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111.
An eigenfunction solution is presented for the dynamic response of vertical circular cylinders to earthquake excitation in a compressible fluid of finite depth. This single eigenseries expansion eliminates the need for a double summation over both the eigenfunctions and the trial functions as required by Rayleigh-Ritz methods. Revised definitions for the added mass and hydrodynamic radiation damping coefficients per unit length are derived from the hydrodynamic fluid pressures. Based on comparisons between these newly defined coefficients, the compressibility of the fluid is found to be relatively more important at dimensionless frequencies greater than unity (ω > 1.0) when analysing both rigid and flexible cylinders having relatively large diameter to water depth ratios,r0/h > 0.25 (squatty type). This conclusion regarding the relative importance of the fluid compressibility is derived from a comparison between the relative magnitudes and the vertical distributions over depth of both the added mass and radiation damping coefficients per unit length for both rigid and flexible squatty cylinders. From additional comparisons with Rayleigh-Ritz solutions that require trial functions, the results for totally immersed flexible slender cylinders (r0/h< 0.10) are shown to be equivalent; but the results for totally immersed flexible squatty cylinders (r0/h > 0.25) are not. The reason for this difference appears to be in the truncation of the trial function series in the Rayleigh-Ritz methods, which excludes the higher mode shapes, and in the definitions of the added mass coefficients. Comparisons with laboratory data for both rigid and flexible cylinders confirm the accuracy of the solutions obtained by the eigenseries in the limited frequency interval above the highest frequency for surface gravity waves (f > 1.0 Hz) and below the first dimensionless cut-off frequency for acoustic waves (ω< 1.0). 相似文献
112.
The vortex structure formed in front of and behind a hemispheric surface hump has been studied in a water recirculating flume. In the recirculation zone behind the hemisphere, arched vortex tubes were formed. Up to a certain critical Reynolds number, each tube was shed individually from the recirculation zone. However, when the Reynolds number exceeded a critical value, several of the tubes coalesced in the recirculation zone before shedding. In front of the hemisphere, some parabolic vortex tubes formed. Their number increased with Reynolds number below its critical value and decreased above this value. The dimensionless height of the parabolic vortex tube decreased with Reynolds number. 相似文献
113.
We present analyses of the soft X-ray iron line spectra of flares obtained from the Bragg Spectrometer on Hinotori. We first present a case of strong K emission at the impulsive phase of the hard X-ray burst, and assess net K emission due to the electron impact by eliminating the fluorescence contribution. Second we discuss on the differences in the electron temperatures and emission measures derived respectively from FeXXVI and FeXXV spectra. A pilot two-temperatures model which can explain the two spectra is presented. Finally, we compare the temporal relations between the soft X-ray and hard X-ray intensities and show two extreme classes of flares, one characterized by the efficient formation of a hot thermal plasma above 30 million degree, and the other characterized by the spiky hard X-ray component. Energetical relation of the thermal plasma to the electron beam is discussed for the two classes. 相似文献
114.
138Ce/142Ce and 143Nd/144Nd isotope ratios of lunar samples are determined to constrain the petrogenetic differentiation and evolution of the moon. High-precision Ce-Nd isotope data, well-defined Rb-Sr isochrons, and rare earth elements (REE) abundances of lunar samples show that unexpectedly low La/Ce ratios of evolved lunar highland samples are preserved from at least 3.9 Ga. Precise analysis of REE abundances indicates that the low La/Ce ratio results from a depletion of La relative to other REE. This depletion can be seen in pristine KREEP basalts and Mg-suite rocks from 3.85 to 4.46 Ga. As REE abundances of all these samples are controlled by the presence of a KREEP component, the depletion was probably inherited from a late crystallization sequence of the lunar magma ocean related to the production of the original KREEP component. 相似文献
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119.
K. Fujimoto A. Ueda T. Ohtani M. Takahashi H. Ito H. Tanaka Anne-Marie Boullier 《Tectonophysics》2007,443(3-4):174
The active fault drilling at Nojima Hirabayashi after the 1995 Hyogoken-nanbu (Kobe) earthquake (MJMA = 7.2) provides us with a unique opportunity to investigate subsurface fault structure and the in-situ properties of fault and fluid. The borehole intersected the fault gouge of the Nojima fault at a depth interval of 623 m to 625 m. The lithology is mostly Cretaceous granodiorite with some porphyry dikes.The fault core is highly permeable due to fracturing. The borehole water was sampled in 1996 and 2000 from the depth interval between 630 and 650 m, just below the fault core. The chemical and isotopic compositions were analyzed. Carbon and oxygen isotope ratios of carbonates from the fault core were analyzed to estimate the origin of fluid.The following conclusions were obtained. (1) The ionic and isotopic compositions of borehole water did not change from 1996 to 2000. They are mostly derived from local ground water as mentioned by Sato and Takahashi [Sato, T., Takahashi, M., 2000. Chemical and isotopic compositions of groundwater obtained from the Hirabayashi well. Geological Survey of Japan Interim Report No. EQ/00/1, 187–192.]. (2) Geochemical speciation revealed that the borehole water was derived from a relatively deep reservoir, which may be situated at a depth of 3 to 4 km where the temperature is about 80–90 °C. (3) The shallower part of the Nojima fault (shallower than the reservoir depth) has not been healed from the hydrological viewpoints 5 years after the event, in contrast to the rapid healing detected by S wave splitting [Tadokoro, K., Ando, M., 2002. Evidence for rapid fault healing derived from temporal changes in S wave splitting, Geophys. Res. Lett., 29, 10.1029/2001GL013644.]. (4) Precipitation of calcite from the present borehole water since drilling supports the idea of precipitation of some calcite in coseismic hydraulic fractures in the fault core [Boullier, A-M., Fujimoto, K., Ohtani, T., Roman-Ross, G., Lewin, E., Ito, H., Pezard, P., Ildefonse, B., 2004. Textural evidence for recent co-seismic circulation of fluids in the Nojima fault zone, Awaji Island, Japan., Tectonophysics, 378, 165–181.]. (5) Carbon and oxygen isotope ratios of calcite indicated that the meteoric water flux had been localized at the fault core. (6) A difference in the carbon isotope ratio between the footwall and the hanging wall suggests that the fault has been acted as a hydrologic barrier, although the permeability along the fault is still high. 相似文献
120.
Shahidul Islam Md. Manabu Hibino Taro Ohta Kouji Nakayama Masaru Tanaka 《Estuaries and Coasts》2006,29(3):519-529
Larval and juvenile Japanese temperate bass (Lateolabrax japonicus) samples were collected from a wide range of spatial gradients (covering a distance of approximately 30 km) in Chikugo estuary,
Ariake Bay, Japan over a period of 8 yr (1997–2004) in order to observe changes in diet. Gut contents were studied by separating,
identifying, counting, and estimating the dry weight of prey organisms. Copepod samples were collected during each cruise
to observe the numerical composition, abundance, and biomass in the estuary. Considerable spatial and temporal variations
were observed in copepod distributions in ambient water and the diets of the fish. Two distinctly different copepod assemblages
were identified in the estuary: One in the upper estuarine turbidity maximum (ETM), dominated by a single speciesSinocalanus sinensis and the other in the lower estuary consisting of a multispecies assemblage, dominated byOithona davisae, Acartia omorii, Paracalanus parvus, andCalanus sinicus. The gut content composition of the fish in the upper estuary was dominated byS. sinensis, while in the lower estuary, it consisted ofP. parvus, O. davisae, andA. omorii. Within the size group analyzed (13.0–27.0 mm SL), the smaller individuals were found to feed on a mixed diet composed of
smaller prey. The diets gradually shifted to bigger prey composed predominantly ofS. sinensis for larger size groups. Greater proportions of empty guts were recorded in the smaller individuals and dropped with increasing
fish size. Higher dry biomass of copepods in the environment, as well as higher dry weights of gut contents, were recorded
in the upper estuary, indicating that the upper estuarine ETM areas are important nursery grounds for the early life stages
of the Japanese temperate bass. The early life stages of the Japanese temperate bass are adapted to use the upstream nursery
grounds and ascending to the nursery areas to useS. sinensis is one of the key survival strategies of the Japanese temperate bass in the Chikugo estuary. 相似文献