RCAAP Repository

This work addresses the problem of the control techniques needed to carry on alcoholic fermentation in wine production. The perspective focuses on adequate techniques to be used with real systems. This implies some price restrictions on the hardware to be used and requires the possibility of working in a distributed environment. (...)

The main purposes of the present dissertation were the specification, implementation and application of an application manager for multimodular systems of cooperative work. Besides making available a basis for the development of computer cooperative work systems, the manager also pretends to use multimodularity as a means to promote support to the development of specific systems and/or for specific users. (...)

The collaboration and the teamwork have been always a way to congregate efforts between individuals, with the goal to achieve tasks that are difficult to achieve alone. Sometimes, the collaboration between people is useful too for the enrichment process of the personal experiente. (...)

The success of new telecommunications technologies, mainly in public networks, is often hindered by the lack of an application which can stimulate its demand by the customers. (...)

Access networks are, in the current panorama of the sector of the telecommunications, of vital importance for the operators since they represent a mayor share of the investments necessary to deploy a telecommunications network and since they influence the capability og introducing new services. (...)

Attacks on computerized systems are increasing at a rapid rate. Due to their very nature, distributed systems are especially vulnerable. Thus, security is if great importance in such systems. (...)

Small embedded microprocessor based systems are today widely used either in stand-alone and in distributed applications. Although hardware architectures are rather similar and C language is almost always used to develop software, a significant effort is still needed to create and debug code for each specific application. (...)

This paper describes a software tool for design, implementation and testing of control circuits in dynamically reconfigurable FPGAs from their graphical specification. It consists of a graphical editor responsible for the control circuit specification, provides a link to the synthesis tool and allows the circuit debugging, for different types of implementations and FPGAs, thus closing the design cycle.

This paper presents two methods to perform an automatic identification of the three major structures of the coronary artery - lumen, internal and external laminae - in images obtained by intracoronary ultrasound: Region Growing and Active Contours or Snakes, with special relevance to the later.

In this article, some solutions that have been developed for the navigation of a mobile robot are presented. These solutions use information perceived by sensors locatedon the robot, only. Using such information, two methods for localisation and navigation were developed. In the first method, called“natural localisation”, the robot uses its sensors to calibrate its position in a previously defined region allowing it to compensate for odometry errors. Another method has been developed to allow the robot to cross narrow passageways using two additional sensors mounted on an appropriately positioned rotating device. This method allowed the robot to detect and cross doors, for example.

Verification of a person identity based in voice alone is an evolving technology with applications in secure access to information, access control to buildings, and telecommunications in general. This work addresses several of the possibilities available in the implementation of an automatic speaker verification system, independent of text, based in phoneme recognition. We studied which parameters to use, their stability over time, and also the phonemes to use for better performance. In this work we used feedforward neural networks in the verification process.

This paper describes a set of laboratory experiments designed to illustrate the main characteristics of the routing protocols used in IP networks.

A Revista do Departamento de Electrónica e Telecomunicações continua a ser um veículo importante de divulgação das actividades do Departamento especialmente os relacionados com trabalhos de final de Licenciatura, dissertações de Mestrado, teses de Doutoramento e material de apoio ao ensino. (...)

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The SMS service of the GSM has been used in some situations that had not been foreseen when of itsspecification by ETSI. The two applications presented inthis communication are of this an example and are used indomotic and alerting to emergency/robbery system ofautomobiles. The first one allows to the sending of commands through one mobile phone to the existing equipment in house, as well as the consultation of the state of the same equipment using short messages. Referring to the second application, a GPS receiver is used to get thevehicle location that is sent to a control center with a message specifying the emergency situation occurred (robbery or accident). This allows to the control center tounchain the adequate means to the situation of emergencyin cause.

The study of some problems in image analysis needs the gathering of different information for the test and training of the systems. Among this problems we can enunciate, for instance, contour detection or, in a general mode, the automatic recognition of forms such as human faces or characters. Is precisely in this area of information’s gathering, for training and test of systems, where the developed sofware is included. It is, in fact, an Image Editor which allows the contour demarcation and/or regions of interest for subsequent use. This demarcations are carried out by points, lines, polygons, ellipses, rectangles and squares which can be associated (optionally) to labels for better identification.

O trabalho que se apresenta neste artigo, tem como objectivo proporcionar uma melhor compreensão do processo de Modulação e Desmodulação de sinais com Espalhamento de Espectro por Sequência Directa. Para cumprir os nossos objectivos, foi desenvolvido um simulador que permite a visualização do sinal em diversos pontos dentro do Emissor e do Receptor. Embora a utilização de simuladores / demonstradores como aplicação didáctica não seja uma ideia inovadora, este trabalho pretende realçar a sua importância no processo de aprendizagem, podendo estas ferramentas serem utilizados como complemento de aulas e livros técnicos.

This work has the pedagogical objective of showing the value of some signal processing techniques for the determination of the transient regime of circuits composed by transmission lines. The analysis method begins with the sinusoidal steady-state response determination, an approach usually followed in any undergraduate guided wave propagation course. Then, the general time domain transient regime is derived by Fourier transform inversion of the previously obtained frequency domain solution. The theoretical problems of signal transmission on dispersive transmission lines, or time domain reflectrometry, are addressed and illustrated by simulating some simple cases.

The requirements for a data acquisition system to be used for propagation experiments are analysed and one solution based on a DSP data acquisition card and PC is suggested. The software for the DSP card and the host PC is presented.

In this paper we present the description of an articulatory speech synthesiser which is to be used as a tool for the study of speech production. The sound might be produced as the result of vocal tract configurations edited by the user. It also allows the study of the inverse problemthe estimation of a vocal tract configuration given a speech sound.