Analysis of secondary electron emission using the fractal method

Based on the rough surface topography with fractal parameters and the Monte–Carlo simulation method for secondary electron emission properties, we analyze the secondary electron yield(SEY) of a metal with rough surface topography. The results show that when the characteristic length scale of the surface, G, is larger than 1 × 10^-7, the surface roughness increases with the increasing fractal dimension D. When the surface roughness becomes larger, it is difficult for entered electrons to escape surface. As a result, more electrons are collected and then SEY decreases. When G is less than 1 × 10^-7,the effect of the surface topography can be ignored, and the SEY almost has no change as the dimension D increases. Then,the multipactor thresholds of a C-band rectangular impedance transfer and an ultrahigh-frequency-band coaxial impedance transfer are predicted by the relationship between the SEY and the fractal parameters. It is verified that for practical microwave devices, the larger the parameter G is, the higher the multipactor threshold is. Also, the larger the value of D,the higher the multipactor threshold.     

Synergistic influences of titanium,boron, and oxygen on large-size single-crystal diamond growth at high pressure and high temperature

The synergistic influences of boron, oxygen, and titanium on growing large single-crystal diamonds are studied using different concentrations of B₂O₃ in a solvent-carbon system under 5.5 GPa-5.7 GPa and 1300 ℃-1500 ℃. It is found that the boron atoms are difficult to enter into the crystal when boron and oxygen impurities are doped using B₂O₃ without the addition of Ti atoms. However, high boron content is achieved in the doped diamonds that were synthesized with the addition of Ti. Additionally, boron-oxygen complexes are found on the surface of the crystal, and oxygen-related impurities appear in the crystal interior when Ti atoms are added into the FeNi-C system. The results show that the introduction of Ti atoms into the synthesis cavity can effectively control the number of boron atoms and the number of oxygen atoms in the crystal. This has important scientific significance not only for understanding the synergistic influence of boron, oxygen, and titanium atoms on the growth of diamond in the earth, but also for preparing the high-concentration boron or oxygen containing semiconductor diamond technologies.     

烷基极化效应与羰基13C化学位移

对羰基化合物中羰基碳的¹³C NMR化学位移与烷基（R）极化效应的内在关系 进行了研究. 结果表明：分子中R的极化效应增加使羰基碳的¹³C化学位移值升 高,其关系可表示为δ=a+b·ΣPEI(R),其中a、b为系数,PEI（R）为R极化效应指数.
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EXISTENCE AND UNIQUENESS THEOREMS FOR HIGHER-ORDER BOUNDARY VALUE PROBLEMS

An existence and uniqueness of solutions for boundary value problemsandare established, by employing a priori estimates for all solutions and the Schau-der fixed point theorem. Some of these results extend earlier results due toUsmani(1979), Yang(1988), and Pei(1997).     

关于均值KIRCHHOFF板非线性边界镇定问题的几点注记

对于均值K IRCHHOFF板非线性边界镇定问题给出几点注记.首先应用G reen公式对具有非线性边界反馈控制的均值K IRCHHOFF板所决定的非线性系统的能量衰减速度进行了重新推导,从而修正了前人的结果.然后应用极大单调函数的定义和分部积分技巧,对均值K IRCHHOFF板非线性边界镇定问题所决定的非线性算子A的极大单调性给出了重新证明,进而更正了已有文献中相应证明的欠妥之处.     

铁电单晶0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3折射率的研究

用最小偏向角法在20℃下精确测量了0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3(0.62PMN-0.38PT)单晶的折射率,给出了该温度下折射率色散的Sellmeier方程.研究了能带结构与折射率的关系,计算了样品的Sellmeier光学系数:对no,E0=5.50eV,λ0=0.226μm,S0=1.004×1014m-2,Ed=28.10eV;对ne,E0=5.57eV,λ0=0.223μm,S0=1.017×1014m-2,Ed=28.10eV.ABO3型钙钛矿材料中,BO6八面体基元决定了晶体的能带结构,对折射率产生重要影响.     

Monte Carlo study of the universal area distribution of clusters in the honeycomb O（n） loop model

We investigate the area distribution of clusters (loops) in the honeycomb O(n) loop model by means of the worm algorithm with n = 0.5, 1, 1.5, and 2. At the critical point, the number of clusters, whose enclosed area is greater than A, is proportional to A-1 with a proportionality constant C. We confirm numerically that C is universal, and its value agrees well with the predictions based on the Coulomb gas method.     

激光刻蚀对镀金表面二次电子发射的有效抑制

使用红外激光刻蚀技术在镀金铝合金表面制备了多种形貌的微孔及交错沟槽阵列.表征了两类激光刻蚀微阵列结构的三维形貌和二维精细形貌,分析了样品表面非理想二级粗糙结构的形成机制.研究了微阵列结构二次电子发射特性对表面形貌的依赖规律.实验结果表明:激光刻蚀得到的微阵列结构能够有效抑制镀金表面二次电子产额(secondary electron yield,SEY),且抑制能力明显优于诸多其他表面处理技术;微阵列结构对SEY的抑制能力与其孔隙率及深宽比呈现正相关,且孔隙率对SEY的影响更为显著.使用蒙特卡罗模拟方法并结合二次电子发射唯象模型和电子轨迹追踪算法,仿真了各微结构表面二次电子发射特性,模拟结果从理论上验证了微阵列结构孔隙率及深宽比对表面SEY的影响规律.本文获得了能够剧烈降低镀金表面SEY的微阵列结构,理论分析了SEY对微结构特征参数的依赖规律,对开发空间微波系统中低SEY表面及提高镀金微波器件性能有重要意义.     

164Lu的三轴超形变核态的研究

利用TRS方法对双奇核¹⁶⁴Lu的位能面进行了计算,确认了¹⁶⁴Lu核的一条三轴超形变带,结果与实验较好地符合,同时指出了三轴超形变带的一个具体的组态     

如何在物理问题解决过程中培养学生创新思维

在物理教学中通过创设恰当的问题情境,诱导学生产生疑问,发现问题并提出问题,可使学生产生强烈的探究的欲望．接下来物理教学就是通过引导学生去探究,经历解决问题的过程,从而使学生理解掌握相关知识,提高学生解决问题的能力,培养学生的创新思维．本文根据笔者多年的教学体会,着重从物理问题的解决过程去讨论学生创新思维的培养．