采用时序InSAR技术监测北京地铁网络沿线地面沉降

随着北京轨道交通的日益完善,地铁成为人们日常出行的重要交通工具,监测和治理地铁工程沿线地面沉降成为保障线性工程正常运营的一项重要基础性工作。本文基于55景覆盖北京地区的3 m高分辨率TerraSAR-X数据,采用时序InSAR分析技术获取2010年4月至2016年12月地铁网络沿线的地面沉降形变信息,系统分析了北京地铁网络沿线地面沉降时空演变规律。同时,结合Peck公式将InSAR监测结果进行建模,以7号线磁器口-广渠门内站区段为例,估算地面沉降槽的空间发展特征。研究发现：北京市地铁线路沿线表现出不同程度的形变,形变严重的路段主要集中在东部及东北部区域,最大沉降速率超过了100 mm/a;相对于其他线路,4号、10线整体情况比较稳定,14号、亦庄线次之,6号、7号线不均匀沉降最为严重;此外,地铁在不同建设时期路段表现出不同的形变特征,施工期路段较运营期沉降严重;7号线磁器口与广渠门内站间沉降槽的宽度和最大值沉降值在2010-2016年呈现增加趋势,沉降槽最大宽度约达180 m。     

北黄海春季海面太阳辐射船基观测与分析

利用"中国近海海洋综合调查与评价"2007年北黄海春季航次的资料,综合分析了短波、长波辐射及海面短波、长波反射辐射特征及与云量、气温、水汽压、海面红外温度等的对应关系。结果显示海面太阳入射辐射远大于海面反射辐射,二者相差约1个量级;海面长波辐射总体上大于大气逆辐射,二者相差约40 W/m2,平均净辐射为153.1 W/m2。观测期间大气透射率约为0.45,并据此分析探讨了云对太阳辐射传输的影响,建立了考虑总云量、低云量及水汽压等因素的海面太阳短波辐射经验估算公式,计算结果与实测结果具有较好一致性,均方根误差为11.3 W/m2。最后讨论了太阳辐射船基观测由于船体晃动可能造成的误差影响。     

气候变化背景下北京市短历时暴雨的强度及雨型变化特征

利用1961—2017年北京观象台站逐分钟降雨资料,根据《城市暴雨强度公式编制和设计暴雨雨型确定技术导则》,建立了北京市1961—1990年和1991—2017年两个气候态下的暴雨强度公式和2 a重现期下历时30 min、60 min、90 min、120 min、150 min、180 min以5 min为时间段的设计暴雨雨型。结果表明：1）P-Ⅲ型分布曲线对北京市两个气候态下各历时降雨量的拟合效果最好,暴雨强度公式精度最高。2）对比1961—1990年和1991—2017年暴雨强度公式,整体而言,后者各历时重现期的暴雨强度值较低,但随着重现期的增大,两者的雨强差值也增大。3）1961—1990年和1991—2017年短历时雨型的雨峰位置系数分别为0.436和0.382,2 a重现期下前者的各历时雨峰位置比后者提前,各历时累积降雨均在初期增长较慢、雨峰前后增长较快,之后增速明显减缓。     

一个概念性水文模型的参数区域化研究:以东江流域为例

氮是引发湖泊富营养化的重要元素之一,湖泊外源和内源氮的去除对湖泊富营养化的控制非常关键,其中填料对氨氮的去除是湖泊外源控制的重要途径．研究了4种填料（天然沸石、陶粒、蛭石和土壤）对氨氮的吸附行为、填料去除氨氮的主要途径以及溶液中pH值和温度对氨氮去除率的影响．结果表明沸石对氨氮的吸附效果明显,蛭石次之,土壤与陶粒效果较差．沸石去除氨氮的途径以离子交换作用为主,物理吸附作用很小;陶粒、土壤和蛭石3种填料的离子交换作用和物理吸附作用的效果相当4种填料的吸附量在温度为15-35℃内均随温度的升高而减小,在pH值为3—9范围内随pH值升高而增大,振荡6h均达到吸附平衡。     

Seismic response analysis of reinforced concrete frames using inelasticity‐separated fiber beam‐column model

Evaluating the inelastic seismic response of structures accurately is of great importance in earthquake engineering and generally requires refined simulation, which is a time‐consuming process. Because the material nonlinearity generally occurs in a small part of the whole structure, many researches focus on taking advantage of this characteristic to improve the computational efficiency and the inelasticity‐separated finite element method (IS‐FEM) proposed recently provide a generic finite element formulation for solving this kind of problems efficiently. Although the fiber beam‐column element is widely used for the simulation of reinforced concrete (RC) framed structures, the inelastic deformation is often detected in a large part of the numerical model under earthquake excitation so that it is hard to achieve high efficient computation when applying the IS‐FEM to the inelastic response analysis of RC fiber models directly. In this paper, a new numerical scheme for seismic response analysis of RC framed structures model by fiber beam‐column element is proposed based on the IS‐FEM. To implement the RC fiber model for use in IS‐FEM and improve the computational performance of proposed scheme, a method of identifying the local domains with severe section inelasticity level is proposed and a modified Kent‐Park concrete material model is developed. Because the Woodbury formula is adopted as the solver, the global stiffness matrix can keep unchanged throughout the analysis and the main computational effort is only invested on a small matrix representing local inelastic behavior. The numerical examples demonstrate the validity and efficiency of the proposed scheme.     

Re‐examination of Bagnold's empirical bedload ­formulae

Bagnold developed his formula for bedload transport over several decades, with the final form of the relation given in his 1980 paper. In this formula, bedload transport rate is a function of stream power above some threshold value, depth and grain size. In 1986, he presented a graph which illustrated the strength of his relation. A double‐log graph of bedload transport rate, adjusted for depth and grain size, versus excess stream power was shown to collapse along a line having a slope of 1·5. However, Bagnold based his analyses on limited data. In this paper, the formula is re‐examined using a large data set in order to define the most consistent empirical representation, and dimensional analysis is performed to seek a rationalization of the formula. Functional analysis is performed for the final version of the equation defined by Bagnold to determine if the slope of 1·5 is preserved and to assess the strength of the relation. Finally, relations between excess stream power and bedload transport are examined for a fixed slope of 1·5 to assess the performance of various depth and grain size adjustment factors. The rational scaling is found to provide the best result. Copyright © 2000 John Wiley & Sons, Ltd.     

海水烟气脱硫恢复系统的实验室模拟评价

恢复系统是海水烟气脱硫(SWFGD)技术的重要组成部分,如何对设计和运行参数进行实验评价一直是难点问题。本文在前期大量工程实践的基础上,建立了一套模拟实际工况多参数变化的循环式实验装置,将曝气深度和池容积按比例缩小,并强化处理海水的循环次数,提出针对气液比计算的缩比模型经验公式。实验中通过调节气体或液体流量、氧化时间、曝气池高度和容积等参数,有效模拟了工厂直排型海水脱硫恢复系统气液比(0.29~7.74)对S(IV)氧化效率、溶液pH值和溶解氧(DO)浓度的影响。此外,还评价了一种电化学-化学复合氧化改进处理技术,考察增加电极保护套对恢复参数的影响,研究结果可为工业放大提供依据。     

中国跨区域纠纷案件网络空间结构特征

本研究旨在评估中国跨区域纠纷案件的空间地理分布特征。借助GIS等分析工具,对跨区域纠纷案件的空间分布特征进行分析,结果表明：①中国纠纷案件网络呈现出“一轴、两心、多组团”的“钻石型”网络结构,形成了“核心-次中心-边缘”层级明显的区域网络结构,局部呈现出“大集聚、小分散”网络格局;②区域纠纷案件网络主要类型有：单中心网络结构、双中心网络结构、多中心网络结构;③主要城市群间的纠纷案件的关联度由强到弱依次为：珠三角洲城市群、长三角洲城市群、成渝城市群、天山北坡城市群、关中平原城市群、京津翼城市群,纠纷案件关联度越强,跨区域的法律纠纷事件发生越频繁;④纠纷案件的网络发展过程中表现出：纠纷案件被行政区分割、发达城市群法律纠纷行为外溢、产生法律纠纷行为向中心城市集聚等特征。     

Wave uplift force on horizontal panels: a laboratory study

Accurate estimation of wave uplift force is essential to the designs of reliable coastal and marine structures.We presents a series of laboratory work here on the impact of regular waves on horizontal panels,from which an empirical formula to estimate accurately the wave uplift force on panels is established.The laboratory measurements show that the wave uplift force depends mainly on the incident wave height,the wave period,the wave length,the panel width,and the clearance between the subsurface of the panel and the still water level.Among these factors,the impact of the panel width on uplift forces is relatively complicated.Result shows that the relative panel width(i.e.,the ratio of panel width to wave length)plays a more important role in estimating the wave uplift force.Based on our comprehensive laboratory measurements,we further developed an empirical formula to compute wave uplift force on horizontal panels through dimensionless analysis.Compared with other empirical formulas,this formula uses dimensionless variables of clear physical meanings,thus can describe the interaction between waves and the panels in a better way.In addition,the efficiency of the formula to estimate wave uplift force on horizontal panels is verified against existing works.Therefore,the findings in this study shall be useful for understanding the mechanism of wave uplift force on horizontal panels and numerical model validation.     

Distribution of wave crests in a non-Gaussian sea

The sea elevation at a fixed point is modelled as a quadratic form of a vector valued Gaussian process with arbitrary mean. With this model, saddlepoint methods are used to approximate the mean upcrossing intensity with which the sea level crosses upwards at a certain height. This estimated intensity is further used to determine the probability distribution of wave crests. The use of saddlepoint technique is particularly important here because it can approximate the crest distribution without the need to perform simulations or use fitted distributions. Several numerical examples are given, including two with measured data. In the cases of real data, the results obtained with the saddlepoint technique are also compared with the results obtained with well known methods commonly used in the industry.