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Articles 1 - 30 of 32
Full-Text Articles in Physical Sciences and Mathematics
Role Of The Inner Shell Architecture On The Various Blinking States And Decay Dynamics Of Core-Shell And Core-Multishell Quantum Dots, Pooja Bajwa
Graduate Theses and Dissertations
Colloidal semiconductor nanocrystals (quantum dots, QDs) have received much attention in recent years due to their uniquely size-tunable properties leading to a number of promising applications. Some of their most popular applications include their use as fluorescent probes in biology, as electro-optical components and in photovoltaic devices. CdSe-based QDs are particularly important because of their ease of synthesis, high photoluminescence quantum yields (PL QYs) across the whole visible spectrum and their photostabilty. Shelling of core QDs is usually carried out to improve their optical properties, minimize outer environmental effects on their properties, and avoid toxic element exposure to the environment. …
Fabrication Of Infrared Photodetectors Utilizing Lead Selenide Nanocrystals, Justin Anthony Hill
Fabrication Of Infrared Photodetectors Utilizing Lead Selenide Nanocrystals, Justin Anthony Hill
Graduate Theses and Dissertations
Colloidal lead selenide and lead selenide / lead sulfide core/shell nanocrystals were grown using a wet chemical synthesis procedure. Absorbance and photoluminescence measurements were made to verify the quality of the produced nanocrystals. Absorbance spectra were measured at room temperature, while photoluminescence spectra were measured at 77 K. Organic ligands were exchanged for shorter ligands in order to increase the conductivity of the nanocrystals. Absorption and PL spectra for both core and core/shell nanocrystals were compared. Interdigital photodetector devices with varying channel widths were fabricated by depositing gold onto a glass substrate. Lead selenide nanocrystals were deposited onto these metallic …
Just In Time Assembly (Jita) - A Run Time Interpretation Approach For Achieving Productivity Of Creating Custom Accelerators In Fpgas, Sen Ma
Graduate Theses and Dissertations
The reconfigurable computing community has yet to be successful in allowing programmers to access FPGAs through traditional software development flows. Existing barriers that prevent programmers from using FPGAs include: 1) knowledge of hardware programming models, 2) the need to work within the vendor specific CAD tools and hardware synthesis. This thesis presents a series of published papers that explore different aspects of a new approach being developed to remove the barriers and enable programmers to compile accelerators on next generation reconfigurable manycore architectures. The approach is entitled Just In Time Assembly (JITA) of hardware accelerators. The approach has been defined …
Measuring Nonlinear Properties Of Graphene Thin Films Using Z-Scan Technique, Thekrayat Hassan Al Abdulaal
Measuring Nonlinear Properties Of Graphene Thin Films Using Z-Scan Technique, Thekrayat Hassan Al Abdulaal
Graduate Theses and Dissertations
The nonlinear studies of two-dimensional (2D) nanomaterials, specifically graphene, are very significant since graphene is finding its usefulness in handling the enormous heat in nanoscale high-density power electronics. Graphene has emerged to be a promising nanomaterial as an excellent heat spreader due to its high thermal conductivity. However, the experimental nonlinear study of graphene materials and their application in developing future optoelectronic devices demands for more developed research.
The research objective is first to build a precise, and sensitive technique to investigate and understand the thermal nonlinear properties, including nonlinear refractive index (n2), nonlinear absorption coefficient (β), and thermo-optic coefficient …
Synthesis, Characterization, And Fabrication Of All Inorganic Quantum Dot Leds, Haider Baqer Salman
Synthesis, Characterization, And Fabrication Of All Inorganic Quantum Dot Leds, Haider Baqer Salman
Graduate Theses and Dissertations
Quantum Dot LEDs with all inorganic materials are investigated in this thesis. The research was motivated by the potential disruptive technology of core shell quantum dots in lighting and display applications. These devices consisted of three main layers: hole transport layer (HTL), electron transport layer (ETL), and emissive layer where the emission of photons occurs. The latter part was formed of CdSe / ZnS core-shell quantum dots, which were synthesized following hot injection method. The ETL and the HTL were formed of zinc oxide nanocrystals and nickel oxide, respectively. Motivated by the low cost synthesis and deposition, NiO and ZnO …
Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix
Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix
Graduate Theses and Dissertations
As is commonly known, the world is full of technological wonders, where a multitude of electronic devices and instruments continuously help push the boundaries of scientific knowledge and discovery. These new devices and instruments of science must be utilized at peak efficiency in order to benefit humanity with the most advanced scientific knowledge. In order to attain this level of efficiency, the materials which make up these electronics, or possibly more important, the fundamental characteristics of these materials, must be fully understood. The following research attempted to uncover the properties and characteristics of a selected family of materials. Herein, zinc …
Soil Moduli Obtained From A Back Pressure Constant Rate Of Strain Bender Element Consolidation Apparatus, Yi Zhao
Graduate Theses and Dissertations
A back-pressure saturated, constant-rate-of-strain consolidation device was modified to incorporate bender elements (BP-CRS-BE) and thus allowed for shear wave measurements during consolidation tests. This newly fabricated system has many advantages over other previous or current devices: 1) it can be utilized not only for laboratory prepared soil samples but also for field sampled soils such as Shelby tube samples, and 2) continuous compression curves, and continuous values of vertical hydraulic conductivity and coefficient of consolidation can be acquired with a significant reduction in testing time. Soil modulus values such as shear modulus and constrained modulus are also able to be …
Chlorine Demand Shows Thresholds And Hierarchy With Source Water Quality At Beaver Lake, Arkansas, Jaime M. Gile
Chlorine Demand Shows Thresholds And Hierarchy With Source Water Quality At Beaver Lake, Arkansas, Jaime M. Gile
Graduate Theses and Dissertations
This study investigated the effects of source water quality in Beaver Lake on the amount of chlorine (Cl) needed to develop decision support system to help guide chlorination practices in pre-treatment of source water. Chlorine demand assays were performed on water samples from Beaver Lake collected from the intake structure at Beaver Water District from March 2014 through August 2015, and using data from these assays, the two points of interest in this study were the Cl dose at which Cl residuals began to accumulate and the mean Cl demand occurring after that dose. Three methods of analysis were used …
Trend Analysis Of Water Quality In Northwest Arkansas Streams Reflects Changes In The Watershed, Zachary Paul Simpson
Trend Analysis Of Water Quality In Northwest Arkansas Streams Reflects Changes In The Watershed, Zachary Paul Simpson
Graduate Theses and Dissertations
Watershed export of nutrients, sediments, and chemicals impacts receiving waters. Changes within the watershed (e.g., anthropogenic or climatic) can alter the transport of constituents in streams. Stream monitoring is crucial for understanding these effects. This study developed a potential improvement to flow-adjusting constituent concentrations in streams, an important step of analyzing monitoring data in lotic systems for trends. The method incorporates a K-fold cross-validation procedure to optimize a model explaining the relationship between the concentration and streamflow, thus providing a valuable tool to researchers in water quality. Additionally, two case studies were conducted on watersheds located in northwest Arkansas using …
Evaluating A Measure-Calculate Method For Determining Sediment Oxygen Demand In Lakes, Adrian Beirise
Evaluating A Measure-Calculate Method For Determining Sediment Oxygen Demand In Lakes, Adrian Beirise
Graduate Theses and Dissertations
A steady-state mass diffusion model used with simple measurable and calculable inputs for determining sediment oxygen demand (SOD) is compared to an intact core incubation (ICI) SOD method using samples from three lakes. The mass diffusion model coupled with inputs is known as the measure-calculate method (M-C) and is a potential alternative to existing methods for measuring SOD which are more complex, time-consuming, and costly. The M-C method requires inputs for volumetric sediment oxygen uptake (Ṅsed), sediment density and porosity, and water properties. Ṅsed was determined by suspending sediment in oxygen-saturated water with a DO probe and determining the steady …
Study Of Plasmonic Properties Of The Gold Nanorods In The Visible To Near Infrared Light Regime, Pijush Kanti Ghosh
Study Of Plasmonic Properties Of The Gold Nanorods In The Visible To Near Infrared Light Regime, Pijush Kanti Ghosh
Graduate Theses and Dissertations
Nanostructures of noble metals show unique plasmonic behavior in the visible to near-infrared light range. Gold nanostructures exhibit a particularly strong plasmonic response for these wavelengths of light. In this study we have investigated optical enhancement and absorption of gold nanorods with different thickness using finite element method simulations. This study reports on the resonance wavelength of the sharp-corner and round-corner rectangles of constant length 100 nm and width 60 nm. The result shows that resonance wavelength depends on the polarization of the incident light; there also exists a strong dependence of the optical enhancement and absorption on the thickness …
Electrodeionization Versus Electrodialysis: A Clean-Up Of Produced Water In Hydraulic Fracturing, Brigitte Marie Rodgers
Electrodeionization Versus Electrodialysis: A Clean-Up Of Produced Water In Hydraulic Fracturing, Brigitte Marie Rodgers
Graduate Theses and Dissertations
Electrodeionization (EDI) is a widely studied process ranging from applications in wastewater clean-up in the food and beverage industry to purifying organic compounds. To date, there are no apparent studies on applying this technology to produced wastewater recovered from hydraulic fracking sites. Water consumption within hydraulic fracturing sites can reach in the upwards of millions of gallons per site, so a need for a water recycling process becomes necessary within areas where water requirements are scarce. Implementation of an EDI module that is capable of handling high salt solutions from produced wastewater in subsequent fracturing practices will decrease overall water …
Initial Structural Subsidence As Reflected In Morrowan And Atokan (Pennsylvanian) Subsurface Stratigraphy, Northern Arkoma Basin, North-Central Arkansas, Fatimah Taher Nahi Al Asadi
Initial Structural Subsidence As Reflected In Morrowan And Atokan (Pennsylvanian) Subsurface Stratigraphy, Northern Arkoma Basin, North-Central Arkansas, Fatimah Taher Nahi Al Asadi
Graduate Theses and Dissertations
The Arkoma Basin is a carboniferous foreland basin that is known for its prolific gas production. The objective of this research is to study the initial subsidence of the basin by analyzing the strati-graphic and structural features of the study area. This was accomplished through IHS Petra, Surf-er 13, and Win-Tensor software. Field work studies comprised a large part of this study. Also, a seismic profile and Google earth elevation profiles are among the methods used to study the initial subsidence of the Arkoma Basin. The study area within the basin represents a transitional zone from the shelf into the …
The Role Of Organic Matter In The Fate And Transport Of Antibiotic Resistance, Metals, And Nutrients In The Karst Of Northwest Arkansas, Victor Lee Roland Ii
The Role Of Organic Matter In The Fate And Transport Of Antibiotic Resistance, Metals, And Nutrients In The Karst Of Northwest Arkansas, Victor Lee Roland Ii
Graduate Theses and Dissertations
Organic matter (OM) in the environment acts as a nutrient, but may also act as a transport vector for harmful chemical compounds and bacteria. Acetate is a labile form of OM produced during fermentation in anaerobic lagoons used to store animal fecal-waste from concentrated animal feeding operations (CAFOs). Dry and liquid fertilizers from CAFOs pose a threat to groundwater by introducing excessive amounts of nutrients (e.g. OM, nitrate and ammonia), metals, and antibiotic compounds. In the epikarst of Northern Arkansas in the Buffalo River watershed additional input of labile dissolved organic carbon (DOC) from liquid CAFO waste-fertilizers was hypothesized to …
Photoluminescence Measurement On Low-Temperature Metal Modulation Epitaxy Grown Gan, Yang Wu
Photoluminescence Measurement On Low-Temperature Metal Modulation Epitaxy Grown Gan, Yang Wu
Graduate Theses and Dissertations
A low-temperature photoluminescence (PL) study was conducted on low-temperature metal modulation epitaxy (MME) grown GaN. By comparing the PL signal from high temperature grown GaN buffer layers, and MME grown cap layers on top of the buffer layers, it was found that MME grown GaN cap has a significantly greater defect-related emission. The band edge PL from MME grown GaN found to be 3.51eV at low temperature. The binding energy of the exciton in GaN is determined to be 21meV through temperature dependence analysis. A PL peak at 3.29eV was found in the luminescence of the MME grown cap layer, …
Asbestos Cement Pipe Condition Assessment And Remaining Service Life Prediction, Abiy Melles Ghirmay
Asbestos Cement Pipe Condition Assessment And Remaining Service Life Prediction, Abiy Melles Ghirmay
Graduate Theses and Dissertations
This research details a condition assessment of asbestos cement (AC) pipe within in the Bella Vista Village Property Owners Association water distribution system. Bella Vista Village contains appropriately 300 miles of AC pipe with nominal diameters from 6-14 inch. The goal of the research is to determine the current condition of AC pipe within the system and predict future performance of the pipes. AC pipe samples were obtained from 23 locations disturbed across the distribution system with nominal pipe diameters of 6-8 inch. Estimates of current level of degradation were obtained using phenolphthalein staining and hardness measurements of each sample. …
Acceleration Of Ddscat Computation By Parallelization On A Supercomputer, Manoj V. Seeram
Acceleration Of Ddscat Computation By Parallelization On A Supercomputer, Manoj V. Seeram
Chemical Engineering Undergraduate Honors Theses
The DDSCAT software is enabled for use of MPI or OpenMP to distribute calculation of different particle orientations amongst multiple processors on a high performance system. Run times for these simulations have been tested to take hours or days however and simulating varying orientations is not always necessary. If a simulation with only one particle orientation is submitted, DDSCAT could still potentially parallelize the simulation by wavelength calculations but it is unknown if this is the case. In this paper, we will be (i) quantifying the reduction in computation time that MPI provides relative to an equivalent MPI disabled simulation …
Validation Of An Internal Camera Based Volume Determination System For Triaxial Testing, Leah D. Miramontes
Validation Of An Internal Camera Based Volume Determination System For Triaxial Testing, Leah D. Miramontes
Civil Engineering Undergraduate Honors Theses
Accurate strain and volume measurements are critical to phase relationships and strength determination for saturated and unsaturated soils. In recent years, laboratory-based photographic techniques of monitoring soil specimens have become more common. These techniques have been used to reconstruct 3D models and to determine strain and volumetric changes of triaxial specimens. A new technique that utilized digital photographs of the soil specimen, captured from within a triaxial testing cell, was utilized. Photographs were processed using photogrammetry software to reconstruct 3D models of the soil specimens. By placing camera equipment within the cell, the technique eliminated the need to account for …
Cfd Model For Ventilation In Broiler Holding Sheds, Christian Heymsfield
Cfd Model For Ventilation In Broiler Holding Sheds, Christian Heymsfield
Biological and Agricultural Engineering Undergraduate Honors Theses
Broiler production in Arkansas was valued at over $3.6 billion in 2013 (University of Arkansas Extension of Agriculture). Consequently, improvement in any phase of the production process can have significant economic impact and animal welfare implications. From the time poultry leave the farm and until they are slaughtered, they can be exposed to harsh environmental conditions, both in winter and in summer. After road transportation, birds are left to wait in holding sheds once they arrive at the processing plant, for periods of approximately 30 minutes to two hours. This project was interested in this holding shed waiting time during …
Developing A Risk Analysis Model To Improve Study Abroad Awareness, Tyler Spain
Developing A Risk Analysis Model To Improve Study Abroad Awareness, Tyler Spain
Industrial Engineering Undergraduate Honors Theses
As international education opportunities increase in popularity among U.S. college students (McMurtrie, 2007), it is becoming more and more necessary for study abroad organizations to be aware of the risks students face as they travel abroad. While some international cities are riskier than others, it can be difficult to distinguish between cities which truly carry a high degree of risk for visiting students, and which cities are only perceived to be risky based on various personal misconceptions. The University of Arkansas Office of Study Abroad & International Exchange currently lacks a way to quantifiably analyze the risk of study abroad …
Nanoscale Frictional Properties Of Nickel With One-Dimensional And Two-Dimensional Materials, Timothy K. Schlenger
Nanoscale Frictional Properties Of Nickel With One-Dimensional And Two-Dimensional Materials, Timothy K. Schlenger
Mechanical Engineering Undergraduate Honors Theses
When looking at the nanoscale, material interface interactions have been observed to exhibit particularly interesting properties. Our research looks into various combinations of carbyne and graphene atop a nickel block to look into the interface friction properties between them. Both the carbyne and graphene are tested using steered molecular dynamics (SMD) in sheering and peeling directions along the surface of the nickel block. These tests are then analyzed by comparing the magnitude of the acting force versus the displacement of the carbon allotrope sample across the nickel block. It is found that as the width of a carbon allotrope sample …
Particle Image Velocimetry Design & Installation, Zach Ritchie
Particle Image Velocimetry Design & Installation, Zach Ritchie
Mechanical Engineering Undergraduate Honors Theses
This work will mainly focus on the design, construction, and installation of the Particle Image Velocimetry (PIV) system in the Chemical Hazards Research Center wind tunnel. The PIV system utilizes a Class IV (double pulsed) laser, optics to produce a light sheet, timing circuitry, and a high-resolution camera (with buffered output) to measure a system’s velocity (two-dimensional) field by determining the displacement of particles over the time between laser pulses. For maximum mobility and functionality, the PIV system was installed in the center of the tunnel on a moveable cart with the laser and camera mounted to an adjustable support. …
Haul Truck Tires Recycling, Jessica N. Lizarazu
Haul Truck Tires Recycling, Jessica N. Lizarazu
Chemical Engineering Undergraduate Honors Theses
The disposal of large Off-the-Road (OTR) tires is an increasingly important concern. These tires can weigh up to 8,450 pounds with an overall diameter and width of approximately 140.7 inches and 45.1 inches respectively. OTR tires are used for mining vehicles such as haul trucks, wheel loaders, backhoes, graders, and trenchers. These new tires cost between $38,000 and $50,000 each, depending on multiple factors including oil prices and the cyclical nature of the industry. Haul trucks contain six tires per vehicle, and mines replace these tires around every 9-12 months. Statistics regarding discarded OTR tires are not provided by the …
Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill
Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill
Mechanical Engineering Undergraduate Honors Theses
Plasmonic nanostructures have been shown to act as optical antennas that enhance optical devices due to their ability to focus light below the diffraction limit of light and enhance the intensity of the incident light. This study focuses on computational electromagnetic (CEM) analysis of two devices: 1) GaAs photodetectors with Au interdigital electrodes and 2) Au thin-film microstructures. Experiments showed that the photoresponse of the interdigital photodetectors depend greatly on the electrode gap and the polarization of the incident light. Smaller electrode gap and transverse polarization give rise to a larger photoresponse. It was also shown that the response from …
Financial Performance In Upstream, Downstream, And Integrated Oil Companies In Response To Oil Price Volatility, Jonathan P. Garcia
Financial Performance In Upstream, Downstream, And Integrated Oil Companies In Response To Oil Price Volatility, Jonathan P. Garcia
Finance Undergraduate Honors Theses
This paper investigates the relation between crude oil price volatility and stock returns among oil companies using a three-part methodology, by using the West Texas Intermediate (WTI) as oil price benchmark. I asses the various indicators that set signals for oil price volatility and the interpretation of each (PMI, S&P500, DJIA, and World Crude Oil Output). This research also focuses on the relation between different types of companies in the oil industry (integrated, upstream, and downstream) and how each type of company will be assessed in a particular way to predict abnormal returns, based on market data and statistical analyses …
Inferring Intrinsic Beliefs Of Digital Images Using A Deep Autoencoder, Seok H. Lee
Inferring Intrinsic Beliefs Of Digital Images Using A Deep Autoencoder, Seok H. Lee
Computer Science and Computer Engineering Undergraduate Honors Theses
Training a system of artificial neural networks on digital images is a big challenge. Often times digital images contain a large amount of information and values for artificial neural networks to understand. In this work, the inference model is proposed in order to absolve this problem. The inference model is composed of a parameterized autoencoder that endures the loss of information caused by the rescaling of images and transition model that predicts the effect of an action on the observation. To test the inference model, the images of a moving robotic arm were given as the data set. The inference …
Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill
Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill
Physics Undergraduate Honors Theses
Plasmonic nanostructures have been shown to act as optical antennas that enhance optical devices due to their ability to focus light below the diffraction limit of light and enhance the intensity of the incident light. This study focuses on computational electromagnetic (CEM) analysis of two devices: 1) GaAs photodetectors with Au interdigital electrodes and 2) Au thin-film microstructures. Experiments showed that the photoresponse of the interdigital photodetectors depend greatly on the electrode gap and the polarization of the incident light. Smaller electrode gap and transverse polarization give rise to a larger photoresponse. It was also shown that the response from …
Experimental And Computational Studies Of Cortical Neural Network Properties Through Signal Processing, Wesley Patrick Clawson
Experimental And Computational Studies Of Cortical Neural Network Properties Through Signal Processing, Wesley Patrick Clawson
Graduate Theses and Dissertations
Previous studies, both theoretical and experimental, of network level dynamics in the cerebral cortex show evidence for a statistical phenomenon called criticality; a phenomenon originally studied in the context of phase transitions in physical systems and that is associated with favorable information processing in the context of the brain. The focus of this thesis is to expand upon past results with new experimentation and modeling to show a relationship between criticality and the ability to detect and discriminate sensory input. A line of theoretical work predicts maximal sensory discrimination as a functional benefit of criticality, which can then be characterized …
Risk Estimation Toward A Natural History Model For Low Grade Glioma Patients, Anh Thi Hoang Pham
Risk Estimation Toward A Natural History Model For Low Grade Glioma Patients, Anh Thi Hoang Pham
Graduate Theses and Dissertations
Glioma is a common type of primary brain tumor that represents 28% of all brain tumors and 80% of malignant tumors. According to a recent study by the Centers for Disease Control and Prevention (CDC), gliomas account for 53%, 35% and 29% of all brain tumors (68%, 74% and 81% of malignant brain tumors) among children (aged 0-14), teenagers (aged 15-19) and young adults, respectively. Gliomas are often diagnosed through radiological imaging and histopathology. There are two main groups of gliomas following World Health Organization’s classification: Low grade gliomas (LGG), or grade I and II gliomas; and high grade gliomas …
Hardware Trojan Detection Via Golden Reference Library Matching, Lucas Weaver
Hardware Trojan Detection Via Golden Reference Library Matching, Lucas Weaver
Graduate Theses and Dissertations
Due to the proliferation of hardware Trojans in third party Intellectual Property (IP) designs, the issue of hardware security has risen to the forefront of computer engineering. Because of the miniscule size yet devastating effects of hardware Trojans, few detection methods have been presented that adequately address this problem facing the hardware industry. One such method with the ability to detect hardware Trojans is Structural Checking. This methodology analyzes a soft IP at the register-transfer level to discover malicious inclusions. An extension of this methodology is presented that expands the list of signal functionalities, termed assets, in addition to introducing …