LD泵浦355nm准连续紫外激光器

报道了一台LD侧面泵浦Nd:YAG晶体的内腔三次谐波转换的全固态准连续紫外激光器。在谐振腔内,1064nm的基频波通过对Ⅱ类相位匹配KTP晶体进行二倍频来产生532nm波长激光,二者再通过对Ⅱ类相位匹配LBO晶体进行和频来获得355nm紫外激光输出。355nm全固态紫外激光器在声光调Q重复频率为2.8kHz下,当输入电流为18A时可得到503mW的激光输出。     

An effective one-axis passive packaging method for a D lens fiber collimator

An effective one-axis passive packaging method for a D lens fiber collimator is presented and compared with the traditional five-axis active packaging method. The dependence of collimator insertion loss on the gap between fiber pigtail and lens is shown experimentally to verify the packaging tolerance. In case of a 20 mm working distance, a 10 μm gap tolerance is obtained for a D lens collimator to obtain an insertion loss of <0.3 dB. In addition, a 2000 h damp heat test was carried out to demonstrate the reliability of this effective packaging method.     

环形光束锥形衍射出射光场偏振特性及光场调控

环形光束的锥形衍射效应对于微粒的操控具有重要的应用价值.本文建立了环状高斯光束的锥形衍射模型,并基于Berry理论给出了线偏振态下环形光束锥形衍射出射光场的计算公式.理论仿真了环状光锥形衍射出射光场的偏振特性,得出环光锥形衍射出射光场的内、外亮环具有相互正交的偏振分布特性.搭建了线偏振态下环状高斯光锥形衍射的实验系统,实验验证了出射光场的偏振特性.针对环形光束锥形衍射出射光场具备的偏振特性,设计了一种组合偏振片,理论和实验研究了该组合偏振片对环光锥形衍射出射光场的调控.结果表明,随着组合偏振片方位角的变化,锥形衍射出射光场的内、外环强度发生周期性的变化.     

微波元件与加速结构的有限元分析

研究了有限元方法在二维均匀结构和轴对称加速结构中的应用,采用了带宽优化技术和子空间求解特征值方法,并给出了部分例子,结果表明该方法精度高、速度快.这些方法可直接用于三维程序、并行计算.     

A Novel Dehumidification Strategy to Reduce Liquid Fraction and Condensation Loss in Steam Turbines

Massive droplets can be generated to form two-phase flow in steam turbines, leading to erosion issues to the blades and reduces the reliability of the components. A condensing two-phase flow model was developed to assess the flow structure and loss considering the nonequilibrium condensation phenomenon due to the high expansion behaviour in the transonic flow in linear blade cascades. A novel dehumidification strategy was proposed by introducing turbulent disturbances on the suction side. The results show that the Wilson point of the nonequilibrium condensation process was delayed by increasing the inlet superheated level at the entrance of the blade cascade. With an increase in the inlet superheated level of 25 K, the liquid fraction and condensation loss significantly reduced by 79% and 73%, respectively. The newly designed turbine blades not only remarkably kept the liquid phase region away from the blade walls but also significantly reduced 28.1% averaged liquid fraction and 47.5% condensation loss compared to the original geometry. The results provide an insight to understand the formation and evaporation of the condensed droplets inside steam turbines.     

单溶剂体系中CdSe纳米晶体的形貌调控研究

采用非水溶液方法,分别在十六胺(HDA)或邻苯二甲酸辛酯(DOP)的单溶剂体系中,通过调节前体加入速度和反应温度制备出六角形、多臂、短棒、长棒状以及四脚架形CdSe纳米晶体,并用透射电镜(TEM)对所得产品进行了表征.结果表明,前体的过饱和度强烈地影响CdSe纳米晶体的形貌,过饱和度的提高有导致六方纤锌矿结构(011-)方向上择向生长的趋势;两种单溶剂体系中在CdSe纳米晶体的形貌调控上有不同的影响;200 ℃不利于得到高质量的CdSe纳米晶体.     

非平衡磁控溅射等离子体频谱特征

利用朗缪尔探针和快速傅里叶变换研究了非平衡磁控溅射等离子体静电波动的驻波共振频谱特征。频带宽度为0~300kHz,典型放电条件下磁控靶前2cm和10cm两个位置的共振本征频率变化范围分别为10~50kHz和1~10kHz,研究了线圈电流、气压和放电功率等参数对共振本征频率的影响;指出了非平衡磁控溅射中能够导致等离子体静电驻波共振的两种势阱结构,提出驻波共振机制解释特征频率出现的原因,根据声驻波共振机制计算的电子温度数值符合实验的结果。     

硅包覆上转换纳米晶制备和表征及生物特异性标记研究

以NaYF₄为代表的上转换纳米晶作为细胞及组织标记的研究越来越热。但易团聚,水溶性、生物兼容性差,没有与生物偶联官能团等缺点限制了其应用,因而表面修饰显得尤为重要。作者通过水热和共沉淀相结合方法,制备了NaYF₄∶Yb3+, Er3+上转换纳米晶,并对其包覆二氧化硅壳层。SEM表征硅包覆前后分别为25和250 nm的单分散粒子,说明硅已成功地包覆于纳米晶表面。980 nm激光照射下,样品的PBS胶体溶液呈可视上转换绿光。上转换荧光光谱和寿命均表明二氧化硅壳层对其发光性质影响很小。圆二色谱说明蛋白分子通过戊二醛与纳米晶偶联前后的二级结构基本不变。基于硅片上的抗原抗体荧光免疫识别试验进一步验证了偶联蛋白分子的特异性,表明该上转换纳米晶适合于生物标记。     

Nonlinear Schrodinger equation with combined power-type nonlinearities and harmonic potential

This paper discusses a class of nonlinear Schrodinger equations with combined power-type nonlinearities and harmonic potential.By constructing a variational problem the potential well method is applied.The structure of the potential well and the properties of the depth function are given.The invariance of some sets for the problem is shown.It is proven that,if the initial data are in the potential well or out of it,the solutions will lie in the potential well or lie out of it,respectively.By the convexity method,the sharp condition of the global well-posedness is given.     

论岩体表征单元体积REV——岩体力学参数取值的一个基本问题

本文论述了岩体力学性质的尺寸效应,提出了与岩体弹性参数相应的表征单元体REV的力学描述,根据中心极限定理推导了估算裂隙岩体REV 的数学表达式。研究表明,岩体表征单元体的大小是岩体力学性质尺寸效应的客观反映。本研究成果为合理选取岩体力学参数提供了一条新途径。