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A.错
B.错
C.正确
D.错
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更多“The cellular system configuration for mobile communications is proposed by a. Hua Wei, b Ericssion c…”相关的问题
A、Stimulate cellular metabolism
B、Bone growth
C、Development of the brain and nervous system
D、Secrete thyroid-stimulating hormone
A、对
B、对
C、对
D、错
Consider a cellular system with cell radus R, cluster size K, and distance between two adjacent BSs d, the distance between two nearest co-channel cells can be calculated by a.
. b.
. c.
.. d.
.
A、对
B、错
C、错
D、对
B．Bone growth
C．Development of the brain and nervous system
D．Secrete thyroid-stimulating hormone
A．which
B．whereas
C．such as
D．is also
A．has matured B．has setup its standards C．is very much in the early development stages D．is in use A．is being developed B．already appeared C．will not appear D．will start to appear A．super fast downloads B．small data requirements for IoT C．4G system has already satisfied these needs D．an enormously wide variation in the requirements
CDMA for cellular system can be described as follows. As with FDMA, each cell is allocated a frequency （71） , when is split into two parts, half for reverse (mobile unit to base station) and half for （72） (base station to mobile unit). For full-duplex （73） , a mobile unit both reverse and forward channels. Transmission is in the form. of direct-sequence spread （74） , which used a chipping code to increase the data rate of the transmission, resulting is an increased signal bandwidth. Multiple access is provided by assigning （75） chipping codes to multiple users, so that the receiver can recover the transmission of an individual unit from multiple transmissions.
A.ware
B.signal
C.bandwidth
D.domain
But specialized mobile radio, as it is known, has been rediscovered. It is now considered one of the biggest prizes in the all-out war for the public airwaves. The reason: high-tech companies have figured out how to profitably rebuild the antiquated dispatching system into an advanced cellular-telephone network that can take on the likes of AT&T and the giant Baby Bells. Upstart Nextel Communications sent shock waves through the industry last week when it agreed to buy Motorola's SMR frequencies for $1.8 billion.
That could pose a serious threat to cellular hegemony. Although both systems are based on the same basic technology, SMR systems are digital and cover almost 25 times as much area as the average cellular network. SMR handsets won't work on cellular systems and tend to be bulkier than cellular phones, though they provide more features, like a digital pager service. And while cellular growth has tripled to some 13 million subscribers since 2000, the technology has been losing ground. It is running out of channel capacity so fast, in fact, that 40% of cellular calls in high-density areas like Manhattan and Los Angeles fail to be completed. SMRs have capacity to spare, and service could eventually be priced 10% to 15% less than cellular. Dispatchers predict they will have at least 10 million subscribers by the end of the decade. There are now about 1.5 million users of SMRs.
The addition of another contender to an already crowded field of telephone systems will surely multiply the confusion. By the year 2010, consumers will be able to choose from at least half a dozen vendors of a dizzying array of wireless-communications services, including pagers, voice mail answering machines and cellular phones. Phone and cable television operators, such as Bell South, MCI and Cox Enterprises, are developing so-called personal communications networks, or PCNs, a highly advanced portable-phone system that is expected to cover a wider area, connect to a greater variety of services and be cheaper to operate than conventional cellular.
And many companies that have gambled on the wrong technological standards, and invested billions trying to develop the same markets, will undoubtedly lose a great deal of money before the shakeout is over. "The winners", says Nextel chairman Morgan O'Brien, "will be those who can make the choice for consumers easy". With all the anticipated confusion—mindful of the early years of personal computers—it is likely to be years before anyone calls the purchase of wireless products an "easy" choice.
How did mobile radio systems find its business competitiveness？
A．Its technological features have radically changed.
B．It has been rebuilt to cater to various subscribers.
C．Its dimensions have been reduced by wide margins.
D．It was connected to a greater variety of services.
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The passage is most likely to be _________.
A.n announcement in a museum
B.an advertisement in a newspaper
C.a leaflet from a travel agency
D.a guide for smart phone
Which of the following statement is NOT true of Consumer Cellular？A.You can save money with easy plans
B.You can ask for your special discount
C.You can change or cancel your plan at any time for no reason
D.You can change your existing phone number with a little cost
The advantage of Post-Paid Billing is _________.A.there are Family Shared Use Plans
B.there is no-obligation return and nothing to lose
C.there is no worry of using up or reloading minutes
D.there is a variety of phones to select
The underlined word ship in Paragraph 6 probably means_________ .A.send
B.carry
C.make
D.copy
From the passage we know that Consumer Cellular is_________ .A.a new cell phone
B.a wireless service
C.a consumers association
D.an educational website
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With an in vitro culturing technique, researchers are deciphering how biochemical agents regulate the secretion of prolactin, the pituitary hormone that promotes milk production. The cultured cells survive for as long as a month, and they do not require serum, a commonly used culture ingredient that can influence cellular function and confound study results. One primate pituitary gland may yield enough cells for as many as 72 culture dishes, which otherwise would require as many animals.
The other technique allows scientists to monitor cellular differentiation in the reproductive tracts of female monkeys. While falling short of the long-sought goal of developing an in vitro model of the female reproductive system, the next-best alternative was achieved. The method involves transplanting oviduct tissue to an easily accessible site under the skin, where the grafted cells behave exactly as if they were in their normal environment. In about 80 percent of the grafts, blood vessels in surrounding abdominal skin grow into and begin nourishing the oviduct tissue. Otherwise, the tissue is largely isolated, walled off by the surrounding skin. A cyst forms that shrinks and swells in tandem with stages of the menstrual cycle. With about 80 percent of the grafts re-establishing themselves in the new site, a single monkey may bear as many as 20 miniature oviducts that are easily accessible for study. Because samples are removed with a simple procedure requiring only local anaesthesia, scientists can track changes in oviduct cells over short intervals. In contrast, repeated analysis of cellular changes within the oviduct itself would require abdominal surgery every time a sample was taken--a procedure that the animals could not tolerate.
Scientists are using the grafting technique to study chlamydia infections, a leading cause of infertility among women. By infecting oviduct tissues transplanted into the abdominal skin of rhesus monkeys, researchers hope to determine how the bacteria cause pelvic inflammatory disease and lesions that obstruct the oviduct. Such research could eventually lead to the development of antibodies to the infectious agent and a strategy for producing a chlamydia vaccine.
This passage deals primarily with ______.
A．reproductive organs of nonhuman primates
B．diseases of the pituitary glands
C．in vitro studies of pituitary hormones
D．techniques for studying hormonal reactions
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