一列沿x轴正向传播的简谐横波,其振幅为2cm,波速为30cm/s,在传播过程中,

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问题:

一列沿x轴正向传播的简谐横波,其振幅为2cm,波速为30cm/s,在传播过程中,介质中相距30cm的两质点a、b,某时刻均在x轴上方距离x轴1cm的位置,此时两质点运动方向相反,如图所示.则下列说法正确的是(  )

A.b质点可能比a质点先回到平衡位置

B.a质点速度最大时,b质点速度为0

C.从此时刻起,经过1秒钟a质点运动到b位置处

D.此时a、b两质点加速度大小相等,方向相反

考点:横波与纵波波长、频率和波速
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用于磷化氢熏蒸环境中的安全监测的仪器是()。

A.毒气检测仪

B.磷化氢检测管

C.磷化氢检测仪

D.磷化氢报警仪

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报关是指进出口货物的收、发货人或他们的代理人向海关报告其进出口货物的情况,并随附有关单证申请海关审查放行的行为。()

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Want a glance of the future of health care Take a look at the way the various networks of people about patient care are being connected to one another, and how this new connectivity is being exploited to deliver medicine to the patient—no matter where he or she may be.
Online doctors offering advice based on normal symptoms are the most obvious example. Increasingly, however, remote diagnosis will be based on real physiological data from the actual patient. A group from the University of Kentucky has shown that by using personal data assistance plus a mobile phone, it is perfectly practical to send a patient’s important signs over the telephone. With this kind of equipment, the cry asking whether there was a doctor in the house could well be a thing of the past.
Other medical technology groups are working on applying telemedicine to rural (countryside) care. And at least one team wants to use telemedicine as a tool for disaster need—especially after earthquakes. On the whole, the trend is towards providing global access to medical data and experts’ opinions.
But there is one problem. Bandwidth is the limiting factor for sending complex medical pictures around the world—CT photos being one of the biggest bandwidth users. Communication satellites may be able to deal with the short-term needs during disasters such as earthquakes or wars. But medicine is looking towards both the second-generation Internet and third-generation mobile phones for the future of remote medical service.
Doctors have met to discuss computer-based tools for medical diagnosis, training and telemedicine. With the falling price of broadband communications, the new technologies should start a new time when telemedicine and the sharing of medical information, experts’ opinions and diagnosis are common.

Which of the following statements is true according to the text

A. Patients don’t need doctors in hospitals any more.
B. It is impossible to send a patient’s signs over the telephone.
C. Many teams use telemedicine dealing with disasters now.
D. Broadband communications will become cheaper in the future.

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火力发电厂中常用的顺序控制项目有哪些?

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水解α-葡萄糖苷键,可采用()

A.转化糖酶

B.麦芽糖酶

C.纤维素酶

D.杏仁苷酶

E.以上都不是

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