Two kinds of moment ratio diagrams and their applications in hydrology

We refocus attention on moment ratio diagrams and their uses in hydrology with four major objectives: (1) to summarize the information available in the literature about possible uses of the traditional moment ratio diagram introduced by Karl Pearson, which uses the coefficient of skewness and of kurtosis to compare the shapes of various distributions commonly used in hydrology; (2) to complete this traditional MRD by integrating into it the regions occupied by the log-Pearson Type III and generalized gamma distributions which are more and more used in hydrology; (3) to present another MRD which uses ratios of moments of orders –1 (harmonic mean), quasi zero (geometric mean) and 1 (arithmetic mean); (4) to stress the need to consider the different MRD's (along with the more recently introduced L-moment ratio diagrams) as complementary tools for choosing between distributions fitted to hydrologic data. Finally, using Monte Carlo simulation we compare the two types of diagrams as tools to identify and discriminate between different distributions.     

Marine boundary layer characteristics during a cyclonic storm over the Bay of Bengal

During the period 12–16 June 1996 a tropical cyclonic storm formed over the southwest Bay of Bengal and moved in a north-northeasterly direction. The thermodynamic characteristics of this system are investigated by utilizing the surface and upper air observations collected onboardORV Sagar Kanya over the Bay of Bengal region. The response of the cyclonic storm is clearly evident from the ship observations when the ship was within the distance of 600–800 km from the cyclonic storm. This study explores why (i) the whole atmosphere from surface to 500 hPa had become warm and moist during the cyclonic storm period as compared to before and after the formation of this system and (ii) the lower layer of the atmosphere had become stable during the formative stage of the cyclonic storm.     

基于Voronoi图的正射影像镶嵌网络生成与优化方法

提出一种基于Voronoi图的正射影像镶嵌网络生成与优化方法.首先以每幅DOM影像有效区域中心点作为种子点生成Voronoi图,确定每幅影像的有效镶嵌多边形并构建全局镶嵌网络;然后结合DSM数据对镶嵌多边形顶点位置进行调整,避免最终镶嵌结果影像出现无数据区域,同时可以使顶点避开建筑、树木等存在投影差的区域,以便对初始镶嵌线进行调整优化.试验表明,本文方法切实可行并且具有较好的自适应性.     

地图点群综合的加权Voronoi算法

提出了一个基于加权Voronoi图的地图点群综合算法。为点群中包含的统计、专题、拓扑和度量信息分别选定量化描述因子,并把这些因子运用到点群综合过程中,来保证对应类型信息的正确传输;点群综合的过程借助于反复构造点群的加权Voronoi图来实现。     

无粘性泥沙的起动条件

对H. A. 爱因斯坦等国内外数10种不同形式和结构的泥沙起动条件进行分析研究,统一转化为无因次起动切力θ_c=τ_c/(γ_s-γ)d的形式,并分析计算出无粘性均匀沙的θ_c值。一般来讲,θ_c是界于0.0231～0.0716之间的一个常数值。从分析结果可看出各种公式之间的差别,为使用选择公式提供了科学的依据。     

基于层次分析法的路段属性求权方法

最优路径搜索功能是车载导航系统的路径规划模块的核心功能之一。车辆在道路路段上的旅行支出是综合考虑道路的各种属性,通过加权、无量纲化等计算后的结果。利用层次分析法对道路的各种属性加权,给出了不同类型属性的无量纲化的标准函数。     

基于位移的RC框架结构与附加消能减震装置一体化设计

消能减震结构中主体结构和附加消能减震装置通常是单独设计的,由于主体结构和附加消能减震装置之间的耦合特性,为实现期望的性能目标需要进行迭代计算。本文提出一种基于位移的主体结构与附加消能减震装置一体化设计方法,首先,基于所选地震动记录和预期性能目标,得出结构阻尼比需求曲面;其次,推导了阻尼器-支撑部件参数计算公式,在已知主体结构基本信息及预期性能目标时,根据阻尼比需求曲面及所提出公式即可获得所需附加消能减震装置的支撑刚度及粘滞系数;再次,引入无量纲成本指数,以成本指数最小为目标函数,在可实现目标性能的附加消能减震装置参数中识别最优设计参数;最后,基于所提出的设计方法,分别以等效SDOF体系、MDOF体系及SAP2000设计的6层RC框架结构为例,对所提出的设计方法的有效性进行了验证,结果表明:经一体化设计的结构体系均可实现性能目标。     

Another Look at the Chemical Relationships in the Dissolved Phase of Complex River Systems

Large rivers are a major pathway for the erosion products of continents to reach the oceans. The riverine transport of dissolved and particulate materials is generally related to a large number of interactions involving climate, hydrological, physico-chemical and biological aspects. Consequently, the investigation of large rivers allows the erosion processes at a global scale to be addressed, with information about biogeochemical cycles of the elements, weathering rates, physical erosion rates and CO₂ consumption by the acid degradation of continental rocks. Today, good databases exist for the major dissolved ions in the world’s largest rivers. Since concentration of ions in river waters has to be considered in a compositional context, it is necessary to study the implications of considering the simplex, with its proper geometry, as the natural sample space. Using the additive (alr) or the isometric (ilr) log-ratio transformations, a composition can be represented as a real vector; but only in the second case can these coordinates be mapped onto orthogonal axes. Using data related to the dissolved load of some of the most important rivers in the world, the relationships among the major ions frequently used in molar ratio mixing diagrams have been investigated with alternative tools. Following the balances approach, an investigation of the properties of aqueous solutions of electrolytes that are often treated in terms of equilibrium constants is undertaken. The role played by the source—rain water, weathering of silic, carbonatic and evaporitic rocks, pollution—from which elements and chemical species can potentially be derived, has been checked through an investigation of a probabilistic model able to describe the relationships among the different components that contribute to the chemical composition of a river water sample.     

Homogenized Hertzsprung‐Russell diagram for the open cluster NGC 188

We considered some selected published stellar catalogues with B – V and V values for the open cluster NGC 188 and estimated the errors from data comparisons. The results are used to homogenize the data by averaging with weights inversely proportional to the errors squared. A recent calibration by Casagrande et al. (2010) of B – V versus effective temperatures for F, G, and K dwarfs and subgiants is used to produce the homogenized effective temperatures for the cluster stars. A homogenized Hertzsprung‐Russell diagram (relationship between the effective temperatures and the absolute magnitudes) is presented and analysed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)