二维多介质欧拉自适应网格方法研究

要对聚能和流场的剧烈变化进行模拟，欧拉方法具有明显的优势。而在这些方面的研究中，所涉及的流场十分复杂，为达到所需的计算精度，必须采用很密的网格才能以较好的分辨率去模拟流场的剧烈变化部分和介质的界面，特别是大空间尺度流场局部细节的数值模拟，有些问题如果用统一网格计算，即使最快的计算机也不能提供足够的分辨率。所以目前计算机的内存和速度限制了整个计算区域的网格细分程度，对计算区域作局部的网格自适应细分、用大的动态空间分辨率划分流场是必要的和迫切的。     

单粒子半单举快度分布的Cluster效应

本文用最小相对信息熵方法(MRIE)给出了高能强子-强子碰撞末态的单粒子半单举快度分布.发现Cluster效应导致了分布曲线峰位置的中心偏离.而且多重数越低,Cluster效应越明显.     

相对论重离子碰撞中有限碰撞时间对能量密度的影响

基于Monte Carlo模型"ODIN"分析了相对论重离子碰撞中能量刻度的时空发展.结果表明,由于有限的碰撞时间,实际达到的能量刻度明显低于Bjorken的估计值.     

等离子体中的迁移系数

从等离子体动力学方程出发,采用玻尔兹曼碰撞项,在粒子分布函数偏离麦克斯韦分布甚小的情况下,作三级矩近似得到了等离子体迁移方程组。迁移方程组中忽略时间微分项后,得出了电子-离子等离子体的张量形式迁移系数,以及与磁场方向成平行(∥)、垂直(⊥)和交叉方向的迁移系数。导出的结果和文献[1]采用朗道碰撞项得出的结果进行了比较。结果表明,迁移系数和等离子体参数的依赖关系是一致的,但对磁场B和离子电荷Z_i值取定时,个别迁移系数要差一倍。此外,导出的迁移系数形式比文献[1]的要简单些。     

类氖氩离子能级及碰撞强度的计算

利用扭曲波波恩近似方法及AUTOSTRUCTURE (AS)程序,快速精确地计算了类氖Ar8+离子2s22p6、2s22p53s、2s22p53p、2s22p53d、2s2p63s、2s2p63p和2s2p63d组态的能级以及当电子碰撞能量为75.0、125.0、175.0、250.0 (Ry)时,从j能态到i能态的碰撞强度.并且与已有的研究成果进行了对比.结果表明,采用扭曲波波恩近似并结合AUTOSTRUCTURE (AS)程序的研究方法,可以成为研究原子或离子碰撞强度的有效途径。     

不等长相移效应滤波器的快速调试方法北大核心CSCD

提出一种基于渐进空间映射算法(ASM)与遗传算法(GA)相结合的I/O端口不等长相移效应的滤波器快速调试方法。渐进空间映射算法能够准确预测精细模型的调试方向与幅度,遗传算法能够准确快速得到I/O端口的相移效应,并且通过柯西法提取粗糙模型。基于有限元的全波电磁仿真软件HFSS,建立精细模型,粗糙模型参数即等效电路参数,则由去除I/O端口处相移效应后的S参数获得。利用该方法对六阶交叉耦合滤波器进行调试,经过几步迭代即可使滤波器满足所要求的响应指标,验证了该调试方法的正确性和有效性。     

势能的对称性与守恒定律

本文分析了势能的时空对称性与三个守恒定律的关系。     

Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B1∏ of 7LiH

The reasonable dissociation limit of the second excited singlet state B¹∏ of ⁷LiH molecule is obtained. The accurate dissociation energy and equilibrium geometry of the B¹\Pi state are calculated using a symmetry-adapted-cluster configuration--interaction method in full active space. The whole potential energy curve for the B¹∏ state is obtained over the internuclear distance ranging from about 0.10nm to 0.54nm, and has a least-square fit to the analytic Murrell--Sorbie function form. The vertical excitation energy is calculated from the ground state to the B¹∏ state and compared with previous theoretical results. The equilibrium internuclear distance obtained by geometry optimization is found to be quite different from that obtained by single-point energy scanning under the same calculation condition. Based on the analytic potential energy function, the harmonic frequency value of the B¹∏ state is estimated. A comparison of the theoretical calculations of dissociation energies, equilibrium interatomic distances and the analytic potential energy function with those obtained by previous theoretical results clearly shows that the present work is more comprehensive and in better agreement with experiments than previous theories, thus it is an improvement on previous theories.     

Spatial interpolation of HRTFs and signal mixing for multichannel surround sound

From the point of spatial sampling, spatial interpolation of HRTFs (head-related transfer functions) and signal mixing for multichannel (surround) sound are analyzed. First, it is proved that they are mathematically equivalent. Different methods for HRTFs interpolation are equivalent to different signal mixing methods for multichannel sound. Then, a stricter derivation for the signal mixing of multichannel sound and the law of sine for stereophonic sound is given. It is pointed out that trying to reconstruct lateral HRTFs by adjacent linear interpolation is wrong. And for accurate sound image localization, the conventional equation of adjacent linear interpolation of HRTFs is revised. At last, it is also pointed out that some methods used in the analysis of HRTFs and multichannel sound can be used for reference mutually.