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排序方式: 共有329条查询结果,搜索用时 31 毫秒
71.
安全管理是企业生产的保障,由于施工项目的流动性大、高空作业多、作业条件差,建设管理水平参差不齐,影响施工安全的因素多,科学管理对做好安全工作来讲是极其必要的. 相似文献
72.
通过变换证明了二阶常微分方程解的存在唯一及迭代收敛性,并给出了收敛速度的估计式. 相似文献
73.
本文从中外社科数据库的发展情况,阐述如何建立中文社科数据库;确定数据库的标准;数据库的设计;加强专业人员的培养;建立完整的管理机构 相似文献
74.
Gas seepage on the sea floor of Okinawa Trough Miyako Section 总被引:1,自引:0,他引:1
LUANXiwu QINYunshan 《科学通报(英文版)》2005,50(13):1358-1365
A marine geophysical survey was carried out,on the R/V Science 1 of the Institute of Oceanography, Chinese Academy of Sciences (IOCAS), in 2000, at the Miyako Section of Okinawa Trough. Here we present seismic and acoustic evidence of a gas seep on the sea floor on the western part of the Okinawa Trough, near the lower slope of the East China Sea Slope and discuss the possibility of related formation of gas hydrate. A gas column reflection was observed in echo-sounder data above a section where the sea floor reflector was missing, on both the echo-sounder and the seismic data for line H14. The seismic data also show an acoustic curtain reflection and a turbidity reflection at this section.These anomalies are the evidence of the existence of a gas seep, which occupies .an area 2.2 km in diameter. Based on the acoustic curtain on line H14, we believe that the amount of gas contained in the sediments below the gas seep is larger than 1% by volume of sediment. Tectonically, the gas seep developed in a small basin controlled by basement uplift in the north, south and east. The thickness of the sediment layer can be greater than 3.5 km. A mud diapir structure was found in layer D beneath the gas seep. Over-pressure may occur due to the large sediment thickness and also the tectonic basement uplift in the north, south, and east. The mud diapir could be the preferential pathway for methane-rich fluids. The acoustic curtain may indicate that free gas related to the gas seep can be formed on the sea floor. We also note that the layer above the acoustic curtain on profile H14 may contain gas hydrate. 相似文献
75.
CHEN Zhaoyang LIU Changjun LUAN Zhaokun ZHANG Zhongguo LI Yanzhong JIA Zhiping 《科学通报(英文版)》2005,50(18):2010-2015
Influence of total aluminum concentration (CAIT) on the generation and transformation of nanosized AI13 and AI30 in hydrolytic polyaluminum aqueous solutions was investigated using high field 27AI NMR and time-developed AI-Ferron complex colorimetry. When prepared at the optimal basicity (B) of Al13 generation and 80℃, the All3 species in polyaluminum solution tends to further polymerize and convert to AI30 and higher polymers when CAI; 〉0.2 mol· L^-1, but Al13 does not convert to AI30 quantificationally, as the formation of Alu from Al13 and AI30 is accelerated in the same way. The conversion rate of All3 is accelerated by the increase in CAIT. When CAlT 〉0.75 mol·.L^-1, Al13 content decreases rapidly, and AI30 content increases continuously and becomes the dominant nanometer polynuclear aluminum species. AIm is one of prerequisites of Al13 conversion to AI30. When CAI; increases and B reduces, the polymerization rate between Al13 and Aim increases, and at the same time, the dissociation reaction rate of All3 and AI30 by H^+ also increases. The latter becomes the dominant reaction in polyaluminum solution with low B value, so AI30 decreases with the increasing CAlT. The hydrolytic polyaluminum solution with Al13 content beyond 80% can only be prepared under the condition of CAlT〈0.5 mol· L^-1 and optimal B value. 相似文献
76.
Surface characteristics of modified carbon nanotubes and its application in lead adsorption from aqueous solution 总被引:2,自引:0,他引:2
WANGShuguang LIYanhui GongXiaoyan ZHAOHuazhang LUANZhaokun XUCailu WUDehai 《科学通报(英文版)》2003,48(5):441-443
Carbon nanotubes(CNT) were modified by nitric acid oxidation.Infrared spectroscopy(IR) demonstrated that hydroxyl(-OH) and carbonyl(-C=O)functional groups were introduced to the surface of modified CNT.Micrometrics ASAP 2000 measurement showed that the surface area of modified CNT was slightly increased.Furthermore,the Pb^2 adsorption behavior on the surface of modified CNT has been investigated.The results indicate that the modified CNT has an exceptional adsorption capability for Pb^2 removal.The adsorption isotherms are well described by the Langmuir equation under test temperatures and the kinetics level is three. 相似文献
77.
场地地震反应非线性分析的有效时域算法 总被引:19,自引:0,他引:19
运用笔者所建议的动态应力-应变关系及推广的加卸载准则考虑土料在循环或瞬时加载下的非线性滞回特性,将时域逐渐积分格式与不平衡荷载转移法相结合提出了动力非线性方程的增量-常刚度迭代算法;以水平成层场地一维剪梁模型为例建立了求解土体地震反应的非线性分析技术。针对某土层剖面,运用这种真非线性算法与以往等价线性化法进行了对比计算,讨论了两者之差别。 相似文献
78.
运用日本田口玄一首创的SN比试验设计法进行提高25Cy14—IB型油泵质量的最佳工艺参数的试验研究,通过对结果的分析与计算,找到最佳工艺条件并应用到生产中,取得显著的技术经济效果. 相似文献
79.
层状饱和砂土振动孔隙水压力扩散与消散简化解法 总被引:4,自引:0,他引:4
针对层状饱和砂土,求解了由Terzaghi固结理论与不排水条件下孔隙水压力增长模式相耦合的含有源项的扩散方程,得到了一个较为一般的孔隙水压力场封闭型解答.辅以一定的数值计算,可以具体地预计层状饱和砂土震动中孔隙水压力扩散与消散过程及液化势.算例分析表明,建议的估算方法简便可行,有一定的实用价值.所得解答可为其他数值方法提供一个验证的基础. 相似文献
80.
本文根据二维扩散方程式并考虑到琼脂相与水相间的平衡关系,推导得杯碟法生物检定的理论方程式。利用放线酮作为试样,在不同瞬间、不同径向距离处取样,测得放线酮在琼脂中的表观扩散系数为0.013cm~2/h(25℃),并计算得浓度随半径和时间变化的理论曲线,与实验结果吻合较好。结合临界浓度和临界时间概念,方程式能对生物检定的实际应用有指导意义。 相似文献