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1993

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Articles 91 - 120 of 1343

Full-Text Articles in Engineering

A Concept For Sled Testing Minuteman Iii Guidance Systems, Hossny El-Sherief, Dave Knight, Daniel J. Simon, Myron Teeter Dec 1993

A Concept For Sled Testing Minuteman Iii Guidance Systems, Hossny El-Sherief, Dave Knight, Daniel J. Simon, Myron Teeter

Electrical and Computer Engineering Faculty Publications

No abstract provided.

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A Physics-Based Heterojunction Bipolar Transistor Model For Integrated Circuit Simulation, James A. Fellows Dec 1993

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 …

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The Effect Of Cutout Dimensionality On The Collapse Characteristics Of Cylindrical Composite Shells Of Varying Thickness, John C. Del Barga Dec 1993

The Effect Of Cutout Dimensionality On The Collapse Characteristics Of Cylindrical Composite Shells Of Varying Thickness, John C. Del Barga

Theses and Dissertations

This study involved a numerical and experimental investigation of the (geometric instability of graphite/epoxy cylindrical panels with free vertical edges undergoing axial compression. Symmetric quasi-isotropic laminates with five different size centralized cutouts, were investigated for two axial lengths of panels and three thicknesses. The study compared experimental data to results from SHELL, a geometrically nonlinear finite-element program which incorporates a parabolic transverse shear strain distribution through the thickness. The research verified that the SHELL program will provide good predictions of the collapse characteristics of a panel with large cutouts of varying dimensions undergoing large displacements and rotations. The best correlation …

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A Virtual Environment For Satellite Modeling And Orbital Analysis In A Distributed Interactive Simulation, Andrea A. Kunz Dec 1993

A Virtual Environment For Satellite Modeling And Orbital Analysis In A Distributed Interactive Simulation, Andrea A. Kunz

Theses and Dissertations

In response to the need for a more realistic, interactive, and immersive space simulation system, the Joint National Intelligence Defense Staff JNIDS has sponsored the development of the Satellite Modeler at the Air Force Institute of Technology AFIT. The Satellite Modeler SM is a virtual environment VE application that allows analyst-users to enter a virtual near- Earth space environment and visualize realistic satellite models performing accurate orbital motion. The Satellite Modeler provides manipulation functions that allow a user to interact with multiple satellite models and satellite constellations. The system affords the user multiple vantage points within the environment to view …

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Human Visual System Enhancement Of Reconstructed Satellite Images, James E. Treleaven Dec 1993

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. …

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Local Area Network Implementation At The 4950th Test Wing: A Study Of The Relationship Between Individual Factors And The Effectiveness Of A Local Area Network, Doyle F. Cone, David J. Donahoo Dec 1993

Local Area Network Implementation At The 4950th Test Wing: A Study Of The Relationship Between Individual Factors And The Effectiveness Of A Local Area Network, Doyle F. Cone, David J. Donahoo

Theses and Dissertations

This research investigated the individual factors which directly impacted the effectiveness of the 4950th Test Wing local area network (LAN). Areas of interest included the relationships between demographic and user attitude factors and LAN effectiveness. A literature review provided the basis for: 1) operationally defining effectiveness as a subjective measure of user satisfaction; 2) identifying specific factors which impact information system effectiveness; and 3) developing a research instrument to measure user attitudes and user satisfaction. A questionnaire was administered to 342 LAN users 173 were returned (a response rate of 51 percent). Sixteen factors (eight demographic factors and eight attitude …

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Parallel Algorithms For Single-Layer Channel Routing, Ronald I. Greenberg, Shih-Chuan Hung, Jau-Der Shih Dec 1993

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 …

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Spectroscopic And Vibrational Energy Transfer Studies In Molecular Bromine, Courtney D. Holmberg Dec 1993

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 …

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Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran Dec 1993

Design And Construction Of The Aerobot Robotic Manipulator (Arm), William L. Cochran

Theses and Dissertations

This thesis designed, constructed, and tested a robotic arm for the Aerobot Aerial Robot. The main purpose of the ARM is to enable the Aerobot to retrieve objects for use in an annual robotics competition. Design of the ARM involved synthesizing the characteristics of simplicity, weight, strength, and size. The result was a three-degree-of-freedom manipulator that uses electric motors, cable linkages, and telescoping tubes to access a work space below the Aerobot. Forward and inverse kinematics were investigated to enable automation of the ARM. Data was collected from infrared sensors to validate the model. Manipulation of the ARM is presently …

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Multiple Model Adaptive Control Of A Large Flexible Space Structure With Purposeful Dither For Enhanced Identifiability, James A. Fitch Dec 1993

Multiple Model Adaptive Control Of A Large Flexible Space Structure With Purposeful Dither For Enhanced Identifiability, James A. Fitch

Theses and Dissertations

Dithering techniques for enhancing uncertain parameter identification with moving-bank Multiple Model Adaptive Estimation MMAE and Control MMAC algorithms are analyzed in this thesis. The dithering techniques and multiple- model adaptive algorithms are applied to the SPICE 2 flexible space structure. The dithering techniques studied include purposefully constructed square wave, sine wave fixed and swept frequency and wide-band noise wave forms. Purposeful rigid-body slew commands are also used in order to excite the structures flexible bending modes. Dither inputs into the structure are performed in an effort to enhance the open-loop identifiability of the uncertain parameter, namely a scalar multiplier on …

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Orbital Applications Of Electrodynamic Propulsion, Troy Irwin Dec 1993

Orbital Applications Of Electrodynamic Propulsion, Troy Irwin

Theses and Dissertations

Electrodynamic propulsion (EDP) uses forces resulting from electric currents in conductors as a spacecraft travels through a magnetic field. A vehicle-independent expression for the specific power required for any maneuver is derived and used to assess EDP feasibility. Analytical expressions for the accelerations and combined current-conductor vector required to change the orbital plane or the argument of perigee are developed based on Lagranges planetary equations. Solutions to the forced Clohessy-Wiltshire equations are developed to study iii-plane rendezvous. Results show EDP can change inclination or right ascension of the ascending mode at approximately 0.4 degrees/day with current spacecraft specific power technology. …

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An Approximate Solution For The Spinup Dynamics Of Near Axisymmetric Axial Gyrostats Using The Method Of Multiple Scales, Stewart J. Kowall Dec 1993

An Approximate Solution For The Spinup Dynamics Of Near Axisymmetric Axial Gyrostats Using The Method Of Multiple Scales, Stewart J. Kowall

Theses and Dissertations

Approximate solutions for the spinup of a near axisymmetric gyrostat are derived using the straightforward expansion method and the method of multiple scales. Two method of multiple scale solutions are presented. The first is derived using cartesian coordinates while the second is derived using cylindrical coordinates. The multiple scales solutions are compared to numerically integrated results for oblate and prolate configurations. A comparison for flat spin recovery is also accomplished. Excellent results are obtained for oblate configurations. Trajectory separatrix crossings hindered the results for prolate configurations and flat spin recoveries.

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Modeling Of A Large Undamped Space Structure Using Time Domain Techniques, Anthony R. Nash Dec 1993

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 …

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Comparison Of The Dynamic Behavior Of Composite Plates And Shells Incorporating Green's Strain Terms With The Von Karman And Donnell Models, Arthur E. Forral Dec 1993

Comparison Of The Dynamic Behavior Of Composite Plates And Shells Incorporating Green's Strain Terms With The Von Karman And Donnell Models, Arthur E. Forral

Theses and Dissertations

The dynamic collapse behavior of thin, composite cylindrical shells subjected to transverse point loads is considered. The dynamic behavior of the undamped cylindrical shells of varying radii is analyzed with a finite element formulation that incorporates all nonlinear Green's strain terms in the in-plane directions; transverse strains are linear and vary parabolically through the shell thickness. This formulation is denoted as the simplified large displacement/rotation (SLR) theory. Graphical representations are used extensively to examine dynamic behaviors not noted in similar research that utilized the DSHELL finite element code. Composite plate behavior is also explored. Comparison of the higher-order formulations to …

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Shock Wave Interaction With L-Shaped Structures, Richard C. Miller Dec 1993

Shock Wave Interaction With L-Shaped Structures, Richard C. Miller

Theses and Dissertations

This study investigated the interaction of shock waves with L-shaped structures using the CTH hydrodynamics code developed by Sandia National Laboratories. Computer models of shock waves traveling through air were developed using techniques similar to shock tube experiments. Models of L-shaped buildings were used to determine overpressures achieved by the reflecting shock versus angle of incidence of the shock front. An L-shaped building model rotated 45 degrees to the planar shock front produced the highest reflected overpressure of 9.73 atmospheres in the corner joining the two wings, a value 9.5 times the incident overpressure of 1.02 atmospheres. The same L-shaped …

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Genetic Algorithms Applied To A Mission Routing Problem, James B. Olsan Dec 1993

Genetic Algorithms Applied To A Mission Routing Problem, James B. Olsan

Theses and Dissertations

This thesis applies genetic algorithms to a mission routing problem. The mission routing problem involves determining an aircraft’s best route between a staging base and a target. The goal is to minimize the route distance and the exposure to radar. Potential routes are mapped to a 3-dimensional mesh where the nodes correspond to checkpoints in the route and the arcs correspond to partial paths of the route. Each arc is weighted with respect to distance and exposure to radar. A genetic algorithm is a probabilistic search technique loosely based on theories of biological evolution. Genetic crossover and survival of the …

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Weapon System Sensor Integration For A Dis-Compatible Virtual Cockpit, Matthew N. Erichsen Dec 1993

Weapon System Sensor Integration For A Dis-Compatible Virtual Cockpit, Matthew N. Erichsen

Theses and Dissertations

This thesis continues the Virtual Cockpit VC research which investigates distributed interactive virtual flying, environments. The VC vl.0 used the SIMNET protocols to only communicate position and orientation over a common network. A simple cockpit instrumentation configuration and limited head- tip display, HUD showed aircraft state. With VC vl.0 weapons or sensors could not interact in the simulation environment. The VC v2.0 transitions from the SIMNET protocol to a partial implementation of the Distributed Interactive Simulation DIS v2.0.3 protocol. Simulated radar and forward looking infra-red FLIR sensors were developed to aid operator detection and designation when employing various munition types. …

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Radar Cross Section Visualization Using Sample Buffer Progressive Refinement Volume Rendering, Alain L. Jones Dec 1993

Radar Cross Section Visualization Using Sample Buffer Progressive Refinement Volume Rendering, Alain L. Jones

Theses and Dissertations

This study developed a prototype for an interactive radar cross section visualization software system. The system, hosted on a Silicon Graphics workstation, is intended to support aircrews, mission planners, aircraft designers, and others who require an understanding of aircraft radar cross section characteristics. The input to the system is a set of radar cross section samples taken at various aspect angles. A pre-processor developed as part of this study transforms the input radar cross section data into a three-dimensional cuberille data volume. This data volume is then visualized using an interactive volume renderer. The interactive volume renderer implements progressive image …

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Synthetic Battlebridge: Information Visualization And User Interface Design Applications In A Large Virtual Reality Environment, Kirk G. Wilson Dec 1993

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 …

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Enhanced Tracking Of Airborne Targets Using Forward Looking Infrared And Laser Return Measurements, Patrick J. Grondin Dec 1993

Enhanced Tracking Of Airborne Targets Using Forward Looking Infrared And Laser Return Measurements, Patrick J. Grondin

Theses and Dissertations

The Air Force Institute of Technology has been involved in developing Kalman filter based trackers of ballistic missiles for 15 years. The goal of this thesis is to develop a Multiple Model Adaptive Estimator MMAE that tracks the missile plume using a forward looking infrared sensor and the missile hardbody center-of-mass additionally using low energy laser returns for the purpose of directing a high power laser to incapacitate the missile. The missile plume pogos about an offset equilibrium point relative to the hardbody center-of-mass with an amplitude and frequency of oscillation that are not precisely known a priori. The MMAE …

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Incorporation Of Carrier Phase Global Positioning System Measurements Into The Navigation Reference System For Improved Performance, Neil P. Hansen Dec 1993

Incorporation Of Carrier Phase Global Positioning System Measurements Into The Navigation Reference System For Improved Performance, Neil P. Hansen

Theses and Dissertations

In order to quantify the performance and accuracy of existing navigation systems, the U.S. Air Force has been using the Completely Integrated Reference Instrumentation System (CIRIS) as a baseline. CIRIS combines information from an inertial navigation unit, a barometric altimeter, and a range/range-rate system of ground transponders to obtain a navigation solution. This research explores the possibilities of enhancing CIRIS by adding measurements obtained from the Global Position System (GPS). Pure pseudorange measurement updates to the CIRIS Extended Kalman Filter form the basis of the Navigation Reference System (NRS). Applying differential corrections to the pseudorange measurements forms the basis of …

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Guidelines For Ensuring Software Supportability In Systems Developed Under The Integrated Weapon System Management Concept, Forrest F. Butts Iii, Anthony C. Johndro Dec 1993

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 …

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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 Dec 1993

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 …

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Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider Dec 1993

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 …

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A Numerical Determination Of Bifurcation Points For Low Reynolds Number Conical Flows, Larry K. Waters Dec 1993

A Numerical Determination Of Bifurcation Points For Low Reynolds Number Conical Flows, Larry K. Waters

Theses and Dissertations

It has long been established that supersonic flow over axisymmetric conical bodies at high angles of attack tend to develop a side force due to vortical asymmetry. One of the proposed reasons for the asymmetry is a bifurcation point in the solution of the Navier-Stokes equations. This study investigated the possible existence of a bifurcation point in the Navier-Stokes equations for subsonic flow. Newton's method, with gauss elimination, was used- to solve the steady-state, viscous, compressible Navier-Stokes equations in spherical coordinates assuming conical similarity.

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Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel Dec 1993

Influence Of Embedded Optical Fibers On Compressive Strength Of Advanced Composites, Stefan B. Dosedel

Theses and Dissertations

This study investigated the effects of embedding optical fibers into advanced composite materials. This combination was meant to simulate 'smart structures' that have been shown to sense several different variables in the composite including strain, temperature, and damage. A laminate orientation taken from an existing aircraft structure was used to fabricate sixteen groups of specimens which were subjected to compression testing in an IITRI fixture to determine the ultimate compressive strength and modulus of elasticity. Ten of these groups were fabricated with optical fibers while the other six were control groups and contained no optical fibers. This study showed that …

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An Object-Oriented Database Interface For Ada, Anthony D. Moyers Dec 1993

An Object-Oriented Database Interface For Ada, Anthony D. Moyers

Theses and Dissertations

Object data management ODM is currently at the forefront of research and development efforts in the database community. In order to take advantage of ODM technology, the Department of Defense DoD needs to ensure that these systems are accessible to Ada programmers. The Air Force Institute of Technology AFIT is conducting research towards the development of an Ada ODM interface to existing ODM systems. The design goals are portability, transparency, and completeness for Ada programmers. Portability means that the ODM system can be changed without affecting any existing application programs. Transparency means that Ada programmers can use the interface without …

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Object Imaging Accomplished With An Integrated Circuit Robotic Tactile Sensor Incorporating A Piezoelectric Polyvinylidene Fluoride Thin Film, John M. Emmert Dec 1993

Object Imaging Accomplished With An Integrated Circuit Robotic Tactile Sensor Incorporating A Piezoelectric Polyvinylidene Fluoride Thin Film, John M. Emmert

Theses and Dissertations

The purpose of this research effort was to investigate the performance of a piezoelectric tactile sensor design and appropriately refine it. The sensor was fabricated from an 8 x 8 electrode array MOS integrated circuit. Each taxel in the array was 400 microns x 400 microns. A 6 mm x 6 mm piece of piezoelectric polyvinylidene fluoride was adhered to the electrode array using a urethane dielectric adhesive to form the active sensing area of the sensor. An amplifier was investigated to enhance the range of the tactile sensor's output signal. The amplifier is a high input' impedance differential amplifier …

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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 Dec 1993

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 …

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Prototype Space Fabrication Platform, James A. Bessel, James M. Ceney, David M. Crean, Edward A. Ingham, David J. Pabst Dec 1993

Prototype Space Fabrication Platform, James A. Bessel, James M. Ceney, David M. Crean, Edward A. Ingham, David J. Pabst

Theses and Dissertations

Current plans for constructing large structures in space entail fabricating the primary components, such as truss segments, on the ground and assembling them in space. This process requires an exorbitant number of support missions, and methods to minimize the number must be considered. Whenever the space shuttle is launched, its external tank is jettisoned and destroyed prior to reaching orbit. This aerospace grade aluminum structure can be carried into orbit and utilized extrusively. The Prototype Space Fabrication Platform SFP fabricates aluminum materials, reduced from external tanks, into functional trusses. The trusses are strong and can be used as the primary …

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