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Articles 2161 - 2190 of 2820
Full-Text Articles in Engineering
Elasto-Plastic And Damage Modeling Of Reinforced Concrete, Ziad N. Taqieddin
Elasto-Plastic And Damage Modeling Of Reinforced Concrete, Ziad N. Taqieddin
LSU Doctoral Dissertations
Modeling the mechanical behavior of Reinforced Concrete (RC) is still one of the most difficult challenges in the field of structural engineering. The Nonlinear Finite Element Analysis (NFEA) and modeling of the behavior of RC members are the primary goals of this study. The macroscopic components of RC, Concrete material and reinforcing steel, are represented herein by separate material models. These material models are combined together using a model that describes the global effect of interaction between reinforcing steel and concrete in order to simulate the behavior of the composite RC material. A thermodynamically consistent constitutive model for concrete that …
Moderately-Rapid Assessment Of Alkaline Desiccation Environmental Systems, David Alan Bates
Moderately-Rapid Assessment Of Alkaline Desiccation Environmental Systems, David Alan Bates
LSU Doctoral Dissertations
A moderately-rapid assessment tool was developed to analyze the waterless desiccation compost toilet investigated in a rural Mexican setting. Over 100 social factors were identified along with the applicable technical factors that influenced the low acceptability of the toilets. A 4-point rating scale was developed to increase the ability and speed of analyzing both the social and technical data. The treatment process was an alkaline-desiccation process with mean pH values of 8.2 ± sd 1.1 and water content of 18.3% ± sd 9.9, which resulted in mean fecal coliform values of 15.0 MPN/g ± sd 31.8, drastically lower than the …
Nonlocal Gradient-Dependent Modeling Of Plasticity With Anisotropic Hardening, Gerald Pekmezi
Nonlocal Gradient-Dependent Modeling Of Plasticity With Anisotropic Hardening, Gerald Pekmezi
LSU Master's Theses
This work is concerned with the formulation of the thermodynamics of nonlocal plasticity using the gradient theory. The formulation is based on the nonlocality energy residual introduced by Eringen and Edelen (1972). Gradients are introduced for those variables associated with isotropic and kinematic hardening. The formulation applies to small strain gradient plasticity and makes use of the evanescent memory model for kinematic hardening. This is accomplished using the kinematic flux evolution as developed by Zbib and Aifantis (1987). Therefore, the present theory is a four nonlocal parameter-based theory that accounts for the influence of large variations in the plastic strain, …
Voltage Dip Mitigation For Motor Starters Using An Adaptive High Speed Relay Protection On The High Voltage Transmission System, Cesar Alberto Rincon
Voltage Dip Mitigation For Motor Starters Using An Adaptive High Speed Relay Protection On The High Voltage Transmission System, Cesar Alberto Rincon
LSU Master's Theses
Currently, the aging state of the protection systems for industrial facilities is calling for a system-wide review of the equipment and the protection schemes used in all these places, calling for a new approach in the design and implementation of these systems. Some of these facilities house critical processes that can be seriously affected by a misoperation of equipment or a disturbance in the system, aspects ranging from safety of plant workers to millions of dollars in loss of production. In this thesis different contingency situations were explored for problems in the utility transmission system that could affect large industrial …
Photocatalytic Oxidation Of Ethanol Using Macroporous Titania, Gibert Merle Magpantay
Photocatalytic Oxidation Of Ethanol Using Macroporous Titania, Gibert Merle Magpantay
LSU Master's Theses
Photocatalytic oxidation (PCO) using TiO2 is a potential means of remediating poor indoor air quality that is attributed to low levels of volatile organic compounds (VOC). In this work, ethanol is chosen as a simple compound representative of VOC’s. The aim of this research is to establish a baseline for the photocatalytic activity of TiO2 in ethanol PCO as well as the photonic efficiency of the photoreactor. The PCO conversion could then be enhanced by using photocatalyst having a macroporous structure. A flat plate photoreactor, UV light delivery and a flow system was designed in this work to accomplish ethanol …
Application Of The Hyman Model To Evaluate The Water And Salt Budgets In Three Mangrove Sites Along Shark River, Everglades, Cheng-Feng Tsai
Application Of The Hyman Model To Evaluate The Water And Salt Budgets In Three Mangrove Sites Along Shark River, Everglades, Cheng-Feng Tsai
LSU Master's Theses
Mangrove trees play an important role in the maintenance and sustainability of coastal wetlands due to their ability to adapt and survive in a wide range of saline and tidal conditions. Hydrologic processes (e.g., inundation frequency) and salinity are important regulators controlling the growth and productivity of mangrove forests. To quantify how changes in landscape-level hydrology will influence these regulators in mangrove forests, the hydrology model (HYMAN) was applied to three sites with distinct tidal forcings along the Shark River estuary in the Everglades National Park. HYMAN model uses mass balance equation to determine daily water and salt budgets as …
Mercury Transport Through A Capped Sediment, Jianrong Liu
Mercury Transport Through A Capped Sediment, Jianrong Liu
LSU Doctoral Dissertations
Laboratory simulation cells were employed to evaluate the effectiveness of a sand cap for containing highly mercury-contaminated lake sediments and the resultant impacts on the mercury fate beneath the cap. Sand cap can delay and reduce the migration of mercury into the overlying water; however, due to the small partition coefficient of mercury between sand and water, a capping material with higher partition coefficient is better for the long-term containment of mercury. In the following study, efforts were made to identify and investigate an active capping material which works effectively at containing and inhibiting the methylation of mercury. Based on …
Degradation And Water Quality Dynamics Of Sugarcane Residue In South Louisiana, Jose Roberto Deras
Degradation And Water Quality Dynamics Of Sugarcane Residue In South Louisiana, Jose Roberto Deras
LSU Doctoral Dissertations
PURPOSE: This research was conducted to assess methods to manage the residue blanket to avoid open field burning in sugarcane. Experiments were conducted in the state of Louisiana to evaluate methods to asses and potentially reduce water quality issues. METHODS: Concentrations and frequencies of biological compost tea were sprayed on sugarcane combine-harvester residue blanket to increase degradation rate and reduce potential for runoff water to transport nutrients and sediments that may impair water bodies, while sustaining suitable sugarcane yield. Carbon dioxide evolution rate (mg CO2-C) and CO2 fluxes were measured in laboratory and in open field conditions; as an index …
Magnetic Field Effects On Diffusion Flames, Diego F. Gonzalez
Magnetic Field Effects On Diffusion Flames, Diego F. Gonzalez
LSU Master's Theses
Magnetic field effects in combustion is an area of study that has previously been overlooked. The influence of magnetic fields on flames has only recently been explored and is of interest both from a scientific and a practical standpoint. This study provides theoretical, numerical and experimental evidence that combustion can be affected with the use of suitable magnetic fields. This thesis focuses on four different types of magnetic field: homogeneous, gradient, oscillating and pre-combustion. For the homogeneous field case, the Gibbs Free Energy method was used to determine the mole fraction of product species. It was found that homogeneous fields …
Lattice Boltzmann Modeling For Mass Transport Equations In Porous Media, Borja Servan Camas
Lattice Boltzmann Modeling For Mass Transport Equations In Porous Media, Borja Servan Camas
LSU Doctoral Dissertations
The aim of this dissertation is to extend the lattice Boltzmann method (LBM) to cope with parameter heterogeneity and anisotropy in mass transport equations in porous media, as well as investigating the stability and accuracy. Although the LBM is a well known and effective numerical method to solve fluid flows, LBM has not been extensively applied to mass transport equations in porous medium flow yet, and only a few works can be found on improving LBM to cope with mass transport equations other than the diffusion and advection-diffusion equations. One of the reasons why LBM has not been extensively used …
A Study Of Regret And Rejoicing And A New Mcdm Method Based On Them, Xiaoting Wang
A Study Of Regret And Rejoicing And A New Mcdm Method Based On Them, Xiaoting Wang
LSU Doctoral Dissertations
Multi-criteria decision-making (MCDM) is one of the most widely used decision methodologies in the sciences, business, and engineering worlds. MCDM methods aim at improving the quality of decisions by making the process more explicit, rational, and efficient. One controversial problem is that some well-known MCDM methods, like the additive AHP methods and the ELECTRE II and III methods, may cause some types of rank reversal problems. Rank reversal means that the ranking between two alternatives might be reversed after some variation occurs to the decision problem, like adding a new alternative, dropping an old alternative or replacing a non-optimal alternative …
Quiescent Current Testing Of Cmos Data Converters, Siva Yellampalli
Quiescent Current Testing Of Cmos Data Converters, Siva Yellampalli
LSU Doctoral Dissertations
Power supply quiescent current (IDDQ) testing has been very effective in VLSI circuits designed in CMOS processes detecting physical defects such as open and shorts and bridging defects. However, in sub-micron VLSI circuits, IDDQ is masked by the increased subthreshold (leakage) current of MOSFETs affecting the efficiency of I¬DDQ testing. In this work, an attempt has been made to perform robust IDDQ testing in presence of increased leakage current by suitably modifying some of the test methods normally used in industry. Digital CMOS integrated circuits have been tested successfully using IDDQ and IDDQ methods for physical defects. However, testing of …
Identification Of Polycyclic Aromatic Hydrocarbons In The Supercritical Pyrolysis Products Of Synthetic Jet Fuel S-8 And Methylcyclohexane, Jorge Oswaldo Ona Ruales
Identification Of Polycyclic Aromatic Hydrocarbons In The Supercritical Pyrolysis Products Of Synthetic Jet Fuel S-8 And Methylcyclohexane, Jorge Oswaldo Ona Ruales
LSU Doctoral Dissertations
Inside the pre-combustor fuel lines of future high-speed aircraft, at supercritical conditions, hydrocarbon fuels react to form polycyclic aromatic hydrocarbons (PAH) and eventually solid deposits. These deposits can block fuel lines and lead to undesirable effects for the aircraft operation. To elucidate the pathways that lead to the formation of PAH (and ultimately, solids formation), the identification of the PAH products generated by the reactions is critical. In this context, two fuels have been analyzed: synthetic jet fuel S-8 and methylcyclohexane. Synthetic jet fuel S-8 is important due to its non-petroleum origin. Methylcyclohexane is important due to its endothermic behavior. …
An Investigation Into Fuel Cells And Flow Cytometers Optimal Design, Etim Sunday Udoetok
An Investigation Into Fuel Cells And Flow Cytometers Optimal Design, Etim Sunday Udoetok
LSU Doctoral Dissertations
The aim of the fuel cells part of this project was to investigate the performance of Proton Exchange Membrane Fuel Cells and closely related fuel cell types like the Alkaline Fuel Cells and Phosphoric Acid Fuel Cells. The investigation involved understanding the performance of fuel cells, addressing the shortcomings of currently used designs, and finding new methods for improving the performance of fuel cells. CFD was used to study flow channels and information learned from the study was used to design a new and improved flow channel. A prototype of the new design was fabricated, tested and found to perform …
Numerical Simulations Of Flow And Mass Transport In Micro-Fluidic Components For Modular Bio-Analytic Chip Applications, Sudheer D. Rani
Numerical Simulations Of Flow And Mass Transport In Micro-Fluidic Components For Modular Bio-Analytic Chip Applications, Sudheer D. Rani
LSU Doctoral Dissertations
Microfluidics has received a great deal of attention in the past decade. The ability of modular microfluidic chips to miniaturize integrate chemical and biological systems (µTAS) can be greatly productive in terms of cost and efficiency. During the design of these modular devices, misalignment of materials, geometrical or both is one of the most common problems. These misalignments can have adverse effect in both pressure driven and electrokinetically driven flows. In the present work, Numerical Simulations have been performed to study the effect of material and geometrical mismatch on the flow behavior and species progression in microfluidic interconnects. In the …
Dynamic Shear Bands In Metals Under High Strain Rates, Amin Hisham Almasri
Dynamic Shear Bands In Metals Under High Strain Rates, Amin Hisham Almasri
LSU Doctoral Dissertations
Adiabatic shear bands have been observed for a long time to occur under different conditions in many applications. Analysis of these localizations highly depends on the selection of the constitutive model. Hence, two constitutive models that take temperature and strain rate effect into account are proposed. The first model is a physically based model that depends on basic physical quantities, such as dislocation densities, Burgers vector, and activation energy. The second model is a simple empirical power model with a softening term. The empirical constitutive law is seen to be more successful in capturing the mechanical behavior of steel alloy …
Electrochemical Fabrication Of Auco Nanostructures, Maoshi Guan
Electrochemical Fabrication Of Auco Nanostructures, Maoshi Guan
LSU Doctoral Dissertations
Electrodeposited Au/CoAu multilayered nanowires are materials with alternating layers of Au and CoAu in a wire where the layer thickness and wire diameter are nanometer size. They can be used for different applications. For example, the wires may exhibit giant magnetoresistance (GMR), a change in the materials resistance with a magnetic field, having applications as a sensor material for microdevices. If Co is etched from CoAu nanowires, rough, porous gold nanostructures will be left behind, which could be used as novel catalysts. In this study, the electrodeposition of Au/CoAu multilayered nanowires and nanotubes in nanoporous templates was explored from a …
Thermomechanical Interaction Analysis Of Bodies Subjected To Oscillatory Heat Source, Jun Wen
Thermomechanical Interaction Analysis Of Bodies Subjected To Oscillatory Heat Source, Jun Wen
LSU Doctoral Dissertations
Surface heating by application of a moving heat source is a common problem in most manufacturing processes as well as in many tribological applications. The existing literature on studies of moving heat source problems primarily concentrates on unidirectional moving heat sources. Yet, a more complete analysis requires understanding of thermal behavior of bodies in relative sliding contacts subjected to oscillatory heat sources and thermomechanical interaction. In this dissertation, two analytical models are developed for rapid evaluation of the transient temperature in solids undergoing oscillatory heat source. In the first model, an analytical technique is presented to treat oscillatory heat source …
Locally Derived Nonpoint Loading Estimates For The Boeuf River/Bayou Lafourche Watershed, Emerald Purser Roider
Locally Derived Nonpoint Loading Estimates For The Boeuf River/Bayou Lafourche Watershed, Emerald Purser Roider
LSU Doctoral Dissertations
There is currently a great demand for data and models that can be used to quantify nonpoint source pollutant loads from different land-use types. The Louisiana Department of Environmental Quality (LDEQ) is in the process of implementing management programs for impacted water bodies based on the Total Maximum Daily Load (TMDL) of a pollutant. Pollutants of concern include total suspended solids (TSS), nitrogen, and phosphorus. One of the key parameters in determining the TMDL of a water body is the nonpoint source pollutant load from different land-use types. To date, such load estimates in Louisiana are lacking. The primary objective …
Measurement Of Metal Migration In Sediment Caps With X-Ray Fluorescene, Ming Yin
Measurement Of Metal Migration In Sediment Caps With X-Ray Fluorescene, Ming Yin
LSU Doctoral Dissertations
ABSTRACT Sand is often used as a passive barrier to slow release of metals from the sediment and to separate benthic organisms from the sediment. Materials that effectively adsorb metals have the potential to provide significantly greater effectiveness by further retarding metal release. In this thesis, the effectiveness of apatite and Phosphil®, which contain phosphate in a form that can absorb many metals, is evaluated with a series of sorption and migration column experiments using Cr, Cu, Zn and Pb. Langmuir shape isotherms were observed suggesting that the effectiveness of these materials decreases at high concentration. The sorption isotherm experiments …
Flow Field And Heat Transfer Analyses Of Mechanical Seals, Zhaogao Luan
Flow Field And Heat Transfer Analyses Of Mechanical Seals, Zhaogao Luan
LSU Doctoral Dissertations
Mechanical seals are widely used in rotating equipment such as pumps, turbines and agitators to prevent leakage. One crucial factor for keeping seals reliable is the thermal behavior of the seal rings. The existing literature on thermal effects in seals primarily concentrates on the conduction of heat into the rings. Yet, a more complete analysis requires understanding of the flow field around the rings. In this dissertation, both the laminar and turbulent flows within the seal chamber are studied and their effects on the heat transfer in the seal rings are evaluated. Based on extensive sets of numerical simulations, heat …
Composite Sandwich Structure With Grid Stiffened Core, Venkata Dinesh Muthyala
Composite Sandwich Structure With Grid Stiffened Core, Venkata Dinesh Muthyala
LSU Master's Theses
Composite sandwich structures have been widely used in aerospace structures, ship building, infrastructure, etc. due to their light weight and high strength to weight ratio. Traditionally, light-weight core materials such as foam core, truss core, honeycomb core have been used in fabricating sandwich structures with limited success. In this study, a new composite sandwich structure with a hybrid core was proposed, fabricated, tested, and modeled. The hybrid core consists of a fiber reinforced polymer grid skeleton that is filled in by extremely light-weight syntactic foam in the bay areas. The new sandwich structure was manufactured using a new manufacturing process. …
Readjustment Of A Regional Geodetic Leveling Network To Account For Temporally And Spatially Variable Vertical Displacement Of Benchmarks, Kurt Shinkle
LSU Doctoral Dissertations
This dissertation describes and analyzes the temporally and spatially non-linear nature of the vertical displacement of 1st order geodetic benchmarks in the lower Mississippi Valley and northern Gulf of Mexico coastal region. The least-squares method of adjusting redundant surveying observations is implemented to compute the most likely value of the most recent rates of displacement at node benchmarks within the network, along with estimates of the uncertainty of those values. Using that result, a modification of the standard method of adjusting geodetic leveling networks is developed and demonstrated to compute new elevations for the node benchmarks which accounts for both …
Aconitic Acid From Sugarcane: Production And Industrial Application, Nicolas Javier Gil Zapata
Aconitic Acid From Sugarcane: Production And Industrial Application, Nicolas Javier Gil Zapata
LSU Doctoral Dissertations
Trans aconitic acid (TAA) is the predominant organic acid in cane leaf matter (CLM) juice. Its concentration is three to six times higher than the level found in sugarcane stalks. The variation of composition in terms of total fermentable sugars (TFS), anions, and cations of the LCP85-384 sugarcane variety during 2003-2006 seasons, as well as the ripener (Polado-L®) effect were analyzed. TAA content ranged between 2.1-3.1 kg / t CLM. The TFS in CLM juice yielded a fermentation efficiency of 92%, four points lower than with sugar molasses. Liquid-liquid extraction (LLE), solid-liquid extraction and ion exchange were evaluated for the …
Optimal Control Of Production And Distribution In A Supply Chain System Operating Under A Jit Delivery Policy, Pablo Biswas
Optimal Control Of Production And Distribution In A Supply Chain System Operating Under A Jit Delivery Policy, Pablo Biswas
LSU Doctoral Dissertations
This research deals with a supply chain system where the production or manufacturing facility operates under a just-in-time (JIT) environment, and the facility consists of raw material suppliers, manufacturers, and retailers where inventory of raw materials, work-in-process, and finished goods are involved, respectively. This work considers that the production of finished goods in one cycle starts just after the production or uptime in preceding cycle to minimize the idle time of the facility. Considering this scenario, inventory models are developed for different delivery situations: (a) perfect matching condition where no finished good remains after the shipments and (b) imperfect matching …
An Experimental Study On Characteristics And Behavior Of Reinforced Soil Foundation, Qiming Chen
An Experimental Study On Characteristics And Behavior Of Reinforced Soil Foundation, Qiming Chen
LSU Doctoral Dissertations
This research study aims at investigating the potential benefits of using the reinforcement to improve the bearing capacity and reduce the settlement of shallow foundations. To implement this objective, a total of one hundred seventeen tests were performed to study the behavior of reinforced soil foundation. The test results showed that the inclusion of reinforcement can significantly improve the soil's bearing capacity and reduce the footing settlement. The geogrids with higher tensile modulus performed better than geogrids with lower tensile modulus. The strain developed along the reinforcement is directly related to the settlement. The test results also showed that the …
Measurements And Computations Of The Flow In Full-Scale Sugar Evaporative-Crystallizers And In Lab-Scale Models, Luis Fernando Echeverri
Measurements And Computations Of The Flow In Full-Scale Sugar Evaporative-Crystallizers And In Lab-Scale Models, Luis Fernando Echeverri
LSU Doctoral Dissertations
The circulation of massecuite is a key factor in achieving efficient heat transfer and crystallization in sugar evaporative crystallizers, and should be as high as practically possible for recovery, quality, and capacity reasons. This research report presents results on the circulation obtained applying modern experimental and numerical techniques. The main goals are contributing to expand the understanding of the process in sugar crystallizers; developing realistic models for the simulation of the circulation; and studying the effect of different design parameters. The circulation of massecuite is driven by buoyancy force due to density difference between the vapor generated and the surrounding …
Development Of Micropump For Microfluidic Applications, Dong Eun Lee
Development Of Micropump For Microfluidic Applications, Dong Eun Lee
LSU Doctoral Dissertations
This dissertation covers the research work on two types of micropumps, one is based on magnetohydrodynamic (MHD) principle that utilizes Lorentz force for actuation, and the other is based on electrochemical actuation. The AC-type MHD micropump was designed and analyzed as a solution to the bubble formation problem encountered in DC-type MHD micropump. A UV-LIGA process using thick layer of SU-8 negative photoresist was successfully developed to microfabricate the AC MHD micropump. Preliminary studies and tests of the AC MHD micropumps demonstrate that bubble formation was significantly reduced to permit the proper function of the micropump. A continuous flow was …
Characterization Of Unsaturated Soils Using Elastic And Electromagnetic Waves, Bashar Alramahi
Characterization Of Unsaturated Soils Using Elastic And Electromagnetic Waves, Bashar Alramahi
LSU Doctoral Dissertations
Recent advances in laboratory instruments and techniques enabled researchers to explore new aspects of the behavior of geomaterials and perform measurements that would be otherwise impossible to acquire using traditional geotechnical laboratory techniques. This dissertation is focused on utilizing elastic and electromagnetic wave measurements and SMCT imaging to non-destructively characterize different aspects of the behavior of unsaturated soils. A model that relates P-wave velocity in soils to the volumetric water content was used to develop a new methodology to determine the in situ density and moisture content of soils. It was numerically and experimentally verified to assess it validity and …
Semantic Image Retrieval Using Relevance Feedback And Transaction Logs, Amin Shah-Hosseini
Semantic Image Retrieval Using Relevance Feedback And Transaction Logs, Amin Shah-Hosseini
LSU Doctoral Dissertations
Due to the recent improvements in digital photography and storage capacity, storing large amounts of images has been made possible, and efficient means to retrieve images matching a user’s query are needed. Content-based Image Retrieval (CBIR) systems automatically extract image contents based on image features, i.e. color, texture, and shape. Relevance feedback methods are applied to CBIR to integrate users’ perceptions and reduce the gap between high-level image semantics and low-level image features. The precision of a CBIR system in retrieving semantically rich (complex) images is improved in this dissertation work by making advancements in three areas of a CBIR …