两类拟线性变型方程第二边值问题整体古典解的不存在性

本文研究两类带有变化的时间方向的非线性变型方程:其中λ=0或1,而函数W(P):R→R,当|P|≥N(N>0)时W′(P)≥δ>0,当|P|相似文献   

New criteria for the existence and non-existence of limit cycles in Liénard differential systems

We provide several new criteria for the non-existence and the existence of limit cycles in Liénard differential systems. Some of these criteria generalize and improve previous ones. Their proofs are based on a general result for planar autonomous differential system that gives an upper bound for the number of limit cycles surrounding the same singular point.     

一维可压Navier—Stokes方程自由边值问题的自模解

研究黏性系数μ（ρ）=1＋θρ^θ时一维可压Navier-Stokes方程自模解的非存在性．首先通过建立能量估计式,熵估计式得到密度函数ρ的正的下界,然后对能量函数进行定量分析,利用能量爆破理论证明了θ〉0时一维可压Navier-Stokes方程不存在具有有限总能量的自模解．最后将常黏性系数Navier-Stokes方程自模解的方法推广到黏性系数依赖于密度的情形,并且把θ的范围扩展到θ〉0．