Climatic forcing on hydrography of a Mediterranean bay (Alfacs Bay)

Time series of meteorological and hydrographic variables were analyzed using Huang's Empirical Mode Decomposition (EMD) to ascertain the relationships among climatic forcings and the hydrographic behavior in an estuarine bay. The EMD method allowed us to separate the different characteristic oscillation patterns (or modes) of a 14 year-long time series of weekly hydrographic (water temperature and salinity) and meteorological (air temperature, pressure, wind and precipitation) data from Alfacs Bay (Ebre delta, NW Mediterranean). In order to explore the relations between couples of oscillation modes from different series, we developed a correlation index based on the phase differences between these modes. Common characteristic modes in the studied series are a seasonal pattern and an inter-annual oscillation. The comparison between series of meteorological and hydrographic variables shows significant correlations of two modes (of 1 year and 2–3 year periods, respectively) of water temperature with the corresponding two modes of air temperature and air pressure. There were also significant positive correlations between wind speed and water temperature. The use of EMD allowed to discover a strong connection between stratification and the use of irrigation channels in the bay; in addition, with the help of this method we can propose a common meteorological forcing mechanism for the observed patterns of variability. Those findings would have been impossible to guess by use of classical Fourier methods, and gives a demonstration of the power of EMD in climatic series analysis.     

生命线网络可靠度分析的改进最小路递推分解算法

在生命线网络最小路递推分解算法的基础上,充分利用分解过程中的信息,采用合并节点的方法,快速降低分解出来子网的复杂程度,从而达到大幅度减少分解出来的不交最小路(割)数量和提高计算效率的目的.计算实例分析表明,与最小路递推分解算法相比,改进算法能更为高效地给出网络可靠度,是一种有效的生命线工程网络抗震可靠性分析工具.     

基于反射地震记录变子波模型提高地震记录分辨率

本文给出了地震记录变子波模型的一种近似数学表达式．基于该表达式研究了反射系数序列不满足白噪假设和子波在地下传播时发生变化这两种情况下地震道谱的组成及结构,讨论了谱白化及反褶积方法在这两种情况下效果不佳的原因．然后基于变子波模型,提出了一种新的提高地震记录分辨率的方法：第一步,用自适应于地震记录的Gabor分子窗把地震记录恰当地划分成若干片断,每段内信号近似平稳,然后将地震记录变换到时间-频率域;第二步,在变换域对每个分子窗内信号的振幅谱进行处理以拓宽频带;最后把处理后的时间-频率域函数反变换回时间域得到提高分辨率后的结果．本文提出的方法具有能较好地适用于反射系数不满足白噪假设的情况及提高分辨率后的地震记录能较好地保持原地震记录的相对能量关系等优点,模型和实际资料算例结果均表明,本文方法在拓宽地震资料频带及保持地震记录局部能量相对关系方面均明显优于谱白化方法．     

生命线工程网络抗震可靠性算法研究

现代城市的迅速发展对生命线工程系统依赖性逐渐增强。地震后生命线工程系统的性能直接决定了灾后生活和生产的恢复以及抢险工作的进行,因此对生命线工程系统进行地震作用下的可靠性分析具有十分重要的意义。本文中主要介绍2种求解大型网络抗震可靠度算法———最小路递推分解算法和最小割递推分解算法。在此基础上,利用这2种算法对沈阳市供气系统进行了分析。研究结果表明,合理选择使用这2种算法可以有效的进行不同地震烈度条件下的大型生命线工程系统的可靠性分析。     

台风“利奇马”(1909)影响期间上海强降水成因诊断分析

2019年第9号台风“利奇马”(1909)在8月9—11日影响上海期间造成了严重的风雨影响。基于ERA5逐小时再分析资料和上海区域高时空分辨率的地面观测资料,采用非地转Q矢量分解等方法诊断分析了此次强降水成因。结果表明,台风“利奇马”在上海造成的强降水主要来自台风东侧的螺旋雨带。强降水区东南西北各边界的相对湿度在垂直方向上随时间的变化差异明显,水汽的垂直输送和大气整层水汽含量在台风强降水中起重要作用。进一步利用非地转Q矢量分解方法揭示了东边界的大尺度和北边界的中尺度系统在强降水中起主要作用。台风登陆时呈现出整层大气被抬升之后最大强迫中心由高层向低层下传的态势,且此下传效应中尺度比大尺度强迫更加明显,从而有利于强降水的发生。     

贵州省61年冰雹气候特征及其成因分析

选取1961—2021年贵州省84个国家站冰雹观测资料,运用回归分析、小波分析和EOF分解对贵州省近61年冰雹发生的时空分布特征进行研究,并通过分析大气环流和外强迫因子的异常,探究冰雹日数极端年份的成因。结果表明：贵州省一年四季均有冰雹,春季最多,秋季最少。冰雹出现时间以14—01时的午后到夜间为主。贵州省冰雹的发生有14年和8年的周期,1995年后主周期变短,出现频次减少。冰雹主要分布在中西部,年均冰雹频次与海拔呈正相关,EOF分解后,贵州省冰雹空间分布前两个模态在空间向量场上呈现为全省一致型和东西相反型,受大尺度环流及地形影响产生的冰雹为减少的趋势,1991年后贵州省中部以东受地形激发及局地对流产生的冰雹有略微上升的趋势,但其方差贡献率较小,因此贵州省整体冰雹日数为下降趋势。通过极端冰雹年的大气环流和外强迫因子的分析,发现La Ni?a年海温的异常激发了热带西北太平洋异常气旋,导致该地区副高偏弱,进一步影响到贵州及其周边的位势高度有负异常,不利于贵州省冰雹的发生,对应贵州的少雹年,而El Ni?o年则相反,对应贵州省的多雹年。     

热分析法研究矿物分解过程动力学

采用热分析方法研究了菱镁矿、高岭石分解过程动力学参数活化能Ｅ、反应级数ｎ,由ＴＧ、ＤＴＡ两种实验数据,用Ｃｏａｔｓ,Ｒｅｄｆｅｒｎ和Ｋｉｓｓｉｎｇｅｒ计算方法对比计算,从而得出高岭石活化能Ｅ＝１８８．７１２ｋＪ／ｍｏｌ,菱镁矿活化能Ｅ＝１８０．８２８ｋＪ／ｍｏｌ。     

利用岩性解释方法圈定岩浆岩侵入煤层范围

岩性地震反演技术是根据钻孔测井数据纵向分辨率很高的有利条件,对井旁地震资料进行约束;并在此基础上对孔间地震资料进行反演,推断煤系地层岩性在平面上的变化情况.谱分解技术是利用薄层调谐体离散频率特性,通过分析复杂岩层内陷频谱变化和局部相位的不稳定性,识别薄地层横向分布特征.本文根据崔庄煤矿三采区的地震资料,综合利用地震反演技术和谱分解技术等岩性解释方法圈定岩浆岩侵入煤层的范围.     

Assessment of the frequency domain decomposition technique by forced‐vibration tests of a full‐scale structure

Dynamic characteristics of buildings are of utmost importance in earthquake engineering. The vibration periods are required to determine design loads, and damping is necessary in time‐history analysis. These parameters are generally obtained through forced‐vibration tests (FVTs) or after a seismic event in the case of permanently instrumented structures. However, for large civil engineering structures, FVTs are often too costly or practically difficult, and ambient or output‐only methods are used. This paper describes a comparison between ambient and FVTs carried out on a two‐story building. Results from both testing methods are compared and discussed in order to assess the vibration properties estimates obtained with the frequency domain decomposition technique. Copyright © 2007 John Wiley & Sons, Ltd.     

Three-dimensional decomposition method of global atmospheric circulation

By adopting the idea of three-dimensional Walker, Hadley and Rossby stream functions, the global atmospheric circulation can be considered as the sum of three stream functions from a global per- spective. Therefore, a mathematical model of three-dimensional decomposition of global atmospheric circulation is proposed and the existence and uniqueness of the model are proved. Besides, the model includes a numerical method leading to no truncation error in the discrete three-dimensional grid points. Results also show that the three-dimensional stream functions exist and are unique for a given velocity field. The mathematical model shows the generalized form of three-dimensional stream func- tions equal to the velocity field in representing the features of atmospheric motion. Besides, the vertical velocity calculated through the model can represent the main characteristics of the vertical motion. In sum, the three-dimensional decomposition of atmospheric circulation is convenient for the further in- vestigation of the features of global atmospheric motions.