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University of South Carolina

1993

Articles 1 - 13 of 13

Full-Text Articles in Engineering

On Stationary And Moving Interface Cracks With Frictionless Contact In Anisotropic Bimaterials, Xiaomin Deng Dec 1993

On Stationary And Moving Interface Cracks With Frictionless Contact In Anisotropic Bimaterials, Xiaomin Deng

Faculty Publications

The asymptotic structure of near-tip fields around stationary and steadily growing interface cracks, with frictionless crack surface contact, and in anisotropic bimaterials, is analysed with the method of analytic continuation, and a complete representation of the asymptotic fields is obtained in terms of arbitrary entire functions. It is shown that when the symmetry, if any, and orientation of the anisotropic bimaterial is such that the in-plane and out-of-plane deformations can be separated from each other, the in-plane crack-tip fields will have a non-oscillatory, inverse-squared-root type stress singularity, with angular variations clearly resembling those for a classical mode II problem when …

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Declarative Representations Of Multiagent Systems, Munindar P. Singh, Michael N. Huhns, Larry M. Stevens Oct 1993

Declarative Representations Of Multiagent Systems, Munindar P. Singh, Michael N. Huhns, Larry M. Stevens

Faculty Publications

This paper explores the specification and semantics of multiagent problem-solving systems, focusing on the representations that agents have of each other. It provides a declarative representation for such systems. Several procedural solutions to a well-known test-bed problem are considered, and the requirements they impose on different agents are identified. A study of these requirements yields a representational scheme based on temporal logic for specifying the acting, perceiving, communicating, and reasoning abilities of computational agents. A formal semantics is provided for this scheme. The resulting representation is highly declarative, and useful for describing systems of agents solving problems reactively.

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Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal Jul 1993

Low‐Cost Technique For Preparing N‐Sb2S3/P‐Si Heterojunction Solar Cells, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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Three Points Of Great Height On Elliptic Curves, Andrew Bremner, Duncan A. Buell Jul 1993

Three Points Of Great Height On Elliptic Curves, Andrew Bremner, Duncan A. Buell

Faculty Publications

We give three elliptic curves whose generators have great height, demonstrating along the way a moderately efficient method for finding such points.

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Mathematical Modeling Of The Formation Of Calcareous Deposits On Cathodically Protected Steel In Seawater, J. F. Yan, T. V. Nguyen, Ralph E. White, R. B. Griffin Jan 1993

Mathematical Modeling Of The Formation Of Calcareous Deposits On Cathodically Protected Steel In Seawater, J. F. Yan, T. V. Nguyen, Ralph E. White, R. B. Griffin

Faculty Publications

A first principle mathematical model of the formation of calcareous deposits on a cathodically protected steel rotatingdisk electrode in seawater is presented. The model includes equations which transport phenomena, electrochemical reactions,precipitation reactions, and a homogeneous reaction involved in the formation of calcareous deposits on an electrodesurface. Predicted concentration profiles show that a high concentration of OH– ions on the electrode surface leads to the formation of calcareous deposits. The calcareous deposits contain mostly CaCO3, but the initial deposits are predicted to contain more Mg(OH)2 than CaCO3. The predicted calcareous deposits on the electrode surface …

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Parametric Studies Of The Formation Of Calcareous Deposits On Cathodically Protected Steel In Seawater, J. F. Yan, Ralph E. White, R. B. Griffin Jan 1993

Parametric Studies Of The Formation Of Calcareous Deposits On Cathodically Protected Steel In Seawater, J. F. Yan, Ralph E. White, R. B. Griffin

Faculty Publications

A first principle mathematical model has been used to study the effects of ocean environment and cathodic protection on the formation of calcareous deposits and their ability to reduce the cathodic current density. These parameters include applied potential, rotation speed, temperature, salinity, and depth. The results showed the applied potential strongly influences the formation of calcareous deposits and their ability to reduce the cathodic current density. Among the environmental factors, rotation speed has the most influence on the cathodic current density. Salinity slightly influences the cathodic current density over the range of interest. Temperature is much more influential than salinity …

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Thermal Analysis Of Spirally Wound Li/Bcx And Li/Socl2 Cells, E. E. Kalu, Ralph E. White Jan 1993

Thermal Analysis Of Spirally Wound Li/Bcx And Li/Socl2 Cells, E. E. Kalu, Ralph E. White

Faculty Publications

A thermal analysis of Li/BCX and high rate Li/SOCl2 cells is presented. The thermal model developed was used to study the effect of ambient temperature of discharge (0–40°C) on Li/BCX cells discharged at the same rate. The model predictions show that ambient temperature of discharge was critical in thermal management of the cell. For forced convection cooled cells, the model predicted that ambient temperature near room temperature (25°C) was required to achieve the lowest maximum temperature rise in the cell. Inclusion of the effects of reaction products to the model predictions showed that a constant composition assumption may be …

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Galvanostatic Pulse And Pulse Reverse Plating Of Nickel-Iron Alloys From Electrolytes Containing Organic Compounds On A Rotating Disk Electrode, Branko N. Popov, Ken-Ming Yin, Ralph E. White Jan 1993

Galvanostatic Pulse And Pulse Reverse Plating Of Nickel-Iron Alloys From Electrolytes Containing Organic Compounds On A Rotating Disk Electrode, Branko N. Popov, Ken-Ming Yin, Ralph E. White

Faculty Publications

Linear sweep voltammetry, galvanostatic pulse, and pulse reverse techniques were used to study the plating of nickel-iron alloys in the presence of organic additives. The effects of pulse current densities, ip, reverse current densities, ir, rotation speed of disk electrode, and the presence of organic additives on deposition of nickel-iron alloys are evaluated. The observed phenomena can be explained by the concentration depletion of reactants (or products), and the surface coverage of the additives on the electrode. A new formulation of the plating bath is defined.

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Impedance Analysis For Oxygen Reduction In A Lithium Carbonate Melt: Effects Of Partial Pressure Of Carbon Dioxide And Temperature, Bhasker B. Dave, Ralph E. White, Supramaniam Srinivasan, A. John Appleby Jan 1993

Impedance Analysis For Oxygen Reduction In A Lithium Carbonate Melt: Effects Of Partial Pressure Of Carbon Dioxide And Temperature, Bhasker B. Dave, Ralph E. White, Supramaniam Srinivasan, A. John Appleby

Faculty Publications

Effects of partial pressure of carbon dioxide and temperature on oxygen reduction kinetics on a gold electrode in a lithium carbonate melt were examined using electrochemical impedance spectroscopic (EIS) and linear sweep voltammetric techniques. The impedance spectra were analyzed by a complex nonlinear least squares method, using the Randles-Ershler equivalent circuit model, to determine the electrode-kinetic and the mass-transfer parameters such as the charge-transfer resistance and the Warburg coefficient. The cyclic voltammetric measurements indicated that the oxygen reduction process in lithium carbonate melt is "reversible" up to 200 mV/s. The product DC0 determined by cyclic voltammetry agreed well …

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A Water And Heat Management Model For Proton-Exchange-Membrane Fuel Cells, Trung V. Nguyen, Ralph E. White Jan 1993

A Water And Heat Management Model For Proton-Exchange-Membrane Fuel Cells, Trung V. Nguyen, Ralph E. White

Faculty Publications

Proper water and heat management are essential for obtaining high-power-density performance at high energy efficiency for proton-exchange-membrane fuel cells. A water and heat management model was developed and used to investigate the effectiveness of various humidification designs. The model accounts for water transport across the membrane by electro-osmosis and diffusion, heat transfer from the solid phase to the gas phase and latent heat associated with water evaporation and condensation in the flow channels. Results from the model showed that at high current densities (> 1 A/cm2) ohmic loss in the membrane accounts for a large fraction of the …

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Surface Treatment For Mitigation Of Hydrogen Absorption And Penetration Into Aisi 4340 Steel, G. Zheng, Branko N. Popov, Ralph E. White Jan 1993

Surface Treatment For Mitigation Of Hydrogen Absorption And Penetration Into Aisi 4340 Steel, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The effectiveness of underpotential deposition of Pb onto a membrane made of AISI 4340 steel on the reduction of the hydrogen evolution reaction on the membrane and the degree of hydrogen ingress into the membrane was determined. In the presence of a monolayer coverage of Pb on the membrane surface, the hydrogen evolution currents were reduced by a factor of two compared with the values obtained on bare steel, and the steady-state hydrogen permeation flux through the steel membranes was reduced by 71%.

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Impedance Spectroscopy As A Nondestructive Health Interrogation Tool For Lithium-Bcx Cells, Branko N. Popov, W. Zhang, E. C. Darcy, Ralph E. White Jan 1993

Impedance Spectroscopy As A Nondestructive Health Interrogation Tool For Lithium-Bcx Cells, Branko N. Popov, W. Zhang, E. C. Darcy, Ralph E. White

Faculty Publications

The objective of this investigation was to study the growth of thick passivating layers on the Li anode in Li/BCX(Li/SOCl2 + BrCl) cells which were stored for a period of 3 years. Impedance spectroscopy and equivalent circuit models were used to determine characterizing parameters for these cells. The equivalent circuit used for virgin cells includes a faradic contribution and diffusion of the electroactive species. The equivalent circuit for batteries stored 1 or 2 years includes the impedance of a metal/passive film interface, the resistance of the film, and the impedance of the passivating film/electrolyte interface. The equivalent circuit used …

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Using Electrochemical Impedance Spectroscopy As A Tool For Organic Coating Solute Saturation Monitoring, Branko N. Popov, Mohammed A. Alwohaibi, Ralph E. White Jan 1993

Using Electrochemical Impedance Spectroscopy As A Tool For Organic Coating Solute Saturation Monitoring, Branko N. Popov, Mohammed A. Alwohaibi, Ralph E. White

Faculty Publications

Electrochemical impedance spectroscopy (EIS) has been used to study the solute uptake for epoxy/phenolic (E/p) andepoxy/amine (E/a) thick-coated mild steel samples immersed for 160 days in 3.5 weight percent NaCl solution exposed to air. Samples with thicknesses of approximately 200 µm with an exposed surface area of 22.6 cm2 were used to follow solute saturation of the organic coating. Good agreement was obtained between the calculated and measured coating capacitance when, according to the diffusion equation, the coating capacitance was plotted against exposure time.

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