Publications

Publications by CRAS

1999

Shallow seismic reflection results in the Vouga basin region (Northern Portugal)

Authors
Marques Moura, R; Senos Matias, M;

Publication
5th EEGS-ES Meeting

Abstract

1999

Impact shear wave generator for dynamic shallow soil characterisation

Authors
E. Almeida, F; Marques Moura, R;

Publication
5th EEGS-ES Meeting

Abstract

1998

Flexible hardware acceleration for nesting problems

Authors
Ferreira, JC; Alves, JC; Albuquerque, C; Oliveira, JF; Ferreira, JS; Matos, JS;

Publication
5th IEEE International Conference on Electronics, Circuits and Systems, ICECS 1998, Surfing the Waves of Science and Technology, Lisbon, Portugal, September 7-10, 1998

Abstract
The nesting (or placement) problem is an NP-hard combinatorial problem with important industrial applications, e.g. in apparel or footwear industry. This paper describes a hardware infrastructure to accelerate the processing of the underlying geometric information. The system consists of an FPGA-based reconfigurable platform enhanced by an ASIC for the processing of irregular polygons. The paper discusses the need for such a platform, establishes the main design guidelines and describes the architecture and modes of operation of both the reconfigurable infrastructure and the dedicated IC.

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1998

RVC - A reconfigurable coprocessor for vector processing applications

Authors
Alves, JC; Matos, JS;

Publication
IEEE SYMPOSIUM ON FPGAS FOR CUSTOM COMPUTING MACHINES, PROCEEDINGS

Abstract
This work presents RVC (Reconfigurable Vector Coprocessor), a FPGA based custom computing machine for vector processing applications. This system was built to serve as an implementation platform for a custom vector processor designed for a digital signal processing application. Although its architecture has been in part dictated by the immediate needs of that dedicated processor, it also serves for other custom machines exhibiting similar requirements of vector processing. © 1998 IEEE.

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1998

On the concept of Instantaneous Frequency

Authors
Oliveira, PM; Barroso, V;

Publication
PROCEEDINGS OF THE 1998 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING, VOLS 1-6

Abstract
The concept of Instantaneous Frequency is still not clearly defined. Current operational definitions give rise to physical paradoxes, difficulting proper interpretation of the obtained results. In this paper, we discuss why those paradoxes appear, and show how they can be avoided. We introduce a new definition of Instantaneous Frequency, which yields physically consistent results. This is confirmed with the help of several examples.

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1998

Instantaneous frequency of mono and multicomponent signals

Authors
Oliveira, PM; Barroso, V;

Publication
PROCEEDINGS OF THE IEEE-SP INTERNATIONAL SYMPOSIUM ON TIME-FREQUENCY AND TIME-SCALE ANALYSIS

Abstract
It has often been reported and is now well established that the traditional definition of Instantaneous Frequency (IFt) fails in the presence of multicomponent signals. New definitions of IFt have recently been proposed, in an attempt to cope with the difficulties of the traditional one. In this paper, we will address the reasons for failure of the traditional definition, show that it can also fail with monocomponent signals, and show how its behaviour can be predicted for any type of signal, thus generalizaing previous results. We will also analyse the performance in noise of one of the recently proposed definitions of IFt.

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