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Articles 1 - 17 of 17
Full-Text Articles in Engineering
Free Carrier Density Profiling By Scanning Infrared Absorption, Jack L. Boone, Michael D. Shaw, Gene Cantwell, William C. Harsch
Free Carrier Density Profiling By Scanning Infrared Absorption, Jack L. Boone, Michael D. Shaw, Gene Cantwell, William C. Harsch
Electrical and Computer Engineering Faculty Research & Creative Works
A prototype instrument for making contactless measurements of free carrier concentration as a function of the surface coordinates has been developed. The instrument requires minimal sample preparation, and the measurements are nondestructive. Measurements are based upon the free carrier absorption of photons at a wavelength of 10.6 μm. The measurement sensitivity is determined by the ability to resolve small variations in the transmitted wave. These variations can be significantly influenced by changes in sample thickness. A scheme has been devised which eliminates thickness variations by rotating the sample through small angles to achieve a transmission maximum at each data point. …
Estimation Of X-Band Scattering Properties Of Tree Components, David E. Pitts, Gautam D. Badhwar, Eddie Reyna, R. Zoughi, Linkim Wu, Richard K. Moore
Estimation Of X-Band Scattering Properties Of Tree Components, David E. Pitts, Gautam D. Badhwar, Eddie Reyna, R. Zoughi, Linkim Wu, Richard K. Moore
Electrical and Computer Engineering Faculty Research & Creative Works
An X-band FM-CW very fine range resolution scatterometer was used to acquire backscattering data for individual branches for a number of tree species. Using a model to describe the scattering source function, dσ/dR = f(η, κ), and an experimental procedure for selected removal of plant parts, allows the estimation of η, the volume backscatter coefficient, and κ, the volume extinction coefficient. It is found that 1) leaves are strong attenuators as well as scatterers, 2) the albedo, ω = η/κ, at a given angle of incidence, is nearly independent of the tree type, 3) the tree …
Measurements Of Radar Backscatter From An Artificial Tree An Indication Of Azimuthal Variations And Polarisation Sensitivity Of Trees, Richard K. Moore, M. S. Osman, R. Zoughi
Measurements Of Radar Backscatter From An Artificial Tree An Indication Of Azimuthal Variations And Polarisation Sensitivity Of Trees, Richard K. Moore, M. S. Osman, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Measurements of radar backscatter from an artificial tree were made in the laboratory at 6 and 10 GHz at horizontal incidence. The system has resolution cylinder 18 cm in diameter and 11 cm long. The tree itself was only 30.5 cm high so about half the tree was within the beam. The scattering was azimuthally uniform. Tilted polarizations gave results favoring an angle corresponding with that of the branches. Measurements were made with and without leaves.
Still-Frame Image Transmission Using Dpcm/Interpolative Coding, Brindala Mallappa, Norman R. Cox
Still-Frame Image Transmission Using Dpcm/Interpolative Coding, Brindala Mallappa, Norman R. Cox
Electrical and Computer Engineering Faculty Research & Creative Works
Two methods of combining DPCM (differential pulse-code modulation) and interpolation are proposed for compressing still-frame teleconferencing signals. The first method uses horizontal subsampling, DPCM, and interpolation to achieve a 4:1 compression. The other method is similar but uses vertical subsampling instead. Simulation results indicate that either method can easily achieve the required 2-b/pel data rate with negligible degradation in image quality. Conventional DPCM is shown to perform slightly better in quantitative terms when fixed-wordlength coding is used. However, the two DPCM/interpolation methods offer other advantages when used with a variable-wordlength coder
A Stochastic Model For Dielectric Breakdown In Thin Capacitors, D. A. Willming, Cheng-Hsiao Wu
A Stochastic Model For Dielectric Breakdown In Thin Capacitors, D. A. Willming, Cheng-Hsiao Wu
Electrical and Computer Engineering Faculty Research & Creative Works
A nontrivial two-dimensional stochastic model for dielectric breakdown within a parallel plate capacitor is presented for the first time. The model has been used to determine geometric properties of parallel plate discharges. Comparisons are made between these properties and known fractal properties of electrostatic discharges within cylindrical geometries. As the spacing between the plates of a capacitor increases, the value of the fractal dimension of the associated discharge structure increases from the minimum value of unity and approaches the limiting value corresponding to the case of infinite spacing. For any given spacing, this fractal exponent is equal to the exponent …
Aircraft Vertical Profile Implementation Using Directed-Graph Methods, L. T. Brewster, Paul D. Stigall
Aircraft Vertical Profile Implementation Using Directed-Graph Methods, L. T. Brewster, Paul D. Stigall
Electrical and Computer Engineering Faculty Research & Creative Works
Aircraft Vertical Profile Simulation is Realized using a Demand-Driven Minimal-Calculation Directed Graph Structure to Reduce Calculation Time and to Force Synchronization of the Performance Measurement Functions with the System State Variables. Performance-Directed Model Adaptation Makes Dynamic Vertical Profile Path Corrections, in the Presence of Fixed Drag Variations, Possible. Drag Variations Ranging from + 10 Percent to - 10 Percent Yielded Fuel Consumption Improvements of Less Than 1 Percent in the Majority of the Cases. Calculation Time Improvement for Path Simulation Ranges from a Factor of 1.19 in the Worst Case to 1.5 in the Best Case. © 1988 IEEE
A Rule-Based Dynamic Economic Dispatch For Power Systems, Badrul H. Chowdhury
A Rule-Based Dynamic Economic Dispatch For Power Systems, Badrul H. Chowdhury
Electrical and Computer Engineering Faculty Research & Creative Works
The author introduces a novel operation tool for economic dispatch. It deals with the development and implementation of a new approach-a dynamic rule-based dispatch algorithm that takes into account the major problems faced by the dispatch operator during a dispatch interval and channels those into a database for use by a rule-based system. The algorithm is very fast and can be used effectively in interconnected systems. It can also handle renewable technologies and is therefore considered useful for major electric power utilities contemplating adding a significant amount of these new generation sources to their existing mix
Distribution Automation For The Association Of Missouri Electric Cooperatives—A Statewide Evaluation Of Load Management, Jack F. Morris, Frank J. Kern
Distribution Automation For The Association Of Missouri Electric Cooperatives—A Statewide Evaluation Of Load Management, Jack F. Morris, Frank J. Kern
Electrical and Computer Engineering Faculty Research & Creative Works
Presented is an in-depth technical and economic feasibility study utilizing one- and two-way management systems for statewide load control and distribution automation. Included are 1) an evaluation of the generation and transmission load patterns of the state cooperatives and the determination of the amount of controllable load for use by a load management system, 2) an in-depth economic cost-benefit study as a result of implementing a load management system on a statewide basis, 3) communication alternatives for implementing the statewide load management and distribution automation system, 4) an investigation into using an existing statewide microwave communications system for direct load …
Simulation Of Communication Systems Using Personal Computers, William H. Tranter, Carl R. Ryan
Simulation Of Communication Systems Using Personal Computers, William H. Tranter, Carl R. Ryan
Electrical and Computer Engineering Faculty Research & Creative Works
Microcomputer simulation provides a powerful tool for computer-aided design and analysis of communication systems and requires a minimum of investment. Two different simulation examples are presented: a fixed topology simulation program for digital data links written in Pascal; and a simulation of an analog link using Fortran. These examples are followed by a consideration of the new 32-bit single-board computers and their potential impact on microcomputer simulation. © 1988 IEEE
Implementation Of Dsp Applications Using The At&T Dsp32 C Compiler And Application Library, J. Tow, J. Hartung, Steven L. Grant
Implementation Of Dsp Applications Using The At&T Dsp32 C Compiler And Application Library, J. Tow, J. Hartung, Steven L. Grant
Electrical and Computer Engineering Faculty Research & Creative Works
The authors briefly introduce the C compiler and the application library for the DSP32 digital signal processor (DSP). Several examples are shown that illustrate the ease of writing C programs for some common filtering applications. In most cases, a small real-time penalty is incurred by using C, rather than assembly language coding. Programming in C, however, allows a dramatic improvement in programmer productivity in terms of implementing, testing, and maintaining an application
New Directions In Subband Coding, Y. Shoham, Steven L. Grant, N. Seshadri, R. V. Cox, S. R. Quackenbush, N. S. Jayant
New Directions In Subband Coding, Y. Shoham, Steven L. Grant, N. Seshadri, R. V. Cox, S. R. Quackenbush, N. S. Jayant
Electrical and Computer Engineering Faculty Research & Creative Works
Two very different subband coders are described. The first is a modified dynamic bit-allocation-subband coder (D-SBC) designed for variable rate coding situations and easily adaptable to noisy channel environments. It can operate at rates as low as 12 kb/s and still give good quality speech. The second coder is a 16-kb/s waveform coder, based on a combination of subband coding and vector quantization (VQ-SBC). The key feature of this coder is its short coding delay, which makes it suitable for real-time communication networks. The speech quality of both coders has been enhanced by adaptive postfiltering. The coders have been implemented …
Is Central Station Photovoltaic Power Dispatchable?, Badrul H. Chowdhury, S. Rahman
Is Central Station Photovoltaic Power Dispatchable?, Badrul H. Chowdhury, S. Rahman
Electrical and Computer Engineering Faculty Research & Creative Works
An operational tool for integrating a photovoltaic system into the utility's generation mix is introduced. The development and implementation of a new approach-a dynamic rule-based (RB) dispatch algorithm-is presented. A Box-Jenkins time-series method is used to model the subhourly solar irradiance. The model is extended to yield forecast parameters which are then used to predict the photovoltaic output expected to occur at certain lead times coinciding with the economic dispatch intervals. The RB dispatch algorithm is introduced to operate as either a substitute for or an aid to the dispatch operator. It is concluded that results depend on the time …
Linear State Variable Dynamic Model And Estimator Design For Allison 1406 Gas Turbine Engine, Vittal S. Rao, D. Moellenhoff, J. A. Jaeger
Linear State Variable Dynamic Model And Estimator Design For Allison 1406 Gas Turbine Engine, Vittal S. Rao, D. Moellenhoff, J. A. Jaeger
Electrical and Computer Engineering Faculty Research & Creative Works
This paper describes a procedure for developing a State Variable Model for the Allison T406 gas turbine engine. This linear model is useful for designing controllers using modern control techniques. The engine and V-22 rotor system is modeled around an operating point by using four state variables and one input variable. For a given power setting, it is observed that two linear models are sufficient to represent the engine dynamics over the entire flight envelope. A relationship between surge margin and the state variables is also developed. It is demonstrated that these linear models are useful in designing an estimator …
A Discussion On The Diversity In The Applications Of Photovoltaic Systems, S. Rahman, Badrul H. Chowdhury, M. A. Khallat
A Discussion On The Diversity In The Applications Of Photovoltaic Systems, S. Rahman, Badrul H. Chowdhury, M. A. Khallat
Electrical and Computer Engineering Faculty Research & Creative Works
References on the diverse applications of photovoltaic (PV) systems around the world are classified. The classes presented are (i) stand-alone, (ii) grid-connected, (iii) PV-thermal, (iv) PV-wind, and (v) dedicated applications. 73 papers are cited and classified into these five categories including a brief summary of each paper. Out of these, 42 papers relate to grid-connected applications in many industrialized countries of the world. These papers reflect the importance given to such applications. Due to the rapidly changing nature of PV and related industries, only papers published during the last ten years are considered.
Simulation Of Photovoltaic Power Systems And Their Performance Prediction, S. Rahman, Badrul H. Chowdhury
Simulation Of Photovoltaic Power Systems And Their Performance Prediction, S. Rahman, Badrul H. Chowdhury
Electrical and Computer Engineering Faculty Research & Creative Works
A number of photovoltaic (PV) performance-analysis models are tested for their ability to estimate the AC power output and validated against historical observations from a PV test facility. A method to estimate meteorological parameters is developed for use in PV performance models for predicting future AC power output from a PV test site. Twelve such PV performance models are examined, and the PVFORM system analysis program and lifetime cost and performance models are extensively tested. These two models are tested using the typical meteorological year and the VPI model-generated estimates of long-term data. Performance prediction results are compared against actual …
A Practical C Language Compiler/Optimizer For Real-Time Implementations On A Family Of Floating Point Dsps, J. Hartung, Steven L. Grant, S. G. Haigh
A Practical C Language Compiler/Optimizer For Real-Time Implementations On A Family Of Floating Point Dsps, J. Hartung, Steven L. Grant, S. G. Haigh
Electrical and Computer Engineering Faculty Research & Creative Works
Digital signal processors (DSPs) have traditionally been used in real-time applications with very high data throughput. For this reason, system designers have been reluctant to accept the degradation in performance inherent in machine code compiled from high-level languages such as C. The problem is compounded by the fact that DSPs use pipelined architectures to achieve their high data throughput, resulting in hazards and latencies between instructions. Simple compiler implementation cannot take advantage of latent instructions, resulting in a conservative and inefficient executable program. This problem has been addressed in the C compiler package for the AT&T WE DSP32 by the …
Analysis Of Interrelationships Between Photovoltaic Power And Battery Storage For Electric Utility Load Management, Badrul H. Chowdhury, S. Rahman
Analysis Of Interrelationships Between Photovoltaic Power And Battery Storage For Electric Utility Load Management, Badrul H. Chowdhury, S. Rahman
Electrical and Computer Engineering Faculty Research & Creative Works
The impact of photovoltaic power generation on an electric utility's load shape under supply-side peak load management conditions is explored. Results show that some utilities utilizing battery storage for peak load shaving might benefit from use of photovoltaic (PV) power, the extent of its usefulness being dependent on the specific load shapes as well as the photovoltaic array orientations. Typical utility load shapes both in the eastern (at Rayleigh, NC) and in the western (at Hesperia, CA) parts of the USA are examined for this purpose. It is concluded that while photovoltaic power generation seems to present a bigger impact …