六西格玛的三个组成部分：6西格玛问题的解决；6西格玛设计；业务流程管理

the six sigma contains three components---- six sigma problems solving, design for six sigma, business process management. I found some black belts completed project very well and had very good impact. But the new process was difficult to maintain. maybe one year later after improvement, the process become worse. so I think the business process management is very important. is there any suggestion or material for reference.I will do appreciate it.
我见到不少成功的黑带项目，但过了一两年后，在去看原来改善过的流程或系统，比以前更糟了。所以业务流程的管理非常的重要，请兄弟姐妹，大虾提供相关的建议或资料。