937 resultados para Hertzian contacts
Resumo:
18th SPACE Annual Conference and EURASHE-SEPHE Seminar 21-24 March 2007 Thursday 22 March 2007
Resumo:
The characteristics of tunable wavelength filters based on a-SiC:H multilayered stacked pin cells are studied both theoretically and experimentally. The optical transducers were produced by PECVD and tested for a proper fine tuning of the cyan and yellow fluorescent proteins emission. The active device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n heterostructures sandwiched between two transparent contacts. Experimental data on spectral response analysis, current-voltage characteristics and color and transmission rate discrimination are reported. Cyan and yellow fluorescent input channels were transmitted together, each one with a specific transmission rate and different intensities. The multiplexed optical signal was analyzed by reading out, under positive and negative applied voltages, the generated photocurrents. Results show that the optimized optical transducer has the capability of combining the transient fluorescent signals onto a single output signal without losing any specificity (color and intensity). It acts as a voltage controlled optical filter: when the applied voltages are chosen appropriately the transducer can select separately the cyan and yellow channel emissions (wavelength and frequency) and also to quantify their relative intensities. A theoretical analysis supported by a numerical simulation is presented.
Resumo:
Mestrado em Intervenção Sócio-Organizacional na Saúde. Área de especialização: Políticas de Administração e Gestão dos Serviços de Saúde.
Resumo:
Combined tunable WDM converters based on SiC multilayer photonic active filters are analyzed. The operation combines the properties of active long-pass and short-pass wavelength filter sections into a capacitive active band-pass filter. The sensor element is a multilayered heterostructure produced by PE-CVD. The configuration includes two stacked SiC p-i-n structures sandwiched between two transparent contacts. Transfer function characteristics are studied both theoretically and experimentally. Results show that optical bias activated photonic device combines the demultiplexing operation with the simultaneous photodetection and self amplification of an optical signal acting the device as an integrated photonic filter in the visible range. Depending on the wavelength of the external background and irradiation side, the device acts either as a short- or a long-pass band filter or as a band-stop filter. The output waveform presents a nonlinear amplitude-dependent response to the wavelengths of the input channels. A numerical simulation and two building-blocks active circuit is presented and gives insight into the physics of the device.
Resumo:
Tunable wavelength division multiplexing converters based on amorphous SiC multilayer photonic active filters are analyzed. The configuration includes two stacked p-i-n structures (p(a-SiC:H)-i'(a-SiC:H)-n(a-SiC:H)-p(a-SiC:H)-i(a-Si:H)-n(a-Si:H)) sandwiched between two transparent contacts. The manipulation of the magnitude is achieved through appropriated front and back backgrounds. Transfer function characteristics are studied both theoretically and experimentally. An algorithm to decode the multiplex signal is established. An optoelectronic model supports the optoelectronic logic architecture. Results show that the light-activated device combines the demultiplexing operation with the simultaneous photodetection and self-amplification of an optical signal. The output waveform presents a nonlinear amplitude-dependent response to the wavelengths of the input channels. Depending on the wavelength of the external background and irradiation side, it acts either as a short- or a long-pass band filter or as a band-stop filter. A two-stage active circuit is presented and gives insight into the physics of the device.
Resumo:
Combined tunable WDM converters based on SiC multilayer photonic active filters are analyzed. The operation combines the properties of active long-pass and short-pass wavelength filter sections into a capacitive active band-pass filter. The sensor element is a multilayered heterostructure produced by PE-CVD. The configuration includes two stacked SiC p-i-n structures sandwiched between two transparent contacts. Transfer function characteristics are studied both theoretically and experimentally. Results show that optical bias activated photonic device combines the demultiplexing operation with the simultaneous photodetection and self amplification of an optical signal acting the device as an integrated photonic filter in the visible range. Depending on the wavelength of the external background and irradiation side, the device acts either as a short- or a long-pass band filter or as a band-stop filter. The output waveform presents a nonlinear amplitude-dependent response to the wavelengths of the input channels. A numerical simulation and a two building-blocks active circuit are presented and give insight into the physics of the device. (c) 2013 Elsevier B.V. All rights reserved.
Resumo:
OBJECTIVE: To assess risk factors for retreatment of leprosy patients. METHODS: A case-control study with patients from two reference care units in Recife, northeastern Brazil, in 2003. The case group included retreated patients (N=155) and the control group comprised those patients who were not retreated (N=155) matched by year of diagnosis and health care unit. Univariate and multivariate analyses were conducted to test the associations and odds ratios and related 95% confidence intervals were estimated. RESULTS: The following factors were found to be significantly associated (p<0.05) with retreatment: occurrence of adverse immunological reactions after treatment completion (OR=2.3; 95% CI=1.18;4.83), final bacterial index > 1 (OR=6.43; 95% CI=1.67;24.74), therapeutic regimen consisting of sulfone monotherapy (OR=10; 95% CI=0.01;0.78) and reports of household contacts (OR=2.2; 95% CI=0.24;0.85). CONCLUSIONS: The study findings reinforce that the use of dapsone monotherapy should be discontinued, and highlight the need for epidemiological monitoring of specific groups of leprosy patients after treatment completion through periodical clinical and laboratory evaluation. Further studies to explore the association between final bacterial index and retreatment are strongly recommended.
Resumo:
We present measurements and numerical simulation of a-Si:H p-i-n detectors with a wide range of intrinsic layer thickness between 2 and 10 pm. Such a large active layer thickness is required in applications like elementary particle detectors or X-ray detectors. For large thickness and depending on the applied bias, we observe a sharp peak in the spectral response in the red region near 700 nm. Simulation results obtained with the program ASCA are in agreement with the measurement and permit the explanation of the experimental data. In thick samples holes recombine or are trapped before reaching the contacts, and the conduction mechanism is fully electron dominated. As a consequence, the peak position in the spectral response is located near the optical band gap of the a-Si:H i-layer. (C) 2009 Elsevier B.V. All rights reserved.
Resumo:
Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Hidráulica
Resumo:
A evolução tecnológica, associada às mudanças sociais a que temos assistido, nomeadamente nas últimas décadas, originou mudanças significativas na forma como os utentes interagem com as instituições, passando a privilegiar a utilização de meios electrónicos, tais como as mensagens de correio electrónico, em detrimento de formas mais tradicionais, como a carta e o telefone. Neste contexto, sendo o ISEP uma instituição de ensino superior que alberga milhares de alunos e recebe centenas de novos alunos todos os anos, necessita de ter condições para que possa responder de forma atempada às inúmeras mensagens de correio electrónico que recebe. Esta necessidade fez com que surgisse um projecto, de nome SiRAC, que servisse para auxiliar na resposta a essas mensagens. O SiRAC tem como objectivo responder a mensagens de correio electrónico de forma automática. De salientar que se admite não ser possível responder a todas as mensagens, privilegiando-se aquelas que são recorrentemente colocadas à Divisão Académica. Assim será possível encurtar o tempo de comunicação entre os diversos intervenientes, criando uma relação mais próxima entre o ISEP e o público que o contacta. O SiRAC analisa as mensagens e procura responder de forma automática sempre que o seu conteúdo possa ser classificado como fazendo parte de um conjunto de questões previamente identificadas pelos recursos humanos da Divisão Académica como recorrentes e para as quais já exista uma resposta tipo. As questões constantes da mensagem são identificadas através de palavras e expressões normalmente associadas aos diferentes tipos de questão. O envio da resposta pressupõe a identificação correcta dos tipos associados e de acordo com requisitos mínimos definidos, de forma a evitar enviar uma resposta errada a uma mensagem. A implementação do SiRAC permite a libertação de recursos humanos da Divisão Académica que anteriormente estavam afectas à resposta de mensagens para o desempenho de outras funções.
Resumo:
Although Mobility is a trendy and an important keyword in education matters, it has been a knowledge tool since the beginning of times, namely the Classical Antiquity, when students were moving from place to place following the masters. Over the time, different types of academic mobility can be found and this tool has been taken both by the education and business sector as almost a compulsory process since the world has gone global. Mobility is, of course, not an end but a means. And as far as academic mobility is concerned it is above all a means to get knowledge, being it theoretical or practical. But why does it still make sense to move from one place to another to get knowledge if never as before we have heaps of information and experiences available around us, either through personal contacts, in books, journals, newspapers or online? With this paper we intend to discuss the purpose of international mobility in the global world of the 21st century as a means to the development of world citizens able to live, work and learn in different and unfamiliar contexts. Based on our own experience as International Coordinator in a Higher Education Institution (HEI) over the last 8 years, on the latest research on academic mobility and still on studies on employability we will show how and why academic mobility can develop skills either in students or in other academic staff that are hardly possible to build in a classroom, or in a non-mobile academic or professional experience and that are highly valued by employers and society in general.
Resumo:
The main objective of this research is to exploit the possibility of using an ex situ solvent extraction technique for the remediation of soils contaminated with semi-volatile petroleum hydrocarbons. The composition of the organic phase was chosen in order to form a single phase mixture with an aqueous phase and simultaneously not being disturbed (forming stable emulsions) by the soil particles hauling the contaminants. It should also permit a regeneration of the organic solvent phase. As first, we studied the miscibility domain of the chosen ternary systems constituted by ethyl acetate–acetone–water. This system proved to satisfy the previous requirements allowing for the formation of a single liquid phase mixture within a large spectrum of compositions, and also allowing for an intimate contact with the soil. Contaminants in the diesel range within different functional groups were selected: xylene, naphthalene and hexadecane. The analytical control was done by gas chromatography with FID detector. The kinetics of the extractions proved to be fast, leading to equilibrium after 10 min. The effect of the solid–liquid ratio on the extraction efficiency was studied. Lower S/L ratios (1:8, w/v) proved to be more efficient, reaching recoveries in the order of 95%. The option of extraction in multiple contacts did not improve the recovery in relation to a single contact. The solvent can be regenerated by distillation with a loss around 10%. The contaminants are not evaporated and they remain in the non-volatile phase. The global results show that the ex situ solvent extraction is technically a feasible option for the remediation of semi-volatile aromatic, polyaromatic and linear hydrocarbons.
Resumo:
O presente trabalho, desenvolvido sob a orientação do Prof. Jaime Gabriel Silva, centra-se na procura e aplicação de metodologias de planeamento com apoio de ferramentas informáticas de análise de risco, que permitem realizar, em tempo útil, o cálculo dos prazos resultantes de inúmeras combinações possíveis associadas à incerteza das durações das atividades, recorrendo a modelos estocásticos. O trabalho aborda inicialmente o contexto da Gestão na Construção, com particular enfase na Gestão do Risco. Nessa fase inicial, fez-se também um pequeno inquérito a profissionais com diferentes níveis de responsabilidade organizacional e empresas do setor. A parte fundamental do trabalho, incide nos procedimentos a adotar na elaboração do planeamento de empreitadas. Nesta parte do trabalho, introduzem-se os conceitos da análise de risco com recurso a uma ferramenta informática de apoio, o @Risk, que permite a utilização do Método de Monte Carlo, para obtenção de resultados num contexto de uma tomada de decisão baseada no risco. Refira-se que houve vários contactos com o fornecedor do programa, que permitiram tirar partido de outro programa da Palisade, Evolver, direcionado para otimização matemática, podendo ser utilizado, por exemplo, na perspetiva da minimização dos custos, o que pode interessar pela relação destes com as opções adotadas na elaboração do planeamento de empreendimentos. Finalmente, toma-se um exemplo real do planeamento de uma empreitada em execução à data da realização deste trabalho, onde se aplicaram os conceitos desenvolvidos no trabalho, confrontando os resultados com o andamento da obra.
Resumo:
Conventional film based X-ray imaging systems are being replaced by their digital equivalents. Different approaches are being followed by considering direct or indirect conversion, with the later technique dominating. The typical, indirect conversion, X-ray panel detector uses a phosphor for X-ray conversion coupled to a large area array of amorphous silicon based optical sensors and a couple of switching thin film transistors (TFT). The pixel information can then be readout by switching the correspondent line and column transistors, routing the signal to an external amplifier. In this work we follow an alternative approach, where the electrical switching performed by the TFT is replaced by optical scanning using a low power laser beam and a sensing/switching PINPIN structure, thus resulting in a simpler device. The optically active device is a PINPIN array, sharing both front and back electrical contacts, deposited over a glass substrate. During X-ray exposure, each sensing side photodiode collects photons generated by the scintillator screen (560 nm), charging its internal capacitance. Subsequently a laser beam (445 nm) scans the switching diodes (back side) retrieving the stored charge in a sequential way, reconstructing the image. In this paper we present recent work on the optoelectronic characterization of the PINPIN structure to be incorporated in the X-ray image sensor. The results from the optoelectronic characterization of the device and the dependence on scanning beam parameters are presented and discussed. Preliminary results of line scans are also presented. (C) 2014 Elsevier B.V. All rights reserved.
Resumo:
Projeto para obtenção do Grau de Mestre em Teatro. Especialização em Artes Performativas — Escritas de Cena.