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Biblioteca Digital do IPB (53.442 recursos)

A Biblioteca Digital do IPB, tem por objectivo divulgar e permitir o livre acesso à produção científica produzida pela comunidade académica, promovendo a integração, partilha e a visibilidade da informação científica e garantindo a preservação da memória intelectual do Instituto Politécnico de Bragança.

IC - Artigos em Revistas Não Indexadas ao ISI

Mostrando recursos 1 - 20 de 40

  1. Infrastructure sharing as an opportunity to promote competition in local access networks

    Pereira, João Paulo; Ferreira, Pedro
    Telecom infrastructures are facing unprecedented challenges, with increasing demands on network capacity. Today, network operators must determine how to expand the existing access network infrastructure into networks capable of satisfying the user’s requirements. Thus, in this context, providers need to identify the technological solutions that enable them to profitably serve customers and support future needs. However, the identification of the “best” solution is a difficult task. Although the cost of bandwidth in the active layer has reduced significantly (and continually) in recent years, the cost of the civil works—such as digging and trenching—represents a major barrier for operators to deploy...

  2. Game theoretic modeling of NGANs: impact of retail and wholesale services price variation

    Pereira, João Paulo; Ferreira, Pedro
    The increasing demand for broadband access leads operators to upgrade the existing access infrastructures (or building new access network). Broadband access networks require higher investments (especially passive infrastructures such as trenches/ducts and base station towers/masts), and before making any decision it is important to analyze all solutions. The selection of the best solution requires understanding the technical possibilities and limitations of the different access technologies, as well as understanding the costs of building and operating the networks. This study analyzes the effect of asymmetric retail and wholesale prices on operators’ NPV, profit, consumer surplus, welfare, retail market, wholesale market, and...

  3. A case studies approach to the analysis of profiling and framing structures for pervasive information systems

    Fernandes, José Eduardo; Machado, Ricardo J.; Carvalho, João Álvaro
    Model-Based/Driven Development (MDD) constitutes an approach to software design and development that potentially contributes to: concepts closer to domain and reduction of semantic gaps, automation andless sensitivity to technological changes, and the capture of expert knowledge and reuse. The widespread adoption of pervasive technologies as basis for new systems and applications lead to the need of effectively design pervasive information systems that properly fulfil the goals they were designed for. This paper presents a profiling and framing structure approach for the development of Pervasive Information Systems (PIS). This profiling and framing structure allows the organization of the functionality that can be...

  4. SPEM 2.0 extension for pervasive information systems

    Fernandes, José Eduardo; Machado, Ricardo J.
    Pervasive computing is a research field of computing technology that aims to achieve a new computing paradigm. In this paradigm, the physical environment has a high degree of pervasiveness and availability of computers and other information technology (IT) devices, usually with communication capabilities. Pervasive Information Systems (PIS), composed by these kinds of devices, bring issues that challenge software development for them. Model-Driven Development (MDD), strongly focusing and relying on models, has the potential to allow: the use of concepts closer to the domain and the reduction of semantic gaps; higher automation and lower dependency to technological changes; higher capture of expert knowledge and reuse; an overall increased...

  5. Applying action research in the adoption of information systems security policies

    Lopes, Isabel Maria; Sá-Soares, Filipe de
    Information Systems Security (ISS) is a critical issue for a wide range of organizations. This paper focuses on organizations belonging to a particular sector, namely Local Public Administration, where public and personal information must be protected by those in charge, and where there must be a concern to view security as a priority. There are several measures which can be implemented in order to ensure the effective protection of information assets, among which stands out the adoption of ISS policies. A recent census concluded that among the 308 Town Councils in Portugal, only 38 indicated to have an ISS policy....

  6. Proposal of a learning styles identification tool for sakai virtual learning environment

    Alves, Paulo; Miranda, Luísa; Morais, Carlos; Alves, Evandro
    We are living in an essentially technological world, in which technology facilitates and promotes the development of institutions and the people who work or study in these institutions. Thus, it is claimed that technology should increasingly meet people’s needs according to their goals, interests and learning styles. Aiming to improve the teaching and learning process, and based on a perspective of adaptation of the learning environment to the learner’s needs, we present, in this article, the integration of learning styles in learning management systems by integrating the Honey-Alonso Learning Styles Questionnaire (CHAEA) in Sakai collaborative learning environment, which was adopted...

  7. Characterization and modeling of top spam botnets

    Rodrigues, Nuno G.; Sousa, Rui; Salvador, Paulo; Nogueira, António Manuel
    The increasing impact of the Internet in the global economy has transformed Botnets into one of the most relevant security threats for citizens, organizations and governments. Despite the significant efforts that have been made over the last years to understand this phenomenon and develop detection techniques and countermeasures, this continues to be a field with big challenges to address. Several approaches can be taken to study Botnets: analyze its source code, which can be a hard task because it is usually unavailable; study the control mechanism, particularly the activity of its Command and Control server(s); study its behavior, by measuring...

  8. Issues of e-learning standards and identity management for mobility and collaboration in higher education

    Alves, Paulo; Uhomoibhi, James
    This paper investigates and reports the status of identity management systems and e-learning standards across Europe for promoting mobility, collaboration and the sharing of contents and services in higher education institutions.The creation of identities federation across Europe has been under discussion by TERENA (Trans-European Research and Education Networking Association) to provide a service federation like the EDUROAM WIFI network that permits the mobility across Europe. This paper reports on some of the issues highlighted in the light of recent developments. It is revealed that it is crucial to create identity management fedeartion to provide for ease of mobility and facilitate collaboration and sharing information amongst staff...

  9. Comparing general-purpose and domain-specific languages: an empirical study

    Kosar, Tomaz; Oliveira, Nuno; Mernik, Marjan; Pereira, Maria João; Crepinsek, Matej; Cruz, Daniela; Henriques, Pedro
    Many domain-specific languages, that try to bring feasible alternatives for existing solutions while simplifying programming work, have come up in recent years. Although, these little languages seem to be easy to use, there is an open issue whether they bring advantages in comparison to the application libraries, which are the most commonly used implementation approach. In this work, we present an experiment, which was carried out to compare such a domain-specific language with a comparable application library. The experiment was conducted with 36 programmers, who have answered a questionnaire on both implementation approaches. The questionnaire is more than 100 pages long....

  10. Computation of conservation laws in optimal control

    Gouveia, Paulo D.F.; Torres, Delfim F.M.
    Making use of a computer algebra system, we define computational tools to identify symmetries and conservation laws in optimal control.

  11. Multivox: conversor texto fala para português

    Teixeira, João Paulo; Freitas, D.; Gouveia, Paulo D.F.; Olaszy, Gabor; Nemeth, G.
    Apresenta-se neste artigo uma visão genérica sobre sistemas de conversão texto-fala. Aborda-se de uma forma mais detalhada o sistema MULTIVOX de conversão texto fala para o português como um modelo de síntese de formantes baseado em regras. Este sistema foi desenvolvido no âmbito da cooperação entre o CEFAT e a Universidade Técnica de Budapeste em duas versões. Uma primeira versão, desenvolvida até 1996, que será descrita por blocos para permitir uma melhor compreensão deste sistema. Uma segunda versão, ainda em desenvolvimento, será apresentada nas suas potencialidades. O sistema corre num processador 386 ou superior com recurso a uma placa de...

  12. Divisão silábica automática do texto escrito e falado

    Gouveia, Paulo D.F.; Teixeira, João Paulo; Freitas, D.
    Este artigo apresenta um algoritmo que permite realizar automaticamente a separação silábica do texto como uma etapa do desenvolvimento de um trabalho mais extenso, que é o estudo de modelos prosódicos para o português europeu, enquadrado no desenvolvimento de um sintetizador de fala. O algoritmo de separação silábica está foi concebido para aplicação em duas situações distintas: na primeira é aplicado ao texto escrito e na segunda à sequência de fonemas realmente produzidos na locução desse mesmo texto. Cada uma das aplicações está envolta nas suas peculiaridades e dificuldades, que são descritas, bem como as soluções adoptadas para a sua...

  13. Computing ODE symmetries from a variational point of view

    Gouveia, Paulo D.F.; Torres, Delfim F.M.

  14. Uma forma bidimensional que maximiza a resistência aerodinâmica newtoniana

    Gouveia, Paulo D.F.; Plakhov, Alexander; Torres, Delfim F.M.
    Um corpo bidimensional, apresentando um ligeiro movimento rotacional, desloca-se num meio rarefeito de partículas que colidem com ele de uma forma perfeitamente elástica. Em investigações que os dois primeiros autores realizaram anteriormente [Plakhov and Gouveia, 2007], procuraram-se formas de corpos que maximizassem a força de travagem do meio ao seu movimento. Dando continuidade a esse estudo, encetam-se agora novas investigações que culminam num resultado que representa um grande avanço qualitativo relativamente aos então alcançados.Esse resultado, que agora se apresenta, consiste numa forma bidimensional que confere ao corpo uma resistência muito próxima do seu limite teórico.

  15. A project of speech input and output in an e-commerce application

    Freitas, D.; Moura, António; Braga, Daniela; Ferreira, Helder; Teixeira, João Paulo; Barros, Maria João; Gouveia, Paulo D.F.; Latsch, Vagner
    The present paper describes the work done during the last year in the development of European Portuguese (EP) speech recognition and synthesis channels for an Internet e-commerce application. The objective of this work was to develop the appropriate speech input and output, to enable the user to more comfortably use an e-commerce web site issuing commands and options under guidance of a menu system. The speech interface operation guidelines are briefly described in their principles and resulting specifications for the speech channels, namely, menu structure and operation dynamics, and in the following, the system software approach and the speech recognition...

  16. Smarandache sequences: explorations and discoveries with a computer algebra system

    Gouveia, Paulo D.F.; Torres, Delfim F.M.
    We study Smarandache sequences of numbers, and related problems, via a Computer Algebra System. Solutions are discovered, and some conjectures presented.

  17. Automatic computation of conservation laws in the calculus of variations and optimal control

    Gouveia, Paulo D.F.; Torres, Delfim F.M.
    We present analytical computational tools that permit us to identify, in an automatic way, conservation laws in optimal control. The central result we use is the famous Noether's theorem, a classical theory developed by Emmy Noether in 1918, in the context of the calculus of variations and mathematical physics, which was extended recently to the more general context of optimal control. We show how a Computer Algebra System can be very helpful in ¯nding the symmetries and corresponding conservation laws in optimal control theory, thus making useful in practice the theoretical results recently obtained in the literature. A Maple implementation...

  18. Computação algébrica no cálculo das variações: determinação de simetrias e leis de conservação

    Gouveia, Paulo D.F.; Torres, Delfim F.M.
    Os problemas de optimização dinâmica (em espaços de funções) tratados pelo cálculo das variações, são normalmente resolvidos por recurso às condições necessárias de Euler-Lagrange, que são equações diferenciais de segunda ordem (ou de ordem superior, quando os problemas variacionais envolvem derivadas de ordem superior a um). Estas equações são, em geral, não lineares e de difícil resolução. Uma forma de as simplificar consiste em obter leis de conservação: primeiros integrais das equações diferenciais de Euler-Lagrange. Se em áreas como a Física e a Economia a questão da existência de leis de conservação é resolvida de forma bastante natural, a própria...

  19. Symbolic computation of variational symmetries in optimal control

    Gouveia, Paulo D.F.; Torres, Delfim F.M.; Rocha, Eugénio A.M.
    We use a computer algebra system to compute, in an efficient way, optimal control variational symmetries up to a gauge term. The symmetries are then used to obtain families of Noether’s first integrals, possibly in the presence of nonconservative external forces. As an application, we obtain eight independent first integrals for the sub-Riemannian nilpotent problem (2, 3, 5, 8).

  20. Problems of maximal mean resistance on the plane

    Plakhov, Alexander; Gouveia, Paulo D.F.
    A two-dimensional body moves through a rarefied medium; the collisions of the medium particles with the body are absolutely elastic.The body performs both translational and slow rotational motion. It is required to select the body, from a given class of bodies, such that the average force of resistance of the medium to its motion is maximal. There are presented numerical and analytical results concerning this problem. In particular, the maximum resistance in the class of bodies contained in a convex body K is proved to be 1.5 times resistance of K. The maximum is attained on a sequence of bodies with...

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