吸收衰减是指超声波在介质中传播时,由于介质的粘滞性而造成质点之间的内摩擦,从而一部分

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问题:

吸收衰减是指超声波在介质中传播时,由于介质的粘滞性而造成质点之间的内摩擦,从而一部分声能变成热能,导致()。

A.电能的损耗

B.频率的损耗

C.波长的损耗

D.声能的损耗

考点:无损探伤工无损探伤工(技师、高级技师)无损探伤工(技师、高级技师)题库
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D

Once there lived an old man.He liked gold better than anything else in the world.He often said,“If I have enough gold,I will be the happiest man in the world.”

One day when he was traveling in the desert(沙漠),the old man lost his way.He was very hungry and thirsty,but there were only rocks and sand around him.Just then,he found a bag lying on the sand.He hoped he would find water and food in it.He took up the bag and opened it.He saw that the bag was full of gold.He was so sad that he threw away the bag and began crying.

Now the old man knew that there was something better than gold in the world.

53.The old man liked        best before he traveled in the desert.

A.food    B.bags    C.books   D.gold

54.When he lost his way,he wanted to get     .

A.some food and water       B.some rocks and sand

C.bags full of gold          D.a map

55.What did he do with the bag?         .

A.He didn't take it up          B.He brought it home

C.He threw it away            D.He cried

56.The old man didn't become the happiest man when he got the bag of gold because        .

A.the bag was too small     B.the gold wasn't his

C.he was very cold        D.he had nothing to eat.

57.In the end,the old man knew that gold was          in the world.

A.the best thing        B.not the best thing

C.the best important    D.better than anything

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下面程序段是将ROM 3000H单元内容送R7。
MOV DPTR,#3000H
CLR A
MOVC A,@R7+DPTR
MOV R7,A
错误:______
改正:______

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可与人体血液中的物质结合导致中毒的空气污染物是

A.H2

B.N2

C.CO2

D.CO

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高强度螺栓摩擦型连接中,螺栓的抗滑移系数主要与:()

A.螺栓直径有关

B.螺栓预拉力值有关

C.连接钢板厚度有关

D.钢板表面处理方法有关

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膨胀压缩机()由过滤器、差压控制阀、流量计、差压开关和压力表组成

A、报警和关断控制系统

B、密封气控制系统

C、润滑油系统

D、轴向负荷自动平衡系统

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