A new 1D approximation for the solution of 2D radiative transfer problems

The simplified M-1D algorithm (M stands for modified) for the calculation of horizontal distribution of reflected brightness coefficient in 2D regions with large homogeneous pixels is presented. This algorithm is based upon modified 3^?N−1 1D-transport equations (where N is the number of large pixels) instead of one 2D-transport equation, usually used in such problems. The method does not rely on empiric assumptions on both optical properties of atmosphere or diffuse radiation intensity. Numerical results demonstrating the accuracy of the presented algorithm for simulating brightening and shadowing effects in a vicinity of the jump of optical properties given. The accuracy of the M-1D approximation strongly depends on the geometry and illumination conditions. However, it remains below 15% and can reach 1% for all cases studied and is strongly higher than the accuracy of usually employed independent pixel approximation. Time reduction via replacing 2D problem via modified 1D problem is about 17 times for all cases considered in this paper.     

Xe54+离子与Xe原子碰撞过程中的辐射电子俘获及退激发辐射的理论研究

基于多组态Dirac-Fock理论方法和冲量近似, 对Xe⁵⁴⁺与Xe在197 MeV/u碰撞能量下, 炮弹离子的俘获及退激发过程进行了理论研究. 计算了炮弹离子从中性靶原子俘获一个电子到nl (n=1, 2, 3, 4, 5; l=s, p, d) 轨道上的辐射电子俘获截面和相应的辐射光子能量, 以及俘获末态退激发辐射跃迁的能量和概率. 结合这些计算结果, 进一步模拟了碰撞产生的炮弹离子的退激发X射线谱的结构, 并与兰州重离子加速器装置上的最新实验观测结果进行了比较, 符合得很好.     

Three-dimensional polarized Monte Carlo atmospheric radiative transfer model (3DMCPOL): 3D effects on polarized visible reflectances of a cirrus cloud

A polarized atmospheric radiative transfer model for the computation of radiative transfer inside three-dimensional inhomogeneous mediums is described. This code is based on Monte Carlo methods and takes into account the polarization state of the light. Specificities introduced by such consideration are presented. After validation of the model by comparisons with adding-doubling computations, examples of reflectances simulated from a synthetic inhomogeneous cirrus cloud are analyzed and compared with reflectances obtained with the classical assumption of a plane parallel homogeneous cloud (1D approximation). As polarized reflectance is known to saturate for optical thickness of about 3, one could think that they should be less sensitive to 3D effects than total reflectances. However, at high spatial resolution (80 m), values of polarized reflectances much higher than the ones predicted by the 1D theory can be reached. The study of the reflectances of a step cloud shows that these large values are the results of illumination and shadowing effects similar to those often observed on total reflectances. In addition, we show that for larger spatial resolution (10 km), the so-called plane-parallel bias leads to a non-negligible overestimation of the polarized reflectances of about 7–8%.     

Radiation symmetry test and uncertainty analysis of Monte Carlo method based on radiative exchange factor

Using Monte Carlo method, the paper investigates the radiative heat transfer in participating media. Based on the radiative exchange factor, an uncertainty analysis of Monte Carlo method is undertaken and the corresponding mathematical expressions are deduced to predict its accuracy. Furthermore, randomness properties of pseudorandom number generators are investigated, and a model to test radiation symmetry is adopted to validate the performance of some generators. The paper studies the effects of energy bundle numbers, discretization schemes, emission location, optical thicknesses, wall emissivity and CPU time on the numerical accuracy. In addition, the simulation results are proved to give a reference for using Monte Carlo method, which is applicable for calculation of the radiative exchange factor.     

Xe~(53+)离子与Xe原子碰撞过程中的辐射电子俘获和辐射退激发光谱的理论研究

基于多组态Dirac-Fock方法和密度矩阵理论,系统地研究了在197 Me V/u的碰撞能量下,Xe~(53+)离子与Xe原子的辐射电子俘获过程(REC)以及电子被俘获到激发态后辐射退激发产生的特征谱线.计算了炮弹Xe~(53+)离子俘获电子到不同壳层np_(1/2,3/2)(n=2—5)的总截面与相应的REC光子能量和角分布,以及由激发组态1snp_(1/2,3/2)(n=2—5)J_f=1向基态1s~2Jd=0辐射退激发的跃迁能量、跃迁概率和特征光子的角分布和线性极化度.计算结果表明,辐射光子具有显著的角各向异性特征.此外,1snp_(3/2)J_f=1→1s~2J_d=0退激发特征光子也显示出很强的线性极化和角各向异性特征,而1snp_(1/2)J_f=1→1s~2J_d=0退激发特征光子的线性极化度趋于零并且角分布也趋于各向同性.     

Prediction of radiative heat transfer in 3D complex geometries using the unstructured control volume finite element method

In this paper, a 3D algorithm for the treatment of radiative heat transfer in emitting, absorbing, and scattering media is developed. The numerical approach is based on the utilization of the unstructured control volume finite element method (CVFEM) which, to the knowledge of the authors, is applied for the first time to simulate radiative heat transfer in participated media confined in 3D complex geometries. This simulation makes simultaneously the use of the merits of both the finite element method and the control volume method. Unstructured 3D triangular element grids are employed in the spatial discretization and azimuthal discretization strategy is employed in the angular discretization. The general discretization equation is presented and solved by the conditioned conjugate gradient squared method (CCGS). In order to test the efficiency of the developed method, several 3D complex geometries including a hexahedral enclosure, a 3D equilateral triangular enclosure, a 3D L-shaped enclosure and 3D elliptical enclosure are examined. The results are compared with the exact solutions or published references and the accuracy obtained in each case is shown to be highly satisfactory. Moreover, this approach required a less CPU time and iterations compared with those of even parity formulation of the discrete ordinates method.     

The Monte Carlo atmospheric radiative transfer model McArtim: Introduction and validation of Jacobians and 3D features

A new Monte Carlo atmospheric radiative transfer model is presented which is designed to support the interpretation of UV/vis/near-IR spectroscopic measurements of scattered Sun light in the atmosphere. The integro differential equation describing the underlying transport process and its formal solution are discussed. A stochastic approach to solve the differential equation, the Monte Carlo method, is deduced and its application to the formal solution is demonstrated. It is shown how model photon trajectories of the resulting ray tracing algorithm are used to estimate functionals of the radiation field such as radiances, actinic fluxes and light path integrals. In addition, Jacobians of the former quantities with respect to optical parameters of the atmosphere are analyzed. Model output quantities are validated against measurements, by self-consistency tests and through inter comparisons with other radiative transfer models.     

Modeling of radiative heat transfer in 3D complex boiler with non-gray sooting media

The radiative heat transfer problem is solved for 3D complex industrial boiler with five baffles containing a mixture of carbon dioxide and water vapor for non-uniform temperature fields. A numerical formulation using the FTn finite volume method coupled with the bounded high-order resolution CLAM scheme, the blocked-off-region procedure and the narrow-band based weighted-sum-of-gray-gases (WSGG) [Kim OJ, Song T-H. Data base of WSGGM-based spectral model for radiation properties of combustion products, JQSRT 2000; 64: 379-94] model is adapted. The effect of soot volumetric fraction, particle temperature and uniform particle concentration on the radiative heat flux and radiative heat source is investigated and discussed. Also the advantages, in non-gray media, of the FTnFVM compared to the classical FVM are highlighted.     

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介绍了EAST偏滤器充气系统的改进措施,压电阀与冷屏一起安装在EAST颈管中,以缩短充气管道,将充气系统的延迟时间减少约200ms。冷屏起冷却阀门并屏蔽电磁场的作用。讨论了在准稳态条件下,延迟时间给偏滤器热流反馈控制带来的负面效应。在中性束加热条件下,通过在外靶板注入 Ar/D2(1：4)混合气体研究了靶板离子饱和流和热流分布的变化及充气对主等离子体的影响,得到了靶板离子饱和流显著降低、热流减少的结果。     

Modified finite-volume method based on a cell vertex scheme for the solution of radiative transfer problems in complex 3D geometries

A modified finite-volume method based on a cell vertex scheme was applied to solve radiative transfer problems within a participating medium of complex three-dimensional shaped domain. The computational spatial domain of interest was divided into four-node tetrahedron elements with unstructured meshes while the adopted formulation was combined with a closure relation based on an exponential scheme. The studied medium was assumed to be grey, non-scattering and was bounded by black surfaces. Our results were then compared with those found in other articles on the subject. The approach shows a very good level of performance for wall heat transfer evaluation. Accurate results were obtained on coarse computational meshes and solution errors were found to decrease with grid refinement.     

EAST辐射偏滤器充气系统改造及初步实验结果

介绍了EAST偏滤器充气系统的改进措施,压电阀与冷屏一起安装在EAST颈管中,以缩短充气管道,将充气系统的延迟时间减少约200ms。冷屏起冷却阀门并屏蔽电磁场的作用。讨论了在准稳态条件下,延迟时间给偏滤器热流反馈控制带来的负面效应。在中性束加热条件下,通过在外靶板注入Ar/D2(1:4)混合气体研究了靶板离子饱和流和热流分布的变化及充气对主等离子体的影响,得到了靶板离子饱和流显著降低、热流减少的结果。     

Radiative Lifetimes of Some 5d10n2F and 5d10n2P Levels of Hg+

Radiative lifetimes of 8p²P_3/1 (15.3 ns) and nf²F (7f²F_5/2 - 24.7 m. 7f²F_7/2 - 5.5 ns, 8f²F_7/2 - 48.5 ns, 8f²F_5/2 - 47.0 ns) levels of Hg⁺ have been measured employing delayed coincidence method. The dependencies of radiative lifetimes vs effective principal quantum number for np²P_3/2 and np²F_7/2 series are non linear.     

Modified finite volume method applied to radiative transfer in 2D complex geometries and graded index media

A modified finite volume method with unstructured triangular meshes is proposed to solve the RTE in 2D complex geometries and for graded index media. In such media, the RTE has an additional term corresponding to “angular redistribution”. This term is due to the change in the orientation of the direction of propagation for the radiation along curved optical paths. Some benchmark cases applied to a slab (1D) and a square cavity (2D) with linear and nonlinear refractive graded index are used to validate the new method. New results are presented for a disk with radial graded index.     

Ionization and single electron capture in collision of highly charged Ar16+ ions with helium

This paper uses the two-centre atomic orbital close-coupling method to study the ionization and the single electron capture in collision of highly charged Ar^16＋ ions with He atoms in the velocity range of 1.2-1.9 a.u.. The relative importance of single ionization （SI） to single capture （SC） is explored. The comparison between the calculation and experimental data shows that the SI/SC cross section ratios from this work are in good agreement with experimental data. The total single electron ionization cross sections and the total single electron capture cross sections are also given for this collision. The investigation of the partial electron capture cross section shows a general tendency of capture to larger n and l with increasing velocity from 1.2 to 1.9 a.u..     

A theoretical investigation of radiative effects and microphysical processes involved in the interaction of aerosol particulates in the atmosphere and validation of the theoretical results with the INDOEX observations

A theoretical approach, which is based on certain physical assumptions and quantum physical concepts, has been extended to investigate the radiative effects and the microphysical properties involved in the interaction of aerosol particulates in the atmosphere which may have important climatic effect. The theoretical findings are used to validate some of the observations of Indian Ocean Experiment (INDOEX) during its First Field Phase-98 (FFP-98) and Intense Field Phase-99 (IFP-99). The aerosol optical depth and the radiative forcing of the surface and the top of the atmosphere are computed and the results are found to have a good correspondence with the INDOEX results.     

用紧耦合方法研究C4+和O6+与He原子碰撞

用双中心原子轨道紧耦合方法计算了C4+-He以及O6+-He碰撞的单俘获总截面,入射离子的能量范围为10～100keV/amu,所得计算结果在实验误差范围内与实验值很好符合.对满壳层入射离子,研究了单俘获截面随入射离子电荷态的变化,并讨论了原子轨道展开波函数数目对计算结果的影响.p     

Discrete ordinate and Monte Carlo simulations for polarized radiative transfer in a coupled system consisting of two media with different refractive indices

We present an algorithm for polarized radiative transfer in a vertically stratified system consisting of two plane-parallel media with different refractive indices. It is based on the discrete ordinate method and includes multiple elastic scattering, thermal radiation, Fresnel reflection and transmission, incident parallel-beam or isotropic radiation at the top of the upper medium and bidirectional reflection at the bottom of the lower medium. Comparisons with results from Monte Carlo simulations show that the discrete-ordinate code provides accurate results for all four elements of the Stokes vector (I, Q, U, and V) at a speed that is orders of magnitude faster.     

Multiple ionization of argon accompanied by electron loss and capture of 0.22-6.35 MeV C^q＋ ions

In this paper a projectile ions recoil ions coincidence technique is employed to investigate the target ionization and projectile charge state changing processes in the collision of 0.22-6.35 MeV Cq^＋ （q = 1 - 4） ions with argon atoms. The partial cross section ratios of the double, triple, quadruplicate ionization to the single ionization （or the single capture） of argon associated with single electron loss （or single electron capture） by the projectile are measured and compared with the previous experimental results. In the present experiment, it is observed that the ratios of ionization cross sections R associated with single loss and single capture depend strongly on the projectile charge state and vary significantly with different reaction channels as impact energy increases. In addition, this paper gets empirical scaling laws for the ionization cross section ratios R corresponding to the projectile single loss and finds that the ratios of the double ionization to the single ionization associated with single electron capture remain constant in the present energy range.     

ZBLAN玻璃中Pr3+掺杂离子3P0和1D2能级的发光特性和寿命

对ZBLAN氟锆酸盐玻璃中Pr³⁺掺杂离子³P₀和¹D₂能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10^-3,5×10^-3)的Pr³⁺:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了³P₀和¹D₂能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10^-3样品的荧光发射强度明显大于5×10^-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对³P₀和¹D₂ 的能级寿命值无显著影响。掺杂浓度为1×10^-3时,Pr³⁺离子³P₀和¹D₂能级的寿命值分别为46,322μ_s。     

Combining the independent pixel and point-spread function approaches to simulate the actinic radiation field in moderately inhomogeneous 3D cloudy media

A fast method is presented for gaining 3D actinic flux density fields, F_act, in clouds employing the Independent Pixel Approximation (IPA) with a parameterized horizontal photon transport to imitate radiative smoothing effects. For 3D clouds the IPA is an efficient method to simulate radiative transfer, but it suffers from the neglect of horizontal photon fluxes leading to significant errors (up to locally 30% in the present study). Consequently, the resulting actinic flux density fields exhibit an unrealistically rough and rugged structure. In this study, the radiative smoothing is approximated by applying a physically based smoothing algorithm to the calculated IPA actinic flux field.