各向异性超导体电阻转变的修正Kosterlitz-Thouless相变模型

从二维系统的Kosterlitz-Thouless (KT) 相变理论出发，在关联长度中引入热激活能和平均钉扎高度，提出了修正的KT相变模型.该模型与库伦气体标度理论和Halperin-Nelson关系具有一致性.应用修正的KT相变模型研究磁场下Tl₂Ba₂CaCu₂O_x(Tl-2212)薄膜电阻转变的标度行为，发现由电阻转变计算得到的平均钉扎高度与温度具有线性依赖关系，实验结果支持修正的KT相变模型. 关键词： 标度行为 各向异性超导体 电阻转变     

Dielectric loss of half-doped manganite Lao.sCao.sMnO3＊

The dielectric loss tanfi of half-doped manganite Lao.sCao.sMnO3 is investigated using Green＇s function technique. The Lao.sCao.sMnO3 is described by the Kondo-lattice model in the double exchange limit, taking into account the Jahn- Teller distortion and the super-exchange interaction between the localized electrons. It is found that the intensity of tans decreases with increasing [e]TI, V, and U. It is also observed that the transition temperature Tp rises as l eJTI and U increase. It is worth noting that Tp remains unchanged and the strength of tans increases with increasing g. The calculated dielectric loss results are explained theoretically, and these behaviors are in qualitative agreement with the experimental results.     

Quenched Fe moment in the collapsed tetragonal phase of Ca_(1-x)Pr_x Fe_2As_2

We report 75As NMR studies on single crystals of rare-earth doped iron pnictide superconductor Ca1-xPrxFe2As2 . In both cases of x = 0.075, 0.15, a large increase of νq upon cooling is consistent with the tetragonal-collapsed tetragonal structure transition. A sharp drop of the Knight shift is also seen just below the structure transition, which suggests the quenching of Fe local magnetism, and therefore offers important understanding of the collapsed tetragonal phase. At even low temperatures, the 1/75T1 is enhanced and forms a peak at T ≈ 25 K, which may be caused by the magnetic ordering of the Pr3+ moments or spin dynamics of mobile domain walls.     

摘要:针对导热系数测定实验中数据处理不准确的问题,对牛筋、橡胶、铝三种不同材料在自然冷却和风扇冷却条件下的导热系数进行了测量,利用Origin软件进行分析比较表明,用二项式拟合和指数拟合即可得到较高的相关度,并且材料的导热系数与降温方式无关.关键词:物理实验;导热系数;Origin软件;数据处理中图分类号:O551.3文献标志码:A

针对导热系数测定实验中数据处理不准确的问题,对牛筋、橡胶、铝三种不同材料在自然冷却和风扇冷却条件下的导热系数进行了测量,利用Origin软件进行分析比较表明,用二项式拟合和指数拟合即可得到较高的相关度,并且材料的导热系数与降温方式无关.     

间接测量中不确定度计算——乒乓球转动惯量

通过测量乒乓球转动惯量,介绍了间接测量中的不确定度传递和计算。研究发现乒乓球的质量是影响其转动惯量的主要因素,而内、外直径则是影响较小因素。     

Origin在不同材料导热系数测定中的应用

针对导热系数测定实验中数据处理不准确的问题,对牛筋、橡胶、铝三种不同材料在自然冷却和风扇冷却条件下的导热系数进行了测量,利用Origin软件进行分析比较表明,用二项式拟合和指数拟合即可得到较高的相关度,并且材料的导热系数与降温方式无关。     

Dielectric loss of half-doped manganite La_(0.5)Ca_(0.5)MnO_3

The dielectric loss tanδ of half-doped manganite La 0.5 Ca 0.5 MnO 3 is investigated using Green's function technique. The La 0.5 Ca 0.5 MnO 3 is described by the Kondo-lattice model in the double exchange limit, taking into account the Jahn-Teller distortion and the super-exchange interaction between the localized electrons. It is found that the intensity of tanδ decreases with increasing | ε JT |, V, and U. It is also observed that the transition temperature T P rises as | ε JT | and U increase. It is worth noting that T P remains unchanged and the strength of tanδ increases with increasing g. The calculated dielectric loss results are explained theoretically, and these behaviors are in qualitative agreement with the experimental results.     

Folding of lattice protein model chains with fixed ends

Using Monte Carlo simulations, we have studied the folding dynamics and thermodynamics of geometricall yconstrained lattice protein model chains. The constraints are realized by fixing one or both terminals of the chains. By comparing the results with that of the free-end chains, we find that the folding behaviours of the end-constralned chains are not completely similar to that of the free-end chains. Both kinds of constraints on the chain ends affect the folding dynamics of the chains: i.e., the folding rate, but not the thermodynamics. The thermodynamic behaviour of the one-end-fixed chains shows less difference from that of the free-end chains, while the thermodynamic behaviour of the two-end-fixed chains has obvious difference from that of the free-end chains. The origin of these differences comes from the differences of the ergodicitv of the chains in the conformational space.     

热源温度对导热系数测量的影响

基于稳态平板法研究了不同热源温度对橡胶样品的导热系数测量值的影响。利用多项式拟合法对实验数据进行处理和分析,并将实验值与公认值相对照。结果表明,热源温度为60℃是最合适的,在此温度下实验的实际总耗时相对较短,并且导热系数测量值最准确,其相对不确定度最小。