HL-2A等离子体边缘的快速单探针测量

介绍了对HL-2A装置中平面边缘等离子体的单探针测量。单探针是安装在可径向移动、并可绕轴旋 转360o的传动杆上的。在1MHz的快速采样频率下,测量了主等离子体边缘的温度、密度、悬浮电位、空间电位、极 向等离子体流速的径向分布。测量的结果表明,利用单探针测量的主等离子体边缘参数与朗缪尔四探针测量结果 基本一致。     

光学频率标准与光钟的实现

综述了时间频率标准的发展过程.对构成光学频率标准的四个要素,即激光冷却、激光稳频、离子捕陷和光学频率梳进行了系统的介绍.详细描述了光钟的原理与系统构成,并对光学频率标准与光钟的应用前景进行了展望.     

Photoelectron angular distributions from above threshold ionization of hydrogen atoms in strong laser fields

We apply a scattering theory of nonperturbative quantum electrodynamics to study the photoelectron angular distributions (PADs) of a hydrogen atom irradiated by linearly polarized laser light. The calculated PADs show main lobes and jetlike structure. Previous experimental studies reveal that in a set of above-threshold-ionization peaks when the absorbed-photon number increases by one, the jet number also increases by one. Our study confirms this experimental observation. Our calculations further predict that in some cases three more jets may appear with just one-more-photon absorption. With consideration of laser-frequency change, one less jet may also appear with one-more-photon absorption. The jetlike structure of PADs is due to the maxima of generalized phased Bessel functions, not an indication of the quantum number of photoelectron angular momentum states.     

基于抖动测试的AFDX端到端延迟紧性修正

AFDX引入虚拟链路(Virtual Link)实现物理带宽资源的逻辑分隔。由于数据帧的异步到达和多路复用输出造成虚拟链路的时延抖动现象,并最终导致流量端到端延迟分析的不确定性。本文提出了一种基于抖动测试值的网络演算紧缩方法。通过分布式测试,获得虚拟链路在网络中的实际传输抖动,并以此为基础,建立了流量传输精确化模型,通过流量模型的逐级修正,使端到端延迟计算结果逐级精确化。通过将抖动实际值与理论分析结果相结合,提供了网络演算悲观度及其扩散影响度量的直观对比,提高了延迟计算的紧性。     

碳纳米管包裹的硅纳米线复合结构的热稳定性研究

采用经典分子动力学方法模拟一定直径[111]晶向的硅纳米线填充不同扶手椅型单壁碳纳米管复合结构的加热过程, 通过可视化和能量分析的方法判断复合结构中硅纳米线和碳纳米管的热稳定性. 通过讨论碳纳米管的空间限制作用和分子间相互作用力的关系, 对碳纳米管和硅纳米线的热稳定性变化进行初步解释. 研究发现碳纳米管中硅纳米线的热稳定性和碳纳米管的直径关系密切: 当管径较小时, 硅纳米线的热稳定性有所提高, 当管径增大到一定大小时, 硅纳米线的热稳定性会突然显著地下降, 直到硅纳米线与管壁不存在分子间相互作用力, 硅纳米线的热稳定性才会恢复. 而硅纳米线填充到碳纳米管中对碳纳米管的热稳定性有着明显的降低作用.     

基于优化核极限学习机的风电功率时间序列预测

针对时间序列预测,在单隐层前馈神经网络的基础上,基于进化计算的优化策略,提出了一种优化的核极限学习机(optimized kernel extreme learning machine,O-KELM)方法.与极限学习机(extreme learning machine,ELM)方法相比,核极限学习机(kernel extreme learning machine,KELM)方法无须设定网络隐含层节点的数目,以核函数表示未知的隐含层非线性特征映射,通过正则化最小二乘算法计算网络的输出权值,它能以极快的学习速度获得良好的推广性.在KELM的基础上,分别将遗传算法、模拟退火、微分演化三种进化算法用于模型的结构输入选择、正则化系数以及核参数的优化选取,以进一步提高网络的性能.将O-KELM方法应用于标准Mackey-Glass混沌时间序列预测及某地区的风电功率时间序列预测实例中,在同等条件下,还与优化的极限学习机(optimized extreme learning machine,O-ELM)方法进行比较.实验结果表明,所提出的O-KELM方法在预测精度上优于O-ELM方法,表明了其有效性.     

旋翼叶片回波建模与闪烁现象机理分析

对旋翼叶片回波建模与闪烁现象进行了综合研究.基于散射点散射系数和分布情况,构建了旋翼叶片回波的散射点模型,并分析了散射点分布对回波的影响;在此基础上研究了回波时域闪烁现象的物理散射机理,并结合时频分析和横向分辨率分析了微多普勒特征及时频域闪烁现象;对两类不同分布间隔的散射点模型进行了仿真,并与积分模型进行对比性实验,结果验证了闪烁现象物理分析的合理性.该研究成果在旋翼目标的探测识别领域具有一定的理论与应用价值.     

Influence of binding energies of electrons on nuclear mass predictions

Nuclear mass contains a wealth of nuclear structure information, and has been widely employed to extract the nuclear effective interactions. The known nuclear mass is usually extracted from the experimental atomic mass by subtracting the masses of electrons and adding the binding energy of electrons in the atom. However,the binding energies of electrons are sometimes neglected in extracting the known nuclear masses. The influence of binding energies of electrons on nuclear mass predictions are carefully investigated in this work. If the binding energies of electrons are directly subtracted from the theoretical mass predictions, the rms deviations of nuclear mass predictions with respect to the known data are increased by about 200 ke V for nuclei with Z, N 8. Furthermore, by using the Coulomb energies between protons to absorb the binding energies of electrons, their influence on the rms deviations is significantly reduced to only about 10 ke V for nuclei with Z, N 8. However, the binding energies of electrons are still important for the heavy nuclei, about 150 ke V for nuclei around Z = 100 and up to about 500 ke V for nuclei around Z = 120. Therefore, it is necessary to consider the binding energies of electrons to reliably predict the masses of heavy nuclei at an accuracy of hundreds of ke V.     

Computational studies on two novel energetic nitrogen‐rich compounds based on tetrazolone

Two novel energetic nitrogen‐rich compounds 1,4‐diaminotetrazol‐5‐one ( DATO ) and 1,4‐dinitrotetrazol‐5‐one ( DNTO ) were proposed first and studied by quantum chemistry method with B3LYP/6‐31G* level of theory. The optimized geometry, IR predicted spectrum and thermochemical parameters, frontier molecular orbitals and molecular electrostatic potential were calculated for inspecting the electronic structure, molecular stability and chemical reactivity. The important macroscopic properties including density, enthalpy of formation, detonation parameters and impact sensitivity have been predicted as well. As a result, two designed compounds DATO and DNTO possess positive enthalpy of formation (395.79 and 342.77 kJ/mol), impressive detonation parameters (D = 8.80 km/s, P = 33.69 GPa; D = 8.89 km/s, P = 34.98 GPa) superior to the remarkable explosive RDX, acceptable sensitivities and might be promising candidates of energetic materials. Copyright © 2015 John Wiley & Sons, Ltd.     

基于遗传算法的混沌系统二自由度比例-积分-微分控制研究

二自由度比例-积分-微分(PID)控制算法简单、实用，但将其应用于复杂非线性系统控制时参数整定困难.运用改进的遗传算法进行二自由度PID控制器参数优化，参数优化的收敛速度快、准确，将其应用于Chen氏混沌系统和同步电动机混沌系统的控制中，仿真研究收到良好的控制效果. 关键词： 混沌系统 遗传算法 比例-积分-微分控制