Although evidence is mounting that asphalt binder oxidizes in pavements, and that oxidation and subsequent hardening of asphalt binder has a profound effect on pavement durability, important implementation issues remain to be better understood. Quantitative assessment of asphalt binder oxidation for a given pavement is a very important, but complex issue. In this dissertation, a fundamentals-based oxygen transport and reaction model was developed to assess quantitative asphalt binder oxidation in pavements. In this model, oxygen transport and reaction were described mathematically as two interlinked steps: 1) diffusion and/or flow of oxygen from the atmosphere above the pavement into the interconnected air voids in the pavement; and 2) diffusion of oxygen from those air voids into the adjoining asphalt-aggregate matrix where it reacts with the asphalt binder. Because such a model calculation depends extensively on accurately representing pavement temperature, understanding oxygen diffusivity in asphalt binders and mastics, and characterizing air voids in pavements, these key model elements were studied in turn. Hourly pavement temperatures were calculated with an improved one-dimensional heat transfer model, coupled with methods to obtain model-required climate data from available databases and optimization of site-specific pavement parameters nationwide; oxygen diffusivity in binders was determined based on laboratory oxidation experiments in binder films of known reaction kinetics by comparing the oxidation rates at the binder surface and at a solid-binder interface at the film depth. The effect of aggregate filler on oxygen diffusivity also was quantified, and air voids in pavements were characterized using X-ray computed tomography (X-ray CT) and image processing techniques. From these imaging techniques, three pavement air void properties, radius of each air void (r), number of air voids (N), and average shell distance between two air voids (rNFB) were obtained to use as model inputs in the asphalt binder oxidation model. Then, by incorporating these model element improvements into the oxygen transport and reaction model, asphalt binder oxidation rates for a number of Texas and Minnesota pavements were calculated. In parallel, field oxidation rates were measured for these corresponding pavement sites and compared to the model calculations. In general, there was a close match between the model calculations and field measurements, suggesting that the model captures the most critical elements that affect asphalt binder oxidation in pavements. This model will be used to estimate the rate of asphalt binder oxidation in pavements as a first step to predicting pavement performance, and ultimately, to improve pavement design protocols and pavement maintenance scheduling.

Treatment of vision impairing diseases involves drug transport through the vitreous humor. Diffusion cells were used to measure macro-scale (mutual) diffusivity (Dm) to understand how solute size affects diffusion through the vitreous humor of rabbit and porcine eyes. Solutes examined included timolol maleate, dexamethasone sodium phosphate (DMSP), sodium fluorescein, and FITC-dextrans (4, 40, and 150kDa). Diffusivity was inversely dependent on solute size. The Dm's of small solutes in the vitreous were 30 – 65% of that in PBS, while the Dm's of large solutes were 40 – 60% of that in PBS. Extrapolations to the human eye produced similar results using diffusivities based on either species. We used Diffusion Ordered NMR Spectroscopy to measure micro-scale (self) diffusivity (Ds) of DMSP through vitreous humor. The Ds and Dm were significantly different in PBS, but similar in vitreous. A method for obtaining in vivo imagery and data of vitreous fluorophore distribution is also presented.

Treatment of vision impairing diseases involves drug transport through the vitreous humor. Diffusion cells were used to measure macro-scale (mutual) diffusivity (Dm) to understand how solute size affects diffusion through the vitreous humor of rabbit and porcine eyes. Solutes examined included timolol maleate, dexamethasone sodium phosphate (DMSP), sodium fluorescein, and FITC-dextrans (4, 40, and 150kDa). Diffusivity was inversely dependent on solute size. The Dm's of small solutes in the vitreous were 30 – 65% of that in PBS, while the Dm's of large solutes were 40 – 60% of that in PBS. Extrapolations to the human eye produced similar results using diffusivities based on either species. We used Diffusion Ordered NMR Spectroscopy to measure micro-scale (self) diffusivity (Ds) of DMSP through vitreous humor. The Ds and Dm were significantly different in PBS, but similar in vitreous. A method for obtaining in vivo imagery and data of vitreous fluorophore distribution is also presented.

Podophyllotoxin is a natural medicine possessing an outstanding anti-tumour activity. It can be extracted from the rhizome of Podophillum peltatum (American Podophyllum). Volumetric heating of a packed bed of particles including solvent during the extraction can eliminate the solvent pre-heating time and provide uniform and quick heating of the bed. RF-assisted extraction has a potential to be a promising extraction alternative over conventional methods. The characterization and assessment of RF-assisted extraction of podophyllotoxin is crucial. Thermal properties including specific heat capacity, thermal conductivity, and thermal diffusivity of a packed bed of P. peltatum with and without ethanol solutions were determined and the associated multiples regression equations were obtained for the purpose of thermal analysis of RF-assisted packed bed extraction process and related modeling investigations.<p> The dielectric properties of the packed bed of rhizome particles were measured from 10 to 30 MHz using a precision LCR meter and a liquid test fixture. The effects of temperature, particle moisture content, volumetric concentration of ethanol and bed porosity on the dielectric constant, dielectric loss factor and power penetration depth were investigated. The dielectric loss factor significantly increased with the particle moisture content for the beds with 100% and 70% ethanol but not with 30% ethanol. The dielectric loss factor was proportional to temperature directly and to frequency inversely. With 30% ethanol (and therefore 70% water), the dielectric loss factor of the bed dramatically increased compared to 70% and 100% ethanol. Porosity had a significant effect on the dielectric constant but not on the dielectric loss factor. The power penetration depth of a packed bed with 100% ethanol was significantly larger than those of the packed bed with 30% and 70% ethanol. Empirical regression equations were developed for simulation and design of an RF-assisted packed bed extraction of podophyllotoxin.<p> A RF-transparent batch reactor was made of glass filled Teflon and the extraction kinetics of podophyllotoxin was characterized. The effects of temperature, ethanol volumetric concentration, solid/liquid ratio, RF heating and particle moisture content on the extraction rate and yield of podophyllotoxin were investigated at different extraction conditions. A generalized diffusion mathematical model taking into account three major particle geometries was developed and coupled with genetic algorithm for determination of effective diffusivity and partition coefficient through an inverse simulation approach. The approach was first verified by reported experimental data of andrographolide extraction followed by determining the effective diffusivity and partition coefficient of podophyllotoxin for different conditions. The optimum batch extraction condition was achieved with 30% ethanol-water solution at 53¢XC. A prototype was developed for RF-assisted extraction of podophyllotoxin using two optical and RF-transparent reactors with horizontal and vertical orientations. Applying the optimum conditions obtained from batch experiments, the potential of RF heating for providing a uniform temperature in the packed bed was evaluated. The effect of solvent dielectric loss factor on uniform RF heating was investigated and the chemical effect of NaCl used for increasing dielectric loss factor of the solvent on podophyllotoxin was assessed. The horizontal packed bed demonstrated a large temperature gradient across the thickness of the bed during RF heating; however, a uniform RF heating was achieved when the vertical packed bed reactor was used for RF-assisted extraction of podophyllotoxin. The concentration of 2.5 g NaCl/L of the solvent at the temperature controller set point of 40aC provided a relatively good uniform temperature of 50aC within the bed. Evaluating three flow rates of 130, 160 and 200 ml/min for the solvent of 30% ethanol with 2.5 g NaCl/L indicated that the flow rate of 160 ml/min could provide better temperature overlap of four positions of the bed height.

This study was concerned with the recovery of aroma compounds from aqueous solutions by pervaporation using poly(ether-block-amide) (PEBA) membranes. Three model aroma compounds (i.e., propyl propionate, C6-aldehyde and benzaldehyde) were used in the study to represent ester, aldehyde and aromatic aroma compounds, respectively. The effects of process conditions (i.e., feed concentration and operating temperature) on the pervaporation performance (in terms of permeation flux and selectivity) for aroma-water separations were investigated. It was found that both the aroma permeation flux and the selectivity were affected significantly by the feed aroma concentration. The aroma permeability was in the order of propyl propionate > C6-aldehyde > benzaldehyde, and the membrane selectivity for aroma/water separation followed the order of C6-aldehyde > propyl propionate > benzaldehyde. In general, the aroma flux was found to be proportional to the aroma compound concentration in the solution. In the concentration range (390-3,200 ppm) tested, the effect of temperature on the permeation flux followed an Arrhenius type of relation. The solubility and diffusivity of the aroma compounds in PEBA membrane, which determine their permeabilities through the membrane, were determined from the pervaporation and sorption/desorption data. It was shown that the solubility of the aroma compounds in the PEBA membrane generally followed the Henry’s law where the sorption uptake was proportional to the feed aroma concentration. Among the three aroma compounds studied, benzaldehyde was found to have the highest solubility selectivity in the PEBA membrane, followed by C6-aldehyde and propyl propionate. The solubilities of pure propyl propionate and water in PEBA membrane were also estimated; the solubility of pure propyl propionate was around 130 times higher than that of pure water. This confirmed that PEBA was an excellent organophilic membrane. The diffusivity of the aroma compounds through PEBA membrane was affected by the feed aroma concentration. From steady state pervaporation and equilibrium sorption data, the diffusivity was calculated on the basis of solution-diffusion model, and the diffusivity was shown to be linearly dependent on the feed aroma concentration. On the other hand, from the sorption kinetics data obtained from the time-dependent sorption experiments, the diffusivity was shown to be affected by the feed aroma concentration exponentially. The main reason may be that the simple form of the solution-diffusion model is unable to precisely describe the mass transport through the membrane during pervaporation. As an alternative to pervaporation where the liquid feed is in contact with the membrane and the mass transport involves permeation and evaporation (thus the word “pervaporation”), evaporation-permeation (or evapermeation, where the feed liquid is not in direct contact with the membrane and the mass transfer involves evaporation and then permeation) was also studied for aroma compound separation from water. It was shown that evapermeation was no better than pervaporation in terms of permeation flux and selectivity. This again demonstrated that the state of the membrane and the location for liquid-vapor phase change were important to the mass transport through the membrane. For aroma recovery from dilute aqueous solutions, batch pervaporation is often preferred. Batch pervaporation coupled with permeate decantation and water phase recycle was studied parametrically. It was demonstrated that compared to the conventional pervaporation, the aroma recovery can be enhanced by recycling the water phase from the permeate decanter to the feed for further recovery. In addition, unlike the conventional batch operation where the product concentration starts to decrease beyond certain time, the modified batch pervaporation allows a longer period of operation without compromising the product purity.

Chitosan membrane has found applications in biomedical, wastewater treatment, and petrochemical fields that involve the use of silver ions (Ag+). However, mobility of Ag+ in chitosan membranes has seldom been studied. In this study, transport properties of Ag+ in chitosan membranes are studied in-depth, to determine diffusivity coefficient, permeability coefficient, and sorption uptake of Ag+ in chitosan. All parameters are evaluated based on the influence of feed concentration, membrane thickness and operating temperature. The diffusivity is determined from the time lag obtained from transient diffusion experiments. The permeability is determined from the steady state of permeation experimentally. The diffusivity and corresponding permeability coefficients of Ag+ in chitosan range from to 2.0 10-7 (cm2/s) and from 6.6 10-8 to 2.0 10-7 {mol m/[m2 s (mol/L)]}, respectively, over the conditions tested. Temperature dependencies of these two parameters are found to follow the Arrhenius relationship. Sorption uptake of the silver salt in chitosan correlates well with the Langmuir isotherm. Also determined from the sorption tests are degree of membrane swelling at different concentrations. This information allows diffusivity coefficients to be determined from the steady state permeation rate. These values of diffusivity are compared with that obtained using the time lag method.

This study was concerned with the recovery of aroma compounds from aqueous solutions by pervaporation using poly(ether-block-amide) (PEBA) membranes. Three model aroma compounds (i.e., propyl propionate, C6-aldehyde and benzaldehyde) were used in the study to represent ester, aldehyde and aromatic aroma compounds, respectively. The effects of process conditions (i.e., feed concentration and operating temperature) on the pervaporation performance (in terms of permeation flux and selectivity) for aroma-water separations were investigated. It was found that both the aroma permeation flux and the selectivity were affected significantly by the feed aroma concentration. The aroma permeability was in the order of propyl propionate > C6-aldehyde > benzaldehyde, and the membrane selectivity for aroma/water separation followed the order of C6-aldehyde > propyl propionate > benzaldehyde. In general, the aroma flux was found to be proportional to the aroma compound concentration in the solution. In the concentration range (390-3,200 ppm) tested, the effect of temperature on the permeation flux followed an Arrhenius type of relation. The solubility and diffusivity of the aroma compounds in PEBA membrane, which determine their permeabilities through the membrane, were determined from the pervaporation and sorption/desorption data. It was shown that the solubility of the aroma compounds in the PEBA membrane generally followed the Henry’s law where the sorption uptake was proportional to the feed aroma concentration. Among the three aroma compounds studied, benzaldehyde was found to have the highest solubility selectivity in the PEBA membrane, followed by C6-aldehyde and propyl propionate. The solubilities of pure propyl propionate and water in PEBA membrane were also estimated; the solubility of pure propyl propionate was around 130 times higher than that of pure water. This confirmed that PEBA was an excellent organophilic membrane. The diffusivity of the aroma compounds through PEBA membrane was affected by the feed aroma concentration. From steady state pervaporation and equilibrium sorption data, the diffusivity was calculated on the basis of solution-diffusion model, and the diffusivity was shown to be linearly dependent on the feed aroma concentration. On the other hand, from the sorption kinetics data obtained from the time-dependent sorption experiments, the diffusivity was shown to be affected by the feed aroma concentration exponentially. The main reason may be that the simple form of the solution-diffusion model is unable to precisely describe the mass transport through the membrane during pervaporation. As an alternative to pervaporation where the liquid feed is in contact with the membrane and the mass transport involves permeation and evaporation (thus the word “pervaporation”), evaporation-permeation (or evapermeation, where the feed liquid is not in direct contact with the membrane and the mass transfer involves evaporation and then permeation) was also studied for aroma compound separation from water. It was shown that evapermeation was no better than pervaporation in terms of permeation flux and selectivity. This again demonstrated that the state of the membrane and the location for liquid-vapor phase change were important to the mass transport through the membrane. For aroma recovery from dilute aqueous solutions, batch pervaporation is often preferred. Batch pervaporation coupled with permeate decantation and water phase recycle was studied parametrically. It was demonstrated that compared to the conventional pervaporation, the aroma recovery can be enhanced by recycling the water phase from the permeate decanter to the feed for further recovery. In addition, unlike the conventional batch operation where the product concentration starts to decrease beyond certain time, the modified batch pervaporation allows a longer period of operation without compromising the product purity.

The main objective of this study was to investigate the effect of spouted bed and microwave assisted spouted bed drying on drying rates and quality parameters of bulgur. The drying experiments were performed at three air temperatures (50, 70, 90oC) and at two microwave powers (288 W, 624 W). Quality parameters were selected as bulk density, apparent density, apparent porosity, internal porosity, microstructure analysis, and color for dried cooked wheat / yield and water absorption capacity for bulgur. The drying rate increased with air temperature and microwave power. Microwave assisted spouted bed drying at microwave power of 288W and 624 W reduced drying time by at least 60% and 85%, respectively compared to spouted bed drying. The effective moisture diffusivities of bulgur in the spouted bed and microwave assisted spouted bed drying were found to be 2.356x10-10 and 8.398x10-10 m2/s on the average, respectively. The effect of air temperature on product quality except color was not significant in spouted bed drying. Interior kernel porosity, sphericity and L* value of dried cooked wheat increased with air temperature and microwave power. Yield and water absorption capacity of bulgur tended to decrease as microwave power increased. According to SEM analysis, more porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. In microwave assisted spouted bed drying, lower water absorption capacity, bulk density and apparent density, higher sphericity and lighter color were observed as compared to spouted bed drying.

Grape pomace is a valuable waste product and various end-products have been obtained after treatments. Recently, these have been commercialized due to their health-promoting effects. Drying is a crucial part of these treatments. This study aimed to analyze the drying kinetics of grape pomace parts, which are seeds and skins. Two grape types were used in this study, namely Emir and Bogazkere varieties of Vitis Vinifera species. Seeds and skins of each variety were dried in a tray dryer at an air velocity of 1 m/s with four different air temperatures / 40, 50, 55 and 60&deg / C. The drying curves showed that the drying r ate increased with the air temperature. Six different drying models were selected from the literature and the best fitted model was determined by application of appropriate statistical methods. It was found that for Bogazkere seeds / Modified Two Term Model, for Bogazkere and Emir skins / Modified Page Model and for Emir skins / Logarithmic Model gave the best fit. The effective moisture diffusivities of each type were found for each temperature and were determined by two different approaches, experimental and estimation. The values and variation of Deff / L2 with temperature were calculated and were found to be increasing with temperature and that the Deff / L2 values were larger for grape skins than grape seeds. Arrhenius type equation was used in order to explain the temperature dependency of Deff / L2.

The accurate description of fluid flow through porous media allows an engineer to properly analyze past behavior and predict future reservoir performance. In particular, appropriate mathematical models which describe fluid flow through porous media can be applied to well test and production data analysis. Such applications result in estimating important reservoir properties such as formation permeability, skin-factor, reservoir size, etc. "Real gas" flow problems (i.e., problems where the gas properties are specifically taken as implicit functions of pressure, temperature, and composition) are particularly challenging because the diffusivity equation for the "real gas" flow case is strongly non-linear. Whereas different methods exist which allow us to approximate the solution of the real gas diffusivity equation, all of these approximate methods have limitations. Whether in terms of limited applicability (say a specific pressure range), or due to the relative complexity (e.g., iterative character of the solution), each of the existing approximate solutions does have disadvantages. The purpose of this work is to provide a solution mechanism for the case of timedependent real gas flow which contains as few "limitations" as possible. In this work, we provide an approach which combines the so-called average pressure approximation, a convolution for the right-hand-side non-linearity, and the Laplace transformation (original concept was put forth by Mireles and Blasingame). Mireles and Blasingame used a similar scheme to solve the real gas flow problem conditioned by the constant rate inner boundary condition. In this work we provide solution schemes to solve the constant pressure inner boundary condition problem. Our new semi-analytical solution was developed and implemented in the form of a direct (non-iterative) numerical procedure and successfully verified against numerical simulation. Our work shows that while the validity of this approach does have its own assumptions (in particular, referencing the right-hand-side non-linearity to average reservoir pressure (similar to Mireles and Blasingame)), these assumptions are proved to be much less restrictive than those required by existing methods of solution for this problem. We believe that the accuracy of the proposed solution makes ituniversally applicable for gas reservoir engineering. This suggestion is based on the fact that no pseudotime formulation is used. We note that there are pseudotime implementations for this problem, but we also note that pseudotime requires a priori knowledge of the pressure distribution in the reservoir or iteration on gas-in-place. Our new approach has no such restrictions. In order to determine limits of validity of the proposed approach (i.e., the limitations imposed by the underlining assumptions), we discuss the nature of the average pressure approximation (which is the basis for this work). And, in order to prove the universal applicability of this approach, we have also applied this methodology to resolve the time-dependent inner boundary condition for real gas flow in reservoirs.