Engineering Commons^™

Understanding The Influence Of Interfacial Chemistry In Core, Core/Shell And Core/Shell/Shell Quantum Dots On Their Fluorescence Properties, Omondi Bernard Omogo

Graduate Theses and Dissertations

Colloidal semiconductor nanocrystals (quantum dots) have received a great deal of attention due to their superior size tunable properties and promising applications in many areas. Some of the most practical areas of their applications include light emitting diodes (LED), photovoltaic and biological studies. Synthetic methods of these crystals is becoming more established with new strategies being reported every now and then. However, quantitative studies connecting the processes at the interface, namely core-ligand, core-shell and shell-shells, to the overall quantum dots fluorescence properties are not well understood. Specifically for cores, relating surface-atoms interactions, solvents, ligands nature, density and functional groups on …

Improved Oxidative Stability In Biodiesel Via Commercially-Viable Processing Strategies, Gregory Lepak

All Theses

Biodiesel made from waste cooking oil (WCO) frequently requires antioxidants to meet oxidation stability specifications set forth in ASTM D6751 or EN 14214. In contrast, unrefined cottonseed oil (CSO), containing tocopherols and high concentrations of gossypol, a toxic polyphenolic antioxidant, is unique for biodiesel processing because it produces biodiesel resulting in higher oxidation stability. During biodiesel production, however, only a portion of these endogenous natural antioxidants are suspected to be retained. Because the economics of biodiesel manufacturing rely upon inexpensive sources of triglycerides, emphasis was placed upon developing improved alternative commercially-viable processing strategies where WCO is the main source of …

Nonlinear Processes In Multi-Mode Optical Fibers, Hamed Pourbeyram Kaleibar

Theses and Dissertations

Nonlinear processes in optical fibers can affect data transmission and power carried by

optical fibers and can limit the bandwidth and the capacity of optical communications.

On the other hand nonlinear phenomena could be utilized to build in-fiber all-optical

light sources and amplifiers. In this thesis new peaks inside an optical fiber have been

generated using nonlinear processes. An intense green pump laser has been launched

into a short fiber and specific modes have been excited to generate two new peaks in

red and blue wavelengths, where two pump photons are annihilated to create two new

photons in red and …

Improved Mixed-Integer Models Of A Two-Dimensional Cutting Stock Problem, William Lassiter

All Theses

This paper is concerned with a family of two-dimensional cutting stock problems that seeks to cut rectangular regions from a finite collection of sheets in such a manner that the minimum number of sheets is used. A fixed number of rectangles are to be cut, with each rectangle having a known length and width. All sheets are rectangular, and have the same dimension. We review two known mixed-integer mathematical formulations, and then provide new representations that both economize on the number of discrete variables and tighten the continuous relaxations. A key consideration that arises repeatedly in all models is the …

Economic, Energy And Ghg Emissions Performance Evaluation Of A Whispergen Mk Iv Stirling Engine Μ-Chp Unit In A Domestic Dwelling, Gerry Conroy, Aidan Duffy, Lacour Ayompe

Articles

This paper presents an assessment of the energy, economic and greenhouse gas emissions performances of a WhisperGen Mk IV Stirling engine μ-CHP unit for use in a conventional house in the Republic of Ireland. The energy performance data used in this study was obtained from a field trial carried out in Belfast, Northern Ireland during the period June 2004 - July 2005 by Northern Ireland Electricity and Phoenix Gas working in collaboration with Whispertech UK. A comparative performance analysis between the µ-CHP unit and a condensing gas boiler revealed that the µ-CHP unit resulted in an annual cost saving of …

Selection Of The Process Parameters For The Mass Plating Of Discrete Electronic Components, Ann Hopper

Articles

The miniaturisation of electronic components coupled with requirements for high temperature lead free soldering has forced the improvement of the termination finish of surface mount components to meet the critical demands of the electronic industry. In the present work the processing parameters necessary to plate miniature multilayer varistors (MLV’s) have been explored. The tooling selected was a “Rotary flow-thru’ plater” which achieved high volume plating with

The Construction And Characterization Of A Magneto-Optical Trap For Rubidium-87 And Electromagnetically-Induced Transparency In Rubidium-87 In A Vapor Cell, Yu Liu

Honors College Theses

Recent years have observed fast developments in neutral atomic vapor based quantum information storage technology. The technique utilizes light fields in the optical wavelength region as signal carrier and retriever and neutral atomic systems (e.g. single atoms, ensembles of atoms, atom-like defects in solids) as storage media. Photons are robust carriers of information due to their high velocity (c = 2.998 x 10⁸ m/s) and ease of transportation (they propagate rectilinearly with low loss). Their high mobility, however, makes it a challenging task to spatially localize and therefore store them. Atoms (or atom-like systems), on the other hand, can …

A Spatial Analysis Of Streambank Heterogeneity And Its Contribution To Bank Stability, Paul Vanterpool Simmons

Masters Theses

Streambank erosion is a function of fluvial detachment and geotechnical failure mechanisms working in combination to cause bank retreat. It is generally agreed that bank stability is dependent on both types of erosion; however, few studies have attempted to correlate the driving and resisting forces between the two. It has been proposed that: (1) streambanks possess a spatial structure and dependence of non-erodible resistant structures such as root masses and rocks; (2) streambanks naturally “armor” themselves from fluvial erosion with a combination of hard points and resistive soil; and (3) the stability of the streambank can be predicted by the …

Algae: Opportunities For Biomass Feedstock Production, Wastewater Treatment And Educational Outreach, Trina Cassandra Halfhide

USF Tampa Graduate Theses and Dissertations

Algae are a diverse group of simple organisms that lack roots, stems or leaves and are able to use sunlight, carbon dioxide, and nutrients to produce complex compounds, such as carbohydrates, proteins and lipids. These compounds, especially lipids, are highly sought-after by agricultural, nutraceutical and energy interests. Although there is great potential for algae derived biofuels, there are technical and economic challenges associated with their cultivation. Relevant to this dissertation, the environmental impacts associated with algae cultivation can be reduced by using municipal and agricultural wastewaters as a water and nutrient source. This research was divided into three sections to …

Assessing The Impacts Of Unrestricted Pesticide Use In Small-Scale Agriculture On Water Quality And Associated Human Health And Ecological Implications In An Indigenous Village In Rural Panam[Aacute], Sarah Louise Watson

USF Tampa Graduate Theses and Dissertations

In 2014, the global pesticide industry's projected worth is $52 billion and by 2020, the developing world will make up one-third of the world's chemical production and consumption. Pesticides can have unintended negative consequences for human health and the environment, especially in the developing world where regulations are loose or nonexistent. One country with unrestricted use of pesticides is Panam[aacute], especially in Santa Rosa de Cucunatí. In this indigenous village, small-scale farmers and ranchers spray paraquat, glyphosate, picloram, and 2,4-D at higher elevations than the spring water source of a gravity-fed water system, the river, and the village. The objective …

Drinking Water In The Developing World: Sources Of Fecal Contamination In Pitcher Pump Systems And Measurement Alternatives, Meghan Wahlstrom

USF Tampa Graduate Theses and Dissertations

It has been reported that globally we have achieved Millennium Development Goal (MDG) Target 7C, to halve the proportion of the population without access to safe drinking water; however, there is a major flaw with this statement. While Target 7C calls for access to `safe' drinking water, what is actually being measured and reported is access to an `improved' water source. The World Health Organization (WHO) maintains that they must use this proxy measure because the methods for water quality testing are too expensive and logistically complicated, but by doing so, they may be over reporting safe water coverage.

This …

Sensitivity Analysis Of A Leaf Photosynthesis-Stomatal Resistance Model, Gabriel A. Garcia

Chancellor’s Honors Program Projects

No abstract provided.

Observability In Traffic Modeling: Eulerian And Lagrangian Coordinates, Sergio Contreras

UNLV Theses, Dissertations, Professional Papers, and Capstones

Traditionally, one of the ways traffic flow has been studied is by using the kinematic wave model. This model is studied in the Eulerian framework. Recently, the kinematic wave model has been transformed into Lagrangian coordinates. This model of traffic flow together with the concept of observability for linear time invariant discrete time systems is applied to study the observability of four sections of a freeway in both Eulerian and Lagrangian coordinates. A system with densities in four sections of a freeway is designed, and the observability of the system is studied with different situations for sensors. When the system …

Post-Occupancy Energy Efficiency Evaluation Of A Leed Platinum Federal Government Facility, Theresa Tincher

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this study was to gain a comprehensive understanding of the Leadership in Energy and Environmental Design (LEED®) certification system and its relevance to Federal policies, building codes, and building standards, develop experience with whole building energy modeling, and determine the actual post-occupancy energy usage as compared with developed model and design projections. This thesis hypothesized the U.S. Green Building Council's LEED rating system compared favorably to other policies, codes, and standards in use at the time, and the U.S. Bureau of Reclamations' LEED Platinum Lower Colorado Regional Office Green Building (LCROGB), located in Boulder City, Nevada, operated …

Co-Emulation Of Scan-Chain Based Designs Utilizing Sce-Mi Infrastructure, Bill Jason Pidlaoan Tomas

UNLV Theses, Dissertations, Professional Papers, and Capstones

Simulation times of complex System-on-Chips (SoC) have grown exponentially as designs reach the multi-million ASIC gate range. Verification teams have adopted emulation as a prominent methodology, incorporating high-level testbenches and FPGA/ASIC hardware for system-level testing (SLT). In addition to SLT, emulation enables software teams to incorporate software applications with cycle-accurate hardware early on in the design cycle. The Standard for Co-Emulation Modeling Interface (SCE-MI) developed by the Accelera Initiative, is a widely used communication protocol for emulation which has been accepted by major electronic design automation (EDA) companies.

Scan-chain is a design-for-test (DFT) methodology used for testing digital circuits. To …

A Novel, Tag-Based File-System, Aaron Laursen

Mathematics, Statistics, and Computer Science Honors Projects

For decades, computer use has largely focused on managing and manipulating files-- creating and consuming media, browsing the web, software development, and even, with such systems as UNIX and Plan$9$, direct device access can largely be reduced to locating, creating, reading, and writing files. To facilitate these operations, developers have created a vast assortment of file-systems, each presenting a unique framework underlying nearly everything people do with a computer.

For various reasons, these file-systems have historically represented only incremental improvements and alterations from their predecessors, leaving the basic design and interaction models relatively unchanged. Because of this, most common file-systems …

Time Correlated Measurements Using Plastic Scintillators With Neutron-Photon Pulse Shape Discrimination, Norman Edison Richardson

UNLV Theses, Dissertations, Professional Papers, and Capstones

Since the beginning of the nuclear age, there has been a strong demand for the development of efficient technologies for the detection of ionizing radiation. According to the United States' Department of Energy, the accurate assessment of fissile materials is essential in achieving the nonproliferation goals of enhancing safety and security of nuclear fuel cycle and nuclear energy facilities [1]. Nuclear materials can be characterized by the measurement of prompt and delayed neutrons and gamma rays emitted in spontaneous or induced fission reactions [2] and neutrons emitted in fission reactions are the distinctive signatures of nuclear materials. Today, the most …

A Quantitative Analysis Of Decision Process In Social Groups Using Human Trajectories, Truc Viet Le, Siyuan Liu, Hoong Chuin Lau, Ramayya Krishnan

Research Collection School Of Computing and Information Systems

A group's collective action is an outcome of the group's decision-making process, which may be reached by either averaging of the individual preferences or following the choices of certain members in the group. Our problem here is to decide which decision process the group has adopted given the data of the collective actions. We propose a generic statistical framework to infer the group's decision process from the spatio-temporal data of group trajectories, where each "trajectory" is a sequence of group actions. This is achieved by systematically comparing each agent type's influence on the group actions based on an array of …

On Understanding Diffusion Dynamics Of Patrons At A Theme Park, Jiali Du, Akshat Kumar, Pradeep Reddy Varakantham

Research Collection School Of Computing and Information Systems

In this work, we focus on the novel application of learning the diffusion dynamics of visitors among attractions at a large theme park using only aggregate information about waiting times at attractions. Main contributions include formulating optimisation models to compute diffusion dynamics. We also developed algorithm capable of dealing with noise in the data to populate parameters in the optimization model. We validated our approach using cross validation on a real theme park data set. Our approach provides an accuracy of about 80$% for popular attractions, providing solid empirical support for our diffusion models.

Decentralized Multi-Agent Reinforcement Learning In Average-Reward Dynamic Dcops, Duc Thien Nguyen, William Yeoh, Hoong Chuin Lau, Shlomo Zilberstein

Research Collection School Of Computing and Information Systems

Researchers have introduced the Dynamic Distributed Constraint Optimization Problem (Dynamic DCOP) formulation to model dynamically changing multi-agent coordination problems, where a dynamic DCOP is a sequence of (static canonical) DCOPs, each partially different from the DCOP preceding it. Existing work typically assumes that the problem in each time step is decoupled from the problems in other time steps, which might not hold in some applications. Therefore, in this paper, we make the following contributions: (i) We introduce a new model, called Markovian Dynamic DCOPs (MD-DCOPs), where the DCOP in the next time step is a function of the value assignments …

Finite Difference Modeling Of Surface-~Wave Scattering For Shallow Cavity Detection, Heston Travis Norcott

UNLV Theses, Dissertations, Professional Papers, and Capstones

Data collection and analysis of scattering of Rayleigh-type surface waves are investigated for locating shallowly buried cavities. Surface-based seismic experiments conducted by others at the University of Nevada, Las Vegas (UNLV) Engineering Geophysics Test Site (EGTS) demonstrate scattering of Rayleigh waves caused by buried empty barrels (essentially air-filled cavities). The interpretation of the data is complicated by factors such as the presence of a high-velocity geologic layer just below the cavity.

This research uses a finite-difference seismic wave propagation code to compute time histories for a model that represents the Engineering Geophysics Test Site. By adding cavities to a background …

Probability Distributions And Threshold Selection For Monte Carlo–Type Tropical Cyclone Wind Speed Forecasts, Steven M. Lazarus, Michael E. Splitt, Sarah Collins, Denis N. Botambekov, William P. Roeder

Aeronautics Faculty Publications

Probabilistic wind speed forecasts for tropical cyclones from Monte Carlo–type simulations are assessed within a theoretical framework for a simple unbiased Gaussian system that is based on feature size and location error that mimic tropical cyclone wind fields. Aspects of the wind speed probability data distribution, including maximumexpected probability and forecast skill, are assessed. Wind speed probability distributions are shown to be well approximated by a bounded power-law distribution when the feature size is smaller than the location error and tends toward a U-shaped distribution as the location error becomes small. Forecast skill (i.e., true and Heidke skill scores) is …

Preparation Of Pt/H-Tio2 Catalyst With Improved Catalytic Performance For Methanol Electrooxidation, Jin Han, Zhi-You Zhou, Qiang Wang, Miao-Qiang Lv, Chi Chen, Shi-Gang Sun

Journal of Electrochemistry

White TiO₂ nanorods were synthesized by hydrothermal method with TiCl4 as a precursor. As-synthesized TiO₂ nanorods were further subjected to high-temperature (550 ^oC) heat treatment for 2 h under H2 atmosphere to prepare gray black hydrogen-treated TiO₂ (H-TiO₂) nanorods with oxygen vacancies and Ti³⁺ interstitial atoms. The Pt nanoparticles of 1.9 nm were supported on these two types of TiO₂ nanorods to form Pt/TiO2 and Pt/H-TiO₂ catalysts. XRD data indicates that the crystal structure of TiO₂ was still reserved as rutile after hydrogen treatment, but the surface was covered by …

Electro-Catalytic Oxidation Of Hydrogen Peroxide On Au/ L-Methionine /Gc Electrode, Jian-Feng Fan, Xue-Mei Luo, Jing Li, Lou-Zhen Fan

Journal of Electrochemistry

The modified electrodes have been fabricated by generation of Au nanoparticle chains, which was produced by reaction between HAuCl4 and sodium citrate without any additional capping agents or surfactants. The self-assembled Au nanoparticles were attached to the surface of glassy carbon electrode (GCE) layer by layer, using L-methionine (L-Met), thiourea (TU), allyl thiourea (ATU) and polyvinylpyrrolidone (PVP) as a crosslinking agent, respectively. The experimental results showed that the electrochemical performance of the different modified electrodes varied in [Fe(CN)₆]^3-/4- solution. The Au/L-Met/GCE exhibited an excellent electrochemical property, which is superior to other modified electrodes. In addition, the catalysis …

Synthesis Of Platinum Nanocrystallites And Possible Electrocatalytic Properties For Methanol, Lei-Lei Lu, Bao-Zhong Du, Sha Sun, Jin-Fen Niu, Jie Zhao

Journal of Electrochemistry

Platinum nanocrystallites were synthesized by the colloidal method using oxamide as the stabilizer. The morphologies and electrocatalytic performances for methanol of platinum nanocrystallites prepared at different pH values and with different reactant ratios of precursor and stabilizer were investigated. It was found that the platinum nanocrystallites synthesized at pH=5 and with the reactant ratio of 1:20 showed the best electrocatalytic activity for methanol. The peak current density reached up to 1709 μA·cm^-2. Furthermore, the electrocatalytic activity of platinum nanocrystallites for methanol reduced significantly although the cyclic voltammograms in the blank solution were not obviously changed after exposing in …

Preparation And Electrochemical Performances Of Cofe2O4/Gns Nanocomposites As Anode Material For Lithium Ion Battery, Mo-Chao Cai, Sen-Rong Cai, Ming-Sen Zheng, Quan-Feng Dong

Journal of Electrochemistry

The CoFe₂O₄/GNS was synthesized by a simple one-pot solvothermal method. The results obtained by X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the CoFe₂O₄ particles with sizes of 15 nm dispersed on the surface of graphene uniformly. Electrochemical tests indicated that the CoFe₂O₄/GNS nanocomposite exhibited excellent cyclic stability with almost 95.8% capacity retention after 100 cycles at the current density of 500 mA·g^-1 and delivered a high reversible capacity of 482 mAh·g^-1 at the current density of 2 A·g^-1.

Effects Of Carbon Interlayer On Electrochemical Performance Of Lithium-Sulfur Cell, Jin-Peng Yu, Ming Zhang, Fei Ding, Zhi-Yuan Tang, Xing-Jiang Liu

Journal of Electrochemistry

Three kinds of conductive carbon films were prepared with Super-P (SP), KB and MWCNTs, and then the as-prepared carbon films were applied as an interlayer between a sulfur electrode and a separator for constructing a coin-type lithium-sulfur (Li-S) cell, respectively. The assessment results show that all the cells delivered the reversible capacities higher than 800 mAh·g^-1 after 40 cycles when the sulfur loading was up to 80% (by mass) in the sulfur electrode. Due to significant differences of physical properties among the carbon materials，the cell with a KB interlayer exhibited higher electrochemical polarization; the cycling performance of the cell …

Effect Of Temperature On The Self-Humidifying Open-Cathode Proton Exchange Membrane Fuel Cell, Si-Chen Zhao, Ben Wang, Qiu-Hong Jia, Ming Han, Yu-Hong Xie

Journal of Electrochemistry

Based on the experiments about the output characteristics of a home-made temperature-controlled PEMFC system with atmospheric pressure and no external humidifying condition in different loading voltages and operating temperatures, the optimum operating temperature at different loading voltages can be obtained by tracking the output characteristics of PEMFC operating over a range of temperatures. By analyzing the fitted data the kinetic parameters are evaluated and the effect of different operating temperatures on the PEMFC performance is discussed from a view of electrode kinetics.

In Situ Detection On Electrochemical Chloride Removal Of Reinforcement In Concrete By Combined Ph/Cl- Probes, Jing-Jing Wang, Shi-Gang Dong, Xiao-Juan Zhang, Hong-Wei Lv, Yun-Chang Wu, Rong-Gui Du, Chang-Jian Lin

Journal of Electrochemistry

In this work, the concrete samples polluted by chloride ion were electrochemically treated using galvanostatic technique, and the distributions of chloride ion concentration and pH value in the polluted concretes were in-situ monitored by embedding a combined pH/Cl^- probe during the electrochemical chloride removal. The corrosion behaviors of reinforcing steel in the concrete were simultaneously studied by using linear polarization and electrochemical impedance spectroscopy techniques (EIS). The micro environment of the concrete and corrosion rate of steel were explored during the electrochemical chloride removal. It was indicated that the Cl^- concentration in the concrete pore solution decreased with …

Effect Of Al-Doping In Li-Rich Material Li1.2Mn0.543Co0.078Ni0.155Al0.030O2 For Lithium-Ion Batteries, Xiao-Xi Jin, Yi-Xiao Li, Yong Yang, Zhou-Cheng Wang

Journal of Electrochemistry

The Al-doped 0.5Li₂MnO₃·0.5Li(Mn_0.4Co_0.2Ni_0.4)O₂ compounds were successfully synthesized as cathode materials for lithium-ion batteries. The pristine and Al-doped materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and laser Raman spectroscopy. The results indicated that all the prepared materials were indexed as a hexagonal structure with R-3m space group, and Al element had been introduced into lattice. When cycled at 180 mA·g^-1 (1 C-rate), the capacity retention of 4% (by mole) Al-doped 0.5Li₂MnO₃·0.5Li(Mn_0.4Co_0.2Ni …