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Some analytical solutions for probelms involving highly frictional granular materialsThamwattana, Ngamta. January 2004 (has links)
Thesis (Ph.D.)--University of Wollongong,2004. / Typescript. Bibliography: leaf 205-214.
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Material flow optimization and systems analysis for biosolids management a study of the city of Columbus municipal operations /Sikdar, Kieran Jonah, January 2008 (has links)
Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 49-52).
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Transport boundaries for pneumatic conveyingYi, Jianglin. January 2001 (has links)
Thesis (Ph.D.)--University of Wollongong, 2001. / Typescript. Bibliographical references: leaf 218-232.
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A study of the phenomenon of bridging of sugarcane bagasseJanuary 1996 (has links)
This work reports the results of a systematic study of the factors that affect
the bridging behaviour of bagasse. It shows that traditional bulk solids theory
is inappropriate for predicting bagasse flow mainly because of the
impossibility of obtaining a reliable measure of internal friction. It
demonstrates the significant influence of fibre length and moisture content
on its handling charateristics.
Correlations of pertinent bulk properties such as compactibility, tensile
strength, surface friction and translation of vertical into horizontal pressure
have been developed. These were derived as a result of measurements in
equipment that was designed for the purpose.
Finally, an empirical model utilising these correlations is proposed by which
the likelihood of bridge formation in any piece of bagasse handling equipment
can be determined. The validity of the model is assessed by comparison with
bridging tests that were performed under controlled conditions. / Thesis (Ph.D.)-University of Natal, 1996
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Effect of Alloy Composition, Free Volume and Glass Formability on the Corrosion Behavior of Bulk Metallic GlassesAyyagari, Venkata Aditya 12 1900 (has links)
Bulk metallic glasses (BMGs) have received significant research interest due to their completely amorphous structure which results in unique structural and functional properties. Absence of grain boundaries and secondary phases in BMGs results in high corrosion resistance in many different environments. Understanding and tailoring the corrosion behavior can be significant for various structural applications in bulk form as well as coatings. In this study, the corrosion behavior of several Zr-based and Fe-Co based BMGs was evaluated to understand the effect of chemistry as well as quenched in free volume on corrosion behavior and mechanisms. Presence of Nb in Zr-based alloys was found to significantly improve corrosion resistance due to the formation of a stable passive oxide. Relaxed glasses showed lower rates compared to the as-cast alloys. This was attributed to lowering of chemical potential from the reduced fraction of free volume. Potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) techniques helped in quantifying the corrosion rate and polarization resistance. The effect of alloy composition was quantified by extensive surface analysis using Raman spectroscopy, energy dispersive x-ray spectroscopy and auger spectroscopy. Pitting intensity was higher in the as-cast glasses than the relaxed glasses. The electrochemical behavior of a Zr-Ti-Cu-Ni-Be bulk metallic glass subjected to high strain processing was studied. High strain processing caused shear band formation and an increase in the free volume. Potentiodynamic polarization and EIS showed a strong correlation between the enthalpy of structural relaxation and corrosion rate and polarization resistance. Pitting was observed to preferentially occur on shear bands in the processed samples, while it was stochastic in unprocessed glass. The corrosion analysis of Co-Fe glasses showed an increase in corrosion current density when Fe content was increased from 0 to 7 at%. The corrosion resistance improved when Fe content was further increased to 15 at%. Similar trend was seen in EIS studies. The improved corrosion resistance at 15 at% Fe can be attributed to the large supercooled region that facilitates the formation of completely amorphous alloy, in contrast to lower Fe containing alloys, where short range ordering may deteriorate the corrosion resistance. Porous metallic glass structure was developed by electrochemical dealloying via cyclic voltammetry. Mechanical properties and changes in electrical conductivity were measured as a function of depth from surface by nano-indentation and nano electrical contact resistance technique. The nanoporous layer was found have hardness of 0.41 GPa and elastic modulus of nearly 22 GPa. The resistivity of the nanoporous layer continuously decreased when moving towards the substrate as the indentation depth increased which is attributed to the gradient in pore size.
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Bulk diffusion of high performance concrete specimens exposed to different levels of sodium chloride and seawaterUnknown Date (has links)
The purpose of this study was to investigate the performance to chloride
penetration of specimens made with three base compositions (three different
supplementary cementitious materials) and water to cementitious ratios of 0.35, 0.41, or
0.47. The specimens were subjected to bulk diffusion test or full immersion. The mixes
were exposed to 0.1 M, 0.6 M, or 2.8 M sodium chloride solution for different periods of
time. Also, partially immersed specimens were exposed to indoor and outdoor exposures
(tidal, splash, barge). Chloride concentration profiles were obtained and the apparent
diffusion coefficient was calculated. The skin effect was found only on some chloride
profiles exposed to 0.1 M sodium chloride solution. The chloride binding capacity was
calculated; specimens with 20% Fly Ash and 8% Silica Fume had the highest binding
capacity (70.99%). The apparent diffusivity coefficient was found to be dependent on the
curing regime as well as the water to cement ratio. The correlation between effective
resistivity and apparent diffusion coefficient was determined. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Estudo teórico e experimental das ações em silos horizontais / Theoretical and experimental study of loads in horizontal silosGomes, Francisco Carlos 19 July 2000 (has links)
O projeto seguro e econômico das estruturas de armazenamento é função das máximas ações impostas e da resistência destas estruturas de suportar tais ações, observadas as combinações mais desfavoráveis. Entre as ações consideradas nos cálculos dos silos horizontais (peso próprio, peso de equipamentos, vento, recalques diferenciais de apoios, impacto de veículos, explosões, etc), a de maior importância é a causada pelo empuxo dos produtos armazenados e que foi objeto de estudo nesta pesquisa. Este trabalho foi realizado em duas etapas, teórica e experimental, procurando avaliar estas ações com base em teorias e métodos de cálculo de diversos autores. Na tremonha do silo, as pressões foram avaliadas através do método de cálculo proposto por Safarian & Harris, da teoria de Walker e da Norma Australiana AS 3774. Nas paredes, foram avaliadas as pressões de acordo com as teorias de Airy, Reimbert & Reimbert, Coulomb e Rankine e da norma americana ANSI/96. Os modelos teóricos foram estudados e comparados com os resultados obtidos através de medições diretas das pressões em modelo piloto e silo horizontal em escala real com a determinação da relação entre as pressões verticais e horizontais (K). Dos resultados obtidos propõe-se um novo método de cálculo com base em um modelo empírico para a determinação das pressões horizontais nestas unidades. / The safe and economic design of storage structures is a function of the loads and of the strenght of these structures, considering unfavorable loads combinations. Among the loads considered in the calculations of the horizontal silos, the most important load is due stored products. Silos are usually designed on the basis of simple theory which is used to predict horizontal pressures on the walls and hoppers. The pressures generally depend on many factors including the physical properties of the stored materials, the flow pattern and also the method of operating the silo. This work is divided in two parts in order to evaluate these loads based in theories and international codes.The silo hopper was evaluate by Walker\'s theory and by AS 3774-1996 code. The silo walls was evaluete by theories of Airy, Rankine, Reimbert & Reimbert, Coulomb, Safarian & Harris and ANSI (1996) code. The theoretical models were studied and compared with the results obtained through pressure measurements in a real and a pilot silos. From the results we proposed a new empiric design method to evaluate the horizontal pressures in the silos wall.
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Modelling of turbulent cross-flow microfiltration of particulate suspensions.Pillay, V. L. January 1991 (has links)
No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1991.
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The anti-dynamic tube in mass flow silosNortje, Desiree January 2003 (has links)
Storage of granular solids in silos has been the practice for many years. Engineers have been faced with the problem of making the silos empty more efficiently and minimising the forces acting on the walls of the silo during material discharge. To this end the anti-dynamic tube was invented. The tube has a smaller diameter than the silo and consists of several portholes along its height and around its circumference. When the discharge gate of the silo is opened the granular material enters the tube through the portholes, flows down the inside of the tube and exits the silo through the discharge gate. Most tubes have been installed such that there was sufficient space between the base of the tube and silo bottom for the granular material to flow simultaneously through the discharge gate. The flowing material causes a down drag on the tube from the friction of the granular material on the walls of the tube. Previous research has underestimated the magnitude of these frictional forces resulting in catastrophic buckling failure of the tubes, blocking the discharge gate of the silo. A blockage of the discharge gate requires top emptying of the silo resulting in financial losses and down time of equipment. A steel model silo with an anti-dynamic tube was set up in the laboratory to measure the friction on the tube during material flow. From the results of these experiments, an equation has been derived to estimate the magnitude of the down-drag force. Furthermore, an empirical expression was developed for the effects of the speed of the flowing material on the magnitude of the down-drag force. To keep construction costs down, it is necessary to optimise the wall thickness of the tube. There is currently no theory for the buckling capacity of a thin walled cylindrical shell with multiple perforations around its height and circumference. Therefore additional experiments were undertaken on a cylindrical shell with multiple perforations subjected to a combination of an axial as well as an external lateral pressure. Following on from the experiments, finite element analyses were undertaken to compare with the experimental results. For each finite element analysis an out-of-roundness was introduced as an initial wall imperfection. From these analyses and the cylinder experiments, a method of producing interaction curves for tubes with varying ratios of open area has been developed.
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The anti-dynamic tube in mass flow silos /Nortje, Desiree. January 2002 (has links)
Thesis (Ph.D.)--University of Western Australia, 2003.
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