En optique quantique, la nature quantique de la lumière se manifeste dans des effets d’ordonnement d’opérateurs, inexistants en optique classique. Cette thèse est consacrée à une étude détaillée de ce type d’effets d’ordonnement dus à la dynamique des systèmes physiques. Nous considérons deux systèmes en particulier, 1) la conversion paramétrique descendante dans un milieu χ (2), et 2) un ion dans un piège de Paul entraı̂né par un champ classique; décrit par un modèle de Jaynes-Cummings non linéaire. Les effets d’ordonnement dans ces systèmes dynamiques sont étudiés via le développement et l’approximation de Magnus. Dans le scénario de conversion paramétrique descendante, nous considérons deux cas, (i) une pompe monochromatique (où une solution exacte de la dynamique est connue) et (ii) une pompe spectralement large. Pour la pompe monochromatique, nous écrivons explicitement la décomposition de Bloch-Messiah et obtenons les modes propres et les paramètres de compression. Nous comparons ces résultats exacts avec les approximations de Magnus en incluant certains ou aucun effets d’ordonnement. Nous effectuons une analyse similaire pour la pompe spectralement large lorsque la décomposition de Bloch-Messiah ne peut être évaluée que numériquement. Pour le modèle dynamique de Jaynes-Cummings non linéaire, nous analysons, à nouveau, les effets d’ordonnement via des approximations de Magnus et obtenons la solution exacte, qui n’avait pas été publiée dans la littérature auparavant. Enfin, nous évaluons pour la première fois les limites supérieures exactes (qui dépassent les limites suffisantes) de la convergence du développement de Magnus pour les deux modèles dynamiques à solutions exactes. / In quantum optics, the quantum nature of light manifests itself in operator ordering effects, nonexistent in classical optics. This thesis is devoted to a detailed study of such ordering effects that are due to the dynamics of physical systems. We consider two systems in particular, 1) parametric down-conversion in a χ(2) medium, and 2) an ion in a Paul trap driven by a classical field; described by a nonlinear Jaynes-Cummings model. Ordering effects in these dynamical systems are studied via the Magnus expansion and approximation. In the parametric down-conversion scenario we consider two cases, (i) a monochromatic pump (where an exact solution of the dynamics is known), and (ii) a spectrally broad pump. For the monochromatic pump, we write explicitly the Bloch-Messiah decomposition and obtain the squeezing eigenmodes and parameters. We compare these exact results with the Magnus approximations that contain some or no ordering effects. We perform similar analysis for the spectrally broad pump, where the Bloch-Messiah decomposition can only be evaluated numerically. For the dynamics in the nonlinear Jaynes-Cummings model we again analyze ordering effects via Magnus approximations and obtain the exact solution, which has not been published in the literature before. Lastly, we evaluate the exact upper bounds (which exceed sufficient bounds) of convergence of the Magnus expansion for the two models with exact solutions, for the first time.

The thesis is based upon research into the historical geography of the pastoral industry in the six major drainage basins in the North West of Western Australia, in an attempt to outline its early development, and to explain how the rangeland degeneration associated with the Big Drought of 1936-1946 was exacerbated by unrealistic official expectations and poor management, particularly of stations in the hands of absentee corporate owners. it discusses the failure of government agencies to appreciate the effects of overstocking in an environment characterised by climatic variability and fragile rangeland resources. It draws attention to the official reluctance to take action against the destructive activities of profit-seeking corporate owners in the period leading up to and including the Big Drought, and of speculative leaseholders in more recent times The thesis attempts to differentiate between the grassmen as leaseholders bent upon generating a sustainable income from the rangeland through conservative management, and the exploitative owners and their (often) incompetent managers. It identifies the specific characteristics of each of the basins in terms of the physical environment, the process of pastoral occupation and the resulting changing patterns of land use. It examines the changing nature of the habitat, economy and society of the Aboriginal people, from the days prior to European penetration up to the late 20th century It also considers the future prospects of the pastoral industry in each basin, with references to such issues as environmental impact, Aboriginal land rights and occupance, and the mining industry. As well as a comprehensive overview of the historical geography of each river basin, the thesis also includes a study of infrastructural elements and bf the activities of all groups of people involved in the development of the river basins.

Hundreds of millions of users each day search the web and other repositories to meet their information needs. However, queries can fail to find documents due to a mismatch in terminology. Query expansion seeks to address this problem by automatically adding terms from highly ranked documents to the query. While query expansion has been shown to be effective at improving query performance, the gain in effectiveness comes at a cost: expansion is slow and resource-intensive. Current techniques for query expansion use fixed values for key parameters, determined by tuning on test collections. We show that these parameters may not be generally applicable, and, more significantly, that the assumption that the same parameter settings can be used for all queries is invalid. Using detailed experiments, we demonstrate that new methods for choosing parameters must be found. In conventional approaches to query expansion, the additional terms are selected from highly ranked documents returned from an initial retrieval run. We demonstrate a new method of obtaining expansion terms, based on past user queries that are associated with documents in the collection. The most effective query expansion methods rely on costly retrieval and processing of feedback documents. We explore alternative methods for reducing query-evaluation costs, and propose a new method based on keeping a brief summary of each document in memory. This method allows query expansion to proceed three times faster than previously, while approximating the effectiveness of standard expansion. We investigate the use of document expansion, in which documents are augmented with related terms extracted from the corpus during indexing, as an alternative to query expansion. The overheads at query time are small. We propose and explore a range of corpus-based document expansion techniques and compare them to corpus-based query expansion on TREC data. These experiments show that document expansion delivers at best limited benefits, while query expansion � including standard techniques and efficient approaches described in recent work � usually delivers good gains. We conclude that document expansion is unpromising, but it is likely that the efficiency of query expansion can be further improved.

Hundreds of millions of users each day search the web and other repositories to meet their information needs. However, queries can fail to find documents due to a mismatch in terminology. Query expansion seeks to address this problem by automatically adding terms from highly ranked documents to the query. While query expansion has been shown to be effective at improving query performance, the gain in effectiveness comes at a cost: expansion is slow and resource-intensive. Current techniques for query expansion use fixed values for key parameters, determined by tuning on test collections. We show that these parameters may not be generally applicable, and, more significantly, that the assumption that the same parameter settings can be used for all queries is invalid. Using detailed experiments, we demonstrate that new methods for choosing parameters must be found. In conventional approaches to query expansion, the additional terms are selected from highly ranked do cuments returned from an initial retrieval run. We demonstrate a new method of obtaining expansion terms, based on past user queries that are associated with documents in the collection. The most effective query expansion methods rely on costly retrieval and processing of feedback documents. We explore alternative methods for reducing query-evaluation costs, and propose a new method based on keeping a brief summary of each document in memory. This method allows query expansion to proceed three times faster than previously, while approximating the effectiveness of standard expansion. We investigate the use of document expansion, in which documents are augmented with related terms extracted from the corpus during indexing, as an alternative to query expansion. The overheads at query time are small. We propose and explore a range of corpus-based document expansion techniques and compare them to corpus-based query expansion on TREC data. These experiments show that document expansion delivers at best limited ben efits, while query expansion, including standard techniques and efficient approaches described in recent work, usually delivers good gains. We conclude that document expansion is unpromising, but it is likely that the efficiency of query expansion can be further improved.

<p>Syftet med denna studie har varit att ta reda på hur det är att vara kvinna och äga och driva ett företag som har flera anställda. Jag valde att undersöka kvinnor som har flera anställda då jag tidigare inte funnit någon forskning på det området samt för att de flesta kvinnliga företagare är soloföretagare, vilket betyder att de inte har några anställda och företaget räknas som levebrödsföretag.</p><p>För att få fram den kunskap som jag eftersträvade har jag använt mig av kvalitativ metod och djupintervjuer då jag samlade in mitt empiriska material. Då jag sedan analyserade detta material har jag använt mig av de analysmetoder som används inom grundad teori och narrativanalys.</p><p>Resultatet blev följande. Kvinnliga företagare expanderar då efterfrågan växer.Kvinnliga företagare har också tagit till sig det kvinnliga ledarskapet som anses vara mjukt och omsorgsfullt. Detta kan även hindra att företaget växer.</p>

<p>Denna uppsats behandlar svårigheter och möjligheter som finns när ett fastighetsmäklarföretag expanderar på en marknad med stor konkurrens. I de tre storstadsregionerna är konkurrensen mellan de olika fastighetsmäklarbyråerna mycket stor. Vad är det då som får nya aktörer att försöka slå sig in på dessa marknader.</p>

Graduation date: 1997

This thesis concerns the study of Ultra Low Frequency (ULF) waves during magnetospheric substorms. A wavelet algorithm which characterises magnetic ULF waves during substorm onset is presented. The algorithm is validated by comparing the spatial and temporal location of ULF wave onset to space-based observations of the aurora. It is demonstrated that the onset of ULF wave power expands coherently away from an ionospheric epicentre during the substorm expansion phase. Further, a case study of the time-domain causality of magnetotail plasma flows and ULF wave Pi2 pulsations is presented. Although highly correlated, it is demonstrated that the plasma flows cannot directly drive the ground magnetic waveforms but may be indirectly linked via a common source. Finally, results from a statistical study of ULF wave power during onset are presented. It is concluded that there is no statistical difference between historical sub-classifications of ULF waves observed during substorms.

An analysis of the Einstein Field Equations within a Robertson-Walker Cosmology. More specifically, what values of the cosmological constant will result in a Big Bang.

We analyse different Gibbsian properties of interactive Brownian diffusions X indexed by the lattice $Z^{d} : X = (X_{i}(t), i ∈ Z^{d}, t ∈ [0, T], 0 < T < +∞)$. In a first part, these processes are characterized as Gibbs states on path spaces of the form $C([0, T],R)Z^{d}$. In a second part, we study the Gibbsian character on $R^{Z}^{d}$ of $v^{t}$, the law at time t of the infinite-dimensional diffusion X(t), when the initial law $v = v^{0}$ is Gibbsian.