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汽车防冻液

汽车在行驶时,发动机的温度会升得很高.为了确保安全,可用水循环进行冷却.实际上,水中往往还要加入不易挥发的防冻液(原液),加入防冻液后的混合液冬天不容易凝固,长时间开车也不容易沸腾.有关资料表明,防冻液与水按不同的比例混合,混合液的凝固点、沸点不同,具体数值参见下表(表中防冻液含量是指防冻液在混合液中所占体积的百分比).

防冻液含量/%

30

40

50

60

70

80

90

混合液的凝固点/℃

-17

-28

-37

-49

-48

-46

-28

混合液的沸点/℃

103

104

107

111

117

124

141

在给汽车水箱中加防冻液时,宜使混合液的凝固点比本地常年最低气温低10~15℃.考虑到混合液比热容的减小会影响散热效果,因此,混合液中防冻液的含量不宜过高.

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    I sat down at my desk and started writing an emotional letter of gratitude(感激). But1it came to actually placing the letter into the mailbox, I froze. I couldn't do it.

    The2was to an old teacher with whom I kept in3through Facebook comments(评论). For the past couple of weeks, her Facebook page had4me to live my life differently—for example, volunteering more.

    Her5efforts weren't huge—she wasn't building wells in Uganda or6 lepers(麻风病人)in India, but instead she was doing7, local good deeds, such as serving as an elementary school crossing guard. These were things that I could do, too. She made me8I could do the same at home. I felt I should let her9 how her example positively influenced my life. That was10I ended up handwriting the letter. But now here I was, standing before the mailbox,11to place the envelope inside. Why was this so hard to do? I thought I felt strange because it wasn't like she was my best friend. I just knew her.12, after thinking it over, I put the envelope in the mailbox at last.

    Weeks later I received a Facebook message from her. She was13a difficult time and my note meant14to her. She said she had no idea that she was making such a15to others. Not only did this letter make her happier,16her response to it increased my level of happiness as well. I decided to write a gratitude letter of17to someone each month. I've been doing this for two years now and it has changed my life greatly. I'm more likely to18out the goodness in others and I am continuously more thankful for this19life I'm living. Expressing gratitude is a great skill to20. Life is too short not to do it.