Repositório RCAAP

This paper discusses the basic approaches involved in the use Object-Oriented Programming (OOP) and Object-Oriented Design (OOD) for application development. It emphasises the principal distinctions between two widely-used and well-known directions insoftware development. At present there are many computerlanguages that incorporate OOP capabilities. One of the most powerful of these languages is C++. This article underlines the main innovation introduced in C++. It recommends some rules for writing C++ object-oriented programs, and considers an animated software tutorial which allows the OOP approach in general, and C++ in particular, to be learned in the fastest possible way.

This paper deals with differential demodulation ofCPFSK signals with modulation index 1/2 (MSK) and 1. Making use of the signal complex envelopes, we show thatthe existence of discrete lines with adequate phase in themodulated signal, can be used in a differential demodulationoperation as a local reference. This has advantages whendemodulating signals with intersymbol interference (ISI). Ingeneral because of its non-linear nature the differentialdemodulator increases the output ISI, unless the signalcarries a component that can be used as a reference. Thisanalysis allows us to understand the reasons of thesuperiority of the modulation index 1 relatively to MSKwhen demodulating through a delay and multiply structuretightly filtered versions of these signals.

In this communication we report the design of a clock recovery circuit produced for the 20 Gbit/s demonstrator of the RACE 2011 project "TRAVEL" of the European Community. The clock recovery circuit is based on an open loop structure using a dielectric resonator narrow bandpass filter with high Q. A detailed electrical characterization of the circuit and alsoits sensitivity to temperature and detuning variations arepresented. The experimental results show that the circuit is avery attractive solution for the forthcoming STM-128 opticallinks.

In this tutorial paper we present a generalization of the transversal filter, called Laguerre filter, and study someof its more remarkable properties. This filter is obtained byreplacing each delay of the transversal filter by a first orderall-pass section, and by applying a first order low-pass filter(with the same pole used in the all-pass sections) to the filter’sinput signal. Both the transversal and the lattice forms of theLaguerre filter are discussed. We also deduce the stationarityconditions of the mean-square error of a Laguerre filter(transversal or lattice) with respect to its pole position.

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.