published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical Engineering / Master / Master of Science in Engineering

No description available.

No description available.

No description available.

No description available.

Approved for public release; distribution is unlimited / The conversion to hydrogen as a naval aviation fuel would allow for independence on fuel cost and supply, as hydrogen is globally accessible. The biggest obstacle to using hydrogen is its very low density, a property that even combined with hydrogen's high heat of combustion still results in very large fuel tanks. Liquid hydrogen (LH2) with its higher density would still require a larger volume than kerosene for the aircraft to achieve the same mission. Another problem with using LH2 is its cryogenic nature, a property that requires complicated fuel tanks and more careful fueling. A design study has been conducted for this report to determine the feasibility of using LH2. A Lockheed-Martin P-3 Orion configuration was modified to accommodate LH2 as its fuel, its mission parameters kept unchanged. It is concluded from this design study that using LH2 would significantly limit the amount of usable cabin space, as the fuel tank takes up 65% of the aircraft's internal volume. Despite the large LH2 tank weight of about 14,865lb, due to the low fuel weight the aircraft's takeoff gross weight is only 113,646lb, about 80% of the current petroleum-fueled P-3. The total cost of LH2 as fuel is currently undetermined. / Ensign, United States Navy

Due to the fast-rising voltage pulses of pulse width modulated drives, the generated shaft voltage of electrical motors causes electrical discharge currents in bearings. These discharges can cause bearing failure leading to costly maintenance and unexpected production stops. To eliminate the raised shaft voltage, several techniques are used such as shaft grounding brushes, insulated bearings and conductive grease. The possibility to measure discharge activity on a PWM driven induction motor offers a tool for researchers to test different bearings in electric motors. In order to measure the shaft voltages and bearing currents, modifications of an induction motor are made firstly using 3D software and then on the physical motor. By insulating the bearing from the frame and attaching a copper ring to the bearings outer race bearing currents can be measured. The combined measurements of shaft voltage, bearing currents and frame currents shows the bearings conductive states at low speed, and insulated state at higher speed. Electrical discharge activity (DA) is observed as shaft voltage raises, resulting in a bearing current spike and shaft voltage drops rapidly while stator current is unaffected. Experimental tests were performed with a sample bearing at different operating conditions, such as operating speed, temperature, motor load, etc., to determine the effect of the common mode voltages on bearing currents and shaft voltages. At low temperatures between 23-26 ˚C and motor speeds above 1000 rpm EDM currents were observed. On temperatures above 40 ˚C no major EDM currents were observed regardless of rpm due to the bearing remaining in an ohmic conductive state. The modifications of the motor have shown to give reliable bearing current and shaft voltage measurements that can help in future research in this area.

Diplomová práce se zabývá corporate identity a strategií integrace značek v automobilovém průmyslu. Integrace je totiž spjata s image značky a změna corporate identity je tedy nezbytností. General Motors v současné době sjednocuje procesy a identitu značek distribuovaných v Evropě. Práce shrnuje dosavadní pokrok General Motors v této iniciativě a navrhuje možné změny procesů nového projektu corporate identity značek Opel, Chevrolet a Saab.