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1.
Jeffrey Wade Laura Lautz Christa Kelleher Philippe Vidon Julianne Davis Julio Beltran Casey Pearce 《水文研究》2020,34(26):5340-5353
Beaver dam analogues (BDAs) are a cost-effective stream restoration approach that leverages the recognized environmental benefits of natural beaver dams on channel stability and local hydrology. Although natural beaver dams are known to exert considerable influence on the hydrologic conditions of a stream system by mediating geomorphic processes, nutrient cycling, and groundwater–surface water interactions, the impacts of beaver-derived restoration methods on groundwater–surface water exchange are poorly characterized. To address this deficit, we monitored hyporheic exchange fluxes and streambed porewater biogeochemistry across a sequence of BDAs installed along a central Wyoming stream during the summer of 2019. Streambed fluxes were quantified by heat tracing methods and vertical hydraulic gradients. Biogeochemical activity was evaluated using major ion porewater chemistry and principal component analysis. Vertical fluxes of approximately 1.0 m/day were observed around the BDAs, as was the development of spatially heterogeneous zones of nitrate production, groundwater upwelling, and anaerobic reduction. Strong contrasts in hyporheic zone processes were observed across BDAs of differing sizes. This suggests that structures may function with size-dependent behaviour, only altering groundwater–surface water interactions after a threshold hydraulic step height is exceeded. Patterns of hyporheic exchange and biogeochemical cycling around the studied BDAs resemble those around natural beaver dams, suggesting that BDAs may provide comparable benefits to channel complexity and near-stream function over a 1-year period. 相似文献
2.
为建立高精度的边坡位移预测模型,采用相空间重构(PSR)将边坡位移时间序列数据转换为多维数据,同时构造小波核函数改进的支持向量机模型,建立PSR-WSVM模型并应用于边坡位移预测。将PSR-WSVM模型预测结果与传统支持向量机(SVM)模型、小波支持向量机(WSVM)模型和基于相空间重构的支持向量机(PSR-SVM)模型预测结果进行对比,通过平均绝对误差(MAE)、平均绝对误差百分比(MAPE)和均方根误差(RMSE)3个精度评价指标验证PSR-WSVM模型的可行性。工程实例结果表明,PSR-WSVM模型预测结果的3个精度评价指标都优于另外3种模型,边坡位移预测的精度明显提升。 相似文献
3.
对青藏东北缘现今块体划分、运动及变形的初步研究 总被引:19,自引:9,他引:10
利用2维非连续变形分析方法(DDA),以位移代替围压作为边界约束力,研究青藏东北缘现今块体划分及其运动变形。根据该地区地质构造及地震活动,以GPS点测量位移作为模拟结果约束点,得出了较合理的块体划分模型和随时间演化的主应变分布图,并把应变高值区与近几年来发生的5级以上地震作对比,得出了研究区内地震危险性可能较大的区域。另外,对模拟的甘青块体与阿拉善块体的边缘带断裂左旋运动做了大概计算。 相似文献
4.
The auriferous veins at Jinniushan occurs within the Jinniushan faulted zone in the Kunyushan Granite. Optical observation reveals that gold ore body formed during the main stage of hydrothermal activity. Detailed geothermometric studies of fluid inclusions from the veins show that the forming temperature ranges between 130℃ and 370℃ and the salinity is from 4.01 to 15.21 wvt percent NaCl. The ore-forming fluid is featured by low to moderate salinity, and low to moderate temperature. According to investigations of the values of vapor/liquid and temperatures of the ore-forming fluids, we propose that the boiling fluid inclusions exist in the main mineralization stages. Fluid boiling is suggested as a mechanism for the precipitation of gold from the hydrothermal fluid in the Jinniushan gold deposit. 相似文献
5.
Majid T. Manzari 《国际地质力学数值与分析法杂志》2004,28(10):1011-1032
A micropolar elastoplastic model for soils is formulated and a series of finite element analyses are employed to demonstrate the use of a micropolar continuum in overcoming the numerical difficulties encountered in application of finite element method in standard Cauchy–Boltzmann continuum. Three examples of failure analysis involving a deep excavation, shallow foundation, and a retaining wall are presented. In all these cases, it is observed that the length scale introduced in the polar continuum regularizes the incremental boundary value problem and allows the numerical simulation to be continued until a clear collapse mechanism is achieved. The issue of grain size effect is also discussed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
笔者(1989)在辽东半岛南部复州湾和金县七顶山寒武系与奥陶系界线附近发现一层笔石,它们为:Airograptus furciferus,Staurograptus sp.,Dendrograptus sp.,并且建立了 Airograptus furciferus-Staurograptus 带,该带相当于华北的 Dictyonema flabelliforme-Staurograptus 带,相当于华南东南区的Staurograptus-Anisograptus 带,其层位相当于英国的特马豆克阶。由于该区寒武系顶部已建立了笔石带Dictyonema kelanense 带,因此,笔者将辽东半岛南部寒武系与奥陶系界线划在 Airograptus furciferus-Staurograptus 带与 Dictyonema kelanense 带之间。 相似文献
7.
8.
长诏断裂带垂直运动与地震关系初探 总被引:5,自引:0,他引:5
黄松风 《大地测量与地球动力学》2003,23(4):99-104
利用跨断层短水准资料分析了长诏断裂带断层活动特征,结果表明:长诏断裂带总体活动性质基本相同.分时段活动性质有所不同。断层各段多数以压性逆断为主,不同于历史地质考察结果。此外,长诏断裂带各断裂都具有分段活动特点。 相似文献
9.
This paper deals with the formation processes and the palaeoenvironmental significance of relict slope deposits located on the uppermost part of the north Portugal mountains. For this purpose, seven key sites representative of the different lithofacies have been selected and analysed in detail. The data show that three main dynamic processes are responsible for the emplacement of regional fossil slope deposits: runoff, debris flows and dry grain flows. The ubiquity of these processes and the lack of frost‐related features or landforms do not support the existence of severe Pleistocene climates in this part of the lberian Peninsula as postulated by previous work. Pedological data gathered at one of the study sites show that a subalpine environment was probably present at 700–800 m altitude between 29 and 14 kyr. Using data from the Pyrenees Mountains, a 6.5 to 12°C depression in mean annual temperature has been tentatively postulated for this Pleniglacial period. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
10.
韩玲 《地球科学与环境学报》2003,25(1):74-75
提出了一种基于格网DEM的粗差检测及剔除方法,其基本思想是对每个表面上的点,在坡度上,高程或突变量引起的形状不连续,可能被怀疑有误差,通过坡度上每个点,应用坡度逼近或改变量来计算,考虑坡度变化的相对值,并以这些相对值计算一个统计值为判断该点合法性的阈值,使计算结果更为可靠。 相似文献