基于空间句法耦合SLEUTH模型的新老城区扩展模拟研究——以开封市为例

在快速城镇化背景下,历史文化名城常扩建新区并形成新老城区联动发展格局,新建城区以"飞地"形式扩张,不易被传统的元胞自动机方法准确模拟.空间句法是基于空间拓扑的整体性交通网络研究方法,其自上而下的建模策略与元胞自动机自下而上的邻域转换规则起到了互补,两种模型相结合提供了解决上述问题的途径.本文在验证交通土地空间关联的基础...     

日喀则近53年气候变化特征分析

利用线性趋势函数及Mann-Kendall突变检测分析法,分析了西藏藏南河谷日喀则气象站气温及降水近53年的气候变化特征。结果表明,年平均气温与极端气温均呈上升趋势,而最高气温的上升趋势尤为明显,年降水量波动上升。冬春季增温趋势较秋、夏季更为明显,春夏季降水呈增加趋势,而秋季降水略有减少。Mann-Kendall突变检测表明,近53年日喀则地区气温有明显的增暖趋势,但20世纪60—70年代变冷趋势亦十分显著,在2001年温度发生一次突变。年降水量在1958年发生了由少向多的突变,但这一突变仅维持到20世纪60年代中期。     

Separate-ice frost heave model for one-dimensional soil freezing process

For one-dimensional soil freezing process, a separate-ice frost heave model is established, and the coupled process of heat transfer, fluid flow and stress development is considered in the model. First, a coupled heat–fluid–stress model describing the growth of a single ice lens is developed by extending the coupled heat–fluid model presented by Zhou and Zhou (Can Geotech J 49(6):686–693, 2012). Second, the mechanism for the formation of a new ice lens in the frozen fringe is studied, and we indicate that if the total vertical disjoining pressure at certain place exceeds the sum of the external pressure and the critical pressure, a new ice lens will emerge. By combining the growth model of a single ice lens and the criterion for the formation of a new ice lens, the separate-ice frost heave model is then established. The difference between the separate-ice model and the rigid-ice model is explained, and the relations for different mathematical models which describe the soil freezing process are also discussed. Numerical analysis of the separate-ice model is conducted using the finite volume method. The freezing tests for Devon silt under no external pressure and Xuzhou silty clay under a constant external pressure are applied to verify the computational results. The consistence between the calculation and the observation validates the separate-ice frost heave model.     

Mercury pollution from artisanal mercury mining in Tongren, Guizhou, China

Concentrations of total Hg (T-Hg) were measured in mine waste, stream water, soil and moss samples collected from the Tongren area, Guizhou, China to identify potential Hg contamination to local environments, which has resulted from artisanal Hg mining. Mine waste contained high T-Hg concentrations, ranging from 1.8 to 900 mg/kg. High concentrations of Hg were also found in the leachates of mine waste, confirming that mine waste contains significant water-soluble Hg compounds. Total Hg distribution patterns in soil profiles showed that top soil is contaminated with Hg, which has been derived from atmospheric deposition. Data suggest that organic matter plays an important role in the binding and transport of Hg in soil. Elevated T-Hg concentrations (5.9–44 mg/kg) in moss samples suggest that atmospheric deposition is the dominant source of Hg to local terrestrial ecosystems. Concentrations of T-Hg were highly elevated in stream water samples, varying from 92 to 2300 ng/L. Particulate Hg in water constituted a large proportion of the T-Hg and played a major role in Hg transport. Methyl–Hg (Me–Hg) concentrations in the water samples was as high as 7.9 ng/L. Data indicate that Hg contamination is dominantly from artisanal Hg mining in the study area, but the extent of Hg contamination is dependent on the mining history and the scale of artisanal Hg mining.     

高地应力区砂岩在卸荷条件下的变形参数劣化试验研究

以锦屏某高边坡砂岩所赋存的高地应力环境为基础,开展峰前卸围压力学特性试验,研究了应力-应变全过程曲线、变形特征及参数劣化效应。试验结果表明,相对于加载试验,岩样卸荷破坏表现出明显的脆性特征,相同初始围压下卸荷破坏所需偏应力较加载试验少;卸荷过程横向应变和体积应变急剧增大,卸荷方向表现出明显的扩容特征;当初始围压小于某一值（30 MPa）,岩样破坏所需卸荷量随初始围压增大而增大,当初始围压达到一定值（40 MPa时）,脆性特征更加明显,很少的卸荷量即可引起岩样破坏。以表征岩石卸荷程度的卸荷量H为参变量,分别对高、低围压下卸荷过程中变形参数（变形模量和泊松比）随卸荷量变化关系进行拟合,得到高、低地应力区卸荷过程中变形劣化参数的关系式。试验结果和计算方法对高应力区边坡开挖的稳定性评价具有一定指导意义。     

Chemical characterization and sources of PM2.5 at 12-h resolution in Guiyang,China

The increasing emission of primary and gaseous precursors of secondarily formed atmospheric particulate matter due to continuing industrial development and urbanization are leading to an increased public awareness of environmental issues and human health risks in China. As part of a pilot study, 12-h integrated fine fraction particulate matter (PM_2.5) filter samples were collected to chemically characterize and investigate the sources of ambient particulate matter in Guiyang City, Guizhou Province, southwestern China. Results showed that the 12-h integrated PM_2.5 concentrations exhibited a daytime average of 51 ± 22 µg m^?3 (mean ± standard deviation) with a range of 17–128 µg m^?3 and a nighttime average of 55 ± 32 µg m^?3 with a range of 4–186 µg m^?3. The 24-h integrated PM_2.5 concentrations varied from 15 to 157 µg m^?3, with a mean value of 53 ± 25 µg m^?3, which exceeded the 24-h PM_2.5 standard of 35 µg m^?3 set by USEPA, but was below the standard of 75 µg m^?3, set by China Ministry of Environmental Protection. Energy-dispersive X-ray fluorescence spectrometry (XRF) was applied to determine PM_2.5 chemical element concentrations. The order of concentrations of heavy metals in PM_2.5 were iron (Fe) > zinc (Zn) > manganese (Mn) > lead (Pb) > arsenic (As) > chromium (Cr). The total concentration of 18 chemical elements was 13 ± 2 µg m^?3, accounting for 25% in PM_2.5, which is comparable to other major cities in China, but much higher than cities outside of China.     

安阳上第三系化学矿物指标显示物源区大地构造

南水北调（中线）安阳主干渠段施工过程中开挖出大量成熟度低且受近源构造影响较大的河湖相沉积岩。对现场采集的上第三系岩石样品开展了化学成分、 岩石骨架成分测试。利用Dickinson法和化学指标法, 研究得到安阳主干渠段西部物源区属于被动陆缘, 在上新世晚期向活动陆缘变化的认识。同期构造活动强烈的克什米尔N—J引水隧洞段的沉积岩, 属于岛弧和活动陆缘的大地构造背景。本文结果丰富了构造稳定和活跃区新近纪沉积构造背景认识, 可为喜马拉雅运动以来不同构造活动背景下的岩石组分和化学指标特征提供参考。     

二维控制场中控制点像点坐标的自动提取与识别

本文给出了一种二维控制场中控制点像点坐标自动提取与识别的原理以及实现方法，并编制程序试验，取得了较高的精度和良好的识别效果。主要实现方法包括直接线性变换、Hough变换、最小二乘拟合等，特别适用于控制点数量较多的大型二维控制场。     

海面温度变化影响台风"海棠"强度的数值研究

通过对台风"海棠"5 d的数值模拟,研究海表温度(SST)变化对台风强度的影响。与NCEP月平均海表温度相对比,在中尺度大气模式中引入热带测雨卫星(TRMM)微波成像仪(TMI)/先进微波扫描辐射计(AMSR-E)来考察SST对台风"海棠"路径和强度的影响。研究结果表明,每天变化SST的试验模拟的台风强度和路径整体效果不错;模拟的台风路径不敏感于SST的变化,而台风强度的变化不仅取决于由于台风移动引发的SST冷却的幅度大小,而且取决于SST冷却区域的相对位置。在台风"海棠"强烈发展过程中,台风中心右侧冷却区对台风中心气压影响很小;台风强烈发展过后,SST冷却区开始影响台风强度,但造成台风中心气压下降幅度不大,6 h内台风中心气压减弱约3.9 hPa。海面热量通量和海面风速与SST的分布都有良好的相关性:在SST变化为正值的暖水区,感热通量和潜热通量都是一个正的通量分布的极值区,并有风速极大值区域存在;在台风右侧相应的冷却区,则存在着负的通量异常和风速极小值区域。     

一种基于指数函数的遥感水体信息提取方法

MODIS数据具有高时相分辨率、高光谱分辨率和中等地面分辨率的特征,利用MODIS数据来监测和提取旱情严重地区的水体信息已经成为一个重要的研究方向.本文利用各类地物在MODIS各个波段上的波谱特征差异性进行水体提取,但与以往水体信息提取方法有创新之处在于:本文借助于非线性的指数函数对低反射的水体的反射率进行了拉伸而对高...