1997
Autores
Araujo, RE; Freitas, DS; Goncalves, JJ;
Publicação
1997 IEEE INTERNATIONAL ELECTRIC MACHINES AND DRIVES CONFERENCE RECORD
Abstract
This paper describe an instrument for real-time visualization of the quantities necessary for analysis, diagnosis and investigations of AC machine drives on an oscillographic display. The instruments needs no shaft position or speed sensor, it uses exclusively the acquired stator currents and voltages and provides information, in electrical and visual form of: stator and rotor flux, torque, reactive power, torque current, flux current, torque angle, slip frequency. The measuring instrument is based in analogue signal processing techniques. The main fields of application are: monitoring systems, control units, research tool for induction motor drives, and test shop. Practical results of the implementation are presented and discussed.
1997
Autores
Marcal, ARS; Wright, GG;
Publicação
PHYSICAL MEASUREMENTS AND SIGNATURES IN REMOTE SENSING, VOLS 1 AND 2
Abstract
NOAA-AVHRR data between April and September of 1995 and 1996 was processed to produce Normalised Difference Vegetation Index (NDVI) Maximum Value Composites (MVCs) for Scotland, The limitations of monthly NDVI MVCs are discussed for Scotland. Overlapping NDVI MVCs were produced from a fixed number of images and temporal NDVI plots were obtained for selected land cover classes. The date assigned to a NDVI MVC on a temporal plot is analysed and discussed.
1997
Autores
Ferreira, LA; Dias, PC; Santos, JL;
Publicação
PURE AND APPLIED OPTICS
Abstract
A passive all-fibre technique for fibre Bragg grating wavelength shift detection which has been discussed previously is used here for the demodulation of two Bragg sensors placed in a tree topology and addressed in time. The scheme involves a light source with a particular spectral profile that allows the direct tracking of the Bragg wavelength shifts, providing satisfactory resolution over a large dynamic range and a direct application in demultiplexing fibre sensing systems. Experimental results are presented relative to the measurement of static and dynamic strain, as well as temperature.
1997
Autores
Jorge, A; Brazdil, PB;
Publicação
INDUCTIVE LOGIC PROGRAMMING
Abstract
Many state-of-the-art ILP systems require large numbers of negative examples to avoid overgeneralization. This is a considerable disadvantage for many ILP applications, namely inductive program synthesis where relativelly small and sparse example sets are a more realistic scenario. Integrity constraints are first order clauses that can play the role of negative examples in an inductive process. One integrity constraint can replace a long list of ground negative examples. However, checking the consistency of a program with a set of integrity constraints usually involves heavy theorem-proving. We propose an efficient constraint satisfaction algorithm that applies to a wide variety of useful integrity constraints and uses a Monte Carlo strategy. It looks for inconsistencies by random generation of queries to the program. This method allows the use of integrity constraints instead of (or together with) negative examples. As a consequence programs to induce can be specified more rapidly by the user and the ILP system tends to obtain more accurate definitions. Average running times are not greatly affected by the use of integrity constraints compared to ground negative examples.
1997
Autores
Storey, R; Alves, A; Ruela, J; Teixeira, L; Andrade, T;
Publicação
MULTIMEDIA APPLICATIONS, SERVICES AND TECHNIQUES - ECMAST '97
Abstract
Today's available solutions for the production of digitally compressed TV programmes require successive decoding and re-coding operations due both to the multiplicity of digital formats currently in use for signal acquisition and to technology limitations. This has the consequence of increasing the production costs and of reducing the overall signal quality. The ability of using compression also at the production stage will contribute to improve the overall signal quality and to reduce storage requirements and associated costs. The ATLANTIC project (ACTS 078) is developing a digital studio for the production of TV programmes using the MPEG2 format throughout the entire process, from the input of the studio to final programme distribution. EXPO'98, the next international exposition to be held in Lisbon, has been identified as an ideal showcase for audio-visual services developed by ACTS projects. The ATLANTIC project will provide basic infrastructures and technology for compressed-based TV programme production and distribution of audio-visual information and entertainment services for the entire EXPO site. This paper describes the studio reference model of the ATLANTIC project and the role ATLANTIC will be playing within the planned demonstrations of ACTS projects at EXPO'98.
1997
Autores
Carvalho, AS; Sousa, AJM;
Publicação
ISIE '97 - PROCEEDINGS OF THE IEEE INTERNATIONAL SYMPOSIUM ON INDUSTRIAL ELECTRONICS, VOLS 1-3
Abstract
Fuzzy Logic is a part of Artificial Intelligence science and provides for control of complex processes, where exact models are not applicable. Such a controller is necessary for the process of drying oil filled transformers. Indeed, this controller needs to tackle with a highly non-linear and time variant process. The development of the controller was fast and the implementation size very small. Its performance proved very robust whilst providing both good dynamical and steady-state behaviour.
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