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971.
江面雾的形成及其预报   总被引:1,自引:1,他引:1  
孙锦铨  任遵海 《气象科学》1997,17(3):280-289
用1989-1992年江心固定囤船平台上观测到的第一手资料分析表明,江面才总日数少于陆地,但一次过程持续时间比陆地长。江面雾发生时常伴有风,最大风速达10m/s,风玫瑰图表明,占优势的风向是SE、E和S,江雾常处于成片雾片区,这些差异,与江、陆之间温度日变化和风切变有关。另外,本文对江面雾的预报也作了探讨。  相似文献   
972.
干旱区城镇发展的理论探讨:以新疆为例   总被引:1,自引:0,他引:1  
本文在实际调查的基础上,通过专家意见咨询与定量方法的结合,探讨了干旱区城镇发展的一般规律:a.经济发展水平仍是干旱区城镇发展的渊源;b.水资源是干旱区域镇发展的限制性因子,但并不能解释干旱区城镇发展一般的规律性;c.应重视科技水平对城市发展的重要作用。  相似文献   
973.
四川兴文石林区的喀斯特与洞穴   总被引:3,自引:6,他引:3  
四川文兴的洞河、龙塘一带,是我国南方重要的峰丛喀斯特区之一。著名的兴文石林风景区即位于其中,世界级规模的大漏斗,大量的流入型洞穴,完整的喀斯特流域,优越的喀斯特发育条件,漫长的喀斯特演化历史,古今不同阶段喀斯特发育的叠置、继承和新生构成了“文兴式”喀斯特的基本特色。本文着重讨论了该区喀斯特与洞穴的形成条件、基本特征,并从一物质与能量的输入-输出系统出发,提出和较详细地讨论了洞穴系统的基本类型组成及其发育的“含水层控制系统演化模式”。  相似文献   
974.
Distribution and formation of high-fluorine groundwater in China   总被引:3,自引:0,他引:3  
In China, high-fluorine groundwater, which contains more than 1.0 mg/l fluorine, is mainly distributed in shallow aquifers of unconsolidated deposits in some arid and semiarid areas, deep aquifers of unconsolidated deposits in semiarid areas, as well as in hot springs of bed rock mountainous area and aquifers of fluorite-mine area. Its formation is controlled by regional climate factors, seepage conditions of groundwater, as well as the hydrogeochemical environment. The physicochemical properties of soil mass of the aeration zone play an important role in fluorine concentration in shallow groundwater. In the coastal plain areas, where groundwater is mainly recharged and discharged vertically, and its regime type belongs to the type of infiltration—evaporation, the grain size of soil mass of aeration zone directly influences the amount of fluorine transferred from solid medium into water; and the chemical constituents of the soil mass of aeration zone controls the chemical characteristics of the shallow groundwater, consequently influencing the concentration condition of fluorine in water. Fluorine ion in groundwater continuously migrates and concentrates under the comprehensive influence of many factors. High-fluorine groundwater exceeding the sanitary standard (1.0 mg/l) has an obvious zonality in regional distribution in China. Based on current statistics, there are roughly 50 million people (Zheng Qifu 1986) who have consumed water which exceeds standards in China. In highfluorine groundwater areas, endemic fluorine-poisoning often arises to different extents, affecting human health seriously. At the end of 1983, over 20 million patients were suffering from fluorine-poisoning diseases in China (Xu Guozhang, unpublished data). Therefore, research of the distribution feature and formation mechanism of fluorine ion in groundwater has become an important task.  相似文献   
975.
976.
山西省临汾西山地区奥陶系沉积相   总被引:1,自引:0,他引:1       下载免费PDF全文
临汾西山为吕梁山南延山岭,其东缘以大断与汾河地堑相接,山边陡峭,基岩裸露,奥系剖面十分清楚,因该区近代剧烈上升,地表保留了奥陶系多个层位的石膏矿产,是研究华北奥系蒸发沉积和华北西部奥陶系沉积相的优良剖面。七十年代后期以来,不少生产、教学、科研单位,先后在此区进行了许多工作,笔者曾参与了该区奥陶系沉积相剖面的测制和研究工作,现综合有关资料,对其沉积相作一初步探讨。  相似文献   
977.
We have obtained altogether heat flux data of 23 drill holes including 2 observational holes of thermal flow in the Haicheng seismic area. These data show roughly thermal structure of the crust in eastern Liaoning and in the Haicheng seismic area. The results indicate that there is higher value of heat flow in the belt north by east from Liaoyang to Xiongyue, the average thermal flux being 8.29× 10−2J/m2·s (2.0 hfu). The average thermal fulx in the Haicheng seismic area is 9.22×102J/m2·s (2.2 hfu). Comparing with other known geophysical data of the Haicheng seismic area, we give a geophysical section of comprehensive interpretation. We suppose the low-velocity layer in the lower crust of the Haicheng seismic area is a result from intrusion of large-scale uper mantle substance. High temperature and low velocity mean that the layer has the nature of plastic mechanics. The focal region of the Haicheng earthquake is situated right in the upper part of that plastic layer. Obviously, this result is significant for studying the seismogenic process of the Haicheng earthquake and other intra-plate earthquakes. We attempt to emphasize that observation of heat flow is necessary for earthquake study. Gu Haoding did the actual writing.  相似文献   
978.
Most of the sulfide nickel deposits in China occur on the margins of platforms and their outer mobilebelts. The ore-bearing basic-ultrabasic rock bodies were formed in the Proterozoic and Variscan. The types ofmetallogenic rock bodies include ultrahasic-basic complexes related to volcanism in eugeosynclines andultrabasic rock bodies, ultrabasic-basic complexes and basic rock bodies related to deep fractures. On the basisof ore-forming processes and modes, nickel sulfide deposits of China may be divided into two major types:in-situ magmatic liquid unmixing deposits and deep-seated magmatic liquid unmixing injection deposits. Thelatter may by subdivided into four types: single injection deposits, multiple injection deposits, and pulsatory in-jection depositis, and late injection deposits which may inject into either comagmatic rocks or other kinds ofcountry rocks. Two metallogenic models for nickel sulfide deposits are proposed in this paper.  相似文献   
979.
本文分析解释了三维重力正、反演的计算结果,提出龙门山重力梯度带并不是一个简单的壳幔斜坡或陡坎。并进一步指出该重力梯度带的范围、发震断裂的深浅关系、次级构造的存在及其复杂图象等一系列深部地震地质问题都有待于揭示和认识。地震地质和地球物理两个学科的密切配合有可能回答上述问题,找出强震在龙门山重力梯度带乃至整个南北地震活动带内的蕴育发生规律。这对地震预报和工程地震都是有意义的,也将丰富大地构造的研究内容  相似文献   
980.
Symmetrical folding of a single layer and folding process of an overfold are analyzed by using the finite element method. In the analysis, the constituent substances are assumed to be isotropic and incompressible and to behave as Newtonian fluids. The penalty function method is used to deal with incompressibility, The results of the analysis are compared with the data measured in the field and with those obtained by the elastopla(?)e finite element analysis, It shows that the overfold geometry may be well simulated by using the viscous fluid model. Thus, a possible mechanism of the formation of overfold is proposed.  相似文献   
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