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Mechanical Engineering Commons

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1993

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Articles 301 - 329 of 329

Full-Text Articles in Mechanical Engineering

Carbon In Fly Ash Analysis Using Photoacoustic Spectroscopy , Jeffrey Raymond Dykstra Jan 1993

Carbon In Fly Ash Analysis Using Photoacoustic Spectroscopy , Jeffrey Raymond Dykstra

Retrospective Theses and Dissertations

Photoacoustic absorption spectroscopy (PAS) was investigated as a method for on-line monitoring of carbon in fly ash from coal-fired boilers. PAS is based on the periodic heating of a gas when amplitude-modulated radiation is absorbed by the gas or by particles suspended in the gas. This periodic heating produces an acoustical wave that can be detected by a microphone. Because the PAS signal is based solely on the absorption of radiation (by carbon) and not scattering of radiation (by mineral matter), it has the potential for distinguishing unburned carbon from mineral matter suspended in the flue gas. Two radiation sources ...


Application Of Displacement And Traction Boundary Integral Equations For Fracture Mechanics Analysis , Seungwon Youn Jan 1993

Application Of Displacement And Traction Boundary Integral Equations For Fracture Mechanics Analysis , Seungwon Youn

Retrospective Theses and Dissertations

A general formulation by dual boundary integral equations and a computational solution algorithm for the general mixed-mode crack in a linearly elastic, isotropic medium is presented. Traction boundary integral equations are collocated at the points on one crack surface while displacement boundary integral equations are collocated at the opposite points on the other surface to ensure a unique solution. The hypersingular and strongly singular integrals in the traction and displacement boundary integral equations are regularized before the numerical implementation. The singular integration elements on both crack surfaces are replaced by smooth curved auxiliary surfaces to avoid the direct integration over ...


Computation Of The Integrated Aerodynamic And Propulsive Flowfields Of A Generic Hypersonic Space Plane , Ganesh Wadawadigi Jan 1993

Computation Of The Integrated Aerodynamic And Propulsive Flowfields Of A Generic Hypersonic Space Plane , Ganesh Wadawadigi

Retrospective Theses and Dissertations

A new upwind, parabolized Navier-Stokes (PNS) code has been developed to compute two- and three-dimensional (3-D) chemically reacting, turbulent flows with hydrogen-air chemistry. The code is a modification of the 3-D upwind PNS (UPS) airflow code. The code solves the PNS equations using a finite-volume, upwind, TVD (Total Variation Diminishing) method based on Roe's approximate Riemann solver that has been modified to account for nonequilibrium effects. The fluid medium is assumed to be a chemically reacting mixture of thermally perfect (but calorically imperfect) gases in thermal equilibrium. Two turbulence models have been incorporated into the code including an algebraic ...


Study Of Melting And Freezing Processes Of Water For Application To Ice Thermal Energy Storage System , Liang Yong Jan 1993

Study Of Melting And Freezing Processes Of Water For Application To Ice Thermal Energy Storage System , Liang Yong

Retrospective Theses and Dissertations

This thesis presents the results of a study of the solid-liquid phase change process of water in a rectangular enclosure for application to thermal energy storage systems. The work performed combined experimental results with analytical and numerical methods to develop computer models of the system;Experiments were performed to obtain data to verify the models under various melting and freezing conditions. A connective heat transfer correlation, for melting of ice in a container confined by two horizontal plates, was obtained based on the experimental work. An analytical model based on heat conduction was developed to predict ice formation in an ...


Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng Jan 1993

Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng

Retrospective Theses and Dissertations

The objective of this research is to investigate sound scattering by an object using a two-surface measurement technique that separates the incident field and the scattered field. The separation technique is developed in cartesian and cylindrical coordinates. The decomposition method in the cartesian coordinate system is based on the principle that any wave form can be decomposed into plane-wave components by using a two dimensional spatial Fourier transform. For the cylindrical coordinate system, a two plane separation technique is based on decomposing the sound field into cylindrical waves. Numerical simulations are performed and the effect of various parameters are investigated ...


Alternative Technologies For Refrigeration And Air Conditioning Applications , Don Carlyle Gauger Jan 1993

Alternative Technologies For Refrigeration And Air Conditioning Applications , Don Carlyle Gauger

Retrospective Theses and Dissertations

A study was conducted to assess refrigeration technologies which are alternatives to vapor-compression for use in five application categories: domestic air conditioning, commercial air conditioning, mobile air conditioning, domestic refrigeration, and commercial refrigeration. A fundamental criteria for the selection of the alternative refrigeration technologies to be assessed was that they are environmentally safe;The study was conducted in three phases: a survey of U.S. patents, system modeling, and a technology assessment;Each refrigeration application was defined by a set of thermal source and sink temperatures. The U.S. patent survey was conducted from 1918 to the present. A method ...


Dimensional Verification And Correction Of Five-Axis Numerically Controlled Milling Tool Paths , Yun-Ching Huang Jan 1993

Dimensional Verification And Correction Of Five-Axis Numerically Controlled Milling Tool Paths , Yun-Ching Huang

Retrospective Theses and Dissertations

A system of algorithms is presented for material removal simulation, automatic dimensional verification and integrated error correction of numerically controlled (NC) milling tool paths. Several different approaches to these problems have been proposed including direct solid modeling, discrete vector intersection, and spatial partitioning. However, each of these methods suffer inherent restrictions that limit their practical application. This dissertation presents a discrete dexel NC verification algorithm based on a spatial partitioning technique (dexel representation) which incorporates the advantages of the discrete vector intersection approach. Hence, real-time animated five-axis milling simulation is supported by efficient regularized Boolean set operations, and dimensional milling ...


Numerical Simulation Of Two And Three-Dimensional Viscous Free Surface Flows In Partially-Filled Containers Using A Surface Capturing Approach , Franklyn Joseph Kelecy Jan 1993

Numerical Simulation Of Two And Three-Dimensional Viscous Free Surface Flows In Partially-Filled Containers Using A Surface Capturing Approach , Franklyn Joseph Kelecy

Retrospective Theses and Dissertations

A new surface capturing method is developed for numerically simulating viscous free surface flows in partially-filled containers. The method is based on the idea that the flow of two immiscible fluids (specifically, a liquid and a gas) within a closed container is governed by the equations of motion for a laminar, incompressible, viscous, nonhomogeneous (variable density) fluid. By computing the flowfields in both the liquid and gas regions in a consistent manner, the free surface can be captured as a discontinuity in the density field, thereby eliminating the need for special free surface tracking procedures;The numerical algorithm is developed ...


Using Sensitivity Derivatives Of Resonant Response To Guide Structural Redesign , Tsung-Hsiun Li Jan 1993

Using Sensitivity Derivatives Of Resonant Response To Guide Structural Redesign , Tsung-Hsiun Li

Retrospective Theses and Dissertations

Finite element-based optimization techniques have emerged as useful tools to control the vibration of a structural or mechanical system. Effective use of these techniques depends on sensitivity calculations. In this dissertation, the resonant frequencies and amplitudes at resonance of a vibrational system are identified as functions of design variables. Based on these features, the variation of resonant frequency is considered in the derivations of sensitivity equations of steady state resonant response;This dissertation presents several methods to compute the sensitivities of steady state resonant response of damped vibrational systems with respect to design parameters and to estimate the resonant frequencies ...


Acoustically Driven Integrated Microstrip Antennas And Electromagnetic Radiation From Piezoelectric Devices , Charles Forrest Campbell Jan 1993

Acoustically Driven Integrated Microstrip Antennas And Electromagnetic Radiation From Piezoelectric Devices , Charles Forrest Campbell

Retrospective Theses and Dissertations

For a receiver system to be considered integrated, the antenna and electronics need to be fabricated on a single semiconductor wafer. To avoid EMI problems, the circuitry must somehow be shielded from the environment where the antenna resides. The required shielding may be accomplished by separating the antenna on one side of the wafer from the electronics on the other side with a conducting ground plane. Energy may be acoustically coupled from the antenna to the circuitry through the ground plane via thin film piezoelectric transducers on either side of the wafer. The radiating side of the wafer would then ...


Tandem Application Of A Genetic Algorithm And Stochastic Quasigradient Method To The Optimization Of An Assembly System, Kraig Alan Downs Jan 1993

Tandem Application Of A Genetic Algorithm And Stochastic Quasigradient Method To The Optimization Of An Assembly System, Kraig Alan Downs

Retrospective Theses and Dissertations

No abstract provided.


The Aerodynamics Of A Baseline Supersonic Throughflow Fan Rotor , Daniel Lawrence Tweedt Jan 1993

The Aerodynamics Of A Baseline Supersonic Throughflow Fan Rotor , Daniel Lawrence Tweedt

Retrospective Theses and Dissertations

A baseline supersonic throughflow fan has been designed and tested at the NASA Lewis Research Center in order to demonstrate proof-of-concept and provide an experimental data base for this unique type of turbomachine. The aerodynamics of the rotor, which was tested in both an isolated and a stage configuration, is discussed in somewhat generic terms for conditions covering most of the practical operating range. Much detailed and quantitative information is also included. In addition to the experimental results, viscous computational fluid dynamics (CFD) results and simple analytical solutions are discussed, having been used extensively to understand and assess the aerodynamic ...


Interaction Of A Streamwise Vortical Flow With A Plate, Alejandro Mayori Jan 1993

Interaction Of A Streamwise Vortical Flow With A Plate, Alejandro Mayori

Theses and Dissertations

No abstract provided.


An Investigation Of Electrorheologial Material Adaptive Structures, David L. Don Jan 1993

An Investigation Of Electrorheologial Material Adaptive Structures, David L. Don

Theses and Dissertations

No abstract provided.


Effect Of Loading Rate On Thermodynamic Equilibrium Stress/Strain States Of Uniaxial Test Specimens, Chao-Hsin Wang Jan 1993

Effect Of Loading Rate On Thermodynamic Equilibrium Stress/Strain States Of Uniaxial Test Specimens, Chao-Hsin Wang

Theses and Dissertations

No abstract provided.


Experimental Investigation Of The Laminar Necklace Vortex System For A Rectangular Block-Flat Plate Junction, Charles V. Seal Jan 1993

Experimental Investigation Of The Laminar Necklace Vortex System For A Rectangular Block-Flat Plate Junction, Charles V. Seal

Theses and Dissertations

No abstract provided.


A Study Of Environmentally Enhanced Creep Crack Growth In Inconel 718 Alloy, Paul F. Valerio Jan 1993

A Study Of Environmentally Enhanced Creep Crack Growth In Inconel 718 Alloy, Paul F. Valerio

Theses and Dissertations

No abstract provided.


Transient Stress And Failure Analysis Of 105 Mm Gun Barrel Caused By Projectile Premature, Chi-Jui Huang Jan 1993

Transient Stress And Failure Analysis Of 105 Mm Gun Barrel Caused By Projectile Premature, Chi-Jui Huang

Theses and Dissertations

No abstract provided.


Assessment Of Bearing Load Alignment On Fracture Site In Dovetail Section Of Turbine Rotor, Bing-Tang Fan Jan 1993

Assessment Of Bearing Load Alignment On Fracture Site In Dovetail Section Of Turbine Rotor, Bing-Tang Fan

Theses and Dissertations

No abstract provided.


An Experimental Investigation Of Real-Time Product Quality Sensing During Molding Processes, Akihisa Kikuchi Jan 1993

An Experimental Investigation Of Real-Time Product Quality Sensing During Molding Processes, Akihisa Kikuchi

Theses and Dissertations

No abstract provided.


Determination Of Losses In The Beaver Valley And Hatfield Ferry Low Pressure Steam Turbine Exhaust Hoods And Their Modifications, Mark J. Pechulis Jan 1993

Determination Of Losses In The Beaver Valley And Hatfield Ferry Low Pressure Steam Turbine Exhaust Hoods And Their Modifications, Mark J. Pechulis

Theses and Dissertations

No abstract provided.


Analysis Of Stress Intensity Factors For An Edge Cracked T- Section In Tension, Michael L. Gentilcore Jan 1993

Analysis Of Stress Intensity Factors For An Edge Cracked T- Section In Tension, Michael L. Gentilcore

Theses and Dissertations

No abstract provided.


A Magnetic Suspension System With A Large Angular Range, Colin P. Britcher, Mehran Ghofrani Jan 1993

A Magnetic Suspension System With A Large Angular Range, Colin P. Britcher, Mehran Ghofrani

Mechanical & Aerospace Engineering Faculty Publications

In order to explore and develop technology required for the magnetic suspension of objects over large ranges of orientation, a small-scale laboratory system, the large-angle magnetic suspension test fixture (LAMSTF) has been constructed at NASA Langley Research Center. This apparatus falls into the category of large-gap, actively stabilized magnetic levitation systems. The hardware comprises five conventional electromagnets in a circular arrangement, each driven from a separate bipolar power amplifier. Electromagnet currents are commanded by a digital control system, implemented on a microcomputer, which in turn derives the position and attitude of the suspended element from an infrared optical system. The ...


Analytical Guidance Laws And Integrated Guidance/Autopilot For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery, J. H. Evers, J. R. Cloutier Jan 1993

Analytical Guidance Laws And Integrated Guidance/Autopilot For Homing Missiles, S. N. Balakrishnan, Donald T. Stansbery, J. H. Evers, J. R. Cloutier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An approach to integrated guidance/autopilot design is considered in this study. It consists of two parts: 1) recognizing the importance of polar coordinates to describe the end game in terms of problem description and measurement acquisition, the terminal guidance problem is formulated in terms of polar coordinates; 2a) through the use of the state transition matrix of the intercept dynamics, a closed form solution for the transverse command acceleration is obtained; and 2b) through a commonly used approximation on time-to-go and a coordinate transformation, a family of proportional navigation optimal guidance laws is obtained in a closed form. A ...


Dynamics Of Fish Assemblages Associated With An Offshore Artificial Reef In The Southern Mid-Atlantic Bight, Aaron J. Adams Jan 1993

Dynamics Of Fish Assemblages Associated With An Offshore Artificial Reef In The Southern Mid-Atlantic Bight, Aaron J. Adams

Dissertations, Theses, and Masters Projects

No abstract provided.


Soil Sampling Made Easier, Mike Bolland, Mike Baker Jan 1993

Soil Sampling Made Easier, Mike Bolland, Mike Baker

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

A new rotary blade soil sampler has taken the hard work out of collecting soil samples from Western Australia's hard-setting soils to test for soil phosphorus levels .

Conceived and developed by Department of Agriculture technical officer Mike Baker, it should enable soil testing to be more widely adopted. Fortunately, the soil calibration tests that were developed using pogo samples can also be used for the new sampler.


Interspecific And Intraspecific Variability In Placoid Scale Morphology In Relation To Body Form Variability In Squaliformes, Christopher R. Tabit Jan 1993

Interspecific And Intraspecific Variability In Placoid Scale Morphology In Relation To Body Form Variability In Squaliformes, Christopher R. Tabit

Dissertations, Theses, and Masters Projects

An ontogenetic series of nine species; Centrophorus granulosus, Centroscymnus coelolepis, Dalatias licha, Deania calcea, Echinorhinus cookei, Isistius brasiliensis, Oxynotus centrina and Squalus acanthias were studied to determine swimming capabilities, boundary-layer flow conditions and placoid scale functional morphologies. Body morphometric variables included the girth and the distance from snout to the orbitals, origin of the median and paired fins, and the caudal peduncle, body and fin surface area, fin aspect ratios and caudal fin angles. Placoid scales were sampled from sixteen regions across the body. Morphometric variables included the number of scales per area of integument, scale crown width, length and ...


Characterization Of Anti-Tumor Immunity In Oyster Toadfish (Opsanus Tau), And The Effects Of 7,12 -Dimethylbenz(A)Anthracene On This Immune Response, Kenneth R. Seeley Jan 1993

Characterization Of Anti-Tumor Immunity In Oyster Toadfish (Opsanus Tau), And The Effects Of 7,12 -Dimethylbenz(A)Anthracene On This Immune Response, Kenneth R. Seeley

Dissertations, Theses, and Masters Projects

Cell-mediated lysis of cultured tumor target cells by nonspecific cytotoxic cells (NCC) was examined in the oyster toadfish (Opsanus tau), an estuarine teleost. NCC activity was evaluated in cells taken from the head kidney, peripheral blood, spleen and peritoneal cavity. NCC activity was a property of plastic nonadherent cells which lacked phagocytic activity, indicating that in terms of their functional capacity, the cells which mediate nonspecific cytoxic immune responses in oyster toadfish do not appear to be monocytes or macrophages. However, light and electron microscopic examination of these cells revealed that morphologically, they resemble monocytes and macrophages. A new technique ...


Theoretical Results Supporting The Use Of Passive Damping As Augmentation To The Active Control Of Flexible Structures, Joseph Vincent Harrell Jan 1993

Theoretical Results Supporting The Use Of Passive Damping As Augmentation To The Active Control Of Flexible Structures, Joseph Vincent Harrell

Mechanical & Aerospace Engineering Theses & Dissertations

One challenge of modern control technology is how to control a flexible structure with accuracy, speed, and economy of effort. Controlling a structure with many degrees of freedom by purely active means implies the implementation of inordinate sensors and actuators and creates the need for numerous calculations that must be done instantly. Experiments have shown that practical structures under active control alone can suffer instabilities due to modal vibrations beyond the bandwidth of the active controller. Furthermore, if there is a high degree of model uncertainty, instabilities can be produced by inputs of modal vibrations not occurring in the system ...