Ionic liquid-assisted hydrothermal synthesis of dendrite-like NaY(MoO4)2:Tb phosphor

Micro-sized NaY(MoO₄)₂:Tb³⁺ phosphors with dendritic morphology was synthesized by a ionic liquid-assisted hydrothermal process. X-ray diffraction (XRD) indicated that the as-prepared product is pure tetragonal phase of NaY(MoO₄)₂. Field emission scanning electron microscopy (FE-SEM) images showed that the as-prepared NaY(MoO₄)₂:Tb³⁺ phosphors have dendritic morphology. The photoluminescent (PL) spectra displayed that the as-prepared NaY(MoO₄)₂:Tb³⁺ phosphors show a stronger green emission with main emission wavelength 545 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺ ion, and the optimal Tb³⁺ doping concentration for obtaining maximum emission intensity was confirmed to be 10 mol%. Based on Van Uitert's and Dexter's models the electric dipole–dipole (D–D) interaction was confirmed to be responsible for the concentration quenching of ⁵D₄ fluorescence of Tb³⁺ in the NaY(MoO₄)₂:Tb³⁺ phosphors. The intrinsic radiative transition lifetime of ⁵D₄ level is found to be 0.703 ms.     

Preparation of Nd-doped BiFeO3 films and their electrical properties

The Nd-doped BiFeO₃ thin films were prepared on SnO₂(FTO) substrates spin-coated by the sol–gel method using Nd(NO₃)₃·6H₂O, Fe(NO₃)₃·9H₂O and Bi(NO₃)₃·5H₂O as raw materials. The microstructure and electric properties of the BiFeO₃ thin films were characterized and tested. The results indicate that the diffraction peak of the Nd-doped BiFeO₃ films is shifted towards right as the doping amounts are increased. The structure is transformed from the rhombohedral to pseudotetragonal phase. The crystal grain is changed from an elliptical to irregular polyhedron. Structure transition occurring in the Bi_0.85Nd_0.15FeO₃ films gives rise to the largest Pr of 64 μC/cm². The leakage conductance of the Nd doped thin films is reduced. The dielectric constant and dielectric loss of Bi_0.85Nd_0.15FeO₃ thin film at 10 kHz are 190 and 0.017 respectively.     

结构与参量不确定的网络与网络之间的混沌同步

进行了结构与参量不确定的网络与网络之间的混沌同步研究．通过设计适当的控制输入,不但实现了两个复杂网络之间的混沌同步,而且网络节点状态方程中的未知参量和网络内部节点之间的耦合强度也被同时确定．通过采用具有调制损耗的CO2激光器的状态方程进行仿真实验,发现网络与网络之间的同步性能非常稳定．     

多量子位Heisenberg XX链中的杂质纠缠

通过分析系统的杂质位与其余部分间的纠缠N_1-A以及单个正常位与其余部分间的纠缠N_L-A研究了匀强磁场作用下含杂质Heisenberg XX链的纠缠特性.研究表明三量子位时纠缠存在的临界温度依赖于杂质参数J₁和匀强磁场B.研究发现,当量子位L为奇数时,纠缠N_1-A随量子位的增加而增大,而L为偶数时则相反,并且量子位L为偶数时的纠缠大于量子位L为奇数时的纠缠;对N_L-A, 量子位L为奇数时,纠缠随杂质参数J₁的变化与L=3类似,而L为偶数时纠缠随杂质参数|J₁|的增加而增加.     

Ultrafast nonlinear optical properties of dye-doped PMMA discs irradiated by 40 fs laser pulses

The two-photon absorption (TPA) characteristics of PMMA discs doped with three different dyes were studied using an fs-pulsed Ti-Sapphire laser as the pump source, and employing the open-aperture Z-scan technique. TPA cross-sections obtained for PMMA doped with the dyes PM597, DCM and rhodamine 6G–rhodamine B (co-doped) were found to be equal to 24.7, 33.3 and 32.3 GM, respectively (1 GM=10^?50 cm⁴ s phot^?1 mol^?1). Furthermore, two-photon fluorescence was measured for the samples containing DCM and rhodamine 6G–rhodamine B (co-doped). Compared to the one-photon fluorescence spectrum, the peaks in the two-photon fluorescence spectrum were red shifted and the extent of red shift increased with increasing doping concentration. We have also observed that the red shift in the two-photon fluorescence peak of the samples in the solid form is much larger than that in the solution state. This phenomenon could be explained by a twisted intra-molecular charge transfer model.     

有机半导体的物理掺杂理论

基于最低未被占据分子轨道（LUMO）和最高被占据分子轨道（HOMO）的高斯态密度分布与载流子在允许量子态中的费米-狄拉克（Fermi-Dirac）分布,提出有机半导体中物理掺杂的理论模型;研究了掺杂浓度、温度和禁带宽度对载流子浓度的影响,并与一些报道的实验结果做了比较.研究发现无论是否掺杂,温度升高时,有机半导体中的载流子浓度都会增大,并且随温度倒数的线性减小而指数增大;对于本征有机半导体,载流子浓度随禁带宽度的增大而指数下降,随高斯分布宽度的平方指数增加;对杂质和主体不同能级关系的掺杂情形下掺杂浓度对载 关键词： 有机半导体 掺杂 高斯态密度 载流子浓度     

Bipartite entanglement of a two-qubit system with anisotropic couplings under nonuniform magnetic fields

This paper investigates bipartite entanglement of a two-qubit system with anisotropic couplings under an inhomogeneous magnetic field. This work is mainly to investigate the characteristics of a Heisenberg XYZ chain and obtains some meaningful results. By the concept of negativity, it finds that the inhomogeneity of magnetic field may induce entanglement and the critical magnetic field is independent of J_z. The inhomogeneous magnetic field can increase the value of critical magnetic field B_c. It also finds that the magnetic field not only suppresses the entanglement but also can induce it to revival for some time.     

双球聚集粒子辐射特性分析

基于广义Mie理论求解方法(GMM),考虑单元粒子之间的相互作用,计算了不同尺度参数不同间距的双球聚集粒子的衰减因子、散射因子等辐射特性参数,同时分析了双球聚集粒子与不考虑相互作用计算所得的辐射特性差异,分析结果表明:考虑相互作用与不考虑相互作用计算所得的双球聚集粒子的辐射特性存在着一定的差别,这种差别随粒子间距、尺度参数的变化而变化,最大偏差达30%左右.     

利用Hyperion数据进行环境星HSI红边参数真实性检验

针对我国新发射运行的HJ-1A星HSI数据,利用高光谱分辨率的Hyperion数据进行了HJ-1A星HSI的光谱模拟,提取了红谷位置、红边位置、红边斜率和红边振幅等4个主要的红边参数,对真实与模拟环境星HSI数据的红边参数进行了对比分析,从而以Hyperion数据为参照检验了环境星HSI红边参数的真实性。研究结果显示,环境星HSI与模拟HSI的红边范围光谱反射率平均相关系数为0.946,标准差为0.011,为极显著相关,两种数据在红边范围内的光谱反射率变化高度一致;4个红边参数的相关系数分别为0.414,0.543,0.808和0.802,并且随植被覆盖度的变化呈现出明显的规律性,模拟与真实红边参数差值标准差分别为5.75,1.86,5.7e-4和0.024,认为环境星HSI的红边参数可以较好反映该区域植被变化所造成的红边光谱特征差异。