Engineering Commons^™

Oxygen Tension Profiles In Tumors Predicted By A Diffusion With Absorption Model Involving A Moving Free Boundary, B. H. Arve, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

The dynamic behavior of the oxygen tension distribution in tumors during radiotherapy is studied by the development and solution of a diffusion with absorption model involving a moving free boundary. The oxygen uptake rates within the tumor are considered to be functions of the oxygen concentration and results are presented for zeroth-, half-, first- and second-order rates of absorption, as well as when the rate of oxygen absorption is described by the Michaelis-Menten expression. The results presented in this work may be used together with the data from the oxygen radiosensitivity curve of a tumor, in order to determine the …

Electrochemical Production And Corrosion Testing Of Amorphous Ni-P, Jose L. Carbajal, Ralph E. White

Faculty Publications

Ni-P alloys were prepared by electrodeposition under different conditions on a rotating disk electrode. A variety of alloys were prepared ranging from Ni-15P to Ni-25P. An indirect reduction of species in solution involving several steps appears to be favored over the direct reduction at the electrode based on the low P content in the alloy. Energy dispersion x-ray microanalysis was used to determine composition of the alloy. Transmission electron microscopy and x-ray diffraction corroborated the amorphous nature of the structure. The physical and chemical homogeneity of the metallic glasses produced electrochemically is substantiated by the absence of electrochemical localized attack. …

Oxygen Reduction On Silver In 6.5 Molar Caustic Soda Solution, Prosper K. Adanuvor, Ralph E. White

Faculty Publications

No abstract provided.

A Two-Dimensional Mathematical Model Of A Porous Lead Dioxide Electrode In A Lead-Acid Cell, E. C. Dimpault-Darcy, T. V. Nguyen, Ralph E. White

Faculty Publications

A two-dimensional mathematical model is presented for a lead dioxide electrode in a lead-acid cell. It is used to simulate the time dependent behavior of the electrode during discharge. The model contains six dependent variables: the concentration of the acid electrolyte, the porosity, the electrical potentials of the solid and solution phases, and the two directional components of the current density in the electrolyte. The effect of the electrode grid was included by varying the conductivity of the solid. Parameters such as electrode conductivity, electrode dimensions, and temperature are investigated to understand their effects on electrode discharge performance.

Secondary Current Distributions Using Topaz2d And Linear Kinetics, E. C. Dimpault-Darcy, Ralph E. White

Faculty Publications

Secondary current density distributions are of interest
to cell designers. The purpose of this note is to illustrate
how to use an existing numerical method to determine
these distributions for cells that contain conducting and
nonconducting bodies between the main anode and cathode.

Analysis Of Electrokinetic Data By Parameter Estimation And Model Discrimination Techniques, Prosper K. Adanuvor, Ralph E. White

Faculty Publications

An alternative approach to classical methods of electrochemical data analysis is presented. This alternative method is based on nonlinear parameter estimation and model discrimination techniques. The method is used to obtain the relevant kinetic and transport parameters and to elucidate the kinetic mechanism of O₂ reduction at carbon and silver electrodes in alkaline electrolytes.

A Mathematical Model For Predicting Cyclic Voltammograms Of Electronically Conductive Polypyrrole, Taewhan Yeu, Trung V. Nguyen, Ralph E. White

Faculty Publications

Polypyrrole is an attractive polymer for use as a high energy density secondary battery because of its potential as an inexpensive, lightweight, and noncorrosive electrode material. A mathematical model to simulate cyclic voltammograms for polypyrrole is presented here. The model is for a conductive porous electrode film on a rotating disk electrode (RDE) and is used to predict the spatial and time dependence of concentration, overpotential, and stored charge profiles within a polypyrrole film. The model includes both faradaic and capacitive charge components in the total current density expression.

Predicting Shunt Currents In Stacks Of Bipolar Plate Cells With Conducting Manifolds, H. S. Burney, Ralph E. White

Faculty Publications

A method is presented for predicting shunt currents in stacks of bipolar plate cells with conducting manifolds. The method is based on the requirement that the potential drop through the solution in a manifold be large enough to force current to leave the solution and to enter the conducting manifold. The current that leaves the solution in the manifold enters the conducting manifold at the anode end of the stack and returns to the solution at the cathode end. This could cause catastrophic failure of a manifold.

Oxygen Reduction On Silver In 6.5m Caustic Soda Solution, Prosper K. Adanuvor, Ralph E. White

Faculty Publications

The cathodic reduction of oxygen in 6.5M membrane-grade caustic soda solution has been studied experimentally at a silver rotating disk electrode at 25°C. The results can be approximated by the parallel mechanism for oxygen reduction with catalytic decomposition of peroxide. Further analysis of this mechanism indicates that the sequential process with catalytic decomposition of peroxide predominates over the direct 4e^– process. Direct application of the sequential mechanism to the data indicates that the latter mechanism with catalytic decomposition of peroxide much more accurately reflects the experimental results. The relevant kinetic parameters are calculated on the basis of …

A Mathematical Model For The Electrodeposition Of Alloys On A Rotating Disk Electrode, Shiuan Chen, Ken-Ming Yin, Ralph E. White

Faculty Publications

A general multiple electrode reaction model for electrodeposition of alloys on a rotating disk electrode is presented. Included in the model are mass transport equations with the effect of ionic migration, Butler-Volmer kinetic rate expressions, and the mole fractions of the individual components in the solid state. The model shows that the effect of ionic migration is important and that plating variables such as applied potential, pH, and bulk concentration can be included. Two examples (Ni-P and Ru-Ni-P) are used to illustrate the predictions of the model.

Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White

Faculty Publications

A mathematical model is developed to simulate the electrodeposition of Cu-Ni alloy from citrate solutions onto a rotating disk electrode under potentiostatic control. The model includes the influence of diffusion, ionic migration, forced convection, and homogeneous equilibria. The three major electrochemical reactions treated in the model are copper deposition, nickel deposition, and hydrogen evolution. Using experimental parameters when available, the model was fitted and tested against experimentally-obtained results for different bath compositions and operating conditions. The model agreed reasonably well with the experimental results particularly in the codeposition region, –1.0 to –1.2V vs. SCE, where hydrogen evolution is not the …

Heats Of Transport From Diffusion Thermoeffect Measurements On Binary Liquid Mixtures Of Carbon Tetrachloride With Benzene, Toluene, 2-Propanone, N-Hexane, And N-Octane, Richard L. Rowley, S. C. Yi

Faculty Publications

Measurements of heats of transport are reported for binary liquid mixtures containing carbon tetrachloride and benzene, toluene, 2-propanone, n-hexane, or n-octane at 298 K and ambient pressure. Additionally, measurements were made at 308 K for carbon tetrachloride with benzene, toluene, and 2-propanone. The corresponding heat-mass Onsager coefficients are also reported, from which thermal diffusion ratios have been calculated based on Onsager reciprocity. These data will be used in a companion paper to report a modified Enskog method for correlation and prediction of heats of transport.

On The Use Of A Modified Square-Well Model For Prediction And Correlation Of Thermal Diffusion Factors In Binary Liquid Mixtures, Richard L. Rowley, S. C. Yi

Faculty Publications

Recently reported thermal diffusion factors obtained from heats of transport have been used to test the ability of existing theories to predict thermal diffusivities using model parameters regressed from pure component transport data. None of the theories tested were able to provide even qualitative agreement with experiment. However, predictions using a square-well Enskog theory, modified here for consistency with normal experimental definitions, were found to be approximately correct using pure-component square-well parameters regressed from viscosity and thermal conductivity and an assumed mixing rule for cross terms. Predicted values are very sensitive to the energy mixing rule, and correlation of experimental …

A Laboratory Simulation Of A Rotary Vacuum Drum Brownstock Washer, Hugh E. Muller

Masters Theses

Mass balances can quantify the dilution and thickening of a liquor/fiber suspension on a brownstock washer. However, the complex displacement process necessitates an empirical approach. Given empirical data, washers can be optimized through use of efficiency factors with mass balances.

Because empirical data is difficult to obtain, a laboratory washing method was developed to empirically generate displacement efficiencies on pulp under mill washer conditions. Reproducible data generated by this method resulted in a displacement/dilution function as seen on mill washers. A laboratory simulation using mill samples, exclusive of problems for one vacuum drum, resulted in comparable efficiencies with less than …

A Computer Simulation Of The Rotary Drum Brownstock Washer System Using The Monte Carlo Method Of Distribution Sampling, Jacqueline K. Pease

Masters Theses

A steady-state probabilistic model is chosen to simulate the brownstock washing system's uncertainty which arises from unpredictable process fluctuations and measurement noise. Distribution sampling is used to construct multiple mass balances of a washing system. Included in this model is a linear relationship describing the correlation between dilution and displacement which allows displacement ratio to be generated based on dilution factor. This is an improvement over a similar, earlier model which considers all variables to be independent. There is no statistical difference between the mean output of the simulation and the means of data sets collected at two different mills. …

Development Of A Parametric Analysis Microcomputer Model For Evaluating The Thermodynamic Performance Of A Reciprocating Brayton Cycle Engine, Thomas Joseph White

Dissertations and Theses

In this thesis, applicable data from research on IC engines have been adapted to PACE engine designs. Data from studies on heat transfer, friction, and pressure losses, in particular, have been used. Certain parameters which define operation and design characteristics appear to influence PACE engine performance very strongly. Some of the more critical parameters, notably friction and heat transfer coefficients, must be determined experimentally if accurate model results are to be expected. Pressure ratio, compressor RPM, and maximum combustor temperature, the independent operating parameters, also have a dramatic effect on engine performance. Other design or operating characteristics and working fluid …

Transient Analysis Of Macromolecular Blood-Tissue Exchange In Microvascular Bed, Alex Yefim Bekker

Dissertations

Movement of macromolecules across microvascular walls was studied in the hamster cheek pouch with intravital fluorescence microscopy. A graded series of Fluorescein Isothiocyanate labeled Dextrans(FITC) of 20,000 -70,000 molecular weight were used as representative macromolecular tracers. The time dependent extravasation of FITC-Dextrans was video taped for approximately two and a half hours. Permeation of macromolecules from individual microvessels was quantified by digital video image processing. Histograms of the light intensity distributions for selected fields at various times have been measured and used to construct integral optical density - time profiles of the extravasated fluorochromes for particular leaky sites. An integrated …

Reactions Of Atomic Hydrogen With Dichloromethane In A Flow System, Shun-Hsien Huang

Theses

The reaction kinetics of atomic hydrogen with dichloromethane were studied in a tubular flow reactor with 2.6 cm I.D. Pyrex tube at pressure of 2.1 to 2.7 torr absolute and room temperature . Hydrogen atoms were generated by a microwave discharge plasma. Atomic hydrogen concentration were measured by chemiluminescence titration with nitrogen dioxide. The concentrations of hydrogen atom ranged from 2.0 * 10¹⁴ to 5.0 * 10¹⁵ atoms per cm³. Chlorocarbon reagent and products were monitored by online gas chromatography (FID).

Major products observed were hydrogen chloride and methane. The conversion of dichloromethane increases first to …

Reaction Of Hydrogen With Methylene Chloride And Carbon Tetrachloride At High Temperature, Hun Tsao

Theses

The reactions of methylene chloride and carbon tetrachloride in hydrogen in the temperature range 500 - 1000° C were studied using tubular flow reactors of three diameters. (ID: 0.40, 1.05, 1.60 cm). Residence time range was from 0.3 to 3.5 seconds. Temperature profiles of the reactors was kept within +/- 5° C of central 85% for the 18 inch long reactor, at a total pressure of 1 atmosphere. No chlorinated hydrocarbon products were observed at or above 950° C. The major products in this temperature range were CH4, C2H₂, C2H₄, C2H₆ and HCl.

The pseudo …

A Theoretical Investigation Of The Possibility Of Coexistence Of Three Microbial Populations Competing Purely And Simply In Configurations Of Three Interconnected Chemostats, Shiuan-Wu Chang

Theses

It is known from the literature that out of any number of microbial populations competing purely and simply in an environment which is homogeneous and has time invariant inputs (e.g. in an ideal chemostat) only one population can survive in a steady state under any conditions. However it has been proven possible for two competitors to coexist in two interconnected chemostats, which indicates that spatial heterogeneities may lead to coexistence of pure and simple competitors. The present study investigates whether the spatial heterogeneities created by three interconnected bioreactors may lead to a mixed culture (i.e. coexistence) of three pure and …

Chemically Driven Convection In A Porous Medium, Hendrik J. Viljoen, V. Hlavacek

Papers in Chemical Reactions

This paper is focused on the analysis of interaction of free convection and exothermic chemical reaction. As a consequence of the chemical reaction, free convection effects can result. It is difficult to perform an analytical bifurcation analysis of the full nonlinear governing equations; however, Fourier expansion combined with a Galerkin approximation results in a small set of ordinary nonlinear differential equations (initial value problem) that are amenable to analysis. Conditions for branching of the solution can be determined in an analytical way. A continuation algorithm makes it possible to calculate the branches of stability. The results of the approximate analysis …

A Mathematical Model Of Photopolymerization In A Batch Reactor, Jyh-Yao Li

Theses

A mathematical model of a photo initiated additionpolymerization in a batch reactor was developed.

The model considered initiation, propagation and, termination to simulate the addition polymerization process, The model has the advantage that the concentration of any particular n-mer may be calculated without calculating all of its precursors. Other methods do not have this property. An analytical solution to the model for the photopolymerization of styrene was solved. The calculations were run on a VAX 8800 computer and the results were then compared with the experimental results. The calculated results fitted the experimental results to some extent. Effects from the …

Studies Directed Toward Beta-Cyclodextrin And Capped Beta-Cyclodextrin Mimics Of Alpha-Chymotrypsin, Preston Marlon Canzius

Theses

Molecular mechanics calculations were used to investigate beta-cyclodextrin and capped beta-cyclodextrin as models for the active site of alpha-chymotrypsin. The Amber molecular mechanics force field was used to investigate the effect that addition of the caps has on the conformation of the beta-cyclodextrin macrocycle.

The RMS module of Amber was used to calculate differences in position between the atoms of the minimized mimics and those of the X-ray crystal structure. The deviation in position of the atoms of the minimized capped beta-cyclodextrin macrocycle was found to be larger than that of the minimized beta-cyclodextrin, indicating that the caps do affect …

Particle Size Distribution In Isothermal Batch Emulsion Polymerization, Bhavin R. Patel

Theses

A detailed modified mathematical model for particle size distribution in isothermal batch emulsion polymerization of Styrene and Vinyl acetate is proposed on the basis of the population balance approach in presence of several kinetic and mass transfer processes. This study is limited to Smith-Ewart's case II, which assumes instantaneous free radical termination within the polymer particles. Radical desor¬ption mechanism from polymer particles is included in the model and the desorption rate is formulated from the diffu¬sion theory which suggests that the rate co-efficient should be inversely proportional to the surface area of polymer particles.

Experimental runs are made using laser …

Theoretical Studies Of A Norbornane Mimic Of Acyl-Alpha-Chymotrypsin, Pin-Nan Chen

Theses

Molecular mechanics calculations were used to investigate the structural flexibility of the norbornane mimic which is a model of an acyl-alpha-chymotrypsin intermediate. The Amber molecular mechanics force field was used to perform the conformational analysis.

Comparison of the optimized conformations of different energy has shown the relative structural rigidity of this molecule. Structural superposition of the minimized mimic to the native conformation of chymotrypsin shows that the mimic has a very similar spatial arrangement of its functional groups compared to the catalytic triad of the real enzyme.

Molecular electrostatic potential maps calculated in planes parallel to the average plane containing …

Hydrodechlorination Reactions On Silica-Supported Rhodium Catalysts, Yung-Ming Chen

Theses

The objectives of this study were to investigate the pathways of the hydrodechlorination reactions over silica-supported Rh catalysts as well as identify selectivities and deactivation properties.

Reaction of 1,2-dichloroethane with hydrogen over Rh/SiO₂ catalyst was studied in the temperature range 200 to 300°C. Formation of two intermediates was proposed while 1,2-dichloroethane was adsorbed on the catalyst, the reactive intermediates then produce ethane, ethylene, chloroethane and methane. From the methane formation, it was inferred that the ethane hydrogenolysis occured over the Rh/SiO₂ catalysts. Higher conversion to C₁ and C₂ hydrocarbons was observed at higher reaction temperature. The …

Separation Of Chromium From Waste Sludges By An Electric Membrane Process, Freeman Nai-Tchun Ho

Theses

The process is characterized by using metallic membrane as a filter which is charged by a separate DC-power supply and it may become experimentally very effective in increasing the separation potency and migration flux. The technique of integrating migration with electromembrane was evaluated for the removal of chromium. The transport was found to be adequately described by an equation in which the rate is proportional to the chromium concentration. The rate of dichromate ions transported across the membranes and the gel water content of membrane increased when the ratio of electromembrane potential and cell system potential was increased. The back …

A Study Of The Dynamics Of Microbial Competition For A Single Resource In A Chemostat Between Reversible Attachment To Solid Surfaces, Pericles Theofilos Lagonikos

Theses

It is known that two microbial populations competing for a single non-renewable resource in a homogeneous environment with time-invariant inputs cannot coexist in a steady state. The case where two microbial populations exhibiting reversible attachment to the walls of a chemostat compete for a single resource is studied theoretically. Because of the cell's attachment to the walls, the environment is no longer homogeneous. The present study considers the case where the attached cells form no more than a monolayer. The Baltzis-Fredrickson model is used to represent the attachment to the walls. In one system the attachment of cells of the …

Hard-Sphere Theory For Correlation Of Tracer Diffusion Of Gases And Liquids In Alkanes, Michael A. Matthews, Aydin Akgerman

Faculty Publications

No abstract provided.

The Effect Of Inorganic Salts On Adsorption Of Organics By Fly Ash, Pai-Yuan Horng

Theses

Optimum amounts of inorganic salts ( monovalent, divalent, and trivalent chlorides ) added to various bituminous coal fly ashes in batch adsorption treatment experiments indicates the possibility of improving adsorption capacity.

Experiments were conducted on aqueous solutions of three priority pollutants : phenol, toluene, benzene. Both high fusion and low fusion fly ashes were used as sorbent materials. Removal of organic pollutants was measured using a total organic carbon analyzer.

Isotherm tests positively indicate that the addition of inorganic salts to fly ash significantly increases adsorption capacity. The study shows that removal of organic pollutants by fly ash depends on …