问题 单项选择题 A3/A4型题

滤线栅是由许多薄的铅条和易透过X线的低密度物质作为充填物,交替排列组成的。在X线摄影中使X线的中心线对准滤线栅板中心,原射线投射方向与滤线栅的铅条排列间隙在同一方向上,能通过铅条间隙而到达胶片产生影像。由于被照体产生的散射线是多中心、多方向的,其中大部分散射线被铅条所吸收,只有一小部分通过。滤线栅的指标:①栅比(R):滤线栅铅条高度与填充物幅度的比值为栅比。②栅密度(n):n表示在滤线栅表面上单位距离(1cm)内,铅条与其间距形成的线对数,常用线/cm表示。

滤线栅使用原则中,X线管管电压须超过()

A.55kV

B.60kV

C.65kV

D.70kV

E.75kVX

答案

参考答案:B

单项选择题 B型题
阅读理解

My grandfather grew up in war-torn Europe. When German soldiers occupied his hometown ,the thriving city of Tarow, Poland, he refused to obey them and eventually joined the Soviet army to fight for his country’s freedom . “Stand straight, stand tall,” he told himself.

After the war, in 1947, he boarded a boat for Manhattan. He was hungry and suffering from seasickness. All alone in a new country, he was frightened about his future .Still, he marched head-on into the hustle and bustle of the streets of New York . Soon he met other European immigrants, each of them trying to find his or her own way .If they could do it, why couldn’t he? “Stand straight, stand tall,” he would remind himself.

Thanks to the help of a loyal and trusting friend, my grandfather gained a jewelry booth on Canal Street, New York City .He once told me how nervous he was on that first day of work. He was not only trying to learn this tough new business, but also a new language.

To his surprise, the men in neighboring booths—who could have taken advantage of him—offered their help and advice. Within months, my grandfather was commanding his spot behind the counter, selling diamonds and cultured pearls as if he’d been doing it his whole life.

Stand straight and stand tall.

In later years, my grandfather would take both my mother and her sister down the aisle at their weddings. As he stood with each of them, he thought about their new beginnings, and of the adventures and journeys they would experience together .He also thought about the children who would one day carry on his family name.

I am so proud to be one of those children. Listening to my grandfather’s remarkable experiences has changed the way I view my own life.

56.Which is the correct order of the things that happened in the passage?

a. My grandfather took both my mother and her sister down the aisle at their weddings.

b. World War II broke out in Europe.

c. My grandfather went to America.

d. My grandfather began to run his diamond business.

e. The men in neighboring booths helped him.

A.b, c, a ,d, e          B.b, c,d ,e ,a           C.b, c ,e , a ,d        D.c, b ,e ,d ,a

57.Which is NOT true according to the passage?

A.My grandfather was a soldier during World War II.

B.My grandfather went to America by sea.

C.My grandfather had been doing a jewelry business his whole life.

D.My grandfather ran his business successfully.

58.Grandpa probably inspired his grandchildren in time of trouble by saying “    ”.

A.A friend in need is a friend indeed

B.God help those who help themselves

C.Stand straight ,stand tall

D.Practice makes perfect

59.It can be concluded that    .

A.Grandpa never lost heart in time of hardships

B.Grandpa never threw doubt upon his fate

C.Grandpa was born to be a businessman

D.Grandpa didn’t live up to his friend’s expectations