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Articles 1 - 11 of 11

Full-Text Articles in Engineering

Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal Oct 1994

Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.


Automating Workflows For Service Provisioning: Integrating Ai And Database Technologies, Munindar P. Singh, Michael N. Huhns Oct 1994

Automating Workflows For Service Provisioning: Integrating Ai And Database Technologies, Munindar P. Singh, Michael N. Huhns

Faculty Publications

Workflows are the structured activities that take place in information systems in typical business environments. These activities frequently involve several database systems, user interfaces, and application programs. Traditional database systems do not support workflows to any reasonable extent: usually human beings must intervene to ensure their proper execution. We have developed an architecture based on AI technology that automatically manages workflows. This architecture, which executes on top of a distributed computing environment, has been applied to automating service provisioning workflows; an implementation that operates on one such workflow has been developed. This work advances the Carnot Project’s goal of developing …


The Asymptotic Structure Of Transient Elastodynamic Fields At The Tip Of A Stationary Crack, Xiaomin Deng Jul 1994

The Asymptotic Structure Of Transient Elastodynamic Fields At The Tip Of A Stationary Crack, Xiaomin Deng

Faculty Publications

The asymptotic structure of the transient elastodynamic near-tip fields around a stationary crack is investigated for all three fracture modes. The transient fields are obtained as the sum of their quasi-static counterparts and corresponding transient correction terms, in terms of variable-separable expansions. By allowing the coefficients of terms in the quasi-static expansion to deviate from their quasi-static restrictions, the correction terms are shown to be the particular solutions of a set of first order (for mixed mode I and II) or second order (for mode III) ordinary differential equations with constant coefficients and non-homogeneous terms involving only sine and cosine …


Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu Jan 1994

Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu

Faculty Publications

A ressessment of existing theories for calculating the strength of random and quasi-random fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common …


Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu Jan 1994

Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu

Faculty Publications

No abstract provided.


Use Of Underpotential Deposition Of Zinc To Mitigate Hydrogen Absorption Into Monel K500, G. Zheng, Branko N. Popov, Ralph E. White Jan 1994

Use Of Underpotential Deposition Of Zinc To Mitigate Hydrogen Absorption Into Monel K500, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

Polarization experiments and a potentiostatic pulse technique have been used to show that a monolayer coverage of zinc effectively inhibits the absorption of hydrogen into Monel K500. By depositing a monolayer of zinc on Monel K500, the hydrogen evolution reaction and hydrogen ingress flux rate were reduced by 60%.


Effect Of Proton Diffusion, Electron Conductivity, And Charge-Transfer Resistance On Nickel Hydroxide Discharge Curves, John W. Weidner, Paul Timmerman Jan 1994

Effect Of Proton Diffusion, Electron Conductivity, And Charge-Transfer Resistance On Nickel Hydroxide Discharge Curves, John W. Weidner, Paul Timmerman

Faculty Publications

Constant-current discharge curves for the nickel hydroxide electrode are simulated assuming resistances due to diffusion of protons and conduction of electrons through the nickel hydroxide film, and charge-transfer resistance at the film/electrolyte interface contribute to the polarization losses of the electrode. Good qualitative agreement is observed between the model predictions and experimental discharge curves. The results suggest that polarization losses due to diffusional limitations of protons is a critical factor in determining the characteristics of the discharge curve. Ohmic resistance has a significant effect on the discharge curves at the end of discharge, and charge-transfer resistance is a minor contributor …


Theoretical Analysis Of The Discharge Performance Of A Niooh/H2 Cell, Z. Mao, P. De Vidts, Ralph E. White, John Newman Jan 1994

Theoretical Analysis Of The Discharge Performance Of A Niooh/H2 Cell, Z. Mao, P. De Vidts, Ralph E. White, John Newman

Faculty Publications

A mathematical model is presented for the discharge of a NiOOH/H2 cell. This model includes diffusion and migration in the electrolyte phase as well as proton diffusion and ohmic drop across the solid active material in the porous nickelelectrode. A theoretical analysis of the cell performance is presented for different design parameters using this model. It is predicted that proton diffusion in the solid active material is the main factor in limiting the cell voltage and the utilizationof the active material. It is also predicted that use of a thick nickel electrode is an effective method for increasing electrode …


A Finite-Difference Method For Pseudo-Two-Dimensional Boundary Value Problems, Z. Mao, Ralph E. White Jan 1994

A Finite-Difference Method For Pseudo-Two-Dimensional Boundary Value Problems, Z. Mao, Ralph E. White

Faculty Publications

A finite-difference method is presented for solving pseudo-two-dimensional boundary-value problems. The sparse and nearly block tridiagonal properties of the matrices generated by using the finite-difference method for problems of this type are fully utilized and maintained, which yields a method that is highly efficient in the use of storage space and computation. An example shows that the central process unit time required by the method is significantly less than that required by an alternative method.


Thermal Characteristics Of A Nickel-Hydrogen Battery, Junbom Kim, T. V. Nguyen, Ralph E. White Jan 1994

Thermal Characteristics Of A Nickel-Hydrogen Battery, Junbom Kim, T. V. Nguyen, Ralph E. White

Faculty Publications

The maximum allowable temperature difference inside a nickel-hydrogen battery to avoid water relocation was calculated by using a graphical method together with a vapor pressure vs. temperature correlation equation for water vapor over potassium hydroxide solution. An equation was developed for this maximum allowable temperature difference for vessel-wall temperatures from 0 to 30°C and potassium hydroxide concentrations from 20 to 32%. A heat-generation equation for the nickel-hydrogen battery was used to investigate the effect of the location of heat generation on the maximum temperature in the cell and the temperature distribution in the cell.


The Role Of Thallium As A Hydrogen Entry Promoter On Cathodically Polarized Hy-130 Steel, G. Zheng, Branko N. Popov, Ralph E. White Jan 1994

The Role Of Thallium As A Hydrogen Entry Promoter On Cathodically Polarized Hy-130 Steel, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

Hydrogen permeation experiments were carried out to investigate the effect of thallium on hydrogen entry into HY-130steel. These experiments show that the presence of thallium ions in an electrolyte drastically increase the hydrogen entry rate. The hydrogen entry efficiency and hydrogen surface coverage were increased by a factor of 10 and 6, respectively. In order to fit the permeation experimental data, the Iyer-Pickering-Zamanzadeh (I-P-Z) hydrogen permeation model was modified by including a mass-transfer term in the discharging equation. The relationship between hydrogen permeation and the hydrogen evolution reaction were investigated and new relationships were obtained.