New Sound Cloak etc.

New Sound Cloak

Recently a cloaking device has been created by a scientist of the Polytechnic University in Valencia， Spain. This device achieves something never done before. It makes objects invisible to sonar. Sonar devices send out sound waves in search of objects in the dark or too far away to be seen. An object is detected when the sound waves bounce off of it and return to their source， like an echo. The new invention is the first acoustic， or sound， cloak that can hide a three-dimensional object.

The only thing it hides right now is a sphere about the size of a Ping-Pong ball. But with some modifications， an improved version of the cloak could help cities reduce noise pollution.

Such a cloaking device might also help submarines cruise through enemy waters without being detected. Submarines use sonar to see who else is in the water. The new device could prevent sound waves that bounce off of a sub from returning to their source.

In the last 10 years， engineers have been figuring out new ways to hide things. Steven Cummer is an engineer at Duke University， who did not work on the new device. But he knows about cloaking. He helped develop the first invisibility cloak for light waves. Light， like sound， travels through space as a wave. And in 2007， Cummer first proposed the idea of a similar cloak to hide objects from sonar.

参考译文

最近，西班牙巴伦西亚理工大学的科学家创造了一种隐形装置，这种装置的发明尚属首次。这种装置会使声呐定位器无法探测到物体。声呐装置通常可以通过发出声波来寻找黑暗中或者远方的物体，当声波触及物体并反弹离开，像回声那样返回到发声源头时，物体就会被探测到，而这项新发明首次使声呐无法探测三维物体成为可能。

目前被该装置所隐身的物体是一个乒乓球大小的球体，但是稍作改进，这项提高后的技术可以用于降低城市噪音污染。

这种隐形装置还可以让潜水艇通过敌方水域而安然无事。潜水艇用声呐来探测周边水域的其他舰船，而这种隐形装置可以防止声波撞击潜水艇后反弹回到声波源头。

在过去的10年中，工程师们一直在探寻新的方法来隐藏物体。美国杜克大学的工程师史蒂文·坎默虽然没有参与此项新发明，但是他了解隐身技术，他曾帮助研发了首例光波隐身物。像声音一样，光也以波浪的形式穿梭于空间。2007年，坎默首先提出了研发类似于声波隐身物、能够躲避声呐探测的隐身物体的想法。

（翻译时请注意斜体字的译法）

World's Most Accurate Clock

U.S. scientists have built the world's most （A） p clock， whose ticking rate varies less than two parts in one quintillion（百万的三次方）， or 10 （1） t better than any other， according to National Institute of Standards and Technology physicist Andrew Ludlow.

The clock， made from the element ytterbium（镱）， could be used for technological advancements beyond timekeeping， such as navigation systems， （B） m fields and temperature. "The stability of the ytterbium lattice clocks（镱晶格钟） opens the door to a （2） n of exciting practical applications of high-performance timekeeping." Andrew Ludlow said in a （C） s . However， some other said， although scientists have proclaimed that this is the world's most stable clock， they do not yet know as much about its （D） a .

While mechanical clocks use the movement of a pendulum to keep time， atomic clocks use an electromagnetic signal of light emitted at an exact frequency to move electrons in caesium（铯） atoms.

According to UK Telegraph， the physicists built the ytterbium clocks using about 10000 rare-earth atoms cooled to 10 microkelvin ， 10 millionths of a degree above （3） a zero， and trapped in an optical lattice made of laser （E） l .

（A， B， C， D， E FOR CROSS， 1， 2， 3 FOR DOWN. The first letters of the absents were given）

The Bermuda Triangle

and the Mysterious Square

The Bermuda Triangle is a place in the Atlantic Ocean where ships and airplanes supposedly disappear without a trace. In the picture below， a square appears when we rearrange the pieces of the upper triangle to form the lower triangle. The pieces in both pictures are identical. Can you explain the origin of the square？ You will need your knowledge of geometry to solve this problem.

上期答案

上期Reading Comprehension答案

1. B 2. hoard stash trap 3. D 4. C

上期Crossword答案

1. specialist 2. companies 3. object 4. problem

A. officers B. pretty C. solution D. helicopter

E. pedestrians F. electric

上期Illation答案

This is a typical algebra problem with two unknowns， and we need to have two equations to solve the problem. Let X be the number of cows， and Y the number of chickens.

The answer is： The farmer has 23 chickens （and 7 cows）.