A type system for access control in an object-oriented language

Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia Informática

Market expansion and the co-opetition of criminal organizations in Italy

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Medium access control design for distributed opportunistic radio networks

Existing wireless networks are characterized by a fixed spectrum assignment policy. However, the scarcity of available spectrum and its inefficient usage demands for a new communication paradigm to exploit the existing spectrum opportunistically. Future Cognitive Radio (CR) devices should be able to sense unoccupied spectrum and will allow the deployment of real opportunistic networks. Still, traditional Physical (PHY) and Medium Access Control (MAC) protocols are not suitable for this new type of networks because they are optimized to operate over fixed assigned frequency bands. Therefore, novel PHY-MAC cross-layer protocols should be developed to cope with the specific features of opportunistic networks. This thesis is mainly focused on the design and evaluation of MAC protocols for Decentralized Cognitive Radio Networks (DCRNs). It starts with a characterization of the spectrum sensing framework based on the Energy-Based Sensing (EBS) technique considering multiple scenarios. Then, guided by the sensing results obtained by the aforementioned technique, we present two novel decentralized CR MAC schemes: the first one designed to operate in single-channel scenarios and the second one to be used in multichannel scenarios. Analytical models for the network goodput, packet service time and individual transmission probability are derived and used to compute the performance of both protocols. Simulation results assess the accuracy of the analytical models as well as the benefits of the proposed CR MAC schemes.

O corpo da Guarda prisional como Órgão de Polícia Criminal e a sua importância na Segurança Interna

The study now presented a research study aimed at the exercise of security activity of the prison guard corps (CGP) in the specific context of the prison system (SP). The study also focused on the phenomenon of globalization and its influence on the current panorama of world crime and their relationship with the prison security object of study was the security activity of the CGP on the current inmate population, as well as the typology of crimes inherent to it and that requires the interpretation of the amendment to the correctional paradigm. In the preparation of the study we have tried to identify the legal framework of the profession based on the main laws and decree-laws governing the institution DGRSP and CGP's career. The difficulties and constraints were analyzed the performance of the security function of the CGP, resulting from the infrastructure, the interaction with the inmates and the need of assigning the status of Criminal Police (OPC). Really connected the relevant importance of OPC so the Corporation can establish a cooperation interaction and sharing of information with different security forces. We noted the importance of the CGP being OPC status before the framework for its action in work situations, specifically, on gatehouses, prison wings, area, and high-complexity operations such as escorts and riot control interventions.The explanation of this study enabled us to assess the importance of the actions of a police officer of the elements of the CGP for maintaining internal security. The analyses and studies were complemented by twenty years of career and exercise of the activity of the master's degree, during which time he served as guard and head of the CGP, the intervention Group and Prison Security, the Lisbon Prison, Prison, Prison of Caxias, Sintra and Monsanto.