中国南京地区L波段电离层闪烁初步统计分析

利用南京地区2008年11月至2009年10月电离层闪烁监测数据, 统计分析了该地区一年间L波段电离层幅度闪烁发生率的逐日变化、逐月变化、地方时变化和空间分布等特征. 统计结果表明, 在此期间, 南京地区L波段电离层幅度闪烁活动比较平静, 主要以0.14<0.2的闪烁为主, S₄>0.2的闪烁很少发生.不同强度幅度闪烁表现出一致的时间变化和空间分布特征, 2008年11月为最小,2009年6月、8至10月闪烁发生率都有明显的增强, 在10月达到最大, 在8月和10月的S₄>0.2的闪烁主要出现于正午到日落前这段时间; 对于闪烁的空间分布, 单站一年数据统计显示, 测站北向闪烁的发生频率高于南向, 但该统计结果需要更多的数据样本进行进一步的验证.      

On developing data-driven turbulence model for DG solution of RANS

High-order Discontinuous Galerkin(DG) methods have been receiving more and more attentions in the area of Computational Fluid Dynamics(CFD) because of their high-accuracy property. However, it is still a challenge to obtain converged solution rapidly when solving the Reynolds Averaged Navier–Stokes(RANS) equations since the turbulence models significantly increase the nonlinearity of discretization system. The overall goal of this research is to develop an Artificial Neural Networks(ANNs) model with low complexity acting as an algebraic turbulence model to estimate the turbulence eddy viscosity for RANS. The ANN turbulence model is off-line trained using the training data generated by the widely used Spalart–Allmaras(SA) turbulence model before the Optimal Brain Surgeon(OBS) is employed to determine the relevancy of input features.Using the selected relevant features, a fully connected ANN model is constructed. The performance of the developed ANN model is numerically tested in the framework of DG for RANS, where the‘‘DG+ANN" method provides robust and steady convergence compared to the ‘‘DG+SA" method. The results demonstrate the promising potential to develop a general turbulence model based on artificial intelligence in the future given the training data covering a large rang of flow conditions.     

Analysis and control of inter-electrode gap during leveling process in counter-rotating electrochemical machining

The inter-electrode gap (IEG) is an essential parameter for the anode shaping process in electrochemical machining (ECM) and directly affects the machining accuracy. In this paper, the IEG during the leveling process of an oval anode workpiece in counter-rotating ECM (CRECM) is investigated. The variation of the minimum IEG is analyzed theoretically, and the results indicate that rather than reaching equilibrium, the minimum IEG in CRECM expands constantly when a constant feed speed is used for the cathode tool. This IEG expansion leads to a poor localization effect and has an adverse influence on the roundness of the machined workpiece. To maintain a small constant IEG in CRECM, a variable feed speed is used for the cathode based on a fitted equation. The theoretical results show that the minimum IEG can be controlled at a small value by using an accelerated feed speed. Experiments have been conducted using a specific experimental apparatus in which the cathode tool is designed as a combined structure of two sectors and a thin sheet. By detecting the machining currents flowing through the minimum IEG, how the latter varies is obtained indirectly. The results indicate that using an accelerated feed speed is effective for controlling the IEG, thereby improving the roundness of the machined workpiece.     

加大改革力度,建立有效机制,为把南航建设成第一流科技大学而奋斗

 今年10月20日是南京航空学院建校40周年纪念日。40年来南航已培养了三万多名高级科技人才,完成了千余项重要科研成果,研制成功无人驾驶飞机、直升机及轻型飞机,为国防现代化及经济建设作出了重大贡献。学院现有6000余名学生,3000余名教职工。有15个系、部,29个专业,22个硕士点,10个博士点,3个国家重点学科,3个博士后流动站;已形成了既是教育中心,又是科研中心的完整体系。今后南航将进一步解放思想,强化竞争意识,主动适应经济建设和社会发展的需要,建立人才培养、科学研究和产业开发的新机制,在教育的数量、质量、结构、效益等方面再上一个新台阶,把南航建设成为一所具有航空航天特色、在国内外有广泛影响的第一流的全国重点科技大学。     

Space law education in China: Status quo,shortcomings and possible ways out

Space law education has an essential role in the space capacity building of a country because of its importance for human resources development in space law. Comparisons between Canada and China, the European Union and China and the United States of America (USA) and China in space law degree education, course, teaching methodology, institute and practice and communication platform are provided in an attempt to review some issues which exist within the Chinese space law educational system and to seek a better choice for China’s space law education reform. Chinese space law education has achieved noticeable progress over the past two decades. However, it is still limited in comparison to its counterparts in Europe and Northern America. The range of the space law degree education programmes and space-law-related courses is comparatively limited. A gap remains between space law education and practice in China. Chinese space law classes are still dominated by the teacher-centred teaching methodology, although several universities have some new teaching practices. The establishment of seven space law-related research institutes plays an increasingly important role in Chinese space law education, space law and policy research and legal advisory services for the Chinese government and non-governmental sectors. However, these institutes still have a long way to go in comparison with their counterparts in Europe and Northern America. While China has established domestic research platforms for space law communication through international cooperation, it does not provide space law practice platforms for space law education. While international space law does not provide a direct legal foundation for space law education in China, Chinese educational laws can lay a profound legal foundation for Chinese space law education. To promote its national expertise and capacity in space law, based on the three-pillar model and the experiences of its counterparts in North America and Europe, China should adopt a systematic and sustainable regime for its space law education.