O sintonizador-demodulador de RF, também chamado de Front End, é definido de uma forma geral como sendo o conjunto ou módulo que está entre a antena e o sistema digital. Para um receptor isto inclui todos os filtros, amplificadores de baixo ruído, misturadores e demoduladores, necessários para processar o sinal modulado recebido na antena, demodulá-lo e entregá-lo em um fluxo de bits (Transport Stream) para o sistema digital de decodificação, também conhecido com Back End. Por esta razão o sintonizador-demodulador é muitas vezes chamado de conversor RF para TS (Rádio Freqüência para Transport Stream). Por ser o primeiro bloco, o Front End é a parte mais importante, e também a mais crítica de qualquer receptor contribuindo muito para o seu bom ou mau desempenho. Esta tese investigou os problemas existentes e que degradam a qualidade do sinal nas transmissões de TV analógica; os testes realizados pelo laboratório de TV Digital do Mackenzie comparando os padrões de transmissão dos sistemas de TV Digital, ATSC, DVB-T e ISDB-T; o modelo proposto e adotado pelo Sistema Brasileiro de TV Digital; e propôs um modelo de sintonizador-demodulador para o SBTVD, que atendesse as necessidades do sistema com robustez e flexibilidade. O sintonizador-demodulador foi desenvolvido, projetado, montado e testado no laboratório e no campo para avaliar a sua eficiência. / The RF front end is generally defined as everything between the antenna and the digital baseband system. For a receiver, it includes all the filters, low-noise amplifiers (LNAs), down-conversion mixers and demodulator needed to process the modulated signals received at the antenna into signals suitable for input into the baseband analog-to-digital converter (ADC), demodulate it and feed with a Transport Stream the Back End part of the system to decode the signal. For this reason, the RF front end is often called the RF-to-TS portion of a receiver. It turns out that this is the most important and critical part of the whole receiver aiming for its good or bad performance. This thesis researched the existing problems that degenerate the analog TV transmission quality; the digital TV tests realized by Mackenzie DTV laboratory comparing the digital TV transmission standards, ATSC, DVB-T and ISDB-T; the proposed and adopted model for the Brazilian Digital TV System; and a proposal of a Front End for the SBTVD that meets the requirements of the system with robustness and flexibility. The Front End was designed, assembled and tested in the DTV laboratory and in the field.

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Quatro páginas são dobráveis / Documento confidencial. Não pode ser disponibilizado para consulta / Tese de mestrado integrado. Engenharia Mecânica (Especialização Automação). Faculdade de Engenharia. Universidade do Porto. 2010

<p>The earlier in the production chain discontinuities in the weld area are discovered the better and less expensive it is to modify the weld. If the weld is bigger than necessary the cost and the weight grow, and if the weld is undersized the strength is put at risk. This report contains a summary of a literature survey for finding means for optical measurements of weld geometry. Some of the articles are about existing devices that can measure welds. One is hand-held and is applied on the weld afterwards and compares the data with pre set parameters. Experiments were performed with two different systems to evaluate their capability to capture the weld geometry. The first system is an in - house built system with a laser line diode and a CMOS - camera, the other system is scanCONTROL, and is a device with integrated camera and laser line. Matlab was used to process and analyse data from both systems. Experiments with the first system ended when it was quite obvious that it did not meet the expected result. The laser line projection was too short to cover enough of the weld area and it was hard to process the image to find defects in the weld area. The data from the scanCONTROL system was ready to use and it was quite easy to find different defects and discontinuities in the weld area. It is possible to find the geometry of the weld and it is possible to find defects like spatter, undercut and sharp edges, with laser line projection and camera. The equipment is important in order to extract data useful for analysis.</p>

Digital libraries are widely used for organizing and presenting large collections of artifacts. However, as the digital libraries grow in size, it is becoming increasingly difficult for the user to find all the resources related to his topic of interest. It is labor intensive, time consuming and error prone to identify and link related materials manually. Thus it is important to develop automatic techniques to help the user discover and view the related resources that are available in the digital library. We have implemented an automatic interlinking mechanism for a music digital library system that spans across batch, online and on-demand phases. Since the task of generating the related links is resource and time intensive, distributing the whole process across these three phases significantly reduces the runtime overhead and improves the response time. This mechanism allows the system to display very large texts, with keywords identified and hyperlinked, with no perceivable delay to the user. Storing the artifacts in a structured manner and using the structural metadata to generate interlinkages allows us to create these links across diverse media like images, audio files, music scores, texts, etc. The implemented interlinking technique also scales well with a rapidly changing collection. The related links are displayed on demand, using AJAX technology. This allows the user to view these links without leaving the text, thus ensuring minimum disruption and continuity of action. We also have developed a generic interlinking framework which abstracts the domain independent logic for generating and displaying related links. This generic interlinking framework can be used by domain specific digital libraries to support interlinking of related resources.

The changes and its effects.

The earlier in the production chain discontinuities in the weld area are discovered the better and less expensive it is to modify the weld. If the weld is bigger than necessary the cost and the weight grow, and if the weld is undersized the strength is put at risk. This report contains a summary of a literature survey for finding means for optical measurements of weld geometry. Some of the articles are about existing devices that can measure welds. One is hand-held and is applied on the weld afterwards and compares the data with pre set parameters. Experiments were performed with two different systems to evaluate their capability to capture the weld geometry. The first system is an in - house built system with a laser line diode and a CMOS - camera, the other system is scanCONTROL, and is a device with integrated camera and laser line. Matlab was used to process and analyse data from both systems. Experiments with the first system ended when it was quite obvious that it did not meet the expected result. The laser line projection was too short to cover enough of the weld area and it was hard to process the image to find defects in the weld area. The data from the scanCONTROL system was ready to use and it was quite easy to find different defects and discontinuities in the weld area. It is possible to find the geometry of the weld and it is possible to find defects like spatter, undercut and sharp edges, with laser line projection and camera. The equipment is important in order to extract data useful for analysis.

This thesis explores the process of translating traditional cinematic lighting into the digital realm by understanding distinctly different lighting styles of three Directors of Photography. These Directors of Photography are Conrad Hall, Gregg Toland, and Zhao Fei. Digital lighting studies representative of the work of each Director of Photography were created. In these studies, the lighting in scenes done by each Director of Photography was digitally mimicked. As a result, the lighting studies provided valuable insight into the approaches of these masters of light. An animation was created to display a scene lit in the three lighting styles of each Director of Photography. The process, learned from the lighting studies, of creating three different lighting styles representative of each Director of Photography was applied to the final animation. The analysis and lighting studies of each Directors' of Photography style expedited the process of lighting the final animation in each different style. As a result, a more complex environment was effectively lit in three different cinematic styles with animated light.

Digital libraries are widely used for organizing and presenting large collections of artifacts. However, as the digital libraries grow in size, it is becoming increasingly difficult for the user to find all the resources related to his topic of interest. It is labor intensive, time consuming and error prone to identify and link related materials manually. Thus it is important to develop automatic techniques to help the user discover and view the related resources that are available in the digital library. We have implemented an automatic interlinking mechanism for a music digital library system that spans across batch, online and on-demand phases. Since the task of generating the related links is resource and time intensive, distributing the whole process across these three phases significantly reduces the runtime overhead and improves the response time. This mechanism allows the system to display very large texts, with keywords identified and hyperlinked, with no perceivable delay to the user. Storing the artifacts in a structured manner and using the structural metadata to generate interlinkages allows us to create these links across diverse media like images, audio files, music scores, texts, etc. The implemented interlinking technique also scales well with a rapidly changing collection. The related links are displayed on demand, using AJAX technology. This allows the user to view these links without leaving the text, thus ensuring minimum disruption and continuity of action. We also have developed a generic interlinking framework which abstracts the domain independent logic for generating and displaying related links. This generic interlinking framework can be used by domain specific digital libraries to support interlinking of related resources.

In the field of optical fiber communication, the IM/DD system had been used to commercial usage for many years. The merits of this scheme are its simple idea and easiness to realize. However, such a system can not afford the requirement of the capacity people demand anymore. Recently, the research of the optical fiber communication is focused on how to increase the spectral efficiency to attend the high speed transmission. Coherent system had been investigated widespreadly a few tens years ago. This technique could improve the spectral efficiency. Nevertheless, the difficulty of coherent system was its receiver circuit was quite complicated and could not be realized at that time. Accompanying with the improvement of the technique, a developed technique called digital signal processing (DSP) could overcome such difficulties. This master thesis is focused on how to cooperate these two techniques that may be required for the next generation high speed transmission system.