五阶非线性下零色散附近的调制不稳定性

在同时考虑光纤损耗、高阶色散以及高阶非线性情况下,从广义非线性薛定谔方程出发,研究了零色散附近的调制不稳定性,分析了四阶色散和五阶非线性对增益谱的影响.结果表明：当光脉冲工作在零色散附近时,四阶色散对调制不稳定性起决定作用,它使反常色散区的增益谱变宽.在光纤正常色散区,正（负）五阶非线性使增益谱的谱宽和峰值增大（减小）;但在反常色散区,五阶非线性仅改变增益谱的峰值,几乎不影响谱宽.     

包含高阶色散的色散缓变光纤中交叉相位调制不稳定性分析

从包含高阶色散的广义非线性薛定谔方程出发,得到了色散缓变光纤中交叉相位调制不稳定增益谱,研究了增益谱随入射功率及光纤纵向色散参量的变化关系.结果表明：由于四阶色散的影响,在色散缓变光纤的正、反常色散区,交叉相位调制不稳定均发生在两个频谱区.反常色散区两频谱区宽度均比正常色散区宽,且反常色散区第二频谱区更靠近零点,说明色散缓变光纤中交叉相位调制不稳定更容易发生在反常色散区.增益谱宽都随两入射光波功率比值的增加而增大.色散缓变光纤中交叉相位调制不稳定增益谱宽比常规光纤的宽,且随着光纤纵向色散参量μ的增大色散缓变光纤中交叉相位调制不稳定越来越明显.     

强制对流条件下侧面散热对导热系数测量的影响

由于在实验过程中需要打开风扇因此侧面散热是平板法测量材料导热系数时不可忽略的一个问题,本文针对这种强制对流条件,根据传热理论得到合理的强制换热系数,研究了系统的侧面散热对测量结果的影响。研究结果表明,相比于加热盘的侧面散热,样品盘和散热盘侧面的散热对实验结果影响更大,这种影响对外界环境温度的变化并不敏感。如果采用自然对流条件进行模拟,散热盘的稳定温度值比实验值高出约17℃。虽然这种偏差会随着室温的升高而减小,但不可忽略。     

Density cavities generated by plasma--field interactions in the far wake region of a space vehicle

Under the consideration of non-steady case, a set of equations is derived, which describes the non-steady nonlinear interactions between plasma and field in the far wake region of a space vehicle. Numerical calculations are also made and the numerical results show that density cavities and electromagnetic solitary waves are generated due to the modulation instability, if the envelope of high frequency modulation field is strong enough. This is of great significance to the detection of disguised space vehicles.     

高阶色散导致的交叉相位调制不稳定性

在考虑光纤损耗及高阶色散的情况下,以三、四阶色散项的耦合非线性薛定谔方程为基础,研究高阶色散对交叉相位调制不稳定性的影响.研究表明:三阶色散对调制不稳定性不起作用;由于四阶色散的影响,在光纤的正常、反常色散区,交叉相位调制不稳定性均发生在两个频谱区.且反常色散区两频谱区都比正常色散区的宽,反常色散区第二频谱区比正常色散区的更靠近零点.光纤损耗对增益谱的谱宽有较大影响,它使增益的谱宽变窄,且随传输距离的增大谱宽变得更窄.     

Effects of a Weakly Interacting Light U Boson on Protoneutron Stars Including the Hyperon-Hyperon Interactions

In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the star maximum mass. The modification to the maximum mass by the U-boson with the strong YY interaction is larger than that with the weak YY interaction. The maximum mass of the protoneutron star is less sensitive to the U-boson than that of the neutron star. The inclusion of the U-boson narrows down the mass window for the hyperonized protoneutron stars. As g~2/μ~2 increases, the species of hyperons, which can appear in a stable protoneutron star decrease. The rotation frequency, the red shift, the momentum of inertia and the total neutrino fraction of PSR J1903-0327 are sensitive to the U-boson and change with g~2/μ~2 in an approximate linear trend. The possible way to constrain the coupling constants of the U-boson is discussed.     

空间飞行器近尾区内场和密度空腔的研究

在静态极限下,通过傅里叶变换,研究了空间飞行器近尾区内等离子体与场之间的非稳态非线性相互作用,并进行了数值求解。数值模拟结果表明,在飞行器近尾区内会产生电磁孤波和密度空腔,由电场的塌缩现象可以探测到它们。因而通过探测电磁孤波和密度空腔的形状和强度,能够探寻具有隐身特性的飞行器。     

四阶色散和五阶非线性对零色散附近交叉相位调制不稳定性的综合影响

从包含高阶色散和高阶非线性的广义非线性薛定谔方程出发,研究了零色散附近交叉相位调制不稳定性增益谱,分析了四阶色散和五阶非线性系数对增益谱的影响.结果表明：当光脉冲工作在零色散附近时,四阶色散对交叉相位调制不稳定性起决定作用,它使增益谱变宽.正（负）五阶非线性使增益谱的谱宽和峰值增大（减小）.随着二阶色散的增加,四阶色散对增益谱的影响越来越小.     

Non-steady interaction of plasma with aircraft in its near wake region

Non-steady interactions between plasmas and aircraft in its near wake region are investigated in detail. Under the non-static limit, a set of equations that describe these interactions are obtained. The results of the numerical simulation show that the cavitons of transverse plasmas are excited and density cavitons appear when the envelope of plasma becomes sufficiently intensive. This is very important for detecting the moving body that has a `stealth' characteristic.     

零色散附近的交叉相位调制不稳定性分析

以三、四阶色散项的耦合非线性薛定谔方程为基础，考虑光纤损耗及高阶色散，研究了双光束在零色散附近的交叉相位调制不稳定性.理论上导出描述交叉相位调制不稳定性的色散方程，并进行数值模拟计算.结果表明：由于四阶色散的影响，在光纤的正常、反常色散区，交叉相位调制不稳定性均发生在两个频谱区.如光脉冲工作在最小群速度色散附近时，四阶色散对光纤的交叉相位调制不稳定性将起决定性作用，可使增益谱出现一个新的峰值.光纤损耗使增益的谱宽变窄.对给定的传输距离，随着光纤向零色散附近靠近，两个频谱区谱宽增加直到相互重叠.数值分析了两光波有差别时的交叉相位调制不稳定性.