Engineering Commons^™

Two Dimensional, Time Dependent Modeling And Simulation Of Semi-Insulating Gaas High-Power Photoconductive Switches, Prakasit Kayasit

Electrical & Computer Engineering Theses & Dissertations

The current-voltage (I-V) characteristics and photoconductive behavior of semi-insulating GaAs (SI GaAs) high-power switches have been investigated by using a two-dimensional, time dependent, drift diffusion transport model. The dc current-voltage behavior as predicted by the results of this model was compared with available experimental data to evaluate the accuracy and validity of the model. The results show very good agreement, Next, research was carried out to investigate the behavior of the switches under high-field operation.

Simulations at high voltages emphasize on the two following processes: (a) The mechanism of impact ionization and the effect of this mechanism on device stability …

Modeling And Simulation Of High-Field, High-Temperature Sic Devices, Sanjay Pathak

Electrical & Computer Engineering Theses & Dissertations

With superior properties such as a large band gap, high thermal conductivity, and large electron drift velocity, SiC is expected to give a new dimension to high power, high temperature electronic devices used in power applications, microwave circuits, and for the space and automobile industries. SiC possesses an inherent advantage over its other large bandgap competitors in terms of inherited processing and device technology from Si. However, there is inadequate understanding of SiC device and its parameters. Simple extrapolations from Si are known to be inadequate. The aim of this dissertation, therefore. is to produce better understanding of SiC devices …

A Summary Report On The Application Of Photovoltaic Systems And Metal Roofs, Florida Solar Energy Center, Stephen Barkaszi

FSEC Energy Research Center®

A recent resurgence of interest in roof-mounted photovoltaic systems has prompted the Florida Solar Energy Center to assess the current state of the technology from a systems viewpoint. A major part of the system that is often underestimated in the performance and economics of the system is the roof structure. The type of roof can significantly affect both the initial cost of an installation and the life cycle costs.

Method For Improving Consolidation Of Powder Resin, David A. Pienkowski, Eric A. Grulke, Robert J. Jacob

Biomedical Engineering Faculty Patents

A method for improving consolidation of powder resin is provided. The method broadly includes the steps of: (1) sorting particles of the powder resin according to their diameter; (2) combining the sorted particles having a first diameter D1 with the sorted particles having a second diameter D2 so as to form a particle mixture; (3) applying a vibration to the particle mixture; (4) heating the particle mixture; and (5) delivering the particle mixture through a nozzle or into a mold. The particle diameters D1 and D2 are chosen so that once combined there is optimal close packing of the three-dimensional …

Chromium Oxides And Lithiated Chromium Oxides. Promising Cathode Materials For Secondary Lithium Batteries, Pankaj Arora, Dong Zhang, Branko N. Popov, Ralph E. White

Faculty Publications

Chromiumoxides and lithiated chromium oxides were synthesized by thermal decompositionof chromium trioxide (CrO₃) at high temperatures and oxygen pressures.Synthesis temperature and pressure markedly affect the performance of thesecathode materials. Higher pressures lead to a higher O/Cr ratioand fewer impurities in the final product. These materials arestable intercalation hosts for lithium, and exhibit a higher capacitythan any of the prominent positive electrodes used in secondarylithium batteries. m-CrO_x has a capacity of 255 mAh/g, while m-LiCrO_xhas a capacity of 210 mAh/g, during the first discharge. Theaverage voltage of these cells is 3.0 V vs. Li/Li …

The Sinmap Approach To Terrain Stability Mapping, Robert T. Pack, David G. Tarboton, C. N. Goodwin

Civil and Environmental Engineering Faculty Publications

A promising approach to modeling the spatial distribution of shallow debris slides combines a mechanistic infinite slope stability model with a steady-state hydrology model. The spatial distribution of a “stability index” is governed primarily by specific catchment area (the upslope area per unit contour length) and slope. The model can be interactively calibrated to the unique characteristics of the topography, rainfall, and soils of a particular study area using simple parameters, graphs and maps. Once a landslide and terrain inventory is completed using aerial photographs, this approach is shown to have the capability of producing a stability classification map of …

Language And Aviation Safety: Sovereignty Versus Sanctity Of Life, Ibpp Editor

International Bulletin of Political Psychology

This article identifies political factors that impede adequate language training for flight crews. These factors also are impediments to aviation safety.

Trends. The Crash Of Swissair Flight 111: Amidst The Tragedy, The Virtue Of Virtual Realities, Ibpp Editor

International Bulletin of Political Psychology

The author discusses the development of a virtual community: a community of relatives of victims of air fatalities throughout the world, a community whose members rarely meet that occurs after an air tragedy.

Seismic Code Improvements Based On Recorded Motions Of Buildings During Earthquake, Anil K. Chopra, Rakesh K. Goel, Juan Carlos De La Llera

Civil and Environmental Engineering

Summarized in this paper are the results of two recent investigations utilizing recorded motions of buildings to develop improvements in two aspects of seismic code provisions for buildings: (1) fundamental vibration period formulas, and (2) accidental torsion.

Cooling Saber With A Miniature Pulse Tube Refrigerator, Scott M. Jensen, J. Clair Batty, William A. Roettker, Matthew J. Felt

Space Dynamics Laboratory Publications

Utah State University/Space Dynamics Laboratory (USU/SDL), teaming with NASA Langley Research Center, is currently building the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER) instrument. Stringent mass and power constraints, together with a greater than two year mission life, led to the selection of a TRW miniature pulse tube refrigerator to cool SABER's infrared detectors to the required temperature of 75 K.

This paper provides an overview of the SABER thermal management plan and the challenges encountered in matching the refrigerator characteristics with instrument performance requirements under the broadly variant space environments expected for this mission. Innovative technologies were developed …

New Cmos Universal Constant-Gm Input Stage, Vladimir I. Prodanov, Michael M. Green

Electrical Engineering

Conceptually new constant-Gm input-stage architecture is presented. It provides near constant net transconductance independent of transistor operating region-strong, moderate or weak inversion. One possible implementation of the proposed architecture is discussed in details. Its operation has been experimentally verified. Results from performed measurements are included.

Orion: A Microsatellite Testbed For Formation Flying, Robert J. Twiggs, Jonathan How

Robert "Bob" Twiggs STEM Education Collection

A PowerPoint Presentation created by Professor Bob Twiggs and Jonathan How titled "ORION: A Microsatellite Testbed for Formation Flying" from September 3, 1998.

Wright State University College Of Engineering And Computer Science Bits And Pcs Newsletter, Volume 14, Number 7, September 1998, College Of Engineering And Computer Science, Wright State University

BITs and PCs Newsletter

An eight page newsletter created by the Wright State University College of Engineering and Computer Science that addresses the current affairs of the college.

The Role Of Air Cargo In California's Goods Movement, H.-S. Jacob Tsao

Faculty Publications

Caltrans began a systematic investigation into the role of air cargo in California’s goods movement, as part of the larger development effort for a statewide goods movement strategy, and funded a research project in 1997 for the Institute of Transportation Studies at U.C. Berkeley to (i) gain a broader understanding of the State’s air cargo industry and the role of air cargo in California’s goods movement, (ii) assess the importance of air cargo to the State’s economy, (iii) begin identification of issues hindering efficient air cargo movement in the State, and (iv) explore possible State roles for resolving the issues. …

Hybrid Force-Feedback Control For Virtual Environments, Carol Chesney

Link Foundation Modeling, Simulation and Training Fellowship Reports

The scope of this project is the design and implementation of a force-feedback device that utilizes brakes as well as motors for hybrid force control.. The device is a pen-sized device for planar point force-feedback. The design and software are implemented with consideration towards extending the force-feedback technology to three dimensions. The benefits of such a hybrid device include increased safety and realism. Larger forces can be reflected safely in the form of impenetrable constraints and instabilities can reduced or eliminated. The passive force component is the only way to accommodate the model of static friction. Delay in force measurement …

Navier-Stokes Analysis Of Lift-Enhancing Tabs On Multi-Element Airfoils, Paul G. Carrannanto, Bruce L. Storms, James C. Ross, Russell M. Cummings

Aerospace Engineering

The flow over multi-element airfoils with flat-plate lift-enhancing tabs was numerically investigated. Tabs ranging in height from 0.25 to 1.25% of the reference airfoil chord were studied near the trailing edge of the main element. The two-dimensional numerical simulation employed an incompressible Navier–Stokes solver using a structured, embedded grid topology. The effects of various tabs were studied at a constant Reynolds number on a two-element airfoil with a slotted flap. Both computed and measured results indicated that a tab in the main-element cove improved the maximum lift and lift-to-drag ratio relative to the baseline airfoil without a tab. Computed streamlines …

A Neural Network Pruning Algorithm With Embedded Gradient-Conjugate Training For The Identification Of Large Flexible Space Structures, Xiao-Hua Yu

Electrical Engineering

The choice of network dimension is a fundamental issue in the design of artificial neural networks. A larger neural network is powerful for solving problems while a smaller neural network is always advantageous in real-time environment where speed is crucial. In this paper, a network pruning algorithm with embedded gradient-conjugate training is investigated and applied to the identification of a large flexible space structure. Computer simulation results show that this approach can dramatically reduce the size of neural network while maintaining compatible identification accuracy.

Sprinkler Irrigation As A Voc Separation And Disposal Method: Innovative Technology Evaluation Report, Teri Richardson, Paul Depercin, Douglas Grosse, Rena Howard, Ann Kern, Endalkachew Sahle-Demissie, Johnny Springer Jr., Richard Schlenker, Roy F. Spalding

United States Environmental Protection Agency: Publications

This report summarizes the findings of an evaluation of sprinkler irrigation as a volatile organic compound (VOC) separation and disposal method.

Background A need for lower cost, effective treatment alternatives for the disposal of treated contaminated groundwater provided the impetus to conduct a SITE demonstration of sprinkler irrigation since it provides both separation and disposal options. Since the application of irrigation is fairly widespread throughout the United States, there may be an opportunity to employ this as a dual purpose technology; concurrent irrigation and disposal of treated groundwater. In order to determine whether this option is viable, it is necessary …

Climate Change And Nebraska

United States Environmental Protection Agency: Publications

The earth’s climate is predicted to change because human activities are altering the chemical composition of the atmosphere through the buildup of greenhouse gases — primarily carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons. The heat-trapping property of these greenhouse gases is undisputed. Although there is uncertainty about exactly how and when the earth’s climate will respond to enhanced concentrations of greenhouse gases, observations indicate that detectable changes are under way. There most likely will be increases in temperature and changes in precipitation, soil moisture, and sea level, which could have adverse effects on many ecological systems, as well as on …

Fuzzy Justification Of Heuristic Methods In Inverse Problems And In Numerical Computations, With Applications To Detection Of Business Cycles From Fuzzy And Intuitionistic Fuzzy Data, Vladik Kreinovich, Hung T. Nguyen, Berlin Wu, Krassimir T. Atanassov

Departmental Technical Reports (CS)

No abstract provided.

Np-Hardness In Geometric Construction Problems With One Interval Parameter, Nuria Mata, Vladik Kreinovich

Departmental Technical Reports (CS)

No abstract provided.

Computer-Assisted Gait Analysis In Equine Orthopaedic Practice: The Case For Inverse Dynamic Analysis, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

No abstract provided.

Acuta Enews September 1998, Vol.27, No. 9

ACUTA Newsletters

In This Issue

Is xDSL Right for Your Campus?

Delegate It!

A Commitment to Service

DC at a Glance

Board Report

Positions Available

Welcome New Member

Optimization Of Solid-State Fermentation Parameters For The Production Of Xylanase By Trichoderma Longibrachiatum On Wheat Bran, Elizabeth R. Ridder, Sue E. Nokes, Barbara L. Knutson

Biosystems and Agricultural Engineering Faculty Publications

Solid-state fermentation has the potential to produce inexpensive enzymes for use in high-volume industrial applications. Process parameters such as substrate moisture content and length of fermentation can have a significant effect on the amount and timing of enzyme production. This study was conducted in two stages, a screening stage and an optimization stage, to determine the effects of moisture content of the substrate, surfactant addition upon inoculation, depth of the substrate, and duration of fermentation on xylanase activity produced by Trichoderma longibrachiatum. Screening fermentations were conducted at 25°C, 50 and 75% wet basis moisture content (w.b.), 0.0 and 0.2% …

Vegetated Filter Strip Removal Of Cattle Manure Constituents In Runoff, Teng T. Lim, Dwayne R. Edwards, Stephen R. Workman, Brian T. Larson, Lloyd Dunn

Biosystems and Agricultural Engineering Faculty Publications

Pasture runoff can contribute to elevated concentrations of nutrients, solids, and bacteria in downstream waters. The objective of this study was to determine the effects of vegetative filter strip (VFS) length on concentrations and transport of nitrogen, phosphorus, solids and fecal coliform in runoff from plots treated with cattle manure. Three plots with dimensions of 2.4 × 30.5 m were used. The upper 12.2 m of each plot was treated with cattle manure, while the lower 18.3 m acted as a VFS. Runoff produced by rainfall simulators was sampled at VFS lengths of 0, 6.1, 12.2, and 18.3 m and …

Use Of Polyurethane Material Models For Simulating Leg-Form Impact In Different Explicit Finite Element Codes, Joe Hassan, Peter Schuster, G. Frederick

Mechanical Engineering

Compressible plastic foams are used throughout the interior and bumper systems of modern automobiles for safety enhancement and damage prevention. Consequently, modeling of foams has become very important for automobile engineers. To date, most work has focused on predicting foam performance up to approximately 80% compression. However, in certain cases, it is important to predict the foam under maximum compression, or 'bottoming-out.' This paper uses one such case-a thin low-density bumper foam impacted by a pedestrian leg-form at 11.1 m/s-to investigate the 'bottoming-out' phenomenon. Multiple material models in three different explicit Finite Element Method (FEM) packages (RADIOSS, FCRASH, and LS-DYNA) …

Truck Route Access Evaluation: Cook Family Foods, Grayson, Site #2663, Joel M. Weber, Kenneth R. Agent, Brian Aldridge, Lisa Aultman-Hall, David Cain, Nicole Lefever, Nikiforos Stamatiadis

Kentucky Transportation Center Research Report

This is a study undertaken on behalf of the Kentucky Transportation Cabinet (KYTC). There are two main objectives of the Freight Movement and Intermodal Access in Kentucky Study (SPR 98-189): evaluation of the access for trucks between intermodal or other truck generating sites and the National Highway System (NHS); and furthering the understanding of freight commodity flows throughout the state. This report summarizes the access evaluation for the Cook Family Foods facility located in Carter county in the FIVCO Area Development District (ADD) and KYTC Highway District #9. The location of the site is shown in Figure 1. Work on …

Response Of Runoff Diazinon Concentration To Formulation And Post-Application Irrigation, Joshua R. Evans, Dwayne R. Edwards, Stephen R. Workman, R. Michael Williams

Biosystems and Agricultural Engineering Faculty Publications

Pesticides used in urban environments can be transported in runoff to downstream waters and cause adverse environmental consequences. This experiment assessed the effects of post-application irrigation depth (0, 6.4, and 12.7 mm) and formulation (liquid and granular) on concentration and transport of diazinon (a pesticide commonly used for lawn insect control) in runoff from “tall” fescue (Festuca arundinacea Schreb.) plots. The post-application irrigation was applied using rainfall simulators immediately following diazinon application. The rainfall simulators were again used approximately 2 h after diazinon application to apply the equivalent of a heavy rainfall (64 mm/h for approximately 1.5 h) to generate …

Entropy Generation In A Rectangular Packed Duct With Wall Heat Flux, Yaşar Demirel, Ramazan Kahraman

Papers in Thermal Mechanics

The entropy generation due to heat transfer and friction has been calculated for fully developed, forced convection flow in a large rectangular duct, packed with spherical particles, with constant heat fluxes applied to both the top (heated) and bottom (cooled) wall. An approximate analytical expression for the velocity profile developed for packed bed with H/dp > 5 has been used together with the energy equation of fully developed flow to calculate the non isothermal temperature profiles along the flow passage. The velocity profile takes into account the increase in the velocity near the wall due to the higher voidage in this …

Assessing And Updating Indot's Traffic Monitoring System For Highways, Volume 2 - Appendices B7 And C, Samuel Labi, Jon D. Fricker

JTRP Technical Reports

This study evaluates the existing resources and procedures ofINDOT's current traffic monitoring program, with the objective of transforming this program into a comprehensive Traffic Monitoring System for Highways (TMS/H). Reliable traffic data is a valuable input for studies and decision-making at various levels and in various phases of highway management including planning and design, finance and taxation, legislation and safety. The nature and scope of the various components comprising a TMS/H for any state were identified in available literature such as the Federal Register and Traffic Monitoring Guide.

A complete inventory of the existing resources (personnel and equipment) and procedures …