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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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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An approach to estimating evapotranspiration in the Urumqi River basin,Tianshan, China,by means of remote sensing and a geographical information system technique     

Wanchang Zhang  Jun Chen  Katsuro Ogawa  Yasushi Yamaguchi 《水文研究》2005,19(9):1839-1854

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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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Activity Profile of the Sextantid Meteor Shower     

Ohtsuka  Katsuhito  Shimoda  Chikara  Yoshikawa  Makoto  Watanabe  Jun-Ichi 《Earth, Moon, and Planets》1997,77(2):83-91

The detailed activity profile of the Sextandids - one of the day-time meteor showers - is poorly known and still unclear. Using the forward-scatter radio technique we have successfully been able to obtain further detailed overall activity profile of the Sextantids for seven consecutive years: 1991–1997. Analysis confirmed the Sextantid activity duration in solar longitude (J2000) of at least 184–193° and the maximum solar longitude at 188.35 ± 0.10° with a full width at half maximum (FWHM) of 2.0 ± 0.2°. Performing the numerical integrations, we also substantiated a possibility of the association between Apollo-type asteroid (3200) Phaethon and the Sextantids. Furthermore, we roughly estimated relative maximum flux rate of Sextantids : Geminids as 1 : 3 amplitude ratio. Depending upon the flux rates and the time lags of the orbital evolution with Phaethon, we conclude that the Sextantids are at a more progressive stage of orbital evolution than the Geminids if both meteor streams are really associated with Phaethon. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Suspended sediment in the Ganges and Brahmaputra Rivers in Bangladesh: observation from TM and AVHRR data     

Mohammad Rezwanul Islam  Yasushi Yamaguchi  Katsuro Ogawa 《水文研究》2001,15(3):493-509

Remote sensing was used to understand the seasonal and spatial variation of suspended sediment in the Ganges and Brahmaputra Rivers in Bangladesh for two different discharge periods. Suspended sediment concentration (SSC) in these rivers was estimated from the reflectance of Landsat TM band 3. During the high discharge period, SSC in the Ganges is higher than that in the Brahmaputra. But in the low discharge period, this is reversed. Both erosional and depositional processes are active on their flood plains. Significant fluctuations in SSC and in suspended sediment load were observed along their courses because of river bank erosion and deposition and/or scouring and aggradation of river beds. Owing to scouring and turbulence, SSC increases markedly at the confluence of these rivers. Reflectance of AVHRR band 1 data was also analysed to study the distribution of suspended sediment along other reaches of these rivers. Like SSC, reflectance at the confluence zone increases compared with that in the Brahmaputra. However, this increase is not marked compared with the Ganges. The influence of their tributaries on the suspended sediment load could be inferred from the pattern of reflectance. Remote sensing data used in this study was corrected for atmospheric effects. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Land use and land cover change in Greater Dhaka, Bangladesh: Using remote sensing to promote sustainable urbanization   总被引：12，自引：0，他引：12  

Ashraf M. Dewan  Yasushi Yamaguchi 《Applied geography (Sevenoaks, England)》2009,29(3):390-401

This study evaluates land use/cover changes and urban expansion in Greater Dhaka, Bangladesh, between 1975 and 2003 using satellite images and socio-economic data. Spatial and temporal dynamics of land use/cover changes were quantified using three Landsat images, a supervised classification algorithm and the post-classification change detection technique in GIS. Accuracy of the Landsat-derived land use/cover maps ranged from 85 to 90%. The analysis revealed that substantial growth of built-up areas in Greater Dhaka over the study period resulted significant decrease in the area of water bodies, cultivated land, vegetation and wetlands. Urban land expansion has been largely driven by elevation, population growth and economic development. Rapid urban expansion through infilling of low-lying areas and clearing of vegetation resulted in a wide range of environmental impacts, including habitat quality. As reliable and current data are lacking for Bangladesh, the land use maps produced in this study will contribute to both the development of sustainable urban land use planning decisions and also for forecasting possible future changes in growth patterns.  相似文献   

The sea surface temperature product algorithm of the Ocean Color and Temperature Scanner (OCTS) and its accuracy     

Futoki Sakaida  Masao Moriyama  Hiroshi Murakami  Hiromi Oaku  Yasushi Mitomi  Akira Mukaida  Hiroshi Kawamura 《Journal of Oceanography》1998,54(5):437-442

The Ocean Color and Temperature Scanner (OCTS) aboard the Advanced Earth Observing Satellite (ADEOS) can observe ocean color and sea surface temperature (SST) simultaneously. This paper explains the algorithm for the OCTS SST product in the NASDA OCTS mission. In the development of the latest, third version (V3) algorithm, the OCTS match-up dataset plays an important role, especially when the coefficients required in the MCSST equation are derived and the equation form is adjusted. As a result of the validation using the OCTS match-up dataset, the algorithm has improved the root mean square (rms) error of the OCTS SST up to 0.698°C although some problems remain in the match-up dataset used in the present study.  相似文献   

HPLC determination of phytoplankton pigments using N,N-dimethylformamide   总被引：9，自引：0，他引：9  

Ken Furuya  Masato Hayashi  Yasushi Yabushita 《Journal of Oceanography》1998,54(2):199-203

The suitability of N,N-dimethylformamide (DMF) as an extractant for the standard reverse-phase HPLC method was examined using algal cultures. Good pigment separations and recovery were achieved with 20% (volume %) addition of an ion-pairing solution in an injection. While slight amounts of degradation products of chlorophylla, i.e., chlorophyllidea, allomeric and epimeric forms, were produced, adequate attention to filtration and extraction prevents the formation of degradation products, confining them to an acceptable level. Because of its strong extractability, which expedites the extraction process, DMF is an efficient solvent for HPLC analysis of phytoplankton pigments.  相似文献   

Observation of Mercury's sodium exosphere during the transit on November 9, 2006     

Ichiro Yoshikawa  Junya Ono  Go Murakami  Shingo Kameda 《Planetary and Space Science》2008,56(13):1676-1680

A rare, but normal, astronomical event occurred on November 9th 2006 (JST) as Mercury passed in front of the Sun from the perspective of the Earth. The abundance of the sodium vapor above the planet limb was observed by detecting an excess absorption in the solar sodium line D₁ during this event. The observation was performed with a 10-m spectrograph of Czerny-Turnar system at Domeless Solar Tower Telescope at the Hida Observatory in Japan. The excess absorption was red-shifted by 10 pm relative to the solar line, and was measured at the dawnside (eastside) and duskside (westside) of Mercury. Between the dawn and dusksides, an asymmetry of total sodium abundance was clearly identified. At the dawnside, the total sodium column density was 6.1×10¹⁰ Na atoms/cm², while it was 4.1×10¹⁰ Na atoms/cm² at the duskside. The investigation of dawn-dusk asymmetry of the sodium exosphere of Mercury is a clue to understand the release mechanism of sodium from the surface rock. Our result suggests that a thermal desorption is a main source process for sodium vapor in the vicinity of Mercury.  相似文献