Engineering Commons^™

Design Of A 3d Printable Mechanical Time Simulating Solar System Model For Use In Stem Education, Mark Bedford Moffett

Theses and Dissertations

The use of designed tools to assist with relating abstract ideas to reality is now a possibility with the use of the modern manufacturing method of 3D printing. The inner four planets’ natural orbital periods with respect to Earth were modeled in SolidWorks and then fabricated using 3D printing. A 3D printable mechanical time simulating solar system model used in science, technology, engineering, and mathematics (STEM) could assist with the user’s understanding of the history of science, planetary orbital mechanics, gearing ratios, 3D printing, and systematically constructing a project using instructions. This paper describes the design of a 3D printable …

Synthesis Of Novel, Highly Bio-Based Monomeric Materials Derived From Lignocellulosic Biomass And Their Respective Epoxy Resins, Polycarbonates, And Polyesters, Joseph Randall Mauck

Theses and Dissertations

The development of high performance polymers from renewable feedstocks is a crucial step toward a global economy that is less dependent on fossil resources and has been a field of increasing study. The development of novel and interesting bio-based monomers, resins, and functional building blocks is critical to the improvement of polymers produced across the field, as well as to increasing the resource base from which chemical and materials engineers can draw to meet specific polymer property requirements. To this end, interesting tri-functional (trisguaiacol) and 4-vinyl guaiacol based hetero-difunctional monomers were developed and screened for preliminary polymer properties. The applications …

Hydrodynamic Resistance Of A Surfboard: An Analytical, Empirical, And Statistical Analysis, Andrew Leonard Kledzik

Theses and Dissertations

The objective of the present study defines a drag coefficient for a 9’0” surfboard. The hydrodynamic drag of a surfboard is derived from theory outlining the mathematical foundation used. Analytical solutions provide values for boundary layer thickness, momentum flux width, shear stress, drag force and the drag coefficient. This study also examines maximum velocities attainable from in-situ observations of surfers paddling in a controlled environment. The theoretical predictions are compared with experimental observations of surfboard resistance; while simultaneously validating instrumentation and methods of measurement. A number of problems are highlighted, ranging from mathematical problems on turbulent flow analysis to impacts …

Interpolation Methods For Coverage Area In Cellular Systems, Abdlmagid Mohamed Basere

Theses and Dissertations

Evaluating the coverage area in a wireless network is very important for cellular system designers in order to provide good service to users. It is hard to collect the Receive Signal Level (RSL) for an entire coverage area because of many obstacles, such as buildings, lakes, and vegetation. Therefore, estimation of the coverage area is essential for locations for which it is difficult to measure the RSL. This dissertation considers the process of RSL interpolation. Two main aspects of the interpolation are considered. Firstly, various interpolation methods are considered and it was determined that a very good performance is obtained …

Automatic Analysis Of Surface Electromyography Of Reflexes For Central Nervous System Inhibition During Pregnancy, Neda Parvin

Theses and Dissertations

Eclampsia is a life-threatening neurological complication (seizures or coma) of pregnancy, and represents progression of pre-eclampsia (high blood pressure and protein in the urine isolated to pregnancy). Even though the exact mechanism of pre-eclampsia and its neurological manifestations have yet to be definitively established, it is known that there is a loss of inhibitory impulses between the cerebral cortex and the spinal cord resulting in exaggerated reflexes. In this work, we establish normative measures for deep tendon reflexes (DTR) during pregnancy. We quantified the surface electromyogram (EMG) at the knee and ankle of DTRs in 279 subjects. The signals were …

Sistemi I Kontraktimit Projekto Ndërto (Design And Build), Nexhat Selmani

Theses and Dissertations

Punimi me titull: Sistemi i Kontraktimit Projekto Ndërto (Design and Build) , përshkruan formulimin e kontratave Fidic, posaçërisht kontratës sipas Librit të Verdhë (Yellow Book), nëpërmjet një analize gjithëpërfshirëse të ndërtimit të kontratave dhe përdorimit te tyre, viteve të fundit në vendin tone. Përqendrimi kryesor është tek analiza cilësore e kushteve, të cilat shtjellohen në Librat e FIDIC-ut (Libri i Verdhë dhe Libri i Kuq). Në këtë studim, pasqyrohet përdorimi i këtyre kontratave në Kosovë, të mirat dhe lehtësimet të cilat sjellin ato. Shembulli konkret i përdorimit të ketyre kontratave është në projektin e rehabilitimit të sistemit të ngrohjes në …

Gëlqerja Si Material Ndërtimi – Prodhimi, Karakteristikat Dhe Ekzaminimi I Vetive, Enver Dreshaj

Theses and Dissertations

1. Gëlqeren si material ndërtimorë ,

2. Eksperimentet në fabrikën New – Lepenci ,Kaçanik

3. Rëndësia e gëlqeres

Me ketë punim unë kam dashur sa do pak të tregoj rendësin e gëlqeres si material i cili ka përdorim te gjerë në të gjitha fushat ekzistuese edhe pse kohet e fundit është duke u zvogëluar përdorimi i saj mirëpo jo edhe rëndësia që ka si material ndërtimor, metalorgjik, industrial dhe biologjik. Ky studim është përpjekur të rendis shkurtimisht kuptimin e zbatimit të përdorimit të gëlqeres në ndërtimtari. Bazuar në këto detyra duhet të japë vetë parimet themelore të proceseve teknologjike tek …

Towards Design And Analysis For High-Performance And Reliable Ssds, Qianbin Xia

Theses and Dissertations

NAND Flash-based Solid State Disks have many attractive technical merits, such as low power consumption, light weight, shock resistance, sustainability of hotter operation regimes, and extraordinarily high performance for random read access, which makes SSDs immensely popular and be widely employed in different types of environments including portable devices, personal computers, large data centers, and distributed data systems.

However, current SSDs still suffer from several critical inherent limitations, such as the inability of in-place-update, asymmetric read and write performance, slow garbage collection processes, limited endurance, and degraded write performance with the adoption of MLC and TLC techniques. To alleviate these …

Nanomedicine Drug Delivery Across Mucous Membranes, Michael G. Lancina Iii

Theses and Dissertations

NANOMEDECINE DRUG DELIVERY ACROSS MUCOUS MEMBRANES

By Michael G. Lancina III

A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University.

Virginia Commonwealth Univeristy, 2017.

Major Director: Dr. Hu Yang, Associate Professor, Chemical and Life Science Engineering

Control over the distribution of therapeutic compounds is a complex and somewhat overlooked field of pharmaceutical research. When swallowing a pill or receiving an injection, it is commonly assumed that drug will spread throughout the body in a more or less uniform concentration and find its way to wherever it is needed. In …

Growth Of Zn-Polar Bemgzno/Zno Heterostructure With Two Dimensional Electron Gas (2deg) And Fabrication Of Silver Schottky Diode On Bemgzno/Zno Heterostructure., Md Barkat Ullah

Theses and Dissertations

Title of dissertation: GROWTH OF Zn POLAR BeMgZnO/ZnO HETEROSTRUCTURE WITH TWO DIMENSIONAL ELECTRON GAS (2DEG) AND FABRICATION OF SILVER SCHOTTKY DIODE ON BeMgZnO/ZnO HETEROSTRUCTURE

By Md Barkat Ullah, Ph.D

A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical and Computer Engineering at Virginia Commonwealth University.

Virginia Commonwealth University,2017

Major Director: Dr. Hadis Morkoç, Professor, Electrical and Computer Engineering

This thesis focuses on growth of Zn polar BeMgZnO/ZnO heterostructure on GaN/sapphire template with two dimensional electron gas (2DEG) for the application of UV photodetector/emitter and high speed electronics. The motivation of using …

Synthesis, Characterization, And Enhanced Magnetic Properties Of Iron Carbide Nanomaterials, Brent M. Williams

Theses and Dissertations

Permanent magnets are classified as hard magnetic materials with the main purpose of generating flux for applications such as electric motors, turbines, and hard drives. High coercivity, magnetic remanence, and saturation values with high stability are some of the requirements for permanent magnets. Rare-earth magnets including neodymium and samarium based magnets are known to have superior magnetic properties due to their high magnetocrystalline anisotropy. However, due to the price of rare-earth materials development of alternate permanent magnets composed of inexpensive materials is an ongoing process. Previously cobalt carbide (Co_xC) have shown promise as a potential rare-earth free magnet …

Comparative Studies Of Diffusion Models And Artificial Neural Intelligence On Electrochemical Process Of U And Zr Dissolutions In Licl-Kcl Eutectic Salts, Samaneh Rakhshan Pouri

Theses and Dissertations

The electrorefiner (ER) is the heart of pyroprocessing technology operating at a high-temperature (723 K – 773 K) to separate uranium from Experimental Breeder Reactor-II (EBR-II) used metallic fuel. One of the most common electroanalytical methods for determining the thermodynamic and electrochemical behavior of elemental species in the eutectic molten salt LiCl-KCl inside ER is cyclic voltammetry (CV). Information from CV can possibly be used to estimate diffusion coefficients, apparent standard potentials, transfer coefficients, and numbers of electron transferred. Therefore, predicting the trace of each species from the CV method in an absence of experimental data is important for safeguarding …

Eye Movement Control: An Index For Athleticism, Brittany L. Oshea

Theses and Dissertations

Athletic potential is one of the most complex human traits. An elite athlete is produced from a complex interaction of an innumerable number of traits exhibited by the athlete. However, it’s not clear whether these traits are innate, allowing the athlete to excel, or, alternatively, are a consequence of practice. To be successful, athletes rely heavily on sensory information from the visual and vestibular systems. This study investigated the relationship eye movement control has with innate athleticism by comparing the saccadic and Vestibulo-Ocular Reflex (VOR) responses of former, no longer practicing, elite athletes against their age and gender matched counterparts …

Enhanced Energy Storage And Conversion Applications By Porous Carbon And Atomic Layer Deposition, Yomna H. Abdelmoaty

Theses and Dissertations

The design and synthesis of porous materials attracted great attention recently because of their potential use in many fields like clean energy and environmental protection. Herein, we introduced new synthetic approaches for the preparation for porous carbons and organic polymers for selective CO₂ and iodine capture application. Regarding CO₂ capture application, Two new

series of porous carbons (PYDCs) and (TRI-Ps) were synthesized by thermally activating Pyrazole and Triazolo Pyridine monomers respectively using KOH as a catalyst, which leads to porous carbon. PYDCs exhibit high surface area according to Brunauer–Emmett–Tellertheory (SA_BET = 1266–2013 m² g⁻¹), …

Modulating The Innate Immune Response To Electrospun Scaffolds And Polymer Degradative Byproducts, Daniel Abebayehu

Theses and Dissertations

Implanted biomaterials often induce inflammation that frequently leads to the foreign body response, fibrosis, and the failure of the implant. Thus, it is important to evaluate how cells interact with materials to promote a more regenerative response. It is critical to determine how to modulate the response of tissue resident innate immune cells, as they are among the first cells to interact with implanted materials. Among tissue resident innate immune cells are mast cells, which are inflammatory sentinels that degranulate and orchestrate the fate of other cell populations, such as monocytes/macrophages and lymphocytes. Mast cells have also been reported to …

A Machine Learning Approach For Enhancing Security And Quality Of Service Of Optical Burst Switching Networks, Adel Dabash A. Rajab

Theses and Dissertations

The Optical Bust Switching (OBS) network has become one of the most promising switching technologies for building the next-generation of internet backbone infrastructure. However, OBS networks still face a number of security and Quality of Service (QoS) challenges, particularly from Burst Header Packet (BHP) flooding attacks. In OBS, a core switch handles requests, reserving one of the unoccupied channels for incoming data bursts (DB) through BHP. An attacker can exploit this fact and send malicious BHP without the corresponding DB. If unresolved, threats such as BHP flooding attacks can result in low bandwidth utilization, limited network performance, high burst loss …

Low-Cost Fishing Net-Reinforced Cement Matrix Overlay For Substandard Concrete Masonry In Coastal Areas, Mohammed A. Mousa

Theses and Dissertations

The aim of this project is to investigate a novel and affordable option to externally strengthen substandard concrete masonry (CM) walls for out-of-plane loads (e.g., high winds and flying debris). Two types of strengthening materials for fiber-reinforced cement mortar (FRCM) overlays are investigated; namely, fishing net (FN) and welded wire steel mesh (WWSM) reinforcements.

Salient mechanical properties of representative materials including substandard concrete masonry unit (CMU) blocks, mortar, nylon FN and WWSM reinforcements, and FRCM composite, were experimentally characterized. A simple bilinear model is proposed to describe the tensile behavior of the FRCM composite. An analytical model was then used …

Promotional Effect Of Molten Carbonates On Proton Conductivity And Oxygen Reduction Reaction – An Experimental And Computational Study, Xiaolei Xiong

Theses and Dissertations

Recent research of Solid oxide fuel cells (SOFCs) is aimed to lower the operating temperature to an intermediate temperature (IT) range of 500 to 700^oC, while maintaining a proper performance. This Ph.D. research project investigates the promotional effects of alkaline carbonate eutectics on the proton conductivity of proton conducting electrolytes and cathodic ORR reactivity in SOFCs by both experimental and computational methods. The ionic conductivity of the MC-BZY composite above 500^oC increases with the higher loading of MC. The sample exhibited nearly a factor of two higher conductivity in H₂-containing atmosphere than in air. …

Reducing Model Selection Computational Cost By Metamodeling The Evidence, Ramin Madarshahian

Theses and Dissertations

Modeling is an abstraction of reality that lets a designer or engineer perform simulations with a “real” object or structure without testing it physically. However, the result of simulations is as good as their models. Selecting the best model among many candidates is another challenge.

Complex models could translate into more accurate predictions, but they also require larger computational effort. The Bayes factor is often used to compare different models considering the data and analyst’s experience. To obtain the Bayes factor, the Bayesian model evidence is calculated; however, calculating the Bayesian model evidence of computationally expensive models is not a …

Study Of Mos2 And Graphene-Based Heterojunctions For Electronic And Sensing Applications, Ifat Jahangir

Theses and Dissertations

Since the discovery of graphene, there has been an increase in two-dimensional (2D) materials research for their scalability down to atomic dimensions. Among the analogs of graphene, transition metal dichalcogenides (TMDs) are attractive due to their exceptional electronic and optoelectronic properties. MoS2, a TMD, has several advantages over graphene and the industry workhorse Si, and has been reported to demonstrate excellent transistor performances. The key obstacle in the commercialization of MoS2 technology is low carrier mobility over large areas for top-down devices. Although there were several early reports on synthesis of atomically thin MoS2 with moderate mobility, transferring large area …

Mechanical Characterization And Non-Destructive Evaluation Of Sicf-Sicm Composite Tubing With The Impulse Excitation Technique, Nathaniel Truesdale

Theses and Dissertations

With growing interest on ceramic fiber reinforced ceramic matrix composites (CMC) for accident tolerant fuel, the need for mechanical characterization of ceramic composite arises. It has been of particular interest to non-destructively evaluate the mechanical performance of these composites. Impulse excitation (IE) is a well-established method for non-destructive mechanical characterization of homogeneous isotropic material of well-defined shapes. In this thesis, impulse excitation technique was applied for non-destructive characterization of composite tube for the first time as far as we know. CMC, when stressed beyond its damage threshold, will experience various forms of structural damage, such as matrix micro-cracking, fiber-matrix debonding, …

Investigating The Feedstock Properties And Process Conditions Influencing The Characteristics Of Products Generated From The Hydrothermal Carbonization Of Organic Feedstocks, Liang Li

Theses and Dissertations

Hydrothermal carbonization (HTC) is a novel environmentally beneficial thermal conversion process for the transformation of organic feedstocks to value-added products. However, little is known about the role of feedstock properties and/or process conditions during carbonization. This study was conducted to determine the parameters most influential during the HTC of organic feedstocks. Experiments and statistical analyses were conducted to: (1) determine the effect of specific feedstocks, feedstock interactions, and process conditions on carbonization product characteristics; (2) understand how initial liquid characteristics influence product characteristics and evaluate the significance of these initial liquid characteristics in predicting product characteristics; and (3) develop statistical …

Fault Protection In Dc Microgrids Based On Autonomous Operation Of All Components, Qiu Deng

Theses and Dissertations

DC power distribution systems (or so called DC microgrids) are of wide interest for various power applications due to their advantages over traditional AC power distribution systems with respect to power density and power distribution efficiency. On the other hand, short-circuit faults present formidable hazards in these systems. It is difficult to extinguish these arc faults via conventional circuit breakers due to the lack of natural zero-crossing of DC current. Also the DC breakers are usually more bulky and costly. Today, fault protection in these systems – to the extent that it exists – relies on over-current time-out limits in …

Structural, Interfacial, And Electrochemical Properties Of Pr2nio4+Δ – Based Electrodes For Solid Oxide Fuel Cells, Emir Dogdibegovic

Theses and Dissertations

Currently, the electrochemical performance and performance durability of solid oxide fuel cells (SOFCs) are limited by cathode materials. The high polarization resistance and phase instability of the cathode are two major challenges to hinder the commercialization of SOFC systems. Two families of oxides are presently known as potential cathode materials for SOFCs: (1) the perovskite family of oxides with a general formula of ABO₃, and (2) the Ruddlesden-Popper (RP) family of oxides (e.g. nickelates) with a general formula of A₂BO₄. The electron-hole conduction in these materials occurs simultaneously with oxygen ion conduction based on …

Three Segment Adaptive Power Electronic Compensator For Non-Periodic Currents, Amin Ghaderi

Theses and Dissertations

In this dissertation, a new technique is proposed for the compensation of nonperiodic load current. The method provides control references for three co-located devices, each corresponding to one moving calculation window and one decomposed part of the compensated current. They are slow compensator with high power rating, large calculation window, and low switching frequency; fast compensator with lower power rating, shorter calculation window, and higher switching frequency; and the reactive compensator which is an ordinary static VAR compensator (SVC). To improve the flexibility of the technique, a fuzzy based adaptive window is proposed for the slow compensator to find the …

Wideband Low Side Lobe Aperture Coupled Patch Phased Array Antennas, Dhruva Poduval

Theses and Dissertations

Low profile printed antenna arrays with wide bandwidth, high gain, and low Side Lobe Level (SLL) are in great demand for current and future commercial and military communication systems and radar. Aperture coupled patch antennas have been proposed to obtain wide impedance bandwidths in the past. Aperture coupling is preferred particularly for phased arrays because of their advantage of integration to other active devices and circuits, e.g. phase shifters, power amplifiers, low noise amplifiers, mixers etc. However, when designing such arrays, the interplay between array performance characteristics, such as gain, side lobe level, back lobe level, mutual coupling etc. must …

An Application Of Dempster-Shafer Fusion Theory To Lithium-Ion Battery Prognostics And Health Management, John Weddington

Theses and Dissertations

Prognostics and Health Management (PHM) is the discipline involving diagnostics and prognostics of components or systems, with the primary objective of increasing the overall reliability and safety of these components or systems. PHM systems convert raw sensor data into features, and utilize state observers to estimate the current damage state online. Popular state observers are the traditional Kalman filter, along with its non-linear extensions, and the particle filter. Each technique has differing advantages. This thesis investigates the fusion of results from different techniques in order to achieve a more trustworthy probability of detection (PoD) during diagnosis and a more reliable …

Growth And Characterization Of Anisotropic Gase Semiconductor For Radiation Detection And Thz Applications, Haseeb Nazir

Theses and Dissertations

Anisotropic wide-bandgap gallium selenide (GaSe) crystals were grown using high purity (7N) Ga and zone refined (ZR) Se precursor materials. The crystal growth was performed using a modified vertical Bridgman method (VBM) with a slow crystallization from the melt and with a pre-determined temperature profile. The structure, surface morphology, and the composition of the grown crystals were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive analysis by x-rays (EDAX), respectively. Optical absorption and transmission properties were characterized and optical bandgap was determined. Electrical resistivity has been determined using current-voltage (I V) measurements using van der Pauw …

Computational All Atom Energy Density Landscape Mappings Of Intra-Protein Interactions From Static And Dynamic Ensemble Structure Data, Oscar H. Bastidas

Theses and Dissertations

Understanding the energetic and dynamic behavior of natural protein fluctuations is critical to elucidating important information associated with a multitude of protein functions including signaling processes, enzyme behavior, aggregation pathways etc... This information is also critically important in the development of novel and effective strategies aimed at target proteins associated with pathologies and disease. In order to obtain such useful information, tools and techniques are lacking that: 1) permit the efficient quantitative analysis of fluctuation behavior of existing protein structure ensembles and 2) permit computationally generated natural fluctuation states of proteins at relatively large timescales demanded by the need for …

Development Of Novel Catalysts For Air Pollution Control, Chao Wang

Theses and Dissertations

The development of economy strongly related with increased consumption of fossil fuels, which causes severe air pollution issue. With more and more strict environmental regulations implemented all over the world, robust and efficient emission control technologies need to be innovated and applied to overcome the pollution challenge. This dissertation focuses on utilizing heterogeneous catalysis to eliminate carbon monoxide (CO), hydrocarbons (CH_x) and nitric oxides (NO_x) emissions produced from fossil fuel combustion.

The first type of catalyst is Pd supported on Mn-Ce solid solution. It achieves 100% CO conversion at room temperature. The high activity is attributed …