Engineering Commons^™

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 …

Characterization And Modeling Of 4h-Sic Low Voltage Mosfets And Power Mosfets, Mihir Mudholkar

Graduate Theses and Dissertations

The integration of low voltage and high voltage circuits on SiC has profound applications. SiC power devices have proved their superiority in terms of high temperature operation, faster switching frequencies and larger power densities when compared with Si power devices. The control of SiC power devices however, lies in the hands of low voltage circuits built on Si. Thus, there exists a separation in the overall system between the low voltage and high voltage side, which increases system cost, weight and reduces efficiency. With the advancement in low voltage SiC processing technology, low voltage control circuits can be made on …

Mott Transition And Electronic Structure In Complex Oxide Heterostructures, Jian Liu

Graduate Theses and Dissertations

Strongly correlated electron systems, particularly transition metal oxides, have been a focus of condensed matter physics for more than two decades since the discovery of high-temperature superconducting cuprates. Diverse competing phases emerge, spanning from exotic magnetism to unconventional superconductivity, in proximity to the localized-itinerant transition of Mott insulators. While studies were concentrated on bulk crystals, the recent rapid advance in synthesis has enabled fabrication of high-quality oxide heterostructures, offering a new route to create novel artificial quantum materials.

This dissertation details the investigation on ultrathin films and heterostructures of 3d⁷(t_2g⁶e_g¹) systems with …

Fabrication Of Vertical Silicon Nanowires Through Metal Assisted Deposition, Matthew Garett Young

Graduate Theses and Dissertations

Controlled and ordered growth of Si nanowires through a low temperature fabrication method compatible with CMOS processing lines is a highly desirable replacement to future electronic fabrication technologies as well as a candidate for a low cost route to inexpensive photovoltaics. This stems from the fact that traditional CMOS based electronics are hitting physical barriers that are slowing the Moore's Law trend as well as the demand for an inexpensive solar cell technology that can obtain grid parity. A fractional factorial growth study is presented that compares the growth of Au and Al catalyzed Si nanowires at temperatures ranging from …

Photocatalytic Reactor Using Tio2 Thin Film On Quartz Tubes, Ram Mahipal Kouda

Graduate Theses and Dissertations

Photocatalysis process, as an environmental application is an advanced oxidation process with tremendous potential in the near future. Previously many researchers, have conducted photocatalysis in different reactor configuration using TiO2 slurry and thin film, using a UV light source, the constraints for these reactors are the need for the removal of TiO2 particles at the outlet stream in a slurry reactor and poor environment for the efficient use of TiO2 film using UV light, as the UV light penetration depth in water is about an inch.

Taking all this into consideration, we propose a design for reactor with efficient contact …

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 …

Implementation Of Orthogonal Frequency Division Multiplexing With Fpga, Qi Hao Yang

Graduate Theses and Dissertations

In recent years, there have been dramatic shifts in cellular and telecommunication industries. As smartphones are dominating on the cellphone market, more and more people use these mobile devices to access internet either through third generation network or IEEE802.11 wireless local area network. Orthogonal frequency division multiplexing (OFDM) has been widely used in IEEE802.11 wireless local area network and fourth generation network. This paper will focus on the design and implementation of an Orthogonal Frequency Division Multiplexing system on field-programmable gate array (FPGA). The major components of an OFDM system include a modulator, an N-input inverse Fast Fourier Transform (IFFT), …

Use Of Ultra High Vacuum Plasma Enhanced Chemical Vapor Deposition For Graphene Fabrication, Shannen Adcock

Graduate Theses and Dissertations

Graphene, what some are terming the "new silicon", has the possibility of revolutionizing technology through nanoscale design processes. Fabrication of graphene for device processing is limited largely by the temperatures used in conventional deposition. High temperatures are detrimental to device design where many different materials may be present. For this reason, graphene synthesis at low temperatures using plasma-enhanced chemical vapor deposition is the subject of much research. In this thesis, a tool for ultra-high vacuum plasma-enhanced chemical vapor deposition (UHV-PECVD) and accompanying subsystems, such as control systems and alarms, are designed and implemented to be used in future graphene growths. …

High Frequency Characterization Of Carbon Nanotube Networks For Device Applications, Emmanuel Decrossas

Graduate Theses and Dissertations

This work includes the microwave characterization of carbon nanotubes (CNTs) to design new CNTs-based high frequency components. A novel developed method to extract the electrical properties over a broad microwave frequency band from 10 MHz to 50 GHz of carbon nanotubes (CNTs) in a powder form is performed. The measured scattering parameters (S-parameters) with a performance network analyzer are compared to the simulated one obtained from an in-house computed mode matching technique (MMT). An optimized first order gradient method iteratively changes the unknown complex permittivity parameters to map the simulated S-parameters with the measured one until convergence criteria are satisfied. …

Ultra-Low Power And Radiation Hardened Asynchronous Circuit Design, Liang Zhou

Graduate Theses and Dissertations

This dissertation proposes an ultra-low power design methodology called bit-wise MTNCL for bit-wise pipelined asynchronous circuits, which combines multi-threshold CMOS (MTCMOS) with bit-wise pipelined NULL Convention Logic (NCL) systems. It provides the leakage power advantages of an all high-Vt implementation with a reasonable speed penalty compared to the all low-Vt implementation, and has negligible area overhead. It was enhanced to handle indeterminate standby states. The original MTNCL concept was enhanced significantly by sleeping Registers and Completion Logic as well as Combinational circuits to reduce area, leakage power, and energy per operation.

This dissertation also develops an architecture that allows NCL …

In Memoria: Art Fry, 1921-2011, Collis Geren

Journal of the Arkansas Academy of Science

No abstract provided.

Powersearch: Augmenting Mobile Phone Search Through Personalization, Xiangyu Liu

Computer Science and Computer Engineering Undergraduate Honors Theses

Cell phone has become a fundamental element of people's life. People use it to call each other, browse websites, send text messages, etc. Among all the functionalities, the most important and frequently used is the search functionality. Based on ComScore, in July 2008, Google was estimated to host 235 millions searches per day. However, unlike the search on desktop, the search on cell phone has one critical constrain: battery. Cell phone performing a normal Google search, the battery drains very fast. The reason is that when sending a query to and fetching the results from Google, cell phone keeps communicating …

Mapping Device With Wireless Communication, Xiangyu Liu

Electrical Engineering Undergraduate Honors Theses

Wireless communication is one of the most powerful communication methods that people use nowadays. The key advantage of wireless communications is that it can cover large distances without having to run any cables from one end to the other. Based on this advantage, wireless communication has many important applications, such as remote controls, cell phones, and global positioning system (GPS). This senior design project is developed to use wireless communication technology to map the geographic characteristics of an unknown place. It contains two wireless communication modules with Atmega1281 microprocessor, two robots with the 8051 microcontroller, six pairs of infrared transmitters …

The Marked Tree Site: Evaluation Of Geosynthetic Reinforcements In Flexible Pavements, Taylor Mitchell Goldman

Graduate Theses and Dissertations

This document presents findings from a three-year, full-scale, field research project aimed at determining the benefits of using geosynthetic reinforcements to improve the performance of flexible pavements constructed over poor subgrade soils. The test site, known as the Marked Tree site, is an 850-ft (258-m) long segment of low-volume frontage road along Highway 63 in the town of Marked Tree, Arkansas. The site, constructed in 2005, consists of seventeen 50-ft (15.2-m) long flexible pavement test sections with various types of geosynthetic reinforcements (woven and nonwoven geotextiles, and geogrids), which were all positioned at the base-subgrade interface, and two different nominal …

Surface Wetting And Friction Studies Of Nano-Engineered Surfaces On Copper Substrate, Julius Sheldon Morehead

Graduate Theses and Dissertations

Nano-engineered-textures on a material surface can dramatically improve the wetting and non-wetting properties of a surface, and they also show promise to address friction issues that affect surfaces in contact. In this work, aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) was used to produce nano-textures on copper (Cu) substrates. A study was performed to examine the effects of changing the annealing conditions and a-Si thickness on nano-texture formation. The creation of various nano-topographies and chemically modifying them using octafluorocyclobutane (C4F8) was performed to control hydrophilicity, hydrophobicity, and oil affinity of nano-textured surfaces. A video-based contact angle measurement system was used …

Influence Of Recycled Asphalt Shingles On Asphalt Binder Content, Mixture Stiffness, And Laboratory Rutting Performance, Joshua David King

Graduate Theses and Dissertations

Recycled asphalt shingles (RAS) is a technology in which pavement costs can be reduced significantly and pavement properties may be enhanced. Also, incorporating shingles into pavements reduces the impacts of waste shingles in landfills, preserving our environment. However, for this new technology to be practical for implementation, a better understanding of how the ground shingles affect the properties of the asphalt is necessary. The purpose of this research was to examine the effects of recycled asphalt shingles on asphalt binder content, mixture stiffness, and laboratory rutting performance. For this project, shingles were added to hot mix asphalt mixtures at 2.5, …

Development Of A Structured Concrete Thermocline Thermal Energy Storage System, Bradley M. Brown

Graduate Theses and Dissertations

The past couple of decades have shown a concern when considering the way the world obtains its power. The focus has been switching from fossil fuels that have been used for hundreds of years to renewable energy sources, such as the sun. Solar energy is readily and infinitely available for harnessing. One problem with solar energy, though, is its inability to be used during the night time and during cloud covered weather. A solution to this problem is the use of energy storage mechanisms. For solar plants that use solar thermal energy (concentrating solar power plants), thermal energy storage (TES) …

Removal Of Disinfection By-Product Precursors Using Magnetic Ion Exchange (Miex(R)): The Effects Of Ph And Source Water Variability, Sarah Cousins

Graduate Theses and Dissertations

Disinfection by-products (DBPs) form as an unintended result of drinking water disinfection, from chemical reactions between disinfectants (e.g., free chlorine) and naturally occurring dissolved organic matter (DOM). At present, 11 DBPs are regulated in treated drinking waters due to potential adverse health effects, including four trihalomethanes (THMs). Despite nearly 40 years of DBP research, compliance with DBP regulations remains a challenge for many drinking water treatment plants (DWTPs), including the four DWTPs located on the Beaver Lake Reservoir in Northwest Arkansas. Due to the high net negative surface charge on DOM, anion exchange is one potentially viable method for removing …

Empirical Analysis Of The Relay Network Design Problem, Sergio Maldonado Soria Galvarro

Industrial Engineering Undergraduate Honors Theses

Definition and optimization of alternative methods for truckloads routing.

Visual, Spectrophotometric, And Colorimetric Measurement Of Red Wine And Wine Blends, Zachary Fricke

Chemical Engineering Undergraduate Honors Theses

Partially due to prevalence and popularity around the world, much research has been done in the field of enology and wine analysis. The visual aspect of wine is one of the key features of wine. This research focused on how blending and storage affected the color and composition of wine. Visual, sensory, color, and composition data were collected. Three primary red wine varietals (Cabernet Sauvignon, Merlot, and Zinfandel) and seven blends were analyzed for color, acidity, polymeric color, and optical density. The ten wine treatments were composed based on a mixture design model. The color and composition results were compared …

Office Hour Scheduling Tool, Tyler Dunlap

Industrial Engineering Undergraduate Honors Theses

When an instructor (with or without student input) specifies her office hours for the semester, the informal process used often results in students experiencing conflicts with other lectures, labs, drills, or office hours. The result of this conflict is the student either scheduling individual meetings with teachers outside of their office hours or students missing the opportunity to get assistance from the instructor all together. Either outcome is undesirable, as it either takes additional faculty time from their other responsibilities or jeopardizes the performance of a student in their classes. One valid approach to solving this problem is through the …

Hydraulic Conductivity Of Environmentally Controlled Landfill Liner Test Pad, Camila Maldonado Soria Galvarro

Civil Engineering Undergraduate Honors Theses

Laboratory and field hydraulic conductivity tests have been conducted on soil samples to develop and verify the zone of acceptance for liner placement. Compaction testing and flexible wall hydraulic conductivity tests were performed on fifteen (15) samples to determine the dry unit weight, molding water content, and laboratory permeability. Five of the fifteen samples were compacted at Standard proctor energy, five were compacted at 75 percent of Standard proctor energy, and five were compacted at 50 percent of Standard proctor energy. The results obtained from the laboratory portion of the testing program (the zone of acceptance) are presented. A ten …

Clean Energy Water Disinfection For Small Rural Remote Communities, Nathan Bearden

Chemical Engineering Undergraduate Honors Theses

The University of Arkansas competed in the 2011 Waste-Management Education and Research Consortium (WERC) competition. The U of A team participated in Task 7, which was titled “Clean Energy Water Disinfection for Small, Remote Rural Communities”. The task looks for a solution to a continuing problem throughout the world: disinfecting water. The task’s problem statement was to develop and a standalone disinfection system that could be used for a small community. It will need at least 3000 gallons of water per day. The solution must address only bacterial disinfection and must be powered by a non-fossil based energy source. Other …

Application Of The Empirical Mode Decomposition On The Characterization And Forecasting Of The Arrival Data Of An Enterprise Cluster, Linh Bao Ngo

Graduate Theses and Dissertations

Characterization and forecasting are two important processes in capacity planning. While they are closely related, their approaches have been different. In this research, a decomposition method called Empirical Mode Decomposition (EMD) has been applied as a preprocessing tool in order to bridge the input of both characterization and forecasting processes of the job arrivals of an enterprise cluster. Based on the facts that an enterprise cluster follows a standard preset working schedule and that EMD has the capability to extract hidden patterns within a data stream, we have developed a set of procedures that can preprocess the data for characterization …

Fabrication Of Composite Nanomaterials For Thin Film Amorphous Silicon Solar Cells, Benjamin Seth Newton

Graduate Theses and Dissertations

A material with the precise combination of amorphous silicon and polycrystalline silicon would be able to take advantage of the high absorption capabilities of amorphous silicon and the electron transport capabilities of polycrystalline silicon. Polycrystalline nanostructures in the form of wires can also take advantage of other properties of light absorption, trapping and scattering inherent in nanowire structures. These properties of high absorption and electron transport in one device would lead to advances in the search for highly efficient low cost solar cells and sensors. In this work a thin film material composed of an array of polycrystalline silicon nanostructures …

Location-Aware Traffic Management On Mobile Phones, Sarath Krishna Mandava

Graduate Theses and Dissertations

The growing number of mobile phone users is a primary cause of congestion in cellular networks. Therefore, cellular network providers have turned to expensive and differentiated data plans. Unfortunately, as the number of smartphone users keeps increasing, changing data plans only provides a temporary solution. A more permanent solution is offloading 3G traffic to networks in orthogonal frequency bands. One such plausible network is open Wi-Fi, which is free by definition. As Wi-Fi networks become ubiquitous, there are several areas where there is simultaneous Wi-Fi and 3G coverage. In this thesis, we study the feasibility of offloading 3G traffic to …

Synthesis Of Zinc Oxide Nanorods And Use In Biosensor Applications, Anishkumar Manoharan

Graduate Theses and Dissertations

The main aim of this research was to develop a nanorod based biosensor for biomedical applications. In this project I use zinc oxide nanorods as the bio-material for biosensor. I fabricated these nanorods using a solution-based technique. Initially I coated a zinc oxide seed layer as the base. This seed layer was then annealed at 350 degrees for almost 1 hour. As a next step, interdigitated electrodes were fabricated on the top of the seed layer using a lift off process. The zinc oxide nanorods were then grown at 90 degrees for almost 4 hours along the electrodes. In this …

Design Of An 866 Mhz On-Chip Frequency Synthesizer, Phaniraj Joshi

Graduate Theses and Dissertations

There is a strong need for stable frequency references with large tuning ranges in today's communication systems. While the crystal oscillators assure good frequency stability, it is not possible to achieve a large frequency range by tuning the passive components attached to them. Frequency synthesizers are usually used for this purpose because of their ability to produce a variety of output frequencies. The Phase Locked Loop (PLL) based frequency synthesizer is the most preferred of all types of synthesizers available because of its additional features like programmability, low noise and low cost as well as high accuracy and stability. The …

Adaptive Intensity Modulated Radiation Therapy Planning Optimization With Changing Tumor Geometry And Biology Enforcing Both Cumulative And Fraction Size Dose Constraints, Behlul Saka

Graduate Theses and Dissertations

Intensity Modulated Radiation Therapy (IMRT) is a modern technique of delivering radiation treatments to cancer patients. In IMRT technology, intensities must be chosen for the many small unit grids into which the beams are divided to produce a desired distribution of dose at points throughout the body with the goal of maximizing dose delivered to the tumor while sparing healthy tissues from excessive radiation and keeping dose homogeneous across the tumor. Although IMRT plans are optimized as a single overall treatment plan, they are delivered over 30-50 treatment sessions (fractions) and both cumulative and per-fraction dose constraints apply. The extended …

Improvements On Just-About-Right (Jar) Scales As Product Optimization Tools Using Kano Modeling Concepts, Bangde Li

Graduate Theses and Dissertations

Attribute Kano characteristics are useful in product design to prioritize development efforts. However, attribute Kano characteristics have not been discussed and applied to product optimization when using Just-About-Right (JAR) scales. Product optimizations without identifying attributes Kano characteristics can be misleading. The two objectives in this research were: 1. Determine attribute Kano categories using a modified classic Kano classification methodology. 2. Propose a method to measure attribute performance and identify attribute Kano characteristics to direct product optimization. Two methodologies of attribute Kano classification were investigated. In experiment one, a modified classic Kano methodology was employed to determine attribute Kano categories through …