WorldCat Identities


Works: 544 works in 563 publications in 1 language and 578 library holdings
Classifications: TA355, 620.3
Publication Timeline
Fundamental Hydrodynamics Research( Book )

4 editions published between 1989 and 1990 in English and held by 3 WorldCat member libraries worldwide

The hydrodynamics research conducted under this program falls into two basic thrust areas: Turbomachinery - To develop an improved understanding of the fluid mechanics and acoustics associated with low-speed turbomachines and marine propulsors. To employ this knowledge to the development of improved propulsor and turbomachine design methods. Drag Reduction -To develop fundamental understanding of the mechanisms that cause drag on bodies and surfaces and to explore novel methods to reduce drag. Under each thrust area, one or more projects are conducted under the direction of the principal investigator who initiated the given task. All tasks are designed to provide results that will improve the scientific understanding of various hydrodynamics phenomena associated with the operation of submerged bodies and surfaces. Keywords: Turbomachinery, Drag reduction, Microbubbles, Pressure gradients, Particle trajectories, Transition, Computational fluids, Unsteady flows, Turbulent flow, Three dimensional flow. (jhd)
Phase Comparison Time Delay Estimation Using Wideband Signals by John David Hatlestad( Book )

2 editions published between 1985 and 1986 in English and held by 2 WorldCat member libraries worldwide

A method of phase comparison time delay estimation using large time-bandwidth product signals is presented. This method compares the phases of the matched filters for each channel, and it is shown that for signals with symmetric power spectra, a meaningful estimate of the time delay can be expected from this phase information and knowledge of the carrier frequency of the signal. The estimator is evaluated while operating in white Gaussian noise which is in general correlated between channels, and curves are given for the density function, mean, and variance of the estimator for various noise assumptions. The estimator is shown to take advantage of the processing gain of large time-bandwidth product signals to reduce the variance of the time delay estimate. Keywords include: Phase comparison time dealy estimator; Matched filters; Large time-bandwidth; Symmetric power spectra; and White gaussian noise
On the radiated noise due to boundary-layer transition by G. C Lauchle( Book )

2 editions published between 1978 and 1979 in English and held by 2 WorldCat member libraries worldwide

A theory is presented for the noise radiated by incompressible boundary-layer transition that occurs on an infinite, rigid flat plate. It is hypothesized that it is the intermittency of the boundary-layer flow within the transition zone that is dominant in noise production. Using Lighthill's analogy, it is shown that dipole, quadrupole, and octupole sources are generated. The dipole sources are attributable to the shear stress fluctuations that occur in transitional flow while the others are due to fluctuating Reynolds stresses and their images. Under the assumption that dipole sources are more efficient than quadrupoles or octupoles when the Mach number is very small, the power spectrum of the radiated noise due to the dipole contribution is derived. The spectral level rises at 6 db/octave, peaks at a frequency corresponding to the time it takes for a turbulence burst to move through the transition region, and then drops off again at 6 dB/octave. The radiation efficiency is analyzed and found to be quite low; it is only 20 percent of that for a fully-developed turbulent boundary layer flow. (Author)
Influence of Process Parameters on Laser Weld Characteristics in Aluminum Alloys by Nagesh Sonti( Book )

1 edition published in 1988 in English and held by 2 WorldCat member libraries worldwide

Multi-kilowatt CO2 lasers are increasingly being used for welding applications due to their capability of producing deep penetration welds at high welding speeds. Although most metals are being successfully welded, laser welding of aluminum alloys is proving to be difficult. Combination of high thermal diffusivity and optical reflectivity to CO2 laser radiation causes difficulty in coupling the laser energy to the material. Much higher laser intensities are required to ensure coupling and to form the keyhole, than to maintain the keyhole and obtain smooth fusion, as absorption of laser energy improves dramatically with the keyhole formation. Laser welds in aluminum alloys contain extensive porosity, and excessive vaporization of alloying elements occurs from the fusion zone. The welds have severe undercuts and large discontinuous cavities on the bead surface. A more precise control of the weld heat input and a better understanding of the influence of process parameters and the alloying content on the weld characteristics is required to improve the laser weldability of aluminum alloys. Keywords: Aluminum alloy welding, Carbon Dioxide laser, Welding, Numerical modeling, Weld defects. (MJM)
Vibration isolation : use and characterization by John C Snowdon( Book )

3 editions published in 1979 in English and held by 2 WorldCat member libraries worldwide

The problem of isolating machinery vibration from rigid and nonrigid substructures is analyzed in detail. The nonrigid substructures are modeled by clamped-clamped beams and by simply supported plates with small internal damping of the solid type. Both simple and compound mounting systems are analyzed. The advantages that result from the use of the compound mounting system are clearly apparent. The loss in isolation is described that results when nonrigid flanges or feet support the simply mounted item or the intermediate mass of the compound mounting system. The use is also analyzed of dynamic vibration absorbers or lumped masses to load the beamlike and platelike substructures at each mount location. The item of machinery is supported either by eight or by four antivibration mounts that have small damping of the solid type. It is shown how the number of beam and plate resonances that are excited can be reduced by judicious placement of the antivibration mountings. (Author)
Correlations by the Entrainment Theory of Thermodynamic Effects for Developed Cavitation in Venturis and Comparisons with Ogive Data( Book )

1 edition published in 1975 in English and held by 2 WorldCat member libraries worldwide

A semi-empirical entrainment theory was employed to correlate the measured temperature depression, Delta T, in a developed cavity for a venturi. This theory correlates Delta t in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, Weber and Peclet, and dimensionless cavity length, L/D. These correlations are then compared with similar correlations for zero and quarter caliber ogives. In addition, cavitation number data for both limited and developed cavitation in venturis are presented. (Author)
A Wavelet Model for Vocalic Speech Coarticulation by Robert C Lange( Book )

1 edition published in 1994 in English and held by 2 WorldCat member libraries worldwide

A known aspect of human speech is that a vowel produced in isolation (for example, ee) is acoustically different from a production of the same vowel in the company of two consonants (deed). This phenomenon natural to the speech of any language, is known as consonant-vowel-consonant coarticulation. The effect of coarticulation results when a speech segment (d) dynamically influences the articulation of an adjacent segment (ee within deed). A recent development in the theory of wavelet signal processing is wavelet system characterization. In wavelet system theory, the wavelet transform is used to describe the time-frequency behavior of a transmission channel, by virtue of its ability to describe the time-frequency content of the system's input and output signals. The present research proposes a wavelet-system model for speech coarticulation: wherein, the system is the process of transformation from a control speech state (input) to an effected speech state (output). Specifically, a vowel produced in isolation is transformed into an effected version of the same vowel produced in consonant-vowel-consonant, via the coarticulation channel. Quantitatively, the channel is determined by the wavelet transform of the effected vowel's signal, using the control vowel's signal as the mother wavelet. A practical experiment is conducted to evaluate the coarticulation channel using samples of real speech. The results show that the model is capable of depicting coarticulation effects associated with certain vowel-consonant combinations. They suggest that elements of the vowel's acoustic composition are continuously present, in a modified form throughout the consonant-vowel transition. For other phonetic combinations. however, the model does not respond to instances of segmental transition in a characteristic way
Beamlike Dynamic Vibration Absorbers( Book )

2 editions published between 1977 and 1978 in English and held by 2 WorldCat member libraries worldwide

The performance of several beamlike dynamic vibration absorbers is analyzed and, in one case, confirmed by experiment. The dynamic absorbers are employed to suppress the transmissibility at resonance across a simple mass-spring vibrator, a stanchion, and a simply supported rectangular panel. The absorbers comprise either single or double cantilever beams that are mass loaded at their free ends, or clamped-clamped beams that are centrally mass loaded. Generally, the beams provide both the absorber stiffness and damping--although, once, the beams are considered to possess little damping, and supplemental viscous damping is introduced by dashpots that link the absorber masses to the vibrating primary system of concern. Graphical or tabular design information is specified for the absorbers in each situation considered. Analyses are based throughout on the Bernoulli-Euler beam and thin-plate theories without simplification. In several of the situations analyzed, transmissibility curves are calculated to emphasize that the beamlike absorbers are broadly effective. (Author)
Dynamic Vibration Absorbers of Conventional and Novel Design by Matthew Anthony Nobile( Book )

1 edition published in 1975 in English and held by 2 WorldCat member libraries worldwide

The behavior of dynamic vibration absorbers of conventional and novel design has been investigated experimentally. Transmissibility and relative displacement measurements have been obtained for absorbers attached to a one-degree-of-freedom primary system, and the resultant data have been compared with the predictions of existing theories. The absorbers tested ranged from those possessing a conventional mass-spring-dashpot configuration, to those possessing novel configurations. In all cases, the experimental results were in close agreement with theoretical predictions. The novel configurations included (1) an absorber employing a viscoelastic (Butyl rubber) material as a combined spring-and-damper element, (2) absorbers employing damped laminated beams as spring-and-damper elements, (3) so-called 'dual dynamic abosrbers' -- a conventional, viscously damped absorber in parallel with a less massive undamped absorber, and (4) a single nominally undamped absorber or a pair of nominally undamped absorbers attached to a heavily damped primary system
Finite Element Modelling of Large Plastic Strains in a Rolling Contact Metal Forming Process by Shirish N Kher( Book )

1 edition published in 1987 in English and held by 2 WorldCat member libraries worldwide

A numerical model to simulate the deformations in gear teeth subjected to rolling loads an in the ausrolling process has been developed. Ausrolling involves applying rolling loads to the gear when it is in the metastable austenitic state. A model of the process must consider material, geometric and surface non-linearities as well as changes in temperature and material properties with time and rolling loads in three dimensions. Only some of these requirements, namely, the elastic-plastic flow; geometric non-linearities due to large deformations; frictional contact conditions at die-workpiece interface; and the travelling loads due to rolling, have been considered here to be of primary importance. The objective of this thesis is, accordingly, to satisfactorily establish the forementioned features in the nonlinear finite element analysis program (NOFEAP). The theoretical aspects of the non-linear formulations have been briefly described and the model of the rolling process has been outlined here. The implemented non-linear formulations have been briefly compared, individually and in various combinations, with existing analytical, numerical and experimental solutions. Since no such results are available in the literature to compare the response of the rolling model, several experiments have been conducted on aluminum 6061 disks. Keywords: Ausrolling, Numerical modelling, Finite element analysis, Plastic strain
Isolation and Absorption of Machinery Vibration by John C Snowdon( Book )

1 edition published in 1976 in English and held by 2 WorldCat member libraries worldwide

The isolation of machinery vibration from rigid and nonrigid substructures is described in uncomplicated terms. One- and two-stage mounting systems, single and multiple antivibration mountings, and beamlike and platelike substructures are examined. A machine and the intermediate mass of a two-stage mounting system are considered to be supported by flanges or feet to demonstrate the loss in isolation that can occur if the flanges are not rigid but are multiresonant because of their poor design. The use of conventional dynamic absorbers to reduce the vibration of such structural members as beams (rails and stanchions) and circular plates (bulkheads) is discussed. A novel dynamic vibration absorber is described that comprises a damped circular plate loaded centrally by a lumped mass and clamped at its perimeter to the vibrating item or structure of concern. (Author)
Thermo-Mechanical Fatigue of Polymer Matrix Composites by Larry H Strait( Book )

1 edition published in 1994 in English and held by 2 WorldCat member libraries worldwide

Thermo-mechanical fatigue occurs when a component is exposed to thermal cycling under mechanical constraint and or superimposed mechanical loading. Thermo-mechanical loading is an increasingly common service condition for polymer matrix composite materials. Unfortunately, little or no information is available regarding the behavior of polymer composites subject to this loading condition. The present thesis research program was undertaken to evaluate the effects of mechanical constraint on the response of polymer matrix composites during thermal cycling. Analytical and experimental techniques were used to characterize the response of carbon fiber reinforced cyanate ester (IM6/ BT3008) and bismaleimide (IM7/5240-4) composites. Cross-ply laminates were subjected to thermal cycles from 24 to 177 deg C in the unconstrained, fully- constrained and over-constrained conditions. Laminate response, damage mechanisms and residual compressive properties were characterized for each material and degree of constraint. Predicted ply stress distributions are significantly different for the various degrees of constraint and are highly sensitive to temperature-dependent lamina properties and laminate stress free temperature. Predictions of laminate response correlate well with experimental results. Deviations are apparent at elevated temperature which are attributed to the effects of time-dependent deformation
Acoustic Radiation from Line- and Point-Loaded Plates: Uniformly Asymptotic Solutions by Xunyou Xu( Book )

1 edition published in 1987 in English and held by 2 WorldCat member libraries worldwide

The theoretical analysis for predicting the acoustic radiation from an infinite fluid-loaded elastic plate excited by a line or a point force is presented. The acoustic pressure radiated by this coupled plate-fluid system is obtained by the use of the Fourier transform method for line force excitation and a Hankel transform for point force excitation. The integral representation of the radiated acoustic pressure is evaluated by three methods based on the steepest descent path (SDP). The first is the widely used saddle point method which can only lead to the farfield solution, The first-order approximation due to the contribution at the saddle point is obtained with the assumption that all the poles of the integrand are located far away from the saddle point and SDP. However the leaky wave pole may approach the saddle point when the frequency is above the coincidence frequency. Thus the saddle point method is modified such that all the singularities of the integrand are explicitly isolated regardless of their proximity to the saddle point. Keywords: Acoustic pressure, Asymptotic series, Saddle point method, Structural damping, Fluid loaded plate, Timoshenko Mindlin theory
Air Pollution Control System Research: An Iterative Approach to Developing Affordable Systems( Book )

2 editions published in 1993 in English and held by 1 WorldCat member library worldwide

The research will be accomplished on lab scale, pilot scale, and production air pollution control systems (APCS). The production system, to be installed at Marine Corps Logistics Base (MCLB) Barstow, CA, will treat the exhaust from three paint booths which will be modified to recirculate a large percentage of their exhaust. These recirculation systems are, themselves, a critical element in the overall R & D effort. The goal of the program is to conduct an R & D effort which will improve and demonstrate a combination of technologies intended to make VOC treatment both effective and affordable. The U.S. Marine Corps, the other services and industry will each benefit
A Kalman Filtering Approach to Wideband Scattering Function Estimation and Updating( Book )

2 editions published in 1999 in English and held by 1 WorldCat member library worldwide

Transmitted signals with high time bandwidth products tend to resolve multiple reflecting structural elements or highlights on the body that is being illuminated. This thesis develops a Kalman filtering approach to estimating the position and velocity of the multiple highlights on a single body undergoing complex motions. First, a general Kalman filter for direct recursive estimation of the spreading function is derived. Second, an algorithm which tracks peak locations within the spreading function is derived via an extended or linearized Kalman filter. The ability of the Kalman filter to track kinematic properties of a multihighlight scatterer is related to the transmitted signal's mean squared bandwidth, mean squared duration, and time-frequency content through the Cramer-Rao lower bound on estimation errors for time scale and time delay. It is shown that the ability of the Kalman filter to track peak locations within the object scattering function and recursively update these peak locations depends strongly on the use of signals with high time-bandwidth products. Finally, a performance monitor which provides a sound, monitorable performance measure of the tracker is introduced via the innovations spectrum. This performance monitor admits the ability of dynamic model updating for adaptive signal processing. This work sets a groundwork for further research into the application areas of image feature tracking, robotic vision, high resolution radar and sonar, and medical imaging
Development of a dual-beam sweep particle image velocimeter using an extended search region algorithm by Gregory A Meyer( Book )

2 editions published in 1998 in English and held by 1 WorldCat member library worldwide

Particle image velocimetry (PIV) is a two-step fluid velocimetry technique which is able to capture 2-D qualitative as well as quantitative velocity information at many points instantaneously with respect to the relevant time scales of the flow field. A pulsing laser light sheet is used in conjunction with an image recording device to record images of fluid embedded particles on one multi-exposed image frame or on successive individual image frames separated by time At. Utilizing 2-D statistical techniques on numerous small regions within the image frame, the average particle displacement, hence the average velocity, within each region is determine. A dual-beam-sweep PIV system, DBS-PIV, utilizing two continuous-beam Argon-ion lasers, was constructed primarily from existing components to avoid the need to fabricate or purchase major parts. Dual-beam-sweep PIV was chosen because of its use of available continuous-beam lasers and its ability to resolve moderately high velocity flow fields
Air Treatment Project: Final Summary Report and Bibliography( Book )

2 editions published in 1996 in English and held by 1 WorldCat member library worldwide

This Summary Report describes the results of more than two years of research conducted with funding provided by SERDP, the Marine Corps Logistic Bases (MCLB) and the Navy Department's LINC (Repair Technology) Program. The research focused on the destruction of VOCs in paint booth exhaust using hybrid air pollution control technologies. The hybrid system selected included three principle modules: UV photochemical destruction; counter-flow packed bed scrubbing using activated oxygen; and granular activation of carbon adsorption with subsequent oxidative regeneration of the carbon. The stated goals of the research included enhanced understanding of this set of technologies to support design of smaller, more affordable treatment system for both DoD and commercial application
Performance Measurements on a Thermoacoustic Refrigerator Driven at High Amplitudes( Book )

2 editions published in 1998 in English and held by 1 WorldCat member library worldwide

Since the power density in a thermoacoustic device is proportional to the square of the acoustic Mach number, there is strong motivation to design thermoacoustic refrigerators to operate at larger pressure amplitudes. Measurements are reported of a modified version of the Space Thermoacoustic Refrigerator (STAR), driven at pressure amplitudes up to 6%. This pressure ratio corresponds to 30 W of cooling power -- five times as large as reported in 1993. The results of these measurements are compared to a DELTAE computer model of the low amplitude (linear) performance that matches experimental conditions on a point-by-point basis. It is found that there is a small but measurable deviation in heat pumping power from the power predicted with a linear acoustic computer model. This deviation in heat pumping power at 6% pressure ratio is about 15%. A large, amplitude independent disagreement in the acoustic power needed to attain a specific pressure ratio is found between measured data and DELTAE results. An overview of the instrumentation, including a measurement of exhaust heat with an absolute accuracy of 65 mW, is also presented
The high reynolds number flow through an axial-flow pump : geometry and data files by W. A Straka( )

2 editions published between 1993 and 1996 in English and held by 0 WorldCat member libraries worldwide

The high Reynolds number pump (HIREP) facility at ARL Penn State has been used to perform a low-speed, large-scale experiment of the incompressible flow of water through a two-blade-row turbomachine. HIREP can involve blade chord Reynolds numbers as high as 6,000,000 and can accommodate a variety of instrumentation in both a stationary and a rotating frame of reference. The objectives of this experiment were to provide a database for comparison with three-dimensional, viscous (turbulent) flow computations, to evaluate the engineering models, and to improve our physical understanding of many of the phenomena involved in this complex flow field. The experimental results include a large quantity of data acquired throughout HIREP. A five-hole probe survey of the inlet flow 37.0% chord upstream of the inlet guide vane (IGV) leading edge is sufficient to give information for the inflow boundary conditions, while some static-pressure information is available to help establish an outflow boundary condition
High Frequency Acoustics and Signal Processing for Weapons( )

2 editions published between 2001 and 2005 in English and held by 0 WorldCat member libraries worldwide

Determine, for a broad range of frequencies (nominally 10-100 kHz), the limitations imposed by the oceanic environment on the exploitation of coherent signal structure. This understanding is required in order to optimize sonar signal processing structures (e.g. channel conditioning, especially in shallow water), for wideband signal and processor design, and for acoustic propagation modeling. Develop the capability to predict the dynamic and spatial characteristics of wakes and the acoustic field behavior in and around the wakes of Navy warships. Seek a predictive capability for how acoustic propagation varies with frequency, source receiver geometry relative to the wake, and the spatial statistics of attenuation and scattering strength in the wake
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