Studies on the superconductivity for the “111” type iron arsenide superconductor

The “111” type Li _x FeAs (x ranges from 0.8 to 1.2) with Cu₂Sb type tetragonal structure was synthesized with T _c 18 K. The isostructure NaFeAs was further studied, which shows superconductivity with T _c up to 26 K. The effect of pressure on superconductivity was investigated.     

Microstructure evolution in the rapidly quenched Fe78Si9B13 ribbons

We report microstructure evolution in as-spun Fe₇₈Si₉B₁₃ ribbons under various wheel speeds (s), which was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). With decreasing s, the volume fraction of the residual amorphous phase (V_a) in the as-spun ribbons decreases gradually, and the total exothermic heat of the crystallization in the DSC curves also decreases, but the ratio of the exothermic heat of the second crystallization to the first one is on the contrary. α-Fe is found in the ribbon with s of 32.9 m/s, while α-Fe, eutectic α-Fe+Fe₂B, and Fe₃Si phases are found in ribbons with s of 25.6 and 18.3 m/s. The phase precipitating behavior in cooling processes is well consistent with the annealing process in the literatures.     

The uncertain premium principle based on the distortion function

In this paper, we discuss the premium principle in uncertain environment. First, the net premium principle for uncertain risks is presented within the framework of uncertainty theory. With the help of distortion function, a new uncertain premium principle is derived from the uncertain net premium. Some properties of uncertain distortion premium principle are proved. Furthermore, a sufficient and necessary condition that an uncertain premium principle is an uncertain distortion premium principle has been characterized. Finally, some examples are given to illustrate the calculations of the uncertain distortion premium.     

Hypersurfaces with isometric Reeb flow in complex hyperbolic two-plane Grassmannians

We classify the real hypersurfaces with isometric Reeb flow in complex hyperbolic two-plane Grassmannians _SU2,m/S(_U2⋅_Um)${\mathit{SU}}_{2,m}/S(U_2\cdot U_m)$, m?2$m?2$. Each can be described as a tube over a totally geodesic _SU2,m−1/S(_U2⋅_Um−1)${\mathit{SU}}_{2,m-1}/S(U_2\cdot U_{m-1})$ in _SU2,m/S(_U2⋅_Um)${\mathit{SU}}_{2,m}/S(U_2\cdot U_m)$ or a horosphere whose center at infinity is singular.     

Optical switching based on the manipulation of microparticles in a colloidal liquid using strong scattering force

This paper demonstrates the realization of an optical switch by optically manipulating a large number of polystyrene spheres contained in a capillary.The strong scattering force exerted on polystyrene spheres with a large diameter of 4.3 μm is employed to realize the switching operation.A transparent window is opened for the signal light when the polystyrene spheres originally located at the beam centre are driven out of the beam region by the strong scattering force induced by the control light.The switching dynamics under different incident powers is investigated and compared with that observed in the optical switch based on the formation of optical matter.It is found that a large extinction ratio of ～ 30 dB and fast switching-on and switching-off times can be achieved in this type of switch.     

吡啰红Y-共振荧光光谱法测定痕量甲醛

研究了吡口罗红Y的共振荧光光谱特征,基于硫酸介质中甲醛能催化溴酸钾氧化吡口罗红Y的反应,使其共振荧光强度减弱。据此建立了催化共振荧光分析法测定甲醛的新方法。方法的线性范围为0.02—1.20μg/mL,检出限为6.1×10-3μg/mL。样品加标回收率为96.5%—98.5%。新建方法简便快速,可用于环境水样中甲醛的测定。     

基于AlN膜结构VCSEL热特性的研究(英文)

本文用ANSYS有限元热分析软件模拟了基于AlN膜钝化层和Si O2膜钝化层的高功率垂直腔面发射半导体激光器(VCSEL)器件内部的热场分布和热矢量分布.目的是证明Al N膜钝化层要比SiO2膜钝化层有具更好的特性,使器件能更稳定的工作,提高器件的特性,经模拟得到基于Al N膜钝化层的VCSEL热阻为3.12℃/W,而基于SiO2膜钝化层的VCSEL的热阻为4.77℃/W.经实验测得基于Al N膜钝化层的VCSEL热阻为3.59℃/W而基于SiO2膜钝化层的VCSEL的热阻为4.82℃/W,模拟结果和实验结果吻合较好.说明AlN膜钝化层要比SiO2膜钝化层具有更好的热特性.     

逆合成孔径成像激光雷达数据采样技术

逆合成孔径成像激光雷达能够实现对运动目标的高分辨实时成像,但激光信号的极大带宽和目标回波信号的微弱性给雷达回波数据的接收和处理带来了较大困难.针对这一问题,提出了基于光外差探测手段和压缩感知理论相结合的信号采样方法,首先通过光外差探测降低回波信号的有效带宽,再结合压缩感知理论实现对信号的稀疏化采样和重构.仿真结果证明了运用本文所提出的采样方法,在使用远低于奈奎斯特定理所规定的采样率时,仍然能够实现对目标的高质量成像.     

计算电容中Fabry-Perot干涉仪测量位移的相位修正方法

计算电容是复现电学阻抗单位的基准装置, 利用计算电容值和量子霍尔电阻值可以准确计算出精细结构常数α. 计算电容的本质是通过高准确度地测量屏蔽电极的位移, 实现对电容量值的测量. 因此, 基于Fabry-Perot干涉仪的精密电极位移测量系统是计算电容装置中最为核心和关键的部分. 在Fabry-Perot干涉仪测位移过程中, 由于高斯激光束存在轴向Gouy相位, 该附加相位将会引起相邻干涉条纹对应位移的变化(大于或者小于λ/2), 导致位移的测量值与实际值存在偏差. 本文阐述了高斯激光场的传播特性, 利用高斯激光束在自由空间和透过薄透镜复振幅的变换关系, 建立了计算电容装置中Fabry-Perot干涉仪透射光束的传输模型; 通过对不同腔长的Fabry-Perot干涉仪透射光场相位的分析, 获得了高斯激光束轴向Gouy相位修正与传输距离的关系. 结果表明, 当腔长从111.3 mm移动至316.3 mm时, 在接收距离为560 mm的情况下, 高斯光束轴向Gouy 相位引起的位移修正的绝对值最小为0.7 nm, 其相对相位修正量|δL|/|ΔL| = 3.4×10^-9.