矿区植被重金属胁迫高光谱分辨率数据分析

研究矿区植被重金属胁迫,植被反射光谱测量必不可少。用成像光谱仪野外测试江西德兴铜矿区典型植被的冠层反射波谱曲线,利用导数光谱评价植被“红边”位置。分析得知,植被红边“蓝移”,最大“蓝移”达11nm。根据红边位置与叶绿素含量的正相关关系,并结合铜矿区地质、地貌特点以及开采情况,初步断定铜矿区植被主要受到重金属胁迫而且胁迫程度与植被冠层重金属含量也呈正相关关系。这可作为高光谱分辨率遥感技术在矿区植被修复方面的决策支持和参考依据。     

中秦岭地带重力异常特征及地壳结构的探榷

对陕西榆林—重庆鱼泉综合地球物理大断面中在陕西户县经中秦岭至镇巴测段的重力场给以分析和探讨.文中给出了中秦岭造山带（或中秦岭块体） 的地壳密度结构、Moho界面深度与山根构造特征.并重点分析研究了本测段的重力异常在其地壳结构与构造解释中所明显反应的断裂构造（带）.即中秦岭北侧断裂构造带;中秦岭中部断裂构造系;中秦岭南侧的宁陕断裂构造带;安康（石泉西南）断裂构造带;芭蕉口断裂构造;城口断裂构造带北延段;镇巴断裂构造带;鱼渡断裂构造和铁溪断裂构造.并对各断裂构造带对应的重力异常段计算其水平方向导数V_xz,给出了断裂构造的分布位置、形态、倾向等要素.最后从重力学角度对中秦岭造山带的地壳结构与断裂构造具有的衔接与过渡特征作了相应的探搉.     

Stochastic seismic response of structures with added viscoelastic dampers modeled by fractional derivative

Viscoelastic dampers, as supplementary energy dissipation devices, have been used in building structures under seismic excitation or wind loads. Different analytical models have been proposed to describe their dynamic force deformation characteristics. Among these analytical models, the fractional derivative models have attracted more attention as they can capture the frequency dependence of the material stiffness and damping properties observed from tests very well. In this paper, a Fourier-transform-based technique is presented to obtain the fractional unit impulse function and the response of structures with added viscoelastic dampers whose force-deformation relationship is described by a fractional derivative model. Then, a Duhamel integral-type expression is suggested for the response analysis of a fractional damped dynamic system subjected to deterministic or random excitation. Through numerical verification, it is shown that viscoelastic dampers are effective in reducing structural responses over a wide frequency range, and the proposed schemes can be used to accurately predict the stochastic seismic response of structures with added viscoelastic dampers described by a Kelvin model with fractional derivative.     

机载LiDAR和高光谱融合实现温带天然林树种识别

将机载LiDAR(Light Detection and Ranging)与高光谱CASI(Compact Airborne Spectrographic Imager)数据融合,充分利用垂直结构信息和光谱信息进行温带森林树种分类,并与仅用高光谱数据的分类结果相比较,评估融合数据的树种分类能力。结合样地实测数据,首先用LiDAR获得的3维垂直结构信息对CASI影像上的林间空隙进行掩膜,提取林木冠层子集;然后对冠层子集分层掩膜,利用光谱曲线的一阶微分及曲线匹配技术,实现各树种训练样本的自动提取;利用SVM分类器对两种数据分类并比较精度。结果表明,融合数据的树种分类总体精度和Kappa系数(83.88%,0.80)优于仅使用CASI数据(76.71%、0.71),优势树种的制图精度为78.43%—89.22%,用户精度为75.15%—95.65%,整体也优于仅使用CASI的制图精度(68.51%—84.69%)和用户精度(63.34%—95.45%)。结果表明,机载LiDAR与CASI基于像元的融合对温带森林树种识别的精度较仅高光谱数据有较大提高。     

Methodological Issues in Researching Migration

Population geographers should consider a mixed methods approach to thestudy of migration. This methodological position arises in response to the challenges of contemporary social theory. It is argued that application of structuration theory favours use of a diversity of methods to investigate the recursive relationship between agency and structure. Similarly a realist stance, as advocated by Sayer (1992), leads to a mixing of methods in order to carry out the synthesising tasks expected of geographers. Postmodernism, when interpreted as method, also points the researcher to consider adopting flexible research practices in order to capture the multiplicities of meaning associated with migration and place. These points are illustrated by a case study of migration to and from Hong Kong.     

基于光谱平滑的浑浊水体叶绿素a浓度一阶微分估算模型

一阶微分处理常用于浑浊水体叶绿素a浓度的遥感估算,直接的微分处理容易扩大噪声的影响,该文使用光谱平滑降低噪声,讨论平滑处理对一阶微分估算模型的影响.对2004年夏季和2011年春季太湖水面实测光谱数据进行核回归平滑处理并建立一阶微分模型,结果表明,平滑处理后的光谱数据建立的一阶微分模型稳健性更好.将2004年7月数据建立的模型用于8月数据,2011年3月建立的模型用于4月数据,平滑处理后模型验证的均方根误差分别降低了13.1 mg/m3和3.9 mg/m3.光谱平滑对一阶微分模型应用精度的改进作用最显著,优于波段比值和三波段模型.平滑处理后的一阶微分和三波段模型应用精度较高,其中一阶微分模型使用的波段信息少,较易用于浑浊水体的叶绿素a浓度估算.     

基于重磁场特征的敦化盆地构造格架研究

依据重力、磁力异常数据及其处理结果( 水平梯度模和斜导数) ,对敦化盆地边界、基底起伏、断裂位置及以火成岩为代表的磁性体分布进行了研究。盆地重力异常的分析和水平梯度模及斜导数的计算结果表明,盆地基底具南部凹陷、中央凸起和北部凹陷的“两凹一凸”的起伏形态特征,盆地内断裂以SW--NE 向为主,盆地为单断半地堑式盆地。依据航磁异常,将盆地划分为4 个异常区: 东北部磁异常区、中部低磁异常区、西南高磁异常区和西南边部相对低磁异常区。结合磁异常水平梯度模和斜导数的计算结果显示,以火成岩为代表的磁性体受SW--NE 向构造控制。     

地面高精度磁测在交点型铀矿勘探中的应用

本次研究区域为赣粤交界处下庄铀矿田区,区内交点型铀矿严格受断裂构造与辉绿岩脉复合轨迹控制,铀矿几乎无磁性但辉绿岩脉磁性较强,研究任务是寻找地下隐伏辉绿岩脉。地面高精度磁测数据显示该区磁异常幅值常在正负几十纳特之间,通过ΔT平面等值线图难以判断辉绿岩脉分布,但其化极后0°方向水平一阶导数等值线图的正值与辉绿岩脉对应关系良好。     

全球大洋混合层深度的计算及其时空变化特征分析

本文利用2005-2009年的全球网格化Argo数据,分别采用温度判据和密度判据计算了全球大洋混合层深度(Mixed Layer Depth, MLD),讨论了障碍层(Barrier Layer, BL)和补偿层(Compensated Layer, CL)对混合层深度计算的影响,得到了合成的混合层深度,并研究了其时空变化特征. 研究表明:(1)在赤道西太平洋(10°S -5°N,150°E-150°W),孟加拉湾,热带西大西洋(10°N-20°N,30°W-60°W)是障碍层高发区域. 冬季的北太平洋副热带区域(30°N附近)以及东北大西洋(40°N-60°N,0°-30°W)是补偿层发生的区域. (2) 在各个半球的夏季MLD都比较浅,在各个半球的冬季MLD则普遍比较深. 北太平洋和北大西洋的MLD的分布和变化比较相似,印度洋MLD受季风影响显著,呈现半年周期变化. 太平洋和大西洋的MLD 的经向分布大致呈现出"两端深,中间浅"的拱形特点. (3)混合层深度距平场EOF第一模态时间变化为周期的年信号,北太平洋和北大西洋、南大洋(尤其是南极绕流区)都是MLD变化剧烈的海域,第二模态显示全球大洋混合层深度距平存在着一个半年的变化周期.     

Spatial and temporal variability of seawater properties,current velocity and SPM concentration off Cassino Beach-Rio Grande-Southern Brazil

Water column profiles and near-bed time series of pressure, current velocity, suspended-particulate matter (SPM) concentration and seawater temperature and salinity were collected during three short cruises carried out in May 2005 in the shoreface and inner shelf area adjacent to Cassino Beach, southern Brazil. The measurements were part of the Cassino Experiment, a project conducted at an open, sandy coastal area known for the occurrence of patches of fairly large amounts of muddy sediments that are sporadically fluidized, transported onshore and eventually stranded on the beach. The study area is close to the Patos Lagoon mouth, being influenced by its water and suspended-sediment discharge. The presence of the Patos Lagoon outflow on the inner shelf was detected in one of the cruises (May 13) through measurements of near-surface salinity: while close to shore salinity was 29.4, a minimum value of 13.8 was measured at ∼10 km from the coast. Four days later, no trace of the plume was detected in the area. Regarding seawater temperature, no large temporal or spatial variability was documented with measured values ranging from 19.3 to 20 °C. Water column currents were prominently to N and NE, except at the outermost station, located ∼42 km from the coast, where NW-directed flows were observed at surface and mid-depth. Maximum near-bed current velocity oscillated between 18 and 42 cm s⁻¹ in the east–west direction and between 14 and 42 cm s⁻¹ in the north–south direction. Near-surface concentration of SPM oscillated between 11 and 99 mg L⁻¹, in general one order of magnitude lower than near-bed values. However, near-bed concentration of SPM showed large spatial variability: the highest value (2200 mg L⁻¹) was yielded by a water sample collected at ∼8 m water depth, at a station located ∼2 km away from the shoreline; two water samples collected 500 m, apart from this station, yielded SPM concentrations of 148 and 205 mg L⁻¹, one order of magnitude lower. Spectral analyses of near-bed current speed and SPM concentration indicate the relevance of oscillations in the low-frequency (<0.05 Hz) range. Detailed sampling of bottom sediment indicated that in May 2005 the mud patch was centered at ∼8.5 m water depth.