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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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Investigation of turbulent Prt model and the segmentation rule for LBE turbulent heat transfer 18

Investigation of turbulent Prt model and the segmentation ru...

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18th International Topical Meeting on Nuclear reactor Thermal Hydraulics, NURETH 2019

作者： Li, Peiying Yu, Hongxing Li, Meifu Du, Sijia Yan, Mingyu Liu, Yu Zhu, Dahuan Zhang, He Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

With liquid metal like lead-bismuth alloy(LBE) acting as a coolant for nuclear reactors, it is necessary to use a more accurate heat transfer relationship and a more reliable Prt model for the low Pr fluid. Because of the low Pr of liquid metal, the thermal conductivity is more dominant than the momentum transfer, which is quite different from ordinary fluids. In this case, the turbulent Prt can better reflect the heat transfer process. In this study, the Prt=A1+A2/Pr form is selected, and the corresponding coefficients are obtained by the renormalization group analysis method, then corrected by Pr. Furthermore, the applicable range and segmentation rule of the turbulent Prt model are discussed, and the obtained Prt segmentation theoretical model is written into CFD. The result shows that, compared with the previously unmodified model, the radial temperature distribution and Nusselt number (Nu) of the annular and bundle channel obtained by RANS method with the improved Prt model is in good agreement with experimental r esults, and the deviations are within 5%. It is proved that the turbulent Prt segmentation theoretical model proposed in this study is effective and can represent the heat transfer characteristics of liquid metal from the mechanism. © 2019 American Nuclear Society. All rights reserved.

关键词： Liquid metals

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Network Learning from Best-Response Dynamics in LQ Games

Network Learning from Best-Response Dynamics in LQ Games

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American Control Conference (ACC)

作者： Yijun Chen Kemi Ding Guodong Shi Australian Centre for Field Robotics the University of Sydney Sydney Australia School of System Design and Intelligent Manufacturing Shenzhen Key Laboratory of Biomimetic Robotics and Intelligent Systems and the Guangdong Provincial Key Laboratory of Human-Augmentation and Rehabilitation Robotics in Universities Southern University of Science and Technology Shenzhen China

In this paper, we focus on network structure inference problem for linear-quadratic (LQ) games from best-response dynamics. An adversary is considered to have no knowledge of the game network structure but have the ability to observe all players’ best-response actions and manipulate some players’ actions. This work presents a comprehensive framework for network learning from best-response dynamics in LQ games. First of all, we establish theoretic results that characterize network structure identifiability and provide numerical examples to demonstrate the usefulness of our theoretic results. Next, in the face of the inherent stability and sparsity constraints for the game network structure, we propose an information-theoretic stable and sparse system identification algorithm for learning the network structure. Finally, the effectiveness of the proposed learning algorithm is tested. The connection between network structure inference problem and classical system identification theory is covered by our work, which advances the literature.

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Spatial Heterogeneity of Point Defect Properties in Refractory Multi-Principal Element Alloy with Short-Range Order: A First-Principles Study

SSRN

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SSRN 2022年

作者： Shi, Tan Lyu, Sixin Su, Zhengxiong Wang, Yunpeng Qiu, Xi Sun, Dan Xin, Yong Li, Wenjie Cao, Jiang Peng, Qing Li, Yuanming Lu, Chenyang School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China Nuclear Power Institute of China Chengdu610213 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610213 China School of Electronic and Optical Engineering Nanjing University of Science and Technology Nanjing210094 China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing100190 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The short-range order is inherently present in the multi-principal element alloys and has a profound impact on the defect behaviour. The effect of short-range order on vacancy and interstitial formation and migration was studied in body-centered cubic multi-principal element alloy NbZrTi by first-principles calculations. Two short-range order structures created by density functional theory and Monte Carlo method at 500 K and 800 K were compared with the random solid solution structure. Both vacancy and interstitial formation energies increase with the degree of short-range order. Point defect formation energies tend to be higher in region enriched in Nb and lower in region enriched in Zr and Ti. Both vacancies and interstitials prefer to migrate towards Zr,Ti-rich regions and away from Nb-rich regions, suggesting that Zr,Ti-rich region can act as recombination center for point defect annihilation. Compared to the random solid solution, the short-range order increases the spatial heterogeneity of point defect energy landscape. Tuning the degree of short-range order can be a viable strategy to optimize the point defect behaviour to achieve enhanced radiation resistance in multi-principal element alloys. © 2022, The Authors. All rights reserved.

关键词： Monte Carlo methods

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Acoustic indeced vibration research of dryer in steam generator 26

Acoustic indeced vibration research of dryer in steam genera...

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26th International Congress on Sound and Vibration, ICSV 2019

作者： Xianhui, Ye Fengshou, Zhang Fengchun, Cai Wenzheng, Zhang Furui, Xiong Haiyang, Song Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9781999181000

The acoustic induced vibration of dryer (also called secondary separator) in steam generator in nuclear power plants is a concern in recent years. Periodic vibrations of long-term operation can lead to fatigue damage of structural components, posing a safety hazard. In this paper, the finite element analysis model of the dryer structure in steam generator of "Hualong-1" nuclear power plant was established, and the acoustic induced vibration characteristics of the structure were studied. Firstly, the acoustic excitation of the dryer structure was discussed, and the excitation inputs were obtained, including the maximum static pressure and the maximum pressure power spectrum density. Then the finite element model was established by ANSYS and the weak parts of the dryer structure were determined by the vibration characteristics combined with the acoustic excitation characteristics analysis. Finally, the structural strength and fatigue characteristics of the dryer structure under two different inputs of the acoustic load were investigated. The analysis of vibration characteristics shows that the main weak parts of the dryer structure are the vertical partition plate and the perforated plate. The static pressure analysis shows that the stress intensity of the two weak plates is less than the limit. In the study of pressure power spectral density, the maximum dynamic stress intensity and alternating stress of the vertical partition plate and the perforated plate are also less than the limit. The research results indicate that the acoustic induced vibration response of the dryer structure is within the acceptable range © Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.

关键词： Steam generators

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Significant Wave Height Prediction Based on VMD-SA-MLP-BP

Significant Wave Height Prediction Based on VMD-SA-MLP-BP

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Chinese Automation Congress (CAC)

作者： Yining Wu Runfeng Zhang Fang Liu Zhenzhong Liu Jianguo Wu Haonan Dong Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology Yichang Research Institute of Testing Technology Yichang China Tianjin Hanhailanfan Marine Technology Co. Ltd. Tianjin China School of Computer Science and Engineering Tianjin University of Technology Tianjin China

Waves seriously impact port construction, worldwide route planning, military activities, and wave power generation. To improve the accuracy of significant wave height prediction, we proposed a novel prediction method, a multi-layer perceptron combined with a backpropagation adjustment (MLP-BP) prediction model that combines mutation mode decomposition (VMD) and a simulated annealing optimization algorithm (SA). Firstly, we use the variable modulus method to decompose the significant wave height sequence data and transform the wave height sequence into multiple different sub-modes (IMF) to reduce the complexity and non-stationarity of the data. Secondly, the simulated annealing algorithm (SA) is used to optimize the weight and bias of the MLP-BP neural network to find the optimal parameter configuration and improve the performance and generalization ability of the prediction model. Finally, the decomposed sub-modal components of each significant wave height sequence are inserted into the MLP-BP neural network and the predicted values of each element are summed to obtain the final significant wave height prediction. The prediction results of the SSA-MLP-BP, PSO-MLP-BP, SA-MLP-BP, and VMD-SA-MLP-BP were compared and demonstrated that the VMD-SA-MLP-BP model performed best. The MAE, MAPE, MSE, RMSE, and R2 of the prediction evaluation indexes were 0.036 m, 11.7%, 0.004 m 2 , 0.067 m, and 0.983, respectively, which performed well in predicting significant wave height.

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Research on the vibration reduction and sound radiation index properties of the cabin with internal equipment 26

Research on the vibration reduction and sound radiation inde...

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26th International Congress on Sound and Vibration, ICSV 2019

作者： Wenzheng, Zhang Bihao, Wang Xiaozhou, Jiang Bin, Lan Haiyang, Song Fengchun, Cai Xianhui, Ye Jiabin, Feng Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9781999181000

Suitable vibration and noise indices which provide technical direction for vibration and noise reduction, play a very important role in structure analysis and validated test. The contribution of foundation impedance is studied by analyzing the vibration reduction index of a single degree of freedom system. The finite element method (FEM) and boundary element method (BEM) are applied to simulate the vibration and noise indices of a cabin along with internal equipment. The vibration reduction and sound radiation indices of the internal isolator have been calculated to analyze the variation trend with frequency. The results indicate that the difference between vibration level difference and insert loss is very small in most frequency band. Interestingly, the power flow difference and radiated sound power are opposite in phase in middle and high frequency band, which have been proved to be appropriate elements to evaluate the vibration and noise indices of the cabin. The analysis method and procedure can be used to objectively evaluate the vibration reduction property of similar vibration isolators © Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.

关键词： Finite element method

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Effects of core peripheral components melting on corium pool configuration in lower plenum of ACP1000 27

Effects of core peripheral components melting on corium pool...

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27th International Conference on Nuclear Engineering: Nuclear Power Saves the World!, ICONE 2019

作者： Chen, Liang Yu, Hongxing Liu, Lili Dong, Huaping Deng, Jian Zhang, Hang Hou, Liqiang Wang, Xiaoji Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9784888983051

The MAAP5 code and CFD method are adopted to estimate the melting behavior of core peripheral components for an Advanced China PWR, called ACP1000 after a large break accident to determine the amount of stainless steel relocating into the corium pool. The results suggest that larger portion of peripheral components melting in CFD method because of considering the radiation of fuel rods on shroud and barrel before core melting and ignoring the cooling of steam on the components in core. Effects of different configurations of corium pool on heat flux imposed on the vessel wall are also investigated in this work. The heat flux in light metal layer for the corium pool that obtained by MAAP5 code could be higher than that of CFD case due to its thinner light metal layer. Copyright © 2018-2019 by JSME

关键词： Heat flux

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An Event-Triggered Adaptive Dynamic Programming Method for Large-Scale HVAC systems*

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IFAC-PapersOnLine 2023年第2期56卷 5281-5286页

作者： Shan Xue Zhiwen Chen Derong Liu Chao Shangt Hongtian Chen School of Computer Science and Engineering South China University of Technology Guangzhou 510006 China School of Automation Central South University Changsha 410083 China Peng Cheng Laboratory Shenzhen 518000 China School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen 518005 China Department of Automation BNRist Tsinghua University Beijing 100084 China Department of Automation Shanghai Jiao Tong University Shanghai 200240 China

In this paper, an event-triggered adaptive dynamic programming (ADP) algorithm is developed for the temperature control of large-scale heating, ventilation, and air conditioning (HVAC) systems. First, the dynamic model of the system is established by using the conservation of mass and energy, which involves the dynamics of the fan and the cooling coil. Second, the multi-zone temperature control problem is treated as a non-zero-sum game, which requires solving the coupled Hamilton-Jacobian (HJ) equations. Then, the ADP algorithm is employed to solve the HJ equation. Importantly, in order to reduce the network transmission burden of large-scale HVAC systems, the ADP algorithm developed in this paper is based on event-triggering mechanism. Theoretical analysis proves that the tracking error and the neural network weight estimation error are uniformly ultimately bounded. Simulation results verify the effectiveness of the algorithm.

关键词： adaptive dynamic programming optimal control event-triggering mechanism neural networks heating, ventilation, and air conditioning

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A new turbulent Prandtl number model for forced fully-developed pipe heat transfer of liquid metals 27

A new turbulent Prandtl number model for forced fully-develo...

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27th International Conference on Nuclear Engineering: Nuclear Power Saves the World!, ICONE 2019

作者： Peiying, Li Hongxing, Yu Sijia, Du Yaou, Shen Mingyu, Yan Hongsheng, Yuan Yu, Liu Xiaoli, Wu Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu China

ISBN: (纸本)9784888983051

With the proposal of liquid metals as coolant of the reactors, the use of accurate heat transfer correlation and reliable turbulent prandtl number（Prt）model of these low prandtl number fluids in turbulent flow is essential. The heat transfer of Liquid metals differ from traditional coolants for their good molecular heat conductivity and this property leads to a separation of the spatial extension of thermal and viscous boundary layers. A constant turbulent prandtl number is proved to be inappropriate for complex conditions for it depends on the Reynolds and molecular Prandtl number. This paper proposes a new turbulent prandtl number model Prt=C+B/Pet, which can be used for accurately predicting the heat transfer for liquid metal flows. The constants C and B of the expression are obtained from the analytic solution of renormalization group procedure. B is further corrected with the physical properties for different liquid metals. The results are in a good agreement with experimental data over the range of experimentally accessible Prandtl numbers. The Nusselt numbers calculated using the proposed model with the Lyon integral are found to be well consistent with the experimental data for forced fully-developed pipe flows with constant heat flow boundary conditions. Computational fluid dynamics(CFD) analysis is also carried out for pipe geometries. With the proposed model for turbulent prandtl number, CFD codes using RANS approach give similar results for local Nusselt numbers measured in the experiments. Copyright © 2018-2019 by JSME

关键词： Liquid metals

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