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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.
41

Normal state properties of high-angle grain Y1-xCaxBa2Cu3O7-delta

Mennema, Sibe January 2006 (has links)
This dissertation describes the investigation of the normal-state properties of high-angle grain boundaries in YBa2Cu3O7-d (YBCO) and Y1-xCaxBa2Cu3O7-d (calcium-doped YBCO). YBCO is a high-temperature superconducting material with a superconducting transition temperature up to 93 K. Grain boundaries are interfaces between two crystals or grains, and severely reduce the attainable currents in practical, polycrystalline material. A grain boundary is characterised by the misorientation angle between the two adjacent crystals, which determines the atomic structure of the interface. The structure of low-angle grain boundaries (misorientation angles < ~7°) is well understood; it consists of a regular array of dislocations. For higher misorientation angles the dislocations merge and form a continuously distorted zone. The structure of these high-angle grain boundaries, and, hence, the mechanism for charge transport across the interface, is less well understood. The current-voltage behaviour of grain boundaries below the transition temperature of the YBCO has been investigated extensively, but less data is available of the resistive behaviour of the grain boundary in the normal state above the transition temperature. The doping of YBCO with calcium is known to decrease its transition temperature, but it can simultaneously improve the charge transport properties of grain boundaries in polycrystalline material. YBCO and calcium-doped YBCO thin films were fabricated on bicrystalline substrates. The grain boundaries had misorientation angles between 18° and 45°. The films were processed in order to obtain microscopic devices that made it possible to determine the resistance of the grain boundary below and above the transition temperature. A measurement system was used with which the voltage across the grain boundary can be measured as a function of applied current between 5 K and room temperature. A detailed model for charge transport by tunnelling across a grain boundary was used to interpret the results of the measurements of grain boundaries. An algorithm based on this model was formulated that made it possible to calculate a shape for the potential barrier at the grain boundary from the temperature dependence of its resistance. The microstructure of the grain boundary was investigated using Transmission Electron Microscopy. It was found that the grain boundary can show considerable deviations from a straight path in line with the substrate grain boundary, but there are also locations where such deviations are not observed. Extensive measurements showed that the resistance of the grain boundary decreases with increasing temperature above the transition temperature, and that resistance and the extent of resistance variation increases with misorientation angle. The resistance below the transition temperature was for certain misorientation angles observed to be independent of temperature at voltages sufficiently high to exclude the influence of the superconducting behaviour of YBCO. A reduction of the oxygen content of YBCO (higher value of d) increases the resistance and the temperature dependence of the resistance. The doping of YBCO with calcium decreases the resistance of the grain boundary below and above the transition temperature. The shape of the potential barrier at the grain boundary was calculated on the basis of most resistance-temperature measurements. The shape and size of potential barriers are used to explain the variation of the grain boundary resistance with misorientation angle, oxygen content and calcium doping percentage. The model shows little validity for grain boundaries with a higher misorientation angle and resistance, which indicates that charge transport across the grain boundary does not necessarily take place according the tunnelling with the assumptions made.
42

Some phases of the boundary problem of Arizona

Schiff, Raymond Irving, 1926- January 1950 (has links)
No description available.
43

Anglo-Scandinavian settlement in the Lower Trent Valley, 750-1066 AD : settlements, fields and boundaries

Nash, Beryl Rose January 1997 (has links)
No description available.
44

Enhancement of Sexual Boundaries: An Online Awareness Project

Sisco, Melissa Marie January 2010 (has links)
Five-hundred forty four students from an urban southwestern University underwent a sexual aggression beliefs and behaviors evaluation and subsequent online intervention. Approximately three-quarters of male and female students experienced a sexual boundary violation during the past year. Though male and female students were equally as likely to experience inappropriate sexual attention and/or contact, female students were significantly more likely to experience attempted and/or completed anal and vaginal rape and significantly most frequently after an explicit verbal indication of objection such as "no." Less than 10% of persons who experienced or enacted acts that met the legal threshold of a crime reported that the act would be defined as such. Thus, it may be that a large amount of college students are incapable of identifying personal victimizations or that sexually aggressive behavior has become more normative in the typical college sexual escapade. The modalities that were implemented exceeded those previously explored (i.e. lying and manipulating the victim directly) to include the use of technology, bets or dares, sexual scare tactics, and social vengeance. When the mechanisms for sexual aggression were explored, it appeared that aggressors typically acted out due to availability of victims and difficulty controlling their sexual urges, thus, traditional awareness efforts that attempt to alter attitudes in an effort to prevent sexual aggression seem ill-fitted to the college population. However, difficulty discerning objection from consent was associated with an increased risk of victimization, self-blame for victimization, and cognitive justification for aggressive behavior. Personality played a major role in intervention receptivity; students who were conscientious were more capable of changing and sensing personal change. Feeling `changed', being high on Psychopathy, and having pre-set ideas regarding rape myths of the opposite sex or pre-existing difficulties deciphering objection from consent impeded intervention receptivity.
45

Surface segregation and its influence on the oxidation of polycrystalline nickel

Ritherdon, Justin January 1996 (has links)
No description available.
46

Optical heterodyne detection with balanced Ga₀.₄₇In₀.₅₃As metal-semiconductor-metal photodetectors.

January 1996 (has links)
by Chan Pak-To. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references. / Chapter 1. --- Introduction / Chapter 1.1 --- Overview --- p.1-3 / Chapter 1.2 --- Current Technology of Coherent Detection --- p.3 -8 / Chapter 1.3 --- About this Project --- p.8 / References --- p.9 -12 / Chapter 2. --- Background Theory / Chapter 2.1 --- MSM Photodetector --- p.1 -6 / Chapter 2.2 --- Optical Coherent Detection --- p.6-7 / Chapter 2.3 --- Shot Noise Limited Detection --- p.8-9 / Chapter 2.4 --- Self Heterodyne Linewidth Measurement --- p.9-11 / References --- p.12 / Chapter 3. --- Instrumentation / Chapter 3.1 --- Steps for fabricating MSM Photodetector --- p.1 -4 / Chapter 3.2 --- Device Characteristics Acquisition --- p.5-6 / Chapter 4. --- Ga0 .47In0. 53as msm Photodetector with al0.1 In0.9p barrier enhancement layer / Chapter 4.1 --- General Description --- p.1 / Chapter 4.2 --- Device Preparation --- p.1-2 / Chapter 4.3 --- Metallization Patterns --- p.2-3 / Chapter 4.4 --- Experimental Results and Discussions --- p.3-12 / Summary --- p.12 / References --- p.13 / Chapter 5. --- Fast Photodetector Frequency Response Measurements / Chapter 5.1 --- General Description --- p.1 / Chapter 5.2 --- Optical Heterodyne Measurement --- p.1 -5 / Chapter 5.3 --- Measurement by Pulse Spectrum Analysis --- p.6 -9 / Chapter 5.4 --- Discussions --- p.10 -13 / Summary --- p.13 / References --- p.14 / Chapter 6. --- Balanced Heterodyne Detection with MSM-PDs / Chapter 6.1 --- General Description --- p.1 / Chapter 6.2 --- Mathematical Description --- p.1-4 / Chapter 6.3 --- Excess Noise Cancellation --- p.4-5 / Chapter 6.4 --- Balanced GalnAs MSM Photodetector --- p.6 -9 / Chapter 6.5 --- Optical Heterodyne Detection --- p.10 -13 / Chapter 6.6 --- Balanced Heterodyne Detection --- p.14 -19 / Summary --- p.19 / References --- p.20 / Chapter 7. --- Polarization Diversity Heterodyne Detection / Chapter 7.1 --- Principle --- p.1-2 / Chapter 7.2 --- Experiment and Discussions --- p.2-6 / Summary --- p.6 / References --- p.6 / Chapter 8. --- Conclusion / Appendix A Discrete Fourier Transform --- p.1-7 / Appendix B External Cavity Laser --- p.1 -2 / List of Accepted Publications during the Period of Study
47

High temperature stress accerated grain boundary oxidation mechanism on INCONEL 783 superalloy

Cisloiu, Cezar. January 2001 (has links)
Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains vii, 64 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 62-64).
48

Crossing through yards : narratives of boundaries in East Austin

Steiner, Audrey Moya 23 January 2012 (has links)
This study examines what individuals of limited pecuniary resources in an urban society have to say about how they conceive of or interact with family, neighborhood, city, and society at large, as well as what some of the material and metaphorical boundaries are they meet, and how these function. The narratives they tell delineate ways, directly or indirectly, the consultants attempt to make sense of their lives, and explicate certain of their intertanglements with and perspectives on boundaries they encounter. When boundaries are placed, according to their characteristics, on a soft to hard continuum, an opening presents itself, signaled by specific, identifiable components, to reveal the constructions of empowerment and disenfranchisement that lie behind some seemingly unbreachable barriers. The consultants for this paper tell of skills and creativity they use to re-frame, ignore, cross, or otherwise get around many prevalent constrictive boundaries in order to conduct fulfilling lives. Since much of the success of ethnography, particularly that based on participant observation, hinges on capabilities to cross boundaries in order to understand different communities, the consultants' knowledge of ways to contend with boundaries can be applied productively to anthropological investigations. / text
49

Optical and electrical characterization of metal/semi-insulating GaAs contacts

羅以琳, Luo, Yilin. January 1997 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
50

The maritime zones of non-self-governing and occupied territories

Burke, Naomi January 2014 (has links)
No description available.

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