核磁共振碳谱研究:烷烃化学位移和(CSS)与分子路径指数矢量(VPM)

系统研究了核磁共振碳谱和化学位移规律及其定量构谱关系(QSSR).本文研究了一组十元素分子路径指数矢量VPM,并发现它与烷烃化学位移和CCS有良好线性相关性.采用多元线性回归进行准确估计与预测,结果优良.     

Reduced s-d model with antiferromagnetically coupled impurity spins

An antiferromagnetic equivalent-neighbour Heisenberg interaction H_i between impurity spins is added to the reduced s-d Hamiltonian H_r previously introduced by simplifying the Kondo s-d exchange Hamiltonian H_K. Asymptotic mean-field theory is developed for H_r + H_i, in the presence and absence of external magnetic field, and applied to (La_1−xCe_x)Al₂ alloys. Specific heat c_i(T) and zero-field susceptibility χ_i(0,T) curves for (La_1−xCe_x)Al₂ are depicted. The coupling constants of H_r + H_i and conduction bandwidth are adjusted so that T_c temperatures for x = 0.2, 0.1 are equal to the experimental values. c_i(T) exhibits a jump at T_c and is decreasing for T < T_c. χ_i(0,T) has a first order pole at T_c which corresponds to the maximum of experimental susceptibility and χ_i(0,0) > 0. These results improve those obtained earlier on the grounds of H_r theory.     

Interrelations of discrete Painlevé equations through limiting procedures

We study the discrete Painlevé equations associated to the affine Weyl group which can be obtained by the implementation of a special limits of -associated equations. This study is motivated by the existence of two -associated discrete both having a double ternary dependence in their coefficients and which have not been related before. We show here that two equations correspond to two different limits of a -associated discrete Painlevé equation. Applying the same limiting procedures to other -associated equations we obtained several -related equations most of which have not been previously derived.     

反向衬底偏压下纳米N沟道金属氧化物半导体场效应晶体管中栅调制界面产生电流特性研究

研究了反向衬底偏压V_B下纳米N沟道金属氧化物半导体场效应晶体管中栅调制界面产生(GMG)电流I_GMG特性, 发现I_GMG曲线的上升沿与下降沿随着|V_B|的增大向右漂移. 基于实验和理论模型分析, 得出了V_B与这种漂移之间的物理作用机制, 漂移现象的产生归因于衬底偏压V_B 调节了表面电势φ_s在栅电压V_G 中的占有比重: |V_B|增大时相同V_G下φ_s会变小, φ_s 的变化继而引发上升沿产生率因子g_r减小以及下降沿产生率因子g_f增大. 进一步发现I_GMG 上升沿与下降沿的最大跨导G_MR, G_MF 在对数坐标系下与V_B成线性关系, 并且随着|V_B|增加而增大. 由于漏电压V_D在I_GMG 上升沿与下降沿中的作用不同, 三种V_D下G_MR-V_B曲线重合而G_MF-V_B曲线则产生差异. 增大V_D 会增强g_f 随V_G的变化, 因此使得给定V_B 下的G_MF变大. 同时这却导致了更大V_D下G_MF-V_B 曲线变化的趋势减缓, 随着V_D从0.2 V变为0.6 V, 曲线的斜率s从0.09减小到0.03. 关键词： 产生电流 表面势 衬底偏压 N沟道金属氧化物半导体场效应晶体管     

Normal-state resistivity of superconducting Bi1.95Sr1.65La0.4CuO6+δ single crystals

The anisotropy of the normal-state resistivity of a number of superconducting Bi_1.95Sr_1.65La_0.4CuO_6+δ single crystals has been measured by using both a six- and a four-terminal technique. We find that the ab-plane resistivity _ab in general increases almost linearly with temperature (d_ab/dT> 0). the temperature variation of the c-axis resistivity _c, however, is strongly sample dependent. Both metallic-like (d_c/dT> 0) and mixed temperature dependences of _c, including d_c/dT < 0 are observed. The mixed _c(T) data can be well described by fitting to _c(T) = A + BT + C/T, indicating that the temperature dependence of _c(T) is the result of a competition between metallic and non-metallic terms. The temperature T_min at which _c reaches a minimum increases with increasing d_ab/dT, suggesting that the metallic term of _c arises from misaligned Cu---O planes. This is confirmed by an electron-microscope (HRTEM) analysis of the samples. The anisotropy ratio _c/_ab is of the order of 10³ but increases monotonically with decreasing temperature, indicating differences in the scattering processes parallel and perpendicular to the Cu---O plane.