井间电磁场的一维、二维联合反演方法

提出了针对轴对称二维井间模型的一维、二维联合反演方法.该方法基于纵向成层背景地层的Green函数,以一维反演结果作为联合反演的迭代初始值,同时反演一维背景地层和二维异常剖面的电导率.采用递推技术计算Green函数的系数,可以很方便地同时得到Green函数对空间坐标的积分和对背景层电导率的微分,大大加快了计算雅可比矩阵〖WTHX〗M〖WTBZ〗的速度并使计算方便、准确.反演实例说明了该方法的有效性.反演实例还显示,背景层电导率较二维成像剖面的电导率收敛速度要快,测量数据的精度对二维剖面电导率成像质量的影响大于对背景层电导率分布的影响.     

二维地震波场的组合型紧致有限差分数值模拟

地震波场数值模拟在地球物理勘探和地震学中具有重要的支撑作用.本文将组合型紧致差分格式用于声波和弹性波方程的数值模拟中.根据泰勒级数展开和声波方程,建立了位移场时间四阶离散格式,并将组合型紧致差分格式用于位移场空间导数的求取,然后对该差分格式进行了精度分析、误差分析、频散分析和稳定性分析.理论研究结果表明：①该差分格式为时间四阶、空间六阶精度,与常规七点六阶中心差分和五点六阶紧致差分相比,具有更小的截断误差和更高的模拟精度;②每个波长仅需要5.6个采样点,且满足稳定性条件的库郎数为0.792,可以使用粗网格和较大时间步长进行计算.所以该方法具有占用内存少、计算效率高和低数值频散等优势.最后,本文进行了二维各向同性完全弹性介质的声波和弹性波方程的数值模拟,实验结果表明本文提出的方法具有更高的计算精度,能够大幅度的节约计算量和内存需求,对于三维大尺度模型问题具有更好的适应性.     

用随机模拟方法研究设定地震地面运动

用随机模拟方法研究设定地震地面运动可分两步进行：（1）采用中小地震的数字观测资料确定研究区路径、场地参数;（2）把确定的参数应用到研究区的强地面运动随机模拟中. 为此,本文首先采用了一种可行的方法,分离软基岩场地效应和非弹性衰减的影响,并把二者分别确定出来. 研究区北部中软基岩场地的平均效应在2～4Hz频率范围为15倍左右;研究区的S波品质因子为QS＝278f[KG*2]0.346. 把这些参数用于研究区的场地和路径模型中,并选择单拐角频率震源谱模型,随机模拟了研究区未来中强地震可能在北天山中段可能造成的地面运动,模拟加速度时程和反应谱可以服务于本地区的地震灾害预测和建筑物可靠性验算.     

储层古应力场的数值模拟

根据古构造变形采用反演与正演相结合的方法,研究储层古构造应力场。开展以下研究：（１）用板模型趋势法反演与储层古构造变形面对应的驱动力和场内应力;（２）建立一个组合单元模型,用（１）中反演的远场应力作为边界条件,计算储层古构造应力场;（３）用含断层滑动模型的三维实体单元和（１）中给出的边界条件,计算储层古构造应力场;（４）对 ３ 种模型的应用及其检验     

A numerical model of wave overtopping on seadikes

This paper describes the development of a numerical model for wave overtopping on seadikes. The model is based on the flux-conservative form of the nonlinear shallow water equations (NLSW) solved with a high order total variation diminishing (TVD), Roe-type scheme. The goal is to reliably predict the hydrodynamics of wave overtopping on the dike crest and along the inner slope, necessary for the breach modelling of seadikes. Besides the mean overtopping rate, the capability of simulating individual overtopping events is also required. It is shown theoretically that the effect of wave breaking through the drastic motion of surface rollers in the surfzone is not sufficiently described by the conventional nonlinear shallow water equations, neglecting wave setup from the mean water level and thus markedly reducing the model predictive capacity for wave overtopping. This is significantly improved by including an additional source term associated with the roller energy dissipation in the depth-averaged momentum equation. The developed model has been validated against four existing laboratory datasets of wave overtopping on dikes. The first two sets are to validate the roller term performance in improving the model prediction of wave overtopping of breaking waves. The last two sets are to test the model performance under more complex but realistic hydraulic and slope geometric conditions. The results confirm the merit of the supplemented roller term and also demonstrate that the model is robust and reliable for the prediction of wave overtopping on seadikes.     

南美洲恐怖袭击事件时空演变研究

采用核密度估计法和重心分析对1970—2017年南美洲恐怖袭击事件时空演变过程进行了分析。结果表明：1980—1999年是南美洲恐怖袭击事件的高发期;南美洲恐怖袭击事件空间分异显著,1970—1979年主要集中于哥伦比亚和阿根廷,高发期主要集中分布于哥伦比亚、秘鲁、智利,2000年以来主要集中分布于哥伦比亚,近年委内瑞拉、巴拉圭的恐怖袭击活动也有抬头之势。南美洲恐怖袭击事件的时空演变是由地理环境、地缘政治博弈、经济社会环境、毒品贸易、政府的应对策略和社会控制体系、武器易获得、边界管控等多因素综合作用的结果。基于上述结论和维护中国在南美洲利益的需要,提出中国应加强与南美洲国家的反恐合作。受南美洲恐怖袭击活动有跨境渗透现象且呈现“毒恐合流”现象的启示,认为中国应警惕东南亚恐怖袭击活动是否会向境内渗透并向“毒恐合流”方向发展。     

喀什经济特区背景下喀阿组合城市研究

目前,城市合作是城市在更大范围内参与区域竞争和国际竞争的重要选择,组合城市是城市合作的表现形式之一。2010年5月国家正式批准建立喀什经济特区,喀什经济特区的建立将吸引大量的人流、物流、资金流和信息流,从而推动喀什市及周边地区经济快速发展,阿图什市需要利用这一机遇积极向喀什市及喀什经济特区寻求深度合作。目前喀阿两市还缺乏同城化和一体化的必要条件,喀阿合作可以借助组合城市模式,以喀什经济特区建设为契机,在两市间合理调整产业布局,以安全协调作为保障推动交通一体化和经济一体化,并最终实现两市的同城化发展。     

Modeling the particle breakage of rockfill materials with the cohesive crack model

A practical combined finite–discrete element method was developed to simulate the breakage of irregularly shaped particles in granular geomaterials, e.g., rockfill. Using this method, each particle is discretized into a finite element mesh. The potential fracture paths are represented by pre-inserted cohesive interface elements (CIEs) with a progressive damage model. The Mohr–Coulomb model with a tension cut-off is employed as the damage initiation criterion to rupture the predominant failure mode occurs at the particle scale. Two series of biaxial tests were simulated for both the breakable and unbreakable particle assemblies. The two assemblies have identical configurations, with the exception that the former is inserted with CIEs and is breakable. The simulated stress–strain–dilation responses obtained for both assemblies are in agreement with experimental observations. We present a comprehensive study of the role of particle breakage on the mechanical behavior of rockfill materials at both the macroscopic and microscopic scales. The underlying mechanism of particle breakage can be explained by the force chain in the assemblies.     

基于卡尔曼滤波递减平均算法的集合预报综合偏差订正

针对集合预报存在的偏差和集合离散度通常偏小的问题,在卡尔曼滤波递减平均的一阶矩和二阶矩偏差订正方案的基础上发展了综合偏差订正方案,并利用B08RDP WWRP(The WWRP Beijing 2008 Olympics Research and Development Project)项目中日本气象厅(JMA)区域集合预报的850 hPa温度资料,将敏感性试验得到的一阶矩和二阶矩订正的最优权重系数应用于综合偏差订正方案,并对其订正效果进行多方面检验分析。试验结果表明,一阶矩订正可以有效减小集合平均偏差,集合平均预报质量得到了明显改善;二阶矩订正对集合离散度具有较强的调整能力,订正后的集合预报可靠性、区分不同天气事件的能力总体上得到了提高;综合偏差订正方案有效融合了一阶矩和二阶矩订正的优势,其各自的最优权重系数适用于综合偏差订正方案,对集合平均偏差和离散度具有良好的订正效果,能够改善集合预报的整体质量。但一阶矩与二阶矩订正对综合偏差订正的贡献程度随评分指标而异,一阶矩订正对等级概率(RPS)评分和异常值百分比评分的贡献分别为83.75%和18.83%,可信度的改善约83.98%源于二阶矩订正,而相对作用特征(ROC)评分中二者的贡献基本相当。     

Relating accretion and erosion at an exposed tidal wetland to the bottom shear stress of combined current-wave action

Sediment dynamics have an important influence on the morphological evolution of tidal wetlands, which consist of mudflats and salt marshes. To understand the nature of sediment behavior under combined current-wave action at an exposed tidal wetland, we measured the waves, currents, water depths, bed-level changes, and sediment properties at a mudflat-salt marsh transition on the Yangtze Delta, China, during five consecutive tides under onshore winds of ~ 8 m/s, and calculated the bed shear stresses due to currents (τ_c), waves (τ_w), combined current-wave action (τ_cw), and the critical shear stress for erosion of the bottom sediment (τ_ce). The bed shear stresses under combined current-wave action (τ_cw) were approximately five times higher on the mudflat (up to 1.11 N/m²; average 0.27 N/m²) than on the salt marsh (up to 0.14 N/m²; average, 0.06 N/m²). On the mudflat, τ_cw was larger than the critical erosion shear stress (τ_ce = 0.103 N/m²) for 70% of the period of submergence, whereas τ_cw was always lower than τ_ce at the salt marsh site (τ_ce = 0.116 N/m²). This result indicates that the sediment dynamics on the mudflat were dominated by erosion, whereas at the salt marsh they were governed by deposition, which is in agreement with the observed bed-level change during the study period (− 3.3 mm/tide on the mudflat and 3.0 mm/tide on the salt marsh). A comparison of τ_cw values calculated using the [van Rijn, 1993] and [Soulsby, 1995] models for bed shear stresses under combined current-wave action indicates that both models are applicable to the present case and effectively predict the bottom shear stress under combined current-wave action. Overall, we conclude that τ_cw in combination with τ_ce is useful in assessing the hydrodynamic mechanisms that underlie the morphological evolution of exposed tidal wetlands.