Effect of Cu doping on the magnetic and electrical properties of n=2 Ruddlesden-Popper manganates

A series of polycrystalline Cu-doped n=2 Ruddlesden-Popper manganates La1.2Sr1.8CuzMn（2-x）O7 （x=0, 0.04, 0.13） were synthesized by the solid state reaction method. The effect of Cu doping on the magnetic and transport properties has been studied. It is found that Cu substitution for Mn greatly affects the magnetic and electrical properties of the parent phase La1.2Sr1.8Mn2O7. With the increase of Cu content, the system undergoes a transition from longrange ferromagnetic order to the spin glass state and further to an antiferromagnetic order. A little of Cu dopant can lead to the samples showing semiconductor or insulator behaviour in the whole observed temperature range while the parent phase has a metal-insulator transition. These samples show colossal magnetoresistance at low temperatures and the value of it decreases with increasing Cu content.     

The Explicit Expressions of Level-k Circulant Matrices of Type(n_1,n_2.…,n_k) and Their Some Properties

In this paper, we give the explicit expressions of level-k circulant matrices of type (n1,n2,…nk) and of order n1n2…nk,and the explicit expressions for the eigenvalues,the determinants and the inverse matrices of the kind level-k circulant matrices are derived,and it is also proved that the sort matrices are unitarily diagonalizable.     

轻丰中子核的壳模型计算

对9≤A≤14,3≤Z≤5的核进行了壳模型计算.以⁸He作为core,选用修正的表面δ相互作用(MSDI)作为残余相互作用,挑选了24个实验能谱数据,定出了MSDI的参数和单粒子能量,并计算了结合能、低激发谱、电磁性质等,得到与实验较符合的结果.并着重讨论了¹¹Be的宇称反转和halo结构的物理机理.计算程序为OXBASH.     

钨(Ⅵ)-4(6-溴-2-苯并噻唑偶氮)邻苯二酚-乳化剂OP三元络合物显色反应的研究及其应用

非离子表面活性剂OP存在下，钨（Ⅵ）与新显色剂4-（6-溴-2-苯并噻唑偶氮）邻苯二酚（6-Br-BTAPC）在pH4.0～5.2介质中反应形成稳定的、带负电荷的、紫红色三元胶束络合物。其中W（Ⅵ）与6-Br-BTAPC的组成比为1∶2；λmax为558nm，表现ε558为7.34X104L·mol-1·cm-1。钨（Ⅵ）含量在0～1.4mg／L范围内遵从比耳定律。建议了络合物的结构。将拟定的分析方法用于合金钢试样中小量或痕量钨的测定，取得了满意的结果。     

磁镜装置中ECR等离子体硬X射线强度观测

本文描述用硬X射线针孔成象法测量简单磁镜装置中ECR等离子体辐射特性的方法及其结果。这种非破坏性的成象法,直接显示了热电子等离子体的空间分布,一次放电可成一帧清晰的象,且由此可得出二维的等发射强度线。大量结果表明电子环是非轴对称的,并非为一个整环,而是在微波注入口的对面有一个缺口。当微波功率改变时,环也在改变。     

Least‐squares mixed finite element methods for the incompressible Navier‐Stokes equations

Least‐squares mixed finite element schemes are formulated to solve the evolutionary Navier‐Stokes equations and the convergence is analyzed. We recast the Navier‐Stokes equations as a first‐order system by introducing a vorticity flux variable, and show that a least‐squares principle based on L² norms applied to this system yields optimal discretization error estimates. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 441–453, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/num.10015     

铁磁材料磁化曲线的智能观测系统

利用单片机系统控制物理实验过程，智能地测绘起始磁化曲线和磁滞回线，从而使学生们看到完整的磁化过程，对铁磁物质的磁滞现象有个充分的认识。     

On time-like surfaces of positive constant Gaussian curvature and imaginary principal curvatures

We establish the Bäcklund transformation for the construction of time-like surfaces with positive Gaussian curvature and imaginary principal curvatures. The construction can be realized by algebraic algorithm via Darboux transformations.     

(Si,Er)双注入热氧化硅的光致发光

采用强流金属蒸汽真空弧（MEVVA）离子源注入机，先将Si大束流注入热氧化SiO2/单晶硅，直接形成镶嵌在SiO2中的纳米晶Si，再小束流注入Er。Er离子在掺杂层中的浓度可达10^21cm^-3量级，大大地提高了作为孤立发光中心的Er^3 浓度。在77K和室温下，观察到了Er^3 的1.54цm特征发射。