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Numerical simulation on directional solidification of Al-Ni-Co alloy based on FEM

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China Foundry 2010年第1期7卷 57-60页

作者： Yang Zhili chen dengming Tian Shilong, Liao Daohan Yang Yu College of Metallurgy ＆ Material Engineering Chongqing University of Science and Technology Chongqing 401331 China

The ratio,of the temperature gradient at the solidifiationfront to the solidification rate of solid-liquid interface,plays a large part in columnar grain *** transient temperature fields of directional solidification of Al-Ni-Co alloy were studied by employing a finite element *** temperature gradient at the solidification front and the solidification rate were analyzed for molten steels pouring at different *** results show that with different initial pouring temperatures,the individual ratio of the temperature gradient at solidification front to the solidification rate soars up in the initial stage of solidification,then varies within 2,000-6,000℃.***-2,and finally goes down rapidly and even tend to be closed to each other when the solidification thickness reaches 5-6 *** simulation result is consistent with the practical production which can provide an available reference for process optimization of directional solidified Al-Ni-Co alloy.

关键词：定向凝固有限元方法铝镍钴合金数值模拟温度梯度凝固速度浇注温度瞬态温度场

Magnetic properties and microstructure of nanocrystalline bulk Nd-Fe-B with Ce-Co addition

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Journal of Rare Earths 2021年第6期39卷 689-695,I0003页

作者： Yilong Ma Qiqi Yang Xiaoli chen Ying He Wenbo Xiang Jiaqi Lai Bin Shao Donglin Guo dengming chen Kejian Li College of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China The Center of Material Analysis and Testing Chongqing University of Science and TechnologyChongqing 401331China

The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline Nd-Fe-B bulk alloy were *** coercivity of Nd-Fe-B bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co ***,when the concentration of Ce-Co is up to 30 wt%,the density of the magnet can reach the maximum value of 7.58 g/cm^(3),but the coercivity does not increase *** the other hand,with the increase of holding time to 10 min,the density and coercivity of magnets increase gradually,reaching up to 7.55 g/cm^(3) and 1134.3 kA/m,*** the addition of Ce-Co alloy,Ce-Co may easily diffuse into the Nd-Fe-B matrix during hot-pressing and under the high pressure and temperature,thus increasing the content of grain boundary phase and the pinning effect of grain boundary,which leads to the increase of *** extension of the hot-pressing holding time may be more conducive to the diffusion of CeCo into the Nd-Fe-B *** addition,the effect of Ce-Co addition on the magnetic properties of Nd-FeB with different content of rare earth was also *** addition of Ce-Co can effectively increase the coercivity of nanocomposite Nd_(2)Fe_(14)B/α-Fe *** addition of Nb to the parent alloy can further improve the *** Nd_(11)Fe_(81.5)Nb_(1)Ga_(0.5)B_(6) alloy with 10 wt% Ce-Co addition,the coercivity can increase from 740.28 to 1098.48 kA/m.

关键词： Nd-Fe-B magnet Ce-Co addition Coercivity Microstructure Nanocomposite Rare earths

Meridional deflection of global eddy propagation derived from tandem altimetry: Mechanism and implication

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Science China Earth Sciences 2024年第3期67卷 811-825页

作者： Ge chen Xiaoyan chen Frontiers Science Center for Deep Ocean Multispheres and Earth System School of Marine TechnologyOcean University of ChinaQindao 266100China Laboratory for Regional Oceanography and Numerical Modeling Laoshan LaboratoryQindao 266237China

A common view on meridional deflection of eddy propagation is poleward for cyclones and equatorward for anticyclones. This widely accepted polarity-sensitive pattern has been increasingly undermined given that it is systematically violated on both zonal and regional scales as recently reported. Here, we approach the problem by exploring these violations in terms of eddy effects of spatiotemporal geostrophy, thermal fading, and flow dragging, yielding the following main conclusions.(1) The polarity-dependent deflection discrepancy is a pseudo feature resulting from a biased fit to the normalized eddy tracks which are spatially asymmetric(though azimuthally symmetric) between the two signs;Instead, the primary pattern of eddy deflection appears to be geographically correlated and polarity independent.(2) Geostrophic adjustment plays a critical role in defining the meridional movement of an eddy. Specifically, a consistent poleward(equatorward) trajectory bending of spatially(temporally) ageostrophic eddies is observed irrespective of their polarity.(3) The mechanism of eddy deflection is also determined by its zonal propagation direction. Westward propagating eddies are substantially affected by thermal fading, while opposite ones by flow dragging. A realistic and comprehensive understanding of eddy deflection mechanisms serves as a significant contribution to the prediction of eddy trajectory, and the protection of ocean environment.

关键词： Mesoscale eddies Eddy propagation Eddy meridional deflection Satellite observation Geostrophic adjustment

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高性能Sm_(2)Fe_(17)N_(x)粉体制备的研究进展

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材料研究学报 2022年第5期36卷 321-331页

作者：何颖李超群陈小立龙芝梅赖嘉琪邵斌马毅龙陈登明董季玲重庆科技学院冶金与材料工程学院重庆401331 纳微复合材料与器件重庆市重点实验室重庆401331

新能源汽车的高速发展,需要能稳定工作在120℃~200℃温度区间的永磁材料。居里温度为476℃、各向异性场为14.7 T的Sm_(2)Fe_(17)N_(3),具有优良的本征磁性能,可应用在这个温度区间。为了提高Sm_(2)Fe_(17)N_(3)粉体的磁性能,必须将颗粒... 详细信息

新能源汽车的高速发展,需要能稳定工作在120℃~200℃温度区间的永磁材料。居里温度为476℃、各向异性场为14.7 T的Sm_(2)Fe_(17)N_(3),具有优良的本征磁性能,可应用在这个温度区间。为了提高Sm_(2)Fe_(17)N_(3)粉体的磁性能,必须将颗粒的粒径减小到临界单畴尺寸以实现高各向异性场;同时,还要避免颗粒尺寸减小产生的表面氧化,以保证高剩磁和最大磁能积。粉体破碎、机械合金化、甩带、薄带连铸、还原扩散以及表面镀覆等多种制备工艺,可用于制备高性能Sm_(2)Fe_(17)N_(3)。目前,实验室制备的Sm_(2)Fe_(17)N_(3)粉体的矫顽力和最大磁能积已经达到28.1 kOe和43.6 MGOe。本文评述近年来Sm_(2)Fe_(17)N_(3)粉体制备的研究成果,包括对制备机理的系统总结并提出仍待解决的关键问题:Sm_(2)Fe_(17)N_(3)粉体的矫顽力、剩磁等与其颗粒尺寸的量化规律以及与颗粒磁畴结构的关联机制;对NH_(3)/H_(2)混合气体中H_(2)对提高氮化效率的作用机制仍需探索;进一步开发在低氧环境下的颗粒粒径均匀化、控制形貌的二次破碎技术;对于还原扩散法,开发适合规模化应用的新前驱体及其制备方法以及快速去除钙副产物的水洗技术等。

关键词：评述金属材料 Sm_(2)Fe_(17)N_(x) 永磁制备方法

A refined representation method of the particle size distribution curve based on grading entropy

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Particuology 2024年第5期88卷 302-311页

作者： Xing Li Qun chen Zhaozhao Liu cheng Zhou chen Wang chen chen State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu610065China

The particle size distribution(PSD)curve is an important expression of the basic properties of the *** characteristic parameters such as median particle size D_(50),effective particle size D_(10),and some combinations of characteristic parameters can only represent some points of the PSD curve,failing to represent all information of the PSD *** this paper,a fraction characteristic parameter F that could reflect the fraction size variation of the PSD curve was introduced based on grading *** a new presentation method of the A-B-F three parameters was proposed for a refined representation of the PSD *** was found that the newly constructed model not only better represents the differences in the width of PSD curves but also has a higher sensitivity than the A-B two-parameter model proposed by Lő*** PSD curves with similar distributions,the new presentation method has a higher degree of discrimination than that of the D_(50)-C_(u)-C_(c) three-parameter or the four-parameter combination G_(c) proposed by ***,the application of this new method in describing the spatial nonuniformity distribution of depositions and predicting the soil hydraulic conductivity was *** research results can provide a reference for the refined representation of PSD curves.

关键词： Grading entropy Particle size distribution curve Refined representation

Track correlation algorithm based on CNN-LSTM for swarm targets

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Journal of Systems Engineering and Electronics 2024年第2期35卷 417-429页

作者： chen Jinyang WANG Xuhua chen Xian Research Institute for National Defense Engineering Academy of Military SciencesLuoyang 471023China Information Engineering University Zhengzhou 450001China School of Computer Science and Technology Xidian UniversityXi’an 710071China

The rapid development of unmanned aerial vehicle(UAV) swarm, a new type of aerial threat target, has brought great pressure to the air defense early warning system. At present, most of the track correlation algorithms only use part of the target location, speed, and other information for *** this paper, the artificial neural network method is used to establish the corresponding intelligent track correlation model and method according to the characteristics of swarm ***, a route correlation method based on convolutional neural networks (CNN) and long short-term memory (LSTM)Neural network is designed. In this model, the CNN is used to extract the formation characteristics of UAV swarm and the spatial position characteristics of single UAV track in the formation,while the LSTM is used to extract the time characteristics of UAV swarm. Experimental results show that compared with the traditional algorithms, the algorithm based on CNN-LSTM neural network can make full use of multiple feature information of the target, and has better robustness and accuracy for swarm targets.

关键词： track correlation correlation accuracy rate swarm target convolutional neural network(CNN) long short-term memory(LSTM)neural network

Two-stage Planning Method for Energy Router Considering Its Optimal Operation in Distribution Networks

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 605-616页

作者： Meifu chen Mingchao Xia Qifang chen School of Electrical Engineering Beijing Jiaotong UniversityBeijing 100044China

An energy router can effectively optimize the network loss and power quality of distribution networks. The optimal configuration of the energy router is relatively complex because issues dynamically influence each other, such as the location of the energy router, optimal number and capacity of its ports, and building new distribution lines for the ports. Presently, there has been very few research studies on the practical problems for the energy router. In this paper, a planning model of an energy router combined with the distribution network is established, which fully exploits the active and reactive power control abilities of the energy router to optimize the operation of the grid. The configuration problem is decoupled into two stages. The upper layer determines the location of the energy router and the parameters of the candidate new distribution lines for the ports. The lower layer calculates the optimal configuration of the energy router by minimizing the total annual cost. Because of the same rated bus voltage in the distribution network, the existing structure of the energy router is changed to be more applicable for the distribution network, and then the power flow model of the energy router is also modified. Due to the nonlinearity of the model, the planning model is converted into a mixed-integer second-order cone model to solve efficiently. In addition, some core factors influencing the optimal scheme of the energy router are also analyzed in this paper. Simulation results show that the optimal scheme of the energy router can significantly improve the economic deployment of the energy router, and optimize the network loss and power quality of the distribution network.

关键词： Capacity allocation distribution network energy router optimal operation

Aerial target threat assessment based on gated recurrent unit and self-attention mechanism

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Journal of Systems Engineering and Electronics 2024年第2期35卷 361-373页

作者： chen chen QUAN Wei SHAO Zhuang School of Automation Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of Intelligent Control and Decision of Complex Systems Beijing 100081China

Aerial threat assessment is a crucial link in modern air combat, whose result counts a great deal for commanders to make decisions. With the consideration that the existing threat assessment methods have difficulties in dealing with high dimensional time series target data, a threat assessment method based on self-attention mechanism and gated recurrent unit(SAGRU) is proposed. Firstly, a threat feature system including air combat situations and capability features is established. Moreover, a data augmentation process based on fractional Fourier transform(FRFT) is applied to extract more valuable information from time series situation features. Furthermore, aiming to capture key characteristics of battlefield evolution, a bidirectional GRU and SA mechanisms are designed for enhanced ***, after the concatenation of the processed air combat situation and capability features, the target threat level will be predicted by fully connected neural layers and the softmax classifier. Finally, in order to validate this model, an air combat dataset generated by a combat simulation system is introduced for model training and testing. The comparison experiments show the proposed model has structural rationality and can perform threat assessment faster and more accurately than the other existing models based on deep learning.

关键词： target threat assessment gated recurrent unit(GRU) self-attention(SA) fractional Fourier transform(FRFT)

Planning Model for Energy Routers Considering Peer-to-Peer Energy Transactions Among Multiple Distribution Networks

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1026-1043页

作者： Meifu chen Mingchao Xia Qifang chen School of Electrical Engineering Beijing Jiaotong UniversityBeijing 100044China IEEE

A high proportion of renewable energy affects the power quality of distribution networks,and surplus energy will be sold to the upstream grid at a low *** this paper,considering peer-to-peer energy transactions,the energy router-based multiple distribution networks are analyzed to solve the above problems and realize collaborative consumption of renewable ***,the investing cost of an energy router is high,and research on the economic operation of energy routers in distribution networks is ***,this paper establishes a planning model for energy routers considering peer-to-peer energy transactions among distribution networks,and explores the benefits of peer-to-peer energy transactions through energy router based multiple distribution networks.A structure of an energy router suitable for peer-to-peer energy transactions is selected,and a power flow calculation model based on a multilayer structure is *** energy router’s scheduling model is established,and unique functions of the energy router and revenue of each distribution network are considered.A power flow calculation model based on peer-to-peer interconnection of multiple distribution networks through energy routers is also ***,simulation results verify the effectiveness of the proposed planning *** show that peer-topeer energy transaction among distribution networks through energy routers can effectively reduce the comprehensive cost of distribution networks,significantly improve the power quality of the distribution networks,and reduce the impact of power fluctuation on the upstream grid incurred by the distribution network.

关键词： Capacity allocation energy router multiple distribution networks peer-to-peer energy transaction power flow optimization