Digital Commons Network^™

Antireflecting And Polarizing Transparent Bilayer Coatings On Absorbing Substrates At Oblique Incidence, R. M.A. Azzam, Karim Javily

Electrical Engineering Faculty Publications

The condition of zero reflection of p- and s-polarized light by a transparent bilayer on an absorbing substrate is derived in the form |g_ν(ø,N_i)| ≤ 1, where g_ν is a function of the angle of incidence ø, the refractive indices N_i(i = 0,1,2,3) of the system, and the polarization state ν (= p or s). As an application, the air-Si₃N₄-SiO₂-Si system is considered at two laser wavelengths λ = 6328 and 3250 Å. The thicknesses of the two films of the bilayer and the …

Study Of Mo, Au, And Ni Implanted Molybdenum Laser Mirrors By Spectroscopic Ellipsometry, Paul G. Snyder, George H. Bu-Abbud, Jae Oh, John A. Woollam, David Poker, D. E. Aspnes, David Ingram, Peter Pronko

Department of Electrical and Computer Engineering: Faculty Publications

The implantation of 150 kev molybdenum ions into polished molybdenum laser mirrors is found to increase the complex dielectric constant in the visible spectrum. Analysis using the Bruggeman effective medium approximation demonstrates that the increase is due to surface smoothing and that the surface is made nearly atomically smooth by a fluence of 5 x 10¹⁵ /cm². Implantation of Au at 1Mev caused considerable microscopic roughening, as well as a change in the bulk optical properties. 3 MeV Ni ion implantation caused only a slight surface roughening. A thin dielectric film (probably a hydrocarbon) is found to …

Fourier Transforms Over Warped Domains., Richard E. Dubroff

Electrical and Computer Engineering Faculty Research & Creative Works

The Author Shows that There May Be an Advantage to Computing Fourier Transforms Over Warped Domains. an Example of Such an Improvement is Provided. It is Also Shown How the Fourier Transform May Be Evaluated from Data Observed over a Warped Domain.

Growth Of Tungsten Selenide Films Through Pyrolytic Conversion And Anodic Electrooxidation Of Ammonium Selenotungstate ((Nh4)2wse4), R. D. Engelken, T. (Thomas) P. Van Doren, Jack L. Boone, A. K. Berry, A. Shahnazary

Electrical and Computer Engineering Faculty Research & Creative Works

WxSey thin films have been prepared by the spray pyrolysis and anodic electrodeposition of solutions of ammonium selenotungstate, (NH4)2WSe4, with y/x usually between two and three for the sprayed films and y x>>1 for the electrodeposited films. The sprayed films indicated regions of crystalline WSe2 and have optical absorbance spectra consistent with a mixture of WSe2, WSe3, and selenium. The electrodeposited films are totally amorphous, highly photoconductive, and have optical absorbance spectra typical of amorphous or vitreous selenium. The sprayed films transform into WO3 at temperatures greater than 350°C in the presence of oxygen wile the electrode-posited films tend …

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) / …

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 …

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 …

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 …

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.

Microcomputer Controlled Instrumentation System For Studies Of Metabolic Changes In Rats, Murat Dertlioglu

Theses

The system measures the respiratory exchange in rats in a controlled experiment. An interface unit provides data, received from several measurement instruments such as gas analyzers, an electronic flowmeters, electronic thermometer and an electronic hygrometer, to the computer. The data is gathered from different chambers in a multiplexed mode.

The computer samples the chambers sequentially and prints out the results and stores them on the disk. The sampling duration of each chamber and the number of the rats to be tested can be programmed. The system can perform experiments with twelve animals, in the following arrangments, either one group of …

Computer Based Instrumentation System For Measurement Of Cardiac Output In Small Animals, Prasad L. Gavaskar

Theses

The task of the instrumentation system is to measure cardiac output in animals like rats, dogs, etc. A thermal-dilution method is used for this purpose. The temperature change due to injection of saline is picked up by thermo-couple microprobes implanted in the blood-vessel. The signal after conditioning is fed to a data acquisition system controlled by a computer.

With the help of a computer it is thus possible to monitor and control an experiment on several animals. The computer can sample the chambers sequentially. The sampling cycle duration and frequency are programmable. The data is collected and processed to determine …

Automated Instrumentation System To Monitor Behavioral Experiments, Dilip S. Gokhale

Theses

An instrumentation system has been designed to monitor behavioral experiments on monkeys. This instrumentation system is capable of performing these experiments in an automated manner without any human intervention. It is capable of monitoring these experiments concurrently in six boxes. It exhibits several features that make it more versatile than previous instrumentation systems. It is also capable of storing the data generated on to a floppy disk and later transmitting it to the mainframe.

Another feature that makes it more versatile is the flexibility of the system. Presently it is configured to run experiments with variable interval schedules. However with …

Decision Rules Applied To Spread Spectrum Signal Detection, Richard Jae Kim

Theses

Decision rules for detection of spread spectrum signals were investigated. For each decision rule, error and erasure probabilities were analyzed. The obtained data was used to plot PE vs Pe for constant signal-to-noise ratio (SNR). With the use of the probability of a word error curves the optimum threshold setting was found for a given SNR.

FSK (orthogonal signalling) and PSK (antipodal signalling) were considered for modulating the chips. When the PE vs Pe plots for FSK and PSK were compared, PSK performed better than FSK by a ratio of 6 dB.

Finally, analog and digital correlation of the received …

An Investigation Of Characteristics Of Blood Velocity In A Simulated Circulation System, Yung-Gang Wu

Theses

The major objective of this thesis is to find the relationship between the blood velocity and the stenosis of the vessel. Tests were performed with different degrees of stenosis at varied logitudinal positions from the testing probe in the vessel of a Z-80 microprocessor controlled artificial circulation system.

Three methods were used to detect the velocity in the vessel: continuous wave Doppler, Pulse Doppler, and a hot-film device. The first method can get the average velocity, while the latter two have the capability to find a velocity profile, and all are important indicators to the arterial occlusion phenomenon.

An analysis …

Performance Modeling And Simulation Of Multiple Microcomputer Systems, Moorthy Narayana Hariharan

Theses

Multiple processor systems are the logical choice for applications demanding high computing power, throughput and reliability. Moderately coupled Multiple Microprocessor systems can be applied to a variety of applications demanding high performance. The structure of Multiple Microprocessor systems is examined. Various interconnection structures are analysed for performance comparisons.

Queueing theory is a powerful tool in modeling and analysing Computer systems. Queueing models are developed for popular Multiple processor interconnection topolog es like the Shared memory, Shared bus, Star and Loop configurations.

The usefulness of Digital computer Simulation techniques in estimating the performance of Multiple processor systems is demonstrated through a …

Division-Of-Wave-Front Polarizing Beam Splitter And Half-Shade Device Using Dielectric Thin Film On Dielectric Substrate, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

The Development Of A Microprocessor Controlled Linearly Actuated Valve Assembly, Raymond H. Wall

Mechanical & Aerospace Engineering Theses & Dissertations

The development of a proportional fluid control valve/assembly is presented. This electro-mechanical system is needed for space applications to replace the current proportional flow controllers that use bulky hydraulic or pneumatic actuation systems. The flow is controlled by a microprocessor system that monitors the control parameters of upstream pressure and requested volumetric flow rate. The microprocessor achieves the ·proper valve stem displacement by means of a digital linear actuator. A linear displacement sensor is used to measure the valve stem position. 'Ibis displacement is monitored by the microprocessor system as a feedback signal to close the control loop. With an …

Block Transform Coding Of Presample Filtered Data, Thomas A. Shull

Electrical & Computer Engineering Theses & Dissertations

This dissertation addresses the application of non-adaptive transform coding for bit rate reduction of presampled filtered data. Transform coding is examined as an alternative to conventional pulse code modulation (PCM) for multi-source, fixed rate data acquisition systems. Typical bandlimiting presample filters introduce redundancy into the sequence of data samples. Linear transformation of successive N-length blocks of the data sequence and subsequent binary coding of the resulting components is shown to lead to reduced average bit rate for the same less distortion as PCM.

Four Butterworth filters, two corresponding to eight bit PCM systems, and two corresponding to ten bit PCM …

Proposal For A Digital Pseudorandom Number Generator, C. Downey

Articles

A digital hardware implementation of a linear congruential sequence generator using shift and add techniques of multiplication is described. The sequence is of long period, low serial correlation and is rectangularly distributed. The method has certain advantages over conventional feedback shift register techniques.

Awqpsk : An Optimum Modulation Technique For Spread Spectrum Communication, Madjid A. Belkerdid

Retrospective Theses and Dissertations

Quadrature phase shift keying (QPSK) and minimum shift keying (MSK) are the two most used M-ary modulation techniques in Direct-Sequence (DS) Spread Spectrum Communication systems. This thesis introduces a new modulation technique that can compete well with QPSK and MSK in many applications. This new modulation technique, made up of a superposition of one QPSK signal and two amplitude weighted QPSK signals, is called Amplitude Weighted Quadrature Phase Shift Keying (AWQPSK). It is found to have the same probability of error as QPSK and MSK techniques. It has a higher bandwidth efficiency in bits/sec/Hz than QPSK and MSK. It has …

Correction To “Two-Dimensional Markov Representations Of Sampled Images”, John A. Stuller

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

A Microprocessor-Controlled Message Display System, Paul D. Stigall, Brian E. Lenharth

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

Distribution System Protection With Decentralized Generation Introduced Into The System, Behruz Fardanesh, Earl F. Richards

Electrical and Computer Engineering Faculty Research & Creative Works

Cogeneration from renewable energy sources has been universally proposed as a partial alternative to the solution of our nation's energy problems. New technical, safety, and operational problems are introduced when this generation is placed into a distribution grid. Addressed is the problem of distribution system protection with the introduction of cogeneration sources and the changes and modifications which may be required in the application of present-day protection devices. A sample system is considered, and system protection and coordination with and without cogeneration has been calculated through a digital fault and system protection coordination program. The results indicate through the study …

Decentralized Optimal Control With Application To Dynamic Routing In Computer Communication Networks, Ning Wang

Dissertations

This research considers the dynamic routing problem of computer communication networks in the framework of decentralized control theory. The routing dynamics are modeled in terms of a state equation with multiple controllers. Routing, or control of message flow, is formulated as an optimal control problem with multiple decision makers. Each decision maker may have access to different set of information and work cooperatively to optimize a common system performance index.

Necessary and sufficient conditions for optimality are derived for a system with a deterministic and a stochastic traffic patterns under a linear information structure and a quadratic performance index. The …

Data Acquisition And Parameter Identification In Electro-Oculography, Wolfgang Poelzleitner

Theses

Electro-Oculography (EOG) is used in clinical ophthalmology to measure the time response of the corneoretinal potential (CRP) to changes in light intensity. An automatized data acquisition and system modeling link has been developed that significantly reduces processing time presently required for EOG. The data acquisition is performed on a microprocessor based instrument, which supervises the EOG-test, measures the potential and, after completion of the test, transfers the results to a mainframe computer. Parameter identification routines provide graphical representation and mathematical models for the CRP. Both nonlinear curve fitting methods and Least Squares System Identification schemes are used.

Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, Partha P. Banerjee, Adrianus Korpel, Karl E. Lonngren

Electrical and Computer Engineering Faculty Publications

Self‐refraction effects have been observed during the propagation of deep‐water capillary‐gravity waves. The observations are shown to be in qualitative agreement with the theory of self‐focusing and defocusing in a cubically nonlinear medium in the presence of diffraction.

Optimization Of A New Linear Fm Detector Using Digital Signal Processing Techniques, Edward J.A. Kratt

Dissertations

This dissertation describes and synthesizes a new member of the family of FM detectors introduced earlier by Klapper and Kratt. A salient property of these detectors is low delay with excellent sensitivity. The emphasis in the new detector is on the ease of digital implementation. In addition, the new detector is also extremely linear. In congruence with the other Klapper-Kratt detectors, it makes use of zero group delay elements, balance at RF, quasi-synchronous detection and carrier cancellation. The Performance of the detector is mathematically analyzed under the conditions of a modulated input wave, sinewave [sic] interference, and noise. The results …

The Role Of Electrical Noise In Screening Transformers Prone To Failure, Rajeev D. Shirodkar

Theses

Insulation used as a barrier between the high voltage and low voltage windings of a transformer has sites of in- homogeneities like pinholes, cracks or voids, developed during the manufacturing process. Thus, these minute air pockets are stressed much more than the solid dielectric, on the application of a voltage stress, because the dielectric constant of the solid insulation is many times that of the air dielectric. As a result, excitation or ionization takes place in the air (gases). The amount of excited or ionized molecules is proportional to the volume of the inhomogenei- ties within the insulation.

Therefore, experiments …

An Experimental System For Observation Of The Rat Coronary Microcirculation Using Digital Image Processing, Wolfgang Braun

Theses

A system was constructed which allows direct observation of the coronary microcirculation of the beating rat heart. An EKG triggered strobe is used on the microscope light source to "stop" the action of the beating heart so the surface microvessels can be observed di rectly under the microscope. Experimental results are recorded on videotape and played back for frame-by-frame analysis of the data using digital Image processing techniques such as digital filtering, image extraction, image enhancement and edge detection.

The application of image enhancement techniques (high order and low order enhancement methods ) as well as edge detection using a …