IMT Institutional Repository: No conditions. Results ordered -Date Deposited. 2024-03-29T07:28:20ZEPrintshttp://eprints.imtlucca.it/images/logowhite.pnghttp://eprints.imtlucca.it/2018-03-28T13:20:52Z2018-03-28T13:20:52Zhttp://eprints.imtlucca.it/id/eprint/4065This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40652018-03-28T13:20:52ZPartitioned coupling of advection–diffusion–reaction systems and Brinkman flowsWe present a partitioned algorithm aimed at extending the capabilities of existing solvers for the simulation of coupled advection–diffusion–reaction systems and incompressible, viscous flow. The space discretisation of the governing equations is based on mixed finite element methods defined on unstructured meshes, whereas the time integration hinges on an operator splitting strategy that exploits the differences in scales between the reaction, advection, and diffusion processes, considering the global system as a number of sequentially linked sets of partial differential, and algebraic equations. The flow solver presents the advantage that all unknowns in the system (here vorticity, velocity, and pressure) can be fully decoupled and thus turn the overall scheme very attractive from the computational perspective. The robustness of the proposed method is illustrated with a series of numerical tests in 2D and 3D, relevant in the modelling of bacterial bioconvection and Boussinesq systems.Pietro LenardaMarco Paggimarco.paggi@imtlucca.itR. Ruiz Baier2018-03-12T11:03:10Z2018-03-12T11:03:10Zhttp://eprints.imtlucca.it/id/eprint/4004This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40042018-03-12T11:03:10ZA Periodic Tracking MPC that is Locally Equivalent to Periodic Economic MPCStability for economic Model Predictive Control (MPC) is in general difficult to establish. In contrast, tracking MPC has well-established stability guarantees, but can yield poor closed-loop performance in terms of the selected economic criterion. In Zanon et al. (2016), a formal procedure to design a tracking MPC scheme so as to locally approximate the behaviour of economic MPC was proposed for the case of optimal steady-state operation. In this paper, we extend that result to the periodic case and provide a procedure to compute the tracking stage cost numerically. We illustrate our developments in a simulated example.Mario Zanonmario.zanon@imtlucca.itSébastien GrosMoritz Diehl2018-03-12T09:18:45Z2018-03-12T09:18:45Zhttp://eprints.imtlucca.it/id/eprint/4009This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40092018-03-12T09:18:45ZDirect Optimal Control and Model Predictive ControlMario Zanonmario.zanon@imtlucca.itAndrea BocciaVryan Gil S. PalmaSonja ParentiIlaria Xausa2018-03-09T14:12:55Z2018-03-09T14:12:55Zhttp://eprints.imtlucca.it/id/eprint/4008This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40082018-03-09T14:12:55ZA Sparsity Preserving Convexification Procedure for Indefinite Quadratic Programs Arising in Direct Optimal ControlQuadratic programs (QP) with an indefinite Hessian matrix arise naturally in some direct optimal control methods, e.g., as subproblems in a sequential quadratic programming scheme. Typically, the Hessian is approximated with a positive definite matrix to ensure having a unique solution; such a procedure is called regularization. We present a novel regularization method tailored for QPs with optimal control structure. Our approach exhibits three main advantages. First, when the QP satisfies a second order sufficient condition for optimality, the primal solution of the original and the regularized problem are equal. In addition, the algorithm recovers the dual solution in a convenient way. Second, and more importantly, the regularized Hessian bears the same sparsity structure as the original one. This allows for the use of efficient structure-exploiting QP solvers. As a third advantage, the regularization can be performed with a computational complexity that scales linearly in the length of the control horizon. We showcase the properties of our regularization algorithm on a numerical example for nonlinear optimal control. The results are compared to other sparsity preserving regularization methods.
Read More: https://epubs.siam.org/doi/10.1137/16M1081543Robin VerschuerenMario Zanonmario.zanon@imtlucca.itRien QuirynenMoritz Diehl2018-03-09T14:11:50Z2018-03-09T14:11:50Zhttp://eprints.imtlucca.it/id/eprint/4005This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40052018-03-09T14:11:50ZDistributed Algorithm for Optimal Vehicle Coordination at Traffic IntersectionsAutomated vehicle coordination can be used to control vehicles across traffic intersections safely and efficiently. This paper proposes a novel parallelizable algorithm, which solves the coordination problem at traffic intersections under a given precedence order by using a tailored variant of the augmented Lagrangian based alternating direction inexact Newton method (ALADIN). Here, each vehicle solves its own optimal control problem and exchanges information about arrivial and departure times at the intersection with its neighbors such that collisions are avoided. We illustrate the performance of ALADIN by analyzing two scenarios, one during rush hour and one at low-traffic conditions.Yuning JiangMario Zanonmario.zanon@imtlucca.itRobert HultBoris Houska2018-03-09T14:09:34Z2018-03-09T14:09:34Zhttp://eprints.imtlucca.it/id/eprint/4006This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40062018-03-09T14:09:34ZPeriodic Optimal Control, Dissipativity and MPCRecent research has established the importance of (strict) dissipativity for proving stability of economic MPC in the case of an optimal steady state. In many cases, though, steady-state operation is not economically optimal and periodic operation of the system yields a better performance. In this technical note, we propose ways of extending the notion of (strict) dissipativity for periodic systems. We prove that optimal P-periodic operation and MPC stability directly follow, similarly to the steady-state case, which can be seen as a special case of the proposed framework. Finally, we illustrate the theoretical results with several simple examples.Mario Zanonmario.zanon@imtlucca.itLars GruneMoritz Diehl2018-03-09T14:07:48Z2018-03-09T14:07:48Zhttp://eprints.imtlucca.it/id/eprint/4001This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40012018-03-09T14:07:48ZNumerical Optimal Control with Periodicity Constraints in the Presence of InvariantsPeriodic optimal control problems (POCPs) based on dynamic models holding invariants are often problematic to treat using standard numerical methods. The difficulty stems from a failure of standard constraint qualifications and typically hinders the convergence of the numerical solver, or even defeats it. Optimisation problems having weak constraint qualifications can be treated using dedicated solvers, at the price of a more involved algorithmic. In this paper, we analyse the constraint qualification of POCPs holding invariants, and propose three simple and computationally inexpensive modifications of the formulation that allow for a recovery of Linear Independence Constraint Qualification (LICQ), while not affecting the Second-Order Sufficient Conditions (SOSC) for optimality. Hence, the resulting POCP can be tackled via standard solvers, without special treatment. The application of these approaches is detailed for the case of POCPs holding index-reduced Differential-Algebraic Equations and representations of the SO(3) Lie group.Sebastien GrosMario Zanonmario.zanon@imtlucca.it2018-03-09T14:06:33Z2018-03-09T14:06:33Zhttp://eprints.imtlucca.it/id/eprint/4002This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40022018-03-09T14:06:33ZPenalty Functions for Handling Large Deviation of Quadrature States in NMPCSebastien GrosMario Zanonmario.zanon@imtlucca.it2018-03-09T14:05:19Z2018-03-09T14:05:19Zhttp://eprints.imtlucca.it/id/eprint/4000This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40002018-03-09T14:05:19ZDay-ahead scheduling and real-time Economic MPC of CHP unit in Microgrid with Smart buildingsThis paper presents a model for day-ahead scheduling of the CHP heat and electric energy production for a residential Microgrid taking into account the economic factors in a liberalized electricity markets, the technical factors in the safety/quality of supply, and the consumer preferences. This day-ahead scheduling model is complemented with a real-time economic MPC model for a subsequent control with respect to the outcomes of the day-ahead scheduling. This combined scheduling and economic MPC provides a general set-up capable of overcoming several major difficulties encountered with a typical scheduling + tracking MPC set-up, e.g. the problems of connecting the economic objectives with different temporal resolution and different requirements in terms of delivery.Josip VasiljSebastien GrosDamir JakusMario Zanonmario.zanon@imtlucca.it2018-03-09T14:01:44Z2018-03-09T14:03:11Zhttp://eprints.imtlucca.it/id/eprint/4003This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/40032018-03-09T14:01:44ZAn Asynchronous Algorithm for Optimal Vehicle Coordination at Traffic IntersectionsMario Zanonmario.zanon@imtlucca.itSébastien GrosHenk WymeerschPaolo Falcone2018-03-05T16:26:29Z2018-03-05T16:26:29Zhttp://eprints.imtlucca.it/id/eprint/3952This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39522018-03-05T16:26:29ZInitial Algebra for a System of Right-Linear FunctorsIn 2003 we showed that right-linear systems of equations over regular expressions, when interpreted in a category of trees, have a solution whenever they enjoy a specific property that we called hierarchicity and that is instrumental to avoid critical mutual recursive definitions. In this note, we prove that a right-linear system of polynomial endofunctors on a cocartesian monoidal closed category which enjoys parameterized left list arithmeticity, has an initial algebra, provided it satisfies a property similar to hierarchicity.Anna LabellaRocco De Nicolar.denicola@imtlucca.it2018-03-05T16:19:42Z2018-03-05T16:20:14Zhttp://eprints.imtlucca.it/id/eprint/3951This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39512018-03-05T16:19:42ZVerifying Properties of Systems Relying on Attribute-Based CommunicationAbC is a process calculus designed for describing collective adaptive systems, whose distinguishing feature is the communication mechanism relying on predicates over attributes exposed by components. A novel approach to the analysis of concurrent systems modelled as AbC terms is presented that relies on the UMC model checker, a tool based on modelling concurrent systems as communicating UML-like state machines. A structural translation from AbC specifications to the UMC internal format is provided and used as the basis for the analysis. Three different algorithmic solutions of the well studied stable marriage problem are described in AbC and their translations are analysed with UMC. It is shown how the proposed approach can be exploited to identify emerging properties of systems and unwanted behaviour.Rocco De Nicolar.denicola@imtlucca.itTan DuongOmar InversoFranco Mazzanti2018-03-05T16:14:42Z2018-03-05T16:14:42Zhttp://eprints.imtlucca.it/id/eprint/3950This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39502018-03-05T16:14:42ZAErlang at WorkAErlang is an extension of the Erlang programming language which is enriched with attribute-based communication. In AErlang, the Erlang send and receive constructs are extended to permit partner selection by relying on predicates over set of attributes. AErlang avoids the limitations of the Erlang point-to-point communication making it possible to model some of the sophisticated interaction features often observed in modern systems, such as anonymity and adaptation. By using our prototype extension, we show how the extended communication pattern can capture non-trivial process interaction in a natural and intuitive way. We also sketch a modelling technique aimed at automatically verifying AErlang systems, and discuss how it can be used to check some key properties of the considered case study.Rocco De NicolaTan DuongOmar InversoCatia Trubiani2018-03-05T16:07:40Z2018-03-05T16:07:40Zhttp://eprints.imtlucca.it/id/eprint/3949This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39492018-03-05T16:07:40ZAErlang: Empowering Erlang with Attribute-Based CommunicationAttribute-based communication provides a novel mechanism to dynamically select groups of communicating entities by relying on predicates over their exposed attributes. In this paper, we embed the basic primitives for attribute-based communication into the functional concurrent language Erlang to obtain what we call AErlang, for attribute Erlang. To evaluate our prototype in terms of performance overhead and scalability we consider solutions of the Stable Marriage Problem based on predicates over attributes and on the classical preference lists, and use them to compare the runtime performance of AErlang with those of Erlang and X10. The outcome of the comparison shows that the overhead introduced by the new communication primitives is acceptable, and our prototype can compete performance-wise with an ad-hoc parallel solution in X10.Rocco De Nicolar.denicola@imtlucca.itTan DuongOmar InversoCatia Trubiani2018-03-05T16:02:13Z2018-03-05T16:02:13Zhttp://eprints.imtlucca.it/id/eprint/3948This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39482018-03-05T16:02:13ZSmart Contract Negotiation in Cloud ComputingA smart contract is the formalisation of an agreement, whose terms are automatically enforced by relying on a transaction protocol, while minimising the need of intermediaries. Such contracts not only specify the service and its quality but also the possible changes at runtime of the terms of agreement. Although smart contracts provide a great deal of flexibility, analysing their compatibility and reaching agreements with this level of dynamism is considerably more challenging, due to the freedom of clients and providers in formulating needs/offers. We introduce a formal language to specify interactions between offers and requests and present a methodology for the autonomous negotiation of smart contracts, which analyses the cost and the necessary changes for reaching an agreement. Moreover, we describe a set of experiments that provides insights on the relative cost of dynamism in negotiating smart contracts and compare the request/offer matching rates of our solution with related works.Scoca VincenzoRafael Brundo UriarteRocco De Nicolar.denicola@imtlucca.it2018-03-05T15:57:39Z2018-03-05T15:57:39Zhttp://eprints.imtlucca.it/id/eprint/3947This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39472018-03-05T15:57:39ZP3445Correlation between vascular age and surrogate markers of atherosclerosis and vascular agingBackground: The evaluation of Vascular Age, according to the definition given using the cardiovascular risk score tables, is a method of estimating individual cardiovascular risk, which may represent a new therapeutic target for physicians. However, the association of Vascular Age with surrogate markers of atherosclerosis and vascular aging, able to identify vascular alterations at the sub-clinical, asymptomatic stages, has not been determined yet.R. Di StefanoFarshad ShamsL. GhiadoniE. ImbalzanoM. NutiS. TaddeiRocco De Nicolar.denicola@imtlucca.it2018-03-05T15:44:57Z2018-03-05T15:44:57Zhttp://eprints.imtlucca.it/id/eprint/3946This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39462018-03-05T15:44:57ZProgramming the Interactions of Collective Adaptive Systems by Relying on Attribute-based CommunicationCollective adaptive systems are new emerging computational systems consisting of a large number of interacting components and featuring complex behaviour. These systems are usually distributed, heterogeneous, decentralised and interdependent, and are operating in dynamic and possibly unpredictable environments. Finding ways to understand and design these systems and, most of all, to model the interactions of their components, is a difficult but important endeavour. In this article we propose a language-based approach for programming the interactions of collective-adaptive systems by relying on attribute-based communication; a paradigm that permits a group of partners to communicate by considering their run-time properties and capabilities. We introduce AbC, a foundational calculus for attribute-based communication and show how its linguistic primitives can be used to program a complex and sophisticated variant of the well-known problem of Stable Allocation in Content Delivery Networks. Also other interesting case studies, from the realm of collective-adaptive systems, are considered. We also illustrate the expressive power of attribute-based communication by showing the natural encoding of other existing communication paradigms into AbC.Yehia Moustafa Abd Alrahmanyehia.abdalrahman@imtlucca.itRocco De Nicolar.denicola@imtlucca.itMichele Loreti2018-03-05T15:40:55Z2018-03-05T15:40:55Zhttp://eprints.imtlucca.it/id/eprint/3945This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/39452018-03-05T15:40:55ZA Behavioural Theory for Interactions in Collective-Adaptive SystemsWe propose a process calculus, named AbC, to study the behavioural theory of interactions in collective-adaptive systems by relying on attribute-based communication. An AbC system consists of a set of parallel components each of which is equipped with a set of attributes. Communication takes place in an implicit multicast fashion, and interaction among components is dynamically established by taking into account "connections" as determined by predicates over their attributes. The structural operational semantics of AbC is based on Labeled Transition Systems that are also used to define bisimilarity between components. Labeled bisimilarity is in full agreement with a barbed congruence, defined by simple basic observables and context closure. The introduced equivalence is used to study the expressiveness of AbC in terms of encoding broadcast channel-based interactions and to establish formal relationships between system descriptions at different levels of abstraction.Yehia Moustafa Abd Alrahmanyehia.abdalrahman@imtlucca.itRocco De Nicolar.denicola@imtlucca.itMichele Loreti2018-01-16T10:10:51Z2018-01-16T10:10:51Zhttp://eprints.imtlucca.it/id/eprint/3862This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38622018-01-16T10:10:51ZMulti-parametric sensitivity analysis of the band structure for tetrachiral acoustic metamaterialsTetrachiral materials are characterized by a cellular microstructure made by a periodic pattern of stiff rings and flexible ligaments. Their mechanical behaviour can be described by a planar lattice of rigid massive bodies and elastic massless beams. The periodic cell dynamics is governed by a monoatomic structural model, conveniently reduced to the only active degrees-of-freedom. The paper presents an explicit parametric description of the band structure governing the free propagation of elastic waves. By virtue of multiparametric perturbation techniques, sensitivity analyses are performed to achieve an analytical asymptotic approximation of the dispersion functions. The parametric conditions for the existence of full band gaps in the low-frequency range are established. Furthermore, the band gap amplitude is analytically assessed in the admissible parameter range. In tetrachiral acoustic metamaterials, stop bands can be opened by the introduction of intra-ring resonators. Perturbation methods can efficiently deal with the consequent enlargement of the mechanical parameter space. Indeed high-accuracy parametric approximations are achieved for the band structure, enriched by the new optical branches related to the resonator frequencies. In particular, target stop bands in the metamaterial spectrum are analytically designed through the asymptotic solution of inverse spectral problems.Marco LepidiAndrea Bacigalupoandrea.bacigalupo@imtlucca.it2018-01-15T08:04:11Z2018-01-15T08:04:11Zhttp://eprints.imtlucca.it/id/eprint/3857This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38572018-01-15T08:04:11ZSpatio-Temporal Patterns of the International Merger and Acquisition NetworkThis paper analyses the world web of mergers and acquisitions (M&As) using a complex network approach. We use data of
M&As to build a temporal sequence of binary and weighted-directed networks for the period 1995-2010 and 224 countries
(nodes) connected according to their M&As flows (links). We study different geographical and temporal aspects of the international
M&A network (IMAN), building sequences of filtered sub-networks whose links belong to specific intervals of distance
or time. Given that M&As and trade are complementary ways of reaching foreign markets, we perform our analysis using
statistics employed for the study of the international trade network (ITN), highlighting the similarities and differences between
the ITN and the IMAN. In contrast to the ITN, the IMAN is a low density network characterized by a persistent giant component
with many external nodes and low reciprocity. Clustering patterns are very heterogeneous and dynamic. High-income
economies are the main acquirers and are characterized by high connectivity, implying that most countries are targets of a few
acquirers. Like in the ITN, geographical distance strongly impacts the structure of the IMAN: link-weights and node degrees
have a non-linear relation with distance, and an assortative pattern is present at short distances.Marco DuenasRossana Mastrandrearossana.mastrandrea@imtlucca.itMatteo BarigozziGiorgio Fagiolo2017-12-28T11:22:45Z2018-01-08T12:39:09Zhttp://eprints.imtlucca.it/id/eprint/3854This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38542017-12-28T11:22:45ZNuove sinergie per la gestione musealeThe article analyses the essential cooperation of public bodies and private operators for the management of museums in different juridical contexts. Moving from the actual legal and institutional environment, the author introduces a comparison between the Italian and British management models in order to recommend an evolution in the national museum management perspective. The analysis is developed through the study of practical cases, such as the comparison between the National Gallery in London and La Galleria Nazionale in Rome which clearly describes the distance between the two national institutional systems and their approach to private bodies. Moreover, thanks to the example offered by the Community Foundations instrument, the article means to express a serious need for Italian museums to be considered and regulated as a common good which asks the whole national community for a firm cooperation.Alice Laboralice.labor@imtlucca.it2017-12-28T10:55:54Z2017-12-28T10:55:54Zhttp://eprints.imtlucca.it/id/eprint/3850This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38502017-12-28T10:55:54ZHeart rate variability analysis during muscle fatigue due to prolonged isometric contractionSummary form only given. Strong light-matter coupling has been recently successfully explored in the GHz and THz 1 range with on-chip platforms. New and intriguing quantum optical phenomena have been predicted in the ultrastrong coupling regime 2, when the coupling strength Ω becomes comparable to the unperturbed frequency of the system ω. We recently proposed a new experimental platform where we couple the inter-Landau level transition of an high-mobility 2DEG to the highly subwavelength photonic mode of an LC meta-atom 3 showing very large Ω/ωc = 0.87. Our system benefits from the collective enhancement of the light-matter coupling which comes from the scaling of the coupling Ω ∝ √n, were n is the number of optically active electrons. In our previous experiments 3 and in literature 4 this number varies from 104-103 electrons per meta-atom. We now engineer a new cavity, resonant at 290 GHz, with an extremely reduced effective mode surface Seff = 4 × 10-14 m2 (FE simulations, CST), yielding large field enhancements above 1500 and allowing to enter the few (<;100) electron regime. It consist of a complementary metasurface with two very sharp metallic tips separated by a 60 nm gap (Fig.1(a, b)) on top of a single triangular quantum well. THz-TDS transmission experiments as a function of the applied magnetic field reveal strong anticrossing of the cavity mode with linear cyclotron dispersion. Measurements for arrays of only 12 cavities are reported in Fig.1(c). On the top horizontal axis we report the number of electrons occupying the topmost Landau level as a function of the magnetic field. At the anticrossing field of B=0.73 T we measure approximately 60 electrons ultra strongly coupled (Ω/ω- ||A. GuidiA. GrecoF. FeliciA. LeoEmiliano Ricciardiemiliano.ricciardi@imtlucca.itM. BianchiA. BicchiG. ValenzaE. P. Scilingo2017-12-28T10:50:23Z2017-12-28T10:50:23Zhttp://eprints.imtlucca.it/id/eprint/3849This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38492017-12-28T10:50:23ZA magnetic compatible supernumerary robotic finger for functional magnetic resonance imaging (fMRI) acquisitions: Device description and preliminary resultsSummary form only given. Strong light-matter coupling has been recently successfully explored in the GHz and THz 1 range with on-chip platforms. New and intriguing quantum optical phenomena have been predicted in the ultrastrong coupling regime 2, when the coupling strength Ω becomes comparable to the unperturbed frequency of the system ω. We recently proposed a new experimental platform where we couple the inter-Landau level transition of an high-mobility 2DEG to the highly subwavelength photonic mode of an LC meta-atom 3 showing very large Ω/ωc = 0.87. Our system benefits from the collective enhancement of the light-matter coupling which comes from the scaling of the coupling Ω ∝ √n, were n is the number of optically active electrons. In our previous experiments 3 and in literature 4 this number varies from 104-103 electrons per meta-atom. We now engineer a new cavity, resonant at 290 GHz, with an extremely reduced effective mode surface Seff = 4 × 10-14 m2 (FE simulations, CST), yielding large field enhancements above 1500 and allowing to enter the few (<;100) electron regime. It consist of a complementary metasurface with two very sharp metallic tips separated by a 60 nm gap (Fig.1(a, b)) on top of a single triangular quantum well. THz-TDS transmission experiments as a function of the applied magnetic field reveal strong anticrossing of the cavity mode with linear cyclotron dispersion. Measurements for arrays of only 12 cavities are reported in Fig.1(c). On the top horizontal axis we report the number of electrons occupying the topmost Landau level as a function of the magnetic field. At the anticrossing field of B=0.73 T we measure approximately 60 electrons ultra strongly coupled (Ω/ω- ||Irfan HussainEmiliano SantarnecchiAndrea LeoEmiliano Ricciardiemiliano.ricciardi@imtlucca.itSimone RossiDomenico Prattichizzo2017-12-28T10:39:05Z2017-12-28T10:39:05Zhttp://eprints.imtlucca.it/id/eprint/3847This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38472017-12-28T10:39:05ZDifferent levels of visual perceptual skills are associated with specific modifications in functional connectivity and global efficiencyThe disembedding ability (i.e., the ability to identify a simple masked figure within a complex one) depends on attentional mechanisms, executive functions and working memory. Recent cognitive models ascribed different levels of disembedding task performance to the efficiency of the subtended mental processes engaged during visuo-spatial perception.
Here we aimed at assessing whether different levels of the disembedding ability were associated to the functional signatures of neural efficiency, defined as a specific modulation in response magnitude and functional connectivity strength in task-related areas. Consequently, brain activity evoked by a visual task involving the disembedding ability was acquired using functional magnetic resonance imaging (fMRI) in a sample of 23 right-handed healthy individuals. Brain activity was analyzed at different levels of information processing, from local responses to connectivity interactions between brain nodes, as far as to network topological properties.
All different levels of information processing were significantly modulated by individual behavioral performance. Specifically, single voxel response magnitude, connectivity strength of the right intrahemispheric and interhemispheric edges, and graph measures (i.e., local and global efficiency) were negatively associated to behavioral performance. Altogether, these results indicate that efficiency during a disembedding task cannot be merely attributed to a reduced neural recruitment of task-specific regions, but can be better characterized as an enhanced functional hemispherical asymmetry.Sabrina DantiGiacomo HandjarasLuca Cecchettiluca.cecchetti@imtlucca.itHelen Beuzeron-ManginaPietro Pietrinipietro.pietrini@imtlucca.itEmiliano Ricciardiemiliano.ricciardi@imtlucca.it2017-12-28T10:32:23Z2017-12-28T10:32:23Zhttp://eprints.imtlucca.it/id/eprint/3846This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38462017-12-28T10:32:23ZFunctional and spatial segregation within the inferior frontal and superior temporal cortices during listening, articulation imagery, and production of vowelsAlessandra Cecilia Rampininialessandra.rampinini@imtlucca.itGiacomo HandjarasAndrea LeoLuca Cecchettiluca.cecchetti@imtlucca.itEmiliano Ricciardiemiliano.ricciardi@imtlucca.itGiovanna MarottaPietro Pietrinipietro.pietrini@imtlucca.it2017-12-28T10:29:31Z2017-12-28T10:29:31Zhttp://eprints.imtlucca.it/id/eprint/3845This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38452017-12-28T10:29:31ZPeripersonal space representation develops independently from visual experienceOur daily-life actions are typically driven by vision. When acting upon an object, we need to represent its visual features (e.g. shape, orientation, etc.) and to map them into our own peripersonal space. But what happens with people who have never had any visual experience? How can they map object features into their own peripersonal space? Do they do it differently from sighted agents? To tackle these questions, we carried out a series of behavioral experiments in sighted and congenitally blind subjects. We took advantage of a spatial alignment effect paradigm, which typically refers to a decrease of reaction times when subjects perform an action (e.g., a reach-to-grasp pantomime) congruent with that afforded by a presented object. To systematically examine peripersonal space mapping, we presented visual or auditory affording objects both within and outside subjects’ reach. The results showed that sighted and congenitally blind subjects did not differ in mapping objects into their own peripersonal space. Strikingly, this mapping occurred also when objects were presented outside subjects’ reach, but within the peripersonal space of another agent. This suggests that (the lack of) visual experience does not significantly affect the development of both one’s own and others’ peripersonal space representation.Emiliano Ricciardiemiliano.ricciardi@imtlucca.itDario MenicagliAndrea LeoMarcello CostantiniPietro Pietrinipietro.pietrini@imtlucca.itCorrado Sinigaglia2017-12-13T16:15:22Z2017-12-13T16:15:22Zhttp://eprints.imtlucca.it/id/eprint/3844This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38442017-12-13T16:15:22ZPersonal Identity and Head Transplant: A Psychological AnalysisGiulia Avvenutigiulia.avvenuti@imtlucca.it2017-11-29T13:25:40Z2017-11-29T13:25:40Zhttp://eprints.imtlucca.it/id/eprint/3841This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38412017-11-29T13:25:40ZCausally consistent reversible choreographies: a monitors-as-memories approachUnder a reversible semantics, computation steps can be undone. This paper addresses the integration of reversible semantics into a process model of multiparty protocols (choreographies). Building upon the monitors-as-memories approach that we developed in prior work for reversible binary protocols, we present a reversible process framework for multiparty communication, which improves on prior models by seamlessly integrating asynchrony, decoupled rollbacks, and process passing. As main technical result, we prove that our multiparty, reversible semantics is causally-consistent.Claudio Antares Mezzinaclaudio.mezzina@imtlucca.itJorge A. Pérez2017-11-15T11:21:01Z2017-11-29T08:50:22Zhttp://eprints.imtlucca.it/id/eprint/3828This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38282017-11-15T11:21:01ZBiomimetic and bioinspired nanoparticles for targeted drug deliveryIn drug targeting, the urgent need for more effective and less iatrogenic therapies is pushing toward a complete revision of carrier setup. After the era of ‘articles used as homing systems’, novel prototypes are now emerging. Newly conceived carriers are endowed with better biocompatibility, biodistribution and targeting properties. The biomimetic approach bestows such improved functional properties. Exploiting biological molecules, organisms and cells, or taking inspiration from them, drug vector performances are now rapidly progressing toward the perfect carrier. Following this direction, researchers have refined carrier properties, achieving significant results. The present review summarizes recent advances in biomimetic and bioinspired drug vectors, derived from biologicals or obtained by processing synthetic materials with a biomimetic approachMariacristina Gagliardimariacristina.gagliardi@imtlucca.it2017-10-31T09:00:18Z2017-10-31T09:00:18Zhttp://eprints.imtlucca.it/id/eprint/3806This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38062017-10-31T09:00:18ZLong-term EVA degradation simulation: climatic zones comparison and possible revision of accelerated testsMariacristina Gagliardimariacristina.gagliardi@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-10-31T08:58:09Z2017-11-29T09:46:34Zhttp://eprints.imtlucca.it/id/eprint/3824This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38242017-10-31T08:58:09ZRecent Advances in Preclinical Studies and Potential Applications of Dendrimers as Drug Carriers in the Central Nervous SystemBackground: The brain is a well-protected organ, with a complex system of cells, proteins and transporters, that acts as a sentinel to prevent potentially harmful substances from entering the brain, stopping also active molecules administered with a therapeutic goal. Although their limited exploitation, dendrimers are currently under evaluation as drug vectors to improve pharmacological treatments, targeting active molecules across the blood-brain barrier and penetrating brain tissues.
Methods: Up to date, only three different families of dendrimers, poly(amidoamine)-, poly(propyleneimine)- and poly(L-lysine)-based, have found application as drug transporters in the Central Nervous System. Their development, functionalization and characterization are reported in the literature, with interesting preliminary outcomes in the treatment of brain disorders. Surface functionalization also affects the interaction between dendrimers and cells or tissues, with effects not only on penetration and retention, but also on the safety profile of this drug carrier.
Conclusion: This review focuses on the application of dendrimers in the field of targeted drug delivery toward the Central Nervous System, highlighting their interesting properties. Discussion will be promising and represent an important starting point for a further diffusion of dendrimers in pharmacological treatment of the Central Nervous System.Mariacristina Gagliardimariacristina.gagliardi@imtlucca.it2017-10-31T08:52:42Z2017-11-29T12:57:03Zhttp://eprints.imtlucca.it/id/eprint/3823This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38232017-10-31T08:52:42ZTime-and Solvent-Dependent Self-Assembly of Photochromic CrystallitesMolecular self-assembly provides complex structures and enables the tuning of system features on the nanoscale. Guided assembly, induced by external stimuli, gives hierarchical but static arrangements, limiting the exploitation in several fields. A dynamic arrangement can confer improved and smarter properties, but adaptive self-assembly requires new molecules and the knowledge of kinetics effects. The interest in adaptive self-assembly is constantly growing and comprises environmental-, chemical-, and field-adaptive molecules. Thus reversible adaptive self-assembly systems, which can be build and destroyed for several times, attract large attention. To contribute in this field, we report the particular post-solvato-control on solid habit morphology of the vinyl-terminated spiropyran derivative named 1-(5-hexenyl)-3,3-dimethyl-6′-nitro-1,3-dihydrospiro[2H-indole-2,2′-[2H][1]benzopyran. For this molecule, the formation of supramolecular structures is solvent- and time-governed and exhibited reversible isomerization upon UV irradiation. We observed different solid habits by varying solvent polarity as well as an increasing degree of arrangement with time. Light-induced precipitation in nonpolar solvent afforded spherical merocyanine aggregates under mild conditions. This example of kinetics-controlled photochromic system has the potential to drive toward adaptive and dynamic self-assembly systems, with application in material science and for polymer functionalization.Mariacristina Gagliardimariacristina.gagliardi@imtlucca.itFrancesca PignatelliVirgilio Mattoli2017-09-28T06:31:59Z2017-09-28T06:31:59Zhttp://eprints.imtlucca.it/id/eprint/3805This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38052017-09-28T06:31:59ZExperimental characterization and numerical simulation of humidity-induced damage in PV cellsMariacristina Gagliardimariacristina.gagliardi@imtlucca.itIrene Berardoneirene.berardone@polito.itMarco Paggimarco.paggi@imtlucca.it2017-09-28T06:29:05Z2017-09-28T06:29:05Zhttp://eprints.imtlucca.it/id/eprint/3811This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38112017-09-28T06:29:05ZEvolution of fatigue damage in flexible photovoltaic modulesClaudia Borriclaudia.borri@imtlucca.itMariacristina Gagliardimariacristina.gagliardi@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-09-28T06:24:42Z2017-09-28T06:32:17Zhttp://eprints.imtlucca.it/id/eprint/3804This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38042017-09-28T06:24:42ZComputational and experimental characterization of thermo-oxidative and corrosion phenomena in photovoltaic modulesIrene Berardoneirene.berardone@polito.itMariacristina Gagliardimariacristina.gagliardi@imtlucca.itPietro Lenardapietro.lenarda@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-09-26T09:19:39Z2017-09-26T09:19:39Zhttp://eprints.imtlucca.it/id/eprint/3765This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37652017-09-26T09:19:39ZEGAC: a genetic algorithm to compare chemical reaction networksDiscovering relations between chemical reaction networks (CRNs)
is a relevant problem in computational systems biology for model
reduction, to explain if a given system can be seen as an abstraction
of another one; and for model comparison, useful to establish an evolutionary
path from simpler networks to more complex ones. This
is also related to foundational issues in computer science regarding
program equivalence, in light of the established interpretation of a
CRN as a kernel programming language for concurrency. Criteria
for deciding if two CRNs can be formally related have been recently
developed, but these require that a candidate mapping be provided.
Automatically finding candidate mappings is very hard in general
since the search space essentially consists of all possible partitions
of a set. In this paper we tackle this problem by developing a genetic
algorithm for a class of CRNs called influence networks, which can
be used to model a variety of biological systems including cell-cycle
switches and gene networks. An extensive numerical evaluation
shows that our approach can successfully establish relations between
influence networks from the literature which cannot be found
by exact algorithms due to their large computational requirements.Stefano TognazziMirco Tribastonemirco.tribastone@imtlucca.itMax Tschaikowskimax.tschaikowski@imtlucca.itAndrea Vandinandrea.vandin@imtlucca.it2017-09-26T08:00:27Z2017-09-26T08:00:27Zhttp://eprints.imtlucca.it/id/eprint/3797This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37972017-09-26T08:00:27ZPhase field modelling of brittle fracture for enhanced assumed strain shells at large deformations: formulation and finite element implementationFracture of technological thin-walled components
can notably limit the performance of their corresponding
engineering systems. With the aim of achieving reliable
fracture predictions of thin structures, this work presents a new phase field model of brittle fracture for large deformation analysis of shells relying on a mixed enhanced assumed strain (EAS) formulation. The kinematic description of the shell body is constructed according to the solid shell concept. This enables the use of fully three-dimensional constitutive models for the material. The proposed phase field formulation integrates the use of the (EAS) method to alleviate locking pathologies, especially Poisson thickness and volumetric locking. This technique is further combined with the assumed natural strain method to efficiently derive a locking-free solid shell element. On the computational side, a fully coupled monolithic framework is consistently formulated.
Specific details regarding the corresponding finite
element formulation and the main aspects associated with
its implementation in the general purpose packages FEAP
and ABAQUS are addressed. Finally, the applicability of the current strategy is demonstrated through several numerical examples involving different loading conditions, and including linear and nonlinear hyperelastic constitutive models.José ReinosoMarco Paggimarco.paggi@imtlucca.itChristian Linder2017-09-26T07:59:20Z2017-09-26T07:59:20Zhttp://eprints.imtlucca.it/id/eprint/3798This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37982017-09-26T07:59:20ZRevisiting the problem of a crack impinging on an interface: a modeling framework for the interaction between the phase field approach for brittle fracture and the interface cohesive zone modelThe problem of a crack impinging on an interface has been thoroughly investigated in the last three decades due to its important role in the mechanics and physics of solids. In the current investigation, this problem is revisited in view of the recent progresses on the phase field approach of brittle fracture. In this concern, a novel formulation combining the phase field approach for modeling
brittle fracture in the bulk and a cohesive zone model for pre-existing adhesive interfaces is herein proposed to investigate the competition between crack penetration and deflection at an interface. The model, implemented within the finite element method framework using a monolithic fully implicit solution strategy, is applied to provide a further insight into the understanding of the role of model parameters on the above competition. In particular, in this study, the role of the fracture toughness ratio between the interface and the adjoining bulks and of the characteristic fracture-length scales of the dissipative models is analyzed. In the case of a brittle interface, the asymptotic predictions based on linear elastic fracture mechanics criteria for crack penetration, single
deflection or double deflection are fully captured by the present method. Moreover, by increasing the size of the process zone along the interface, or by varying the internal length scale of the phase field model, new complex phenomena are emerging, such as simultaneous crack penetration and deflection and the transition from single crack penetration to deflection and penetration with
subsequent branching into the bulk. The obtained computational trends are in very good agreement with previous experimental observations and the theoretical considerations on the competition and interplay between both fracture mechanics models open new research perspectives for the simulation and understanding of complex fracture patterns.Marco Paggimarco.paggi@imtlucca.itJosé Reinoso2017-09-26T07:57:29Z2017-09-26T07:57:29Zhttp://eprints.imtlucca.it/id/eprint/3799This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37992017-09-26T07:57:29ZA nonlocal adaptive discrete empirical interpolation method combined with modified hp-refinement for order reduction of molecular dynamics systemsModel order reduction is an emerging technique to tackle the computational complexities of molecular
dynamics (MD) simulations. Different strategies are required to adequately obtain the reduced solutions
of different classes of molecular dynamics systems. In this work, a proper orthogonal decomposition
(POD) is combined with the discrete empirical interpolation method (DEIM) to study atomic systems.
Due to the limitations of the DEIM in capturing the nonlocal response of the nonlinear force field of
MD systems, a nonlocal adaptive discrete empirical interpolation method (ADEIM) is proposed.
Furthermore, a modified hp-refinement algorithm is introduced to extend the application of the PODDEIM
approach to order reduction of multi-dimensional MD systems. In the DEIM, the distance between
atoms and hence the reduced internal force vector is estimated based on a local interpolation of the state
variables. The internal forces of a multi-dimensional MD system depend on the distance between the
atoms, represented in space by more than one coordinate. Therefore, the ADEIM approach seeks to obtain
a nonlocal interpolation of the state variables to accurately predict the distance between the interpolated
atoms and hence the reduced force vector. Simulation of MD systems with frequently changing neighbour
atoms leads to change in the system dynamics, which further leads to change of properties of the
snapshots. Therefore, the temporal domain is adaptively subdivided into smaller sub-domains using
the adopted hp-refinement procedure. The reduced system parameters are effectively derived over the
sub-domains. Considering the computational cost, a modified hp-refinement algorithm is developed in
this study, which is further coupled with the POD-ADEIM approach to obtain the reduced-order solution
of the MD systems. The results of the proposed approach demonstrate the efficiency and accuracy of the
reduced solutions.Saheed Olalekan Ojosaheed.ojo@imtlucca.itPattabhi R. Budarapupattabhi.budarapu@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-09-26T07:55:57Z2017-09-26T07:55:57Zhttp://eprints.imtlucca.it/id/eprint/3800This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38002017-09-26T07:55:57ZStrength prediction of notched thin ply laminates using finite fracture mechanics and the phase field approachThin ply laminates are a new class of composite materials with great potential for application in the design of thinner and highly optimized components, resulting in potential weight savings and improved mechanical performance. These new composites can stir the development of lighter structures, overcoming current design limitations as well as notably reducing the onset and development of matrix cracking and delamination events. This paper presents the application of two recent modeling methods for the failure analysis and strength prediction of open-hole thin ply laminates under tensile loading,
which exhibit a brittle response upon failure: (i) the analytical coupled energy-stress Finite Fracture Mechanics (FFMs) technique, and (ii) the FE-based Phase Field (PF) approach for fracture that is incorporated into an enhanced assumed solid shell element. The predictions obtained using both strategies are compared with experimental data. These correlations exhibit a very satisfactory level of agreement, proving the robustness and reliability of both methods under consideration.José ReinosoA. ArterioMarco Paggimarco.paggi@imtlucca.itP.P. Camanho2017-09-26T07:53:06Z2017-09-26T07:53:06Zhttp://eprints.imtlucca.it/id/eprint/3801This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/38012017-09-26T07:53:06ZA new analytical critical thrust force model for delamination analysis of laminated composites during drilling operationFibre reinforced polymer (FRP) composite laminates are employed in many industrial applications due to
their attractive mechanical and structural properties. Machining operation, such as drilling of FRP
laminates, plays a significant role in the assembly of parts in aircraft and spacecraft production. Among
other production bottlenecks, drilling-induced delamination remains a major defect which adversely
affects the quality of assembly parts. An efficient strategy in preventing this problem is the calculation of
the critical thrust force above which delamination is initiated. Therefore, in this study, a new analytical
model is proposed to predict the critical thrust force for delamination. Unlike the general models in the
literature which derived only mode I strain energy release rate based on the assumption of classical
laminate plate theory (CLPT) combined with linear elastic fracture mechanics (LEFM) mode I considerations
in the elliptic delamination zone, the proposed analytical model is derived based on first-order
shear deformation theory (FSDT) and accounts for mode I and mode II strain energy release rates in
the delamination zone. This strategy allows to activate mixed mode criteria for delamination initiation
which is a valid assumption for laminates with layers of different orientations. The present model is
partly derived for general laminates subject to distributed loading and further extended to cross-ply
laminate sequence subject to a mixed load condition. The results show that the effect of shear deformation
in the prediction of the critical thrust force is influential with increasing ply thickness and the
effect of chisel edge on shear deformation is more profound in the distributed load regime.Saheed Olalekan Ojosaheed.ojo@imtlucca.itS.O. IsmailMarco Paggimarco.paggi@imtlucca.itH.N. Dhakal2017-09-26T07:48:16Z2017-09-26T08:01:46Zhttp://eprints.imtlucca.it/id/eprint/3795This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37952017-09-26T07:48:16ZSimulated hail impacts on flexible photovoltaic laminates: testing and modellingThe problem of simulated low-velocity
hail impacts on flexible photovoltaic (PV) modules
resting on a substrate with variable stiffness is investigated.
For this type of PV module it is shown that the
prescriptions of the IEC 61215 International Standard
for quality control used for rigid (glass-covered) PV
modules should be augmented by taking into account
their real mounting condition and the stiffness of the
substrate in the simulated hail impact tests. Moreover,
electroluminescence inspection of the crack pattern
should be made in addition to electric power output
measurements.An implicit finite element simulation of
the contact problem in dynamics is also proposed, with
two different degrees of accuracy, to interpret the
experimentally observed extension of cracking.
Results pinpoint the important role of stress wave
propagation and reflection in the case of soft substrates.Mauro Corradomauro.corrado@polito.itAndrea InfusoMarco Paggimarco.paggi@imtlucca.it2017-09-21T14:41:04Z2017-09-21T14:41:04Zhttp://eprints.imtlucca.it/id/eprint/3794This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37942017-09-21T14:41:04ZReliability and Fault-Tolerance by Choreographic DesignDistributed programs are hard to get right because they are required to be open, scalable, long-running, and tolerant to faults. In particular, the recent approaches to distributed software based on (micro-)services where different services are developed independently by disparate teams exacerbate the problem. In fact, services are meant to be composed together and run in open context where unpredictable behaviours can emerge. This makes it necessary to adopt suitable strategies for monitoring the execution and incorporate recovery and adaptation mechanisms so to make distributed programs more flexible and robust. The typical approach that is currently adopted is to embed such mechanisms in the program logic, which makes it hard to extract, compare and debug. We propose an approach that employs formal abstractions for specifying failure recovery and adaptation strategies. Although implementation agnostic, these abstractions would be amenable to algorithmic synthesis of code, monitoring and tests. We consider message-passing programs (a la Erlang, Go, or MPI) that are gaining momentum both in academia and industry. Our research agenda consists of (1) the definition of formal behavioural models encompassing failures, (2) the specification of the relevant properties of adaptation and recovery strategy, (3) the automatic generation of monitoring, recovery, and adaptation logic in target languages of interest.Ian CassarAdrian FrancalanzaClaudio Antares Mezzinaclaudio.mezzina@imtlucca.itEmilio Tuosto2017-09-18T12:18:33Z2017-09-18T12:18:33Zhttp://eprints.imtlucca.it/id/eprint/3788This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37882017-09-18T12:18:33ZAnalytical and computational methods for modeling mechanical filters against bloch wave propagationThe free propagation of elastic waves through periodic microstructured materials
can be studied by the analytical formulation of beam lattice models for the elementary cell, in
combination with the Floquet-Bloch theory. Within this framework, the present paper deals
with periodic tetrachiral materials characterized by a monoatomic cell. Alternative analytical
formulations can be developed by continualization-homogenization techniques in micropolar
equivalent continua, characterized by overall elastic and inertial tensors. Valid approaches
for the solution of the wave propagation problems are offered by perturbation methods, numerical
continuation techniques, and – finally – computational analyses, suited to account for
some mechanical updates or improvements that can hardly be included in synthetic formulations.
Based on these considerations, the dispersion curves achievable by different formulations
are compared and discussed. The major interest is focused on the spectral effects
determined by changes in the geometry, inertia, elasticity of the microstructural elements and,
finally, by variations in the cellular symmetry. Some attention is paid to the parameter combinations,
which might open band gaps in the low-frequency range, useful to filter undesired
dynamic signals for vibration shielding purposes.Francesca VadalàAndrea Bacigalupoandrea.bacigalupo@imtlucca.itMarco LepidiLuigi Gambarotta2017-09-18T10:54:34Z2017-09-18T10:54:34Zhttp://eprints.imtlucca.it/id/eprint/3787This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37872017-09-18T10:54:34ZAsymptotic approximation of the band structure for tetrachiral metamaterialsTetrachiral materials are characterized by a cellular microstructure made by a periodic pattern of stiff rings and flexible ligaments. Their mechanical behaviour can be described by a planar lattice of rigid massive bodies and elastic massless beams. Therefore, the periodic cell dynamics is governed by a monoatomic structural model, conveniently reduced to the only active degrees-of-freedom. The paper presents an explicit parametric description of the Floquet-Bloch spectrum (or band structure) governing the propagation of elastic waves through the tetrachiral material. By virtue of multiparametric perturbation techniques, an analytical asymptotic approximation is achieved for the dispersion surfaces in the Brillouin zone. Since different optimization strategies tend to fail in opening low-frequency band gaps in the material spectrum, this specific design purpose is commonly pursued by introducing interring inertial resonators. The paper demonstrates that multiparametric perturbation methods can efficiently deal with the consequent enlargement of the parameter space, necessary to describe the resulting inertial metamaterial. Indeed, paying due attention to the doubling of internal resonance conditions, an accurate parametric approximations of the enriched band structure can be achieved. From the applicative perspective, the research findings furnish suited analytical tools for the optimal design of pass and stop bands.Marco LepidiAndrea Bacigalupoandrea.bacigalupo@imtlucca.it2017-09-18T09:47:53Z2017-09-18T09:49:02Zhttp://eprints.imtlucca.it/id/eprint/3786This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37862017-09-18T09:47:53ZDamped Bloch Waves in Lattices Metamaterials with Inertial ResonatorsThe present paper is focused on the acoustic behaviour of periodic beam-lattices metamaterials containing inertial viscoelastic resonators connected with elastic slender ligaments. A simplified model is considered where the ligaments are considered as massless and the viscoelastic resonators are contained inside rigid rings located at the lattice nodes. Firstly, a Lagrangian model is formulated in order to assess the influence of the dynamic and viscoelastic properties of the resonators on the acoustic behaviour. An equivalent generalized micropolar model is obtained through a continualization of the discrete model and the constitutive tensors and the equation of motion are formulated. The propagation of harmonic waves is assumed and the Christoffel equation for both the discrete and the continuum model are obtained. It is shown that the hermitian matrix governing the Christoffel equation of the Lagrangian model is approximated by the corresponding one from the micropolar model with an error O (|k|3)Andrea Bacigalupoandrea.bacigalupo@imtlucca.itLuigi Gambarotta2017-09-08T10:47:54Z2017-09-08T10:47:54Zhttp://eprints.imtlucca.it/id/eprint/3782This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37822017-09-08T10:47:54ZGenetically-Driven Enhancement of Dopaminergic Transmission Affects Moral Acceptability in Females but Not in Males: A Pilot StudyMoral behavior has been a key topic of debate for philosophy and psychology for a long time. In recent years, thanks to the development of novel methodologies in cognitive sciences, the question of how we make moral choices has expanded to the study of neurobiological correlates that subtend the mental processes involved in moral behavior. For instance, in vivo brain imaging studies have shown that distinct patterns of brain neural activity, associated with emotional response and cognitive processes, are involved in moral judgment. Moreover, while it is well-known that responses to the same moral dilemmas differ across individuals, to what extent this variability may be rooted in genetics still remains to be understood. As dopamine is a key modulator of neural processes underlying executive functions, we questioned whether genetic polymorphisms associated with decision-making and dopaminergic neurotransmission modulation would contribute to the observed variability in moral judgment. To this aim, we genotyped five genetic variants of the dopaminergic pathway [rs1800955 in the dopamine receptor D4 (DRD4) gene, DRD4 48 bp variable number of tandem repeat (VNTR), solute carrier family 6 member 3 (SLC6A3) 40 bp VNTR, rs4680 in the catechol-O-methyl transferase (COMT) gene, and rs1800497 in the ankyrin repeat and kinase domain containing 1 (ANKK1) gene] in 200 subjects, who were requested to answer 56 moral dilemmas. As these variants are all located in genes belonging to the dopaminergic pathway, they were combined in multilocus genetic profiles for the association analysis. While no individual variant showed any significant effects on moral dilemma responses, the multilocus genetic profile analysis revealed a significant gender-specific influence on human moral acceptability. Specifically, those genotype combinations that improve dopaminergic signaling selectively increased moral acceptability in females, by making their responses to moral dilemmas more similar to those provided by males. As females usually give more emotionally-based answers and engage the “emotional brain” more than males, our results, though preliminary and therefore in need of replication in independent samples, suggest that this increase in dopamine availability enhances the cognitive and reduces the emotional components of moral decision-making in females, thus favoring a more rationally-driven decision process.Silvia PellegriniSara PalumboCaterina IofridaErika MelissariGiuseppina RotaVeronica MariottiTeresa AnastasioAndrea ManfrinatiRino RumiatiLorella LottoMichela SarloPietro Pietrinipietro.pietrini@imtlucca.it2017-08-08T09:06:01Z2017-08-08T09:06:01Zhttp://eprints.imtlucca.it/id/eprint/3766This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37662017-08-08T09:06:01ZERODE: A Tool for the Evaluation and Reduction of Ordinary Differential EquationsWe present ERODE, a multi-platform tool for the solution and exact reduction of systems of ordinary differential equations (ODEs). ERODE supports two recently introduced, complementary, equivalence relations over ODE variables: forward differential equivalence yields a self-consistent aggregate system where each ODE gives the cumulative dynamics of the sum of the original variables in the respective equivalence class. Backward differential equivalence identifies variables that have identical solutions whenever starting from the same initial conditions. As back-end ERODE uses the well-known Z3 SMT solver to compute the largest equivalence that refines a given initial partition of ODE variables. In the special case of ODEs with polynomial derivatives of degree at most two (covering affine systems and elementary chemical reaction networks), it implements a more efficient partition-refinement algorithm in the style of Paige and Tarjan. ERODE comes with a rich development environment based on the Eclipse plug-in framework offering: (i) seamless project management; (ii) a fully-featured text editor; and (iii) importing-exporting capabilities.Luca CardelliMirco Tribastonemirco.tribastone@imtlucca.itMax Tschaikowskimax.tschaikowski@imtlucca.itAndrea Vandinandrea.vandin@imtlucca.it2017-08-04T11:50:27Z2017-08-04T11:50:27Zhttp://eprints.imtlucca.it/id/eprint/3760This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37602017-08-04T11:50:27ZA SOM-based Chan–Vese model for unsupervised image segmentationActive Contour Models (ACMs) constitute an efficient energy-based image segmentation framework. They usually deal with the segmentation problem as an optimization problem, formulated in terms of a suitable functional, constructed in such a way that its minimum is achieved in correspondence with a contour that is a close approximation of the actual object boundary. However, for existing ACMs, handling images that contain objects characterized by many different intensities still represents a challenge. In this paper, we propose a novel ACM that combines—in a global and unsupervised way—the advantages of the Self-Organizing Map (SOM) within the level set framework of a state-of-the-art unsupervised global ACM, the Chan–Vese (C–V) model. We term our proposed model SOM-based Chan–Vese (SOMCV) active contour model. It works by explicitly integrating the global information coming from the weights (prototypes) of the neurons in a trained SOM to help choosing whether to shrink or expand the current contour during the optimization process, which is performed in an iterative way. The proposed model can handle images that contain objects characterized by complex intensity distributions, and is at the same time robust to the additive noise. Experimental results show the high accuracy of the segmentation results obtained by the SOMCV model on several synthetic and real images, when compared to the Chan–Vese model and other image segmentation models.Mohammed M. AbdelsameaGiorgio Gneccogiorgio.gnecco@imtlucca.itMohamed Medhat Gaber2017-08-04T11:47:46Z2017-08-04T11:47:46Zhttp://eprints.imtlucca.it/id/eprint/3759This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37592017-08-04T11:47:46ZLQG Online LearningOptimal control theory and machine learning techniques are combined to formulate and solve in closed form an optimal control formulation of online learning from supervised examples with regularization of the updates. The connections with the classical linear quadratic gaussian (LQG) optimal control problem, of which the proposed learning paradigm is a nontrivial variation as it involves random matrices, are investigated. The obtained optimal solutions are compared with the Kalman filter estimate of the parameter vector to be learned. It is shown that the proposed algorithm is less sensitive to outliers with respect to the Kalman estimate (thanks to the presence of the regularization term), thus providing smoother estimates with respect to time. The basic formulation of the proposed online learning framework refers to a discrete-time setting with a finite learning horizon and a linear model. Various extensions are investigated, including the infinite learning horizon and, via the so-called kernel trick, the case of nonlinear models.Giorgio Gneccogiorgio.gnecco@imtlucca.itAlberto Bemporadalberto.bemporad@imtlucca.itMarco GoriMarcello Sanguineti2017-08-04T11:42:06Z2017-08-04T11:42:06Zhttp://eprints.imtlucca.it/id/eprint/3758This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37582017-08-04T11:42:06ZGraph-restricted Game Approach for Investigating Human Movement QualitiesA novel computational method for the analysis of expressive full-body movement qualities is introduced, which exploits concepts and tools from graph theory and game theory. The human skeletal structure is modeled as an undirected graph, where the joints are the vertices and the edge set contains both physical and non-physical links. Physical links correspond to connections between adjacent physical body joints (e.g., the forearm, which connects the elbow to the wrist). Nonphysical links act as "bridges" between parts of the body not directly connected by the skeletal structure, but sharing very similar feature values. The edge weights depend on features obtained by using Motion Capture data. Then, a mathematical game is constructed over the graph structure, where the vertices represent the players and the edges represent communication channels between them. Hence, the body movement is modeled in terms of a game built on the graph structure. Since the vertices and the edges contribute to the overall quality of the movement, the adopted game-theoretical model is of cooperative nature. A game-theoretical concept, called Shapley value, is exploited as a centrality index to estimate the contribution of each vertex to a shared goal (e.g., to the way a particular movement quality is transferred among the vertices). The proposed method is applied to a data set of Motion Capture data of subjects performing expressive movements, recorded in the framework of the H2020-ICT-2015 EU Project WhoLoDance, Project no. 688865. Preliminary results are presented.Ksenia KolykhalovaGiorgio Gneccogiorgio.gnecco@imtlucca.itMarcello SanguinetiAntonio CamurriGualtiero Volpe2017-08-04T10:23:17Z2017-08-04T10:23:17Zhttp://eprints.imtlucca.it/id/eprint/3746This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37462017-08-04T10:23:17ZModality-independent encoding of individual concepts in the left parietal cortexAbstract The organization of semantic information in the brain has been mainly explored through category-based models, on the assumption that categories broadly reflect the organization of conceptual knowledge. However, the analysis of concepts as individual entities, rather than as items belonging to distinct superordinate categories, may represent a significant advancement in the comprehension of how conceptual knowledge is encoded in the human brain. Here, we studied the individual representation of thirty concrete nouns from six different categories, across different sensory modalities (i.e., auditory and visual) and groups (i.e., sighted and congenitally blind individuals) in a core hub of the semantic network, the left angular gyrus, and in its neighboring regions within the lateral parietal cortex. Four models based on either perceptual or semantic features at different levels of complexity (i.e., low- or high-level) were used to predict fMRI brain activity using representational similarity encoding analysis. When controlling for the superordinate component, high-level models based on semantic and shape information led to significant encoding accuracies in the intraparietal sulcus only. This region is involved in feature binding and combination of concepts across multiple sensory modalities, suggesting its role in high-level representation of conceptual knowledge. Moreover, when the information regarding superordinate categories is retained, a large extent of parietal cortex is engaged. This result indicates the need to control for the coarse-level categorial organization when performing studies on higher-level processes related to the retrieval of semantic information.Giacomo HandjarasAndrea LeoLuca Cecchettiluca.cecchetti@imtlucca.itPaolo PapaleAlessandro LenciGiovanna MarottaPietro Pietrinipietro.pietrini@imtlucca.itEmiliano Ricciardiemiliano.ricciardi@imtlucca.it2017-08-04T10:05:21Z2017-08-04T10:05:21Zhttp://eprints.imtlucca.it/id/eprint/3743This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37432017-08-04T10:05:21ZMulti-field asymptotic homogenization of thermo-piezoelectric materials with periodic microstructureAbstract This study proposes a multi-field asymptotic homogenization for the analysis of thermo-piezoelectric materials with periodic microstructures. The effect of the microstructural heterogeneity is taken into account by means of periodic perturbation functions, which derive from the solution of nonhomogeneous recursive cell problems defined over the unit periodic cell. A strong coupling is present between the microdisplacement field and the microelectric potential field, since the mechanical and the electric problems are fully coupled in the asymptotically expanded microscale field equations. The microdisplacement, the electric potential, and the relative temperature fields have been related to the macroscopic quantities and to their gradients in the derived down-scaling relations. Average field equations of infinite order have been obtained and the closed form of the overall constitutive tensors has been determined for the equivalent first-order homogenized continuum. A formal solution of such equations has been derived by means of an asymptotic expansion of the macrofields. The accuracy of the proposed formulation is assessed in relation to illustrative examples of a bi-material periodic microstructure subjected to harmonic body forces, free charge densities, and heat sources, whose periodicity is much greater than the characteristic microstructural size. The good agreement obtained between the solution of the homogenized model and the finite element solution of the original heterogeneous material problem confirms the validity of the proposed formulation.Francesca FantoniAndrea Bacigalupoandrea.bacigalupo@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-08-04T10:04:05Z2017-08-04T10:04:05Zhttp://eprints.imtlucca.it/id/eprint/3742This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37422017-08-04T10:04:05ZDispersive wave propagation in two-dimensional rigid periodic blocky materials with elastic interfacesAbstract Dispersive waves in two-dimensional blocky materials with periodic microstructure made up of equal rigid units, having polygonal centro-symmetric shape with mass and gyroscopic inertia, connected with each other through homogeneous linear interfaces, have been analyzed. The acoustic behavior of the resulting discrete Lagrangian model has been obtained through a Floquet–Bloch approach. From the resulting eigenproblem derived by the Euler–Lagrange equations for harmonic wave propagation, two acoustic branches and an optical branch are obtained in the frequency spectrum. A micropolar continuum model to approximate the Lagrangian model has been derived based on a second-order Taylor expansion of the generalized macro-displacement field. The constitutive equations of the equivalent micropolar continuum have been obtained, with the peculiarity that the positive definiteness of the second-order symmetric tensor associated to the curvature vector is not guaranteed and depends both on the ratio between the local tangent and normal stiffness and on the block shape. The same results have been obtained through an extended Hamiltonian derivation of the equations of motion for the equivalent continuum that is related to the Hill-Mandel macro homogeneity condition. Moreover, it is shown that the hermitian matrix governing the eigenproblem of harmonic wave propagation in the micropolar model is exact up to the second order in the norm of the wave vector with respect to the same matrix from the discrete model. To appreciate the acoustic behavior of some relevant blocky materials and to understand the reliability and the validity limits of the micropolar continuum model, some blocky patterns have been analyzed: rhombic and hexagonal assemblages and running bond masonry. From the results obtained in the examples, the obtained micropolar model turns out to be particularly accurate to describe dispersive functions for wavelengths greater than 3-4 times the characteristic dimension of the block. Finally, in consideration that the positive definiteness of the second order elastic tensor of the micropolar model is not guaranteed, the hyperbolicity of the equation of motion has been investigated by considering the Legendre–Hadamard ellipticity conditions requiring real values for the wave velocity.Andrea Bacigalupoandrea.bacigalupo@imtlucca.itLuigi Gambarotta2017-08-04T09:59:14Z2017-08-04T09:59:14Zhttp://eprints.imtlucca.it/id/eprint/3741This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37412017-08-04T09:59:14ZMulti-parametric sensitivity analysis of the band structure for tetrachiral inertial metamaterialsTetrachiral materials are characterized by a cellular microstructure made by a periodic pattern of stiff rings and flexible ligaments. Their mechanical behaviour can be described by a planar lattice of rigid massive bodies and elastic massless beams. The periodic cell dynamics is governed by a monoatomic structural model, conveniently reduced to the only active degrees-of-freedom. The paper presents an explicit parametric description of the band structure governing the free propagation of elastic waves. By virtue of multiparametric perturbation techniques, sensitivity analyses are performed to achieve analytical asymptotic approximation of the dispersion functions. The parametric conditions for the existence of full band gaps in the low-frequency range are established. Furthermore, the band gap amplitude is analytically assessed in the admissible parameter range. In inertial tetrachiral metamaterials, stop bands can be opened by the introduction of intra-ring resonators. Perturbation methods can efficiently deal with the consequent enlargement of the mechanical parameter space. Indeed high-accuracy parametric approximations are achieved for the band structure, enriched by the new optical branches related to the resonator frequencies. In particular, target stop bands in the metamaterial spectrum are analytically designed through the asymptotic solution of inverse spectral problems.
Subjects: Materials Science (cond-mat.mtrl-sci)
Cite as: arXiv:1706.08754 [cond-mat.mtrl-sci]
(or arXiv:1706.08754v1 [cond-mat.mtrl-sci] for this version)Marco LepidiAndrea Bacigalupoandrea.bacigalupo@imtlucca.it2017-08-04T09:55:23Z2017-08-04T09:55:23Zhttp://eprints.imtlucca.it/id/eprint/3740This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37402017-08-04T09:55:23ZIdentification of higher-order continua equivalent to a Cauchy elastic compositeA heterogeneous Cauchy elastic material may display micromechanical effects that can be modeled in a homogeneous equivalent material through the introduction of higher-order elastic continua. Asymptotic homogenization techniques provide an elegant and rigorous route to the evaluation of equivalent higher-order materials, but are often of difficult and awkward practical implementation. On the other hand, identification techniques, though relying on simplifying assumptions, are of straightforward use. A novel strategy for the identification of equivalent second-gradient Mindlin solids is proposed in an attempt to combine the accuracy of asymptotic techniques with the simplicity of identification approaches. Following the asymptotic homogenization scheme, the overall behaviour is defined via perturbation functions, which (differently from the asymptotic scheme) are evaluated on a finite domain obtained as the periodic repetition of cells and subject to quadratic displacement boundary conditions. As a consequence, the periodicity of the perturbation function is satisfied only in an approximate sense, nevertheless results from the proposed identification algorithm are shown to be reasonably accurate.Andrea Bacigalupoandrea.bacigalupo@imtlucca.itMarco Paggimarco.paggi@imtlucca.itF. Dal CorsoD. Bigoni2017-07-20T10:44:54Z2017-07-20T10:44:54Zhttp://eprints.imtlucca.it/id/eprint/3725This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37252017-07-20T10:44:54ZPredictive Control for Linear and Hybrid SystemsModel Predictive Control (MPC), the dominant advanced control approach in industry over the past twenty-five years, is presented comprehensively in this unique book. With a simple, unified approach, and with attention to real-time implementation, it covers predictive control theory including the stability, feasibility, and robustness of MPC controllers. The theory of explicit MPC, where the nonlinear optimal feedback controller can be calculated efficiently, is presented in the context of linear systems with linear constraints, switched linear systems, and, more generally, linear hybrid systems. Drawing upon years of practical experience and using numerous examples and illustrative applications, the authors discuss the techniques required to design predictive control laws, including algorithms for polyhedral manipulations, mathematical and multiparametric programming and how to validate the theoretical properties and to implement predictive control policies. The most important algorithms feature in an accompanying free online MATLAB toolbox, which allows easy access to sample solutions. Predictive Control for Linear and Hybrid Systems is an ideal reference for graduate, postgraduate and advanced control practitioners interested in theory and/or implementation aspects of predictive control.Francesco BorrelliAlberto Bemporadalberto.bemporad@imtlucca.itManfred Morari2017-07-20T10:37:23Z2017-07-20T10:37:23Zhttp://eprints.imtlucca.it/id/eprint/3724This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37242017-07-20T10:37:23ZReversibility in session-based concurrency: A fresh lookMuch research has studied foundations for correct and reliable communication-centric software systems. A salient approach to correctness uses verification based on session types to enforce structured communications; a recent approach to reliability uses reversible actions as a way of reacting to unanticipated events or failures. In this paper, we develop a simple observation: the semantic machinery required to define asynchronous (queue-based), monitored communications can also support reversible protocols. We propose a framework of session communication in which monitors support reversibility of (untyped) processes. Main novelty in our approach are session types with present and past, which allow us to streamline the semantics of reversible actions. We prove that reversibility in our framework is causally consistent, and define ways of using monitors to control reversible actions.
KeywordsClaudio Antares Mezzinaclaudio.mezzina@imtlucca.itJorge A. Pérez2017-06-21T13:17:10Z2017-06-21T13:17:10Zhttp://eprints.imtlucca.it/id/eprint/3714This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37142017-06-21T13:17:10ZIn favor of the phonemic principle: a review of neurophysiological and neuroimaging explorations into the neural correlates of phonological competenceIn the last thirty years, in vivo brain structural and functional exploration has sparked vivid light on the neural correlates of language. Along these lines, the study of phono- logical competence has offered a ‘neural view’ into the organization of basic speech- sensitive areas, improving the sensitivity of pre-surgical mapping and brain-computer interface-based communication. Nevertheless, only rarely the significance of these results has been recognized in the context of a century-long discussion around the theoretical, physical and cognitive consistency of the phoneme itself. Here we review recent investigations into speech perception, imagery and production at the segmen- tal level through neuroimaging and neurophysiological techniques, showing that phonemes are processed as discrete entities, which are categorized in cognition as unique products of their acoustic and articulatory features, despite the seamless flow of the speech signal. These results seem to expand the scope of the motor theory of speech perception.Alessandra Cecilia Rampininialessandra.rampinini@imtlucca.itEmiliano Ricciardiemiliano.ricciardi@imtlucca.it2017-06-07T11:10:53Z2017-06-07T11:10:53Zhttp://eprints.imtlucca.it/id/eprint/3711This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/37112017-06-07T11:10:53ZBlock Placement Strategies for Fault-Resilient Distributed Tuple Spaces: An Experimental Study - (Practical Experience Report)The tuple space abstraction provides an easy-to-use programming paradigm
for distributed applications. Intuitively, it behaves like a distributed shared
memory, where applications write and read entries (tuples). When deployed over
a wide area network, the tuple space needs to efficiently cope with faults of links
and nodes. Erasure coding techniques are increasingly popular to deal with such
catastrophic events, in particular due to their storage efficiency with respect to
replication. When a client writes a tuple into the system, this is first striped into
k blocks and encoded into n > k blocks, in a fault-redundant manner. Then, any
k out of the n blocks are sufficient to reconstruct and read the tuple. This paper
presents several strategies to place those blocks across the set of nodes of a
wide area network, that all together form the tuple space. We present the performance
trade-offs of different placement strategies by means of simulations and a
Python implementation of a distributed tuple space. Our results reveal important
differences in the efficiency of the different strategies, for example in terms of
block fetching latency, and that having some knowledge of the underlying network
graph topology is highly beneficialRoberta BarbiVitaly BuravlevClaudio Antares Mezzinaclaudio.mezzina@imtlucca.itValerio Schiavoni2017-05-08T12:26:53Z2017-05-08T12:26:53Zhttp://eprints.imtlucca.it/id/eprint/3696This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36962017-05-08T12:26:53ZPreface for the special issue on Interaction and Concurrency Experience 2015This special issue contains extended versions of selected papers from the 8th Interaction and Concurrency Experience workshop (ICE 2015). The workshop was held in Grenoble, France, on June 4-5th, 2015. ICE workshops form a series of international scientific meetings oriented to theoretical computer science researchers with special interest in models, verification, tools, and programming primitives for complex interactions.
The general scope of the venue includes theoretical and applied aspects of interactions and the synchronization mechanisms used among components of concurrent/distributed systems, related to several areas of computer science in the broad spectrum ranging from formal specification and analysis to studies inspired by emerging computational models.
The authors of the most prominent papers presented at ICE 2015 were invited to submit an extended version to this special issue. In order to guarantee the fairness and quality of the selection process, each submission received at least three reviews. The review process has ensured that the accepted articles significantly extend and improve the original workshop contributions.
We want to thank all the authors who contributed to this volume. We would like to thank all the members of the Program Committee of ICE, who helped us in the selection of the papers and who helped the authors to improve their contributions in several ways. Additional referees were involved in the review of the papers invited for this special issue and we thank their timely contributions. We would also like to thank the editors of JLAMP, for their support during the whole editorial process.Ivan LaneseAlberto Lluch LafuenteSophia KnightHugo Torres Vieirahugo.torresvieira@imtlucca.it2017-05-08T08:07:14Z2017-05-08T08:07:14Zhttp://eprints.imtlucca.it/id/eprint/3698This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36982017-05-08T08:07:14ZPhenotiki: an open software and hardware platform for affordable and easy image-based phenotyping of rosette-shaped plantsPhenotyping is important to understand plant biology, but current solutions are costly, not versatile or are difficult to deploy. To solve this problem, we present Phenotiki, an affordable system for plant phenotyping that, relying on off-the-shelf parts, provides an easy to install and maintain platform, offering an out-of-box experience for a well-established phenotyping need: imaging rosette-shaped plants. The accompanying software (with available source code) processes data originating from our device seamlessly and automatically. Our software relies on machine learning to devise robust algorithms, and includes an automated leaf count obtained from 2D images without the need of depth (3D). Our affordable device (~€200) can be deployed in growth chambers or greenhouse to acquire optical 2D images of approximately up to 60 adult Arabidopsis rosettes concurrently. Data from the device are processed remotely on a workstation or via a cloud application (based on CyVerse). In this paper, we present a proof-of-concept validation experiment on top-view images of 24 Arabidopsis plants in a combination of genotypes that has not been compared previously. Phenotypic analysis with respect to morphology, growth, color and leaf count has not been performed comprehensively before now. We confirm the findings of others on some of the extracted traits, showing that we can phenotype at reduced cost. We also perform extensive validations with external measurements and with higher fidelity equipment, and find no loss in statistical accuracy when we use the affordable setting that we propose. Device set-up instructions and analysis software are publicly available (http://phenotiki.com).Massimo MinerviniMario Valerio Giuffridavalerio.giuffrida@imtlucca.itPierdomenico PerataSotirios A. Tsaftaris2017-04-28T09:28:28Z2017-04-28T09:28:28Zhttp://eprints.imtlucca.it/id/eprint/3661This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36612017-04-28T09:28:28ZCausal-consistent rollback in a tuple-based languageElena GiachinoIvan LaneseClaudio Antares Mezzinaclaudio.mezzina@imtlucca.itFrancesco Tiezzi2017-04-18T08:57:40Z2017-04-18T08:57:40Zhttp://eprints.imtlucca.it/id/eprint/3689This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36892017-04-18T08:57:40ZModeling confirmation bias and polarizationOnline users tend to select claims that adhere to their system of beliefs and to ignore dissenting information. Confirmation bias, indeed, plays a pivotal role in viral phenomena. Furthermore, the wide availability of content on the web fosters the aggregation of likeminded people where debates tend to enforce group polarization. Such a configuration might alter the public debate and thus the formation of the public opinion. In this paper we provide a mathematical model to study online social debates and the related polarization dynamics. We assume the basic updating rule of the Bounded Confidence Model (BCM) and we develop two variations a) the Rewire with Bounded Confidence Model (RBCM), in which discordant links are broken until convergence is reached; and b) the Unbounded Confidence Model, under which the interaction among discordant pairs of users is allowed even with a negative feedback, either with the rewiring step (RUCM) or without it (UCM). From numerical simulations we find that the new models (UCM and RUCM), unlike the BCM, are able to explain the coexistence of two stable final opinions, often observed in reality. Lastly, we present a mean field approximation of the newly introduced models.Michela Del Vicariomichela.delvicario@imtlucca.itAntonio ScalaGuido Caldarelliguido.caldarelli@imtlucca.itH. Eugene StanleyWalter Quattrociocchiwalter.quattrociocchi@imtlucca.it2017-04-18T08:50:07Z2017-04-18T08:50:07Zhttp://eprints.imtlucca.it/id/eprint/3688This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36882017-04-18T08:50:07ZIt’s Always April Fools’ Day! On the Difficulty of Social Network Misinformation Classification via Propagation FeaturesGiven the huge impact that Online Social Networks (OSN)
had in the way people get informed and form their opinion,
they became an attractive playground for malicious entities
that want to spread misinformation, and leverage their effect.
In fact, misinformation easily spreads on OSN and is a huge
threat for modern society, possibly influencing also the outcome
of elections, or even putting people’s life at risk (e.g.,
spreading “anti-vaccines” misinformation). Therefore, it is
of paramount importance for our society to have some sort
of “validation” on information spreading through OSN. The
need for a wide-scale validation would greatly benefit from
automatic tools.
In this paper, we show that it is difficult to carry out an automatic
classification of misinformation considering only structural
properties of content propagation cascades. We focus on
structural properties, because they would be inherently dif-
ficult to be manipulated, with the the aim of circumventing
classification systems. To support our claim, we carry out an
extensive evaluation on Facebook posts belonging to conspiracy
theories (as representative of misinformation), and scientific
news (representative of fact-checked content). Our
findings show that conspiracy content actually reverberates
in a way which is hard to distinguish from the one scientific
content does: for the classification mechanisms we investigated,
classification F1-score never exceeds 0.65 during content
propagation stages, and is still less than 0.7 even after
propagation is complete.Mauro ContiDaniele LainRiccardo LazzerettiGiulio LovisottoWalter Quattrociocchiwalter.quattrociocchi@imtlucca.it2017-04-18T08:40:58Z2017-04-18T08:40:58Zhttp://eprints.imtlucca.it/id/eprint/3687This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36872017-04-18T08:40:58ZPublic discourse and news consumption on online social media: A quantitative, cross-platform analysis of the Italian ReferendumThe rising attention to the spreading of fake news and unsubstantiated rumors on online social media and the pivotal role played by confirmation bias led researchers to investigate different aspects of the phenomenon. Experimental evidence showed that confirmatory information gets accepted even if containing deliberately false claims while dissenting information is mainly ignored or might even increase group polarization. It seems reasonable that, to address misinformation problem properly, we have to understand the main determinants behind content consumption and the emergence of narratives on online social media. In this paper we address such a challenge by focusing on the discussion around the Italian Constitutional Referendum by conducting a quantitative, cross-platform analysis on both Facebook public pages and Twitter accounts. We observe the spontaneous emergence of well-separated communities on both platforms. Such a segregation is completely spontaneous, since no categorization of contents was performed a priori. By exploring the dynamics behind the discussion, we find that users tend to restrict their attention to a specific set of Facebook pages/Twitter accounts. Finally, taking advantage of automatic topic extraction and sentiment analysis techniques, we are able to identify the most controversial topics inside and across both platforms. We measure the distance between how a certain topic is presented in the posts/tweets and the related emotional response of users. Our results provide interesting insights for the understanding of the evolution of the core narratives behind different echo chambers and for the early detection of massive viral phenomena around false claims.Michela Del Vicariomichela.delvicario@imtlucca.itSabrina GaitoWalter Quattrociocchiwalter.quattrociocchi@imtlucca.itMatteo ZignaniFabiana Zollofabiana.zollo@imtlucca.it2017-04-18T08:35:43Z2017-08-04T11:33:20Zhttp://eprints.imtlucca.it/id/eprint/3686This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36862017-04-18T08:35:43ZAnatomy of news consumption on FacebookThe advent of social media and microblogging platforms has radically changed the way we consume information and form opinions. In this paper, we explore the anatomy of the information space on Facebook by characterizing on a global scale the news consumption patterns of 376 million users over a time span of 6 y (January 2010 to December 2015). We find that users tend to focus on a limited set of pages, producing a sharp community structure among news outlets. We also find that the preferences of users and news providers differ. By tracking how Facebook pages “like” each other and examining their geolocation, we find that news providers are more geographically confined than users. We devise a simple model of selective exposure that reproduces the observed connectivity patterns.Ana Lucía SchmidtFabiana Zollofabiana.zollo@imtlucca.itMichela Del Vicariomichela.delvicario@imtlucca.itAlessandro BessiAntonio ScalaGuido Caldarelliguido.caldarelli@imtlucca.itH. Eugene StanleyWalter Quattrociocchiwalter.quattrociocchi@imtlucca.it2017-04-18T08:31:54Z2017-04-18T08:31:54Zhttp://eprints.imtlucca.it/id/eprint/3685This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36852017-04-18T08:31:54ZInside the Echo ChamberDespite optimistic talk about “collective intelligence,” the Web has helped create an echo chamber where misinformation thrives. Indeed, the viral spread of hoaxes, conspiracy theories, and other false or baseless information online is one of the most disturbing social trends of the early 21st century.
Social scientists are studying this echo chamber by applying computational methods to the traces people leave on Facebook, Twitter and other such outlets. Through this work, they have established that users happily embrace false information as long as it reinforces their preexisting beliefs.
Faced with complex global issues, people of all educational levels choose to believe compact—but false—explanations that clearly identify an object of blame. Unfortunately, attempts to debunk false beliefs seem only to reinforce them. Stopping the spread of misinformation is thus a problem with no apparent simple solutions.Walter Quattrociocchiwalter.quattrociocchi@imtlucca.it2017-04-18T08:25:38Z2017-04-18T08:25:38Zhttp://eprints.imtlucca.it/id/eprint/3684This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36842017-04-18T08:25:38ZMapping social dynamics on Facebook: The Brexit debateAbstract Nowadays users get informed and shape their opinion through social media. However, the disintermediated access to contents does not guarantee quality of information. Selective exposure and confirmation bias, indeed, have been shown to play a pivotal role in content consumption and information spreading. Users tend to select information adhering (and reinforcing) their worldview and to ignore dissenting information. This pattern elicits the formation of polarized groups – i.e., echo chambers – where the interaction with like-minded people might even reinforce polarization. In this work we address news consumption around Brexit in {UK} on Facebook. In particular, we perform a massive analysis on more than 1 million users interacting with Brexit related posts from the main news providers between January and July 2016. We show that consumption patterns elicit the emergence of two distinct communities of news outlets. Furthermore, to better characterize inner group dynamics, we introduce a new technique which combines automatic topic extraction and sentiment analysis. We compare how the same topics are presented on posts and the related emotional response on comments finding significant differences in both echo chambers and that polarization influences the perception of topics. Our results provide important insights about the determinants of polarization and evolution of core narratives on online debating.Michela Del VicarioFabiana Zollofabiana.zollo@imtlucca.itGuido Caldarelliguido.caldarelli@imtlucca.itAntonio ScalaWalter Quattrociocchiwalter.quattrociocchi@imtlucca.it2017-04-03T08:56:38Z2017-04-03T08:56:38Zhttp://eprints.imtlucca.it/id/eprint/3682This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36822017-04-03T08:56:38ZNot in one metric: Neuroticism modulates different resting state metrics within distinctive brain regionsIntroduction Neuroticism is a complex personality trait encompassing diverse aspects. Notably, high levels of neuroticism are related to the onset of psychiatric conditions, including anxiety and mood disorders. Personality traits are stable individual features; therefore, they can be expected to be associated with stable neurobiological features, including the Brain Resting State (RS) activity as measured by fMRI. Several metrics have been used to describe {RS} properties, yielding rather inconsistent results. This inconsistency could be due to the fact that different metrics portray different {RS} signal properties and that these properties may be differently affected by neuroticism. To explore the distinct effects of neuroticism, we assessed several distinct metrics portraying different {RS} properties within the same population. Method Neuroticism was measured in 31 healthy subjects using the Zuckerman-Kuhlman Personality Questionnaire; {RS} was acquired by high-resolution fMRI. Using linear regression, we examined the modulatory effects of neuroticism on {RS} activity, as quantified by the Amplitude of low frequency fluctuations (ALFF, fALFF), regional homogeneity (REHO), Hurst Exponent (H), global connectivity (GC) and amygdalae functional connectivity. Results Neuroticism modulated the different metrics across a wide network of brain regions, including emotional regulatory, default mode and visual networks. Except for some similarities in key brain regions for emotional expression and regulation, neuroticism affected different metrics in different ways. Discussion Metrics more related to the measurement of regional intrinsic brain activity (fALFF, {ALFF} and REHO), or that provide a parsimonious index of integrated and segregated brain activity (HE), were more broadly modulated in regions related to emotions and their regulation. Metrics related to connectivity were modulated across a wider network of areas. Overall, these results show that neuroticism affects distinct aspects of brain resting state activity. More in general, these findings indicate that a multiparametric approach may be required to obtain a more detailed characterization of the neural underpinnings of a given psychological trait.Claudio GentiliIoana Alina CristeaEmiliano Ricciardiemiliano.ricciardi@imtlucca.itNicola VanelloCristian PopitaDaniel DavidPietro Pietrinipietro.pietrini@imtlucca.it2017-03-22T10:06:42Z2017-03-22T10:06:42Zhttp://eprints.imtlucca.it/id/eprint/3681This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36812017-03-22T10:06:42ZReference trajectory planning under constraints and path tracking using linear time-varying model predictive control for agricultural machinesA method for the control of autonomously and slowly moving agricultural machinery is presented. Special emphasis is on offline reference trajectory generation tailored for high-precision closed-loop tracking within agricultural fields using linear time-varying model predictive control. When optimisation is carried out, high-level logistical processing can result in edgy reference paths for field coverage. Subsequent trajectory smoothing can consider specific actuator rate constraints and field geometry. The latter step is the subject of this paper. Focussing on forward motion only, the role of non-convexly shaped field geometry, repressed area minimisation and spraying gap avoidance is analysed. Three design methods for generating smooth reference trajectories are discussed: circle-segments, generalised elementary paths, and bi-elementary paths.Mogens M. Graf PlessenAlberto Bemporadalberto.bemporad@imtlucca.it2017-03-21T14:13:22Z2017-03-21T14:13:22Zhttp://eprints.imtlucca.it/id/eprint/3680This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36802017-03-21T14:13:22ZA nonlinear finite thickness cohesive interface element for modeling delamination in fibre-reinforced composite laminatesAbstract Delamination events are major issues which notably affect the integrity of composite structures. To minimize the experimental efforts, there is an increasing demand for developing reliable numerical tools that can accurately simulate delamination initiation and propagation under mixed-mode loading conditions. The current investigation is concerned with the formulation and the finite element (FE) implementation of a new nonlinear finite thickness cohesive interface model for delamination analysis of fibre-reinforced composite laminates relying on the solid shell concept. The incorporation of geometrically nonlinear effects into the proposed interface formulation is motivated by the recent trend of producing composite structures that can experience large displacements prior to failure, as is the case of postbuckling in stiffened panels. The inelastic material behavior of the interface is modeled using two standard nonlinear decohesion laws: (i) an exponential-based, and (ii) a polynomial-based interface laws. Finally, the performance of the proposed interface element is demonstrated by means of several examples focusing on double cantilever beam (DCB) and rib-stiffened specimens. A excellent level of accuracy is achieved when comparing the numerical predictions and the available experimental data.José ReinosoMarco Paggimarco.paggi@imtlucca.itA. Blázquez2017-03-21T13:32:35Z2017-08-04T10:14:43Zhttp://eprints.imtlucca.it/id/eprint/3677This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36772017-03-21T13:32:35ZForeground Enhancement and Background Suppression in Human Early Visual System During Passive Perception of Natural ImagesOne of the major challenges in visual neuroscience is represented by foreground-background segmentation, a process that is supposed to rely on computations in cortical modules, as information progresses from V1 to V4. Data from nonhuman primates (Poort et al., 2016) showed that segmentation leads to two distinct, but associated processes: the enhancement of cortical activity associated to figure processing (i.e., foreground enhancement) and the suppression of ground-related cortical activity (i.e., background suppression). To characterize foreground-background segmentation of natural stimuli in humans, we parametrically modulated low-level properties of 334 images and their behaviorally segmented counterparts. A model based on simple visual features was then adopted to describe the filtered and intact images, and to evaluate their resemblance with fMRI activity in different visual cortices (V1, V2, V3, V3A, V3B, V4, LOC). Results from representational similarity analysis (Kriegeskorte et al., 2008) showed that the correspondence between behaviorally segmented natural images and brain activity increases throughout the visual processing stream. We found evidence of foreground enhancement for all the tested visual regions, while background suppression occurs in V3B, V4 and LOC. Our results suggest that foreground-background segmentation is an automatic process that occurs during natural viewing, and cannot be merely ascribed to differences in objects size or location. Finally, neural images reconstructed from V4 and LOC fMRI activity revealed a preserved spatial resolution of foreground textures, indicating a richer representation of the salient part of natural images, rather than a simplistic model of objects shape.Paolo PapaleAndrea LeoLuca Cecchettiluca.cecchetti@imtlucca.itGiacomo HandjarasKendrick KayPietro Pietrinipietro.pietrini@imtlucca.itEmiliano Ricciardiemiliano.ricciardi@imtlucca.it2017-03-21T13:26:39Z2017-03-21T13:26:39Zhttp://eprints.imtlucca.it/id/eprint/3676This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36762017-03-21T13:26:39ZIs investigator background related to outcome in head to head trials of psychotherapy and pharmacotherapy for adult depression? A systematic review and meta-analysisBackground The influence of factors related to the background of investigators conducting trials comparing psychotherapy and pharmacotherapy has remained largely unstudied. Specializations emphasizing biological determinants of mental disorders, like psychiatry, might favor pharmacotherapy, while others stressing psychosocial factors, like psychology, could promote psychotherapy. Yet financial conflict of interest (COI) could be a confounding factor as authors with a medical specialization might receive more sponsoring from the pharmaceutical industry. Method We conducted a meta-analysis with subgroup and meta-regression analysis examining whether the specialization and affiliation of trial authors were associated to outcomes in the direct comparison of psychotherapy and pharmacotherapy for the acute treatment of depression. Meta-regression analysis also included trial risk of bias and author conflict of interest in relationship to the pharmaceutical industry. Results We included 45 trials. In half, the first author was psychologist. The last author was psychiatrist/MD in half of the trials, and a psychologist or statistician/other technical in the rest. Most lead authors had medical affiliations. Subgroup analysis indicated that studies with last authors statisticians favored pharmacotherapy. Univariate analysis showed a negative relationship between the presence of statisticians and outcomes favoring psychotherapy. Multivariate analysis showed that trials including authors with financial COI reported findings more favorable to pharmacotherapy. Discussion We report the first detailed overview of the background of authors conducting head to head trials for depression. Trials co-authored by statisticians appear to subtly favor pharmacotherapy. Receiving funding from the industry is more closely related to finding better outcomes for the industry’s elective treatment than are factors related to authors’ background. Limitations For a minority of authors we could not retrieve background information. The number of trials was insufficient to evidence subtler effects.Ioana A. CristeaClaudio GentiliPietro Pietrinipietro.pietrini@imtlucca.itPim Cuijpers2017-03-21T12:24:42Z2017-09-18T09:30:16Zhttp://eprints.imtlucca.it/id/eprint/3675This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36752017-03-21T12:24:42ZAuxetic behavior and acoustic properties of microstructured piezoelectric strain sensorsThe use of multifunctional composite materials adopting piezo-electric periodic cellular lattice structures with auxetic elastic behavior is a recent and promising solution in the design of piezoelectric sensors. In the present work, periodic anti-tetrachiral auxetic lattice structures, characterized by different geometries, are taken into account and the mechanical and piezoelectrical response are investigated. The equivalent piezoelectric properties are obtained adopting a first order computational homogenization approach, generalized to the case of electro-mechanical coupling, and various polarization directions are adopted. Two examples of in-plane and out-of-plane strain sensors are proposed as design concepts. Moreover, a piezo-elasto-dynamic dispersion analysis adopting the Floquet–Bloch decomposition is performed. The acoustic behavior of the periodic piezoelectric material with auxetic topology is studied and possible band gaps are detected.Maria Laura De BellisAndrea Bacigalupoandrea.bacigalupo@imtlucca.it2017-03-21T12:19:26Z2017-03-21T12:19:26Zhttp://eprints.imtlucca.it/id/eprint/3674This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36742017-03-21T12:19:26ZMulti-field asymptotic homogenization of thermo-piezoelectric materials with periodic microstructureThis study proposes a multi-field asymptotic homogenization for the analysis of thermo-piezoelectric materials with periodic microstructures. The effect of the microstructural heterogeneity is taken into account by means of periodic perturbation functions, which derive from the solution of non homogeneous recursive cell problems defined over the unit periodic cell. A strong coupling is present between the micro displacement field and the micro electric potential field, since the mechanical and the electric problems are fully coupled in the asymptotically expanded microscale field equations. The micro displacement, the electric potential, and the relative temperature fields have been related to the macroscopic quantities and to their gradients in the derived down-scaling relations. Average field equations of infinite order have been obtained and the closed form of the overall constitutive tensors has been determined for the equivalent first-order homogenized continuum. A formal solution of such equations has been derived by means of an asymptotic expansion of the macro fields. The accuracy of the proposed formulation is assessed in relation to illustrative examples of a bi-material periodic microstructure subjected to harmonic body forces, free charge densities, and heat sources, whose periodicity is much greater than the characteristic microstructural size. The good agreement obtained between the solution of the homogenized model and the finite element solution of the original heterogeneous material problem confirms the validity of the proposed formulation.Francesca FantoniAndrea Bacigalupoandrea.bacigalupo@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-03-21T12:16:36Z2017-03-21T12:16:36Zhttp://eprints.imtlucca.it/id/eprint/3673This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36732017-03-21T12:16:36ZParametric design of the band structure for lattice materialsLattice materials are often investigated to determine how small parameter variations in the periodic microstructrure can influence the elastic wave propagation. A general hierarchical scheme, based on asymptotic perturbation techniques, is outlined to analytically assess the parametric sensitivity of the material band structure to a generic multi-parametric perturbation (direct problem). Modeling refinements, parameters updates, microstructural damages and manufacturing irregularities can be treated indifferently and simultaneously. According to a converse strategy, based on the inversion of the sensitivity problem, a hierarchical scheme is sketched to identify the parameter combinations which realize a design band structure (inverse problem). The direct and inverse problem are applied to the sensitivity analysis and band structure design of the anti-tetrachiral lattice material. Despite the high spectral density and the high-dimensional parameter space, the multi-parameter perturbation technique demonstrates its suitability in, first, analytically---although asymptotically---describe the material spectrum and, second, designing the material microstructure to obtain the desired spectral components. The inverse problem solution is discussed in terms of existence, uniqueness, asymptotic consistency and physical admissibility.Marco LepidiAndrea Bacigalupoandrea.bacigalupo@imtlucca.it2017-03-21T12:04:34Z2017-09-21T14:58:45Zhttp://eprints.imtlucca.it/id/eprint/3670This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36702017-03-21T12:04:34ZWave propagation in non-centrosymmetric beam-lattices with lumped masses: discrete and micropolar modellingThe in-plane acoustic behavior of non-centrosymmetric lattices having nodes endowed with mass and rotational inertia and connected by massless ligaments with asymmetric elastic properties has been analyzed through a discrete model and a continuum micropolar model. In the first case the propagation of harmonic waves and the dispersion functions have been obtained by the discrete Floquet–Bloch approach. It is shown that the optical branch departs from a critical point with vanishing group velocity and is decreasing for increasing the norm of the wave vector. A micropolar continuum model has been derived through a continualization method based on a down-scaling law from a second-order Taylor expansion of the generalized macro-displacement field. It is worth noting that the second order elasticity tensor coupling curvatures and micro-couples turns out to be negative-definite also in the general case of non-centrosymmetric lattice. The eigenvalue problem governing the harmonic propagation in the micropolar non-centrosymmetric continuum results in general characterized by a hermitian full matrix that is exact up to the second order in the wave vector.
Examples concerning square and equilateral triangular lattices have been analyzed and their acoustic properties have been derived with the discrete and continuum models. The dependence of the Floquet–Bloch spectra on the lattice non-centrosymmetry is shown together with validity limits of the micropolar model. Finally, in consideration of the negative definiteness of the second order elastic tensor of the micropolar model, the loss of strong hyperbolicity of the equation of motion has been investigated.Andrea Bacigalupoandrea.bacigalupo@imtlucca.itLuigi Gambarotta2017-03-01T11:41:43Z2017-03-01T11:41:43Zhttp://eprints.imtlucca.it/id/eprint/3656This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36562017-03-01T11:41:43ZSimulation of reaction-diffusion systems to assess EVA degradation in accelerated and environmental ageing conditions: a tool to design novel accelerated climate testsMariacristina Gagliardimariacristina.gagliardi@imtlucca.itPietro Lenardapietro.lenarda@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-03-01T11:37:15Z2017-03-01T11:38:28Zhttp://eprints.imtlucca.it/id/eprint/3655This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36552017-03-01T11:37:15ZA reaction-diffusion formulation to simulate EVA polymer degradation in environmental and accelerated ageing conditionsAmong polymers used as encapsulant in photovoltaic (PV) modules, poly(ethylene-co-vinyl acetate), or EVA, is the most widely used, for its low cost and acceptable performances. When exposed to weather conditions, EVA undergoes degradation that affects overall PV performances. Durability prediction of EVA, and thus of the module, is a hot topic in PV process industry. To date, the literature lacks of long-term predictive computational models to study EVA aging. To fill this gap, a computational framework, based on the finite element method, is proposed to simulate chemical reactions and diffusion processes occurring in EVA. The developed computational framework is valid in either case of environmental or accelerated aging. The proposed framework enables the identification of a correspondence between induced degradation in accelerated tests and actual exposure in weathering conditions. The developed tool is useful for the prediction of the spatio-temporal evolution of the chemical species in EVA, affecting its optical properties. The obtained predictions, related to degradation kinetics and discoloration, show a very good correlation with experimental data taken from the literature, confirming the validity of the proposed formulation and computational approach. The framework has the potential to provide quantitative comparisons of degradation resulting from any environmental condition to that gained from accelerated aging tests, also providing a guideline to design new testing protocols tailored for specific climatic zones.Mariacristina Gagliardimariacristina.gagliardi@imtlucca.itPietro Lenardapietro.lenarda@imtlucca.itMarco Paggimarco.paggi@imtlucca.it2017-02-01T08:49:17Z2017-02-01T08:49:17Zhttp://eprints.imtlucca.it/id/eprint/3652This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36522017-02-01T08:49:17ZStatistical shape modeling of the left ventricle: myocardial infarct classification challengeStatistical shape modeling is a powerful tool for visualizing and quantifying geometric and functional patterns of the heart. After myocardial infarction (MI), the left ventricle typically remodels in response to physiological challenges. Several methods have been proposed in the literature to describe statistical shape changes. Which method best characterizes left ventricular remodeling after MI is an open research question. A better descriptor of remodeling is expected to provide a more accurate evaluation of disease status in MI patients. We therefore designed a challenge to test shape characterization in MI given a set of three-dimensional left ventricular surface points. The training set comprised 100 MI patients, and 100 asymptomatic volunteers (AV). The challenge was initiated in 2015 at the Statistical Atlases and Computational Models of the Heart workshop, in conjunction with the MICCAI conference. The training set with labels was provided to participants, who were asked to submit the likelihood of MI from a different (validation) set of 200 cases (100 AV and 100 MI). Sensitivity, specificity, accuracy and area under the receiver operating characteristic curve were used as the outcome measures. The goals of this challenge were to (1) establish a common dataset for evaluating statistical shape modeling algorithms in MI, and (2) test whether statistical shape modeling provides additional information characterizing MI patients over standard clinical measures. Eleven groups with a wide variety of classification and feature extraction approaches participated in this challenge. All methods achieved excellent classification results with accuracy ranges from 0.83 to 0.98. The areas under the receiver operating characteristic curves were all above 0.90. Four methods showed significantly higher performance than standard clinical measures. The dataset and software for evaluation are available from the Cardiac Atlas Project website1.A. SuinesiaputraP. AblinX. AlbaM. AlessandriniJ. AllenW. BaiS. CimenP. ClaesB. R. CowanJ. D'hoogeN. DuchateauJ. EhrhardtA. F. FrangiA. GooyaV. GrauK. LekadirA. LuA. MukhopadhyayIlkay Oksuzilkay.oksuz@imtlucca.itX. PennecM. PereanezC. PintoP. PirasM. M. RoheD. RueckertM. SermesantK. SiddiqiM. TabassianL. TeresiS. A. TsaftarisM. WilmsA. A. YoungX. ZhangP. Medrano-Gracia2017-01-30T11:29:16Z2017-09-21T14:32:15Zhttp://eprints.imtlucca.it/id/eprint/3648This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36482017-01-30T11:29:16ZConcurrently coupled solid shell based adaptive multiscale method for fractureA solid shell-based adaptive atomistic–continuum numerical method is herein proposed to simulate complex crack growth patterns in thin-walled structures. A hybrid solid shell formulation relying on the combined use of the enhanced assumed strain (EAS) and the assumed natural strain (ANS) methods has been considered to efficiently model the material in thin structures at the continuum level. The phantom node method (PNM) is employed to model the discontinuities in the bulk. The discontinuous solid shell element is then concurrently coupled with a molecular statics model placed around the crack tip. The coupling between the coarse scale and the fine scale is realized through the use of ghost atoms, whose positions are interpolated from the coarse scale solution and enforced as boundary conditions to the fine scale model. In the proposed numerical scheme, the fine scale region is adaptively enlarged as the crack propagates and the region behind the crack tip is adaptively coarsened in order to reduce the computation costs. An energy criterion is used to detect the crack tip location. All the atomistic simulations are carried out using the LAMMPS software. A computational framework has been developed in MATLAB to trigger LAMMPS through system command. This allows a two way interaction between the coarse and fine scales in MATLAB platform, where the boundary conditions to the fine region are extracted from the coarse scale, and the crack tip location from the atomistic model is transferred back to the continuum scale. The developed framework has been applied to study crack growth in the energy minimization problems. Inspired by the influence of fracture on current–voltage characteristics of thin Silicon photovoltaic cells, the cubic diamond lattice structure of Silicon is used to model the material in the fine scale region, whilst the Tersoff potential function is employed to model the atom–atom interactions. The versatility and robustness of the proposed methodology is demonstrated by means of several fracture applications.Pattabhi R. Budarapupattabhi.budarapu@imtlucca.itJosé ReinosoMarco Paggimarco.paggi@imtlucca.it2017-01-30T10:33:52Z2017-01-30T11:33:18Zhttp://eprints.imtlucca.it/id/eprint/3647This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36472017-01-30T10:33:52ZLattice orientation and crack size effect on the mechanical properties of GrapheneThe effect of lattice orientation and crack length on the mechanical properties of Graphene are studied based on molecular dynamics simulations. Bond breaking and crack initiation in an initial edge crack model with 13 different crack lengths, in 10 different lattice orientations of Graphene are examined. In all the lattice orientations, three recurrent fracture patterns are reported. The influence of the lattice orientation and crack length on yield stress and yield strain of Graphene is also investigated. The arm-chair fracture pattern is observed to possess the lowest yield properties. A sudden decrease in yield stress and yield strain can be noticed for crack sizes <10 nm. However, for larger crack sizes, a linear decrease in yield stress is observed, whereas a constant yield strain of ≈≈0.05 is noticed. Therefore, the yield strain of ≈≈0.05 can be considered as a critical strain value below which Graphene does not show failure. This information can be utilized as a lower bound for the design of nano-devices for various strain sensor applications. Furthermore, the yield data will be useful while developing the Graphene coating on Silicon surface in order to enhance the mechanical and electrical characteristics of solar cells and to arrest the growth of micro-cracks in Silicon cells.Pattabhi R. Budarapupattabhi.budarapu@imtlucca.itB. JavvajiV. K. SutrakarD. Roy MahapatraMarco Paggimarco.paggi@imtlucca.itG. ZiT. Rabczuk2017-01-26T14:11:24Z2017-01-26T14:11:24Zhttp://eprints.imtlucca.it/id/eprint/3640This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36402017-01-26T14:11:24ZSpatial-based predictive control and geometric corridor planning for adaptive cruise control coupled with obstacle avoidanceM. Graf PlessenDaniele BernardiniHasan EsenAlberto Bemporadalberto.bemporad@imtlucca.it2017-01-24T13:21:02Z2017-08-28T15:36:22Zhttp://eprints.imtlucca.it/id/eprint/3638This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36382017-01-24T13:21:02ZOptimal energy management of a small-size building via hybrid model predictive controlAbstract This paper presents the design of a Model Predictive Control (MPC) scheme to optimally manage the thermal and electrical subsystems of a small-size building (“smart house”), with the objective of minimizing the expense for buying energy from the grid, while keeping the room temperature within given time-varying bounds. The system, for which an experimental prototype has been built, includes {PV} panels, solar collectors, a battery pack, an electrical heater in a thermal storage tank, and two pumps on the solar collector and radiator hydraulic circuits. The presence of binary control inputs together with continuous ones naturally leads to using a hybrid dynamical model, and the {MPC} controller solves a mixed-integer linear program at each sampling instant, relying on weather forecast data for ambient temperature and solar irradiance. The procedure for controller design is reported with focus on the specific application, and the proposed method is successfully tested on the experimental site.Albina KhakimovaAliya KusatayevaAkmaral ShamshimovaDana SharipovaAlberto Bemporadalberto.bemporad@imtlucca.itYakov FamiliantAlmas ShintemirovViktor TenMatteo Rubagotti2017-01-24T13:07:45Z2017-01-24T13:07:45Zhttp://eprints.imtlucca.it/id/eprint/3635This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36352017-01-24T13:07:45ZOptimal distributed task scheduling in volunteer cloudsAbstract The ever increasing request of computational resources has shifted the computing paradigm towards solutions where less computation is performed locally. The most widely adopted approach nowadays is represented by cloud computing. With the cloud, users can transparently access to virtually infinite resources with the same aptitude of using any other utility. Next to the cloud, the volunteer computing paradigm has gained attention in the last decade, where the spared resources on each personal machine are shared thanks to the users’ willingness to cooperate. Cloud and volunteer paradigms have been recently seen as companion technologies to better exploit the use of local resources. Conversely, this scenario places complex challenges in managing such a large-scale environment, as the resources available on each node and the presence of the nodes online are not known a-priori. The complexity further increases in presence of tasks that have an associated Service Level Agreement specified, e.g., through a deadline. Distributed management solutions have then be advocated as the only approaches that are realistically applicable. In this paper, we propose a framework to allocate tasks according to different policies, defined by suitable optimization problems. Then, we provide a distributed optimization approach relying on the Alternating Direction Method of Multipliers (ADMM) for one of these policies, and we compare it with a centralized approach. Results show that, when a centralized approach can not be adopted in a real environment, it could be possible to rely on the good suboptimal solutions found by the ADMM.Stefano SebastioGiorgio Gneccogiorgio.gnecco@imtlucca.itAlberto Bemporadalberto.bemporad@imtlucca.it2017-01-16T08:16:29Z2017-01-16T08:16:29Zhttp://eprints.imtlucca.it/id/eprint/3627This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36272017-01-16T08:16:29ZMolecularly Imprinted Biodegradable NanoparticlesBiodegradable polymer nanoparticles are promising carriers for targeted drug delivery in nanomedicine applications. Molecu- lar imprinting is a potential strategy to target polymer nanoparticles through binding of endogenous ligands that may promote recognition and active transport into specific cells and tissues. However, the lock-and-key mechanism of molecular imprinting requires relatively rigid cross-linked structures, unlike those of many biodegradable polymers. To date, no fully biodegradable molecularly imprinted particles have been reported in the literature. This paper reports the synthesis of a novel molecularly- imprinted nanocarrier, based on poly(lactide-co-glycolide) (PLGA) and acrylic acid, that combines biodegradability and molec- ular recognition properties. A novel three-arm biodegradable cross-linker was synthesized by ring-opening polymerization of glycolide and lactide initiated by glycerol. The resulting macromer was functionalized by introduction of end-functions through reaction with acryloyl chloride. Macromer and acrylic acid were used for the synthesis of narrowly-dispersed nanoparticles by radical polymerization in diluted conditions in the presence of biotin as template molecule. The binding capacity of the imprinted nanoparticles towards biotin and biotinylated bovine serum albumin was twentyfold that of non-imprinted nanoparti- cles. Degradation rates and functional performances were assessed in in vitro tests and cell cultures, demonstrating effective biotin-mediated cell internalization.Mariacristina Gagliardimariacristina.gagliardi@imtlucca.itAlice BerteroAngelo Bifone2017-01-09T09:22:18Z2017-08-04T10:15:18Zhttp://eprints.imtlucca.it/id/eprint/3618This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36182017-01-09T09:22:18ZRandomized trial on the effects of a combined physical/cognitive training in aged MCI subjects: the Train the Brain studyAge-related cognitive impairment and dementia are an increasing societal burden. Epidemiological studies indicate that lifestyle factors, e.g. physical, cognitive and social activities, correlate with reduced dementia risk; moreover, positive effects on cognition of physical/cognitive training have been found in cognitively unimpaired elders. Less is known about effectiveness and action mechanisms of physical/cognitive training in elders already suffering from Mild Cognitive Impairment (MCI), a population at high risk for dementia. We assessed in 113 MCI subjects aged 65–89 years, the efficacy of combined physical-cognitive training on cognitive decline, Gray Matter (GM) volume loss and Cerebral Blood Flow (CBF) in hippocampus and parahippocampal areas, and on brain-blood-oxygenation-level-dependent (BOLD) activity elicited by a cognitive task, measured by ADAS-Cog scale, Magnetic Resonance Imaging (MRI), Arterial Spin Labeling (ASL) and fMRI, respectively, before and after 7 months of training vs. usual life. Cognitive status significantly decreased in MCI-no training and significantly increased in MCI-training subjects; training increased parahippocampal CBF, but no effect on GM volume loss was evident; BOLD activity increase, indicative of neural efficiency decline, was found only in MCI-no training subjects. These results show that a non pharmacological, multicomponent intervention improves cognitive status and indicators of brain health in MCI subjects.L. MaffeiE. PicanoM. G. AndreassiA. AngelucciF. BaldacciL. BaroncelliT. BegenisicP.F. BellinviaN. BerardiL. BiagiJ. BonaccorsiE. BonanniU. BonuccelliAndrea BorghiniC, BraschiM. BroccardiR.M. BrunoM. CaleoC. CarlesiL. CarnicelliG. CartoniLuca Cecchettiluca.cecchetti@imtlucca.itM.C. CenniR. CeravoloL. ChicoS. CintoliG. CioniM. CosciaM. CostaG. D’AngeloP. D’AscanioM. De NesS. Del TurcoE. Di CoscioM. Di GalanteN. Di LascioF. FaitaI. FalorniU. FaragunaA. FenuL. FortunatoR. FrancoL. GarganiR. GargiuloL. GhiadoniF. S. GiorgiR. IannarellaC. IofridaC. KusmicF. LimongiM. MaestriM. MaffeiS. MaggiM. MainardiL. MammanaA. MarabottiV. MariottiE. MelissariA. MercuriS. MiceraS. MolinaroR. NarducciT. NavarraM. NoaleC. PagniS. PalumboR. PasquarielloS. PellegriniPietro Pietrinipietro.pietrini@imtlucca.itT. PizzorussoA. PoliL. PrataliA. ReticoE. RicciardiG. RotaA. SaleS. SbranaG. ScabiaM. ScaliD. ScelfoR. SicariG. SicilianoF. SteaS. TaddeiG. TognoniA. TonacciM. TosettiS. TurchiL. Volpi2016-11-23T10:26:36Z2017-01-09T09:55:38Zhttp://eprints.imtlucca.it/id/eprint/3601This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36012016-11-23T10:26:36ZLongitudinal monitoring of heartbeat dynamics predicts mood changes in bipolar patients: A pilot studyObjectives
Recent research indicates that Heart Rate Variability (HRV) is affected in Bipolar Disorders (BD) patients. To determine whether such alterations are a mere expression of the current mood state or rather contain longitudinal information on BD course, we examined the potential influence of states adjacent in time upon HRV features measured in a target mood state.
Methods
Longitudinal evaluation of HRV was obtained in eight BD patients by using a wearable monitoring system developed within the PSYCHE project. We extracted time-domain, frequency-domain and non-linear HRV-features and trained a Support Vector Machine (SVM) to classify HRV-features according to mood state. To evaluate the influence of adjacent mood states, we trained SVM with different HRV-feature sets: 1) belonging to each mood state considered alone; 2) belonging to each mood state and normalized using information from the preceding mood state; 3) belonging to each mood state and normalized using information from the preceding and subsequent mood states; 4) belonging to each mood state and normalized using information from two randomly chosen states.
Results
SVM classification accuracy within a target state was significantly greater when HRV-features from the previous and subsequent mood states were considered.Claudio GentiliGaetano ValenzaMimma NardelliAntonio LanatàGilles BertschyLuisa WeinerMauro MauriEnzo Pasquale ScilingoPietro Pietrinipietro.pietrini@imtlucca.it2016-11-23T09:04:15Z2017-11-29T13:22:13Zhttp://eprints.imtlucca.it/id/eprint/3600This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/36002016-11-23T09:04:15ZPolymer Nanoparticles as Smart Carriers for the Enhanced Release of Therapeutic Agents to the CNSBackground: The brain is the most protected organ in the human body; its protective shield, relying on a complex system of cells, proteins and transporters, prevents potentially harmful substances from entering the brain from the bloodstream but, on the other hand, it also stops drugs administered via the systemic route. To improve the efficacy of pharmacological treatments, targeted drug delivery by means of polymer nanoparticles is a challenging but, at the same time, efficient strategy.
Methods: Thanks to a highly multidisciplinary approach, several ways to overcome the brain protection have provided effective solutions to treat a large number of diseases. Important advances in polymer science, together with the development of novel techniques for nanocarrier preparation, and the discovery of novel targeting ligands and molecules, allow a fine-tuning of size, shape, chemicophysical properties and surface chemistry of functional particulate systems; it enables the improvement of the therapeutic performances for several drugs, also toward districts that are difficult to be treated, such as the brain.
Conclusion: This review focuses on the great strides made from scientists and doctors in the development of polymer nano-sized drug delivery systems for brain diseases. Even though the optimal nanocarrier was not yet discovered, important advances were made to strive for safer, performant and successful systems, with the expectation to find soon better solutions to cure some still untreatable pathologies.Mariacristina Gagliardimariacristina.gagliardi@imtlucca.itClaudia Borriclaudia.borri@imtlucca.it2016-10-06T15:03:20Z2017-08-08T09:10:56Zhttp://eprints.imtlucca.it/id/eprint/3575This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/35752016-10-06T15:03:20ZA computational approach to steady-state convergence of fluid limits for Coxian queuing networks with abandonmentMany-server queuing networks with general service and abandonment times have proven to be a realistic model for scenarios such as call centers and health-care systems. The presence of abandonment makes analytical treatment difficult for general topologies. Hence, such networks are usually studied by means of fluid limits. The current state of the art, however, suffers from two drawbacks. First, convergence to a fluid limit has been established only for the transient, but not for the steady state regime. Second, in the case of general distributed service and abandonment times, convergence to a fluid limit has been either established only for a single queue, or has been given by means of a system of coupled integral equations which does not allow for a numerical solution. By making the mild assumption of Coxian-distributed service and abandonment times, in this paper we address both drawbacks by establishing convergence in probability to a system of coupled ordinary differential equations (ODEs) using the theory of Kurtz. The presence of abandonments leads in many cases to ODE systems with a global attractor, which is known to be a sufficient condition for the fluid and the stochastic steady state to coincide in the limiting regime. The fact that our ODE systems are piecewise affine enables a computational method for establishing the presence of a global attractor, based on a solution of a system of linear matrix inequalities.Max Tschaikowskimax.tschaikowski@imtlucca.itMirco Tribastonemirco.tribastone@imtlucca.it