共查询到20条相似文献,搜索用时 93 毫秒
1.
2.
3.
考虑刚度及边界条件的短索索力求解与试验研究 总被引:1,自引:1,他引:0
建立了一个非齐次边界拉索力学模型,基于拉索线性振动理论,推导了考虑拉索抗弯刚度及边界条件的拉索频率方程;根据双曲函数的数理特性对频率方程进行了合理简化,得到了实用的频率简化方程,提出了逆过程求解索力的方法和步骤,并探讨了不同支承刚度对索力的影响。设计了室内拉索试验模型并进行了27种工况索力试验,比较了不同工况下的计算索力与实际索力,验证了本文提出的频率简化方程和逆过程求解方法的实用可靠性。 相似文献
4.
基于地震易损性的框架结构的优化方法 总被引:1,自引:0,他引:1
给出了一种框架结构地震易损性优化的准则算法.根据优化准则构造了一种修改设计变量的格式,提出了设计方案可行性调整的方法并推导了计算公式,给出了优化算法的计算步骤,并通过一个算例阐述了这种算法的应用。 相似文献
5.
6.
7.
综述了地震综合观测与综合分析预报的工作概况,首先对日、苏、美、中等四国的这方面状况进行了回顾,并列表作了比较,继而论述了地震预报的探索与实用化问题,文章最后作了某些分析并提出了今后的展望。 相似文献
8.
生命线工程系统抗震可靠度算法复杂性及简化原则 总被引:4,自引:0,他引:4
研究了生命线工程系统抗震可靠度常规算法的适用性,定义了算法的时间复杂性和结构复杂性,分析了使可行算法失效的原因,给出了回路分解公式,提出了优先降低结构复杂性的简化原则。 相似文献
9.
周建国 《地震地磁观测与研究》2003,24(4):32-35
介绍了多道直流电测仪的配套设备,研制了电极—电缆查线器,解决了以往检测电极—电缆线的低效和不准确的弱点;完成了野外使用的高压供电装置,并改进了电极棒。 相似文献
10.
11.
通过室内动三轴试验,研究了西北地区遗址土体的动本构关系,得到了模型参数,分析了遗址土体的动剪模量比和阻尼比的特性,并通过归一化处理得出模型参数,结果表明:遗址土体符合Hardin-Dinevich双曲线模型,其相关系数均大于0.991 7,模型参数a、b与土样密度不存在相关性;在相同荷载下,密度越大,动应变和动残余应变越小,其中陕西定边陡沟子明长城墙体土承受动荷载能力下降较快,而草滩段秦长城墙体、瞭望台台基处初始弹性模量和初始剪切模量较小,三处土体硬度较小,易于遭受病害侵蚀破坏,需进行重点加固维护;遗址墙体所建窑洞处土体强度和硬度明显大于长城墙体,动弹性模量和动剪切模量约为其墙体2倍。草滩段瞭望台土体强度和硬度明显大于同地区长城墙体;遗址土体的动剪切模量G/G0随着动剪应变γd的增加而减小,且密度越大,衰减速度越快,阻尼比D随着动剪应变γd的增长,呈现先缓慢增加-急剧增加-缓慢增加的过程,且密度越大,阻尼比越大。按建造年代、建造形制和用途划分、所处地区对典型遗址进行动力特性的对比分析,为今后土遗址加固保护提供理论基础和参考依据。 相似文献
12.
防震减灾科普作品的创作与传播是防震减灾宣传工作的基础与核心。随着防震减灾科普作品的增多,一些共性问题凸显出来,地震科普工作者一直在思考和探索解决的措施。以云南省地震局举办的防震减灾科普知识小小讲解员线上比赛为实践案例,分析人民群众在防震减灾科普作品创作中的作用,获得启示:防震减灾科普作品创作要“从群众中来,到群众中去”,动员和依靠人民群众的力量去创作,在人民群众的实践中创作,为了满足人民群众的地震安全需求、筑牢防震减灾的人民防线而创作。 相似文献
13.
14.
15.
XiaoQiang Li 《中国科学:地球科学(英文版)》2013,56(12):2027-2036
Global climate change and its possible ecological consequences have become the focused issue (IPCC, 2007; Mann et al., 2008; Ding et al., 2009). The Holocene contains the analogous characteristic of future climatic change and the continuous agriculture activity, providing the ideal “similar pattern” for studying the climate change and human adaption and impact in the future. Based on the recent studies of stalagmite, ice core, ocean, and lake etc., the paper introduces the new progress in the Holocene climate and agriculture research in China as follows: (1) Discuss the variability, amplitude, and unstable characteristic of climate, as well as the abrupt events and mechanisms of climate. (2) Analyze the botanical index records for studying the early agriculture. (3) Review the agricultural origin, expanding, and development. (4) Reveal the style and intensity of early agriculture and understand the agricultural impact and adaption to the environmental changes. (5) Introduce ongoing research projects in China and emphasize the significance of increasing the dating precision and the indicative effectiveness of proxies. (6) Realize how the ecosystem and environmental factors respond to the increasing temperature process, understand how the human adapt to the rapid climate change, and provide the scientific basis for assessing the effects of climate change and the human adaption in the future. 相似文献
16.
INTRODUCTIONItisknownthatChinaisanearthquake pronecountryintheworldandisalsoacountrysufferingmostsevereseismiccalamitiesintheworld .China’sterritoryoccupiesabout 1 1 4oftheglobalconti nentalarea ,whileabout 1 3ofglobalM≥ 7.0continentalearthquakesoccurredinCh… 相似文献
17.
Silicate melts are very active in the interior of the Earth and other terrestrial planets, and are important carriers for the transport of material and energy. The determination of the equation of state(EOS) for silicate melts and the acquisition of a precise quantitative relationship between molar volume(or density) and temperature, pressure, and composition is essential for simulating the generation, migration, and eruption processes of magmas and the evolution of the magma ocean stage during the early formation of the Earth and other terrestrial planets, for calculating and modeling the phase equilibria involving silicate melts, and for revealing the variation of the microstructure of silicate melts with pressure. However, it is experimentally challenging to determine the volumetric properties of silicate melts and the accumulated density data at high pressure are still very limited due to a series of problems such as: the high liquidus temperature of silicate rocks; proneness for silicate melts to react with sample capsules to change the melt composition; and proneness for melts to flow and leak during the high pressure and high temperature experiments. In recent years, there is rapid progress in the high pressure and high temperature experimental techniques, in terms of not only the extension of temperature and pressure ranges but also the improvement on the accuracy of measurements, and the emergence of new methods for in-situ measurements. Here, we review the widely-used theoretical models of ambient-pressure and high-pressure EOS for silicate melts, and illustrate some problems that need to be solved urgently:(1) the room pressure EOS for iron-and titanium-bearing silicate melts needs to be improved;(2) the partial molar properties of the H2 O and CO2 components in silicate melts containing volatile components may vary markedly with the melt composition, which need to be addressed in high-pressure EOS;(3) how the formulation and applicable range of EOS correspond to changes in melt structure and compression mechanism requires further study. We highlight the basic principle and applicable range of various methods for determining the EOS for silicate melts, and compare the advantages and disadvantages of doublebob Archimedes method, fusion curve analysis, shock compression experiments, sink-float method, X-ray absorption, X-ray diffraction and ultrasonic interferometry. Future trends in this field are to develop experimental techniques for in situ measurements on melt density or sound velocity at high temperature and high pressure and to accumulate more experimental data,and on the other hand, to improve the theoretical models of the EOS for silicate melts by a combination of research on the microstructure and compression mechanisms of silicate melts. 相似文献
18.
19.
ChangSong Lin HaiJun Yang JingYan Liu Li Peng ZhenZhong Cai XiaoFa Yang YongHeng Yang 《中国科学D辑(英文版)》2009,52(6):823-834
Inclined eastward and consisting of the Hetianhe, Hetianhedong, Tazhong paleouplifts and Bachu paleoslope, the central paleouplift
belt in the Tarim Basin was a large composite paleouplift and paleoslope belt with complicated palaeogeomorphic features during
the Middle to early Late Ordovician. A number of paleostructural geomorphic elements have been identified in the paleouplift
belt and surrounding areas, such as the high uplift belts, the faulted uplift platforms, the marginal slopes and slope break
zones flanking the paleouplift belt, the surrounding shelf slopes or low relief ramps, the shelf slope break zones and deep
basin plains. They exerted great influence on the development of paleogeography of the basin. The marginal slopes and slope
break zones flanking the uplift belt constrained the formation and deposition of the high-energy facies including reefal and
shoal deposits during the Late Ordovician, which comprise the major reservoirs of the Lower Paleozoic in the basin. Toward
the end of the Ordovician, the Tazhong paleouplift hinged westward and became a westward-dipped nose as the southeastern margin
of the basin was strongly compressed and uplifted. The tectono-paleogeomorphic framework of the central northern basin during
the Early Silurian and the Late Devonian to Early Carboniferous changed remarkably in topography from the initial low in east
and high in west to high in northeast and low in southwest. The major paleogeomorphic elements developed in these periods
included the strong eroded uplift high, the uplift marginal slope, the gentle ramp of the depression margin and the depression
belt. The sandstones of the lowstand and the early transgressive systems tracts were deposited along the uplift marginal slopes
and the gentle ramps of the depressions comprise the prolific reservoirs in the basin. The study indicates that the distribution
patterns of the unconformities within the basin are closely related to the paleogeomorphic features and evolution of the paleouplift
belt. From the high uplift belt to the depression, we found the composed unconformity belts at the high uplift, the truncated
and onlap triangular unconformity belts along the uplift marginal slopes, the minor angular unconformity or discontinuity
belts along the transitional zones from the uplift marginal slopes to depression and the conformity belt in the central depression.
The truncated and the onlap triangular unconformity belts are the favorable zones for the formation of stratigraphic trap
reservoirs.
Supported by National Basic Research Program of China (Grant No. 2006CB202302), National Natural Science Foundation of China
(Grant No. 40372056) and Frontier Research Project of Marine Facies 相似文献
20.
Graziela Miot da Silva Patrick Hesp Janice Peixoto Sérgio R. Dillenburg 《地球表面变化过程与地形》2008,33(10):1557-1573
This paper examines patterns of foredune vegetation along an embayment in southern Brazil and the relationships between variations in percent cover and diversity, and environmental factors such as beach/surfzone type and exposure to wind and wave energy. The study was conducted on Moçambique Beach, Brazil, which displays significant alongshore variations in exposure to the prevailing winds and waves, beach/surfzone morphodynamic type, type and dimensions of the dune systems and foredune vegetation cover and diversity. Two vegetation surveys were carried out in contiguous 1 m2 quadrats across the foredune. The presence/absence, percent cover of the species, diversity and similarity between the vegetation of the profiles surveyed and their relation with environmental conditions are examined. The results show that the vegetation cover decreases from south to north, possibly reflecting the increasing exposure to wind and wave energy. Distinct patterns of species distributions occur along Moçambique beach, such that different plant species are dominant on the southern, middle and northern ends of the beach. A cluster analysis demonstrated two associations: the first one is represented by the profiles located in the lower energy zone of the beach, and the second association is represented by the profiles more exposed to wind and wave energy, sediment deposition and salt spray. The diversity of species decreases northwards, possibly influenced by the surfzone type, number of breaking waves and degree of aeolian transport. The presence/absence of the species and the vegetation cover on the foredune reflect the varying levels of exposure of the beach and foredune to the winds and waves and also reflect the volume of sediment deposition on the foredune and the beach mobility determined by the morphodynamic beach/surfzone type. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献