The listening sub-test in IELTS is divided into four sections:section one and two test candidates’survival skills in the U.K.;section three and four,candidates’study skills,Ih trainingpractice,the instructor may div...The listening sub-test in IELTS is divided into four sections:section one and two test candidates’survival skills in the U.K.;section three and four,candidates’study skills,Ih trainingpractice,the instructor may divide the listening material intotwo parts.In the first part—survival English,culturalbackground knowledge of daily life in the U.K.should be takenas the training focus.Dialogues concerning a new arrival’s dailyactivities in the U.K.may be chosen as listening material.Thesecond part,Academic English training is the most challengingtask.To understand a university lecture or academic interview,a good command of academic vocabulary is essential,so theinstructor should design some exercises to help students memorizeacademic vocabulary.The training focus for the academicEnglish part is the skill of grasping the main points of a lecture orinterview.Students should show how to write outlines andsummaries.Gap-fill and T&F&N forms may be adopted forsummary and outline training.展开更多
由于仪器传递函数(Instrument Transfer Function,ITF)能准确反映仪器在空间频率上的响应特征,被广泛应用于仪器规范之中。目前多采用刻有单一台阶特征或不同周期正弦特征的平面测试板对干涉仪的ITF进行检测。针对平面测试板无法完成高...由于仪器传递函数(Instrument Transfer Function,ITF)能准确反映仪器在空间频率上的响应特征,被广泛应用于仪器规范之中。目前多采用刻有单一台阶特征或不同周期正弦特征的平面测试板对干涉仪的ITF进行检测。针对平面测试板无法完成高陡度球面/非球面镜检测时ITF标定的问题,提出了根据球面台阶测试板标定高陡度镜面检测的子孔径拼接ITF的方法。通过超精密车削技术制作了球面台阶测试板,并对其进行拼接检测,根据梯度定位法和旋转矩阵完成检测孔径中台阶的定位及采样,利用傅里叶变换方法实现对台阶实测面形的功率谱密度求解,最后与理想面形功率谱密度做比获得ITF。对口径100 mm、曲率半径100 mm、带有同心圆环台阶结构的球面台阶测试板进行拼接检测以及数据分析,实验结果表明:在1 mm-1的空间频率范围内,各个子孔径对高陡度镜面的检测水平平均可达到82.72%,具有较好的检测精度,随后ITF逐渐衰减,当空间频率在1.5 mm^(-1)左右时,仅能达到40%~60%。展开更多
文摘The listening sub-test in IELTS is divided into four sections:section one and two test candidates’survival skills in the U.K.;section three and four,candidates’study skills,Ih trainingpractice,the instructor may divide the listening material intotwo parts.In the first part—survival English,culturalbackground knowledge of daily life in the U.K.should be takenas the training focus.Dialogues concerning a new arrival’s dailyactivities in the U.K.may be chosen as listening material.Thesecond part,Academic English training is the most challengingtask.To understand a university lecture or academic interview,a good command of academic vocabulary is essential,so theinstructor should design some exercises to help students memorizeacademic vocabulary.The training focus for the academicEnglish part is the skill of grasping the main points of a lecture orinterview.Students should show how to write outlines andsummaries.Gap-fill and T&F&N forms may be adopted forsummary and outline training.
