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Rare earth element Ce enables high thermoelectric performance in n-type SnSe polycrystals

Journal of Materials Science & technology 2023年第12期143卷 234-241页

作者： Shan Li Li Yin Yijie Liu Xiaodong Wang Chen Chen Qian Zhang School of Civil Aviation Northwestern Polytechnical UniversityXi’an 710072China School of Materials Science and Engineering and Institute of Materials Genome&Big DataHarbin Institute of TechnologyShenzhen 518055China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

SnSe exhibits excellent thermoelectric performance in both n-and p-type single crystals,but its n-type polycrystals are restricted because of the lower electrical ***,we dually introduced rare earth element Ce and PbTe to optimize the thermoelectric properties of n-type SnSe *** is demonstrated that Ce is an effective cationic dopant to convert SnSe from p-to n-type conductor,and an enhanced peak zT value of∼0.9 at 823 K was obtained in Sn 0.97 Ce 0.03 Se due to the improved power ***,PbTe alloying not only reduced the band gap to increase the carrier concentration,but also enhanced the density-of-states effective mass,and hence further increased the power factor in the whole measured temperature ***,the lattice thermal conductivity was significantly reduced owing to the enhanced phonon scattering by the mass and strain *** a result,the peak zT value was increased to∼1.3 for Sn 0.9 Pb 0.07 Ce 0.03 Se 0.93 Te 0.07 together with a high average zT value of∼0.52 in the temperature range of 300 to 823 K.

关键词： Thermoelectric N-type SnSe Ce doping PbTe alloying

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Numerical Study of Pipeline Distribution Effect on the Performance of Pasty Propellant Rocket Motor

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Space(Science & technology) 2023年第1期3卷 572-584页

作者： Renjie Hu Weizong Wang Advanced Space Propulsion and Energy Laboratory(ASPEL) School of AstronauticsBeihang UniversityBeijingChina Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of EducationBeijingChina Aircraft and Propulsion Laboratory Ningbo Institute of TechnologyBeihang UniversityNingboChina

This paper reports the numerical research on PPRM(pasty propellant rocket motor)through computational fluid dynamics simulation along with pipeline design comparison based on simulation *** structure of PPRM includes feed pipelines,and the propellant is distributed in a cone shape when burnt steadily in the combustion *** a result,the internal flow field presents strong 3-dimensional characteristics,which may lead to the flow *** accurately understand the combustion flow field and flow instability in the PPRM,a numerical simulation of the combustion chamber considering propellant pyrolysis and chemical reaction,coupled with the feed system module,is employed in the *** effect of pipeline distribution,including the pipeline location and the nonuniformity of pipeline diameter on the internal combustion flow characteristics as well as the motor thrust,was *** results show that the vortex caused by the special conical shape of the burning surface leads to pressure *** adjusting the pipeline location and the nonuniformity of pipeline diameter,the distribution of vortex varies dramatically,which leads to different oscillation frequencies and *** some pipeline distribution schemes,there is almost no large vortex in the rocket motor,which greatly eliminates the flow acoustic coupling oscillation of the *** oscillation amplitude decreases from about 5.7%to less than 0.1%.The results will help guide the design of the high-performance feed system and combustion chamber of PPRM.

关键词： vortex oscillation eliminate

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A simulation and Test Method for Fault Current Suppression Branch in DC Grid

A Simulation and Test Method for Fault Current Suppression B...

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7th International Conference on Electronics technology, ICET 2024

作者： Li, Fangyuan Gu, Huaiguang Zhou, Jiapei Gao, Yang State Grid Smart Grid Research Institute CO. LTD. State Key Laboratory of Advanced Power Transmission Technology Beijing China Beijing Key Laboratory of Dc Grid Technology & Simulation Beijing China

ISBN: (纸本)9798350363951

This paper is aimed at the research and verification requirements of fault current suppression devices applied in DC grids as actual physical test equipment. A joint test method based on digital and physical hybrid simulation is proposed, and a digital physical interface scheme is provided. It has engineering practical digital physical interface stability and accuracy, and plays a technical support role in the development of fault current suppression devices in DC grids. A fault current suppression branch is proposed for the combination of a current limiter and a high-voltage DC circuit breaker. The testing topology, main circuit interface, communication interface, and communication protocol requirements for the digital physical hybrid simulation of the fault suppression branch are proposed, and a platform for the connection of the current limiting device is developed. The experiment results show that after adding a current limiter to the current limiting branch, the maximum fault current decreases, the breaking current of the circuit breaker is reduced, and the requirements for the technical parameters of the circuit breaker are lowered. © 2024 IEEE.

关键词： Digital devices

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Agent Optimization Decision-making Method Based on Self-Play

Agent Optimization Decision-making Method Based on Self-Play

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2024 IEEE International Conference on Unmanned Systems, ICUS 2024

作者： Duan, Chunyi Xiong, Rongling Zhang, Luyou Ran, Huaming Yang, Qing National Key Laboratory of Complex Aviation System Simulation China Electronics Technology Group Corporation Tenth Research Institute Chengdu China Unit 93216 People's Liberation Army of China Beijing China

ISBN: (纸本)9798350384185

Aiming at the problem that the traditional deep reinforcement learning algorithm has poor generalization ability of generating strategies when solving complex game problems such as real-time strategy games, an agent strategy optimization method based on the combination of expert knowledge and self-play is ***, the opponent strategy of the agent is designed based on expert knowledge, and the corresponding strategy is generated by the proximal policy optimization algorithm (PPO), and the generated strategy is continuously put into the opponent strategy pool to provide a variety of opponent strategies for the agent in the training *** continuous iterative confrontation, the agent's autonomous decision-making ability in the face of different opponent strategies is *** simulation results show that compared with the traditional deep reinforcement learning algorithm, the introduction of the self-play training framework can significantly improve the average confrontation rate of the agent strategy, improve the robustness and generalization ability of the agent confrontation strategy, guide the agent to learn more effective tactical strategy, and achieve the adversarial advantage of "Priority first enemy discovery, Priority enemy launch". © 2024 IEEE.

关键词： Deep reinforcement learning

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The dielectric behavior and efficient microwave absorption of doped nanoscale LaMnO_(3)at elevated temperature

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Nano Research 2022年第8期15卷 7731-7741页

作者： Zhigang Mu Guoke Wei Hang Zhang Lu Gao Yue Zhao Shaolong Tang Guangbin Ji College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China Aviation Key Laboratory of Science and Technology on Advanced Surface Engineering AVIC Manufacturing Technology InstituteBeijing 100024China National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China

LaMnO_(3)perovskite has great potential in microwave absorption at high temperature due to its complex doping effect and super *** current research mainly focuses on the doping ratio regulation,while the mechanism of doping effect at high temperature is still lack of sufficient *** this work,La1−xSrxMn1−yFeyO_(3)(LaMnO_(3),La_(0.7)Sr_(0.3)MnO_(3),and La_(0.7)Sr_(0.3)Mn_(0.8)Fe_(0.2)O_(3))nanostructures with different doping sites were successfully prepared by the solid phase reaction ***,the high temperature dielectric test samples were obtained by mixing with cordierite(2MgO·2Al_(2)O_(3)·5SiO_(2)(MAS)).The results showed that the temperature dependence of Mn ion spin state had a significant impact on the high temperature dielectric behavior of La_(1−x)Sr_(x)Mn_(1−y)FeyO_(3).Particularly,when the thickness is only 1.9 mm,La_(0.7)Sr_(0.3)Mn_(0.8)Fe_(0.2)O_(3)/MAS can achieve the widest bandwidth of 4.2 GHz covered the entire X-band(8.2–12.4 GHz)and a minimum reflection loss(RL)value of−17.99 dB at 500℃.In order to improve the operating temperature of La_(0.7)Sr_(0.3)Mn_(0.8)Fe_(0.2)O_(3)/MAS,a cellular array structure was designed by using computer simulation technology(CST)software to introduce magnetic *** the outer length of the hexagon is 1 mm and the coating thickness is 1.9 mm,the widest bandwidth covers the X-band and the minimum RL value is−15.35 dB at 800℃.Therefore,La_(0.7)Sr_(0.3)Mn_(0.8)Fe_(0.2)O_(3)has a great prospect as an efficient high temperature microwave absorber.

关键词： microwave absorption doping perovskite high temperature dielectric behavior

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Deformation Mechanism of Bimodal Structured 2205 Duplex Stainless Steel in Two Yield Stages

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Journal of Wuhan University of technology(Materials Science) 2023年第1期38卷 184-191页

作者：盛捷 DU Mingchen LI Yufeng MA Guocai CHEN Weiqian ZHENG Yuehong ZHAN Faqi REN Junqiang G I Raab 喇培清 State Key Laboratory of Gansu Advanced Non-Ferrous Metal Materials Lanzhou University of TechnologyLanzhou 730050China Jiuquan Iron and Steel(Group)Co. Ltd.Jiayuguan 735100China Key Laboratory of Solar Power System Engineering Jiuquan Vocational and Technical CollegeJiuquan 735000China Institute of Physics of Advanced Materials Ufa State Aviation Technical University12 K.Marx StreetUfa 450008Russia

A kind of micro/nanostructured 2205 duplex stainless steel(DSS)with uniform distribution of nanocrystals was prepared via aluminothermic reaction *** analysis of stress-strain curve showed that the fracture strength and elongation of the specimen were 946 MPa and 24.7%,*** present,the research on microstructure of bimodal 2205 DSS at room temperature(RT)mainly depended on scanning electron microscope(SEM)observation after loading *** test result indicates that there are two different yield stages in stress-strain curve of specimen during tensile *** microstructure of duplex bimodal structured stainless steel consists of two pairs of soft hard regions and *** studying deformation mechanism of bimodal structured stainless steel,the interaction between soft phase and hard phase are *** principle of composition design and microstructure control of typical duplex stainless steel is obtained,which provides an important research basis for designing of advanced duplex stainless steel.

关键词： 2205 duplex stainless steel bimodal structure in-situ tensile test deformation mechanism two different yield stages

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Technical and Economic Analysis of Multiple Types of Wind Power Convergence and Transmission Methods in Typical Scenarios of Land and Sea 6

Technical and Economic Analysis of Multiple Types of Wind Po...

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6th International Conference on HVDC, HVDC 2024

作者： Chi, Chengbin Wu, Yanan Zhou, Jing Zhu, Lin Liu, Qi Yan, Jun State Grid Smart Grid Research Institute Co. Ltd State Key Laboratory of Advanced Power Transmission Technology Beijing China State Grid Smart Grid Research Institute Co. Ltd Beijing Key Laboratory of Dc Grid Technology and Simulation Beijing China

ISBN: (纸本)9798350387759

With the global demand for renewable energy sources on the rise, wind power has emerged as a pivotal form of renewable energy, witnessing rapid expansion in its development and utilization worldwide. This article addresses large-scale wind power transmission scenarios both offshore and onshore. Based on the analysis of technical principles and engineering cost estimation data, it has designed 12 corresponding technical schemes for six advanced wind power collection and transmission methods from both technical and economic dimensions. A scenario with a transmission capacity of 1000MW was selected to conduct a comparative analysis of various types of power transmission technology schemes. The article provides a detailed exposition of the transmission capacity, reactive power compensation requirements, technical maturity, adaptability to scenarios, and economic viability for each scheme, and analyzes the technical and economic characteristics of each scheme. The research results indicate that the diode rectifier transmission scheme has the best economic performance, the VSC transmission scheme is the most technically mature, and the flexible low-frequency transmission scheme has certain economic advantages at medium and short distances. The diode parallel MMC and cascaded MMC schemes are economically second only to the diode rectifier scheme and also have the feature of not requiring wind farm networking. The aim of this paper is to provide guidance for the selection of scaled wind power transmission methods, to promote energy transformation, and to accelerate the construction of a new type of power system. © 2024 IEEE.

关键词： adaptability to scenarios economic comparison multiple types of wind power collection and transmission methods selection of wind power collection and transmission methods technical characteristics

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Toughening Effects through Optimizing Cell Structure and Deformation Behaviors of Al–Mg Foams

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Acta Metallurgica Sinica(English Letters) 2022年第12期35卷 2014-2026页

作者： Hao Yu Xudong Yang Weiting Li Xudong Rong Siyuan Guo Lishi Ma Lizhuang Yang Junwei Sha Naiqin Zhao Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and EngineeringTianjin UniversityTianjin 300350China Sino-European Institute of Aviation Engineering Civil Aviation University of ChinaTianjin 300300China School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory of Advanced Ceramics and Machining Technology Ministry of EducationTianjin 300350China

As widely used protective materials,the application of Al foams is still limited by their low intrinsic mechanical properties caused by the brittleness of *** introduction of Mg is recently demonstrated effective to improve the mechanical performance of Al foams;however,the mechanism of Mg modification is still not *** this work,Al-Mg foams are developed through a powder metallurgy process with excellent compression performance and high energy absorption *** effects of Mg modification on the cell structure,toughness,and deformation behavior are investigated *** a result,the small cell size of~1.8 mm and the high sphericity of 0.92 are achieved with 5% of Mg addition,delivering high compression stress of 8.5±0.43 MPa and energy absorption capacity of 6.9±0.36 MJ/m^(3),*** synergistic mechanism for the improved mechanical performance is also demonstrated to be the combination of stress transfer and plastic deformation behavior of *** results provide a new strategy to develop high-performance foam materials by improving toughness and further promote the practical application.

关键词： Powder metallurgy Aluminum foam Al-Mg alloy Plastic deformation Cell structure

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Microstructures and high-temperature self-lubricating wearresistance mechanisms of graphene-modified WC–12Co coatings

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Friction 2021年第2期9卷 315-331页

作者： Haoliang TIAN Changliang WANG Mengqiu GUO Yongjing CUI Junguo GAO Zhihui TANG Aviation Key Laboratory of Science and Technology on Advanced Corrosion and Protection for Aviation Material Beijing Aero Engine Corporation of China Beijing Institute of Aeronautical MaterialsBeijing 100095China

To reduce the friction coefficient of cobalt-cemented tungsten carbide(WC–12Co)wear-resistant coatings,graphene was compounded into WC–12Co powder via wet ball milling and spray *** and wear-resistant graphene coatings were prepared via detonation gun *** presence,morphologies,and phase compositions of graphene in the powders and coatings that are obtained through different powder preparation processes were *** analysis was performed using the following technologies:energy-dispersive X-ray-spectroscopy(EDXS),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and Raman *** mechanical properties of the coatings were studied using a microhardness tester and a universal drawing *** friction and wear properties of the coatings were studied using an SRV-4 friction and wear *** results showed that the graphene content in the WC–12Co coating modified with graphene was higher than that without modification;graphene was embedded in the structure in a transparent and thin-layer *** adhesive strength of this coating at approximately 25°C was approximately 60.33 MPa,and the hardness was approximately 984 *** high-temperature treatment,the adhesive strength and hardness of the graphene oxide(GO)/WC–12Co coating decreased slightly(the lowest adhesive strength of 53.16 MPa was observed after treatment at 400°C,and the lowest hardness of approximately 837 HV0.3 was observed after treatment at 300°C).Compared to the friction coefficient(0.6)of the WC–12Co coating obtained at room temperature,the friction coefficient of the GO/WC–12Co coating was decreased by approximately 50%of that *** graphene-modified coating was continuously exposed to the wear tracks on the surface of the contacting materials during friction,and a lubricating film was formed in the microareas in which the wear tracks were *** coating exhibited improved self-lubricating and wear-resistant effects

关键词： graphene wear-resistant coating detonation gun spraying self-lubricating wear-resistance mechanism high-temperature friction

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Free vibration exploration of axially functionally graded carbon nanotube-reinforced beams through an innovative perturbative methodology 3

Free vibration exploration of axially functionally graded ca...

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2024 3rd International Conference on Aerospace, Aerodynamics and Mechatronics Engineering, AAME 2024

作者： Chen, Chen Zhou, Lilin Ye, Tianyu Li, Daokui College of Aerospace Science and Engineering National University of Defense Technology Hunan Changsha410073 China Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Missions Hunan Changsha410073 China Aviation Engineering Institute Civil Aviation Flight University of China Sichuan Guanghan618307 China

Axially functionally graded (AFG) carbon nanotube-reinforced composite (CNTRC) emerges as a promising solution for tailoring the stiffness and strength of various beam-like structures. Applications range from optimizing the weight-to-strength ratio of airplane wings to fine-tuning the frequency of micro-beam sensors, and even alleviating stresses induced by centrifugal forces or temperature gradients in turbine blades. However, the challenge of solving variable coefficient partial differential equations (VCPDEs) arising from the axial material gradient limits conventional methods to numerical and simulation techniques. In this study, a novel perturbation approach (PA) customized for AFG-CNTRC is highlighted for solving the problem analytically, simply, and precisely. First, the vibration model of an AFG-CNTRC beam is established according to the Euler-Bernoulli theory (EBT). Second, the vibration governing equations are solved by the PA and the state space method (SSM) analytically. Finally, the adaptivity and accuracy of the PA are validated and the effects of carbon nanotubes (CNTs) distribution patterns are analyzed. It is found that increasing CNT content at either end will increase the natural frequency for symmetric boundary conditions (BCs). The frequency decreases with the degree of nonlinearity distribution of CNTs. The frequency under the C-F BC exhibits low sensitivity to parameter effects. © Published under licence by IOP Publishing Ltd.

关键词： State space methods

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