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Articles 5191 - 5220 of 5698

Full-Text Articles in Engineering

Strategies For Optimal Control Design Of Normal Acceleration Command Following On The F-16, James C. Baird Dec 1992

Strategies For Optimal Control Design Of Normal Acceleration Command Following On The F-16, James C. Baird

Theses and Dissertations

Weight shapes and locations are investigated for H2, H∞, and the general mixed H2/H infinity optimization methodologies. The design model is normal acceleration command following for the F-16 (SISO) at Mach 0.6 and Sea Level, which yields a nonminimum phase and unstable plant. H2 design types include LQG, LQG/Sensitivity, and LQG/Tracking. Robustness and tracking are the objectives of the central H infinity process. Both H∞ optimal and suboptimal controllers are examined, with the suboptimal controller shown as the practical choice for this plant. The mixed H2/H∞ setup allows the tradeoff between …

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Behavior Of A Titanium Matrix Composite Under Quasi-Static Tensile And Compressive Loading, Keith L. Bearden Dec 1992

Behavior Of A Titanium Matrix Composite Under Quasi-Static Tensile And Compressive Loading, Keith L. Bearden

Theses and Dissertations

Quasi-Static tensile and compressive testing was performed on a unidirectional titanium matrix composite. The specific material was SCS-9/β 21S. The initial tensile and compressive modulus for both laminates was the same. The ninety degree laminate had a tensile and compressive modulus of 115.89 GPa. The zero degree laminate had a tensile and compressive modulus of 197.51 GPa. The ninety degree laminate exhibited a three stage stress/strain response in tension. The first stage is completely linearly elastic, however, partial debonding of the fiber from the matrix was observed. This partial debased did not effect the stress/strain response. The second stage is …

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Characterization Of Stall Inception In High-Speed Single-Stage Compressors, Keith M. Boyer Dec 1992

Characterization Of Stall Inception In High-Speed Single-Stage Compressors, Keith M. Boyer

Theses and Dissertations

Two single-stage, transonic compressor designs were tested under various undistorted operating conditions to characterize the process leading up to aerodynamic stall. The rig case was instrumented with eight high-response static pressure transducers equally spaced around the annulus for stall development detection. High-response measurements were low-pass filtered and both spatially and temporally analyzed using discrete Fourier techniques. At all speeds tested for both designs, stall inception was characterized by growth of a small amplitude' rotating wave. The waves did not grow significantly until just prior to the instability, when exponential growth into fully-developed rotating stall occurred very rapidly, within 6-10 rotor …

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Stratified Plate Model For Composite Plate Analysis, Richard A. Coveno Dec 1992

Stratified Plate Model For Composite Plate Analysis, Richard A. Coveno

Theses and Dissertations

This study continues the investigation of the stratified plate model for the analysis of composites plates. The strata theory models a composite plate as a stack of isotropic matrix and orthotropic, fiber dominated layers. Energy methods are used to derive a set of partial differential equations and boundary conditions as a function of the displacement. An assumed displacement field, of a polynomial in z and a Sine/Cosine function in x and y, generates a solution to a simply supported composite plate with cross plies. A cylindrical bending example is also solved with a polynomial in z and Sine/Cosine function in …

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Effect Of Thickness And Ply Layup On The Collapse Characteristics Of Cylindrical Composite Shells With Large Cutouts, James C. Hatfield Dec 1992

Effect Of Thickness And Ply Layup On The Collapse Characteristics Of Cylindrical Composite Shells With Large Cutouts, James C. Hatfield

Theses and Dissertations

This study involved a numerical and experimental investigation of the geometric instability(collapse loads/displacements) of vertically unsupported graphite/epoxy cylindrical shell panels undergoing axial compression. Symmetric quasi-isotropic and cross-ply laminates, with and without 4 X4 centralized cutouts, were investigated for three thicknesses:8,16,and 24 plies. The experimental data was compared to results from SHELL, a geometrically nonlinear finite-element computer program which incorporates a parabolic transverse shear strain distribution through the thickness. Good correlation was obtained for shells with large cutouts between the SHELL numerical data and the experimental results. This research verified that the SHELL program will provide good predictions of the collapse …

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Nozzle/Cowl Optimization For A Hypersonic Vehicle On A Typical Trajectory, Michael J. Bonaparte Dec 1992

Nozzle/Cowl Optimization For A Hypersonic Vehicle On A Typical Trajectory, Michael J. Bonaparte

Theses and Dissertations

An investigation of the effects of simultaneous variation of the nozzle attachment and cowl deflection angle on the performance of a two- dimensional nozzle used on a hypersonic vehicle such as the National Aero-Space Plane (NASP) was performed using a two parameter optimization procedure. Total thrust optimization was accomplished using a Flux-Difference-Split (FDS) cods, a RAMJET Performance Analysis program, and an oblique shock wave solver program, at sixteen points on a 1000 psf dynamic pressure trajectory for Mach numbers from 10.0 to 25.0. A single parameter optimization of the total thrust using a variable nozzle attachment angle was accomplished first …

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Development Of An Engine/Airframe Performance Matching Scheme For Jet Engine Retrofit, Alan Lach Dec 1992

Development Of An Engine/Airframe Performance Matching Scheme For Jet Engine Retrofit, Alan Lach

Theses and Dissertations

This investigation developed a procedure and new analysis tools for identifying retrofit engine designs for use in existing airframes. The goal was to find a replacement engine for the air-to-air fighter, AAF, developed in the textbook Aircraft Engine Design. This paper introduced the ideas of solution surfaces, constraint/thrust diagrams, quality measures and linear regression analysis for the engine design problem. It considered the application of the jet engine design software ACSYS, MISS, and ONX along with statistical analysis software, SAS. Modeling techniques and linear regression analysis were used to minimize iteration while searching a wide range of design variables. Improvements …

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Optimal Control Of The Starfire Beam Director, Troy V. Lanier Dec 1992

Optimal Control Of The Starfire Beam Director, Troy V. Lanier

Theses and Dissertations

The Starfire Beam Director (SBD) is located at the Starfire Optical Range at Kirtland Air Force Base in Albuquerque, New Mexico. The SBD capabilities include tracking celestial objects and active or passive tracking of artificial satellites to support the Phillips Laboratory Ground Based Laser Acquisition, Tracking, and Pointing (GBL ATP) program. The pointing and tracking accuracy needed to support such experiments is micron rad to sub-grad level. To accomplish this goal requires precise pointing of the massive 6 ton 1 -meter clear aperture coelostat. The purpose of this thesis is to use optimal control design techniques to develop a controller …

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The Effects Of Viscosity On A Conically Derived Waverider, James A. Mundy Dec 1992

The Effects Of Viscosity On A Conically Derived Waverider, James A. Mundy

Theses and Dissertations

This study investigated the effects of the interaction between the viscous boundary layer and the shock wave produced by a Mach 10 inviscid optimized waverider. An implicit, Roe flux-splitting algorithm, developed by WL/FIMM, was used to solve the flow field. A validation for the inviscid version of the CFD algorithm was accomplished by comparing the numerical -data produced by the CFD code to the analytic results derived by Rasmussen, and by comparison to results of the explicit version of the same Roe flux-splitting code. The computational results compared favorably. The inviscid case studied using the implicit code produced results identical, …

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Improvements To Lqgi/Ltr Methodology For Plants With Lightly Damped Or Low Frequency Poles, An-Chi Ju Dec 1992

Improvements To Lqgi/Ltr Methodology For Plants With Lightly Damped Or Low Frequency Poles, An-Chi Ju

Theses and Dissertations

LQG/LTR design has a tendency to invert the plant's dynamics, which is undesirable if there are plant poles near the imaginary axis. In this study, Static Output Feedback (SOF) is applied to reassign plant poles before LQG/LTR is applied. Alternatively, Robust Eigenstructure Assignment (REA) was used to design the target loop transfer function with an ideal eigenstructure to avoid the undesirable cancellations. Both methods were applied to several aircraft design problems. Results showed that the methods can be effectively used so that the LQG/LTR design has improved stability and performance; however, it was found that each method had strengths and …

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Experimental Investigation Of The Aerodynamics Of Independently Rotating Cylindrical Shells, Walter C. Howerton Dec 1992

Experimental Investigation Of The Aerodynamics Of Independently Rotating Cylindrical Shells, Walter C. Howerton

Theses and Dissertations

The purpose of this thesis was to investigate experimentally the aerodynamic forces on two adjacent, independently rotating cylinders in a cross- flow. This investigation involved a force measurement setup which had the two cylinders mounted on a common support shaft, extending beyond the span of the wind tunnel test section, and supported by spoke rings with strain gages in the vertical and horizontal directions. This setup proved capable of measuring aerodynamic forces. The lift on the independently rotating cylinders was found to increase as one cylinder's angular speed increased while the other's remained constant, and decrease as the relative angular …

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Open And Filled Hole Static Tensile Strength Characterization Of Metal Matrix Composite Scs-9/Β21s, Jacob T. Roush Dec 1992

Open And Filled Hole Static Tensile Strength Characterization Of Metal Matrix Composite Scs-9/Β21s, Jacob T. Roush

Theses and Dissertations

SCS-9/β21s has a reduced gauge thickness, in comparison with other metal matrix composites, due to a smaller diameter fiber. This reduced gauge thickness makes it an attractive candidate for the skin of hypersonic vehicles. Tensile testing of (0/90)2s and (O/±45/90)s laminates was performed at room temperature, 482°C, and 650°C. Both notched and unnotched specimens were tested. Notched specimens, open and filled hole, had a width-to-diameter ratio of six. Materials 7075-T6 and Mar-m-246 were used as pins in the filled hole tensile testing. Analytical work was completed to predict material properties, elastic and plastic stress concentration factors, residual stresses, …

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Application Of The Program Profile For The Design Of Low-Speed, Low- Observable Configuration Airfoils, Gregory A. Sharp Dec 1992

Application Of The Program Profile For The Design Of Low-Speed, Low- Observable Configuration Airfoils, Gregory A. Sharp

Theses and Dissertations

This study investigated-the use of the program PROFILE for the design of low-speed, low-observable configuration airfoils. For our purposes, low- observable configuration is defined as being characterized by a small leading- edge radius of less than 1.18 percent chord and a thickness-to-chord ratio of 2. 5 to 5.5 percent. A methodology was developed whereby the input parameters to prescribe the velocity distribution over the airfoil could be determined by a power law relationship. This relationship enables the designer to develop symmetric airfoils with the desired thickness-to-chord and leading-edge radius within the stated constraints. The resulting symmetric airfoils compared very well …

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Behavior Of A Centrally Notched Cross-Ply And Unidirectional Ceramic Matrix Composite In Tension-Compression Fatigue, William A. Weidenaar Dec 1992

Behavior Of A Centrally Notched Cross-Ply And Unidirectional Ceramic Matrix Composite In Tension-Compression Fatigue, William A. Weidenaar

Theses and Dissertations

Centrally notched (hole), cross-ply, ((0/90)2)s, and unidirectional, (0)8 laminates of Silicon Carbide fiber-reinforced Aluminosilicate glass, SiC/1723, were fatigue tested under tension-compression loading with a load ratio of -1. Damage accumulated continuously for both lay- ups, leading to eventual failure and a reduced fatigue life. Critical damage in the cross-ply consisted of longitudinal cracks in the 90° plies growing and combining with transverse cracks to effectively eliminate the 90° plies' load carrying capability and allowing the specimen to buckle. Critical damage in the unidirectional lay-up consisted of longitudinal cracks which initiated at the shear stress concentration …

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The Influence Of Structural Optimization On The Aeroelastic Properties Of A Vertical Tail, David G. Miller Dec 1992

The Influence Of Structural Optimization On The Aeroelastic Properties Of A Vertical Tail, David G. Miller

Theses and Dissertations

The purpose of this thesis is to investigate the influence of structural optimization parameters on the structural and aeroelastic behavior of a vertical tail. The outside geometry of the tail is assumed fixed. The objective of the optimization is to reduce the structural member sizes so that the overall weight of the tail is minimized. The influence that design loads, design constraints, design variable linking has on the optimal design is observed examining several design cases. The static aeroelastic properties a flutter speeds of the various design cases are then compared. The doublet lattice method is used to calculate the …

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An Interactive Life Cycle Cost Forecasting Tool, Nicolas M. Habash Dec 1992

An Interactive Life Cycle Cost Forecasting Tool, Nicolas M. Habash

Theses and Dissertations

This thesis is about computing life cycle cost and culminates with a life cycle cost forecasting tool (software). The software is written in FORTRAN 77 and uses IMSL subroutine extensively for random number generation from various distributions. The algorithm can compute life cycle cost for the following types of cost elements: constant, stochastic, and cost estimating relationships (CERs). The use of a trapezoid approximation of payment allocation is allowed. Percent allocation of payments is also allowed and is recommended where the trapezoid fails to correctly represent the payment schedule. The CER algorithm handles cost data that was estimated in base …

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A Two-Stage Intercontinental Ballistic Missile (Icbm) Design Optimization Study And Life Cycle Cost Analysis, David P. Blanks, Douglas M. Bruce, Anthony M. Logue, Ralph A. Sandfry, Stephen J. Skotte, Michael L. Zywien Dec 1992

A Two-Stage Intercontinental Ballistic Missile (Icbm) Design Optimization Study And Life Cycle Cost Analysis, David P. Blanks, Douglas M. Bruce, Anthony M. Logue, Ralph A. Sandfry, Stephen J. Skotte, Michael L. Zywien

Theses and Dissertations

Realities of recent changes in the fiscal environment and the international domestic security structure have caused the strategic community to make some difficult decisions to preserve the capability of the current ICBM force. One of these decisions is to view Minuteman Ill as the centerpiece of the strategic force well into the next century. Extending the life of the 24-year- old Minuteman III system requires system solutions that provide required performance at an affordable life cycle cost. The intent of this study is to demonstrate the feasibility of designing a 2-stage ICBM to perform the Minuteman III mission. The main …

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Comparison Of Artificial Neural Networks With A Conventional Heuristic Technique For Optimization Problems, Jeffrey S. Gruner Dec 1992

Comparison Of Artificial Neural Networks With A Conventional Heuristic Technique For Optimization Problems, Jeffrey S. Gruner

Theses and Dissertations

This research investigates the utility of the Hopfield and Kohonen artificial neural networks to the traveling salesman optimization problem. A third, non-neural-network technique (the Christofides Algorithm - a competitive, bounded-solution operations research technique) is also investigated for comparison to the artificial neural network solutions. An eight and forty-two city distribution are chosen for comparison of the solutions.

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Analysis Of Titan Iv Launch Responsiveness, Michael T. Dunn Dec 1992

Analysis Of Titan Iv Launch Responsiveness, Michael T. Dunn

Theses and Dissertations

This research investigates the feasibility of developing responsive space systems through responsive launch operations with the Titan IV, the only expendable heavy-lift launch vehicle in the United States inventory. A definition for responsive launch has not been firmly established by Air Force Space Command for this launch vehicle. For benchmark purposes, this study uses the responsive launch definition contained in the proposal request for the Medium Launch Vehicle Ill: launch vehicle ignition within 60 days of mission need notification. Titan IV launch processing at Cape Canaveral Air Force Station (CCAFS), Florida currently requires in excess of six months, rendering Titan …

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Recurrent Neural Networks For Radar Target Identification, Eric T. Kouba Dec 1992

Recurrent Neural Networks For Radar Target Identification, Eric T. Kouba

Theses and Dissertations

A real-time recurrent learning algorithm was applied to a five class radar target identification problem. The wideband radar was assumed to measure both kinematic (tracking information expressed as estimated aspect angles) and high range resolution data from a single, isolated aircraft. The aspect angles (azimuth and elevation) of the aircraft relative to the radar were assumed to be constantly chancing. This created temporal sequences of high range resolution radar signatures that changed as the aspect angles changed. These sequences were used as input features to a recurrent neural network for three radar target identification test cases. The first test case …

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A Toposcopic Investigation Of Brain Electrical Activity Induced By Motion Sickness, Dwight A. Roblyer Dec 1992

A Toposcopic Investigation Of Brain Electrical Activity Induced By Motion Sickness, Dwight A. Roblyer

Theses and Dissertations

A toposcope was constructed as a new tool to study signal frequency and phase relationships in electroencephalogram (EEG) records collected while subjects were experiencing motion sickness. This new tool, named TOPOS, is a software-based, multi-featured version of Grey Walter and Harold Shipton's device which they first produced in the late 1940s. The TOPOS graphical display permits the study of instantaneous frequency relationships between the input channels and a reference signal of fixed or varying frequency. TOPOS adds a correlation grid to aid observers in detecting channel-to-reference correlation levels. Users can also vary several display parameters via menus to optimize the …

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Software Support Measurement And Estimating For Oracle Database Applications Using Mark Ii Function Points, Steven D. Radnov Dec 1992

Software Support Measurement And Estimating For Oracle Database Applications Using Mark Ii Function Points, Steven D. Radnov

Theses and Dissertations

This study investigated the results of measuring software support of Oracle database applications and estimating the effort and schedule required to provide support. Software measurement was accomplished with a variant of the function points metric, called Mark II function points, which is comprised of three weighted parameters, inputs, entities, and outputs. A technique for mapping Mark II function points to Oracle DBMS components was developed, and the size of the software support for each project, per team, was measured by tabulating and weighting the number of inputs, entities, and outputs that are added, changed, and/or deleted. Software support effort was …

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A Model Of Global Positioning System (Gps) Master Control Station (Mcs) Operations, David N. Koster Dec 1992

A Model Of Global Positioning System (Gps) Master Control Station (Mcs) Operations, David N. Koster

Theses and Dissertations

The United States Air Force's Navstar Global Positioning System (GPS) provides high-accuracy space-based navigation and time distribution to suitably- equipped military and civilian users. The system consists of earth-orbiting satellites and a world-wide network of ground stations. A single operational control center, the GPS Master Control Station (MCS) monitors, maintains, and commands the GPS satellite constellation. The on-going deployment of the complete satellite constellation and recent changes in the operational crew structure may invalidate previously used planning and management paradigms. There is currently no analytical method for predicting the impact of these and other environmental changes on system parameters and …

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Retinal Modeling: Segmenting Motion From Spatio-Temporal Inputs Using Neural Networks, David E. Swanson Dec 1992

Retinal Modeling: Segmenting Motion From Spatio-Temporal Inputs Using Neural Networks, David E. Swanson

Theses and Dissertations

We applied two first-order, linear, time-varying, differential equations to the task of segmenting motion from sequences of images. The equations are modified Grossberg formulas for long-term and short-term memory models characterizing the neurotransmitter and cell-activity levels of a synapse and neuron. We described how a two layered, sensory, neural network can be built using the equations to simulate the amacrine neurons of the retina. The model is defined using adaptive input nodes (adaptive model) and is compared to a similar model without these nodes (O and G model). By replicating the basic amacrine neuron model to form both one- and …

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Development Of A Prototype Air Force Institute Of Technology (Afit) Research Management System (Arms), David N. Schaaf, Carl W. Scott Dec 1992

Development Of A Prototype Air Force Institute Of Technology (Afit) Research Management System (Arms), David N. Schaaf, Carl W. Scott

Theses and Dissertations

The goal of this study was to design, develop, test, and evaluate an initial prototype information system to enhance the conduct and management of research in the School of Systems and Logistics at the Air Force Institute of Technology (AFIT). To accomplish this goal, the researchers developed and completed a methodology that was generally patterned after the milestones in a typical system development life cycle. The proof-of-concept nature of this research caused the researchers to also map the study's seven major objectives into a second system development model called the Spiral Model (Boehm, 1988:61). This hybrid approach provided better defined …

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Integrated Blade Inspection System (Ibis) Upgrade Study, Tony J. Deliberato, Steven W. Perkins, Steven K. Saplin, John G. Snyder, Gregory J. Toussaint Dec 1992

Integrated Blade Inspection System (Ibis) Upgrade Study, Tony J. Deliberato, Steven W. Perkins, Steven K. Saplin, John G. Snyder, Gregory J. Toussaint

Theses and Dissertations

The purpose of this design study was to identify ways to improve the Integrated Blade Inspection System. The Air Force requires inspection of jet engine compressor and turbine blades to locate defects and prevent engine failure. The current inspection process uses fluorescent penetrant as an aid to identify cracked blades. A systems engineering design process was applied to evaluate the current inspection techniques and to develop alternative methods to satisfy the Air Force requirements. Three different inspection systems were developed and compared to the current process: manual, semi-automated, and fully automated inspection. This study made several noteworthy contributions: development of …

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An Analysis Of Usspacecom's Space Surveillance Network (Ssn) Sensor Tasking Methodology, Jeff M. Berger, Joseph B. Moles, David G. Wisley Dec 1992

An Analysis Of Usspacecom's Space Surveillance Network (Ssn) Sensor Tasking Methodology, Jeff M. Berger, Joseph B. Moles, David G. Wisley

Theses and Dissertations

This study provides the basis for the development of a cost/benefit assessment model to determine the effects of alterations to the Space Surveillance Network (SSN) on orbital element (OE) set accuracy. It provides a review of current methods used by NORAD and the SSN to gather and process observations, an alternative to the current Gabbard classification method, and the development of a model to determine the effects of observation rate and correction interval on OE set accuracy. The proposed classification scheme is based on satellite J2 perturbations. Specifically, classes were established based on mean motion, eccentricity, and inclination Since J2 …

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An Assessment Of Software Safety As Applied To The Department Of Defense Software Development Process, Peter W. Colan, Robert W. Prouhet Dec 1992

An Assessment Of Software Safety As Applied To The Department Of Defense Software Development Process, Peter W. Colan, Robert W. Prouhet

Theses and Dissertations

This research analyzed the relationships between the DOD software development process, system safety requirements, and current structured software safety analysis techniques. The current state of software safety was assessed within the aerospace industry and DOD, and a training program for DOD System Safety Managers was developed. A telephone survey was conducted to gather information on current software safety analysis techniques and methodologies. Personal interviews were conducted with Aeronautical System Center System Safety Managers to gather data on job perception and perceived training needs. The results of the study indicate that the DOD guidance and policy documents needed to implement and …

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Analysis Of Whole-Sky Imager Data To Determine The Validity Of Pcflos Models, Richard W. Boltz, George R. Kather Dec 1992

Analysis Of Whole-Sky Imager Data To Determine The Validity Of Pcflos Models, Richard W. Boltz, George R. Kather

Theses and Dissertations

Models used to predict the probability of a cloud-free line-of-sight (PCFLOS) from the ground to space have existed since the 1960s. Unfortunately, an adequate data set has not been available to check the validity of these models until the deployment of the Whole-Sky Imager (WSI) system in 1989. Now that a three-year database has been collected from the WSI system, it is possible to validate, or refute, the existing models. This study investigates the most generally accepted models. Specifically, we investigate three questions: (1) Is the Lund and Shank-lin PCFLOS model assumption of azimuthal independence valid; (2) Does the Lund …

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Reliability, Maintainability, And Supportability (Rms) Education In Engineering Schools, Gregory T. Hurst, Barry N. Kinter Dec 1992

Reliability, Maintainability, And Supportability (Rms) Education In Engineering Schools, Gregory T. Hurst, Barry N. Kinter

Theses and Dissertations

The purpose of this research is to show how engineering schools, as a whole, perceive the role of reliability, maintainability, and supportability in the engineering field. This includes the degree to which these concepts are included in their curricula, whether industry recruiters look for reliability, maintainability, and supportability training when they visit college campuses and to what degree college faculties are teaching reliability, maintainability, and supportability. This is done through research of existing literature and the analysis of data from a survey completed by engineering schools. General analyses are presented of the overall responses and detailed analysis of contrasts and …

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