Engineering Commons^™

Characterization Of The Rheological, Optical, And Flow-Induced Structural Features Of Polymer Liquid Crystals, David Neal Lewis

Doctoral Dissertations

Two related sets of experiments were conducted to explore the interaction between supramolecular structures, material properties, and flow-induced stresses in selected lyotropic and thermotropic polymers. The first set of experiments focused on the quiescent and rheological characterization of polymers. The objective was to develop a flow-structure model based on the general phenomenological features of the liquid crystalline state. The second set of experiments concerned the characterization of the crystal structure, crystalline orientation, and tensile properties of a model thermotropic polymer, melt spun under varying conditions of extrusion rate, extrusion temperature, drawdown ratio, and die exit conditions. The objective was to …

The Effect Of Particle Dynamics On Turbulence Measurements With The Laser Doppler Velocimeter, Robert H. Nichols

Doctoral Dissertations

The laser velocimeter (LV) is currently being used by many researchers to nonintrusively obtain velocity data in complex flow fields. The LV measures the velocity of small particles entrained in the flow field of interest. The fluid velocity and turbulent velocity correlations are then inferred from statistical analysis of these particle velocity measurements under the assumption that the particles exactly reproduce the motion of the fluid. This assumption needs careful evaluation since it is fundamental to the application of the LV.

The particle equation of motion was carefully analyzed to determine what form is required for evaluating the turbulence response …

Predictive Model For The Pulse Pressure In A Pulse-Jet Fabric Filter, Satoru Mitsutomi

Doctoral Dissertations

Pulse-jet cleaned fabric filters are being utilized to filter dust from particulate laden gas streams. The pulse-jet fabric filter consists of a reservoir, a solenoid valve, a lateral pipe and a venturi/bag. The compressed air is released periodically through a solenoid valve and fills the lateral pipe. Then high velocity air is ejected from a series of orifices on the lateral pipe. As a result, the bag is rapidly inflated and dust is dislodged from the bag.

A predictive model for the pulse pressure in a pulse-jet fabric filter has been developed. Two types of models are presented: Simplified Static …

Comparative Gene Mapping In Baboon (Papio) Species, Kathleen Lou Moore Thiessen

Doctoral Dissertations

Gene mapping in nonhuman mammalian species is a field of increasing importance in man's efforts to understand genome organization, to develop animal models for human genetic diseases, and to investigate phylogenetic relationships and evolutionary mechanisms. The primates are of particular interest in these studies because of their morphological and physiological similarities to man. The availability and convenient size of the baboons (Papio species) make them the primates of choice for various areas of research having applications to man. The baboons also appear to have many chromosomal and genetic homologies to man as well as to the other primates, although …

Determination And Interpretation Of Dispersion Of Small Particles In Thermoplastics, Yoshiyuki Suetsugu

Doctoral Dissertations

It is the purpose of the present research to characterize the particulate structure in the compounds for a range of small solid particulates. These include a wide range of calcium carbonates both in uncoated and coated modes, carbon blacks, uncoated and coated talc, mica, etc. The matrix polymers used are polystyrene and polypropylene.

The present research involves (i) development of methods and the interpretation of them to characterize the state of particles and their structure in plastics, (ii) to determine how these particulate structures are developed in the mixing process.

The primary particulate structure of concern is the state of …

Development And Applicability Of A Mathematical Model For The High Speed Melt Spinning Of Crystallizable Polymers, Kenneth F. Zieminski

Doctoral Dissertations

A mathematical model was developed to describe the high speed melt spinning behavior of crystallizable polymers. This model included the effects of acceleration, gravity and friction on the kinematics of the process, temperature and molecular orientation on the crystallization kinetics of the polymer and temperature, molecular weight and crystallinity on the elongational viscosity of the material. Experimental online diameter, birefringence and temperature profiles were obtained for a 12000 Mn nylon-66 at 2.5 gm/min spun at take-up speeds ranging from 2800 to 6600 meters/minute. These profiles were qualitatively and reasonably quantitatively in agreement with the predicted profiles. They indicated that orientation …

Transient Response Of A Packed Bed For Both Sensible And Latent Thermal Energy Storage, Shi-Hong Ji

Doctoral Dissertations

The present work was undertaken to provide a model which accurately predicts the performance of a packed bed energy storage system utilizing spherically encapsulated phase-change material (PCM). Two models were developed which are referred to as the first-order and second-order models. Both models involve modeling of the phase-change material as a conduction problem with both sensible and latent energy storage and include consideration of the temperature gradients in both phases. Both models include the solution of the energy equation for the fluid passing through the packed bed. In the second-order model, both the intra-particle conduction and the dispersion effects in …

The Modeling And Analysis Of Multi-Component, Multivalent Biospecific Adsorption, Bo Henrik Arve

Doctoral Dissertations

"A general model is presented and used to predict the dynamic behavior of the adsorption, wash, and elution stages of biospecific adsorption (affinity chromatography) in finite bath and column operations. The model accounts for film and pore diffusional mass transfer resistances and the rates of interaction between adsorbates and ligands. For column operations the effect of axial dispersion in the flowing fluid stream is included. The model is applicable to single and multi-component biospecific as well as non-specific adsorption, and the adsorbates may be monovalent or multivalent. In the elution stage both non-selective and selective elution of monovalent adsorbates is …

Web Crippling Of High Strength Cold-Formed Steel Beams, Chiravut Santaputra

Doctoral Dissertations

"The structural behavior of high strength cold-formed steel beams subjected primarily to web crippling was investigated analytically and experimentally. In this study hat sections and I-beams, formed from five different types of high strength sheet steels commonly used in the automobile industry, were investigated under various loading conditions. The yield strengths of these sheet steels vary from 58 to 165 ksi.

In addition to the test data gathered in this phase of study, the experimental results obtained from the beam tests conducted at Inland Steel Company and Ford Motor Company were carefully evaluated. The evaluation indicated that the present available …

Oxidation Kinetics Of Polycrystalline Srtio₃ And Lacro₃, Chi-Kung Jerry Yu

Doctoral Dissertations

"The oxidation kinetics of polycrystalline SrTiO₃ and LaCrO₃ were determined by measuring the time and temperature dependence of the weight and conductivity change of reduced samples. A region of fast diffusion followed by a reduced diffusion tail was observed in the TGA measurements. This observation can be interpreted as the initial diffusion along the boundaries and then spreading out into the lattice. The absence of the tail in the conductivity measurements is due to the high electron and hole mobility at the boundaries. The electrical conductivity and TGA results on Nb-doped LaCrO₃ show that at low oxygen …

An Investigation Of Signs For Median Crossovers, Gillian M. Worsey

Doctoral Dissertations

“This paper describes a study of advance warning signs for median crossovers on divided highways. Candidate crossover signs were identified from a literature review, survey of current State practices and discussions with FHWA personnel. Seven of these signs were selected for further testing in a laboratory study for legibility, understanding and driver preference. Sixty subjects representing a cross-section of drivers took part in the study, thirty at the Turner-Fairbanks Highway Research Center in McLean, Virginia and thirty at the University of Missouri--Rolla in Rolla, Missouri.

Two of the seven signs were word messages and five were symbolic signs. The results …

Structural Design Of Coal-Fueled Power Plant Ductwork, Stanley Pearce Rader

Doctoral Dissertations

"An absence of a comprehensive procedure for design of coal-fueled power plant ductwork currently exists in the publicly available literature. This dissertation presents such a procedure.

An overview of the ductwork design environment, including major components of the air and flue gas flow paths, design loads and temperatures, corrosion considerations, and physical configurations, is given. Design criteria for materials, corrosion inhibition, minimum plate thicknesses, temperature effects, allowable stresses and deflections, and vibrations are proposed. A detailed design procedure based on the allowable stress design philosophy is presented, and computer programs implementing the design procedure are provided. An alternate design procedure …