排序方式： 共有16条查询结果，搜索用时 15 毫秒
1.
Factors controlling typhoons and storm rain on the Korean Peninsula during the Little Ice Age 总被引：1，自引：0，他引：1
2.
A new method was developed to compare the classifications of different kind of data maps based on the self-organizing map (SOM) analysis. The surface current maps of the northern coast of Ishigaki and Iriomote Islands, East China Sea, observed by high-frequency (HF) radar were classified by SOM. Winds, sea surface temperatures (SST), and reanalysis data were also classified by SOM. The optimum area for classification was determined objectively by the new method, which relates these patterns to HF radar current patterns. We found two typical surface patterns: the first was that northeastward flows are dominant in the observation area and the second was that a clockwise eddy was also dominant in this area. The southwestward wind pattern was strongly related to the dominant clockwise eddy pattern of the HF radar current field. 相似文献
3.
A. Kouchi Y. Sugawara K. Kashima I. Sunagawa 《Contributions to Mineralogy and Petrology》1983,83(1-2):177-184
Sector zoning has been experimentally reproduced in CaMgSi2O6-CaTiAl2O6 clinopyroxene crystals by isothermal crystallization using seed crystals. Element partitioning in different growth sectors and between the core and rim portions in single crystals was analysed in relation to growth rate R and degree of supercooling T. The TiO2 and Al2O3 contents increase with increase in R and T, but when they are compared between different sectors in a single crystal grown at the same T, they correlate negatively with R. The order of faces in respect of contents of TiO2 and Al2O3 is (100)>(110)(010)(111) at T= 13° C and 18° C but changes to (110)>(100)>(010)>(111) at T= 25° C. The growth mechanism is concluded to be controlled by interface kinetics at T= 13–25° C for all these faces, while at T=45° C this relation holds for (100) and (010) faces, but not for (110) and (111), based on the growth rate versus supercooling relation and surface microtopographic observations. The interface kinetics play the essential role in the formation of sector zoning, when the layer growth mechanism takes place. 相似文献
4.
Raman spectra of Ni2SiO4 spinel (O h 7 Z=8) have been measured in the temperature range from 20 to 600 °C and the Raman active vibrations (A 1g +E g +3F 2g ) have been assigned. A calculation of the optically active lattice vibrations of this spinel has been made, assuming a potential function which combines general valence and short range force constants. The values of the force constants at 20 and 500 °C have been calculated from the vibrational frequencies of the observed Raman spectra and infrared (IR) spectral data. The Ni spinel at 20 °C has a prominently small Si-O bond stretching force constant of K(SiO)=2.356 ～ 2.680 md/Å and a large Ni-O bond stretching constant of K(NiO)=0.843 ～ 1.062 md/Å and these force constants at 500 °C decrease to K(SiO)=2.327 ～ 2.494 md/Å and K(NiO)=0.861 ～ 0.990 md/Å. The Si-O bond is noticeably weakened at high temperatures, despite the small thermal expantion from 1.657 Å (20 °C) to 1.660 Å (500 °C). These changes of the interatomic force constants of the spinel at high temperatures are in accord with the thermal structure changes observed by X-ray diffraction study. The weakened Si-O bond is consistent with the fact that Si atoms in the spinel lattice can diffuse at significant rates at elevated temperature. 相似文献
5.
Yuki Asahara Motohiko Murakami Yasuo Ohishi Naohisa Hirao Kei Hirose 《Earth and Planetary Science Letters》2010,289(3-4):479-485
We extended the pressure range of sound velocity measurements for liquid water to 25 GPa and 900 K along the melting curve using a laser heated diamond anvil cell with a combined system of Brillouin scattering and synchrotron X-ray diffraction. Experimental pressure and temperature were obtained by solving simultaneous equations: the melting curve of ice and the equation of state for gold. The sound velocities obtained in liquid water at high pressures and melting temperatures were converted to density using Murnaghan's equation of state by fitting a parameter of the pressure derivative of bulk modulus at 1 GPa. The results are in good agreement with the values predicted by a previously reported equation of state for water based on sound velocity measurements. The equation of state for water obtained in this study could be applicable to water released by dehydration reactions of dense hydrous magnesium silicate phases in cold subducting slabs at lower mantle conditions, although the validity of Murnaghan's equation of state for water should be evaluated in a wider pressure and temperature ranges. The present velocity data provides the basis for future improvement of the accurate thermodynamic model for water at high pressures. 相似文献
6.
Lidong Dai Yuki Kudo Kei Hirose Motohiko Murakami Yuki Asahara Haruka Ozawa Yasuo Ohishi Naohisa Hirao 《Physics and Chemistry of Minerals》2013,40(3):195-201
The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na0.4Mg0.6Al1.6Si0.4O4 (40 % NaAlSiO4–60 % MgAl2O4). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G 0 = 121.960 ± 0.087 GPa and its pressure derivative G’ = 1.961 ± 0.009 for the NAL phase, and G 0 = 129.653 ± 0.059 GPa and G’ = 2.340 ± 0.004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5.601 ± 0.005 km/sec and 5.741 ± 0.001 km/sec, respectively. We also found that shear velocity increases by 2.5 % upon phase transition from NAL to CF at around 40 GPa. 相似文献
7.
Site effects by generalized inversion technique using strong motion recordings of the 2008 Wenchuan earthquake 总被引：3，自引：1，他引：2
The generalized inversion of S-wave amplitude spectra from the free-field strong motion recordings of the China National Strong Motion Observation Network System (NSMONS) are used to evaluate the site effects in the Wenchuan area. In this regard, a total of 602 recordings from 96 aftershocks of the Wenchuan earthquake with magnitudes of M3.7-M6.5 were selected as a dataset. These recordings were obtained from 28 stations at a hypocenter distance ranging from 30 km to 150 km. The inversion results have been verified as reliable by comparing the site response at station 62WUD using the Generalized Inversion Technique (GIT) and the Standard Spectral Ratio method (SSR). For all 28 stations, the site predominant frequency F p and the average site amplification in different frequency bands of 1.0–5.0 Hz, 5.0–10.0 Hz and 1.0–10.0 Hz have been calculated based on the inversion results. Compared with the results from the horizontal-to-vertical spectral ratio (HVSR) method, it shows that the HVSR method can reasonably estimate the site predominant frequency but underestimates the site amplification. The linear fitting between the average site amplification for each frequency band and the V s20 (the average uppermost-20 m shear wave velocity) shows good correlation. A distance measurement called the asperity distance D Aspt is proposed to reasonably characterize the source-to-site distance for large earthquakes. Finally, the inversed site response is used to identify the soil nonlinearity in the main shock and aftershocks of Wenchuan earthquake. In ten of the 28 stations analyzed in the main shock, the soil behaved nonlinearly, where the ground motion level is apparently beyond a threshold of PGA > 300 cm/s2 or PGV > 20 cm/s, and only one station coded 51SFB has evidence of soil nonlinear behavior in the aftershocks. 相似文献
8.
9.
Etsuo Uchida Takuro Haitani Takayuki Suetsugu Takahiro Kashima Ken Tsutsui 《Resource Geology》2003,53(2):155-161
Abstract. The distribution of Na, K, Ca, Mg, Mn and Fe between the granodiorite JG-la, one of the geochemical standard rocks, and 2M NaCl aqueous solution was experimentally determined at temperatures of 300 to 800C and a pressure of 1 kb using standard cold seal-type pressure vessels. The solid run products melted partially at 800C. Only K shows a significantly different behavior from the experiments using the basalt JB-la (Uchida and Tsutsui, 2000) due to the presence of ortho-clase in the JG-la. The transition elements tend to be preferably partitioned into the aqueous chloride solutions with increasing temperature. At 800C and 1 kb, the Fe concentration of the aqueous chloride solutions reached up to 5,000 ppm, and the Mn concentration up to 350 ppm. The distribution coefficient, KD, i = Ci, sol /Ci , rock, is in the order of Na>K>Mn>Ca> Fe>Mg at 300C, but changed in the order of Mn>N>K>Fe>Ca>Mg at 800C. The distribution coefficients of the divalent cations for the JG-la are higher than those for the JB-1a. The distribution coefficient of the transition elements, Fe and Mn, increases significantly with increasing temperature. The thermodynamic analysis for aqueous speciation revealed that this is attributable to the formation of the tri-chloro complexes of the transition elements at higher temperatures. 相似文献
10.
Motohiko Murakami Yasuo Ohishi Naohisa Hirao Kei Hirose 《Earth and Planetary Science Letters》2009,277(1-2):123-129
The aggregate shear wave velocities of MgO (periclase) have been determined throughout Earth's lower mantle pressure regime approaching 130 GPa using Brillouin spectroscopy in conjunction with synchrotron X-ray diffraction technique in a diamond anvil cell apparatus. We found that the extrapolations of the high-pressure shear wave velocities and shear moduli to ambient pressure are highly consistent with earlier studies. However, the measurements over a wide pressure range revealed that the pressure derivative of the shear modulus (dG/dP = G0′) of MgO is 1.92(2), which is distinctly lower than that of previous lower-pressure experiments. Compared with the previous results on (Mg,Fe)O ferropericlase, there is no clear correlation between iron content and G0′. We calculate that the shear wave velocity profile of lower mantle along the adiabatic geotherm applied by the lower G0′ value of periclase can remarkably well reproduce the global seismological 1-D velocity profile model with uniform composition model. The best-fitting result indicates the possibility of a lower mantle mineralogy with ~ 92 vol.% silicate perovskite phase, implying that the bulk composition of lower mantle is likely not to be pyrolitic but more chondritic. The present acoustic measurements performed over the large pressure range have thus led us to a better understanding of compositional model of the Earth's lower mantle. 相似文献