dehydrated
purged
plugged
evacuated
第1题：
Low compressor head pressure in a refrigeration system can be caused by ___.
A.insufficient condenser cooling water
B.excessive condenser cooling water
C.air in the refrigeration system
D.excessive refrigerant in the system
第2题：
A.Increasing the size of a logical volume also increases the size of the file system
B.Reducing the size of a logical volume requires reducing the size of the file system first
C.Increasing the size of a file system requires increasing the size of the logical volume first
D.Increasing the size of a file system also increases the size of the logical volume when necessary
第3题：
Frequent ______ is important: fixing or changing faulty parts of the propulsion system when necessary.
第4题：
insufficient condenser cooling water
excessive condenser cooling water
air in the refrigeration system
excessive refrigerant in the system
第5题：
Which of the following statements is NOT true?（）
第6题：
第一组
An automatic system usually consists of a control system and an information system. A control system is a system which measures the condition of some entity and, with the information, governs the state of a variable; i.e., speed, temperature, pressure, position, etc. The open-loop system is the simplest form. a control system may assume. It is distinguished from the closed-loop system by the lack of an input which measures the state of the controlled variable; such an input is called a feedback. In modern ships the open-loop system has practically disappeared and the closed-loop system which operates with a feed-back is extensively used. An information system serves the parallel function of monitoring system or plant performance. The monitoring function may serve a number of purposes; specifically it may indicate values of controlled variables to guide remote control operations, warn of off-limit conditions and provide record of performance. In many cases a visual and audible alarm may be provided to warn of off-limit conditions on board ship and, associated with this, the important variables will be recorded on demand. The automatic control system can be more sophisticated by incorporating digital-processing equipment, that is, a computer. This computer is usually fed with signals from all sensors. It scans the values of the sensors and generates alarm signals for off-limit conditions, acting as a super-supervisor. Sometimes, it can even make necessary and take the necessary action to optimize performance without human intervention.
The closed-loop system differs from the open-loop system by
A.the lack of a feedback
B.the presence of a feed back
C.the lack of a computer
D.the presence of a computer
第7题：
Which of the following statements is NOT true?（）
AThe open field system provided a good opportunity to experiment.
BThe open field system wasted land.
CThe open field system was wasteful of labor and time.
DThe open field system made livestock farming difficult.
第8题：
When adding oil to a refrigeration system, precautions must be taken to ensure that
A.the compressor suction pressure is not too high
B.all air is purged from the pump and charging fittings
C.the high pressure cutout switch is held open to prevent accidental starting
D.the condenser is completely shutdown first
第9题：
在网络体系结构中，OSI表示（）
第10题：
adding small amounts of oil to the system
the system has been overheated
the system has been drained and then filled with new oil
the system has been idle for a long period of time