Physical Sciences and Mathematics Commons^™

Numerical Studies Of Regularized Navier-Stokes Equations And An Application Of A Run-To-Run Control Model For Membrane Filtration At A Large Urban Water Treatment Facility, Jeffrey Belding

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation consists of two parts. The first part consists of research on accurate and efficient turbulent fluid flow modeling via a family of regularizations of the Navier-Stokes equation which are known as Time Relaxation models. In the second part, we look into the modeling application for the filtration/backwash process at the River Mountains Water Treatment Facility in Henderson, NV.

In the first two chapters, we introduce the Time Relaxation models and their associated differential filter equations. In addition, we develop the regularization method which employs the Nth van Cittert deconvolution operator, which gives rise to the family of models. …

From Language Comprehension Towards General Ai, Binay Dahal

UNLV Theses, Dissertations, Professional Papers, and Capstones

Language comprehension or more formally, natural language understanding is one of the major undertakings in Artificial Intelligence. In this work, we explore a few of the problems in language understanding using fixed deep learning models. Specifically, first, we look into question generation. Asking questions relates to the cognitive ability of language comprehension and context understanding. For that reason, making progress in question generation is significant. We introduce a novel task called “question generation with masked target answer” and propose various models and present the baseline result for the task. Next, we extend on the question generation task and develop a …

Calculating The Learning Rate Of A Neural Network Using A Genetic Algorithm, Eric Miller

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the field of Computer Science, neural networks and genetic algorithms have become very popular tools in solving complex problems. Because of this growing popularity, there has been several attempts to combine the two concepts. Some of these attempts focused on using genetic algorithms to determine the best architecture, starting weights, or feature selection, to name of few of the applications. While a lot of the research that is available focuses on solving more than one element of the neural network design or is looking to use genetic algorithms to replace a part of the traditional neural network, such as …

Ab-Initio And Empirical Simulations Of Aluminum And Copper Metal, William Wolfs

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this work, I perform detailed calculations on the bulk and electronic properties of aluminum and copper metal. Originally, I was motivated by experimental work on the solidsolid phase changes in pure aluminum. These phase changes were well predicted by density functional theory(DFT) but difficult or impossible to predict using embedded atom method potentials(EAM). EAM potentials are in wide use to describe many properties of bulk materials, and it seemed worrying that something so basic as a phase change could not be predicted. I began running high precision calculations with DFT and compared the results to EAM potentials which had …

Data Analytics In Hotel And Integrated Resort Brands: An Evaluation Of Past Literature And Proposed Research For The Future, Luke Andrew Walocko

UNLV Theses, Dissertations, Professional Papers, and Capstones

Data analytics in hotel and integrated resort brands is a growing strategy implemented to support business decisions designed to generate revenue or save costs. This study utilizes a literature review of data analytics related publications to provide recommendations on future research topics to improve the quality of literature related to data analytics in hotel and integrated resort brands. The study is not limited to hospitality specific research and uses research from all industries to identify gaps in publications for hospitality scholars to explore. Three proposed research questions for future exploration were composed based on the comparison of literature written for …

Characteristics Of Flow Over Rectangular Labyrinth Weirs With Round Corners, Omed S.Q. Yousif, Kawa Z. Abdulrahman, Wazira Qadir, Ahang S. Ali, Moses Karakouzian

Civil and Environmental Engineering and Construction Faculty Research

The hydraulic performance of round-cornered rectangular labyrinth weirs with varying weir heights and effective lengths has not been explored in the existing literature to the authors’ knowledge. The purpose of this experimental study was to see how the height and effective length of round-cornered rectangular labyrinth weirs affect their discharge efficiency. Nine flat-crested rectangular labyrinth weirs made of high-density polyethylene (HDPE) were tested in a rectangular flume under various discharges to fulfill the goals of this study. The discharge coefficients for the weirs were then calculated. The hydraulic efficiency of weirs with round corners increases as the weir height (P) …

Nonperiodic Type I Be/X-Ray Binary Outbursts, Rebecca G. Martin, Alessia Franchini

Physics & Astronomy Faculty Research

Type I Be/X-ray binary outbursts are driven by mass transfer from a Be star decretion disk to a neutron star companion during each orbital period. Treiber et al. recently observed nonperiodic type I outbursts in RX J0529.8-6556 that has unknown binary orbital properties. We show that nonperiodic type I outbursts may be temporarily driven in a low eccentricity binary with a disk that is inclined sufficiently to be mildly unstable to Kozai-Lidov oscillations. The inclined disk becomes eccentric and material is transferred to the neutron star at up to three locations in each orbit: when the neutron star passes the …

Material Handling With Embodied Loco-Manipulation, Jean Chagas Vaz

UNLV Theses, Dissertations, Professional Papers, and Capstones

Material handling is an intrinsic component of disaster response. Typically, first responders, such as firefighters and/or paramedics, must carry, push, pull, and handle objects, facilitating the transportation of goods. For many years, researchers from around the globe have sought to enable full-sized humanoid robots to perform such essential material handling tasks. This work aims to tackle current limitations of humanoids in the realm of interaction with common objects such as carts, wheelbarrows, etc. Throughout this research, many methods will be applied to ensure a stable Zero Moment Point (ZMP) trajectory to allow a robust gait while loco-manipulating a cart. The …

A Human-Embodied Drone For Dexterous Aerial Manipulation, Dongbin Kim

UNLV Theses, Dissertations, Professional Papers, and Capstones

Current drones perform a wide variety of tasks in surveillance, photography, agriculture, package delivery, etc. However, these tasks are performed passively without the use of human interaction. Aerial manipulation shifts this paradigm and implements drones with robotic arms that allow interaction with the environment rather than simply sensing it. For example, in construction, aerial manipulation in conjunction with human interaction could allow operators to perform several tasks, such as hosing decks, drill into surfaces, and sealing cracks via a drone. This integration with drones will henceforth be known as dexterous aerial manipulation.

Our recent work integrated the worker’s experience into …

Exploring The Latent Space Of Image Captioning Networks, Mikian J. Musser

UNLV Theses, Dissertations, Professional Papers, and Capstones

State-of-the-art image captioning models can successfully produce a diverse set of accurate captions. Previous research has focused on improving caption diversity while maintaining a high level of fidelity. We shift the focus from accuracy and diversity to controllability. We use a modified version of the traditional encoder-decoder network that allows the model to produce a meaningful and structured latent space. We then explore the latent space using several latent cartographic methods: lerp, slerp, analogy completion, attribute vector rotation, and interpolation graphs. Additionally, we discuss different categories of latent space and provide modifications for each of the cartographic methods. Finally, we …

Hybridity, Ecocriticism, And Feminist Perspectives In She-Ra And The Princesses Of Power, Sarah Warso

UNLV Theses, Dissertations, Professional Papers, and Capstones

Children’s cartoons are growing increasingly nuanced in the twenty-first century. She-Ra and the Princesses of Power (2018) is an animated television series targeted towards young girls that includes themes of ecocriticism and feminism. The show does this by introducing cyborg, or hybrid, characters. My research explores how cyborg identities in children’s media and their feminist, ecocritical meanings in She-Ra and the Princesses of Power. The cyborg, as a feminist mythic hero, breaks down binaries and recodes communication between opposing forces. The She-Ra is filled with characters that inhabit multiple identities. The main character, Adora, identifies as both a former Evil …

Machine Learning Analysis Of Single Nucleotide Polymorphism (Snp) Data To Predict Bone Mineral Density In African American Women, Erick Githua Wakayu

UNLV Theses, Dissertations, Professional Papers, and Capstones

Osteoporosis is a debilitating disease in which an individual’s bones weaken, making bones fragile and more susceptible to fracture. While commonly found amongst postmenopausal Caucasian and Asian women based on previous studies, those of African descent (African American/Black) have largely been ignored when it comes to osteoporotic studies, especially when it comes to Genome Wide Association Studies (GWAS). From GWA studies, we gain access to single nucleotide poly-morphisms (SNPs) that may contribute to certain illnesses, such as osteoporosis. With low Bone Mineral Density (BMD) being one of the primary markers of potential osteoporosis, it is prudent that proper research is …

What Do General And Organic Chemistry Students Consider When Making Decisions About Acids And Bases? A Phenomenographic Study, Sarah Wood

UNLV Theses, Dissertations, Professional Papers, and Capstones

Chemistry students often struggle in organic chemistry courses. In fact, these courses are viewed by some as “weed-out” classes. There are many fundamental concepts covered in general chemistry that contribute to students’ ability to succeed in organic chemistry. One of those fundamental topics, and the focus of this study, is the topic of acids and bases. Acid–base topics are featured in both general and organic chemistry courses, and the interests of this study lie not only within the realm of organic chemistry but also general chemistry.

The purpose of this study was to determine both undergraduate general and organic chemistry …

Statistical Measurements Of Dispersion Measure Fluctuations Of Frbs, Siyao Xu, David H. Weinberg, Bing Zhang

Physics & Astronomy Faculty Research

Extragalactic fast radio bursts (FRBs) have large dispersion measures (DMs) and are unique probes of intergalactic electron density fluctuations. By using the recently released First CHIME/FRB Catalog, we reexamined the structure function (SF) of DM fluctuations. It shows a large DM fluctuation similar to that previously reported in Xu & Zhang, but no clear correlation hinting toward large-scale turbulence is reproduced with this larger sample. To suppress the distortion effect from FRB distances and their host DMs, we focus on a subset of CHIME catalog with DM < 500 pc cm-3. A trend of nonconstant SF and nonzero correlation function (CF) at angular separations θ less than 10 is seen, but with large statistical uncertainties. The difference found between SF and that derived from CF at θ ≲ 10 can be ascribed to the large statistical uncertainties or the density inhomogeneities on scales on the order of 100 Mpc. The possible correlation of electron density fluctuations and inhomogeneities of density distribution should be tested when several thousands of FRBs are available.

Investigating The Growth Of Algae Under Low Atmospheric Pressures For Potential Food And Oxygen Production On Mars, Leena M. Cycil, Elisabeth M. Hausrath, Douglas W. Ming, Christopher T. Adcock, James Raymond, Daniel Remias, Warren P. Ruemmele

Geoscience Faculty Research

With long-term missions to Mars and beyond that would not allow resupply, a self-sustaining Bioregenerative Life Support System (BLSS) is essential. Algae are promising candidates for BLSS due to their completely edible biomass, fast growth rates and ease of handling. Extremophilic algae such as snow algae and halophilic algae may also be especially suited for a BLSS because of their ability to grow under extreme conditions. However, as indicated from over 50 prior space studies examining algal growth, little is known about the growth of algae at close to Mars-relevant pressures. Here, we explored the potential for five algae species …

Global 3d Radiation Hydrodynamic Simulations Of Proto-Jupiter’S Convective Envelope, Zhaohuan Zhu, Yan-Fei Jiang, Hans Baehr, Andrew N. Youdin, Philip J. Armitage, Rebecca G. Martin

Physics & Astronomy Faculty Research

The core accretion model of giant planet formation has been challenged by the discovery of recycling flows between the planetary envelope and the disc that can slow or stall envelope accretion. We carry out 3D radiation hydrodynamic simulations with an updated opacity compilation to model the proto-Jupiter’s envelope. To isolate the 3D effects of convection and recycling, we simulate both isolated spherical envelopes and envelopes embedded in discs. The envelopes are heated at given rates to achieve steady states, enabling comparisons with 1D models. We vary envelope properties to obtain both radiative and convective solutions. Using a passive scalar, we …

Initial Acoustoelastic Measurements In Olivine: Investigating The Effect Of Stress On P- And S-Wave Velocities, Taryn K. Traylor, Pamela C. Burnley, M. L. Whitaker

Geoscience Faculty Research

It is well known that elasticity is a key physical property in the determination of the structure and composition of the Earth and provides critical information for the interpretation of seismic data. This study investigates the stress-induced variation in elastic wave velocities, known as the acoustoelastic effect, in San Carlos olivine. A recently developed experimental ultrasonic acoustic system, the Directly Integrated Acoustic System Combined with Pressure Experiments (DIASCoPE), was used with the D-DIA multi-anvil apparatus to transmit ultrasonic sound waves and collect the reflections. We use the DIASCoPE to obtain longitudinal (P) and shear (S) elastic wave velocities from San …

Thermal Analysis Of Benzotriazolium Perrhenate And Its Implication To Rhenium Metal, James Louis-Jean, Harry Jang, Andrew J. Swift, Frederic Poineau

Chemistry and Biochemistry Faculty Research

The thermal analysis behavior of C6H6N3[ReO4] was studied by simultaneous thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) up to 700 °C under argon. Such analysis afforded rhenium metal, which was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. XRD peak broadening due to crystallite size and lattice strain was analyzed by both Williamson-Hall (W-H) and Debye-Scherrer (D-S) methods. Efforts to isolate Re metal from the thermal treatment of benzotriazole (BTA = C6H5N3) with NH4ReO4 and Re2O7 under various atmospheres and temperatures are also reported. The results provide a significant insight into …

Physical And Mental Disabilities Among The Gender-Diverse Population Using The Behavioral Risk Factor Surveillance System, Brfss (2017–2019): A Propensity-Matched Analysis, Jennifer R. Pharr, Kavita Batra

Environmental & Occupational Health Faculty Publications

This propensity-matched analysis utilized the publicly available Behavioral Risk Factor Surveillance System (2017–2019) data to compare the burden of disabilities among transgender/non-binary (TGNB) and cisgender groups. The groups were matched (1:1 ratio) on demographic variables using Nearest Neighborhood Matching. Categorical variables were compared among groups using a Chi-square analysis to test differences in the proportions. Multivariate logistic regression analysis was fit to predict the likelihood of the physical and mental disabilities among the TGNB group compared with the cisgender group while controlling for healthcare access factors, income, and employment. Survey weights were included in the model to account for the …

Shallow Rupture Propagation Of Pleistocene Earthquakes Along The Hurricane Fault, Ut, Revealed By Hematite (U-Th)/He Thermochronometry And Textures, Madison P. Taylor, Alexis K. Ault, Margaret L. Odlum, Dennis L. Newell

Geoscience Faculty Research

The material properties and distribution of faults above the seismogenic zone promote or inhibit earthquake rupture propagation. We document the depths and mechanics of fault slip along the seismically active Hurricane fault, UT, with scanning and transmission electron microscopy and hematite (U-Th)/He thermochronometry. Hematite occurs as mm-scale, striated patches on a >10 m2 thin, mirror-like silica fault surface. Hematite textures include bulbous aggregates and cataclasite, overlain by crystalline Fe-oxide nanorods and an amorphous silica layer at the slip interface. Textures reflect mechanical, fluid, and heat-assisted amorphization of hematite and silica-rich host rock that weaken the fault and promote rupture propagation. …

Novel Theorems And Algorithms Relating To The Collatz Conjecture, Michael R. Schwob, Peter Shiue, Rama Venkat

Mathematical Sciences Faculty Research

Proposed in 1937, the Collatz conjecture has remained in the spotlight for mathematicians and computer scientists alike due to its simple proposal, yet intractable proof. In this paper, we propose several novel theorems, corollaries, and algorithms that explore relationships and properties between the natural numbers, their peak values, and the conjecture. These contributions primarily analyze the number of Collatz iterations it takes for a given integer to reach 1 or a number less than itself, or the relationship between a starting number and its peak value.

Gw Ori: Circumtriple Rings And Planets, Jeremy L. Smallwood, Rebecca Nealon, Cheng Chen, Rebecca G. Martin, Jiaqing Bi, Ruobing Dong, Christophe Pinte

Physics & Astronomy Faculty Research

GW Ori is a hierarchical triple star system with a misaligned circumtriple protoplanetary disc. Recent Atacama Large Millimeter/submillimeter Array observations have identified three dust rings with a prominent gap at 100 au and misalignments between each of the rings. A break in the gas disc may be driven by the torque from either the triple star system or a planet that is massive enough to carve a gap in the disc. Once the disc is broken, the rings nodally precess on different time-scales and become misaligned. We investigate the origins of the dust rings by means of N-body integrations and …

Inelastic, Exchange, And Reactive Processes In Rovibrationally Excited Collisions Of Hd With H, Boyi Zhou, Benhui Yang, Balakrishnan Naduvalath, B. K. Kendrick, Maodu Chen, P. C. Stancil

Chemistry and Biochemistry Faculty Research

The HD molecule is an important coolant in early universe chemistry models and a tracer of H2 in star-forming regions. Rate coefficients for collisional excitation and de-excitation of HD rotational and vibrational levels form important ingredients in astrophysical models. While collisions with He, H2, and H are the most important, available data for H + HD collisions are largely limited to temperatures less than 1000 K for the vibrational ground state, low-lying rotational levels of the v = 1 HD vibrational level, or computed without reactive contributions. Here, through explicit quantum scattering calculations, we report extensive data for rovibrational transitions …

On The Solutions Of Three-Variable Frobenius-Related Problems Using Order Reduction Approach, Tian-Xiao He, Peter J.-S. Shiue, Rama Venkat

Mathematical Sciences Faculty Research

This paper presents a new approach to determine the number of solutions of three-variable Frobenius-related problems and to find their solutions by using order reducing methods. Here, the order of a Frobenius-related problem means the number of variables appearing in the problem. We present two types of order reduction methods that can be applied to the problem of finding all nonnegative solutions of three-variable Frobenius-related problems. The first method is used to reduce the equation of order three from a three-variable Frobenius-related problem to be a system of equations with two fixed variables. The second method reduces the equation of …

Transcontinental Retroarc Sediment Routing Controlled By Subduction Geometry And Climate Change (Central And Southern Andes, Argentina), Eduardo Garzanti, Tomas Capaldi, Giovanni Vezzoli, Mara Limonta, Numa Sosa

Geoscience Faculty Research

Central Argentina from the Pampean flat-slab segment to northern Patagonia (27°–41°S) represents a classic example of a broken retroarc basin with strong tectonic and climatic control on fluvial sediment transport. Combined with previous research focused on coastal sediments, this actualistic provenance study uses framework petrography and heavy-mineral data to trace multistep dispersal of volcaniclastic detritus first eastwards across central Argentina for up to ca. 1,500 km and next northwards for another 760 km along the Atlantic coast. Although detritus generated in the Andes is largely derived from mesosilicic volcanic rocks of the cordillera, its compositional signatures reflect different tectono-stratigraphic levels …

Singlet Fission In Acene Blends, Katharina Broch, Clemens Zeiser, Chad Cruz, Luca Moretti, Margherita Maiuri, Eric Chronister, David Reichman, Roel Tempelaar, Giulio Cerullo, Christopher Bardeen

Chemistry and Biochemistry Faculty Research

Singlet fission (SF), the photophysical process converting an excited singlet exciton into two triplet excitons, is a promising approach to boost solar cell efficiencies. It is controlled by various parameters such as intermolecular interactions, energetics, entropy and vibronic coupling and a controlled modification of these parameters is key to a fundamental understanding. Blends of organic semiconductors present an interesting alternative to established methods of chemical functionalization and their potential for the study of SF pathways will be discussed using acene blends as example. Mixed thin films of SF chromophores and weakly interacting, high-bandgap spacer molecules allow one to study the …

Controllable Co2 Electrocatalytic Reduction Via Ferroelectric Switching On Single Atom Anchored In2se3 Monolayer, Lin Ju, Xin Tan, Xin Mao, Yuantong Gu, Sean Smith, Aijun Du, Zhongfang Chen, Changfeng Chen, Liangzhi Kou

Physics & Astronomy Faculty Research

Efficient and selective CO2 electroreduction into chemical fuels promises to alleviate environmental pollution and energy crisis, but it relies on catalysts with controllable product selectivity and reaction path. Here, by means of first-principles calculations, we identify six ferroelectric catalysts comprising transition-metal atoms anchored on In2Se3 monolayer, whose catalytic performance can be controlled by ferroelectric switching based on adjusted d-band center and occupation of supported metal atoms. The polarization dependent activation allows effective control of the limiting potential of CO2 reduction on TM@In2Se3 (TM = Ni, Pd, Rh, Nb, and Re) as well as the reaction paths and final products on …

Vacancy Control In Acene Blends Links Exothermic Singlet Fission To Coherence, Clemens Zeiser, Chad Cruz, David R. Reichman, Michael Seitz, Jan Hagenlocher, Eric L. Chronister, Christopher J. Bardeen, Roel Tempelaar, Katharina Broch

Chemistry and Biochemistry Faculty Research

The fission of singlet excitons into triplet pairs in organic materials holds great technological promise, but the rational application of this phenomenon is hampered by a lack of understanding of its complex photophysics. Here, we use the controlled introduction of vacancies by means of spacer molecules in tetracene and pentacene thin films as a tuning parameter complementing experimental observables to identify the operating principles of different singlet fission pathways. Time-resolved spectroscopic measurements in combination with microscopic modelling enables us to demonstrate distinct scenarios, resulting from different singlet-to-triplet pair energy alignments. For pentacene, where fission is exothermic, coherent mixing between the …

Terrestrial Planet Formation In A Circumbinary Disc Around A Coplanar Binary, Anna C. Childs, Rebecca G. Martin

Physics & Astronomy Faculty Research

With N-body simulations, we model terrestrial circumbinary planet (CBP) formation with an initial surface density profile motivated by hydrodynamic circumbinary gas disc simulations. The binary plays an important role in shaping the initial distribution of bodies. After the gas disc has dissipated, the torque from the binary speeds up the planet formation process by promoting body-body interactions but also drives the ejection of planet building material from the system at an early time. Fewer but more massive planets form around a close binary compared to a single star system. A sufficiently wide or eccentric binary can prohibit terrestrial planet formation. …

The Large Area Burst Polarimeter (Leap) A Nasa Mission Of Opportunity For The Iss, Bing Zhang, Numerous Authors, See Full List Below

Physics & Astronomy Faculty Research

The LargE Area Burst Polarimeter (LEAP) will radically improve our understanding of some of the most energetic phenomena in our Universe by exposing the underlying physics that governs astrophysical jets and the extreme environment surrounding newborn compact objects. LEAP will do this by making the highest fidelity polarization measurements to date of the prompt gamma-ray emission from a large sample of Gamma-Ray Bursts (GRBs). The science objectives are met with a single instrument deployed as an external payload on the ISS-a wide FOV Compton polarimeter that measures GRB polarization from 50-500 keV and GRB spectra from ∼10 keV to 5 …