Engineering Commons^™

The Column Multiplicity Problem In Decomposition Of Functions And Relations, Rahul Malvi

Dissertations and Theses

Finding the column multiplicity in Functional Decomposition has been known to be one of the most important problems to be solved in the process of functional decomposition of discrete functions. A lot of research has been done in this field with many new heuristics generated to find the column multiplicity, but there has not been an evaluation of the algorithms on the kinds of graphs that occur in decomposition and whether having an exact method to calculate the column multiplicity is useful from the overall design goals.The intent of this thesis was to investigate the column multiplicity problem, in order …

Optimization Considerations For Adaptive Optics Digital Imagery Systems, Robert T. Brigantic

Theses and Dissertations

This dissertation had three objectives. The first objective was to develop image quality metrics that characterize Adaptive Optics System (AOS) performance. The second objective was to delineate control settings that maximize AOS performance. The third objective was to identify and characterize trade-offs between fully and partially compensated adaptive. For the first objective, three candidate image quality metrics were considered: the Strehl ratio, a novel metric that modifies the Strehl ratio by integrating the modulus of the average system optical transfer function to a 'noise-effective-cutoff' frequency at which some specified image spectrum signal-to-noise-ratio level is attained, and the noise-effective-cutoff frequency. It …

Thickness Effects On A Cracked Aluminum Plate With Composite Patch Repair, Joel J. Schubbe

Theses and Dissertations

Post-repair fatigue crack growth was investigated in 3.175, 4.826, and 6.35 mm thick aluminum panels asymmetrically repaired with boron/epoxy composite patches bonded to the plates with FM73 sheet adhesive. Patches were uniaxial with patch to panel stiffness ratios ranging from 0.46 to 1.3. Experimental fatigue tests were carried out at 120 MPa, R=0.1, and 10 Hz (sinusoidal) to measure patched and unpatched face crack lengths, center crack opening displacements, and selected strains. Crack growth data was acquired using optical, eddy current, and post-test analysis methods. Crack growth rates were calculated using the incremental polynomial method. A three-layer Mindlin plate finite …

Control Of Nonlinear Systems Via State Feedback State-Dependent Riccati Equation Techniques, Kelly D. Hammett

Theses and Dissertations

Nonlinear regulation and nonlinear H-infinity control via state-dependent Riccati equation (SDRE) techniques are considered. Relationships between SDREs and Hamilton-Jacobi/Bellman inequalities/equations are examined, and a necessary condition for existence of solutions involving nonlinear stabilizability is derived. A single additional necessary criterion is given for the SDRE methods to yield the optimal control or guaranteed induced L2 gain properties. Pointwise stabilizability and detectability of factorizations prove necessary and sufficient, respectively, for well-posedness of standard numerical implementations of suboptimal SDRE regulators, but neither proves necessary if analytical solutions are allowed. For scalar analytic systems or those with full rank constant control input matrices, …

Stepped Tip Gap Effects On A Transonic Axial-Flow Compressor Rotor, Donald W. Thompson

Theses and Dissertations

The effects of stepped tip gaps and clearance levels on the performance, flowfield, and stall characteristics of a transonic axial-flow compressor rotor were experimentally and numerically determined. A theory and mechanism for relocation of blockage in the rotor tip region was developed. A two-stage compressor with no inlet guide vanes was tested in the Wright Laboratories Compressor Research Facility located at Wright-Patterson Air Force Base, Ohio. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were …

Residual Strength After Fatigue Of A Cross-Ply Metal Matrix Composite At Elevated Temperature, Alvin N. Ruiz

Theses and Dissertations

The objective of this study was to investigate the residual strength of a cross-ply, SCS-6/Ti-15-3, metal matrix composite (MMC) at elevated temperature (427 °C) when exposed to fatigue loading. Several specimens were subjected to a strain-controlled, fully reversed loading (R=-1), at various strain levels. The specimens were fatigued up to a portion of their life expectancy and then loaded to failure. Stress and strain data obtained during the test provided useful information for the macro-mechanical behavior of the material. It was determined that the residual strength was directly related to the amount of damage present in the matrix, meanwhile, the …

Diffraction Analysis And Tactical Applications Of Signal Propagation Over Rough Terrain, You-Cheol Jang

Theses and Dissertations

The free space propagation model is inadequate to predict the mean path-loss in ground wireless communication. Also, many existing propagation channel models do not adequately predict path-loss in rough terrain because most of them were based on measurements in urban areas. Hence, a channel model that estimates mean path-loss over many different kinds of terrain conditions is desired. In this thesis, two new propagation channel models, Real Terrain Diffraction Model (RTDMOD) and Universal Terrain Channel Model (UTCMOD), were developed. Other geometric theory of diffraction (GTD) methods (Epstein-Peterson (EP) and Deygout (DG)) agree within 5 % from 3 MHz to 3GHz …

Design And Development Of A User Interface Between Mapics/Db And Factor 5.2, Raghu Pothuri

Masters Theses

An interface program was designed to transfer production data from MAPICS/DB, a MRP II software, to FACTOR 5.2, a Finite Capacity Scheduling software. Since FACTOR 5.2 is designed to be used in a stand-alone mode with its own independent data base, this interface program extracts data from the MRP II System and converts it to formats specified by the Scheduling System. To create a computer model of the manufacturing process, information about manufacturing orders, routings, and production facilities was obtained from MAPICS/DB files. Certain information needed by FACTOR 5.2, which is not available in MAPICS/DB, was supplemented by the program …

Estimating Kc-137 Aircraft Ownership Costs In The Brazilian Air Force, Ulisses O. Bonasser

Theses and Dissertations

This research addresses the estimation of operation and support (O&S) costs of the Brazilian Air Force KC-137 aircraft. BAF lacks an established set of procedures for computing ownership costs of such aircraft, which prejudices the elaboration of cost-benefit analysis and allocation of budget resources. The purpose of the study is to develop an O&S cost breakdown structure and a set of cost estimating equations that will be used to estimate the ownership costs of the KC-137 aircraft during their expected service life.

The Highly-Automated Airplane: Its Impact On Aviation Safety And An Analysis Of Training Philosophy, Kuo K. Liu

Theses and Dissertations

Two Airbus accidents at Nagoya, Japan and Toulouse, France in April and June 1994 highlighted the problem of the highly-automated airplane and its interface with pilots. As technologies in the engineering design progress so quickly in airplane automation, training philosophies toward the 'glass cockpit' may need to be re-evaluated. Many pilots, young and old, praise the advantages brought by the new technology. On the other hand, many have complained about the increasing workload and the danger of automation features which are not in their control. In this thesis, I evaluate the accidents of the highly-automated airplane and the probable solutions …

Analysis Of Tethers In Sampling Near Earth Objects, John W. Wong

Theses and Dissertations

This study investigated the feasibility of a SAIC proposal to sample Near Earth Objects (NEOs) from an orbiting spacecraft using a tethered landing device. The parameters for suitable targets were derived from an analysis of a proposed point design as applied to current knowledge of NEOs. Tether strength and lifetime for the point design were also assessed. First order modeling of tether dynamics showed that deployment and attachment to a NEO are feasible. The dynamics of retrieving a sample via a crawler unit which crawls up the tether requires further exploration.

Recycling Pet (Polyethylene Terephthalate) Soda Bottle Wastes To Produce Carpet Fibers, Sherry Halim Yacoub

Archived Theses and Dissertations

The problem of plastics wastes has increased tremendously since the use of plastics increased in more than one application increasing in return the amount of wastes. The possible ways for handling these wastes include landfilling, reusing through chemical recycling techniques, mechanical recycling and reprocessing into a new product, or finally incineration to get energy out of it . In Egypt, recycling takes place for a number of plastic items, but no recycling efforts are yet established for the PET plastic bottles used for soda beverages. It is the concern of this thesis therefore, to find a solution for these unused …

High Performance Distributed Storage Architectures, Ahmed M Amer

Archived Theses and Dissertations

No abstract provided.

Recovery Of Scrap Tire Rubber Waste, Dalia Adel Habib Nakhla

Archived Theses and Dissertations

No abstract provided.

Fuzzy Based Forebody Vortex Flow Controller For The X-29a Aircraft, Jin Suzuki

Masters Theses

This paper demonstrates the development and performance of A Fuzzy Logic based regulator for an aircraft which is equipped with pneumatic forebody Vortex Flow Controller at high angle-of-attack flight condition. The VFC provides the pilot additional control power at flight conditions where conventional effectors such as rudder and differential flaps lose effectiveness.

Fuzzy Logic Control (FLC) is applied to a mixed bang-bang and conventional type control system. This unique configuration ensures robustness of the system and simplifies the controller design. Performance of the FLC based regulator shows a 10.3% reduction in cost function compared to the system controlled by a …

An Efficient Technique For Evaluating The Modal Parameters Of Damped Dynamic Systems, Hany Jim Gross

Archived Theses and Dissertations

No abstract provided.

Design, Simulation, Fabrication And Testing Of Microprobes For A New Mems Wafer Probe Card, Yanwei Zhang

Dissertations

A new type of MEMS cantilever wafer probe card consists of an array of microcantilevers individually actuated by bimorph heating to make contact with the test chip was designed and fabricated. This probe card is called the CHIPP (Conformable, High-Pin count, Programmable ) card and can be designed to contact up to 800 I/O pads along the perimeter of a 1 cm² chip with a microprobe repeat distance of ~50 µm. Each microcantilever had an internal heater and a separate electrode carrying the signal under test and contained four separate layers plus a fifth material for the contact tip …

Design Fabrication And Characterization Of High Performance In Gaas/Inp Focal Plane Array In The 1-2.6 Μm Wavelength Region, Krishna R. Linga

Dissertations

This research thesis describes a new In_xGa_1-xAs/InA_ysP_1-y/InP technology for long wavelength photodetectors and photodetector arrays. A unique and novel detector structure was designed and fabricated using Hydride Vapor Phase Epitaxy, for low leakage current photodetector arrays in the 1-2.6 µm wavelength region. Potential applications of InGaAs focal plane arrays include near-infrared spectroscopy, fluorescence, remote sensing, environmental sensing, space and astronomical applications. The unique design concepts included the step grading of InAsP layers, lower lattice mismatch between the two InAsP graded layers, lattice matched InAsP cap layer and InGaAs absorption layer, sulphur doping …

The Design And Fabrication Of A Thermal Microprobe Integrated On An Atomic Force Microscope Probe Tip, Yongxia Zhang

Dissertations

A thermal microprobe has been designed and built for high resolution temperature sensing. The thermal microprobe consists of a very-thin-film thermocouple junction confined to the very end of a low mass Atomic Force Microscope (AFM) probe tip. Essential to high resolution temperature sensing is the confinement of the thermocouple junction to a short distance at the AFM tip. This confinement is achieved by controlled photoresist coating.

Experimental prototypes have been made with the junction confined to within 0.3 µm of the tip. The couple is made of Au/Pd, and the two metals are electrically separated elsewhere by a thin insulating …

Distribution Of Velocities And Velocity Gradients In Mixing And Flocculation Vessels : Comparison Between Ldv Data And Cfd Predictions, Changgen Luo

Dissertations

Flocculation is an operation of significant industrial relevance commonly encountered in many processes, including water and wastewater treatment. The physico-chemical phenomena of this process is strongly affected by the magnitude of the velocity gradients generated, typically through agitation, in rapid mix devices and flocculation vessels.

In this work the fluid dynamic characteristics of mechanically agitated systems, namely three different types of stirred tanks, which can be used as flocculation vessels, were studied. Both the mean and fluctuating velocities in all three directions were measured by using a Laser-Doppler Velocimeter (LDV). The velocity distribution, fluctuating velocities, power consumption and local velocity …

Adaptive Space-Time Processing For Digital Mobile Radio Communication Systems, Amit Shah

Dissertations

The performance of digital mobile radio communication systems is primarily limited by cochannel interference and multipath fading. Antenna arrays, with optimum combining (OC), have been shown to combat multipath fading of the desired signal and are capable of reducing the power of interfering signals at the receiver through spatial filtering. With OC, the signals received by several antenna elements are weighted and combined to maximize the output signal-to-interference-plus-noise ratio (SLNR). We derive new closed-form expressions for (1) the probability density function (PDF) of the SINR at the output of the optimum combiner, (2) the average probability of bit error rate …

Multi-Wavelength Pyrometric Systems For Emissivity-Independent Non-Contact Temperature Sensing, Michael B. Kaplinsky

Dissertations

A Multi-Wavelength Imaging Pyrometer (M-WIP) for real-time remote sensing of temperature profiles of targets with unknown emissivity was developed and demonstrated. To measure the spectral radiance of a target at several distinct wavelengths an M-WIP system was implemented based on an 320x122-element PtSi IR-CCD imager with an assembly of 7 narrow-band 1k filters in the range from 1790nm to 4536nm. A real-time algorithm for simultaneous estimation of the temperature and model parameters of the target emissivity from the least-squares fit of the theoretical model of 1k camera output signal to the experimental spectral measurements was developed and implemented. This rea1-time …

Development Of A Mathematical Model Of Gait Dynamics, Tae Ho Choi

Dissertations

There exists hypothesis that gait selection is strongly correlated with mechanical energy efficiency in normal subjects. The hypothesis is experimentally proven, and intuitively taken for granted. However, it is not mathematically proven that the minimum energy consumption hypothesis is the underlying principle for the normal human gait. To prove the hypothesis we have developed a mathematical model of human walking, in which it is possible to predict an optimal gait at any given speed of walking based on the principle of minimum mechanical energy consumption.

This improved model, which includes the double-support phase of walking as well as the swing …

Particle Deposition From Turbulent Flow In A Divergent Channel, Wai-Ting Huang

Dissertations

This dissertation presents a numerical analysis of particle deposition from a dilute gas-solid two-phase suspension in a divergent channel. The Lagrangian governing equations for particle motion include inertia force, viscous force, gravity force and image force from electrostatic charge on the particle. The incompressible two-dimensional turbulent flow field in a divergent channel is solved by employing a Κ-ε modeling technique with FIDAP finite element CFD software. A computational procedure is developed to incorporate the flow field into numerical simulation of particle trajectories from which the fraction of deposition is determined. Several divergent channels (half divergent angles of 0°, 7.5°, 10° …

Scheduling In Assembly Type Job-Shops, Nutthapol Asadathorn

Dissertations

Assembly type job-shop scheduling is a generalization of the job-shop scheduling problem to include assembly operations. In the assembly type job-shops scheduling problem, there are n jobs which are to be processed on in workstations and each job has a due date. Each job visits one or more workstations in a predetermined route. The primary difference between this new problem and the classical job-shop problem is that two or more jobs can merge to foul' a new job at a specified workstation, that is job convergence is permitted. This feature cannot be modeled by existing job-shop techniques. In this dissertation, …

Motion Compensation And Very Low Bit Rate Video Coding, Shu Lin

Dissertations

Recently, many activities of the International Telecommunication Union (ITU) and the International Standard Organization (ISO) are leading to define new standards for very low bit-rate video coding, such as H.263 and MPEG-4 after successful applications of the international standards H.261 and MPEG-1/2 for video coding above 64kbps. However, at very low bit-rate the classic block matching based DCT video coding scheme suffers seriously from blocking artifacts which degrade the quality of reconstructed video frames considerably. To solve this problem, a new technique in which motion compensation is based on dense motion field is presented in this dissertation.

Four efficient new …

Performance Optimization Of Very High Frame Rate Ccd Burst-Image Sensors, Zeynep M. Pektas

Dissertations

The primary objective of this work was to demonstrate the feasibility of an image sensor that is capable of capturing images at 10⁷ frames per second. Such high frame rate operation is based on storage of a certain (N) number of frames into the BCCD memory registers and readout at a slower rate at the end of the frame collection period. To accommodate an optical frame time of 100ns, a high-speed virtual-gate photodetector with six multiple n-type implants was proposed and a novel design strategy was developed. The feasibility of this design was demonstrated by simulating the entire photodetector …

Modeling Of 3d Swept Volumes Using Sde/Sede Methods And Its Application To Five-Axis Nc Machining, Liping Wang

Dissertations

This research falls in two important areas in solid modeling and manufacturing automation: (1) swept-volume modeling; (2) computer-based NC (Numerically controled) machining simulation and verification. The swept volume is defined as the volume swept by an object undergoing an arbitrary motion. Modeling of 3D swept volumes includes the boundary computation and representation of a swept volume generated by a general object undergoing general motion in three dimensional space. The Sweep Differential Equation (SDE) and Sweep Envelope Differential Equation (SEDE) methods are two of the important swept volume modeling methods employed in this dissertation. They exploit differential equations to obtain the …

Membrane-Based Reactors For Ozonolysis Of Organic Pollutants In Aqueous And Gaseous Streams, Purushottam V. Shanbhag

Dissertations

Many gaseous and aqueous waste streams contain multiple organic pollutants at low concentration levels. It is not economical to recover and reuse these compounds; it would be advantageous to destroy them efficiently within the waste stream. This work employed ozone, a powerful oxidizing agent, in concert with a compact membrane-based phase-contacting device. Three types of membrane devices were studied: two of them (the single-phase membrane ozonator and the two-phase membrane ozonator) treated organic pollutants in wastewater, while the third (the integrated absorption-oxidation membrane ozonator) removed volatile organic compounds (VOCs) from a gaseous waste stream.

In the single-phase membrane ozonator, the …

The Fatigue Problems Of Cracks Subjected To Obliquely Incident Stress Waves, I-Chung Weng

Dissertations

Catastrophic failure of aircraft and other structures are often caused by undetected cracks. Fracture mechanics has been developed to augment traditional static and fatigue design. In the static theory of fracture mechanics, extensive treatment has been given to the stress distribution around sharp cracks and notches under various loading conditions. Previous works on the problems of dynamic loadings are not accurate in dealing with singularities at high frequencies. The numerical solutions become unrealistic at high frequencies in many practical applications.

To address the need to obtain the stress intensity factor in high frequency dynamic loading situations, we studied the use …