The morphology and hydrology of small spring-dominated channels

Small, low order channels located in wet meadows along the Mogollon Rim of northern Arizona that receive the bulk of their flow from spring discharge exhibit a morphology that differs markedly from channels that receive the bulk of their flow from runoff. These small, spring-dominated channels generally have dense vegetation cover, vertical (or near vertical) banks with flat channel beds that are armored with clasts up to 60 mm. Clasts armoring the spring-dominated channels become mobile at 45 to 85% of the bankfull depth. The lack of fine-grained material in the bed of the spring-dominated channels reflects the small drainage size, lack of fine grain input from the spring, and winnowing affect of the consistent discharge. Minor amounts of large woody debris were present in some of the spring-dominated channels, however, unlike previous studies it does not appear to play a role in the spring-dominated channel morphology. Sinuosity values for spring-dominated channels averaged 1.19, while the average sinuosity values for the runoff-dominated channels, 1.08, were significantly lower. Measured width-to-depth ratios averaged 2.4 in the spring-dominated channels, much lower than the average ratio of 11.6 found for the runoff-dominated channels. The standard deviation of width-to-depth ratios was higher for runoff-dominated channels, reflecting a more variable channel profile. A third channel type, here referred to as hybrid channels, receive significant flow from both springs and runoff. These channels have characteristics that fall between spring-dominated and runoff-dominated channels.Elevation, gradient, organic matter content, and sediment grain size distribution of the wet meadows in which the channels are formed do not exhibit significant differences between channel types, suggesting that these factors are not responsible for the observed differences in channel morphologies. The major differences in controls on the channel morphology found between the spring-dominated and runoff-dominated channels are the discharge regime and the sediment input. The hydrology unique to the spring-dominated channels and the lack of fine-grained sediment input combine to create the observed differences.     

数学形态学和模式识别在建筑物多边形化简中的应用

针对居民地图形化简的一个方面--建筑物多边形的化简,提出一种在与地图比例尺相关的动态栅格和矢量数据相结合的数据模型支持下,综合利用数学形态学和神经网络支持下的模式识别的化简方法.在Visual C 环境下实现基于此方法的系统并进行实验,实验结果说明此方法在保持街区的形态特征上效果明显.这种方法将制图综合知识融入图形化简操作之中,是自动制图综合智能化的一次新的尝试.     

海洋脊椎动物甲状腺系统的研究与应用

甲状腺(Glandulathyreoidea)是海洋脊椎动物体内重要的内分泌腺,从海洋脊椎动物开始,才有了独立的甲状腺结构。海洋脊椎动物的甲状腺一般为实质性的组织。实质由甲状腺滤泡组成,构成滤泡的上皮细胞合成、贮存和分泌的甲状腺激素是调节机体生长发育的关键激素。从海洋脊椎动物开始才有了独立的甲状腺结构。对于动物甲状腺的研究多集中在甲状腺形态及甲状腺与生长发育关系方面,而对海洋脊椎动物的甲状腺的研究则越来越多的集中于环境因素所引起的甲状腺病变方面,环境因素对甲状腺功能的影响也逐渐成为科学研究的重点。海洋水体污染导致的甲状腺机能受损,使海洋脊椎动物不能正常生长发育,数目与种类骤减之时,我们不得不重视对海洋脊椎动物甲状腺的研究。     

基于数学形态学的位场数据边缘增强方法

位场数据边缘增强对于地质构造研究和矿床勘查具有重要意义。现有的边缘增强方法多数基于位场数据的导数构建,往往存在对噪声敏感的缺点,且处理结果中常有虚假边界的出现。本文基于数学形态学良好的形状分析和噪声压制性能,通过数学形态学基本算子的组合叠加,提出了一种新的位场数据边缘增强方法。该方法容易实现,且不需要计算位场数据的水平和垂向导数。板状体模型试验结果表明,该方法能有效地对重力异常和化极后的磁异常数据进行边缘增强。针对三维模型试验中正负异常同时存在的情况,相比以往几种方法,该方法输出的边缘更清晰且没有额外边缘的产生,并表现出更强的抗噪能力。最后将该方法和以往几种方法应用到老挝万象地区实际重力异常数据的处理中,结果显示该方法刻画出的边缘更加连续清晰;同时结合以往地质资料,推断了成矿的有利部位。     

山西中部一次积层混合云降水微物理特征研究

基于2011年5月9日山西中部地区一次积层混合云降水的机载探测和地面雨滴谱观测资料,分析了空中云系微物理参量的垂直分布、冰晶形态及演变和地面降水的微物理特征。结果表明：此次积层混合云为冷云结构,垂直分布不均匀,云中过冷水较为丰沛,对流泡的存在造成云内不同区域云水含量不均匀。云滴的凝华增长导致5.3 km处大云粒子和降水粒子数浓度明显增加。小云粒子谱分布以单峰型为主,峰值直径主要位于5～6 μm或9～10 μm,大云粒子谱分布呈多峰型,不同高度处变化较大。此次降水观测到的冰晶形态包括板状、针柱状、柱帽状、辐枝状和不规则形状,4.9 km处受聚合和淞附过程的共同影响,辐枝状和针柱状冰晶增多,在4.1 km处融化层附近淞附状冰晶明显增加。地面降水受到雨滴谱仪布设位置的影响,其微物理结构主要呈现为层状云降水的特征。     

Intensity of in‐lake processes in floodplain lakes within the Bug River zone of fluvial activity

The paper presents a new approach to calculating the erosion and deposition values of floodplain lake basins, the erosion–deposition index (EDI). The EDI is a sum of the basin geometry indices (BGIs), which can be calculated for a separate cross section of the lake. The distribution of processes within the basin was investigated in two selected floodplain lakes with the use of BGIs. Field research was carried out in the Bug River valley from 1 November 2006 to 31 October 2011. The highest erosion was observed in the lakes located close to the parent river. Deposition processes were observed in lakes with high inflow of groundwater. The results showed that EDI values of 48 out of the 71 floodplain lakes ranged from ?0.2 to 0.2. Spatial distribution of erosion and deposition processes within the lake basins resulted from a velocity of water inflowing or flowing through the basin. This was observed especially in contrafluent–confluent lake. Inflow of rivers water via upstream crevasse occurred later than via downstream one, but energy of flowing water was higher, which favoured erosion of this part of the lake basin. Copyright © 2013 John Wiley & Sons, Ltd.     

The influence of organic debris on channel morphology and bedload transport in a New Zealand forest stream

The behaviour and form of, and bedload sediment transport through, a 3.5 m wide forest stream have been monitored for nearly three years. Bedload transport is highly episodic and spatially variable, and is controlled less by water discharge than by sediment availability. Organic debris in the channel creates temporary base levels and sites at which coarse sediment may remain stored for long periods; collapse or disruption of log and debris jams makes sediment available for transport in only a small proportion of the runoff events that are actually competent to move the material. Even then, sediment travels only a short distance before being redeposited, frequently behind debris accumulations further downstream. Rates of sediment transport during a given runoff event can vary markedly over short distances along the stream, again depending on whether sediment was made available for transport by log jam collapse upstream. Organic debris is therefore a major constraint on the application of physical laws and theories to explaining sediment movement in, and the morphology of, this stream.     

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。     

水合物赋存形式对石英砂电性特征影响的数值模拟研究

天然气水合物储层精确评价关系到储层的生产与开发过程.由于储层微观结构具有非均质性, 且水合物合成分解过程中分布形式复杂, 水合物储层物性变化规律尚不明晰, 从而难以对储层水合物饱和度进行准确预测.为明确水合物赋存模式对电性特征的影响规律, 本文基于石英砂样品采用随机模拟的方法实现了颗粒包裹型、孔隙填充型和团簇状分布三类赋存模式的水合物数字岩心构建, 并进一步提取孔径分布分析不同水合物分布模式下的微观结构变化特征, 利用有限元方法对含水合物数字岩心进行电性模拟, 结合阿尔奇公式得到适用于含水合物石英砂介质的经验参数取值, 并采用实验室内水合物合成实验电阻率测量数据与实际储层电阻率测井数据对比验证了阿尔奇经验参数取值的正确性及有效性.结果表明, 随着水合物饱和度逐渐增加, 在相同水合物饱和度下, 颗粒包裹型生长引起的微观结构变化对电传导过程的影响最为显著; 孔隙填充型水合物生长引起的孔隙结构变化对电传导过程影响最小; 不同水合物赋存形式下, 沉积物孔径分布变化规律从微观角度解释了三类分布模式的电性差异.研究结果有助于研究储层内含水合物沉积物合成分解过程中的电性特征演化规律.

     

Analysis, synthesis and modelling of high-resolution observations of salt-marsh eco-geomorphological patterns in the Venice lagoon

The present paper describes observations, analyses and models of salt-marsh channel network and vegetation patterns with the aim of contributing to the development of predictive models of ecological and morphological co-evolution. Existing and new observations are described, with particular emphasis on remote sensing and ancillary field surveys, which are shown to allow reliable, accurate and repeatable quantitative characterizations of landform and vegetation properties over the spatial scales of interest. The observed channel network morphological characters are then used as the basis and validation of models describing the emergence of channel network and vegetation spatial patterns. In particular, with reference to observations performed in the Venice Lagoon, the note describes: (i) new, 2-cm resolution, characterizations of channel network geometry obtained from “proximal sensing” photographic observations; (ii) the reliable quantitative maps of salt-marsh vegetation which may be retrieved from hyperspectral remote sensing data and field ancillary observations; (iii) a synthesis of recent and new analyses of the statistical properties of vegetation and landform spatial organization, that may be inferred from the maps so derived; (iv) recent and new conceptual and quantitative ecological and geomorphic models developed and validated by remote-sensing and field observations. A coherent observational and theoretical eco-morphodynamic framework is then proposed.