01-08T14:09:38Z
Control as a key technology for a radical innovation in wind energy generation
This paper is concerned with an innovative technology, denoted as Kitenergy, for the conversion of high-altitude wind energy into electricity. The research activities carried out in the last five years, including theoretical analyses, numerical simulations and experimental tests, indicate that Kitenergy could bring forth a revolution in wind energy generation, providing renewable energy in large quantities at lower cost than fossil energy. After an overview of the main features of the technology, this work investigates three important aspects: the evaluation of the performance achieved by the employed control law, the optimization of the generator operating cycle and the possibility to generate continuously a constant and maximal power output. These issues are tackled through the combined use of advanced modeling, control and optimization methods, which results to be key technologies for a significant breakthrough in renewable energy generation.
Mario Milanese
Lorenzo Fagiano
Dario Piga
dario.piga@imtlucca.it
2014-12-04T09:41:14Z
2014-12-04T09:41:14Z
http://eprints.imtlucca.it/id/eprint/2398
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2398
2014-12-04T09:41:14Z
Stability as a natural selection mechanism on interacting networks
Biological networks of interacting agents exhibit similar topological properties for a wide range of scales, from cellular to ecological levels, suggesting the existence of a common evolutionary origin. A general evolutionary mechanism based on global stability has been proposed recently [J I Perotti, et al., Phys. Rev. Lett. 103, 108701 (2009)]. This mechanism was incorporated into a model of a growing network of interacting agents in which each new agent's membership in the network is determined by the agent's effect on the network's global stability. In this work, we analyze different quantities that characterize the topology of the emerging networks, such as global connectivity, clustering and average nearest neighbors degree, showing that they reproduce scaling behaviors frequently observed in several biological systems. The influence of the stability selection mechanism on the dynamics associated to the resulting network, as well as the interplay between some topological and functional features are also analyzed.
Sergio A. Cannas
Juan I. Perotti
juanignacio.perotti@imtlucca.it
Orlando V. Billoni
Francisco A. Tamarit
2014-11-10T13:11:37Z
2015-03-25T09:16:39Z
http://eprints.imtlucca.it/id/eprint/2360
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2360
2014-11-10T13:11:37Z
Cosmogenic radioisotopes in the Almahata Sitta ureilite
Asteroid 2008 TC3 was predicted to fall in Sudan on October 7, 2008, and 2 months later, 15 meteorite fragments were recovered from the Nubian Desert. Most of these fragments were classified as polymict ureilites. In the largest ureilitic fragment #15, weighing 75 g, we have measured six gamma emitting radionuclides (46Sc, 57Co, 54Mn, 22Na, 60Co, and 26Al) by nondestructive whole rock counting using a sensitive gamma-ray spectrometer. The activities of 60Co, produced mainly by neutron capture in cobalt, and 26Al indicate that fragment #15 was located at a depth of 41 ± 14 cm inside the 1.5–2 m radius asteroid. The activity of other radionuclides is also consistent with this shielding depth within the asteroid. The 22Na/26Al activity ratio is higher than expected for the average cosmic ray flux, probably due to the unusually prolonged solar minimum before the fall.
Carla Taricco
Narendra Bhandari
Paolo Colombetti
Alberto Romero
Gianna Vivaldo
gianna.vivaldo@imtlucca.it
Neeharika Sinha
Peter Jenniskens
Muawia H. Shaddad
G. M. Ballabh
2014-11-10T13:01:12Z
2015-03-25T09:16:39Z
http://eprints.imtlucca.it/id/eprint/2358
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2358
2014-11-10T13:01:12Z
A multiparametric HPGe-Nal acquisition system for low gamma activity measurements of meteorites
The study of long-term solar activity variations in the past requires the use of radioisotopic
data planetary reservoirs. At the Laboratory of Monte dei Cappuccini in Torino
(IFSI-Torino, INAF) for many years we have been studying radioisotopes in meteorites,
because their production, which is related to galactic cosmic ray flux in the heliosphere, is
anticorrelated with the heliospheric magnetic field variations. We have developed very sensitive
gamma detection techniques, in particular to measure 44Ti activity in meteorites; due
to its half-life (t1=2 = 59:2 years), this radioisotope is an ideal index to reveal the imprint of
solar activity variations on the centennial scale. Recently we have improved the spectrometer
by a new multiparametric acquisition system, which allows to extract efficiently the 44Ti
peak from the natural background.
Carla Taricco
Narendra Bhandari
Paolo Colombetti
I. Mariani
Neeharika Verma
Gianna Vivaldo
gianna.vivaldo@imtlucca.it
2014-10-08T13:56:17Z
2015-04-08T10:37:32Z
http://eprints.imtlucca.it/id/eprint/2300
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2300
2014-10-08T13:56:17Z
A calculus for modeling and analyzing conversations in service-oriented computing
The service-oriented computing paradigm has motivated a large research effort in the past few years. On the one hand, the wide dissemination of Web-Service technology urged for the development of standards, tools and formal techniques that contributed for the design of more reliable systems. On the other hand, many of the problems presented in the study of service-oriented applications find an existing work basis in well-established research fields, as is the case of the study of interaction models that has been an active field of research in the last couple of decades. However, there are many new problems raised by the service-oriented computing paradigm in particular that call for new concepts, dedicated models and specialized formal analysis techniques. The work presented in this dissertation is inserted in such effort, with particular focus on the challenges involved in governing interaction in service-oriented applications. One of the main innovations introduced by the work presented here is the way in which multiparty interaction is handled. One reference field of research that addresses the specification and analysis of interaction of communication-centric systems is based on the notion of session. Essentially, a session characterizes the interaction between two parties, a client and a server,that exchange messages between them in a sequential and dual way. The notion of session is thus particularly adequate to model the client/server paradigm, however it fails to cope with interaction between several participants, a scenario frequently found in real service-oriented applications. The approach described in this dissertation improves on the state of the art as it allows to model and analyze systems where several parties interact, while retaining the fundamental flavor of session-based approaches, by relying on a novel notion of conversation: a simple extension of the notion of session that allows for several parties to interact in a single medium of communication in a disciplined way, via labeled message passing. The contributions of the work presented in this dissertation address the modeling and analysis of service-oriented applications in a rigorous way: First, we propose and study a formal model for service-oriented computing, the Conversation Calculus, which, building on the abstract notion of conversation, allows to capture the interactions between several parties that are relative to the same service task using a single medium of communication. Second, we introduce formal analysis techniques, namely the conversation type system and progress proof system that can be used to ensure, in a provably correct way and at static verification time (before deploying such applications), that systems enjoy good properties such as “the prescribed protocols will be followed at runtime by all conversation participants”(conversation fidelity)and “the system will never run into a stuck state” (progress). We give substantial evidence that our approach is already effective enough to model and type sophisticated service-based systems, at a fairly high level of abstraction. Examples of such systems include challenging scenarios involving simultaneous multiparty conversations, with concurrency and access to local resources, and conversations with a dynamically changing and unanticipated number of participants, that fall out of scope of previous approaches.
Hugo Torres Vieira
hugo.torresvieira@imtlucca.it
2014-10-08T13:47:34Z
2015-04-08T10:37:32Z
http://eprints.imtlucca.it/id/eprint/2299
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2299
2014-10-08T13:47:34Z
Conversation types
We present a type theory for analyzing concurrent multiparty interactions as found in service-oriented computing. Our theory introduces a novel and flexible type structure, able to uniformly describe both the internal and the interface behavior of systems, referred respectively as choreographies and contracts in web-services terminology. The notion of conversation builds on the fundamental concept of session, but generalizes it along directions up to now unexplored; in particular, conversation types discipline interactions in conversations while accounting for dynamical join and leave of an unanticipated number of participants. We prove that well-typed systems never violate the prescribed conversation constraints. We also present techniques to ensure progress of systems involving several interleaved conversations, a previously open problem.
Luis Caires
Hugo Torres Vieira
hugo.torresvieira@imtlucca.it
2014-07-01T14:48:34Z
2014-07-01T14:48:34Z
http://eprints.imtlucca.it/id/eprint/2229
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2229
2014-07-01T14:48:34Z
Optimization-based automatic flatness control in cold tandem rolling
For the problem of automatic flatness control (AFC) in cold tandem mills this paper proposes control techniques based on quadratic optimization and delay compensation. Three different strategies are presented and compared: a centralized solution based on a global quadratic programming (QP) problem that decides the commands to all the actuators, and two decentralized solutions where each actuator command is optimized locally. All schemes are based on a global exchange of information about the commands generated at the previous time step at each stand to compensate for the numerous delays present in the mill. Control algorithms are tested in simulation considering a tandem mill with five stands as a benchmark, and results are shown to demonstrate the performance of the proposed schemes.
Alberto Bemporad
alberto.bemporad@imtlucca.it
Daniele Bernardini
daniele.bernardini@imtlucca.it
Francesco Alessandro Cuzzola
Andrea Spinelli
2014-03-27T14:26:48Z
2014-03-27T14:26:48Z
http://eprints.imtlucca.it/id/eprint/2186
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2186
2014-03-27T14:26:48Z
Structure and growth of weighted networks
We develop a simple theoretical framework for the evolution of weighted networks that is consistent with a number of stylized features of real-world data. In our framework, the Barabási–Albert model of network evolution is extended by assuming that link weights evolve according to a geometric Brownian motion. Our model is verified by means of simulations and real-world trade data. We show that the model correctly predicts the intensity and growth distribution of links, the size–variance relationship of the growth of link weights, the relationship between the degree and strength of nodes, and the scale-free structure of the network.
Massimo Riccaboni
massimo.riccaboni@imtlucca.it
Stefano Schiavo
2014-03-03T14:22:13Z
2014-03-03T14:22:13Z
http://eprints.imtlucca.it/id/eprint/2171
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2171
2014-03-03T14:22:13Z
Separation of particles from suspensions using transverse force field: a mass transport analysis
We report the calculation of the efficiency for particle separation processes occurring in suspension under transverse force field in a circular duct. The calculation has been performed for a laminar fluid flow directed toward the duct vertical axis. The force field acting on the suspended particles only, is orthogonal to the duct. In the dimensionless calculations occurs a dimensionless group, Ca, which provides a tool for the dimensioning of the purification section.
Alessandro Lavacchi
Ugo Bardi
Claudia Borri
claudia.borri@imtlucca.it
M. Orfei
Alexander Tolstogouzov
2014-03-03T14:05:58Z
2014-03-03T14:05:58Z
http://eprints.imtlucca.it/id/eprint/2168
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2168
2014-03-03T14:05:58Z
Isothermal oxidation resistance comparison between air plasma sprayed, vacuum plasma sprayed and high velocity oxygen fuel sprayed CoNiCrAlY bond coats
Commercial CoNiCrAlY powders with the same chemical composition were sprayed by vacuum plasma spraying (VPS), air plasma spraying (APS) and high velocity oxygen fuel (HVOF) onto Hastelloy X superalloy substrates obtaining coatings of comparable thickness. After coating, samples were maintained at 1273 K in air for different periods up to 3000 h. Morphological, microstructural and compositional analyses were performed in order to assess the high temperature oxidation resistance provided by the different spraying systems. HVOF technique provided bond coats with higher oxidation resistance compared to APS and VPS.
Martina Di Ferdinando
Alessio Fossati
Alessandro Lavacchi
Ugo Bardi
Francesca Borgioli
Claudia Borri
claudia.borri@imtlucca.it
Carlo Giolli
Andrea Scrivani
2014-01-24T11:48:20Z
2014-01-24T13:10:57Z
http://eprints.imtlucca.it/id/eprint/2116
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2116
2014-01-24T11:48:20Z
Multicolored dynamos on toroidal meshes
Detecting on a graph the presence of the minimum number of nodes (target set) that will be able to "activate" a prescribed number of vertices in the graph is called the target set selection problem (TSS) proposed by Kempe, Kleinberg, and Tardos. In TSS's settings, nodes have two possible states (active or non-active) and the threshold triggering the activation of a node is given by the number of its active neighbors. Dealing with fault tolerance in a majority based system the two possible states are used to denote faulty or non-faulty nodes, and the threshold is given by the state of the majority of neighbors. Here, the major effort was in determining the distribution of initial faults leading the entire system to a faulty behavior. Such an activation pattern, also known as dynamic monopoly (or shortly dynamo), was introduced by Peleg in 1996. In this paper we extend the TSS problem's settings by representing nodes' states with a "multicolored" set. The extended version of the problem can be described as follows: let G be a simple connected graph where every node is assigned a color from a finite ordered set C = {1, . . ., k} of colors. At each local time step, each node can recolor itself, depending on the local configurations, with the color held by the majority of its neighbors. Given G, we study the initial distributions of colors leading the system to a k monochromatic configuration in toroidal meshes, focusing on the minimum number of initial k-colored nodes. We find upper and lower bounds to the size of a dynamo, and then special classes of dynamos, outlined by means of a new approach based on recoloring patterns, are characterized.
Sara Brunetti
Elena Lodi
Walter Quattrociocchi
walter.quattrociocchi@imtlucca.it
2014-01-20T11:20:51Z
2014-01-20T11:20:51Z
http://eprints.imtlucca.it/id/eprint/2098
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2098
2014-01-20T11:20:51Z
Simulating opinion dynamics in heterogeneous communication systems
Since the information available is fundamental for our perceptions and opinions, we are interested in understanding the conditions allowing for a good information to be disseminated. This paper explores opinion dynamics by means of multi-agent based simulations when agents get informed by different sources of information. The scenario implemented includes three main streams of information acquisition, differing in both the contents and the perceived reliability of the messages spread. Agents' internal opinion is updated either by accessing one of the information sources, namely media and experts, or by exchanging information with one another. They are also endowed with cognitive mechanisms to accept, reject or partially consider the acquired information. We expect
that peer-to-peer communication and reliable information sources are able both to reduce biased perceptions and to inhibit information cheating, possibly performed by the media as stated by the agenda-setting theory. In the paper, after having shortly presented both the hypotheses and the model, the simulation design will be specified and results will be discussed with respect to the hypotheses. Some considerations and ideas for future studies will conclude the paper.
Walter Quattrociocchi
walter.quattrociocchi@imtlucca.it
Rosaria Conte
Elena Lodi
2014-01-20T10:23:48Z
2014-01-20T10:23:48Z
http://eprints.imtlucca.it/id/eprint/2097
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2097
2014-01-20T10:23:48Z
Dealing with Interaction for Complex Systems Modelling and Prediction
The increasing complexity of problems in the context of system modeling is leading to a new epistemological approach able to provide a representation which allows from one hand, to model complex phenomena with the support of mathematical and computational instruments, and on the other hand able to capture the global system description. In this article is presented a methodology for complex dynamical systems modeling which is an extension of the supervised learning paradigm. The theoretical aspects of our methodology are introduced and then two different and heterogeneous case studies are presented.
Walter Quattrociocchi
walter.quattrociocchi@imtlucca.it
Daniela Latorre
Elena Lodi
Mirco Nanni
2013-12-20T10:17:03Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/2081
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2081
2013-12-20T10:17:03Z
Nonlinear interface crack propagation in concrete gravity dams under seismic loading
In this paper, the phenomenon of interface crack propagation in concrete gravity dams under seismic
loading is addressed. This problem is particularly important from the engineering point of view. In fact,
besides Mixed-Mode crack growth in concrete, dam failure is often the result of crack propagation along
the rock-concrete interface at the dam foundation. To analyze such a problem, the generalized interface
constitutive law recently proposed by the first author is used to proper modelling the phenomenon of
crack closing and reopening at the interface. A damage variable is also introduced in the cohesive zone
formulation in order to predict crack propagation under repeated loadings. Numerical examples will
show the capabilities of the proposed approach applied to concrete gravity dams.
Marco Paggi
marco.paggi@imtlucca.it
Giuseppe Ferro
2013-12-20T10:13:04Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/2080
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2080
2013-12-20T10:13:04Z
Singular harmonic problems at multi-material wedges: mathematical analogies between elasticity, diffusion and electromagnetism
Multi-material wedges are frequently observed in composite materials. They consist of two or more
sectors of dissimilar materials joined together, whose interfaces converge to the same vertex. Due to the
mismatch in the material properties, such as Young’s modulus, thermal conductivity, dielectric permittivity,
or magnetic permeability, these geometrical configurations may lead to singular fields at the junction
vertex. In this paper, focusing the attention on singular harmonic problems, the mathematical analogies
intercurring between antiplane shear problem in elasticity due to Mode III loading or torsion, the
steady-state heat transfer problem, and the diffraction of waves in electromagnetism are presented. The
proposed unified mathematical formulation is particularly convenient for the identification of common
types of singularities (power-law or logarithmic type), for the use of a standardized method for solving
the nonlinear eigenvalue problems, and for the determination of common geometrical and material
configurations permitting to relieve or remove the singularities.
Marco Paggi
marco.paggi@imtlucca.it
Alberto Carpinteri
2013-12-20T08:53:58Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/2079
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2079
2013-12-20T08:53:58Z
A computational homogenization approach for a three-level hierarchical composite material
Marco Paggi
marco.paggi@imtlucca.it
Peter Wriggers
2013-12-16T11:59:08Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/2070
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2070
2013-12-16T11:59:08Z
Cohesive-Overlapping Crack Model describing the size-scale effects on the rotational capacity of RC beams in bending
A numerical algorithm is proposed for the prediction of the mechanical behavior of the plastic hinges taking place in RC beams at the ultimate loading conditions. The main novelty of such an approach is the introduction of the Overlapping Crack Model, based on nonlinear fracture mechanics concepts, to describe concrete crushing, along with the well-known Cohesive Crack Model for concrete in tension and a stress versus crack opening displacement relationship for steel reinforcement. As a result of a systematic application of the proposed algorithm, new practical design diagrams are proposed for the improvement of the current codes of practice, which completely disregard the size-scale effects. In this context, Dimensional Analysis is also applied in order to obtain further simplifications in the description of the overall response. It is in fact demonstrated that only two nondimensional numbers, NP and NC, are responsible for the available ductility. A new interpretation of the experimental results on the plastic rotations in terms of NP and NC is also proposed.
Mauro Corrado
Marco Paggi
marco.paggi@imtlucca.it
Alberto Carpinteri
2013-12-16T11:48:50Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/2069
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2069
2013-12-16T11:48:50Z
Limits to plastic analysis design due to size-scale effects on the rotational capacity of plastic hinges
Mauro Corrado
Marco Paggi
marco.paggi@imtlucca.it
Alberto Carpinteri
2013-12-12T13:43:38Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/2061
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2061
2013-12-12T13:43:38Z
Applicazioni di meccanica della frattura all’analisi di stabilitá delle fessure nelle dighe in calcestruzzo
RIASSUNTO. Nel presente lavoro si propone una disamina delle applicazioni di meccanica della frattura
all’analisi del processo fessurativo nelle dighe in calcestruzzo. In tale contesto, ripercorrendo gli studi
pionieristici e i casi di studio affrontati negli anni 1980 e 1990, si illustra nel dettaglio come applicare le
metodologie proprie della meccanica della frattura elastica lineare alla valutazione della stabilità delle fessure e
della loro lunghezza critica. Tale disamina riguarderà sia sollecitazioni quasi-statiche, quali il peso proprio e la
pressione idrostatica esercitata dall’acqua, che sollecitazioni sismiche, tema di particolare complessità ed
attualità. Infine, si illustreranno le problematiche relative alla corretta valutazione dei parametri meccanici per
strutture ciclopiche quali le dighe, tenendo propriamente in conto i forti effetti di scala osservati
sperimentalmente.
ABSTRACT. In the present study, a detailed analysis of the applications of fracture mechanics to the
phenomenon of fracture taking place in concrete dams is proposed. In this context, recalling the pioneering
approaches and the case studies proposed in the 1980s and in the 1990s, it will be shown how to apply the
methodologies of linear elastic fracture mechanics to the assessment of crack stability and to the determination
of the corresponding critical crack length. Such an analysis will concern both quasi-static loads, such as the
weight load and the hydraulic pressure, as well as seismic actions, a topic of high complexity and actuality.
Finally, the problems related to the proper evaluation of the mechanical parameters of huge structures such as
dams will be analyzed, taking into account the strong size-scale effects observed in experimental tests.
Marco Paggi
marco.paggi@imtlucca.it
Giuseppe Ferro
2013-12-04T10:23:50Z
2013-12-04T10:23:50Z
http://eprints.imtlucca.it/id/eprint/2035
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2035
2013-12-04T10:23:50Z
Johannes Kepler's 'School of Athens' for Astronomy
Stefano Gattei
stefano.gattei@imtlucca.it
2013-12-03T15:47:46Z
2013-12-03T15:47:46Z
http://eprints.imtlucca.it/id/eprint/2023
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2023
2013-12-03T15:47:46Z
"Per desiderio del vero e delle sue cause": Galileo astronomo filosofo
This paper provides the framework for understanding Galileo’s request to the Grand Duke of Tuscany, in 1610, to be appointed in Florence as both Mathematician and Philosopher. By explicitly choosing such a title, he wished to stress the fact that his own work aimed at contributing to the new physical astronomy with which Copernicus inaugurated what is now called the Scientific Revolution. As opposed to Ptolemy, who understood astronomy as a purely mathematical tool in order to “save the phenomena” and allow for accurate predictions, Galileo – very much in line with Copernicus and Kepler, as well as Newton after him – supported the reality of the Copernican system not only against Aristotle and Ptolemy, but also against Tycho Brahe. And, as it turned out after 1616, against the Church itself, which, in full accord with Osiander’s unsigned preface to the De revolutionibus, refused to see in the Copernican theory anything more than a mere working hypothesis to which astronomers were allowed to appeal only for computations.
Stefano Gattei
stefano.gattei@imtlucca.it
2013-12-03T15:43:30Z
2013-12-03T15:43:30Z
http://eprints.imtlucca.it/id/eprint/2024
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2024
2013-12-03T15:43:30Z
Copernicus' Terse Argument: Scientific and Philosophical Foundations of the Heliocentric Hypothesis
Stefano Gattei
stefano.gattei@imtlucca.it
2013-12-02T11:29:32Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1990
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1990
2013-12-02T11:29:32Z
Limits to plastic analysis due to size-scale effects on the rotational capacity of reinforced concrete cross sections
Reinforced concrete (RC) structures are usually designed to provide a ductile response under bending loadings. To this aim, most codes of practice impose lower and upper limits to the steel ratio in order to prevent unstable crack propagation and to avoid brittle failure due to concrete crushing without steel yielding. Within these limitations, elastic analysis with moment redistribution or even plastic analysis can be adopted for RC structures. In this context, size-scale effects are usually disregarded, leading to unsafe design conditions in the case of large structures.
In the present study, the limitations of the prescriptions provided by the European and American building codes concerning the admissible plastic rotation and moment redistribution are highlighted. In particular, using a numerical algorithm based on the finite element method and on nonlinear fracture mechanics concepts recently developed by the present authors, the mechanical behaviour of the plastic hinge region of RC beams in bending is simulated. The results show that the effect of the structural dimension should be explicitly introduced in the code prescriptions for a safe structural design, by considering different design curves depending on the size-scale of the beams.
Mauro Corrado
Marco Paggi
marco.paggi@imtlucca.it
Alberto Carpinteri
2013-12-02T11:20:20Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1989
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1989
2013-12-02T11:20:20Z
Singular, hypersingular and singular free electromagnetic fields at wedge tips in metamaterials
The engineering response of metamaterials has a dramatic impact on the physics, optics and engineering communities, because they offer electromagnetic properties that are difficult or impossible to achieve with conventional materials. In this paper, an asymptotic analysis of the electromagnetic fields at multi-material wedges composed of metamaterials is proposed. This is made possible by removing the assumption of positive electric permittivities and magnetic permeabilities, an hypothesis which usually applies to conventional materials. Exploring the whole range of variability of these electromagnetic properties, it is shown that, in addition to the classical real eigenvalues 0 ⩽ λ < 1 leading to power-law singularities of the type O(rλ−1) as r → 0, it is also possible to find imaginary eigenvalues leading to hypersingular solutions, as well as nonsingular configurations for a suitable choice of the negative electric permittivities and magnetic permeabilities of the media. Moreover, to fully characterize the asymptotic fields, the analysis is not only restricted to the determination of the lowest real and complex eigenvalues, but is also extended to the evaluation of the higher-order nonsingular ones. The obtained analytical results collected in synthetic diagrams are expected to have impact on the design of micro- and nano-electro-mechanical systems.
Marco Paggi
marco.paggi@imtlucca.it
2013-12-02T11:08:47Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1988
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1988
2013-12-02T11:08:47Z
The coefficient of proportionality κ between real contact area and load, with new asperity models
Most recent numerical works on fractal surfaces have simply compared the low load limit of the coefficient of proportionality κ of the relationship between real contact area and load. In particular, that provided by Persson's theory, and that obtained from the Bush, Gibson and Thomas (BGT-A) asperity contact theory, which is a generalized form of the Greenwood and Williamson (GW) one. The two theories differ only by a numerical constant κ = √8/π ≈ 1.6 vs κ = √2 π ≈ 2.5 , but neither of the two provide an accurate prediction, Persson's value being generally too low, and BGT-A's limit being only valid for extremely large separations. A detailed numerical comparison using a range of generated fractal surfaces permits to compare the existing models, finding for example that bandwidth is more important than Gaussianity of the surfaces. Then, we propose two new theoretical equations generalizing {GW} and {BGT} to take into account interaction effects in an approximate way (GW-I and BGT-I, respectively), which significantly improve the accuracy of original asperity models. Further, as a practical alternative to the tribologist, we suggest a new very simple discrete form of the {GW} model (called GW-RI) whose accuracy is similar to BGT-I, but with much lower computational cost, comparable to analytical solutions since the latter require the evaluation of the variance of the profile slopes, σ m 2 , with a surface defined at a given set of points. The GW-RI model additionally avoids an ambiguity over how to define numerically the variance of the profile slopes, σ m 2 .
Marco Paggi
marco.paggi@imtlucca.it
Michele Ciavarella
2013-12-02T11:06:15Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1987
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1987
2013-12-02T11:06:15Z
A mathematical analogy and a unified asymptotic formulation for singular elastic and electromagnetic fields at multimaterial wedges
In the present contribution, the mathematical analogy existing between the singular stress field in elasticity due to antiplane loading and the singular electromagnetic fields in electromagnetism is derived with reference to the problem of isotropic multimaterial wedges. These configurations, where dissimilar sectors converge to the same vertex, are commonly observed in composite materials and may lead to singularities. The proposed analogy permits to extend several elastic solutions for the power of the stress-singularity already available in the elasticity literature to the analogous electromagnetic problems and viceversa. Finally, electromagnetic structures that cannot be treated according to the proposed analogy, such as those related to bi-isotropic multimaterial wedges, are discussed.
Marco Paggi
marco.paggi@imtlucca.it
Alberto Carpinteri
Renato Orta
2013-12-02T11:02:49Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1986
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1986
2013-12-02T11:02:49Z
An integrated cohesive/overlapping crack model for the analysis of flexural cracking and crushing in RC beams
In the present paper, a new fracture-mechanics based model is proposed for the analysis of reinforced concrete beams in bending describing both cracking and crushing growths taking place during the loading process by means of the concept of strain localization. In particular, the nonlinear behaviour of concrete in compression is modelled by the Overlapping Crack Model, which considers a material interpenetration when the elastic limit is overcome, in close analogy with the Cohesive Crack Model, routinely adopted for modelling the tensile behaviour of concrete. On the basis of different nonlinear contributions due to concrete and steel, a numerical finite element algorithm is proposed. According to this approach, the flexural behaviour of reinforced concrete structural elements is analyzed by varying the main geometrical and mechanical parameters. Particular regard is given to the role of the size-scale effects on the ductility of plastic hinges, which is available at the ultimate load conditions.
Alberto Carpinteri
Mauro Corrado
Marco Paggi
marco.paggi@imtlucca.it
2013-12-02T10:59:47Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1985
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1985
2013-12-02T10:59:47Z
A generalisation of the Hillerborg's model for the analytical evaluation of ductility of RC beams in bending
In this study, a generalised analytical model for the evaluation of the plastic rotations of reinforced concrete beams in bending is proposed. To this aim, the pioneering Hillerborg's model is here extended by taking into account also the contribution of reinforcement in compression. Moreover, a detailed comparison with the experimental results by Bosco and Debernardi on three-point bending reinforced concrete beams by varying the reinforcement percentage and the size-scale of the structural elements is carried out. This permits study of the influence of the parameter β, related to the length of strain localisation of concrete in compression, on the ductility response and how to tune this parameter according to experiments. The proposed generalisation of the Hillerborg model is then suitably applied to over-reinforced concrete beams in bending, where concrete crushing is the prevailing non-linearity; it is shown that the model is able to capture the phenomenon of size-scale effects
Erica Cadamuro
Marco Paggi
marco.paggi@imtlucca.it
Alberto Carpinteri
2013-12-02T10:55:31Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1984
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1984
2013-12-02T10:55:31Z
Analysis of snap-back instability due to end-plate debonding in strengthened beams
The problem of end-plate debonding of the external reinforcement in strengthened concrete beams is analyzed in this paper. As experimentally observed, this mode of failure is highly brittle and poses severe limitations to the efficacy of the strengthening technique. A numerical analysis of the full-range behavior of strengthened beams in bending is herein proposed to study the stages of nucleation and propagation of interfacial cracks between the external reinforcement and the concrete substrate. This is achieved by modeling the nonlinear interface behavior according to a cohesive law accounting for Mode Mixity. The numerically obtained load versus midspan deflection curves for three- or four-point bending beams show that the process of end-plate debonding is the result of a snap-back instability, which is fully interpreted in the framework of the Catastrophe Theory. To capture the softening branch with positive slope, the interface crack-length control scheme is proposed in the numerical simulations. The results of a wide parametric study exploring the effect of the relative reinforcement length, the mechanical percentage of fiber-reinforced polymer sheets, the beam slenderness, and the ratio between Mode II and Mode I fracture energies are collected in useful diagrams. Finally, an experimental assessment of the proposed model completes the paper.
Alberto Carpinteri
Marco Paggi
marco.paggi@imtlucca.it
2013-12-02T10:38:28Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1983
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1983
2013-12-02T10:38:28Z
Technical Papers: Linear elastic fracture mechanics approach to plate end debonding in rectilinear and curved plated beams
This paper proposes a linear elastic fracture mechanics approach for the prediction of plate end debonding in rectilinear and curved plated beams. The analytical model results in simple equations, suitable for immediate design use. The load-deflection curve of a plated beam, from the onset of debonding up to the complete separation of the plate, is obtained by controlling the length of the interfacial debonding crack. Its shape clearly shows that snap-back or snap-through instabilities may arise when the beam is loaded under displacement or force control. Analytical predictions are also compared with finite element results based on an interfacial cohesive crack model. It is shown that the predictions of the proposed analytical model match closely the numerical solution, provided that an effective crack length accounting for the size of the fracture process zone is used in the calculations.
Giorgio Zavarise
Alberto Carpinteri
Marco Paggi
marco.paggi@imtlucca.it
Laura De Lorenzis
2013-12-02T10:29:18Z
2014-10-09T09:20:24Z
http://eprints.imtlucca.it/id/eprint/1982
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1982
2013-12-02T10:29:18Z
A unified fractal approach for the interpretation of the anomalous scaling laws in fatigue and comparison with existing models
In this paper, a critical reexamination of the fractal models for the analysis of crack-size effects in fatigue is proposed. The enhanced ability to detect and measure very short cracks has in fact pointed out the so-called anomalous behavior of short cracks with respect to their longer counterparts. The crack-size dependencies of both the fatigue threshold and the Paris’ constant C are only two notable examples of these anomalous scaling laws. In this context, a unified theoretical model seems to be missing and the behavior of short cracks can still be considered as an open problem. A new generalized theory based on fractal geometry is herein proposed, which permits to consistently interpret the short crack-related anomalous scaling laws within a unified theoretical framework. The proposed model is used to interpret relevant experimental data related to the crack-size dependence of the fatigue threshold in metals. As a main result, the model gives an explanation to the experimentally observed variability in the slope of the asymptote of the scaling law for the fatigue threshold in the short crack regime.
Alberto Carpinteri
Marco Paggi
marco.paggi@imtlucca.it
2013-11-08T10:00:18Z
2013-11-08T10:00:18Z
http://eprints.imtlucca.it/id/eprint/1894
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1894
2013-11-08T10:00:18Z
Modeling commuting systems through a complex network analysis: a study of the Italian islands of Sardinia and Sicily
This study analyzes the inter-municipal commuting systems of the Italian islands of Sardinia and Sicily, employing weighted network analysis technique. Based on the results obtained for the Sardinian commuting network, the network analysis is used to identify similarities and dissimilarities between the two systems.
Andrea De Montis
Alessandro Chessa
alessandro.chessa@imtlucca.it
Michele Campagna
Simone Caschili
Giancarlo Deplano
2013-11-08T09:23:45Z
2013-11-08T09:23:45Z
http://eprints.imtlucca.it/id/eprint/1893
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1893
2013-11-08T09:23:45Z
Urban management in the face of complexity: commuting networks in insular Italy
Complex networks theory allows researchers to deal with systems characterised by uncertainty and unpredictability. It also enables investigating interactions between transport networks and their topology. Recently it has been used to analyse socio-economic processes in urban, regional, and environmental planning. In the light of these advances, the aim of this paper is to present the results of the application of complex networks theory techniques to the characterisation of topological, traffic and spatial properties of commuters' systems in insular Italy.
Andrea De Montis
Simone Caschili
Alessandro Chessa
alessandro.chessa@imtlucca.it
Michele Campagna
2013-11-08T09:02:03Z
2014-09-02T09:52:15Z
http://eprints.imtlucca.it/id/eprint/1892
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1892
2013-11-08T09:02:03Z
Interaction design e tecniche di sviluppo agile
Luca Secchi
Alessandro Chessa
alessandro.chessa@imtlucca.it
2013-11-08T08:53:20Z
2014-07-07T10:30:16Z
http://eprints.imtlucca.it/id/eprint/1891
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1891
2013-11-08T08:53:20Z
Complex network analysis on a cloud computing architecture
Vincenzo De Leo
Gianni Fenu
Michelangelo Puliga
michelangelo.puliga@imtlucca.it
Luca Secchi
Lorenzo Zolesio
Alessandro Chessa
alessandro.chessa@imtlucca.it
2013-11-05T15:14:26Z
2013-11-05T15:14:26Z
http://eprints.imtlucca.it/id/eprint/1864
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1864
2013-11-05T15:14:26Z
Assessing the Competitive Behaviour of Firms in the Single Market: A Micro-based Approach
This Report analyses and compares a number of indicators related to the evolution of the competitive behaviour of firms in the Single Market, from 1999 to 2007, in a selected number of both manufacturing and services industries and eight EU countries: Belgium, Germany, France, Italy, Poland, Romania, Spain and Sweden. A novelty of the approach is that the analysis is derived from firm-level observable data, which allow to grasp not only information on the average changes taking place in each industry and across countries, but also the distribution and sources of these changes in terms of individual firms' pricing behaviour and market shares, an information which is impossible to gather in detail from aggregate, traditional sector-level measures
Carlo Altomonte
Marcella Nicolini
Armando Rungi
armando.rungi@imtlucca.it
Laura Ogliari
2013-11-05T13:25:52Z
2013-11-05T15:01:49Z
http://eprints.imtlucca.it/id/eprint/1858
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1858
2013-11-05T13:25:52Z
From Export Dependency to Dynamic Comparative Advantages
Introduction: A modern race to resources is underway to assure that present and future generations can benefit from the availability of a stock necessary for the maintenance of an acceptable level of economic development.
In this brief chapter we collect some economic literature that could be of help in understanding the conflict of interest between export and import dependent countries, which are often also polarized between developing and developed countries. We don’t pretend to be exhaustive of all the literature that in the last decades has coped with the issues. Instead we suggest only a few tools to interpret an ever-changing reality that we consider useful for future progress of our research.
Given the geographical dispersion of natural resources, we have countries that specializes in trade of natural resources and countries that exchange manufacturing and services for them. A better knowledge of the reciprocal weaknesses of these two groups of countries can avoid the emergence of future conflicts. In particular we have adopted the side of export dependent countries, that are often also underdeveloped, in order to understand the problems that can hinder a worldwide stable and secure supply of natural resources
Armando Rungi
armando.rungi@imtlucca.it
2013-11-05T12:08:17Z
2013-11-07T13:32:52Z
http://eprints.imtlucca.it/id/eprint/1857
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1857
2013-11-05T12:08:17Z
Abbondanza di risorse naturali e mancate opportunità di sviluppo
In the worldwide race to resources to ensure an acceptable level of economic development for present and future generations, the African continent assumes a central role for its abundant natural capital. Notwithstanding the renewed interest of advanced economies, and more recently of the emerging Asian economies, Africa is a continent rich in resources but poorly integrated within the new global economic system.
Armando Rungi
armando.rungi@imtlucca.it
Silvia Merler
2013-10-04T10:11:06Z
2013-11-21T12:19:48Z
http://eprints.imtlucca.it/id/eprint/1823
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1823
2013-10-04T10:11:06Z
Theoretical Perspectives on Protein Folding
Understanding how monomeric proteins fold under in vitro conditions is crucial to describing their functions in the cellular context. Significant advances in theory and experiments have resulted in a conceptual framework for describing the folding mechanisms of globular proteins. The sizes of proteins in the denatured and folded states, cooperativity of the folding transition, dispersions in the melting temperatures at the residue level, and timescales of folding are, to a large extent, determined by N, the number of residues. The intricate details of folding as a function of denaturant concentration can be predicted by using a novel coarse-grained molecular transfer model. By watching one molecule fold at a time, using single-molecule methods, investigators have established the validity of the theoretically anticipated heterogeneity in the folding routes and the N-dependent timescales for the three stages in the approach to the native state. Despite the successes of theory, of which only a few examples are documented here, we conclude that much remains to be done to solve the protein folding problem in the broadest sense.
D. Thirumalai
Edward P. O'Brien
Greg Morrison
greg.morrison@imtlucca.it
Changbong Hyeon
2013-09-17T13:10:16Z
2013-09-17T13:10:16Z
http://eprints.imtlucca.it/id/eprint/1768
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1768
2013-09-17T13:10:16Z
Information Complexity of Functional Optimization Problems and Their Approximation Schemes
Functional optimization is investigated using tools from information-based complexity. In such optimization problems, a functional has to be minimized with respect to admissible solutions belonging to an infinite-dimensional space of functions. This context models tasks arising in optimal control, systems identification, machine learning, time-series analysis, etc. The solution via variable-basis approximation schemes, which provide a sequence of nonlinear programming problems approximating the original functional one, is considered. Also for such problems, the information complexity is estimated.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-17T13:09:59Z
2013-09-17T13:09:59Z
http://eprints.imtlucca.it/id/eprint/1761
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1761
2013-09-17T13:09:59Z
Error Bounds for Suboptimal Solutions to Kernel Principal Component Analysis
Suboptimal solutions to kernel principal component analysis are considered. Such solutions take on the form of linear combinations of all n-tuples of kernel functions centered on the data, where n is a positive integer smaller than the cardinality m of the data sample. Their accuracy in approximating the optimal solution, obtained in general for n = m, is estimated. The analysis made in Gnecco and Sanguineti (Comput Optim Appl 42:265–287, 2009) is extended. The estimates derived therein for the approximation of the first principal axis are improved and extensions to the successive principal axes are derived.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-17T13:09:43Z
2013-09-17T13:09:43Z
http://eprints.imtlucca.it/id/eprint/1759
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1759
2013-09-17T13:09:43Z
Editorial for the special issue: “Mathematical problems in engineering, aerospace and sciences”
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-17T13:09:23Z
2013-09-17T13:09:23Z
http://eprints.imtlucca.it/id/eprint/1788
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1788
2013-09-17T13:09:23Z
Suboptimal Solutions to Team Optimization Problems
with Statistical Information Structure
Network team optimization problems with statistical information structure are investigated. A team of n Decision Makers (DMs), each having at disposal
some information (obtained, e.g., by measurement devices or by exit polls) and various possibilities of decisions, coordinate their efforts to achieve a common goal, expressed via a team utility function. Decisions are generated by the DMs via strategies, on the basis of the available information y1, . . . , yn that each of
them has and in the presence of uncertainties in the "state of the external world’ x (which the DMs do not control). Such uncertainties are modeled via a joint
probability density p(x, y1, . . . , yn). For these problems, optimal solutions in closed form can be derived only in special cases, so a methodology of approximate
solution is proposed. Suboptimal solutions are searched for, taking the form of linear combinations of elements from sets of basis functions, possibly with adjustable "inner’ parameters. Upper bounds on the accuracy of such
suboptimal solutions are obtained. The estimates are expressed in dependence of the number of trigonometric and Gaussian basis functions. The trade-off between the level of decentralization and the smoothness assumptions on the
utility function and the probability density, required to derive the upper bounds, is investigated. Numerical results are presented for an instance of the network team optimization problem under study, which models optimal production in a multidivisional firm.
Mauro Gaggero
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-17T13:07:38Z
2013-09-17T13:07:38Z
http://eprints.imtlucca.it/id/eprint/1773
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1773
2013-09-17T13:07:38Z
On Call Admission Control with Nonlinearly Constrained
Feasibility Regions
A simple criterion is proposed to improve suboptimal coordinate-convex policies in Call Admission Control problems with nonlinearly constrained feasibility regions. To test the criterion, numerical simulation results are given.
Finally, some structural properties of the optimal coordinate-convex policies are proven, which do not depend on a complete knowledge of the nonlinear boundary of the feasibility region.
Marco Cello
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Mario Marchese
Marcello Sanguineti
2013-09-17T08:23:42Z
2013-09-17T08:23:42Z
http://eprints.imtlucca.it/id/eprint/1758
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1758
2013-09-17T08:23:42Z
On Spectral Windows In Supervised Learning From Data
For Tikhonov regularization in supervised learning from data, the effect on the regularized solution of a joint perturbation of the regression function and the data is investigated. Spectral windows in the finite-sample and population cases are compared via probabilistic estimates of the differences between regularized solutions.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-17T08:11:59Z
2013-09-17T08:11:59Z
http://eprints.imtlucca.it/id/eprint/1754
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1754
2013-09-17T08:11:59Z
Computationally Efficient Approximation Schemes for Functional Optimization
Angelo Alessandri
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-17T08:11:38Z
2013-09-17T08:11:38Z
http://eprints.imtlucca.it/id/eprint/1755
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1755
2013-09-17T08:11:38Z
Decentralized Optimization Problems with Cooperating Decision Makers
Mauro Gaggero
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-13T10:33:43Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1716
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1716
2013-09-13T10:33:43Z
Minimizing Sequences for a Family of Functional Optimal Estimation Problems
Rates of convergence are derived for approximate solutions to optimization problems associated with the design of state estimators for nonlinear dynamic systems. Such problems consist in minimizing the functional given by the worst-case ratio between the ℒ p -norm of the estimation error and the sum of the ℒ p -norms of the disturbances acting on the dynamic system. The state estimator depends on an innovation function, which is searched for as a minimizer of the functional over a subset of a suitably-defined functional space. In general, no closed-form solutions are available for these optimization problems. Following the approach proposed in (Optim. Theory Appl. 134:445–466, 2007), suboptimal solutions are searched for over linear combinations of basis functions containing some parameters to be optimized. The accuracies of such suboptimal solutions are estimated in terms of the number of basis functions. The estimates hold for families of approximators used in applications, such as splines of suitable orders.
Angelo Alessandri
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-13T10:30:44Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1715
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1715
2013-09-13T10:30:44Z
Suboptimal Solutions to Dynamic Optimization Problems via Approximations of the Policy Functions
The approximation of the optimal policy functions is investigated for dynamic optimization problems with an objective that is additive over a finite number of stages. The distance between optimal and suboptimal values of the objective functional is estimated, in terms of the errors in approximating the optimal policy functions at the various stages. Smoothness properties are derived for such functions and exploited to choose the approximating families. The approximation error is measured in the supremum norm, in such a way to control the error propagation from stage to stage. Nonlinear approximators corresponding to Gaussian radial-basis-function networks with adjustable centers and widths are considered. Conditions are defined, guaranteeing that the number of Gaussians (hence, the number of parameters to be adjusted) does not grow “too fast” with the dimension of the state vector. The results help to mitigate the curse of dimensionality in dynamic optimization. An example of application is given and the use of the estimates is illustrated via a numerical simulation.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-13T10:27:37Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1714
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1714
2013-09-13T10:27:37Z
Estimates of Variation with Respect to a Set and Applications to Optimization Problems
A variational norm that plays a role in functional optimization and learning from data is investigated. For sets of functions obtained by varying some parameters in fixed-structure computational units (e.g., Gaussians with variable centers and widths), upper bounds on the variational norms associated with such units are derived. The results are applied to functional optimization problems arising in nonlinear approximation by variable-basis functions and in learning from data. They are also applied to the construction of minimizing sequences by an extension of the Ritz method.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-13T10:17:39Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1713
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1713
2013-09-13T10:17:39Z
Regularization Techniques and Suboptimal Solutions to Optimization Problems in Learning from Data
Various regularization techniques are investigated in supervised learning from data. Theoretical features of the associated optimization problems are studied, and sparse suboptimal solutions are searched for. Rates of approximate optimization are estimated for sequences of suboptimal solutions formed by linear combinations of n-tuples of computational units, and statistical learning bounds are derived. As hypothesis sets, reproducing kernel Hilbert spaces and their subsets are considered.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-09-10T15:08:56Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1669
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1669
2013-09-10T15:08:56Z
Some Comparisons of Model Complexity in Linear and Neural-Network Approximation
Capabilities of linear and neural-network models are compared from the point of view of requirements on the growth of model complexity with an increasing accuracy of approximation. Upper bounds on worst-case errors in approximation by neural networks are compared with lower bounds on these errors in linear approximation. The bounds are formulated in terms of singular numbers of certain operators induced by computational units and high-dimensional volumes of the domains of the functions to be approximated.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Věra Kůrková
Marcello Sanguineti
2013-09-10T14:59:37Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1668
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1668
2013-09-10T14:59:37Z
On call admission control with nonlinearly constrained
feasibility regions
A simple criterion is proposed to improve suboptimal coordinate-convex policies in Call Admission Control problems with nonlinearly constrained feasibility regions. To test the criterion, numerical simulation results are given.
Finally, some structural properties of the optimal coordinate-convex policies are proven, which do not depend on a complete knowledge of the nonlinear boundary of the feasibility region.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marco Cello
Marcello Sanguineti
2013-09-10T14:56:16Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1667
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1667
2013-09-10T14:56:16Z
Suboptimal solutions to team optimization problems
with statistical information structure
Network team optimization problems with statistical information structure are investigated. A team of n Decision Makers (DMs), each having at disposal
some information (obtained, e.g., by measurement devices or by exit polls) and various possibilities of decisions, coordinate their efforts to achieve a common goal, expressed via a team utility function. Decisions are generated by the DMs via strategies, on the basis of the available information y1, . . . , yn that each of
them has and in the presence of uncertainties in the "state of the external world’ x (which the DMs do not control). Such uncertainties are modeled via a joint
probability density p(x, y1, . . . , yn). For these problems, optimal solutions in closed form can be derived only in special cases, so a methodology of approximate
solution is proposed. Suboptimal solutions are searched for, taking the form of linear combinations of elements from sets of basis functions, possibly with adjustable "inner’ parameters. Upper bounds on the accuracy of such
suboptimal solutions are obtained. The estimates are expressed in dependence of the number of trigonometric and Gaussian basis functions. The trade-off between the level of decentralization and the smoothness assumptions on the
utility function and the probability density, required to derive the upper bounds, is investigated. Numerical results are presented for an instance of the network team optimization problem under study, which models optimal production in a multidivisional firm.
Marcello Sanguineti
Mauro Gaggero
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
2013-09-10T14:42:52Z
2013-09-16T12:03:00Z
http://eprints.imtlucca.it/id/eprint/1666
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1666
2013-09-10T14:42:52Z
Smooth Optimal Decision Strategies for Static Team Optimization Problems and Their Approximations
Sufficient conditions for the existence and uniqueness of smooth optimal decision strategies for static team optimization problems with statistical information structure are derived. Approximation methods and algorithms to derive suboptimal solutions based on the obtained results are investigated. The application to network team optimization problems is discussed.
Giorgio Gnecco
giorgio.gnecco@imtlucca.it
Marcello Sanguineti
2013-07-09T14:50:01Z
2013-07-09T14:50:01Z
http://eprints.imtlucca.it/id/eprint/1637
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1637
2013-07-09T14:50:01Z
Application of logit model and self-organizing maps (SOMs) for the prediction of financial crisis periods in US economy
Purpose – The purpose of this paper is to examine two different approaches in the prediction of the economic recession periods in the US economy.
Design/methodology/approach – A logit regression was applied and the prediction performance in two out-of-sample periods, 2007-2009 and 2010 was examined. On the other hand, feed-forwards neural networks with Levenberg-Marquardt error backpropagation algorithm were applied and then neural networks self-organizing map (SOM) on the training outputs was estimated.
Findings – The paper presents the cluster results from SOM training in order to find the patterns of economic recessions and expansions. It is concluded that logit model forecasts the current financial crisis period at 75 percent accuracy, but logit model is useful as it provides a warning signal three quarters before the current financial crisis started officially. Also, it is estimated that the financial crisis, even if it reached its peak in 2009, the economic recession will be continued in 2010 too. Furthermore, the patterns generated by SOM neural networks show various possible versions with one common characteristic, that financial crisis is not over in 2009 and the economic recession will be continued in the USA even up to 2011-2012, if government does not apply direct drastic measures.
Originality/value – Both logistic regression (logit) and SOMs procedures are useful. The first one is useful to examine the significance and the magnitude of each variable, while the second one is useful for clustering and identifying patterns in economic recessions and expansions.
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-07-09T14:46:57Z
2013-07-09T14:46:57Z
http://eprints.imtlucca.it/id/eprint/1636
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1636
2013-07-09T14:46:57Z
Application of Feed-Forward Neural Networks Smoothing Transition Autoregressive Models in Stock Returns Forecasting
In this paper we propose and examine new approaches in smoothing transition autoregressive (STAR) models. Firstly, a new STAR function is proposed, which is the hyperbolic tangent sigmoid function. Secondly, we propose Feed-Forward Neural Networks Smoothing Transition Autoregressive (FFNN-STAR) models. We examine the stock returns of US S&P 500, FTSE-100 in UK stock index, DAX index in Germany and CAC-40 in France and we apply bootstrapping ordinary least squares simulated regressions, while also GARCH models with bootstrapping simulations can be applied as well. The results are in favor of neural networks, while in almost all cases the forecasting performance of Feed-Forward Neural Networks STAR models is superior to conventional STAR models. This paper can be a guide and set up the fundamentals for further advanced research in econometrics and time-series analysis.
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-07-09T14:36:19Z
2013-07-09T14:36:19Z
http://eprints.imtlucca.it/id/eprint/1635
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1635
2013-07-09T14:36:19Z
A Study of Panel Logit Model and Adaptive Neuro-Fuzzy Inference System in the Prediction of Financial Distress Periods
The purpose of this paper is to present two different
approaches of financial distress pre-warning models appropriate for risk supervisors, investors and policy makers. We examine a sample of the financial institutions and electronic companies of Taiwan Security Exchange (TSE) market from 2002 through 2008. We present a binary logistic regression with paned data analysis. With the pooled binary logistic regression we build a model including more variables in the regression than with random effects, while the in-sample and out-sample forecasting performance is higher in random effects estimation than in pooled regression. On the other hand we estimate an Adaptive Neuro-Fuzzy Inference System (ANFIS) with Gaussian and Generalized Bell (Gbell) functions and we find that ANFIS outperforms significant Logit regressions in both in-sample and out-of-sample periods, indicating that ANFIS is a
more appropriate tool for financial risk managers and for the economic policy makers in central banks and national statistical services.
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-07-09T13:54:08Z
2013-07-09T13:54:08Z
http://eprints.imtlucca.it/id/eprint/1634
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1634
2013-07-09T13:54:08Z
A study on the day-of-the-Week Effect in Fifty Five Stock Markets: Evidence from Asymmetric GARCH Models
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-07-09T13:40:34Z
2013-07-09T13:40:34Z
http://eprints.imtlucca.it/id/eprint/1633
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1633
2013-07-09T13:40:34Z
Smoothing Transition Autoregressive (STAR) Models for the Day of the Week Effect : An Application to S&P 500 Stock Index
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-07-08T14:07:40Z
2013-07-08T14:07:40Z
http://eprints.imtlucca.it/id/eprint/1632
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1632
2013-07-08T14:07:40Z
Applications of Neural Network Radial Basis Function in Economics and Financial Time Series
In this paper we present the Radial Basis Neural Network Function. We examine some simple numerical examples of time-series in economics and finance. The forecasting performance is significant superior, especially in financial time-series, to traditional econometric modeling indicating that artificial intelligence procedure are more appropriate. Some MATLAB routines are presented for further application research.
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-07-08T14:04:53Z
2014-01-24T14:20:52Z
http://eprints.imtlucca.it/id/eprint/1631
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1631
2013-07-08T14:04:53Z
Applications of Feed-Forward Neural Networks with Error Backpropagation Algorithm and Non-Linear Methods in MATLAB
In this paper we examine and present the methodology of feed-forward neural networks with error backpropagation algorithm and non-linear methods. We test some applications of time-series analysis in economics. The first part is consisted by applications following the traditional approach of neural networks. In the second part we propose a weighted input regression. Additionally, we present full programming routines in MATLAB in order to replicate the results and for further research applications, modifications, expansions and improvements.
Eleftherios Giovanis
eleftherios.giovanis@imtlucca.it
2013-05-03T11:39:43Z
2013-05-03T11:39:43Z
http://eprints.imtlucca.it/id/eprint/1564
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1564
2013-05-03T11:39:43Z
A tool for rapid development of WS-BPEL applications
WS-BPEL is imposing itself as a standard for orchestration
of web services. However, there are still some well-known
difficulties that make programming in WS-BPEL a tricky
task. In this paper, we present BliteC, a software tool we
have developed for supporting a rapid and easy development
of WS-BPEL applications. BliteC translates service orches-
trations written in Blite, a formal language inspired to but
simpler than WS-BPEL, into readily executable WS-BPEL
programs. We illustrate our approach by means of a few
practical programming examples.
Luca Cesari
Rosario Pugliese
Francesco Tiezzi
francesco.tiezzi@imtlucca.it
2013-02-14T08:56:34Z
2013-09-12T12:16:45Z
http://eprints.imtlucca.it/id/eprint/1478
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1478
2013-02-14T08:56:34Z
Collaborative development of predictive toxicology applications
OpenTox provides an interoperable, standards-based Framework for the support of predictive toxicology data management, algorithms, modelling, validation and reporting. It is relevant to satisfying the chemical safety assessment requirements of the REACH legislation as it supports access to experimental data, (Quantitative) Structure-Activity Relationship models, and toxicological information through an integrating platform that adheres to regulatory requirements and OECD validation principles. Initial research defined the essential components of the Framework including the approach to data access, schema and management, use of controlled vocabularies and ontologies, architecture, web service and communications protocols, and selection and integration of algorithms for predictive modelling. OpenTox provides end-user oriented tools to non-computational specialists, risk assessors, and toxicological experts in addition to Application Programming Interfaces (APIs) for developers of new applications. OpenTox actively supports public standards for data representation, interfaces, vocabularies and ontologies, Open Source approaches to core platform components, and community-based collaboration approaches, so as to progress system interoperability goals.
The OpenTox Framework includes APIs and services for compounds, datasets, features, algorithms, models, ontologies, tasks, validation, and reporting which may be combined into multiple applications satisfying a variety of different user needs. OpenTox applications are based on a set of distributed, interoperable OpenTox API-compliant REST web services. The OpenTox approach to ontology allows for efficient mapping of complementary data coming from different datasets into a unifying structure having a shared terminology and representation.
Two initial OpenTox applications are presented as an illustration of the potential impact of OpenTox for high-quality and consistent structure-activity relationship modelling of REACH-relevant endpoints: ToxPredict which predicts and reports on toxicities for endpoints for an input chemical structure, and ToxCreate which builds and validates a predictive toxicity model based on an input toxicology dataset. Because of the extensible nature of the standardised Framework design, barriers of interoperability between applications and content are removed, as the user may combine data, models and validation from multiple sources in a dependable and time-effective way.
Barry Hardy
Nicki Douglas
Christoph Helma
Micha Rautenberg
Nina Jeliazkova
Vedrin Jeliazkov
Ivelina Nikolova
Romualdo Benigni
Olga Tcheremenskaia
Stefan Kramer
Tobias Girschick
Fabian Buchwald
Joerg Wicker
Andreas Karwath
Martin Gutlein
Andreas Maunz
Haralambos Sarimveis
Georgia Melagraki
Antreas Afantitis
Pantelis Sopasakis
pantelis.sopasakis@imtlucca.it
David Gallagher
Vladimir Poroikov
Dmitry Filimonov
Alexey Zakharov
Alexey Lagunin
Tatyana Gloriozova
Sergey Novikov
Natalia Skvortsova
Dmitry Druzhilovsky
Sunil Chawla
Indira Ghosh
Surajit Ray
Hitesh Patel
Sylvia Escher
2013-02-14T08:45:32Z
2013-03-12T14:57:38Z
http://eprints.imtlucca.it/id/eprint/1476
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1476
2013-02-14T08:45:32Z
Consensus QSAR modeling and domain of applicability: an integrated approach
Consensus modelling is a term that has been used in many scientific disciplines to define methods by which a group of individuals can come to an agreement. The QSAR community has used this term for methodologies that aggregate the predictions of several QSAR models to arrive at a single prediction. Literature reports on the validity of consensus modelling approaches are quite conflicting. Many publications present advantages of consensus models: More accurate QSAR models, greater confidence in predictions, regulatory significance, improved robustness. Several other references however, have criticized consensus modelling for complexity, lack of portability, transparency and mechanistic interpretation and for not showing significant improvements over single QSAR models.
Many consensus QSAR models that have appeared in the literature use a naive approach that calculates the average value among all the individual model predictions. More sophisticated methods consider only the models for which the compound to be predicted falls into their domain of applicability. Alternative consensus modelling methods consider the individual model predictions as attributes in an overall multiple linear regression model, where the model coefficients play the role of weights. This way, the contribution of each individual model in the overall prediction is weighted.
In this work, we present a new approach, integrating three basic components in the process of building a QSAR model: variable selection, regression/classification, and domain of applicability. In particular, the proposed method requires a single wrapper variable selection method, a single method for defining the domain of applicability and many regression/classification algorithms depending on the type of the problem. The wrapper variable selection method is applied separately to each QSAR algorithm and produces a QSAR model which used a certain subset of features. In general, different sets of features are selected by the various QSAR models that are generated. Thus, for each QSAR model, a different domain of applicability is defined, by applying the domain of applicability method on the respective set of descriptors. For a new compound, the proposed method first calculates the individual QSAR models predictions. Then it checks for each model, if the compound falls into its domain of applicability. In the case of a negative answer, the model is not taken into account in the calculation of the aggregated prediction. If the answer is positive, a weight is produced depending on the location of the compound inside the domain of applicability. Obviously the weight becomes lower when the location of the compound is closer to the boundaries of the domain of applicability. The weights are finally normalized, so they add to 1. The normalized weights are used to produce the final aggregated prediction. The results of the application of the method to QSAR problems illustrate the advantages and limitations of the method.
Georgia Melagraki
Pantelis Sopasakis
pantelis.sopasakis@imtlucca.it
Antreas Afantitis
Haralambos Sarimveis
2013-02-14T08:31:40Z
2013-03-12T14:57:38Z
http://eprints.imtlucca.it/id/eprint/1475
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1475
2013-02-14T08:31:40Z
Decibell: A novel approach to the ORM software in Java
DeciBell is an open source and free tool developed to tackle in a uniform and structured way the problem of Java and SQL cooperation (available at http://github.com/hampos/DeciBell). In DeciBell, Java classes are related to relational database entities automatically and in a transparent way as far as the background operations are concerned. So, on one hand, non-expert users can work on Java code exclusively while expert ones are able to focus on more algorithmic aspects of the problem they try to solve rather than be wasted with trivial database management issues. In contrast to the existing O.R.M. programs, DeciBell does not require any configuration files or composite query structures, but only a proper annotation of certain fields of the classes. This annotation is carried out by means of the Java Annotations which is a modern trend in Java programming. Among its supported facilities, DeciBell supports primary keys (single and multiple), foreign keys, constraints, one-to-one, one- to-many, and many-to-many relations and all these using pure Java predicates and no SQL or other Query Languages.
Haralambos Chomenides
Pantelis Sopasakis
pantelis.sopasakis@imtlucca.it
Haralambos Sarimveis
2012-11-30T08:34:15Z
2012-11-30T08:34:15Z
http://eprints.imtlucca.it/id/eprint/1441
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1441
2012-11-30T08:34:15Z
Simulation-optimization under uncertainty through metamodeling and bootstrapping
Most methods in simulation-optimization assume known environments, whereas this research accounts for uncertain environments combining Taguchi's world view with either regression or Kriging (Gaussian Process) metamodels (response surfaces). These metamodels are combined with Non-Linear Mathematical Programming (NLMP) to find a robust optimal solution. Varying the constraint values in the NLMP model gives an estimated Pareto frontier. To account for the variability of the estimated Pareto frontier, this research uses bootstrapping which gives confidence regions for the robust optimal solution. This methodology is illustrated through the Economic Order Quantity (EOQ) inventory-management model, accounting for the uncertainties in the demand rate and the cost coefficients.
Gabriella Dellino
gabriella.dellino@imtlucca.it
Jack P.C. Kleijnen
Carlo Meloni
2012-10-12T10:53:19Z
2013-06-11T12:04:11Z
http://eprints.imtlucca.it/id/eprint/1392
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1392
2012-10-12T10:53:19Z
Cyberpunk. Le reti alternative tra Italia e Germania
Starting from a historiografical critique of the principal studies about the history of the relations between Italy and Germany in the 19. and 20. centuries, that traditionally have ignored the role of the civil society as autonomous instrument for creating network between the Italians and Germans, in this article the Author analyses the network of German and Italian people emerging during the globalisation of the punk and cyberpunk culture in the 70s and 80s.
Fiammetta Balestracci
fiammetta.balestracci@imtlucca.it
2012-09-24T13:13:27Z
2013-03-07T12:56:25Z
http://eprints.imtlucca.it/id/eprint/1372
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1372
2012-09-24T13:13:27Z
Deciding Full Branching Time Logic by Program Transformation
We present a method based on logic program transformation, for verifying Computation Tree Logic (CTL*) properties of finite state reactive systems. The finite state systems and the CTL* properties we want to verify, are encoded as logic programs on infinite lists. Our verification method consists of two steps. In the first step we transform the logic program that encodes the given system and the given property, into a monadic ω -program, that is, a stratified program defining nullary or unary predicates on infinite lists. This transformation is performed by applying unfold/fold rules that preserve the perfect model of the initial program. In the second step we verify the property of interest by using a proof method for monadic ω-programs
Alberto Pettorossi
Maurizio Proietti
Valerio Senni
valerio.senni@imtlucca.it
2012-09-18T15:24:04Z
2013-03-07T12:56:25Z
http://eprints.imtlucca.it/id/eprint/1364
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1364
2012-09-18T15:24:04Z
The Transformational Approach to Program Development
We present an overview of the program transformation techniques which have been proposed over the past twenty-five years in the context of logic programming. We consider the approach based on rules and strategies. First, we present the transformation rules and we address the issue of their correctness. Then, we present the transformation strategies and, through some examples, we illustrate their use for improving program efficiency via the elimination of unnecessary variables, the reduction of nondeterminism, and the use of program specialization. We also describe the use of the transformation methodology for the synthesis of logic programs from first-order specifications. Finally, we illustrate some transformational techniques for verifying first-order properties of logic programs and their application to model checking for finite and infinite state concurrent systems.
Alberto Pettorossi
Maurizio Proietti
Valerio Senni
valerio.senni@imtlucca.it
2012-09-18T15:15:57Z
2013-03-07T12:56:25Z
http://eprints.imtlucca.it/id/eprint/1362
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1362
2012-09-18T15:15:57Z
Transformations of logic programs on infinite lists
We consider an extension of logic programs, called ω-programs, that can be used to define predicates over infinite lists. ω-programs allow us to specify properties of the infinite behavior of reactive systems and, in general, properties of infinite sequences of events. The semantics of ω-programs is an extension of the perfect model semantics. We present variants of the familiar unfold/fold rules which can be used for transforming ω-programs. We show that these new rules are correct, that is, their application preserves the perfect model semantics. Then we outline a general methodology based on program transformation for verifying properties of ω-programs. We demonstrate the power of our transformation-based verification methodology by proving some properties of Büchi automata and ω-regular languages.
Alberto Pettorossi
Maurizio Proietti
Valerio Senni
valerio.senni@imtlucca.it
2012-09-18T13:56:51Z
2013-03-07T12:56:25Z
http://eprints.imtlucca.it/id/eprint/1359
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1359
2012-09-18T13:56:51Z
A Transformation Strategy for Verifying Logic Programs on Infinite Lists
We consider an extension of the class of logic programs,
called !-programs, that can be used to define predicates over infinite lists. The ω-programs allow us to specify properties of the infinite behaviour of reactive systems and, in general, properties of infinite sequences of events. The semantics of ω-programs is an extension of the
perfect model semantics. We present a general methodology based on an extension of the unfold/fold transformation rules which can be used for verifying properties of ω-programs. Then we propose a strategy for
the mechanical application of those rules and we demonstrate the power of that strategy by proving some properties of ω-regular languages and Büchi automata.
Alberto Pettorossi
Maurizio Proietti
Valerio Senni
valerio.senni@imtlucca.it
2012-09-04T08:34:26Z
2013-11-20T10:24:03Z
http://eprints.imtlucca.it/id/eprint/1334
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1334
2012-09-04T08:34:26Z
Dual contrast cellular MRI
Negative contrast MRI methods utilizing local magnetic susceptibility shifting (LMS) agents have become an active area of cellular imaging research. However, visualizing and tracking labeled cells on the basis of negative contrast is often plagued by limited specificity and/or sensitivity. Here we report on a cellular MRI method that generates a new contrast with a distinct topology for identifying labeled cells permitting significant improvement in
sensitivity and specificity. Specifically, we show that FLAPS MRI [1],MRI can be used to generate fast three-dimensional images of tissue that can be rapidly
processed to generate quantitative metrics enabling color overlays indicative of regions containing labeled cells.
Rohan Dharmakumar
Zheng Zhang
Ioannis Koktzoglou
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Debiao Li
2012-07-02T13:25:07Z
2013-04-16T14:20:56Z
http://eprints.imtlucca.it/id/eprint/1298
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1298
2012-07-02T13:25:07Z
Picasso and the Paris avant-garde
Silvia Loreti
silvia.loreti@imtlucca.it
2012-05-16T10:25:22Z
2012-05-17T08:57:16Z
http://eprints.imtlucca.it/id/eprint/1270
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1270
2012-05-16T10:25:22Z
Georg Simmel
Linda Bertelli
linda.bertelli@imtlucca.it
2012-03-28T12:48:36Z
2012-04-03T07:52:20Z
http://eprints.imtlucca.it/id/eprint/1250
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1250
2012-03-28T12:48:36Z
Monitoring of human movements for fall detection and activities recognition in elderly care using wWireless sensor network: a survey
Stefano Abbate
stefano.abbate@alumni.imtlucca.it
Marco Avvenuti
Paolo Corsini
Janet Light
Alessio Vecchio
2012-03-26T11:14:18Z
2012-07-05T10:08:53Z
http://eprints.imtlucca.it/id/eprint/1241
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1241
2012-03-26T11:14:18Z
The evolution of environmental and labor productivity dynamics
This paper provides new empirical evidence on delinking in income–environment dynamic relationships for CO 2 and air pollutants at the sector level. A panel dataset based on the Italian NAMEA (National Accounting Matrix including Environmental Accounts) over 1990–2007 is analyzed, focusing on both emissions efficiency (EKC model) and total emissions (IPAT model). Results show that, looking at sector evidence, both decoupling and also eventually re-coupling trends could emerge along the path of economic development. The overall performance on greenhouse gases, here CO 2 , is not compliant with Kyoto targets. SOx and NOx show decreasing patterns, though the shape is affected by some outlier sectors with regard to joint emission-productivity dynamics. Services tend to present stronger delinking patterns across emissions than manufacturing. Trade expansion validates the pollution haven in some cases, but also shows negative signs when only EU 15 trade is considered. This may due to technology spillovers and a positive ‘race to the top’ rather than the bottom among EU 15 trade partners. General R&D expenditure shows weak correlation with emissions efficiency. SUR estimators (Seemingly Unrelated Regressions) suggest that, as regards manufacturing, the slope varies across sectors. Further research should be directed towards deeper investigation of trade relationship at the sector level and increased research into and efforts to produce specific sectoral data on ‘environmental innovations’.
Giovanni Marin
giovanni.marin@alumni.imtlucca.it
Massimiliano Mazzanti
2012-03-06T13:08:24Z
2013-09-30T12:28:55Z
http://eprints.imtlucca.it/id/eprint/1218
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1218
2012-03-06T13:08:24Z
Optimal disturbance rejection via integral sliding mode control for uncertain systems in regular form
This paper considers the problem of using an integral sliding mode strategy to reduce the disturbance terms acting on nonlinear systems in regular form. It is proved that the definition of a suitable sliding manifold and the generation of sliding modes upon it can guarantee the minimization of the disturbance terms. Simulation examples shows the effectiveness of the proposal.
Matteo Rubagotti
Antonio Estrada
Fernando Castanos
Antonella Ferrara
Leonid Fridman
2012-03-06T12:14:28Z
2013-09-30T12:28:34Z
http://eprints.imtlucca.it/id/eprint/1217
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1217
2012-03-06T12:14:28Z
Second order sliding mode control of a perturbed double integrator with state constraints
This paper introduces a second order sliding mode controller for double integrators subject to external disturbances and model uncertainties, with both control and state constraints. The proposed control strategy proves to be able to robustly steer the system state to zero in a finite time, fulfilling the state constraints in spite of the uncertainties, provided that the initial state is inside a given region. The effectiveness of the proposal is then tested on a simulation example.
Matteo Rubagotti
Antonella Ferrara
2012-03-06T12:06:46Z
2013-09-30T12:27:36Z
http://eprints.imtlucca.it/id/eprint/1216
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1216
2012-03-06T12:06:46Z
A nonlinear model predictive control scheme with multirate integral sliding mode
In this paper, a hierarchical multirate control scheme for nonlinear discrete-time systems is proposed, composed of a robust model predictive controller (MPC) and a multirate integral sliding mode (MISM) controller. In particular, the MISM controller acts at a faster sampling time than the MPC controller, and reduces the effect of model uncertainties and external disturbances, in order to obtain, at the next sampling instant of the MPC controller, a value of the system state that is as close as possible to the nominal one. To obtain this result, the control variable is composed of two parts: one generated by the MPC controller, and the other by the MISM controller. The a-priori reduction of the disturbance terms turns out to be very useful in order to improve the convergence properties of the MPC controller.
Matteo Rubagotti
Davide Martino Raimondo
Colin Neil Jones
Lalo Magni
Antonella Ferrara
Manfred Morari
2012-03-06T11:57:29Z
2013-09-30T12:29:22Z
http://eprints.imtlucca.it/id/eprint/1214
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1214
2012-03-06T11:57:29Z
A smart embedded control unit for electro-hydraulic aircraft actuators
The design and experimental characterization of a novel electronic control unit for fly-by-wire aircraft actuators are presented. Thanks to a carefully-engineered compact volume, it is embedded in the actuator body, providing local closed-loop control. Various digital control laws can be implemented in the easily reconfigurable digital platform. After system modeling and tuning, a variable-gain controller has been selected. Beyond reduction of weight (900g), power dissipation (7W) and cabling connections (required only for power supply and digital communication bus), the advantages provided by this smart unit are both in terms of performance and safety improvement. In fact, fast (1Hz) and precise (1mm resolution, 2mm accuracy, no overshoot) closed-loop linear displacement regulation is here demonstrated. Furthermore, this robust and rugged unit is endowed with self-diagnostic capabilities: fault detection of all critical electronic and electro/mechanical sections is implemented by dedicated analog circuits. It is suitable for fully-electrical and hybrid electro-hydraulic actuators. Extensive thermal characterization has confirmed the fulfillment of specifications over the whole -40 C° ÷ +70 C° operating range.
Marco Carminati
Matteo Rubagotti
Riccardo Grassetti
Giorgio Ferrari
Marco Sampietro
2012-02-27T10:32:54Z
2012-02-27T10:32:54Z
http://eprints.imtlucca.it/id/eprint/1190
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1190
2012-02-27T10:32:54Z
Networks in cell biology
The science of complex biological networks is transforming research in areas ranging from evolutionary biology to medicine. This is the first book on the subject, providing a comprehensive introduction to complex network science and its biological applications. With contributions from key leaders in both network theory and modern cell biology, this book discusses the network science that is increasingly foundational for systems biology and the quantitative understanding of living systems. It surveys studies in the quantitative structure and dynamics of genetic regulatory networks, molecular networks underlying cellular metabolism, and other fundamental biological processes. The book balances empirical studies and theory to give a unified overview of this interdisciplinary science. It is a key introductory text for graduate students and researchers in physics, biology and biochemistry, and presents ideas and techniques from fields outside the reader's own area of specialization.
Mark Buchanan
Guido Caldarelli
guido.caldarelli@imtlucca.it
Paolo De Los Rios
Francesco Rao
Michele Vendruscolo
2012-01-26T10:23:28Z
2012-01-26T10:23:28Z
http://eprints.imtlucca.it/id/eprint/1082
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1082
2012-01-26T10:23:28Z
A Networked World
Just over a decade ago, in June 1998, a curious three-page paper appeared in Nature. In it, the authors - two applied mathematicians - reported a link between the structure of the US electrical grid and the wiring of a nematode worm's neural system. They also noted that these patterns were strikingly similar in their structure to the social networks of Hollywood actors, one of the few such networks for which the authors could find extensive data. It is hard to imagine a more bizarre melding of topics in one study.
Mark Buchanan
Guido Caldarelli
guido.caldarelli@imtlucca.it
2012-01-26T10:01:25Z
2012-01-26T10:55:18Z
http://eprints.imtlucca.it/id/eprint/1081
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1081
2012-01-26T10:01:25Z
A PageRank-based preferential attachment model for the evolution of the World Wide Web
We propose a model of network growth aimed at mimicking the evolution of the World Wide Web. To this purpose, we take as a key quantity, in the network evolution, the centrality or importance of a vertex as measured by its PageRank. Using a preferential attachment rule and a rewiring procedure based on this quantity, we can reproduce most of the topological properties of the system.
P. Giammatteo
Debora Donato
Vinko Zlatic
Guido Caldarelli
guido.caldarelli@imtlucca.it
2012-01-26T09:16:41Z
2016-04-07T08:03:08Z
http://eprints.imtlucca.it/id/eprint/1080
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1080
2012-01-26T09:16:41Z
Topologically biased random walk and community finding in networks
We present an approach of topology biased random walks for undirected networks. We focus on a one-parameter family of biases, and by using a formal analogy with perturbation theory in quantum mechanics we investigate the features of biased random walks. This analogy is extended through the use of parametric equations of motion to study the features of random walks vs parameter values. Furthermore, we show an analysis of the spectral gap maximum associated with the value of the second eigenvalue of the transition matrix related to the relaxation rate to the stationary state. Applications of these studies allow ad hoc algorithms for the exploration of complex networks and their communities.
Vinko Zlatic
Andrea Gabrielli
Guido Caldarelli
guido.caldarelli@imtlucca.it
2012-01-19T13:11:43Z
2014-01-24T14:23:18Z
http://eprints.imtlucca.it/id/eprint/1069
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1069
2012-01-19T13:11:43Z
The structure and growth of international trade
The paper develops a model of proportionate growth to describe the dynamics of international trade flows. We show that a large number of the empirical regularities characterizing international trade -such as the fraction of zero trade flows across pairs of countries, the positive relationship between intensive and extensive margins, the high concentration of trade with respect to both products and destinations, the core-periphery structure of exchanges- are well explained by this simple stochastic setup. This helps us to distinguish among economically relevant regularities and those simply resulting from the mechanical interactions among agents. Furthermore, our model can be used to describe the process of `self-discovery' that lie at the foundations of suc- cessful export-led growth and is thought to play a crucial role in the process of economic development. Our model correctly predicts that large export flows are rare events, as pointed out in the empirical literature: yet, countries characterized by large `discovery' efforts are much more likely to draw a `big hit' due to the (very skewed) shape of the distribution of bilateral export flows.
Massimo Riccaboni
massimo.riccaboni@imtlucca.it
Stefano Schiavo
2012-01-18T13:19:30Z
2012-01-18T13:19:30Z
http://eprints.imtlucca.it/id/eprint/1063
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1063
2012-01-18T13:19:30Z
L'illusione del controllo nelle politiche pubbliche
It is quite common that public policies take as benchmark mean values of relevant policy variables (average firm size, average productivity, average income, etc.). In such case the policy maker introduces incentives that should change individual behaviour in order to increase average values of the policy relevant variables. When this kind of policies are unsuccessful it is thought that the incentives are badly designed so that the entire problem is considered a problem of "mechanism design". In this paper the Authors maintain that policy makers should always take into account that incentives have an impact not only on individual behaviour but also on the distribution and law of motion of the aggregate phenomena that may be different from the sum of micro behaviours. Three different cases of proportional growth phenomena (firm's size growth, income distribuition and research production) are analyzed, in the paper, through simulations. Some tentative general principles for public policies are identified.
Massimo Riccaboni
massimo.riccaboni@imtlucca.it
Sandro Trento
Enrico Zaninotto
2012-01-16T09:44:29Z
2013-11-21T11:39:24Z
http://eprints.imtlucca.it/id/eprint/266
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/266
2012-01-16T09:44:29Z
Bankruptcy risk model and empirical tests
We analyze the size dependence and temporal stability of firm bankruptcy risk in the US economy by applying Zipf scaling techniques. We focus on a single risk factor—the debt-to-asset ratio R—in order to study the stability of the Zipf distribution of R over time. We find that the Zipf exponent increases during market crashes, implying that firms go bankrupt with larger values of R. Based on the Zipf analysis, we employ Bayes’s theorem and relate the conditional probability that a bankrupt firm has a ratio R with the conditional probability of bankruptcy for a firm with a given R value. For 2,737 bankrupt firms, we demonstrate size dependence in assets change during the bankruptcy proceedings. Prepetition firm assets and petition firm assets follow Zipf distributions but with different exponents, meaning that firms with smaller assets adjust their assets more than firms with larger assets during the bankruptcy process. We compare bankrupt firms with nonbankrupt firms by analyzing the assets and liabilities of two large subsets of the US economy: 2,545 Nasdaq members and 1,680 New York Stock Exchange (NYSE) members. We find that both assets and liabilities follow a Pareto distribution. The finding is not a trivial consequence of the Zipf scaling relationship of firm size quantified by employees—although the market capitalization of Nasdaq stocks follows a Pareto distribution, the same distribution does not describe NYSE stocks. We propose a coupled Simon model that simultaneously evolves both assets and debt with the possibility of bankruptcy, and we also consider the possibility of firm mergers.
Boris Podobnik
Davor Horvatic
Alexander M. Petersen
alexander.petersen@imtlucca.it
Branko Urošević
H. Eugene Stanley
2011-12-05T10:30:11Z
2011-12-05T10:30:11Z
http://eprints.imtlucca.it/id/eprint/1024
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1024
2011-12-05T10:30:11Z
Variable selection in nonlinear modeling based on RBF networks and evolutionary computation
In this paper a novel variable selection method based on Radial Basis Function (RBF) neural networks and genetic algorithms is presented. The fuzzy means algorithm is utilized as the training method for the RBF networks, due to its inherent speed, the deterministic approach of selecting the hidden node centers and the fact that it involves only a single tuning parameter. The trade-off between the accuracy and parsimony of the produced model is handled by using Final Prediction Error criterion, based on the RBF training and validation errors, as a fitness function of the proposed genetic algorithm. The tuning parameter required by the fuzzy means algorithm is treated as a free variable by the genetic algorithm. The proposed method was tested in benchmark data sets stemming from the scientific communities of time-series prediction and medicinal chemistry and produced promising results.
Panagiotis Patrinos
panagiotis.patrinos@imtlucca.it
Alex Alexandridis
Konstantinos Ninos
Haralambos Sarimveis
2011-12-05T10:20:42Z
2011-12-05T10:20:42Z
http://eprints.imtlucca.it/id/eprint/1023
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1023
2011-12-05T10:20:42Z
A new algorithm for solving convex parametric quadratic programs based on graphical derivatives of solution mappings
In this paper we derive formulas for computing graphical derivatives of the (possibly multivalued) solution mapping for convex parametric quadratic programs. Parametric programming has recently received much attention in the control community, however most algorithms are based on the restrictive assumption that the so called critical regions of the solution form a polyhedral subdivision, i.e. the intersection of two critical regions is either empty or a face of both regions. Based on the theoretical results of this paper, we relax this assumption and show how we can efficiently compute all adjacent full dimensional critical regions along a facet of an already discovered critical region. Coupling the proposed approach with the graph traversal paradigm, we obtain very efficient algorithms for the solution of parametric convex quadratic programs
Panagiotis Patrinos
panagiotis.patrinos@imtlucca.it
Haralambos Sarimveis
2011-10-31T12:04:05Z
2011-11-03T13:19:36Z
http://eprints.imtlucca.it/id/eprint/978
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/978
2011-10-31T12:04:05Z
Central limit theorems for multicolor urns with dominated colors
An urn contains balls of d≥2 colors. At each time n≥1, a ball is drawn and then replaced together with a random number of balls of the same color. Let A n = diag (An,1,…,An,d) be the n-th reinforce matrix. Assuming that EAn,j=EAn,1 for all n and j, a few central limit theorems (CLTs) are available for such urns. In real problems, however, it is more reasonable to assume that EA n,j = EA n,1 whenever n ≥ 1 and 1 ≤ j ≤ d0 , liminfn EAn,1 > limsupn EAn,j whenever j > d0 for some integer 1≤d0≤d. Under this condition, the usual weak limit theorems may fail, but it is still possible to prove the CLTs for some slightly different random quantities. These random quantities are obtained by neglecting dominated colors, i.e., colors from d0+1 to d, and they allow the same inference on the urn structure. The sequence (An : n ≥ 1) is independent but need not be identically distributed. Some statistical applications are given as well.
Patrizia Berti
Irene Crimaldi
irene.crimaldi@imtlucca.it
Luca Pratelli
Pietro Rigo
2011-10-31T11:30:01Z
2011-11-03T13:19:36Z
http://eprints.imtlucca.it/id/eprint/976
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/976
2011-10-31T11:30:01Z
Conditionally identically distributed species sampling sequences
In this paper the theory of species sampling sequences is linked to the theory of conditionally identically distributed sequences in order to enlarge the set of species sampling sequences which are mathematically tractable. The conditional identity in distribution (see Berti, Pratelli and Rigo (2004)) is a new type of dependence for random variables, which generalizes the well-known notion of exchangeability. In this paper a class of random sequences, called generalized species sampling sequences, is defined and a condition to have conditional identity in distribution is given. Moreover, two types of generalized species sampling sequence that are conditionally identically distributed are introduced and studied: the generalized Poisson-Dirichlet sequence and the generalized Ottawa sequence. Some examples are discussed.
Federico Bassetti
Irene Crimaldi
irene.crimaldi@imtlucca.it
Fabrizio Leisen
2011-10-18T13:24:08Z
2011-10-18T13:24:08Z
http://eprints.imtlucca.it/id/eprint/961
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/961
2011-10-18T13:24:08Z
Tra Longhi e Berenson: Ragghianti ‘conoscitore’
Emanuele Pellegrini
emanuele.pellegrini@imtlucca.it
2011-10-18T13:04:11Z
2011-10-18T13:04:11Z
http://eprints.imtlucca.it/id/eprint/958
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/958
2011-10-18T13:04:11Z
La fine della prima serie de «La Critica d’Arte» : Bianchi Bandinelli, Longhi, Ragghianti
Emanuele Pellegrini
emanuele.pellegrini@imtlucca.it
2011-10-12T13:37:04Z
2011-10-12T13:37:04Z
http://eprints.imtlucca.it/id/eprint/926
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/926
2011-10-12T13:37:04Z
Pollaiolo e il berretto degli alpini: cronaca di cent’anni di solitudine
Emanuele Pellegrini
emanuele.pellegrini@imtlucca.it
2011-10-12T13:27:43Z
2011-10-13T13:05:10Z
http://eprints.imtlucca.it/id/eprint/925
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/925
2011-10-12T13:27:43Z
(a cura di) Carlo Ludovico Ragghianti : il valore del patrimonio culturale : scritti dal 1935 al 1987
L'impegno di Carlo Ludovico Ragghianti per la salvaguardia, la promozione e per un'adeguata gestione del patrimonio culturale fu costante e generoso snodandosi con continuità e pervicacia dagli anni giovanili fino alla morte nell'agosto del 1987. Gli scritti di Ragghianti qui dentro riportati hanno l'obiettivo di presentare un materiale che tratta di problemi assolutamente attuali: dalla carenza dei finanziamenti alla difficoltà nel far rispettare le disposizioni legislative; passando per la farraginosità legislativa che spesso rallenta o impedisce il funzionamento della macchina della tutela
Monica Naldi
Emanuele Pellegrini
emanuele.pellegrini@imtlucca.it
2011-10-12T13:20:49Z
2011-10-12T13:20:49Z
http://eprints.imtlucca.it/id/eprint/924
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/924
2011-10-12T13:20:49Z
(a cura di) Descrivere Lucca : indici delle fonti manoscritte e a stampa
Questo album di indici costituisce un'appendice al volume Descrivere Lucca. Non contiene però soltanto l'indicizzazione dei nomi dei manoscritti pubblicati in quel libro, bensì li integra con l'indice di una serie di altre guide storiche che compongono il ricco panorama della periegetica lucchese tra Settecento e Ottocento. Il Forestiere informato di Vincenzo Marchiò del 1721, il Diario sacro di Gabriele Grammatica nelle versioni del 1734 e del 1741 - e quindi quella accresciuta da Giovan Domenico Mansi del 1753 -, la Guida di Tommaso Trenta del 1820, poi ampliata e rivista da Antonio Mazzarosa nel 1829, il Diario sacro di Domenico Barsocchini del 1836 e, infine, la Guida dello stesso Mazzarosa del 1843 sono state incluse nell'indicizzazione.
In un unico prospetto è quindi possibile trovare non solo l'indicizzazione completa dei nomi degli artisti presenti in tutte queste guide a stampa, in origine senza indici, ma anche effettuare una collazione con quelle manoscritte. In un'unica tabella le une sono affiancate alle altre secondo l'ordine cronologico di scrittura o pubblicazione. Seguendo il criterio base del nome dell'artista, per ciascuna fonte sono stati indicati pagina, carta, luogo di collocazione dell'opera e altre brevi note esplicative. Un vero e proprio strumento di lavoro che intende facilitare ulteriori ricerche documentarie e favorire al contempo le indagini sul patrimonio artistico lucchese, specialmente per quelle opere oggi disperse o ancora non identificate.
Maria Francesca Pozzi
Chiara Del Prete
Emanuele Pellegrini
emanuele.pellegrini@imtlucca.it
2011-09-22T13:32:37Z
2014-01-24T14:23:59Z
http://eprints.imtlucca.it/id/eprint/900
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/900
2011-09-22T13:32:37Z
Short-term contracts in Italy: who is the winner?
Short-term contracts have been used extensively in the Italian labor market in the last ten years. This article analyzes a new Italian panel data set, WHIP, and the Bank of Italy labor force survey, SHIW, to understand the effects of the introduction of this new typology of contracts. The goal of this paper is to investigate whether the objectives of the reforms have been accomplished and to identify the winners (the people benefiting the most) and the losers (the ones who are carrying the consequences of a less protected labor market) of this pivotal reform
Cristina Tealdi
cristina.tealdi@imtlucca.it
2011-09-22T13:32:33Z
2014-01-24T14:23:35Z
http://eprints.imtlucca.it/id/eprint/901
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/901
2011-09-22T13:32:33Z
Regulatory framework regarding short-term contracts in Italy
Cristina Tealdi
cristina.tealdi@imtlucca.it
2011-09-13T14:43:04Z
2014-12-02T09:51:39Z
http://eprints.imtlucca.it/id/eprint/872
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/872
2011-09-13T14:43:04Z
Symposium
Maria Luisa Catoni
marialuisa.catoni@imtlucca.it
2011-09-13T14:31:06Z
2014-12-02T09:54:38Z
http://eprints.imtlucca.it/id/eprint/871
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/871
2011-09-13T14:31:06Z
Immagini, parole e canto nell'Atene del VI secolo a.C.: la voce di chi?
Maria Luisa Catoni
marialuisa.catoni@imtlucca.it
2011-09-13T10:35:43Z
2014-12-02T09:55:45Z
http://eprints.imtlucca.it/id/eprint/864
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/864
2011-09-13T10:35:43Z
Bere vino puro : immagini del simposio
"In vino veritas": così il lirico Alceo cantava durante una "bevuta insieme" che si svolgeva sull'isola di Lesbo, nel VII secolo avanti Cristo. Questo motto, ancor oggi così popolare, condensa un principio fondamentale del simposio greco: attraverso l'assunzione del pharmakon, cioè del vino che è insieme veleno e medicinale svela la vera natura di un uomo. Ma il simposio non è un'allegra bevuta senza regole: il bere vi è ritualizzato, il grado di ubriachezza che tutti devono raggiungere viene deciso in anticipo, i partecipanti fissano regole per poi sperimentarne la violazione e i modi della violazione. Il simposio è in questo senso un'istituzione politica, religiosa e sociale, attraverso cui i gruppi aristocratici sperimentano, in un luogo protetto, le regole e i comportamenti da tenere nel più ampio contesto della città. Al suo interno si canta e si definisce l'opposizione tra amici e nemici, fra inclusi ed esclusi, fra valenti e uomini dappoco. Al suo interno si godono le gioie dell'eros, si ostenta la propria cultura, si esibisce il privilegio dell'otium, si stringono alleanze. Questo libro guarda alla concretezza della pratica del simposio e rilegge il rapporto tra i canti dei simposiasti e i vasi dipinti in cui bevevano.
Maria Luisa Catoni
marialuisa.catoni@imtlucca.it
2011-09-08T13:30:49Z
2013-03-05T15:33:17Z
http://eprints.imtlucca.it/id/eprint/849
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/849
2011-09-08T13:30:49Z
Tracking-optimal pre- and post-processing for H.264 compression in traffic video surveillance applications
The compression of video can reduce the accuracy of automated tracking algorithms. This is problematic for centralized applications such as transportation surveillance systems, where remotely captured and compressed video is transmitted to a central location for tracking. In typical systems, the majority of communications bandwidth is spent on representing events such as capture noise or local changes to lighting. We propose a pre- and post-processing algorithm that identifies and removes such events of low tracking interest, significantly reducing the bitrate required to transmit remotely captured video while maintaining comparable tracking accuracy. Using the H.264/AVC video coding standard and a commonly used state-of-the-art tracker we show that our algorithm allows for up to 90 bitrate savings while maintaining comparable tracking accuracy.
Eren Soyak
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Aggelos K. Katsaggelos
2011-09-08T13:25:13Z
2013-03-05T15:33:33Z
http://eprints.imtlucca.it/id/eprint/848
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/848
2011-09-08T13:25:13Z
Video anomaly detection in spatiotemporal context
Compared to other approaches that analyze object trajectories, we propose to detect anomalous video events at three levels considering spatiotemporal context of video objects, i.e., point anomaly, sequential anomaly, and co-occurrence anomaly. A hierarchical data mining approach is proposed to achieve this task. At each level, the frequency based analysis is performed to automatically discover regular rules of normal events. The events deviating from these rules are detected as anomalies. Experiments on real traffic video prove that the detected video anomalies are hazardous or illegal according to the traffic rule.
Fan Jiang
Junsong Yuanc
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Aggelos K. Katsaggelos
2011-09-08T13:20:48Z
2013-03-05T15:33:50Z
http://eprints.imtlucca.it/id/eprint/847
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/847
2011-09-08T13:20:48Z
Quantization optimized H.264 encoding for traffic video tracking applications
The compression of video can reduce the accuracy of post-compression tracking algorithms. This is problematic for centralized applications such as traffic surveillance systems, where remotely captured and compressed video is transmitted to a central location for tracking. We propose a low complexity optimization framework that automatically identifies video features critical to tracking and concentrates bitrate on these features via quantization tables. Using the H.264 video coding standard and two commonly used state-of-the-art trackers we show that our algorithm allows for over 60 bitrate savings while maintaining comparable tracking accuracy.
Eren Soyak
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Aggelos K. Katsaggelos
2011-09-08T12:42:01Z
2013-03-05T15:39:18Z
http://eprints.imtlucca.it/id/eprint/845
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/845
2011-09-08T12:42:01Z
A new quantitative imaging biomarker for identifying critical coronary artery stenosis with myocardial BOLD MRI
Blood-oxygen-level dependent (BOLD) MRI may be used for detecting myocardial oxygenation changes secondary to coronary artery stenosis (CAS). Under pharmacological stress, areas of the myocardium supplied by a stenotic coronary artery appear hypointense relative to healthy regions in BOLD images. The purpose of this work is to present a fundamentally new approach for visualizing and quantifying regional myocardial BOLD signal changes. This approach, tested in canines, relies on the statistical identification of myocardial pixels affected by CAS, correlates strongly with true flow measurements, and most importantly, leads to a significant increase in sensitivity to microvascular flow changes compared to previous approaches.
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Xiangzhi Zhou
Debiao Li
Rohan Dharmakumar
2011-09-08T12:36:10Z
2013-03-05T15:39:03Z
http://eprints.imtlucca.it/id/eprint/844
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/844
2011-09-08T12:36:10Z
Automated assessment of ghost artifacts in MRI
Flow artifacts in MR images can appear as image ghosts within and outside the body cavity. Technical improvements aimed at suppressing these image ghosts often rely on expert scoring (1,2) or on semi-automated methods demanding tissue segmentation and estimation of statistical properties of intensity distribution (3) to evaluate the efficacy of the methods. These approaches can be labor intensive, introduce observer bias, computationally demanding, and error-prone if tissue segmentation is used. Herein we propose two fully automated image-processing methods that rely on the statistical properties of background (noise) pixels to assess the presence of flow artifacts (appearing as image ghosts) without requiring tissue segmentation. The first method rapidly evaluates the presence of flow artifacts in a global fashion, while the second one provides a more detailed characterization
of the artifacts. We evaluate the proposed methods in the setting of cardiac phase-resolved myocardial blood-oxygen-level-dependent (BOLD) MRI where different cine SSFP imaging strategies are proposed for overcoming flow artifacts. Finally we assess the utility of our automated approaches against expert scoring results.
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Xiangzhi Zhou
Rohan Dharmakumar
2011-09-08T12:09:36Z
2013-03-05T15:38:47Z
http://eprints.imtlucca.it/id/eprint/843
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/843
2011-09-08T12:09:36Z
Unsupervised reconstruction for ungated ghost angiography by clustering of image features
Ghost magnetic resonance angiography (MRA) has been proposed as an unenhanced and ungated method for angiography that is based on the presence of ghost artifacts resulting from pulsatile blood flow (1). Although the method is simple to acquire in that cardiac gating is not required, it requires manual post-processing to identify suitable slices in a large stack from which to create an interpretable angiogram. To maximize the contrast of the final angiogram it is necessary to eliminate slices located within the body and to carefully select the slices that contain conspicuous ghost artifacts. This manual post-processing step is time-consuming and can introduce unwanted inter- and intra- observer variability. The purpose of this work was to completely automate the reconstruction process during ungated and non-contrast-enhanced Ghost MRA using image analysis and clustering.
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Erik Offerman
Robert R. Edelman
Ioannis Koktzoglou
2011-09-08T11:59:34Z
2013-03-05T15:39:32Z
http://eprints.imtlucca.it/id/eprint/842
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/842
2011-09-08T11:59:34Z
Automated synchronization of cardiac phases for myocardial BOLD MRI
It is particularly important for the evaluation of cardiac phase-resolved myocardial blood-oxygen-level-dependent (BOLD) MRI studies, to robustly and reproducibly synchronize images from rest and stress studies. The possibility of visualizing BOLD signal changes in multiple cardiac phases is expected to increase the diagnostic confidence for identifying the affected myocardial territories. The purpose of this work is to develop automated statistical methods to facilitate in the robust and reproducible evaluation of cardiac phase-resolved myocardial BOLD MRI through temporal synchronization of rest and stress images acquired at different heart rates, without resorting to LV segmentation.
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Xiangzhi Zhou
Richard Tang
Rachel Klein
Aggelos K. Katsaggelos
Rohan Dharmakumar
2011-09-07T15:02:38Z
2013-03-05T15:40:24Z
http://eprints.imtlucca.it/id/eprint/839
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/839
2011-09-07T15:02:38Z
Myocardial BOLD imaging using flow compensated 2D cine bSSFP
Robust image quality is critical for reliable detection and evaluation of myocardial oxygenation changes with blood-oxygen-level-dependent (BOLD) imaging. Recently, balanced Steady-State Free Precession (bSSFP) methods have been employed to overcome image quality limitations associated
with myocardial BOLD methods. However, the long TRs required for optimal BOLD contrast can lead to unwanted flow/motion artifacts, ultimately compromising image quality. In this work we evaluate the utility of 2D first-order motion compensation scheme to minimize flow/motion artifacts in cardiac phase-resolved bSSFP BOLD imaging.
Xiangzhi Zhou
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Ying Liu
Richard Tang
Rachel Klein
Sven Zuehlsdorff
Debiao Li
Rohan Dharmakumar
2011-09-07T14:58:10Z
2013-03-05T15:39:59Z
http://eprints.imtlucca.it/id/eprint/838
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/838
2011-09-07T14:58:10Z
On the origin of myocardial edema contrast in T2-STIR images
Acute myocardial infarcts (AMI) are typically discriminated with T2-weighted short TI inversion recovery (STIR) with turbo spin echo (TSE) readouts [1], albeit with limited specificity [2]. Guided by the association that T2-STIR images identify AMI territories on the basis of edema-related T2 changes, even some of the recently proposed improvements [2,3] have relied on preferential sensitization of magnetization to T2- weighting. However, whether T2-STIR imaging itself may also be sensitive to other sources of image contrast have not been fully investigated. We hypothesize that in addition to T2-weighting, edema detection with T2-STIR imaging has substantial weighting from proton density (PD) changes.
Xiangzhi Zhou
Veronica Rundell
Ying Liu
Richard Tang
Rachel Klein
Shivraman Giri
Saurabh Shah
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Sven Zuehlsdorff
Orlando Simonetti
Debiao Li
Rohan Dharmakumar
2011-09-07T14:48:43Z
2013-03-05T15:39:46Z
http://eprints.imtlucca.it/id/eprint/837
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/837
2011-09-07T14:48:43Z
On the mechanism of myocardial edema contrast in T2-STIR images
Acute myocardial infarcts (AMI) are typically discriminated with T2-STIR imaging [1], albeit with limited specificity [2]. Guided by the association that T2-STIR images identify AMI territories on the basis of edema-related T2 changes, even some of the recently proposed improvements [2,3] have relied on preferential sensitization of magnetization to T2-weighting. However, whether T2-STIR imaging itself may also be sensitive to other sources of contrast have not been fully investigated.
Xiangzhi Zhou
Veronica Rundell
Ying Liu
Richard Tang
Shivraman Giri
Saurabh Shah
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Sven Zuehlsdorff
Orlando Simonetti
Debiao Li
Rohan Dharmakumar
2011-09-07T14:23:16Z
2013-03-05T15:40:11Z
http://eprints.imtlucca.it/id/eprint/835
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/835
2011-09-07T14:23:16Z
Artifacts-reduced 2D cine SSFP with flow compensation for myocardial BOLD imaging
Robust image quality is critical for reliable detection and evaluation of myocardial oxygenation changes with blood-oxygen-level-dependent (BOLD) imaging. Recently, balanced SSFP methods have been employed to overcome image quality limitations associated with myocardial BOLD methods. However, the long TRs required for BOLD contrast, can lead to unwanted flow/motion artifacts, ultimately compromising image quality.
Xiangzhi Zhou
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Ying Liu
Richard Tang
Rachel Klein
Sven Zuehlsdorff
Debiao Li
Rohan Dharmakumar
2011-09-07T14:17:53Z
2013-03-05T15:34:20Z
http://eprints.imtlucca.it/id/eprint/833
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/833
2011-09-07T14:17:53Z
Content-aware H.264 encoding for traffic video tracking applications
The compression of video can reduce the accuracy of tracking algorithms, which is problematic for centralized applications that rely on remotely captured and compressed video for input. We show the effects of high compression on the features commonly used in real-time video object tracking. We propose a computationally efficient Region of Interest (ROI) extraction method, which is used during standard-compliant H.264 encoding to concentrate bitrate on regions in video most likely to contain objects of tracking interest (vehicles). This algorithm is shown to significantly increase tracking accuracy, which is measured by employing a commonly used automatic tracker.
Eren Soyak
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Aggelos K. Katsaggelos
2011-08-12T09:37:36Z
2013-03-05T15:34:33Z
http://eprints.imtlucca.it/id/eprint/798
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/798
2011-08-12T09:37:36Z
Fully automated reconstruction of ungated ghost magnetic resonance angiograms
To completely automate the reconstruction process during noncardiac-gated unenhanced ghost magnetic resonance angiography (MRA).Ungated unenhanced ghost MRA of the calf was performed in 16 volunteers. K-means and fuzzy c-means (FCM) clustering algorithms using prominent image features were applied to automatically create angiograms of the calf in volunteers undergoing ungated ghost MRA. Ghost angiograms reconstructed automatically were compared to those created manually on the basis of diagnostic image quality and apparent arterial-to-background contrast-to-noise ratio (CNR). Images were also ranked by an expert user in their order of preference using an ordinal scale.Compared with the ghost angiograms created manually, ghost angiograms reconstructed automatically with the use of clustering analysis provided similar arterial-to-background CNR values. No differences in diagnostic quality or preference were identified between images reconstructed manually and automatically.We present fully automated image reconstruction algorithms for use with ungated and unenhanced ghost MRA. These automated algorithms, based on the use of k-means or FCM clustering, can be used to eliminate manual postprocessing that is time-consuming and subject to variability.
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Erik Offerman
Robert R. Edelman
Ioannis Koktzoglou
2011-08-11T11:04:04Z
2013-03-05T15:34:05Z
http://eprints.imtlucca.it/id/eprint/799
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/799
2011-08-11T11:04:04Z
Artifact-reduced two-dimensional cine steady state free precession for myocardial blood- oxygen-level-dependent imaging
To minimize image artifacts in long TR cardiac phase-resolved steady state free precession (SSFP) based blood-oxygen-level-dependent (BOLD) imaging.Nine healthy dogs (four male, five female, 20-25 kg) were studied in a clinical 1.5 Tesla MRI scanner to investigate the effect of temporal resolution, readout bandwidth, and motion compensation on long repetition time (TR) SSFP images. Breath-held 2D SSFP cine sequences with various temporal resolutions (10-204 ms), bandwidths (239-930 Hz/pixel), with and without first-order motion compensation were prescribed in the basal, mid-ventricular, and apical along the short axis. Preliminary myocardial BOLD studies in dogs with controllable coronary stenosis were performed to assess the benefits of artifact-reduction strategies.Shortening the readout time by means of increasing readout bandwidth had no observable reduction in image artifacts. However, increasing the temporal resolution in the presence of first-order motion compensation led to significant reduction in image artifacts. Preliminary studies demonstrated that BOLD signal changes can be reliably detected throughout the cardiac cycle.Artifact-reduction methods used in this study provide significant improvement in image quality compared with conventional long TR SSFP BOLD MRI. It is envisioned that the methods proposed here may enable reliable detection of myocardial oxygenation changes throughout the cardiac cycle with long TR SSFP-based myocardial BOLD MRI.
Xiangzhi Zhou
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Ying Liu
Richard Tang
Rachel Klein
Sven Zuehlsdorff
Debiao Li
Rohan Dharmakumar
2011-08-10T13:16:39Z
2013-03-05T15:38:32Z
http://eprints.imtlucca.it/id/eprint/787
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/787
2011-08-10T13:16:39Z
Contribution to "Matisse: radical invention, 1913 - 1917"
Sotirios A. Tsaftaris
sotirios.tsaftaris@imtlucca.it
Aggelos K. Katsaggelos
2011-08-08T13:55:08Z
2011-09-27T13:12:23Z
http://eprints.imtlucca.it/id/eprint/771
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/771
2011-08-08T13:55:08Z
A theory of military dictatorships
We investigate how nondemocratic regimes use the military and how this can lead to the emergence of military dictatorships. The elite may build a strong military and make the concessions necessary for the military to behave as their perfect agent, or they may risk the military turning against them. Once the transition to democracy takes place, a strong military poses a threat against the nascent democratic regime until it is reformed. We study the role of income inequality and natural resources in the emergence of military dictatorships and show how the national defense role of the military may facilitate democratic consolidation
Daron Acemoglu
Davide Ticchi
davide.ticchi@imtlucca.it
Andrea Vindigni
andrea.vindigni@imtlucca.it
2011-08-08T13:32:27Z
2011-09-27T13:12:23Z
http://eprints.imtlucca.it/id/eprint/770
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/770
2011-08-08T13:32:27Z
Endogenous constitutions
We present a theory of the choice of alternative democratic constitutions, a majoritarian or a consensual one, in an unequal society. A majoritarian democracy redistributes resources from the collectivity toward relatively few people, and has a relatively small government and low level of taxation. A consensual democracy redistributes resources toward a broader spectrum of social groups but also has a larger government and a higher level of taxation. We show that a consensual system turns out to be preferred by society when ex ante income inequality is relatively low, while a majoritarian system is chosen when income inequality is relatively high. We also obtain that consensual democracies should be expected to be ruled more often by center-left coalitions while the right should have an advantage in majoritarian constitutions. The implications for the relationship between inequality and redistribution are discussed. Historical evidence and a cross-sectional analysis support our results.
Davide Ticchi
davide.ticchi@imtlucca.it
Andrea Vindigni
andrea.vindigni@imtlucca.it
2011-08-08T13:04:15Z
2011-09-27T13:12:23Z
http://eprints.imtlucca.it/id/eprint/769
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/769
2011-08-08T13:04:15Z
Persistence of civil wars
A notable feature of post-World War II civil wars is their very long average duration. We provide a theory of the persistence of civil wars. The civilian government can successfully defeat rebellious factions only by creating a relatively strong army. In weakly-institutionalized polities this opens the way for excessive influence or coups by the military. Civilian governments whose rents are largely unaffected by civil wars then choose small and weak armies that are incapable of ending insurrections. Our framework also shows that when civilian governments need to take more decisive action against rebels, they may be forced to build over-sized armies, beyond the size necessary for fighting the insurrection, as a commitment to not reforming the military in the future.
Daron Acemoglu
Andrea Vindigni
andrea.vindigni@imtlucca.it
Davide Ticchi
davide.ticchi@imtlucca.it
2011-08-01T13:34:28Z
2011-08-08T08:38:45Z
http://eprints.imtlucca.it/id/eprint/755
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/755
2011-08-01T13:34:28Z
A rollout algorithmic approach for complex parallel machine scheduling in healthcare operations
Michele Ciavotta
Gabriella Dellino
gabriella.dellino@imtlucca.it
Carlo Meloni
Marco Pranzo
2011-08-01T12:52:38Z
2011-08-04T07:30:21Z
http://eprints.imtlucca.it/id/eprint/753
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/753
2011-08-01T12:52:38Z
Parametric and distribution-free bootstrapping in robust simulation-optimization
Most methods in simulation-optimization assume known environments, whereas this research accounts for uncertain environments combining Taguchi's world view with either regression or Kriging (also called Gaussian Process) metamodels (emulators, response surfaces, surrogates). These metamodels are combined with Non-Linear Mathematical Programming (NLMP) to find robust solutions. Varying the constraint values in this NLMP gives an estimated Pareto frontier. To account for the variability of this estimated Pareto frontier, this contribution considers different bootstrap methods to obtain confidence regions for a given solution. This methodology is illustrated through some case studies selected from the literature.
Gabriella Dellino
gabriella.dellino@imtlucca.it
Jack P.C. Kleijnen
Carlo Meloni
2011-08-01T10:23:29Z
2011-08-04T07:30:21Z
http://eprints.imtlucca.it/id/eprint/746
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/746
2011-08-01T10:23:29Z
Robust optimization in simulation: Taguchi and response surface methodology
Optimization of simulated systems is tackled by many methods, but most methods assume known environments. This article, however, develops a `robust' methodology for uncertain environments. This methodology uses Taguchi's view of the uncertain world, but replaces his statistical techniques by Response Surface Methodology (RSM). George Box originated RSM, and Douglas Montgomery recently extended RSM to robust optimization of real (non-simulated) systems. We combine Taguchi's view with RSM for simulated systems. We illustrate the resulting methodology through classic Economic Order Quantity (EOQ) inventory models, which demonstrate that robust optimization may require order quantities that differ from the classic EOQ.
Gabriella Dellino
gabriella.dellino@imtlucca.it
Jack P.C. Kleijnen
Carlo Meloni
2011-07-29T10:52:50Z
2011-08-04T07:29:05Z
http://eprints.imtlucca.it/id/eprint/739
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/739
2011-07-29T10:52:50Z
Scenario-based stochastic model predictive control for dynamic option hedging
For a rather broad class of financial options, this paper proposes a stochastic model predictive control (SMPC) approach for dynamically hedging a portfolio of underlying assets. By employing an option pricing engine to estimate future realizations of option prices on a finite set of one-step-ahead scenarios, the resulting stochastic optimization problem is easily solved as a least-squares problem at each trading date with as many variables as the number of traded assets and as many constraints as the number of predicted scenarios. After formulating the dynamic hedging problem as a stochastic control problem, we test its ability to replicate the payoff at expiration date for plain vanilla and exotic options. We show not only that relatively small hedging errors are obtained in spite of price realizations, but also that the approach is robust with respect to market modeling errors.
Alberto Bemporad
alberto.bemporad@imtlucca.it
Tommaso Gabbriellini
Laura Puglia
Leonardo Bellucci
2011-07-29T10:52:40Z
2011-11-17T11:01:57Z
http://eprints.imtlucca.it/id/eprint/738
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/738
2011-07-29T10:52:40Z
Stochastic model predictive control with driver behavior learning for improved powertrain control
In this paper we advocate the use of stochastic model predictive control (SMPC) for improving the performance of powertrain control algorithms, by optimally controlling the complex system composed of driver and vehicle. While the powertrain is modeled as the deterministic component of the dynamics, the driver behavior is represented as a
stochastic system which affects the vehicle dynamics. Since stochastic MPC is based on online numerical optimization, the driver model can be learned online, hence allowing the control algorithm to adapt to different drivers and drivers' behaviors. The proposed technique is evaluated in two applications: adaptive cruise control, where the driver behavioral model is used to predict the leading vehicle dynamics, and series hybrid electric vehicle (SHEV) energy management, where the driver model is used to predict the future power requests.
M. Bichi
Giulio Ripaccioli
Stefano Di Cairano
Daniele Bernardini
daniele.bernardini@imtlucca.it
Alberto Bemporad
alberto.bemporad@imtlucca.it
Ilya Kolmanovsky
2011-07-29T10:52:30Z
2011-08-05T12:20:39Z
http://eprints.imtlucca.it/id/eprint/736
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/736
2011-07-29T10:52:30Z
Hierarchical multi-rate control design for constrained linear systems
This paper proposes a hierarchical multi-rate control design approach to linear systems subject to linear constraints on input and output variables. At the lower level, a linear controller stabilizes the open-loop process without considering the constraints. A higher-level controller commands reference signals at a lower sampling frequency so as to enforce linear constraints on the variables of the process. By optimally constraining the magnitude and the rate of variation of the reference signals applied to the lower control layer, we provide quantitative criteria for selecting the ratio between the sampling rates of the upper and lower layers to preserve closed-loop stability without violating the prescribed constraints.
Davide Barcelli
Alberto Bemporad
alberto.bemporad@imtlucca.it
Giulio Ripaccioli
2011-07-29T10:49:00Z
2011-08-04T07:29:05Z
http://eprints.imtlucca.it/id/eprint/737
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/737
2011-07-29T10:49:00Z
Synthesis of stabilizing model predictive controllers via canonical piecewise affine approximations
This paper proposes the use of canonical piecewise affine (PWA) functions for the approximation of linear MPC controllers over a regular simplicial partition of a given set of states of interest. Analysis tools based on the construction of PWA Lyapunov functions are provided for certifying the asymptotic stability of the resulting closed-loop system. The main advantage of the proposed controller synthesis approach is that the resulting stabilizing approximate MPC controller can be implemented on chip with sampling times in the order of tens of nanoseconds.
Alberto Bemporad
alberto.bemporad@imtlucca.it
Alberto Oliveri
Tomaso Poggi
Marco Storace
2011-07-29T10:18:42Z
2011-11-17T11:05:36Z
http://eprints.imtlucca.it/id/eprint/735
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/735
2011-07-29T10:18:42Z
Synthesis of networked switching linear decentralized controllers
This paper proposes an approach based on linear matrix inequalities for synthesizing a set of decentralized regulators for discrete-time linear systems subject to input and state constraints. Measurements and command signals are exchanged over a sensor/actuator network, in which some links are subject to packet dropout. The resulting closed-loop system is guaranteed to asymptotically reach the origin, even if every local actuator can exploit only a (possibly time-varying) subset of state measurements. A model of packet dropout based on a finite-state Markov chain is also considered to exploit available knowledge about the stochastic nature of the network. For such model, a set of decentralized switching linear controllers is synthesized that guarantees mean-square stability of the overall controlled process under packet dropout and soft input and state constraints.
Davide Barcelli
Daniele Bernardini
daniele.bernardini@imtlucca.it
Alberto Bemporad
alberto.bemporad@imtlucca.it
2011-07-29T10:18:25Z
2011-11-16T11:50:12Z
http://eprints.imtlucca.it/id/eprint/734
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/734
2011-07-29T10:18:25Z
A model predictive control approach for stochastic networked control systems
In this paper we present a stochastic model predictive control (SMPC) approach for networked control systems (NCSs) that are subject to time-varying sampling intervals and time-varying transmission delays. These network-induced uncertain parameters are assumed to be described by random processes, having a bounded support and an arbitrary continuous probability density function. Assuming that the controlled plant can be modeled as a linear system, we present a SMPC formulation based on scenario enumeration and quadratic programming that optimizes a stochastic performance index and provides closed-loop stability in the mean-square sense. Simulation results are shown to demonstrate the performance of the proposed approach.
Daniele Bernardini
daniele.bernardini@imtlucca.it
M.C.F. Donkers
Alberto Bemporad
alberto.bemporad@imtlucca.it
W.P.M.H. Heemels
2011-07-29T10:18:09Z
2011-08-05T12:30:43Z
http://eprints.imtlucca.it/id/eprint/733
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/733
2011-07-29T10:18:09Z
Decentralized model predictive control of drinking water networks using an automatic subsystem decomposition approach
This paper proposes an automatic model decomposition approach for decentralized model predictive control (DMPC) of drinking water networks (DWNs). For a given DWN, the proposed algorithm partitions the network in a set of subnetworks by taking advantage of the topology of the network, of the information about the use of actuators, and of system management heuristics. The derived suboptimal DMPC strategy results in a hierarchical solution with a set of MPC controllers used for each partition. A comparative study between centralized MPC (CMPC) and DMPC approaches is described for the considered case study, which consists of an aggregate version of the Barcelona DWN. Results on several simulation scenarios show the effectiveness of the proposed DMPC approach in terms of the reduced computation burden and, at the same time, of the admissible lost of performance.
Davide Barcelli
Carlos Ocampo-Martinez
Vincenç Puig Cayuela
Alberto Bemporad
alberto.bemporad@imtlucca.it
2011-07-28T10:49:45Z
2014-07-02T14:14:52Z
http://eprints.imtlucca.it/id/eprint/731
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/731
2011-07-28T10:49:45Z
Decentralized model predictive control
Decentralized and distributed model predictive control (DMPC) addresses the problem of controlling a multivariable dynamical process, composed by several interacting subsystems and subject to constraints, in a computation and communication efficient way. Compared to a centralized MPC setup, where a global optimal control problem must be solved on-line with respect to all actuator commands given the entire set of states, in DMPC the control problem is divided into a set of local MPCs of smaller size, that cooperate by communicating each other a certain information set, such as local state measurements, local decisions, optimal local predictions. Each controller is based on a partial (local) model of the overall dynamics, possibly neglecting existing dynamical interactions. The global performance objective is suitably mapped into a local objective for each of the local MPC problems.
This chapter surveys some of the main contributions to DMPC, with an emphasis on a method developed by the authors, by illustrating the ideas on motivating examples. Some novel ideas to address the problem of hierarchical MPC design are also included in the chapter.
Alberto Bemporad
alberto.bemporad@imtlucca.it
Davide Barcelli
2011-07-27T12:50:39Z
2011-08-04T07:29:05Z
http://eprints.imtlucca.it/id/eprint/724
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/724
2011-07-27T12:50:39Z
(edited by) Networked Control Systems
There has been a recent surge in research activities related to networked control of large-scale systems. These "cyber-physical" systems can be found throughout society, from industrial production plants, to water and energy distribution networks and transportation systems. They are characterized by tight coordination of a pervasive sensing infrastructure, distributed computing elements, and the physical world. Developed from work presented at the 3rd WIDE PhD School on Networked Control Systems held in Siena in July 2009, Networked Control Systems contains tutorial introductions to key research topics in the area of networked control.
Alberto Bemporad
alberto.bemporad@imtlucca.it
W.P.M.H. Heemels
Mikael Johansson
2011-07-27T08:32:36Z
2014-07-02T14:16:49Z
http://eprints.imtlucca.it/id/eprint/443
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/443
2011-07-27T08:32:36Z
Model predictive powertrain control: an application to idle speed regulation
Model Predictive Control (MPC) can enable powertrain systems to satisfy more stringent vehicle requirements. To illustrate this, we consider an application of MPC to idle speed regulation in spark ignition engines. Improved idle speed regulation can translate into improved fuel economy, while improper control can lead to engine stalls. From a control point of view, idle speed regulation is challenging, since the plant is subject to time delay and constraints. In this chapter, we first obtain a control-oriented model where ancillary states are added to account for delay and performance specifications. Then the MPC optimization problem is defined. The MPC feedback law is synthesized as a piecewise affine function, suitable for implementation in automotive microcontrollers. The obtained design has been extensively tested in a vehicle under different operating conditions. Finally, we show how competing requirements can be met by a switched MPC controller.
Stefano Di Cairano
Diana Yanakiev
Alberto Bemporad
alberto.bemporad@imtlucca.it
Ilya Kolmanovsky
Davor Hrovat
2011-07-27T08:30:07Z
2011-08-04T07:29:06Z
http://eprints.imtlucca.it/id/eprint/426
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/426
2011-07-27T08:30:07Z
On the synthesis of piecewise affine control laws
Piecewise affine (PWA) control laws offer an attractive solution to real-time control of linear, nonlinear and hybrid systems. In this paper we provide a compact exposition of the existing state-of-the-art methods for the synthesis of PWA control laws using optimization-based methods.
Alberto Bemporad
alberto.bemporad@imtlucca.it
W.P.M.H. Heemels
Mircea Lazar
2011-07-27T08:29:39Z
2011-11-17T11:26:40Z
http://eprints.imtlucca.it/id/eprint/427
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/427
2011-07-27T08:29:39Z
A stochastic model predictive control approach for series hybrid electric vehicle power management
This paper illustrates the use of stochastic model predictive control (SMPC) for power management in vehicles equipped with advanced hybrid powertrains. Hybrid vehicles use two or more distinct power sources for propulsion, and their complex powertrain architecture requires the coordination of all the subsystems to achieve target performances in terms of fuel consumption, driveability, component life-time, exhaust emissions. Many control strategies have been presented and successfully applied, mainly based on heuristics or rules and tuned on certain reference drive cycles. To take into account that cycles are not exactly known a priori in driving routine, this paper proposes a stochastic approach for the power management problem. We focus on a series hybrid electric vehicle (HEV), which combines an internal combustion engine and an electric motor. The power demand from the driver is modeled as a Markov chain estimated on several driving cycles and used to generate scenarios in the SMPC law. Simulation results over a standard driving cycle are presented to demonstrate the effectiveness of the proposed stochastic approach and compared with other deterministic approaches.
Giulio Ripaccioli
Daniele Bernardini
daniele.bernardini@imtlucca.it
Stefano Di Cairano
Alberto Bemporad
alberto.bemporad@imtlucca.it
Ilya Kolmanovsky
2011-07-27T08:29:32Z
2011-11-17T11:10:29Z
http://eprints.imtlucca.it/id/eprint/428
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/428
2011-07-27T08:29:32Z
Stability analysis of stochastic networked control systems
In this paper, we study the stability of Networked Control Systems (NCSs) that are subject to time-varying transmission intervals, time-varying transmission delays, packet-dropouts and communication constraints. Communication constraints impose that, per transmission, only one sensor or actuator node can access the network and send its information. Which node is given access to the network at a transmission time is orchestrated by a so-called network protocol. This paper considers NCSs, in which the transmission intervals and transmission delays are described by a random process, having a continuous probability density function (PDF). By focussing on linear plants and controllers and periodic and quadratic protocols, we present a modelling framework for NCSs based on stochastic discrete-time switched linear systems. Stability (in the mean-square) of these systems is analysed using convex overapproximations and a finite number of linear matrix inequalities. On a benchmark example of a batch reactor, we illustrated the effectiveness of the developed theory.
M.C.F. Donkers
W.P.M.H. Heemels
Daniele Bernardini
daniele.bernardini@imtlucca.it
Alberto Bemporad
alberto.bemporad@imtlucca.it
Vsevolod Shneer
2011-07-27T08:29:22Z
2016-04-06T10:25:58Z
http://eprints.imtlucca.it/id/eprint/425
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/425
2011-07-27T08:29:22Z
Steering vehicle control by switched model predictive control
We propose a switching Model Predictive Control (MPC) strategy to control vehicle steering by actuating active front steering (AFS) and electronic stability control (ESC). After describing the piecewise affine prediction model used for MPC design, where the nonlinearities arise from the relation between sideslip angles and tire forces, a switching MPC strategy is implemented, where different local MPC controllers are used depending on the current tire force conditions. The designed controller maintains most of the benefits of a previously designed hybrid model predictive controller, but it has lower complexity and allows more flexible design. The controller stability is verified and the controller behavior during challenging step steering maneuvers is tested in closed-loop simulations against a nonlinear vehicle model.
Stefano Di Cairano
H. E. Tseng
Daniele Bernardini
daniele.bernardini@imtlucca.it
Alberto Bemporad
alberto.bemporad@imtlucca.it
2011-07-27T08:29:14Z
2012-07-27T07:16:41Z
http://eprints.imtlucca.it/id/eprint/439
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/439
2011-07-27T08:29:14Z
Model predictive control tuning by controller matching
The effectiveness of model predictive control (MPC) in dealing with input and state constraints during transient operations is well known. However, in contrast with several linear control techniques, closed-loop frequency-domain properties such as sensitivities and robustness to small perturbations are usually not taken into account in the MPC design. This technical note considers the problem of tuning an MPC controller that behaves as a given linear controller when the constraints are not active (e.g., for perturbations around the equilibrium that remain within the given input and state bounds), therefore inheriting the small-signal properties of the linear control design, and that still optimally deals with constraints during transients. We provide two methods for selecting the MPC weight matrices so that the resulting MPC controller behaves as the given linear controller, therefore solving the posed inverse problem of controller matching, and is globally asymptotically stable.
Stefano Di Cairano
Alberto Bemporad
alberto.bemporad@imtlucca.it
2011-07-08T12:40:57Z
2012-03-02T15:23:59Z
http://eprints.imtlucca.it/id/eprint/438
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/438
2011-07-08T12:40:57Z
Equivalent piecewise affine models of linear hybrid automata
In this technical note we examine the relationship between linear hybrid automata (LHA) and piecewise affine (PWA) systems. While a LHA is an autonomous non-deterministic model, a PWA is a deterministic model with inputs. Through the key idea of modeling the uncertainty associated with LHA transitions as input disturbances in a PWA model, by extending continuous-time PWA models to include the dynamics of discrete states and resets we show in a constructive way that a LHA can be equivalently represented as a PWA system, where equivalent means that the two systems generate the same trajectories. Besides filling in a missing theoretical link between the LHA modelling framework and the PWA modelling framework, the result has the practical advantage of enabling the use of several existing control theoretical tools developed for PWA models to a wider class of hybrid systems.
Stefano Di Cairano
Alberto Bemporad
alberto.bemporad@imtlucca.it
2011-07-07T14:09:25Z
2011-08-04T07:29:06Z
http://eprints.imtlucca.it/id/eprint/441
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/441
2011-07-07T14:09:25Z
Hybrid model predictive control based on wireless sensor feedback: An experimental study
Design and experimental validation of model predictive control (MPC) of a hybrid dynamical laboratory process with wireless sensors is presented. The laboratory process consists of four infrared lamps, controlled in pairs by two on/off switches, and of a transport belt, where moving parts equipped with wireless sensors are heated by the lamps. The process, which is motivated by heating processes in the plastic and printing industry, presents interesting hybrid dynamics. By approximating the stationary heat spatial distribution as a piecewise affine function of the position along the belt, the resulting plant model is a hybrid dynamical system. The control architecture is based on the reference governor approach: the process is actuated by a local controller, while a hybrid MPC algorithm running on a remote base station sends optimal belt velocity setpoints and lamp on/off commands over a wireless link, exploiting the sensor information received through the wireless network. A discrete-time hybrid model of the process is used for the hybrid MPC algorithm and for the state estimator. The physical modelling of the process and the hybrid MPC algorithm are presented in detail, together with the hardware and software architectures. The experimental results show that the presented theoretical framework is well suited for control of the new laboratory process, and that the process can be used as a prototype system for evaluating hybrid and networked control strategies
Alberto Bemporad
alberto.bemporad@imtlucca.it
Stefano Di Cairano
Erik Henriksson
Karl Henrik Johansson
2011-07-07T13:46:12Z
2011-11-17T10:55:29Z
http://eprints.imtlucca.it/id/eprint/440
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/440
2011-07-07T13:46:12Z
Optimization-based feedback control of flatness in a cold tandem rolling
For the problem of automatic flatness control (AFC) in cold tandem mills this paper proposes control techniques based on quadratic optimization and delay compensation. Three different strategies are presented and compared: a centralized solution based on a global quadratic programming (QP) problem that decides the commands to all the actuators, and two decentralized solutions where each actuator command is optimized locally. All schemes are based on a global exchange of information about the commands generated at the previous time step at each stand to compensate for the numerous delays present in the mill. Control algorithms are tested in simulation considering a tandem mill with five stands as a benchmark, and results are shown to demonstrate the performance of the proposed schemes.
Alberto Bemporad
alberto.bemporad@imtlucca.it
Daniele Bernardini
daniele.bernardini@imtlucca.it
Francesco Alessandro Cuzzola
Andrea Spinelli
2011-07-06T10:42:15Z
2011-07-11T14:37:42Z
http://eprints.imtlucca.it/id/eprint/711
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/711
2011-07-06T10:42:15Z
Dynamics of Dependence Properties for Lifetimes Influenced by Unobservable Environmental Factors
We consider non-negative conditionally independent and identically distributed random variables and analyze conditions for monotonicity of survival copulas of residual lifetimes. Concentrating attention on the bivariate copula, we compare its behavior at the instant of default with its evolution between two defaults. The assumptions for our results will be expressed in terms of conditional hazard rates.
Rachele Foschi
rachele.foschi@imtlucca.it
Fabio Spizzichino
2011-07-06T10:28:16Z
2011-07-11T14:37:42Z
http://eprints.imtlucca.it/id/eprint/709
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/709
2011-07-06T10:28:16Z
Distorted Copulas: Constructions and Tail Dependence
Given a copula C, we examine under which conditions on an order isomorphism ψ of [0, 1] the distortion C ψ: [0, 1]2 → [0, 1], C ψ(x, y) = ψ{C[ψ−1(x), ψ−1(y)]} is again a copula. In particular, when the copula C is totally positive of order 2, we give a sufficient condition on ψ that ensures that any distortion of C by means of ψ is again a copula. The presented results allow us to introduce in a more flexible way families of copulas exhibiting different behavior in the tails.
Fabrizio Durante
Rachele Foschi
rachele.foschi@imtlucca.it
Peter Sarkoci
2011-07-06T09:56:58Z
2011-07-11T14:37:42Z
http://eprints.imtlucca.it/id/eprint/708
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/708
2011-07-06T09:56:58Z
Aging functions and multivariate notions of NBU and IFR
For d≥2, let X=(X1, …, Xd) be a vector of exchangeable continuous lifetimes with joint survival function $\overline{F}$. For such models, we study some properties of multivariate aging of $\overline{F}$ that are described by means of the multivariate aging function $B_{\overline{F}}$, which is a useful tool for describing the level curves of $\overline{F}$. Specifically, the attention is devoted to notions that generalize the univariate concepts of New Better than Used and Increasing Failure Rate. These multivariate notions are satisfied by random vectors whose components are conditionally independent and identically distributed having univariate conditional survival function that is New Better than Used (respectively, Increasing Failure Rate). Furthermore, they also have an interpretation in terms of comparisons among conditional survival functions of residual lifetimes, given a same history of observed survivals.
Fabrizio Durante
Rachele Foschi
rachele.foschi@imtlucca.it
Fabio Spizzichino
2011-07-04T09:39:00Z
2013-10-10T08:36:14Z
http://eprints.imtlucca.it/id/eprint/695
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/695
2011-07-04T09:39:00Z
Bankruptcy risk model and empirical tests
We analyze the size dependence and temporal stability of firm bankruptcy risk in the US economy by applying Zipf scaling techniques. We focus on a single risk factor—the debt-to-asset ratio R—in order to study the stability of the Zipf distribution of R over time. We find that the Zipf exponent increases during market crashes, implying that firms go bankrupt with larger values of R. Based on the Zipf analysis, we employ Bayes’s theorem and relate the conditional probability that a bankrupt firm has a ratio R with the conditional probability of bankruptcy for a firm with a given R value. For 2,737 bankrupt firms, we demonstrate size dependence in assets change during the bankruptcy proceedings. Prepetition firm assets and petition firm assets follow Zipf distributions but with different exponents, meaning that firms with smaller assets adjust their assets more than firms with larger assets during the bankruptcy process. We compare bankrupt firms with nonbankrupt firms by analyzing the assets and liabilities of two large subsets of the US economy: 2,545 Nasdaq members and 1,680 New York Stock Exchange (NYSE) members. We find that both assets and liabilities follow a Pareto distribution. The finding is not a trivial consequence of the Zipf scaling relationship of firm size quantified by employees—although the market capitalization of Nasdaq stocks follows a Pareto distribution, the same distribution does not describe NYSE stocks. We propose a coupled Simon model that simultaneously evolves both assets and debt with the possibility of bankruptcy, and we also consider the possibility of firm mergers.
Boris Podobnik
Davor Horvatic
Alexander M. Petersen
alexander.petersen@imtlucca.it
Branko Urošević
H. Eugene Stanley
2011-07-04T09:21:40Z
2016-04-06T08:01:12Z
http://eprints.imtlucca.it/id/eprint/264
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/264
2011-07-04T09:21:40Z
Common scaling behavior in finance and macroeconomics
In order to test whether scaling exists in finance at the world level, we test whether the average growth rates and volatility of market capitalization (MC) depend on the level of MC. We analyze the MC for 54 worldwide stock indices and 48 worldwide bond indices. We find that (i) the average growth rate r of the MC and (ii) the standard deviation (r) of growth rates r decrease both with MC as power laws, with exponents w = 0.28 ± 0.09 and w = 0.12 ± 0.04. We define a stochastic process in order to model the scaling results we find for worldwide stock and bond indices. We establish a power-law relationship between the MC of a country’s financial market and the gross domestic product (GDP) of the same country.
Boris Podobnik
Davor Horvatic
Alexander M. Petersen
alexander.petersen@imtlucca.it
M. Njavro
H. Eugene Stanley
2011-07-04T09:21:21Z
2016-04-06T08:01:33Z
http://eprints.imtlucca.it/id/eprint/268
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/268
2011-07-04T09:21:21Z
Scale-invariant properties of public-debt growth
Public debt is one of the important economic variables that quantitatively describes a nation's economy. Because bankruptcy is a risk faced even by institutions as large as governments (e.g., Iceland), national debt should be strictly controlled with respect to national wealth. Also, the problem of eliminating extreme poverty in the world is closely connected to the study of extremely poor debtor nations. We analyze the time evolution of national public debt and find "convergence": initially less-indebted countries increase their debt more quickly than initially more-indebted countries. We also analyze the public debt-to-GDP ratio {\cal R} , a proxy for default risk, and approximate the probability density function P({\cal R}) with a Gamma distribution, which can be used to establish thresholds for sustainable debt. We also observe "convergence" in {\cal R} : countries with initially small {\cal R} increase their {\cal R} more quickly than countries with initially large {\cal R} . The scaling relationships for debt and {\cal R} have practical applications, e.g. the Maastricht Treaty requires members of the European Monetary Union to maintain {\cal R} < 0.6 .
Alexander M. Petersen
alexander.petersen@imtlucca.it
Boris Podobnik
Davor Horvatic
H. Eugene Stanley
2011-07-04T09:21:14Z
2014-12-18T15:30:08Z
http://eprints.imtlucca.it/id/eprint/269
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/269
2011-07-04T09:21:14Z
Methods for measuring the citations and productivity of scientists across time and discipline
Publication statistics are ubiquitous in the ratings of scientific achievement, with citation counts and paper tallies factoring into an individual’s consideration for postdoctoral positions, junior faculty, and tenure. Citation statistics are designed to quantify individual career achievement, both at the level of a single publication, and over an individual’s entire career. While some academic careers are defined by a few significant papers (possibly out of many), other academic careers are defined by the cumulative contribution made by the author’s publications to the body of science. Several metrics have been formulated to quantify an individual’s publication career, yet none of these metrics account for the collaboration group size, and the time dependence of citation counts. In this paper we normalize publication metrics in order to achieve a universal framework for analyzing and comparing scientific achievement across both time and discipline. We study the publication careers of individual authors over the 50-year period 1958–2008 within six high-impact journals: CELL, the New England Journal of Medicine (NEJM), Nature, the Proceedings of the National Academy of Science (PNAS), Physical Review Letters (PRL), and Science. Using the normalized metrics (i) “citation shares” to quantify scientific success, and (ii) “paper shares” to quantify scientific productivity, we compare the career achievement of individual authors within each journal, where each journal represents a local arena for competition. We uncover quantifiable statistical regularity in the probability density function of scientific achievement in all journals analyzed, which suggests that a fundamental driving force underlying scientific achievement is the competitive nature of scientific advancement.
Alexander M. Petersen
alexander.petersen@imtlucca.it
Fengzhong Wang
H. Eugene Stanley
2011-07-04T09:21:07Z
2014-12-18T15:24:33Z
http://eprints.imtlucca.it/id/eprint/270
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/270
2011-07-04T09:21:07Z
Quantitative law describing market dynamics before and after interest-rate change
We study the behavior of U.S. markets both before and after U.S. Federal Open Market Commission meetings and show that the announcement of a U.S. Federal Reserve rate change causes a financial shock, where the dynamics after the announcement is described by an analog of the Omori earthquake law. We quantify the rate n(t) of aftershocks following an interest-rate change at time T and find power-law decay which scales as n(t−T)∼(t−T)−Ω, with Ω positive. Surprisingly, we find that the same law describes the rate n′(|t−T|) of “preshocks” before the interest-rate change at time T. This study quantitatively relates the size of the market response to the news which caused the shock and uncovers the presence of quantifiable preshocks. We demonstrate that the news associated with interest-rate change is responsible for causing both the anticipation before the announcement and the surprise after the announcement. We estimate the magnitude of financial news using the relative difference between the U.S. Treasury Bill and the Federal Funds effective rate. Our results are consistent with the “sign effect,” in which “bad news” has a larger impact than “good news.” Furthermore, we observe significant volatility aftershocks, confirming a “market under-reaction” that lasts at least one trading day.
Alexander M. Petersen
alexander.petersen@imtlucca.it
Fengzhong Wang
Shlomo Havlin
H. Eugene Stanley
2011-07-04T09:19:17Z
2014-12-18T15:21:18Z
http://eprints.imtlucca.it/id/eprint/422
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/422
2011-07-04T09:19:17Z
Market dynamics immediately before and after financial shocks: Quantifying the Omori, productivity, and Bath laws
We study the cascading dynamics immediately before and immediately after 219 market shocks. We define the time of a market shock Tc to be the time for which the market volatility V(Tc) has a peak that exceeds a predetermined threshold. The cascade of high volatility “aftershocks” triggered by the “main shock” is quantitatively similar to earthquakes and solar flares, which have been described by three empirical laws—the Omori law, the productivity law, and the Bath law. We analyze the most traded 531 stocks in U.S. markets during the 2 yr period of 2001–2002 at the 1 min time resolution. We find quantitative relations between the main shock magnitude M≡log10 V(Tc) and the parameters quantifying the decay of volatility aftershocks as well as the volatility preshocks. We also find that stocks with larger trading activity react more strongly and more quickly to market shocks than stocks with smaller trading activity. Our findings characterize the typical volatility response conditional on M, both at the market and the individual stock scale. We argue that there is potential utility in these three statistical quantitative relations with applications in option pricing and volatility trading.
Alexander M. Petersen
alexander.petersen@imtlucca.it
Fengzhong Wang
Shlomo Havlin
H. Eugene Stanley
2011-06-30T14:27:43Z
2014-12-18T15:28:35Z
http://eprints.imtlucca.it/id/eprint/634
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/634
2011-06-30T14:27:43Z
Scale-free models for the structure of business firm networks
We study firm collaborations in the life sciences and the information and communication technology sectors. We propose an approach to characterize industrial leadership using k-shell decomposition, with top-ranking firms in terms of market value in higher k-shell layers. We find that the life sciences industry network consists of three distinct components: a “nucleus,” which is a small well-connected subgraph, “tendrils,” which are small subgraphs consisting of small degree nodes connected exclusively to the nucleus, and a “bulk body,” which consists of the majority of nodes. Industrial leaders, i.e., the largest companies in terms of market value, are in the highest k-shells of both networks. The nucleus of the life sciences sector is very stable: once a firm enters the nucleus, it is likely to stay there for a long time. At the same time we do not observe the above three components in the information and communication technology sector. We also conduct a systematic study of these three components in random scale-free networks. Our results suggest that the sizes of the nucleus and the tendrils in scale-free networks decrease as the exponent of the power-law degree distribution λ increases, and disappear for λ≥3. We compare the k-shell structure of random scale-free model networks with two real-world business firm networks in the life sciences and in the information and communication technology sectors. We argue that the observed behavior of the k-shell structure in the two industries is consistent with the coexistence of both preferential and random agreements in the evolution of industrial networks.
Maksim Kitsak
Massimo Riccaboni
massimo.riccaboni@imtlucca.it
Shlomo Havlin
Fabio Pammolli
f.pammolli@imtlucca.it
H. Eugene Stanley
2011-06-30T14:23:17Z
2011-08-31T14:40:38Z
http://eprints.imtlucca.it/id/eprint/674
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/674
2011-06-30T14:23:17Z
Come velocizzare il passaggio al sistema di calcolo contributivo delle pensioni? Una proposta operativa per rafforzare l'aggancio alla vita attesa
Fabio Pammolli
f.pammolli@imtlucca.it
Nicola C. Salerno
2011-06-29T11:11:34Z
2011-10-25T12:50:10Z
http://eprints.imtlucca.it/id/eprint/672
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/672
2011-06-29T11:11:34Z
Legislative Malapportionment and Institutional Persistence
This paper argues that legislative malapportionment, denoting a discrepancy between the share of legislative seats and the share of population held by electoral districts, serves as a tool for pre-democratic elites to preserve their political power and economic interests after a transition to democracy. The authors claim that legislative malapportionment enhances the pre-democratic elite's political influence by over-representing areas that are more likely to vote for parties aligned withthe elite. This biased political representation survives in equilibrium as long as it helps democratic consolidation. Using data from Latin America, the authors document empirically that malapportionment increases the probability of transitioning to a democracy. Moreover, the data show that over-represented electoral districts are more likely to vote for parties close to pre-democracy ruling groups. The analysis also finds that overrepresented areas have lower levels of political competition and receive more transfers per capita from the central government, both of which favor the persistence of power of pre-democracy elites.
Miriam Bruhn
Francisco A. Gallego
Massimiliano Gaetano Onorato
massimiliano.onorato@imtlucca.it
2011-06-15T12:10:14Z
2011-07-11T14:35:30Z
http://eprints.imtlucca.it/id/eprint/404
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/404
2011-06-15T12:10:14Z
A tool for rapid development of WS-BPEL applications
We present BliteC, a software tool we have developed for supporting a rapid and easy development of WS-BPEL applications. BliteC translates service orchestrations written in Blite, a formal language inspired to but simpler than WS-BPEL, into executable WS-BPEL programs. We illustrate our approach by means of an example borrowed from the official specification of WS-BPEL.
Luca Cesari
Alessandro Lapadula
Rosario Pugliese
Francesco Tiezzi
francesco.tiezzi@imtlucca.it
2011-06-15T11:51:52Z
2011-07-11T14:35:30Z
http://eprints.imtlucca.it/id/eprint/403
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/403
2011-06-15T11:51:52Z
A criterion for separating process calculi
We introduce a new criterion, replacement freeness, to discern the relative expressiveness of process calculi. Intuitively, a calculus is strongly replacement free if replacing, within an enclosing context, a process that cannot perform any visible action by an arbitrary process never inhibits the capability of the resulting process to perform a visible action. We prove that there exists no compositional and interaction sensitive encoding of a not strongly replacement free calculus into any strongly replacement free one. We then define a weaker version of replacement freeness, by only considering replacement of closed processes, and prove that, if we additionally require the encoding to preserve name independence, it is not even possible to encode a non replacement free calculus into a weakly replacement free one. As a consequence of our encodability results, we get that many calculi equipped with priority are not replacement free and hence are not encodable into mainstream calculi like CCS and pi-calculus, that instead are strongly replacement free. We also prove that variants of pi-calculus with match among names, pattern matching or polyadic synchronization are only weakly replacement free, hence they are separated both from process calculi with priority and from mainstream calculi.
Federico Banti
Rosario Pugliese
Francesco Tiezzi
francesco.tiezzi@imtlucca.it
2011-05-24T08:47:29Z
2011-07-11T14:36:24Z
http://eprints.imtlucca.it/id/eprint/273
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/273
2011-05-24T08:47:29Z
From Flow Logic to static type systems for coordination languages
Coordination languages are often used to describe open-ended systems. This makes it challenging to develop tools for guaranteeing the security of the coordinated systems and the correctness of their interaction. Successful approaches to this problem have been based on type systems with dynamic checks; therefore, the correctness properties cannot be statically enforced. By contrast, static analysis approaches based on Flow Logic usually guarantee properties statically. In this paper, we show how the insights from the Flow Logic approach can be used to construct a type system for statically ensuring secure access to tuple spaces and safe process migration for an extension of the language Klaim.
Rocco De Nicola
r.denicola@imtlucca.it
Daniele Gorla
Rene Rydhof Hansen
Flemming Nielson
Hanne Riis Nielson
Christian W. Probst
Rosario Pugliese
2011-05-23T15:10:18Z
2012-07-06T10:03:20Z
http://eprints.imtlucca.it/id/eprint/272
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/272
2011-05-23T15:10:18Z
Tree-functors, determinacy and bisimulations
We study the functorial characterisation of bisimulation-based equivalences over a
categorical model of labelled trees. We show that in a setting where all labels are visible,
strong bisimilarity can be characterised in terms of enriched functors by relying on the
reflection of paths with their factorisations. For an enriched functor F, this notion requires
that a path (an internal morphism in our framework) π going from F(A) to C corresponds
to a path p going from A to K, with F(K) = C, such that every possible factorisation of π
can be lifted in an appropriate factorisation of p. This last property corresponds to a
Conduch´e property for enriched functors, and a very rigid formulation of it has been used by
Lawvere to characterise the determinacy of physical systems. We also consider the setting
where some labels are not visible, and provide characterisations for weak and branching
bisimilarity. Both equivalences are still characterised in terms of enriched functors that
reflect paths with their factorisations: for branching bisimilarity, the property is the same as
the one used to characterise strong bisimilarity when all labels are visible; for weak
bisimilarity, a weaker form of path factorisation lifting is needed. This fact can be seen as
evidence that strong and branching bisimilarity are strictly related and that, unlike weak
bisimilarity, they preserve process determinacy in the sense of Milner.
Rocco De Nicola
r.denicola@imtlucca.it
Daniele Gorla
Anna Labella
2011-05-23T14:22:04Z
2011-07-11T14:36:24Z
http://eprints.imtlucca.it/id/eprint/271
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/271
2011-05-23T14:22:04Z
Uniform Labeled Transition Systems for Nondeterministic, Probabilistic, and Stochastic Processes
Rate transition systems (RTS) are a special kind of transition systems introduced for defining the stochastic behavior of processes and for associating continuous-time Markov chains with process terms. The transition relation assigns to each process, for each action, the set of possible futures paired with a measure indicating the rates at which they are reached. RTS have been shown to be a uniform model for providing an operational semantics to many stochastic process algebras. In this paper, we define Uniform Labeled TRAnsition Systems (ULTraS) as a generalization of RTS that can be exploited to uniformly describe also nondeterministic and probabilistic variants of process algebras. We then present a general notion of behavioral relation for ULTraS that can be instantiated to capture bisimulation and trace equivalences for fully nondeterministic, fully probabilistic, and fully stochastic processes.
Marco Bernardo
Rocco De Nicola
r.denicola@imtlucca.it
Michele Loreti
2011-05-18T09:02:33Z
2011-07-11T14:34:34Z
http://eprints.imtlucca.it/id/eprint/145
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/145
2011-05-18T09:02:33Z
An Algebra of Hierarchical Graphs and its Application to Structural Encoding
We define an algebraic theory of hierarchical graphs, whose axioms
characterise graph isomorphism: two terms are equated exactly when
they represent the same graph. Our algebra can be understood as
a high-level language for describing graphs with a node-sharing, embedding
structure, and it is then well suited for defining graphical
representations of software models where nesting and linking are key
aspects. In particular, we propose the use of our graph formalism as a
convenient way to describe configurations in process calculi equipped
with inherently hierarchical features such as sessions, locations, transactions,
membranes or ambients. The graph syntax can be seen as an
intermediate representation language, that facilitates the encodings of
algebraic specifications, since it provides primitives for nesting, name
restriction and parallel composition. In addition, proving soundness
and correctness of an encoding (i.e. proving that structurally equivalent
processes are mapped to isomorphic graphs) becomes easier as it can
be done by induction over the graph syntax.
Roberto Bruni
Fabio Gadducci
Alberto Lluch-Lafuente
alberto.lluch@imtlucca.it
2011-04-01T09:52:50Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/251
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/251
2011-04-01T09:52:50Z
Translation: La moderna biblioteca d’Alessandria. Il progetto «Google Books» e il sindacato antitrust, by Rudolph J.R. Peritz, Marc Miller
Il contributo ricostruisce la storia di Google relativa al progetto noto come «Google Books», teso a creare una libreria digitale planetaria, per tempo intercettato da azioni collettive intentate dalle associazioni degli autori ed editori nord-americane e poi approdato ad un tentativo di composizione della controversia in base ad un accordo transattivo. Dopo aver illustrato gli ambiti fattuali del progetto e ricostruito la storia processuale relativa alle "class action", gli autori incentrano l'analisi sulle questioni concorrenziali sollevate dall'iniziativa, con una duplice prospettiva: anzitutto per domandarsi se la composizione del contenzioso tra privati nell'ambito di una "class action" rappresenti strumento idoneo di "public policy"; e, ancora, per valutare se la condotta di Google sia nel complesso illecita in base alla normativa nord-americana.
Andrea Giannaccari
a.giannaccari@imtlucca.it
2011-03-31T13:40:00Z
2011-07-11T14:34:34Z
http://eprints.imtlucca.it/id/eprint/141
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/141
2011-03-31T13:40:00Z
Exploiting the Hierarchical Structure of Rule-Based Specifications for Decision Planning
Rule-based specifications have been very successful as a declarative approach in many domains, due to the handy yet solid foundations offered by rule-based machineries like term and graph rewriting. Realistic problems, however, call for suitable techniques to guarantee scalability. For instance, many domains exhibit a hierarchical structure that can be exploited conveniently. This is particularly evident for composition associations of models. We propose an explicit representation of such structured models and a methodology that exploits it for the description and analysis of model- and rule-based systems. The approach is presented in the framework of rewriting logic and its efficient implementation in the rewrite engine Maude and is illustrated with a case study.
}
Alberto Lluch-Lafuente
alberto.lluch@imtlucca.it
Roberto Bruni
Artur Boronat
Ugo Montanari
Generoso Paolillo
2011-03-31T10:55:12Z
2011-07-11T14:34:34Z
http://eprints.imtlucca.it/id/eprint/142
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/142
2011-03-31T10:55:12Z
On GS-Monoidal Theories for Graphs with Nesting
We propose a sound and complete axiomatisation of a class of graphs with nesting and either locally or globally restricted nodes. Such graphs allow to represent explicitly and at the right level of abstraction some relevant topological and logical features of models and systems, including nesting, hierarchies, sharing of resources, and pointers or links. We also provide an encoding of the proposed algebra into terms of a gs-monoidal theory, and through these into a suitable class of wellscoped term graphs, showing that this encoding is sound and complete with respect to the axioms of the algebra.
Roberto Bruni
Andrea Corradini
Fabio Gadducci
Alberto Lluch-Lafuente
alberto.lluch@imtlucca.it
Ugo Montanari
2011-03-31T10:44:27Z
2016-07-13T09:46:04Z
http://eprints.imtlucca.it/id/eprint/143
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/143
2011-03-31T10:44:27Z
Counterpart semantics for a second-order mu-calculus
We propose a novel approach to the semantics of quantified μ-calculi, considering models where states are algebras; the evolution relation is given by a counterpart relation (a family of partial homomorphisms), allowing for the creation, deletion, and merging of components; and formulas are interpreted over sets of state assignments (families of substitutions, associating formula variables to state components). Our proposal avoids the limitations of existing approaches, usually enforcing restrictions of the evolution relation: the resulting semantics is a streamlined and intuitively appealing one, yet it is general enough to cover most of the alternative proposals we are aware of.
Fabio Gadducci
Alberto Lluch-Lafuente
alberto.lluch@imtlucca.it
Andrea Vandin
andrea.vandin@imtlucca.it
2011-03-31T10:44:09Z
2011-07-11T14:34:34Z
http://eprints.imtlucca.it/id/eprint/144
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/144
2011-03-31T10:44:09Z
An Algebra of Hierarchical Graphs
We define an algebraic theory of hierarchical graphs, whose axioms characterise graph isomorphism: two terms are equated exactly when they represent the same graph. Our algebra can be understood as a high-level language for describing graphs with a node-sharing, embedding structure, and it is then well suited for defining graphical representations of software models where nesting and linking are key aspects.
Roberto Bruni
Fabio Gadducci
Alberto Lluch-Lafuente
alberto.lluch@imtlucca.it
2011-03-30T10:17:10Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/221
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/221
2011-03-30T10:17:10Z
Single entity theory ed immunità antitrust: il caso American Needle
Andrea Giannaccari
a.giannaccari@imtlucca.it
2011-03-30T10:16:58Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/222
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/222
2011-03-30T10:16:58Z
Le linee direttrici sugli accordi di cooperazione orizzontale: quid novi?
Il contributo analizza il progetto di riforma relativo delle Linee direttrici sull'applicazione della normativa antitrust agli accordi di cooperazione orizzontale. In particolare, dopo aver ricostruito le ragioni che hanno spinto la Commissione europea ad aggiornare il quadro analitico applicabile alle forme più comuni di accordo, vengono passati in rassegna gli elementi di novità rispetto alle Linee direttrici tuttora in vigore. In tale prospettiva, viene posta enfasi sulle indicazioni fornite relativamente alla valutazione delle pratiche di scambio di informazioni e alle modifiche apportate alla sezione concernente gli accordi di normazione tecnica.
/
The paper analyzes the draft Guidelines on the application of competition law to horizontal cooperation agreements. In particular, after shedding light on the reasons that have led the European Commission to update the analytical regime applicable to the most common forms of agreement, it is undertaken a review of the most relevant changes as compared to the guidelines still in force. In this perspective, specific emphasis is devoted to the assessment of information exchange practices, which substantially crystallize existing EU case law, as well as to the revised guidance provided in the section on standardization agreements.
Andrea Giannaccari
a.giannaccari@imtlucca.it
2011-03-30T10:16:49Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/223
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/223
2011-03-30T10:16:49Z
Il caso Lega Calcio. Antitrust e vendita collettiva dei diritti TV su manifestazioni sportive
Andrea Giannaccari
a.giannaccari@imtlucca.it
2011-03-30T10:13:47Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/244
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/244
2011-03-30T10:13:47Z
Nota a sentenza: Corte d’Appello di Milano; ordinanza 24 febbraio 2010.
Andrea Giannaccari
a.giannaccari@imtlucca.it
Roberto Pardolesi
2011-03-30T10:13:13Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/247
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/247
2011-03-30T10:13:13Z
Nota a sentenza: Tribunale di Milano; ordinanza 24 maggio 2010.
Andrea Giannaccari
a.giannaccari@imtlucca.it
Roberto Pardolesi
2011-03-30T09:50:53Z
2011-07-11T14:21:53Z
http://eprints.imtlucca.it/id/eprint/243
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/243
2011-03-30T09:50:53Z
Immunità antitrust e leghe sportive americane: «zeru tituli»
Nota a sentenza: Corte Suprema degli Stati Uniti d’America; sentenza 24 maggio 2010.
Andrea Giannaccari
a.giannaccari@imtlucca.it
Roberto Pardolesi
2011-03-10T13:24:44Z
2011-07-11T13:54:05Z
http://eprints.imtlucca.it/id/eprint/188
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/188
2011-03-10T13:24:44Z
La transizione francese del 1958 nella storiografia degli ultimi anni
Lucia Bonfreschi
lucia.bonfreschi@imtlucca.it
Christine Vodovar
2011-03-10T13:23:14Z
2011-07-11T13:54:05Z
http://eprints.imtlucca.it/id/eprint/189
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/189
2011-03-10T13:23:14Z
Raymond Aron
Lucia Bonfreschi
lucia.bonfreschi@imtlucca.it
2011-03-01T16:14:40Z
2011-07-11T14:33:42Z
http://eprints.imtlucca.it/id/eprint/117
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/117
2011-03-01T16:14:40Z
Toward a Game-Theoretic Model of Grid Systems
Computational Grid is a promising platform that provides a vast range of heterogeneous resources for high performance computing. To grasp the full advantage of Grid systems, efficient and effective resource management and Grid job scheduling are key requirements. Particularly, in resource management and job scheduling, conflicts may arise as Grid resources are usually owned by different organizations, which have different goals. In this paper, we study the job scheduling problem in Computational Grid by analyzing it using game theoretic approaches. We consider a hierarchical job scheduling model that is formulated as a repeated non-cooperative game among Grid sites, which may have selfish concerns. We exploit the concept of Nash equilibrium as a stable solution for our game which eventually is convenient for every player.
Maria Grazia Buscemi
m.buscemi@imtlucca.it
Ugo Montanari
Sonia Taneja
2011-03-01T16:05:39Z
2011-07-11T14:33:42Z
http://eprints.imtlucca.it/id/eprint/116
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/116
2011-03-01T16:05:39Z
Adaptive Fuzzy-valued Service Selection
Service composition concerns both integration of heterogeneous distributed applications and dynamic selection of services. QoS-aware selection enables a service requester with certain QoS requirements to classify services according to their QoS guarantees. In this paper we present a method that allows for a fuzzy-valued description of QoS parameters. Fuzzy sets are suited to specify both the QoS preferences raised by a service requester such as 'response time must be as lower as possible and cannot be more that 1000ms' and approximate estimates a provider can make on the QoS capabilities of its services like 'availability is roughly between 95% and 99%'. We propose a matchmaking procedure based on a fuzzy-valued similarity measure that, given the specifications of QoS parameters of the requester and the providers, selects the most appropriate service among several functionally-equivalent ones. We also devise a method for dynamical update of service offers by means of runtime monitoring of the actual QoS performance.
Davide Bacciu
Maria Grazia Buscemi
m.buscemi@imtlucca.it
Lusine Mkrtchyan
2011-02-25T10:47:07Z
2013-05-29T12:37:08Z
http://eprints.imtlucca.it/id/eprint/107
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/107
2011-02-25T10:47:07Z
La transizione spagnola un processo dalle origini di lungo periodo
This article aim at updating the new field of research in Spain and it provides the new outcomes of the historiographic research. It is divided into four parts. In the first one it recollects the major theories on the Spanish transition to democracy written from the end of the Eighties up to nowadays. In the second part it describes the origin of long run of the transition and it focus basically on domestic actors such as political parties, trade unions, social movements. In the third part it analyses the role of foreign relationship Spain took during the mid Seventies and the strategy adopted to get in touch with international institutions. In the four and latest part it describes the role played by the memory of the Civil War during the process of transition. How it influenced public opinion and government institutions.
Maria Elena Cavallaro
m.cavallaro@imtlucca.it
2011-02-25T10:30:10Z
2013-05-29T12:29:34Z
http://eprints.imtlucca.it/id/eprint/105
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/105
2011-02-25T10:30:10Z
Le transizioni mediterranee e il declino del modello continentale
The article made a distinction between the “continental model” and the “anglosaxon model” in order to understand the different role politics and state institutions played in Europe and in Usa. Afterword it explains how the State gain power during the Twenties and how it tried to maintain the role developed during the First World War and how it expanded its control on the economic field, coping with the raising role of interest groups and how the new trend made parliaments to loose part of its traditional functions obtaining a less important role in comparison with the one acquired during the liberal age. This trend in some state such as Italy and Germany led to dictatorship, whereas in other state even after the Second World War kept alive some “authoritarian relationship” within the industrial economic organization in exchange of a widespread wealth system.
How long did it last? In the article I explain how and why it started to crumble during the Sixties when the model of social integration party went in crisis. In the last part I take into account three national cases – Italy, France and Spain ,and I analyze how they react to the new trend from the Fifties up to the Nineties according to their experience of institutional change.
Maria Elena Cavallaro
m.cavallaro@imtlucca.it
Gaetano Quagliariello
2011-02-25T10:17:27Z
2013-05-29T12:30:34Z
http://eprints.imtlucca.it/id/eprint/106
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/106
2011-02-25T10:17:27Z
El uso público comparado del antifascismo y del antifranquismo en Italia y en España
This article proposes a comparison between antifascist movement in Italy and the antifrancoist one in Spain and in particular it refers to the heritage both movements left as a legacy in the building of the democratic system in the two countries during their transition to democracy in the late Forties and in the late Seventies. The article came from a round table we held within the activities sponsored by the Escuela de Historia y Arquelogia in Rome and UNED university and with several collegues coming from different Spanish and Italian universities.
Maria Elena Cavallaro
m.cavallaro@imtlucca.it
Abdón Mateos López
2011-02-25T09:30:03Z
2011-07-11T14:00:42Z
http://eprints.imtlucca.it/id/eprint/101
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/101
2011-02-25T09:30:03Z
Understanding the Doctrine of Patentable Subject
Matter
The doctrine of patentable subject matter precludes basic inventions such as abstract
ideas and laws of nature from patent protection. However, current economic
thinking of the patent systemstresses the necessity of rewarding pioneering inventors
in the cumulative innovation process. In a two-stage innovation modelwhere the first
stage invention (basic invention) has no stand-alone value and the pioneer can also
participate in the second stage, I show that patent protection to the basic invention
may increase rather than hamper the second stage performance. Rejecting patents
on the basic invention can promote technology progress when the pioneer has high
capacity, but the follower has low capacity to engage in the second stage innovation.
Jing-Yuan Chiou
jy.chiou@imtlucca.it
2011-02-25T09:26:20Z
2011-07-11T14:00:42Z
http://eprints.imtlucca.it/id/eprint/100
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/100
2011-02-25T09:26:20Z
Technology Adoption and Fuzzy Patent Rights
This paper considers why a patentee may have little incentives to reduce the uncertainty
of patent boundary. Clearer patent rights, i.e., when patent examination results
better predict subsequent court decisions, provide better guidance to technologyspecific
investment and encourage technology adoption. Undermild conditions, however,
the patentee’s post-adoption payoff decreases in clarity. The patentee prefers to
maintain “fuzzy” patent rights in order to monopolize the use of the technology, or
when promoting technology adoption is not a strong concern. The latter happens
when the patentee, as a pure licensor, has a low (ex ante) quality invention.
Jing-Yuan Chiou
jy.chiou@imtlucca.it
2011-02-25T09:00:22Z
2011-07-11T14:00:42Z
http://eprints.imtlucca.it/id/eprint/97
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/97
2011-02-25T09:00:22Z
Revisiting Antitrust Limits to Probabilistic Patent
Disputes: Strategic Entry and Asymmetric
Information
We consider separately strategic entry and asymmetric information in the design
of the settlement policy governing patent disputes, with a focus on Shapiro (2003)’s
consumer protection rule. We show that, when a potential entrant strategically incurs
an entry cost before engaging in a patent dispute, a more stringent settlement policy
of deterring costly entry is preferable to the patent-holder and may lead to higher
static efficiency. Concerning asymmetric information, when the disputants, but not
the court, learn the patent validity, we derive an “expectation test,” which requires
that a laxer settlement policy be coupled with higher expected patent validity under
settlement.
Jing-Yuan Chiou
jy.chiou@imtlucca.it
Richard Schmidtke
2011-02-22T15:56:07Z
2011-07-11T14:25:31Z
http://eprints.imtlucca.it/id/eprint/86
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/86
2011-02-22T15:56:07Z
Voting in the Bicameral Congress: Large Majorities as a Signal of Quality
We estimate a model of voting in Congress that allows for dispersed information
about the quality of proposals in an equilibrium context. The results highlight the
effects of bicameralism on policy outcomes. In equilibrium, the Senate imposes an
endogenous supermajority rule on members of the House. We estimate this super-
majority rule to be about four-fifths on average across policy areas. Moreover, our
results indicate that the value of the information dispersed among legislators is significant, and that in equilibrium a large fraction of House members (40-50 %) vote in
accordance with their private information. Taken together, our results imply a highly
conservative Senate, in the sense that proposals are enacted into law only when it is
extremely likely that their quality is high.
Matias Iaryczower
Gabriel Katz
g.katz@imtlucca.it
Sebastian Saiegh
2011-02-22T15:50:30Z
2011-07-11T14:25:31Z
http://eprints.imtlucca.it/id/eprint/83
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/83
2011-02-22T15:50:30Z
Correcting for Survey Misreports Using Auxiliary Information with an Application to Estimating Turnout
Misreporting is a problem that plagues researchers who use survey data. In this article, we develop a parametric model that corrects for misclassified binary responses using information on the misreporting patterns obtained from auxiliary data sources. The model is implemented within the Bayesian framework via Markov Chain Monte Carlo (MCMC) methods and can be easily extended to address other problems exhibited by survey data, such as missing response and/or covariate values. While the model is fully general, we illustrate its application in the context of estimating models of turnout using data from the American National Elections Studies.
Jonathan N. Katz
Gabriel Katz
g.katz@imtlucca.it
2011-02-16T11:46:46Z
2011-07-11T13:50:58Z
http://eprints.imtlucca.it/id/eprint/74
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/74
2011-02-16T11:46:46Z
Investment Discrimination and the Proliferation of Preferential Trade
Agreements
The proliferation of bilateral and regional trade agreements has arguably been the main
change to the international trading system since the end of the Uruguay Round in the mid-
1990s. We argue that investment discrimination plays a major role in this development.
Preferential trade agreements can lead to investment discrimination because of tariff
differentials on intermediary products and as result of provisions that relax investment rules
for the parties to the agreement. Excluded countries are sensitive to the costs that this
investment discrimination imposes on domestic firms and react by signing a trade agreement
that aims at leveling the playing field. We test our argument using a spatial econometric
model and a newly compiled dataset that includes 166 countries and covers a period of 18
years (1990-2007). Our findings strongly support the argument that investment discrimination
is a major driver of the proliferation of trade agreements.
Leonardo Baccini
leonardo.baccini@imtlucca.it
Andreas Duer
2011-02-16T11:46:25Z
2011-07-11T13:50:58Z
http://eprints.imtlucca.it/id/eprint/76
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/76
2011-02-16T11:46:25Z
Easing the Pain of Adjustment? Preferential Trading Agreements, Foreign Aid, and Credible Commitment to Economic Reform
In this article, we propose that wealthy donors give foreign aid to developing countries to
facilitate political adjustment, such as compensation for losers and side payments to influential
elite constituencies, towards mutually profitable economic reform. Only democratic developing
countries can credibly commit to using fungible revenue in ways that benefit the donor,
so the adjustment effect only applies to democracies. A quantitative test against data on preferential
trading agreements lends strong support to the theory. Strikingly, fully democratic
developing countries that form a preferential trading agreement obtain a threefold increase in
foreign aid in the short run. Additional tests show that this increase is not driven by macroeconomic
difficulties and that the beneficial effect on foreign aid is temporary. Both findings
are consistent with the theory. An important implication of these results is that if foreign aid
facilitates economic reform through preferential trading agreements, previous research could
have underestimated the benefits thereof.
Leonardo Baccini
leonardo.baccini@imtlucca.it
Johannes Urpelainen
2011-02-16T10:46:19Z
2011-07-11T13:50:58Z
http://eprints.imtlucca.it/id/eprint/75
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/75
2011-02-16T10:46:19Z
Why Do States Commit to International Labour Standards?
The Importance of “Rivalry” and “Friendship”
Ratifying conventions adopted by the International Labour Organization creates legal
obligations to improve labour standards in the domestic economy. Why do states
choose to ratify them? Two influential theoretical approaches offer contrasting
explanations. Rational institutionalist theory expects states to use institutions such as
the ILO to improve or consolidate their preferred standards while reducing the risk of
suffering competitive disadvantages in world markets. In this view, ILO conventions
are devices for the prevention and mitigation of regulatory “races to the bottom”
among trade rivals. By contrast, sociological institutionalism expect states to ratify
ILO conventions if doing so conforms to a norm of appropriate behaviour that is
prevalent in the states’ respective peer groups. The paper develops observable
implications of the two explanations and tests them by applying spatial regression
models to seven core ILO conventions, 187 countries, and 40 years. The paper finds
some evidence in support of both explanations, but sociological institutionalism is
supported more strongly than rational institutionalism.
Leonardo Baccini
leonardo.baccini@imtlucca.it
Mathias Koenig-Archibugi
2011-02-15T15:32:19Z
2011-07-11T14:32:25Z
http://eprints.imtlucca.it/id/eprint/46
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/46
2011-02-15T15:32:19Z
On the Interpretability of Law: Lessons from the Decoding of National Constitutions
A critical component of law is the ease by which experts and lay persons can understand it. If a law is unclear, it is unlikely to generate compliance and enforcement. Using data from a project conceived to understand the content of national constitutions, we assess the effect of contextual, textual, and interpreter characteristics on the interpretability of constitutional documents. We find that constitutions do vary in their degree of clarity. However, contextual barriers do not seem to matter: constitutions written in bygone eras, in different languages, or in far different cultural milieus are no less interpretable by readers than are those written in closer temporal and cultural proximity. On the other hand, several textual characteristics do have a sizable impact on interpretability, a result that emphasizes the important role that constitutional drafters play in the implementation of their product.
James Melton
james.melton@imtlucca.it
Zachary Elkins
Tom Ginsburg
2011-02-15T15:31:43Z
2011-07-11T14:32:25Z
http://eprints.imtlucca.it/id/eprint/47
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/47
2011-02-15T15:31:43Z
Why is Voting Habit-Forming: Evidence from Sweden
For decades, scholars of electoral behavior have noted persistence in individuals' turnout decisions
and hypothesized that such persistence is the result of habit. Recent empirical studies provide
persuasive evidence supporting the habitual voting hypothesis, but we still do not know why
individuals develop habits for voting. One theory is that voting causes individuals' to view
themselves as "voters," increasing their future probabilities of voting. Another theory asserts that
voting may ease institutional barriers, making future voting less costly and changing conative
attitudes towards voting. This study seeks to disentangle these two causal mechanisms by testing
the habitual voting hypothesis in Sweden. Since institutional barriers to voting are minimal in
Sweden, evidence in favor of the habitual voting hypothesis will lend credence to a psychological
mechanism. The opposite result will point to an institutional mechanism. Ultimately, habitual
voting is found in Sweden, which suggests the psychological mechanism is valid.
James Melton
james.melton@imtlucca.it
2011-02-15T15:31:05Z
2011-07-11T14:32:25Z
http://eprints.imtlucca.it/id/eprint/45
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/45
2011-02-15T15:31:05Z
Credibly Committing to Property Rights: The Roles of Precedent and the Constitution.
In cross-national studies, scholars typically ignore the moderating effect of credibility on the
relationship between property rights protection and economic growth. However, both theory
and case evidence suggest that credibility is necessary for this relationship to exist. Using panel
data spanning more than 100 countries from 1985-2005, this paper investigates if two credibility
mechanisms - precedent and the constitution - moderate the relationship between property rights
protection and economic growth. The findings suggest that a credible commitment to property
rights protection is a necessary condition for such protection to enhance economic performance.
The implications of these findings are twofold: 1) property rights reforms are unlikely to be
successful in countries that cannot credibly commit to those reforms, and 2) unsuccessful property
rights reforms at present may reduce the likelihood that future reforms will be successful.
James Melton
james.melton@imtlucca.it
2011-02-15T15:09:44Z
2011-07-11T14:32:25Z
http://eprints.imtlucca.it/id/eprint/41
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/41
2011-02-15T15:09:44Z
Democratic Compromise: A Latent Variable Analysis of Ten Measures of Regime Type
Using a Bayesian latent variable approach, we synthesize a new measure of democracy, the Unified Democracy Scores (UDS), from 10 extant scales. Our measure eschews the difficult—and often arbitrary—decision to use one existing democracy scale over another in favor of a cumulative approach that allows us to simultaneously leverage the measurement efforts of numerous scholars. The result of this cumulative approach is a measure of democracy that, for every country-year, is at least as reliable as the most reliable component measure and is accompanied by quantitative estimates of uncertainty in the level of democracy. Moreover, for those who wish to continue using previously existing scales or to evaluate research performed using those scales, we extract information from the new measure to perform heretofore impossible direct comparisons between component scales. Specifically, we estimate the relative reliability of the constituent indicators, compare the specific ordinal levels of each of the existing measures in relationship to one another and assess overall levels of disagreement across raters. We make the UDS and associated parameter estimates freely available online and provide a detailed tutorial that demonstrates how to best use the UDS in applied work.
Daniel Pemstein
Stephen A. Meserve
james.melton@imtlucca.it
James Melton
2011-02-15T14:50:22Z
2011-07-11T13:50:58Z
http://eprints.imtlucca.it/id/eprint/38
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38
2011-02-15T14:50:22Z
Globalization and Economic Crisis: Does Information Really Matter?
Leonardo Baccini
leonardo.baccini@imtlucca.it
Soo Yeon Kim
2011-02-15T14:48:52Z
2011-07-11T13:50:58Z
http://eprints.imtlucca.it/id/eprint/37
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37
2011-02-15T14:48:52Z
Explaining Formation and Design of EU Trade Agreements: The Role of Transparency and Flexibility
What political factors explain the selection of countries for preferential trade agreements by the European Union? I argue that when forming a trade agreement the EU is more likely to target countries that have a higher degree of political and economic transparency than other developing countries. In highly transparent countries the EU is able to monitor effectively whether or not these countries follow its forms of conditionality, which is the main rationale of EU regionalism. Moreover, economic and political transparency plays a particularly important role in determining the degree of flexibility in trade agreements. Evidence based on data from 138 developing countries supports these arguments.
Leonardo Baccini
leonardo.baccini@imtlucca.it
2011-02-15T10:41:37Z
2011-07-11T14:24:17Z
http://eprints.imtlucca.it/id/eprint/59
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/59
2011-02-15T10:41:37Z
L’idea di Kuhn: un nuovo ruolo per la storia
Stefano Gattei
stefano.gattei@imtlucca.it
2011-02-15T10:36:17Z
2011-07-11T14:24:17Z
http://eprints.imtlucca.it/id/eprint/60
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/60
2011-02-15T10:36:17Z
Imre Lakatos, the Man Who would be Philosopher-King
Stefano Gattei
stefano.gattei@imtlucca.it
2011-02-10T16:01:59Z
2011-07-11T13:20:51Z
http://eprints.imtlucca.it/id/eprint/48
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/48
2011-02-10T16:01:59Z
Electoral participation and communicative voting in Europe
This paper provides an empirical investigation of electoral participation and communicative voting in 14 European countries. We estimate a multi-level voting process where individuals face a participation decision (whether to vote or abstain) and a voting decision (whether to vote strategically for a likely winner party or as communicating for a sure loser party). Our main findings can be summarized as follows. First, individuals who are either independent or uninformed are less likely to turnout. However, being both independent and uninformed does not have any statistically significant effect on electoral participation. Thus, our results question the empirical relevance of the swing voter's curse theory in large elections. Second, the probability of voting as communicating is positively related with the level of education and the degree of dissatisfaction with the political system. Finally, political preferences and institutional features characterizing the functioning of the political system and of the media market have a significant effect both on electoral participation and on the voting decision.
Francesco Sobbrio
f.sobbrio@imtlucca.it
Pietro Navarra
2011-02-07T11:25:03Z
2011-09-29T13:46:58Z
http://eprints.imtlucca.it/id/eprint/17
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/17
2011-02-07T11:25:03Z
The Political Economy of Fiscal Prudence in Historical Perspective
This paper uses a new panel dataset to perform a statistical analysis of political regimes and financial rectitude over the long run. Old Regime polities in Europe typically suffered from fiscal fragmentation and absolutist rule. By the start of World War I, however, many such countries had centralized institutions and limited government. Panel regressions indicate that political transformations toward centralized and limited regimes led to significant improvements in fiscal prudence. Dynamic estimations and structural breaks tests reinforce these findings. The results suggest that good financial housekeeping is one mechanism through which political reforms reduce sovereign credit risk.
Mark Dincecco
m.dincecco@imtlucca.it
2011-02-07T11:18:55Z
2011-09-29T13:47:07Z
http://eprints.imtlucca.it/id/eprint/15
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/15
2011-02-07T11:18:55Z
Fragmented Authority from Ancien Régime to Modernity: a Quantitative Analysis
This paper performs a systematic analysis that examines institutional fragmentation in terms of customs tariffs within states west of the Rhine from 1700 to 1815 and between states east of the Rhine from 1815 to 1871. Internal customs zones are measured in two ways: physical size and urban population. Both methods use 175 sample cities as described by De Vries (1984) in England, France, the Netherlands, and Spain as the basic unit of account. The results indicate that customs zones west of the Rhine were small prior to the French Revolution but grew dramatically from 1789 onwards. They thus provide definitive evidence of divided authority in Ancien Régime Europe. The measurement of external customs zones uses 117 sample cities in the German and Italian territories. The findings indicate a remarkable degree of institutional consolidation between states east of the Rhine over the 1800s.
Mark Dincecco
m.dincecco@imtlucca.it