Development of magnetohydrodynamic acceleration technology is expected to improve wind tunnel simulation capability and testing capability.The underlying premise is to produce uniform and stable plasma in supersonic a...Development of magnetohydrodynamic acceleration technology is expected to improve wind tunnel simulation capability and testing capability.The underlying premise is to produce uniform and stable plasma in supersonic air flow,and gas discharge is an effective way to achieve this.A nanosecond pulsed discharge experimental system under supersonic conditions was established,and a pin-to-plate nanosecond pulsed discharge experiment in Mach 2 air flow was performed to verify that the proposed method produced uniform and stable plasma under supersonic conditions.The results show that the discharge under supersonic conditions was stable overall,but uniformity was not as good as that under static conditions.Increasing the number of pins improved discharge uniformity,but reduced discharge intensity and hence plasma density.Under multi-pin conditions at 1000Hz,the discharge was almost completely corona discharge,with the main current component being the displacement current,which was smaller than that under static conditions.展开更多
高精度测定水中氧同位素组成对于了解区域和全球水文气候变化过程具有重要意义.近年来,随着测试技术的不断发展,稳定同位素比值质谱(质谱法)和波长扫描光腔衰荡光谱(光谱法)技术均被证明可以获得高精度的水中三氧同位素指标(^(17)O-exce...高精度测定水中氧同位素组成对于了解区域和全球水文气候变化过程具有重要意义.近年来,随着测试技术的不断发展,稳定同位素比值质谱(质谱法)和波长扫描光腔衰荡光谱(光谱法)技术均被证明可以获得高精度的水中三氧同位素指标(^(17)O-excess).本研究在国内率先建立了高精度水三氧同位素测试新技术,使用质谱和光谱两种技术测量多个国际标准水样三氧同位素组成,并将数据与已有研究结果对比.结果表明,两种测试技术的精度均能够达到低于10 per meg(1 per meg=10^(-6)),但在样品需求量、测试效率、受外界干扰程度等方面各有优劣.使用质谱法测试GISP的标准化值为δ^(18)O_(VSMOW-SLAP)=-24.82‰±0.04‰、δ^(17)O_(VSMOW-SLAP)=-13.16‰±0.03‰、^(17)O-excess=21±6 per meg(1σ);使用光谱法测定的GISP的标准值为δ^(18)O_(VSMOW-SLAP)=-24.80‰±0.03‰、δ^(17)O_(VSMOW-SLAP)=-13.15‰±0.02‰、^(17)O-excess=26±8 per meg(1σ).两种技术的测定值均与IAEA推荐值或已有研究结果在误差范围内一致.对于USGS 45和USGS 47的测定结果与已有数据或推荐值接近,特别是两者之间大于20per meg的^(17)O-excess值的差异也与已有研究结果一致.本研究使用两种技术测试中国不同气候区的冬夏季节降水,结果显示两种技术所测同一样品的值均具有良好的一致性,并初步观测到不同季节降水样品的^(17)O-excess值的变化,为利用三氧同位素指标研究水文循环过程提供重要的技术支撑.展开更多
基金National Natural Science Foundation of China (Nos. 11372352, 51776222)the China Postdoctoral Science Foundation (Nos. 2017T100772, 2016M590972).
文摘Development of magnetohydrodynamic acceleration technology is expected to improve wind tunnel simulation capability and testing capability.The underlying premise is to produce uniform and stable plasma in supersonic air flow,and gas discharge is an effective way to achieve this.A nanosecond pulsed discharge experimental system under supersonic conditions was established,and a pin-to-plate nanosecond pulsed discharge experiment in Mach 2 air flow was performed to verify that the proposed method produced uniform and stable plasma under supersonic conditions.The results show that the discharge under supersonic conditions was stable overall,but uniformity was not as good as that under static conditions.Increasing the number of pins improved discharge uniformity,but reduced discharge intensity and hence plasma density.Under multi-pin conditions at 1000Hz,the discharge was almost completely corona discharge,with the main current component being the displacement current,which was smaller than that under static conditions.
文摘高精度测定水中氧同位素组成对于了解区域和全球水文气候变化过程具有重要意义.近年来,随着测试技术的不断发展,稳定同位素比值质谱(质谱法)和波长扫描光腔衰荡光谱(光谱法)技术均被证明可以获得高精度的水中三氧同位素指标(^(17)O-excess).本研究在国内率先建立了高精度水三氧同位素测试新技术,使用质谱和光谱两种技术测量多个国际标准水样三氧同位素组成,并将数据与已有研究结果对比.结果表明,两种测试技术的精度均能够达到低于10 per meg(1 per meg=10^(-6)),但在样品需求量、测试效率、受外界干扰程度等方面各有优劣.使用质谱法测试GISP的标准化值为δ^(18)O_(VSMOW-SLAP)=-24.82‰±0.04‰、δ^(17)O_(VSMOW-SLAP)=-13.16‰±0.03‰、^(17)O-excess=21±6 per meg(1σ);使用光谱法测定的GISP的标准值为δ^(18)O_(VSMOW-SLAP)=-24.80‰±0.03‰、δ^(17)O_(VSMOW-SLAP)=-13.15‰±0.02‰、^(17)O-excess=26±8 per meg(1σ).两种技术的测定值均与IAEA推荐值或已有研究结果在误差范围内一致.对于USGS 45和USGS 47的测定结果与已有数据或推荐值接近,特别是两者之间大于20per meg的^(17)O-excess值的差异也与已有研究结果一致.本研究使用两种技术测试中国不同气候区的冬夏季节降水,结果显示两种技术所测同一样品的值均具有良好的一致性,并初步观测到不同季节降水样品的^(17)O-excess值的变化,为利用三氧同位素指标研究水文循环过程提供重要的技术支撑.
