掺Yb3+双包层大模场面积光纤锁模激光器

报道了一种结构简单、运转稳定并可以输出高脉冲能量的被动锁模光纤激光器.激光器的增益介质为掺Yb³⁺双包层大模场面积光纤,具有非常低的非线性系数.利用非线性偏振旋转效应和半导体可饱和吸收镜结合实现自启动锁模,获得了平均功率为160mW、重复频率为55.9MHz(对应于3nJ的单脉冲能量)、脉冲宽度为10.6ps的激光脉冲输出. 关键词： 大模场面积光纤 光纤激光器 锁模     

Simulating high Reynolds number flow in two-dimensional lid-driven cavity by multi-relaxation-time lattice Boltzmann method

By coupling the non-equilibrium extrapolation scheme for boundary condition with the multi-relaxation-time lattice Boltzmann method, this paper finds that the stability of the multi-relaxation-time model can be improved greatly, especially on simulating high Reynolds number (Re) flow. As a discovery, the super-stability analysed by Lallemand and Luo is verified and the complex structure of the cavity flow is also exhibited in our numerical simulation when Re is high enough. To the best knowledge of the authors, the maximum of Re which has been investigated by direct numerical simulation is only around 50,000 in the literature; however, this paper can readily extend the maximum to 1000,000 with the above combination.     

Heteroleptic [Cu(NN)P2]+-type cuprous complexes and their structural modulation on phosphorescent color: Synthesis,structural characterization,properties, and theoretical calculations

Four new heteroleptic [Cu(NN)P₂]⁺-type cuprous complexes— 1 -TPP, 2 -POP, 3 -Xantphos, and 4 -DPPF—were designed and synthesized using a diimine ligand 2-(2′-pyridyl)benzoxazole (2-PBO) and different phosphine ligands (TPP, triphenylphosphine; POP, bis[2-(diphenylphosphino)phenyl]ether; Xantphos, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; DPPF, 1,1′-bis(diphenylphosphino)-ferrocene). All complexes were characterized using single-crystal X-ray diffraction, spectroscopic analysis (infrared, UV–Vis.), elemental analysis, and photoluminescence (PL). Single-crystal X-ray diffraction revealed complexes 1 – 4 as isolated cation complex structures with a tetrahedral CuN₂P₂ coordination geometry and diverse P–Cu–P angles. Their UV–Vis. absorption spectra exhibited a blue-shift sequence in wavelength with an enlarged P–Cu–P angle from 4 to 2 then to 3 and then to 1 . The PL emission peaks of 1 – 3 also exhibited a similar blue-shift sequence ( 2 → 3 → 1 ). Their PL lifetime in microseconds (~7.5, 5.1, and 4.7 μs for 1 , 2 , and 3 , respectively) indicated that their PL behavior represents phosphorescence. Time-dependent density functional theory (TD-DFT) calculation and wavefunction analysis revealed that S₁ and T₁ states of 1 – 3 should be assigned as metal–ligand and ligand–ligand charge-transfer (ML + L'L)CT states. Their UV–Vis. absorption and phosphorescence should be attributed to the charge transfer from the P–Cu–P segment to the 2-PBO ligand. Therefore, as the P–Cu–P angle increased (lower HOMO), the energy of S₁ and T₁ states also increased, following the change of PL color.     

Exact controllability for some degenerate wave equations

In this paper, we study one-dimensional linear degenerate wave equations with a distributed controller. We establish observability inequalities for degenerate wave equation by multiplier method. We also deduce the exact controllability for degenerate wave equation by Hilbert uniqueness method when the control acts on the nondegenerate boundary. Moreover, an explicit expression for the controllability time is given.     

Rational design of perfluorinated sulfonic acid ionic sieve modified separator for high-performance Li-S battery

Journal of Solid State Electrochemistry - Practical application of Li-S battery is limited by the fast capacity decay and low coulombic efficiency caused by the shuttling phenomenon. Modification...     

A Mesoporous Сarbon Prepared by Сarbonizing Cu(II)–p-Phenylenediamine Polymer for the Adsorption of Methyl Orange from Water

Russian Journal of Physical Chemistry A - A new mesoporous carbon containing nitrogen and copper was prepared by carbonizing a polymer obtained by blending p-phenylenediamine, copper(II) sulfate,...     

Flashlamp-pumped laser performance of LiCaAIF6:Cr3+

The results of flashlamp pumping of the LiCaAIF₆:Cr³⁺ (Cr:LiCAF) laser crystal are reported. We have so far obtained slope efficiencies as high as 1.55% in a close-coupled, diffusely reflecting cavity. Based on the measured insertion loss of the presently available material, we predict that an efficiency of about 4% will be obtained when low-loss material becomes available. This extrapolated efficiency is comparable with the performance of a high-quality alexandrite laser rod in the same apparatus.     

Investigation of the local structure and the effects of the orbit reduction factor on the EPR g-factors for octahedral (CrO6) cluster in TiO2:Cr and MgO:Cr systems

A theoretical method for studying the inter-relation between electronic and molecular structure has been proposed based on the complete energy matrices for a d³ configuration ion in a tetragonal ligand-field. By means of this method, the local structure for Cr³⁺ ion doped in oxides TiO₂ (anatase) and MgO has been determined. The calculated results indicate that the local structure of the (CrO₆)⁹⁻ cluster in TiO₂:Cr³⁺ and MgO:Cr³⁺ systems exists as a compressed distortion relative to the regular octahedron. Meanwhile, the dependence of the EPR zero-field splitting parameter D on the local structure parameter ΔR (ΔR=R₁−R₂) has been revealed. In addition, the relation between the EPR g-factors (g,g,Δg) and the orbit reduction factor k has been discussed for the two systems, suggesting that the orbit reduction factor k is very important to understand the EPR g-factors.     

A Multiobjective Hybrid Metaheuristic Approach for GIS-based Spatial Zoning Model

This paper presents a multiobjective hybrid metaheuristic approach for an intelligent spatial zoning model in order to draw territory line for geographical or spatial zone for the purpose of space control. The model employs a Geographic Information System (GIS) and uses multiobjective combinatorial optimization techniques as its components. The proposed hybrid metaheuristic consists of the symbiosis between tabu search and scatter search method and it is used heuristically to generate non-dominated alternatives. The approach works with a set of current solution, which through manipulation of weights are optimized towards the non-dominated frontier while at the same time, seek to disperse over the frontier by a strategic oscillation concept. The general procedure and its algorithms are given as well as its implementation in the GIS environment. The computation has resulted in tremendous improvements in spatial zoning.     

大口径光学元件功率谱密度的统计法测量

针对ICF系统要求,提出了一种基于统计理论的大口径光学元件功率谱密度测量方法。该方法将大口径波前划分成足够多个子区域,分别求得每个子区域波前的功率谱密度,根据统计理论可将大口径波前功率谱密度表示为各个子区域波前功率谱密度的加权平均,其权重因子是各子区域对应的面积。模拟计算和实验结果验证了统计法测量的有效性,并表明当子区域个数大于等于8×8时,统计法测量和子孔径拼接测量得到的功率谱密度吻合较好。统计法测量对平台移动精度和环境稳定性要求不高,可应用于大口径光学元件功率谱密度的过程检测。