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信源信息速率是 4000bit/s，采用 QPSK传输时，如果此 QPSK调制采用了滚降系数为1的根升余弦频谱成形，那么发送信号的带宽是()kHz。
A.2
B.3
C.4
D.5
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（请给出正确答案）
A.2
B.3
C.4
D.5
答案
更多“信源信息速率是 4000bit/s，采用 QPSK传输时，如果此 QPSK调制采用了滚降系数为1的根升余弦频谱成形，那么发送信号的带宽是()kHz。”相关的问题
第4题
将英语短文译为中文
3 Self-Powered Nanotech (10分)
Nanosize machines need still tinier power plants
By Zhong Lin Wang
The watchmaker in the 1920s who devised the self-winding wristwatch was on to a great idea: mechanically harvesting energy from the wearer’s moving arm and putting it to work rewinding the watch spring.
Today we are beginning to create extremely small energy harvesters that can supply electrical power to the tiny world of nanoscale devices, where things are measured in billionths of a meter. We call these power plants nanogenerators. The ability to make power on a minuscule scale allows us to think of implantable biosensors that can continuously monitor a patient’s blood glucose level, or autonomous strain sensors for structures such as bridges, or environmental sensors for detecting toxins — all running without the need for replacement batteries. Energy sources are desperately needed for nanorobotics, microelectromechanical systems (MEMS), homeland security and even portable personal electronics. It is hard to imagine all the uses such infinitesimal generators may eventually find.
In Brief
★Nanotechnology has huge potential — but those minuscule devices will need a power source that is better than a battery.
★ Waste energy, in the form. of vibrations or even the human pulse, could provide sufficient power to run such tiny gadgets.
★ Arrays of piezoelectric nanowires could capture and transmit that waste energy to nanodevices.
★ Medical devices will likely be a major application. A pacemaker’s battery could be charged so it would not need replacing, or implanted wireless nanosensors could monitor blood glucose for diabetics.
第6题
将英语短文译为中文
2. Kin Recognition (10分)
Many organisms, from sea squirts to primates, can identify their relatives. Understanding how and why they do so has prompted new thinking about the evolution of social behavior. by David W. Pfennig and Paul W. Sherman Kinship is a basic organizing principle of all societies. Humans possess elaborate means by which to identify relatives, such as using surnames and maintaining detailed genealogies.
Mechanisms for distinguishing kin also occur throughout the plant and animal kingdoms regardless of an organism’s social or mental complexity, in creatures as diverse as wildflowers and wasps. Scientists are beginning to discover that an understanding of the origin and mechanisms of kin recognition offers fresh insights into such diverse topics as how living things choose their mates, how they learn and how their immune system works.
BELDING’S GROUND SQUIRRELS live in groups in which mothers, daughters and sisters cooperate extensively. By using odors, the squirrels can distinguish familiar nestmates, who are close kin, from nonnestmates. They can also discriminate between full sisters and half sisters.
第10题
A.新闻单位被经营者唆使对其他经营者从事诋毁商誉的行为，可与经营者构成共同的不正当竞争行为
B.经营者通过新闻发布会形势发布影响其他同业经营者商誉的信息，只要该信息是真实的，构成诋毁行为
C.诋毁行为只能是针对市场上某一特定竞争对手实施的
D.经营这对其他竞争者进行诋毁，其主观心态既可以是故意，也可以是过失
第11题
A.正确
B.错误
