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The tiny Isle of Man in the Irish Sea is not known as a vanguard of technology, but this month it was to serve as the test bed for the highly acclaimed third-generation mobile phones. A subsidiary of British Telecom (BT), the British phone company, cobbled together a network and prepared to hand out prototype mobile handsets to about 200 volunteers. But problems arose in the software that keeps track of each call as it moves from one tower’s range to another’s. BT postponed the trial until late summer, after a similar delay announced a few weeks earlier by NTT DoCoMo in Japan. What’s the big deal? Aren’t thousands of mobile calls “handed off” every day from one “cell” to another without a glitch? They are indeed. But third-generation technology, or 3G, is so radically new that it requires a rethinking of just about every aspect of how mobile phones work, from the handset to the transmission masts to the software that runs them. For this reason, 3G are a massive engineering and construction project that will take years to complete and cost hundreds of billions of dollars. The magnitude of this effort has somehow been forgotten in the mad scramble to be first out. The handover problem is a case in point. When you talk on a conventional mobile phone, your call is beamed as a continuous stream of digital data to the nearest receiver. The technology for handing these calls off from one area to the next was worked out years ago. But a 3G phone is different it bundle up the data into little packets and sends them through the airwaves, one at a time. This creates the impression of an Internet connection’s being”always on,” which is good news. But keeping rack of these data bundles from one region to the next is a daunting engineering problem — and, more to the point, a brand-new one. NEC, the Japanese phone company that supplies BT with equipment for its Isle of Man trail, hasn’t had time to work it out. Handset makers also have work to do. The 3G technologies have so many features; only a wonder gizmo could handle all of them, which is why none exists. The phones are not only supposed to work with 3G networks but also with the less sophisticated ( but cheaper and more useful) General Packet Radio Service (GPRS) technology already being installed on the continent and also with the current mobile phone standard, Global System for Mobile (GSM). Phones for corporate executives are also supposed to adapt to dozens of other standards around the world. Doing all this requires powerful, custom-built computer chips, which are tough to make quickly. A device that does so many things is bound to guzzle a lot of power. Prototype 3G phones drain so much juice that they’ve been known to get uncomfortably hot. Batteries that can keep a conventional phone running for days would fizzle in a 3G handset in a matter of minutes. Engineers are searching for alternative, but at the moment the lack of a long-lasting battery is a major hurdle. None of these problems is insurmountable, but neither will they be resolved quickly. Analysts at Forrester Research in the Netherlands predict that even in 2005, when more than half of Europe’s phones will be connected to the Internet, fewer than 15 percent of them will use 3G. That’s a measure of this technology’s complexity and immaturity.
下列病毒感染后可引起胎儿畸形的是（）
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下列关于“价值”概念的理解，符合作者原意的一项是（ ）。
从制定的方法来看，制定企业定员的方法主要有（）。
下列选项中符合办事公道的是（）
（）是计算机信息网络安全员培训的核心。
女，63岁，高血压史20年，近2年纳差，夜尿增多，10天前出现胸闷、恶心、呕吐、纳差，尿量减少。400～500ml／d。血压22／14kPa，心率94次／分，早搏3～4次／分，肺无异常发现，下肢浮肿，血尿素氮20mmol／L，血肌酐445μmol／L。尿密度1．015g／cm3，尿蛋白2g／L。其少尿的原因最可能是（）。
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