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991.
建立科学高效的管理体制和运行机制 ,即建立房地合一管理体制和一体化测绘架构 ,进行现代地籍调查测绘 ,实行必要的地籍测绘保障是现代地籍管理的具体体现。通过现代地籍调查测绘 ,建立信息系统 ,可实现多种管理功能 ,提高城市地籍管理水平 相似文献
992.
应用地震CT技术研究长白山火山的岩浆囊 总被引:13,自引:3,他引:10
中国火山学专家报导了长白山火山存在一定的潜在的喷发危险性及其地质背景等研究成果;美国、日本、德国的火山学家到该火山区进行过考察,也认为该火山存在一定的潜在危险性;国家科委根据有关方面的建议,已将“长白山火山危险性的研究”列入专项计划之中;其中有一个子课题是“应用地震CT技术研究长白山火山的岩浆囊”.本文报导的主要内容有:1)1994年张禹慎发展的“上地幔S波三维速度结构的方法”建立上地幔S波RG5.5速度模型,该模型能显示全球任一地区、任一剖面、深至500公里的三维速度结构;他作出世界上20个火山区,其中有17个火山区下面均有明显的S波低速层,在不同程度上反映了"低速层岩浆囊"的存在;已作出通过长白山天地火山的3条速度剖面;该模型显示出:在长白山天池火山下面存在速度的负异常达2.5%的“低速囊”,其深度从38—65公里;其展布范围约100—200公里的范围;2)改进面波品质因数Q值的成像方法,进一步收集200次地震面波记录资料,应用“卷积反投影方法反演地壳面波品质因数Q值的成像系统”长白山火山及其邻近地区面波Q值分布,看出天池地区Q=161比中国地区Q值的平均值偏低很多;这很可能与该地区下面地温偏高和岩层的 相似文献
993.
994.
含裂隙双相各向异性介质中的地震波传播 总被引:5,自引:0,他引:5
基于各向异性介质和含裂隙双相介质中的地震波传播理论,导出了具有四阶对称轴的含裂隙双相各向异性介质的本构关系与波传播的运动方程.指出在含裂隙双相各向异性介质中可能传播6种类型的准纵横波,即快纵波QP1,慢纵波QP2,两个分裂的快横波QSV1,QSH1和两个分裂的慢横波QSV2,QSH2.并以平面波传播为例作了进一步分析 相似文献
995.
Irena Grgić Andreja Dovžan Gorazd Berčič Vida Hudnik 《Journal of Atmospheric Chemistry》1998,29(3):315-337
Laboratory experiments were conducted with real atmospheric aerosol particles as well as with synthetic solutions under dark conditions, to simulate some of the chemical features of aerosols. In solutions obtained by the leaching of aerosols (size range >D
ae: 0.4–1.6 m) that contained sufficient amounts of transition metal ions (e.g. Fe) and organic species (e.g. oxalate), S(IV) oxidation rates were significantly lower than those expected from the Fe-catalyzed S(IV) autoxidation in Milli-Q water. The results suggest that oxalate is responsible for much of the observed inhibition. Acetate and formate also inhibit the reaction, but to a much lesser extent. Oxalate has a strong inhibiting effect on the Fe-catalyzed S(IV) autoxidation at all investigated pH values (2.8, 3.7 and 4.5). It was established that Fe(III)-oxalato complexes affect the redox cycling of Fe(II)/Fe(III) and that the observed decrease of the reaction rate is caused by the reduced amount of catalytically active Fe(III) due to the complexation with oxalate. For the system Fe-S(IV)-O2-oxalate at initial pH 3.7 the reaction rate was calculated using exponential simplification to account for oxalate influence on the amount of free Fe(III) by the following equation:–rS(IV) = k · [S(IV)] · [Fe(III))] · e
-b·[Ox] 相似文献
996.
997.
地理信息系统(GIS)在农业上的应用现状概述 总被引:27,自引:3,他引:27
在概述地理信息系统(GIS)的概念、功能、应用领域的基础上,对GIS在农业资源管理与动态监测、作物估产、土地适宜性评价、病虫害预测预报与风险评价、精确农业等方面的应用现状进行了综述,并对GIS在农业中的应用前景以及新动态进行了探讨和分析,讨论了地理信息系统在农业上应用研究的重要性。 相似文献
998.
During 1990–1996 the United States experienced record-setting insured property losses due to numerous weather catastrophes,
each event causing $100 million or more in losses (1991 dollars). The total loss in this 7-year period, after adjustment to
inflation and other factors, was $39.65 billion with $15 billion coming from one event, Hurricane Andrew. In the 1990s, 72
catastrophes occurred, half of the total number in the 40 preceding years, 1950–1989. Although the total loss and the number
of catastrophes were exceptionally high in the 1990s, the average loss per event was $551 million, only slightly more than
the $467 million average for catastrophes during 1950–1989. Furthermore, storm intensities in the 1990s were slightly less
than those during the preceding 40 years, revealing the excess losses of the 1990s to be a result of an extremely large number
of damaging storms causing losses exceeding $100 million. Examination of historical values of most weather extremes including
hurricanes, floods, and tornadoes, did not show an increase during the 1990s, revealing that weather changes were not the
principal cause of more catastrophes. Examination of recent demographic shifts in the U.S. reveals two changes, each based
on major re-locations to higher-valued property concentrated in areas either with a high frequency of damaging storms (Gulf
and East Coast), or to where even a small but intense storm can cause huge losses (urban areas and West Coast). These shifts,
plus the continuing growth of population in other storm-prone areas have greatly increased society's vulnerability to storm
damage. An in-depth analysis of many conditions was required to establish that the high losses and numerous catastrophes of
the 1990s were largely the result of societal changes and not major weather changes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
999.
In this paper we use a Von Mises transformation to study brine transport in porous media. The model involves mass balance
equations for fluid and salt, Darcy's law and an equation of state, relating the salt mass fraction to the fluid density.
Application of the Von Mises transformation recasts the model equations into a single nonlinear diffusion equation. A further
reduction is possible if the problem admits similarity. This yields a formulation in terms of a boundary value problem for
an ordinary differential equation which can be treated by semi‐analytical means. Three specific similarity problems are considered
in detail: (i) one‐dimensional, stable displacement of fresh water and brine in a porous column, (ii) flow of fresh water
along the surface of a salt rock, (iii) mixing of parallel layers of brine and fresh water.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1000.