Engineering Commons^™

Numerical Simulation Of Dynamic-Stall Suppression By Tangential Blowing, Matthew C. Towne

Theses and Dissertations

The use of tangential blowing to suppress the dynamic stall of a pitching airfoil is investigated numerically. The laminar two-dimensional, compressible Navier-Stokes equations are solved time-accurately using a Beam- Warming algorithm. A slot is located at four different positions along the surface of a NACA 0015 airfoil and air is injected in a nearly tangential sense along the upper surface. Suction control is also employed at one of these slot locations to directly compare with tangential-blowing control. Solution sensitivity to grid refinement, time-step size, numerical smoothing, and initial conditions is investigated at a Reynolds number of 2.4 x 10exp 4. …

Stress Fields In Composites With A Variable Interphase Under Thermo-Mechanical Loadings, Nianfeng Chen

Mechanical & Aerospace Engineering Theses & Dissertations

An interphase in a composite material has a important role for the composite performance. It influences directly or indirectly the strength, fatigue performance and effective properties of the composite. Recently, interphase has drawn increasing attention in composite mechanics. To the best of our knowledge, however, no one seems to have considered the effect of the variable material prope1ty in the interphase on the stress field in the composite material. In this research, the stress fields are determined in the continuous fiber composite and the particulate composite by using the four concentric circular cylinders model and the four phase spheres model, …

Development Of Vibration And Sensitivity Analysis Capability Using The Theory Of Structural Variations, Ting-Yu Rong

Mechanical & Aerospace Engineering Theses & Dissertations

In the author's previous work entitled "General Theorems of Topological Variations of Elastic Structures and the Method of Topological Variation," 1985, some interesting properties of skeletal structures have been discovered. These properties have been described as five theorems and synthesized as a theory, called the theory of structural variations (TSV). Based upon this theory, an innovative analysis tool, called the structural variation method (SVM), has been derived for static analysis of skeletal structures (one-dimensional finite element systems).

The objective of this dissertation research is to extend TSV and SVM from one-dimensional finite element systems to multi-dimensional ones and from statics …

Use Of The Genetic Algorithm In Positioning Sacrificial Anodes For Optimum Cathodic Protection, Chi-Cheng Tsao

Mechanical & Aerospace Engineering Theses & Dissertations

A systematic design methodology is developed in this thesis to automatically determine the best locations to place the anodes in order to obtain the maximum cathodic protection. The design methodology numerically solves a design optimization problem which selects the locations to place the anodes to maximize the difference between the minimum current density supplied by sacrificial anodes on the surface of the cathodic materials and its free corrosion current density. The numerical tools used in this design methodology are the finite element analysis and the genetic algorithm. The former analyzes the current density distribution in the field of concern and …

Investigation Of Computational And Spectral Analysis Methods For Aeroacoustic Wave Propagation, Florence Odile Vanel

Mechanical & Aerospace Engineering Theses & Dissertations

Most computational fluid dynamics (CFD) schemes are not adequately accurate for solving aeroacoustics problems, which have wave amplitudes several orders of magnitude smaller yet with frequencies larger than the flow field variations generating the sound. Hence, a computational aeroacoustics (CAA) algorithm should have minimal dispersion and dissipation features. A dispersion relation preserving (DRP) scheme is, therefore, applied to solve the linearized Euler equations in order to simulate the propagation of three types of waves, namely: acoustic, vorticity, and entropy waves. The scheme is derived using an optimization procedure to ensure that the numerical derivatives preserve the wave number and angular …

The Design, Realization And Testing Of The Ilu Of The Ccm2 Using Fpga Technology, David W. Foote

Dissertations and Theses

Most existing computers today are built upon a subset of the arithmetic system which is based upon the foundation of set theory. All formal systems can be expressed in terms of arithmetic and logic on current arithmetic computers through an appropriate model, then work with the model using software manipulation. However, severe speed degradation is the price one must pay for using a software-based approach, making several high-level formal systems impractical.

To improve the speed at which computers can implement these high-level systems, one must either design special hardware, implementing specific operations much like math and image processing coprocessors, or …

An Empirical Study Of Just-In-Time And Total Quality Management Principles Implementation In Manufacturing Firms In The U.S., Loknath Sriparavastu

Masters Theses

Literature in vogue points out that, in the last decade, American manufacturing companies came a long way in their renewed emphasis on the quality process. Justin- Time (JIT) and Total Quality Management (TQM) are the two magical phrases that are being frequently used in almost all the articles published on quality and productivity. Nevertheless, the literature does not provide any satisfactory explanation as to how JIT and TQM principles are implemented in the manufacturing industries.

This research, through a nationwide empirical survey, analyzed the effects of JIT and TQM strategies implementation. Survey results showed that implementing both JIT and TQM …

Calibration And Initial Testing Of A New Hydraulic Simulator, Cristian A. Puebla

Theses and Dissertations

In the present research, the flow field associated with the ejection of a crew capsule from the fuselage of a high speed generic aircraft was experimentally investigated by means of the modified gas hydraulic analogy. For this, an existing hydraulic simulator was calibrated and modified to adapt it to the needs of the experiment. The analogy was evaluated for a five-sided capsule alone, and good quantitative agreement with the 2-D shock-expansion theory was obtained. It was found that the size of the model played a key role in the determination of good quantitative data. The analysis of the capsule interacting …

An Empirical Investigation Of Total Quality Management (Tqm) Effectiveness In Healthcare Organizations, Lokesh S. Basappa

Masters Theses

American hospitals are implementing quality programs to offer higher quality service at reduced cost. However, the results of these programs in many hospitals have often not met expectations.

This research analyzed the effectiveness of Total Quality Management (TQM). The objective of the study was to better understand how TQM strategies can best be applied by hospitals. An empirical survey was distributed to Michigan hospitals and an analysis was performed to meet this objective.

The survey results show that hospitals involved indirectly with quality programs haven't realized that they are implementing TQM strategies. On the other hand some hospitals say that …

Recent Advances In Engineering Design: Theory And Practice, Andrew J. Moskalik

Masters Theses

In the last few years, industry and academia have focused greater attention on the area o f engineering design. Manufacturers have implemented new design methods such as concurrent engineering and design for manufacture, and academia has increased research in design-related issues. This paper will attempt to summarize the recent advances, both scholarly and industrial, relating to the field of design. I will examine new methodologies and supporting tools for the design process, both in use and under research. This paper will cover concurrent engineering, design for manufacture, quality methods, design theory research, computer-aided design, expert systems, analysis programs, manufacturing, and …

The Application Of Nepa Requirements To Cercla Remedial Actions, Connie L. Strobbe

Theses and Dissertations

This study investigated the application of National Environmental Policy Act NEPA requirements to Comprehensive Environmental Response, Compensation, and Liability Act CERCLA actions. Similarities in the documentation and public participation requirements of NEPA and CERCLA include identification and evaluation of alternatives and public participation. Differences include document contents and timing of public participation. This study presented four options for ensuring NEPA compliance at CERCLA sites. Option one included a Programmatic Environmental Impact Statement PEIS with subsequent combined FSEIS report for each subunit. Option two eliminated the PEIS, but retained a stand-alone NEPA document for each CERCLA subunit. Option three included a …

Expert System For The Material Selection Of Aircraft Structure, Bassem R Iskandar

Archived Theses and Dissertations

No abstract provided.

The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee

Theses and Dissertations

This study on praseodymium Pr luminescence in Al_xGa_1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 10¹² to 5 x 10¹³ cm² into Al_xGa_1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …

Spatio-Temporal Pattern Recognition Using Hidden Markov Models, Kenneth H. Fielding

Theses and Dissertations

A new spatio-temporal method for identifying 3D objects found in 2D image sequences is presented. The Hidden Markov Model technique is used as a spatio-temporal classification algorithm to identify 3D objects by the temporal changes in observed shape features. A new information theoretic argument is developed that proves identifying objects based on image sequences can lead to higher classification accuracies than single look methods. A new distance measure is proposed that analyzes the performance of Hidden Markov Models in a multi-class pattern recognition problem. A three class problem identifying moving light display objects provides experimental verification of the sequence processing …

Embedded Chaotic Time Series: Applications In Prediction And Spatio-Temporal Classification, James R. Stright

Theses and Dissertations

The Deterministic Versus Stochastic algorithm developed by Martin Casdagli is modified to produce two new, methodologies, each of which selectively uses embedding space nearest neighbors. Neighbors which are considered prediction relevant are retained for local linear prediction, while those which are considered likely to represent noise are ignored. For many time series, it is shown possible to improve on local linear prediction with both of the new algorithms. Furthermore, the theory of embedology is applied to determine a length of test sequence sufficient for accurate classification of moving objects. Sequentially recorded feature vectors of a moving object form a training …

A Diffraction-Based Model Of Anisoplanatism Effects In Adaptive Optic Systems, Steven E. Troxel

Theses and Dissertations

This dissertation presents a new model for computing the angle dependent performance measures of an adaptive-optics system. By incorporating diffraction caused by the index-of-refraction variations of the atmosphere, the phase and amplitude fluctuations of the propagating wave are computed. New theory is presented, that uses the diffraction-based propagation model to yield optical transfer function (OTF) expressions that are more accurate as compared to current theory that neglects diffraction. An evaluation method for calculating the OTF is presented that utilizes a layered atmospheric model and normalized OTF expressions. The diffraction model is also used to present the first OTF signal-to-noise ratio …

H2 Optimal Control With H∞, Μ, And L1 Constraints, David E. Walker

Theses and Dissertations

H₂ optimization with convex constraints is considered. The optimal order-free solution is shown to be unique through convex analysis. H_∞ constraints with feedforward terms and singular constraints are also allowed. The optimal fixed-order solution is shown to have the same characteristics as a mixed problem with regular H_∞ constraints. Furthermore, these results are shown to hold for controller orders as low as the optimal H₂ order. A numerical method is developed based on analytical gradients which results in sub- and super-optimal fixed-order controllers. The problem is extended to include an upper bound on a mu constraint …

Noise Reduction For Speech Enhancement Using Non-Linear Wavelet Processing, Hassan Dehmani

Theses and Dissertations

The problem of speech enhancement presents many obstacles in the speech processing field. This thesis develops several speech de-noising systems that can be used in the time, fourier, and wavelet domains. We present two thresholding techniques soft and hard. The application of these thresholding techniques to noisy speech data is discussed. The combination of both wavelets and the Fourier domains with noisy phase restoration proves to yield the best results in terms of intelligibility. Informal listening tests were conducted in order to compare the effects and differences between the speech de-noising systems.

Computational Investigation Of An Improved Cowl Concept For Hypersonic Propulsive Nozzles, Mark C. Butler

Theses and Dissertations

The effects of placing a gas generator into the cowl of a hypersonic nozzle/afterbody were investigated computationally. Gas generator mass flow and deflection angle effects were analyzed for two nozzle/cowl geometries; an experimentally validated nozzle/cowl configuration evaluated at off-design conditions and a generic hypersonic propulsive nozzle evaluated at more realistic on design conditions. A combination of Van Leer flux-vector splitting and Roe flux-difference splitting finite volume computational algorithms were used to solve the unsteady two-dimensional Navier-Stokes equations based on planar, laminar flow, perfect gas equation of state assumptions. For the low speed off-design cases analyzed, gas generator effects on nozzle …

Effects Of Thickness And Curvature On The Natural Frequencies Of Cylindrical Composite Shells, Jose L. Monteverde E.

Theses and Dissertations

An analytical study is performed to determine the dynamic response, natural frequencies and mode shapes, of deep composite cylindrical shells, including the effect of through the thickness shear strain. The DSHELL finite element program is used to predict the first four natural frequencies and the results are compared to a reference using the Galerkin technique. The program was extended to problems considering simply supported-free boundary conditions. As is well know, the free boundary is rather difficult to represent using the Galerkin technique approach. The mode shapes are created by plotting a surface-contour plot of the eigenvector output from DSHELL.

A …

Mixed H2-H∞ Optimization With Multiple H Infinity Constraints, Julio C. Ullauri

Theses and Dissertations

A general mixed H₂/H_∞ optimal control design with multiple H_∞ constraints is developed and applied to two systems, one SISO and the other MIMO. The SISO design model is normal acceleration command following for the F- 16. This design constitutes the validation for the numerical method, for which boundaries between the H₂ design and the H_∞ constraints arc shown. The MIMO design consists of a longitudinal aircraft plant (short period and phugoid modes) with stable weights on the H₂ and H_∞ transfer functions, and is linear- time-invariant. The controller order is reduced …

Dynamic Load Balancing For A Parallel Discrete-Event Battlefield Simulation, Seth R. Guanu

Theses and Dissertations

This thesis investigates issues involved in developing a dynamic load balancing model for a parallel discrete event battlefield simulation. The research covers issues in task management, discrete-event simulation, parallel simulation, and load balancing. There are four primary issues discussed concerning the design of a dynamic load balancing model. The first issue is processor load evaluation which deals with the calculation of the amount of work on a processor. The second issue is load balancing profitability determination which deals with the decision to load balance or not based on some cost-gain relationship. The third issue is task migration which deals with …

Design And Analysis Of A Mode B And Mode Jd Satellite Earth Station, Dennis J. Hance

Theses and Dissertations

This thesis focuses on the design, integration, and analysis of an amateur radio service mode B and mode JD satellite earth station. Preliminary designs were investigated to determine the optimum configuration for the earth station. Modern digital modems, cabling structures, an 80386-based computer system, satellite tracking software, transmission and reception antennas, preamplifiers, and sophisticated performance measurement technologies were integrated into a functioning earth station. Initially, component availability and station design dictated the selection and acquisition of the requisite station equipment, integration of the transmitter, receiver preamplifiers, antennas, and computer equipment followed. Preliminary testing of the various components in the integration …

Particle Dynamics Modeling Of Vibrating Granular Beds, Yidan Lan

Dissertations

Particle dynamics modeling is done to study the behavior of granular beds subjected to vibrations imposed by a plane boundary which oscillates sinusoidally about a zero mean speed. Significant differences between the lower and higher shaking acceleration regions are found for the granular temperature and solids fraction depth profiles, which characterize the effectiveness of the boundary in fluidizing the beds. When higher accelerations are applied, the temperature is maximum at the vibrating floor and attenuates through the depth, while the solids fraction profiles exhibit a maximum at some intermediate depth. At lower acceleration values, most of the mass is located …

Oxidation Of Pollutants In A Batch Recirculation Bioreactor With Immobilized Microorganisms, Jongtai Jung

Dissertations

The purpose of this work was to study bio-oxidative destruction of several substrates in an immobilized cell batch bioreactor in recirculation configuration. This system was used in three cases: a series of substrates usually used as monomers, ethylene glycol and its tetramer, and phenol under magnetic irradiation. In addition, kinetic studies were performed and experimental versus predicted results compared.

The substances styrene, methyl methacrylate (MMA), and β-hydroxybutyric acid (HBA), common monomers, were biologically treated using an acclimated mixed microbial community immobilized in calcium alginate gel. A comparison of biodegradation rates (3.3, 9.4, and 15 ppm/hr for styrene, MMA, and HBA, …

Motion Estimation Using Optical Flow Field, Jingning Pan

Dissertations

Over the last decade, many low-level vision algorithms have been devised for extracting depth from intensity images. Most of them are based on motion of the rigid observer. Translation and rotation are constants with respect to space coordinates. When multi-objects move and/or the objects change shape, the algorithms cannot be used.

In this dissertation, we develop a new robust framework for the determination of dense 3-D position and motion fields from a stereo image sequence. The framework is based on unified optical flow field (UOFF). In the UOFF approach, a four frame mode is used to compute six dense 3-D …

Adaptive Nonlinear Control Using Fuzzy Logic And Neural Networks, Shu-Chieh Chang

Dissertations

The problem of adaptive nonlinear control, i.e. the control of nonlinear dynamic systems with unknown parameters, is considered. Current techniques usually assume that either the control system is linearizable or the type of nonlinearity is known. This results in poor control quality for many practical problems. Moreover, the control system design becomes too complex for a practicing engineer. The objective of this thesis is to provide a practical, systematic approach for solving the problem of identification and control of nonlinear systems with unknown parameters, when the explicit linear parametrization is either unknown or impossible.

Fuzzy logic (FL) and neural networks …

Removal Of Vapors From Air By Selective Membrane Processes, Junseok Cha

Dissertations

The behaviors of different membrane modules for the selective removal and recovery of water vapor and some volatile organic compounds (VOCs) from N₂ have been studied. For the selective permeation-based removal of water vapor from N₂, a polymeric water-swollen gel membrane in the form of Cuprophan hollow fiber was employed. A thin film composite type rubbery membrane module was studied for the selective removal of VOCs like toluene or methanol from N₂ by permeation. The usefulness of pore-condensation phenomenon-based removal of toluene or xylene from N₂ was explored using a microporous ceramic tubular membrane.

The …

Estimation And Cancellation Of Friction In Control Systems, Sofia Mentzelopoulou

Dissertations

The research reported in this dissertation concerns the estimation and cancellation of friction in control systems. For purposes of analysis, the Coulomb friction model, the "extended" Coulomb friction model as well as dynamic friction models are used. In addition, for systems with multiple degrees-of-freedom, a general matrix representation of friction is presented.

For the design of the friction estimators, the theory of nonlinear observers is applied. In particular, for a system with multiple degrees-of-freedom, holonomic constraints, and multiple friction sources, three different observers are presented to estimate the friction force or torque. The first (Generalized Coulomb Friction Observer) is designed …

Investigation Of Paraelectric Ptl Thin Films Using Reactive Magnetron Sputtering, Hyun Hoo Kim

Dissertations

The study of methods to prepare paraelectric perovskite PLT (Pb_1-xLa_xTi_1-x/4O₃; x=0.28) thin films has been important because thin films of this high dielectric strength material are required to make high density capacitors for dynamic random access memory. In this research, paraelectric PLT thin films were prepared on multi-layer (Pt/Ti/SiO₂/Si) and MgO substrates in a unique way by the reactive magnetron sputtering method using a multi-component metal target. The individual control of each metal area on the sputtering target had considerable influence on the stoichiometry and electrical properties of the thin …