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Effect Of Impurity Trapping On The Capacitance‐Voltage Characteristics Of N‐Gaas/N‐Algaas Heterojunctions, K. L. Tan, Mark S. Lundstrom, Michael R. Melloch

Department of Electrical and Computer Engineering Faculty Publications

We have studied the capacitance-voltage (C- V) characteristics of Schottky barriers on inverted nGaAs/ N-AIGaAs and normal N-AIGaAs/n-GaAs heterojunctions. Impurities introduced during film growth produced a negative sheet charge of 6.0 X 10 II cm -2 at the interface of the inverted n-GaAs/N-AIGaAs heterojunction. The effectiveness of GaAs quantum wells in trapping these impurities was investigated. GaAs quantum wells 20 A wide were placed in intervals of 2500 A for the first 0.75 pm of the AIGaAs layer; in the last 0.25 pm, the periodicity of the quantum wells was progressively decreased by half with the last quantum well placed …

An Exact Analysis For Efficient Computation Of Random-Pattern Testability In Combinational Circuits, Sharad C. Seth, Bhargab B. Bhattacharya, Vishwani Agrawal

School of Computing: Conference and Workshop Papers

Experimental evidence shows that low testability in a typical circuit is much more likely due to poor observability than poor controllability. Thus, from theoretical and practical standpoints, it is important to develop an accurate model for observability computation. One such model, in terms of supergates, is proposed in the first part of this paper thus complimenting our earlier work. It is now possible to obtain exact random-pattern testability for each line in a circuit.

The second part of the paper analyzes the supegate structure of a circuit from a graph theoretic viewpoint. Finding a supergate is related to determining the …

A Loran-C Antenna Coupling Unit., Timothy Andrew Reilly 1963-

Electronic Theses and Dissertations

This project is the design of an antenna-coupling unit (ACU) that will operate with the Texas Instruments LORAN-C receiver and a 28-inch antenna. The height of the antenna used at the present is eight feet. Since the application of LORAN-C positioning is being expanded to vehicular location, an eight-foot antenna is not practical. The shorter antenna is necessary to prohibit striking trees, overpasses, etc. The newly designed ACU has more voltage gain to compensate for the attenuation of the incoming signal due to the shortening of the antenna. It also has a bandpass of 90 KHz-110 KHz with the center …

Automation Of A High-Potential Test Instrument, Jeffery D. Breshears

Masters Theses

"Microcomputer controlled automation of a high-potential test set is presented. The design and development of a controller, the support circuits used to interface between the existing electronics and the controller, the IEEE-488 Bus Interface, and a new control panel design with options for manual, automatic, or computer-controlled operation of the instrument are given. Software subroutine listings which exemplify the computer-automation feature of the instrument are also presented. Recommendations for modification and improvement of the given design conclude the paper"--Abstract, page ii.

Propagation Of Optical Waves In Tapered Fibers And Metallic Wave Guides, Bahram Zandi

Dissertations and Theses

The equations tor the propagation of Electromagnetic and Optical waves in tapered fibers and metallic waveguides are derived. Solutions are derived for the displacement of the beam from the waveguide axis as a function of distance along the axis, and also tor the beam width as a function of distance. These equations are solved numerically for a variety of tapered guides. Experiments are conducted which verify the theoretical results.

Faceting At The Silicon (100) Crystal-Melt Interface: Theory And Experiment, Uzi Landman, W.D. Luedtke, R.N. Barnett, C.L. Cleveland, M.W. Ribarsky, Emil Arnold, S. Ramesh, H. Baumgart, A. Martinez, B. Khan

Electrical & Computer Engineering Faculty Publications

Molecular-dynamics simulations and in situ experimental observations of the melting and equilibrium structure of the crystalline Si(100)-melt interface are described. The equilibrium interface is structured, exhibiting facets established on (111) planes.

Silicon-On-Insulator Technology By Crystallization On Quartz Substrates, Helmut Baumgart

Electrical & Computer Engineering Faculty Publications

The purpose of the novel zone-melting recrystallization process (ZMR) is to produce single crystalline Si films on Si02 of high crystalline perfection, which are suitable for device fabrication and subsequent industrial applications. However, silicon films grown on amorphous insulating substrates without seeding contain regularly spaced subgrain boundaries as their predominant growth defect and to a lesser degree twin boundaries and some grain boundaries. Detailed materials studies have revealed the core structure of these extended defects and the fundamental mechanisms responsible for subgrain boundary formation. The nature and origin of subgrain boundaries is reviewed and a model for polygonization of the …

Total Refraction At Oblique Incidence By A Transparent Bilayer Coating On A High-Index Transparent Or Absorbing Substrate, R. M.A. Azzam, Karim Javily

Electrical Engineering Faculty Publications

Transparent bilayer coatings that produce total refraction (TR) of obliquely incident monochromatic light into an underlying substrate are considered. When the substrate is transparent, it is shown that TR takes place without any accompanying change of polarization. Totally refracting bilayers are realizable in the IR where high-refractive-index substrates are available. This is illustrated by a BaF₂–ZnSe bilayer on a Ge substrate at a 10.6-μm (CO₂-laser) wavelength and 45° angle of incidence. Limited changes of the angle of incidence, wavelength, and refractive indices and thicknesses of the two films of the bilayer are introduced, and their effects …

Investigation Of Electronic Holography Using Spice Computer Simulation Experiments, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

Using SPICE experiments, it has been possible to verify most of the important aspects of electronic holography. The generation and properties of dynamic echoes under different types of nonlinearities have been extensively tested, and some new information has been garnered in the process. The case of pulse and generalized memory echoes has also been tested, and the results have been fairly satisfactory. Most of all, the simplicity with which the intriguing concept of memory echoes has translated into the circuit implementation on SPICE, and the closeness of the results to predicted behavior have been somewhat of a pleasant surprise.

Since …

Beam Propagation In Periodic Quadratic-Index Waveguides, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Several techniques are described for studying the propagation of off-axis polynomial Gaussian beams in media having straight axes and periodic z variations of the quadratic refraction and loss coefficients. For some periodic variations, exact analytical solutions of the paraxial equations are possible, and for sufficiently slow variations, WKB solutions can always be obtained. All results are expressed in conventional beam matrix form.

Free Electron Density Measurements By Ir Absorption In Cds, Jack L. Boone, Gene Cantwell, Michael D. Shaw

Electrical and Computer Engineering Faculty Research & Creative Works

A contactless method for determining the spatial variation of the free carrier density in CdS is presented. The method involves the correlation of IR transmission with the free carrier density via the IR absorption coefficient. Preliminary measurements indicate a free electron density sensitivity of less than 5x1014 cm-3 and a spatial resolution which is limited only by the spot size of a CO2 (λ=10.6 μm) laser; this should be of the order of 100 μm. Experimental results indicate that the predominate scattering is due to impurity interaction at room temperature; this is indicative of the high degree of compensation in …

Retrospective Data Filter, Richard J. Prengaman, Robert E. Thurber, Joe Phipps, Ronald I. Greenberg, Wai L. Hom, James F. Jaworski, Guy W. Riffle

Computer Science: Faculty Publications and Other Works

In a target detection communication system, apparatus and method for determining the presence of probable targets based on contacts (which can indicate the presence of a target, noise, chatter, or objects not of interest) detected within a predefined position sector or sectors over a specified number of scans. The position of each detected contact, as a contact of interest, is compared with the positions of contacts detected at previous times or scans. Velocity profiles indicate which previous contacts support the likelihood that the contact of interest represents a target having a velocity within a defined band. The likelihood, which can …

Bonding In Metal Hexacarbonyls, Ramiro Arratia‐Perez, Cary Y. Yang

Electrical and Computer Engineering

A detailed analysis of the valence molecular orbitals (MO) in Cr(CO)₆, Mo(CO)₆, and W(CO)₆is presented. A generalized bonding scheme, which includes participation of metal p electrons in the metal–ligand bond, emerges from our results. The metal p electrons are also responsible for effecting mixings between different sets of carbonyl 5σ and 1π orbitals. In these hexacarbonyls, this ‘‘σ’’+‘‘π’’ metal–ligand bonding contribution is quantitatively as significant as the well known σ donation and π‐back‐donation components. The MO’s obtained with the Dirac scattered‐wave (DSW) method are also used to determine the importance of relativistic effects in …

Electronic Control Of Electric Motors, Armando Castillo

Graduate Research Papers

The purpose of this study was to investigate the theoretical information on electronic control of electric motors as well as the current state-of-the-art on this topic. It was also intended to carry out some of the experimental circuits discussed, for future instructional situations.

Design Of Multivariable Feedback Control Systems Via Spectral Assignment, Mohsen Marefat

Electrical & Computer Engineering Theses & Dissertations

During the past 15 year s significant advances have been made towards developing viable synthesis- techniques for multivariable feedback control systems. The entire aggregate of this theoretical work has been reviewed and consolidated. Diverse notations have been standardized into a single system. A two-step design philosophy for spectral assignment has been developed which first meets stability and time response requirements by assigning eigenvalues and eigenvector s and then provides for attainment of secondary objectives without significant deviation from the initial assignment. Finally, a computer-aided design package has been created to streamline the process of mathematical calculation and to allow users …

High Performance Switching Circuits For Vlsi, Ali Reza Feizi

Electrical & Computer Engineering Theses & Dissertations

Interconnection topology and device performance are of major concern in the design of LSI/VLSI systems, Pass networks are very suitable in this regard because of low power consumption, high density, and simple interconnection topology. A special type of pass networks called Binary Tree Structured (BTS) pass networks uses almost minimum number of transistors for the design of switching circuits. An algorithmic procedure is developed here for BTS pass networks which is very efficient in terms of both execution time and memory space. Based on these networks, the necessary and sufficient conditions are derived for the design of multiple-output pass networks. …

Randomized Routing On Fat-Trees, Ronald I. Greenberg

Computer Science: Faculty Publications and Other Works

Fat-trees are a class of routing networks for hardware-efficient parallel computation. This paper presents a randomized algorithm for routing messages on a fat-tree. The quality of the algorithm is measured in terms of the load factor of a set of messages to be routed, which is a lower bound on the time required to deliver the messages. We show that if a set of messages has load factor lambda on a fat-tree with n processors, the number of delivery cycles (routing attempts) that the algorithm requires is O(lambda+lgnlglgn) with probability 1-O(1/ …

Reliability Evaluation Of Liquid Crystal Displays Under Accelerated Test Conditions, Ravi Sankar Kalyandrug

Theses

This study has determined the effects of high temperature and humidity on the reliability of liquid crystal dis-plays.

Reliability life testing was done on variety of LCD samples under different operating conditions. All the besting was done under accelerated conditions, including high temperature of 85°C and relative humidity of 70%. A number of failure modes were identified in the long series'of tests.

Among many failure modes such as peeling of seal, degradation of polarizers etc., the most important is the degradation of alignment of liquid crystal molecules. Leakage current measurements were made on all the LCD samples before and after …

Frequency Characterization Of A Thin Linear Antenna Using Diakoptic Theory, Howard Harold Smith

Theses

A frequency dependent analytical expression for the input impedance of a thin wire antenna is obtained using diakoptic theory. In diakoptic theory the linear antenna is seperated into electrically short segments where each segment is treated as a two-port network. This approach eliminates the need for an integral equation formulation. An impedance matrix is found which characterizes coupling between all segments. By expanding the free space Green's function in a power series in wavenumber k each entry in the resultant impedance matrix is obtained as a function of frequency. Enforcement of the continuity of currents and equality of scalar potentials …

Present Reliability Of Liquid Crystal Display Devices, C. N. Suresh

Theses

The purpose of this Thesis is to study the life of liquid crystal display devices as at present available in the market place. To accomplish this, accelerated tempera-ture conditions at 77°C and 85°C were used.

During the last few years, there has grown a tremendous interest in wide range temperature operating and fast LCDs. It is therefore important to understand how LCDs behave under these conditions.

The reliability of a liquid crystal display is usually measured in terms of a quantative degradation in electrical performance and a degradation in visual appearance. The degradation in visual appear6knce may manifest itself as …

Further Development Of Preparation And Measurement Techniques For Triode-Sputtered Mercury Cadmium Telluride Thin Films, Tai-On Chan

Theses

The modified MRC 8800 R.F. triode sputtering system was used for mercury vapor sputtering (Hg^1-xCd^x)Te targets onto N-type (111) silicon substrates with a resistivity of 70 to 90 ohm-cm. Deposition rates were in the 2.6 to 3.6 A/sec range, A Hall mobility value, at 87°K, of 2550 Cm²/V•sec with a carrier concentration of 7(10¹⁵) cm^-3 was obtained for 9 μm thick films with an X-value of 0.25. Obtaining good sputtered films reliably was dependent on having targets that would not crack when bombarded with mercury ions. Improvements in the methods used …

An Application Of A Heuristic Search Algorithm In Biomedical Images On The Magiscan Ii Image Analysis System, Patricia S. Humes

Masters Theses

The goal of this project was to successfully apply a heuristic search algorithm in the image analysis environment of the Magiscan II Image Analysis System. The purpose of this particular application was to enable the specific segmentation of a white blood cell image by outlining the boundary of the cell nucleus, a process not currently possible with the existing system software.

The method used involved tracing boundaries by choosing points based on a calculated cost factor. The cost factor has several input parameters that will enable it to be applied in a wide variety of applications. Several different cells' nuclei …

An Inventory Of Maine's Telecommunications System, Maine State Planning Office

Maine Collection

An Inventory of Maine's Telecommunications System

Prepared for the Maine State Planning Office by Joseph M. Chaisson and Valerie Lamont of the Telecommunications Research Program at Westbrook College in Portland, Maine. July, 1985.

"The Primary purpose of this report is to provide information for Governor Brennan's Task Force on Telecommunications. The inventory also can be widely used as a reference by persons and organizations concerned with providing telecommunications services in Maine."

Contents: Introduction / Local Telephone Service / Mobile Telephone Service / Digital Termination Service / Cable Television / Paging Systems / Intra-State (Intra-LATA) Public Services / Intra-State (Intra-LATA) Private …

The Unification And Decomposition Of Processing Structures Using Lattice Theoretic Methods, David L. Livingston

Electrical & Computer Engineering Theses & Dissertations

The purpose of this dissertation is to demonstrate that lattice theoretic methods can be used to decompose and unify computational structures over a variety of processing systems. The unification arguments provide a better understanding of the intricacies of the development of processing system decomposition. Since abstract algebraic techniques are used, the decomposition process is systematized which makes it conducive to the use of computers as tools for decomposition. A general algorithm using the lattice theoretic method is developed to examine the structures and therefore decomposition properties of integer and polynomial rings. Two fundamental representations, the Sino-correspondence and the weighted radix …

Color Display Of Vowel Spectra As A Training Aid For The Deaf, Amir Jalali Jagharghi

Electrical & Computer Engineering Theses & Dissertations

The objective of this research was to develop a transformation for mapping speech parameters to color parameter. This transformation is done in real-time, and the resulting color parameter are continuously displayed on a color monitor. This visual speech display is to be used as a speech articulation training aid for the deaf. The conversion of speech acoustic signals into speech parameter was accomplished using special -purpose electronics. The real-time conversion of speech parameter to display parameter was controlled by an 8086/8088 microprocessor operating in an S-100 bus structure. The coefficients of the Karhunen-Loeve series expansion of speech power spectra were …

Minimum Probability Of Electron-Hole Pair Generation By Blackbody Radiation, Cheng-Hsiao Wu

Electrical and Computer Engineering Faculty Research & Creative Works

Using the small-perturbation assumption that all the useful work is in the form of electron-hole pairs when photons from a blackbody radiation source are incident on a quantum device, we derive the minimum probability of generation of one or more pairs of electron holes. Using the Planck radiation formula for the solar spectrum at 6000 K and for the quantum device at 300 K, this minimum probability is about 0.8 at low photon frequency and approaches the limiting value of 0.95 at high frequency. Its relation to maximum efficiency of a quantum device is discussed.

Investigation Of Pre-Detection Signal Processing Of Pseudonoise Communication Signals In The Presence Of Additive White Gaussian Noise And Cw And Bursty Interference, Israel Mayk

Dissertations

By comparison to conventional communication systems, spread-spectrum systems are known to be less affected by interference because of their large dimensionality in signal space. Nevertheless, significant performance degradation is experienced when large interference exists in a few or even one signal coordinates. In this case, interference reduction techniques are also known to provide additional processing gain. A novel class of pseudonoise (PN) invariant algorithms is derived to reduce the impact of interference and restore much of the structure of PN signals received in the presence of interference and noise. A PN signal received by a pre-detection signal process (PDSP) implementing …

The Mean Return Time To A State For A Markov Chain Representing In Telephone Conversations, M Luhanga

Tanzania Journal of Engineering and Technology (TJET)

The mean return time to a state for a Markov chain representing N off-hook telephone conversations can be obtained by using ergodic flow rates [1] or renewal theory [2]. In this paper it is shown that the same result may be obtained by using no more knowledge of stochastic processes than the solution of time-homogeneous Chapman-Kolmogorov equations.

An Electro Hydrodynamic Study Of The Negative Corona Electric Wind, Henry Thadei Kadete

Tanzania Journal of Engineering and Technology (TJET)

The velocity of corona generated electric wind is measured. From the velocity profile mass movement and electrokinetic conversion efficiencies are deduced. High speed schlieren photographs illustrate the form of the velocity distribution function as well as its high degree of turbulence.

Identification Of Defect Centers In Hg1-XCdXTe Using Their Energy Ievel Composition Dependence, Charles W. Myles, P. F. Williams, R. A. Chapman, E. G. Bylander

P. F. (Paul Frazer) Williams Publications

We have extended the Kobayashi, Sankey, and Dow [Phys. Rev. B 25,6367 (1982)] theory of deep levels in Hg_1-xCd_xTe to include (vacancy, impurity) nearest-neighbor pairs. In qualitative agreement with the results obtained by these workers for isolated point defects, we find that the composition dependences (dE /dx) of the defect energy levels associated with such complexes depend on the site occupied by the impurity atom. Furthermore, we find that the composition dependences of some of the defect levels produced by such a complex are very different than the dE /dx of levels associated with …