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31.
John W. Morgan Marie-Josée Janssens H. Takahashi Jan Hertogen Edward Anders 《Geochimica et cosmochimica acta》1985,49(1):247-259
We have analyzed 10 H-chondrites for 20 trace elements, using RNAA. The meteorites included 4 of petrologic type 4 and 2 each of types 3, 5 and 6.The data show that H-chondrites are not isochemical. H3's are depleted by some 10% not only in Fe (Dodd, 1976), but also in the siderophiles Os, Re, Ir, Ni, Pd, Au, and Ge. Moreover, the abundance pattern of siderophiles varies systematically with petrologic type. As similar fractionations of REE have been observed by Nakamura (1974), it appears that both the proportions and compositions of the main nebular condensates varied slightly during accretion of the H-chondrites. Thus the higher petrologic types are independent nebular products, not metamorphosed descendants of lower petrologic types.Abundances of highly volatile elements (Cs, Br, Bi, Tl, In, Cd, Ar36) correlate with petrologic type, declining by ≤ 10?3 from Type 3 to Type 6. The trends differ from those for artificially heated Type 3's (Ikramuddinet al., 1977b; Herzoget al., 1979), but agree passably with theoretical curves for nebular condensation. Apparently the low volatile contents of higher petrologic types are a primary feature, not the result of metamorphic loss.The mineralogy of chondrites suggests that they accreted between 405 K (absence of Fe3O4) and 560 K (presence of FeS), and the abundances of Tl, Bi, and In further restrict this interval to 420–500 K. Accretion at 1070 ± 100 K, as proposed by Hutchisonet al. (1979, 1980), leads to some extraordinary problems. Volatiles must be injected into the parent body after cooling, which requires permeation of the body by 1011 times its volume of nebular gas. This process must also achieve a uniform distribution of the less volatile elements (Rb, Cu, Ag, Zn, Ga, Ge, Sn, Sb, Se, F), without freezeout in the colder outer layers.Factor analysis of our data shows 3 groupings: siderophiles (Os, Re, Ir, Ni, Pd, Au, and Ge), volatiles (Ag, Br, In, Cd, Bi, and Tl) and alkalis (Rb and Cs). The remaining 5 elements (U, Zn, Te, Se, and Sb) remain unassociated. 相似文献
32.
Naoki Niwa Takuji Kobori Motoichi Takahashi Tomohiko Hatada Haruhiko Kurino Jun Tagami 《地震工程与结构动力学》1995,24(5):655-671
This paper describes a feasibility study on a high-damping device (HiDAM) installed in a building structure by way of a bracing mechanism. A seismic response analysis with respect to a high-rise building approximately 100 m high is reported. Proper adjustment of the damping coefficient of the HiDAM (oil damper) provided an over all damping factor of about 10–20 per cent to the building structure, and reductions in the response, deformation and shear forces were verified analytically. This paper reports also the performance confirmation tests conducted on a model device of the HiDAM which satisfied the specifications determined from the analytical results. The test results demonstrate the feasibility of the HiDAM and the possibility of utilizing it in high-rise buildings. 相似文献
33.
Tomoyuki Takahashi Takeyuki Takahashi Nobuo Shuto Fumihiko Imamura Modesto Ortiz 《Pure and Applied Geophysics》1995,144(3-4):747-767
A source model for the 1993 Hokkaido Nansei-Oki tsunami must satisfy certain conditions. Such conditions are presented in this paper, and two methods are used to determine the best source model for this event. A trial-and-error method selects DCRC-17a as the best among 24 different models. This model has three fault planes dipping westward. To reproduce well the tide gauge records at two locations, an inversion analysis is used to modify the dislocation of DCRC-17a. 相似文献
34.
ACTIVE system for monitoring volcanic activity: A case study of the Izu-Oshima Volcano,Central Japan
Hisashi Utada Yuji Takahashi Yuichi Morita Takao Koyama Tsuneomi Kagiyama 《Journal of Volcanology and Geothermal Research》2007
A system is proposed for the monitoring of changes in the underground structure of an active volcano over time by applying a transient electromagnetic method. The monitoring system is named ACTIVE, which stands for Array of Controlled Transient-electromagnetics for Imaging Volcano Edifice. The system consists of a transmitter dipole used to generate a controlled transient electromagnetic (EM) field and an array of receivers used to measure the vertical component of the transient magnetic field at various distances, with automatic operation of both units. In order to verify the performance of the proposed system, numerical and field experiments were carried out by application of the system to the Izu-Oshima volcano, where a remarkable change in the apparent DC resistivity over time had been detected in association with the eruption in 1986. 相似文献
35.
1 IntroductionSalinization is one of the major problems in arid and semi-arid regions in relation to land use and in particular to agricultural production[1]. Excessive salinity leads to toxicity in crops and reduction of the availability of water to crops, by reducing the osmotic potential of the soil solution[2]. Movement of soil water induces solute transport, and solutes are transferred towards the ground surface by the upward soil-water movement caused by evaporation, resulting in an accu… 相似文献
36.
ObservationandresearchonULFandVLFseismo-electromagneticradiationJIA-ZHIYUAN(袁家治);KozoTakahashi;SHU-QINGQIAN(钱书清),YokioFujinaw... 相似文献
37.
38.
Hung Tran Daisuke Uchihama Shiro Ochi Yoshifumi Yasuoka 《International Journal of Applied Earth Observation and Geoinformation》2006
This study focuses on using remote sensing for comparative assessment of surface urban heat island (UHI) in 18 mega cities in both temperate and tropical climate regions. Least-clouded day- and night-scenes of TERRA/MODIS acquired between 2001 and 2003 were selected to generate land-surface temperature (LST) maps. Spatial patterns of UHIs for each city were examined over its diurnal cycle and seasonal variations. A Gaussian approximation was applied in order to quantify spatial extents and magnitude of individual UHIs for inter-city comparison. To reveal relationship of UHIs with surface properties, UHI patterns were analyzed in association with urban vegetation covers and surface energy fluxes derived from high-resolution Landsat ETM+ data. This study provides a generalized picture on the UHI phenomena in the Asian region and the findings can be used to guide further study integrating satellite high-resolution thermal data with land-surface modeling and meso-scale climatic modeling in order to understand impacts of urbanization on local climate in Asia. 相似文献
39.
Fog and rain water chemistry at Mt. Fuji: A case study during the September 2002 campaign 总被引:2,自引:0,他引:2
Koichi Watanabe Yusaku Takebe Nobuhiro Sode Yasuhito Igarashi Hiroshi Takahashi Yukiko Dokiya 《Atmospheric Research》2006,82(3-4):652
Measurements of fog and rain water chemistry at the summit of Mt. Fuji, the highest peak in Japan, as well as at Tarobo, the ESE slope of Mt. Fuji in September 2002. The pH of fog and rain water sampled at Mt. Fuji varied over a range of 4.0–6.8. Acidic fogs (pH < 5.0) were observed at the summit when the air mass came from the industrial regions on the Asian continent. The ratio of [SO42−]/[NO3−] in the fog water was lower at Tarobo than at the summit. High concentrations of Na+ and Cl− were determined in the rain water sampled at the summit, possibly because of the long-range transport of sea-salt particles raised by a typhoon through the middle troposphere. The vertical transport of sea-salt particles would influence the cloud microphysical properties in the middle troposphere. Significant loss of Mg2+ was seen in the rain water at the summit. The concentrations of peroxides in the fog and rain water were relatively large (10–105 μM). The potential capacity for SO2 oxidation seems to be strong from summer to early autumn at Mt. Fuji. The fog water peroxide concentrations displayed diurnal variability. The peroxide concentrations in the nighttime were significantly higher than those in the daytime. 相似文献
40.
Partitioning of Ni2+, Co2+, Fe2+, Mn2+ and Mg2+ between olivine and silicate melts: compositional dependence of partition coefficient 总被引:1,自引:0,他引:1
Eiichi Takahashi 《Geochimica et cosmochimica acta》1978,42(12):1829-1844
Partitioning of Ni2+, Co2+, Fe2+, Mn2+ and Mg2+ between olivine and silicate melts has been determined near the join (Mg0.5·-Fe0.5)2SiO4-K2O 4SiO2 and for seven different basaltic compositions. The experiments were made at 1 atm total pressure, 1500-1100°C, and under moderate to reducing oxygen fugacities. The concentration factor, defined as KMO = (MO)ol/(MO)liq (molar ratio), increases markedly for all the cations studied as the olivine component of the liquid decreases. Much of the increase in KMO is considered as due to the compositional effect of the coexisting liquid: the temperature effect on KMO is probably opposite to the compositional effect (KMO decreases as temperature decreases).The partition coefficient KMO-MgO = (MO/MgO)ol/(MO/MgO)liq for the reaction, Mol2+ + Mgliq2+ = Mliq2+ + Mgol2+. is relatively constant over a wide range of SiO2 content of the liquid, except in the case of Ni2+. The partition coefficients have similar ranges both in synthetic and natural rock systems: KNiO-MgO = 1.8–3.0, KCoO-MgO = 0.6–0.8, KFeO-MgO = 0.27–0.38, and KMnO-MgO = 0.23–0.32. There is a systematic variation in the partition coefficient KMO-MgO with the composition of liquid; KMO-MgO increases with increasing SiO2 content of melt. The partition coefficients for Co2+, Fe2+ and Mn2+ are useful to test the equilibration of olivine with magma of a wide compositional range. 相似文献