| 58/2003 |
Potential, Eletric Field and Surface Charges Close to the Battery for a Resistive Cylindrical Shell Carrying a Steady Longitudinal Current J. A. Hernandes, Edmundo Capelas de Oliveira, André K. T. Assis In this work we consider a long, resistive cylindrical shell carrying a steady current. A battery in the middle of the wire generates the current. We study the behavior of the potential, electric field and surface charges close to the battery. |
| 57/2003 |
Heurísticas para Empacotamento em Cointaners Clovis Perin, Valéria de Podestá Gomes, Antônio Carlos Moretti Carregamento de caixas de embalagens em containers e em paletes constituem importantes aplicações de modelos matemáticos de corte e empacotamento no planejamento da produção em indústrias de papel, aço, madeira, vidro, etc. Em geral, o problema real é apresentado de tal forma que para construir um modelo de programação matemática que o represente é necessário gerar um conjunto de padrões de empacotamento. Trata-se de um problema NP-Hard. Neste trabalho, são estudadas estratégias heurísticas alternativas para a geração de empacotamentos. Testes computacionais foram realizados para comparar tempos de processamento e qualidade dos empacotamentos obtidos para exemplares de problemas de empacotamento tridimensionais disponíveis na internet.  rp-2003-57.pdf |
| 56/2003 |
Resistive Plates Carrying a Steady Current: Eletric Potential and Surface Charges Close to the Battery J. A. Hernandes, Edmundo Capelas de Oliveira, André K. T. Assis We treat the problem of resistive plates carrying a steady current. We consider a linear battery orthogonal to the direction of the current in the middle of the plates. We study the behavior of the surface charges close to the battery. We calculate the potential and electric field in the space outside the plates. rp-2003-56.pdf |
| 55/2003 |
Modelo Matemático e Simulação Numérica de uma Dinâmica Populacional de Capivaras numa Situação de Migração Dispersão em Presença de uma Epizootia Silvio A. Pregnolatto, João Frederico C. A. Meyer rp-2003-55.pdf |
| 54/2003 |
On the Resolvent Technique for Nonlinear Stability of Plane Couette Flow Pablo Braz e Silva We discuss the application of the resolvent technique to prove stability of plane Couette flow. Using this technique, we derive a threshold amplitude for perturbations that can lead to turbulence in terms of the Reynolds number. Our main objective is to show exactly how much control one should have over the perturbation to assure stability via this technique. rp-2003-54.pdf |
| 53/2003 |
Again on Lorentz Force and Minkowshi Geometry Ricardo A. Mosna, Márcio A. F. Rosa Here the problem of associating a Lorentz transformation valued function or a Lorentz moving frame to a given massive particle's worldline, describing the evolution of its four-velocity, will be discussed. This is equivalent to the problem of finding a Lorentz Force field that, acting on the massive particle, would produce its given worldline. We emphasise the geometrical character of Lorentz Force, its naturalness in Special Relativity and in other space-time theories having the Minkowskian one as its typical tangent space.The problem can also be viewed as a gauge choice in a SO(3) principal fiber bundle over the particle's worldline. This is a modern view of the approach to the problem given by Walker 1932 and unifies all the possible Lorentz force laws describing the same curve, since the magnetic parts of the fields associated to such forces are the local expressions, under the gauge choice, of a unique global SO(3) connection while the electric part of these fields are local expressions of a section of anassociated bundle.These discussions, as they are presented here, have the didactic value of linking many disciplines as Special and General Relativity, Differential Geometry, Manifolds, Gauge Theories and Connections, in a precise but very comprehensible way. Therefore they could be a stimulating complement for a course in Special Relativity, followed by advanced undergraduate students. rp-2003-53.pdf |
| 52/2003 |
A New Choice for the Forcing Term and a Global Convergent Inexact Newton Method Márcia A. Gomes-Ruggiero, Véra L. R. Lopes, Julia Victoria Toledo-Benavides Inexact Newton methods for solving $F(x) = 0,\,F:D \subset \R^{n} \rightarrow \R^{n}$ with $F \in C{^1}(D)$,where $D$ is an open and convex set, find approximation to the step $s_{k}$ of the Newton's systems $J(x_{k})s = - F(x_{k})$, instead of solving this system exactly as done by Newton's method. This means that $s_{k}$ must satisfy a condition like $||F(x_{k}) + J(x_{k})s_{k}|| \leq \eta_{k}||F(x_{k})||$ for a forcing term $\eta_{k} \in [0,1]$ (\cite{des}). Many authors have presented possible choices for $\eta_{k}$ (see \cite{ew}). In this work, a new choice for $\eta_{k}$ is introduced, the new method obtained is globalized by the introduction of a robust backtracking strategy (see \cite{natasha}, \cite{dglm}), and its convergence properties are proved. The numerical performance of the new method is presented by plotting the performance profile of the method as proposed in \cite{dm}. The results obtained show a competitive new inexact Newton method. rp-2003-52.pdf |
| 51/2003 |
On Factorization of Hilbert-Schmidt Mappings Cristiane de Andrade Mendes We present some results on factorization of Hilbert-Schmidt multilinear mappings and polynomials through infinite dimensional Banach spaces, $\mathcal{L}_1 $ and $\mathcal{L}_{\infty}$ spaces. We conclude this work with a result on factorizationof holomorphic mappings of Hilbert-Schmidt type. rp-2003-51.pdf |
| 50/2003 |
On Factorization of Schatten Class Type Mappings Cristiane de Andrade Mendes We present some results on factorization of multilinear mappings and polynomials of Schatten class type $\mathcal{S}_2$ through infinite dimensional Banach spaces, $\mathcal{L}_1 $ and $\mathcal{L}_{\infty}$ spaces. We conclude this work with a factorization result for holomorphic mappings of Schatten class type $\mathcal{S}_2$. rp-2003-50.pdf |
| 49/2003 |
The Performance of a Reversible Jump Markov Chain Monte Carlo Algorithm for DNA Sequences Alignment Luis J. Álvarez, Nancy L. Garcia, Eliane R. Rodrigues Assume that K independent copies are made from a common prototype DNA sequence whose length is considered to be a random variable. In this paper the problem of aligning these copies and therefore the problem of estimating the prototype sequence that produced the copies is addressed. A hidden Markov chain is used to model the copying procedure and a reversible jump Markov chain Monte Carlo algorithm is used to sample the parameters of the model from their posterior distribution. Using the sample obtained, the Bayesian model selection may be made and the prototype sequence may be selected using the maximum a posteriori estimate. A prior distribution for the prototype DNA sequence that incorporates a correlation among neighbouring bases is also considered. Additionally, an analysis of the performance of the algorithm is presented when different scenarios are taken into account. rp-2003-49.pdf |
