VRF F system is a kind of direct evaporation refrigerant system.

多联机系统是一种直接蒸发式冷媒系统。

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In the A, B, C, D and F grading system, the first four letters are typically considered passing grades.

在 A、B、C、D 和 F 评分体系中，前四个字母通常被认为是及格。

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Northrop Grumman leads a joint venture with Raytheon to design, develop, and produce the F-22 radar system.

诺·格公司领导一个与雷声公司的合资公司，设计、开发和生产F-22雷达系统。

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Most American colleges and universities use the grading system of A,B,C,D and F.

VOA: special.2009.03.05

The A.F.L.also opposed extremists who used labor protests to change the social system.

VOA: special.2010.05.06

F. system is a nice touch, we largely suspect you'll be making a decision to buy these based on your feelings for the brand.

ENGADGET: blogger-avatar

They also failed to note that the F-35 management system was designed to track all costs associated with operations and support, whereas legacy aircraft lacked comprehensive accounting systems.

FORBES: Massive Cost Estimate For Fighter Program Is Misleading

So he curbed or cancelled more than 30 weapons systems including the army's Future Combat System, the F-22 Stealth fighter, two missile defence systems and the Zumwalt-class destroyer.

ECONOMIST: American military spending