薄膜和半无限大介质间的近场辐射换热研究

研究了硼掺杂硅(记为Si-19)薄膜和半无限大物体(Si-19和SiC)在100 nm真空间距下的近场辐射换热随薄膜厚度的变化。研究结果表明,当半无限大物体和薄膜为相同的Si-19材料时,由于表面波激发并相互耦合,使得近场辐射换热随薄膜的厚度变化比较复杂。当半无限大物体为SiC材料时,由于表面波的耦合遭到破坏以及辐射体的高发射率频率区和吸收体的高吸收率频率区不匹配,导致表面波的激发对不同材料间的近场辐射换热的增强程度降低,因此在相同计算区域内热流密度随厚度的增加单调增加,没有出现极值点。     

降雨对C波段散射计测风的影响及其校正

传统观点认为C波段散射计工作波长大于雨滴直径,受降雨散射衰减的影响很小, 因此往往忽略降雨对C波段散射计测风的影响.本文基于降雨引起C波段散射计信号的衰减、 后向体散射及雨滴落入海面后的扰动作用,推导了降雨条件下的雷达方程, 构建了2010年全年的ASCAT散射计、降雨雷达和欧洲中期天气预报中心数值预报的匹配数据集, 定量分析了降雨对C波段散射计测风的影响,发现其信号衰减随降雨强度和入射角的增大而增强; 后向体散射和雨表面扰动作用随降雨强度的增大而增强、随入射角的增大而减小, 其中雨表面扰动作用对散射计测风的影响大于后向体散射.另外, 利用降雨条件下的雷达方程和匹配数据集,本文建立了降雨条件下的C波段主动微波辐射传输模型, 实验表明,该模型能够改善降雨条件下C波段散射计测风的精度.     

The radiative transfer equation with a nonhomogeneous reflectivity boundary condition coupled with the heat conduction equation

In this paper, we make a rigorous mathematical analysis of the radiative heating of a semitransparent body made of a glass by a black radiative source surrounding it. This requires the study of the coupling between quasi‐steady radiative‐transfer boundary value problems with nonhomogeneous reflectivity boundary conditions (one for each wavelength band in the semitransparent electromagnetic spectrum of the glass) and a nonlinear heat‐conduction evolution equation with a nonlinear Robin boundary condition, which takes into account those wavelengths for which the glass behaves like an opaque body. We prove existence and uniqueness of the solution and give also uniform bounds on the solution, ie, on the absolute temperature distribution inside the body and on the radiative intensities.     

基态介子辐射衰变中的屏蔽效应

利用屏蔽位对基态介子辐射衰变宽度进行了计算．通过与线性位的结果相比较，得到了屏蔽位结果的一些特点．     

光子穿透系数及同质异能态俘获截面的研究

合理地给出了复合核反应光子穿透系数及同质异能态俘获截面的计算公式,其中包括统计和非统计过程.通过求解级联γ退激过程计算光子穿透系数,既合理地扣除(n,γn)过程,又包括首次γ跃迁至中子分离能B_n以上能级的贡献.以4MeV以下中子和⁵⁹Co及¹⁰³Rh的反应为例,比较用不同方法计算的光子穿透系数,计算同质异能态俘获截面并和实验数据进行比较,最后对结果进行了分析和讨论.     

Temperature response in participating media with anisotropic scattering caused by pulsed lasers

It is not by isotropic scattering but by anisotropic scattering that radiant energy is redistributed in some materials containing real particles, fibers, or impurities. In some instances, great difference can be caused in transient thermal behavior between isotropic scattering and anisotropic scattering media. Ray tracing method combined with Hottel's zonal method is introduced to deduce thermal radiative source term for various optical boundary conditions induced by collimated incidence passing through translucent boundary. Temperature response caused by laser pulse at non-incident side of participating and anisotropic scattering media is examined. We investigate effects of scattering albedo, scattering phase function, initial temperature of media and thickness of media on temperature response. Results obtained for anisotropic scattering media are compared with those for isotropic scattering one and show that anisotropic scattering must be considered in the simulating measurement of thermophysical properties by the laser flash method for some materials with big scattering albedo which behave anisotropically, or big error will be introduced; forward scattering can increase excess temperature and backward scattering can decrease it at non-incident side of the considered sample irradiated by laser pulse.     

Blue Sky and Hot Piles: The Evolution of Radiative Transfer Theory from Atmospheres to Nuclear Reactors

Radiative transfer theory has mirrored many of the trends in the development of applied mathematics during the past century. It began with the development of the phenomenological equation of transfer at the start of the century, designed to treat the passage of light through foggy opaque atmospheres. By the mid-1940s, the theory provided detailed modeling of stellar and planetary atmospheres and subsequently transformed into the remote sensing problem of remote diagnoses of physical conditions and abundances in such environments. During the late 1940s, the need to treat neutron transfer in complex geometries led to an interest in applying these methods to nuclear reactors, using methods of invariant imbedding. Monte Carlo simulations, and integral equations, all areas of continuing study. The formative period, mainly analytic in thrust, ended by the mid-1960s with the comprehensive treatises by Chandrasekhar, Ambartsumian, Kourganoff, Busbridge, Sobolev, and Davison and the 11th AMS Applied Mathematics Symposium on nuclear reactors. Invariant imbedding and doubling methods have been widely developed for scattering problems, mainly in planetary atmospheres and nebular transfer, while improvements in computational methods over the past 30 years have introduced advances in multidimensional, multigroup transfer codes for neutron physics (Boltzmann equation solvers), neutrinos, and significant advances in radiative transfer and the growth of the field of radiation hydrodynamics. © 2002 Elsevier Science (USA).Die Theorie des Strahlungstransport reflektiert viele der Strömungen der angewandten Mathematik des letzten Jahrhunderts wieder. Es begann am Anfang des 20sten Jahrhunderts mit der Entwicklung der phänomenologischen Transportgleichung, die darauf abzielte den Durchgang von Licht duch eine nebelig undurchlässige Atmosphäre zu beschreiben. Mitte der 1940er Jahre erlaubte die Theorie detailliertes modellieren sowohl von Sternatmosphären als auch von planetaren Atmosphären, und entwickelte sich in der Folge in ein diagnostisches Werkzeug das es ermöglichte physikalische Bedingungen und Elementeverteilungen in solchen Situationen zu analysieren. Gegen Ende der 1940er erweckte die Notwendigkeit Neutronentransport in komplizierten Geometrien zu behandeln Interesse an der Anwendung dieser Methoden in Kernreaktoren, insbesondere mittels der Techniken der invarianten Einbettung. Monte Carlo Simulationen und Integralgleichungen, allesamt Gebiete denen fortwährende Aufmerksamkeit gewidmet wurde. Die formgebende Periode, die hauptsächlich analytischer Natur war, ging Mitte der 1960er zu Ende, einerseits mit den umfassenden Monographien von Chandrasekar, Ambartsumian, Kourganoff, Busbridge, Sobolev, und Davison, und andererseits mit dem 11ten AMS Symposium über Angewandte Mathematik im Kontext von Kernreaktoren. Sowohl Methoden der invarianten Einbettung als auch Verdopplungsmethoden wurden weiter entwickelt, insbesondere für Streuprobleme hauptsächlich in Planetenatmosphären und Transport in Nebeln, während Verbesserungen in numerischen Methoden in den letzten 30 Jahren nicht nur zu Fortschritten in höherdimensionalen, multigruppen Transportprogrammen für Neutronenphysik (Boltzmann Gleichung) und Neutrinos geführt haben, sondern auch zu entscheidendem Fortschritt beim Strahlungstransportproblem und zur Entwicklung des Feldes der Strahlungshydrodynamik. © 2002 Elsevier Science (USA).MSC 1991 subject classifications: 01A60; 80A20; 85-03; 85A25.     

碲酸盐玻璃中稀土离子发光寿命的研究

掺稀土碲酸盐玻璃是宽带光纤放大器的一种非常重要的材料,具有传送区域宽、玻璃稳定性好等特点.讨论了在980 nm     

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.