If the two media have really different densities, like air and water, then most of the energy is going to be reflected back, very little of it will keep going and get transmitted into the new medium.

而如果这两种介质的密度相差较大，就像空气和水那样，那么大部分的能量将会折射回来，只有一小部分会继续传播进入到新的介质中。

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All large and medium-sized Chinese cities will have greater air quality monitoring by 2010, says a government official.

一位政府官员表示，到2010年，中国所有大中型城市的空气质量监测都将得到加强。

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The result indicates that the sound speed of gas liquid two phase flow is much lower than single phase liquid or air medium.

结果表明：气液二相流音速比单相液体或空气介质低得多，流动机构对音速变化有显著影响。

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The self-guided Russian R-77 medium-range air-to-air missile is almost as good as the U.S. AIM-120 AMRAAM.

CENTERFORSECURITYPOLICY: Center For Security Policy

So if the C919 is to be commercially viable, COMAC needs to get the plane up in the air on or close to its ambitious schedule while the market for medium-range aircraft remains hot.

FORBES: China's Aviation ABCs: Airbus, Boeing, and COMAC

These include: eight sophisticated diesel submarines, advanced SU-30 fighter aircraft, modern air-to-air and air-to-surface weapons, supersonic anti-ship cruise missiles and as many as 350 short- and medium-range ballistic missiles.

CENTERFORSECURITYPOLICY: Back on the China Front