Single-frequency linearly-polarized 1083?nm all fiber nanosecond laser

Single-frequency linearly-polarized 1083?nm all fiber nanosecond master-oscillator power amplifier laser system is demonstrated. A ring laser, whose key components are one saturable absorber and two polarization controllers, delivers a single-frequency continuous wave laser. Using an electro-optic modulator as the modulator, the pulse laser seed is obtained by modulating the CW laser. By amplifying the pulse seed to the average power of 61.6?W in three stages, a single-frequency linearly-polarized laser with pulse duration of 16?ns, repetition rate of 10?MHz and pulse energy of 6.16???J is obtained. No nonlinear effect is observed in our experiment. Higher output power can be obtained by increasing LDs of the main amplifier.     

Experimental study on kilowatt fiber laser in an all-fiber configuration

A high-power fiber laser in an all-fiber format is reported. The system consists of 36 pump ports, which use both counter and forward pump configuration. In the experiment, 1 008-W output power is obtained when 24 pump ports are used with a total pump power of 1477 W. The optical-to-optical conversion efficiency is 68% and the 3-dB bandwidth of laser output increases with output power. Presently, the output power is only limited by the pump source. It can be predicted that the laser power can be further scaled if more pump sources are utilized.     

直接光谱法水体COD检测多场景优化方法

提出一种多场景优化的光谱分类建模解算方法:首先,通过颗粒物Mie散射仿真分析,构建幂函数修正方程,以直接拟合法对样本光谱进行精确浊度校正;然后,利用吸光度归一化法获取不同场景的线性特征光谱,形成场景特征库;使用偏最小二乘法(PLS)为每个场景建立解算模型,形成化学需氧量(COD)解算模型库.对未知水样本进行COD检测时,先通过杰卡德(Jaccard)相似性理论将其归一化光谱与场景库线性特征谱进行匹配,识别其归属场景,再获取解算库中的最优解算参数来计算COD浓度.实验结果表明,所提方法可获得较高的场景匹配精度,有效降低多场景条件下的COD解算误差,具备良好的实用价值.     

基于修正Linde模型的复材层板的损伤模拟

基于连续损伤力学方法,建立含初始损伤的三维复合材料层合板的有限元模型.采用Linde等提出的应变失效准则,并引入参数对损伤函数进行修正,模拟层合板的纤维和基体的失效行为.参数的改变可以描述损伤变量随应变的变化程度.数值模拟表明,计算结果随着参数的变化幅度较大,在试验值的±15%范围内变动.本文引入的参数一方面可以拓宽Linde材料损伤判据的适用范围,另一方面在适用范围内可以达到更为精确的数值模拟结果,为后续的结构分析打下基础.     

新型键合纤维素手性固定相的制备及其拆分性能评价

键合型多糖手性固定相因具有化学稳定性高和溶剂耐受性好的特点而受到研究者的极大关注。采用施陶丁格（Staudinger）反应将6-叠氮-6-脱氧纤维素-3,5-二氯苯基氨基甲酸酯键合到氨丙基硅胶上得到一种新的键合型手性固定相（ImCel）,研究了其手性分离性能,并探讨了非常规流动相（如氯仿、四氢呋喃等）的影响。结果表明,在20对手性化合物中,17对在合适的流动相下得到基线分离。ImCel在正相条件下的分离性能优于反相条件,且在含氯仿的流动相中仍对手性化合物表现出良好的分离能力。在分离一系列芴甲氧羰基（fmoc）-氨基酸衍生物时,ImCel与键合6-叠氮-6-脱氧纤维素-3,5-二甲基苯基氨基甲酸酯的手性固定相表现出互补性,出现了固定相改变引起的对映体洗脱反转现象。本研究丰富了键合型多糖手性固定相的种类和合成方法,为开发新的键合型手性固定相提供了参考。     

Elastic and thermodynamic properties of vanadium nitride under pressure and the effect of metallic bonding on its hardness

By the particle-swarm optimization method, it is predicted that tetragonal P42mc, 141md, and orthorhombic Amm2 phases of vanadium nitride （VN） are energetically more stable than NaCl-type structure at 0 K. The enthalpies of the predicted three new VN phases, along with WC, NaC1, AsNi, CsCl type structures, are calculated each as a function of pressure. It is found that VN exhibits the WC-to-CsCl type phase transition at 256 GPa. For the considered seven crystal- lographic VN phases, the structures, elastic constants, bulk moduli, shear moduli, and Debye temperatures are investigated. Our calculated equilibrium structural parameters are in very good agreement with the available experimental results and the previous theoretical results for the NaC1 phase. The Debye temperatures of VN predicted three novel phases, which are all higher than those of the remaining structures. The elastic constants, thermodynamic properties, and elastic anisotropies of VN under pressure are obtained and the mechanical stabilities are analyzed in detail based on the mechanical stability criteria. Moreover, the effect of metallic bonding on the hardness of VN is also investigated, which shows that VNs in P42mc, 141md, and Amm2 phases are potential superhard phases. Further investigation on the experimental level is highly recommended to confirm our calculations presented in this paper.     

Dynamics of rotator chain with dissipative boundary

We study the deternfinistic dynanfics of rotator chain with purely mechanical driving on the boundary by stability analysis and numerical sinmlation. Globally synchronous rotation, clustered synchronous rotation, and split synchronous rotation states are identified. In particular, we find that the single-peaked wariance distribution of angular momenta is the consequence of the deterministic dynamics. As a result, the operational definition of temperature used in the previous studies on rotator chain should be revisited.     

精确延时控制爆破振动的实验研究

为了探讨电子雷管在降低爆破振动和改善岩石破碎效果方面的作用机理,基于地震波传播过程中的能量变化,给出了孔间毫秒延时时间的计算公式。根据目前国内露天矿生产实际,设计并开展了模型实验。实验结果表明,合理的孔间延时控制能够降低爆破振动。在本文的模型实验中,12 ms延时间隔下爆破振动瞬时能量最大值分别是2、7和9 ms延时间隔下爆破振动瞬时能量最大值的19%、25%和36%,4和12 ms延时间隔下爆破振动速度峰值最大值是其他延时间隔下爆破振动速度峰值最大值的50%左右。提出的计算公式在实际工程中获得了良好的应用效果,同时验证了该计算公式的可行性。     

Nonlinear progressive damage model for composite laminates used for low-velocity impact

In order to effectively describe the progressively intralaminar and interlam- inar damage for composite laminates, a three dimensional progressive damage model for composite laminates to be used for low-velocity impact is presented. Being applied to three-dimensional （3D） solid elements and cohesive elements, the nonlinear damage model can be used to analyze the dynamic performance of composite structure and its failure be- havior. For the intralaminar damage, as a function of the energy release rate, the damage model in an exponential function can describe progressive development of the damage. For the interlaminar damage, the damage evolution is described by the framework of the continuum mechanics through cohesive elements. Coding the user subroutine VUMAT of the finite element software ABAQUS/Explicit, the model is applied to an example, i.e., carbon fiber reinforced epoxy composite laminates under low-velocity impact. It is shown that the prediction of damage and deformation agrees well with the experimental results.