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61.
Osamu Abe Atsushi Watanabe V. V. S. S. Sarma Yohei Matsui Hiroya Yamano Naohiro Yoshida Toshiro Saino 《Journal of Oceanography》2010,66(3):363-372
We estimated gas exchange rates in Kabira Reef at Ishigaki Island, southwest Japan, using a mass balance calculation with
dual “biological” tracers: dissolved inorganic carbon (DIC) and dissolved oxygen (DO). The nighttime results allowed us to
obtain reasonable gas transfer velocity k
w values, all of which exceeded those obtained in wind-dominant studies. The difference is likely due to the contribution of
turbulence generated by the interaction between the current and bottom topography. The k
w obtained during high tides is consistent with that reported by Raymond and Cole (2001), whereas k
w during low tides is significantly higher, which seems to be caused by enhanced friction with the bottom of the reef and/or
bubble-induced gas transfer by wave breaking at the reef crest. 相似文献
62.
Hydrographic conditions in the Tsushima Strait revisited 总被引:1,自引:1,他引:0
Long-term averaged temperature and salinity distributions in the Tsushima Strait are investigated on the basis of a concurrent
dataset of the eastern and western channels during 1971–2000. Both temperature and salinity show a clear seasonal variation
with weak and strong stratifications in December–April and June–October, respectively. The largest standard deviations occur
in summer around the thermocline for temperature and in the surface layer for salinity. This indicates large interannual variability
in the development of a thermocline and low salinity water advection from the East China Sea. The water masses in both channels
are distinctly different from each other; the water in the western channel is generally colder and fresher than that in the
eastern channel throughout the year. Baroclinic transport based on the density distributions shows a seasonal variation with
a single peak in August for the eastern channel and double peaks in April and August for the western channel. However, this
cannot explain the seasonal variation in the total volume transport estimated from the sea level differences across the channels.
The spatial distribution of baroclinic transport shows a year-round negative transport towards the East China Sea behind the
Iki Island in the eastern part of the eastern channel. This negative transport reflects the baroclinic structure between the
offshore Tsushima Current Water and cold coastal water. The corresponding southwestward currents are found in both Acoustic
Doppler Current Profiler (ADCP) and high frequency (HF) radars observations. 相似文献
63.
64.
Akira Ohtsuki Masanori Hirota Kikuo Ishimura Kazutomo Yokoyama Kiyoshi Fukutake 《地震工程与结构动力学》1992,21(7):591-607
The verification of a two-dimensional non-linear analysis based on a hybrid constitutive model, which consists of the Ramberg-Osgood model extended to two-dimensional problems and a dilatancy model, is discussed through a comparison of the shaking-table test results for a one-storey structure standing on a dry sandy deposit with those for the same on a saturated sandy deposit. Since the relationships G vs. γ and h vs. γ for shear strains of 10?5?10?3 can be obtained accurately by an inversion analysis of the resonance curve of the sandy deposit the proposed non-linear method can represent well the observed non-linear response of the dry or the saturated sandy deposit including the structure. This method, however, should be applied carefully to assess the response of a soil-structure system when the three-dimensional interaction affects significantly the response of the model. An equivalent linear analysis using a sway-rocking model is applied to simulate the non-linear ground motion including the three-dimensional interaction, and it is found that the sway-rocking model can also represent well the non-linear response of the system. 相似文献
65.
Masanori Matsui 《Physics and Chemistry of Minerals》1996,23(6):345-353
Molecular dynamics (MD) simulations have been used to calculate the structures and bulk moduli of crystals in the system CaO-MgO-Al2O3-SiO2 (CMAS) using an interatomic potential model (CMAS94), which is composed of pairwise additive Coulomb, van der Waals, and repulsive interactions. The crystals studied, total of 27, include oxides, Mg meta- and ortho-silicates, Al garnets, and various Ca or Al bearing silicates, with the coordination number of cations ranging 6 to 12 for Ca, 4 to 12 for Mg, 4 to 6 for Al, and 4 and 6 for Si. In spite of the simplicity of the CMAS94 potential and the diversity of the structural types treated, MD simulations are quite satisfactory in reproducing well the observed structural data, including the crystal symmetries, lattice parameters, and average and individual nearest neighbour Ca-O, Mg-O, Al-O, and Si-O distances. In addition MD simulated bulk moduli of crystals in the CMAS system compare well with the observed values. 相似文献
66.
Abstract Very large scale mapping (1/250) was experimented on the basis of FMC camera, high resolution film and total station surveying. The future attractive combination of precision photogrammetry and personal computer assisted terrestrial surveying was investigated from the point of view of accuracy, time effectiveness and total procedures control. 相似文献
67.
Hiroshi Imanaka Bishun N. Khare Emma L.O. Bakes Dale P. Cruikshank Takafumi Matsui 《Icarus》2004,168(2):344-366
Titan, the largest satellite of Saturn, has a thick nitrogen/methane atmosphere with a thick global organic haze. A laboratory analogue of Titan's haze, called tholin, was formed in an inductively coupled plasma from nitrogen/methane=90/10 gas mixture at various pressures ranging from 13 to 2300 Pa. Chemical and optical properties of the resulting tholin depend on the deposition pressure in cold plasma. Structural analyses by IR and UV/VIS spectroscopy, microprobe laser desorption/ionization mass spectrometry, and Raman spectroscopy suggest that larger amounts of aromatic ring structures with larger cluster size are formed at lower pressures (13 and 26 Pa) than at higher pressures (160 and 2300 Pa). Nitrogen is more likely to incorporate into carbon networks in tholins formed at lower pressures, while nitrogen is bonded as terminal groups at higher pressures. Elemental analysis reveals that the carbon/nitrogen ratio in tholins increases from 1.5-2 at lower pressures to 3 at 2300 Pa. The increase in the aromatic compounds and the decrease in C/N ratio in tholin formed at low pressures indicate the presence of the nitrogen-containing polycyclic aromatic compounds in tholin formed at low pressures. Tholin formed at high pressure (2300 Pa) consists of a polymer-like branched chain structure terminated with CH3, NH2, and CN with few aromatic compounds. Reddish-brown tholin films formed at low pressures (13-26 Pa) shows stronger absorptions (almost 10 times larger k-value) in the UV/VIS range than the yellowish tholin films formed at high pressures (160 and 2300 Pa). The tholins formed at low pressures may be better representations of Titan's haze than those formed at high pressures, because the optical properties of tholin formed at low pressures agree well with that of Khare et al. (1984a, Icarus 60, 127-137), which have been shown to account for Titan's observed geometric albedo. Thus, the nitrogen-containing polycyclic aromatic compounds we find in tholin formed at low pressure may be present in Titan's haze. These aromatic compounds may have a significant influence on the thermal structure and complex organic chemistry in Titan's atmosphere, because they are efficient absorbers of UV radiation and efficient charge exchange intermediaries. Our results also indicate that the haze layers at various altitudes might have different chemical and optical properties. 相似文献
68.
The gas permeability of 11 ordinary chondrites was measured at various gas pressures (0.5-2.5 bars) under confining pressures up to 120 bars. The gas permeability ranges from less than a nanodarcy to a few millidarcies. There is a positive correlation between the permeability and the porosity. The permeability decreased by as much as 50% when the confining pressure was increased from 10 to 100 bars, suggesting that the permeability of some chondrites is partly due to cracks. A linear relation between gas flow pressure dependence and confining pressure dependence of the gas permeability is observed, suggesting that on average, crack apertures are larger than pore spaces. The permeability of heavily-shocked chondrites is less than that of mildly shocked chondrites. Using the measured permeability data we estimated the size of a possible shocked-chondrite precursor body. 相似文献
69.
Thermal histories of chondrite parent bodies are calculated from an initial state with material in a powder-like form, taking into account the effect of consolidation state on thermal conductivity. The very low thermal conductivity of the starting materials makes it possible for a small body with a radius of less than 100 km to be heated by several hundred degrees even if long-lived radioactive elements in chondritic abundances are the only source of heat. The maximum temperature is determined primarily by the temperature at which sintering of the constituent materials occurs. The thermal state of the interior of a chondrite parent body after sintering has begun is nearly isothermal. Near the surface, however, where the material is unconsolidated and the thermal conductivity is much lower, the thermal gradient is quite large. This result contradicts the conventional “onion-shell” model of chondrite parent bodies. But because the internal temperature is almost constant through the whole body, it supports a “multiple-parent bodies” model, according to which each petrologic type of chondrite comes from a different parent body. 相似文献
70.
We show that the surface of a planet growing by planetesimal impact is heated over the melting temperature of the surface materials due to the blanketing effect of an impact induced H2O atmosphere with the present H2O abundance of the Earth even when the accretion time is as long as 108 years. Hence, a magma ocean covering the entire surface was formed on the Earth and Moon and other terrestrial planets during their formations. 相似文献