(BiPb)-Sr-Ca-Cu-O2223相高Tc超导体磁通钉扎与蠕动

本文介绍了(BiPb)-Sr-Ca-Cu-O2223相高T_c超导体烧结工艺,用振动样品磁强计测量了磁化强度地豫率随外磁场的变化,并相应求得钉扎势U₀随外磁场的依赖关系。发现在0—0.23T外磁场范围内U₀与外磁场B的关系为U₀-B^-1/2与Palstra对单晶用电阻展宽实验所得结果有类似的函数形式。 关键词：     

多用途磁测量恒温器及性能研究

本文介绍了一种磁测量低温液氮恒温器的结构、特点,以及致冷量、样品室最低工作温度等物理参数的理论与实验结果,为改善低温磁测量恒温器的性能,扩展其用途揭示了新的途径.     

多晶YBCO超导体的中场磁化曲线特性

用振动样品磁强计测量了多晶 YBCO 超导体 LN_2温度下的初始磁化曲线、中场磁滞回线和场冷磁化曲线,对曲线的形状特征及其形成原因进行了讨论.为了解释磁滞量的峰效应,提出了颗粒内部的两种钉扎机制:弱连接的等效钉扎和正常相钉扎.     

THERMALLY ACTIVATED FLUX MOTION IN HIGH-Tc SUPERCONDUCTORS

Using the modified Anderson-Kim theory of flux creep and the Bean model, we derive an analytical ex-pression for magnetic relaxation of high-T_c superconductors, which is applicable in the whole flux creep region. The high driving force limit of the expression gives the usual logarithmic decay law and its low driving force limit takes the exponential form. Theoretical analysis is in agreement with the existing experimental results.     

YBa2Cu3Oy中氧缺位的磁通钉扎效应

制备了一组不同氧含量(T_cmid>90K)的YBa₂Cu₃O_y单相多晶样品。对其结构、超导电性和磁通钉扎行为的观测结果表明:氧缺位导致临界电流密度J_c和钉扎力密度F_p同时增加,存在一最佳的氧缺位浓度,可使J_c和F_p有最大程度提高。与氧含量y=6.96和6.83时的情况不同,对y=6.94和6.86的样品,其J_c 关键词：     

Bellman不等式的证明、应用及推广

使用三种方法证明Bellman不等式,并使用这个不等式证明一阶微分方程在Lipschitz条件下解的唯一性,顺便证明解的存在性;最后将Bellman不等式中的常量改为变量并证明它仍成立．     

矩阵的拟直和分解与Craig定理

讨论了矩阵的和与其加项之间,在等价关系及(对称阵的)合同关系上的联系.并进一步讨论了矩阵和的非零特征值与其加项的非零特征值之间的联系,给出了C ra ig定理的一个代数形式和代数证明.     

INVESTIGATION OF THE EFFECT OF SLOW NEUTRON IRRADIATION ON HALOGEN-DOPED HIGH-Tc SUPERCONDUCTORS AND ITS MECHANISM

Irradiation effect of low-fluence (-10⁸ n/cm² ) slow neutrons on halogen-doped superconductors is presented in this paper. And the mechanism of the effect is also described from the viewpoint of nuclear physics for both fast and slow neutrons on high-temperature superconductors (HTSC). It is shown ex-perimentally and theoretically that slow neutrons of low fluence has a similar irradiation effect to that of fast neutron beams with an energy E_n>0.1 MeV and fluence 10¹⁶-10¹⁸ n/cm²-However,quite differ-ent mechanisms are involved in them: Fast neutrons transfer their energies through elastic scattering in HTSC, whereas slow neutrons give off their energies during the slow neutron capture (n,γ) reaction.     

Increasing the rewriting e-paper by selecting speed of optical rewritable proper liquid crystals

The effect of interaction between liquid crystal （LC） and photoalignment material on the speed of optical rewriting process is investigated. The theoretical analysis shows that a smaller frank elastic constant K22 of liquid crystal corresponds to a larger twist angle, which gives rise to a larger rewriting speed. Six different LC cells with the same boundary conditions （one substrate is covered with rubbed polyimide （PI） and the other with photo sensitive rewritable sulfuric dye I（SD1）） are tested experimentally under the same illumination intensity （450 nm, 80 mW/cm2）. The results demonstrate that with a suitable liquid crystal, the LC optical rewriting speed for e-paper application can be obviously improved. For two well known LC materials E7 （K22 is larger） and 5CB （K22 is smaller）, they require 11 s and 6 s corresponding to change alignment direction for generating image information.