Thesis (MS)-Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Stephen w. Sofie. Includes bibliographical references (leaves 88-90).

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph.D.)--McMaster University, 2004. / Advisor: Daniel T. Cassidy. Includes bibliographical references (p. 124-127).

La migration de particules fines dans un milieu poreux fait l’objet de nombreuses études dans différents domaines. Par exemple, la présence de particules fines dans les nappes phréatiques constitue des voies de transfert de polluants (e.g. bactéries, virus, métaux lourds) à travers les sols. Par ailleurs, les phénomènes complexes d’adsorption et de désorption des particules fines dans le milieu poreux sont la cause de multiples dégâts dans les systèmes hydrauliques (e.g. digues, puits pétroliers, filtres de traitements des eaux). Les particules fines forment des agrégats et se déposent autour des grains collecteurs affectant la perméabilité du milieu poreux. Ainsi, différents processus mécaniques et/ou physico-chimiques contrôlent le colmatage de la matrice poreuse. L’objectif de ce travail est d’étudier l’effet de l’hétérogénéité du milieu poreux (i.e. granulométrie, porosité) sur les phénomènes de transport et de dépôt des particules colloïdales en suspension. La finalité de ce travail est de donner un modèle prédictif de perméabilité afin de pouvoir estimer la pérennité du système. Dans ce but, une campagne d’essais expérimentaux est menée sur le suivi du transport et du dépôt des particules fines argileuses dans différents milieux naturels sableux. Ces travaux ont été réalisés dans des colonnes de laboratoire pour lesquels les conditions hydrauliques peuvent être contrôlées et où la concentration des fines à l’entrée de la colonne est imposée. Après injection des particules fines, le suivi de la matrice poreuse dans l’espace et dans le temps est réalisé en utilisant un banc gamma-densimétrique. L’évolution de la perméabilité caractérisant le colmatage du matériau est analysée par l’intermédiaire de la mesure de la chute de pression dans la colonne. Les expériences menées dans les différentes colonnes ont permis de mettre en évidence l’importance de la taille des grains et la porosité du milieu ainsi que la vitesse d’injection dans la formation du dépôt. D’après nos résultats, au début de l’essai le dépôt de particules se fait autour des collecteurs sur des sites de surface. Ensuite les ponts de liaison sont créés entre les grains collecteurs. Nous avons constaté que la première partie du dépôt est plus importante dans le cas de grains de taille importante. Afin d’interpréter les résultats de l’évolution de la perméabilité, nous avons utilisé le modèle de Kozeny-Carman, où nous avons introduit l’évolution du dépôt dans l’estimation de la surface spécifique du milieu. Ce modèle nous a permis également de prendre en compte l’hétérogénéité du milieu et l’évolution de chaque couche par l’intermédiaire des paramètres tels que la porosité et la tortuosité du milieu. Les observations microscopiques et les mesures de porosités sur les échantillons colmatés ont étayé les schémas de dépôt et de saturation des sites de rétention. Ce travail expérimental s’accompagne d’une modélisation par l’équation de convection dispersion avec un terme de puits simulé par une cinétique du second ordre. Elle met en évidence l’importance des particules déjà déposées ainsi que la porosité initiale du milieu et la vitesse d’écoulement. / The migration of fine particles in a porous medium is the subject of many studies in various fields. For example, the presence of fine particles in groundwater constitutes pathways of pollutants (e.g. bacteria, viruses, heavy metals) through the soil. Furthermore, the complex processes of adsorption and desorption of the fine particles in the porous medium are the cause of damage to multiple hydraulic systems (e.g. dams, oil wells, filters for water treatment). The fine particles form aggregates and settles around collecting grains affecting the permeability of the porous medium. Thus, various mechanical and / or physico -chemical processes control the clogging of the porous matrix. The objective of this work is to study the effect of heterogeneity of the porous medium (i.e. grain size, porosity) on the phenomena of transport and deposition of colloidal particles in suspension. The purpose of this work is to provide a predictive model of permeability in order to estimate the sustainability of the system. For this purpose, a campaign of experimental tests are conducted on the monitoring of transport and deposition of fine particulate clay in different natural environments sandy. These studies were conducted in laboratory columns for which the hydraulic conditions can be controlled and where the concentration of fines in the entry of the column is imposed. After injection of the fine particles, the monitoring of the porous matrix in space and time is carried out using a gamma - densimetric bench. Changes in permeability characterizing the clogging material is analyzed by means of the measurement of the pressure drop in the column. Experiences in the different columns have helped highlight the importance of grain size and porosity of the medium and the injection rate in the formation of the deposit. Our results at the beginning of the test particle deposition is around collectors on surface sites. Then the connecting bridges are created between the grains collecting. We found that the first portion of the deposit is larger in the case of large-sized grains. To interpret the results of the evolution of permeability, we used the Kozeny - Carman model, where we have introduced the evolution of the repository in estimating the surface area of the medium. This model also allowed us to take into account the heterogeneity of the environment and the evolution of each layer by using parameters such as porosity and tortuosity of the medium. Microscopic observations and measurements of porosity on samples clogged supported schemes and deposit saturation retention sites. This experimental work is accompanied by modeling the dispersion equation convection with a term well simulated by a second order kinetics. It highlights the importance of particles already deposited and the initial porosity of the medium and the flow velocity.

O objetivo deste estudo foi avaliar in vitro a capacidade seladora de alguns materiais odontológicos em retrobturações e para tanto, utilizou-se o MTA Ângelus® Branco, MBPc, CPM® e Pasta Lysanda®, através da análise da infiltração do Enterococcus faecalis. Noventa dentes humanos unirradiculares extraídos e instrumentados, tiveram seu ápice radicular cortado num plano perpendicular ao longo eixo onde foram preparadas cavidades retrógradas com 3mm de profundidade, para selamento com os materiais em teste já relacionados. Culturas específicas de Enterococcus faecalis foram preparadas e inoculadas nos condutos radiculares dos dentes previamente fixados em aparatos especiais que tinham do lado oposto um meio de cultura estéril e específico para a bactéria em questão, separados apenas pelas retrobturações dos grupos de materiais em teste. Diariamente, o meio estéril era checado para constatar sua possível turvação; caso ocorresse demonstrava a passagem bacteriana pela retrobturação. Os quatro grupos experimentais apresentaram ao menos um espécime com infiltração bacteriana logo nas primeiras 24 horas do teste, entretanto, o número de espécimes que apresentavam turvação foi diminuindo numericamente no decorrer do período experimental, que foi de 120 dias. Os cimentos MTA Ângelus® Branco, MBPc e CPM® mostraram capacidade seladora eficaz e também comportamento semelhante entre si, pois a turvação das poucas amostras ocorreu logo nos três primeiros dias. A pasta Lysanda® apresentou o maior número de amostras infiltradas (18), em maior período de tempo. / The objective of this study was to in vitro evaluate the sealing ability of some dental retrofilling material and for that, we used the White MTA Angelus®, MBPc, CPM® cements and Lysande® paste, by examining Enterococcus faecalis infiltration. Ninety human extracted single-rooted teeth were instrumented, had their apex cut perpendicular to the long axis where the retrograde cavities were prepared with 3 mm deep, sealed with the retrofilling materials used on the study. Specific cultures of Enterococcus faecalis were prepared and inoculated into the teeths root canals previously fixed in special apparatuses that had in their opposite side a sterile type of culture specific for the bacteria in question, separated only by the retrofilling materials under test. Daily, the sterile culture was checked to verify their possible turbidity; and when there was, it demonstrated the bacterials passage by the retrofilling material. All experimental groups showed at least one specimen with bacterial infiltration in the very first 24 hour testing, however, the number of specimens that showed turbidity had decreased numerically during the trial period of 120 days. White Angelus MTA®, CPM® and MBPC cements showed effective sealing capacity and also similar behavior among themselves, because the turbidity of the few samples occurred just in the first three days. Lysanda® paste presented the greatest number of samples infiltrated (18), in a greater period of time.

O meio corporativo, principalmente quando se trata de montadoras automotivas, é carente de conhecimento dos fatores que podem influenciar o processo de união entre pares tribológicos. Quando há um fim específico, como o tema deste trabalho: assegurar níveis de controle capazes de eliminar os riscos de uma vedação deficiente na câmara de combustão com custo mínimo, tal carência é ainda maior. O estudo da tribologia inerente à união entre cabeçote e bloco do motor diesel é fundamental para se compreender a que ponto é possível garantir a melhor estanqueidade possível, especialmente no que esteja relacionado ao processo rotineiro de aperto na linha de produção. Nesse sentido, a investigação proposta neste trabalho tem o claro objetivo de propor melhores condições técnicas de vedação ao caso particular da união entre cabeçote e bloco do motor de forma a eliminar / minimizar qualquer influência externa durante o aparafusamento do par supracitado. Adicionalmente, o conhecimento aqui exposto poderá ser difundido a muitas outras aplicações similares nas quais a fixação aparafusada está atrelada a funções que não apenas de fixação, podendo estas estarem inclusive em outros universos do produto, tais como motores, cabinas, eixos e transmissão. / The automobile corporate field has a lack of knowledge when the subject is related to tightening specific issues, especially regarding tribological studies. When there is a specific goal as this thesis theme: ensure all the control levels to eliminate sealing deficiency risks inside combustion chamber in a low investment cost, the needs are even higher. The tribological study between diesel engine block and its cylinder heads assembly is essential to comprehend what is necessary to have the best possible sealing, mostly when it\'s related to the routine on the assembly tightening process. Thinking on that, this work has the goal to propose the best condition on fastening technique that guarantees the sealing to any superficial topography roughness. Additionally, the acquired knowledge will be spread to other similar applications that are not unequally associated to bolted joints, but also in other vehicle universes, such as engines, cabs, axles and transmissions.

Na confecção de uma prótese ocular a íris artificial é a estrutura responsável pela sua dissimulação e estética. O propósito do presente trabalho foi avaliar a interação tinta e selamento utilizados na pintura da íris protética, verificando as falhas e insucessos na fase de prensagem da íris no corpo escleral. Para este estudo, foram confeccionados quatro tipos de corpos de prova sendo, dez calotas lisas utilizando cianoacrilato como selante, dez calotas lisas utilizando polímero de acetato de vinila como selante, dez calotas despolidas utilizando cianoacrilato como selante e dez calotas despolidas utilizando polímero de acetato de vinila como selante. Os corposde- prova foram submetidos a uma análise em uma lupa estereoscópica para verificação da presença de falhas, e um corpo de prova de cada grupo foi levado a um microscópio eletrônico de varredura para estudo morfológico. Nenhum corpo de prova apresentou alteração macroscopicamente, comprovando que o protocolo utilizado é eficaz podendo-se concluir que as falhas que ocorrem na confecção de próteses oculares são decorrentes de falhas em alguma fase do protocolo. Entretanto foram observados defeitos microscópicos nos grupos selados com cola de cianoacrilato. / In the manufacturing of ocular prosthesis, the artificial iris is the structure responsible for its dissimulation and esthetic. The aim of this study was to evaluate interaction between paint and sealing material used in prosthetic iris painting, attempting to failures on packing of iris shell in sclera resin. It were studied four different groups, ten smooth shells sealed with cianoacrylate, ten smooth shells sealed with vinyl acetate polymer, ten rough shells sealed with ciaoacrylate and ten rough shells sealed with cianoacrylate. Specimens were analyzed with a stereoscopic magnifying glass for detection of failures, and one specimen of each group was analyzed in a scanning electron microscope for morphological analysis. None of the specimens presented failures macroscopically, which demonstrates that the protocol employed in the present study is effective; it can be concluded that failures in manufacturing of ocular prosthesis are consequence of mistakes in one of the steps of the protocol. However, it was detected microscopic defects in specimens of the groups sealed with cianoacrylate adhesive.

The thermal effects of stitch welding the coolant conduits of a water-cooled flat plate solar collector to its absorber plate have been studied. A physical model of the heat transfer process from the plate to the fluid flowing inside the tube has been presented. The heat transfer coefficient based on the difference between bond temperature and fluid bulk mean temperature is an important factor in determining the collector efficiency factor F'. The upper and lower limits of the actual value of F' have been predicted by considering two extreme boundary conditions to which the fluid is subjected. For a thick and conductive tube wall, F' does not depend on spot size and spot spacing, and tends to an upper limit of 0.883. For a thin and non-conductive tube wall, the boundary condition comprises of a series of step changes in both the axial and circumferential directions of the heat flux. In this case, the heat transfer coefficient and hence F' approach their lower limits which are determined by the welding spot configuration. It was also found that F' increases with the following parameters: the spot angle; the percentage of tube length being welded; and the number of spots among which the welding is being distributed. Furthermore, the temperature distribution inside the fluid has also been computed for this case. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Please read the abstract in the section 00front of this document / Dissertation (MSc (Odont) (Community Dentistry))--University of Pretoria, 2007. / Community Dentistry / unrestricted

Magister Chirurgiae Dentium (MChD) / Background: Lack of appropriate bone thickness is a common clinical limitation for tooth replacement, often requiring narrow implants, which have shown better results when combined with Morse taper connections. Little is known about the sealing of the abutment-implant interface of narrow implants with Morse taper connections against oral bacteria. Aims: To investigate the in vitro ability of four commercially available narrow diameter implant (< 3.5 mm) with Morse-taper type implant abutment connections to impede bacterial penetration of their implant abutment interface (IAI). Material and Methods: Four commercially available narrow implant systems with Morse taper connections were subjected to Streptococcus sanguinis cultures in vitro and evaluated for contamination and microgaps through Scanning Electron Microscopy (SEM). Results: Bacterial penetration of the IAI was observed in all systems (n=12), ranging from 65 to >300 CFU. There were no statistically significant differences in the average log CFU between the four implant groups (χ2= 5.244, P=0.155). Microgaps ranging from 5-10 μm were observed in all assemblies when analyzed under SEM, with no statistically significant differences between the different systems (P>0.05). Conclusions: Despite the advantages of Morse taper systems, the evaluated narrow diameter implants using this type of abutment geometry failed to provide bacterial sealing. The observed microgaps can form reservoirs and potentially lead to inflammation in the peri-implant tissues and micromovements.