YAG∶Cr3+ 晶体精细光谱结构研究

采用不同的晶体畸变模型，利用CDM(complete diagonalization method)方法对YAG∶Cr3+ 晶体的EPR参量进行了系统研究.通过计算结果对晶格畸变模型进行了分析.结果表明,在三角对称下，对杂质离子电荷与中心离子电荷相等的情况，不适合用杂质离子沿C3轴位移的模型来研究晶体的局域结构，而且由于基态和第一激发态的零场分裂都对局域结构微变非常敏感，因此仅由基态零场分裂来确定晶格局域结构是不可靠的.同时结果表明，Cr3+ 离子进入YAG晶体后，产生了Δθ=1.88°的三角畸变.从而成功统一地解释了YAG∶Cr3+ 晶体的EPR参量和精细光谱结构.     

Sierpinski Carpet格点图上边渗流及其临界现象

本文讨论了一种非平移不变格点图──格点分形图上的边渗流及其临界现象。     

Overpartitions, lattice paths, and Rogers-Ramanujan identities

We extend partition-theoretic work of Andrews, Bressoud, and Burge to overpartitions, defining the notions of successive ranks, generalized Durfee squares, and generalized lattice paths, and then relating these to overpartitions defined by multiplicity conditions on the parts. This leads to many new partition and overpartition identities, and provides a unification of a number of well-known identities of the Rogers-Ramanujan type. Among these are Gordon's generalization of the Rogers-Ramanujan identities, Andrews' generalization of the Göllnitz-Gordon identities, and Lovejoy's “Gordon's theorems for overpartitions.”     

Dictatorship from majority rule voting

Majority rule voting in a multi-level system is studied using tools from the physics of disorder. We are not dealing with nation-wide general elections but rather with hierarchical organisations made of small committees. While in theory, for a two candidate election, the critical threshold to absolute power is , the usual existence of some local and reasonable bias makes it asymmetric, transforming a democratic system in effect to a dictatorship. The underlying dynamics of this democratic self-elimination is studied using a simulation which visualizes the full process. In addition the effect of non-voting persons (abstention, sickness, apathy) is also studied. It is found to have an additional drastic effect on the asymmetry of the threshold value to power. Some possible applications are mentioned. Received 21 July 2000     

代数系列课程习题讨论课的改革与实践

通过作者多年教学实践和总结 ,提出代数习题讨论课对培养学生分析解决问题的能力 ,初步的研究创新意识和提高代数课的教学质量是一个很有益的教学环节 .     

Rapid evaluation of oscillating lattice sums

We have generalized a method for the rapid evaluation of oscillating lattice sums for layered geometries, based on the Ewald's summation technique. Different types of long range interactions as well as different lattice symmetries can be considered, in particular modulated magnetic structures, periodic domain patterns, or periodic lattice distortions. As examples the demagnetizing energies for different thin films systems and magnetic excitations in a single atomic layer are calculated.     

关于格蕴涵代数的结构的一些讨论

讨论格蕴涵代数的一些格论性质，证明不存在含中界元的非链的有限格蕴涵代数，为进一步讨论由语言真值构成的格蕴涵代数的结构提供条件。     

Lattice gas with “interaction potential”

We present an extension of a simple automaton model to incorporate nonlocal interactions extending over a spatial range in lattice gases. From the viewpoint of statistical mechanics, the lattice gas with interaction range may serve as a prototype for non-ideal-gas behavior. From the density fluctuations correlation function, we obtain a quantity which is identified as a potential of mean force. Equilibrium and transport properties are computed theoretically and by numerical simulations to establish the validity of the model at macroscropic scale.     

Doping effects on the thermoelectric properties of Cu-intercalated Bi2Te2.7Se0.3

We herein report an enhancement of the thermoelectric performance of spark plasma sintered polycrystalline n-type Bi₂Te_2.7Se_0.3 by the intercalation of Cu and the doping of Al on Bi-sites. Through the intercalation of a small amount of Cu (0.008), the reproducibility could be significantly improved, with ZT was enhanced from 0.64 to 0.73 at 300 K due to the reduced lattice thermal conductivity benefiting from intensified point-defect phonon scattering. We also found that Al is an effective doping element for power factor enhancement and for reducing the lattice thermal conductivity of Cu-intercalated Bi₂Te_2.7Se_0.3. With these synergetic effects, an enhanced ZT values of 0.78 at 300 K and 0.81 at 360 K were obtained in 1 at% Al-doped Cu_0.008Bi₂Te_2.7Se_0.3 (Cu_0.008Bi_1.98Al_0.02Te_2.7Se_0.3).     

嵌段共聚物相容剂对聚合物共混体系力学性能影响的连续介观模拟

结合介观动力学方法和三维弹簧格子模型,研究了嵌段共聚物相容剂对相容性较差的聚合物二元共混体系力学性能的影响.在适当范围内不断增加嵌段共聚物相容剂的用量,研究了相容剂含量对体系杨氏模数及拉伸强度的影响,同时也对不同体系材料的破碎位点进行了分析.结果表明,未加入相容剂的二元共混体系在拉伸模拟中表现出较低的拉伸强度,而适量添加相容剂可以显著提升材料的拉伸强度,随着相容剂含量的增加,共混体系的破碎位点会发生转移并最终改善材料的整体性能.而相容剂的加入对体系杨氏模数的影响较小.该连续模拟方法为关联聚合物复合体系的微观结构和宏观力学性能提供了一条高效的途径.