Co-P （4.9% P） powders with a chain-like morphology were prepared by a novel chemical reduction method. The Co-P and germanium powders were mixed at various mass ratios to form Co-P composite electrodes. Charge and d...Co-P （4.9% P） powders with a chain-like morphology were prepared by a novel chemical reduction method. The Co-P and germanium powders were mixed at various mass ratios to form Co-P composite electrodes. Charge and discharge test and electrochemical impedance spectroscopy （EIS） were carried out to investigate the electrochemical performance, which can be significantly improved by the addition of germanium. For instance, when the mass ratio of Co-P powders to germanium is 5：1, the sample electrode shows a reversible discharge capacity of 350.3 mA·h/g and a high capacity retention rate of 95.9% after 50 cycles. The results of cyclic voltammmetry （CV） show the reaction mechanism of Co/Co（OH）2 within Co-P composite electrodes and EIS indicates that this electrode shows a low charge-transfer resistance, facilitating the oxidation of Co to Co（OH）2.展开更多
Effective spin-polarized injection from magnetic semiconductor （MS） to nonmagnetic semiconductor （NMS） has been highlighted in recent years. In this paper we study theoretically the dependence of nonequilibrium sp...Effective spin-polarized injection from magnetic semiconductor （MS） to nonmagnetic semiconductor （NMS） has been highlighted in recent years. In this paper we study theoretically the dependence of nonequilibrium spin polarization （NESP） in NMS during spin-polarized injection through the magnetic p-n junction. Based on the theory in semiconductor physics, a model is established and the boundary conditions are determined in the case of no external spin-polarized injection and low bias. The control parameters that may influence the NESP in NMS are indicated by calculating the distribution of spin polarization. They are the doping concentrations, the equilibrium spin polarization in MS and the bias. The effective spin-polarized injection can be realized more easily by optimizing the above parameters.展开更多
The author studies the global convergence of a solution of p-Ginzburg-Landau equations when the parameter tends to zero. The convergence is in C^α sense, which is derived by establishing a uniform gradient estimate f...The author studies the global convergence of a solution of p-Ginzburg-Landau equations when the parameter tends to zero. The convergence is in C^α sense, which is derived by establishing a uniform gradient estimate for some solution of a regularized p-Ginzburg-Landau equations.展开更多
Broadband three-component seismic data recorded by Beijingstation (BJI) of CDSN were used to calculate P-wave polarization of teleseismic events. These polarization data were then used in the inversion for the undergr...Broadband three-component seismic data recorded by Beijingstation (BJI) of CDSN were used to calculate P-wave polarization of teleseismic events. These polarization data were then used in the inversion for the underground structure around the Beijing station, especially for the details of velocity discontinuities. The result shows that a conspicuous low velocity zone exists in the crust on the west of the station, which is in good agreement with previous studies. It proves the theory that polarization data could be applied to inversion for velocity structures, especially for boundaries with large velocity gradient. It also demonstrates the feasibility of velocity structure inversion with polarization data from high-quality broadband data recorded by a single station. Therefore, travel-times and polarization data can be jointly used to study velocity structure. Polarization data are more suitable for delineating the boundary of velocity anomalies. Moreover, if the polarization method is combined with receiver function method to fully exploit their complementarity, it is possible to obtain the lateral velocity variation around the station as well as the detailed vertical variation below the station.展开更多
The basic physical properties of La_2CuBiS_5 are studied by the first-principle calculations and the semiclassical Boltzmann theory.Charge density difference calculations show that electrons accumulate between Bi-S at...The basic physical properties of La_2CuBiS_5 are studied by the first-principle calculations and the semiclassical Boltzmann theory.Charge density difference calculations show that electrons accumulate between Bi-S atoms,indicating considerable covalent bonding of Bi and S atoms.A similar charge density difference indicates that the Cu-S bonds also exhibit covalent character.The calculated minimum thermal conductivity of La_2CuBiS_5 is low,which is conducive to its use as a thermoelectric material.Owing to a bipolar effect,induced by thermal excitation,the material＇s Seebeck coefficient decreases sharply at T = 800 K.For the n-type and p-type doping conditions,the largest values of S^2σ/τ were calculated as-1.71×10^（11） and 1.837×10^（11） W K^（-2）ms^（-1）,respectively.The combination of a large dispersion and a high band degeneracy along the Γ-Y direction in the band structure simultaneously induces the highest S_y value and a high σ/τ_y value.Thus,the thermoelectric performance of La_2CuBiS_5 is anisotropic and most favorable along the y direction.展开更多
基金Project supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions of ChinaProject(CXLX11_0359)supported by Research Innovative Projects for Average College Graduate Students of 2011 in Jiangsu Province,China+2 种基金Project(RERU2011010)supported by Open Subject of State Key Laboratory of Rare Earth Resource Utilization,ChinaProject(51201089)supported by the National Natural Science Foundation of ChinaProject(CPSF2012M521064)supported by China Postdoctoral Science Foundation
文摘Co-P （4.9% P） powders with a chain-like morphology were prepared by a novel chemical reduction method. The Co-P and germanium powders were mixed at various mass ratios to form Co-P composite electrodes. Charge and discharge test and electrochemical impedance spectroscopy （EIS） were carried out to investigate the electrochemical performance, which can be significantly improved by the addition of germanium. For instance, when the mass ratio of Co-P powders to germanium is 5：1, the sample electrode shows a reversible discharge capacity of 350.3 mA·h/g and a high capacity retention rate of 95.9% after 50 cycles. The results of cyclic voltammmetry （CV） show the reaction mechanism of Co/Co（OH）2 within Co-P composite electrodes and EIS indicates that this electrode shows a low charge-transfer resistance, facilitating the oxidation of Co to Co（OH）2.
基金Project supported by the National Natural Science Foundation of China （Grant No 60606021）, the Specialized Research Fund for the Doctoral Program of Higher Education of China （Grant No 20060003067） and the Key Fundamental Research Foundation of Tsinghua University of China （Grant No Jz2001010）.
文摘Effective spin-polarized injection from magnetic semiconductor （MS） to nonmagnetic semiconductor （NMS） has been highlighted in recent years. In this paper we study theoretically the dependence of nonequilibrium spin polarization （NESP） in NMS during spin-polarized injection through the magnetic p-n junction. Based on the theory in semiconductor physics, a model is established and the boundary conditions are determined in the case of no external spin-polarized injection and low bias. The control parameters that may influence the NESP in NMS are indicated by calculating the distribution of spin polarization. They are the doping concentrations, the equilibrium spin polarization in MS and the bias. The effective spin-polarized injection can be realized more easily by optimizing the above parameters.
基金NNSF of China (19271086)Tianyuan Fund of Mathematics (A0324628) (China)
文摘The author studies the global convergence of a solution of p-Ginzburg-Landau equations when the parameter tends to zero. The convergence is in C^α sense, which is derived by establishing a uniform gradient estimate for some solution of a regularized p-Ginzburg-Landau equations.
基金The data are provided by CDSN of China Seismological Bureau, Mr. Zhang Decun and other colleagues in the Institute of Geophysics of CSB gave great help The discussion with colleagues in the research group was greatly beneficial The authors are deeply
文摘Broadband three-component seismic data recorded by Beijingstation (BJI) of CDSN were used to calculate P-wave polarization of teleseismic events. These polarization data were then used in the inversion for the underground structure around the Beijing station, especially for the details of velocity discontinuities. The result shows that a conspicuous low velocity zone exists in the crust on the west of the station, which is in good agreement with previous studies. It proves the theory that polarization data could be applied to inversion for velocity structures, especially for boundaries with large velocity gradient. It also demonstrates the feasibility of velocity structure inversion with polarization data from high-quality broadband data recorded by a single station. Therefore, travel-times and polarization data can be jointly used to study velocity structure. Polarization data are more suitable for delineating the boundary of velocity anomalies. Moreover, if the polarization method is combined with receiver function method to fully exploit their complementarity, it is possible to obtain the lateral velocity variation around the station as well as the detailed vertical variation below the station.
基金supported by the National Natural Science Foundation of China(11047108)the Program for Excellent Younger teachers in the universities in Henan Province of China,the Program for the Research Project of Basic and Frontier Technology of Henan Province(112300410183)the Program for Henan Postdoctoral Science Foundation,and the Foundation of Henan Educational Committee(2011B140002,14A140016,14A430029 and 14B140003)
文摘The basic physical properties of La_2CuBiS_5 are studied by the first-principle calculations and the semiclassical Boltzmann theory.Charge density difference calculations show that electrons accumulate between Bi-S atoms,indicating considerable covalent bonding of Bi and S atoms.A similar charge density difference indicates that the Cu-S bonds also exhibit covalent character.The calculated minimum thermal conductivity of La_2CuBiS_5 is low,which is conducive to its use as a thermoelectric material.Owing to a bipolar effect,induced by thermal excitation,the material＇s Seebeck coefficient decreases sharply at T = 800 K.For the n-type and p-type doping conditions,the largest values of S^2σ/τ were calculated as-1.71×10^（11） and 1.837×10^（11） W K^（-2）ms^（-1）,respectively.The combination of a large dispersion and a high band degeneracy along the Γ-Y direction in the band structure simultaneously induces the highest S_y value and a high σ/τ_y value.Thus,the thermoelectric performance of La_2CuBiS_5 is anisotropic and most favorable along the y direction.
