%20scale(3)'%3E%3Cpath%20id='s'%20d='M0,-30%2017.63355,24.27051%20-28.53171,-9.27051H28.53171L-17.63355,24.27051z'%20fill='%23FF0'/%3E%3C/g%3E%3Cuse%20xlink:href='%23s'%20transform='translate(300,60)%20rotate(23.036243)'/%3E%3Cuse%20xlink:href='%23s'%20transform='translate(360,120)%20rotate(45.869898)'/%3E%3Cuse%20xlink:href='%23s'%20transform='translate(360,210)%20rotate(69.945396)'/%3E%3Cuse%20xlink:href='%23s'%20transform='translate(300,270)%20rotate(20.659808)'/%3E%3C/svg%3E){kind=small}
搜索当前职位空缺：
显示过滤器
在海员简历数据库中搜索：
家 在线测试 CES 所有类型的船舶 Ch-Eng / 2nd-Eng Test about Engine department for all types of vessels (CES v6.0)
在线测试： Test about Engine department for all types of vessels (CES v6.0)
1
选择测试模式：
教育
在线测试
描述
评论 1
该测试由 80 个随机问题组成。
有关此主题的总问题： 171
有关此主题的总问题： 171
问题 1 从 80
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
When carrying LNG cargoes it is useful to have information about its thermodynamic properties. What is a common source of information that can be used to obtain values for a wide range of these properties?
A Mollier chart.
Material safety data sheet.
The cargo manifest.
The IGC code.
On a container vessel, where should a mid-bay guide be positioned?
On the tank top mid-way in 40′ guides to prevent transverse movement of 20′ containers.
On the tank top at the ends of 40′ container bays.
At the base of cell guides.
Between 20′ container bays on deck.
What is a steering wheel?
A helm used to steer the ship.
A drum for heaving of ropes.
A steering compass.
Another name for a lifebuoy.
If a seaman has to walk across a stow of cartons containing perishable foodstuffs what should he do to minimise the risk of damage to the contents? Select the most appropriate option from those given.
He should step on the edges of the cartons.
All parts of the carton are of equal strength and therefore it doesn’t matter which part he steps on.
He should step on the comers of the cartons.
He should step on the middle of the cartons.
When is a tank gas free?
A tank is only to be considered as gas free when no traces of flammable and/or poisonous gas are measured and in addition O2 content is measured to be 21 %.
A tank is only to be considered as gas free when it has been cleaned and the O2 content is measured to be 21 %.
A tank is only to be considered as gas free when it has been cleaned, ventillated and there is no smell in the tank.
A tank is only to be considered as gas free when it has been cleaned and there is no smell in the tank.
Why are all RoRo passengers ships divided into vertical “zones”?
Vertical zones are fire zones which can be divided from each other with fire doors. In case of fire, all fire doors in front and aft of the fire will be closed to prevent spreading of smoke/fire.
Vertical zones are separated with fire doors which will be closed automatically when the fire alarm start.
All vertical zones are separated with watertight doors, which will be closed in the case of a grounding, etc.
There is one fire team in each zone.
When 3 phase alternators are operating in parallel, it is very important that the reactive load is evenly shared so that the total alternator loads are evenly shared. If the total alternator load is the vector sum of active and reactive loads, which side of vector diagram (power triangle) shown represents the reactive load?
(X).
(Y).
Either (X) or (Y).
None of the mentioned alternatives.
How will you calculate transverse accelerations?
Multiply the values taken from tables 2, 3 and 4 of the Cargo Stowage and Security (CSS) Code.
Multiply the values taken from tables 3 and 4 of the Cargo Stowage and Security (CSS) Code.
From formulae given in the Cargo Securing Manual (CSM).
Rule of thumb and past experience.
You are the Officer in Charge during the loading of a tanker at a terminal in the Persian Gulf. The deck watchman reports “There is a lot of oil on the water to starboard”. What should be your FIRST action?
Tell the jettyman to stop loading immediately.
Call the Master.
Check the Oil Discharge Monitoring Equipment (ODME).
Find out if the oil is coming from your vessel.
When you are taking an “ullage” on a cargo tank on an oil tanker, what are you actually doing?
Measuring the distance from the surface of the cargo to the ullage reference point.
Measuring the distance from the bottom of the tank to the ullage reference point.
Measuring the distance from the bottom of the tank to the surface of cargo.
Measuring the distance from the surface of the cargo to the underside of the maindeck.
What colour flare is used to signal a highly dangerous landing place?
Yellow.
Orange.
Blue.
Red.
The frequency 121,5 MHz is used for:
SARSAT-COSPAS EPIRBS.
INMARSAT E EPIRBS.
SART transpondeur.
DSS VHF calls.
Normally ventilation fans in enclosed ro-ro spaces must be run continuously whenever vehicles are on board, why?
An increased number of air changes may be required when vehicles are being loaded or unloaded, or where flammable gases or liquids are stowed in closed ro-ro spaces.
It is better to run the fans continuously instead of testing the atmosphere.
It is easier for the crew, they don’t have to think about starting and stopping of fans.
The manufacturer of the fans recommends continuous operation to reduce maintenance cost.
On board a DSC-call is to be made in case of an OBS. Choose the category:
Ship’s business.
Routine.
Safety.
Don’t know.
If the heat transfer capacity in a heat exchanger is dropping, the following action should be taken:
Clean the heat transfer surface.
Increase the flowrate.
Decrease the flowrate.
Increase pressure.
When will a ro-ro vessel pitch heavily?
When wave lengths are equal to the ship’s length.
When wave lengths are equal to half the ship’s length.
When wave lengths are equal to twice the ship’s length.
In confused seas.
You have just joined a chemical tanker. Where would you find a description of the ship’s cargo handling equipment, details on the ship’s cargo unloading procedures and tank stripping and details on procedures relating to the cleaning of cargo tanks, the discharge of residues, ballasting and deballasting?
The Annex II Procedures and Arrangements Manual.
The applicable equipment manufacturer’s maintenance and operation manuals.
The Cargo Handling Logbook.
MARPOL 73/78.
What action should be taken if the heat transfer capacity of a heat exchanger operating as a lubricating oil cooler is reducing?
The heat transfer surfaces should be cleaned.
Increase the cooling water pressure.
Increase the lubricating oil flowrate.
Decrease the lubricating oil flowrate.
According to 33 CFR 156, oil tankers trading in US waters are required to test and document the testing of cargo transfer hoses and transfer pipe system. What is the minimum requirement when testing these components?
That no leakage occurs under static liquid pressure of at least 1,5 times the maximum allowable working pressure.
That no leakage occurs under dynamic fluid pressure of less than 1,5 times the maximum allowable working pressure.
That no leakage occurs at the nominal anticipated working pressure.
That no leakage occurs under static liquid pressure of at least 1,25 times the maximum allowable working pressure.
To make a “call-request” one should:
Select the telex in on-line position.
Select the ID of the NCS.
Select the telex in off-line position.
Don’t know.
In the type of fluorescent lamp system shown in the illustration, the role of the starter is to perform which of the following?
To change the ballast to a high inductive current and then divert this current through the lamp.
To create a high starting current.
To pass current through the lamp heaters and then interrupt the inductive striking current.
To switch on current through the lamp and to disconnect the ballast once the lamp has started.
Enthalpy is an expression of how much energy is tied up in one kilo of a substance. A substance’s total energy consists of:
External and internal energy.
Internal energy.
Latent energy.
External energy.
A vessel’s forward draught reading is 8,50 m a correction factor of 0,0242 m; draught marks are painted abaft the forward perpendicular. What is the corrected forward draught if the vessel is trimmed by the stern?
8,5242 m.
8,5484 m.
8,4758 m.
8,4516 m.
Which of this information must be included in a piracy attack alert?
Your ship’s name and call sign.
The number of crew onboard.
The number of pirates/highjackers.
The type of weapons being carried by the pirates/highjackers.
In which provision of the Act is the responsibility of the master for the observation of the provisions relating to supervision of maritime service stated?
In Section 6 of the Act.
In Section 3 of the Act.
In Section 2 of the Act.
In Section 1 of the Act.
What is the main requirement of a lookout posted on the bridge?
Good eyesight and able to communicate with the OOW (officer on watch).
To see changing weather patterns.
To assess ship types.
To detect new targets when they break the line of horizon.
Having a CO2 alarm during normal working hours, what immediate action should be taken?
Ignore the alarm.
Get out of the engine room as soon as possible.
Awaiting further order.
Get into the control room.
What is the purpose of the LD (low duty) compressors on an LNG carrier?
To handle the LNG boil-off vapour for fuelling the boiler.
To discharging the LNG cargo at a slow rate.
To deliver inert gas and to aid cooling down of the cargo tanks.
To transfer cargo vapour to the shore installation during loading operations.
What will you do if the heat transfer capacity is dropping, and we know that flow and heat energy corresponds to the specifications?
Add some more plates to the exchanger.
Use the “cleaning in place” arrangement to open the heat exchanger for visual inspection and manual cleaning.
Increase the pressure.
Try to increase the flow.
What is the weather associated with being in the centre of an Anticyclone (a region of High Pressure)?
Light winds and fair weather, sometimes fog.
Strong winds but with very little rain.
Strong winds and heavy rain.
Persistent rain and very humid weather.
If you use chemicals for cleaning up an oil-spill on the water, what would the chemicals do?
Contain the oil within a small area.
Disperse or dissolve the oil into the water.
Remove the oil from the water.
Absorb the oil for easy removal.
On a RoRo vessel, when loading Double Stacked containers on Maffi Trailers how many twist locks should have used between 2 containers?
One on every corner, 4 in total.
One at each end, 2 in total.
One at each end, 2 in total.
Three in total, 2 at the door end, 1 at the opposite end.
What symptom would you think shows that the freon filter drier has become blocked?
Pressure rise before the drier.
A large temperature drop across the drier.
A hammering noise from the drier.
A hammering noise from the compressors.
What is the colour of the smoke signal used by life-saving stations or rescue units indicating that distress signals are observed in daylight?
Orange.
Blue.
Yellow.
Green.
What contributes most to rust formation on vehicles/Ro-Ro units?
Cargo hold ventilation systems and associated ducting.
Pipes passing through cargo holds.
Vehicles loaded wet.
Hydraulic units in cargo holds.
Which is the “FORWARD BREAST LINE”, in the figure?
The forward breast line is indicated by B, in the figure.
The forward breast line is indicated by C, in the figure.
The forward breast line is indicated by D, in the figure.
The forward breast line is indicated by A, in the figure.
What are the compressors fitted as part of the cargo system onboard LNG carriers normally used for?
Removing boil-off gas.
Inerting and gas freeing the cargo tanks.
Discharging the cargo.
Loading the cargo.
Part of the outer surface of a refrigeration compressor crankcase and the refrigerant return line near the compressor ice up heavily during normal operation. Which of the options given is the most likely cause of this problem?
The superheat control setting for the thermostatic expansion valve is set too low.
The filter drier unit in the liquid line is partly blocked.
The seawater flow control valve for the condenser is faulty allowing insufficient cooling water flow.
The oil separator is not functioning correctly and is allowing lubricating oil to pass into the system.
At what calendar interval is a “Special Survey” required?
Beach.
Bleach.
Blanch.
Breach.
If oil out of the bowl casing drain of a solids ejecting separator what is the most likely problem?
Oil has been fed to the separator before full speed.
Insufficient amount of bowl closing water.
The sludge tank is full.
The flow rate is too high.
During duplex mode you are able to:
Interrupt.
Not to interrupt.
Talk to two stations simultaneously.
Interrupt after releasing the PTT-switch.
Give the meaning of the following symbol:
Start water-spray.
Secure lifeboat hatches.
Rescue boat with waterproof canopy.
Lower lifeboat to water.
When discussing the properties of an oil cargo, what is the “wax content”?
The percentage of paraffinic wax by volume, based on a representative sample of the crude oil.
The amount of additive in an oil product, expressed in ppm, designed to inhibit solidification at lower temperatures.
The observed volume percentage of waxy deposits found in a cargo tank after discharge in relation to the total volume of cargo previously carried.
The percentage of wax, expressed as a percentage, remaining in an oil product after distillation.
There is requirement in MARPOL for the slop tank capacity of oil tankers. What is the requirement for SBT tankers?
2 % where segregated ballast tanks or dedicated clean ballast tanks are provided in accordance with MARPOL.
3 % where segregated ballast tanks or dedicated clean ballast tanks are provided in accordance with MARPOL.
5 % where segregated ballast tanks or dedicated clean ballast tanks are provided in accordance with MARPOL.
1 % where segregated ballast tanks or dedicated clean ballast tanks are provided in accordance with MARPOL.
Which is the preferred method for starting an air conditioning refrigeration compressor which has been shut down for a period of time?
Start with suction valve throttled in to minimise risk of drawing liquid refrigerant into the compressor.
Start and stop repeatedly until suction pressure and oil pressure are normal.
Start with all system valves fully opened.
Start with the discharge valve throttled in to prevent excess condenser pressure.
The Training Manual shall contain instructions and information on the life-saving appliances and the best method of survival. The training manual shall contain detailed explanations of crew duties in relation to emergency situations. Which of the following tasks or duties shall be included in the manual according to present regulations?
The use of the ship’s line throwing apparatus.
The use of escape routes and other escape methodes.
The use of surface to air visual signals to be used by survivors.
The use of navigational equipment for survival crafts.
This circuit consists of two resistances, R1 = 6 ohm and R2 = 12 ohm, connected in series. Calculate the equivalent resistance R(S) of the two resistances.
R(S) = 18 ohm.
R(S) = 4 ohm.
R(S) = 2 ohm.
R(S) = 1,5 ohm.
Indicate the correct name for the tool:
Flexible pipe.
Water pump pliers.
Adjustable wrench.
Padlock.
Reduced capacity accompanied by vibration and noise at the suction of a centrifugal pump results from the action of vapor pockets in the fluid being pumped caused by:
Water hammer.
Cavitation.
Steam knock.
Fluid friction.
You are in open water and clear conditions. You are approaching the pilot station when you hear this signal from a vessel ahead of you. What does it signify?
That the vessel is operating astern propulsion.
That the vessel is starting his engine and resuming his passage.
That the vessel is picking up his pilot.
That the vessel is altering his course to starboard.
What is the correct name of the tool shown in the sketch?
Grinding machine.
Flat file.
Chisel.
Pliers.
What is the fog signal for a vessel which is engaged in towing?
Two prolonged blasts followed by one short blast at intervals of not more than 1 minute.
One short blast, one prolonged blast and one short blast at intervals of not more than 2 minutes.
One long blast followed by two short blasts at intervals of not more than 2 minutes.
Two prolonged blasts at intervals not exceeding 2 minutes.
According to the IMO Gas Codes, what is the minimum number of “Firemen’s outfits” required to be carried on an LNG carrier (gas tanker) with a cargo capacity above 5 000 m3?
5 sets.
3 sets.
4 sets.
2 sets.
Cargo gear/cranes should at regular intervals be thoroughly examined and load tested by a recognised company/yard. How often should such examination/load test take place?
Every 4th year.
Every 5th year.
Every 2 1/2 year.
Annually.
What is the status and function of a Panama canal pilot?
He shall have control of the navigation and movement of the vessel.
He will take over all the responsibilities of the master on embarkation.
He will be responsible for canal crew mooring gangs and use of locomotives during lock transits.
He is an advisor to the vessel’s master.
What types of fire extinguishers shall be used in the engine room?
Fire extinguishers equipped for powder or CO2 only.
Any fire extinguisher with a weight of less than 100 lbs.
Fire extinguishers filled with fresh water only.
Fire extinguishers of the handy-size types only.
According to the industry guidelines in the ISGOTT Guide and assuming terminal regulations do not require otherwise, what action should be taken to drain accumulated water from the deck during cargo handling operations in rainy conditions?
The accumulated water is to be drained periodically and the scupper plugs to be immediately closed once the water has been run off. Water containing oily residues is to be transferred to a slop tank or other suitable receptacle.
The scupper plugs are to be kept closed and sealed; any volume of water that is not contained should be allowed to flood over the fishplate.
During periods of heavy rain, it is considered prudent and safe to allow water to drain continuously; therefore scupper plugs should be removed in such conditions.
The accumulated water is to be transferred to a spare tank.
Most fruit cargoes carried under refrigeration require introduction of fresh air into the cargo space to remove any excess carbon dioxide and ethylene produced by respiration of the cargo and sensors are fitted to detect these gases. Shipper’s instructions will often indicate “constant air change” as a requirement for a cargo. Why, even though this is a crude method for controlling the cargo space atmosphere, is this type of instruction given?
It is the standard method and it is always done that way for simplicity.
Fresh air helps to acclimatise the cargo to the prevailing ambient conditions.
Some cargoes are very sensitive to ethylene levels and it may be difficult to accurately measure the low levels that would affect a cargo.
As much fresh air as possible should always be introduced into the cargo space throughout the voyage to maintain cargo quality.
When there is doubt about the freshness of the atmosphere in enclosed or confined spaces, what actions should be taken?
Arrangements should be made for testing of the atmosphere to ensure maintenance of 21 % oxygen and a carbon monoxide content below 50 ppm in the atmosphere of the space.
Supply filter masks to all crew working on ro-ro deck.
Ro-ro decks are always ventilated in advance of an operation.
Open both bow- and stern doors.
When will a hatch cover cross-joint wedge need replacement?
When the wedge is rusty.
When the flat spring is missing.
When the flat spring is bent.
When the flat spring is rusty.
What is the purpose of the unscheduled inspectors on board ships?
To determine whether the ship is seaworthy.
To issue a certificate of seaworthiness.
To issue a trading permit.
Mainly to determine whether the manning regulations have been adhered to.
On a Container vessel, what determines how containers should be lashed?
SOLAS 74/88.
Advice from shore planners.
The cargo securing manual.
OSHA regulations.
The circuit consists of two inductors, L(1) = 6 H and L(2) = 12 H, in series. Calculate the equivalent total inductance L(S).
L(S) = 18 H.
L(S) = 4 H.
L(S) = 2 H.
L(S) = 1,5 H.
Considering the range of sensitive liquid chemicals which routinely require wall-wash prior to loading, what product is mainly used as the rinsing agent in wall-washing?
Methanol.
Industrial Ethanol.
Iso-propanol.
Water.
What is the normal thickness of the primary barrier (membrane) on membrane containment type systems as used in LNG carriers?
0,7-1,5 mm.
1,5-2,0 mm.
2,0-2,5 mm.
0,2-0,5 mm.
What is the most likely reason for vibration and noise at the suction side of a centrifugal pump when it is running?
Fluid friction in the suction line.
Collapsing vapour bubbles due to cavitation.
Water hammer in the pump casing.
Pump suction valve fully open.
This circuit consists of a voltage source V, a change-over switch S, a resistor R and a capacitor C. The voltage/time figures 1 to 4 show changes in the voltage V (C) when the switch S is suddenly shifted from position 1 to 2 at time t = 0. Only one of the diagrams is correct. Which?
Figure 1.
Figure 2.
Figure 3.
Figure 4.
What are the requirements regarding slop tank capacity on combination carriers with smooth walls (bulkheads)?
Not less than 3 % of the oil-carrying capacity of the ship.
Not less than 1 % of the oil-carrying capacity of the ship.
Not less than 1,5 % of the oil-carrying capacity of the ship.
Not less than 2 % of the oil-carrying capacity of the ship.
Does the Health & Safety Executive (HSE) have authority in dealing with shipping matters?
The HSE has authority only where an interface exists between the ship and shore e. g. means of access regs. In a serious case, they would contact the local Marine Officer.
They can insist that alcohol/drug tests be carried out after an incident involving a ship or shipping.
They have exactly the same powers as that of a Marine Officer.
They have no legal responsibility over ships or shipping.
How many lifebuoys can you expect to find on board a cargo ship of 190 metres in length (including those of the quick-release system)?
At least 8 distributed on both sides of the ship.
At least 10 distributed on both sides of the ship.
At least 12 distributed on both sides of the ship.
At least 14 distributed on both sides of the ship.
High Voltage (HV) cables are smaller than low voltage cables for a given power rating. Why is this?
The HV cable carriers a smaller current and therefore requires less copper.
The HV cable uses Aluminium conductors and therefore requires them to be a smaller cross-sectional area.
The HV cable uses higher quality copper conductors and therefore requires them to be a smaller cross-sectional area.
The HV cable has a thinner wall of special insulation material.
One water fog applicator is required for each pair of breathing apparatus on board which type of ship?
Passenger ships carrying more than 36 passengers.
Chemical tankers.
Tankers.
Passenger ships fitted with car decks.
A lifejacket is so constructed that a person can correctly do it within a period of:
30 sec.
2 min.
1 min.
10 sec.
Which type of compressors is used as cargo compressors onboard gas carriers?
Oil free piston compressors.
Three stage piston compressors.
Piston, screw and centrifugal type compressors.
Three stage screw compressors.
Which of the given options characterizes a 2-stroke diesel engine?
The piston always has a short skirt.
A 2-stroke engine always has 2 or more turbochargers.
A 2-stroke engine has an air inlet valve in the cylinder cover.
A 2-stroke engine completes a full cycle every revolution.
In a smoke filled alleyway where will the cleanest air be found, and how should you proceed out?
Near to the deck, crawl out keeping your face as near to the deck as possible.
Sit and wait for the rescue party.
It will be the same in all parts, therefore I would just leave as quickly as possible.
Towards the upper part, stand as tall as possible and walk out.
A rocket parachute flare reaches an altitude of:
Not less than 300 m.
Not less than 40 m.
Not less than 180 m.
Not less than 450 m.
Which of the following is a chemical commonly added to cleaning substances used to clean galley areas?
Beach.
Blanch.
Breach.
Bleach.
Which one of the listed requirements regarding fire protected lifeboats do not correspond to present regulations? Water spray systems shall:
Have separate draining pumps of sufficient capacity.
Be arranged for flushing with fresh water and allowing complete draining.
Protect the occupants through a continuous oil fire for a period of not less than 8 minutes.
Have means for “turn on/turn off” the flow of water over the exterior of the lifeboat.
In respect of washings from the cargo area of an oil tanker, what is the maximum instantaneous rate of oil that can be pumped into the sea when a vessel is outside a special area, proceeding en route, has in operation a monitoring and control system for the discharge of oil and is located more than 50 nautical miles from the nearest land?
30 litres per nautical miles.
300 litres per nautical miles.
60 litres per nautical miles.
0,03 litres per nautical miles.
Добро пожаловать на страницу, где вы можете пройти CES тест (Crew Evaluation Test) онлайн в области "Engine Department" (специальность инженер-механик, на всех типах судов). Этот тест разработан для морских специалистов, работающих в инженерном отделе, и предназначен для помощи в им улучшить свои знания и навыки с помощью эффективного электронного обучения и оценочной тренировки.
CES тесты компании Seagull, ранее известной как OTG, представляют собой онлайновый инструмент оценки, созданный для оценки базовых знаний моряков и выявления потребностей в профессиональной подготовке в различных областях знаний, как это определено в ПДНВ.
Наши тесты охватывают различные версии, включая 4.1, 5.0, 5.1 и 6.0.0, соответствующие международным стандартам STCW. Вопросы в тесте охватывают обширный спектр тем, включая управление кризисными ситуациями, интегрированные навигационные системы, управление балластными водами, обработку и укладку грузов, управление эксплуатацией судна, морскую инженерию, техническое обслуживание и ремонт, и множество других тем.
Эта страница содержит вопросы Seagull CES, относящиеся к области "Engine Department", которые собраны из тестового симулятора как для проверки компетентности команды судна, так и для личного тестирования знаний.
Тест предназначен для инженеров-механиков, работающих на разных типах судов. Он включает в себя как теоретическую, так и практическую информацию, необходимую для работы в этой профессии. Инженер-механик на судне отвечает за техническое состояние механических систем судна, включая двигатели, генераторы, компрессоры, насосы и другое оборудование. Кроме того, механик контролирует запасы топлива, масла и воды на борту судна. Наш тест поможет вам повысить вашу профессиональную компетентность в этой области.
只有水手才能发表评论。要发表评论，请使用您的水手帐户登录该网站。
07.07.2024
ok
自动翻译