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661.
宝钢轧机旋流池深基坑的监测分析   总被引:8,自引:0,他引:8  
边亦海  黄宏伟  张冬梅 《岩土力学》2004,25(Z2):491-495
介绍了宝钢一个采用半逆作法施工深基坑的现场监测实例.通过对地下连续墙侧向位移、孔隙水压力、土压力、钢筋应力及坑底隆起等监测结果的分析,得出一些有价值的结论,可以为类似工程的设计、施工和监测提供一些借鉴.  相似文献   
662.
从四川盆地南北缘近古陆的下志留统中所获干酪根显示,主要以Ⅲ型为主,其中含有管胞、木质素、纤维素等维管植物成分,而在盆地内的远离古陆地区干酪根则表现出以Ⅰ型为主。据此不仅说明在早志留世早期本区古陆上已出现有维管植物,而且进一步证实环境因素对植物演化具有重要影响  相似文献   
663.
介绍一个可用于多路信号自动测量系统或自动切换系统的高隔离射频多路转换开关的设计与制作。开关制式为双刀16掷;控制采取本地(利用本机面板控制)和遥控(IEEE—488标准接口)两种方式工作频率范围为DC~100MHz;路与路之间的串扰,隔离度优于120dB(5MHz)[1]。  相似文献   
664.
IntroductionWhetherearthquakescanbepredictedornotisstilaproblemincontroversyintheseismologicalcircle.Atanyrate,however,peopl...  相似文献   
665.
Four large and superlarge copper-multimetal ore deposits hosted in the Mid-Proterozoic Zhartaishan Group along northwestern margin of North China Plate are stratabound hydrothermal sedimentary deposits, and these deposits formed in mid-late stage of the Mid-Proterozoic Langshan-Zhartaishan rifting system. Four necessary conditions are proposed for the formation of these large and superlarge ore deposits: (i) favorable geological background and tectonic environment; (ii) abundant sources of metallogenic material; (iii) favorable sedimentary lithofacies and paleogeographic conditions; (iv) sudden change events during metallogenic processes.  相似文献   
666.
A map showing the three-dimensional velocity anomaly on the southwestern edge of Yangtze craton is first compiled. Based on the map, it is suggested that there is a low-velocity plume on the edge of Yangtze craton. The low-velocity plume is the effect of mantle plume, plays an important role in controlling the upwelling of asthenosphere, mantle rise and the formation of intracrustal low-velocity lens, and is also the carrier and provider of vast amount of fluids, mineralizers, minerogenetic materials and energy. Therefore, it is concluded that the low-velocity plume is closely related to Mesozoic and Cenozoic superlarge ore deposits in time and space and genesis.  相似文献   
667.
CO2湍流通量误差的修正和不确定性研究进展   总被引:1,自引:0,他引:1       下载免费PDF全文
目前国内外对能量和CO2涡动相关通量的测量误差的谱修正缺乏一致性,导致各测量站之间的资料对比难以进行,给全球尺度资料的合成造成很大困难。因此在强调长期CO2通量测量精度的同时,还应该注重确定对测量误差修正的首选方法和研究重点。该文主要介绍了两种用于修正测量仪器误差的谱方法;二维和三维的气流运动对通量误差的影响;资料处理中的误差;夜间CO2通量的测量问题。  相似文献   
668.
To study the impacts of climate change on water resources in the western U.S., global climate simulations were produced using the National Center for Atmospheric Research/Department of Energy (NCAR/DOE) Parallel Climate Model (PCM). The Penn State/NCAR Mesoscale Model (MM5) was used to downscale the PCM control (20 years) and three future(2040–2060) climate simulations to yield ensemble regional climate simulations at 40 km spatial resolution for the western U.S. This paper describes the regional simulations and focuses on the hydroclimate conditions in the Columbia River Basin (CRB) and Sacramento-San Joaquin River (SSJ) Basin. Results based on global and regional simulations show that by mid-century, the average regional warming of 1 to 2.5 °C strongly affects snowpack in the western U.S. Along coastal mountains, reduction in annual snowpack was about70% as indicated by the regional simulations. Besides changes in mean temperature, precipitation, and snowpack, cold season extreme daily precipitation increased by 5 to 15 mm/day (15–20%) along theCascades and the Sierra. The warming resulted in increased rainfall at the expense of reduced snowfall, and reduced snow accumulation (or earlier snowmelt) during the cold season. In the CRB, these changes were accompanied by more frequent rain-on-snow events. Overall, they induced higher likelihood of wintertime flooding and reduced runoff and soil moisture in the summer. Changes in surface water and energy budgets in the CRB and SSJ basin were affected mainly by changes in surface temperature, which were statistically significant at the 0.95 confidence level. Changes in precipitation, while spatially incoherent, were not statistically significant except for the drying trend during summer. Because snow and runoff are highly sensitive tospatial distributions of temperature and precipitation, this study shows that (1) downscaling provides more realistic estimates of hydrologic impacts in mountainous regions such as the western U.S., and (2) despite relatively small changes in temperature and precipitation, changes in snowpack and runoff can be much larger on monthly to seasonal time scales because the effects of temperature and precipitation are integrated over time and space through various surface hydrological and land-atmosphere feedback processes. Although the results reported in this study were derived from an ensemble of regional climate simulations driven by a global climate model that displays low climate sensitivity compared with most other models, climate change was found to significantly affect water resources in the western U.S. by the mid twenty-first century.  相似文献   
669.
利用测震台网记录获得加速度波形的方法研究   总被引:3,自引:0,他引:3  
研究了从测震台网速度记录获得高质量加速度波形的方法,并以天津蓟县台安装的CTSI-EDAS24速度型甚宽带地震仪和EST-Q4128型强。震仪对同一地震记录的处理分析为例,对计算步骤和处理方法进行了详细论述。处理结果的对比分析表明,该方法简单有效,拓宽了数字测震台网波形记录的服务应用范围。  相似文献   
670.
Modeling photochemistry in the stratosphere requires solution of the equationof radiative transfer over an extreme range of wavelengths and atmosphericconditions, from transmission through the Schumann–Runge bands ofO2 in the mesosphere, to multiple scattering from troposphericclouds and aerosols. The complexity and range of conditions makes photolysiscalculations in 3-D chemical transport models computationally expensive. Thisstudy pesents a fast and accurate numerical method, Fast-J2, for calculatingphotolysis rates (J-values) and the deposition of solar flux in stratosphere.Fast-J2 develops an optimized, super-wide 11-bin quadrature for wavelengthsfrom 177 to 291 nm that concatenates with the 7-bin quadrature (291–850nm) already developed for the troposphere as Fast-J. Below 291 nm the effectsof Rayleigh scattering are implemented as a pseudo-absorption, and above 291nm the full multiple-scattering code of Fast-J is used. Fast-J2 calculates themean ultraviolet-visible radiation field for these 18 wavelength binsthroughout the stratosphere, and thus new species and new cross sections canbe readily implemented. In comparison with a standard, high-resolution,multiple-scattering photolysis model, worst-case errors in Fast-J2 do notexceed 5% over a wide range of solar zenith angles, altitudes(0–60 km), latitudes, and seasons where the rates are important inphotochemistry.  相似文献   
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