Engineering Commons^™

Nonlinear Dynamic Finite Element Simulation Of Hydroelastic Mounts For Light Weight Vehicles, Talla Jayapal Reddy

Masters Theses

Modern light weight vehicles generate large noise levels, that may need bulky classical rubber mounts to suppress. Hydroelastic mounts can significantly reduce the vibration level of current production automobiles without weight penalty. However, the highly nonlinear behavior of hydroelastic mounts has not been established yet and its use is, therefore, limited to trial and error design methods.

This study discusses the implementation of nonlinear finite element simulation of hydroelastic mounts using the ANSYS finite element code. Fluid elements are limited to linear analysis and therefore are incompatible with the nonlinear hyperelastic elements. A method is proposed to simulate the fluid …

Drainage Basins And Flash Flood Hazards In Al-Ain Area, United Arab Emirates, Moza Hamad Al-Shamsi

Civil and Environmental Theses

Flash flood strike different parts of Al-Ain area virtually every year causing Serious property loses this study investigates the main factors control ling this Flooding, namely. (a) Climate, (b) geomorphology, and (c) hydrogeology Climatically, mo t of rainstorms do occur during the month of February. Geomorphologic ally, the landforms and drainage systems are the main factors. Hydrogeological, twenty basins were carefully identified and their morphometric Parameters were measured the relations between these morphometric parameters and flash floods were accordingly assessed. The results show that most severe damage did occur in buildings and farms in Al Ain Area the most influential …

A Generalized Data Conversion System, Kevan Morgan

Undergraduate Honors Capstone Projects

To assist in the processing of data files collected by the Space Dynamics Laboratory at Utah State University, the software project GENDACS has been completed. GENDACS, acronym for A Generalized Data Conversion System, will contribute to its research program.

Data are collected from various sensory instruments by the Computer Data Acquisition System. The instrument readings are brought in, tagged with the time they were taken, and stored on an optical disk in a compact, binary (non-ASCII) format. GENDACS is designed so that the program can read in such files, sort out the data, and convert them into a new ASCII …

A Comparison Of Computational And Experimental Data For A Subscale High Speed Propulsive Nozzle At Low Mach Numbers, Yonghee Hyun

Theses and Dissertations

This computational study of a hypersonic sub-scale nozzle/cowl configuration compares numerical solutions with experimental data for nozzle performance at off design conditions (subsonic through supersonic Mach numbers. A combination of Van Leer and Roe flux-splitting algorithms was used to solve the flow field. The explicit formulation assumed laminar planar flow and the perfect gas equation of state. A validation for the numerical algorithm was accomplished by comparing with experimental data for a variety of cases. Grid refinement, geometry, and operating conditions all influenced the comparison of the experimental and computational data. Generally, as the Mach number and nozzle pressure ratio …

Development Of An Air-To-Air Refueling Automatic Flight Control System Using Quantitative Feedback Theory, Dennis W. Trosen

Theses and Dissertations

Quantitative Feedback Theory and the improved method Quantitative Feedback Theory are enhanced to include the rejection of disturbance at the system output. The enhanced Quantitative Feedback Theory and improved method Quantitative Feedback Theory processes are applied to the design of an automatic flight control system to regulate position of the C-135B fuel receiving aircraft relative to the tanker during air-to-air refueling. A simple feedback control system is developed that will achieve stable position regulation. State-space aircraft models &re generated. An inner loop autopilot is designed to reduce the plant cutoff frequency and provide the system inputs for the Quantitative Feedback …

A Decision Criteria To Select An Associative-Memory Organization That Minimizes The Execution Time Of A Mix Of Associative-Search Operations, David W. Banton

Theses and Dissertations

The dissertation develops a decision criteria to select an associative-memory organization that minimizes the execution time of a mix of associative-search operations and a decision criteria to estimate the layout dimensions of each organization for a specified memory size. The dissertation reclassifies Feng's associative-search operations into three hardware-influenced categories: bit-position independent (BPI), record-content independent (RCI); bit-position dependent (BPD), RCI; and BPD, record-content dependent (RCD). It develops a relationship between the categories and three associative-memory organizations: the CAM, the bit-serial word-parallel associative memory (BSWPAM) , and the extreme-search associative memory (ESAM). A version of the CAM, three versions of the BSWPAM, …

Radome Depolarization Effects On Monopulse Receiver Tracking Performance, Michael A. Temple

Theses and Dissertations

Boresight Error (BSE), defined as the angular deviation between the true position and the apparent position of a target as indicated by a radar, is an important figure of merit for a tracking radar. A significant contributor to system BSE is the protective radome. This research effort employed a GO technique to investigate the effects of a radome on BSE, expanding previous ray- trace receive techniques to include: (1) a uniquely defined/developed mathematical description for each surface within arbitrary multi-layer tapered radomes, (2) an 'ideal' taper function concept for obtaining optimum BSE prediction performance, (3) a generalized technique for calculating …

Phased Array Antenna Analysis Using Hybrid Finite Element Methods, Daniel T. Mcgrath

Theses and Dissertations

This research in computational electromagnetics developed a new method for predicting the near-field mutual coupling effects in phased array antennas, using the finite element method (FEM) in combination with integral equations. Accurate feed modeling is accomplished by enforcing continuity between the FEM solution and an arbitrary number of wave guide models across a ground plane aperture. A periodic integral equation is imposed above the antenna's physical structure in order to enforce the radiation condition and to confine the analysis to an array unit cell. The electric field is expanded in terms of vector finite elements, and Galerkin's method is used …

Linear Characteristic Spatial Quadrature For Discrete Ordinates Neutral Particle Transport On Arbitrary Triangles, Dennis J. Miller

Theses and Dissertations

A new discrete ordinates spatial quadrature for arbitrary triangular cells is derived and compared to its rectangular cell linear characteristic counterpart. The triangular mesh is more flexible, allowing curved surfaces and off-axis angles to be approximated with many fewer spatial cells. The triangle method is consistently more accurate on example problems tested here. Arbitrary orientation and size of the triangles allow non-patterned meshes to be developed which appears to ameliorate numerical diffusion. The triangle linear characteristic quadrature converges at nearly the same rate as rectangular Linear characteristic on Lathrop's problem. Mesh sensitivity measurements show large variations in triangle vertex locations …

Constitutive Equation For Concrete Using Strain-Space Plasticity Model, Yuxiang Xing

Dissertations

Plasticity theory has been used to model the concrete constitutive relationship for about two decades. With the modifications and refinement based on experimental data, achievement has been made in these plasticity models for concrete. Almost all the existing models are developed in stress space. With a lot of experimental data and more understanding about stress states of concrete, the stress-space model shows many advantages. Because of this and also due to conventional engineering practice, the stress-space plasticity approach has been in the dominant position. However, the conventional stress-space plasticity method has one inherent drawback in which it cannot deal with …

On Orthogonal Collocation Solutions Of Partial Differential Equations, Herli Surjanhata

Dissertations

In contrast to the h-version most frequently used, a p-version of the Orthogonal Collocation Method as applied to differential equations in two-dimensional domains is examined. For superior accuracy and convergence, the collocation points are chosen to be the zeros of a Legendre polynomial plus the two endpoints. Hence the method is called the Legendre Collocation Method. The approximate solution in an element is written as a Lagrange interpolation polynomial. This form of the approximate solution makes it possible to fully automate the method on a personal computer using conventional memory.

The Legendre Collocation Method provides a formula for …

Minimum Redundancy Array Structure For Interference Cancellation, Wan-Ling Chen

Dissertations

Adaptive antenna arrays are widely used in many advanced radar, sonar, and communication systems because of their effectiveness in cancelling intentional or unintentional interferers. A uniformly spaced linear array, referred to as a Uniform Regular Array (URA), is the usual structure used for interference cancellation. The Minimum Redundancy Array (MRA) structure proposed in this work is a special kind of thinned array whose application was limited in the past to direction finding. MRAs with the same number of array elements can resolve directions of much more closely spaced signals than URAs.

The URA structure is customarily utilized for interference cancellation, …

Tensile Behavior Of Concrete And Mortar Under Direct Impact Tensile Load, Kayumars Emad

Dissertations

Structures are often subjected to impact loadings during their lifetime. Most structural specifications including the special provisions for seismic design in the current ACI building codes, have been developed on the basis of quasi-static assumptions. Cement composites are strain rate sensitive materials therefore, their properties determined under quasi-static condition should not be used to predict their performance under high strain rates.

The objectives of this investigation are:

• to develop a standard test set-up for direct tensile testing of cementitious composites.
• to study the tensile behavior of mortar and concrete under direct impact tensile load.
• to develop a simplified formula to …

Characterization Of Advanced Etching Reactors Using Novel Diagnostic Tools, Vipulkumar Patel

Dissertations

Plasma etching equipment used for sub-micron integrated circuit fabrication at present are exclusively based on 13.56 MHz, capacitively coupled, parallel-plate geometry. The underlying mechanisms of plasma processes in these reactors are not well understood and there is even less understanding of how the etch-tool parameters relate to the plasma discharge characteristics which actually determine the etch process. In this thesis, new diagnostic techniques were applied for the characterization and optimization of plasma etching processes in various reactor configurations.

Specifically, diode and triode configurations were studied extensively using tuned scanning Langmuir probes. Both radial and axial distributions of plasma density were …

Kinetic Study Of Decomposition Of Azo Dyes And Phenol In Advanced Oxidation Processes Reaction Mechanisms, Pathways And Intermediates, Hung-Yee Shu

Dissertations

Advanced Oxidation Processes (AOP) are an emerging technology for treatment of various hazardous organics in wastewater and groundwater. However, the kinetics and mechanisms for AOP have not been well understood. A mechanism including light intensity was studied for the decomposition of azo dyes and phenol in an AOP reactor with a 5,000 watt low pressure mercury lamp. UV light absorption is an important parameter. The effect of pH, hydrogen peroxide dosage, and dye concentration on the decomposition of azo dyes in an H₂O₂/UV reactor were also studied. Reaction pathways and intermediates of phenol oxidation by different …

Unreinforced Masonry Structures : Nonlinear Analysis And Evaluation Of Some Rehab Schemes, Sanjay Mehta

Dissertations

Unreinforced masonry (URM) structures have been a common type of construction in the past and are still used in regions of low seismicity. Retrofitting of these structures is necessary because of two reasons: Firstly, observed damage after earthquakes reveals that URM construction is one of the most hazardous constructions even in the region of low seismicity; secondly, reclassification of seismic zones would require retrofitting of existing structures to comply with new guidelines for earthquake design.

Retrofitting measures require that the response of original and new structural systems as well as their interaction be considered. It is therefore important to correctly …

Utilization Of Fly Ash In Concrete, Chai Jaturapitakkul

Dissertations

Fly ash, a by-product of coal burning power plants, is produced in large quantities each year. It is commonly known that fly ash possesses pozzolanic behavior which can enhance the properties of concrete. Due to a lack of proper understanding on the formation of fly ash and its performance in concrete, the question of quality assurance has frequently been a major concern of engineers using fly ash in their construction projects. As a result, much fly ash is disposed of as waste material in landfills. Recent environmental concerns and a shortage of landfill space have rapidly escalated the disposal cost …

Competition Between Two Microbial Populations In A Sequencing Fed-Batch Reactor And Its Implications For Waste Treatment Applications, Sitaram Dikshitulu

Dissertations

Pure and simple competition between two microbial populations in a sequencing fed-batch reactor (SFBR) was studied both at the theoretical and experimental level. Competition occurred for a single chemical pollutant which could serve as the sole carbon and energy source for both competitors. A mathematical model describing the process under inhibitory kinetics (as is usually the case with hazardous and toxic substances) was derived and theoretically analyzed. The model predicts that the dynamics of a SFBR, and the kinetics of biodegradation, result in a complex set of operating regimes in which neither species, only one species, or both species survive …

An Experimental Investigation Of Wear Behavior Of Ultra-High Molecular Weight Polyethylene Under Sliding Motion, Elham Zand-Moghaddam

Theses

This project investigates the effect of sliding motion on the materials that are used as bearing surfaces of human total-joint replacement prostheses.

The tests are performed with a specially designed equipment based on pin-on-disk machine. The testing machine is designed and constructed to reproduce sliding motion, applied to spherical ended metal "Canine-Head" components such as dog hip acting on a flat polyethylene surface. The sliding motion is performed by applying different constant loads for 5,000,000 cycles. The tests are carried out with the wear specimen lubricated by deionized water.

The purpose is to produce delamination, which is the severe wear …

Coordinate Measuring Machines : A Modern Inspection Tool In Manufacturing, Matthias Richard Mantel

Theses

Coordinate Measuring Machines (CMM) are flexible and universal dimensional measuring devices with the capability for full integration into a CIM information network. Developed as highly precise measuring machines for specially designed measuring rooms, today's CMMs are more and more used in shop floor applications which is a hostile environment for a precise measuring tool. CMMs are offered in a variety of configurations and levels of automation. For the CMM buyer it is therefore essential to have an overview of the different types of CMMs and their subsystems before making a purchasing decision.

To obtain reliable measuring results that are used …

A Mathematical Model For The Prediction Of Depth Of Cut In The Course Of Awj Machining, Naijian Ma

Theses

The objective of this study is to develop a practical mathematical model for prediction of the depth of cut in the course of Abrasive Water Jet (AWJ) machining. Semi-empirical method which is an integration of theoretical derivation and statistical analysis is used for process description. A theoretical model was constructed based on kinetic energy conservation equation, physical relationship among operating parameters, abrasive size, material properties and cutting results. Then, correlation between the depth of cut and operational parameters was analyzed in order to improve the theoretical model. Finally, a regression equation representing 1000 samples was constructed.

Three statistical criteria were …

Adaptive Two-Stage Detection Scheme In Synchronous Two-User Cdma Systems, Yong Jiang

Theses

A conventional single user detector is not optimum in the multiuser environment because the multiuser interference can not be modeled as an additive Gaussian process. Such a receiver is very vulnerable to the near far situation. The receiver that is optimum for multiuser environment has high complexity and requires a knowledge of the received signal energies. Various versions of the receiver that handle the near far situation have been proposed in the literature. In this work, an adaptive two stage scheme for a synchronous two user environment with unknown received energies is proposed. It consists of a, tandem of the …

Mechanism Of Pneumatic Fracturing, Trevor Compton King

Theses

This thesis investigates the mechanism of pneumatic fracturing in geologic materials such as soil and rock. Pneumatic fracturing is a recently developed technique for increasing the permeability of geologic formations by the controlled injection of high pressure air. Present applications are focusing on the in situ remediation of contaminated soil and ground water, although pneumatic fracturing has other geotechnical uses such as pumping well enhancement.

A comprehensive literature review of a related technology known as hydraulic fracturing is presented, which serves as background for development of a pneumatic fracturing model. Pressure-time histories from actual pneumatic injections are analyzed in detail …

Integration Of Pneumatic Fracturing To Enhance In Situ Bioremediation, Conan Dante Fitzgerald

Theses

The purpose of this thesis was to study the anticipated benefits of integrating pneumatic fracturing with in situ bioremediation. Since pneumatic fracturing increases subsurface air flow in low permeability formations, it has the potential to overcome many of the major limiting factors of microbial growth and activity. A new innovation called pneumatic bio-injection can further enhance in situ bioremediation by efficiently dispersing biological solutions, including microorganisms, into a formation.

Bench scale experiments were conducted to examine the ability of microorganisms to survive the pressures and stresses associated with pneumatic injection. Tests conducted at pressures ranging from 60 to 500 psi …

Tantalum Silicide Variable Capacitance Rotary Micromotors : Design And Fabrication, Michael Steven Berry

Theses

Tantalum silicide was studied as an alternative microelectromechanical material by fabricating a rotary micromotor utilizing a proven design. This material was used for the rotor, stators, and bearing over a silicon substrate. It has the attraction of potentially reducing the friction which is a major problem with polysilicon-to-polysilicon bearings.

The necessity of high aspect ratio features required that a plasma or reactive ion etch with a high degree of anisotropy be developed to etch tantalum silicide films in excess of 1.5μm. A sulfur hexafluoride/Freon 115 plasma provided the necessary process control during the etches. The stress present in annealed tantalum …

Modeling And Simulation Of Magnetic Micromotor Performance, Ping Wang

Theses

The objective of this research was to model the performance and optimize geometries for two types of magnetic micromotors: yoke-type (YTMM) and yokeless (YSMM). The two selected micromotor types matched the designs that have been described in the recent research literature. Modeling was accomplished using MAXWELL, an advanced 2-D and 3-D simulator. The micromotors with nickel and nickel-iron magnetic thin films for the rotor and stator were simulated for torque performance. Three-phase power supplies with overlapping and non-overlapping phases were used. Rotor diameter dimensions were varied from 285 to 600µm, and the rotor-stator air gap was varied from 3 to …

Modeling And Analysis Of Semiconductor Manufacturing Processes Using Petri Nets, Xinyao Wang

Theses

This thesis addresses the issues in modeling and analysis of multichip module (MCM) manufacturing processes using Petri nets. Building such graphical and mathematical models is a crucial step to understand MCM technologies and to enhance their application scope.

In this thesis, the application of Petri nets is presented with top-down and bottom-up approaches. The theory of Petri nets is summarized with its basic notations and properties at first. After that, the capability of calculating and analyzing Petri nets with deterministic timing information is extended to meet the requirements of the MCM models. Then, using top-down refining and system decomposition, MCM …

Blur Identification And Restoration Of Images Of Coronary Microvessel, Kuen Tak Wong

Theses

The objective of this research was to identify the blur characteristics of the blurred images of the rat coronary microvessel, and the information of the blur characteristics was used to restore the blurred images. The blur characteristics were analyzed by using the image power cepstrum. The Wiener filter was implemented to restore the images. There were two types of point spread functions proposed and studied for the restoration. They were: defocus blur PSF and motion blur PSF. The images were transferred from HP A900 system to an AVS workstation. The images were processed and manipulated by the AVS, and showed …

Modeling And Investigation Of Current Transport Phenomena In Schottky Structures, Yan Zeng

Theses

We have used a numerical method to describe the importance of the contribution of generation-recombination current to the I-V characteristics of Schottky barrier contacts. The current-voltage relationship is derived directly from the fundamental set of equations such as Poisson; current-density and continuity equations, without having to make many simplifications or approximations. The final result includes not only the thermionic emission or drift diffusion mechanisms of current flow, but also the generation recombination processes.

The experimental devices used for this work are very common low barrier height Schottky structures, Al/T_0.3W_0.7/n-Si/A1 and Ti_0.3W_0.7/n-Si/Al. The …

Microengineered Mass Spectrometer With Field Emission Ionization Source, Chao Sun

Theses

This thesis describes a design for a microengineered mass spectrometer. This mass spectrometer device uses VLSI processing techniques to scale down the dimensions of an existing mass spectrometer and make it portable. It can be manufactured economically and has the potential to be integrated with more complex structures and including transistor integrated circuits. An optimized device is proposed. This device is to be fabricated using two silicon substrates approximately 1cm by 1cm, where one is a cathode electron source and the other is the ion collector. External ion sources are not needed. Electrons are emitted from the array of cathode …