The Cepheid period–luminosity zero-point from radial velocities and Hipparcos proper motions

A value for the zero-point (ρ) of the Cepheid period–luminosity relation, <  M _V  >= 2.81 log P  + ρ, is deduced by comparing the value of the Oort constant, A , derived from radial velocities with that derived from Hipparcos proper motions. We find in this way that ρ =−1.47 ± 0.13, in excellent agreement with the value derived from Hipparcos trigonometrical parallaxes, ρ = −1.43 ± 0.10, by Feast &38; Catchpole in a recent paper.     

Prediction of local scour around circular piles under waves using a novel artificial intelligence approach

Abstract

The scour phenomena around vertical piles in oceans and under waves may influence the structure stability. Therefore, accurately predicting the scour depth is an important task in the design of piles. Empirical approaches often do not provide the required accuracy compared with data mining methods for modeling such complex processes. The main objective of this study is to develop three data-driven methods, locally weighted linear regression (LWLR), support vector machine (SVR), and multivariate linear regression (MLR) to predict the scour depth around vertical piles due to waves in a sand bed. It is the first effort to develop the LWLR to predict scour depth around vertical piles. The models simulate the scour depth mainly based on Shields parameter, pile Reynolds number, grain Reynolds number, Keulegan–Carpenter number, and sediment number. 111 laboratory datasets, derived from several experimental studies, were used for the modeling. The results indicated that the LWLR provided highly accurate predictions of the scour depths around piles (R?=?0.939 and RMSE = 0.075). Overall, this study demonstrated that the LWLR can be used as a valuable tool to predict the wave-induced scour around piles.     

实验水槽常规流速模拟的缩尺方法

提出了一种实验室水槽中流速模拟的方法,该方法可根据需要提供合适的模型缩尺比,用来完成相关海洋工程的模型水动力性能实验,可以近似地模拟出实际设备在水中的工作状态,为在实验水槽中模拟水流动力参数提供有效的参考,方便水槽中的科学实验的开展。     

二密铜矿控矿构造特征及找矿方向探讨

二密铜矿位于二密中生代火山盆地中,矿床产于松顶山序列石英闪长岩与侏罗系火山岩接触带附近,矿体受多组断裂联合控制,矿体多呈脉状,主成矿期在花岗斑岩株侵入固结之后。成矿热液来源于深部,沿300°±断裂带及34°±断裂带运移至容矿构造中成矿。300°(4)与34°(6)两条主干断裂带交汇部位一带可能是主要成矿区。     

银川平原植被生长与地下水关系研究

干旱区植被生长与地下水的关系是生态水文地质学研究的热点之一。西北内陆干旱地区降水稀少,植被的生长发育与地下水的关系极为密切,从大尺度上研究地下水变化的生态效应问题对生态环境的保护和恢复具有重要的意义。借助遥感方法,结合地下水观测数据,在区域尺度上定量地研究了中国银川平原地区地下水埋深及矿化度与植被生长的关系。结果表明:适宜植被生长的地下水埋深范围约为1~6m,当地下水位埋深为3.5m左右时,植被长势最好。而在水位埋深为3.5m左右的地区,植被生长的相对好坏又受地下水矿化度的影响。当地下水矿化度为0.9g/L时对该地区植被的生长最为有利。     

渭河河漫滩宏观弥散度计算

宏观弥散度的确定对地下水溶质运移至关重要。利用竖管法野外现场测定900个点的垂向饱和渗透系数Kv值,然后进行统计分布检验,运用地质统计学中负指数模型在有块金效应影响的条件下拟合出ln Kv的空间相关尺度λ值,进而利用λ与宏观弥散度关系式求解渭河漫滩非饱和带的宏观弥散度。结果表明,研究区整体Kv平均值为0.012cm/s,方差为1.33,表明Kv空间差异性较大;垂向渗透系数基本服从对数正态分布规律,满足宏观弥散度计算条件;估算整体纵向宏观弥散度为21.27m,各排计算结果约2.11~4.65m。     

Original technologies for proven performances for the new LCPC earthquake simulator

The European Quaker project has been a powerful opportunity to accelerate the development of the ability to carry out earthquake simulations at reduced scale in the centrifuge in LCPC—France. This paper summarizes the main original technologies of this simulator. The quality of the checked performances is demonstrated in terms of ability to perform since earthquakes as well as to simulate scaled records of real earthquakes. The consistancy of the results is presented in the time and in the frequency domains.     

垂直上升管中油气水三相流流型多尺度熵分析

为了研究垂直上升管中油气水三相流流动特性,本文利用纵向多极阵列电导式传感器（VMEA）和阵列电导探针组合测量方法在内径为125 mm多相流流动环中采集了油气水三相流电导波动信号,在定义6种油气水三相流流型基础上,绘制了4种油水混合液量下油气水三相流流型转换图,分析了含油率对流型转化及气相流速对油水相态逆转的影响.对水为连续相的5种流型VMEA传感器波动信号进行了多尺度熵分析,研究结果表明：含油率增加可使水包油段塞流在较低气相表观速度下产生;较低流速下的油水相态逆转可发生在油液比为0.9左右,气相流速增加使得逆转点向含油率低的方向偏移;多尺度熵细节可以刻画油气水三相流非线性动力学特性,而低尺度的多尺度熵变化率敏感地反映流型转变,是划分油气水三相流流型的有效准则.多尺度熵有助于理解油气水三相流流型非线性动力学特征.     

Copula-based mixed models for bivariate rainfall data: an empirical study in regression perspective

A comprehensive parametric approach to study the probability distribution of rainfall data at scales of hydrologic interest (e.g. from few minutes up to daily) requires the use of mixed distributions with a discrete part accounting for the occurrence of rain and a continuous one for the rainfall amount. In particular, when a bivariate vector (X, Y) is considered (e.g. simultaneous observations from two rainfall stations or from two instruments such as radar and rain gauge), it is necessary to resort to a bivariate mixed model. A quite flexible mixed distribution can be defined by using a 2-copula and four marginals, obtaining a bivariate copula-based mixed model. Such a distribution is able to correctly describe the intermittent nature of rainfall and the dependence structure of the variables. Furthermore, without loss of generality and with gain of parsimony this model can be simplified by some transformations of the marginals. The main goals of this work are: (1) to empirically explore the behaviour of the parameters of marginal transformations as a function of time scale and inter-gauge distance, by analysing data from a network of rain gauges; (2) to compare the properties of the regression curves associated to the copula-based mixed model with those derived from the model simplified by transformations of the marginals. The results from the investigation of transformations’ parameters are in agreement with the expected theoretical dependence on inter-gauge distance, and show dependence on time scale. The analysis on the regression curves points out that: (1) a copula-based mixed model involves regression curves quite close to some non-parametric models; (2) the performance of the parametric regression decreases in the same cases in which non-parametric regression shows some instability; (3) the copula-based mixed model and its simplified version show similar behaviour in term of regression for mid-low values of rainfall. An erratum to this article can be found at