A set of novel graph-theoretical parameters, called the atomic distance-edge (ADE) vector, was developed. Baaed on the connecting C-C bond number between central carbon atom and the other ones, various carbon atoms of...A set of novel graph-theoretical parameters, called the atomic distance-edge (ADE) vector, was developed. Baaed on the connecting C-C bond number between central carbon atom and the other ones, various carbon atoms of alkanes were classified as four types, i.e., type 1, 2, 3 and 4 for primary, secondary, ternary and quaternary carbon, respectively; and then four regression equations were obtained to link carbon-13 chemical shift (CS) of each type of atoms. Furthermore, these regression models were used to predict the carbon-13 nuclear magnetic resonance spectra of alkanes and it was found that the estimated CS were in agreement with the experimental results.展开更多
Sinee Mssbauer effect was discovered in 1958, it has been widely used to study thedifferent kinds of minerals. Mineralogists are interested in the complex structures of silicateminerals and Mssbauer effect can provide...Sinee Mssbauer effect was discovered in 1958, it has been widely used to study thedifferent kinds of minerals. Mineralogists are interested in the complex structures of silicateminerals and Mssbauer effect can provide some useful information concerning irondistribution among crystal sites. Therefore, silicate minerals were investigated in detail展开更多
The surface structure of Cu,Al and γ Al2O3 have been investigated b y SEELFS and obtained nearest neighbor distances of the central atoms.The value s compared with those calculated according to theories shows that th...The surface structure of Cu,Al and γ Al2O3 have been investigated b y SEELFS and obtained nearest neighbor distances of the central atoms.The value s compared with those calculated according to theories shows that the errors wer e about 0.01－0.03nm before correcting the phase shifts.These results show the p ossibility of performing SEELFS technique by Auger electron spectrometer.展开更多
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
The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to...The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to the surface. Rapid decrease of the temperature and number of the atoms is found when the atom-surface distance is 〈 100 ttm. A gain of about a factor of five on the phase-space density is obtained. It is found that the efficiency of the surface-induced evaporative cooling depends on the atom-surface distance and the shape of the evaporative trap. When the atoms are moved very close to the surface, severe heating is observed, which dominates when the holding time is 〉 8 ms. It is important that the surface-induced evaporative cooling offers novel possibilities for the realization of a continuous condensation, where a spatially varying evaporative cooling is required.展开更多
构建了基于分子三维结构计算的原子电负性距离矢量(atomic electronegative space distance vector,AESDV),用以描述各芳香醚类化合物分子中不同等价碳原子的化学微环境,并结合原子自身杂化状态指数(AHSI),建立了^(13)C核磁共振定量结...构建了基于分子三维结构计算的原子电负性距离矢量(atomic electronegative space distance vector,AESDV),用以描述各芳香醚类化合物分子中不同等价碳原子的化学微环境,并结合原子自身杂化状态指数(AHSI),建立了^(13)C核磁共振定量结构波谱关系的多元线性回归模型,复相关系数(R)为0.964,标准误差(SD)为8.673.经留一法交互检验的复相关系数(R_(CV))为0.948,标准误差(SD_(CV))为10.362.随机抽出样本进行外部检验,得到测试集的复相关系数(R_(test1)及R_(test2))分别为0.979和0.939,标准误差(SD_(test1)及SD_(test2))分别为6.400和10.162.研究结果表明,使用该方法所建模型具有良好的预测能力和稳定性.展开更多
基金supported by the National Natural Science Foundation of China(51071084,21273113,21121091,11204120)National Key Technology R&D Program of China(2012BAF03B05)~~
文摘A set of novel graph-theoretical parameters, called the atomic distance-edge (ADE) vector, was developed. Baaed on the connecting C-C bond number between central carbon atom and the other ones, various carbon atoms of alkanes were classified as four types, i.e., type 1, 2, 3 and 4 for primary, secondary, ternary and quaternary carbon, respectively; and then four regression equations were obtained to link carbon-13 chemical shift (CS) of each type of atoms. Furthermore, these regression models were used to predict the carbon-13 nuclear magnetic resonance spectra of alkanes and it was found that the estimated CS were in agreement with the experimental results.
文摘Sinee Mssbauer effect was discovered in 1958, it has been widely used to study thedifferent kinds of minerals. Mineralogists are interested in the complex structures of silicateminerals and Mssbauer effect can provide some useful information concerning irondistribution among crystal sites. Therefore, silicate minerals were investigated in detail
文摘The surface structure of Cu,Al and γ Al2O3 have been investigated b y SEELFS and obtained nearest neighbor distances of the central atoms.The value s compared with those calculated according to theories shows that the errors wer e about 0.01－0.03nm before correcting the phase shifts.These results show the p ossibility of performing SEELFS technique by Auger electron spectrometer.
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.
基金Project supported by the State Key Basic Research Program (Grant No 2006CB921202)the National Natural Science Foundation of China (Grant No 10334050)
文摘The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to the surface. Rapid decrease of the temperature and number of the atoms is found when the atom-surface distance is 〈 100 ttm. A gain of about a factor of five on the phase-space density is obtained. It is found that the efficiency of the surface-induced evaporative cooling depends on the atom-surface distance and the shape of the evaporative trap. When the atoms are moved very close to the surface, severe heating is observed, which dominates when the holding time is 〉 8 ms. It is important that the surface-induced evaporative cooling offers novel possibilities for the realization of a continuous condensation, where a spatially varying evaporative cooling is required.
基金Youth Foundation of Education Bureau,Sichuan Province(13ZB0003)Natural Science Foundation of Education Bureau,Sichuan Province(15ZB0272)
文摘构建了基于分子三维结构计算的原子电负性距离矢量(atomic electronegative space distance vector,AESDV),用以描述各芳香醚类化合物分子中不同等价碳原子的化学微环境,并结合原子自身杂化状态指数(AHSI),建立了^(13)C核磁共振定量结构波谱关系的多元线性回归模型,复相关系数(R)为0.964,标准误差(SD)为8.673.经留一法交互检验的复相关系数(R_(CV))为0.948,标准误差(SD_(CV))为10.362.随机抽出样本进行外部检验,得到测试集的复相关系数(R_(test1)及R_(test2))分别为0.979和0.939,标准误差(SD_(test1)及SD_(test2))分别为6.400和10.162.研究结果表明,使用该方法所建模型具有良好的预测能力和稳定性.
