We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining...We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density j^Ts,xi and j^Ts,yi（i=x, y, z）. We find that the elements j^Ts,xx and j^Ts,yy have a antisymmetrical relation and the element j^Ts,yz has the same amount levelas j^Ts,xx and j^Ts,yy. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.展开更多
The flow of a freely falling liquid film of low Reynolds number down a vertical long periodic sine-shaped wavy plate of small corrugations is researched theoretically. A model based on perturbation method and power se...The flow of a freely falling liquid film of low Reynolds number down a vertical long periodic sine-shaped wavy plate of small corrugations is researched theoretically. A model based on perturbation method and power series is presented. A stream function is introduced into the governing equations and two sets of equations describing the film flow separately at zeroth and first order are developed. The zeroth order equation is solved directly. The first order equations is solved at the leading approximation. Effect of parameters Re, M, λ and ε on the free surface wave of film is discussed.展开更多
AC / DC converter is a kind of devices applicable to reactive power compensation. Three parameters including losses, Total Harmonic Distortion （THD） and compensation capacity have important role in designing procedu...AC / DC converter is a kind of devices applicable to reactive power compensation. Three parameters including losses, Total Harmonic Distortion （THD） and compensation capacity have important role in designing procedure that these parameters are affected by the firing angle. Consideration trade of between these parameters can cause be selected suitable firing angle for optimal working of the compensator. In this paper is defined an objective function which includes the above parameters. This objective function is optimized through appropriate weighting factor for any parameters and the optimal firing angle will be obtained. So, the mention parameters can be selected optimally.展开更多
An admissible manifold wavelet kernel is proposed to construct manifold wavelet support vector machine(MWSVM) for stock returns forecasting.The manifold wavelet kernel is obtained by incorporating manifold theory into...An admissible manifold wavelet kernel is proposed to construct manifold wavelet support vector machine(MWSVM) for stock returns forecasting.The manifold wavelet kernel is obtained by incorporating manifold theory into wavelet technique in support vector machine(SVM).Since manifold wavelet function can yield features that describe of the stock time series both at various locations and at varying time granularities,the MWSVM can approximate arbitrary nonlinear functions and forecast stock returns accurately.The applicability and validity of MWSVM for stock returns forecasting is confirmed through experiments on real-world stock data.展开更多
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20060542002the Hunan Provincial Natural Science Foundation of China under Grant No.06JJ2097the Hunan College of Science and Technology Research Foundation of China under Grant No.07XKYTB001
文摘We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density j^Ts,xi and j^Ts,yi（i=x, y, z）. We find that the elements j^Ts,xx and j^Ts,yy have a antisymmetrical relation and the element j^Ts,yz has the same amount levelas j^Ts,xx and j^Ts,yy. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.
基金Acknowledgement： This work is supported by Natural Science Foundation of Tianjin of China （No. 07JCYBJC01300）.
文摘The flow of a freely falling liquid film of low Reynolds number down a vertical long periodic sine-shaped wavy plate of small corrugations is researched theoretically. A model based on perturbation method and power series is presented. A stream function is introduced into the governing equations and two sets of equations describing the film flow separately at zeroth and first order are developed. The zeroth order equation is solved directly. The first order equations is solved at the leading approximation. Effect of parameters Re, M, λ and ε on the free surface wave of film is discussed.
文摘AC / DC converter is a kind of devices applicable to reactive power compensation. Three parameters including losses, Total Harmonic Distortion （THD） and compensation capacity have important role in designing procedure that these parameters are affected by the firing angle. Consideration trade of between these parameters can cause be selected suitable firing angle for optimal working of the compensator. In this paper is defined an objective function which includes the above parameters. This objective function is optimized through appropriate weighting factor for any parameters and the optimal firing angle will be obtained. So, the mention parameters can be selected optimally.
基金the Hunan Natural Science Foundation(No. 09JJ3129)the Hunan Key Social Science Foundation (No. 09ZDB04)the Hunan Social Science Foundation (No. 08JD28)
文摘An admissible manifold wavelet kernel is proposed to construct manifold wavelet support vector machine(MWSVM) for stock returns forecasting.The manifold wavelet kernel is obtained by incorporating manifold theory into wavelet technique in support vector machine(SVM).Since manifold wavelet function can yield features that describe of the stock time series both at various locations and at varying time granularities,the MWSVM can approximate arbitrary nonlinear functions and forecast stock returns accurately.The applicability and validity of MWSVM for stock returns forecasting is confirmed through experiments on real-world stock data.
