Engineering Commons^™

Optical Down-Conversion In Doped Znse:Tb3+ Nanocrystals, Sandip Das, K. C. Mandal

Faculty Publications

No abstract provided.

Experimental Determination Of Electron-Hole Pair Creation Energy In 4h-Sic Epitaxial Layer: An Absolute Calibration Approach, S. K. Chaudhuri, K. J. Zavalla, K. C. Mandal

Faculty Publications

No abstract provided.

Hydrophobic Hydrogel Caged H3Po4 As A New Class Of High-Temperature Proton Exchange Membranes With Enhanced Acid Retention, Qunwei Tang, Guoging Qian, Kevin Huang

Faculty Publications

We herein report a new class of high-temperature proton exchange membranes comprised of poly(acrylic acid-graft-hexadecyltrimethylammonium bromide) (PAA-g-CTAB) or poly(acrylic acid)-graft-poly(ethylene glycol) (PAA-g-PEG) hydrophobic hydrogel caged H₃PO₄. The membranes exhibit reasonable proton conductivity, enhanced H₃PO₄ retention ability and low solubility in water, making them promising as potential high performance and robust electrolytes for high-temperature proton exchange membrane fuel cells. Although the proton conductivity is still lower than that of H₃PO₄ doped PBI membranes, the new concept provides a different approach to proton exchange membranes for acid retention.

Investigation Of Longitudinal Joints Between Precast Prestressed Deck Bulb Tee Girders Using Latex Modified Concrete, Clark Baer

Theses and Dissertations

This study investigates the behavior and performance of latex modified concrete (LMC) as a closure pour material with a U-bar connection detail in longitudinal joints between precast deck bulb tee bridge girders with integral concrete decks. The objective was to determine if the joint detail was capable of resisting service shear and moment stresses as well as eliminate the formation of cracks in the joint during fatigue loading. This study tested two large scale reinforced concrete slab specimens measuring 6 ft x 6 ft x 8 in joined together by the longitudinal joint detail in fatigue flexure shear loading. The …

Phylogeny And Ancestral Genome Reconstruction From Gene Order Using Maximum Likelihood And Binary Encoding, Fei Hu

Theses and Dissertations

Over the long history of genome evolution, genes get rearranged under events such as rearrangements, losses, insertions and duplications, which in all change the ordering and content along the genome. Recent progress in genome-scale sequencing renews the challenges in the reconstructions of phylogeny and ancestral genomes with gene-order data. Such problems have been proved so interesting that a large number of algorithms have been developed rigorously over the past few years in attempts to tackle these problems following various principles. However, difficulties and limitations in performance and scalability largely prevent us from analyzing emerging modern whole-genome data, our study presented …

A Model Experiment To Assess The Effects Of Inclusions On Wave Propagation In Soil Media, Thomas Houston

Theses and Dissertations

The research described involved analyzing and characterizing changes to propagating surface waves that are caused by items embedded in a half-space consisting of a soil medium. Numerical and experimentally obtained data of three-dimensional surface wave responses to dynamic impulse loading were examined. Results from this research are compared to changes to surface waves observed in previous investigations that were caused by the presence of voids and inclusions embedded in an elastic half space. The focus of this work was to identify whether the characteristic responses identified in previous studies, based substantially on analytical and finite element analyses results, can be …

Toward Directing Cell Fate: Carbon Nanotubes As Modulators Of Extracellular And Transporters Of Intracellular Cues, Qingsu Cheng

Theses and Dissertations

The unique properties of CNTs lead CNTs attractive in biological engineering applications. It is expected to use CNT based biomaterials for clinic use in the near future. CNTs can be used to tune cellular fate through bother extracellular pathway and intracellular pathway. CNT based biomaterials has been applied into bone, nerves, and cardiovascular system. There has also been progress in the use of CNTs in controlling cellular alignment, to enhance tissue regeneration, growth factor delivery and gene delivery.

Pluripotent stem cells (hPSCs) offer a promising tool in tissue engineering strategies, as their differentiated derivatives can be used to reconstruct most …

Simulation Studying Effects Of Multiple Primary Aberrations On Donut-Shaped Gaussian Beam, Chen Zhang, K. Wang, J. Bai, Y. Liu, Guiren Wang

Faculty Publications

In this paper, we demonstrate the variation of donut-shaped depletion pattern which influenced by multiple primary aberrations. The simulation is base on a common stimulation emission of depletion (STED) system composed by Gaussian laser and vortex phase plate. The simulation results are helpful guidelines for analyzing the aberration of depletion patterns in real situations.

Wave Propagation In Metamaterial Using Multiscale Resonators By Creating Local Anisotropy, Raiz U. Ahmed, Sourav Banerjee

Faculty Publications

Directional guiding, passing or stopping of elastic waves through engineered materials have many applications to the engineering fields. Recently, such engineered composite materials received great attention by the broader research community. In elastic waves, the longitudinal and transverse motion of material particles are coupled, which exhibits richer physics and demands greater attention than electromagnetic waves and acoustic waves in fluids. Waves in periodic media exhibit the property of Bragg scattering and create frequency band gaps in which the energy propagation is prohibited. However, in addition to the Bragg scattering, it has been found that local resonance of artificially designed resonators …

Nanopillar Array With A Λ/11 Diameter Fabricated By A Kind Of Visible Cw Laser Direct Lithography System, Chen Zhang, K. Wang, J. Bai, S. Wang, W. Zhao, F. Yang, C. Gu, Guiren Wang

Faculty Publications

Nanoscale functional structures are indispensable elements in many fields of modern science. In this paper, nanopillar array with a pillar diameter far smaller than Abbe's diffraction limit is realized by a new kind of continuous wave (CW) laser direct lithography technology. With atomic force microscopy technology, the average diameter of nanopillars on thin OIR906 photoresist film is about 65 nm and the smallest diameter is 48 nm, which is about 1/11 of the incident laser wavelength. Also, the influences of coma and astigmatism effects to the shape and size of nanopillar are numerically simulated by utilizing vector integral. As far …

The Effect Of Isostatic Pressing On The Dielectric Properties Of Screen Printed Ba0.5Sr0.5Tio3 Thick Films, Siwei Wang, Lingling Zhang, Jiwei Zhai, Fanglin Chen

Faculty Publications

Ba_0.5Sr_0.5TiO₃ thick films with B₂O₃–Li₂O glass sintering aid were prepared by the screen printing method on Al₂O₃ substrates. A 200 MPa isostatic pressure was applied to the films before sintering. After being sintered at 950^∘C, lower porosity and denser microstructure was obtained compared with the films without isostatic pressing. The dielectric constant and dielectric loss were 238 and 0.0028, respectively. A tunability of 61.7% was obtained for the isostatic pressed films, a 27.8% enhancement compared to unpressurized films. These results suggest that isostatic pressing …

Selection And Clustering For Disease Associated Genetic Variants, Yubo Zou

Theses and Dissertations

Epigenetics is the study of chemical reactions, which are orchestrated for the development and maintenance of an organism. Genetic or epigenetic variants (GEVs) encompass different types of genetic measures, such as Deoxyribonucleic acid (DNA) methylation at different CpG sites, expression level of genes, or single nucleotide polymorphisms (SNPs). With the development of technology, huge amount of genetic and epigenetic information is produced. However, the rich information potentially brings in challenges in data analyses. Thus it is necessary to reduce the dimension of data to improve efficiency. In my dissertation, I will focus on two directions of dimension reduction: variable selection …

Computational Analysis And Prediction Of Genome-Wide Protein Targeting Signals And Localization, Jhih-Rong Lin

Theses and Dissertations

Computational prediction of protein subcellular localization can greatly help to elucidate its functions. Despite the existence of dozens of protein localization prediction algorithms, the prediction accuracy and coverage are still low. Several ensemble algorithms have been proposed to improve the prediction performance, which usually include as many as 10 or more individual localization algorithms. However, their performance is still limited by the running complexity and redundancy among individual prediction algorithms. In the first part of the dissertation, we propose a novel method for rational design of minimalist ensemble algorithms for practical genome-wide protein subcellular localization prediction. The algorithm is based …

Role Of Microrna-155 In A Mouse Model Of Colon Cancer., Claire Mitchell Midyette

Theses and Dissertations

Colorectal cancer remains the third most common malignancy and the fourth most common cause of cancer mortality worldwide. Dysregulated miRNA levels are associated with several types of malignancies and may serve as important biomarkers and/or therapeutic targets in colorectal cancer. We examined the role of miRNA-155 on tumorigenesis and associated symptoms using a well-characterized mouse model of colorectal cancer. C57BL/6 wild-type mice and miRNA-155-/- mice (n=7-13 group) were given a single injection of AOM (10mg/Kg) followed by 3 cycles of DSS (2% in the water for 1 week followed by 2 weeks of plain water). A C57BL/6 wild-type group that …

Modeling And Simulation Study Of A Dynamic Gas Turbine System In A Virtual Test Bed Environment, Eshwarprasad Thirunavukarasu

Theses and Dissertations

Gas Turbine is a complex system and highly non linear in its overall performance. For power generation applications, it is essential to develop a reliable gas turbine model for simulating the impact on electric power generated under various load conditions. This research focuses on development of a dynamic gas turbine model to simulate both single shaft and twin shaft engines. The model is developed on a virtual test bed platform which is an advanced dynamic multidisciplinary simulation environment. The modeling approach starts by developing mathematical models for individual components of gas turbines based on the thermodynamic laws and is coupled …

Investigation Of Start Domain Proteins In Human Luteinized Cells And Cos-1 Cells, Bo Shi

Theses and Dissertations

After the luteinizing hormone surge of the menstrual cycle, the ovarian follicular granulosa and theca cells terminally differentiate to form the luteal cells of the corpus luteum. During this process known as luteinization, granulosa cells begin to synthesize large quantities of progesterone, a hormone essential for pregnancy. The rate limiting step for the de novo synthesis of pregnenolone (the precursor to progesterone) is the transport of cholesterol from the outer to the inner mitochondrial membrane, a process mediated by STARD1. STARD1 contains a C-terminal lipid binding domain holding one molecule of cholesterol, and an N-terminal domain targeting STARD1 to the …

Improving Robustness And Scalability Of Available Ner Systems, Amber Mckenzie

Theses and Dissertations

The focus of this research is to study and develop techniques to adapt existing NER resources to serve the needs of a broad range of organizations without expert NLP manpower. My methods emphasize usability, robustness and scalability of existing NER systems to ensure maximum functionality to a broad range of organizations. Usability is facilitated by ensuring that the methodologies are compatible with any available open-source NER tagger or data set, thus allowing organizations to choose resources that are easy to deploy and maintain and fit their requirements. One way of making use of available tagged data would be to aggregate …

A Method For Evaluating Power Generation Concepts Considering The Optimal Concept Of Operations, Tianlei Zhang

Theses and Dissertations

When trying to select an appropriate power generation plant for a micro-grid power distribution system like an electric ship, designers must consider both the physical characteristics (e.g., weight, volume, power ratings) and performance characteristics (e.g., fuel consumption, quality of service) of all the design alternatives. Comparing the design alternatives in terms of the physical characteristics is relatively straightforward, but in terms of performance characteristics each design alternative has to be evaluated within its own optimal performance points to make a fair comparison. However, at present no effective method or software tools exist to enable this evaluation at the earliest design …

Modeling Of Sic Power Semiconductor Devices For Switching Converter Applications, Ruiyun Fu

Theses and Dissertations

Thanks to recent progress in SiC technology, SiC JFETs, MOSFETs and Schottky diodes are now commercially available from several manufactories such as Cree, GeneSiC and Infineon. SiC devices hold the promise of faster switching speed compared to Si devices, which can lead to superior converter performance, because the converter can operate at higher switching frequencies with acceptable switching losses, so that passive filter size is reduced. However, the ultimate achievable switching speed is determined not only by internal semiconductor device physics, but also by circuit parasitic elements. Therefore, in order to accurately predict switching losses and actual switching waveforms, including …

Investigation Of Three-Way (Twc), Lean Nox Trap (Lnt) And Selective Catalytic Reduction (Scr) Catalysts For Control Of Nox Emissions From Lean-Burn Engines, Christopher Dominic Digiulio

Theses and Dissertations

Lean-burn gasoline engines are approximately 10% more fuel efficient than conventional, stoichiometric-burn ones. Although relatively modest, if implemented across the entire U.S. automotive fleet, this improvement in fuel economy could have far-reaching implications on the amount of gasoline imported in the country on an annual basis. However, the development of a cost-effective catalytic converter catalyst capable of meeting emission regulations for lean-burn vehicles still represents a major technical challenge. Currently, lean NOX trap (LNT) and selective catalytic reduction (SCR) catalysts are used for this purpose, but both systems suffer from significant drawbacks. For example, LNT catalysts generally require high platinum …

Fabrication And Characterization Of Compact High Resolution Radiation Detectors Based On 4h-Sic N-Type Epilayer And Cdznte, Kelvin Juvenal Zavalla Mendoza

Theses and Dissertations

The need of room-temperature, compact, and high resolution radiation detectors has opened the path for the development of new materials with suitable properties. Silicon carbide (SiC) and CdZnTe (CZT) are semiconductor materials with wide band gap that can operate efficiently at room temperatures (RT) and above. CZT has a high average atomic number (Z) which offers a high photoelectric absorption coefficient for x-/gamma rays. SiC allows high energy heavy ion detection due to its high radiation hardness even at temperatures much higher than room temperatures (RT). This thesis focuses on the fabrication and characterization of semiconductor based radiation detectors for …

Experimental Study On Piping Failure Of Earthen Levee And Dams, Yusuf Ahmed Sharif

Theses and Dissertations

Piping in an earthen levee, one of the main causes of failure, is a complex phenomenon. Most of the available research on piping failure has been on non-cohesive sandy soils. Jet Erosion Test and Hole Erosion Test have been conducted to study piping failure in an indirect manner. However, no general purpose formula is presently available to describe the erosion process due to complex erosion characteristics of cohesive soils in earthen levees.

Experimental investigations in a flume to understand the piping erosion process in an earthen levee are conducted in this research. One of the sidewalls and the bottom of …

Electrokinetic Mixing And Separation In Microfluidic Systems, Fang Yang

Theses and Dissertations

Electrokinetics involves the study of liquid or particle motion under the action of an electric field; it includes electroosmosis, electrophoresis, dielectrophoresis, and electrowetting, etc. The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) for use in biological and chemical assays. Here we present our works of electrokenitic based mixing and separation in microfluidics …

Synthesis And Characterization Of New Ionic And Mixed Ionic/Electronic Conductors, Kevin Gregory Romito

Theses and Dissertations

In a constantly growing and developing world, there is a great need to develop new forms of clean energy generation. Many solutions have been proposed to ameliorate these global concerns, which include fuel cell technology and new processes for reducing polluting chemicals in the atmosphere. These technologies are still in their infancy and require further development before becoming viable options.

In the case of fuel cells, particularly solid oxide fuel cells, and CO2 separation membranes, there is a need to develop ion conducting materials that are highly efficient, less costly to synthesize, and can perform strongly under many real-world conditions. …

Predicting The Crack Response For A Pipe With A Complex Crack, Robert George Lukess

Theses and Dissertations

Traditional flaw evaluation in the nuclear field uses conservative methods to predict maximum load carrying capacity for flaws in a given pipe. There is a need in the nuclear industry for more accurate estimates of the load carrying capacity of nuclear piping such that probabilistic tools can be used to predict the time to failure for various types of cracks. These more accurate estimates will allow the nuclear industry to repair flaws at a more appropriate time considering external factors such as costs and man-rem planning along with the flaw repair. Analysis of the maximum load carrying capacity of a …

Application Of Computational Fluid Dynamics Methods To Improve Thermal Hydraulic Code Analysis, Dennis Shannon Sentell, Jr.

Theses and Dissertations

A computational fluid dynamics code is used to model the primary natural circulation loop of a proposed small modular reactor for comparison to experimental data and best-estimate thermal-hydraulic code results. Recent advances in computational fluid dynamics code modeling capabilities make them attractive alternatives to the current conservative approach of coupled best-estimate thermal hydraulic codes and uncertainty evaluations. The results from a computational fluid dynamics analysis are benchmarked against the experimental test results of a 1:3 length, 1:254 volume, full pressure and full temperature scale small modular reactor during steady-state power operations and during a depressurization transient. A comparative evaluation of …

Evolution Of Microstructure Of Haynes 230 And Inconel 617 Under Mechanical Testing At High Temperatures, Kyle Hrutkay

Theses and Dissertations

Haynes 230 and Inconel 617 are austenitic nickel based superalloys, which are candidate structural materials for next generation high temperature nuclear reactors. High temperature deformation behavior of Haynes 230 and Inconel 617 have been investigated at the microstructural level in order to gain a better understanding of mechanical properties. Tensile tests were performed at strain rates ranging from 10-3-10-5 s-1 at room temperature, 600 °C, 800 °C and 950 °C. Subsequent microstructural analysis, including Scanning Electron Microscopy, Transmission Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, and X-Ray Diffraction were used to relate the microstructural evolution at high temperatures to that of room …

Electromagnetic Modeling Of Gan Varactor Microwave Switches, Yi-Hsuan Yang

Theses and Dissertations

Microwave switches are important components which have been widely used in many microwave systems, such as electronic products, satellites communications, antennas, and radars etc. Traditionally, microwave switches are fabricated using pin diodes or MEMS, Si MOSFETs or GaAs HEMTs. These devices, due to the material limitations are suffering from a low breakdown voltage and are unable to handle high power. III-Nitride based varactor microwave switches provide opportunities for high power microwave devices, due to highly conducting 2D electron gas in the channel and high breakdown electric field.

Designing microwave switches typically involves modeling and simulation using tools such as MATLAB, …

Fault Location In Power Networks Using Synchronized Phasor Measurements, Cuong Nguyen

Theses and Dissertations

Faults in electric power systems can lead to cascading power outages which cause tremendous loss to the economy and affect people’s lives. Technical reports of recent blackout events in the United States pointed out the lack of situational awareness as one of the main causes of widespread outages. Time synchronized phasor measurement is recommended as a technology that can improve the monitoring of power system condition. By knowing exactly where a fault occurs, necessary actions can be taken in a timely manner and thus, damage caused by that fault can be limited. In this thesis, first, a method for precise …

Improved Limits And Portability Over Currently Employed Cadmium Monitoring Systems Through Preconcentration For Detection By Way Of Micro-/Nanofluidic Mechanisms, Paul F. Wach

Theses and Dissertations

Due to risk of environmental and biological accumulation of Cadmium (Cd), improved methods of early detection and monitoring must be explored as a preventative measure. Listed as one of the top three toxic heavy metals by the Environmental Protection Agency (EPA), the effects on ecological and human systems have well documented side-effects of physical mutation, reproductive sterility, kidney failure, liver disease, bone loss, and death. Found in batteries, metal plating, pigments, plastics, and cigarettes, Cd is also used as a neutron absorber in the nuclear industry as well as having 3 known radioactive isotopes. Urine Cd levels, which have been …