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Accelerating ab initio real-space electronic structure calculations for low-dimensional materials using an atom-sphere grid truncation method

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Physical Review B 2024年第15期110卷 155157页

作者： Lantian Xue Qiang Xu Cheng Ma Wenhui Mi Yanchao Wang Yu Xie Yanming Ma Key Laboratory of Material Simulation Methods & Software of Ministry of Education College of Physics State Key Lab of Superhard Materials College of Physics International Center of Future Science Key Laboratory of Physics and Technology for Advanced Batteries of Ministry of Education College of Physics

In recent decades, the real-space finite-difference implementations of Kohn–Sham density functional theory have exhibited substantial improvements in computational efficiency for large-scale systems. However, the substantial memory consumption arising from the numerous grid points has begun to limit the widespread adoption of this method. In this study, a general method is presented—applicable to both periodic and Dirichlet boundary conditions—to reduce the number of real-space grids. This approach introduces a truncation of the real-space grids based on atomic positions, which reduces memory requirements and enables a more efficient real-space scheme tailored for simulating low-dimensional and porous materials with uneven spatial distributions. By testing the method on zero-dimensional clusters, one-dimensional tubes, two-dimensional clusters adsorbed on graphene, and three-dimensional metal-organic framework materials, a 30–73% reduction in grid points and a 36–71% reduction in computational time per step are observed for simulations with a 2 meV/atom energy difference.

关键词： Electronic structure Density functional theory development First-principles calculations Numerical techniques

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Overvoltage Suppression Strategy Based on Active Control of Current for Half-Wave Commutated Modular Multilevel Converters 14

Overvoltage Suppression Strategy Based on Active Control of ...

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14th International Conference on Power and Energy Systems, ICPES 2024

作者： Liu, Bao Xu, Yunfei Zhao, Guoliang Fu, Nan Jia, Chen China Electric Power Research Institute State Key Laboratory of Advanced Power Transmission Technology Beijing China Tsinghua University State Key Laboratory of Control and Simulation of Power System and Generation Equipment Beijing China Electric Power Research Institute State Grid Liaoning Electric Power Co. Ltd. Shenyang China

ISBN: (纸本)9798350391329

Flexible low-frequency AC transmission technology combines the advantages of 50 Hz AC transmission and DC transmission, and has good application scenarios. High voltage and large capacity AC/AC converters are the core equipment of flexible low-frequency AC transmission systems. The proposal of half-wave commutated modular multilevel converters effectively reduces the number of components and improves system economy. In view of this, this paper proposes an overvoltage suppression strategy for active control of inductor current, which effectively reduces the overvoltage level during commutation. The article first introduces the sparse topology and mathematical model of the half-wave commutated modular multilevel converters. Secondly, the mechanism of overvoltage generation is analyzed. Then, overvoltage suppression strategies are proposed. Finally, a PSCAD simulation model is built to verify the effectiveness and feasibility of the proposed method through simulation. © 2024 IEEE.

关键词： Flexible AC transmission systems

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The Low Cycle Fatigue Behavior of a First Generation Single Crystal Superalloy CMSX-6 at 770 °C 9th

The Low Cycle Fatigue Behavior of a First Generation Single ...

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9th International Symposium on Hydrogen Energy, Renewable Energy and Materials, HEREM 2023

作者： Shuai, Zheng Wei, Xu Xueqin, Hou Jian, Zhang Yanfei, Liu Jianwei, Xu Xuanning, Zhang Science and Technology On Advanced High Temperature Structural Materials Laboratory AECC Beijing Institute of Aeronautical Materials Beijing100095 China Beijing Key Laboratory of Aeronautical Materials Testing and Evaluation AECC Beijing Institute of Aeronautical Materials Beijing100095 China Aviation Key Laboratory of Science and Technology On Materials Testing and Evaluation Beijing100095 China AECC Sichuan Gas Turbine Establishment Chengdu610500 China

ISBN: (纸本)9789819736850

The investigation of the low cycle fatigue behavior of a first generation single crystal superalloy CMSX-6 were presented. Specimen of CMSX-6 alloy with standard heat treated were test by the fatigue testing machines. The study indicate the low cycle fatigue of CMSX-6 is about 965MPa at 770 °C, R = 0 with a cycle number of 106. Subjected to periodic loads, the dislocation movement in the alloy is restricted to a small part of the crystal plane at the stress concentration area and intensive local slip occurs, resulting in plastic deformation in the local area, and the straight shape of the specimen side became crooked. SEM observation indicate that the fatigue cracks initiate from the internal microporosity of the specimen, and the transient fracture is formed after the crack propagation. The oxidation in crack propagation zone is serious, and the fatigue bands are not visible. Shear dimples were found at the transient fault zone. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Single crystals

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Modeling and simulation Method of Offshore Power Delivery System with Hydrogen Production 4

Modeling and Simulation Method of Offshore Power Delivery Sy...

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4th International Conference on Electrical Engineering and Control Technologies, CEECT 2022

作者： Gu, Huaiguang Zhang, Jian Kou, Longze Zhou, Jiapei State Key Laboratory of Advanced Transmission Technology China Beijing Key Laboratory of Dc Power Grid Technology and Simulation China State Grid Smart Grid Research Institute Co. LTD. Beijing China

ISBN: (纸本)9781665498999

With the depletion of global fossil energy and the worsening of global environmental problems, the development and utilization of renewable clean energy has become an important direction in the world's energy technological change. Hydrogen energy, as a highly clean renewable energy, has become a research hotspot in the world. In this paper, a typical offshore energy system model is proposed. Firstly, according to the thermodynamic phenomena and electrochemical dynamic characteristics of the alkaline electrolyzer, the electromagnetic transient model of hydrogen production unit is established. Then, a grid-connected control scheme based on the direct current of the electrolyzer is proposed to connect the offshore wind farm with the hydrogen production system. Finally, a complete model is built on PSCAD and the electromagnetic transient simulation analysis is carried out. The results show that the system can provide stable and reasonable dc current to hydrogen production system through 60 mw wind farm, which verifies the correctness and effectiveness of the model. © 2022 IEEE.

关键词： Hydrogen production

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Optimization of Li-ion Battery Charge and Discharge Model Based on Genetic Algorithm 14th

Optimization of Li-ion Battery Charge and Discharge Model Ba...

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14th International Conference on Genetic and Evolutionary Computing, ICGEC 2021

作者： Li, Xiang Yang, Wen Wang, Huan Chang, Xiaopeng Dang, Rongxin Wang, Dejun Key Laboratory of Materials Design and Quantum Simulation College of Science Changchun University Changchun130022 China Key Laboratory of Advanced Structural Materials Ministry of Education & Advanced Institute of Materials Science Changchun University of Technology Changchun130012 China

ISBN: (纸本)9789811684296

In this paper, a strategy using genetic algorithm to optimize the charging process of lithium-ion batteries is proposed, which is based on the coupling of computer optimization algorithm and battery charging model. Visual Studio 2010 is used for programming, and COMSOL Multiphysics 5.5 is used to establish an electrochemical model of the battery to simulate various processes in the battery to verify the reliability and accuracy of the design algorithm. The genetic algorithm can be used to find the suitable charging current, and the optimization can be picked in a large number of databases by using the optimal strategy to reduce the time complexity. By comparing the battery's discharge curve and SOC result, it is found that the battery using genetic algorithm and intelligent optimization is better than that using the traditional constant current and constant voltage charging algorithm in charging time, cycle life, charging efficiency and other performance indicators. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Genetic algorithms

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Joint Signal Adaptive Modulation Recognition and Radio Frequency Fingerprinting Based on Multi-task Learning 14th

Joint Signal Adaptive Modulation Recognition and Radio Freq...

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14th EAI International Conference on Wireless and Satellite Systems, WiSATS 2024

作者： Li, Zhuo He, Zhongqiu Xu, Congan Zhang, Wei Zha, Haoran Wang, Yu Tang, Zeyu Harbin Engineering University Harbin150001 China Naval Aviation University Yantai26400 China Advanced Technology Research institute Beijing institute of Technology Jinan250300 China National Key Laboratory of Electromagnetic SpaceSecurity Sichuan Chengdu610036 China Nanjing University of Posts and Telecommunications NanJing210003 China

ISBN: (纸本)9783031861956

Radio Frequency Fingerprinting Identification (RFFI) leverages inherent discrepancies in radiation source hardware, which are challenging to mimic and counterfeit. This attribute enhances the security of wireless networks and ensures the protection of data privacy, vital for secure communications. Inherent challenges such as channel fading and frequency drift affect radio signals. This paper explores the synergy between Automatic Modulation Recognition (AMR) and RFFI by employing a multi-label dataset to strategically influence the relationship between signal labels and individual radiation sources. We propose an advanced multi-gate mixture-of-experts convolutional neural network model, the MMOE-CNN-Transformer, which operates within a multi-task soft sharing framework. Our empirical results reveal that this model significantly enhances RFFI classification accuracy, particularly at a 0dB signal-to-noise ratio, outperforming traditional single-task learning (STL) approaches and surpassing the efficacy of hard sharing architectures, exemplified by the Shared-Bottom model. This study underscores the potential of integrating sophisticated neural network architectures in enhancing the robustness and precision of radio frequency identification systems. © ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2025.

关键词： Signal to noise ratio

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Modeling and Fault Diagnosis of Pressurizer Based on Bond Graph 29

Modeling and Fault Diagnosis of Pressurizer Based on Bond Gr...

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2022 29th International Conference on Nuclear Engineering, ICONE 2022

作者： Zhou, Zhuoran Peng, Minjun Wang, Hang Jiang, Yingying Key Subject Laboratory of Nuclear Safety and Simulation Technology Harbin Engineering University Harbin150001 China Key Laboratory of Nuclear Safety and Advanced Nuclear Energy Technology Harbin150001 China Key Laboratory of Nuclear Power Plant Performance and Equipment Harbin150001 China

ISBN: (纸本)9780791886502

The bond graph can be used to simulate and model conservation processes in different energy domains. In this paper, based on bond graph, the pressurizer was modeled and diagnosed at full power. Two parameters of pressure and mass flow were selected. Firstly, the bond graph of pressurizer was established. The pressurizer was divided into three zones: the fluctuating zone, the saturated liquid zone and the gaseous zone. The conservation equations of mass and energy were given respectively for these three regions. Secondly, the conservation equations of mass and energy were combined with the conservation of volume, and the model was constructed according to the combination rules. Then, according to the established bond graph model, the time causality diagram was established to determine the influence relationship between the coefficients and listed the fault characteristic matrix. Meanwhile, the reasoning structure between the coefficient was realized by the expert system G2. Finally, the fault data simulated by simulator was imported into the bond graph model. The failure of the safety valve, the spray valve and the immersion type heater were introduced to verify the modeling and diagnosis effect. It concludes that the diagnosis effect is consistent with the imported fault. Compared with the data-driven method, the bond graph method is more reliable, and compared with the expert knowledge method, the bond graph method can diagnose unknown faults and has a wide range of applications. In addition, a new method for nuclear power plant simulation modeling was provided. This was a new attempt to model bond graphs outside the research of mechanic, electronic and hydraulic. © 2022 by ASME.

关键词： Failure analysis

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A Staged Strategy for MMC Offshore Converter Station Under Asymmetric AC Fault 7

A Staged Strategy for MMC Offshore Converter Station Under A...

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7th IEEE Conference on Energy Internet and Energy System Integration, EI2 2023

作者： Li, Fangyuan Kou, Longze Zhou, Jiapei Hao, Jie State Key Laboratory of Advanced Power Transmission Technology Beijing China Beijing Key Laboratory of Dc Grid Technology & Simulation State Grid Smart Grid Research Institute CO.LTD. Beijing China State Grid Shanxi Electric Power Company Electric Power Science Research Institute Shanxi China

ISBN: (纸本)9798350345094

At present, offshore wind power has become an important development direction for wind power generation. Offshore wind farms often use high-voltage direct current transmission technology with modular multi-level voltage source converters (MMC-HVDC) to transmit electricity to the grid. However, the fault response characteristics of offshore wind farms through the MMC-HVDC transmission system are different from those through AC transmission way. Therefore, it is significant that studying the fault ride through (FRT) technology of offshore wind farms through the MMC-HVDC grid connection system for practical engineering. An electromagnetic transient simulation model for an offshore wind farm composed of a direct drive permanent magnet synchronous generator (D-PMSG) connected to the grid is established through MMC-HVDC transmission technology. The mechanism and suppression strategy of overvoltage generation in the transmission network are provided during the fault clearance and recovery phase of the offshore wind farm HVDC transmission system under AC asymmetric faults. A two-stage improved control strategy for MMC-HVDC offshore converter station in response to asymmetric faults has been proposed, which is beneficial for the joint system to quickly recover from the post fault system voltage and suppress the overvoltage risk during the fault clearing phase. Finally, the proposed strategy is validated based on a domestic ± 500kV project in China, demonstrating its effectiveness. © 2023 IEEE.

关键词： Offshore wind farms

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Structure Design and Energy Absorption Mechanism of a New Type of Armor Inspired from Armadillos

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Acta Mechanica Solida Sinica 2021年第5期34卷 718-728页

作者： Chunan Du Gang Yang De’an Hu Xu Han Key Laboratory of Advanced Design and Simulation Techniques for Special Equipment Ministry of EducationHunan UniversityChangsha410082China School of Mechanical Engineering Hebei University of TechnologyTianjin300401China

Dermal armor,such as fish scales or armadillo osteoderms,has been known to exhibit high performance and good flexibility defending against *** top layer of the dermal armor usually consists of a segmented hard bony *** soft inner layer composed of collagen fibers connects and holds the hard *** by the dermal armor of armadillos,bioinspired protection armor is studied for impact *** hexagonal scales tessellate the surface continuously and work as the hard bony layer protecting the soft inner layer from ***-high molecular weight polyethylene(UHMWPE)is used as the connectivity layer to support and hold the *** investigate the dynamic response of the bioinspired protection armor,drop weight impact tests are carried out.A finite element model is established to study the dynamic response of bioinspired protection *** impact process images captured by a high speed camera and the experimental data of drop hammer acceleration tests verify the validity of the numerical *** dynamic resistance behavior and the synergy effect of each part of the bioinspired protection armor combined with the protected objects are studied in detail by numerical *** results show that the bioinspired protection armor has marked energy absorption ability.A synergistic dissipation mechanism is activated in the impact process,which can dissipate impact energy and make the impact load distribution more *** UHMWPE between the outer layer and the soft substrate plays a significant role not only related to support and connection,but also for the force balance and energy *** mechanism of energy absorption of the bioinspired protection armor revealed in this paper can be taken as a new guideline for designing a novel protective armor.

关键词： Bioinspired Armor Impact Energy absorption Numerical simulation

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Multi-View Subspace Clustering Via Simultaneously Cycle Projection and Similarity Learning

Multi-View Subspace Clustering Via Simultaneously Cycle Proj...

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International Conference on Wavelet Active Media technology and Information Processing (ICWAMTIP)

作者： Xiang Tao Liu Jie Qiao Wenshen Xiao Siying Ye Mao National Key Laboratory of Complex Aviation System Simulation Southwest China Institute of Electronic Technology Chengdu China University of Electronic Science and Technology of China Chengdu China

ISBN: (数字)9798331519254

ISBN: (纸本)9798331519261

At present, most of the existing methods combine the data from different views mechanically to obtain the latent subspace with complementary information, which not only fails to make full use of the data information from specific perspectives but also brings redundancy. Therefore, we propose a novel multi-view subspace clustering method. It utilizes cycle projection to obtain a subspace construction model. At the same time, by learning the global structure and local manifold structure of this subspace while assigning learnable weights to different views, the consensus information among views and specific information from different views are captured according to the importance of different views. In this way, our method effectively reduces the original noise and redundancy, and further carries out the improvement of complementarity and consistency among views. The proposed method is optimized by using the Augmented Lagrangian Multiplier with Alternating Direction Minimization (ALM- ADM) algorithm. Experiment results on benchmark datasets confirm the effectiveness of our method.

关键词： Manifolds Technological innovation Clustering methods Redundancy Noise Clustering algorithms Information processing Media Minimization Similarity learning

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