IMT Institutional Repository: No conditions. Results ordered -Date Deposited. 2024-10-15T03:59:55ZEPrintshttp://eprints.imtlucca.it/images/logowhite.pnghttp://eprints.imtlucca.it/2018-03-09T12:19:05Z2018-03-09T12:19:05Zhttp://eprints.imtlucca.it/id/eprint/3987This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39872018-03-09T12:19:05Z(a cura di) Elementi di management e dinamica aziendale. Andamenti, decisioni, risultatiLuca AnselmiNicola Lattanzinicola.lattanzi@imtlucca.it2018-03-09T12:15:48Z2018-03-09T12:15:48Zhttp://eprints.imtlucca.it/id/eprint/3986This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39862018-03-09T12:15:48ZLinee di privatizzazione: il sistema delle ferrovie in GermaniaNicola Lattanzinicola.lattanzi@imtlucca.it2018-03-09T11:58:10Z2018-03-09T11:58:10Zhttp://eprints.imtlucca.it/id/eprint/3985This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39852018-03-09T11:58:10Z(a cura di ) Elementi di management e dinamica aziendale. Andamenti, decisioni, risultatiLuca AnselmiNicola Lattanzinicola.lattanzi@imtlucca.it2016-04-06T12:58:48Z2016-04-06T12:58:48Zhttp://eprints.imtlucca.it/id/eprint/3382This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/33822016-04-06T12:58:48ZLongitudinal PET Evaluation of Cerebral Metabolic Decline in Dementia: A Potential Outcome Measure in Alzheimer’s Disease Treatment StudiesOBJECTIVE: It is well established that regional cerebral metabolic rates for glucose assessed by [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in patients with Alzheimer’s disease in the mental resting state (eyes and ears covered) provide a sensitive, in vivo metabolic index of Alzheimer’s disease dementia. Few studies, however, have evaluated longitudinal declines in regional cerebral glucose metabolism in patients with dementia caused by Alzheimer’s disease. In addition, the available studies have not used recently developed brain mapping algorithms to characterize the progression of Alzheimer’s disease throughout the brain, and none considered the statistical power of regional cerebral glucose metabolism in testing the ability of treatments to attenuate the progression of dementia. METHOD: The authors used FDG PET and a brain mapping algorithm to investigate cross-sectional reductions in regional cerebral glucose metabolism, longitudinal decline in regional cerebral glucose metabolism after a 1-year follow-up, and the power of this method to evaluate treatments for Alzheimer’s disease in patients with mild to moderate dementia. PET scans were initially acquired in 14 patients with Alzheimer’s disease and 34 healthy comparison subjects of similar age and sex. Repeat scans were obtained in the patients 1 year later. Power analyses for voxels showing maximal decline over the 1-year period in regional cerebral glucose metabolism (mg/100 g per minute) were computed to estimate the sample sizes needed to detect a significant treatment response in a 1-year, double-blind, placebo-controlled treatment study. RESULTS: The patients with Alzheimer’s disease had significantly lower glucose metabolism than healthy comparison subjects in parietal, temporal, occipital, frontal, and posterior cingulate cortices. One year later, the patients with Alzheimer’s disease had significant declines in glucose metabolism in parietal, temporal, frontal, and posterior cingulate cortices. Using maximal glucose metabolism reductions in the left frontal cortex, we estimated that as few as 36 patients per group would be needed to detect a 33% treatment response with one-tailed significance of p≤0.005 and 80% power in a 1-year, double-blind, placebo-controlled treatment study. CONCLUSIONS: These findings indicate that brain metabolism as assessed by FDG PET during mental rest is a sensitive marker of disease progression in Alzheimer’s disease over a 1-year period. These findings also support the feasibility of using FDG PET as an outcome measure to test the ability of treatments to attenuate the progression of Alzheimer’s disease.Gene E. AlexanderKewei ChenPietro Pietrinipietro.pietrini@imtlucca.itStanley I. RapoportEric M. Reiman2016-04-06T12:55:25Z2016-09-13T10:19:13Zhttp://eprints.imtlucca.it/id/eprint/3380This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/33802016-04-06T12:55:25ZNeural Activity in Ventral Extrastriate Cortex during Tactile
Discrimination of Faces and Other Objects in Congenitally Blind and
Sighted SubjectsPietro Pietrinipietro.pietrini@imtlucca.itMaura L. FureyEmiliano Ricciardiemiliano.ricciardi@imtlucca.itMaria Ida GobbiniW.-H. Carolyn WuLeonardo CohenMario GuazzelliJames V. Haxby2016-04-06T12:37:18Z2016-09-13T10:19:35Zhttp://eprints.imtlucca.it/id/eprint/3379This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/33792016-04-06T12:37:18ZNuove metodologie per lo studio del cervelloEmiliano Ricciardiemiliano.ricciardi@imtlucca.itMaura L. FureyMario GuazzelliErica PanicucciPietro Pietrinipietro.pietrini@imtlucca.it2016-04-06T12:34:07Z2016-04-06T12:34:07Zhttp://eprints.imtlucca.it/id/eprint/3378This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/33782016-04-06T12:34:07ZRegional gray matter atrophy in frontotemporal dementia evaluated by voxel-based MRI morphometryGene E. AlexanderHeather RiceDiana J. LewisMark PorathKewei ChenEric M. ReimanPietro Pietrinipietro.pietrini@imtlucca.itJack KrasuskiDiane TeichbergStanley I. RapoportStefan J. TeipelHarald HampelMark B. SchapiroJordan Grafman2016-03-23T13:20:02Z2016-04-06T09:43:17Zhttp://eprints.imtlucca.it/id/eprint/3322This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/33222016-03-23T13:20:02ZLongitudinal PET evaluation of cerebral metabolic decline in dementia: A potential outcome measure in Alzheimer's disease treatment studiesObjective: It is well established that regional cerebral metabolic rates for glucose assessed by 18Ffluorodeoxyglucose (FDG) positron emission tomography (PET) in patients with Alzheimer's disease in the mental resting state (eyes and ears covered) provide a sensitive, in vivo metabolic index of Alzheimer's disease dementia. Few studies, however, have evaluated longitudinal declines in regional cerebral glucose metabolism in patients with dementia caused by Alzheimer's disease. In addition, the available studies have not used recently developed brain mapping algorithms to characterize the progression of Alzheimer's disease throughout the brain, and none considered the statistical power of regional cerebral glucose metabolism in testing the ability of treatments to attenuate the progression of dementia. Method: The authors used FDG PET and a brain mapping algorithm to investigate cross-sectional reductions in regional cerebral glucose metabolism, longitudinal decline in regional cerebral glucose metabolism after a 1-year follow-up, and the power of this method to evaluate treatments for Alzheimer's disease in patients with mild to moderate dementia. PET scans were initially acquired in 14 patients with Alzheimer's disease and 34 healthy comparison subjects of similar age and sex. Repeat scans were obtained in the patients 1 year later. Power analyses for voxels showing maximal decline over the 1-year period in regional cerebral glucose metabolism (mg/100 g per minute) were computed to estimate the sample sizes needed to detect a significant treatment response in a 1-year, double-blind, placebo-controlled treatment study. Results: The patients with Alzheimer's disease had significantly lower glucose metabolism than healthy comparison subjects in parietal, temporal, occipital, frontal, and posterior cingulate cortices. One year later, the patients with Alzheimer's disease had significant declines in glucose metabolism in parietal, temporal, frontal, and posterior cingulate cortices. Using maximal glucose metabolism reductions in the left frontal cortex, we estimated that as few as 36 patients per group would be needed to detect a 33% treatment response with one-tailed significance of p≤0.005 and 80% power in a 1-year, double-blind, placebo-controlled treatment study. Conclusions: These findings indicate that brain metabolism as assessed by FDG PET during mental rest is a sensitive marker of disease progression in Alzheimer's disease over a 1-year period. These findings also support the feasibility of using FDG PET as an outcome measure to test the ability of treatments to attenuate the progression of Alzheimer's disease.Gene E. AlexanderKewei ChenPietro Pietrinipietro.pietrini@imtlucca.itStanley I. RapoportEric M. Reiman2016-01-13T12:53:11Z2016-09-14T10:21:18Zhttp://eprints.imtlucca.it/id/eprint/2990This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/29902016-01-13T12:53:11ZL'esecuzione indiretta di decisioni comunitarie: i fondi strutturali e il Programma operativo multiregionale (POM)Lorenzo Casinilorenzo.casini@imtlucca.itElisabetta Midena2016-01-13T12:32:46Z2016-09-14T10:21:18Zhttp://eprints.imtlucca.it/id/eprint/2989This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/29892016-01-13T12:32:46ZL'attività edilizia: gli immobili vincolati. Commento alla legge 21 dicembre 2001, n. 443, c.d. "legge obiettivo"Lorenzo Casinilorenzo.casini@imtlucca.it2016-01-13T12:30:57Z2016-09-14T10:21:18Zhttp://eprints.imtlucca.it/id/eprint/2988This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/29882016-01-13T12:30:57ZLa tutela dei beni culturali in Vaticano. Commento alla legge Stato Città del Vaticano 25 luglio 2001, n. CCCLVLorenzo Casinilorenzo.casini@imtlucca.it2014-07-09T14:35:09Z2014-07-09T14:47:41Zhttp://eprints.imtlucca.it/id/eprint/2257This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22572014-07-09T14:35:09ZHYSDEL 2.0. 5- User manualThis is the HYSDEL user guide. HYSDEL allows to model a class of hybrid systems described by interconnections of linear dynamic systems, automata, if-then-else and propositional logic rules. For this class of systems we present general techniques for transforming an abstract
representation into a set of constrained linear difference equations involving integer and continuous variables. The resulting model can be immediately used for optimization, to
solve, e.g., optimal control problems or as an intermediate step to obtain other popular representations such as piecewise a±ne systems.
The developer's manual [39] completes the present document with the details on the implementation of HYSDEL and is included in the source distribution.Fabio Danilo TorrisiAlberto Bemporadalberto.bemporad@imtlucca.itGioele BertiniPeter HertachDominic JostDomenico Mignone2014-07-09T14:20:39Z2014-07-09T14:20:39Zhttp://eprints.imtlucca.it/id/eprint/2256This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/22562014-07-09T14:20:39ZOptimal control of discrete time linear hybrid systemsIn this paper we study the solution to optimal control problems for constrained discrete-time linear hybrid systems based on quadratic or linear performance criteria. The aim of the paper it twofold. First we give basic theoretical results on the structure of the optimal state feedback solution and of the value function. Second we describe how the state feedback optimal control law can be efficiently constructed by combining multiparametric programming and dynamic programming. Alberto Bemporadalberto.bemporad@imtlucca.itFrancesco BorrelliManfred Morari2014-02-27T09:05:18Z2014-02-27T09:05:18Zhttp://eprints.imtlucca.it/id/eprint/2141This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21412014-02-27T09:05:18ZRipensando il razionalismo critico, IIStefano Gatteistefano.gattei@imtlucca.it2014-02-27T08:51:46Z2014-02-27T08:51:46Zhttp://eprints.imtlucca.it/id/eprint/2142This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/21422014-02-27T08:51:46ZRipensando il razionalismo critico, IStefano Gatteistefano.gattei@imtlucca.it2013-12-04T11:15:45Z2013-12-04T11:15:45Zhttp://eprints.imtlucca.it/id/eprint/2016This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20162013-12-04T11:15:45ZRipensando il razionalismo critico, IIStefano Gatteistefano.gattei@imtlucca.it2013-12-04T11:14:40Z2013-12-04T11:14:40Zhttp://eprints.imtlucca.it/id/eprint/2014This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20142013-12-04T11:14:40ZRipensando il razionalismo critico, IStefano Gattei2013-12-04T11:11:15Z2013-12-04T11:12:02Zhttp://eprints.imtlucca.it/id/eprint/2019This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20192013-12-04T11:11:15ZRazionalità senza fondamentiStefano Gatteistefano.gattei@imtlucca.it2013-12-04T11:10:27Z2013-12-04T11:10:27Zhttp://eprints.imtlucca.it/id/eprint/2020This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/20202013-12-04T11:10:27ZLa ragione come libera sceltaStefano Gatteistefano.gattei@imtlucca.it2013-11-21T13:54:59Z2014-10-09T09:20:26Zhttp://eprints.imtlucca.it/id/eprint/1920This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/19202013-11-21T13:54:59ZA comparison of the mechanical behavior of microscopical contact modelsGiorgio ZavariseMauro Borri BrunettoMarco Paggimarco.paggi@imtlucca.it2012-10-12T13:15:20Z2013-06-11T12:09:45Zhttp://eprints.imtlucca.it/id/eprint/1398This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/13982012-10-12T13:15:20ZImmigrati e Pci a Torino 1950-1970In this essay Balestracci analyses the policy of the Italian Communist Party for the immigrants in a big industrial city of the North of the country during the big wave of Italian internal migrations from the South to the North since the late 50s. In this special activity of the party played an important role the basic sections and generally the organization, like so some personality that unfortunately was unable to convince the party of the dramatic urgency of the question of the integration of the immigrants into the new urban contest. Fiammetta Balestraccifiammetta.balestracci@imtlucca.it2012-02-27T11:35:45Z2014-06-26T11:17:43Zhttp://eprints.imtlucca.it/id/eprint/1193This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11932012-02-27T11:35:45ZA numerical study on the evolution of portfolio rulesIn this paper we test computationally the performance of CAPM in an evolutionary setting. In particular we study the stability of distribution of wealth in a financial market where some traders invest as prescribed by CAPM and others behave according to different portfolio rules. Our study is motivated by recent analytical results that show that, whenever a logarithmic utility maximiser enters the market, CAPM traders vanish in the long run. Our analysis provides further insights and extends these results. We simulate a sequence of trades in a financial market and: first, we address the issue of how long is the long run in different parametric settings; second, we study the effect of heterogeneous savings behaviour on asymptotic wealth shares. We find that CAPM is particularly “unfit” for highly risky environments.Guido Caldarelliguido.caldarelli@imtlucca.itMarina PiccioniEmanuela Sciubba2012-02-21T12:03:48Z2012-02-21T14:06:17Zhttp://eprints.imtlucca.it/id/eprint/1140This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11402012-02-21T12:03:48ZProbabilistic approach to the Bak-Sneppen modelWe study here the Bak-Sneppen model, a prototype model for the study of self-organized criticality. In this model several species interact and undergo extinction with a power-law distribution of activity bursts. Species are defined through their “fitness” whose distribution in the system is uniform above a certain threshold. Run time statistics is introduced for the analysis of the dynamics in order to explain the peculiar properties of the model. This approach based on conditional probability theory, takes into account the correlations due to memory effects. In this way, we may compute analytically the value of the fitness threshold with the desired precision. This represents a substantial improvement with respect to the traditional mean field approach.Guido Caldarelliguido.caldarelli@imtlucca.itMaddalena FeliciAndrea GabrielliLuciano Pietronero2012-02-21T11:53:24Z2012-02-21T14:07:19Zhttp://eprints.imtlucca.it/id/eprint/1139This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11392012-02-21T11:53:24ZLocal rigidity in sandpile modelsWe address the problem of the role of the concept of local rigidity in the family of sandpile systems. We define rigidity as the ratio between the critical energy and the amplitude of the external perturbation and we show, in the framework of the dynamically driven renormalization group, that any finite value of the rigidity in a generalized sandpile model renormalizes to an infinite value at the fixed point, i.e., on a large scale. The fixed-point value of the rigidity allows then for a nonambiguous distinction between sandpilelike systems and diffusive systems. Numerical simulations support our analytical results.Stefano CilibertiGuido Caldarelliguido.caldarelli@imtlucca.itVittorio LoretoLuciano Pietronero2012-02-21T10:52:51Z2014-12-05T09:27:10Zhttp://eprints.imtlucca.it/id/eprint/1137This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11372012-02-21T10:52:51ZScale-Free networks from varying vertex intrinsic fitnessA new mechanism leading to scale-free networks is proposed in this Letter. It is shown that, in many cases of interest, the connectivity power-law behavior is neither related to dynamical properties nor to preferential attachment. Assigning a quenched fitness value xi to every vertex, and drawing links among vertices with a probability depending on the fitnesses of the two involved sites, gives rise to what we call a good-get-richer mechanism, in which sites with larger fitness are more likely to become hubs (i.e., to be highly connected).Guido Caldarelliguido.caldarelli@imtlucca.itAndrea CapocciPaolo De Los RiosMiguel A. Muñoz2012-02-21T10:37:14Z2012-02-27T10:37:03Zhttp://eprints.imtlucca.it/id/eprint/1136This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/11362012-02-21T10:37:14ZMulti-layer model for the web graphThis paper studies stochastic graph models of the WebGraph. We present a new model that describes the WebGraph as an ensemble of different regions generated by independent stochastic processes (in the spirit of a recent paper by Dill et al. [VLDB 2001]). Models such as the Copying Model [17] and Evolving Networks Model [3] are simulated and compared on several relevant measures such as degree and clique distribution.Luigi LauraStefano LeonardiGuido Caldarelliguido.caldarelli@imtlucca.itPaolo De Los Rios2012-01-19T12:00:39Z2012-01-19T12:00:39Zhttp://eprints.imtlucca.it/id/eprint/1067This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/10672012-01-19T12:00:39ZLa dinamica dei rapporti tra grandi e piccole imprese: alcune riflessioni tra teoria ed analisi storica Giovanni DosiMassimo Riccabonimassimo.riccaboni@imtlucca.itRiccardo Varaldo2011-11-02T11:17:55Z2011-11-14T11:35:21Zhttp://eprints.imtlucca.it/id/eprint/999This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/9992011-11-02T11:17:55ZIntroduzione alla teoria delle misure aleatorie puntualiIl presente lavoro è un'introduzione alla teoria delle misure aleatorie puntuali. Gli argomenti trattati sono i seguenti:
concetto di classe fondamentale,
concetto di misura aleatoria,
indipendenza di misure aleatorie,
misure aleatorie puntuali e misure aleatorie di Poisson, esistenza di una misura aleatoria di Poisson di assegnata intensità, misure aleatorie puntuali semplici, nucleo di Poisson e misure aleatorie di Cox, estensione aleatoria di una misura puntuale, estensione aleatoria di una misura aleatoria puntuale, misure aleatorie marcate.Irene Crimaldiirene.crimaldi@imtlucca.it2011-10-31T15:04:57Z2011-11-03T13:19:36Zhttp://eprints.imtlucca.it/id/eprint/989This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/9892011-10-31T15:04:57ZConvergence results for a normalized triangular array of symmetric random variablesFor a triangular array of symmetric random variables (without any integrability condition) we replace the classical assumption of row-wise independence by that of row-wise joint symmetry. Under this weaker assumption we prove some results concerning the convergence in distribution of a suitable sequence of randomly normalized sums to the standard normal distribution. Then we exhibit a class of row-wise independent triangular arrays for which the ordinary sums fail to converge in distribution, while our results enable us to affirm the convergence in distribution of the normalized sums.Irene Crimaldiirene.crimaldi@imtlucca.it2011-08-11T13:23:35Z2013-03-05T15:50:45Zhttp://eprints.imtlucca.it/id/eprint/807This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/8072011-08-11T13:23:35ZFast MPEG watermarking for copyright protectionIn this paper, a new technique for watermarking of MPEG compressed video streams is proposed. The watermarking scheme operates directly in the domain of MPEG multiplexed streams. Perceptual models are used during the embedding process in order to preserve the quality of the video. The watermark is embedded in the compressed domain and is detected without the use of the original video sequence. Experimental evaluation demonstrates that the proposed scheme is able to withstand a variety of attacks. The resulting watermarking system is very fast and reliable, and is suitable for copyright protection and real-time content authentication applications.Dimitrios SimitopoulosSotirios A. Tsaftarissotirios.tsaftaris@imtlucca.itNikolaos BoulgourisMichael Strintzis2011-08-11T13:20:09Z2013-03-05T15:50:33Zhttp://eprints.imtlucca.it/id/eprint/806This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/8062011-08-11T13:20:09ZCompressed-domain video watermarking of MPEG streams A new technique for watermarking of MPEG compressed video streams is proposed. The watermarking scheme operates directly in the domain of MPEG program streams. Perceptual models are used during the embedding process in order to preserve the video quality. The watermark is embedded in the compressed domain and is detected without the use of the original video sequence. Experimental evaluation demonstrates that the proposed scheme is able to withstand a variety of attacks. The resulting watermarking system is fast and reliable, and is suitable for copyright protection and real-time content authentication applications.Dimitrios SimitopoulosSotirios A. Tsaftarissotirios.tsaftaris@imtlucca.itNikolaos BoulgourisMichael Strintzis2011-07-27T10:59:59Z2011-08-08T08:08:51Zhttp://eprints.imtlucca.it/id/eprint/424This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4242011-07-27T10:59:59ZPredictive control for hybrid systems and its application to process controlK AsanoKoji TsudaAlberto Bemporadalberto.bemporad@imtlucca.itManfred Morari2011-07-27T09:08:04Z2011-08-08T08:13:22Zhttp://eprints.imtlucca.it/id/eprint/547This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5472011-07-27T09:08:04ZComputation and approximation of piecewise affine control via binary search treeWe present an algorithm for generating a binary search tree that allows efficient computation of piecewise affine (PWA) functions defined on a polyhedral partition. This is useful for PWA control approaches, such as explicit model predictive control (MPC), as it allows the controller to be implemented on-line with small computational effort. The computation time is logarithmic in the number of regions in the PWA partition. A method for generating an approximate PWA function based on a binary search tree is also presented, giving further simplification of PWA control.Petter TondelTor Arne JohansenAlberto Bemporadalberto.bemporad@imtlucca.it2011-07-27T09:08:02Z2011-08-08T08:11:46Zhttp://eprints.imtlucca.it/id/eprint/588This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5882011-07-27T09:08:02ZScheduling of hybrid systems: multi product batch plantThe paper proposes a solution to a class of scheduling problems where the goal is to minimize the schedule (production) time. The algorithm. which takes into account a model of a hybrid system described as MLD (mixed logical dynamical) system, is based on performance driven reachability analysis. The algorithm abstracts the behavior of the hybrid system by building a tree of evolution. Nodes of the tree represent reachable states of a process, and the branches connect two nodes if a transition exists between the corresponding states. To each node a cost function value is associated and based on this value. the tree exploration is driven. As soon as the tree is explored. the global solution to the scheduling problem is obtained.Bostjan PotocnikAlberto Bemporadalberto.bemporad@imtlucca.itFabio Danilo TorrisiGasper MusicBorut Zupancic2011-07-27T09:08:00Z2011-08-04T07:29:09Zhttp://eprints.imtlucca.it/id/eprint/590This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5902011-07-27T09:08:00ZAn iterative algorithm for the optimal control of continuous-time switched linear systemsFor continuous-time switched linear systems, this paper proposes an approach for solving infinite-horizon optimal control problems where the decision variables are the switching instants and the sequence of operating modes. The procedure iterates between a "master" procedure that finds an optimal switching sequence of modes, and a "slave" procedure that finds the optimal switching instants. The effectiveness of the approach is shown through simple simulation examples.Alberto Bemporadalberto.bemporad@imtlucca.itAlessandro GiuaCarla Seatzu2011-07-27T09:07:57Z2011-08-04T07:29:09Zhttp://eprints.imtlucca.it/id/eprint/548This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5482011-07-27T09:07:57ZA hybrid system approach to modeling and optimal control of DISC enginesThis paper illustrates the application of hybrid modeling and optimal control to the problem of air-to-fuel ratio and torque control in advanced technology gasoline direct injection stratified charge (DISC) engines. DISC engines have two discrete modes of operation, stratified and homogeneous, and their dynamic behavior can be easily captured by a hybrid model. We show that the design flow (hybrid modeling and controller synthesis) is simple in terms of problem setup and tuning, provides good closed-loop performance, and leads to a control law that can be implemented on automotive hardware as a piecewise affine function of the measured and estimated quantities.Alberto Bemporadalberto.bemporad@imtlucca.itNicolò GiorgettiIlya KolmanovskyDavor Hrovat2011-07-27T09:07:53Z2011-08-04T07:29:09Zhttp://eprints.imtlucca.it/id/eprint/546This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5462011-07-27T09:07:53ZHybrid modeling and control of a direct injection stratified charge engineThis paper illustrates the application of hybrid modeling and optimal control to the problem of air-to-fuel ratio and torque control in advanced technology gasoline direct injection stratified charge (DISC) engines. DISC engines have two discrete modes of operation, stratified and homogeneous, and their dynamic behavior can be easily captured by a hybrid model. We show that the design flow (hybrid modeling and controller synthesis) is simple in terms of problem setup and tuning, provides good closed-loop performance, and leads to a control law that can be implemented on automotive hardware as a piecewise affine function of the measured and estimated quantities. Alberto Bemporadalberto.bemporad@imtlucca.itNicolò GiorgettiIlya KolmanovskyDavor Hrovat2011-07-27T09:07:50Z2011-08-08T08:09:47Zhttp://eprints.imtlucca.it/id/eprint/587This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5872011-07-27T09:07:50ZMax-plus-algebraic problems and the extended linear complementarity problem - algorithmic aspectsMany fundamental problems in the max-plus-algebraic system theory for discrete event systems--among which the minimal state space realization problem--can be solved using an Extended Linear Complementarity Problem (ELCP). We present some new, more efficient methods to solve the ELCP. We show that an ELCP with a bounded feasible set can be recast as a standard Linear Complementarity Problem (LCP). Our proof results in three possible numerical solution methods for a given ELCP: regular ELCP algorithms, mixed integer linear programming algorithms, and regular LCP algorithms. We also apply these three methods to a basic max-plus-algebraic benchmark problem.Bart De SchutterW.P.M.H. HeemelsAlberto Bemporadalberto.bemporad@imtlucca.it2011-07-27T09:07:45Z2011-08-04T07:29:09Zhttp://eprints.imtlucca.it/id/eprint/524This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5242011-07-27T09:07:45ZOn the optimal control law for linear discrete time hybrid systemsIn this paper we study the solution to optimal control problems for discrete time linear hybrid systems. First, we prove that the closed form of the state-feedback solution to finite time optimal control based on quadratic or linear norms performance criteria is a time-varying piecewise afine feedback control law. Then, we give an insight into the structure of the optimal state-feedback solution and of the value function. Finally, we briefly describe how the optimal control law can be computed by means of multiparametric programming. Alberto Bemporadalberto.bemporad@imtlucca.itFrancesco BorrelliManfred Morari2011-07-27T09:07:43Z2011-08-04T07:29:09Zhttp://eprints.imtlucca.it/id/eprint/551This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5512011-07-27T09:07:43ZAn efficient technique for translating mixed logical dynamical systems into piecewise affine systemsFor linear hybrid systems consisting of linear dynamic equations interacting with linear threshold events, automata, and logic propositions, provided in mixed-logical dynamical (MLD) form, this paper describes an efficient technique for transforming such systems into an equivalent piecewise affine (PWA) form, where equivalent means that for the same initial conditions and input sequences the trajectories of the system are identical.Alberto Bemporadalberto.bemporad@imtlucca.it2011-07-27T09:05:54Z2011-08-04T07:29:09Zhttp://eprints.imtlucca.it/id/eprint/444This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4442011-07-27T09:05:54ZThe Explicit Linear Quadratic Regulator for Constrained SystemsFor discrete-time linear time invariant systems with constraints on inputs and states, we develop an algorithm to determine explicitly, the state feedback control law which minimizes a quadratic performance criterion. We show that the control law is piece-wise linear and continuous for both the finite horizon problem (model predictive control) and the usual infinite time measure (constrained linear quadratic regulation). Thus, the on-line control computation reduces to the simple evaluation of an explicitly defined piecewise linear function. By computing the inherent underlying controller structure, we also solve the equivalent of the Hamilton–Jacobi–Bellman equation for discrete-time linear constrained systems. Control based on on-line optimization has long been recognized as a superior alternative for constrained systems. The technique proposed in this paper is attractive for a wide range of practical problems where the computational complexity of on-line optimization is prohibitive. It also provides an insight into the structure underlying optimization-based controllers.Alberto BemporadManfred MorariVivek DuaEfstratios N. Pistikopoulos2011-07-27T09:05:50Z2011-08-08T08:07:22Zhttp://eprints.imtlucca.it/id/eprint/486This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4862011-07-27T09:05:50ZOn-line optimization via off-line parametric optimization toolsIn this paper, model predictive control (MPC) based previous termoptimizationnext term problems with a quadratic performance criterion and linear constraints are formulated as multi-previous termparametricnext term quadratic programs (mp-QP), where the input and state variables, corresponding to a plant model, are treated as previous termoptimizationnext term 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-previous termline optimizationnext term problem is solved previous termoff-line via parametricnext term programming techniques. Hence (i) no previous termoptimizationnext term solver is called on-previous termline,next term and (ii) only simple function evaluations are required, to obtain the optimal inputs to the plant for the current state of the plant.Efstratios N. PistikopoulosVivek DuaNikolaos A. BozinisAlberto Bemporadalberto.bemporad@imtlucca.itManfred Morari2011-07-27T09:05:47Z2014-07-17T12:52:10Zhttp://eprints.imtlucca.it/id/eprint/473This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4732011-07-27T09:05:47ZOn hybrid systems and closed-loop MPC systemsThe following five classes of hybrid systems were recently proven to be equivalent: linear complementarity, extended linear complementarity, mixed logical dynamical systems, piecewise affine systems and max-min-plus-scaling systems. Some of the equivalences were obtained under additional assumptions, such as boundedness of certain system variables. In this paper, for linear or hybrid plants in closed-loop with a model predictive control (MPC)controller based on a linear model fulfilling linear constraints on input and state variables and utilizing a quadratic cost criterion, we provide a simple and direct proof that the closed-loop system is a subclass of any of the former five classes of hybrid systems. This result is of extreme importance, as it opens up the use of tools developed for the mentioned hybrid model classes, such as (robust) stability and safety analysis tools, to study closed-loop properties of MPCAlberto Bemporadalberto.bemporad@imtlucca.itW.P.M.H. HeemelsBart De Schutter2011-07-27T09:05:45Z2014-07-17T12:51:46Zhttp://eprints.imtlucca.it/id/eprint/449This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4492011-07-27T09:05:45ZOn the equivalence of linear complementarity problemsWe show that the Extended Linear Complementarity Problem (ELCP) can be recast as a standard Linear Complementarity Problem (LCP) provided that the surplus variables or the feasible set of the ELCP are bounded. Since many extensions of the LCP are special cases of the ELCP, this implies that these extensions can be rewritten as an LCP as well. Our equivalence proof is constructive and leads to three possible numerical solution methods for a given ELCP: regular ELCP algorithms, mixed integer linear programming algorithms, and regular LCP algorithms.Bart De SchutterW.P.M.H. HeemelsAlberto Bemporadalberto.bemporad@imtlucca.it2011-07-27T09:05:43Z2014-07-17T12:51:18Zhttp://eprints.imtlucca.it/id/eprint/589This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5892011-07-27T09:05:43ZL2 anti-windup via receding horizon optimal controlThe nonlinear L2 anti-windup framework introduced by Teel and Kapoor (1997) reduces the anti-windup synthesis problem to a state feedback synthesis problem for linear systems with input saturation and input matched L2 disturbances. In this paper, such a state feedback is synthesized using receding horizon optimal control techniques, and its equivalent piecewise affine closed-form is computed using the techniques of Bemporad et al. (2002). The properties of the resulting anti-windup compensation scheme are analyzed in the paper, and its performance is investigated through a simulation example.Alberto Bemporadalberto.bemporad@imtlucca.itAndrew R. TeelLuca Zaccarian2011-07-27T09:05:40Z2014-07-17T12:50:59Zhttp://eprints.imtlucca.it/id/eprint/550This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5502011-07-27T09:05:40ZA master-slave algorithm for the optimal control of continuous-time switched affine systemsFor continuous-time switched affine systems, this paper proposes an approach for solving infinite-horizon optimal control problems where the decision variables are the switching instants and the sequence of operating modes. The procedure iterates between a "master" procedure that finds an optimal switching sequence of modes, and a "slave" procedure that finds the optimal switching instants.Alberto Bemporadalberto.bemporad@imtlucca.itAlessandro GiuaCarla Seatzu2011-07-27T09:05:38Z2014-07-17T12:50:41Zhttp://eprints.imtlucca.it/id/eprint/549This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/5492011-07-27T09:05:38ZSynthesis of state-feedback optimal controllers for switched linear systemsThe paper deals with the optimal control of switched piecewise linear autonomous systems, where the objective is to minimize a performance index over an infinite time horizon. We assume that the switching sequence has a finite length: the unknown switching times and the switching sequence are the optimization parameters. We also assume that a cost may be associated to each switch. The optimal control for this class of systems takes the form of a state feedback, i.e., it is possible to identify a set of regions of the state space such that an optimal switch should occur if and only if the present state belongs to one of them. We show how the tables containing these regions can be computed off-line through a numerical procedure.Alberto Bemporadalberto.bemporad@imtlucca.itAlessandro GiuaCarla Seatzu2011-07-27T09:05:35Z2014-07-17T12:50:21Zhttp://eprints.imtlucca.it/id/eprint/474This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/4742011-07-27T09:05:35ZModel Predictive Control Based on Linear Programming - The Explicit SolutionWe study model predictive control (MPC) schemes for discrete-time linear time-invariant systems with constraints on inputs and states, that can be formulated using a linear program (LP). In particular, we focus our attention on performance criteria based on a mixed 1 -norm, namely, 1-norm with respect to time and -norm with respect to space. First we provide a method to compute the terminal weight so that closed-loop stability is achieved. We then show that the optimal control profile is a piecewise affine and continuous function of the initial state and briefly describe the algorithm to compute it. The piecewise affine
form allows to eliminate online LP, as the computation associated with MPC becomes a simple function evaluation. Besides practical advantages, the availability of the explicit structure of the MPC controller provides an insight into the type of control action in different
regions of the state space, and highlights possible conditions of degeneracies of the LP, such as multiple optima.Alberto Bemporadalberto.bemporad@imtlucca.itFrancesco BorrelliManfred Morari2011-07-05T10:55:07Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/702This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/7022011-07-05T10:55:07ZInnovation and competitiveness in European biotechnologyFabio Pammollif.pammolli@imtlucca.itA. AllansdottirAndrea BonaccorsiAlfonso GambardellaM. MarianiLuigi OrsenigoMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-07-01T13:08:51Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/688This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6882011-07-01T13:08:51ZOn firm growth in networks This paper is explorative in nature. Based on an empirical analysis of two different industrial settings (life sciences, LS; information and communication technologies, ICT), it investigates network growth and firm growth in networks. We find a remarkable correspondence between a few fundamental findings of the `old' stochastic approach to the analysis of firm internal growth, and empirically observed patterns of firm external growth through collaborative agreements. We show that scale-free behavior in real-world industrial networks can be accounted for by a general and parsimonious model, originally developed by Herbert Simon in 1955, based on entry and proportional growth. However, relevant departures from the stochastic benchmark are revealed that cannot be ascribed to the effect of mergers and acquisitions (M&As) and growth autocorrelation. Moreover, different regimes of growth are found to be at work in the life sciences for originators versus developers of new business opportunities, reflecting the fact that growth is driven by specialization and division of labor in the processes of generation and attraction/development of technological opportunities.Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-30T14:28:02Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/630This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6302011-06-30T14:28:02ZA Comparison of U. S. and European University-Industry Relations in the Life SciencesWe draw on diverse data sets to compare the institutional organization of upstream life science research across the United States and Europe. Understanding cross-national differences in the organization of innovative labor in the life sciences requires attention to the structure and evolution of biomedical networks involving public research organizations (universities, government laboratories, nonprofit research institutes, and research hospitals), science-based biotechnology firms, and multinational pharmaceutical corporations. We use network visualization methods and correspondence analyses to demonstrate that innovative research in biomedicine has its origins in regional clusters in the United States and in European nations. But the scientific and organizational composition of these regions varies in consequential ways. In the United States, public research organizations and small firms conduct R&D across multiple therapeutic areas and stages of the development process. Ties within and across these regions link small firms and diverse public institutions, contributing to the development of a robust national network. In contrast, the European story is one of regional specialization with a less diverse group of public research organizations working in a smaller number of therapeutic areas. European institutes develop local connections to small firms working on similar scientific problems, while cross-national linkages of European regional clusters typically involve large pharmaceutical corporations. We show that the roles of large and small firms differ in the United States and Europe, arguing that the greater heterogeneity of the U. S. system is based on much closer integration of basic science and clinical development.Fabio Pammollif.pammolli@imtlucca.itJason Owen-SmithMassimo Riccabonimassimo.riccaboni@imtlucca.itWalter W. Powell2011-06-30T14:24:03Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/666This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6662011-06-30T14:24:03ZEurope and the United States: The Power of Networks. Lessons from Technology TransferFabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.itJason Owen-SmithWalter W. Powell2011-06-30T14:23:56Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/667This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6672011-06-30T14:23:56ZThe intensity of competition after patent expiry in pharmaceuticals. A cross-country analysisThis paper shows that the relationships between the dynamics of drug priees, patent expiry, and competition by multisource
drugs vary significantly across countries. A clear distinction seems to emerge. On the one side, systems that rely on market
based competition (particularly the US) promote a clear distinction between firms that act as innovators and firms that act as
imitators after patent expiry. Original products enjoy premium prices under patent protection, and face fierce price competition
after patent expiry. On the contrary, systems that rely on administered prices (particularly France and Italy) nurture strategies of
pre-emptive brand proliferation and horizontal differentiation by imitative brand name products, well before patent expiry. Our
work confirms that that systems that rely on administered prices have tended to stifle price competition, to protect less efficient
companies, and to encourage strategies of incremental innovation and imitation.Fabio Pammollif.pammolli@imtlucca.itLaura MagazziniLuigi Orsenigo2011-06-30T14:23:48Z2011-08-31T14:40:39Zhttp://eprints.imtlucca.it/id/eprint/668This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/6682011-06-30T14:23:48ZTechnological Regimes and the Growth of Networks: An Empirical AnalysisThis paper shows how specific technological
and relational regimes have shaped the growth of the network
of R&D collaborative agreements in pharmaceuticals in the
1990s. Our analysis reveals the existence of a complex set of
regimes of firm growth within the network, providing additional
evidence supporting prediction that both growth and
innovative activities of large and small firms respond, even
within a given industry, to considerably different technological
and economic factors. Moreover, the paper shows, in the
context of a specific industry and by means of a series of
preliminary and explorative empirical analyses, that information
on the topological properties of a given industrial settings
and on roles/positions of organizations within it can be used
to disentangle some fundamental generative processes underlying
observed processes of growth. This result contributes
to the “old” stochastic approach to firm growth, in the
direction of building parsimonious and, at the same time, more
realistic, representations of processes of industrial growth.Fabio Pammollif.pammolli@imtlucca.itMassimo Riccabonimassimo.riccaboni@imtlucca.it2011-06-08T13:32:07Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/320This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3202011-06-08T13:32:07ZFormalizing Properties of Mobile Agent SystemsThe wide-spreading of Internet has stimulated the introduction of new programming paradigms and languages that model interactions among hosts by means of mobile agents, and that are centered around the notions of location awareness. In this paper we show how to use formal tools, specifically a modal logic, for formalizing properties for mobile agent systems. We concentrate on one of these new languages, Klaim, and we use it to specify a system that permits maintaining the software installed on several heterogeneous computers distributed over a network by taking advantage of the mobile agent paradigm.Lorenzo BettiniRocco De Nicolar.denicola@imtlucca.itMichele Loreti2011-06-06T09:48:21Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/326This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3262011-06-06T09:48:21ZKlava: a Java package for distributed and mobile applicationsHighly distributed networks have now become a common infrastructure for wide-area distributed applications whose key design principle is network awareness, namely the ability to deal with dynamic changes of the network environment. Network-aware computing has called for new programming languages that exploit the mobility paradigm as a basic interaction mechanism. In this paper we present the architecture of KLAVA, an experimental Java package for distributed applications and code mobility. We describe how KLAVA permits code mobility by relying on Java and present a few distributed applications that exploit mobile code programmed in KLAVA.Lorenzo BettiniRocco De Nicolar.denicola@imtlucca.itRosario Pugliese2011-06-06T09:41:26Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/325This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3252011-06-06T09:41:26ZAn Equational Axiomatization of Bisimulation over Regular ExpressionsWe provide a finite equational axiomatization for bisimulation equivalence of nondeterministic interpretation of regular expressions. Our axiomatization is heavily based on the one by Salomaa, that provided an implicative axiomatization for a large subset of regular expressions, namely all those that satisfy the non‐empty word property (i.e. without 1 summands at the top level) in *‐contexts. Our restriction is similar, it essentially amounts to recursively requiring that the non‐empty word property be satisfied not just at top level but at any depth. We also discuss the impact on the axiomatization of different interpretations of the 0 term, interpreted either as a null process or as a deadlock. Flavio CorradiniRocco De Nicolar.denicola@imtlucca.itAnna Labella2011-06-06T08:53:15Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/322This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3222011-06-06T08:53:15ZSoftware update via mobile agent based programmingWe describe a system that permits maintaining the software installed on several heterogeneous computers distributed over a network by taking advantage of the mobile agent paradigm. The applications are installed and updated only on the central server. When a new release of an application is installed on the server, agents are scattered along the network to update the application on the clients.To build a prototype system we use X-KLAIM, a programming language specifically designed to program distributed systems composed of several components interacting through multiple tuple spaces and mobile code.Lorenzo BettiniRocco De Nicolar.denicola@imtlucca.itMichele Loreti2011-06-06T08:06:32Z2014-10-07T14:45:22Zhttp://eprints.imtlucca.it/id/eprint/328This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3282011-06-06T08:06:32ZXKlaim and Klava: Programming Mobile CodeHighly distributed networks have now become a common infrastructure for a new kind of wide-area distributed applications whose key design principle is network awareness, namely the ability to deal with dynamic changes of the network environment. Network-aware computing has called for new programming languages that exploit the mobility paradigm as the basic interaction mechanism. In this paper we present the Klaim (Kernel Language for Agent Interaction and Mobility) framework for programming mobile code applications, namely the X Klaim programming language and the Java-based run-time system Klava. In particular, we illustrate how Klava handles mobile code. Finally, an example is shown that is implemented using this framework.Lorenzo BettiniRocco De Nicolar.denicola@imtlucca.itRosario Pugliese2011-06-03T14:23:10Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/321This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3212011-06-03T14:23:10ZA Java Middleware for Guaranteeing Privacy of Distributed Tuple SpacesThe tuple space communication model, such as the one used in Linda, provides great flexibility for modeling concurrent, distributed and mobile processes. In a distributed setting with mobile agents, particular attention is needed for protecting sites and information. We have designed and developed a Java middleware, Klava, for implementing distributed tuple spaces and operations to support agent interaction and mobility. In this paper, we extend the Klava middleware with cryptographic primitives that enable encryption and decryption of tuple fields. We describe the actual implementation of the new primitives and provide a few examples. The proposed extension is general enough to be applied to similar Java frameworks using multiple distributed tuples spaces possibly dealing with mobility.Lorenzo BettiniRocco De Nicolar.denicola@imtlucca.it2011-06-01T09:33:19Z2011-07-11T14:36:26Zhttp://eprints.imtlucca.it/id/eprint/324This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3242011-06-01T09:33:19ZTrace and Testing Equivalence on Asynchronous ProcessesWe study trace and may-testing equivalences in the asynchronous versions of CCS and π-calculus. We start from the operational definition of the may-testing preorder and provide finitary and fully abstract trace-based characterizations for it, along with a complete in-equational proof system. We also touch upon two variants of this theory by first considering a more demanding equivalence notion (must-testing) and then a richer version of asynchronous CCS. The results throw light on the difference between synchronous and asynchronous communication and on the weaker testing power of asynchronous observations. Michele BorealeRocco De Nicolar.denicola@imtlucca.itRosario Pugliese2011-05-13T13:07:05Z2011-07-11T14:34:35Zhttp://eprints.imtlucca.it/id/eprint/169This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1692011-05-13T13:07:05ZPartial Order Reduction in Directed Model CheckingPartial order reduction is a very succesful technique for avoiding the state explosion problem that is inherent to explicit state model checking of asynchronous concurrent systems. It exploits the commutativity of concurrently executed transitions in interleaved system runs in order to reduce the size of the explored state space. Directed model checking on the other hand addresses the state explosion problem by using guided search techniques during state space exploration. As a consequence, shorter errors trails are found and less search effort is required than when using standard depth-first or breadth-first search. We analyze how to combine directed model checking with partial order reduction methods and give experimental results on how the combination of both techniques performs.
Alberto Lluch-Lafuentealberto.lluch@imtlucca.itStefan EdelkampStefan Leue2011-03-08T11:04:35Z2011-07-11T14:33:43Zhttp://eprints.imtlucca.it/id/eprint/181This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1812011-03-08T11:04:35ZPi-Calculus Early Observational Equivalence: A First Order Coalgebraic ModelIn this paper, we propose a compositional coalgebraic semantics of the pi-calculus based on a novel approach for lifting calculi with structural axioms to coalgebraic models. We equip the transition system of the calculus with permutations, parallel composition and restriction operations, thus obtaining a bialgebra. No prefix operation is introduced, relying instead on a clause format defining the transitions of recursively defined processes. The unique morphism to the final bialgebra induces a bisimilarity relation which coincides with observational equivalence and which is a congruence with respect to the operations. The permutation algebra is enriched with a name extrusion operator delta a' la De Brujin, that shifts any name to the successor and generates a new name in the first variable. As a consequence, in the axioms and in the SOS rules there is no need to refer to the support, i.e., the set of significant names, and, thus, the model turns out to be first order. Maria Grazia Buscemim.buscemi@imtlucca.itUgo Montanari2011-03-01T10:58:52Z2011-07-11T14:33:43Zhttp://eprints.imtlucca.it/id/eprint/133This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1332011-03-01T10:58:52ZExperimenting with STA, a Tool for Automatic Analysis of Security ProtocolsWe present STA (Symbolic Trace Analyzer). a tool for the analysis
of security protocols. STA relies on symbolic techniques that avoid
explicit construction of the whole, possibly infinite, state-space of
protocols. This results in accurate protocol modeling, increased
efficiency and mere direct formalization, when compared to finitestate
techniques. We illustrate the use of STA by analyzing the
well-known asymmetric Needham Schroeder protocol. We discuss
the results of this analysis, and contrast them with previous work
based on finite-state model checking.Michele BorealeMaria Grazia Buscemim.buscemi@imtlucca.it2011-03-01T10:35:11Z2011-07-11T14:33:43Zhttp://eprints.imtlucca.it/id/eprint/132This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1322011-03-01T10:35:11ZA Framework for the Analysis of Security ProtocolsProperties of security protocols such as authentication and secrecy are often verified by explictly generating an operational model of the protocol and then seeking for insecure states. However, message exchange between the intruder and the honest participants induces a form of state explosion that makes the model infinite in principle. Building on previous work on symbolic semantics, we propose a general framework for automatic analysis of security protocols that make use of a variety of crypto-functions. We start from a base language akin to the spi-calculus, equipped with a set of generic cryptographic primitives. We propose a symbolic operational semantics that relies on unification and provides finite and effective protocol models. Next, we give a method to carry out trace analysis directly on the symbolic model. Under certain conditions on the given cryptographic primitives, our method is proven complete for the considered class of properties.Michele BorealeMaria Grazia Buscemim.buscemi@imtlucca.it2011-03-01T10:28:27Z2011-07-11T14:33:43Zhttp://eprints.imtlucca.it/id/eprint/131This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/1312011-03-01T10:28:27ZA First Order Coalgebraic Model of pi-Calculus Early Observational EquivalenceIn this paper, we propose a compositional coalgebraic semantics of the π-calculus based on a novel approach for lifting calculi with structural axioms to coalgebraic models. We equip the transition system of the calculus with permutations, parallel composition and restriction operations, thus obtaining a bialgebra. No prefix operation is introduced, relying instead on a clause format defining the transitions of recursively defined processes. The unique morphism to the final bialgebra induces a bisimilarity relation which coincides with observational equivalence and which is a congruence with respect to the operations. The permutation algebra is enriched with a name extrusion operator δ à la De Brujin, that shifts any name to the successor and generates a new name in the first variable x 0. As a consequence, in the axioms and in the SOS rules there is no need to refer to the support, i.e., the set of significant names, and, thus, the model turns out to be first order.Maria Grazia Buscemim.buscemi@imtlucca.itUgo Montanari2011-02-15T10:27:38Z2011-07-11T14:24:17Zhttp://eprints.imtlucca.it/id/eprint/70This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/702011-02-15T10:27:38ZThe Positive Power of Negative ThinkingBook reviewed in this article:Science and Scepticism. By John W.N. Watkins.Stefano Gatteistefano.gattei@imtlucca.it2011-02-15T10:27:15Z2011-07-11T14:24:17Zhttp://eprints.imtlucca.it/id/eprint/71This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/712011-02-15T10:27:15ZThe Ethical Nature of Karl Popper's Solution to the Problem of RationalityStefano Gatteistefano.gattei@imtlucca.it