Put into use in April 2000 (=When it was put into use in April 2000), the hotline was meant for residents reporting water and heating supply breakdowns. (2005上海) 分词短语作时间状语
Blamed for the breakdown of the school computer network (=Because she was blamed for the breakdown of the school computer network), Alice was in low spirits. (2006福建) 分词短语作原因状语
Given time (=If he is given time), he’ll make a fist-class tennis player. （03北京）分词短语作条件状语
We often provide our children with toys, footballs or basketballs, thinking that all children like these things. (= and think that all children like these things.) (2006全国3) 分词短语作伴随状语
2. 有时为了强调，分词前可带when, while, if, though, as if, unless等连词一起作状语，以便使句子的意思更清楚、更连贯。例如：
When comparing different cultures, we often pay attention only to the differences without noticing the many similarities. （2006浙江）
Though tired, he still continued reading.
When compared with the size of the whole earth , the biggest ocean does not seem big at all. （04湖北）
分词部分相当于When the biggest ocean is compared with the size of the whole earth, 主语与分词是被动关系，所以用过去分词。
When comparing it with the size of the whole earth, we find that the biggest ocean does not seem big at all.
When we compare it with the size of the whole earth... 主语与分词是主动关系, 所以用现在分词。
Faced with a bill for＄10,000(=Because he is faced with a bill for＄10,000), John has taken an extra job. (2006全国2)
Whenever he was asked why he was late for class, he would answer carelessly, always saying the same thing (= and he would say the same thing). （2006江苏）
1. 现在分词有两种时态：一般式doing和完成式having done。一般式通常表示与主句的谓语动词所表示的动作同时发生或无先后；完成式则强调分词所表示的动作先于谓语动词所表示的动作。 如：
While walking in the street, we met some friends of ours.（同时发生）
Having waited in the queue for half an hour, Tom suddenly realized that he had left his wallet at home. （04北京） （“等待”先于谓语动词“意识到”）
2. 分词的否定式的构成: not +分词。 Not having received a reply, he decided to write again.