冻融岩石核磁共振检测及冻融损伤机制分析

以花岗岩为岩样在最低冻结温度为-40 ℃、融化温度为20 ℃的条件下对5组岩样开展了冻融循环试验,最高累积冻融循环次数为100次,并采用核磁共振（NMR）技术检测岩样内部损伤变化。试验结果表明,冻融作用会对岩石内部造成损伤,循环次数达到一定值时岩样表面产生明显裂纹;NMR T2谱图和成像结果表明,冻融作用使岩样孔隙结构重新分布,孔隙数量随循环次数增加而增加,产生裂纹后T2曲线信号幅度发生显著变化。最后使用损伤力学原理对花岗岩冻融损伤机制进行探讨,得到材料连续性与孔隙率的损伤关系、有效应力与孔隙率的关系表达式,并以岩样核磁共振结果为基础,得出其有效应力与循环次数的表达式。     

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.     

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].     

北斗卫星导航系统试运行服务性能评估

针对北斗区域卫星导航系统试运行服务,给出了系统覆盖区、服务精度、服务连续性、服务可用性的测试方法及计算公式。测试结果表明,北斗区域卫星导航系统运行稳定、可靠,能够为覆盖区内用户提供20m(95%)左右的定位精度,且其服务连续性指标优于0.92/h,可用性指标优于90%。随着系统研制建设的全面完成,有望全面达到系统设计的指标要求。     

山东一次大范围持续性霾过程的气象条件分析

2016年12月30日至2017年1月8日，山东出现了以PM2.5为首要污染物、持续几天、大部地区重度以上污染的霾天气。基于多种实况观测资料和ERA Interim再分析资料，分析了此次过程天气背景和边界层特征等。结果发现：高空平直纬向环流、地面弱气压场、典型的静稳天气，有利于霾维持较长时间。此次过程期间有3次冷空气影响，冷空气的强度影响霾的变化，弱冷空气难以破坏近地层逆温结构，并会从上游向下输送污染物，有利于污染物的累积；较强冷空气带来较强的垂直运动，破坏了静稳天气形势，有利于污染物的扩散及清除。此次过程稳定层结形势下，边界层高度是一个对霾有指示意义的物理量。边界层高度和AQI的变化呈滞后负相关关系，边界层高度降低之后对应AQI指数升高。逆温层长时间的存在是此次霾持续的重要条件，另外由于地理原因东南风增湿和逆温层顶高度降低都会导致污染物浓度增大，使霾加重。     

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。     

JJG自动气象站气象要素计量性能要求合理性探讨

针对自动气象站的温度、雨量对应的检定规程,就其相关指标和规定的合理性进行探讨。目的在于让检定规程更加完善、合理。根据相应仪器本身的特性,结合实际工作经验,以分析误差构成进行理论推导,得出温度（地温）,雨量计量性能要求中最大允许误差等不合理的结果,从误差公式中重新确定了温度、雨量的最大允许误差,分别对规程指标的确定提出了修改建议。     

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.     

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.     

南海东北部陆架坡折海域跃层判定探讨

以南海东北部陆架坡折海域为例,探讨了浅海(水深<200m)和开阔海区(水深>200m)跃层在陆架坡折海域的水平衔接问题。对多组实测CTD断面水温、盐度和声速跃层的诊断分析结果表明,冬季和春季基本可不考虑陆架坡折海域跃层的水平衔接问题;夏季和秋季陆架坡折海域温、盐、声速跃层判据可分别取0.1℃.m-1、0.02m-1和0.30s-1,来保证跃层的水平连续分布。此外,在可能的内潮存在情况下,为保证跃层水平分布的连续性,可统一取开阔海区的跃层判据。