Pulsatory characteristics of wind velocity in sand flow over typical underlying surfaces

Pulsatory characteristics of wind velocity in sand flow over Gobi and mobile sand surface have been investigated experimentally in the wind tunnel. The primary goal of this paper is to reveal the relation- ship between pulsatory characteristics of instantaneous wind speed in sand flow and the motion state of sand grains. For a given underlying surface, pulsation of wind velocities in sand flow on different heights has a good correlation. As the space distance among different heights increases, fluctuation of instantaneous wind speed presents a decreasing trend and its amplitude is closely related to the mo- tion state of sand grains and their transport. Pulsatory intensity increases with the indicated wind speed, but its relative value does not depend on it, only agrees with height.     

移动状态边界面法在黏性土不排水蠕变孔压分析中的应用

在黏性土的各种流变现象的数学模拟研究中,不排水蠕变孔压方程几乎是空白。基于临界状态土力学理论,采用与时间相关的移动状态边界面法,给出了适用于正常固结黏性土的不依赖状态边界面具体形态的不排水蠕变孔压公式。正常固结黏性土的不排水蠕变孔压可以看作是体积蠕变势和剪应力水平增大造成的剪缩这两种作用的结果,前者与参数 有关（ 为次压缩指数, 为压缩指数）,后者则与状态边界面的具体形态有关。在此基础上进一步给出了可方便用于试验数据分析的双对数和单对数形式的两个公式。以修正剑桥模型椭圆形状态边界面为例,分析了双对数和单对数坐标系下蠕变孔压曲线的斜率m和m′与土的流变参数 的关系。采用提出的方法,很好地预测了Walkers给出的Leda clay黏土的蠕变孔压系数,并基于以上两种作用解释了Leda clay黏土的蠕变孔压形成的机制。     

利用CFP技术解决复杂近地表问题综述

复杂近地表条件会降低地震数据的质量,通常采用基于地表一致性的时移静校正消除其影响.但静校正与速度是密不可分的,而确定复杂近地表速度是非常困难的.基于CFP技术处理复杂近地表问题时避免了对速度的直接操作,使得静校正和速度的确定相互独立.首先根据叠前数据估算出波场的传播算子,然后依据等时原理在DTS模板中进行算子更新,再用这些更新的算子重建基准面和实现近地表单程时间成像.获得正确的算子振幅也是重建基准面的关键.     

A coupled microphysical/radiative transfer model of albedo and emissivity of planetary surfaces covered by volatile ices

A new model of albedo and emissivity of planetary surfaces covered by volatile ices in the form of porous slab-like deposits is described. In the model, a radiative transfer model is coupled with a microphysical model in order to link changes in albedo and emissivity to changes in porosity caused by ice metamorphism. Preliminary results for Triton, Pluto, and Io are presented (the martian CO₂ caps will be the subject of a separate publication). The coupled model will aid in the interpretation of ground-based and spacecraft observations and should lead to advances in surface and atmospheric modeling.     

青藏高原春季土壤湿度异常与我国夏季降水的联系

利用 197-2014年 GLDAS-CLM(Global Land Data Assimilation System-the Community Land Mod-el)地表参量数据集、中国区域逐日观测资料格点化数据集(CN05.1)和ERA-nterim大气环流再分析数据,研究青藏高原5月(春季)土壤湿度的异常变化...     

大型射电望远镜主反射面调整方法研究

随着毫米波天文学和空间通信的重要性日益提高, 对天线性能提出了越来越高的要求, 而天线性能往往受到其反射器表面精度的限制. 微波全息技术是一种快速有效的检测反射面天线表面轮廓的测量技术. 通过微波全息测量得到天线口径场, 计算天马65m射电望远镜反射面与理想抛物面的偏差. 天马65m射电望远镜的主反射面板是放射状的, 有14圈. 面板的每个角都固定在面板下方促动器的螺栓上进行上下移动, 且相邻面板交点处的拐角共用一个促动器. 采用平面拟合的方法可以计算各块面板拐角处的调整值, 但是同一个促动器会得到4个不同的调整量. 通过平面拟合, 同时以天线照明函数为权重的平差计算方法得到相邻面板拐角的一个平差值, 即天马65m射电望远镜1104个促动器的最佳调整值. 通过多次调整和新算法的应用, 天马65m射电望远镜反射面的面形精度逐渐提高到了0.24mm.     

陆表自然和人文要素相互作用——“全球变化及应对”重点专项研究进展

在国家重点研发计划支持下,项目提出了陆表不均一性检测和订正的新方法,解决了渐变型不均一性检测和订正的难题,构建了中国地表太阳辐射、气温、地温、风速和降水等参数均一化站点和格点数据集,修订了关于中国地表风速变化趋势、增温格局及其形成机制的结论。融合多源数据,构建并验证了千米级、流域级或县域级的电厂、人口、生物质能、取水量、氮排放、二氧化碳排放等影响自然系统的关键人文要素历史和未来预估数据集。构建了未来关键人文要素情景,研制了碳中和目标下甲烷和氧化亚氮排放情景和用于驱动全球模式的未来情景,预估了中国碳中和战略的实施对全球变暖的减缓作用,发现中国碳中和对远期和中期全球变暖的减缓作用显著。给出了中国各省份水体氮排放安全阈值及超越时间,阐明了中国粮食产量与氮施肥的关系,提出了在保障粮食安全的前提下减少水体氮排放的有效途径,指出重构城乡养分循环体系是同时保障粮食安全和恢复水质的必要途径。发现全球饱和水汽压差的年际变化与大气二氧化碳浓度上升速率的年际变化显著相关,阐明了饱和水汽压差变化在调控生态系统生产力中的重要角色以及多因素耦合作用在生态系统生产力变化中的复杂影响。建议更全面细致地评估中国各种碳中...     

太阳活动上升期源表面太阳风质量流量的速度关系分析

以ＩＰＳ速度、光球磁场、Ｋ─日冕偏振亮度和卫星实地观测数据为基础,综合生成处于太阳活动上升期的１９７６年１０个太阳周（１６４３─１６５２卡林顿周）的源表面高度（Ｒ＝２．５Ｒｓ,Ｒｓ为太阳半径）和日球空间中（ＩＡＵ）太阳同质量流量速度谱。结果表明,速度谱存在与太阳活动上升期一致的＂三段＂结构,且各段分别与不同的磁结构区相对应。     

Heterogeneity influences on stream water–groundwater interactions in a gravel-dominated floodplain

ABSTRACT

Floodplains are composed of complex depositional patterns of ancient and recent stream sediments, and research is needed to address the manner in which coarse floodplain materials affect stream–groundwater exchange patterns. Efforts to understand the heterogeneity of aquifers have utilized numerous techniques typically focused on point-scale measurements; however, in highly heterogeneous settings, the ability to model heterogeneity is dependent on the data density and spatial distribution. The objective of this research was to investigate the correlation between broad-scale methodologies for detecting heterogeneity and the observed spatial variability in stream/groundwater interactions of gravel-dominated alluvial floodplains. More specifically, this study examined the correlation between electrical resistivity (ER) and alluvial groundwater patterns during a flood event at a site on Barren Fork Creek, in the Ozark ecoregion of Oklahoma, USA, where chert gravels were common both as streambed and as floodplain material. Water table elevations from groundwater monitoring wells for a flood event on 1–5 May 2009 were compared to ER maps at various elevations. Areas with high ER matched areas with lower water table slope at the same elevation. This research demonstrated that ER approaches were capable of indicating heterogeneity in surface water–groundwater interactions, and that these heterogeneities were present even in an aquifer matrix characterized as highly conductive. Portions of gravel-dominated floodplain vadose zones characterized by high hydraulic conductivity features can result in heterogeneous flow patterns when the vadose zone of alluvial floodplains activates during storm events.

EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR X. Chen     

杭州某地铁站基坑开挖侧向位移预测与分析

介绍了杭州某地铁站基坑开挖过程中的监测的侧向位移变化情况,总结了其变化规律,对施工过程提供了参考。用FLAC软件对基坑的侧向位移进行了数值模拟,然后与实际监测结果进行了对比,阐述了影响模拟结果准确性的影响因素。