Repositório RCAAP

The Micro-Hole and Strip Plate (MHSP) is a hybrid microstructure that combines within the same KaptonTM substrate the capabilities of a Gas Electron Multiplier (GEM) and a Micro-strip Gas Detector (MSGD).Due to its two multiplication stages it is able to achieve better gains than eather the GEM or the MSGD alone. In this work, the 2D imaging capabilities of such a microstructure are being studied, and some very encouraging results have already been achieved, with spatial resolutions of less than 300 mm for one of the dimensions.

This work is based on the use of a simulation system dedicated for small animal PET imaging. GATE, a Monte Carlo simulation platform based on the Geant4 libraries, is well suited for modelling microPET systems like the microPET® FOCUS 220 and to implement realistic phantoms, such as the MOBY phantom, and radioactive distribution maps obtained from real exams. We used the validated microPET® FOCUS 220 simulation model, with GATE, to produce real simulated PET mouse exams. Results from simulated real studies of the mouse body using [18F] fluoride and the 2-Deoxy-[18F] fluoro-D-glucose (FDG) imaging protocols are presented. These simulations include the injections of real radioactive doses into the animal and the use of real time frames. We also simulate the respiratory mouse motion during an FDG PET exam using the model proposed in the dynamic MOBY phantom. The qualitative and quantitative results from simulated data are in good agreement with the experimental data.

The electroluminescence yield was studied for xenon gas as a function of the electric field in the scintillation region, for room temperature using a gas proportional scintillation counter. A large area avalanche photodiode was used for the readout of the VUV secondary scintillation produced in the gas, together with the 5.9-keV x-rays directly absorbed in the photodiode. Using the latter as a reference for the number of charge carriers produced by the scintillation pulse, it was possible to determine the number of VUV photons impinging the photodiode. This way, a scintillation amplification parameter of 140 photons/kV was obtained. The attained results are in good agreement with those predicted, for room temperature, by Monte Carlo simulation and Boltzmann calculations, as well as with those obtained for saturated xenon vapour, at cryogenic temperatures, and are about a factor of two higher than former results measured at room temperature.

We report on the performance of a Micro-Hole & Strip Plate (MHSP) electron multiplier operating in pure Xe, Kr, Ar and Ne at the pressure range of 1 to 6 bar and in Ar – Xe mixtures at pressures ranging from 1 to 7 bar. The maximal gains at 1 bar Xe and Kr are 5*104 and 105, respectively; they drop by about one order of magnitude at 2bar and by almost another order of magnitude at 5-6 bar; they reach gains of 500 and 4000 at 5 bar in Xe and Kr, respectively. In Ar, the gain varies very little with pressure, from 3*103 to 9*103; in Ne the maximum attainable gain, about 105, is pressure independent above 2 bar. The results are compared with that of single- and triple-GEM multipliers operated in similar conditions. Potential applications are in hard X-ray imaging and in cryogenic radiation detectors. In the Ar - Xe mixture no significant reduction of the maximum achievable gain was measured. Absolute gains of 1–4*103 were reached in Ar/50 mbar Xe over this pressure range from 1 to 7 bar. Energy resolutions between 14% and 16% were reached for 6 keV X-rays.

Information about the polarization of x-ray photons can be determined by probing the direction of emission of photoelectrons and the profile of the electron cloud produced in the detecting medium. In this work we present Monte Carlo results for the electron clouds produced in xenon by the absorption of x-rays, considering a simple non-relativistic dipole approach to the angular differential photoionization cross-sections.

We present the recent results regarding the application of cascades of GEMs and a MHSP in the detection and imaging of X-rays and UV-photons. The imaging system tested consisted in a micropattern gas detector based in multi-GEM or multi-GEM/MHSP electron multipliers, a 20´20 mm2 Wedge & Strip (W&S) readout electrode with 1.6 mm pitch positioned below and at close distance of a resistive electrode, and a position enconding electronics with a DAQ system. Spatial resolutions in the x and y coordinates lower than ~100 mm RMS, were measured in Ar/5%CH4 gas mixture at atmospheric pressure.

The purpose of this work was the Monte Carlo simulation of the Siemens E.Cam Dual Head Gamma Camera and consequent experimental validation, with the aim to further study and to improve the current understandingconcerning the operation of these systems, this way contributing to the development of detectors with betterenergy resolution, sensitivity, spatial resolution and linearity. The geometry and characteristics of this Gamma Camera, physics processes involved, and necessary radiation sources were implemented in GEANT4 code, to be as realistic as feasible. (...)

Surge este número da Revista numa altura de mudanças significativas que directa ou indirectamente influenciará o nosso quotidiano profissional na Universidade de Aveiro. Em primeiro lugar é de referir a alteração do nome do Departamento para Departamento de Electrónica e Telecomunicações e Informática (DETI). Trata-se para além duma mera alteração de nome, duma forma de manifestar um posicionamento estratégico do Departamento face à área científica de Informática e da sua actual importância não só nos universos da Electrónica e das Telecomunicações mas em muitas outras instâncias multidisciplinares perante as quais o agora designado DETI deverá ter de responder cabalmente. Em segundo lugar e provavelmente com um mais rápido e significativo impacto surgem as alterações curriculares decorrentes da Declaração de Bolonha. (...)

Analysis Services disposes three Access Mechanisms: Direct Access, HTTP/HTTPS Access and XMLA Access. From among these mechanisms, the Direct Access is that one that guarantees the lowest response time and the strongest security, characteristics that turn it the mechanism of preferential use. But this mechanism can be used only in intradomain accesses, by imposition of the Authentication Mechanism that it uses, the Integrated Windows Authentication. When the Client and the Analysis Services doesn’t share the same domain, or when the access must be made by Internet, can be used the HTTP/HTTPS Access Mechanism. However, the use of this mechanism is not trivial, presenting some peculiarities; a consequence of Analysis Services doesn’t to support, by him self, HTTP/HTTPSAccesses. In fact, HTTP/HTTPS Access to Analysis Services is provided by the IIS Web Server.In this paper, the Logical Model and the Physical Models, used by Analysis Services, to provide HTTP/HTTPS access thought the IIS Web Server, will be analyzed, and will be explained the steps required to setting it up. The Mechanisms of Security and Access Control, used by Analysis Services, will be analyzed too, being covered both Users Authentication and Security Roles Definition.

The Information and Communication Technologies associated with the Internet have today an important role for data quality and fast data transfer in the scope of the healthcare in general and haemophilia care in particular. As such, the purpose of this work is to study the potentialities of those technologies in the registry and transference of home treatment records, as well as, to study the feasibility of an integrated Information System, tomanage clinical information of this specific pathology, inhaematology services of the Coimbra Hospital Center.

This paper is focused on issues of dynamic process modeling and model-based optimization of batch and fed-batch industrial crystallization processes applying the concept of artificial neural networks as computational tools. The objective is to drive the process to its optimal state of profit  maximization and cost minimization. The simulation results demonstrate that the very tight and conflicting end-point objectives are simultaneously feasible in the presence of hard process constrains.

This paper describes the project FootVR, carried out within the 3D Modeling and Visualization course. FootVR allows to visualize football games from log files in a virtual reality environment. For visualization had been used VisualizationToolkit (VTK).

No summary/description provided

Este número da Revista do DET continua a evidenciar a habitual diversidade de interesses científicos e pedagógicos que determinam a nossa actividade como membros do DET. Basta uma rápida análise do índice para identificar, entre outros, temas nas áreas das telecomunicações, sistemas de informação, processamento de sinal e imagem e sistemas computacionais, e robótica. (...)

This paper describes an application developed for Windows platforms in order to allow data acquisition, instance solution and results visualization in the scope of Location-Routing Problems. The main goal of this proposal is to provide a Decision Support System capable of providing a set of good solutions for this type of problems; however, having an intuitive and easy to use user interface is a fundamental concern so as to make this system usable for a large audience.

Nesta comunicação são descritos os esforços desenvolvidos para a criação de um ambiente de custo reduzido que permite a investigação e o desenvolvimento de aplicações em Realidade Virtual e Aumentada. A utilização de um Head-Mounted Display e de sensores de orientação e de aceleração, conjugados com toolkits gráficos de domínio público, permitiram o desenvolvimento da arquitectura de um primeiro protótipo e a rápida implementação de ambientes virtuais, bem como o teste de diferentes métodos de navegação. A posterior adição de uma câmara de vídeo passou a permitir, também, a criação de ambientes aumentados do tipo video see-through e com algum grau de interacção.

Real-time systems are typically reactive systems implemented with a set of concurrent tasks running on top of an executive or operating system. Due to concurrent task execution and access to shared resources, it is fundamental that the execution of critical regions is performed in a safe way, i.e. controlled by appropriate synchronization primitives (e.g.semaphores). To reduce the sources of unbounded priority inversions the semaphores must be managed by protocols adequate for real-time systems. This paper describes some protocols used for such purposes, namely the Priority Inheritance Protocol (PIP), the Priority Ceiling Protocol (PCP) and the Stack Resource Policy (SRP).

Este artigo descreve sumariamente um sistema de displays universais e autónomos para equipar elevadores. A solução desenvolvida consiste numa arquitectura distribuída de módulos inteligentes, munidos de displays gráficos do tipo LCD (liquid cristal display), ligados pelo barramento CAN (controller area network). Os módulos incluem microcontrolador PIC 18F, memória Flash externa para armazenamento das configurações de pisos, e um conjunto de interfaces que permitem a sua adaptação a dois tipos de display LCD e a uma variedade de quadros de controlo de elevadores.

This paper presents the methods used for the development of a project that intends to contribute for the implementation of a logistic system of identification, management and flow control of materials (raw materials, products in assembly stage, tools and support machinery) for application in industrial environments. This work was the final project to obtain a degree in Electronics and Telecommunications Engineering. It was developed by its authors in collaboration with the “Programa Aveiro-Norte” and the “Grupo de Sistemas de Banda Larga” of the Electronics and Telecommunications Department of the University of Aveiro. The intent of this work was to enhance the identification, usage management and flow control of moulds for plastics in Simoldes Plásticos, an industrial unit of Simoldes, an industrial group responsible for injection of plastic products, especially for the automotive industry.

The work reported in this paper deals with the impact of a nonlinear channel with noise in a FDMA system. The system is simulated using a time domain simulator, based on simulink. Five GSM channels are combined andthen traverse a nonlinear noisy channel. Finally some results are discussed.