Resumo em Inglês:

The Kalman-Bucy method is here analized and applied to the solution of a specific filtering problem to increase the signal message/noise ratio. The method is a time domain treatment of a geophysical process classified as stochastic non-stationary. The derivation of the estimator is based on the relationship between the Kalman-Bucy and Wiener approaches for linear systems. In the present work we emphasize the criterion used, the model with apriori information, the algorithm, and the quality as related to the results. The examples are for the ideal well-log response, and the results indicate that this method can be used on a variety of geophysical data treatments, and its study clearly offers a proper insight into modeling and processing of geophysical problems.

Resumo em Inglês:

Hermite approximation in multiple dimensions is investigated. As an example, a spectral scheme and a pseudospectral scheme for the Logistic equation are constructed, respectively. The stability and the convergence of the proposed schemes are proved. Numerical results show the high accuracy of this new approach.

Resumo em Inglês:

In this paper, we consider a slab represented by the interval 0 < x < 1, at the initial temperature u0(x) > 0 and having a heat flux q(t) on the left face and a nonlinear condition on the right face x = 1. We consider the corresponding heat conduction problem and we assume that the phase-change temperature is 0ºC. We prove that certain conditions on the data are necessary and sufficient in order to obtain estimations of the occurrence of a phase-change in the material.

Resumo em Inglês:

We introduce a simplified theoretical model to describe a virtual virus propagation process in a set of interacting computers. The propagation mechanisms considered here are those related to the reception of messages through internet as well as the ones concerning the simple exchange of files using recording devices as compact disks or the commonly used floppy disks. In spite of its inherent simplicity, this model provides a good idea of the infection process and trends. From the mathematical point of view, the nonlinear delay integral equation that we obtain here presents certain interesting features which are explored and enlightened in this paper.

Resumo em Inglês:

Alternant codes over arbitrary finite commutative local rings with identity are constructed in terms of parity-check matrices. The derivation is based on the factorization of x s - 1 over the unit group of an appropriate extension of the finite ring. An efficient decoding procedure which makes use of the modified Berlekamp-Massey algorithm to correct errors and erasures is presented. Furthermore, we address the construction of BCH codes over Zm under Lee metric.

Resumo em Inglês:

This paper considers a pair of transmission problems for the system of piezoelectricity having piecewise constant coefficients. Under suitable monotonicity conditions on the coefficients and certain geometric conditions on the domain and the interfaces where the coefficients have a jump discontinuity, results on simultaneous boundary observation and simultaneous exact control are established.

Resumo em Inglês:

We present optimal upper bounds for the deviation of a fuzzy continuous function from its fuzzy average over [a,b] <FONT FACE=Symbol>Ì</FONT> R, error is measured in the D-fuzzy metric. The established fuzzy Ostrowski type inequalities are sharp, in fact attained by simple fuzzy real number valued functions. These inequalities are given for fuzzy Hölder and fuzzy differentiable functions and these facts are reflected in their right-hand sides.