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TEXTBOOKS? YEAH, STUDENTS PRACTICE SPELLING THE NAMES AND ADDING UP THE PRICES OF THINGS IN THE CATALOGS. WAS EVERYBODY THAT THRILLED ABOUT IT? THAT'S DOUBTFUL. SAY THEY DROVE SOME SMALL STORE OWNERS OUT OF BUSINESS. SEARS AND WARD1 SOLD STUFF IN SUCH LARGE QUANTITIES. THEY WERE ABLE TO UNDERCUT THE PRICES AT SOME SMALL FAMILY OWNED STORES. 35.WHAT IS THE CONVERSATION MAINLY ABOUT? 36. WHY WAS THE WOMAN READING A CATALOG? 37.WHO WERE THE MAIN CUSTOMERS OF SEARS AND WARD'S BUSINESS? 38. WHAT UNUSUAL WAY WERE THE CATALOG USED? 39. WHAT WAS ONE OF THE NEGATIVE EFFECTS OF THE CATALOG BUSINESS? Q40-42 THE BIRDS U SEE HERE IN THIS SLIDE ARE PEREGRINE FALCONS2. THESE BIRDS REPRESENT A SUCCESS STORY AMONG ANIMALS ON THE ENDANGED SPECIES LIST.. IN THE 1970S, THE PEREGRINE FALCONS ALMOST DISAPPEARED AS A RESULT OF THE CONTAMINATION OF THE FOOD CHAIN BY THE DDT IN PESTICIDE4. THE PRESENCE OF THE POISON IN THEIR SYSTEMS RESULTED IN EGGS TOO WEAK TO SUPPORT THE INCUBATING CHICKS. THEIR REMARKABLE5 RECOVERY IS A RESULT OF THE BAN OF DDT AS A PESTICIDE, AGGRESSIVE CAPTIVE FEEDING PROGRAMS AND THEIR OWN RESILIENCY. THE PEREGRINE FALCON3 IS ONE OF THE FASTEST BIRDS ALIVE. THEY'VE BEEN CLOCKED AT 140 TO 200 MILES PER HOUR IN SUCCESSFUL PURSUIT OF PRAY. IN ADDITION TO SPEED, THESE BIRDS FLY DIRECTLY INTO HEAD WINDS AND THEY ARE CAPABLE OF FLYING MORE THAN 600 MILES PER DAY WITH FAVORABLE TAIL WINDS. TODAY WITH THE SOPHISTICATION OF TELEMETTY, THE SPEEDS OF THESE BIRDS CAN BE TRACKED BY ORBITING SATELLITES, BY MEANS OF TRANSMITTERS ATTACHED TO THE BIRD. FOR EXAMPLE , PEREGRINE FALCONS STAGE IN WARMER CLIMATE, IN OTHER WORDS,THEY SPEND TIME IN THE SOUTHERN US OVER CHANGES PREPARING THEM TO BREED IN THE ARCTIC. THEN THEY MIGRATE NORTH TO THE MUCH COLDER ARCTIC REGIONS. BIRDS HAVE BEEN TRACKED FROM TEXAS IN LATE APRIL TO THEIR NESTING GROUND IN ALASKA, CANADA AND GREENLAND. NOW LET'S MOVE ON TO ANOTHER SPECIES OF BIRDS, THE BALD EAGLES. 40 WHAT IS THE TALK MAINLY ABOUT? 41.ACCORDING TO THE PASSAGE, WHAT MAKES THE PEREGRINE FALCON A GOOD HUNTER? 42. HOW DID BIOLOGISTS TRACK PEREGRINE FALCONS OVER LONG DISTANCES? Q43-46 OK, SO IN OUR LAST CLASS WE WERE DISCUSSING BIG BANDS SWING MUSIC.,U REMEMBER THIS WAS A KIND OF DANCE MUSIC WITH A STEADY RHYTHM. BUT TODAY WE DEAL WITH MUSIC PLAYED BY SMALLER JAZZ BANDS. IT'S CALLED BEBOP MAY USE ALL SORTS OF NEW TYPES OF RHYTHMS, SOME OF THEM VERY IRREGULAR. WE'LL TALK MORE ABOUT THAT LATER. BUT FIRST I WANT TO TALD ABOUT SOME OF THE SOCIAL ELEMENTS THAT I BELIEVE CONTRIBUTED TO THE DEVELOPMENT OF BEBOP MUSIC. TO DO THIS, WE HAVE TO LOOK AT WHEN BEBOP AROSE AND STARTED BECOMING SO POPULAR,WHICH WAS FROM THE LATE 1930S THROUGH THE 1940S, FROM THE TIME OF THE ENVIRONMENT FOR BEBOP MUSIC WAS THE DECLINE OF THE US ECONOMY. DURING THE GREAT DEPRESSION. THE ECONOMY SUFFERED TREMENDOUSLY. AND FEWER PEOPLE HAD MONEY TO SPEND ON ENTERTAINMENT. THEN DURING THE 2ND WORLD WAR THE GOVERNMENT IMPOSED A NEW TAX ON PUBLIC ENTERTAINMENT, WHAT U MIGHT CALL PERFORMANCE TAX. THE GOVERNMENT COLLECTED MONEY ON PERFORMANCES THAT INCLUDED ANY TYPES OF ACTING,DANCING OR SINGING, BUT NOT INSTRUMENTAL MUSIC. SO TO AVOID THIS NEW TAX, SOME JAZZ BANDS STOP USING SINGER ALTOGETHER. THEY STARTED RELYING ON THE CREATIVITY OF THE INSTRUMENTALIST TO ATTRACT AUDIENCES. THIS WAS WHAT BEBOP BANDS DID. NOW REMEMBER A LOT OF BANDS HAVE SINGERS. SO THE INSTRUMENTALISTSSIMPLY PLAYED IN THE BACKGROUND AND HAD OCCASIONAL SOLOS WHILE THE SINGER SANG THE MELODY TO THE SONGS,BUT NOT BEBOP BANDS. SO THE INSTRUMENTALISTS HAD MUCH MORE FRREDOM TO BE CREATIVE. SO THEY EXPERIMENTED, PLAYING THE MUSIC FASTER AND USING NEW IRREGULAR SORTS OF RHYTHMS. 43.WHAT IS THE TALK MAINLY ABOUT? 44. HOW DIDI THE BEBOP BANDS AVOID THE PERFORMANCE TAX? 45 WHY DOES THE PROFESSOR MENTION THE DECLINE OF THE US ECONOMY DURING THE GREAT DEPRESSION? 46. WHAT DOSE THE PROFESSOR DESCRIBE AS A SIGNIFICANT CHARACTERISTIC OF BEBOP MUSIC? Q47-50 UR PROFESSOR HAS ASKED ME TO TALK TO U TODAY ABOUT THE TOPIC THAT SHOULD BE OF REAL CONCERN TO CIVIL ENGINEERS: THE EROSION OF THE US BEACHES. LET ME START WITH SOME STATISTICS. DID UKNOW THAT 90% OF THE COAST IN THIS COUNTRY IS ERODING6, ON THE GULF7 OF MEXICO FOR INSTANCE, EROSION AVERAGES 4 TO 5 FEET PER YEAR. OVER THE PAST 20 YEARS, THERE HAS BEEN AN INCREASE IN BUILDING ALONG THE COAST, EVEN THOUGH GEOLOGISTS8 AND ENVIRONMENTALISTS HAVE BEEN WARNING COMMUNITIES ABOUT PROBLEMS LIKE EROSION. SOMEWAY COMMUNITIES HAVE TRIED TO PROTECT THEIR BUILDING AND ROADS AND TO BUILD SEAWALLS. HOWEVER GEOLOGISTS HAVE FOULD THAT SUCH STABILIZING9 STRUCTURE ACTUALLY SPEED UP THE DESTRUCTION OF THE BEACHES. THESE BEACHES WITH SEAWALLS, CALLED STABILIZED10 BEACHES, ARE MUCH NARROWER THAN BEACHES WITHOUT THEM. U MAY WONDER HOW SEAWALLS SPEED UP BEACH LOSS. THE EXPLANATIONS IS SIMPLE.IF THE FLOW OF THE BEACHES IS GENTLE, THE WATER ENERGY IS LESSENED11 AS IT WASHES UP ALONG THE SHORE. IT IS REDUCED EVEN MORE THAT RETURNS TO THE SEA SO IT DOESN'T CARRY BACK MUCH SAND. ON THE OTHER HAND, WHEN THE WATER HIT THE NEARLY VERTICAL12 FACE OF THE SEAWALL. IT GOES STRAIGHT BACK TO THE SEA WITH THE FULL FORCE OF ITS ENERGY AND IT CARRIES BACK A GREAT DEAL OF SAND. BECAUSE OF THE REAL RISK OF LOSING BEACHES, MANY GEOLOGISTS SUPPORT A BAN ON ALL TYPES OF STABILIZING CONSTRUCTION ON SHORE LINES. 47. WHAT IS THE SPEAKER MAINLY DISCUSSING? 48. WHY DO COMMUNITIES BUILD SEAWALLS? 49. HOW DOES A GENTLY SLOPING BEACH HELP PREVENT EROSION? 50.WHAT WOULD THE SPEAKER PROBABLY ADVISE ENGINEERS TO DO? 点击收听单词发音
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