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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.
1

An Appraisal of the Characteristic Modes of Composite Objects

Alroughani, Hamad 28 October 2013 (has links)
The theory of electromagnetic characteristic modes was published roughly forty years ago, for both conducting and penetrable objects. However, while the characteristic mode analysis of conducting objects has found renewed interest as a tool for antenna designers, computed results for the characteristic mode eigenvalues, eigencurrents and eigenfields for penetrable objects have not appeared, not even in the seminal papers on the subject. In this thesis both volume and surface integral equation formulations are used to compute the characteristic modes of penetrable objects for what appears to be the first time. This opens the way for the use of characteristic mode theory in the design of antennas made of penetrable material whose polarization current densities constitute the main radiating mechanism of the antenna. Volume formulations are shown to be reliable but computationally burdensome. It is demonstrated that surface formulations are computationally more efficient, but obtrude some non-physical modes in addition to the physical ones. Fortunately, certain field orthogonality checklists can be used to provide a straightforward means of unambiguously selecting only the physical modes. The sub-structure characteristic mode concept is extended to problems involving both perfectly conducting and penetrable materials. It is also argued that sub-structure modes can be viewed as characteristic modes that implicitly use modified Green’s functions, but without such Green’s functions being needed explicitly. This makes the concept really practical, since the desired modified Green’s functions are not known explicitly in most cases.
2

An Appraisal of the Characteristic Modes of Composite Objects

Alroughani, Hamad January 2013 (has links)
The theory of electromagnetic characteristic modes was published roughly forty years ago, for both conducting and penetrable objects. However, while the characteristic mode analysis of conducting objects has found renewed interest as a tool for antenna designers, computed results for the characteristic mode eigenvalues, eigencurrents and eigenfields for penetrable objects have not appeared, not even in the seminal papers on the subject. In this thesis both volume and surface integral equation formulations are used to compute the characteristic modes of penetrable objects for what appears to be the first time. This opens the way for the use of characteristic mode theory in the design of antennas made of penetrable material whose polarization current densities constitute the main radiating mechanism of the antenna. Volume formulations are shown to be reliable but computationally burdensome. It is demonstrated that surface formulations are computationally more efficient, but obtrude some non-physical modes in addition to the physical ones. Fortunately, certain field orthogonality checklists can be used to provide a straightforward means of unambiguously selecting only the physical modes. The sub-structure characteristic mode concept is extended to problems involving both perfectly conducting and penetrable materials. It is also argued that sub-structure modes can be viewed as characteristic modes that implicitly use modified Green’s functions, but without such Green’s functions being needed explicitly. This makes the concept really practical, since the desired modified Green’s functions are not known explicitly in most cases.
3

Faciliter la téléopération d'un robot mobile non-holonome : application au maintien à domicile des personnes âgées / Facilitating the remote control of a non-holonomuous mobile robot : application to home-support for the elderly people

Nadrag, Paul 05 December 2011 (has links)
Le maintien de personnes âgées au domicile le plus longtemps possible est censé apporter une réponse à la croissance de l’espérance de vie en occident et a des coûts toujours croissants pour la société. ce travail de thèse a été réalisé dans le cadre du projet CompanionAble, qui vise a fournir une solution intégrée maison intelligente - robot aux personnes âgées, vivant seules. L'objectif est de maintenir un confort en fin de vie à un niveau élevé et à traiter les situations dangereuses pour elles, comme les chutes, avant que les conséquences ne deviennent trop importantes. Les éléments qui m’intéressent dans ce cadre sont le robot et l’opérateur, qui se trouve à l’extérieur de la maison, et qui peut téléopérer le robot en vue d’interagir avec la personne âgée, soit pour des activités ludiques (visioconférence, exercices de stimulation cognitive), soit pour des situations d’urgence (chute, perte de connaissance… de la personne âgée). Pour maintenir les coûts du système à un niveau raisonnable, on a envisagé l’utilisation de l’internet public pour la connexion entre le site maître (où se trouve l‘opérateur) et le site esclave (où se trouve le robot). Une autre spécificité du notre système est le fait que les utilisateurs ne sont pas des spécialistes de la téléopération. J’ai donc cherché à faciliter la tâche de pilotage du robot, dans ce contexte spécifique. Du côté de l’interface, on a cherché à aider l’opérateur traitant les problèmes liés aux délais de transmission (possibles à cause de l’utilisation de l’internet) et lui donner la possibilité d’utiliser une interface écologique, qui utilise des éléments de réalité augmentée. Du côté du robot, on a rajouté un nouveau mode de commande, semi-autonome, pour que l’opérateur soit plus à l’aise pendant qu’il le déplace. Pour finir, on a examiné la possibilité de passer d’un mode de commande à un autre, pour que l’opérateur soit le moins affecté que possible par des perturbations et que les performances du système restent acceptables. Les solutions proposées ont été implantée sur un système réel et évaluées au laboratoire et en situations réelles dans le cadre du projet européen CompanionAble. / Enabling older people to live in their homes as long as possible is supposed to respond to the growth of life expectancy in the west and the increasing costs to society. The present thesis was conducted in the framework of the companionable, which aims to provide an integrated smart home - robot for the elderly, which are living alone. The objective is to maintain the end of life comfort at a high level and to deal with dangerous situations for them, such as falls, before the consequences become too costly. The elements that interest me in this context are the robot and the remote operator, which is outside the home, and can teleoperate the robot to interact with the elderly, for recreational activities ( videoconferencing, cognitive stimulation exercises) or for emergency situations (falls, loss of consciousness, etc.). To keep the system costs to a reasonable level, we considered using the public internet as the connection between the master site (where the operator is) and the slave site (where the robot is). another unique feature of our system is that users are not specialists in teleoperation. As such, i tried to ease the task of controlling the robot, in this specific context. On the remote control interface side, we tried to help the operator in dealing with the problems associated with transmission delays (due to the possible use of the internet) and we gave him/her the option of using an ecological interface, which uses elements of augmented reality. On the robot side, we added a new command mode, semi-autonomous, so that the operator is more at ease as he/she controls the robot. finally, we examined the possibility of switching from one control mode to another, so that the operator is the least affected by possible disturbances and system performance is kept acceptable. The proposed solutions have been implemented on a real system and evaluated in the laboratory and in real situations, in the framework of the european CompanionAble project.
4

Statistical method for identification of sources of electromechanical oscillations in power systems

McNabb, Patrick James January 2011 (has links)
The use of real-time continuous dynamics monitoring often indicates dynamic behaviour that was not anticipated by model-based studies. In such cases it can be difficult to locate the sources of problems using conventional tools. This thesis details the possibility of diagnosing the causes of problems related to oscillatory stability using measurement-based data such as active power and mode decay time constant, derived from system models. The aim of this work was to identify dynamics problems independently of an analytical dynamic model, which should prove useful in diagnosing and correcting dynamics problems. New statistical techniques were applied to both dynamic models and real systems which yielded information about the causes of the long decay time constants observed in these systems. Wavelet transforms in conjunction with General Linear Models (GLMs) were used to improve the statistical prediction of decay time constants derived from the system. Logic regression was introduced as a method of establishing important interactions of loadflow variables that contribute to poor damping. The methodology was used in a number of case studies including the 0.62Hz Icelandic model mode and a 0.48Hz mode from the real Australian system. The results presented herein confirm the feasibility of this approach to the oscillation source location problem, as combinations of loadflow variables can be identified and used to control mode damping. These ranked combinations could be used by a system operator to provide more comprehensive control of oscillations in comparison to current techniques.
5

Models of the heat-induced circulation in the tropical atmosphere

Phlips, P. J. January 1986 (has links)
No description available.
6

Entry Modes - A banking perspective

Hägg, Gustav, Jonsson, Niklas, Björk, Josefine January 2008 (has links)
<p>In the European Union the borders are being wiped out and this is creating new business markets for companies that before never had dreamt of going international. Today we see it as natural that companies act world-wide to gain success and increase the growth and profit. They need to do this to be competitive on the ever changing market that we have nowadays. One of the most important things to have in mind when thinking of expanding to other countries is which entry mode to choose. There are several ways of entering a market and if you do it right you might be very successful, but if you do not spend time on this decision the internationalization process can become very short and the company can lose a lot of capital. With this thesis we want to investigate how two large Scandinavian banks made their presence into the Baltic market in the mid 90’s, which kind of entry modes they went for and if one of them made a wiser choice than the other. In the thesis we have also gone in to the factors that have been of high importance when making the decision on why they chose the Baltic market and also which kind of entry mode. Our main findings after having made this thesis is that it was the profit and growth potential that was the main driving force for establishing on the Baltic market, but also the short distance and the low costs of going in on the market. The choice of entry mode differs between the two banks and that was expected since they have different strategies when going international. And even the know-how of the market in question and resources of the company have been important factors.</p>
7

Modes of Innovation and the Evolution of the South African National System of Innovation

Scerri, M 01 June 2009 (has links)
Abstract This paper uses the concepts of means of innovation and modes of innovation to introduce an alternative approach to the understanding of the evolution of the South African system of innovation. Modes of innovation are defined in terms of ownership and control patterns of the means of innovation, as well as the role played by human capital. The relationship between ideology and modes of innovation is briefly examined. This paper lays the basis for an alternative approach to the analysis of the transition of South Africa’s economic structure from apartheid to democracy and of the rifts and continuities in that transition.
8

Entry Modes - A banking perspective

Hägg, Gustav, Jonsson, Niklas, Björk, Josefine January 2008 (has links)
In the European Union the borders are being wiped out and this is creating new business markets for companies that before never had dreamt of going international. Today we see it as natural that companies act world-wide to gain success and increase the growth and profit. They need to do this to be competitive on the ever changing market that we have nowadays. One of the most important things to have in mind when thinking of expanding to other countries is which entry mode to choose. There are several ways of entering a market and if you do it right you might be very successful, but if you do not spend time on this decision the internationalization process can become very short and the company can lose a lot of capital. With this thesis we want to investigate how two large Scandinavian banks made their presence into the Baltic market in the mid 90’s, which kind of entry modes they went for and if one of them made a wiser choice than the other. In the thesis we have also gone in to the factors that have been of high importance when making the decision on why they chose the Baltic market and also which kind of entry mode. Our main findings after having made this thesis is that it was the profit and growth potential that was the main driving force for establishing on the Baltic market, but also the short distance and the low costs of going in on the market. The choice of entry mode differs between the two banks and that was expected since they have different strategies when going international. And even the know-how of the market in question and resources of the company have been important factors.
9

On the Oscillations of Jupiter as Observed by Voyager 2

Burr, Wesley 18 December 2007 (has links)
Data recorded from Voyager 2 in 1979 during closest approach to Jupiter is prepared and analyzed for evidence of Jovian modal forcing. Comparisons are drawn between the data set in question and previously performed analysis by Mosser et al. [27], [29], [6] and also to the models presented by Gudkova and Zharkov in [19]. The theory of stationary processes and multitaper spectrum estimation are em- ployed extensively in the analysis, along with intensive use of the harmonic frequency variance test as a tool for separating signal from noise. The splitting of low-order p-modes is briefly examined and found to be in-line with that discovered earlier by Mosser et al.. / Thesis (Master, Mathematics & Statistics) -- Queen's University, 2007-12-12 20:16:46.187
10

Grating alignment of liquid crystals

Hallam, Benjamin Thomas January 2000 (has links)
No description available.

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