Diffraction of normal shock wave by yawed wedges

The diffraction of normal shock with yawed wedges of small angles have been considered in this paper. Vorticity distribution of the fluid particle over the diffracted shock has been determined for several Mach numbers of the shock wave. The Mach reflection effects have also been investigated when the bend is concave to the flow.     

On an Extension and a Refinement of Van der Corput's Inequality

By introducing a parameterα,we give an extension of Van der Corput's inequal- ity.Also a new strengthened version of it is considered.     

Mathematical modelling and analytical solution for workpiece temperature in grinding

This paper deals with modelling the workpiece temperature field produced during the grinding process. The proposed model is given in terms of a two-dimensional boundary-value problem where the interdependence among the grinding wheel, the workpiece and the coolant is described by two variable functions in the boundary condition. An explicit integral form solution is constructed using the Laplace and Fourier transforms and the Green’s function method.     

Remarks on sufficient conditions for fixed points of multivalued nonexpansive mappings

In recent papers [S. Dhompongsa, T. Domínguez-Benavides, A. Kaewcharoen, A. Kaewkhao, B. Panyanak, The Jordan–von Neumann constants and fixed points for multivalued nonexpansive mappings, J. Math. Anal. Appl. 320 (2006) 916–927; S. Dhompongsa, A. Kaewcharoen, A. Kaewkhao, The Domínguez–Lorenzo condition and multivalued nonexpansive mappings, Nonlinear Anal. 64 (2006) 958–970], two sufficient conditions, namely the Domínguez–Lorenzo condition and property (D$D$), for fixed points of multivalued nonexpansive mappings are introduced. The authors also give some sufficient conditions for the Domínguez–Lorenzo condition and property (D$D$). In their proofs, it seems reasonable to use the James and von Neumann–Jordan constants. With slight modifications, significant improvements are obtained. Some new estimates are tight in Hilbert spaces.     

最小风险组合证券非负投资比例系数的确定

研究非负投资比例系数约束条件下,实现风险最小化的组合证券投资问题.应用罚函数法,对最小风险组合证券的非负投资比例系数进行研究.实例表明:这一方法是可行的、有效的.     

一个改进的Hardy-Hilbert不等式

通过建立权系数的不等式,得到一个改进的Hardy-Hilbert不等式.     

关于纤维锥的Hilbert系数

Let （R, m） be a Cohen-Macaulay local ring of dimension d, I an mprimary ideal and K an ideal containing I. Assuming that I has minimal （almost minimal） mixed multiplicity with respect to K, we get some results on the Hilbert coefficients of fiber cones.     

Optimal reconstruction of the solution of the wave equation from inaccurate initial data

In the present paper, we consider the problem of the optimal reconstruction of the solution of the wave equation from the approximate values of the Fourier coefficients of the function specifying the initial form of the string. For an operator defined on the weight space of vectors from l ₂, we present the solution of the more general problem of reconstruction from the approximate values of the coordinates of these vectors.     

On the structure of stationary sets

We isolate several classes of stationary sets of [k]ωand investigate implications among them. Under a large cardinal assumption, we prove a structure theorem for stationary sets.     

湖南省各市州经济发展水平评价

本文利用主成分分析法分析了湖南各市州的经济发展水平和经济综合实力,对湖南省14个市州的经济发展情况做出综合评价,得出了各市州在湖南省的经济地位.最后用系统聚类分析法进行了验证,结果表明用多元统计分析法来评价地区经济发展水平是可行的.