中国科学的“杰出改革者”——记“两弹一星功勋奖章”获得者周光召

2024年8月17日,中国科学院院士、中国科学院原院长,中国科学技术协会名誉主席周光召在北京逝世,享年95岁。“两弹一星”是中国科技史上的一个奇迹,它的成功得益于在特殊历史环境下宽松民主的研究氛围。周光召就是“两弹一星”的杰出代表之一,周光召主要从事爆炸物理、辐射流体力学、高温高压物理、二维流体力学、中子物理等研究工作。诺贝尔奖获得者杨振宁曾表示:“周光召在做人、做事、做学问上面都做得非常成功。”

Surface composites fabricated by vacuum infiltration casting technique

Alumina （Al2O3） particles reinforced copper matrix surface composites were fabricated on the bronze substrate using the vacuum infiltration casting technique. Three cases were obtained in the vacuum infiltration casting technique： no infiltration, partial infiltration and full infiltration （the thickness of preforms do not exceed 3.5mm）. The reason of no infiltration is that the vacuum degree is not enough so that the force acting on the liquid metal is lower than the resistance due to the surface tension. Partial infiltration is because of somewhat lower vacuum degree and pouring temperature. Full desired infiltration is on account of suitable infiltration casting conditions, such as vacuum degree, pouring temperature, grain size and preheating temperature of the preform. The most important factor of affecting formation of surface composites is the vacuum degree, then pouring temperature and particle size. The infiltration mechanism was discussed on the bases of different processing conditions. The surface composite up to 3.5 mm in thickness with uniformly distributed Al2O3 particles could be fabricated via the vacuum infiltration casting technique.

神奇宇宙的探索者--记理论物理学家蔡荣根院士

黑洞,是爱因斯坦广义相对论预言的特殊的天体。天文学家普遍认为,黑洞是恒星坍缩的产物。黑洞的存在已经被观测所证实,2019年科学家们得到了第一张黑洞照片。蔡荣根是拓扑黑洞的早期研究者之一。从农家子弟到中国科学院院士,蔡荣根用行动践行了自己永不止步、追求梦想的人生信条,也展现了他对浩瀚宇宙、未知领域不断探索的精神与渴望。

Numerical simulation of water-slag elbow erosion-inhibiting by regulating the slag injection position with a novel preceding rotating sheet structure

The elbow erosion seriously jeopardizes the safe and stable operation of water–slag discharge pipeline of the coal gasification system.This work simulated water–slag elbow characteristics with various slag injection positions by simulating five simplified and representative erosion categories,including A-type horizontal-vertical elbow with an upstream flow,B-type horizontal-vertical elbow with a downstream flow,C-type vertical-horizontal elbow with an upstream flow,D-type vertical-horizontal elbow with a downstream flow and E-type horizontal-horizontal elbow.Compared with the C/D-type elbow,where particles were injected uniformly,the A-type elbow and E-type elbow were found to increase erosion rate,while the B-type elbow decreases erosion rate.An interesting discovery is that the elbow erosion rate is relatively low for small particles when particles are injected from the middle and bottom positions of the inlet section of the elbow.Based on the observation,a novel preceding rotating sheet structure was developed to regulate the particle injection position.It shows an excellent anti-erosion performance by reducing the maximum erosion rate of particles with diameters of 50,100,and 200μm by 23%,35%,and 43%,respectively.

旋流器结构对主吸收塔内流动特性的影响

高含硫天然气净化主吸收塔需要定期堆焊修复腐蚀部位,修复前后各需采用内燃法整体热处理技术进行消氢、消应处理。旋流器布置对空气分布及热处理过程中火焰调控具有重要影响,本工作分别对双级旋流器、单级旋流器Ⅰ和Ⅱ在吸收塔内的流动特性进行了模拟。结果表明,双级旋流器上方未产生明显回流区且速度分布均匀,内外两侧旋流叶片上方均产生较大的切向速度,空气入口速度为9.8 m/s的工况下产生的最大切向速度为8.33 m/s,其次为单级旋流器Ⅱ的4.5 m/s和单级旋流器Ⅰ的3.12 m/s。双级旋流器对应的塔内压降变化最小,证明其可有效产生低阻旋流场,且对应的塔底流线占比随气体质量流量变化可保持平稳,约为14%,与塔底壁面占塔体总表面积的百分比一致,能保证足够的气体介质回流塔底,促进气体对流。双级旋流器对应的90%塔内停留时间随气体质量流量增大而线性增长。总体上,双级旋流器的旋流效果优于其他两种旋流器,本研究可为内燃法整体热处理工艺旋流装置的优化设计提供参考。

Hybrid-driven Gaussian process online learning for highly maneuvering multi-target tracking

The performance of existing maneuvering target tracking methods for highly maneuvering targets in cluttered environments is unsatisfactory.This paper proposes a hybrid-driven approach for tracking multiple highly maneuvering targets,leveraging the advantages of both data-driven and model-based algorithms.The time-varying constant velocity model is integrated into the Gaussian process(GP)of online learning to improve the performance of GP prediction.This integration is further combined with a generalized probabilistic data association algorithm to realize multi-target tracking.Through the simulations,it has been demonstrated that the hybrid-driven approach exhibits significant performance improvements in comparison with widely used algorithms such as the interactive multi-model method and the data-driven GP motion tracker.

Generalized labeled multi-Bernoulli filter with signal features of unknown emitters

A novel algorithm that combines the generalized labeled multi-Bernoulli(GLMB) filter with signal features of the unknown emitter is proposed in this paper. In complex electromagnetic environments, emitter features(EFs) are often unknown and time-varying. Aiming at the unknown feature problem, we propose a method for identifying EFs based on dynamic clustering of data fields. Because EFs are time-varying and the probability distribution is unknown, an improved fuzzy C-means algorithm is proposed to calculate the correlation coefficients between the target and measurements, to approximate the EF likelihood function. On this basis, the EF likelihood function is integrated into the recursive GLMB filter process to obtain the new prediction and update equations.Simulation results show that the proposed method can improve the tracking performance of multiple targets,especially in heavy clutter environments.