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问题 问答题 简答题

与单侧制动相比，双侧制动有哪些优缺点？

答案

参考答案：

与单侧制动相比，双侧制动具有制动力较大，无轴承偏磨等优点。

其缺点是双侧制动需要较多的杆件，结构比较复杂，一般侧架式货车转向架不易实现；

自重较大、成本较高、检修和制造也比较麻烦。

选择题

一台家用彩色电视机正常工作时的电功率最接近于（　　）

A．1000W

B．200W

C．10W

D．1W
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单项选择题

Scientists around the world are racing to learn how to rapidly diagnose, treat and stop the spread of a new, deadly disease. SARS — Severe Acute Respiratory Syndrome — was (1) for the first time in February 2003 in Hanoi, (2) since then has infected more than 1,600 people in 15 countries, killing 63. At this (3) , there are more questions than answers surrounding the disease.

Symptoms start (4) a fever over 100.4 degrees F, chills, headache or body (5) . Within a week, the patient has a dry cough, which might (6) to shortness of breath. In 10% to 200% of cases, patients require (7) ventilation to breathe. About 3.5% die from the disease. Symptoms (8) begin in two to seven days, but some reports suggest it (9) take as long as 10 days. Scientists are close to (10) a lab test to diagnose SARS. In the meantime, it is diagnosed by its symptoms. There is no evidence (11) antibiotics or anti-viral medicines help, (12) doctors can offer only supportive care. Patients with SARS are kept in isolation to reduce the risk of (13) . Scientists aren’t sure yet, but some researchers think it’s a (14) discovered coronavirus, the family of viruses that cause some common colds.

Most cases appear to have been passed (15) droplets expelled when infected patients cough or sneeze. Family members of infected people and medical workers who care for them have been most likely to (16) the illness. But recent developments in Hong Kong suggest that the (17) might spread through air, or that the virus might (18) for two to three hours on doorknobs or other (19) Health experts say it is (20) , though, that sharing an elevator briefly with an infected person would be enough to pass the virus.

13（）

A.communication

B.transportation

C.transformation

D.transmission
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