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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 02 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 January 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


Piirainen, Helena, Seta, Dzejna January 2008 (has links)
The purpose of this study is to examine how the social/cultural, legal, economic, political and technological environment in international markets affects a firm’s standardization and adaptation of the marketing mix. This study investigates Getinge ABs actions on the German and the Chinese market. The aim is to see how the company has been forced to adapt the marketing mix in order to penetrate these markets. The study is based on a theoretical framework that includes relevant theories regarding the standardization and adaptation of the marketing mix, and the environmental influences that a firm has to take into consideration. The research has been performed on a Swedish company that provides medical equipment for institutions – Getinge AB. A qualitative personal interview has been carried out with the Vice president of sales and services of Getinge AB and the managing director of the area of infection control – Harald Castler. This study has shown that the environmental factors on the Chinese market have affected the adaptation of the product, price and promotion. The distribution channels have on the other hand only been affected by the social/cultural conditions. On the German market product adaptation has been influenced by the social/cultural, legal, economic and political conditions. Only the social/cultural, legal and economic conditions have affected the price adaptation. Further, the adaptation of the promotion has only been affected by the social/cultural and political conditions. Finally the distribution channels on the German market have been affected by the social/cultural, legal and political conditions. The results have also shown that it has been a challenge for Getinge AB to find a balance between the degree of standardization and local adaptation of the different elements in the marketing mix – a challenge that they have succeeded to deal with. Further more the study shows the importance of adapting the marketing mix to the local situation since it is the key to manage to design offers that will lead to success and increased market shares. The overall conclusion of this study is that Getinge AB needs to think globally, but act locally and take environmental influences such as the social/cultural, legal, economic, political and technological ones, into consideration.

Conception et réalisation d’un front-end analogique pour un récepteur multistandard multi-mode / Design of an analogue front-end for a multistandard multimode receiver

Izquierdo, Christian 24 May 2011 (has links)
L‘objectif de la thèse est la conception d’un front-end analogique RF large bande pour récepteurs cellulaires multistandard multi-mode. La principale limitation des récepteurs actuels par rapport à cet objectif est la nécessité d’un filtre SAW externe afin de protéger le LNA et le mélangeur des bloqueurs hors bande. Nous proposons dans cette thèse une technique de contre-réaction positive, basée sur la transposition de fréquences, qui permet un filtrage RF sélectif dès l’entrée du récepteur. Cette architecture diminue les contraintes de linéarité dès l’entrée du LNA. Ce filtrage est en plus reconfigurable en fréquence et en largeur de bande. Un circuit expérimental a été réalisé en technologie CMOS 65nm. La contre-réaction permet une amélioration de 17dB de l’IIP3 hors bande de l’amplificateur faible bruit. La fréquence centrale est accordable de 1,3GHz à 2,85GHz ; la consommation est de 30 mW pour un facteur de bruit maximal de 6,5dB. / The aim of this thesis is the design of a wide-band RF analogue front-end for a cellular multi-standard and multiband receiver. The main limitation of receivers today is the need of external SAW filters to protect the LNA and mixer from out-of-band interferers. In this thesis we propose a new technique of positive feed-back which transposes the filters transfer function in RF. Thus, a selective RF filter is created in the LNA input to improve non-linearity performances of the receiver. This RF filter is also configurable in bandwidth and center frequency. An experimental prototype has been made in 65nm CMOS technology. The positive feed-back improves the LNA out-of-band IIP3 by 17dB. The center frequency is configurable from 1.3GHZ to 2.85GHz. Power consumption is of 30mW, while maximal NF is of 6.5dB.

Some aspects of the physiological adaptation of lower vertebrates to marine environments

McBean, Ralph Lachlan January 1963 (has links)
I STUDIES ON THE GLOMERULAR FILTRATION RATE OF RAINBOW TROUT (SALMO GAIRDNERI) Upon adaptation of rainbow trout to 80% sea water, the glomerular filtration rate, as measured by the method of inulin clearance, was reduced from 156 ± 8.9 to 10.0 ± 2.6 ml./kg. body weight/day. Return to fresh water after one month in sea water was accompanied by a rapid re-establishment of the high glomerular filtration rate. This lability of the glomerular filtration rate in the trout is probably an important factor contributing to the reduction of urine flow associated with the adaptation of the euryhaline form to sea water. The effects of adrenocortical and mammalian neurohypophysial hormones on the glomerular filtration rate were studied. Vasopressin and oxytocin, when administered either separately or together, significantly increased the filtration rate, aldosterone had no effect, while corticosterone caused a significant reduction. II STUDIES ON ELECTROLYTE EXCRETION IN THE GREEN TURTLE (CHELONIA MYDAS) The extracellular concentrations of sodium and potassium in the marine turtle, Chelonia mydas mydas, were unchanged after adaptation to a fresh water environment. At the same time the urinary concentrations of these ions were significantly reduced. In addition, the "salt glands" of fresh water adapted juvenile turtles showed a 38% regression in absolute weight. Feeding and saline-loading of sea water adapted turtles elicited rates of sodium and potassium excretion greatly in excess of those possible via the kidney. Failure to detect significant changes in these rates following occlusion of the cloaca further indicated that the major site of electrolyte excretion after feeding or saline-loading was the salt gland. Suppression of adrenocorticosteriod synthesis by treatment with amphenone "B" immediately after feeding or saline-loading reduced the excretion of sodium and potassium to unfed or non-loaded levels. The normal pattern of sodium excretion but not of potassium excretion could be restored in the amphenone-treated animals by the simultaneous administration of corti-costerone. The significance of the ingestion of sea water is discussed in relation to the high electrolyte intake associated with the diet of these turtles. / Science, Faculty of / Zoology, Department of / Graduate

Mitotic aberrations induced by sunflower seed oil in Allium cepa root-tip cells

Peterson, Alma Ness January 1962 (has links)
Abnormal mitotic divisions and chromosomal aberrations were observed in onion root-tip cells treated with various concentrations of sunflower seed oil and for varying times. All treatments induced similar chromosomal aberrations but the number and extent of the deviations were influenced by the concentration and duration of the exposure. Abnormalities included pycnosis, "sticky" anaphase and telophase bridges with or without fragments, c-mitosis and inhibition of cell division. Chromosome and chromatid breakage with erosion and fragmentation were maximum at metaphase and anaphase four hours after treatment with 0.1 ppm oil concentration. Binucleate cells, micro-and macronuclei and some polyploidy appeared following recovery in -tap water. Spindle abnormalities were indicated by arrested meta-phases, multipolar anaphases and misdivision at anaphase. It is suggested that these chromosomal and spindle aberrations were induced by the carbon-carbon double bonds present in the unsaturated acids of the sunflower seed oil which enabled them to function as electron donors and to undergo such reactions as the addition of hydrogen, of water and of acids. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate

Philopatry, inbreeding, and the adaptive advantages of sex /

Shields, William Michael January 1979 (has links)
No description available.

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

Sampson, James Baldwin. January 1975 (has links)
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;

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

Anderzén, Ingrid, January 1900 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

Studies on children's psychological adjustment to diabetes /

Lernmark, Barbro, January 1900 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 7 uppsatser.

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