Engineering Commons^™

A Synthetic Environment For Satellite Modeling And Satellite Orbital Motion, David L. Pond

Theses and Dissertations

Analysts tasked to study satellites moving in space must often rely on photographs to conduct their analysis. Often these photographs do not adequately represent how satellites move in space, their spatial relationships, or their interaction with other satellites. What analysts need is a three- dimensional synthetic environment that depicts satellites as they actually move and interact in space. This thesis addresses the early development of the Satellite Modeler (SM), a system that allows analysts to study, satellite motion and maneuvering of computer aided design (CAD) models of those satellites in a three-dimensional orbit. The system contains equipment that allows analysts …

An Object-Oriented Computer Aided Design Program For Modern Control Systems Analysis, Frederick L. Trevino

Theses and Dissertations

This investigation is a continuation of the ICECAP-PC research project conducted under Prof. Gary B. Lamont at the Air Force Institute of Technology. It is an ongoing development of a public domain Computer Aided Design (CAD) package for Control Engineering students and faculty, with a special emphasis on education. This investigation focuses on three areas. First, an object-oriented environment is specified, designed and implemented. The functional structure of ICECAP-PC is then converted into an object-oriented structure because object-orientation provides an advanced logic and implementation structure and effectively addresses common software engineering issues. Additionally, a new interface featuring pull-down menus, mouse …

A Study Of The Effects Of Polyacrylates On Water Retention And Binder Migration Tendencies Of Coatings, Wichan Charoenkitsupat

Masters Theses

Five commercial polyacrylate samples were used to study their effects on viscosity, water holding, and binder migration under non-pressure conditions. The polyacrylates used were different in acid level, degree of crosslinking, and type of polymer (copolymer and terpolymer). A series of coatings was prepared using a number two clay and three styrene-butadiene latexes of similar particle size and T⋁g but different degrees of carboxylation, then the polyacrylates were added at several levels. The coatings were evaluated for rheological properties, water loss rate and binder migration. The results show that with increasing amounts of polyacrylates, the viscosity increased and the water …

A Computer Simulation Of The Rotary Vacuum Filter Brown Stock Washing System Using Distribution Sampling, Edison G. Yiu

Masters Theses

A probabilistic model was utilized to simulate the brown stock washing system's error due to process variability and measurement noise. Mass balances of the washing system were performed using distribution sampling. This model relies on a nonlinear relationship between displacement and dilution, which permitted the generation of displacement ratio based upon wash liquor ratio. Experimental trials were performed on a pilotscale rotary vacuum single-stage washer. Nonlinear first-order relationship appears to characterize a pilotscale washer adequately. Differences were observed between the means and standard deviations of the measured results compared to the simulation output. Future work is needed to identify the …

Optical Haar Wavelet Transforms Using Computer Generated Holography, Peter G. Block

Theses and Dissertations

This research introduces an optical implementation of the continuous wavelet transform to filter images. The wavelet transform is modeled as a correlation process and is implemented with a Vander Lugt correlator. The orthonormal basis set used is composed of two one-dimensional Haar functions and a two-dimensional Haar function. Each wavelet, as well as its first two dyadic scalings, is implemented with computer generated holography. The Interferogram method, which represents a function only in terms of its phase, is used to encode the wavelet functions. The results are imaged onto a CCD array and captured using a framegrabber. The optical results …

Cathodoluminescence Spectroscopy Of Zinc Germanium Phosphide Zngep2, Michael R. Gregg

Theses and Dissertations

Zinc Germanium Phosphide (ZnGeP₂) is a nonlinear semiconductor suitable for use as a laser tuning element over the two to six micron wavelength range. Although this crystal has been studied in the past, its luminescent properties are not yet well understood. In this present study, ZnGeP₂ has been examined using cathodoluminescence spectroscopy (CL). Specifically, the spectral dependence of the CL was obtained as a function of electron beam energy, beam current and temperature. The resulting CL was found to be polarized with a peak structure that was dependent on the polarization. This peak structure observed by CL …

An Approximate Solution For The Linearized Spinup Dynamics Of A Dual-Spin Spacecraft, David L. Kinney

Theses and Dissertations

An approximate solution is obtained for the linearized equations of motion for the spinup dynamics of a dual-spin spacecraft. The approximation is obtained from the WKB (Wentzel, Kramers, and Brillouin) method, which usually generates a divergent series. Comparison between the WKB solution and the numerically integrated solution are used to study the effects of spinup torque magnitude and the number of WKB terms used on the accuracy of the approximation. The WKB method generates accurate approximations for small spinup torques using as few as two terms in the series when no singularities are present in the WKB terms during the …

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 …

Behavior Of A Quasi-Isotropic Ply Metal Matrix Composite Under Thermo-Mechanical And Isothermal Fatigue Loading, Karl A. Hart

Theses and Dissertations

This study investigated the behavior of the SCS6/Ti-15-3 metal matrix composite with a quasi-isotropic layup when tested under static and fatigue conditions. Specimens were subjected to in-phase and out-of-phase thermo- mechanical and isothermal fatigue loading. In-phase and isothermal loading produced a fiber dominated failure while the out-of-phase loading produced a matrix dominated failure. Also, fiber domination in all three profiles was present at higher maximum applied loads and al three profiles demonstrated matrix domination at lower maximum applied loads. Thus, failure is both profile dependent and load equipment. Additional analyses, using laminated plate theory, Halpin-Tsai equations, METCAN, and the Linear …

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 …

A Comparison Of Computational Fluid Dynamics Computer Programs For Hypersonic Propulsive Nozzle Flowfields, Kennedy B. Wilson Jr.

Theses and Dissertations

This study compared the results of two computer programs, a flux- difference-splitting (FDS) Godunov-based scheme and the SCPAMjet Hypersonic Nozzle (SCHNOZ) paraobolized Navier-Stoke's code using MacCormack's method, applied to a hypersonic nozzle flowfield. Two different nozzle geometries were investigated at three Mach numbers along a typical hypersonic flight trajectory. A direct compariosn between the SCHNOZ and FDS programs was made by numerically solving the steady Euler equations using a frozen flow assumption in the nozzle. The frozen flow SCHNOZ code is currently 6 to 10 times more efficient in terms of computational time than the FDS frozen flow code. The …

A Radiosity Approach To Realistic Image Synthesis, Richard L. Remington

Theses and Dissertations

The Air Force Institute of Technology (AFIT) has not had the capability to generate photorealistic images. This thesis is a research effort to implement such a system at AFIT, and to apply knowledge from the particle transport community to this problem. Investigation into various techniques for generating photorealistic images led to the conclusion that the radiosity method would serve as the foundation for development. This is because of the increased accuracy of the diffuse reflections with the radiosity method and the fact that the images produced with radiosity axe view-independent. Two distinct tools to generate photorealistic images axe described. The …

Etann Hardware Implementation For Radar Emitter Identification, James B. Calvin Jr.

Theses and Dissertations

This study investigated classification of 30 radar emitters with 16 signal features using Intel's 80170NX chip, the Electronically Trainable Analog Neural Network (ETANN). Software tools were developed to characterize the ETANN sigmoidal transfer function for use in a custom simulator, known as Neural Graphics. Neural Graphics operates on a Silicon Graphics workstation. The Intel Neural Network Training System simulators were used in early experiments, but were found to be inefficient in training on data used in this research. Using a modified Neural Graphics simulator, single chip and multi-chip experiments were performed to provide benchmark results prior to performing chip-in-loop training. …

A Generic Template Extractor (Gentex) In C For Vlsi Design Verification, Kenneth J. Mcclellan Jr.

Theses and Dissertations

The problem of VLSI design verification through circuit extraction was analyzed. The problems of creating a simple template format, the permutability of pins, maintaining connectivity, and performance were focused on. A generic template extractor (GENTEX) was developed in the C programming language for use as a testbed to find solutions to these problems. Six different extraction algorithms were tested with GENTEX and compared based on performance. EDIF translation programs were used to interface with GENTEX on both the input and output sides. One translation program converted an EDIF representation of a schematic into the template format used by GENTEX. The …

Signal Approximation With A Wavelet Neural Network, Charles M. Westphal

Theses and Dissertations

This study investigated the use of Wavelet Neural Networks (WNN) for signal approximation. The particular wavelet function used in this analysis consisted of a summation of sigmoidal functions (a sigmoidal wavelet). The sigmoidal wavelet has the advantage of being easily implemented in hardware via specialized electronic devices like the Intel Electronically Trainable Analog Neural Network (ETANN) chip. The WNN representation allows the determination of the number of hidden-layer nodes required to achieve a desired level of approximation accuracy. Results show that a bandlimited signal can be accurately approximated with a WNN trained with irregularly sampled data. Signal approximation, Wavelet neural …

An Integrated Simulation Model Development Environment For Slam Ii Using Object-Oriented Paradigm, Rizvan Erol

Masters Theses

An integrated simulation model development environment was implemented to assist the modeler by automating certain activities of simulation modeling. The system included interactive model definition, experimental design, automatic simulation program generation in SLAM II. Object-oriented paradigm at software development stage was extensively used to conceptualize the structure, and rules of the SLAM II language in order to generate efficient, and modular program code. The present system targeted modeling of various probabilistic inventory control system problems. The remarkable advantages of the system were rapid model development time, and achieving reliable program code without requiring any knowledge in SLAM II. Object-oriented programming …

A Study Of The Effects Of Pigment Size And Shape On Binder Migration, Hee Jong Yang

Masters Theses

The effects of pigment size and shape on coating structure and binder migration has been investigated. Clays and ground calcium carbonates of different particle size distributions were used in coatings with 15 pph SB latex.

Coatings were applied to Mylar and a special Tyvek using a wire wound rod. The coatings were dried slowly under ambient conditions, and using hot air immediately or after having been allowed to reach immobilization through penetration into the Tyvek. The dried coatings were evaluated for water holding, relative pore size and migration using the UV technique to measure the increase in SB latex at …

Laser Doppler Velocimetry Research Of The Blowby Gas Characteristics In An Internal Combustion Engine, Mark Kevin Coffill

Masters Theses

The project was designed to measure a reciprocating engine fluid flow (blowby gases past the piston rings) using a laser doppler velocimeter (LDV). Blowby gases were obtained by introducing compressed air into an engine cylinder (piston held at TDC) to simulate engine combustion pressures. Beginning the proposed research included starting an LDV/reciprocating engine laboratory at Western Michigan University and determining the limits of the measurement devices (LDV system in particular).

The limitations which were found in the LDV system only allowed for limited results of in cylinder optical measurements. The results obtained were for cylinder pressures below 0.6 kPa gauge …

An Experimental Determination Of The Effects Of Blending Collocated And Non-Collocated Sensor Measurements To Control A Flexible Structure, Richard G. Cobb

Theses and Dissertations

An experimental investigation was performed controlling a cantilevered beam in bending using proportional feedback on a blend of collocated and non-collocated sensor measurements using a single actuator. Exact transfer functions between the control input and the measurements were developed and compared to the finite element method. By analyzing the open loop pole-zero locations as a function of the measurement blending, insight into the closed loop behavior is obtained. Minimum phase behavior can be maintained for a range of the blending ratio. Results using blended control were compared to both proportional collocated feedback and compensated collocated feedback using LQG methods. The …

Conceptual Design Of The Modular Transuranic Shipping Cask Mts-54, Vojislav Banjac

Nuclear Engineering ETDs

The storage, transportation, and disposal of radioactive waste has become a problem of immense proportions in the United States. This Thesis focuses on the transportation of defense transuranic (TRU) waste to the Waste Isolation Pilot Plant (WIPP) repository near Carlsbad, New Mexico. The objective of the cask conceptual design was based on the following:

• Taking into account the latest available data on TRU waste drum mass, investigate the possibility of increased drum capacity per shipment over the current design;
• Present a new TRU cask design with increased drum capacity and the potential for transporting both Contact-handled (CH and Remote-handled (RH) …

Excitation And De-Excitation Mechanisms Of Er-Doped Gaas And Algaas, David W. Elsaesser

Theses and Dissertations

Electrical and optical characterization have been performed on GaAs and Al_xGa_1-xAs samples doped with Er either by ion implantation or during Molecular Beam Epitaxial (MBE) growth. Deep Level Transient Spectroscopy (DLTS) and Temperature-Dependent Hall Effect (TDH) measurements indicated the presence of two hole traps in Er-doped GaAs, at 35 and 360 meV above the valence band maximum. The former (shallower) center was thought to be due to Er substituting for a Ga atom (Er_Ga) and giving rise to an isoelectronic impurity potential. The second center was attributed to an Er atom occupying an interstitial …

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 …

Solution To A Multicriteria Aircraft Routing Problem Utilizing Parallel Search Techniques, James J. Grimm Iii

Theses and Dissertations

Pilots select routes based on factors such as threats, fuel, time on target, distance, and refueling points. This is a time consuming task. This thesis presents the software engineering synthesis of a software tool, based on a parallelized A* search algorithm, to select routes. For simplicity only threats and distance are used. A centralized open list is used with one processor managing the list while the other processors perform the node expansions. This decomposition result in a dynamically load balanced system. A number of parameters are changed to study their impact on the execution time. The use of a branch …

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 …

Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha

Theses and Dissertations

Most advanced composite materials have nonlinear stress versus strain curves--grossly so in the laminas shear direction. If linear approximations are used, overly conservative design will result. This thesis expands the usefulness of the Automated Structural Optimization System (ASTROS) finite element (FE) program by incorporating a newly developed capability to include material nonlinearities. By dividing a FE problem into several intervals, and incorporating the changing nature of the nonlinear material properties within each element, a good approximation of the laminate's actual stresses and strains can be obtained without the undue experimentation involved in testing every individual configuration. Each material property is …

Effect Of Transverse Vibration On The Capillary Limit Of A Wrapped Screen Wick Copper/Water Heat Pipe, Mark C. Charlton

Theses and Dissertations

The effect of transverse vibration on the capillary limit of a copper/water heat pipe with a tightly wrapped screen wick was investigated. The capillary limit was measured over a range of operating temperatures under static conditions. A bench-top shaker was used to provide vibration normal to the longitudinal axis of the pipe, and the capillary limit was measured at vibration frequencies of 30, 250, and 1000 Hz. At each of these frequencies, tests were run at vibration levels of 1.0, 2.5, and 5.0 G. The pipe was maintained at a zero degree inclination angle and power throughput was increased until …

Rewet Performance Of A Rectangular Grooved Heat Pipe Wick After Gravitationally Induced Dryout, Lowell S. Hawthorne

Theses and Dissertations

The effects of increased acceleration forces on the transient dryout and rewet performance of an axial groove heat pipe wick were experimentally studied using inclination to simulate increased acceleration forces. Two durations of increased acceleration were investigated, one being less than the time required for the groove to reach steady-state dryout conditions, the other being sufficient to ensure the groove had reached steady-state dryout conditions. The groove's extent of dryout was found to be greater at increased levels of acceleration. The period of time required for the groove to rewet after an acceleration induced dryout increased as acceleration increased. The …

Extended Lyapunov Exponents For Second Order Systems, Janice M. Horn

Theses and Dissertations

It is shown that the concept of the Lyapunov exponent can be extended to include an imaginary part. A numerical technique used to calculate these extended Lyapunov exponents for second order systems is presented. There are two requirements to make this extension possible: the definition of a coordinate frame on the tangent space of the differential equation, and an extension of the classical limit, called the limit of the mean. An application of the technique to the van der Pol equation for the constant coefficient and periodic coefficient cases is given. The extended Lyapunov exponents found using this technique totally …

Canonical Floquet Perturbation Theory, David J. Pohlen

Theses and Dissertations

Classical Floquet theory is examined in order to generate a canonical transformation to modal variables for periodic system This transformation is considered canonical if the periodic matrix of eigenvectors is symplectic at the initial time. Approaches for symplectic normalization of the eigenvectors had to be examined for each of the different Poincare eigenvalue cases. Particular attention was required in the degenerate case, which depended on the solution of a generalized eigenvector. Transformation techniques to ensure real modal variables and real periodic eigenvectors were also needed. Periodic trajectories in the restricted three-body case were then evaluated using the canonical Floquet solution. …

A Study Of Heat Flux Induced Dryout In Capillary Grooves, Timothy J. Murphy

Theses and Dissertations

This is an experimental study of ethanol flowing in the narrow grooves of a copper plate which is subjected to heat fluxes sufficient to evaporate more liquid than can be replaced by capillary pumping. Three groove geometries are used: square, rectangle, and trapezoid. The objective is to simulate aspects of liquid flow in heat pipes with axial grooves. In order to validate analytical models of capillary flow in grooves, the capillary limit, dryout front location, and dryout front movement in response to power draw downs are documented. The results show the rewet performance of the groove is dependent on geometry. …