Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11799
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Item About analyticity for the coupled system of linear thermoviscoelastic equations(Applied Mathematics and Computation, 2015-11-01) Alves, Margareth S.; Rivera, Jaime E. Muñoz; Sepúlveda, Mauricio; Vera, OctavioIn this paper we consider the classical linear theory of thermoviscoelasticity for inhomogeneous and anisotropic materials in three dimensional space. We show that under suitable conditions, the semigroup associated with the system of the viscoelastic equation of motion coupled with the parabolic equation of energy is analytic.Item An analysis of a mathematical model describing the geographic spread of dengue disease(Journal of Mathematical Analysis and Applications, 2016-12-01) Araujo, Anderson L. A. de; Boldrini, José Luiz; Calsavara, Bianca Morelli RodolfoWe consider a system of nonlinear partial differential equations corresponding to a generalization of a mathematical model for geographical spreading of dengue disease proposed in the article by Maidana and Yang (2008) [5]. As in that article, the mosquito population is divided into subpopulations: winged form (mature female mosquitoes) and aquatic form (comprising eggs, larvae and pupae); the human population is divided into the subpopulations: susceptible, infected and removed (or immune). On the other hand, differently from the work by Maidana and Yang, who considered just the one dimensional case with constant coefficients, in the present we allow higher spatial dimensions and also parameters depending on space and time. This last generalization is done to cope with possible abiotic effects as variations in temperature, humidity, wind velocity, carrier capacities, and so on; thus, the results hold for more realistic situations. Moreover, we also consider the effects of additional control terms. We perform a rigorous mathematical analysis and present a result on existence and uniqueness of solutions of the problem; furthermore, we obtain estimates of the solution in terms of certain norms of the given parameters of the problem. This kind of result is important for the analysis of optimal control problems with the given dynamics; to exemplify their utility, we also briefly describe how they can be used to show the existence of optimal controls that minimize a given optimality criteria.Item Analyticity and smoothing effect for the coupled system of equations of Korteweg-de vries type with a single point singularity(Acta Applicandae Mathematicae, 2011-01) Alves, Margareth S.; Calsavara, Bianca M. R.; Rivera, Jaime E. Muñoz; Sepúlveda, Mauricio; Villagrán, Octavio VeraUsing Bourgain spaces and the generator of dilation P=3t ∂ t +x ∂ x , which almost commutes with the linear Korteweg-de Vries operator, we show that a solution of the initial value problem associated for the coupled system of equations of Korteweg-de Vries type which appears as a model to describe the strong interaction of weakly nonlinear long waves, has an analyticity in time and a smoothing effect up to real analyticity if the initial data only have a single point singularity at x=0.Item A branch-price-and-cut method for the vegetable crop rotation scheduling problem with minimal plot sizes(European Journal of Operational Research, 2015-09-01) Santos, Lana M.R.; Munari, Pedro; Costa, Alysson M.; Santos, Ricardo H.S.Crop rotation plays an important role in agricultural production models with sustainability considerations. Commonly associated strategies include the alternation of botanical families in the plots, the use of fallow periods and the inclusion of green manure crops. In this article, we address the problem of scheduling vegetable production in this context. Vegetables crop farmers usually manage a large number of crop species with different planting periods and growing times. These crops present multiple and varied harvesting periods and productivities. The combination of such characteristics makes the generation of good vegetable crop rotation schedules a hard combinatorial task. We approach this problem while considering two additional important practical aspects: standard plot sizes (multiples of a base area) and total area minimisation. We propose an integer programming formulation for this problem and develop a branch-price-and-cut algorithm that includes several performance-enhancing characteristics, such as the inclusion of a family of subadditive valid inequalities, two primal heuristics and a strong branching rule. Extensive computational experiments over a set of instances based on real-life data validate the efficiency and robustness of the proposed method.Item A comment on Bonnor–Steadman closed timelike curves(General Relativity and Gravitation, 2008-09-07) Rosa, Valéria M.; Letelier, Patricio S.The existence and stability closed timelike curves in a Bonnor–Ward spacetime without torsion line singularities is shown by exhibiting particular examples.Item Critical points of higher order for the normal map of immersions in R^ d(Topology and its Applications, 2012-02-01) Monera, M. G.; Montesinos-Amilibia, A.; Moraes, S. M.; Sanabria-Codesal, E.We study the critical points of the normal map ν : N M → R k + n , where M is an immersed k-dimensional submanifold of R k + n , N M is the normal bundle of M and ν ( m , u ) = m + u if u ∈ N m M. Usually, the image of these critical points is called the focal set. However, in that set there is a subset where the focusing is highest, as happens in the case of curves in R 3 with the curve of the centers of spheres with contact of third order with the curve. We give a definition of r-critical points of a smooth map between manifolds, and apply it to study the 2 and 3-critical points of the normal map in general and the 2-critical points for the case k = n = 2 in detail. In the later case we analyze the relation with the strong principal directions of Montaldi (1986) [2].Item Critical singular problems on unbounded domains(Abstract and Applied Analysis, 2004-04-30) Morais Filho, D. C. de; Miyagaki, O. H.We present some results of existence for the following problem: − ∆u = a(x)g(u)+u | u | 2 − 2 , x ∈ R N (N ≥ 3), u ∈ D 1,2 ( R N ), where the function a is a sign-changing function with a singularity at the origin and g has growth up to the Sobolev critical exponent 2 ∗ = 2N/(N − 2).Item Critical singular problems via concentration-compactness lemma(Journal of Mathematical Analysis and Applications, 2007-02-01) Miyagaki, Olimpio Hiroshi; Assunção, Ronaldo B.; Carrião, Paulo CesarIn this work we consider existence and multiplicity results of nontrivial solutions for a class of quasilinear degenerate elliptic equations in RN of the form (P)−div[|x|−ap|∇u|p−2∇u]+λ|x|−(a+1)p|u|p−2u=|x|−bq|u|q−2u+f, where x∈RN, 1Item Critical singular problems via concentration-compactness lemma(Journal of Mathematical Analysis and Applications, 2007-02-01) Miyagaki, Olimpio Hiroshi; Assunção, Ronaldo B.; Carrião, Paulo CesarIn this work we consider existence and multiplicity results of nontrivial solutions for a class of quasilinear degenerate elliptic equations in RN of the form (P)−div[|x|−ap|∇u|p−2∇u]+λ|x|−(a+1)p|u|p−2u=|x|−bq|u|q−2u+f, where x∈RN, 1Item Curves with no tritangent planes in space and their convex envelopes(Journal of Geometry, 1990-11) Ballesteros, Juan J. Nuño; Fuster, M. Carmen RomeroItem Darboux integrability for polynomial vector fields invariant under action of finite group(Qualitative Theory of Dynamical Systems, 2011-12-27) Corrêa Jr., MaurícioIn this paper we present a Darboux–Jouanolou integrability type theorem for polynomial vector fields invariant under action of finite group. As corollary, we obtain a generalization of Darboux–Jouanolou integrability theorem for affine algebraic varieties with quotient singularities.Item Darboux–Jouanolou–Ghys integrability for one-dimensional foliations on toric varieties(Bulletin des Sciences Mathématiques, 2010-10) Corrêa, J. R. MaurícioWe use the existence of homogeneous coordinates for simplicial toric varieties to prove a result analogous to the Darboux–Jouanolou–Ghys integrability theorem for the existence of rational first integrals for one-dimensional foliations.Item Edge-pairing isometries and counting Dirichlet domains on the densest tessellation {12g - 6; 3} for signal set design(Journal of the Franklin Institute, 2012-04) Souza, Mário José de; Faria, Mercio Botelho; Palazzo Jr., Reginaldo; Firer, MarceloIn this paper we present a systematic procedure for the establishment of edge-pairing isometries in order to achieve the largest possible number (2g+1) of transformations pairing diametrically opposite edges and the angle between any two adjacent edges being equal to 2PI/3 as well as a procedure for counting the number of Dirichlet domains on the densest tessellation {12g - 6,3} for signal set design with applications in space-time block codes.Item Envelope of Mid-Planes of a surface and some classical notions of affine differential geometry(Results in Mathematics, 2017-05-26) Cambraia Jr., Ady; Craize, MarcosFor a pair of points in a smooth locally convex surface in 3-space, its mid-plane is the plane containing its mid-point and the intersection line of the corresponding pair of tangent planes. In this paper we show that the limit of mid-planes when one point tends to the other along a direction is the Transon plane of the direction. Moreover, the limit of the envelope of mid-planes is non-empty for at most six directions, and, in this case, it coincides with the center of the Moutard’s quadric. These results establish a connection between these classical notions of affine differential geometry and the apparently unrelated concept of envelope of mid-planes of a surface. We call the limit of envelope of mid-planes the affine mid-planes evolute and prove that, under some generic conditions, it is a regular surface in 3-space.Item Existence of solutions and optimal control for a model of tissue invasion by solid tumours(Journal of Mathematical Analysis and Applications, 2015-01-01) Araujo, Anderson L.A. de; Magalhães, Paulo Marcelo Dias DeIn this paper we study the distributed optimal control problem for the two-dimensional mathematical model of cancer invasion. Existence of optimal state-control and stability is proved and an optimality system is derived.Item Existence results for quasilinear elliptic exterior problems involving convection term and nonlinear Robin boundary conditions(Journal of Mathematical Analysis and Applications, 2010-08-15) Miyagaki, Olímpio H.; Faria, Luiz F. O.; Pereira, Fábio R.In this paper, the authors establish the existence of solutions for a class of elliptic exterior problems involving convection terms and nonlinear Robin boundary conditions. The proof of the result is made by combining Galerkin method with a priori estimates for this kind of problem.Item Exponential decay in a thermoelastic mixture of solids(International Journal of Solids and Structures, 2009-04) Alves, M .S.; Rivera, J. E. Muñoz; Quintanilla, R.In this paper, we investigate the asymptotic behaviour of solutions to the initial boundary value problem for a one-dimensional mixture of thermoelastic solids. Our main result is to establish a necessary and sufficient condition over the coefficients of the system to get the exponential stability of the corresponding semigroup. We also prove the impossibility of time localization of solutions.Item Exponential stability in thermoviscoelastic mixtures of solids(International Journal of Solids and Structures, 2009-12-01) Alves, Margareth S.; Rivera, Jaime E. Muñoz; Sepúlveda, Mauricio A.; Villagrán, Octavio Paulo VeraIn this paper we investigate the asymptotic behavior of solutions to the initial boundary value problem for a one-dimensional mixture of thermoviscoelastic solids. Our main result is to establish the exponential stability of the corresponding semigroup and the lack of exponential stability of the corresponding semigroup.Item A four vertex theorem for strictly convex space curves(Journal of Geometry, 1993-03) Ballesteros, Juan J. Nuño; Fuster, M. Carmen RomeroItem Generalized edge-pairings for the family of hyperbolic tessellations {10λ,2λ}(Computational and Applied Mathematics, 2016-04) Faria, Mercio Botelho; Vieira, Vandenberg Lopes; Palazzo Jr., ReginaldoIn this paper we present generalized edge-pairings for the family of hyperbolic tessellations {10λ,2λ}{10λ,2λ} , with the purpose to obtain the corresponding discrete group of isometries. These tessellations have greater density packing than the self-dual tessellations {4λ,4λ}{4λ,4λ} implying that the associated codes achieve the least error probability, or equivalently, that these codes are optimum codes.
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