The dynamical properties of one-dimensional random transverse Ising model(RTIM) with a double-Gaussian disorder is investigated by the recursion method. Based on the first twelve recurrences derived analytically, the ...The dynamical properties of one-dimensional random transverse Ising model(RTIM) with a double-Gaussian disorder is investigated by the recursion method. Based on the first twelve recurrences derived analytically, the spin autocorrelation function(SAF) and associated spectral density at high temperature were obtained numerically. Our results indicate that when the standard deviation σJ(or σB) of the exchange couplings Ji(or the random transverse fields Bi) is small, no long-time tail appears in the SAF. The spin system undergoes a crossover from a central-peak behavior to a collectivemode behavior, which is the dynamical characteristics of RTIM with the bimodal disorder. However, when σJ(or σB) is large enough, the system exhibits similar dynamics behaviors to those of the RTIM with the Gaussian disorder, i.e., the system exhibits an enhanced central-peak behavior for large σJ or a disordered behavior for large σB. In this instance,SAFs exhibit a similar long-time tail, i.e., C(t) ～ t-2for large t. Similar properties are obtained when Ji(or Bi) satisfy the double-exponential distribution or the double-uniform distribution. Besides, when both the standard deviations and the mean values of the exchange couplings are small, the effects of the Gaussian random bonds may drive the system undergo two crossovers from a triplet state to a doublet state, and then to a collective-mode state.展开更多
We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio timedependent density functional theory.The dipole responses are investigated each as a function of chain length.Th...We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio timedependent density functional theory.The dipole responses are investigated each as a function of chain length.They converge into a single resonance in the longitudinal mode but split into two transverse modes.As the chain length increases,the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction (blueshifts).In addition,the energy gap between the two transverse modes reduces with chain length increasing.We find that there are unique characteristics,different from those of other metallic chains.These characteristics are crucial to atomic-scale engineering of single-molecule sensing,optical spectroscopy,and so on.展开更多
Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxatio...Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxation time (T_(2)) of the xenon nuclear spin in the atomic cell of the NMRG directly affects the angular random walk of the gyro. Accurate and rapid measurement of T_(2) is conducive to further improvement of gyroscope. At present, for the measurement of T_(2), the schemes of two orthogonal lasers for pumping and detecting are usually used. By applying two fast-switching orthogonal static magnetic fields and a single beam of circularly polarized laser with corresponding wavelength to pump the atomic cell, the xenon nuclear macroscopic magnetic moment Larmor precession is generated. The cesium atoms parametric magnetometer in cell is formed to detect the free induction decay signal generated by nuclear spin precession of xenon atoms. The measurement of T_(2) by a single laser simplifies the measurement equipment compared with traditional method with two lasers. The experimental results show that the T_(2) of xenon atoms is more than 10 s, and the effects of temperature are studied, which lay the foundation for the subsequent improvement of gyro performance.展开更多
为研究胡萝卜切片在干燥过程中内部水分变化的特征,采用电热恒温干燥箱在40、50、60、70和80℃的条件下对胡萝卜切片进行热风干燥试验,应用低场核磁共振(low field nuclear magnetic resonance,LF-NMR)的横向弛豫时间(T2)反演谱分析胡...为研究胡萝卜切片在干燥过程中内部水分变化的特征,采用电热恒温干燥箱在40、50、60、70和80℃的条件下对胡萝卜切片进行热风干燥试验,应用低场核磁共振(low field nuclear magnetic resonance,LF-NMR)的横向弛豫时间(T2)反演谱分析胡萝卜切片在干燥过程中内部水分的变化。试验结果表明:干燥过程改变了胡萝卜样品中水的结合状态,自由度高的水分向自由度低的迁移;随着干燥温度升高,干燥速率加快,但温度为80℃时,由于物料表面结壳阻碍了水分的外迁从而影响干燥速率。试验数据为果疏变温联合干燥工艺和干燥转换点的确定提供参考。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11302118 and 11275112)the Natural Science Foundation of Shandong Province of China(Grant Nos.ZR2013AQ015 and ZR2011AM018)the Postdoctoral Science Foundation of Qufu Normal University(Grant No.BSQD2012053)
文摘The dynamical properties of one-dimensional random transverse Ising model(RTIM) with a double-Gaussian disorder is investigated by the recursion method. Based on the first twelve recurrences derived analytically, the spin autocorrelation function(SAF) and associated spectral density at high temperature were obtained numerically. Our results indicate that when the standard deviation σJ(or σB) of the exchange couplings Ji(or the random transverse fields Bi) is small, no long-time tail appears in the SAF. The spin system undergoes a crossover from a central-peak behavior to a collectivemode behavior, which is the dynamical characteristics of RTIM with the bimodal disorder. However, when σJ(or σB) is large enough, the system exhibits similar dynamics behaviors to those of the RTIM with the Gaussian disorder, i.e., the system exhibits an enhanced central-peak behavior for large σJ or a disordered behavior for large σB. In this instance,SAFs exhibit a similar long-time tail, i.e., C(t) ～ t-2for large t. Similar properties are obtained when Ji(or Bi) satisfy the double-exponential distribution or the double-uniform distribution. Besides, when both the standard deviations and the mean values of the exchange couplings are small, the effects of the Gaussian random bonds may drive the system undergo two crossovers from a triplet state to a doublet state, and then to a collective-mode state.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11074176 and 10976019)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100181110080)
文摘We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio timedependent density functional theory.The dipole responses are investigated each as a function of chain length.They converge into a single resonance in the longitudinal mode but split into two transverse modes.As the chain length increases,the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction (blueshifts).In addition,the energy gap between the two transverse modes reduces with chain length increasing.We find that there are unique characteristics,different from those of other metallic chains.These characteristics are crucial to atomic-scale engineering of single-molecule sensing,optical spectroscopy,and so on.
基金the Shanghai Aerospace Advanced Technology Joint Research Fund(No.USCAST2019-23)。
文摘Nuclear magnetic resonance gyroscope (NMRG) has the characteristics of high precision and miniaturization, and is one of the main applications of quantum technology in the field of navigation. The transverse relaxation time (T_(2)) of the xenon nuclear spin in the atomic cell of the NMRG directly affects the angular random walk of the gyro. Accurate and rapid measurement of T_(2) is conducive to further improvement of gyroscope. At present, for the measurement of T_(2), the schemes of two orthogonal lasers for pumping and detecting are usually used. By applying two fast-switching orthogonal static magnetic fields and a single beam of circularly polarized laser with corresponding wavelength to pump the atomic cell, the xenon nuclear macroscopic magnetic moment Larmor precession is generated. The cesium atoms parametric magnetometer in cell is formed to detect the free induction decay signal generated by nuclear spin precession of xenon atoms. The measurement of T_(2) by a single laser simplifies the measurement equipment compared with traditional method with two lasers. The experimental results show that the T_(2) of xenon atoms is more than 10 s, and the effects of temperature are studied, which lay the foundation for the subsequent improvement of gyro performance.
文摘为研究胡萝卜切片在干燥过程中内部水分变化的特征,采用电热恒温干燥箱在40、50、60、70和80℃的条件下对胡萝卜切片进行热风干燥试验,应用低场核磁共振(low field nuclear magnetic resonance,LF-NMR)的横向弛豫时间(T2)反演谱分析胡萝卜切片在干燥过程中内部水分的变化。试验结果表明:干燥过程改变了胡萝卜样品中水的结合状态,自由度高的水分向自由度低的迁移;随着干燥温度升高,干燥速率加快,但温度为80℃时,由于物料表面结壳阻碍了水分的外迁从而影响干燥速率。试验数据为果疏变温联合干燥工艺和干燥转换点的确定提供参考。
