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A theoretical treatment has been combined with practical methods to obtain quantitative measurements from the transient responses of electrically coupled cells. Communication via electrical synapses is characterized as a low resistance pathway, whereas membrane response is represented by a resistance in parallel with a capacitance. / The validity and consequences of this model have been investigated using data from identified pairs of electrically coupled neurons in the freshwater snail, Helisoma trivolvis. An automated procedure has been developed to monitor the degree of coupling over extended periods of time and transform these measurements into equivalent electrical units. / The model has been used to: functionally assess the coupled system employing a single micropipette; provide a spatial profile of cell load; monitor induced changes in coupling; examine the role of coupling in controlling the rate of spread of excitation; and evaluate electrical changes which occur within cells during axonal injury and subsequent recovery.

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Overall heat transfer coefficient (U) and fluid to particle heat transfer coefficient (h$ sb{ rm fp}$) in canned liquid/particle mixtures, subjected to end-over-end processing, were experimentally evaluated. A methodology was developed to measure heat transfer coefficients, while allowing the movement of the particle inside the can, by attaching it to a flexible fine wire thermocouple. Heat transfer coefficients were evaluated under two conditions: (1) with a single particle in the can, (2) with multiple particles in the can. / In the single particle experiments, a spherical particle was used to evaluate the influence of system parameters and product parameters on associated U and h$ sb{ rm fp}$. Increasing values of all four system variables improved the heat transfer coefficients. The effects of rotational speed and headspace were most significant. The particle density had no significant effect, but liquid viscosity and rotational speed had significant effects on U. The h$ sb{ rm fp}$ values were influenced by rotational speed, liquid viscosity and particle density, with particle density most significant. / With multiple particles (Nylon) in cans, the associated convective heat transfer coefficients (U and h$ sb{ rm fp}$) were evaluated. Heat transfer coefficients increased with decreasing particle diameter, increasing particle concentration and increasing sphericity. / Flow visualization studies were carried out. With a single particle, liquid viscosity, particle density and rotational speed influenced particle motion. With multiple particles, motion/mixing was influenced by particle concentration, size, and shape, liquid viscosity and rotational speed. / Dimensionless correlations were developed for the predictive modeling of convective heat transfer coefficients. For U with a single particle, Nusselt number (Nu) was correlated to Reynolds number (Re), Prandtl number (Pr) and relative can headspace while with multiple particles, Re, Pr, ratio of particle to liquid concentration, relative particle diameter and particle sphericity were found to be significant. For h$ sb{ rm fp}$ with a single particle in the can, three different correlations, one each for a sphere, a cylinder and a cube were developed and the Nu was correlated to Re, Pr, density simplex, relative can headspace and the ratio of the sum of the diameter of rotation and diameter of the can to the can diameter. With multiple particles Nu was correlated to Re or Peclet number, ratio of particle to liquid thermal conductivity, particle to liquid concentration and particle sphericity. / A multi-layer artificial neural network (ANN) was used to model heat transfer parameters under conduction and convection heating conditions. The network was found to predict optimal sterilization temperatures with an accuracy of $ pm$0.5$ sp circ$C, and other responses such as process time and integrated heating time for quality attribute with less than 5% associated errors. Multi-layer neural network models were trained based on the experimental values of U and h$ sb{ rm fp}$, was obtained. The trained network was found to predict U and h$ sb{ rm fp}$ with less than 3% and 5% errors, respectively. The neural network models were more accurate than the dimensionless number models, for predicting U and h$ sb{ rm fp}$. (Abstract shortened by UMI.)

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A study of heat transfer to tubes in the freeboard region of a fluidized bed was conducted in a column of cross section 0.254 m x 0.432 m and height 3.00 m. The operating variables covered included superficial gas velocity (up to 1.7 m/s), average particle diameter (102, 470, and 890 (mu)m), height of the instrumented tube above the expanded bed surface (up to 0.6 m), horizontal tube spacing, position of tube within the tube bundle, and number of tubes. Silica sand particles were fluidized by air in all experimental runs. An instrumented oil-cooled tube of outer diameter 25.4 mm was used to collect heat transfer data. / Heat transfer coefficients to tubes in the freeboard were found to be significantly influenced by the superficial gas velocity, average particle diameter, and height of the tube above the expanded bed surface. The heat transfer coefficient increased with increasing superficial gas velocity and decreasing distance between the tube and the bed surface due to increased impingement of particles on the tube. The heat transfer coefficient for a tube in the freeboard was found to increase with decreasing particle size as for immersed tubes. The effects of horizontal tube spacing and single tube versus bundle were found to be small, less than 20%, over the range of experimental conditions investigated. / Values of heat transfer coefficients for a tube in the splash zone, in the immediate vicinity of the expanded bed, are nearly as favourable as for immersed tubes. The high rates of heat transfer are associated with impingement of particles on the heat transfer tube. / The experimental results are in qualitative agreement with the few data available in the literature. The present experimental data were correlated in a form suitable for design purposes. The correlation approaches limits at low and high heights above the expanded bed surface. At the bed surface, heat transfer coefficients correspond to in-bed values. Heat transfer coefficients for tubes far removed from the bed surface correspond to dilute phase suspension or to air alone in cross flow, depending on particle size. The correlation fits the data obtained in this work to within (+OR-) 12%. / Entrainment rates for the finest silica sand particles were measured with and without tubes in the freeboard. Under conditions of the present experimental work, entrainment rates were affected very little by the presence of tubes in the freeboard. The entrainment rates were compared with entrainment correlations available in the literature. There were substantial differences between data and almost all of the correlations. Fair agreement was obtained with the Zenz and Weil correlation for saturation carrying capacity. / Hydrodynamics of bed and particles motion around tubes were also investigated visually, photographically and by means of pressure profiles. The information obtained was helpful in explaining the heat transfer results.

In this thesis, the problem of calculating power transmission line induced or radiated electromagnetic fíelds is studied by decomposing the line into a large number of snall segments, k¡own as Hertzian dipoles. Since the presence of lossy ground makes the electromagnetic fìeld distribution very different from that of the same dipole over perfectly conducting ground, different approaches should be followed for the lossy and lossless ground assumptions. The contribution of each dipole on the total electric and magnetic field is calculated using three analytical techniques. Two of these methods are frequency-domain solutions for the problem of dipole radiation above lossy ground, while the third method is a time-domain exact solution for the same problem based on the assumption of perfectly conducting ground. The theoretical background and extent of validity of each technique are reviewed in this thesis. Tlie results derived by applying each method are compared with those obtained using a commercial software package. The time-domain solution for the problem of power transmission line electromagnetic fields is obtained using Fourier and inverse Fourier transforms, rvhich enables us to obtain the electromagnetic waveforms associated with power system transients. The effect of different parameters such as conductivity and relative permittivity of the ground, the line{o-observation point distance, height, and sag of the transmission line is studied. Further, the impact of downscaling of transmission line on different electromagnetic parameters is analyzed, and the appropriate scale factor for each parameter is derived.

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