河北中南部平原土壤重金属元素存在形态及生物有效性分析

本文以河北省中南部平原农田表层土壤为研究对象,对表层土壤中7种重金属元素的形态含量进行了统计和分析,对重金属元素的生物有效性进行了评价,并运用相关分析法,对影响重金属元素生物有效性的因素进行了研究。结果表明,研究区表层土壤7种重金属元素的有效态含量以Cd最高,达36.83%,潜在生态危害性较大;其次为Pb,达13.37%,其中碳酸盐结合态达到12.38%,由于土壤呈中性或偏碱性,Pb元素的迁移能力较弱,其潜在危害性较小;Cu、Hg、Cr、As、Zn重金属元素含量均以稳定态的含量存在,之和均在90%以上,表明其潜在危害性较小;研究区土壤重金属元素的活性系数和迁移系数大小顺序为:CdPbHgCuZnAsCr和CdHgAsCuPbZnCr,其中Cd的活性系数和迁移系数平均值分别达到0.330和0.160,展现出较强的生物活性、不稳定性和迁移能力,其他重金属元素在土壤中活性系数(Pb除外)和迁移系数均较小,生物活性较弱,在土壤中稳定存在,由土壤中向植物中的迁移能力弱;研究区不同的重金属的生物有效性与其影响因素的关系不尽相同,其主要因素是土壤重金属元素全量,其次为p H、TOC、CEC、粘粒含量等,二者关系复杂。     

Strenulagus (Mammalia: Lagomorpha) from the Middle Eocene Irdin Manha Formation of the Erlian Basin, Nei Mongol, China

New material of Strenulagus solaris, a stem lagomorph, from the lower part of the Middle Eocene Irdin Manha Formation at the Irdin Manha and Huheboerhe localities, Erlian Basin, Nei Mongol, China includes remains of isolated cheek teeth, fragmentary upper incisors(d I2) and postcranial elements, reported from the species for the first time. The tarsal bones display advanced features, such as a wide calcaneofibular articulation surface and, along with an increase in hypsodonty, the new data document the early stage of lagomorph evolution in the Middle Eocene of the Erlian Basin. This finding is stratigraphically well constrained and probably predates that of the type material of S. solaris from the Khaychin Formation, Bugin-Tsav Basin, Mongolia.     

融合光谱-空间信息的高光谱遥感影像增量分类算法

提出了一种融合光谱和空间结构信息的高光谱遥感影像增量分类算法INC_SPEC_MPext。通过主成分分析(PCA)提取高光谱影像的若干主成分,利用数学形态学提取各主分量影像对应的形态学剖面(MP),再将所有主分量影像的形态学剖面归并联结,组成扩展的形态学剖面(MPext)。将MPext与光谱信息相结合以增加知识,最大限度地挖掘未标记样本的有用信息,优化分类器的学习能力。不断从分类器对未标记样本的预测结果中甄选置信度高的样本加入训练集,并迭代地利用扩大的训练集进行分类器构建和样本预测。以不同地表覆盖类型的AVIRIS Indian Pines和Hyperion EO-1Botswana作为测试数据,分别与基于光谱、MPext、光谱和MPext融合的分类方法进行比对。试验结果表明,在训练样本数量有限情况下,INC_SPEC_MPext算法在降低分类成本的同时,分类精度和Kappa系数都有不同程度的提高。     

地理国情水系要素的自动提取

在地表覆盖水系图斑采集的基础上,利用Rosenfeld细化算法实现地理国情水系要素中心线的自动提取。首先兼顾提取质量确定图像由矢量转换为栅格的最佳像素值,然后根据内存访问效率和图像块大小的关系选择图像分块处理技术。此外,采用图像形态学的膨胀与腐蚀算法、线段长度条件约束和曲线节点抽稀等技术确保中心线提取质量。试验结果表明,本文提出的方法准确、高效,在生产实践中具有一定的应用价值。     

结合Gabor纹理与几何特征的高分辨率遥感影像城区道路提取方法

在充分考虑道路频谱在不同频带、不同方向上能量分布的基础上,提出一种基于Gabor纹理与几何特征相结合的高分辨率遥感影像城区道路提取方法。首先通过Gabor滤波器组得到遥感影像不同频带、不同方向上的Gabor纹理特征,并利用K-means方法对遥感影像进行分割;然后利用形态学方法分割与道路相连的地物,并选取适当的几何特征剔除非道路地物;最后利用形态学方法对道路网进行修整。实验结果表明,该方法可以有效、便捷地从高分辨率遥感影像中提取城区主干道路网。     

基于区域多次回波点密度分析的城区LiDAR建筑物提取

以正确提取城区Li DAR点云中建筑物为目标,综合利用不同类别目标点云的回波特征以及地形信息,提出了一种基于区域多次回波密度分析的Li DAR点云建筑物提取方法。首先,将点云构建不规则三角网(triangulated irregular network,TIN),获取封闭的等高线;然后,利用等高线间的拓扑关系得到等高线族区域;最后,统计每一区域的多次回波点云密度信息,通过建筑物和树木区域多次回波点云在区域密度上的巨大差异来识别建筑物点云和树木点云。研究结果表明:该方法既充分利用了建筑物表面与植被间多次回波特性的差异,又不否定建筑物边缘同样存在多次回波的现象;通过封闭的等高线自适应地检测出地物目标的轮廓,弥补了传统Li DAR建筑物提取方法的不足;该方法能够较其他方法更准确地提取建筑物。     

Radio‐tracking gravel particles in a large braided river in New Zealand: a field test of the stochastic theory of bed load transport proposed by Einstein

Hans A. Einstein initiated a probabilistic approach to modelling sediment transport in rivers. His formulae were based on theory and were stimulated by laboratory investigations. The theory assumes that bed load movement occurs in individual steps of rolling, sliding or saltation and rest periods. So far very few attempts have been made to measure stochastic elements in nature. For the first time this paper presents results of radio‐tracing the travel path of individual particles in a large braided gravel bed river: the Waimakariri River of New Zealand. As proposed by Einstein, it was found that rest periods can be modelled by an exponential distribution, but particle step lengths are better represented by a gamma distribution. Einstein assumed an average travel distance of 100 grain‐diameters for any bed load particle between consecutive points of deposition, but larger values of 6·7 m or 150 grain‐diameters and 6·1 m or 120 grain‐diameters were measured for two test particle sizes. Together with other available large scale field data, a dependence of the mean step length on particle diameter relative to the D₅₀ of the bed surface was found. During small floods the time used for movement represents only 2·7% of the total time from erosion to deposition. The increase in percentage of time being used for transport means that it then has to be regarded in stochastic transport models. Tracing the flow path of bed load particles between erosion and deposition sites is a step towards explaining the interactions between sediment transport and river morphology. Copyright © 2001 John Wiley & Sons, Ltd.     

Gaseous Jets in Comet Hale-Bopp (1995 O1)

We report the identification of gas jets in comet Hale-Bopp in OH, NH, CN, C₂ and C₃. This is the first time OH and NH jets without an obvious optical dust jet counterpart have been identified in narrowband comet images. We also confirm the existence of CN jets as reported by Larson et al. (1997) and Mueller et al. (1998). Jet features can be seen in the March and April 1997 datasets, approximately a month before and after perihelion. Our results contribute to the understanding of both the chemical properties of the comet as well as the physical mechanisms necessary to produce these features. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Gastric Shield and the Undrelying Epithelium of Chlamys Farreri:Morphological,Histological and Histochemical Characterizations

The gastric shield and underlying stomach epithelium of Chlymas ffarreri were examined at the light and ultrastructural levels.The results showed that the gastric shield consisted of two different size lobes joined together by a narrow middle piece,the thicker lobe was shaped like a funnel,but unclosed at the lateral side;the other lobe was irregularly triangular-shaped.The transverse section of the thicker lobe was obviously laminated and gradually decreased in thickness from the peak to the margins of the shield.The underlying epithelium bore numerous about 3μm diameter spherical processes formed by the apical plasmalemma of the epithelial cells becoming blunt pseudopodia.Microvilli and some interspersed cilia were present in the areas among the spherical processes regions where only microvilli existed.Rough endoplasmic reticulum,Golgi apparatus,different-sized electron-dense secretory granules and electron-lucent vacuoles as well las abundant mitochondria were present in the underlying epithelial cells.Fused droplets of the secretion from the underlying epithelial cells formed the gastric shield.     

基于特征点的高分辨率遥感影像城镇道路提取

根据高分辨率遥感影像中城镇道路的特点,提出了一种基于特征点的道路信息提取方法。首先,对影像进行增强处理并选取感兴趣的子区域,利用改进的分水岭分割理论和阈值选择算法,结合八邻域检测方法得到道路的特征点;然后,利用回归分析方法在一定的坐标系统下得到每条道路的回归方程,根据端点坐标信息得到道路信息图;最后,利用数学形态学算法获取道路骨架图。结果表明,本方法能够精确有效地提取高分辨率遥感影像的城镇道路信息。