Simulation analysis on the regulation of overflow ecological water consumption in arid areas——A case study in the Canmrik ecological area of the mainstream zone of the Tarim River     

CHEN Xi  HUANG Yue  QIAN Jing  LIU HaiLong  FENG XianWei  LIU Ying  BAO AnMing  WANG WeiSheng 《中国科学D辑(英文版)》2007,50(Z1)

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中—β尺度强对流风暴和暴雨数值模拟中的一些问题   总被引：1，自引：0，他引：1       下载免费PDF全文

程锐  潘晓滨等 《气象科学》2002,22(1):28-39

本文利用数值模拟方法探讨各环境背景因子对强对流及暴雨系统发生发展所起的作用，分析了暴雨和强对流风暴的形成机制。结果表明：温度场和湿度场的垂直分布，决定着对流是否可以形成；其水平非均匀性只是改变风暴发展强度、生命期以及分裂特性。风场的动力影响对强风暴的移动、分裂及强度特征也十分重要。最后，对第三运动方程做了量纲分析，发现热浮力是对流风暴发展的决定性因素；而热浮力冲量能更细致地反映对流风暴的发展演变特征。  相似文献   

高速公路砂井地基固结度时空变化规律探讨     

周爱国  刘晓  刘增贤 《水文地质工程地质》2002,29(1):28-30,34

软基固结度时空变化规律的研究对解决高速公路软基沉降预测问题具有十分重要的意义。本文在讨论固结度时空变化的实质与计算方法的基础上，结合京珠高速公路广珠段某软基试验资料，初步探讨了高速公路砂井地基固结度的时空变化规律，特别提出固结的滞后效应及其对固结沉降曲线形态的影响，并简要讨论了砂井直径和间距对固结度的影响，认为软基沉降中地下水微观动力学过程的研究将有助于揭示固结度时空变化规律。  相似文献   

西部大开发中的农业结构调整思考   总被引：2，自引：2，他引：2  

侯京林 《干旱区地理》2001,24(2):113-117

西部地区的农业发展直接影响到我国国民经济是否能够持续快速健康的发展，这是由于我国是农业大国，农业人口大约占全国人口比例的80％，而实现西部地区持续健康发展的关键在于对传统农业产业结构的调整，提高农业增长的结构变动效益，树立大农业观念，延长农业产业链，在联产承包责任制的基础上通过经营权的集中规模种植，达到实现农业结构调整生态化和产业一体化目标。西部地区在大开发战略实施中，如何将自身的发展环境劣势转变为优势，提出了农业结构调整模式的构想。  相似文献   

天马山硫金矿床金的赋存状肪及分布规律   总被引：2，自引：3，他引：2       下载免费PDF全文

吕俊武  夏元法 《地质与勘探》2001,37(3):29-31

矿床中金主要以独立矿物相存在，少数为细粒分散相，金的载体矿物主要有黄铜矿，毒砂，黄铁矿，综合脉石和磁黄铁矿等，金矿物主要为自然金，银金矿，平均成色745．57，金的嵌布类型有粒间金，包裹金，裂隙金3种，金在矿石中及不同矿体中的分布不均匀，金与流，金与砷的相关性因矿体类型及矿石类型的不同而有差异。  相似文献   

Latent heat effects of the major mantle phase transitions on low-angle subduction     

Jeroen van Hunen  Arie P van den Berg  Nico J Vlaar 《Earth and Planetary Science Letters》2001,190(3-4):125-135

Very low to zero shallow dip angles are observed at several moderately young subduction zones with an active trenchward moving overriding plate. We have investigated the effects of latent heat for this situation, where mantle material is pushed through the major mantle phase transitions during shallow low-angle subduction below the overriding plate. The significance of the buoyancy forces, arising from the latent heat effects, on the dynamics of the shallowly subducting slab is examined by numerical modeling. When a 32-Ma-old slab is overridden with 2.5 cm/yr by a continent, flat subduction occurs with a 4–5 cm/yr convergence rate. When latent heat is included in the model, forced downwellings cause a thermal anomaly and consequently thermal and phase buoyancy forces. Under these circumstances, the flat slab segment subducts horizontally about 350 km further and for about 11 Ma longer than in the case without latent heat, before it breaks through the 400-km phase transition. The style of subduction strongly depends on the mantle rheology: increasing the mantle viscosity by one order of magnitude can change the style of subduction from steep to shallow. Similarly, an overriding velocity of less than 1 cm/yr leads to steep subduction, which gradually changes to flat subduction when increasing the overriding velocity. However, these model parameters do not change the aforementioned effect of the latent heat, provided that low-angle subduction occurs. In all models latent heat resulted in a substantial increase of the flat slab length by 300–400 km. Varying the olivine–spinel transition Clapeyron slope γ from 1 to 6 MPa/K reveals a roughly linear relation between γ and the horizontal length of the slab. Based on these results, we conclude that buoyancy forces due to latent heat of phase transitions play an important role in low-angle subduction below an overriding plate.  相似文献   

Internal wave characteristics in the eastern Arabian Sea during summer monsoon     

P G K Murthy  G S Sharma  V V James  K V Suseela 《Journal of Earth System Science》1992,101(4):317-327

The time series BT profiles and surface winds and atmospheric pressure, collected in the deep waters off Ratnagiri and Karwar during summer monsoon were utilized to document the characteristics of internal waves (IW). Low-frequency (≤2, cycle per day (cpd)) IW off Ratnagiri are found to propagate at 83 cm/s with wavelengths of 45 km and wave heights upto 40 m. These parameters for high-frequency (>2 cpd) IW off Karwar correspond to 99 cm/s, 3 km and 23 m. The IW off Karwar appear to leave the station at 70° (±10°) (measured from the horizontal). The data sets were further analysed to address the harmonic composition of the IW and identify the possible sources for the observed IW fields. Power spectra of the IW indicated energy peaks at inertial (0·6 cpd) and tidal (1 and 2 cpd) frequencies off Ratnagiri and in the high-frequency band of 0·5–2·0 cycles per hour off Karwar. The coherence between the IW and wind/tide is found to be good at several frequencies within the IW spectrum. This feature probably suggests tides as a source for the IW of tidal frequencies and winds and tides as a joint source for the IW at the remaining frequencies.  相似文献   

泥沙起动条件与卵石浅滩航道整治线宽度的确定     

钱恩清 《地理研究》1992,11(2):17-25

在简述泥沙起动条件表达式的基础上,本文分析卵石浅滩整治与泥沙起动条件的关系。根据起动拖曳力和起动流速的概念,分别导出了卵石浅滩航道整治宽度计算公式,并用北江整治河段的实测资料对诸公式作了比较。结果表明,式(16)的计算值与实际采用值有较好的一致性。  相似文献   

吉林省东部贵金属、有色金属矿床的时空分布规律   总被引：4，自引：0，他引：4  

关键  孙炜 《吉林地质》2003,22(2):27-33

将吉林省东部地区的贵金属、有色金属矿床在成矿作用时间上与全球性成矿事件及区域性成矿事件对比分析,总结成矿的相似性和本区成矿的特点及具中国特色的燕山期成矿的重要性,提出区内大型矿田(或矿集区)的空间分布特点及主控因素,对成矿预测具指导意义。  相似文献   

辐射井在强透水弱调节含水层地下水开采中的应用     

赵宝峰  王润兰  李文智  康卫东  宋寿鹏 《地下水》2006,28(4):49-51

本文通过在强透水弱调节含水层研究区建立了地下水流数模型、并在研究区域进行数值模拟计算的基础上,分析了不同取水构筑物的取水效果.得出了强透水弱调节含水层地下水采用辐射井开采的优越性和辐射井的设计参数,总结出辐射井是开采强透水弱调节含水层较为合理的取水构筑物.  相似文献