ASCA observations of colliding stellar winds in gamma velorum     

I. R. Stevens  S. L. Skinner  F. Nagase  M. F. Corcoran  A. J. Willis  A. M. T. Pollock  K. Koyama 《Astrophysics and Space Science》1995,224(1-2):569-570

We present new high spectral resolution X-ray observations of the colliding wind binary Vel taken with the ASCA satellite. We find two spectral components, one of which is post-shock emission from the colliding winds. Spectral variability is also seen, consistent with current notions of colliding wind phenomena.  相似文献   

Intergranular trace elements in mantle xenoliths from Russian Far East: Example for mantle metasomatism by hydrous melt     

Junji  Yamamoto  Shun'ichi  Nakai  Koshi  Nishimura  Ichiro  Kaneoka  Hiroyuki  Kagi  Keiko  Sato  Tasuku  Okumura  Vladimir S.  Prikhod'ko  Shoji  Arai 《Island Arc》2009,18(1):225-241

Based on both major and trace element chemistry, the occurrence of the intergranular component in mantle-derived xenoliths from far eastern Russia has been constrained. Whole-rock trace element measurements of one xenolith show apparent negative anomalies in Ce, Th, and high field strength elements on normalized trace element patterns. The trace element pattern of the whole rock differs from those of constituent minerals, indicating that the anomalies in the whole rock are attributable to the presence of an intergranular component. That assumption was confirmed using in situ analysis of trace elements in the intergranular substance and melt inclusion using laser ablation inductively coupled plasma–mass spectrometry. Both the intergranular component and the melt inclusions have identical trace element patterns, which mean that these materials are a cognate metasomatizing agent. The anomalies are regarded as mantle metasomatism related to an aqueous fluid. Hydrous minerals were observed on the wall of the melt inclusions using micro-Raman spectroscopy, indicating that the melt inclusions contained a large amount of water. Thus, this study reveals a trace element composition of a hydrous metasomatizing agent in the mantle.  相似文献   

岩溶作用对任丘古潜山碳酸盐岩油藏赋存的控制作用   总被引：7，自引：0，他引：7  

韩宝平  刘仁达  罗承建  于俊吉  于礼山 《中国岩溶》1998,17(1):75-80

根据大量钻井及开发动态资料,研究了任丘古潜山雾迷山组白云岩岩溶发育牲特征对油藏赋存的控制作用。溶蚀孔洞是最重要的储集空间,岩溶不发育的泥质白云岩段的分隔作用,导致在全油田统一油水界面以下有残余油区赋存,古潜山面上的溶蚀残丘等局部高点是残余油赋存的有利地段。  相似文献   

On the importance of accurately ray-traced troposphere corrections for Interferometric SAR data     

Thomas Hobiger  Youhei Kinoshita  Shingo Shimizu  Ryuichi Ichikawa  Masato Furuya  Tetsuro Kondo  Yasuhiro Koyama 《Journal of Geodesy》2010,84(9):537-546

Numerical weather models offer the possibility to compute corrections for a variety of space geodetic applications, including remote sensing techniques like interferometric SAR. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction. Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy. Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing. By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected. In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution.  相似文献   

Asymmetric tropospheric delays from numerical weather models for UT1 determination from VLBI Intensive sessions on the baseline Wettzell–Tsukuba     

Johannes Böhm  T. Hobiger  R. Ichikawa  T. Kondo  Y. Koyama  A. Pany  H. Schuh  K. Teke 《Journal of Geodesy》2010,84(5):319-325

One-baseline 1-h Very Long Baseline Interferometry (VLBI) Intensive sessions are carried out every day to determine Universal Time (UT1). Azimuthal asymmetry of tropospheric delays around the stations is usually ignored and not estimated because of the small number of observations. In this study we use external information about the asymmetry for the Intensive sessions between Tsukuba (Japan) and Wettzell (Germany), which are carried out on Saturdays and Sundays (1) from direct ray-tracing for each observation at Tsukuba and (2) in the form of linear horizontal north and east gradients every 6 h at both stations. The change of the UT1 estimates is at the 10 μs level with maximum differences of up to 50 μs, which is clearly above the formal uncertainties of the UT1 estimates (between 5 and 20 μs). Spectral analysis reveals that delays from direct ray-tracing for the station Tsukuba add significant power at short periods (1–2 weeks) w.r.t. the state-of-the-art approach, and comparisons with length-of-day (LOD) estimates from Global Positioning System (GPS) indicate that these ray-traced delays slightly improve the UT1 estimates from Intensive sessions.  相似文献   

Modeling the interaction between fluid flow and particle movement with discontinuous deformation analysis (DDA) method     

Tomofumi Koyama  Satoshi Nishiyama  Meng Yang  Yuzo Ohnishi 《国际地质力学数值与分析法杂志》2011,35(1):1-20

Coupled hydro‐mechanical processes in granular media represent the interaction between solid particles movement and fluid flow during external and/or internal loading. The processes attract attention in geotechnical engineering since they cause many disasters such as landslide, slope collapse, boiling/quicksand and soil liquefaction, etc. This study presents a numerical method combining discontinuous deformation analysis (DDA) for mechanical calculation and finite element method for fluid flow simulation to model the interaction between solid particles' movement and fluid flow from microscopic point of view. The term of hydraulic pressure was newly formulated and introduced to the original DDA. The simplified examples are given to verify the new method, and the computational results correlate well with the theoretical calculations, further development is also considered. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Chemical composition of PM2.5 at an urban site of Chengdu in southwestern China     

陶俊  成天涛  张仁健  曹军骥  朱李华  王启元  罗磊  张雷鸣 《大气科学进展》2013,30(4):1070-1084

PM2.5 aerosols were sampled in urban Chengdu from April 2009 to January 2010, and their chemical compositions were characterized in detail for elements, water soluble inorganic ions, and carbonaceous matter. The annual average of PM2.5 was 165g m－3, which is generally higher than measurements in other Chinese cities, suggesting serious particulate pollution issues in the city. Water soluble ions contributed 43.5% to the annual total PM2.5 mass, carbonaceous aerosols including elemental carbon and organic carbon contributed 32.0%, and trace elements contributed 13.8%. Distinct daily and seasonal variations were observed in the mass concentrations of PM2.5 and its components, reflecting the seasonal variations of different anthropogenic and natural sources. Weakly acidic to neutral particles were found for PM2.5. Major sources of PM2.5 identified from source apportionment analysis included coal combustion, traffic exhaust, biomass burning, soil dust, and construction dust emissions. The low nitrate: sulfate ratio suggested that stationary emissions were more important than vehicle emissions. The reconstructed masses of ammonium sulfate, ammonium nitrate, particulate carbonaceous matter, and fine soil accounted for 79% of the total measured PM2.5 mass; they also accounted for 92% of the total measured particle scattering.  相似文献   

Effects of rainfall amount and frequency on vegetation growth in a Tibetan alpine meadow   总被引：1，自引：0，他引：1  

Baocheng Zhang  Junji Cao  Yanfen Bai  Xuhui Zhou  Zhigang Ning  Songjie Yang  Lin Hu 《Climatic change》2013,118(2):197-212

Over the past decades, rainfall amount and frequency changed considerably on the Tibetan Plateau. However, how altered rainfall pattern affects vegetation growth and phenology in Tibetan alpine grasslands is poorly understood. In this study, we investigated the long-term effects of rainfall amount and frequency on production (i.e., aboveground biomass, AGB) and phenology of three perennial plants in a Tibetan alpine meadow from 1994 to 2005. Growth period (i.e., the dates from greening to senescence) was referred to plant phenology here. Our results showed that annual precipitation and total rainfall from large events (≥ 5 mm per day) were mainly distributed in the growing season, which increased significantly from 1994 to 2005 with more increment in May and July (p?<?0.05). Total AGB and growth periods of three plants were linearly correlated with annual precipitation and total rainfall from large events, but have insignificant correlations with total rainfall from small events (< 5 mm per day) and rainfall frequency (including small, large, and all events). The results suggest that aboveground plant production and phenology are more sensitive to changes in large rainfall events (≥ 5 mm per day) than small events (< 5 mm per day) in the alpine meadow ecosystems.  相似文献   

无人机倾斜摄影在露天矿山开采监测中的应用     

朱守信  李军吉  梁作前 《地理空间信息》2022,20(5):60-62

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Numerical modelling of fluid flow tests in a rock fracture with a special algorithm for contact areas     

T. Koyama  B. Li  Y. Jiang  L. Jing 《Computers and Geotechnics》2009,36(1-2):291-303

The fluid flow in rock fractures during shear processes has been an important issue in rock mechanics and is investigated in this paper using finite element method (FEM), considering evolutions of aperture and transmissivity with shear displacement histories under different normal stress and normal stiffness conditions as measured during laboratory coupled shear-flow tests. The distributions of fracture aperture and its evolution during shearing were calculated from the initial aperture, based on the laser-scanned sample surface roughness results, and shear dilations measured in the laboratory tests. Three normal loading conditions were adopted in the tests: simple normal stress and mixed normal stress and normal stiffness to reflect more realistic in situ conditions. A special algorithm for treatment of the contact areas as zero-aperture elements was used to produce more accurate flow field simulations, which is important for continued simulations of particle transport but often not properly treated in literature. The simulation results agree well with the measured hydraulic apertures and flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow fields with changing normal loading conditions and increasing shear displacements. With the new algorithm for contact areas, the tortuous flow fields and channeling effects under normal stress/stiffness conditions during shearing were more realistically captured, which is not possible if traditional techniques by assuming very small aperture values for the contact areas were used. These findings have an important impact on the interpretation of the results of coupled hydro-mechanical experiments of rock fractures, and on more realistic simulations of particle transport processes in fractured rocks.  相似文献