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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

Analytical methods in eddy current non-destructive evaluation

Harfield, Nicola January 1994 (has links)
The two-dimensional problem of a long crack in a non-magnetic, half-space conductor lying perpendicular to the flow of eddy-currents induced by a one-dimensional external current sheet is studied in the context of eddy-current non-destructive evaluation. Impedance changes due to closed, surface-breaking cracks and deep, subsurface cracks are calculated. The Wiener-Hopf technique is used to obtain an approximate solution for the magnetic field scattered by a subsurface crack and hence the impedance change. The solution is accurate to within 5% for cracks whose edges lie more than one electromagnetic skin depth (8) below the conductor surface. For the surface-breaking crack the Wiener-Hopf method yields a high-frequency asymptotic series solution for the magnetic field. The first term corresponds to the limit in which the field perturbations by the edge and corners of the crack are decoupled. The impedance change in this limit is found in closed form. Use of the Wiener-Hopf procedure in rigorously treating the open crack problem is investigated. The opening of a deep, subsurface crack whose width is much less than 0 is found to be undetectable to first order in the opening. A geometrical theory of eddy-current scattering is developed, based on the optical Geometrical Theory of Diffraction. The theory includes a procedure which accounts for multiple scattering of the fields between the edge of a crack and its image. The method is applied to subsurface and surface-breaking cracks, yielding solutions for a subsurface crack whose edge lies only 0.48 below the conductor surface and for a surface-breaking crack of depth 8 or more. Finally, perturbation theory is applied to the surface-breaking crack problem in the lowfrequency limit, giving the impedance change for a crack of depth up to 0.40
2

Multipole NMR studies : Dynamics of some spin-3/2 systems

Osment, P. A. January 1987 (has links)
No description available.
3

The fabrication and dynamic characteristics of novel magnetic bubble devices

Ronan, G. A. January 1985 (has links)
No description available.
4

The study of defects in single GaN nanorod

Lee, Guan-Hua 19 August 2010 (has links)
In this article, we report the study of defects between single and bulk GaN nanorods in temperature dependence. High quality of GaN nanorods have been investigated by £g-photoluminescence. Optical properties and surface morphology have been analyzed by a series of measurements, including field-emission electron microscopy (FESEM), and cathodoluminescence (CL). CL data reveal that the intensity of surface state emission is larger than near-band-edge emission at 20K . The 3.21eV peak reveals the structural defect at GaN/Si interface. The surface state emission from bottom is larger than top.
5

Computer simulation of gallium arsenide semi-conductor devices

Warriner, R. A. January 1976 (has links)
No description available.
6

Partial oxidation of propene using solid electrolyte membrane reactors

Al-Musa, Abdullah Abdulaziz January 2002 (has links)
This study investigates the efficiency of a calcia stabilised zirconia (CaSZ) solid electrolyte as an oxygen ion conductor. The study also examines the behaviour of the oxygen species conducted by the solid electrolyte compared to species provided in the gas phase for partial oxidation of hydrocarbons. In this work, an electrochemical cell of the form Air, AgHCaSZ//Ag, Carrier gas was used to investigate the electrochemical efficiency and stability of the solid electrolyte CaSZ conducting of oxygen ions under atmospheric pressure conditions at 500 degrees C by applying a range of electrical potentials from I to 16 volts across the electrochemical cell. Due to the applied potential oxygen anions are transferred across the solid electrolyte from the cathode side of the cell to the anode side. It was found that the employed electrolyte is approximately a 100% purely ionic conductor of oxygen ions in the range of electrical voltage applied from I to 10 volts. Above that range the cell started to degrade and loose its ionic efficiency. It was possible to generate gas mixtures containing trace quantities of oxygen. The viscosity of these gas mixtures as a function of oxygen concentration was determined using an established flow perturbation technique (Flux Response Technology). Partial oxidation of propene was used to investigate the difference between the oxygen species produced electrochemically via electrical potential application across the electrochemical cell Air, AgHCaSZ//Ag, Propene, Ar and oxygen provided in the gaseous state co-fed with propene over silver electrode under atmospheric pressure and 450 degrees C and 500 degrees C. It was found that the method of electrochemical provision of oxygen caused the silver catalyst to be more selective to 1,5-hexadeine, whereas the gaseous oxygen provision produced acrolein as the major product. Carbon dioxide formation was not affected by the method of oxygen provision. The Ag electrode was compared to an Au-rich Ag alloy electrode for propene partial oxidation using electrochemical provision. It was found that 1,5-hexadiene was the major product over both electrodes, but the Au-rich alloy was more selective for acrolein than the Ag electrode. This might be due to the gold serving as a separator between Ag particles which hinder the back-spill over of oxygen and allow desorption of molecular oxygen in the gas phase, which then re-adsorb molecularly on silver sites producing acrolein. The effect of the sequence of the method of oxygen provision on the partial oxidation of propene was tested using the electrochemical cell Y-BiMoHAg//CaSZ//Ag at 450 degrees C and atmospheric pressure. A sharp decrease in acrolein selectivity was found when oxygen was provided in the gas phase after treatment with electrochemical oxygen, while no significant effect was noticed when the electrochemical oxygen was used after treatment with gaseous oxygen. This large decrease in acrolein selectivity might be attributed to the severe reduction of the catalyst, which is probably caused by high electrical potential application. A temperature increase from 450 to 500 degrees C seemed to suppress the formation of acrolein for both methods of oxygen provision and enhance the 1,5-hexadiene formation.
7

Observations and Insights into the Life and Vocal Work of Joseph Bologne (Chevalier de Saint-Georges)

January 2016 (has links)
abstract: ABSTRACT Chevalier de Saint-Georges, the brilliant swordsman, unequalled equestrian, athlete, dancer, violin virtuoso, composer and orchestral conductor is, and remains a singularly unique historical figure of the 18th century French Court of Louis XVI. Believed to be the first man of mixed race to compose classical music, Saint-Georges, who was frequently invited to the court at Versailles to make music with Marie Antoinette not only thrived, but excelled during the height of an appalling slave trade and one of the most explosive periods in European history: the French Revolution. Saint-Georges’ ever evolving talent, and without preamble composed six operas. This research document will introduce to the reader important milestones that influenced the direction of his life, as well as a survey of two arias and duet from the opera L’Amant Anonyme using the paradigm of dance metrics as described in “Rhythmic Gesture in Mozart, Le Nozze di Figaro and Don Giovanni,” by Wye Jamison Allanbrook and “Classical Music, Expression, Form and Style” by Leonard Ratner. / Dissertation/Thesis / Doctoral Dissertation Music 2016
8

Benjamin Britten: Composer as Conductor and the Art of Self Interpretation

January 2014 (has links)
abstract: In the triumvirate of composer-performer-listener, while the listener always wins, the performer is the interpreter through which the listener experiences the writings of the composer. When the composer and performer are combined, however, a unique situation arises: the link from the composer to the listener becomes a direct line and the composer becomes his/her own interpreter. Such is the case with Benjamin Britten. Britten conducted almost his entire repertoire in recordings for Decca (the exceptions being Paul Bunyan, Owen Wingrave, and Death in Venice). A comparative analysis of the recordings of four of Britten's works, the Serenade for Tenor, Horn, and Strings, Op. 31; Albert Herring, Op. 39; Spring Symphony, Op. 44; and the Nocturne, Op. 60, shows that despite his complaints about performers not following his tempo markings, Britten often deviated from them himself, tending slower. Britten also occasionally added additional rubato, ritardandi, and accelerandi to his works. Additionally, a discrepancy regarding a pitch in the "Prelude" of the Serenade comes to light. Video of Britten conducting the Nocturne in rehearsal with the Canadian Broadcasting Company (CBC) Vancouver provides additional insight into his methodology. Benjamin Britten succeeded as a composer-conductor, and his catalogue of recordings provides essential primary reference material when studying his works. / Dissertation/Thesis / D.M.A. Music 2014
9

TRANSMISSION LINE FEATURES AND THEIR INFLUENCE ON GHz CONDUCTOR LOSS

Vincent, Tracey S 01 June 2009 (has links)
"Transmission loss needs to be considered in the design of telecommunication systems. If telecommunication systems have high transmission loss, the signals lose too much of their strength, which results in poor reception in television networks and lost calls in cellular networks. Total transmission loss, in the MHz-GHz range, has several different loss components, some of which are poorly characterized. Conductor loss is the largest loss component and the most difficult to predict. It is known that the conductor geometry or features influences the conductor loss. However, current numerical, analytical and empirical tools do not accurately predict this loss component, and there is little experimental data available to explain and show the impact of these conductor geometries. The conductor shape is heavily influenced by the ceramic substrate surface roughness, and this is especially true for printed circuit boards fabricated with thick-film technology. The two conductor features of interest are the conductor-edge angle and conductor-ceramic interface. For thick-film circuits, the edge of the conductor does not have a square cross section but has a tapered shape or angle. The conductor-ceramic interface is also rough at the micron scale. Since the current density is concentrated at the extremities of the conductor then these features, conductor-ceramic interface and conductor edges, can potentially have a large impact on conductor loss. For this study, the surfaces of ceramic substrates were subjected to different surface finishes that resulted in distinctly different surface characteristics. This in turn resulted in a range of conductor-ceramic interfaces and conductor-edge angle geometries. The impact of the conductor-edge angle and conductor-ceramic interface features on conductor loss was measured over a range of frequencies and conductor conductivities to ascertain the level of their contribution. It was shown quantitatively that the conductor-edge angle was significantly altered by the surface roughness and heavily influenced the conductor loss result. The consensus for decades has been that greater surface roughness causes the ceramic-conductor interface geometry to have a greater impact on conductor loss, increasing the conductor loss. However, this study has shown that greater surface roughness also causes the conductor-edge angle feature to have a smaller or reduced impact on conductor loss, improving the conductor loss result - this has not been considered previously. Focusing on only one of these features can give an anomalous loss prediction; both features need to be considered for the calculation of conductor loss for thick-film applications. The low frequency loss results are as expected but the high frequency (greater than 5GHz) results depend on edge angle and therefore thick-film paste viscosity, and substrate surface roughness. "
10

Research of Value Chain in Taiwan Foundry Industry Investment in China

Tsou, Li-Jen 17 June 2002 (has links)
Abstract This research describes the value chain development of Taiwan foundry industry¡¦s investment in China and analyzes how the foundry firm establishes its value chain and strategy in the different industry environment. The research also raises inferences about Taiwan foundry industry¡¦s value-chain mode and business model and expects to be reference materials for the industry and government. The research content includes the analysis of Taiwan and China semi-conductor industries¡¦ environment, the analysis of the industry value chain, and the scenario analysis of China¡¦s industry environment and Taiwan¡¦s foundry industry de velopment. Finally, here come the research findings of this thesis: 1. The foundry industry in Taiwan already established a stable competitive advantage. After investing in China, it will also play a key role in the development of China¡¦s semi-conductor industries. 2. Taiwan foundry industry will be the coordinator of China¡¦s semi-conductor industry value-chain, and promote the development there. 3. There exist the demand and trend which the foundry industry will raise its added value in the semi-conductor industry value-chain, especially after investing in China. 4. When the foundry industry tries to raise its added value, some activities like IP providing and IC design service will be the optimum alternatives. 5. After investing in China, the development of the foundry industry will be highly related to the progress of local system industry and IC design industry. 6. No matter how industry environment evolve, the foundry industry will change its value chain structure on the basis of reducing the transaction cost and developing the synergy. 7. The foundry industry won¡¦t do the real integration unless the foundry¡¦s potential profit be limited or the real integration can bring the huge profit. 8. No matter integrate or not, the foundry industry shouldn¡¦t compete with its customer. 9. The foundry industry establish a symbiosis system with its customer, but it will form the different strategies depend the customer classification.

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