地铁车站钢支撑结构中的临时立柱施工实践     

李贤军 《中国煤炭地质》2010,(3):37-39,49

对于地下空间超宽的地下车站,为了确保钢支撑结构的安全,需要设置支撑钢作为临时立柱。以北京望京西站为例,介绍了临时立柱设计及施工工艺流程,并针对格构柱尺寸狭小难以设立临时立柱的问题,采用了普通焊接钢管灌注混凝土工艺的解决方法。  相似文献   

Approach to delimiting metropolitan regions’ boundary and grading urban hierarchy within a metropolitan region—A case study of Shanghai metropolitan region   总被引：1，自引：1，他引：0  

Shougui Luo  Andrew Johnston  Dongchun Chen 《中国地理科学(英文版)》2008,18(3):197-205

In metropolitan regions, the change in the strength of＂flows＂ between a core city and surrounding cities reflects the range of the core city＇s influence, while the gravity between core city and other cities reflects the strength of potential relation between them. This article firstly attempts to delimit the boundary of metropolitan regions with the two dimensions measure combining ＂flows＂ and gravitation. The former is measured through the flow of people between the core city and surrounding cities, and the latter is measured through both population and gross domestic products （GDP） of the core city and surrounding cities. The hierarchy of the cities within a metropolitan region is classified in order to emphasize the roles of the cities belonging to the metropolitan regions, different from the general way through population scale and administrative level, and is typical in China. This paper uses the Shanghai metropolitan region as a research case, determining boundary of this metropolitan region clearly and classifying hierarchy of the cities within the region. The final results are significantly different to previous work, even overthrowing the traditional system of urban hierarchy partly. It is helpful to highlight the function of cities in organizing the regional economy, the level structure of metropolitan regions, and each city＇s relative importance in a metropolitan region, which can be taken as scientific basis for planning integrated regions or urban systems.  相似文献   

Millimetre continuum observations of southern massive star formation regions – I. SIMBA observations of cold cores     

T. Hill  M. G. Burton  V. Minier  M. A. Thompson  A. J. Walsh  M. Hunt-Cunningham  G. Garay 《Monthly notices of the Royal Astronomical Society》2005,363(2):405-451

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Ballast water risk assessment: principles, processes, and methods     

Barry  Simon C.; Hayes  Keith R.; Hewitt  Chad L.; Behrens  Hanna L.; Dragsund  Egil; Bakke  Siri M. 《ICES Journal of Marine Science》2008,65(2):121-131

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A photoionization-modelling study of 30 Doradus: the case for small-scale chemical inhomogeneity     

Yiannis G. Tsamis †‡  Daniel Péquignot 《Monthly notices of the Royal Astronomical Society》2005,364(2):687-704

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Towards an energy‐based runoff generation theory for tundra landscapes     

William L. Quinton  Sean K. Carey 《水文研究》2008,22(23):4649-4653

Runoff hydrology has a large historical context concerned with the mechanisms and pathways of how water is transferred to the stream network. Despite this, there has been relatively little application of runoff generation theory to cold regions, particularly the expansive treeless environments where tundra vegetation, permafrost, and organic soils predominate. Here, the hydrological cycle is heavily influenced by 1) snow storage and release, 2) permafrost and frozen ground that restricts drainage, and 3) the water holding capacity of organic soils. While previous research has adapted temperate runoff generation concepts such as variable source area, transmissivity feedback, and fill‐and‐spill, there has been no runoff generation concept developed explicitly for tundra environments. Here, we propose an energy‐based framework for delineating runoff contributing areas for tundra environments. Aerodynamic energy and roughness height control the end‐of‐winter snow water equivalent, which varies orders of magnitude across the landscape. Radiant energy in turn controls snowmelt and ground thaw rates. The combined spatial pattern of aerodynamic and radiant energy control flow pathways and the runoff contributing areas of the catchment, which are persistent on a year‐to‐year basis. While ground surface topography obviously plays an important role in the assessment of contributing areas, the close coupling of energy to the hydrological cycles in arctic and alpine tundra environments dictates a new paradigm. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Stellar X-ray Sources in the Rosette Nebula     

W.P.Chen  P.S.Chiang  J.Z.Li 《中国天文和天体物理学报》2004,4(2):153-165

We present optical photometric and spectroscopic studies of ROSAT X-ray stellar sources in the Rosette Nebula star-forming region. The brightest X-ray sources are either massive stars or active T Tauri stars associated with the open cluster NGC 2244, or are foreground stars. Some of the spectra of the young stars newly identified in the region are presented.  相似文献   

A three-dimensional Monte Carlo photoionization code for modelling diffuse ionized gas     

Kenneth Wood  John S. Mathis  Barbara Ercolano 《Monthly notices of the Royal Astronomical Society》2004,348(4):1337-1347

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关于西部大开发的哲学思考   总被引：1，自引：0，他引：1  

李佩成张林  段联合 《地球信息科学学报》2001,3(2):66-71

本文运用哲学思维从八个方面探讨了西部大开发面临的重大认识和决策问题,旨在西部人民中唤起艰苦奋斗的创业精神,要把西部大开发的立足点建立在主要依靠中国人自己的基础上。  相似文献   

Interaction of a nonstationary ionization-shock front with an inhomogeneous interstellar medium     

K. V. Krasnobaev 《Astronomy Letters》2001,27(9):568-573

We consider the interaction of an ionization-shock front with isothermal waves in an H I region. Based on a two-front model in the linear approximation, we have detected a significant (approximately by an order of magnitude) periodic amplification of perturbations as they penetrate from the interstellar medium into an H II region. Numerical simulations have revealed that even when the shock-and ionization-front velocities differ and the relative density perturbations in the interstellar medium are ～10^?1, the variations in gas parameters near the ionization front are comparable to those observed at the boundaries of H II regions.  相似文献