Space debris cumulative flux considering the Interval Distance-based method

The availability of engineering models to estimate the risk from space debris is essential for space missions. According to current research, cumulative flux calculation is mostly carried out based on the equal-width interval discretization. The method discretizes the volume around the Earth into cells defined in earth centered inertial coordinates. The resulting debris flux onto a target object is shown to depend on the chosen size of the cells. To avoid a discretization error, this must be accounted for. In order to present reliable flux predictions for space mission, the algorithm improvement is an ongoing topic for the related research field. The aim of this study was to examine the discretization error during the cumulative flux determination process. Both the effect of interval step length and the orbital boundary are under investigation. Several typical orbits are selected as examples here and the 2018/01/03 TLE (Two Line Element) data published by the US Space Surveillance Network is used as the debris background in this paper. Furthermore, the Interval Distance-Based method for Discretization (IDD) is adopted in this paper. A position-centered flux determination method is introduced based on the IDD method. According to the example analysis, the IDD used in the flux calculation process provides results which are less affected by the interval step-size setup; and the orbital boundary has no effect on the calculation process. In other words, the discretization error is significantly reduced. The position-centered method provided a possible suggestion for the improvement of space debris environment models.     

从分子生物学思路理解中医治疗癌症思想

癌症是组织细胞受到外界物理的、化学的、生物的、心理性的、长时间多重刺激而引起细胞多种基因突变 ,使得细胞信息调节和控制系统紊乱 ,机体免疫功能失调 ,而导致细胞自主性增殖的病变。中医通过调整脏腑阴阳平衡及气血津液失调状态 ,对细胞组织产生长期的、多重的良性刺激 ,让突变基因逆转 ,使癌细胞逆转为正常细胞 ,并进行正常分化、凋亡 ,最终使癌组织退行 ,消失     

Simple and robust h-adaptive shock-capturing method for flux reconstruction framework

In this paper, a simple and robust shock-capturing method is developed for the Flux Reconstruction(FR) framework by combining the Adaptive Mesh Refinement(AMR) technique with the positivity-preserving property. The adaptive technique avoids the use of redundant meshes in smooth regions, while the positivity-preserving property makes the solver capable of providing numerical solutions with physical meaning. The compatibility of these two significant features relies on a novel limiter designed for...     

紫外辐照影响硅橡胶出气污染模型及效应研究

基于有机材料出气污染过程分析,并结合辐射化学有关理论,建立材料在紫外辐照后的分子污染模型;在ASTM E1559标准测试方法的基础上,以硅橡胶材料为污染源开展试验,测试其经过不同紫外辐照时间后的出气污染沉积量,并对辐照后材料表面的微观特性进行测试分析。根据沉积量测试结果对模型待定参数进行拟合,并结合微观测试结果,分析得到紫外辐照导致硅橡胶分子链中Si-O键以及Si-C键断裂,且部分小分子物质提前挥发,从而使得出气成分中小分子污染物含量下降,大分子污染物含量上升,并最终导致总污染量在前期有所下降,在后期显著增加。     

N2O4在氟醚橡胶中扩散和吸附行为的分子动力学模拟

利用全原子分子动力学与巨正则蒙特卡洛模拟方法,研究不同四氧化二氮(N_2O_4)含量、温度和压力对N_2O_4在氟醚橡胶中扩散和吸附行为的影响。结果表明,随着N_2O_4含量增加,体系自由体积越大,因而增加了N_2O_4的扩散速率。当体系压力增大时,体系自由体积逐渐变小,N_2O_4扩散速率减小。此外,温度的上升既提高了自由体积又增大了原子的运动速度,因此提高了N_2O_4的扩散速率,并表现出阿伦尼乌斯关系。进一步地,N_2O_4在氟醚橡胶中的溶解度系数随着温度的上升迅速下降。所以,N_2O_4在氟醚橡胶中的渗透系数随着温度的上升先微弱上升然后迅速下降。     

中性聚合物键合剂的分子设计和合成

中性聚合物键合剂（ＮＰＢＡ）是美国ＫｉｍＣＳ发明的一种新助剂，它显著提高了ＮＥＰＥ推进剂的力学性能，根据有关专利和论文。介绍了降温相分离沉积包覆的原理，归纳了ＮＰＢＡ的分子设计方法和合成条件，而且举例进行了说明。     

NC/NG共混体系的塑化行为

为了解硝化纤维素(NC)/硝化甘油(NG)塑化行为的实质,用动态流变学方法和红外光谱法对其塑化行为的宏观性质表现进行测量,并在此基础上通过分子动力学模拟揭示NC在塑化过程中的微观结构变化.结果表明,NC/NG共混体系的储能模量(G′)和损耗模量(G＂)随塑化时间逐渐增大,且G′逐渐接近并超过G”,二者最终趋于稳定,此过程中体系的某些与氢键有关的红外特征频率向低波数移动.分子动力学模拟表明,在NC/NG共混体系塑化过程中,NG分子的空间位阻作用使NC分子链自由体积增加;另一方面NG分子与NC分子形成的氢键替代了NC分子内氢键,使NC分子链内部作用力减弱,回转半径增大.     

Validation of a novel mixing-plane method for multistage turbomachinery steady flow analysis

The steady calculation based on the mixing-plane method is still the most widely-used three-dimensional flow analysis tool for multistage turbomachines. For modern turbomachines, the trend of design is to reach higher aerodynamic loading but with still further compact size. In such a case, the traditional mixing-plane method has to be revised to give a more physically mean-ingful prediction. In this paper, a novel mixing-plane method was proposed, and three representa-tive test cases including a transonic compressor, a highly-loaded centrifugal compressor and a high-pressure axial turbine were performed for validation purpose. This novel mixing-plane method can satisfy the flux conservation perfectly. Reverse flow across the mixing-plane interface can be resolved naturally, thus making this method numerically robust. Artificial reflection at the mixing-plane interface is almost eliminated, and then its detrimental impact on the flow field is min-imized. Generally, this mixing-plane method is suitable to simulate steady flows in highly-loaded multistage turbomachines.     

Coronal Hole Oscillations as inferred from SDO/AIA data

With high temporal resolution (12 s) of about two hours duration, data of a coronal hole structure in 171 Å$\AA$, 193 Å$\AA$ and 211 Å$\AA$ taken from SDO/AIA images is considered for examination of oscillations. After estimating the total DN counts of a whole coronal hole structure in three wavelength bands, the resulting time series are subjected to FFT and wavelet analysis. Significant periods in all the three wavelength bands are detected that are mainly concentrated around 500 s as a fundamental mode and its odd (167, 100, 71, 56, 46, 39, 33, 29, 26, 24 s) harmonics. Computed phases in all the three wavelengths band are estimated to be constant.