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391.
Tsutomu Takahashi 《Pure and Applied Geophysics》1975,113(1):949-969
Work done initially with Y. Ogura and later by the present author was reviewed, with special emphasis on physical concepts in a cloud model. The present paper consists of two parts: a warm rain study and a graupel cloud model. The process of continuous improvement on physical ideas taken to formulate warm rain are described in the first part of this paper. It is shown that the number concentration of cloud droplets is the most sensitive factor in determining rainfall, and that there is a critical drop size distribution for initiation of rain. The second part describes a graupel cloud model and shows that graupel formation is the mechanism most likely to lead to precipitation from continental shallow convective clouds. 相似文献
392.
Possibilities of backswing of fault displacement are investigated on the basis of a simple crack model. Although it has been suggested that the backswing would not occur in real earthquakes because of friction, there is evidence that some earthquakes might have caused return motion “locally” on the fault surface. This paper attempts to derive conditions for such local return motion. Spatial extension of the crack beyond the stress-filled region into the stress-deficient region gives a favorable site for the return motion, the site being just outside the stress-filled region. In our model the return motion occurs at this site when the frictional stress is less than about 30% of the regional stress in the stress-filled region. The overall return motion, on the other hand, would not occur unless the frictional stress is less than 10% of the regional stress. 相似文献
393.
Masayuki Kikuchi 《Physics of the Earth and Planetary Interiors》1981,27(2):100-105
Multiple scattering from cracks is considered in the two-dimensional plane-strain condition. It is assumed that identical cracks are distributed uniformly in space and that the effective waves propagate normal to the crack surfaces. Then, the apparent dispersion and attenuation are calculated as functions of frequency for three independent modes of wave propagation: SV, P and SH.The calculated results show that, in each case, the attenuation coefficient Q?1 takes a peak value when the wavelength is nearly twice the crack width, while phase velocity has a maximum deviation from the intrinsic value at a frequency lower than the peak frequency for Q?1. 相似文献
394.
395.
Masayuki Komatsu 《Contributions to Mineralogy and Petrology》1980,74(4):329-338
Multiply-twinned clinoenstatite has been found in andesitic rocks from Chichi-jima and Mukojima in the Bonin Islands.The clinoenstatite occurs as (1) reaction rims around olivine, (2) composite crystals with bronzite, and (3) anhedral phenocrysts rimmed or included by bronzite.The clinoenstatite is chemically characterized by low contents of Ca (less than 0.5 wt.% oxide), Fs (9.2–11.5) and Al (less than 0.6 wt.% oxide) relative to the coexisting bronzite. The partition coefficient, K
D
op
cp
=(Mg/Fe2+)cp/(Mg/Fe2+)op between coexisting clinoenstatite and bronzite, ranges from 1.02 to 1.32 (average 1.17). The Fe2+/Mg+Fe2+ ratios of coexisting clinoenstatite and bronzite are different in different rock types, which suggests variable inversion temperatures of protoenstatite to orthopyroxene in boninite.Bronzite phenocrysts in a specimen, ranging from Fs15 to Fs30, coexist with augite phenocrysts, whereas those in the other specimens, ranging from Fs12 to Fs18, do not coexist with augite phenocrysts. These differences in petrographical nature and mineral chemistry among the specimens examined may be due to variations in their quenching stages.The boninite clinoenstatite and bronzite are relatively rich in Ca and Mg, compared with the Papuan and Mariana pyroxenes, which seems to depend upon the rock chemistry. 相似文献
396.
H. Takahashi Y. Sahai B.R. Clemesha P.P. Batista N.R. Teixeira 《Planetary and Space Science》1977,25(6):541-547
In this paper the results of OH (8,3) emission intensity and rotational temperature measurements made in the Brazilian sector (23°S) from 1972 to 1974 are presented. Diurnal variations of both the parameters are found to fall into distinct classes, showing significant seasonal effects. A correlative study with the OI 5577 Å emission measured simultaneously is also presented. It is shown that both the phase and amplitude of the major part of the mean nocturnal intensity variations of the two emissions can be explained by the density and temperature perturbations caused by the solar semidiurnal tide. The OH emission is found to increase slightly during magnetic disturbances. 相似文献
397.
The nightglow OH(9,4) and O2 atmospheric (0,1) band emission intensities and their rotational temperatures T(OH) and T(O2), respectively, observed at Cachoeira Paulista (23° S, 45°W), Brazil, during the period from October 1989 to December 1990, have been analyzed to study the nighttime mesospheric energy loss rates through the radiations from the vibrationally excited OH* and electronically excited O*2 bands. The total emission rates of the OH Meinel bands, O2 atmospheric (0,0) and O2 infrared atmospheric (1g) bands were calculated using reported data for the relative band intensities
and
. It was found that there is a minimum in equivalent energy loss rate by the OH* Meinel bands during December/January (equivalent energy loss rate of 0.39 K/day*, where day* means averaged over the night) and maximum in equivalent energy loss rate during September (equivalent energy loss rate of 0.98 K/day*). Energy loss rate by the O*2 radiation, on the other hand, is weaker than that by the OH* Meinel bands, showing equivalent energy loss rates of 0.12 K/day* and 0.22 K/day* during January and September, respectively. 相似文献
398.
Herbert Palme Marie-Josée Janssens H. Takahashi Edward Anders Jan Hertogen 《Geochimica et cosmochimica acta》1978,42(3):313-323
Sixteen crater samples were analyzed by radiochemical neutron activation analysis for Ge, Ir, Ni, Os, Pd and Re. Two impact melt rock samples from Clearwater East (22 km) showed strong, uniform enrichments in all elements except Ge, corresponding to 7.4% C1 chondrite material. Interelement ratios suggest that the meteorite was a C1 (or C2) chondrite, not an iron, stony iron, or chondrite of another type. An Ivory Coast tektite (related to the 10 km Bosumtwi crater) was enriched in Ir + Os and Ni to about 0.04 and 1.6% of C1 chondrite levels, but in the absence of data on country rocks, the meteorite cannot yet be characterized.Impact melt rock samples from Clearwater West (32km), Manicouagan (70km), and Mistastin (28 km) showed no detectable meteoritic component. Upper limits, as Cl chondrite equivalent, were Os ≤ 2 × 10?3% (~0.01 ppb), Ni ≤ 2 × 10?1% (~20ppm). Possible causes are high impact velocity and/or a chemically inconspicuous meteorite (achondrite, Ir,Os-poor iron or stony iron). However, a more likely reason is that some fraction of the impact melt remains meteorite-free, especially at craters with central peaks.Clearwater East is the first terrestrial impact crater found to be associated with a stony meteorite. Apparently the consistent absence of stony projectiles at small craters (< 1 km diameter) reflects their destruction in the atmosphere, as proposed by Öpik. 相似文献
399.
Akane Arasuna Masayuki Okuno Liliang Chen Tsutomu Mashimo Hiroki Okudera Tomoyuki Mizukami Shoji Arai 《Physics and Chemistry of Minerals》2016,43(7):493-502
A shock-wave compression experiment using synthesized silica gel was investigated as a model for a comet impact event on the Earth’s surface. The sample shocked at 20.7 GPa showed considerable structural changes, a release of water molecules, and the dehydration of silanol (Si–OH) that led to the formation of a new Si–O–Si network structure containing larger rings (e.g., six-membered ring of SiO4 tetrahedra). The high aftershock temperature at 20.7 GPa, which could be close to 800 °C, influenced the sample structure. However, some silanols, which were presumed to be the mutually hydrogen-bonded silanol group, remained at pressures >20.7 GPa. This type of silanol along with a small number of water molecules may remain even after shock compression at 30.9 GPa, although the intermediate structure of the sample recovered was similar to that of silica glass. 相似文献
400.
Multiple equilibria and their stability in tropical atmosphere are investigated through β-plane
barotropic models with consideration of heating and dissipation. We have derived the solutions of the model
equations corresponding to the multiple equilibria or the steady flows first, and then establish the criteria for the stability of steady flow by use of the Liapunov direct Method. When these criteria are applied to the solutions of equilibria obtained, stable flows, which are closely related to the different patterns of quasi-stationary circulation in the tropical region, are found. The configurations of these stable flows and the shift between two of them as season changes provide quite reasonable explanations to many fundamental problems of tropical circulation features such as the catastrophe mechanism of the onset and the break-active cycle of the Asian summer
monsoon. It follows that the onset or the abrupt transition of the Asian summer monsoon could be attributed to
the multiple equilibrium property of the tropical circulation resulted from the advective nonlinearity, which
provide another explanation among others. 相似文献