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561.
562.
563.
Devendra Lal William G. Large Stephan G. Walker 《Journal of Earth System Science》2007,116(3):171-177
This paper attempts at full characterization of the unique global 8.2 Kyr B.P. cooling event. Significant atmospheric cooling
started during 9.5–8.5 Kyr B.P. when the Sun was extremely quiet during three periods of ∼ 50–100 years. The flood of melt
water in the N. Atlantic from glacial lakes during the demise of the Laurentide ice sheet, starting at ∼ 8.5 Kyr B.P., adds
to the atmospheric cooling. Climatic forcing events occurred at 8.5 Kyr B.P., at 8.2 Kyr B.P. and finally at 8.06 Kyr B.P.,
leading to concurrent increases or decreases in the atmospheric Δ14C levels, completely consistent with the climatic forcing proposed here. 相似文献
564.
TAO Zhen SHEN ChengDe GAO QuanZhou SUN YanMin YI WeiXi & LI YingNian School of Geography Planning Sun Yat-sen University Guangzhou China Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Northwest Plateau Institute of Biology Chinese Academy of Sciences Xining China 《中国科学D辑(英文版)》2007,50(7)
High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research. 相似文献
565.
In this study we utilize marine shell samples from two levels of historically uplifted sessile mollusk assemblages and raised wave-cut benches to evaluate the marine reservoir correction (ΔR) for the Pacific coast of central Japan. Elevation measurements of the uplifted marine shells indicate that the lower assemblage emerged during the 1923 Taisho Kanto earthquake (M7.9), whereas uplift of the upper assemblage is most likely but less confidently ascribed to the 1703 Genroku Kanto earthquake (M8.2). Radiocarbon dating of carefully selected samples from the upper and lower assemblages yielded very similar ΔR values of 82 ± 33 and 77 ± 32 yr, respectively. We regard the former ΔR value as a representative and more reliable value given the uncertainty in correlation of the upper assemblage with the 1703 earthquake. This result is consistent with previously reported ΔR values for the Pacific coast of south-central Japan and areas around the Sea of Japan that are influenced by warm ocean currents. Radiocarbon dating of coseismically uplifted shells can aid in estimating marine reservoir ages in the tectonically active Japan Islands. 相似文献
566.
基于COM的MATLAB和C++ Builder在测量软件开发中的应用 总被引:1,自引:0,他引:1
本文运用MATLAB 6.5中的MATLAB COM Builder模块为转换工具,将MATLAB的M函数文件转换为COM组件后应用在Borland C++ Builder6.0,集成后的软件不仅能够充分发挥两种语言的优势,还可以完全脱离MATALB的运行环境。文中以测量平差中法方程的全主元分解法求解的编译过程为例,进行了MATLAB应用程序(组件)的发布研究。 相似文献
567.
在地理信息系统的Web站点开发中,我们遇到了很多棘手的问题,最直接的是矢量显示的问题,因为浏览器作为容器不具有处理矢量的能力,要达到这个目的,它需要嵌入其他有处理矢量能力的容器。目前,解决这个问题有两个方案:一是ActiveX控件技术;二是Java Applet技术。本文简单介绍一下两种技术,并主要讨论JavaApplet技术怎样实现矢量数据的显示。 相似文献
568.
S.W. Allen G.B. Taylor P.E.J. Nulsen R.M. Johnstone L.P. David S. Ettori A.C. Fabian W. Forman C. Jones B. McNamara 《Monthly notices of the Royal Astronomical Society》2001,324(4):842-858
We examine the properties of the X-ray gas in the central regions of the distant ( z =0.46) , X-ray luminous cluster of galaxies surrounding the powerful radio source 3C 295, using observations made with the Chandra Observatory . Between radii of 50 and 500 kpc, the cluster gas is approximately isothermal with an emission-weighted temperature, kT ∼5 keV . Within the central 50-kpc radius this value drops to kT ∼3.7 keV . The spectral and imaging Chandra data indicate the presence of a cooling flow within the central 50-kpc radius of the cluster, with a mass deposition rate of approximately 280 M⊙ yr−1 . We estimate an age for the cooling flow of 1–2 Gyr , which is approximately 1000 times older than the central radio source. We find no evidence in the X-ray spectra or images for significant heating of the X-ray gas by the radio source. We report the detection of an edge-like absorption feature in the spectrum for the central 50-kpc region, which may be caused by oxygen-enriched dust grains. The implied mass in metals seen in absorption could have been accumulated by the cooling flow over its lifetime. Combining the results on the X-ray gas density profile with radio measurements of the Faraday rotation measure in 3C 295, we estimate the magnetic field strength in the region of the cluster core to be B ∼12 μG . 相似文献
569.
Henry Florence Bockelée-Morvan Dominique Crovisier Jacques Wink Jörn 《Earth, Moon, and Planets》2002,90(1-4):57-60
CO was observed on March 11, 1997 in comet Hale–Bopp with theIRAM Plateau de Bure interferometer. The maps show evidence for
asymmetrical patterns, due to the Existence of CO jets. Analysis of the spectra and their velocity shifts shows that there
is a spiral CO jet rotating in a plane almost perpendicular to the sky plane.This is the first time that rotating jets are
observed for parent molecules.We have developed a 3-D model simulating rotating spiral jets of CO gas.We present here the
comparison between the observations and our model. 相似文献
570.
Amateur astronomers have always represented an important observing group in cometary astronomy. Much of our knowledge of cometary
light curves has come from amateur data, initially in the form of total visual magnitude estimates and now increasingly in
the form of CCD observations. The increasingly widespread use by amateur astronomers of CCD cameras of excellent sensitivity
and good cosmetic quality has revolutionised astrometry, allowing far more intensive astrometric monitoring of comets to be
carried out down to magnitude 18 and fainter, with a corresponding enormous increase in the quality of calculated orbits.
Although amateur CCD photometry is extensively available in the Internet, its use has been less widespread. The reason is
the lack of standardisation in the way that this data is taken that leads to amateur CCD light curves having enormous dispersion.
All amateur CCD photometry is aperture photometry, but it is seen that neither does it represent well the equivalent of m1
(total visual magnitude), even with a large aperture, nor is it close to the definition of m2 (the nucleus magnitude). The problem is examined using data from the Spanish Comet Observers Group archives to show that
by careful standardisation of data acquisition amateur CCD data can produce high quality, well-sampled and physically meaningful
light curves. Examples are presented of the results for recent comets including 19P/Borrelly, 51P/Harrington, C/2001 TU80
(LINEAR-NEAT), C/2000 WM1 (LINEAR) & C/2001 A2 (LINEAR). 相似文献