共查询到20条相似文献,搜索用时 125 毫秒
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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: 相似文献
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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。 相似文献
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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 总被引:6,自引:4,他引:2
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 相似文献
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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。 相似文献
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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。 相似文献
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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。 相似文献
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针对扩展卡尔曼滤波同时定位与地图创建算法中难以建立准确的先验噪声模型的问题, 提出一种基于改进雁群粒子群算法的模糊自适应卡尔曼滤波算法. 利用分数阶微积分改进粒子进化速度, 利用混沌来改进粒子的初始化和发生早熟时的处理. 改进后的雁群粒子群算法在收敛速度与避免早熟方面有了很大改进, 并将改进的雁群粒子群算法用于模糊自适应扩展卡尔曼滤波同时定位与地图创建算法的训练, 并与用雁群粒子群算法训练的模糊自适应扩展卡尔曼滤波同时定位与地图创建算法进行对比, 其在定位与构图方面有很大的提高.
关键词:
同时定位与地图创建
雁群粒子群算法
分数阶微积分
混沌 相似文献
11.
C. Andreeva A. Krasteva A. Markovski S. Tsvetkov S. Gateva S. Gozzini S. Cartaleva 《Optical and Quantum Electronics》2018,50(5):213
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. 相似文献
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Hssaine Amamou Andre BoisBelkacem Ferhat Roland RedonBruno Rossetto Pascal Matheron 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,75(6):747-763
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. 相似文献
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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. 相似文献
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V.P. Kochanov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(18):2762-2770
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 mb/ma≤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. 相似文献
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S.J. Pestehe G.J. Tallents 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,72(6):853-878
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. 相似文献
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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。 相似文献
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Aubrecht V. Bartlova M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(5):815-823
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 相似文献
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A. D. Bykov A. M. Pshenichnikov L. N. Sinitsa A. P. Shcherbakov 《Optics and Spectroscopy》2004,96(4):497-502
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. 相似文献
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A.J.D. Farmer R.D. Cutting 《Journal of Quantitative Spectroscopy & Radiative Transfer》1974,14(9):975-978
Band-model calculations for CO2, using a statistical model, are shown to be in agreement with measured furnace emissivities for known line intensities, line width and line spacings. For best agreement, an empirical wavelength shift was required for the calculated intensity profiles. 相似文献