Ziel der vorliegenden retrospektiven Studie war es, die Exaktheit der Pedikelschraubenlage bei der dorsalen Implantation von internen Fixateuren an der Brustwirbelsäule zu untersuchen. Es wurden die Verletzungs- und Krankheitsentitäten Frakturen, Tumore bzw. Metastasen und Spondylodiszitiden der Brustwirbelsäule in die Studie aufgenommen. In den Jahren von 2005 bis 2010 wurden an der Klinik und Poliklinik für Unfall-, Wiederherstellungs - und Plastische Chirurgie der Universität Leipzig eine Vielzahl dieser Operationen durchgeführt. Insgesamt 196 Patienten wurden in die Studie aufgenommen, zusammen wurden bei diesen Patienten 1379 Schrauben implantiert. Intraoperativ wurden verschiedenen Bildgebungen angewandt, um die Lage der Schrauben zu bestimmen. Zum einen die konventionelle zweidimensionale Darstellung mittels eines Bildwandlers, zum anderen zwei Verfahren der Navigation, welche dreidimensionale Bilder liefern: die computertomographie-basierte Navgiation und die 3D-C-Arm Navigation. Postoperativ erhielten alle Patienten eine computertomographische Untersuchung der instrumentierten Region. Anhand dieser Bilder konnte die genaue Lage jeder einzelnen Schrauben im Wirbelbogen bestimmt und ausgemessen werden. Sämtliche laterale und mediale Fehllagen wurden bestimmt, um anschließend einen Vergleich der drei Verfahren hinsichtlich ihrer Genauigkeit zu vollziehen. Es zeigte sich, dass die 3D-C-Arm Navigation die niedrigste Anzahl an Schraubenfehllagen aufwies. Die konventionelle und auch die computertomographie-basierte Navigation brachten hingegen ähnliche Fehllagenraten von über 20 Prozent. Die 3D-C-Arm Navigation bringt demnach eine größere Sicherheit für den Patienten mit sich, da Komplikationen aufgrund von Schraubenfehllagen, wie beispielsweise neurologische Schäden und instabilen Osteosynthesen, seltener auftreten. Darüber hinaus könnte bei Anwendung dieses Navigationssystems eine postoperative Computertomographie entbehrlich werden, da durch den bereits intraoperativ erfolgten dreidimensionalen Scan eine hinreichende Beurteilung der Schraubenlagen möglich ist. In der Konsequenz kann somit die Strahlenexposition für den Patienten minimiert werden.

Signalling the beginning of a new era to international civil aviation, the concept of the CNS/ATM systems came into being as the result of joint efforts of the international community, under the aegis of ICAO, in search for a solution to the limitations of the ground-based air navigation systems, which would otherwise inhibit further development of air transport on a global scale. Employing digital and satellite technologies in support of a seamless air traffic management system, it will bring improvements upon the present levels of safety, efficiency and accuracy, as well as increased capacity and economic benefits. / An analysis of the existing legal tools hereby confirms the need for the development of an appropriate legal framework for the GNSS. In considering the fundamental principles to be contained therein, this thesis examines the adequacy of an international convention as the long-term means to provide for the legal guarantees which will inspire world-wide confidence in the integrity of the system. Finally, it provides detailed examination of the relevant legal issues, such as liability, certification, administration, financing and cost recovery, as well as future operating structures. (Abstract shortened by UMI.)

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, 1914. / Pub. also as no. XIII of Hart, Schaffner & Marx prize essays. Includes bibliographical references (p. [459]-465).

Thesis (M.S.)--Ohio University, November, 1991. / Title from PDF t.p.

Thesis (Ph. D.)--University of Chicago, 1914. / Pub. also as no. XIII of Hart, Schaffner & Marx prize essays. Includes bibliographical references (p. [459]-465).

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2009. / Title from PDF title page (University of Texas Digital Repository, viewed on Sept. 9, 2009). Vita. Includes bibliographical references.

L’autonomie d’un robot mobile autonome requiert la réalisation coordonnée de tâches de commande et de perception de l’environnement. Parmi celles-ci, la navigation joue un rôle de pivot dans l’interaction du robot avec son terrain d’évolution. Elle consiste en la détermination de trajectoires réalisables par le robot pour suivre un chemin préétabli, tout en assurant la non collision avec les obstacles, mobiles ou fixes. Pour effectuer cette tâche, notre approche s’appuie sur le modèle cinématique direct du véhicule pour générer des trajectoires admissibles par le robot. En premier lieu, une trajectoire de référence est construite à partir du chemin à suivre. Le problème de navigation est alors modélisé sous la forme d’un problème d’optimisation sous contraintes dont la fonction coût quantifie l’écart entre la trajectoire prédite du robot et la trajectoire de référence. Les obstacles sont intégrés sous forme de contraintes en pénalisant le critère, et sa minimisation détermine la commande optimale à appliquer. Cette navigation par commande prédictive nous permet d’anticiper les mouvements de contournement d’obstacles sur l’horizon de prédiction choisi, tout en gardant une certaine réactivité vis-à-vis de la dynamique des obstacles et du robot. En outre, l’utilisation de familles de trajectoires paramétrées permet de maitriser le comportement du véhicule. / Autonomous robots have to perform both control and perception tasks coordinately. Among these ones, the navigation task is a key in the interaction between the robot and its environment. It consists of determining the trajectories which the robot can follow in order to negotiate correctly around static and dynamic obstacles, assuming that it is programmed to map out its environment and situate itself within that environment. To perform this task, our approach rests on the direct kinematics model of the robot to generate admissible trajectories for the robot. Firstly, a reference trajectory is computed from the reference path provided by a path planer. Then the navigation task is modelized as an optimization under constraints problem, whose the cost function quantify the gap between the reference trajectory and the predicted trajectory of the robot. The obstacles are taken into account as constraints, and the minimization of the resulting cost function determinate the optimal control for the robot on a prediction horizon. This predictive navigation allows the robot to anticipate bi-pass movements on the chosen prediction horizon, Moreover, the behaviour of the robot is mastered by the use of parametered trajectories families.

Thesis (Masters Diploma(Post School Education))--Peninsula Technikon, Cape Town,1992 / Electronic navigation systems (ENS) have undergone phenomenal growth and development since the Second World War and there is every indication that it will continue to do so for as long as the threat of war prevails. A positive effect in this rapidly developing science, has been its application commercially, especially in aeronautical systems. To the ENS (Fisherman) course students of the Training Centre for Seamen (TCS), a technical college based in Cape Town, the advent of these modern navigation aids (navaids) made a marked impact on their, previously, simple existence and certain problems with regard to their training became evident. An empirical study, by means of a questionnaire, was thus undertaken in order to identify and possibly solve problems experienced by these students during both the sea-going and college-based phases. Specific areas investigated included, * academic, vocational and socio-economic background * language competency * lack of on-board exposure to instrumentation within junior ranks and * large age differences as well as differing levels of experience and competency in the same class group. In a bid to seek possible solutions, a comparative study was made of similar courses offered by institutions both locally, viz. the Cape Technikon and the South African Navy and abroad, viz. Australia, Denmark, Germany, United Kingdom and United States of America. Structured interviews were also held with ENS (Fisherman) course lecturers, representatives of ship owners and the South African Department of Transport officials to test their opinions with regard to the existing ENS training structures and the associated problems identified. Based on the information obtained in this study, conclusions and recommendations on the following have been made, viz. * Formulation of a new maritime training dispensation for South Africa * In-house training facilities * Academic background of students * Living and working conditions on-board * Heterogenous composition of ENS (Fisherman) class * Amalgamation of existing ENS training resources * On-board training programmes * Formal teaching qualifications * Marketing careers at sea and * Research in maritime education and training