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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.

Simulation numérique de la propagation d'une décharge dans un plasma sur maillage non stucturés adaptés dynamiquement Numerical simulation of streamer propagation on unstructured dynamically adapted grids

Karel, Jan 2 December 2014 (has links)
L'objectif de cette thèse est la simulation numérique de la propagation d'une décharge électrique dans un champ électrique à haute tension. Un modèle minimal est utilisé pour la description de la physique. Le modèle consiste en un modèle d'équations de convection-diffusion-réaction de particules électrique couplé à l'équation de Poisson pour le potentiel électrique. Nous simulons la propagation d'une décharge en 3D, qui présente des ramifications causées par des perturbations locales dans le champ électrique. Nous avons mis en oeuvre une méthode basée sur l'adaptation dynamique de maillages pour la simulation numérique. Les propriétés de la méthode sont testées d'abord sur un simple problème analogue en 2D. Cette approche a été suffisante pour le développement de la méthode, même si en 2D le problème est d'un type différent (décharge plane), et cela a permis une transition simple au vrai problème 3D. The aim of this thesis is a numerical simulation of a streamer propagation (electric discharge in a high voltage electric field). The minimal model is used for the streamer description. The model consists of a system of convection-diffusion-reaction equations for electric particles coupled with Poisson’s equation for an electric potential. We simulate a general streamer motion in 3D which is presented by streamer branching. It is caused by local disturbances in the electric field. We have developed a method based on a dynamically adaptation of grids for the simulation. The properties of the method are tested on simpler problems in 2D (less time consuming). This approach is sufficient for the development of the method even if it is different type of problem (planar discharge) and it allows a simple transition to 3D. Tato dizertační práce se zabývá numerickou simulací propagace streameru (elektrický výbojve vysokonapět'ovém elektrickém poli). Pro popis streameru je použit minimální model, který se skládá ze soustavy transportních rovnic pro elektricky nabité částice spárovaných s Poissonovou rovnicí pro elektrický potenciál. V práci simulujeme obecný pohyb streameru ve 3D. Tento obecný pohyb je prezentován rozvětvením streameru, kterého se dosáhne pomocí lokálních poruch v elektrickem poli. Pro numerickou simulaci streameru jsme vyvinuli meto du založenou na dynamické adaptaci síte, jejíž vlastnosti byly otestováný na jednodušších problé-mech ve 2D (menší časová náročnost). I když jde o jiný typ problému (rovinný výboj), pro vývoj metody je dostatečný a umožňuje snadný přechod do 3D.

A study of dark adaptation in ocular hypertensives using a two-filter method

Patton, Danalee Goldthwaite 1972 (has links)
Dark adaptation thresholds have been determined for a group of ocular hypertensives and a group of equivantly aged normal controls under two separate conditions of colored pre-adaptation and test. The method relies on the Purkinje shift to obtain two dark adaptation curves for each subject that cross when the initially favored long wavelength (yellow) curve is superceded by the shorter one (blue-green): under photopic conditions, the yellow and blue-green stimuli are equally efficient in stimulating the retina, as they are equated for brightness during pre-adaptation; as dark adaptation proceeds the blue-green and yellow thresholds display an early relation wherein yellow light has the lower thresholds; then the curves cross and blue-green light displays lower thresholds. Each curve is obtained separately with a pre-adaptation of 80 ft. lamberts for 5 minutes and a centrally fixated 11° test patch that matches the spectral composition of the pre-adaptation. A variety of variables are derived from threshold intensity measurements and they are analyzed for age effects, disease effects, and their interactions. Age and disease both depress blue-green and yellow cone sensitivity, delay cross-over time, and increase the total change in sensitivity over 13 minutes of dark adaptation. Interactions magnify differences. Color discrimination is found to be associated with dark adaptation thresholds, sometimes specifically as to the type of color defect and the colored dark adaptation curve showing losses. Intraocular pressure, macular sensitivity, and diastolic blood pressure are also significantly correlated with dark adaptation thresholds. Disease and age effects are elaborated in terms of changes in the ocular media, macular pigmentation changes, as well as deterioration of rod and cone processes. In addition, aging is seen to be complicated by peculiarities in the selection of the normal population. The associations demonstrated for clinical and color vision variables with dark adaptation thresholds suggest (1) that open angle glaucoma may be caused by deficient nutrition to the optic nerve head or to the retina itself, (2) that central rod and cone vision undergo changes very early in the course of the disease. A preliminary study using the two-filter method with well-established glaucoma confirms that similar, more pronounced losses in dark adaptation take place later in the disease's development. Arts, Faculty of Psychology, Department of Graduate

Die lehre von der natürlichen anpassung in ihrer entwicklung, anwendung und bedeutung.

Münsterberg, Hugo Unknown Date (has links)
Inaug.-diss.--Leipzig. Bibliographical footnotes.

The internationalization of work : psychophysiological predictors of adjustment to foreign assignment

Anderzén, Ingrid 1998 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. Härtill 6 uppsatser.

Studies on children's psychological adjustment to diabetes

Lernmark, Barbro 1999 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. Härtill 7 uppsatser.

Postural adjustments in sitting position : effect of development, training and brain lesions

Brogren, Eva 1999 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. Härtill 6 uppsatser.

Anticipating, experiencing and valuing the transition from worker to retiree : a longitudinal study of retirement as an occupational transition

Jonsson, Hans 2000 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. Härtill 5 uppsatser.

Clinical management of children with type I diabetes mellitus : a prospective, randomized psycho-educational intervention trial

Forsander, Gun 2000 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. Härtill 5 uppsatser.

The influence of psychosocial variables on the emotional and finger temperature responses to acute cold exposure

Sampson, James Baldwin. 1975
Thesis (Ph.D.)--Tufts University, 1975. Submitted to the Dept. of Psychology. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Adaptation, Aktiviertheit und Valenz

Schönpflug, Wolfgang. 1971 (has links)
Habilitationsschrift--Bochum. Bibliography: p. [88]-97.

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