Hydrological Simulation Using TRMM and CHIRPS Precipitation Estimates in the Lower Lancang-Mekong River Basin

Satellite-based products with high spatial and temporal resolution provide useful precipitation information for data-sparse or ungauged large-scale watersheds. In the Lower Lancang-Mekong River Basin, rainfall stations are sparse and unevenly distributed, and the transboundary characteristic makes the collection of precipitation data more difficult, which has restricted hydrological processes simulation. In this study, daily precipitation data from four datasets(gauge observations, inverse distance weighted(IDW) data, Tropical Rainfall Measuring Mission(TRMM) estimates, and Climate Hazards Group InfraRed Precipitation with Stations(CHIRPS) estimates), were applied to drive the Soil and Water Assessment Tool(SWAT) model, and then their capability for hydrological simulation in the Lower Lancang-Mekong River Basin were examined. TRMM and CHIRPS data showed good performances on precipitation estimation in the Lower Lancang-Mekong River Basin, with the better performance for TRMM product. The Nash-Sutcliffe efficiency(NSE) values of gauge, IDW, TRMM, and CHIRPS simulations during the calibration period were 0.87, 0.86, 0.95, and 0.93 for monthly flow, respectively, and those for daily flow were 0.75, 0.77, 0.86, and 0.84, respectively. TRMM and CHIRPS data were superior to rain gauge and IDW data for driving the hydrological model, and TRMM data produced the best simulation performance. Satellite-based precipitation estimates could be suitable data sources when simulating hydrological processes for large data-poor or ungauged watersheds, especially in international river basins for which precipitation observations are difficult to collect. CHIRPS data provide long precipitation time series from 1981 to near present and thus could be used as an alternative precipitation input for hydrological simulation, especially for the period without TRMM data. For satellite-based precipitation products, the differences in the occurrence frequencies and amounts of precipitation with different intensities would affect simulation results of water balance components, which should be comprehensively considered in water resources estimation and planning.     

Study on fault-controlled hydrocarbon migration and accumulation process and models in Zhu I Depression

Through the analysis of the faults and their internal structure in Zhu I Depression, it is found that the internal structure of the late fault is obviously segmented vertically. It develops unitary structure(simple fault plane) in shallow layers, binary structure(induced fracture zone in hanging wall and sliding fracture zone in footwall) in middle, layers and ternary structure(induced fracture zone in hanging wall and sliding fracture zone in middle,and induced fracture zone in footwall) in deep layers. Because the induced fracture zone is a high porosity and permeability zone, and the sliding fracture zone is a low porosity and ultra-low permeability zone, the late fault in middle layers has the character of "transporting while sealing". The late fault can transport hydrocarbon by its induced fracture zone in the side of the hanging wall and seal hydrocarbon by its sliding fracture zone in the side of the footwall. In deep layers, the late fault has the character of "dual-transportation", induced fracture zones in both sides of hanging wall and footwall can transport hydrocarbon. The early fault that only developed in the deep layers is presumed to be unitary structure, which plays a completely sealing role in the process of hydrocarbon migration and accumulation due to inactivity during the hydrocarbon filling period. Controlled by hydrocarbon source, early/late faults, sand bodies and traps, two reservoir-forming models of "inverted L" and "stereo-spiral"can be proposed in middle layers, while two reservoir-forming models of "cross fault" and "lateral fault sealing"are developed in the deep layers of Zhu I Depression.     

融合点、体素和对象特征的多基元点云分类

单一基元分类方法难以全面描述复杂的点云场景,采用多基元进行分类成为一种趋势,提出了一种融合点、体素和对象特征的点云分类方法。主要包括4个方面:(1)分别确定各层面分类基元,点基元方面采用最优邻域方法,体素基元方面基于八叉树方法进行体素划分,对象基元方面使用改进的多要素分割方法进行点云分割;(2)提取各基元分类特征,首先提取点基元分类特征并进行局部线性约束编码(Locality-constrained Linear Coding, LLC),然后以此为基础提取体素基元和对象基元的潜在狄利克雷分布特征(Latent Dirichlet Allocation, LDA)和最大池化特征(Max Pooling, MP);(3)降低分类特征维度,利用随机森林变量重要性算法对分类特征进行筛选与降维;(4)进行点云分类,使用随机森林算法实现点云分类。采用3种不同类型的点云数据进行试验,结果表明融合3种基元特征的分类精度相比于点基元分类分别提升了1.43%、7.02%和2.48%,分类特征降维可以有效降低特征冗余度,分类器分类时间减少约70%;通过与其他算法的对比,新算法分类精度更优,且适用于多种场景...     

美国联邦应急管理局城市搜寻及救助反应系统搜救策略简介

美国国家城市搜寻及救助快速反应系统是美国联邦应急管理局于1989年组建成立的,它的主要任务是定位、营救那些受困于有限空间的幸存者,并完成初期的医疗救助工作。该系统适用于地震、飓风、洪水、暴风雪、意外事故、恐怖袭击、危险物质泄漏等多种灾害的紧急救援。     

A computational framework to predict the water‐leakage pressure of segmental joints in underwater shield tunnels using an advanced finite element method

The construction of shield tunnels under riverbeds and seabeds has considerably increased over the past decades. Due to the ultra‐high water head, water leakage through tunnel joints is a major concern during a tunnel's service life. One practical solution to prevent groundwater penetration is to implement ethylene‐propylene‐diene‐monomer gaskets at the segmental joints. However, numerical simulation of fluid pressure penetration into rubber materials remains a challenging problem in computational mechanics. Severe mesh distortions can occur due to large deformation. Consequently, a convergent solution is difficult to achieve. This paper presents an Abaqus‐based numerical framework to solve the previously mentioned problem using the implicit finite element solver. The key aspects of this framework are twofold: (1) a remesh and re‐map algorithm to overcome the excessive mesh distortion, and (2) simulation of fluid penetration into the contact interface of the gaskets to reproduce the water‐leakage process at the tunnel joints. The proposed framework is first tested to simulate the gasket‐in‐groove mechanical behavior and is then validated using experimental data and the solution produced by an explicit finite element solver. The developed framework is then adopted to predict the water‐leakage pressure at gasketed tunnel joints to illustrate the practical applications. Finally, the numerical results are compared with experimental data to demonstrate the accuracy and robustness of the proposed method and confirm its superiority and effectiveness over existing methods. This novel method can be used by tunnel designers to analyze and estimate the waterproof behavior of gasketed joints in shield tunnels without performing extensive experimental testing works.     

CLDAS融合土壤相对湿度产品适用性评估及在气象干旱监测中的应用

基于2008—2017年全国自动气象观测站逐旬土壤相对湿度观测数据,综合评估中国气象局陆面数据同化系统（CMA Land Data Assimilation System,CLDAS）0～20 cm层融合土壤相对湿度产品在中国地区的适用性,评估表明CLDAS土壤相对湿度产品在中国东北、西北、江南大部及华南等地区存在较大系统性误差,总体上适用性较差。为消除CLDAS土壤相对湿度产品的系统性误差,采用回归订正法、7旬滑动平均订正法和临近加权前旬订正法对CLDAS土壤相对湿度产品进行误差订正处理,对订正结果评估发现：订正处理后CLDAS土壤相对湿度产品与站点观测的相关性显著增加,系统偏差基本消除,适用性明显提高,3种订正方法中临近加权前旬订正法的订正效果最优。最后,采用经不同方法订正后的CLDAS土壤相对湿度产品对2017年5月东北—华北地区一次气象干旱个例进行重现,对比验证表明：相对其他两种订正方法,经临近加权前旬订正法处理后的CLDAS土壤相对湿度产品能更为精准地重现2017年5月东北—华北地区气象干旱的落区和强度。〖JP〗     

井一震结合进行高分辨率层序地层划分——以南苏门答腊盆地N油田U组为例

N油田U组上段地层发育粉砂岩和钙质泥页岩的三角洲前缘一浅海过渡相,多变的沉积相加大了小层对比的难度。针对此特点,结合层序地层学理论以及地震地层学的理论与研究方法,进行井一震结合对比划分地层,利用地震资料和标准层控制,构建大套地层等时格架;然后运用地震反射轴的等时性结合沉积旋回在地层格架内对比小层,确定研究区80口井6个分界界面。建立了区域高分辨率层序地层格架,形成了可容纳空间控制下的高级次层序格架建立的技术方法。     

基于农业可持续发展的土地利用结构最优化研究——以长沙县为案例

由于过度施用化肥、使用农药、侵占农田等行为造成的农业环境和社会问题日益严重,尤其是在城郊农业区和高集约化农区问题更为突出,因此现代农业发展不仅仅追求经济效益,更应该关注生态功能提升和农村社会稳定。本研究旨在提出一套生态、经济和社会协调发展的土地利用结构优化方法,实现农业综合效益最大化和土地可持续发展。本研究以高集约化农业区长沙县为案例,首先构建经济-生态-社会效益评价指标体系,采用熵权-TOPSIS法对农业土地利用经济效益、生态效益和社会效益进行综合评价;其次采用耦合协调度模型和障碍因子模型,识别出影响农业综合效益的障碍因子;最后运用多目标线性规划法,构建生态、经济、社会约束条件和目标函数,计算得出土地利用最大综合效益和最优化结构,并提出了相关政策建议。研究结果表明:(1)长沙县农业综合效益呈现增长趋势,评价值从1996年的0.20上升到2016年的0.79;(2)经济因素不再是影响农业效益协调发展的障碍因子,而社会因素,例如粮食安全指数等成为主要影响因子;(3)综合考虑经济发展、环境保护和社会需求提出了长沙县土地利用优化结构,农业综合效益可由99.83亿元增长到129.34亿元,增长29.56%。本研究采用了一系列的模型和方法得出了长沙县农业综合效益最大化值和土地利用最优结构,可为农业土地空间格局优化和农业可持续发展提供科学的建议和依据。     

阳江复杂地形对特大暴雨影响机理的数值研究

采用中尺度天气预报模式WRF (Weather Research Forecast)对广东省阳江地区2019年5月26日00时—28日00时暴雨事件进行数值模拟,并通过一系列的地形敏感试验,讨论地形对暴雨发生和发展的影响。结果表明:地形对暴雨的影响显著,地形的高度影响暴雨的强度和位置;与未作任何改变的控制试验相比,地形降低试验和细网格地形高度取平均试验无山脉的阻挡,阳江地区无爬流和绕流运动及相对涡度减小,南风将低层水汽和能量带到更北的位置,暴雨中心随之北抬;增高地形试验,由于山脉阻挡,更多水汽和能量堆积,以及地形的阻挡产生绕流和爬流运动,绕流有利于局地涡旋生成,爬流运动会增加垂直运动速度,正涡度中心增强,低层的水汽辐合上升凝结,造成更大暴雨。