Spatio-temporal variability in sea surface wind stress near and off the east coast of Korea

Sea surface wind stress variabilities near and off the east coast of Korea, are examined using 7 kinds of wind datasets from measurements at 2 coastal (land) stations and 2 ocean buoys,satellite scatterometer (QuikSCAT), and global reanalyzed products (ECMWF,NOGAPS,and NCEP/NCAR). Temporal variabilities are analyzed at 3 frequency bands; synoptic (2-20 d), intra-seasonal (20-90 d),and seasonal (>90 d).Synoptic and intra-seasonal     

喀斯特地区嵌岩混凝土摩擦桩的反算

云南南盘江大桥为7跨预应力钢构连续桥, 1、2号墩为桩基,采用人工挖孔灌注桩。No. 2嵌岩桩底下部12m处为强风化白云岩。对拟定的端承区域勘探发现在桩底的岩石- 混凝土接触区域有一溶洞,溶洞高约20m,垂直发育,洞底有粘土、碎石土充填,结构松散,粘土为软塑状。东南大学采用与O-cel l试验类似的平衡内部千斤顶系统进行了桩的荷载实验。O-cell试验安装在距桩底12m处,即靠近桩下部的弱风化与强风化岩石之间的接触区域。本文阐述了O-cell试验数值分析中用来反算桩体/岩石交接区域特性的部分。采用的数值分析软件为BAQUS,版本6. 4 ( ABAQ US, 2004) 。同时采用二维轴对称模型来对桩径2. 5m、桩长49m的钻孔桩进行O-cell试验数值模拟。假设加载的钻孔桩的变形与屈服发生在混凝土桩体与岩石的交接区域,混凝土桩为线弹性,强风化白云岩与弱风化白云岩为弹- 塑性,并可用Drucker- Prag er 模型( ABAQUS, 2004)表示,对岩石和混凝土- 岩体接触面的特性进行反算,然后用反算结果模拟桩顶荷载特征。数值模拟计算和现场载荷试验检测的载荷- 位移曲线对比表明,除了非弹性和永久变形外,整个向上与向下的变形与试验检测到的值基本相同。这主要是由于接触面模型的弹性性质所决定的,即它在卸载过程中会将滑动的接触面复原;而永久变形是岩体-混凝土接触面屈服的结果。必须指出的是,由于桩的承载力相对较高( 2. 5m桩径,嵌岩长度37m) ,试验不能达到最终荷载, 所以检测到的变形也较小( <10mm)。分别在桩端、O-单元荷载盒上37m处检测向上弯沉,并将结果与O-单元荷载盒顶部的弯沉作比较。结果发现,由于桩是由O-单元荷载盒底部向上加载,所以桩端的弯沉预计比O-单元荷载盒的弯沉小约5mm。这一差值几乎等于施加荷载状态下无限制(Δ= P L /A E )桩体的理论弹性缩短量。通过O-cell现场试验可以有效地观测加载状态下荷载弯沉反应情况和调整或校准数值分析中的材料模型,并可将之推广应用到相同地质条件下类似项目施工的其它桩的反应过程中。此外,还可以通过溶洞区域中的高承载力桩的O-cell试验结果来构建桩体摩擦反应的模型; 在模型摩擦反应基础上,可以估计桩端预计的变形反应值; 在交接面反应中,可以采用正弦接触面有效地引入人工粘结和表面粘结。      

层流区Shields曲线分布规律试验

为探明层流条件下Shields曲线的分布规律,运用电荷耦合组件(Charge Coupled Device,CCD)成像技术结合激光扫描及计算机图像处理技术,在水和甘油混合液中对无黏性均匀玻璃颗粒的起动拖曳力进行测量,并根据层流绕流理论建立了无黏性均匀颗粒的滚动起动模型,提出层流条件下无黏性均匀颗粒的量纲一起动拖曳力公式.试验观测发现在层流范围内希尔兹数呈规则的带状分布,流体作用引起颗粒床表面粗化并导致床面颗粒突起减小,使颗粒起动拖曳力增大1倍以上.结果表明颗粒床表面结构性状直接影响着颗粒起动拖曳力的大小,在层流区Shields曲线具有带状分布特性.     

利用OICC-SBAS技术提取岗普冰川表面流速时空变化特征

本文利用Sentinel-2数据,通过光学影像互相关技术(OICC),并借鉴小基线集(SBAS)思路,提取并分析了岗普冰川2015—2022年时序表面运动速度及时空变化特征。结果表明：岗普冰川表面流速存在明显的空间差异性,流速高值主要集中在上游的物质积累区,该区域形变特征复杂,年最高流速为82.5 m/a;冰川主体流速整体波动较小,位于40～50 m/a之间;时间特征上,冰川在研究时段内流速较为稳定,年际之间流速相差不大;利用东西向和南北向偏移量获取的最终偏移方向,与冰川实际流动方向相符,选取的稳定区域的偏移量误差仅占冰川最大流速的0.04%～0.7%,证实了冰川时序表面流速结果的可靠性。     

广东省东海岛大岭剖面沉积物粒度、微形态特征与沉积环境北大核心CSCD

沉积物粒度与表面微形态特征是反映沉积环境及源区等信息的重要指征。基于粒度分析和扫描电镜影像,研究广东省东海岛海岸大岭剖面的海岸风沙沉积物石英颗粒与微形态特征,以揭示其沉积环境和沉积过程。结果表明:(1)大岭剖面的粒度特征总体具有典型风成砂的特点。(2)大岭剖面沉积物石英颗粒磨圆度适中,表面具有麻点/麻面、碟形坑、新月形撞击坑、水下磨光面、鳞片状剥落等特征。东海岛大岭剖面石英颗粒先受到流水磨蚀与搬运作用,再受到风力的二次搬运和改造作用,风力作用特征显著。(3)大岭剖面整体上记录了从温暖湿润环境向寒冷干旱环境演变的历史。     

Word绘制简易地理图形的技巧与方法

正一、经纬网平面经纬网:⑴绘制直线和45°圆弧代表相应的经纬线;⑵双击或右击,选择"设置对象格式/虚实/虚线"代表回归线和极圈,然后组合。立体经纬网:⑴经线绘制选取"弧形",按住Shift键沿大圆绘制从极点至赤道的45°圆弧;⑵将圆弧拉至赤道1/6处,复制、粘贴该弧形,点击"绘图工具/旋转/水平翻转/垂直翻转"进行经线对接即可。二、光照图平面图阴影1:⑴选取"基本图形/曲线",绘制曲线同时按住Ctrl键可以实现折线效果,这对平面阴影面积的选取非常重要,在需要折曲处单击鼠标左键,双     

南极冰盖地形数据库BEDMAP 2述评

南极冰盖物质收支与不稳定性对全球气候变化和海平面升高有着重要影响,而冰盖厚度和冰下地形则是研究南极冰盖的物质平衡、动力及不稳定性极为重要的参数。自20世纪50年代以来,国际上针对南极冰盖开展了大量的冰雷达以及重、磁测量,这些测量结果被汇集并形成冰厚和冰下地形数据库,进而服务于冰盖模式和地球系统研究,最新推出的成果便是BEDMAP 2(Bedrock Mapping Project 2)。首先介绍了BEDMAP 2的数据来源、结构以及数据处理,并讨论了数据的质量评价,然后分析了BEDMAP 2中展示的整个南极冰盖与冰下地形及其特点。最后,对于BEDMAP 2对中国在南极冰盖考察和研究方面的作用进行了一些讨论与展望。     

世界银行拟筹资10亿美元绘制非洲矿产地

<正>总面积约3,000万平方公里的非洲有着丰富的矿产资源。然而,由于缺乏勘探数据,这片广袤大地上的矿产储量到底有多少却一直是个未知数。为了摸清世界第二大洲矿产潜力的家底,世界银行将启动一个10亿美元的基金项目,用于非洲矿产地图的绘制。今年2月初,在南非举行的"第20届非洲矿业投资大会"上,世界银行持续能源司油气和矿产部经理保罗·德·萨提出,虽然非洲有丰富的矿     

Retrieval of aerosol optical properties over a vegetation surface using multi-angular,multi-spectral,and polarized data

An algorithm to retrieve aerosol optical properties using multi-angular,multi-spectral,and polarized data without a priori knowledge of the land surface was developed.In the algorithm,the surface polarized reflectance was estimated by eliminating the atmospheric scattering from measured polarized reflectance at 1640 nm.A lookup table （LUT） and an iterative method were adopted in the algorithm to retrieve the aerosol optical thickness （AOT,at 665 nm） and the （A）ngstr（o）m exponent （computed between the AOTs at 665 and 865 nm）.Experiments were performed in Tianjin to verify the algorithm.Data were provided by a newly developed airborne instrument,the Advanced Atmosphere Multi-angle Polarization Radiometer （AMPR）.The AMPR measurements over the target field agreed well with the nearby ground-based sun photometer.An algorithm based on Research Scanning Polarimeter （RSP） measurements was introduced to validate the observational measurements along a flight path over Tianjin.The retrievals were consistent between the two algorithms.The AMPR algorithm shows potential in retrieving aerosol optical properties over a vegetation surface.     

Parameterizations of surface radiation in the semiarid grasslands of Inner Mongolia under clear-sky conditions using MODIS data

A set of improved and efficient radiation parameterization schemes for surface radiation balance components under clear- sky conditions was developed by using general surface measurements and MODIS data. The set of schemes was then adapted for regions similar to the present study sites under different grazing intensities and varying degrees of drought in the semiarid grasslands of Inner Mongolia. Specifically, we mainly improved two schemes for estimating downward shortwave and longwave radiation at the surface, which could be applied to regions with certain degrees of drought. The validation datasets were from ground-based observations at various grazing sites during the growing season （May to September） of different drought years, 2005 and 2006. Through comparisons of parameterized versus measured radiation values, the increased or modified factors in the original schemes demonstrated improved estimation accuracy, and the rationalities of input parameters and variables were analyzed. The regional instantaneous net radiation estimations had root-mean-square errors of less than 30 W m-2 compared with ground measurements at the sites during the study period. The statistical results showed the improved schemes are suitable for estimating surface net radiation in regional semiarid areas during the growing season. Analyses of the sensitivity of the schemes to corresponding variables were conducted to ascertain the major error sources of the schemes and potential variables for improving the performance of the schemes in agreement with observations.