无缝线路当轨温变化10℃时，钢轨内部就会产生约重量的温度力，要重点防范换轨、放散作业风险（）

A. 163

B. 192

C. 24.78

D. 49.56

A．80.（45480）50kg/m不能伸缩的钢轨，当轨温变化10℃时，钢轨内产生_______的温度力。 参考答案：约163kN

B．：约163kN

此题为判断题(对，错)。

A．30%

B．40%

C．50%

D．60%

A. 100

B. 1

C. 1.4

D. 1/100

天然气和空气混合，当天然气浓度在一定范围内时，遇明火就会发生燃烧和爆炸。燃烧时，燃烧波的传播速度较慢，约0.3～2.4m/s，而爆炸时，会迅即产生高压高温，波速达到1000～3000m/s，对管线和容器的破坏力很大。天然气产生爆炸的浓度范围为5～15％，随温度、压力升高，爆炸浓度的上限提高，爆炸范围扩大。Natural gas and air mix, when the concentration of natural gas within a certain range, open fire will occur combustion and explosion. In combustion, the propagation speed of combustion wave is slow, about 0.3 ~ 2.4m/s, while in explosion, the high pressure and temperature will be generated immediately, and the wave speed reaches 1000 ~ 3000m/s, which is very destructive to pipelines and containers. The explosion concentration range of natural gas is 5 ~ 15%. With the increase of temperature and pressure, the upper limit of explosion concentration increases and the explosion range expands.