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Articles 4621 - 4650 of 5600
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Characterization Of Spatial And Temporal Anisotropy In Turbulent Mixing Layers Using Optical Techniques, Patrick J. Gardner
Characterization Of Spatial And Temporal Anisotropy In Turbulent Mixing Layers Using Optical Techniques, Patrick J. Gardner
Theses and Dissertations
The optical aberrations induced by mixing layers of dissimilar gases are recorded and analyzed in order to characterize the spatial and temporal properties of the flow. Laser light was propagated through a mixing layer of Helium and Nitrogen gas, having velocities of 8.5 m/sec and 1.5 m/sec, respectively. The light was propagated in a direction perpendicular to the plane of the mixing layer. The mixing layer was evaluated in two experimental regimes: free turbulent mixing, where the mixing layer spreads into the surrounding air; and channel flow, where the mixing layer is confined to a rectangular channel. The optical perturbations …
A Response Surface Methodology Approach To Groundwater Model Calibration, Jeffrey B. Rowland
A Response Surface Methodology Approach To Groundwater Model Calibration, Jeffrey B. Rowland
Theses and Dissertations
This thesis examined the effect of parameter bounding, a reduced data set, and data enrichment techniques on a response surface methodology (RSM) approach to groundwater model calibration. The four phases of the study included a calibration using a very dense data matrix, a calibration using a sparse calibration matrix, an evaluation of several data enrichment techniques, and a calibration using a data matrix enlarged with the use of the best enrichment technique. All calibrations were conducted using only a first order approximation to the response surface and with bounds placed on the input parameters. The first two calibrations using the …
Generalized Hidden Filter Markov Models Applied To Speaker Recognition, John M. Colombi
Generalized Hidden Filter Markov Models Applied To Speaker Recognition, John M. Colombi
Theses and Dissertations
Classification of time series has wide Air Force, DoD and commercial interest, from automatic target recognition systems on munitions to recognition of speakers in diverse environments. The ability to effectively model the temporal information contained in a sequence is of paramount importance. Toward this goal, this research develops theoretical extensions to a class of stochastic models and demonstrates their effectiveness on the problem of text-independent (language constrained) speaker recognition. Specifically within the hidden Markov model architecture, additional constraints are implemented which better incorporate observation correlations and context, where standard approaches fail. Two methods of modeling correlations are developed, and their …
International Space Station Traffic Modeling And Simulation, Jillene B. Rylaarsdam
International Space Station Traffic Modeling And Simulation, Jillene B. Rylaarsdam
Theses and Dissertations
In an effort to provide NASA with an alternative perspective and some insights to the operational planning of the International Space Station (ISS), this research developed a simulation environment for the ISS and devised a method to evaluate various altitude strategies. The simulation environment allowed us to incorporate the natural random behaviors which affect the lifetime of objects in low earth orbit. We created prototype models of the operational planning process to analyze current altitude strategy approaches and acquire new strategies from insights observed. In addition, by extrapolating random future solar activity values from the interpolation of historical data, we …
A Generic Intelligent Architecture For Computer-Aided Training Of Procedural Knowledge, Freeman A. Kilpatrick Jr.
A Generic Intelligent Architecture For Computer-Aided Training Of Procedural Knowledge, Freeman A. Kilpatrick Jr.
Theses and Dissertations
Intelligent Tutoring System (ITS) development is a knowledge-intensive task, suffering from the same knowledge acquisition bottleneck that plagues most Artificial Intelligence (AI) systems. This research presents an architecture that requires knowledge only in the form of a shallow knowledge base and a simulation to produce a training system. The knowledge base provides the basic procedural knowledge while the simulation provides context. The remainder of the knowledge required for training is learned through the interaction of these components in a state-space scenario exploration process and inductive machine learning. These knowledge components are used only at the interface level, allowing the internal …
Linear And Non-Linear Preprocessing Of Wavefront Sensor Slope Measurements For Improved Adaptive Optics Performance, Dennis A. Montera
Linear And Non-Linear Preprocessing Of Wavefront Sensor Slope Measurements For Improved Adaptive Optics Performance, Dennis A. Montera
Theses and Dissertations
New methods for preprocessing wavefront sensor (WFS) slope measurements are presented. Methods are developed to improve the accuracy of WFS slope measurements, as well as estimating key atmospheric and system parameters from the slope signals. Both statistical and artificial neural network solutions are investigated. Also, new atmospheric models for generating slope and phase data with the proper spatial and temporal statistics are developed. The experiments in improving the accuracy of WFS slope measurements include reducing the WFS slope measurement error and compensating for adaptive optics system time delay through temporal slope prediction. The experiments in key parameter estimation include estimating …
Structural Damage Identification From Limited Measurement Data, Richard G. Cobb
Structural Damage Identification From Limited Measurement Data, Richard G. Cobb
Theses and Dissertations
The research focused on the development of a new method to identify damaged structural elements from a large flexible space structure on-orbit, using limited measured modal data. Limited measured modal data is loosely defined as measured data containing only a few modal frequencies and less than 10% of the total structural degrees-of-freedom. This effort was decomposed into four specific tasks. The first is the identification of partial modal properties from measured data of the nominal space structure. Second, the finite element model must be adjusted to match the measured nominal partial data. The third task is an analysis of the …
Comparison Of The Control Anticipation Parameter And The Bandwidth Criterion During The Landing Task, David A. Kivioja
Comparison Of The Control Anticipation Parameter And The Bandwidth Criterion During The Landing Task, David A. Kivioja
Theses and Dissertations
Many handling qualities criteria have been developed which predict pilot opinion of landing aircraft. MIL-STD-1797A, 'Flying Qualities of Piloted Aircraft' lists six different criteria. However, applying all six criteria to one aircraft can lead to conflicting results. The Air Force Institute of Technology (AFIT) along with the Flight Dynamics Laboratory have conducted research to evaluate differences among the handling qualities criteria in MIL-STD-1797A. The overall objective of this thesis was to determine similarities and discrepancies between the Control Anticipation Parameter (CAP) and bandwidth criteria, and to evaluate the advantage of including a dropback criterion with the bandwidth criterion. Results of …
Modeling Space In The Air Force Command Exercise System (Aces), Robert Payne Jr.
Modeling Space In The Air Force Command Exercise System (Aces), Robert Payne Jr.
Theses and Dissertations
In response to the increased influence of space forces on today's battlefield, several theater level models were analyzed for the presentation of space forces. These models were the Extended Air Defense Simulation (EADSIM), the Joint Theater Level Simulation (JTLS), the Integrated Theater Engagement Model (ITEM), the Tactical Warfare Model (TACWAR), Thunder, Janus, and the Aggregate Level Simulation Protocol (ALSP). While ALSP is not a model but a simulation protocol connecting various models, it was studied because it appears to be the future of modeling. The consensus of the analysis was that space forces are virtually ignored by most of the …
Requirement For C-130 Aircraft In The Intratheater Korean Scenario, Philip B. Oglesby
Requirement For C-130 Aircraft In The Intratheater Korean Scenario, Philip B. Oglesby
Theses and Dissertations
In an effort to provide a timely and reasonably accurate methodology for determining C-130 intratheater airlift requirements, this research concentrated on a rough-cut capacity approach using a straight forward linear programming spreadsheet model. To provide more detailed analysis, a more sophisticated linear program was investigated. Specifically, the spreadsheet model calculated the minimum number of C-130s required to carry required cargo, passenger, and aeromedical loads based on user-defined daily requirements. For a given scenario, inputs include the daily requirements and the expected capacity for C-130 aircraft, trucks, and 22-car trains. Included in the capacity inputs are the number of daily cycles …
Airlift System Sensitivity To Perturbed Time-Phased Force Deployment Data, Glenn G. Rousseau
Airlift System Sensitivity To Perturbed Time-Phased Force Deployment Data, Glenn G. Rousseau
Theses and Dissertations
This research evaluated the effects of perturbations in time phased force deployment data (TPFDD) on airlift system performance. Four characteristics of two TPFDD files were perturbed according to a 2(4-1) fractional factorial experimental design and then fed into the Airlift Flow Module (AFM) simulation. Specifically, small, constrained perturbations were made to the specified locations, the timeline, the amounts of cargo and passengers, and the proportion of outsize and oversize cargo categories. The effects these perturbations had on AFM output were interpreted using factor analysis. The computed factor scores, when plotted against one another, provided sensitivity plots, graphically depicting the sensitivity …
A Methodology For The Analysis And Prediction Of Air Force Officer Retention Rates, Mark A. Basalla
A Methodology For The Analysis And Prediction Of Air Force Officer Retention Rates, Mark A. Basalla
Theses and Dissertations
The purpose of this study is to investigate the effects of certain national economic conditions and certain Air Force related conditions on officer retention rates and to build, verify, and validate a multivariate linear regression model to be used by Air Force personnel management officials that will predict officer retention rates for rated and non-rated line officers aggregated by Yeargroups and AFSC groups. Previous retention models were reviewed to study possible predictors and methodologies.
Modeling Diminishing Marginal Returns: An Application To The Aircraft Availability Model, Wayne L. Zorn
Modeling Diminishing Marginal Returns: An Application To The Aircraft Availability Model, Wayne L. Zorn
Theses and Dissertations
The Aircraft Availability Model (AAM) provides the Air Force with a worldwide peacetime requirement for reparable spare parts. This research models AAM methodology as it relates to the concept of diminishing marginal returns in resource application. Three separate modeling techniques are investigated with the goal of reformulating the AAM as a mathematical programming model that provides a comparable solution and a capable tool for the conduct of sensitivity analysis. The general formulations presented here are continuous non-linear, continuous linear, and piecewise linear discrete/continuous models. Two formulations of the piecewise linear discrete/continuous model are presented. The piecewise linear model based on …
Measuring The Impact Of Programmed Depot Maintenance Funding Shortfalls On Weapon System Availability, Donald F. Hurry
Measuring The Impact Of Programmed Depot Maintenance Funding Shortfalls On Weapon System Availability, Donald F. Hurry
Theses and Dissertations
This study used the Poisson regression technique, bootstrap estimates, and the Kaplan-Meier estimates for survivor curves to determine the impact of Programmed Depot Maintenance (PDM) on weapon system availability. More specifically, these techniques estimated the effect in the number failures per year due to PDM, but the bootstrap technique also estimated the effect in the amount of downtime experienced by a weapon system due to PDM. Although the Poisson regression model did not pass the rigors of statistical testing, the Poisson regression suggested differences in the number of failures per year between PDM and no-PDM weapon systems. The results of …
A Methodology To Assess The Air Force Materiel Command's Exercise Support Program's Weighting Scheme, Gilbert D. Ness
A Methodology To Assess The Air Force Materiel Command's Exercise Support Program's Weighting Scheme, Gilbert D. Ness
Theses and Dissertations
This research performs analysis on the Air Force Materiel Command's Exercise Support Program's Weighting Scheme so that decision makers can create a more efficient and effective Resource Allocation - Integrated Process Team (RA-IPT) manpower allocation process. A linear programming (LP) model was derived from the Exercise Support Program (ESP) to assign manpower reductions throughout the Mission Element Board (MEB) organizational level in AFMC. Parametric analysis was performed on the LP model by simultaneously changing multiple objective function coefficients with the use of various direction vectors. These direction vectors were applied with the use of an incrementally increasing scalar step size …
Development Of A Decision Support System For The Department Of Energy's Selection Of Waste Site Remediation Technologies, Brian E. Ralston
Development Of A Decision Support System For The Department Of Energy's Selection Of Waste Site Remediation Technologies, Brian E. Ralston
Theses and Dissertations
The Department of Energy is faced with the complex decision of selecting technologies for waste site remediation. This research focused on developing a decision support system to aid the decision maker in selecting the best strategy of remediation technologies. A decision analysis model was developed which incorporates life cycle cost data, risk information, and user input, to analyze the technology choices. The research outlined the use of multiple attribute utility theory using exponential attribute utility functions with a simple additive objective function. The best available data was used to demonstrate the capabilities of the model. The model provides the decision …
An Investigation Of Preliminary Feature Screening Using Signal-To-Noise Ratios, David B. Sumrell
An Investigation Of Preliminary Feature Screening Using Signal-To-Noise Ratios, David B. Sumrell
Theses and Dissertations
A new saliency metric and a new saliency screening method are developed. This new metric, the SN saliency metric, is based upon signal-to-noise ratios, where the signal is provided by a sum of squared weights associated with a given feature, and the noise is based upon a sum of squared weights associated with a reference noise feature which is injected into the data. The resultant metric allows for a direct comparison of the feature of interest with a reference noise feature which is known to be nonsalient. The SN saliency screening method, which uses the SN saliency metric, offers the …
Optimization Analysis For Design And Planning Of Multi-Project Programs, Victor D. Wiley
Optimization Analysis For Design And Planning Of Multi-Project Programs, Victor D. Wiley
Theses and Dissertations
Program Management concerns the long-term planning, coordination, and control of major technological, engineering, scientific, and/or developmental activities. In general, programs tend to be exceptionally large, consisting of several parallel or sequential projects or groups of projects. While many of the approaches developed for projects have been used in program management, there are critical differences between programs and projects. A key difference is the magnitude of programs, both in program duration and number of tasks to be coordinated. In addition, project parameters are driven by program decisions. While a large number of modeling efforts have focused at the project level, very …
Applying Response Surface Methodology To Readiness-Based Leveling Of Reparable Items, Todd E. May
Applying Response Surface Methodology To Readiness-Based Leveling Of Reparable Items, Todd E. May
Theses and Dissertations
Reparable items play a large role in determining the readiness of United States Air Force weapon systems. Many factors characterizing flying tempo and item repair and transit time influence the level of fleet readiness. Readiness-Based Leveling (RBL) considers these factors as it seeks to maximize aircraft readiness as it allocates spare reparable items between bases and a depot. The purpose of this research was to demonstrate the validity of using response surface methodology (RSM) within the context of RBL in an effort to quantify the influences these factors have on aircraft readiness. RSM applied designed experiments and least squares regressions …
Riblet Effects On Gortler Vortex Development Over A Concave Surface, James A. Rothenflue
Riblet Effects On Gortler Vortex Development Over A Concave Surface, James A. Rothenflue
Theses and Dissertations
Riblet effects on Goertler vortex development in laminar and transitional flows were measured using three-dimensional laser-Doppler anemometry. Three freestream velocities were tested such that riblet spacing corresponded to Goertler vortex (GV) wavelengths which presumably would be either strongly amplified, weakly amplified, or attenuated by centrifugal forces on a curved surface. Experiments revealed the development of paired, counterrotating vortices within the riblet valleys over both flat and concave surfaces. For riblet spacings equivalent to weakly or non-amplified GV wavelengths, GV development on a curved surface was above the riblets and was delayed by the addition of riblets. The GV wavelength was …
Application Of Autoregressive Moving Average Linear Prediction Filters To The Characterization Of Solar Wind-Magnetosphere Coupling, Carter N. Borst
Application Of Autoregressive Moving Average Linear Prediction Filters To The Characterization Of Solar Wind-Magnetosphere Coupling, Carter N. Borst
Theses and Dissertations
Linear prediction filtering techniques have been used in studying the coupling processes between the solar wind and magnetosphere. The magnetosphere is a complex, dynamic system with at least two independent coupling methods for energy input, driven and unloading. Linear models were built and tested on the Bargatze data set, consisting of over 70 days of geomagnetic indices and solar wind data ordered in 34 intervals of increasing geomagnetic activity. Linear filtering techniques employing single-and multiple-input, autoregressive models predicted values of the magnetic index AL from solar wind data. The impulse response curves of the AL-coupling function groups showed amplitude peaks …
Transforming Algebraically-Based Object Models Into A Canonical Form For Design Refinement, Charles G. Beem
Transforming Algebraically-Based Object Models Into A Canonical Form For Design Refinement, Charles G. Beem
Theses and Dissertations
The understandability of object-oriented design techniques and the rigor of formal methods have improved the state of software development; however, both ideas have limitations. Object-oriented techniques, which are semi-formal, can still result in incorrect designs, while formal methods are complex and require an extensive mathematical background. The two approaches can be coupled, however, to produce designs that are both understandable and verifiable, and to produce executable code. This research proposes an approach where object-oriented models are first represented algebraically in a formal specification language such as LARCH and then transformed into a canonical form suitable for design refinement. In the …
The Application Of Hybridized Genetic Algorithms To The Protein Folding Problem, Robert L. Gaulke
The Application Of Hybridized Genetic Algorithms To The Protein Folding Problem, Robert L. Gaulke
Theses and Dissertations
The protein folding problem consists of attempting to determine the native conformation of a protein given its primary structure. This study examines various methods of hybridizing a genetic algorithm implementation in order to minimize an energy function and predict the conformation (structure) of Met-enkephalin. Genetic Algorithms are semi-optimal algorithms designed to explore and exploit a search space. The genetic algorithm uses selection, recombination, and mutation operators on populations of strings which represent possible solutions to the given problem. One step in solving the protein folding problem is the design of efficient energy minimization techniques. A conjugate gradient minimization technique is …
An Object-Oriented, Formal Methods Approach To Organizational Process Modeling, Vincent S. Hibdon
An Object-Oriented, Formal Methods Approach To Organizational Process Modeling, Vincent S. Hibdon
Theses and Dissertations
This document presents a methodology for developing an organizational process model which is based on the principles of object oriented design and formal software engineering methods. The methodology begins with the development of an object oriented Rumbaugh model (27). The Rumbaugh model is then formally specified in Z (Zed) schemas. Finally, the Z specifications are translated into an executable model in the Software Refinery Environment(TM). This model is described based on the AF wing domain and developed in this domain. The proposed methodology is then shown to produce a very general model which is extendable across almost any domain. The …
Determining The Effects Of Waste Coal Ash On Landfill Radon Levels, Richard S. Krysiak Jr.
Determining The Effects Of Waste Coal Ash On Landfill Radon Levels, Richard S. Krysiak Jr.
Theses and Dissertations
Coal contains trace amounts of the primary radionuclides 40K, and elements of the 4n (232Th), 4n+2 (238U), and 4n+3 (235U) series including 220Rn and 222Rn. Combustion of coal by electric power and heat plants result in concentration of noncombustible mineral matter, including most of the radionuclides, in the coal ash. The increased radiation due to the concentration of radionuclides is known as technologically enhanced natural radiation. The purpose of this research was to determine the effects of landfilled coal ash on one specific aspect of technologically enhanced natural radiation, radon levels. …
The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold
The Role Of Frame Selection And Bispectrum Phase Reconstruction For Speckle Imaging Through Atmospheric Turbulence, Elizabeth A. Harpold
Theses and Dissertations
Frame selection using quality sharpness metrics have been shown in previous AFIT theses, to be effective in improving the final product of images obtained using adaptive optics. This thesis extends this idea to noncompensated speckle image data. Speckle image reconstruction is simulated with and without frame selection. Speckle images require the processing of hundreds of data frames. Frame selection is a method of reducing the amount of data required to reconstruct the image. A collection of short exposure image data frames of a single object are sorted based on sharpness metrics. Only the highest quality frames are retained and processed …
A Comparison Of Methods For Estimating Rms Error: A `Brute Force" Approach Versus A Mathematically-Elegant Approach, As Applied To The Calculation Of A Specific Retrieval Error For A Limb-Scanning Microwave Radiometer-Spectrometer, Larry L. Johnson
Theses and Dissertations
The Millimeter-wave Atmospheric Sounder (MAS) is a high resolution limb- scanning microwave radiometer-spectrometer which has been flown aboard the Space Shuttle. The instrument was designed to sense the microwave emission from several upper atmospheric constituents, including water vapor and ozone. The resonant frequencies of water vapor and ozone are extremely close (183 and 184 GHz, respectively), so that the high-frequency wing of the water vapor spectrum overlaps the low frequency wing of the ozone spectrum. Consequently, the measured ozone spectrum incorporates a slight water vapor contribution; therefore, the retrieved ozone profile is dependent on the true water vapor profile. The …
A System Dynamics Approach To Modelling The Degradation Of Biochemical Oxygen Demand In A Constructed Wetland Receiving Stormwater Runoff, Leslie A. Mudgett
A System Dynamics Approach To Modelling The Degradation Of Biochemical Oxygen Demand In A Constructed Wetland Receiving Stormwater Runoff, Leslie A. Mudgett
Theses and Dissertations
The objective of this research was to develop a tool to aid the Air Force Environmental Manager in the identification of the design parameters of a constructed wetland system that may be optimized to provide a desired biochemical oxygen demand (BOD) removal efficiency during the treatment of Air Force stormwater runoff. The objective is achieved through the development and use of a system dynamics model which simulates the hydrological functions of a constructed wetland as well as the processes within the wetland responsible for degradation of BOD. Based on literature review, the primary mechanism responsible for the degradation of BOD …
Modified Model For Transient Response Of Mrna Synthesis To Magnetic Field Exposure, Timothy W. Crosnoe
Modified Model For Transient Response Of Mrna Synthesis To Magnetic Field Exposure, Timothy W. Crosnoe
Theses and Dissertations
It is a well-known fact that high frequency, or radio frequency, radiation can be directly harmful to biological tissue. The radiation frequencies to which humans are most exposed, however, are the extremely low frequencies, or ELFs. To date there has been no definitive measure for predicting the ability of low frequency electromagnetic radiation to cause adverse biological effects. Two specific measures, average magnetic field and kinetic index, have been used in studies to determine if they are useful predictors of adverse effects, specifically leukemia. Unfortunately, both have shown only marginal results. This thesis analyzed and improved the kinetic index measure …
Velocity Determination For An Inverted Pseudolite Navigation Reference System, Jeffrey M. Hebert
Velocity Determination For An Inverted Pseudolite Navigation Reference System, Jeffrey M. Hebert
Theses and Dissertations
As navigation systems continue to improve in performance and features, the Air Force must develop better Navigation Reference Systems (NRS) to keep pace with technology. Specifically, with the advent of enhanced, integrated Global Positioning System (GPS) and Inertial Navigation System (INS) navigators, emphasis is placed on the measuring performance in the presence of GPS jamming. To meet these needs, a new NRS, dubbed the Sub-Meter Accuracy Reference System (SARS), is being developed by the 746th Test Squadron, Holloman AFB, New Mexico. SARS uses a unique, inverted GPS pseudolite positioning system to determine a reference trajectory. This research investigates two post …