| To fight a noise by making more noise
sounds strange, but that’s exactly what motor engineers are doing in Germany and
some other countries. Carmaker’s research and development laboratories have already proved that mixing more noise with the help of loudspeakers can reduce the unwanted noise. Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency (频率) mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle (周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise killing systems (系统) both inside and outside the cars. Another good t A. make a car lighter B. make a car quieter C. reduce the cost of a silencer D. improve the performance of a silencer [简答题]叙述车刀各主要角度的定义
[单选题]CRH1的风挡门不能完全关闭,其原因可能是( )。
A.红外线传感器损坏 B.自动复位机构失效 C.主电源开关损坏 D.关到位隔离开关损坏 [单选题]从事特种作业的劳动者必须经过专门培训并取得( )。
A.学历 B.特种作业资格 C.安全工作资格 [多项选择]可用于耐氯喹疟疾时控制症状治疗的有（ ）
A. 氯喹 B. 伯氨喹啉 C. 甲氟喹 D. 磷酸咯萘啶 E. 青蒿素 [单选题]（）是境内居民通过境内银行办理境内收入款项业务的必要凭证。
A.境内收入申报单 B.境外汇款申请书 C.对外付款/承兑通知书 D.境内汇款申请书 [判断题]使用手推式气体检测仪时，先打开机器，再按下收集器踏板,否则会引起机器故障。
A.正确 B.错误 [单选题]消防技术标准根据其性质可分为强制性标准和推荐性标准。()
A.是 B.否 [多选题].我国对三大改造都采取了( )方式。
A.. 区别对象 B.利用限制 C.积极引导 D.逐步过渡 [单项选择]
The terms college and university originally had very similar meanings. Only (1) the passing of centuries did "university" come to (2) an educational (3) composed of more than one college. [报关编码]稻米米糠
[判断题]强制式水冷系的冷却强度不能随发动机负荷和冷却液流量大小而变化。( )
A.正确 B.错误 [单项选择]除哪项外。均为腹痛的常见病因
A. 它病转移 B. 阳气素虚 C. 外感时邪 D. 情志失调 E. 饮食不节 [单选题]劳务分包队伍应按（ ）的书面指示，参加与其劳务作业有关的分部分项工程施工质量验收。
A.施工总包方 B.施工监理方 C.劳务质检员 D.工程建设方 我来回答: 提交
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