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1991

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Articles 151 - 180 of 181

Full-Text Articles in Mechanical Engineering

Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch Jan 1991

Application Of The Boundary Element Method To Elastic Wave Scattering Problems In Ultrasonic Nondestructive Evaluation , Paul Jay Schafbuch

Retrospective Theses and Dissertations

The boundary element method (BEM) is used to numerically simulate the interaction of ultrasonic waves with material defects such as voids, inclusions, and open cracks. The time harmonic formulation is in 3D and therefore allows flaws of arbitrary shape to be modeled. The BEM makes such problems feasible because the underlying boundary integral equation only requires a surface (2D) integration and difficulties associated with the seemingly infinite extent of the host domain are not encountered. The computer code utilized in this work is built upon recent advances in elastodynamic boundary element theory such as a scheme for self adjusting integration ...


A Study Of High Speed Flows In An Aircraft Transition Duct , Bruce A. Reichert Jan 1991

A Study Of High Speed Flows In An Aircraft Transition Duct , Bruce A. Reichert

Retrospective Theses and Dissertations

Circular-to-rectangular transition ducts are used on aircraft with rectangular exhaust nozzles to connect the engine and nozzle. Often, the incoming flow of these transition ducts includes a swirling velocity component remaining from the gas turbine engine. Previous transition duct studies have either not included inlet swirl or when inlet swirl was considered, only overall performance parameters were evaluated. This dissertation reports the study of circular-to-rectangular transition duct flows with and without inlet swirl. This study was completed in order to understand the effect of inlet swirl on the transition duct flow field and to provide detailed duct flow data for ...


Drag On Object Moving Through Foam , Chinwha Chung Jan 1991

Drag On Object Moving Through Foam , Chinwha Chung

Retrospective Theses and Dissertations

Foams consist of small gas bubbles separated by thin liquid films. Although many complex models have been developed to describe the rheological properties of foam, very little information is available concerning the flow charateristics of foam flowing past an object. The purpose of this research was to investigate foam flow properties by performing simple experiments to determine the drag charateristics of simple-shaped bodies moving through foam;A rotating tank apparatus was built and used as the equivalent of a wind tunnel in aerodynamic testing. Foam with consistent properties was produced and models of various shapes were suspended in the moving ...


Control Of A Very Flexible Robot In Gravity , Jay E. Shannan Jan 1991

Control Of A Very Flexible Robot In Gravity , Jay E. Shannan

Retrospective Theses and Dissertations

This thesis presents several algorithms used to control a very flexible robot in gravity. The flexible arm is modelled using an assumed modes method to characterize the elastic behavior. Gravity is included in the model. Control algorithms are developed and simulated numerically. The control schemes include proportional-derivative (PD), linear quadratic regulator (LQR), and linear quadratic regulator with a prescribed degree of stability algorithms. The PD algorithms use only hub position and velocity for feedback. Simulations show fast response times with large overshoot and long settling times. The LQR algorithms have the benefit of modal feedback. These responses settle quicker than ...


Prediction Of Diesel Engine Particulate Emission During Transient Cycles, Qiqing Jiang Jan 1991

Prediction Of Diesel Engine Particulate Emission During Transient Cycles, Qiqing Jiang

Retrospective Theses and Dissertations

A computer model has been developed to predict diesel engine particulate emission during transients in speed and torque. The computer model consists of a quasi-steady-state engine combustion model, a dynamic engine model, and a dynamic turbocharger model. The model predictions were compared to experimentally measured particulate emissions. Particulate matter was measured under steady-state conditions, over an EPA transcient cycle, and for discrete segments of various transient cycles;The computer model accurately predicts engine air flow rate, turbocharger speed, and instantaneous engine equivalence ratio. The fuel consumption given by the model is within 3% of the experimental measurement over the transient ...


A Genetic Algorithm Approach To Optimization Of Asynchronous Automatic Assembly Systems, Mark A. Wellman Jan 1991

A Genetic Algorithm Approach To Optimization Of Asynchronous Automatic Assembly Systems, Mark A. Wellman

Retrospective Theses and Dissertations

No abstract provided.


A Study Of The Relative Importance Of Jit Implementation Techniques Using The Analytic Hierarchy Process Model, Sutthira Thanyavanich Jan 1991

A Study Of The Relative Importance Of Jit Implementation Techniques Using The Analytic Hierarchy Process Model, Sutthira Thanyavanich

Retrospective Theses and Dissertations

No abstract provided.


Characterization And Analysis Of The Bulk-Acoustic-Wave Thin Film Resonator In Sub-Nanogram Mass Detection, Ronald Patrick O'Toole Jan 1991

Characterization And Analysis Of The Bulk-Acoustic-Wave Thin Film Resonator In Sub-Nanogram Mass Detection, Ronald Patrick O'Toole

Retrospective Theses and Dissertations

No abstract provided.


Effects Of Coal Properties And Process Variables On Cleaning Efficiency In A Fluidized Bed Separator, Ridvan Amir Sahan Jan 1991

Effects Of Coal Properties And Process Variables On Cleaning Efficiency In A Fluidized Bed Separator, Ridvan Amir Sahan

Theses and Dissertations

No abstract provided.


Experimental Investigation Of The Stress Singularity Power By Moiré Interferometry, Leng-Tsun Tsai Jan 1991

Experimental Investigation Of The Stress Singularity Power By Moiré Interferometry, Leng-Tsun Tsai

Theses and Dissertations

No abstract provided.


Interactive Boundary Layer Solutions For Vortex-Induced Separation, Ta-Wei Lou Jan 1991

Interactive Boundary Layer Solutions For Vortex-Induced Separation, Ta-Wei Lou

Theses and Dissertations

No abstract provided.


A Mechanical Biventricular Assist Device, Andrew Armour Jan 1991

A Mechanical Biventricular Assist Device, Andrew Armour

Theses and Dissertations

No abstract provided.


A Parametric Study Of The Factors Affecting Strain Levels In Electronic Packages, Pei-Haw Tsao Jan 1991

A Parametric Study Of The Factors Affecting Strain Levels In Electronic Packages, Pei-Haw Tsao

Theses and Dissertations

No abstract provided.


Nc Machining From Solid Representations, U. Tugrul Daim Jan 1991

Nc Machining From Solid Representations, U. Tugrul Daim

Theses and Dissertations

No abstract provided.


Effect Of The Coefficient Of Thermal Expansion Of A Coating On Waterwalls In A Super-Critical Coal Fired Utility Boiler, Charles Patrick Erksine Jan 1991

Effect Of The Coefficient Of Thermal Expansion Of A Coating On Waterwalls In A Super-Critical Coal Fired Utility Boiler, Charles Patrick Erksine

Theses and Dissertations

No abstract provided.


Control Of Wake Instabilities From A Thick Trailing Edge By Boundary Layer Suction, Semmi Suphi Konak Jan 1991

Control Of Wake Instabilities From A Thick Trailing Edge By Boundary Layer Suction, Semmi Suphi Konak

Theses and Dissertations

No abstract provided.


Analysis Of The Dynamic Characteristics Of Bubble/Tube Impacts, Ahmet Pinarbasi Jan 1991

Analysis Of The Dynamic Characteristics Of Bubble/Tube Impacts, Ahmet Pinarbasi

Theses and Dissertations

No abstract provided.


Measurement Of Solubility, Density, And Viscosity Of Lubricant/Refrigerant Mixtures For Hcfc-22 And Hfc-134a, Steven Charles Zoz Jan 1991

Measurement Of Solubility, Density, And Viscosity Of Lubricant/Refrigerant Mixtures For Hcfc-22 And Hfc-134a, Steven Charles Zoz

Retrospective Theses and Dissertations

No abstract provided.


Computer-Aided Process Planning (Capp) Sorich, Sohail Pirzada Jan 1991

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.


Petri Net Modeling Of A Flexible Assembly Station For Printed Circuit Boards, M. Zhou, Ming-Chuan Leu Jan 1991

Petri Net Modeling Of A Flexible Assembly Station For Printed Circuit Boards, M. Zhou, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Petri net modeling approaches are presented for a flexible workstation for automatic assembly of printed circuit boards. In order to improve the productivity of such a system, the building of mathematical models is a crucial step. Concentrating on the operational aspects, the authors construct ordinary and temporal Petri net models for the AT&T FWS-200 physical flexible workstation. Three outcomes follow from such models. First, designers can have a better understanding of concurrency, synchronization, mutual exclusion, and sequential relations involved in the system control from the graphical representations of Petri nets. Second, the performance analysis of system operations under different ...


Decoupled Dynamics For Control And Estimation, S. N. Balakrishnan Jan 1991

Decoupled Dynamics For Control And Estimation, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Decoupling of the dynamical equations in polar coordinates is used to develop a control scheme for use in target-intercept problems with passive measurements. By defining a pseudo control variable in the radial coordinate, the radial dynamics is made independent of the transverse dynamics. After solving for the radial control, the transverse control is determined through solutions to a two-point boundary value problem. Numerical results from a six degree-of-freedom simulation which used the decoupled control indicate that it is better than the completely Cartesian coordinate control for most of the cases considered. Decoupled control, though, is obtained iteratively through a two-point ...


Hierarchical Neurocontroller Architecture For Intelligent Robotic Manipulation, Xavier J. R. Avula, Luis C. Rabelo Jan 1991

Hierarchical Neurocontroller Architecture For Intelligent Robotic Manipulation, Xavier J. R. Avula, Luis C. Rabelo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A hierarchical neurocontroller architecture consisting of two artificial neural network systems for the manipulation of a robotic arm is presented. The higher-level neural system participates in the delineation of the robot arm workspace and coordinates transformation and the motion decision-making process. The lower one provides the correct sequence of control actions. The capabilities, including speed, adaptability, and computational efficiency, of the developed architecture are illustrated by an example.


Development Of An Advisory System For Indoor Radon Mitigation, Patricia Hiromi Byrne Jan 1991

Development Of An Advisory System For Indoor Radon Mitigation, Patricia Hiromi Byrne

Dissertations and Theses

A prototype hybrid knowledge-based advisory system for indoor radon mitigation has been developed to assist Pacific Northwest mitigators in the selection and design of mitigation systems for existing homes. The advisory system employs a heuristic inferencing strategy to determine which mitigation techniques are applicable, and applies procedural methods to perform the fan selection and cost estimation for particular techniques. The rule base has been developed employing knowledge in existing publications on radon mitigation. Additional knowledge has been provided by field experts. The benefits of such an advisory system include uniform record-keeping and consistent computations for the user, and verification of ...


Drainage Of Sandplain Seeps For Salinity Control And Stock Water Supplies, Richard George, Peter Frantom Jan 1991

Drainage Of Sandplain Seeps For Salinity Control And Stock Water Supplies, Richard George, Peter Frantom

Journal of the Department of Agriculture, Western Australia, Series 4

Sandplain seeps are derived from a shallow groundwater system which flows from the deep sandplain soils upslope. Seeps result in small areas of salinity and waterlogging, which can be the focus of soil erosion. Sandplain seeps may represent as much as 10 per cent of Western Australia's salt problem in the drier agricultural area. Several drainage experiments conducted between 1986 and 1989 determined the best methods of reclaiming sandplain seeps.

This article discusses the results of these drainage experiments. It comments on the most suitable method for reclaiming sandplain seeps and developing them for stock water supplies.


Methods Of Measuring The Solubility And Viscosity Of Lubricating Oil/Refrigerant Mixtures At High Discharge Pressures And Temperatures, Nolan Van Gaalen Jan 1991

Methods Of Measuring The Solubility And Viscosity Of Lubricating Oil/Refrigerant Mixtures At High Discharge Pressures And Temperatures, Nolan Van Gaalen

Faculty Work Comprehensive List

The design and construction of a test facility and methodology for measuring the solubility and viscosity of lubricating oil/refrigerant mixtures at high pressures and temperatures are described. An auxiliary charging system, developed to provide precisely measured quantities of oil and refrigerant to the test facility, is also presented. The test facility was developed under the sponsorship and supervision of ASHRAE which funded this research project (RP-580);The solubility, viscosity and density of mixtures of R-22 and of R-502 with commonly used 150 SUS lubricants have been measured by using this facility. Specifically, results for liquid mixtures of 10% to ...


A Computer Simulation Model Of Waterhyacinth And Weevil Interactions, Kunter S. Akbay, F. G. Howell, J. W. Wooten Jan 1991

A Computer Simulation Model Of Waterhyacinth And Weevil Interactions, Kunter S. Akbay, F. G. Howell, J. W. Wooten

Mechanical Engineering Faculty Research and Publications

A personal computer simulation model termed "INSECT" has been developed to evaluate biological control of waterhyacinth (Eichhornia crassipes (Mart.) Solms.) by two species of weevil (Neochetina eichhorniae Warner, and N. bruchi Hustache). The model results were compared with the data from three different locations. For each data set, the simulated plant biomass, adult and larva populations were plotted aqainst the 95% confidence intervals of the actual field observations. In many cases, the simulation results were within the 95% confidence intervals, and especially during the growing season, they indicated trends similar to those seen in the field data. However, there were ...


Narrow-Winged Seeder Points Reduce Water Erosion And Maintain Crop Yields, Kevin Bligh Jan 1991

Narrow-Winged Seeder Points Reduce Water Erosion And Maintain Crop Yields, Kevin Bligh

Journal of the Department of Agriculture, Western Australia, Series 4

Sowing crops without loosening the topsoil by tillage reduces water erosion. It can increase infiltration of rainfall into loamy soils, thereby reducing runoff and increasing potential crop yields. Crop yields were maintained after I1 seasons of seeding an Avon Valley loam near Beverley with minimum and no-tillage seeding operations. Infiltration increased significantly from 80 per cent of the 1983 growing-season rainfall under the traditional three tillage operations, to 87per cent under a single tillage operation using a combine seed drill. Infiltration increased further to 96 per cent under a no-tillage system using a triple^lisc drill. At Gnowangerup, 80 per ...


Identification Of Tetragonal And Cubic Structures Of Zirconia Using Synchrotron X-Radiation Source, Ram Srinivasan, Robert J. De Angelis, Gene Ice, Burtron H. Davis Jan 1991

Identification Of Tetragonal And Cubic Structures Of Zirconia Using Synchrotron X-Radiation Source, Ram Srinivasan, Robert J. De Angelis, Gene Ice, Burtron H. Davis

Mechanical & Materials Engineering Faculty Publications

X-ray diffraction from a synchrotron source was employed in an attempt to identify the crystal structures in zirconia ceramics produced by the sol-gel method. The particles of chemically precipitated zirconia, after calcination below 600 °C, are very fine, and have a diffracting particle size in the range of 7-15 nm. As the tetragonal and cubic structures of zirconia have similar lattice parameters, it is difficult to distinguish between the two. The tetragonal structure can be identified only by the characteristic splittings of the Bragg profiles from the "c" index planes. However, these split Bragg peaks from the tetragonal phase in ...


Numerical Modeling Of Flame Lift-Off Phenomenon And Calculation Of Thermal Loads On A Methane Fuel Injector With Complex Geometry, Taj O. Mohieldin Jan 1991

Numerical Modeling Of Flame Lift-Off Phenomenon And Calculation Of Thermal Loads On A Methane Fuel Injector With Complex Geometry, Taj O. Mohieldin

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study has been conducted to analyze a fuel injector with three in-line cylinder geometry that has been adopted as a model for investigating the combustion phenomenon in the 8-Foot High Temperature Tunnel (HTT) combustor at the NASA Langley Research Center. The primary objective here is to analyze the flame lift-off phenomenon in the three cylinder fuel injector geometry in two-dimensions. The fluid mechanics model used in the analysis includes time-averaged Navier-Stokes equations that are employed in conjunction with a two-equation k-$\epsilon$ model for predicting the effects of turbulence. Calculations were performed with three chemistry models, namely fast ...


Micromechanics Of Granular Materials And Its Relation To Wave Velocity, Tarun K. Agarwal Jan 1991

Micromechanics Of Granular Materials And Its Relation To Wave Velocity, Tarun K. Agarwal

Civil & Environmental Engineering Theses & Dissertations

The macro characters of the granular materials depend upon micromechanical parameters such as the void ratio, particle shape, contact force distribution, and initial state of the fabric of the assembly. Since it is difficult to evaluate these internal parameters from laboratory experiments, a macro measure is desired which depends directly on these internal parameters. One such measure has been shown to be dynamic shear modulus but it was incomplete in predicting directional changes in the internal parameters. Therefore, it is hypothesized here that the complete elastic moduli matrix will have more direct information about the internal parameters, especially the dynamic ...