三维拟线性热弹性力学方程区域内部解的奇性传播规律

本文利用频率分析对角化的方法,研究了三维拟线性热弹性力学方程区域内部解的奇性传播规律.首先从微局部观点出发,利用仿微分算子和拟微分算子将方程仿线性化和对角化.然后,利用穿梭法和经典的双曲方程和抛物方程理论,证明了区域内部解的奇性传播也是沿耦合方程组的双曲算子的零次特征带传播,并且当初值的奇性沿方程组的双曲算子的前向光锥传播时,时间t也具有很好的正则性.     

微伸缩的热弹性力学方程组柯西问题解的奇性传播

用频率分析对角化的方法,研究了一维线性微伸缩的热弹性力学方程组柯西问题解的奇性传播规律.首先从微局部观点出发,利用拟微分算子将双曲抛物的耦合方程组弱解耦.然后利用经典的双曲抛物方程理论和穿梭法,证明了柯西问题解的奇性传播具有有限传播速度、解的奇性沿双曲算子的零次特征带进行传播.     

仿Fourier积分算子在非线性奇性传播中的应用

本文应用文献[1,2]中建立的仿Fourier积分算子概念以及仿微分算子的EropoB定理,对主型的仿微分算子进行微局部化简。并由此建立它们的奇性传播定理,然后用此定理讨论非线性方程解的低频奇性传播。     

一类具非正则奇性的拟微分算子的局部可解性和奇性传播

近年来已有许多人对具重特征的正则奇性拟微分算子进行研究;尤其对Fuchs型方程更有了较多的结果.但是对非正则奇性的情况讨论甚少.本文研究一类具重特征的非正则奇性双曲拟微分算子.根据此类算子的特性,可以微局部地化简为非Fuchs型的情况;即如下形式的算子     

关于实效双曲算子的Cauchy问题解的C~∞-奇性分析

本文讨论了较大一类实效双曲算子的 Cauchy 问题的解在边界上重特征点附近的 C~∞-奇性传播情况.为此先找一个保持 Cauchy 问题形式不变的典则变换进行微局部化简,然后用拟基本解工具展开讨论.结果表明,尽管实效算子的Cauchy 问题的适定性与低阶项无关,但解的奇性在边界上重特征点附近出现分叉传播现象,且它紧密联系低阶项的性质.由本文结果就可研究所论算子的 Lax-Nirenberg 型的边界奇性反射问题.     

有限级Fourier积分算子及其应用Ⅱ

本文继续讨论有限级Fourier 积分算子。在建立了这类算子的基本运算规则以后,我们证明了一般拟线性方程(包括非主型的方程)的解的奇性传播定理。并将这个结果应用于讨论一个非线性混合型方程与一个无旋定常流方程的解的奇性分析,得到了相应的奇性传播的结论。     

微分特征列法在拟微分算子和Lax表示中的应用

微分特征列法用于拟微分算子和非线性发展方程Lax表示的计算.首先,利用微分特征列法和微分带余除法计算拟微分算子的逆和方根,由于不必求解常微分方程组,并将解代入,因此,使得计算得以简化.其次,利用微分特征列法,约化从广义Lax方程和Zakharov-Shabat推出的非线性偏微分方程,并得到相应的非线性发展方程.在Mathematica计算机代数系统上,编写了相关程序,从而可以利用计算机辅助完成一些非线性发展方程Lax表示的计算.     

一类热弹性板的空间衰减估计

研究了二维空间中半无限带形区域上一类含有双调和算子的热弹性系统板解的空间性质.首先构造一个能量表达式,然后利用微分不等式技术,推导出该能量表达式是可由它本身的一阶导数控制的微分不等式,最后得到解的空间衰减估计.该结果可看成是Saint-Venant原则在双曲抛物耦合双调和方程组上的应用.     

一类Fuchs型方程的椭圆正则性定理

本文研究了一类锥Sobolev空间上的Fuchs型方程的解的性态,利用Bony的仿微分算子理论的方法,运用仿积、仿复合、仿线性化等工具,并结合Mellin象征的性质,得到了此类方程的椭圆正则性定理.推广了在经典Sobolev空间中的椭圆正则性结果.     

Banach空间超线性算子方程的多解定理及其应用

本文利用两对平行上下解,讨论了一类超线性算子方程的多解的存在性,得到了六解定理和七解定理.文中所得结果本质地改进了著名的Amann三解定理.作为应用,考虑了二阶微分方程组,得到了新的结论.     

Propagation of singularities in Cauchy problems for quasilinear thermoelastic systems in three space variables

By using microlocal analysis, the propagation of weak singularities in Cauchy problems for quasilinear thermoelastic systems in three space variables are investigated. First, paradifferential operators are employed to decouple the quasilinear thermoelastic systems. Second, by investigating the decoupled hyperbolic-parabolic systems and using the classical bootstrap argument, the property of finite propagation speeds of singularities in Cauchy problems for the quasilinear thermoelastic systems is obtained. Finally, it is shown that the microlocal weak singularities for Cauchy problems of the thermoelastic systems are propagated along the null bicharacteristics of the hyperbolic operators.     

On a local in time solvability of the Neumann problem of quasilinear hyperbolic parabolic coupled systems

We prove a local in time existence theorem of classical solutions to some coupled system of quasilinear hyperbolic equations and quasilinear parabolic equations with Neumann boundary condition. This coupled system contains a non-linear thermoelastic equation as an important physical example.     

Propagation of Singularities of Solutions to Hyperbolic‐Parabolic Coupled Systems

In this paper, the authors study the propagation of singlarities for a semilinear hyperbolic‐parabolic coupled system, which comes from the model of thermoelasticity. Both of the Cauchy problem and the problem inside of a domain are considered. We obtain that the microlocal singularities of solutions to the semilinear hyperbolic‐parabolic coupled system are propagated along null bicharacteristics of the hyperbolic operator by using the theory of paradifferential operators. Furthermore, for the Cauchy problem of the semilinear coupled system, if the initial data have singularities at the origin, we prove that the solutions have the same order regularity with respect to spatial variables as in hyperbolic problems in the forward characteristic cone issuing from the origin, which improves the previous results for semilinear systems in thermoelasticity.     

Propagation of singularities for Cauchy problems of semilinear thermoelastic systems with microtemperatures

The propagation of singularities of solutions to the Cauchy problem of a semilinear thermoelastic system with microtemperatures in one space variable is studied. First, by using a diagonalization argument of phase space analysis, the coupled thermoelastic system with microtemperatures will be decoupled microlocally. Second, using a classical bootstrap argument, the property of finite propagation speed of singularities for the semilinear thermoelastic system is obtained. Finally, it is also shown that the microlocal weak singularities propagate along the null bicharacteristics of the hyperbolic operators of the coupled semilinear system (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Global classical solutions for a class of quasilinear hyperbolic systems

In this paper we investigate the mechanism of singularity formation to the Cauchy problem of quasilinear hyperbolic system.Moreover, we present some examples to show some significant problems.     

Pseudo‐reflection phenomena for singularities in thin elastic shells

We consider problems of statics of thin elastic shells with hyperbolic middle surface subjected to boundary conditions ensuring the geometric rigidity of the surface. The asymptotic behaviour of the solutions when the relative thickness tends to zero is then given by the membrane approximation. It is a hyperbolic problem propagating singularities along the characteristics. We address here the reflection phenomena when the propagated singularities arrive to a boundary. As the boundary conditions are not the classical ones for a hyperbolic system, there are various cases of reflection. Roughly speaking, singularities provoked elsewhere are not reflected at all at a free boundary, whereas at a fixed (or clamped) boundary the reflected singularity is less singular than the incident one. Reflection of singularities provoked along a non‐characteristic curve C are also considered. Copyright © 2003 John Wiley & Sons, Ltd.     

CONSTRUCTION OF SOLUTIONS TO M-D RIEMANN PROBLEMS FOR A2×2 QUASILINEAR HYPERBOLIC SYSTEM

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Continuity of solutions of a quasilinear hyperbolic equation with hysteresis

This paper is devoted to the investigation of quasilinear hyperbolic equations of first order with convex and nonconvex hysteresis operator. It is shown that in the nonconvex case the equation, whose nonlinearity is caused by the hysteresis term, has properties analogous to the quasilinear hyperbolic equation of first order. Hysteresis is represented by a functional describing adsorption and desorption on the particles of the substance. An existence result is achieved by using an approximation of implicit time discretization scheme, a priori estimates and passage to the limit; in the convex case it implies the existence of a continuous solution.     

A thermoelastic system of memory type in noncylindrical domains

In this paper, we consider a hyperbolic thermoelastic system of memory type in domains with moving boundary. The problem models vibrations of an elastic bar under thermal effects according to the heat conduction law of Gurtin and Pipkin. Global existence is proved by using the penalty method of Lions.     

Exact controllability of nodal profile for 1‐D first order quasilinear hyperbolic systems with internal controls

For 1‐D first order quasilinear hyperbolic systems without zero eigenvalues, based on the theory of exact boundary controllability of nodal profile, using an extension method, the exact controllability of nodal profile can be realized in a shorter time by means of additional internal controls acting on suitably small space‐time domains. On the other hand, using a perturbation method, the exact controllability of nodal profile for 1‐D first order quasilinear hyperbolic systems with zero eigenvalues can be realized by additional internal controls to the part of equations corresponding to zero eigenvalues. Furthermore, by adding suitable internal controls to all the equations on suitable domains, the exact controllability of nodal profile for systems with zero eigenvalues can be realized in a shorter time.