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Faculty Publications

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1998

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Articles 1 - 30 of 47

Full-Text Articles in Engineering

The Evolution Of Probability Functions In An Inelasticly Deforming Two-Phase Medium, Brent L. Adams, H. Garmestani, S. Lin Dec 1998

The Evolution Of Probability Functions In An Inelasticly Deforming Two-Phase Medium, Brent L. Adams, H. Garmestani, S. Lin

Faculty Publications

A formulation is introduced here for the evolution of correlation functions in an inelastically deforming two phase medium. Probability functions play a major role in describing the statistical distribution of different phases in a heterogeneous medium in the development of statistical continuum theory. Proper formulation of statistical continuum model for inelastic deformation requires better understanding of the evolution of the corresponding probability functions. A two point probability function representation is used to approximate the statistical correlation functions. The evolution of these functions requires the information from higher order probability functions, in this case, a three point probability function. A decomposition …

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A Recursive Green's Function Method For Boundary Integral Analysis Of Inhomogeneous Domains, Jim D. Freeze, Michael A. Jensen Dec 1998

A Recursive Green's Function Method For Boundary Integral Analysis Of Inhomogeneous Domains, Jim D. Freeze, Michael A. Jensen

Faculty Publications

The recursive Green's function method (RGFM) for computation of fields scattered by two-dimensional (2-D) inhomogeneous dielectric bodies is presented. The algorithm efficiently constructs the Green's function for the inhomogeneous region by recursively combining known Green's functions from smaller subdomains. The fields on the scatterer surface are then computed using a boundary integral formulation. Proper implementation of the RGFM results in computational and storage complexities which scale as N1.5 and N, respectively, where N is the total number of discrete cells in a domain. Comparisons of results obtained using the RGFM with those computed from moment method and exact solutions show …

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What Can Humor And Advertising Teach Us About Legal Drafting?, Dallin D. Oaks, Jeremy Lewis Dec 1998

What Can Humor And Advertising Teach Us About Legal Drafting?, Dallin D. Oaks, Jeremy Lewis

Faculty Publications

In his book Legal Drafting in a Nutshell, Haggard includes a useful chapter of nearly 50 pages in which he lists various lexical and structural elements and explains how these can lead to ambiguous writing. The kind of inventory approach that he presents is helpful and reveals that ambiguity doesn't just happen but often results from the careless use of identifiable structures or particular words.

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Successive Galerkin Approximation Algorithms For Nonlinear Optimal And Robust Control, Timothy Mclain, Randal W. Beard Nov 1998

Successive Galerkin Approximation Algorithms For Nonlinear Optimal And Robust Control, Timothy Mclain, Randal W. Beard

Faculty Publications

Nonlinear optimal control and nonlinear H infinity control are two of the most significant paradigms in nonlinear systems theory. Unfortunately, these problems require the solution of Hamilton-Jacobi equations, which are extremely difficult to solve in practice. To make matters worse, approximation techniques for these equations are inherently prone to the so-called 'curse of dimensionality'. While there have been many attempts to approximate these equations, solutions resulting in closed-loop control with well-defined stability and robustness have remained elusive. This paper describes a recent breakthrough in approximating the Hamilton-Jacobi-Bellman and Hamilton-Jacobi-Isaacs equations. Successive approximation and Galerkin approximation methods are combined to derive …

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Deriving Of Single Intensive Picosecond Optical Pulses From A High-Power Gain-Switched Laser Diode By Spectral Filtering, S. N. Vainshtein, Grigory Simin, J. T. Kostamovaara Oct 1998

Deriving Of Single Intensive Picosecond Optical Pulses From A High-Power Gain-Switched Laser Diode By Spectral Filtering, S. N. Vainshtein, Grigory Simin, J. T. Kostamovaara

Faculty Publications

Single 25 ps/16 W optical pulses were achieved by spectral filtering from a multiheterostructure gain-switched laser diode with its quasisteady-state modes suppressed by a factor of 103 as compared with the peak power. A significant transient spectrum broadening makes this possible provided that a very high dI/dt rate of the pumping current pulse is used. A simple numerical model is suggested which describes adequately both the spectral and transient features of the observed phenomenon. It follows from the model that single picosecond optical pulses can be obtained from any type of high power semiconductor laser.

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The Role Of Air Cargo In California's Goods Movement, H.-S. Jacob Tsao Sep 1998

The Role Of Air Cargo In California's Goods Movement, H.-S. Jacob Tsao

Faculty Publications

Caltrans began a systematic investigation into the role of air cargo in California’s goods movement, as part of the larger development effort for a statewide goods movement strategy, and funded a research project in 1997 for the Institute of Transportation Studies at U.C. Berkeley to (i) gain a broader understanding of the State’s air cargo industry and the role of air cargo in California’s goods movement, (ii) assess the importance of air cargo to the State’s economy, (iii) begin identification of issues hindering efficient air cargo movement in the State, and (iv) explore possible State roles for resolving the issues. …

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Nonlinear Optimal Control Design Of A Missile Autopilot, Tim Mclain, Randal W. Beard Aug 1998

Nonlinear Optimal Control Design Of A Missile Autopilot, Tim Mclain, Randal W. Beard

Faculty Publications

The application of a new nonlinear optimal control strategy to the design of missile autopilots is presented. The control approach described and demonstrated here is based upon the numerical solution of the Hamilton-Jacobi-Bellman equation by Successive Galerkin Approximation. Using this approach, feedback controllers are computed by an iterative application of a numerical Galerkin-type PDE solver. Simulation results demonstrating the application of this approach to the design of a missile autopilot are presented.

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Evaluation Of Personal Communications Dual-Antenna Handset Diversity Performance, Michael A. Jensen, Joseph S. Colburn, Yahya Rahmat-Samii, Gregory J. Pottie Aug 1998

Evaluation Of Personal Communications Dual-Antenna Handset Diversity Performance, Michael A. Jensen, Joseph S. Colburn, Yahya Rahmat-Samii, Gregory J. Pottie

Faculty Publications

In personal wireless communications systems, multipath propagation has a significant effect on system design and performance. Signal strength fading caused by destructive interference between multiple replicas of the signal of interest arriving at the receiver over different paths often is the limiting factor in system range/fidelity. Antenna diversity is one technique that can be used to help overcome multipath fading. This paper presents a description of experiments, data processing, and results used to evaluate the diversity performance of three candidate dual-antenna handset configurations: two side-mounted planar-inverted F antennas (PIFAs), a back-mounted PIFA with a top-mounted helix, a top-mounted PIFA, and …

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Binary Multilevel Convolutional Codes With Unequal Error Protection Capabilities, Robert H. Morelos-Zaragoza, Hideki Imai Jul 1998

Binary Multilevel Convolutional Codes With Unequal Error Protection Capabilities, Robert H. Morelos-Zaragoza, Hideki Imai

Faculty Publications

Binary multilevel convolutional codes (CCs) with unequal error protection (UEP) capabilities are studied. These codes belong to the class of generalized concatenated (GC) codes. Binary CCs are used as outer codes. Binary linear block codes of short length, and selected subcodes in their two-way subcode partition chain, are used as inner codes. Multistage decodings are presented that use Viterbi decoders operating on trellises with similar structure to that of the constituent binary CCs. Simulation results of example binary two-level CC's are also reported.

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Successive Galerkin Approximations To The Nonlinear Optimal Control Of An Underwater Robotic Vehicle, Timothy Mclain, Randal W. Beard Jul 1998

Successive Galerkin Approximations To The Nonlinear Optimal Control Of An Underwater Robotic Vehicle, Timothy Mclain, Randal W. Beard

Faculty Publications

The application of a new nonlinear optimal control strategy to the station-keeping control of an underwater robotic vehicle is considered. The control approach described and demonstrated here is based upon the numerical approximation of solutions to the Hamilton-Jacobi-Bellman equation. These solutions are computed by an iterative application of Galerkin's method. Preliminary simulation results demonstrating the application of this approach to the control of an underwater vehicle in the horizontal plane are presented.

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Development And Experimental Validation Of An Underwater Manipulator Hydrodynamic Model, Timothy W. Mclain, Stephen M. Rock Jul 1998

Development And Experimental Validation Of An Underwater Manipulator Hydrodynamic Model, Timothy W. Mclain, Stephen M. Rock

Faculty Publications

Hydrodynamic forces can be large and hence have a significant effect on the dynamic performance of underwater manipulation systems. this paper investigates these forces for a cylindrical single-link arm undergoing motions that are characteristics of a robotic manipulator. Based on flow visualization, theoretical analysis, and experimental measurements, a new model is developed that describes these forces. This model differs from previous models in that the drag and added-mass coefficients are state-dependent functions that depend on the distance traveled by the arm. A factor of four improvement in accuracy is demonstrated over standard constant-coefficient models.

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Preparing An Assessment Plan At San Jose State University, Michael Jennings, Thalia Anagnos Jun 1998

Preparing An Assessment Plan At San Jose State University, Michael Jennings, Thalia Anagnos

Faculty Publications

The College of Engineering at San Jose State University is scheduled for an accreditation visit in Fall 1999 and has decided to seek reaccreditation under the ABET 2000 criteria. An assessment implementation project has been active for the past two years within the College; with primary objectives of refining missions for programs, defining program outcome objectives, determining which components to assess, and developing appropriate metrics and methods. Longer term objectives of this project are to establish a continuous quality improvement philosophy in the College and to provide information for the ABET accreditation review.This paper is an evaluation of the status …

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Fuel Equalized Retargeting For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh Jun 1998

Fuel Equalized Retargeting For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh

Faculty Publications

Motivated by NASA's proposed Deep Space 3 interferometer mission, the paper considers the problem of reorienting a constellation of spacecraft such that the total fuel distributed across the constellation is both conserved and expended uniformly. The spacecraft constellation is controlled to reorient as if it were a rigid body. Two approaches to fuel equalization are investigated. The first approach picks a point of rotation a priori that optimizes an objective function that trades off minimum-fuel maneuvers and maneuvers that equalize the fuel. Since the point of rotation is selected a priori and is fixed during the rotation, this approach is …

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A Practical Algorithm For Designing H∞ Control Laws, Timothy Mclain, Randal W. Beard Jun 1998

A Practical Algorithm For Designing H∞ Control Laws, Timothy Mclain, Randal W. Beard

Faculty Publications

We describe an approximation method for the Hamilton-Jacobi-Isaacs (HJI) equation that results in feedback control. The approximation is accomplished via a two-step successive Galerkin approximation scheme. An application of the technique to the control of the forward motion of an underwater vehicle is described.

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Determination Of The Asymmetry Parameter And Scattering Coefficient Of Turbid Media From Spatially Resolved Reflectance Measurments, Matthew R. Jones, Yukio Yamada Mar 1998

Determination Of The Asymmetry Parameter And Scattering Coefficient Of Turbid Media From Spatially Resolved Reflectance Measurments, Matthew R. Jones, Yukio Yamada

Faculty Publications

We present a technique for determining the asymmetry parameter and scattering coefficient of turbid media from spatially resolved reflectance measurements. This technique will contribute to the development of medical applications in which it is necessary to predict the distribution and propagation of light in tissue. Based on Monte Carlo simulations, we derived correlations which relate the reduced scattering coefficient and the asymmetry parameter to the relative reflectance curve. Initial estimates of the optical properties are obtained from these correlations. Final values are obtained by adjusting the optical parameters and repeating the Monte Carlo simulations until the simulated reflectance pattern matches …

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Spatial Resolution Enhancement Of Ssm/I Data, David G. Long, Douglas L. Daum Mar 1998

Spatial Resolution Enhancement Of Ssm/I Data, David G. Long, Douglas L. Daum

Faculty Publications

One of the limitations in using Special Sensor Microwave/Imager (SSM/I) data for land and vegetation studies is the relatively low-spatial resolution. To ameliorate this limitation, resolution-enhancement algorithms can be applied to the data. In this paper, the Backus-Gilbert inversion (BGI) technique and the scatterometer image-reconstruction (SIR) algorithm are investigated as possible methods for creating enhanced resolution images from SSM/I data. The two algorithms are compared via both the simulation and the actual SSM/I data. The algorithms offer similar resolution enhancement, though SIR requires significantly less computation. Sample results over two land regions of South America are presented.

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Understanding Comics: The Invisible Art, Alan D. Manning Mar 1998

Understanding Comics: The Invisible Art, Alan D. Manning

Faculty Publications

INSIGHTS about professional communication may come from odd and unexpected places. McCloud's Understanding Comics (hereafter UC) is a case in point. Despite the juvenile connotations evoked by any discussion of comic books, the theory of visual communication presented in UC arguably rivals the best of contemporary semiotics (that is, the study of how we make meaning out of gestures, words, paragraphs, pictures, and so on).

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Computer Simulations Of Branched Alkanes: The Effect Of Side Chain And Its Position On Rheological Behavior, Richard L. Rowley, Tapani A. Pakkanen, Maija Lahtela, Mikko Linnolahti Feb 1998

Computer Simulations Of Branched Alkanes: The Effect Of Side Chain And Its Position On Rheological Behavior, Richard L. Rowley, Tapani A. Pakkanen, Maija Lahtela, Mikko Linnolahti

Faculty Publications

Nonequilibrium molecular dynamics simulations have been performed on model fluids representing eicosane isomers in order to investigate the effect of branching and side chain position on fluid rheology. A heterogeneous, united-atom model with 20 Lennard-Jones interaction sites located at carbon centers was used to model the fluids. Vibrations and bond rotations were frozen, but torsional rotation was included. It was found that viscosity increases significantly from the n-alkane structure to a branch on carbon 2, but the movement of the branch along the carbon backbone has a smaller increasing than decreasing effect. The size of the group in a branched …

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Derivation Of An Analytical Model To Calculate Junction Depth In Hgcdte Photodiodes, Stacy H. Gleixner, H. G. Robinson, C. R. Helms Feb 1998

Derivation Of An Analytical Model To Calculate Junction Depth In Hgcdte Photodiodes, Stacy H. Gleixner, H. G. Robinson, C. R. Helms

Faculty Publications

Presents an enhanced analytical model to calculate junction depth and Hg interstitial profile during n-on-p junction formation in HgCdTe photodiodes. Detailed information on the enhanced model; Function of the model; Information on HgCdTe; Detailed information on how the model was obtained.

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On Block-Coded Modulation Using Unequal Error Protection Codes Over Rayleigh-Fading Channels, Robert H. Morelos-Zaragoza, Tadao Kasami, Shu Lin, Hideki Imai Jan 1998

On Block-Coded Modulation Using Unequal Error Protection Codes Over Rayleigh-Fading Channels, Robert H. Morelos-Zaragoza, Tadao Kasami, Shu Lin, Hideki Imai

Faculty Publications

This paper considers block-coded 8-phase-shift-keying (PSK) modulations for the unequal error protection (UEP) of information transmitted over Rayleigh-fading channels. Both conventional linear block codes and linear UEP (LUEP) codes are combined with a naturally labeled 8-PSK signal set, using the multilevel construction of Imai and Hirakawa (1977). Computer simulation results are presented showing that, over Rayleigh-fading channels, it is possible to improve the coding gain for the most significant bits with the use of binary LUEP codes as constituent codes, in comparison with using conventional binary linear codes alone.

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Agent Jurisprudence, Michael N. Huhns, Munindar P. Singh Jan 1998

Agent Jurisprudence, Michael N. Huhns, Munindar P. Singh

Faculty Publications

The agent metaphor comes packaged with a number of powerful abstractions. Some of these are psychological, such as beliefs, knowledge, and intentions-abstractions that were traditionally studied in AI. However, there are a number of other abstractions that the agent metaphor brings to the fore. Of these, one has been emphasizing the social abstractions. Close cousins of the social abstractions are the ethical and legal abstractions. These too are being recognized as increasingly important in developing agents that are not only sociable, but also well behaved.

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Measurement Of Thin Liquid Film Drainage Using A Novel High-Speed Impedance Analyzer, K. O. Hool, R. C. Saunders, Harry J. Ploehn Jan 1998

Measurement Of Thin Liquid Film Drainage Using A Novel High-Speed Impedance Analyzer, K. O. Hool, R. C. Saunders, Harry J. Ploehn

Faculty Publications

This work describes the design and implementation of a new instrument, called the thin film impedance analyzer, which measures the rate of drainage of thin oil films. The instrument forms an oil film by elevating a planar oil–water interface into a water drop hanging from a stainless steel capillary tube immersed in the oil. The instrument measures the magnitude of the impedance of the matter between the capillary tube and a screen electrode immersed in the lower water phase. Under appropriate conditions, the capacitance of the oil film dominates the impedance. The instrument records the increase in the magnitude of …

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Proton Diffusion In Nickel Hydroxide: Prediction Of Active Material Utilization, Sathya Motupally, Christopher C. Streinz, John W. Weidner Jan 1998

Proton Diffusion In Nickel Hydroxide: Prediction Of Active Material Utilization, Sathya Motupally, Christopher C. Streinz, John W. Weidner

Faculty Publications

Galvanostatic charge and discharge experiments reveal that the active material in nickel electrodes cannot be fully accessed at high currents or for thick films. It has been proposed that the utilization of the active material is controlled by the diffusion rate of protons through the film. This hypothesis is supported by the good agreement between mathematical simulations of material utilization and experimental data over a range of charge and discharge currents and film thicknesses. Furthermore, the fraction of material utilized is larger on charge than on discharge. The asymmetry on charge and discharge is due to a diffusion coefficient that …

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Studies On Electroless Cobalt Coatings For Microencapsulation Of Hydrogen Storage Alloys, Bala S. Haran, Branko N. Popov, Ralph E. White Jan 1998

Studies On Electroless Cobalt Coatings For Microencapsulation Of Hydrogen Storage Alloys, Bala S. Haran, Branko N. Popov, Ralph E. White

Faculty Publications

LaNi4.27Sn0.24 alloy was microencapsulated with cobalt by electroless deposition from an alkaline hypophosphite bath. Discharge curves of the encapsulated alloy indicate an additional contribution to the capacity arising from the cobalt on the surface. Studies on cobalt thin films reveal the presence of adsorbed hydrogen in cobalt. The amount of hydrogen adsorbed was observed to increase with time of cathodic polarization and to reach a maximum. Polarization techniques have been used to characterize the cobalt-plated alloy as a function of state of charge. The equilibrium potential of the microencapsulated electrode at low hydrogen concentration is determined by …

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Nitrogen Transformations In Coal During Pyrolysis, Simon R. Kelemen, Martin L. Gorbaty, P J. Kwiatek, Thomas H. Fletcher, Mathew Watt, Mark S. Solum, Ronald J. Pugmire Jan 1998

Nitrogen Transformations In Coal During Pyrolysis, Simon R. Kelemen, Martin L. Gorbaty, P J. Kwiatek, Thomas H. Fletcher, Mathew Watt, Mark S. Solum, Ronald J. Pugmire

Faculty Publications

X-ray photoelectron spectroscopy (XPS) was used to identify and quantify the changes in organically bound nitrogen forms present in the tars and chars of coals after pyrolysis. For fresh coal, pyrrolic nitrogen is the most abundant form of organically bound nitrogen, followed by pyridinic, quaternary, and amino types. Some of the quaternary nitrogen species initially present in coal are lost upon mild pyrolysis, prior to hydrocarbon devolatilization. These quaternary species are attributed to pyridinic or basic nitrogen species associated with hydroxyl groups from carboxylic acids or phenols. A portion of the quaternary nitrogen species is lost at the very earliest …

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Evaluation Of Ch4/Nox Reduced Mechanisms Used For Modeling Lean Premixed Turbulent Combustion Of Natural Gas, Hemant P. Mallampalli, Thomas H. Fletcher, J Y. Chen Jan 1998

Evaluation Of Ch4/Nox Reduced Mechanisms Used For Modeling Lean Premixed Turbulent Combustion Of Natural Gas, Hemant P. Mallampalli, Thomas H. Fletcher, J Y. Chen

Faculty Publications

This study has identified useful reduced kinetic schemes that can be used in comprehensive multi-dimensional gas-turbine combustor models. Reduced mechanisms lessen computational cost and possess the capability to accurately predict the overall flame structure, including gas temperatures and key intermediate species such as CH4, CO and NOx. In this study, four-new global mechanisms with 5, 6, 7, and 9 steps based on the full GRI 2.11 mechanism, were developed and evaluated for their potential to model natural-gas chemistry (including NOx chemistry) in gas turbine combustors. These new reduced mechanisms were optimized to model the high …

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Modeling Soot Derived From Pulverized Coal, Alexander L. Brown, Thomas H. Fletcher Jan 1998

Modeling Soot Derived From Pulverized Coal, Alexander L. Brown, Thomas H. Fletcher

Faculty Publications

A semiempirical model has been developed for predicting coal-derived soot. The main feature of the model is a transport equation for soot mass fraction. Tar prediction options include either an empirical or a transport equation approach, which directly impacts the source term for soot formation. Also, the number of soot particles per unit mass of gas may be calculated using either a transport equation or an assumed average. Kinetics are based on Arrhenius rates taken from published measurements. Radiative properties are calculated as a function of averaged optical constants, predicted gas temperatures, predicted gas densities, and the soot mass fractions. …

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Sr‐ And Ni‐Doped Lacoo3 And Lafeo3 Perovskites: New Cathode Materials For Solid‐Oxide Fuel Cells, Kevin Huang, Hee Y. Lee, John B. Goodenough Jan 1998

Sr‐ And Ni‐Doped Lacoo3 And Lafeo3 Perovskites: New Cathode Materials For Solid‐Oxide Fuel Cells, Kevin Huang, Hee Y. Lee, John B. Goodenough

Faculty Publications

An improved cathode material for a solid‐oxide fuel cell would be a mixed electronic and oxide‐ion conductor with a good catalytic activity for oxygen reduction at an operating temperature T op ≥ 700°C and a thermal expansion matched to that of the electrolyte and interconnect. We report on the properties of Sr‐ and Ni‐doped LaCoO3 and LaFeO3 perovskites that meet these criteria. Single‐phase regions were determined by X‐ray diffraction, and thermogravimetric analysis measurements were used to obtain the temperatures above which oxygen loss, and hence oxide‐ion conductivity, occurs. The conductivity and Seebeck measurements indicate the coexistence of both …

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Macros By Example In A Graphical Uims, Dan R. Olsen Jr., Jonathan Turner, Stephen Bart Wood, John R. Dance Jan 1998

Macros By Example In A Graphical Uims, Dan R. Olsen Jr., Jonathan Turner, Stephen Bart Wood, John R. Dance

Faculty Publications

A macro facility that allows end users to extend interactive graphical applications is presented as part of a user-interface management system (UIMS). Such macros are expressed by example; that is, the end user programs the macro in the application's generated user interface. Problems with macros-by-example in graphical applications are explored, and requirements to accommodate such a facility are defined for the UIMS dialogue model. Existing UIMS models are reviewed relative to these requirements, and the unique facilities of the MIKE (menu interaction kontrol environment) semantics-based model are presented. The implementation of the macro-by-example system is discussed, as well as the …

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Cognitive Agents, Michael N. Huhns, Munindar P. Singh Jan 1998

Cognitive Agents, Michael N. Huhns, Munindar P. Singh

Faculty Publications

Several researchers have proposed using cognitive concepts as a semantic basis for agent communications (M.N. Huhns and M.P. Singh, 1997). One of the leading candidates for such a semantics is based on Arcol, the communication language used within Artimis. Interestingly, this application (not only of Arcol, but also in general) appears extremely misguided. The intentional concepts are well suited to designing agents, but are not suited to giving a basis to a public, standardizable view of communication. A challenge for using the cognitive concepts is that although they are natural in several respects and can guide implementations, full blown implementations …

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