Repositório RCAAP

This paper studies the problem of software construction for mathematical applications, and proposes a different structuring technique following the Object-Oriented paradigm. A short study about the “classic” functional structure used in this area is made, pointing out its qualities and drawbacks. An Object-Oriented analysis and design is performed, and from it is enumerated a set of requirements to impose on programming languages to use in implementation. At the end, the main advantages and disadvantages of this new structure are enumerated. To help to understand this work, one section is dedicated to an introduction to the usual software construction paradigms.

A Decision Support System based on Factor Analysis was designed to offer the user the possibility to perform easily four types of Factor Analysis: Principal Component, Discriminant, Correspondence and Distance. We will describe the user interface of such a system, developed for Windows using Visual Basic TM 3.0.

The phenomenon of categorical perception has played an enormous role in the theory of speech perception. One reason is that categorical perception is at the interfacebetween the analog sensory signal and the discrete andsimbolic nature of language. Another phenomenon involvedin speech perception is selective adaptation. Adaptationeffects appear with respect to the location of the categoricalboundary along a speech continuum. To reproduce andaccount the categorization of speech sounds within a voicingcontinuum we propose a dynamic neural model. We showthat this model is able to reproduce the tipical patternsobserved in experiments of categorical perception, histeresisand adaptation effects. We compare the model predictions toexperiments with subjects. From this study we conclude thatcategorical perception may be understood as resulting fromcompetition within a neural representation of sensoryinformation.

In 1990 INESC (Institute of System Engineering and Computers) was contracted hy PT-Portugal Telecom -the Portuguese telecom operator - to develop the prototype ofa telesurveilling system supported on ISDN (IntegratedServices Digital Network), in the context of the R&Dactivities promoted hy PT concerning the introduction ofISDN in Portugal, project that was concluded in 1994. Thispaper includes a hrief survey and discussion on thestructured techniques evaluated for the system specification,and presents and discusses the analysis and design processesof the software developed to support the real timefunctionalities of the system (images alarms, ...) focused on the most complex of its components, the Central Telesurveilling Station.

The TeleCommunity project in the context of RACE program is a set of Advanced Communications Experiments that aim to study the implementation of advanced communications services for disabled people. The paper presents the support services and the terminal equipment developed for the Portuguese experiment within the TeleCommunity Project. The services (Learning and Training, Remote Delivery ofExpertise, Collaborative Decision Making and InterpersonalCommunication) have been designed to exploit the potentialof ISDN to support and improve the professional care ofdisabled people, namely elderly, visual and mental impaired. The terminal equipment are modular multimedia terminals, based in personal  computers with video codecs, that presentan integrated capability to set-up, simultaneously, point-topoint videophony and data connections. Various terminalshave been distributed among several Institutions, which aremajor Portuguese social care Institutions.

Local Area Networks have been spread over the world during the last decade with an increasing installation rate. The expansion of each LAN, caused the introduction of new systems, usually implies more network traffic. It's important to the network manager to know the characteristics of this traffic in order to study, by simulation, the expected grow on data interchange and to plan future redesign of the network segments. This paper presents a set of tools to make network traffic analysis and to predict someresources requirements, over an Ethernet network. It presents as well some traffic measures, namely, daily utilization rate, impact of new hosts on network traffic and a study of the inter-packet time distribution.

This paper describes the work developed under thePh.D. course of its author [I]. It is devided in four main partswhich refer to the motivation, theoretical background ofamplifier linearization circuits design, GaAs MESFETmodeling, and finally, experimental validation. That wasacheived by the design and test of a MMIC power amplifier, linearized by means of active feedback.

In this paper we present a new method to compute brain maps. It is based on the power estimation of the filtered signal on a11 channels which is faster to compute than the traditional aproach using DFT. Reducing the time needed for computation we can have a better dynamic display of the evolution of the brain potentials on the scalp.

The goal of this paper is to describe a generic Digital Image Processing Package in Microsoft WINDOWS environment. Several tecniques are used, such as Image Transforms ( Fourier, Walsh, Hadamard ), Histogram processing, Spatial Filtering and Color Map processing. An automatic character recognition tecnique isalso described.

A receiver circuit for use in Fiber to the Home (FTTH) Cable TV Systems is presented. The design is based on low cost small signal GaAs FET devices and proposes a new scheme for the reduction of the 2nd order non-linear distortion generated by the active devices.

In practical optical communication systems, the transmitter laser is polarised with a finite current. A given optical power plateau is, thus, observed at the receiver. This contribution includes this phenomenon in an analytical formulation for statistical description of a optically preamplified direct-detection system.

This paper describes a monolithic EEG acquisitionsystem. A very low noise and power comsumption areessencial in this systems, so they are the main targets toachieve. Because the instrumentation amplifier (IA) is the mostcritical part of the system, particular attention is given to thiselement, where the use of current feedback techniques provedto be the best solution. The circuit was fabricated in a standard 2.4-pm n-well, double poly, double metal technology.

This paper gives a description of the Simulator part of the SWIFT I, AN Manager prototype, developed at INESC, as a contribution to the EURET/SWIFT Project. The editor to01 used to manipulate simulator event files and the encoding used to represent actions are also described.

This paper proposes a unified programming application interface for applications based on ISDN or TCP/IP networks.

This paper presents a Tele-radiology system supported in the ISDN, and includes discussion on several aspects of the system, such as digital imaging processing, image compression techniques, communications and human machine interfacing.

This article is a proposal of a telesurveillingsystem based on the ISDN - Integrated Services DigitalNetwork. The article is structured in several sections covering thefollowing subjects: system architecture and ISDN services, functional description, structured analysis and project, andperformance evaluation of implemented system. The basic components of the system are a centraltelesurveilling station and one or several remote stations, thatcommunicate through the ISDN. The purpose of the system isto allow the transfer of images (still or moving pictures) fromthe remote station whenever it is requested by the operator ofthe central station or when an abnormal situation occurs in aremote station; in this late case this is related with theactivation of one of the sensing devices installed in the remotestation. The performance evaluation of the system leads tothe conclusion that its behaviour is appropriate to itspurpose, and also that ISDN provides a good support, for thistype of application.

This work presents an experimental study on a personal computer based implementation of a 64 kbit/s voicecommunication system over the Ethernet local network. Voiceldata integration is achieved without resorting to anynew packet switching protocol and without any changes tothe CSMAICD protocol specifications. System performance isevaluated according to its average transmission delay andpercentage of packet loss as a function of network load, packet size, buffers size, and traffic characteristics. Anestimate of the maximum number of voice channels that canbe supported without significant degradation of the reconstructed signal is also presented. A reference is made to synchronisation problems in packet voice systems and amethod to eliminate clock drift is suggested. A non packetdiscarding reconstruction algorithm for a system with nosilence detection is proposed. Finally, a voice channelimplementation over TCP/IP protocols is presented.

Neste trabalho é apresentado o desenvolvimento de um agente de monitoração. O agente é construído sobre uma plataforma SNMP que permite o desenvolvimento de aplicações de gestão que utilizam o Simple Network Management Protocol (SNMP) como protocolo de comunicação. No agente é implementada a Remote Network Monitoring Management Information Base (RMON MIB) que reúne um conjunto de objectos de gestão relacionados com a informação de monitoração. No intuito de permitir ao agente um modo de funcionamento local e remoto, este é dotado de algumas capacidades de visualização e manipulação da informação de gestão, de modo a tornar possível a monitoração quer localmente no agente, quer remotamente no gestor. Para isso é apresentado um módulo de visualização gráfica, no qual o acesso à informação é feita através de uma interface genérica por forma a permitir a sua portabilidade para qualquer aplicação de gestão.

Neste trabalho apresenta-se uma experiência no uso de uma rede neuronal dinâmica, a Rede Gama Concentrada, na área do Reconhecimento do Orador, nas suas duas variantes de Verificação e Identificação. A abordagem utilizada é baseada no modelo clássico em Reconhecimento de Voz. Primeiro são extraídos atributos relevantes usando um banco de filtros. As propriedades são comparadas com referências previamente construídas usando a rede neuronal. A decisão é feita usando as saídas da rede neuronal. Foi utilizada uma rede dinâmica devido à natureza variável no tempo dos padrões. Foi usada uma rede por cada orador cliente e vários oradores por rede. A primeira abordagem deu os melhores resultados, e por ser modular, torna possível a construção de sistemas com muitos clientes. Os resultados obtidos são promissores e mostram que o método é robusto.

O trabalho aqui apresentado consiste numa plataforma SNMP para o desenvolvimento de objectos de gestão, constituída por um gestor SNMP e um agente SNMP com possibilidade de definição de novos objectos de gestão. Esta plataforma foi desenvolvida de forma genérica, podendo ser instalada em qualquer sistema de comunicações e/ou sistema operativo.