The existing estimation techniques for grouped data models can be analyzed as a class of estimators of instrumental variable-Generalized Method of Moments (GMM) type with the matrix of group indicators being the set of instruments. Econometric literature (e.g. Smith, 1997; Newey and Smith, 2004) show that, in some cases of empirical relevance, GMM can have shortcomings in terms of the large sample behaviour of the estimator being different from the finite sample properties. Generalized Empirical Likelihood (GEL) estimators are developed that are not sensitive to the nature and number of instruments and possess improved finite sample properties compared to GMM estimators. In this thesis, with the assumption that the data vector is iid within a group, but inid across groups, we developed GEL estimators for grouped data model having population moment conditions of zero mean of errors in each group. First order asymptotic analysis of the estimators show that they are √N consistent (N being the sample size) and normally distributed. The thesis explores second order bias properties that demonstrate sources of bias and differences between choices of GEL estimators. Specifically, the second order bias depends on the third moments of the group errors and correlation among the group errors and explanatory variables. With symmetric errors and no endogeneity all three estimators Empirical Likelihood (EL), Exponential Tilting (ET) and Continuous Updating Estimator (CUE) yield unbiased estimators. A detailed simulation exercise is performed to test comparative performance of the EL, ET and their bias corrected estimators to the standard 2SLS/GMM estimators. Simulation results reveal that while, with a few strong instruments, we can simply use 2SLS/GMM estimators, in case of many and/or weak instruments, increased degree of endogeneity, or varied signal to noise ratio, bias corrected EL, ET estimators dominate in terms of both least bias and accurate coverage proportions of asymptotic confidence intervals even for a considerably large sample. The thesis includes a case where there are within group dependent data, to assess the consequences of a key assumption being violated, namely the within-group iid assumption. Theoretical analysis and simulation results show that ignoring this feature can result in misleading inference. The proposed estimators are used to estimate the returns to an additional year of schooling in the UK using Labour Force Survey data over 1997-2009. Pooling the 13 years data yields roughly the same estimate of 11.27% return for British-born men aged 25-50 using any of the estimation techniques. In contrast using 2009 LFS data only, for a relatively small sample and many weak instruments, the return to first degree holder men is 13.88% using EL bias corrected estimator, where 2SLS estimator yields an estimate of 6.8%.

A "Geometrodynamical Analog to Electric Charge" (or "p-charge") is defined (as in the earlier paper by Unruh, [Gen. Rel. and Grav., 2, (1971), pp 27-33 ] to be the period on a p-cycle (p = 1, 2, or 3) of a p-form which is constructed out of only the Riemann tensor or its derivatives. A previously-unpublished proof by Unruh is briefly summarized which proves that no non-zero p-charges can exist on a completely unrestricted metric field. The metric field is then constrained to obey Einstein's equations for empty space, and sets of linearly-independent, purely-gravitational p-forms are analyzed to determine if p-charges can be defined under these conditions. A scheme is developed, based on the spin-tensor representation of the gravitational field, to generate complete sets of such p-forms, arid calculate their derivatives, with a symbolic-manipulation computer program. It is shown that no gravitational p-forms that are linear combinations of less than five Riemann tensors and less than nine derivatives will result in p-charges. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

La conception robuste de pièce mécaniques consiste à prendre en compte dans la modélisation les sources d'incertitudes.Le modèle devient alors assez représentatif de la réalité pour pouvoir diminuer les marges de sécurité, qui permettent de garantir que la pièce en fonctionnement ne sera pas mise en défaut.Dans le cas de pièces aérospatiales, une diminution des marges de sécurité est un enjeu économique majeur car cela entraîne une diminution du poids des pièces.La probabilité de défaillance est une des quantités critiques lors de la conception robuste. Celle-ci quantifie le risque de défaillance de la pièce en comparant la probabilité de résistance du matériau (caractérisée à partir d'essais sur éprouvettes) avec la probabilité de sollicitation du matériau, qui est déterminée à partir des contraintes extérieures à la pièce et des caractéristiques du matériau. C'est ce dernier problème qui a fait l'objet de cette thèse.Dans le cas d'un comportement non linéaire du matériau, la détermination de la probabilité de sollicitation impose d'exécuter de nombreuses fois un calcul de la pièce pour différentes valeurs des conditions aux limites et des paramètres du comportement matériau.Ceci devient rapidement hors de portée sans une stratégie adaptée, un calcul pouvant prendre jusqu'à 12 heures.Une stratégie dédiée à la résolution de l'ensemble de ces calculs est proposée dans ce travail. Elle tire parti de la similarité des calculs pour diminuer le temps total nécessaire. Un gain allant jusqu'à 30 est atteint sur des pièces industrielles simples en quasi-statique avec un comportement élasto-viscoplastique. / The robust design of mechanical parts consists in modeling the sources of uncertainty.The model becomes fairly representative of the reality in order to reduce safety margins, which guarantee that the operating part will not been at fault.In the case of aerospace parts, a reduction of safety margins is a major economic issue as it leads to a decrease in weight.The probability of failure is a critical quantity in the robust design. It quantifies the risk of failure of the part by comparing the likelihood of resistance of the material (characterized from tests on specimens) with the probability of solicitation of the material, which is determined from external constraints to the part and characteristics of the material. This last problem has been the subject of this thesis.In the case of a non-linear behavior of the material, determining the probability of solicitation requires to run many times a calculation of the part for different values of boundary conditions and parameters values of the material constitutive law.This is quickly becoming out of reach without an appropriate strategy, as one calculation can take up to 12 hours.A strategy dedicated to solving all of these calculations is proposed in this work. It takes advantage of the similarity of the calculations to reduce the total time required. A gain of up to 30 is reached on industrial parts with quasi-static elastic-viscoplastic behavior.

Aujourd'hui, les outils de simulations numériques sont omniprésents dans l'industrie, que ce soit dans l'industrie aéronautique, aérospatiale, ferroviaire ou automobile.En effet leur utilisation limite la fabrication (souvent très couteuse) de prototype, et permettent ainsi de réduire les couts et d'accélérer la phase de conception d'un nouveau produit.Dans le cadre des applications acoustiques, il est souvent recommandé de calculer la réponse sur l'ensemble de la bande de fréquences d'intérêt.Les outils de simulation numérique sur une bande de fréquences impliquent généralement plusieurs calculs à fréquences fixes.Même si c'est un moyen simple et naturel pour répondre au problème posé, une telle stratégie peut facilement conduire à des calculs énormes. Cela est particulièrement vrai dans la gamme des moyennes fréquences, où la réponse est particulièrement sensible à la fréquence.Dans cette thèse, la PGD (Proper Generalized Decomposition), est appliqué pour trouver une représentation fonctionnelle distincte de la fréquence et de l'amplitude des inconnues de la TVRC (théorie variationnelle des rayons complexes) sur une bande de fréquences donnée.Ceci permet d'obtenir une réponse de haute qualité sur une large bande en moyennes fréquences, sans nécessité de discrétisation fine de la plage de fréquences considérées. En outre, la représentation PGD de la solution permet d'économiser une grande quantité d'espace en terme de stockage de données. Dans un second temps, la technique PGD a été étendue à la stochastique. / In many industrial contexts, such as aerospace applications or cars design, numerical prediction techniquesbecome more and more useful. They restrict the use of real prototypes to a minimum and make easier thedesign phase. In such industries and in the specific for acoustic, engineers are interested in computing theresponses of systems on frequency bands. In order to predict the vibration behavior of systems overfrequency bands, standard numerical techniques usually involve many frequency-fixed computations, atmany different frequencies. Although it is a straightforward and natural mean to answer to the posed problem,such a strategy can easily lead to huge computations, and the amount of data to store often increasessignificantly. This is particularly true in the context of medium frequency bands, where these responses havea strong sensitivity to the frequency. In this work PGD (Proper Generalized Decomposition), in a first time, isapplied to found a separate functional representation over frequency and space of the unknown amplitude ofVTCR (Variational Theory of Complex Rays) formulation on a reduced frequency space. This allows tocalculate an high quality mid-frequency response over a wide band without a fine frequency discretization,saving computational resources. Moreover the PGD representation of the solution allows to save a hugeamount of space in term of stored data. In a second time, PGD technique as been applied to extend itspeculiarity to mid-frequency wide band with uncertainty.

京都大学 / 新制・課程博士 / 博士(情報学) / 甲第23313号 / 情博第749号 / 新制||情||128(附属図書館) / 京都大学大学院情報学研究科知能情報学専攻 / (主査)教授 鹿島 久嗣, 教授 山本 章博, 教授 吉川 正俊 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

Microwave photonic applications in the terahertz (THz) region of the spectrum are attracting increasing attention due to the need to find solutions for next-generation (5G/6G) wireless communication systems capable of handling unprecedented data rates. It is crucial to develop millimeter-wave (mm-wave) (30-300GHz) fiber supported transport networks. One of the key questions is, which carrier frequency generation technique will be the most suitable for THz signals above 300 GHz; electronics-based or photonics-based. Since the backbone of the wireless networks is composed by very high-capacity fibre optic cables, the microwave photonic approach has the ultimate advantage of seamless integration with existing optical fibre networks. Although the cost effectiveness is still an open question, simplistic base station architecture with simplified antenna units and high optical component reuse is necessary for enabling a compatible mobile network backhaul. For THz applications a broadband electro-optic modulator (EOM) with a frequency response extending to the sub-terahertz range, high power handling, and very low nonlinear distortions, is required. The objective of this thesis is to study the feasibility of photonic integration and, proof of concept implementations with the effective use of optical components with reduced energy consumption, reduced footprint and offer speed beyond all-electronic implementations. The first study presents a coherent electro-optic photonic integrated circuit deploying generalized Mach-Zehnder interferometer (GMZI) substituting N×1 combiner by an optical N×N discrete Fourier transform (DFT) in order to generate a regularly spaced frequency comb. The proposed design comprises of 1×N splitter that feeds light into a parallel array of N electro-optic phase modulators electrically driven by RF signal with a progressive phase shift with their phase modulated optical outputs processed by an N×N optical DFT. A pragmatic design approach and analytical formulation for implementing MMI based optical DFT in photonic networks composed of waveguide splitters, combiners, and phase-shift elements with necessary circuit diagram for even and odd dimensions are presented. Recently, there has been impressive progress toward ultra-wide band low voltage EOM. The heterogeneous approach of utilizing silicon nitride on lithium niobate waveguide integrated on a single chip is demonstrated for the best optical modulation performance that opens a wide range of opportunities for universal linear optical networks, chip-scale MWP systems, ultra-speed switching of optical communications. Finally, the third study de-scribes the architecture for compact on-chip spectrometry targeting high resolution across the entire C-band to measure the spectral profile of WDM signals reliably and accurately in fixed and flex-grid architectures. The design architecture of technologically viable com-pact on-chip high-resolution wideband spectrometer such as Mach-Zehnder delay interferometers (MZDI), 2×2 directional couplers and multimode interference couplers is presented and verified by software simulation using an industry standard tool. The components simulations that supported the assessment of the feasibility of a spectrometer compliant with the specification made use of the LioniX asymmetric double strip (ADS) waveguide and the low-cost photolithography.

Social anxiety disorder (SAD) is characterized by fear and avoidance of social interactions and situations in which an individual is being the focus of attention. This current thesis aims to examine the efficacy of pharmacological treatment, particularly selective serotonin reuptake inhibitors (SSRIs) in individuals with a generalized social anxiety disorder (gSAD) in comparison with placebo (no active medication). In this systematic review, Scopus and Web of Science were searched for relevant research regarding the efficacy of the SSRI medication (paroxetine, sertraline, fluvoxamine and escitalopram) in comparison with placebo. Sixteen articles were included in this analysis. Results demonstrated that SSRI medication has greater efficacy in comparison with placebo both in short- and long-term time, prevent relapse in the long-term treatment of SAD and had a beneficial effect on different areas of individuals life's such as work, performance, romantic relationships etc.

Philosophiae Doctor - PhD / This dissertation explored the degree and distribution of social capital forms-social networks, volunteer associations, generalized trust, particularized trust and norms of reciprocity in rural Ethiopia. It aims to contribute to the academic understanding of social capital formation in Africa. Whereas the extent of literature focused on uncovering difference in the distribution of social capital at macro, meso and micro levels, this dissertation instead unpacks how political and economic conditions in rural Ethiopia shape the extent of the different forms of social capital at different levels.

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