容积卡尔曼滤波在空间目标轨道确定中的应用

针对空间监视雷达的近地目标轨道确定问题,提出了基于容积卡尔曼滤波的精密轨道确定方法,与被广泛应用的扩展卡尔曼滤波方法相比,所提方法具有更高的定轨精度. 同时,由于容积卡尔曼滤波在理论上具有严格的数学证明,其在处理空间目标复杂运动问题的过程中具有更好的数值稳定性. 通过引入递推形式的后验克拉美罗界,分析了不同观测模型对定轨性能的影响. 利用仿真数据进一步验证了所提出方法的有效性和分析的正确性.     

CXM型超细分级磨风口环气相流场的数值模拟

为探究CXM型超细分级磨风口环处结构参数与操作参数对粉碎区粉碎效果的影响,采用标准k-ε两方程湍流模型及多重参考系MRF模型对粉碎室内气相流场进行数值模拟。结果表明:在相同空气进风量及同一转速下,减小径向间隙有利于破坏物料环流层,当间隙为5～10 mm时,所形成的上升气流有助于物料的粉碎与分级。转盘转速的大小,一方面考虑转盘材质对转速的限制,另一方面应根据物料的物化特性结合生产经验确定转盘转速,以达到能量利用率最高。     

Empirical Assessment of Bacillus Calmette-Guérin Vaccine to Combat COVID-19

COVID-19 has become one of the critical health issues globally, which surfaced first in latter part of the year 2019. It is the topmost concern for many nations’ governments as the contagious virus started mushrooming over adjacent regions of infected areas. In 1980, a vaccine called Bacillus Calmette-Guérin (BCG) was introduced for preventing tuberculosis and lung cancer. Countries that have made the BCG vaccine mandatory have witnessed a lesser COVID-19 fatality rate than the countries that have not made it compulsory. This paper’s initial research shows that the countries with a long-term compulsory BCG vaccination system are less affected by COVID-19 than those without a BCG vaccination system. This paper discusses analytical data patterns for medical applications regarding COVID-19 impact on countries with mandatory BCG status on fatality rates. The paper has tackled numerous analytical challenges to realize the full potential of heterogeneous data. An analogy is drawn to demonstrate how other factors can affect fatality and infection rates other than BCG vaccination only, such as age groups affected, other diseases, and stringency index. The data of Spain, Portugal, and Germany have been taken for a case study of BCG impact analysis.     

融合多种特征点信息的最小生成树医学图像配准

针对医学图像配准鲁棒性强、准确性高和速度快的要求,提出了一种基于融合多种特征点信息的最小生成树医学图像配准算法.该算法首先提取3种特征点,Harris-Laplace,Laplacian of Gaussian和网格点;然后使用遗传算法去除特征点集的冗余,并通过对位映射构建无向完全图顶点集合;进而使用改进的Kruskal算法来构造最小生成树;最后使用得到的最小生成树估计Rényi熵.该算法较好地解决了在噪声数据中使用最小生成树估计Rényi熵面临的特征点不稳定导致鲁棒性低和构造最小生成树遇到的速度瓶颈.实验结果表明:在图像含有噪声、灰度不均匀以及初始误配范围较大的情况下,该算法在达到良好配准精度的同时,具有较强的鲁棒性和较快的速度.     

带多参数的四次Bézier曲线的扩展

给出了一组带三个形状参数的类四次Bernstein基函数,它是四次Bernstein基函数的扩展,讨论它的基本性质,基于这组基定义了带三个形状参数的类四次Bézier曲线,该曲线和四次Bézier曲线有类似的性质,并具体分析了形状参数的几何意义和曲线间的光滑拼接。实例表明,该方法在设计曲线曲面时十分有效。     

信任网络下的TODIM群体决策方法

针对在群体决策中如何利用专家之间的社会关系和决策专家的有限理性的问题,提出一种信任网络下的TODIM群体决策方法。首先,根据专家讨论次数,在每一次讨论中,每个专家会根据信任接受程度参考信任者的决策矩阵,并通过信息交互和协商修改决策矩阵;其次,当达到设定的专家讨论次数时,计算最终的群体决策矩阵;最后,分别运用信任网络下的TODIM群体决策方法和TODIM群体决策方法计算各方案排序。对所得结果进行对比分析,并对专家讨论次数和信任接受程度进行灵敏度分析。案例分析结果表明,信任网络下的TODIM群体决策方法能充分结合信任网络,保证了决策过程中的多阶段信息交互和反馈过程,并在对比分析和灵敏度分析上优于对比方法。     

Stability analysis of Alfvén eigenmodes in China Fusion Engineering Test Reactor fully non-inductive and hybrid mode scenarios

In this paper, NOVA/NOVA-K codes are used to investigate the stability of Alfvén eigenmodes(AEs) in the China Fusion Engineering Test Reactor(CFETR). Firstly, the stability of AEs excited by energetic alpha particles is investigated. For the fully non-inductive scenario, it is found that all AEs are stable, and the least stable toroidal mode number is n= 8. However, for the hybrid mode scenario, it is found that many AEs are unstable, and the least stable toroidal mode numbers are n= 7, 8. Secondly, the effect of energetic alpha-particle parameters and beam ions on AE stability is also presented. The threshold of the least stable AE is about β_(crit,α) = 1.12%,crit,less than the value of alpha-particle beta(β_α=1.34%). The result demonstrates that the AEs excited by alpha particles are weakly unstable. The effect of the beam ions on AE stability is found to be very weak in CFETR.