No description available.

Thesis (M.S.)--Cornell University, May, 2004. / "PCA R&D serial no. 2806." "©Scott Burlingame 2004. All rights reserved. Reprinted by permission of Scott Burlingame." (Reprinted 2004 by Portland Cement Association, Skokie, Ill.) Includes bibliographical references (p. 460-465).

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references.

In this report a relationship is established between the variables of compaction temperature, compaction effort, mixture gradation and, density, air void content and stability of asphalt mixtures. The Marshall method of mix design was used, and Vibratory Kneading Compactor was utilized for compaction. Results include Marshall Stability and density-air void analysis for 4 and 6-inch specimens. It was found that the densities generally increased with increase of compaction temperatures and compaction efforts. From selected sets of 6-inch specimens, 4-inch cores were obtained. Density and stability studies were carried out on these cores and the results obtained were found to have the same trends. The air void content and voids in the mineral aggregates decreased with the increase of compaction effort. Stability increased with the increase in density. All the results found, indicate strong effects of compaction temperature and compactive effort on the amount of air voids, VMA, density, and stability of the mixes used.

The purpose of this work is to develop a continuum theory that may be used to predict the effects of anisotropic boundary vibrations on loose granular assemblies. In order to do so, we extend statistical averaging techniques employed in the kinetic theory to derive an anisotropic flow theory for rapid, dense flows of identical, inelastic spheres. The theory is anisotropic in the sense that it treats the full second moment of velocity fluctuations, rather than only its isotropic piece, as a mean field to be determined. In this manner, the theory can, for example, predict granular temperatures that are different in different directions. The flow theory consists of balance equations for mass, momentum, and full second moment of velocity fluctuations, as well as constitutive relations for the pressure tensor, the flux of second moment, and the source of second moment. The averaging procedure employed in deriving the constitutive relations is based on a Maxwellian that is perturbed due to the presence of a deviatoric second and full third moment of velocity fluctuations. Because the theory is anisotropic, it can predict the normal stress differences observed in granular shear flows, as well as the evolution to isotropy in an assembly with granular temperatures that are initially highly anisotropic. In order to complement the theory, we employ similar statistical techniques to derive boundary conditions that ensure that the flux of momentum as well as the flux of second moment are balanced at the vibrating boundary. The bumps are hemispheres arranged in regular arrays, and the fluctuating boundary motion is described by an anisotropic Maxwellian distribution function. The bumpiness of the surface may be adjusted by changing the size of the hemispheres, the spacing between the hemispheres in two separate array-directions, and the angle between the two directions. Statistical averaging consistent with the constitutive theory yields the rates at which momentum and full second moment are transferred to the flow. In order to present results in a form that is easy to interpret physically, the statistical parameters that describe the boundary fluctuations are related in a plausible manner to amplitudes and frequencies of sinusoidal vibrations that may differ in three mutually perpendicular directions, and to phase angles that may be adjusted between the three directions of vibration. The focus of the results presented here is on the steady response of unconfined granular assemblies that are thermalized and driven by horizontal bumpy vibrating boundaries. In a first detailed study of the effects of the boundary geometry and boundary motion on the overall response of the assemblies, the anisotropic theory is reduced to a more familiar isotropic form. The resulting theory predicts the manner in which the profiles of isotropic granular temperature and solid volume fraction as well as the uniform velocity and corresponding flow rate vary with spacings between the bumps, angle of the bump-array, energy of vibration, direction of vibration, and phase angles of the vibration. In a second study, we solve the corresponding, but more elaborate, boundary value problem for anisotropic flows induced by anisotropic boundary vibrations. The main focus in presenting these results is on the differences between granular temperatures in three perpendicular directions normal and tangential to the vibrating surface, and how each is affected by the bumpiness of the boundary and the direction of the vibration. In each case, we calculate the corresponding nonuniform velocity profile, solid volume fraction profile, and mass flow rate.

Composite construction of floor systems with steel joist or I-beam stiffeners supporting a concrete slab have a tendency to sustain perceptible vibration due to small impacts. An engineering design aid, utilizing a small micro-computer and a BASIC computer program, was developed to analyze rectangular floor systems for susceptibility to sustain vibrations perceptible to humans. The analytical method for the normal modes of vibration using the Rayleigh-Ritz method and the superposition of the normal mode response is derived. A vibration index is calculated to qualitatively rate the floor. The computer method was validated using published data for an I-beam supported concrete slab and a design application for a steel-joist supported floor is demonstrated using a representative human induced impact load.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The aim of this work was study the phenomenological concepts, operational and, above all, mass productivity in the crystallization of citric acid in vibrated bed, using large population of seeds (dense phase). It was used a truncated conical stainless steel crystallizer, containing a mobile central axis with coupled perforated disks, transferring vibrational energy to the crystallization environment. It was conducted a representation of the crystallization suspension environment flow of crystalline particles that illustrated the process of bed fluidization. The solution initially saturated, to its saturate temperature, was taken to the crystallization temperature 55°C, becoming supersaturated, and seeded with commercial grainy citric acid crystals. It was used as statistic toll a central composite design to construct a representative model and influence verification of process significant variables: crystallization time, a degree of supersaturation and intensity of vibration. The response analyzed was the productivity (mass percentage increase) in crystallization process. Using the model obtained, it was calculated the maximum productivity condition in mass, which consisted a percentage increase in mass of 164.7%. This condition was posteriorly tested in the experimental unit resulting in an productivity of 187.7%. The crystallizers in series simulation occurred using commercial citric acid seeds with the same final diameter of the tests using the optimized conditions, keeping other variables constant, resulting in a mass percentage increase, for the second step, of 166.9%. These showed efficiency in obtaining crystals with larger end. Was performed to evaluate the secondary nucleation by capturing the image of crystals in crystallization trials, where was noticed the appearance of small polycrystalline structures in the crystalline surface of the crystals, caused by the high degree of supersaturation, or due to the systematic separation of these / Este trabalho tem como objetivo o estudo de conceitos fenomenológicos, operacionais e, sobretudo, produtividade mássica, na cristalização de ácido cítrico em leito vibrado, utilizando grande população de sementes (fase densa). Foi utilizado um cristalizador tronco-cônico de aço inoxidável, contendo um eixo central móvel com discos perfurados acoplados, que transferiu energia vibracional ao meio de cristalização. Efetuou-se uma representação do escoamento da suspensão com as partículas cristalinas que ilustrou o processo de fluidização do leito. A solução inicialmente saturada, à respectiva temperatura de saturação, foi levada à temperatura de cristalização 55°C, tornando-se supersaturada, e semeada com cristais comerciais de ácido cítrico granular. Foi utilizado como ferramenta estatística um planejamento composto central para construção de um modelo representativo e na verificação da influência das variáveis significativas do processo: tempo de cristalização, concentração de supersaturação e intensidade de vibração. A resposta analisada foi a produtividade (aumento percentual de massa) no processo de cristalização. Através do modelo obtido, foi calculada a condição de máxima produtividade em termos mássicos, que consistiu em um aumento percentual mássico de 164,7%. Esta condição foi posteriormente testada na unidade experimental resultando em uma produtividade de 187,7%. A simulação de cristalizadores em série se deu com a utilização de sementes de ácido cítrico comercial com o mesmo diâmetro final dos testes utilizando a condição otimizada, mantendo-se as demais variáveis constantes, resultando em um aumento percentual mássico, para a segunda etapa de cristalização, de 166,9 %. Estes mostraram eficiência na obtenção de cristais com maior dimensão final. Foi realizada a avaliação da nucleação secundária através da captura de imagem dos cristais nos experimentos de cristalização, onde notou-se o aparecimento de pequenas estruturas policristalinas na superfície cristalina dos cristais, causados pelo alto grau de supersaturação, ou devido à sistemática de separação dos mesmos. / Mestre em Engenharia Química

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Crystallization is a unit operation widely used in the chemical and food industries for production of high purity compounds, even in presence of other substances in solution. The aim of this work was to study the operation of isothermal crystallization in den se phase, of alpha-lactose monohydrate in whey, a byproduct of the dairy industry. Initially, to obtain drivers initial parameters were performed a central composite design, using commercial lactose monohydrate for prepare the solutions and seeds, cylindrical-conical vibrated bed crystallizer and operating temperature of 50.0°C. This has enabled a study of significant variables in the operation, construction of prediction models, analysis of response surfaces and selection of an optimal operation point within the experimental range adopted and associated responses, which were the mass percentage increase and Sauter mean diameter. To evaluate the reduction in the average diameter of the crystallization products against seeds, obtained in the first planning, we propose a second, with similar process conditions, but with seeds produced by cooling to 7°C for 24 h, to remove the effect of microparticles adhered on the surface of commercial lactose crystals, which probably influencing the crystallization. The average size of the crystals in the process increased from 5.61 ± 0.050 × 10-6 m (seeds) to 8.06 ± 0.22 × 10-6 m, with average mass percentage increase of 119%. For operation with whey, an initial study was conducted to reduce the amount of fats and proteins. The coagulant used was of organic origin, based on tannin. Using a concentration of 2.0 × 10-3 L Tanfloc.L-1of whey, was obtained a removal of 40.3% of protein and 90% fat. The crystallization of lactose using cheese whey concentrated and purified was performed under similar conditions to the optimization performed in the central composite design with seeds obtained by cooling. The responses indicated growth of seeds added, even in the presence of interferents and possible crystallization inhibitors. The growth rate was also evaluated for the step. Using concentrated and purified whey cheese too, was performed a analysis in situ of crystallization operation, with evaluation of population and crystal habit during the procedure, in conventional agitation and vibration units, where it was found interfering action from the beginning of the crystallization step and intense effect of secondary nucleation in high degrees of agitation, especially in a conventional unit. / A cristalização é uma operação unitária muito utilizada nas indústrias química e alimentícia para produção de componentes com elevada pureza, mesmo na presença de outras substâncias em solução. Sendo assim, o objetivo deste trabalho foi estudar a operação de cristalização isotérmica, em fase densa, de alfalactose monoidratada em soro de queijo, subproduto da indústria de laticínios. Inicialmente, para obtenção de parâmetros direcionadores iniciais foi realizado um planejamento composto central, utilizando lactose monoidratada comercial para preparo das soluções e sementes, operando com cristalizador em leito troncocônico vibrado e temperatura de operação de 50,0°C. Isto possibilitou um estudo das variáveis significativas na operação, construção de um modelo de previsão de respostas, análise de superfícies de resposta e seleção de um ponto de operação ótimo dentro da faixa experimental adotada e respostas associadas, que foram: aumento de massa percentual e diâmetro de Sauter. Visando avaliar a diminuição do diâmetro médio nos produtos da cristalização em relação às sementes, obtido no primeiro planejamento, foi proposto um segundo, com condições de processo similares, porém com sementes produzidas por resfriamento a 7°C, durante 24 h, para eliminar o efeito de micropartículas aderidas na superfície dos cristais da lactose comercial, que possivelmente influenciavam na cristalização. O tamanho médio dos cristais no processo aumentou de 5,61 ± 0,050 × 10-6 m (sementes), para 8,06 ± 0,22 × 10-6 m, com aumento mássico de 119%. Para operação com soro de queijo foi realizado um estudo inicial para reduzir a quantidade de gorduras e proteínas presentes. O coagulante utilizado foi de origem orgânica, à base de tanino. Utilizado em concentração de 2,0×10-3 L Tanfloc.L de soro-1 promoveu uma remoção de 40,3% de proteínas e 90% de gorduras. A cristalização de lactose utilizando soro de leite concentrado e purificado foi realizada em condições similares à otimização realizada no planejamento composto central com sementes obtidas por resfriamento. As repostas indicaram crescimento cristalino das sementes adicionadas, mesmo na presença de interferentes residuais e possíveis inibidores da cristalização. A taxa de crescimento também foi avaliada para a etapa. Utilizando também soro de queijo concentrado e purificado, foi realizada a análise in situ da operação de cristalização com avaliação da população e hábito cristalino no decorrer do procedimento, em unidade com agitação convencional e por vibração, na qual foi constatada a ação de interferentes desde o início do da etapa de cristalização e intenso efeito da nucleação secundária em altos graus de agitação, principalmente na unidade convencional. / Doutor em Engenharia Química