594 resultados para 1081


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This paper describes an experimental investigation of the behaviour of embedded retaining walls under seismic actions. Nine centrifuge tests were carried out on reduced-scale models of pairs of retaining walls in dry sand, either cantilevered or with one level of props near the top. The experimental data indicate that, for maximum accelerations that are smaller than the critical limit equilibrium value, the retaining walls experience significant permanent displacements under increasing structural loads, whereas for larger accelerations the walls rotate under constant internal forces. The critical acceleration at which the walls start to rotate increases with increasing maximum acceleration. No significant displacements are measured if the current earthquake is less severe than earthquakes previously experienced by the wall. The increase of critical acceleration is explained in terms of redistribution of earth pressures and progressive mobilisation of the passive strength in front of the wall. The experimental data for cantilevered retaining walls indicate that the permanent displacements of the wall can be reasonably predicted adopting a Newmark-type calculation with a critical acceleration that is a fraction of the limit equilibrium value.

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The coherence properties of a transient electron-hole state developing during superradiance emission in semiconductor laser structures have been studied experimentally using a Michelson interferometer and Young's classic double-slit configuration. The results demonstrate that, in the lasers studied, the first-order correlation function, which quantifies spatial coherence, approaches unity for superradiant emission and is 0.2-0.5 for laser emission. The supercoherence is due to long-range ordering upon the superradiant phase transition. © 2012 Kvantovaya Elektronika and Turpion Ltd.

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采用RACE方法 ,从鲤鱼脑组织克隆了两个差异的sGnRH(salmonGnRH ,[Trp7Leu8]GnRH)cDNAs ,即cDNA1和cDNA2 ,其长度分别为 393和 4 78bp。两个cDNAs都包括一个 2 85bp开放阅读框 ,编码的sGnRH前体为 94个氨基酸残基 ,由一个信号肽、sGnRH十肽和一个由蛋白水解位点 (Gly Lys Arg)连接的促性腺激素释放激素相关肽共 3部分组成。用内含子捕获得到相应的两个差异sGnRH基因 ,即sGnRHgene1和 gene2 ,其基本结构

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实现灵活方便的企业业务集成一直是信息领域的核心问题,也是B2B电子商务应用的关键。为此将Web服务和传统的工作流技术相结合,设计并实现了支持复合Web服务运行和管理的框架WSFlow。给出了WSFlow的总体结构,描述了其中的关键技术,包括Web服务与工作流活动的动态配置和绑定技术,复合Web服务流程的动态修改以及复合Web服务的运行监控等技术。

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近十多年来,利用太阳能制冷已引起人们的关注。不少国家对太阳能空调降温、食品冷藏进行了大量的试验研究工作。由于建筑物空调降温在技术上容易达到、经济性较好,因此太阳能空调技术的发展比较快。美国、日本等国已从示范性实验阶段逐步走向实用化。广东地处亚热带,全年平均气温较高,夏季时间长,气候炎热,太阳辐射资源比较丰富。随着人民生活水平的不断提高,对建筑物空调降温的需求日益增大。太阳能空调

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Far infrared magnetophotoconductivity performed on high purity GaAs reveals the existence of fine structures in the resonant magnetopolaron regions. The fine structures are attributed to the presence of bound phonons due to multiphonon processes. We demonstrate that the magnetopolaron energy spectrum consists of bound phonon branches and magnetopolaron branches. Our results also indicate that different phonons are bound to a single impurity, and that the bound phonon in Si-doped GaAs is a quasilocalized mode.

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