题目内容
（请给出正确答案）
Sometimes cooling systems have to be installed ______.
A．to keep the computer from becoming too hot
B．in order to save power
C．because they are necessary for a modern computer to work efficiently
D．to ensure the normal working of a mini-computer
安装简答题APP，拍照搜题省时又省心！
更多“Sometimes cooling systems have…”相关的问题
A.recirculating
B.total loss
C.cooling
D.refrigeration
A.Diesel oil
B.Hydraulic oil
C.Lube oil
D.Mineral oil
But weight is not the only factor. The smaller the computer the faster it can work. The signals go to and fro at a very high but almost constant speed. So if one can scale down all dimensions to, let us say, one tenth, the average lengths of the current-paths will be reduced to one tenth. So, very roughly speaking, scaling down of all linear dimensions in the ratio of one to ten also gives a valuable bonus: the speed of operation is scaled up 10 times. Other techniques allow even further speed increases.
This increase of operation is a real advantage. There are some applications in which computers could be used which require very fast response times. Many of these are military, of course; but military applications also have applications in engineering sooner or later. For example, automatic blind landing of aircraft requires continuous computer calculations which result in control of the aircraft flight. The more immediate the responses are, the more stable that control can be.
Another advantage is that less power is required to run the computer. In space vehicles and satellites this is an important matter; but even in a trial application we need not waste power. Sometimes a computer takes so much power that cooling systems which require still more power have to be installed to keep the computer from getting too hot, which would increase the risk of faults developing. So a computer which does not need to be cooled saves power on two counts.
Another advantage is reliability. Mini-computers have been made possible by the development of integrated circuits. Instead of soldering bits of wire to join separate components such as resistors and capacitors sometimes in the most intricate networks, designers can now produce many connected circuits in one unit which involves no soldering and therefore no risk of broken joints at all.
Which of the following is NOT one of the advantages of mini-computers？
A．The increase of operation speed.
B．The decrease of power needed.
C．The development integrated circuits.
D．Their reliability.
The Advantages and Disadvantages of Buying Lottery
Tomato Ripening
Tomatoes give off minute quantities of ethylene gas which is active in starting the natural ripening process. If left to nature, however, the tomatoes ripen in a random way. The trickled ethylene gas process of tomato ripening consists of exposing the tomatoes to a low concentration of ethylene gas under controlled temperature conditions in a special tomato-ripening room. This treatment initiates and controls the speed of the natural ripening and colouring process in the tomatoes.
Controlled ripening and colouring enables the grower to market tomatoes of more uniform. colour and quality than is possible with green or fieldripened produce. Timing of harvesting and marketing may, within limits, also be regulated by the use of controlled ripening and colouring in order to achieve maximum returns and make the best use of labour and equipment.
Ripening Conditions
All fruit must be mature green at harvest for controlled ripening to be successfully carried out. Relative humidity does not appear to be of great importance in the tomato-ripening process. Little moisture loss from the tomatoes occurs during the ripening process due to the relatively impermeable nature of the tomato skin. Ripening time will depend on the ripening temperature range, however, ripening temperature above 24℃will result in poor colour development with yellow or orange fruit rather than red. The heating and cooling capacity should be such that the tomatoes can be brought to the recommended ripening temperature within 24 hours.
Room Size and Construction
For efficiency and convenience in operation, on-farm, tomato ripening rooms are usually sized to accommodate the normal daily tomato pick during the peak harvest time. The room capacity is generally in the range of two to ten tonnes of tomatoes. However, larger rooms may sometimes he installed. Since the average ripening time is three or four days, tile provision of multiple rooms on the farm is generally desirable.
Air Circulation and Ventilation System
Fan-forced air circulation is required tbr adequate and uniform. temperature control and ethylene gas distribution in the ripening room. An air circulation rate of two room air volumes per minute is recommended for good results. This is equivalent to around 480 cubic metres of air per hour per tonnes of tomatoes. At the recommended heating or cooling capacity of 0. 6 to 1.2kw per tonne of tomatoes, this gives an air circulation rates are necessary to limit variations in temperature in different parts of the room to acceptable levels and to achieve an adequate rate of heating or cooling of the tomatoes.
The ventilation system circulates the room air continuously, introducing a small proportion of fresh air and exhausting a similar amount of air at the same time. This prevents a build up of ethylene gas in the room and also removes carbon dioxide produced by the fruit during respiration. If this car- bon dioxide were allowed to build up to too high a level in the room atmosphere, it would interfere with the ripening process.
Temperature Control System
The temperature of tomatoes in the ripening room has a great influence on the ripening process. In fact, the product heat load usually represents around 80% of the total heat load. The remainder is due to heat transmission through the exterual walls of the room anti the fresh air exchange rate. In some cases, both heating anti cooling are required to maintain the room temperature within the required range. The time required for ripening can be reduced to some extent by increasing the temperature. Reverse cycle air-conditioners are successfully used for both heating and cooling in tomato-ripening rooms where humidity control does not
A．Y
B．N
C．NG
For example, an atom of radioactive rubidium decays to form. an atom of strontium (another element) by converting a neutron in its nucleus to a proton and releasing an electron, generating energy in the process. The radiogenic daughter products of the decay-in this case strontium atoms--diffuse away and are lost above a certain very high temperature. So by measuring the exact proportions of rubidium and strontium atoms that are present in a mineral, researchers can work out how long it has been since the mineral cooled below that critical "blocking" temperature. The main problems with this dating method are the difficulty in finding minerals containing rubidium, the accuracy with which the proportions of rubidium and strontium are measured, and the fact that the method gives only the date when the mineral last cooled below the blocking temperature. Because the blocking temperature is very high, the method is used, mainly for recrystallized (igneous or metamorphic) rocks, not for sediments--rubidium-bearing minerals in sediments simply record the age of cooling of the rocks which were eroded to form. the sediments, not the age of deposition of the sediments themselves.
Potassium decays to form. (a gas) which is sometimes lost from its host mineral by escaping through pores. Although potassium-argon dating is therefore rather unreliable, it can sometimes be useful in dating sedimentary rocks because potassium is common in some minerals which form. in sediments at low temperatures. Assuming no argon has escaped, the potassium-argon date records the age of the sediments themselves.
Carbon dating is mainly used in archaeology. Most carbon atoms (carbon-12) are stable and do not change over time. However, cosmic radiation bombarding the upper atmospheres constantly interacting with nitrogen in the atmosphere to create an unstable form. of carbon, carbon-14.
What is the common feature of rubidium, potassium and carbon？
A．They can be made into clocks.
B．They are rich in content.
C．Their decay is slow but regular.
D．The products of their decay are the same.
SECTION B INTERVIEW
Directions: In this section you will hear everything ONCE ONLY. Listen carefully and then answer the questions that follow. Questions 1 to 5 are based on an interview. At the end of the interview you will be given 10 seconds to answer each of the following five questions.
Now listen to the interview.
听力原文：Mr. Green:While you’re here, I wish you'd have a look around the house. I had a terrible fuel bill last winter. My mother-in-law was staying with us and she wanted the temperature around 80°F all the time.
Engineer:Yes,lots of people overheat their houses. Actually 70 °F is comfortable, if you let yourself get used to it.
Mr. Green: What’s the most popular heating system used nowadays？
Engineer:The warm air system, the kind you have, has be-come more common because of economy and convenience. A heat chamber heats air, which passes through ducts and openings into the rooms by blowers or by convection. These openings are called outlets. Fitters are installed in the ducts to collect others. Fitters are installed in the ducts to collect dust. They can also control humidity to some extent. The fuel is usually coal, oil, or gas.
Mr. Green:What kind of cooling systems are used in homes？
Engineer:Either central or localized air conditioning is used. With the central system, air ducts bring cool air into the rooms. Sometimes, if the house has warm air heating, the same ducts may be used for air conditioning. This system provides an even temperature throughout the house. However, in homes which are not constructed for the central system, small individual air conditioners are installed at several windows. This is probably the easiest way. But the temperature of the rooms is quite uneven.
Mr. Green:How important is the insulation of the house？
Engineer: Very important, and sometimes this is not appreciated. The roof, for example, should have adequate insulation with glass fiber, aluminum toil, or something similar. It is important to have vapor seals on the warm side, to avoid moisture when the air cools. Double glazing of windows is also very important.
Why did Mr. Green have a terrible fuel bill last winter？
A．Because his wife overheated the house.
B．Because his mother overheated the house.
C．Because his wife’s mother overheated the house.
D．Because he overheated the house.
.
A. fresh water cooling system and sea water system
B. sea water cooling system and lubricating oil cooling system
C. fresh water cooling system and lubricating oil cooling system
D. jacket cooling system and piston cooling system
为了保护您的账号安全，请在“简答题”公众号进行验证，点击“官网服务”-“账号验证”后输入验证码“”完成验证，验证成功后方可继续查看答案！
微信搜一搜
简答题
微信搜一搜
简答题
如搜索结果不匹配，请 
