Engineering Commons^™

Study Of Ultra Wide Band Gap Alxga1-Xn Field Effect Transistors For Power Electronic Applications, Sakib Mohammed Muhtadi

Theses and Dissertations

High Aluminum content Al_xGa_1-xN (x > 30%) has attracted intense research interest nowadays as “Ultra Wide Band Gap (UWBG)” material due to large band gap (> 3.4 eV). The critical electric field (EC) of UWBG semiconductor AlGaN is significantly higher than GaN. Moreover, electron saturation velocity is also comparable to GaN. These attractive material properties are the needs for getting large breakdown voltage and high thermal stability which are the requirements for next generation power semiconductor devices. Theoretical possibilities show UWBG AlGaN based devices are an emerging class and can outperform conventional GaN based devices even at …

Integrating Nano-Patterned Ferromagnetic And Ferroelectric Materials For Smart Tunable Microwave Applications, Tengxing Wang

Theses and Dissertations

The wireless communication market has been ever-growing in the recent decades. Radios with high performance and capabilities to support wireless connections are increasingly demanded. Recent developments in wireless communications targeting ubiquitous connections have resulted in ever more complex system structures for supporting multiple frequency bands and standards. Reconfigurable and tunable RF/microwave technologies have the potential to significantly simplify the systems. The main objective of this dissertation is to develop tunable technologies and design concepts, and propose a new design methodology to implement dually electrically tunable microwave components by integrating both selectively patterned ferromagnetic and ferroelectric materials.

The first part of …

Growth And Characterization Of Anisotropic Gase Semiconductor For Radiation Detection And Thz Applications, Haseeb Nazir

Theses and Dissertations

Anisotropic wide-bandgap gallium selenide (GaSe) crystals were grown using high purity (7N) Ga and zone refined (ZR) Se precursor materials. The crystal growth was performed using a modified vertical Bridgman method (VBM) with a slow crystallization from the melt and with a pre-determined temperature profile. The structure, surface morphology, and the composition of the grown crystals were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive analysis by x-rays (EDAX), respectively. Optical absorption and transmission properties were characterized and optical bandgap was determined. Electrical resistivity has been determined using current-voltage (I V) measurements using van der Pauw …

Cable Health Monitoring System Built Into Power Converter Using Time Domain Reflectometry, Hossein Baninajar

Theses and Dissertations

Aging cables are a critical reliability concern for many electrical systems. Cables run over long distances, are often exposed to harsh environments and are intended to work for several decades. Cable faults can be a serious problem because cables are usually hard to repair or replace. Condition based maintenance is a popular approach that provides high reliability and low maintenance cost at the same time. This is a non-destructive method that collects information about the health condition of the cable under test without causing any potential damage.

Nowadays, in several applications power cables are connected to power converters and it …

Fault Protection In Dc Microgrids Based On Autonomous Operation Of All Components, Qiu Deng

Theses and Dissertations

DC power distribution systems (or so called DC microgrids) are of wide interest for various power applications due to their advantages over traditional AC power distribution systems with respect to power density and power distribution efficiency. On the other hand, short-circuit faults present formidable hazards in these systems. It is difficult to extinguish these arc faults via conventional circuit breakers due to the lack of natural zero-crossing of DC current. Also the DC breakers are usually more bulky and costly. Today, fault protection in these systems – to the extent that it exists – relies on over-current time-out limits in …

Software Modelling For Real World Faults On Ac Transmission Protective Systems Analysis And Effects, Iandale Tualla

Theses and Dissertations

The Electric Power Utilities serves many diverse customers from regular households to major processing plants that develop parts for gasoline vehicles. Those varying customer usages has adverse effects on the Electric Grid in many ways, that requires continuing analysis by the engineers and technical skills specialists who keep the Electric Grid stable. Several papers have been written about harmonics and Non- Sinusoidal waveforms and its effect on the Electric Grid. This thesis will exam a realworld fault event on a transmission line, its effects on the AC Transmission Protection Systems (TPS) that provides electrical energy to a nonlinear load, specifically …

Evaluation Of Multicarrier Air Interfaces In The Presence Of Interference For L-Band And C-Band Air-Ground Communications, Hosseinali Jamal

Theses and Dissertations

The use of aeronautical vehicles and systems is continuously growing, and this means current aeronautical communication systems, particularly those operating in the very high frequency (VHF) aviation band, will suffer from severe congestion in some regions of the world. For example, it is estimated that air-to-ground (AG) communication traffic density will at least double by 2035 over that in 2012, based on the most-likely growth scenario for Europe. This traffic growth (worldwide) has led civil aviation authorities such as the FAA in the USA, and EuroControl in Europe, to jointly explore development of future communication infrastructures (FCI). According to international …