Nonlinear Wave in a Disc-Shaped Bose-Einstein Condensate

We discuss the possible nonlinear waves of atomic matter wave in a Bose-Einstein condensate. One and two of two-dimensional （2D） dark solitons in the Bose-Einstein condensed system are investigated. A rich dynamics is studied for the interactions between two solitons. The interaction profiles of two solitons are greatly different if the angle between them are different. If the angle is small enough, the maximum amplitude during the interaction between two solitons is even less than that of a single soliton. However, if the angle is large enough, the maximum amplitude of two solitons can gradually attend to the sum of two soliton amplitudes.     

双势阱中玻色-费米混合气体的周期调制效应

在周期调制场下, 通过对双势阱中费米子数目及相互作用参数的调节, 研究了该系统中玻色子的自俘获现象. 研究发现, 系统中费米子数目及相互作用参数都会影响玻色子的自俘获现象, 并且随着 相互作用及粒子数目的变化, 玻色子的自俘获发生临界现象. 关键词： 玻色-费米混合气体 周期调制 自俘获     

费米超流气体在幺正极限区域的非线性Ramsey干涉

该文分别研究了在三种极限情况下费米超流气体在幺正极限区域的非线性Ramsey干涉图样的频率与系统参数之间的关系, 研究发现费米子间的相互作用以及双势阱间最低能量差对干涉图样的角频率有显著的影响. 通过数值模拟和理论分析, 得到了干涉图样的角频率和系统参数之间的关系, 发现数值和解析结果符合得很好.     

修正Jacobi椭圆函数展开法及其应用

对Jacobi椭圆函数展开法进行了扩展, 且应用修正过的方法获得了若干非线性波动方程的更多的准确周期解, 补充了前面研究所得的结果. 关键词： Jacobi椭圆函数展开法 非线性演化方程 精确解 周期解     

ENVELOPE SOLITON UNDER DISSIPATION IN A FLUID-FILLED ELASTIC TUBE

By using the reductive perturbation method, the carrier wave modulation propagating in a weakly viscous fluid-filled elastic tube is investigated. It is shown that such a process can be described by equation A_τ+iBA_ξξ+iC|A|²A+DA=0 and the amplitude of envelope soliton will decrease as it propagates away.     

Toda晶格中特定孤立子的碰撞

给出了Ｔｏｄａ晶格中单孤立子的粒子运动速度的最大值，对特定的两孤立子的碰撞进行了分析，给出了碰撞前阪立子振幅的关系，如果两孤立子的振幅差别较大，方向相同，则在碰撞过程中粒子运动速度的最大值正归是原来二孤立子运动速度振幅之差，如果方向相反，则在碰撞过程中粒子运动速度的最大值正好是原来未碰撞前两孤立子运动速度振幅之和。     

杂质对Nb2GeC性质影响的第一性原理研究

为进一步研究Nb₂GeC在辐照环境中的稳定性, 本文研究了O, H和He杂质在Nb₂GeC中的稳定情况. 所有杂质的研究都是从替代和间隙两个方面来进行的, 计算得到了替代和间隙的形成能, 存在替代和间隙时Nb₂GeC的晶格常数, 以及单胞体积, 并且与完美的晶胞进行了比较. 此外, 通过电荷密度分布和Mulliken 布居, 分析了O, H, He杂质对Nb₂GeC 的电子性质的影响.     

两分量Bose-Einstein凝聚体的非线性Ramsey干涉

以非线性Rosen-Zener隧穿理论为基础,用两分量Bose-Einstein凝聚体设计了非线性Ramsey干涉计.通过数值模拟实验在时间域上观察到了丰富的Ramsey干涉图样,凝聚体中原子间重要的非线性相互作用导致这些干涉图样明显不同于线性Ramsey干涉时的正弦型条纹.通过进一步对干涉图样作Fourier分析,发现干涉图样的基频能够精确反映系统的非线性和不对称性特征,从而为测量原子的相关性质提供了理论依据. 关键词： Bose-Einstein凝聚 非线性Ramsey干涉 Rosen-Zener隧穿     

mKdV方程的双扭结单孤子及其稳定性研究

基于双曲函数法的思想,通过选择新的展开函数,得到了modified Korteweg-de Vries(mKdV)方程的几类精确解,其中一类为具有扭结—反扭结状结构的双扭结单孤子解.在不同的极限情况下,该解分别退化为mKdV方程的扭结状或钟状孤波解.文中对双扭结型孤子解的稳定性进行了数值研究,结果表明:在长波和短波简谐波扰动、钟型孤立波扰动与随机扰动下,该孤子均稳定.     

Generation of high quality ion beams through the stable radiation pressure acceleration of the near critical density target

In order to generate high quality ion beams through the stable radiation pressure acceleration(RPA) of the near critical density(NCD) target, we propose a new type of target where an ultra-thin high density(HD) layer is attached to the front surface of an NCD target, which has a preferable self-supporting property in the RPA experiments than the ultra-thin foil target. It is found that in one-dimensional particle-in-cell(PIC) simulation, by the block of the HD layer in the new target,there emerges the hole-boring process rather than propagation in the NCD layer when the intense laser pulse impinges on this target. As a result, a typical RPA structure that the compressed electron layer overlaps the ion layer as a whole is formed and a high quality ion beam is obtained, e.g., a circularly polarized laser pulse with normalized amplitude a_0= 120 impinges on this new target and a 1.2 GeV monoenergetic ion beam is generated through the RPA of the NCD layer. Similar results are also found in the two-dimensional PIC simulation.