偏硅酸钙中Pr3+的4f5d态的光谱特性及Pr3+→Gd3+的能量传递

合成了高效发射UV光的CaSiO3:Pr^3 新型荧光体，研究了室温下Pr^3 的4f5d态的发射和激发光谱，Pr^3 的4f5d态的最低子能级向4f^2组态的^3H4，^3H6和^1G4能级跃迁产生UV发射，并不伴随有4f-4f能级跃迁的可见光发射。Pr^3 的浓度猝灭是由于辐射和无辐射能量传递造成的，同时，在CaSiO3中，存在Pr^3 →Cd^3 的能量传递，探讨了其能量传递特性。     

Multiple positive solutions for one-dimensional p-Laplacian boundary value problems

By means of the Leggett-Williams fixed-point theorem, criteria are developed for the existence of at least three positive solutions to the one-dimensional p-Laplacian boundary value problem, ((y′))′ + g(t)f(t,y) = 0, y(0) - B₀(y′(0)) = 0, y(1) + B₁(y′(1)) = 0, where (v) |v|^p−2v, p > 1.     

Pt(110)表面自吸附原子能量和力的改进分析型嵌入原子法分析

采用改进分析型嵌入原子法计算了Pt(110)表面自吸附原子的能量和法向力.当Pt吸附原子位于Pt(110)表面第一层原子的二重对称洞位上0.11nm时最稳定.Pt吸附原子的最佳迁移路径是由一个二重对称洞位沿密排方向迁移到最近邻的另一个二重对称洞位.在吸附原子远离表面的过程中，将依次经过排斥、过渡和吸引等三个区域.在排斥区和过渡区，由于吸附原子与表面原子间强的相互作用势，吸附原子的能量和法向力的形貌图均为(110)面原子排列的复形，与对势理论和嵌入原子法得到的结果一致.在吸引区，由于多体相互作用及晶体中原子 关键词： 金属表面 自吸附 能量 力     

光子晶体中四能级系统的量子相干效应

研究了处于光子带隙材料中的四能级原子系统的电磁感应透明、自发辐射和光子开关效应，分析了其稳态与瞬态特性, 发现特殊的模密度能够导致反常的吸收、色散、自发辐射及瞬态无反转增益, 并可以通过外加调制场进行控制.详细讨论了特殊频率处模密度的变化对透明窗口和光子开关效应的影响. 关键词： 光子带隙材料 电磁感应透明 模密度 光子开关     

Entangling Two Multi-atomic Clusters Through a Cavity Field

Two atomic clusters, which have NA and Ns two-level atoms, respectively, are placed in a cavity but separated spatially. There is no direct interaction between the atoms. All the atoms interact with a single-mode of the cavity field. Quantum entanglement between the two atomic clusters is investigated for various initial states of the two atomic clusters and the field. When the cavity field is initially in a Fock state, we find that the time evolution of entanglement quasi-periodically oscillates regardless of the initial states of atoms. The oscillation period increases as the initial photon number increases. When all the atoms in both of the atomic clusters are initially in the excited state, we show that there is no entanglement between the atomic clusters with NA = NB = 1 regardless the initial state of the cavity field. However, when either NA or NB is larger than one, we find that the entanglement always exists even for a strong thermal field. In cases with different initial states of the atomic clusters, we notice that the entanglement becomes stronger as number of the atoms increases. When all the atoms in both of the clusters in the ground state, we also find that the entanglement can be enhanced even by a thermal field. We also notice that a single qubit can be entangled with multi-atoms which are initially in the ground state by the cavity field initially being in vacuum, thermal, coherent, and squeezed states.     

DESIGN OF A NOVEL 2-D UNIPLANAR CRLH-TL STRUCTURE

A novel uniplanar 2-D composite right/left-handed transmission line (CRLH-TL) structure is proposed based on a general transmission line theory and the way to increase the relative operating bandwidth in the left-handed (LH) region and lower the LH operating frequency is illustrated. In addition, a new method to extract parameters and calculate the Bloch impedance of the structure is presented. Numerical results of the dispersion as well as the extracted parameters are given, which are calculated based on full-wave simulation. The present 2-D uniplanar CRLH-TL structure is applicable to 2-D left-handed materials in lower and wider LH frequency range. Supported by the National Natural Science Foundation of China (No. 60371010) (No. 60471037) (No. 63531020)     

Successive column correction algorithms for solving sparse nonlinear systems of equations

This paper presents two algorithms for solving sparse nonlinear systems of equations: the CM-successive column correction algorithm and a modified CM-successive column correction algorithm. Aq-superlinear convergence theorem and anr-convergence order estimate are given for both algorithms. Some numerical results and the detailed comparisons with some previously established algorithms show that the new algorithms have some promise of being very effective in practice.This research was partially supported by contracts and grants: DOE DE-AS05-82ER1-13016, AFOSR 85-0243 at Rice University, Houston, U.S.A. and Natural Sciences and Engineering Research Council of Canada grant A-8639.     

Mn位W掺杂对La0.3Ca0.7MnO3体系磁结构的影响

通过对La0.3Ca0.7Mn1-xWxO3(x=0.00,0.04,0.08,0.12,0.15)多晶样品M-T曲线、M-H曲线及ESR谱的测量,研究了Mn位W掺杂对电荷有序体系La0.3Ca0.7MnO3磁结构的影响.结果表明,当掺杂量为0.00≤x≤0.08时,体系存在电荷有序(CO)相,AFM/CO态共存于相变温度以下,电荷有序温度TCO随着W掺杂量的增加而增加;x=0.04时,样品在低温下为FM相与AFM/CO相共存,在CO相建立前、后均有FM从PM中分离出来;当x≥0.12时,CO态融化,在极低温度下存在顺磁-铁磁(PM-FM)相变.     

具有高机械强度的掺Er~(3 )∶TeO_2-Nb_2O_5玻璃的光谱性质研究

熔制了掺铒碲铌玻璃样品(100-X)TeO2-XNb2O5(X=5,10,15,20mol%),测试了其密度、折射率、转变温度、析晶温度、维氏机械强度、吸收光谱、荧光光谱、荧光寿命等参量。利用Judd-Ofelt和McCumber理论分别计算了铒离子强度参量Ωt(t=2,4,6)和受激发射截面σemi的大小,研究了掺铒碲铌玻璃样品光谱参量对Nb2O5成分的依赖性,并与典型的碲锌钠玻璃(75TeO2-20ZnO-5Na2O)在热学、机械强度、光谱性质和放大品行四个方面进行了比较.     

Nonlinear dynamics of a spinor Bose-Einstein condensate in a double-well potential

We examine the nonlinear dynamical behavior of a spinor Bose-Einstein condensate in a double-well potential. Considering a condensate with large number of atoms, such that it can be described using the mean field theory, we separate the spinor dynamics from the spatial dynamics under the single-mode approximation. We limit ourselves to certain initial conditions under which the spatial mode is frozen so that we can focus on the spinor dynamics only. Identifying collective spin variables of our system, we derive the corresponding nonlinear equations of motion for them. Employing standard stability analysis, we find and characterize fixed points of the system. For a wide range of physical parameters such as tunneling strength and non-linear interactions, as well as for various initial preparations of the system, we identify qualitatively different dynamical regimes possible in the system. In particular, complete and incomplete oscillations of spin variables between quantum wells are found. We also show that by bringing some fixed points close to each other in the phase space of the system, it is possible to induce amplitude modulation to those otherwise regular tunneling oscillations.