爆炸解体空间碎片的空间密度分布

利用NASA爆炸解体模型研究了由爆炸解体而产生的空间碎片的分布情况,并通过对大种群空间碎片进行快速轨道演化,获得了所有历史上爆炸解体而产生的空间碎片在当前时刻的分布情况,为建立空间碎片环境工程模型提供了一部分参考数据。文中对后续的研究工作具有一定的参考价值。     

非均匀磁化等离子体层的电磁特性分析

基于分层传播原理提出了一种计算电磁波在非均匀磁化等离子体层中反射率和吸收率的模型,并数值分析了等离子体密度与碰撞频率,以及背景磁场强度对电磁波的反射和吸收特性的影响.研究表明:该法所得结果与文献的传播矩阵(SMM)法一致.数值分析发现:低密度高碰撞频率等离子体可减少等离子体层对入射波的功率反射;高密度高碰撞频率等离子体可改善其对入射波的功率反射宽频带吸收特性;背景磁场强度可明显改变等离子共振吸收频段.     

基于学习的并行免疫量子进化算法

提出了基于学习的多宇宙并行免疫量子进化算法,算法中将种群分成若干个独立的子群体,称为宇宙。并给出了多宇宙的并行拓扑结构,其中各宇宙独立演化．宇宙内采用免疫量子进化算法,宇宙间采用基于学习机制的移民、模拟量子纠缠的种群交叉等信息交互方式．使得进化算法具有更好的种群多样性,更快的收敛速度和全局寻优能力。仿真实验结果表明该算法比串行的免疫量子进化算法运算效率更高。     

Observations of the atmospheres and winds of O-stars,LBVs and Wolf-Rayet stars

This review summarises recent studies of O-stars, Luminous Blue Variables (LBVs) and Wolf-Rayet (WR) stars, emphasising observations and analyses of their atmospheres and stellar winds yielding determinations of their physical and chemical properties. Studies of these stellar groups provide important tests of both stellar wind theory and stellar evolution models incorporating mass-loss effects. Quantitative analyses of O-star spectra reveal enhanced helium abundances in Of and many luminous O-supergiants, together with CNO anomalies in OBN and Ofpe/WN9 stars, indicative of evolved objects. Enhanced helium, and CNO-cycle products are observed in several LBVs, implying a highly evolved status, whilst for the WR stars there is strong evidence for the exposition of CNO-cycle products in WN stars, and helium-burning products in WC and WO stars. The observed wind properties and mass-loss rates derived for O-stars show, in general terms, good agreement with predictions from the latest radiation-driven wind models, although some discrepancies are apparent. Several LBVs show similar mass-loss rates at maximum and minimum states, contrary to previous expectations, with the mechanism responsible for the variability and outbursts remaining unclear. WR stars exhibit the most extreme levels of mass-loss and stellar wind momenta. Whilst alternative mass-loss mechanisms have been proposed, recent calculations indicate that radiation pressure alone may be sufficient, given the strong ionization stratification present in their winds.     

The massive star distribution in the Galaxy and the Magellanic Clouds

The numbers and distribution of Population I O-type stars and Wolf-Rayet stars are reviewed. The numbers of known WR stars in the Galaxy, the LMC and the SMC are 185, 114, and 9, respectively. Distances and galactic distributions determined by various authors are compared. The single star and binary distributions are discussed in the light of evolutionary studies.     

A spectroscopic analysis of B stars in the SMC cluster NGC 330

Medium resolution (2A/px) but high s/n spectra of approximately twenty of the brightest blue stars in the young open cluster NGC 330 in the SMC have been analyzed in order to determine their atmospheric parameters and the evolutionary status. Stellar parameters are determined by comparison with LTE and NLTE model atmosphere calculations and an HR diagram constructed. Luminosities of the sample stars lie in the range 4.0L _*/L )<5.0 and spectral types between O9 and late-B. The stars in our sample appear to define 4 groups: main-sequence B-stars (B2-B4), B-supergiants (B4) in a blue-loop phase of evolution, a small number of blue stragglers (O9-B0 near main-sequence stars) and a group of luminous giants (B1-B2) which reside in the so-called post main-sequence gap of the HR diagram. Furthermore, we have confirmed spectroscopically the very high incidence of Be stars in this cluster. Finally the almost complete absence of metal lines (at this resolution) is in keeping with the expected very low metallicity of the SMC.     

基于适当控制翼型演化历程的气动设计方法

本文提出一种翼型设计的新方法,它基于适当控制翼型演化历程,采用求解非定常流动控制方程的方法,实现了翼型反问题的高效求解.同时在笛卡尔坐标系中应用Level-Set函数,避免了贴体动网格的采用,从而大大减少了所需计算工作量.     

Water in Space: The Water World of ISO

In this review we present the main results obtained by the ISO satellite on the abundance and spatial distribution of water vapor in the direction of molecular clouds, evolved stars, galaxies, and in the bodies of our Solar System. We also discuss the modeling of H₂O and the difficulties found in the interpretation of the data, the need of collisional rates and the perspectives that future high angular and high spectral resolution observations of H₂O with the Herschel Space Observatory will open.     

Gamma-rays from Active Galactic Nuclei: Emission processes and particle acceleration

It is argued that the high-energy X-ray and -ray emission from flaring blazars is beamed radiation from the relativistic jet supporting the relativistic beaming hypothesis and the unified scenario for AGNs. Most probably the high-energy emission results from inverse Compton scattering by relativistic electrons and positrons in the jet of radiation originating external to the jet plus pair annihilation radiation from the jet. Future positive TeV detections of EGRET AGN sources will be decisive to identify the prominent target photon radiation field. Direct -ray production by energetic hadrons is not important for the flaring phase in -ray blazars, but the acceleration of energetic hadrons during the quiescent phase of AGNs is decisive as the source of secondary electrons and positrons through photo-pair and photo-pion production. Injection of ultrahigh energy secondary electrons and positrons into a stochastic quasilinear acceleration scheme during the quiescent AGN phase leads to cooling electron-positron distribution functions with a strong cut-off at low but relativistic energy that under certain local conditions may trigger a plasma instability that gives rise to an explosive event and the flaring -ray phase.