In this work, we present the results of a ship propeller design optimization campaign carried out in the framework of the research project PRELICA, funded by the Friuli Venezia Giulia regional government. The main idea of this work is to operate on a multidisciplinary level to identify propeller shapes that lead to reduced tip vortex-induced pressure and increased efficiency without altering the thrust. First, a specific tool for the bottom-up construction of parameterized propeller blade geometries has been developed. The algorithm proposed operates with a user defined number of arbitrary shaped or NACA airfoil sections, and employs arbitrary degree NURBS to represent the chord, pitch, skew and rake distribution as a function of the blade radial coordinate. The control points of such curves have been modified to generate, in a fully automated way, a family of blade geometries depending on as many as 20 shape parameters. Such geometries have then been used to carry out potential flow simulations with the Boundary Element Method based software PROCAL. Given the high number of parameters considered, such a preliminary stage allowed for a fast evaluation of the performance of several hundreds of shapes. In addition, the data obtained from the potential flow simulation allowed for the application of a parameter space reduction methodology based on active subspaces (AS) property, which suggested that the main propeller performance indices are, at a first but rather accurate approximation, only depending on a single parameter which is a linear combination of all the original geometric ones. AS analysis has also been used to carry out a constrained optimization exploiting response surface method in the reduced parameter space, and a sensitivity analysis based on such surrogate model. The few selected shapes were finally used to set up high fidelity RANS simulations and select an optimal shape.

JF - VIII International Conference on Computational Methods in Marine Engineering ER - TY - CHAP T1 - Computational methods in cardiovascular mechanics T2 - Cardiovascular Mechanics Y1 - 2018 A1 - Auricchio, Ferdinando A1 - Conti, Michele A1 - Lefieux, Adrian A1 - Morganti, Simone A1 - Alessandro Reali A1 - Gianluigi Rozza A1 - Veneziani, Alessandro ED - Michel F. Labrosse AB -The introduction of computational models in cardiovascular sciences has been progressively bringing new and unique tools for the investigation of the physiopathology. Together with the dramatic improvement of imaging and measuring devices on one side, and of computational architectures on the other one, mathematical and numerical models have provided a new, clearly noninvasive, approach for understanding not only basic mechanisms but also patient-specific conditions, and for supporting the design and the development of new therapeutic options. The terminology in silico is, nowadays, commonly accepted for indicating this new source of knowledge added to traditional in vitro and in vivo investigations. The advantages of in silico methodologies are basically the low cost in terms of infrastructures and facilities, the reduced invasiveness and, in general, the intrinsic predictive capabilities based on the use of mathematical models. The disadvantages are generally identified in the distance between the real cases and their virtual counterpart required by the conceptual modeling that can be detrimental for the reliability of numerical simulations.

JF - Cardiovascular Mechanics PB - CRC Press UR - https://www.taylorfrancis.com/books/e/9781315280288/chapters/10.1201%2Fb21917-5 ER - TY - JOUR T1 - Currents and dislocations at the continuum scale JF - Methods and Applications of Analysis Y1 - 2016 A1 - Riccardo Scala A1 - Nicolas Van Goethem AB -A striking geometric property of elastic bodies with dislocations is that the deformation tensor cannot be written as the gradient of a one-to-one immersion, its curl being nonzero and equal to the density of the dislocations, a measure concentrated in the dislocation lines. In this work, we discuss the mathematical properties of such constrained deformations and study a variational problem in finite-strain elasticity, where Cartesian maps allow us to consider deformations in $L^p$ with $1\leq p<2$, as required for dislocation-induced strain singularities. Firstly, we address the problem of mathematical modeling of dislocations. It is a key purpose of the paper to build a framework where dislocations are described in terms of integral 1-currents and to extract from this theoretical setting a series of notions having a mechanical meaning in the theory of dislocations. In particular, the paper aims at classifying integral 1-currents, with modeling purposes. In the second part of the paper, two variational problems are solved for two classes of dislocations, at the mesoscopic and at the continuum scale. By continuum it is here meant that a countable family of dislocations is considered, allowing for branching and cluster formation, with possible complex geometric patterns. Therefore, modeling assumptions of the defect part of the energy must also be provided, and discussed.

PB - International Press of Boston VL - 23 ER - TY - JOUR T1 - A compatible-incompatible decomposition of symmetric tensors in Lp with application to elasticity JF - Mathematical Methods in the Applied Sciences Y1 - 2015 A1 - Maggiani, Giovanni Battista A1 - Riccardo Scala A1 - Nicolas Van Goethem KW - 35J58 KW - 35Q74 KW - compatibility conditions KW - elasticity KW - Korn inequality KW - strain decomposition KW - subclass74B05 AB -In this paper, we prove the Saint-Venant compatibility conditions in $L^p$ for $p\in(1,∞)$, in a simply connected domain of any space dimension. As a consequence, alternative, simple, and direct proofs of some classical Korn inequalities in Lp are provided. We also use the Helmholtz decomposition in $L^p$ to show that every symmetric tensor in a smooth domain can be decomposed in a compatible part, which is the symmetric part of a displacement gradient, and in an incompatible part, which is the incompatibility of a certain divergence-free tensor. Moreover, under a suitable Dirichlet boundary condition, this Beltrami-type decomposition is proved to be unique. This decomposition result has several applications, one of which being in dislocation models, where the incompatibility part is related to the dislocation density and where $1 < p < 2$. This justifies the need to generalize and prove these rather classical results in the Hilbertian case ($p = 2$), to the full range $p\in(1,∞)$. Copyright © 2015 John Wiley & Sons, Ltd.

VL - 38 UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/mma.3450 ER - TY - RPRT T1 - Dynamics of screw dislocations: a generalised minimising-movements scheme approach Y1 - 2015 A1 - Giovanni A. Bonaschi A1 - Patrick Van Meurs A1 - Marco Morandotti AB - The gradient flow structure of the model introduced in [CG99] for the dynamics of screw dislocations is investigated by means of a generalised minimising-movements scheme approach. The assumption of a finite number of available glide directions, together with the "maximal dissipation criterion" that governs the equations of motion, results into solving a differential inclusion rather than an ODE. This paper addresses how the model in [CG99] is connected to a time-discrete evolution scheme which explicitly confines dislocations to move each time step along a single glide direction. It is proved that the time-continuous model in [CG99] is the limit of these time-discrete minimising-movement schemes when the time step converges to 0. The study presented here is a first step towards a generalization of the setting in [AGS08, Chap. 2 and 3] that allows for dissipations which cannot be described by a metric. PB - SISSA UR - http://urania.sissa.it/xmlui/handle/1963/34495 U1 - 34692 U2 - Mathematics U4 - 1 ER - TY - JOUR T1 - Adler-Gelfand-Dickey approach to classical W-algebras within the theory of Poisson vertex algebras Y1 - 2014 A1 - Alberto De Sole A1 - Victor G. Kac A1 - Daniele Valeri AB - We put the Adler-Gelfand-Dickey approach to classical W-algebras in the framework of Poisson vertex algebras. We show how to recover the bi-Poisson structure of the KP hierarchy, together with its generalizations and reduction to the N-th KdV hierarchy, using the formal distribution calculus and the lambda-bracket formalism. We apply the Lenard-Magri scheme to prove integrability of the corresponding hierarchies. We also give a simple proof of a theorem of Kupershmidt and Wilson in this framework. Based on this approach, we generalize all these results to the matrix case. In particular, we find (non-local) bi-Poisson structures of the matrix KP and the matrix N-th KdV hierarchies, and we prove integrability of the N-th matrix KdV hierarchy. PB - SISSA UR - http://hdl.handle.net/1963/7242 N1 - 45 pages ER - TY - JOUR T1 - Classical W-algebras and generalized Drinfeld-Sokolov hierarchies for minimal and short nilpotents JF - Communications in Mathematical Physics 331, nr. 2 (2014) 623-676 Y1 - 2014 A1 - Alberto De Sole A1 - Victor G. Kac A1 - Daniele Valeri AB - We derive explicit formulas for lambda-brackets of the affine classical W-algebras attached to the minimal and short nilpotent elements of any simple Lie algebra g. This is used to compute explicitly the first non-trivial PDE of the corresponding intgerable generalized Drinfeld-Sokolov hierarchies. It turns out that a reduction of the equation corresponding to a short nilpotent is Svinolupov's equation attached to a simple Jordan algebra, while a reduction of the equation corresponding to a minimal nilpotent is an integrable Hamiltonian equation on 2h-3 functions, where h is the dual Coxeter number of g. In the case when g is sl_2 both these equations coincide with the KdV equation. In the case when g is not of type C_n, we associate to the minimal nilpotent element of g yet another generalized Drinfeld-Sokolov hierarchy. PB - SISSA UR - http://hdl.handle.net/1963/6979 N1 - 46 pages U1 - 6967 U2 - Mathematics U4 - 1 U5 - MAT/07 FISICA MATEMATICA ER - TY - JOUR T1 - A correction and an extension of Stampacchia's work on the geometric BVP Y1 - 2014 A1 - Giovanni Vidossich AB - G. Stampacchia introduced the geometric boundary value problem for ODEs in his doctoral thesis and published four papers related to it. Here we point out that the proof of his last theorem on the subject is incorrect and we provide a substitute for it as well as a generalizations of some of his earlier results. PB - Advanced Nonlinear Studies UR - http://urania.sissa.it/xmlui/handle/1963/35023 U1 - 35263 U2 - Mathematics U4 - 1 ER - TY - JOUR T1 - Dirac reduction for Poisson vertex algebras JF - Communications in Mathematical Physics 331, nr. 3 (2014) 1155-1190 Y1 - 2014 A1 - Alberto De Sole A1 - Victor G. Kac A1 - Daniele Valeri AB - We construct an analogue of Dirac's reduction for an arbitrary local or non-local Poisson bracket in the general setup of non-local Poisson vertex algebras. This leads to Dirac's reduction of an arbitrary non-local Poisson structure. We apply this construction to an example of a generalized Drinfeld-Sokolov hierarchy. PB - SISSA UR - http://hdl.handle.net/1963/6980 N1 - 31 pages U1 - 6968 U2 - Mathematics U4 - 1 U5 - MAT/07 FISICA MATEMATICA ER - TY - RPRT T1 - Dislocations at the continuum scale: functional setting and variational properties Y1 - 2014 A1 - Riccardo Scala A1 - Nicolas Van Goethem UR - http://cvgmt.sns.it/paper/2294/ ER - TY - JOUR T1 - Editorial Y1 - 2014 A1 - Ciro Ciliberto A1 - Gianni Dal Maso A1 - Pasquale Vetro PB - Springer UR - http://urania.sissa.it/xmlui/handle/1963/34712 U1 - 34926 U2 - Mathematics U4 - 1 ER - TY - RPRT T1 - Integrability of Dirac reduced bi-Hamiltonian equations Y1 - 2014 A1 - Alberto De Sole A1 - Victor G. Kac A1 - Daniele Valeri AB - First, we give a brief review of the theory of the Lenard-Magri scheme for a non-local bi-Poisson structure and of the theory of Dirac reduction. These theories are used in the remainder of the paper to prove integrability of three hierarchies of bi-Hamiltonian PDE's, obtained by Dirac reduction from some generalized Drinfeld-Sokolov hierarchies. PB - SISSA UR - http://hdl.handle.net/1963/7247 N1 - 15 pages U1 - 7286 U2 - Mathematics U4 - 1 U5 - MAT/07 FISICA MATEMATICA ER - TY - CONF T1 - Reduced basis method for the Stokes equations in decomposable domains using greedy optimization T2 - ECMI 2014 proceedings Y1 - 2014 A1 - Laura Iapichino A1 - Alfio Quarteroni A1 - Gianluigi Rozza A1 - Volkwein, Stefan JF - ECMI 2014 proceedings ER - TY - JOUR T1 - Six-dimensional supersymmetric gauge theories, quantum cohomology of instanton moduli spaces and gl(N) Quantum Intermediate Long Wave Hydrodynamics Y1 - 2014 A1 - Giulio Bonelli A1 - Antonio Sciarappa A1 - Alessandro Tanzini A1 - Petr Vasko AB - We show that the exact partition function of U(N) six-dimensional gauge theory with eight supercharges on C^2 x S^2 provides the quantization of the integrable system of hydrodynamic type known as gl(N) periodic Intermediate Long Wave (ILW). We characterize this system as the hydrodynamic limit of elliptic Calogero-Moser integrable system. We compute the Bethe equations from the effective gauged linear sigma model on S^2 with target space the ADHM instanton moduli space, whose mirror computes the Yang-Yang function of gl(N) ILW. The quantum Hamiltonians are given by the local chiral ring observables of the six-dimensional gauge theory. As particular cases, these provide the gl(N) Benjamin-Ono and Korteweg-de Vries quantum Hamiltonians. In the four dimensional limit, we identify the local chiral ring observables with the conserved charges of Heisenberg plus W_N algebrae, thus providing a gauge theoretical proof of AGT correspondence. PB - Springer UR - http://urania.sissa.it/xmlui/handle/1963/34546 U1 - 34771 U2 - Physics U4 - 2 ER - TY - JOUR T1 - Some remarks on the seismic behaviour of embedded cantilevered retaining walls Y1 - 2014 A1 - Riccardo Conti A1 - F. Burali D'Arezzo A1 - Giulia M.B. Viggiani AB - This paper is a numerical investigation of the physical phenomena that control the dynamic behaviour of embedded cantilevered retaining walls. Recent experimental observations obtained from centrifuge tests have shown that embedded cantilevered retaining walls experience permanent displacements even before the acceleration reaches its critical value, corresponding to full mobilisation of the soil strength. The motivation for this work stems from the need to incorporate these observations in simplified design procedures. A parametric study was carried out on a pair of embedded cantilevered walls in dry sand, subjected to real earthquakes scaled at different values of the maximum acceleration. The results of these analyses indicate that, for the geotechnical design of the wall, the equivalent acceleration to be used in pseudo-static calculations can be related to the maximum displacement that the structure can sustain, and can be larger than the maximum acceleration expected at the site. For the structural design of the wall, it is suggested that the maximum bending moments of the wall can be computed using a realistic distribution of contact stress and a conservative value of the pseudo-static acceleration, taking into account two-dimensional amplification effects near the walls. PB - Thomas Telford UR - http://urania.sissa.it/xmlui/handle/1963/35073 U1 - 35308 U2 - Physics U4 - 2 ER - TY - JOUR T1 - The stringy instanton partition function Y1 - 2014 A1 - Giulio Bonelli A1 - Antonio Sciarappa A1 - Alessandro Tanzini A1 - Petr Vasko AB - We perform an exact computation of the gauged linear sigma model associated to a D1-D5 brane system on a resolved A_1 singularity. This is accomplished via supersymmetric localization on the blown-up two-sphere. We show that in the blow-down limit C^2/Z_2 the partition function reduces to the Nekrasov partition function evaluating the equivariant volume of the instanton moduli space. For finite radius we obtain a tower of world-sheet instanton corrections, that we identify with the equivariant Gromov-Witten invariants of the ADHM moduli space. We show that these corrections can be encoded in a deformation of the Seiberg-Witten prepotential. From the mathematical viewpoint, the D1-D5 system under study displays a twofold nature: the D1-branes viewpoint captures the equivariant quantum cohomology of the ADHM instanton moduli space in the Givental formalism, and the D5-branes viewpoint is related to higher rank equivariant Donaldson-Thomas invariants of P^1 x C^2. PB - Springer UR - http://urania.sissa.it/xmlui/handle/1963/34589 U1 - 34796 U2 - Physics U4 - 2 ER - TY - RPRT T1 - Structure of classical (finite and affine) W-algebras Y1 - 2014 A1 - Alberto De Sole A1 - Victor G. Kac A1 - Daniele Valeri AB - First, we derive an explicit formula for the Poisson bracket of the classical finite W-algebra W^{fin}(g,f), the algebra of polynomial functions on the Slodowy slice associated to a simple Lie algebra g and its nilpotent element f. On the other hand, we produce an explicit set of generators and we derive an explicit formula for the Poisson vertex algebra structure of the classical affine W-algebra W(g,f). As an immediate consequence, we obtain a Poisson algebra isomorphism between W^{fin}(g,f) and the Zhu algebra of W(g,f). We also study the generalized Miura map for classical W-algebras. PB - SISSA UR - http://hdl.handle.net/1963/7314 N1 - 40 pages U1 - 7359 U2 - Mathematics U4 - 1 U5 - MAT/07 FISICA MATEMATICA ER - TY - JOUR T1 - Vortex Partition Functions, Wall Crossing and Equivariant Gromov–Witten Invariants Y1 - 2014 A1 - Giulio Bonelli A1 - Antonio Sciarappa A1 - Alessandro Tanzini A1 - Petr Vasko AB - In this paper we identify the problem of equivariant vortex counting in a (2,2) supersymmetric two dimensional quiver gauged linear sigma model with that of computing the equivariant Gromov–Witten invariants of the GIT quotient target space determined by the quiver. We provide new contour integral formulae for the I and J-functions encoding the equivariant quantum cohomology of the target space. Its chamber structure is shown to be encoded in the analytical properties of the integrand. This is explained both via general arguments and by checking several key cases. We show how several results in equivariant Gromov–Witten theory follow just by deforming the integration contour. In particular, we apply our formalism to compute Gromov–Witten invariants of the C3/Zn orbifold, of the Uhlembeck (partial) compactification of the moduli space of instantons on C2, and of An and Dn singularities both in the orbifold and resolved phases. Moreover, we analyse dualities of quantum cohomology rings of holomorphic vector bundles over Grassmannians, which are relevant to BPS Wilson loop algebrae. PB - Springer UR - http://urania.sissa.it/xmlui/handle/1963/34652 U1 - 34859 U2 - Physics ER - TY - JOUR T1 - Classical W-algebras and generalized Drinfeld-Sokolov bi-Hamiltonian systems within the theory of Poisson vertex algebras JF - Communications in Mathematical Physics 323, nr. 2 (2013) 663-711 Y1 - 2013 A1 - Alberto De Sole A1 - Victor G. Kac A1 - Daniele Valeri AB - We provide a description of the Drinfeld-Sokolov Hamiltonian reduction for the construction of classical W-algebras within the framework of Poisson vertex algebras. In this context, the gauge group action on the phase space is translated in terms of (the exponential of) a Lie conformal algebra action on the space of functions. Following the ideas of Drinfeld and Sokolov, we then establish under certain sufficient conditions the applicability of the Lenard-Magri scheme of integrability and the existence of the corresponding integrable hierarchy of bi-Hamiltonian equations. PB - Springer UR - http://hdl.handle.net/1963/6978 N1 - 43 pages. Second version with minor editing and corrections U1 - 6966 U2 - Mathematics U4 - 1 U5 - MAT/07 FISICA MATEMATICA ER - TY - RPRT T1 - Dislocation dynamics in crystals: a macroscopic theory in a fractional Laplace setting Y1 - 2013 A1 - Serena Dipierro A1 - Giampiero Palatucci A1 - Enrico Valdinoci KW - nonlocal Allen-Cahn equation AB - We consider an evolution equation arising in the Peierls-Nabarro model for crystal dislocation. We study the evolution of such dislocation function and show that, at a macroscopic scale, the dislocations have the tendency to concentrate at single points of the crystal, where the size of the slip coincides with the natural periodicity of the medium. These dislocation points evolve according to the external stress and an interior repulsive potential. PB - SISSA UR - http://hdl.handle.net/1963/7124 U1 - 7124 U2 - Mathematics U4 - 1 U5 - MAT/05 ANALISI MATEMATICA ER - TY - JOUR T1 - Existence and symmetry results for a Schrodinger type problem involving the fractional Laplacian JF - Le Matematiche (Catania), Vol. 68 (2013), no. 1: 201-216 Y1 - 2013 A1 - Serena Dipierro A1 - Giampiero Palatucci A1 - Enrico Valdinoci AB -This paper deals with the following class of nonlocal Schr\"odinger equations $$ \displaystyle (-\Delta)^s u + u = |u|^{p-1}u \ \ \text{in} \ \mathbb{R}^N, \quad \text{for} \ s\in (0,1). $$ We prove existence and symmetry results for the solutions $u$ in the fractional Sobolev space $H^s(\mathbb{R}^N)$. Our results are in clear accordance with those for the classical local counterpart, that is when $s=1$.

PB - University of Catania U1 - 7318 U2 - Mathematics U4 - -1 ER - TY - JOUR T1 - Fields of bounded deformation for mesoscopic dislocations Y1 - 2013 A1 - Nicolas Van Goethem AB - In this paper we discuss the consequences of the distributional approach to dislocations in terms of the mathematical properties\\r\\nof the auxiliary model fields such as displacement and displacement gradient which are obtained directly from \\r\\nthe main model field here considered as the linear strain. We show that these fields cannot be introduced rigourously without \\r\\nthe introduction of gauge fields, or equivalently, without cuts in the Riemann foliation associated to the dislocated crystal.\\r\\nIn a second step we show that the space of bounded deformations follows from the distributional approach in a natural way and \\r\\ndiscuss the reasons why it is adequate to model dislocations. The case of dislocation clusters is also addressed, as it represents an important issue in industrial crystal growth while from a mathematical point of view, peculiar phenomena might appear at the set of accumulation points. \\r\\nThe elastic-plastic decomposition of the strain within this approach is also given a precise meaning. PB - SISSA UR - http://hdl.handle.net/1963/6378 U1 - 6311 U2 - Mathematics U4 - 1 U5 - MAT/05 ANALISI MATEMATICA ER - TY - RPRT T1 - Minimal partitions and image classification using a gradient-free perimeter approximation Y1 - 2013 A1 - Samuel Amstutz A1 - Nicolas Van Goethem A1 - Antonio André Novotny KW - Image classification, deblurring, optimal partitions, perimeter approximation AB - In this paper a new mathematically-founded method for the optimal partitioning of domains, with applications to the classification of greyscale and color images, is proposed. Since optimal partition problems are in general ill-posed, some regularization strategy is required. Here we regularize by a non-standard approximation of the total interface length, which does not involve the gradient of approximate characteristic functions, in contrast to the classical Modica-Mortola approximation. Instead, it involves a system of uncoupled linear partial differential equations and nevertheless shows $\Gamma$-convergence properties in appropriate function spaces. This approach leads to an alternating algorithm that ensures a decrease of the objective function at each iteration, and which always provides a partition, even during the iterations. The efficiency of this algorithm is illustrated by various numerical examples. Among them we consider binary and multilabel minimal partition problems including supervised or automatic image classification, inpainting, texture pattern identification and deblurring. PB - SISSA UR - http://hdl.handle.net/1963/6976 U1 - 6964 U2 - Mathematics U4 - 1 U5 - MAT/05 ANALISI MATEMATICA ER - TY - JOUR T1 - Asymptotics of the s-perimeter as s →0 JF - Discrete Contin. Dyn. Syst. 33, nr.7 (2012): 2777-2790 Y1 - 2012 A1 - Serena Dipierro A1 - Alessio Figalli A1 - Giampiero Palatucci A1 - Enrico Valdinoci AB -We deal with the asymptotic behavior of the $s$-perimeter of a set $E$ inside a domain $\Omega$ as $s\searrow0$. We prove necessary and sufficient conditions for the existence of such limit, by also providing an explicit formulation in terms of the Lebesgue measure of $E$ and $\Omega$. Moreover, we construct examples of sets for which the limit does not exist.

PB - American Institute of Mathematical Sciences U1 - 7317 U2 - Mathematics U4 - -1 ER - TY - JOUR T1 - On the behaviour of flexible retaining walls under seismic actions JF - Geotechnique, Volume 62, Issue 12, December 2012, Pages 1081-1094 Y1 - 2012 A1 - Riccardo Conti A1 - G.S.P. Madabhushi A1 - Giulia M.B. Viggiani KW - Centrifuge modelling AB - This paper describes an experimental investigation of the behaviour of embedded retaining walls under seismic actions. Nine centrifuge tests were carried out on reduced-scale models of pairs of retaining walls in dry sand, either cantilevered or with one level of props near the top. The experimental data indicate that, for maximum accelerations that are smaller than the critical limit equilibrium value, the retaining walls experience significant permanent displacements under increasing structural loads, whereas for larger accelerations the walls rotate under constant internal forces. The critical acceleration at which the walls start to rotate increases with increasing maximum acceleration. No significant displacements are measured if the current earthquake is less severe than earthquakes previously experienced by the wall. The increase of critical acceleration is explained in terms of redistribution of earth pressures and progressive mobilisation of the passive strength in front of the wall. The experimental data for cantilevered retaining walls indicate that the permanent displacements of the wall can be reasonably predicted adopting a Newmark-type calculation with a critical acceleration that is a fraction of the limit equilibrium value. PB - ICE Publishing UR - http://hdl.handle.net/1963/6933 U1 - 6912 U2 - Mathematics U4 - -1 ER - TY - JOUR T1 - Numerical modelling of installation effects for diaphragm walls in sand JF - Acta Geotechnica, Volume 7, Issue 3, September 2012, Pages 219-237 Y1 - 2012 A1 - Riccardo Conti A1 - Luca de Sanctis A1 - Giulia M.B. Viggiani KW - Constitutive relations AB - The scopes of this work are to study the mechanisms of load transfer and the deformations of the ground during slurry trenching and concreting in dry sand and to evaluate their effects on service structural loads, wall deflections and ground displacements behind the wall caused by subsequent excavation. A series of three-dimensional finite element analyses was carried out modelling the installation of diaphragm walls consisting of panels of different length. The soil was modelled as either linearly elastic-perfectly plastic or incrementally non-linear (hypoplastic) with elastic strain range. Plane strain analyses of diaphragm walls of identical cross section were also carried out in which wall installation was either modelled or the wall was wished in place (WIP). The analyses predict ground movements consistent with the experimental observations both in magnitude and trend. The results also show that the maximum horizontal wall deflections and structural loads reduce with increasing panel aspect ratio towards a minimum which is about twice the value computed for WIP analyses. Panel aspect ratios should be larger than about three to take advantage of the three-dimensional effects. The pattern and magnitude of surface vertical displacements obtained from linearly elastic-perfectly plastic analyses, no matter whether three- or two-dimensional, are unrealistic. PB - Springer UR - http://hdl.handle.net/1963/6934 U1 - 6916 U2 - Mathematics U4 - -1 ER - TY - RPRT T1 - Topological sensitivity analysis for high order elliptic operators Y1 - 2012 A1 - Samuel Amstutz A1 - Antonio André Novotny A1 - Nicolas Van Goethem KW - Topological derivative, Elliptic operators, Polarization tensor AB - The topological derivative is defined as the first term of the asymptotic expansion of a given shape functional with respect to a small parameter that measures the size of a singular domain perturbation. It has applications in many different fields such as shape and topology optimization, inverse problems, image processing and mechanical modeling including synthesis and/or optimal design of microstructures, fracture mechanics sensitivity analysis and damage evolution modeling. The topological derivative has been fully developed for a wide range of second order differential operators. In this paper we deal with the topological asymptotic expansion of a class of shape functionals associated with elliptic differential operators of order 2m, m>=1. The general structure of the polarization tensor is derived and the concept of degenerate polarization tensor is introduced. We provide full mathematical justifications for the derived formulas, including precise estimates of remainders. PB - SISSA UR - http://hdl.handle.net/1963/6343 U1 - 6272 U2 - Mathematics U4 - 1 U5 - MAT/05 ANALISI MATEMATICA ER - TY - JOUR T1 - Cluster solutions for the Schrödinger-Poisson-Slater problem around a local minimum of the potential JF - Rev. Mat. Iberoamericana Y1 - 2011 A1 - David Ruiz A1 - Giusi Vaira PB - Real Sociedad Matemática Española VL - 27 UR - https://projecteuclid.org:443/euclid.rmi/1296828834 ER - TY - JOUR T1 - Infinitely many positive solutions for a Schrödinger–Poisson system JF - Nonlinear Analysis: Theory, Methods & Applications Y1 - 2011 A1 - Pietro d’Avenia A1 - Alessio Pomponio A1 - Giusi Vaira KW - Non-autonomous Schrödinger–Poisson system KW - Perturbation method AB -We are interested in the existence of infinitely many positive solutions of the Schrödinger–Poisson system −Δu+u+V(|x|)ϕu=|u|p−1u,x∈R3,−Δϕ=V(|x|)u2,x∈R3, where V(|x|) is a positive bounded function, 1<p<5 and V(r

VL - 74 UR - http://www.sciencedirect.com/science/article/pii/S0362546X11003518 ER - TY - JOUR T1 - Gene expression analysis of the emergence of epileptiform activity after focal injection of kainic acid into mouse hippocampus. JF - The European journal of neuroscience. 2010 Oct; 32(8):1364-79 Y1 - 2010 A1 - Dario Motti A1 - Caroline Le Duigou A1 - Nicole Chemaly A1 - Lucia Wittner A1 - Dejan Lazarevic A1 - Helena Krmac A1 - Troels Torben Marstrand A1 - Eivind Valen A1 - Remo Sanges A1 - Elia Stupka A1 - Albin Sandelin A1 - Enrico Cherubini A1 - Stefano Gustincich A1 - Richard Miles AB -We report gene profiling data on genomic processes underlying the progression towards recurrent seizures after injection of kainic acid (KA) into the mouse hippocampus. Focal injection enabled us to separate the effects of proepileptic stimuli initiated by KA injection. Both the injected and contralateral hippocampus participated in the status epilepticus. However, neuronal death induced by KA treatment was restricted to the injected hippocampus, although there was some contralateral axonal degeneration. We profiled gene expression changes in dorsal and ventral regions of both the injected and contralateral hippocampus. Changes were detected in the expression of 1526 transcripts in samples from three time-points: (i) during the KA-induced status epilepticus, (ii) at 2 weeks, before recurrent seizures emerged, and (iii) at 6 months after seizures emerged. Grouping genes with similar spatio-temporal changes revealed an early transcriptional response, strong immune, cell death and growth responses at 2 weeks and an activation of immune and extracellular matrix genes persisting at 6 months. Immunostaining for proteins coded by genes identified from array studies provided evidence for gliogenesis and suggested that the proteoglycan biglycan is synthesized by astrocytes and contributes to a glial scar. Gene changes at 6 months after KA injection were largely restricted to tissue from the injection site. This suggests that either recurrent seizures might depend on maintained processes including immune responses and changes in extracellular matrix proteins near the injection site or alternatively might result from processes, such as growth, distant from the injection site and terminated while seizures are maintained.

PB - Wiley UR - http://hdl.handle.net/1963/4480 U1 - 4244 U2 - Neuroscience U3 - Neurobiology U4 - -1 ER - TY - JOUR T1 - Positive solutions for some non-autonomous Schrödinger–Poisson systems JF - Journal of Differential Equations Y1 - 2010 A1 - Giovanna Cerami A1 - Giusi Vaira PB - Academic Press VL - 248 ER - TY - JOUR T1 - Solutions of the Schrödinger–Poisson problem concentrating on spheres, part I: necessary conditions JF - Mathematical Models and Methods in Applied Sciences Y1 - 2009 A1 - Ianni, Isabella A1 - Giusi Vaira AB -In this paper we study a coupled nonlinear Schrödinger–Poisson problem with radial functions. This system has been introduced as a model describing standing waves for the nonlinear Schrödinger equations in the presence of the electrostatic field. We provide necessary conditions for concentration on sphere for the solutions of this kind of problem extending the results already known.

VL - 19 UR - https://doi.org/10.1142/S0218202509003589 ER - TY - JOUR T1 - On concentration of positive bound states for the Schrödinger-Poisson problem with potentials JF - Advanced nonlinear studies Y1 - 2008 A1 - Ianni, Isabella A1 - Giusi Vaira AB -We study the existence of semiclassical states for a nonlinear Schrödinger-Poisson system that concentrate near critical points of the external potential and of the density charge function. We use a perturbation scheme in a variational setting, extending the results in [1]. We also discuss necessary conditions for concentration.

PB - Advanced Nonlinear Studies, Inc. VL - 8 ER - TY - JOUR T1 - Noncommutative families of instantons JF - Int. Math. Res. Not. vol. 2008, Article ID rnn038 Y1 - 2008 A1 - Giovanni Landi A1 - Chiara Pagani A1 - Cesare Reina A1 - Walter van Suijlekom AB - We construct $\\\\theta$-deformations of the classical groups SL(2,H) and Sp(2). Coacting on the basic instanton on a noncommutative four-sphere $S^4_\\\\theta$, we construct a noncommutative family of instantons of charge 1. The family is parametrized by the quantum quotient of $SL_\\\\theta(2,H)$ by $Sp_\\\\theta(2)$. PB - Oxford University Press UR - http://hdl.handle.net/1963/3417 U1 - 918 U2 - Mathematics U3 - Mathematical Physics ER - TY - JOUR T1 - On periodic elliptic equations with gradient dependence JF - Communications on Pure and Applied Analysis Y1 - 2008 A1 - Massimiliano Berti A1 - Matzeu, M A1 - Enrico Valdinoci AB - We construct entire solutions of Δu = f(x, u, ∇u) which are superpositions of odd, periodic functions and linear ones, with prescribed integer or rational slope. VL - 7 N1 - cited By (since 1996)1 ER - TY - JOUR T1 - The Dirac operator on SU_q(2) JF - Commun. Math. Phys. 259 (2005) 729-759 Y1 - 2005 A1 - Ludwik Dabrowski A1 - Giovanni Landi A1 - Andrzej Sitarz A1 - Walter van Suijlekom A1 - Joseph C. Varilly AB - We construct a 3^+ summable spectral triple (A(SU_q(2)),H,D) over the quantum group SU_q(2) which is equivariant with respect to a left and a right action of U_q(su(2)). The geometry is isospectral to the classical case since the spectrum of the operator D is the same as that of the usual Dirac operator on the 3-dimensional round sphere. The presence of an equivariant real structure J demands a modification in the axiomatic framework of spectral geometry, whereby the commutant and first-order properties need be satisfied only modulo infinitesimals of arbitrary high order. PB - Springer UR - http://hdl.handle.net/1963/4425 N1 - v2: minor changes U1 - 4175 U2 - Mathematics U3 - Mathematical Physics U4 - -1 ER - TY - JOUR T1 - The local index formula for SUq(2) JF - K-Theory 35 (2005) 375-394 Y1 - 2005 A1 - Walter van Suijlekom A1 - Ludwik Dabrowski A1 - Giovanni Landi A1 - Andrzej Sitarz A1 - Joseph C. Varilly AB - We discuss the local index formula of Connes-Moscovici for the isospectral noncommutative geometry that we have recently constructed on quantum SU(2). We work out the cosphere bundle and the dimension spectrum as well as the local cyclic cocycles yielding the index formula. UR - http://hdl.handle.net/1963/1713 U1 - 2438 U2 - Mathematics U3 - Mathematical Physics ER - TY - JOUR T1 - Principal fibrations from noncommutative spheres JF - Comm. Math. Phys. 260 (2005) 203-225 Y1 - 2005 A1 - Giovanni Landi A1 - Walter van Suijlekom AB - We construct noncommutative principal fibrations S_\\\\theta^7 \\\\to S_\\\\theta^4 which are deformations of the classical SU(2) Hopf fibration over the four sphere. We realize the noncommutative vector bundles associated to the irreducible representations of SU(2) as modules of coequivariant maps and construct corresponding projections. The index of Dirac operators with coefficients in the associated bundles is computed with the Connes-Moscovici local index formula. The algebra inclusion $A(S_\\\\theta^4) \\\\into A(S_\\\\theta^7)$ is an example of a not trivial quantum principal bundle. UR - http://hdl.handle.net/1963/2284 U1 - 1732 U2 - Mathematics U3 - Mathematical Physics ER - TY - JOUR T1 - Periodic orbits close to elliptic tori and applications to the three-body problem JF - Ann. Sc. Norm. Super. Pisa Cl. Sci. (5) 3 (2004) 87-138 Y1 - 2004 A1 - Massimiliano Berti A1 - Luca Biasco A1 - Enrico Valdinoci AB - We prove, under suitable non-resonance and non-degeneracy ``twist\\\'\\\' conditions, a Birkhoff-Lewis type result showing the existence of infinitely many periodic solutions, with larger and larger minimal period, accumulating onto elliptic invariant tori (of Hamiltonian systems). We prove the applicability of this result to the spatial planetary three-body problem in the small eccentricity-inclination regime. Furthermore, we find other periodic orbits under some restrictions on the period and the masses of the ``planets\\\'\\\'. The proofs are based on averaging theory, KAM theory and variational methods. (Supported by M.U.R.S.T. Variational Methods and Nonlinear Differential Equations.) PB - Scuola Normale Superiore di Pisa UR - http://hdl.handle.net/1963/2985 U1 - 1348 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - Solving Honig generic problem about Volterra integral equations JF - Bull. Polish Acad. Sci. Math. 44 (1996), no. 4, 495--498 Y1 - 1996 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/941 U1 - 3513 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - A general existence theorem for boundary value problems for ordinary differential equations JF - Nonlinear Anal. 15 (1990), no. 10, 897--914 Y1 - 1990 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/632 U1 - 3821 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - On the continuous dependence of solutions of boundary value problems for ordinary differential equations JF - J. Differential Equations 82 (1989), no. 1, 1--14 Y1 - 1989 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/633 U1 - 3820 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - On the continuous dependence of solutions of boundary value problems for ordinary differential equations (Revised version) JF - J. Differential Equations 82 (1989), no. 1, 1-14 Y1 - 1989 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/666 U1 - 3260 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - Hyperbolic equations as ordinary differential equations in Banach spaces Y1 - 1989 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/773 U1 - 3018 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - A pointwise regularity theory for the two-obstacle problem JF - Acta Math. 163 (1989), no. 1-2, 57-107 Y1 - 1989 A1 - Gianni Dal Maso A1 - Umberto Mosco A1 - Maria Agostina Vivaldi PB - SISSA Library UR - http://hdl.handle.net/1963/643 U1 - 3810 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - On the solvability of boundary value problems for higher order ordinary differential equations (Revised version) JF - Nonlinear Anal. 13 (1989), no. 10, 1171-1179 Y1 - 1989 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/662 U1 - 3264 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - On the solvability of boundary value problems for higher order ordinary differential equations JF - Nonlinear Anal. 13 (1989), no. 10, 1171-179 Y1 - 1989 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/631 U1 - 3822 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - The two-point boundary value problem from the Cauchy problem JF - J. Differential Equations 60 (1985), no. 1, 1--20 Y1 - 1985 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/332 U1 - 3635 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - On the asymptotic behaviour of solutions to Pazy\\\'s class of evolution equations Y1 - 1983 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/276 U1 - 3691 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - Towards a theory for periodic solutions to first order ordinary differential equations. Y1 - 1983 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/295 U1 - 3672 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - A criterion for he existence of maximal solutions of strongly nonlinear elliptic problems Y1 - 1982 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/161 U1 - 3806 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - On the obstacle problem for strongly nonlinear elliptic equations Y1 - 1982 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/162 U1 - 3805 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - Three uniqueness theorems for strongly non-linear elliptic problems Y1 - 1982 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/167 U1 - 3800 U2 - Mathematics U3 - Functional Analysis and Applications ER - TY - JOUR T1 - Uniqueness and multiplicity of periodic solutions to first order ordinary differential equations JF - Not Found Y1 - 0 A1 - Giovanni Vidossich PB - SISSA Library UR - http://hdl.handle.net/1963/321 U1 - 3646 U2 - Mathematics U3 - Functional Analysis and Applications ER -