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16th Annual Conference of China Electrotechnical Society, ACCES 2021

作者： Zhang, Yun Zheng, Zedong Li, Chi State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

ISBN: (纸本)9789811915314

By replacing multiple two-winding transformers with a multi-winding transformer (MWT) in the isolated DC-DC converter, it can reduce the volume and increase the power density. Due to magnetic coupling in MWT, power will flow between any two windings. The relationship between the leakage inductance of multi-winding, inductance of external inductors and transmission power is studied. The power balance condition about leakage inductance and external inductance is analyzed based on different cascaded DC-DC series-parallel conversion system. The leakage inductance characteristic with different winding arrangement of MWT is analyzed. By choosing and designing appropriate winding arrangement, it can increase the power density and achieve power balancing. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： DC-DC converters

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Machine learning driven rational design of dual atom catalysts on graphene for carbon dioxide electroreduction

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Nano Research 2025年第1期18卷 186-194页

作者： Dongxu Jiao Xinyi Li Mingzi Sun Lin Liu Jinchang Fan Jingxiang Zhao Bolong Huang Xiaoqiang Cui State Key Laboratory of Automotive Simulation and Control School of Materials Science and Engineeringand Key Laboratory of Automobile Materials of MOEJilin UniversityChangchun 130012China Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina College of Chemistry and Chemical Engineering and Key Laboratory of Photonic and Electronic Bandgap MaterialsMinistry of EducationHarbin Normal UniversityHarbin 150025China

The development of high-performance atomiccatalysts for the carbon dioxide reduction reaction(CO_(2)RR)is atime-consuming process due to the complexity of the reactionmechanism and the uncertainty of the active ***,wehave proposed combining density functional theory(DFT)andmachine learning(ML)to investigate the potential of topologicalgraphene-based dual-atom catalysts(DACs)as CO_(2)*** analyzing the ML results,we identify thenumber of d-orbital electrons in the active site as a key factorinfluencing the CO_(2)RR catalytic ***,wepropose a simple descriptor to measure the CO_(2)RR activity ofthese *** findings provide plausible explanations for thesynergistic interactions between bimetallic atoms in CO_(2)RR andallow us to screen the homogeneous Ni-Ni pair as the mostpromising dual-atom *** work offers a fast MLapproach based on limited DFT calculations to predict the mostelectroactive and stable DACs on carbon support for CO_(2)RR,facilitating rapid screening of high-performance dual-atomcatalysts.

关键词： CO_(2)reaction reduction dual-atom catalysts density functional theory machine learning

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Enhancing ozone catalytic decomposition through acid treatment ofα-MnO_(2) for improved activity and humidity resistance

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Journal of Environmental Sciences 2025年第3期149卷 35-45页

作者： Shangchao Xiong Kai Zhang Zhenghao Xu Hongjun Ou Yuanyuan Zheng Xi Li Yue Peng Xubiao Luo Junhua Li School of Life Sciences Jinggangshan UniversityJi’an 343009China Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengdu 610031China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China

Post-etching method using dilute acid solutions is an effective technology to modulate the surface compositions of metal-oxide *** theα-MnO_(2) catalyst treated with 0.1 mol/L nitric acid exhibits higher ozone decomposition activity at high relative humidity than the counterpart treated with acetic *** the increases in surface area and lattice dislocation,the improved activity can be due to relatively higher Mn valence on the surface and newly-formed Brønsted acid sites adjacent to oxygen *** remnant nitro species deposited on the catalyst by nitric acid treatment is ideal hydrophobic groups at ambient *** decomposition route is also proposed based on the DRIFTS and DFT calculations:ozone is facile to adsorb on the oxygen vacancy,and the protonic H of Brønsted acid sites bonds to the terminal oxygen of ozone to accelerate its cleavage to O_(2),reducing the reaction energy barrier of O_(2) desorption.

关键词： Ozone decomposition α-MnO_(2) Brønsted acid sites H-bonds Post-etching

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Effects of Rectangular Wing Vortex Generators on the Thermal-Hydraulic Performance of Louvered Fin and Flat Tube Heat Exchanger

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Journal of Thermal Science 2023年第2期32卷 628-642页

作者： ZHANG Jinglong HU Xingjun LUO Yufei HUI Zheng WANG Jingyu YU Tianming State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130022China Automobile Research Institute of China Heavy Duty Automobile Group Co.Ltd. Ji'nan 250031China

In this paper,a novel composite heat transfer enhancement technique comprised of louvered fins(LFs)and rectangular wing vortex generators(RWVGs)is proposed to improve the LF side thermal-hydraulic performance of louvered fin and flat tube heat exchangers(LFHEs).After validation of the LF side pressure dropΔP and heat transfer coefficient hLFof the baseline by experiments,the numerical method is applied to investigate the influential mechanisms of the RWVG parameters(the number N(7 to 15),attack angleβ(30°to 90°),height H_(VG)(0.8 mm to 2 mm)and width W_(VG)(0.8 mm to 1.2 mm))on the performance of the LFHE in the velocity range of 3 m/s to 10 m/*** show that thermal-hydraulic performance of the LFHE is significantly impacted by the RWVGs,and according to the performance evaluation criteria(PEC),the LFHE achieves its optimal thermal-hydraulic performance when N=7,β=45°,H_(VG)=1.8 mm and W_(VG)=1 *** to the baseline,the maximum,minimum and average increments of PEC for the optimal case are 13.85%,4.67%and 8.39%,respectively.

关键词： composite heat transfer enhancement louvered fin rectangular wing vortex generator numerical simulations thermal-hydraulic performance

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Attitude control of Active Suspension All-Terrain Vehicle Based on LQR

Attitude Control of Active Suspension All-Terrain Vehicle Ba...

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2023中国汽车工程学会年会暨展览会

作者： Wu Liang Li Shucheng Xu Guangjian Zhang Weizhou Jia Weiwei The State Key Laboratory of Automotive Simulation and Control Jilin University Jilin University of Finance and Economics

ISBN: (纸本)9789819702510

In order to enhance the attitude control ability of all-terrain vehicles in complex terrain,a dual closed-loop control strategy based on LQR controller is designed with series active suspension all-terrain vehicles as the research ***,considering the kinematic and dynamic relationships between each mechanism of the all-terrain vehicle,a vehicle dynamic model based on the speed control of the actuator is constructed on the basis of the traditional active suspension force ***,a terrain estimation algorithm based on all-terrain vehicle model is studied,and a LQR controller suitable for attitude adjustment is ***,three pavement models are established to simulate real road conditions for verifying the accuracy of the dynamic model with terrain estimation model and the effectiveness of attitude *** results show that the collaborative control strategy proposed in this paper has good adaptability to working conditions,and the peak and Root mean square values of vertical displacement,pitch angle and roll angle of allterrain vehicle body are reduced by 30%-50%,which can greatly improve the ride comfort and attitude stability of all-terrain vehicle.

关键词： active suspension all-terrain vehicle attitude control LQR

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Vibration Transfer Function of Railway Vehicle system and its Spatial Coherence Under Vertical Track Irregularity Conditions

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Chinese Journal of Mechanical Engineering 2025年第2期38卷 380-399页

作者： Peng Lu Xi Wang Yu Hou State Key Laboratory of Advanced Rail Autonomous Operation Beijing Jiaotong University Frontiers Science Center for Smart High-speed Railway System Beijing Jiaotong University School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University

Current research on rail vehicle system vibrations primarily relies on numerical methods, with vibration transfer functions commonly derived through data fitting. However, the physical mechanisms underlying these vibrations are not well understood. To clarify the vibration transfer function and its characteristics, four basic input vectors are defined, and an analytical method is proposed. The vibration transfer functions of the vehicle system are solved, and their spatial coherence is analyzed. The results show that there are two spatial scales and four coherent modes in the vehicle system. The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence. Four coherent modes are involved in wheel-rail force and primary suspension force; two coherent modes are involved in bogie vertical motion; and their dominant modes vary with the input frequency. On the other hand, the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency. This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.

关键词： Dominant mode Spatial coherence Transfer matrix method Vertical track irregularity Vibration transfer function

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A Simple Open-loop Soft Startup Method Based on Operation Mode Analysis for LCC Converters Used in High-voltage DC Power Supply 10

A Simple Open-loop Soft Startup Method Based on Operation Mo...

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10th IEEE International Power Electronics and Motion control Conference, IPEMC 2024 ECCE Asia

作者： Zhang, Kai Liu, Hanyu Sun, Kai Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering China

ISBN: (纸本)9798350351330

LCC converters incorporate the stray parameters of high frequency transformer and are commonly employed as the initial stage of high-voltage DC power supplies, enhancing both efficiency and power density. However, the significant overshoot that occurs during the startup phase of high-voltage DC power supply poses considerable difficulties for the circuit. In this article, a simple open-loop soft startup control method is proposed: First, the operation mode analysis method is used to accurately solve the time-domain model of the LCC converter under different duty cycles in continuous current mode (CCM). Second, an open-loop variable duty cycle soft startup control strategy from the energy transmitted view is derived. Finally, soft startup process corresponding to different startup time requirements are verified on a 200V/20kV experimental prototype. © 2024 IEEE.

关键词： Time domain analysis

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A Core Loss Estimation Method Based on Data-driven Technology with Multi-head Attention Mechanism 10

A Core Loss Estimation Method Based on Data-driven Technolog...

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10th IEEE International Power Electronics and Motion control Conference, IPEMC 2024 ECCE Asia

作者： Su, Bowen Sun, Kai Yang, Min Xiao, Yunhao Zhang, Kai Liu, Bo Tsinghua University State Key Laboratory of Power System Operation and Control Department of Electrical Engineering China

ISBN: (纸本)9798350351330

Magnetic components play an important role in power electronic equipment, but there is still lack of accurate magnetic core loss estimation model. The data-driven methods are well-developed in recent years, and they are also more robust and accurate than conventional model-driven methods like Steinmetz Equation (SE) and improved Generalized Steinmetz Equation (iGSE). However, existing data-driven methods often focus on single excitation waveform like sinusoidal excitation waveform, which is not robust enough when facing complex excitation waveform with many high-frequency harmonic waveform. This paper presents a data-driven model based on attention mechanism which can capture the inner relationship within the input excitation waveform to present a more accurate core loss estimation results. And the comparison results with Multi-layer Perceptron (MLP) and Long Short-Term Memory(LSTM) models indicates that the proposed model has much more accuracy when facing complex excitation waveform. The proposed model can help to design magnetic components. © 2024 IEEE.

关键词： Facings

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Methane and nitrous oxide emissions from municipal wastewater treatment plants in China:A plant-level and technology-specific study

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Environmental Science and Ecotechnology 2024年第4期20卷 123-130页

作者： Haiyan Li Liangfang You He Du Bowen Yu Lu Lu Bo Zheng Qiang Zhang Kebin He Nanqi Ren School of Civil and Environmental Engineering Harbin Institute of TechnologyShenzhen518055China Shenzhen Key Laboratory of Ecological Remediation and Carbon Sequestration Institute of Environment and EcologyTsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen518055China Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceTsinghua UniversityBeijing100084China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing100084China

Wastewater treatment is an important source of greenhouse gases(GHGs).Yet large uncertainties remain in the quantification of GHG emissions from municipal wastewater treatment plants(MWWTPs)in China.A high-resolution and technology-specific emission inventory is still lacking to support mitigation strategies of *** we develop a plant-level and technology-based MWWTP emission inventory for China covering 8703 plants and 19 treatment technology categories by compiling and harmonizing the most up-to-date facility-level ***'s methane(CH_(4))and nitrous oxide(N_(2)O)emissions from MWWTPs in 2020 are estimated to be 150.6 Gg and 22.0 Gg,respectively,with the uncertainty range of-30%to 37%and-30%to 26%at 95%confidence *** find an emission inequality across cities,with the richest cities emitting two times more CH_(4)and N_(2)O per capita from municipal wastewater treatment than the poorest *** emitted CH_(4)and N_(2)O are dominated by Anaerobic/Anoxic/Oxic-,Sequencing Batch Reactor-,Oxidation Ditch-,and Anoxic/Oxic-based MWWTPs of less than 20 years *** the relatively young age structure of China's MWWTPs,the committed emissions highlight the importance of reducing on-site GHG emissions by optimization of operating conditions and innovation *** emission differences among our estimates,previous studies,and the Intergovernmental Panel on Climate Change guidelines are largely attributed to the uncertainties in emission factors,implying the urgent need for more plant-integrated measurements to improve the accuracy of emission accounting.

关键词： Methane Nitrous oxide Emissions Municipal wastewater treatment plants

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Numerical investigation of dynamic characteristics of dual throat nozzle and bypass dual throat nozzle in thrust vectoring starting process

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Chinese Journal of Aeronautics 2024年第10期37卷 184-206页

作者： Yuqi ZHANG Jinglei XU Minglei CAO Ruifeng PAN Shuai HUANG Key Laboratory of Inlet and Exhaust System Technology of Ministry of Education Nanjing University of Aeronautics and AstronauticsNanjing 210016China College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China State Key Laboratory of Mechanics and Control of Aeronautics and Astronautics Structures Nanjing 210016China

The Bypass Dual Throat Nozzle(BDTN)is a novel fluidic Thrust Vectoring(TV)nozzle,it switches to TV state by opening the valve in the *** greatly manipulate the BDTN,the dynamic characteristics in the TV starting process should be *** paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of BDTN and Dual Throat Nozzle(DTN).The dynamic responses of TV starting in typical DTN models are investigated at ***,the TV starting processes of BDTN in different Nozzle Pressure Ratio(NPR)conditions are simulated,and the valve opening durations(T)are also *** the expected TV direction is achieved in the DTN,the jet is deflected to the opposite direction at the beginning of the dynamic process,which is called the reverse TV ***,this phenomenon disappears in the *** larger injection width of DTN intensifies unsteady oscillations,and the reverse TV phenomenon is *** the BDTN,T determines the delay degree of performance variations compared to the static results,which is called hysteresis *** NPR=10,the hysteresis affects the final stable performance of *** study analyses the dynamic characteristics in DTN and BDTN,laying a foundation for further design of nozzles and control strategies.

关键词： Dual Throat Nozzle(DTN) Bypass Dual Throat Nozzle(BDTN) Dynamic characteristic Thrust vectoring starting process Cavity vortex Hysteresis effect

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