检索结果-内蒙古大学图书馆

Ultrathin two-dimensional medium-entropy oxide as a highly efficient and stable electrocatalyst for oxygen evolution reaction

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Nano Research 2024年第4期17卷 2555-2562页

作者： Guangyuan Yan Tianlu Wang Biwei Zhao Wenjing Gao Tong Wu Liming Ou School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

Medium-entropy oxides(MEOs)with broad compositional tunability and entropy-driven structural stability,are receiving booming attention as a promising candidate for oxygen evolution reaction(OER)***,ultrathin two-dimensional(2D)nanostructure offers extremely large specific surface area and is therefore considered to be an ideal catalyst ***,it remains a grant challenge to synthesize ultrathin 2D MEOs due to distinct nucleation and growth kinetics of constituent multimetallic elements in 2D anisotropic *** this work,an ultrathin 2D MEO(MnFeCoNi)O was successfully synthesized by a facile and low-temperature ionic layer epitaxy *** from multi-metal synergistic effects within ultrathin 2D nanostructure,this 2D MEO(MnFeCoNi)O revealed excellent OER electrocatalytic performance with a quite low overpotential of 117 mV at 10 mA·cm^(-2) and an impressive stability for 120 h continuous operation with only 6.9%***,the extremely high mass activity(5584.3 A·g^(-1))was three orders of magnitude higher than benchmark RuO_(2)(3.4 A·g^(-1))at the same overpotential of 117 *** work opens up a new avenue for developing highly efficient and stable electrocatalysts by creating 2D nanostructured MEOs.

关键词： medium-entropy oxide two-dimensional nanomaterials ionic layer epitaxy oxygen evolution reaction electrocatalysis

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Multimode Design and Analysis of an Integrated Leg-Arm Quadruped Robot with Deployable Characteristics

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Chinese Journal of mechanical engineering 2024年第3期37卷 41-61页

作者： Fuqun Zhao Yifan Wu Xinhua Yang Xilun Ding Kun Xu Sheng Guo Xiaodong Jin School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

To improve locomotion and operation integration, this paper presents an integrated leg-arm quadruped robot(ILQR) that has a reconfigurable joint. First, the reconfigurable joint is designed and assembled at the end of the legarm chain. When the robot performs a task, reconfigurable configuration and mode switching can be achieved using this joint. In contrast from traditional quadruped robots, this robot can stack in a designated area to optimize the occupied volume in a nonworking state. Kinematics modeling and dynamics modeling are established to evaluate the mechanical properties for multiple modes. All working modes of the robot are classified, which can be defined as deployable mode, locomotion mode and operation mode. Based on the stability margin and mechanical modeling, switching analysis and evaluation between each mode is carried out. Finally, the prototype experimental results verify the function realization and switching stability of multimode and provide a design method to integrate and perform multimode for quadruped robots with deployable characteristics.

关键词： Quadruped robot Multimode design Mode switching Locomotion Operation

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Effects of ignition voltage and electrode structure on electric ignition and combustion characteristics of Ammonium Dinitramide(ADN)-based liquid propellants in electric ignition mode in inert gas environment

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Chinese Journal of Aeronautics 2024年第4期37卷 229-242页

作者： Lei LI Guoxiu LI Hongmeng LI Zhaopu YAO Tao ZHANG Jinze WU Shuo ZHANG School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing Institute of Control Engineering Beijing 100190China

Hydrazine is toxic and carcinogenic, which greatly increases the difficulty of application and no longer meets the needs of green aerospace. As a green propellant, the Ammonium Dinitramide(ADN)-based liquid propellant has the advantages of higher specific impulse, being non-toxic,pollution-free, and easy storage. However, an ADN-based space engine in orbit has exposed the problems of high-temperature deactivation of catalysts and cold-start failure. An active ignition technology—electric ignition technology was explored in this paper to break through the technical bottleneck of catalyst deactivation and the inability to a cold start. An experimental system of a constant-volume combustor for the ADN-based liquid propellant based on the electric ignition method was established. The electric ignition and combustion characteristics of the ADN-based liquid propellant in a volume combustor with an electric ignition method were studied. The influencing mechanisms of the ignition voltage and the electrode structure on the electric ignition characteristics of the ADN-based liquid propellant were investigated. An elevation of the ignition voltage could facilitate the ignition process of the ADN-based liquid propellant, curtail electric energy input and heating effect, while exerting an adverse impact on the combustion process of the *** increase in the ignition voltage enhanced the ignition process of the propellant while simultaneously suppressing its combustion process when utilizing mesh electrodes. Compared to the strip electrodes, the mesh electrodes increased the contact area between the electrodes and the propellant,increased the electric energy input power in the electric ignition process, and reduced the ignition delay time. The mesh electrodes could promote the combustion process of the propellant to a certain extent.

关键词： ADN-based liquid propellant Resistive ignition Electrical ignition characteristic Combustion Inert gas

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Low-temperature chemistry in plasma-driven ammonia oxidative pyrolysis

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Green Energy & Environment 2024年第9期9卷 1477-1488页

作者： Mingming Zhang Qi Chen Guangzhao Zhou Jintao Sun He Lin School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China

Ammonia is gaining increasing attention as a green alternative fuel for achieving large-scale carbon emission reduction. Despite its potential technical prospects, the harsh ignition conditions and slow flame propagation speed of ammonia pose significant challenges to its application in engines. Non-equilibrium plasma has been identified as a promising method, but current research on plasma-enhanced ammonia combustion is limited and primarily focuses on ignition characteristics revealed by kinetic models. In this study, low-temperature and low-pressure chemistry in plasma-assisted ammonia oxidative pyrolysis is investigated by integrated studies of steady-state GC measurements and mathematical simulation. The detailed kinetic mechanism of NH_(3) decomposition in plasma-driven Ar/NH_(3) and Ar/NH_(3)/O_(2) mixtures has been developed. The numerical model has good agreements with the experimental measurements in NH_(3)/O_(2) consumption and N_(2)/H_(2) generation, which demonstrates the rationality of modelling. Based on the modelling results, species density profiles, path flux and sensitivity analysis for the key plasmaproduced species such as NH_(2), NH, H_(2), OH, H, O, O(^(1)D), O_(2)(a^(1)△_(g)), O_(2)(b^(1)∑_(g)^(+)), Ar^(*), H^(-), Ar^(+), NH_(3)^(+), O_(2)^(-) in the discharge and afterglow are analyzed in detail to illustrate the effectiveness of the active species on NH_(3) excitation and decomposition at low temperature and relatively higher E/N values. The results revealed that NH_(2), NH, H as well as H_(2) are primarily generated through the electron collision reactions e + NH_(3)→ e + NH_(2)+ H, e + NH_(3)→ e + NH + H_(2) and the excited-argon collision reaction Ar^(*) + NH_(3)+ H → Ar + NH_(2)+ 2H, which will then react with highly reactive oxidative species such as O_(2)^(*), O^(*), O, OH, and O_(2) to produce stable products of NOx and H_(2)O. NH_(3)→ NH is found a specific pathway for NH_(3) consumption with plasma assistance, which further highlig

关键词： Non-equilibrium plasma Ammonia fuel Oxidative pyrolysis Pathway flux analysis Sensitivity analysis

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F-doping effects on microstructure and electrochemical performance of cathode material Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)

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Particuology 2024年第12期95卷 82-91页

作者： Xiaoqian Sun Yunhui Du Weiyi Zhang Mengjiao Jin Ruiang Fan Peng Zhang School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing10004China School of Department of Mechanical Engineering Stanford UniversityStanfordCA94305United States

Lithium-rich manganese-based(Li-rich Mn-based)cathode materials possess high specific capacity,low self-discharge rate and steady working voltage,but cycle performance and rate performance need to be further *** this study,cathode materials Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2-x)F_(x)(x=0,0.02,0.05,0.08)are synthesized by the co-precipitation method with the two-step calcination *** the F-doping effects on the microstructure and the electrochemical performance are investigated in the cathode materials Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2).The results indicate that among all the F-doped cathode materials,the crystal lattice parameters are increased,order degree and stability of the layered structure are *** for x=0.05,cathode material Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(1.95)F_(0.05)(LMO-F_(0.05))shows the best cycle performance and rate performance with its capacity retention rate 87.7%after 100 cycles at 0.2 C and discharge capacity 117 mAh g−1 at 5 C high *** can be seen that F doping is a simple and crucial strategy to promote the Li ion diffusion and develop high performance layered cathode materials.

关键词： F-doped Li-rich Mn-Based cathode material Microstructure Cycling performance Rate performance

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Topological Structure Design and Obstacle-climbing Capability Analysis of a Lizard-inspired Torso-leg-foot Biomimetic Robot

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Journal of Bionic engineering 2025年第1期22卷 65-82页

作者： Yuting Du Yan-an Yao Qiang Ruan Wenbo Mi School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China Beijing Institute of Aerospace Control Devices Beijing100039China

Lizards are one of the most primitive reptiles in existence,with special limb structures that enable them to move quickly across diverse and complex terrains such as rock piles,shallow shoals,and deserts.A thorough exploration was conducted on the biomimetic mechanism and ground-touching mechanism of lizard limbs from both micro and macro *** by the intricate torso and limb configurations of lizards,a novel Torso-leg-foot biomimetic robot has been conceptualized based on the design of the Big-Foot *** robot integrates a Torso-leg-foot system,featuring a parallel torso biomimetic structure with a 2-SPR/UPU/UPR(P)*** utilizes the theory of finite screws to articulate the instantaneous movements of the parallel torso,and the inverse kinematics of this mechanism have been *** reachable workspace of the 2-SPR/UPU/UPR parallel mechanism using FIS theory,which is closely related to the climbing height of the robot.A comprehensive dimension synthesis was conducted on the leg-foot system,and the adoption of the three-pair rod drive method was determined by investigating its Variable Rotating Velocity Characteristics(VRVC).Simulation tests have shown that with an integrated torso,the robot can climb vertical obstacles up to 600 mm in *** experimental tests of climbing steps and slopes using physical prototypes have confirmed the robot's obstacle-crossing *** potential applications of this Torso-leg-foot biomimetic robot is to carry heavy objects across obstacles to perform tasks such as planetary exploration and disaster relief.

关键词： Torso-leg-foot Lizard biomimetics Topological structure Variable Rotating Velocity Characteristics(VRVC) Obstacle-climbing capability

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Design and Analysis of a Bimanual Parallel Dexterous Hand with Cooperative Manipulation Capability

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Journal of Mechanisms and Robotics 2025年第6期17卷 061014页

作者： Xu, Donglai Guo, Sheng Zhao, Fuqun Jin, Xiaodong School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing100044 China

A bimanual parallel dexterous hand with cooperative manipulation capability is proposed to solve the problem that one hand cannot achieve continuous in-hand manipulation. The bimanual parallel dexterous hand is composed of two parts: the inner ring fingers and the outer ring fingers. It is possible not only to perform a 6-degree-of-freedom manipulation with the inner ring fingers or six fingers but also to cooperate with the inner ring fingers and the outer ring fingers to achieve in-hand manipulation. Firstly, the inverse kinematics of the dexterous hand is analyzed and the velocity Jacobian matrices are established. Then, the workspace, dexterity, and stiffness of the dexterous hand during the inner ring finger manipulation and the six finger manipulation are analyzed and compared. Finally, a prototype of the dexterous hand is constructed and its performance is tested. It proves that continuous manipulation and assembly tasks can be achieved through the cooperation of the bimanual dexterous hand. At the same time, the workspaces of the dexterous hand manipulating objects of six different shapes are measured to demonstrate the in-hand manipulation capability. The proposed bimanual parallel dexterous hand provides a feasible reference scheme for the development and application of cooperative manipulation of dexterous hands with multiple fingers. Copyright © 2025 by ASME.

关键词： Inverse kinematics

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A novel approach for the composition design of high-entropy fluorite oxides with low thermal conductivity

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Journal of Advanced Ceramics 2024年第9期13卷 1369-1381页

作者： Guangjin Chen Cuiwei Li Huaiming Jia Yuwei Zhang Bo Gong Xue Li Tianyu Liu Kepi Chen School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China

High-entropy fluorite oxides(HEFOs)show significant potential for thermal protection applications due to their advantageous combination of low thermal conductivity and high Yong’s ***,the factors influencing its formation have not been well studied,and a systematic method for compositional design has not yet been *** this paper,the effects of oxygen vacancy concentration(O_(vac))and mean cation radius(r¯)on formability of HEFOs were investigated to develop a compositional design *** results indicate that an appropriate r¯and Ovac is crucial for promoting the formability of single-phase(Ca_(x)Ce_(y1)Zr_(y2)Hf_(z)Sn_(z)Ti_(z))O_(2−δ)*** mass/size disorder and an appropriate Ovac(10%)result in(Ca_(0.2)Ce_(0.1)4Zr_(0.1)2Hf_(0.18)Sn_(0.18)Ti_(0.18))O_(2−δ)exhibiting the lowest thermal conductivity of 1.24 W·m^(−1)·K^(−1).Building upon these insights and employing a valence combination strategy,three new single-phase HEFOs with low thermal conductivity were successfully designed and synthesized,namely,(La_(0.28)Y_(0.28)Ce_(0.18)Zr_(0.18)W_(0.08))O_(2−δ),(La_(_(0.3))Y_(_(0.3))Ce_(0.2)Nb_(0.1)Ta_(0.1))O_(2−δ),and(Yb_(0.52)Ce_(0.12)Zr_(0.12)Sn_(0.12)Nb_(0.12))O_(2−δ).This design approach will provide a valuable reference for the design of other high-entropy oxides.

关键词： composition design high-entropy fluorite oxides oxygen vacancy phonon scattering thermal conductivity

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Ammonia pyrolysis oxidation excited by nanosecond pulsed discharge:Global/fluid models hybrid solution

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Journal of Energy Chemistry 2025年第1期100卷 385-396页

作者： Mingming Zhang Hanyu Wu Qi Chen Jiaxin Yang Bonan Liu School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China China University of Petroleum Beijing 102299China

The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution ***,the stable products of plasma-assisted oxidative pyrolysis of ammonia are *** results show that the consumption of NH_(3)/O_(2)and the production of N_(2)/H_(2)change linearly with the increase of voltage,which indicates the decoupling of nonequilibrium molecular excitation and oxidative pyrolysis of ammonia at low ***,the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is *** on the reaction path analysis,the simplified mechanism is *** detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified ***,based on the simplified mechanism,the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key *** results show that the generation,development,and propagation of the pre-sheath have a great influence on the formation and consumption of *** consumption of NH_(3)by the cathode pre-sheath is greater than that by the anode pre-sheath,but the opposite is true for OH and O(1S).However,within the sheath,almost all reactions do not ***,by changing the parameters of nanosecond pulse power supply voltage,it is found that the electron number density,electron current density,and applied peak voltages are not the direct reasons for the structural changes of the sheath and ***,the discharge interval has little effect on the sheath structure and gas mixture *** research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also hel

关键词： Nanosecond pulsed discharge Ammonia Oxidative pyrolysis Fluid model Global model

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Development and performance analysis of water electrolysis propulsion system with microwave igniter

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International Journal of Hydrogen Energy 2025年 136卷 1185-1197页

作者： Liu, Xiaodan Yu, Yusong Chen, Jun Zhang, Shurui Zhang, Shaoyun Mou, Yue School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing100044 China Beijing Institute of Control Engineering Beijing100190 China

The water propulsion system offers advantages such as high performance, low toxicity, low manufacturing costs, and ease of integration with other propulsion systems. The microwave ignition technology provides benefits including high ignition energy, faster combustion speeds, and better control. This study develops a water electrolysis chemical propulsion system based on microwave ignition technology, combining the strengths of both water electrolysis propulsion and microwave ignition. It addresses the needs for high thrust and specific impulse while eliminating the catalytic bed design to avoid issues related to catalyst lifespan. The propulsion system we designed consists of a water storage module, a water electrolysis module, a gas supply module, and an ignition module. The thruster utilizing the microwave ignition method has been developed. This study conducts experimental research using this propulsion system at various hydrogen and oxygen mixture ratios. The high-speed camera, spectrometer, and pressure sensors were used to capture images of the flame and quantify information. The results indicate that the combustion of hydrogen and oxygen using the microwave ignition method excites the hydrogen and oxygen atoms to higher energy levels, resulting in different flame colors during the ignition phase due to plasma effects. In the stable combustion phase, the flame at the nozzle exit appears as a bright white conical inner region. As the mixture ratio increases, both the brightness of the flame inner and outer regions intensify, and the length of the outer region significantly increases, accompanied by a noticeable pale blue color. The mixture ratio decreased from 1083 to 694, representing a 36% reduction. More intense combustion was observed, leading to a 6.7% increase in combustion pressure. The spectral intensity increased by 1525.6%, and the velocity at the nozzle exit increased by 3.16%. Furthermore, spectral data reveal the presence of O2, H2, and H2O molecul

关键词： High speed cameras

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