Results of seismic surveys are routinely used to assess the presence of methane hydrate in deep ocean sediments. Accurate estimates of hydrate distribution and volume within the sediment are required to assess the potential of gas hydrate as an energy resource, driver for climate change or as a geotechnical hazard. However, seismic velocity may be affected not only by the quantity and morphology of the hydrate, but also by the properties of the host sediment, for example its particle size distribution and grain shape. This paper reports the results of experiments conducted to determine dynamic geophysical properties such as compressional wave velocity (Vp), shear wave velocity (Vs) and their respective attenuation measurements (Qp -1 and Qs -1) of specimens with varying amounts of disseminated methane hydrate within materials with different particle shapes and sizes. The results show that the impact of disseminated hydrate is affected both by mean particle size and by particle sphericity, with the surface area of the sediment grains influencing the spread of hydrate throughout a material and therefore it’s bonding capabilities. The sediments with 10% hydrate content show the highest surface areas correspond to the least increase in seismic velocity while sediments with low surface areas gives the most.

Pleistocene New Jersey shelf sedimentology is strongly influenced by glacially driven sea level changes. A combination of regressive shoreline processes, subaerial exposure, fluvial downcutting, and deposition and reworking during transgression has influenced the NJ shelf sediment composition. Sediment provenance and transport history may be determined on a shelf environment through analysis of grain size distribution, heavy mineral content, magnetic mineral concentrations, and isotopic dating methods. A combination of surface grab and stratigraphic samples were analyzed within the study area. Relatively high percentages of heavy minerals were found in the 2 phi and 3 phi size fractions and hornblende grains provided K-Ar age values indicating two groups of sediment sources. The first source is Grenville with apparent ages above 900 Ma deposited during marine OIS 1. The second source is a mixed assemblage of Grenvillian and Paleozoic sources deposited during marine OIS 3, with apparent ages of approximately 850 ± 20 Ma.

This work concerns the microstructure of CSS-grown CdTe layers used for CdTe/CdS solar cells. Particular attention is given to how the development of microstructure on annealing with CdCl(_2) may correlate with increases in efficiency. By annealing pressed pellets of bulk CdTe powder, it is shown that microstructural change does occur on heating the material, enhanced by the inclusion of CdCl(_2) flux. However, the temperature required to cause significant effects is demonstrated to be higher than that at which heavy oxidation takes place. The dynamics of this oxidation are also examined. To investigate microstructural evolution in thin-films of CdTe, bi-layers of CdTe and CdS are examined by bevelling, thus revealing the microstructure to within ~1 µm of the interface. This allows optical microscopy and subsequent image analysis of grain structure. The work shows that the grain- size, which is well described by the Rayleigh distribution, varies linearly throughout the layer, but is invariant under CdCl(_2) treatment. Electrical measurements on these bi-layers, however, showed increased efficiency, as is widely reported. This demonstrates that the efficiency of these devices is not dictated by the bulk microstructure. Further, the region within 1 µm of the interface, of similar bi-layers to above, is examined by plan-view TEM. This reveals five-fold grain-growth on CdCl(_2) treatment. Moreover, these grains show a considerably smaller grain size than expected from extrapolating the linear trend in the bulk. These observations are explained in terms of the pinning of the CdTe grain size to the underlying CdS, and the small grain size this causes. A simple model was proposed for a link between the grain-growth to the efficiency improvement. The study also examines the behaviour of defects within grains upon CdCl(_2) treatment provided the first direct evidence of recovery on CdCl(_2) treatment in this system. Finally, a computer model is presented to describe the evolution of microstructure during growth. This is shown to be capable of reproducing the observed variation in grain size, but its strict physical accuracy is questioned.

This study is part of the Diavik Waste-Rock Pile Project taking place at the Diavik Diamond Mine in the Northwest Territories, Canada. The project involves the construction of three 15m-scale low sulfide test waste-rock piles and monitoring of fluid flow, geochemical reactions, heat and gas transport within the waste-rock piles and characterization of the physical properties of the waste-rock piles. The focus of this thesis is characterizing grain-size distribution of the waste-rock and quantifying gas transport in the test waste-rock piles. Grain size of waste rock ranges from millimeters to meters. Sieve analysis typically only provides information of grain size <0.1 m at a single location. A computer program was developed using digital image-processing techniques to obtain a spatial grain-size distribution from photographs of tip faces of the test waste-rock piles acquired in the field. The program characterizes grain size >0.1 m and employs a region-growing algorithm for segmentation of waste-rock grains with pre- and post-processing techniques to improve the accuracy of segmentation. The program was applied to photographs of six different tip faces of the test waste-rock piles. For grain size <0.1 m, data from sieve analyses were attached to the grain-size curves generated from image grain-size analyses to obtain a full spectrum grain-size analyses ranging from boulders to fines. The results show that fine fractions are retained at the top of the tip faces and grain size increases non-linearly from top to bottom of a waste-rock pile. Calculations show that although the greatest mass is associated with the medium and coarse fractions, the greatest surface area is associated with the fine fractions. The results are consistent with field observation that the initial solute concentrations are greatest at the top of the pile and saturated hydraulic conductivity are lower at the top of the pile than in the pile interior. Statistical moments show that the test waste-rock piles have mean grain size of granules and are very poorly sorted, coarse skewed and leptokurtic. Permeability is calculated using empirical formulae and good agreement is obtained between calculated values and field measurements. The heterogeneity of grain size obtained from this study can provide a basis for future modeling efforts. Gas transport analysis focused on 1) substantiating the relationship between wind flow external to the waste-rock pile and gas pressures within the pile, 2) determining the gas flow regime in the pile, and 3) quantifying the temporal variation in wind speed and direction and determining the relevant time scales. Differential gas pressures were measured in 2008 at 49 locations within one of the three test waste-rock piles and 14 locations on the surface of the pile at one-minute intervals. Wind speed and direction were measured at 10-min intervals. Correlations between wind vectors and pressure measurements show that the wind influences pressure fluctuations in the test pile. The strength of the correlation is roughly inversely proportional to the distance between measurement ports and the atmospheric boundary. The linear relationship between internal pressure measurements and surface pressure measurements demonstrate that gas flow is Darcian within the test waste-rock pile. Spectral analysis of wind data and a one-dimensional analytical solution to the flow equations show that the persistence of wind in a certain direction has most pronounced effects on transient gas flow within the pile. The penetration depth of wind-induced gas pressure wave is a function of the periodicity of the wind and permeability of the waste-rock pile.

Thesis (M. En.)--Miami University, Institute of Environmental Sciences, 2006. / Title from first page of PDF document. Includes bibliographical references (p. 33-35).

Στην παρούσα εργασία μελετήθηκαν η κοκκομετρία των επιφανειακών ιζημάτων του Αμβρακικού κόλπου. Τα ιζήματα που καθιζάνουν στον πυθμένα μιας θάλασσας καθώς και ο ρυθμός με τον οποίον αυτά αποτίθονται είναι εξαιρετικοί δείκτες του τρόπου λειτουργίας του υδάτινου αυτού σώματος. Επίσης μέσω των ιζημάτων γίνονται αντιληπτές οι σχέσεις αλληλοεξάρτησης του υδάτινου σώματος με τη στεριά και πως οι διεργασίες που λαμβάνουν χώρα στην στεριά επηρεάζουν τη ζωή στη θάλασσα. / The present study have examined the grain size of the surficial sediments of Amvrakikos gulf. The sediments that subside at the bottom of the sea and the speed of these deposits are excellent ways to find out the mechanisms and the way they faction. In addition, we can examine the correlation between sediments and water column. The processes that take place on land might affect the sea’s living life. The aim of the present study is to sustain laboratory results in order to establish the relationships between grain size of surfacial sediments in Amvrakikos gulf, using statistical parameters.

abstract: The infrastructure is built in Unsaturated Soils. However, the geotechnical practitioners insist in designing the structures based on Saturated Soil Mechanics. The design of structures based on unsaturated soil mechanics is desirable because it reduces cost and it is by far a more sustainable approach. The research community has identified the Soil-Water Characteristic Curve as the most important soil property when dealing with unsaturated conditions. This soil property is unpopular among practitioners because the laboratory testing takes an appreciable amount of time. Several authors have attempted predicting the Soil-Water Characteristic Curve; however, most of the published predictions are based on a very limited soil database. The National Resources Conservation Service has a vast database of engineering soil properties with more than 36,000 soils, which includes water content measurements at different levels of suctions. This database was used in this study to validate two existing models that based the Soil-Water Characteristic Curve prediction on statistical analysis. It was found that although the predictions are acceptable for some ranges of suctions; they did not performed that well for others. It was found that the first model validated was accurate for fine-grained soils, while the second model was best for granular soils. For these reasons, two models to estimate the Soil-Water Characteristic Curve are proposed. The first model estimates the fitting parameters of the Fredlund and Xing (1994) function separately and then, the predicted parameters are fitted to the Fredlund and Xing function for an overall estimate of the degree of saturation. Results show an overall improvement on the predicted values when compared to existing models. The second model is based on the relationship between the Soil-Water Characteristic Curve and the Pore-Size Distribution of the soils. The process allows for the prediction of the entire Soil-Water Characteristic Curve function and proved to be a better approximation than that used in the first attempt. Both models constitute important tools in the implementation of unsaturated soil mechanics into engineering practice due to the link of the prediction with simple and well known engineering soil properties. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2011

Submitted by Socorro Pontes (socorrop@ufersa.edu.br) on 2017-04-18T13:28:19Z No. of bitstreams: 1 AllyssandraMLRM_TESE.pdf: 4987928 bytes, checksum: 19600c5eb7712a422e9f2e1fea4261c4 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-26T12:14:23Z (GMT) No. of bitstreams: 1 AllyssandraMLRM_TESE.pdf: 4987928 bytes, checksum: 19600c5eb7712a422e9f2e1fea4261c4 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-26T12:14:36Z (GMT) No. of bitstreams: 1 AllyssandraMLRM_TESE.pdf: 4987928 bytes, checksum: 19600c5eb7712a422e9f2e1fea4261c4 (MD5) / Made available in DSpace on 2017-04-26T12:16:52Z (GMT). No. of bitstreams: 1 AllyssandraMLRM_TESE.pdf: 4987928 bytes, checksum: 19600c5eb7712a422e9f2e1fea4261c4 (MD5) Previous issue date: 2015-02-26 / The objective was to analyze aspects of population ecology (age structure, distribution, density, spatial and temporal evaluation) of bivalve Anomalocardia brasiliana in an estuary beaches of Rio Grande do Norte semiarid region. Samples were collected for 37 months (April / 09 to April / 12), which transects (placed in each collection) 300 m long in the region of intertidal established every 400 meters between them, were put in order extracting the shellfish and sediment for size analysis. Still were measured temperature and salinity of the water. We used the nonparametric Kruskal-Wallis and Wilcoxon rank sum subsequent test to check the differences in the density of A. brasiliana with respect to distance from the estuary (0, 400, 800, 1200 and 1600m). During the study (April / 09 to April / 12), the growth curves of A. brasiliana suggest the presence of nine well-defined cohorts, indicating a continuous play with recruitment peaks, growth parameters were estimated as L∞ = 30 45 mm and k = 1.00 y-1 and longevity of 4.88 years. The average values of density obtained ranged 26-322 plants / m2. The highest values were found in the average density of the shellfish from November / 2010 to July / 2011. In July / 11, the average density of individuals presented the highest value (322 ind / m2) that after a decrease in the months of August and September / 2011, these values tended to oscillate in October / November and December / 2011. It was verified at baseline, a lower density of A. brasiliana, especially in the months of April, May / 11, which was increasing during the study. Mean values were observed density in the months of June and July / 11, October and December / 11, which was probably related to the breeding period and recruitment of the species. It was also identified that, in the distance from 800 to 1600m estuary there was an increase in the density of individuals, during most months of collection. In the distance 0m estuary in almost every month, the occurrence of A. brasiliana was reduced or individuals were noted. The research showed that the prevalence of A. brasiliana, is probably related to the higher percentage of texture classes sand and very 25 fine, silt and clay sediment in which there is a preference for the species. The results showed that despite being which results in increased density of A. brasiliana, this still presents lower values than those found before the rains in 2008 and 2009, a period when the rain rate was very high, showing that the disorder affected the density of the species / O objetivo do trabalho foi analisar aspectos da ecologia populacional (estrutura etária, distribuição, densidade, avaliação espacial e temporal) do bivalve Anomalocardia brasiliana em praias de uma região estuarina do semiárido do Rio Grande do Norte. As coletas foram realizadas durante 37 meses (abril/09 a abril/12), onde transectos (colocados em cada coleta) de 300 m de comprimento na região de entre marés, estabelecidos a cada 400 m de distância entre eles, foram colocados a fim de extrair os moluscos e o sedimento para as análises granulométricas. Ainda foram medidas temperatura e salinidade da água. Aplicou-se o teste não-paramétrico de Kruskal-Wallis, e a posteriori Wilcoxon rank sum test para verificar as diferenças na densidade de A. brasiliana com relação à distância do estuário (0, 400, 800, 1200 e 1600m). Durante o estudo (abril/09 a abril/12), as curvas de crescimento de A. brasiliana sugerem a presença de nove coortes bem definidas, indicando uma reprodução contínua com picos de recrutamento, os parâmetros de crescimento foram estimados em L∞ = 30,45 mm e k = 1,00 ano-1 e longevidade de 4,88 anos. Os valores médios de densidade obtidos variaram de 26 a 322 indivíduos/m2. Foram constatados os maiores valores na densidade média do molusco no período de novembro/2010 a julho/2011. No mês de julho/11, a densidade média de indivíduos apresentou o maior valor (322 ind/m2) que após um decréscimo nos meses de agosto e setembro/2011, esses valores tenderam a oscilar nos meses de outubro/novembro e dezembro/2011. Pôde-se verificar no início da pesquisa, uma menor densidade de A. brasiliana, especialmente nos meses de abril, maio/11, e que foi aumentando no decorrer do estudo. Foram observados valores médios da densidade nos meses de junho e julho/11, outubro e dezembro/11, o que provavelmente esteve associado ao período de reprodução e recrutamento da espécie. Foi identificado ainda que, na distância de 800 a 1600m do estuário houve um aumento na densidade de indivíduos, durante a maioria dos meses de coleta. Na distância 0m do estuário em quase todos os meses, a ocorrência de A. brasiliana foi reduzida, ou não foram constatados indivíduos. A pesquisa evidenciou que a maior ocorrência de A. brasiliana, provavelmente está relacionada com a maior 24 porcentagem das classes texturais areia fina e muito fina, silte e argila, sedimento pelo qual há preferência pela espécie. Os resultados mostraram que apesar de estar ocorrendo um aumento da densidade de A. brasiliana, esta ainda apresenta valores inferiores aos encontrados antes das chuvas nos anos de 2008 e 2009, período em que o índice de pluviosidade foi muito alto, mostrando que esse distúrbio afetou a densidade da espécie / 2017-04-17

A fusão zonal compreende uma família de métodos para controle e distribuição de impurezas na qual uma pequena zona fundida é deslocada lentamente ao longo de um material sólido, redistribuindo o soluto. Ela é utilizada na purificação de materiais, num processo denominado refino zonal, mas também pode ser usada na distribuição homogênea ou descontínua de impurezas e no crescimento de cristais. A fusão zonal aplicada ao crescimento de grãos, visando a obtenção de materiais mono ou policristalinos com grãos grosseiros é denominada recristalização por fusão zonal (ZMR) e seu uso principal é na preparação de materiais para fabricação de dispositivos eletrônicos e fotovoltaicos, especialmente em silício. Na última década, o progresso na tecnologia ZMR foi feito principalmente em três campos: desenvolvimento de equipamento, controle de processo e modelagem numérica, mas somente algumas pesquisas abordam a fusão zonal a baixas temperaturas e restringem a aplicação do método a outros materiais semicondutores como os elementos do grupo III, IV ou V. Deste modo, o presente trabalho tem como objetivo verificar a influência da velocidade de varredura, da largura da zona fundida e do número de passadas no processo de fusão zonal de materiais de baixo ponto de fusão, em relação à obtenção de materiais policristalinos com grãos grosseiros. Para tanto, construiu-se um equipamento de fusão zonal horizontal e barras de alumínio puro (P0610) foram submetidas ao processo, variando os parâmetros acima referidos. A macroestrutura das amostras foi analisada e os resultados obtidos do número de grãos/área foram interpretados, verificando a influência dos parâmetros físicos anteriormente citados, do gradiente térmico e do super-resfriamento constitucional. Verificou-se que a redução na velocidade de varredura e na largura da zona fundida, de modo geral, mostrou-se eficiente em relação à diminuição do número de grãos por área. Os resultados obtidos indicam que a fusão zonal foi efetiva na obtenção de alumínio policristalino com grãos grosseiros e colaboram para melhorar a compreensão do processo. / The zone melting comprises a family of methods to control and to distribute impurities in which a small molten zone is moved slowly along a solid material, redistributing solute. It is used in materials purification, in a so-called zone refining process, but can also be used in homogeneous or discontinuous distribution of impurities and crystal growth. The zone melting applied to grain enlargement, leading to attain singlecrystalline or polycrystalline materials with coarse grains is so-called zone melting recrystallization (ZMR) and its major use is the preparation of materials for electronic and photovoltaic devices process especially silicon. In the last decade, progress in ZMR technology was done mainly in three areas: equipment development, process control, and numerical modeling, but only a few researches handle on zone melting at low temperatures and it limits the application of the method to other semiconductor materials such as III, IV or V group elements. Thus, this study aims to examine the influence of scan rate, zone width and the number of zone passes in the zone melting process of low melting point materials about getting polycrystalline materials with coarse grains. For this, horizontal zone melting equipment was built and pure aluminum bars (P0610) were zone melted, varying the parameters mentioned above. The macrostructure of the samples was analyzed and the results of the number of grains per area were assessed by checking the influence of physical parameters previously mentioned and the thermal gradient and the constitutional supercooling. It was found that scan rate and zone width reduction in general, proved to be efficient in reducing the number of grains per area. The results indicate that the zone melting was effective in obtaining aluminum polycrystalline coarse-grained and collaborate to improve the understanding of the process.

Peças cerâmicas são normalmente produzidas através da aplicação de calor sobre argilas transformadas, de matérias-primas naturais ou materiais sintéticos, utilizando água e/ou outros aditivos como agentes de ligação, para formar um produto rígido, seguido por um processo de conformação. Alguns dos métodos mais comuns de conformação incluem extrusão, colagem, prensagem, colagem em fita e moldagem por injeção. No entanto, o uso de tecnologias de prototipagem rápida na fabricação de materiais cerâmicos tem aumentado nos últimos anos devido às suas muitas vantagens, porém poucos estudos foram realizados utilizando como matéria-prima a alumina em impressão 3D. Desta forma, o objetivo deste trabalho foi avaliar a influência de diferentes ligantes (PVA, PVAc e Goma Arábica) nas propriedades físicas de peças de alumina obtidas por impressão 3D por jato de tinta. Além disto, avaliar também a influência da granulometria do pó na confecção destas peças. Porosidade aparente, densidade aparente, retração após tratamento térmico, resistência mecânica e tamanho de poro foram avaliados. Os resultados obtidos demonstraram que as peças com melhor acabamento e propriedades fisicas foram as com o ligante PVA. Ainda, foi aumentado o teor de ligante de 3 para 5% em massa. Nas amostras com 3%, uma granulometria média favoreceu a obtenção de melhores resultados estruturais e de aparência, sendo, por exemplo, os valores de resistência mecânica de 47MPa, porosidade aparente média de 30% e tamanho médio de poro próximo de 21μm. Para a concentração de 5%, foi a granulometria menor que obteve os melhores resultados, onde os valores de resistência mecânica, porosidade aparente média e tamanho de poro, por exemplo, foram de 63MPa, 22% e 21 μm, respectivamente. Para todos os ligantes e granulometrias a retração volumétrica média foi de ~50%. Conclui-se desta forma, que comparativamente, as peças impressas com os resultados mais satisfatórios foram as peças da composição com 5% de ligante PVA, passante em peneira 325 ABNT. / Ceramics pieces are typically produced by the application of heat upon processed clays, natural raw materials or chemically synthetic materials, accomplished of water and/other additives as binders, to form a rigid product followed by a shape forming process. Some of the most common forming methods for ceramics include extrusion, slip casting, pressing, tape casting and injection molding. However, the use of rapid prototyping technologies in the manufacture of ceramic materials in the biomedical area has increased in recent years due to its many advantages and few studies are conducted on obtaining alumina pieces intended for biomedical applications by 3D printing. Thus, the aim of this work was to evaluate the influence of different binders (PVA, PVAc and gum arabic) on the final properties of alumina parts obtained by inkjet printing. Moreover, was evaluated the influence of particle size in manufacturing parts. Apparent porosity, apparent density, retraction after thermal treatment, mechanical strength and pore size were evaluated. The results showed that the parts with PVA binder achieved a better appearance and better final properties. Further, the binder amount of 3 was increased to 5%wt. Samples with 3%wt and a mean particle size promoted to obtain the major structural results and appearance being, which for example, the mechanical strength was 47MPa, mean apparent porosity was 30% and mean pore size of 21μm. Samples with 5%wt and the minor particle size achieved the major results, where, for example, the values of mechanical strength, mean apparent porosity and mean pore size were 63MPa, 22% and 21μm, respectively. To all binders and particle size the volumetric shrinkage was ~ 50%. It was concluded, comparatively, the printed parts with the most satisfactory results were samples with 5%wt PVA, sieved at 325 mesh.