Understanding high-density matter through analysis of surface spectral lines and burst oscillations from accreting neutron stars

We discuss millisecond period brightness oscillations and surface atomic spectral lines observed during type I X-ray bursts from a neutron star in a low mass X-ray binary system. We show that modeling of these phenomena can constrain models of the dense cold matter at the cores of neutron stars. We demonstrate that, even for a broad and asymmetric spectral line, the stellar radius-to-mass ratio can be inferred to better than 5%. We also fit our theoretical models to the burst oscillation data of the low mass X-ray binary XTE J1814-338, and find that the 90% confidence lower limit of the neutron star’s dimensionless radius-to-mass ratio is 4.2.     

基于SVR多学科设计优化代理模型技术研究

为挖掘设计潜力,提高飞机设计质量,通过代理模型方法研究了多学科设计优化(MDO)。基于径向基函数模型,研究了一种新的代理模型技术--支持向量回归方法(SVR)。通过数值算例和某通用航空飞机多学科设计优化应用算例对支持向量回归方法的有效性进行了验证。研究结果表明,支持向量回归是一种比较有效的代理模型方法,在飞机多学科设计优化的理论研究和工程实践方面具有重要的参考意义。     

固体火箭发动机燃烧室结构径向振动与内弹道性能的耦合计算

研究了由推进剂药柱和壳体组成的燃烧室结构径向振动对发动机内弹道性能的影响。在一维非定常内弹道方程中,分别考虑了结构径向振动对内弹道方程和燃速的影响,研究了在给定燃烧截面内,由于燃烧室压强变化引起的结构径向振动。据弹性力学理论和振动机理,得到了简化的等效径向振动方程;对内弹道和结构径向振动进行了耦合计算,分析表明当内弹道出现周期性的压强振荡时,会引发与结构径向振动之间的耦合作用,使得燃烧室压强振荡振幅上升一个量级,对发动机的工作安全产生危害。     

涡轮叶片径向槽轴向长度对超紧凑燃烧室

为探究涡轮叶片径向槽轴向长度对超紧凑燃烧室性能的影响,对3种不同轴向长度的径向槽分别在2种当量比条件下,用FLUENT软件对超紧凑燃烧室内流动及燃烧进行了数值模拟。结果表明：随着径向槽轴向长度的减小,燃烧环内未完全燃烧的微小燃油颗粒和燃气沿着槽的径向迁移量也减少,从而使燃油颗粒和燃油蒸气在燃烧环内的驻留时间增加;当叶片径向槽的轴向长度与燃烧环轴向长度之比等于0.75且燃烧环当量比为0.81时,燃烧室的燃烧性能较好。这对超紧凑燃烧室的优化设计有重要的参考价值。     

Collisional profiles of ionized calcium perturbed by helium

The spectra of many cool DZ white dwarfs show extremely broad resonance lines of ionized calcium and magnesium in the optical and ultraviolet region. When the line center is strongly saturated, these wings may become a significant source of additional opacity in cool white dwarf atmospheres. The omission of this opacity results in systematic errors in the predicted flux distribution and hence in the effective temperatures and element abundances. In a continuation of Homeier et al. (2007) and Allard et al. (2012), where we presented absorption spectra of Na–He in cool white dwarfs, we extend this work to the Ca⁺–He system.     

LiHe spectra from brown dwarfs to helium clusters

The detection of Li I lines is the most decisive spectral indicator of substellarity for young brown dwarfs with masses below about 0.06 solar mass. Due to the weakness of the Li resonance lines, it is important to be able to model precisely both their core widths and their wing profiles. This allows an adequate prediction of the mass at which Li lines reappear in the spectra of brown dwarfs for a given age, or reversely an accurate determination of the age of a cluster. We report improved line profiles and the dependence of line width on temperature suitable for modeling substellar atmospheres that were determined from new LiHe molecular potential energies. Over a limited range of density and temperature, comparison with laboratory measurements was used to validate the potential energies which support the spectral line profile theory.     

Stark broadening data for spectral lines of rare-earth elements: Nb III

The electron-impact widths for 15 doubly charged Nb ion lines have been theoretically determined by using the modified semiempirical method. Using the obtained results, we considered the influence of the electron-impact mechanism on line shapes in spectra of chemically peculiar stars and white dwarfs.     

一种磁悬浮飞轮用新型永磁偏置径向磁轴承

为了克服现有永磁偏置径向混合磁轴承的缺陷,提出了一种磁悬浮飞轮用新型永磁偏置径向混合磁轴承,分析了其工作原理,并分别利用等效磁路法及有限元方法对该永磁偏置径向混合磁轴承进行了电磁分析.分析结果表明:所提出的新型永磁偏置径向混合磁轴承采用永磁磁场作为偏置磁场,并且其永磁磁路与电励磁磁路在任一径向截面中共面,可使磁轴承轴向长度大为减小,与现有永磁偏置径向混合磁轴承相比具有体积更小的优点,同时该种永磁偏置径向混合磁轴承产生的偏置磁场在X,Y方向上不会产生耦合,可使控制更加容易,特别适用于高速、低功耗等场合.      

Constraints on Coronal Outflow Velocities Derived from UVCS Doppler Dimming Measurements and in-Situ Charge State Data

We constrain coronal outflow velocity solutions, resolved along the line-of-sight, by using Doppler dimming models of H I Lyman alpha and O VI 1032/1037 Å emissivities obtained with data from the Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO. The local emissivities, from heliocentric heights of 1.5 to 3.0 solar radii, were determined from 3-D reconstructions of line-of-sight intensities obtained during the first Whole Sun Month Campaign (10 August to 8 September 1996). The models use electron densities derived from polarized brightness measurements made with the visible light coronagraphs on UVCS and LASCO, supplemented with data from Mark III at NCAR/MLSO. Electron temperature profiles are derived from 'freezing-in' temperatures obtained from an analysis of charge state data from SWICS/Ulysses. The work concentrates on neutral hydrogen outflow velocities which depend on modeling the absolute coronal H I Lyα emissivities. We use an iterative method to determine the neutral hydrogen outflow velocity with consistent values for the electron temperatures derived from a freezing-in model.     

两种高精度高效率静气弹数据传递函数

遵循静气弹问题中气动/结构网格之间的数据传递要求,引入了基于径向基函数的流固耦合界面数据传递方法,确定了紧支半径的选取原则,并编制相应的计算程序。以M6机翼为例,将不同径向基函数的插值精度及计算效率进行比较,结果表明体样条（Volume Spline）函数和C2函数具有良好的插值精度和计算效率。这两种流固耦合界面数据传递方法非常适用于工程应用。