疏勒河径流量与绿洲面积、农业产值及生态效益的关系

基于1954-2010 年疏勒河干流出山径流量、2000-2010年流域内灌区水资源供应量、灌区农作物种植类型、农作物及林草地面积等资料,通过建立系统动力学模型,探讨了气候变化背景下疏勒河径流量对绿洲的影响。结果表明:绿洲受径流量变化影响显著,若出山径流量按1954-2010 年变化趋势增加,绿洲面积、农业产值、生态效益将有不同程度增加; 若出山径流量减小,绿洲面积、农业产值、生态效益亦相应减小。2020年出山径流量较2010年分别减少5%、10%、15%时,绿洲面积和农业产值相应减小4.5%、8.9%、13.4%。在径流量不变情况下,若普及常规节水,林、草地面积均增加16%以上; 若普及高效节水,林、草地面积均扩大54.7%; 若提高渠系利用率到0.70,林草地面积扩大5%以上,总产值增加5.4%; 若提高渠系利用率到0.75,林草地面积增加12%以上,总产值增加12.2%。     

南极长城站海雾特征分析

本文根据对海雾气象要素场、大气层结和天气形势的分析及其持续时间和季节、年际变化的统计分析,结合个例,讨论了南极长城站海雾的特征和形成机制。认为长城站海雾大多为平流冷却雾,高频率的偏北风和南大洋极锋附近显著的经向海温梯度是长城站多海雾的根本原因;夏半年海雾要多于冬半年,海雾的年际分布差异明显;海雾可出现于0-17m/s的各级风力中,3-11m/s偏北风最有利于海雾的维持;气温为-2-4℃、气-海温差为0-2℃时最易出现海雾;海雾的发生一般伴有稳定的大气层结;"东高西低"是长城站海雾的主要天气形势;海雾的持续时间取决于高压在南极半岛维持时间的长短,平均有10个小时。     

Estimated mass and stiffness matrices of shear building from modal test data

A method that estimates mass and stiffness matrices of shear building from modal test data is presented in this paper. The method depends on only measurable points that are less in number than the total structural degrees of freedom, and on the first two orders of structural mode measured. So it is applicable to most of the general test. Based on this method modal data of unmeasurable points are estimated, then global mass and stiffness matrices of structure are obtained by using the first two orders of modal data. Taking advantage of iteration the optimum global mass and stiffness matrices are gained. Finally, an example is studied in this paper. Its result shows that this method is reliable. © 1998 John Wiley & Sons, Ltd.     

Lithospheric thermal and compositional structure of South China jointly inverted from multiple geophysical observations

The detailed lithospheric structure of South China is the basis for the understanding of tectonic processes of eastern China.Specifically,two essential issues in the study of lithospheric structure are the thermal and compositional structures,which are usually derived from either geophysical or geochemical observations.However,inversions from single geophysical or geochemical datasets have certain limitations,making it necessary to develop joint inversions of geophysical,geochemical and petrological datasets.In this paper,through thermodynamic simulation and probabilistic inversion,we inverted multiple datasets including topography,geoid height,surface heat flow and surface wave dispersion curves for the 3D lithospheric thermal and compositional structure of South China.The results reveal a thin(<100 km)and flat LAB beneath the South China Fold System Block and the lower Yangtze Craton.Also,we found that the lithospheric mantle is primarily composed of saturated peridotite,indicating that the ancient refractory lithospheric mantle has been replaced by new materials.The dominant dynamic mechanism for lithospheric thinning in eastern South China may be the flat subduction of ancient Pacific slab,while thermal erosion may have also played a significant role.In contrast,the LAB depth beneath the Sichuan Basin is much thicker(>200 km),suggesting that the thick and cold craton lithospheric roots are retained.There may exist a discontinuous interface beneath the Sichuan Basin,with the saturated lower layer thicker than the refractory upper layer.As a result,the lithospheric mantle of the Sichuan Basin and surrounding regions is mainly composed of saturated and transitional peridotite.     

西藏措勤地区典中组火山岩同位素特征及地质意义

西藏冈底斯岩浆岩带西段北侧的林子宗群火山岩含有从板块俯冲机制向大陆碰撞机制转变的丰富信息。将措勤地区典中组火山岩与冈底斯岩浆岩带东段林周盆地的典中组火山岩在同位素地球化学、演化特征方面进行对比,探讨冈底斯岩浆岩带西段与东段在演化过程中的异同性。结果表明,措勤地区典中组火山岩的87Sr/86Sr初始比值变化范围为0.710352~0.713423,具较高的87Sr/86Sr比值;143Nd/144Nd初始比值为0.512293~0.512407,具较低的143Nd/144Nd比值;林周盆地典中组火山岩的87Sr/86Sr初始比值为0.7057~0.7063之间,143Nd/144Nd初始比值范围为0.5125~0.5126。同位素特征显示措勤地区典中组源区物质可能来自于富集Ⅱ型地幔,即源区为俯冲和再循环的大陆地壳物质与地幔岩发生了混合作用的产物,源区受控于冈底斯地壳基底。林周盆地典中组火山岩源区物质可能与富集Ⅰ型地幔有关。     

频率域全波形反演方法研究进展

全波形反演是一种利用地震波传播的动力学特征来获取地下介质物性参数的反演方法,可为揭示地下精细结构提供重要依据。本文以弹性波方程作为数学模型来模拟地震波传播规律并进行相应的反演方法研究。为提高计算效率与反演结果的准确性,可将近似解析离散化（NAD）算子用于频率域弹性波方程的正演模拟。本文在频率域NAD离散的基础上推导阻抗矩阵的稀疏分块结构与反演目标函数对模型参数的梯度计算公式,由此建立基于NAD算子的频率域弹性波全波形反演方法。为验证该方法的有效性,文中通过数值实验对多种典型介质模型进行反演计算,均得到了理想的反演结果。

     

厦蓉高速公路某隧道洞口段开挖对仰坡变形影响的数值分析

针对一座浅埋偏压隧道,采用FLAC3D对该隧道进口段进洞开挖进行动态施工三维数值模拟。基于围岩应力分布特征,仰坡坡面轴向和横向位移的变化特征,分析了偏压浅埋隧道洞口段开挖引起的仰坡变形规律。计算结果揭示：仰坡后缘下沉,前缘向洞心外有移动趋势;隧道开挖引起隧洞洞身附近岩体出现较大应力集中和变形现象,洞口段洞身以上仰坡坡面主要以竖向沉降为主,洞身两侧向洞内挤压。在此基础上提出了保证仰坡稳定和安全进洞的一些建议。     

地壳中流体的大规模流动系统及其成矿意义

地壳中的水量相当于海洋体积的水量,已确定的水溶液活动深度可达２０ｋｍ,根据驱动力的不同,地壳中主要存在三大流动系统,即重力,浮力和应力驱动系统。本文评述了当前国际上有关大规模流体运移研究扩要进展和发展趋势,介绍了有关流动系统的模式和运动机制,并简要论述了其成矿意义。文章指出,目前区域古流体场地球化学背景问题已成为区域规律和热液成矿理论中一个不容回避的关键课题,地壳中大规模流动系统将成为今后地质流体研究的重要方向之一。     

STUDIES ON TERRACES AND RIVER SYSTEM CHANGES OF THE UPPER YELLOW RIVER

Ｉ.ＴｈｅＴｅｒｒａｃｅｓｏｆｔｈｅＵｐｐｅｒＹｅｌｌｏｗＲｉｖｅｒＴｈｅｔｅｒｒａｃｅｓｏｆｔｈｅｕｐｐｅｒＹｅｌｌｏｗＲｉｖｅｒａｒｅｍｏｓｔｌｙｄｉｓｐｅｒｓｅｄａｌｏｎｇｔｈｅｗｉｄｅｒｃｏｕｒｓｅｓｉｎｓｅｖｅｒａｌＭｅｓｏｚｏｉｃＣｅｎｏｚｏｉｃｂａｓｉｎｓ(Ｆｉｇｕｒｅ1).1.ＴｅｒｒａｃｅｓｂｅｔｗｅｅｎＮｇｏｒｉｎｇＬａｋｅａｎｄＧｙａｒｉｎｇＬａｋｅＴｈｅｓｕｒｆａｃｅｌａｙｅｒｓｏｆｔｈｅｓｅｄｉｍｅｎｔｉｎｔｈｅｗｉｄｅａｎｄｓｈａｌｌｏｗｂａｓｉｎｓｗｈｅｒｅｔｈｅＹｅｌｌ…