A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four...A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.展开更多
An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a ...An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.展开更多
介绍了用γ谱仪测量环境中210Pb的分析方法。用醋酸纤维滤膜采集气溶胶样品,或用马林杯直接封装环境水样,在γ谱仪上测量210Pb发射的46.5 ke V射线,通过解谱分析技术获得210Pb的放射性活度。该方法具有快速、非破坏性、无需化学分离及...介绍了用γ谱仪测量环境中210Pb的分析方法。用醋酸纤维滤膜采集气溶胶样品,或用马林杯直接封装环境水样,在γ谱仪上测量210Pb发射的46.5 ke V射线,通过解谱分析技术获得210Pb的放射性活度。该方法具有快速、非破坏性、无需化学分离及样品处理等优点,但存在低γ发射几率及射线能量低导致的高自吸收等不足,分析的关键在于γ谱仪效率刻度。实验结果表明:γ谱法可用于环境样品中210Pb的放射性活度测量。展开更多
基金Project supported by Ministry of Education "Chunhui Program" and Fok Ying Tung Education Foundation.
文摘A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.
文摘An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.
文摘介绍了用γ谱仪测量环境中210Pb的分析方法。用醋酸纤维滤膜采集气溶胶样品,或用马林杯直接封装环境水样,在γ谱仪上测量210Pb发射的46.5 ke V射线,通过解谱分析技术获得210Pb的放射性活度。该方法具有快速、非破坏性、无需化学分离及样品处理等优点,但存在低γ发射几率及射线能量低导致的高自吸收等不足,分析的关键在于γ谱仪效率刻度。实验结果表明:γ谱法可用于环境样品中210Pb的放射性活度测量。
