Engineering Commons^™

Surface Flashover Of Silicon, Frank E. Peterkin, Tim Ridolfi, Lonnie L. Buresh, Brian J. Hankla, D. K. Scott, P. F. Williams, William C. Nunnally, B. L. Thomas

P. F. (Paul Frazer) Williams Publications

The development of high-voltage semiconductor devices has been hampered by the occurrence of flashover at the surface of the semiconductor. The physical mechanisms responsible for this phenomenon are not understood. We present new empirical information which clarifies the processes responsible for surface flashover in a vacuum ambient by showing clearly that in flashover current flows primarily inside the semiconductor surface rather than in the ambient. This observation is in fundamental disagreement with the standard model for vacuum flashover of insulator surfaces.

Modeling AiXGa1-XAs Optical Constants As Functions Of Composition, Paul G. Snyder, John A. Woollam, Samuel A. Alterovitz, Blaine D. Johs

Department of Electrical and Computer Engineering: Faculty Publications

Three models for the dielectric function ε_x (hv) of Ag_xGa1_1-xAs are reviewed. All are based on measured optical constants at discrete compositions. The validity of each mode1 near critical pint energies, and otherwise, is evaluated. Only the energy-shift model is appropriate over the entire available spectrum ( 1.5-6.0 eV), including the band-gap (E₀) region.

Technological Upgradation Policies Of The Steel Industry And Impact Of The Steel Industry In The Indian Economy, K K Saxena, Binayak Rath

IIMB Management Review

In India, the iron and steel industry in general occupies an important Position among the manufacturing industries. The priorities attached to this sector can be explained from the Second Five Year Plan document which mentioned that the expansion of iron and steel industry has obviously the highest priority than other industries because the tempo of progress of the economy. Hence, Second Plan onwards the industry has made a rapid stride in our economy. A number of Integrated Steel Plants (ISPs) in the public sector have been set up to boost up production. Today these ISPs contribute a significant portion of …

Linear Programming By G.V. Shenoy, New Delhi: Wiley Eastern Limited, 1989., A K Rao

IIMB Management Review

No abstract provided.

Composite Structure Ultimate Strength Prediction From Acoustic Emission Amplitude Data, James Lewis Walker Ii

Master's Theses - Daytona Beach

The acoustic emission (AE) given off by a structure as it is stressed provides a passive means to characterize flaw growth activity in complex structures. This thesis demonstrates how the qualitative analysis of AE data can be refined to provide a quantitative tool for predicting the ultimate strength of composite tensile test specimens. From an original sample set of only six specimens, a multivariate statistical analysis was used to generate an ultimate strength prediction equation. The variables of the multivariate statistical analysis were obtained through the mathematical modeling of the specimen’s AE amplitude distributions produced during proof testing. Ultimate strengths …

A Multi-Scale Approach For Recognizing Complex Annotations In Engineering Documents., Andrew Francis Laine, William Ball, Arun Kumar

All Computer Science and Engineering Research

This paper describes a novel method of character recognition targeted for extracting complex annotations found in engineering documents. The results of this work will make it possible to capture the information contained in documents used to support facilities management and manufacturing. The recognition problem is made difficult in part because characters and text may be expressed in arbitrary fonts and orientations. Our approach includes a novel incremental strategy based on the multi-scale representation of wavelet decompositions. Our approach is motivated by biological mechanisms of the human visual systems. Using wavelets as a set of basis functions, we may decompose an …

Lake Mead Nutrient Enhancement Project, Peter D. Vaux, Larry J. Paulson, Nevada Department Of Wildlife, National Oceanic And Atmospheric Administration

Publications (WR)

The Lake Mead Fertilization Project is a research program designed to investigate the potential for using large-scale artificial fertilization to enhance the game fisheries of this reservoir through an increase in the population of threadfin shad, the system's primary forage species. A substantial decline in the population of largemouth bass, together with poor condition of adult striped bass, are the two major issues affecting the Lake Mead game fisheries. Both issues have been hypothesized to be a result of an inadequate amount of forage in the reservoir. Previous studies have in turn suggested that a major factor limiting the shad …

Dendrite Tip Radii In Directionally Solidified Pb-8.4-Atmospheric-Percent-Au, Surendra N. Tewari

Chemical & Biomedical Engineering Faculty Publications

The cell/dendrite tip radii in directionally solidified Pb-8.4at.%Au have been investigated as a function of the growth speed and thermal gradient in the liquid at the tip. Dendrite growth models are not able to predict quantitatively the tip radii and tip compositions separately because of the occurrence of thermosolutal convection during growth. However, the relationship between the destabilizing solutal gradient, the stabilizing thermal gradient and the capillarity at the tip assumed using the ''marginal stability'' criterion is supported by the experimental data.

Feasibility Of Incorporation Of By-Pass Dust In Clay Bricks, Amr Aly Gamal El-Din

Archived Theses and Dissertations

No abstract provided.

Assessment Of Flat Plate Collectors For Solar Powered Rankine Cycle, Inas Mokbel Ghanem

Archived Theses and Dissertations

No abstract provided.

Sahkti Limited, Sanjoy Goel

IIMB Management Review

No abstract provided.

Comparison Of Digital Controllers Used In Magnetic Suspension And Balance Systems, William A. Kilgore

Mechanical & Aerospace Engineering Faculty Publications

Dynamic systems that were once controlled by analog circuits are now controlled by digital computers. Presented is a comparison of the digital controllers presently used with magnetic suspension and balance systems. The overall responses of the systems are compared using a computer simulation of the magnetic suspension and balance system and the digital controllers. The comparisons include responses to both simulated force and position inputs. A preferred digital controller is determined from the simulated responses.

Microwave Nondestructive Detection And Evaluation Of Disbonding And Delamination In Layered-Dielectric Slabs, R. Zoughi, Sasan Bakhtiari

Electrical and Computer Engineering Faculty Research & Creative Works

A microwave nondestructive technique for detection and evaluation of disbonding and delamination in layered-dielectric-slabs backed by a conducting plate is discussed. The theoretical development begins by considering an incident wave illuminating such a medium and then formulating the characteristics of the wave reflected by the metal plate. An effective reflection coefficient is determined in this way whose phase characteristics are used in the detection and evaluation of delaminations in the media. The characteristics of this phase as a function of several parameters such as delamination dielectric constant and thickness, slab dielectric constant, and thickness and the frequency of operation are …

The Waveform Relaxation Method For Systems Of Differential/Algebraic Equations, Marija D. Ilić, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

An extension of the waveform relaxation (WR) algorithm to systems of differential/algebraic equations (DAE) is presented. Although this type of application has been explored earlier in relation to VLSI circuits, the algorithm has not been generalized to include the vast array of DAE system structures. The solvability and convergence requirements of the WR algorithm for higher-index systems are established. Many systems in robotics and control applications are modeled with DAE systems having an index greater than two. Computer simulation of these systems has been hampered by numerical integration methods which perform poorly and must be explicitly tailored to the system. …

Effect Of Refining On The Brightness Of Softwood Ctmp And Tmp Pulps, Ashok Kumar Mishra

Masters Theses

The main objective of this study was to investigate the effect of refining on the brightness of softwood chemithermomechanical (CTMP) and thermomechanical (TMP) pulps. Seven different pulps were refined using a laboratory Valley beater. Brightness, opacity, tensile index, TEA, and fines content of these pulps were determined at four different freeness levels. Scattering (s) and absorption (k) coefficients of these pulps were calculated. One-way analyses of variance (ANOVA) were applied to determine the significance of change in brightness.

Changes in s-values were significantly affected by fiber morphology of different wood species. Refining increased the k-values of the pulps. When the …

Extraction And Measurement Of Multi-Level Parallelism In Productions Systems, George A. Sawyer

Theses and Dissertations

Productions systems provide a flexible and powerful means for expressing and solving problems using high-level reasoning approaches. Unfortunately applications based on the production system paradigm are very compute intensive and therefore execute very slowly on conventional computer architectures. Lack of execution speed therefore limits the use of production systems in many time sensitive and complex tasks. Researchers have demonstrated that increasing the execution speed of production systems through the use of small scale parallel computer architecture is possible, however demonstrated execution speed is still several orders of magnitude below the desired level of performance. Past research indicates that there exists …

Graphical Representation Of Parallel Algorithmic Processes, Edward M. Williams

Theses and Dissertations

Algorithm animation is a visualization method used to enhance understanding of functioning of an algorithm or program. Visualization is used for many purposes, including education, algorithm research, performance analysis, and program debugging. This research applies algorithm animation techniques to programs developed for parallel architectures, with specific on the Intel iPSC/2 hypercube. While both P-time and NP-time algorithms can potentially benefit from using visualization techniques, the set of NP-complete problems provides fertile ground for developing parallel applications, since the combinatoric nature of the problems makes finding the optimum solution impractical. The primary goals for this visualization system are: Data should be …

Model-Based Reasoning In Electronic Repair, Kenneth B. Cohen

Theses and Dissertations

Diagnosis is the process of identifying the cause for an observed behavior of a system. Model-based reasoning uses knowledge of the behavior of the component and the interconnection of the components to diagnose a system. This thesis investigates the application of model-based reasoning to the problem of isolating faulty components of an analog electronic circuit. More specifically, this thesis describes an architecture for a model-based diagnostic system for electronic modules, implements an assumption-based truth maintenance system (one of the component parts of a model-based diagnostic system), and creates the interface between the truth maintenance system and the diagnostic system.

Nonlinear Analysis Of A Spinning Symmetric Satellite In An Elliptical Orbit, Michael Ulisse

Theses and Dissertations

Controlled and uncontrolled equations of motion for a spinning symmetric satellite in an elliptical orbit are analysed using Floquet theory, Poincare maps, and continuation. The equations of motion for the uncontrolled system are derived via energy methods. A simple feedback controller design and one based on Floquet theory are presented. Parameters varied in the equations of motion include the spin about the symmetry axis of the satellite, the inertia ratio of the satellite, the eccentricity of the orbit, and the controller gains. Floquet analyses determine local stability and bifurcation points. Poincare maps exhibit some interesting and complex structure in the …

Realistic Orbits About The Martian Moons, Samuel R. Bryant

Theses and Dissertations

Orbits about the Martian moons, Phobos and Deimos, previously found to be stable by the Poincare surface of section technique in a restricted three- body system, were investigated with non-zero eccentricity of the moons added to the dynamics of the planar four-body system (Mars, moon sun, artificial satellite). Although not strictly applicable to this case, the surface of section technique was used to verify whether or not the previously found stable orbits were realistic when a real world perturbation was added to the system dynamics. The surface of section technique involves the numerical integration of several orbits with the same …

Recursive Optimization Of Digital Circuits, John Knutson

Theses and Dissertations

The goal of this thesis is twofold: first, to identify the advantages and disadvantages of existing optimization systems and second, to develop an optimization system that uses Boolean principles to generate a recursive realization of combinational logic. Current multi-level optimization systems fall into two categories: local optimization which removes redundancy by pattern matching on a local scale and global optimization which works with the equations that specify a circuit rather than with the circuit implementation itself. While global systems are very flexible and can produce near-optimal solutions, they are inherently complex. This research effort demonstrates that an effective global optimization …

A Numerical Investigation Of The Series Reversion/Inversion And Series Reversion Of Lambert's Time Function, Michael P. Ward

Theses and Dissertations

An expression for the semi-major axis as a function of time may be determined by performing a series reversion and inversion of Lambert's Time Function. Since the resulting series contains a singularity, it is desirable to perform only a reversion on the original series to obtain an expression for the inverse of the semi-major axis. Using a Lagrange expansion to obtain the coefficients for this series is very computer intensive. Therefore, alternative methods are presented. Also, each series was expanded into a continued fraction which provided greater accuracy than the series using the same number of coefficients. The accuracy was …

Use Of Grasp Force Focus Positioning To Enhance The Torque Resistance Capability Of Robotic Grasps, Stephen G. Edwards

Theses and Dissertations

Three-point-contact grasps are unique in that the homogeneous solution for the contact forces always produces a grasp force focus. Careful positioning of this focus point in the grasp plane can help avoid two things; slipping at the contact points, and violation of joint torque limits. The focus placement method is explored theoretically by examining two types of grasps on cylinders; 1) fingertip grasps using three independently operated fingers, and 2) single-finger power grasps with one contact point on each of three links. Constraint maps are generated for various fingertip grasps in order to show how proper placement of the grasp …

Investigation Of Direct And Indirect Optimization Algorithms For Aerospace Structures, Harry Hopkins Iii

Theses and Dissertations

This thesis investigated the performance of two direct and two indirect methods of structural optimization. A gradient calculator and overall design system was created with the finite element code FRAME. Three of the methods were employed using this system with the fourth being a commercial available code. The algorithms were applied to two different sized trusses using static constraints and were measured for accuracy, reliability, and efficiency. Results for the problems tested showed the Direct methods were sensitive to starting designs and their performance depended on the proper selection of internal parameters. They were also shown to have a high …

A Low-Cost Part-Task Flight Training System: An Application Of A Head Mounted Display, David A. Dahn

Theses and Dissertations

To investigate the feasibility of using head-mounted display(HMD) and Computer Image Generators(CIG) in a low cost part-task trainer, we created a prototype system. Our approach was to build a virtual world interface using a HMD to an existing flight simulator application. This allowed a CIG with only one graphics channel to drive the display. To investigate which class of computing platform was suitable for use as the CIG, a cooperative thesis effort was launched to host the simulator on a mini-computer and micro-computer platform. The appropriate CIG could then be determined through demonstration and comparison between the systems. A software …

Autonomous Navigation Of A Satellite Cluster, Stephen C. Johnston

Theses and Dissertations

The relative position determination of a cluster of satellites operating in a low earth orbit is investigated. A U-D Covariance Factorization Kalman Filter is used for the on-board estimator with dynamics based on the Clohessy-Wiltshire equations. Measurements consist of range data between a single host satellite and the remaining cluster. Therefore only relative position and velocity states with respect to the host satellite can be determined. A 15 sample Monte Carlo simulation was conducted with clusters of 2, 5, and 10 satellites, respectively. Performance results consists of average error, average true error and filter covariance as a function of time.

Real-Time Flight Simulation And The Head-Mounted Display - An Inexpensive Approach To Military Pilot Training, Philip A. Platt

Theses and Dissertations

The integration of the low-cost head-mounted display (HMD), an inexpensive graphics workstation-based flight simulator, and a communications network was investigated to determine if the prototype of an inexpensive multi- aircraft Virtual Flight Simulator could be built. Previous research efforts have coupled HMD technology and flight simulation; however, the cost of these systems has been high. This thesis effort emphasized the use of joystick devices to emulate pilot control, the implementation of a fully enclosed virtual flight simulator, and the utilization of low-cost NTSC-based television technology to produce a prototype. The virtual flight simulator also contained a basic set of instruments …

Implementation Of The Modified Monte Carlo Technique Using Importance Sampling On The Block Oriented System Simulator, John B. Bennett

Theses and Dissertations

The purpose of this thesis was to implement the Modified Monte Carlo technique using Importance Sampling on the Block Oriented System Simulator (BOSS). Computer simulation techniques of communications systems were reviewed. Next, conventional Monte Carlo techniques and Modified Monte Carlo techniques using Importance Sampling were reviewed. Models of Binary Phase Shift Keying (BPSK) systems using both Monte Carlo techniques were implemented and simulated. Reasons for the model using Importance Sampling not working correctly are postulated. The Monte Carlo technique is a method of ensuring the an inherently infinite procedure, such as determining system bit error rate (BER), can be determined …

Brightness Invariant Port Recognition For Robotic Aircraft Refueling, Richard A. Bennett

Theses and Dissertations

The purpose of this thesis effort was to develop and test a brightness invariant recognition algorithm that would locate and identify the half-scale mock up of a Universal Aerial Refueling Receptacle Slipway Installation (UARRSI) aerial refueling port in different lightening conditions. This was accomplished by developing a brightness invariant port recognition of identifiable attributes of the refueling port to locate and identify the UARRSI port. Based on this approach, a brightness invariant port recognition system (BIPRS) was demonstrated which identified the refueling receptacle in different lightening conditions. The BIPRS was also invariant to orientation and size of the UARRSI port. …

A Study Of The Effects Of Noise Jamming On Radar Receivers, Paul E. Bishop

Theses and Dissertations

A comprehensive study of the effects of noise jamming on various pulsed radar receiver types is proposed. First, a literature review on the sources of electrical noise and various jamming waveforms is presented. The power spectra for three noise jamming waveforms are rigorously derived. These cases are shot noise in a parallel-plate diode, a series of pulses with random amplitudes and intervals, and for a series of pulses with random amplitudes, spacing and phases. Next, the probability density functions for the output of linear and quadratic detectors are developed. For each detector type, the probability density functions for the cases …