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提问人：网友smiley
发布时间：2022-01-07
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How to judge a digital modulation scheme, and how to select a scheme for real world mobile communication applications？
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更多“How to judge a digital modulation scheme, and how to select a scheme for real world mobile communica…”相关的问题
第2题
Hypoxia stimulates respiration through
A、peripheral chemoreceptors
B、central chemoreceptors
C、respiratory center in medulla
D、respiratory center in pons
E、direct excitation of respiratory muscle.
第3题
We are a leading corporation _____ industrial chemicals, and would like to have the details of your products.
A、dealing in
B、in the line
C、handling in
D、specializing with
第4题
MEMORANDUM
TO: Mr. S. Wilson
DATE: 10 December, 2005
FROM: Mackintosh Smith
I have pleasure in submitting for your consideration the attached report on the redecoration and reorganization of the Sales Office.
Mackintosh Smith
THE
REDECORATION AND REORGANISATION
OF THE SALES OFFICE
As the Sales Office will soon need redecoration and reorganization to accommodate an increased number of staff, I suggest the additions and alterations(改变) detailed below. A plan is attached to the report as a guide to layout(Appendix 1), together with a color scheme(Appendix 2), and a detailed estimate of costs(Appendix 3).
1. NEW OFFICE EQUIPMENT
a) Desks. The existing desks are in good condition and can be retained. New desks will be needed for the shorthand(速记) typist who will join us shortly and for the two new sales representatives. As the desks in present use are of teak(柚木), it would maintain uniformity(一致) if similar desks were ordered.
b) Cabinets and cupboards. The office filing cabinets and cupboards are in very poor condition. It would therefore be preferable to order six new cupboards in a bright color.
One of the new circular(圆的) filing systems would prove indispensable(不可缺的) to the secretarial staff and would not take up as much space as the old filing cabinets.
c) Carpeting(铺地毯). The existing floor covering seems to be quite adequate; this gray corded(用绳索绑接的)carpeting is hard-wearing and will fit in with any color scheme.
d) Chairs, telephones and typewriters. The appearance of the office would be improved if new chairs were ordered in some bright color, the same color perhaps as the filing cabinets. These chairs should be comfortable. The three existing telephones are adequate for the needs of the office, but a new typewriter will have to be ordered before the new shorthand typist begins work.
2. OFFICE LAYOUT
I have included a diagram of the proposed layout(Appendix 1), which is self-explanatory. I should, however, like to make the following comments on the masons for my choice of layout:
a) Windows. I have made every effort to ensure that desks are placed as near to windows as possible so that all employees are aided by a certain amount of daylight. The present lighting is adequate.
b) Doors. I have placed the desks in such a way that anyone entering the office may immediately see all members of staff at work.
c) Heating. By next month under-floor electric central heating will have been installed in the entire office block. I have not proposed any air-conditioning/system as this would prove very expensive. However, electric fans could be most useful in the summer months.
3. REDECORATION
In deciding upon a color scheme (see Appendix 2) I had to consider several factors. Too much bright color would be overwhelming(压倒性的) and so I confined this to chairs and cabinets. Walls should be painted with a hard gloss(平滑) so that they can be cleaned easily, and walls and ceilings should be of a color that is light but easy on the eye.
4. ESTIMATE OF COSTS
The total estimated cost of these alterations is ￡1,750. A detailed breakdown is given in Appendix 3. I hope that the plans for the reorganization meet with your approval and that this total estimated cost does not appear to be excessive.
第5题
Genetically-modified (GM) foodstuffs are here to stay.That’s not to say that food produced by conventional agriculture will disappear, but simply that food-buying patterns will polarize: there will be a niche market for conventional foodstuffs just as there is for organic food.It may even be that GM food will become the food of preference because consumers come to appreciate the health benefits of reduced pesticide use.
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Currently there are some 20,000 chemicals in use, but the scientists only have detailed information around 1,000 of them.To see the advantages of GM food you have only to consider the recent press revelation that the average lettuce receives eleven pesticide applications before it reaches the supermarket shelf.I’m sure chemicals and their role in disease will become a big issue in the 21st century as the population of the developed world worries increasingly about its health.
The reason GM food will not go away is that we need a three-fold increase in food production by the year 2050 to keep pace with the world’s predicted population growth to ten or eleven billion.It’s not just a question of more mouths to feed either.What is often forgotten is that all these extra people will take up space, reducing the overall land available for agriculture.
The world has 800 million hungry people.Until now, food supplies have been increased by improved varieties, pesticides and artificial fertilizers: the green revolution.Now we’re on the edge of a new one: a genetic revolution.
It may well be that in the long term it is the developing world that benefits most from GM food.It is true that for the next years or so GM crops may be too expensive.
6. According to the passage, food supplies have been increased by all the following except_____________.
A.pesticides
B.artificial fertilizers
C.improved varieties
D.transportation
7.How many chemicals are still less familiar to the scientists?()
A.20,000.
B.1,000
C.19,000
D.21,000.
8.Why will people prefer GM food in the future?()
A.Because it uses less pesticides.
B.Because it is much cheaper.
C.Because the production is increased.
D.Because it is organic food.
9.Which of the following is NOT true?()
A.By 2050, the world population will grow to ten or eleven billion.
B.In the 21st century, GM food will take the place of conventional food.
C.More and more people will reduce the overall land available for farming.
D.More and more people will consume more food and occupy more space.
10.The author’s attitude towards GM food is _______.
A.negative
B.positive
C.critical
D.uncertain
第6题
Write the MATLAB codes to realize the modulation and demodulation simulations of QPSK in AWGN. Draw the BER versus SNR curve and compare the results with theoretical results.
第7题
Please explain the auto-correlation property of the PN sequence. According to the property, can you give an effective application of PN sequences in wireless communications?
