Electrical and Computer Engineering Commons^™

Tailoring And Remotely Switching Performance Of Ultrafiltration Membranes By Magnetically Responsive Polymer Chains, Anh Vu, Arijit Sengupta, Emily Freeman, Xianghong Qian, Mathias Ulbricht, S. Ranil Wickramasinghe

Chemical Engineering Faculty Publications and Presentations

Magnetically responsive ultrafiltration membranes were prepared by grafting poly(2-hydroxyethyl methacrylate) chains from the outer surface of 100-kDa regenerated cellulose ultrafiltration membranes. Surface-initiated atom transfer radical polymerization was used to graft the polymer chains. Grafting from the internal pore surface was suppressed by using glycerol as a pore-filling solvent during initiator immobilization at varied densities. Glycerol suppresses the initiator attachment to the pore surface. Polymerization times of up to four hours were investigated. Superparamagnetic nanoparticles were covalently attached to the chain end. Membrane performance was determined using bovine serum albumin and dextran as model solutes. Increasing the grafted polymer chain density …

Inversion Modeling Of Japonica Rice Canopy Chlorophyll Content With Uav Hyperspectral Remote Sensing, Yingli Cao, Kailun Jiang, Jingxian Wu, Fenghua Yu, Wen Du, Tongyu Xu

Electrical Engineering Faculty Publications and Presentations

Chlorophyll content is an important indicator of the growth status of japonica rice. The objective of this paper is to develop an inversion model that can predict japonica rice chlorophyll content by using hyperspectral image of rice canopy collected with unmanned aerial vehicle (UAV). UAV-based hyperspectral remote sensing can provide timely and cost-effective monitoring of chlorophyll content over a large region. The study was based on hyperspectral data collected at the Shenyang Agricultural College Academician Japonica Rice Experimental Base in 2018 and 2019. In order to extract the salient information embedded in the high-dimensional hyperspectral data, we first perform dimension …

Signals And Systems, Jingxian Wu

Open Educational Resources

Signals and Systems is a core Electrical Engineering undergraduate course. This course covers the topics of signal and system analysis, with an emphasis on the analysis of linear time-invariant systems. The materials presented in this course are designed for a 15-week course for junior or senior level students. The open access materials for this course include:

Course outline and guides: a detailed guideline that provides a week-by-week teaching schedule for a 15-week semester.

Lecture notes: a complete set of lecture notes with detailed explanations and a large number of examples that cover all the contents that are offered in this …

Interdisciplinary Education Outreach With Traffic Sensor Build Kits, Sarah V. Hernandez, Mariah B. Crews

Civil Engineering Teaching and Learning

The goal of this project was to attract K-12 students to transportation engineering careers through STEM outreach programs. To accomplish this goal, the object of the project was to design and implement maritime freight oriented educational outreach activities centered on traffic sensing technologies for middle, high school, and first-year college students. In MarTREC Project 5011 (Evaluating the Performance of Intermodal Connectors), the research team designed a low-cost, easily implementable LiDAR and Bluetooth sensor bundle that was capable of detecting, characterizing, and tracking freight trucks as they traveled to and from inland waterway port areas. The sensor provided data necessary to …

Design Of Control System With Feedback Loop For A Pulsatile Pump, Ian Scott Sanders

Graduate Theses and Dissertations

This paper describes the design and implementation of a closed-loop proportional, integral, differential (PID) control system for a custom in-house pulsatile pump apparatus for the University of Arkansas Biomedical Department. The control system is designed to control a MOONS’ PL34HD0L8500 hybrid stepper motor using a dual H-bridge motor driver network with four pulse-width modulated (PWM) inputs to drive a pulsatile pump apparatus at motor stepping frequencies up to 2kHz. The speed of the motor is controlled from a pressure profile transmitted from an external source over RS-232 communication that specifies the motor speed, number of datapoints, and an array of …

Development Of A Reference Design For A Cyber-Physical System, Nicholas Paul Blair

Graduate Theses and Dissertations

The purpose of this thesis is to develop a reference design to assist in the selection of security practices in power electronics design. A prototype will be developed from this reference design for evaluation. This evaluation will include a brief cost/benefit analysis to gauge the efficacy of implementing each layer of security throughout the power electronics design process. This thesis will also describe the obstacles and effectiveness of integrating a Trusted Platform Module (TPM) into a cyber-hardened grid-connected device. The TPM device is a secured crypto processor that assists in generating, storing, and restricting the use of cryptographic keys. The …

What Difference Does A Catalyst Make?, Tammy Guthrie, Mike Jackson, Holly Haney

High School Lesson Plans

Students will use different catalysts for the decomposition of Hydrogen Peroxide, to determine if different catalysts affect the energy that is generated during the reaction.

Synthesis And Application Of Ceramic Paste For High-Temperature Electronic Packaging, Ardalan Nasiri

Graduate Theses and Dissertations

This dissertation research focused on the synthesis and application of ceramic paste for high-temperature applications. An alumina paste material comprising aluminum dihydric phosphate and alumina powder was developed for high-temperature electronic packaging. Nano aluminum nitride and nano-silica powders were embedded to promote the paste curing process, limit the grain growth, and increase its bond shear strength. The chip-to-substrate bond strength was enhanced and met the MIL-STD requirements for die-attach assembly. Its encapsulation property was improved with fewer cracks compared to similar commercial ceramic encapsulants. The die-attach material and encapsulation properties tested at 500°C showed no defect or additional cracks. Thermal …

Converter- And Module-Level Packaging For High Power Density And High Efficiency Power Conversion, Amol Rajendrakumar Deshpande

Graduate Theses and Dissertations

Advancements in the converter- and module-level packaging will be the key for the development of the emerging high-power, high power-density, high-eciency power conversion applications, such as traction, shipboards, more-electric-aircraft, and locomotive. Wide bandgap (WBG) devices such as silicon carbide (SiC) MOSFET attract much attention in these applications for their fast switching speeds, resulting in low loss and a consequent possibility for high switching frequency to increase the power density. However, for high-current, high power implementations, WBG devices are still available in small die sizes. Multiple SiC devices need to be connected in parallel to replace a large IGBT die. It …

Design And Optimization Of Multichip Gan Module Enabling Improved Switching Performance, Asif Imran Emon

Graduate Theses and Dissertations

Wide bandgap semiconductors (SiC & GaN) due to their enhanced performance and superior material properties compared to traditional silicon power devices have become the ultimate choice for future high-performance power electronics energy conversion. GaN high electron mobility transistor (HEMT) offers very fast switching capability enabling the designer to push switching frequency to the MHz range. Traditional device packaging becomes a limiting factor in fully harnessing the benefits offered by these advanced power devices, and thus, improved and advanced packaging structures are a must to bridge the gap between GaN devices and their applications. A co-design, co-optimization method has been followed …

Conducted Emi Mitigation In Power Converters Using Active Emi Filters, Balaji Narayanasamy

Graduate Theses and Dissertations

Wide bandgap devices enable high power density power converters. Despite the advantages of increased switching frequency, the passive components are still a major bottleneck towards enabling high power density. Among the passive components in the converter, the passive EMI filters are unavoidable to ensure compliance with conducted EMI standards. Active EMI filters help reduce the volume of the passive components and have been around for three decades now. Firstly, this work presents a summary of all the different active EMI filters based on the type of noise-sensing, noise-processing, the type of active circuits used and the type of control methods. …

Towards High Efficiency And High Power Density Converter: System Level Design, Modulation, And Active Emi Filters, Hongwu Peng

Graduate Theses and Dissertations

Power converter exposes strong challenges to its efficiency, power density and reliability. For the grid-connected inverter application, three-level (3-L) T-type neutral-point-clamped (TNPC) inverters has higher efficiency and lower total harmonic distortion (THD) compared to two-level inverter. Hybrid switch concept combines the benefit of both silicon carbide (SiC) MOSFET and Si IGBT. By applying hybrid switch structure in 3-L T-type inverter, the total power density of 3-L TNPC inverter will be higher while the cost will be lower than that of all-SiC 3-L T-type inverter. The hybrid switch based 3-L TNPC inverter also imposes challenge to its modulation and control, a …

Investigation Of The Structural, Electronic, And Thermoelectric Properties Of Mono- Chalcogenides, Aida Sheibani

Graduate Theses and Dissertations

The structural, electronic, and thermoelectric properties of GeTe are studied using density functional theory and Boltzmann transport equations. This material has a rhombohedral crystal structure in ambient temperature with a ferroelectric behavior due to lack of inversion symmetry. This study suggests that the presence of asymmetry in GeTe can lead to an improvement in the thermoelectric properties of this material. In addition, studies on introducing Group III, IV, and V dopants to GeSe show that while these impurities can improve the power factor and decrease the lattice thermal conductivity, they cannot enhance the figure of merit.

Development Of High-Density Propulsion System Technologies For Interplanetary Small Satellites And Cubesats, Morgan Andrew Roddy

Graduate Theses and Dissertations

The goal of this research was to support the development of a novel propulsion system for small satellites (<180 kg) and CubeSats. This was pursued by conducting a collection of studies that were designed to provide engineering data that would be critical in designing a functional prototype. The novel propulsion system was conceived by the author to provide best-in-class performance for the small satellite and CubeSat families of spacecraft. This context presents specific design requirements that the presented technology attempts to satisfy. The most critical among these is high density; the propellant was designed to be stored with high density and the thruster was designed to be as compact as possible. The propulsion system is composed of two primary elements, a propellant generator and a thruster. The propellant generator works by sublimating a solid crystal into vapor and then using this vapor to etch a dense metal. The resulting gaseous byproducts of this reaction are the propellant. This dissertation used xenon difluoride (XeF2) vapor to etch tungsten (W) which react to form xenon gas (Xe) and tungsten hexafluoride (WF6). This approach gave a theoretical propellant storage density 5.40 g/cm3; and 5.17 g/cm3 was demonstrated. The sublimation dynamics of the XeF2 were studied as a function of surface area and temperature and it was found to be suitable for the intended application due to its high effluence rate; that is, it sublimates fast enough to be useful. The sublimation rates are on the order of 10’s of µg/s. The etch rate of XeF2 on W was also studied and found to be suitably fast to provide useful amounts of reactants for use as a propellant, again on the order of 1’s of µg/s. The thruster is an electrostatic radio frequency (RF) ion thruster design and is manufactured with Low Temperature Co-Fired Ceramic (LTCC) materials system and manufacturing technology. Manufacturing samples of the thruster were built at the University of Arkansas in July 2015 and tested at NASA’s Marshall Space Flight Center in May 2018. Testing validated the viability of the LTCC thruster and provided valuable information on how to improve the thruster’s design.

Methods Of High-Fidelity, High-Efficiency Class-D Audio Amplification, Kaleb Kassaw

Electrical Engineering Undergraduate Honors Theses

Gallium nitride-based field effect transistors (FETs) have opened a path for full-frequency-range class-D audio amplifiers with low distortion and noise, thanks to their ability to switch at much higher frequencies than that of the upper range of human hearing. Compared to traditional silicon-based transistors, GaN-based transistors offer superior efficiencies, particularly at power levels below their maxima. Paired with an analog-to-digital converter, digital signal processor, and pulse-code modulation to pulse-width modulation converter, these transistors are used to design and implement a solid-state amplifier capable of generating 100 watts of output through speakers with an impedance of 8 ohms using a 1-volt …

Smart Textiles As The Digital Interface Of The Future, Audra Beneux

Electrical Engineering Undergraduate Honors Theses

The growing field of smart textiles could change everyday life, adding an element of interactivity to commonly used items such as clothing and furniture. Smart textiles measure then respond to external stimuli. For scalability in the future, smart textiles must be produced using conventional textile manufacturing craftsmanship. The resulting textile must be durable and comfortable while retaining electrical capabilities. Smart textiles can be fabricating through embroidery, weaving, and knitting using conductive threads. Electronics can also be printed onto textiles. Researchers are also creating higher-order electronics, such as the transistor, on the fiber-level to make the technology in smart textiles as …

Ohmic Contact Metallization For Silicon Carbide In Future Transportation And Aviation Systems, Tanner W. Rice

Electrical Engineering Undergraduate Honors Theses

This paper analyzes metallization stacks in both n-type and p-type used in Silicon Carbide to create Ohmic Contacts. Silicon Carbide has shown its significance in usage as a semiconductor in high temperatures, and other extreme environments compared to its silicon counterpart. Additionally, silicon carbide exhibits many other favorable attributes such as strong radiation hardness, high power capability, and high-temperature tolerance. These attributes translate into great components for use in aviation and other future transportations by increasing reliability in a sector that already requires high reliability. Applications of this material could prove useful in fields such as aviation, among others. This …

Simultaneous Ohmic Contacts To N And P-Type Silicon Carbide For Future Electric Vehicles, Hayden Hunter

Electrical Engineering Undergraduate Honors Theses

The paper explores possible metallization schemes to form simultaneous ohmic contacts to n-type and p-type silicon carbide contacts. Silicon carbide has shown promise in revolutionizing the power electronics market due to its increased switching speed, compact design, and higher temperature tolerance when compared to Silicon, the market standard. With the continuing development of silicon carbide technology, higher efficiency in future electric vehicles can be achieved by employing this new technology. This paper discusses theoretical contact formation between metals and semiconductors along with a proposed experiment to create a Ni/Al metallization scheme on both n and p-type contacts simultaneously on a …

Reducing Emi In Sic Direct Torque Controlled Motor Drive, Michael Sykes

Electrical Engineering Undergraduate Honors Theses

This paper covers the comparison between Silicon (Si) vs Silicon Carbide (SiC) for Motor Drive systems and a possible control algorithm to limit the increased Electromagnetic Interference (EMI) caused by using SiC transistors for the inverter. Motor Drive systems need constant improvements if the world is going to move on from machines that emit CO₂ and other harmful gases into the Earth’s atmosphere. One reason these electric machines are not commonplace today is because of their efficiency and other problems they may cause. Silicon transistors are the most commonplace transistor around the world today, but advances over the past …

Improving Pv Module Efficiency Through Cooling, Blake Bradley

Chemical Engineering Undergraduate Honors Theses

The Solarbacks researched and designed a variety of cooling methods that could be used to improve the efficiency of photovoltaics. These cooling methods can be separated into two categories: active and passive methods. The active cooling method of hydraulic cooling and the passive cooling methods of heat sinks (fins), optical coatings, thermosyphons, phase change materials, and thermoelectric generators were all taken into consideration as potential cooling methods. Passive cooling methods were preferred because the use of electricity required for the cooling mechanism would reduce the net electricity and subsequent profit from the panels.

Two variations of hydraulic cooling were researched: …

Improving Pv Module Efficiency Through Cooling, Megan Reynolds

Chemical Engineering Undergraduate Honors Theses

The Solarbacks researched and designed a variety of cooling methods that could be used to improve the efficiency of photovoltaics. These cooling methods can be separated into two categories: active and passive methods. The active cooling method of hydraulic cooling and the passive cooling methods of heat sinks (fins), optical coatings, thermosyphons, phase change materials, and thermoelectric generators were all taken into consideration as potential cooling methods. Passive cooling methods were preferred because the use of electricity required for the cooling mechanism would reduce the net electricity and subsequent profit from the panels.

Two variations of hydraulic cooling were researched: …

Cybersecurity Methods For Grid-Connected Power Electronics, Stephen Joe Moquin

Graduate Theses and Dissertations

The present work shows a secure-by-design process, defense-in-depth method, and security techniques for a secure distributed energy resource. The distributed energy resource is a cybersecure, solar inverter and battery energy storage system prototype, collectively called the Cybersecure Power Router. Consideration is given to the use of the Smart Green Power Node for a foundation of the present work. Metrics for controller security are investigated to evaluate firmware security techniques. The prototype's ability to mitigate, respond to, and recover from firmware integrity degradation is examined. The prototype shows many working security techniques within the context of a grid-connected, distributed energy resource. …

Design And Simulation Of Power Electronics Modules, Haonan Jia

Graduate Theses and Dissertations

Silicon carbide (SiC), a wide-bandgap semiconductor material, greatly improves the performance of power semiconductor devices. Its electrical characteristics have a positive impact on the size, efficiency, and weight of the power electronics systems. Parasitic circuit elements and thermal properties are critical to the power electronics module design. This thesis investigates the various aspects of layout design, electrical simulation, thermal simulation, and peripheral design of SiC power electronic modules. ANSYS simulator was used to design and simulate the power electronic modules. The parasitic circuit elements of the power module were obtained from the device parameters given in the datasheet of these …

A Power Constrained 433-Mhz Low Noise Amplifier, Pablo Alvarez Arellano

Graduate Theses and Dissertations

Within wireless communication systems, low noise amplifiers are critical for the performance of receivers. They are primarily responsible for providing enough gain while adding little noise to overcome the noise of the subsequent stages. The LNA presented here is part of a battery-powered transceiver meant to measure crop nutrient data and relay the information. Therefore, power consumption and area become import considerations. To design for a specific power level, a power-constrained noise optimization method is used. The method sizes the amplifying transistor for a fixed source impedance, power dissipation, technology, and operating frequency. The chosen topology is the cascode stage …

A Virtual Space Vectors Based Model Predictive Control For Three-Level Converters, Waleed Saad S. Alhosaini

Graduate Theses and Dissertations

Three-phase three-level (3-L) voltage source converters (VSC), e.g., neutral-point clamped (NPC) converters, T-type converters, etc., have been deemed to be suitable for a wide range of medium- to high-power applications in microgrids (MGs) and bulk power systems. Compared to their two-level (2-L) counterparts, adopting 3-L VSCs in the MG applications not only reduces the voltage stress across the power semiconductor devices, which allows achieving higher voltage levels, but also improves the quality of the converter output waveforms, which further leads to considerably smaller output ac passive filters.

Various control strategies have been proposed and implemented for 3-L VSCs. Among all …

Improving Pv Module Efficiency Through Cooling, Harrison Dawson

Chemical Engineering Undergraduate Honors Theses

The Solarbacks researched and designed a variety of cooling methods that could be used to improve the efficiency of photovoltaics. These cooling methods can be separated into two categories: active and passive methods. The active cooling method of hydraulic cooling and the passive cooling methods of heat sinks (fins), optical coatings, thermosyphons, phase change materials, and thermoelectric generators were all taken into consideration as potential cooling methods. Passive cooling methods were preferred because the use of electricity required for the cooling mechanism would reduce the net electricity and subsequent profit from the panels.

Two variations of hydraulic cooling were researched: …

Design And Verification Of Search Coil Inductance For Pulse Induction Metal Detection, David Desrochers

Electrical Engineering Undergraduate Honors Theses

As violent attacks have increased at different venues such as schools, the need for affordable and effective metallic weapon detection has increased. Probing and scanning detection wands are the most common seen in use by guards. This project seeks to combine both probing and scanning coils into one pulse induction metal detector. The use of one drive circuit for both LC coil tank circuits further economizes the system. ANSYS Maxwell electromagnetic simulations are used to develop the geometries needed for sensitive metal detection. Analytical, simulation, and experimental methods are used to first verify the design flow for solenoid inductors. These …

Improving Pv Module Efficiency Through Cooling, Ashley Cox

Chemical Engineering Undergraduate Honors Theses

The Solarbacks researched and designed a variety of cooling methods that could be used to improve the efficiency of photovoltaics. These cooling methods can be separated into two categories: active and passive methods. The active cooling method of hydraulic cooling and the passive cooling methods of heat sinks (fins), optical coatings, thermosyphons, phase change materials, and thermoelectric generators were all taken into consideration as potential cooling methods. Passive cooling methods were preferred because the use of electricity required for the cooling mechanism would reduce the net electricity and subsequent profit from the panels.

Two variations of hydraulic cooling were researched: …

Design Of Submicron Structured Guided-Mode-Resonance Near-Infrared Polarizer, Marzia Zaman

Graduate Theses and Dissertations

The objective of this research is to design a larger submicron linear polarizer in the near-infrared wavelength range with a wide bandwidth which can be fabricated using the conventional thin-film microfabrication technology to reduce cost. For this purpose, a gold (Au) wire-grid transmission-type transverse-magnetic (TM) polarizer and a silicon (Si) wire-grid reflection-type TM polarizer, were designed using the guided-mode-resonance filter. The Au wire-grid TM polarizer of 700nm grating width and 1200nm grating period has 95% transmittance at 2400nm, more than 1000nm resonance peak bandwidth, and an extinction ratio (ER) of around 300 with a moderated level of sidebands. The 700nm …

Area Efficient Device Optimization For Esd Protection In High Speed Interface Ics, Dan Thomas Jarard

Graduate Theses and Dissertations

Electrostatic discharge (ESD) protection is considered as a vital step in integrated circuit (IC) manufacturing process. IC chips are unable to overcome the effects of transient events without adequate discharge protection. Recent trend in the industry has seen the incorporation of system level ESD protection within the IC chip. Incorporating system level on-chip ESD protection often increases cost, degrades circuit performance and consumes layout area which could otherwise be used for improving the circuit performance. These design challenges could be easily overcome if the parasitic components in a circuit were used for ESD protection. Despite the various design challenges, on-chip …