Doktorsavhandling--Department of Economic history--Uppsala, 1995. / Résumé en anglais.

L'une des finalités de la Biologie Moléculaire est l'étude de l'architecture spatiale des molécules. Les expérimentations in silico permettant la modélisation 3D utilisent le plus souvent des approches automatiques. Or, ces approches présentent certains inconvénients: temps de traitement important, modélisation souvent partielle, modèle 3D généralement figé, etc.L'apport des connaissances des experts, de manière interactive, pendant le processus de modélisation automatique peut pallier certains défauts des méthodes calculatoires usuelles. Il s'agit de placer le biologiste au centre des essais virtuels plutôt qu'en observateur de résultats de simulations. C'est ce que nous appelons l'approche hybride, qui associe les avantages des expérimentations in silico (capacité de calcul) à ceux des Interactions Homme-Machine et de la Réalité Virtuelle: commande naturelle, immersion dans l'environnement virtuel (EV), multimodalité, etc. Le résultat de cette approche est la création d'analyses in virtuo, qui comportent trois phases fondamentales: la modélisation 3D, la visualisation et l'interaction 3D (I3D). Cependant, des domaines complexes tels que la Biologie sont régis par un ensemble de contraintes qui peuvent être locales (liées aux objets 3D ou aux tâches d'I3D) et globales (liées à l'espace des objets 3D ou au système d'I3D). Par conséquent, l'intervention des experts ne peut pas être réalisée efficacement par des techniques d'I3D classiques, indépendantes de la complexité et des contraintes du domaine. Plus généralement, nous sommes confrontés au problème innovant de l’I3D sous contraintes qui intègre les règles de comportement imposées par l'EV. Pour y répondre, nous formalisons un modèle d'assistance qui associe les contraintes, les tâches d'interaction et des outils d'assistance que sont les guides virtuels. Nous avons appliqué ces deux concepts, d'approche hybride et d'assistance à l'I3D sous contraintes, au problème de la modélisation 3D du chromosome. Les contraintes identifiées sont ici architecturales (données physico-chimiques) et fonctionnelles (modèles biologiques). Ces contraintes issues des lois de la Biologie imposent l'ordonnancement spatial du chromosome. Le système d'interaction Hommme-Molécule in virtuo proposé peut être considéré plus crédible puisqu'il respecte les contraintes environnementales, tant au niveau de la structure 3D qu'au niveau de l'I3D. / One of the aims of Molecular Biology (MB) is the study of the molecules' 3D structure. In silico experiments (ie. computing simulations) for 3D modeling usually use automatic approaches. However, these approaches have limits: important computing time, local modeling, 3D model generally fixed, etc. The contribution of expert knowledge, interactively during the automatic modeling process, can overcome some limits of the usual computational methods. It involves placing the biologist in the center of virtual experiments, rather than an observer of automatic simulation results. This is what we call hybrid approach, that combines the advantages of in silico experiments and those of Human-Computer Interaction (HCI) and Virtual Reality (VR): natural interaction, immersion in the virtual environment (VE), multimodality, etc. The result of this approach is the creation of in virtuo experiments which has three components: the 3D modeling, the visualization and the 3D interaction (3DI). However, complex domains such as MB are governed by several constraints that may be local (linked to 3D objects or 3DI techniques) or global (linked to virtual environment or to the 3DI system). Therefore, experts intervention can not be efficiently realized by conventional 3DI techniques, without taking into account the domain complexity (ie. constraints). More generally, we are confronted to the problem of constrained 3DI which includes behavior rules imposed by the VE.The solution we propose is an assistance model that associates constraints, interaction task and assistance tools. The assistance tools are Virtual Fixtures. We applied these two concepts, hybrid approach and assistance model, to the chromosome 3D modeling. The identified constraints are architectural (ie. physico-chemical data) and functional (ie. biological models). These biological constraints dictate the chromosome spatial organization. The in virtuo Human-Molecule interaction system can be considered more credible because it respects the environment constraints, both in the 3D structure and at the level of 3DI.

No description available.

Thesis (M.Sc.)--University of Adelaide, 1946. / C.S.I.R. Typewritten copy. Includes bibliographical references.

Thesis (M.S.)--Ohio University, November, 1982. / Title from PDF t.p.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 62-63.

This work consists of two parts. The first part is a comprehensive study of surface-wave propagation along dielectric tube waveguides. It includes the derivation of the characteristic equations and expressions for group velocity and attenuation coefficient, the latter by a perturbation method. Mode designations are justified and the physical distinction between the HE₁₁ and EH₁₁ modes is further illustrated by showing three-dimensional plots of the field configurations. Computed characteristics are given for a wide range of parameters, and are compared with those of standard rectangular waveguides. Finally, a method of shielding the tube from weather conditions is proposed and the resulting changes in characteristics are noted. The second part of this work is essentially a unified analysis of all slow-wave modes in eight cylindrical waveguides. Characteristic equations are derived and expressions are obtained for the group velocity and the attenuation coefficients by a perturbation method. Accurate propagation characteristics for the dominant TM₀₁ mode are computed for four waveguides with no restrictions on their radial dimensions. These guides are the Goubau line and a coaxial cable with dielectric linings on the inner, outer, or both conductors. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This thesis is mainly concerned with the effects of periodic loading of nonreciprocal waveguides by regular placement of discontinuitie and with the associated problem of the evaluation of a transverse discontinuity in a nonreciprocal ferrite loaded waveguide. The mode-matching technique is used to analyse a transverse discontinuity in a nonreciprocal waveguide. The difficult orthogonality relations are circumvented using a Galerkin approach. The elements of an exact three-element equivalent circuit for an infinitely thin metallic diaphragm are evaluated. Each element has two values, one for each direction of propagation. The numerical results show the same trends as those obtained experimentally in a similar configuration. The properties of a nonreciprocal, ferrite loaded, rectangular waveguide, which is periodically loaded by thin metallic "inductive" diaphragms, are investigated experimentally. The propagation constants of the structures are measured and are compared with predictions based on measured values of the scattering parameters of a single diaphragm in the nonreciprocal waveguide. The agreement between theory and experiment is generally good except for the smaller spacings between the diaphragms. This discrepancy is attributed to the effects of higher mode interaction. An investigation was also made of a magnetized ferrite loaded ridged waveguide. A theoretical and experimental investigation was first made of the preliminary problem of a reciprocal, inhomogeneous ridged waveguide and guided by these results an approximate, theoretical technique was formulated to analyse the nonreciprocal ferrite loaded ridged waveguide problem. It was found that introduction of the ridge had detrimental effects on the differential phase shift characteristics except for a few special cases. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Unknown

Ray-optical methods are used to calculate the coupling between open-ended parallel-plate waveguides, as well as the radiation patterns of finite arrays of coupled parallel-plate waveguides with only the central guide driven. These methods require extensive ray tracing, particularly for the larger arrays, to take into account the many possible ray paths. The coupling coefficients between both two and three guides in isolation agreed remarkably well with those previously derived in the presence of other guides, groundplanes etc., indicating a general lack of sensitivity of the coupling coefficients to the details of the surrounding structure. The calculated patterns were compared with experimental patterns using an H-plane sectoral horn to simulate the parallel-plate waveguide array. Radiation patterns of both three and five element arrays with all waveguide edges in the aperture plane, as well as that of a three element staggered array with the outer edges not in the aperture plane agreed well with the experimental patterns. A wide variety of patterns could be obtained by varying the width, depth, and number of the outer guides in the array. Ray-optical methods may thus be useful in the development of waveguide antennas for a variety of applications. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate