Digital Commons Network^™

Multigrid Methods For H(Div) In Three Dimensions With Nonoverlapping Domain Decomposition Smoothers, Susanne C. Brenner, Duk Soon Oh

Faculty Publications

We design and analyze V-cycle multigrid methods for an H(div) problem discretized by the lowest-order Raviart–Thomas hexahedral element. The smoothers in the multigrid methods involve nonoverlapping domain decomposition preconditioners that are based on substructuring. We prove uniform convergence of the V-cycle methods on bounded convex hexahedral domains (rectangular boxes). Numerical experiments that support the theory are also presented.

Social Class Divergence In Family Transitions: The Importance Of Cohabitation, Heather M. Rackin, Christina M. Gibson-Davis

Faculty Publications

Objective: This study examined trends in familial transitions by maternal education and whether transitions rose because of changes in prevalence (the share of children exposed to a relationship state, either marriage or cohabitation) or churning (the number of entrances and exits conditional on being exposed to a relationship state). Background: Children's experiences of transitions, an important predictor of well-being, have leveled off in recent decades. Plateauing in transitions may reflect heterogeneity by socioeconomic status. Method: Data came from the National Survey of Family Growth on firstborn children observed from ages 0 to 5 among mothers aged 15 to 34 at …

Nonlinear Equations With Gradient Natural Growth And Distributional Data, With Applications To A Schrödinger Type Equation, Karthik Adimurthi, Nguyen Cong Phuc

Faculty Publications

We obtain necessary and sufficient conditions with sharp constants on the distribution (Formula presented.) for the existence of a globally finite energy solution to the quasi-linear equation with a gradient source term of natural growth of the form (Formula presented.) in a bounded open set (Formula presented.). Here (Formula presented.), (Formula presented.), is the standard (Formula presented.) -Laplacian operator defined by (Formula presented.). The class of solutions that we are interested in consists of functions (Formula presented.) such that (Formula presented.) for some (Formula presented.) and the inequality (Formula presented.) holds for all (Formula presented.) with some constant (Formula presented.). …

Enhanced Sorption Of Hexavalent Chromium [Cr(Vi)] From Aqueous Solutions By Diluted Sulfuric Acid-Assisted Mgo-Coated Biochar Composite, Ran Xiao, Jim J. Wang, Ronghua Li, Jonghwan Park, Yili Meng, Baoyue Zhou, Scott Pensky, Zengqiang Zhang

Faculty Publications

Metal oxide-Carbon composites have aroused great interesting towards specific anionic contaminants removal from the polluted environment. In this study, aiming at removing toxic chromate ion [Cr(VI)] from aqueous solutions, a novel approach was developed to produce surface-enhanced MgO-coated biochar adsorbent from sugarcane harvest residue (SHR). It was found that sulfuric acid hydrolysis and MgO-coating both facilitated the removal of Cr(VI) by biochars, and the maximum sorption capacities for the pristine biochar (SHR550), MgO-coated biochar (MgSHR550), and acid-assisted MgO-coated biochar (MgASHR550) that derived from the Langmuir isotherm model were 20.79, 54.64, and 62.89 mg g−1, respectively. Additionally, the Cr(VI) removal was …

Response Of Microbial Populations Regulating Nutrient Biogeochemical Cycles To Oiling Of Coastal Saltmarshes From The Deepwater Horizon Oil Spill, Hee Sung Bae, Laibin Huang, John R. White, Jim Wang, Ronald D. Delaune, Andrew Ogram

Faculty Publications

Microbial communities play vital roles in the biogeochemistry of nutrients in coastal saltmarshes, ultimately controlling water quality, nutrient cycling, and detoxification. We determined the structure of microbial populations inhabiting coastal saltmarsh sediments from northern Barataria Bay, Louisiana, USA to gain insight into impacts on the biogeochemical cycles affected by Macondo oil from the 2010 Deepwater Horizon well blowout two years after the accident. Quantitative PCR directed toward specific functional genes revealed that oiled marshes were greatly diminished in the population sizes of diazotrophs, denitrifiers, nitrate-reducers to ammonia, methanogens, sulfate-reducers and anaerobic aromatic degraders, and harbored elevated numbers of alkane-degraders. Illumina …

A Parameterized Proximal Point Algorithm For Separable Convex Optimization, Jianchao Bai, Hongchao Zhang, Jicheng Li

Faculty Publications

In this paper, we develop a parameterized proximal point algorithm (P-PPA) for solving a class of separable convex programming problems subject to linear and convex constraints. The proposed algorithm is provable to be globally convergent with a worst-case O(1 / t) convergence rate, where t denotes the iteration number. By properly choosing the algorithm parameters, numerical experiments on solving a sparse optimization problem arising from statistical learning show that our P-PPA could perform significantly better than other state-of-the-art methods, such as the alternating direction method of multipliers and the relaxed proximal point algorithm.

Measurement Of Source Star Colors With The K2c9-Cfht Multi-Color Microlensing Survey, Weicheng Zang, Matthew T. Penny, Wei Zhu, Shude Mao, Pascal Fouqué, Andrzej Udalski, Kyu Ha Hwang, Tianshu Wang, Chelsea Huang, Tabetha S. Boyajian, Geert Barentsen

Faculty Publications

Microlensing events observed from locations separated by ∼au have different peak times and peak magnifications due to microlensing parallax. K2 Campaign 9 (K2C9) was the first space-based microlensing parallax survey capable of measuring microlensing parallaxes of free-floating planet candidate microlensing events. Simultaneous to K2C9 observations we conducted the K2C9 Canada–France–Hawaii Telescope Multi-Color Microlensing Survey (K2C9-CFHT MCMS) in order to measure the colors of microlensing source stars to improve the accuracy of K2C9’s parallax measurements. We describe the difference imaging photometry analysis of the K2C9-CFHT MCMS observations, and present the project’s first data release. This includes instrumental difference flux light curves …

Measurement And Modeling Of The Spatiotemporal Dynamics Of Beach Surface Moisture Content, Phillip P. Schmutz, Steven L. Namikas

Faculty Publications

The spatiotemporal dynamics of surface moisture exert a significant influence on the operation of aeolian transport systems at many beaches. However, we currently lack the detailed understanding of variability in surface moisture required to incorporate it into aeolian models. This problem is addressed here through direct measurements and simulation modeling of beach surface moisture over a twelve-day period, and through quantification of the relative contributions of evaporation, condensation and groundwater inputs to surface moisture. It was found that the beach surface can be characterized spatially in terms of three moisture zones: a consistently dry zone (40%). The relative influence of …

F18rs Sgr No. 24 (Thousand Oaks), Drake Brignac

Student Senate Enrolled Legislation

A RESOLUTION

To offer condolences to the city of Thousand Oaks, California, the Ventura County Sheriff’s Office, Pepperdine University, and the families of those killed at the Borderline Bar & Grill on November 7, 2018

F18rs Sgr No. 15 (Floor Crew), Edouard D'Espalungue

Student Senate Enrolled Legislation

A RESOLUTION

To congratulate the LSU Building Services Floor Crew for their outstanding work during the year 2018

A Study On Amplitude Transmission In Ultrasonic Welding Of Thermoplastic Composites, Genevieve Palardy, Huajie Shi, Arthur Levy, Steven Le Corre, Irene Fernandez Villegas

Faculty Publications

Ultrasonic welding of thermoplastic composite materials is a promising joining technique that is now moving towards up-scaling, i.e. the assembling of large industrial parts. Despite its growing technological maturation, the assumed physical mechanisms underlying ultrasonic heating (viscoelastic heating, friction) are still insufficiently understood and modelled. In particular, the hammering phenomenon, resulting from the periodic loss of contact between the sonotrode and adherends due to the high frequency vibration caused to the former, directly impacts the heating efficiency. We propose in this work an original experimental and modelling approach towards a better understanding of the hammering effect. This approach makes combined …

Enhancing The Durability And The Service Life Of Asphalt Pavements Through Innovative Light-Induced Self-Healing Materials, Marwa Hassan

Publications

The objective of this study was to evaluate the efficiency of a new generation of Ultraviolet (UV) light-induced selfhealing polymers in enhancing the durability and self-healing properties of asphalt mixtures. Self-healing polymers were successfully synthesized in the laboratory and were characterized using Fourier Transform Infrared Spectroscopy (FTIR). In addition, Thermogravimetric Analysis (TGA) results showed that the synthesized polymers achieved the required thermal stability to resist asphalt mixture production processes. Viscosity results showed that addition of 5% Recycled Asphalt Shingle (RAS) and/or 20% Reclaimed Asphalt Pavement (RAP) caused an increase in the viscosity of the binder blends. However, a reduction in …

Evaluation Of The Performance And Cost-Effectiveness Of Engineered Cementitious Composites (Ecc) Produced From Region 6 Local Materials, Gabriel Andres Arce Amador, Tyson Rupnow, Marwa Hassan

Publications

The project objective is to develop cost-effective Engineered Cementitious Composites (ECC) with locally available ingredients in Region 6 to address the deficiencies observed in ordinary concrete materials. The study explored the utilization of two types of river sands (coarse and fine), two types of PVA fibers (long and short), four levels of cement replacement with Class F fly ash, and the implementation of recycled crumb rubber in the performance of ECC materials. A total of 24 mix designs were prepared and evaluated in compression, tension, and bending to assess its mechanical properties. Furthermore, the cracking characteristics of the materials produced …

Modeling Sulfate Attack In Modern Concrete For Building Sustainable And Resilient Infrastructure, Zachary Grasley

Publications

External sulfate attack is a complex phenomenon and is manifested in the form of large expansion, cracking, and spalling depending on the exposure solution and material constituent properties. Several models were developed in the past to demonstrate sulfate attack mechanisms that account for the diffusion of sulfate ions into the porous concrete and the successive deformation triggered by the chemical reaction and precipitation of expansive agents. However, none of these models accounts for the effect of the migration of solvent water from the low solute concentration solution to high solute concentration solution driven by the osmotic pressure. Osmotic pressure is …

In-Situ Mechanical Characterization For Compacted Aggregates, Douglas Cortes, Paola Bandini

Publications

The evaluation of compacted unbound aggregate layers is perhaps the most common undertaking in transportation-related projects. The assessment of compaction compliance in engineered fills, subgrades, subbases, and bases in roadways and railways is central to ensure longevity of ground transportation infrastructure. In many cases, premature failures in roadways that originate in the unbound aggregate layers can be traced back to inadequate compaction. These failures are preventable, provided the problem areas can be identified by a suitable field test during construction. The most widely used method for compaction assessment during construction is the nuclear density gauge (NDG) test. While the device …

Bridge Inspecting With Unmanned Aerial Vehicles R&D, Paul Darby, Vijaya Gopu

Publications

The project achieves through research including literature, on site interviews, and experimentation: 1) a recommendation for a UAV-based system to practically assist in routine bridge inspection work in the State of Louisiana, 2) the identification and description of advantages, disadvantages, and limitations in the use of UAVs for routing bridge inspection work in Louisiana, and 3) provided recommendations for future work. The Yuneec H520 aircraft and its E90 camera are recommended, as is the need for a boat to be included as part of the system. The recommended system has advantages in reaching portions of the bridge that are difficult …

Use Of Rice Hull Ash (Rha) As A Sustainable Source Of Construction Material, Zahid Hossain, Ashraf Elsayed

Publications

With the imminent shortage of natural resources, the need to find sustainable development is the highest in recent history. Therefore, this study examines the potential uses of Rice Hull Ash (RHA) as a sustainable cementitious material (SCM) in preparation of concrete. This study also assesses the use of RHA as an alternative of commonly used polymers in preparing high-grade asphalt binders. RHA is a potential sustainable solution because it is currently being treated as an agricultural waste material, yet its high silica content makes it a potential construction material. Three different sizes of RHA (600 µm, 150 µm, and 44 …

Use Of Nanoclays As Alternatives Of Polymers Toward Improving Performance Of Asphalt Binders, Zahid Hossain, Ashraf Elsayed

Publications

The main goal of this study is to assess the feasibility of the use of nanoclay as an alternative to commonly used polymers such as styrene-butadiene-styrene (SBS), which are used to modify the performance grade (PG) of asphalt binders. Three types of nanoclay and two types of neat binders were selected for laboratory investigation. Different amounts (1, 2, and 3%) of nanoclays were used. A blending protocol has been developed to mix the nanoclay with the asphalt binder. Rotational Viscosity (RV), Dynamic Shear Rheometer (DSR), Optical Contact Analyzer (OCA) and Atomic Force Microscope (AFM) were conducted to evaluate the properties …

Development Of A Self-Healing And Rejuvenating Mechanisms For Asphalt Mixtures Containing Recycled Asphalt Shingle, Marwa Hassan

Publications

The objective of this study was to test the hypothesis that hollow-fibers encapsulating a rejuvenator product could improve both self-healing, rejuvenation, and mechanical properties of asphalt mixtures. Hollow-fibers containing a rejuvenating product were synthesized via a wet spinning procedure with sodium-alginate polymer as the encapsulating material. An optimization of the production parameters for the synthesis of fibers was performed to develop fibers suitable for high-temperature and shear stress environment typical of asphalt mixture production. A self-healing experiment was conducted to evaluate the healing/rejuvenation capabilities of sodium-alginate fibers in asphalt mixtures with varying types of binders and recycled materials. Based on …

Development Of A Standard Test Method For Characterization Of Asphalt Materials And Aging-Related Degradation Using An Extensional Rheometer, Nazimuddin Wasiuddin

Publications

An extensional deformation test method using a Sentmanat Extensional Rheometer (SER) fixture inside a Dynamic Shear Rheometer (DSR) is developed in this study to investigate the degradation of the polymer due to aging and to investigate the effect of modifier type. A relationship between different percentages of modifier and ductility of the modified binder is also investigated. The sample geometrics used in this study are 1 mm x 0.72 mm and 3 mm x 0.72 mm. A total of one hundred and sixty-two samples were tested. Three modifiers Styrene-Butadiene-Styrene (SBS), Polyphosphoric Acid (PPA) and latex were used. One PG 76-22, …

Development Of Environmentally-Friendly Stabilization Methods For Transportation Infrastructure Based On Geopolymers, Miladin Radovic, Anand Puppala

Publications

Geopolymers (GPs) have received much attention as an eco-friendly and sustainable alternative to conventional chemical additives, since they can be processed at room temperatures from aqueous solutions by utilizing waste materials (e.g. fly ash) or abundant natural sources (e.g. clay). A collaborative research study is carried out by teams from Texas A&M University (TAMU) and University of Texas at Arlington (UTA) to investigate the effectiveness of GPs for stabilizing base and subgrade materials by considering the strength and shrink-swell characteristics. Two types of clay, obtained from the North Dallas area, were mixed with a potassium-based GP synthesized from metakaolin and …

Sustainable And Equitable Financing For Pedestrian Infrastructure Maintenance, Gregory Rowangould

Publications

In many communities, pedestrian infrastructure is discontinuous, inaccessible to those with physical disabilities, and poorly maintained. Correcting these problems would be a first step in providing infrastructure to achieve the active travel and related transportation goals of many communities. One nearly universal challenge to maintaining sidewalks in a state of good repair and addressing environmental justice concerns is an adequate, sustainable, and equitable source of funding. Municipal governments across the country maintain and repair their streets and roadways; however, most require residents to maintain and repair public sidewalks adjacent to their property. These policies are difficult to enforce and may …

Bridge Deck Overlays Using Ultra-High Performance Concrete, Craig Newtson, Brad Weldon

Publications

This study investigated the use of a locally produced ultra-high performance concrete (UHPC) as an alternative to typical overlay materials. Several bond strength tests including slant-shear, splitting tension, and direct tension tests were performed to assess the bond strength between UHPC and normal strength concrete (NSC) substrate with varying surface textures. Tests were also conducted to assess the early-age and longer-term shrinkage behavior and coefficient of thermal expansion of the UHPC as well as rapid chloride permeability testing. Good bond between UHPC and NSC substrate was observed even with inadequate surface texture. Combined shrinkage and thermal effects were investigated for …

Limits To Atom-Vapor-Based Room-Temperature Photon-Number-Resolving Detection, Elisha S. Matekole, Hwang Lee, Jonathan P. Dowling

Faculty Publications

We study the atom-vapor-based photon-number-resolving detection from first principles, including quantum-mechanical treatment of the electromagnetic field. We study a photon detector model that combines coherently controlled absorption of light and resonance fluorescence to achieve photon counting at room temperature. In particular we identify the fundamental limits to this particular scheme of photon detection. We show that there exists a time-energy uncertainty between the incident pulse strength and the time period of the incident pulse. We verify the role of a large ensemble of atoms to boost the efficiency of such a detector.

Proximity-Induced Superconductivity At Nonhelical Topological Insulator Interfaces, David J. Alspaugh, Mahmoud M. Asmar, Daniel E. Sheehy, Ilya Vekhter

Faculty Publications

We study how nonhelical spin textures at the boundary between a topological insulator (TI) and a superconductor (SC) affect the proximity-induced superconductivity of the TI interface state. We consider TIs coupled to both spin-singlet and spin-triplet SCs, and show that for the spin-triplet parent SCs, the resulting order parameter induced onto the interface state sensitively depends on the symmetries which are broken at the TI-SC boundary. For chiral spin-triplet parent SCs, we find that nodal proximity-induced superconductivity emerges when there is broken twofold rotational symmetry which forces the spins of the nonhelical topological states to tilt away from the interface …

Design, Simulation, And Construction Of An Ieee 14-Bus Power System, John Albert Boudreaux

LSU Master's Theses

Today’s bulk power system is massive, complex, and very dynamic. The U.S. power grid spans from coast to coast and even as far reaching as Canada. With the addition of new technologies such as renewable energies and power electronics to aid in power conversion and control, the power system grows more complex by the day. The most common approach of analyzing power system stability is through computer modeling and simulation. Due to the vast size and inaccessibility of transmission systems, real time testing can prove difficult. The motivation of this project was to design, simulate, and construct an IEEE 14 …

Qualitative Dynamics And Inflationary Attractors In Loop Cosmology, Bao Fei Li, Parampreet Singh, Anzhong Wang

Faculty Publications

Qualitative dynamics of three different loop quantizations of spatially flat isotropic and homogeneous models is studied using an effective spacetime description of the underlying quantum geometry. These include the standard loop quantum cosmology (LQC), its recently revived modification (referred to as mLQC-I), and another related modification of LQC (mLQC-II) of which the dynamics is studied in detail for the first time. Various features of LQC, including quantum bounce and preinflationary dynamics, are found to be shared with the mLQC-I and mLQC-II models. We study universal properties of dynamics for chaotic inflation, fractional monodromy inflation, Starobinsky potential, nonminimal Higgs inflation, and …

Selling, General, And Administrative Cost Stickiness And Gdp Predictions, Russell Barber

LSU Doctoral Dissertations

This study examines whether selling, general, and administrative (SG&A) cost stickiness is informative in predicting GDP growth and in explaining GDP forecast errors. Prior research has examined how accounting earnings growth is informative in predicting GDP. However, up to this point there has been a lack of research examining how accounting cost behavior is informative in predicting GDP growth. Managers make SG&A cost decisions based on projections of future demand, so the main hypothesis of this study is that cost stickiness has an informational role in predicting GDP growth and in explaining GDP forecast errors. The empirical findings of this …

Chemically Modified Cellulosic Materials As Multi-Functional Agents In Polymer Composites, Jinlong Zhang

LSU Doctoral Dissertations

Comparative flame retardancy of micro wood fiber plastic composites (WPCs) with fire retardants (1,2-bis(pentabromophenyl) ethane, metal hydroxides and nanoclay) was studied. The fire additives (1,2-bis(pentabromophenyl) ethane as well as magnesium hydroxide) obviously enhanced the fire retarding properties of WPCs. Especially, 1,2-bis(pentabromophenyl) ethane significantly reduced the total heat release as well as heat release rate. In addition, a synergistic effect of 1,2-bis(pentabromophenyl) and nanoclay was achieved for the enhanced fire retarding performance of WPCs.

A copolymer of cellulose nanocrystals (CNCs) and poly(N-vinylcaprolactam) (PVCL) (PVCL-g-CNCs) for use as thermally-responsive polymers with low critical solution temperatures (LCSTs) was synthesized via atom transfer radical …

Bfd, A New Class Of [2fe-2s] Protein That Functions In Bacterial Iron Homeostasis, Requires A Structural Anion Binding Site, Harshani Wijerathne, Huili Yao, Yan Wang, Scott Lovell, Kevin P. Battaile, Mario Rivera

Faculty Publications

Copyright © 2018 American Chemical Society. Mobilization of iron from bacterioferritin (BfrB) requires specific interactions with a [2Fe-2S] ferredoxin (Bfd). Blocking the BfrB:Bfd interaction results in irreversible iron accumulation in BfrB and iron deficiency in the cytosol [Eshelman, K., et al. (2017) Metallomics 9, 646-659]. The only known Bfd structure, which was obtained in complex with BfrB (Protein Data Bank entry 4E6K), indicated a new fold and suggested that the stability of Bfd is aided by an anion binding site consisting of R26, R29, and K46. We investigated the Bfd fold using site-directed mutagenesis, X-ray crystallography, and biochemistry in solution. …