Thesis (M.S.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (leaf 70).

Thesis (M.A. Sc.)--University of Toronto, 2006. / Source: Masters Abstracts International, Volume: 45-03, page: 1546.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica. / Made available in DSpace on 2012-10-21T04:36:01Z (GMT). No. of bitstreams: 1 194766.pdf: 5543965 bytes, checksum: ab650dc44c3be8121dcabd1c307b48f8 (MD5)

abstract: The rationale of this thesis is to provide a thorough understanding of spalling for semiconductor materials and develop a low temperature spalling technology that reduces the surface roughness of the spalled wafers for Photovoltaics applications. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2020

Few experiments have been carried out in the past to deter mine the effect of the lift and the drag forces on the trajectory of a ball used in any game. In a baseball game, it was reported that sometimes the ball took a sharp turn aburptly in the region of 15 to 20 feet from the home plate. This indicated a sudden change of the forces acting on the ball. The principal forces acting w ere as fol lows: 1. Weight of the ball. 2. Drag force acting in the direction parallel to the relative wind. 3. Lift force acting perpendicular to the relative wind.

A l'heure où le monde entier appelle à développer de nouvelles technologies de transport afin de faire face au défi écologique, des projets de dirigeables gros porteurs permettent de relever ce défi. En outre, les dernières avancées technologiques dans le domaine de l'aérospatiale ont permis de résoudre un certain nombre de problèmes responsables de l'hibernation des grands dirigeables pendant plus d'un demi-siècle. Ceci a donné naissance à de nouveaux types de dirigeables gros porteurs. Dans cette thèse, le modèle dynamique du dirigeable gros porteur est défini afin de concevoir un contrôleur efficient.La particularité du dirigeable présenté est sa capacité de charger et de décharger le fret en vol stationnaire, ce qui permet de réduire l'apport logistique et humain par rapport à des scénarios comportant un atterrissage et permet ainsi l'utilisation de cet engin dans des zones ayant peu ou pas d'infrastructure.Ce dirigeable est muni d'une grue formée par un robot parallèle à câbles (RPC) permettant d'optimiser le chargement et déchargement. Cette phase étant la plus sensible, car la charge suspendue peut osciller dangereusement notamment sous l'effet de bourrasques de vent sur le dirigeable. Nous avons concentré nos efforts dans cette thèse à l'analyse de cette phase critique.Le dirigeable gros porteur sera représenté par un système multi-corps composé de plusieurs corps reliés entre eux par des articulations. Les contributions de la thèse sont présentées en deux parties. Dans la première partie, nous supposons qu'il n'y a pas de couplage inertiel entre le dirigeable et le RPC. Ainsi nos recherches ne concernent que le RPC en tenant compte de la mobilité de la base suspendue par des câbles considérés dans un premier temps comme idéaux, puis les phénomènes d'affaissement et de flexibilité des câbles seront pris en compte. La conception de la commande de ce système doit aussi intégrer une répartition optimale de la tension car les câbles doivent à chaque configuration rester tendus. Dans la deuxième partie, nous abordons l'analyse du système global en considérant l'effet de couplage inertiel entre la charge utile suspendue et le dirigeable. Le modèle dynamique de ce système multicorps formé par le dirigeable et le RPC peut être modélisé comme une interconnexion de sous-systèmes d'ordre inférieur. Nous supposons que le dirigeable gros porteur est un sous-système faiblement couplé. En se basant sur cette hypothèse, un contrôleur décentralisé est proposé permettant de contrôler indépendamment le dirigeable et le RPC. Les résultats des simulations numériques sont présentés et montrent la puissance de ce contrôleur. / In the recent years, researchers have become increasingly interested in the development of radically new and sustainable transportation modes for both passengers and cargo. These challenges have led to study in areas of knowledge that were dormant, such as the potential of using lighter than air aircraft for cargo transportation. The focus of this thesis is the development of a control architecture that can be integrated on autonomous heavy lift airship and thereby enables safe cargo exchange process. Besides, the dynamic model of the heavy lift airship must be clarified before designing a controller. This system makes use of a Cable Driven Parallel Manipulator (CDPM), allowing the airship to load and unload cargo while hovering. The heavy lift airship is a multi-body systems in which multiple rigid bodies are joined together. During loading and unloading process, the transferred cargo can oscillate due toairship maneuvers. On the other hand, the pendulum-like behavior of suspended load canalter the flight characteristics of the airship. The thesis contributions are presented in two parts. In the first part, we assume that there is no inertial coupling between the airship and CDPM. Hence, our researches concern only the CDPM tacking into account the base mobility at first and then the cable sagging phenomena. The control design should integrate an optimal tension distribution since cables must remain in tension.In the second part, we address the analysis of the heavy lift airship considering the coupling effect between the suspended payload and the airship. To describe the dynamics coupling, the basic motion of one subsystem is regarded as an external disturbance input for the other one. Hence, the dynamic model of this multi-body system composed of the airship and the CDPM can be modeled as an interconnection of lower order subsystems. We assume that the heavy lift airship is a weakly coupled subsystems. Based on this assumption, we design a decentralized controller, which makes it possible to control the airship and the CDPM independently. Numerical simulation results are presented and stability analysis are provided to confirm the accuracy of our derivations.

The history of aerial ropeways and cableways is reviewed. Aerial transport systems are classified according to their design differences. The construction and application of monocable and bicable ropeways are discussed. Cableways are separated into two systems- the tautline and slackline cableway. Their design and use are reviewed. The types of chair lift intermediate support tower are examined. Structural models of four types were built, strain gaged and tested. Experimental stresses are compared to theoretical prediction for each model subkected to external loads. The engineering problems involved in locating the intermediate towers of a chair lift are discussed. / Thesis / Master of Engineering (MEngr)

An investigation of the dynamic lift on the central tube in square tube arrays is conducted. Three array spacing ratios with P/ D = 3.37, 2.18 and 1.58, corresponding to large, intermediate and small spacing ratios are investigated. These three classes exhibit specific flow characteristics and distinct behavior during acoustic resonance. The aim of the present investigation is to determine the effect of the acoustic pressure field and its contribution to dynamic lift during acoustic resonance. During acoustic resonance there are two sources of dynamic lift. One source is provided by the sound field. The standing wave excited during resonance causes dynamic lift from the acoustic pressure distribution on the surface of the cylinder. In the absence of flow, loud speakers are used to excite the first transverse acoustic mode over a range of sound pressure levels, effectively determining the relationship between the resultant dynamic lift and sound pressure level of the acoustic standing wave. The dynamic lift due to the sound field is well predicted by numerical simulation of the acoustic pressure distribution in the tube array. Using the validated numerical simulation it is possible to extend the results to a large range of cylinder diameter to wavelength ratios. The other source of dynamic lift is provided by the periodic flow though the tube array, known as vortex shedding, which is enhanced during resonance. The total dynamic lift is dependant on the phase shift between the sound field and aerodynamic lift components. For small and intermediate tube arrays, acoustic resonance occurs before coincidence of the natural vortex shedding frequency and the acoustic mode. For the large tube array, frequency coincidence occurs within the resonance range. The phase shift between the dynamic lift due to sound and that due to the aerodynamic lift is small for the pre-coincidence resonance range observed for small and intermediate tube arrays and therefore the total dynamic lift is well predicted by the sum of the magnitudes of the dynamic lift due to the sound field and aerodynamic lift components caused by vortex shedding. Past the frequency of coincidence, a phase jump occurs in the aerodynamic lift causing a large phase shift between the sound field and aerodynamic lift components in the large spacing ratio array. The summation of the aerodynamic lift and the lift due to the sound field over predicts the total dynamic lift measured during acoustic resonance in this case. The present results are used to develop a conservative guideline for estimating the total dynamic lift during acoustic resonance. / Thesis / Master of Applied Science (MASc)

Comparisons have been made between a general three-dimensional characteristics solution and available experimenta1 data with regard to the pressure distributions and force and moment coefficients for a spherically-capped 9-degree semivertex angle circular cone, up to angles of attack of 20 degrees. Also, predictions were computed using modified Newtonian theory since this theory has been widely used for bodies flying at hypersonic speeds. Several significant results have been found fran these comparisons. These are briefly summarized in the following statements: 1. The GASL program is adequate to the task of predicting the inviscid pressure distribution and the resultant aerodynamic forces for bodies at angle of attack. 2.The irregularities that occur in the GASL solution on the leeward side of a body at large angle of attack may limit its applicability in its present form to small angles of attack. For the blunt cone body considered here it appears that a 10-degree angle of attack would be an upper limit of applicability. 3. The GASL program represents a new capability which can be employed to begin a more rigorous analysis of the viscous effects which are known to be prevalent in the hypersonic speed range. 4. Only under very special conditions is modified Newtonian theory useful. Inasmuch as these conditions are defined in only general terms, no reasonable range of applicability can be stated. In those cases where it is employed, reliability remains to be proven, In the present application the method was shown to be unreliable. 5. The GASL program represents a first step towards the ability to compute the supersonic inviscid flow field about bodies at angle of attack, both for the study of inviscid and viscous flow fields. However, if progress is to be made towards a complete understanding of these flow fields, the problems revealed in the present comparisons would indicate that much more research and analysis is required. / Master of Science

Ducted fan VTOL UAVs are currently being designed for use by the Army for surveillance and reconnaissance in the battlefield. The vehicle tested in this research is part of the Honeywell MAV program. Able to be carried in a backpack by a single soldier, it has a duct diameter of 11.5-in. and weighs approximately 20-lbs at takeoff. It is designed for flight up to 50-knots with fan speeds varying between 5000 and 8500 RPM. Reynolds numbers, based on the duct diameter, were on the order of Re = 0.96 x 106 to 4.6 x 106. Various control effectors were mounted to the vehicle and tested for maximum control authority to reduce the nose-up pitch moment created during forward flight or with crosswinds present. Static and wind tunnel tests were conducted to measure each control effector's performance. Box vanes, mounted downstream of the duct, utilized four assemblies, each with three vanes and one flap. This configuration showed adequate results in generating a nose-down pitch moment. Duct deflectors, mounted on the windward strut upstream of the duct, reduced the windward lift produced by both the fan and duct, resulting in a nose-down pitch moment. Opposed vanes, utilizing two vanes and flaps for each of the four assemblies, were designed with the same surface area as the box vanes. With each pair capable of independent vane movement, the opposed vanes were tested with the vanes rotating in tandem for a basic elevator deflection and with the leading edges touching, disrupting the flow at the duct exit. Opposed vanes combined the capabilities of the box vanes and duct deflector. Results show that the opposed vanes were the most practical control effector, offering the most control authority for maximum nose-down pitch moment (up to 80% better) with minimal loss in thrust. / Master of Science