Engineering Commons^™

Non-Destructive Evaluation Of Space Shuttle Thermal Protection System Tile Bond Integrity, George David Mulligan

Retrospective Theses and Dissertations

Experimental modal analysis (EMA) is used as a non-destructive technique for the evaluation of Space Shuttle thermal protection system (TPS) tile bond integrity. Finite element (FE) models for tile systems were developed and were used to generate their vibration characteristics (i.e. natural frequencies and mode shapes). Various TPS tile assembly configurations as well as different bond conditions were analyzed. Results of finite element analyses demonstrated a drop in natural frequencies and a change in mode shapes which correlate with both size and location of disband. Results of experimental testing of tile panels correlated with FE results and demonstrated the feasibility …

Particle Size And Velocity Measurements In Two Phase Flows Using Laser Doppler Velocimetry, Joseph Parker

Honors Theses

Laser Doppler Velocimetry is used in fluid mechanics to measure the velocity of particles in fluid flows. A small particle exhibits motion closely corresponding to the fluid behavior because of its ability to follow high frequency flow fluctuations. Large particles do not follow the flow field precisely but represent a second phase. This project used LDV to measure the size and velocity of particles in two phase flows by computer analysis of the Doppler signal.

Transition From Laminar To Turbulent Flow Around An Airfoil, Chang-Ren Chen

Doctoral Dissertations

"A computational fluid dynamics (CFD) code has been developed for two-dimensional incompressible turbulent flows and employed to solve the Navier Stokes equations around an airfoil of arbitrary shape. A low-Reynolds-number k — e turbulence model including curvature effect was used to consider the gain and loss of turbulent kinetic energy. To include laminar sublayer into the computational domain, a multi-layer grid and a cubic-slpine grid were introduced through a conservative form of coordinate transformation. The flow structure varies with the Reynolds numbers. For an airfoil at low Reynolds numbers (below ten thousand), distinct vortex shedding patterns can be found in …

Approaches To Control Of The Large Angle Magnetic Suspension Test Fixture, Mehran Ghofrani

Mechanical & Aerospace Engineering Theses & Dissertations

The Large Angle Magnetic Suspension Test Fixture is a five degree-of-freedom system, developed and built at NASA Langley Research Center. It is intended for study of control techniques in magnetic suspension systems with large angular capabilities. In this study, steps have been taken to prove the system in practice, using the existing hardware. A classical control approach, using dual phase advance compensators, is applied in simulation and hardware. A single decoupled degree-of-freedom of the system is stabilized and controlled in simulation. The procedure is then employed for all five degrees-of-freedom. The design and implementation of an analog and a digital …

Topics In Nonlinear Stochastic Control, Estimation, And Decision, Using A Measure Transformation Approach, Charalambos Demetriou Charalambous

Electrical & Computer Engineering Theses & Dissertations

We discuss topics in the theory of nonlinear stochastic control, estimation, and decision via a probabilistic approach using measure transformations and martingale theory. First, we investigate the problem of estimating a diffusion process using coordinate transformations and measure transformations, both locally and globally; this is the analog of nonlinear coordinate and state feedback transformations used to obtain exact linearization in nonlinear deterministic control problems. Our results are new in that we use a probabilistic approach rather than a purely geometric one, and also in that we derive representations when the processes are defined locally rather than just globally. A gauge …

Explicit Multistage Schemes For The Solution Of The Three-Dimensional Compressible Euler/Navier-Stokes Equations, Alaa Ahmed Elmiligui

Mechanical & Aerospace Engineering Theses & Dissertations

The objective of this study was to develop a high-resolution-explicit-multi-block numerical algorithm, suitable for efficient computation of the three-dimensional, time-dependent Euler and Navier-Stokes equations. The resulting algorithm has employed a finite volume approach, using MUSCL-type differencing to obtain state variables at cell interface. Variable interpolations were written in the $\kappa$-scheme formulation. Inviscid fluxes were calculated via Roe's flux-difference splitting, and van Leer's flux-vector splitting techniques, which are considered state of the art. The viscous terms were discretized using a second-order, central-difference operator.

Two classes of explicit time integration has been investigated for solving the compressible inviscid/viscous flow problems--two-stage predictor-corrector schemes, …

Bounds On Constraint Weight Parameters Of Hopfield Networks For Stability Of Optimization Problem Solutions, Gursel Serpen

Electrical & Computer Engineering Theses & Dissertations

The purpose of the presented research is to study the convergence characteristics of Hopfield network dynamics. The relation between constraint weight parameter values and the stability of solutions of constraint satisfaction and optimization problems mapped to Hopfield networks is investigated. A theoretical development relating constraint weight parameter values to solution stability is presented. The dependency of solution stability on constraint weight parameter values is shown employing an abstract optimization problem. A theorem defining bounds on the constraint weight parameter magnitudes for solution stability of constraint satisfaction and optimization problems is proved. Simulation analysis on a set of optimization and constraint …

A Comparison Of Alphanumeric, Direct Manipulation Graphic, And Equivalent Interface Design For A Production Scheduling Task, Ann C. Fulop

Psychology Theses & Dissertations

Scheduling is an essential factor influencing the efficiency of any production system. The effectiveness of the scheduling system depends upon the interaction of the human and machine. Thus, to effectively design the interface between the human and the machine, the human factors professional must understand scheduling behavior and the information requirements of the scheduling task. The present study modeled human scheduling behavior and determined the information requirements of the scheduling task. The study also compared alphanumeric, direct manipulation graphic, and equivalent interfaces to determine which interface best supports scheduling. The results of the study show that schedulers monitor the current …

Seismic Response Of Pipeline Systems In A Soil Liquefaction Environment, Hongzhi Zhang

Civil & Environmental Engineering Theses & Dissertations

This research is a study of the general seismic response behavior of buried pipeline systems during a soil liquefaction process. To aid the design of buried pipelines in a soil liquefaction environment, the purpose of this research is to provide the basic dynamic seismic response of different pipeline systems. Several important parameters such as pipe diameter, buried depth, additional mass and the size of the liquefiable soil zone have been introduced. The pipeline systems under study are cross-types, T-types and straight pipelines, with or without a manhole, buried in a soil liquefiable zone.

Time-varying soil spring constants are used for …

Smimd - A Synchronous Multiple Instruction Multiple Data Computer Architecture, Cathy C. Roberts

Computer Science Theses & Dissertations

This thesis assesses the feasibility of utilizing a hypercube interconnect topology to link a heterogeneous processor array in a very long instruction word (VLIW) computer architecture. The research focused upon the selection of a suitable arrangement of processors for the computer and the subsequent demonstration of the architecture's capability to handle simple loop iterations. Previous attempts at VLIW computer design are summarized, the new SMIMD architecture is presented, and suggestions for future research are given. The thesis concludes with results of the initial performance evaluations of the architecture design.

Factors Affecting The Development Of Unassigned Patents In Iowa, Diane Darlene Wheeler Schou

Dissertations and Theses @ UNI

Inventors granted patents from 1975 to 1990 in Iowa identified, via a questionnaire, where they perceived their invention on Bright's scale of eight stages of development. Stages were: idea, rationalization (has merit), experimentation, demonstration of prototypes, working model, commercial (market entry), commercial acceptance (sales), and commercial proliferation (other markets). The questions identified factors affecting development. The factors included: resources assisting development, events influencing start-up, sources of money for development, method of manufacturing, experiences with manufacturers, marketing techniques, sales, profit/loss, concerns, patent renewals, and age of patents. Open-ended questions allowed for additional comments.

Commercial acceptance or commercial proliferation was achieved by …

Industrial Technology Faculty's Valuation Of Consulting And Professional Performance, Daniel Richard Meyer

Dissertations and Theses @ UNI

The purpose of this study was to investigate university industrial technology faculty relationships between their consulting with industrial and perceptions of professional performance. The question addressed was that if effects on teaching ability, research activity, scholarly publishing, and public service arising from this activity. The information obtained adds to knowledge and may be useful for administrators in supporting this form of public service. The result should be increased faculty competence, better prepared students, and increased industrial competitiveness.

Exogenous variables of consulting with industry, competency maintenance, theory testing, enthusiasm regeneration, research opportunity, and scholarly publishing were identified as having potential impact …

A Wear Analysis Study Of Selected Alternative Foundry Tooling Materials Using Impact Abrasion Testing, L. Fred Vondra

Dissertations and Theses @ UNI

The purpose of this study was to simulate the wear characteristics of foundry tooling using an impact abrasion test apparatus. The wear characteristic was exhibited by non-metallic materials and was measured as a function of percentage weight loss and was benchmarked against Class 30 gray iron. The research question focused on whether or not a non-metallic material exists that exhibits comparable or superior wear characteristics to Class 30 gray iron for possible consideration as tooling materials for foundry applications. The information obtained adds to knowledge and is useful to foundry professionals in making tooling decisions.

The 34 test materials were …

The Relationships Between Technical Operator Turnover Rate And Selected Working Condition Factors In Taiwan's Printing Industry, Ling-Hsiao Lee

Dissertations and Theses @ UNI

The purpose of this study was to determine how technical operator turnover rate related to selected working condition factors in Taiwan's printing industry. These factors, as defined in this study, included wages, employee benefits, alternative work schedules, training programs, and gainsharings. If the results of this study showed that technical operator turnover rate was related to these selected factors, then the findings of this study would be helpful to a manager making decisions on turnover management.

The data for this study were collected by using three sets of questionnaires: (a) one designed for personnel directors, (b) one targeted at financial …

Development Of An Automated Ultrasonic Inspection Cell For Detecting Subsurface Discontinuities In Cast Iron, John Scott Burningham

Dissertations and Theses @ UNI

Manufacturing of value added products by companies in todays global marketplace requires the vendors to meet certain minimum standards, SAE, ASTM, ISO, etc. In a global economy, as a manufacturer for the year 2000 and beyond, preferred vendors will become ISO 9000 certified to maintain a market share of produced goods.

An automated inspection cell was developed for the inspection of cast iron ports to detect subsurface discontinuities. The cell consists of an ultrasonic flaw detector (UFD), transducer, robot, immersion tank, computer, and software. Normal beam pulse-echo ultrasonic nondestructive testing is performed on each rough casting.

Using test blocks and …

Job Characteristics Of Construction Craftsmen And Their Relationships To Affective Work Outcomes, Musibau Adeola Shofoluwe

Dissertations and Theses @ UNI

This research was undertaken to investigate the extent to which employee-perceived job characteristics were related to internal work motivation and general satisfaction. Research shows that the structure of work has a significant influence on the motivation and general satisfaction of workers.

A job characteristic model developed by Hackman and Oldham (1980) was used as a basis for conducting this study. The study population consisted of construction craft workers who were registered members of the bricklayers, carpenters, and electrical unions located in a mid-western state. Job diagnostic survey questionnaires were mailed to 650 craftsmen. A total of 236 (36.3%) instruments were …

A New Method For Calculating The Economic Benefits Of Varying Degrees Of Power Factor Correction For Industrial Plant Loads, Mohammed Ishaque

Dissertations and Theses

A comparative study of the economic benefits that can be obtained from different degrees of power factor correction for medium and small scale industrial installations is shown. A new approach for precise calculation of kws and kvars required at different power factors is presented. These calculated values are used to find the return on investments for the capacitors needed for power factor correction. The developed method is easy to use, cost effective, accurate and will help electrical engineers with minimum knowledge of power systems to precisely determine the savings available by improving the power factor of an industrial load.

Performance Analysis Of Doa Estimation Algorithms Using Physical Parameters, Hui Liu

Dissertations and Theses

Analytical performance analysis on Direction-Of-Arrival (DOA) estimation algorithms has attracted much excellent research in recent years, various statistical properties have been revealed. However, in most of these analyses, insights of the performance were masked because of the involvement of singular values and singular vectors which depend on the character of the algorithms and data structures in a complex and nonlinear manner.

Multiplexed Pipelining : A Cost Effective Loop Transformation Technique, Satish Pai

Dissertations and Theses

Parallel processing has gained increasing importance over the last few years. A key aim of parallel processing is to improve the execution times of scientific programs by mapping them to many processors. Loops form an important part of most computational programs and must be processed efficiently to get superior performance in terms of execution times. Important examples of such programs include graphics algorithms, matrix operations (which are used in signal processing and image processing applications), particle simulation, and other scientific applications. Pipelining uses overlapped parallelism to efficiently reduce execution time.

Spontaneous Coherent Pulsations In Standing-Wave Laser Oscillators : Stability Criteria, Pitak Chenkosol

Dissertations and Theses

The stability criteria for single-mode standing-wave laser oscillators in the strongly homogeneously broadened limit are reported for the first time. Two types of stability criteria are presented. The first type, called type 1, corresponds to the minimum value of threshold parameter for which an infinitesimal perturbation away from steady state grows into an oscillatory solution. Another type of stability criteria, called type 2, corresponds to the minimum value of threshold parameter for which large amplitude oscillatory solutions do not decay to the steady state solution. Undamped pulsations in single mode strongly homogeneously broadened standing-wave laser oscillators are found to occur …

A Partitioning-Based Approach To The Fitting Problem In Special Architecture Eplds, Steffan Goller

Dissertations and Theses

In this thesis, we describe an architecture-driven fitting algorithm for an Application-Specific EPLD, the CY7C361, from Cypress Semiconductor. Traditional placement and routing tools for PLDs perform placement and routing separately. Several placement possibilities are created and the router tries to realize the connections between the physical locations of the cells on the chip. The Cypress CY7C361 has a very unique chip architecture with a highly limited connectivity between the physical cells. Therefore, it is necessary to consider the mutability when the placement of cells is performed. The combination of the two stages is called fitting. The specific architecture-dependent constraints, imposed …

Tapered Radio Frequency Transmission Lines, Vincent D. Matarrese

Dissertations and Theses

A transformation used to obtain solutions for the beam parameter equation of fiber optics is applied to the second order differential equation for nonuniform transmission lines. Methods are developed for deriving possible transmission line tapers from known solutions of the transformed equation. This study begins with a comprehensive overview of previous work done to obtain closed-form solutions for the transmission line equations. Limitations of the lumped parameter model are also discussed. As part of this thesis, a tapered transmission line is constructed, based on one of the solutions obtained from the fiber optics studies. A discussion of the design and …

Characterization Of Quantization Noise In Oversampled Analog To Digital Converters, Eric W. Multanen

Dissertations and Theses

The analog to digital converter (ADC) samples a continuous analog signal and produces a stream of digital words which approximate the analog signal. The conversion process introduces noise into the digital signal. In the case of an ideal ADC, where all noise sources are ignored, the noise due to the quantization process remains. The resolution of the ADC is defined by how many bits are in the digital output word. The amount of quantization noise is clearly related to the resolution of the ADC. Reducing the quantization noise results in higher effective resolution.

Parameter Uncertainty And Modeling Of Sludge Dewatering In One Dimension, Joseph H. Plaskett

Dissertations and Theses

Separation of liquid from solids is a necessary step in the ultimate disposal of wastewater sludges. Most commonly, sludges are dewatered by pressure-filtration methods. Mathematical models of the physics of the sludge dewatering process would provide the ability to predict dewatering performance and optimize the design and operation of dewatering facilities.

Behavior Of Square And L-Shaped Slender Reinforced Concrete Columns Under Combined Biaxial Bending And Axial Compression, Wen Hu Tsao

Dissertations

A numerical analysis was developed to evaluate the complete load-deflection and moment-curvature relationships for square and L-shaped slender reinforced concrete columns subjected to biaxial bending and axial load. This computer model can be used for any cross section geometry and material properties of normal concrete. The analysis was based on a deformation control and both the ascending and descending branches of curves can be studied. The finite difference method was introduced to calculate the deflections which satisfy the compatibility equations. Six square slender columns and eight L-shaped slender columns were tested to compare their experimental load-deformation results with the analytical …

A Generalized, Parametric Pr-Qmf/Wavelet Transform Design Approach For Multiresolution Signal Decomposition, Hakan Caglar

Dissertations

This dissertation aims to emphasize the interrelations and the linkages of the theories of discrete-time filter banks and wavelet transforms. It is shown that the Binomial-QMF banks are identical to the interscale coefficients or filters of the compactly supported orthonormal wavelet transform bases proposed by Daubechies.

A generalized, parametric, smooth 2-band PR-QMF design approach based on Bernstein polynomial approximation is developed. It is found that the most regular compact support orthonormal wavelet filters, coiflet filters are only the special cases of the proposed filter bank design technique.

A new objective performance measure called Non-aliasing Energy Ratio(NER) is developed. Its merits …

Analytical Methodology For Atm Control Panel Design, Donald C. Johnson

Theses

This thesis presents a methodology for control panel design and layout along with a case study of an automated teller machine (ATM). A predictive model of human endurance and fatigue is developed from anthropometric, biomechanical and kinematics research. The layout problem is formulated to assign controls to locations to minimize the fatigue imposed on an operator performing a known set of tasks. A family of optimal and near-optimal layouts are found using conventional algorithms. The final hardware design refinements are suggested by human factors concerns. Ergonomic guidelines are also proposed for software aspects of the design. The methods and guidelines …

Computer-Aided Process Planning (Capp) Sorich, Sohail Pirzada

Theses

The last two decades have witnessed the increasing role of the computer in the process planning function. This has been further enhanced by the advent of the knowledge based expert system, and its impact on Computer Aided Process Planning (CAPP). CAPP has emerged as a strategic link between design and manufacture. This thesis discusses the various methods used in the process planning function. Group Technology (GT) plays a pivotal role in establishing CAPP. The utilization of Artificial Intelligence techniques in CAPP is listed. This study also presents an Interactive Software adaptive to product/part configuration variables.

Redesign Of Parts And Simulation Of Flexible Assembly Cell For Safety Water Shower Assembly, Balraj Y. Gardilla

Theses

A Design for Assembly (DSA) method is used to analyze the safety water shower assembly and to redesign the components with emphasis on meeting the criteria of allowing for flexible Assembly Cell (FAS). An Expert System is developed to select the right Assembly using VP-Expert. This thesis contrasts the old and new safety water shower assembly designs and describes the design of a final Flexible Assembly Cell. A PUMA 550 robot was investigated for use in the cell design. The flexible Assembly cell is simulated on silicon graphics using the IGRIP software. The economics of each part presentation method is …

Error Detection And Correction In Compressed Data, Nadir Sezgin

Theses

Encoded data is very sensitive to the channel errors. Especially if the data is compressed by Arithmetic Encoding procedure, then the error propagation is very high. The error propagation in Arithmetic Coding is studied. Exploiting the high error propagation property when compressing data by Arithmetic encoding procedure, two different algorithms have been proposed for error detection and correction. Under certain conditions these algorithms detect and with a very high probability correct the errors introduced to the compressed data.