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
The backward-facing step is a critical problem existing in many engineering and industrial applications.In this study,a semi-porous baffle(the root of the baffle is a porous medium and the tip is solid) is placed behi...The backward-facing step is a critical problem existing in many engineering and industrial applications.In this study,a semi-porous baffle(the root of the baffle is a porous medium and the tip is solid) is placed behind the step.The effects of the length of the porous part,and the baffle location on the energy transfer and pressure drop are studied in different Reynolds numbers(Re=100,200,300,400,500).The effect of the Darcy number of the porous medium on the aforementioned parameters is also investigated.Both the local maximum and average relative Nusselt numbers(divided by the Nusselt of the base case with no baffle at the same Reynolds) and relative pressure drop(calculated as the relative Nusselt number) are reported.The results show that by adoption of the proper length of the porous medium,the average relative and maximum local Nusselt numbers could be enhanced by 20% and 90%,respectively.Low permeable porous media give better energy transfer.For example,porous media with Da=10^(-5) give 30% better maximum local Nusselt number and about 7% higher average Nusselt number with respect to the same case with Da=10^(-2).展开更多
为了满足3300 V FRD反向漏电低,反向恢复软度大的应用要求,本文介绍了一种新的FRD设计。该设计通过优化阳极掺杂,采用轻离子辐照和电子辐照相结合的寿命控制方式来增加FRD的反向恢复软度,降低FRD的漏电流,通过台阶形场板保护环结构来降...为了满足3300 V FRD反向漏电低,反向恢复软度大的应用要求,本文介绍了一种新的FRD设计。该设计通过优化阳极掺杂,采用轻离子辐照和电子辐照相结合的寿命控制方式来增加FRD的反向恢复软度,降低FRD的漏电流,通过台阶形场板保护环结构来降低保护环的漏电流。采用8英寸平面栅加工工艺得到的芯片封装成了3300 V/1500 A FRD模块。模块在高温150℃下的V_(F)为2.18 V,漏电流I_(R)为10 mA,反向恢复能量(E_(rec))为1665 mJ,关断软度为3.67,反向恢复极限di/dt为8000A/us时承受的功率可达3210 kW。展开更多
文摘The backward-facing step is a critical problem existing in many engineering and industrial applications.In this study,a semi-porous baffle(the root of the baffle is a porous medium and the tip is solid) is placed behind the step.The effects of the length of the porous part,and the baffle location on the energy transfer and pressure drop are studied in different Reynolds numbers(Re=100,200,300,400,500).The effect of the Darcy number of the porous medium on the aforementioned parameters is also investigated.Both the local maximum and average relative Nusselt numbers(divided by the Nusselt of the base case with no baffle at the same Reynolds) and relative pressure drop(calculated as the relative Nusselt number) are reported.The results show that by adoption of the proper length of the porous medium,the average relative and maximum local Nusselt numbers could be enhanced by 20% and 90%,respectively.Low permeable porous media give better energy transfer.For example,porous media with Da=10^(-5) give 30% better maximum local Nusselt number and about 7% higher average Nusselt number with respect to the same case with Da=10^(-2).
文摘为了满足3300 V FRD反向漏电低,反向恢复软度大的应用要求,本文介绍了一种新的FRD设计。该设计通过优化阳极掺杂,采用轻离子辐照和电子辐照相结合的寿命控制方式来增加FRD的反向恢复软度,降低FRD的漏电流,通过台阶形场板保护环结构来降低保护环的漏电流。采用8英寸平面栅加工工艺得到的芯片封装成了3300 V/1500 A FRD模块。模块在高温150℃下的V_(F)为2.18 V,漏电流I_(R)为10 mA,反向恢复能量(E_(rec))为1665 mJ,关断软度为3.67,反向恢复极限di/dt为8000A/us时承受的功率可达3210 kW。
