This thesis presents an axisymmetric numerical model to simulate interfacial flows near a sharp corner, where contact line pinning occurs. The method has been used to analyze drop imbibition into a capillary. To evaluate the performance of the numerical method, for a liquid drop initially placed partially within a capillary, a thermodynamic model has also been developed, to predict equilibrium states. The first part of this thesis presents an axisymmetric VoF algorithm to simulate interfacial flows near a sharp corner. (1) A new method to exactly calculate the normals and curvatures of any circle with a radius as small as the grid size is presented. This method is a hybrid least squares height function technique which fits a discretized osculating circle to a curve, from which interface normals and curvature can be evaluated. (2) A novel technique for applying the contact angle boundary condition has been devised, based on the definition of an osculating circle near a solid phase. (3) A new flux volume construction technique is presented, which can be applied to any split advection scheme. Unlike the traditional approach where the flux volumes are assumed rectangular, the new flux volumes can be either trapezoidal or triangular. The new technique improves the accuracy and consistency of the advection scheme. (4) Explicit PLIC reconstruction expressions for axisymmetric coordinates have been derived. (5) Finally, a numerical treatment of VoF for contact line motion near a sharp corner is presented, base on the idea of contact line pinning and an edge contact angle. The second part of the thesis is on the imbibition of a drop into an open capillary. A thermodynamic analysis based on minimization of an interfacial surface energy function is presented to predict equilibrium configurations of drops. Based on the drop size compared to the hole size, the equilibrium contact angle, and the geometry of the capillary, the drop can be totally imbibed by the capillary, or may not wet the capillary at all. The thesis concludes with application of the numerical scheme to the same problem, to examine the dynamics of wetting or dewetting of a capillary. All of the simulations yield results that correspond to the equilibrium states predicted by the thermodynamic analysis, but offer additional insight on contact line motion and interface deformation near the capillary edge.

This study examined the associations between social adversity, barriers-to-care (logistical obstacles, wait-time) and participation in children’s mental health treatment. The theoretical role of child symptoms (impact on the child, family burden) was addressed. Records were obtained for 1,963 parents who had accessed community-based care for their child (3-17 years). Data were collected as part of a provincial (Ontario, Canada) screening and outcome measurement initiative. The data were analyzed using multivariate logistic regression. Children with behavioural problems were at increased risk for attrition from treatment (OR=1.47, p < 0.001). The effect held upon controlling for age, gender, and co-morbid emotional symptoms; however, it was explained by child functional impairment. Similar effects were not found for the impact of symptoms on the family. Dropout was greater for adolescents (OR=1.43, p < 0.01) than younger children. Disadvantaged youth were more likely to drop out than more advantaged clients (OR=1.86, p < 0.001). Perceptions of difficulties in attending treatment were associated with a decreased risk (OR=0.89, p < 0.001). The adversity and service relationships were not mediated by child behavioural symptoms, functioning, or family burden. Waiting for care did not influence parent decisions to participate. Moderation analyses showed effects for adversity, service obstacles, emotional symptoms, functional impairment, and family burden for clients with behavioural problems. These children were more likely to drop out if they were socially disadvantaged, or had functional impairment at intake to services. However, completion was more likely for co-morbid children, and parental reports of burden. Families were also willing to overcome access difficulties in order to continue with treatment. There were few findings for children without behavioural problems. The results suggest a focus on other constructs, such as parent cognitions, that may link adversity and barriers with participation. The effects for symptoms as a moderator, suggests different levels of service provision based on sub-types of children. Efforts to engage “high-risk” clients are necessary. On the other hand, resources for intensive services would be appropriate for clients with more severe problems.

Despite previous research in this area, the relationship between immigration and crime in the United States remains ambiguous and surrounded by misconceptions. However, recently, scholars have suggested that, despite the claims of policy-makers and popularized sociological theories, large immigrant concentrations may be linked with lower as opposed to higher crime rates. In the past, research in this area has been imprecise due to it its implementation of cross-sectional analyses for a limited selection of geographic regions. However, through the implementation of time-series procedures and the use of annual data for metropolitan statistical areas during the 2005–2010 periods, the present study evaluates the impact of changes in immigration concentration on changes in crime rates, both violent and non-violent. These multivariate analyses specify that violent and property crime rates generally decreased as metropolitan areas experienced increases in their proportion of immigrants. These results confirm the hypothesis that the recent decline in crime is partially due to increases in the concentration of foreign-born individuals.

No description available.

No description available.

Being able to study at the Municipal Adult Education, Komvux, is a privilege available to adults in Sweden of age 20 and above. Although almost 200 000 people attended Komvux 2011 in Sweden, a fifth of the participants discontinued their studies before completing their course(s). This becomes costly for the society, but it is also diminishes the future chances of a career and college studies. In our thesis we have done a quantitative investigation trying to determine what the reasons for dropping out could be. A request to participate in our survey were sent out to all 64 people who dropped out one or more courses during the fall semester 2012 at a Municipal Adult Education in southern Norrland. Almost half, 32 people, agreed to participate. The results indicated that most students applied to Komvux because they were lacking complete exams of high school or part of it. According to the home-background, most of the 32 pupils came from homes where none of the parents had a college degree. One third of the pupils in the survey dropped out because of work related reasons. More than half of those who had dropped off studied a distance learning course, or a combination of distance and regular courses. / Att studera inom kommunal vuxenutbildning, Komvux, är en förmån som finns i Sverige för vuxna från och med det andra kalenderhalvåret då man fyller 20 år. Nästan 200 000 personer var inskrivna på Komvux i Sverige år 2011, men var femte kursdeltagare beslutade ändå att hoppa av sina studier innan de avslutat kursen/eller kurserna. Detta är både kostsamt för samhället men också en fråga om individens möjliga framtid inom högre studier och arbetsmarknaden. Studiens syfte var att undersöka vad anledningarna av avhoppen kan vara, och detta har vi gjort i en kvantitativ undersökning. En förfrågan skickades ut till samtliga 64 personer som hoppat av en eller flera kurser under höstterminen i en kommunal vuxenskola i södra Norrland, om de vill medverka i vår enkätundersökning via telefon. Nästan hälften, 32 personer, ville medverka. Slutsatsen av svaren vi fick in tydde på att de flesta elever som sökte Komvux saknade grundläggande behörighet eller slutbetyg. En tredjedel av eleverna hoppade av på grund av arbete. De flesta kom från ett hem där ingen av föräldrarna hade högskoleutbildning samt att över hälften av eleverna gick på distansutbildning eller kombinerade distans och reguljär kurs.

Forced air cooling of electronic packages is enhanced through the use of extended surfaces or heat sinks that reduce boundary resistance allowing heat generating devices to operate at lower temperatures, thereby improving reliability. Unfortunately, the clearance zones or bypass regions surrounding the heat sink, channel some of the cooling air mass away from the heat sink, making it difficult to accurately estimate thermal performance. The design of an "optimized" heat sink requires a complete knowledge of all thermal resistances between the heat source and the ambient air, therefore, it is imperative that the boundary resistance is properly characterized, since it is typically the controlling resistance in the path. Existing models are difficult to incorporate into optimization routines because they do not provide a means of predicting flow bypass based on information at hand, such as heat sink geometry or approach velocity. <br /><br /> A procedure is presented that allows the simultaneous optimization of heat sink design parameters based on a minimization of the entropy generation associated with thermal resistance and fluid pressure drop. All relevant design parameters such as geometric parameters of a heat sink, source and bypass configurations, heat dissipation, material properties and flow conditions can be simultaneously optimized to characterize a heat sink that minimizes entropy generation and in turn results in a minimum operating temperature of an electronic component. <br /><br /> An analytical model for predicting air flow and pressure drop across the heat sink is developed by applying conservation of mass and momentum over the bypass regions and in the flow channels established between the fins of the heat sink. The model is applicable for the entire laminar flow range and any type of bypass (side, top or side and top both) or fully shrouded configurations. During the development of the model, the flow was assumed to be steady, laminar, developing flow. The model is also correlated to a simple equation within 8% confidence level for an easy implementation into the entropy generation minimization procedure. The influence of all the resistances to heat transfer associated with a heat sink are studied, and an order of magnitude analysis is carried out to include only the influential resistances in the thermal resistance model. Spreading and material resistances due to the geometry of the base plate, conduction and convection resistances associated with the fins of the heat sink and convection resistance of the wetted surfaces of the base plate are considered for the development of a thermal resistance model. The thermal resistance and pressure drop model are shown to be in good agreement with the experimental data over a wide range of flow conditions, heat sink geometries, bypass configurations and power levels, typical of many applications found in microelectronics and related fields. Data published in the open literature are also used to show the flexibility of the models to simulate a variety of applications. <br /><br /> The proposed thermal resistance and pressure drop model are successfully used in the entropy generation minimization procedure to design a heat sink with bypass for optimum dimensions and performance. A sensitivity analysis is also carried out to check the influence of bypass configurations, power levels, heat sink materials and the coverage ratio on the optimum dimensions and performance of a heat sink and it is found that any change in these parameters results in a change in the optimized heat sink dimensions and flow conditions associated with the application for optimal heat sink performance.

No description available.

Forced air cooling of electronic packages is enhanced through the use of extended surfaces or heat sinks that reduce boundary resistance allowing heat generating devices to operate at lower temperatures, thereby improving reliability. Unfortunately, the clearance zones or bypass regions surrounding the heat sink, channel some of the cooling air mass away from the heat sink, making it difficult to accurately estimate thermal performance. The design of an "optimized" heat sink requires a complete knowledge of all thermal resistances between the heat source and the ambient air, therefore, it is imperative that the boundary resistance is properly characterized, since it is typically the controlling resistance in the path. Existing models are difficult to incorporate into optimization routines because they do not provide a means of predicting flow bypass based on information at hand, such as heat sink geometry or approach velocity. <br /><br /> A procedure is presented that allows the simultaneous optimization of heat sink design parameters based on a minimization of the entropy generation associated with thermal resistance and fluid pressure drop. All relevant design parameters such as geometric parameters of a heat sink, source and bypass configurations, heat dissipation, material properties and flow conditions can be simultaneously optimized to characterize a heat sink that minimizes entropy generation and in turn results in a minimum operating temperature of an electronic component. <br /><br /> An analytical model for predicting air flow and pressure drop across the heat sink is developed by applying conservation of mass and momentum over the bypass regions and in the flow channels established between the fins of the heat sink. The model is applicable for the entire laminar flow range and any type of bypass (side, top or side and top both) or fully shrouded configurations. During the development of the model, the flow was assumed to be steady, laminar, developing flow. The model is also correlated to a simple equation within 8% confidence level for an easy implementation into the entropy generation minimization procedure. The influence of all the resistances to heat transfer associated with a heat sink are studied, and an order of magnitude analysis is carried out to include only the influential resistances in the thermal resistance model. Spreading and material resistances due to the geometry of the base plate, conduction and convection resistances associated with the fins of the heat sink and convection resistance of the wetted surfaces of the base plate are considered for the development of a thermal resistance model. The thermal resistance and pressure drop model are shown to be in good agreement with the experimental data over a wide range of flow conditions, heat sink geometries, bypass configurations and power levels, typical of many applications found in microelectronics and related fields. Data published in the open literature are also used to show the flexibility of the models to simulate a variety of applications. <br /><br /> The proposed thermal resistance and pressure drop model are successfully used in the entropy generation minimization procedure to design a heat sink with bypass for optimum dimensions and performance. A sensitivity analysis is also carried out to check the influence of bypass configurations, power levels, heat sink materials and the coverage ratio on the optimum dimensions and performance of a heat sink and it is found that any change in these parameters results in a change in the optimized heat sink dimensions and flow conditions associated with the application for optimal heat sink performance.

The imperfections in the semiconductor fabrication process and uncertainty in operating environment of VLSI circuits have emerged as critical challenges for the semiconductor industry. These are generally termed as process and environment variations, which lead to uncertainty in performance and unreliable operation of the circuits. These problems have been further aggravated in scaled nanometer technologies due to increased process variations and reduced operating voltage. Several techniques have been proposed recently for designing digital VLSI circuits under variability. However, most of them have targeted ASICs and custom designs. The flexibility of reconfiguration and unknown end application in FPGAs make design under variability different for FPGAs compared to ASICs and custom designs, and the techniques proposed for ASICs and custom designs cannot be directly applied to FPGAs. An important design consideration is to minimize the modifications in architecture and circuit to reduce the cost of changing the existing FPGA architecture and circuit. The focus of this work can be divided into three principal categories, which are, improving timing yield under process variations, improving power yield under process variations and improving the voltage profile in the FPGA power grid. The work on timing yield improvement proposes routing architecture enhancements along with CAD techniques to improve the timing yield of FPGA designs. The work on power yield improvement for FPGAs selects a low power dual-Vdd FPGA design as the baseline FPGA architecture for developing power yield enhancement techniques. It proposes CAD techniques to improve the power yield of FPGAs. A mathematical programming technique is proposed to determine the parameters of the buffers in the interconnect such as the sizes of the transistors and threshold voltage of the transistors, all within constraints, such that the leakage variability is minimized under delay constraints. Two CAD techniques are investigated and proposed to improve the supply voltage profile of the power grids in FPGAs. The first technique is a place and route technique and the second technique is a logic clustering technique to reduce IR-drops and spatial variation of supply voltage in the power grid.