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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.
41

Estimativa de dose nos pulmões para procedimentos de tomografia computadorizada / Lung dose estimates for computed tomography procedures

Martins, Juliana Cristina 07 December 2015 (has links)
Desde o seu desenvolvimento na década de 1970 a tomografia computadorizada (TC) passou por grandes mudanças tecnológicas, tornando-se uma importante ferramenta diagnóstica para a medicina. Consequentemente o papel da TC em diagnóstico por imagem expandiu-se rapidamente, principalmente devido a melhorias na qualidade da imagem e tempo de aquisição. A dose de radiação recebida por pacientes devido a tais procedimentos vem ganhando atenção, levando a comunidade científica e os fabricantes a trabalharem juntos em direção a determinação e otimização de doses. Nas últimas décadas muitas metodologias para dosimetria em pacientes têm sido propostas, baseadas especialmente em cálculos utilizando a técnica Monte Carlo ou medições experimentais com objetos simuladores e dosímetros. A possibilidade de medições in vivo também está sendo investigada. Atualmente as principais técnicas para a otimização da dose incluem redução e/ou modulação da corrente anódica. O presente trabalho propõe uma metodologia experimental para estimativa de doses absorvidas pelos pulmões devido a protocolos clínicos de TC, usando um objeto simulador antropomórfico adulto e dosímetros termoluminescentes de Fluoreto de Lítio (LiF). Sete protocolos clínicos diferentes foram selecionados, com base em sua relevância com respeito à otimização de dose e frequência na rotina clínica de dois hospitais de grande porte: Instituto de Radiologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (InRad) e Instituto do Câncer do Estado de São Paulo Octávio Frias de Oliveira (ICESP). Quatro protocolos de otimização de dose foram analisados: Auto mA, Auto + Smart mA, Baixa Dose (BD) e Ultra Baixa Dose (UBD). Os dois primeiros protocolos supracitados buscam redução de dose por meio de modulação da corrente anódica, enquanto os protocolos BD e UBD propõem a redução do valor da corrente anódica, mantendo-a constante. Os protocolos BD e UBD proporcionaram redução de dose de 72,7(8) % e 91(1) %, respectivamente; 16,8(1,3) % e 35,0(1,2) % de redução de dose foram obtidas com os protocolos Auto mA e Auto + Smart mA, respectivamente. As estimativas de dose para os protocolos analisados neste estudo são compatíveis com estudos similares publicados na literatura, demonstrando a eficiência da metodologia para o cálculo de doses absorvidas no pulmão. Sua aplicabilidade pode ser estendida a diferentes órgãos, diferentes protocolos de CT e diferentes tipos de objetos simuladores antropomórficos (pediátricos, por exemplo). Por fim, a comparação entre os valores de doses estimadas para os pulmões e valores de estimativas de doses dependentes do tamanho (Size Specific Dose Estimates SSDE) demonstrou dependência linear entre as duas grandezas. Resultados de estudos similares exibiram comportamentos similares para doses no reto, sugerindo que doses absorvidas pelos uma órgãos podem ser linearmente dependente dos valores de SSDE, com coeficientes lineares específicos para cada órgão. Uma investigação mais aprofundada sobre doses em órgãos é necessária para avaliar essa hipótese. / Since its development in 1970s the computer tomography (CT) technique have gone through major technological advances, becoming an important diagnostic tool in medicine. Consequently the role of CT in diagnostic imaging expanded rapidly, mainly due to improvements in image quality and speed of acquisition. The radiation dose imparted in patients undergoing CT scans has gained attention, leading the radiology community (radiologists, medical physicists and manufacturers) to work together towards dose estimation and optimization. New methodologies for patients dosimetry have been proposed in the past decades, based specially on Monte Carlo calculations or experimental measurements with phantoms and dosimeters. In vivo methodologies are also under investigation. Current dose optimization strategies include mainly tube current reduction and/or tube current modulation. The present work proposes a methodology to experimentally estimate lung absorbed doses due to clinical CT protocols using an adult anthropomorphic phantom and Lithium Fluorite (LiF) thermoluminescent dosimeters (TLD). Seven clinical protocols were selected for phantom irradiation, based on their relevance regarding dose optimization and frequency in two major hospitals routine: the Institute of Radiology from the Medical Faculty from the University of São Paulo (Instituto de Radiologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo InRad) and the Cancer Institute of the State of São Paulo Octávio Frias de Oliveira (Instituto do Câncer do Estado de São Paulo Octávio Frias de Oliveira ICESP). Fours thorax protocols for dose optimization were analyzed: Auto mA, Auto + Smart mA, Low Dose (LD) and Ultra Low Dose (ULD) thorax. The first two aforementioned protocols seek dose reduction by tube current modulation, while the last two propose a decrease on the constant tube current value. Values of 72.9(8) % and 91(1) % of lung dose reduction were achieved with LD and ULD protocols, respectively. Auto mA and Auto + Smart mA provided 16.8(1.3) % and 35.0(1.2) % of lung dose reduction, respectively. The results from all analyzed protocols are compatible with similar studies published in literature, demonstrating the efficiency of the methodology to lung absorbed dose estimation. Its applicability could be extended to different organs, different clinical CT protocols and pediatric phantoms. Moreover, comparison of lung absorbed doses and Size Specific Dose Estimates (SSDE) for the studied protocols exhibited a tendency of linear dependency. Results from similar studies demonstrate a similar behavior between rectal doses and SSDE, suggesting that organ absorbed doses and SSDE values may be linearly dependent, with organ-specific linear coefficients. Further investigation in organ doses is necessary to evaluate this assumption.
42

Análise tomográfica da formação óssea em defeito segmentar na mandíbula de coelhos preenchido com osso bovino liofilizado em bloco com colágeno / Tomographic analysis of bone formation in segmental defect in the mandible of rabbits filled with lyophilized bovine bone block with collagen

Madeira, Maria Fernanda Conceição 19 February 2014 (has links)
Atualmente a implantodontia tem evoluído muito na intenção de substituir perdas dentárias, porém infelizmente nem sempre isto é capaz, uma vez que após a perda dentária, na grande maioria das vezes, o osso remanescente também é reabsorvido, dificultando ou impossibilitando a instalação de implantes osseointegrados. Esse tipo de perda óssea nos maxilares ou as perdas ósseas resultantes de ressecções cirúrgicas, constituem uma preocupação importante na atualidade, uma vez que os cirurgiões dentistas pesquisam um substituto ósseo que devolva a forma e o contorno dos ossos da face e dos maxilares, e/ou que permita a instalação de implantes osseointegrados. Dentre os biomateriais, a utilização do osso bovino liofilizado tem se popularizado e vem ganhando mercado uma vez que reduz a morbidade do paciente evitando a retirada de enxertos autógenos e tem apresentado uma boa previsibilidade de resultados. No presente estudo, foram criados defeitos ósseos na base da mandíbula de coelhos, onde foram enxertados blocos de osso bovino liofilizado com colágeno suíno nos grupos experimentais e deixados vazios nos grupos controle. Os animais foram sacrificados nos tempos 0 (imediatamente após a cirurgia), 3 e 6 meses após o procedimento cirúrgico. As mandíbulas foram coletadas e analisadas através de tomografias computadorizadas de feixe cônico, em que se analisou a capacidade do enxerto de auxiliar no reparo ósseo de defeitos de tamanho crítico criados na mandíbula de coelhos, bem como sua capacidade de manter o contorno e forma do osso. Através da análise tomográfica das áreas enxertadas foi possível concluir que de acordo com a metodologia proposta o enxerto de osso bovino com 10% de colágeno suíno não foi capaz de auxiliar em 100% no reparo ósseo dos defeitos de tamanho crítico criados na mandíbula dos coelhos, mostrando uma camada fina de tecido mole entre o enxerto e o leito Tendo sido eficiente no preenchimento do espaço do defeito e manutenção do contorno ósseo. / Currently implant dentistry has evolved tremendously in the intention of replacing missing teeth, but unfortunately this is not always able, since after tooth loss, in most cases, also the remaining bone is reabsorbed, making it difficult or impossible to install dental implants. This type of bone loss in the jaw or bone loss resulting from surgical resections, are a major concern at present, since the dentists researching bone substitute that restores the shape and contour of the bones of the face and jaws, and/or enabling installation of dental implants. Among the biomaterials, the use of lyophilized bovine bone has become popular and has been gaining ground as it reduces the morbidity of the patient avoiding the removal of autogenous grafts has shown a good and predictable results. In the present study, bone defects were created on the basis of mandible in rabbits, which were grafted blocks lyophilized bovine bone with swines collagen in the experimental groups and control groups left empty. The animals were sacrificed at 0 (immediately after surgery), 3 and 6 months after surgery. The jaws were collected and analyzed using cone beam computed tomography, which analyzed the ability of the graft to aid in bone repair of critical-size defects created in the mandible of rabbits as well as its ability to maintain the contour and shape of the bone. Through the analysis of the tomographic grafted areas was concluded that according to the methodology proposed bovine bone graft with 10% swines collagen was not able to assist in 100% of the bone repair critical size defects created in rabbit jaw, showing a thin layer of soft tissue between the graft and the bed having been efficient space filling of the defect and maintain the bone contour.
43

A multi method approach towards the study and characterisation of simulated Enhanced Actinide Removal Plant particulates

Foster, Richard January 2017 (has links)
The introduction of the Enhanced Actinide Removal Plant (EARP) at Sellafield in 1994 was designed to decontaminate radioactive effluents produced during nuclear fuel reprocessing. Through the action of flocculation with iron, followed by filtration, the effluents are decontaminated before being discharging to sea. The plant has been in successful operation for the past 20 years, and has made a significant difference to the level of radioactivity of the waste. However, little is known about the formed flocs. Particular concern focuses around future changes to the effluent compositions to be processed through EARP. These future feeds will potentially contain significantly less iron, thus potentially impacting upon the flocculation process and the efficiency of the decontamination process. The effluents currently treated contain significant concentrations of iron, stemming from the Magnox fuel reprocessing plant, along with actinides, fission and corrosion products. The flocculation of these acidic radioactive ferric feeds results in the formation of solid iron hydroxide flocs with encapsulated radioactivity. The flocs are then filtered, encapsulated and stored. It is envisioned that by characterising the floc properties, both physically and chemically a greater understanding of EARP can be obtained, ultimately leading to a maintained process efficiency with alternative feed compositions. The effect of a reduction in iron concentration on the chemical and physical properties of the flocs has been studied. The presence of any iron in the mock effluents was found to beneficially increase the contaminant decontamination factors (DF). However, the efficacy of this increase varied between contaminates. The DFs of group I and II metals ranged from 7.10 to 1.19 while lead ranged from 4x105 to 1.60, dependent upon iron concentration. Transition metal and lanthanide contaminants were marginally affected. With the use of agar embedding, the 'liquid form' of the flocs has been retained for two and three dimensional observations. SEM/EDX analysis has allowed for the inspection and chemical characterisation of the flocs while 2D microscope image analysis has allowed for the study of floc size and shape. A range of diameters, 300 - 1500 micro metre were found. Three dimensional X-ray Computer Tomography (3D X-ray CT) conducted at the Manchester X-ray Imaging Facility (MXIF) has led to the physical characterisation and classification of the flocs. Further, by studying the 3D shape it has been possible to classify a floc as a granule, fibre, chip or blade according to the Zingg classification with the majority of formed flocs being classified as granules.
44

Practical approaches to reconstruction and analysis for 3D and dynamic 3D computed tomography

Coban, Sophia January 2017 (has links)
The problem of reconstructing an image from a set of tomographic data is not new, nor is it lacking attention. However there is still a distinct gap between the mathematicians and the experimental scientists working in the computed tomography (CT) imaging community. One of the aims in this thesis is to bridge this gap with mathematical reconstruction algorithms and analysis approaches applied to practical CT problems. The thesis begins with an extensive analysis for assessing the suitability of reconstruction algorithms for a given problem. The paper presented examines the idea of extracting physical information from a reconstructed sample and comparing against the known sample characteristics to determine the accuracy of a reconstructed volume. Various test cases are studied, which are relevant to both mathematicians and experimental scientists. These include the variance in quality of reconstructed volume as the dose is reduced or the implementation of the level set evolution method, used as part of a simultaneous reconstruction and segmentation technique. The work shows that the assessment of physical attributes results in more accurate conclusions. Furthermore, this approach allows for further analysis into interesting questions in CT. This theme is continued throughout the thesis. Recent results in compressive sensing (CS) gained attention in the CT community as they indicate the possibility of obtaining an accurate reconstruction of a sparse image from severely limited or reduced amount of measured data. Literature produced so far has not shown that CS directly guarantees a successful recovery in X-ray CT, and it is still unclear under which conditions a successful sparsity regularized reconstruction can be achieved. The work presented in the thesis aims to answer this question in a practical setting, and seeks to establish a direct connection between the success of sparsity regularization methods and the sparsity level of the image, which is similar to CS. Using this connection, one can determine the sufficient amount of measurements to collect from just the sparsity of an image. A link was found in a previous study using simulated data, and the work is repeated here with experimental data, where the sparsity level of the scanned object varies. The preliminary work presented here verifies the results from simulated data, showing an "almost-linear" relationship between the sparsity of the image and the sufficient amount of data for a successful sparsity regularized reconstruction. Several unexplained artefacts are noted in the literature as the `partial volume', the 'exponential edge gradient' or the 'penumbra' effect, with no clear explanation for their cause, or established techniques to remove them. The work presented in this paper shows that these artefacts are due to a non-linearity in the measured data, which comes from either the set up of the system, the scattering of rays or the dependency of linear attenuation on wavelength in the polychromatic case. However, even in monochromatic CT systems, the non-linearity effect can be detected. The paper shows that in some cases, the non-linearity effect is too large to ignore, and the reconstruction problem should be adapted to solve a non-linear problem. We derive this non-linear problem and solve it using a numerical optimization technique for both simulatedand real, gamma-ray data. When compared to reconstructions obtained using the standard linear model, the non-linear reconstructed images show clear improvements in that the non-linear effect is largely eliminated. The thesis is finished with a highlight article in the special issue of Solid Earth, named "Pore-scale tomography & imaging - applications, techniques and recommended practice". The paper presents a major technical advancement in a dynamic 3D CT data acquisition, where the latest hardware and optimal data acquisition plan are applied and as a result, ultra fast 3D volume acquisition was made possible. The experiment comprised of fast, free-falling water-saline drops traveling through a pack of rock grains with varying porosities. The imaging work was enhanced by the use of iterative methods and physical quantification analysis performed. The data acquisition and imaging work is the first in the field to capture a free falling drop and the imaging work clearly shows the fluid interaction with speed, gravity and more importantly, the inter- and intra-grain fluid transfers.
45

Electromechanical behaviour of three-dimensional (3D) woven composite plates

Saleh, Mohamed January 2016 (has links)
Three dimensional (3D) woven composites have attracted the interest of academia and industry thanks to their damage tolerance characteristics and automated fabric manufacturing. Although much research has been conducted to investigate their out-of-plane "through thickness" properties, still their in-plane properties are not fully understood and rely on extensive experimentation. The aim of this work is to study the electromechanical behaviour of three different fibre architectures of 3D woven composites "orthogonal (ORT), layer-to-layer (LTL) and angle interlock (AI)" loaded, in three different orientations "warp (0º), weft (90º) and off-axis (45º)", in quasi-static tension. Stress/strain response is captured as well as damage initiation and evolution up to final failure. The ORT architecture demonstrated a superior behaviour, in the off-axis direction, demonstrated by high strain to failure (~23%) and high translaminar energy absorption (~40 MJ/m3). The z-binder yarns in ORT suppress delamination and allow larger fibre rotation during the fibre "scissoring motion" that enables further strain to be sustained. In-situ electrical resistance variation is monitored using a four-probe technique to correlate the resistance variation with the level of damage induced while loading. Monotonic and cyclic "load/unload" tests are performed to investigate the effect of piezo-resistivity and residual plasticity on resistance variation while damage is captured by X-ray scanning during interrupted tests at predefined load levels. In addition, this study investigates the potential of using 3D woven composites in joint assemblies through open-hole tension and "single fastener double-lap joint" bearing strength tests. 3D woven composites in the off-axis orientation, especially ORT, demonstrate a potential for overcoming some of the major challenges for composite joints' applications which are the pseudo-ductility, stress redistribution away from the notch and notch insensitivity. Finally, the study proposes a micro-mechanics based damage model to simulate the response of 3D orthogonal woven composites loaded in tension. The proposed model differs from classical damage mechanics approaches in which the evolution law is obtained by retrofitting global experimental observations.
46

Análise tomográfica da formação óssea em defeito segmentar na mandíbula de coelho preenchido com bloco de osso bovino liofilizado / Tomographic analysis of bone formation in segmental defects created in the mandible of rabbits filled with lyophilized bovine bone block

Corrêa, Danilo da Silva 04 December 2013 (has links)
O recente aumento da procura por implantes osseointegráveis consequentemente levou ao aumento dos procedimentos de enxertos ósseos. Com isso, novos materiais têm surgido para estes procedimentos. Um destes materiais é o osso bovino integral (OBIN), cujo diferencial é o seu método de processamento, que visa manter suas características o mais próximas possível ao osso in natura. Por se tratar de um material novo, ainda existem poucos estudos avaliando seu desempenho, sendo a maioria deles estudos pré-clínicos testando sua biocompatibilidade. Portanto, o objetivo deste trabalho foi avaliar o desempenho do OBIN na região maxilofacial através de um modelo experimental em animais. Foram criados defeitos ósseos na base da mandíbula de coelhos, onde foram enxertados blocos de OBIN nos grupos experimentais e deixados vazios nos grupos controle. Os animais foram sacrificados nos tempos 0 (imediatamente após a cirurgia), 3 e 6 meses após o procedimento cirúrgico. As mandíbulas foram analisadas através de tomografias computadorizadas de feixe cônico, onde foi analisada a regeneração óssea qualitativamente e quantitativamente. Na análise qualitativa observou-se que aos três e seis meses, nos animais do grupo controle, não houve regeneração total, restando um defeito côncavo na base da mandíbula, confirmando que o defeito criado possuía tamanho crítico. No grupo experimental, no tempo 0, observou-se grande variação de densidade entre os enxertos e esta variação pareceu influenciar seu desempenho, havendo mais regeneração óssea nos menos densos. No tempo 3, todos os enxertos haviam integrados, com perda de densidade, sugerindo uma reabsorção parcial. Aos seis meses, a reabsorção e regeneração pareciam mais avançadas do que aos três meses. Na análise quantitativa houve diferença estatisticamente significante nos grupos controles entre os tempos 0 e os tempos 3 e 6. Nos grupos experimentais não houve diferença entre os tempos e na comparação entre os grupos controles e experimentais houve diferença estatisticamente significante entre todos os tempos. Os resultados observados sugerem que o OBIN é um material indicado para a realização de procedimentos de enxerto na região maxilofacial, com aparente reabsorção e substituição por osso regenerado, ideal para a reabilitação com implantes ósseo integráveis. / The recent increase in the demand for dental implants consequently led to increased bone grafting procedures. Therefore, new materials have emerged for these procedures. One of these materials is integral bovine bone (IBB) whose differential is its processing, which aims to maintain its characteristics as close as possible to the raw bone. Because it is a new material, there are only a few studies evaluating its performance, with the majority of them constituted of preclinical studies testing its biocompatibility. For this reason, the aim of this study was to evaluate the performance of the IBB at the maxillofacial region through an experimental model in animals. Bone defects were created on the basis of the mandible of rabbits, which were grafted with blocks of IBB in the experimental groups, while control groups were left empty. The animals were sacrificed at time 0 (immediately after surgery), 3 and 6 months after surgery. The jaws were analyzed using cone beam computed tomography, where bone regeneration was analyzed qualitatively and quantitatively. Qualitative analysis showed that at three and six months, in the control group, there was not full regeneration, leaving a concave defect in the base of the mandible, confirming that the defect created had critical size. In the experimental group, at time 0, there was wide variation in density between the grafts and this variation appeared to influence their performance, seeming to be more bone regeneration in less dense ones. At time 3, all grafts were integrated, and a density loss, suggesting a partial resorption of the graft, was also observed. At six months, resorption and regeneration seemed more advanced than at three months. The quantitative analysis did not showed statistically significant difference in controls between time 0 and times 3 e 6. In experimental groups there was no difference between times and comparison between control and experimental groups were statistically significant different between all time. The data suggest that the IBB is a material suitable for the realization of grafting procedures in the maxillofacial region, with apparent resorption and replacement by regenerated bone, ideal for rehabilitation with dental implants.
47

IMPROVING MIX DESIGN AND CONSTRUCTION OF PERMEABLE FRICTION COURSE MIXTURES

Alvarez Lugo, Allex Eduardo 2009 December 1900 (has links)
Permeable friction course (PFC), or new generation open-graded friction course (OGFC) mixtures, are hot mix asphalt (HMA) characterized by high total air voids (AV) content (minimum 18 %) as compared to the most commonly used dense-graded HMA. The high AV content confers to PFC mixtures both high permeability and noise reduction effectiveness. These characteristics and the high values of surface friction exhibited by PFC mixtures, as compared to dense-graded HMA, lead to improvements in safety and the environment, which make PFC one of the safest, cleanest, and quietest alternatives currently available for surface paving. The main objective of this study was improving the current PFC mix design method and construction practices in terms of compaction control. Corresponding results were integrated in an improved mix design method that is based on the guidelines of the current mix design method used by the Texas Department of Transportation. The improved mix design included modified computation of the inputs required to determine mixture density (or corresponding total AV content). These changes led to a proposed modification of the density specification for mix design from 78-82 % to 76-80 %. In addition, the water-accessible AV content was proposed as a surrogate of the total AV content for mix design and evaluation. The improved mix design method also includes verification of drainability, durability, and stone-on-stone contact. Computation of the expected value of permeability (E[k]) and measurement of the water flow value were recommended, respectively, for verification of drainability in the laboratory (using specimens compacted in the Superpave Gyratory Compactor (SGC)) and in the field. The Cantabro loss test conducted in both dry- and wet-conditions was suggested for assessing mixture durability. Improved criteria were proposed for verification of stone-on-stone contact based on the evaluation of the AV content in the coarse aggregate fraction of the mixture. In addition, comparison of the internal structure of field-and laboratory-compacted mixtures supported recommendation of a field-compaction control. Recommendations to reduce the horizontal heterogeneity of AV encountered in PFC specimens included using road cores with a minimum 152.4 mm diameter and coring SGC specimens from 152.4 to 101.6 mm in diameter
48

Simulations on flow and soot deposition in diesel particulate filters

Ohori, Shinya, Yamamoto, Kazuhiro 08 1900 (has links)
No description available.
49

Análise tomográfica Cone Beam e histológica do preparo do canal radicular com três sistemas rotatórios /

Moraes, Sergio Herrero. January 2010 (has links)
Orientador: Marcelo Gonçalves / Banca: Yara Teresinha Correa Silva Sousa / Banca: Ivaldo Gomes de Moraes / Banca: Fábio Luiz Camargo Villela Berbert / Banca: Mario Tanomaru Filho / Resumo: O presente estudo teve como objetivos as análise tomográfica e histológica do preparo do canal radicular com três sistemas rotatórios de NiTi: ProTaper (grupo 1), Mtwo (grupo 2) e K3 (grupo 3). Trinta e seis molares superiores foram radiografados pela técnica de tomografia cone beam (feixe cônico) antes e depois do preparo rotatório do canal mésio-vestibular. Os dentes foram pesados antes e depois do preparo para analisar a capacidade de corte dos instrumentos pela remoção de dentina. Aumento na área do canal, no alargamento do comprimento mésio-distal do canal, centralização e transporte do canal nos terços cervical, médio e apical foram analisadas nas tomografias computadorizadas transferidas para o software Canvas 11. Após o preparo dos canais radiculares as raízes foram descalcificadas, cortadas com 6 μm de espessura e coradas com hematoxilina-eosina, para exame das irregularidades das paredes de dentina do canal radicular e da presença de resíduos no canal. Para avaliar estatisticamente os resultados foi utilizado o método de variância (ANOVA).Os resultados revelaram que houve diferença estatisticamente significante entre os grupos. ProTaper removeu significativamente mais dentina do que Mtwo e K3 (p<0,05). Mtwo removeu mais do que o K3 (p<0,05). Protaper, Mtwo e K3 aumentaram significativamente a área do canal depois do preparo (p<0,05). A diferença foi significativa no terço cervical entre ProTaper e K3 (p<0,05), Mtwo e K3; terço médio entre ProTaper e K3 (p<,0,05), Mtwo e K3 (p<0,05); no terço apical entre ProTaper e K3 (p<0,05), Mtwo e K3.p<0,05). Protaper, Mtwo e K3 aumentaram significativamente o comprimento mésio-distal do canal. A diferença foi significativa entre ProTaper e K3 (p<0,05) , Mtwo e K3 nos terços cervical, médio e apical. Na avaliação da centralização do canal foi encontrada diferença significativa de desvio entre os grupos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The key goal of the present study was the histological and tomographic analysis of the root canal preparation with three NiTi rotatory systems: ProTaper (group 1), Mtwo (group 2) e K3 (group 3). Thirty six maxillary molar teeth were radiographed with the cone beam technique before and after the mesial-buccal root canal preparation. The teeth were weighted before and after preparation to analyse dentine removal capacity of the cutting instruments. Images from computed tomography were transferred to the software Canvas 11 to allow for analysis of the increase of the root canal area, the widening of the mesial-distal distance, and the root canal centring and transport in the cervical, mesial and apical thirds. After the root canal preparation, the roots were decalcified, cut to 6 μm thickness, from the cervical third to the apical one and dyed with hematoxylin-eosin. The roots were then analysed as to irregularities in the dentine wall of the root canal, and presence of any residue. The variance method (ANOVA) was used to statistically evaluate the results, which presented statistically relevant difference amongst the groups. ProTaper removed dentine more significantly than Mtwo and K3 (p<0,05). Mtwo removed more than K3 (p<0,05). All groups presented significant increase in the area of the root canal after preparation (p<0,05), mainly in the cervical third and the apical third. Cervical third the difference was ProTaper and K3 (p<0,05), Mtwo and K3, and in the apical third the difference was ProTaper and K3 (p<0,05), Mtwo and K3 (p<0,05). Protaper, Mtwo e K3 significantly increased the mesial-distal distance... (Complete abstract click electronic access below) / Doutor
50

INTELLIGENT NON-DESTRUCTIVE EVALUATION EXPERT SYSTEM FOR CARBON-CARBON COMPOSITES USING THERMOGRAPHY, ULTRASONICS, AND COMPUTED TOMOGRAPHY

Pan, Yicheng 01 May 2010 (has links)
This study develops a reliable intelligent non-destructive evaluation (NDE) expert system for carbon-carbon (C/C) composites based on thermography, ultrasonic, computed tomography and post processing by means of fuzzy expert system technique. Data features and NDE expert knowledge are seamlessly combined in the intelligent system to provide the best possible diagnosis of the potential defects and problems. As a result, this research help ensure C/C composites' integrity and reliability. Four types of orthotropic aerospace composite material groups, which include 2-D pitched based commercial aircraft disc brakes and asmolds, 3-D PAN based C/C composites, and carbon fiber reinforced plastic (CFRP) panels, were tested. Based on the performance testing results of thermography, air-coupled ultrasonic, and x-ray computed tomography, the testing data pattern corresponding to feature and quantification of defects were found. This NDE knowledge databases were transformed to fuzzy logic expert system models. The models succeefully classified and indicated the defect's size and distribution and the intelligent systems perform NDE better than human operators. These fuzzy expert systems not only eliminate human errors in defect detection but also function as NDE experts. In addition, fuzzy expert systems improve the defect detection by incorporating fuzzy expert rules to remove noises and to measure defect size more accurately. In the future, the expert system model could be continuously updated and modified to quantify the size and distribution of defects. The systems developed here can be adapted and applied to build an intelligent NDE expert system for better quality control as well as automatic defect and porosity detection in C/C composite production process.

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