1、大学英语四级（阅读）模拟试卷 37（无答案）Section BDirections: 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.0 GPSThe Global Positioning System is a space-based
2、 triangulation system using satellites and computers to measure positions anywhere on earth. It is first and foremost a defense system developed by the United States Department of Defense, and is referred to as the “Navigation Satellite Timing and Ranging Global Positioning System“ or NAVSTAR GPS. T
3、he uniqueness of this navigational system is that it avoids the limitations of other land-based systems such as limited geographic coverage, lack of continuous 24-hour coverage, and the limited accuracies of other related navigational instruments. The high accuracies obtainable with the Global Posit
4、ioning System also make it a precision survey instrument.GPS Components: the Space Segment, the Control Segment, and the User Segment. Space SegmentThe Space Segment of the system consists of the GPS satellites. These space vehicles (SVs) send radio signals from space.The GPS Operational Constellati
5、on consists of 24 satellites that orbit the earth in 12 hours. There are often more than 24 operational satellites as new ones are launched to replace older satellites. The satellite orbits repeat almost the same ground track (as the earth turns beneath them) once each day. The orbit altitude is suc
6、h that the satellites repeat the same track and area over any point approximately each 24 hours (4 minutes earlier each day). There are six orbital planes (with four SVs in each), equally spaced (60 degrees apart), and inclined at about fifty-five degrees with respect to the equatorial (赤道的) plane.
7、This constellation provides the user with between five and eight SVs visible from any point on the earth. Control SegmentThe Control Segment consists of a system of tracking stations located around the world.The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in
8、Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute precise orbital data and SV clock corrections for each satellite. The Master Control station uploads orbital data and clock data to the SVs. The SVs then s
9、end subsets of the orbital ephemeris (星历表) data to GPS receivers over radio signals. User SegmentThe GPS User Segment consists of the GPS receivers and the user community. GPS receivers change SV signals into position, speed, and time estimates. Four satellites are required to compute the four dimen
10、sions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time distribution, and other research.Navigation in three dimensions is the primary function of GPS. Navigation receivers are made for aircraft, ships, ground vehicles, and for hand carrying by individuals.Prec
11、ise positioning is possible using GPS receivers at reference locations providing corrections and relative positioning data for remote receivers. Surveying, geodetic control, and plate tectonic studies are examples.Time and frequency distribution, based on the precise clocks on board the SVs and cont
12、rolled by the monitor stations, is another use for GPS. Astronomical observatories, telecommunications facilities, and laboratory standards can be set to precise time signals or controlled to accurate frequencies by special purpose GPS receivers.Research projects have used GPS signals to measure atm
13、ospheric parameters. GPS AccuracyAt present the system consists of 24 satellites at an altitude of about 20,000 km having an orbital inclination of 55 degrees. The orbits are almost circular and it takes 12 hours for a satellite to complete a pass around the Earth. GPS signals are broadcast from a c
14、luster of 24 or more earth orbiting satellites. Because the GPS signals are derived from the atomic frequency standards on board each satellite, they are widely used as a reference for time synchronization and frequency adjustment. The real time positioning accuracy of a single receiver is normally
15、up to 100 meters horizontally and 150 meters vertically. However, various methods have been developed which enable much higher accuracy (centimeter level). GPS ReceiversThere are a variety of different types of GPS receivers on the market for commercial and public use. Prices range from $500$30,000,
16、 reflecting the accuracy and capabilities of the instruments. For the general outdoorsman, a good GPS receiver should have 8 satellite tracking capability and be capable of receiving the GPS satellite signals through forest covering in northern Ontario shield area; for the professional user, a minim
17、um 8 satellite tracking capability, high memory capacity, differential GPS capability, and resistance to signal weakening under forest covering is essential; for the professional surveyor requiring high level precision and accuracy capability, they should assess the project or application for which
18、the technology is to be used with the help of an unbiased consultant, in order to determine the most cost effective and appropriate instrument. Navigational UnitsSmall hand held units at relatively low cost allow boaters and hikers to know their position within a few hundred meters. This accuracy is
19、 sufficient for recreational use. MappingA hand held or similar unit at mid-range price that is linked to a fixed broadcast base station. These units allow utility companies, municipalities and others to locate various items (telephone poles, waterlines, valves) with a positional tolerance of severa
20、l meters. This is suitable for some Geographical Information Systems (GIS) mapping purposes. GPS and PolicingGPS technology offers numerous benefits to law enforcement agencies of all types. For some agencies, the navigational capabilities offered by GPS enhance efficiency and safety. These navigati
21、onal applications can be used to support a variety of policing and criminal justice functions. Other agencies use GPS positioning technologies to carry out special operations or to provide enhanced personnel safety.For example, using computerized maps of their rights given by law, cooperated with GP
22、S, aviation personnel can determine location, speed and time.The positioning capabilities offered by GPS may also contribute to the success of specialized law enforcement operations such as in controlling vehicles. One such program operated in Minneapolis led to a 60% reduction in auto theft after o
23、nly one month. The automatic vehicle location systems can not only provide efficiency of response and help ensure officer safety, but also provide officer with accurate information concerning the best response route to an incident. Whats more, they can provide officers information that allows the cl
24、osest patrol officers to be dispatched to a particular incident.Advanced Transportation Management Systems (ATMS) are heavily dependant upon GPS technology to provide data about the road system. GPS allows for law enforcement personnel to clear roadway blockages to ensure the safety of motorist.Most
25、 people associate law enforcement with the prevention, reduction, and prosecution of criminal activity. In fact, a large portion of local law enforcement resources are involved in facilitating the movement of people and vehicles in a safe manner.In conclusion, large-volume commercial applications su
26、ch as cellular phones, personal communication systems, and in-vehicle navigation systems will fuel continued development of these technologies. What was ultimately the domain of the Department of Defense is rapidly becoming available for business, private, and general government use. Policing and pu
27、blic safety in general, will benefit from these market forces. It is clear that there are a number of GPS applications for policing.1 The components of GPS include _.（A）the Space Segment, the Control Segment, Navigational Units（B） the Space Segment, the Control Segment, GPS Receivers（C） the Space Se
28、gment, the Control Segment, the User Segment（D）the Space Segment, the User Segment, GPS Receivers2 GPS satellites send radio signals _.（A）from space（B） to space（C） from the earth（D）to other satellites3 What kind of data does Navigation, the primary function of GPS, involve?（A）Data of two dimensions.
29、（B） Data of three dimensions.（C） Data of four dimensions.（D）Data of one dimension.4 The highest positioning accuracy of a receiver can now reach _.（A）meter-level（B） kilometer-level（C） centimeter-level（D）millimeter-level5 GIS mapping may be done with a hand held or similar unit at _.（A）high-range pri
30、ce（B） medium-range price（C） low-range price（D）unaffordable price6 With the help of GPS, aviation personnel can find out _.（A）location, speed and time（B） time, speed and height（C） location, time and height（D）location, time and wind speed7 Thanks to the GPS system, the auto theft rate in Minneapolis h
31、ad been reduced by_.（A）fifty percent in a month（B） seventy percent in a month（C） sixty percent in a month（D）forty percent in a month8 Limited geographic coverage, lack of continuous 24-hour coverage, and the limited accuracies of other related navigational instruments are the disadvantages of_.9 The
32、 prices of various GPS receivers are determined by_.10 The accuracy of a hand held GPS unit at relatively low price is good enough for _10 Adults who had been fed plenty of fruit when they were children are less likely to suffer from certain types of cancer, British scientists said on Wednesday.A me
33、dical study of【11】4,000 men and women showed that the more fruits the adults had eaten when they were【12】the less likely they were to suffer from lung, bowel and breast cancer.“This study shows that childhood fruit consumption may have a long term【13】effect on cancer risk in adulthood,“ Dr. Maria Ma
34、ynard of the Medical Research Council in London said.All of the adults in the study had filled in a food【14】during the 1930s for a research study looking into the eating habits of families in【15 】and urban areas of England and Scotland. Maynard and her colleagues studied the medical records of the g
35、roup up to July 2000, by which time 483 cases of cancer had been【16】. In addition to fewer cases of cancer, a high consumption of fruit was【17】with a lower death rate from all causes.Fruits are loaded with antioxidants, vitamins and other nutrients, which can help to prevent genetic【18】that can lead
36、 to the development of cancer.The scientists also studied the【19】of vitamins C, E and beta carotene on cancer but they did not find any【20】 that individual antioxidants were as protective as fruit.A. impact B. efficiency C. associated D. insertE. protective F. furthermore G. decent H. diagnosedI. da
37、mage J. young K. inventory L. ruralM. nearly N. evidence O. grab11 【11】12 【12】13 【13】14 【14】15 【15】16 【16】17 【17】18 【18】19 【19】20 【20】20 In America alone, tipping is now a $16 billion-a-year industry. Consumers acting rationally ought not to pay more than they have to for a given service. So why do
38、they? The conventional wisdom is that tips both reward the efforts of good service and reduce uncomfortable feelings of inequality. The better the service, the bigger the tip.A paper analyzing data from 2,547 groups dining at 20 different restaurants shows that the relationship between larger tips a
39、nd better service was very weak. Customers who rated a meal as “excellent“ still tipped anywhere between 8% and 37% of the meal price.Tipping is better explained by culture than by economics. In America, the custom has become established; it is regarded as part of the accepted cost of a service. In
40、a New York restaurant, failing to tip at least 15% could well mean abuse from the waiter. Hairdressers can expect to get 15-20%, the man who delivers your groceries $2. In Europe, tipping is less common; in many restaurants, free tipping is being replaced by a standard service charge. In many Asian
41、countries, tipping has never really caught on at all.How to account for these national differences? Look no further than psychology. According to Michael Lynn, the Cornell papers co-author, countries in which people are more outgoing, sociable or neurotic (神经质 的) tend to tip more. Tipping relieves a
42、nxiety about being served by strangers. “And,“ says Mr. Lynn, “in America, where people are outgoing and expressive, tipping is about social approval. If you tip badly, people think less of you. Tipping well is a chance to show off.“ Icelanders, by contrast, do not usually tipa measure of their intr
43、oversion (内向) and lack of neuroses, no doubt.While such explanations may be crude, the hard truth seems to be that tipping does not work. It does not benefit the customer. Nor, in the case of restaurants, does it actually encourage the waiter, or help the restaurant manager to monitor and assess his
44、 staff. The cry of mean tippers that service people should “just be paid a decent wage“ may actually make economic sense.21 From the passage we can understand that Americans _.（A）are reluctant to give tips, but they still do so（B） like to give tips to service people to help them financially（C） are w
45、illing to give tips because they love the practice（D）are giving fewer and fewer tips22 We can learn from the third paragraph that _.（A）tips are voluntary in America（B） tipping is rare in many Asian countries（C） people dont tip in Europe（D）tipping is now popular in Iceland23 Based on Michael Lynns th
46、eory, which of the following is true?（A）Nervous people do not usually tip.（B） American people are anxious.（C） Icelanders dont like to show off.（D）People will ignore you if you tip badly.24 Michael Lynn is most probably _.（A）an economist（B） a writer（C） a psychologist（D）a sociologist25 What does the a
47、uthor think about the relationship between service and tip?（A）Bigger tips bring about better service.（B） Good service should be rewarded with tips.（C） Tips are effective in improving service.（D）Tips cannot help prompt better service.25 Its 10 pm. You may not know where your child is, but the chip do
48、es.The chip will also know if your child has fallen and needs immediate help. Once doctors arrive, the chip will also be able to tell them which drugs are not suitable for little Johnny or Janie. At the hospital, the chip will tell doctors his or her complete medical history. And of course, when you
49、 arrive to pick up your child, settling the hospital bill with your health insurance policy will be a simple matter of waving your own chip the one embedded in your hand.To some, this may sound unbelievable. But the technology for such chips is no longer the stuff of science fiction. And it may soon offer many other benefits besides locating lost children or elderly patients. It could be used as credit cards and people wont have to carry wallets anymore.On the other hand, some are already wondering what
