Thesis (MSc)--Stellenbosch University, 2013. / Please refer to full text to view abstract.

It is known that record values and order statistics are closely related. When record values and order statistics are viewed as point processes, the two processes both share the order statistics property. The results of Beg and Balasubramanian(1990), Wu and Ouyang(1996), and Huang and Su(1999) about record values and order statistics motivated us to investigate more general results of characterization for order statistics point processes by using conditional expectations based on order statistics. On the other hand, in the class of point processes, there are a lot of characterizations of homogeneous Poisson processes based on the memoryless property of exponential distribution. The result of Asadi(1999) about characterization of the Gumble bivariate exponential or the bivariate geometric distribution inspired us be interested in investigating some similar results about non-independent bivarite homogeneous Poisson processes.

Cette étude introduit une nouvelle approche appelée Bivariate 2D-EMD pour séparer le mouvement organisé à grande échelle, soit la composante basse fréquence de l’écoulement des fluctuations turbulentes, soit la composante haute fréquence dans un champ de vitesse instantané bidimensionnel.Cette séparation nécessite un seul champ de vitesse instantané contrairement aux autres méthodes plus couramment utilisées en mécanique des fluides, comme le POD. La méthode proposée durant cette thèse est tout à fait appropriée à l’analyse des écoulements qui sont intrinsèquement instationnaires et non linéaires comme l'écoulement dans le cylindre lorsque le moteur fonctionne dans des conditions transitoires. Bivariate 2D-EMD est validé à travers différents cas test, sur un écoulement turbulent homogène et isotrope (THI) expérimental, qui a été perturbé par un tourbillon synthétique de type Lamb-Ossen, qui simule le mouvement organisé dans le cylindre. Enfin, Il est appliqué sur un écoulement expérimental obtenu dans un cylindre et les résultats de la séparation d'écoulement sont comparés à ceux basés sur l'analyse POD. L’évolution d’écoulement dans le cylindre pendant le fonctionnement du moteur transitoire, c’est à dire une accélération du régime moteur de 1000 à 2000tr/min en différentes rampes, sont mesurée en utilisant de PIV 2D-2C haute cadence. Les champs de vitesse sont obtenus dans le plan de tumble dans un moteur un moteur GDI mono-cylindre transparent et forment une base de données nécessaire pour valider les résultats de simulation numérique. / This study introduces a new approach called Bivariate 2D-EMD to separate large-scale organizedmotion i.e., flow low frequency component from random turbulent fluctuations i.e., high frequency onein a given in-cylinder instantaneous 2D velocity field. This signal processing method needs only oneinstantaneous velocity field contrary to the other methods commonly used in fluid mechanics, as POD.The proposed method is quite appropriate to analyze the flows intrinsically both unsteady and nonlinearflows as in in-cylinder. The Bivariate 2D-EMD is validated through different test cases, by optimize itand apply it on an experimental homogeneous and isotropic turbulent flow (HIT), perturbed by asynthetic Lamb-Ossen vortex, to simulate the feature of in-cylinder flows. Furthermore, it applies onexperimental in-cylinder flows. The results obtained by EMD and POD analysis are compared. Theevolution of in-cylinder flow during transient engine working mode, i.e., engine speed acceleration from1000 to 2000 rpm with different time periods, was obtained by High speed PIV 2D-2C. The velocityfields are obtained within tumble plane in a transparent mono-cylinder DISI engine and provide a database to validate CFD.

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近年來台灣面臨了人口高齡化的現象，有關中高齡人口的議題成為了學者與社會大眾關注的焦點，其中，自1988以來中高齡已婚男性勞動參與率至2008年為止已下降了約十個百分點，這個現象值得我們去深入了解。本篇論文主要在探討中高齡已婚男性勞動參與的決定因素，研究的資料來源為1988至2008年的人力資源及人力運用調查。其中，我選擇了55至64歲的已婚男性為對象，而總樣本數為51,730，本論文先以probit與bivariate probit模型估計每一個變數對中高齡已婚男性勞動決策的邊際影響效果，再以Oaxaca與DiNardo, Fortin, and Lemieux (DFL)分解模式，試著拆解每一個變數對整體中高齡已婚男性勞動參與率的影響性。 此篇論文著重在兩個主要變數對中高齡已婚男性勞動參與的影響:妻子的勞動參與以及地區性的失業率。近年來越來越多已婚婦女投入職場，我想了解婦女勞動參與率的上升，對整體丈夫勞動參與率的影響；另外地區的失業率是表現出地區勞動市場的重要指標之一，過去的文獻提到失業嚴重的地區可能使當地勞工失業後找不到工作，或使想進入職場的勞工卻步。此篇論文研究結果顯示妻子的勞動參與會顯著的影響先生對勞動市場去留的決定，妻子影響個人的勞動參與機率6~18%左右，而1%地區性失業率的上升，則是對個人的勞動參與機率下降的影響約1.5%左右。在1988年至2008年整體中高齡已婚男性勞動參與率的分解中，勞動參與率下降了3.5%（占整體變化40%），可歸咎於地區失業率的升高。而若妻子的勞動參與沒有提升，仍維持1988年的水準，整體丈夫的勞動參與率將會下降1%（占整體變化10%）左右，本論文認為若政府能維持良好的就業市場環境，將有助於提高中高齡已婚男性人口勞動參與的比率，進一步能有效提高勞動生產力及降低社會負擔。 / As the proportion of the old population increases in Taiwan, issues of older individuals’ behavior attract public attention. During 1988 to 2008, labor force participation rate of older married men declined over 10 percent. What can explain this decline? This thesis tries to find out the determinants of older married men’s labor force participation in Taiwan. I use the data from Manpower Survey and Manpower Utilization Survey from 1988 to 2008, conducted by Directorate General of Budget, Accounting and Statistics (DGBAS). The sample comprise 51,730 observations of married men aged 55-64. Older married men’s labor participation decision is treated as a dependent variable and estimates are made with a probit and a bivariate probit model. Decompositions with methodology of DiNardo, Fortin, and Lemieux (1996) and Oaxaca (1973) are conducted for explaining the decline in labor participation rate of older married men between 1988 and 2008. The results indicate that the increase in wives’ labor force participation increases husband’s likelihood of participation and prevents aggregate husbands’ participation rate from declining about 1 percentage point (-8 percent of total decline). However, regional unemployment rate negatively affects husband’s likelihood of participation and can explain at least 3.5 percent (40 percent of total decline) of the decline in husband’s participation rate. This thesis suggests the labor force participation rate could be stopped from declining if the government maintains good labor market condition.

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The increasingly serious pedestrian safety issue in the City of Austin aroused the concern. Other than conducting quantitative analysis at aggregate level via collecting and examining the secondary data extracted from the existing datasets, the authors shifted towards the disaggregate level analysis, focusing on twenty-six hotspots of pedestrian collisions via mixed method research. Qualitative data was collected in the field survey to precisely capture the contextual features of collision locations, and was interpreted and coded as explanatory variables for the quantitative analysis. Instead of the frequency of pedestrian collision, crash rate measured by incident count per million pedestrians was the dependent variable to identify the factors truly influencing the pedestrian safety issue, not just the total number of walkers. The stepwise bivariate analysis and negative binomial regression examined the association between pedestrian collision rate and independent variables. Finally, the average block length, speed limit posted, sidewalk condition, and the degree of proximity to major pedestrian attractors were statistically significant factors correlating with the pedestrian collision risk. / text

In this thesis the utility of a bivariate gamma distribution is explored. In the field of nutritional epidemiology a nutrition density transformation is used to reduce collinearity. This phenomenon will be shown to result due to the independent variables following a bivariate gamma model. In the field of radiation oncology paired comparison of variances is often performed. The bivariate gamma model is also appropriate for fitting correlated variances. A method for simulating bivariate gamma random variables is presented. This method is used to generate data from several bivariate gamma models and the asymptotic properties of a test statistic, suggested for the radiation oncology application, is studied.

Neste trabalho propomos a representação de uma densidade bivariada segundo a natureza geométrica das marginais. Uma densidade contínua pode ser aproximada pela exponencial de um polinômio num domínio limitado. Tal aproximação permite estudar a influência do comportamento marginal e condicional sobre a densidade conjunta. Esse estudo é realizado encontrando os conjuntos dos possíveis valores dos coeficientes do polinômio segundo a informação dada sobre as densidades marginais ou as densidades condicionais. Também analisamos os coeficientes segundo algumas medidas de dependência. Concluímos mostrando a influência do comportamento marginal e condicional sobre variáveis aleatórias discretas. / In this work we propose a representation of a bivariate density according to the geometrical nature of the marginals. A continuous density can be approximated by the exponencial of a polynomial in a finite domain. Such approximation let us study the influence of the marginal and conditional behavior on the joint density. This study is done by finding the possible values of the polynomial coefficients upon the given information about the marginal or the conditional densities. We also analyze the coefficients according some dependence measures. We conclude showing the influence of the marginal and conditional behavior on discrete random variables.