关于G-Matlis自反模的换环定理

设Ｒ和Ｔ是Ｎｏｅｔｈｅｒ完备半局部环，Ｒ→Ｔ是环同态．本文证明了，若Ｔ是有限生成或ＡｒｔｉｎＲ－模，Ｍ为Ｇ－Ｍａｔｌｉｓ自反Ｒ－模，则对所有ｎ≥０，Ｅｘｔ^Ｒ_ｎ（Ｔ，Ｍ），Ｅｘｔ^Ｒ_ｎ（Ｍ，Ｔ），Ｔｏｒ^Ｒ_ｎ（Ｔ，Ｍ）以及Ｔｏｒ^Ｒ_ｎ（Ｍ，Ｔ）均是Ｇ－Ｍａｔｌｉｓ自反Ｔ－模．所得结果推广了Ｒ．Ｂｅｌｓｈｏｆ的结果．     

THERMODYNAMIQUE DES ENSEMBLES DE CANTOR AUTOSIMILAIRES（THERMODYNAMICS OF SELF-SIMILAR CANTOR SETS）

ＴＨＥＲＭＯＤＹＮＡＭＩＱＵＥＤＥＳＥＮＳＥＭＢＬＥＳＤＥＣＡＮＴＯＲＡＵＴＯＳＩＭＩＬＡＩＲＥＳ（ＴＨＥＲＭＯＤＹＮＡＭＩＣＳＯＦＳＥＬＦ－ＳＩＭＩＬＡＲＣＡＮＴＯＲＳＥＴＳ）￥Ｇ．ＭＩＣＨＯＮ;Ｊ．ＰＥＹＲＩＥＲＥ（ＵｎｉｖｅｒｓｉｔｙｄｅＢｏｕ...     

在熵损失函数下定数截尾情形的参数估计——指数分布情形

本文研究了在熵损失函数下，定数截尾时指数分布的参数估计，得出在熵损失函数下的最小风险同变（ＭＲＥ）估计的精确形式．证明了（ｃＴ＋ｄ）~(－１)形式的一类估计的可容许性和不可容许性．     

一类非线性中立型差分方程解的振动性

本文我们证明了下列两个差分方程Δ（ｘｎ － ｘｎ－ ｋ）α＋ ｑｎｆ（ｘｎ－ Ｔ） ＝ ０Δ（Δｙｎ－ １）α＋ ｋ－ αｑｎｆ（ｙｎ） ＝ ０振动的等价性．其中ｑｎ０,ｋ,Ｔ为正整数,α为两奇数之商,ｆ∈Ｃ（Ｒ,Ｒ）是非减的并满足ｘｆ（ｘ）＞ ０（ｘ≠０）．获得了这些方程振动的一些充分条件．     

EXPONENTIALLY BOUNDED C－SEMIGROUPS AND INTEGRATED SEMIGROUPS WITH NONDENSELY DEFINED GENERATORS──Ⅲ：ANALYTICITY

ＥＸＰＯＮＥＮＴＩＡＬＬＹＢＯＵＮＤＥＤＣ－ＳＥＭＩＧＲＯＵＰＳＡＮＤＩＮＴＥＧＲＡＴＥＤＳＥＭＩＧＲＯＵＰＳＷＩＴＨＮＯＮＤＥＮＳＥＬＹＤＥＦＩＮＥＤＧＥＮＥＲＡＴＯＲＳ──Ⅲ：ＡＮＡＬＹＴＩＣＩＴＹＺｈａｎｇＱｕａｎ（郑权）（Ｄｅｐｔ．ｏｆＭａｔ...     

求解不等式约束最优化问题的MBF—ODE方法

１引言考虑用基于修正内罚函数的常微分方程（ＭＢＦ－ＯＤＥ）方法求解下列不等式约束极小化问题：其中ｆi∈ｃ２：Ｒ,ｉ=0,１,…,ｍ．求解无约束极小化问题的ＯＤＥ的一般形式是其中,φ（ｘ）∈Ｃ１：ΩＲｎ→Ｒ;ｓ（ｘ）∈Ｃ１：ΩＲｎ→Ｒｎ且满足φ（ｘ）＞０,ｓＴ（ｘ）ｆ（ｘ）＜０,ｆ（ｘ）∈Ｃ１：Ｒｎ→Ｒ为目标函数．为便于用ＯＤＥ方法求解（１．ｌ）,可藉助于罚函数将（１．ｌ）变换为无约束极小化问题（见［７］．但由于经典罚函数（ＣＢＦ）在计算上有较大的困难,我们采用修正内罚函数（ＭＢＦ）．其基本思想是用…     

线性模型中M估计的渐近性质

线性模型中Ｍ估计的渐近性质吴耀华（中国科学技术大学数学系，合肥２３００２６）ＡＳＹＭＰＴＯＴＩＣＢＥＨＡＶＩＯＲＯＦＭ－ＥＳＴＩＭＡＴＯＲＳＩＮＬＩＮＥＡＲＭＯＤＥＬＳ￥ＷｕＹＡＯＨＵＡ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，Ｕｎｉｖｅｒｓ...     

ON NONOSCILLATORY SEQUENCES OVER DISCRETE HARDY FIELDS

ＯＮＮＯＮＯＳＣＩＬＬＡＴＯＲＹＳＥＱＵＥＮＣＥＳＯＶＥＲＤＩＳＣＲＥＴＥＨＡＲＤＹＦＩＥＬＤＳＡ．Ｒａｍａｙｙａｎ（Ｄｅｐｔ．ｏｆＭａｔｈ．，ＭａｄｒａｓＵｎｉｖ．Ｐ．Ｇ．Ｃｅｎｔｒｅ，Ｓａｌｅｍ－６３０Ｏｌｌ．ＴｕｍｉｌＮａｄｕ，Ｉｎｄｉａ）Ａｂ...     

Hamilton系统的奇异环在自治小扰动下的分歧现象

Ｈａｍｉｌｔｏｎ系统的奇异环在自治小扰动下的分歧现象李宝毅（天津师范大学数学系，天津３０００７３）ＢＩＦＵＲＣＡＴＩＯＮＰＨＥＮＯＭＥＮＯＮＯＦＴＨＥＨＥＴＥＲＯＣＬＩＮＩＣＣＹＣＬＥＩＮＨＡＭＩＬＴＯＮＩＡＮＳＹＳＴＥＭＷＩＴＨＡＵＴＯＮＯＭＯＵＳ...     

区域分解界面预条件子构造的一般框架

1．引言考虑模型问题：其中ΩR2是多边形区域,常数n≥0．将Ω作非重叠区域分解：Ω＝假定：（i）当i≠j时,（ii）当Ωi与Ωj相邻时,是Ωi和Ωj的一条公共边记称为界面）;（iii）每个闪的尺寸为d,即存在常数co和q,使出包含（包含在）一个直径为C（）（Cod）的圆（国内）．非重叠区域分解方法的实质是,引进两个变量：内部变量。h和界面变量～．先在几上并行未解子问题,将。。消去（即用～表示）,得到～的方程（称为界面方程）;再求解界面方程,得到～的值;最后将～回代,得到。人的值（即原问题的解）．这类区域分解方法是否比重…     

Interactions of delta shock waves and stability of Riemann solutions for nonlinear chromatography equations

This paper is devoted to studying the simplified nonlinear chromatography equations by introducing the change of state variables. The Riemann solutions containing delta shock waves are presented. In order to study wave interactions of delta shock waves with elementary waves, the global structure of solutions is constructed completely when the initial data are taken as three pieces of constants and the delta shock waves are included. In particular, the strength of delta shock wave is expressed explicitly and the delta contact discontinuity is discovered during the process of wave interactions. Moreover, by analyzing the limits of the solutions as the middle region vanishes, we observe that the Riemann solutions are stable for such a local small perturbation of the Riemann initial data.     

Stability of the Riemann solutions for a nonstrictly hyperbolic system of conservation laws

We prove that the Riemann solutions are stable for a nonstrictly hyperbolic system of conservation laws under local small perturbations of the Riemann initial data. The proof is based on the detailed analysis of the interactions of delta shock waves with shock waves and rarefaction waves. During the interaction process of the delta shock wave with the rarefaction wave, a new kind of nonclassical wave, namely a delta contact discontinuity, is discovered here, which is a Dirac delta function supported on a contact discontinuity and has already appeared in the interaction process for the magnetohydrodynamics equations [M. Nedeljkov and M. Oberguggenberger, Interactions of delta shock waves in a strictly hyperbolic system of conservation laws, J. Math. Anal. Appl. 344 (2008) 1143-1157]. Moreover, the global structures and large time asymptotic behaviors of the solutions are constructed and analyzed case by case.     

The singular solutions to a nonsymmetric system of Keyfitz-Kranzer type with initial data of Riemann type

The solutions to the Riemann problem for a nonsymmetric system of Keyfitz-Kranzer type are constructed explicitly when the initial data are located in the quarter phase plane. In particular, some singular hyperbolic waves are discovered when one of the Riemann initial data is located on the boundary of the quarter phase plane, such as the delta shock wave and some composite waves in which the contact discontinuity coincides with the shock wave or the wave back of rarefaction wave. The double Riemann problem for this system with three piecewise constant states is also considered when the delta shock wave is involved. Furthermore, the global solutions to the double Riemann problem are constructed through studying the interaction between the delta shock wave and the other elementary waves by using the method of characteristics. Some interesting nonlinear phenomena are discovered during the process of constructing solutions; for example, a delta shock wave is decomposed into a delta contact discontinuity and a shock wave.     

The asymptotic limits of Riemann solutions for the isentropic drift-flux model of compressible two-phase flows

The formation of vacuum state and delta shock wave are observed and studied in the limits of Riemann solutions for the one-dimensional isentropic drift-flux model of compressible two-phase flows by letting the pressure in the mixture momentum equation tend to zero. It is shown that the Riemann solution containing two rarefaction waves and one contact discontinuity turns out to be the solution containing two contact discontinuities with the vacuum state between them in the limiting situation. By comparison, it is also proved rigorously in the sense of distributions that the Riemann solution containing two shock waves and one contact discontinuity converges to a delta shock wave solution under this vanishing pressure limit.     

Interactions of delta shock waves for a class of nonstrictly hyperbolic system of conservation laws

In this paper, we study the perturbed Riemann problem for a class of nonstrictly hyperbolic system of conservation laws, and focuse on the interactions of delta shock waves with the shock waves and the rarefaction waves. The global solutions are constructed completely with the method of splitting delta function. In solutions, we find a new kind of nonclassical wave, which is called delta contact discontinuity with Dirac delta function in both components. It is quite different from the previous ones on which only one state variable contains the Dirac delta function. Moreover, by letting perturbed parameter $\varepsilon$ tend to zero, we analyze the stability of Riemann solutions.     

Fine structures for the solutions of the two-dimensional Riemann problems by high-order WENO schemes

The two-dimensional Riemann problem with polytropic gas is considered. By a restriction on the constant states of each quadrant of the computational domain such that there is only one planar centered wave connecting two adjacent quadrants, there are nineteen genuinely different initial configurations of the problem. The configurations are numerically simulated on a fine grid and compared by the 5th-order WENO-Z5, 6th-order WENO-??6, and 7th-order WENO-Z7 schemes. The solutions are very well approximated with high resolution of waves interactions phenomena and different types of Mach shock reflections. Kelvin-Helmholtz instability-like secondary-scaled vortices along contact continuities are well resolved and visualized. Numerical solutions show that WENO-??6 outperforms the comparing WENO-Z5 and WENO-Z7 in terms of shock capturing and small-scaled vortices resolution. A catalog of the numerical solutions of all nineteen configurations obtained from the WENO-??6 scheme is listed. Thanks to their excellent resolution and sharp shock capturing, the numerical solutions presented in this work can be served as reference solutions for both future numerical and theoretical analyses of the 2D Riemann problem.     

Wave interactions and stability of the Riemann solutions for the chromatography equations

We prove that the Riemann solutions are stable for the chromatography system under the local small perturbations of the Riemann initial data. The proof is based on the detailed analysis of the wave interactions by applying the method of characteristic analysis. It is noteworthy that both the propagation directions of the shock wave S and rarefaction wave R are unchanged when they interact with the contact discontinuity J. Moreover, the global structures and large time asymptotic behaviors of the perturbed Riemann solutions are constructed and analyzed case by case.     

Interactions of delta shock waves for the chromatography equations

This paper is devoted to the interactions of the delta shock waves with the shock waves and the rarefaction waves for the simplified chromatography equations. The global structures of solutions are constructed completely if the delta shock waves are included when the initial data are taken three piece constants and then the stability of Riemann solutions is also analyzed with the vanishing middle region. In particular, the strength of delta shock wave is expressed explicitly and the delta contact discontinuity is discovered during the process of wave interaction.     

Isothermal flow behind a shock wave propagating in the solar wind

A Parker-type blast wave, which is headed by a strong shock, driven out by a propelling contact surface, moving into an ambient solar wind having a strictly inverse square law radial decay in density, is studied. Assuming the self-similar flow behind the shock to be isothermal, approximate analytical and exact numerical solutions are obtained. There is a good agreement between the approximate analytical and exact numerical solutions. It is observed that the mathematical singularity in density at the contact surface is removed for the isothermal flow.     

Riemann problem in non-ideal gas dynamics

In this paper we consider the Riemann problem for gas dynamic equations governing a one dimensional flow of van der Waals gases. The existence and uniqueness of shocks, contact discontinuities, simple wave solutions are discussed using R-H conditions and Lax conditions. The explicit form of solutions for shocks, contact discontinuities and simple waves are derived. The effects of van der Waals parameter on the shock and simple waves are studied. A condition is derived on the initial data for the existence of a solution to the Riemann problem. Moreover, a necessary and sufficient condition is derived on the initial data which gives the information about the existence of a shock wave or a simple wave for a 1-family and a 3-family of characteristics in the solution of the Riemann problem.