Visible and near-infrared spectral survey of Martian meteorites stored at the National Institute of Polar Research     

Takahiro Hiroi  Hiroshi Kaiden  Keiji Misawa  Takafumi Niihara  Hideyasu Kojima  Sho Sasaki 《Polar Science》2011,5(3):337-344

Martian meteorite chip samples stored at the National Institute of Polar Research (NIPR) have been studied by a visible and near-infrared (VNIR) spectrometer. Measured spots are about 3 × 2 mm in size, which are clearly marked on photographs of the meteorite chips. Rock types and approximate mineral compositions of studied meteorites have been identified or obtained through this spectral survey with no sample preparation required. This study demonstrates that this kind of spectral survey is effective in classifying and describing Marian meteorites, and that such a VNIR spectrometer on a Mars rover would be useful for identifying these kinds of unaltered Mars rocks. Further studies which utilize a smaller spot size are desired for improving the accuracy of identifying the clasts and mineral phases in the rocks.  相似文献   

Validation of TRMM Precipitation Radar satellite data over Indonesian region     

Rakhmat Prasetia  Abd. Rahman As-syakur  Takahiro Osawa 《Theoretical and Applied Climatology》2013,112(3-4):575-587

Research has been conducted to validate monthly and seasonal rain rates derived from the Tropical Rainfall Measuring Mission Precipitation Radar (PR) using rain gauge data analysis from 2004 to 2008. The study area employed 20 gauges across Indonesia to monitor three Indonesian regional rainfall types. The relationship of PR and rain gauge data statistical analysis included the linear correlation coefficient, the mean bias error (MBE), and the root mean square error (RMSE). Data validation was conducted with point-by-point analysis and spatial average analysis. The general results of point-by-point analysis indicated satellite data values of medium correlation, while values of MBE and RMSE tended to indicate underestimations with high square errors. The spatial average analysis indicated the PR data values are lower than gauge values of monsoonal and semi-monsoonal type rainfall, while anti-monsoonal type rainfall was overestimated. The validation analysis showed very good correlation with the gauge data of monsoonal type rainfall, high correlation for anti-monsoonal type rainfall, but medium correlation for semi-monsoonal type rainfall. In general, the statistical error level of monthly seasonal monsoonal type conditions is more stable compared to other rainfall types. Unstable correlations were observed in months of high rainfall for semi-monsoonal and anti-monsoonal type rainfall.  相似文献   

Pulsation at the tip of the first giant branch?     

Yoshifusa Ita  Toshihiko Tanabé  Noriyuki Matsunaga  Yasushi Nakajima  Chie Nagashima  Takahiro Nagayama  Daisuke Kato  Mikio Kurita  Tetsuya Nagata  Shuji Sato  Motohide Tamura  Hidehiko Nakaya  Yoshikazu Nakada 《Monthly notices of the Royal Astronomical Society》2002,337(3):L31-L34

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Proper motion dispersions of red clump giants in the galactic bulge: observations and model comparisons     

Nicholas J. Rattenbury  Shude Mao  Victor P. Debattista  Takahiro Sumi  Ortwin Gerhard  Flavio De Lorenzi 《Monthly notices of the Royal Astronomical Society》2007,378(3):1165-1176

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Search for TeV Gamma-Rays from 3EG J1234-1318 with the Cangaroo-II Telescope     

Takahiro Hattori  Kyoshi Nishijima 《Astrophysics and Space Science》2005,297(1-4):327-334

We observed 3EG J1234-1318 with the CANGAROO-II telescope in March, 2002. This source is a steady unidentified EGRET gamma-ray source at high Galactic latitude which has been associated with a dynamically merging clusters of galaxies, and is therefore a candidate TeV source. TeV gamma-ray emission is also expected as a result of large-scale cosmological structure formation. We here report the resulting upper limit on the TeV gamma-ray emission from 3EG J1234-1318. For the CANGAROO Collaboration.  相似文献   

An optical and near-infrared search for brown dwarfs in the Pleiades cluster     

Chie Nagashima †  Paul D. Dobbie  Takahiro Nagayama  Yasushi Nakajima  Tetsuya Nagata  Motohide Tamura  Tadashi Nakajima  Koji Sugitani  Hidehiko Nakaya  Simon T. Hodgkin  rew J. Pickles  Shuji Sato 《Monthly notices of the Royal Astronomical Society》2003,343(4):1263-1270

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Observations of wind-driven deepening of the surface mixing layer in the Tsushima strait     

Takahiro Endoh  Takeshi Matsuno  Yutaka Yoshikawa  Yasuto Tatsuyama  Joji Ishizaka 《Journal of Oceanography》2009,65(2):273-279

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Kinematic dynamos associated with large scale fluid motions     

Takahiro Nakajima  Masaru Kono 《地球物理与天体物理流体动力学》2013,107(1-4):177-209

Abstract

A standard approach to the kinematic dynamo problem is that pioneered by Bullard and Gellman (1954), which utilizes the toroidal-poloidal separation and spherical harmonic expansion of the magnetic and velocity fields. In these studies, the velocity field is given as a combination of small number of toroidal and poloidal harmonics, with their radial dependences prescribed by some physical considerations. Starting from the original paper of Bullard and Gellman (1954), a number of authors repeated such analyses on different combination of velocity fields, including the most recent and comprehensive effort by Dudley and James (1989). In this paper, we re-examine the previous kinematic dynamo models, using the computer algebra approach initiated by Kono (1990). This method is particularly suited to this kind of research since different velocity fields can be treated by a single program. We used the distribution of magnetic energies in various harmonics to infer the convergence of the results.

The numerical results obtained in this study for the models of Bullard and Gellman (1954), Lilley (1970), Gubbins (1973), Pekeris et al. (1973), Kumar and Roberts (1975), and Dudley and James (1989) are consistent with the previously reported results, in particular, with the extensive calculation of Dudley and James. In addition, we found that the combination of velocities used by Lilley can support the dynamo action if the radial dependence of the velocity is modified.

We also examined the helicity distributions in these dynamo models, to see if there is any correlation between the helicity and the efficiency of dynamo action. A successful dynamo can result both from the cases in which the helicity distributions are symmetric or antisymmetric with respect to the equator. In both cases, it appears that the dynamo action is efficient if the volume integral of helicity over a hemisphere is large.  相似文献   

Variable stars in the Magellanic Clouds: results from OGLE and SIRIUS     

Yoshifusa Ita  Toshihiko Tanabé  Noriyuki Matsunaga  Yasushi Nakajima  Chie Nagashima  Takahiro Nagayama  Daisuke Kato  Mikio Kurita  Tetsuya Nagata  Shuji Sato  Motohide Tamura  Hidehiko Nakaya  Yoshikazu Nakada 《Monthly notices of the Royal Astronomical Society》2004,347(3):720-728

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Unique Origin of Skarn at the Ohori Base Metal Deposit,Yamagata Prefecture,NE Japan: C,O and S Isotopic Study     

Yu Yokoro  Takahiro Hanamuro  Kazuo Nakashima 《Resource Geology》2013,63(4):384-393

The Ohori ore deposit is one of the Cu–Pb–Zn deposits in the Green Tuff region, NE Japan, and consists of skarn‐type (Kaninomata) and vein‐type (Nakanomata) orebodies. The former has a unique origin because its original calcareous rocks were made by hydrothermal precipitation during Miocene submarine volcanism. Carbon and oxygen isotope ratios of skarn calcite and sulfur isotope ratios of sulfides were measured in and around the deposit. Carbon and oxygen isotope ratios of the skarn calcite are δ¹³C = ?15.51 to ?5.1‰, δ¹⁸O = +3.6 to +22.5‰. δ¹³C values are slightly lower than those of the Cretaceous skarn deposits in Japan. These isotope ratios of the Kaninomata skarn show that the original calcareous rocks resemble the present submarine hydrothermal carbonates at the CLAM Site, Okinawa Trough, than Cenozoic limestones, even though some isotopic shifts had occurred during later skarnization. δ³⁴S ratios of the sulfide minerals from the Kaninomata and Nakanomata orebodies are mostly in a narrow range of +4.0 to +7.0‰ and they resemble each other, suggesting the same sulfur origin for the both deposits. The magnetite‐series Tertiary Kaninomatasawa granite is distributed just beneath the skarn layer and has δ³⁴S ratios of +7.5 to 8.1‰. The heavy sulfur isotope ratio of the skarn sulfides may have been affected by the Kaninomatasawa granite.  相似文献