乌鲁木齐河流域积雪面积变化及其对径流的影响

积雪面积是干旱区分布式水文模型的重要输入因子,为了研究其与径流间的关系,基于MODIS数据提取乌鲁木齐河流域英雄桥站以上积雪面积,分析了流域近年来积雪面积变化特征,采用偏相关分析法阐明了降水和气温变化对积雪面积的影响,并利用多元逐步回归与通径分析研究了径流同积雪面积、降水、气温间的关系。结果表明:(1)流域积雪面积12月份达到最大,7月份达到最小,多年积雪面积变化呈不明显下降趋势;(2)气温对积雪面积的变化较降水更加敏感;(3)流域内各因素间的相互影响促进了径流的产生。     

A laboratory study of collapse behaviour of remoulded loess under controlled wetting and flooding

This paper presents the effect of initial placement conditions and flooding stress (vertical compressive stress at flooding) on the collapse potential of remoulded loess. Compacted specimens of loess were tested in a one-dimensional consolidometer to study the collapse behaviour. Initial water content, dry unit weight and flooding stress were varied. Collapse potential was found to be dependent on initial water content, initial dry unit weight and flooding stress. Partial collapse was studied by allowing measured increments of water into the specimens.     

Large-eddy simulation of the flow past a circular cylinder at sub- to super-critical Reynolds numbers

Large-eddy simulation of turbulent flow past a circular cylinder at sub- to super-critical Reynolds numbers is performed using a high-fidelity orthogonal curvilinear grid solver. Verification studies investigate the effects of grid resolution, aspect ratio and convection scheme. Monotonic convergence is achieved in grid convergence studies. Validation studies use all available experimental benchmark data. Although the grids are relatively large and fine enough for sufficiently resolved turbulence near the cylinder, the grid uncertainties are large indicating the need for even finer grids. Large aspect ratio is required for sub-critical Reynolds number cases, whereas small aspect ratio is sufficient for critical and super-critical Reynolds number cases. All the experimental trends were predicted with reasonable accuracy, in consideration the large facility bias, age of most of the data, and differences between experimental and computational setup in particular free stream turbulence and roughness. The largest errors were for under prediction of turbulence separation.     

Metamorphism of high‐P metagreywacke from the Eastern Himalayan syntaxis: phase equilibria and P–T path

High‐pressure (HP) metagreywacke from the Namche Barwa Complex, Eastern Himalayan Syntaxis (EHS), consists of garnet, biotite, plagioclase, quartz, rutile and ilmenite with or without K‐feldspar, sillimanite, cordierite, spinel and orthopyroxene. Two types of metagreywacke are recognized: medium‐temperature (MT) and high‐temperature (HT) types. Garnet in the MT metagreywacke shows significant growth zoning and contains lower MgO than the weakly zoned garnet in the HT metagreywacke. Petrographic observations and phase equilibria modelling for four representative samples indicate that both types of metagreywacke experienced clockwise P–T paths subdivided into three stages: stage I is the pre‐peak prograde to pressure peak (P_max) stage characterized by progressive increase in P–T conditions. The P_max conditions are estimated using the garnet composition with maximum CaO, being 12.5–13.5 kbar and 685–725 °C for the MT metagreywacke, and 15–16 kbar and 825–835 °C for the HT one. Stage II is the post‐P_max decompression with heating or near‐isothermal to T_max stage and the T_max conditions, constrained using the garnet compositions with maximum MgO, are 11 kbar and 760 °C for the MT metagreywacke, and ~12 kbar and 830–845 °C for the HT one. The modelled mineral assemblages at T_max are garnet + biotite + K‐feldspar + rutile + plagioclase ± ilmenite in the presence of melt for both types of metagreywacke, consistent with the petrographic observations. Stage III is the post‐T_max retrograde metamorphism, characterized by decompression and cooling. The modelling suggests that the melts with high Na/K ratios (1.7–5.2) have been produced during stages I and II, which could be responsible for the formation of sodium‐rich leucogranites. This study and previous results indicate that the Higher Himalayan Crystallines in the EHS consist of MT–HP and HT–HP metamorphic units separated by a speculated tectonic contact. Petrological and structural discontinuities within the EHS cannot be easily interpreted with ‘tectonic aneurysm’ model.     

Soil moisture estimation using ERS 2 SAR data: a case study in the Solani River catchment/Estimation de l’humidité du sol grâce à des données ERS-2 SAR: étude de cas dans le bassin de la rivière Solani

Abstract

Abstract The information regarding spatial and temporal variation of soil moisture in a catchment is of utmost importance in hydrological, as well as many other studies. Point measurements from gravimetric and other methods for soil moisture determination are insufficient to understand the spatial behaviour of soil moisture in a region. Microwave remote sensing data from active sensors on board various satellites are increasingly being used to map spatial distribution of soil moisture within the 0–10 cm top surface. The northern part of India has a network of large rivers and canals and, therefore, spatial and temporal distribution of soil moisture in this region has a significant bearing on the hydrology of the region. In this paper, results on estimation of soil moisture from an ERS-2 SAR image in the catchment of the Solani River (a tributary to the River Ganga) in and around the town of Roorkee, India, have been presented. The radar backscatter coefficient for each pixel of the image has been modelled from the digital numbers of the SAR image. Gravimetric measurements have been made simultaneously during the satellite pass to determine the concurrent value of volumetric soil moisture at a large number of sample points within the satellite sweep area. The backscatter coefficient is found to vary from –30 dB to –42 dB for a variation in soil moisture from 30 to 75%. Regression analyses between volumetric soil moisture and both the digital numbers and backscatter coefficients were performed. Strong correlations between volumetric soil moisture and digital number were observed with R ² values of 0.84, 0.75 and 0.83 for bare soil, vegetative and combined surfaces, respectively. A similar trend was observed with the relationship between backscatter and volumetric soil moisture with R ² values of 0.60, 0.89 and 0.67 for bare soil, vegetative and combined surfaces, respectively. These results demonstrate the utilization of SAR data for estimation of spatial distribution of soil moisture in the region of the present study.     

API圆螺纹连接上卸扣过程中温度场分布的实验研究

粘扣是油套管接头的主要失效形式之一,直接影响油套管的密封性能和连接强度。以J55Φ73.03mm×5.51mmAPI不加厚圆螺纹油管为实验样本,利用TH7102型热像仪对在不同上卸扣速度和扭矩作用下螺纹连接部位温度场的分布进行了动态测试。根据摩擦磨损理论对影响螺纹连接部位温度场的分布和粘扣失效的主要因素进行了研究和总结,实验表明螺纹连接部位温度场分布不均匀,当接箍螺纹外表面温度超过60℃时,油管啮合螺纹一般会出现粘扣失效现象。     

西藏林周县扎雪地区林子宗群帕那组火山岩的地球化学特征及其地质意义

分布于西藏林周县扎雪地区的林子宗群帕那组火山岩,主要由流纹质-粗安质熔岩和火山碎屑岩组成。岩石总体上反映出高Al高K的特点,Al₂O₃的质量分数平均为14.55%,K₂O+Na₂O的质量分数平均为8.78%,K₂O质量分数平均为.77%,K₂O/Na₂O比值平均为2.07,显示了高钾钙碱性-钾玄质火山岩的特征。稀土配分曲线呈轻稀土富集的右倾形式,并具有中等-强烈的负Eu异常。微量元素Rb、Th强烈富集,Ta、Ba、U相对富集,而Y、Yb、Sr等相对亏损。岩石地球化学特征显示了陆壳重熔的特点。研究表明,扎雪地区帕那组火山岩是40 Ma左右陆壳加厚并部分熔融形成的,是印度板块和欧亚板块后碰撞作用的产物。     

基于盲数理论的地下水允许开采量计算初探

基于地下水系统所具有的多种不确定性特征,运用盲数理论,定义了水文地质参量盲数等基本概念,在此基础上,尝试性地提出了盲信息下地下水资源允许开采量计算模型。由此模型不仅可以求得地下水补给量(或允许开采量)的各种可能取值区间,也能得到各灰区间对应的主观可信度,从而为地下水资源管理决策提供了更为科学、丰富的信息,也为地下水开采的风险分析提供了依据。实例研究表明,运用盲数理论进行地下水允许开采量计算,所得结果较传统水文地质学方法计算结果更加符合实际情况。     

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.     

塔里木河中游植物群落的数量分类与分析

Plant communities were sampled in the lower reaches of the Tarim River,Xinjiang,The results showed that there are 23 species belonging to 21 genera in 11 families,most of which have low occurrence frequency in quadrats.The most common species is Tamarix ramosissima,which occurred in 17 sites accounting for 89.47% of the total 19 sites,Quantitative classification (TWINSPAN) and ordination(CCA) methods were used to study the distribution Patterns of 23 plant species in 19 sites in this valley.TWINSPAN results showed that the plant communities in the middle reaches of the Tarim River could be divided into 3 groups and the sampling sites could be diveded into 7 types in 3 groups .CCA results were consistent with TWINSPAN results ,and showed species distribution patterns correlated with major environmental variables of groundwater level and soil moisture.