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Articles 91 - 108 of 108
Full-Text Articles in Engineering
Aqueous Atmospheric Species, A Dual Study: 1. Comparison Of The Effects Of Temperature, Oxygen Level, Ionic Strength, And Ph On The Reaction Of Benzene With Hydroxyl Radicals At The Air-Water Interface To The Bulk Aqueous Phase. 2. Determination Of Carbonyl Compounds In Fog Water Samples Via Online Concentration And Hplc, Aubrey Anne Heath
LSU Doctoral Dissertations
The air-water interface is the largest interface in the environment. Atmospheric droplets, such as fog, which can have an exceptionally high surface area-to-volume ratio, also have a large range of physical and chemical properties (e.g. temperature, pH, ionic strength, and chemical composition) based on location, time of day, and emission source. Unlike larger atmospheric droplets, which are predominately characterized by bulk aqueous phase conditions, reactions that take place in fog droplets are determined by both the bulk-aqueous phase and the air-water interface due to a high surface area-to-volume ratio. In order to have a greater understanding of atmospheric processes and …
Image-Based Modeling Of Porous Media Using Fem And Lagrangian Particle Tracking, Paula Cysneiros Sanematsu
Image-Based Modeling Of Porous Media Using Fem And Lagrangian Particle Tracking, Paula Cysneiros Sanematsu
LSU Doctoral Dissertations
The study of fundamental flow and transport processes at the pore scale is essential to understanding how the mechanisms affect larger, field-scale, processes that occur in oil and gas recovery, groundwater flow, contaminant transport, and CO2 sequestration. Pore-scale imaging and modeling is one of the techniques used to investigate these fundamental mechanisms. Although extensive development of pore-scale imaging and modeling has occurred recently, some areas still need further advances. In this work, we address two areas: (1) imaging of bulk proppants and proppant-filled fractures under varying loading stress and flow simulation in these systems and (2) nanoparticle (NP) transport modeling …
Deposition And Characterization Of Ceramic Thin Films And A New Experimental Approach To Evaluate The Mechanical Integrity Of Film/Substrate Interfacial Layers, Yang Mu
LSU Doctoral Dissertations
Due to their corrosion resistance, high temperature stability, high strength, and high hardness, refractory ceramic thin films and coatings have been utilized for surface engineering of mechanical components and mechanical fabrication tools. Adhesion between ceramic thin films and coatings and the substrate is of critical concern for performance and life time of coated systems. In this dissertation, a custom designed and constructed ultra-high-vacuum (UHV) vapor phase deposition system was used for the preparation of ceramic thin films through low-pressure high-density plasma assisted physical vapor deposition (PVD) methods. Deposited thin films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), …
Interorganizational Collaboration And Systemic Change Framework For Building Information Modeling (Bim) Adoption, Rehema Joseph Monko
Interorganizational Collaboration And Systemic Change Framework For Building Information Modeling (Bim) Adoption, Rehema Joseph Monko
LSU Doctoral Dissertations
It was found that an integrated framework needs to be developed for the construction industry that allows optimized interorganizational collaboration and systemic change while using Building Information Modeling (BIM) technologies. The framework needs to be effective so the industry can adopt BIM through a set of interdependent activities beyond their organizational boundaries. The adoption has been proven difficult because of industry competitiveness and a fragmented work environment. Meanwhile, existing frameworks vary between studies. This research developed an integrated framework, identified critical factors, and provided an evaluation guide for interorganizational collaboration and set of coordinated changes necessary to adopt BIM. This …
Uncertainty Analyses Of Climate Change Impact On Hydrologic Projections, Ehsan Beigi
Uncertainty Analyses Of Climate Change Impact On Hydrologic Projections, Ehsan Beigi
LSU Doctoral Dissertations
This study conducts uncertainty analysis on future region-scale hydrologic projections under the uncertain climate change projections of the IPCC Fifth and Forth Assessment Reports. The hierarchical Bayesian model averaging (HBMA) method is adopted to segregate and prioritize sources of climate projection uncertainty, obtain ensemble mean of hydrologic projection, and quantify the hydrologic projection uncertainty arising from individual uncertainty sources. This study deals with the choices of greenhouse gas (GHG) concentration trajectories, global climate models (GCMs), and GCM initial conditions as three major uncertainty sources in downscaled precipitation and temperature projections. The method is applied to investigate future hydrologic projections in …
Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali
Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali
LSU Doctoral Dissertations
Irreversible material degradation due to cyclic mechanical loading is investigated utilizing the concept of thermodynamic entropy, plastic strain energy, and temperature slope measurement. Uniaxial tension-compression and fully-reversed bending fatigue tests are performed over a wide range of loading conditions with metallic and composite materials subject to both constant- and variable-amplitude loading. A methodology is developed for the estimation of the fatigue fracture entropy (FFE) and fatigue toughness of metallic specimens in a rapid fashion. It is found that the FFE and the fatigue toughness of each material tested are within a small band. The value of FFE is found to …
Product Parameters Optimization For Double Purge Of C-Magma Integrated With Conventional Three-Boiling Crystallization Scheme To Improve Raw Sugar Whole Color, Luz Stella Polanco
Product Parameters Optimization For Double Purge Of C-Magma Integrated With Conventional Three-Boiling Crystallization Scheme To Improve Raw Sugar Whole Color, Luz Stella Polanco
LSU Doctoral Dissertations
Efficient crystallization in raw sugar production is the result of a combination of factors and responses that meet specific criteria. Matching a sugar quality standard, maximizing sugar yield, maximizing crystallization equipment capacity and minimizing heat requirement are all necessary optimization criteria. A double centrifugation or purge of C-magma is intended to improve raw sugar whole color by the reduction of color recirculation with the sugar crystal. Combining a three boiling crystallization scheme with a second centrifugation after the last crystallization stage required optimizing the input/output product parameters (purities) and the location of the liquid recycle component (double purge molasses) for …
Time-Resolved Investigations Of Continuous Flow Synthesis Of Nanomaterials And Catalysis Using Millifluidic Reactors For Biomass Conversion Reactors, Chelliah V Navin
Time-Resolved Investigations Of Continuous Flow Synthesis Of Nanomaterials And Catalysis Using Millifluidic Reactors For Biomass Conversion Reactors, Chelliah V Navin
LSU Doctoral Dissertations
Millifluidics can be used as a simple tool and convenient platform to perform in-situ investigations on nanoparticles synthesis to generate real-time information in a continuous flow fashion. These investigations can be used to observe the relationship between the structure and performance of nanoparticles for catalytic applications as a function of space and time. These improvements in nanoparticles research offer unique advantages to develop catalysts with molecular strategies. In order to showcase these advantages of the millifluidic reactors, here we: A. Extensively covered a complete literature review on Lab-on-a-chip devices for gold nanoparticle synthesis and as a catalyst support for continuous …
Clinical Probe Utilizing Surface-Enhanced Raman Scattering (Sers) For In-Situ Molecular Imaging Applications, Jeonghwan Kim
Clinical Probe Utilizing Surface-Enhanced Raman Scattering (Sers) For In-Situ Molecular Imaging Applications, Jeonghwan Kim
LSU Doctoral Dissertations
In this research, a clinical probe utilizing Surface-Enhanced Raman Scattering (SERS) is developed for molecular imaging application which is a visualizing technology to support early diagnosis by providing images in molecular level. In addition to other molecular imaging applications using magnetic resonance, light, and ultrasound, Raman spectroscopy has great potential in terms of non-invasiveness, safety, imaging agent-free, and scanning multiple molecules at a time. However, the critical limitation of Raman spectroscopy using in-vivo molecular imaging application is the inherent low sensitivity of Raman effect. The challenge is overcome by employing SERS enhancing Raman scattering with concentrated electromagnetic oscillation in nanometallic …
Chemical Structure And Dynamics In Laminar Flame Propagation, Mohsen Ayoobi
Chemical Structure And Dynamics In Laminar Flame Propagation, Mohsen Ayoobi
LSU Doctoral Dissertations
The objective of this dissertation is to investigate fundamental aspects of premixed flame structures as well as flame dynamics that arise due to conjugate heat transfer in narrow channels. Laminar premixed combustion simulations in narrow 2D channels show that conjugate heat transfer allows for combustion of mixtures at small scales that are not flammable at normal conditions. To investigate the impact of conjugate heat transfer, preheated 1D cases with premixed H2/Air fuel are simulated for a wide range of operating conditions based on inlet temperature and equivalence ratio. For post-processing, Chemical Explosive Mode Analysis (CEMA, an eigen-analysis technique) is used …
Constitutive Modeling And Experiments For The Micro And Nano Behaviors In Metals, Cheng Zhang
Constitutive Modeling And Experiments For The Micro And Nano Behaviors In Metals, Cheng Zhang
LSU Doctoral Dissertations
This work addresses the micro- and nano-behaviors in metals through constitutive modeling and experiments. The size effect encountered during nanoindentation experiments, which is known as indentation size effect (ISE), is investigated for metal materials. The ISE is believed to be related with the strain gradient at small indentation depths. Geometrically necessary dislocations (GNDs) are formed in order to accommodate the strain gradient, which results in the increase in the material hardness. The grain boundaries in polycrystalline materials play an important role on the material hardness during nanoindentation experiments as there is a soften-hardening segment in the curve of hardness as …
Bioplastic Production In Cyanobacteria And Consensus Degenerate Pcr Probe Design, Courtney Edward Lane
Bioplastic Production In Cyanobacteria And Consensus Degenerate Pcr Probe Design, Courtney Edward Lane
LSU Doctoral Dissertations
Cyanobacteria show much promise in reducing biodegradable thermoplastic production costs; however, most currently characterized strains are ill-equipped to do so. The result of Objective I produced a high-throughput assay designed to discover existing cyanobacterial strains and rapidly characterize them as PHA-producers or potential PHA-producers. This assay will play an instrumental role in the attainment of a novel cyanobacteria environmental isolate capable of accumulating high levels of PHA naturally. Objective II produced an open source computer program which dramatically speeds the design of similar assays for any arbitrary genetic screening purpose. The program is not limited to this implementation alone. In …
Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan
Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan
LSU Doctoral Dissertations
Welding is a fabrication process that joint materials, is extensively utilized in almost every field of metal constructions. Heterogeneity in mechanical properties, metallurgical and geometrical defects, post-weld residual stresses and distortion due to non-linear welding processes are prime concerns for performance reduction and failures of welded structures. Consequently, structural integrity analysis and performance improvement of weld joints are important issues that must be considered for structural safety and durability under loading. In this study, an extensive experimental program and analysis were undertaken on the challenges towards structural integrity analysis and performance improvement of different welded joints. Two widely used welding …
Experimental Designs For Model Discrimination And Uncertainty Reduction In Groundwater Modeling, Hai Van Pham
Experimental Designs For Model Discrimination And Uncertainty Reduction In Groundwater Modeling, Hai Van Pham
LSU Doctoral Dissertations
Groundwater systems are complex and subject to multiple interpretations due to a lack of sufficient information. Different propositions (or alternatives) are often proposed to represent uncertain model components resulted in many conceptual models using the same data. Yet considering too many models may lead to high prediction uncertainty and may lose the purpose of model development. To decrease the prediction uncertainty due to conceptual model uncertainty, two experimental designs are proposed. The first experimental design intends to identify model propositions in each uncertain model component. A discrimination criterion is developed based on posterior model probability. Bayesian model averaging (BMA) is …
Molecular Dynamics Simulation Of The Structure, Dynamics And Crystallization Of Ionic Liquids Under Confinement And Low Temperature, Xiaoxia He
LSU Doctoral Dissertations
Ionic liquids (ILs) have sparked widespread interest due to their peculiar properties and the resulting possibility of manifold applications. In this dissertation, molecular dynamics (MD) simulations have been used to elucidate the dynamics, structure and crystallization of ionic liquids in the bulk and confinement. First we studied the properties of the ILs [dmim+][Cl-] and [emim+][NTf2-] when they are confined inside nanomaterials such as CMK-3, CMK-5 and an isolated amorphous carbon nanopipe (ACNP). The results indicate that the ions of the ILs form different layers inside these nanomaterials and their dynamics are slower due to the confinement. We also found significant …
Coupled Gradient Enhanced Damage - Viscoplasticity Model Using Phase Field Method, Navid Mozaffari
Coupled Gradient Enhanced Damage - Viscoplasticity Model Using Phase Field Method, Navid Mozaffari
LSU Doctoral Dissertations
The aim of this dissertation is developing a framework to describe damage evolution as a phase transformation in solid materials and couple it to the well-known Perzyna type viscoplastic model to account for inelastic behavior of ductile materials. To accomplish this task, the following steps have been performed. First, a new nonlocal, gradient based damage model is proposed for isotropic elastic damage using the phase field method in order to show the evolution of damage in brittle materials. The general framework of the phase field model (PFM) is discussed and the order parameter is related to the damage variable in …
New Identification And Decoding Techniques For Low-Density Parity-Check Codes, Tian Xia
New Identification And Decoding Techniques For Low-Density Parity-Check Codes, Tian Xia
LSU Doctoral Dissertations
Error-correction coding schemes are indispensable for high-capacity high data-rate communication systems nowadays. Among various channel coding schemes, low-density parity-check (LDPC) codes introduced by pioneer Robert G. Gallager are prominent due to the capacity-approaching and superior error-correcting properties. There is no hard constraint on the code rate of LDPC codes. Consequently, it is ideal to incorporate LDPC codes with various code rate and codeword length in the adaptive modulation and coding (AMC) systems which change the encoder and the modulator adaptively to improve the system throughput. In conventional AMC systems, a dedicated control channel is assigned to coordinate the encoder/decoder changes. …
Development Of Satellite-Assisted Forecasting System For Oyster Norovirus Outbreaks, Jiao Wang
Development Of Satellite-Assisted Forecasting System For Oyster Norovirus Outbreaks, Jiao Wang
LSU Doctoral Dissertations
Norovirus outbreaks can cause the closure of oyster harvesting waters and acute gastroenteritis in humans associated with consumption of contaminated raw oysters. The overall goal of this study was to develop a satellite-assisted forecasting system for oyster norovirus outbreaks. The forecasting system is comprised of three components: (1) satellite algorithms for retrieval of environmental variables, including salinity, temperature, and gage height, (2) an Artificial Neural Network (ANN) based model, called NORF model, for predicting relative risk levels of oyster norovirus outbreaks, and (3) a mapping method for visualizing spatial distributions of norovirus outbreak risks in oyster harvest areas along Louisiana …