问题 单项选择题 A1型题

从图像滤波的观点看,重建断层时采用的斜坡滤波与窗口函数相乘的方法,是为了实现()。

A.低通滤波

B.最佳滤波

C.恢复滤波

D.时间平滑

E.反滤波

答案

参考答案:B

解析:要得到准确的重建图像,必须恢复投影的频率成分,恢复的幅度与频率相等,频率越高的成分恢复越多。实现恢复的方法是滤波。

阅读理解

阅读理解。

     Plants are very important living things. Life could not go on if there were no plants. This is because plants

can make food from air, water and sunlight. Animals and man cannot make food from air, water and sunlight.

Animals get their food by eating plants and other animals. Therefore animals and man need plants in order to

live. This is why we find that there are so many plants around us. If you look carefully at the plants around

you, you will find that there are two kinds of plants: flowering plants and non-flowering plants. Flowering

plants can make seeds. The seeds are protected by the fruits. Some fruits have one seed, some have two,

three or four, and some have many seeds. But a few fruits have no seeds at all. An example of a fruit without

seeds is the banana fruit. Most non-flowering plants do not grow from seeds. They grow from spores (胚芽).

Spores are very small. Some spores are so small and light that they can float in the air. We may say that spores

are quite the same as seeds. When these spores are all on wet and shady places, they usually grow into new

plants.

1. The main idea of the first paragraph is that _____. [ ]

A. plants are important for life

B. plants cannot grow without air

C. there are many plants in the world

D. we can not live without water

2. Plants can make food from _____. [ ]

A. flower, water and air

B. water, sunlight and air

C. air, water and soil

D. air, sun and light

3. What can we infer (推断) from the passage? [ ]

A. Of all living things animals are most important

B. Spores are seeds

C. All fruits of flowering plants have seeds

D. Without plants, man will die out

4. This passage may be taken from _____. [ ]

A. a medicine book

B. a novel

C. a science magazine

D. an experiment report

单项选择题