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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Gråzonens barn -En studie i gränslandet mellan normalitet och avvikelse, mellan individen och kollektivet

Vassiliou, Spiridoula January 2007 (has links)
The purpose of this study is to research into the role of the citizen and the educational system in Sweden throughout periods of time based on previous theoretic works, and also to deepen the understanding of students with special needs in Swedish education focusing on the primary school years. This shall be carried out by illustrating the different points of view and choices within the educational system that are at hand for students with concentration difficulties and social difficulties. I will analyze these points through a cultural and social perspective on contemporary society in order to contribute towards today’s discourse on the norm. The result of this empirical investigation presents a dilemma existing in the democratic educational system of today. Nationally and internationally, the educational system has been structured around a normative system containing both rights and duties that effect everyone working within it. It is not seldom that the rights of the individual collide with collective duties within the school. This study shows that the educational system, and society at large, is founded upon a norm shaping the way people exist, behave and act within its boundaries. When an individual cannot live up to it’s ideals society perceives this as a fault that needs correcting. The students that cannot live up to the standards and the ideas of the system become marginalised in society. These students become exposed to various tests performed by the school’s professionals as a means to redefining the individual in question
122

Postmating Sexual Selection and its Role in Population Divergence in Beetles

Fricke, Claudia January 2006 (has links)
Speciation is the process describing the formation of new species and is at the heart of evolutionary biology. According to the biological species concept only reproductively isolated forms are regarded good species. This thesis aims at identifying evolutionary processes that cause population divergence and, ultimately, speciation. Natural and sexual selection are two major candidates driving changes in traits that could render populations reproductively incompatible. In recent years, biologists have recognized that most animal species are polygamous. Therefore, sexual selection does not end at mating but continues to include interactions between individuals after mating has occurred but before zygote formation. Male-male sperm competition and cryptic female choice are two main forms of postmating sexual selection shaping reproductive traits like behaviour. The studies presented in this thesis focus on laboratory experiments attempting to identify the role of postmating sexual selection in causing reproductive divergence across populations in beetles. The majority of studies were performed using a Bruchid beetle, Callosobruchus maculatus, a common, worldwide pest on stored leguminose seeds. I used two major methodological approaches. One approach seeks to identify the traces left by past selection among extant conspecific populations, by assessing the pattern of female reproductive responses to mating with males of decreasing relatedness. Second, I used a selection experiment to disentangle the joint effect of natural and sexual selection acting simultaneously on diverging replicated selection lines. In general, these experiments revealed that postmating sexual selection can be a powerful engine of incipient divergence between allopatric populations. Changes in traits underlying variables such as female reproductive output, female mating rate or male success in sperm competition evolved rapidly and could in some cases effectively reduce gene flow between conspecific populations. While postmating sexual selection per se can drive divergence, I found that interactions with natural selection can limit divergence in reproductive characters. Sexual selection tended to reinforce natural selection under strong directional selection. In contrast, sexual selection inflicted a reproductive load on populations under weak natural selection. Thus, the joint effects of natural and sexual selection on allopatric populations are non-trivial and should be considered in greater detail in future studies of early divergence.
123

Multidisciplinary Design And Optimization Of A Composite Wing Box

Hasan, Muvaffak 01 October 2003 (has links) (PDF)
In this study an automated multidisciplinary design optimization code is developed for the minimum weight design of a composite wing box. The multidisciplinary static strength, aeroelastic stability, and manufacturing requirements are simultaneously addressed in a global optimization environment through a genetic search algorithm. The static strength requirements include obtaining positive margins of safety for all the structural parts. The modified engineering bending theory together with the coarse finite element model methodology is utilized to determine the stress distribution. The nonlinear effects, stemming from load redistribution in the structure after buckling occurs, are also taken into account. The buckling analysis is based on the Rayleigh-Ritz method and the Gerard method is used for the crippling analysis. The aeroelastic stability requirements include obtaining a flutter/divergence free wing box with a prescribed damping level. The root locus method is used for aeroelastic stability analysis. The unsteady aerodynamic loads in the Laplace domain are obtained from their counterparts in the frequency domain by using Rogers rational function approximations. The outer geometry of the wing is assumed fixed and the design variables included physical properties like thicknesses, cross sectional dimensions, the number of plies and their corresponding orientation angles. The developed code, which utilizes MSC/NASTRAN&reg / as a finite element solver, is used to design a single cell, wing box with internal metallic substructure and composite skins.
124

Etude des processus de spéciation associés à une zone de transition biogéographique : exemple de l'algue brune Lessonia nigrescens

Tellier, Florence 10 July 2009 (has links) (PDF)
Le travail réalisé au cours de cette thèse s'intègre dans la problématique générale de l'étude des processus de spéciation, en prenant comme espèces modèles de grandes algues brunes marines (Ordre des Laminariales, appelées " kelps "). Ces algues forment de véritables forêts dans les eaux tempérées froides et ont une importance économique, pour l'industrie des alginates et pour la récolte d'invertébrés marins vivant dans ces forêts. Malgré leur importance écologique et économique, et leur grande diversité en nombre d'espèces dans certaines régions du monde, les mécanismes favorisant la spéciation et contribuant à l'isolement reproducteur ont été très peu étudiés chez ces espèces. Mon travail de thèse a permis de mettre en évidence l'existence de deux espèces cryptiques au sein du complexe " Lessonia nigrescens " le long des côtes chiliennes. Je me suis tout d'abord attachée à comprendre l'histoire des deux taxa, et à discuter les différentes hypothèses à l'origine de cette spéciation. Ensuite, je me suis intéressée aux mécanismes qui permettent actuellement le maintien de l'intégrité des espèces cryptiques de L. nigrescens, en particulier dans la région de contact entre leurs aires de distribution.
125

How two different predators affect size distribution and behavior of an aquatic isopod

Karlsson, Johanna January 2011 (has links)
The aquatic isopod Asellus aquaticus can in some lakes be found as two different ecotypes; one in the habitat dominated by reed and one in stonewort stands. These ecotypes have been shown to differ in size, color and behavior. The reed ecotype is larger, darker and more active compared to the stonewort ecotype. In the two habitats there are different dominating predators: Invertebrate predators in the reed habitat and fish in the stonewort habitat. This project aims to examine how the presence of invertebrate predators and fish affect the two ecotypes of the isopod in regard to behavior and size composition in different substrates. To examine the effect on behavior the activity of isopods collected from Lake Tåkern was measured without and with chemical cues from perch and damselfly larva. The result of the behavior experiment showed no difference between the ecotypes nor the treatments. The lack of differences in the behavior indicates that there could be a variation between lakes. The effect on the size composition was examined by subjecting groups of isopods to predation by perch or damselfly larva in different substrate. The mean length of the group was measured before and after the trials. The size decreased significantly for the reed ecotype in stonewort substrate when subjected to predation by perch. The size for the stonewort ecotype increased significantly in reed substrate with damselfly larva as predator. The effect on size supports that the predators are the cause of the size difference between the ecotypes.
126

PLEUROCARPOUS MOSSES IN SPACE AND TIME: BIOGEOGRAPHY AND EVOLUTION OF THE HOOKERIALES

Pokorny Montero, Cristina Isabel January 2012 (has links)
<p>Morphological characters from the gametophyte and sporophyte generations have been used in land plants to infer relationships and construct classifications, but sporophytes provide the vast majority of data for the systematics of vascular plants. In bryophytes both generations are well developed and characters from both are commonly used to classify these organisms. However, because morphological traits of gametophytes and sporophytes can have different genetic bases and experience different selective pressures, taxonomic emphasis on one generation or the other may yield incongruent classifications. The moss order Hookeriales has a controversial taxonomic history because previous classifications have focused almost exclusively on either gametophytes or sporophytes. The Hookeriales provide a model for comparing morphological evolution in gametophytes and sporophytes, and its impact on alternative classification systems. Sometimes, placement of certain groups within Hookeriales remains challenging even at the molecular level. That is the case of the genus <italic>Calyptrochaeta</italic>. We study diversification dynamics in this genus to elucidate possible mechanisms obscuring its placement and we address biogeographic questions using the Tropical Conservatism scenario as our null hypothesis. Furthermore, to better understand biogeographic patterns in the Southern Hemisphere, infraspecific molecular patterns are compared in two species of the genus <italic>Calyptrochaeta</italic> (i.e., <italic>C. apiculata</italic> and <italic>C. asplenioides</italic>) and vicariance and recent long distance dispersal are tested to explain the disjunct distributions observed in these species. </p><p>In this study we reconstruct relationships among pleurocarpous mosses in or associated to the Hookeriales, in <italic>Calyptrochaeta</italic>, and within <italic>Calyptrochaeta</italic>. Six molecular markers are explored in total from all three genome compartments to reconstruct the evolution of morphological characters and habitat preferences in our phylogenies. Divergence times are estimated in a Bayesian framework using a relaxed molecular clock, and diversification rates are calculated on the chronograms resulting from these estimations. </p><p>As a result, we found that the Hookeriales, as currently circumscribed, are monophyletic and that both sporophyte and gametophyte characters are labile. We documented parallel changes and reversals in traits from both generations. We show that diversification rates in <italic>Calyptrochaeta</italic> have changed through its history. Also, though we lack support to clearly reject the tropical conservatism hypothesis, our data point to a more complex scenario where both temperate and tropical species can be ancient and give rise to one another, since shifts between tropical and temperate regions seem to be possible in any direction. Finally, we have show that recent long distance dispersal best explains the distribution of both <italic>C. apiculata</italic> and <italic>C. asplenioides</italic> in the Southern Hemisphere.</p> / Dissertation
127

Aeroelastic Analysis Of An Unmanned Aerial Vehicle

Susuz, Umut 01 January 2008 (has links) (PDF)
In this thesis aeroelastic analysis of a typical Unmanned Aerial Vehicle (UAV) using MSC&reg / FlightLoads and Dynamics module and MSC&reg / NASTRAN Aero 1 solver was performed. The analyses were carried out at sea level, 1000m, 2000m and 4000m altitudes for Mach Numbers M=0.2, 0.4 and 0.6 for the full model of the UAV. The flutter characteristics of the UAV for different flight conditions were obtained and presented. The effect of altitude on flutter characteristics has been examined and compared with the theoretical and experimental trends in the literature. Also the divergence characteristics of the full model UAV was obtained. In the study, some verification and test cases are also included. The results of the analyses of an untapered swept-wing and AGARD 445.6 wing models were compared with wind tunnel data and a maximum error of 1.3 % in the flutter speed prediction was obtained. In two different wing models the effect of taper was investigated.
128

Innovation-diffusion processes in urban design movements: application of the model-prototype-adaptation framework to new urbanism and neighborhood development practices in Atlanta

Kim, Jaecheol 27 August 2010 (has links)
This dissertation investigates the transitions of urban design models in practice: the ways in which practitioners have adopted the urban design models and the factors that have influenced such adoption. In particular, this dissertation focused on the unexpected consequences of the adaptations of urban design models and distinguished these effects from those stemming from the inherent limitations of urban design models themselves. The major goal of this dissertation is to clarify the patterns of the transitions associated with urban design models in practice (particularly adaptation) to ensure a better understanding their impact on the urban environment. However, the transitions of urban design models in practice are complex phenomena that multiple actors with diverse interests have participated in and implemented numerous principles of the models over a long period of time and in diverse contexts. Therefore, to minimize such complexities while capturing important elements of the diffusion and adaptation processes, this dissertation presented a theoretical framework, the Model-Prototype-Adaptation (MPA) framework, based on recurring patterns of urban design movements. In the MPA framework, a "model" refers to an integrated set of urban design principles derived from a consensus of opinion of the enthusiastic proponents of an urban design movement; "prototypes" are projects developed by enthusiastic proponents who have strong commitment to the model and the movement; and "adaptations" are projects developed by eclectic followers who have weak commitment to the model and the movement and take advantage of the model for their interests and concerns. With these three key elements, the MPA framework hypothesizes two distinct transitions of urban design models in practice: "evolution," the developmental transition from old prototypes to new prototypes by enthusiastic proponents seeking to more effectively embody the model; and "divergence," a "watered down" application of the model in practice by eclectic followers responding to external factors such as market forces. This dissertation fleshed out the proposed basic MPA framework with historical reviews of the three urban design movements (Garden City, City Beautiful, and Modern) and a literature review of innovation-diffusion theories. In particular, the literature review focused on theories that present major factors influencing the adoption of innovations. The theories suggested that the ways in which adopters, who have different innovativeness and roles, perceive the attributes of innovations influence their decisions to adopt the innovations. In addition to the theoretical construction of the MPA framework, this dissertation presented a comparative case study with New Urbanist practices to test the MPA framework in a real world context. In particular, "divergence" of New Urbanism principles was examined specifically through a comparison of the six matched prototype-adaptation pairs of neighborhood developments in the Atlanta area. The case study first hypothesized three predictions about the perceptions and implementation of New Urbanism principles based on the MPA framework, that is, 1) enthusiastic proponents of New Urbanism perceive New Urbanism principles more positively than eclectic followers; 2) prototypes developed by enthusiastic proponents incorporate more New Urbanism principles and do so more thoroughly than adaptations developed by eclectic followers; and 3) New Urbanism principles that actors perceive more positively are implemented more often and more thoroughly. Data for the case study have been collected through interviews, surveys, field observations, planning documents, and local periodicals. The methods of analysis that were used in this study were pattern matching between predictions and observations, the explanation-building for the findings from pattern matching based on detailed contextual information derived from each case, and finally, cross-case synthesis. The comparative analysis showed that the case observations generally confirmed the three predictions. For example, among the New Urbanism principles, the "creation of an identifiable neighborhood" was perceived the most positively and also implemented the most often and thoroughly by both the enthusiastic proponents and the eclectic followers while "access to public transit" was perceived the least positively and implemented least often by both groups. In addition to the general confirmation of the three predictions, the analysis also revealed numerous unexpected findings, and efforts to build explanations for such findings based on the detailed contexts of each case yielded several important insights: the issue of compatibility between the thorough implementation of the New Urbanism model and the supply of affordable housing; the possibility of positive externalities from the proximity of prototypes to adaptations; two distinct flexibility arguments--flexibility for incremental accomplishment and that for contexts; the extent of public-private partnerships that broaden the influence of the New Urbanism principles beyond project boundaries; and communication problems between enthusiastic proponents and eclectic followers.
129

Commercial Vehicle Stability - Focusing on Rollover

Dahlberg, Erik January 2001 (has links)
No description available.
130

Propriétés ergodiques du feuilletage horosphérique d'une variété à courbure négative

Schapira, Barbara 26 November 2003 (has links) (PDF)
Cette thèse est consacrée à l'étude des propriétés ergodiques du feuilletage horosphérique d'une variété géométriquement finie à courbure négative $M$. Un de nos principaux résultats est la classification des mesures transverses quasi-invariantes dont la dérivée de Radon-Nikodym est un cocycle höldérien fixé, associé à une mesure de Gibbs. À un tel cocycle, nous associons certaines moyennes sur les horosphères et montrons qu'elles s'équidistribuent vers la mesure de Gibbs correspondante lorsque $M$ est compacte ou convexe-cocompacte. Lorsqu'elle n'est ni compacte ni convexe-cocompacte, nous limitons l'étude aux moyennes associées à la mesure d'entropie maximale. Nous montrons qu'elles forment une suite tendue, ce qui, dans le cas des surfaces, nous permet d'obtenir leur équidistribution vers cette mesure d'entropie maximale. En corollaire, nous obtenons l'équidistribution des orbites du flot horocyclique d'une surface hyperbolique géométriquement finie mais de volume infini.

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