This paper considers the upper orthant and extremal tail dependence indices for multivariate t-copula. Where, the multivariate t-copula is defined under a correlation structure. The explicit representations of the tai...This paper considers the upper orthant and extremal tail dependence indices for multivariate t-copula. Where, the multivariate t-copula is defined under a correlation structure. The explicit representations of the tail dependence parameters are deduced since the copula of continuous variables is invariant under strictly increasing transformation about the random variables, which are more simple than those obtained in previous research. Then, the local monotonicity of these indices about the correlation coefficient is discussed, and it is concluded that the upper extremal dependence index increases with the correlation coefficient, but the monotonicity of the upper orthant tail dependence index is complex. Some simulations are performed by the Monte Carlo method to verify the obtained results, which are found to be satisfactory. Meanwhile, it is concluded that the obtained conclusions can be extended to any distribution family in which the generating random variable has a regularly varying distribution.展开更多
Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigat...Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigated by X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical performance was characterized by long-term cycling, cyclic voltammetry, and in-situ impedance spectroscopy. The results indicated that high temperature rendered layered oxides to lose lithium/oxygen in the interior and exterior, and induced cationic disordering. Besides, the solid-phase synthesis process promoted phase transformation for electrode materials, causing the coexisting multi-phase in a single particle. High temperature can foster the growth of single particles, but it caused unstable structure of layered phase.展开更多
Peroxy radicals （ROx） concentrations were measured by Peroxy Radical Chemical Amplifier （PERCA） technique during the field campaign RISFEX 2003 （RiShifi Fall Experiment 2003）, which was performed in September 20...Peroxy radicals （ROx） concentrations were measured by Peroxy Radical Chemical Amplifier （PERCA） technique during the field campaign RISFEX 2003 （RiShifi Fall Experiment 2003）, which was performed in September 2003 at Rishiri island （45.07 N, 141.12 E, and 35 m asl） in the sea of Japan. The concentrations of nighttime ROx radicals had temporal variations around an average of 7.9±5.8 （1σ） pptv and showed a positive correlation with the summed mixing ratio of four monoterpene species. Model calculations suggested that local nighttime ROx radicals were dominated by the reactions of monoterpene with ozone （03） and nitrate radical （NO3）, contributing ca. 76% and 19%, respectively. The comparisons between the observed ROx and ones modeled had implied that the current model may be overestimated the yields of peroxy radicals from the reactions of monoterpenes with ozone and an important source of peroxy radicals was possibly missed. Abnormal high concentrations of observed ROx radicals were found during high relative humidity （RH） period （especially 〉 95%）, and the possible explanation was that the humidity correction of ROx radicals under high RH conditions may be inaccurate and overestimates ROx concen-展开更多
基金The National Natural Science Foundation of China(No.11001052,11171065)the National Science Foundation of Jiangsu Province(No.BK2011058)the Science Foundation of Nanjing University of Posts and Telecommunications(No.JG00710JX57)
文摘This paper considers the upper orthant and extremal tail dependence indices for multivariate t-copula. Where, the multivariate t-copula is defined under a correlation structure. The explicit representations of the tail dependence parameters are deduced since the copula of continuous variables is invariant under strictly increasing transformation about the random variables, which are more simple than those obtained in previous research. Then, the local monotonicity of these indices about the correlation coefficient is discussed, and it is concluded that the upper extremal dependence index increases with the correlation coefficient, but the monotonicity of the upper orthant tail dependence index is complex. Some simulations are performed by the Monte Carlo method to verify the obtained results, which are found to be satisfactory. Meanwhile, it is concluded that the obtained conclusions can be extended to any distribution family in which the generating random variable has a regularly varying distribution.
基金financial supports from the National Natural Science Foundation of China (51974368)the Fundamental Research Funds of the Central South University,China。
文摘Single-crystal Ni-rich cathode material LiNi0.88Co0.09Al0.03O2(SC) was synthesized by a high-temperature solid-state calcination method. Physicochemical properties of primary and delithiated SC samples were investigated by X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical performance was characterized by long-term cycling, cyclic voltammetry, and in-situ impedance spectroscopy. The results indicated that high temperature rendered layered oxides to lose lithium/oxygen in the interior and exterior, and induced cationic disordering. Besides, the solid-phase synthesis process promoted phase transformation for electrode materials, causing the coexisting multi-phase in a single particle. High temperature can foster the growth of single particles, but it caused unstable structure of layered phase.
基金supported by the Special Funds in Marine Public Service Project of State Oceanic Administration (201005025)National High-Tech Research and Development Plan (863) of China (2007AA092101)the International Scientific and Technological Cooperation Projects(2009DFB20610)
文摘Peroxy radicals （ROx） concentrations were measured by Peroxy Radical Chemical Amplifier （PERCA） technique during the field campaign RISFEX 2003 （RiShifi Fall Experiment 2003）, which was performed in September 2003 at Rishiri island （45.07 N, 141.12 E, and 35 m asl） in the sea of Japan. The concentrations of nighttime ROx radicals had temporal variations around an average of 7.9±5.8 （1σ） pptv and showed a positive correlation with the summed mixing ratio of four monoterpene species. Model calculations suggested that local nighttime ROx radicals were dominated by the reactions of monoterpene with ozone （03） and nitrate radical （NO3）, contributing ca. 76% and 19%, respectively. The comparisons between the observed ROx and ones modeled had implied that the current model may be overestimated the yields of peroxy radicals from the reactions of monoterpenes with ozone and an important source of peroxy radicals was possibly missed. Abnormal high concentrations of observed ROx radicals were found during high relative humidity （RH） period （especially 〉 95%）, and the possible explanation was that the humidity correction of ROx radicals under high RH conditions may be inaccurate and overestimates ROx concen-
