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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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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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Enhancing deformation characteristics prediction of coarse-grained soils with time-series generative adversarial network-based data augmentation and pre-training

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Frontiers of Structural and Civil Engineering 2025年第3期19卷 396-410页

作者： Ying ZHANG Meng JIA Xuedong ZHANG Liping CAO Ziying AN Hongchao WANG Jinyu WANG School of Control and Computer Engineering North China Electric Power UniversityBeijing 102206China The State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing 100038China

Coarse-grained soils are fundamental to major infrastructures like embankments,roads,and *** their deformation characteristics is essential for ensuring structural *** methods,such as triaxial compression tests and numerical simulations,face challenges like high costs,time consumption,and limited generalizability across different soils and *** address these limitations,this study employs deep learning to predict the volumetric strain of coarse-grained soils as axial strain changes,aiming to obtain the axial strain(ε_(a))-volumetric strain(ε_(v))curve,which helps derive key mechanical parameters like cohesion(c),and elastic modulus(E).However,the limited data from triaxial tests poses challenges for training deep learning *** propose using a Time-series Generative Adversarial Network(TimeGAN)for data ***,we apply feature importance analysis to assess the quality of the numerical augmented data,providing feedback for improving the TimeGAN *** further enhance model performance,we introduce the pre-training strategy to reduce bias between augmented and real *** results demonstrate that our approach effectively predictscurve,with the mean absolute error(MAE)of 0.2219 and the R^(2) of *** analysis aligns with established findings in soil mechanics,underscoring the potential of our method in engineering applications.

关键词： coarse-grained soils deformation characteristics TimeGAN data augmentation pre-training

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Study on Insulation Characteristics of Moisture in the Buffer Layer of 66 kV AC XLPE Cables 19th

Study on Insulation Characteristics of Moisture in the Buffe...

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19th Annual Conference of China Electrotechnical Society, ACCES 2024

作者： Cao, Kangyangyong Xing, Hongquan Huang, Dawei Wei, Zhenhao Liu, Shili State Grid Changchun Power Supply Company Jilin China Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education Northeast Electric Power University Jilin China

ISBN: (纸本)9789819613861

To address the frequent failure issues caused by defects in the buffer layer of high-voltage cross-linked polyethylene (XLPE) cables, research on buffer layer has become a hot topic at present. This paper first introduces the input impedance model of the 66 kV cable buffer layer and the corrugated aluminum sheath. The water content can change its resistance and capacitance, thereby affecting the resistivity and dielectric constant. Secondly, the paper introduces the intrinsic principles of frequency domain dielectric spectroscopy technology, where changes in water content alter the relaxation time of the Debye model, thereby changing the dielectric loss factor. Then, by conducting resistance and capacitance measurement experiments on a 6 cm long cable buffer layer, the paper derives the resistivity and dielectric constant variation curves. Through dielectric loss factor measurement experiments, it derives the dielectric loss factor curve, demonstrating the correlation between water content and the dielectric loss factor. The paper concludes that the dielectric loss factor curve is more sensitive to insulation conditions at low frequencies. © Beijing Paike Culture Commu. Co., Ltd. 2025.

关键词： Dielectric losses

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Capacity Allocation of Hybrid Power system with Hot Dry Rock Geothermal Energy,Thermal Storage,and PV Based on Game Approaches

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Journal of Modern Power systems and Clean Energy 2023年第1期11卷 290-301页

作者： Yang Si Laijun Chen Xuelin Zhang Xiaotao Chen Shengwei Mei Qinghai Key Lab of Efficient Utilization of Clean Energy(Tus-Institute for Renewable Energy) University of QinghaiXining 810016China State Key Laboratory of Control and Simulation of Power System and Power Generation Equipment(Electric Machinery Department Tsinghua University)Beijing 100084China Technical Institute of Physics and Chemistry Beijing 100190China IEEE

This study utilizes hot dry rock(HDR)geothermal energy,which is not affected by climate,to address the capacity allocation of photovoltaic(PV)-storage hybrid power systems(HPSs)in frigid plateau *** study replaces the conventional electrochemical energy storage system with a stable HDR plant assisted by a flexible thermal storage(TS)*** HPS consisting of an HDR plant,a TS plant,and a PV plant is *** approaches are introduced to establish the game pattern model of the proposed HPS as the *** annualized income of each player is used as the payoff ***,non-cooperative game and cooperative game approaches for capacity allocation are proposed according to the interests of each player in the proposed ***,the proposed model and approaches are validated by performing calculations for an HPS in the Gonghe Basin,Qinghai,China as a case *** results show that in the proposed non-cooperative game approach,the players focus only on the individual payoff and neglect the overall system *** proposed cooperative game approach for capacity allocation improves the flexibility of the HPS as well as the payoff of each game ***,the HPS can better satisfy the power fluctuation rate requirements of the grid and increase the equivalent firm capacity(EFC)of PV plants,which in turn indirectly guarantees the reliability of grid operation.

关键词： Capacity allocation equivalent firm capacity game theory hot dry rock hybrid power system

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Study on the Effects of Moisture on Dielectric Loss and Capacitance Parameters of 66 kV AC XLPE Cable Insulation 19th

Study on the Effects of Moisture on Dielectric Loss and Capa...

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19th Annual Conference of China Electrotechnical Society, ACCES 2024

作者： Cao, Kangyangyong Xing, Hongquan Huang, Dawei Zong, Guanbo Liu, Shili State Grid Changchun Power Supply Company Jilin China Key Laboratory of Modern Power System Simulation and Control & Renewable Energy Technology Ministry of Education Northeast Electric Power University Jilin China

ISBN: (纸本)9789819613861

Long-term operation or external forces may cause damage to the outer sheath of the cable, allowing moisture to enter the cable body and affecting the insulation and dielectric performance of the main XLPE insulation of the cable. For 66 kV cables, there are no clear values provided for the changes in the dielectric loss tangent and capacitance after water ingress into the main insulation. Using a self-built experimental platform, dielectric spectroscopy curves were plotted for the main insulation under 1 kV voltage, showing the variation of the dielectric loss tangent with water content and frequency. The unit capacitance changes of the main insulation due to moisture were also measured. The study indicates that at 0.01 Hz, when the water content in the main insulation increases from 0.86% to 1.29%, the dielectric loss tangent value changes by several times. Additionally, this value is not affected by the location of the moisture—whether it is accumulated, evenly distributed, or symmetrically distributed, the dielectric loss tangent remains unchanged. When the volumetric water content increases by 0.48%, the unit capacitance value increases by 0.8%. © Beijing Paike Culture Commu. Co., Ltd. 2025.

关键词： Dielectric losses

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