题干

如图,以点O为圆心的两个圆中,大圆的弦AB切小圆于点C,OA交小圆于点D,若OD=2,tan∠OAB=
1
2
,则AB的长是____

上一题 下一题 0.0难度 选择题 更新时间:2018-10-27 12:16:23

答案(点此获取答案解析)

8

同类题2

配对阅读:下表左栏是五个人物介绍,右栏是家电用品介绍,请根据每个人对家电用品需求,为他们选择合适的家电用品。

( B )

____Bob is often late for school because he always gets up late. This makes his teacher mad. He needs to buy something to wake him up in the morning.

____Tim likes listening to music when he is free. And he has to send e-mails to his customers every day. He wants to buy something that can help him.

____Summer has come. Tony is fat and he can't sleep well on such hot days. This troubles him a lot. He'd like to buy something to make him feel cool.

____Alice often washes her hair late at night. It is often wet when she goes to bed. She is going to buy something that can dry her hair in a short time.

____Susan is a housewife. She has to do the washing for her family every day. She gets tired of it. She is in need of a product to do it for her. 

A. This electric product can make you cool during the hot days. It can help you change the temperature and control the humidity(湿度)of your room.

B. You can do many things with this product, such as sending e-mails, playing games, getting on line and so on. You can also listen to music with it when you want to relax.

C. This electric product is useful to all of us. People often have one at home. It is often put up on the wall. If you want to know the time, just take a look at it.

D. This can help you wash your dirty clothes and dry them. What you need to do is to turn it on and later hang the clothes on the line. With this electric product, life will be a lot easier for you.

E. Each family needs this product. You can use it to store meat, vegetables, fruits, drinks and medicine. It can keep them cool and fresh so that they will not go bad easily on hot days.

F. It is a very helpful product which tells you the time. It can wake you up with a piece of music any time you want, but you have to set the time first.

G. When you wash your hair, you need this product. It can make your wet hair dry in a minute. It can also be used for drying your wet clothes or some other wet things.

同类题3

阅读下面的文字,完成小题。

石化工匠张恒珍

安蓓

    她是中专学历,却发明了以她的名字命名的裂解装置分离系统操作法,参与完成重大科技攻关项目20多项,提出并参与解决影响裂解装置长周期运行效率的瓶颈问题136项,为企业直接创造效益6100万元,书写了石化行业大国工匠的传奇。

    她就是全国优秀共产党员、中国石油化工集团公司茂名分公司首席技师张恒珍。

    1994年,中专毕业的张恒珍被分配到茂名石化裂解车间工作。“第一次打开装置流程图的时候,管线上标注的各种标识,我都读不懂。”说起刚开始工作时的状态,张恒珍形容自己是白纸一张。“学习铁人精神,争做最优秀的石化工人。”张恒珍暗下决心。

    立志容易践行难。裂解装置是乙烯生产的“龙头”,操作条件苛刻,高温时达摄氏1200度、低温达摄氏零下165度,压力达13.2兆帕,工艺流程非常复杂,仅控制参数就有1.2万多个。如何把重要而“敏感”的装置操作技术吃透?倔强的张恒珍铆足了劲,硬是把十几本技术资料啃下,摘抄的笔记本摞起来有两尺多高;为了熟记工艺流程,她天天“泡”在现场,110米的乙烯塔,她说爬就爬,令所有男同事目瞪口呆;塔里61层塔盘的分布和设计情况,如数家珍;为了不放过任何一个细微的变化,她常常在操作台前一坐就是三四个小时。    “大家都说张恒珍是一台复印机。”回忆起当年的学习情景,和张恒珍一起进裂解车间的职工史建波说,“当时经常考试,张恒珍的试卷几乎和标准答案一模一样。”1996年茂名乙烯开工前,张恒珍就已成为裂解装置第一位“问不倒”的“活流程”。如今,张恒珍不但是“活流程”,还是“全流程”,百万吨乙烯装置的8个岗位,她都能进行操作;裂解车间12000多个岗位参数,她绝大多数都记得。

    “把每个指标都当作工艺品去雕琢”。在茂名石化流传着一个“传奇”——张恒珍保持着“零差错”的操作纪录!张恒珍面对的裂解装置是最“敏感”最“桀骜不驯”的,稍有不慎,反应器就会“飞温”,导致装置停车。但张恒珍当班时,碳二加氢反应器却总是出奇地“温驯”,从没出现影响生产和产品质量的情况,张恒珍因此成为当之无愧的碳二加氢最佳“操盘手”。

    22年,40多万次操作,她始终保持着零差错的纪录,为1号裂解装置连续运行79个月,2号裂解装置连续运行1369天,分别创出国内长周期新纪录和连续运行最长纪录立下了汗马功劳。

    2004年12月,我国首套国产化大乙烯装置投入使用。如何驾驭这套开先河的国产化裂解装置?张恒珍主动请缨,运用十多年的积累,查出制约装置安全生产的瓶颈问题105项,发现了影响正常运行的仪表问题556个。

    2007年3月,投用仅半年的国产装置出现一个令人揪心的问题:脱甲烷塔塔顶带乙烯,导致乙烯产品不合格。张恒珍一次次到现场检查,对一个个操作参数反复调试。终于,她找到了处理问题的突破口。经过优化的脱甲烷塔塔顶温度趋于稳定,每年增效高达3542万元。

    为了让工友少走弯路,张恒珍结合自己多年的心得和经验写成《茂名乙烯“1#裂解装置分离系统张恒珍操作法”》。这套操作法如今已成了茂名石化工人解决日常操作难题的“宝典”。她还编写了近8万字的工艺培训教材,并担任培训班教师,将绝技倾囊授予青年工人。

    面对外企和民企的高薪聘请,她始终不为所动,二十年如一日坚守岗位。“守着装置,心里才踏实。”这是一位石油工匠最朴实的心里话。