2.5-Dmodelling of elastic waves using the pseudospectral method     

Takashi Furumura  Hiroshi Takenaka 《Geophysical Journal International》1996,124(3):820-832

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Interplate coupling and relative plate motion in the Tokai district, central Japan, deduced from geodetic data inversion using ABIC   总被引：1，自引：0，他引：1  

Shoichi Yoshioka  Tetsuichiro Yabuki  Takeshi Sagiya  Takashi Tada  Mitsuhiro Matsu'ura 《Geophysical Journal International》1993,113(3):607-621

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Along-arc lateral variation of Rb−Sr and K−Ar ages of Cretaceous granitic rocks in Southwest Japan     

Takashi Nakajima  Teruo Shirahase  Ken Shibata 《Contributions to Mineralogy and Petrology》1990,104(4):381-389

Cretaceous granitic rocks were emplaced over a distance of 700 km along arc in Southwest Japan. Rb–Sr and K–Ar ages of a major group of these granitic rocks, with ilmenite series ore mineralogy, were examined. Rb–Sr whole rock ages of 92.8±4.0 Ma and Rb–Sr and K–Ar biotite ages of 80–88 Ma were obtained on one group of these granitic rocks from Kamo-Sera area of central Hiroshima Prefecture. The K–Ar ages of various minerals, combined with the Rb–Sr whole-rock age, give a smooth cooling curve, which suggests a 5 to 10 Ma time-lag between intrusion and cooling at 300° C for the Cretaceous granitic rocks. The Rb–Sr whole-rock and Rb–Sr/K–Ar biotite ages of these granitic rocks become younger eastward along the Southwest Japan arc, and the time-lag between the two systems remains constant at 5 to 10 Ma over the entire area. The along-arc age variation does not support the genetical relationship of the Cretaceous granitoids with steady-state subduction. The Cretaceous granitic province at the eastern margin of Eurasian continent was, at least partly, formed by an episodic event such as ridge subduction.  相似文献   

Anthropogenic influence on sedimentation during the last 100 years inferred from magnetic properties in the Changjiang Estuary, China   总被引：1，自引：1，他引：0  

Yonghong Wang  Takashi Oguchi  Peter V. Ridd  Huanting Shen 《Environmental Earth Sciences》2013,70(4):1671-1680

A 100-year sedimentary record in the Changjiang Estuary was examined to elucidate natural and anthropogenic influences on the morphodynamic evolution of the estuary. Two gravity cores were acquired and their magnetic properties, sediment size, chemical elements and ²¹⁰Pb geochronology were analyzed to infer the sedimentation. The results indicate that these sedimentological indexes, especially magnetic properties and trace elements, changed significantly during the last 100 years, with an abrupt change occurring at around 1960. This abrupt change is likely the result of a reduction in hydrodynamic energy caused by the narrowing of an upstream estuary reach due to reclamation. An increase of terrigenous input, due to soil erosion in the upper and middle reaches of the Changjiang, and increases in steel production may have also had a significant influence, as indicated by studies of other locations in the Changjiang drainage basin.  相似文献   

High-rate precise point positioning (PPP) to measure seismic wave motions: an experimental comparison of GPS PPP with inertial measurement units   总被引：2，自引：1，他引：1  

Peiliang Xu  Chuang Shi  Rongxin Fang  Jingnan Liu  Xiaoji Niu  Quan Zhang  Takashi Yanagidani 《Journal of Geodesy》2013,87(4):361-372

High-rate GPS has been widely used to construct displacement waveforms and to invert for source parameters of earthquakes. Almost all works on internal and external evaluation of high-rate GPS accuracy are based on GPS relative positioning. We build an experimental platform to externally evaluate the accuracy of 50-Hz PPP displacement waveforms. Since the shake table allows motion in any of six degrees of freedom, we install an inertial measurement unit (IMU) to measure the attitude of the platform and transform the IMU displacements into the GPS coordinate system. The experimental results have shown that high-rate PPP can produce absolute horizontal displacement waveforms at the accuracy of 2–4 mm and absolute vertical displacement waveforms at the sub-centimeter level of accuracy within a short period of time. The significance of the experiments indicates that high-rate PPP is capable of detecting absolute seismic displacement waveforms at the same high accuracy as GPS relative positioning techniques, but requires no fixed datum station. We have also found a small scaling error of IMU and a small time offset of misalignment between high-rate PPP and IMU displacement waveforms by comparing the amplitudes of and cross-correlating both the displacement waveforms.  相似文献   

A model for the infrared dust emission from forming galaxies     

Tsutomu T. Takeuchi †  Takako T. Ishii ‡  Takaya Nozawa  Takashi Kozasa  Hiroyuki Hirashita ‡ 《Monthly notices of the Royal Astronomical Society》2005,362(2):592-608

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Orbital evolution of asteroids with the effects of mutual gravitational attraction     

M. Yoshikawa 《Earth, Moon, and Planets》1996,72(1-3):317-320

The effects of the mutual gravitational attraction between asteroids were analyzed by two N-body calculations, in which N=4,516 (the Sun, the nine planets, and 4,506 asteroids). In one calculation the gravity of the asteroids was taken into account, and in the other it was ignored. These calculations were carried out for a time period of about 100 years. The largest difference in the positions of the asteroids between these two calculations is about 10^?3 AU. For the orbital elements of the semimajor axis, the eccentricity, and the inclination, the largest differences were 9 × 10^?6 AU, 4 × 10^?6, and 5 × 10^?4 degrees, respectively. It was found that the distribution of the differences of the semimajor axis between the two calculations is quite similar to the Cauchy distribution.  相似文献   

An experimental study on Fischer‐Tropsch catalysis: Implications for impact phenomena and nebular chemistry     

Yasuhito SEKINE  Seiji SUGITA  Takafumi SHIDO  Takashi YAMAMOTO  Yasuhiro IWASAWA  Toshihiko KADONO  Takafumi MATSUI 《Meteoritics & planetary science》2006,41(5):715-729

Abstract— Fischer‐Tropsch catalysis, by which CO and H₂ are converted to CH₄ on the surface of transition metals, has been considered to be one of the most important chemical reactions in many planetary processes, such as the formation of the solar and circumplanetary nebulae, the expansion of vapor clouds induced by cometary impacts, and the atmospheric re‐entry of vapor condensate due to asteroidal impacts. However, few quantitative experimental studies have been conducted for the catalytic reaction under conditions relevant to these planetary processes. In this study, we conduct Fischer‐Tropsch catalytic experiments at low pressures (1.3 times 10^?4 bar ≤ P ≤ 5.3 times 10^?1 bar) over a wide range of H₂/CO ratios (0.25–1000) using pure iron, pure nickel, and iron‐nickel alloys. We analyze what gas species are produced and measure the CH₄ formation rate. Our results indicate that the CH₄ formation rate for iron catalysts strongly depends on both pressure and the H₂/CO ratio, and that nickel is a more efficient catalyst at lower pressures and lower H₂/CO ratios. This difference in catalytic properties between iron and nickel may come from the reaction steps concerning disproportionation of CO, hydrogenation of surface carbon, and the poisoning of the catalyst. These results suggest that nickel is important in the atmospheric re‐entry of impact condensate, while iron is efficient in circumplanetary subnebulae. Our results also indicate that previous numerical models of iron catalysis based on experimental data at 1 bar considerably overestimate CH₄ formation efficiency at lower pressures, such as the solar nebula and the atmospheric re‐entry of impact condensate.  相似文献   

Halo model predictions of the cosmic magnification statistics: the full non-linear contribution     

Masahiro Takada  Takashi Hamana 《Monthly notices of the Royal Astronomical Society》2003,346(3):949-962

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Non-Gaussian tails of cosmological density distribution function from dark halo approach     

Atsushi Taruya  Takashi Hamana  Issha Kayo 《Monthly notices of the Royal Astronomical Society》2003,339(2):495-504

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