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Microstructure and Electronic Structures of Er-Doped Si Nano-particles Synthesized by Vapor Phase Pyrolysis

Microstructure and Electronic Structures of Er-Doped Si Nano-particles Synthesized by Vapor Phase Pyrolysis

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Date: May 2000
Creator: Chen, Yandong
Description: Si nanoparticles are new prospective optoelectronic materials. Unlike bulk Si cry-stals, Si nanoparticles display intriguing room-temperature photoluminescence. A major challenge in the fabrication of Si nanoparticles is the control of their size distribution. The rare-earth element Er has unique photo emission properties, including low pumping power, and a temperature independent, sharp spectrum. The emission wavelength matches the transmission window of optical fibers used in the telecommunications industry. Therefore, the study of Er-doped Si nanoparticles may have practical significance. The goals of the research described in this dissertation are to investigate vapor phase pyrolysis methods and to characterize the microstructure and associated defects, particles size distributions and photoluminescence efficiencies of doped and undoped Si nanoparticles using analytical transmission electron microscopy, high resolution electron microscopy, and optical spectroscopy. Er-doped and undoped Si nanoparticles were synthesized via vapor-phase pyrolysis of disilane at Texas Christian University. To achieve monodisperse size distributions, a process with fast nucleation and slow growth was employed. Disilane was diluted to 0.48% with helium. A horizontal pyrolysis oven was maintained at a temperature of 1000 °C. The oven length was varied from 1.5 cm to 6.0 cm to investigate the influence of oven length on the properties of the nanoparticles. ...
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Microstructure Evolution in Laser Deposited Nickel-Titanium-Carbon in situ Metal Matrix Composite

Microstructure Evolution in Laser Deposited Nickel-Titanium-Carbon in situ Metal Matrix Composite

Date: December 2010
Creator: Gopagoni, Sundeep
Description: Ni/TiC metal matrix composites have been processed using the laser engineered net shaping (LENS) process. As nickel does not form an equilibrium carbide phase, addition of a strong carbide former in the form of titanium reinforces the nickel matrix resulting in a promising hybrid material for both surface engineering as well as high temperature structural applications. Changing the relative amounts of titanium and carbon in the nickel matrix, relatively low volume fraction of refined homogeneously distributed carbide precipitates, formation of in-situ carbide precipitates and the microstructural changes are investigated. The composites have been characterized in detail using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy (XEDS) mapping and electron backscatter diffraction (EBSD)), Auger electron spectroscopy, and transmission (including high resolution) electron microscopy. Both primary and eutectic titanium carbides, observed in this composite, exhibited the fcc-TiC structure (NaCl-type). Details of the orientation relationship between Ni and TiC have been studied using SEM-EBSD and high resolution TEM. The results of micro-hardness and tribology tests indicate that these composites have a relatively high hardness and a steady-state friction coefficient of ~0.5, both of which are improvements in comparison to LENS deposited pure Ni.
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Microwave-Assisted Synthesis, Characterization, and Photophysical Properties of New Rhenium(I) Pyrazolyl-Triazine Complexes

Microwave-Assisted Synthesis, Characterization, and Photophysical Properties of New Rhenium(I) Pyrazolyl-Triazine Complexes

Date: May 2010
Creator: Salazar Garza, Gustavo Adolfo
Description: The reaction of the chelating ligand 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazin-2-yl]-N,N-diethyl-benzenamine, L, with pentacarbonylchlororhenium by conventional heating method produces the complexes fac-[ReL(CO)3Cl2] and fac-[Re2L(CO)6Cl2] in a period of 48 hours. The use of microwaves as the source of heat and the increase in the equivalents of one of the reactants leads to a more selective reaction and also decreases the reaction time to 1 hour. After proper purification, the photophysical properties of fac-[ReL(CO)3Cl] were analyzed. The solid-state photoluminescence analysis showed an emission band at 628 nm independent of temperature. However, in the solution studies, the emission band shifted from 550 nm in frozen media to 610 nm when the matrix became fluid. These results confirm that this complex possess a phenomenon known as rigidochromism.
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Microwave Cavity Method for Measuring Plasma Properties

Microwave Cavity Method for Measuring Plasma Properties

Date: August 1969
Creator: Freeman, Ronald H.
Description: This discussion is concerned primarily with communications blackout during spacecraft entry into a planetary atmosphere. The gas in the shock layer, between shock wave and vehicle surface, ionizes from the intense heating which takes place in the bow shock wave and a viscous region of high gas enthalpy. This ionization may persist throughout the subsequent flow over the vehicle and into the wake, thus completely engulfing the vehicle and its communications elements. The problem will be to simulate a plasma model that will be of interest for hypervelocity reentry vehicles and to provide meaningful expressions for the various plasma parameters of interest (electron density, electron temperature, collision frequency, etc.) in terms of the microwave measurables (amplitude, phase shifts, frequency shifts, polarization, etc.)
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Microwave Cavity Test for Superconductivity

Microwave Cavity Test for Superconductivity

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Date: December 2001
Creator: Tang, Shan
Description: The first part of this paper describes the Meissner effect in superconductors which serves as the most definitive evidence for superconductivity. It is shown that the microwave perturbation technique may be used to demonstrate this effect. By measuring the changes of resonant frequency and inverse quality factor Q of a microwave cavity with a small volume of sample loading, the Meissner effect can be shown by using the Slater perturbation equation. The experimental system is described with details and the basic principle of each component discussed. The second part of this work describes the technique employed to do the actual measurements. The experiments were conducted on samples of Gallium Arsenide (GaAs) and lead zirconate titanate (PZT) to look for the possible high temperature superconductivity properties. Results of these experiments are presented and discussed. Conclusion and suggestions to future exploration are made.
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A Microwave Spectrometer for Narrow-line Electron Spin Resonance Studies

A Microwave Spectrometer for Narrow-line Electron Spin Resonance Studies

Date: January 1966
Creator: Neie, Van ElRoy
Description: This thesis explores the basic theory, design and construction of electron spin resonance spectrometer.
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Middle Men: Establishing Non-Anglo Masculinity in Southwestern Literature

Middle Men: Establishing Non-Anglo Masculinity in Southwestern Literature

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Date: August 2003
Creator: King, Charla
Description: By examining southwestern masculinity from three separate lenses of cultural experience, Mexican American, Native American and female, this thesis aims to acknowledge the blending of masculinities that is taking place in both the fictitious and factual southwest. Long gone are the days when the cowboys chased down the savage Indians or the Mexican bandits. Southwestern literature now focuses on how these different cultures and traditions can re-construct their masculinities in a way that will be beneficial to all. The southwest is a land of borders and liminal spaces between the United States and Mexico, between brown and white, legal and illegal. All of these borders converge here to create the last American frontier. These converging borders also encompass converging traditions, cultures, and genders. By blending the cowboy, the macho, and the warrior, perhaps these Southwestern writers can construct a liminal masculinity more representative of the southwest itself.
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Middle School Students in Virtual Learning Environments

Middle School Students in Virtual Learning Environments

Date: August 2010
Creator: Wyatt, Erin Drankwalter
Description: This ethnographic study examined middle school students engaged in a virtual learning environment used in concert with face-to-face instruction in order to complete a collaborative research project. Thirty-eight students from three eighth grade classes participated in this study where data were collected through observation of student work within the virtual learning environment, an online survey, and focus group sessions with students involved in the project. Results indicated students found the virtual learning environment to be valuable as a platform to complete a collaborative research assignment because of portability, ease of use, and organization. Embedded resources within the environment were helpful because of the convenience. Other people, including peers and teachers, were the preferred source of help when problems navigating the environment or finding information arose. Students communicated within the virtual learning environment as a social outlet, a way to check in, and a means to offer content related comments. Ideally the study's findings will give insight into student experiences in a virtual learning environment in order to help educators design more effective learning experiences and incorporate useful supports within such environments.
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Middle Voice Construction in Burushaski: From the Perspective of a Native Speaker of the Hunza Dialect

Middle Voice Construction in Burushaski: From the Perspective of a Native Speaker of the Hunza Dialect

Date: May 2013
Creator: Karim, Piar
Description: This study is about voice system in Burushaski, focusing especially on the middle voice (MV) construction. It claims that the [dd-] verbal prefix is an overt morphological middle marker for MV constructions, while the [n-] verbal prefix is a morphological marker for passive voice. The data primarily come from the Hunza dialect of Burushaski, but analogous phenomena can be observed in other dialects. This research is based on a corpus of 120 dd-prefix verbs. This research has showed that position {-2} on the verb template is occupied by voice-marker in Burushaski. The author argues that the middle marker is a semantic category of its own and that it is clearly distinguished from the reflexive marker in this language. The analysis of the phenomenon in this study only comes from the dialect of Hunza Burushaski, so a lot of research remains to be done on the other three dialects of Burushaski: Yasin dialect, Nagar dialect and Srinagar dialect.
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Miguel Yuste: His Works for Clarinet and His Influence on the Spanish Clarinet School of Playing in the Twentieth Century, A Lecture Recital, Together with Three Recitals of Selected Works by Bax, Mason, Khachaturian, Chausson, Bozza, Beethoven, and Others

Miguel Yuste: His Works for Clarinet and His Influence on the Spanish Clarinet School of Playing in the Twentieth Century, A Lecture Recital, Together with Three Recitals of Selected Works by Bax, Mason, Khachaturian, Chausson, Bozza, Beethoven, and Others

Date: May 2005
Creator: McLaren, Malena Rachel
Description: The popularity of the clarinet in Spain is second only to that of the guitar, and there is a rich tradition of clarinet playing that is accompanied by an equally rich repertoire of music for the clarinet by Spanish composers. The works for clarinet and piano by Miguel Yuste (1870-1947) are among this little known repertoire. In the early twentieth century it was thought that Miguel Yuste wrote over one hundred works for clarinet. However, current research suggests that this is incorrect. What is known is that seven works for clarinet and piano have been published. Miguel Yuste and his music are pivotal in the establishment of the strong clarinet tradition for which Spain is presently known. In his thirty years as the clarinet professor at the Real Conservatorio Superior de Música de Madrid (1910-1940), Miguel Yuste's music and pedagogical ideas became, and continue to be among the foundations of Spanish clarinet playing. This project discusses each published work and presents current research on the works composed for clarinet and piano by Miguel Yuste. After a brief history of Spain's music and social climate in which it developed (Ch. 2), this document discusses the introduction of the clarinet in Spain, ...
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