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INTRODUCTIONItisknownthatChinaisanearthquake pronecountryintheworldandisalsoacountrysufferingmostsevereseismiccalamitiesintheworld .China’sterritoryoccupiesabout 1 1 4oftheglobalconti nentalarea ,whileabout 1 3ofglobalM≥ 7.0continentalearthquakesoccurredinCh… 相似文献
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流域管理是以水资源的自然流域特性和多功能属性为基础的管理制度,它的目标是使有限的水资源实现优化配置和发挥最大效益.流域管理的问题直接关系到以水资源的可持续利用支持经济社会的可持续发展的大局.通过分析我国流域管理存在的问题,借鉴国外成功的流域管理经验,提出要进一步明确流域管理和行政区域管理的事权,加快流域管理相应的法律法规建设,加大流域管理的支撑保障能力建设,充分发挥流域管理机构科学规划决策、有效配置调控和有力监督控制的作用,进一步探索适合不同流域的管理模式,加大构建公共参与和民主协商机制力度,探索建立流域水资源管理可持续利用的市场机制. 相似文献
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Textural heterogeneities in pumices from the climactic eruption of Mount Pinatubo, 15 June 1991, and implications for magma ascent dynamics 总被引:1,自引:0,他引:1
The climactic event of Mount Pinatubo represents one of the most thoroughly studied eruptions of the century and has provided important insights into the dynamics of explosive volcanism. We have performed detailed textural analyses of the white and gray pumices of the plinian and pyroclastic flow deposits, and found that differences in color and clast density reflect different crystal and vesicle amounts and size distributions. White pumice has higher vesicularity, deformed and highly coalesced vesicles with thin walls, euhedral phenocrysts and microlite-free groundmass. Gray pumice shows lower vesicularity, wider ranges in vesicle number density, limited coalescence, vesicles with thick walls that are less deformed, phenocrysts and microphenocrysts with abundant solution pitting, and groundmass containing ubiquitous microlites and crystal fragments. The presence of white and gray pumice varieties and the broad range in vesicularity and vesicle number density that characterizes both of them appear to record the complexities of conduit processes such as magma vesiculation and fragmentation and the development of conduit regions marked by different rheological behaviors. In particular, the results of this study suggest the likely importance of intense shear and viscous dissipation at the conduit walls, a mechanism that may be responsible for the creation and discharge of the gray pumice of this eruption along with the dominant white variety. 相似文献
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本文采用从法国引进的Metravib热机械分析仪用正弦波加载方式,首次对四种不同孔隙度的饱和砂岩的衰减进行了实验研究,在5~400 Hz的频率,-50 ℃~100 ℃的温度范围获得衰减的热弛豫规律,由此求得它们的激活能和原子振动频率,其激活能和弛豫时间是处在原子和电子的激活能和弛豫时间之间.可见,在饱和岩石的晶粒间界缺陷处参与扩散的是原子、电子.并得出随孔隙度增大,衰减强度和激活能增大,原子的振动速率加快,弛豫时间缩短.在交变应力作用下,由多种矿物晶体胶结而成的饱和砂岩是一种多晶、多相的固体,由于内部结构复杂,损伤、缺陷广布,弛豫衰减是普遍存在的.饱和砂岩中存在的晶界、相界等许多缺陷,以及缺陷间的相互作用,比如饱和岩石中的饱和液体与岩石骨架之间的作用等等都可以产生弛豫衰减峰,弛豫过程还受晶界上原子扩散所控制.由于饱和岩石中的种种缺陷、相界等等导致上述矿物颗粒或晶界之间的多重弛豫,才使弛豫衰减峰变宽,分布宽度增大.用饱和砂岩中特有的饱和液体及砂岩内部结构的复杂性解释了饱和砂岩的衰减机理,很自然地将其宏观衰减特征与微细观结构紧紧联在一起.衰减及其机理的研究既具有科学意义,对地球物理勘探又具有实用价值. 相似文献
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Some aspects of the monsoon circulation and monsoon rainfall 总被引:1,自引:0,他引:1
R. Ananthakrishnan 《Pure and Applied Geophysics》1977,115(5-6):1209-1249
Summary The south Asian summer monsoon from June to September accounts for the greater part of the annual rainfall over most of India and southeast Asia. The evolution of the summer and winter monsoon circulations over India is examined on the basis of the surface and upper air data of stations across India. The salient features of the seasonal reversals of temperature and pressure gradients and winds and the seasonal and synoptic fluctuations of atmospheric humidity are discussed. The space-time variations of rainfall are considered with the help of climatic pentad rainfall charts and diagrams. The rainfall of several north and central Indian stations shows a minimum around mid-August and a maximum around mid-February which seem to be connected with the extreme summer and winter positions of the ITCZ and the associated north-south shifts in the seasonal circulation patterns. Attention is drawn to the characteristic features of the monsoon rainfall that emerge from a study of daily and hourly rainfall of selected stations. Diurnal variations of temperature, pressure, wind and rainfall over the monsoon belt are briefly treated. 相似文献
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结构健康监测系统设计标准化评述与展望 总被引:4,自引:1,他引:3
阐述了结构健康监测的概念和内涵。详细介绍了结构健康监测系统的功能、组成和应用现状。结构健康监测系统设计标准化能够促进健康监测的应用和发展,具有重要的工程意义。对世界范围内相关研究进展进行了综述和评价。强调在我国建立监测系统设计标准的重要性,并提出了相应的说明和建议。设计标准可以分为总则、外观检查与无损检测、传感器的选择与布置、信息采集与处理系统、通信与传输系统、损伤识别和评估系统、应用实例等7部分。结构健康监测系统设计标准的实现将有力地推动健康监测的研究。 相似文献
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利用安康地区3个形变台2017—2020年地形变资料,对比分析6套形变仪器的映震能力,并从面波延迟时间、最大响应幅度及同震持续时间等方面系统探讨同震形变波的特征参数与震源参数的关系,获知形变仪器映震效能的影响因素和同震形变波的物理分布特征。结果表明:形变仪器的映震能力受仪器自身响应特性、地下介质特性及仪器系统误差等因素的影响;同震形变波物理分布特征表明面波延迟时间与震中距、同震响应最大幅度与震级、同震持续时间与震级及震中距之间存在一定的比例关系。 相似文献