问题
问答题 简答题
提速区段，列车最高运行速度为160km/h，车体横向自振频率为1.2Hz，求线路横向不平顺敏感坡长。
答案
参考答案：
L＝160∕（3.6-1.2）＝37m
线路横向不平顺敏感坡长为37m。
搜题请搜索小程序“爱下问搜题”
提速区段，列车最高运行速度为160km/h，车体横向自振频率为1.2Hz，求线路横向不平顺敏感坡长。
参考答案：
L＝160∕（3.6-1.2）＝37m
线路横向不平顺敏感坡长为37m。
Photography is about taking photographs. In 1826, a Frenchman named Niepce needed pictures for his business. But he was not a good artist. So he invented a very simple camera. He put it in a window of his house and took a picture of his garden. That was the first photograph. The next important date in the history of photograph was 1837. That year, Daguerre, another Frenchman, took a picture of his studio. He used a new kind of camera and a different process. In his pictures, you could see everything very clearly, even the smallest details. This kind of photograph was called a daguerreotype. Soon, other people began to use Daguerre’s process. Travelers brought back daguerreotypes from all around the world. People photographed famous buildings, cities and mountains. In about 1840, the process was improved. The photographers could take pictures of people and moving things. The process was not simple. The photographers had to carry lots of films and processing equipment(设备). But this did not stop the photographers, especially in the United States. Mathew Brady was a well-known American photographer. He took many pictures of famous people. The pictures were unusual because they were very life-like and full of personality. Brady was also the first person to take pictures of war. His 1862 Civil War pictures showed dead soldiers and destroyed cities. They made the war seem more real and more terrible. In the 1880s, new inventions began to change photograph. Photographers could buy films readymade in rolls(卷). So they did not have to make the film themselves. Also, they did not have to process(冲洗) the film at once. They could bring it back to their studios and develop it later. They did not have to carry lots of equipment. And finally, the invention of the small hand-held camera made photography less expensive. Photography is also a form of art. Some photographs were not just copies of the real world. They showed ideas and feelings, like other art forms. Title: The 1 of Photography
| ||||||||||||