速度滤波

阅读下面短文，根据所读内容在表格中的空白处填入恰当的单词。
注意：每个空格只填一个单词。
Although stressful and unpleasant, examinations are a part of education that students all over the world have to experience. Exams are not recent methods of testing knowledge. They have been used since ancient times and our ancestors probably went through the same anxious preparation as students today.
China, exams were first introduced more than 1,300 years ago during the Sui Dynasty. Known as the Imperial Examinations or keju, the ten subject tests were used to select people for government jobs. A career in public service was considered the highest profession, and the examinations attracted millions of hopeful participants each time they were held. The tests had three levels: for local, provincial and national government. Only about 5% of those taking each level passed, and the number of students who passed all the levels was even smaller－ perhaps as low as 0.0004%.
The exams were so important in China that some people spent nearly their whole lives retaking the exams in the hope of eventually passing. Others tried to cheat by hiding notes in cakes or on their clothes. Historians found one undergarment that had 353 model essays written on it. Perhaps if this particular student had spent as much time studying as he did writing on his clothes, he would have passed!
The Imperial Examinations lasted until 1905, when they were replaced. Exams, however, are still a compulsory part of education in China. As nobody has yet come up with an alternative method of judging students’ abilities, it seems likely that the system of examinations will continue for more years.