Problems involving mechanical behavior of materials with microstructure are receiving an increasing amount of attention in the literature. First of all, it can be attributed to the fact that a number of recent experiments shows a significant discrepancy between results of the classical theory of elasticity and the actual behavior of materials for which microstructure is known to be significant (e. g. synthetic polymers, human bones). Second, materials, for which microstructure contributes significantly in the overall deformation of a whole body, are becoming more and more important for applications in different areas of modern day mechanics, physics and engineering. <br /><br /> Since the classical theory is not adequate for modeling the elastic behavior of such materials, a new theory, which allows us to incorporate microstructure into a classical model, should be used. <br /><br /> The foundations of a theory allowing to account for the effect of material microstructure were developed in the beginning of the twentieth century and is known as the theory of Cosserat (micropolar, asymmetric) elasticity. For the last forty years significant results have been accomplished leading to a better understanding of processes occurring in Cosserat continuum. In particular, significant progress has been achieved in the investigation of three-dimensional problems of micropolar elasticity, plane and anti-plane problems, bending of micropolar plates. These problems can be effectively solved in a very elegant manner using the boundary integral equation method. <br /><br /> However, the boundary integral equation method imposes significant restrictions on properties of boundaries of domains under consideration. In particular, it requires that the boundary be represented by a twice differentiable curve which makes it impossible to apply the method for domains with reduced boundary smoothness or domains containing cuts or cracks. Therefore, the rigorous treatment of boundary value problems of Cosserat elasticity for domains with irregular boundaries has remained untouched until today. <br /><br /> A mathematically sophisticated, but very effective approach which allows to overcome the difficulty relating to the boundary requirement consists of the formulation of the corresponding boundary value problems in terms of the distributional setting in Sobolev spaces. In this case the appropriate weak solution may be found in terms of the corresponding integral potentials which perfectly works for domains with reduced boundary smoothness. <br /><br /> The objective of this work is to develop such a method that allows us to describe and solve the boundary value problems of plane Cosserat elasticity for domains with non-smooth boundaries and for domains weakened by cracks. We illustrate the method by establishing the analytical solutions for boundary value problems of plane Cosserat elasticity, which plays an important role as a pilot problem for the investigation of more challenging problems of three-dimensional theory of micropolar elasticity. We show that the analytical solutions derived in this work may be successfully approximated numerically using the boundary element method and that these solutions can be extremely important for applications in engineering science. <br /><br /> One of the important applied problems considered herein is the problem of stress distribution around a crack in a human bone. The bone is modeled under assumptions of plane Cosserat elasticity and the solution derived on the basis of the method developed in this dissertation shows that material microstructure does indeed have a significant effect on stress distribution around a crack.

In this study, CORSIM 5.0 simulation model results were used to evaluate the effectiveness of the contraflow segment on westbound I-10 out of the City of New Orleans. The Louisiana State Police plan for the contraflow segment was used to construct the CORSIM network. Alternative plans were also developed in this study to compare the effectiveness of the contraflow operation. With the use of CORSIM, traffic flow on the contraflow segment was determined based on the amount of evacuating vehicles leaving the exit nodes. In addition the time and speed to travel the contraflow segment was estimated. The results showed that the use of contraflow lanes could increase the traffic flow significantly. In addition, from the comparison of the alternatives plans it was found that the plan that used multiple entry nodes in the segment had the largest traffic flow. This was because that plan used the available roadway more effectively.

The Marshland Upwelling System (MUS) is an alternative method for coastal dwellers to treat their wastewater. Past studies have dealt with the removal of fecal pathogens from wastewater. However the objectives of this research were to: 1) evaluate the treatment capability of the MUS under high hydraulic loadings and cool temperatures with respect to CBOD₅, TKN, TAN, NO₂^--N, NO₃^--N, TP, and PO₄-P, and 2) determine the ideal flowrate and injection frequency to achieve satisfactory nitrogen removal without hydraulic failure. The artificial wastewater study was performed to evaluate the treatment of CBOD₅, TKN, TAN, TP, and PO₄-P under high hydraulic loadings and cold temperatures. According to the pressure data, there were no signs of hydraulic dysfunction (clogging and/or channelization) during the study. CBOD₅ was reduced from an influent value of 227 mg/l to an effluent value of 19 mg/l. TKN was reduced from 120 to 3 mg/l-N. The concentration of TAN was reduced from 110 to 1.5 mg/l. The influent TP and PO₄-P concentrations were 14 and 7.2 mg/l-P, respectively. However, the effluent concentrations of TP and PO₄-P were 0.3 and 0.7 mg/l-P. A flow rate of 2.8 L/min injecting for 30 minutes every 3 hours provided effective reduction of nitrogen. The concentrations of TKN in the influent were reduced from 168 to 1.8 mg/l-N. The influent TAN concentrations were reduced from 160 to 1.1 mg/l-N. Laboratory studies demonstrated the importance macrophytes have on the redox potential of the underlying media. By increasing the redox potential, the macrophytes also accelerated the production/reduction of NO₂^--N.

The research objective was the optimization of light dynamics in a Hydraulically Integrated Serial Turbidostat Algal Reactor (HISTAR). A deterministic model of HISTAR productivity that was responsive to manipulations of photosynthetic photon flux fluence rate (PPFFR) was developed, calibrated, and applied. A series of experiments was conducted to define the mathematical equations that best describe three relationships. The first relationship was between the elevation (E) of the light source and the culture surface PPFFR (I_o). The second relationship was between the biomass concentration (X) in the experimental unit and the average PPFFR in the reactor (I_a). The final relationship was between average PPFFR and the net specific growth rate (U). Parameters for these three relationships varied for light sources having different spectra. The light source specific parameters investigated were the light attenuation coefficient (k_aw), maximum specific growth rate (μ_max) and optimum average PPFFR (I_opt). These parameters were estimated experimentally (using Selenastrum capricornutum as the surrogate microalgal species) for metal halide, high-pressure-sodium (HPS), fluorescent, and Son Agro® lights. Using the experimentally estimated parameters for metal halide and the three experimentally defined relationships, a HISTAR productivity model was developed using the Stella® modeling platform and calibrated using actual HISTAR data. Biorhythms were discovered in the residuals during a calibration attempt. These harmonics were modeled and incorporated into the productivity model before completing calibration. The HISTAR productivity model was then used to simulate the effects of light source type, system dilution rate (D_s), number of CFSTRs, wattage, lamp elevations, and culture depth on daily productivity in HISTAR. It was concluded from simulation studies that using HPS lamps, a D_s of 0.641 d^-1, changing lamp elevations to 25.4 cm, and changing culture depth in the last four CFSTRs of HISTAR would be cost beneficial. The production lighting cost (LC, based on $0.10 killowatthour^-1) may be reduced from $48 (kg dry wt)^-1 to $36 (kg dry wt)^-1. Decreasing the number of CFSTRs in HISTAR or increasing lamp wattage was not predicted to be cost effective. The outcome of this type of research for other species adapted to different habitats would probably differ.

Floating Bead Biofilters (FBFs) have been applied to aquacultural recirculating tanks and domestic wastewater treatment systems for controlling total ammonia nitrogen (TAN), biochemical oxygen demand (BOD), and total suspended solids (TSS). Support modified media in these FBFs provide a large surface area (1150~1475 m2/m3) so that the active biofilm can be retained in the FBF by attaching to the media surface. Understanding the theories involved in biofilm processes greatly helps in sizing, designing, and modeling of FBF systems. Fundamental biofilm processes like mass transport of various substrates into the biofilm and the substrate utilization within the biofilm were studied. A mathematical model (MSB Model) was set up to predict the development of the FBFs characteristics such as biofilm growth, substrates utilization, dissolved oxygen consumption, BOD loading removal, volumetric oxygen consumption rate by filter (OCF), and bead bed volume under the different conditions. This model was then calibrated with a set of bioclarification data. The model results were consistent with literature defining the relationships between dissolved oxygen consumption, BOD loading removal, and biofilm growth. This model is specifically used to predict design parameters for FBFs in a municipal sewage treatment systems. The entire study was based on the following experimental parameters: OCF, dissolved oxygen (DO), hydraulic loading, BOD loading, maximum ratio of BOD removal to OCF (MX-factor).

Prior studies showed that most evacuation contraflow designs have never been implemented. As a result, the effectiveness of these contraflow termination point designs remains unknown. To address this problem, a microscopic traffic simulation tool, CORSIM 5.0, was used. Ten simulation models were conducted and determined the factors that affect traffic operations in the vicinity of the various planned contraflow termination point with median crossover designs. The performance of various models was ranked by statistical test in terms of the total number of vehicles processed, traffic flow, speed, density and delay. The results that were based on theoretical simulations and assumptions showed that it was important to maintain a substantial number of exit opportunities along the intermediate segments of the evacuation section, because it increased the overall evacuation efficiency ultimately.

Recent household travel surveys are encountering problems with non-response, non-coverage, non-reporting, and even incorrect or incomplete reporting of trips. In addition, data from survey samples are affected by the social, and economic conditions of the respondents, as well as the survey instrument used to collect the data. As a result, household travel survey data are invariably associated with some level of bias. These threats to the integrity of the data are often ignored while analyzing the sample survey data. However, considering the importance of information derived from such surveys, it is necessary that the survey must provide an accurate reflection of the population it represents. Given current conditions, the accuracy of travel survey data has become a matter of concern. The present study is an attempt to address the issue, and to develop standard procedures that can be applied to every household or person in a survey to assess, analyze, and adjust bias associated with that household or person. In developing these standards the study has reviewed a few recent household travel surveys in depth. The review has focused on the presence and extent of bias observed in those surveys, identified variables that were used for assessing bias, appraised the instruments and the methods of data collection used, and finally, observed the methods used for adjustment of biased data. The quality of past surveys is assessed by comparing the values (mean and proportion) of selected survey variables with those from some standard secondary data source (e.g. census, PUMS), as well as, by considering their variability (sampling) error. The study demonstrates the application of weighting and factoring (expansion) techniques on a sampled data by applying a simplified weighting and factoring techniques at the household, person, and trip levels.

This dissertation tests the hypothesis that the early phases of deltaic bar and distributary channel formation and sediment transport on an adverse slope could be simulated with a 2D finite element sediment transport model. The models used were RMA2 and SED2D modules of the TABS-MD model suite. A finite element mesh of the lower Atchafalaya River and the delta was developed, using the Surface Water Modeling System (SMS) software package. Calibration and validation of the model were performed, using data collected during field surveys and from available Atchafalaya River archived flow, suspended sediment, and dredging records. In a test simulation in which adequate flow and sediment supply were provided in large quantity, sub-aqueous distributary mouth bar formed at the end of the feeder channel. As simulation continued, a more prominent distributary channel and sub-aerial levees were developed. When the model was changed to impose a no flood conditions on high points, formation of new distributary channels was observed. The same model was used to determine a self-sustainable adverse slope or sediment ramp that could be used to divert sediments efficiently in a deltaic setting similar to the Atchafalaya Bay. A test slope of 1V to 51H was used in the model. After several simulations, the model tends to produce a much milder slope close to 1V to 412H. Five adverse natural slopes observed in the Wax Lake Outlet delta were compared with the model-suggested slopes. Adverse slopes at the Wax Lake Outlet delta varied from 1V to 340H 850H, with 1V to 543H as the average. Finally, a calibrated model of the Atchafalaya River and the delta was applied to develop a set of sedimentation/erosion curves that could be used by the engineers to estimate scour and deposition for proposed artificial feeder channels. These curves suggest that a discharge of at least 11,325 cms (400,000 cfs) at Morgan City is necessary to transport sand into the delta. It was observed that even for a very high flood, sand deposition should be limited to within 1000 m (3281 ft) of distributary channel mouths.

Soil reinforcement interaction is a key issue in the design of reinforced soil structures. Therefore, it is important to analyze the pull-out mechanism, and to evaluate the interaction between the soil and geosynthetic reinforcement. Majority of pull-out tests performed to date were in granular soils, and very few tests were reported in cohesive soils. The shortage of in-situ granular materials and the availability of cohesive soils in Louisiana have initiated a growing interest in using the marginal soils as backfill material. To investigate the soil-geosynthetic interaction parameters, series of laboratory and field pull-out tests were conducted using various geosynthetics (geogrids: UX750, UX1500, UX1700, Stratagrid-500, and geotextiles: Woven (4x4), Woven (6x6) and Non-woven) with different lengths under various confining pressures. This research program is based on the analysis of the pull-out tests, which includes (i) the comparison of laboratory and field pull-out tests, (ii) the contribution of passive bearing resistance to the total pull-out resistance, (iii) the evaluation of coefficient of interaction (Ci), and (iv) the evaluation of the scale correction factor (α). The results of this study indicate that (i) the laboratory and field pull-out test results are close to each other and show more consistency for high strength geosynthetics compared to weak strength geosynthetics, (ii) the contribution of passive bearing resistance ranges from 5-30 percent of the total pull-out resistance, (iii) the coefficient of interaction (Ci) ranged from 0.5 to 1.0 for laboratory tests and 0.3 to 1.2 for field pull-out tests, and decreases with increasing length and increasing confining pressure, and (iv) the scale correction factor (α) values estimated for the geogrids ranges from 0.32 to 0.82.

Phosphogypsum (PG, CaSO₄·2H₂O) is a waste by-product produced during the wet manufacturing phosphoric acid process. Phosphoric acid is manufactured by processing phosphate rock that contains relatively high concentrations of naturally occurring radioactive impurities which makes PG a radioactive material. PG also contains certain trace metals including As, Ba, Cd, Cr and Pb and radioactive contaminants such as Radium²²⁶ and Uranium²³⁸ that pose potential hazard to human health and the environment. According to USEPA, the current allowable disposal method for PG is stack piling. This research was focused on stabilizing PG with Portland Type II cement and Class C fly ash for use in marine environments. The specific objectives included the development of a PG briquette composition that under submerged conditions: 1) maintained physical integrity, 2) minimized dissolution of Ca²⁺, SO₄^2-, Ra²²⁶ and toxic metal concentrations in saltwater, 3) possessed appropriate engineering properties for its potential as a fill material and 4) was economically feasible to fabricate. The 73%:25%:02%, 67%:30%:03%, 63%:35%:02% and 62%:35%:03% PG:Class C fly ash:Portland Type II cement composites showed promising results with no signs of degradation after 12-months of natural saltwater submergence. The leaching behavior of all the PG composites was found to be similar and the effective calcium and sulfate diffusion coefficients ranged 1.36-8.04x10^-13 m²·s^-1 and 2.96-7.20x10^-13 m²·s^-1, respectively. The Ra²²⁶ concentrations leached were observed to be safe, and ranged well below the current EPA regulation for the amount of Ra²²⁶ concentration in safe drinking water (5 pCi·L^-1). The metal concentrations in the TCLP leachate were well below the USEPA toxicity characteristics limits. The engineering properties test results indicated that the composite material could be classified as well-graded gravel or well-graded sand with little or no fines. The USCS classification would also qualify the PG briquettes as a potential fill material in embankment construction having excellent workability characteristics. The 73%:25%:02% PG:Class C fly ash:Portland Type II cement composite demonstrated the lowest production cost ($10.62 per ton for the year 2001 in Tampa, Florida) among the best four selected combinations.