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Articles 31 - 60 of 1295
Full-Text Articles in Engineering
A Physics-Based Heterojunction Bipolar Transistor Model For Integrated Circuit Simulation, James A. Fellows
A Physics-Based Heterojunction Bipolar Transistor Model For Integrated Circuit Simulation, James A. Fellows
Theses and Dissertations
The purpose of this research effort was to derive a physics-based dc model for a Heterojunction Bipolar Transistor HBT. The dc model was then linearized to arrive at a small-signal model that accurately predicts the devices electrical behavior at microwave frequencies. This new model offers features not found in previous analytical or physics-based HBT models such as consideration of a cylindrical emitter-base geometry and is direct implementation into SPICE Simulation Program with Integrated Circuit Emphasis. The device model parameters were determined from a knowledge of the device material, geometry, and fabrication process. The model was then developed by using semiconductor …
Developing A Graphical User Interface To Support A Real-Time Digital Signal Processing System, Jeffrey C. Miller
Developing A Graphical User Interface To Support A Real-Time Digital Signal Processing System, Jeffrey C. Miller
Theses and Dissertations
A graphical software user interface for a VMEbus-based real-time digital signal processing system was designed. Use, requirements were defined and the Rumbaugh object-oriented analysis and design technique was applied to analyze the requirements and produce an object-oriented design. The software design includes a graphical, mouse- and keyboard driven user interface, specialized hardware driver modules, and operating system interfaces. An implementation plan was also developed to map the design into the C programming language using existing system code, automatically generated code, and newly written code. Based on the implementation plan, a limited software system prototype w successfully developed and demonstrated. The …
An Evaluation Of The Software Engineering Institute's Capability Maturity Model As A Framework For Software Process Improvement At Three Air Logistics Centers, Brian G. Hermann, Raymond J. Lewis Jr.
An Evaluation Of The Software Engineering Institute's Capability Maturity Model As A Framework For Software Process Improvement At Three Air Logistics Centers, Brian G. Hermann, Raymond J. Lewis Jr.
Theses and Dissertations
This research sought to determine whether a relationship exists between the maturity level of the software process, as determined by the Software Engineering Institutes Capability Maturity Model SEI CMM, and the actual success of particular software projects at three US Air Force Air Logistics Centers. Project success is defined in terms of cost, schedule, and quality criteria. In addition, each organizations acceptance of the SEI assessment as well as its effectiveness in setting up follow-on process improvement programs were evaluated. Finally, the process improvement programs were reviewed individually inasmuch as these programs are the mechanisms for achieving improved quality, lower …
An Assessment Of The Appropriateness To The Royal Australian Air Force Of A Masters Level Professional Program In Information Systems, Ralph G. L. Kettle, Joseph R. Taylor
An Assessment Of The Appropriateness To The Royal Australian Air Force Of A Masters Level Professional Program In Information Systems, Ralph G. L. Kettle, Joseph R. Taylor
Theses and Dissertations
This study assessed the appropriateness, to the Royal Australian Air Force RAAF, of a graduate professional program in Information Systems (IS) based on the Association for Computing Machinery’s ACM curriculum model. The ACM curriculum model is an archetype of graduate education in IS. Programs based on this model produce graduates with knowledge, skills, and abilities (KSAs) that are required by IS practitioners. The usefulness of twenty KSAs that underlie the ACM curriculum model were evaluated by 33 incumbents of RAAF information Systems Agencies and Directorate of Communications and Information Systems - Air Force. Although uncertain about the educational background suited …
Demonstration Of Improved Software Support Labor Estimation For Air Force Operational Flight Programs Through Functional Orientation, Ronald R. Warner Jr., Darrel L. Wright
Demonstration Of Improved Software Support Labor Estimation For Air Force Operational Flight Programs Through Functional Orientation, Ronald R. Warner Jr., Darrel L. Wright
Theses and Dissertations
This study demonstrated two approaches to improve current software support effort estimation models for aircraft software. Both approaches involved a functional orientation not used by existing models. The first approach demonstrated how to orient a model to reflect the block change cycle modification process and how to represent support effort changes over time in order to improve effort estimation accuracy. Current software models do not reflect the support environment or the temporal characteristics of aircraft software support. The second approach demonstrated how to calibrate a model by properly selecting source data in order to increase accuracy. Support calibration is not …
System Design Analysis Of A Lightweight Laser Satellite Terminal, Brian C. Page
System Design Analysis Of A Lightweight Laser Satellite Terminal, Brian C. Page
Theses and Dissertations
This study investigated the technological feasibility of a man- portable satellite laser communications system. Areas of interest were an end- to-end system analysis on the communications link evaluation of atmospheric effects and evaluation of semi-conductor lasers as the laser source. A literature search revealed that satellite laser communication research is primarily directed at inter-satellite links. There have been some proposed systems for space-to-ground laser communications systems, but they all utilize large fixed ground stations. The focus of this research effort is directed at a small man-portable ground station capitalizing on recent advances in semiconductor laser devices. Baseline satellite communication systems …
Measuring User Satisfaction Of The Electronic Mail System At Air Force Materiel Command Headquarters As An Indicator Of The System's Effectiveness, Randall R. Bradford
Measuring User Satisfaction Of The Electronic Mail System At Air Force Materiel Command Headquarters As An Indicator Of The System's Effectiveness, Randall R. Bradford
Theses and Dissertations
The purpose of this study was to evaluate the effectiveness of the electronic mail system at the Air Force Materiel Command Headquarters. User satisfaction was measured as an indicator of the systems effectiveness. In order to provide an objective measurement of system effectiveness, the following research questions were addressed: (1) What is system effectiveness in relation to this particular electronic mail system, and how should it be measured? (2) What measurement instruments can be adapted, modified, or created to measure effectiveness as it is defined for problem? (3) If a measurement instrument is administered what do the results of the …
Guidelines For Ensuring Software Supportability In Systems Developed Under The Integrated Weapon System Management Concept, Forrest F. Butts Iii, Anthony C. Johndro
Guidelines For Ensuring Software Supportability In Systems Developed Under The Integrated Weapon System Management Concept, Forrest F. Butts Iii, Anthony C. Johndro
Theses and Dissertations
This thesis studied the software maintenance planning and practices of the pilot Integrated Weapon System Management IWSM programs. Before IWSM, a System Program Office SPO acquired an Air Force weapon system then passed it to an Air Logistics Center ALC for follow-on support. The ALC was forced to maintain the software despite its questionable maintainability. The SPO de- emphasized maintainability because maintenance was an ALC responsibility and building maintainable software increased development costs and lengthened schedules. The IWSM philosophy closes the gap between development and maintenance. A System Program Director SPD, who oversees both system development and maintenance, has an …
Primary Coolant Flow Characteristics As It Exits The Palisades Reactor, Gregory Alan Baustian
Primary Coolant Flow Characteristics As It Exits The Palisades Reactor, Gregory Alan Baustian
Masters Theses
During fuel cycles 9 and 10 at the Palisades Nuclear Power Plant, new phenomena have been observed using the resistance temperature devices installed in the reactor coolant piping. Oscillations in the temperature readings have been observed leading to the assumptions that there is temperature stratification of the coolant in the reactor hot-legs and that the coolant rotates as it leaves the reactor. In addition, oscillations in the bulk coolant flow within the two hot legs have been postulated. This report outlines work performed using computational fluid dynamics modelling which predict the observed and assumed flow characteristics of the Palisades reactor …
Toward Virtual Digital Mammograms For Research And Training In Tumor Detection, Charles F. Babbs, Leslie A. Geddes
Toward Virtual Digital Mammograms For Research And Training In Tumor Detection, Charles F. Babbs, Leslie A. Geddes
Weldon School of Biomedical Engineering Faculty Working Papers
Research in the processing, compression, transmission, and interpretation of digital radiographic images requires evaluation of a wide variety of test images, varying in format, in spatial resolution, and in anatomic content. To evaluate the diagnostic performance of observers using novel versus conventional image formats, large numbers of test images containing known abnormalities are required. This report describes a method for creating high resolution, virtual digital mammograms from computational models of the human breast that include branched lobulated ducts and suspensory ligaments embedded in fatty subcutaneous tissue. Breast phantoms may include any of three types of simulated tumors (fibroadenomas, invasive ductal …
Development Of Stereoscopic Particle Tracking Velocimetry For Turbulent Flow Field Diagnostics, Veera P. Rajendran
Development Of Stereoscopic Particle Tracking Velocimetry For Turbulent Flow Field Diagnostics, Veera P. Rajendran
Electronic Theses and Dissertations
Stereoscopic particle tracking velocimetry (SPTV) was used to analyze a turbulent submerged jet of Reynolds number (based on the diameter of the nozzle) 8000. SPTV involves tracking the motion of tracer particles over time in a flow in three dimensions. The first part of this work consisted of developing a stereoscopic particle tracking technique using two high-speed video cameras. This included calibration of the cameras with "known" points, and developing an algorithm to automatically match and track particles. The second part was to apply the same to a submerged water jet in order to measure velocities. The velocities were subsequently …
An Empirical Investigation Of Quality And Productivity Management Practices In Manufacturing Firms, Kiran Vuppalapati
An Empirical Investigation Of Quality And Productivity Management Practices In Manufacturing Firms, Kiran Vuppalapati
Masters Theses
A growing number of firms are implementing the concept of Just In Time (JlT) manufacturing and Total Quality Management (TQM). This research examines the impact of these management philosophies in manufacturing firms.
This research identifies a set of critical organizational variables necessary for a successful . implementation and the organizational problems faced during their implementation. The major object is to test the performance of firms implementing both JlT and TQM against firms implementing none of these philosophies. Results show that JIT-TQM firms are more customer focused and have better employee relations than traditional firms. This study also compares the performance …
Modeling Of A Large Undamped Space Structure Using Time Domain Techniques, Anthony R. Nash
Modeling Of A Large Undamped Space Structure Using Time Domain Techniques, Anthony R. Nash
Theses and Dissertations
The first phase of this project was the selection of accurate time domain state space modeling techniques by comparing the models generated by various methods, against a known system. The techniques selected were the Eigensystem Realization Algorithm and the Backward Least Squares method. These modeling techniques were applied to the vibration data from the PACOSS dynamic test article. The resulting model transfer function was then compared to the frequency response function of the actual system, and was found to be an accurate match for the system poles, but not for the system zeros. Large Space structures, Dynamic Control, System Mode …
Parallel Algorithms For Single-Layer Channel Routing, Ronald I. Greenberg, Shih-Chuan Hung, Jau-Der Shih
Parallel Algorithms For Single-Layer Channel Routing, Ronald I. Greenberg, Shih-Chuan Hung, Jau-Der Shih
Computer Science: Faculty Publications and Other Works
We provide efficient parallel algorithms for the minimum separation, offset range, and optimal offset problems for single-layer channel routing. We consider all the variations of these problems that have linear-time sequential solutions rather than limiting attention to the ``river-routing'' context, where single-sided connections are disallowed. For the minimum separation problem, we obtain O(lgN) time on a CREW PRAM or O(lgN/lglgN) time on a CRCW PRAM, both with optimal work (processor-time product) of O(N), where N is the number of terminals. For the offset range problem, we obtain the same time and processor bounds as long as only one side of …
An Experimental Study Into The Role Of Routing Flexibility In The Justification Of Advanced Manufacturing Systems, Sanjay Pathak
An Experimental Study Into The Role Of Routing Flexibility In The Justification Of Advanced Manufacturing Systems, Sanjay Pathak
Masters Theses
Increased competition in manufacturing has focused attention on advanced technologies. These costly technologies lead to difficulty in purchase justification using traditional methods. New methods quantify attributes relating to the flexibility of advanced systems. One such attribute is routing flexibility.
This thesis presents results of experiments into evaluation of routing flexibility. The performance of conventional dedicated machinery when compared with that of machines having routing flexibility indicates an advantage of flexible machinery. The thesis indicates a procedure for evaluation of different flexibilities and their comparison with conventional machinery in reality.
An empirical formula is developed that helps in quantifying routing flexibility …
Adsorption Equilibrium Of Benzene-P-Xylene Vapor Mixture On Silicalite, Jianmin Li, Orhan Talu
Adsorption Equilibrium Of Benzene-P-Xylene Vapor Mixture On Silicalite, Jianmin Li, Orhan Talu
Chemical & Biomedical Engineering Faculty Publications
Adsorption equilibrium of benzene-p-xylene vapor mixture on silicalite is measured at 70^oC with a specially designed cyclic volumetric apparatus at pressure levels of 2.53 and 1.20 kPa. The isobaric isotherms are S-shaped, and selectivity curves at different pressures cross over; the p-xylene selectivity at 2.53 kPa is higher than that at 1.20 kPa over a certain composition range. The heterogeneous ideal adsorption solution (HIAS) model implemented on two patches qualitatively predicts these highly unusual behavior. The observed extraodinary phenomena are attributed to structural heterogeneity, a result of the tight-fit of sorbate molecules in silicalite …
Development And Implementation Of A Scramjet Cycle Analysis Code With A Finite-Rate-Chemistry Combustion Model For Use On A Personal Computer, Clarence F. Chenault
Development And Implementation Of A Scramjet Cycle Analysis Code With A Finite-Rate-Chemistry Combustion Model For Use On A Personal Computer, Clarence F. Chenault
Theses and Dissertations
This study compared the performance of an equilibrium combustion model to a finite-rate-chemistry combustion model for a fixed geometry Scramjet flying at the flight conditions of Mach 12, 15, and 18 with a constant dynamic pressure of 50,000 Pa. An integrated PC-based code, developed specifically for this study, models the combustor as an equilibrium combustion process or as finite-rate-chemistry combustion process. This integrated program is based on two existing programs, Ramjet Performance Analysis (RJPA) and 3 STREAM. The effects of mixing schedule, combustor length, and combustor exit area were investigated. The results of this study indicate that inefficient mixing is …
Performance Of The Crash Cushion Attenuating Terminal (Cat) In Traffic Accidents, Kenneth R. Agent, Jerry G. Pigman
Performance Of The Crash Cushion Attenuating Terminal (Cat) In Traffic Accidents, Kenneth R. Agent, Jerry G. Pigman
Kentucky Transportation Center Research Report
The objective of this study was to report the results of the continued monitoring of the performance of the Crash Cushion Attenuating Terminal (CAT) in traffic accidents.
The documented performance of the CAT system in traffic accidents justifies additional use. A recommended location would be at median piers and bridge abutments in narrow medians. While accidents involving this system should continue to be evaluated, this evaluation results in the conclusion that the CAT system could be classified as operational.
The performance of the CAT system indicates a couple of areas which should be addressed. For installations in a raised median, …
Binaural Room Simulation, Brian A. Smith
Binaural Room Simulation, Brian A. Smith
Theses and Dissertations
Research in binaural and spatial hearing is of particular interest to the Air Force. Applications in cockpit communication, target recognition, and aircraft navigation are being explored. This thesis examines human auditory localization cues and develops a mathematical model for the transfer function of a sound signal traveling from an isotropic point source through a rectangular room to both ears of a listener. Using this model as a guide, non-head coupled binaural sound signals are generated in a binaural room simulation. Reflection and attenuation cues included in the computer generated signals are varied in order to determine which cues enhance the …
Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gregory J. Schiller
Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gregory J. Schiller
Theses and Dissertations
The purpose of this thesis is to apply moving-bank multiple model adaptive estimation and control MMAEMMAC algorithms to an actual space structure SPICE being examined at Phillips Laboratory at Kirtland AFB, NM. The structure consists of a large platform and a smaller platform connected by three legs in a tripod fashion. Kalman filtering and LQG control techniques are utilized as the primary design tool. Implementing a bank of filters increases the robustness of the LQG controller when uncertainties exist in the system model, whereas the moving bank is utilized to reduce the computational load. Several reduced-order models are developed from …
Analysis Of The Effects Of Wake Passage On Heat Transfer In A Linear Turbine Cascade, Kevin S. Allen
Analysis Of The Effects Of Wake Passage On Heat Transfer In A Linear Turbine Cascade, Kevin S. Allen
Theses and Dissertations
This study investigated the effect of wake passage on the heat transfer in a linear turbine cascade. The apparatus used was the Air-Force Institute of Technology linear Turbine Cascade Test Facility (TCTF). The TCTF was fitted with a be Pulley system to facilitate a series of translating bars. The bars, when passed d upstream of the cascade, created a series of wakes. The parameters varied were freestream model Reynolds number and bar conditions, i.e. , bars in, bars out, and bar passing frequency. One blade in the TCTF was instrumented to allow pressure and temperature measurements at discrete points on …
The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch
The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch
Theses and Dissertations
Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …
A Method For Populating The Knowledge Base Of Aptas, A Domain-Oriented Application Composition System, Raleigh A. Sandy Iii
A Method For Populating The Knowledge Base Of Aptas, A Domain-Oriented Application Composition System, Raleigh A. Sandy Iii
Theses and Dissertations
A formal process is described for populating the knowledge base of the Automatic Programming Technologies for Avionics Software APTAS system. This process was developed using a general knowledge base population process that applies to many knowledge-based software engineering systems. This general process is also described. The formal process for APTAS was demonstrated by storing new information from the radar tracking domain into the knowledge base of APTAS. Several procedures some automatic and some manual were implemented to support the formal process.
Synthetic Battlebridge: Information Visualization And User Interface Design Applications In A Large Virtual Reality Environment, Kirk G. Wilson
Synthetic Battlebridge: Information Visualization And User Interface Design Applications In A Large Virtual Reality Environment, Kirk G. Wilson
Theses and Dissertations
With shrinking budgets and fewer personnel, future military training will rely heavily on simulated environments. The goal for this training is to reduce cost while maintaining readiness and unparalleled capability for all levels of military command. This thesis effort, the Synthetic Battle Bridge SBB , provides a real-time simulated environment for military commanders to observe on-going computer simulations of varying participation levels and helps them wring the most from a simulation. The SBB, designed for higher ranking personnel with little time to spend learning how to run the system, must exhibit three capabilities ease-of-use, long-term retention, and adaptability. Based on …
Human Visual System Enhancement Of Reconstructed Satellite Images, James E. Treleaven
Human Visual System Enhancement Of Reconstructed Satellite Images, James E. Treleaven
Theses and Dissertations
This research investigated the enhancement of satellite images. The goal was to develop and test a suite of image enhancement software routines to improve the quality of reconstructed images for the human visual system. The primary focus was to enhance satellite features. Enhancement was accomplished in both the spatial domain and the frequency domain. In the spatial domain, routines were developed to enhance image contrast and edges. In the frequency domain, a routine was developed using research into the human visual system. The transfer function of the human visual system was used to develop a filter for frequency domain enhancement. …
Creation Of Prototype Aircrew Protection Equipment Based On Face Anthropometry, Martin E. Piccus, Gary A. Smith, Brian K. Standley, Tami L. Volk, Linda B. Wildes
Creation Of Prototype Aircrew Protection Equipment Based On Face Anthropometry, Martin E. Piccus, Gary A. Smith, Brian K. Standley, Tami L. Volk, Linda B. Wildes
Theses and Dissertations
The objective of this research is to develop a process which will analyze and group human faces, concentrating on the oxygen mask seal area, into a minimum number of generic yet distinct face types. The shape and size, or form, of the face is described by bending energies. This bending energy provides the features for the grouping of similar face types, while distinguishing representatives for each cluster. The face tariffs are the percentage of faces grouped under a representative face. The representative faces are then transformed Into three-dimensional solids using computer-aided design. A rapid prototype creates the solids or plugs …
Spectroscopic And Vibrational Energy Transfer Studies In Molecular Bromine, Courtney D. Holmberg
Spectroscopic And Vibrational Energy Transfer Studies In Molecular Bromine, Courtney D. Holmberg
Theses and Dissertations
Vibrational transfer and electronic quenching in the lower vibrational levels (v' < 3) of the B3π(0u+) state of 79Br2 were investigated using spectrally resolved, temporally resolved laser induced fluorescence techniques. Spectrally resolved emissions from collisionally populated Br2(B) vibrational levels were observed for Br2 and rare gas collision partners. Vibrational transfer was efficient in the non-predissociative vibrational levels and was adequately described by the Montroll-Shuler model for harmonic oscillators. A single fundamental rate coefficient for vibrational transfer from v' = 1 to v' = 0, kv(1,0), characterizes vibrational relaxation. For Br2, the …
Modal Control Of A Satellite In An Unstable Periodic Orbit About The Earth-Sun Interior Lagrange Point, Douglas J. Hopper
Modal Control Of A Satellite In An Unstable Periodic Orbit About The Earth-Sun Interior Lagrange Point, Douglas J. Hopper
Theses and Dissertations
A periodic halo orbit which exists about the interior Lagrange point for the Earth-sun system was decomposed using Floquet theory into modal variables, which are dynamically decoupled subspaces for the six degree of freedom system. Modal control consisted of evaluating the diverging mode and maneuvering to counteract its divergence. In the unperturbed system, this was successful. Control costs were low, and the significance is that the controller did nothing to suppress modes that were oscillatory or converging. The effect of the moons motion allowed the scheme to operate with reasonable control costs, but the effect of eccentricity caused divergence in …
Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider
Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider
Theses and Dissertations
A linear turbine cascade was used to investigate the effects of wake passage due to stator-rotor interaction. The wakes were modeled by passing 1.98 mm (0.078 in) diameter bars upstream of a linear cascade blade row. Total pressure loss coefficients, mass averaged total pressure loss coefficients and velocities were used to characterize the effects of wake passage. Bar passing frequencies of 80, 160, 320 bars/sec were tested. These frequencies were tested, with the bars at 6.35 mm (0.25 in) intervals and at two Reynolds numbers, 341, 000 and 45,5000 Bar spacings of 12.7 mm (0.5 in), and 89 mm (3.5 …
Off-Design Performance Of Crenulated Blades In A Linear Compressor Cascade, Michael J. Costello
Off-Design Performance Of Crenulated Blades In A Linear Compressor Cascade, Michael J. Costello
Theses and Dissertations
The effects of using compressor blades with a crenulated (notched) trailing edge in a low aspect ratio (AR= 1) linear compressor cascade at four incidence angles (-1.08°, +4.49°, +9.32° and +12.44°) were investigated. Blade performance and wake mixing characteristics for crenulated blades were compared with similar data for blades with a straight trailing edge. A seven-bladed cascade was operated with a flow Mach number of 0.4 and a blade chord Reynolds number of 4.1 (10)5. The diffusion factor ranged from 0.22 to 0. 42 and strong three-dimensional flow effects were present. Total pressure losses were measured with a …