Generation of an extreme ultraviolet supercontinuum with a multicycle chirped laser and a static electric field

We theoretically present a method for generating an ultrabroad extreme ultraviolet(XUV) supercontinuum by using the combination of a multicycle chirped laser and a static electric field.At a low laser intensity,the spectral cutoff is extended to the 495th order harmonic,and the bandwidth of the supercontinuum spectrum is broadened to 535 eV.At a high laser intensity,the harmonic cutoff is enlarged to the 667th order,and a supercontinuum covering a bandwidth of 1035 eV is generated.In these two cases,the long quantum path is removed,and the short quantum path is selected.Especially for the relatively high laser intensity,an isolated 23-attosecond pulse with a bandwidth of about 170.6 eV is directly obtained.Finally,we also analyze the influences of the chirp parameter and the duration of the chirped pulse as well as the static field strength on the supercontinuum.     

企业电力营销策略研究

最近几年,我们国家在很多领域都取得了非常高的成就,然而细分起来,任何的行业取得的所有成就都离不开一项非常关键的内容——电力。电力是所有行业进行工作所必须的条件,而且电力还会影响到我们的日常生活,还会影响到国家的建设活动,因此我们必须要做好相关的各项工作,确保我们国家的电力安稳运行,不会出现过大的问题。笔者基于目前的这种形势背景,认真的分析研究了电力销售方法,目的是为了更好地促进经济前进,国家富裕。     

中红外组合激光场产生低于50阿秒的单个脉冲

研究了氦离子在中红外组合激光场作用下的高次谐波辐射和孤立阿秒脉冲的产生.研究结果表明,当主脉冲强度相对低时,谐波截止在657阶次处,形成一个宽度为287eV的连续谱.当主脉冲强度相对高时,可使谐波截止拓展到1795阶次,连续谱加宽到834eV.在两种情况下,我们实现了长量子路径选取,并且产生转换效率较高的连续谱.特别是对于相对高的激光强度,叠加450～1590阶次内任意87eV的谐波都可以直接得到50as以内的单个脉冲.     

利用多周期空间非均匀啁啾场产生单个短阿秒脉冲

提出了一种直接生成单个短阿秒脉冲的有效方案.采用数值求解一维含时薛定谔方程,理论研究了多周期空间非均匀啁啾场驱动预激发氦离子的高次谐波辐射和阿秒脉冲的产生.结果表明：在空间非均匀啁啾场作用下,谐波截止可扩展至1050阶次,并且高于300阶次以上的谐波是连续的.由于连续谱来自单一量子路径的贡献,滤出连续谱上880-1120阶次的谐波,直接产生了一个脉宽为11.4 as的单个脉冲.通过增加驱动脉冲的持续时间,可获得一个脉宽短至10 as的单个脉冲.     

r重紧支撑对称-反对称正交多小波的构造

提出了由一个紧支撑正交单小波函数构造二重紧支撑对称一反对称正交多小波函数的构造方法.通过选取合适的正交矩阵,二重紧支撑时称-反对称正交多小波函数可由所给的正交单小波函数平移后与正交矩阵做乘积得到,并将其推广到重.这种多小波函数不但具备紧支性和对称反对称性,而且具有正交性.     

Generation of an isolated sub-30 attosecond pulse in a two-color laser field and a static electric field

We theoretically investigate high-order harmonic generation(HHG) from a helium ion model in a two-color laser field,which is synthesized by a fundamental pulse and its second harmonic pulse.It is shown that a supercontinuum spectrum can be generated in the two-color field.However,the spectral intensity is very low,limiting the application of the generated attosecond(as) pulse.By adding a static electric field to the synthesized two-color field,not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased,but also the quantum paths of the HHG can be significantly modulated.As a result,the extension and enhancement of the supercontinuum spectrum are achieved,producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV.In particular,we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation.     

求解无约束全局优化问题的新型混合遗传算法

目的更好地解决遗传算法在求解全局优化问题时易陷入局部最优点的缺陷。方法将传统优化的无约束搜索和黄金分割法应用到局部搜索阶段,提出一种改进算法局部寻优能力的新型混合遗传算法（NHA）。结果与结论测试函数的数值实验结果表明该算法对改进遗传算法的缺陷是十分有效的。     

中红外非均匀组合场产生单个超短阿秒脉冲

目的 提出一种直接获得单个超短阿秒脉冲的新方法.方法 通过数值求解一维含时薛定谔方程,研究中红外非均匀组合场驱动氦离子产生的高次谐波辐射.结果 这种时空组合场不仅实现了单一量子路径的控制,而且产生了一个频带极宽的超连续谱.结论 对连续谱上一些适当的谐波直接进行滤波,在没有任何相位补偿的情况下可获得脉宽仅为19.3 as的单个脉冲.     

求解无约束全局优化问题的新型混合遗传算法

目的更好地解决遗传算法在求解全局优化问题时易陷入局部最优点的缺陷。方法将传统优化的无约束搜索和黄金分割法应用到局部搜索阶段,提出一种改进算法局部寻优能力的新型混合遗传算法(NHA)。结果与结论测试函数的数值实验结果表明该算法对改进遗传算法的缺陷是十分有效的。     

Ground-state structure determination and mechanical properties of palladium seminitride

Combining first-principles calculations with the particle swarm optimization （PSO） algorithm, we have explored the ground-state structure of Pd2N, whose structure is in debate although it is the first synthesized binary platinum group nitride. The ground-state structure is predicted to be tetragonal with space group P^-4m2, which is energetically more favorable than the previously proposed orthorhombic Co2N-type structure. The stability is confirmed by the subsequent calculations on the phonon dispersion curves and elastic constants. Furthermore, the calculated mechanical properties indicate that Pd2N has low incompressibility and is a common hard material.