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51.
Geophysical exploration of the Boku geothermal area, Central Ethiopian Rift   总被引:1,自引:0,他引:1  
The Boku central volcano is located within the axial zone of the Central Ethiopian Rift near the town of Nazareth, Ethiopia. An integrated geophysical survey involving thermal, magnetic, electrical and gravimetric methods has been carried out over the Boku geothermal area in order to understand the circulation of fluids in the subsurface, and to localize the “hot spot” providing heat to the downward migrating groundwaters before they return to the surface. The aim of the investigations was to reconstruct the geometry of the aquifers and the fluid flow paths in the Boku geothermal system, the country's least studied. Geological studies show that it taps heat from the shallow acidic Quaternary volcanic rocks of the Rift floor. The aquifer system is hosted in Quaternary Rift floor ignimbrites that are intensively fractured and receive regional meteoric water recharge from the adjacent escarpment and locally from precipitation and the Awash River. Geophysical surveys have mapped Quaternary faults that are the major geologic structures that allow the ascent of the hotter fluids towards the surface, as well as the cold-water recharge of the geothermal system. The shallow aquifers are mapped, preferred borehole sites for the extraction of thermal fluids are delineated and the depths to deeper thermal aquifers are estimated.  相似文献   
52.
Reconnaissance surveys undertaken since the 1960s show that more than 200 geothermal prospects with significant active surface manifestations occur throughout Indonesia. Some 70 of these were identified by the mid-1980s as potential high-temperature systems using geochemical criteria of discharged thermal fluids. Between 1970 and 1995, about 40 of these were explored using geological mapping, geochemical and detailed geophysical surveys. Almost half of the surveyed prospects were tested by deep (0.5–3 km) exploratory drilling, which led to the discovery of 15 productive high-temperature reservoirs. Several types of reservoirs were encountered: liquid-dominated, vapour-dominated, and a vapour layer/liquid-saturated substratum type. All three may be modified by upflows (plumes) containing magmatic fluid components (volcanic geothermal systems). Large, concealed outflows are a common feature of liquid-dominated systems in mountainous terrain. All explored prospects are hosted by Quaternary volcanic rocks, associated with arc volcanism, and half occur beneath the slopes of active or dormant stratovolcanoes. By 1995, five fields had been developed by drilling of production wells; three of them supplied steam to plants with a total installed capacity of 305 MWe. By 2000, with input from foreign investors, the installed capacity had reached 800 MWe in six fields, but geothermal developments had stalled because of the 1997–1998 financial crisis.  相似文献   
53.
Using monthly data on national housing prices from July 1998 to June 2015, we investigate the effect of the ‘Tender, Auction and Listing’ (hereafter TAL) system on housing prices in land, implemented on 31 August 2004. We apply the additional polynomial regression discontinuity method which effectively eliminates the effects of several confounding factors such as financial crisis, ‘New National Ten Provisions’ and ‘9.30 New Regime’. We find that, although the TAL has caused the national average housing prices to go up by 10%, accounting for 11% of total increase in housing prices in the last year, it does not constitute the major driver for housing prices. Furthermore, our results indicate that TAL has exerted a larger impact on commercial and residential properties, especially in the middle and west regions. By examining the transmission mechanisms, we find that the effects of TAL are mainly via government’s starvation-style land supply effect and market-reshuffling effect.  相似文献   
54.
设计制作了双面直剪型陶粒轻骨料混凝土与普通混凝土叠合浇筑试块并进行剪切破坏试验,发现各组试块的最终剪切破坏面层不同程度地由两侧混凝土及初始浇筑面层共同组成.为此,给出了具有内部分层式速度间断面的剪切破坏机构模型,并选用Mises屈服条件及Coulomb剪破条件,根据塑性极限分析原理建立了2种混凝土黏结层剪切破坏强度的解析解.结果表明:陶粒轻骨料混凝土与普通混凝土叠合浇筑时,考虑浇筑结合面处理方式、浇筑间隔时间及法向力影响的最终剪切破坏遵循Mohr-Coulomb强度准则.  相似文献   
55.
聊城某酒店C区为多项不规则的超限复杂高层建筑,采用框架结构体系。针对结构多项超限问题,结合抗震性能化设计目标,通过不同程序对结构进行小震弹性分析、中震弹性和不屈服计算,以及大震弹塑性分析。根据分析结果,采取了相应抗震加强措施,使结构满足抗震性能目标,并顺利通过抗震设防专项审查。本文的有关方法和结论可为工程提供参考。  相似文献   
56.
第二次全国土地调查工作已经接近尾声,对土地调查成果进行逐级检查验收,是确保数据真实、准确的有效途径。笔者全程参与了湖南省土地调查的省级预检工作,分析了疑问图斑的影像特征、主要类型及分布特点,总结了查找疑问图斑的体会,认为查找疑问图斑是提高调查成果质量的关键。  相似文献   
57.
采用矢量有限元方法结合PML吸收边界条件分析波导不连续性问题。利用PML吸收边界条件截断计算区域,可以减少内存消耗;采用模式正交性计算波导结构的S参数,可以获得更加精确的解。在结果验证阶段,分别对PML参数设置、厚度选择、波导介质不连续性以及波导结构不连续性模型进行分析,将计算结果与文献对比,验证了PML吸收边界条件的有限元法分析波导不连续性问题的准确性。  相似文献   
58.
拉伸载荷作用下无限大板中三角孔-裂纹问题   总被引:1,自引:0,他引:1  
针对Bueckner原理普遍化,提出了一种求解远方载荷作用下无限大板中孔边裂纹问题的数值方法.通过把适于单一裂纹的Bueckner原理扩充到远方载荷作用下无限大板中孔边裂纹问题,将原问题分解为承受远方载荷不含孔边裂纹的均匀问题和在远方不承受载荷但在裂纹面上和孔的表面上承受面力的问题.算例说明本数值方法对分析无限大板中孔...  相似文献   
59.
郁大照  陈跃良  高永 《中国机械工程》2013,24(20):2747-2752
飞机搭接件结构在疲劳载荷下会产生裂纹并扩展,而目前对搭接件结构参数与其疲劳寿命的关系研究还不够系统,且寿命估算模型只考虑了全寿命的一部分。对不同结构参数的三螺栓单搭接件的疲劳特性进行了试验研究,并以现有工程方法为基础,构建了基于材料初始不连续状态的搭接件全寿命估算模型。结果表明,搭接件的疲劳破坏具有一定的隐蔽性,在一定条件下,采用直孔形式、增大孔间距和螺栓预紧力、减小孔直径等都可以改善搭接件的疲劳特性。数值估算结果与试验结果的对比表明,所建寿命模型具有一定的精度,能满足工程需要,计算结果和结论可作为该类结构损伤容限设计的参考依据。  相似文献   
60.
Our empirical analysis focuses on the effect of regional policies on migration attraction factors in Europe. We employ a regression discontinuity design to assess the causal relationship between the reception of large amounts of public funds and migration flows in the EU-15 regions. In highly-subsidised regions, we find a large increase in the share of foreign citizens from less-developed countries when compared to low-subsidised regions with similar pre-treatment characteristics. The analysis shows that such an increase is due to the positive impact of the European regional policy on job market opportunities as well as the improvement of public goods supply.  相似文献   
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