IMT Institutional Repository: No conditions. Results ordered -Date Deposited. 2024-10-12T04:05:52ZEPrintshttp://eprints.imtlucca.it/images/logowhite.pnghttp://eprints.imtlucca.it/2018-03-09T12:33:50Z2018-03-09T12:33:50Zhttp://eprints.imtlucca.it/id/eprint/3992This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39922018-03-09T12:33:50ZLa valorizzazione degli scambi in presenza di rapporti partecipativiNicola Lattanzinicola.lattanzi@imtlucca.it2018-03-09T12:31:41Z2018-03-09T12:31:41Zhttp://eprints.imtlucca.it/id/eprint/3991This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39912018-03-09T12:31:41ZLe relazioni tra sistema economico e condizioni di aziendalità ed il processo di privatizzazione delle ferrovie in GermaniaNicola Lattanzinicola.lattanzi@imtlucca.it2018-03-09T12:29:47Z2018-03-09T12:29:47Zhttp://eprints.imtlucca.it/id/eprint/3990This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39902018-03-09T12:29:47ZIl sistema delle relazioni aziendali. Schema di analisi per le decisioniIl lavoro tratta delle relazioni aziendali proponendo una scomposizione delle stesse in sottoinsieme al fine di un governo pieno e consapevole per la formazione del pensiero strategico.Nicola Lattanzinicola.lattanzi@imtlucca.it2018-03-09T12:26:20Z2018-03-09T12:26:20Zhttp://eprints.imtlucca.it/id/eprint/3989This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39892018-03-09T12:26:20ZProblems of Management and Governance in Italian Small Sized BusinessSmall and Medium Sized Business Problems in Management and GovernanceNicola Lattanzinicola.lattanzi@imtlucca.it2018-03-09T12:23:48Z2018-03-09T12:23:48Zhttp://eprints.imtlucca.it/id/eprint/3988This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39882018-03-09T12:23:48ZSignificato delle relazioni esterne nella PMI italianaNicola Lattanzinicola.lattanzi@imtlucca.it2016-04-12T10:14:24Z2016-04-12T10:14:24Zhttp://eprints.imtlucca.it/id/eprint/3429This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34292016-04-12T10:14:24ZDiagnostic accuracy of FDG-PET in evaluation of dementia: International multicenter pooled brain scan and autopsy dataDaniel H. S. SilvermanGary W. SmallMichelle A. Kung de AburtoJohn M. HoffmanEric SalmonMony J. de LeonRuediger MielkeWilliam J. JagustPietro Pietrinipietro.pietrini@imtlucca.itGene E. AlexanderJohannes CzerninMichael E. Phelps2016-04-12T09:27:59Z2016-04-12T09:28:28Zhttp://eprints.imtlucca.it/id/eprint/3423This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34232016-04-12T09:27:59ZCorpus callosum measurement as an in vivo indicator for neocortical neuronal integrity, but not white matter pathology, in Alzheimer's diseaseHarald HampelStefan J. TeipelGene E. AlexanderBarry HorwitzPietro Pietrinipietro.pietrini@imtlucca.itHanns HippiusHans-Jurgen MollerMark B. SchapiroStanley I. Rapoport2016-04-12T09:08:26Z2016-04-12T09:08:26Zhttp://eprints.imtlucca.it/id/eprint/3418This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34182016-04-12T09:08:26ZThe neurometabolic landscape of cognitive decline: in vivo studies with positron emission tomography in Alzheimer’s diseaseAlzheimer’s disease, the most common form of dementia in the elderly, is characterized by the progressive, global and irreversible deterioration of cognitive abilities. The development of positron emission tomography (PET) methodologies has made it possible to study the in vivo brain metabolic correlates of human cognitive and behavioral functions. Moreover, as PET scan examinations can be repeated, the progression of the neuropathological process and its relation to cognitive dysfunction can be followed over time. In an effort to understand the changes in neural function that precede and accompany onset of dementia and their relation to clinical manifestations, in the last several years, we have conducted clinical, neuropsychological and brain metabolic studies in groups of Alzheimer’s disease patients at different stages of dementia severity or with distinct clinical pictures and in populations at risk for developing the disease. Here, we discuss the main findings and implications obtained from these studies.Pietro Pietrinipietro.pietrini@imtlucca.itGene E. AlexanderMaura L. FureyHarald HampelMario Guazzelli2016-04-12T09:05:58Z2016-04-12T09:05:58Zhttp://eprints.imtlucca.it/id/eprint/3414This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34142016-04-12T09:05:58ZTime course of pharmacodynamic and pharmacokinetic effects of physostigmine assessed by functional brain imaging in humansIn imaging studies of brain functions using pharmacological probes, identification of the time point at which central effects of intravenously infused drugs become stable is crucial to separate the effects of experimental variables from the concomitant changes in drug effects over time. We evaluated the time courses of the pharmacokinetics and pharmacodynamics, including butyrylcholinesterase inhibition and central neural responses, of physostigmine in healthy young subjects. Ten positron emission tomography (PET) scans that alternated between a rest condition (eyes open, ears unplugged) and a working memory for faces (WM) task were acquired in healthy subjects. Subjects in the drug group received a saline infusion for the first two scans, providing a baseline measure, then received an infusion of physostigmine for all subsequent scans. Subjects in the control group received a placebo infusion of saline for all scans. Physostigmine plasma levels and percent butyrylcholinesterase inhibition increased over time (p < 0.0001), and both became stable by 40 min. Physostigmine decreased reaction time (RT) (p = 0.0005), and this effect was detected after 20 min of infusion and stable thereafter. Physostigmine also decreased regional cerebral blood flow (rCBF) in right prefrontal cortex during task (p = 0.0002), and this effect was detected after 40 min of infusion and stable thereafter. No change in RT or rCBF was observed in the control group. These results indicate that a 40-min infusion of physostigmine was necessary to obtain stable central effects. More generally, we have demonstrated that experimental effects can vary with time, especially during the initial phases of a drug infusion, indicating that it is critical that these changes are controlled.Maura L. FureyPietro Pietrinipietro.pietrini@imtlucca.itGene E. AlexanderMarc J. MentisJoanna SzczepanikUmesha ShettyNigel H. GreigHarold W. HollowayMark B. SchapiroUlderico Freo2016-04-12T08:52:37Z2016-04-12T08:52:37Zhttp://eprints.imtlucca.it/id/eprint/3412This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34122016-04-12T08:52:37ZCholinergic enhancement improves performance on working memory by modulating the functional activity in distinct brain regions: a positron emission tomography regional cerebral blood flow study in healthy humansPreviously, we have shown that physostigmine, an acetylcholinesterase inhibitor, improved performance on a working memory for faces task, as reflected by reduced reaction time (RT), and reduced task-specific regional cerebral blood flow (rCBF) in right prefrontal cortex and, further, that these reductions in RT and right frontal rCBF were significantly correlated. Here we investigated the relation between the effects of physostigmine on task performance and task-specific functional brain response throughout the cortex by examining correlations between physostigmine-related changes in rCBF in all brain areas and changes in RT. In subjects who received an infusion of physostigmine, reduced RT correlated (p < 0.001) positively with reduced rCBF in right frontal cortex, left temporal cortex, anterior cingulate, and left hippocampus; and correlated with increased rCBF in medial occipital visual cortex. In subjects who received a placebo infusion of saline, no significant correlations between changes in RT and cortical rCBF were observed. The results show that cholinergically induced improvements in working memory performance are related to alterations in neural activity in multiple cortical regions, including increased neural activity in regions associated with early perceptual processing and decreased neural activity in regions associated with attention, memory encoding, and memory maintenance.Maura L. FureyPietro Pietrinipietro.pietrini@imtlucca.itGene E. AlexanderMark B. SchapiroBarry Horwitz2016-04-12T08:48:15Z2016-04-12T08:48:15Zhttp://eprints.imtlucca.it/id/eprint/3410This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34102016-04-12T08:48:15ZNeural correlates of imaginal aggressive behavior assessed by positron emission tomography in healthy subjectsOBJECTIVE: Neurodegenerative or traumatic lesions of the frontal lobes often lead to abnormally aggressive behavior. The authors hypothesized that the imaginal evoking of scenarios involving aggressive behavior would be associated with a modulation of the functional activity in the human frontal cortex. METHOD: Regional cerebral blood flow (rCBF) determinations by positron emission tomography and psychophysiological measures of emotional responsivity were obtained in a group of 15 young healthy volunteers with good visual imagery abilities and no history of abnormal behavior while they imagined the same scenario with four variations involving emotionally neutral behavior and aggressive behavior. RESULTS: Compared to the imagined neutral scenario, the imagined scenarios involving aggressive behavior were associated with significant emotional reactivity and rCBF reductions in the ventromedial prefrontal cortex, suggesting that a functional deactivation of this cortical area occurs when individuals respond to the eliciting of imagined aggressive behavior. CONCLUSIONS: These results in healthy subjects further expand previous findings from animal and human studies by providing an in vivo functional demonstration of the involvement of the orbitofrontal cortex in the expression of aggressive behavior. They are also consistent with the hypothesis that a functional alteration of this cortical region may be present in individuals with pathological aggressive behavior.Pietro Pietrinipietro.pietrini@imtlucca.itMario GuazzelliGianpaolo BassoKaren JaffeJordan Grafman2016-04-12T08:42:32Z2016-04-12T08:42:32Zhttp://eprints.imtlucca.it/id/eprint/3409This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34092016-04-12T08:42:32ZDissociating the role of the medial and lateral anterior prefrontal cortex in human planningThe anterior prefrontal cortex is known to subserve higher cognitive functions such as task management and planning. Less is known, however, about the functional specialization of this cortical region in humans. Using functional MRI, we report a double dissociation: the medial anterior prefrontal cortex, in association with the ventral striatum, was engaged preferentially when subjects executed tasks in sequences that were expected, whereas the polar prefrontal cortex, in association with the dorsolateral striatum, was involved preferentially when subjects performed tasks in sequences that were contingent on unpredictable events. These results parallel the functional segregation previously described between the medial and lateral premotor cortex underlying planned and contingent motor control and extend this division to the anterior prefrontal cortex, when task management and planning are required. Thus, our findings support the assumption that common frontal organizational principles underlie motor and higher executive functions in humans.Etienne KoechlinGregory CorradoPietro Pietrinipietro.pietrini@imtlucca.itJordan Grafman2016-04-12T08:32:42Z2016-04-12T08:32:42Zhttp://eprints.imtlucca.it/id/eprint/3408This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34082016-04-12T08:32:42ZCholinergic enhancement and increased selectivity of perceptual processing during working memoryUsing functional magnetic resonance imaging, we investigated the mechanism by which cholinergic enhancement improves working memory. We studied the effect of the cholinesterase inhibitor physostigmine on subcomponents of this complex function. Cholinergic enhancement increased the selectivity of neural responses in extrastriate cortices during visual working memory, particularly during encoding. It also increased the participation of ventral extrastriate cortex during memory maintenance and decreased the participation of anterior prefrontal cortex. These results indicate that cholinergic enhancement improves memory performance by augmenting the selectivity of perceptual processing during encoding, thereby simplifying processing demands during memory maintenance and reducing the need for prefrontal participation.Maura L. FureyPietro Pietrinipietro.pietrini@imtlucca.itJames V. Haxby2016-04-12T08:27:29Z2016-04-12T08:50:02Zhttp://eprints.imtlucca.it/id/eprint/3407This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34072016-04-12T08:27:29ZOutcomes of patients with schizophrenia in a family-style, residential, community-based program in ItalyMario GuazzelliLaura PalaginiLoretta GiuntoliPietro Pietrinipietro.pietrini@imtlucca.it2016-04-12T08:17:52Z2016-04-12T08:17:52Zhttp://eprints.imtlucca.it/id/eprint/3404This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34042016-04-12T08:17:52ZCerebral metabolic response to passive audiovisual stimulation in patients with Alzheimer's disease and healthy volunteers assessed by PETAlzheimer'sdiseaseis associated with reductions in resting-state brain metabolism, as measured by PET, progressing with dementia severity. The purpose of this study was to see to what extent brain regions with reduced resting-state metabolicrates in Alzheimer patients could be activated by a passive audiovisual stimulation test and to compare the result with activation in age-matched healthy volunteers. The extent of activation in Alzheimer's disease is considered to reflect the integrity of synapticfunction, or inherent viability, and the potential responsiveness of the Alzheimer brain to drug therapy. Methods: Regional cerebral metabolicrates for glucose (rCMRgc,in mg/ 100 9 tissue/mm) were measured in the resting state (eyes and ears covered) and during passive audio visual stimulation (watch ing a movie) in 15 otherwise healthy Alzheimer patients of differing dementia severity (Maths Dementia Rating Scale score, 23â€”128) and in 14 age-matched healthy volunteers (score, 141 Â±3) using PET with 2 sequential injections of FDG. Results: In the volunteers, audio visual stimulation caused significant rCMRgc increases in visual and auditory cortical areas but significant decreases in frontal areas. In the mildly demented patients, rCMRgc responses were within 2 SDs of the mean in volunteers. However, the magnitude of the rCMRgc responses during stimulation declined significantly with dementia severity in the right occipitotemporal, right and left occipital association, and left calcarine cortical regions. Conclusion: Functional brain responsiveness, evaluated by a passive audio visual stimulation paradigm with PET, is with in normal limits in mildly demented Alzheimer patients but fails with worsening dementia severity. Declining responsiveness may account for the limited success of neurotransmitter replacement therapy in Alzheimer patients with moderate-to-severe dementia.Pietro Pietrinipietro.pietrini@imtlucca.itGene E. AlexanderMaura L. FureyAlessio DaniMarc J. MentisBarry HorwitzMario GuazzelliMark B. SchapiroStanley I. Rapoport2016-04-11T10:18:47Z2016-04-11T10:19:51Zhttp://eprints.imtlucca.it/id/eprint/3403This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34032016-04-11T10:18:47ZAspetti biochimici del cervellettoGiovanni RoncaA. ContePietro Pietrinipietro.pietrini@imtlucca.it2016-04-11T09:58:59Z2016-04-11T09:58:59Zhttp://eprints.imtlucca.it/id/eprint/3402This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/34022016-04-11T09:58:59ZFunctional brain imaging: cerebral blood flow and glucose metabolism in healthy human agingPietro Pietrinipietro.pietrini@imtlucca.itStanley I. Rapoport2014-07-09T14:51:32Z2014-07-09T14:51:32Zhttp://eprints.imtlucca.it/id/eprint/2259This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22592014-07-09T14:51:32ZModel-varying predictive control of a nonlinear systemModel Predictive Control (MPC) can be used for nonlinear systems if they are working around an operating point. If the operating point is moved away from the nominal working point the controller is less effective due to model mismatch. This situation can be tackled by using a Model-Varying Predictive Controller (MVPC), which changes its internal model, switching among a set of liner models, according to the working point.C. PedretK. StadlerA. TollerA.H. GlattfelderAlberto Bemporadalberto.bemporad@imtlucca.itDomenico Mignone2014-07-09T14:47:22Z2014-07-09T14:47:22Zhttp://eprints.imtlucca.it/id/eprint/2258This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22582014-07-09T14:47:22Zmiqp. m: a Matlab function for solving Mixed Integer Quadratic Programs Version 1.02 - User GuideThis manual describes miqp.m, a Matlab function for solving mixed integer quadratic programs and mixed integer linear programs. The solver is implemented using a branch and
bound technique and allows the user to specify various options, like tree exploring strategies,
branching variable selection rules, and many more.Alberto Bemporadalberto.bemporad@imtlucca.itDomenico Mignone2014-07-03T13:33:27Z2014-07-03T13:33:27Zhttp://eprints.imtlucca.it/id/eprint/2246This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22462014-07-03T13:33:27ZSmall firms and technological change in markets for technology. The pharmaceutical industry after the revolution in molecular biologyFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2014-06-30T13:07:14Z2014-06-30T13:07:14Zhttp://eprints.imtlucca.it/id/eprint/2222This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22222014-06-30T13:07:14ZInvestment and uncertainty with recursive preferencesThis paper analyses the relationship between uncertainty and investment when firms are risk averse and have a costant return to scale technology. Using recursive preferences, the paper demonstrates that not only the degree of risk aversion is important in determining the sign of the investment uncertainty relationship but that the intertemporal substitution elasticity also plays a crucial role. The model presented suggests the existence of a positive relationship between investment and uncertainty for reasonable values of the parameters. In the second part of the paper we extend the analysis taking into consideration the presence of adjustment costs in the investment process. Except for particular values of the preference parameters, the uncertainty-investment relationship has a not a definite sign anymore.Davide Ticchidavide.ticchi@imtlucca.it2014-06-30T13:00:57Z2014-06-30T13:00:57Zhttp://eprints.imtlucca.it/id/eprint/2220This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22202014-06-30T13:00:57ZCan risk aversion really explain the negative investment-uncertainty relationship?This paper shows the role of risk aversion and intertemporal substitutability in the investment-uncertainty relationship. Using recursive preferences, the paper demonstrates that not only the degree of risk aversion is important in determining the sign of the investmentuncertainty relationship but that the intertemporal substitution elasticity also plays a crucial role. This cannot be captured in the traditional expected utility set-up as risk aversion and intertemporal substitutability are determined by the same parameter. In particular, the paper shows that risk aversion can explain the negative relationship between investment and uncertainty only in a static context. In a dynamic framework, the linkage between periods can lead risk aversion to have a positive e¤ect on investment when uncertainty increases. Indeed, the e¤ects deriving from the linkage between periods depend by the intertemporal substitution elasticity: under low intertemporal substitutability, greater risk aversion can lead to higher investment when uncertainty increases. Moreover, the paper shows that with CRRA preferences investment should be positively correlated with the degree of uncertainty for reasonable values of the coe¢cient of relative risk
aversionEnrico SaltariDavide Ticchidavide.ticchi@imtlucca.it2013-12-04T10:55:17Z2013-12-04T10:55:17Zhttp://eprints.imtlucca.it/id/eprint/2031This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20312013-12-04T10:55:17ZPublications of Thomas S. KuhnStefano Gatteistefano.gattei@imtlucca.it2013-12-04T10:51:45Z2013-12-04T10:51:45Zhttp://eprints.imtlucca.it/id/eprint/2029This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20292013-12-04T10:51:45ZTom e PaulStefano Gatteistefano.gattei@imtlucca.it2013-12-04T10:49:04Z2013-12-04T10:52:25Zhttp://eprints.imtlucca.it/id/eprint/2030This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20302013-12-04T10:49:04ZNota biograficaStefano Gatteistefano.gattei@imtlucca.it2013-12-03T15:23:22Z2013-12-03T15:23:22Zhttp://eprints.imtlucca.it/id/eprint/2011This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20112013-12-03T15:23:22ZDogma contro critica : mondi possibili nella storia della scienza / Thomas S. Kuhn ; con due lettere di Paul K. Feyerabend ; a cura di Stefano GatteiThomas S. KuhnStefano Gatteistefano.gattei@imtlucca.it2013-11-06T11:44:31Z2013-11-20T09:00:49Zhttp://eprints.imtlucca.it/id/eprint/1875This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/18752013-11-06T11:44:31ZSystems with correlations in the variance: Generating power law tails in probability distributionsWe study how the presence of correlations in physical variables contributes to the form of probability distributions. We investigate a process with correlations in the variance generated by i) a Gaussian or ii) a truncated Lévy distribution. For both i) and ii), we find that due to the correlations in the variance, the process "dynamically" generates power law tails in the distributions, whose exponents can be controlled through the way the correlations in the variance are introduced. For ii), we find that the process can extend a truncated distribution beyond the truncation cutoff, which leads to a crossover between a Lévy stable power law and the present "dynamically generated" power law. We show that the process can explain the crossover behavior recently observed in the S&P500 stock index.Boris PodobnikPlamen Ch. IvanovYoungki LeeAlessandro Chessaalessandro.chessa@imtlucca.itH. Eugene Stanley2012-10-12T13:21:52Z2013-06-11T12:10:49Zhttp://eprints.imtlucca.it/id/eprint/1399This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/13992012-10-12T13:21:52ZI Consigli dei contadini nella crisi rivoluzionaria tedesca (1918-1919): le peculiarità regionaliIn this article Balestracci represented the birth of the revolutionary councils in the German countryside after the World War One, illustrating three different regional cases of Prussia, Bavaria and Saxony.Fiammetta Balestraccifiammetta.balestracci@imtlucca.it2012-02-24T10:07:42Z2013-11-20T14:03:52Zhttp://eprints.imtlucca.it/id/eprint/1164This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11642012-02-24T10:07:42ZThe fractal properties of InternetIn this paper we show that the Internet web, from a user's perspective, manifests robust scaling properties of the type P(n) propto n−τ, where n is the size of the basin connected to a given point, P represents the density of probability of finding n points downhill and τ = 1.9 ± 0.1 s a characteristic universal exponent. This scale-free structure is a result of the spontaneous growth of the web, but is not necessarily the optimal one for efficient transport. We introduce an appropriate figure of merit and suggest that a planning of few big links, acting as information highways, may noticeably increase the efficiency of the net without affecting its robustness.Guido Caldarelliguido.caldarelli@imtlucca.itRiccardo MarchettiLuciano Pietronero2012-02-24T09:50:48Z2014-12-05T09:37:29Zhttp://eprints.imtlucca.it/id/eprint/1163This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11632012-02-24T09:50:48ZDiscretized diffusion processesWe study the properties of the “rigid Laplacian” operator; that is we consider solutions of the Laplacian equation in the presence of fixed truncation errors. The dynamics of convergence to the correct analytical solution displays the presence of a metastable set of numerical solutions, whose presence can be related to granularity. We provide some scaling analysis in order to determine the value of the exponents characterizing the process. We believe that this prototype model is also suitable to provide an explanation of the widespread presence of power law in a social and economic system where information and decision diffuse, with errors and delay from agent to agent.Stefano CilibertiGuido Caldarelliguido.caldarelli@imtlucca.itPaolo De Los RiosLuciano PietroneroYi-Cheng Zhang2012-02-24T09:39:55Z2012-02-24T09:39:55Zhttp://eprints.imtlucca.it/id/eprint/1161This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11612012-02-24T09:39:55ZSelf-affine properties of fractures in brittle materialsWe present the result of numerical simulations for a fracturing process in a three-dimensional solid subjected to a mode-I load in a quasi-static regime. The solid is described using the Born model on an FCC lattice with a starting notch. We obtain a value of the roughness exponent ζ≃0.5 in agreement with the value measured in microfracturing experiments. Our result supports the idea that at small length scales the fracturing process can be considered as quasi-static, which is the basic of the possible application of the model of line depinning to the case of fractures.Andrea ParisiGuido Caldarelliguido.caldarelli@imtlucca.it2012-02-23T11:26:35Z2014-12-05T09:35:17Zhttp://eprints.imtlucca.it/id/eprint/1160This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11602012-02-23T11:26:35ZAngular structure of lacunarity, and the renormalization groupWe formulate the angular structure of lacunarity in fractals, in terms of a symmetry reduction of the three point correlation function. This provides a rich probe of universality, and first measurements yield new evidence in support of the equivalence between self-avoiding walks (SAW's) and percolation perimeters in two dimensions. We argue that the lacunarity reveals much of the renormalization group in real space. This is supported by exact calculations for random walks and measured data for percolation clusters and SAW's. Relationships follow between exponents governing inward and outward propagating perturbations, and we also find a very general test for the contribution of long-range interactions.Robin C. BallGuido Caldarelliguido.caldarelli@imtlucca.itAlessandro Flammini2012-02-23T11:15:18Z2013-11-20T14:01:16Zhttp://eprints.imtlucca.it/id/eprint/1159This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11592012-02-23T11:15:18ZDamage and cracking in thin mud layersWe present a detailed study of a two-dimensional lattice model introduced to describe mud cracking in the limit of extremely thin layers. In this model to each bond in the lattice is assigned a (quenched) random breaking threshold. Fractures proceed by selecting the `weakest' part of the material (i.e. the smallest value of the threshold). A local damage rule is also implemented, by using two different types of weakening of the neighbouring sites, corresponding to different physical situations. We present the results of numerical simulations on this model. We also derive some analytical results through a probabilistic approach known as run time statistics. In particular, we find that the total time to divide the sample scales with the square power L2 of the linear size L of the lattice. This result is not straightforward since the percolating cluster has a non-trivial fractal dimension. Furthermore, we present here a formula for the mean weakening of the whole sample during the evolution.Raffaele CafieroGuido Caldarelliguido.caldarelli@imtlucca.itAndrea Gabrielli2012-02-23T10:47:10Z2013-11-20T13:59:43Zhttp://eprints.imtlucca.it/id/eprint/1157This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11572012-02-23T10:47:10ZInvasion percolation with temperature and the nature of self-organized criticality in real systemsIn this paper we present a theoretical approach that allows us to describe the transition between critical and noncritical behavior when stocastic noise is introduced in extremal models with disorder. Namely, we show that the introduction of thermal noise in invasion percolation (IP) brings the system outside the critical point. This result suggests a possible definition of self-organized criticality systems as ordinary critical systems where the critical point corresponds to set to 0 one of the parameters. We recover both the IP and Eden models for T⃗0 and T⃗∞, respectively. For small T we find a dynamical second-order transition with correlation length diverging when T⃗0.Andrea GabrielliGuido Caldarelliguido.caldarelli@imtlucca.itLuciano Pietronero2012-02-23T10:19:33Z2013-11-20T14:16:49Zhttp://eprints.imtlucca.it/id/eprint/1156This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11562012-02-23T10:19:33ZPutting proteins back into waterWe introduce a simplified protein model where the solvent (water) degrees of freedom appear explicitly (although in an extremely simplified fashion). Using this model we are able to recover the thermodynamic phenomenology of proteins over a wide range of temperatures. In particular we describe both the warm and the cold protein denaturation within a single framework, while addressing important issues about the structure of model proteins.Paolo De Los RiosGuido Caldarelliguido.caldarelli@imtlucca.it2011-11-02T11:27:05Z2011-11-14T11:35:18Zhttp://eprints.imtlucca.it/id/eprint/1000This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10002011-11-02T11:27:05ZLo spazio di SkorohodLo spazio di Skorohod, la cui introduzione risale agli anni '60 è ormai divenuto uno strumento classico nello studio di quei processi stocastici le cui traiettorie siano funzioni cadlag, ossia funzioni continue a destra e dotate di limite a sinistra in ciascun punto. Esso è ottenuto considerando, sull'insieme di tutte le funzioni di questo tipo, un'opportuna topologia (detta topologia di Skorohod). La sua utilità si rivela soprattutto nello studio di problemi di convergenza o di compattezza per leggi di processi dotati di traiettorie cadlag. Il presente lavoro vuol essere un'introduzione all'argomento. Esso si propone di rendere più chiare e più semplici alcune delle dimostrazioni presenti in [Billingsley,1968] e di puntualizzare certi particolari tecnici un po' delicati che, in alcune esposizioni, sono trattati con eccessiva disinvoltura. Particolare attenzione è rivolta alla tribù boreliana dello spazio di Skorohod.Irene Crimaldiirene.crimaldi@imtlucca.it2011-10-31T15:12:09Z2011-11-14T11:37:17Zhttp://eprints.imtlucca.it/id/eprint/990This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/9902011-10-31T15:12:09ZSur la tribu borélienne de l'espace de SkorohodDans le chapitre VII de [Parthasarathy, 1967], consacré à l'espace de Skorohod, l'auteur introduit tout d'abord un espace un peu plus grand: à savoir l'espace costitué par les fonctions réglée, définies das [0,1], pour lesquelles chaque point de ]0,1[ est, soit un point de continuité à droite, soit un point de continuité à gauche (le type de continuité pouvant dépendre du point considéré). Dans le présent article, aprés avoir montré que la définition et un certain nombre de propriétés de la topologie de Skorohod s'étendent de manière quasi automatique à cet espace plus grand, on prouve qu'il n'en est pas de meme pour les propriétées concernant la tribu borélienne: dans le nouveau cadre, non seulement la tribu borélienne n'est plus engendrée par les projections canoniques, mais celles-ci ne sont meme pas boréliennes.Irene Crimaldiirene.crimaldi@imtlucca.itGiorgio Letta2011-10-18T09:05:08Z2011-10-18T09:05:08Zhttp://eprints.imtlucca.it/id/eprint/946This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/9462011-10-18T09:05:08ZIl Cinquecento ed il Seicento: documenti e qualche ipotesi su pittori pesciatini poco conosciutiEmanuele Pellegriniemanuele.pellegrini@imtlucca.it2011-09-09T13:30:10Z2013-03-05T15:51:19Zhttp://eprints.imtlucca.it/id/eprint/857This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/8572011-09-09T13:30:10ZCopyright protection of MPEG 1&2 video sequences using digital watermarkingSotirios A. Tsaftarissotirios.tsaftaris@imtlucca.it2011-08-09T10:49:14Z2011-08-12T15:18:50Zhttp://eprints.imtlucca.it/id/eprint/780This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/7802011-08-09T10:49:14ZIncertezza e partite correntiQuesto lavoro analizza la relazione tra incertezza di origine tecnologica e saldo delle partite correnti. L'analisi viene svolta utilizzando un modello di equilibrio economico generale in cui l'impresa è una attivita' rischiosa il cui tasso di rendimento viene determinato sul mercato delle attivita'. Si tiene cosi' conto non soltanto dell'effetto dell'incertezza sul risparmio ma, diversamente dalla letteratura tradizionale, anche sull'investimento. Sebbene l'effetto dell'incertezza sul saldo delle partite correnti sia complessivamente ambiguo, qualora l'effetto indiretto (positivo) sul risparmio generato dall'incremento del tasso di interesse rischioso sia superiore all'effetto diretto (negativo) si avra' un miglioramento di tale saldo.Enrico SaltariDavide Ticchidavide.ticchi@imtlucca.it2011-07-27T09:16:40Z2014-07-17T12:22:02Zhttp://eprints.imtlucca.it/id/eprint/574This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5742011-07-27T09:16:40ZPerformance analysis of piecewise linear systems and model predictive control systemsBemporad and Morari (1999) provided a tool for obtaining the explicit solution of constrained model predictive control (MPG) problems by showing that the control law is a continuous piecewise affine (PWA) function of the state vector. Therefore, the feedback interconnection between the MPC controller and a linear system, or a PWA system (e.g., a PWA approximation of a nonlinear system), is a PWA system. For discrete-time PWA and hybrid systems, the present authors (2000) presented an algorithm for verification/reachability analysis. In this paper, we formulate the performance analysis problem of closed-loop PWA systems (including MPC feedback loops where the prediction model and the plant model could be different) as a reachability analysis problem, and use our algorithm to obtain a tool for characterizing (i) the set of states for which the evolution is feasible, (ii) the domain of stability, (iii) the performance of the closed-loopAlberto Bemporadalberto.bemporad@imtlucca.itFabio Danilo TorrisiManfred Morari2011-07-27T09:16:38Z2014-07-17T12:21:35Zhttp://eprints.imtlucca.it/id/eprint/499This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4992011-07-27T09:16:38ZOptimization-based verification and stability characterization of piecewise affine and hybrid systemsIn this paper, we formulate the problem of characterizing the stability of a piecewise affine (PWA) system as a verification problem. The basic idea is to take the whole IR n as the set of initial conditions, and check that all the trajectories go to the origin. More precisely, we test for semi-global stability by restricting the set of initial conditions to an (arbitrarily large) bounded set X(0), and label as “asymptotically stable in T steps” the trajectories that enter an invariant set around the origin within a finite time T, or as “unstable in T steps” the trajectories which enter a set X inst of (very large) states. Subsets of X(0) leading to none of the two previous cases are labeled as “non-classifiable in T steps”. The domain of asymptotical stability in T steps is a subset of the domain of attraction of an equilibrium point, and has the practical meaning of collecting the initial conditions from which the settling time to a specified set around the origin is smaller than T. In addition, it can be computed algorithmically in finite time. Such an algorithm requires the computation of reach sets, in a similar fashion as what has been proposed for verification of hybrid systems. In this paper we present a substantial extension of the verification algorithm presented in [6] for stability characterization of PWA systems, based on linear and mixed-integer linear programming. As a result, given a set of initial conditions we are able to determine its partition into subsets of trajectories which are asymptotically stable, or unstable, or non-classifiable in T steps. Alberto Bemporadalberto.bemporad@imtlucca.itFabio Danilo TorrisiManfred Morari2011-07-27T09:16:35Z2014-07-17T12:22:57Zhttp://eprints.imtlucca.it/id/eprint/482This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4822011-07-27T09:16:35ZOn-line optimization via off-line parametric optimization toolsIn this paper, on-line optimization problems with a quadratic performance criteria and linear constraints are formulated as multi-parametric quadratic programs, where the input and state variables, corresponding to a plant, are treated as optimization variables and parameters, respectively. The solution of such problems is given by (i) a complete set of profiles of all the optimal inputs to the plant as a function of state variables, and (ii) the regions in the space of state variables where these functions remain optimal. It is shown that these profiles are linear and the corresponding regions are described by linear inequalities. An algorithm for obtaining these profiles and corresponding regions of optimality is also presented. The key feature of the proposed approach is that the on-line optimization problem is solved off-line via parametric programming techniques, hence, at each time interval (i) no optimization solver is called on-line, (ii) simple function evaluations are required for obtaining the optimal inputs to the plant for the current state of the plant.Efstratios N. PistikopoulosVivek DuaNikolaos A. BozinisAlberto Bemporadalberto.bemporad@imtlucca.itManfred Morari2011-07-27T09:16:33Z2014-07-17T12:21:08Zhttp://eprints.imtlucca.it/id/eprint/569This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5692011-07-27T09:16:33ZThe explicit solution of model predictive control via multiparametric quadratic programming The control based on online optimization, popularly known as model predictive control (MPC), has long been recognized as the winning alternative for constrained systems. The main limitation of MPC is, however, its online computational complexity. For discrete-time linear time-invariant systems with constraints on inputs and states, we develop an algorithm to determine explicitly the state feedback control law associated with MPC, and show that it is piecewise linear and continuous. The controller inherits all the stability and performance properties of MPC, but the online computation is reduced to a simple linear function evaluation instead of the expensive quadratic program. The new technique is expected to enlarge the scope of applicability of MPC to small-size/fast-sampling applications which cannot be covered satisfactorily with anti-windup schemesAlberto Bemporadalberto.bemporad@imtlucca.itManfred MorariVivek DuaEfstratios N. Pistikopoulos2011-07-27T09:16:32Z2014-07-17T12:20:00Zhttp://eprints.imtlucca.it/id/eprint/517This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5172011-07-27T09:16:32ZPredictive control of constrained hybrid systemsThis paper proposes a framework for modeling and controlling systems described by interdependent physical laws, logic rules, and operating constraints, denoted as Mixed Logical Dynamical (MLD) systems. These are described by linear dynamic equations subject to linear inequalities involving real and integer variables. MLD systems include linear hybrid systems, finite state machines, some classes of discrete event systems, constrained linear systems, and nonlinear systems which can be approximated by piecewise linear functions. A predictive control scheme is proposed which is able to stabilize MLD systems on desired reference trajectories while fulfilling operating constraints, and possibly take into account previous qualitative knowledge in the form of heuristic rules. Due to the presence of integer variables, the resulting on-line optimization procedures are solved through Mixed Integer Quadratic Programming (MIQP), for which efficient solvers have been recently developed. Some examples and a simulation case study on a complex gas supply system are reported. Alberto Bemporadalberto.bemporad@imtlucca.itManfred Morari2011-07-27T09:16:29Z2014-07-17T12:22:25Zhttp://eprints.imtlucca.it/id/eprint/613This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6132011-07-27T09:16:29ZMulti-objective prioritisation and reconfiguration for the control of constrained hybrid systemsIn many applications, the control objectives and constraints can be assigned a hierarchy of levels of priority. Often a disturbance or a fault occurs, resulting in some constraints or objectives being violated. Inadequate handling of this situation might result in component or even system-wide failures. This paper presents several methods for handling a large class of multi-objective formulations and prioritisations for model predictive control of hybrid systems, using the new mixed logic dynamical (MLD) framework. A new method, which does not require logic variables for prioritising soft constraints, is also presentedEric C. KerriganAlberto Bemporadalberto.bemporad@imtlucca.itDomenico MignoneManfred MorariJan M. Maciejowski2011-07-27T09:16:26Z2014-07-17T12:19:29Zhttp://eprints.imtlucca.it/id/eprint/570This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5702011-07-27T09:16:26ZRobust simulation of nonlinear electronic circuitsThis paper proposes robust simulation of piecewise linear systems as a tool for the analysis of nonlinear electronic circuits. Rather than computing the evolution of a single trajectory, robust simulation computes the evolution from a set of initial conditions in the state space, for all forcing input signals within a given class. We describe here a tool to perform this analysis using mathematical programming. Among various applications, the tool allows to estimate the domain of attraction of equilibria, and to
determine if some design speci£cations — expressed
themselves in terms of reachability of subsets of the
state-space — are met. A test of the tool on Chua’s
circuit is presented.Alberto Bemporadalberto.bemporad@imtlucca.itL. GiovanardiFabio Danilo Torrisi2011-07-27T09:16:24Z2014-07-17T12:19:02Zhttp://eprints.imtlucca.it/id/eprint/575This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5752011-07-27T09:16:24ZPerformance driven reachability analysis for optimal scheduling and control of hybrid systemsWe deal with the optimal control problem for piecewise linear and hybrid systems by using a computational approach based on performance-driven reachability analysis. The idea consists of coupling a reach-set exploration algorithm, essentially based on a repetitive use of linear programming, to a quadratic programming solver which selectively drives the exploration. In particular, an upper bound on the optimal cost is continually updated during the procedure, and used as a criterion to discern non-optimal evolutions and to prevent their exploration. The result is an efficient strategy of branch-and-bound nature, which is especially attractive for solving long-horizon hybrid optimal control and scheduling problemsAlberto Bemporadalberto.bemporad@imtlucca.itL. GiovanardiFabio Danilo Torrisi2011-07-27T09:16:21Z2014-07-17T12:18:33Zhttp://eprints.imtlucca.it/id/eprint/456This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4562011-07-27T09:16:21ZOutput-feedback predictive control of constrained linear systems with disturbances via set-membership state estimationThis paper combines model predictive control (MPC) and set-membership (SM) state estimation techniques for controlling systems subject to hard input and state constraints. Linear systems with unknown but bounded disturbances and partial state information are considered. The adopted approach guarantees that the constraints are satisfied for all the states which are compatible with the available information and for all the disturbances within given bounds. Properties of the proposed MPC-SM algorithm and simulation studies are reported.Alberto Bemporadalberto.bemporad@imtlucca.itAndrea Garulli2011-07-27T09:11:28Z2014-07-17T12:18:14Zhttp://eprints.imtlucca.it/id/eprint/571This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5712011-07-27T09:11:28ZOn convexity recognition of the union of polyhedra
In this paper we consider the following basic problem in polyhedral computation: given two polyhedra in $R^d$, $P$ and $Q$, decide whether their union is convex, and eventually compute it. We consider the three natural specializations of the problem: 1) when the polyhedra are given by half-spaces (H-polyhedra) 2) when they are given by vertices and extreme rays (V-polyhedra) 3) when both H- and V-polyhedral representations are available. Both the bounded (polytopes) and the unbounded case are considered. We show that the first two problems are polynomially solvable, and that the third problem is solvable in linear time.Alberto Bemporadalberto.bemporad@imtlucca.itKomei FukudaFabio Danilo Torrisi2011-07-27T09:11:24Z2014-07-17T12:17:57Zhttp://eprints.imtlucca.it/id/eprint/612This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6122011-07-27T09:11:24ZModel predictive control: a multi-parametric programming approachIn this paper, linear model predictive control problems are formulated as multi-parametric quadratic programs, where the control variables are treated as optimization variables and the state variables as parameters. It is shown that the control variables are affine functions of the state variables and each of these affine functions is valid in a certain polyhedral region in the space of state variables. An approach for deriving the explicit expressions of all the affine functions and their corresponding polyhedral regions is presented. The key advantage of this approach is that the control actions are computed off-line: the on-line computation simply reduces to a function evaluation problem.Alberto Bemporadalberto.bemporad@imtlucca.itNikolaos A. BozinisVivek DuaManfred MorariEfstratios N. Pistikopoulos2011-07-27T09:11:21Z2014-07-17T12:17:38Zhttp://eprints.imtlucca.it/id/eprint/568This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5682011-07-27T09:11:21ZPiecewise linear optimal controllers for hybrid systemsWe propose a procedure for synthesizing piecewise linear optimal controllers for discrete-time hybrid systems. A stabilizing controller is obtained by designing a model predictive controller, which is based on the minimization of a weighted l1/∞-norm of the tracking error and the input trajectories over a finite horizon. The control law is obtained by solving a multiparametric mixed-integer linear program, which avoids solving mixed-integer programs online. As the resulting control law is piecewise affine, online computation is drastically reduced to a simple linear function evaluationAlberto Bemporadalberto.bemporad@imtlucca.itFrancesco BorrelliManfred Morari2011-07-27T09:11:18Z2014-07-17T12:17:22Zhttp://eprints.imtlucca.it/id/eprint/572This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5722011-07-27T09:11:18ZOptimal controllers for hybrid systems: stability and piecewise linear explicit formWe propose a procedure for synthesizing piecewise linear optimal controllers for hybrid systems and investigate conditions for closed-loop stability. Hybrid systems are modeled in discrete-time within the mixed logical dynamical framework, or, equivalently, as piecewise affine systems. A stabilizing controller is obtained by designing a model predictive controller, which is based on the minimization of a weighted 1/∞-norm of the tracking error and the input trajectories over a finite horizon. The control law is obtained by solving a mixed-integer linear program (MILP) which depends on the current state. Although efficient branch and bound algorithms exist to solve MILPs, these are known to be NP-hard problems, which may prevent their online solution if the sampling-time is too small for the available computation power. Rather than solving the MILP online, we propose a different approach where all the computation is moved off line, by solving a multiparametric MILP. As the resulting control law is piecewise affine, online computation is drastically reduced to a simple linear function evaluation. An example of piecewise linear optimal control of a heat exchange system shows the potential of the methodAlberto Bemporadalberto.bemporad@imtlucca.itFrancesco BorrelliManfred Morari2011-07-27T09:11:16Z2014-07-17T12:16:28Zhttp://eprints.imtlucca.it/id/eprint/573This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5732011-07-27T09:11:16ZExplicit solution of LP-based model predictive controlFor discrete-time linear time-invariant systems with constraints on inputs and states, we develop an algorithm to determine explicitly, as a function of the initial state, the solution to optimal control problems that can be formulated using a linear program. In particular, we focus our attention on a receding horizon control scheme where the performance criterion is based on a mixed 1/∞-norm. We show that the optimal control profile is a piecewise linear and continuous function of the initial state. Thus, when the optimal control problem is solved at each time step according to a moving horizon scheme, the online computation of the resultant model predictive controller is reduced to a simple linear function evaluation, instead of the typical expensive linear program required up to now. The technique proposed has both theoretical and practical advantages. The proposed technique is attractive for a wide range of applications where the simplicity of the online computational complexity is a crucial requirementAlberto Bemporadalberto.bemporad@imtlucca.itFrancesco BorrelliManfred Morari2011-07-27T09:11:14Z2014-07-17T12:15:37Zhttp://eprints.imtlucca.it/id/eprint/448This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4482011-07-27T09:11:14ZSonar-based wall-following control of mobile robotsIn this paper, the wall-following problem for low-velocity mobile robots, equipped with incremental encoders and one sonar sensor, is considered. A robust observer-based controller, which takes into account explicit constraints on the orientation of the sonar sensor with respect to the wall and the velocity of the wheels, is designed. The feedback controller provides convergence and fulfillment of the constraints, once an estimate of the position of the mobile robot, is available. Such an estimate is given by an Extended Kalman Filter (EKF), which is designed via a sensor fusion approach merging the velocity signals from the encoders and the distance measurements from the sonar. Some experimental tests are reported to discuss the robustness of the control scheme. Alberto Bemporadalberto.bemporad@imtlucca.itMauro Di MarcoAlberto Tesi2011-07-27T09:11:12Z2014-07-17T12:15:01Zhttp://eprints.imtlucca.it/id/eprint/446This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4462011-07-27T09:11:12ZObservability and controllability of piecewise affine and hybrid systemsWe prove, in a constructive way, the equivalence between piecewise affine systems and a broad class of hybrid systems described by interacting linear dynamics, automata, and propositional logic. By focusing our investigation on the former class, we show through counterexamples that observability and controllability properties cannot be easily deduced from those of the component linear subsystems. Instead, we propose practical numerical tests based on mixed-integer linear programming.Alberto Bemporadalberto.bemporad@imtlucca.itGiancarlo Ferrari-TrecateManfred Morari2011-06-14T10:23:47Z2014-01-15T10:30:02Zhttp://eprints.imtlucca.it/id/eprint/336This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3362011-06-14T10:23:47ZMobile Applications in X-KLAIMNetworking has turned computers from isolated data
processors into powerful communication and elaboration
devices, called global computers; an illustrative example is
the World–Wide Web. Global computers are rapidly evolving
towards programmability. The new scenario has called
for new programming languages and paradigms centered
around the notions of mobility and location awareness. In
this paper, we briefly present X-KLAIM, an experimental
programming language for global computers, and show a
few programming examples.Lorenzo BettiniRocco De Nicolar.denicola@imtlucca.itGianLuigi FerrariRosario Pugliese2011-06-09T09:55:06Z2014-01-15T10:23:07Zhttp://eprints.imtlucca.it/id/eprint/338This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3382011-06-09T09:55:06ZTypes for access controlKlaim is an experimental programming language that supports a programming paradigm where both processes and data can be moved across different computing environments. The language relies on the use of explicit localities, and on allocation environments that associate logical localities to physical sites. This paper presents the mathematical foundations of the Klaim type system; this system permits checking statically the access rights violations of mobile agents. Types are used to describe the intentions (read, write, execute, ...) of processes relative to the different localities that they are willing to interact with, or that they want to migrate to. Type checking then determines whether processes comply with the declared intentions, and whether they have been assigned the necessary rights to perform the intended operations at the specified localities. The Klaim type system encompasses both subtyping and recursively defined types. The former occurs naturally when considering hierarchies of access rights, while the latters are needed to model migration of recursive processes. Rocco De Nicolar.denicola@imtlucca.itGianLuigi FerrariRosario PuglieseBetti Venneri2011-06-09T09:24:10Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/337This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3372011-06-09T09:24:10ZLinda-based applicative and imperative process algebrasThe classical algebraic approach to the specification and verification of concurrent systems is tuned to distributed programs that rely on asynchronous communications and permit explicit data exchange. An applicative process algebra, obtained by embedding the Linda primitives for interprocess communication in a CCS/CSP-like language, and an imperative one, obtained from the applicative variant by adding a construct for explicit assignment of values to variables, are introduced. The testing framework is used to define behavioural equivalences for both languages and sound and complete proof systems for them are described together with a fully abstract denotational model (namely, a variant of Strong Acceptance Trees).Rocco De Nicolar.denicola@imtlucca.itRosario Pugliese2011-06-09T09:20:22Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/335This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3352011-06-09T09:20:22ZProcess Algebraic Analysis of Cryptographic ProtocolsRecent approaches to the analysis of crypto-protocols build on concepts which are well-established in the field of process algebras, such as labelled transition systems (lts) and observational semantics. We outline some recent work in this direction that stems from using cryptographic versions of the pi-calculus -- most notably Abadi and Gordon's spi-calculus -- as protocol description languages. We show the impact of these approaches on a specific example, a simplified version of the Kerberos protocol. Michele BorealeRocco De Nicolar.denicola@imtlucca.itRosario Pugliese2011-06-09T08:43:49Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/334This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3342011-06-09T08:43:49ZProving the Correctness of Optimising Destructive and Non-destructive Reads over Tuple SpacesIn this paper we describe the proof of an optimisation that can be applied to tuple space based run-time systems (as used in Linda). The optimisation allows, under certain circumstances, for a tuple that has been destructively removed from a shared tuple space (for example, by a Linda in) to be returned as the result for a non-destructive read (for example, a Linda rd) for a different process. The optimisation has been successfully used in a prototype run-time system.Rocco De Nicolar.denicola@imtlucca.itRosario PuglieseAntony I. T. Rowstron2011-06-06T15:00:33Z2014-01-15T10:30:16Zhttp://eprints.imtlucca.it/id/eprint/333This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3332011-06-06T15:00:33ZProgramming Access Control: The KLAIM ExperienceIn the design of programming languages for highly distributed systems where processes can migrate and execute on new hosts, the integration of security mechanisms is a major challenge. In this paper, we report our experience in the design of an experimental programming language, called Klaim, which provides mechanisms to customize access control policies. Klaim security architecture exploits a capability-based type system to provide mechanisms for specifying and enforcing policies that control uses of resources and authorize migration and execution of processes. By means of a few programming examples, we illustrate the flexibility of the Klaim approach to support the specification of control policies and to guarantee their enforcement.
Rocco De Nicolar.denicola@imtlucca.itGianLuigi FerrariRosario Pugliese2011-06-01T09:24:50Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/332This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3322011-06-01T09:24:50ZA Modal Logic for KLAIMKlaim is an experimental programming language that supports a programming paradigm where both processes and data can be moved across different computing environments. The language relies on the use of explicit localities, and on allocation environments that associate logical localities to physical sites. This paper presents a temporal logic for specifying properties of Klaim programs. The logic is inspired by Hennessy-Milner Logic (HML) and the ν-calculus, but has novel features that permit dealing with state properties to describe the effect of actions over the different sites. The logic is equipped with a consistent and complete proof system that enables one to prove properties of mobile systems. Rocco De Nicolar.denicola@imtlucca.itMichele Loreti2011-02-15T10:43:53Z2011-07-11T14:24:17Zhttp://eprints.imtlucca.it/id/eprint/58This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/582011-02-15T10:43:53ZJohn WN Watkins, 1924-1999Stefano Gatteistefano.gattei@imtlucca.it2011-02-15T10:26:01Z2011-07-11T14:24:17Zhttp://eprints.imtlucca.it/id/eprint/72This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/722011-02-15T10:26:01ZLa filosofia della scienza di Thomas S. Kuhn: una ricostruzioneStefano Gatteistefano.gattei@imtlucca.it