问题 单项选择题

关于针状成像板的描述,错误的是()

A.属于结构化的存储荧光体

B.成像板的厚度可显著减小

C.荧光的传播方向性更好

D.影像锐利度更高

E.X线吸收效率显著增加

答案

参考答案:B

解析:结构化存贮荧光体(针状成像板)是在严格控制温度、压力和机械条件下,形成的大致垂直于基板的长条晶体棒或针状物。针状结构有许多优势,最明显的是,针状阵列能够保持自身产生的发光沿针形传播,从而有助于保持影像锐利度。另外,因为针状物是从基板生长出来的,不需要任何黏合剂。这意味着有效层内几乎都是荧光体,因此在同等厚度的荧光层时,针状结构可以显著增加(约两倍)X线吸收。荧光层还可以制作得更厚些,轻微降低影像锐利度,再次换来X线吸收率的显著增加。这种吸收率和分辨力之间的折中给系统设计带来新的灵活性。最后,结构化荧光体的有效层比粉状荧光体具有更好的空间一致性,由此可以降低屏的结构噪声。

选择题
完形填空

完形填空(共20小题;每小题1.5分,满分30分)

阅读下面短文,从短文后所给各题的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。

My father and I were standing at the top of a church tower. He  31  me to this place in a small Italian town not far from our home in Rome. I  32  why he did so.

“Look down, Elsa,” Father said to me. I looked down and  33  the square in the centre of the village and I saw many turning streets  34  to the square.

“ See, my dear. There is more than one  35  to the square. Life is like that. If you can’t get to the place   36   you want to go by one road,  37  another,” he said to me.

Now I  38  why I was there. My father wanted to tell me how to  39  and deal with the difficulties.

In the years that  40  I often remembered the lesson Fathere taught me. I knew where I wanted to go in  41 . I wanted to be a fashion  42 . And on the way to my first small success I found the road  43 . What could I do ? Accept the failure? Or use my imagination and wisdom to find another road to my  44 ?

I had come to Paris, the  45  of the world of fashion , with some clothes I  46 . But none of the famous fashion designers seemed  47  in them. Then one day I met a friend who was wearig a very beautiful sweater. It had a lovely and  48  stitch (针法).

“Did you knit that sweater ?” I asked her.

“No,”she answered. “ It was done by a woman here in Paris.”

“ What an interesting stitch !” I continued.

My friend had an  49 . “The woman’s name is Mrs Vidian    she learned the stitch in Armenia, her motherland.”

Suddenly a good idea  50  me. why not open my own house of fashin? Why not design, make and sell clothes? I would do it, and I would begin with a sweater.

31. A . brought        B. carried        C. got      D. took

32. A. wondered      B. doubted       C. knew    D. guessed

33. A. noticed  B. saw      C. realized        D. observed

34. A. directing         B. going   C. leading         D. turning

35. A. way        B. path     C. road     D. method

36. A. when      B. why      C. which   D. where

37. A. try B. attempt       C. experiment D. manage

38. A. witnessed      B. understood C. imagined      D. supposed

39. A. settle     B. face      C. solve    D. handle

40. A. caught   B. followed       C. approached D. wasted

41. A. heart      B. work    C. class    D. life

42. A. designer         B. seller   C. worker          D. teacher

43. A. smoothed      B. passed          C. blocked         D. approved

44. A. success B. failure  C. comfort        D. intelligence

45. A. capital   B. country         C. attraction    D. centre

46. A. recommended       B. designed      C. performed   D. chose

47. A. occupied         B. absorbed     C. buried  D. interested

48. A. rough     B. ordinary       C. unusual        D. perfect

49. A. cause     B. reason C. description  D. explanation

50. A. struck    B. thought        C. entered        D. came