A remote sensing model of CO2 flux for wheat and studying of regional distribution

A model for calculating CO₂ flux in the wheat field and an algorithm for estimating CO₂ flux in the mejonal scale were presented using the remote sensing data and supplementary micpo-met~orological data. First of all a-longertenn measurement wae carried out during winter wheat growing period in Yucheng Experimental Station udng the spectmradiometer system, the thermal infrared radiometer system, the Bowen-ratio device as well as the eddy-correlation device. Two kinds of issues concerning remote sensing and CO₂ flux can be obtained. Based on the obeervations a remote sensing model was estabilished. Then when the NOAA-AVHRR passed over the experimental area simultaneous measurements were carried out with the satellites. A regional distribution image for CO₂ flux over wheat canopy in North China (500×500 km²) was made using the supplementary ground data and NOAA-AVHRR remote sensing data which was calibrated by the synchronous observation. The sources and sinks for CO₂ fluxes in the region can be seen obviously. Project supported by the National Natural Science Foundation of China (Grant Nos. 49671058, 49890330)     

协因数阵秩亏时扩建网极大条件密度估计的精度

作者曾〔3〕推导了当联系参数函数不独立时,扩建网极大条件密度估计的等价法方程和参数的协因数矩阵。在其基础上,本文作者继续推导单位权方差因子的估计公式。     

粤港澳大湾区一次局地极端强降水过程的多尺度观测特征与演变分析

2020年5月22日凌晨粤港澳大湾区发生了一次极端强降水过程,最大小时雨量和3小时雨量打破广东省内“龙舟水”期间的历史最高纪录。利用多源观测数据以及ERA5再分析资料对引发局地极端降水的中尺度对流系统(MCS)的演变过程与中尺度特征开展研究。(1)此次强降水过程主要集中在凌晨时段,具有持续时间短、局地雨强极端、累积雨量大等特点,在3小时的降水过程中出现了两个降水峰值。(2)这次过程为一次暖区暴雨过程,低层西南季风提供了充足的暖湿水汽,低涡切变线提供了良好的抬升条件。中α尺度季风云团呈准静止状态并升尺度增长为MCC(中尺度对流复合体)的过程引发了大湾区夜间局地的极端降水。(3)过程中两个阶段的峰值降水与中γ尺度对流单体生消发展期间的传播与移动矢量发生的改变有密切联系。数个中γ尺度对流单体构成多单体风暴形态,呈西北-东南侧向排列,这些单体先后触发发展并有着各自的地面辐合线。对流单体在环境风引导下向偏东南方向移动引发第一阶段峰值降水。随后不同单体的辐合线连接,对流向西南方向传播显著加快,使对流系统移动矢量发生改变,因而造成第二阶段峰值降水。(4)造成两段峰值降水的中γ尺度对流单体结构存在明显...     

珊瑚岛礁孤立波爬坡的平面二维数值模拟研究

为了探究岛屿周围珊瑚礁在抵御海啸灾害中的作用,采用激波捕捉类Boussinesq模型FUNWAVE-TVD,对孤立波在理想化三维岛礁地形上的传播及爬坡开展了现场尺度的平面二维数值模拟,分析了入射波高、礁坪水深、礁坪宽度、礁前斜坡坡度、礁后斜坡坡度、珊瑚礁糙率对岛屿四周孤立波爬高分布的影响。结果表明,珊瑚礁的存在总体上可有效降低岛屿四周孤立波的最大爬坡高度;入射波高、礁坪水深、礁坪宽度、珊瑚礁糙率是影响珊瑚岛礁四周孤立波爬坡分布的主要因素,岛礁四周最大爬坡高度会随入射波高和礁坪水深的增大、礁坪宽度和珊瑚礁糙率的减小而不断增大;当礁坪水深增大到一定程度时,珊瑚礁主要会对岛屿背浪面的爬高失去影响,而当礁坪宽度和珊瑚礁糙率减小至一定程度时,会出现岛礁四周最大爬高高于无珊瑚礁时爬高的现象;礁后斜坡的变缓会使岛礁周围的最大爬高有所减小,而礁前斜坡坡度对珊瑚岛礁周围的最大爬高几乎没有影响。     

湖南栗山铅锌铜多金属矿床闪锌矿微量元素特征及成矿指示意义

位于江南造山带中段的湘东北地区是我国华南重要的金铅锌铜钴多金属矿产地之一,栗山铅锌铜多金属矿床是该区近年来找矿勘查新发现的一大型矿床。该矿床位于晚侏罗世—早白垩世幕阜山岩体南缘,矿体主要赋存于岩体及其与地层接触带的构造破碎带内,空间上与岩体关系密切,然而目前关于该矿床的研究十分薄弱。本文采用电子探针和激光剥蚀电感耦合等离子质谱仪开展了闪锌矿的原位微区微量元素分析。微量元素组成分析结果表明,闪锌矿以富集Co、Ga而贫Fe、Cd、Ge为特征,其中Fe、Mn、Cd、Co、Ga等元素以类质同象形式产出,而Cu、Pb、Ag和Sn等元素则还以包裹体形式赋存于闪锌矿中。根据不同微量元素间的相关关系,认为闪锌矿中可能存在Zn²⁺↔Fe²⁺、4 Zn²⁺↔2 Fe²⁺+Ge⁴⁺+□(其中□表示空位)、3 Zn²⁺↔2 Cu⁺+Ge⁴⁺、2 Zn²⁺↔Ag⁺+Sb³⁺等简单和复杂替代关系。闪锌矿的Zn/Fe、Ga/Ge、Ge/In、Ga/In比值和Fe温度计等指示闪锌矿形成于中低温(240~250 ℃)、低硫逸度(lgf(S₂)=-13.3~-9.6)环境。栗山矿区闪锌矿的微量元素组成特征有别于金顶砂岩型、SEDEX型、VMS型、MVT型和夕卡岩型铅锌矿,结合低的Cd/Fe(0.03~0.14,平均0.06)、Cd/Mn(1.54~6.30,平均2.91)比值和Ge含量,暗示该矿床成矿作用与岩浆活动有关。综合矿区地质特征和区域构造-岩浆演化,认为该矿床是在太平洋板块俯冲后撤引起的伸展构造背景下形成的与燕山期幕阜山岩体有关的中低温岩浆热液充填交代型矿床。该类型矿床闪锌矿具有鲜明的微量元素组成特征,可为判别具相似地质特征的矿床成因提供借鉴。     

基于改进的数学形态学算法的LiDAR点云数据滤波

数学形态学在数字图像处理中有广泛的应用.首先介绍传统数学形态学算法的特点,对这一理论用于LiDAR点云数据滤波的不足进行了分析.在此基础上,对相应的算法进行扩展和改进,提出针对不同地形特点的自适应滤波算法.在数学形态学"开"算子的基础上,提出增加一个"带宽"参数用于点云数据滤波的方法.最后利用三组实际点云数据进行试验,以验证这一算法的有效性.     

Short Communication: A numerical method for diffusive transport with moving boundaries and discontinuous material properties

A method for the numerical simulation of diffusive transport with moving boundaries is developed and tested. The variable domain is mapped onto a fixed region, which introduces a term of convective form to the transformed governing equation. The resulting convection/diffusion equation is solved by a finite-difference method. An ‘Immersed Interface’ Method (IIM) is introduced in order to retain second-order accuracy near discontinuities in material properties, where the solution is not smooth. The method performs well in benchmark calculations against an analytical solution. The IIM scheme is capable of treating a strong discontinuity in the gradient, and it is readily extended to two or three dimensions. The methods are illustrated through a calculation for the temperature profile in a growing continental ice sheet, in which the thermal properties are discontinuous at the rock/ice interface. © 1997 by John Wiley & Sons, Ltd.     

沾化县实施土地开发整理努力实现两个平衡

沾化县是黄河三角洲综合开发的重点区域，也是“海上山东”建设的前沿阵地。全县土地面积2114．km^2，其中耕地面积6．11万hm^2，总人口38．5万，人均耕地面积0．17hm^2。沾化县现有耕地后备资源34641．99hm^2，其中国家级耕地后备资源31694．57hm^2，省级耕地后备资源2941．41hm^2，通过土地开发整理，将来可净增耕地2947．41hm^2。     

转型期北京社区公共空间对邻里交往的影响机理：本地居民与移民的对比分析

利用2017年北京市36个小区的居民问卷调查数据,并基于POI数据测量小区尺度上步行道、公园、交通站点、商业设施、学校5类公共空间与设施的可达性,采用结构方程模型考察社区公共空间对本地居民、外来移民邻里交往的不同影响作用和机理。研究发现,在城市转型与居住分异的背景下：典型公共空间（步行道、公园）在促进邻里交往的作用上不如交通站点、商业设施等准公共空间设施;相较于外来移民,本地居民的邻里交往水平更容易受到社区公共空间的影响。     

面向流媒体传输的空间数据变化累积模型

将流媒体技术引入到以矢量数据为主的网络GIS传输中,其关键是建立逐级精细化的多层次表达模型,并在服务器端数据预组织上建立线性索引结构.本研究针对该目标建立一种矢量数据多重表达的新模型,即变化累积模型,认为尺度空间中从粗到细的数据表达过程是一些"变化"的累积,"变化"表现为两个连续尺度表达间的差别,通过"变化"元素的逐渐增加或减少来实现渐进传输.基于该模型对面状数据渐进式传输进行研究,将多边形分级剖分为一系列凸壳或外接矩形的基础上建立变化累积模型,通过剖分元素的组合完成渐进式流媒体传输.

Abstract：

The streaming transfer method which makes data immediately available application during the progress of transfer becomes a welcome transfer way over Web. The progressive transmission of map data provides the users witha self-adaptive strategy to access remote data. It not only speeds up the Web transfer but also offers an efficient navigation guide in information acquisition. The key technology in this transmission is the efficient multiple representation of spatial data and pre-organization on server site. This paper aims at vector data offering a new multiple representation model called changes accumulation model, which considers the spatial representation from one scale to another scale as an accumulation of set of changes. The difference between two consecutive representations is recorded in a linear index and through gradually addition or subtraction realizes the progressive transmission. As an example, the progressive transmission of area feature based on changes accumulation model is investigated in the paper. The model is built by hierarchical decomposition of polygon into series of convex hulls or bounding rectangles and through component of the decomposed elements to accomplish the progressive transmission.