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Articles 91 - 120 of 120
Full-Text Articles in Engineering
Text-Independent, Open-Set Speaker Recognition, Stephen V. Pellissier
Text-Independent, Open-Set Speaker Recognition, Stephen V. Pellissier
Theses and Dissertations
Speaker recognition, like other biometric personal identification techniques, depends upon a person's intrinsic characteristics. A realistically viable system must be capable of dealing with the open-set task. This effort attacks the open-set task, identifying the best features to use, and proposes the use of a fuzzy classifier followed by hypothesis testing as a model for text-independent, open-set speaker recognition. Using the TIMIT corpus and Rome Laboratory's GREENFLAG tactical communications corpus, this thesis demonstrates that the proposed system succeeded in open-set speaker recognition. Considering the fact that extremely short utterances were used to train the system (compared to other closed-set speaker …
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 …
Performance Study Of Shared Versus Nonshared Bandwidth On A Packet-Switched Network, John P. Stevens
Performance Study Of Shared Versus Nonshared Bandwidth On A Packet-Switched Network, John P. Stevens
Theses and Dissertations
In wide area computer data communications, many networks have evolved by satisfying increased user demands in the most expedient manner. In some cases, new users’ demands are satisfied by installing a new link, rather than sharing the links that are already in place. This research investigates the differences in performance between using a dedicated link for each source destination pair (nonshared bandwidth) and using a single link to be used by all source destination pairs (shared bandwidth). Simulation models are developed for a wide area network using shared bandwidth, and a wide area network using nonshared bandwidth. The quality of …
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 …
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 …
Statistical Process Control In Medical Surveillance. An Application Using Spirometry, Paul W. Mcaree
Statistical Process Control In Medical Surveillance. An Application Using Spirometry, Paul W. Mcaree
Theses and Dissertations
This research effort concentrated on applying statistical process control techniques to the results of seven years worth of spirometry exams of workers at Wright-Patterson AFB in helping the occupational health squadron identify potential work hazard areas. Each spirometry exam was classified as abnormal or normal based on a comparison with established normals or a significant loss of function from the previous year's exam for the individual. Each test was classified into the work area of the individual and the number of abnormalities per population of the work area was examined.
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 …
An Investigation Into The Effects Of Lateral Aerodynamic Asymmetries, Lateral Weight Asymmetries, And Differential Stabilator Bias On The F-15 Directional Flight Characteristics At High Angles Of Attack, David R. Evans
Theses and Dissertations
The F-15 is a stable aircraft throughout most of its flight envelope. However, it still exhibits an uncommanded yawing and rolling tendency at high angles-of-attack. Identified influencing factors of this uncommanded motion are lateral aerodynamic asymmetries, lateral weight asymmetries, and differential stabilator bias. Previous research into the effects of these influencing factors has been qualitative. This thesis quantifies the effects and then identifies a symmetric F-15 configuration. The quantifying metric presented is net yaw acceleration. This thesis used both computer simulation and experimental flight test to quantify these effects. A discussion of each influencing factors effects on the F-15B high …
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 …
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 …
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 …
Modeling Of Progressive Damage In Fiber-Reinforced Ceramic Matrix Composites, James P. Solti
Modeling Of Progressive Damage In Fiber-Reinforced Ceramic Matrix Composites, James P. Solti
Theses and Dissertations
An analytic methodology is developed to model the response of fiber-reinforced ceramic matrix composites (CMOs) when subjected to monotonic and fatigue loadings. The analysis requires the formulation of (1) a micromechanics model which defines the laminate's geometry and constitutive relationship; (2) failure criteria which estimate the extent of microstructural damage, and, finally, (3) a means of analyzing frictional slip, fiber pull-out, interfacial wear and laminate failure. For the present study, the behavior of unidirectional and crossply CMOs is investigated using modified shear-lag theory in conjunction with a set of failure criteria with a minimum reliance on empirical data. The damage …
Compressible Turbulence Measurements In A Supersonic Boundary Layer With Impinging Shock Wave Interaction, Michael J. Meyer
Compressible Turbulence Measurements In A Supersonic Boundary Layer With Impinging Shock Wave Interaction, Michael J. Meyer
Theses and Dissertations
No abstract provided.
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 …
Replicative Use Of An External Model In Simulation Variance Reduction, Thomas H. Irish
Replicative Use Of An External Model In Simulation Variance Reduction, Thomas H. Irish
Theses and Dissertations
The use of control variates is a well-known variance reduction technique for discrete event simulation experiments. Currently, internal control variates are used almost exclusively by practitioners and researchers when using control variates. The primary objective of this study is to explore the variance reduction achieved by the replicative use of an external, analytical model to generate control variates. Performance for the analytical control variates is compared to the performance of typical internal and external control variates for both an open and a closed queueing network. Performance measures used are confidence interval width reduction, realized coverage, and estimated Mean Square Error. …
Forecasting And Explanatory Models For Middle Eastern Defense Budgets: A Case Study Of Saudi Arabia, Robert S. Renfro Ii
Forecasting And Explanatory Models For Middle Eastern Defense Budgets: A Case Study Of Saudi Arabia, Robert S. Renfro Ii
Theses and Dissertations
This thesis focuses on means of forecasting Saudi Arabian military expenditures and the effect of such expenditures on the United States. Saudi Arabia is one of the largest purchasers of American arms and will continue to be for many years. Saudi Arabia has experienced several recent changes in economic and government policy. Using exponential smoothing techniques and linear regression, we isolated several trends in Saudi Arabian military expenditures. Using two linear regression models, military expenditures were then forecast with excellent results. The first model considered the assumption that Gulf War spending would continue. This model uses Saudi Arabian Gross Domestic …
Estimating Risks In Emerging Soil Remediation Technologies, Thomas J. Timmerman
Estimating Risks In Emerging Soil Remediation Technologies, Thomas J. Timmerman
Theses and Dissertations
The Department of Energy is focusing a long-term development effort on producing cheaper, safer, and faster state-of-the-art soil remediation technologies. To assist with the management of these innovative technology development projects, ways of quantifiably measuring technical risk were investigated through a detailed literature review. 'Technical risk' was defined in this study as the combination of the consequences of undesired events and their likelihood. Careful design of the inputs into a technology selection decision support system accounted for the uncertainty in forecasting final characteristics of remediation technologies still in the early phases of R&D. Experts made subjective probability estimates of these …
Modeling Mobility Engineering In A Theater Level Combat Model, Brian K. Hobson
Modeling Mobility Engineering In A Theater Level Combat Model, Brian K. Hobson
Theses and Dissertations
This thesis describes the development of a methodology to model theater-level mobility engineering assets in the Joint Staff's Joint Warfare Analysis Experimental Prototype (JWAEP) and to quantify the joint and Army doctrine that guides the task organization of engineers for combat and which quantifies engineer mobility effects in combat. The methodology incorporates theater-level mobility engineering assets into the JWAEP by using Mission, Enemy, Troops available, Terrain, and Time (MET-T principles which reflect joint and Army doctrine, and combines them with the existing basic concepts in other theater-level models. Additional aspects of the problem include determining the manmade and natural obstacles' …
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 …
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 …
Statistical Process Control And Medical Surveillance. An Application With Liver Function Tests, Bryan D. Richardson
Statistical Process Control And Medical Surveillance. An Application With Liver Function Tests, Bryan D. Richardson
Theses and Dissertations
Traditionally, medical surveillance of liver disease generally involves a battery of tests. This research used multivariate analysis techniques to reduce the number of measures required to identify liver dysfunction and found using a Transferase Index (a combination of three tests; ALT, AST, and GGT) provided the most satisfying assessment, but the single best indicator, ALT, may be sufficient. Transferase Index and ALT criterion were both applied to SPC control charts. Through the use of statistical process control (SPC), this research identified work zones possessing signs of adverse effects to an individual's liver as a possible result of their work environment …
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 …
Surveillance Plan For Monitoring The Shelf-Life Of Chemical Defense Coveralls, Robert E. Neher Jr.
Surveillance Plan For Monitoring The Shelf-Life Of Chemical Defense Coveralls, Robert E. Neher Jr.
Theses and Dissertations
This thesis found a surveillance plan to be used to monitor the shelf-life of the Air Force's chemical defense coveralls. The sampling tests are destructive and the objective was to find a surveillance plan that would minimize the number of suits sampled yet provide enough information to accurately determine if the chemical defense coveralls had degraded past a minimum acceptable level. Six sampling plans were developed and analyzed. The sampling plans included the Air Force's original fixed sampling plan, several variations of sequential sampling plans, a Bayesian sampling plan, and an ad hoc pre-posturing plan. Each of the sampling plans …
A Crosstalk Correcting Router That Uses Online Noise Simulation To Route High-Speed Multichip Modules, Kenneth J. Mcclellan Jr.
A Crosstalk Correcting Router That Uses Online Noise Simulation To Route High-Speed Multichip Modules, Kenneth J. Mcclellan Jr.
Theses and Dissertations
Existing Multi Chip 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 …
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 …
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 …
Procedures For Testing Deterministic Scheduling Models: A Dakota Case Study, Keith H. Mccready
Procedures For Testing Deterministic Scheduling Models: A Dakota Case Study, Keith H. Mccready
Theses and Dissertations
The DAKOTA scheduling system has been proposed for use in the United States Air Forces Europe's (USAFE's) Operational Support Airlift (OSA) scheduling. This thesis examines the OSA scheduling topic and reviews the relevant literature on vehicle routing, concluding that exact methods are intractable for large problem sizes. Consequently, heuristic methods must be considered. This thesis takes a detailed look at the DAKOTA heuristic. It examines the concepts of Validation, Verification and Accreditation (VV&A), particularly as they apply to heuristics and algorithms. It then defines what measures of performance may prove useful in judging heuristics and algorithms in general, and details …
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 …
Issues And Challenges In Validating Military Simulation Models, Michael R. Elmer
Issues And Challenges In Validating Military Simulation Models, Michael R. Elmer
Theses and Dissertations
The purpose of this thesis is to address the challenges of validating simulation models, especially those challenges facing military simulation analysts. Three distinct issues are of concern to the military simulation analyst: (1) What type of validation effort do the academic experts recommend? (2) What does the military policy say is necessary for a proper validation effort? (3) What can a simulation practitioner realistically accomplish given time and resource constraints? Four methodologies were chosen to represent the academic perspective on validation. A model of validation methods is integrated from the methodologies of these four simulation validation references. The validation policies …
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 …