Lustre并行文件系统的发展及在气象领域的应用前景

Lustre是一个在Linux集群环境中广为应用的并行文件系统。该文介绍Lustre相关技术, 并针对气象应用的特点和国家气象信息中心的现状和发展, 设计了一个基于Lustre的多集群全局文件系统整合模型。分析表明:这一模型可以为气象应用提供高效、灵活和统一的在线存储资源, 同时能够较好地满足总体计算环境对“业务连续性”的需求。     

BDS空间信号连续性的初步评估

针对BDS空间信号的连续性评估问题,分析GPS和Galileo系统的连续性评估情况,并给出BDS空间信号连续性评估的模型和统计步骤。算例采用2013年1月1日至2013年3月24日的数据,评估结果发现:不考虑中断类型,连续性的均值为0.996 235,考虑计划中断的前提下,连续性的均值为0.998 064;GEO星的平均连续性都是最好,MEO卫星的平均连续性都是最差,IGSO卫星居中,对比BDS的公开服务性能规范中的指标,发现三类卫星的平均值都满足指标的要求。     

结合像元空间邻域信息的高光谱影像分类

针对传统的光谱角匹配分类算法仅考虑光谱信息,导致混合像元易出现错分和分类结果中出现"麻点"等问题,该文考虑地物连续性这一特点,提出了一种结合像元空间邻域信息对光谱角进行修正的光谱角匹配分类算法。该方法不仅保留了传统光谱角度匹配算法不受增益因素影响和减弱地形对照度影响等优点,并且减小了混合像元被错分的概率。基于ROSIS获取的Pavia大学校园的高光谱影像分类结果表明:加入像元空间邻域信息后的光谱角匹配算法在保证分类精度的同时,有效地减弱了分类结果中的"麻点"现象,验证了该文方法的可行性、有效性。     

Analysis of soil resistance on laterally loaded piles based on 3D soil–pile interaction

The load distribution and deflection of large diameter piles are investigated by lateral load transfer method (p–y curve). Special attention is given to the soil continuity and soil resistance using three-dimensional finite element analysis. A framework for determining a p–y curve is calculated based on the surrounding soil stress. The appropriate parametric studies needed for verifying the p–y characteristic are presented in this paper. Through comparisons with results of field load tests, the three-dimensional numerical methodology in the present study is in good agreement with the general trend observed by in situ measurements and thus, represents a realistic soil–pile interaction for laterally loaded piles in clay than that of existing p–y method. It can be said that a rigorous numerical analysis can overcome the limitations of existing p–y methods to some extent by considering the effect of realistic three-dimensional combination of pile–soil forces.     

三种系统误差平差方法的研究

系统误差是指由于某种客观原意造成的可再现误差,其数值符号保持不变或按某种规定的规律变化.在相同的观测条件下,误差在大小、符号上表现出系统性,或者在观测过程中按一定的规律变化,或者为某一常数,传统测量中系统误差可以在平差前后得到很好的补偿.随着现在测量仪器和测绘技术的发展,许多系统误差难以从观测手段中予以剔除,为尽量消除或减弱系统误差的影响以达到高精度测量的目的.本文介绍了系统误差的三种处理方法,主要包括：附加系统参数法、半参数回归法及基于系统误差延续性的附加系统参数法[1][7].     

Continuity markers as an aid for children in finding the peripheral continuity of world maps

ABSTRACT

Many map readers, including both children and adults, find it difficult to determine where they would be located along the edge of a world map after crossing that edge. Different types of markers have long been drawn close to the map’s edge – for example, in an atlas – to help map readers identify the map upon which they will find themselves if that edge is passed. In this study, a method similar to that used to show the continuity between maps in an atlas has been tested to determine whether continuity markers can also be used to help map readers find a world map’s actual peripheral continuity. The study involved children between the ages of 10 and 13 years and showed that continuity markers do help children determine the map’s actual peripheral continuity, in combination with a lesson that describes how to find the actual peripheral continuity of a world map. This article, therefore, concludes that continuity markers for world maps can be a useful part of map design that clarifies how the edges of a world map fit together for children who have learned to use this tool.     

指示变异函数在裂隙介质渗透性参数空间分布规律研究中的应用

简要介绍了变异函数和指示变异函数的概念,以拉西瓦水电站坝址区右岸花岗岩体裂隙介质渗透性研究为例,利用一般统计法、变异函数和指示变异函数的方法分析了单位吸水量数据。结果表明,指示变异函数能够很好地表征裂隙介质的非均质和各向异性特征,特别是极端值（极端大或极端小）的空间连续性程度,是进行裂隙介质渗透性研究的有效工具。     

Phase‐shifts in shear stress as an explanation for the maintenance of pool–riffle sequences

The stability of the pool–rif?e sequence is one of the most fundamental features of alluvial streams. For several decades, the process of velocity, or shear stress, reversal has been proposed as an explanation for an increase in the amplitude of pool–rif?e sequence bars during high ?ows, offsetting gradual scour of rif?es and deposition in pools during low ?ows. Despite several attempts, reversal has rarely been recorded in ?eld measurements. We propose that, instead of being reversed, maxima and minima in shear stress are phase‐shifted with respect to the pool–rif?e sequence bedform pro?le, so that maximum shear stress occurs upstream of rif?e crests at high ?ow, and downstream at low ?ow. Such phase‐shifts produce gradients of shear stress that explain rif?e deposition, and pool scour, at high ?ow, in accord with sediment continuity. The proposal is supported by results of a one‐dimensional hydraulic model applied to the surveyed bathymetry of a pool–rif?e sequence in a straight reach of a gravel‐bed river. In the sequence studied, the upstream phase‐shift in shear stress at high ?ow was associated with variations in channel width, with width minima occurring upstream of rif?e crests, approximately coincident with shear stress maxima, and width maxima occurring downstream of rif?e crests. Assuming that the width variation is itself the result of ?ow de?ection by rif?e crests at low ?ow, and associated bank‐toe scour downstream, low and high ?ow can be seen to have complementary roles in maintaining alluvial pool–rif?e sequences. Copyright © 2004 John Wiley & Sons, Ltd.     

Modeling vertical stratification of CO2 injected into a deep layered aquifer

The vertical stratification of carbon dioxide (CO₂) injected into a deep layered aquifer made up of high-permeability and low-permeability layers, such as Utsira aquifer at Sleipner site in Norway, is investigated with a Buckley–Leverett equation including gravity effects. In a first step, we study both by theory and simulation the application of this equation to the vertical migration of a light phase (CO₂), in a denser phase (water), in 1D vertical columns filled with different types of porous media: homogeneous, piecewise homogeneous, layered periodic and finally heterogeneous. For each case, we solve the associated Riemann problems and propose semi-analytical solutions describing the spatial and temporal evolution of the light phase saturation. These solutions agree well with simulation results. We show that the flux continuity condition at interfaces between high-permeability and low-permeability layers leads to CO₂ saturation discontinuities at these interfaces and, in particular, to a saturation increase beneath low-permeability layers. In a second step, we analyze the vertical migration of a CO₂ plume injected into a 2D layered aquifer. We show that the CO₂ vertical stratification under each low-permeability layer is induced, as in 1D columns, by the flux continuity condition at interfaces. As the injection takes place at the bottom of the aquifer the velocity and the flux function decrease with elevation and this phenomenon is proposed to explain the stratification under each mudstone layer as observed at Sleipner site.