耗能-隔震柔性底层钢管混凝土-钢筋混凝土组合框架的实验研究   总被引：1，自引：1，他引：1  

欧进萍  邱法维 《地震工程与工程振动》1995,(2)

本文用钢管混凝土柱作为结构底层耗能柱、用承重墙和隔震器控制结构底层倒塌破坏,从而提出了一种新的耗能-隔震柔性底层结构体系。通过本文12根钢管混凝土柱和文献[7]中7根钢管混凝土柱的低周疲劳实验,初步确定了钢管混凝土柱地震损伤模型的参数;通过两个钢管混凝土-钢筋混凝土三层框架模型和一个纯钢筋混凝土三层框架模型的拟动力实验,研究和比较了两类结构体系的地震损伤。  相似文献   

Seismic risk of circum-pacific earthquakes I. Strain energy release   总被引：1，自引：0，他引：1  

Kostas C. Makropoulos  Paul W. Burton 《Pure and Applied Geophysics》1983,121(2):247-267

Commonly used earthquake “whole process” frequency - magnitude and strain energy - magnitude laws are merged to obtain an analytic expression for an upper bound magnitude to regional earthquake occurrenceM ₃, which is expressed primarily in terms of the annual maximum magnitudeM ₁ and the magnitude equivalent of the annual average total strain energy releaseM ₂. Values ofM ₃ are also estimated graphically from cumulative strain energy release diagrams. Both methods are illustrated by application to the high seismicity of the circum-Pacific belt, using Duda’s (1965) data and regionalisation. Values ofM ₃ obtained analytically, with their uncertainties, are in agreement with those obtained graphically. Empirical relations are then obtained betweenM ₁,M ₂, andM ₃, which could be of general assistance in regional seismic risk considerations if they are found to be of a universal nature. For instance.M ₃ andM ₂ differ by one magnitude unit in subregions of the circum-Pacific.  相似文献   

Further Studies Of Atmospheric Turbulence In Layers Near The Surface: Scaling The Tke Budget Above The Roughness Sublayer   总被引：2，自引：0，他引：2  

Paul Frenzen  Christoph A. Vogel 《Boundary-Layer Meteorology》2001,99(2):173-206

The second of two experimental studies of the TKE budget conducted on sites of different roughness is described, and results are compared. The first took place within a shallow layer above a small field of mostly bare, cultivated soil; the second was carried out above a roughness sublayer of significant depth on an extensive plain of tall dry grass. Budget terms observed in the second study were scaled with a modified u which compensated for effects of an unusually large stress gradient and ensured that the _m functions would be collinear. By showing that the modification becomes negligible in smaller gradients, it is demonstrated that in normal conditions, budgets observed above significant roughness sublayers should be normalized by scaling in terms of the unreduced Reynolds stress at the sublayer's upper surface. This procedure is shown to be consistent with the expectation that TKE budgets in layers near the surface all scale in fundamentally the same way.Other findings include: (1) the fact that most _m functions previously reported are not quite collinear is attributed to a type of overspeeding known to affect three-cup anemometers; (2) revised _m functions, collinear and largely free of the effects of overspeeding, are determined from a well-established characteristic of the linear _m relation for the stable case; (3) data that define collinear _m functions can also be represented with single hyperbolic curves; (4) dissipation is found to be 10 to 15% too small to balance total TKE production in unstable and neutral conditions and to decrease with increasing z/L in thestable regime; and (5) new relations for based on the observed behaviour of the dissipation deficit provide an improved closure for the set of equations that express the budget terms as functions of _m and z/L.  相似文献   

绿洲荒漠交界处波文比能量平衡法适用性的气候学分析   总被引：13，自引：0，他引：13  

黄妙芬 《干旱区地理》2001,24(3):259-264

对广泛使用的计算蒸散和显热通量的气候学方法－波文比能量平衡法在绿洲荒漠交界处的适用性从气候学角度进行分析。结果表明,波文化－能量平衡法在干旱区绿洲的平衡层内是适用的,在平衡层外及荒漠上空却失效。因而,应用波文比能量平衡法估算绿洲上的蒸发与显热时,测点的位置是至关重要的。  相似文献   

斜拉桥纵向设置粘滞阻尼器参数分析   总被引：4，自引：2，他引：4  

韩万水  黄平明  兰燕 《地震工程与工程振动》2005,25(6):146-151

采用Maxwell阻尼模型模拟了粘滞阻尼器的滞回耗能特性。通过对设置粘滞阻尼器斜拉桥纵向非线性地震反应的分析，讨论了粘滞阻尼器各参数对结构地震响应的影响，并通过计算证实了粘滞阻尼器具有良好的消能减振效果。  相似文献   

高能射线工业CT最新进展   总被引：3，自引：2，他引：3  

陈志强  李亮  冯建春 《CT理论与应用研究》2005,14(4):1-4

本文主要介绍了清华大学在高能射线工业CT研究及产业化方面的新进展,介绍了其中的多项成果:小体积、大功率的直线加速器,低噪声、高效率的阵列固体探测器,旋转极坐标反投影快速图像重建算法等.高能工业CT技术的研制成功及产业化,使我国高能工业CT技术达到国际先进水平,结束了我国无自主研制大型工业CT检测系统的历史,解决了我国大型工件无损检测难题,对提高我国高能无损检测技术水平具有重大意义.  相似文献   

Significance of variations in the wind energy environment over the past 50 years with respect to dune activity and desertification in arid and semiarid northern China   总被引：1，自引：1，他引：1  

Xunming Wang  Hasi Eerdun  Zijiang Zhou  Xiaoping Liu   《Geomorphology》2007,86(3-4):252-266

Climate data from 339 meteorological stations collected from the 1950s to the early 2000s was employed to discuss aeolian activity in arid and semiarid northern China. The results show that at decadal time scales, erosivity varied greatly in this region. Most of arid and semiarid northern China was characterised by environments with moderate to low wind energy. After the 1980s, the erosivity was only 20 to 50% of that beforehand, and this difference had a significant impact on the environmental changes observed during the two periods. The dune mobility index was consistent with the observed dune activity. After the 1980s dune activity decreased and in some deserts with vegetated dune systems during the 1970s most of the dune plinths were active until the 1980s, after which only the crests were active. Some mobile dunes that had developed at the margins of mobile deserts were replaced by semi-anchored or anchored dunes. Because most desert areas with vegetated dune systems in arid and semiarid northern China are used for farming or grazing, the results of our monitoring show that the desertification trends were consistent with the trends in erosivity and dune activity in this region. Desertification was controlled much more by climatic changes than has previously been acknowledged, and especially by fluctuations in wind energy.  相似文献   

Heat capacity of γ-Fe2SiO4 between 5 and 303 K and derived thermodynamic properties     

Wenjun Yong  E. Dachs  A. C. Withers  E. J. Essene 《Physics and Chemistry of Minerals》2007,34(2):121-127

A multi-anvil device was used to synthesize 24 mg of pure γ-Fe₂SiO₄ crystals at 8.5 GPa and 1,273 K. The low-temperature heat capacity (C _p) of γ-Fe₂SiO₄ was measured between 5 and 303 K using the heat capacity option of a physical properties measurement system. The measured heat capacity data show a broad λ-transition at 11.8 K. The difference in the C _p between fayalite and γ-Fe₂SiO₄ is reduced as the temperature increases in the range of 50–300 K. The gap in C _p data between 300 and 350 K of γ-Fe₂SiO₄ is an impediment to calculation of a precise C _p equation above 298 K that can be used for phase equilibrium calculations at high temperatures and high pressures. The C _p and entropy of γ-Fe₂SiO₄ at standard temperature and pressure (S°₂₉₈) are 131.1 ± 0.6 and 140.2 ± 0.4 J mol⁻¹ K⁻¹, respectively. The Gibbs free energy at standard pressure and temperature (ΔG° _f,298) is calculated to be −1,369.3 ± 2.7 J mol⁻¹ based on the new entropy data. The phase boundary for the fayalite–γ-Fe₂SiO₄ transition at 298 K based on current thermodynamic data is located at 2.4 ± 0.6 GPa with a slope of 25.4 bars/K, consistent with extrapolated results of previous experimental studies.  相似文献   

河西走廊风能时空特征   总被引：3，自引：0，他引：3  

王毅荣 《干旱区地理》2007,30(3):43-350

利用河西走廊地区1970-2004年风速气候资料和2004年9月-2005年8月周年风塔精细资料,采用气候订正和即时风速订正,得到接近自然的风速,依此研究了该区域近地面70 m层内风能分布。结果表明:河西走廊区域风速变幅较小、气候变化趋势较稳定;有效风速(≥3 m/s)时数在6 000 h/a,10 m高度风能大多在150 w/m2以上,风能随高度线形增长(在70 m高度层内),平均每升高10 m风能增加28 w/m2;10~70 m层内总风能年储量相当丰富,普遍在1.5×1016kWh/m2(千瓦时/平方米)以上,潜在年产值达千万亿元。河西走廊风能存在明显周日和月季变化,风能和有效风速时数存在空间差异,其时空差异与河西走廊独特的戈壁下垫面关系密切。  相似文献   

Ethanol Production: Energy and Economic Issues Related to U.S. and Brazilian Sugarcane   总被引：1，自引：0，他引：1  

David Pimentel  Tad Patzek 《Natural Resources Research》2007,16(3):235-242

For a thorough and up-to-date evaluation of all the fossil energy costs of ethanol production from sugarcane in both the U.S. and Brazil, every energy input in the biomass production and ultimate conversion process must be included. In this study, more than 12 energy inputs in average U.S. and Brazilian sugarcane production are evaluated. Then in the fermentation/distillation operation, nine more fossil fuel inputs are identified and included. Some energy and economic credits are given for the bagasse to reduce the energy inputs required for steam and electricity. Based on all the fossil energy inputs in U.S. sugarcane conversion process, a total of 1.12 kcal of ethanol is produced per 1 kcal of fossil energy expended. In Brazil a total of 1.38 kcal of ethanol is produced per 1 kcal of fossil energy expended. Some pro-ethanol investigators have overlooked various energy inputs in U.S. and Brazilian sugarcane production, including farm labor, farm machinery, processing machinery, and others. In other studies, unrealistic low energy costs were attributed to such energy inputs, as nitrogen fertilizer, insecticides, and herbicides. Both the U.S. and Brazil heavily subsidize ethanol production. Thus billions of dollars are invested in subsidies and this significantly increases the costs to the consumers. The environmental costs associated with producing ethanol in the U.S. and Brazil are significant but have been generally overlooked. The negative environmental impacts on the availability of cropland and freshwater, as well as on air pollution and public health, have yet to be carefully assessed. These environmental costs in terms of energy and economics should be calculated and included in future ethanol analyses so that sound assessments can be made. In addition, the production of ethanol in the U.S. and Brazil further confirms that the mission of converting biomass into ethanol will not replace oil. This mission is impossible. General concern has been expressed about taking food crops to produce ethanol for burning in automobiles instead of using these crops as food for the many malnourished people in the world. The World Health Organization reports that more than 3.7 billion humans are currently malnourished in the world—the largest number of malnourished ever in history.  相似文献