Electrical and Computer Engineering Commons^™

Data Acquisition And Control Program For Chromatography, M. Keith Hudson, William G. Hood

Journal of the Arkansas Academy of Science

No abstract provided.

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 …

Reduced Order H∞ Controller Design, Seng Chu Chow

Masters Theses

"The problem formulation and the development of the H_∞ optimal control theory are reviewed. Various H_∞ robust controller design techniques, including both state and output feedback cases, together with a brief comparison and some remarks on these methodologies arc presented. Also included are a review of the controller order reduction alternatives and various balanced truncation model reduction methods.

A new model reduction technique with reduced error bound is proposed. This proposed technique introduces a new parameter which can be used to select the spectral norm of the model reduction error at low and high frequency ranges according to …

Standardised Control Techniques For Induction Generators In Both Grid-Connected And Isolated Applications, John Brazil, Aidan O'Dwyer, M. Murphy

Conference papers

Induction generators are particularly suitable for small hydro applications and are widely used at present. However, with conventional grid-connected techniques, it is not always possible to use them in regions with weak grids because of excessive connection transients. Consequently, their many advantages cannot be fully exploited in these regions. Standardised control systems have been developed by ECS for isolated applications of induction generators and these will now be further developed to permit reduced-transient grid connections.

Linear Interpolation Lattice, Cameron K. Coursey, John A. Stuller

Electrical and Computer Engineering Faculty Research & Creative Works

The Well-Known Analysis and Synthesis Filters of Linear Prediction Theory Are Extended Here to Include Linear Interpolation. © 1991 IEEE

Occupation Dynamics Of Trap States In An A-Si:H Thin-Film Transistor, J. N. Bullock, Cheng-Hsiao Wu

Electrical and Computer Engineering Faculty Research & Creative Works

We calculate the dynamical behavior of a-Si:H thin-film transistors with an emphasis on the occupation dynamics of trap states. The appropriate rate equation for the occupation function of trap states is included. We show the relations of filling the trap states with the switch-on time and of emptying the trap charges with the switch-off time. The occupation functions in both cases are non-Fermi distribution. The quasi-equilibrium approximation underestimates those two time constants. Thus, transit time theory cannot describe the speeds of transistors made from disordered materials.

Experimental Determination Of The Effects Of Degenerate Fermi Statistics On Heavily P‐Doped Gaas, E. S. Harmon, Michael R. Melloch, Mark S. Lundstrom, Michael L. Lovejoy

Department of Electrical and Computer Engineering Faculty Publications

The effects of degenerate Fermi statistics on electron injection currents for p+‐GaAs grown by molecular beam epitaxy are presented. To achieve Be dopant concentrations of greater than 8×10¹⁹ cm⁻³, the substrate temperature during growth was reduced to approximately 450 °C from the usual 600 °C. In this heavily doped material, we measure unexpectedly large electron injectioncurrents which are interpreted in terms of an effective narrowing of the band gap. At extremely heavy doping densities, the Fermi level pushes into the valence band and degenerate Fermi statistics must be taken into account. For doping concentrations greater than …

Zero-Field Time-Of-Flight Measurements Of Electron Diffusion In P+-Gaas, Michael L. Lovejoy, B. M. Keyes, M. E. Klausmeier-Brown, Michael R. Melloch, R. K. Ahrenkiel, Mark S. Lundstrom

Department of Electrical and Computer Engineering Faculty Publications

Minority electron diffusivities in p+-GaAs-doped NA =~1.4×10¹⁸ and ~10¹⁹ cm^-3 have been measured in zero-field conditions with an extension of the zero-field time-of-flight technique. Extension of the technique to make it applicable to heavily doped p+-GaAs is described and zero-field data are discussed. Unexpectedly, majority carrier drag effects are not evident in a comparison of this data with recently reported high-field data. Low zero-field mobility of electrons in p+-GaAs has important implications for high-speed devices such as heterojunction bipolar transistors.

Transistor-Based Studies Of Heavy Dop-Ing Effects In N-Gaas, M. P. Patkar, Mark S. Lundstrom, Michael R. Melloch

Department of Electrical and Computer Engineering Faculty Publications

The n2ieDp product (where n2ie is the np product and Dp is the minority hole mobility) in heavily doped n‐GaAs has been measured by electrical characterization of p‐n‐p GaAs homojunction transistors with base dopings ranging from approximately 1×1017 to 9×1018 cm−3. The measured n2ieDp product decreases as the doping density increases. These results suggest that nie is roughly constant with doping density, in sharp contrast to the large increase observed for p‐type GaAs. This work shows that when designing GaAs bipolar devices, …

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

Faculty Publications

No abstract provided.

Study Of Ingaas-Based Modulation Doped Field Effect Transistor Structures Using Variable-Angle Spectroscopic Ellipsometry, S. A. Alterovitz, R. M. Sieg, H. D. Yao, Paul G. Snyder, John A. Woollam, J. Pamulapati, P. K. Bhattacharya, P. A. P. A. Sekula-Moise

John A. Woollam Publications

Variable-angle spectroscopic ellipsometry was used to estimate the thicknesses of all layers within the optical penetration depth of InCaAs-based modulation doped field effect transistor structures. Strained and unstrained InGaAs channels were made by molecular beam epitaxy (MBE) on InP substrates and by metal-organic chemical vapor deposition on GaAs substrates. In most cases. ellipsometrically determined thicknesses were within 10% of the growth-calibration results. The MBE-made InCaAs strained layers showed large strain effects, indicating a probable shift in the critical points of their dielectric function toward the InP lattice-matched concentration.

Photorefractive Materials For Optical Signal Processing, William B. Lawler

Retrospective Theses and Dissertations

The optical response of the photorefractive crystals KNbO₃:Ta, KNbO₃:Fe, LiNbO₃:Fe, and nominally pure BaTiO₃ is investigated. In the experiment, a holographic grating is built in the crystal under investigation via a two-wave mixing scheme that utilizes the signal-processing capacities of two acousto-optic Bragg cells. The dynamic interaction of the Bragg cells with the photorefractive grating causes a heterodyned RF signal to appear on the output laser beam, enabling the real-time, direct measurement of the amplitude and phase of the space-charge fields in the crystal. Experimental results are presented for the amplitude and phase …

Application Of A Six-State Passive Track Filter Within A Weapon-Delivery System For A Lock-On-After-Launch Missile, Lynda Jeanne Ciaponi

Retrospective Theses and Dissertations

Knowing the benefits that a passive air target tracking system gives the host aircraft attempting to conceal its own presence on the battlefield, it is desired to determine whether the aircraft can also deliver one of its own lock-on-after-launch air-to-air missiles to the target via use of the same passive system. The objective of this thesis is to demonstrate that a passive six-state track filter can be successfully used within such a weapon delivery system. The role of the filter within the system is to track the enemy target in cartesian space utilizing only line-of-sight measurements and to track the …

Texture Segmentation And Classification Using Fractal And Energy Measures, Qing Chen

Retrospective Theses and Dissertations

This thesis introduces a multi-feature based texture segmentation and classifi­ cation algorithm. We first present general background on segmentation approaches which can be categorized into three groups : characteristic thresholding and clus­ tering, edge detection, and region merging. According to our texture segmentation objective, we choose characteristic thresholding and clustering along with region merging as our segmentation method which is accomplished by a popular K-mean algorithm applied in the feature space. Fractal geometry is receiving increasing attention as a model for natural phe­ nomena. We present an efficient method for estimating the fractal dimension of image surfaces and show that …

Rs170 Image Processing Interface, Charlotte Christou

Retrospective Theses and Dissertations

This thesis deals with the hardware design and implementation of an image processing board that digitizes RS-170 video, passes it thru a sobel filter and sends the results to a high-resolution color printer. Most sobels deal with black and white images, but this thesis uses a static color image. The hardware design will allow direct printing from a RGB separate channel RSl 70 video source to a Tektronix 4693DX Color Printer through a Centronics port. It will also allow the red, blue and green video channels to pass through a sobel filter, with the resulting image being sent out to …

Observation Of The Visible Absorption Spectrum Of H2o+, Biswajit Das, John W. Farley

Electrical & Computer Engineering Faculty Research

The Ã ² Ã₁–X̃ ² B̃₁ system of H₂O⁺ has been observed, using laser absorption spectroscopy in a velocity‐modulated discharge. A total of 78 transitions between 14 794 and 15 475 cm⁻¹ have been observed with an uncertainty (1 SD) of 0.02 cm⁻¹, including 76 transitions in the (0,7,0)–(0,0,0) band and 2 in the (0,8,0)–(0,0,0) band. This species is important for cometary astronomy, and intriguing for molecular physics because of its prominent Renner–Teller interaction. Careful measurements were made of the relative intensities of the absorption lines, …

A New Design Approach For Numeric-To-Symbolic Conversion Using Neural Networks, Zibin Tang

Dissertations and Theses

A new approach is proposed which uses a combination of a Backprop paradigm neural network along with some perceptron processing elements performing logic operations to construct a numeric-to-symbolic converter. The design approach proposed herein is capable of implementing a decision region defined by a multi-dimensional, non-linear boundary surface. By defining a "two-valued" subspace of the boundary surface, a Backprop paradigm neural network is used to model the boundary surf ace. An input vector is tested by the neural network boundary model (along with perceptron logic gates) to determine whether the incoming vector point is within the decision region or not. …

Freeway Control Via Ramp Metering: Development Of A Basic Building Block For An On-Ramp, Discrete, Stochastic, Mesoscopic, Simulation Model Within A Contextual Systems Approach, Mohamed Yaser Alkadri

Dissertations and Theses

One of the most effective measures of congestion control on freeways has been ramp metering, where vehicle entry to the freeway is regulated by traffic signals (meters). Meters are run with calibrated influx rates to prevent highway saturation. However, recent observations of some metering sites in San Diego, CA indicate that metering, during peak hour demand, is helping freeway flow while sometimes creating considerable traffic back-ups on local streets, transferring congestion problems from the freeway to intersections. Metering problems stem largely from the difficulty of designing an integrated, dynamic metering scheme that responds not only to changing freeway conditions but …

Parplum : A System For Evaluating Parallel Program Optimization Methods, Jingsong Fu

Dissertations and Theses

The diversity of application programs and parallel architectures makes the mapping problem complicated and hard to evaluate. The quality of mapping is machine and application dependent and varies due to inaccurate values of application and architecture characteristics.

A system for developing, applying and evaluating mappings must have four characteristics: (1) Simplicity: A mapping procedure can be evaluated by separately evaluating its submapping, so the complicated problem can be simplified. (2) Generality: A wide range of application programs and architectures can be easily represented and all mapping algorithms can be easily implemented. (3) Multifunctionality: all the mapping steps, application programs, target …

Neural Network Character Recognition With A 2-D Fourier Transform Preprocessor, Daqiao Du

Dissertations and Theses

In pattern recognition applications, it is usually important that the same identification be given for a pattern, independent of a variety of positions, rotations and /or distortions of the pattern within the recognition device's field of view. This research relates to development of a preprocessor for a neural network character recognition system, where the role of the preprocessor is to assist in minimizing the difficulties related to variations of position and rotations of a character within the field of view. The preprocessor explored here was suggested in 1970' (Lendaris & Stanly, 1970), and is implemented here with more recent advances …