采用随机有限断层法生成最大可信地震

本文依据基于地震学理论合成地震动的随机方法和能够细致描述震源复杂性的有限断层模型,采用随机有限断层法直接生成最大可信地震。重点比较了随机有限断层法的静拐角频率和动拐角频率理论,开发基于静拐角频率方法的Fortran程序SFFMSIM,作为对比,引进了动拐角频率程序EXSIM。选用1994年Northridge地震数据检验本文采用的随机有限断层模拟方法和程序。最后以大岗山水电站工程为例,采用随机有限断层法生成磨西断裂发震时工程场址可能产生的最大可信地震的加速度时程曲线。结果显示：随机有限断层法合成时程的放大系数谱均值与80条基岩记录平均谱的一致性较好。预测震源位错分布形式未知的地震时,动拐角频率和静拐角频率方法的模拟结果有差异。     

防潮设计水位计算方法研究

对目前我国水利水电工程有关规范中规定的防潮设计水位计算方法进行了总结和归纳,并根据我国海岸工程和河口工程的不同情况和洪潮组合方式对沿海地区的设计潮(洪)水位计算方法进行了研究。     

水电站调压室的稳定性研究

调压室的几何形状与断面尺寸是和水头损失是密切相关的,减少尾水调压室的水头损失是优化调压室系统设计的重要内容之一.对待建及已建电站的调压室的稳定性进行分析,具有非常重要的现实意义.文章讨论了"理想"调速器情况下,忽略压力管道水流、机组和负载频率的调节过程中,调压室所需满足的断面要求.最后,重点探讨了不同水位波动情况对调压...     

2010年长江流域暴雨洪水初步分析

分析2010年长江流域暴雨洪水,有利于更全面认识长江流域暴雨洪水特性,可为今后更好开展长江流域防汛水情保障工程。从主汛期长江流域暴雨及气候特征、干支流主要洪水过程及洪水特性等方面,进行了初步的总结和分析。2010年长江主汛期洪水发生范围广、持续时间长且局部地区洪水量级大,通过与三峡水库蓄水前后几次大的历史洪水分析对比,初步认为,2010年长江流域主汛期出现的洪水为长江上中游区域性较大洪水。     

重庆主城区水环境质量和社会经济关系分析

为了在发展经济的同时,控制水环境污染,需要分析水环境污染与社会经济发展的关系。根据2003~2009年两江(长江、嘉陵江) 重庆主城区段主要污染物的水质监测数据和典型社会经济指标,采用偏相关分析与多元线性回归方法分析了主城区水环境质量和社会经济关系。分析结果表明：两种方法结果基本一致;COD指标主要受到工业点源排放的影响,农业面源和生活废水垃圾排放对NH3-N的贡献最大,TP受城镇化率即人口结构的影响最显著,而对TN和Pb影响最为显著的是农业面源污染。     

对水文频率分析中目估适线法的思考

水文频率分析方法在水文实践工作中应用广泛,然而也存在缺陷.介绍了目估适线法的发展历史及简况,指出在平时的学习和工作中使用该法时遇到的负偏情况,通过与正常结果对比、计算和绘图查找出原因,并提出应对建议,包括:使用长系列数据,将人类活动的影响进行径流还原,对气候反常特大值进行处理等,帮助水文工作者得出更为合理的结果.     

FACTORS INFLUENCING BENDING RIGIDITY OF SUBMERGED VEGETATION

The bending rigidity of submerged vegetation is closely related with vegetative drag force. This work aims at determining the effects of flow conditions and characteristics of vegetation on the bending rigidity of submerged vegetation. Based on the dimensional analysis method, the factors influencing the bending rigidity of individual submerged vegetation were analyzed. The relationship between the relative bending rigidity and its influencing factors was investigated by experimental observation, and a rela...     

Compressed sensing of superimposed chirps with adaptive dictionary refinement

The compressed sensing （CS） theory shows that accurate signal reconstruction depends on presetting an appropriate signal sparsifying dictionary. For CS of superimposed chirps, this dictionary is typically taken to be a waveform-matched dictionary formed by blindly diseretizing the frequency-chirp rate plane. However, since practical target parameters do not lie exactly on gridding points of the assumed dictionary, there is always mismatch between the assumed and the actual sparsifying dictionaries, which will cause the performance of conventional CS reconstruction methods to degrade considerably. To address this, we model the waveform- matched sparsifying dictionary as a parameterized one by treating its sampled frequency-chirp rate grid points as the underlying parameters. As a consequence, the sparsifying dictionary becomes refinable and its refinement can be achieved by optimizing the underlying parameters. Based on this, we develop a novel reconstruction algorithm for CS of superimposed chirps by utilizing the variational expectation-maximization （EM） algorithm. By alternating between steps of sparse coefficients estimation and dictionary parameters optimization, the algorithm integrates the process for dictionary refinement into that of signal reconstruction, and thus can achieve sparse reconstruction and dictionary optimization simultaneously. Experimental results demonstrate that the algorithm effectively deals with the performance degradation incurred by dictionary mismatch, and also outperforms the state-of-the-art CS reconstruction methods both in compressing the signal measurements and in suppressing the measurement noise.     

PowerPoint2013实用技巧三则

很多朋友已经开始使用Office 2013,Word、Excel的操作技巧想必已经相当熟悉,不过职场用户使用频率更高的却是PowerPoint组件。这里介绍三则比较实用的技巧。