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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.
381

Modeling Variable Viscosity Forced and Free Convection in Porous Media

Kamel Hooman Unknown Date (has links)
This thesis addresses modeling transport phenomena in porous media with special attention being paid to convective characteristics of variable viscosity fluids in a homogeneous and isotropic medium. Two different categories of flows, with totally different driving forces, are considered being forced and free convection (both side and bottom heating, for a square enclosure, are studied). To account for property variation, the density is modeled by an Oberbeck–Boussinesq approximation while the viscosity is modeled by an exponential function. The limitations of the previous work, addressing the issue, are discussed in detail and improvements, in terms of thermo-hydraulic performance of the system are suggested. Dealing with the global aspects of the problem, the two major methods being the reference temperature and the property ratio approach are implemented. For natural convection problems, the former method is used; while for forced convection the latter is undertaken. New correlations, which are proved to be more accurate, are proposed for both forced and free convection problems. Besides, closed form solutions are reported for some cases of constant and variable viscosity. Convection visualization is also studied in detail where the concept of Energy Flux Vectors is put forward along with the application of heatlines and energy streamlines. It was mathematically shown that in two-dimensional space heatlines and energy streamlines, which were invented independently, are the same as each other. Moreover, the newly developed concept, energy flux vectors serve as a new tool for convection visualization with the main advantage that this new technique, unlike heatlines and energy streamlines, does not require further (and sometimes complicated) numerical analysis in addition to solving momentum and thermal energy equations. This, in its turn, reduces the time and computer resources required to see the flow of energy. Finally, in Chapter 7, the summary of the work along with the conclusions are presented. Finally, recommendations for future studies are put forward.
382

Development of a Variable Stability Flight Simulation Facility Re-engineering of Flight Control Loading and Motion Systems

Scamps, Alexander January 2003 (has links)
A Variable Stability Flight Simulator is being developed in the School of Aerospace, Mechanical and Mechatronic Engineering at the University of Sydney, Australia. The device is being developed both as a teaching tool for use in flight mechanics courses in the department and as a research tool. It is reasonable to state that learning is enhanced through the experience of concepts outside of the classroom environment. It is intended that the device will be integrated into the department�s teaching program in aircraft flight mechanics. Initial studies centred around a PC based flight simulation developed at the Cranfield College of Aeronautics in the United Kingdom. This system utilises a distributed architecture with several computers connected via Ethernet. It also employs a Primary Image three channel visual system. The system has been further enhanced by the addition of a Link flight simulator provided by the Royal Australian Air Force (RAAF). The RAAF had been using the simulator as a training tool for some years until it had become surplus to requirements. Most of the work in the project has centred around re-engineering this simulator into a viable research/education tool. The Cranfield system has been incorporated into the Link simulator�s hardware to provide a fixed base simulation. The majority of the work described in this thesis revolved around the re-engineering of the flight control loading and motion systems. Previously these items were controlled by analogue circuitry with minimal digital interfaces to the main simulation software. The systems have been re-designed to replace much of the single model analogue circuitry with re-configurable digital control software. Doing so allows changes to be made to the systems in real time through a software interface. The software resides on a common computer that extensively interfaces with the rest of the simulation. To support the hardware involved and to provide for system operation and safety, an extensive Supervisory system has also been implemented. This system along with the motion and control loading software has been implemented in the Matlab / Real-Time Workshop environment. This gives the capability of making real-time changes to any part of the overall simulation. A variable stability module (vsm) is under development. The addition of this module will allow changes to be made to the simulation itself in real-time. The simulator is now functional with the motion and control loading systems operating as designed. Tuning of both systems has been done subjectively by the author. An initial objective analysis of the motion system has been undertaken in an attempt to verify the fidelity of the motion cues generated. A significant outcome of this project has been to create a safe, easily maintainable, re-configurable flight simulator from a large, complex, legacy system. The facility now forms a significant research and teaching tool in areas such as flight mechanics, propulsion, aircraft handling qualities and human factors.
383

Runge-Kutta methods for stochastic differential equations

Burrage, Pamela Marion Unknown Date (has links)
In this thesis, high order stochastic Runge-Kutta methods are developed for the numerical solution of (Stratonvich) stochastic differential equations and numerical results are presented. The problems associated with non-communativity of stochastic differential equation systems are addressed and stochastic Runge-Kutta methods particularly suited for such systems are derived. The thesis concludes with a discussion on various implementation issues, along with numerical results from variable stepsize implementation of a stochastic embedded pair of Runge-Kutta methods.
384

Lime induced changes in the surface and soil solution chemistry of variable charge soils

Chintala, Rajesh. January 2008 (has links)
Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 128 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
385

Adjustable speed drive bearing fault detection via support vector machine incorporating feature selection using genetic algorithm

Teotrakool, Kaptan, January 2007 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 3, 2008) Vita. Includes bibliographical references.
386

A study of white dwarfs in the solar neighbourhood /

Kawka, Adela. January 2003 (has links)
Thesis (Ph.D.)--Murdoch University, 2003. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 255-267.
387

The adaptive immune system of sea lamprey

Alder, Matthew N. January 2008 (has links) (PDF)
Thesis (Ph.D.)--University of Alabama at Birmingham, 2008. / Title from first page of PDF file (viewed on June 23, 2009). Includes bibliographical references.
388

Dynamic response of a cooling and dehumidifying coil to variations in air flow rate /

Ip, Kai-ming. January 1997 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1998. / "1998"--Cover. Includes bibliographical references (leaves 176-184).
389

Long-term optical studies of cataclysmic variables

Van Amerongen, Stephanus Franciscus. January 1989 (has links)
Thesis (Ph. D.)--Universiteit van Amsterdam, 1989. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
390

Die Entschädigung der Wartezeiten bei der Arbeit auf Abruf

Rieder, Stefan. January 2007 (has links) (PDF)
Master-Arbeit Univ. St. Gallen, 2007.

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