It has been observed, in earlier computations of bifurcation diagrams for dissipative partial differential equations, that the use of certain explicit approximate inertial forms can give rise to numerical artifacts su...
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The response of transport measures (Nusselt number, drag and lift force) for two- and three-dimensional flow past a heated cylinder reaching a chaotic state is investigated numerically using a spectral element discret...
The response of transport measures (Nusselt number, drag and lift force) for two- and three-dimensional flow past a heated cylinder reaching a chaotic state is investigated numerically using a spectral element discretization at a Reynolds number Re = 500. The undisturbed two-dimensional flow remains periodic at this Reynolds number, unless a suitable forcing is applied on the naturally produced system. Three-dimensional simulations establish that three-dimensionality sets in at Re almost-equal-to 200. Successive supercritical states are established through a series of period-doublings, before a chaotic state is reached at a Re almost-equal-to 500. For the two-dimensional forced flow, all transport measures oscillate aperiodically in time and undergo a "crisis," i.e., a sudden and dramatic increase in their amplitude. The corresponding three-dimensional, naturally produced chaotic state corresponds to a less drastic change of the transport quantities with both rms and mean values lower than their two-dimensional counterparts.
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SKOLNICK, DHSKOLNICK, ADavid H. Skolnickhas practiced naval engineering in both government and industry. He has supported the Military Sealift Command and the Naval Sea Systems Command Ship Design Group and Amphibious Ship Acquisition Program Office
participating in the design and assessment of ship structure evaluation of intact and damaged stability and arrangements during design and construction phases of acquisition conversion and overhaul. He is currently involved in systems engineering and integration. Recent responsibilities have included requirements analyses and feasibility studies interface analyses and computer aided analyses. He received his B.S. in naval architecture and marine engineering from Webb Institute of Naval Architecture in 1982 (as an ASNE scholar) and is currently an M.S. candidate in systems engineering at the University of Virginia. Alfred Skolnickserved over 30 years as an engineering duty officer and retired from the Navy with the rank of captain in 1983. His early assignments included tactical missile engineering
shipboard duty and Polaris submarine inertial navigation. He later served in the Deep Submergence Systems Project was project director
surface effect ships (SES) David Taylor Model Basin director of technology
Joint Navy-Commerce SES Program director
combat systems Naval Sea Systems Command and project manager directed energy weapons. His awards include the Navy League's Parsons Award in 1979 for scientific and technical progress ASNE's Gold Medal in 1981 for high energy laser development the Navy Legion of Merit in 1983 National Capital Engineer of the Year in 1986 and the American Defense Preparedness Association Gold Medal in 1988 for contributions to strategic defense. He was president of ASNE from 1985–1989. He received his B.S. in mathematics from Queens College his M.A. in mathematics from Columbia University his M.S. in electrical engineering from U.S. Naval Postgraduate School and his Ph.D. in electrical engineering/applied mathematics from Polytechnic University. He w
Changing threat requirements and radical budget shifts imply that Navy operational needs will broaden and engineering solutions will face tougher constraints. Existing and emerging technology promise increased combat ...
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Changing threat requirements and radical budget shifts imply that Navy operational needs will broaden and engineering solutions will face tougher constraints. Existing and emerging technology promise increased combat capability in smaller packages;space-based assets will allow operator orchestration of widely dispersed naval units via connectivity attributes previously unavailable. Tactical data relay by downlink may permit reallocation of responsibilities among several platforms, space, air, or seaborne, so ships can be outfitted for custom-use (sensing, unique data processing, high-firepower) and optimized to meet specific mission needs. These evolving capabilities demand a fresh look at ship concepts and prospective force structures consistent with global and fiscal realities. Warfighting performance formerly unknown in small ship design may offer a very effective solution to the intricate, interacting issues of falling defense budgets, diverse operational requirements and complex national priorities. Multimission ships which take advantage of new or current technology to reduce ship size, manning and cost could be affordable in sufficient numbers to meet our continuing worldwide obligations, complement our larger ships' force structure, and produce a balanced fleet. These same ships could satisfy U.S. maritime needs beyond the Navy and improve export trade through foreign military sales (FMS).
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YEARSLEY, ENCROWDER, REIRONS, LAElliot N. Yearsley is a geological engineer and log analyst for Colog Inc. (Borehole Geophysical Services
1019 Eighth St. Golden CO 80401). He received his B.Sc. in geological engineering from the Colorado School of Mines (CSM) in 1981 later returning to CSM to earn a M.Sc. in engineering mechanics in 1989. Between degrees Yearsley was employed as a geological engineer for Tenneco Oil Co. where he pioneered the use of measurement while drilling (MWD) formation evaluation. He is currently working on new borehole geophysical techniques applied to geotechnical and hydrogeological investigations including monitoring well completion evaluation and full waveform acoustic analysis applied to permeability determinations. Robert E. Crowder is president of Colog Inc. (Borehole Geophysical Services
1019 Eighth St. Golden CO 80401) and has 12 years of diversified experience in borehole geophysical applications including environmental geotechnical and mineral investigations. Prior to forming Colog he was operations manager for Colorado Well Logging for eight years. He has taught numerous courses for client groups in borehole geophysical logging and log interpretation both domestic and international. He received his degree in engineering geophysics from Colorado School of Mines in 1978. Larry A. Irons is a senior associate geophysicist at Ebasco Environmental Services (143 Union Blvd.
Ste. 1010 Lakewood CO 80228). He graduated from the University of Nebraska in 1977 with a B.Sc. in geology. During 1977–79 he conducted research for the Antarctic Research Program of the University of Nebraska earning an M.Sc. in geology with a mathematics minor. During 1979–86 Irons worked as an exploration geophysicist for several major oil companies. He is currently conducting remedial investigations of hazardous waste sites using borehole magnetic gravity electromagnetic and seismic geophysical methods.
Grout continuity and the location of the bentonite seal and sand pack in PVC-cased monitoring wells can be evaluated with cased-hole geophysical density logs. This method relies upon density contrasts among various co...
Grout continuity and the location of the bentonite seal and sand pack in PVC-cased monitoring wells can be evaluated with cased-hole geophysical density logs. This method relies upon density contrasts among various completion conditions and annular materials. Notably, the lack of annular material behind pipe (i.e., void space) creates a low-density zone that is readily detected by borehole density measurements. Acoustic cement bond logging has typically been applied to the evaluation of cement in the annular space of completed oil and gas production wells, and in some cases to ground water monitoring wells. These logs, however, can only be obtained in the fluid-filled portion of the borehole, and their interpretation is severely hindered by the presence of the micro-annulus between casing and cement. The influence of the micro-annulus on cement bond logs can be mitigated in steel-cased wells by pressurizing the wellbore during acquisition of the log, but this procedure is not feasible in PVC-cased monitoring wells. The micro-annulus does not affect cased-hole density logs or their interpretation. Empirical measurements made in the laboratory with density probes provide information on their depths of investigation and response to specific completion conditions. These empirical data, and general knowledge of the density of annular completion materials (sand, bentonite, cement), are used to support interpretations of cased-hole density logs acquired in the field. Three field examples demonstrate the applicability of geophysical density logs to the evaluation of PVC-cased monitoring well completions.
We present a fast numerical method for solving the incompressible Euler's equation in two dimensions for the special case when the flow field can be represented by patches of constant vorticity. The method is an a...
We present a fast numerical method for solving the incompressible Euler's equation in two dimensions for the special case when the flow field can be represented by patches of constant vorticity. The method is an adaptive vortex method in which cells (vortex blobs) of multiple scales are used to represent the patches so that the number of vortex blobs needed to approximate the patches is proportional to the length of the boundary curve of the patch and inversely proportional to the width of the smallest blob (cell) used. Points along the boundaries of the patches are advected according to the velocity obtained from the approximating vortices.
We describe a new approach to the Monte-Carlo simulations of two-dimensional gravity. Standard dynamical triangulation technique was combined with results of direct enumeration of the cubic graphs. As a result we were...
We describe a new approach to the Monte-Carlo simulations of two-dimensional gravity. Standard dynamical triangulation technique was combined with results of direct enumeration of the cubic graphs. As a result we were able to build large (128K vertices) statistically independent random graphs directly. The quantitative correspondence between our results and those obtained by standard methods has been observed. The algorithm proved to be so efficient that we were able to conduct all the simulations, which usually require the most powerful computers, on an Iris workstation. An opportunity to generate large random graphs allowed us to observe that the internal geometry of random surfaces is more complicated than simple fractals. External geometry also proved to be rather peculiar.
A three‐dimensional computational simulator of nonplanar substrates coated with positive photoresists is presented. The model includes four major steps: projection printing, exposure, post‐exposure baking (PEB), and...
A three‐dimensional computational simulator of nonplanar substrates coated with positive photoresists is presented. The model includes four major steps: projection printing, exposure, post‐exposure baking (PEB), and dissolution. Projection printing is based on Hopkins’ classical work. The exposure model employs the full nonlinear wave equation coupled with the photoactive compound (PAC) bleaching rate equation. These equations are solved using a spectral element iterative scheme. The PEB is treated as a material diffusion equation employing ideas introduced by Mack and the dissolution algorithm is our LEAD (least action dissolution) algorithm modified for nonplanar substrates. Several realistic examples are presented displaying final profiles at various dissolution times.
We report first results of a large-scale simulation of two-dimensional quantum gravity using the dynamical triangulation model for systems of up to sixteen thousand triangles. Our results for the internal geometry sho...
We report first results of a large-scale simulation of two-dimensional quantum gravity using the dynamical triangulation model for systems of up to sixteen thousand triangles. Our results for the internal geometry show an unexpectedly complicated behavior of the internal volume as function of the internal radius. A simple fractal characterization is inadequate to describe the geometry of the states in the system.
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