激光脉冲对氢负离子在金属面附近光剥离的影响

利用闭合轨道理论和金属面附近氢负离子的双脉冲光剥离截面的计算公式,计算了氢负离子在金属面附近激光脉冲作用下的光剥离截面.计算结果表明:如果脉冲宽度远大于闭合轨道的回归周期时,它对光剥离截面的影响很小;当脉冲宽度小于闭合轨道的周期或者可以和闭合轨道的周期相比较时,光剥离截面的振荡幅度大大地减弱.光剥离截面除了与脉冲宽度有关外,还与双脉冲之间的时间延迟、相位差有关.对于某些相位差, 双脉冲光剥离截面的取值增大; 而对于另外一些相位差, 光剥离截面的取值减小.因此,可以利用脉冲激光来控制氢负离子在表面附近光剥离 关键词： 激光脉冲 光剥离截面 金属面 闭合轨道理论     

Two new discrete integrable systems

In this paper,we focus on the construction of new(1+1)-dimensional discrete integrable systems according to a subalgebra of loop algebra A 1.By designing two new(1+1)-dimensional discrete spectral problems,two new discrete integrable systems are obtained,namely,a 2-field lattice hierarchy and a 3-field lattice hierarchy.When deriving the two new discrete integrable systems,we find the generalized relativistic Toda lattice hierarchy and the generalized modified Toda lattice hierarchy.Moreover,we also obtain the Hamiltonian structures of the two lattice hierarchies by means of the discrete trace identity.     

冲击条件下含纳米空洞的单晶铜的塌缩

利用分子动力学方法研究了单晶铜中不同大小的球形空洞在冲击波下的演化过程.模拟结果表明不同大小空洞的塌缩过程不同.模拟中冲击波由空洞左边扫向空洞右边.在较大尺寸的空洞塌缩过程中会产生系列的位错环.当空洞半径较小时,先在空洞的右侧形成位错环,当空洞半径增大到某一临界大小时,在空洞左右两侧同时产生位错环,当空洞半径较大时,先在空洞左侧形成位错环.当空洞左右两侧的位错环均形成以后,其右侧位错环前端的生长速度大于其左侧的.空洞半径增大,相应的位错环前端的生长速度变化不大.当空洞半径增大时,空洞中心指向位错源的矢量方 关键词： 纳米空洞 位错环 冲击波 塑性变形     

氦、氘对纯铁辐照缺陷的影响

在核聚变堆的辐照环境中, 核嬗变产物氢、氦对结构材料的抗辐照性能将产生很大的影响. 本实验采用离子注入和电子辐照模拟研究了氦和氘对具有体心立方结构的纯铁的影响. 采用离子加速器在室温分别对纯铁注入氦离子和氘离子, 经500℃时效1 h后在高压电镜下进行电子辐照.结果表明: 室温注氦和室温注氘的纯铁在500℃时效后分别形成间隙型位错环和空位型位错环. 在电子辐照下, 间隙型位错环吸收间隙原子而不断长大, 而空位型位错环吸收间隙原子不断缩小. 通过计算位错环的变化速率发现, 空位型位错环比间隙型位错环吸收了更多的间隙原子, 即室温注氘纯铁的位错偏压比室温注氦纯铁的偏压参量大, 这意味着相同实验条件下空位型位错环对辐照肿胀的贡献大于间隙型位错环对辐照肿胀的贡献. 利用氦-空位复合体和氘-空位复合体的结构, 分析了注氦和注氘后在纯铁中形成不同类型位错环的原因. 关键词： 氦 氘 辐照损伤 位错环     

基于SOA和NOLM的光脉冲放大与压缩的设计模型

设计了一种基于半导体光放大器(SOA)和非线性光学环镜(NOLM)的光脉冲放大与压缩的模型。数值研究结果表明:在NOLM中,当调节合适的控制脉冲的输入和初始时延时,具有较低峰值功率、宽度为几十皮秒的高斯信号脉冲经此模型放大压缩后,可以得到脉冲峰值增益高、脉冲宽度窄以及基本无基座的高质量超短信号光脉冲。     

基于圆环形薄壁截面梁的光纤光栅传感研究

提出将圆环形薄壁截面梁应用于光纤光栅传感，用一个光栅实现了对温度与应力的同时区分测量；对圆环形薄壁截面梁的应变进行了理论与实验分析，结果表明圆环形薄壁截面梁各点应变与该点角度的二倍呈余弦变化关系. 关键词： 光纤光栅传感 圆环形薄壁截面梁 啁啾     

Zero—field—cooled and field—cooled magnetizations and magnetic susceptibility of itinerant ferromagnet SrRuO3

Zero-field-cooled(ZFC) magnetization,field-cooled(FC) magnetization,ac magnetic susceptibility and major hysteresis loops of itinerant ferromagnet SrRuO3 have been measured at magnetic ordering temperatures ranging from 5 to 160K.An empirical model is proposed to calculate the measured ZFC magnetization.The result indicates that the calculated ZFC magnetization compares well with the measured one.Based on the generalized Preisach model.both the ZFC and FC curves are reproduced by numerical simulations.The critical temperature and critical exponents are determined by measuring the ac magnetic susceptibility in different bias magnetic fields at temperatures in the vicinity of the point of phase transition.     

Non-local order in Mott insulators,duality and Wilson loops

It is shown that the Mott insulating and superfluid phases of bosons in an optical lattice may be distinguished by a non-local ‘parity order parameter’ which is directly accessible via single site resolution imaging. In one dimension, the lattice Bose model is dual to a classical interface roughening problem. We use known exact results from the latter to prove that the parity order parameter exhibits long range order in the Mott insulating phase, consistent with recent experiments by Endres et al. [M. Endres, M. Cheneau, T. Fukuhara, C. Weitenberg, P. Schauß, C. Gross, L. Mazza, M.C. Bañuls, L. Pollet, I. Bloch, et al., Science 334 (2011) 200]. In two spatial dimensions, the parity order parameter can be expressed in terms of an equal time Wilson loop of a non-trivial U(1)$U\left(1\right)$ gauge theory in 2+1$2+1$ dimensions which exhibits a transition between a Coulomb and a confining phase. The negative logarithm of the parity order parameter obeys a perimeter law in the Mott insulator and is enhanced by a logarithmic factor in the superfluid.     

Observational effects from quantum cosmology

The status of quantum cosmologies as testable models of the early universe is assessed in the context of inflation. While traditional Wheeler–DeWitt quantization is unable to produce sizable effects in the cosmic microwave background, the more recent loop quantum cosmology can generate potentially detectable departures from the standard cosmic spectrum. Thus, present observations constrain the parameter space of the model, which could be made falsifiable by near‐future experiments.     

少节点基因调控网络的控制

近年来,自组织振荡网络受到越来越多科学家的关注,对生物体的生长、发育起调控作用的基因调控网络即是其中的一种.本文研究了少节点基因调控网络的控制问题.运用多相位超前驱动方法对该种网络进行调控,可以有效地提高对网络的控制效率.通过数值模拟,发现对于少节点基因调控网络,当系统参数确定时,网络的有效控制率可以达到95％以上(10节点网络);当系统参数不确定时,控制的效率也非常高.