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Search Results: 1 - 10 of 4840 matches for " Renata Frigeri "
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Massacre in Realengo: the imagery coverage of Veja’s magazine in a woman-hater attack Massacre em Realengo: a cobertura imagética da revista Vejaem ataque misógino
Hertez Wendel de Camargo,Renata Frigeri
Semina : Ciências Sociais e Humanas , 2011, DOI: 10.5433/1679-0383.2011v32n2p107-116
Abstract: This work studies the photographic coverage by Veja magazine of the massacre of Realengo, in Rio de Janeiro, when a former student entered the classroom killed and ten girls and two boys. The study is limited to photographs published by Veja magazine, the vehicle chosen for the object of study. The objective of this workis to verify the intent of photographers covered the attack on the construction of images and generating senses. Este trabalho estuda a cobertura fotográfica do massacre de Realengo, no Rio de Janeiro, quando um ex-aluno entrou em salas de aula e assassinou a tiros dez meninas e dois meninos. O estudo limita-se às fotografias publicadas pela revista Veja, veículo eleito para objeto de estudo. O objetivo deste trabalho é verificar a intencionalidade dos fotógrafos que realizaram a cobertura do ataque na constru o de imagens e gera o de sentidos.
Global existence of weak solutions for a nonlocal model for two-phase flows of incompressible fluids with unmatched densities
Sergio Frigeri
Mathematics , 2015,
Abstract: We consider a diffuse interface model for an incompressible isothermal mixture of two viscous Newtonian fluids with different densities in a bounded domain in two or three space dimensions. The model is the nonlocal version of the one recently derived by Abels, Garcke and Gr\"{u}n and consists in a Navier-Stokes type system coupled with a convective nonlocal Cahn-Hilliard equation. The density of the mixture depends on an order parameter. For this nonlocal system we prove existence of global dissipative weak solutions for the case of singular double-well potentials and non degenerate mobilities. To this goal we devise an approach which is completely independent of the one employed by Abels, Depner and Garcke to establish existence of weak solutions for the local Abels et al. model.
Visualizzazione stereoscopica collaborativa di geodati tridimensionali con software libero
Alessandro Frigeri,Costanzo Federico
GEOmedia , 2012,
Abstract: La visualizzazione dell'informazione sussiste da quando esiste l'informazione stessa e nasce dalla necessità sia dicomprendere meglio particolari aspetti di un insieme di dati, sia di comunicarli. Collaborative three-dimensional stereoscopic visualization of geodata with free software Geodata are inherently three-dimensional, when referred to heights and depths. This article describes the development and applications of a interactive and collaborative stereoscopic visualization system built by off-the-shelf hardware and focusing on the use of a completely free open source software stack, from the operative system to the graphics drivers and the users space applications.
Global and trajectory attractors for a nonlocal Cahn-Hilliard-Navier-Stokes system
Sergio Frigeri,Maurizio Grasselli
Mathematics , 2011, DOI: 10.1007/s10884-012-9272-3
Abstract: The Cahn-Hilliard-Navier-Stokes system is based on a well-known diffuse interface model and describes the evolution of an incompressible isothermal mixture of binary fluids. A nonlocal variant consists of the Navier-Stokes equations suitably coupled with a nonlocal Cahn-Hilliard equation. The authors, jointly with P. Colli, have already proven the existence of a global weak solution to a nonlocal Cahn-Hilliard-Navier-Stokes system subject to no-slip and no-flux boundary conditions. Uniqueness is still an open issue even in dimension two. However, in this case, the energy identity holds. This property is exploited here to define, following J.M. Ball's approach, a generalized semiflow which has a global attractor. Through a similar argument, we can also show the existence of a (connected) global attractor for the convective nonlocal Cahn-Hilliard equation with a given velocity field, even in dimension three. Finally, we demonstrate that any weak solution fulfilling the energy inequality also satisfies an energy inequality. This allows us to establish the existence of the trajectory attractor also in dimension three with a time dependent external force.
Trajectory attractors for the Sun-Liu model for nematic liquid crystals in 3D
Sergio Frigeri,Elisabetta Rocca
Mathematics , 2012, DOI: 10.1088/0951-7715/26/4/933
Abstract: In this paper we prove the existence of a trajectory attractor (in the sense of V.V. Chepyzhov and M.I. Vishik) for a nonlinear PDE system coming from a 3D liquid crystal model accounting for stretching effects. The system couples a nonlinear evolution equation for the director d (introduced in order to describe the preferred orientation of the molecules) with an incompressible Navier-Stokes equation for the evolution of the velocity field u. The technique is based on the introduction of a suitable trajectory space and of a metric accounting for the double-well type nonlinearity contained in the director equation. Finally, a dissipative estimate is obtained by using a proper integrated energy inequality. Both the cases of (homogeneous) Neumann and (non-homogeneous) Dirichlet boundary conditions for d are considered.
Nonlocal Cahn-Hilliard-Navier-Stokes systems with singular potentials
Sergio Frigeri,Maurizio Grasselli
Mathematics , 2012,
Abstract: Here we consider a Cahn-Hilliard-Navier-Stokes system characterized by a nonlocal Cahn-Hilliard equation with a singular (e.g., logarithmic) potential. This system originates from a diffuse interface model for incompressible isothermal mixtures of two immiscible fluids. We have already analyzed the case of smooth potentials with arbitrary polynomial growth. Here, taking advantage of the previous results, we study this more challenging (and physically relevant) case. We first establish the existence of a global weak solution with no-slip and no-flux boundary conditions. Then we prove the existence of the global attractor for the 2D generalized semiflow (in the sense of J.M. Ball). We recall that uniqueness is still an open issue even in 2D. We also obtain, as byproduct, the existence of a connected global attractor for the (convective) nonlocal Cahn-Hilliard equation. Finally, in the 3D case, we establish the existence of a trajectory attractor (in the sense of V.V. Chepyzhov and M.I. Vishik).
"Eppur si muove", Software Libero e Ricerca Riproducibile
Alessandro Frigeri,Gisella Speranza
Computer Science , 2011,
Abstract: This article describes similarities of the scientific method and the free open source software development, and how reproducibility is the key of an healthy scientific production.
Attractors for Damped Semilinear Wave Equations with a Robin--Acoustic Boundary Perturbation
Sergio Frigeri,Joseph L. Shomberg
Mathematics , 2015,
Abstract: Under consideration is the damped semilinear wave equation \[ u_{tt}+u_t-\Delta u + u + f(u)=0 \] on a bounded domain $\Omega$ in $\mathbb{R}^3$ with a perturbation parameter $\varepsilon>0$ occurring in an acoustic boundary condition, limiting ($\varepsilon=0$) to a Robin boundary condition. With minimal assumptions on the nonlinear term $f$, the existence and uniqueness of global weak solutions is shown for each $\varepsilon\in[0,1]$. Also, the existence of a family of global attractors is shown to exist. After proving a general result concerning the upper-semicontinuity of a one-parameter family of sets, the result is applied to the family of global attractors. Because of the complicated boundary conditions for the perturbed problem, fractional powers of the Laplacian are not well-defined; moreover, because of the restrictive growth assumptions on $f$, the family of global attractors is obtained from the asymptotic compactness method developed by J. Ball for generalized semiflows. With more relaxed assumptions on the nonlinear term $f$, we are able to show the global attractors possess optimal regularity and prove the existence of an exponential attractor, for each $\varepsilon\in[0,1].$ This result insures that the corresponding global attractor inherits finite (fractal) dimension, however, the dimension is {\em{not}} necessarily uniform in $\varepsilon$.
Circular planar nearrings: geometrical and combinatorial aspects
Anna Benini,Achille Frigeri,Fiorenza Morini
Mathematics , 2010,
Abstract: Let $(N,\Phi)$ be a circular Ferrero pair. We define the disk with center $b$ and radius $a$, $\mathcal{D}(a;b)$, as \[\mathcal{D}(a;b)=\{x\in \Phi(r)+c\mid r\neq 0,\ b\in \Phi(r)+c,\ |(\Phi(r)+c)\cap (\Phi(a)+b)|=1\}.\] We prove that in the field-generated case there are many analogies with the Euclidean geometry. Moreover, if $\mathcal{B}^{\mathcal{D}}$ is the set of all disks, then, in some interesting cases, we show that the incidence structure $(N,\mathcal{B}^{\mathcal{D}},\in)$ is actually a balanced incomplete block design.
Global Existence of Weak Solutions to a Nonlocal Cahn-Hilliard-Navier-Stokes System
Pierluigi Colli,Sergio Frigeri,Maurizio Grasselli
Mathematics , 2011,
Abstract: A well-known diffuse interface model consists of the Navier-Stokes equations nonlinearly coupled with a convective Cahn-Hilliard type equation. This system describes the evolution of an incompressible isothermal mixture of binary-fluids and it has been investigated by many authors. Here we consider a variant of this model where the standard Cahn-Hilliard equation is replaced by its nonlocal version. More precisely, the gradient term in the free energy functional is replaced by a spatial convolution operator acting on the order parameter phi, while the potential F may have any polynomial growth. Therefore the coupling with the Navier-Stokes equations is difficult to handle even in two spatial dimensions because of the lack of regularity of phi. We establish the global existence of a weak solution. In the two-dimensional case we also prove that such a solution satisfies the energy identity and a dissipative estimate, provided that F fulfills a suitable coercivity condition.
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