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TIME VARIATIONS OF THE RADIAL VELOCITY OF H2O MASERS IN THE SEMI-REGULAR VARIABLE R CRT
Hiroshi Sudou,Motoki Shiga,Toshihiro Omodaka,Chihiro Nakai,Kazuki Ueda,Hiroshi Takaba 한국천문학회 2017 Journal of The Korean Astronomical Society Vol.50 No.6
H$_2$O maser emission {at 22 GHz} in the circumstellar envelope is one of the good tracers of detailed physics and inematics in the mass loss process of asymptotic giant branch stars. Long-term monitoring of an H$_2$O maser spectrum with high time resolution enables us to clarify acceleration processes of the expanding shell in the stellar atmosphere. We monitored the H$_2$O maser emission of the semi-regular variable R Crt with the Kagoshima 6-m telescope, and obtained a large data set of over 180 maser spectra over a period of 1.3 years with an observational span of a few days. Using an automatic peak detection method based on least-squares fitting, we exhaustively detected peaks as significant velocity components with the radial velocity on a 0.1 km s$^{-1}$ scale. This analysis result shows that the radial velocity of red-shifted and blue-shifted components exhibits a change between acceleration and deceleration on the time scale of a few hundred days. These velocity variations are likely to correlate with intensity variations, in particular during flaring state of H$_2$O masers. It seems reasonable to consider that the velocity variation of the maser source is caused by shock propagation in the envelope due to stellar pulsation.However, it is difficult to explain the relationship between the velocity variation and the intensity variation only from shock propagation effects. We found that a time delay of the integrated maser intensity with respect to the optical light curve is about 150 days.
일본 기수호 (Lake Obuchi)에서 생태계 모델의 개발과 적용
( Ueda Shinji ),( Kunio Kondo ),( Jiro Inaba ),( Masahiro Hosoda ),( Hiroshi Kutsukake ),( Yasushi Seike ),( Kisaburo Nakata ) 한국하천호수학회 2004 생태와 환경 Vol.37 No.4
In order to evaluate the water quality (N, P and C) and the biological mass balance of semi-enclosed brackish Lake Obuchi, Japan, an ecosystem model was developed and applied to the lake, using the flow field calculated by a hydrodynamic model. The time series data of the observed tide level, river discharge and meteorological parameters from January 2001 to December 2002 were incorporated as the parameters of the hydrodynamic model. Water quality and biomass balance were estimated by the ecosystem model, and simulated fluctuations in water quality agreed with our observations. The carbon contents of POC, phytoplankton and zooplankton in the lake were calculated by the model at an average 7200, 1500 and 22 ㎏, respectively, which somewhat agreed with our observations of POC (5900 ㎏), phytoplankton (3800 ㎏), and zooplankton (150 ㎏).
Ueda, Kohei,Yoshida, Masaaki,Isegawa, Kazuhisa,Shirahata, Naoki,Amemiya, Kenta,Mase, Kazuhiko,Mun, Bongjin Simon,Kondoh, Hiroshi American Chemical Society 2017 The Journal of Physical Chemistry Part C Vol.121 No.3
<P>The nitric oxide (NO) reduction by carbon monoxide (CO) on Ir(111) surfaces under near ambient pressure conditions was studied by a combination of near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and mass spectrometry (MS), particularly paying attention to the dominant reaction pathway to formation of molecular nitrogen (N-2). Under a relatively low CO pressure condition (50 mTorr NO + 10 mTorr CO), two reaction pathways to form N-2 are clearly observed at different ignition temperatures (280 and 400 degrees C) and attributed to a reaction of NO adsorbed at atop site (NOatop) with atomic nitrogen (N-ad) and associative desorption of N-ad, respectively. Since the adsorption of NOatop is inhibited by CO adsorbed at atop site (COatop), the ignition of the NOatop + N-ad reaction strongly depends on the coverage of COatop; the ignition temperature shifts to higher temperature as increasing CO pressure. In contrast, for the Nad + Nad reaction the ignition temperature keeps almost constant (similar to 400 degrees C). The online MS results indicate that the latter reaction is the dominant pathway to N-2 formation and the, former one less contributes to N-2 formation with accompanying a small amount of nitrous oxide (N2O). No evidence for contribution of the isocyanate (NCO) species as an intermediate was observed in the operando NAP-XP spectra.</P>