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Thermal stability improvement and microstructure optimization of high cobalt content Nd-Fe-B magnets via terbium grain boundary diffusion

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Journal of Rare Earths 2024年第8期42卷 1531-1538,I0004页

作者： Jiyuan Xu Ruiyang Meng Jing Liu Jiateng Zhang Rui Han Yikun Fang Shengzhi Dong Wei Li division of Functional Materials research Central Iron and Steel Research InstituteBeijing100081China

The substitution of Fe by Co in the 2:14:1 phase is an effective method to increase the Curie temperature and enhance the thermal stability of the Nd-Fe-B ***,the accumulation of Co ele ment at the grain boundaries(GBs) changes the GBs from nonmagnetic to ferromagnetic and causes the thinlayer GBs to become rare,In this paper,the method of diffusing Tb element was chosen to improve the microstructure and temperature stability of high-Co *** original sintered Nd_(28.5)Dy_(3)-CO_(x)e_(bal)M_(0.6)B_(i)(x=0,6 wt%,12 wt%;M = Cu,Al,Zr) magnets with different Co contents were diffused with Tb by grain boundary diffusion(GBD).After GBD,high-Co magnets exhibit more continuously distributed thin-layer GBs,and their thermal stability is significantly *** high-Co magnets(x=6 wt%),the absolute value of the temperature coefficient of coercivity decreases from 0.603%/K to0.508%/K in the temperature range of 293-413 K,that of remanence decreases from 0.099%/K to 0.091%/K,and the coercivity increases from 18.44 to 25.04 *** electron microscopy(TEM)characterization reveals that there are both the 1:2 phase and the amorphous phase in the high-Co magnet before and after GBD,EDS elemental analysis shows that Tb element is more likely to preferentially replace the rare earth elements in the 2:14:1 main phase than in the 1:2 phase and the amorphous *** concentration of Tb at the edge of the main phase is much higher than that in the 1:2phase and amorphous phase,which is beneficial to the improvement of the *** preferential replacement of Tb elements at the edge of the 2:14:1 phase and thin-layer GBs with a more continuous distribution are synergistically responsible for improving the thermal stability of high-Co *** study indicates that GBD is an effective method to improve the microstructure and thermal stability of high-Co magnets.

关键词： Nd-Fe-B magnets Coercivity Grain boundary diffusion Thermal stability Micro structure Rare earths

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A Novel Prescribed-Performance Path-Following Problem for Non-Holonomic Vehicles

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IEEE/CAA Journal of Automatica Sinica 2024年第6期11卷 1476-1484页

作者： Zirui Chen Jingchuan Tang Zongyu Zuo Seventh research division Beihang University(BUAA)Beijing 100191China IEEE

The issue of achieving prescribed-performance path following in robotics is addressed in this paper,where the aim is to ensure that a desired path within a specified region is accu-rately converged to by the controlled *** this context,a novel form of the prescribed performance guiding vector field is introduced,accompanied by a prescribed-time sliding mode con-trol ***,the interdependence among the pre-scribed parameters is *** validate the effectiveness of the proposed method,numerical simulations are presented to demonstrate the efficacy of the approach.

关键词： Guiding vector field non-holonomic vehicle path following prescribed performance sliding mode control

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Finite-Time Stabilization for Constrained Discrete-time Systems by Using Model Predictive Control

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IEEE/CAA Journal of Automatica Sinica 2024年第7期11卷 1656-1666页

作者： Bing Zhu Xiaozhuoer Yuan Li Dai Zhiwen Qiang IEEE the Seventh research division Beihang UniversityBeijing 100191China the School of Automation Beijing Institute of TechnologyBeijing 100081China

In this paper, a model predictive control(MPC)framework is proposed for finite-time stabilization of linear and nonlinear discrete-time systems subject to state and control constraints. The proposed MPC framework guarantees the finite-time convergence property by assigning the control horizon equal to the dimension of the overall system, and only penalizing the terminal cost in the optimization, where the stage costs are not penalized explicitly. A terminal inequality constraint is added to guarantee the feasibility and stability of the closed-loop *** feasibility can be improved via augmentation. The finite-time convergence of the proposed MPC is proved theoretically,and is supported by simulation examples.

关键词： Constraints deadbeat control finite-time stabilization model predictive control(MPC)

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Effects of Co and Nb on the Crack of Additive Manufacturing Nickel-Based Superalloys

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Acta Metallurgica Sinica(English Letters) 2024年第9期37卷 1601-1610页

作者： Kejie Tan Jinli Xie Hailong Qin Bin Xu Guichen Hou Jinguo Li Zhongnan Bi Ji Zhang beijing Key Laboratory of Advanced High Temperature Materials Central Iron&Steel Research InstituteBeijing100081China beijing GAONA Materials&Technology Co. LTDBeijing100081China Superalloys division Institute of Metal ResearchChinese Academy of SciencesShenyang110016China

Increasing the print quality is the critical requirement for the additive manufactured complex part of aero-engines of nickel-based superalloys.A study of the effects of Co and Nb on the crack is performed focusing on the selective laser melting(SLM)nickel-based *** this paper,the solvus temperature of γ',crack characteristics,microstructure,thermal expansion,and mechanical properties of SLM nickel-based superalloy are investigated by varying the content of Co and *** alloy with 15Co/0Nb shows the highest comprehensive *** increases the crack risk and thermal deformation,and then Co accelerates the stress ***,Co is an extremely important alloying element for improving the quality of SLM nickel-based ***,the crack growth kinetics and the strain difference are discussed to reveal the SLM crack regular that is affected by time or *** analysis work on the effect of alloying elements can obtain an effective foundational theory to guide the composition optimization of SLM nickel-based superalloys.

关键词： Nickel-based superalloys Selective laser melting Element effect Crack

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High-performance anisotropic SmCo-based magnet with novel microstructure

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Journal of Rare Earths 2024年第8期42卷 1539-1545,I0005页

作者： Yingchang Li Zicao Xing Nengjun Yu Zesong Ren Minxiang Pan Qiong Wu Hongliang Ge Minggang Zhu Wei Li College of Materials and Chemistry China jiliang UniversityHangzhou 310018China division of Functional Materials research Central Iron and Steel Research InstituteBeijing 100081China

A novel micro structure of magnetically anisotropic Sm Co-based magnet with high-performance is *** magnet consists of SmCo_(7)-H(TbCu_(7)-hexagonal type),Sm_(2)Co_(17)-H(Th_(2)Ni_(17)-hexagonal type)and SmCo_(3)-R(SmCo_(3)-rhombohedral type)*** maximum magnetic energy product of the magnet is 231.69 kj/m^(3),and the intrinsic coercivity is 1005.47 kA/*** outstanding intrinsic coercivity temperature coefficient(β)of-0.125%/K between 298 and 773 K is obtained,which is very close to theβof commercial high-temperature Sm_(2)Co_(17)-based sintered *** initial magnetization curve indicates that the coercivity mechanism is controlled by a domain wall pinning *** SmCo_(3)-R lamellar phase may be a potential pinning center or self-pinning *** microstructure of the magnet is different from that of any previous SmCo-based *** findings provide a new idea for preparing high-performance SmCo-based permanent magnets.

关键词： Rare earths Permanent magnet Composite magnet Melt-spinning Microstructure

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The Investigation of Data Voting Algorithm for Train Air-Braking System Based on Multi-Classification SVM and ANFIS

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Chinese Journal of Electronics 2024年第1期33卷 274-281页

作者： Juhan WANG Ying GAO Yuan CAO Tao TANG School of Electronics and Information Engineering Beijing Jiaotong University graduate Department China Academy of Railway Science National Engineering research Center of Rail Transportation Operation and Control System Beijing Jiaotong University

The pressure data of the train air braking system is of great significance to accurately evaluate its operation state. In order to overcome the influence of sensor fault on the pressure data of train air braking system, it is necessary to design a set of sensor fault-tolerant voting mechanism to ensure that in the case of a pressure sensor fault, the system can accurately identify and locate the position of the faulty sensor, and estimate the fault data according to other normal data. A fault-tolerant mechanism based on multi-classification support vector machine(SVM) and adaptive network-based fuzzy inference system(ANFIS) is introduced. Multi-classification SVM is used to identify and locate the system fault state, and ANFIS is used to estimate the real data of the fault sensor. After estimation, the system will compare the real data of the fault sensor with the ANFIS estimated data. If it is similar,the system will recognize that there is a false alarm and record it. Then the paper tests the whole mechanism based on the real data. The test shows that the system can identify the fault samples and reduce the occurrence of false alarms.

关键词： Support vector machines Fault diagnosis Pressure sensors Fuzzy logic Fault tolerance Adaptive systems Fault tolerant systems

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Influences of Co-Flow and Counter-Flow Modes of Reactant Flow Arrangement on a PEMFC at Start-Up

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 1337-1356页

作者： Qianqian Shao Min Wang Nuo Xu School of Petroleum Engineering Guangdong University of Petrochemical TechnologyMaoming525000China Mechanics division Beijing Computational Science Research CenterBeijing100193China

To investigate the influences of co-flowand counter-flowmodes of reactant flowarrangement on a proton exchange membrane fuel cell(PEMFC)during start-up,unsteady physical and mathematical models fully coupling the flow,heat,and electrochemical reactions in a PEMFC are *** continuity equation and momentum equation are solved by handling pressure-velocity coupling using the SIMPLE *** electrochemical reaction rates in the catalyst layers(CLs)of the cathode and anode are calculated using the Butler-Volmer *** multiphase mixture model describes the multiphase transport process of gas mixtures and liquid water in the fuel *** validation,the influences of co-flow and counter-flow modes on the PEMFC performance are investigated,including the evolution of the current density,flow field,temperature field,and reactant concentration field during start-up,as well as the steady distribution of the current density,reactant concentration,andmembrane water content when the start-up ***-flow and counter-flow modes influence the current density distribution and temperature *** the one hand,the co-flow mode accelerates the start-up process of the PEMFC and leads to a more evenly distributed current density than the counter-flow *** the other hand,the temperature difference between the inlet and outlet sections of the cell is up to 10.1℃ under the co-flow mode,much larger than the 5.0℃ observed in the counter-flow ***,the counter-flowmode results in a more evenly distributed temperature and a lower maximum temperature than the co-flow ***,in the flow field design of a PEMFC,the reactant flow arrangements can be considered to weigh between better heat management and higher current density distribution of the cell.

关键词： PEMFC full coupling model Butler-Volmer equation multiphase mixture model co-flow mode counter-flow mode

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Design and fabrication of Nd-Fe-B magnet with excellent thermal stability

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Journal of Rare Earths 2024年第5期42卷 980-986,I0006页

作者： Rui Han Shengzhi Dong Dong Li Dongmin Zhang Hongsheng Chen Jiyuan Xu George CHadjipanayis Zhuolin Li Ying Zhang Wei Li division of Functional Materials research Central Iron and Steel Research InstituteBeijing100081China Department of Physics and Astronomy Sharp Lab University of DelawareNewarkDE19716USA beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing100190China

A novel Nd-Fe-B type permanent magnet with excellent thermal stability was designed by Co replacing Fe in the main phase and the grain boundary *** remanence and coercivity temperature coefficient reach 0.058%/℃and 0.465%/℃in the te mperature range from 25 to 100℃,which are much lower than those of commercial Nd-Fe-B *** enhanced Curie temperature is obtained for the novel magnet due to the Co substitution,which significantly improves the operating *** microstructure result reveals that an amorphous phase exists in the intergranular grains which is probably responsible for the deterioration of intrinsic *** work can provide a reference for the design and optimization of components of sintered Nd-Fe-B magnets with excellent thermal stability.

关键词： Thermal stability Remanence temperature coefficient Operating temperature Atomic substitution Rare earths

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The principle and amelioration of lithium plating in fast-charging lithium-ion batteries

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Journal of Energy Chemistry 2024年第10期97卷 453-459,I0009页

作者： Yi Yang Xia-Lin Zhong Lei Xu Zhuo-Lin Yang Chong Yan Jia-Qi Huang School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Yangtze River Delta graduate School of beijing Institute of Technology Jiaxing 314003ZhejiangChina

Fast charging is restricted primarily by the risk of lithium(Li)plating,a side reaction that can lead to the rapid capacity decay and dendrite-induced thermal runaway of lithium-ion batteries(LIBs).Investigation on the intrinsic mechanism and the position of Li plating is crucial to improving the fast rechargeability and safety of ***,we investigate the Li plating behavior in porous electrodes under the restricted transport of Li^(+).Based on the theoretical model,it can be concluded that the Li plating on the anodeseparator interface(ASI)is thermodynamically feasible and kinetically ***,the prior deposition of metal Li on the ASI rather than the anode-current collector interface(ACI)is verified *** order to facilitate the transfer of Li^(+)among the electrode and improve the utilization of active materials without Li plating,a bilayer asymmetric anode composed of graphite and hard carbon(GH)is *** and simulation results suggest that the GH hybrid electrode homogenizes the lithiated-rate throughout the electrode and outperforms the pure graphite electrode in terms of the rate performance and inhibition of Li *** work provides new insights into the behavior of Li plating and the rational design of electrode structure.

关键词： Graphite Hard carbon Fast charging Lithium plating Lithium-ion batteries

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Molecular dynamics study of primary radiation damage in TiVTa concentrated solid-solution alloy

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Chinese Physics B 2024年第3期33卷 530-535页

作者：赵永鹏豆艳坤贺新福曹晗王林枫邓辉球杨文 Reactor Engineering Technology research division China Institute of Atomic EnergyBeijing 102413China School of Physics and Electronics Hunan UniversityChangsha 410082China

The primary radiation damage in pure V and TiVTa concentrated solid-solution alloy(CSA)was studied using a molecular dynamics *** have performed displacement cascade simulations to explore the generation and evolution behavior of irradiation *** results demonstrate that the defect accumulation and agglomeration in TiVTa CSA are significantly suppressed compared to pure *** peak value of Frenkel pairs during cascade collisions in TiVTa CSA is much higher than that in pure V due to the lower formation energy of point ***,the longer lifetime of the thermal spike relaxation and slow energy dissipation capability of TiVTa CSA can facilitate the recombination of point *** defect agglomeration rate in TiVTa CSA is much lower due to the lower binding energy of interstitial clusters and reduced interstitial ***,the occurrence probability of dislocation loops in TiVTa CSA is lower than that in pure *** reduction in primary radiation damage may enhance the radiation resistance of TiVTa CSA,and the improved radiation tolerance is primarily attributed to the relaxation stage and long-term defect evolution rather than the ballistic *** results can provide fundamental insights into irradiation-induced defects evolution in refractory CSAs.

关键词： concentrated solid-solution alloy primary radiation damage molecular dynamics simulation

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