Engineering Commons^™

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 …

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 …

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 …

Proteome Based Development Of Novel Affinity Tail For Immobilized Metal Affinity Chromatography And Hydrophobic Interaction Chromatography, Neha Tiwari

Graduate Theses and Dissertations

At industrial scale, reducing the step in purification and recovery is desired; this not only decreases the cost but also increases the yield. Hydrophobic Interaction Chromatography (HIC) and Immobilized Metal Affinity Chromatography (IMAC) both are not harsh on biological structure or activity of proteins; also both the techniques are economical and therefore a suitable choice at industrial level. This dissertation comprises of three parts. Purpose for the Part I was to identify and characterize Escherichia coli proteins which display affinity towards both IMAC and Hydrophobic Interaction Chromatography (HIC). Co (II) IMAC was chosen as the primary capture step, followed by …

Design And Fabrication Of Nanofluidic Systems For Biomolecule Characterizations, Orain Ansel Hibbert

Graduate Theses and Dissertations

Nanofluidic channel systems were designed and fabricated by combining MEMS microfabrication with AFM nanolithography. In the fabrication process flow, photolithography was first utilized to pattern microfluidic channels and reservoirs on a 4" Pyrex substrate. Subsequently, atomic force microscopy (AFM) based nanolithography was used to mechanically fabricate nanochannels to connect the microreservoirs which formed the inlet and outlet of the nanofluidic system. A Tap190 Diamond-Like Carbon (DLC) AFM tip with a force constant of 48 N/m and a radius of less than 15 nm was used as the nanolithography tool. The resultant nanochannel ranges from 20 to 80 µm in length …

Modeling Of Sic P-Channel Insulated Gate Bipolar Transistors (Igbts), Mahmood Saadeh

Graduate Theses and Dissertations

A new physics-based IGBT compact model has been developed for circuit simulation of silicon (Si) or silicon carbide (SiC) devices. The model accurately predicts the steady-state output, transfer and switching characteristics of the IGBT under a variety of different conditions. This is the first IGBT model to predict the behavior of p-channel SiC IGBTs. Previous work on IGBT models has focused on Si n-channel IGBTs [1-3]. This unified model is not limited to SiC p-channel IGBTs; the user has the option to select between Si or SiC, and n-channel or p-channel, making it the first IGBT model that captures the …

Inventory Models For Intermittent Highly Variable Demand And Policy Parameter Adjustments To Meet Desired Service Level Requirements, Yasin Unlu

Graduate Theses and Dissertations

This dissertation consists of three assays. The first assay examines the robustness of lead time demand models for the continuous review (r;Q) inventory policy. A number of classic distributions as well as distribution selection rules are examined under a wide variety of demand conditions. First, the models are compared to each other by assuming a known demand process and evaluating the errors associated with using a different model. Then, the models are examined using a large sample of simulated demand conditions. Approximation results of inventory performance measures - ready, rate excepted number of backorders and on-hand inventory levels are reported. …

Fabrication Of Horizontal Silicon Nanowires Using A Thin Aluminum Film As A Catalyst, Khaja Hafeezuddin Mohammed

Graduate Theses and Dissertations

Silicon nanowires have been the topic of research in recent years for their significant attention from the electronics industry to grow even smaller electronic devices. The semiconductor industry is built on silicon. Silicon nanowires can be the building blocks for future nanoelectronic devices. Various techniques have also been reported in fabricating the silicon nanowires. But most of the techniques reported, grow vertical silicon nanowires. In the semiconductor industry, integrated circuits are designed and fabricated in a horizontal architecture i.e. the device layout is flat compared to the substrate. When vertical silicon nanowires are introduced in the semiconductor industry, a whole …

Integrated Planning For Rural Rail Transportation, Jeffrey Cohan Gwaltney

Graduate Theses and Dissertations

Population growth in rural areas has led to new interest in rail transportation. Planning a passenger rail system involves numerous difficult decisions, most representing a trade-off between customer service and cost. In this work, we attempt to integrate many of these planning decisions. We consider strategic decisions such as station location and vehicle procurement, as well as tactical issues that include vehicle scheduling. Our integrated model exploits the linear network structure that best suits many rural American communities, including Northwest Arkansas. Due to the intractability of the integrated rail planning problem, we have developed a customized heuristic approach to solve …

Design Of A Low Noise Amplifier For Wireless Sensor Networks, Ting Liu

Graduate Theses and Dissertations

CMOS technology becomes important in Radio Frequency (RF) communication systems which include both a receiver and a transmitter. In a high performance radio receiver, the Low Noise Amplifier (LNA) is the first circuit, and its noise performance dominates the entire receiver. Depending upon the system in which they are used, LNAs can be designed according to various topologies and structures. The LNA needs to have matched input impedance, and at the same time it should amplify the small amplitude input signal without adding too much noise and still have the minimal power consumption. It also needs a good interface with …

Degradation Of Polystyrene Foam Under Radiant Heat Flux, James Butler

Graduate Theses and Dissertations

As the demand for liquefied natural gas has increased, safety concerns about the performance of transport vessels under fire conditions have been raised. Current codes for the sizing of the pressure relief systems require that the vessels are able to withstand an emmissive heat flux of 108kW/m2 and do not take into account the effects of insulation loss due to thermal decomposition of the insulation materials. To address this possible oversight in the current code models were presented to a working group organized by the Society of International Gas Tanker and Terminal Operators Ltd. focusing on the decomposition rate of …

Water Quality Trends For Section 319 Priority Watersheds In Northwest Arkansas, 1997-2010, Bryan William Bailey

Graduate Theses and Dissertations

Northwest Arkansas contains two Section 319 Priority Watersheds that the Arkansas Natural Resources Commission (ANRC) has identified as being impacted by point and nonpoint sources of pollution (i.e., phosphorus, nitrogen, and sediment), and the Arkansas Water Resources Center (AWRC) has monitored the water quality at several sites within these watersheds. Water-quality data has been collected over the last decade within the Illinois River Watershed (HUC #11110103) and the Upper White River Basin (Beaver Reservoir HUC# 11010001), each watershed containing three sampling sites. The Illinois River Watershed sites are located on the Illinois River, Osage Creek, and Ballard Creek, and the …

Photodetectors And Photovoltaic Devices Based On Semiconductor Nanomaterials, Jiang Wu

Graduate Theses and Dissertations

Photodetectors based various nanostructures and plasmon enhanced solar cells are investigated in this dissertation. The motivation of the dissertation rise is driven by urgent need of both high efficiency photodetectors and solar cells.

First, quantum dot infrared photodetectors have been intensely investigated due to their promise in high performance photodetectors. However, the strain-driven growth of quantum dots has hindered the progress of quantum dot photodetectors. The presence of strain in the device presents complexity in designing as well as defects. Therefore, in this project, new designs of quantum dot photodetector structures are presented to improve the control over detection wavelength. …

Investigation Of A Floating Load Buck Dc-Dc Switching Converter, Hong Tan

Graduate Theses and Dissertations

A floating load buck DC-DC switching converter was analyzed, simulated, designed and prototyped. The floating load buck converter is first compared to the conventional buck converter. It was found that both the floating load buck converter and conventional buck converter exhibit similar conversion characteristics despite the differences in the placement of their output inductors. A floating load buck converter was designed to be used as a high-voltage off-line light-emitting diodes (LEDs) driver using a Texas Instruments' TPS92001 controller. Finally, the characteristics of this floating load buck converter LED driver were experimentally examined.