简约PF-环

本文首先说明简约PF－环与零可换PF－环是一致的，接着证明环R是简经RF－环当仅当对于R－的任一元r，如果x∈lR(r),则存在y∈lR（r）使得x=xy=yx，利用这一内刻划，获知正规几乎PP－环是简约PF－环，并获得简约PF－环的一些性质。     

广义Liénard系统零解的全局渐近稳定性

研究广义Liénard系统{dx/dt=y,dy/dt=-f(x,y)y-g(x),(E)零解的全局渐近稳定性,获得了该方程的零解全局渐近稳定的充分条件.     

Reverberation nulling and echo enhancement at low frequency using waveguide invariance

Based on the fact that the transfer function vector between a source receiver array and the dominant scatterer of boundary reverberation at a range can be obtained from the corresponding reverberations scattered from this range cell, a reverberation nulling concept using time reversal processing has been proposed. However, current reverberation nulling methods have certain limitations when applied into practice, which would null boundary reverberation and target echo simultaneously. As a solution, a passive reverberation nulling and echo enhancement method at low frequency using waveguide invariance is proposed in this paper. In this method, the reverberation subspace for the target range cell is not obtained directly from the return signals scattered by the target range cell but from the return signals scattered by a range cell located before the target using waveguide invariance, so as to suppress the reverberation embodied in the target echo by passive reverberation nulling. Besides, a range-dependent optimal weighting vector rather than conventional projector matrix is deduced to null the reverberation component meanwhile maximizing the target echo, thereby enhancing the echo-to-reverberation ratio furthest. Numerical simulations in typical range-independent shallow water environment demonstrate the efficacy and the improved performance of the proposed method for echo-to-reverberation enhancement.     

浅谈称重传感器的现场使用维护检修问题

文章介绍了电阻应变式称重传感器的使用特性以及使用中的故障诊断与分析,现场使用的注意事项。     

关于非幂零极大子群皆正规的有限群具有Sylow塔的注记

设G是所有非幂零极大子群皆正规的有限群,不应用群G的可解性,证明了G具有Sylow塔。     

非线性Volterra方程零解的全局渐近稳定性

利用不动点理论,研究具有可变时滞的非线性Volterra方程x′(t)=-a(t)x(t)+q(t, x(t-τ1(t)), x′(t-τ1(t)))+∫_(t-τ2(t))~t k(t, s) f(t, x(s), x′(s))ds,给出了该方程在C1空间上零解全局渐近稳定的新条件。这些新条件不需要时滞τ可微,也不要求τ′≠1。所得结论推广了已有文献中的相应结果,并给出了一个实例验证了所得结论的有效性。     

三角代数上Lie积为平方零元的非线性Jordan高阶可导映射

设U是一个 2-无挠的三角代数,D ={d_n}_n∈N是U上一个Lie积为平方零元的非线性Jordan高阶可导映射。证明了三角代数U上的每一个Lie积为平方零元的非线性Jordan高阶可导映射都是高阶导子。作为结论的应用,得到套代数或 2-无挠的上三角分块矩阵代数上的每一个Lie积为平方零元的非线性Jordan高阶可导映射都是高阶导子。     

一类拟幂等半群的构造

本文给出一类拟幂等半群──所谓带的强幂零扩张的结构定理．     

铁磁—反铁磁双层系统的零温磁矩

在线性近似下导出二维各向异性四套子格子简立方 Heisenberg 铁磁—反铁磁双层系统模型的哈密顿量,采用矩阵格林函数运动方程技术,得到自旋波的色散关系.数值计算结果表明,层间和层内耦合强度对铁磁—反铁磁双层系统的磁性质有重要影响.     

非齐次线性微分方程亚纯解的零点和极点分布

以ρ（ｇ）表示亚纯函数ｇ（ｚ）的增长级；λ（ｇ），λ（１／ｇ）分别表示ｇ（ｚ）的零点、极点序列收敛指数；λ（ｇ），λ（１／ｇ）分别表示ｇ（ｚ）的不同零点，极点序列收敛指数。