Engineering Commons^™

Electromagnetic Scattering From A Cavity In A Ground Plane: Theory And Experiment, William D. Wood Jr.

Theses and Dissertations

The electromagnetic scattering from an arbitrarily shaped open cavity embedded in a perfectly conducting, infinite ground plane is examined. The cavity is filled with a linear, isotropic, homogeneous material. The fields in the cavity interior and above the ground plane are expressed in terms of the tangential fields on the cavity surface and aperture. A coupled set of three integral equations is developed governing the tangential fields on the aperture and cavity surface. The support of the unknown tangential fields is finite. A moment-method based algorithm to approximate the solution to the integral equations for axisymmetric geometries is developed. The …

A Crosstalk Correcting Router That Uses Online Noise Simulation To Route High Speed Multichip Modules, Kenneth J. Mcclellan Jr.

Theses and Dissertations

Existing MultiChip Module (MCM) auto-routers either ignore crosstalk or use over simplified crosstalk approximations. Of the routers that do consider crosstalk, very few have the capability to correct crosstalk problems after they occur. This dissertation describes a router that not only has an internal crosstalk model for high speed MCMs which is more accurate than that of other existing routers, but also has the capability to use an online simulator to more accurately determine noise levels. After crosstalk problems occur, the router has the ability to correct these problems. Through memory usage reductions and routing efficiency improvements, this maze router …

Nested Fork-Join Queuing Networks And Their Application To Mobility Airfield Operations Analysis, Craig J. Willits

Theses and Dissertations

A single-chain nested fork-join queuing network (FJQN) model of mobility airfield ground processing is proposed. In order to analyze the queuing network model, advances on two fronts are made. First, a general technique for decomposing nested FJQNs with probabilistic forks is proposed, which consists of incorporating feedback loops into the embedded Markov chain of the synchronization station, then using Marie's Method to decompose the network. Numerical studies show this strategy to be effective, with less than two percent relative error in the approximate performance measures in most realistic cases. The second contribution is the identification of a quick, efficient method …

Numerical And Experimental Investigation Of The Flowfield Near A Wrap-Around Fin, Carl P. Tilmann

Theses and Dissertations

A wall-mounted semi-cylindrical model fitted with a single wrap-around fin (WAF) has been investigated both numerically and experimentally, with the objective of characterizing the mean and turbulent flowfield in the vicinity of the fin. Numerical and experimental results are used to determine the nature of the flowfield and quantify the effects of fin curvature on the character of the flow near WAFs. This research has been motivated by the need to identify possible sources of a rolling moment reversal observed at high speeds in sub-scale flight tests. Detailed mean flow and turbulence measurements were obtained in the AFIT Mach 3 …

Advances In Time-Domain Electromagnetic Simulation Capabilities Through The Use Of Overset Grids And Massively Parallel Computing, Douglas C. Blake

Theses and Dissertations

A new methodology is presented for conducting numerical simulations of electromagnetic scattering and wave propagation phenomena. Technologies from several scientific disciplines, including computational fluid dynamics, computational electromagnetics, and parallel computing, are uniquely combined to form a simulation capability that is both versatile and practical. In the process of creating this capability, work is accomplished to conduct the first study designed to quantify the effects of domain decomposition on the performance of a class of explicit hyperbolic partial differential equations solvers; to develop a new method of partitioning computational domains comprised of overset grids; and to provide the first detailed assessment …

Modern Flight Control Design, Implementation, And Flight Test, Phillip T. Edwards

Theses and Dissertations

This thesis addresses the application issues raised implementing flight control designs derived from optimal control theory and the challenges in obtaining acceptable handling qualities when using these techniques. Using the USAF TPS FCS project as the controller architecture, four controllers were designed using classical methods, and H2, H3, and mixed H2/H optimal control theory. These designs were implemented in the Calspan VSS II Learjet, simulating unstable aircraft longitudinal dynamics and a limited handling qualities flight test evaluation was performed. The design phase found the optimal control techniques, as applied, difficult to design to handling qualities specifications. The H2, H3 and …

The Effects Of Elevator Rate Limiting And Stick Dynamics On Longitudinal Pilot-Induced Oscillations, Patrick J. Peters

Theses and Dissertations

This report presents the results of an investigation into the effects of elevator rate limiting and stick dynamics on longitudinal pilot-induced oscillations (PIO). A simulation study was conducted to prepare for the flight test, but also to gain insight into the effects of rate limiting and stick dynamics. Due to the non-numerical nature of the simulation results, a flexible three-phase flight test plan was developed, first varying the rate limits, then varying the stick dynamics, and finally flying a matrix determined in the first two phases. There were three major conclusions. First, the offset landing task flown was insufficient to …

A Framework For An Automated Compilation System For Reconfigurable Architectures, George R. Roelke Iv

Theses and Dissertations

The advent of the Field Programmable Gate Array has allowed the implementation of runtime reconfigurable computer systems. These systems are capable of configuring their hardware to provide custom hardware support for software applications. Since these architectures can be reconfigured during operation, they are able to provide hardware support for a variety of applications, without removal from the system. The Air Force is currently investigating reconfigurable architectures for avionics and signal processing applications. This thesis investigates the problem of automating the application development process for reconfigurable architectures. The lack of automated development support is a major limiting factor in the use …

Sensitivity Analysis Of A Combat Simulation Using Response Surface Methodology, William J. Berg

Theses and Dissertations

This thesis provides a methodology to analyze the sensitivity of a combat simulation relative to the capabilities of the modeled weapon systems. Response Surface Methodology (RSM) was the primary technique used for analysis. A ground battle scenario was developed with a commercial PC wargame Empire II: The Art of War(TM). In the computer verses computer mode, the wargame was transformed into a combat simulation'. A screening experiment was used to determine which of an original 23 weapon factors were actually significant to this scenario. After analyzing the remaining five factors, only three ended up as truly significant to the battle …

Statistical Modeling And Optimization Of Nuclear Waste Vitrification, Todd E. Combs

Theses and Dissertations

This thesis describes the development of a methodology to minimize the cost of vitrifying nuclear waste. Pacific Northwest Laboratory (PNL) regression models are used as baseline equations for modeling glass properties such as viscosity, electrical conductivity, and two types of durability. Revised PNL regression models are developed that eliminate insignificant variables from the original models. The Revised PNL regression model for electrical conductivity is shown to better predict electrical conductivity than the original PNL regression model. Neural networks are developed for viscosity and the two types of durability, PCT-B and MCC-1 B. The neural network models are shown to outperform …

Ranking And Generating Alternatives For The National Air Intelligence Center's (Naic) Resource Allocation Strategy, Steven M. Cox

Theses and Dissertations

Allocating resources is never an easy task, especially when requirements call for more resources than those available. It gets more difficult when the availability of resources shrinks from year to year. This is the case at the National Air Intelligence Center (NAIC). In each of the past five years, NAIC has been forced to make their resource allocation decision with fewer dollars and less manpower. This decision has been time consuming, manpower intensive, and sometimes very heated. In an effort to lessen these three consequences, a resource allocation model, based upon the NAIC Commander's values and preferences, was developed. The …

Modeling Mirv Footprint Constraints In The Weapons Assignment Model, Elliot T. Fair

Theses and Dissertations

US Strategic Command (USSTRATCOM) is developing a new linear programming model called the Weapons Assignment Model (WAM) to perform weapons assignment for the Strategic Integrated Operations Plan (SIOP). One of the major improvements WAM will have over its predecessor is the ability to include Multiple Independently Targetable Reentry Vehicle (MIRV) footprinting constraints in the optimization process. In order to include MIRV footprint constraints in WAM, a methodology is needed to model the MIRV footprints in a manner that is consistent with the limitations of linear programming. Two techniques for modeling MIRV footprints were developed. The first, Geometric Approximation (GA), uses …

Modeling A Chemical Battlefield And The Resulting Effects In A Theater-Level Combat Model, Todd M. Gesling

Theses and Dissertations

This thesis describes the development of a methodology to model chemical weapons use in the Joint Staff's Joint Warfare Analysis Experimental Prototype (JWAEP) and to quantify the resulting effects. The methodology incorporates organic unit assets and theater-level chemical assets into JWAEP by using the three principles of nuclear, biological, and chemical defense (NBC) which reflect joint and Army doctrine, and combines them with the basic concepts already used in existing theater-level models. Other aspects of the problem include representing chemical 'packages' on the battlefield, determining attrition and time effects, adjusting unit effectiveness, determining chemical package intelligence acquisition procedures, identifying solution …

Linking Procurement Dollars To An Alternative Force Structures' Combat Capability Using Response Surface Methodology, James B. Grier

Theses and Dissertations

A General Officer Steering Group, chaired by HQ USAF/XOM tasked action to develop and implement evaluation and analysis support to lead turn' the Program Objective Memorandum (POM) and Joint Warfare Capability Assessment (JWCA) process. This evaluation process should be designed to supply measures of the 'health' of the Air Force program in light of the Defense Planning Guidance (DPG) and the Chairman's Program Assessment (CPA). The Air Force needs to be able to quickly evaluate various alternative force structures with regards to its combat capability, measured in terms of theater level campaign objectives (CO). HQ USAF/XOM tasked HQ USAF/XPY to …

A Decision Support System For Joint Force Air Component Commander (Jfacc) Combat Planning, Donald W. Hinton

Theses and Dissertations

This system allows assessment of the Master Air Attack Plan (MAAP) during construction and at completion. The system functions around a relational database management system providing a decision support tool for the Guidance, Apportionment, & Targeting (GAT) cell of Central Command's JFACC Combat Plans. A Microsoft Access application is programmed to provide PC-based, real time evaluation of air campaign goals and constraints. The decision support system was validated in February 1997 by the CENTAF combat plans staff at Blue Flag 97-1. The software and user's manual are maintained at HQ ACC/XP-Studies and Analysis Squadron.

Tool Condition Monitoring: A Computational Approach, Anthony Clinch

Dissertations and Theses

Tool Condition Monitoring offers a new approach to reducing the costs associated with catastrophic tool failure. The manufacturing process is becoming more computationally oriented all the time. Computational methods of determining the condition of cutting tools will lend themselves to easy integration with current and forthcoming manufacturing techniques. Coupling the results of this computational approach with a cost analysis will provide a means of maximizing the investment in cutting tools, while minimizing the damage caused by tool failure. Tool Condition Monitoring, as defined here, is a method of computationally determining the condition of a cutting tool. The problem of determining …

Automatic Synthesis Of Vlsi Layout For Cmos Continuous-Time Filters, Wei Han

Dissertations and Theses

Automatic synthesis of digital VLSI layout has been available for many years. It has become a necessary part of the design industry as the window of time from conception to production shrinks with ever increasing competition. However, automatic synthesis of analog VLSI layout remains rare.

With digital circuits, there is often room for signal drift. In a digital circuit, a signal can drift within a range before hitting the threshold which triggers a change in logic state. The effect of parasitic capacitances for the most part, hinders the timing margins of the signal, but not its functionality. The logic functionality …

Interaction Of Fluctuating River Flow With A Barotropic Tide: A Demonstration Of Wavelet Tidal Analysis Methods, David A. Jay, Edward P. Flinchem

Civil and Environmental Engineering Faculty Publications and Presentations

Wavelet transforms provide a valuable new tool for analysis of tidal processes that deviate markedly from an assumption of exact periodicity inherent in traditional harmonic analysis. A wavelet basis adapted to nonstationary tidal problems is constructed and employed to analyze the modulation of the external tide in a river by variations in streamflow. Interaction of a surface tide with river flow is the best available demonstration of the continuous wavelet transform (CWT) methods developed. It is the simplest and perhaps the only nonstationary tidal process for which both sufficient data and dynamical understanding exist to allow detailed comparisons between CWT …

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Building Services Engineering

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Polarization Properties Of Corner-Cube Retroreflectors: Theory And Experiment, Jian Liu, R. M.A. Azzam

Electrical Engineering Faculty Publications

Polarization properties of the corner-cube retroreflector are discussed theoretically by use of ray tracing and analytical geometry. The Jones matrices and eigenpolarizations of the six propagation trips of the corner-cube retroreflector are derived. An experiment is also set up for the determination of the linear eigenpolarizations and the output states of polarization for incident linearly polarized light. The experimental results are consistent with theoretical expectations.

Performance Of Mhpm In Rician And Rayleigh Fading Mobile Channels, Fuqin Xiong, S Bgatnyket

Electrical and Computer Engineering Faculty Publications

This paper evaluates the error probability of the rectangular frequency pulse multi-h modulation (MHPM) scheme in slowly-fading, frequency-nonselective or frequency-selective Rician and Rayleigh channels. The evaluation is performed with a method combining analysis and computer simulation. Performance degradations are evaluated for various direct-to-reflected signal ratio, Doppler shifts, and relative time delays in Rician fading channels. Compared with minimum shift keying (MSK), MHPM schemes appear to have retained their coding gains

Theoretical Study Of A Linear Accelerator Used As A Vuv/X-Ray Source Using The Inverse Compton Scattering Mechanism: Comparisons And Applications, Robert A. Schill Jr., Edward Mccrea

Electrical & Computer Engineering Faculty Research

A classical linear theory is used to compare large synchrotron sources to a rf linear accelerator employed as a VUV/X-ray source. Comparisons are made on a per-pulse basis. It is demonstrated that the linear accelerator as an X-ray source is comparable to large synchrotron accelerators with wiggler insertion devices at the experiment. Applications to lithography, X-ray microscopy, X-ray spectroscopy and detector calibration are examined. Excluding lithography, the linear accelerator with an appropriate laser source is a useful source of X rays for these applications. As verification, classical results are compared with quantum mechanical results and are shown to be in …

Us/Remax Manual Vs. 2.7, Richard C. Peralta, Alaa H. Aly

Civil and Environmental Engineering Faculty Publications

US/REMAX is designed to assist water managers in developing optimal groundwater and/or surface water strategies for a wide range of management problems. US/REMAX uses the response matrix method, which assumes that physical system response to stimuli is linear. However, US/REMAX can also address nonlinear systems via cycling. In one application, astrategy computed using US/REMAX required 40% less pumping than one obtained via a normal simulation model. US/REMAX also easily computes tradeoffs for multiobjective problems.

Modeling Driver's Route Choice Behavior Under The Influence Of Advanced Traveler Information Systems (Vol. 2; Vol. 1: 96/10), Samer Madanat, Nitin K. Jain

JTRP Technical Reports

This research consisted of two parts; this report is volume 2 of 2 volumes; Volume 1 is Report No. FHWA/IN/JHRP-96/10. The first part developed a set of incident clearance time prediction models for the Borman Expressway. The second part consisted of modeling driver’s route choice behavior under the influence of advanced traveler information systems.

Volume 2 of this report describes the modeling driver's route choice behavior under the iinfluence of Advanced Traveler Information Systems. These models can help in understanding the behavior and response of travelers under the influeince of Advanced Traveler Information Systmes.r

The products of this research project …

Kinetics Of Transesterification Of Soybean Oil, Hossein Noureddini, D Zhu

Papers in Biomaterials

Transesterification of soybean oil with methanol was investigated. Three stepwise and reversible reacttons are believed to occur. The effect of variations in mixing intensity (Reynolds number = 3,100 to 12,400) and temperature (30 to 70'CJ on the rate oireaction were studied while the molar ratio of alcohol to triglycerol (6:l) and the concentration of catalyst (0.20 wt% based on soybean oil) were held constant. The variations in mixing intensity appear to effect the reaction parallel to the variations in temperature. A reaction mechanism consisting of an initial mass transfer-controlled region followed by a kinetically controlled region is proposed. The experimental …

Performance And Cost Effectiveness Of Pavement Edge Drains, L. John Fleckenstein, David L. Allen

Kentucky Transportation Center Research Report

It is apparent from research conducted under this study that edge drains increase subgrade strength through the removal of water. It is also apparent in most cases that the edge drains increase pavement life by approximately seven years. Current cost benefit analysis indicates that edge drains can provide a cost savings of approximately $200,000 dollars a mile over the life of the pavement. Research also indicates that if edge drains are not properly installed and maintained they can doe more damage then good. It is evident that edge drains should be inspected with a pipeline camera prior to final acceptance …

Analysis And Design Of Bridges Susceptible To Barge Impact, Michael W. Whitney, Issam E. Harik

Kentucky Transportation Center Research Report

The current American Association of State Highway Traffic Organizations (AASHTO) Guide Specification for Collision Design of Highway Bridges provides three statistical methods(methods I, II, and III) for determining the design vessel for impact analysis. These methods focus mainly on ship impact and not on barge impact design for bridges susceptible to vessel (ship or barge) impact. This is due to the tremendous variation in flotilla sizes, barge types, and barge sizes. This study presents an analysis procedure by which the statistical design methods of the AASHTO Guide Specification can be applied to inland waterway bridge design.

Design of bridges susceptible …

Electrochemical Synthesis And Characterization Of Ba-Pb-O And Bi-Pb-O Oxides, Min Xie, Liangzhong Zhao, Cuiying Xu, Jinbiao Zhang

Journal of Electrochemistry

Pb-based oxides Ba-Pb-O and Bi-Pb-O were synthesized from aqueous solutions by using electrochemical method. The resulting Ba-Pb-O and Bi-Pb-O were characterized using XPS, EDX and XRD. The results show that perovskite BaPb_0.9O₃ can be electrodeposited on the anode only from strong alkaline solution. In acid aqueous solution, conducting BiPb₂O_z oxide is fromed on the anode. In these oxides the nominal valence of lead is +4.

Electrochemical Studies Of Spinel Limn2O4 Rechargeable Lithium Battery, Li Feng, Yuqin Chang, Lie Wu, Hong Li, Yibin San, Tianhong Lu

Journal of Electrochemistry

The spinel Li intercalation compound LiMn₂O₄ was prepared and studied using ac impedance and cyclic voltammogram techniques. It was first discussed that the impedance behaviors of LiMn₂O₄ electrode varied as lithium ion was intercalated in or out the electrode with the help of fractal theory. The Li reversible behaviors in LiMn₂O₄ electrode were shown by the cyclic voltammogram results.

Study On The Hydrophilicity Of Nafion Membrane Surface, Yanbing Zu, Chuansin Cha

Journal of Electrochemistry

Due to its high chemical stability and ion selective permeability, Nafion membrane has been applied in many electrochemical systems. The surface hydrophilicity is one of the main factors affecting its performance. In this paper, the bound bubble method is introduced as a suitable way to measure the contact angles between Nafion membrane and various aqueous solutions. During the measurement, Nafion membrane is saturated with given electrolyt solution. The hysteresis of the contact angles observed in the measurement is attributed to the co existance of hydrophobic and hydrophilic domains at the membrane surface. The effect of the solution surface tension on …