The difficulty in operation increases with the age of young and full age patients but decreases with the age of old people.
青壮年时期手术难度随年龄增加而增加，老年期则随年龄增加而减少。
We think one of the important reason is the long waiting period and great difficulty in operation before being listed on domestic stock market.
我们分析这其中一个重要原因是国内证券市场上市要经过很长的等待期，并且操作难度大。
This kind of packer overcomes many disadvantages of the previous ones, such as difficulty in operation, and high possibility of not setting and not releasing.
它的研制与成功应用，克服了原来多种热采封隔器的缺点，如操作困难，不座封和不解封的几率较高等。
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