Physical Sciences and Mathematics Commons^™

Characterization Of Iron Oxide Thin Films For Photoelectrochemical Hydrogen Production, Kyle Eustace Nelson George

UNLV Theses, Dissertations, Professional Papers, and Capstones

Solar energy is the most sustainable source of energy available. However, solar applications such as photovoltaic cells represent only a partial solution to weaning our dependence upon fossil fuels. Several methods of storing solar energy are currently being pursued, and chemical storage stands out as a promising option - combining design simplicity with high energy density, with hydrogen being particularly attractive because of its abundance and inherently clean nature. A monolithic Photoelectrochemical (PEC) device that produces hydrogen by electrolyzing water directly from sunlight has the benefit of utilizing "free" solar energy to drive the reaction.

Although α-Fe 2 O 3 …

Parametric Study Of Efficiency Measures For Home Energy Conservation In Las Vegas, Nevada, Todd M. France

UNLV Theses, Dissertations, Professional Papers, and Capstones

Pulte Homes, a production home builder and community developer partnering with the U.S. Department of Energy's Building America program, has collaborated with the Center for Energy Research at the University of Nevada, Las Vegas and NV Energy, the local electric utility, on an energy conservation project in the Las Vegas Valley.

This study entails four model homes at a new development in the Summerlin community of Las Vegas, Nevada, named Villa Trieste. The home models, ranging in floor plan area from 1,487 to 1,777 square feet, have been constructed under the Environments for Living program and are LEED (Leadership in …

Optimization Of Solid Oxide Fuel Cell Interconnect Design, Krishna C. Pulagam

UNLV Theses, Dissertations, Professional Papers, and Capstones

Performance of solid oxide fuel cells (SOFC) is dependent of a set of complex physical and chemical processes occurring simultaneously. Interconnect for SOFC is important as it provides electrical connection between anode of one individual cell to the cathode of neighboring one. It also acts as a physical barrier to protect the air electrode material from the reducing environment of the fuel on the fuel electrode side, and it equally prevents the fuel electrode material from contacting with oxidizing atmosphere of the oxidant electrode side. A three-dimensional numerical model has been developed to evaluate the SOFC including the current collector, …

An Evaluation Of Lead Hazards In Pre-1978 Residental Housing Within Clark County, Nevada, Usa, Erika Raquel Torres

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lead poisoning remains a public health concern due to leads persistence in the environment from anthropogenic uses. Initial efforts to address the impacts of lead on vulnerable communities have included secondary prevention measures which typically occur after a child has been poisoned. However, in recent years there has been a pragmatic shift toward primary prevention efforts.

This study evaluates lead hazards identified through primary prevention activities in residential housing within Clark County, Nevada, USA. It is the first study to systematically address and evaluate pre-1978 housing in Southern Nevada. Risk assessments were conducted in 81 dwellings built prior to 1979 …

Empirically Derived Formulas To Predict Indoor Maximum, Average, And Minimum Temperatures In Roofpond Buildings Using Minimum Climatic Information, Ibrahim Kivarkis Kako

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis introduces an empirically developed formula to predict the comfort conditions and thermal performance of a Skytherm(TM) Southwest Roofpond placed over a light-weight un-insulated structure built at the School of Architecture at the University of Nevada, Las Vegas.

The predictive formula introduced in this study may be used in different parts of the world (particularly developing nations where insulation and air-conditioning are rarely used) to predict the performance of a Skytherm(TM) Southwest Roofpond using minimal climate data.

The data collected in the experimental setup at the Natural Energies Advanced Technologies Laboratory included outside and inside temperatures of various surfaces …

Mineralogy And Micromorphology Of An Atacama Desert Soil, Chile: A Model For Hyperarid Pedogenesis, Michael S. Howell

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Atacama Desert is the oldest and driest desert on Earth. Hyperarid soils in this desert are dominated by rare (or exclusive) salt minerals and assemblages. Previous research details salt origins and abundance, however pedogenic processes involved in salt distribution are not adequately explained. Therefore, the main goal of this investigation was to identify and document evidence for hyperarid pedogenesis (via salt mineralogy and soil micromorphology) at a field site, Oficina Ercilla, located ~80 km northeast of Antofagasta, Chile within the Central Depression and hyperarid core of the Atacama Desert. This study presents an interpretational model for hyperarid pedogenesis, which …

Analytical Method Development For Determination Of Volatile Organic Compounds In Calcareous Desert Soil, Mary F. Turner

UNLV Theses, Dissertations, Professional Papers, and Capstones

Soil sample preservation for volatile organic compound analysis generally requires short sample holding times or preservation of the sample's chemical constituents with sodium bisulfate (NaHSO 4 ). Calcareous soils cannot be preserved using NaHSO4 because effervescence will promote the loss of analytes, and short holding times before analysis are not practical for remote sampling locations. An experimental approach was developed for determination of volatile organic compounds (VOCs) in soil that utilizes solid sorbents for sample preservation and solid-phase microextraction (SPME) sample preparation technique coupled with gas chromatography/mass spectrometry (GC/MS) for analysis. Solid sorbents are used to sequester readily extractable (vapor …

Sequence And Chemostratigraphic Study Across The Basal Eureka Quartzite Unconformity In The Great Basin, Nevada: Implications For The Origin Of The Late Ordovician Carbon Isotope Excursion, Apostolos Paul Kosmidis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The positive carbon isotope (δ 13 C) excursion from the late Middle Ordovician Copenhagen Formation that underlies the Eureka Quartzite in central Nevada has been hypothesized to record a global cooling event ∼10 Myr prior to the well-recognized Late Ordovician Hirnantian glaciation (∼443 Ma). However, direct evidence for pre-Hirnantian continental glaciation remains scarce, raising uncertainties in the relationship between the inferred eustatic sea-level fall and the origin of the positive δ 13 C excursion. Additionally, previous stratigraphic studies from southern Nevada and California suggest relative sea-level fall in excess of ∼ 150 meters, which exceeds estimates for younger glacial periods …

Efficient Clustering Techniques For Managing Large Datasets, Vasanth Nemala

UNLV Theses, Dissertations, Professional Papers, and Capstones

The result set produced by a search engine in response to the user query is very large. It is typically the responsibility of the user to browse the result set to identify relevant documents. Many tools have been developed to assist the user to identify the most relevant documents. One such a tool is clustering technique. In this method, the closely related documents are grouped based on their contents. Hence if a document turns out to be relevant, so are the rest of the documents in the cluster. So it would be easy for a user to sift through the …

In Situ Element Quantification In The Hydrothermal Diamond Anvil Cell Using Synchrotron X-Ray Fluorescence With Applications Toward Subduction Zone Processes, Steven Joseph Maglio

UNLV Theses, Dissertations, Professional Papers, and Capstones

Yttrium is used in geochemical investigations of arc volcanics and metamorphic geothermometers. The ability to use Y as a geochemical tool is predicated on an understanding of the mobility of Y during fluid-saturated conditions attending metamorphic and igneous processes. The goal of this work was to use the hydrothermal diamond anvil cell (HDAC) and synchrotron radiation X-ray fluorescence to quantify, in situ, the concentration of Y in aqueous fluids at 2-5 GPa and 650 - 800 °C; conditions likely at the oceanic lithosphere - mantle wedge interface in subduction zones. Previous studies have used modified diamond anvils which limits their …

Experimental And Numerical Study Of A Proton Exchange Membrane Electrolyzer For Hydrogen Production, Sachin S. Deshmukh

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hydrogen as a fuel source has received attention from researchers globally due to its potential to replace fossil based fuels for energy production. Research is being performed on hydrogen production, storage and utilization methods to make its use economically feasible relative to current energy sources. The PEM electrolyzer is used to produce hydrogen and oxygen using water and electricity. Focus of our study is to provide a benchmark experiment and numerical model of a single cell electrolyzer that can assist in improving the current state of understanding of this system. Parametric analysis of an experimental cell was performed to understand …

Geoelectrical Response Of Surfactant Solutions In A Quartzitic Sand Analog Aquifer, Meghan Therese Magill

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this project, the resistivity and phase shift of ten surfactant aqueous solutions in a sand matrix were measured using spectral induced polarization (SIP). In addition, specific conductivity, pH, dissolved oxygen, and dielectric constant measurements of the solutions were also evaluated. The frequency range assessed was 0.091-12000Hz. The surfactants, which are typically used in the remediation of tetrachloroethylene, were Aerosol MA 80-I, Dowfax 8390, and Steol CS-330. The surfactants were mixed into solutions of both deionized and tap water at varying concentrations and injected into a closed system of silica sand. The surfactant treatments altered resistivity, specific conductivity, and pH …

Provenance Of The Miocene-Pliocene Muddy Creek Formation Near Mesquite, Nevada, Steven Wayne Forrester

UNLV Theses, Dissertations, Professional Papers, and Capstones

The provenance, stratigraphy, and depositional history of the Miocene-Pliocene Muddy Creek Formation (MCF) in southern Nevada are poorly studied and poorly constrained. Previous studies of the MCF have concluded that the formation consists of lacustrine, eolian, and fluvial deposits. Currently the age of deposition is loosely constrained between 8.5 and 4.1 Ma. This study documents the evolution of one portion of the eastern extent of the MCF and determines its provenance and depositional history at Flat Top and Mormon Mesas in Nevada; and near Beaver Dam and Littlefield, Arizona.

This study intended to determine whether the MCF was deposited by …

Optimization Of The Microprecipitation Procedure For Nuclear Forensics Applications, Lyndsey Renee Kelly

UNLV Theses, Dissertations, Professional Papers, and Capstones

Microprecipitation has become one of the most widely used sample preparation techniques for alpha spectroscopy. Many factors during the precipitation process can affect the yield and energy resolution by adding unwanted mass to the sample. Current applications in nuclear forensics call for an optimization of energy resolution and yield in order to improve identification and quantify specific radionuclides. The purpose of this research is to determine the optimal parameters used for microprecipitation. The optimal solution temperature, precipitation time, carrier amount, and hydrofluoric acid amount are used to investigate the influence of varying the type of carrier, as well as, the …

Statistical Inferences For Functions Of Parameters Of Several Pareto And Exponential Populations With Application In Data Traffic, Sumith Gunasekera

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this dissertation, we discuss the usability and applicability of three statistical inferential frameworks--namely, the Classical Method, which is sometimes referred to as the Conventional or the Frequentist Method, based on the approximate large sample approach, the Generalized Variable Method based on the exact generalized p -value approach, and the Bayesian Method based on prior densities--for solving existing problems in the area of parametric estimation. These inference procedures are discussed through Pareto and exponential distributions that are widely used to model positive random variables relevant to social, scientific, actuarial, insurance, finance, investments, banking, and many other types of observable phenomena. …

Bending Of Woody Riparian Vegetation As A Function Of Hydraulic Flow Conditions, John O. Goreham

UNLV Theses, Dissertations, Professional Papers, and Capstones

Vegetation encroachment reduces channel conveyance capacity below design objectives and greatly increases the risk for loss of life and property damage in the case of large flood events. Given minimal knowledge of hydraulic roughness for shrubs and woody vegetation, accurate estimation of channel capacity and water surface elevation is difficult. The ability to predict a tree's bent, reduced height in the presence of flow permits more accurate prediction of hydraulic roughness and water surface elevation.

In this study, field tests were performed to elucidate tree bending properties, which in turn served as input parameters for a numerical algorithm designed to …

Optimization Of Channel Geometry In A Proton Exchange Membrane (Pem) Fuel Cell, Jephanya Kasukurthi

UNLV Theses, Dissertations, Professional Papers, and Capstones

Bipolar plates are the important components of the PEM fuel cell. The flow distribution inside the bipolar plate should be uniform. Non-uniform flow distribution inside the bipolar leads to poor performance of the fuel cell and wastage of expensive catalyst. A single channel PEM fuel cell is taken and electrochemical analysis is carried out on it. The results are compared with the available published experimental data obtained by other research group, and they are found to be in good agreement. A baseline design of the bipolar plate is taken and numerical analysis is carried out. The results show that the …

Examining The Influence Of Restaurant Green Practices On Customer Return Intention, Audrey L. Szuchnicki

UNLV Theses, Dissertations, Professional Papers, and Capstones

In recent years there has been an increased awareness of how the actions of the foodservice industry are effecting the environment. With this awareness we have begun to see a change in priorities for both new and existing businesses. At the forefront of this change in the "green" direction is the GRA who certifies how eco-friendly an establishment is based on its' environmental guidelines. This study will examine the correlation between customer return intention and the institution of green practices within a restaurant setting. The expected outcome would be that a restaurant that is certified green or, implementing measures to …

Soil Moisture And Water Stage Estimation Using Precipitation Radar, Sumit Puri

UNLV Theses, Dissertations, Professional Papers, and Capstones

In south-western United States, soil moisture data is important for drought studies in the region which is experiencing a drought for many years, whereas in South Florida, water stage data is required by hydrologists to monitor the hydrological flow in wetlands. Soil moisture data and water stage data are not sufficiently available due to sparse monitoring stations. Installation of dense measuring stations over an extended area is costly and labor intensive. Therefore, there is a need to develop an alternative method of measuring soil moisture and water stage. Microwave remote sensing has proven to be a useful tool in the …

Substituent Effect On The Electronic And Assembling Properties Of Asymmetric Phenazine Derivatives, Bin Cao

UNLV Theses, Dissertations, Professional Papers, and Capstones

Currently, one-dimensional (1-D) nanostructures have drawn much interest because of their potential applications for nanoscale optoelectronic devices. Self-assembly (SA) based on π-conjugated systems through various intermolecular interactions has been widely used to produce 1-D nanostructure. Morphology of the assembled structures can be modified by incorporating substituents, which provide additional secondary interactions. Meanwhile, those substituents also influence the electronic properties of the molecules. Previous studies have made little effort to systematically study subsistent effects on both electronic and SA properties.

The primary objective of this research is to generate controllable 1-D structures through SA, and to provide a fundamental understanding of …

Water Use And Natural Limits In The Las Vegas Valley: A History Of The Southern Nevada Water Authority, Christian Harrison

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis examines the history of the Southern Nevada Water Authority (SNWA) and how it has helped transform various aspects of southern Nevada's economy and environment. Prior to the establishment of the SNWA in 1991 the Las Vegas Metropolitan Area (LVMA) possessed several competing water providers whose opposition to one another adversely affected the management of water in the region. These water providers recognized this problem, came together, and negotiated the creation of a regional water agency, the SNWA. This organization, comprised of representatives from each of the LVMA's water providers has the power to institute policy across municipal boundaries. …

Two-Tank Indirect Thermal Storage Designs For Solar Parabolic Trough Power Plants, Joseph E. Kopp

UNLV Theses, Dissertations, Professional Papers, and Capstones

The performance of a solar thermal parabolic trough plant with thermal storage is dependent upon the arrangement of the heat exchangers that ultimately transfer energy from the sun into steam. The steam is utilized in a traditional Rankine cycle power plant. The most commercially accepted thermal storage design is an indirect two-tank molten salt storage system where molten salt interacts with the solar field heat transfer fluid (HTF) through a heat exchanger. The molten salt remains in a closed loop with the HTF and the HTF is the heat source for steam generation. An alternate indirect two tank molten salt …

Effects Of Similarity Metrics On Document Clustering, Rushikesh Veni

UNLV Theses, Dissertations, Professional Papers, and Capstones

Document clustering or unsupervised document classification is an automated process of grouping documents with similar content. A typical technique uses a similarity function to compare documents. In the literature, many similarity functions such as dot product or cosine measures are proposed for the comparison operator.

For the thesis, we evaluate the effects a similarity function may have on clustering. We start by representing a document and a query, both as a vector of high-dimensional space corresponding to the keywords followed by using an appropriate distance measure in k-means to compute similarity between the document vector and the query vector to …

Systematic Analysis Of Identifying Key Dimensions Of Environmentally And Socially Responsible Hotels, Courtney Suess

UNLV Theses, Dissertations, Professional Papers, and Capstones

Development in Southeast Asia involves making good decisions for the future, so the idea that good planning can ignore sustainability is something of an oxymoron. Good development has to be sustainable and we have reached a point where the old ways of tourism development are intolerable. For example, hotels spring up without planning for the future. This short sightedness means natural endowments, like coastlines, erode and forests are cut down, chasing away the wildlife; or cultural history in the form of temples, historic buildings, and sacred places are destroyed. Ironically, tourism development is eradicating the very forms of product that …