Collisional dynamics of symmetric two-dimensional quantum droplets

The collisional dynamics of two symmetric droplets with equal intraspecies scattering lengths and particle number density for each component is studied by solving the corresponding extended Gross−Pitaevskii equation in two dimensions by including a logarithmic correction term in the usual contact interaction. We find the merging droplet after collision experiences a quadrupole oscillation in its shape and the oscillation period is found to be independent of the incidental momentum for small droplets. With increasing collision momentum the colliding droplets may separate into two, or even more, and finally into small pieces of droplets. For these dynamical phases we manage to present boundaries determined by the remnant particle number in the central area and the damped oscillation of the quadrupole mode. A stability peak for the existence of droplets emerges at the critical particle numberN_c ≃ 48 for the quasi-Gaussian and flat-top shapes of the droplets.     

Optical properties of two-dimensional perovskites

The optical properties of two-dimensional (2D) perovskites recently receive numerous research focus thanks to the strong quantum and dielectric confinement effects. In addition to the strong excitonic effect at room temperature, 2D perovskites also have appealing features that their optical properties can be flexibly tuned by alternating organic or inorganic layers. Particularly, 2D chiral perovskites and 2D perovskites based heterostructures are emerging as new platforms to extend their functionalities. To optimize performance of 2D perovskites-based optoelectronic devices, it is critical to understand the fundamentals and explore the strategies to engineer their optical properties. This review begins with an introduction to the excitons and self-trapped excitons of 2D perovskites. Subsequently, inorganic/organic layer effects on optical properties and 2D perovskites based heterostructures are discussed. We also discussed the nonlinear optical properties of 2D perovskite. We are looking forward to that this review can stimulate more efforts to understand and optimize the optical properties of 2D perovskites.     

ComBn(m+n≤6)团簇的结构，电子特性和磁性研究

基于密度泛函理论和卡里普索结构预测方法,系统研究了ComBn(m+n≤6)团簇的结构,电子特性和磁性。首先,通过卡里普索结构预测方法获得了体系的基态和亚稳态结构。基于基态结构,利用HOMO-LUMO能隙,垂直电离势,垂直电子亲和势和化学硬度分析了掺杂体系的稳定性。最后,研究了基态结构对应的自然布局分布,自然电子组态等电子特性和磁性。     

Asymmetric nonlinear-mode-conversion in an optical waveguide withPT symmetry

Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect, while it is challenging to achieve asymmetric nonlinear-mode-conversion (NMC) due to the limitations imposed by phase-matching. In this work, we theoretically proposed a new scheme for realizing asymmetric NMC by combining frequency-doubling process and periodic PT symmetric modulation in an optical waveguide. By engineering the one-way momentum from PT symmetric modulation, we have demonstrated the unidirectional conversion from pump to second harmonic with desired guided modes. Our findings offer new opportunities for manipulating nonlinear optical fields with PT symmetry, which could further boost more exploration on on-chip nonlinear devices assisted by non-Hermitian optics.     

加强型Bi-2212超导股线有限元拉伸性能分析

为探究加强型Bi-2212超导股线的力学性能以及不锈钢包带对超导股线力学性能的影响,运用Ansys软件建立加强型Bi-2212超导股线的三维模型,采用有限元分析方法,对其机械结构进行仿真,模拟高温高压热处理后轴向受拉形变量和应力应变分布情况。仿真结果显示,在同样施加100 N拉力的情况下,与超导原线（Bi-2212超导线）相比,密绕Ni₈₀Cr₂₀包带后的加强型Bi-2212超导股线轴向受拉形变程度减小,约10%;应力应变均降低,约30%。采用Ni₈₀Cr₂₀作为外包带制成的加强型Bi-2212超导股线力学性能显著,是未来超导线发展方向之一。     

继电器动态过程中动态参数的测试方法

本文介绍了一种测试继电器在动态过程中动态参数测试的方法。采用此方法能直接测量和观察继电器动态过程中的线圈电压、电流 ,同时可测出继电器的动作时间 ,还可了解其接点在接触过程是否有振动现象存在。所以 ,此方法是一种多用途的继电器动态参数测量方法     

Raman and optical absorption spectroscopic investigation of Yb-Er codoped phosphate glasses containing SiO_2

Yb-Er codoped Na2O-Al2O3-P2O5-xSiO2 glasses containing 0 - 20 mol% SiO2 were prepared successfully. The addition of SiO2 to the phosphate glass not only lengthens the bond between pS＋ and non-bridging oxygen but also reduces the number of P=O bond. In contrast with silicate glass in which there is only four-fold coordinated Si4＋, most probably there coexist [SiO4] tetrahedron and [SiO6] oetahedron in our glasses. Within the range of 0 - 20 mol% SiO2 addition, the stimulated emission cross-section of Era＋ ion only decreases no more than 10%. The Judd-Ofelt intensity parameters of Er3＋, Ω2 does not change greatly, but Ω4 and Ω6 decrease obviously with increasing SiO2 addition, because the bond between Er3＋ and O2- is more strongly eovalently bonded.     

大模场面积光子晶体光纤激光器展宽脉冲锁模域的束缚态运转

实验研究了大模面积光子晶体光纤飞秒激光器在近零色散点展宽脉冲锁模的束缚态运转.获得了双脉冲束缚态锁模,以及脉冲间隔不相等的多脉冲束缚态锁模,实验发现束缚态的子脉冲间距具有随机性.通过建立光纤锁模激光器的数值模型,分析了激光器束缚态锁模建立的动力学过程,在一定抽运强度下,激光器存在多个稳态,或者单脉冲运转,或者子脉冲间隔不相等的束缚态运转,这取决于锁模建立阶段半导体可饱和吸收镜(SESAM)对噪声信号的随机提取.并提出了抑制束缚态的方法,模拟得出此项技术可直接获得的最大单脉冲能量为19.6 nJ,考虑到40%左右的压缩损耗,可得到压缩至76 fs的最短脉冲,单脉冲能量为11.8 nJ.数值模拟结果能很好的与实验相符合.     

等离子体喷射X光时空分辨测量

在“神光”强激光装置上对０．５３μｍ激光产生的等离子体喷射进行了Ｘ光时空分辨诊断。首次利用多针孔阵列成像技术结合软Ｘ光扫描相机观察激光加热区和Ｘ光加热区等离子体的运动，获得了初级和次级等离子体膨胀速度等结果．     

Improved Synthesis and Structure of 3-Carboxy-2-pyrazinecarbohydroxamic Acid

3-Carboxy-2-pyrazinehydroxamic acid was prepared by a one pot reaction starting from pyrazine-2,3-dicarboxylic anhydride with a high yield, and characterized by IR, Mass spectrum, 1H NMR and 13C NMR spectra and single-crystal X-ray diffraction. It crystallizes in triclinic, space group Pī with a=4.8659(10), b=7.4233(15), c=11.602(2), α=96.904(2), β=92.422(3), γ=107.454(2)°, V=395.51(14)3 , Z=2, Dc=1.689g/cm3 , F(000)=208, μ(MoKα)=0.149 mm-1 , the final R=0.0473 and wR=0.1306 for 2853 observed reflections (I>2σ (I)). A three-dimensional framework was assembled through intermolecular hydrogen bonding between water and 3-carboxy-2-pyrazine-carbohydroxamic acid molecules.