Made available in DSpace on 2014-10-09T12:43:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:51Z (GMT). No. of bitstreams: 1 05404.pdf: 2708504 bytes, checksum: 1041726f601369567f34c17cf8a9d296 (MD5) / Dissetacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

No description available.

Paying specific attention to influences of life events and different timing of taking compulsory military service for Taiwanese people, this dissertation explores time-dependence of job mobility and class mobility throughout careers. The author criticizes that previous research of social mobility focusing on either differences between father’s and son’s classes or the relationship between one’s initial and current statuses do not realize the process of status attainment in which individual characteristics and life courses continuously interact with external structures in the labor market. The analyses in this dissertation demonstrate the dynamics of career mobility by specifying two career stages and investigating the differences in paces and mechanisms of job change and class mobility. All findings lead to the conclusion that the time dependence of career mobility is deeply embedded in the context of life course in a society. For Taiwanese men, the timing of taking CMS (i.e., before or after their first entry into the labor force), which is strongly correlated with their educational level, is crucial to the pace and type of career development. For Taiwanese women, their trajectories of mobility follow the typical scenario of career mobility in which job change happens often during the early career and then settles into relatively stable employment in the later stage. Compared to job mobility, status attainment is more stable and consistent throughout the life time. After specifying the directions of job mobility, results show that upward and downward mobility, which bring significant change in occupational prestige, do not show gender differences in their transition rates, and their patterns are consistent throughout careers. With respect to the transition between social classes, moving into ownership (including employers and self-employed) in later careers is a mainstream transition for all Taiwanese people in spite the fact that women have much lower transition rates than do men. Moreover, this dissertation also examines inter-sector and intra-sector mobility in segmented labor market in Taiwan. Taking selection bias into consideration, this research found that under the assumption of homogeneity, the treatment effects of initial attainment in the public sector have negative effects on job mobility throughout careers. However, when heterogeneity of treatment effects are taken into account, findings reveal that there is no significant heterogeneity in this treatment effect for Taiwanese men, but for Taiwan women, the more likely they are to attain a position in the public sector at the time of first entry into the labor market, based on their educational achievement and social background, the more they benefit via low transition rates of job mobility in their work lives. / text

Our sample (Xit; Yit) consists of pairs of variables. The real variable Xit measures the creditworthiness of individual i in period t. The Bernoulli variable Yit is the default indicator of individual i in period t. The objective is to estimate a credit rating system, i.e. to particularly divide the range of the creditworthiness into several rating classes, each with a homogeneous default risk. The field of change point analysis provides a way to estimate the breakpoints between the rating classes. As yet, the literature only considers models without dependencies or with dependence only in cross section. This contribution proposes multi-period models including dependencies in cross section as well as in longitudinal section. Furthermore, estimators for the model parameters are suggested. The estimators are applied to a data set of a German credit bureau.

Our sample (Xit; Yit) consists of pairs of variables. The real variable Xit measures the creditworthiness of individual i in period t. The Bernoulli variable Yit is the default indicator of individual i in period t. The objective is to estimate a credit rating system, i.e. to particularly divide the range of the creditworthiness into several rating classes, each with a homogeneous default risk. The field of change point analysis provides a way to estimate the breakpoints between the rating classes. As yet, the literature only considers models without dependencies or with dependence only in cross section. This contribution proposes multi-period models including dependencies in cross section as well as in longitudinal section. Furthermore, estimators for the model parameters are suggested. The estimators are applied to a data set of a German credit bureau.

No description available.

近年來台灣房屋仲介市場可說發展的相當快速，許多賣方和買方常基於成本的考量，而透過仲介公司來買賣房屋。當然，委託給仲介公司來買賣房屋。其中可能主要因素即著眼於縮短交易的時間或者是提高成交的機率，本研究的整個重心將圍繞在賣方的訂價高低(底價)賣屋動機與房屋的屬性來解釋銷售期間和成交機率的高低，並且本文擬得用搜尋理論和代理人理論來詮釋房地產仲介市場的交易行為。 本研究主要分成六章，第一章為緒論。第二章從搜尋理論的觀點來研究訂價與成交價和銷售期間的關係。我們從賣方決定訂價之後，買方會依據訂價要求折扣率，而賣方也會決定一願意給買方的最小折扣率的角度出發，來建構房屋搜尋模型。由理論得知，賣方折扣率底線愈大，則預期銷售期間愈長；銷售期間愈長，則預期賣方折扣率底線愈低；搜尋成本愈大，則預期賣方折扣率底線愈小；買方要求折扣率分配的平均數愈大，則預期賣方折扣率底線愈大。在實證研究上，利用信義房屋仲介公司所提供的資料(1990－1993)，以銷售期間和訂價相對於成交價的比例為應變數，採用聯立方程式的方式來估計分析。實證結果發現上述幾項論點皆獲得驗證與支持。 第三章模型同時考慮賣方和仲介業的行為，一方面說明賣方搜尋成本和買方所要求折扣率分配對銷售期間和成交機率的影響，另一方面提供未來修正理論模型的基礎。利用存活分析法(survival analysis)來估計銷售期間。一方面，我們要探究影響房屋交易之銷售期間的可能原因為何？另一方面，我們也想了解銷售期間是否具有時間相依性(time dependence)，是否銷售期間越長者，越不易賣出？或越容易賣出？ 第四章利用logit模型來估計房屋成交的機率，由於危險模型為純粹之計量模型，而非由理論模型所導出，所以分配之假設將限制其估計模型與理論的關連性，而logit模型則無此問題，因此本研究亦嘗試用logit模型來做估計。 第五章利用代理與搜尋模型來分析賣方和仲介業間的行為關係。不同的仲介收費制度--固定百分比收費(fixed-percentage commission)、定額制(flat－fee)、代銷(consignment sale)，對雙方利益衝突的衝擊為何，是否潛藏著嚴重的道德危險(moral hazard)。透過本篇的分析，可瞭解何以固定百分比收費制度是台灣房屋仲介市場的收費趨勢。最後一章為結論與未來研究方向。 / This paper employs search theory to study the re1ationships between the list price, the transaction price,and marketing duration in the Taiwan real estate market. Theoretically, buyer uses the a set of criteria together,with the listing price to develop an offer which is based on a (guest) minimurn discount rate guideline form the listing price to determine a price that will be acceptable to the seller. We attempt to describe the impact of pricing strategies (seller's minimum discoun rate) and marketing duration by incorporating the minimurn discount rate in a search model. The derived search model indicates the presence of a positbive retalionship between the minimurn discount rate and marketing duration;an inverse relationship beteween marketing duration and munimurn discount rate; an inverse relationship between searching costs and mininurn discount rate; and a positive relationship between the buyer's average discount rate of distribution function and minimum discount rate. The study uses data collected during the l990-1993 time period and provided by Hsin Yi Realty Co., with the dependent variables being the marketing duration and the ratio of the listing price to the transaction price. A simultaneous equation is developed and used to analyze the following hypotheses: firstly, the higher the ratio of the listing price against the transaction price, the longer it takes to reach the marketing duraion; secondly, the longer it takes to reach the marketing duraion, the higher the ratio of the listing price against the transaction price; thirdly, the longer the period of consignment, the longer it takes to reach the marketing duration; and the fourth,if the seller is not in a hurry to sell,then the marketing duration becomes longer. Our empirical findings verify and support all the above stated analyses.

Cette thèse est dédiée à améliorer la compréhension neuro-scientifique à l'aide d'imagerie par résonance magnétique de diffusion (IRMd). Nous nous concentrons sur la modélisation du signal de diffusion et l'estimation par IRMd des biomarqueurs liés à la microstructure, appelé «Microstructure Imaging». Cette thèse est organisée en trois parties. Dans partie I nous commençons par la base de l'IRMd et un aperçu de l'anisotropie en diffusion. Puis nous examinons la plupart des modèles de microstructure utilisant PGSE, en mettant l'accent sur leurs hypothèses et limites, suivi par une validation par l'histologie de la moelle épinière de leur estimation. La partie II présente nos contributions à l'imagerie en 3D et à l’estimation de microstructure. Nous proposons une régularisation laplacienne de la base fonctionnelle MAP, ce qui nous permet d'estimer de façon robuste les indices d'espace q liés au tissu. Nous appliquons cette approche aux données du Human Connectome Project, où nous l'utilisons comme prétraitement pour d'autres modèles de microstructure. Enfin, nous comparons les biomarqueurs dans une étude ex-vivo de rats Alzheimer à différents âges. La partie III présente nos contributions au représentation de l’espace qt - variant sur l'espace q 3D et le temps de diffusion. Nous présentons une approche initiale qui se concentre sur l'estimation du diamètre de l'axone depuis l'espace qt. Nous terminons avec notre approche finale, où nous proposons une nouvelle base fonctionnelle régularisée pour représenter de façon robuste le signal qt, appelé qt-IRMd. Ce qui permet l'estimation des indices d’espace q dépendants du temps, quantifiant la dépendance temporelle du signal IRMd. / This thesis is dedicated to furthering neuroscientific understanding of the human brain using diffusion-sensitized Magnetic Resonance Imaging (dMRI). Within dMRI, we focus on the estimation and interpretation of microstructure-related markers, often referred to as ``Microstructure Imaging''. This thesis is organized in three parts. Part I focuses on understanding the state-of-the-art in Microstructure Imaging. We start with the basic of diffusion MRI and a brief overview of diffusion anisotropy. We then review and compare most state-of-the-art microstructure models in PGSE-based Microstructure Imaging, emphasizing model assumptions and limitations, as well as validating them using spinal cord data with registered ground truth histology. In Part II we present our contributions to 3D q-space imaging and microstructure recovery. We propose closed-form Laplacian regularization for the recent MAP functional basis, allowing robust estimation of tissue-related q-space indices. We also apply this approach to Human Connectome Project data, where we use it as a preprocessing for other microstructure models. Finally, we compare tissue biomarkers in a ex-vivo study of Alzheimer rats at different ages. In Part III, we present our contributions to representing the qt-space - varying over 3D q-space and diffusion time. We present an initial approach that focuses on 3D axon diameter estimation from the qt-space. We end with our final approach, where we propose a novel, regularized functional basis to represent the qt-signal, which we call qt-dMRI. Our approach allows for the estimation of time-dependent q-space indices, which quantify the time-dependence of the diffusion signal.