题目内容
A typical combustion process is the burning of gasoline in an automobile engine. The vaporized fuel is mixed with air, compressed in the engine's cylinder, and ignited by a spark. As the fuel flames up, the heat produced flows into the adjacent layer of unburned fuel and ignites it. In this way a zone of first spreads throughout the fuel mixture until the combustion wave.
The speed at which such a combustion wave travels through a fuel mixture is called the burning velocity of the mixture. The burning velocity of a gas such as methane quietly burning in air is only about one foot per second. By comparison, the burning velocity of more reactive combinations such as the rocket fuels, hydrogen and fluorine, can be hundreds of feet per second.
If the fuel flows at the same speed as the combustion wave, the result is a stationary flame, like the one in your kitchen gas burner. In the kitchen burner a jet of gas mixed with airflows from the openings in the head of the burner. If the velocity of the fuel mixture flowing from the opening is greater than its burning velocity, the flame blows out.
In jet engines speeding through the air at 500 to 600 miles per hour, the engine's flame is sometimes blown out by the blast of air entering the combustion chamber at high speeds. Jet pilots call this condition "flameout."
Combustion can sometimes occur very slowly. A familiar example of slow combustion is the drying of ordinary oil based paint. In this chemical reaction, called oxidation, the oxygen in the air reacts with the drying oil in the paint to provide a tough film. The linseed oil molecules link together, forming an insoluble coating. Another example is the hardening, and cracking of rubber with age. One way to avoid this is to incorporate certain chemicals called inhibitors into the compound.
How can the chemical reaction involved in such a quiet process as the drying of paint also produce spectacular flames and explosions？ The main difference between the two is the temperature at which they occur.
At lower temperatures the reaction must take place over a long time. The heat, which is slowly produced, is dissipated to the surroundings and does not speed up the reaction. When the heat produced 'by the low temperature reaction is retained instead of being dissipated, the system breaks into flame. This is the process that accounts for a major fire hazard, spontaneous combustion, as when oily rags suddenly burst into flame.
In a flame or explosion, the reactions are extremely fast. In many chemical processes, however, such a rapid oxidation process would be extremely destructive.
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A．Greater degree of one's contribution to work.B．Freedom to choose one's way of doing
Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
Major cultural differences in selling techniques include the relationship between the salesperson and the customer. "Cold calling", which is the relatively unannounced call or visit to a prospective customer, is virtually non existent in any countries in which there is a close and long term relationship between a salesperson and a client based on mutual trust. As one insider (内行) advises his colleagues: "In many foreign countries, personal relationships are more important than company regulations and products. Developing relationships takes time, but it is crucial (至关重要的) to the selling process."
International trade fairs have become extremely important venues for conducting business, yet very few domestically based sales organizations have an understanding of how to take advantage of the opportunities that these shows present. Unlike U.S. trade shows, at which there is an open display of one's goods and services and a lot of looking but no buying, a European trade show is relatively closed and only open those who are there to conduct business. The U.S. company often will spend a lot of money to set up an open display with personable sales people with little seniority or authority. The exhibit is saying, in effect, everyone and anyone is welcome but do not ask too many questions or expect to conduct any serious business. A comparable German exhibit will be more like a fortress (要塞) where savvy gatekeepers will quickly weed out all but the most important clients who, once allowed into the inner sanctum (内室), will meet directly with senior managers. The message that this exhibit is sending out is that only very special people are welcome and that it is privilege to be allowed to stay.
In some societies, the first thing people care about is quality ("Is it the best？"); in other societies, the first thing on a customer's mind is the cost ("How cheap is it？"); and in other countries, the concern is style. ("How does it look？"). The color, size, and quantity of items need to be considered in the packaging of any product. The color blue is for funerals in some countries, smaller items are preferred over large items, and the number of items in a package can be critical. For example, a golf ball manufacturer unknowingly packaged their golf balls in groups of four and then sent 50,000 units to their Asian distributor who promptly sent them all back, advising the manufacturer to repackage the golf balls in packages of three. In many of the countries where the golf balls were to be distributed, the number "4" was equated with death whereas the number "3" is symbolic of long life. For golfers who are known to be superstitious, the number of golf balls in each package was more important to the distributor than the quality of the product.
The relationship between the salesman and the customer is ______.
A．67%.B．76%.C．70%.D．66%.
A．Since 2002.B．Since 2003.C．Since 2004.D．Since 2005.
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