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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
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 …
A Recursive Green's Function Method For Boundary Integral Analysis Of Inhomogeneous Domains, Jim D. Freeze, Michael A. Jensen
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 …
What Can Humor And Advertising Teach Us About Legal Drafting?, Dallin D. Oaks, Jeremy Lewis
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.
Successive Galerkin Approximation Algorithms For Nonlinear Optimal And Robust Control, Timothy Mclain, Randal W. Beard
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 …
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
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.
The Role Of Air Cargo In California's Goods Movement, H.-S. Jacob Tsao
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. …
Nonlinear Optimal Control Design Of A Missile Autopilot, Tim Mclain, Randal W. Beard
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.
Evaluation Of Personal Communications Dual-Antenna Handset Diversity Performance, Michael A. Jensen, Joseph S. Colburn, Yahya Rahmat-Samii, Gregory J. Pottie
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 …
Development And Experimental Validation Of An Underwater Manipulator Hydrodynamic Model, Timothy W. Mclain, Stephen M. Rock
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.
Binary Multilevel Convolutional Codes With Unequal Error Protection Capabilities, Robert H. Morelos-Zaragoza, Hideki Imai
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.
Successive Galerkin Approximations To The Nonlinear Optimal Control Of An Underwater Robotic Vehicle, Timothy Mclain, Randal W. Beard
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.
Preparing An Assessment Plan At San Jose State University, Michael Jennings, Thalia Anagnos
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 …
A Practical Algorithm For Designing H∞ Control Laws, Timothy Mclain, Randal W. Beard
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.
Fuel Equalized Retargeting For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh
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 …
Determination Of The Asymmetry Parameter And Scattering Coefficient Of Turbid Media From Spatially Resolved Reflectance Measurments, Matthew R. Jones, Yukio Yamada
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 …
Spatial Resolution Enhancement Of Ssm/I Data, David G. Long, Douglas L. Daum
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.
Understanding Comics: The Invisible Art, Alan D. Manning
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).
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
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 …
Derivation Of An Analytical Model To Calculate Junction Depth In Hgcdte Photodiodes, Stacy H. Gleixner, H. G. Robinson, C. R. Helms
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.
On Block-Coded Modulation Using Unequal Error Protection Codes Over Rayleigh-Fading Channels, Robert H. Morelos-Zaragoza, Tadao Kasami, Shu Lin, Hideki Imai
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.
Sr‐ And Ni‐Doped Lacoo3 And Lafeo3 Perovskites: New Cathode Materials For Solid‐Oxide Fuel Cells, Kevin Huang, Hee Y. Lee, John B. Goodenough
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 …
Agent Jurisprudence, Michael N. Huhns, Munindar P. Singh
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.
The Role Of Oxygen At The Second Discharge Plateau Of Nickel Hydroxide, Sathya Motupally, Mukul Jain, Venkat Srinivasan, John W. Weidner
The Role Of Oxygen At The Second Discharge Plateau Of Nickel Hydroxide, Sathya Motupally, Mukul Jain, Venkat Srinivasan, John W. Weidner
Faculty Publications
It was shown that the appearance of a secondary discharge plateau approximately 400 mV below the primary plateau can result from the reduction of oxygen. During the galvanostatic discharge of planar nickel-hydroxide films at room temperature and in 3 weight percent KOH solutions, the second discharge plateau was observed only in the presence of dissolved oxygen in the electrolyte. When the solution was deoxygenated, no residual capacity could be extracted from the films even at low discharge rates or from overcharged films. In addition, the duration of the second plateau is inversely proportional to the square of the discharge current, …
Studies On Electroless Cobalt Coatings For Microencapsulation Of Hydrogen Storage Alloys, Bala S. Haran, Branko N. Popov, Ralph E. White
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 …
Theoretical Analysis Of Metal Hydride Electrodes: Studies On Equilibrium Potential And Exchange Current Density, Bala S. Haran, Branko N. Popov, Ralph E. White
Theoretical Analysis Of Metal Hydride Electrodes: Studies On Equilibrium Potential And Exchange Current Density, Bala S. Haran, Branko N. Popov, Ralph E. White
Faculty Publications
A theoretical model for the metal hydride electrode has been developed assuming that hydrogen diffusion in the alloy and charge-transfer at the surface control the discharge process. Theoretical equations for the dependence of equilibrium potential and exchange current density on the surface hydrogen concentration have been derived. These parameters have been used to correlate experimental data with the theoretical electrode discharge model. Analysis of both the experimental and theoretical discharge curves reveals a potential plateau determined by the magnitude of the interactions between the hydrogen in the alloy and the unhydrided metal. Neglecting these hydrogen-metal site interactions results in simulations …
A Nonisothermal Nickel‐Hydrogen Cell Model, Pauline De Vidts, Javier Delgado, B. Wu, D. M. See, K. Kosanovich, Ralph E. White
A Nonisothermal Nickel‐Hydrogen Cell Model, Pauline De Vidts, Javier Delgado, B. Wu, D. M. See, K. Kosanovich, Ralph E. White
Faculty Publications
No abstract provided.
Electrochemical Investigations Of Cobalt-Doped Limn2O4 As Cathode Material For Lithium-Ion Batteries, P. Arora, Branko Popov, Ralph E. White
Electrochemical Investigations Of Cobalt-Doped Limn2O4 As Cathode Material For Lithium-Ion Batteries, P. Arora, Branko Popov, Ralph E. White
Faculty Publications
A wide range (y = 0.05–0.33) of Co-doped LiCoyMn2–yO4 spinels were synthesized and electrochemically characterized. These Co-doped spinels showed improved specific capacity and capacity retention over pure spinels. Electrochemical impedance spectroscopy and the linear polarization resistance technique were used to determine the transport and electrochemical kinetic parameters of Co-doped spinels. The presence of Co in the spinel inhibits the passivation process occurring on the surface of the cathode. Also, Co increases the exchange current density and facilitates the charge-transfer reaction of the active material. The lower self-discharge observed for Co-doped spinels was attributed …
Measurement Of Thin Liquid Film Drainage Using A Novel High-Speed Impedance Analyzer, K. O. Hool, R. C. Saunders, Harry J. Ploehn
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 …
Proton Diffusion In Nickel Hydroxide: Prediction Of Active Material Utilization, Sathya Motupally, Christopher C. Streinz, John W. Weidner
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 …
Steady-State Modeling Of A Parallel-Plate Electrochemical Fluorination Reactor, Kamal Jha, Gerald L. Bauer, John W. Weidner
Steady-State Modeling Of A Parallel-Plate Electrochemical Fluorination Reactor, Kamal Jha, Gerald L. Bauer, John W. Weidner
Faculty Publications
A steady-state mathematical model of a parallel-plate reactor was developed for studying the electrochemical fluorination of organic compounds dissolved in anhydrous hydrogen fluoride. The model incorporates two-phase flow with differential material, energy, and pressure balances. Profiles of temperature, pressure, vapor volume fraction, and current density in the reactor are presented at two inlet temperatures to provide insight into the operation of the reactor. The effects of the inlet temperature, feed flow rate, and cell current on the cell pack voltage and current efficiency of the reactor are presented to determine problematic operating regions for the reactor. Optimum operating currents based …