Ｅｌｅｃｔｒｏｌｕｍｉｎｅｓｃｅｎｔ Ｂｉｋｅ

Not long after Chris Niezrecki was hired as a professor of mechanical engineering at the University of Florida, he noticed that many students rode their bicycles around town after dark. He also noticed how hard it was to see the bikes.

A light went on in Niezrecki's head. Why not make bikesthatlight upinthe dark? Niezreckiandtwo students set to work on the idea and have now built the world's first electroluminescent bike-one that gives off light when electricity runs through it.

Niezrecki and the students glued stripes of phosphorus material to the frame and the outer edges of the bike. Then they stuck a 9-volt battery under the bike's seat and wired it to the material. When an electrical current supplied by the battery passes through the material, the phosphorus is excited and gives off light.

Niezrecki said the bright bikes can be seen easily from a distance of 180 meters. "It's just really cool." He said. "You've got thiswhole bikeandit'slitup. It'sjust really neat."

The bright bike is not commercially available yet. However, Niezreckihasbeentalking tomanufactures about mass-producing it. Existing bikes could be retrofitted with the electroluminescent material for about the same price, he estimated.

Arecentreportfrom the Insurance Institute for Highway Safety revealed that four out of ten bike-riding deaths happened between 6 p.m. and midnight. Anotherreport, publishedbythe Consumer Product Safety Commission, stated that after such accidents, motorists usually said they couldn't see the cyclist.

1. What the professor has done is _____.

A. toraise thesafetyofthe bike

B. to change the construction of the bike

C. tocontrolthespeedofthe bike

D. tomakethebikelook nicer

2. Thephosphorusmaterial can give off light _____.

A. naturally

B. only in the dark

C. whenglued tometal frame and rims

D. when excited by electricity

3. The mostimportantfeature of the new bike is that _____.

A. it is really cool and neat

B. it can beseen from adistance

C. itisbothcheap and convenient

D. it can be mass-produced

4. The phrase"beretrofitted with" (Line 3, Para. 5) most probably means _____.

A. be exchange for

B. be replaced with

C. be equipped with

D. be made fit for

5. Thelastparagraphaimsto _____.

A. point out the danger of bike-riding

B. emphasize the significance of the invention

C. show thenecessityofinsurance

D. remindmotoristsof the importance of safe riding

What Makes Popcorn Pop

The smell of popcorn popping is one that arouses the senses of both young and old andmakes the (A) mwater fora tastyhandful. It is one of the beloved snacks of all time, but where did it come from and how does it pop?

No oneknows (B) ewherepopcorn camefrom orwhen it wasfirst popped, butarchaeologists havebeen "hot" onthepopcorn trail, and theyhave found popcorn in some most unusual places. One such place was the tombs on the east coast of Peru where they found grains of popcorn that were a 1,000 years old. These grains were so well (1) pthat they still popped! Ears of popcorn were also found in the Bat Cave of West Central New Mexico that were (C) n5600 years old. Oneoftheoldestfindsof popcornwasmade in Mexico City where 80000-year-old fossilized corn pollen was found buried 200 feet below the city!Archaeologists believe that popcorn (2) oin Mexico, but they know that it was grown in China, Sumatra, and India years (3) bColumbus visited America! By the time Columbus arrived in 1492, popcorn was widespread throughout North and South America and was enjoyed by most Native American tribes.

So just? Only popcorn kernels can pop, and the (D) sis water. Each kernel contains a small (4) aof water stored in a circle of soft starch inside the hard outercasing. Whenheatedtoaround450degreesFahrenheit, the (E) mturns to steam, creating pressure within. As the pressure builds, thecasingeventually gives way, andthekernel (F) e and pops, allowing the water to escape as steam and turning the kernel inside out. If you have ever popped popcorn, you know that it explodes everywhere!

(A,B,C,D,E,F FOR CROSS, 1,2,3,4 FORDOWN. Thefirst lettersof the absents were given)

The King's Salary

After the revolution, each of the 66 citizens of a certain country, including the king, has a salary of one dollar. The king can no longer vote, but he does retain the power to suggest changes -namely, redistribution of salaries. Each person's salary must be a whole number of dollars, and the salaries must sum to 66. Eachsuggestionis voted on, and carried if there are more votes for than against. Each voter can be counted ontovote "yes" ifhis salary is tobe increased, "no" if decreased, and otherwise not to bother voting.

The king is both selfish and clever. What isthemaximum salary he can obtain for himself, and how long does it take him to get it?

上期Crossword

A. device B. landslide

C. monotor D. benefit

1. common2. erosion

3. moving4. transmit

5. vibration 6. system

上期Illation答案

The solution required 15 moves. It may be effected by moving first a white pawn, then successively two black pawns, three white pawns, three black pawns, three white pawns, two black pawns, and then one white pawn.