During the past decades, the establishment of external shopping centers have been increasing, causing debates on how they affect the viability and vitality of city centers. Instead of studying them as individual actors that are in competition with each other, it is interesting to examine them as components that together make cities complete trading destinations.  The purpose of this thesis is to study the coexistence and collaboration between different retail agglomerations. Retail agglomeration attributes are implemented to distinguish existing strengths and weaknesses for each trading venue, in order to identify where they complement each other. The research method is qualitative with an abductive approach. Six semi-structured interviews were conducted with respondents who represent different associations.  The findings of the research revealed that city centers and external shopping establishments are able to coexist if they complement each other through their individual offerings and experiences. Different retail agglomerations attract contrasting customer groups, allowing them to coexist. Collaboration between retail agglomerations can be implemented in several ways and can enhance the attractiveness of cities as trading destinations. The collaboration can occur by implementing shared marketing, shuttle bus services or collective events.  This research is limited to only investigating one medium sized city and three retail agglomeration formats. Furthermore, the choice of participants did not include consumers and store owners, which could have provided additional perspectives. The findings contribute to the study field by highlighting how retail agglomerations can coexist and collaborate and can be useful for other medium sized cities.

La coexistence de parcelles de maïs implique des transferts de pollen inter-parcellaire, sous l'action du vent, qui peuvent altérer la pureté des productions en grains ou être le vecteur de dissémination de transgènes. Pour limiter ces transferts, différents isolements spatiaux sont préconisés (distances, barrières polliniques). Cependant, aucun outil n'est à disposition des professionnels pour estimer l'efficacité de ces isolements. Ma thèse, réalisée à l'INRA (UMR EGC, Grignon, 78) et financée par une bourse CIFRE en partenariat avec Arvalis - Institut du végétal, entreprend de compléter et d'intégrer les connaissances au sein d'un modèle opérationnel de pollinisation inter-parcellaire efficace. Son originalité est de prendre en compte l'effet des conditions météorologiques sur un pas de temps horaire tout au long de la saison d'émission du pollen. Le modèle résulte du couplage de trois sous-modèles, formant les axes de mon projet, qui prédisent: l'émission en termes de quantité et de qualité ainsi que la dispersion atmosphérique. Chacun des sous-modèles est simple et opérationnel et s'appuie sur des expérimentations menées en grande partie durant la thèse. (1) Une étude statistique sur un vaste jeu de données collecté sur cinq ans a permis de développer un modèle de dynamique d'émission ayant une composante saisonnière et une composante journalière. Les paramètres des dynamiques ont été reliés aux conditions météorologiques en utilisant un modèle de développement et des arbres de régression. (2) La qualité du pollen correspond à sa viabilité et sa vitesse de sédimentation. Des relations empiriques ont été mises en évidence entre ces caractéristiques et la teneur en eau du pollen à partir de mesures expérimentales collectées sur 2 ans. Un modèle de qualité du pollen a été développé sur la base de ces relations et d'un modèle existant de déshydratation en fonction de l'humidité de l'air. (3) La modélisation de la dispersion aérienne repose sur une solution analytique des équations d'advection-diffusion de la littérature. Elle a été validée sur des données expérimentales d'une année et sur les simulations d'un modèle mécaniste de type lagrangien. Le modèle a été utilisé pour comparer l'efficacité de différents isolements pour des scénarios météorologiques contrastés en estimant des pourcentages moyens de pollen exogène viable arrivant sur une parcelle réceptrice. Il a permis de constater que l'augmentation de la pollinisation inter-parcellaire lorsque les distances d'isolement sont réduites peut être compensée par une barrière pollinique. Il a aussi révélé les rôles déterminant de la vitesse du vent et des productions totales de pollen des parcelles qui coexistent.

L'océan est un milieu fortement turbulent caractérisé notamment par de nombreuses structures tourbillonnaires très énergétiques interagissant entre elles. Dans les couches de surface, les observations ainsi que les modèles montrent que cette dynamique mésoéchelle et submésoéchelle combinée à la dynamique de la couche mélangée, contraint fortement la distribution des espèces phytoplanctoniques. L'objet de cette thèse est de réaliser une étude de processus en modélisation numérique afin de rationaliser l'effet de la turbulence méso- et subméso-échelle d'une part et du mélange vertical d'autre part, sur la diversité phytoplanctonique. L'étude analytique de la dynamique intrinsèque d'un modèle d'écosystème simple avec deux espèces de phytoplancton à l'aide de la théorie des systèmes dynamiques a tout d'abord permis de déterminer les équilibres non-linéaires ainsi que leur stabilité en fonction des paramètres. Nous avons montré ensuite que la diffusion verticale turbulente est un moteur de la coexistence des espèces phytoplanctoniques. La sensibilité de ces résultats a été testée à la fois vis à vis de la profondeur de la couche mélangée, de l'intensité du mélange et du nombre d'espèces phytoplanctoniques. Enfin, nous avons montré que la turbulence quasi-géostrophique de surface permet également la coexistence de deux espèces phytoplanctoniques sur une ressource limitante à l'équilibre statistique. De plus, ce type de turbulence organise différemment les espèces selon les structures : les structures filamentaires sont favorables au grand phytoplancton alors que les tourbillons apparaissent comme des niches écologiques pour le petit phytoplancton. Cette étude révèle que dans tous les cas, les injections verticales de nutriments sont un facteur important induisant cette différence de distribution entre les espèces.

<p>This report consider a system describing three competing species with populations <em>x</em>, <em>y</em> and <em>z</em>. Sufficient conditions for every positive equilibrium to be asymptotically stable have been found. First it is shown that conditions on the pairwise competitive interaction between the populations are needed. Actually, these conditions are equivalent to asymptotic stability for any two-dimensional competing system of the three species. It is also shown that these alone are not enough, and that a condition on the competitive interaction between all three populations is also needed. If all conditions are fulfilled, each population will survive on a long-term basis and there will be a stable coexistence.</p>

Cette étude expérimentale est consacrée à la structure cristalline et aux propriétés magnétiques des phases orthorhombiques ANb2O6 (A = métaux magnétiques) qui ont retenues notre attention en tant que système Ising modèle quasi 1D. Ce comportement magnétique original de basse dimension résulte à la fois de la force des interactions magnétiques le long des chaînes d'atomes magnétiques quasi-unidimensionnelles, et à la faiblesse des interactions entre les chaînes qui sont de nature antiferromagnétique. Lorsque ces composés sont ordonnés l'ensemble de ces interactions inter et intra chaîne conduit à un ordre antiferromagnétique. Notre investigation s'appuie sur une caractérisation systématique de la série de composés AxA'1-xNb2O6 (A et A' = Ni, Fe et Co), par des mesures variées et complémentaires, notamment: diffraction des rayons X à température ambiante, diffraction de neutrons au dessus et en dessous de la température d'ordre magnétique, mesures magnétiques : évolution thermique de courbes d'aimantation isochamp et mesures d'aimantation isotherme. De plus, des mesures de la chaleur spécifique et de spectroscopie Mössbauer ont été réalisées sur certains échantillons sélectionnés. Nous avons mis à jour, selon la concentration, des comportement très différents dans les systèmes pseudo binaires Fe-Co, Ni-Fe ou Co-Ni qui peuvent soit présenter un état ordonné soit conserver un état paramagnétique jusqu'à de très basses températures. Nos mesures démontrent que la température d'ordre magnétique et les vecteurs de propagations diffèrent sensiblement selon la composition car ces systèmes sont caractérisés par une compétition entre les interactions magnétiques mises en jeu dans un réseau triangulaire interchaines. Cette étude montre que le désordre cationique Fe/Co induit une réduction substantielle des interactions tant inter que intra chaînes, ce qui traduit la tendance à défavoriser l'établissement d'un ordre magnétique à longue portée. De manière similaire, le système NixFe1-xNb2O6 ne présente pas d'ordre magnétique pour x=0,2 et ceci jusqu'à 400 mK au moins.

This report consider a system describing three competing species with populations x, y and z. Sufficient conditions for every positive equilibrium to be asymptotically stable have been found. First it is shown that conditions on the pairwise competitive interaction between the populations are needed. Actually, these conditions are equivalent to asymptotic stability for any two-dimensional competing system of the three species. It is also shown that these alone are not enough, and that a condition on the competitive interaction between all three populations is also needed. If all conditions are fulfilled, each population will survive on a long-term basis and there will be a stable coexistence.

Characteristics of wireless home and office services and the corresponding networking issues are discussed. Local Area Networking (LAN) and Personal Area Networking (PAN) technologies such as IEEE 802.11 and Ultra Wideband (UWB) are introduced. IEEE 802.11a and UWB systems are susceptible to interference from each other due to their overlapping frequencies. The major contribution of this work is to provide a framework for coexistence of the two systems. The interference between the two systems is evaluated theoretically by developing analytical models, and by simulations. It is shown that the interference from UWB on IEEE 802.11a systems is generally insignificant. IEEE 802.11a interference on UWB systems, however, is very critical and can significantly increase the bit error rate (BER) and degrade the throughput of the UWB system. A novel idea in the MAC layer is presented to mitigate this interference by means of temporal separation. Simulation results validate our technique. Implications to wireless home services such as high definition television (HDTV) are provided. Future research directions are discussed.

Globalization refers to the reduction of economic, cultural and social differences among different regions. It describes the process of these regional aspects to become integrated through the advancement of transportation, communication and trade. The goal is to form a more unify entity through exchange, interaction and interdependence between each nations without being limited by the distances. Under the globalization influences, the world¡¦s marine affairs has been in focusing on the peaceful coexistence and sustainable development of the sea. A single country is no longer independent off the development and activities around the sea without join cooperation at regional territory or with the world, especially the nontraditional maritime security. Nations have been dealing with these problems through international convention, regional conventions and multilateral agreements. The present work carried out a comparative analysis with regard to the recent development of marine affairs between China and Taiwan. The research has perceived to examine the differences of policy, legal system and institutional management, and enforcement that exist at the cross-strait. The main focus is to identify the feasible issues for cooperation in order to breaking the dead lock among the cross-strait maritime affairs. There are problems of direct talk without communication platform and appropriate mechanism at the both sides of cross-strait. In addition, both sides have different focus on policy, legal systems, management, and enforcement compare to international trends. As a result, the differences cause the difficulties for the integration between the cross-strait on the sustainable development, maritime safety, cooperation development, and peaceful coexistence. This thesis conclude that the cross-strait could resolve the issue through proper communication platform and cooperation mechanism to deal with the low political sensitivity issues such as the marine affairs, by implementing a cross talk on a regular basis , and lead to the signing of the agreement for marine affairs at least for the short term. In the long run, the cross-strait shall create a legal system abided by both sides, where it meets with the international framework. For this it is imperative to establish the marine affair department responsible for integrating the marine management between the cross-strait. The research survey provides the key issues and suggestions that the cross-strait can precede a radical improvement in marine affairs and improve practical cooperation without causing serious dispute or disagreement.

The biological diversity on planet Earth is astounding. Understanding the origins of this diversity, and how it is maintained, are the twin goals of ecology and evolutionary biology. An early and oft-repeated insight in this investigation is that that similar organisms cannot coexist indefinitely. Theory predicts that individuals and species will compete for limited resources and whichever has even a slight advantage will drive all others extinct in a process known as ‘competitive exclusion’. By diversifying, species avoid competition, thereby ‘stabilizing’ their coexistence. Yet natural systems often display levels of diversity that are surprisingly high, given this theory and investigations of how the similarity of coexisting species is maintained have received much less attention. Using a combination of field studies and experiments I demonstrate that highly similar species of freshwater amphipods may compete for resources without resulting in competitive exclusion. These findings suggest that there exist a range of interactions among Hyalella amphipods, ranging from strong stabilizing effects due to ecological trade-offs, to weakly stabilizing effects, to a total lack of stabilizing effects among various pairs of species in this system. These findings demonstrate how the relative strength of stabilizing forces may vary among coexisting species. Although much effort has been dedicated to enumerating and classifying the ways in which ecological and evolutionary forces promote diversity among species, there has been far less attention paid to mechanisms such as convergent evolution, habitat filtering, competition for non-substitutable resources, and non-ecological speciation, among others. I surveyed current theory that may explain the high levels of similarity among species often found in natural systems. I describe how several ecological and evolutionary mechanisms may operate to promote the coexistence of similar species and present results from new theoretical combinations of mechanisms to demonstrate how they may further act in concert with one another. / text

Colombia's protracted civil war between Marxist insurgencies and the state has brought grave consequences for the civilian population and the prospects for constructing a viable political community in the country. With up to 5 million internally displaced people, rampant impunity for perpetrators of crimes against humanity and human rights and International Humanitarian Law violations, dozens of politicians and countless members of the armed forces linked to paramilitary organizations, along with increasing social injustices and inequalities, Colombia presents a troubling social-political panorama that has led to what is often referred to as a profound social and institutional 'moral crisis'. Much discussion has centred on the question of achieving some degree of minimal moral and political consensus and 'collective conscience' to humanize and slowly transform the conflict at local, regional and national levels. However, the philosophical and political parameters of this discussion have been and continue to be set firmly within variants of the liberal tradition which, it is argued, does not provide the necessary resources for adequately conceptualizing the problem and conceiving the task of addressing conflict, constructing moral consensus, and seeking social and political coexistence. The thesis argues that the philosophy of Alasdair MacIntyre can provide such resources. MacIntyre provides a convincing account of the philosophical problems that underlie ongoing intractable disagreement and the conflicts it breeds, offering a philosophy that can inform and underpin efforts at social transformation, resistance, and coexistence as well as aiding the necessary task of social scientific research and analysis of the conflict. The thesis analyses the moral dimensions of the conflict in light of MacIntyre's philosophy but also critically explores the adequacy of his politics of local community for the Colombian context. MacIntyre argues that a rational political community can only be constructed through the praxis of local communities engaging in shared moral-political deliberation. Through an empirical case study of a Constituent Assembly process in a rural community that has suffered the impacts of armed conflict for decades, the thesis explores an attempt at constructing peaceful social and political coexistence in light of MacIntyre's moral-sociological framework.