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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Dispositivo de varredura laser 3D terrestre e suas aplicações na engenharia, com ênfase em túneis. / Terrestrial laser scanner and its engineering applications, with emphasis in tunnels.

Gonçales, Rodrigo 18 April 2007 (has links)
Novas tecnologias estão sendo desenvolvidas constantemente para coletar informações de superfícies ou de sólidos para diversas finalidades. Alguns métodos clássicos, como a Topografia e a Fotogrametria terrestre, com o passar dos anos, tiveram uma grande evolução. Na Fotogrametria terrestre todo o processo está sendo feito em meio digital. Na topografia, as estações totais automatizaram a medição de ângulos e distâncias. Essa evolução tecnológica fez com que os levantamentos se tornassem cada vez mais rápidos e precisos, aumentando a produtividade. O mais recente nessa evolução é o levantamento através do sistema de varredura a laser (Laser Scanner) 3D. São muitas as aplicações dessa tecnologia, dentre as quais pode-se citar: túneis, levantamento do como construído (as-built), mineração (principalmente subterrânea), arqueologia, levantamento de monumentos para restauração, refinarias e instalações industriais e outras, caracterizadas pela grande complexidade dos elementos envolvidos. A presente dissertação apresenta os conceitos envolvidos em todos os processos, desde a coleta de dados até o produto final. Desenvolve uma metodologia de uso que possa ser útil em diversas áreas, mostra uma aplicação completa na área de túneis, complementada por uma visão geral da área de plantas industriais e procura apresentar testes para quantificar a precisão que se obtém por essa tecnologia. / New technologies are constantly being developed in order to collect information of surfaces or solids for diverse purposes. Some classic methods such as topography and terrestrial photogrammetry have had a great evolution in the past. For example, all the processes of the terrestrial photogrammetry are made in digital way and the Total Stations have automated the measurements of angles and distances. This technical evolution made the surveying faster and accurate, increasing the productivity. However this evolution does not stop for there; in other words, the last technology in the area of topography is the surveying with the system known as Laser Scanner 3D. The Laser Scanner technology 3D has a lot of applications such as: tunnel, as-built, mining (mainly in the underground); archaeology (for restore monuments), refineries, industrial installations, etc., characterized by the great complexity of the involved elements. This work presents concepts involved in all the processes, since from data collection to the final product. It develops a methodology of use that can be applied in several areas, with emphasis in tunnels surveying area and presents some tests to quantization the accuracy.
32

Validation d'un dosimètre patient temps réel basé sur fibre optique pour la tomodensitométrie X à l'aide de simulations Monte Carlo / Validation of a real time detector for CT dosimetry based on a scintillating optical fiber using Monte Carlo simulations

Gillet, Pierre 07 December 2018 (has links)
Ce travail porte sur la simulation d’examen scanner dans le but de valider une nouvelle méthode de mesure de dose au patient en temps réel basé sur une fibre optique scintillante. Dans un premier temps nous avons étudié la réponse en énergie de notre dosimètre, et montré qu’elle était proche de celle des chambres d’ionisation utilisées actuellement. Par la suite, un scanner a été modélisé avec succès et il a été observé que lors de l’examen, la dose au patient et la dose mesurée n’était pas impactée de la même manière par certains paramètres tels que la hauteur de la table, la position du patient, ou sa morphologie. Cependant en tenant compte de ceux-ci, il a été possible de déterminer la dose reçue par le patient durant un examen à l’aide de la mesure par fibre scintillante. Nous estimons que couplée à des simulations monte-carlo adaptées, cette mesure pourrait permettre une estimation précise de la dose délivrée aux organes à risques durant un examen. / This work focuses on the simulation of CT exam, and aims to validate a new real-time patient dose measurement method that uses a scintillating optical fiber. First, we studied our dosimeter’s energy response, and we showed that it was close to the response of the ion chambers currently used. Then, we successfully modeled a scanner, and found that during the exam, patient dose and measured dose were affected differently by parameters such as the table height, the patients positioning or the patients morphology. However, when accounting for such parameters, it was possible to compute the dose delivered to the patient during an exam using the scintillating fiber measurement. We consider that when coupled with monte-carlo simulations, this measurement could be used to estimate accurately the organ dose delivered during an exam.
33

Estudo de um túnel em maciço rochoso fraturado por investigação geológico-geotécnica e análises pelo método dos elementos distintos. / Study of a tunnel in a fractured rock mass by geological and geotechnical investigation and analysis with the distinct element method.

Pedro Pazzoto Cacciari 23 July 2014 (has links)
O comportamento geomecânico de túneis em rocha é fortemente influenciado pelas estruturas geológicas (descontinuidades) presentes no maciço. Do ponto de vista geométrico, estas estruturas são caracterizadas por parâmetros que descrevem suas orientações, frequências e comprimentos. Estes parâmetros, na maioria dos casos, são determinados em campanhas de campo, com bússola geológica e trena. Entretanto, limitações de tempo e acesso dificultam a execução destes trabalhos, impossibilitando a obtenção de números elevados de dados, que possibilitam análises estatísticas mais complexas. Para superar estas dificuldades, no presente estudo, o mapeamento das descontinuidades foi realizado em imagens do túnel Monte Seco, pertencente a Estrada de Ferro Vitória Minas (EFVM), obtidas por scanner a laser 3D. Neste mapeamento, tanto a orientação, quanto a posição e o comprimento dos traços das descontinuidades foram determinados com boa precisão, possibilitando a verificação da distribuição da intensidade de fraturamento de diferentes trechos, ao longo do túnel. Utilizando estes trechos diferenciados pela intensidade de fraturamento, foram elaboradas análises estatísticas mais complexas e adequadas (por janelas de amostragem e linhas de varredura) para determinação da orientação, comprimento médio dos traços e espaçamentos médios das famílias de descontinuidades. Com os parâmetros geométricos das descontinuidades, o modelo probabilístico de blocos rígidos foi construído, utilizando o software 3DEC. Assim, os parâmetros mecânicos das descontinuidades foram estimados utilizando correlações empíricas (a partir de descrições do maciço rochoso realizadas em mapeamentos geológicos por dentro do túnel), além de alguns ensaios de campo e laboratório. As análises com este modelo foram executadas para verificação da queda de blocos, e comparadas com as seções atuais do túnel. Os resultados indicaram que diferentes critérios de ruptura devem ser utilizados para diferentes tipos de descontinuidades (fraturas e foliação), e evidenciaram a importância de estimativas mais coerentes de parâmetros geométricos das descontinuidades nos resultados finais das análises. / The geomechanical behaviour of rock tunnels is strongly influenced by geological structures in the rock mass. Rock discontinuities are geometrically characterized by parameters that describes their orientations, frequency and lengths. In most cases, these parameters are determined in field inspections, using geological compass and measuring tapes. However, timeframes and access limitation hinder this procedure, making it impossible to obtain large amount of data that allow complex statistical analysis. To overcome these difficulties, here the discontinuity mapping was performed using images of the Monte Seco tunnel, obtained by 3D terrestrial laser scanning. In this case, the orientation, position and trace length of each discontinuity was determined with precision, allowing the verification of the fracture intensity distribution in different parts of the tunnel. Using these parts (differentiated by its fracture intensities), statistical analyses were performed, using sampling windows and scanlines, in order to determine the orientation mean trace length and spacing of discontinuity sets. Once the geometrical parameters of discontinuity sets were determined, a probabilistic model of rigid blocks was generated, using the 3DEC software. Thus, the mechanical parameters of discontinuity sets were estimated by empirical correlations (performed using descriptions of the rock mass obtained during geological inspections in the tunnel), and some laboratory and field tests. The analyses with this model were performed to verify the instability of blocks (block falls), and compared with actual cross sections of the tunnel. The results indicate that different failure criteria must be used for different discontinuity types (fractures and foliation), and revealed the importance of consistent estimated of geometrical parameters of discontinuity sets.
34

Design and construction of a new actuator for the LHC wire scanner / Conception d'un actionneur pour le nouveau Wire Scanner du LHC

Koujili, Mohamed 08 February 2013 (has links)
Le LHC met en collision deux faisceaux de protons avec une énergie de 7 Tevchacun, entrainant ainsi un taux de particules d'environ 109 Hz. Le taux departicules est déterminé la production d'une coupe transversale, une constancenaturelle, la luminosité et un paramétre dépendant de l'accélérateurcapable de décrire les faisceaux de particules. La luminosité dépend dunombre de particules dans chaque faisceau linéairement et des dimensionstransversales du faisceau inversement. Elle augmente avec la densité dufaisceau de particules et en conséquence, la probabilité d'interactions estaccrue. Pour optimiser les tailles des faisceaux transversaux, on utilisedes dispositifs de contrle de pro_le, qui permettent de mesurer les changementsde paramétres dépendants. A l'intérieur du LHC, trois di_érentstypes de dispositifs de contrle des pro_les sont installés, savoir le WireScanner (WS), le Synchroton Light Monitor et le Rest Gas Pro_le Monitor.Le WS est considéré comme étant le plus précis de ces trois dispositifsde contrle et sert d'appareil de calibrage pour les deux autres. Ils'agit d'un appareil électromécanique qui mesure l'état de densité du faisceautransversale de faon intermittente. Lorsque le cble traverse le faisceau,l'interaction particule-matiére génére une cascade de particules secondaires.Ces derniers sont interceptés par un scintillateur, lequel est attaché un photo-multiplieur, et ce a_n de mesurer l'intensité de la lumiéreainsi produite. L'amplitude du signal lumineux est proportionnelle la densité de la portion de faisceau interceptée. L'acquisition de la position du_l et celle de l'intensité du signal sont synchronisées avec la fréquence dela révolution de particules puis sont combinées pour construire le pro_lede densité du faisceau transversal. Le WS est installé et mis en marchedans tous les accélérateurs circulaires du CERN sur une base réguliére / The LHC collides two protons beams with an energy of 7 TeV each resultingin a aimed total particle rate of about 109 Hz. The particle rateis determined by the production cross section, a natural constant and theluminosity accelerator dependent parameter describing the particle beams.The luminosity depends on the number of particles in each beam linearlyand on the transverse dimensions of the particle beam inversely. It increaseswith the particle beam density and therefore the probability of interactions.To optimize the transverse beams sizes, pro_le monitors are used to measureparameter depending changes. Within the LHC, three di_erent typesof pro_le monitors are installed: Wire scanner (WS), Synchrotron lightmonitor and Rest Gas Pro_le Monitor. The WS monitor is considered tobe the most accurate of these monitors and serves as a calibration devicefor the two others. The WS is an electro-mechanical device which measuresthe transverse beam density pro_le in an intermittent way. As the wirepasses through the beam, the particle-matter interaction generates a cascadeof secondary particles. These are intercepted by a scintillator, which isattached to a photomultiplier in order to measure the intensity of the lightthereby produced. The light signal amplitude is proportional to the densityof the intercepted beam portion. The acquisitions of the wire position andthe intensity signal are synchronized with the particle revolution frequencyand are combined to construct the transverse beam density pro_le. TheWS is installed and operated in all circular accelerators of CERN on a dailybasis.
35

Automated registration of unorganised point clouds from terrestrial laser scanners

Bae, Kwang-Ho January 2006 (has links)
Laser scanners provide a three-dimensional sampled representation of the surfaces of objects. The spatial resolution of the data is much higher than that of conventional surveying methods. The data collected from different locations of a laser scanner must be transformed into a common coordinate system. If good a priori alignment is provided and the point clouds share a large overlapping region, existing registration methods, such as the Iterative Closest Point (ICP) or Chen and Medioni’s method, work well. In practical applications of laser scanners, partially overlapping and unorganised point clouds are provided without good initial alignment. In these cases, the existing registration methods are not appropriate since it becomes very difficult to find the correspondence of the point clouds. A registration method, the Geometric Primitive ICP with the RANSAC (GPICPR), using geometric primitives, neighbourhood search, the positional uncertainty of laser scanners, and an outlier removal procedure is proposed in this thesis. The change of geometric curvature and approximate normal vector of the surface formed by a point and its neighbourhood are used for selecting the possible correspondences of point clouds. In addition, an explicit expression of the position uncertainty of measurement by laser scanners is presented in this dissertation and this position uncertainty is utilised to estimate the precision and accuracy of the estimated relative transformation parameters between point clouds. The GP-ICPR was tested with both simulated data and datasets from close range and terrestrial laser scanners in terms of its precision, accuracy, and convergence region. It was shown that the GP-ICPR improved the precision of the estimated relative transformation parameters as much as a factor of 5. / In addition, the rotational convergence region of the GP-ICPR on the order of 10°, which is much larger than the ICP or its variants, provides a window of opportunity to utilise this automated registration method in practical applications such as terrestrial surveying and deformation monitoring.
36

Controlling the speed of film with high precision in a line scanner / Styrning av filmhastighet med hög precision i linjescanner

Rosenius, Magnus January 2003 (has links)
<p>In this master thesis, a system has been designed that is used to detect the perforation holes on a film in a line-scanning film scanner. The film scanner is used to scan regular film taken by high-speed cameras during tests of for example missile launches or vehicle crash tests. </p><p>The system consists of a PLD that detects the perforation holes on the film using a signal from a digital line-scanning CCD camera. A main issue has been to make the detection procedure robust and independent of the different types of films encountered in real life situations. </p><p>The result from the detection is used to generate control signals to the film speed regulation mechanism inside the film scanner that then regulates the velocity of the film. To make the detection and regulation more sensitive, a part-of-line precision has been developed to calculate where, inside a line, the actual hole is positioned. </p><p>The system has been programmed in VHDL, synthesized, implemented and fitted into a Xilinx Spartan (XCS10-3-PC84) Field Programmable Gate Array (FPGA). The implementation has been simulated but not in real hardware.</p>
37

Controlling the speed of film with high precision in a line scanner / Styrning av filmhastighet med hög precision i linjescanner

Rosenius, Magnus January 2003 (has links)
In this master thesis, a system has been designed that is used to detect the perforation holes on a film in a line-scanning film scanner. The film scanner is used to scan regular film taken by high-speed cameras during tests of for example missile launches or vehicle crash tests. The system consists of a PLD that detects the perforation holes on the film using a signal from a digital line-scanning CCD camera. A main issue has been to make the detection procedure robust and independent of the different types of films encountered in real life situations. The result from the detection is used to generate control signals to the film speed regulation mechanism inside the film scanner that then regulates the velocity of the film. To make the detection and regulation more sensitive, a part-of-line precision has been developed to calculate where, inside a line, the actual hole is positioned. The system has been programmed in VHDL, synthesized, implemented and fitted into a Xilinx Spartan (XCS10-3-PC84) Field Programmable Gate Array (FPGA). The implementation has been simulated but not in real hardware.
38

Avaliação Comparativa dos Scanners 3D Artec MHT e Cyberware WBX para aplicações em Antropometria e Ergonomia / Comparative assessment of Artec MHT and Cyberware WBX 3D Scanners for applications in Anthropometry and Ergonomic Studies

Denise Silva Batista 29 January 2014 (has links)
A partir das dimensões dos indivíduos pode-se definir dimensionamentos adequados para os produtos e postos de trabalho, proporcionando segurança e conforto aos usuários. Com o avanço da tecnologia de digitalização de imagens (escaneamento) 3D, é possível tirar algumas medidas de maneira mais rápida e com a redução da presença do entrevistado durante o processo. No entanto, faltam estudos que avaliem estas tecnologias no Brasil, sendo necessária a realização de uma comparação das tecnologias e das respectivas precisões para que seu uso em pesquisas. Com o objetivo de oferecer métodos comparativos para escolha dos marcadores e equipamentos a serem utilizados em uma pesquisa antropométrica tridimensional da população brasileira, no presente estudo estão comparadas duas tecnologias de escaneamento: o sistema a laser WBX da empresa norte americana Cyberware e o sistema MHT da empresa russa Artec Group. O método para avaliação da precisão dimensional dos dados advindos desses equipamentos de digitalização de imagens 3D teve cinco etapas: Estudo dos processos de escaneamento; Escaneamento dos marcadores de pontos anatômicos; Escaneamento utilizando um corpo de prova cilíndrico; Escaneamento de um manequim; Escaneamento de um voluntário que teve seus pontos anatômicos marcados para a retirada de medidas. Foi feita uma comparação entre as medidas retiradas manualmente, por meio de antropômetro e virtualmente, com o auxílio do software de modelagem tridimensional Rhinoceros. Em relação aos resultados obtidos na avaliação do manequim e do voluntário, concluiu-se que a magnitude do erro absoluto é semelhante para ambos os scanners, e permanece constante independentemente das dimensões sob análise. As principais diferenças são em relação às funcionalidades dos equipamentos. / Only from the dimensions of individuals it is possible to define appropriate sizing for products and workplaces, providing security and comfort to users. With the evolution of 3D digital imaging technology (3D scanning), it is possible to take some measurements faster and reduce the need of the interviewee during the process. However, there are few studies that evaluate these technologies in Brazil. It is necessary to compare these equipments in order to know their precision so they can be used in researches. In order to choose anatomical markers and equipments, this study compares two different equipments: Cyberware WBX laser scanner and Artec Group MHT white light scanner. The method for assessing the dimensional accuracy of the data obtained from those scanning 3D imaging equipment had five steps: Study of the scanning processes; Scanning using a cylindrical object; Scanning a mannequin; Scanning a volunteer who had his anatomical points marked for taking measurements. The comparison was made between the measurements taken manually with an anthropometer and virtually using the 3D modeling software Rhinoceros. Based on results obtained in the evaluation of the mannequin and volunteer, it was concluded that the absolute error is similar for both scanners and remains constant regardless of the size under consideration. The main differences are the features of each equipment.
39

Avaliação Comparativa dos Scanners 3D Artec MHT e Cyberware WBX para aplicações em Antropometria e Ergonomia / Comparative assessment of Artec MHT and Cyberware WBX 3D Scanners for applications in Anthropometry and Ergonomic Studies

Denise Silva Batista 29 January 2014 (has links)
A partir das dimensões dos indivíduos pode-se definir dimensionamentos adequados para os produtos e postos de trabalho, proporcionando segurança e conforto aos usuários. Com o avanço da tecnologia de digitalização de imagens (escaneamento) 3D, é possível tirar algumas medidas de maneira mais rápida e com a redução da presença do entrevistado durante o processo. No entanto, faltam estudos que avaliem estas tecnologias no Brasil, sendo necessária a realização de uma comparação das tecnologias e das respectivas precisões para que seu uso em pesquisas. Com o objetivo de oferecer métodos comparativos para escolha dos marcadores e equipamentos a serem utilizados em uma pesquisa antropométrica tridimensional da população brasileira, no presente estudo estão comparadas duas tecnologias de escaneamento: o sistema a laser WBX da empresa norte americana Cyberware e o sistema MHT da empresa russa Artec Group. O método para avaliação da precisão dimensional dos dados advindos desses equipamentos de digitalização de imagens 3D teve cinco etapas: Estudo dos processos de escaneamento; Escaneamento dos marcadores de pontos anatômicos; Escaneamento utilizando um corpo de prova cilíndrico; Escaneamento de um manequim; Escaneamento de um voluntário que teve seus pontos anatômicos marcados para a retirada de medidas. Foi feita uma comparação entre as medidas retiradas manualmente, por meio de antropômetro e virtualmente, com o auxílio do software de modelagem tridimensional Rhinoceros. Em relação aos resultados obtidos na avaliação do manequim e do voluntário, concluiu-se que a magnitude do erro absoluto é semelhante para ambos os scanners, e permanece constante independentemente das dimensões sob análise. As principais diferenças são em relação às funcionalidades dos equipamentos. / Only from the dimensions of individuals it is possible to define appropriate sizing for products and workplaces, providing security and comfort to users. With the evolution of 3D digital imaging technology (3D scanning), it is possible to take some measurements faster and reduce the need of the interviewee during the process. However, there are few studies that evaluate these technologies in Brazil. It is necessary to compare these equipments in order to know their precision so they can be used in researches. In order to choose anatomical markers and equipments, this study compares two different equipments: Cyberware WBX laser scanner and Artec Group MHT white light scanner. The method for assessing the dimensional accuracy of the data obtained from those scanning 3D imaging equipment had five steps: Study of the scanning processes; Scanning using a cylindrical object; Scanning a mannequin; Scanning a volunteer who had his anatomical points marked for taking measurements. The comparison was made between the measurements taken manually with an anthropometer and virtually using the 3D modeling software Rhinoceros. Based on results obtained in the evaluation of the mannequin and volunteer, it was concluded that the absolute error is similar for both scanners and remains constant regardless of the size under consideration. The main differences are the features of each equipment.
40

Dispositivo de varredura laser 3D terrestre e suas aplicações na engenharia, com ênfase em túneis. / Terrestrial laser scanner and its engineering applications, with emphasis in tunnels.

Rodrigo Gonçales 18 April 2007 (has links)
Novas tecnologias estão sendo desenvolvidas constantemente para coletar informações de superfícies ou de sólidos para diversas finalidades. Alguns métodos clássicos, como a Topografia e a Fotogrametria terrestre, com o passar dos anos, tiveram uma grande evolução. Na Fotogrametria terrestre todo o processo está sendo feito em meio digital. Na topografia, as estações totais automatizaram a medição de ângulos e distâncias. Essa evolução tecnológica fez com que os levantamentos se tornassem cada vez mais rápidos e precisos, aumentando a produtividade. O mais recente nessa evolução é o levantamento através do sistema de varredura a laser (Laser Scanner) 3D. São muitas as aplicações dessa tecnologia, dentre as quais pode-se citar: túneis, levantamento do como construído (as-built), mineração (principalmente subterrânea), arqueologia, levantamento de monumentos para restauração, refinarias e instalações industriais e outras, caracterizadas pela grande complexidade dos elementos envolvidos. A presente dissertação apresenta os conceitos envolvidos em todos os processos, desde a coleta de dados até o produto final. Desenvolve uma metodologia de uso que possa ser útil em diversas áreas, mostra uma aplicação completa na área de túneis, complementada por uma visão geral da área de plantas industriais e procura apresentar testes para quantificar a precisão que se obtém por essa tecnologia. / New technologies are constantly being developed in order to collect information of surfaces or solids for diverse purposes. Some classic methods such as topography and terrestrial photogrammetry have had a great evolution in the past. For example, all the processes of the terrestrial photogrammetry are made in digital way and the Total Stations have automated the measurements of angles and distances. This technical evolution made the surveying faster and accurate, increasing the productivity. However this evolution does not stop for there; in other words, the last technology in the area of topography is the surveying with the system known as Laser Scanner 3D. The Laser Scanner technology 3D has a lot of applications such as: tunnel, as-built, mining (mainly in the underground); archaeology (for restore monuments), refineries, industrial installations, etc., characterized by the great complexity of the involved elements. This work presents concepts involved in all the processes, since from data collection to the final product. It develops a methodology of use that can be applied in several areas, with emphasis in tunnels surveying area and presents some tests to quantization the accuracy.

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