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Articles 661 - 690 of 693

Full-Text Articles in Electrical and Computer Engineering

Diffraction Properties Of Stratified Volume Holographic Optical Elements, Gregory P. Nordin, R. V. Johnson, A. R. Tanguay Dec 1992

Diffraction Properties Of Stratified Volume Holographic Optical Elements, Gregory P. Nordin, R. V. Johnson, A. R. Tanguay

Faculty Publications

We present a unified treatment of the diffraction properties of stratified volume holographic optical elements (SVHOE's). We show that the relative phasing of the diffraction orders as they propagate from layer to layer gives rise to a unique notched diffraction response of the +1 order (for the case of Bragg incidence) as a function of the normalized buffer-layer thickness, the grating spatial frequency, and the readout wavelength. For certain combinations of these parameters Bragg diffraction behavior characteristic of volume holographic optical elements (VHOE's) is observed, whereas for other combinations pure Raman-Nath behavior periodically recurs. By using these same relative-phasing arguments, …

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Photopolymer-Based Stratified Volume Holographic Optical Elements, Gregory P. Nordin, A. R. Tanguay Dec 1992

Photopolymer-Based Stratified Volume Holographic Optical Elements, Gregory P. Nordin, A. R. Tanguay

Faculty Publications

We report the implementation of stratified volume holographic optical elements (SVHOE's) using DuPont's Omnidex holographic photopolymer material and an in situ exposure technique for simultaneous multilayer grating recording. Experimental measurement of the +1-order angular sensitivity of a seven-layer SVHOE structure shows remarkable agreement with both theory and numerical simulation for incidence angles near the Bragg angle. For SVHOE's having modulation layers that individually operate in the Bragg or transition diffraction regimes, the envelope of the SVHOE angular sensitivity is experimentally shown to approximate closely that of a single modulation layer.

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Unequal Error Protection Qpsk Modulation Codes, Robert H. Morelos-Zaragoza, Shu Lin Jan 1992

Unequal Error Protection Qpsk Modulation Codes, Robert H. Morelos-Zaragoza, Shu Lin

Faculty Publications

The authors use binary linear UEP (LUEP) codes, in combination with a QPSK signal set and Gray mapping, to obtain new efficient block QPSK modulation codes with unequal minimum squared Euclidean distances. They give several examples of codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes of the same rate and length. A new suboptimal two-stage soft-decision decoding is applied to LUEP QPSK modulation codes.

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Characterizations Of Antimony Tri‐Sulfide Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal Jan 1992

Characterizations Of Antimony Tri‐Sulfide Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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A Note On Repeated-Root Cyclic Codes, Robert H. Morelos-Zaragoza Nov 1991

A Note On Repeated-Root Cyclic Codes, Robert H. Morelos-Zaragoza

Faculty Publications

In papers by Castagnoli et al. and Van Lint, cyclic codes with repeated roots are analyzed. Both papers fail to acknowledge a previous work by Chen, dating back to 1969, which includes an analysis of even, length binary cyclic codes. Results from Chen’s study are presented.

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Spaceborne Radar Measurement Of Wind Velocity Over The Ocean-An Overview Of The Nscat Scatterometer System, David G. Long, F. M. Naderi, Michael H. Freilich Jun 1991

Spaceborne Radar Measurement Of Wind Velocity Over The Ocean-An Overview Of The Nscat Scatterometer System, David G. Long, F. M. Naderi, Michael H. Freilich

Faculty Publications

Scatterometry and scatterometer design issues are reviewed. The design of the NASA Scatterometer (NSCAT) to be flown on the Japanese ADEOS mission is presented. Building on Seasat experience, the NSCAT system includes several enhancements, such as three antenna azimuths in each of two swaths, and an onboard digital Doppler processor to allow backscatter measurements to be colocated everywhere within the orbit. These enhancements will greatly increase the quality of the NSCAT wind data. The ground processing of data is discussed, and scatterometers of the next decade are briefly described.

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Identifiability In Wind Estimation From Scatterometer Measurements, David G. Long, Jerry M. Mendel Mar 1991

Identifiability In Wind Estimation From Scatterometer Measurements, David G. Long, Jerry M. Mendel

Faculty Publications

The problem of identifiability of a wind vector that is estimated from wind scatterometer measurements of the radar backscatter of the ocean's surface is addressed. The traditional wind estimation approach produces multiple estimates of the wind direction. A second processing step, known as dealiasing or ambiguity removal, is used to select a single wind estimate from these multiple solutions. Dealiasing is typically based on various ad hoc considerations. The traditional wind estimation approach results in multiple solutions associated with local minima in an objective function formed from the noisy backscatter measurements. The authors discuss the question of the uniqueness of …

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Set-Valued Filtering And Smoothing, Wynn C. Stirling, Darryl Morrell Feb 1991

Set-Valued Filtering And Smoothing, Wynn C. Stirling, Darryl Morrell

Faculty Publications

A theory of discrete-time optimal filtering and smoothing based on convex sets of probability distributions is presented. Rather than propagating a single conditional distribution as does conventional Bayesian estimation, a convex set of conditional distributions is evolved. For linear Gaussian systems, the convex set can be generated by a set of Gaussian distributions with equal covariance with means in a convex region of state space. The conventional point-valued Kalman filter is generated to a set-valued Kalman filter consisting of equations of evolution of a convex set of conditional means and a conditional covariance. The resulting estimator is an exact solution …

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Convex Bayes Decision Theory, Wynn C. Stirling, Darryl Morrell Feb 1991

Convex Bayes Decision Theory, Wynn C. Stirling, Darryl Morrell

Faculty Publications

The basic concepts of Levi's epistemic utility theory and credal convexity are presented. Epistemic utility, in addition to penalizing error as is done with traditional Bayesian decision methodology, permits a unit of informational value to be distributed among the hypotheses of a decision problem. Convex Bayes decision theory retains the conditioning structure of probability-based inference, but addresses many of the objections to Bayesian inference through relaxation of the requirement for numerically definite probabilities. The result is a decision methodology that stresses avoiding errors and seeks decisions that are likely to be highly informative as well as true. By relaxing the …

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A Median-Filter-Based Ambiguity Removal Algorithm For Nscat, David G. Long, Scott J. Shaffer, R. Scott Dunbar, S. Vincent Hsiao Jan 1991

A Median-Filter-Based Ambiguity Removal Algorithm For Nscat, David G. Long, Scott J. Shaffer, R. Scott Dunbar, S. Vincent Hsiao

Faculty Publications

A description is given of the baseline NSCAT (the NASA scatterometer) ambiguity removal algorithm and the method used to select the set of optimum parameter values. An extensive simulation of the NSCAT instrument and ground data processor provides a means of testing the resulting tuned algorithm. This simulation generates the ambiguous wind-field vectors expected from the instrument as it orbits over a set of realistic mesoscale wind fields. The ambiguous wind field is then de-aliased using the median-filter-based ambiguity removal algorithm. Performance is measured by comparison of the selected wind fields with the true wind fields. Results have shown that …

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Novel Chemical Preparative Route For Semiconducting Mose2 Thin Films, K. C. Mandal, O. Savadogo Jan 1991

Novel Chemical Preparative Route For Semiconducting Mose2 Thin Films, K. C. Mandal, O. Savadogo

Faculty Publications

No abstract provided.

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In Situ Infrared Evidence For The Electrochemical Incorporation Of Hydrogen Into Si And Ge, K. C. Mandal, F. Ozanam, J.-N. Chazalviel Dec 1990

In Situ Infrared Evidence For The Electrochemical Incorporation Of Hydrogen Into Si And Ge, K. C. Mandal, F. Ozanam, J.-N. Chazalviel

Faculty Publications

No abstract provided.

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Model-Based Estimation Of Wind Fields Over The Ocean From Wind Scatterometer Measurements. Ii. Model Parameter Estimation, David G. Long, Jerry M. Mendel May 1990

Model-Based Estimation Of Wind Fields Over The Ocean From Wind Scatterometer Measurements. Ii. Model Parameter Estimation, David G. Long, Jerry M. Mendel

Faculty Publications

For pt.I see ibid., vol.28, no.3, p.349-360 (1990). The feasibility of a model-based approach to wind field estimation is discussed. In this approach the parametric model for near-surface mesoscale wind fields developed in pt.I is used. The parameters of the model are estimated from the wind scatterometer measurements; the wind field estimate is then computed from the estimated model parameters. Unlike the traditional pointwise approach, this approach takes advantage of the inherent correlation in the winds at different sample points to estimate the wind field more accurately and resolve directional ambiguity. The accuracies of wind field estimates obtained using the …

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Model-Based Estimation Of Wind Fields Over The Ocean From Wind Scatterometer Measurements. I. Development Of The Wind Field Model, David G. Long, Jerry M. Mendel May 1990

Model-Based Estimation Of Wind Fields Over The Ocean From Wind Scatterometer Measurements. I. Development Of The Wind Field Model, David G. Long, Jerry M. Mendel

Faculty Publications

For pt.II see ibid., vol.28, no.3, p.361-373 (1990). A parametric model for near-surface mesoscale wind fields suitable for use in a model-based approach to estimate the wind field over a large region of the scatterometer measurement swath from measurements of the radar backscatter of the ocean's surface is discussed. The assumptions made in developing the model are described, and the accuracy of the resulting model is evaluated. The model is based only on scatterometer data and is computationally tractable, consisting of a linear equation relating the near-surface wind field to a vector of model parameters which is estimated from the …

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Surface-To-Surface Transition Via Electromagnetic Coupling Of Coplanar Waveguides, Robert W. Jackson, David W. Matolak Nov 1987

Surface-To-Surface Transition Via Electromagnetic Coupling Of Coplanar Waveguides, Robert W. Jackson, David W. Matolak

Faculty Publications

A transition is investigated which couples coplanar waveguide on one substrate surface (a motherboard) to coplanar waveguide on another substrate surface (a semiconductor chip or subarray) placed above the first. No wire bonds are necessary. A full-wave analysis using coupled line theory is presented and verified experimentally. The use of this transition for coupling to millimeter-wave integrated circuits is discussed.

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Moment Method Analysis Of The Electric Field Under Ehv Transmission Lines, T. L. Simpson, Charles W. Brice Oct 1987

Moment Method Analysis Of The Electric Field Under Ehv Transmission Lines, T. L. Simpson, Charles W. Brice

Faculty Publications

The charge moment method is applied to the analysis of electric fields under EHV transmission lines over irregular terrain.

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Decision-Directed Multivariate Empirical Bayes Classification With Nonstationary Priors, Wynn C. Stirling, A. Lee Swindlehurst Sep 1987

Decision-Directed Multivariate Empirical Bayes Classification With Nonstationary Priors, Wynn C. Stirling, A. Lee Swindlehurst

Faculty Publications

A decision-directed learning strategy is presented to recursively estimate (i.e., track) the time-varying a priori distribution for a multivariate empirical Bayes adaptive classification rule. The problem is formulated by modeling the prior distribution as a finite-state vector Markov chain and using past decisions to estimate the time evolution of the state of this chain. The solution is obtained by implementing an exact recursive nonlinear estimator for the rate vector of a multivariate discrete-time point process representing the decisions. This estimator obtains the Doob decomposition of the decision process with respect to the a-field generated by all past decisions and corresponds …

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Simultaneous System Identification And Decision-Directed Detection And Estimation Of Jump Inputs To Linear Systems, Wynn C. Stirling Jan 1987

Simultaneous System Identification And Decision-Directed Detection And Estimation Of Jump Inputs To Linear Systems, Wynn C. Stirling

Faculty Publications

A decision-directed approach is presented for analyzing linear systems with unknown jump inputs. The system model parameters are estimated using a Kalman filter, and an empirical Bayes detection procedure is introduced to set the detector parameters, resulting in a decision-directed generalized likelihood ratio test coupled with recursive system parameter estimation. Monte Carlo results are presented to validate the performance of the algorithm.

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Editing Templates: A User Interface Generation Tool, Dan R. Olsen Jr. Nov 1986

Editing Templates: A User Interface Generation Tool, Dan R. Olsen Jr.

Faculty Publications

This article discusses a basic architecture for a user interface management system and the problem of updating a display in response to interactive commands. The basic architecture is then extended to include basic editing and browsing processes on arbitrary data structures. Editing templates are presented as a technique embodying the entire manipulation process for a particular data structure/data display combination. In conjuction with the user interface management system, Such templates are able to automatically provide a majority of the code required in an interactive applicaton.

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Evidence For Amphoteric Behavior Of Ru On Cdte Surfaces, D. N. Bose, S. Basu, K. C. Mandal, D. Mazumdar Feb 1986

Evidence For Amphoteric Behavior Of Ru On Cdte Surfaces, D. N. Bose, S. Basu, K. C. Mandal, D. Mazumdar

Faculty Publications

No abstract provided.

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A Theoretical Basis For Practical Amplifier Design Using Cascaded Operational Amplifiers, David J. Comer Aug 1985

A Theoretical Basis For Practical Amplifier Design Using Cascaded Operational Amplifiers, David J. Comer

Faculty Publications

A procedure is developed for the design of amplifiers to meet specified gain and bandwidth figures. The number of required operational amplifier stages is minimised. A figure of merit is introduced to determine if a particular operational amplifier can be used to satisfy a given set of specifications.

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High Discharge Rate Characteristics Of Nickel-Cadmium Batteries For Pulse Load Filtering, Gregory M. Gearing, Michael B. Cimino, David H. Fritts, John F. Leonard, Anthony J. Terzuoli Jr. Jul 1985

High Discharge Rate Characteristics Of Nickel-Cadmium Batteries For Pulse Load Filtering, Gregory M. Gearing, Michael B. Cimino, David H. Fritts, John F. Leonard, Anthony J. Terzuoli Jr.

Faculty Publications

Several tests of specially fabricated nickel-cadmium batteries having circular disk type electrodes were considered. These batteries were evaluated as filter elements between a constant current power supply and a five hertz pulsed load demanding approximately twice the power supply current during the load on portion of the cycle. Short tests lasting 10,000 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 Joules per pound. In addition, two batteries were subjected to 107 charge/discharge cycles, one at a 6.5 C rate and the other at a 13 C rate. Assuming an …

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Modeling And System Identification Of Residential Air Conditioning Load, Anil Pahwa, Charles W. Brice Jan 1985

Modeling And System Identification Of Residential Air Conditioning Load, Anil Pahwa, Charles W. Brice

Faculty Publications

A fairly detailed physically-based model of the residential air condit$ oning system is presented. It has been shown that the paramstors of tho model can be identified by making a sequenco of measuremonts of on/off cycles of the air conditioner and the onvironment variables. A scheme to determine aggregate demand of the air conditionors using duty factors is presented. The effect on energy consumption and poak duty fa9tor of change in model parameters is determined. Also, the effect of reduction in the supply voltage is studied using this model and it has been found that the steady state air conditioning …

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A Unique Microprocessor Instruction Set, D. A. Fairclough May 1982

A Unique Microprocessor Instruction Set, D. A. Fairclough

Faculty Publications

New instruction sets have been based on traditather than on the application of scientific method. Here, the latter has yielded a simple, optimal, en-member instruction set.

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Multiple Scattering Of Protons And Deuterons By Thick Foils, D. R. Dixon, G. L. Jensen, S. M. Morrill, C. J. Connors, R. L. Walter, C. R. Gould, P. M. Thambiduria Apr 1981

Multiple Scattering Of Protons And Deuterons By Thick Foils, D. R. Dixon, G. L. Jensen, S. M. Morrill, C. J. Connors, R. L. Walter, C. R. Gould, P. M. Thambiduria

Faculty Publications

Protons and deuterons from the Triangle Universities Nuclear Laboratory (TUNL) tandem Van de Graaff of energies 3.0, 4.0, and 5.0 MeV were scattered from foils of Al, Ni, Mo, and Ta having thicknesses of 6.14 to 47 mg/cm2. Multiple scattering angular distributions were measured using a position-sensitive detector to collect data at nine different angles simultaneously. Gaussian curves were fitted to the central points of the distributions and the Θ1/e angles thus derived are presented graphically. The data points are compared with calculations using a common method of determining multiple scattering angles. An empirical correction for extending this method into …

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Proton Induced X-Ray Emission Analysis - A Complement To Analytical Methods Used In Environmental Studies, N. F. Mangelson, D. J. Eatough, N. L. Eatough, L. D. Hansen, M. W. Hill, M. L. Lee, L. R. Phillips, M. E. Post, B. E. Richter, J. F. Ryder Apr 1981

Proton Induced X-Ray Emission Analysis - A Complement To Analytical Methods Used In Environmental Studies, N. F. Mangelson, D. J. Eatough, N. L. Eatough, L. D. Hansen, M. W. Hill, M. L. Lee, L. R. Phillips, M. E. Post, B. E. Richter, J. F. Ryder

Faculty Publications

Particle induced X-ray emission (PIXE) analysis is a highly versatile method of element analysis. Thus it is well suited for use as a complement to other methods of analysis in experimental programs requiring both chemical and elemental analyses. This paper reports some results of two projects where PIXE was used in conjunction with titration calorimetry, ion chromatography, atomic absorption spectroscopy, gas chromatography/mass spectrometry, X-ray fluorescence spectroscopy and some other methods. The first is a study of sulfur chemistry in a copper smelter plume. Arsenic was found to be a conservative tracer of the plume and was used for calculation of …

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Two Preliminary Studies Of The Intelligibility Of Predictor-Coefficient And Formant-Coded Speech, L. Keeler, G. Clement, W. Strong, E. Palmer Oct 1976

Two Preliminary Studies Of The Intelligibility Of Predictor-Coefficient And Formant-Coded Speech, L. Keeler, G. Clement, W. Strong, E. Palmer

Faculty Publications

Two preliminary studies comparing the intelligibilities of predictor-coefficient versus formant-frequency-coded speech and the intelligibilities of predictor-coefficient-coded speech using different numbers of coefficients are reported.

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The Topolotron: A High Beta Device With Topological Stability, Keith H. Brown, H. R. P. Ferguson, J. H. Gardner, Larry V. Knight, H. Mark Nelson Sep 1976

The Topolotron: A High Beta Device With Topological Stability, Keith H. Brown, H. R. P. Ferguson, J. H. Gardner, Larry V. Knight, H. Mark Nelson

Faculty Publications

The concept of topological or structural stability is introduced and its importance in the magnetic confinement of plasmas is discussed. Topological stability requires the presence of a pair of limit cycles in the magnetic field configuration. This paper deals with the design of an experimental device possessing limit cycles. The design includes a high beta (b=1), high density (10^16), hot (100 eV) hydrogen plasma which is to be compressed by a factor of about 5 in a torodial device of 25 cm average major radius with a capacitor bank rise time of less than 2 µsec. Two shaped toroidal coils …

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A Circular Active Reflector Atenna (Cara), Energy Distribution Calculations, And An Experimental Test, Larry V. Knight, George H. Barry Mar 1975

A Circular Active Reflector Atenna (Cara), Energy Distribution Calculations, And An Experimental Test, Larry V. Knight, George H. Barry

Faculty Publications

Conventional high-frequency (HF) circular phased arrays, such as the Wullenweber circular array, have a cost factor that increases at a greater-than-square law rate as its radius is increased to produce larger apertures. A new method of forming simultaneous beams in an HF circular array has been proposed in which beams are formed in the space within the array from pickup element energy that has been amplified and reradiated. Such a device is called a circular active reflector antenna (CARA), and its cost increases at a substantially linear rate as its radius is increased to form larger apertures. This paper describes …

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An Intensity-Dependent Filter, James M. Thorne, Thomas R. Loree, George Mccall Jun 1973

An Intensity-Dependent Filter, James M. Thorne, Thomas R. Loree, George Mccall

Faculty Publications

It is useful in optically driven Kerr-cell shutters and other laser applications to have intense pulses with extremely low light levels between pulses. We describe here a device that accomplishes this objective external to the laser cavity.

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