Boundedness of economic variables and Olech's theorem

On the basis of Olech's theorem we derive conditions on which any solution path starting from an arbitrary initial point in a two-dimensional bounded region ultimately converges to a unique equilibrium point without escaping from the region during a transition period. Then, using the result, we render one proposition more exact from the economic point of view.I would like to thank two anonymous referees for valuable comments and advices. Remaining errors are, of course, wholly due to myself.     

Significant Issues for the Future of Product Innovation

What's happening in the world of product innovation? What are the tough issues that managers are facing? And what's going to happen in the remaining years of this decade? In this article, several members of the Editorial Board of The Journal of Product Innovation Management offer their ideas about where the important problems lie. This is the fodder for a good round table discussion and through the medium of this journal we'll engage in such a discussion in this and a subsequent issue.     

程控交换机全数字音信号及多频信号设计方法

本文以新型数字交换机系统为背景,提出了全数字音信号和多频互控信号的设计方法。讨论了电路原理、编码方式,电平设计和脉冲信号的时序关系。最后给出了电原理图和试验数据结果。     

锁相同步技术在不间断电源中应用的几个问题

本文研究了三种相位反馈控制方案,讨论了它们应用的条件和应注意的问题。实验结果对进一步改进UPS电源的性能有实际价值。