An obstruction to quantizing compact symplectic manifolds

We prove that there are no nontrivial finite-dimensional Lie representations of certain Poisson algebras of polynomials on a compact symplectic manifold. This result is used to establish the existence of a universal obstruction to quantizing a compact symplectic manifold, regardless of the dimensionality of the representation.

     

Unsteady shock generated vorticity

Abstract. A two-dimensional theory is developed for the vorticity just downstream of a curved, unsteady shock wave. By utilizing Crocco's equation, an explicit formula is obtained for the vorticity that does not require a perfect gas and that holds for arbitrary conditions upstream of the shock wave. The analysis is applied to the flow just downstream of the reflected shock that occurs in a single-Mach reflection pattern. Flow conditions are based on an interferometric photograph of Ben-Dor and Glass (1978). In this case, the reflected shock is weak everywhere from its upstream intersection with the wall to the triple point. The vorticity has a singularity and a change of sign near the triple point that indicates the presence of a weak shear layer downstream of this location. Received 20 December 1999 / Accepted 19 March 2000     

基于模拟退火算法的曲面最短路径求解

通过对路径的节点序列内在关联性的分析,提出了适合曲面最短路径问题的邻域结构,使整段路径的优化问题能够通过局部调整得以实现．将模拟退火算法的框架引入路径寻优中,提出了解决曲面最短路径的随机搜索算法．最后给出了数值仿真实例．     

Rigidity of Noncompact Finsler Manifolds

For a Euclidean space or a Minkowski space, we change the metric in a compact subset and show that the resulting Finsler manifold is isometric to the original standard space under certain conditions. We assume that the mean tangent curvature vanishes and the metric satisfies some curvature conditions or have no conjugate points.     

Symmetry Results for Positive Solutions of Some Elliptic Equations on Manifolds

We adapt the method of moving planes in order to obtainsymmetry results for positive solutions of some elliptic equations onmanifolds, in the case where our problem satisfies certain symmetryhypothesis. We also obtain monotonicity results using the slidingmethod.     

LOCALIZATION AND APPROXIMATION OF ATTRACTORS FOR THE KURAMOTO-SIVASHINSKY EQUATIONS

1Intr0ducti0nThestudy0fglobalattrartorhasagreatdealtodowiththatofthelargetimebehavi0urofthesolutionsofdissipativepartialdtherentialequations.Usually,theattractoristypicallyacomplicated,fractalsubset0fthephasespace.Hellcetheconceptofinertialmallif0ld(IM),apositivelyinvariantfinite-dimensi0nalLipschitzmanifoldthatexponentiallyattractseveryorbit,wasdevelopedandithasbecomeakeytoolinthisareaofstudy.(See,e-g-,[l],[21andreferencestherein.)Themotivatingideabehindtheinertialmanif0ldist0embedtheattrac…     

Dense Subsets of H1/2(S2, S1)

We prove that the maps from S ² intoS ¹ having a finite number of isolated singularities ofdegree ±1 are dense for the strong topology inH ^1/2(S ², S ¹). We also prove that smooth maps are densein H ^1/2(S ², S ¹)for the sequentially weak topology andthat this is no more the case in H ^s (S ², S ¹) for s> 1/2.     

Theoretical study on the bifurcation of vortexes structure for flow in curved tube

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｃｕｒｖｅｄｔｕｂｅｉｓｎｏｔｏｎｌｙｃｏｍｍｏｎｉｎｉｎｄｕｓｔｒｙ ,ｂｕｔａｌｓｏａｔｔｒａｃｔｓｓｐｅｃｉａｌａｔｔｅｎｔｉｏｎｏｆｒｅｓｅａｒｃｈｅｒｓｉｎｂｉｏｍｅｃｈａｎｉｃｓｂｅｃａｕｓｅａｏｒｔｉｃａｒｃｈｉｓｔｈｅｐｌａｃｅｗｈｅｒｅａｔｈｅｒｏｓｃｌｅｒｏｓｉｓｈａｐｐｅｎｓｍｏｓｔｆｒｅｑｕｅｎｔｌｙ[1～ 3].Ｓｉｎｃｅｔｈｅｐｈｙｓｉｏｌｏｇｉｃａｌｆｅａｔｕｒｅｏｆｒｅａｌｂｌｏｏｄｖｅｓｓｅｌｉｓｖｅｒｙｃｏｍｐｌｉｃａｔｅｄ ,ｔｈｅｆｌｏ…     

电场的MATLAB可视化方法

将导体球放到匀强电场中,研究电势和电场各分量的分布规律,是一个典型的电动力学问题.详细推导了极坐标和直角坐标系中的电势公式,求出了电场强度的表达式,推导电场线的方程,将公式无量纲化,应用MATLAB画出了电场强度的分布曲线和电场线以及等势线,充分反映了电场分布的规律.附录中列出了两个相关程序,可供读者参考.     

张拉结构非线性分析两节点曲线单元有限元法

提出适合张拉结构几何非线性分析的两节点曲线单元有限元方法．假定索元的初始形状呈二次抛物线,根据单索的平衡条件、几何和物理关系建立了索元的位移函数;由拉格朗日应变的定义建立了可以考虑任意次高阶位移影响的索元轴向应变的精确表达式,并基于拉格明日描述方法和虚功原理得到了索元的非线性平衡方程与切线刚度矩阵．采用荷载增量法与Newton－Raphson法相结合的混合法进行了实例计算,结果表明：本文方法的精度明显优于两节点直线索单元,适合于大跨度索阿、索穹顶等张拉结构的几何非线性分析．