Structural phase transition in substituted La2CuO4 and Pr2CuO4−y

The structural phase transition from orthorhombic (T) phase to tetragonal (T′) phase in substituted La_2−x R _x CuO₄ (R = Pr, Nd, Sm, Eu and Gd) and T′ to T-phase in Pr_2−x M _x CuO_4−y (M = Sr, Ca) has been studied by X-ray diffraction technique. The T-phase of La₂CuO₄ is transferred to T′ phase abruptly atx=0.8, 0.4, 0.4, 0.3 and 0.4 respectively for substitution of Pr, Nd, Sm, Eu and Gd for La in La₂CuO₄ without evidence of the T* phase. The T′ structure of Pr₂CuO₄ (x = 0.0) gets transformed to the T* structure at 30% Ca doping (x=0.6) and then to the T structure at 50% Ca doping (x=1.0), while for Sr-contentx=0.0, 0.4 and 1.0 it shows T′, T* and T structure respectively.     

Strong,large distance impurity dipole interaction in KNbO3 single crystals

It is found that the unrelaxed impurity dipoles can arrange themselves linearly in the structure joining each other end-to-end in pseudocubic [110] direction at the tetragonal to the orthorhombic phase transition. It is shown that this alignment precedes the domain formation at the phase transition, which implies quick movements of the dipoles in the structure, and a strong dipolar interaction. The experiments with the application of dc fields to the crystals showed that the dipolar interaction becomes stronger with the field. The dipoles can see each other across the existing domain walls implying the large distance nature of the interaction. The observation of impurity clusters arranged in pseudocubic [110] direction confirmed the large distance nature of the interaction. It is concluded that this strong, large distance interaction is very interesting in as much as such an interaction of dipoles forms the basis of ferroelectricity.     

关于CVD 矩阵的n- 宽度

本文证明了d_2k =δ_2k =d^2k ≥b_2k，其中d_2k ,δ_2k , b_2k分别表示Ａ（Ｂｌ^M_p）在ｌ^N_q下的Ｋｏｌｍｏｇｏｒｏｖ，线性，Ｂｅｒｎｓｔｅｉｎ ２ｋ－宽度，ｄ^2k 表示Ａ^Ｔ（Ｂｌ^N相似文献   

转动喇曼散射截面的群论计算

本文利用群链U(4)U(3)O(3)描述双原子分子N_2和O_2振转谱的对称性质,并利用群论方法计算了N_2和O_2分子转动喇曼散射的跃迁矩阵元,给出了它们的转动喇曼散射的截面。结果与实验较好地符合。     

Topochemically Controlled Redox Reactions in the System In/Sn/Cl

The difference in reactivity of the two modifications of InCl in solid state reactions with SnCl₂ is discussed. It is explained on the basis of semi‐empirical and ab initio calculations giving the density of states diagrams of InCl and the energies of possible disproportionation reactions. Their general features are discussed on the basis of a simple bonding picture for open‐packed structures involving inert pair elements. A detailed analysis of the DOS distribution allows to pinpoint the observed redox instability to a specific structural feature of α‐InCl.     

关于可达矩阵的求法探讨

在《离散数学》、《图论》课程中 ,用矩阵表示图时 ,涉及到一类重要的矩阵——可达矩阵 ,它是判别图中任意两点是否有通路的重要手段 ,也是求强分图的重要方法 ,但是可达矩阵的求法比较复杂 .本文针对这一问题 ,对可达矩阵的求法进行了改进 ,提出了一种简单可行的算法 .     

Transfer matrix approach of vibration isolation analysis of periodic composite structure

The transmission properties of elastic waves propagating in a three-dimensional composite structure embedded periodically with spherical inclusions are analyzed by the transfer matrix method in this paper. Firstly, the periodic composite structures are divided into many layers, the transfer matrix of monolayer structure is deduced by the wave equations, and the transfer matrix of the entire structure is obtained in the case of boundary conditions of displacement and stress continuity between layers. Then, the effective impedance of the structure is analyzed to calculate its reflectivity and transmissivity of vibration isolation. Finally, numerical simulation is carried out; the experiment results validate the accuracy and feasibility of the method adopted in the paper and some useful conclusions are obtained. Project (No. 50075029) supported by the National Natural Science Foundation of China.     

Regularization of singular systems of linear algebraic equations by shifts

Regularization of singular systems of linear algebraic equations by shifts is examined. New equivalent conditions for the shift regularizability of such systems are derived.     

极性晶体外表面电子的量子像势及其极化子的基态能量

本从与真空接触的存在二支声子的半无限极性晶体表面附近极化子的哈密顿算符入手，应用二支模型理论，分别对GaAs和ZnO两种材料计算了外表面电子的量子像势及其极化子的基态能量，计算结果表明，利用二支模型理论求出的外表面极化子的基态能量与利用一支模型理论求出的外表在面极化子的基态能量相差较大，对GaAs，误差约为31.1%, 对ZnO，误差约为14.8%。     

Charge order and spin order in Nd_(0.5)Sr_(0.5)Mn_(1-x)(Ga_x, Ti_x)O_3 system

Magnetic properties of Nd_(0.5)Sr_(0.5)Mn_(1-x)(Ga_x, Ti_x)O_3 system (0.04≤x≤0.4) were inves- tigated through magnetization and electron spin resonance (ESR) measurements. It was observed that a small amount of Ti substitution for Mn will destroy the charge-ordering (CO) phase completely and induce the cluster-spin-glass phase in the system, which displays a procedure of collapse of CO and of an enhancement of spin ordering (SO) phase. In contrast, the Ga substitution for Mn induces a melt- ing of CO phase in the system. It was observed that with substitution the CO phase is suppressed gradually and the remanent CO phase is retained all the while, and withal, there is a co-existence of AFM CO phase and FM SO at low temperature. In addition, an abrupt rise of magnetization was observed in M-T curves. We attributed this abnormal phenomenon to a transition from canted AFM SO to FM SO in CO region.