Engineering Commons^™

Multi-Threshold Cmos Circuit Design Methodology From 2d To 3d, Ross Josiah Thian

Graduate Theses and Dissertations

A new and exciting approach in digital IC design in order to accommodate the Moore's law is 3D chip stacking. Chip stacking offers more transistors per chip, reduced wire lengths, and increased memory access bandwidths. This thesis demonstrates that traditional 2D design flow can be adapted for 3D chip stacking. 3D chip stacking has a serious drawback: heat generation. Die-on-die architecture reduces exposed surface area for heat dissipation. In order to reduce heat generation, a low power technique named Multi-Threshold CMOS (MTCMOS) was incorporated in this work. MTCMOS required designing a power management unit (to control when and which gates …

The Effects Of Roof Solar Absorptance On Building Energy Performance In A Variety Of U.S. Climate Zones, Zachary Eubanks

Mechanical Engineering Undergraduate Honors Theses

The solar absorptance of a roof surface directly affects the solar heat gain through the roof. It has been shown that buildings in hot climates benefit from roofs with low absorptance. Cold and moderate climates have received less attention in previous studies. This paper simulates the effects on annual energy use, carbon dioxide emission, and utility cost of varying the solar absorptance of warehouse and small office building roofs in a wide variety of U.S. climate zones using EnergyPlus software and the DOE Commercial Building Benchmark Models. Results show that the optimum absorptance not only depends on the climate zone, …

Hardware Microkernels - A Novel Method For Constructing Operating Systems For Heterogeneous Multi-Core Platforms, Jason M. Agron

Graduate Theses and Dissertations

Today's standard operating systems (OSes) do not have the proper structure, nor support for executing on heterogeneous multi- and many-core platforms. These deficiencies manifest in symptomatic issues that range from relatively low-level application binary interface (ABI) compatibility problems, to higher-level concerns such as application programmer interface (API) compatibility, synchronization, and caching issues. These issues in turn reflect back up to the programmer through a lack of a standard set of OS services. Non-uniformities in the hardware architecture are also reflected back into the programming model. In total these issues combined break down the most fundamental benefit of modern operating systems; …

Electrospun Scaffolds For Directed Pancreatic Differentiation Of Human Ips Cells, Karl Sonntag

Biological and Agricultural Engineering Undergraduate Honors Theses

In this work, an electrospinning device for fabricating three-dimensional scaffolds was constructed. The device can be used to produce tissue engineered scaffolds electrospun for directing the differentiation of human induced pluripotent stem (iPS) cells into glucose-responsive, insulin-secreting cells for diabetes treatment. Electrospinning utilizes high electrical charge to generate nanofibers from polymers dissolved in solution. A standard setup for such a device includes a high-voltage power source, a syringe pump, and a grounded collector. The process works by dissolving the polymer in a volatile solvent, and filling a syringe with the polymer/solvent mixture. Next, the syringe is locked into place in …

In-Vivo Testing Of Vertically Aligned Nanowire Implantable Titanium Electrodes In The Rattus Norvegicus Hippocampus, Lauren Kegley

Inquiry: The University of Arkansas Undergraduate Research Journal

Miniaturized multielectrode arrays are MEMS devices that have found use as neural prosthetics (Neuro-MEMS). As implants, they can interface with neurons as sensors or actuators and help compensate for loss of sensory input, motor control, or cognitive functions. The microelectrodes studied here were developed in-house. They have a vertically aligned gold nanowire array and are mounted on a sturdy titanium needle with a fine gauge. Hence, the bill of materials and design characteristics encourage their use as a neural probe. For this study, a probe was tested in vivo for signal acquisition in the hippocampus of a Rattus Norvegicus (Sprague …

A Study On The Effect Of Random Placement And Orientation On The Resonance Of Multiple Split Ring Resonators, Michael Buscher

Electrical Engineering Undergraduate Honors Theses

This thesis project experimentally studies the effect of placing split-ring oscillators (SRR) in a non-periodic arrangment with random orientation. This is contrary to typical structures which are simulated as a single unit cell with a periodic boundry condition to emulate an infinite array of SSR's. Samples are measured using a near-field free-space measurement system with full Thru, Reflect, Line (TRL) calibration and the application of time domain gating. Results, in the form of scattering (S) parameters, are compared with previous measurments of periodic SRR structures in order to study the influence, if any, of periodicity in the frequency response of …

Morphology Of Ingaas Multilayer Nanostructure On Gaas High-Index Surfaces, Yanze Xie

Graduate Theses and Dissertations

This work aimed to explore nanostructure configuration by growing multiple layers of strained InGaAs on GaAs high index surface. The knowledge learned would help to achieve a comprehensive picture of strain-driven nanostructure evolution. Ordered arrays of InGaAs quantum dots were demonstrated on GaAs(311)B. The ordering patterns depended on the thickness of GaAs interlayer between InGaAs Quantum Dots (QDs). With an increased interfacial thickness, a transition from two dimensional (2D) lateral ordering to 1D dot chains was observed. InGaAs growth on GaAs(311)A and GaAs(331)A ended up with 1D quantum wires (QWRs). Straight InGaAs QWRs were uniformly distributed across the surfaces owing …

Factors Affecting Redox Magnetohydrodynamics For Flow In Small Volumes, Matthew D. Gerner

Graduate Theses and Dissertations

Lab-on-a-chip technologies offer the possibility of developing analytical devices that are low-cost, portable, disposable, fast, and operable by non-technical personnel. Such devices require automated methods to manipulate ultra-small volumes (picoliters) of samples and solution, including pumping, stirring, and positioning. Current methods for ultra-small volume microfluidics have limitations that restrict their use including high voltage requirements, disadvantageous flow profiles or rates, and relatively complicated fabrication due to mechanical parts. Redox magnetohydrodyanmics (RMHD) that utilizes permanent magnets for portability shows promise as a micropump with ease of switching flow direction, no moving parts, compatibility with both aqueous and non-aqueous solutions, low voltages …

Proton Irradiation Effects On Semiconductor Cdse/Zns Core/Shell Nanocrystals, Stephen Graham Charter

Graduate Theses and Dissertations

The absorbance and photoluminescence measurement of semiconductor CdSe/ZnS core shell nanocrystals were reviewed and investigated after they were exposed to proton irradiation. The CdSe/ZnS core shell nanocrystals of 3.2nm and 4.4nm were commercially purchased and investigated. These nanocrystals were embedded in UV resin. Proton irradiation of energy 2MeV was applied at doses from 3 x 1013 protons cm-2 to 1.47 x 1015 protons cm-2 for both nanocrystal sizes. Absorbance measurements were conducted at 300K. Results from absorbance measurements showed slight broadening of the first exciton peak of both samples but was most noticeable in the 3.2nm nanocrystal sample. UV resin …

Nano-Surface Engineering On Copper Substrate For Friction Reduction, Julius Morehead

Mechanical Engineering Undergraduate Honors Theses

Nano-engineered-textures on a material surface used to conduct fluids can significantly improve the hydrophobicity or wetting property of the surface, resulting in lower resistance of the surface to the fluid?s movement. In this work, aluminum-induced crystallization of amorphous silicon was investigated for generating nano-textures on copper substrates, a common material in heating, ventilating, air conditioning, and refrigeration systems. Flat copper substrate was utilized. Several experiments were conducted to study the effects of annealing temperature, annealing duration, a-Si and Al thickness, and the sequence of film structure. Scanning electron microscopy was employed to characterize the surface nano-topography. The results showed that …

Production Of Biobutanol From Biomass Using Novel Membrane Reactor, Natalie Thibodeaux

Chemical Engineering Undergraduate Honors Theses

Producing biobutanol from a waste product on a large scale is a novel idea. Because of this, there is very little research available in this area. Previous fermentation research has primarily focused on the production of ethanol or biobutanol using cellulosic or agricultural feed stocks. The Phase I research team, Team R azorbacks E ngineering FU el S olutions for E veryone (Team REFUSE), sought to design a fermentation process that would produce butanol from food waste. Team REFUSE cultivated a partnership with Chartwells, the campus food service provider for the University of Arkansas, for the acquisition of food waste. …

Computational Modeling Of The Internal Structure In The Breast, Jordan Greenlee

Electrical Engineering Undergraduate Honors Theses

Many researchers who are using microwave modality in the area of breast cancer detection employ oversimplified models of the internal structure of the breast. Use of engineered or biologically inaccurate models could render inaccurate results. Therefore, a mathematical biological model is implemented in this work and aims to bridge the gap between biologists and engineers. The results of the proposed breast duct model show that older women have smaller breast ducts leading to less dense breasts, which is in agreement with medical knowledge. Also, younger women have larger breast ducts leading to more dense breasts which are consistent with the …

Low Voltage, Low Power, Bulk-Driven Amplifier, Shama Huda

Electrical Engineering Undergraduate Honors Theses

The importance of low voltage and low powered electronics is increasing with advances in medical electronics. This branch of electronics specifically requires low voltage and low power to make efficient innovative medical equipment. Low power electronics are also desirable because it conserves energy and power. This paper proposes a design of a differential in - differential our amplifier that uses a bulk-driven differential pair for the input pair. In addition, it also used bulk-driven current mirrors for the tail current sink and the active loads. The bulkdriven technique helps to achieve the low voltage design. 90nm CMOS technology was considered …

Preliminary Study Based On The Ddscat Software To Explore Increasing The Contrast Of Breast Tumors For Microwave Imaging, Rachel Megee

Electrical Engineering Undergraduate Honors Theses

Microwave technology is being researched for its capabilities to detect breast tumors less painfully and at earlier stages. It is necessary to have a large contrast between cancerous and healthy tissue when the microwaves are reflected off the breast tissue. To model the increasing contrast between cancerous breast tissue and healthy breast tissue, the DDSCAT code is investigated for its capabilities and analyzed for its accuracy in scattering calculations. The DDSCAT is used to model homogenous and inhomogeneous targets. Simulations of the scattering field by the homogeneous and inhomogeneous targets are conducted and compared to Mie theory calculations for accuracy. …

Developing Equivalent Second Order System Models And Robust Controls For Servo-Drive Related Systems, Christopher Hoyt

Electrical Engineering Undergraduate Honors Theses

Numerous industrial and other plant processes today represent systems in which a motor supplies torque to a drive disk, which in turn through a pulley system drives a larger load. Developing models for these complex systems can become time consuming and expensive. A simple second order system approximation can be developed for these systems under certain system conditions which can greatly reduce the complexity of controlling and modeling the system. A second order feed-forward notch controller can then be introduced to the system which greatly improves performance. The results of this proposed method of approximating complex servo-drive systems show that …

Production Of Biobutanol From Biomass Using Novel Membrane Reactor: A P3 Experience, Ashley Haub

Chemical Engineering Undergraduate Honors Theses

Producing biobutanol from a waste product on a large scale is a novel idea. Because of this, there is very little research available in this area. Previous fermentation research has primarily focused on the production of ethanol or biobutanol using cellulosic or agricultural feed stocks. The Phase I research team, Team R azorbacks E ngineering FU el S olutions for E veryone (Team REFUSE), sought to design a fermentation process that would produce butanol from food waste. Team REFUSE cultivated a partnership with Chartwells, the campus food service provider for the University of Arkansas, for the acquisition of food waste. …

A Robust Process For Biodiesel Production Using Supercritical Methanol, Meagan Magie

Chemical Engineering Undergraduate Honors Theses

The overarching purpose of Phase I was to test, at the bench scale, a continuous supercritical methanol reactor, and to determine the feasibility of implementing the technology at full scale. Specific objectives in reaching this purpose included:
Objective 1: Choose a viable feedstock
Objective 2: Perform experiments for oil extraction
Objective 3: Design, build and operate a continuous supercritical methanol reactor
Objective 4: Design and simulate full scale biodiesel facility
Objective 4a: Perform life-cycle and economic analysis on full scale design
Objective 5: Prepare a Phase II P3 project to demonstrate the entire biodiesel process
Project Scope: The students performed …

A Robust Process For Biodiesel Production Using Supercritical Methanol, Travis Roberts

Chemical Engineering Undergraduate Honors Theses

The overarching purpose of Phase I was to test, at the bench scale, a continuous supercritical methanol reactor, and to determine the feasibility of implementing the technology at full scale. Specific objectives in reaching this purpose included:
Objective 1: Choose a viable feedstock
Objective 2: Perform experiments for oil extraction
Objective 3: Design, build and operate a continuous supercritical methanol reactor
Objective 4: Design and simulate full scale biodiesel facility
Objective 4a: Perform life-cycle and economic analysis on full scale design
Objective 5: Prepare a Phase II P3 project to demonstrate the entire biodiesel process
Project Scope: The students performed …

Automated Flight Through Inertial Navigation And Digital Fly-By-Wire Systems, Aaron French

Mechanical Engineering Undergraduate Honors Theses

With technology advancing by leaps and bounds by the year, the uses of Unmanned Aerial Vehicles are becoming more apparent. The possibilities for an aerial vehicle that is fully autonomous are endless. Such aerial vehicles could divert manpower to humanitarian efforts, airlift, and other non‐attack operations. Leaders can put their focus elsewhere on the battlefield with the knowledge that the skies over their heads will be well guarded. These desires give life to projects such as this. No advancement in civilization has ever been made without the collective revolutionary research of great minds, trial by fire, and daring to dream.

Hot Mix Asphalt Longitudinal Joint Evaluation, Annette Porter

Civil Engineering Undergraduate Honors Theses

Longitudinal joints are the portion of the road where two lanes meet and are formed because the lanes are paved at different times. Longitudinal joints tend to be the weakest portion of the roadway, and yet few regulations exist to control their quality. Currently, Arkansas specifications for asphalt pavement do not include any requirements for the measurement of joint quality. The purpose of this research project is to determine the most effective method for evaluating longitudinal joints in hot-mix asphalt (HMA) pavements. Most of the literature concerning longitudinal joints focuses on density as the determining factor of quality because density …

Production Of Biobutanol From Biomass Using Novel Membrane Reactor: A P3 Experience, Ellen Draehn

Chemical Engineering Undergraduate Honors Theses

Producing biobutanol from a waste product on a large scale is a novel idea. Because of this, there is very little research available in this area. Previous fermentation research has primarily focused on the production of ethanol or biobutanol using cellulosic or agricultural feed stocks. The Phase I research team, Team R azorbacks E ngineering FU el S olutions for E veryone (Team REFUSE), sought to design a fermentation process that would produce butanol from food waste. Team REFUSE cultivated a partnership with Chartwells, the campus food service provider for the University of Arkansas, for the acquisition of food waste. …

Detection Of Escherichia Coli Using The Bacteriophage-Based Fluorescent Technique, Aung Khaing

Biological and Agricultural Engineering Undergraduate Honors Theses

The detection of viable Escherichia coli (E. coli) by the bacteriophage-based fluorescent technique using the enhanced green fluorescent protein (EGFP) was tested in this project. EGFP, a mutant of green fluorescent protein (GFP), was used due to its high fluorescent efficiency compared to wild-type GFP. First, E. coli bacteria were cultured to the mid-exponential phase in the 2× YT medium and then they were infected with the M13 bacteriophages containing the EGFP gene. Infected bacteria were incubated for different time intervals, and the expression of EGFP on the E. coli membrane was tested by the PerkinElmer LS 55 Luminescence Spectrometer, …

A Robust Process For Biodiesel Production Using Supercritical Methanol, Thomas Kasprowicz

Chemical Engineering Undergraduate Honors Theses

The overarching purpose of Phase I was to test, at the bench scale, a continuous supercritical methanol reactor, and to determine the feasibility of implementing the technology at full scale. Specific objectives in reaching this purpose included:
Objective 1: Choose a viable feedstock
Objective 2: Perform experiments for oil extraction
Objective 3: Design, build and operate a continuous supercritical methanol reactor
Objective 4: Design and simulate full scale biodiesel facility
Objective 4a: Perform life-cycle and economic analysis on full scale design
Objective 5: Prepare a Phase II P3 project to demonstrate the entire biodiesel process
Project Scope: The students performed …

Proximate Characterization And Lycopene Determination In Bitter Melon Seed Aril, Luis Raul Jimenez Interiano

Chemical Engineering Undergraduate Honors Theses

Bitter melon aril is the mucilage covering the fruit's seeds which could contain beneficial dietary ingredients. The bright red color of bitter melon aril suggests that it could contain lycopene. The purpose of this study was to determine the proximate composition of bitter melon aril and to explore this material as a potential rich source of lycopene that has health benefits. Bitter melon aril from Sri Lanka, harvested in Arkansas, USA in 2005, 2006, and 2007 was analyzed. An investigation to develop an extraction method for lycopene from bitter melon was performed using liquid-liquid and a polar liquid extraction. The …

Understanding The Effects Of Hydrophobicity For The Detection Of Methylated Dna By Microchannel Electrophoresis, Micah Fritsche

Chemical Engineering Undergraduate Honors Theses

DNA methylation is an epigenetic mechanism used for long - term silencing of gene expression. This silencing of gene expression can be involved in the down regulation of genes involved in apoptosis, which is a process of regulated cell death, and this inability to break down cells can ultimately lead to tumor formation in cancer. Methylation of DNA follows a certain pattern through developmental stages of an individual, and this pattern is normally maintained throughout that individual's life. However, in the DNA of older individuals, this methylation is commonly seen to be altered. This altered pattern of methylation can be …

Free Fridays: An Alternative Way To Conserve Energy, Lauren Kuenzel

Mechanical Engineering Undergraduate Honors Theses

In February 2007, the University of Arkansas at Fayetteville (UAF) signed the President's Climate Commitment to set a goal of becoming climate neutral. A large part of any strategy to become climate neutral includes energy conservation. In light of that, a four-day school week is proposed for UAF as an alternative energy savings possibility. This reduced schedule has been applied to K-12 schools and state government institutions, but not yet to universities. Along with numerous benefits such as energy conservation of buildings on the free day, a more effective use of time and building space and the positive emotional repercussions …

Nickel-Induced Crystallization Of Amorphous Silicon, Robert Fleming

Mechanical Engineering Undergraduate Honors Theses

One- and two-dimensional silicon nanostructures, such as nanodots, nanowires, and surface topography, have potential uses in a variety of fields, including microelectronics, photonics, and tribology. In this thesis research, nickel-induced crystallization (NIC) of amorphous silicon (a-Si) was investigated to determine the suitability of NIC of a-Si to produce silicon nanostructures on silicon substrates. The results show that formation of both surface topography and nanowires is possible with NIC of a-Si. In addition, the formation of nanostructures is very sensitive to Ni thickness, and the resulting nanostructures and films display a high degree of repeatability. The results obtained from this research …

Droplet Assisted Self-Assembly Of Semiconductor Nanostructures, Kimberly Annosha Sablon

Graduate Theses and Dissertations

There is increasing interest in quantum dot (QD) structures for a plethora of applications, including optoelectronic devices, quantum computing and energy harvesting. While strain driven surface diffusion via stranski-krastanow (SK) method has been commonly used to fabricate these structures, a more recent technique, droplet epitaxy (DE) does not require mismatch strain and is therefore much more flexible in the combination of materials utilized for the formation of QDs.

As reported in this work, a hybrid approach that combines DE and SK techniques for realizing lateral ordering of QDs was explored. First, the droplet formation of various materials was discussed and …

Carbon Nanotube Cluster Based Micro-Fluidic System For Bacteria Capture, Concentration, And Separation, Christopher Nelson

Biological and Agricultural Engineering Undergraduate Honors Theses

Disease-causing pathogens continue presenting enormous global health problems, especially due to their easy transmittance to people via water supply systems. The detection, filtration, and purification of bacteria contaminated water samples are complex and subject to a great amount of error. Here we present a new and highly effective micro-fluidic system with carbon nanotube clusters for effective and efficient detection, filtration, and purification of bacteria contaminated medium. The developed system is based upon two unique properties of carbon nanotubes (CNTs): high bacterial affinity and magnetic susceptibility. The CNTs' high affinity to bacteria cells makes them a key candidate for the bacteria …

Analysis Of Ecosystem Services At Mullins Creek On The University Of Arkansas Campus, Kathryn Mccoy

Biological and Agricultural Engineering Undergraduate Honors Theses

The University of Arkansas has been a site of population and urban growth since its inception in 1871. This urban development has caused extreme changes in land use, and with this has also come a change in ecosystem services provided by the area. Ecosystem services are benefits acquired by humans that are provided by functions are an ecosystem (Constanza et al., 1997). Constanza developed a method for quantifying ecosystem services. In this method, Constanza valuated ecosystem services for biomes. These service values were based on the economic value of the service provided, and were given in dollar per hectare-year. A …