As a hygroscopic salt, granular potash can easily absorb large quantities of water vapor from humid air during storage and transportation processes. Subsequent drying will result in potash particles sticking together to form clumps or cakes. In order to avoid or decrease caking, it is essential to know the local history of moisture content and moisture movement in a bed of potash. In this thesis, experimental measurements and numerical simulations are used to investigate moisture transport and redistribution by capillarity, gravity and diffusion effects within a potash bed. <p> The important properties required to model moisture transfer in granular porous potash (i.e. porosity, permeability, specific surface area and irreducible saturation) are investigated experimentally and theoretically. It is shown that for a mixture with a wide range of particle sizes the potash bed properties can be predicted knowing the properties for each narrow range of particle size in the mixture. <p> An experimental test facility was designed and constructed to test moisture transfer within a potash bed. The test procedures are presented along with an uncertainty analysis. The moisture content spatial distribution for different particle sizes under different initial conditions is investigated and data are presented. <p>A one-dimensional transient numerical model of moisture transport accounting for diffusion, capillarity and gravity effects within potash beds is developed. Two different moisture transport mechanisms are presented. In a wet region, where local moisture saturation level, S, is larger than an irreducible saturation, S0, liquid water exists as continuous liquid film on the particles; moisture is transferred by liquid film movement due to capillarity and gravity effects. In a dry region where S is less than S0, water vapor diffusion is the only mechanism of moisture transfer and water is adsorbed in layers on the surfaces. <p> From the experimental data and numerical simulation analysis, it is shown that the irreducible saturation, S0, is a strong function of particle size. It will decrease with a particle size increase. <p> The numerical model is validated by comparison with some typical experimental case studies. Agreement between the experimental data and simulation results is well within the experimental 95% uncertainty bounds. It is concluded from this research that the complex moisture transport process by diffusion, capillarity and gravity effects within a potash bed can be modeled and simulated. Experimental and simulation results indicate that direct water drainage will more readily occur for large particle sizes than for small particles for the same initial moisture content.

As a hygroscopic salt, granular potash can easily absorb large quantities of water vapor from humid air during storage and transportation processes. Subsequent drying will result in potash particles sticking together to form clumps or cakes. In order to avoid or decrease caking, it is essential to know the local history of moisture content and moisture movement in a bed of potash. In this thesis, experimental measurements and numerical simulations are used to investigate moisture transport and redistribution by capillarity, gravity and diffusion effects within a potash bed. <p> The important properties required to model moisture transfer in granular porous potash (i.e. porosity, permeability, specific surface area and irreducible saturation) are investigated experimentally and theoretically. It is shown that for a mixture with a wide range of particle sizes the potash bed properties can be predicted knowing the properties for each narrow range of particle size in the mixture. <p> An experimental test facility was designed and constructed to test moisture transfer within a potash bed. The test procedures are presented along with an uncertainty analysis. The moisture content spatial distribution for different particle sizes under different initial conditions is investigated and data are presented. <p>A one-dimensional transient numerical model of moisture transport accounting for diffusion, capillarity and gravity effects within potash beds is developed. Two different moisture transport mechanisms are presented. In a wet region, where local moisture saturation level, S, is larger than an irreducible saturation, S0, liquid water exists as continuous liquid film on the particles; moisture is transferred by liquid film movement due to capillarity and gravity effects. In a dry region where S is less than S0, water vapor diffusion is the only mechanism of moisture transfer and water is adsorbed in layers on the surfaces. <p> From the experimental data and numerical simulation analysis, it is shown that the irreducible saturation, S0, is a strong function of particle size. It will decrease with a particle size increase. <p> The numerical model is validated by comparison with some typical experimental case studies. Agreement between the experimental data and simulation results is well within the experimental 95% uncertainty bounds. It is concluded from this research that the complex moisture transport process by diffusion, capillarity and gravity effects within a potash bed can be modeled and simulated. Experimental and simulation results indicate that direct water drainage will more readily occur for large particle sizes than for small particles for the same initial moisture content.

No description available.

This thesis aims to present a color segmentation approach for traffic sign recognition based on LVQ neural networks. The RGB images were converted into HSV color space, and segmented using LVQ depending on the hue and saturation values of each pixel in the HSV color space. LVQ neural network was used to segment red, blue and yellow colors on the road and traffic signs to detect and recognize them. LVQ was effectively applied to 536 sampled images taken from different countries in different conditions with 89% accuracy and the execution time of each image among 31 images was calculated in between 0.726sec to 0.844sec. The method was tested in different environmental conditions and LVQ showed its capacity to reasonably segment color despite remarkable illumination differences. The results showed high robustness.

A method used to calculate the fundamental properties that predict the overall wicking performance of a fabric was proposed and executed. The combination of a horizontal and downward wicking test provided detailed measurements of the pertinent properties to wicking performance: capillary pressure and permeability. This method was proposed due to flaws found in standard vertical wicking tests as well as erroneous assumptions made in other wicking tests. Assumptions that capillary pressure and permeability are characteristic constants of porous structures are incorrect and will produce misleading information about that substrate. It was experimentally proven that these properties were a function of the saturation level found within the voids of a fabric. To obtain relevant capillary pressure and permeability data for a given fabric, a range of saturation levels were tested and analyzed. It was shown that saturation levels decreased as the vertical distance traveled by moisture increased. This phenomenon occurs as a result of capillary pressure within the voids dropping below the functional range needed to support flow in those voids at increasing heights. As height is increased, capillary pressure needs to also increase; therefore, only smaller radii pores will fill. Once saturation levels are known at specific heights, capillary pressure and permeability calculations were made using Darcys law and the Lucas-Washburn equation. Although this phenomenon is well known in civil engineering, it has not been widely addressed in the textile sciences, especially in its implications for wicking tests.

Mineral oils and coal tars are complex nonaqueous phase liquids (NAPLs), which can serve as long-term sources of ground water contamination. Very limited data are available on mineral oil and coal tar entrapment in and removal from porous media. Thus, the objectives of this research were to evaluate the behavior of these NAPLs in porous media, and investigate the mechanisms governing NAPL entrapment in and recovery from porous media. Quantification of properties of three commercial mineral oils and six MGP coal tars reveals that mineral oils are slightly viscous LNAPLs (density: ~0.88 g/cm3; viscosity: 10-20 cP), whereas coal tars are highly viscous DNAPLs (density: 1.052-1.104 g/cm3; viscosity: 32-425 cP). Measured oil (tar)-water interfacial tensions (IFT) were lower than that of pure NAPLs. Properties of 16 field soil samples (soil particle size distribution, specific surface area, total carbon content, cationic exchange capacity and soil moisture release curves) were characterized. Correlations between residual NAPL saturation and NAPL and soil properties were developed, and show that the entrapment of NAPL dependent upon soil particle size distribution, total carbon content, NAPL viscosity and NAPL-water IFT. Aqueous pH and ionic strength were found to influence the interfacial properties in tar-water-silica systems. At pHs greater than 7.0, observed reduction in contact angle were attributed to the repulsive electrostatic force between coal tar and solid surface. When pH less than 4, hydration forces played a role on the contact angle decrease. The IFT reduction was resulted from the accumulation of surface-active molecules at the tar-water interface. The effect of ionic strength on interfacial properties was not significant below 0.5 M. The effects of temperature and surfactant or surfactant/polymer addition on coal tar removal was investigated by conducting coal tar displacement experiments at three different temperatures (22, 35, and 50??with sequential flushing of water, surfactant and surfactant/polymer. Coal tar removal from porous media was enhanced by elevating temperature and surfactant flushing due to the viscosity and IFT reduction, respectively. Xanthan gum was used as the polymer to increase the viscosity of the displacing fluid. In summary, these results provide tools for the prediction of NAPL entrapment in porous media, and for the selection of remediation strategies for coal tar contaminated source zone.

No description available.

The colonias along the Texas-Mexico border are one of the most rapidly growing areas in Texas. Because of the relatively low income of the residents and an inadequate availability of transportation services, the need for basic social activities for the colonias cannot be properly met. The objectives of this study are to have a better comprehension of the status quo of these communities by examining the potential demand for an improved transportation service and evaluate the capacity and optimum service time interval of a new demand responsive transit "feeder" service within one representative colonia, El Cenizo. A comprehensive analysis of the results of a survey conducted through a questionnaire is presented to explain the existing travel patterns and potential demand for a feeder service. The results of this thesis and work from the subsequent simulation analysis showed that a single shuttle would be able to comfortably serve 150 passengers/day. It further showed that the optimal cycle length between consecutive departures from the terminal should be between 11-13 minutes for best service quality. This exploratory study should serve as a first step towards improving transportation services within these growing underprivileged communities especially those with demographics and geography similar to the target area of El Cenizo.

An objective in the design of high performance machinery is to minimize weight so magnetic bearings are often designed to operate slightly lower than the magnetic material saturation. Further weight reduction in the bearings requires operation in the nonlinear portion of the B-H curve. This necessitates a more sophisticated analysis at the bearing and rotordynamic system levels during the design stage. This dissertation addresses this problem in a unique manner by developing a fully nonlinear homopolar magnetic bearing model. The nonlinear dynamics of permanent magnet-biased homopolar magnetic bearing (PMB HoMB) system with 2-dof rigid and 4-dof flexible rotor is analyzed. The dynamic behavior of the rotor-bearing system is examined in the feedback control loop that includes low pass filter effects. An analytical magnetization curve model is proposed to predict the nonlinear magnetic force under the influence of the magnetic flux saturation more accurately. The modified Langmuir method with the novel correction terms for the weak flux region is used to curve-fit the experimental magnetization data of Hiperco 50. A new curve fit model of the B-H curve is shown to have significantly better agreement with the measured counterpart than conventional piecewise linear and other models. PMB HoMB characteristics with flux saturation, such as forces depending on the rotor position and bearing stiffness, are compared with these other models. Frequency response curve, bifurcation diagram, Poincare plot, and orbit plot are utilized to demonstrate the effects of the nonlinearities included in the 2-dof rotorbearing system. Due to heavy static loads applied to the rotor, it operates within the magnetic flux saturation region at the bearing clearance. The voltage saturation in the power amplifier of the magnetic bearing introduces lag in the control loop and the response of the heavily loaded 4-dof rotor-bearing system shows that limit cycle stability can be achieved due to the magnetic flux saturation or current saturation in the amplifier; otherwise the system would experience a destructive instability. These simulation results provide the first explanation of this commonly observed limit cycle which is referred to as ‘virtual catcher bearings’.

No description available.