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Articles 4741 - 4770 of 5600
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The Dependence Of The Time-Asymptotic Structure Of 3-D Vortex Breakdown On Boundary And Initial Conditions, Jeffrey C. Tromp
The Dependence Of The Time-Asymptotic Structure Of 3-D Vortex Breakdown On Boundary And Initial Conditions, Jeffrey C. Tromp
Theses and Dissertations
The three-dimensional, compressible Navier-Stokes equations are solved numerically to simulate vortex breakdown in tubes. Time integration is performed with an implicit Beam-Warming algorithm, which uses fourth-order compact operators to discretize spatial derivatives. Initial conditions are obtained by solving the steady, compressible, and axisymmetric form of the Navier-Stokes equations using Newton's method. Stability of the axisymmetric initial conditions is assessed through 3-D time integration. Unique axisymmetric solutions at a Reynolds number of 250 lose stability to 3-D disturbances at a critical value of vortex strength, resulting in 3-D and time-periodic flow. Axisymmetric solutions at a Reynolds number of 1000 contain regions …
Optimal Mixed-Norm Control Synthesis For Discrete-Time Linear Systems, David R. Jacques
Optimal Mixed-Norm Control Synthesis For Discrete-Time Linear Systems, David R. Jacques
Theses and Dissertations
A mixed-norm approach to control synthesis for discrete time linear systems is developed. Specifically, the problem of minimizing the H2 norm of a transfer function, subject to a combination of ℓ1 and-or H∞ norm constraints on dissimilar but related transfer functions is considered. The uniqueness of the optimal solution is shown, and numerical methods for approximating the optimal solution to within arbitrary accuracy are developed. These methods generally result in high order compensators which can not be implemented in most practical applications. In response to this, a numerical method is developed which solves for suboptimal solutions of …
Design, Fabrication, Modeling, And Testing Of Surface-Micromachined Micromirror Devices, M. Adrian Michalicek
Design, Fabrication, Modeling, And Testing Of Surface-Micromachined Micromirror Devices, M. Adrian Michalicek
Theses and Dissertations
The Flexure-Beam Micromirror Device (FBMD) is a phase-only piston style spatial light modulator demonstrating properties which can be used for phase adaptive- corrective optics. This thesis presents a complete study of new designs of FBMDs and other micromirror devices, from original design considerations through final device testing and verification of ideal and advanced models. The models relate the electrical and mechanical properties of the device by equating the electrostatic force of a parallel- plate capacitor with the counteracting spring force of the device's support flexures. For the advanced model of the Flexure-Beam micromirror device, the capacitor solution is derived via …
Determination Of The Temperature Coefficients Of Selected Material Constants Of Dilithium Tetraborate, Gregory S. Weaver
Determination Of The Temperature Coefficients Of Selected Material Constants Of Dilithium Tetraborate, Gregory S. Weaver
Theses and Dissertations
The first and second order temperature coefficients of the material constants cE11, cE12, cE44, cE66, and e15 of dilithium tetraborate (Li2B4O7) have been measured over a temperature range of 20°C to 150°C. An improved resonator method was used to measure the fundamental zero mass loading antiresonant frequencies of selected pure-mode orientations of Li2B4O7. Material constants extraction was performed using a linear least squares matrix method. The resulting material constant curves were fit with a third …
Optimal Wavefront Reconstruction For A Coherent Diffracted Field, William W. Arrasmith
Optimal Wavefront Reconstruction For A Coherent Diffracted Field, William W. Arrasmith
Theses and Dissertations
In sheared coherent beam interferometric imaging, an estimate of the average reflectivity profile of the object can be computed from measurements of point to point phase differences in the far field interference pattern and a suitable phase reconstruction technique. The phase difference information is encoded in the irradiance of three identical, shifted and superimposed speckled laser beam patterns. A minimum variance phase reconstruction technique is presented to estimate the phase of the field in the measurement plane from the phase differences and evaluate its performance. Prior knowledge of the phase covariance is used in the minimum variance reconstructor. Analytic calculations …
The Mathematics Of Measuring Capabilities Of Artificial Neural Networks, Martha A. Carter
The Mathematics Of Measuring Capabilities Of Artificial Neural Networks, Martha A. Carter
Theses and Dissertations
Researchers rely on the mathematics of Vapnik and Chervonenkis to capture quantitatively the capabilities of specific artificial neural network (ANN) architectures. The quantifier is known as the V-C dimension, and is defined on functions or sets. Its value is the largest cardinality 1 of a set of vectors in Rd such that there is at least one set of vectors of cardinality 1 such that all dichotomies of that set into two sets can be implemented by the function or set. Stated another way, the V-C dimension of a set of functions is the largest cardinality of a set, such …
Biomedical Data Interpolation For 3-D Visualization, Ming-Chung Chen
Biomedical Data Interpolation For 3-D Visualization, Ming-Chung Chen
Theses and Dissertations
Medical imaging devices that produce three-dimensional data usually produce the data in the form of image slices. In such images, the resolution in z direction is lower than in x and y directions. Before extracting and displaying objects in such images, an interpolated 3-D gray-scale volume image can be generated via image interpolation techniques to fill in the missing information. The subject of this thesis is the applying three different interpolation techniques to generate intermediate slices and comparing their qualities. The three interpolation techniques are linear interpolation, cubic spline interpolation, and Fourier interpolation. We also apply the CT image matching …
Physiologically-Based Pharmacokinetic Modeling Of Skin Absorption Using Dermal Subcompartments, Richard L. Bookout Jr.
Physiologically-Based Pharmacokinetic Modeling Of Skin Absorption Using Dermal Subcompartments, Richard L. Bookout Jr.
Theses and Dissertations
Dermal penetration of chemicals and drugs is important to both toxicologists and pharmacologists. Drug developers try to enhance and environmental professionals try to limit penetration of chemicals through the skin. Both can use predictive biologically-based mathematical models to assist in understanding the processes involved. When these models are based on physiological and biochemical parameters which can be measured in the laboratory, they can be extremely useful. Appropriately validated models based on first principles can be predictive of human exposures when the processes involved are adequately understood. In this thesis we develop four new physiologically-based pharmacokinetic (PBPK) models to predict blood …
A Robust Method Of Solving Nonlinear Boundary Value Problems Via Modified Compromise Programming, John L. Zornick
A Robust Method Of Solving Nonlinear Boundary Value Problems Via Modified Compromise Programming, John L. Zornick
Theses and Dissertations
This study is an extension of Ng's previous work in which goal programming was used to determine an approximate solution to a boundary value problem. This approach follows the same basic approach developed by Ng in which the method of collocation was recast as a compromise programming model. Hence, instead of solving a system of simultaneous nonlinear equations, one seeks a compromise solution which minimizes (in a weighted residual sense) a vector norm of the differential equation residuals. A difference in this approach is that it makes use of a genetic algorithm as the optimizing engine as opposed to the …
The Effect Of Repeatedly Sampling An Embedded Metamodel On The Simulation Response, John Kent Patterson
The Effect Of Repeatedly Sampling An Embedded Metamodel On The Simulation Response, John Kent Patterson
Theses and Dissertations
This study investigated the effect on simulation output of repeatedly sampling an embedded metamodel. A metamodel is said to be embedded within a simulation if it is used to replace a submodule of that simulation. Replacing a deterministic module with an embedded deterministic metamodel poses no apparent mathematical problems. However, using a deterministic metamodel to replace a stochastic simulation component could require additional corrective actions. This research was performed in two phases. The first phase dealt with a set of tandem queues. It was shown that as each queue was sequentially replaced with a metamodel, the total system variance was …
Dynamic Maintenance Scheduling For A Stochastic Telecommunication Network: Determination Of Performance Factors, Todd S. Patterson
Dynamic Maintenance Scheduling For A Stochastic Telecommunication Network: Determination Of Performance Factors, Todd S. Patterson
Theses and Dissertations
This research proposes an analytical approach to access the relationship between maintenance facility location and communication network performance measurement using a selected dynamic maintenance scheduling protocol. There were three objectives established for this effort. The first objective was the determination of an upper-bound upon the level of performance for a telecommunication network using dynamically scheduled maintenance to evaluate maintenance depot location. This was achieved by using a two-stage algorithm, first locate a maintenance depot by using stochastic algorithms, and then to measure the resulting impact upon performance with a multi-commodity network flow model. The second objective was to develop the …
Applications Of Statistical Process Control In Monitoring Aircrew Bombing Proficiency, Kirk G. Horton
Applications Of Statistical Process Control In Monitoring Aircrew Bombing Proficiency, Kirk G. Horton
Theses and Dissertations
The current tools used by squadron supervisors to monitor the bombing performance of aircrews flying F-111E aircraft are monthly reports that have little predictive capability. No real-time methodology exists for monitoring and predicting aircrew bombing performance and preventing bombing problems that might cause an individual to become unqualified. It has been suggested that Statistical process Control (SPC) can be applied to the bombing process to develop tools for managing the process, correcting problems, and improve the bombing performance of a squadron. This study investigates the application of SPC to the bombing process. It examines data taken from an F-111E Fighter …
An Improved Solution Methodology For The Arsenal Exchange Model (Aem), Jeffery D. Weir
An Improved Solution Methodology For The Arsenal Exchange Model (Aem), Jeffery D. Weir
Theses and Dissertations
The purpose of this research was to design a solution methodology for the Arsenal Exchange Model (AEM) that is faster and contains less precision error than the current one. The current solution methodology modifies some of the original constraints and uses a computationally slow matrix inverter. The improved methodology uses a revised simplex algorithm to first solve a subproblem having only the weapon constraints generated by the AEM. Given this optimal allocation, hedge constraints and target constraints that are violated by the current solution are added to the original subproblem. A dual simplex algorithm is used to find the optimal …
Groundwater Model Parameter Estimation Using Response Surface Methodology, Richard M. Cotman
Groundwater Model Parameter Estimation Using Response Surface Methodology, Richard M. Cotman
Theses and Dissertations
This thesis examined the use of response surface methodology (RSM) to estimate the parameters of a finite-element groundwater model. An existing two-dimensional, steady-state flow model of a fractured carbonate groundwater system in southwestern Ohio served as the calibration target data set. A Plackett-Burman screening design showed that only four of the ten hydraulic conductivity zones significantly contributed to the output of the finite-element model. Also, the effective porosity parameter did not significantly affect the model's output. Using only the four significant hydraulic conductivity parameters; four two-level, four-factor designed experiments were conducted to exploit the first-order response surface defined by a …
Right-Hand-Side Multidimensional Optimality Analysis Of A Large Scale Linear Program Using Metamodelling Techniques, Osman Iyde
Theses and Dissertations
A methodology for optimality analysis of linear programs was developed by Johnson, Bauer, Moore, and Grant to create metamodels using response surface methodology techniques such as experimental design and least squares regression, and a geostatistical estimation technique, namely kriging. Metamodels have the form of a simple polynomial, and they predict the optimal objective function value of an LP for various levels of the constraints. They eliminate the necessity of determining which critical region contains the right-hand-side (RHS) vector of interest since they are valid over multiple critical regions. The methodology of Johnson, et al. can be applied to large scale …
Modified Goodness-Of-Fit Tests For The Inverse Gaussian Distribution With Two Unknown Parameter, Huseyin Gunes
Modified Goodness-Of-Fit Tests For The Inverse Gaussian Distribution With Two Unknown Parameter, Huseyin Gunes
Theses and Dissertations
Modified Kolmogorov- Smirnov (KS), Anderson-Darling (AD), Cramer-von Mises (CV), Kupier (V), and Watson (W) goodness-of-fit tests are generated for the inverse Gaussian distribution with unknown parameters. The inverse Gaussian parameters are estimated by maximum likelihood estimation. A Monte Carlo simulation of 50,000 repetitions is used to generate critical values for sample sizes of 5 through 50 with an increment of five, sample sizes of 60 through 100 with an increment of 10, and 24 different values of the inverse Gaussian shape parameter. A 50,000-repetition Monte Carlo power study is carried out using data with sample sizes of 5 through 100 …
Formal Foundations For The Specification Of Software Architecture, Mark J. Gerken
Formal Foundations For The Specification Of Software Architecture, Mark J. Gerken
Theses and Dissertations
This investigation establishes a formal foundation for software architecture that allows for the specification of large, non-trivial software systems using well founded, consistency preserving construction techniques. Two fundamental problems were addressed: how to define and express architectures formally using the concept of theories, and how architecture theories can be practically applied in specification construction. The initial stages of this investigation sought to establish a formal, mathematical relationship between functional specifications of behavior and specifications defining system structure. Experimental results lead to the conclusion that architectures defining the structure of functional operations can be defined using functional logic, but more complex …
Investigation Of Ground Target Detection Methods In Fully Polarimetric Wide Angle Synthetic Aperture Radar Images, Wayne B. Mclaggan
Investigation Of Ground Target Detection Methods In Fully Polarimetric Wide Angle Synthetic Aperture Radar Images, Wayne B. Mclaggan
Theses and Dissertations
Target detection is a high priority of the Air Force for the purpose of reconnaissance and bombardment. This research investigates and develops methods to distinguish ground targets from clutter (i.e. foliage, landscape etc.) in Wide Angle Synthetic Aperture Radar (WASAR) images. WASAR uses multiple aspect angle SAR images of the same target scene. The WASAR data was generated from a pre-release software package (XPATCH-ES) provided by the sponsor (WL-AARA). A statistical analysis and feature extraction is performed on the XPATCH-ES data. Polarimetric and wide angle covariance matrices are estimated and analyzed. From an analysis of the wide angle covariance matrix …
A Decision Model For Environmental Assessment Of Process Waste Products, Kyle F. Byard
A Decision Model For Environmental Assessment Of Process Waste Products, Kyle F. Byard
Theses and Dissertations
Environmental managers must compare the potential impacts of waste products when deciding upon courses of action. The estimation and comparison of these impacts is a subjective process, and few methods of comprehensive, quantitative comparison of waste products currently exist. The intent of this study is to develop a decision methodology to evaluate the environmental impacts of waste products and to score them for comparison. The method will follow established system design principles and incorporate significant characteristics of the waste material. Scores derived to represent the environmental impacts of materials will then he analyzed employing statistical and probabilistic methods to assess …
Analysis And Modeling Of An Airport Departure Process, Joseph E. Hebert
Analysis And Modeling Of An Airport Departure Process, Joseph E. Hebert
Theses and Dissertations
This study analyzes departure delays at a major airport using probability models to represent this non-homogeneous process. The models developed in this study expand on the Markovian models presently used by employing the method of stages to represent some of the model processes. This technique improves the user's ability to achieve a close fit for the service time probability distribution while maintaining the advantages of the Markovian model. The three types of models developed and compared all assume a Markovian system entry process. The first model uses an exponential distribution to model the service process. The second uses an Erlang …
Life-Cycle Cost Analysis For Radioactive Waste Remediation Alternatives, Thomas P. White, Ronald J. Toland, Dorian Y. Buitrago
Life-Cycle Cost Analysis For Radioactive Waste Remediation Alternatives, Thomas P. White, Ronald J. Toland, Dorian Y. Buitrago
Theses and Dissertations
This research has two primary objectives. The first is to develop a generic, interactive, spreadsheet-based life-cycle cost model that uses net present value and risk analysis techniques for cost comparison. The second is to apply the model specifically to the vitrification and cementation methods of waste remediation. By using spreadsheet analysis and graphics capabilities, the model will provide direct and objective comparisons of remediation alternatives. Since vitrification is a new technology, the plant design and operations are conceptual. Therefore, computer simulation and engineering judgement are integral to the vitrification LCC estimate.
Patient-Aircraft Forecasting For The Strategic Aeromedical Evacuation "Lift-Bed Process", Donald F. Kimminau
Patient-Aircraft Forecasting For The Strategic Aeromedical Evacuation "Lift-Bed Process", Donald F. Kimminau
Theses and Dissertations
The goal of this research is to develop a tool for the Global Patient Movement Requirements Center (GPMRC) to efficiently forecast Aeromedical Evacuation (AE) aircraft and schedule patients in the lift-bed process. During a contingency, GPMRC is responsible for requesting required airlift, and providing lift-bed candidates to the Theater Patient Movement Requirements Center. The objective is to evacuate all waiting patients while minimizing the number of C-141 aircraft which must be dedicated to the AE mission. In the solution process, a short-term forecast of patient movement requirements is input, including number of patients, bed and aircraft availability, and hub preferences. …
Response Surface Methodology As A Sensitivity Tool In Decision Analysis, David A. Meyers
Response Surface Methodology As A Sensitivity Tool In Decision Analysis, David A. Meyers
Theses and Dissertations
The purpose of this study is to evaluate response surface methodology as a sensitivity analysis tool in the area of decision analysis. The advent of low-cost personal computer software, such as DPLTM, has created an accessible tool with the ability to frame and solve influence diagrams for decision problems. This study provides a comparison of current sensitivity analysis techniques vs those made possible through response surface methodology (RSM). Sensitivity analysis alternatives are demonstrated on a decision problem concerning the evaluation of force structure options for the Department of Defense. Sensitivity analysis is performed on both one-way and two-way perturbations of …
Nonlinear Time Series Analysis, James A. Stewart
Nonlinear Time Series Analysis, James A. Stewart
Theses and Dissertations
This thesis applies neural network feature selection techniques to multivariate time series data to improve prediction of a target time series. Two approaches to feature selection are used. First, a subset enumeration method is used to determine which financial indicators are most useful for aiding in prediction of the S&P 500 futures daily price. The candidate indicators evaluated include RSI, Stochastics and several moving averages. Results indicate that the Stochastics and RSI indicators result in better prediction results than the moving averages. The second approach to feature selection is calculation of individual saliency metrics. A new decision boundary-based individual saliency …
A Methodology To Generate Air Force Materiel Command Manpower Reduction Alternatives, Steven T. Bishop
A Methodology To Generate Air Force Materiel Command Manpower Reduction Alternatives, Steven T. Bishop
Theses and Dissertations
The purpose of this study is to generate manpower authorization reduction alternatives for Air Force Materiel Command. The advent of low-cost personal computer software applications, such as Excel, has created an assessable tool with the ability to solve linear programming problems. This research examines the manpower resource reduction process of Air Force Materiel Command and models the Resources Allocation - Integrated Process Team (RA-IPT) decision process. A linear programming model is developed to assign these reduction through a weighted sum. The linear programming model is developed as a Microsoft Excel spreadsheet model, the Exercise Support Program (ESP), using Visual Basic …
Modeling Corps Artillery In A Theater Level Combat Model, Richard F. Bowyer
Modeling Corps Artillery In A Theater Level Combat Model, Richard F. Bowyer
Theses and Dissertations
This thesis describes the development of a methodology to explicitly model corps artillery assets in the Joint Staff's Joint Stochastic Analysis Research (J-STOCHWAR) and to quantify Army doctrine that guides organization of artillery for combat. The methodology incorporates corps artillery into the J-STOCHWAR by using the five fundamentals for organizing for combat, which reflect Army doctrine, and combines them with basic concepts already used in existing theater-level models. Other aspects of the problem include determining the appropriate level of detail, identifying techniques to solve the problem, and verifying the results. The proposed decision analysis solution technique provides a feasible method …
The Development Of A Metamodel For A Major Weapon System Cost Model, Paul W. Campbell
The Development Of A Metamodel For A Major Weapon System Cost Model, Paul W. Campbell
Theses and Dissertations
Cost estimation is an integral part of the procurement process of major weapon systems. Despite this essential role, the cost estimation process is able to provide the decision makers and analysts with a limited amount of insight. This is due to the complex nature of the cost models that typically contain 20-30 cost estimating relationships (CERs) and 50-100 variables. In an effort to provide the decision makers and analysts with additional insight to the cost estimate, this research demonstrates a methodology that will (1) identify the cost drivers of the cost model, ( 2) estimate the effects of these cost …
Estimation Of The Captive-Carry Survival Function For The Advanced Medium Range Air-To-Air Missile (Amraam), David R. Denhard
Estimation Of The Captive-Carry Survival Function For The Advanced Medium Range Air-To-Air Missile (Amraam), David R. Denhard
Theses and Dissertations
This thesis considers the problem of estimating the survival function of an item (probability that the item functions for a time greater than a given time t) from sampling data subject to partial right censoring (a portion of the items in the sampling data have not yet been observed to fail). Specifically the thesis describes several parametric and non-parametric statistical models that can be used when the sampling data is subject to partial right censoring. These models are applied to the case of estimating the captive-carry survival function of the AIM-120A Advanced Medium Range Air-to-Air Missile (AMRAAM).
A New Goodness-Of-Fit Test For The Gamma Distribution Based On Sample Spacings From Complete And Censored Samples, Huseyin Duman
A New Goodness-Of-Fit Test For The Gamma Distribution Based On Sample Spacings From Complete And Censored Samples, Huseyin Duman
Theses and Dissertations
This thesis studies a new goodness-of-fit test for the gamma distribution with known shape parameter. This test statistic, Z*, is based on spacings from complete or censored samples. The size of samples varied between 5 and 35. The critical value tables were generated for the Z* test statistic for complete and censored samples. The critical values were obtained for five different significance levels: 0.20 0.15, 0.10, 0.05, and 0.01. An extensive power study, containing 50,000 Monte Carlo runs was conducted using nine alternative distributions, Ha. It was observed that the Z* test statistic was more powerful against certain …
An Analytical Framework For Assessing Future Force Structure Requirements Under Uncertainty, Michael L. Fredley
An Analytical Framework For Assessing Future Force Structure Requirements Under Uncertainty, Michael L. Fredley
Theses and Dissertations
The objective of this research was to develop an analytical framework to assess future force structure requirements under the major uncertainties inherent in the post-Cold War era. Among the uncertainties are the frequency and nature of future threats to U.S. interests and the cost of maintaining, building, and demobilizing forces. The centerpiece of the methodology is a computer model which simulates the development of threats to U.S. interests and the actions the U.S. takes to protect those interests. From this simulation, the costs and risks associated with different policy alternatives can be estimated. The simulation is set within a broader …