随着高功率脉冲电源(Pulse Power Supply)在电磁轨道炮、电磁弹射器及电磁推射装置中的广泛应用,对其产生的脉冲大电流的精确测量显得尤为重要,但目前电流测试领域常用的测试方法由于稳定性不足、量程有限、测量精度不高等缺陷,无法满...随着高功率脉冲电源(Pulse Power Supply)在电磁轨道炮、电磁弹射器及电磁推射装置中的广泛应用,对其产生的脉冲大电流的精确测量显得尤为重要,但目前电流测试领域常用的测试方法由于稳定性不足、量程有限、测量精度不高等缺陷,无法满足具有兆安级放电电流的高功率脉冲电源的测试需求。因此,提出了一种基于罗氏线圈和积分器的超大电流测试技术。首先通过COMSOL有限元分析软件的AC/DC磁场模块建立模型对该电磁环境进行仿真分析,以确定采集系统在该电磁环境中的安全测试距离,并对罗氏线圈和积分器的测试原理做了具体说明,最后搭建硬件平台在实际的试验中证明该方案能够实现对兆安级脉冲大电流的测试,论证了该测试方法的可行性。展开更多
Nonpolar a-plane （1120） GaN films have been grown on r-plane （1102） sapphire by metal-organic chemical vapor deposition （MOCVD） under different growth pressures. The as-grown films are investigated by optical mi...Nonpolar a-plane （1120） GaN films have been grown on r-plane （1102） sapphire by metal-organic chemical vapor deposition （MOCVD） under different growth pressures. The as-grown films are investigated by optical microscopy, high-resolution X-ray diffraction （HRXRD） and Raman scattering. As growth pressure rises from 100 mbar to 400 mbar, the surface gets rougher, and the in-plane XRD full width at half maximum （FWHM） along the c-axis [0001] increases while that along the m-axis [1100] decreases. Meanwhile, residential stresses are reduced along both the c-axis and the m-axis. The structural anisotropy feature under 400 mbar is inverted with respect to 100 mbar, and the weakened anisotropy is achieved under a moderate pressure of 200 mbar, probably due to the suppressed Ga atomic migration along the c-axis under a larger pressure. We propose that pressure can affect a-plane growth through the V/III ratio.展开更多
文摘随着高功率脉冲电源(Pulse Power Supply)在电磁轨道炮、电磁弹射器及电磁推射装置中的广泛应用,对其产生的脉冲大电流的精确测量显得尤为重要,但目前电流测试领域常用的测试方法由于稳定性不足、量程有限、测量精度不高等缺陷,无法满足具有兆安级放电电流的高功率脉冲电源的测试需求。因此,提出了一种基于罗氏线圈和积分器的超大电流测试技术。首先通过COMSOL有限元分析软件的AC/DC磁场模块建立模型对该电磁环境进行仿真分析,以确定采集系统在该电磁环境中的安全测试距离,并对罗氏线圈和积分器的测试原理做了具体说明,最后搭建硬件平台在实际的试验中证明该方案能够实现对兆安级脉冲大电流的测试,论证了该测试方法的可行性。
基金supported by the National Natural Science Foundation of China (Grant Nos. 60890192 and 50872146)
文摘Nonpolar a-plane （1120） GaN films have been grown on r-plane （1102） sapphire by metal-organic chemical vapor deposition （MOCVD） under different growth pressures. The as-grown films are investigated by optical microscopy, high-resolution X-ray diffraction （HRXRD） and Raman scattering. As growth pressure rises from 100 mbar to 400 mbar, the surface gets rougher, and the in-plane XRD full width at half maximum （FWHM） along the c-axis [0001] increases while that along the m-axis [1100] decreases. Meanwhile, residential stresses are reduced along both the c-axis and the m-axis. The structural anisotropy feature under 400 mbar is inverted with respect to 100 mbar, and the weakened anisotropy is achieved under a moderate pressure of 200 mbar, probably due to the suppressed Ga atomic migration along the c-axis under a larger pressure. We propose that pressure can affect a-plane growth through the V/III ratio.
