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1994

Faculty Publications

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Full-Text Articles in Engineering

The Nuts & Bolts Of Cooperative Learning In Engineering, Nikos J. Mourtos Nov 1994

The Nuts & Bolts Of Cooperative Learning In Engineering, Nikos J. Mourtos

Faculty Publications

A great number of engineering students work alone. But in industry, teamwork is required most of the time. Incorporating Cooperative Learning (CL) into an engineering program gives students an opportunity to practice problem solving and communication skills in a "simulated" professional environment. The paper briefly discusses the motivation behind using CL in engineering courses. Then, the essential elements to make CL successful in the classroom are examined and examples of how these elements have been incorporated into engineering courses taught by the author are given. Problems that have been encountered along with possible fixes are also mentioned.

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Ultrasonic Enhancement Of Antibiotic Action On Gram-Negative Bacteria, William G. Pitt, Michael O. Mcbride, Jared K. Lunceford, Randall J. Roper, Richard D. Sagers Nov 1994

Ultrasonic Enhancement Of Antibiotic Action On Gram-Negative Bacteria, William G. Pitt, Michael O. Mcbride, Jared K. Lunceford, Randall J. Roper, Richard D. Sagers

Faculty Publications

The effect of gentamicin upon planktonic cultures of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and Staphylococcus aureus was measured with and without application of 67-kHz ultrasonic stimulation. The ultrasound was applied at levels that had no inhibitory or bactericidal activity against the bacteria. Measurements of the MIC and bactericidal activity of gentamicin against planktonic cultures of P. aeruginosa and E. coli demonstrated that simultaneous application of 67-kHz ultrasound enhanced the effectiveness of the antibiotic. A synergistic effect was observed and bacterial viability was reduced several orders of magnitude when gentamicin concentrations and ultrasonic levels which by themselves did not reduce …

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Characterization Of The Near-Interface Region Of Chemical Vapor Deposited Diamond Films On Silicon By Backscatter Kikuchi Diffraction, Brent L. Adams, K. Kunze, S. Geier, R. Hessmer, M. Schreck, B. Rauschembach, B. Stritzker Oct 1994

Characterization Of The Near-Interface Region Of Chemical Vapor Deposited Diamond Films On Silicon By Backscatter Kikuchi Diffraction, Brent L. Adams, K. Kunze, S. Geier, R. Hessmer, M. Schreck, B. Rauschembach, B. Stritzker

Faculty Publications

The lattice orientations near the interface of chemical vapor deposited diamond films on Si(001) have been studied by orientation imaging microscopy. This technique is based on the automated analysis of electron backscatter Kikuchi diffraction patterns. The electron beam has been scanned in discrete steps over the reverse side of the diamond film after having removed the substrate. The obtained data have allowed us to determine the texture and to visualize quantitatively the orientational arrangement of and among individual diamond crystallites in the near-interface region. A comparison with the orientation of the substrate has proved the existence of epitaxially nucleated grains. …

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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.

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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 …

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Performance Analysis Of Antennas For Hand-Held Transceivers Using Fdtd, Michael A. Jensen, Yahya Rahmat-Samii Aug 1994

Performance Analysis Of Antennas For Hand-Held Transceivers Using Fdtd, Michael A. Jensen, Yahya Rahmat-Samii

Faculty Publications

The design of antennas for hand-held communications devices depends on the implementation of simulation tools that can accurately model general topologies. The paper presents the analysis of small antennas mounted on hand-held transceivers using the finite-difference time-domain (FDTD) method. The key features of the FDTD implementation are discussed, with particular emphasis placed upon modeling of the source region. The technique is used to predict the gain patterns and broadband input impedance behavior of monopole, planar inverted F, and loop antenna elements mounted on the handset. Effects of the conducting handset chassis, the plastic casing around the device, and lumped elements …

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Characterization Of The Near-Interface Region Of Chemical Vapor Deposited Diamond Films On Silicon By Backscatter Kikuchi Diffraction, Brent L. Adams, K. Kunze, S. Geier, R. Hessmer, B. Rauschembach, M. Schreck, B. Stritzker Jul 1994

Characterization Of The Near-Interface Region Of Chemical Vapor Deposited Diamond Films On Silicon By Backscatter Kikuchi Diffraction, Brent L. Adams, K. Kunze, S. Geier, R. Hessmer, B. Rauschembach, M. Schreck, B. Stritzker

Faculty Publications

B.L.A. and K.K. gratefully acknowledge support under a Materials Research Group Award by the National Science Foundation No. DMR-9001278. Also the software support by Th. Bollmeier is greatly appreciated. The lattice orientations near the interface of chemical vapor deposited diamond films on Si(001) have been studied by orientation imaging microscopy. This technique is based on the automated analysis of electron backscatter Kikuchi diffraction patterns. The electron beamhas been scanned in discrete steps over the reverse side of the diamond film after having removed the substrate. The obtained data have allowed us to determine the texture and to visualize quantitatively the …

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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 …

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A Functional Architecture For Automated Highway Traffic Planning, H.-S. Jacob Tsao Jul 1994

A Functional Architecture For Automated Highway Traffic Planning, H.-S. Jacob Tsao

Faculty Publications

In a fully automated Automated Highway System (AHS), the roadside control system and the vehicles themselves are responsible for moving the large number of vehicles safely and efficiently. Therefore, the task of operating an AHS is drastically different from and much more complex than its conventional counterpart. Resulting from a large number of design options, there exist many possible ways to operate an AHS. Each of these possible operating scenarios will support a different set of functions. A crucial task in AHS R&D is to evaluate and compare these potentially large number of different AHS operating scenarios with respect to …

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Defense Industrial Base Policy: Revisited, Michael E. Heberling Jul 1994

Defense Industrial Base Policy: Revisited, Michael E. Heberling

Faculty Publications

In an era of decreasing defense budgets and enemy threats, problems associated with maintaining a healthy defense industrial base have become pronounced. This article discussed defense industrial policy goals and argues that these goals may be collectively unobtainable.

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Inversion Of Light Scattering Measurements For Particle Size And Optical Constants: Theoretical Study, Matthew R. Jones, Bill P. Curry, M. Quinn Brewster, Keng H. Leong Jun 1994

Inversion Of Light Scattering Measurements For Particle Size And Optical Constants: Theoretical Study, Matthew R. Jones, Bill P. Curry, M. Quinn Brewster, Keng H. Leong

Faculty Publications

We invert the Fredholm equation representing the light scattered by a single spherical particle or a distribution of spherical particles to obtain the particle size distribution function and refractive index. We obtain the solution by expanding the distribution function as a linear combination of a set of orthonormal basis functions. The set of orthonormal basis functions is composed of Schmidt-Hilbert eigenfunctions and a set of supplemental basis functions, which have been orthogonalized with respect to the Schmidt-Hilbert eigenfunctions by using the Gram-Schmidt orthogonalization procedure. We use the orthogonality properties of the basis functions and of the eigenvectors of the kernel …

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Inversion Of Light Scattering Measurements For Particle Size And Optical Constants: Experimental Study, Matthew R. Jones, Keng H. Leong, M. Quinn Brewster, Bill P. Curry Jun 1994

Inversion Of Light Scattering Measurements For Particle Size And Optical Constants: Experimental Study, Matthew R. Jones, Keng H. Leong, M. Quinn Brewster, Bill P. Curry

Faculty Publications

Measurements of the light scattered by a sample contain information regarding the physical properties of the sample. Laser light-scattering measurements can be made unobtrusively in environments that are inaccessible to other types of measurements, so laser light-scattering techniques have become an important tool in aerosol research. The primary difficulty associated with using light-scattering techniques to determine aerosol particle properties is inverting the measurements or extracting the desired information from the measurements. In this study we use a 15-channel polar nephelometer to measure the light-scattering patterns of monodisperse polystyrene spheres. The light-scattering measurements are inverted, and the particle size distribution function …

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Demonstration Of A Novel 3-D Autostereoscopic Display, M. W. Jones, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka Jun 1994

Demonstration Of A Novel 3-D Autostereoscopic Display, M. W. Jones, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka

Faculty Publications

We report what we believe is the first static implementation of the partial-pixel architecture, which provides a conceptual framework for the construction of real-time three-dimensional displays that are functionally equivalent to holographic stereograms (i.e., the simultaneous display of a series of stereoscopic images). The device is physically realized as a set of amplitude diffraction gratings on a chrome mask that was fabricated by standard photolithographic techniques. The intended three-dimensional object encoded in the display was strikingly visible on readout with an incoherent illumination source.

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High Resolution Liquid Crystal Phase Grating Formed By Fringing Fields From Interdigitated Electrodes, Gregory P. Nordin, M. Friends, J. M. Jarem, S. T. Kowel, J. H. Kulick, T. Leslie, R. G. Lindquist May 1994

High Resolution Liquid Crystal Phase Grating Formed By Fringing Fields From Interdigitated Electrodes, Gregory P. Nordin, M. Friends, J. M. Jarem, S. T. Kowel, J. H. Kulick, T. Leslie, R. G. Lindquist

Faculty Publications

We report the formation of thin anisotropic phase gratings in a nematic liquid-crystalline film by use of lateral (fringing) electric fields induced by transparent interdigitated electrodes. These gratings yield high diffraction efficiency (>30%) with a strong dependence on the readout beam incidence angle. In addition, the formation of a defect wall is observed that has a significant effect on the diffraction properties of the phase grating.

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Characterization Of Electromagnetically Coupled Superquadric Loop Antennas For Mobile Communications Applications, Michael A. Jensen, Yahya Rahmat-Samii Apr 1994

Characterization Of Electromagnetically Coupled Superquadric Loop Antennas For Mobile Communications Applications, Michael A. Jensen, Yahya Rahmat-Samii

Faculty Publications

Analysis of two mutually coupled loop antennas with arbitrary relative orientation and position and possibly different geometries is presented. The antennas are represented by generalised superquadric curves, which include circular, elliptical, and rectangular loop geometries, and they may be located either in a homogeneous region or next to an infinite ground plane. A Galerkin-type moment method with piecewise sinusoidal subsectional basis and weighting functions is used. Special consideration is given to implement the solution using curved wire segments instead of the commonly employed linear segments to improve computational efficiency. This very general computational tool is used to investigate the behaviour …

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Vegetation Studies Of The Amazon Basin Using Enhanced Resolution Seasat Scatterometer Data, David G. Long, Perry J. Hardin, Peter T. Whiting Mar 1994

Vegetation Studies Of The Amazon Basin Using Enhanced Resolution Seasat Scatterometer Data, David G. Long, Perry J. Hardin, Peter T. Whiting

Faculty Publications

The Seasat-A scatterometer (SASS) was designed to measure the near-surface wind field over the ocean by inferring the wind from measurements of the surface radar backscatter. While backscatter measurements were also made over land, they have been primarily used for the calibration of the instrument. This has been due in part to the low resolution of the scatterometer measurements (nominally 50 km). In a separate paper the present authors introduced a new method for generating enhanced resolution radar measurements of the Earth's surface using spaceborne scatterometry. In the present paper, the method is used with SASS data to study vegetation …

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Capacity Of Automated Highway Systems: Effect Of Platooning And Barriers, H.-S. Jacob Tsao, Randolph Hall, Bruce Hongola Feb 1994

Capacity Of Automated Highway Systems: Effect Of Platooning And Barriers, H.-S. Jacob Tsao, Randolph Hall, Bruce Hongola

Faculty Publications

The concept of Automated Highway Systems (AHS) is based on the belief that an appropriate integration of control and communication technologies placed on the vehicle and on the highway can lead to a large improvement in capacity and safety without requiring a significant amount of additional highway right-of-way. Stemming from this belief are various conceptual scenarios for vehicle/highway automation.An AHS consists of two major components: vehicle/highway automation technology and highway operating strategy. In this paper, we study the capacity of key AHS operating scenarios.

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Electromagnetic Characteristics Of Superquadric Wire Loop Antennas, Michael A. Jensen, Yahya Rahmat-Samii Feb 1994

Electromagnetic Characteristics Of Superquadric Wire Loop Antennas, Michael A. Jensen, Yahya Rahmat-Samii

Faculty Publications

The analysis of antenna configurations in the form of a generalized superquadric loop, which includes circular, elliptical and rectangular loop geometries, is presented in this paper. Use of a Galerkin form of the moment method with piecewise sinusoidal subsectional basis and testing functions provides rapid numerical convergence and accurate representation of the antenna current. A convenient parametric representation for the superquadric curve is developed to allow a subsectional formulation using curved wire segments, rather than the commonly employed piecewise linear segments, to construct the geometry. Both magnetic frill and delta gap source models are implemented to allow a detailed study …

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Epistemic Decision Theory Applied To Multiple-Target Tracking, Wynn C. Stirling, T. K. Moon, S. E. Budge, J. B. Thompson Feb 1994

Epistemic Decision Theory Applied To Multiple-Target Tracking, Wynn C. Stirling, T. K. Moon, S. E. Budge, J. B. Thompson

Faculty Publications

A decision philosophy that seeks the avoidance of error by trading off belief of truth and value of information is applied to the problem of recognizing tracks from multiple targets (MTT). A successful MTT methodology should be robust in that its performance degrades gracefully as the conditions of the collection become less favorable to optimal operation. By stressing the avoidance, rather than the explicit minimization, of error, the authors obtain a decision rule for trajectory-data association that does not require the resolution of all conflicting hypotheses when the database does not contain sufficient information to do so reliably. This rule, …

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A Probabilistic Model For Avcs Longitudinal Collision/Safety Analysis, Jacob Tsao, Randolph Hall Jan 1994

A Probabilistic Model For Avcs Longitudinal Collision/Safety Analysis, Jacob Tsao, Randolph Hall

Faculty Publications

This paper develops a probabilistic model for analyzing longitudinal collision/safety between an abruptly decelerating vehicle and its immediate follower. The input parameters are the length of the gap between the two vehicles, their common speed prior to the failure, the reaction delay of the following vehicle and a bivariate distribution for the two deceleration rates. The output includes the probability of a collision and the probability distribution of the relative speed at collision time We use this model to compare the safety consequences associated with the platooning and “free-agent” longitudinal-separation rules. We also demonstrate that the free-agent rule implemented with …

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Constraints On Initial Ahs Deployment And The Concept Definition Of A Shuttle Service For Ahs Debut, Jacob Tsao Jan 1994

Constraints On Initial Ahs Deployment And The Concept Definition Of A Shuttle Service For Ahs Debut, Jacob Tsao

Faculty Publications

Highway automation and its evolution involve a multitude of systems issues. Particularly important and difficult in defining a deployment sequence is the very first step, i.e. the first user service involving fully automated freeway driving. However, this importance and the difficulty imply that many factors may severely constrain the initial deployment. After discussing the paramount importance of initial AHS deployment, this paper points out major high-level issues and constraints. Any realistic deployment strategy must take into consideration gradual technology maturation, introduction of new driver role and diminishing conventional driver role for automated driving, high cost of early-generation automation-equipped vehicles, gradual …

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Block Qpsk Modulation Codes With Two Levels Of Error Protection, Robert H. Morelos-Zaragoza, Shu Lin Jan 1994

Block Qpsk Modulation Codes With Two Levels Of Error Protection, Robert H. Morelos-Zaragoza, Shu Lin

Faculty Publications

A class of block QPSK modulation codes for unequal error protection (UEP) is presented. These codes are particularly suitable either for broadcast channels or for communication systems where parts of the information messages are more important than others. An example of the latter is coded speech transmission. Not much is known on the application of block UEP codes in combined coding and modulation schemes. We exhibit a method to combine binary linear UEP (LUEP) block codes of even length, using a Gray mapping, with a QPSK signal set to construct efficient block QPSK modulation codes with nonuniform error protection capabilities …

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On A Class Of Optimal Nonbinary Linear Unequal-Error-Protection Codes For Two Sets Of Messages, Robert H. Morelos-Zaragoza, Shu Lin Jan 1994

On A Class Of Optimal Nonbinary Linear Unequal-Error-Protection Codes For Two Sets Of Messages, Robert H. Morelos-Zaragoza, Shu Lin

Faculty Publications

Several authors have addressed the problem of designing good linear unequal error protection (LUEP) codes. However, very little is known about good nonbinary LUEP codes. We present a class of optimal nonbinary LUEP codes for two different sets of messages. By combining t-error-correcting ReedSolomon (RS) codes and shortened nonbinary Hamming codes, we obtain nonbinary LUEP codes that protect one set of messages against any t or fewer symbol errors and the remaining set of messages against any single symbol error. For t ≥ 2, we show that these codes are optimal in the sense of achieving the Hamming lower bound …

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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 …

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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.

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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%.

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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 …

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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 …

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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.

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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.

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