Engineering Commons^™

Investigation Of Fes2 Nanoparticles For Use In Optoelectronic And Thermoelectric Applications, Rick Tefal Eyi Nkoghe

Graduate Theses and Dissertations

Iron pyrite (FeS2) is the most abundant sulfide material on earth. This material has been widely investigated by researchers because of its optical properties. However, it has been difficult to produce High efficiency FeS2 based solar cells. This is due to many different impurities that arise when making the materials. The ability to synthesize pure pyrite FeS2 material is therefore critical for applications.

Pure Iron pyrite nanocrystals were synthesized using hot injection by mixing sulfur with an iron precursor in the presence of an amine. To improve the stability, shorter ligands replaced the native amines ligands. The stability of the …

Channel Estimation Overhead Reduction For Downlink Fdd Massive Mimo Systems, Abderrahmane Mayouche

Graduate Theses and Dissertations

Massive multiple-input multiple-output (MIMO) is the concept of deploying a very large number of antennas at the base stations (BS) of cellular networks. Frequency-division duplexing (FDD) massive MIMO systems in the downlink (DL) suffer significantly from the channel estimation overhead. In this thesis, we propose a minimum mean square error (MMSE)-based channel estimation framework that exploits the spatial correlation between the antennas at the BS to reduce the latter overhead. We investigate how the number of antennas at the BS affects the channel estimation error through analytical and asymptotic analysis. In addition, we derive a lower bound on the spectral …

High Step-Up/Down Transformerless Multilevel Converter For Renewable Energy Applications, Haider Ghazi Mhiesan

Graduate Theses and Dissertations

This thesis focuses on a high step-up/down transformerless dc-dc modular multilevel converter (MMC) that would be applicable to dc power systems. The design achieves high voltage ratios for interfacing renewable energy sources such as photovoltaic and line interactive Uninterruptible Power System (UPS) systems. The circuit topology provides for high step-up/down dc-dc conversion ratios using an MMC approach operating in resonant mode in order to improve overall efficiency. This topology operates to step-up the input voltage with 1:10 or larger conversion ratio. As a bidirectional converter, it also provides step-down capability at the same voltage ratio (10:1 or greater). The MMC …

Design And Development Of A Wearable Wireless Health Monitoring System: A Smart Watch Approach, Keerthi Paranikumar

Graduate Theses and Dissertations

According to Statistics, every year, about 610,000 people die because of heart disease in United States of America. (i.e. 1 in every 4 deaths.*) Heart disease is common for both men and women. Annually, about 370,000 people die because of coronary heart disease, which is the most common type of heart disease [1]. About 735,000 Americans have heart attack every year. In this, 210,000 people gets heart attack who already has heart problems and 525,000 people get heart attack for the first time [2]. Not many people know that they have heart problems. Around 47% of the people in United …

Epitaxial Growth Of Si-Ge-Sn Alloys For Optoelectronic Device Application, Aboozar Mosleh

Graduate Theses and Dissertations

Microelectronics industry has experienced a tremendous change over the last few decades and has shown that Moore’s law has been followed by doubling the number of transistors on the chip every 18 months. However, continuous scaling down of the transistors size is reaching the physical limits and data transfer through metal interconnects will not be able to catch up with the increasing data processing speed in the future. Therefore, optical data transfer between chips and on-chip has been widely investigated. Silicon based optoelectronics has received phenomenal attention since Si has been the core material on which microelectronic industry has been …

High-Frequency Transformer Design For Solid-State Transformers In Electric Power Distribution Systems, Roderick Javier Garcia Montoya

Graduate Theses and Dissertations

The objective of this thesis is to present a high- or medium-frequency transformer design methodology for Solid-State Transformer (SST) applications. SSTs have been proposed as a replacement of the traditional 50/60 Hz transformer in applications demanding high-power density. Moreover, due to the high penetration of distributed generation, DC grids, energy storage systems, and sensitive loads, SSTs have been considered as an enabling technology for envisioned future energy systems. These applications demand additional functionalities that may not be achieved with traditional transformers. For example, active power flow control, harmonic suppression, voltage regulation, voltage sag compensation, and reduced size and volume.

In …

Model Development And Validation For Wind Generation Transmission Systems, Mahmood Shihadeh Saadeh

Graduate Theses and Dissertations

In this research a new benchmark system is proposed for wind energy transmission systems. New model development, validation, and calibration methods for power transmission systems are proposed and implemented as well. First, a model reduction criteria is chosen based on electrical interconnection and geographical information. Model development is then done using reduction techniques on an operation model provided by a transmission operator based on the chosen criteria. Then model validation is performed using actual PMU synchrophasor measurements provided by a utility company. The model development and validation process ensures the accuracy of the developed model and makes for a realistic …

Semi-Automated Switching Regulator Modeling Method And Tool, Michael Heath Leonard

Graduate Theses and Dissertations

This thesis presents the results of research targeted at automating the behavioral modeling process for switching voltage regulators. These regulators are commonly used in many application areas including discrete use in larger systems, integrated in a System on a Chip (SoC), or as the primary use case for a design. When used in an integrated system these regulators can be a significant force in slowing down simulations. A common method for removing this slowdown is to use a behavioral model of the switching regulator.

Creating behavioral models can be very time consuming and requires expertise.

The thesis discussion begins by …

Investigation Of The Effects Of Rapid Thermal Annealing On Mbe Grown Gaasbi/Gaas Heterostructures For Optoelectronic Devices, Perry C. Grant

Graduate Theses and Dissertations

High efficiency optoelectronic devices rely on high quality materials making up the device structure. The scope of this thesis investigates the effectiveness of rapid thermal annealing (RTA) at improving the material quality of GaAsBi/GaAs heterostructures. During the fabrication of a device, the contacts of the device had the rapid thermal annealing process accomplished to produce ohmic contacts and this research explored if this annealing treatment degraded the quantum wells that made up the active region of a device. To investigate these effects, a system to measure the photoluminescence of the material system was constructed utilizing Fourier Transform Infrared Spectroscopy. The …

A Reconfigurable Digital-To-Analog Converter With Supply Invariant Linearity, Nicholas J. Chiolino

Graduate Theses and Dissertations

A novel reconfigurable digital-to-analog converter (DAC) with supply independent linearity is presented. The process agnostic converter achieves wide supply range operation and re-configurability by being charge based. This converter consists of a 7-bit parallel digital input control core and an analog "summing" core utilizing charging capacitors with an operational transconductance amplifier in a voltage-follower configuration. This topology is highly configurable to allow for optimization across process voltages, step sizes and low power operation. The specification of the DAC is (1) supply independence (2) low power operation (3) operation up to 200 kHz and (4) conversion control through a DAC enable …

A Wide Bandgap Silicon Carbide (Sic) Gate Driver For High Temperature, High Voltage, And High Frequency Applications, Ranjan Raj Lamichhane

Graduate Theses and Dissertations

The potential of silicon carbide (SiC) for modern power electronics applications is revolutionary because of its superior material properties including substantially better breakdown voltage, power density, device leakage, thermal conductivity, and switching speed. Integration of gate driver circuitry on the same chip, or in the same package, as the power device would significantly reduce the parasitic inductance, require far less thermal management paraphernalia, reduce cost and size of the system, and result in more efficient and reliable electrical and thermal performance of the system.

The design of a gate driver circuit with good performance parameters in this completely new under-development …

Microfluidics Guided By Redox-Magnetohydrodynamics (Mhd) For Lab-On-A-Chip Applications, Vishal Sahore

Graduate Theses and Dissertations

Unique microfluidic control actuated by simply turning off and on microfabricated electrodes in a small-volume system was investigated for lab-on-a-chip applications. This was accomplished using a relatively new pumping technique of redox-magnetohydrodynamics (MHD), which as shown in this dissertation generated the important microfluidic features of flat flow profile and fluid circulation. MHD is driven by the body force, FB = j × B, which is the magnetic part of the Lorentz force equation, and its direction is given by the right hand rule. The ionic current density, j, was generated in an equimolar solution of potassium ferri/ferro cyanide by applying …

Analysis And Optimization Of Cooperative Wireless Networks, Phuong Thanh Tran

Open Access Dissertations

Recently, cooperative communication between users in wireless networks has attracted a considerable amount of attention. A significant amount of research has been conducted to optimize the performance of different cooperative communication schemes, subject to some resource constraints such as power, bandwidth, and time. However, in previous research, each optimization problem has been investigated separately, and the optimal solution for one problem is usually not optimal for the other problems.

This dissertation focuses on joint optimization or cross-layer optimization in wireless cooperative networks. One important obstacle is the non-convexity of the joint optimization problem, which makes the problem difficult to solve …

Electrical Design Considerations And Packaging Of Power Electronic Modules, Shijie Wang

Graduate Theses and Dissertations

A modern power electronic module can save significant energy usage in the power electronic systems by improving their switching efficiencies. One way to improve the efficiency of the power electronic module is to reduce its parasitic circuit elements. The purpose of this thesis is to investigate the mitigation of parasitic circuit elements in power electronic modules. General methods of mitigating parasitic inductances were analyzed by the Q3D Extractor and verified by the time-domain reflectometry (TDR) measurements. In most cases, the TDR measurement results closely matched those predicted by the Q3D Extractor. These methods were applied to design and analyze a …

High Voltage Direct Current Energy Transmission Using Modular Multilevel Converters, David Alejandro Guzman Pinzon

Graduate Theses and Dissertations

This thesis focus on high voltage direct current (HVdc) energy transmission using modular multilevel converter (MMC) based terminals. It provides a brief comparison between different HVdc technologies, focusing on voltage source converters (HVdc-VSC) with the MMC-based terminal emerging as the topology of choice for ratings less than 1 GW. The controllers for a two-terminal HVdc-link are analyzed and Matlab/Simulink^TM simulation models are presented. The simplified models and full Matlab/Simulink^TM based model are used to select the gains for the MMC controllers. Simulation results carried out on the full model validated the proposed methodologies. A new control technique that …

System Design And Motion Artifact Removal Algorithm Implementation For Ambulatory Women Ecg Measurement System:E-Bra System, Hyeokjun Kwon

Graduate Theses and Dissertations

Cardio Vascular Disease (CVD) leads to sudden cardiac death due to irregular phenomenon of the cardiac signal by the abnormal case of blood vessel and cardiac structure. For last three decades, there is an enhanced interest in research for cardiac diseases.. As a result, the death rate by cardiac disease in men has been falling gradually compared with relatively increasing the death rate for women due to CVD. The main reason for this phenomenon is due to the lack of seriousness to female CVD and different symptoms of female CVD compared with the symptoms of male CVD. Usually, because the …

Design And Fabrication Of Inverter And Rectifier Modules For Indirect Matrix Converter Applications, Saikishore Talakokkula

Graduate Theses and Dissertations

In power converter applications, silicon carbide (SiC) power semiconductor devices are preferred over their silicon counterparts due to many advantages such as wide bandgap, high junction temperatures and low on-state resistance. The SiC devices provide reduced conduction and switching losses. Due to the above mentioned advantages the power conversion efficiency of SiC devices is better compared to that of silicon (Si) devices.

This thesis studies the implementation of 1200V/17A Normally-off SiC JFETs for an indirect matrix converter (IMC) application. A discussion on the parasitic inductance optimization is presented based on the electromagnetic simulation results extracted from the Ansoft Q3D extractor. …

Synthesis Of Optimized Inp/Zns Core/Shell Nanocrystals And Tio2 Nanotubes For Quantum Dot Sensitized Solar Cells, Seungyong Lee

Graduate Theses and Dissertations

Synthesis of InP/ZnS core/shell nanocrystals and TiO₂ nanotubes and the optimization study to couple them together were explored for quantum dot sensitized solar cells. Its intrinsic nontoxicity makes the direct band gap InP/ZnS core/shell be one of the most promising semiconductor nanocrystals for optoelectric applications, with the advantage of tuning the optical absorption range in the desired solar spectrum region. Highly luminescent and monodisperse InP/ZnS nanocrystals were synthesized in a non-coordinating solvent. By varying the synthesis scheme, different size InP/ZnS nanocrystals with emission peaks ranging from 520 nm to 620 nm were grown. For the purpose of ensuring air …

Synthesis And Characterization Of Iron Pyrite Nanocrystals For Photovoltaic Devices, Scott Curtis Mangham

Graduate Theses and Dissertations

Iron pyrite nanocrystals have been synthesized using a hot-injection method with a variety of amines and characterized with properties necessary for photovoltaic devices. The iron pyrite nanocrystals were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, optical absorption, micro-Raman, and micro-Photoluminescence. The optical absorbance spectra showed the large absorption in the visible and near infrared spectral range for the nanocrystals as well as to show the band gap. The face-centered cubic crystal structure of the iron pyrite nanocrystals was shown by matching the measured X-ray diffraction pattern to a face-centered cubic iron pyrite reference pattern. Using Bragg's law …

Design And Implementation Of Wireless Point-Of-Care Health Monitoring Systems: Diagnosis For Sleep Disorders And Cardiovascular Diseases, Se Chang Oh

Graduate Theses and Dissertations

Chronic sleep disorders are present in 40 million people in the United States. More than 25 million people remain undiagnosed and untreated, which accounts for over $22 billion in unnecessary healthcare costs. In addition, another major chronic disease is the heart diseases which cause 23.8% of the deaths in the United States. Thus, there is a need for a low cost, reliable, and ubiquitous patient monitoring system. A remote point-of-care system can satisfy this need by providing real time monitoring of the patient's health condition at remote places. However, the currently available POC systems have some drawbacks; the fixed number …

Intermediate Band Solar Cells Based On Inas Quantum Dots Embedded In Ingaas Quantum Well, Ramesh Vasan

Graduate Theses and Dissertations

Intermediate band solar cells based on quantum dots and quantum wells with anti-reflection coating are investigated in this thesis. The demand for high efficient solar cells as an alternate source of energy is the main motivation for this research project. Intermediate band solar cells based on quantum dots were the subject of intensive research in recent years. High power conversion efficiency was predicted from InAs/GaAs intermediate band solar cells as the presence of InAs quantum dots increased the absorption below the band gap of the host material.

In this thesis, an attempt has been made to further increase the absorption …

Information Measures For Statistical Orbit Determination, Alinda Kenyana Mashiku

Open Access Dissertations

The current Situational Space Awareness (SSA) is faced with a huge task of tracking the increasing number of space objects. The tracking of space objects requires frequent and accurate monitoring for orbit maintenance and collision avoidance using methods for statistical orbit determination. Statistical orbit determination enables us to obtain estimates of the state and the statistical information of its region of uncertainty given by the probability density function (PDF). As even collision events with very low probability are important, accurate prediction of collisions require the representation of the full PDF of the random orbit state. Through representing the full PDF …

Computational Design Of The Electrical And Mechanical Performance Of Steerable Mems Antennas, Morgan Andrew Roddy

Graduate Theses and Dissertations

This thesis describes the origins, improvements, and variations of a broadband microwave antenna that can be beam-steered by a micro-electromechanical system (MEMS). The steerable MEMS antenna of this work was comprised of a planar antenna on top of a Silicon membrane. The membrane is etched to create a gimbal hinge structure and a platform which supported the antenna and gave it one or two degrees of freedom of rotation. The antennas presented were broadband and fed by a coplanar waveguide (CPW) transmission line which traversed the hinge structure. The antenna's orientation in space was designed to be changed through electrostatic …

Study Of Current Optocoupler Techniques And Applications For Isolation Of Sensing And Control Signals In Dc-Dc Converters, Jake Williams

Graduate Theses and Dissertations

There is a need for power switches that can operate at high voltage, high temperature, and high switching frequencies with low losses. Power switches fabricated from wide bandgap materials such as silicon carbide (SiC) or gallium nitride (GaN) can outperform conventional silicon switches due to material property advantages. Another common problem in grid-connected applications is the need for high voltage-isolation of gate drivers and control circuitry while operating efficiently at the high switching frequencies, high power density, and high temperatures made possible by wide bandgap devices. Transformers cannot operate at the temperatures of these wide bandgap devices and a new …

Thermal And Electrical Parasitic Modeling For Multi-Chip Power Module Layout Synthesis, Zihao Gong

Graduate Theses and Dissertations

This thesis presents thermal and electrical parasitic modeling approaches for layout synthesis of Multi-Chip Power Modules (MCPMs). MCPMs integrate power semiconductor devices and drive electronics into a single package. As the switching frequency of power devices increases, the size of the passive components are greatly reduced leading to gains in efficiency and cost reduction. In order to increase switching frequency, electrical parasitics in MCPMs need to be reduced through tighter electronic integrations and smaller packages. As package size is decreased, temperature increases due to less heat dissipation capability. Thus, it is crucial to consider both thermal and electrical parasitics in …

Design And Analysis Of An Adaptive Asynchronous System Architecture For Energy Efficiency, Brent Michael Hollosi

Graduate Theses and Dissertations

Power has become a critical design parameter for digital CMOS integrated circuits. With performance still garnering much concern, a central idea has emerged: minimizing power consumption while maintaining performance. The use of dynamic voltage scaling (DVS) with parallelism has shown to be an effective way of saving power while maintaining performance. However, the potency of DVS and parallelism in traditional, clocked synchronous systems is limited because of the strict timing requirements such systems must comply with. Delay-insensitive (DI) asynchronous systems have the potential to benefit more from these techniques due to their flexible timing requirements and high modularity. This dissertation …

Delay Insensitive Ternary Logic Utilizing Cmos And Cntfet, Ravi Sankar Parameswaran Nair

Graduate Theses and Dissertations

As digital circuit design continues to evolve due to progress of semiconductor processes well into the sub 100nm range, clocked architectures face limitations in a number of cases where clockless asynchronous architectures require substantially less power, generate less noise, and produce less electromagnetic interference (EMI). This dissertation develops the Delay Insensitive Ternary Logic (DITL) asynchronous design paradigm that combines the designs aspects of similar Dual-Rail asynchronous paradigms and Boolean logic to create a single wire per bit, three voltage signaling and logic scheme.

DITL is designed at the transistor level using multi-threshold CMOS and carbon nanotube (CNT) FETs to develop …

Ultra-Low Voltage Digital Circuits And Extreme Temperature Electronics Design, Aaron J. Arthurs

Graduate Theses and Dissertations

Certain applications require digital electronics to operate under extreme conditions e.g., large swings in ambient temperature, very low supply voltage, high radiation. Such applications include sensor networks, wearable electronics, unmanned aerial vehicles, spacecraft, and energyharvesting systems. This dissertation splits into two projects that study digital electronics supplied by ultra-low voltages and build an electronic system for extreme temperatures. The first project introduces techniques that improve circuit reliability at deep subthreshold voltages as well as determine the minimum required supply voltage. These techniques address digital electronic design at several levels: the physical process, gate design, and system architecture. This dissertation analyzes …

Design Of A High Dynamic Range Cmos Variable Gain Amplifier For Wireless Sensor Networks, Yue Yu

Graduate Theses and Dissertations

This thesis presents the design, simulation, layout and testing results for a dB-linear, high dynamic gain range CMOS variable gain amplifier (VGA). The design adopts a new approximated exponential equation called the pseudo exponential equation to implement the dB-linear function. The proposed VGA is designed to have an extremely wide gain variation, small chip area, low supply voltage, and controllable dynamic gain range. The gain variation of the 3-stage VGA is implemented by a voltage to current converter. It controls the bias currents of each VGA cell, so that the output gain of each cell can be controlled. In order …

Design Of An Rf Cmos Power Amplifier For Wireless Sensor Networks, Hua Pan

Graduate Theses and Dissertations

The Power Amplifier (PA) is the last Radio Frequency (RF) building block in a transmitter, directly driving an antenna. The low power RF input signal of the PA is amplified to a significant power RF output signal by converting DC power into RF power. Since the PA consumes a majority of the power, efficiency plays one of the most important roles in a PA design. Designing an efficient, fully integrated RF PA that can operate at low supply voltage (1.2V), low power, and low RF frequency (433MHz) is a major challenge. The class E Power Amplifier, which is one type …