• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 141
  • 116
  • 43
  • 23
  • 18
  • 14
  • 10
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • Tagged with
  • 431
  • 114
  • 108
  • 95
  • 43
  • 42
  • 41
  • 40
  • 38
  • 28
  • 23
  • 22
  • 22
  • 21
  • 21
  • 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.
201

Remodelação da tábua óssea vestibular em implantes imediatos e em alvéolos pós-extração, utilizando cirurgias sem retalho, com ou sem biomaterial. Estudo comparativo em cães / Buccal bone plate remodeling after immediate implants and tooth extraction using the flapless approach with or without grafting material

Flavia Adelino Suaid 30 March 2012 (has links)
Recentes estudos em animais tem demonstrado pronunciada reabsorção da tábua óssea vestibular, após a colocação de implantes imediatos. A realização de cirurgias sem retalho para a colocação de implantes imediatos, e a utilização de enxertos ósseos nos gaps, representam alternativas viáveis para minimizar a reabsorção da tábua óssea vestibular e, dessa forma, otimizar a osseointegração. O presente trabalho se propôs a investigar a remodelação da tábua óssea vestibular, associada ou não ao enxerto ósseo sintético no gap entre a superfície do implante e a tábua vestibular, em cirurgias sem retalho. Neste contexto, implantes posicionados ao nível da tábua óssea vestibular, e 2.0 mm subcrestal foram comparados. Metodologicamente, os pré-molares mandibulares bilaterais de 8 cães foram extraídos sem retalho, 4 implantes foram instalados nos alvéolos de cada lado, e posicionados 2.0 mm da tábua óssea vestibular originando o gap. Os seguintes grupos foram testados: implantes equicrestal associado com o enxerto ósseo sintético (grupo teste equicrestal-GTEC), implantes equicrestal com coágulo sanguíneo (grupo controle-GCEC), implantes 2.0 mm subcrestal associado com o enxerto ósseo sintético (grupo teste subcrestal-GTSC) e implantes 2.0 mm subcrestal com coágulo sanguíneo (grupo controle-GCSC). Uma semana após as cirurgias, próteses metálicas foram instaladas. Marcadores ósseos foram administrados 1, 2, 4 e 12 semanas após as cirurgias para a análise da fluorescência. Doze semanas após a colocação dos implantes os animais foram sacrificados. Para a análise radiográfica, cortes vestíbulo-linguais foram realizados nos blocos com os implantes individualizados, e imagens digitais radiográficas foram obtidas. Para a análise histomorfométrica, lâminas foram preparadas através dos blocos seccionados. A análise radiográfica revelou que o grupo teste subcrestal apresentou maior perda da tábua óssea vestibular com diferença estatisticamente significante quando comparado com os grupos equicrestais (p<0,05). Não foi observada diferença significativa entre os grupos em relação à distância linear, e a presença ou ausência de neoformação tecidual no gap residual. A avaliação histomorfométrica demonstrou resultados significativos para o grupo teste equicrestal, sem perda da tábua óssea vestibular. Em relação aos outros parâmetros, o grupo controle subcrestal apresentou melhores resultados. A nova formação de tecido ósseo foi determinada pela quantificação da fluorescência dos marcadores em áreas adjacentes e distantes às superfícies dos implantes. As áreas adjacentes mostraram diferentes resultados entre os grupos, e pequeno um decréscimo na 12a semana, exceto para o grupo controle subcrestal, que apresentou um aumento. As áreas distantes mostraram um aumento contínuo na formação óssea. Os implantes equicrestais apresentaram insignificativa perda da tábua óssea vestibular. No entanto, os implantes subcrestais mostraram maior perda da tábua óssea vestibular, mesmo com a presença do enxerto ósseo. No entanto, a tábua vestibular manteve-se sempre coronal ao ombro do implante. Ambos os grupos equicrestais e subcrestais testes e controles foram beneficiados nas fases iniciais do processo de formação óssea como evidenciado pela análise de fluorescência. / Recent studies in animals have shown pronounced resorption of the buccal bone plate after immediate implantation. The use of flapless surgical procedures prior to the installation of immediate implants, as well as the use of synthetic bone graft in the gaps represent viable alternatives to minimize buccal bone resorption and to favor osseointegration. The aim of this study was to evaluate the healing of the buccal bone plate following immediate implantation using the flapless approach, and compare this process with sites in which a synthetic bone graft was or was not inserted into the gap between the implant and the buccal bone plate. Lower bicuspids from 8 dogs were bilaterally extracted without the use of flaps and 4 implants were installed in the alveoli in each side of the mandible and were positioned 2.0 mm from the buccal bone plate (gap). Four groups were devised: 2.0 mm subcrestal implants (3.3 x 8 mm) using bone grafts (SCTG), 2.0 mm subcrestal implants without bone grafts (SCCG), equicrestal implants (3.3 x 10 mm) with bone grafts (ECTG) and equicrestal implants without bone grafts (ECCG). One week following the surgical procedures, metallic prostheses were installed and within 12 weeks the dogs were sacrificed. The blocks containing the individual implants were turned sideways and radiographic imaging was obtained to analyze the remodeling of the buccal bone plate. In the analysis of the resulting distance between the implant shoulder and the bone crest (IS-BC), statistically significant differences were found in the SBTG when compared to the ECTG (p=0.02) and ECCG (p=0.03). For meanvalue comparison of the resulting linear distance between the implant surface and the buccal plate (GAP-L) no statistically significant difference was found between all the groups (p>0.05). The same result was observed in the parameter for presence or absence of tissue formation between the implant surface and buccal plate (GAPA). Equicrestally placed implants, in this methodology, presented little or no loss of the buccal bone. The subcrestally positioned implants presented loss of buccal bone, even though synthetic bone graft was used. The buccal bone, however, was always coronal to the implant shoulder.
202

Avaliação do pH, da liberação de íons cálcio e da adesividade de cimentos endodônticos contendo hidróxido de cálcio ou à base de MTA /

Bier, Carlos Alexandre Souza January 2009 (has links)
Orientador: Mário Tanomaru Filho / Banca: Luis Geraldo Vaz / Banca: Idomeo Bonetti Filho / Banca: Marco Antônio Hungaro Duarte / Banca: Marcus Vinicius Reis Só / Resumo: O objetivo desse estudo foi a avaliação da liberação de íons cálcio, do pH e da adesividade de alguns cimentos utilizados em Endodontia: Sealapex (G1), Sealer 26 (G2), Acroseal (G3), Epiphany (G4), MTA Branco (G5), Endo CPM Sealer (G6). Após a espatulação, os materiais foram inseridos em tubos de polietileno medindo 1,5 mm de diâmetro interno e 1 cm de comprimento com ambas extremidades abertas e imersos em frascos de vidro contendo 10 mL de água ultra pura. Nos períodos de 2, 6, 12, 24 e 48 horas, 7, 14 e 28 dias foram realizadas as análises, sendo o tubo contendo o cimento transferidos para novo frasco a cada período. O pH e a liberação de íons cálcio foram avaliados, respectivamente por meio de pH metro e espectrofotometria de absorção atômica. Para a avaliação da adesividade dos cimentos endodônticos às paredes dentinárias, os canais radiculares de 28 dentes humanos uniradiculados foram dilatados com brocas de Gates Glidden número 1, 2 e 3 e brocas largo número 1, 3 e 5. As raízes foram cortadas em máquina de corte para confecção de discos de 2 mm de espessura. Durante o preparo e depois da secção os espécimes foram irrigados com solução de hipoclorito de sódio a 2,5% e com EDTA a 17 % para a remoção da smear layer. Após a divisão aleatória nos grupos experimentais, os espécimes foram secos e preenchidos com os cimentos endodônticos, sendo mantidos em estufa a 37oC e 95% de umidade relativa do ar por 48 hs. Em seguida, cada conjunto dentina/cimento endodôntico foi submetido ao teste push-out em uma máquina de ensaio mecânico e a tensão necessária para a remoção do cimento medida em Mega Pascal (MPa). Após a coleta dos dados estes foram submetidos à análise estatística de Análise Variância e teste Tukey, com nível de 5% de significância. Os maiores valores de pH foram obtidos pelos G6, seguido por G2 e G5 após 2 horas (P<0,05)... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to evaluate in vitro the pH, calcium ion release and adhesiveness provide by 6 endodontic filling materials: Sealapex (G1), Sealer 26 (G2), Acroseal (G3), Epiphany (G4), White MTA (G5), Endo CPM Sealer (G6). After manipulation, the sealers (n=10) were placed in tubes with 10 mm-long and 1.5 mm in diameter and immediately immersed in a glass flask containing 10 ml of ultra pure water, which was hermetically sealed and stored at 37°C. At 2, 6, 12, 24 and 48 hr, and at 7, 14 and 28 days after mixing the tubes were moved to new flask with fresh solution and the water in which they were immersed was analyzed for pH with a pH meter and for released calcium by atomic absorption spectrophotometry. To evaluate the adhesiveness of the sealers to the root canal wall, 28 teeth were enlarged to size 5 Largo drill and cut in a cutting machine to create 2 mm thickness slices. During all this procedure the root canal was irrigated with sodium hypochlorite 2.5% and with EDTA 17% to remove the smear layer. The slices were randomly allocated to one of the groups, dried and filled with the sealers and kept in a controlled environment (37oC and 95% humidity) to allow the setting of the sealers. After that, the slice root/endodontic sealer was submitted to push out test in a mechanical testing machine and the results were expressed in Mega Pascal (MPa). The results obtained at each time were statistically evaluated. After 2 hours the uppermost pH was found in the G6, followed by G2 and G5 (P<0,05). From 6 h till 24 h the highest value were observed in groups G5, G6 and G2. After 48 hours, the pH of groups G5 and G6 were stood out. Finally from the 7th to 28th days of evaluation G2, G5 and G6 presented the utmost pH. With regards to calcium ions release in beginning periods the G6 was statistical significantly from the other groups until the 7th day (P<0.05)... (Complete abstract click electronic access below) / Doutor
203

Remodelação da tábua óssea vestibular em implantes imediatos e em alvéolos pós-extração, utilizando cirurgias sem retalho, com ou sem biomaterial. Estudo comparativo em cães / Buccal bone plate remodeling after immediate implants and tooth extraction using the flapless approach with or without grafting material

Suaid, Flavia Adelino 30 March 2012 (has links)
Recentes estudos em animais tem demonstrado pronunciada reabsorção da tábua óssea vestibular, após a colocação de implantes imediatos. A realização de cirurgias sem retalho para a colocação de implantes imediatos, e a utilização de enxertos ósseos nos gaps, representam alternativas viáveis para minimizar a reabsorção da tábua óssea vestibular e, dessa forma, otimizar a osseointegração. O presente trabalho se propôs a investigar a remodelação da tábua óssea vestibular, associada ou não ao enxerto ósseo sintético no gap entre a superfície do implante e a tábua vestibular, em cirurgias sem retalho. Neste contexto, implantes posicionados ao nível da tábua óssea vestibular, e 2.0 mm subcrestal foram comparados. Metodologicamente, os pré-molares mandibulares bilaterais de 8 cães foram extraídos sem retalho, 4 implantes foram instalados nos alvéolos de cada lado, e posicionados 2.0 mm da tábua óssea vestibular originando o gap. Os seguintes grupos foram testados: implantes equicrestal associado com o enxerto ósseo sintético (grupo teste equicrestal-GTEC), implantes equicrestal com coágulo sanguíneo (grupo controle-GCEC), implantes 2.0 mm subcrestal associado com o enxerto ósseo sintético (grupo teste subcrestal-GTSC) e implantes 2.0 mm subcrestal com coágulo sanguíneo (grupo controle-GCSC). Uma semana após as cirurgias, próteses metálicas foram instaladas. Marcadores ósseos foram administrados 1, 2, 4 e 12 semanas após as cirurgias para a análise da fluorescência. Doze semanas após a colocação dos implantes os animais foram sacrificados. Para a análise radiográfica, cortes vestíbulo-linguais foram realizados nos blocos com os implantes individualizados, e imagens digitais radiográficas foram obtidas. Para a análise histomorfométrica, lâminas foram preparadas através dos blocos seccionados. A análise radiográfica revelou que o grupo teste subcrestal apresentou maior perda da tábua óssea vestibular com diferença estatisticamente significante quando comparado com os grupos equicrestais (p<0,05). Não foi observada diferença significativa entre os grupos em relação à distância linear, e a presença ou ausência de neoformação tecidual no gap residual. A avaliação histomorfométrica demonstrou resultados significativos para o grupo teste equicrestal, sem perda da tábua óssea vestibular. Em relação aos outros parâmetros, o grupo controle subcrestal apresentou melhores resultados. A nova formação de tecido ósseo foi determinada pela quantificação da fluorescência dos marcadores em áreas adjacentes e distantes às superfícies dos implantes. As áreas adjacentes mostraram diferentes resultados entre os grupos, e pequeno um decréscimo na 12a semana, exceto para o grupo controle subcrestal, que apresentou um aumento. As áreas distantes mostraram um aumento contínuo na formação óssea. Os implantes equicrestais apresentaram insignificativa perda da tábua óssea vestibular. No entanto, os implantes subcrestais mostraram maior perda da tábua óssea vestibular, mesmo com a presença do enxerto ósseo. No entanto, a tábua vestibular manteve-se sempre coronal ao ombro do implante. Ambos os grupos equicrestais e subcrestais testes e controles foram beneficiados nas fases iniciais do processo de formação óssea como evidenciado pela análise de fluorescência. / Recent studies in animals have shown pronounced resorption of the buccal bone plate after immediate implantation. The use of flapless surgical procedures prior to the installation of immediate implants, as well as the use of synthetic bone graft in the gaps represent viable alternatives to minimize buccal bone resorption and to favor osseointegration. The aim of this study was to evaluate the healing of the buccal bone plate following immediate implantation using the flapless approach, and compare this process with sites in which a synthetic bone graft was or was not inserted into the gap between the implant and the buccal bone plate. Lower bicuspids from 8 dogs were bilaterally extracted without the use of flaps and 4 implants were installed in the alveoli in each side of the mandible and were positioned 2.0 mm from the buccal bone plate (gap). Four groups were devised: 2.0 mm subcrestal implants (3.3 x 8 mm) using bone grafts (SCTG), 2.0 mm subcrestal implants without bone grafts (SCCG), equicrestal implants (3.3 x 10 mm) with bone grafts (ECTG) and equicrestal implants without bone grafts (ECCG). One week following the surgical procedures, metallic prostheses were installed and within 12 weeks the dogs were sacrificed. The blocks containing the individual implants were turned sideways and radiographic imaging was obtained to analyze the remodeling of the buccal bone plate. In the analysis of the resulting distance between the implant shoulder and the bone crest (IS-BC), statistically significant differences were found in the SBTG when compared to the ECTG (p=0.02) and ECCG (p=0.03). For meanvalue comparison of the resulting linear distance between the implant surface and the buccal plate (GAP-L) no statistically significant difference was found between all the groups (p>0.05). The same result was observed in the parameter for presence or absence of tissue formation between the implant surface and buccal plate (GAPA). Equicrestally placed implants, in this methodology, presented little or no loss of the buccal bone. The subcrestally positioned implants presented loss of buccal bone, even though synthetic bone graft was used. The buccal bone, however, was always coronal to the implant shoulder.
204

Data-led methods for the analysis and interpretation of eddy covariance observations

Stauch, Vanessa Juliane January 2006 (has links)
The terrestrial biosphere impacts considerably on the global carbon cycle. In particular, ecosystems contribute to set off anthropogenic induced fossil fuel emissions and hence decelerate the rise of the atmospheric CO₂ concentration. However, the future net sink strength of an ecosystem will heavily depend on the response of the individual processes to a changing climate. Understanding the makeup of these processes and their interaction with the environment is, therefore, of major importance to develop long-term climate mitigation strategies. Mathematical models are used to predict the fate of carbon in the soil-plant-atmosphere system under changing environmental conditions. However, the underlying processes giving rise to the net carbon balance of an ecosystem are complex and not entirely understood at the canopy level. Therefore, carbon exchange models are characterised by considerable uncertainty rendering the model-based prediction into the future prone to error. Observations of the carbon exchange at the canopy scale can help learning about the dominant processes and hence contribute to reduce the uncertainty associated with model-based predictions. For this reason, a global network of measurement sites has been established that provides long-term observations of the CO₂ exchange between a canopy and the atmosphere along with micrometeorological conditions. These time series, however, suffer from observation uncertainty that, if not characterised, limits their use in ecosystem studies. The general objective of this work is to develop a modelling methodology that synthesises physical process understanding with the information content in canopy scale data as an attempt to overcome the limitations in both carbon exchange models and observations. Similar hybrid modelling approaches have been successfully applied for signal extraction out of noisy time series in environmental engineering. Here, simple process descriptions are used to identify relationships between the carbon exchange and environmental drivers from noisy data. The functional form of these relationships are not prescribed a priori but rather determined directly from the data, ensuring the model complexity to be commensurate with the observations. Therefore, this data-led analysis results in the identification of the processes dominating carbon exchange at the ecosystem scale as reflected in the data. The description of these processes may then lead to robust carbon exchange models that contribute to a faithful prediction of the ecosystem carbon balance. This work presents a number of studies that make use of the developed data-led modelling approach for the analysis and interpretation of net canopy CO₂ flux observations. Given the limited knowledge about the underlying real system, the evaluation of the derived models with synthetic canopy exchange data is introduced as a standard procedure prior to any real data employment. The derived data-led models prove successful in several different applications. First, the data-based nature of the presented methods makes them particularly useful for replacing missing data in the observed time series. The resulting interpolated CO₂ flux observation series can then be analysed with dynamic modelling techniques, or integrated to coarser temporal resolution series for further use e.g., in model evaluation exercises. However, the noise component in these observations interferes with deterministic flux integration in particular when long time periods are considered. Therefore, a method to characterise the uncertainties in the flux observations that uses a semi-parametric stochastic model is introduced in a second study. As a result, an (uncertain) estimate of the annual net carbon exchange of the observed ecosystem can be inferred directly from a statistically consistent integration of the noisy data. For the forest measurement sites analysed, the relative uncertainty for the annual sum did not exceed 11 percent highlighting the value of the data. Based on the same models, a disaggregation of the net CO₂ flux into carbon assimilation and respiration is presented in a third study that allows for the estimation of annual ecosystem carbon uptake and release. These two components can then be further analysed for their separate response to environmental conditions. Finally, a fourth study demonstrates how the results from data-led analyses can be turned into a simple parametric model that is able to predict the carbon exchange of forest ecosystems. Given the global network of measurements available the derived model can now be tested for generality and transferability to other biomes. In summary, this work particularly highlights the potential of the presented data-led methodologies to identify and describe dominant carbon exchange processes at the canopy level contributing to a better understanding of ecosystem functioning. / Der Kohlenstoffhaushalt der Erde wird maßgeblich von der bewachsenen Landoberfläche beeinflusst. Insbesondere tragen terrestrische Ökosysteme dazu bei, den Anstieg der atmosphärischen Kohlenstoffdioxid- (CO₂-) Konzentration durch anthropogen verursachte Emissionen fossiler Brennstoffe zu verlangsamen. Die Intensität der Netto-CO₂-Aufnahme wird allerdings in einem sich verändernden Klima davon abhängen, wie einzelne Prozesse auf Änderungen der sie beeinflussenden Umweltfaktoren reagieren. Fundierte Kenntnisse dieser Prozesse und das Verständnis ihrer Wechselwirkungen mit der Umwelt sind daher für eine erfolgreiche Klimaschutzpolitik von besonderer Bedeutung. Mit Hilfe von mathematischen Modellen können Vorhersagen über den Verbleib des Kohlenstoffs im System Boden-Pflanze-Atmosphäre unter zukünftigen Umweltbedingungen getroffen werden. Die verantwortlichen Prozesse und ihre Wechselwirkungen mit der Umwelt sind jedoch kompliziert und bis heute auf der Ökosystemskala nicht vollkommen verstanden. Entwickelte Modelle und deren Vorhersagen sind deshalb derzeit mit erheblichen Unsicherheiten behaftet. Messungen von CO₂-Austauschflüssen zwischen einem Ökosystem und der Atmosphäre können dabei helfen, Vorgänge besser verstehen zu lernen und die Unsicherheiten in CO₂-Austausch-Modellen zu reduzieren. Allerdings sind auch diese Beobachtungen, wie alle Umweltmessungen, von Unsicherheiten durchsetzt. Ziel dieser Arbeit ist es Methoden zu entwickeln, die physikalisches Prozessverständnis mit dem dennoch großen Informationsgehalt dieser Daten vorteilhaft zu vereinigen. Dabei soll vereinfachtes Prozessverständnis dazu genutzt werden, Zusammenhänge zwischen dem CO₂-Austausch und den umgebenden Umweltbedingungen aus den Beobachtungen abzuleiten. Das Besondere hierbei ist, dass diese Zusammenhänge direkt aus den Daten geschätzt werden, ohne vorher Annahmen über ihre funktionale Form zu machen. Die Daten als Ausgangspunkt der Modellentwicklung zu wählen gewährleistet, dass die Komplexität der Modelle dem Informationsgehalt der Messungen entspricht. Auf diese Weise lassen sich diejenigen Prozesse identifizieren, welche für den CO₂-Austausch mit der Atmosphäre dominant sind. Die gewonnenen Erkenntnisse können dann in robuste CO₂-Austauschmodelle für Ökosysteme überführt werden und zur Vorhersage von Kohlenstoffbilanzen beitragen. In der vorliegenden Arbeit werden diese entwickelten, datenbasierten Methoden zur Analyse und Interpretation von Netto-CO₂-Flüssen eingesetzt. Die erste Studie führt ein datenbasiertes Modell ein, das unvermeidliche Lücken in Messzeitreihen zuverlässig interpoliert. Dies ermöglicht erweiterte Anwendungen der Daten. In einer nächsten Studie wird ein Verfahren vorgestellt, mit dem die Unsicherheiten in den Beobachtungen charakterisiert werden können. Dies ist nötig, um jährliche Kohlenstoffbilanzen von Ökosystemen unter Berücksichtigung der Messungenauigkeiten direkt aus den Daten herzuleiten. Dabei liegt die Unsicherheit in den betrachteten Waldstandorten bei maximal 11% des Jahreswertes. In einer weiteren Studie werden dieselben Modelle genutzt, um die Netto-CO₂-Flüsse in Einzelkomponenten der CO₂-Assimilation und -Abgabe zu bestimmen. Diese Komponenten sowie die Nettobilanz sind zusammen mit ihren Ungenauigkeiten für Vorhersagen über das Kohlenstoffsenkenpotential eines Ökosystems von besonderer Bedeutung und können Abschätzungen des globalen Kohlenstoffhaushaltes maßgeblich unterstützen. Abschließend zeigt die letzte Studie ein Beispiel für die datenbasierte Entwicklung eines Modells, das die dominanten Prozesse des Kohlenstoffaustausches in Waldökosystemen beschreibt und erfolgreich vorhersagen kann. Dies unterstreicht insbesondere das Potenzial des vorgestellten Modellierungsansatzes, vorherrschende Prozesse zu identifizieren, zu beschreiben und damit zum verbesserten Verständnis des CO₂-Austauschs zwischen Ökosystem und Atmosphäre beizutragen.
205

3d Object Recognition From Range Images

Izciler, Fatih 01 September 2012 (has links) (PDF)
Recognizing generic objects by single or multi view range images is a contemporary popular problem in 3D object recognition area with developing technology of scanning devices such as laser range scanners. This problem is vital to current and future vision systems performing shape based matching and classification of the objects in an arbitrary scene. Despite improvements on scanners, there are still imperfections on range scans such as holes or unconnected parts on images. This studyobjects at proposing and comparing algorithms that match a range image to complete 3D models in a target database.The study started with a baseline algorithm which usesstatistical representation of 3D shapesbased on 4D geometricfeatures, namely SURFLET-Pair relations.The feature describes the geometrical relationof a surface-point pair and reflects local and the global characteristics of the object. With the desire of generating solution to the problem,another algorithmthat interpretsSURFLET-Pairslike in the baseline algorithm, in which histograms of the features are used,isconsidered. Moreover, two other methods are proposed by applying 2D space filing curves on range images and applying 4D space filling curves on histograms of SURFLET-Pairs. Wavelet transforms are used for filtering purposes in these algorithms. These methods are tried to be compact, robust, independent on a global coordinate frame and descriptive enough to be distinguish queries&rsquo / categories.Baseline and proposed algorithms are implemented on a database in which range scans of real objects with imperfections are queries while generic 3D objects from various different categories are target dataset.
206

Analyse d'une base de données pour la calibration d'un code de calcul

Feuillard, Vincent 21 May 2007 (has links) (PDF)
Cette recherche s'insère dans le contexte général de la calibration, en vue d'applications industrielles. Son objectif est d'évaluer la qualité d'une base de données, représentant la manière dont celle-ci occupe, au mieux des objectifs recherchés, son domaine de variation. Le travail réalisé ici fournit une synthèse des outils mathématiques et algorithmiques permettant de réaliser une telle opération. Nous proposons en outre des techniques de sélection ou d'importation de nouvelles observations permettant d'améliorer la qualité globale des bases de données. Les méthodes élaborées permettent entre autres d'identifier des défauts dans la structure des données. Leurs applications sont illustrées dans le cadre de l'évaluation de paramètres fonctionnels, dans un contexte d'estimation par fonctions orthogonales.
207

A Comparative Evaluation of Plastic Property Test Methods for Self-consolidating Concrete and Their Relationships with Hardened Properties

Shindman, Benjamin 25 August 2011 (has links)
Self-consolidating concrete (SCC) is a special type of concrete that flows under its own weight and spreads readily into place while remaining stable. Although SCC technology has been rapidly progressing over the last 20 years and continues to develop, the relationships between the fresh, hardened and durability properties of SCC are not well documented. The focus of this investigation is twofold. Firstly, the use of SCC necessitates reliable and accurate characterization of material properties. A variety of laboratory test methods are used to evaluate SCC’s plastic properties. Recognizing that various test methods evaluate the same plastic properties, there is a need to critically investigate the adequacy and sensitivity of each test. Secondly, outcomes from this project are expected to advance the fundamental understanding of the interplay between the fresh properties of SCC and their implications on hardened properties and durability performance.
208

A Comparative Evaluation of Plastic Property Test Methods for Self-consolidating Concrete and Their Relationships with Hardened Properties

Shindman, Benjamin 25 August 2011 (has links)
Self-consolidating concrete (SCC) is a special type of concrete that flows under its own weight and spreads readily into place while remaining stable. Although SCC technology has been rapidly progressing over the last 20 years and continues to develop, the relationships between the fresh, hardened and durability properties of SCC are not well documented. The focus of this investigation is twofold. Firstly, the use of SCC necessitates reliable and accurate characterization of material properties. A variety of laboratory test methods are used to evaluate SCC’s plastic properties. Recognizing that various test methods evaluate the same plastic properties, there is a need to critically investigate the adequacy and sensitivity of each test. Secondly, outcomes from this project are expected to advance the fundamental understanding of the interplay between the fresh properties of SCC and their implications on hardened properties and durability performance.
209

Multi-layer designs and composite gaussian process models with engineering applications

Ba, Shan 21 May 2012 (has links)
This thesis consists of three chapters, covering topics in both the design and modeling aspects of computer experiments as well as their engineering applications. The first chapter systematically develops a new class of space-filling designs for computer experiments by splitting two-level factorial designs into multiple layers. The new design is easy to generate, and our numerical study shows that it can have better space-filling properties than the optimal Latin hypercube design. The second chapter proposes a novel modeling approach for approximating computationally expensive functions that are not second-order stationary. The new model is a composite of two Gaussian processes, where the first one captures the smooth global trend and the second one models local details. The new predictor also incorporates a flexible variance model, which makes it more capable of approximating surfaces with varying volatility. The third chapter is devoted to a two-stage sequential strategy which integrates analytical models with finite element simulations for a micromachining process.
210

Analysis and Design for the Photonic-Crystal-Fiber Components

Chiang, Jung-Sheng 19 January 2006 (has links)
The dissertation focuses on the analysis and design for the new fiber-optic passive components based on the photonic-crystal-fiber (PCF). The vector boundary element method (VBEM) and the finite-difference time-domain (FDTD) method are employed to the propagation characteristics of PCF components. A novel octagonal microstructured fiber (OMF) with eight air-holes in the first ring has been proposed. The OMF has significantly wider wavelength range for single-mode operation, more circular-like field distribution, and less confinement loss. In addition, a novel compact polarization beam splitter (PBS) based on the twin-elliptical-core PCF (TEC-PCF) has also been proposed. It behaves with high extinction ration and broad bandwidth with significantly short splitter length. The design concept and the coupling mechanism are presented in this dissertation based on the normal-mode coupling theory and VBEM.

Page generated in 0.5399 seconds