This thesis consists of four self-contained studies in empirical labor economics. Micro data on both employers and workers are used to analyze the questions asked in the essays. By using disaggregated information, issues related to firm and individual heterogeneity can be studied.The first essay, The Impact of Temporary Contracts on Gross Job and Worker Flows (with Mahmood Arai), examines job and worker flow dynamics for temporary and permanent contracts. The micro approach to job flows concerns changes in employment at the plant or firm level. Data used in earlier research on gross labor flows do not allow for a distinction between different types of employment contracts (an exception is Abowd et al. (1999). This distinction is especially important in Europe since several European countries discriminate between permanent and temporary contracts in their employment legislation.The data contain quarterly information on the stock of permanent and temporary contracts, as well as direct information on hires and separations for permanent and temporary workers. The information is from a representative sample of around 10,000 Swedish private establishments.The results indicate that temporary contracts, covering only around 10 percent of all contracts, stand for half of all gross job (and worker) flows. This means that gross job (and worker) flow rates for temporary contracts are around 10 times larger than job (and worker) flows for permanent contracts. Our results imply that job reallocation associated with temporary contracts is acyclical in both manufacturing and non-manufacturing sectors. For permanent contracts, job reallocation only exhibits a countercyclical pattern in manufacturing, characterized by a low fraction of temporary contracts. Services employing a higher fraction of temporary contracts exhibit no cyclical pattern in job reallocation, implying that establishments in services use temporary contracts as an adjustment buffer and can adjust its labor input more smoothly.The share of temporary contracts varies with the industry structure and changes as a result of sectoral shifts. This implies that cross-country comparisons, as well as studies of the dynamics of job and worker flows, based on aggregated time-series data, can be distorted by the impact of the fraction of temporary labor on gross labor flows. This, in turn, makes the distinction between permanent and temporary contracts crucial in analyzing job and worker flows, especially when labor protection laws discriminate between short-and long-term employment contracts. The second essay, Wage Dispersion and Allocation of Jobs, investigates the relationship between job turnover and the distribution of wages. One possible explanation for similar labor reallocation rates across labor markets with very different employment-protection legislations is related to differences in wage setting institutions. Bertola and Rogerson (1997) argue that although job-security laws lead to lower job flows, their impact might be reduced if differences in wage-setting institutions have opposite effects. Bertola and Rogerson’s conclusion is that when labor protection laws and wages are jointly considered, the result might very well be that job flows in countries with high adjustment costs and a compressed wage structure mimic those in countries with low adjustment costs and decentralized wages.Using establishment data on job turnover and wages for a panel of around 10,000 establishments in the Swedish private sector, the relationship between wage compression and job reallocation is studied at the industry level.Estimating industry fixed-effects models for 14 two-digit industries yield results indicating large sector differences regarding the effect of the degree of wage dispersion on job reallocation. In accordance with the Bertola and Rogerson hypothesis, this effect is positive in the manufacturing sector. Running separate regressions for job creation and job destruction shows a negative and significant effect of wage dispersion on job destruction, whereas it is insignificant in the job-creation equation. These results are in accordance with wages being more rigid downwards than upwards. The quantitative effect of the impact of wage dispersion on job turnover is limited, however. A one standard deviation increase in wage dispersion reduces the total job reallocation by around 10 percent. Turning to the non-manufacturing sector, the Bertola and Rogerson hypothesis is not supported.Further results include (i) a strong positive effect of the industry-share of temporary employees on job reallocation and (ii) a negative relationship between the use of overtime and job turnover.In the third essay, Wages, Profits and Individual Unemployment Risk: Evidence from Matched Worker-Firm Data (with Mahmood Arai), the impact of firm performance on individual wages is studied. Several studies have found a positive and significant effect of profits on wages. The most widely suggested interpretation for this phenomenon is that employers and employees engage in rent-sharing, thereby splitting the profits created between themselves.The purpose of this study is to examine the extent of rent-sharing and the impact of individual and aggregated unemployment risk on wages of individual workers. We use a sample of over 170,000 Swedish employees for 1991 and 1995 matched with their employing firm’s profits and the unemployment registers. The matched data contain detailed information on individual characteristics, including their unemployment experience during 1992-1995 as well as annual profits as reported in the firms’ balance-sheet reports.The contribution of this paper is that it provides evidence on the wage determination, based on disaggregated individual and firm data dealing with the problems of firm and worker heterogeneity, and the endogeneity of profits. Our results imply positive effects of profits on wages, both in 1991 and 1995. The reported elasticities imply that the wage inequality in Sweden due to the spread in profits is as high as 13% of the mean wages in 1991, according to Lester’s range of pay. These correlations are robust for controlling for time-invariant unobserved individual- and firm characteristics.Using firm-reported short-term product market elasticity and the number of competitors as instruments for profits suggest Lester’s measure of wage inequality due to profits to be as high as 50% of the mean wages.Finally, we investigate the impact of individual heterogeneity with respect to unemployment risk that might also affect wages. We include the individuals’ unemployment event record in our regressions, and our results confirm that individuals with a higher unemployment risk also have lower wages. Including aggregated measures along with individual unemployment risk in our estimations show results suggesting that there exists a robust negative correlation between unemployment risk and wages at various aggregation levels.The final essay, Pay Inequality and Firm Performance: Evidence from Matched Employer-Employee Data, tests several implications from tournament models on the same matched employer-employee data set as in essay 3.According to a variety of theories, the wage distribution both within and between firms can have important effects on individual productivity and firm performance. One argument for high wage differentials, based on incentive effects, is found in Lazear and Rosen’s (1981) tournament theory. Higher wage differentials lead to higher individual effort, and are therefore productivity enhancing. This, in turn, suggests that there is a positive relationship between wage dispersion and productivity. The opposite relationship is found in theories stressing fairness and cooperation between co-workers.For white-collar workers, the results show a positive effect of intra-firm pay spread on firm performance for 1991 and 1995. This applies to different measures of wage dispersion, capturing both raw differences and differences corrected for the fact that part of the wage spread is due to differences in human capital accumulation. To take firm heterogeneity into account, difference equations are estimated on a panel of firms. Once more, consistent with tournament theory, a positive and significant effect of wage dispersion on profits is found. The results for managers are based on information on about 10,000 managers. For various measures of wage dispersion and specifications, a positive and significant association between managerial pay and profits is found. No support is found for the hypothesis of a positive relationship between the number of managers (contestants) and wage spread. Instead, the results show a negative and significant effect of the number of executives and pay spread among managers.Finally, consistent with tournament theory, higher wage dispersion is found in firms operating in volatile product markets characterized by a high degree of output uncertainty. / Diss. Stockholm : Handelshögsk., 2002

Background: Non-disclosure of HIV positive status to a partner threatens to reverse gains made in prevention of mother-to-child transmission (PMTCT) in resource limited settings. Determining the association between non-disclosure and infant HIV acquisition is important to justify focussing on disclosure as a strategy in PMTCT programmes. Objective: To determine the association between non-disclosure of HIV positive status to a partner and mother-to-child transmission (MTCT). Methods: Using a matched case-control design, we compared 34 HIV positive infants to 146 HIV negative infants and evaluated whether the mothers had disclosed their HIV status to their partner. Results: Non-disclosure was more frequent among cases (overall, 16.7%; cases, 52.8%; controls 7.6%), p<0.001 and significantly associated with MTCT (aOR 8.9 (3.0-26.3); p<0.0001), with male partner involvement partially mediating the effect of non-disclosure on MTCT. Conclusions: There is a need for PMTCT programs to focus on strategies to improve male partner involvement and partner disclosure without compromising the woman’s safety. / Health Studies / M. (Public Health)

La thèse porte sur la simulation, en régime fréquentiel, du rayonnement acoustique en écoulement subsonique quelconque et dans un domaine infini. L'approche choisie s'appuie sur la résolution d'un système équivalent aux équations d'Euler linéarisées : le modèle de Galbrun. Ce modèle repose sur une représentation mixte Lagrange-Euler et aboutit à une équation dont l'unique inconnue est la perturbation du déplacement Lagrangien. Une des difficultés de l'approche de Galbrun est qu'une discrétisation directe de cette équation par une méthode d'éléments finis standard n'est pas stable. Un moyen de contourner cet obstacle est d'écrire une équation augmentée en ajoutant une nouvelle inconnue, le rotationnel du déplacement, appelée par abus vorticité. Cette approche conduit à un système qui couple une équation de type équation des ondes avec une équation de transport en régime fréquentiel. Et elle permet l'utilisation de couches parfaitement adaptées (PML) pour borner le domaine de calcul. La première partie du manuscrit est dédiée à l’étude de l’équation de transport harmonique et de sa résolution numérique, en particulier par un schéma de type Galerkin discontinu. Un des points délicats est lié au caractère oscillant des solutions de l'équation. Une fois cette étape franchie, la résolution du problème de propagation acoustique a été abordée. Une approximation basée sur l'utilisation d'éléments finis mixtes continus-discontinus avec couches parfaitement adaptées (PML) a été étudiée. En particulier, les caractères bien posés des problèmes continu et discret ainsi que la convergence du schéma numérique ont été démontrés sous certaines conditions sur l'écoulement porteur. Enfin, une mise en œuvre a été effectuée. Les résultats montrent la validité de cette approche mais aussi sa pertinence dans le cas d'écoulements complexes, voire d'écoulements dits instables / This thesis deals with the numerical simulation of time harmonic acoustic propagation in an arbitrary mean flow in an unbounded domain. Our approach is based on an equation equivalent to the linearized Euler equations called the Galbrun equation. It is derived from a mixed Eulerian-Lagrangian formulation and results in a single equation whose only unknown is the perturbation of the Lagrangian displacement. A direct solution using finite elements is unstable but this difficulty can be overcome by using an augmented equation which is constructed by adding a new unknown, the vorticity, defined as the curl of the displacement. This leads to a set of equations coupling a wave like equation with a time harmonic transport equation which allows the use of perfectly matched layers (PML) at artificial boundaries to bound the computational domain. The first part of the thesis is a study of the time harmonic transport equation and its approximation by means of a discontinuous Galerkin scheme, the difficulties coming from the oscillating behaviour of its solutions. Once these difficulties have been overcome, it is possible to deal with the resolution of the acoustic propagation problem. The approximation method is based on a mixed continuous-Galerkin and discontinuous-Galerkin finite element scheme. The well-posedness of both the continuous and discrete problems is established and the convergence of the approximation under some mean flow conditions is proved. Finally a numerical implementation is achieved and numerical results are given which confirm the validity of the method and also show that it is relevant in complex cases, even for unstable flows

De nombreux éléments de structures de génie civil sont élancés et partiellement enfouis dans un milieu solide. Les ondes guidées sont souvent utilisées pour le contrôle non destructif (CND) de ces éléments. Ces derniers sont alors considérés comme des guides d’ondes ouverts, dans lesquels la plupart des ondes sont atténuées par des fuites dans le milieu environnant. D’autre part le problème est non borné, ce qui le rend difficile à appréhender sur le plan numérique. La combinaison d’une approche par éléments finis semi-analytique (SAFE) et de la méthode des couches parfaitement adaptées (PML) a été utilisée dans une thèse antérieure pour calculer numériquement trois types de modes (modes piégés, modes à fuite et modes de PML). Seuls les modes piégés et à fuite sont utilisés pour la représentation des courbes de dispersion. Les modes de PML sont non intrinsèques à la physique. L’objectif premier de cette thèse est d’obtenir, par superposition modale sur les modes calculés, les champs émis et diffracté dans les guides d’ondes ouverts. Nous montrons dans un premier temps que les trois types de modes appartiennent à la base modale. Une relation d’orthogonalité est obtenue dans la section du guide(incluant la PML) pour garantir l’unicité des solutions. La réponse forcée du guide peut alors être calculée rapidement par une somme sur les modes en tout point du guide. Des superpositions modales sont également utilisées pour construire des frontières transparentes au bord d’un petit domaine élément fini incluant un défaut, permettant ainsi de calculer le champ diffracté. Au cours de ces travaux, nous étudions les conditions d’approximation des solutions par des superpositions modales, limitées seulement aux modes à fuite, ce qui permet de réduire le coût des calculs. De plus, la généralité des méthodes proposées est démontrée par des calculs hautes fréquences (intéressantes pour le CND) et sur des guides tridimensionnels. Le deuxième objectif de cette thèse est de proposer une méthode d’imagerie pour la localisation de défauts. La méthode de l’imagerie topologique est appliquée aux guides d’ondes. Le cadre théorique général, de type optimisation sous contrainte, est rappelé. Le formalisme modal permet un calcul rapide de l’image. Nous l’appliquons pour simuler un guide d’onde endommagé, et nous montrons l’influence du type de champ émis (monomodal, dispersif,multimodal) ainsi que des configurations de mesure sur la qualité de l’image obtenue. / Various elements of civil engineering structures are elongated and partially embedded in a solid medium. Guided waves can be used for the nondestructive evaluation (NDE) of such elements. The latteris therefore considered as an open waveguide, in which most of waves are attenuated by leakage losses into the surrounding medium. Furthermore, the problem is difficult to solve numerically because of its unboundedness. In aprevious thesis, it has been shown that the semi-analytical finite-element method (SAFE) and perfectly matched layers(PML) can be coupled for the numerical computation of modes. It yields three types of modes: trapped modes,leaky modes and PML modes. Only trapped and leaky modes are useful for the post-processing of dispersion curves. PML modes are non-intrinsic to the physics. The major aim of this thesis is to obtain the propagated and diffracted fields, based on modal superpositions on the numerical modes. First, we show that the three types of modes belong to the modal basis. To guarantee the uniqueness of the solutions an orthogonality relationship is derived on the section including the PML. The forced response can then be obtained very efficiently with a modal expansion at any point of the waveguide. Modal expansions are also used to build transparent boundaries at the cross-sections of a small finite-element domain enclosing a defect, thereby yielding the diffracted field. Throughout this work, we study whether solutions can be obtained with modal expansions on leaky modes only, which enables to reduce the computational cost. Besides, solutions are obtained at high frequencies (which are of interest for NDE) and in tridimensional waveguides, which demonstrates the generality of the methods. The second objective of this thesis is to propose an imaging method to locate defects. The topological imaging method is applied to a waveguide configuration. The general theoretical framework is recalled, based on constrained optimization theory. The image can be quickly computed thanks to the modal formalism. The case of a damaged waveguide is then simulated to assess the influence on image quality of the emitted field characteristics (monomodal, dispersive or multimodal)and of the measurement configuration.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-20T15:14:06Z No. of bitstreams: 1 bernardosottomaiorperalva.pdf: 4608167 bytes, checksum: c63c1f7fc453965f36158791fb85964e (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-24T16:49:03Z (GMT) No. of bitstreams: 1 bernardosottomaiorperalva.pdf: 4608167 bytes, checksum: c63c1f7fc453965f36158791fb85964e (MD5) / Made available in DSpace on 2017-04-24T16:49:04Z (GMT). No. of bitstreams: 1 bernardosottomaiorperalva.pdf: 4608167 bytes, checksum: c63c1f7fc453965f36158791fb85964e (MD5) Previous issue date: 2012-05-07 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta dissertação, são apresentados métodos para detecção de sinais e estimação de energia para calorimetria de altas energias aplicados no calorímetro hadrônico (TileCal) do ATLAS. A energia depositada em cada célula do calorímetro é adquirida por dois canais eletrônicos de leitura e é estimada, separadamente, através da reconstrução da amplitude do pulso digitalizado amostrado a cada 25 ns. Este trabalho explora a aplicabilidade de uma aproximação do Filtro Casado no ambiente do TileCal para detectar sinais e estimar sua amplitude. Além disso, este trabalho explora o impacto na detecção de eventos válidos e estimação da amplitude quando somam-se os sinais referentes à mesma célula antes da aplicação do filtro. O método proposto é comparado com o Filtro Ótimo atualmente utilizado pelo TileCal para reconstrução de energia. Os resultados para dados simulados e de colisão mostram que, para condições em que a linha de base do sinal de entrada pode ser considerada estacionária, a técnica proposta apresenta uma melhor eficiência de detecção e estimação do que a alcançada pelo Filtro Ótimo empregada no TileCal. / The Tile Barrel Calorimeter (TileCal) is the central section of the hadronic calorimeter of ATLAS at LHC. The energy deposited in each cell of the calorimeter is read out by two electronic channels for redundancy and is estimated, per channel, by reconstructing the amplitude of the digitized signal pulse sampled every 25 ns. This work presents signal detection and energy estimation methods for high energy calorimetry, applied to the TileCal environment. It investigates the applicability of a Matched Filter and, furthermore, it explores the impact when summing the signals belonging to the same cell before the estimating and detecting procedures. The proposed method is compared to the Optimal Filter algorithm, that is currently been used at TileCal for energy reconstruction. The results for simulated and collision data sets showed that for conditions where the signal pedestal could be considered stationary, the proposed method achieves better detection and estimation efficiencies than the Optimal Filter technique employed in TileCal.

Denna studie syftar till att undersöka den matchade förvärvsgraden för kvinnor och män, i Dalarna och i Sverige, samt att förklara eventuella skillnader. Om en stor andel av utbildningsgruppen vid avklarad examen blir anställda inom andra yrkesområden än vad utbildningen gav kompetens för, är den matchade förvärvsgraden inom utbildningsgruppen låg. Datamaterialet är hämtat från Statistiska centralbyrån (SCB) och studeras genom en multipel linjär regressionsanalys. Både kvinnor och män med universitets-/högskoleutbildning påverkar den matchade förvärvsgraden mer jämförelsevis med gymnasial utbildning. Resultatet visar även att om andelen kvinnor i utbildningsgruppen ökar påverkas andelen anställda med matchning positivt för kvinnor och negativt för män, det omvända sambandet gäller också, den matchade förvärvsgraden för män ökar när andelen män i utbildningsgruppen ökar. Detta visar att könsdiskriminering råder på arbetsmarknaden. / This study aims at examining the matched employment rate for women and men, in Dalarna and Sweden, as well as explaining possible differences. If a group of individuals within a education group with a graduate degree are employed in a different field of employment than the education provided competence (than the education is meant for), the matched employment rate within the education group is low. The data is obtained from Statistiska centralbyrån (SCB) and is studied through a multiple linear regression analysis. Both women and men with university/college education affect the matched degree of employment more comparatively with upper secondary education. The result also shows that if the proportion of women in the education group increases, the proportion of employees with matching gives positive results for women and negative for men; the reverse relationship also applies; the matched male employment rate increases as the proportion of men in the education group increases. This shows that gender discrimination prevails in the Swedish labor market.

To analyse drill samples in a mine, a scanner that uses a gamma ray detector can be used. The scanner can analyse the drill sample to quickly see the elements present in the sample without destroying it. To improve the performance of the scanner, the electric signal from the detector needs to be less noisy, and different pulse shaping methods, filters and smoothers can be used on the sampled data to achieve an improved performance. In this master thesis, the electric noise model of the electronics around the detector was modeled, and analysed. Different pulse shaping method, filters and smoothers was also tested to see which method gave the best performance in FWHM sense. The Full Width at Half Maximum (FWHM) is the energy resolution of a detector, and is defined as the full width of a photopeak at the half maximum. The noise model of the schematic for the preamplifier was made by hand with support from MATLAB. The resulting noise model was compared between MATLAB and LTspice, and the conclusion is that the JFET is the main contributor of the significant noise, contributing to 98 % of the total noise at 10 GHz. The adopted filters and pulse shaping method are, matched filter, custom filter, CR-RC shaping, mean filter, median filter and clustering. The results from the tests indicated that custom filter with a FWHM of 1.96 keV and CR-RC with a FWHM of 1.67 keV shaping were more accurate than the matched filter with the FWHM of 5.1 keV. But the results also showed that it is important to take into account the waveform variance, due to inherent properties in the detector, with this consideration the FWHM of CR-RC shaper was improved from 2.29 keV to 1.67 keV. The clustering method was the most promising method but due to time constraints this method was never fully tested and no FWHM value was achieved.

No description available.

L’accélération par sillage laser (ASL) repose sur l’interaction entre un faisceau laser intense et un plasma sous-dense. Au travers de cette interaction, une onde de plasma est générée avec un fort champ accélérateur, de trois ordres de grandeur plus élevé que celui d’un accélérateur conventionnel, rendant envisageable la réalisation d’accélérateurs futurs plus compacts. Pour la conception d’un futur accélérateur, un faisceau d’électrons de forte charge, faible dispersion en énergie et faible émittance doit être accéléré à des grandes énergies. Pour ce faire, la solution consiste à accélérer ces électrons dans un schéma multi-étages, qui est composé de trois étages: un injecteur, une ligne de transport et un accélérateur. Ce travail de thèse porte sur la modélisation de l’injecteur avec le code PIC Warp et sur les méthodes numériques telles que la technique de Lorentz-boosted frame pour diminuer le temps de calcul et la couche absorbante parfaite de Bérenger (PML) pour assurer la précision des calculs numériques. Ce travail de thèse a démontré l’efficacité de la PML dans les schémas FDTD à des ordres élevés et pseudo-spectral. Il a aussi démontré la convergence des résultats des simulations réalisées avec la technique de Lorentz-boosted frame dans un régime fortement non-linéaire de l’injecteur, permettant d’accélérer les calculs d’un facteur important (36) tout en assurant leur précision. La modélisation effectuée dans cette thèse a permis d’analyser et de comprendre les résultats expérimentaux, ainsi que de prédire les résultats des futures expériences. Plusieurs méthodes d’optimisation de l’injecteur ont également été proposées pour la génération d’un faisceau d’électrons conforme aux spécifications d’un futur accélérateur. / Laser Wakefield Acceleration (LWFA) relies on the interaction between an intense laser pulse and an under-dense plasma. This interaction generates a plasma wave with a strong accelerating field, which is three orders of magnitude higher than the one of the conventional accelerator; more compact accelerator is therefore theoretically possible. In the design of a future accelerator, a high quality electron bunch with a high charge, low energy spread and low emittance has to be accelerated to high energies. A solution for this is a multi-stage accelerator, which consists of an injector, a transport line and accelerator stages. This research work focuses on the modelling of the injector using the PIC code Warp and on the numerical methods such as the Lorentz-boosted frameto speedup calculations and the Perfectly Matched Layer (PML) to ensure the precision in numerical calculations. The outcome of this thesis has demonstrated the efficiency of the PML in the high-order FDTD and the pseudo-spectral solvers. Besides, it has also demonstrated the convergence of the results performed in simulations using the Lorentz-boosted frame technique. This technique speeds up simulations by a large factor (36) while preserving their accuracy. The modelling work in this thesis has allowed analysis and understanding of experimental results, as well as prediction of results for future experiments. This thesis has also shown ways to optimize the injector to deliver an electron bunch that conforms with the specifications of future accelerators.

This thesis deals with methods for optimization in image processing. There is described some of optimization techniques and some applications in image processing. There is also described detailed procedure and realization of bee algorithm, genetic algorithm, PSO algorithm and their realization in image registration, matched filtering, image segmentation and image reconstruction. Algorithms and their efficiencies are compared in the particular application for image processing.