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It is hard to track the blue whale, the ocean’’s largest creature, which has almost been killed off by commercial whaling and is now listed as an endangered species. Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior. So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, monitoring its sounds. This was possible because of the Navy’’s formerly top-secret system of underwater listening devices spanning the oceans. Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies. Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption (爆发) for the first time and that they plan similar studies. Other scientists have proposed to use the network for tracking ocean currents and measuring changes in ocean and global temperatures. The speed of sound in water is roughly one mile a second -- slower than through land but faster than through air. What is most important, different layers of ocean water can act as channels for sounds, focusing them in the same way a stethoscope (听诊器) does when it carries faint noises from a patient’’s chest to a doctor’’s ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles. It can be inferred from the passage that ________.
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希赛公司有A、B两个办公大楼，两楼之间距离大于350m，信息中心在A楼三层，中心采用了三层交换机，划分了VLAN。每个楼层都设置了一个配线间，配线间到用户桌面的距离不大于90m。请回答以下问题。 【问题4】 希赛公司欲建立一套远程VPN接入办公网络，远程办公仅限于访问基于HTTP服务的邮件和公文处理系统，请问采用什么方式的VPN比较合适
B.C.G疫苗的制造是
Do you wake up every day feeling too tired, or even upset If so, then a new alarm clock could be just for you.The clock, called SleepSmart, measures your sleep cycle, and waits (1) you to be in your lightest phase of sleep (2) rousing you. Its makers say that should (3) you wake up feeling refreshed every morning.As you sleep you pass (4) a sequence of sleep states—light sleep, deep sleep and REM(rapid eye movement) sleep—that (5)f approximately every 90 minutes. The point in that cycle at which you wake can (6) how you feel later, and may (7) have a greater impact than how much or little you have slept. Being roused during a light phase (8) you are more likely to wake up energetic.SleepSmart (9) the distinct pattern of brain waves (10) during each phase of sleep, via a headband equipped (11) electrodes (电极)and a microprocessor. This measures the electrical activity of the wearer’s brain, in much the (12) way as some machines used for medical and research (13) , and communicates wirelessly with a clock unit near the bed. You (14) the clock with the latest time at (15) you want to be wakened, and it (16) duly(适时地)wakes you during the last light sleep phase before that.The (17) was invented by a group of students at Brown University in Rhode Island (18) a friend complained of waking up tired and performing poorly on a test. " (19) sleep-deprived people ourselves, we started thinking of (20) to do about it," says Eric Shashoua, a recent college graduate and now chief executive officer of Axon Sleep Research Laboratories, a company created by the students to develop their idea. 7().
For many people today, reading is no longer relaxation To (31) their work they must read letters, reports, newspapers... In getting a job or advancing in one, the ability to read and comprehend (32) can mean the (33) between success and failure. Yet the unfortunate fact is that most of us are poor readers. Most of us (34) poor reading habits at an early age, and never get (35) them. The main (36) lies in the actual stuff of language itself—words. (37) individually, words have little meaning (38) they are strung together into phrased, sentences and paragraphs. (39) , however, the untrained reader does not read groups of words. He laboriously reads one word (40) often regressing to read words or passages. Regression, the (41) to look back over (42) you have just read, is a common bad habit in reading. Another habit which (43) down the speed of reading is vocalization—sounding each word either orally or mentally (44) one reads. To (45) these bad habits, some reading clinics use a device (46) an accelerator, which moves a bar down the page at a predetermined speed. The bar is set at a slightly faster rate than the reader finds (47) , in order to "stretch" him. The accelerator forces the reader to read fast, making word-by-word reading, regression and subvocalization, (48) impossible. At first (46) is sacrificed for speed. (50) when you learn to read ideas and concepts, you will not only read faster, but your comprehension will improve.
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