问题 问答题 简答题

简述雷达相对运动显示方式有哪些特点?在哪种场合使用比较好?

答案

参考答案:

1.船首向上图像不稳相对运动显示特点有:1)扫描中心代表本船位置在屏上不动,船首线代表本船船首方向,显示周围运动物标相对于本船的运动状态,固定物标则与本船等速反向运动。

2.船首线指固定方位盘(圈)的零度并代表船首方向。在方位盘上可读得物标的相对方位(舷角)。故这种显示方式又称为“相对方位显示方式”。3)本船转向时,船首线不动而物标回波反转,图像留下一段弧形余辉。特别是在船首有偏荡或频繁改向时。会使图像模糊不清,影响观测。

3.运用场合:判明前方来船处在本船的左舷还是右舷,判断碰撞危险十分方便,所以常用作观测瞭望。

单项选择题

Congress makes the laws in the United States. It has two pans, which are more or less equal in power. They are known as the House of Representatives and the Senate. The House of Representatives is larger than the Senate whose 100 members (two from each state) serve for six years. The 435 members of the House are elected every two years, and the number from each state is determined by the population of the state. For example, California, which has a large population, has 43 representatives, while the State of Nevada has only one.

The House and Senate are divided into small groups which take care of special matters such as education or foreign affairs. The most important work of Congress is often done in these groups, which are called subcommittees.

According to the Constitution of the United States, a senator must be at least 30 years old and he must have been a citizen of the United States for nine years at the time of his election. To be elected to the House a person must be 25 years old and must have been a United States citizen for seven years. At the present time, members of Congress include businessmen, farmers, teachers, and especially lawyers. In general, senators are better known than representatives because they are fewer in number and serve for a longer time. Many American presidents served in Congress before they became president.

Which of the following is true().

A. A representative serves for two years.

B. To become a senator is easier than to become a representative.

C. A senator performs his duties for a shorter time than a representative.

D. All presidents were representatives and then senators before becoming president of the United States.

问答题