但传统的CAD系统多以单独系统设计为主要形式，具有产品设计开发周期长、资源共享性低、管理维护困难、开放性差等固有局限性。
But most conventional CAD systems are in single form, and they have much inherent limitation such as long period of product-design, bad resource sharing, hard management and low openness.
本文主要讨论我国电信网中程控交换局时钟频率维护周期的确定问题。
This article mainly addresses the maintenance period of clock frequency of SPC exchanges in China's telecommunication network.
IOC容器部分与具体业务领域相关，主要用于流程构件的实例化，生命周期的管理以及维护它们之间的依赖关系。
The IOC container section is associated with specific business domain, mainly used to complete components instantiation, management of life cycle and maintain the dependency of them.
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