Made available in DSpace on 2014-06-11T19:28:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-11Bitstream added on 2014-06-13T18:57:55Z : No. of bitstreams: 1 ranieri_mga_me_guara.pdf: 6336398 bytes, checksum: d7e3a48d3e8f9a4df8300a3b5bfbb42b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A cidade de Cunha, no interior de São Paulo, é hoje reconhecida como um dos principais centros de cerâmica artística de alta temperatura. Nessa cidade, há a maior concentração de fornos noborigama da América do Sul, que é um forno de tradição milenar oriental. As peças produzidas nesse tipo de forno são reconhecidas como sendo cerâmica artística com alto valor agregado. Os ceramistas não possuem nenhum tipo de apoio técnico em relação à matéria-prima utilizada, que é a argila. Então, foi realizada neste trabalho a caracterização tecnológica de duas argilas da região, uma de coloração escura e outra de coloração clara, que são misturadas em três proporções diferentes, com o intuito de obter uma massa com boa trabalhabilidade para o processo de conformação. Foram utilizadas algumas técnicas para a caracterização mineralógica como análise térmica diferencial, análise termogravimétrica e difração de raios X. Para a caracterização física pré-queima realizou-se ensaios de análise granulométrica, massa específica dos grãos de solo e limites de Atterberg. Também, foram avaliadas as propriedades tecnológicas pós-queima em três temperaturas diferentes a 950°C, 1.150°C e 1.350°C, as propriedades avaliadas foram porosidade aparente, absorção de água, massa específica aparente, retração linear, rugosidade e resistência mecânica por flexão (3 pontos). A argila de cor clara apresentou melhores resultados na maioria dos ensaios quando comparados com os resultados obtidos com a argila de coloração escura e as respectivas misturas. Em relação a essas misturas, não houve variações significativas nas propriedades avaliadas. Observou-se que a temperatura de queima teve forte influência nas propriedades finais, principalmente a 1.350°C. / Cunha, a small Town located in São Paulo State, Brazil, is known today as one of the major centers of high temperature artistic ceramics. It is the place with the largest concentration of “noborigamas”, which are secular traditional oriental ovens. The items, made in this kind of ovens are recognized as being artistic ceramics with a high aggregated value. The ceramists do not have any kind of technical support regarding the clay, the raw material used by them. In this work the technical characterization was performed in two types of clay from Cunha: a dark colored one and a light colored one, both mixed in three different proportions in order to obtain a paste of good workability for the shaping process. Some techniques were used to get the mineralogical characteristics such as differential thermal analysis (DTA), thermogravimetric analysis (TGA) and X-ray diffraction technique. Experiments of particle size analysis, grain specific mass and Atterberg’s limit were done for the preburning physical characterization. The technological properties were also estimated before and after burning the clay in three different temperatures: 950° C, 1.150° C and 1.350° C. The properties estimated were: apparent porosity, water absorption, bulk density, linear shrinkage, roughness and flexural strength (3 points) The light colored clay reached better results in most of the experiences compared to the results obtained from the dark one and the respective mixtures. There were not expressive variations regarding these mixtures. It was observed that the burning temperature had a strong influence over the final properties, especially at 1.350°C. Both types of clay and their respective mixtures get through a “cure” process or “soting” in the ceramists workshop. The samples of clay analyzed in this experience were obtained from the mine without the previous treatment used by the ceramists. The “cure” process can alter the clay properties.

Orientador: Sandra Helena Pulcinelli / Orientador: Anne-Marie Flank / Banca: Marian Rosaly Davolos / Banca: Fabrice Leroux / Banca: Bluma Guenther Soares / Banca: Pedro de Oliveira / Resumo: Uma das maneiras de aumentar a estabilidade térmica de polímeros consiste na adição de baixas quantidades de argila dispersas em escala nanométrica. Tais materiais são chamados de nanocompósitos. Existem várias explicações de como as argilas promovem a estabilização térmica dos polímeros. Algumas delas bem estabelecidas, como os efeitos de barreira de difusão e formação de carvão. E outras em curso de verificação, como os efeitos de seqüestro de radicais por parte de íons que participam de reações tipo Fenton. Nesse trabalho buscou-se, através do monitoramento in situ das transformações químicas da fase argila, melhor compreender como essas nanoestruturas lamelares retardam a decomposição de polímeros. Para tanto preparam-se três tipos de nanocompósitos: i) Poli(metil metacrilato)-co- Poli(trimetoxisilil propil metacrilato) e argilas montmorilonita (MMT) do tipo Cloisite (PMMA-co-PTMSM-Cloisite); ii) PMMA-argilas montmorilonita naturais contendo diferentes razões de íons Fe3+ nas camadas octaédricas (PMMA-MMT); iii) PMMAhidróxidos duplos lamelares (HDL), com diferentes proporções de íons Zn2+, Cu2+ e Fe3+ PMMA-HDL. A termo-decomposição das argilas primitivas e dos respectivos nanocompósitos foram acompanhadas por análises térmicas, espalhamento de raios X a baixos e altos ângulos (SAXS e WAXS) e espectroscopia de absorção de raios X (EXAFS). Os efeitos da atmosfera, composição química das lamelas, e quantidade de argila empregada na obtenção dos nanocompósitos foram avaliadas. O estudo dos nanocompósitos, PMMA-co-PTMSM-Cloisite mostrou que a estabilização térmica aumenta como função da quantidade de argila dispersa no polímero. O efeito de estabilização é mais pronunciado sob atmosfera de ar, do que em atmosfera de N2. A formação de carvão também foi observada apenas sob... (Resumo completo, clicar acesso eletrônico abaixo) / Resumé: Une des manières d'augmenter la stabilité thermique de polymères consiste à leur ajouter de faibles quantités d'argile dispersées dans échelle nanométrique. De tels matériaux sont appelés de « nanocomposites ». Il existe plusieurs explications à ce phénomène, comme les effets de barrière de diffusion et la formation de charbon. D'autres sont en cours de vérification, comme les effets de piégeage de radicaux par les ions qui participent à des réactions de type Fenton. Notre objectif a été de suivre in situ des transformations chimiques de la phase argile, afin de mieux comprendre comment ces nanostructures lamellaires retardent la décomposition de polymères. Pour ce faire, trois types de nanocomposites ont été préparés: i) Poly(méthyl méthacrylate)-co-Poly(trimetoxysilil propyl méthacrylate) et argiles montmorillonite (MMT) du type Cloisite (PMMA-co-PTMSM-Cloisite); ii) PMMA-argiles montmorillonites naturelles contenant différents taux d'ions Fe3+ dans les couches octaédrique (PMMA-MMT); iii) PMMA-hydroxydes doubles lamellaires (HDL), avec différentes proportions d' ions Zn2+, Cu2+ et Fe3+ PMMA-HDL. La thermo-décomposition des argiles primitives et de leurs nanocomposites ont été suivies par des analyses thermiques, de diffusion de rayons X (SAXS et WAXS) et par spectroscopie d'absorption de rayons X (EXAFS). Les effets de l'atmosphère, de la composition chimique des lamelles, et de la quantité d'argile employée dans l'obtention des nanocomposites ont été évalués. L'étude des nanocomposites, PMMA-co-PTMSM-Cloisite a mis en évidence deux mécanismes de stabilisation. Elle a montré que l'addition d'argiles résulte en une stabilisation plus importante sous atmosphère d'air, que sous atmosphère de N2, et est aussi plus importante selon la quantité d'argile dispersée dans le polymère. La formation... (Résumé complet accès életronique cidessous) / Doutor

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This paper discusses several proposed methods for estimating undrained shear strength from cone penetration tests. This correlation has been studied in the past, however, most have focussed only on the cone bearing. In addition to discussing these traditional methods, this paper evaluates recently proposed methods of estimating Su from CPT pore pressure data. The results of field vane and cone penetration tests from five lower mainland sites are presented in relation to the different proposed correlation techniques. The results show that there is no unique cone factor for estimating Su from CPT for all clays, however, a reasonable estimate of Su can be made by comparing the predictions from several of the proposed methods. With local correlations these techniques can be quite reliable. The results also show that the estimation of Su from CPT is influenced by various factors relating to: the choice of a reference Su, cone design, CPT test procedures and the soil characteristics. In particular, the estimation of Su from CPT is strongly influenced by such soil parameters as stress history, sensitivity and stiffness. Increases in OCR and sensitivity were reflected by increases in the traditional cone factors Nc and Nk. The use of pore pressure data appears to be a promising means of estimating. Su from CPT. Expressions have been developed that predict excess pore pressures based on cavity expansion theory and attempt to include the effects of sensitivity, stress history and stiffness. In addition, comparisons between friction sleeve measurements and Su and a method for estimating sensitivity from friction ratios are presented. Lastly, recommended procedures for estimating Su from CPT are given. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

M.Tech. (Ceramics) / The research project attempts to fill a void by assembling data dealing with a comprehensive range of South African clay and glaze materials, suited to the needs of the studio potter, and recording test results. South African kaolins, ball clays, fireclays, miscellaneous clays, grogs, bentonites, felspathic materials, alkaline earths, silica, refractory materials (other than clays) and mineral pigments are dealt with. A limited selection of foreign materials, frequently referred to in studio-potter publications, was also used in comparative tests. The materials are recorded with reference to the ultimate analysis, seger formula, proximate analysis (where applicable), properties and results of trials using the materials in clay bodies and/or glazes. It was demonstrated that South African materials are largely of good quality e.g. kaolin, felspars and silica. Variability of clay supplies because of lack of stockpiling and blending practices, especially by small suppliers, is often a problem. When the composition of glaze materials and trials indicated that imported equivalents were superior because of variability of local supplies or poor grade material, then substitutes were tested using South African materials. Basic clay bodies and glazes covering a wide temperature range from Egyptian Paste, low-fired wares such as raku, terracotta-and-white-earthenwares, stoneware and soft-porcelain bodies and glazes are dealt with giving a brief outline of the requirements for each type. Suggestions of suitable South African materials for their composition are made. Trials and results are recorded. The knowledge gained of South African materials available and a study of the materials enables the studio potter to utilize local materials with awareness and confidence

Pineview clay originates from a lacustrine deposit and has a clay content of approximately 55%. During the spring the soil is generally quite moist due to melting snow and rainfall, while ambient air temperatures are relatively cool. These factors cause soil warming on Pineview clay to be slow. Due to the slow soil warming process in the spring and due to the fine texture of this soil, it is important that the Pineview clay maintains a good soil structure. Little research has been carried out on Pineview clay as to the effect of tillage practices on soil structure. It was the purpose of this project to study changes in the properties of Pineview clay brought about by different tillage systems. In the first part of the project major adverse soil conditions that occur on Pineview clay were evaluated with respect to the emergence of barley. In the laboratory the effects of soil compaction and soil temperature were evaluated in terms of barley seedling emergence. The second part of the study consisted of determining the feasibility of several tillage systems and the use of a herbicide prior to tillage on Pineview clay. In the last part of the study four fall sod breaking tillage systems were evaluated in terms of their effect on soil physical properties, N transformations, crop growth and development, and economic returns. Barley seedling emergence in the laboratory was found to be affected by soil compaction and soil temperature. Between 5⁰ and 20⁰C the rate of barley emergence approximately doubled for every 5⁰C increment in soil temperature. Applying the herbicide Gramaxone prior to tillage improved soil break-up and control of sod regrowth, but the cost of this herbicide may be prohibitive. For sod breaking operations a stubble plow proved to be inadequate and a special sod breaking plow should be used. Rotovation prior to moldboard plowing improved soil break-up and control of sod re-growth. Chisel plowing resulted in a rough, mulched soil surface condition, which required many passes before a satisfactory level soil surface had been created. The four fall sod breaking systems were moldboard plowing (using a sod breaking plow) with and without prior rotovation, and chisel plowing with and without prior rotovation. The results indicate major differences due to the type of plow used (moldboard vs chisel) rather than the additional use of the rotovator prior to plowing. Moldboard plowing resulted in superior soil physical conditions, higher soil NO₃-N levels, higher crop yields and N uptake by the crop, and better economic returns than chisel plowing. The four tillage systems reached maximum profits under various fertilizer rates; $208.00/ha for moldboard plowing at 112 kg N/ha, $104.00/ha for rotovating and moldboard plowing at 56 kg N/ha, $71.00/ha for chisel plowing at 168 kg N/ha, and $39.00/ha for rotovating and chisel plowing at 0 kg N/ha. / Land and Food Systems, Faculty of / Graduate

Basal reinforcement, where high tensile geogrids are employed beneath structures, is becoming an increasingly accepted construction technique along the eastern coast of southern Africa. The presence of compressible, soft, thin and shallow clay horizons usually associated with complex estuarine or lagoonal deposits are a major consideration when using basal reinforcement as a founding technique. Basal reinforcement involves the use of high tensile strength geogrids beneath a structure to form a reinforced sand foundation. Deformation behaviour under loading is an important component of stability analysis of earth structures. If reinforcement is used, the mechanisms become altered. Geotechnical centrifuge modelling is a unique physical modelling technique, as it allows replication of in situ stresses, which is most important because soil behaviour is a function of stress. This is achieved by placing the model at the end of the centrifuge arm, and subjecting it to an increased gravitational field, which creates the correct stress distribution in the model. Centrifuge modelling provides an appropriate technique to observe the behaviour of compressible, soft, thin and shallow clay horizons when basal reinforcement is utilized. An appropriate centrifuge model was constructed and compared the behaviour of the clay horizon under unreinforced and reinforced conditions. Reinforcement configurations were adjusted to observe the influence of additional geogrid layers, and extension of the width of the reinforcement. It was found that deformation behaviour is distinctly different between unreinforced and reinforced tests. Vertical deformation in the unreinforced test localised to the region directly beneath the platform, with little lateral disturbance to the clay horizon beyond the platform edge. As such, the sand directly beneath the platform acts as a deeper rigid platform. The deformation behaviour of the clay horizon changes with the inclusion of reinforcement. When reinforcement is included a wider portion of clay is deformed. The lateral width of this deformation zone is controlled by the width of the reinforcement, as the applied load is spread. A ‘wide-slab’ effect is evident with an increase in the geogrid width, as the tensioned membrane-effect is mobilised to increase the capacity of the reinforced foundation sand. This results in a wider portion of the clay deforming. Addition of geogrid reinforcement to the sand foundation under a wide platform load enhances deformation of the clay, but has the advantage of an increased load-bearing capacity of the system. Furthermore, the addition of multiple layers of reinforcement contributes to this increase in load-bearing capacity. Additionally, increasing the installation width of the reinforcement contributes to an increased vertical load-bearing capacity. However, this resultant increase is only mobilised after a certain amount of vertical displacement. This is likely due to the reinforcement requiring a certain amount of vertical displacement to mobilise tension in order to support the applied load. The behaviour of a thin compressible clay horizon changes with the inclusion of reinforcement under a wide platform load. The deformation behaviour of the clay is increased by additional layers of reinforcement as well as an increase in the width of the reinforcement. However, the increase in deformation comes at the benefit of an increased vertical load-bearing capacity of the reinforced foundation sand. / Dissertation (MSc)--University of Pretoria, 2014. / gm2014 / Geology / unrestricted

This study is an attempt to determine the relationship between humus and the water found in it and how both effect soil in Denton county, Texas.

Aflatoxins are naturally occurring carcinogens found on grains, particularly in warmer climates. Because of their carcinogenic properties, they are strictly regulated and are only allowed in minimal amounts. Aflatoxin B1, the most potent naturally occurring carcinogen known, is metabolized in the liver to form aflatoxin M1, which is present in the milk of lactating animals. If aflatoxin concentrations are elevated above legal limits, the milk cannot be used for human consumption. Because of this, research has been conducted to evaluate ways to mitigate its absorption in the animal and prevent transfer to the milk. One such way is through the use of clay adsorbents. The current studies aimed to evaluate the efficacy of two different clay adsorbents at preventing aflatoxin transfer to the milk of Holsteins fed a known concentration of aflatoxin.