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University of Texas Rio Grande Valley

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Soil Chemistry Modification By Guinea Grass In Semi-Arid Soils: A Litter Mediated Positive Feedback, Vanessa Elizabeth Thomas Aug 2021

Soil Chemistry Modification By Guinea Grass In Semi-Arid Soils: A Litter Mediated Positive Feedback, Vanessa Elizabeth Thomas

Theses and Dissertations

Nutrients are a key component of healthy soils. Their composition plays an important role in plant growth through nutrient cycling and directly influences the functioning of plant communities in both agricultural and natural ecosystems. Shifts in macronutrients such as phosphorus and nitrogen may be initiated by invasive growth as a driver for competition with native plants. The goal of this study is to explore the plant soil feedback in an exotic invasive plant, Guinea grass (Pancium maximum), an invasive bunch grass originally from Africa, across different habitat types in the Lower Rio Grande Valley (LRGV). To determine a positive plant …

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Machinability Of Carbon Fiber Reinforced Polymer (Cfrp) Composites: Modeling And Optimization Using Taguchi Analysis And Multi-Objective Genetic Algorithm, S M Abdur Rob Aug 2021

Machinability Of Carbon Fiber Reinforced Polymer (Cfrp) Composites: Modeling And Optimization Using Taguchi Analysis And Multi-Objective Genetic Algorithm, S M Abdur Rob

Theses and Dissertations

Carbon Fiber Reinforced Polymer (CFRP) composites have been widely used in aerospace, automotive, nuclear, and biomedical industries due to their high strength to weight ratio, corrosion resistant durability and excellent thermo-mechanical properties in non-oxidative atmospheres. Machining of CFRP composites has always been a challenge for the manufacturers. In this study, turning operation has been performed on CFRP composites to investigate the effects of cutting parameters namely cutting speed, feed rate and depth of cut on the output characteristics including cutting force, surface roughness and tool wear using Taguchi Analysis. Regression Analysis has been used to develop mathematical model for cutting …

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Knn Based Piezo-Triboelectric Lead-Free Hybrid Energy Films, Abu Masa Abdullah, Muhtasim Ul Karim Sadaf, Farzana Tasnim, Horacio Vasquez, Karen Lozano, M. Jasim Uddin Aug 2021

Knn Based Piezo-Triboelectric Lead-Free Hybrid Energy Films, Abu Masa Abdullah, Muhtasim Ul Karim Sadaf, Farzana Tasnim, Horacio Vasquez, Karen Lozano, M. Jasim Uddin

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

In recent times, the triboelectric and piezoelectric effects have garnered significant attention towards developing advanced material composites for energy harvesting and sensory applications. In this work, potassium sodium niobate (KNN) based energy films (EF) have been developed to utilize mechanical energy while simultaneously taking advantage of triboelectric and piezoelectric mechanisms. The KNN particles were synthesized using a wet ball milling technique and then incorporated into a polyvinylidene difluoride (PVDF) matrix together with addition of multi wall carbon nanotubes (MWCNT). The film was used to develop a piezoelectric nanogenerator (PENG) fitted with copper electrodes. The piezoelectric output of the film was …

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Uptake Analysis Of As(Iii) And As(V) By Cassia Fistula Seedlings, Valeria Velazquez Aug 2021

Uptake Analysis Of As(Iii) And As(V) By Cassia Fistula Seedlings, Valeria Velazquez

Theses and Dissertations

The natural and anthropogenic contamination of water by arsenic has become a major concern to the environment and public health. Phytoremediation is an attractive alternative to ecologically friendly remove contaminants at a potential high efficiency and low cost. Absorption of As(III) and As(V) was evaluated by the measuring the content of arsenic in the roots, leaves and stems Cassia fistula grown under controlled conditions in a hydroponics system. After seeds were germinated, the plants were grown in Hoagland nutrient solution individually supplemented with 1, 2, 5 ppm of As(III) and As(V). After two weeks of exposure, samples of leaves, roots, …

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Detecting Optical Transients Using Artificial Neural Networks And Reference Images From Different Surveys, Katarzyna Wardęga, Adam Zadrozny, Martin Beroiz, Richard S. Camuccio, Mario C. Diaz Jul 2021

Detecting Optical Transients Using Artificial Neural Networks And Reference Images From Different Surveys, Katarzyna Wardęga, Adam Zadrozny, Martin Beroiz, Richard S. Camuccio, Mario C. Diaz

Physics & Astronomy Faculty Publications

We present a technique to detect optical transients based on an artificial neural networks method. We describe the architecture of two networks capable of comparing images of the same part of the sky taken by different telescopes. One image corresponds to the epoch in which a potential transient could exist; the other is a reference image of an earlier epoch. We use data obtained by the Dr. Cristina V. Torres Memorial Astronomical Observatory and archival reference images from the Sloan Digital Sky Survey. We trained a convolutional neural network and a dense layer network on simulated source samples and then …

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Search For Anisotropic Gravitational-Wave Backgrounds Using Data From Advanced Ligo And Advanced Virgo's First Three Observing Runs, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang Jul 2021

Search For Anisotropic Gravitational-Wave Backgrounds Using Data From Advanced Ligo And Advanced Virgo's First Three Observing Runs, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang

Physics & Astronomy Faculty Publications

We report results from searches for anisotropic stochastic gravitational-wave backgrounds using data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. For the first time, we include Virgo data in our analysis and run our search with a new efficient pipeline called PyStoch on data folded over one sidereal day. We use gravitational-wave radiometry (broadband and narrow band) to produce sky maps of stochastic gravitational-wave backgrounds and to search for gravitational waves from point sources. A spherical harmonic decomposition method is employed to look for gravitationalwave emission from spatially-extended sources. Neither technique found evidence of …

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An Introduction To Generalized Entropy And Some Quantum Applications, Paul Bracken Jul 2021

An Introduction To Generalized Entropy And Some Quantum Applications, Paul Bracken

School of Mathematical & Statistical Sciences Faculty Publications

The concept of generalized entropy is introduced and some of its properties are studied. Irreversible time evolution can be generated by a non-Hermitian superoperator on the states of the system. The case when irreversibility comes about from embedding the system in a thermal reservoir is looked at. The time evolution is found compatible both with equilibrium thermodynamics and entropy production near the final state. Some examples are presented as well as a longer introduction as to how this might play a role in the black hole information loss paradox.

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Non-Archimedean Models Of Morphogenesis, Wilson A. Zuniga-Galindo Jul 2021

Non-Archimedean Models Of Morphogenesis, Wilson A. Zuniga-Galindo

School of Mathematical & Statistical Sciences Faculty Publications

We study a p-adic reaction-diffusion system and the associated Turing patterns. We establish an instability criteria and show that the Turing patterns are not classical patterns consisting of alternating domains. Instead of this, a Turing pattern consists of several domains (clusters), each of them supporting a different pattern but with the same parameter values. This type of patterns are typically produced by reaction-diffusion equations on large networks.

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Upper Limits On The Isotropic Gravitational-Wave Background From Advanced Ligo And Advanced Virgo's Third Observing Run, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang Jul 2021

Upper Limits On The Isotropic Gravitational-Wave Background From Advanced Ligo And Advanced Virgo's Third Observing Run, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang

Physics & Astronomy Faculty Publications

We report results of a search for an isotropic gravitational-wave background (GWB) using data from Advanced LIGO’s and Advanced Virgo’s third observing run (O3) combined with upper limits from the earlier O1 and O2 runs. Unlike in previous observing runs in the advanced detector era, we include Virgo in the search for the GWB. The results of the search are consistent with uncorrelated noise, and therefore we place upper limits on the strength of the GWB. We find that the dimensionless energy density ΩGW≤5.8×10−9 at the 95% credible level for a flat (frequency-independent) GWB, using a prior which is uniform …

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Positive Solutions For The Fractional Schrödinger Equations With Logarithmic And Critical Non-Linearities, Haining Fan, Zhaosheng Feng, Xingjie Yan Jul 2021

Positive Solutions For The Fractional Schrödinger Equations With Logarithmic And Critical Non-Linearities, Haining Fan, Zhaosheng Feng, Xingjie Yan

School of Mathematical & Statistical Sciences Faculty Publications

In this paper, we study a class of fractional Schrödinger equations involving logarithmic and critical non-linearities on an unbounded domain, and show that such an equation with positive or sign-changing weight potentials admits at least one positive ground state solution and the associated energy is positive (or negative). By applying the Nehari manifold method and Ljusternik–Schnirelmann category, we investigate how the weight potential affects the multiplicity of positive solutions, and obtain the relationship between the number of positive solutions and the category of some sets related to the weight potential.

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From Reaction Kinetics To Dementia: A Simple Dimer Model Of Alzheimer’S Disease Etiology, Michael R. Lindstrom, Manuel B. Chavez, Elijah A. Gross-Sable, Eric Y. Hayden, David B. Teplow Jul 2021

From Reaction Kinetics To Dementia: A Simple Dimer Model Of Alzheimer’S Disease Etiology, Michael R. Lindstrom, Manuel B. Chavez, Elijah A. Gross-Sable, Eric Y. Hayden, David B. Teplow

School of Mathematical & Statistical Sciences Faculty Publications

Oligomers of the amyloid β-protein (Aβ) have been implicated in the pathogenesis of Alzheimer’s disease (AD) through their toxicity towards neurons. Understanding the process of oligomerization may contribute to the development of therapeutic agents, but this has been difficult due to the complexity of oligomerization and the metastability of the oligomers thus formed. To understand the kinetics of oligomer formation, and how that relates to the progression of AD, we developed models of the oligomerization process. Here, we use experimental data from cell viability assays and proxies for rate constants involved in monomerdimer-trimer kinetics to develop a simple mathematical model …

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Hidden Treasures In The Unknown 3cr Extragalactic Radio Sky: A Multiwavelength Approach, V. Missaglia, F. Massaro, E. Liuzzo, A. Paggi, R. P. Kraft, W. R. Forman, A. Jimenez-Gallardo, Juan P. Madrid, F. Ricci, C. Stuardi Jul 2021

Hidden Treasures In The Unknown 3cr Extragalactic Radio Sky: A Multiwavelength Approach, V. Missaglia, F. Massaro, E. Liuzzo, A. Paggi, R. P. Kraft, W. R. Forman, A. Jimenez-Gallardo, Juan P. Madrid, F. Ricci, C. Stuardi

Physics & Astronomy Faculty Publications

We present the analysis of multiwavelength observations of seven extragalactic radio sources, listed as unidentified in the Third Cambridge Revised Catalog (3CR). X-ray observations, performed during Chandra Cycle 21, were compared to Very Large Array (VLA), Wide-field Infrared Survey Explorer, and Pan-STARRS observations in the radio, infrared, and optical bands, respectively. All sources in this sample lack a clear optical counterpart, and are thus missing their redshift and optical classification. In order to confirm the X-ray and infrared radio counterparts of core and extended components, here we present for the first time radio maps obtained manually reducing VLA archival data. …

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Study Of Friction And Wear Effects In Aluminum Parts Manufactured Via Single Point Incremental Forming Process Using Petroleum And Vegetable Oil-Based Lubricants, Jose M. Diabb Zavala, Oscar Martinez-Romero, Alex Elias-Zuniga, Hector Manuel Leija Gutierrez, Alejandro Estrada-De La Vega, Jaime Taha-Tijerina Jul 2021

Study Of Friction And Wear Effects In Aluminum Parts Manufactured Via Single Point Incremental Forming Process Using Petroleum And Vegetable Oil-Based Lubricants, Jose M. Diabb Zavala, Oscar Martinez-Romero, Alex Elias-Zuniga, Hector Manuel Leija Gutierrez, Alejandro Estrada-De La Vega, Jaime Taha-Tijerina

Manufacturing & Industrial Engineering Faculty Publications

This paper focuses on studying how mineral oil, sunflower, soybean, and corn lubricants influence friction and wear effects during the manufacturing of aluminum parts via the single point incremental forming (SPIF) process. To identify how friction, surface roughness, and wear change during the SPIF of aluminum parts, Stribeck curves were plotted as a function of the SPIF process parameters such as vertical step size, wall angle, and tool tip semi-spherical diameter. Furthermore, lubricant effects on the surface of the formed parts are examined by energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM) images, the Alicona optical 3D measurement system, …

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Protistan Grazing Impacts Microbial Communities And Carbon Cycling At Deep-Sea Hydrothermal Vents, Sarah K. Hu, Erica L. Herrera, Amy R. Smith, Maria G. Pachiadaki, Virginia P. Edgcomb, Sean P. Sylva, Eric W. Chan, Jeffrey S. Seewald, Christopher R. German, Julie A. Huber Jul 2021

Protistan Grazing Impacts Microbial Communities And Carbon Cycling At Deep-Sea Hydrothermal Vents, Sarah K. Hu, Erica L. Herrera, Amy R. Smith, Maria G. Pachiadaki, Virginia P. Edgcomb, Sean P. Sylva, Eric W. Chan, Jeffrey S. Seewald, Christopher R. German, Julie A. Huber

School of Earth, Environmental, & Marine Sciences Faculty Publications

Microbial eukaryotes (or protists) in marine ecosystems are a link between primary producers and all higher trophic levels, and the rate at which heterotrophic protistan grazers consume microbial prey is a key mechanism for carbon transport and recycling in microbial food webs. At deep-sea hydrothermal vents, chemosynthetic bacteria and archaea form the base of a food web that functions in the absence of sunlight, but the role of protistan grazers in these highly productive ecosystems is largely unexplored. Here, we pair grazing experiments with a molecular survey to quantify protistan grazing and to characterize the composition of vent-associated protists in …

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Comparative Study Of Leachate Characterization: Implication For Sustainable Environmental Management, Osakpolor Marvellous Omorogieva, Victory Itua Igberase Jul 2021

Comparative Study Of Leachate Characterization: Implication For Sustainable Environmental Management, Osakpolor Marvellous Omorogieva, Victory Itua Igberase

School of Earth, Environmental, & Marine Sciences Faculty Publications

Understanding the sources of environmental stressors, the role of geology, climate and technology would provide a guide to solving the problems posed by such stressor. The study examine the sources of wastes in Ikhueniro open dumpsite located in Benin city, Nigeria and characterize the leachate emanating from it. This will assist in adequate design of managerial scheme to tackle the menace posed by it while putting into consideration the role of geology, climate and technology. The key objectives are to carry out field study, characterize wastes in the dumpsite and collect raw leachate emanating from the wastes heap in order …

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Premium-Cnn: Propagating Uncertainty Towards Robust Convolutional Neural Networks, Dimah Dera, Nidhal Carla Bouaynaya, Ghulam Rasool, Roman Shterenberg, Hassan M. Fathallah-Shaykh Jul 2021

Premium-Cnn: Propagating Uncertainty Towards Robust Convolutional Neural Networks, Dimah Dera, Nidhal Carla Bouaynaya, Ghulam Rasool, Roman Shterenberg, Hassan M. Fathallah-Shaykh

Electrical and Computer Engineering Faculty Publications

Deep neural networks (DNNs) have surpassed human-level accuracy in various learning tasks. However, unlike humans who have a natural cognitive intuition for probabilities, DNNs cannot express their uncertainty in the output decisions. This limits the deployment of DNNs in mission-critical domains, such as warfighter decision-making or medical diagnosis. Bayesian inference provides a principled approach to reason about model's uncertainty by estimating the posterior distribution of the unknown parameters. The challenge in DNNs remains the multi-layer stages of non-linearities, which make the propagation of high-dimensional distributions mathematically intractable. This paper establishes the theoretical and algorithmic foundations of uncertainty or belief propagation …

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Search For Gravitational Waves Associated With Gamma-Ray Bursts Detected By Fermi And Swift During The Ligo–Virgo Run O3a, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Amit Aich, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov Jul 2021

Search For Gravitational Waves Associated With Gamma-Ray Bursts Detected By Fermi And Swift During The Ligo–Virgo Run O3a, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Amit Aich, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov

Physics & Astronomy Faculty Publications

We search for gravitational-wave transients associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the first part of the third observing run of Advanced LIGO and Advanced Virgo (2019 April 1 15:00 UTC–2019 October 1 15:00 UTC). A total of 105 GRBs were analyzed using a search for generic gravitational-wave transients; 32 GRBs were analyzed with a search that specifically targets neutron star binary mergers as short GRB progenitors. We find no significant evidence for gravitational-wave signals associated with the GRBs that we followed up, nor for a population of unidentified subthreshold signals. We consider several …

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Resolving Galactic Binaries In Lisa Data Using Particle Swarm Optimization And Cross-Validation, Xue-Hao Zhang, Soumya Mohanty, Xiao-Bo Zou, Yu-Xiao Liu Jul 2021

Resolving Galactic Binaries In Lisa Data Using Particle Swarm Optimization And Cross-Validation, Xue-Hao Zhang, Soumya Mohanty, Xiao-Bo Zou, Yu-Xiao Liu

Physics & Astronomy Faculty Publications

The space-based gravitational wave detector Laser Interferometric Space Antenna is expected to observe signals from a large population of compact object binaries, comprised predominantly of white dwarfs, in the Milky Way. Resolving individual sources from this population against its self-generated confusion noise poses a major data analysis problem. We present an iterative source estimation and subtraction method to address this problem based on the use of particle swarm optimization (PSO). In addition to PSO, a novel feature of the method is the cross-validation of sources estimated from the same data using different signal parameter search ranges. This is found to …

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Assessing Climate Change Impacts On Live Fuel Moisture And Wildfire Risk Using A Hydrodynamic Vegetation Model, Wu Ma, Lu Zhai, Alexandria Pivovaroff, Jacquelyn Shuman, Polly Buotte, Junyan Ding, Bradley O. Christoffersen, Ryan G. Knox, Max Moritz, Rosie A. Fisher Jul 2021

Assessing Climate Change Impacts On Live Fuel Moisture And Wildfire Risk Using A Hydrodynamic Vegetation Model, Wu Ma, Lu Zhai, Alexandria Pivovaroff, Jacquelyn Shuman, Polly Buotte, Junyan Ding, Bradley O. Christoffersen, Ryan G. Knox, Max Moritz, Rosie A. Fisher

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Biology)

Live fuel moisture content (LFMC) plays a critical role in wildfire dynamics, but little is known about responses of LFMC to multivariate climate change, e.g., warming temperature, CO2 fertilization, and altered precipitation patterns, leading to a limited prediction ability of future wildfire risks. Here, we use a hydrodynamic demographic vegetation model to estimate LFMC dynamics of chaparral shrubs, a dominant vegetation type in fire-prone southern California. We parameterize the model based on observed shrub allometry and hydraulic traits and evaluate the model's accuracy through comparisons between observed and simulated LFMC of three plant functional types (PFTs) under current climate conditions. …

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Tunable Non-Hermitian Acoustic Filter, S. Puri, J. Ferdous, A. Shakeri, A. Basiri, M. Dubois, Hamidreza Ramezani Jul 2021

Tunable Non-Hermitian Acoustic Filter, S. Puri, J. Ferdous, A. Shakeri, A. Basiri, M. Dubois, Hamidreza Ramezani

Physics & Astronomy Faculty Publications

We propose, design, and experimentally test a non-Hermitian acoustic superlattice that acts as a tunable precise filter. The superlattice is composed of two concatenated sublattices. The first sublattice is Hermitian, while the other can be adjusted to be Hermitian or non-Hermitian. The existence of non-Hermiticity, in terms of an induced loss in the second sublattice, results in the generation of absorption resonances that appear in the reflected spectrum. This provides us with a powerful knob to absorb or reflect several frequencies at will with high accuracy. The number of filtered frequencies can be controlled by designing the resonances in the …

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Association Of Hiv-1 Infection And Antiretroviral Therapy With Type 2 Diabetes In The Hispanic Population Of The Rio Grande Valley, Texas, Usa, Juan Carlos Lopez Alvarenga, Dora A. Martinez, Alvaro Diaz-Badillo, Liza D. Morales, Rector Arya, Christopher Jenkinson, Joanne E. Curran, John Blangero, Ravi Duggirala, Srinivas Mummidi, Ruben D. Martinez Jul 2021

Association Of Hiv-1 Infection And Antiretroviral Therapy With Type 2 Diabetes In The Hispanic Population Of The Rio Grande Valley, Texas, Usa, Juan Carlos Lopez Alvarenga, Dora A. Martinez, Alvaro Diaz-Badillo, Liza D. Morales, Rector Arya, Christopher Jenkinson, Joanne E. Curran, John Blangero, Ravi Duggirala, Srinivas Mummidi, Ruben D. Martinez

School of Medicine Publications

The Rio Grande Valley (RGV) in South Texas has one of the highest prevalence of obesity and type 2 diabetes (T2D) in the United States (US). We report for the first time the T2D prevalence in persons with HIV (PWH) in the RGV and the interrelationship between T2D, cardiometabolic risk factors, HIV-related indices, and antiretroviral therapies (ART). The PWH in this study received medical care at Valley AIDS Council (VAC) clinic sites located in Harlingen and McAllen, Texas. Henceforth, this cohort will be referred to as Valley AIDS Council Cohort (VACC). Cross-sectional analyses were conducted using retrospective data obtained from …

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Reshaping The Landscape Of The Future: Software-Defined Manufacturing, Lei Xu, Lin Chen, Zhimin Gao, Hiram Moya, Weidong Shi Jul 2021

Reshaping The Landscape Of The Future: Software-Defined Manufacturing, Lei Xu, Lin Chen, Zhimin Gao, Hiram Moya, Weidong Shi

Computer Science Faculty Publications

We describe the concept of software-defined manufacturing, which divides the manufacturing ecosystem into software definition and physical manufacturing layers. Software-defined manufacturing allows better resource sharing and collaboration, and it has the potential to transform the existing manufacturing sector.

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Observation Of Gravitational Waves From Two Neutron Star–Black Hole Coalescences, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang Jul 2021

Observation Of Gravitational Waves From Two Neutron Star–Black Hole Coalescences, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang

Physics & Astronomy Faculty Publications

We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star–black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO–Virgo detectors. The source of GW200105 has component masses and , whereas the source of GW200115 has component masses and (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is …

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Machine Learning Using Host/Guest Energy Histograms To Predict Adsorption In Metal–Organic Frameworks: Application To Short Alkanes And Xe/Kr Mixtures, Zhao Li, Benjamin J. Bucior, Haoyuan Chen, Maciej Haranczyk, J. Ilja Siepmann, Randall Q. Snurr Jul 2021

Machine Learning Using Host/Guest Energy Histograms To Predict Adsorption In Metal–Organic Frameworks: Application To Short Alkanes And Xe/Kr Mixtures, Zhao Li, Benjamin J. Bucior, Haoyuan Chen, Maciej Haranczyk, J. Ilja Siepmann, Randall Q. Snurr

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

A machine learning (ML) methodology that uses a histogram of interaction energies has been applied to predict gas adsorption in metal–organic frameworks (MOFs) using results from atomistic grand canonical Monte Carlo (GCMC) simulations as training and test data. In this work, the method is first extended to binary mixtures of spherical species, in particular, Xe and Kr. In addition, it is shown that single-component adsorption of ethane and propane can be predicted in good agreement with GCMC simulation using a histogram of the adsorption energies felt by a methyl probe in conjunction with the random forest ML method. The results …

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Hydraulic Characterization Of Porous Media For Remediation Applications In Geo-Environmental Engineering: Laboratory Experiment And Numerical Modeling, Syed Istiyak Ahmed Jul 2021

Hydraulic Characterization Of Porous Media For Remediation Applications In Geo-Environmental Engineering: Laboratory Experiment And Numerical Modeling, Syed Istiyak Ahmed

Theses and Dissertations

Hydraulic properties of porous media are very important characters for various geotechnical and geo-environmental applications. In this study, multi-step outflow experiments and numerical modeling were performed for homogeneous and layered column conditions with fine to coarse sands to investigate water flow mechanisms and better predict water flow and solute transport with the van Genuchten-Mualem (VGM) hydraulic model. Inversed modeling under HYDRUS-1D was performed to estimate six VGM soil hydraulic parameters. Forward modeling was conducted to evaluate the impacts of VGM hydraulic parameters along with saturated hydraulic conductivity to solute transport. Scaling effects such as column length, time, and chemical parameters …

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Latinx Students’ Mathematics Anxiety And Their Study Habits: Exploring Their Relationship At The Postsecondary Level, Luis M. Fernandez, Xiaohui Wang, Olga Ramirez, Cristina Villalobos Jul 2021

Latinx Students’ Mathematics Anxiety And Their Study Habits: Exploring Their Relationship At The Postsecondary Level, Luis M. Fernandez, Xiaohui Wang, Olga Ramirez, Cristina Villalobos

School of Mathematical & Statistical Sciences Faculty Publications

Increasing Latinx students’ success in college-level mathematics calls for exploration on their mathematics anxiety as it relates to study habits. Using a sample of Latinx students in a Hispanic Serving Institution and their levels of mathematics anxiety, pairwise analyses revealed significant differences among subgroups. Moreover, regression analyses showed Latinx students’ study habits being predictive of mathematics anxiety. As a result, recommendations are provided that could alleviate mathematics anxiety and its effects on Latinx college students.

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Effects Of Scarification, Phytohormones, Soil Type, And Warming On The Germination And/Or Seedling Performance Of Three Tamaulipan Thornscrub Forest Species, Paula Luera, Kimberly Wahl-Villarreal, Bradley O. Christoffersen, Abeny Treviño, Pushpa Soti, Christopher A. Gabler Jul 2021

Effects Of Scarification, Phytohormones, Soil Type, And Warming On The Germination And/Or Seedling Performance Of Three Tamaulipan Thornscrub Forest Species, Paula Luera, Kimberly Wahl-Villarreal, Bradley O. Christoffersen, Abeny Treviño, Pushpa Soti, Christopher A. Gabler

School of Earth, Environmental, & Marine Sciences Faculty Publications

The Tamaulipan thornforests of south Texas and northeast Mexico are an ecologically and economically important conservation hotspot. Thornforest restoration is limited by native tree and shrub seedling availability for planting. Seedling shortages arise from low seed availability and knowledge gaps regarding best practices for germinating and growing the 70+ thornforest species desired for restoration plantings. To fill key knowledge gaps, we investigated three ecologically important thornforest species with low or highly variable germination or seedling survival rates: Ebenopsis ebano, Cordia boissieri, and Zanthoxylum fagara. For each, we quantified the effects of different dosages of chemical seed treatments used to promote …

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Stability Of Peakons And Periodic Peakons For A Nonlinear Quartic Camassa-Holm Equation, Aiyong Chen, Tongjie Deng, Zhijun Qiao Jul 2021

Stability Of Peakons And Periodic Peakons For A Nonlinear Quartic Camassa-Holm Equation, Aiyong Chen, Tongjie Deng, Zhijun Qiao

School of Mathematical & Statistical Sciences Faculty Publications

In this paper, we study the orbital stability of peakons and periodic peakons for a nonlinear quartic Camassa-Holm equation (QCHE).We first verify that the QCHE has global peakon and periodic peakon solutions. Then by the invariants of the equation and controlling the extrema of the solution, we prove that the shapes of the peakons and periodic peakons are stable under small perturbations in the energy space.

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Assessing The Impact Of The Lead/Lag Times On The Project Duration Estimates In Highway Construction, Mohamed Abdel-Raheem, Jennifer Reyes, Xiaohui Wang, Grecia Silva Sanchez Jul 2021

Assessing The Impact Of The Lead/Lag Times On The Project Duration Estimates In Highway Construction, Mohamed Abdel-Raheem, Jennifer Reyes, Xiaohui Wang, Grecia Silva Sanchez

Civil Engineering Faculty Publications

The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction, such as weather, location, and soil conditions. However, there are other factors that have not been explored, yet they can have significant impact on the accuracy of the project time estimate. Recently, TxDOT raised a concern regarding the importance of the proper estimating of the lead/lag times in project schedules. These lead/lag times are often determined based on the engineer’s experience. However, inaccurate estimates of the lead/lag time can result in unrealistic project durations. In order to investigate this claim, the study …

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The Conservation Status Of The World’S Freshwater Molluscs, M. Böhm, N. I. Dewhurst-Richman, M. Seddon, C. Albrecht, D. Allen, A. E. Bogan, K. Cummings, G. Darrigran, W. Darwall, Kathryn E. Perez Jul 2021

The Conservation Status Of The World’S Freshwater Molluscs, M. Böhm, N. I. Dewhurst-Richman, M. Seddon, C. Albrecht, D. Allen, A. E. Bogan, K. Cummings, G. Darrigran, W. Darwall, Kathryn E. Perez

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Biology)

With the biodiversity crisis continuing unchecked, we need to establish levels and drivers of extinction risk, and reassessments over time, to effectively allocate conservation resources and track progress towards global conservation targets. Given that threat appears particularly high in freshwaters, we assessed the extinction risk of 1428 randomly selected freshwater molluscs using the IUCN Red List Categories and Criteria, as part of the Sampled Red List Index project. We show that close to one-third of species in our sample are estimated to be threatened with extinction, with highest levels of threat in the Nearctic, Palearctic and Australasia and among gastropods. …

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