In this paper a novel low power online chromatic dispersion (CD) monitoring method is presented, which employs spectral shift in the semiconductor optical amplifier (SOA). The advantage of this method lies in that the...In this paper a novel low power online chromatic dispersion (CD) monitoring method is presented, which employs spectral shift in the semiconductor optical amplifier (SOA). The advantage of this method lies in that the required input power can be much reduced, and the filter output can be used in the dynamic CD compensation system. The simulation indicates that the filtered power decreases with CD increases, and that the monitoring range increases as the filter bandwidth increases.展开更多
The finite volume wave propagation method and the finite element RungeKutta discontinuous Galerkin(RKDG)method are studied for applications to balance laws describing plasma fluids.The plasma fluid equations explored ...The finite volume wave propagation method and the finite element RungeKutta discontinuous Galerkin(RKDG)method are studied for applications to balance laws describing plasma fluids.The plasma fluid equations explored are dispersive and not dissipative.The physical dispersion introduced through the source terms leads to the wide variety of plasma waves.The dispersive nature of the plasma fluid equations explored separates the work in this paper from previous publications.The linearized Euler equations with dispersive source terms are used as a model equation system to compare the wave propagation and RKDG methods.The numerical methods are then studied for applications of the full two-fluid plasma equations.The two-fluid equations describe the self-consistent evolution of electron and ion fluids in the presence of electromagnetic fields.It is found that the wave propagation method,when run at a CFL number of 1,is more accurate for equation systems that do not have disparate characteristic speeds.However,if the oscillation frequency is large compared to the frequency of information propagation,source splitting in the wave propagation method may cause phase errors.The Runge-Kutta discontinuous Galerkin method provides more accurate results for problems near steady-state as well as problems with disparate characteristic speeds when using higher spatial orders.展开更多
An algorithm to compute three-dimensional sediment transport effect was proposed in this paper to enhance the capability of depth-averaged numerical models. This algorithm took into account of non-uniform distribution...An algorithm to compute three-dimensional sediment transport effect was proposed in this paper to enhance the capability of depth-averaged numerical models. This algorithm took into account of non-uniform distributions of flow velocities and suspended sediment concentrations along water depth, it significantly enhanced the applicability of 2D models in simulating open channel flows, especially in channel bends. Preliminary numerical experiments in a U-shaped and a sine-generated experimental channel indicate that the proposed method performs quite well in predicting the change of bed-deformation in channel bends due to suspended sediment transport. This method provides an effective alternative for the simulations of channel morphodynamic changes.展开更多
基金This work was supported by the National Natural Science Foundation under Grant No. 90104003.
文摘In this paper a novel low power online chromatic dispersion (CD) monitoring method is presented, which employs spectral shift in the semiconductor optical amplifier (SOA). The advantage of this method lies in that the required input power can be much reduced, and the filter output can be used in the dynamic CD compensation system. The simulation indicates that the filtered power decreases with CD increases, and that the monitoring range increases as the filter bandwidth increases.
文摘The finite volume wave propagation method and the finite element RungeKutta discontinuous Galerkin(RKDG)method are studied for applications to balance laws describing plasma fluids.The plasma fluid equations explored are dispersive and not dissipative.The physical dispersion introduced through the source terms leads to the wide variety of plasma waves.The dispersive nature of the plasma fluid equations explored separates the work in this paper from previous publications.The linearized Euler equations with dispersive source terms are used as a model equation system to compare the wave propagation and RKDG methods.The numerical methods are then studied for applications of the full two-fluid plasma equations.The two-fluid equations describe the self-consistent evolution of electron and ion fluids in the presence of electromagnetic fields.It is found that the wave propagation method,when run at a CFL number of 1,is more accurate for equation systems that do not have disparate characteristic speeds.However,if the oscillation frequency is large compared to the frequency of information propagation,source splitting in the wave propagation method may cause phase errors.The Runge-Kutta discontinuous Galerkin method provides more accurate results for problems near steady-state as well as problems with disparate characteristic speeds when using higher spatial orders.
基金Project support by the National Natural Science Foundation of China (Grant No: 50479034), the Natural Science Foundation of Tianjin (Grant No: 05YFSZSF02100).
文摘An algorithm to compute three-dimensional sediment transport effect was proposed in this paper to enhance the capability of depth-averaged numerical models. This algorithm took into account of non-uniform distributions of flow velocities and suspended sediment concentrations along water depth, it significantly enhanced the applicability of 2D models in simulating open channel flows, especially in channel bends. Preliminary numerical experiments in a U-shaped and a sine-generated experimental channel indicate that the proposed method performs quite well in predicting the change of bed-deformation in channel bends due to suspended sediment transport. This method provides an effective alternative for the simulations of channel morphodynamic changes.
