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Translate the paragraph into Chinese.Social networking sites are an important part of life in the US. About two-thirds of American adults online use social media platforms such as Facebook, Twitter, MySpace or LinkedIn. Connecting with family members and friends is a primary consideration in their adoption of social media tools. Some media users go to these sites in order to stay in touch with current friends and family members, while others try to connect with old friends they’ve lost touch with. Sharing hobbies or interests, making new friends, reading comments by public figures and finding potential romantic partners are also among the reasons for using social networking sites. Social networking sites can also serve as information networks where people share information with other users. Instead of searching through a news source such as the website of The New York Times or ESPN that caters to all people, a person can check their Twitter account and find out about their favorite team’s scores and news.

Translate the paragraph into English.最近的调查显示，中国手机网民的数量查过电脑网民，网民的手机上网率高达85.5%。手机已成为继电视、广播、报纸、杂志之后的第五大媒体。中国人通过手机上网，享受微博、微信、播客等新媒体所带来的的便利与好处。新媒体生动、实时、互动的特点吸引了大批的年轻人。微信朋友圈让人们能够经常与朋友互动交流，而播客则满足人们表达自我、张扬个性的需要。

从反应机理推导速率方程时通常有哪几种近似方法？各有什么适用条件？

简述碰撞理论和过渡态理论所用的模型、基本假设和忧缺点。