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911.
C. C. Kuranz H.-S. Park B. A. Remington R. P. Drake A. R. Miles H. F. Robey J. D. Kilkenny C. J. Keane D. H. Kalantar C. M. Huntington C. M. Krauland E. C. Harding M. J. Grosskopf D. C. Marion F. W. Doss E. Myra B. Maddox B. Young J. L. Kline G. Kyrala T. Plewa J. C. Wheeler W. D. Arnett R. J. Wallace E. Giraldez A. Nikroo 《Astrophysics and Space Science》2011,336(1):207-211
The National Ignition Facility (NIF) is capable of creating new and novel high-energy-density (HED) systems relevant to astrophysics. Specifically, a system could be created that studies the effects of a radiative shock on a hydrodynamically unstable interface. These dynamics would be relevant to the early evolution after a core-collapse supernova of a red supergiant star. Prior to NIF, no HED facility had enough energy to perform this kind of experiment. The experimental target will include a 340 ??m predominantly plastic ablator followed by a low-density SiO2 foam. The interface will have a specific, machined pattern that will seed hydrodynamic instabilities. The growth of the instabilities in a radiation-dominated environment will be observed. This experiment requires a ??300?eV hohlraum drive and will be diagnosed using point projection pinhole radiography, which have both been recently demonstrated on NIF. 相似文献
912.
913.
Jeffrey Park Craig R. Lindberg David J. Thomson 《Geophysical Journal International》1987,91(3):755-794
We present a new method for estimating the frequencies of the Earth's free oscillations. This method is an extension of the techniques of Thomson (1982) for finding the harmonic components of a time series. Optimal tapers for reducing the spectral leakage of decaying sinusoids immersed in white noise are derived. Multiplying the data by the best K tapers creates K time series. A decaying sinusoid model is fit to the K time series by a least squares procedure. A statistical F -test is performed to test the fit of the decaying sinusoid model, and thus determine the probability that there are coherent oscillations in the data. The F -test is performed at a number of chosen frequencies, producing a measure of the certainty that there is a decaying sinusoid at each frequency. We compare this method with the conventional technique employing a discrete Fourier transform of a cosine-tapered time-series. The multiple-taper method is found to be a more sensitive detector of decaying sinusoids in a time series contaminated by white noise. 相似文献
914.
This paper presents the feasibility of using an impedance‐based health monitoring technique in monitoring a critical civil facility. The objective of this research is to utilize the capability of the impedance method in identifying structural damage in those areas where a very quick condition monitoring is urgently needed, such as in a post‐earthquake analysis of a pipeline system. The basic principle behind this technique is to utilize high‐frequency structural excitation (typically greater than 30 kHz) through surface‐bonded piezoelectric sensors/actuators to detect changes in structural point impedance due to the presence of damage. Real‐time damage detection in pipes connected by bolted joints was investigated, and the capability of the impedance method in tracking and monitoring the integrity of the typical civil facility has been demonstrated. Data collected from the tests illustrates the capability of this technology to detect imminent damage under normal operating conditions and immediately after a natural disaster. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
915.
916.
917.
Dae Choul Kim Gwang Hoon Lee Young Kyo Seo Gil Young Kim Seok Yun Kim Jeong Chang Kim Soo Chul Park Roy Wilkens 《Marine Georesources & Geotechnology》2004,22(1):21-31
Shallow gas in the Korea Strait shelf mud (KSSM) off SE Korea, revealed by high-resolution subbottom profiles, is associated with acoustic blanking, acoustic turbidity, seepages with plumes in the water column, and seafloor depressions. The acoustic blanking, characterized by strong, consistent top reflection and wipeout below, is most dominant. The seaward edge of the acoustic blanking zone generally coincides with the 100-m water-depth contour, suggesting that the water depth (the pressure) may control the distribution of shallow gas. The acoustic turbidity, characterized by diffuse top reflection, is a dark smear, partially blanking the data below. The seepages with plumes, characterized by vertical smearing and disturbed seafloor, are seen only along the shallowest, landward edge of the acoustic blanking zone. This may suggest that the decreased gas solubility at shallow water depths, caused by the lowered pressure, increases the volume of free gas in the sediments, facilitating the gas escape. The seafloor depressions, interpreted as pockmarks, are accompanied by cone-shaped acoustic masking, which is probably the reflection from a narrow vent of gas. The gas-related acoustic anomalies appear to occur mostly in the upper, recent mud of the KSSM. Neither permeable beds nor faults, which can act as vertical migration pathways for deep thermogenic gas, are evident in the recent mud. We interpret that the bacterial degradation of organic matter in situ is the main source for the gas in the KSSM. The upwelling off SE Korea may be an important source for the increased organic matter in the area. 相似文献
918.
Thermal and haline fronts in the Yellow/East China Seas: Surface and subsurface seasonality comparison 总被引:1,自引:0,他引:1
Seasonal variability of surface and subsurface thermal/haline fronts in the Yellow/East China Seas (YES) has been investigated
using three-dimensional monthly-mean temperature and salinity data from U.S. Navy’s Generalized Digital Environmental Model
(Version 3.0). The density-compensated Cheju-Yangtze Thermal/Haline Front has (northern and southern) double-tongues. The
northern tongue is most evident throughout the depth from December to April. The southern tongue is persistent at the subsurface
with conspicuous haline fronts. The thermal (haline) frontal intensity of the northern tongue is controlled mainly by the
temperature (salinity) variation on the shoreward (seaward) side of the front. The cold water over the Yangtze Bank is influential
in generating the southern tongue and intensifying the Tsushima Thermal Front. The year-round Cheju-Tsushima Thermal Front
is evident throughout the depth and intensifies from July to December. The northern arc of the Yangtze Ring Haline Front is
manifest in spring and is sustained until summer, whereas the southern one is fully developed in summer because of eastward
migration of the Yangtze Diluted Water. The area showing strong frontal intensity in the Chinese Coastal Haline Front shifts
seasonally north and south along the Zhejiang-Fujian coast. The Generation and evolution of YES fronts are closely associated
with YES circulation (inferred from the linkage of the water masses). Moreover, the subsurface temperature/salinity evolution
on the fronts in the Yellow Sea differs from that in the East China Sea owing to local factors such as wintertime vertical
mixing and a summertime strong thermocline above the Yellow Sea Bottom Cold Water. 相似文献
919.
Jinhae Bay, a semi-enclosed, tide-dominated coastal embayment on the southeastern coast of Korea, receives large amounts of sediment derived from the Nakdong River. The irregular surface of the acoustic basement is overlain by a modern sedimentary sequence up to 25 m thick, characterized by an acoustically semitransparent subbottom. Sediments, consisting mainly of terrigenous and bioturbated mud, accumulate at a rate of 2–5 mm/yr. About 21% of the suspended sediments discharged from the Nakdong River, that is approximately 1.0 × 106 tons per year, accumulate in Jinhae Bay. Modern sedimentation began probably at about 5000 yr BP, when sea level approached its present level. 相似文献
920.
Three-dimensional hydrodynamic-eutrophication model (HEM-3D): application to Kwang-Yang Bay, Korea 总被引:9,自引:0,他引:9
The purpose of this paper is twofold: to describe the water quality model of Three-Dimensional Hydrodynamic-Eutrophication Model (HEM-3D) and to present an application of HEM-3D to a coastal system in Korea. HEM-3D, listed as a tool for the development of Total Maximum Daily Load by US Environmental Protection Agency, is a general-purpose modeling package for simulation of the flow field, transport, and eutrophication processes throughout the water column and of diagenetic processes in the benthic sediment. This paper describes the water quality model of HEM-3D with emphasis on its unique features. Excessive loadings of organic wastes have significantly deteriorated water quality conditions of Korean coastal waters. This paper presents an application of HEM-3D to Kwang-Yang Bay, a coastal system in Korea, which is one of the first water quality modeling efforts for Korean coastal waters accompanied by a relatively comprehensive field program. The current status of data availability for water quality modeling in Korea is discussed. 相似文献