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Articles 4441 - 4470 of 5699
Full-Text Articles in Engineering
Speaker Verification In The Presence Of Channel Mismatch Using Gaussian Mixture Models, Robert B. Reid
Speaker Verification In The Presence Of Channel Mismatch Using Gaussian Mixture Models, Robert B. Reid
Theses and Dissertations
A channel compensation method is sought for use in speaker identification (ID) and verification applications under matched and mismatched training and testing conditions. This work expands on previous work on matched conditions by investigating three techniques on matched and mismatched conditions using the TIMIT and NTIMIT speech databases. First, previous results on 168 speakers are reproduced for matched conditions using Gaussian mixture models (GMM) and mel-frequency cepstral coefficients. Next, cepstral mean subtraction with band limiting (CMSBL) is investigated. The third method, developed in this thesis uses a modified Wiener filtering approach to channel compensation. New GMMs are created for each …
Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb
Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb
Theses and Dissertations
This research effort investigated the effects of evaporation of water on the heat transferred to the wall of the diverging portion of a porous walled nozzle The AFIT High Pressure Shock Tube was used with a two-dimensional Mach 3 nozzle. One flat surface of the nozzle was fitted with a layer of porous stainless steel from the nozzle throat to the exit. This porous material was saturated with water to simulate liquid transpiration cooling. Surface temperature data was taken in this region using fast response coaxial thermocouple. Heat transfer was determined from the surface temperature history. Data was taken for …
Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer
Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer
Theses and Dissertations
Recent research efforts have applied the receding horizon Model Predictive Control (MPC) strategy to linearized high performance aerospace systems. The research contained in this thesis used these recent results in order to apply the MPC strategy to a nonlinear high performance aerospace system, specifically an F-16 fighter aircraft model. The model was commanded to follow dynamic trajectories of roll angle and altitude. Further, adaptive constraint techniques were used to improve system tracking. To accomplish these tasks, code and block diagrams were generated using the commercial software packages of Matlab and Simulink. Numerous simulations were conducted with the goal of achieving …
A Performance Analysis Of The Faugeras Color Space As A Component Of Color Histogram-Based Image Retrieval, Chad A. Vander Meer
A Performance Analysis Of The Faugeras Color Space As A Component Of Color Histogram-Based Image Retrieval, Chad A. Vander Meer
Theses and Dissertations
The use of color histograms for image retrieval from databases has been implemented in many variations. Selecting the appropriate color space for similarity comparisons is an important part of a color histogram technique. This paper serves to introduce and evaluate the performance of a color space through the use of color histograms. Performance is evaluated by correlating the similarity results obtained from various color feature vector techniques (including color histgramming) to those gathered through a human perceptual test. The perceptual test required 36 human subjects to evaluate the similarity of 10 military aircraft images. The same 10 images were also …
A System Dynamics Model Of The Bioavailability Of Metals In Constructed Wetland Sediment, Timothy S. Wood
A System Dynamics Model Of The Bioavailability Of Metals In Constructed Wetland Sediment, Timothy S. Wood
Theses and Dissertations
Constructed wetlands used for storm water treatment accumulate metals primarily in their sediment. This sediment has the potential to produce toxic effects in benthic organisms at some period in time. Bioavailability of metals in sediment is directly linked to pore water metal activity. The mechanisms that influence pore water metal activity are included in physical, chemical, and biological processes. A system dynamics model was developed to represent these processes and the major influences affecting pore water metal activity in a treatment wetland receiving storm water influent. The model structure and behavior was tested and validated using several system dynamics validation …
Optimal Pulsed Pumping For Remediation Of Aquifers When Sorption Is Rate-Limited, Lawrence J. Schmitt
Optimal Pulsed Pumping For Remediation Of Aquifers When Sorption Is Rate-Limited, Lawrence J. Schmitt
Theses and Dissertations
A variational optimization technique is developed to acquire an optimal schedule of pulsed pumping operations for use at existing pump-and-treat aquifer remediation sites. The optimization problem is stated as a minimization of a generic management objective functional, constrained by the contaminant transport equations in two-dimensional or three-dimensional flow models which account for rate-limited sorption. The two-dimensional case is fully developed and a first-order rate equation is used to describe the transport of sorbing contaminant. The first variation provides necessary optimality conditions that must be met by any optimal solution, in turn leading to a pulsed pumping schedule of operation. The …
Space Shuttle East Coast Abort Modes For High Inclination Launches, Richard K. Neufang
Space Shuttle East Coast Abort Modes For High Inclination Launches, Richard K. Neufang
Theses and Dissertations
This study investigated the possibility of abort landing the Space Shuttle at east coast airports when launched at inclinations of 51.6 degrees or more. Computer modeling was used to characterize both the Shuttle launch out of Cape Canaveral and two methods of unpowered abort descents from various points in the launch following Solid Rocket Booster SRB separation. The first method used varying values of pitch and roll held constant to control the descent. By plotting the latitude and longitude of the point in the descent when the nominal landing altitude was achieved against locations of east coast airports it was …
The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson
The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson
Theses and Dissertations
The rational resolution analysis RRA is introduced and developed as a generalization of the integer, dilation multiresolution analyses MRA developed by Mallat and Meyer. Rational dilation factors are achieved by relaxing the condition on MRAs that successive approximation spaces be embedded. Conditions for perfect reconstruction are discussed and it is shown that perfect reconstruction is possible with specific constraints on the scaling function the scaling filter must have its roots on the unit circle. Furthermore, the required arrangement of the roots indicate the scaling function must be derived from a B-spline of some degree. It is proven the only compactly …
Message-Bundle Converting In Intenet Protocol Multicast-Based High Level Architecture Exercises, Tracy A. Bobo
Message-Bundle Converting In Intenet Protocol Multicast-Based High Level Architecture Exercises, Tracy A. Bobo
Theses and Dissertations
The Department of Defense is pushing for more wide-spread and realistic interactive training simulations which increases the demand on network capacity and resources. While network bandwidth is a measurable resource, packet bandwidth, or the number of packets-per-second (Pk/s) a host can handle, is a shifting commodity. This research analyzes host performance characteristics under varying data loads. The hosts include SGI single and multi-processor systems and Intel Pentium platforms using both Windows 95 and Linux Operating Systems. The networking media covers Ethernet, ATM and FDDI. For the ATM network, both AAL5 and IP over ATM were analyzed. With the data from …
Modeling Uptake And Translocation Of Lead (Pb) In Maize For The Purposes Of Phytoextraction, Mark A. Brennan
Modeling Uptake And Translocation Of Lead (Pb) In Maize For The Purposes Of Phytoextraction, Mark A. Brennan
Theses and Dissertations
Phytoextraction is a remediation technology that uses plants to remove heavy metals from soil. This technology has the potential to decrease the costs of remediating contaminated sites by several orders of magnitude compared to traditional technologies. To effectively implement this technology requires an understanding of the plant processes that control uptake and translocation of metals from the soil. Currently these processes are poorly understood, and especially so for Pb. The purpose of this thesis was to gain insights concerning the plant mechanisms that control uptake and translocation of Pb and how these mechanisms interact to control levels of Pb accumulation …
Investigation Of Biodegradation Processes In Solid Waste Landfills, Philip A. Colborn
Investigation Of Biodegradation Processes In Solid Waste Landfills, Philip A. Colborn
Theses and Dissertations
Greater demands on landfill capacity, stricter regulations intended to minimize landfill environmental impacts, and the economic potential associated with landfill operations have shifted the emphasis of landfill disposal toward methods concerned with the long term performance and capacity of landfills. Two opposing philosophies have emerged in constructing and managing landfills: the dry tomb and the wet cell. The key to managing a landfill from the wet cell viewpoint is first understanding the biodegradation processes occurring within the landfill. This thesis attempts to determine the fundamental processes responsible for the degradation of solid waste by employing a system dynamics approach. A …
Fatigue Behavior Of A Quasi-Isotropic Graphite/Epoxy Laminate Embedded With A Piezoelectric Sensor, Jon M. Coleman
Fatigue Behavior Of A Quasi-Isotropic Graphite/Epoxy Laminate Embedded With A Piezoelectric Sensor, Jon M. Coleman
Theses and Dissertations
This study primarily investigated the mechanical effects of embedding piezoelectric sensors on the tensile and fatigue strength of a quasi-isotropic, carbon-epoxy laminate. A secondary focus was the investigation of the sensor degradation under tensile loading. A [0 | ±45 | 90]s laminate was fabricated from Hercules AS4/3501-6 pre-preg tape. Specimens were first tested monotonically to obtain an average ultimate tensile strength and to detail the progression of damage. The fatigue tests were tension-tension, R=0.1, 10 Hz, constant amplitude. Results indicated that the embedded piezoelectric sensors did not have a significant effect on the tensile strength of the laminate. Specimens …
Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer
Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer
Theses and Dissertations
CAD, serving as a second reader, has been shown to improve the success of radiologists at detecting breast cancer. This thesis will develop a new algorithm to identify masses in mammograms. The system developed for this thesis will be capable of assisting a radiologist in making decisions.
Applications Of Unsupervised Clustering Algorithms To Aircraft Identification Using High Range Resolution Radar, Dzung Tri Pham
Applications Of Unsupervised Clustering Algorithms To Aircraft Identification Using High Range Resolution Radar, Dzung Tri Pham
Theses and Dissertations
Identification of aircraft from high range resolution (HRR) radar range profiles requires a database of information capturing the variability of the individual range profiles as a function of viewing aspect. This database can be a collection of individual signatures or a collection of average signatures distributed over the region of viewing aspect of interest. An efficient database is one which captures the intrinsic variability of the HRR signatures without either excessive redundancy typical of single-signature databases, or without the loss of information common when averaging arbitrary groups of signatures. The identification of 'natural' clustering of similar HRR signatures provides a …
Effects Of Near-Field Scatterers On Space-Time Adaptive Processing, Jonathan W. Fitton
Effects Of Near-Field Scatterers On Space-Time Adaptive Processing, Jonathan W. Fitton
Theses and Dissertations
Near-field scatterers, such as the wing of an airplane, can affect the ability of the processor to null out clutter and jammer signals. The target, clutter, and jammer signals will reflect off the near-field scatterers into the array and appear to be coming from a direction different from their true sources. This thesis develops a theoretical model for the direct path and scattered path signals from the target, clutter, and jamming signals. The optimum weight vector, normally computed using the steering vector to the target and the covariance matrix of the undesired signals, must now include the effects of the …
Scheduling And Sequencing Arrivals To A Stochastic Service System, Peter M. Vanden Bosch
Scheduling And Sequencing Arrivals To A Stochastic Service System, Peter M. Vanden Bosch
Theses and Dissertations
Optimization of scheduled arrival times to an appointment system is approached from the perspectives of both queueing and scheduling theory. The appointment system is modeled as a one-server, first-come-first-served, transient queue with independent, distinctly distributed service times and no-show rates. If a customer does show, it is assumed to be punctual. The cost of operating the appointment system is a convex combination of customers' waiting times and the server's overtime. While techniques for finding the optimal static and dynamic schedules of arrivals have been proposed by other researchers, they mainly have focused on identical customers and strictly punctual arrivals. This …
Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun
Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun
Theses and Dissertations
An analysis and assessment of three mechanisms describing plasma/shock wave interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of ion-acoustic wave damping, post-shock energy addition and thermal inhomogeneities were examined by numerically solving the Euler equations with appropriate source terms adapted for each mechanism. Ion-acoustic wave damping was examined by modeling the partially ionized plasma as two fluids in one spatial dimension using the Riemann problem as a basis. Post-shock energy addition in the form of nonequilibrium vibrational energy relaxation was also examined in one spatial dimension using the Riemann problem as a …
Focused Graduate Education: An Invisible But Real Competitive Edge, Roland D. Kankey, Jan P. Muczyk, Neal M. Ely
Focused Graduate Education: An Invisible But Real Competitive Edge, Roland D. Kankey, Jan P. Muczyk, Neal M. Ely
Faculty Publications
The future mission of the Air Force will be diverse and complex. Advanced technology will play an increasingly prominent role; a smaller force must accomplish more. To support this mission, our acquisition corps must be intellectually capable, well educated and trained. Focused graduate education will be essential to sustain this effort.
Reducing Cannon Plug Connector Pin Selection Time And Errors Through Enhanced Data Presentation Methods, Robert R. Webb
Reducing Cannon Plug Connector Pin Selection Time And Errors Through Enhanced Data Presentation Methods, Robert R. Webb
Theses and Dissertations
The purpose of this research is to investigate the effects of data presentation methods on technician performance when the procedures are presented on a monocular, head mounted display (HMD) in a static maintenance environment. This research used two different methods to present the maintenance task data to the technicians. The first method showed the task as it is typically described in standard technical manuals. It described the task to perform and provided a basic picture of the cannon plug to be tested (unenhanced). The second method provided the same information as the first, but it also modified the information by …
Case Studies In The Analysis Of The Dod Migration System Selection Process, Paul E. Boley Ii
Case Studies In The Analysis Of The Dod Migration System Selection Process, Paul E. Boley Ii
Theses and Dissertations
One of the focuses of Corporate Information Management (CIM) initiative in the Department of Defense is the elimination of duplicate automated information systems. This thesis is a case study examination of the selection process in the logistics, transportation, and health functional areas. The case studies were performed through a one-time review of documents relating to system selections in each functional area. A review of strategic information systems planning and systems implementation literature is used to examine the results in the three areas. The thesis concludes with three suggestions for improving the selection process with an emphasis on systems implementation.
Economic Analysis For An F-22 Organic Vs. Contractor Aircraft Battle Damage Repair Ownership Decision, John A. Kitchens
Economic Analysis For An F-22 Organic Vs. Contractor Aircraft Battle Damage Repair Ownership Decision, John A. Kitchens
Theses and Dissertations
The purpose of this study was to evaluate whether Contractor Logistics Support (CLS) is a viable alternative to Combat Logistics Support Squadrons (CLSSs) for providing F-22 Aircraft Battle Damage Repair (ABDR). Legalities, practicalities, and cost-effectiveness were key ownership concerns. United States Code, Office of Management and Budget, Department of Defense (DoD), and United States Air Force (USAF) requirements were reviewed to address legal and policy issues and whether F-22 ABDR is military essential. The Army's Logistics Civil Augmentation Program (LOCCAP) award fee history was used to assess the potential performance of F-22 ABDR CLS personnel. F-117 ABDR team requirements and …
How The Presence Of A Risk Ladder, Time Interval Comparison, And Smoking Comparison Affect Risk Perception, Steve A. Dinzart
How The Presence Of A Risk Ladder, Time Interval Comparison, And Smoking Comparison Affect Risk Perception, Steve A. Dinzart
Theses and Dissertations
The objective of this study is to increase the knowledge available on the relative effectiveness of risk ladders as a presentation format for explaining risk magnitudes to the public. An experiment was conducted to test the hypotheses that an individual's risk perception varies with the presence of a risk ladder, time interval comparison, and smoking comparison. Subjects were AFIT Professional Continuing Education students, asked to assume a particular level of a health hazard in their homes, to read a brochure explaining the hazard, and then to complete a questionnaire. Results demonstrated that subjects exposed to a graphical risk ladder perceived …
Cost Per Flying Hour Analysis Of The C-141, Christopher J. Omlor
Cost Per Flying Hour Analysis Of The C-141, Christopher J. Omlor
Theses and Dissertations
This paper sought to examine if DoD's current transfer pricing method places AMC in a price competitive position with the government commercial rates and promotes managers to make the best decisions. Attention was paid to the stated customer concerns that current transfer pricing methods incorporate overhead and sunk costs that are not attributable to routine movement of peacetime cargo and could make AMC non price competitive with commercial vendors. The findings are that AMC currently uses full cost transfer pricing, as required by DoD policy, that includes significant overhead and sunk costs associated with its wartime responsibilities. The full cost …
The Effects Of Extraneous Presentation Graphics On Decision Making, Thomas S. Tingley
The Effects Of Extraneous Presentation Graphics On Decision Making, Thomas S. Tingley
Theses and Dissertations
Almost every professional presentation includes some form of graphics. Many previous researchers have analyzed the relative effectiveness of graphical decision aids, such as pie charts or bar graphs. Very little research, however, has been conducted to determine the effects of extraneous graphics, such as pictures and logos, on decision making. This study employed an experiment to determine whether extraneous graphics hinder or enhance a decision maker's ability to obtain the pertinent information from a professional presentation. Other factors such as gender and graphics training were also analyzed for any influence on the results obtained. The results of the study indicated …
Aerial Port Location Study, Levenchi L. Dingle
Aerial Port Location Study, Levenchi L. Dingle
Theses and Dissertations
This study performed an investigation on determining the appropriate number and locations of continental United States aerial ports. To accomplish this a linear programming formulation was adapted with the optimizing function based on trading off the cost of shipping cargo against port operating costs. Cargo would travel from CONUS origin, through aerial port of embarkation (APOE), to aerial port of debarkation (APOD) at minimum cost to the DoD. The need for the study was precipitated by continued reductions in the military budget, consolidation of defense depots, and the reduction in the number of personnel stationed overseas. Cargo movement data was …
Identification And Reduction Of Bottlenecks Concerning Micap Re-Supply Of F-16 Weapons System Avionics Line Replaceable Units, Karl N. Muno, Patrick K. Pezoulas
Identification And Reduction Of Bottlenecks Concerning Micap Re-Supply Of F-16 Weapons System Avionics Line Replaceable Units, Karl N. Muno, Patrick K. Pezoulas
Theses and Dissertations
This thesis evaluates selected F-16 avionics Line Replaceable Units (LRUs) transiting the logistics pipeline in order to examine the existence of bottlenecks and explore potential solutions within the current Department of Defense (DoD) logistics reparable pipeline. A previous study reported that a reduction in the overall pipeline resupply time of at least one day equates to a savings of approximately $25.45 million (Hill et al, 1990:iii). Bottlenecks cause movement delays to the entities moving through the logistics reparable pipeline. The pipeline segments are: AO (requisition), AE (item availability), AS (shipment status), and D6 (receipt). The bottlenecks of concern are those …
Relative Equilibria Of A Rigid Satellite In A Central Gravitational Field, Jeffrey A. Beck
Relative Equilibria Of A Rigid Satellite In A Central Gravitational Field, Jeffrey A. Beck
Theses and Dissertations
We apply noncanonical Hamiltonian methods to examine relative equilibria of a rigid body in a central gravitational field. These equilibria correspond to fixed points of a reduced set of equations expressed in a rotating frame and are representative of an orbiting satellite with fixed attitude relative to an observer rotating at the orbital rate. Our objective is to clarify the relationship between the classical approximation and a recent noncanonical Hamiltonian treatment. In contrast to the classical approximation, the orbital and attitude equations of motion for the noncanonical system remain coupled and the general solution is a circular orbit for which …
Aerospace Ground Equipment's Impact On Aircraft Availability And Deployment, Jeffrey D. Havlicek
Aerospace Ground Equipment's Impact On Aircraft Availability And Deployment, Jeffrey D. Havlicek
Theses and Dissertations
The first purpose of this thesis was to study the effects of four factors on aircraft availability: the aerospace ground equipment (AGE) design configuration, the mean time between failure (MTBF) of AGE, the mean time to repair (MTTR) AGE, and the travel time to transport the AGE around the flightline. A simulation developed by Carrico (1996) that has its foundation based on the Logistics Composite Model (LCOM) was used. ANOVA results indicated that the present estimates of these factors are too broad for trade studies that include an estimate of aircraft availability to begin. The time it takes AGE to …
Fiber Volume Fraction Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Coghlan
Fiber Volume Fraction Effects On Fatigue Response Of A Scs-6/Ti-15-3 Metal Matrix Composite At Elevated Temperature, Sean C. Coghlan
Theses and Dissertations
The purpose of this study was to determine the effects of fiber volume fraction on the fatigue behavior of Silicon Carbide fiber-reinforced Titanium alloy, SCS-6/Ti-15-3. Three fiber volume fractions were investigated; 15%, 25%, and 42%. The tests were performed under fully-reversed, strain-controlled conditions at 427 °C. The primary objectives of this study were to develop a fatigue life diagram and to document the damage and failure mechanisms. Compressive loads on the slender specimens were kept from buckling the specimens through the use of a buckling guide. This device allows unrestricted axial movement of the composite, while preventing any out-of-plane motion. …
Improved Load Alleviation Capability For The Kc-135, Adam L. Mortensen
Improved Load Alleviation Capability For The Kc-135, Adam L. Mortensen
Theses and Dissertations
The Air Force will greatly increase its use of Unmanned Aerial Vehicles (UAVs) in the next century and the latter part of this decade. These UAVs will require refueling like their manned counterparts. The KC-135 and the KC-10 are candidates to provide this refueling task. The KC-10 is equipped with an automatic load alleviation system on its refueling boom which minimizes radial loads at the receiver of the aircraft being refueled. The KC-135 does not have such a system on its boom. Because the boom operator relies on visual cues to tell him when the boom is bending to adjust …