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One of two project reports. Part B is available at http://hdl.handle.net/11375/17552 / <p> The design, construction, and initial operation of a surface analysis station were undertaken. The final UHV system is equipped for ion surface scattering, low energy electron diffraction, Auger analysis, secondary ion mass spectroscopy and residual gas analysis. </p> <p> The main goal of this project was the preliminary operation of the ion surface scattering equipment. A complete beam transport system was constructed utilizing an Einzel lens and electrostatic quadroles. </p> <p> The ion surface scattering was effected through the use of a time-of-flight (TOF) technique to obtain an energy spectrum of particles backscattered from a target surface. The TOF spectrum and subsequent energy spectrum were for 5.1 keV hydrogen ions incident on a practical silver target. </p> / Thesis / Master of Engineering (ME)

The global shift towards Electric Vehicles (EVs) is driven by their energy efficiency, lower emissions, and reduced dependence on fossil fuels. As the demand for EVs continues to rise, the need for EV ultra-fast chargers becomes paramount to enable faster charging times and facilitate long-distance travel without compromising convenience. In this context, solid-state transformers (SSTs) have emerged as a promising technology to replace traditional line-frequency transformers (LFTs) in various applications, including EV charging stations. SSTs offer improved system controllability, power factor correction capabilities, and reduced size and weight through the utilization of medium-frequency transformers (MFTs). This thesis focuses on enhancing the efficiency and power density of the MFT used in SSTs. A 1.2 MVA SST for EV ultra-fast charging stations is designed and simulated. The SST incorporates average controllers responsible for regulating the output voltage and the input power factor, as well as, voltage and power balancing controllers to ensure stable operation among its cells. Furthermore, a design methodology for optimizing the MFT used in DC-to-DC converters for SST-based ultra-fast chargers is introduced. The methodology is optimizing the efficiency and power density of the transformer based on the transformer parameters input by the designer. A software tool is developed to streamline the design process and enable the optimization of various parameters, such as core material, size, and winding configurations. The tool facilitates the development of high-performance MFTs for SST applications. The developed MFT optimization methodology is utilized to design a 100 kW, 20 kHz MFT, resulting in a remarkable 22.7% improvement in power density compared to conventional design methods. The transformer showed superior efficiency and power density compared to MFT designs in literature. Additionally, two scaled-down transformers are designed and tested at 5 kW, employing both conventional and optimization methods. The results demonstrate a significant 57.8% improvement in specific power. / Thesis / Master of Applied Science (MASc)

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No description available.

Since the Fukushima Daiichi nuclear accident, there have been ongoing efforts to enhance the modelling capabilities for severe accidents in nuclear power plants. The primary severe accident analysis code used in Canada for its CANDU reactors is MAAP-CANDU (adapted from MAAP-LWR). In order to meet the new requirements that have evolved since Fukushima, upgrades to MAAP-CANDU have been made most recently by the Canadian nuclear industry. While the newest version (i.e. MAAP5-CANDU) offers several important improvements primarily in core nodalization and core collapse modelling, it still lacks mechanistic models for many key thermo-mechanical deformation phenomena that may significantly impact accident progression and event timings. It is also a general consensus that having alternative analysis tools is beneficial in improving our confidence in the simulation results, especially given the complex nature of severe accident phenomena in CANDU and the limited experimental support. This thesis seeks a novel approach to CANDU severe accident modelling by combining the best-estimate thermal-hydraulic code RELAP5, the severe accident models in SCDAP, and several CANDU-specific mechanistic deformation models developed by the author. This work mainly consists of two parts. The first part is focused on the assessment of natural circulation heat sinks following crash-cooldown in the early-phase of a Station Blackout (SBO) accident where fuel channel deformation can be precluded. The effectiveness of steam generator heat removal after crash-cooldown and that of the several water make-up options were demonstrated through the simulation of several SBO scenarios with/without crash-cooldown, sensitivity studies, as well as benchmarking against station and experimental measurements. In the second part, several mechanistic severe accident models were developed to enhance the simulation fidelity beyond the initial steam generator heat sink phase to the moderator boil-off and core disassembly phases. This includes models for predicting the pressure tube ballooning and sagging phenomena during the fuel channel heat-up phase and models for the sagging and disassembly of fuel channel assemblies during the core disassembly phase. After benchmarking against relevant channel deformation experiments, the models were successfully integrated into the RELAP/SCDAPSIM/MOD3.6 code as part of the SCDAP subroutines. The advantage of utilizing a code such as SCDAP is that generic models for fission product release and hydrogen generations, which are well benchmarked, can be directly applied to CANDU simulations. With the modified MOD3.6 code the early-phase SBO simulations were extended to include the later stages of SBO until the calandria vessel dryout. The current modelling approach replaced the simple threshold-type models commonly seen in the integrated severe accident codes such as MAAP-CANDU with more mechanistic models thereby providing a more robust treatment of the core degradation process during severe accident in CANDU. / Thesis / Doctor of Philosophy (PhD)

Smart antenna systems are employed to overcome multipath fading, extend range, and increase capacity by using diversity or beamforming techniques in wireless communication systems. Understanding of the smart base antenna performance mechanisms for various environments is important to design cost effective systems and network. This dissertation focuses on the experimental characterization and modeling of the smart base station antenna performance for various propagation environment scenarios. An eight-channel Virginia Tech smart base station antenna testbed was developed to investigate performances of three reverse link diversity methods. The experiment campaign resulted in 245 sets of collected data over 83 measurement sites, which were used to compare the performance of space, polarization, and angle diversity under identical conditions. Measured propagation path loss, envelope correlation coefficients, power imbalances, and mean effective gain (MEG) are characterized as a function of distance between the base station and the mobile terminal to illustrate the diversity performance mechanisms over different propagation environments. The performance of the three base station diversity methods with selection combining (SC), maximal ratio combining (MRC), and equal gain combining (EGC) techniques for both urban and suburban non-line-of-sight (NLOS) environments are presented and summarized using the measured data. Forward-link performance of a twelve-fixed narrow-beam base station antenna system for urban NLOS environments is investigated using the same measured data. A new procedure is introduced to experimentally model the forward-link performance of muitlple-fixed narrow-beam (MFNB) antennas using the measured reverse-link vector channel response. The experimentally calculated lower bound performance result shows that it achieves 2.5 to 2.8 times higher average RF SIR compared to the conventional three-sector base station system for typical urban NLOS multipath fading environment conditions. Also, a new mobile user angle estimation algorithm using the muitlple-fixed narrow-beam antennas for NLOS multipath fading environment conditions is developed and the experiment results are presented. / Ph. D.

In the last decade the world has seen a steadily increasing number of Cube Satellites deployed to Low Earth Orbit. Traditionally, these cubesats rely on Amateur Radio communications technology that are proven to work from space. However, as data volumes increase, the existing Amateur Radio protocols, combined with the restrictions of use for the Amateur Radio Spectrum, as well as the trend to build one control station per cubesat, result in a bottle neck effect whereby existing communications methods are no longer sufficient to support the increasing data volumes of the spacecraft. This Masters Thesis work explores the concept of deploying a network of distributed ground station receiver nodes for the purposes of increasing access time to the spacecraft, and thereby increasing the potential amount of data that can be transferred from orbit to the ground. The current trends in cubesat communications will be analyzed and an argument will be made in favor of transitioning to more modern digital communications approaches for on orbit missions. Finally, a candidate ground station receiver node design is presented a possible design that could be used to deploy such a network. / Master of Science

The project is dreamed as a monumental edifice standing beside the rail corridor of South-Western Virginia. Two pairs of towers rise from the earth transitioning from squares to ellipses. The towers are cut mid-ascent to shape an eastern face, orienting the project and the rail traffic beneath. / Master of Architecture

This paper focuses on issues faced by the individual partners involved in the International Space Station. Specifically addressed are the economic troubles in Russia and Japan, political problems in the United States and Canada, and the issue of cooperation in the European Union. Using Linkage, Post-Internationalist, and Practice Theories to demonstrate how this unique project will proceed, this thesis suggests several strategies to help ensure the proposition's success.