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51.
A negative lift force (attraction) can be induced on a near-bed pipeline in a horizontal current due to asymmetric flow. This negative lift force has a significant influence on the behaviour of the near-bed pipeline, causing two remarkable failure patterns. One failure pattern is due to stability loss, and the pipeline fully rests on the seabed. The other is due to the excessive stress or deformation even if the pipeline is stable in a position between the original equilibrium position and the seabed. A quantitative method to assess these two failure patterns by combining boundary element and finite element methods is proposed in this paper. This is a nonlinear fluid–structure interaction problem, and an iteration procedure is used herein to solve it. Numerical examples reveal that there exists a critical current velocity, above which the pipeline fails. The relationship between the critical velocity and the distance from the pipeline to the seabed is given. 相似文献
52.
We extend the constant fugacity MC method of Redner et al.[7] to study the linear and branched polymers. A constant fugacity MC enumeration method for the calculation of the canonical and grand canonical ensemble properties of the linear and branched polymers is proposed. The advantage of the present method over the conventional ones is that it is efficient and statistically bias free. Comparison of the MC results with that of the exact enumeration is made. 相似文献
53.
本文研究了有一个修理的可修Consecutive-k-out-of-n:G系统。这个G系统是由n个相同且独立的部件构成的环形或直线系统,假定每个部件的工作时间和修理时间都是指数分布。我们引进了广泛转移概率和关键部件的概念,并假定一个关键部件具有较高的修理优先权,从而确定了系统状态的转移概率,同时讨论了系统的几种可靠性指标。 相似文献
54.
Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｏｐｔｉｃａｌｌｙａｃｔｉｖｅｓｅｃｏｎｄａｒｙａｌｃｏｈｏｌｓａｒｅｕｓｅｆｕｌｂｕｉｌｄ ｉｎｇｂｌｏｃｋｓｆｏｒｐｈａｒｍａｃｅｕｔｉｃａｌｓ ,ａｇｒｏｃｈｅｍｉｃａｌｓａｓｗｅｌｌａｓｏｔｈｅｒｍａｔｅｒｉａｌｓ .1Ａｖａｒｉｅｔｙｏｆａｓｙｍｍｅｔｒｉｃｃａｔａｌｙｔｉｃｒｅａｃ ｔｉｏｎｓｈａｖｅｂｅｅｎｄｅｖｅｌｏｐｅｄｆｏｒｐｒｅｐａｒｉｎｇｓｕｃｈｉｍｐｏｒｔａｎｔｓｅｃｏｎｄａｒｙａｌｃｏｈｏｌｓ .2 Ｉｎａｄｄｉｔｉｏｎｔｏｓｔｒａｉｇｈｔｆｏｒｗａ… 相似文献
55.
本文从一名物理学家的视角出发,讲述了作者将物理教学实践和科学传播活动相结合的经历。作者认为,二者的良好结合不仅对自身的物理学研究有所帮助,还使他摸索到了以物理学方法研究历史的新手段,并对了解科学史有所启迪。结合自身的实践,作者向活跃在实践领域的科学家们提出以下建议:(1)将科普书的阅读融合于教学实践中;(2)在学科研讨会中加入科普内容,或举行专门的科普研讨会;(3)举办全校规模的科普系列讲座;(4)科学家可在中学、社区,以及其他场所宣传科普;(5)促进科普作为新兴学科的出现;(6)将科学与人文学科相结合。 相似文献
56.
We investigate the property of ^1S0 superfluidity of neutrons and protons in the neutron star matter. On the basis of the result, we study the effects of hyperons on the ^1S0 pairing gaps of the two species of the particles. The parameter sets we use are for the Hartree approximation of the relativistic σ - ω model and the mean field approximation of the Walecka model, respectively. The predicted domain of superfluidity is very close to other works, whereas differences appear in the predicted value of the maximum gap. It is found that ∑^-, A and ∑^- have some influences, the scales of which depend on hyperon-meson coupling constants we use besides other factors, on the ^1S0 superfluidity of protons in some density range, and do not have influence on superfluidity of neutrons. Other hyperons have no influence on the ^1S0 superfluidity of neutron and proton due to these hyperons appearing after ^1S0 neutron and proton pairs disappear. 相似文献
57.