Trimble　4000　SST双频GPS定位仪的“零基线”检验   总被引：2，自引：0，他引：2  

蔡宏翔  兰蔚 《时间频率学报》1994

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Spectrum characteristics of major ion concentrations at Wuhan sectoin of the Changjiang Rriver     

Xing-hui Xia  Jing-sheng Chen  Xu-yi Cai 《中国地理科学(英文版)》2001,11(4):315-320

Spectrum analyses of water quality time series have been carried out for five hydrometric stations including Wuhan hydrometric station of the Changjiang(Yangtze) River, etc. The fluctuations of Ca²⁺, Mg²⁺ and HCO ₃ ⁻ concentrations in river water under different physical geography conditions have about two-year cycle which is corresponding to hydrometeorological quasi-biannual-oscillation (QBO). Na⁺, Cl⁻ SO ₄ ²⁻ have about two-year cycle in the area lightly affected by human activities while two-year cycle doesn’t exist in the area heavily affected by human activities. All the fluctuations of major ions have about three-month cycle. The river diseharge fluctuation accounts for 43.9%, 45.1%, 54.3%, 33.9%, 30.3% and 42.7% of the variance of Ca²⁺, Mg²⁺, HCO ₃ ⁻ , Na⁺, Cl⁻, SO ₄ ²⁻ , respectively, at Wuhan from 1962 to 1985. According to the spectrum characteristic of major ions, the duration of the time series has to be at least 13 years for trend analysis of monthly water quality data. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 49671017). Biography: XIA Xing-hui(1971-), female, a native of Hunan Province, Ph. D. Her research interest includes environmental chemistry.  相似文献   

贵州与印度的夏季风的异同分析   总被引：3，自引：0，他引：3  

于俊伟  赵彩  田英 《成都信息工程学院学报》2001,16(1):17-20

季风作了气象科学的一个重要课题，许多人都作了大量研究，中国和印度均处于季风区，印度季风和中国季风的研究已作了大量研究，揭露了不少事实，但中国季风的研究多指我国的东部，而贵州位于我国西南部，地处东亚季风和印度季风之间的过渡区，因此，对贵州省的论及较少，从气候的角度出发，把贵州和印度的季风的某些特征量，如降雨、风、环流等进行对比分析，在一定程度上反映了贵州和印度夏季风的主要异同。  相似文献   

Grain-size related nitrogen distribution in southern Yellow Sea surface sediments   总被引：1，自引：0，他引：1  

吕晓霞宋金明  袁华茂李学刚  詹天荣李宁高学鲁  石学法 《中国海洋湖沼学报》2005,23(3):306-316

Forty-eight surface sediments of the southern Yellow Sea are separated into three grain-size fractions. Four forms of extractable nitrogen (nitrogen in ion-exchangeable form (Nie), nitrogen in weak-acid extractable form (Nwa), nitrogen in strong-alkali extractable form (Nsa) and nitrogen in strong-oxidant form (N50))are obtained by the sequential extraction. The results show that the contents and the distributions of the extractable nitrogen in the southern Yellow Sea surface sediments are closely related to sediment grain size. The distributions ofNie, Nso and total nitrogen (TN) present positive correlations with fine particles content, while Nwa and Nsa does not have such correlation. The net contents of all the forms of nitrogen increase with sediment grain size finer.  相似文献   

The X-ray Emission and the Magnetic Fields of Late-Type Stars     

J.R. Shi  G. Zhao  Y. Zhao 《Astrophysics and Space Science》2002,282(3):477-488

We present the results of X-ray luminosities of some active late-type stars, based on data primarily from the ROSAT position sensitive proportional counter (PSPC). According to the observations, we divide the stars into four groups: single, wide binary, binary and RS CVn. We investigated the correlation between the X-ray emission and the hardness ratio, coronal temperature, magnetic field strength, magnetic flux density. Our results suggest that the magnetic field plays a very important role in stellar X-ray emission.  相似文献   

青田芝溪头鹤溪群浅变质岩系中发现动物化石     

朱德寿  胡耀华  石关根 《浙江国土资源》1994,(2)

作者于1993年4月在浙江青田芝溪头鹤溪群剖面上采集了白云质大理岩标本样品，送南京地质古生物研究所进行标本浸泡处理。首次获得鱼骨、管状化石及土菱子介等海相化石，经鉴定认为其时代可能属石岩—二叠纪。本文根据以往的同位素资料、沉积环境分析和区域对比，认为这套变质岩系的原岩为二叠纪含煤沉积岩，可与福建的童子岩组中上部层位对比。  相似文献   

顾及GRACE季节影响的华北平原水储量变化反演     

李圳  章传银  柯宝贵  刘阳  李婉秋  尹财 《测绘学报》2018,47(7):940-949

基于移去-恢复方法,利用GRACE卫星重力数据研究了华北平原2003年1月—2014年6月的陆地水变化,提出了一种顾及季节影响尺度因子计算方法,用于减小GRACE后处理误差。将本文方法所得结果与水文模式和降水模型结合进行比较分析,结果表明：2008年之前华北平原发生比较明显的干旱现象,陆地水和地表水分别以（-7.9±2.4）mm/a和（-7.3±2.8）mm/a的速度下降,但地下水仅以（-0.6±1.4）mm/a的速度减少;2008年之后,陆地水和地表水分别以（4.3±1.3）mm/a和（10.9±2.1）mm/a的速度上升,期间地下水的超采严重,平均以（-6.5±1.2）mm/a的速度下降,但下降速度以0.9 mm/a²的趋势减缓。研究期间内,华北平原的陆地水、地表水和地下水整体分别呈现（-2.0±0.6）、（2.9±0.7）和（-4.8±0.7）mm/a的变化趋势。最后,利用交叉小波谱分析了GRACE滞后于降水的现象。研究结论表明,降水和地下水开采是影响华北平原水储量变化的两大决定性因素。  相似文献   

Mechanical and microseismic characteristics of sandstones subject to moderate low-frequency differential cyclic loading (DCL) followed by monotonic loading up to failure     

Song  Zhengyang  Konietzky  Heinz  Wu  Yunfeng  Cai  Xin 《Acta Geotechnica》2023,18(1):187-215

Acta Geotechnica - This work aims to experimentally investigate the behaviour of sandstone drilled from an underground coal mine exposed to low-frequency cyclic loading with distinct...  相似文献   

柴达木盆地马仙地区古近系沉积特征及其主控因素     

樊妍  鞠俊成  向才富  韩宏伟  刘嘉  杨明慧 《地质论评》2023,69(Z1):9-12

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晚更新世以来珠江三角洲钻孔年代及沉积演化     

林鹏辉  李宏卫  詹伟琪  凌恳  宋盈瑾  徐晓琳  赖忠平 《地质论评》2023,69(Z1):333-335

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