Digital Commons Network^™

The Extraction Of The Equivalent Circuit Parameters Of Surface Acoustic Wave Resonators, Brent H. Horine

Retrospective Theses and Dissertations

The application of the Electronic Industries Association suggested standard, EIA-512 [1], has been successfully applied to quartz crystal resonators for extraction of the equivalent circuit model parameters. This technique has been shown to be very successful in the operation range to several hundred megahertz. This same technique is proposed to be applied to many differing types of resonators through the full spectrum of frequencies. This thesis will discuss measurement and testing of Surface Acoustic Wave (Saw) resonators at the higher frequencies. The packaging configuration in conjunction with SAW devices can lead to significant parasitic effects. In order to successfully extract …

A Model Of Dc Glow Discharges With Abnormal Cathode Fall, Karl H. Schoenbach, Hao Chen, G. Schaefer

Bioelectrics Publications

A model for an abnormal glow discharge, including a self‐consistent analysis of the cathode fall, was developed. It combines microscopic particle simulation by means of Monte Carlo methods with a fluid model of the gas discharge. The model allows calculations of the steady‐state electrical field distribution, the charged‐particle densities, and the current densities along the axis of the discharge. The model was used to simulate a glow discharge in 80% He and 20% SF₆ at a pressure of 8 Torr with a current density of 1 A/cm². The computed discharge voltage agrees well with measured values. The …

Reduced Order Robust Controllers For An Experimental Flexible Grid, Vittal S. Rao, M. Westerheide, Alok Das

Electrical and Computer Engineering Faculty Research & Creative Works

A procedure for the design and implementation of reduced-order robust controllers for active vibration control on an experimental flexible grid structure is presented. The experimental structure consists of a 5-ft x 5-ft grid made of 2-in-wide, 1/8-in-thick aluminum strips. The grid hangs vertically, being cantilevered at the top to a large T-beam anchored to a cinder block wall. The grid structure is represented by a 75-degree-of-freedom finite-element model, and the controller uses three piezoelectric accelerometer sensors to command three Non collocated DC motor torquers. The modified balance-truncation model-reduction method is used to derive a control synthesis model. These reduced-order models …

Design Of Robust Controllers For Gas Turbine Engines, David E. Moellenhoff, Vittal S. Rao, Charles A. Skarvan

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes robust controller design methodologies for gas turbine engines. A linear state variable model for the engine is derived using partial derivatives. The Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) and the Parameter Robust Linear Quadratic Gaussian (PRLQG) robust controller design methodologies have been used to design a controller for gas turbine engines. A new method is proposed by combining the features of LQG/LTR and PRLQG methods and yields good robustness properties with respect to both unstructured uncertainties in the frequency domain and structured parameter variations in the time domain. The new procedure is illustrated with the …

Reduced Order Modeling Methods For Turret-Gun System, Vittal S. Rao, Norman P. Coleman

Electrical and Computer Engineering Faculty Research & Creative Works

Reduced-order modeling techniques are used to design lower order robust controllers for a turret-gun system. The balance-truncation, Routh approximation, and L. Litz's (1980) modal techniques are used to derive the models. A critical comparison of the time and frequency response characteristics of the original and reduced order models is made. The spillover problem associated with a reduced-order model is investigated.

The Parallel Implementation Of The Waveform Relaxation Method For Transient Stability Simulations, Marija D. Ilić, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, the authors extend the results of their earlier paper on waveform relamtion (WR), which is a parallel algorithm for transient stability analysis. The WR algorithm is extended to a structure-preserving power system model in which the loads are retained. This results in a system of differential/ algebraic equations (DAEs). Power systems exhibit several unique dynamic properties which may be exploited in an advantageous manner by the WR algorithm. This leads to a greater computational efficiency than most other direct methods of simulation. This paper presents several theoretical results as well as computational results on parallel implementation.

Influence Of Copper Doping On The Performance Of Optically Controlled Gaas Switches, St. T. Ko, V. K. Lakdawala, K. H. Schoenbach, M. S. Mazzola

Electrical & Computer Engineering Faculty Publications

The influence of the copper concentration in silicon-doped gallium arsenide on the photoionization and photoquenching of charge carriers was studied both experimentally and theoretically. The studies indicate that the compensation ratio (N_Cu/N_Si) is an important parameter for the GaAs:Si:Cu switch systems with regard to the turn-on and turn-off performance. The optimum copper concentration for the use of GaAs:Si:Cu as an optically controlled closing and opening switch is determined.

Principles And Clinical Applications Of Magnetic Resonance, Rao P. Gullapalli, Teresa T. Evans, Roger M. Hawk

Journal of the Arkansas Academy of Science

A review is presented which covers the basic theory of nuclear magnetic resonance (NMR) with regard to angular momentum, magnetic moments, and the classical mechanical description of the NMR experiment. Longitudinal (T,) and Transverse (T2) relaxation times are defined as well as the basic pulse sequences used for their measurement. In particular, the 180°-t-90° and the Hahn Spin Echo pulse sequences are described in detail. Basic Magnetic Resonance Imaging (MRI) theory is discussed with regard to slice selection, frequency encoding, and phase encoding to define the imaged volume element. The equations defining the amount of Tt , T2 , and …

Instrument Matrix Of The Four-Detector Photopolarimeter: Physical Meaning Of Its Rows And Columns And Constraints On Its Elements, R. M.A. Azzam

Electrical Engineering Faculty Publications

The four-detector photopolarimeter (FDP) is an arrangement of four photodetectors for measuring the state of polarization of light. The output current vector I of the FDP is related to the input Stokes vector S by I = AS, where A is the instrument matrix. The rows of A can be viewed as projection operators that determine the output currents of the detectors. This leads to the recognition of four special totally polarized input states, each of which maximizes the output of one detector. The associated four orthogonal states produce minimum signals. Because each detector is absorptive and its output is …

Measurement Of Magnetic Fluctuations By O-X Mode Conversion, L. L. Vahala, G. Vahala, N. Bretz

Electrical & Computer Engineering Faculty Publications

The possibility of measuring magnetic fluctuations in a fusion plasma is considered by examining the O→X mode conversion. Under certain conditions and with good angular resolution, this mode conversion can be attributed to the presence of magnetic fluctuations even though the level of these fluctuations is much lower than that of density fluctuations. Some nonideal effects such as mode polarization mismatch at the plasma edge are also discussed.

A Review Of Recent Advances In Economic Dispatch, Badrul H. Chowdhury, S. Rahman

Electrical and Computer Engineering Faculty Research & Creative Works

A survey is presented of papers and reports that address various aspects of economic dispatch. The time period considered is 1977-88. Four related areas of economic dispatch are identified and papers published in the general areas of economic dispatch are classified into these. These areas are: optimal power flow, economic dispatch in relation to AGC, dynamic dispatch, and economic dispatch with nonconventional generation sources.

A Balancing Method For Reduced Order Modelling Of Unstable Systems, Rajiva Prakash, Vittal S. Rao

Electrical and Computer Engineering Faculty Research & Creative Works

Moore's balancing method of model reduction has many attractive properties and is used widely in practice. However, this method suffers from the drawback that it is not applicable for unstable systems. This paper introduces a balancing method of model reduction to overcome this problem. The proposed technique obtains the reduced order model by balancing and truncating frequency domain controllability and observability Gramians. Analytical treatment is given for associated properties of the Gramians, and the balancing and truncation steps of model reduction. A numerical example is used to demonstrate the new approach. © 1990.

Fixed Mode Elimination In Decentralized Control Systems Using Eigenvalue Sensitivities, Jorge R.B. Souza, Vittal S. Rao

Electrical and Computer Engineering Faculty Research & Creative Works

The knowledge of fixed modes plays an important role in the design of decentralized controllers for large scale systems. An approach based on a parametric sensitivity of eigenvalues is proposed to select the information to be exchanged between control stations in order to eliminate decentralized fixed modes. The procedure is illustrated with an example. © 1990.

Threaded Octree Structures For Fast Neighbor Voxel Processing In A Parallel Ray Tracer, B.R. Naveen Chandra

Dissertations and Theses

In the field of Computer Graphics, Ray Tracing has so far been the the best algorithm for rendering of realistic three dimensional images created by mathematical models. Ray Tracing is also known for its very large computation times, where the computation depends on the picture resolution, the number of objects and the complexity of the scene.

Contours Of Constant Pseudo-Brewster Angle In The Complex Є Plane And An Analytical Method For The Determination Of Optical Constants, R. M.A. Azzam, Ericson E. Ugbo

Electrical Engineering Faculty Publications

The locus of all points in the complex plane of the dielectric function є[є_r + jє_i = |є| exp(jθ)], that represent all possible interfaces characterized by the same pseudo-Brewster angle θ_pB of minimum p reflectance, is derived in the polar form: |є| = l cos(ζ/3), where l = 2(tan²Φ_pB)k, ζ = arccos(- cosθ cos²Φ_pB/k³), and k = (1 - 2/3 sin²Φ_pB)½. Families of iso-Φ_pB contours for (I) 0° ≤ Φ_pB ≤ …

Transient Stability Hierarchical Control In Multimachine Power Systems, A Rubbai, F. Eugenio Villaseca

Electrical and Computer Engineering Faculty Publications

The authors present the optimal transient stability control problem in a hierarchical structure for multimachine power systems. The two-level structure retains the local closed-loop controls, thereby easing its implementation on existing systems. The formulation accounts for nonlinearities and interconnections, and the optimization of the system transient performance is obtained with less computational effort. Since the computations are distributed among the many local feedback subsystems, the storage and solution times are considerably less than those required by a single overall centralized controller. This advantage becomes much stronger as the system size increases. For illustration purposes, this technique was applied successfully to …

Accurate Calibration Of The Four-Detector Photopolarimeter With Imperfect Polarizing Optical Elements, R. M.A. Azzam, Ali G. Lopez

Electrical Engineering Faculty Publications

The first three columns of the instrument matrix A of the four-detector photopolarimeter (FDP) are determined by Fourier analysis of the output current vector I(P) as a function of the azimuth angle P of the incident linearly polarized light. Therefore 12 of the 16 elements of A are measured free of the imperfections of the (absent) quarter-wave retarder (QWR). The effect of angular beam deviation by the polarizer is compensated for by taking the average, (1/2) [I(P) + I(P + 180°)], of the FDP output at 180°-apart, optically equivalent, angular positions of the polarizer. The remaining fourth column of A …

Robotic Arms With Flexible Links As The Links Approach Rigidity, George A. Downes

Theses

The dynamics of single link flexible robotic arms are modeled using the Bernoulli-Euler beam equation and Lagrange's equation. The Bernoulli-Euler beam equation derivation is reviewed and is studied in the limiting case as the flexiblity approaches zero. Using the Bernoulli-Euler beam equation, a procedure is developed to calculate the position of the endpoint of a link given the displacement, slope or curvature of any point on the link. Also a procedure is developed to calculate the minimum Young's modulus of elasticity, E, given a specified endpoint displacement tolerance.

A rigid link model based on Lagrange's equation and a flexible link …

Design And Analysis Of An Intracranial Pressure And Temperature Sensor Telemetry System, Anshumat Parasar

Theses

This thesis presents a signal conditioning and telemetry system for an implantable pressure and temperature transducer. The initial target application is for measuring the epidural intracranial pressure in the range of 25-100 millitorr and temperature over the range 90 — 110° F. The implant, based on custom silicon IC design can be packaged within a volume of 2cm3 and will require surgical procedures for placement and removal. Effort has been made in this thesis to design the transducer, associated signal conditioning and telemetry circuits for useful operation over a wide range of power supply voltage. The implanted device is powered …

Recursive System Identification Using Least Squares Method, Gholamreza Ghorbani Moghadam

Theses

Input and output sampling, in addition to computer simulations, are now an integral part of system identification. In this thesis, the concept of analyzing any time invariant continuous deterministic system will be developed by identifying a linear discrete - time system equivalent to the continuous one. In this method, two computer programs are written in pascal. The first program applies the Recursive Least Squares Method to discrete - time systems in order to estimate the system components. The second program estimates the future output of the system. Four systems have then identified using the programs.

In this process, system identification …

Adaptive Transform Coding Of Video With Motion Compensation And Vector Quantization, Jung-Hui Chien

Theses

This thesis proposes an efficient transform coding scheme for the low bit rate video sequence. The redundancy within adjacent video frame is exploited by motion compensated interframe prediction using the efficient independent orthogonal search technique, and the motion compensated frame difference (MCFD) signal is transform coding by 1-D DCT, 1-D HDCT and 2-D DCT, the coefficients are zonal masked, and vector quantizatied adaptively. The encoded MCFD as well as the motion information and variance grouping (side informations) are transmitted to the receiver to reconstruct the frame. The transform MCFD signal is classified into the four groups according to the coefficient …

Efficient Interconnection Schemes For Vlsi And Parallel Computation, Ronald I. Greenberg

Computer Science: Faculty Publications and Other Works

This thesis is primarily concerned with two problems of interconnecting components in VLSI technologies. In the first case, the goal is to construct efficient interconnection networks for general-purpose parallel computers. The second problem is a more specialized problem in the design of VLSI chips, namely multilayer channel routing. In addition, a final part of this thesis provides lower bounds on the area required for VLSI implementations of finite-state machines. This thesis shows that networks based on Leiserson's fat-tree architecture are nearly as good as any network built in a comparable amount of physical space. It shows that these "universal" networks …

Effects Of N>M Clos Networks On Edge Coloring And Matrix Decomposition Algorithms, Ming-Hsing Lin

Theses

Considered in this thesis are n > m Clos networks on edge coloring and matrix decomposition algorithms. This work uses a two-fold approach to examine the effects of n > m Clos networks on edge coloring and matrix decomposition algorithms. First, edge coloring and matching on bipartite multigraphs are applied to routing on Clos networks. It is demonstrated that edge coloring algorithms which find a minimum edge coloring set up the routing for n > m Clos networks with redundancy. The results presented here indicate that the Euler coloring algorithm has applications on n > m Clos networks because it has fast time complexity …

Optimization Of Throughput And Stability For Csma/Cd Channel, Liangshyng Jou

Theses

Multiple access technologies plays an important role in designing distributed computer communication system. Here, CSMA/CD has attracted researchers' attentions in the last ten years. In this paper, based on attributions of the slotted, nonpersistent CSMA/CD system, performance of CSMA/CD channel is analyzed. Adaptive Retransmission Technique is adopted to obtain the maximum throughput. Also, equilibrium contours are derived to discuss the stability of the system. And use FET to measure the stability of CSMA/CD channel that FET gives an approximate measure of the average uptime of an unstable channel.

Analytical Determination Of The Complex Dielectric Function Of An Absorbing Medium From Two Angles Of Incidence Of Minimum Parallel Reflectance, R. M.A. Azzam

Electrical Engineering Faculty Publications

The real and imaginary parts of the complex dielectric function (or complex refractive index) of an opaque substrate or a thick film can be determined from two pseudo-Brewster angles measured in two transparent incidence media of different refractive indices. This two-angle method is simple in that it involves no photometric or polarimetric analysis and in that the solution for the optical properties in terms of the measured angles is explicit, analytical, and direct (i.e. noniterative). The two-angle method is demonstrated for an opaque TiN film on a Cleartran ZnS substrate as a specific example. The effect of angle-of-incidence errors on …

Spontaneous Mode Locking In Long-Cavity Xenon Lasers, Manuela Fe Tarroja, Mohammad Sharafi, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Spontaneous mode locking in Fabry—Perot xenon lasers has been experimentally investigated for cavity lengths up to 66 m. Our results show dependence of the number of pulses per round-trip time on the cavity length and the excitation current. Other dynamical effects such as the ringing and modulation of the mode-locked pulses have been observed. A semiclassical model for the self-locking of an inhomogeneously broadened laser is also presented. Numerical results based on this model describe many dynamical features observed in our experiments.

Theory Of A Synchronously Pumped Mode-Locked Dye Laser In The Short Pump Pulse Limit, Duncan Leo Macfarlane, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

We study the operation of a synchronously pumped mode-locked dye laser when the pump pulse is taken as a Dirac delta function, a limit that is sometimes experimentally reasonable. We find that in this limit the model simplifies considerably and that with further assumptions the physical interpretation of synchronously pumped mode-locked operation becomes apparent. Specifically, our nonlinear dynamical model reduces to the same set of equations that govern a prepumped Q-switched laser, and from this simple picture we are able to derive approximate analytic formulas for the synchronously pumped mode-locked laser pulse width and peak intensity. Additionally, we present a …

Fault-Tolerant Interconnection Networks For Multiprocessor Systems, Hamed Mohamed Nassar

Dissertations

Interconnection networks represent the backbone of multiprocessor systems. A failure in the network, therefore, could seriously degrade the system performance. For this reason, fault tolerance has been regarded as a major consideration in interconnection network design. This thesis presents two novel techniques to provide fault tolerance capabilities to three major networks: the Baseline network, the Benes network and the Clos network.

First, the Simple Fault Tolerance Technique (SFT) is presented. The SFT technique is in fact the result of merging two widely known interconnection mechanisms: a normal interconnection network and a shared bus. This technique is most suitable for networks …

An Intelligent Electrocardiogram Tutoring Package Ekgchallenger, Santosh K. Ananthraman

Theses

This thesis presents the development and implementation of an intelligent electrocardiogram tutoring package, namely, EKGCHALLENGER which is meant for use in medical schools to teach medical students a method of diagnosing electro cardiograms.

EKGCHALLENGER is an IBM - PC based, user friendly package. It works in two basic modes. The first is a tutorial mode wherein the user is taught the step-by-step diagnosis of electrocardiograms ( EKGs ) which are presented in order of increasing difficulty. The second is the challenger mode wherein the user is asked to diagnose EKGs which are randomly chosen from an EKG database. The diagnosis …

Adaptive Subband Video Coding With Motion Compensation, Manjunatha S. Kadur

Theses

An efficient scheme for video sequence coding is presented here. The interframe redundancy present in the video sequence is exploited by motion compensation using the efficient independent orthogonal search technique, which requires least number of computations in the worst case. The motion compensated frame difference signal is encoded with a new technique — subband adaptive vector quantization.

Subband coding like transform coding results in signals of unequal energy patterns, which is efficiently utilized for bit allocation. In addition, the subband approach offers means for efficient (but suboptimal) Vector Quantization (VQ) by splitting the signal into several signals. By rate distortion …