Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) ar...Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) are considered,namely,the vacancy migration of Na ions in the fully intercalated and the migration of Na ions in the fully de-intercalated.The Na-vacancy and Na^(+)distribution in NaMnO_(2) migrated along oxygen dumbbell hop(ODH)and tetrahedral site hop(TSH),and the migration energy barriers were 0.374 and 0.296 eV,respectively.In NaLi_(1/6)Mn_(5/6)O_(2),the inhomogeneity of Li doping leads to the narrowing of the interlayer spacing by 0.9%and the increase of the energy barrier by 53.8%.On the other hand,due to the alleviation of Jahn-Teller effect of neighboring Mn,the bonding strength of Mn-O was enhanced,so that the energy barrier of path 2-3 in Mn-L1 and Mn-L2 was the lowest,which was 0.234 and 0.424 eV,respectively.In Na_(1/6)Li_(1/6)Mn_(5/6)O_(2),the migration energy barriers of Na-L2 and Na-L3 are 1.233 and 0.779 eV,respectively,because Li+migrates from the transition(TM)layer to the alkali metal(AM)layer with Na^(+)migration,which requires additional energy.展开更多
The influence of the interaction between surrounding rock and lining on the long-term behaviour of a tunnel in service is significant.In this paper,we proposed a mechanical model of the circular lined tunnel with the ...The influence of the interaction between surrounding rock and lining on the long-term behaviour of a tunnel in service is significant.In this paper,we proposed a mechanical model of the circular lined tunnel with the alterable mechanical property under hydrostatic stress and radially inner surface pressure of the lining.The alterable mechanical properties of the surrounding rock and the lining are embodied by the changing of their elasticity modulus with service time and radial direction of the tunnel,respectively.The proposed mechanical model is successfully validated by comparison with the existing theoretical models and the numerical simulation,respectively.The influences of the main parameters of the proposed mechanical model,such as the radial power-law indexes and the time-varying coefficients of the surrounding rock and the lining,as well as the radially inner surface pressure of the lining,on the interface displacement and pressure between surrounding rock and lining are investigated.The research results can provide some valuable references for timely diagnosis and correct evaluation of the long-term behaviours of a tunnel in service.展开更多
Among all segmentation techniques, Otsu thresholding method is widely used. Line intercept histogram based Otsu thresholding method(LIH Otsu method) can be more resistant to Gaussian noise, highly efficient in computi...Among all segmentation techniques, Otsu thresholding method is widely used. Line intercept histogram based Otsu thresholding method(LIH Otsu method) can be more resistant to Gaussian noise, highly efficient in computing time, and can be easily extended to multilevel thresholding. But when images contain salt-and-pepper noise, LIH Otsu method performs poorly. An improved LIH Otsu method(ILIH Otsu method) is presented, which can be more resistant to Gaussian noise and salt-and-pepper noise. Moreover, it can be easily extended to multilevel thresholding. In order to improve the efficiency, the optimization algorithm based on the kinetic-molecular theory(KMTOA) is used to determine the optimal thresholds. The experimental results show that ILIH Otsu method has stronger anti-noise ability than two-dimensional Otsu thresholding method(2-D Otsu method), LIH Otsu method, K-means clustering algorithm and fuzzy clustering algorithm.展开更多
基金Projects(51602352,51974373,51874358,51772333,61533020) supported by the National Natural Science Foundation of ChinaProject(2019JZZY020123) supported by the Major Scientific and Technological Innovation Projects of Shandong Province,China。
文摘Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) are considered,namely,the vacancy migration of Na ions in the fully intercalated and the migration of Na ions in the fully de-intercalated.The Na-vacancy and Na^(+)distribution in NaMnO_(2) migrated along oxygen dumbbell hop(ODH)and tetrahedral site hop(TSH),and the migration energy barriers were 0.374 and 0.296 eV,respectively.In NaLi_(1/6)Mn_(5/6)O_(2),the inhomogeneity of Li doping leads to the narrowing of the interlayer spacing by 0.9%and the increase of the energy barrier by 53.8%.On the other hand,due to the alleviation of Jahn-Teller effect of neighboring Mn,the bonding strength of Mn-O was enhanced,so that the energy barrier of path 2-3 in Mn-L1 and Mn-L2 was the lowest,which was 0.234 and 0.424 eV,respectively.In Na_(1/6)Li_(1/6)Mn_(5/6)O_(2),the migration energy barriers of Na-L2 and Na-L3 are 1.233 and 0.779 eV,respectively,because Li+migrates from the transition(TM)layer to the alkali metal(AM)layer with Na^(+)migration,which requires additional energy.
基金Project(U1934210) supported by the Key Project of High-speed Rail Joint Fund of National Natural Science Foundation of ChinaProject(8202037) supported by the Natural Science Foundation of Beijing,China。
文摘The influence of the interaction between surrounding rock and lining on the long-term behaviour of a tunnel in service is significant.In this paper,we proposed a mechanical model of the circular lined tunnel with the alterable mechanical property under hydrostatic stress and radially inner surface pressure of the lining.The alterable mechanical properties of the surrounding rock and the lining are embodied by the changing of their elasticity modulus with service time and radial direction of the tunnel,respectively.The proposed mechanical model is successfully validated by comparison with the existing theoretical models and the numerical simulation,respectively.The influences of the main parameters of the proposed mechanical model,such as the radial power-law indexes and the time-varying coefficients of the surrounding rock and the lining,as well as the radially inner surface pressure of the lining,on the interface displacement and pressure between surrounding rock and lining are investigated.The research results can provide some valuable references for timely diagnosis and correct evaluation of the long-term behaviours of a tunnel in service.
基金Project(61440026)supported by the National Natural Science Foundation of ChinaProject(11KZ|KZ08062)supported by Doctoral Research Project of Xiangtan University,China
文摘Among all segmentation techniques, Otsu thresholding method is widely used. Line intercept histogram based Otsu thresholding method(LIH Otsu method) can be more resistant to Gaussian noise, highly efficient in computing time, and can be easily extended to multilevel thresholding. But when images contain salt-and-pepper noise, LIH Otsu method performs poorly. An improved LIH Otsu method(ILIH Otsu method) is presented, which can be more resistant to Gaussian noise and salt-and-pepper noise. Moreover, it can be easily extended to multilevel thresholding. In order to improve the efficiency, the optimization algorithm based on the kinetic-molecular theory(KMTOA) is used to determine the optimal thresholds. The experimental results show that ILIH Otsu method has stronger anti-noise ability than two-dimensional Otsu thresholding method(2-D Otsu method), LIH Otsu method, K-means clustering algorithm and fuzzy clustering algorithm.
