Lo studio dell'idrologia polare e' legato alla glaciologia ma anche alla paleobio- logia e alla bioastronomia, alla planetologia. Per quest'ultima vale la similitudine fra la crosta ghiacciata dei satelliti del pianeta Giove - Europa ed Encelado - e la calotta ghiacciata Antartica, sotto cui scorre, nell'ordine, un oceano d'acqua (da accertare) e una complessa rete idrografica di 379 laghi subglaciali con torrenti col- legati al mare. Lo studio dell'idrologia polare ha un riscontro diretto e propone estrapolazioni sui pianeti. La paleobiologia e' invece interessata ai laghi subglaciali isolati, custodi di segreti della vita primordiale: microrganismi antichi, nell'oscurita', con bassissimi scambi energetici, senza contatti con altre forme di vita. Siamo al confine con la bioastronomia che ricerca sui pianeti tracce di acqua e di vita. La modellistica matematica e la simulazione numerica giungono a supporto di opera- zioni di carotaggio o, al contrario, per evitarle al fine di non contaminare queste banchedati naturali, oppure per proiezioni diagnostiche o prognostiche. Discutero' il problema dell'accertamento del primo lago subglaciale alle isole Svalbard, di cui e' traccia (da interpretare) nei rilevamenti Ground Penetrating Radar. Il modello matematico adottato contiene la descrizione della dinamica e termodinamica del si- stema ghiacciaio/lago corredato di dati da spedizione polare. Il sistema differenziale viene risolto con il metodo ai volumi finiti e uno schema implicito di secondo ordine; la tecnica di front-tracking viene adottata per la frontiera di fase evolutiva (dettagli in [1]). La procedura di validazione della congettura da noi proposta, totalmente nuova ai glaciologi, ha portato a risultati numerici con ottimo riscontro con i dati di misura e conferma la possibilita' di esistenza del lago subglaciale (conclusioni in [2]). Bibliografia [1] Mansutti, D., E. Bucchignani, J. Otero and P. Glowacki, 'Modelling and numerical sensitivity study on the conjecture of a subglacial la- ke at Amundsenisen, Svalbard', (in stampa) Appl. Math. Modelling, http://dx.doi.org/10.1016/j.apm.2014.12.043, 2015. [2] Mansutti, D., E. Bucchignani, J. Otero and P. Glowacki, 'Numerical validation of the conjecture of a subglacial lake at Amundsenisen, Svalbard', (sottomesso) Appl. Math. Modelling, 2015.

First asymptotic relations of Voronovskaya-type for rational operators of Shepard-type are shown. A positive answer in some senses to a problem on the pointwise approximation power of linear operators on equidistant nodes posed by Gavrea, Gonska and Kacs is given. Direct and converse results, computational aspects and Gruss-type inequalities are also proved. Finally an application to images compression is discussed, showing the outperformance of such operators in some senses.

The accurate segmentation of the optic disc (OD) offers an important cue to extract other retinal features in an automated diagnostic system, which in turn will assist ophthalmologists to track many retinopathy conditions such as glaucoma. Research contributions regarding the OD segmentation is on the rise, since the design of a robust automated system would help prevent blindness, for instance, by diagnosing glaucoma at an early stage and a condition known as ocular hypertension. Among the evaluated OD segmentation schemes, the active contour models (ACMs) have often been preferred by researchers, because ACMs are endowed with several attractive properties. To this end, we designed an OD segmentation scheme to infer how the performance of the well-known gradient vector flow (GVF) model compares with nine popular/recent ACM algorithms by supplying them with the initial OD contour derived from the circular Hough transform. The findings would hopefully equip a diagnostic system designer with an empirical support to ratify the choice of a specific model as we are bereft of such a comparative study. A dataset comprising 169 diverse retinal images was tested, and the segmentation results were assessed by a gold standard derived from the annotations of five domain experts. The segmented ODs from the GVF-based ACM coincide to a greater degree with those of the experts in 94% of the cases as predicted by the least overall Hausdorff distance value (33.49 +/- 18.21). Additionally, the decrease in the segmentation error due to the suggested ACM has been confirmed to be statistically significant in view of the p values (<= 1.49e-09) from the Wilcoxon signed-rank test. The mean computational time taken by the investigated approaches has also been reported. (C) 2014 Elsevier Ltd. All rights reserved.

We evaluate a mathematical model of the predator-prey population dynamics in a fragmented habitat where both migration processes between habitat patches and prey control policies are taken into account. The considered system is examined by applying the aggregation method and different dynamical scenarios are generated. The resulting implications are then discussed, their primary aim being the conservation of the wolf population in the Alta Murgia National Park, a protected area situated in the Apulian Foreland and also part of the Natura 2000 network. The Italian wolf is an endangered species and the challenge for the regional authorities is how to formulate conservation policies which enable the maintenance of the said wolf population while at the same time curbing that of the local wild boars and its negative impact on agriculture. We show that our model provides constructive suggestions in how to combine wild boar abatement programs awhile maintaining suitable ecological corridors which ensure wolf migration, thus preserving wolves from extinction.

We examine spatially explicit models described by reaction-diffusion partial differential equations for the study of predator-prey population dynamics. The numerical methods we propose are based on the coupling of a finite difference/element spatial discretization and a suitable partitioned Runge-Kutta scheme for the approximation in time. The RK scheme here implemented uses an implicit scheme for the stiff diffusive term and a partitioned RK symplectic scheme for the reaction term (IMSP schemes). We revisit some results provided in the literature for the classical Lotka-Volterra system and the Rosenzweig-MacArthur model. We then extend the approach to metapopulation dynamics in order to numerically investigate the effect of migration through a corridor connecting two habitat patches. Moreover, we analyze the synchronization properties of subpopulation dynamics, when the migration occurs through corridors of variable sizes.

In this paper we consider the final distribution of fuel oil from a storage depot to a set of petrol stations faced by an oil company, which has to decide the weekly replenishment plan for each station, and determine petrol station visiting sequences (vehicle routes) for each day of the week, assuming a fleet of homogeneous vehicles (tankers). The aim is to minimize the total distance travelled by tankers during the week, while loading tankers possibly near to their capacity in order to maximize the resource utilization. The problem is modelled as a generalization of the Periodic Vehicle Routing Problem (PVRP). Due to the large size of the real instances which the company has to deal with, we solve the problem heuristically. We propose a hybrid genetic algorithm that successfully address the problem inspired to a known hybrid genetic algorithm from the literature for the PVRP. However, the proposed algorithm adopts some techniques and features tailored for the particular fuel oil distribution problem, and it is specifically designed to deal with real instances derived from the fuel oil distribution in the European context that are profoundly different from the PVRP instances available from literature. The proposed algorithm is evaluated on a set of real case studies and on a set of randomly generated instances that hold the same characteristics of the former.

The aim of this paper is to study a Bike Sharing Touring (BST) applying a mathematical model known in operation research as Orienteering Problem (OP). Several European Cities are developing BST in order to reduce the exhaust emissions and to improve the sustainability in urban areas. The authors offer a Decision Support Tool useful for the tourist and the service's manager to organize the tourists' paths on the basis of tourists' desires, subject to usable time, place of interest position and docking station location. The model analyzed presents two innovative aspects compared to a classic OP. The first one is that the start and the arrival point of routes aren't necessary coinciding and pre-conditioned. The last one is that the knowledge of tourist tours allows to book the visit to a point of interest and doing so to optimize efficiency of the whole system and not only of the single tourist tour.

In this work we proposed an integrated support system combining a meta-heuristic algorithm and a multicriteria decision analysis method to solve an orienteering problem applied to car-pooling system. For this purpose a Genetic Algorithm (GA), an Analytical Hierarchy Process (AHP) are implemented. The research is based on the awareness that decision makers (DMs) often face situations in which different conflicting viewpoints (goals or criteria) are to be considered. Current car-pooling web platforms are focused on the exchange of information among potential users and drivers. The aim of this work is to include in web platform a decision procedure to support driver to organize the tour considering more criteria. The driver has to decide which tour does and which users to take into the trip Preliminary test are given to validate the functionality and usefulness of created integrated decision support system.

This work describes two applications of the vehicle routing problem (VRP) to the design of fixed and periodic routes. The first application is an industrial case in the field of touristic cruise planning where point of interests should be visited within exactly one of multiple time windows on a weekly time basis. The second application is in retail distribution of fuel oils where petrol stations must be refueled with given fuel oil amounts periodically within a given time horizon. The work studies the VRP models for the two described applications evaluating intersections between them and studying possible unified modeling formulation.

Bruno de Finetti è senza dubbio una delle figure più importanti per la storia della Statistica e del Calcolo delle Probabilità in Italia. Però i suoi interessi furono molto più ampi e compresero molti settori della cosiddetta matematica applicata. In particolare giocò un ruolo importante nella nascita del calcolo numerico e dell'informatica in Italia, settori che peraltro costituiscono importanti strumenti per l'applicazione dei suoi studi principali. Come è naturale questa sua attività venne svolta nell'ambito di un'intensa collaborazione con Mauro Picone e con l'Istituto Nazionale per le Applicazioni del Calcolo. Essa nasce dal comune interesse per le applicazioni della matematica in ambito economico e finanziario e raggiunge forse il suo apice nell'immediato dopoguerra, periodo in cui de Finetti ha un incarico presso l'INAC. Oltre a sviluppare ricerche comuni, si reca con Picone e Fichera negli Stati Uniti per esaminare i nuovi calcolatori elettronici, cura l'installazione all'INAC di un sistema IBM a schede perforate e conduce, di concerto con Picone, un'intensa campagna per promuovere l'arrivo in Italia di un primo calcolatore elettronico.

Eugenio Elia Levi (1883-1917) fu uno dei più grandi matematici italiani del 900, come del resto il fratello Beppo. La sua produzione scientifica fu tanto profonda quanto differenziata, venne immediatamente apprezzata negli ambienti matematici internazionali e, a distanza di un secolo, conserva grande attualità in diversi campi della matematica. Momento importantissimo per la sua formazione fu la permanenza nella Scuola Normale Superiore di Pisa. Qui, dal punto di vista scientifico, venne formato da grandi maestri come Luigi Bianchi e Ulisse Dini e, nonostante la minima differenza di età, influenzò moltissimo la formazione di Mauro Picone che lo considerò sempre un proprio maestro. Dal punto di vista politico-culturale, sempre in Normale, il Levi venne in contatto e condivise le idee di diversi giovani esponenti del socialismo riformista, con i quali condividerà gli ideali irredentisti. Tra queste amicizie ha particolare importanza quella con Giuseppe Lombardo Radice per la fitta corrispondenza che intratterranno negli anni successivi e che si estenderà anche ai fratelli di Levi, continuando anche dopo la morte di quest'ultimo. Allo scoppio del conflitto, le forti convinzioni interventiste porteranno Levi ad arruolarsi ed a rifiutare qualsiasi richiamo in università o in seconda linea finché, nelle giornate convulse che seguirono Caporetto, venne ucciso da un cecchino mentre, al comando di una compagnia di genieri, tentava di allestire una linea di difesa sopra Cormons.

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.