粒径对激光驱动颗粒溅射动力学特征的影响

激光脉冲辐照材料靶面产生的等离子体的演化过程会对靶面施加一脉冲式冲击压.当被辐照的靶材为离散颗粒堆积物时,激光冲击压在靶面能够驱动颗粒发生溅射现象.本文选用中值直径分别为84, 109, 184,234μm且具有窄粒径分布的干燥石英砂堆积形成离散颗粒靶,并采用波长为1064 nm的Nd:YAG纳秒激光脉冲与其相互作用产生的冲击压驱动石英颗粒发生溅射,同时通过高速摄像机记录溅射过程,研究了粒径对激光驱动颗粒溅射动力学特征的影响.通过分析高速影像发现,激光驱动的颗粒溅射在时间尺度上可以分为两个特征明显的过程,即持续百微秒垂直于靶面方向的快速早期溅射过程和持续几十毫秒扇形颗粒帘结构的慢速后期溅射过程.前者对应的颗粒出射动能呈现出了随粒径的增加而增大的趋势,后者对应的沿径向扩张的帘底直径D随时间t的演化规律遵循点源模型的描述:D(t)=αt~β,系数α的拟合值随粒径的增加而减小,幂指数β的拟合值却呈现出了随粒径增加而增大的趋势.通过细致考虑粒径依赖的颗粒在气流中的冲量耦合效率,以及粒径依赖的激光与颗粒靶相互作用产生的等离子体特征,对以上实验观察给予了合理的解释.本研究加深了人们对激光驱动颗粒溅...     

New Zn(Ⅱ)/M(Ⅰ)(M=Na,K and Rb) Metal-organic Frameworks Based on 5-Methylisophthalic Acid Ligand:Syntheses,Structures and Fluorescent Property

Reactions of Zn(NO3)2·6H2O and MNO3(M = Na, K and Rb) with H2mip(H2mip = 5-methylisophthalic acid) in DMF(DMF = N,N′-dimethylformamide) resulted in the formation of novel heterometallic metal-organic frameworks(Me2NH2)[ZnM(mip)2](1: M = Na; 2: M = K; 3: M = Rb, mip = 5-methylisophthalate dianion for 1~3). These complexes belong to the monoclinic system, space group P2/c and have been fully characterized by satisfactory elemental analysis, FT-IR spectra, TGA and single-crystal X-ray diffraction. Single-crystal X-ray diffraction studies reveal that 1~3 are 3D isomorphic structures based on a trinuclear unit {ZnM2(?2-COO)2(?3-COO)2} and exhibit pcu topological net and blue fluorescence.     

Uniform difference scheme for a singularly perturbed linear 2nd order hyperbolic problem with zeroth order reduced equation

In this paper a singularly perturbed linear second order hyperbolic problem with zeroth order reduced equation is discussed. Firstly, an energy inequality of the solution and an estimate of the remainder term of the asymptotic solution are given. Then an exponentially fitted difference scheme is developed in an equidistant mesh. Finally, uniform convergence in small parameter is proved in the sense of discrete energy norm.     

HA888(Ⅲ)P/TSD电话机故障检修

ＨＡ８８８（Ⅲ）Ｐ／ＴＳＤ电话机故障检修林平故障现象铃声响后不久，通话指示灯亮，铃声中断，机内免提扬声器出现噪声，同时主叫的受话器中有忙音信号，且出现的时间长短不一。分析检修由图可见，外线送来的铃流信号输入振铃电路的同时，经ＶＤ１－ＶＤ４桥式整流，Ｒ...     

彩电亮度失控故障检修一例

故障现象:一台CPT—1838型彩电亮度失控,图像有一层白雾,模糊不清,且有回扫线。分析检修:该机亮度控制电路是由亮度电位器R_(319)控制IC501内部的亮度信号放大电路。IC501输出的色差信号和亮度信号经矩阵和视放电路变换和放大后分别     

E-mail谈

E-mail收发失败的原因经常使用免费电子信箱的网友恐怕都有过邮件收发延误、甚至丢失的经历.网站并不会对这些邮件投递错误承担任何责任,这使经常使用电子邮件的网友们有苦难言. 据有关统计数据显示,目前我国上网用户平均每周发出电子邮件10封,收到电子邮件18封,其中有数封电子邮件是因为发送或接收失败造成的,那么,造成电子邮件收发送或接收失败的原因是什么呢?     

A New Acentric Heterometallic Inorganic-organic Hybrid Framework [ZnK_2(m-BDC)_2(H_2O)_2]n: Fluorescent,NLO and Ferroelectric Properties

Solvothermal reactions of Zn(NO3)2·6H2O with isophthalic acid in the presence of potassium nitrate lead to an acentric three-dimensional(3D) hetero-metallic inorganic-organic hybrid framework [ZnK2(m-BDC)2(H2O)2]n(1, m-H2 BDC = benzene-1,3-dicarboxylic acid). The crystal was characterized by elemental analysis, IR spectroscopy, TGA and single-crystal X-ray diffraction analysis. Complex 1 is of orthogonal crystal system, acentric space group Cmc21 with a = 19.764(6), b = 19.948(6), c = 12.039(4) , V = 4746(3) 3, Z = 4, C32H20O19K4Zn2, Mr = 995.66, Dc = 1.393 g/cm3, F(000) = 2000 and μ = 1.426 mm-1. The final R = 0.0761 and wR = 0.1841. The crystal exhibits remarkable blue luminescence emissions with high quantum yield of 56.02% and displays modest powder SHG efficiency of about 0.7 times that produced by a potassium dihydrogen phosphate(KDP) powder. In addition, it also exhibits potential ferroelectric property.     

NUMERICAL SOLUTION OF THE SINGULARLY PERTURBED PROBLEM FOR THE HYPERBOLIC EQUATION WITH INITIAL JUMP

In this paper we consider the initial-boundary value problem for a second orderhyperbolic equation with initial jump.The bounds on the derivatives of the exact solutionare given.Then a difference scheme is constructed on a non-uniform grid.Finally,uniformconvergence of the difference solution is proved in the sense of the discrete energy norm.     

A CLASS OF VARIATIONAL DIFFERENCE SCHEMES FOR A SINGULAR PERTURBATION PROBLEM

In this paper,a singularly perturbed boundary value problem for second order self-adjoint ordinary differential equation is discussed.A class of variational difference schemesis constructed by the finite element method.Uniform convergence about small parameter isproved under a weaker smooth condition with respect to the coefficients of the equation.The schemes studied in refs.[1],[3],[4]and[5]belong to the class.