In the framework of variable exponent Sobolev spaces, we prove that the variational eigenvalues defined by inf sup procedures of Rayleigh ratios for the Luxemburg norms are all stable under uniform convergence of the exponents. (C) 2015 Elsevier Ltd. All rights reserved.

Credit and debit card data theft is one of the earliest forms of cybercrime. Still, it is one of the most common nowadays. Attackers often aim at stealing such customer data by targeting the Point of Sale (for short, PoS) system, i.e. the point at which a retailer first acquires customer data. Modern PoS systems are powerful computers equipped with a card reader and running specialized software. Increasingly often, user devices are leveraged as input to the PoS. In these scenarios, malware that can steal card data as soon as they are read by the device has flourished. As such, in cases where customer and vendor are persistently or intermittently disconnected from the network, no secure on-line payment is possible. This paper describes FRoDO, a secure off-line micro-payment solution that is resilient to PoS data breaches. Our solution improves over up to date approaches in terms of flexibility and security. To the best of our knowledge, FRoDO is the first solution that can provide secure fully off-line payments while being resilient to all currently known PoS breaches. In particular, we detail FRoDO architecture, components, and protocols. Further, a thorough analysis of FRoDO functional and security properties is provided, showing its effectiveness and viability.

This comprehensive resource presents a highly informative overview of cloud computing security issues. This book focuses on relevant approaches aimed at monitoring and protecting computation and data hosted on heterogeneous computing resources. The most critical security aspects are thoroughly discussed, highlighting the importance of reliable secure computation over remote heterogeneous cloud nodes. This book shows that present cloud computing is inherently insecure therefore advanced execution models have to be developed to prevent unauthorized users from accessing or affecting others' data and computation. The cloud approach enables on-demand scalable services that allow performing large computations without the costs and maintenance/management issues of costly server farms (thus enabling a novel kind of outsourced computing). Essential reading for software and computer engineers as well as data architects and IT professionals to better understand the complexity and heterogeneity of modern cloud- based scenarios.

Cavitation in a liquid moving past a constraint is numerically investigated by means of a free-energy lattice Boltzmann simulation based on the van der Waals equation of state. The fluid is streamed past an obstacle, and depending on the pressure drop between inlet and outlet, vapor formation underneath the corner of the sack-wall is observed. The circumstances of cavitation formation are investigated and it is found that the local bulk pressure and mean stress are insufficient to explain the phenomenon. Results obtained in this study strongly suggest that the viscous stress, interfacial contributions to the local pressure, and the Laplace pressure are relevant to the opening of a vapor cavity. This can be described by a generalization of Joseph's criterion that includes these contributions. A macroscopic investigation measuring mass flow rate behavior and discharge coefficient was also performed. As theoretically predicted, mass flow rate increases linearly with the square root of the pressure drop. However, when cavitation occurs, the mass flow growth rate is reduced and eventually it collapses into a choked flow state. In the cavitating regime, as theoretically predicted and experimentally verified, the discharge coefficient grows with the Nurick cavitation number. (C) 2015 AIP Publishing LLC.

The increasing need for performing expensive computations has motivated outsourced computing, as in crowdsourced applications leveraging worker cloud nodes. However, these outsourced computing nodes can potentially misbehave or fail. Exploiting the redundancy of nodes can help guaranteeing correctness and availability of results. This entails that reliable distributed computing can be achieved at the expense of convenience. In this paper, we provide a solution for a generic class of problems that distribute a parallel computation over a set of nodes where trustworthiness of the outsourced computation is important. In particular, we discuss AntiCheetah, an approach modeling the assignment of input elements to cloud nodes as a multi-round system. AntiCheetah is resilient to node cheating, even in scenarios where smart cheaters return the same fake values. To this end, cost-efficient redundancy is used to detect and correct anomalies. Furthermore, we discuss the benefits and pitfalls of the proposed approach over different scenarios, especially with respect to cheaters' behavior. Extensive experimental results are analyzed, showing the effectiveness and viability of our approach.

Malware for smartphones has rocketed over the last years. Market operators face the challenge of keeping their stores free from malicious apps, a task that has become increasingly complex as malware developers are progressively using advanced techniques to defeat malware detection tools. One such technique commonly observed in recent malware samples consists of hiding and obfuscating modules containing malicious functionality in places that static analysis tools overlook (e.g., within data objects). In this paper, we describe ALTERDROID, a dynamic analysis approach for detecting such hidden or obfuscated malware components distributed as parts of an app package. The key idea in ALTERDROID consists of analyzing the behavioral differences between the original app and a number of automatically generated versions of it, where a number of modifications (faults) have been carefully injected. Observable differences in terms of activities that appear or vanish in the modified app are recorded, and the resulting differential signature is analyzed through a pattern-matching process driven by rules that relate different types of hidden functionalities with patterns found in the signature. A thorough justification and a description of the proposed model are provided. The extensive experimental results obtained by testing ALTERDROID over relevant apps and malware samples support the quality and viability of our proposal.

We present a lattice Boltzmann realization of Grad's extended hydrodynamic approach to nonequilibrium flows. This is achieved by using higher-order isotropic lattices coupled with a higher-order regularization procedure. The method is assessed for flow across parallel plates and three-dimensional flows in porous media, showing excellent agreement of the mass flow with analytical and numerical solutions of the Boltzmann equation across the full range of Knudsen numbers, from the hydrodynamic regime to ballistic motion.

We investigate the slip properties of water confined in graphite-like nanochannels by non-equilibrium molecular dynamics simulations, with the aim of identifying and analyze separately the influence of different physical quantities on the slip length. In a system under confinement but connected to a reservoir of fluid, the chemical potential is the natural control parameter: we show that two nanochannels characterized by the same macroscopic contact angle --but a different microscopic surface potential-- do not exhibit the same slip length unless the chemical potential of water in the two channels is matched. Some methodological issues related to the preparation of samples for the comparative analysis in confined geometries are also discussed.

I consider a thin metallic plate whose top side is inaccessible and in contact with an aggressive environment (a corroding fluid, hard particles hitting the boundary, ...). On first approximation, heat exchange between metal and fluid follows linear Newtons cooling lawat least as long as the inaccessible side is not damaged. I assume that deviations from Newton's law are modelled by means of a nonlinear perturbative term h. On the other hand, I am able to heat the conductor and take temperature maps of the accessible side (Active Infrared Thermography). My goal is to recover the nonlinear perturbation of the exchange law on the inaccessible side. The problem is stated as an inverse ill-posed problem for the heat equation with nonlinear boundary conditions. I prove that the nonlinear term is identified by one Cauchy data set and produce approximated solutions by means of optimization. In conclusion, I try to drive mathematical modelling as far as possible: although I use advanced results in mathematical analysis (theory of nonlinear boundary value problems, domain derivative), I apply them immediately to technical problems.

Linear combinations of iterates of Bernstein polynomials exponentially converging to the Lagrange interpolating polynomial are given. The results are applied in CAGD to get an exponentially fast weighted progressive iterative approximation technique to fit data with finer and finer precision.

On the occasion of the 140th anniversary of the birth of the famous Italian mathematician Beppo Levi (1875-1961), we publish an interview with his daughter Emilia. We also recall his brother Eugenio Elia Levi, a well-known and brilliant mathematician whose life was cut short at the front during World War I. A brief outline of Beppo Levi's life is followed by an introduction to a letter that he wrote to the periodical Israel in 1919, in part regarding the foundation of the state of Israel. Finally, we publish an English translation of the letter in its entirety.

In questo rapporto viene presentato un nuovo algoritmo per il calcolo di flussi a superficie libera con forte deformazione e frammentazione. L'algoritmo è ottenuto accoppiando un classico schema ai Volumi Finiti (FV), in cui le equazioni di Navier-Stokes sono discretizzate su una griglia Euleriana, con un approccio basato su un metodo Lagrangiano, basato sulla Smoothed Particle Hydrodynamics (SPH). L'algoritmo è formulato in modo da sfruttare al meglio le caratteristiche di ogni schema nella maniera più efficiente e accurata: lo schema ai Volumi Finiti è usato per risolvere la zona del flusso lontana dalla superficie libera e i flussi a parete, mentre il solutore SPH è implementato solo nella regione con superficie libera, al fine di catturare i dettagli della evoluzione del fronte. I risultati discussi provano che l'uso combinato dei due solutori è conveniente sia dal punto di vista dell'accuratezza che da quello del tempo di calcolo.

In this short communication we present an original way to couple the Brownian motion and the heat equation. More in general, we suggest a way for coupling the Langevin equation for a particle, which describes a single realization of its trajectory, with the associated Fokker-Planck equation, which instead describes the evolution of the particle's probability density function. Numerical results show that it is indeed possible to obtain a regularized Brownian motion and a Brownianized heat equation still preserving the global statistical properties of the solutions. The results also suggest that the more macroscale leads the dynamics the more one can reduce the microscopic degrees of freedom.

Presentazione a convegno

The SAP4PRISMA project research activities aimed at supporting the Italian hyperspectral PRISMA mission by developing preliminary processing chains suitable for PRISMA to obtain high level hyperspectral data products for agriculture, land degradation, natural and human hazards.

Additive partial linear models with nonparametric additive components of heterogeneous smoothness are studied. To achieve optimal rates in large sample situations we use block wavelet penalisation techniques combined with adaptive (group) LASSO procedures for selecting the variables in the linear part and the the additive components in the nonparametric part of the models. Numerical implementations of our procedures for proximal like algorithms are discussed. Large sample properties of the estimates and of the model selection are presented and the results are illustrated with simulated examples and a real data analysis.

In transportation networks with limited capacities and travel times on the arcs, a class of problems attracting a growing scientific interest is represented by the optimal routing and scheduling of given amounts of flow to be transshipped from the origin points to the specific destinations in minimum time. Such problems are of particular concern to emergency transportation where evacuation plans seek to minimize the time evacuees need to clear the affected area and reach the safe zones. Flows over time approaches are among the most suitable mathematical tools to provide a modelling representation of these problems from a macroscopic point of view. Among them, the Quickest Path Problem (QPP), requires an origin-destination flow to be routed on a single path while taking into account inflow limits on the arcs and minimizing the makespan, namely, the time instant when the last unit of flow reaches its destination. In the context of emergency transport, the QPP represents a relevant modelling tool, since its solutions are based on unsplittable dynamic flows that can support the development of evacuation plans which are very easy to be correctly implemented, assigning one single evacuation path to a whole population. This way it is possible to prevent interferences, turbulence, and congestions that may affect the transportation process, worsening the overall clearing time. Nevertheless, the current state-of-the-art presents a lack of studies on multicommodity generalizations of the QPP, where network flows refer to various populations, possibly with different origins and destinations. In this paper we provide a contribution to fill this gap, by considering the Multicommodity Quickest Path Problem (MCQPP), where multiple commodities, each with its own origin, destination and demand, must be routed on a capacitated network with travel times on the arcs, while minimizing the overall makespan and allowing the flow associated to each commodity to be routed on a single path. For this optimization problem, we provide the first mathematical formulation in the scientific literature, based on mixed integer programming and encompassing specific features aimed at empowering the suitability of the arising solutions in real emergency transportation plans. A computational experience performed on a set of benchmark instances is then presented to provide a proof-of-concept for our original model and to evaluate the quality and suitability of the provided solutions together with the required computational effort. Most of the instances are solved at the optimum by a commercial MIP solver, fed with a lower bound deriving from the optimal makespan of a splittable-flow relaxation of the MCQPP.

In an attempt to study the accuracy and utility of 'coarse grained' models for methane-clathrate systems, molecular-dynamics simulations were run for three different potential models. One was fully atomistic of TIP4P water and fully atomistic methane, the next model was atomistic SPC water and coarse-grained UA methane, whilst the final model was the fully coursed-grained mW model. All models were run at two different sizes (8 and 64 fully-occupied sI clathrate unit cells) at 250 K and 60 bar. It was found that the coarse-grained models had a high level of accuracy in recreating structural properties, such as density or radial distribution functions (RDFs), with the obvious exception of not being able to create RDFs for atoms which are neglected by the model. More coarse grained models were shown to have lower accuracy for time-dependent phenomena, such as identifying the density or velocity fluctuations' frequencies.

We present the calculation of the gradients of the profiles to be passed to ORM MTR to define the initial guess and the assumed profiles for the interfering species.

We discuss the items to be modified to introduce the HG in the ORM MTR