题目内容

如果美联储提高联邦基金率,下面哪种情况会发生?

A. 美元在外汇市场上的价格上升
B. 投资增加
C. 总需求增加
D. 净出口增加
E. 消费支出增加

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You can`t keep these things,such as (),in your carry-on baggage.

A. a passenger
B. big scissors
C. kitchen
D. mobile phone

According to the passage, we can infer that the pole piece diameter must be tooth height.

A. as same as
B. much less than
C. much more than
D. not confirmed

what is your position (station ) in the muster lists ,for example ,during the fire fighting ,abandon vessel ,oil pollution prevention etc ?

第一组: The Wartsila 50DF operates on the lean-bum principle: the mixture of air and gas in the cylinder has more air than is needed for complete combustion. Lean combustion reduces peak temperatures and therefore NOx emissions. Efficiency is increased and higher output is reached while avoiding knocking. Combustion of the lean air-fuel mixture is initiated by injecting a small amount of LFO (pilot fuel) into the cylinder. The pilot fuel is ignited in a conventional diesel process, providing a high-energy ignition source for the main engine. To obtain the best efficiency and lowest emissions, every cylinder is individually controlled to ensure operation at the correct air-fuel ratio and with the correct amount and timing of pilot fuel rejection. Wartsila has developed a special electronic control system to cope with the demanding task of controlling the combustion in each cylinder, and to ensure optimal performance in terms of efficiency and emissions under all conditions by keeping each cylinder within the operating window. Stable and well-controlled combustion also contributes to less mechanical and thermal load on the engine components. Current stringent emission regulations demand the reduction of NOx emissions. In an internal combustion engine this means controlling peak temperature and residence time, which are the main parameters governing NOx formations. In the Wartsila 50DF engine, the air-fuel ratio is very high (typically 2.2). Since the same specific heat quantity released by combustion is used to heat up a larger mass of air, the maximum temperature and consequently NOx formation are lower. The mixture is uniform. throughout the cylinder since the fuel and air are premixed before introduction into the cylinders, which helps to avoid local NOx formation points within the cylinder. Benefiting from this unique feature, NOx emissions from the Wartsila 50DF are extremely and comply with the most stringent existing legislation.
What is the combustion feature of the Wartsila 50DF?

A. Lean air in the cylinder
B. Excessive fuel in the cylinder
C. Excessive air in the cylinder
D. Spark ignition

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