Simple models of cooling flows     

Christian R. Kaiser  James Binney 《Monthly notices of the Royal Astronomical Society》2003,338(4):837-845

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ASCA and ROSAT observations of nearby cluster cooling flows     

S. W. Allen  A. C. Fabian  R. M. Johnstone  K. A. Arnaud  P. E. J. Nulsen 《Monthly notices of the Royal Astronomical Society》2001,322(3):589-613

We present a detailed analysis of the X-ray properties of the cooling flows in a sample of nearby, X-ray-bright clusters of galaxies using high-quality ASCA spectra and ROSAT X-ray images. We demonstrate the need for multiphase models to consistently explain the spectral and imaging X-ray data for the clusters. The mass deposition rates of the cooling flows, independently determined from the ASCA spectra and ROSAT images, exhibit reasonable agreement. We confirm the presence of intrinsic X-ray absorption in the clusters using a variety of spectral models. We also report detections of 100-μm infrared emission, spatially coincident with the cooling flows, in several of the systems studied. The observed infrared fluxes and flux limits are in good agreement with the predicted values owing to reprocessed X-ray emission from the cooling flows. We present precise measurements of the abundances of iron, magnesium, silicon and sulphur in the central regions of the Virgo and Centaurus clusters. Our results firmly favour models in which a high mass fraction (70–80 per cent) of the iron in the X-ray gas in these regions originates from Type Ia supernovae. Finally, we present a series of methods which may be used to estimate the ages of cooling flows from X-ray data. The results for the present sample of clusters indicate ages of between 2.5 and 7 Gyr. If the ages of cooling flows are primarily set by subcluster merger events, then our results suggest that in the largest clusters, mergers with subclusters with masses of ∼30 per cent of the final cluster mass are likely to disrupt cooling flows.  相似文献   

Ground fissures within the Main Ethiopian Rift: Tectonic,lithological and piping controls     

Jan Valenta  Kryštof Verner  Karel Martínek  Tomáš Hroch  David Buriánek  Leta Alemayehu Megerssa  Jan Boháč  Muluken Kassa  Ferdawok Legesse  Meheret Yakob  Bisrat Kebede  Jiří Málek 《地球表面变化过程与地形》2021,46(15):3158-3174

Ground fissures, especially if they open due to a sudden collapse of the surface, is a serious risk for populated areas. Their common occurrence in unconsolidated sediments of the Main Ethiopian Rift was found to be mostly a result of piping. The fissures start by piping in linear sub-horizontal underground voids, which often propagate upwards resulting in ceiling collapse and formation of deep and long ground fissures with vertical walls. In the southern and central Main Ethiopian Rift the fissures pose a serious risk to infrastructure and settlements. The ground fissures are often linear (up to several kilometres long and often tens of metres deep) and accompanied by sinkholes (along the length). A detailed field mapping of the geological (rock composition, orientation and character of lithological boundaries, primary fabrics and brittle structures) and geomorphological features (especially a length, width and depth of fissures, sinkholes and gullies) followed by in situ seismic anisotropy measurements and a laboratory determination of the geomechanical properties of volcanoclastic deposits was carried out to investigate the ground fissures' origin. The conditions and factors leading to the formation of the ground fissures have been linked to: (a) the presence of regional normal faults and the associated extensional joints and (b) the alternation of lithological units with contrasting hydraulic permeability. The latter corresponds to a sequence of less permeable hard rocks (e.g., rhyolitic ignimbrites) overlain by heterogeneous, soft and permeable, unconsolidated volcaniclastic deposits with a low amount of clay (less than 10%). The ground fissures' occurrence has shown affiliation to areas which have a significantly high seismic anisotropy (more than 20% at the study sites), which can be used as a proxy to map out high risk areas prone to piping and ground fissure formation.  相似文献   

The convection cooling system of the Yakutsk permafrost seed repository     

Vladimir N. Panin  Georgii P. Kuzmin 《寒旱区科学》2014,6(4):0309-0313

Temperature is critical to maintaining seed viability under long-term storage conditions. It has been common practice to use refrigeration systems to maintain required storage temperatures. A seed repository constructed in permafrost in Yakutsk, Russia is the first seed storage facility that relies solely on natural cold. This paper describes the design and performance of the cooling system of the repository. An innovative aspect of the cooling system is that it utilizes the patterns of temperature wave propagation in permafrost. Predicted and measured ground temperatures for the first year of operation are presented and analyzed. Results indicate that convection air cooling systems can be used to control the temperature regime in underground facilities in permafrost.  相似文献   

便携式声波钻机在河道堤防勘探中应用分析研究   总被引：1，自引：0，他引：1  

杨正春  伍宛生  马东亮  徐连锋 《安徽地质》2015,(2):126-128

便携式声波钻机具有取样连续完整、轻便、场地适应能力强、用工少、节能高效等特点,在河道堤防勘探中具有独特优势。  相似文献   

长距离顶管工程施工测量控制技术     

白兰  曾风山 《测绘与空间地理信息》2011,34(3):237-238,241

针对某饮水顶管工程顶进距离长、精度要求高的特点,根据顶管工程实际需要选择测量控制手段.采用分阶段的综合测量方法,取得了良好的测量控制效果,采用的措施可为类似工程提供经验.  相似文献   

市政排水管网节点汇水面积自动化计算的方法和应用     

吴小平  陈苏红  赵文光  王定涛 《武汉大学学报(信息科学版)》2011,(3):355-357,362

针对排水管网节点汇水面积的自动化计算问题,提出了将排水管网图转化为有向图,首先运用图论中的广度优先搜索算法得到任意指定节点的上游节点,然后计算其上游节点各关联边,最后根据上游节点及其关联边的汇水面积得到该节点总的汇水面积的方法。  相似文献   

综合管沟竣工测量数据处理的技术     

樊惠萍  张汉春 《地理空间信息》2011,(4):16-18

综合管沟近年来在广州得到越来越多的推广应用,因而研究综合管沟的数据信息系统显得十分必要。介绍了广州大学城、广州亚运城的综合管沟的基本情况,管沟类型,沟内管线分布,内业成图的图层设计、数据库设计,重点探讨了新出现的立交型综合管沟处理技术,实现了综合管沟数据库的科学管理。  相似文献   

MDD法和裂变径迹法相结合模拟样品的低温热历史——以柴达木盆地北缘赛什腾山中新生代构造演化为例   总被引：2，自引：1，他引：1       下载免费PDF全文

万景林  郑德文  郑文俊  王伟涛 《地震地质》2011,33(2):369-382

MDD法和裂变径迹法是2种最常用的低温热年代学方法.通过对它们的测试结果的模拟,揭示出样品经历的热历史,可以有效地延伸这2种方法的研究范围.但是由于模拟的多解性,使得如何制约模拟过程,获得合理的模拟结果显得尤为重要.通过柴达木盆地北缘的模拟过程,展示了模拟中可能存在的问题及提高模拟结果的方法.同时揭示了柴达木盆地北缘中...  相似文献   

漠河盆地天然气水合物钻探施工中的泥浆冷却系统及其应用   总被引：4，自引：0，他引：4  

陈大勇 《地质与勘探》2011,47(4):705-709

本文对泥浆冷却系统进行了详细介绍。泥浆冷却系统由冷凝机制冷载冷剂回路和泥浆冷却两个回路组成,泥浆和载冷剂在同轴套管式换热器内通过逆向流动实现热交换。本套系统在漠河盆地天然气水合物钻探施工中进行了应用,此次水合物钻探从8月16日开始,耗时2个月,完成了一个终孔直径Фl08mm、深度为500m的钻孔。泥浆冷却系统良好的泥浆...  相似文献