Propagation properties of linearly tapered parabolic-index optical waveguides are investigated. Tapers with planar (two-dimensional) and fiber (three-dimensional) geometries are considered. A ray optics approach is used in the analysis, assuming that the characteristic dimensions of tapered waveguides are small compared to the wavelength of light. Closed form analytical solutions are obtained for ray trajectories in tapers with small slope and small index difference between the core and cladding. To assess the accuracy of analytical solutions, exact ray trajectories in planar waveguides are determined using numerical techniques and compared to those obtained from the analytical method. The agreement between the analytical and numerical solutions is excellent. It is observed that ray trajectories exhibit the behavior of modulated sinusoidal functions with decreasing amplitude and period as light travels toward the smaller end of the taper. This illustrates the power concentrating capability of the taper. Applications of these graded-index tapers when used to couple power from light sources to planar and fiber waveguides and when they are used to connect two waveguides of different core sizes are addressed. Coupling efficiencies for light source coupling and radiation loss of tapers when used to connect two dissimilar waveguides are calculated. Numerical results for example cases are provided. A novel application of the taper as collimated beam concentrator is also proposed. / Master of Science

Consider the problem of developing an algorithm that computes optimal preprogrammed evasive maneuvers for a Maneuvering Reentry Vehicle (MaRV) attacking a target defended with Anti-Ballistic Missiles (ABMs). The problem is large in terms of the number of optimization parameters, and perhaps in terms of the number of nonlinear constraints. Since both MaRV and ABM trajectories are expensive to compute, rapid convergence of the optimization algorithm is of prime concern. This paper examines a discontinuity in the cost function that degrades both the speed and the reliability of optimizer convergence. A solution is offered, proposing that the optimization algorithm be operated in a new parameter space, in which the discontinuity occurs at infinity. Effectively, the mapping prevents the optimization algorithm from crossing the discontinuity thereby improving optimizer convergence. Results comparing convergence with and without the parameter mapping demonstrate the effectiveness of the procedure. / Master of Science

No / Z. W. Pylyshyn and R. W. Storm (1988) have shown that human observers can accurately track four to five items at a time. However, when a threshold paradigm is used, observers are unable to track more than a single trajectory accurately (S. P. Tripathy & B. T. Barrett, 2004). This difference between the two studies is examined systematically using substantially suprathreshold stimuli. The stimuli consisted of one (Experiment 1) or more (Experiments 2 and 3) bilinear target trajectories embedded among several linear distractor trajectories. The target trajectories deviated clockwise (CW) or counterclockwise (CCW) (by 19°, 38°, or 76° in Experiments 1 and 2 and by 19°, 38°, or 57° in Experiment 3), and observers reported the direction of deviation. From the percentage of correct responses, the ¿effective¿ number of tracked trajectories was estimated for each experimental condition. The total number of trajectories in the stimulus and the number of deviating trajectories had only a small effect on the effective number of tracked trajectories; the effective number tracked was primarily influenced by the angle of deviation of the targets and ranged from four to five trajectories for a ±76° deviation to only one to two trajectories for a ±19° deviation, regardless of whether the different magnitudes of deviation were blocked (Experiment 2) or interleaved (Experiment 3). Simple hypotheses based on ¿averaging of orientations,¿ ¿preallocation of resources,¿ or pop-out, crowding, or masking of the target trajectories are unlikely to explain the relationship between the effective number tracked and the angle of deviation of the target trajectories. This study reconciles the difference between the studies cited above in terms of the number of trajectories that can be tracked at a time.

Charles University in Prague Faculty of Philosophy and Arts Department of Sociology Study Program: Sociology Family and work arrangements in the context of social changes in the Czech Republic after 1989. Transformations in family and professional starts Mgr. Jana Chaloupková Supervisor: PhDr. Dana Hamplová, Ph.D. 2011 Dissertation abstract This dissertation explores the changes in professional and family starts of young men and women in the Czech Republic. It compares an early family and work trajectories of persons, who reached adulthood in 1990s and those theirs family and work starts occurred before 1989. Theoretical and methodological background of this study draws upon a holistic approach to the life-course study and a sequence analysis. The empirical analyses focus on three domains: 1) a normative context of family and work starts, 2) the development of variability of family and work starts, 3) analysis of similarity (types) of early family and work trajectories. Using ISSP 2002 data, the analysis deals with a sequence of family and work statuses held between 18 and 35 years of age. The analyses of the normative context show that in most European countries social adulthood is more strongly linked to becoming financially independent than to starting a family. In the Czech society dominates a norm of...

Thesis advisor: Eric Dearing / Socioemotional difficulties in childhood have been associated with body weight status and the subsequent development of obesity later in life. However, existing research often overlooks the developmental and dynamic nature of socioemotional functioning. Additionally, there is a lack of systematic examination of this relation across varied aspects of socioeconomic risks. Recent research has highlighted a seemingly paradoxical effect, wherein socioemotional competence is associated with adverse health outcomes among socioeconomically disadvantaged minority youths. Yet, obesity per se has received little attention in this literature. The present dissertation adds to the extant literature by examining links between socioemotional well-being and body weight across socioeconomic contexts. Specifically, the present dissertation provides three empirical papers using secondary analyses of large-scale longitudinal studies of children and adolescents to examine associations between sustained socioemotional competency and body weight. In each paper, the potential moderating role of socioeconomic risks and concerns for robustness across children’s racial/ethnic backgrounds are foci. Paper 1 estimated developmental trajectories of behavior problems from ages 5-6 to 13-14 and assessed whether body mass index (BMI) at ages 21-22 varied by behavior problem trajectory patterns, poverty status, and their interaction. Paper 2 identified self-control trajectories during elementary school, examined their impact on fifth-grade BMI, and explored whether the association between self-control trajectories and BMI differed by poverty status. Lastly, Paper 3 examined associations between self-control across the elementary school years and BMI at the end of elementary school, while allowing these associations by poverty dynamics and exposure to an accumulation of socioeconomic and contextual risks. Across three papers, all analyses were conducted for the entire sample and by racial/ethnic group. Results generally supported the protective role of socioemotional competency in preventing unhealthy body weight, regardless of socioeconomic risks. However, this relation was often less evident for children of color than for White children. These findings are interpreted with concern for the complex roles of disadvantage in children’s lives as pertains to social-emotional adjustment and body weight. The practical significance of the papers is focused on informing intervention efforts based on improved understandings of when, for whom, and under what conditions socioemotional competency is associated with health benefits, risks, or neither. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Lynch School of Education. / Discipline: Counseling, Developmental and Educational Psychology.

Alors que les personnes âgées de 65 ans et plus consomment des substances psychoactives (SPA), le nombre de consultations en centre de réadaptation en dépendance (CRD) au Québec se serait accentué au cours des dernières années. Deux types de trajectoires sont principalement identifiés dans les études épidémiologiques. Certains auraient une consommation de SPA persistante sur plusieurs années. Pour d’autres, la trajectoire addictive commencerait dans une période liée au vieillissement où la consommation servirait à compenser des évènements difficiles de la vie. Jusqu’à maintenant, très peu d’études portent sur la perspective des personnes âgées de 65 ans et plus quant à leur consommation de SPA et aux motifs pouvant les amener à rechercher de l’aide. Le but de cette étude est de décrire et de comprendre les trajectoires addictives en lien avec les trajectoires de recherche d’aide et d’utilisation de services selon le point de vue de personnes âgées de 65 ans et plus. Un devis qualitatif descriptif interprétatif a été utilisé. Des entrevues semi-structurées en profondeur auprès de 11 personnes âgées en suivi thérapeutique ont été réalisées dans deux régions du Québec. Une analyse de trajectoire en tenant compte de la chronologie des évènements a été croisée à une analyse thématique. Trois types de trajectoires addictives chez les personnes âgées de l’étude émergent des données. Différents éléments influencent ces trajectoires, dont les problématiques associées de santé mentale et physique ainsi que des expériences de vie et le parcours d’utilisation de services. Les trajectoires de recherche d’aide et d’utilisation de services en dépendance sont également influencées par le réseau social qui comprend les membres de l’entourage, mais également les professionnels de la santé. Ces derniers semblent être un levier important à une référence vers un traitement en dépendance. L’étude a permis de mettre en lumière la complexité du phénomène de consommation, mais également l’hétérogénéité des expériences du vieillissement pouvant influencer la consommation de SPA. Les aspects directement liés à l’expérience du vieillissement doivent être pris en considération afin de bien saisir les raisons et les éléments contextuels influençant le parcours de consommation problématique. / Abstract : The problematic use of psychoactive substances (PS; alcohol, drugs, prescription medication) is a significant phenomenon among people aged 65 and over. Moreover, in addiction treatment services of the Québec Province, the presence of elderly persons has increased. Epidemiological studies have identified two types of addiction trajectories: some elderly has a PS use that has started long time ago and has persisted for several years and for others the addiction trajectory has begun recently, in a period associated with aging to cope with stressful life events. Diverse reasons can explain this difference, but very few studies have explored the point of view of the elderly about their use of PA and their reasons for seeking-help The aim of the study is to describe and understand the addiction trajectories in relation to help-seeking and service use trajectories from the perspectives of elderly people in addiction treatment for PA. A descriptive interpretative study design was used. It was based on in-depth interviews conducted with 11 elderly people receiving addiction treatment in two regions of the Québec Province. A trajectory analysis taking into account the chronology of the events was crossed with a thematic analysis The results suggest that there are three types of addiction trajectories in the elderly of the study. These trajectories are influenced by different factors, including the associated health, mental and physical problems and life experiences and the use of services in the past. The trajectories of seeking help and using dependency services are also influenced by their social network, which includes members of the entourage, but also health professionals. These seem to be a lever to a reference to addictive treatment. The study not only shows the complexity of the drug use phenomenon among the elderly, but also how the heterogeneity of the aging experiences could influence the consumption of elderly. Certain aspects related to the aging experience such as retirement, social participation are particularly important to understand how addictions could influence the elderly.

Les liens entre facteurs socio démographiques et trajectoires de consommation d’alcool chez les jeunes restent peu connus. De même, les études sur les liens entre trajectoire socio-économique et consommation d’alcool ont échoué à montrer un effet propre de la trajectoire socio-économique. Enfin, la littérature qui est disponible actuellement ne permet pas de dégager un consensus sur l'effet du sexe des enfants et des parents dans la transmission intergénérationnelle de la consommation d'alcool. L’objectif de cette thèse a été d’identifier les déterminants sociaux, économiques et démographiques des trajectoires de consommation d’alcool chez les jeunes. Il s’est agi d’une étude de cohorte prospective menée en population générale dans la cohorte TEMPO [(n=2.582, âgées de 4 à 16 ans en 1991), (n=1.333, âgés de 12 à 25 ans en 1999), (n=1.103, âgés de 22 à 35 ans en 2009)], et pour lesquels les données ont été recueillies par auto-questionnaire postal, incluant des jeunes dont un des parents participe à la cohorte GAZEL. Il est ressorti de nos analyses que la consommation excessive d’alcool qui s’installe au début de l’adolescence est un phénomène limité dans le temps chez la majorité des jeunes. Elle persiste dans des sous populations particulières comme les personnes issues de catégorie sociale défavorisée et les jeunes femmes. La situation sociale, mesurée par la trajectoire sociale de l’enfance au début de l’âge adulte, est un facteur prédictif de la consommation d’alcool au début de l’âge adulte. Les tendances de certains de nos résultats laissent penser que les mécanismes à l’œuvre dans un possible lien parents-descendance pour l'abus d'alcool pourraient être en lien avec le sexe des jeunes. Ces résultats suggèrent que la trajectoire de consommation d’alcool chez les jeunes est en partie déterminée par des facteurs sociodémographiques présents précocement, au cours de l’enfance et l’adolescence. Etant donné les risques de l’abus d'alcool chez les jeunes tant sur leur santé que sur leur devenir social et professionnel à long terme, les trajectoires d'abus d'alcool devraient faire l'objet d'une surveillance plus accrue. La prise en compte des mécanismes sociaux à l’œuvre dans les trajectoires d'abus d'alcool chez les jeunes pourrait être contributive. / Young adulthood is a critical period in terms of establishing lifelong health behaviors, including alcohol use. Yet, trajectories of alcohol abuse from adolescence onwards are not well known.Using data from a longitudinal cohort study set up in France [(n=2,582, age 4-16 years in 1991), (n=1,333, age 12-25 years in 1999), (n=1,103, age 22-35 years in 2009)], we examined the relationship between repeated alcohol intoxication in adolescence and later alcohol abuse, testing whether this association varies depending on individuals’ sociodemographic characteristics. We also studied the hypothesis that patterns of alcohol use in young adulthood are associated with lifecourse socioeconomic trajectory. In addition, we examined the relationship between parental history of alcohol use and offspring’s alcohol use in young adulthood, testing differences according to sex.In most adolescents, alcohol abuse is a time-limited behavior. Nonetheless, in adolescent participants from low income families, in girls, the likelihood of persistent alcohol abuse beyond adolescence may be increased. We also found that young adults who had a persistently low socioeconomic position from childhood to young adulthood were more likely to abstain from alcohol even after controlling for demographic, social, psychological and family characteristics. Additionally, participants with a downward social trajectory were disproportionately likely to abuse alcohol. In addition, parental history of alcohol use is especially predictive of offspring’s young adulthood alcohol misuse in men.Our findings suggest that alcohol use patterns in young adulthood may be influenced by early socioeconomic factors, which should be confirmed by additional studies in the future. Given young people alcohol abuse risks about their health and their future social and professional situation, alcohol use trajectories from adolescence onwards should be better monitored. Taking into account social mechanisms that influence trajectories of alcohol abuse among young people could be contributive, which should be brought to the attention of policymakers and mental health specialists.

Cette thèse propose une analyse de l'investissement éducatif au niveau individuel. Elle développe une perspective dynamique qui cherche à analyser les liens entre éducation et trajectoires sur le long terme. Pour ce faire, nous utilisons un modèle de microsimulation dynamique. La première partie de la thèse porte sur l'éducation initiale. Elle cherche à évaluer l'impact de la diversité des trajectoires sur l'hétérogénéité des gains monétaires associés à différents niveaux de diplôme. Nous y montrons tout d'abord que certains diplômés, en raison des trajectoires défavorables qu'ils connaissent sur le marché du travail, ont une probabilité non négligeable de ne pas valoriser financièrement leurs études. L'analyse des gains liés à l'éducation initiale est ensuite élargie aux comportements conjugaux des individus. En particulier, nous montrons que la prise en compte des revenus salariaux des conjoints réduit les inégalités entre les diplômés, et ce, malgré l'existence de phénomènes d'homogamie éducative. La seconde partie de la thèse est consacrée à la « formation continue » (FC) ou « postscolaire ». En tenant compte des facteurs familiaux et professionnels qui peuvent jouer sur l'accès à la FC, cette partie a pour objectif de mesurer le niveau des dépenses dont bénéficient les individus pour se former une fois leurs études initiales terminées. Les résultats mettent en lumière une forte hétérogénéité de ces dépenses et le rôle divergent des différents dispositifs de formation. Ils montrent également que les montants investis dans la formation postscolaire des individus demeurent faibles au regard de ceux engagés pour la formation initiale. / This thesis provides an analysis of investment in education from an individual point of view. Using a microsimulation model, we develop a dynamic perspective that aims to take into account the long-term relationships between education and individual trajectories. The first part of the thesis focuses on initial education. Its objective is to assess the impact of the diversity of trajectories on the heterogeneity of education benefits. We first show that some graduates, because of their vulnerable position on the labour market, are exposed to negative return to initial education. Our analysis of initial education benefits is then extended to marital behaviour. We more particularly show that taking into account spouse's labour market income reduces inequality between individuals despite the existence of educational homogamy. The second part of the thesis deals with further education and training (FET). Considering family and professional factors that may affect access to FET, we measure the level of expenditure received by individuals to train throughout their career. The results point out the heterogeneity of these spending and indicate that investments in FET are low compared to those invested in initial education.

Extremely fine liquid droplets or solid particles, those remain suspended in the air, are known as aerosols. They are produced by natural sources and anthropogenic activities. Several types of aerosols produced by different processes are present in the atmosphere and every type of aerosol species exhibit different types of physical and chemical properties. Though making up only a small fraction of atmospheric mass aerosols are capable of altering Earth’s climate by scattering and absorbing incoming solar radiation and absorbing outgoing radiation. Adding to the complexity, they can act as cloud condensation nuclei and modify cloud properties. Major objective of this thesis is to study absorption due to aerosols and factors controlling the absorbing efficiency of aerosols over various environments. We have demonstrated a new method to quantify the organic carbon in terms of optical depth. Our studies demonstrate large “anomalous” absorption in the UV wavelength region over several regions. Further investigations revealed that a major part of this additional absorption is contributed by organic carbon aerosols and partly due to dust aerosols. We show that it is possible to discriminate UV absorption by dust and organic carbon by making use of the fact that dust aerosols are much larger in size compared to organic aerosols. Examination of aerosol optical depth values measured at cities south of Saharan desert indicates high short wave absorption due to coarse mode aerosols probably dust. Even at low values of Angstrom wavelength exponent, which indicates the presence of large aerosols (e.g., dust over land), absorption was found reasonably high compared to that of pure dust. On the other hand, over regions in the northern part of the Sahara close to Europe, short wave absorption was found to be lower. The enhanced short wave absorption due to coarse particles is unexpected. It appears that the deposition of anthropogenic aerosols such as black carbon over dust aerosols is likely to be responsible for this enhanced short wave absorption. This is a typical example of how anthropogenic aerosols can modify the properties of natural aerosols. We have carried out source apportionment using backward air parcel trajectories by applying k-means method of clustering and obtained various aerosol terms corresponding to each cluster. We have selected three island sites and one site in the middle of Saharan desert for this study. High aerosol radiative forcing values are observed even over remote island locations. Our study demonstrates the role of aerosols transported from the main land in influencing the aerosol environment even over remote marine regions.

In dieser Arbeit wird das Verhalten der Fahrer vor, während und nach dem Spurwechsel anhand eines Datensatzes untersucht. Dieser wurde im Jahr 2006 in den USA erhoben und enthält die genauen Trajektoriendaten für jedes Fahrzeug. Es konnte gezeigt werden, dass schnellere Fahrzeuge ihren Spurwechsel auch schneller abschließen. Es ist auch erkennbar, dass bei einem Wechsel nach rechts kein kleinerer Abstand zum Vorderfahrzeug in Kauf genommen wird. Eine Untersuchung der freiwilligen und notwendigen Wechsel konnte keine signifikanten Unterschiede feststellen. Im zweiten Teil der Auswertung wurden die Spurwechselentscheidungen mittels eines generellen Modells und MOBIL untersucht. Die einzusetzenden Werte wurden mit den Fahrzeugfolgemodellen OVM, Gipps-Modell und IDM erzeugt. Die Entscheidungen der Spurwechselmodelle fielen nur selten so aus, wie sie in der Realität getroffen wurden. Damit werden die Modelle ihrem eigenen Anspruch nicht gerecht, die Realität möglichst gut nachzubilden. / The topic of this master thesis is the investigation of the behaviour of the drivers before, during and after lane changes on highways. For this purpose a data set of the I-80 in the USA was used. It was collected in 2006 and contains the trajectories of all vehicles. It could be shown that faster cars even do a faster lane change. The drivers also do not accept a smaller gap to the preceding car after a lane change to the right. A comparison of voluntary and necessary lane changes did not show significant differences. In the second part of the analysis the lane change decision was examined using a general model and MOBIL. The data to be inserted were generated using the car-following models OVM, Gipps-model and IDM. But the outcomes of the lane change models only rarely matched reality. Therefore, the models did not fulfill their own standards to picture the existing reality.