Electrical and Electronics Commons^™

Metal Assisted Nanowire Growth For Silicon Nanowire/Amorphous Silicon Composite Solar Cell, Asmaa Ali Sadoon

Graduate Theses and Dissertations

Solar cells are photovoltaic devices that convert the energy of light to electricity by the photovoltaic effect. Crystalline silicon-based solar cells are the most dominant solar cells in the market today due to the high efficiency and relatively low cost. However, the cost of such solar cell is still high due to the large amount of material that is consumed in fabricating such a device. Polycrystalline/amorphous thin films and nanomaterial technologies have emerged to reduce the high cost of c-Si based solar cells and increase the efficiency. In this research, we combined these two technologies to propose and fabricate silicon …

The Role Of Quantum Dot Size On The Performance Of Intermediate Band Solar Cells, Najla Alnami

Graduate Theses and Dissertations

The goal of this thesis is to understand possible mechanisms for the reported decrease of the open circuit voltage and solar cell efficiency in quantum dot (QD) intermediate band solar cells (IBSCs). More specifically, the effect of indium arsenide (InAs) QD height on the open circuit voltage and solar cell efficiency was studied in a systematic way. To explore this effect in QD solar cells, several solar cells (SCs) were grown with varying InAs QD heights. All experimental characteristics of the QD solar cells were compared to a reference structure without QDs. All samples were grown by Molecular Beam Epitaxy …

Gesn Light-Emitting Devices, Yiyin Zhou

Graduate Theses and Dissertations

Silicon based optoelectronic devices have been investigated for decades. However, due to the indirect band gap nature of Si and Ge, developing of efficient light-emitting source on Si is still a challenging topic. GeSn based optoelectronic devices have the great potential to overcome this deficiency for several reasons. By adding more fraction of Sn into Ge, GeSn band gap could be reduced. The narrowed band gap could be developed for near to mid infrared applications. The alloy can even become the direct band gap material with a large Sn composition (beyond 8%). This feature could enhance the light emission from …

Designing And Implementing A Micro-Controller Based Primary-Side Sensing Flyback Converter For Leds Driver, Nam Nhat Tran

Graduate Theses and Dissertations

The fast development of LED and its applications has enabled a new generation of lighting device with higher efficiency and long lifespan. By employing a primary-side sensing flyback converter and the PIC18F micro-controller series, an LED driver could achieve two important features: (1) the compatibility with the available lighting fixtures, and (2) reducing unit price. The flyback converter was chosen for its simplicity, competitive low cost, and its ability to provide a constant output current, a necessarily important factor to an LED driver. Meanwhile, the PIC18F micro-controller series offer numerous advanced features which include but not limited to pulse-width modulation …

Low-Power Analog Processing, Daniel J. White

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

This dissertation presents the analog harmonic transform (AHT) and a first implementation in an integrated circuit. The transform is designed for a regular and simple hardware structure. It provides coefficients relating to an input signal's spectrum. These coefficients also have a simple relationship to the signal's Fouri\'er series coefficients.

The AHT is defined in its ideal form and evaluated for two example signal classification applications. Both military vehicle and bearing fault classification tasks are presented which validate the ability of a neural network to use the AHT coefficients to correctly classify the input signals. Because any real use of the …

A Low-Power Compact Nuclear Quadrupole Resonance (Nqr) Based Explosive Detection System, Xinwang Zhang

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Abandoned landmines and terrorist bomb attacks are severe issues threatening our society. These issues necessitate the development of prompt and accurate explosive detection systems. The detection mechanisms commonly-used nowadays usually search for explosive containers, which suffer numerous false alarms caused by external detection circumstance changes. Alternatively, explosive substances inside the bombs and landmines can be detected by means of biology, chemistry and physics techniques. Nuclear Quadrupole Resonance (NQR) detection technology has proven to be a highly effective solution for detecting explosives unambiguously.

In this work, a portable NQR-based explosive detection system that employs state-of-the-art semiconductor technologies is presented. This system …

Printed Triple-Band Circularly Polarised Antenna For Wireless Systems, Xiulong Bao, Max Ammann

Articles

A triple-band circularly polarised microstrip patch antenna operating in the 2.4, 3.5 and 5.7 GHz bands is presented. The antenna consists of two substrate layers with an electromagnetically coupled low-band patch in the middle layer and a probe-fed dual-band patch on the top layer. The impedance bandwidths (voltage standing wave ratio (VSWR) < 2.5) for the three frequency bands are 112, 118 and 427 MHz with 3 dB axial-ratio bandwidths of 15, 44 and 36 MHz, respectively. The peak gains across the operating bands are 4.2, 5.5 and 4 dBic, respectively.

Uv Laser-Assisted Diamond Deposition, Mengxiao Wang

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Diamond, due to its unique properties, has been studied for decades. Many diamond synthesis methods have been developed as well. As one of the synthesis methods, combustion flame chemical vapor deposition (CVD) is considered as the most flexible way. Combined with laser irradiation, laser-assisted combustion flame CVD can enhance the deposition process of diamond films. In this thesis work, efforts were made to explore the capability of a laser-assisted combustion flame CVD technique with krypton fluoride (KrF) excimer laser irradiation for improving diamond thin film quality and deposition rate. The research efforts mainly focus on following activities, including: 1) studying …

Modeling And Characterization Of Non-Ideal Effects In High-Performance Rf Mems Tuners, Juan Zeng

Open Access Dissertations

The emerging standards for the next-generation wireless communication system demand for multi-band RF front-ends. Reconfigurable RF devices based on MEMS technology have emerged with the potential to significantly reduce the system complexity and cost. Robust operation of RF MEMS tuners under the non-ideal effects due to fabrication uncertainties and environmental variations is critical in achieving reliable RF MEMS reconfigurable devices. Therefore, it is essential to model and characterize these non-ideal effects, and further to alleviate these non-ideal effects by design optimization.^ In this dissertation, the effects of non-perfect anchor support, residual stress, and temperature sensibility of MEMS tuners have been …

Application Of Integer Quadratic Programming To Detection Of High-Dimensional Wireless Systems, Jamal Yousuf Alsawalhi

Open Access Dissertations

This work introduces a novel permanent-magnet synchronous machine (PMSM) architecture that employs rotational asymmetry to increase the torque density output in constant power variable speed applications. A population based multi-objective design optimization algorithm is used to design and analyze the new machine topology. A number of design studies are presented to show that the proposed machine structure outperforms a conventional PMSM machine. Validation of the analytical machine design model using a three dimensional finite element analyses is performed and the results are presented. Finally, a case study in which a hybrid electric bus traction motor is designed is presented.

Developing A Practical Wireless Monitoring Solution For A Size-Constrained, Low-Power, Biomechanical, Sports Telemetry System, Jeffery Ray King

Open Access Theses

As sport-related concussions become more prevalent, the ability to quickly and reliably assess brain injury risk is increasingly essential. Commercially-available systems exist with the goal of assessing the risk of traumatic brain injury in athletes in real-time. These systems utilize a pre-determined acceleration threshold, discarding all captured information below this arbitrary threshold. The use of an event-based model to assess the risk of traumatic brain injury has been shown to be inadequate. Therefore, these systems falsely promote "accurate" real-time communication of risk. Research conducted by the Purdue Neurotrauma Group (PNG) seeks to advance the field by developing a biomechanical sports …

Quantifying Aesthetics Of Visual Design Applied To Automatic Design, Ali Jahanian

Open Access Dissertations

In today's "Instagram" world, with advances in ubiquitous computing and access to social networks, digital media is adopted by art and culture. In this dissertation, we study what makes a good design by investigating mechanisms to bring aesthetics of design from realm of subjection to objection. These mechanisms are a combination of three main approaches: learning theories and principles of design by collaborating with professional designers, mathematically and statistically modeling good designs from large scale datasets, and crowdscourcing to model perceived aesthetics of designs from general public responses. We then apply the knowledge gained in automatic design creation tools to …

Material And Device Aspects Of Semiconducting Two-Dimensional Crystals, Han Liu

Open Access Dissertations

Two-dimensional (2D) crystals have attracted much attention in recent years due to their unique physical, chemical, and mechanical properties. Semiconducting 2D crystals with van der Waals structures, such as transition metal dichalcogenides, are considered promising candidates for future device applications, as many have large band gaps, high carrier mobilities, and enable devices with immunity to short channel effects in addition to compatibility with silicon CMOS processes.^ In this thesis, the fundamental device implications of using semiconducting 2D crystals are investigated. This includes: 1) the optimization of device fabrication processing for better device performance, 2) comparing the device physics in 2D …

Nearly Orthogonal, Doppler Tolerant Waveforms And Signal Processing For Multi-Mode Radar Applications, Uttam Kumar Majumder

Open Access Dissertations

In this research, we investigate the design and analysis of nearly orthogonal, Doppler tolerant waveforms for diversity waveform radar applications. We then present a signal processing framework for joint synthetic aperture radar (SAR) and ground moving target indication (GMTI) processing that is built upon our proposed waveforms. ^ To design nearly orthogonal and Doppler tolerant waveforms, we applied direct sequence spread spectrum (DSSS) coding techniques to linear frequency modulated (LFM) signals. The resulting transmitted waveforms are rendered orthogonal using a unique spread spectrum code. At the receiver, the echo signal can be decoded using its spreading code. In this manner, …

Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park

Open Access Dissertations

The exponential miniaturization of Si CMOS technology has been a key to the electronics revolution. However, the continuous downscaling of the gate length becomes the biggest challenge to maintain higher speed, lower power, and better electrostatic integrity for each following generation. Hence, novel devices and better channel materials than Si are considered to improve the metal-oxide-semiconductor field-effect transistors (MOSFETs) device performance. III-V compound semiconductors and multi-gate structures are being considered as promising candidates in the next CMOS technology. III-V and Si nano-scale transistors in different architectures are investigated (1) to compare the performance between InGaAs of III-V compound semiconductors and …

Power-Efficient High-Speed Interface Circuit Techniques, Elkim Felipe Roa Fuentes

Open Access Dissertations

Inter- and intra-chip connections have become the new challenge to enable the scaling of computing systems, ranging from mobile devices to high-end servers. Demand for aggregate I/O bandwidth has been driven by applications including high-speed ethernet, backplane micro-servers, memory, graphics, chip-to-chip and network onchip. I/O circuitry is becoming the major power consumer in SoC processors and memories as the increasing bandwidth demands larger per-pin data rate or larger I/O pin count per component. The aggregate I/O bandwidth has approximately doubled every three to four years across a diverse range of standards in different applications. However, in order to keep pace …

Theory Of Topological Insulators And Its Applications, Parijat Sengupta

Open Access Dissertations

An important pursuit in semiconductor physics is to discover new materials to sustain the continuous progress and improvements in the current electronic devices. Traditionally, three material types are in use: 1) Metals 2) Semiconductors 3) Insulators. All the three material types are classified according to the energy gap between conduction and valence bands derived from band theory of solids. Recent theoretical predictions and confirmed by experimental observations have provided evidence that there exists materials which behave as insulators in the bulk but possess gapless conducting states on the surface. These new class of materials are called topological insulators (TI). In …

Computing With Spintronics: Circuits And Architectures, Rangharajan Venkatesan

Open Access Dissertations

This thesis makes the following contributions towards the design of computing platforms with spintronic devices. 1) It explores the use of spintronic memories in the design of a domain-specific processor for an emerging class of data-intensive applications, namely recognition, mining and synthesis (RMS). Two different spintronic memory technologies — Domain Wall Memory (DWM) and STT-MRAM — are utilized to realize the different levels in the memory hierarchy of the domain-specific processor, based on their respective access characteristics. Architectural tradeoffs created by the use of spintronic memories are analyzed. The proposed design achieves 1.5X-4X improvements in energy-delay product compared to a …

Design And Analysis Of Solar Cells By Coupled Electrical - Optical Simulation, Xufeng Wang

Open Access Dissertations

Careful electrical design and optical design are both crucial for achieving high-efficiency solar cells. It is common to link these two aspects serially; the optical design is first done to minimize reflection and maximize light trapping, and then the resulting optical generation rate is input to the electrical simulation. For very high efficiency solar cells that approach the Shockley-Queisser limit, however, electrical and optical transports are tightly coupled in both directions. Photons generated by radiative recombination can be reabsorbed to create additional electron-hole pairs (so-called photon recycling), which decreases losses. A variety of novel photon management schemes are currently being …

Estimating Toner Usage With Laser Electrophotographic Printers, And Object Map Generation From Raster Input Image, Lu Wang

Open Access Dissertations

Accurate estimation of toner usage is an area of on-going importance for laser, electrophotographic (EP) printers. In Part 1, we propose a new two-stage approach in which we first predict on a pixel-by-pixel basis, the absorptance from printed and scanned pages. We then form a weighted sum of these pixel values to predict overall toner usage on the printed page. The weights are chosen by least-squares regression to toner usage measured with a set of printed test pages. Our two-stage predictor significantly outperforms existing methods that are based on a simple pixel counting strategy in terms of both accuracy and …