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A Reduced-order Extrapolation Model Based on Proper Orthogonal Decomposition Technique for Rayleigh-Bénard convection

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Journal of Physics: Conference Series 2019年第2期1176卷

作者： Jinghua Yang Dengfeng Lu Zhiguang Deng Xiang Guan Qing Shi Sichuan Electric Power Design & Consulting Co. Ltd Chengdu Sichuan 610041 China National Key Labortory of Science and Technology on Reactor System Design Technology Sichuan 610213 China

In order to quickly calculate the flow characteristics in the simulated two-dimensional Rayleigh-Bénard convection model, a reduced-order extrapolation difference model for solving two-dimensional Rayleigh-Bénard is established based on the Proper Orthogonal Decomposition (POD) method. Firstly, the classical difference format is used to calculate the flow field on the initial time span, the sample data is to construct the POD basis, and the truncation error generated in the process of constructing the POD base is analysed. Then, the two-dimensional reduced-order extrapolation Rayleigh-Bénard model is constructed by combining the SVD and POD methods. By numerical examples, the classical difference model and the reduced-order extrapolation model are numerically simulated under the given initial boundary value. The reliability and effective of the reduced-order method are verified by comparing the flow field temperature cloud maps in the two calculation stages.

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Load-bearing behaviors of sandwich plates with non-uniformly distributed grid cores: Dynamic impact and blast

Research Square

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Research Square 2024年

作者： Wang, Youlong Yang, Haixia Chen, Jie Ma, Quanjin Song, Yiheng Key Laboratory of Concrete and Prestressed Concrete Structures Ministry of Education School of Civil Engineering Southeast University Nanjing211189 China School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen518055 China School of Engineering The University of Tokyo Tokyo113-8656 Japan

Sandwich plates with grid-core structures possess extensive applications, and non-uniform grid plates (NUGPs) show enhanced potential under varied loading modes. The current study embarks on an investigation into NUGPs by adjusting the dimensions of transverse and longitudinal grid walls. This comprehensive analysis explores the dynamic responses of these plates when subjected to impact and blast loads, focusing on deformation patterns, damage, and the underlying processes. The findings are illustrated as follows. 1) NUGPs, specifically those with an optimized configuration of grid walls termed the d2 structure, display improved resistance to blast and impact loads compared to their uniformly distributed grid plate counterparts. Notably, designs featuring a less dense grid in the central area yield a more evenly distributed damage pattern under impact loads and a lesser severity of damage from blast loads. 2) The study also reveals that under impact loads, the sandwich structure showcases distinct behaviors through three stages evident in the load-displacement curves: initial localized indentation, followed by overall deformation, and ending with deformation recovery. 3) Moreover, when facing blast loads, the initial response involves rapid plastic deformation of the upper skin, succeeded by compression and buckling of the core. This sequence effectively dissipates energy, acting as a protective shield for the lower skin. 4) The optimized NUGPs design achieves a perfect balance between stiffness and ductility, reducing displacement through adequate stiffness while ensuring the effective absorption of dynamic forces through significant ductility, thus preventing catastrophic failure. This research significantly advances topology optimization for sandwich plates, providing essential insights for designing lightweight structures resilient under various modes. © 2024, CC BY.

关键词： Stiffness

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Study on Processing Process of SiC Single Crystal Cut with Wire Saw Excited by Ultrasonic

Study on Processing Process of SiC Single Crystal Cut with W...

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International Conference on Mechanical, Control and Computer Engineering (ICMCCE)

作者： Lun Li Shaodong Yang Bofeng Du Shiyu Xu Jishun Li Henan Key Laboratory for Machinery Design and Transmission System Henan University of Science and Technology Luoyang China Zhongqi Changxing (Luoyang) Mechanical and Electrical Equipment Engineering Co. Ltd. Luoyang China Shenzhen Zhaowei Machinery & Electronics Co. Ltd. Shenzhen China

ISBN: (数字)9781728146898

ISBN: (纸本)9781728146904

Owing to high hardness and brittleness, SiC single crystal is the typical difficult-to-machine material. The SiC single crystal workpiece was cut by wire saw excited by transverse ultrasonic, and the cutting process was analyzed in current research. The kinematics equation of ultrasonic excitation wire saw and ordinary wire saw were established, and two different kinematics characteristics were analyzed respectively. The trajectory of abrasive particles in two cutting mode changed fundamentally. The finite element simulation model of single diamond abrasive cutting SiC single crystal was established. The influence of processing parameters on sawing force, surface morphology of SiC single crystal cut with abrasive excited by ultrasonic and ordinary diamond abrasive cutting was analyzed. The results show that sawing force of diamond abrasive excited by ultrasonic is much less than that of ordinary diamond abrasive cutting and the surface morphology is fairly flat. The cutting depth of abrasive has a significant influence on the sawing force and wafer surface.

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Boosting weather forecast via generative superensemble

arXiv

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arXiv 2024年

作者： Nai, Congyi Chen, Xi Yang, Shangshang Liang, Yuan Xiao, Ziniu Pan, Baoxiang Key Laboratory of Earth System Numerical Modeling and Application Institute of Atmospheric Physics Chinese Academy of Science Beijing China Institute of Atmospheric Physics Chinese Academy of Science Beijing China School of Engineering and Design Technical University of Munich Munich Germany Potsdam Institute for Climate Impact Research Potsdam Germany TianJi Weather Science and Technology Company Beijing China

Accurate weather forecasting is essential for socioeconomic activities. While data-driven forecasting demonstrates superior predictive capabilities over traditional Numerical Weather Prediction (NWP) with reduced computational demands, its deterministic nature and limited advantages over physics-based ensemble predictions restrict operational applications. We introduce the generative ensemble prediction system (GenEPS) framework to address these limitations by randomizing and mitigating both random errors and systematic biases. GenEPS provides a plug-and-play ensemble forecasting capability for deterministic models to eliminate random errors, while incorporating cross-model integration for cross-model ensembles to address systematic biases. The framework culminates in a superensemble approach utilizing all available data-driven models to further minimize systematic biases. GenEPS achieves an Anomaly Correlation Coefficient (ACC) of 0.679 for 500hPa geopotential (Z500), exceeding the ECMWF Ensemble Prediction system’s (ENS) ACC of 0.646. Integration of the ECMWF ensemble mean further improves the ACC to 0.683. The framework also enhances extreme event representation and produces energy spectra more consistent with ERA5 reanalysis. GenEPS establishes a new paradigm in ensemble forecasting by enabling the integration of multiple data-driven models into a high-performing super-ensemble system. © 2024, CC BY-NC-SA.

关键词： Prediction models

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Information Freshness in A Dual Monitoring system

Information Freshness in A Dual Monitoring System

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GLOBECOM 2022 - 2022 IEEE Global Communications Conference

作者： Dapeng Deng Zhengchuan Chen Howard H. Yang Nikolaos Pappas Limei Hu Min Wang Yunjian Jia Tony Q.S. Quek School of Microelectronics and Communication Engineering Chongqing University Chongqing China National Mobile Communications Research Laboratory Southeast University Nanjing China Zhejiang University/University of Illinois at Urbana-Champaign Institute Zhejiang University Haining China Department of Computer and Information Science Linkoping University Linkoping Sweden School of Optoelectronics Engineering Chongqing University of Posts and Telecommunications Chongqing China Information System Technology and Design Pillar Singapore University of Technology and Design Singapore

ISBN: (纸本)9781665435413

We study the average age of information (AoI) and peak AoI (PAoI) of a dual-queue status update system that monitors a common stochastic process. We capture the state transition characteristics of the considered system by establishing a Markov chain. Using the state flow graph analysis method, we derive closed-form expressions of the average peak age of information (PAoI) and the average age of information (AoI) for the dual-queue update system. The numerical results show that compared with the single-queue update system, the average PAoI of the dual-queue update system is reduced by 33.5% and the average AoI dropped by 37.5%.

关键词： Closed-form solutions Markov processes Reliability theory Information age Sensor systems Real-time systems Sensors

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Investigation of Heat Transfer and Flow Boiling Characteristics of a New Symmetric Cosine Mini-Channel Heat Exchanger with High Heat Flow Density

SSRN

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SSRN 2023年

作者： Xu, Zhanying Liu, Huan-Ling Xie, Gongnan Shaanxi Key Laboratory of Space Solar Power Station System School of Electromechanical Engineering Xidian University Xi’an710071 China Key Laboratory of Electronic Equipment Structure Design Ministry of Education School of Electromechanical Engineering Xidian University Xi’an710071 China School of Marine Science and Technology Northwestern Polytechnical University Xi’an710072 China

A novel symmetric cosωx mini-channel heat exchanger (SCMC) with a combined bionic leaf vein diverter with ethanol as coolant is designed to meet the heat dissipation requirements for high heat flux chips. The mini-channel is firstly passed through a bionic leaf vein diverter to ensure the uniformity of the liquid distribution in the different mini-channels. Firstly, the homogeneity of the liquid distribution in different mini-channels is ensured by a bionic leaf vein divertor. Then, in order to obtain the flow characteristics and bubble features in the channel under conjugate conditions, a systematic three-dimensional numerical study is carried out by coupling the phase transition model with the volume of fluid (VOF) model. It is found that the symmetric distribution structure of the SCMC flow channel not only provides nucleation points for bubble generation, but also provides rupture points for large bubbles that can block the flow channel due to bubble aggregation, which reduces the instability of phase transition heat. Compared with the smooth flow channel structure of ω=1 and ω=1.5, the steep structure of ω=2 not only helps the mixing of coolant, but also increases the probability of bubbles hitting the sharp structure, which is more helpful for the rupture of large bubbles. In addition, the effects of waviness (ω ~ 0-2) and inlet velocity (Re ~ 234.07-1170.37) on the heat transfer performance under non-constant flow boiling conditions are investigated. The results show that the heat transfer capacity of SCMC increases firstly and then decreases with the increase of ω and subsequently increases again with the constant Re. The performance factor shows a decrease and then increases, which gets the maximum value at ω=2 and still shows an increasing trend. In the case of constant ω, the heat transfer capacity of SCMC is enhanced with the increase of Re, but the enhancement trend gradually slows down, and the performance factor shows a trend of increasing at first an

关键词： Heat exchangers

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Erratum to: The formation mechanism of aqueous hydrogen peroxide in a plasma-liquid system with liquid as the anode

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The European Physical Journal D 2020年第7期74卷 1-2页

作者： Lin, Jiao He, Xinyi Chen, Qiang Xiong, Qing Li, Junshuai Wang, Xin Chen, Guolong Liu, Qing Huo Ostrikov, Kostya (Ken) Institute of Electromagnetics and Acoustics Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance Department of Electronic Science Xiamen University Xiamen P.R. China State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing P.R. China Key Laboratory of Special Function Materials & Structure Design of the Ministry of Education School of Physical Science & Technology Lanzhou University Lanzhou P.R. China Department of Electrical and Computer Engineering Duke University Durham USA Institute for Future Environments and School of Chemistry Physics and Mechanical Engineering Queensland University of Technology Brisbane Australia CSIRO-QUT Joint Sustainable Processes and Devices Laboratory Commonwealth Scientific and Industrial Research Organization Lindfield Australia

We find that we made a mistake in the estimation of the H2O2 concentration by the colorimetric method in our previous paper (J. Lin et al., Eur. Phys. J. D (2020) 74: 80) [1].

关键词： Atomic and Molecular Collisions

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design of a new solution for the wheeled hopping robot

Design of a new solution for the wheeled hopping robot

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UKACC International Conference on Control (CONTROL)

作者： Jingjing Liu Hongbo Wang Hongnian Yu Lili Zhang Luige Vladareanu Adrian Bruja Gal I. Alexandru Parallel Robot and Mechatronic System Laboratory of Hebei Province Key Laboratory of Advanced Forging & Stamping Technology and Science of Ministry of Education Yanshan University Qinhuangdao China College of Electrical Engineering Yanshan University Qinhuangdao China School of Design Engineering and Computing Bournemouth University Poole UK Robotics and Mechatronic Department Institute of Solid Mechanics Bucharest Romania

In recent years many researchers are trying to combine wheeled movement with legged movement or hopping movement to strengthen the robots adaptability to environment. Hybrid robots are playing a more and more important role in our modern life. However, their controls are mostly complicated. So in this paper we present a new solution for the wheeled hopping robot. Based on the mechanical design, this robot has two movement modes: wheeled and hopping movement mode. While the center of gravity of the mechanism is under the wheels center, the wheeled hopping robot which is like a tumbler can keep its stability even when the wheels' velocity is zero. In this paper, we firstly introduce the description and design of the wheeled hopping robot. Then we explain how to choose the robot parameters and lastly we describe, how the robot through hopping, successfully traverses obstacles and ditches.

关键词： Mobile robots Shafts Wheels Springs Robot kinematics Force

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Investigations on the Two-Phase Flow and Heat Transfer Behaviors in a Central Uniform Dispersion-Type Heat Exchanger

SSRN

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SSRN 2022年

作者： Guo, Qi Liu, Huan-Ling Xie, Gongnan Guo, Chao Shao, Xiao-Dong Shaanxi Key Laboratory of Space Solar Power Station System School of Electromechanical Engineering Xidian University Xi'An710071 China Key Laboratory of Electronic Equipment Structure Design Ministry of Education School of Electromechanical Engineering Xidian University Xi'An710071 China School of Marine Science and Technology Northwestern Polytechnical University Xi’an710072 China

In order to improve the temperature uniformity of multiple chips, a central uniform distributed heat exchanger (CUD) is designed. Firstly, using ethanol solution as coolant, the cooling ability of the heat exchanger is numerically investigated by using VOF gas-liquid two-phase flow model, and the two-phase flow experimental system is established to verify the correctness of the numerical results. The results verifies the accuracy of the numerical simulation method. Secondly, the two-phase flow boiling heat transfer behavior are compared with that of single-phase flow with water as coolant. The results show that with the increase of inlet flow, the thermal resistance and average temperature of two-phase flow change less than that of single-phase flow. This indicating that two-phase flow has better advantages in improving the temperature uniformity of multiple heat sources. Thirdly, the heat transfer characteristics of radiators with different Wi are studied. Finally, the prediction functions of the boiling heat transfer coefficient and pressure drop is established, and the multi-objective genetic algorithm is used to obtain the best parameters of this heat exchanger.. Furthermore, the heat dissipation of the optimized heat exchanger design is studied numerically. The simulated results are in good agreement with the optimization results. © 2022, The Authors. All rights reserved.

关键词： Two phase flow

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Distilling Autoregressive Models to Obtain High-Performance Non-Autoregressive Solvers for Vehicle Routing Problems with Faster Inference Speed

arXiv

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arXiv 2023年

作者： Xiao, Yubin Wang, Di Li, Boyang Wang, Mingzhao Wu, Xuan Zhou, Changliang Zhou, You Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education College of Computer Science and Technology Jilin University China Joint NTU-UBC Research Centre of Excellence in Active Living for the Elderly Nanyang Technological University Singapore WeBank-NTU Joint Research Institute on Fintech Nanyang Technological University Singapore School of Computer Science and Engineering Nanyang Technological University Singapore School of System Design and Intelligent Manufacturing Southern University of Science and Technology China

Neural construction models have shown promising performance for Vehicle Routing Problems (VRPs) by adopting either the Autoregressive (AR) or Non-Autoregressive (NAR) learning approach. While AR models produce high-quality solutions, they generally have a high inference latency due to their sequential generation nature. Conversely, NAR models generate solutions in parallel with a low inference latency but generally exhibit inferior performance. In this paper, we propose a generic Guided Non-Autoregressive Knowledge Distillation (GNARKD) method to obtain high-performance NAR models having a low inference latency. GNARKD removes the constraint of sequential generation in AR models while preserving the learned pivotal components in the network architecture to obtain the corresponding NAR models through knowledge distillation. We evaluate GNARKD by applying it to three widely adopted AR models to obtain NAR VRP solvers for both synthesized and real-world instances. The experimental results demonstrate that GNARKD significantly reduces the inference time (4∼5× faster) with acceptable performance drop (2∼3%). To the best of our knowledge, this study is first-of-its-kind to obtain NAR VRP solvers from AR ones through knowledge distillation. Copyright © 2023, The Authors. All rights reserved.

关键词： Distillation

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