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arXiv 2024年

作者： Long, Feifei Xia, Xiangze Liu, Jian Liu, Zixi Wu, Xiaodong Wu, Xiaohe Wan, Chenguang Gao, Xiang Li, Guoqiang Luo, Zhengping Qian, Jinping Department of Plasma Physics and Fusion Engineering University of Science and Technology of China Hefei230031 China Advanced Algorithm Joint Lab National Supercomputing Center in Jinan Shandong Jinan250014 China

The accurate construction of tokamak equilibria, which is critical for the effective control and optimization of plasma configurations, depends on the precise distribution of magnetic fields and magnetic fluxes. Equilibrium fitting codes, such as EFIT relying on traditional equilibrium algorithms, require solving the Grad–Shafranov equation by iterations based on the least square method constrained with measured magnetic signals. The iterative methods face numerous challenges and complexities in the pursuit of equilibrium optimization. Furthermore, these methodologies heavily depend on the expertise and practical experience, demanding substantial resource allocation in personnel and time. This paper reconstructs magnetic equilibria for the EAST tokamak based on artificial neural networks through a supervised learning method. We use a fully connected neural network to replace the Grad-Shafranov equation and reconstruct the poloidal magnetic flux distribution by training the model based on EAST datasets. The training set, validation set, and testing set are partitioned randomly from the dataset of poloidal magnetic flux distributions of the EAST experiments in 2016 and 2017 years. The accuracy of reconstructions is evaluated using a variety of indices, such as the mean squared error (MSE), peak signal-to-noise ratio (PSNR), and structural similarity index measure (SSIM), and similarity (S) with Fréchet distance. The feasibility of the neural network model is verified by comparing it to the offline EFIT results. It is found that the neural network algorithm based on the supervised machine learning method can accurately predict the location of different closed magnetic flux surfaces at a high efficiency. The similarities of the predicted X-point position and last closed magnetic surface are both 98%. The Pearson coherence of the predicted q profiles is 92%. Compared with the target value, the model results show the potential of the neural network model for practical use

关键词： Iterative methods

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High Reliability Transmission Scheme for Anchored Indoor New Radio Unlicensed Systems

High Reliability Transmission Scheme for Anchored Indoor New...

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IEEE Conference on Vehicular Technology (VTC)

作者： Jiankang Wang Peng Xue Hongliang Bian Yue Yuan Ying Wang Nan Cao Advanced Algorithm Lab Samsung Research China-Beijing Beijing China Air Technology Group Samsung Electronics Co. Ltd. Suwon Korea

This paper considers high reliability transmission for anchored indoor New Radio Unlicensed (NR-U) systems, in which unlicensed spectrum with wideband operation is combined with other NR licensed spectrum as anchor. To achieve high reliable transmission using unlicensed spectrum, success transmission ensuring scheme is investigated for indoor NR-U deployment. By modeling of Success Transmission Probability (STP) with nonlinear Levenberg-Marquardt method, STP-based packet request algorithm and STP-based channel allocation algorithm are proposed for initial transmission and Automatic Repeat reQuest (ARQ) retransmission, respectively. Simulation results show that the proposed success transmission ensuring scheme significantly decreases retransmission ratio and further provides less transmission latency and higher throughput. In a word, this paper provides an effective solution which satisfies high reliable transmission requirement for NR-U.

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Adaptive energy-preserving algorithms for guiding center system

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Plasma Science and Technology 2023年第4期25卷 11-22页

作者：朱贝贝刘健张嘉炜祝爱卿唐贻发 Department of Applied Mathematics School of Mathematics and PhysicsUniversity of Science and Technology BeijingBeijing 100083Peopleʼs Republic of China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026Peopleʼs Republic of China Advanced algorithm Joint Lab Shandong Computer Science CenterQilu University of TechnologyJinan 250014Peopleʼs Republic of China The State Key Laboratory of Scientific and Engineering Computing The Institute of Computational Mathematics and Scientific/Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190Peopleʼs Republic of China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049Peopleʼs Republic of China

We develop two types of adaptive energy preserving algorithms based on the averaged vector field for the guiding center dynamics,which plays a key role in magnetized *** adaptive scheme is applied to the Gauss Legendre’s quadrature rules and time stepsize respectively to overcome the energy drift problem in traditional energy-preserving *** new adaptive algorithms are second order,and their algebraic order is carefully *** results show that the global energy errors are bounded to the machine precision over long time using these adaptive algorithms without massive extra computation cost.

关键词： guiding center system energy-preserving methods adaptive energy conservation

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High-resolution simulations of nonlinear electromagnetic turbulence in tokamak devices

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The European Physical Journal Special Topics 2025年 1-14页

作者： Liu, Yanjun Liu, Zixi Liu, Jian Gao, Baofeng Zhang, Wei Xia, Tianyang Liu, Haiqing Zhuang, Ge Gao, Xiang Institute of Plasma Physics Chinese Academy of Sciences Anhui China KTX Laboratory and Department of Engineering and Applied Physics University of Science and Technology of China Anhui China Weihai Institute for Interdisciplinary Research Shandong University Shandong China SDU-ANU Joint Science College Shandong University Shandong China Shandong Computer Science Center (National Supercomputing Center in Jinan) Qilu University of Technology (Shandong Academy of Sciences) Shandong China Advanced Algorithm Joint Lab National Supercomputing Center in Jinan Shandong China

To achieve long-pulse steady operation, the physical mechanisms of boundary turbulence need further investigation. We employ the two-fluid model with flute reduction on BOUT++ to simulate the boundary plasma in Tokamaks. The space and time scales of turbulence reproduced by our simulations closely relate to the spatial mesh size and time step size, respectively. As an inherent time scale, the Alfven time is sufficient to resolve MHD instabilities. The spatial scale can be refined by increasing mesh resolutions, which necessitates larger scale parallel computing resources. We have conducted nonlinear simulations using more than 33 million spatial meshes with 16,384 CPU processors in parallel. The results indicate that while the decrease in parallel efficiency with an increase in core numbers does not necessarily lead to shorter runtimes, higher computational complexity improves parallel efficiency for the same number of cores. In addition, the mesh resolution required for convergence conditions differs between linear and nonlinear simulations, with nonlinear simulations demanding higher resolution. Besides finer structure obtained, the fluctuation characteristic of density similar to WCM, which is more consistent with the experimental observation, also shows the requirement for high-resolution meshes and large-scale computing in the future.

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Fast Heuristic algorithms for the Multiple Strip Packing Problem 1

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20th International Conference on Mathematical Optimization Theory and Operations Research , MOTOR 2021

作者： Vasilyev, Igor Ushakov, Anton V. Barkova, Maria V. Zhang, Dong Ren, Jie Chen, Juan Matrosov Institute for System Dynamics and Control Theory of SB RAS 134 Lermontov Street Irkutsk664033 Russia Algorithm and Technology Development Department Global Technical Service Department Huawei Technologies Co. Ltd. Dongguan China Moscow Advanced Software Technology Lab Huawei Russian Research Institute Moscow Russia

ISBN: (数字)9783030864330

ISBN: (纸本)9783030864323

In this paper we address the so-called two-dimensional Multiple Strip Packing Problem (MSPP). There is a set of rectangles and a set of strips, where each strip has a pre-defined width. The problem is to find a feasible packing of all the rectangles into the strips so as the maximal height of the packing over all the strips is minimized. A packing is feasible if all the rectangles are placed into the strips and not overlapped. In case of only one strip, the problem is widely known as the Strip Packing Problem (SPP). Many effective constructive heuristics for SPP are based on the so-called skyline representation of a packing pattern. We generalized this approach for the case of multiple strips and developed a randomized local search, which embeds the proposed skyline heuristic to compute the objective value for a packing. We also introduced the two-dimensional level multiple strip packing problem and developed some level-based constructive heuristics. We report computational results on real-life problem instances arisen in an application of MSPP in scheduling computing jobs on multiple Spark computer clusters. © 2021, Springer Nature Switzerland AG.

关键词： Heuristic algorithms

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Traffic simulation and impact analysis for alternative mobility services in the city of Shenzhen 9

Traffic simulation and impact analysis for alternative mobil...

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9th International Conference on advanced Cloud and Big Data, CBD 2021

作者： Zhu, Xueying Li, Ye Bilali, Aledia Zhou, Biyun Zhang, Jun Dai, Hao Zhang, Fan Zhang, Rui Hou, U. Leong Shenzhen Institute of Beidou Applied Technology Ltd. Strategic Research Department Shenzhen China University of Macau Faculty of Science and Technology China Bmw Group Mobility Products My Journey Concepts Munich Germany Bmw China Services Ltd. Technology Office China Shanghai China Shenzhen Institute of Beidou Applied Technology Ltd. Algorithm Lab Shenzhen China Chinese Academy of Sciences Shenzhen Institute of Advanced Technology Shenzhen China Shenzhen Institute of Beidou Applied Technology Ltd. Shenzhen China

ISBN: (纸本)9781665407458

Alternative Mobility Services (AMS) could change travellers' mobility and possibly fleets of pooled autonomous vehicles will replace the need for current personal vehicles. Contrary to the previous studies, the goal of this paper is to investigate the impact that AMS have on traffic efficiency based on the real data. This study provides a multi-model simulation of AMS behaviour including micro mobility, on- demand mobility (ODM), automated driving (AD), and intermodal mobility. A three-side benefiting model (customer, operator and society) is introduced for real-time ride pooling. In addition, we compared the current traffic situation and AMS scenarios on the Shenzhen city network. Overall, the simulation results show how AMS will affect fleet size, total vehicle kilometre, average velocity, trip distance, as well as trip time. Generally, we can observe moderate traffic improvement by introducing AMS. © 2022 IEEE.

关键词： Fleet operations

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Three-dimensional Turbulent Reconnection within Solar Flare Current Sheet

arXiv

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arXiv 2023年

作者： Wang, Yulei Cheng, Xin Ding, Mingde Liu, Zhaoyuan Liu, Jian Zhu, Xiaojue School of Astronomy and Space Science Nanjing University Nanjing210023 China Ministry of Education Nanjing210023 China Qilu University of Technology Shandong Academy of Sciences Jinan250014 China Advanced Algorithm Joint Lab Shandong Computer Science Center Qilu University of Technology Jinan250014 China School of Nuclear Science and Technology University of Science and Technology of China Hefei230026 China Max Planck Institute for Solar System Research GottingenD-37077 Germany

Solar flares can release coronal magnetic energy explosively and may impact the safety of near-earth space environments. Their structures and properties on macroscale have been interpreted successfully by the generally-accepted two-dimension standard model invoking magnetic reconnection theory as the key energy conversion mechanism. Nevertheless, some momentous dynamical features as discovered by recent high-resolution observations remain elusive. Here, we report a self-consistent high-resolution three-dimension magnetohydrodynamical simulation of turbulent magnetic reconnection within a flare current sheet. It is found that fragmented current patches of different scales are spontaneously generated with a well-developed turbulence spectrum at the current sheet, as well as at the flare loop-top region. The close coupling of tearing-mode and Kelvin-Helmholtz instabilities plays a critical role in developing turbulent reconnection and in forming dynamical structures with synthetic observables in good agreement with realistic observations. The sophisticated modeling makes a paradigm shift from the traditional to three-dimension turbulent reconnection model unifying flare dynamical structures of different scales. © 2023, CC BY.

关键词： Earth (planet)

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Integer Programming Approach to the Data Traffic Paths Recovering Problem 19th

Integer Programming Approach to the Data Traffic Paths Recov...

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19th International Conference on Mathematical Optimization Theory and Operations Research, MOTOR 2020

作者： Vasilyev, Igor Zhang, Dong Ren, Jie Matrosov Institute for System Dynamics and Control Theory of Siberian Branch of Russian Academy of Sciences Irkutsk Russia Algorithm and Technology Development Department Global Technical Service Department Huawei Technologies Co. Ltd. Dongguan China Moscow Advanced Software Technology Lab Huawei Russian Research Institute Moscow Russia

ISBN: (纸本)9783030499877

In this paper, we propose a novel approach to recovering path relationships in communication networks. The path relationship is one of the key input data which is necessary for network operation and maintenance. We have a continuous network transformation, upgrades, expansions, service allocations, thus the network physical topology and paths relationship are permanently changing with high frequency. Our approach is aimed at recovering the path relationships through flow information of each arc in the network. Getting the flow information is not a big technical problem and its control is included in the basic toolbox for network monitoring. We consider two scenarios which lead us to integer linear programs. The both of them minimize the flow deviation, where in the first one we look for a directed spanning tree (r-arborescence) and, in the second one—more general origin/destination paths (OD-paths). We propose mixed integer linear programming formulations for both problems. Their feature is that they contain the non-polynomial number of constraints which are considered implicitly by the cutting planes approach. The preliminary computation results showed that the large-scale instances of the first scenario can easily be solved. At the same time, the optimal solutions of second scenario problems can be found only on small- and medium-size instances, which inspires for the further research. © 2020, Springer Nature Switzerland AG.

关键词： Integer programming

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VPNets: Volume-preserving neural networks for learning source-free dynamics

arXiv

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arXiv 2022年

作者： Zhu, Aiqing Zhu, Beibei Zhang, Jiawei Tang, Yifa Liu, Jian LSEC ICMSEC Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China School of Mathematical Sciences University of Chinese Academy of Sciences Beijing100049 China School of Mathematics and Physics University of Science and Technology Beijing Beijing100083 China School of Nuclear Science and Technology University of Science and Technology of China Anhui Hefei230026 China Advanced Algorithm Joint Lab Shandong Computer Science Center Qilu University of Technology Shandong Jinan250014 China

We propose volume-preserving networks (VPNets) for learning unknown source-free dynamical systems using trajectory data. We propose three modules and combine them to obtain two network architectures, coined R-VPNet and LA-VPNet. The distinct feature of the proposed models is that they are intrinsic volume-preserving. In addition, the corresponding approximation theorems are proved, which theoretically guarantee the expressivity of the proposed VPNets to learn source-free dynamics. The effectiveness, generalization ability and structure-preserving property of the VP-Nets are demonstrated by numerical experiments. Copyright © 2022, The Authors. All rights reserved.

关键词： Dynamics

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