周期参数扰动的T混沌系统同宿轨道分析

针对一类周期参数扰动的T混沌系统, 通过变换将系统转化为具有广义Hamilton结构的周期参数扰动的慢变系统, 运用Melnikov方法对系统的同宿轨道进行了分析计算, 并给出了系统的同宿轨道参数分支条件. 同时, 通过数值实验, 对周期参数扰动控制策略及同宿轨道进行了仿真, 验证了文中理论分析的正确性. 关键词： Hamilton系统 Melnikov方法 同宿轨道 周期参数扰动     

Melamine trisulfonic acid-catalyzed N-formylation of amines under solvent-free conditions

A highly convenient method for N-formylation of amines via treatment by formic acid in the presence of melamine trisulfonic acid as a catalyst has been developed. This method showed improvements over previous reports in terms of yield, reaction time and chemoselectivity.     

The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis

The electron swarm parameters including the density-normalized effective ionization coefficients(α-η)/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend(SST) experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td(1 Td = 10-17V·cm2),while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of(αη)/N with the CF3I mixture ratio k,the limiting field strength(E/N) lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of(E/N) lim are essentially the same as that for pure SF 6.Additionally,the global warming potential(GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.     

Echelle dif fraction grating based high-resolution spectrometer-on-chip on SiON waveguide platform

An echelle diffraction grating based high-resolution spectrometer-on-chip on silicon oxynitride (SiON) waveguide platform operated at a wavelength range of 850 nm is demonstrated. The chip comprises 120 output waveguides with 0.25-nm wavelength channel spacing and has a size of only 11 × 6 (mm). The experimental results show that the insertion loss is-14 dB, the measured adjacent channel crosstalk is less than -25 dB, the 3 dB channel bandwidth is < 0.1 nm, and the channel non-uniformity is 3 dB for 56 channels with a wavelength ranging from 838 to 852 nm.     

Resonantly pumped Q-switched Er:GdVO4 laser

We describe a Q-switched Er:GdVO₄ laser resonantly pumped by a MgO-doped periodically poled LiNbO₃ optical parametric oscillator （MgO: PPLN OPO） at 1536 nm. In continuous-wave lasing, the maximum output power is 1.14 W with an incident pump power of 4.7 W and a slope efficiency of 27%. In Q-switched operation, 1.1 mJ of output pulse energy is achieved at 200 Hz. The upper-state lifetime at different pulse repetition frequencies is also calculated.     

一级相变磁制冷材料的基础问题探究

由于一级相变磁制冷材料发生磁相变时有晶胞体积的突变,相变过程中有相变潜热存在,其磁化过程中有许多磁学问题有待于进一步探究.本文以LaFe13-xSix合金为研究对象,在现有对磁一级相变基础问题的分析基础上,对一级相变材料中系统熵变、等温熵变、绝热温变、热滞、磁滞、铁磁与顺磁态两相共存的温度区间和磁场区间、制冷能力的计算等磁学基础问题进行了较为细致的探究.分析表明,在忽略完全铁磁态和顺磁态对磁热效应的贡献时,Maxwell方程和Clausius-Clapeyron方程计算熵变的值具有等效性.等温磁化过程中升温和降温曲线包围的面积SABCE(磁滞的大小),实际上是升温过程和降温过程中磁场做的净功,等于相变潜热之差.磁滞和热滞的大小与磁化过程数据测量的时间有关,测量时间越长则滞后越小,当相变是平衡相变则滞后为零.另外,对温度和磁场诱导磁相变过程进行了分析,提出了一级相变磁制冷材料制冷能力的不同计算模型.本文对一级相变磁制冷材料的磁学基础问题研究有一定的参考价值.     

Hcp-icosahedron structural transformation induced by the change in Ag concentration during the freezing of （CoAg）561 clusters

The synergy effect of alloy elements in bimetallic clusters can be used to tune the chemical and physical properties. Research on the influences of alloy concentration and distribution on the frozen structure of bimetallic clusters plays a key rolc in exploring new structural materials. In this paper, we study the influence of Ag concentration on the frozen structure of the （AgCo）561 cluster by using molecular dynamics simulation with a general embedded atom method. The results indicate that tt~e structure and chemical ordering of the （AgCo）561 cluster are strongly related to Ag concentration. Hcp-icosahedron structural transformation in the frozen （CoAg）561 cluster can be induced by changing Ag concentration. The chemical ordering also transforms to Janus-like Co Ag from core-shell Co-Ag.     

高电荷态离子207Pbq+(24≤q≤36)与Si(110)固体表面作用的电子发射研究

报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子²⁰⁷Pb^q+(24≤q≤36)入射到Si(110)表面产生的电子发射的实验测量结果.结果表明,高电荷态离子与固体表面相互作用产生的电子发射产额Y与入射离子的电荷态q、入射角度ψ和入射能量E都有很强的关联.首次发现,电子发射产额Y与入射角度ψ间有接近1/tanψ的关系.理论分析认为,这些过程与基于经典过垒模型的势能电子发射过程密切相关. 关键词： 高电荷态离子 经典过垒模型 电子发射产额     

X射线光场成像技术研究

X射线三维成像技术是目前国内外X射线成像研究领域的一个研究热点.但针对一些特殊成像目标,传统X射线计算层析(CT)成像模式易出现投影信息缺失等问题,影响CT重建的图像质量,使得CT成像的应用受到一定的限制.本文主要研究了基于光场成像理论的X射线三维立体成像技术.首先从同步辐射光源模型出发,对X射线光场成像进行建模;然后,基于光场成像数字重聚焦理论,对成像目标场在深度方向上进行切片重建.结果表明:该方法可以实现对成像目标任一视角下任一深度的内部切片重建,但是由于光学聚焦过程中的离焦现象,会引入较为严重的背景噪声.当对其原始数据进行滤波后,再进行X射线光场重聚焦,可以有效消除重建伪影,提高图像的重建质量.本研究既有算法理论意义,又可应用于工业、医疗等较复杂目标的快速检测,具有较大的应用价值.