相对论性力学系统的Birkhoff对称性与守恒量

提出了相对论性力学系统的一种新的对称性,并给出了此对称性导致的守恒量.提出了相对论性力学系统的Birkhoff对称性,即对应于相对论性力学系统的一组Birkhoff动力学函数的运动微分方程的解都满足从另一组Birkhoff动力学函数得到的运动微分方程.证明了与两组Birkhoff动力学函数分别给出的相对论性Birkhoff方程相关联的系数矩阵的各次幂的迹是系统的一个守恒量,从而将Currie和Saletan提出的力学系统的等效Lagrange函数定理拓展到了相对论性Birkhoff动力学系统.给出了两个例子以说明结果的正确性.     

Spectroscopic properties of thulium ions in bismuth silicate glass

A new type of bismuth silicate glass (Bi2O3-SiO2-ZnO-Al2O3-La2O3) doped with Tm2O3 is prepared by melt-quenching method. The thermal stability of the glass is examined by differential scanning calorimetry. No crystallization peak is found. Using the absorption and emission spectra, the absorption and emission cross-sections are calculated. Their maximum data are 2.9×10-21cm2 at 1663 nm and 4.7×10-21cm2 at 1826 nm, respectively. Using the Judd-Ofelt theory, the radiation transition probabilities and radiative lifetimes are obtained. The extended overlap integral method is applied to analyze energy transfer process among the Tm3+ ions. The transfer constants of cross-relaxation and energy migration among the Tm3+ ions at the 3H4 level are 7.60×10-40 and 14.98×10-40 cm6 /s, respectively. The critical transfer radius for cross-relaxation is 0.99 nm. The cross relaxation process is easy to realize and is favorable for obtaining ～2-μm laser.     

完整系统Appell方程的Lie-Mei对称性与守恒量

研究了完整系统Appell方程的Lie-Mei对称性与守恒量.在完整系统Appell方程的基础上,给出了Appell方程的Lie-Mei对称性的定义和判据,得到了Appell方程的Lie-Mei对称性导致的Hojman守恒量和Mei守恒量.举例说明结果的应用.     

Capacitance of Organic Schottky Diodes Based on Copper Phthalocyanine （CuPc）

The capacitance of an organic Schottky diode based on copper phthalocyanine （CuPc） is investigated. Based on the organic small-signal equivalent model established, we calculate the reverse capacitance CMetal Of the organic Schottky diode with different kinds of metal cathodes （Mg, Al, Au）. It is found that the reverse capacitance of the organic Schottky diode shows behavior as CMg 〉 CAl 〉 CAu at the same frequency, and according to our analysis, the reverse Schottky junction capacitance Cj is expected to have little effect on the reverse capacitance of the organic Schottky diode, and the space-charge limited current capacitance Us is considered to dominate the reverse capacitance, which limits the improvement of frequency characteristics of organic Schottky diodes.     

用推广的等效两体方法求解类氦离子三体问题

介绍了求解三体问题的等效两体方法,将等效两体方法推广到原子系统,利用该方法求解类氦离子的基态,与一般的单参数变分法相比得到了与实验值符合得更好的结果,进而利用双参数变分法对所得结果进行了检验。 结果表明,等效两体方法同样适用于求解原子系统中的三体问题。 An extended equivalent two body method for three body systems is introduced in this article. The method is applied to an atomic three body system. Energies and wave functions of a helium like ion are calculated,which are consistent with the experimental data much better,in contrast to the results obtained by a one parameter calculus of variations approach. Then we use a two parameter calculus of variations approach to verify the precision of the ground state energy and wave function obtained by the extended equivalent two body method. These results indicated that the extended equivalent two body method is applicable to an atomic three body problem.     

“用油膜法估测分子的大小”实验的几个问题

用油膜法估测分子直径的大小是中学物理实验中的一个具有特别意义的实验,因为利用宏观量的测量求出微观量的大小,这在中学物理实验中是唯一的一个,体现了一个很重要的思想.对于提高学生对微观世界的认识非常重要,教师一定要认真引导学生做好.原理很简单,但实验产生的误差较大,不易成功,众说纷纭,值得探究.     

声矢量锥形阵的高阶累积量波达方向估计

为解决信源在较低信噪比情况下的测向分辨率问题,提出阵列可扩展的声矢量锥形阵测向算法。算法基于四阶累积量的阵列扩展和高斯噪声抑制特性,计算声矢量传声器不同输出分量的四阶累积量,使其在三维方向上扩展与原阵型结构相同的虚拟阵,从而构造包含角度信息的旋转不变矩阵进行测向。推导给出了算法的克拉美罗界,理论分析了算法性能受信噪比、采样快拍以及入射声源俯仰角的影响。仿真实验验证了该算法较常规声矢量阵ESPRIT算法有更优的噪声抑制能力及更高分辨的DOA估计性能。     

Z箍缩软X射线辐射能量薄膜量热计改进技术

薄膜量热计是进行Z箍缩辐射总能量测量的主要手段之一,准确可信的总能量参数对Z箍缩研究具有重要意义。对薄膜量热计装置进行技术改进,采用脉冲恒流源代替脉冲恒压源驱动镍薄膜量热计,撤除了回路中的串接电阻,可直接测量薄膜探测器的电阻变化,从而有效提高了辐射总能量测量的精度,拓宽了该设备的适用范围,使其可对目前强光一号加速器Z箍缩实验中所有典型负载进行测量。改进后平面型铝丝阵负载实验中总能量测量的相对不确定度由49.0%降低为19.6%。与闪烁探测系统功率测量结果积分值进行了对比,二者比值在0.87~1.04之间。     

Bianchi Type-V Magnetized String Cosmological Model with Variable Magnetic Permeability for Viscous Fluid distribution

We investigate the Bianchi type-V magnetized string cosmological model with variable magnetic permeability for viscous fluid distribution. The magnetic field is due to an electric current produced along the x-axis. Thus the magnetic field is in yz-plane and F23 is the only non-vanishing component of electromagnetic field tensor Fij. To obtain the deterministic model in terms of cosmic time t, we assume the condition ξθ const where ξ is the coefficient of bulk viscosity and θ the expansion in the model.     

浙江省电力系统噪声综合治理研讨会在杭州举行

为贯彻执行江泽民主席2001年第60号令[中华人民共和国职业病防治法],浙江省电力工业局于2001年11月30日在杭州召开了所属各发电厂、电力公司、研究所等23个单位50名代表参加的噪声综