青岛地铁3号线二次衬砌混凝土耐久性设计     

杜丰岩  王命平  赵铁军 《海岸工程》2011,30(3):18-27

分析了青岛地铁3号线所在地域的环境作用,并对地铁二次衬砌混凝土的耐久性进行研究。结果表明,青岛地铁要达到100 a设计使用年限,其内陆区域段混凝土强度等级应取C45,水胶比≤0.40;近海区域段混凝土强度等级应取C50,水胶比≤0.36,并分别确定围岩侧与行车侧的混凝土钢筋保护层厚度。  相似文献   

近海主体功能区划指标体系研究     

徐丛春  赵锐  宋维玲  朱凌  李宜良 《海洋通报》2011,30(6):650-655

在深入研究全国主体功能区划指标体系基本思路和指标设置的基础上,充分考虑近岸海域的特殊性,提出了近海主体功能区划的指标设计原则,构建了近海主体功能区划指标体系,同时对近海主体功能区划指标体系设置的若干问题进行了探讨.  相似文献   

生物硅在东南极湖泊古初级生产力研究中的应用   总被引：1，自引：0，他引：1       下载免费PDF全文

姜珊  刘晓东  徐利强  孙立广 《极地研究》2011,23(1):26-34

本文对南极中山站区的莫愁湖和大明湖沉积物中生物硅、有机质等环境指标进行了分析,并在对比研究的基础上,探讨了生物硅在重建东南极湖泊沉积生态环境记录研究中的应用.研究结果表明,大量保存较好的硅藻出现在东南极淡水湖泊沉积物中,生物硅含量在深度剖面上表现出显著波动,与有机质等生物地球化学指标具有一致的垂向变化趋势,表明它们具有...  相似文献   

The impacts of permafrost change on NPP and implications: A case of the source regions of Yangtze and Yellow Rivers     

Yiping Fang  Dahe Qin  Yongjian Ding  Jianping Yang  Keyan Xu 《山地科学学报》2011,8(3):437-447

This paper studies the relationship between net primary productivity (NPP) and annual average air temperature (GT) at 0cm above ground in permafrost regions by using revised Chikugo NPP model,cubic spline interpolating functions,and non-linear regression methods.The source regions of the Yangtze and Yellow Rivers were selected as the research areas.Results illustrate that:(1) There is significant non-linear relationship between NPP and GT in various typical years;(2) The maximum value of NPP is 6.17,5.87,7....  相似文献   

鄂尔多斯盆地低渗透油气藏形成研究现状与展望   总被引：6，自引：0，他引：6  

李荣西  段立志  张少妮  陈宝赟  石彬  阎改萍 《地球科学与环境学报》2011,33(4):364-372

鄂尔多斯盆地是中国规模最大的低渗透油气资源勘探与开发基地,其低渗透油气藏具有油层物性差、非均质性强、油藏成藏因素复杂、油藏分布受多种因素联合控制等特点.在回顾鄂尔多斯盆地低渗透油气藏成藏理论研究和勘探历史经验基础上,认为目前鄂尔多斯盆地低渗透油气藏成藏研究存在两大理论体系,即沉积学控制成藏理论和运移动力学控制成藏理论,...  相似文献   

The Milky Way Galaxy as a strong gravitational lens     

E. M. Shin  N. W. Evans 《Monthly notices of the Royal Astronomical Society》2007,374(4):1427-1436

We study the gravitational lensing effects of spiral galaxies by taking a model of the Milky Way and computing its lensing properties. The model is composed of a spherical Hernquist bulge, a Miyamoto–Nagai disc and an isothermal halo. As a strong lens, a spiral galaxy like the Milky Way can give rise to four different imaging geometries. They are (i) three images on one side of the galaxy centre ('disc triplets'), (ii) three images with one close to the centre ('core triplets'), (iii) five images and (iv) seven images. Neglecting magnification bias, we show that the core triplets, disc triplets and fivefold imaging are roughly equally likely. Even though our models contain edge-on discs, their image multiplicities are not dominated by disc triplets. The halo is included for completeness, but it has a small effect on the caustic structure, the time delays and brightnesses of the images.
The Milky Way model has a maximum disc (i.e. the halo is not dynamically important in the inner parts). Strong lensing by nearly edge-on disc galaxies breaks the degeneracy between the relative contributions of the disc and halo to the overall rotation curve. If a spiral galaxy has a submaximum disc, then the astroid caustic shrinks dramatically in size, whilst the radial caustic shrinks more modestly. This causes changes in the relative likelihood of the image geometries, specifically (i) core triplets are now ∼9/2 times more likely than disc triplets, (ii) the cross-section for threefold imaging is reduced by a factor of ∼2/3, whilst (iii) the cross-section for fivefold imaging is reduced by ∼1/2. Although multiple imaging is less likely (the cross-sections are smaller), the average total magnification is greater. The time delays are smaller, as the total projected lensing mass is reduced.  相似文献   

Probing dark matter substructure with pulsar timing     

E. R. Siegel  M. P. Hertzberg  J. N. Fry 《Monthly notices of the Royal Astronomical Society》2007,382(2):879-885

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The velocity dispersion and mass profile of the Milky Way     

Walter Dehnen  Dean E. McLaughlin  Jalpesh Sachania 《Monthly notices of the Royal Astronomical Society》2006,369(4):1688-1692

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On the origin of the radial mass density profile of the Galactic halo globular cluster system     

Geneviève Parmentier †  Eva K. Grebel 《Monthly notices of the Royal Astronomical Society》2005,359(2):615-623

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利用微引力透镜效应搜寻银河系内的重子暗物质     

富坚  杨晓峰闫震 《中国科学院上海天文台年刊》2007,(1):66-79

该文综述了利用微引力透镜效应来搜寻银河系内重子暗物质的原理、观测方法和结果以及当前国际上几个小组的工作和主要进展。简要回顾了对重子暗物质的认识过程，其中广泛分布于星系之中的暗天体被称为晕族大质量致密天体（MACHO）。综述了一些关于引力透镜的一些基本概念和基本公式，其中简单讨论了强引力透镜、弱引力透镜和微引力透镜的区别，并列出微引力透镜的两个重要参数光深和光变时标的定义及表达式。详细阐述了对于MACHO探测的方法和一些观测效应细节。综述了目前几个小组的工作，包括MACHO小组和EROS小组等，其中MACHO小组近来的工作得出MACHO为银晕的重要组成部分，其质量比例约为20％；而EROS最近工作得出的质量比例上限为7％。  相似文献