Physical Sciences and Mathematics Commons^™

Web Based Recommender Systems And Rating Prediction, Tho Nguyen

Master's Projects

This project implements a recommender system on large dataset of Netflix’s movies. This project also tries to improve recommender systems by incorporating confidence interval and genres of movies. This new approach enhances the performance and quality of service of recommender systems and gives better result than Netflix commercial recommender system, Cinematch.

Hunting For Undetectable Metamorphic Viruses, Da Lin

Master's Projects

Commercial anti-virus scanners are generally signature based, that is, they scan for known patterns to determine whether a file is infected by a virus or not. To evade signature-based detection, virus writers have adopted code obfuscation techniques to create highly metamorphic computer viruses. Since metamorphic viruses change their appearance from generation to generation, signature-based scanners cannot detect all instances of such viruses. To combat metamorphic viruses, detection tools based on statistical analysis have been studied. A tool based on hidden Markov models (HMMs) was previously developed and the results are encouraging—it has been shown that metamorphic viruses created by a …

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. …

Controlled Functionalization Of Crystalline Polyolefins And Their Application In Soluble Polymer Support, Jihoon Shin

UNLV Theses, Dissertations, Professional Papers, and Capstones

Functionalization of polyolefins has been recognized as a useful methodology for the generation of new materials with a wide range of applications. Recently, crystalline or semi-crystalline polyolefins have drawn increasing attention in both industrial and academic fields as one of the most interesting engineering plastics, due to their remarkable physical and mechanical properties. This dissertation describes: (1) novel methods for the direct postfunctionalization of crystalline polyolefins to introduce functionality, (2) characterizations for the functionalized polymers to analyze their structures, molecular-weight properties, thermal properties, and hydrophilicity, and (3) an application of the modified crystalline polystyrene as a soluble polymer support for …

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 …

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. …

Zirconia-Magnesia Inert Matrix Fuel And Waste Form: Synthesis, Characterization And Chemical Performance In An Advanced Fuel Cycle, Kiel Steven Holliday

UNLV Theses, Dissertations, Professional Papers, and Capstones

There is a significant buildup in plutonium stockpiles throughout the world, because of spent nuclear fuel and the dismantling of weapons. The radiotoxicity of this material and proliferation risk has led to a desire for destroying excess plutonium. To do this effectively, it must be fissioned in a reactor as part of a uranium free fuel to eliminate the generation of more plutonium. This requires an inert matrix to volumetrically dilute the fissile plutonium. Zirconia-magnesia dual phase ceramic has been demonstrated to be a favorable material for this task. It is neutron transparent, zirconia is chemically robust, magnesia has good …

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 …

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 …

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 …

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 …

X-Ray Diffraction Study Of Dysprosium Single Crystal Samples In A Diamond Anvil Cell (Dac), Ognjen Grubor-Urosevic

UNLV Theses, Dissertations, Professional Papers, and Capstones

X-ray diffraction is the basis of crystallography, the study of the structure of crystals. It uses X-rays of a wavelength on the order of the size of atoms, so it can resolve the positions of individual atoms in a crystal. Illuminating the crystal with a well-collimated X-ray beam produces X-rays diffracted in a certain direction for a specific crystal orientation. By analyzing the relative phase of the incoming and outgoing scattered X-rays, the unique arrangements of atoms can be determined and the structure of the crystal can be solved.

There is a long standing controversy regarding the crystal structures and …

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 …

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 …

Evaluation Of Extraction Chromatography Resins For Rapid Actinide Analysis, Julie Marisa Gostic

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this work, physical and chemical parameters associated with extraction chromatography separation procedures were investigated for rapid actinide analysis. A vacuum box system was designed in-house and was characterized in terms of flow rate reproducibility, matrix effects on flow rate for sequential elution, and actinide separation efficiency using different types of resin (TEVA, DGA and TRU). Results indicated that the columnar kinetics of the resins were sufficiently rapid to run high purity samples through the unit over a wide range of flow rates for all resin types. Single matrix interferences at a metal ion ratio of 1:10 6 relative to …

Hierarchical Routing In Manets Using Simple Clustering, Adam Carnine

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis presents both a review of current MANET routing protocols and a new MANET routing algorithm. The routing protocols reviewed include representative samples from the three primary forms of routing found in MANETS: proactive routing, reactive routing and hybrid routing. Secure algorithms are given special treatment in the review. In addition several protocol enhancements are discussed.

The proposed routing protocol is designed to support networks of a medium size, containing over 200 nodes but less than 3,000 nodes. The design is intentionally simple to allow ease of implementation in comparison with other MANET protocols that provide similar functionality.

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, …

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 …

Study Of Corrosion Of Materials In The Sulfur-Iodine Hydrogen Production Cycle, Thao Trung Ho

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hydrogen is of great interest since the availability of traditional fossil fuels is in decline. Strictly speaking, hydrogen is not a primary source of energy but is an energy carrier, since energy typically must be used from another source (electricity, natural gas, coal, etc.) to produce it. Of hydrogen production techniques, the Sulfur-Iodine thermochemical water splitting process (S-I cycle), which was proposed by General Atomics (GA), is promising with its simplicity and high efficiency. Most of the chemicals are recycled except water. However, the S-I cycle operates in a harsh, corrosive environment in the presence of a mixture of iodine …

Ac Susceptibility And Heat Capacity Studies Of The Geometrically Frustrated Pyrochlores Terbium Titanium Tin Oxides And Holmium Titanates, Daniel Antonio

UNLV Theses, Dissertations, Professional Papers, and Capstones

Materials with a geometrically frustrated magnetic pyrochlore lattice have been of interest due to their unusual ground states. Tb 2 Ti 2 O 7 is known for having a spin liquid ground state which does not transition to a long-range ordered state down to at least 50 mK. Ho 2 Ti 2 O 7 has a macroscopically degenerate spin ice ground state which resembles that of the proton ordering in water ice. Heat Capacity measurements of Tb 2 Ti 2- x Sn x O 7 were done down to 0.36 K and AC magnetic susceptibility measurements of Ho 2- x …

High Pressure Phase Transistions In The Lanthanide Sesquioxides, Jason Patrick Mcclure

UNLV Theses, Dissertations, Professional Papers, and Capstones

Crystallizing into 5 known polymorphic forms, the rare-Earth sesquioxides RE 2 O 3 represent a family of 4-f electron compounds that have been the subject of study for many years. Aspects of the systematics in the structural phase transitions for RE 2 O 3 (RE=La, Sm, Eu, Gd, Y, Er, Yb, Lu) under pressure were studied using diamond anvil cells (DACs). As a part of this study, detailed equation of state (EOS) data for all these compounds were obtained through the use of angle-dispersive x-ray diffraction (XRD) where anomalies in compression data led to the detailed investigation into one particular …

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 …

Spectroscopic Investigation Of Palladium-Copper Bimetallic Systems For Pem Fuel Cell Catalysts, Timo Hofmann

UNLV Theses, Dissertations, Professional Papers, and Capstones

One of the main barriers to commercialization of polymer electrolyte membrane fuel cells systems is cost, which is largely due to the need of platinum (Pt)-containing catalysts. In this thesis we investigate bimetallic systems consisting of a base metal (copper) and a noble metal (palladium) that, as an alloy on the nanoscale, mimic the electronic properties that make Pt desirable as a catalyst.

We present a detailed investigation of the electronic structure of carbon-supported Pd/Cu nanoparticle catalysts, model bilayer thin film systems, alloys, and various metal reference samples. We have investigated the valence band structure of the catalysts using a …

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 …

Static High Pressure Ft-Ir Spectroscopic Studies Of Tatb, Brian F. Yulga

UNLV Theses, Dissertations, Professional Papers, and Capstones

Static high-pressure experiments utilizing diamond anvil cells (DACs) provide an alternative method to shockwave studies for extracting precise information on the physical and chemical properties of energetic materials. Due to mechanical restraints (e.g. small sample sizes and apertures), synchrotron radiation sources are ideal for probing the structure of materials at the molecular level. 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is an insensitive (tertiary) high explosive (iHE) useful in military applications. Compared to other conventional iHEs, it is a safer and more stable energetic material. Its unique properties cause it to be of interest in the energetic materials research community. A series of Fourier-transform infrared …

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 …

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 …

Interconnections Of Nonlinear Systems Driven By L₂-Itô Stochastic Processes, Luis A. Duffaut Espinosa

Electrical & Computer Engineering Theses & Dissertations

Fliess operators have been an object of study in connection with nonlinear systems acting on deterministic inputs since the early 1970's. They describe a broad class of nonlinear input-output maps using a type of functional series expansion, but in most applications, a system's inputs have noise components. In such circumstances, new mathematical machinery is needed to properly describe the input-output map via the Chen-Fliess algebraic formalism. In this dissertation, a class of L₂-Itô stochastic processes is introduced specifically for this purpose. Then, an extension of the Fliess operator theory is presented and sufficient conditions are given under which …