基于GIS的城市暴雨积涝模拟教学实验项目设计

结合城市暴雨内涝分析教学内容,设计了基于GIS结合SWMM暴雨管理模型仿真模拟城市暴雨溢流的实验项目,建立了试验示例。试验项目形象直观地模拟暴雨排水管网溢流各个过程,真实精确地反映了城市暴雨溢流过程,能够较好地锻炼学生分析处理数据能力。     

Combined effects of cadmium and butachlor on soil enzyme activities and microbial community structure

The combined effects of cadmium (Cd, 10 mg/kg of soil) and butachlor (5, 10 and 50 mg/kg of soil) on enzyme activities and microbial community structure were assessed in phaeozem soil. The result showed that phosphatase activities were decreased in soils with Cd (10 mg/kg of soil) alone whereas urease acitivities were unaffected by Cd. Urease and phosphatase activities were significantly reduced by high butachlor concentration (50 mg/kg of soil). When Cd and butachlor concentrations in soils were added at milligram ratio of 2:1 or 1:2, urease and phosphatase activities were decreased, while enzyme activities were greatly improved at the ratio of 1:5. This study indicates that the combined effects of Cd and butachlor on soil urease and phosphatase activities depend largely on the addition concentration ratios to soils. The random amplified polymorphic DNA (RAPD) analysis showed that the changes occurring in RAPD profiles of different treated samples included variation in loss of normal bands and appearance of new bands compared with the control soil. The RAPD fingerprints showed substantial differences between the control and treated soil samples, with apparent changes in the number and size of amplified DNA fragments. The results showed that the addition of high concentration butachlor and the combined applied Cd and butachlor significantly affected the diversity of microbial community. The present results suggest that RAPD analysis in conjunction with other biomarkers such as soil enzyme parameter etc. would prove a powerful ecotoxicological tool.     

漫溃堤洪水联算全二维水动力模型及应用

为应对河道洪峰流量增大和漫溃堤长历时相伴发生的洪灾现象,借鉴全二维气相色谱理论提出全二维水动力模型概念,建立了模拟河道和灌区洪水演进的漫溃堤洪水联算全二维水动力模型,并采用Roe格式的近似Riemann解对界面通量进行数值求解。模型内通过漫溃堤堰流公式成功实现河道与灌区的耦联,考虑溃口展宽变化,加密处理河道网格,采用热启动与干湿水深理论对模型进行优化,并利用加大糙率法对村庄较为密集的地形进行优化处理,尽可能反应地面真实情况。将该模型应用于黄河宁蒙段河道与左右岸灌区的漫溃堤洪水演进模拟,计算结果合理可靠,流场分布均匀光滑,初步验证了模型的精度及可靠性,研究成果对河道溃决洪水的精细仿真模拟和该地区洪水风险分析决策具有重要意义。     

Fast computation of satellite gravitational gradient

The computation of the Earth's potential function at high order and degree with the method of reference [1], causes overflow most of the time. The normalized method [2–6] can eliminate the overflows, but leads to formulae much more involved than those in reference [1]; besides, the programming is more complex and the computer time required larger. The method presented in this paper has the following features: each component of the satellite gravitational gradient can be computed; the formulae are short and easy to be programme; the method is much quicker than the normalization method and can be carried out with a micro‐computer, without overflow even in the case of Earth's spherical harmonics of order and degree as high as 1025 or higher. This method satisfies the present demand to compute satellite gravitational gradient with high accuracy. Furthermore, we present formulae for the fast computation, without overflow, of the gravitational gradient corresponding to Earth's spherical harmonics up to order and degree of 3170 × 3170 or higher. This revised version was published online in July 2006 with corrections to the Cover Date.     

中巴经济走廊极端低温事件风险评估

危险性、暴露度、脆弱性是极端低温事件风险评估的关键因素。基于1961—2015年中巴经济走廊地区逐日最低气温、人口和耕地等数据,选取极端低温事件强度、频次、持续时间,人口密度,耕地面积占比,植被覆盖度,数字高程模型（DEM),脆弱人口比重和性别比重9个指标,采用层次分析法和熵权法确定各指标组合权重,对中巴经济走廊地区极端低温事件进行风险评估,实现了中巴经济走廊极端低温事件不同风险等级（低、较低、中、较高、高风险）的区划。研究表明,中巴经济走廊内极端低温事件风险分布具有显著的空间差异,极端低温事件风险受极端低温事件强度、人口密度和地形影响较大。区域内绝大部分地区属于低风险地区,高风险地区有巴基斯坦的阿扎德克什米尔地区、吉尔吉特-巴尔蒂斯坦地区、开普省地区、联邦直辖部落地区和中国的喀什地区。其中,阿扎德克什米尔高风险面积占比最高（约35%),联邦直辖部落地区较高风险面积占比最高（约7.7%),吉尔吉特-巴尔蒂斯坦地区中风险地区面积占比最高（约24.6%);中风险地区占比超过10%的还有开普省（12.5%)、阿扎德克什米尔（20%)、联邦直辖部落地区（10.2%)、中国喀什地区（14.3%)。评估结果与历史灾情吻合,可为区域气象灾害风险评估和防灾减灾提供参考。     

A new kind of nonlinear mild-slope equation for combined refraction-diffraction of multifrequency waves

This paper presents the numerical solution of a new nonlinear mild-slope equation governing waves with different frequency components propagating in a region of varying water depth. There are two new nonlinear equations. The linear part of the equations is the mild-slope equation, and one of the models has the same non-linearity as the Boussinesq equations. The new equations are directly applicable to the problems of nonlinear wave-wave interactions over variable depth. The equations are first simplified with the parabolic approximation, and then solved numerically with a finite difference method. The Crank-Nicolson method is used to discretize the models. The numerical models are applied to a set of published experimental cases, which are nonlinear combined refraction-diffraction with generation of higher harmonic waves. Comparison of the results shows that the present models generally predict the measurements better than other nonlinear numerical models which have been applied to the data set.     

南四湖的形成与水环境演变

Through high-resolution research of sedimental chronology and the sediment environmental indexes,such as graininess ,minerals,magnetic parameters,pigment content organic carbon and chronology in Ds-core and Ws-core in Nansihu Lake,the authors analyze the formation cause of the Nansihu Lake and its water environmental changes,Historical documents are also analyzed here in order to reach the conclusion .Researches indicate that the Nansihu Lake came into being about 2500 aBP and its evolution succession can be divided into four stages.In this evolution process ,several scattered lakes merge into one large lake in the east of China,This process is distinctively affected by the overflow of the Yellow River,the excavation of the Grand Canal and other human activities.     

Mid-depth Lagrangian pathways in the North Atlantic and their impact on the salinity of the eastern subpolar gyre

The role of Mediterranean Overflow Water (MOW) in creating subsurface salinity anomalies within the Rockall Trough, a gateway to high latitude areas of deep convection, has been examined closely in recent years. Eulerian investigations of high latitude property fields have suggested that these subsurface anomalies are likely the result of variability in the zonal extent of the eastern limb of the subpolar gyre: when expanded into the eastern North Atlantic, the gyre is presumed to limit the extent to which MOW is able to penetrate northward to subpolar latitudes. However, though the depth of the subsurface salinity anomalies in the Rockall Trough supports the hypothesis that the intermittent presence of MOW is involved in creating the anomalies, MOW pathways to the Rockall Trough have not yet been established. Here, Lagrangian trajectories from floats released in the eastern North Atlantic between 1996 and 1997 and synthetic trajectories launched within an eddy-resolving ocean general circulation model are used to demonstrate that two main density neutral transport pathways lead to the Rockall Trough. One pathway involves the transport of relatively fresh waters as part of the North Atlantic Current and the other involves the transport of relatively salty waters from the eastern reaches of the subtropical North Atlantic. The results from this study indicate that changes in these pathways over time can explain the subsurface salinity variability in the Rockall Trough.     

CRITICAL HYDROLOGIC CONDITIONS FOR OVERFLOW BURST OF MORAINE LAKE

1OVERFLOWBURSTOFMORAINELAKEFloodwater and debris flow caused by glacial lake burst is an important land process and a serious moun-tain disaster in glacial area. Glacial lakes with burst can divided into the glacier-obstructed lake (ice dam lake) and the terminal moraine lake (XU and FENG, 1988). Typical burst of ice dam lake happens in the modern glacier area of the upper reaches of the Kele-qing River in Uygur Autonomous Region of Xinjiang (WANG, 1990). But most of burst gla…