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Numerical Simulations Of Incompressible Flows In Complex Geometries., Konstantinos Vogiatzis
Numerical Simulations Of Incompressible Flows In Complex Geometries., Konstantinos Vogiatzis
LSU Historical Dissertations and Theses
A mainly spectral code along with domain-decomposition, a combination that is not widely in use in complex problems, has been developed for the solution of the 3-D unsteady incompressible Navier-Stokes equations. The code uses fully spectral or a combination of spectral-collocation and finite difference approximations and a 3-step splitting time-marching scheme. The developed Poisson solver utilizes matrix diagonalization and incorporates a direct sub-structuring method based on the influence matrix technique. As a first step, laminar and turbulent confined flows were simulated, initially with DNS, then with LES, using a modified Smagorinksi model. The domain-decomposition technique and parallel implementation were tested …
Analysis And Mathematical Modeling Of Autonomously Oscillating Yeast Cultures., Abdelqader M. Zamamiri
Analysis And Mathematical Modeling Of Autonomously Oscillating Yeast Cultures., Abdelqader M. Zamamiri
LSU Historical Dissertations and Theses
The conditions that precede the onset of autonomous oscillations in continuous yeast cultures were studied in three different types of experiments. It was found that the final state of the culture depends on the protocol used to start-up the reactor. Reaching the desired operating point by slow dilution rate changes gave rise to different final states, two oscillatory states and one steady state, depending on the rate of change in dilution rate. The multiplicity of stable states at a single operating point is not explained by current distributed models and points towards a segregated mechanism of these oscillations. The ability …
Novel Formulation And Application Of Model Predictive Control., Guang-Yan Zhu
Novel Formulation And Application Of Model Predictive Control., Guang-Yan Zhu
LSU Historical Dissertations and Theses
Model predictive control (MPC) has been extensively studied in academia and widely accepted in industry. This research has focused on the novel formulation of model predictive controllers for systems that can be decomposed according to their nonlinearity properties and several novel MPC applications including bioreactors modeled by population balance equations (PBE), gas pipeline networks, and cryogenic distillation columns. Two applications from air separation industries are studied. A representative gas pipeline network is modeled based on first principles. The full-order model is ill-conditioned, and reduced-order models are constructed using time-scale decomposition arguments. A linear model predictive control (LMPC) strategy is then …
Active Control Of Thermoacoustical Instabilities., Daniel Ulises Campos-Delgado
Active Control Of Thermoacoustical Instabilities., Daniel Ulises Campos-Delgado
LSU Historical Dissertations and Theses
This dissertation presents some advances in active control of thermoacoustic instabilities in combustion chambers. Large-size gaseous and liquid fueled swirl stabilized combustors were used during the studies. Active control was implemented using different types of actuators. Proportional (loudspeakers and fuel valves) and discrete actuators (open-close automotive fuel injectors) were investigated. Acoustic and fuel modulation control were successfully applied. In large-scale combustors, flame stabilization techniques such as swirl add three dimensional characteristics to the flow. Moreover, the induced turbulence creates highly nonlinear interactions in the system. Thus, in order to capture these characteristics nonlinear partial differential equations have to be used. …
Design, Fabrication, And Testing Of Cross Flow Micro Heat Exchangers., Chad Randall Harris
Design, Fabrication, And Testing Of Cross Flow Micro Heat Exchangers., Chad Randall Harris
LSU Historical Dissertations and Theses
Cross flow micro heat exchangers were designed to maximize heat transfer from a liquid (water) to a gas (air) for a given frontal area while holding the pressure drop across the heat exchanger of each fluid to values characteristic of conventional scale heat exchangers (car radiators). The cross flow micro heat exchanger design is unique since it produces a very high rate of heat transfer/volume between dissimilar fluids with low fluid pressure drops. Predicted performance for two types of cross flow micro heat exchangers is compared to each other and to current innovative car radiators. Although the cross flow micro …
Control Of Supply Chain Systems By Kanban Mechanism., Shaojun Wang
Control Of Supply Chain Systems By Kanban Mechanism., Shaojun Wang
LSU Historical Dissertations and Theses
This research studies the control mechanism of a supply chain system to operate it efficiently and economically under the just-in-time (JIT) philosophy. To implement a JIT system, kanbans are employed to link different plants' production processes in a supply pipeline. Supply chain models may be categorized into single-stage, multi-stage, and assembly-line types of production systems. In order to operate efficiently and economically, the number of kanbans, the manufacturing batch size, the number of batches, and the total quantity over one period are determined optimally for these types of supply chains. The kanban operation at each stage is scheduled to minimize …
Plant Uptake Of Desorption Resistant Organic Chemicals From Sediments., Cesar Miguel Gomez Hermosillo
Plant Uptake Of Desorption Resistant Organic Chemicals From Sediments., Cesar Miguel Gomez Hermosillo
LSU Historical Dissertations and Theses
Two types of wetland plants, a woody species, black willow ( Salix nigra), and a non-woody, the macrophyte three-square bulrush (Scirpus olneyi), were used in laboratory studies to evaluate relationships between sorption, plant uptake, translocation and transpiration of phenanthrene, a model polycyclic aromatic hydrocarbon and chlorobenzene, a model chlorinated benzene from the reversible and desorption-resistant compartment of a sediment for Phenanthrene (PHEN) and a wetland soil for chlorobenzene (CB). The wetland soil is from The Petro Processors Inc. site (PPI), a 77-acre CERCLA facility located about 10 miles north of Baton Rouge, Louisiana. Other studies have evaluated the plant uptake …
A Study Of The Applicability Of Intrusion Technology For Evaluating Resilient Modulus Of Subgrade Soil., Ananda H. M. P. J Herath
A Study Of The Applicability Of Intrusion Technology For Evaluating Resilient Modulus Of Subgrade Soil., Ananda H. M. P. J Herath
LSU Historical Dissertations and Theses
The cone penetration test may be applied for estimation of the resilient modulus of subgrade soil. The main objectives of this study were to assess the applicability of the intrusion technology in evaluating the resilient characteristics of subgrade soil, develop models among the cone penetration test parameters, resilient modulus, soil properties, and stresses of subgrade soil, and to validate these models. Field cone penetration and laboratory tests were performed on different soil types. Disturbed and undisturbed soil samples were obtained close to the cone penetration test locations. Laboratory tests were also performed to obtain the resilient modulus, strength parameters, compaction …
Robust Control Of Uncertain Time -Delay Systems., Yun-Ping Huang
Robust Control Of Uncertain Time -Delay Systems., Yun-Ping Huang
LSU Historical Dissertations and Theses
Time-delay systems are common in industries. Direct analysis and synthesis of control systems with time delays are complicated and approximation methods such as Pade approximation are usually applied. However, the issues of control system robustness with respect to model uncertainties and approximation errors have not been sufficiently addressed. This dissertation focus on robustness of time-delay systems, especially robustness with respect to time delays, which has been discussed extensively using Lyapunov second method. We propose two methods in this dissertation to reformulate the problems into standard mu or Hinfinity problems. The first method involves representing the systems in linear functional transformation …
Mass Transfer Of 2,4,6-Trinitrotoluene And Lower Chlorinated Benzenes From Sediment Into Water., Marti Charleen Blad
Mass Transfer Of 2,4,6-Trinitrotoluene And Lower Chlorinated Benzenes From Sediment Into Water., Marti Charleen Blad
LSU Historical Dissertations and Theses
Bioremediation and phytoremediation are in their infancy and this research addresses concerns for application of these technologies. This laboratory and mathematical modeling effort predicts the pollutant flux from soils and sediments to the overlying waters. Little work has been done on transport in surface waters such as the slow moving and stagnant areas of the southern U.S. Mass transfer is a proposed rate limiting factor for biological transformation when using phytoremediation or natural attenuation. The research quantified mass transport of two dfferent contaminants, TNT and chlorinated benzenes, under different advective conditions. The TNT study was part of a "riffle-bed reactor" …
Development And Characterization Of Velocity Workspaces For The Human Knee., John Eric Fuller
Development And Characterization Of Velocity Workspaces For The Human Knee., John Eric Fuller
LSU Historical Dissertations and Theses
The knee joint is the most complex joint in the human body. A complete understanding of the physical behavior of the joint is essential for the prevention of injury and efficient treatment of infirmities of the knee. A kinematic model of the human knee including bone surfaces and four major ligaments was studied using techniques pioneered in robotic workspace analysis. The objective of this work was to develop and test methods for determining displacement and velocity workspaces for the model and investigate these workspaces. Data were collected from several sources using magnetic resonance imaging (MRI) and computed tomography (CT). Geometric …
Material Properties And Characteristics For Development Of An Expert System For Coal -Tar Sealers., James Edwin Shoenberger
Material Properties And Characteristics For Development Of An Expert System For Coal -Tar Sealers., James Edwin Shoenberger
LSU Historical Dissertations and Theses
Coal-tar sealers are used to protect asphalt pavements from damage by fuel spillage. The durability of these coal-tar sealers has been limited by the formation of cracks that occur in both in trafficked and non-trafficked areas and in all climatic regions. This cracking severely limits the useful life of the coal-tar sealer. Various coal-tar mixtures were evaluated through existing standard test methods. The mixtures varied through the source of the coal-tar emulsion, amount of aggregate, and amount of polymer used in the mixtures. The material properties of these mixtures were determined through curing, thermal, bending, tensile and stress-relaxation testing. The …
Biodegradation Of Desorption -Resistant Organic Contaminants In Wetland Soils., Sangjin Lee
Biodegradation Of Desorption -Resistant Organic Contaminants In Wetland Soils., Sangjin Lee
LSU Historical Dissertations and Theses
Contaminant bioavailability depends on physicochemical processes such as adsorption/desorption, diffusion, and dissolution. The rates of sorption and desorption of trichloroethylene (TCE) and 1,3-Dichlororbenzene (1,3-DCB) were studied. Desorption kinetics of 3-month and 5-month old contaminated soils showed that progressively less amount of contaminant was available for facile desorption compared to freshly contaminated soil in an empirical non-linear model. Microcosm batch studies were conducted to study the biodegradation of 1,3-DCB in the aqueous and soil phase containing a freshly contaminated soil and a soil containing only the desorption resistant fraction. The presence of the soil reduced the rates of biodegradation. It is …
Investigation Of Amphoteric Materials For Treatment Of Heavy Metals In Storm Water., Dingfang Liu
Investigation Of Amphoteric Materials For Treatment Of Heavy Metals In Storm Water., Dingfang Liu
LSU Historical Dissertations and Theses
Urban storm water runoff mobilizes and transports significant loads of heavy metals. Promulgation of NPDES Phase II regulations has spurred development of Best Management Practices (BMPs) for in-situ control of heavy metals. In this study, Amphoteric materials such as manganese oxides and iron oxides on the various substrates including silica sands, polymeric beads and cementitious particles were investigated. Surface characterization results indicated that oxide coatings ranged from 20 to 200-mum in depth, and surface areas were significantly increased by greater than a factor of one thousand compared to uncoated media. Point of zero charge (PZC) for manganese oxide coated media …
A Neural Network Approach To Dependent *Reliability Estimation., Roya Javadpour
A Neural Network Approach To Dependent *Reliability Estimation., Roya Javadpour
LSU Historical Dissertations and Theses
This research presents the creation of a new model for automating the generation of component and system reliability estimates from simulated field data for tightly coupled systems. The model utilizes the CMAC neural network architecture, which resembles the human cerebellum and is capable of approximating nonlinear functions. An analysis and testing of the network as a tool for reliability prediction of dependent components within an assembly has been performed. In order to evaluate the performance of the model, the network has been tested on simulated data and provided over 90% performance accuracy in learning non-linear functions that represent the dependency …