A Simple proof for the stability of global FIFO queueing networks

We study the stability of multiclass queueing networks under the global FIFO （first in first out） service discipline, which was established by Bramson in 2001. For these networks, the service priority of a customer is determined by his entrance time. Using fluid models, we describe the entrance time of the most senior customer in the networks at time t, which is the key to simplify the proof for the stability of the global FIFO queueing networks.     

A second-order pseudo-transient method for steady-state problems

This article gives a second pseudo-transient method for a special system of nonlinear equations, which arises from chemical reaction rate equations. This method uses a special second-order Rosenbrock method as the discrete difference scheme, which satisfies a linear conservation law. Moreover, it adaptively adjusts the time step in inverse proportion to an arithmetic mean of the current residual and the previous residual at every iteration step. For a singular system of nonlinear equations, under some standard assumptions, local convergence of the new method is addressed. Finally, some promise numerical results are also reported.     

Cladding-ring-equivalent effective index method for analyzing the propagation characteristics of multi-cladding photonic crystal fibers

Cladding-ring-equivalent effective index method (CREEIM) is proposed to analyze the propagation characteristics in the multi-cladding photonic crystal fibers (MCPCFs). The effective indices and dispersions of the step index two and three-cladding structures are calculated with the Sellmeier formula. The accuracy of CREEIM is competitive to the results calculated by the multipole method (MPM). With different structure parameters, the differences between two methods are evaluated with the relative error R_E of effective index and relative difference R_D of dispersion. This method is also used to analyze the mode cut-off and nonlinear characteristics in the three-cladding structure PCFs by calculating the mode effective index n_eff instead of complex mode field distribution.     

Multisoliton excitations for the Kadomtsev–Petviashvili equation and the coupled Burgers equation

In high dimensions, there are abundant coherent soliton excitations. From the variable separation approach of the celebrated Kadomtsev–Petviashvili(KP) equation and the coupled Burgers equation, several new multisoliton excitations are derived and some novel features or interesting behaviors of these structures are revealed.     

Application of carbon materials as counter electrodes of dye-sensitized solar cells

Hard carbon spherule (HCS) has been investigated as a counter electrode for dye-sensitized solar cells. The overall conversion efficiency of the cell reached 5.7%, which is comparable to 6.5% of the counter electrode of platinum-sputtered fluorine-doped tin oxide used in Grätzel-type solar cells under the same experimental condition. It is found that the photovoltaic performance was strongly affected by the specific surface areas of the carbon materials.     

Symbolic-computation construction of transformations for a more generalized nonlinear Schrödinger equation with applications in inhomogeneous plasmas,optical fibers,viscous fluids and Bose-Einstein condensates

Currently, the variable-coefficient nonlinear Schr?dinger (NLS)-typed models have attracted considerable attention in such fields as plasma physics, nonlinear optics, arterial mechanics and Bose-Einstein condensates. Motivated by the recent work of Tian et al. [Eur. Phys. J. B 47, 329 (2005)], this paper is devoted to finding all the cases for a more generalized NLS equation with time- and space-dependent coefficients to be mapped onto the standard one. With the computerized symbolic computation, three transformations and relevant constraint conditions on the coefficient functions are obtained, which turn out to be more general than those previously published in the literature. Via these transformations, the Lax pairs are also derived under the corresponding conditions. For physical applications, our transformations provide the feasibility for more currently-important inhomogeneous NLS models to be transformed into the homogeneous one. Applications of those transformations to several example models are illustrated and some soliton-like solutions are also graphically discussed.     

级联光交叉连接和光分插复用系统串扰研究

分析了光网络节点串扰产生的原因以及级联光交叉连接(OXC)和光分插复用(OADM)系统的串扰,对级联系统进行模拟,计算并分析了光开关隔离度、上路信号的功率差对系统误码率的影响,得出了光开关隔离度是产生串扰的主要原因、在光开关前进行功率均衡有利于提高系统误码性能等结论.     

On the solitonic structures of the cylindrical dust-acoustic and dust-ion-acoustic waves with symbolic computation

Dusty plasmas can support the dust-ion-acoustic and dust-acoustic modes, modelled by the cylindrical Korteweg–de Vries equation as proposed. In this Letter, we point out that there exist a couple of problems in the plasma-physics literature on the cylindrical Korteweg–de Vries equation, i.e., the claim of non-existence of exact analytic solutions and omission of varying ambient field, to which we provide our answers. With symbolic computation, we obtain a family of exact analytic, solitonic solutions, of which the previous solutions in plasma physics turn out to be the special cases. With figures, we work out some possibly observable effects for the future plasma experiments, featured by a solitonic pulse aboard the varying ambient field propagating with its varying velocity and amplitude.     

单模光纤二阶偏振模色散的Jones矩阵

利用单模光纤PMD矢量与Jones矩阵之间的关系,推导了由该矢量表示的光纤二阶PMD的Jones矩阵解析表达式,利用该矩阵可以确定输出端时域脉冲在二阶PMD近似下的表达式,并由此仿真二阶PMD对信号传输质量的影响.通过比较输入与输出信号脉冲波形和眼图发现,随着传输速率和传输距离的增加输出信号劣化.最后结果表明,当主偏振态的旋转速率为零时,二阶PMD的影响可以忽略;但当其值增大时,输出信号劣化严重.在光纤通信系统设计时,需要考虑偏振模色散影响分析结果,可提供参考依据.     

资源受限下森林火灾应急救援多目标调度优化

许多森林火灾由于救援资源受限而不能在第一时间扑灭,导致火灾扩大蔓延,进而造成更大的森林资源损失。因此,在救援资源受限情形下,如何对消防救援车辆进行合理的调度安排以快速和低成本地扑灭火灾已成为亟待解决的现实问题。本文研究了一类资源受限下森林火灾应急救援多目标调度优化问题,为该问题构建了多目标混合整数非线性规划模型,优化目标为同时最小化总灭火救援时间和救援车辆总行驶距离。为有效求解该问题,首先将上述非线性模型等价转化为线性模型。然后提出ε-约束法和模糊逻辑相结合的算法对问题进行求解。最后,以大兴安岭山发生的火灾案例和随机生成仿真算例对模型和算法有效性进行验证,结果表明所提出的模型和算法能够有效解决资源受限下森林火灾应急救援问题,并为决策者提供最优的消防调度方案。