Engineering Commons^™

Phase Statistics For A Lightwave Traveling Through Turbulent Media, Donald J. Link

Retrospective Theses and Dissertations

A probability density function is developed for the phase of light that is the result of adding a signal to noise with K-distributed amplitude and uniform phase. The probability density function of the phase associated with the I-K distribution is also developed. In the process of deriving the probability density function of the phase much I as learned about the relationships between different probability density functions. Three different methods of deriving homodyned K statistics are shown to be equivalent. Two different methods of deriving I-K statistics are shown to be equivalent. Theoretical moments of the homodyned K distribution are compared …

Spontaneous Coherent Pulsations In Ring-Laser Oscillators, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Complex spontaneous-pulsation phenomena have been reported in xenon lasers operating at 3.51-μm wavelength, and a theoretical explanation for these effects has been given. However, the published models contain various simplifications and have so far yielded only qualitative agreement with xenon-laser experiments. Reported here is a more rigorous analytical model, which for the first time provides quantitative agreement with experimental observations. This model should also find direct application in interpreting or predicting the behavior of other spontaneously pulsing laser systems.

Two New Parallel Processors For Real Time Classification Of 3-D Moving Objects And Quad Tree Generation, Farjam Majd

Dissertations and Theses

Two related image processing problems are addressed in this thesis. First, the problem of identification of 3-D objects in real time is explored. An algorithm to solve this problem and a hardware system for parallel implementation of this algorithm are proposed. The classification scheme is based on the "Invariant Numerical Shape Modeling" (INSM) algorithm originally developed for 2-D pattern recognition such as alphanumeric characters. This algorithm is then extended to 3-D and is used for general 3-D object identification. The hardware system is an SIMD parallel processor, designed in bit slice fashion for expandability. It consists of a library of …

The Direct Summation Of Totally Self-Checking Checkers, Stefean Andrew Fedyschyn

Electrical & Computer Engineering Theses & Dissertations

A new technique for reducing the complexity of designing Totally Self-Checking (TSC) checkers for m-out-of-n codes is presented. The method is based on the partitioning of the input variables into r classes, then partitioning the code groups generated into Z output partitions. Comparison with earlier results reveals improvements in design simplicity and logic and testing complexity.

This thesis also presents a new method of TSC checker design where a j-level m₁/n₁ code and a k-level m₂/n₂ code TSC checker are directly summed to form a max [j,k]-level (m₁ + m₂) / …

Negative Corona Current Characteristics Of An Electric Wind System, Aviti Kadete

Tanzania Journal of Engineering and Technology (TJET)

The corona current characteristics of an electric wind system are investigated. First a brief summary of the negative point to plate corona mechanism and characteristics are presented. Then empirical equations for corona currents of an electric wind system are derived. Current waveform characteristics are also discussed. The effects of placing parallel rods in between a point-plate electrode gap to the corona currents are highlighted.

Engineer Education: Disciplinary Preferences In The Faculty Of Engineering University Of Dar Es Salaam, S Mosha

Tanzania Journal of Engineering and Technology (TJET)

Most practising engineers can hardly recall the days they had to make up their minds on whether engineering was their chosen career. This decision may have been approached with ignorance and very high expectations. Later after registering in a Faculty of Engineering the freshman was given a chance to choose a department; sometimes this had already been done for him by his sponsors so all he had to do was to walk into the preselected department.

A generation later, University entrants are faced with a similar predicament. This paper high-lights the procedures involved and proceeds to recommend the necessary fundamental …

Load Flow And Contingency Analysis In Power Systems, Kianfar Sorooshian

Dissertations and Theses

A load flow and contingency analysis program for secure design, planning and operation of power systems. Depending on the application either Newton-Raphson or Fast-Decoupled method is employed to solve the load flow. Fault analysis is done by Z bus method. Contingency analysis may be done following the load flow solution by Fast-Decoupled method. The program is also interfaced with a graphic system which displays a single line diagram of the system on the graphic screen along with relevant data and informs the operator of any change by flashing the faulted bus or the line outage.

Study Of Longitudinal Landing Flying Qualities Evaluation Using Pilot Model Theory, Eric D. Didomenico

Theses and Dissertations

Control Anticipation Parameter (CAP), used in MIL-SPEC-8785C as a longitudinal handling qualities criterion does not adequately distinguish between different flight phases. Recent flight test data from the Landing Approach Higher Order Systems (LAHOS) study further indicate the inadequacy of the second order approximations for higher order longitudinal landing flying qualities. Nine Aircraft that fall within the Level 1 boundary reveal pilot ratings ranging from 1.5 to 10 (Cooper/Harper). These nine aircraft are studied by combining their longitudinal dynamics with pilot modelling to examine a better method of landing flying quality prediction and evaluation. Pilot model theory (cross-over pilot model) is …

Solvable Hill Equation, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

A second-order linear differential equation with continuous periodic coefficients is solved exactly in terms of elementary functions. Equations of this type arise commonly in several areas of physics, and the solutions may find practical applications. As an illustration, the results are applied to the problem of an electron in a one-dimensional periodic potential.

Multiple Determination Of The Optical Constants Of Thin-Film Coating Materials, D. P. Arndt, R. M.A. Azzam, J. M. Bennett, J. P. Borgogno, C. K. Carniglia, W. E. Case, J. A. Dobrowolski, U. J. Gibson, T. Tuttle Hart, F. C. Ho, V. A. Hodgkin, W. P. Klapp, H. A. Macleod, E. Pelletier, M. K. Purvis, D. M. Quinn, D. H. Strome, R. Swenson, P. A. Temple, T. F. Thonn

Electrical Engineering Faculty Publications

The seven participating laboratories received films of two different thicknesses of Sc₂O₃ and Rh. All samples of each material were prepared in a single deposition run. Brief descriptions are given of the various methods used for determination of the optical constants of these coating materials. The measurement data are presented, and the results are compared. The mean of the variances of the Sc₂O₃refractive-index determinations in the 0.40–0.75-nm spectral region was 0.03. The corresponding variances for the refractive index and absorption coefficient of Rh were 0.35 and 0.26, respectively.

Design Of Infrasound-Detection System Via Adaptive Lmstde Algorithm, Camille S. Khalaf

Electrical & Computer Engineering Theses & Dissertations

A proposed solution to an aviation safety problem is based on passive detection of turbulent weather phenomena through their infrasonic emission. This thesis describes a system design that is adequate for detection and bearing evaluation of infrasounds. An array of four sensors, with the appropriate hardware, is used for the detection part. Bearing evaluation is based on estimates of time delays between sensor outputs. The generalized cross correlation (GCC), as the conventional time-delay estimation (TOE) method, is first reviewed. An adaptive TUt approach, using the least mean square (LMS) algorithm, is then discussed. A comparison between the two techniques is …

A Method For The Identification Of Parameters In Nonlinear Time-Varying Discrete Systems, Somo Coulibaly

Theses

The purpose of this thesis is to present a new technique for estimating the unknown parameters of nonlinear discrete time-varying systems.

The method is based on the model-reference control system where the model and the plant are controlled to exhibit the same output trajectory. The model is chosen to be linear and stationary. To develop the procedure of identification we assume that the structure of the nonlinear system is known and all the measurements are free of noise. A feedback input is adapted to improve the scheme. This scheme can be used to simultaneously identify the parameters when the control …

Modeling And Analysis Of Switching Dc-To-Dc Converters, Suresh Hariharan

Theses

Modeling and analysis of switching dc-to-dc converters has been achieved through several techniques. The state space averaging technique is valid only for disturbances which are less than one-tenth the switching frequency. The discrete technique does not yield accurate results. In this thesis a new approach to the stability analysis of switching regulators has been discussed and the model is far more accurate than the state space averaging technique or the discrete technique. It can be easily programmed into any computer and the results compare well with the experimental results. It also gives a good insight into the design of the …

Optimization Of The Sputtering Technology For Preparation Of Hg1-[Subscript X] Cd[Subscript X] Te Heterojunction Diodes, Kyriacos Kokkinos

Theses

The deposition of (Hg_1-xCd_x)Te onto Si and (Hg_1-yCd_y)Te (x>y) substrates by rf triode sputtering was studied. Ionized mercury vapor, in the 0.6 to 1.2 micron pressure range, was used to bombard pressed-powder targets, consisting of HgTe and CdTe particles, with effective target x value of 0.3, 0.35, and 0.4. The sputtering procedure, parameters, and system were modified to optimize film characteristics. Higher substrate temperature (270°C) was required to obtain metallic gray films with x>0.3. With substrate temperatures less than 270°C and deposition rates 0.5-1.0 micron per hour the films were …

Reliability Screening Of Transformers, Bharat M. Shah

Theses

The purpose of this project is to study screening of components from the reliability point of view. The component used is electronic transformer. The screen chosen is Electrical Noise generated in the transformer insulation system and the failure mode selected is leakage current in the transformer insulation.

Experiments were conducted to monitor electrical noise generated due to partial ionization of the tiny air gaps in the transformer insulation. The voltage stress, regiured to be applied to the insulation system, for constant 59 units of noise, recorded for the sample of three hundred seventeen transformers.

The voltage readings were analyzed statiscally …

Three-Reflection Halfwave And Quarterwave Retarders Using Dielectric-Coated Metallic Mirrors, T. F. Thonn, R. M.A. Azzam

Electrical Engineering Faculty Publications

A design procedure is described to determine the thicknesses of single-layer coatings of a given dielectric on a given metallic substrate so that a specified net phase retardance (and/or a net relative amplitude attenuation) between the p and s polarizations is achieved after three reflections from a symmetrical arrangement of three mirrors that maintain collinearity of the input and output beams. Examples are presented of halfwave and quarterwave retarders (HWR and QWR) that use a ZnS-Ag film-substrate system at the CO₂-laser wavelength λ = 10.6 µm. The equal net reflectances for the p and s polarizations are computed …

A 250-Kv Two-Pulse Modulator For The Gas Flow Switch Test Facility, David Michael Barrett

Electrical & Computer Engineering Theses & Dissertations

High-pressure spark gap switches are often used in pulsed power systems because of their high power capabilities. Unfortunately, these switches cannot be operated at high repetition rates because of the time required for the switch to recover. However, the recovery rate of a spark gap may be improved by flowing a gas through the interelectrode region so as to remove the hot gases and debris.

A test facility has been designed and constructed at Old Dominion University to evaluate the performance of gas-flow spark gap switches operating over a wide range of voltages and flow parameters. The facility consists of …

Inverting The Ratio Of The Complex Parallel And Perpendicular Reflection Coefficients Of An Absorbing Substrate Using A Transparent Thin-Film Coating, R. M.A. Azzam

Electrical Engineering Faculty Publications

An absorbing substrate can be coated with a transparent thin film of refractive index N₁ (within a certain range) and thickness d such that the ratio of complex reflection coefficients for the p_and s polarizations of the film-covered substrate ρ = R_p/R_s is the inverse of that of the film-free substrate ρ¯ = R¯_p/R¯_s at an angle of incidence ø. A method to determine the relationship among ø, N₁, and d that inverts ρ (i.e., makes ρ = 1/ρ¯) for a given substrate at a given wavelength is described and is …

Inverting The Ratio Of The Complex Parallel And Perpendicular Reflection Coefficients Of An Absorbing Substrate Using A Transparent Thin-Film Coating, Rasheed M.A. Azzam

Electrical Engineering Faculty Publications

An absorbing substrate can be coated with a transparent thin film of refractive index N₁ (within a certain range) and thickness d such that the ratio of complex reflection coefficients for the p_and s polarizations of the film-covered substrate ρ = R_p/R_s is the inverse of that of the film-free substrate ρ¯ = R¯_p/R¯_s at an angle of incidence ø. A method to determine the relationship among ø, N₁, and d that inverts ρ (i.e., makes ρ = 1/ρ¯) for a given substrate at a given wavelength is described and is …

Power Characteristics Of Single‐Mode Semiconductor Lasers, Jaroslava Z. Wilcox, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The basic aspects of power calculations for high‐gain semiconductor lasers are briefly reviewed, and a straightforward one‐dimensional model is described. The relative importance of spontaneous emission, distributed losses, band‐to‐band absorption, and high single‐pass gain are investigated in detail.

Wetlands Preservation And The Protection Of Endangered Species As Limits On Western Water Development, A. Dan Tarlock

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

25 pages.

[Section] 404 Panel Discussion, Gregory J. Hobbs, Jr.

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

5 pages.

Supplemental materials. Includes proposed bill language for Department of the Interior appropriations bill. Outline of key events and dates in the history of water law.

Panel: Section 404 Of The Clean Water Act And Section 7 Of The Endangered Species Act: Potential Impacts On Water Supplies [Supplemental Materials], Wendy C. Weiss

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

57 pages.

Supplemental materials. Includes text of Riverside Irrigation District v. Andrews, 568 F.Supp 563 and Opening Brief of Plaintiff-Intervenor-Appellants in Riverside Irrigation District v. Andrews, Cases No. 83-2114, 83-2115, 83-2119, 83-2230, April 3, 1984.

Groundwater Control Programs Affecting Water Development, Arthur L. Littleworth

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

19 pages.

Ferc, Purpa And The Federal Power Act, Lawrence J. Wolfe

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

62 pages.

Contains references.

The Case For A Legislative Solution To Indian Water Claims, James M. Bush

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

57 pages.

Reserved Water Rights Of Indian Allotments, Richard B. Collins

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

10 pages.

Contains references.

Instream Flows As Reserved Rights On Federal Reservations After United States V. New Mexico, Hank Meshorer

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

10 pages.

Effects Of The Clean Water Act On Water Availability And Development, Paula C. Phillips

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

12 pages.

Introduction To Reserved Water Rights, Ralph W. Johnson

The Federal Impact on State Water Rights (Summer Conference, June 11-13)

16 pages.