Experimental studies have been performed on two-pass rectangular internal coolant channels with aspect ratio AR 4:1 with high rotation numbers. Three passages are investigated: smooth, 90 deg ribbed and 45 deg ribbed. A maximum Reynolds number of 150,000 and a maximum rotation number of 0.6 are achieved in the study. These maximum parameter values are considerably higher than those previously reported for the 4:1 AR geometry, and provide data for parameter ranges that may be representative of certain modern turbine blades. Heat transfer behaviors with rotation in the three passages are presented. Rotation effects, density effects and buoyancy effects are discussed. Friction factors and thermal performance factors are also provided. In addition, innovative finning strategies are proposed and tested in a straight stationary rectangular channel using transient liquid crystal method aiming to enhance the heat transfer rate of heat exchangers. The test results show an overall heat transfer rate of 3 and above for Reynolds numbers up to 65,000.

This dissertation focuses on the study of maintenance management for repairable systems based on optimal stopping theory. From reliability engineerings point of view, all systems are subject to deterioration with age and usage. System deterioration can take various forms, including wear, fatigue, fracture, cracking, breaking, corrosion, erosion and instability, any of which may ultimately cause the system to fail to perform its required function. Consequently, controlling system deterioration through maintenance and thus controlling the risk of system failure becomes beneficial or even necessary. Decision makers constantly face two fundamental problems with respect to system maintenance. One is whether or when preventive maintenance should be performed in order to avoid costly failures. The other problem is how to make the choice among different maintenance actions in response to a system failure. The whole purpose of maintenance management is to keep the system in good working condition at a reasonably low cost, thus the tradeoff between cost and condition plays a central role in the study of maintenance management, which demands rigorous optimization. The agenda of this research is to develop a unified methodology for modeling and optimization of maintenance systems. A general modeling framework with six classifying criteria is to be developed to formulate and analyze a wide range of maintenance systems which include many existing models in the literature. A unified optimization procedure is developed based on optimal stopping, semi-martingale, and lambda-maximization techniques to solve these models contained in the framework. A comprehensive model is proposed and solved in this general framework using the developed procedure which incorporates many other models as special cases. Policy comparison and policy optimality are studied to offer further insights. Along the theoretical development, numerical examples are provided to illustrate the applicability of the methodology. The main contribution of this research is that the unified modeling framework and systematic optimization procedure structurize the pool of models and policies, weed out non-optimal policies, and establish a theoretical foundation for further development.

Cotton is the most important textile fiber for apparel use and is preferred to synthetic fibers for reasons such as comfort and feel. Cotton may also be used to produce the regenerated cellulose fibers, such as lyocell and viscose, which have numerous textile applications. A major drawback of cotton, and other cellulosic fibers, is its inherent ability to burn. Many finishes have been developed to impart flame resistance to cotton. These finishes have limited use in textiles for apparel due to problems with the finish not being durable during laundering and increasing the susceptibility of the fabric to wear. Most of these finishes have been developed for products that are not laundered, such as drapery and furnishing fabrics. The development of cellulose/clay nanocomposites for use as flame retardant materials based on cotton is reported in this paper. These materials are designed to take advantage of the thermal stability and flame resistance imparted by silicate filler materials and should require no fire retardant finish. The use of cellulose/clay nanocomposites can allow for the use of natural fibers in applications which are currently limited to synthetic fibers. The use of cellulosic fibers as a feedstock for the composite materials makes use of renewable resources and reduces the use of harsh chemicals normally found in flame retardant materials and finishes. Novel nanocomposite materials have been produced from cellulose with layered silicate clays used as the nanofiller material. Three exfoliation and intercalation methods using different solvents and clay pretreatment techniques were attempted in production of these organic-inorganic hybrids. The method that resulted in superior cellulose/clay nanocomposites utilized a pretreatment of the clay and 4-methylmorpholine-N-oxide as the cellulose solvent. The nanocomposites show significant improvements in thermal properties when compared with cellulose control sources and cellulose processed under the conditions for nanocomposite preparation. The degradation temperature of the nanocomposites increased by 45 °C and the char yields for some compositions doubled those of the controls. The crystalline melt of the materials decreased by 15 °C.

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 by a worse one etc. Usually such a rank reversal is undesirable for decision-making problems. If a method does allow it to happen, the validity of the method could be questioned. However, some recent studies indicate that rank reversals could also happen because of peoples rational preference reversal which may be caused by their emotional feelings, like regret and rejoicing. Since regret and rejoicing may play a pivotal role in evaluating alternatives in MCDM problems, sometimes the decision maker (DM) may want to anticipate these emotional feelings and consider them in the decision-making process. Most of the regret models in the literature use continuous functions to measure this emotional factor. This dissertation proposes to use an approach based on a linguistic scale and pairwise comparisons to measure a DMs anticipated regret and rejoicing feelings. The approach is shown to exhibit some key advantages over existing approaches. Next a multiplicative MCDM model is adopted to aggregate the alternatives associated regret and rejoicing values with their performance values to get their final priorities and then rank them. A simulated numerical example is used to illustrate the process of the proposed method. Some sensitivity analyses which aim at examining how changes of regret and rejoicing values might affect the ranking results of the decision problems are also developed. Then a fuzzy version of the new method is introduced and illustrated by a numerical example. Finally, some concluding remarks are made. Ranking intransitivity and some other issues about the proposed method are analyzed too.

Work-related musculoskeletal disorders (MSD) of the neck or cervical spine result in longer sick leaves, substantial levels of human suffering, and high costs for society. Epidemiological studies clearly indicate strong associations between MSD of the neck and the work activities requiring forceful arm exertions and heavy lifting. However, studies evaluating the loading of the cervical spine during forceful arm exertions and heavy lifting tasks are limited. Major neck muscles, the sternocleidomastoid and the upper trapezius, run parallel to the cervical spine and couple the shoulder to the skull. It was hypothesized that such anatomical orientation may require these muscles to play an active role in supporting the shoulder during lifting activities and thus affecting the compressive forces acting on the cervical spine. The loading of the cervical spine during a variety of manual material handling tasks was studied using electromyography (EMG) and biomechanical modeling techniques. In the EMG study, thirty healthy participants simulated isometric lifting, pushing, and pulling tasks at different heights (e.g., knuckle, elbow, shoulder, and overhead) exerting 25%, 50%, and 75% of their respective maximum static strengths in different neck postures (e.g., neutral, fully flexed, and fully extended neck postures). An increase in the weight significantly affected the activation of neck muscles (P<0.001). Independent of the weight lifted, the sternocleidomastoid showed the highest activation at the extended neck posture, while the upper trapezius showed the highest activation at the flexed neck posture (P<0.001). The activities of the neck muscles increased significantly with an increase in lifting height from elbow to shoulder to overhead (P<0.001). A biomechanical model of the neck consisting of four bilateral pairs of muscles was formulated and a double optimization procedure was used to determine the forces generated by the neck muscles. The total compressive forces exerted by the four neck muscles at the C4-C5 level during isometric lifting task at elbow height were 72.6(19.4), 128.5(37.7), and 184.4(56.1) N, corresponding to the 25%, 50%, and 75% weight conditions. The results of this study demonstrate that the neck muscles play an active role during lifting activities and may influence MSD development due to resulting physiological changes.

This project assessed short-term temperature effects on total ammonia nitrogen (TAN) utilization rates in a batch laboratory-scale recirculating system. The tank system was designed for experiments on short term steady state and diurnal temperatures. A set of numerical models was developed to simulate observed results. The performance of the biofilters was determined with three tank replicates at fixed temperatures of 13, 20 and 300C; and at diurnal transient (sinusoidal) temperature regimes of (20 ± 30C; 30 ± 30C). Ammonia utilization rates and biofilter performance for beads acclimated at different temperatures regimes separated and mixed were also determined. Total ammonia utilization rates increased with increased temperatures. The ammonia removal rates (Pseudo Zero Order) with slope (K) did not significantly differ (P > 0.05) for 130C (K = -0.02) and 200 C (K = -0.04); but differed (P < 0.05) for 13 and 300C (K = -0.12) and also differed (P<0.05) for 200C and 300C. Diurnal temperatures values differed (P = 0.001) for 200C ± 30C (K = -0.08) and 300C ± 30C (K = -0.19). Ammonia utilization rate values for beads that were acclimated and mixed at temperatures of 13, 20, 300C and subjected to diurnal temperatures differed (P = 0.024) at 200C ± 30C (K = -0.12); and 300C ± 30C (K = -0.36). Biofilter performance increased with temperature linearly with increased performance occurring at higher temperatures and high bacterial mass. Ammonia utilization rate simulated models matched the observed data and assisted in determination of bacterial mass. Future designs and acclimation of the bead filters may be further enhanced by decreasing biofilter acclimation periods using higher temperatures in recirculating systems.

Chlorinated solvent contamination continues to plague sites around the world. In many cases, lower chlorinated daughter products build up and remain in ground waters and soils. A Bio-Filter/Phytobed (BFP) system has been developed to replace a traditional pump and treat technology currently operating at the ReSolve Superfund site in North Dartmouth, MA. Pilot scale testing at the facility displayed a significant acclimation period prior to microbial dechlorination, as well as delayed degradation of chlorinated ethanes. Microcosm studies suggest that acidic conditions, possibly created by the peat mixture used to construct the bio-filter, inhibited bacterial growth. The neutralization of trench pH appeared to coincide with the start of chlorinated solvent degradation in pilot scale studies. In subsequent microcosm studies, lactate, hydrogen, and acetate were added to promote bacterial growth and enhance reductive dechlorination, yet lactate failed to enhance the degradation capabilities of either chlorinated ethenes or ethanes. In an effort to increase the availability of hydrogen, larger concentrations of hydrogen gas in the headspace replaced the lactate. Although the hydrogen eliminated chlorinated ethane lag time, the degradation rates remained lower than desired. However, the addition of acetate successfully stimulated chlorinated ethane degradation and increased degradation rates. Recommendations for the final design include the use of carbon filtration and a two trench BFP system. A life cycle analysis depicting the BFP system as a more sustainable remediation technology as compared to the currently operating pump and treat system is included.

Fuel Cells are attractive power source for use in electronic applications. Physical phenomena (water generation, saturation effect in fuel cell, poisoning, and thermal stress) are studied that governs the operation of a Proton Exchange Membrane Fuel Cell (PEMFC) and Solid Oxide Fuel cell (SOFC). Additionally, experimental studies and numerical simulations on PEMFC gas flow channel, the determination of the impact of the single channel fuel cell are presented. Furthermore, preliminary study is done for the application of APS (Air Plasma Spray) to SOFC and adhesion of anode and cathode with electrolytes for the determination of parameters involved in manufacturing the components of fuel cell. The new aspects on physical phenomena are significantly different from the currently popular relationships used in fuel cells as they are simplified from simulation and experimental results. In prior work, the physical phenomena such as water generation, saturation effect in fuel cell, poisoning, and thermal stress etc. are either assumed or used as adjustment parameters to simplify them or to achieve best fits with polarization data. In this work, physical phenomena are not assumed but determined via newly developed experimental and numerical techniques. The experimental fixtures and procedures were used to find better ways to control parameters of gas flow channel configurations for optimizing gas flow rates and performance, and gas flow channel pressure swing for CO poisoning recovery. The experimental results reveal controlling parameters for the mentioned cases and innovative design for Fuel cells. Numerical modeling were used to 2D and later 3D for simplification of single channel fuel cell model, transient localized heating to the catalyst layer for CO recovery, thermal stress that developed during SOFC fabrication by High Temperature vacuum Tube Furnace (HTVTF), and Gas Diffusion Layer and Gas Flow Channel (GDL-GFC) interfacial conditions with results based on commonly used relationships from the PEMFC literature. The modeling works reveal substantial impact on predicted GDL saturation, and consequently cause a significant impact on cell performance. Computational parametric relations and polarization curve results are compared to experimental polarization behavior which achieved a comparable relation.

World competition has encouraged United States rice farmers and rice mills to be efficient in farming and production practices. Efforts to augment economic competitiveness include development of new varieties, improvements in milling practices, and identification of uses for rice products and by-products. The research detailed in this dissertation adds to the body of knowledge in milling practices and identification of uses for rice bran. To improve the prediction of milled rice quality at industrial scale, correlations for milling quality among laboratory, pilot, and industrial scale mills were identified for Clearfield 161. Final industrial product whiteness was ten points higher than for polished rice at medium and high pilot scale settings. Jazzman, the first US-bred jasmine-type rice variety, was released by the LSU AgCenter Rice Research Station in 2009 to compete for a share of the aromatic rice market. Pilot scale evaluation of Jazzmans milling quality supported lab scale evaluation and provided additional data for milling optimization. With milling yields from 86 to 93%, Jazzman presented as a high-yield, good-milling aromatic long grain rice variety. A purple rice variety (line number MCR02-1576) was assessed for milling quality, and its bran for oil and anthocyanin concentration. Results showed a low milling recovery (<50%); low whiteness (<15%) values indicated pigment remained in the kernel. Anthocyanin concentration increased linearly across the entire bran layer. Oil concentration increased linearly across the inner bran layer with a mean of 22 percent. Processing the inner bran layer would maximize anthocyanin and oil recovery. As rice bran oil is a potential renewable energy source, the oil concentration across the bran layer of Jazzman, Clearfield 161, and Cocodrie were determined with hexane extraction and near infrared technology (NIT). Clearfield 161 had total oil concentration 1.83 times that of Jazzman and 2.11 times that of Cocodrie. Predictions of oil content across the bran layer were made from NIT measurements and compared to hexane extraction results. Collectively this research indicates that value-added processing of rice and rice bran which optimizes milling yields and recovery of high-value components from the bran layer would favorably impact economic competitiveness.

The aim of this dissertation project is to extend the standard Lattice Boltzmann method (LBM) for shallow water flows in order to deal with three dimensional flow fields. The shallow water and mass transport equations have wide applications in ocean, coastal, and hydraulic engineering, which can benefit from the advantages of the LBM. The LBM has recently become an attractive numerical method to solve various fluid dynamics phenomena; however, it has not been extensively applied to modeling shallow water flow and mass transport. Only a few works can be found on improving the LBM for mass transport in shallow water flows and even fewer on extending it to model three dimensional shallow water flow fields. The application of the LBM to modeling the shallow water and mass transport equations has been limited because it is not clearly understood how the LBM solves the shallow water and mass transport equations. The project first focuses on studying the importance of choosing enhanced collision operators such as the multiple-relaxation-time (MRT) and two-relaxation-time (TRT) over the standard single-relaxation-time (SRT) in LBM. A (MRT) collision operator is chosen for the shallow water equations, while a (TRT) method is used for the advection-dispersion equation. Furthermore, two speed-of-sound techniques are introduced to account for heterogeneous and anisotropic dispersion coefficients. By selecting appropriate equilibrium distribution functions, the standard LBM is extended to solve three-dimensional wind-driven and density-driven circulation by introducing a multi-layer LB model. A MRT-LBM model is used to solve for each layer coupled by the vertical viscosity forcing term. To increase solution stability, an implicit step is suggested to obtain stratified flow velocities. Numerical examples are presented to verify the multi-layer LB model against analytical solutions. The models capability of calculating lateral and vertical distributions of the horizontal velocities is demonstrated for wind- and density- driven circulation over non-uniform bathymetry. The parallel performance of the LBM on central processing unit (CPU) based and graphics processing unit (GPU) based high performance computing (HPC) architectures is investigated showing attractive performance in relation to speedup and scalability.