空间：一个解读刘三姐山歌文化的有力维度——刘三姐山歌文化深层底蕴的探讨之一

以往对刘三姐山歌文化的解读,学术界多从历史的时间的维度进行,这固然可以多少触及到其流传原因,但固守这种维度的直接后果就是很难揭示出刘三姐山歌文化的深层底蕴。而空间观念的引入,则为刘三姐山歌文化的深层底蕴的解读提供了一个有力维度。其实作为壮民族文化代表的刘三姐山歌文化就是壮民族及其地区文化空间建构和认同的巨大隐喻,其生命力与流传至今且经久不息的真正原因,都可从空间这一维度得到解读。     

Painlevé analysis and exact solutions of the nonlinear diffusion equation with a polynomial source

Nonlinear diffusion equation with a polynomial source is considered. The Painlevé analysis of equation has been studied. Exact traveling wave solutions in the simplest cases have been found. Copyright © 2015 John Wiley & Sons, Ltd.     

Monte Carlo approximate tensor moment simulations

An algorithm to generate samples with approximate first‐order, second‐order, third‐order, and fourth‐order moments is presented by extending the Cholesky matrix decomposition to a Cholesky tensor decomposition of an arbitrary order. The tensor decomposition of the first‐order, second‐order, third‐order, and fourth‐order objective moments generates a non‐linear system of equations. The algorithm solves these equations by numerical methods. The results show that the optimization algorithm delivers samples with an approximate residual error of less than 10¹⁶ between the components of the objective and the sample moments. The algorithm is extended for a n‐th‐order approximate tensor moment version, and simulations of non‐normal samples replicated from distributions with asymmetries and heavy tails are presented. An application for sensitivity analysis of portfolio risk assessment with Value‐at‐Risk (VaR) is provided. A comparison with previous methods available in the literature suggests that the methodology proposed reduces the error of the objective moments in the generated samples. ? ? JEL Classification: C14, C15, G32.
Copyright © 2016 John Wiley & Sons, Ltd.     

Exact solutions for the flow of an Oldroyd-B fluid due to an infinite flat plate

The unsteady flow of an Oldroyd-B fluid due to an infinite flat plate, subject to a translation motion of linear time-dependent velocity in its plane, is studied by means of the Laplace transform. The velocity field and the associated tangential stress corresponding to the flow induced by the constantly accelerating plate as well as those produced by the impulsive motion of the plate are obtained as special cases. The solutions that have been determined, in all accordance with the solutions established using the Fourier transform, reduce to those for a Newtonian fluid as a limiting case. The similar solutions for a Maxwell fluid are also obtained.     

Numerical approximation of the boundary control for the wave equation with mixed finite elements in a square

Sorin Micu ^{This paper studies the numerical approximation of the boundarycontrol for the wave equation in a square domain. It is knownthat the discrete and semi-discrete models obtained by discretizingthe wave equation with the usual finite-difference or finite-elementmethods do not provide convergent sequences of approximationsto the boundary control of the continuous wave equation as themesh size goes to zero. Here, we introduce and analyse a newsemi-discrete model based on the space discretization of thewave equation using a mixed finite-element method with two differentbasis functions for the position and velocity. The main theoreticalresult is a uniform observability inequality which allows usto construct a sequence of approximations converging to theminimal L2-norm control of the continuous wave equation. Wealso introduce a fully discrete system, obtained from our semi-discretescheme, for which we conjecture that it provides a convergentsequence of discrete approximations as both h and t, the timediscretization parameter, go to zero. We illustrate this factwith several numerical experiments.}     

The pressure in operator algebras

We introduce two notions of the pressure in operator algebras, one is the pressure Pα（π, T） for an automorphism α of a unital exact C^＊-algebra A at a self-adjoint element T in A with respect to a faithful unital ＊-representation π the other is the pressure Pτ,α（T） for an automorphism α of a hyperfinite von Neumann algebra M at a self-adjoint element T in M with respect to a faithful normal α-invariant state τ. We give some properties of the pressure, show that it is a conjugate invaxiant, and also prove that the pressure of the implementing inner automorphism of a crossed product A×α Z at a self-adjoint operator T in A equals that of α at T.     

Exact solutions for the flow of non-Newtonian fluid with fractional derivative in an annular pipe

Generally speaking, rheological properties of materials are specified by their so-called constitutive equations. The simplest constitutive equation for a fluid is a Newtonian one, on which the classical Navier-Stokes theory is based. The mechanical behavior of many fluids is well described by this theory. However, there are many rheologically compli- cated fluids such as polymer solutions, blood and heavy oils which are inadequately de- scribed by a Newtonian constitutive equation that does …     

Toroidal source around a static black hole

A sequence of exact solutions of Einstein equations is obtained describing the fields of a Schwarzschild black hole surrounded by static, axially symmetric, thick toroids. Its properties are illustrated by plotting the shape of the gravitational field, the deformation of the black-hole horizon and several types of time-like geodesics, in dependence on parameters of the toroid.Dedicated to Professor Jií Horáek on the occasion of his 60th birthday.     

一维非自治经典谐振子的精确解析解

一维时间相关的经典谐振子是一个SU(1,1) 非自治经典系统,物理上十分有用,而数学上难于得到其精确解析解. 首次把新颖的代数动力学方法用于经典动力学系统,得到了这个模型的一般精确解;当时间相关的弹性系数为某些初等函数时,给出了精确解的解析形式. 这是关于这一问题的重要结果. 从精确解出发,推导出最近文献中提出的"解析近似解",并指出该近似解的适用条件.     

On certain random simplices in

The exact density is given for the r-content of the simplicial convex hull of r + 1 independent points in ⁿ, each having a type II β distribution. The density is given in the form of an integral of Mellin-Barnes type, which even in the most general cases can be evaluated to give a series representation for the density. Some special cases are evaluated to observe the types of series that can arise. It is also shown that the r-content is asymptotically normal for large values of n, a result analogous to a result conjectured by R. E. Miles (1971, Adv. in Appl. Probab., 3 353–382).