两个距离特征相结合的3D模型检索技术

基于内容的3D模型检索是多媒体信息检索的热点研究问题之一。针对单个距离特征在描述三维模型形状上存在的不足，提出了两个不同的距离特征相结合的3D模型检索技术。实验表明，检索技术具有较好的检索效果，且明显优于采用单个距离特征的检索技术。     

基于改进的HD距离的星图识别算法

在基于星敏感器的航天飞行器的自主天文导航中,星图识别是关键技术之一。将改进的HD距离算法用于星图识别,避免了由于个别星体出现较大噪声,以及流星等干扰星出现时发生误匹配的问题。在匹配时利用了星图的全部空间结构信息,具有强的抗星敏感器畸变、噪声和旋转能力,同时也不需要复杂的特征提取算法。仿真实验显示它具有较高的实用价值。     

Theoretical light curves of Type II-P supernovae and applications to cosmology

Based on an extensive grid of stellar models between 13 and  25 M_⊙  and a wide range of metallicities, we have studied the light curves of core collapse supernovae, their application to cosmology and their evolutionary effects with redshift. The direct link between the hydrodynamics and radiation transport allows us to calculate monochromatic light curves.
With decreasing metallicity, Z , and increasing mass, progenitors tend to explode as compact blue supergiants (BSG) and produce subluminous supernovae that are approximately 1.5 mag dimmer than normal Type II supernovae (SNe II) with red supergiant (RSG) progenitors. Progenitors with small masses tend to explode as RSGs even at low Z . The consequence for testing the chemical evolution is obvious, namely a strong bias when using the statistics of core collapse supernovae to determine the history of star formation.
Our study is limited in scope with respect to the explosion energies and the production of radioactive Ni. Within the class of extreme SNe II-P supernovae, the light curves are rather insensitive with respect to the progenitor mass and explosion energy compared with analytic models based on parametrized stellar structures. We expect a wider range of brightness due to variations in ⁵⁶Ni because radioactive energy is a significant source of luminosity. However, the overall insensitivity of light curves may allow their use as quasi-standard candles for distance determination.     

Modeling and distance determination of planetary nebulae

The monthly probability of occurrence of southward (B _z ^– ) component of IMF estimated independent of the sector polarity observed near earth is found to change with the magnitude of solar wind velocity. The above analysis is done for each month during two years around sunspot minima and maxima in cycle 21. The results will be interpreted in terms of association of southwardB _z events with solar wind flows of distinct solar origin such as low and high speed solar wind.     

Power spectrum shape from peculiar velocity data

We constrain the velocity power spectrum shape parameter Γ in linear theory using the nine bulk flow and shear moments estimated from four recent peculiar velocity surveys. For each survey, a likelihood function for Γ was found after marginalizing over the power spectrum amplitude  σ₈Ω^0.6_m  using constraints obtained from comparisons between redshift surveys and peculiar velocity data. In order to maximize the accuracy of our analyses, the velocity noise σ_* was estimated directly for each survey. A statistical analysis of the differences between the values of the moments estimated from different surveys showed consistency with theoretical predictions, suggesting that all the surveys investigated reflect the same large-scale flows. The peculiar velocity surveys were combined into a composite survey yielding the constraint  Γ= 0.13^+0.09_−0.05  . This value is lower than, but consistent with, values obtained using redshift surveys and cosmic microwave background data.