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什么是爆震燃烧？影响它的因素有哪些？画出爆震时的P-V图.

答案

参考答案：

爆震是燃烧室中末端混合气在火焰前锋面到达之前发生的自燃，在燃烧室中产生多个火焰中心，引发爆炸式燃烧反应。

造成爆震最主要有以下几点原因：

一、燃料品质

二、末端混合气的压力和温度

三、火焰前锋传到末端混合气的时间

四、表面点火

单项选择题

Questions 6 to 10 are based on the following passage: (10 分)In previous generations, young people were under their parents’ control; now the teenagechildren of the West’s richest generation were ready for something to get excited about. The Beatlessimply put a spark to a fuse (导火线) that was waiting to be lit.Everything changed, and what changed for the Beatles was their lives and their working habits,in the midst of the hysterical (歇斯底里的)following the band attracted.. Because of the demand ofthe fans to see them perform, they played bigger and bigger venues (meeting places), especially inAmerica.But John, Paul, George and Ringo became increasingly unhappy that, because of the screamingof their fans, neither the band nor the audience could hear the music. Creatively frustrated and tiredof the pressures of life under siege (围攻) from their fans, they retired from playing concerts in 1966and decided to concentrate on recording.It was from this point that the brilliance of the Beades really began to reveal itself: they wouldrecord over their career some 200 songs. Never before nor since has any recording and writing groupeven developed and yet remained the same in the way the Beades did. Their songs never lost their universal appeal thanks to the warmth and timelessness of theirmelodies and lyrics.John and Paul were powerful singers with distinctive styles. It became apparent that, despite thefact that the songwriting credits were always equally attributed to them, Paul and John wrote andsang their own songs. George also contributed two or three of his own compositions to each of theBeatles eleven albums. Even Ringo wrote and sang the occasional song.

The Beatles’outstanding qualities were really shown when( )

A．they concentrated on recording and composition

B．they played on the American continent

C．they played their own lyrics and melodies on the stage

D．they sang on the stage pop songs they wrote themselves
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单项选择题

某投资方案建设期为2年，建设期内每年年初投资400万元，运营期每年年末净收益 150万元。若基准收益率为12%，运营期为18年，残值为零，并已知(P/A， 12%，18)＝7.249 7，则该投资方案的财务净现值和静态投资回收期分别为( )。

A．109.77万元，6.33年
B．109.77万元，7.33年
C．213.80万元，6.33年
D．213.80万元，7.33年
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