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排序方式: 共有137条查询结果,搜索用时 31 毫秒
91.
92.
XU Xing CHENG Yennien WANG Xiaolin CHANG Chunhsiang Institute of Vertebrate Paleontology Paleoanthropology Chinese Academy of Sciences Beijing Chin E-mail: xu.xing@ivpp.ac.cn Division of Geology National Museum of Natural Science Taichung China Wang Si''en Xie Guanglian 《《地质学报》英文版》2003,77(3):294-298
Pygostyle was previously considered as a unique structure of ornithothoracine birds, used to maneuver tail feathers. A similar structure from an oviraptorosaurian dinosaur was considered functionally associated with the rectrices as in birds. We report a pygostyle-like structure from a therizinosauroid dinosaur. The presence of filamentous integuments, but absence of rectrices, on the tail of this therizinosauroid, combined with other lines of evidence, suggests that the initial function of the pygostyle was not related to the rectrices. 相似文献
93.
94.
T.SONG Post-Doctoral Fellow School of Civil Structural Engineering Nanyang Technological University Nanyang Avenue Singapore . Presently Civil Engineer Engineering Depatment Technology Division Maritime Port Authority of Singapore. 《国际泥沙研究》1997,(3)
I.INTRODUCTIONBedloadtransportinsteadyuniformopenchannelflowhasbeenextensiVelystudied.Manyoftheformulasdevelopedforthepredictionofbedloadtransportinuniformopen-channelflowcanbebroughtinthefollowingform(ChienandWan,1983);ac=f(O)(l)xvhereacisthedimensionlessparameterofbedloadtranSPortandOisthedimensionlessparameterofflowintensity.TheseparametersaredefinedasfwheregsisthebedloadtranspoftratePerunitwidthindryweight;disthesedimentdiameter,Sisthebedslopeofthechannel;Rbisthehydraulicradiusdue… 相似文献
95.
波动数值模拟中透射边界的稳定实现 总被引:21,自引:0,他引:21
从波动能量在计算区内累积增大的观点出发,通过简单的一维弹性波模型,系统地阐明了在近场波动数值模拟中透射边界两类数值失稳--"高频振荡"和"零频飘移"的机理:前者源于对波动数值模拟无意义的高频波动在人工边界上的放大和波在有限计算区内多次反射产生的反复放大;后者则源于透射边界允许零频和接近零频的分量不断进入计算区. 由此提出了稳定实现透射边界的完整方案包括两项简单措施:第一,在全部计算区内按文中建议的方法注入小阻尼,以消除高频振荡;第二, 给出一种具有明确物理意义的消除零频飘移的算子算法. 最后,提供了三维波源问题和散射问题的详细数值试验结果. 相似文献
96.
Lei Xinhai Qian Qin Huang Yuying Zhu Dashan Lecturer Dept. of Mechanics Huazhong University of Science Technology 《中国海洋工程》1993,(3)
This paper presents a new finite element method for solving static and dynamic problems in laying operation of pipelines. The effect of the viscoelastic soil behavior is considered by using the Pasternak foundation model. Some examples are also presented. 相似文献
97.
Zhu Dashan Huang Yuying Cheng Jiangtian
Asso. Prof. Dept. of Mechanics Huazhong University of Science Technology 《中国海洋工程》1991,(1)
A plastic ring-beam model simulating the longitudinal transition zone of submarine pipelines in the buckle propagation is presented. The nonlinear relationships between the buckle propagation pressure and the length of the transition zone and the position parameter of the longitudinal plastic hinge are derived using the energy principle. The related values are obtained by means of solving a set of nonlinear equations. The model conforms better to reality than the ring models for considering the effect of the longitudinal plastic bending of the transition zone. The computations for some stainless steel and aluminium tubes with different geometrical parameters are performed. The results obtained agree better with the experimental results than existing theoretical predictions. 相似文献
98.
Jiang Jinren Lu Qinnian and Sun JingjiangInstitute of Engineering Mechanics SSB Harbin ChinaHarbin University of Architecture Engineering Harbin China 《中国地震研究》1995,(4)
The statistical characteristics of strong ground motion specified by response spectrum and power spectral density function are studied using 190 strong-motion records of the Haicheng and Tangshan earthquakes in China and 138 earthquakes in the western United States.The response spectrum is normalized by the peak ground acceleration(i.e.,represented as spectral magnification factor),and the power spectral density function is described by the Kanai-Tajimi spectrum.The statistics and dependence of parameters are evaluated,and correlations between the spectral magnification factor or Kanai-Tajimi spectral parameters and the site condition,epicentral distance,or local magnitude are investigated.The statistical characteristics of spectra China and the U.S.A.are compared.Based on the results obtained the values of the statistics on spectral parameters for earthquake engineering applications in China are suggested. 相似文献
99.
本文在文献[1]基础上,进一步分析了用Wilson—θ法求解具有折线型非线性特性的结构动力反应分析中拐点处理的精确方法,并详细讨论了变步长Δt’的取值问题。 相似文献
100.
目前研究地震动空间变化的主要方法是利用密集台阵(如SMART1台阵等)的强震观测记录进行统计分析,由于地震动观测资料的不足,因而缺少基岩及不同场地类别地震动相干函数模型. 本文利用数值方法了模拟理论地震图,进而研究采用震源位错模型的基岩随机地震动的空间变化规律,并考虑震源破裂速度、子源个数、震源深度和介质传播速度等因素的影响. 其具体思路为:首先对应于每个样本,用有限差分数值模拟方法计算弹性半空间近场地震动场,而后对所有样本的计算结果进行统计,给出了一个走滑断层情形下的近场基岩表面及沿基岩竖直方向水平分量地震动的相干函数模型. 相似文献