非均匀磁场磁镜粒子约束的Monte-Carlo模拟

本文在碰撞区和无碰撞区之间的过渡区,就LAMEX和抛物线轮廓两种空间变化磁场磁镜,用Monte-Carlo模拟研究了粒子约束问题。在过渡区,粒子约束时间高于其它两区公式的外推值,并与磁镜比成正比关系。这一模拟还用自洽解的方法得到了密度轮廓,并研究了这一轮廓和等离子体参数的关系。 关键词：     

鲸群优化的粒子滤波算法研究

针对标准的粒子滤波存在粒子贫化问题,提出了一种鲸群优化的粒子滤波算法。用粒子表征鲸鱼个体, 模拟鲸鱼群体搜寻猎物的过程,引导粒子向高似然区域移动。将粒子滤波中粒子的状态值作为鲸鱼群的个体位置,将粒子的状态估计转化为对鲸鱼群的寻优;通过鲸群的螺旋运动方式优化粒子的重要性采样过程,使粒子分布更加合理,对鲸群算法中的全局最优值引入最优邻域随机扰动策略,并在鲸鱼位置更新过程中加入自适应权重因子;选用一种典型的单静态非增长模型进行仿真测试。测试结果表明:提出的方法与传统的粒子滤波以及引力场优化的粒子滤波相比,在保证相同粒子数的前提下,算法的均方误差分别降低了28%和9%,证明了鲸群优化的粒子滤波算法具有更高的估计精度,并且在粒子数较少的情况下,可实现更准确的状态估计。     

ICP—AES中光谱干扰的计算机模拟：Ⅱ.有效谱线轮廓宽度的计算

在电感耦合等离子体原子发射光谱法(ICP-AES)中,利用计算机模拟光谱线对于光谱干扰的快速准确预测是一种有效的方法。在模拟过程中,主要步骤在于计算光谱线轮廓。前人在谱线轮廓的计算方面已进行过探讨,但所涉及的大多为谱线的物理轮廓。实际上,任何光谱分析均需通过一定的光谱仪器进行。分析粒子所发射的谱线除了在光源中因各种因素发生变宽外,在经过仪器光学系统时亦会发生变宽。在检测     

基于分子运动对流换热和热辐射下煤粉颗粒群粒子的加热分析

本文建立了在烟气对流加热和辐射状态下的煤粉颗粒群加热模型,通过数值模拟,模拟研究了不同锅炉炉膛尺寸下不同煤粉粒子粒径的煤粉群粒子加热时间以及粒子温升的关系,对对流换热和辐射换热在着火热源中所占比重进行了分析,模型很好的模拟了粒子的升温,能够较好的反映出煤粉粒子加热升温机理,为煤粉射流微元加热及着火提供了计算方法。     

面向等离子体部件沉积特性的数值模拟研究

采用粒子模拟研究方法，利用PEGASUS 程序对等离子体环境下面向等离子体部件的沉积特性进行了模拟研究。结果显示部件表面连接缝隙尺寸、表面粗糙度、粒子入射的角度以及流量对沉积影响显著。在能量较小、溅射可忽略时，能量对沉积的影响很小。粗糙度越小，沉积量越小；同一种粗糙度，不同轮廓也会使沉积发生较大变化，轮廓一致的更有利于减小沉积。该模拟对研究等离子体与材料相互作用，分析瓦片缝隙尺寸、瓦片加工工艺和等离子体参数对面向等离子体部件沉积行为的影响具有重要意义。     

粒子群及遗传算法在相对论返波管中的应用

在全三维粒子模拟软件CHIPIC平台上,分别开发了粒子群及基因算法模块.以相对论返波管为例,采用三种不同类型的参数(连续参数、离散参数、混合参数),对粒子群及基因算法进行比较.优化结果表明:粒子群算法的收敛速度更快,在有限的迭代步数内得到的目标结果也更优良,总体表现优于基因算法.     

基于多粒子群算法的视频跟踪研究

粒子群算法是一种新的进化算法,算法思路适合于进行视频跟踪,但是由于在视频跟踪过程中以跟踪窗口作为粒子,因此该粒子具有中心点横坐标、中心点纵坐标和窗口半径三维特征向量,计算冗余较大,难以满足视频跟踪的实时性要求。提出了一种多粒子群视频跟踪算法,即在跟踪过程中使用多个粒子群,粒子群与粒子群之间粒子半径不同,在各粒子群以评价函数收敛到最佳中心点后,再完成各自半径的一维粒子群计算。这样就可将三维粒子群计算分为一个两维和一个一维粒子群计算,最后通过比较得出最佳粒子,作为搜索结果。分析了这一算法成立的必要条件,即当选择Bhattacharyya系数计算方法作为粒子群算法的评价函数时,大于目标的固定窗体的中心点可以收敛到目标的形心。实验证明,这种基于多粒子群的跟踪算法可以应用于实时视频跟踪,其跟踪效果优于传统算法。     

共振吸收的自洽场结构和密度轮廓分布

 用二维多时标全电磁相对论粒子模拟程序，对斜入射P极化强激光与具有线性密度分布的非均匀等离子体平板相互作用中的共振吸收进行了模拟计算，给出了冕区自洽场的结构和等离子体密度轮廓分布，粒子模拟结果观察到了临界面附近等离子体波的激发、等离子体密度轮廓的变陡和空穴的产生。     

基于MATLAB的布朗运动数值模拟

运用MATLAB软件平台模拟T--维布朗运动的动态画面。并定义了粒子群分布离散度尺,研究迭代步数后,噪声强度系数。与粒子群分布离散度R的关系,通过曲线拟合得到关系式R∝√k与R∝Cs。     

量子势阱粒子群优化算法的改进研究

为提高量子势阱粒子群优化算法的优化能力, 通过分析目前量子势阱粒子群优化算法的设计过程, 提出了改进的量子势阱粒子群优化算法. 首先, 分别基于Delta势阱、谐振子和方势阱 提出了改进的量子势阱粒子群优化算法, 并提出了基于统计量均值的控制参数设计方法. 然后, 在势阱中心的设计方面, 为强调全局最优粒子的指导作用, 提出了基于自身最优粒子加权平均和动态随机变量的两种设计策略. 实验结果表明, 三种势阱粒子群优化算法性能比较接近, 都优于原算法, 且Delta势阱模型略优于其他两种.     

Excitation transfer from second to first resonance line of potassium observed in hot atomic vapor

We present experimental investigation on the fluorescence profiles observed by excitation of the hyperfine transitions of the second resonance line of potassium with a wavelength of 404.4 nm in dependence on the atomic density. This leads to both direct decay of the excited level population to the ground state (violet fluorescence), and to cascade decay via the first resonance lines (infrared fluorescence). It has been shown that the behavior of these two fluorescence profiles is different: increasing the atomic density, the violet fluorescence profile exhibits a well-pronounced self-absorption dip, while the infrared line does not show any narrow-width reduced absorption structure. Moreover, the profiles of the infrared line have a higher signal-to-noise ratio than that of the violet line. Our investigations show that beside atomic population, atomic polarization is also transferred by the cascade transitions. This is evidenced by registration of coherent magneto-optical resonances at the two fluorescence lines. The signal-to-noise ratio of these resonances registered at the first resonance line is significantly higher than at those obtained at the second resonance line. The proposed study makes it possible to examine cascade transitions in alkali atoms, particularly the preservation of atomic polarization, i.e. the coherence transfer by cascade transitions.     

Correction of self-absorption spectral line and ratios of transition probabilities for homogeneous and LTE plasma

Expressions for fundamental spectral line parameters are reported for Gaussian and Lorentzian shape profiles for homogeneous plasma at equilibrium in presence of the self-absorption. These expressions for Lorentzian profiles are applied to the determination of the ratios of transition probabilities and the ratios of optical thicknesses by a new method that we propose in this article. The self-absorption is computed by spectral line profiles with a Simplex algorithm program fitting. Applications to some experimental lines illustrate the appropriate corrections.     

Optogalvanic detection as a quantitative method in spectroscopy

The use of the optogalvanic effect for measuring spectroscopic quantities such as wavelengths, line profiles and line integrals is discussed. The quantitative aspects of absorption and optogalvanic spectroscopy are compared. It is experimentally demonstrated for calcium that optogalvanic line integral measurements are not simply linearly related to the oscillator strength. Measured optogalvanic and absorption profiles for Ne, Ar and Cu are compared and it is shown that both methods yield the same result for certain conditions of the observed plasma. The dependence of the optogalvanic profiles on the current in the plasma is demonstrated.     

Analytical approximations for speed-dependent spectral line profiles

Analytical approximate expressions for speed-dependent Rautian-Sobel'man, Voigt, and general line profiles, including spectral line mixing, were obtained. Systematic errors of the approximate profiles are within 0.7% for the mass ratios of perturbing and absorbing molecules m_b/m_a≤9. The calculation time of the approximate line profiles is much shorter than the time required for calculating exact expressions for the line profiles. An approximate analytical expression for the observable homogeneous line width was derived. A least-square fitting of the singlet methane absorption line centered at 6107.17 cm⁻¹ was performed, using the approximate line profiles obtained.     

相对论性开普勒环的谱线轮廓

对于一个围绕强引力场物体(例如黑洞)作开普勒运动的环状发光物,它所发射的光线要受多普勒频移,引力红移和光线偏折等效应的作用,这种作用决定了远处观察者所看到的谱线轮廓,本文利用光子输运方程方法,求出在Schwarzschild度规中的开普勒环所发射的谱线的轮廓的精确解。 关键词：     

Escape factors for laser-plasmas

A method of parameterizing escape factors (transmission factors and net radiative brackets) for conditions typical of laser-produced plasmas is introduced. The assumptions of planar geometry, exponentially decreasing emissivity and absorption coefficient with distance with a step rise at a particular point, and spatially constant Doppler broadened line profiles have been made. The effect of velocity gradients in spectrally shifting the absorption and emission line profiles relative to each other is taken into account assuming linear velocity gradients with distance. A parameter R representing the ratio of the spatial scale-length of the absorption coefficient to the Doppler decoupling length is introduced. Fitting formulae for transmission factors and net radiative brackets are given which are valid for all R and all optical depths. In the limit of small R (large Doppler decoupling length), the escape factors asymptotically approach formulae developed originally by, for example, Holstein assuming negligible plasma velocities. For large R (small Doppler decoupling length), the escape factors have been shown to asymptotically approach the Sobolev approximation. The parameterized net radiative bracket has been used in the hydrodynamic and atomic physics code ‘EHYBRID’ for the calculation of the effect of radiation trapping on population densities in laser-produced plasmas. The output of the modified EHYBRID code has then been post processed using the parameterised transmission factors to simulate 123 Ne-like and 399 F-like germanium resonance line intensities emitted in typical X-ray laser experiments. We obtain an agreement between the simulated and experimental spectra.     

输入参数的不确定对激光大气分子透过率计算结果的影响

研究分子光谱和气象参数的不确定对单色吸收系数和对应的科线路径透过率计算结果的影响,并导出一般的误差表达式。数值计算表明,对所采用的大气廓线和分子光谱参数,其典型的不确定将导致透过率计算结采的标准相对误差大于3■,吸收系数和透过率对谱线频率、强度、半宽以及大气温度廓线的不确定最为灵敏。     

Calculation of radiative heat transfer in SF6 arcplasmas

Radiation transport in SF₆ are plasmas have been treated for pressures of 0.101, 0.5, and 1.0 MPa. We have investigated the use of an approximate method of partial characteristics. We have calculated spectral absorptivities for SF₆ plasmas for temperatures from 300 to 35 000 K, and have used these absorptivities to calculate the two functions designated ΔI and ΔSim. These functions are integrals over all radiation frequencies for given line segments with a linear variation of temperature along the line. The ΔI and ΔSim values are functions of the end temperatures and the length of the line, and are used to evaluate radiation transfer from line segments in the plasma where the temperature variation for each line segment is approximated as being linear. The validity of this method of partial characteristics has been demonstrated by comparing exact calculations with the approximate calculations to evaluate radiation intensities, radiation fluxes, and divergence of radiation fluxes for specified temperature profiles. The method of partial characteristics has been applied to one- and three-dimensional calculations of radiative heat transfer in simplified temperature profiles. Agreement up to 10% is obtained with exact calculations, but with a large reduction of computation time     

Application of pattern recognition in molecular spectroscopy: Automatic line search in high-resolution spectra

An expert system has been developed for the initial analysis of a recorded spectrum, namely, for the line search and the determination of line positions and intensities. The expert system is based on pattern recognition algorithms. Object recognition learning allows the system to achieve the needed flexibility and automatically detect groups of overlapping lines, whose profiles should be fit together. Gauss, Lorentz, and Voigt profiles are used as model profiles to which spectral lines are fit. The expert system was applied to processing of the Fourier transform spectrum of the D₂O molecule in the region 3200–4200 cm^?1, and it detected 4670 lines in the spectrum, which consisted of 439000 dots. No one experimentally observed line exceeding the noise level was missed.     

The static approximation in the interpretation of collision broadening

The validity of the static approximation for analyses of spectral line profiles is considered. The Fourier transform of the profile of an isolated line is compared for representative cases with the unified theory, and it is shown that the simple static approximation can be used effectively to interpret low spectral resolution experiments. This result applies to the entire profile in the limit of high density, but it also applies at low density if the instrumental line width is sufficiently large. Furthermore, in the absence of turning points in the interatomic potential, the unified and static theories produce almost identical line-wing profiles. Easily evaluated criteria are provided to guide application of the straightforward static theory to the interpretation of interatomic potentials.