正确答案: B

等温淬火

题目：一般螺丝刀要求硬度高，耐磨性好、韧性好时，最好采用的热处理是( )。

解析：B

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举一反三的答案和解析：

[单选题]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?

Excessive air in the cylinder

[单选题]开始装货时，()应首先检查确认所有与装载有关的阀，均己处在正确的开关位置。

船上负责的船员

[单选题]除非未到达相应配电盘所必须，配电板馈线的布置应避免穿过______。

厨房

[单选题]亚共析钢的室温平衡组织是( )。

F+P

[单选题]在GMDSS的设备工作要求中，船舶在航行期间对EPIRB和SART的定期试验时间分别为_____。

三个月和一个月

[单选题]油船进行油类作业时，制溢油应急计划所采取的应急措施中，双方商定的联络信号以()为主。

受方

[单选题]两船中的一船应给另一船让路时，另一船应________。

C均可采取

[单选题]墨卡托海图的比例尺是：()

B或C