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Articles 1 - 30 of 85
Full-Text Articles in Engineering
Computer-Based Methods For Constructing Two-Level Fractional-Factorial Experimental Designs With A Requirement Set, Steven L. Forsythe
Computer-Based Methods For Constructing Two-Level Fractional-Factorial Experimental Designs With A Requirement Set, Steven L. Forsythe
Theses and Dissertations
This dissertation developed four methodologies for computer-aided experimental design of two-level fractional factorial designs with requirement sets (DOE/RS). The requirement sets identify all the experimental factors and the appropriate interaction terms to be evaluated in the experiment. Taguchi graphs and similar manual methods provide techniques for solving the DOE/RS problem. Unfortunately, these methods are limited because they become difficult to use as the number of factors or interaction terms exceeds ten. This research showed that the DOE/RS problem belongs to a class of difficult-to-solve problems known as NP-Complete. It is the combinatorial nature of NP-Complete problems that causes them to …
Estimating Budget Relationships With A Leontief Input-Output Model, Guenever L. R. Shariff
Estimating Budget Relationships With A Leontief Input-Output Model, Guenever L. R. Shariff
Theses and Dissertations
Forty years ago, the Office of the Secretary of Defense proposed using the Leontief input-output model to assess tradeoffs in the Department of Defense's (DoD) budget. We demonstrate that the Leontief input-output model can assess tradeoffs in the Air Force's budget. To increase one part of the Air Force's budget, we need to know the interrelationships between that budget area and the other areas. In this research, we look at different methods of how the functional areas might interact. We demonstrate our methodology on two data sets - DoD and the Air Force aggregate budget data. By looking at how …
Covalidation Of Dissimilarly Structured Models, Samuel A. Wright
Covalidation Of Dissimilarly Structured Models, Samuel A. Wright
Theses and Dissertations
A methodology is presented which allows comparison between models constructed under different modeling paradigms. Consider the following situation: Two models are constructed to study different aspects of the same system. One model simulates a fleet of aircraft moving a given combination of cargo and passengers from an onload point to an offload point. A second model is a linear programming model that optimizes the aircraft and route selection required for the same scenario. We develop a methodology to structure the comparison between large-scale models such as these. Models that compare favorably using this methodology are deemed covalid. Models that perform …
Simulation And Analysis Of Wing Rock Physics For A Generic Fighter Model With Three Degrees-Of-Freedom, Ahmed Saad
Simulation And Analysis Of Wing Rock Physics For A Generic Fighter Model With Three Degrees-Of-Freedom, Ahmed Saad
Theses and Dissertations
Modern fighter designs have been associated with lateral self-excited oscillations own as "Wing Rock". Simulations of wing rock by flow visualization utilities have been encouraged to develop a complete understanding of the fluid mechanism that drives the motion as well as for prediction purposes. Previous wind/water tunnel simulations have been limited to a single degree-of freedom (DoF) in roll. In this study, for the first time, wing rock is computationally simulated in three DoF: roll, sideslip, and vertical motion to study the effect of adding file sideslip and vertical motion. The results are for a generic fighter model consisting of …
Three-Dimensional Dynamic Stress Analysis Of Sandwich Panels, Victor Y. Perel
Three-Dimensional Dynamic Stress Analysis Of Sandwich Panels, Victor Y. Perel
Theses and Dissertations
A layerwise geometrically nonlinear theory for a thick sandwich plate was developed by introducing assumptions on a variation of transverse strains in the thickness direction of the faces and the core of the plate. An effect of transverse extensibility or compressibility of the core and the face sheets is taken into account, and the terms associated with transverse shear strain of the face sheets and the core are included into the expression for the strain energy. Displacements, obtained by integration of the strain-displacement relations, depend nonlinearly on a coordinate in the thickness direction, and are continuous at the boundaries between …
Turbo Codes For Wireless Mobile Communication Systems Applications, Moataz M. Salah
Turbo Codes For Wireless Mobile Communication Systems Applications, Moataz M. Salah
Theses and Dissertations
Research in coding theory has seen many proposals aimed at the construction of powerful codes using block and convolutional codes. Recently, a new forward error control code, known as turbo code, was introduced. This new code yields very good performance (near the Shannon limit) with relatively simple component codes and large interleavers in combination with an iterative decoding process. Among the most important applications of turbo codes are wireless mobile communication systems. A significant performance metric for this application is the minimization of end-to-end delay. In this dissertation, different ways to enhance the performance of turbo codes with short frames …
Obtaining Objective Measurements Of Reaction Times To Auditory Alarms, Andrew George Neubauer
Obtaining Objective Measurements Of Reaction Times To Auditory Alarms, Andrew George Neubauer
Theses and Dissertations
Several pulse parameters that were believed to affect response time to auditory alarms were investigated in a factorial experiment. 18 subjects, (14 male, 4 female), participated in an experiment where the effects of inter-pulse interval (125, 250, and 500 milliseconds) and pulse format (sine, sawtooth, and square waves) on both selfreported ratings of workload and reaction time to alarms (auditory and visual) were explored. The results show that alarms with a shorter inter-pulse interval produced the fastest reaction times. Subjective preferences were rated as equal. Accuracy was equal across groups as measured by amount of errors in responding to auditory …
Tool-Based Integration And Code Generation Of Object Models, Michael Ray Ashby
Tool-Based Integration And Code Generation Of Object Models, Michael Ray Ashby
Theses and Dissertations
Today many organizations are faced with multiple large legacy data stores in different formats and the need to use data from each data store with tools based on the other data stores' formats. This thesis presents a tool-based methodology for integrating object-oriented data models with automatic generation of code. The generated code defines a global data format, generates views of global data in individual integrated data formats, and parses data from individual formats to the global formats and from the global format to the individual formats. This allows for legacy data to be translated into the global format, and all …
Empirical Evaluation Of The Civil Engineer Career Pyramid And Career Guidance, Travis K. Leighton
Empirical Evaluation Of The Civil Engineer Career Pyramid And Career Guidance, Travis K. Leighton
Theses and Dissertations
Air Force civil engineer officers rely on published guidance to assist in establishing their career objectives. This thesis uses empirical data to evaluate the published Air Force career guidance. The data set is comprised of complete duty histories from all active duty lieutenant colonels in the civil engineer career field. The guidance implies a career path to become a civil engineer squadron commander but provides no empirical validation. This thesis follows a rigorous procedure to objectively evaluate the Air Force guidance. The guidance is translated into 24 research questions based on its main tenets. Each duty occurrence is categorized by …
A Hybrid Jump Search And Tabu Search Metaheuristic For The Unmanned Aerial Vehicle (Uav) Routing Problem, Gary W. Kinney Jr.
A Hybrid Jump Search And Tabu Search Metaheuristic For The Unmanned Aerial Vehicle (Uav) Routing Problem, Gary W. Kinney Jr.
Theses and Dissertations
In this research, we provide a new meta-heuristic, a jump search I tabu search hybrid, for addressing the vehicle routing problem with real-life constraints. A tour construction heuristic creates candidate solutions or jump points for the problem. A tabu search algorithm uses these jump points as starting points for a guided local search. We provide statistical analysis on the performance of our algorithm and compare it to other published algorithms. Our algorithm provides solutions within 10% of the best known solutions to benchmark problems and does so in a fraction of the time required by competing algorithms. The timeliness of …
Post-Processing Resolution Enhancement Of Open Skies Photographic Imagery, Daniel E. Sperl
Post-Processing Resolution Enhancement Of Open Skies Photographic Imagery, Daniel E. Sperl
Theses and Dissertations
The Treaty on Opens Skies allows any signatory nation to fly a specifically equipped reconnaissance aircraft anywhere over the territory of any other signatory nation. For photographic images, this treaty allows for a maximum ground resolution of 30 cm. The National Air Intelligence Center (NAIC), which manages implementation of the Open Skies Treaty for the US Air Force, wants to determine if post-processing of the photographic images can improve spatial resolution beyond 30 cm, and if so, determine the improvement achievable. Results presented in this thesis show that standard linear filters (edge and sharpening) do not improve resolution significantly and …
The Air Force Institute Of Technology (Afit) Micro Electro-Mechanical Systems (Mems) Interferometric Gyroscope (Mig), Jeremy P. Stringer
The Air Force Institute Of Technology (Afit) Micro Electro-Mechanical Systems (Mems) Interferometric Gyroscope (Mig), Jeremy P. Stringer
Theses and Dissertations
With the invention of Micro Electro-Mechanical Systems (MEMS) it has become possible to fabricate micro-inertial sensors. These new sensors have application in creating autonomous guided weapons systems. New technologies like Micro Unmanned Aerial Vehicles (UAVs), which cannot use conventional inertial sensors, rely on technologies like micro-inertial sensors to operate. Also, such sensors have the capability to reduce both power and space consumption on conventional aircraft. This technology is not yet mature, and current micro-inertial sensors do not have the accuracy required for highly precise navigation. To try to increase the accuracy of micro-inertial sensors, researchers are turning toward micro-optical gyroscopes. …
Realtime Color Stereovision Processing, Byron P. Formwalt
Realtime Color Stereovision Processing, Byron P. Formwalt
Theses and Dissertations
Recent developments in aviation have made micro air vehicles (MAVs) a reality. These featherweight palm-sized radio-controlled flying saucers embody the future of air-to-ground combat. No one has ever successfully implemented an autonomous control system for MAVs. Because MAVs are physically small with limited energy supplies, video signals offer superiority over radar for navigational applications. This research takes a step forward in real time machine vision processing. It investigates techniques for implementing a real time stereovision processing system using two miniature color cameras. The effects of poor-quality optics are overcome by a robust algorithm, which operates in real time and achieves …
Evaluation Of A Method For Kinematic Gps Carrier-Phase Ambiguity Resolution Using A Network Of Reference Receivers, Brian L. Bracy
Evaluation Of A Method For Kinematic Gps Carrier-Phase Ambiguity Resolution Using A Network Of Reference Receivers, Brian L. Bracy
Theses and Dissertations
New applications for GPS have driven a demand for increased positioning accuracy. The emerging GPS technology particularly affects the test community. The testing equipment and method must provide a solution that is an order of magnitude more precise than the tested equipment to achieve the desired accuracy. Carrier-phase differential GPS methods using a network of reference receivers can provide the centimeter-level accuracy required over a large geographical area. This thesis evaluates the performance of a 5-receiver network over a 50 km x 120 km area of New Mexico, using a GPS network algorithm called NetAdjust. The percentage of time a …
Linking Engineer Career Orientation And Human Resource Management Practices: Does Fit Affect Retention?, Cynthia M. Davis
Linking Engineer Career Orientation And Human Resource Management Practices: Does Fit Affect Retention?, Cynthia M. Davis
Theses and Dissertations
Turnover of the Air Force civil engineering (CE) officers is becoming increasingly important, as levels of CE Captains consistently decreases. Allen and Katz (1986) identified three career orientations of engineers based on their job preference-project, professional, and management engineers. Shepard (1958) suggested a dual-ladder promotion system to meet the cancer desires of technical and management workers. Additional research has proposed "desired" Human Resource Management (HRM) practices to facilitate the retention of each type of career-based engineer (Lee and Maurer, 1997). In an effort to determine if these career orientations, along with Air Force HRM practices, were linked to declining retention, …
Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner
Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner
Theses and Dissertations
Current space-based imaging platforms are significantly constrained in both size and weight by the launch vehicle. Increased payload size and weight results in increased cost and a decrease in launch responsiveness. The USAF Scientific Advisory Board (SAB) identified "Large lightweight structures for optics and antennas" as a revolutionary primary technology to be developed for the Air Force of the 21st Century. A membrane primary mirror in a space-based imaging system has the ability to overcome current payload constraints and meet evolutionary needs of the future. The challenge of membrane optics in space is the process of implementing adaptive optics technology …
Improving Uav Handling Qualities Using Time Delay Compensation, Andrew J. Thurling
Improving Uav Handling Qualities Using Time Delay Compensation, Andrew J. Thurling
Theses and Dissertations
This research investigated control loop time delay and its effect on UAV handling qualities. Compensation techniques to improve handling qualities in the presence of varying amounts of time delay were developed and analyzed. One technique was selected and successfully flight-tested on a UAV. Flight-testing occurred at a constant flight condition with varying levels of additional time delay introduced into the control loop. Research pilots performed a pitch tracking task and gave Cooper-Harper ratings and comments. Tracking errors were used as a quantitative measure of Pilot/Display/UAV system performance. Predictive pitch compensation was found to significantly reduce pilot workload and improve Cooper-Harper …
Modeling Piezoceramic Twist Actuation In Single-Cell Anisotropic Torque Box Of Low-Observable Uav Wing, Peter Cseke Jr.
Modeling Piezoceramic Twist Actuation In Single-Cell Anisotropic Torque Box Of Low-Observable Uav Wing, Peter Cseke Jr.
Theses and Dissertations
The reduction of an aircraft's radar cross section can increase its survivability in hostile airspace by making it more difficult to locate and track by enemy radar. Replacing articulated flight control surfaces with adaptive controls will reduce surface discontinuities, and enhance low observability. Actuation of the aerodynamic surfaces is achieved by an electric field applied to PZT actuators embedded in the top and bottom skins, creating differential strain and shear in the host substrate. This creates torsion about the elastic axis, and a change in the wing lift coefficient. The torsion of the designed baseline UAV's wing torquebox was modeled …
A Java Universal Vehicle Router In Support Of Routing Unmanned Aerial Vehicles, Robert W. Harder
A Java Universal Vehicle Router In Support Of Routing Unmanned Aerial Vehicles, Robert W. Harder
Theses and Dissertations
Unmanned Aerial Vehicles (UAVs) help the military gather information in times of peace and war. During a mission, typically 100 sites or more, a UAV will frequently be re-tasked to visit a pop-up threat, leaving the operator to determine the best way to finish the day's list of sites after the re-tasking. I develop a prototype application to serve the needs of a specific customer, the 11th Reconnaissance Squadron, by helping them preplan missions and dynamically re-task UAVs. This prototype application is built on a reusable airframe router called the core AFIT Router, which can later be added to more …
Chemical Mechanical Polishing Optimization For 4h-Sic, Craig L. Neslen
Chemical Mechanical Polishing Optimization For 4h-Sic, Craig L. Neslen
Theses and Dissertations
Scratch free surfaces are required for substrates used in epitaxial growth. Silicon carbide (SiC) is a substrate material that is used in the epitaxial growth of SiC, GaN, and InGaN electronic devices. Preliminary chemical mechanical polishing (CMP) studies of 1 3/8" 4H-SiC wafers were performed in an attempt to identify the polishing parameter values that result in a maximum material removal rate and thus reduce substrate polishing time. Previous studies reported increased material removal rates associated with increasing polishing temperature, slurry pH, pressure, and polishing pad speed. In the current study, the effects of temperature, slurry pH, polishing pressure, and …
Nonuniformly Spaced Array Elements, Daniel R. Richards Jr.
Nonuniformly Spaced Array Elements, Daniel R. Richards Jr.
Theses and Dissertations
This thesis provides a method to reduce physical resource requirements along with cost reduction in Space Based Radar (SBR) platforms, and provides a rule of thumb for randomization effects on arrays. A trend analysis is performed on 4, 8, 12, and 16 square meter arrays. Three aperiodic thinning approaches are examined. They are an equal current density element distribution, a random periodic grid of elements, and random element distribution based a peak sidelobe indicator. According to the metrics used, the statistical and deterministic array thinning approaches performed best for these small arrays. However, the statistical arrays have a scan angle …
An Intelligent User Interface To Support Air Force Weather Product Generation And Automated Metrics, Darryl N. Leon
An Intelligent User Interface To Support Air Force Weather Product Generation And Automated Metrics, Darryl N. Leon
Theses and Dissertations
Air Force pilots require dependable weather reports so they may avoid unsafe flying conditions. In order to better gauge the accuracy of its weather products, Air Force Weather has established the requirement for an Air Force-wide automated weather metrics program. Under the guidelines for this program, forecasts will automatically be compared to observed weather to determine their accuracy. Statistics will be collected in the hopes of determining forecast error trends that can be corrected through education and training. In order for the statistical data produced by such a program to draw reliable conclusions about forecast accuracy, however, the correct format …
A Tabu Search Metaheuristic For The Air Refueling Tanker Assignment Problem, Shay R. Capehart
A Tabu Search Metaheuristic For The Air Refueling Tanker Assignment Problem, Shay R. Capehart
Theses and Dissertations
In a joint effort between Air Mobility Command (AMC) and the Air Force Institute of Technology, we present a Tanker Assignment Problem (TAP) Tool capable of providing tanker mission plans for deployment scenarios. Due to the complex nature of extracting a mission plan from the Combined Mating and Ranging Planning System (CMARPS), AMC requires a tool to provide similar results in a simpler and less time consuming manner. The tool developed allows AMC to input several receiver groups consisting of various aircraft types and numbers. Each receiver group contains a point of origin and destination, with the option of providing …
Using Rsm, Doe, And Linear Regression To Develop A Metamodel To Predict Cargo Delivery Of A Time Phase Force Deployment Document, Kenneth S. Browne
Using Rsm, Doe, And Linear Regression To Develop A Metamodel To Predict Cargo Delivery Of A Time Phase Force Deployment Document, Kenneth S. Browne
Theses and Dissertations
Air Mobility Command (AMC) uses the Airlift Flow Model as their primary tool to estimate the amount of cargo delivered in a Time Phase Force Deployment Document (TPFDD). The primary objective of this research was an exploratory investigation in the development of a metamodel to predict the amount of cargo delivered from a TPFDD by AMC into a theater. In creating a valid metamodel the analyst would be able to quickly provide the decision-maker with accurate insights should input parameters change. This would save valuable time and replace the need to physically change the input parameters and re-run the simulation. …
Navigation Of Satellite Clusters, Jeffrey S. Davis
Navigation Of Satellite Clusters, Jeffrey S. Davis
Theses and Dissertations
The relative position determination of a cluster of satellites in near circular orbit was investigated in previous thesis work. The purpose of this thesis is to extend the concept to cover absolute position determination. A Bayes filter is used for the estimator with dynamics based on the two-body problem extended to account for J2 perturbations. Measurements consist of combining Global Positioning System (GPS) data for each satellite and range data between the satellites. Simulations were conducted investigating the accuracy obtainable when combining the measurements for input into the filter. Performance results consist of comparing the magnitude of the time error …
Determining The Aircraft Requirement For Turkish Air Mobility System, Mehmet M. Ari
Determining The Aircraft Requirement For Turkish Air Mobility System, Mehmet M. Ari
Theses and Dissertations
Aircraft technology develops very rapidly. To keep up with the modem technology, we should update our systems and material over time. In order to do so, we should keep track of modem technologies, and implement them in our military. Turkish Air Force Command operates a vital logistical system for which routing and scheduling are done on a weekly basis. This research reviewed weekly schedules and determined the average required weekly missions which would be flown during the week. By carefully examining the job - machine formulation, this research devised a method for determining the aircraft required to perform for weekly …
A Tabu Search For Scheduling And Rescheduling Combat Aircraft, Kevin M. Calhoun
A Tabu Search For Scheduling And Rescheduling Combat Aircraft, Kevin M. Calhoun
Theses and Dissertations
Scheduling an air campaign is time and labor intensive. Exacerbating the problem, combat planners use manual methods to accomplish much of this daunting but critical task. While some work has been done to automate the process, the approaches used generate schedules that must undergo major modifications before they are "flyable." Planners, therefore, distrust the results and use the automated features of the software sparingly. Additional problems arise due to the lag time between the publication of the Air Tasking Order (ATO) and the start of the ATO day. During this time, conditions change in the dynamic battlespace (aircraft break, runways …
Using Simulation To Model An Army Recruiting Station With Seasonality Effects, David C. Longhorn
Using Simulation To Model An Army Recruiting Station With Seasonality Effects, David C. Longhorn
Theses and Dissertations
One of the toughest jobs in the Army is that of the recruiter. Recruiters are tasked with the awesome job of convincing young men and women to lay down their lives and freedoms for their country, and oftentimes for less money than can be earned in the safer environment of America's booming economy. Recruiters face enormous pressure from commanders to meet the mandated Army manning levels set each year by Congress. As the Army begins the 21st century, it is faced with having to support an increasing number of deployments with fewer soldiers. Soldiers face long and difficult days with …
Mechanics Of A Functionally-Graded Titanium Matrix Composite, G. Brandt Miller
Mechanics Of A Functionally-Graded Titanium Matrix Composite, G. Brandt Miller
Theses and Dissertations
Functionally-graded Titanium Matrix Composites, (F/G TMCs) combine the ideal properties of titanium matrix composites with the more practical machining qualities of monolithic (unreinforced) alloy. This material shows great promise in application to aerospace structural components - even in parts whose design requirements have defied the use of composite materials in the past. Successful implementation of such a material would lead to enhanced aircraft performance. However, the basic properties of a functionally-graded titanium matrix composite need to be investigated. The composite/alloy transition region, or joint area, may be less strong than its constituents and therefore determine the overall performance of the …
The Distributor’S Three-Dimensional Pallet-Packing Problem: A Mathematical Formulation And Heuristic Solution Approach, Brian P. Ballew
The Distributor’S Three-Dimensional Pallet-Packing Problem: A Mathematical Formulation And Heuristic Solution Approach, Brian P. Ballew
Theses and Dissertations
It is through practice and experience Air Force loadmasters are able to pack the Air Force standard HCU-6/E (463L) pallets efficiently. Although the loadmasters perform their jobs exceptionally well, the Air Force is in search of a model that will more efficiently pack the pallets. We have developed a mathematical formulation of the three-dimensional pallet-packing problem which minimizes the amount of unused space on a pallet. The formulation ensures each box is packed with the correct volume and dimensions, and ensures the volume of all the boxes packed is less than the available pallet volume. Additionally, the formulation ensures that …