Pose consensus based on dual quaternion algebra with application to decentralized formation control of mobile manipulators

This paper presents a solution based on dual quaternion algebra to the general problem of pose (i.e., position and orientation) consensus for systems composed of multiple rigid-bodies. The dual quaternion algebra is used to model the agents' poses and also in the distributed control laws, making the proposed technique easily applicable to time-varying formation control of general robotic systems. The proposed pose consensus protocol has guaranteed convergence when the interaction among the agents is represented by directed graphs with directed spanning trees, which is a more general result when compared to the literature on formation control. In order to illustrate the proposed pose consensus protocol and its extension to the problem of formation control, we present a numerical simulation with a large number of free-flying agents and also an application of cooperative manipulation by using real mobile manipulators

Using OMA DRM 2.0 protected content: Ogg vorbis protected audio under symbian OS

The lack of control inherent to digital content has been put on the spotlight by copyright infringement coupled with massive content distribution online (e.g., Peer-to-Peer). Digital Rights Management seems to be the solution to counter this problem advocating the use of cryptography and other related security mechanisms to protect digital content and to associate rights with it which determine how, when and by whom it can be consumed. The Open Mobile Alliance (OMA) specifies mobile service enablers in order to ensure interoperability throughout the mobile spectrum. As prominent mobile devices, Symbian OS smartphones offer an interesting platform for the demonstration of OMA DRM for the consumption of multimedia content. This article outlines the mechanisms enabling the protected consumption of the open and patent-free audio format (Ogg Vorbis Website), Ogg Vorbis using an OMA DRM 2.0 compliant audio player application running under Symbian OS (directed for mobile devices).info:eu-repo/semantics/acceptedVersio

Uso de forum no ensino cooperativo de programação

A utilização de Tecnologias da Informação e Comunicação no âmbito de actividades de ensino / aprendizagem, necessita de aliar, à disponibilidade efectiva dessas tecnologias, estratégias de integração nas actividades lectivas que permitam a satisfação das expectactivas dos docentes e dos alunos. Este artigo descreve a utilização de um forum numa disciplina de introdução à programação numa perspectiva de partilha de boas práticas, e discute alguns problemas e possíveis soluções