38. 实对称矩阵A为正定矩阵的充要条件是A的特征值全为正。 ( ) 正确错误

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38. 实对称矩阵A为正定矩阵的充要条件是A的特征值全为正。 ( )
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14[翻译题] The Birth of Rock In some ways, the origin of rock and roll can be traced to a rivalry between two economic organizations in the music industry: ASCAP and BMI. The American Society of Composers, Authors, and Publishers (ASCAP) were formed in 1914 to guarantee that its members received a fee for the playing of their songs. ASCAP'right to collect this fee from the radio stations stood one court test after another.ASCAP charged each radio station a blanket amount to use its material. In 1941 it announced a 100 percent fee increase. Radio stations refused to go along, and as a result all songs protected by ASCAP were taken off the air. This included the work of many of the popular songwriters of the time and left radio stations with little music. The dispute was settled, at least temporarily, towards the end of 1941, but by that time radio stations had begun to rely on music provided by a new guild of composers. Broadcast Music, Incorporated (BMI), was formed to scout for fresh talent who could provide radio stations with music. This became increasingly important as more stations switched to the deejay format.BMI were looking for a new sound. The sound they found was rock and roll. By the mid1950's BMI was a powerful force and so was the new sound. In 1956 the Anti-Trust Committee of the House Judiciary Committee investigated BMI's domination of the recording industry. Songwriter Billy Rose, an ASCAP member, outlined BMI's role in the rise of rock and roll. Not only are more of the BMI song junk, but in some cases they are obscene junk pretty much on the level with dirty comic magazines… It is the current climate on radio and TV which makes Elvis Presley and his animal posturing possible… When ASCAP's songwriters were permitted to be heard,Al Joslon,Nora Bays, and Eddie Cantor were all big salesmen of songs. Today it is a set of untalented twitchers and twisters whose appeal is largely to the zootsuiter and the juvenile delinquent. But of course there was much more to it than that. Rock and roll had come at a time when young people were finding it difficult to relate to the likes or Doris Day and Patti Page. There had been too many “adult”bands and too many tired crooners. Youth now wanted a sound of its own something new, different, and vital. Rock was actually a blend of country music and rhythm and blues(R&B) that was popular among black people during the early 1950's.But record producers suspected that national white audiences would never idolize a black popular singer, no matter how much they liked the R&B beat. Sam Phillips, a lawyer and former disco jockey who formed Sun Records in the early 1950s,was a tireless researcher. He drove all over the South looking for new talent and promoting his records.“What I need,”he said, unabashedly,“is a white boy who can sing colored.” In 1954 he found him. Elvis Presley recorded “That's Alright Mama”,and the song enjoyed moderate success on the country music charts. Within two years Presley became the Sinatra of the 1950s, and by the end of the decade, the older generation was explaining to the young that Sinatra had been the Elvis Presley of the 1940's. The father of rock and roll was Cleveland Deejay Alan Freed, who had started mixing R&B songs with Al Martino and Frank Sinatra records as early as 1951 on W/W. It was he who coined the term rock and roll to make R&B palatable to his white audience. In 1954 Freed moved to WINS in New York, where his Moodog's Rock and Roll Party was an instant success. WINS was soon the number one station in New York. Freed helped introduce Bill Haley's “Rock around the Clock”,the first rock and roll single to reach the top of the charts. The Blackboard Jungle, a film about juvenile delinquency, featured “Rock around the Clock”as part of the soundtrack. The pulsating, uninhibited new sound was linked with restless, rebellious youth. Young people flocked to the screen to see that film and others in a similar vein. Radio, movies, and print media all contributed to the rise of rock and roll as the king of popular music. “Rock around the Clock”was the bestselling song of 1955.In 1956 Elvis Presley had five of the year's 16 best sellers, including the number one and number two records,“Don't Be Cruel” and “Heartbreak Hotel”.I was one of the millions of kids who stood in front of the mirror with a plastic guitar and tried my best to imitate his wild pelvic movements. Dick Clark's American Bandstand sent the latest songs out to millions of America's teenagers. Many artists like Frankie Avlon, Fabian, Paul Anka, Bobby Dorin, and Bobby Rydell used the dance show as a stepping stone in their careers. Every one of them was a teenage idol in the mold of Sinatra and Presley; all made millions of dollars and were worshiped everywhere they went. But none surpassed Presley; he remained “the King”.Though he died in 1977, his music and the impact it had on American youth will be felt for decades to come. Another change that happened during the 1950's was the disappearance of the 78——rpm discs that had taken over from Edison's cylinders. The 78s were too large and too breakable, so they were replaced by the smaller, more durable 45—rpm records. Teenagers could pick up a couple of dozen of these and take them to a “sock hop”.This helped records and the music to become an important part of the youth culture. Despite the anguished pleas of the older generation and of songwriters like Billy Rose, rock and roll was here to stay. Translation: Rock was actually a blend of country music and rhythm and blues (R & B) that was popular among black people during the early 1950's. 河南理工大学

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