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2015 Rapporto tecnico metadata only access

On the modulus of continuity of solutions to n-Laplacian equation

Angela Alberico ; Andrea Cianchi ; Carlo Sbordone
2015 Rapporto tecnico metadata only access

Continuity properties of solutions to p-Laplacian type elliptic equations

Angela Alberico ; Andrea Cianchi ; Carlo Sbordone
2015 Rapporto tecnico metadata only access

A comparison result for solutions of anisotropic elliptic problems via symmetrization

Angela ALBERICO ; Giuseppina DI BLASIO ; Filomena FEO
2015 Articolo in rivista metadata only access

Modeling Dry-Port-Based Freight Distribution Planning

Teodor Gabriel Crainic ; Paolo Dell'Olmo ; Nicoletta Ricciardi ; Antonino Sgalambro

In this paper we review the dry port concept and its outfalls in terms of optimal design and management of freight distribution. Some optimization challenges arising from the presence of dry ports in intermodal freight transport systems are presented and discussed. Then we consider the tactical planning problem of defining the optimal routes and schedules for the fleet of vehicles providing transportation services between the terminals of a dry-port-based intermodal system. An original service network design model based on a mixed integer programming mathematical formulation is proposed to solve the considered problem. An experimental framework built upon realistic instances inspired by regional cases is described and the computational results of the model are presented and discussed.

Service network design; Dry port; Logistics; Optimization; Mixed integer programming
2015 Articolo in rivista metadata only access

Modeling rationality to control self-organization of crowds: an environmental approach

In this paper we propose a classification of crowd models in built environments based on the assumed pedestrian ability to foresee the movements of other walkers. At the same time, we introduce a new family of macroscopic models, which make it possible to tune the degree of predictiveness of the individuals. By means of these models we describe both the natural behavior of pedestrians, i.e., their expected behavior according to their real limited predictive ability, and a target behavior, i.e., a particularly efficient behavior one would like them to assume (for, e.g., logistic or safety reasons). Then we tackle a challenging shape optimization problem, which consists in controlling the environment in such a way that the natural behavior is as close as possible to the target one, thereby inducing pedestrians to behave more rationally than what they would naturally do. We present numerical tests which elucidate the role of rational/predictive abilities and show some promising results about the shape optimization problem.

Pedestrian dynamics conservation laws Hamilton-Jacobi-Bellman equations minimum time problem obstacles shape optimization
2015 Articolo in rivista metadata only access

Radiation drag in the field of a non-spherical source

Bini D ; Geralico A ; Passamonti A

The motion of a test particle in the gravitational field of a non-spherical source endowed with both mass and mass quadrupole moment is investigated when a test radiation field is also present. The background is described by the Erez-Rosen solution, which is a static spacetime belonging to the Weyl class of solutions to the vacuum Einstein's field equations, and reduces to the familiar Schwarzschild solution when the quadrupole parameter vanishes. The radiation flux has a fixed but arbitrary (non-zero) angular momentum. The interaction with the radiation field is assumed to be Thomson-like, i.e., the particles absorb and re-emit radiation, thus suffering for a friction-like drag force. Such an additional force is responsible for the PoyntingRobertson effect, which is well established in the framework of Newtonian gravity and has been recently extended to the general theory of relativity. The balance between gravitational attraction, centrifugal force and radiation drag leads to the occurrence of equilibrium circular orbits which are attractors for the surrounding matter for every fixed value of the interaction strength. The presence of the quadrupolar structure of the source introduces a further degree of freedom: there exists a whole family of equilibrium orbits parametrized by the quadrupole parameter, generalizing previous works. This scenario is expected to play a role in the context of accretion matter around compact objects.

Poynting-Robertson effect
2015 Articolo in rivista metadata only access

Particles under radiation thrust in Schwarzschild space-time: a flux perpendicular to the equatorial plane

Bini D ; Geralico A ; Jantzen RT ; Semerak O

Motivated by the picture of a thin accretion disc around a black hole, radiating mainly in the direction perpendicular to its plane, we study the motion of test particles interacting with a test geodesic radiation flux propagating perpendicular to the equatorial plane in a Schwarzschild space-time. We assume that the interaction (kind of Poynting-Robertson effect) is modelled by an effective term corresponding to a Thomson-type radiation drag. After approximating the individual photon trajectories in quite an accurate way, we solve the continuity equation (up to linear order in M) in order to find a consistent radiation-flux density, prescribing a certain plausible equatorial profile. The combined effect of gravitation and radiation is illustrated on several figures; they confirm that the particles are generically strongly influenced by the flux, in particular, they are both collimated and accelerated in the direction perpendicular to the disc, but the acceleration received in this manner is not enough to explain highly relativistic outflows emanating from some black-hole-disc sources. Main improvement needed is a more realistic description of the radiation-particle interaction, allowing for Compton-type frequency-dependent effect and particle heating/cooling.

2015 Articolo in rivista metadata only access

Convergence of a numerical method for the solution of non-standard integro-differential boundary value problems

M Basile ; E Messina ; W Themistoclakis ; A Vecchio

In a recent paper we proposed a numerical method to solve a non-standard non-linear second order integro-differential boundary value problem. Here, we answer two questions remained open: we state the order of convergence of this method and provide some sufficient conditions for the uniqueness of the solution both of the discrete and the continuous problem. Finally, we compare the performances of the method for different choices of the iteration procedure to solve the non-standard nonlinearity.

Numerical solution of boundary value problems; Non-linear non-standard integro-differential equations; Half-line; Order of convergence; Uniqueness
2015 Articolo in rivista metadata only access

Satellite Earth observation data to identify anthropogenic pressures in selected protected areas

Nagendra H ; Mairota P ; Marangi C ; Lucas R ; Dimopoulos P ; Honrado JP ; Niphadkar M ; Mücher CA ; Tomaselli V ; Panitsa M ; Tarantino M ; Manakos I ; Blonda P

tProtected areas are experiencing increased levels of human pressure. To enable appropriate conserva-tion action, it is critical to map and monitor changes in the type and extent of land cover/use and habitatclasses, which can be related to human pressures over time. Satellite Earth observation (EO) data andtechniques offer the opportunity to detect such changes. Yet association with field information and expertinterpretation by ecologists is required to interpret, qualify and link these changes to human pressure.There is thus an urgent need to harmonize the technical background of experts in the field of EO dataanalysis with the terminology of ecologists, protected area management authorities and policy makers inorder to provide meaningful, context-specific value-added EO products. This paper builds on the DPSIRframework, providing a terminology to relate the concepts of state, pressures, and drivers with the appli-cation of EO analysis. The type of pressure can be inferred through the detection of changes in state (i.e.changes in land cover and/or habitat type and/or condition). Four broad categories of changes in stateare identified, i.e. land cover/habitat conversion, land cover/habitat modification, habitat fragmentationand changes in landscape connectivity, and changes in plant community structure. These categories ofchange in state can be mapped through EO analyses, with the goal of using expert judgement to relatechanges in state to causal direct anthropogenic pressures. Drawing on expert knowledge, a set of pro-tected areas located in diverse socio-ecological contexts and subject to a variety of pressures are analysedto (a) link the four categories of changes in state of land cover/habitats to the drivers (anthropogenic pres-sure), as relevant to specific target land cover and habitat classes; (b) identify (for pressure mapping) themost appropriate spatial and temporal EO data sources as well as interpretations from ecologists andfield data useful in connection with EO data analysis. We provide detailed examples for two protectedareas, demonstrating the use of EO data for detection of land cover/habitat change, coupled with expertinterpretation to relate such change to specific anthropogenic pressures. We conclude with a discussionof the limitations and feasibility of using EO data and techniques to identify anthropogenic pressures,suggesting additional research efforts required in this direction

Positive symplectic integratorsm predator-prey dynamics
2015 Articolo in rivista metadata only access

Splitting schemes and energy preservation for separable Hamiltonian systems

It is known that symplectic algorithms do not necessarily conserve energy even for the harmonic oscillator. However, for separable Hamiltonian systems, splitting and composition schemes have the advantage to be explicit and can be constructed to preserve energy. In this paper we describe and test an integrator built on a one-parameter family of symplectic symmetric splitting methods, where the parameter is chosen at each time step so as to minimize the energy error. For second-degree polynomial Hamiltonian functions as the one describing the linear oscillator, we build up second and fourth order symmetric methods which are symplectic, energy-preserving and explicit. For non-linear examples, it is possible to construct schemes with minimum error on energy conservation. The methods are semi-explicit in the sense that they require, as additional computational effort, the search for a zero of a scalar function with respect to a scalar variable. Therefore, our approach may represent an effective alternative to energy-preserving implicit methods whenever multi-dimensional problems are dealt with as is the case of many applications of interest.

Separable Hamiltonian problems
2015 Articolo in rivista metadata only access

A patient with PMP22-related hereditary neuropathy and DBH-gene-related dysautonomia

BartolettiStella A ; Chiaro G ; CalandraBuonaura G ; Contin M ; Scaglione C ; Barletta G ; Cecere A ; Garagnani P ; Tieri P ; Ferrarini A ; Piras S ; Franceschi C ; Delledonne M ; Cortelli P ; Capellari S

Recurrent focal neuropathy with liability to pressure palsies is a relatively frequent autosomal-dominant demyelinating neuropathy linked to peripheral myelin protein 22 (PMP22) gene deletions. The combination of PMP22 gene mutations with other genetic variants is known to cause a more severe phenotype than expected. We present the case of a patient with severe orthostatic hypotension since 12 years of age, who inherited a PMP22 gene deletion from his father. Genetic double trouble was suspected because of selective sympathetic autonomic disturbances. Through exome-sequencing analysis, we identified two novel mutations in the dopamine beta hydroxylase gene. Moreover, with interactome analysis, we excluded a further influence on the origin of the disease by variants in other genes. This case increases the number of unique patients presenting with dopamine-?-hydroxylase deficiency and of cases with genetically proven double trouble. Finding the right, complete diagnosis is crucial to obtain adequate medical care and appropriate genetic counseling.

Dopamine-?-hydroxylase deficiency Exome sequencing dysautonomia Recurrent focal neuropathy with liability to pressure palsies
2015 Editoriale, Commentario, Contributo a Forum in rivista metadata only access

Editorial: Multi-omic data integration.

multi-omics multi-omic data integration integration systems biology network analysis
2015 Curatela di monografia / trattato scientifico metadata only access

Multi-omic Data Integration

P Tieri ; C Nardini ; J Dent et al

Stable, predictive biomarkers and interpretable disease signatures are seen as a signi cant step towards personalized medicine. In this per- spective, integration of multi-omic data com- ing from genomics, transcriptomics, glycomics, proteomics, metabolomics is a powerful strat- egy to reconstruct and analyse complex mul- ti-dimensional interactions, enabling deeper mechanistic and medical insight. At the same time, there is a rising concern that much of such different omic data -although often publicly and freely available- lie in data- bases and repositories underutilised or not used at all. Issues coming from lack of stand- ardisation and shared biological identities are also well-known. From these considerations, a novel, pressing request arises from the life sciences to design methodologies and approaches that allow for these data to be interpreted as a whole, i.e. as inter- twined molecular signatures containing genes, proteins, mRNAs and miRNAs, able to capture inter-layers connections and complexity. Papers discuss data integration approaches and methods of several types and extents, their application in understanding the pathogenesis of speci c diseases or in identifying candidate biomarkers to exploit the full bene t of multi-omic datasets and their intrinsic information content. Topics of interest include, but are not limited to: o Methods for the integration of layered data, including, but not limited to, genomics, transcrip- tomics, glycomics, proteomics, metabolomics; o Application of multi-omic data integration approaches for diagnostic biomarker discovery in any eld of the life sciences; o Innovative approaches for the analysis and the visualization of multi-omic datasets; o Methods and applications for systematic measurements from single/undivided samples (com- prising genomic, transcriptomic, proteomic, metabolomic measurements, among others); o Multi-scale approaches for integrated dynamic modelling and simulation; o Implementation of applications, computational resources and repositories devoted to data integration including, but not limited to, data warehousing, database federation, semantic integration, service-oriented and/or wiki integration; o Issues related to the de nition and implementation of standards, shared identities and seman- tics, with particular focus on the integration problem.

multi-omics multi-omic data integration integration systems biology network analysis
2015 Articolo in rivista metadata only access

Muscl reconstruction and haar wavelets

MUSCL extensions (Monotone Upstream-centered Schemes for Conservation Laws) of the Godunov numerical scheme for scalar conservation laws are shown to admit a rather simple reformulation when recast in the formalism of the Haar multi-resolution analysis of L<sup>2</sup>(R). By pursuing this wavelet reformulation, a seemingly new MUSCL-WB scheme is derived for advection-reaction equations which is stable for a Courant number up to 1 (instead of roughly 1/2 ). However these highorder reconstructions aren't likely to improve the handling of delicate nonlinear wave interactions in the involved case of systems of Conservation/Balance laws.

Godunov scheme Haar wavelets Multi-resolution analysis MUSCL reconstruction Second-order resolution (SOR) Slope-limiter Wave interactions Well-balanced (WB) scheme
2015 Articolo in rivista metadata only access

Locally inertial approximations of balance laws arising in (1 + 1)-dimensional general relativity

An elementary model of (1 + 1)-dimensional general relativity, known as "R = T " and mainly developed by Mann and coworkers in the early 1990s, is set up in various contexts. Its formulation, mostly in isothermal coordinates, is derived and a relativistic Euler system of selfgravitating gas coupled to a Liouville equation for the metric's conformal factor is deduced. First, external field approximations are carried out: both a Klein-Gordon equation is studied along with its corresponding density, and a Dirac one inside a hydrostatic gravitational field induced by a static, piecewise constant mass repartition. Finally, the coupled Euler-Liouville system is simulated, by means of a locally inertial Godunov scheme: the gravitational collapse of a static random initial distribution of density is displayed. Well-balanced discretizations rely on the treatment of source terms at each interface of the computational grid, hence the metric remains flat in every computational cell.

1+1 general relativity Dirac and Klein-Gordon equations Intrinsic finite differences Locally inertial scheme Relativistic hydrodynamics Schemes Structure-preserving and well-balanced
2015 Monografia o trattato scientifico metadata only access

Error Estimates for Well-Balanced Schemes on Simple Balance Laws

Debora Amadori ; Laurent Gosse

This monograph presents, in an attractive and self-contained form, techniques based on the L1 stability theory derived at the end of the 1990s by A. Bressan, T.-P. Liu and T. Yang that yield original error estimates for so-called well-balanced numerical schemes solving 1D hyperbolic systems of balance laws. Rigorous error estimates are presented for both scalar balance laws and a position-dependent relaxation system, in inertial approximation. Such estimates shed light on why those algorithms based on source terms handled like "local scatterers" can outperform other, more standard, numerical schemes. Two-dimensional Riemann problems for the linear wave equation are also solved, with discussion of the issues raised relating to the treatment of 2D balance laws. All of the material provided in this book is highly relevant for the understanding of well-balanced schemes and will contribute to future improvements.

analytical and numerical aspects of 1D hyperbolic balance laws accuracy of well-balanced numerical schemes wavefront tracking 2D Riemann problems
2015 Articolo in rivista metadata only access

Application of dynamic overlapping grids to the simulation of the flow around a fully-appended submarine

Abstract The hydrodynamic characterization of control appendages for ship hulls is of paramount importance for the assessment of maneuverability characteristics. However, the accurate numerical simulation of turbulent flow around a fully appended maneuvering vessel is a challenging task, because of the geometrical complexity of the appendages and of the complications connected to their movement during the computation. In addition, the accurate description of the flow within the boundary layer is important in order to estimate correctly the forces acting on each portion of the hull. To this aim, the use of overlapping multi-block body fitted grids can be very useful to obtain both a proper description of each particular region in the computational domain and an accurate prediction of the boundary layer, retaining, at the same time, a good mesh quality. Moreover, block-structured grids with partial overlapping can be fruitfully exploited to control grid spacing close to solid walls, without propagation of undesired clustering of grid cells in the interior of the domain. This approach proved to be also very useful in reducing grid generation time. In the present paper, some details of the flow simulation around a fully appended submarine is reported, with emphasis on the issues related to the complexities of the geometry to be used in the simulations and to the need to move the appendages in order to change the configuration of the various appendages.

Dynamic overlapping grids CFD Maneuvering submarine Fully-appended ship
2015 Articolo in rivista metadata only access

Numerical simulations of aggregate breakup in bounded and unbounded turbulent flows

M Bäbler ; L Biferale ; L Brandt ; U Feudel ; K Guseva ; A S Lanotte ; C Marchioli ; F Picano ; G Sardina ; A Soldati ; F Toschi

Breakup of small aggregates in fully developed turbulence is studied by means of direct numerical simulations in a series of typical bounded and unbounded flow configurations, such as a turbulent channel flow, a developing boundary layer and homogeneous isotropic turbulence. The simplest criterion for breakup is adopted, whereby aggregate breakup occurs when the local hydrodynamic stress "1=2, with " being the energy dissipation at the position of the aggregate, overcomes a given threshold cr, which is characteristic for a given type of aggregate. Results show that the breakup rate decreases with increasing threshold. For small thresholds, it develops a scaling behaviour among the different flows. For high thresholds, the breakup rates show strong differences between the different flow configurations, highlighting the importance of non-universal mean-flow properties. To further assess the effects of flow inhomogeneity and turbulent fluctuations, the results are compared with those obtained in a smooth stochastic flow. Furthermore, we discuss the limitations and applicability of a set of independent proxies.

breakup/coalescence multiphase and particle-laden flows turbulent flows
2015 Contributo in volume (Capitolo o Saggio) metadata only access

From five key questions to a System Sociology theory

Ajmone Marsan Giulia ; Bellomo Nicola ; Herrero Miguel Angel ; Tosin Andrea

This chapter presents some speculations focused on the design of a System Sociology approach. A key feature of that approach consists in the modeling of social and economical systems viewed as living complex systems subject to dynamical evolution. At the technical level, the mathematical techniques proposed to the modeling of social and economic systems make use of the framework of the kinetic theory for active particles, where nonlinear interactions among subjects are modeled according to game-theoretical tools. Applications focus on the interplay between individual competition for wealth distribution that, when coupled with political stances coming from support or opposition to the government, may give rise to strongly self-enhanced effects resulting in the onset of extreme conflicts. The latter may be thought of as describing early stages of massive, unpredictable events known as Black Swans.

Active particles stochastic games social conflicts irrational behaviors large deviations
2015 Contributo in Atti di convegno metadata only access

Improving predictive quality of Kriging metamodel by variogram adaptation

Application of interpolation/approximation techniques (metamodels, for brevity) is commonly adopted in numerical optimization, typically to reduce the overall execution time of the optimization process. A limited number of trial solution are computed, cov- ering the design variable space: those trial points are then used for the determination of an estimate of the objective function in any desired location of the design space. The behaviour of the prediction of the objective function in between two trial points depends on the structure of the adopted metamodel, and there is no possibility, in principle, to determine a priori if one method is preferable to another. Nevertheless, some metamodels require the adjustment of a set of tuning parameters, and this operation is critical for the prevision qualities of the metamodel. In this paper, some base parameters of the kernel of the kriging metamodel are tuned in order to improve the overall quality of the prediction.

Interpolation/approximation methods Metamodels Kriging In