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【单选题】
Vibrations in the ground are a poorly understood but probably widespread means of communication between animals. It seems unlikely that these animals could have detected seismic 'pre-shocks' that were missed by the sensitive vibration-detecting equipment that clutters the world’s earthquake laboratories. But it is possible. And the fact that many animal species behave strangely before other natural events such as storms, and that they have the ability to detect others of their species at distances which the familiar human senses could not manage, is well established. Such observations have led some to suggest that these animals have a kind of extra-sensory perception. What is more likely, though, is that they have an extra sense—a form. of perception that people lack. The best guess is that they can feel and understand vibrations that are transmitted through the ground. Almost all the research done into animal signaling has been on sight, hearing and smell, because these are senses that people possess. Humans have no sense organs designed specifically to detect terrestrial vibrations. But, according to researchers who have been meeting in Chicago at a symposium of the society for Integrative and Comparative Biology, this anthropocentric approach has meant that interactions via vibrations of the ground (a means of communication known as seismic signaling) have been almost entirely over-looked. These re- searchers believe that such signals are far more common than biologists had realized—and that they could explain a lot of otherwise inexplicable features of animal behavior. Until recently, the only large mammal known to produce seismic signals was the elephant seal, a species whose notoriously aggressive bulls slug it out on beaches around the world for possession of harems of females. But Caitlin O’Connell-Rodwell of Stanford University, who is one of the speakers at the symposium, suspects that a number of large terrestrial mammals, including rhinos, lions and elephants also use vibration as a means of communication. At any rate they produce loud noises that are transmitted through both the ground and the air—and that can travel farther in the first than in the second. Elephants, according to Dr O’Connell-Rodwell, can transmit signals through the ground this way for distances of as much as 50kin when they trumpet, make mock charges or stomp their feet. A seismic sense could help to explain certain types of elephant behavior, One is an apparent ability to detect thunderstorms well beyond the range that the sound of a storm can carry. Another is the foot-lifting that many elephants display prior to the arrival of another herd. Rather than scanning the horizon with their ears, elephants tend to freeze their posture and raise and lower a single foot. This probably helps them to work out from which direction the vibrations are traveling—rather as a person might stick a finger first in one ear and then in the other to work out the direction that a sound is coming from. In the past decade many insects, spiders, scorpions, amphibians, reptiles and rodents, as well as large mammals, have been shown to use vibrations for purposes as diverse as territorial defense, mate location and prey detection. Lions, for example, have vibration detectors in their paws and probably use them in the same way as scorpions use their vibration detectors—to locate meals. Dr. Hill herself spent years trying to work out how prairie mole crickets, a highly territorial species of burrowing insect, manage to space themselves out underground. After many failed attempts to provoke a reaction by playing recordings of cricket song to them, she realized that they were actually more interested in her own footfalls than in the airborne music of their fellow crickets. This suggests that it is the seismic component of the song that the insects are picking up and using to distribute themselves. Whether any o
A.
the world’s earthquake laboratories were not effective in detecting seismic 'pre-shocks'.
B.
seismic signaling was the major communication form. of many animal species.
C.
those animal species can feel and understand all kinds of vibrations.
D.
all storage animal behaviors can be explained by extra-sensory perception.
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参考答案:
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【单选题】以下关于超声波的说法不正确的是:
A.
频率比声波大
B.
媒质中传播的速度比声速快
C.
强度比同振幅的声波大
D.
方向性比声波好
【判断题】服务器应该安装网络操作系统。
A.
正确
B.
错误
【多选题】关于电磁波的波速,以下说法正确的是
A.
真空中电磁波速最大
B.
电磁波在 各向异性的介质中 传播时 ,不同方向速度不同 。
C.
线性均匀介质磁导率越大,电磁波速越大 。
D.
线性均匀介质介电常数越大,电磁波速越大 。
【单选题】以下关于波长的说法,正确的是:
A.
在波的传播方向上相邻两个振动相位相同点的距离
B.
在波的传播方向上相邻两个位移相同点的距离
C.
在波的传播方向上相邻两个运动速度相同点的距离
D.
以上说法均不正确
【单选题】泥浆护壁成孔灌注桩成孔时,泥浆的作用不包括( )
A.
携渣
B.
冷却
C.
护壁
D.
防止流沙
【单选题】20 ×1年度,甲公司发生的相关交易或事项如下:(1)4月1日,甲公司收到先征后返的增值税600万元。(2)6月30日,甲公司以8 000万元的拍卖价格取得一栋已达到预定可使用状态的房屋,该房屋的预计使用年限为50年。当地政府为鼓励甲公司在当地投资,于同日拨付甲公司2 000万元,作为对甲公司取得房屋的补偿。(3)8月1日,甲公司收到政府拨付的300万元款项,用于正在建造的新型设备。至12月31日...
A.
600 万元
B.
620万元
C.
900万元
D.
3 400万元
【单选题】关于波速测试,下列说法正确的是()。
A.
压缩波的速度比剪切波慢,剪切波为初至波
B.
正、反向锤击木板两端得到的剪切波波形相位差180°,而压缩波不变
C.
压缩波传播能量衰减比剪切波慢
D.
在波形图上,以剪切波为主的部分振幅小、频率高
【多选题】以下关于波的说法正确的是:
A.
溪水潺潺,桃花尽日随水流,水流的运动是波;漂浮在一潭死水上的树叶只在原处摇曳,水的运动不是波。
B.
子弹掠空而过发出呼啸的声,超音速飞机发出的裂空之声震耳欲聋,空气的运动是波动。
C.
微波背景辐射是宇宙空间无处不在的一种电磁辐射,即各种频率的电磁波。
D.
波动是振动状态的传播,是能量的传播,是振动相位的传播。
【单选题】以下关于波速的说法不正确的是 ( )
A.
振动速度等于波速
B.
振动状态传播的速度等于波速
C.
位相传播的速度等于波速
D.
波形传播的速度就是波速
【单选题】某一公司计划建设网络系统。该网络有1台服务器,安装Windows 2000 Server 操作系统;40台工作站,安装Windows 98 操作系统,则Windows 2000 Server的许可协议应选择何种模式比较合理?
A.
选择每服务器模式
B.
选择每客户模式
C.
选择混合模式
D.
忽略该选项
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