Abstract
It is shown that in using the Laplace transform one has to start with the condition that imposes f(0-) = 0 in order to avoid errors in the derivative and integral operations. In that case the matrix representation of the circuits using the Laplace transform becomes possible and the resolution of integral-differential equations is straightforward. Nevertheless, it is possible to use the Laplace transform with signals that have no null initial conditions, keeping the mathematical coherence, by choosing between two ways: (1) shifting the origin of time domains to the left to obtain the null initial conditions, and (2) using the superposition theorem to obtain one partial signal with null initial conditions.

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Abstract

Abstract
In this paper the work of the Computer Graphics & CAD group at INESC.Norte, in Solid Modelling, Surface Generation, Visibility and other 3D areas, is described. This group has created a working environment, based on a 3D kernel developed at INESC, which allowed the easy integration of other works, ranging from Solid Modelling to Surface Generation to Visibility, ect. The results achieved seem to be good enough to encourage to continue our effort, so that, in the near future, we can have a stronger and more flexible 3D kernel, good enough to be used in industrial developments and as a research starting point, for areas like Image Synthesis, 3D Graphics User Interfaces, and so on. © 1990.

Abstract