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841.
为便于城际铁路企业及时、合理地调整城际铁路运输属性,使其能在区域交通走廊各种交通工具竞争激烈的条件下健康运营和可持续性发展,分析了城际间各交通工具的属性特征,并对其进行了定量化描述。以城际铁路企业利润最大化为优化目标,考虑了城际铁路应取得最小社会效益的约束,建立了城际铁路运输属性设置及调整的多元非线性模型。利用罚函数法把模型转化为无约束的非线性模型,运用步长加速法进行求解。最后,把所设计的模型及算法应用到长株潭城际铁路初期运输属性设置中,结果表明本文所建立的模型及采用的算法是可行的,得到的城际铁路的技术经济特征设置值能为企业决策提供参考。 相似文献
842.
843.
本文研究了激光尾场实验中的透射光谱。和标准尾场实验不同的是,我们采用了更高的等离子体密度。实验中仍然观察到了明显的频谱加宽与频谱分裂,这是光子加速的显著标志。为解释该现象,我们做了二维粒子模拟。模拟结果证明在该高密度等离子体中, 光子加速仍然可以发生。 相似文献
844.
Effects of ions charge-mass ratio on energy and energy spread of accelerated ions in laser driven plasma are investigated in detail by proposing a simple double-layer model for a foil target driven by an ultrastrong laser. The radiation pressure acceleration mechanism plays an important role on the studied problem. For the ions near the plasma mirror, i.e. electrons layer, the dependence of ions energy on their charge-mass ratio is derived theoretically. It is found that the larger the charge-mass ratio is, the higher the accelerated ions energy gets. For those ions far away from the layer, the dependence of energy and energy spread on ions charge-mass ratio are also obtained by numerical performance. It exhibits that, as ions charge-mass ratio increases, not only the accelerated ions energy but also the energy spread will become large. 相似文献
845.
Xiuquan Huang Hangkong Wu 《International Journal of Computational Fluid Dynamics》2013,27(4-5):218-232
ABSTRACTThis paper presents efficient alternative numerical methods for an implicit solution of the harmonic balance equation system for analysing temporal periodic unsteady flows. The proposed method employs approximate factorisation to decouple the common residual term and the time spectral source term of a harmonic balance equation system when it is discretised implicitly. With this approximate factorisation, the complexity of implicit solution of the discrete system is greatly reduced. The common residual term can be dealt with using a lower-upper symmetric-Gauss-Seidel (LU-SGS) method and the time spectral source term is integrated using a Jacobi iteration (JI) or one step Gauss-Seidel (GS) iteration, leading to the LU-SGS/JI method or LU-SGS/GS method. The NASA stage 35 compressor and the 1.5 stage Aachen turbine were used to demonstrate the effectiveness of the proposed methods in stabilising solution and its advantages in comparison with the existing lower-upper symmetric-Gauss-Seidel/block Jacobi (LU-SGS/BJ) method. The LU-SGS/GS method and the LU-SGS/JI method are more robust than the LU-SGS/BJ method in stabilising solution. The LU-SGS/GS method also has faster and tighter convergence and lower memory consumption in comparison with the LU-SGS/BJ method. 相似文献
846.
847.
A scheme of generating energetic ions by the interaction
of an ultrahigh-intensity laser pulse and a thin solid foil is
studied. The combination of the effects of radiation pressure and
Coulomb explosion makes the ion acceleration more effective. The
maximum ion velocity variation with time is predicted theoretically
while the temporal evolution of the electrostatic field due to the
Coulomb explosion is taken into consideration. Two-dimensional
particle-in-cell simulations are done to verify the theory. 相似文献
848.
The direct acceleration of electrons by using two linearly polarized crossed
Bessel--Gaussian (BG) beams with equal frequency and amplitude in vacuum is proposed
and studied. It is shown that two linearly polarized BG beams of the same order (0
or 1) with a \textit{\pi }-rad phase difference have a resultant non-zero
longitudinal electric field on the z-axis and can be used, in principle, to
accelerate electrons. 相似文献
849.
为了研究在激光驱动的等离子体尾场中被加速正电子的动力学,使用了由电子、正电子、离子组成的等离子体,通过采用数值模拟方法得到了非对称脉冲驱动的尾波场中被加速的正电子的运动相图、动能变化,势能。数据结果表明:非对称激光脉冲驱动尾场中正电子得到很高的能量。提高等离子体中的正电子比例会使电子和正电子的加速效果减弱。在非对称激光脉冲驱动的激光尾场中,为了有效地加速正电子,要选择恰当的上升激光脉冲长度和下降激光脉冲长度。 相似文献
850.
The dephasing time of a positron in the total field associated with a laser pulse in a plasma J28is studied numerically. It is shown that the dynamics of the positron is quite different from that of an electron due to the electrostatic potential in the body of the pulse. The dephasing time of the positron increases with the pulse length and decreases with the pulse intensity nonlinearly. In the long pulse case (L》λp) the dephasing time is proportional to the pulse length. These results provide a scientific basis for experiments to observe the positron acceleration scheme, and may be important to the physics of laser-article interactions in multi-component plasmas. 相似文献