Conical fluidized bed dryers are widely used in the pharmaceutical industry due to their high heat and mass transfer characteristics. Despite their widespread use, very little is known about the hydrodynamics of conical fluidized bed dryers. Wet pharmaceutical granule has high moisture content and wide particle size distribution (PSD), which can lead to poor mixing and non uniform drying. Uneven moisture content in the final product can adversely affect the quality and shelf life of these high value drugs. Previous studies on the conical fluidized bed dryers focused on the study of the gas phase, however motion of particulate phase has never been studied. Particle tracking is an important tool to study the motion of the particulate phase. Two particle tracking techniques were developed and used to study the motion of the particulate phase in a conical fluidized bed dryer. The first technique was radioactive particle tracking (RPT) which was developed at the University of Saskatchewan laboratory for a vessel having conical geometry. Experiments were conducted using dry pharmaceutical granule and during the actual drying of wet pharmaceutical granule. Two radioactive tracers of different sizes (1.6 to 2.6 mm) were tracked in each set of experiments to determine the effect of particle size on particle motion and particle mixing. Superficial gas velocities of 1, 1.5, 2 and 2.5m/s were used in dry bed studies to quantify the effect of superficial gas velocity. The second particle tracking technique was developed at the labs of Merck Frosst Canada Inc. Movies were captured using a high speed video camera coupled to a borescope and then analyzed off-line using image analysis software.Three powders having mean particle diameters of 774, 468 and 200 microns were used. Experiments were conducted at superficial gas velocities of 1.5, 2 and 3 m/s. <p>RPT revealed that there is a distinct circulation pattern of the particulate phase. Particles move upwards at high velocities near the centre of the bed and fall slowly near the walls. Furthermore, most of the gas flow is concentrated near the centre of the bed and the circulation pattern was observed at all the superficial gas velocities. Particle size of the tracer particle and PSD of the bed material had an appreciable impact on particle mixing with bigger particles exhibiting higher segregation tendencies than the smaller ones in the case of dry granule having a broad PSD. Particle segregation due to size difference was more pronounced at a superficial gas velocity of 1 m/s. However, segregation decreased with an increase in superficial gas velocity. During drying of wet granule, particle mixing and motion of the tracer particle was poor during the first 7 minutes of drying suggesting that most of the gas flow was concentrated near the centre of the bed. Particle mixing and average particle speeds increased considerably when the moisture content in the granule was less than 18 wt% suggesting a change in the hydrodynamics of the bed with the gas being more evenly distributed throughout the bed. Image analysis of high speed movies also suggested that a dilute region existed at the center of the bed. These observations were in agreement with the observations made by RPT.

Conical fluidized bed dryers are widely used in the pharmaceutical industry due to their high heat and mass transfer characteristics. Despite their widespread use, very little is known about the hydrodynamics of conical fluidized bed dryers. Wet pharmaceutical granule has high moisture content and wide particle size distribution (PSD), which can lead to poor mixing and non uniform drying. Uneven moisture content in the final product can adversely affect the quality and shelf life of these high value drugs. Previous studies on the conical fluidized bed dryers focused on the study of the gas phase, however motion of particulate phase has never been studied. Particle tracking is an important tool to study the motion of the particulate phase. Two particle tracking techniques were developed and used to study the motion of the particulate phase in a conical fluidized bed dryer. The first technique was radioactive particle tracking (RPT) which was developed at the University of Saskatchewan laboratory for a vessel having conical geometry. Experiments were conducted using dry pharmaceutical granule and during the actual drying of wet pharmaceutical granule. Two radioactive tracers of different sizes (1.6 to 2.6 mm) were tracked in each set of experiments to determine the effect of particle size on particle motion and particle mixing. Superficial gas velocities of 1, 1.5, 2 and 2.5m/s were used in dry bed studies to quantify the effect of superficial gas velocity. The second particle tracking technique was developed at the labs of Merck Frosst Canada Inc. Movies were captured using a high speed video camera coupled to a borescope and then analyzed off-line using image analysis software.Three powders having mean particle diameters of 774, 468 and 200 microns were used. Experiments were conducted at superficial gas velocities of 1.5, 2 and 3 m/s. <p>RPT revealed that there is a distinct circulation pattern of the particulate phase. Particles move upwards at high velocities near the centre of the bed and fall slowly near the walls. Furthermore, most of the gas flow is concentrated near the centre of the bed and the circulation pattern was observed at all the superficial gas velocities. Particle size of the tracer particle and PSD of the bed material had an appreciable impact on particle mixing with bigger particles exhibiting higher segregation tendencies than the smaller ones in the case of dry granule having a broad PSD. Particle segregation due to size difference was more pronounced at a superficial gas velocity of 1 m/s. However, segregation decreased with an increase in superficial gas velocity. During drying of wet granule, particle mixing and motion of the tracer particle was poor during the first 7 minutes of drying suggesting that most of the gas flow was concentrated near the centre of the bed. Particle mixing and average particle speeds increased considerably when the moisture content in the granule was less than 18 wt% suggesting a change in the hydrodynamics of the bed with the gas being more evenly distributed throughout the bed. Image analysis of high speed movies also suggested that a dilute region existed at the center of the bed. These observations were in agreement with the observations made by RPT.

Thermcapillary convection has been known as the dominant force in the flow and heat transfer during metals processings such as welding, drilling, cutting, and crystial growth, etc. Convection in the molten metal is typically vigorous and significant to the results of the process, in that it affects the size and shape of the pool, heat transfer, mixing of solutes, and ultimately microstructure of the finished product. In a melting or solidification process, thermocapillary effects may induce variations in local heat transfer, melting or solidification rates at the solid-liquid interface. thermocapillary flow originates at the hot wall and forms a surface layer along the free surface. The surface layer is driven by the thermocapillary force balanced by viscous stress. This region is followed by a region where the thermocapillary driving force has diminished due to a reduced temperature gradient. steady-state convection induced by thermocapillary and buoyant forces near a corner region of an enclosure having an inclined wall is numerically studied.Introducing an immobilizationt transformation, the shapes of the free surface subject to an incident flux are predicted by simultaneously solving mass, momentum and energy equations in the liquid and energy equation in the surrounding solid. The results provide a deep insight into local heat transfer, melting ¡Nsolidification rates at the solid-liquid interface and defects such as rippling, undercutting, humping, porosity, segregation, etc.

Multiphase and non-Darcy flow effects in hydraulically fractured gas wells reduce effective fracture conductivity. Typical proppant pack laboratory experiments are oriented in such a way such that phase segregation is not possible, which results in mixed flow. Tidwell and Parker (1996), however, showed that in proppant packs, gravity segregation occurs for simultaneous gas and liquid injection at laboratory scale (1500 cm2). Although the impact of gravity on flow in natural fractures has been described, previous work has not fully described the effect of gravity on multiphase non-Darcy flow in hydraulic fractures. In this work, reservoir simulation modeling was used to determine the extent and impact of gravity segregation in a hydraulic fracture at field scale. I found that by ignoring segregation, effective fracture conductivity can be underestimated by up to a factor of two. An analytical solution was developed for uniform flux of water and gas into the fracture. The solution for pressures and saturations in the fracture agrees well with reservoir simulation. Gravity segregation occurs in moderate-to-high conductivity fractures. Gravity segregation impacts effective fracture conductivity when gas and liquid are being produced at all water-gas ratios modeled above 2 Bbls per MMscf. More realistic, non-uniform-flux models were also run with the hydraulic fracture connected to a gas reservoir producing water. For constant-gas-rate production, differences in pressure drop between segregated cases and mixed flow cases range up to a factor of two. As the pressure gradient in the fracture increases above 1 to 2 psi/ft, the amount of segregation decreases. Segregation is also less for fracture half-length-to-height ratios less than or close to two. When there is less segregation, the difference in effective conductivity between the segregated and mixed flow cases is reduced. I also modeled the water injection and cleanup phases for a typical slickwater fracture treatment both with and without gravity effects and found that for cases with segregation, effective fracture conductivity is significantly higher than the conductivity when mixed flow occurs. Gravity segregation is commonly ignored in design and analysis of hydraulically fractured gas wells. This work shows that segregation is an important physical process and it affects effective fracture conductivity significantly. Hydraulic fracture treatments can be designed more effectively if effective fracture conductivity is known more accurately.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 34-38).

Nearly all studies of gender differences in wages and advancement find that the primary difference between the economic standing of women and men lies in their distribution across occupations and industries. In my dissertation I use micro-econometric techniques to examine different aspects of the evolution and impact of gender-specific occupational structures. The first essay evaluates the capacity of a hierarchical model of discrimination and segregation to explain the gender wage gap within firms for a regional grocery store chain that lost a title VII class action lawsuit for not promoting women into the higher managerial positions. In the process the analysis raises questions about the appropriateness of standard wage model specifications for making inferences about wage determination in a setting where wages for each job are set equal for men and women by precise union rules. The second essay expands the theory of hierarchical segregation to examine changes in the wage and occupational structure over time with panel data. This allows one to analyze the effects of hierarchical segregation over time and observe whether the filing of the lawsuit alone is sufficient to change discriminatory behavior by the firm. The final essay examines how major economic crises, including two World Wars and a Great Depression, led to changes in gender segregation in industrial and clerical jobs.

This statement helps explain what I personally experience after having travelled half way across the world and stayed in Canada for almost two years. Accordingly, this work is an attempt to look back into the educational systems in the different territories of my homeland, Malaysia, and to examine them from a broader perspective and in terms of other systems. [...]

No description available.

There is no abstract available for this dissertation.

The purpose of this study was to compare the reading achievement of pupils bussed from two predominantly Negro central-city schools to several predominantly white receiving schools, with the reading achievement of a group of pupils remaining in the two predominantly Negro sending schools.ProceduresThe sample of the present study was drawn from the public school system of a midwest city of approximately 200,000 population. The subjects in the study were those pupils who had been enrolled in the third grade in two central-city schools during the 1965-66 school year, and who continued to reside within the school districts served by the two central-city schools through the 1968-69 school year. The bussed group included sixty-one Negro and three white pupils who were transported from the two predominantly Negro schools at the beginning of the fifth grade and through the sixth grade to ten predominantly white schools. The non-bussed group included forty-three Negro and two white pupils who remained in the two predominantly Negro sending schools through the sixth grade. Data on the individuals included in the sample were obtained from the cumulative folders of the students which were on file at the twelve schools involved in the study. Measuring instruments used to collect data were: the Otis Quick Scorinq Mental Ability Tests, which were given at the sixth grade level; the assessment of reading achievement for grade three, four, and five were based on the reading subtest of the Stanford Achievement Test; and the assessment of the reading achievement for grade six which was based on the reading subtest of the SRA Achievement Series. An informal questionnaire, prepared for the purpose of this study to discover the bussed pupils' feelings toward the situation in the receiving school was administered by the author to the bussed pupils in May, 1969.ConclusionsThe following conclusions are based upon the findings secured from the data and within the limitations established for the study.1. One or two years of bussing for pupils at the fifth and sixth grade level has a positive effect on reading achievement scores. This conclusion is based on the finding that the evidence was statistically significant in favor of the bussed group. This significant difference between the bussed and non-bussed group on the basis of reading achievement increased after two years of bussing.2. One or two years of bussing at the fifth and sixth grade levels has a positive effect on pupils' growth toward reading expectancy levels. This conclusion is based on the finding that after one year of bussing the bussed group gained slightly over the non-bussed group. After two years of bussing the difference in favor of the bussed group was statistically significant at the .05 level of confidence.3. Two years of bussing at the fifth and sixth grade levels has little effect on the number of times pupils are above the median of the four discrepancy scores. This conclusion is based on the finding that there was no statistically significant difference between the bussed and non-bussed groups.4. Students' attitudes toward the receiving school do not seem to affect reading achievement. This conclusion is based on the finding that the relationship between the two does not exceed chance.