Empregamos a segunda lei de Newton para descrever o sistema de oscilador com massa variável. Um aparato experimental para medir as oscilações e outros parâmetros importantes é montado e aqui descrito com a ajuda de equipamentos disponíveis comercialmente. Usando um modelo pré-concebido para tal sistema somos capazes de ajustar os resultados experimentais com boa concordância. Para realizarmos essa tarefa desenvolvemos um programa na linguagem C++ ao qual pode extrair os valores experimentais da amplitude do movimento oscilatório bem como rotacionar o sistema de coordenadas para separar o movimento translacional do movimento oscilatorio.

We employ the Newton's second law to describe the variable mass oscillator system. We describe and set up an experimental apparatus in order to measure the oscillations and other parameters with the help of equipments available commercially. By using a preconceived model for such a system we are able to fit the experimental results with a good agreement. To accomplish this task we developed a C++ program which can extract the experimental values of the amplitude of the oscillatory movement as well as to rotate the coordinates system in order to set apart the translational movement from the oscillatory one.

We propose a new method to estimate the percolation threshold p c and the critical index t associated with strength reduction in networks of random fused conductors. It relies on a recently proposed expression for the yield strength of a network as a function of the probability p that each element is removed from it. The values of critical indices are confirmed using finite size scaling. Further, we systematically study effects of different damage modalities, which are chosen to reflect age-related changes in the porous inner segments of human bone. In particular, we find that p c and t depend on damage modalities.

Electrical networks provide a natural model to study transport processes such us dielectric breakdown and metal insulator transition in disordered inhomogeneous conductors. We present a calculation for current distribution on an infinite hyper-cubic network due to an external applied current. This is used to compute, analytically, the redistribution of current due to variations in the conductance of a finite number of elements of the network.

We present the Quantum Section Method as a quantization technique to compute the eigenvalues and the eigenfunctions of quantum systems. As an instructive example we apply this procedure to quantize the annular billiard. The method uses the symmetry of the system to determine an auxiliary section separating the system into partial regions and computes the Green's functions for Schroedinger's equation, obeying the same boundary conditions imposed on the eigenfunctions of the system. The eigenvalues are obtained as zeroes of a finite real determinant and the eigenfunctions are also determined. The present analytical and numerical results are in total agreement with those obtained by other procedures, which shows the efficiency of the method.