[外语类试卷]大学英语四级改革适用(阅读)模拟试卷190及答案与解析.doc
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1、大学英语四级改革适用(阅读)模拟试卷 190及答案与解析 Section A 0 It is common for new students to share a room with other university students. The number of roommates will depend upon the university, but will【 C1】 _anywhere from one to three. The most【 C2】 _setting is for two students to share one room. The room will have
2、beds, desks, closets and storage compartments(drawers)for personal items. The【 C3】 _will be plain but adequate. A key to【 C4】 _in your studies is a good understanding and a positive relationship with your roommate. You will need to learn your roommates【 C5】_and activities in order to have a positive
3、 experience from the beginning. Your roommate may become your close friend or you may not spend much time together. It all【 C6】 _on you and your roommate. Respect your roommates possessions and privacy and ask your roommate to do the same for you. Some roommates are very【 C7】 _and some are not. A go
4、od rule to go by is “If you value something, keep it out of sight and under lock and key.“ This will keep your roommate from being【 C8】_to take something that belongs to you. If you discover that your schedule and your roommates schedule【 C9】 _and you have little time to study, you will find the lib
5、rary a nice quiet place to get away and study. Some【 C10】 _are not very quiet and if you need a quiet place to study, you may need to go to the library. A intimate B. tempted C. success D. furnishings E. conflict F. loyal G. dormitories H. succeeds I. gracefully J. common K. depends L. schedule M. r
6、ange N. discharged O. trustworthy 1 【 C1】 2 【 C2】 3 【 C3】 4 【 C4】 5 【 C5】 6 【 C6】 7 【 C7】 8 【 C8】 9 【 C9】 10 【 C10】 Section B 10 GPS A)The Global Positioning System is a space-based triangulation system using satellites and computers to measure positions anywhere on earth. It is first and foremost a
7、 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. The uniqueness of this navigational system is that it avoids the limitations of other land-based systems such as limited
8、 geographic coverage, lack of continuous 24-hour coverage, and the limited accuracies of other related navigational instruments. The high accuracies obtainable with the Global Positioning System also make it a precision survey instrument. GPS Components: the Space Segment, the Control Segment, and t
9、he User Segment. B)The Space Segment of the system consists of the GPS satellites. These space vehicles(SVs)send radio signals from space. The GPS Operational Constellation consists of 24 satellites that orbit the earth in 12 hours. There are often more than 24 operational satellites as new ones are
10、 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 such that the satellites repeat the same track and area over any point approximately each 24 hours(4 minutes earlier each day). There a
11、re 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. This constellation provides the user with between five and eight SVs visible from any point on the earth. C)The Control Segment consists
12、 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 Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute preci
13、se 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 send subsets of the orbital ephemeris(星历表 )data to GPS receivers over radio signals. D)The GPS User Segment consists of the GPS receivers and the user
14、community. GPS receivers change SV signals into position, speed, and time estimates Four satellites are required to compute the four dimensions of X, Y, Z(position)and Time. GPS receivers are used for navigation, positioning, time distribution, and other research. Navigation in three dimensions is t
15、he primary function of GPS. Navigation receivers are made for aircraft, ships, ground vehicles, and for hand carrying by individuals. Precise positioning is possible using GPS receivers at reference locations providing corrections and relative positioning data for remote receivers. Surveying, geodet
16、ic control, and plate tectonic studies are examples. E)Time and frequency distribution, based on the precise clocks on board the SVs and controlled by the monitor stations, is another use for GPS. Astronomical observatories, telecommunications facilities, and laboratory standards can be set to preci
17、se time signals or controlled to accurate frequencies by special purpose GPS receivers. Research projects have used GPS signals to measure atmospheric parameters. F)At present the system consists of 24 satellites at an altitude of about 20,000 km having an orbital inclination of 55 degrees. The orbi
18、ts are almost circular and it takes 12 hours for a satellite to complete a pass around the Earth. GPS signals are broadcast from a cluster 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
19、 a reference for time synchronization and frequency adjustment. The real time positioning accuracy of a single receiver is normally up to 100 meters horizontally and 150 meters vertically. However, various methods have been developed which enable much higher accuracy(centimeter level). G)There are a
20、 variety of different types of GPS receivers on the market for commercial and public use. Prices range from $500 to $30,000, 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 rec
21、eiving the GPS satellite signals through forest covering in northern Ontario shield area; for the professional user, a minimum 8 satellite tracking capability, high memory capacity, differential GPS capability, and resistance to signal weakening under forest covering is essential; for the profession
22、al surveyor requiring high level precision and accuracy capability, they should assess the project or application for which the technology is to be used with the help of an unbiased consultant, in order to determine the most cost effective and appropriate instrument. H)Small hand held navigational u
23、nits at relatively low cost allow boaters and hikers to know their position within a few hundred meters. This accuracy is sufficient for recreational use. A hand held or similar mapping unit at mid-range price that is linked to a fixed broadcast base station. These units allow utility companies, mun
24、icipalities and others to locate various items(telephone poles, waterlines, valves)with a positional tolerance of several meters. This is suitable for some Geographical Information Systems(GIS)mapping purposes. I)GPS technology offers numerous benefits to law enforcement agencies of all types. For s
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