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Study of the fracturing behaviour of an electrohydraulic shock wave in sandstone under static pressure

JOURNAL OF PHYSICS D-APPLIED PHYSICS 2021年第49期54卷

作者： Xiong, Liangli Liu, Yi Yuan, Wei Li, Hua Lin, Fuchang Pan, Yuan Huazhong Univ Sci & Technol Sch Elect & Elect Engn State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Hubei Peoples R China Huazhong Univ Sci & Technol Minist Educ Key Lab Pulsed Power Technol Wuhan 430074 Hubei Peoples R China Shijiazhuang Tiedao Univ Sch Civil Engn Shijiazhuang 050043 Hebei Peoples R China

To understand the application of electrohydraulic shock waves (EHS) in deep rock formations, the fracturing behaviour of repetitive EHS under a static pressure environment is studied in this paper. The static pressure environment of sandstone is simulated and a load model of the transmission wave of EHS at the liquid-rock interface is proposed. Analysis of the spatial distribution, dense zone and fracture zone of microcracks shows that static pressure has a significant inhibitory effect on the formation, distribution and growth of microcracks under repetitive EHS. Compared with normal pressure, cracks in a static pressure environment are mainly concentrated around the well hole, the microcracks are denser and the extension length is shorter. At the same time, the degree of damage is established to evaluate the overall cumulative damage to the sandstone. The coupling relationship between degree of damage, static pressure, discharge energy and discharge times is fitted. The fitting model shows a behaviour of continuous decelerating growth of microcracks, which can be divided into two phases, an initial growth phase and a slow-growth phase. The increase in static pressure mainly suppresses the initial growth phase, and the discharge energy needs to be increased to promote the initial degree of damage and the rate of accumulation of microcracks in the slow-growth phase. The rate of accumulation of microcracks in the slow-growth phase can be controlled through multi-level adjustment of the discharge energy. This paper provides guidance and simulation methods for rock fracturing applications of EHS in static pressure environments.

关键词： electrohydraulic discharge shock wave sandstone static pressure discharge energy damage degree

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Effects of Active and Reactive Power Control on Inertia in DFIG-Based Wind Turbines

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IEEE Transactions on Power Electronics 2025年第9期40卷 13673-13685页

作者： Guo, Xiang Tang, Qingbo Zhu, Donghai Zhou, Yini Zou, Xudong Hu, Jiabing Kang, Yong China University of Mining and Technology School of Electrical Engineering Xuzhou221116 China Hubei Key Laboratory of Marine Electromagnetic Detection and Control Wuhan430064 China Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Technology School of Electrical and Electronic Engineering Wuhan430074 China

The inertia analysis for wind turbines (WTs) typically focuses on the electromechanical timescale. Active power control (APC) and phase-locked loop (PLL) are essential considerations while reactive power control (RPC) is often deemed negligible, particularly in stiff grid. However, such assumptions may be inappropriate. Therefore, this article aims to comprehensively examine the effects of APC and RPC on the inertia for doubly fed induction generator (DFIG)-based WTs. Firstly, phase motion models are developed by incorporating various combinations of control loops, including APC, RPC, and different PLL configurations. Subsequently, the impacts of the APC and RPC on the inertia are examined in detail. The analysis reveals that the APC diminishes inertia, whereas the RPC significantly enhances the inertia. Additionally, special attention should be given to phase characteristics of the inertia transfer function, as they can substantially influence inertial performance. Furthermore, an improved frequency support method is proposed, which achieves superior frequency response without necessitating the PLL bandwidth to be adjusted to extremely low values, such as 1 Hz or lower. Finally, the analysis and the proposed method are validated through experiments. © 1986-2012 IEEE.

关键词： Wind turbines

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Multifunctional phase-change composites for green electromagnetic interference shielding and thermal response prepared under the guidance of an impedance matching strategy

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NANOSCALE 2024年第35期16卷 16622-16631页

作者： He, Jie Wu, Jiaozu Park, Chul B. Gong, Pengjian Liang, Chaobo Li, Guangxian Sichuan Univ Sch Aeronaut & Astronaut Chengdu 610065 Peoples R China Sichuan Univ Coll Polymer Sci & Engn State Key Lab Polymer Mat Engn Chengdu 610065 Peoples R China Univ Toronto Dept Mech & Ind Engn Microcellular Plast Mfg Lab Toronto ON M5S 3G8 Canada North Univ China Sch Mat Sci & Engn Key Lab Funct Nanocomposites Shanxi Prov Taiyuan 030051 Peoples R China

With the advent of the information age, electromagnetic hazards are becoming more serious. In view of environmental protection, green electromagnetic interference (EMI) shielding materials with little or no secondary reflection have become the ideal choice. In this paper, by freeze-drying, high-temperature carbonization, coating and impregnation backfilling, we prepared carbonized Ni-MOF/reduced graphene oxide/silver nanowire-polyimide@polyethylene glycol composites (Ni@C/r-GO/AgNW-PI@PEG) with gradient conductivity based on impedance matching. The impedance matching layer Ni@C/r-GO-300 reduces the reflection of electromagnetic waves from the surface of the material, the dissipation layer Ni@C/r-GO-600 provides excellent electromagnetic wave dissipation capability, and the reflection layer AgNW-PI ensures that the electromagnetic waves are reflected back into the material. Meanwhile, the EMI shielding performance value of Ni@C/r-GO/AgNW-PI@PEG reaches 62.3 dB with an ultra-low reflectivity (R) of 0.04. In CST simulations, the intrinsic mechanism of electromagnetic energy loss within the material is revealed by energy loss density cloud maps. In addition, heat from high-temperature objects is transferred through the highly thermally conductive AgNW-PI membrane to the long-channel Ni@C/r-GO backbone. Therefore, the composites prepared on the basis of impedance matching will accelerate the use of EMI shielding materials for the thermal management of portable electronic devices and battery heat dissipation packaging. Schematic diagram of heat dissipation of composite materials.

关键词： electromagnetic shielding

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In situ doping Pt single atoms into 3D flower-like 1T-MoS2 via Pt-S bond for efficient hydrogen evolution reaction

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JOURNAL OF COLLOID AND INTERFACE SCIENCE 2025年 689卷 137282页

作者： Li, Ziya Zhang, Chao Wang, Haipeng Zhang, Delu Zhuang, Tao Lv, Zhiguo Qingdao Univ Sci & Technol Sch Chem Engn Qingdao 266042 Peoples R China Qingdao Univ Sci & Technol Shandong Prov Key Lab Rubber Plast Minist Educ Qingdao 266042 Peoples R China

Combining single atoms via phase transition engineering (from 2H to 1T) remains a challenge in MoS2-based catalysts. Herein, we report that Pt single atoms (PtSA) were doped into a 3D flower-like 1T-MoS2 catalyst (PtSA@MoS2) using a Pt-S bonding strategy. Doping with PtSA induced a phase transition in MoS2 from the 2H phase to the 1T phase. PtSA@MoS2 exhibited outstanding hydrogen evolution reaction (HER) performance, featuring an overpotential of 25 mV at 10 mA cm- 2, a Tafel slope of 43.6 mV dec-1, and excellent long-term stability. The Pt-S first-shell scattering of PtSA@MoS2 in extended X-ray absorption fine structure (EXAFS) directly indicated that the PtSA was anchored near S atoms, forming Pt-S bonds. Furthermore, S atoms proximal to Pt functioned as catalytically active sites for HER, with Pt acting as an electron transfer mediator, facilitating the electron transfer from Mo to Pt and then to S. The p-band center of S showed a positive shift, indicating that PtSA@MoS2 interacted weakly with hydrogen, thereby accelerating the desorption of H atoms to generate H2. Additionally, PtSA@MoS2 exhibited a Delta GH* of only-0.13 eV, which also favored H2 production.

关键词： Pt single atoms Molybdenum disulfide Phase transition Electrocatalytic hydrogen

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Optimizing Training Efficiency and Cost of Hierarchical Federated Learning in Heterogeneous Mobile-Edge Cloud Computing

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IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS 2023年第5期42卷 1518-1531页

作者： Cui, Yangguang Cao, Kun Zhou, Junlong Wei, Tongquan East China Normal Univ Sch Comp Sci & Technol Shanghai Key Lab Trustworthy Comp Shanghai 200062 Peoples R China East China Normal Univ Shanghai Trusted Ind Internet Software Collaborat Shanghai 200062 Peoples R China Jinan Univ Coll Informat Sci & Technol Guangzhou 510632 Peoples R China Nanjing Univ Sci & Technol Sch Comp Sci & Engn Nanjing 210094 Peoples R China Chinese Acad Sci State Key Lab Comp Architecture Inst Comp Technol Beijing 100190 Peoples R China

Federated learning (FL), an emerging distributed machine learning (ML) technique, allows massive embedded devices and a server to work together for training a global ML model without collecting user data on a server. Most existing approaches adopt the traditional centralized FL paradigm with a single server: one is the cloud-centric FL paradigm and the other is the edge-centric FL paradigm. The cloud-centric FL paradigm is able to manage a large-scale FL system across massive user devices with high communication cost, whereas the edge-centric FL paradigm is capable of coordinating a small-scale FL system benefiting from the low communication delay over wireless networks. To fully exploit the advantages of both, in this article, we develop a distinctive hierarchical FL framework for the promising mobile-edge cloud computing (MECC) system, called HELCHFL, to achieve high-efficiency and low-cost hierarchical FL training. In particular, we formulate the corresponding theoretical foundation for our HELCHFL to ensure hierarchical training performance. Furthermore, to address the inherent communication and user heterogeneity issues of FL training, our HELCHFL develops a utility-driven and heterogeneity-aware heuristic user selection strategy to enhance training performance and reduce training delay. Subsequently, by analyzing and utilizing the slack time in FL training, our HELCHFL introduces a device operating frequency determination approach to reduce training energy cost. Experiments demonstrate that our HELCHFL can enhance the highest accuracy by up to 52.93%, gain the training speedup of up to 483.74%, and obtain up to 45.59% training energy savings compared to state-of-the-art baselines.

关键词： Training Servers Cloud computing Delays Costs Computational modeling Prototypes Device frequency determination federated learning (FL) high efficiency low cost mobile-edge cloud computing (MECC) user selection

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Harmonization of heterointerface states to enhance built-in electric field effects for electromagnetic wave absorption

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JOURNAL OF MATERIALS SCIENCE & technology 2025年 229卷 223-234页

作者： Zhu, Hongbao Yan, Yi Zhou, Jintang Tao, Jiaqi Zou, Kexin Cheng, Zhenyu Yao, Zhengjun Tao, Xuewei Lei, Yiming Ma, Yao Liu, Peijiang Huang, Hexia Nanjing Univ Aeronaut & Astronaut Minist Ind & Informat Technol Nanjing 211100 Peoples R China Nanjing Inst Technol Jiangsu Key Lab Adv Struct Mat & Applicat Technol Nanjing 210008 Peoples R China Ningbo Univ Key Lab Impact & Safety Engn Minist Educ China Ningbo 315000 Peoples R China Army Engn Univ Natl Key Lab Electromagnet Environm Effects & Elec Nanjing 210007 Peoples R China Minist Ind & Informat Technol Elect Res Inst 5 Sci & Technol Reliabil Phys & Applicat Technol Ele Guangzhou 511370 Guangdong Peoples R China Nanjing Univ Aeronaut & Astronaut Coll Energy & Power Engn Nanjing 210016 Peoples R China

Heterointerface engineering based on built-in electric field (BIEF) has been well-received in electromagnetic wave (EMW) absorption. However, the influence of interface size and number of interfaces on the BIEF and interface polarization loss mechanism remains unclear. Here, we designed a ternary dual heterointerfaces Co@C/SiO2 nanocomposite. Experimental and theoretical analyses show that Co@C/SiO2 has abundant Mott-Schottky heterointerfaces, and a reasonable increase in the heterointerface area leads to a strong BIEF effect, where the charge accumulates at the interface and subsequently migrates along the direction of the alternating electromagnetic field to promote the dissipation of EMW by polarization loss. However, an excessive number of interfaces leads to many carriers being bound by the interfaces, which is not conducive to forming electron channels. By coordinating the heterointerface states to achieve optimal EMW absorption performance, SZ-3 can accomplish an effective absorption width (EAB) of 5.93 GHz at a thickness of 1.91 mm. This work provides new ideas and methods for BIEF-based heterointerface engineering applied to EMW absorption materials. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & technology.

关键词： electromagnetic wave absorption Heterointerface Built-in electric field Polarization loss Interface state

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Advances in In Situ Characterization Techniques for Failure Mechanisms of Zinc Anode Interfaces

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ENERGY MATERIAL ADVANCES 2025年 6卷

作者： Zhang, Di Lu, Hongfei Duan, Chenxu Yuan, Xinyao Zhu, Zhenjie Qin, Yi Song, Yuhang Jin, Yang Zhengzhou Univ Res Ctr Grid Energy Storage & Battery Applicat Sch Elect & Informat Engn Zhengzhou 450001 Henan Peoples R China

Aqueous zinc-ion batteries are considered an ideal choice for energy storage technology in new power systems due to their high theoretical capacity, high safety, and environmental friendliness. However, in practical applications, Zn anodes face a series of problems and challenges, such as Zn dendrite irregular growth, electrode cross-section corrosion, and hydrogen reduction side reactions. This has importantly impeded the large-scale utilization of zinc-ion batteries. Therefore, it is necessary to characterize the failure mechanism of zinc-metal anodes, but the current failure mechanism of Zn anodes is not well characterized, leading to different mechanism elaborations. Although many studies have been conducted to improve the interfacial stability of Zn-metal anode interfaces, there are few systematic summaries of the key role played by in situ characterization in revealing the interfacial mechanisms of Zn-metal anodes. In this paper, the main problems and failure mechanism of zinc anode interface are discussed. Then, the application of in situ characterization technology in zinc anode interfaces and the latest research progress are summarized from different aspects. The purpose of this review is to better understand the development of zinc-ion batteries and the improvement of the stability of the Zn anode interface, thus accelerating the large-scale production of zinc batteries. Finally, the research direction of the in situ characterization of zinc anodes is summarized and suggested.

关键词： Anodes

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Research on the ignition characteristics and discharge performance of LaB6/W composite cathode arcjet thruster

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ACTA ASTRONAUTICA 2025年 235卷 69-82页

作者： Wang, Yong Zhu, Yangkai Ding, Yongjie Harbin Inst Technol Lab Plasma Prop Harbin 150001 Peoples R China Minist Ind & Informat Technol Key Lab Aerosp Plasma Prop Harbin 150001 Peoples R China Harbin Inst Technol State Key Lab Space Environm Interact Matters Harbin 150001 Peoples R China Harbin Inst Technol Zhengzhou Res Inst Zhengzhou 450000 Peoples R China

A 200 W class low-power arcjet thruster with a LaB6/W composite cathode has been developed, and a hot-start ignition method has been proposed. This method reduces the ignition voltage to 350 V with a heating power of 90 W, approximately 80 %-90 % lower than the high-frequency or high-voltage ignition methods (several kilovolts). After ignition, the discharge current rises to approximately 25 A within 50 mu s, decreases to the operating current after 1-2 ms, oscillating with a fluctuation of f0.5 A before stabilizing. Meanwhile, the discharge voltage rapidly drops from 350 V to the operating voltage within 100 mu s and stabilizes with an oscillation amplitude of f0.2 V. No transition occurs from low-voltage to high-voltage modes during the hot-start ignition process. Experimental tests using krypton and argon propellants were conducted, showing optimal performance for krypton at 100 W, producing 35.4 f 0.2 mN of thrust, a specific impulse of 71 f 2 s, and a thrust efficiency of 8.0 f 0.3 %. For argon, the optimal parameters were 115 W, producing 26.4 f 0.2 mN of thrust, a specific impulse of 81 f 2 s, and a thrust efficiency of 7.0 f 0.3 %. After 100 ignition cycles and 20 h of operational testing, no erosion was observed on the cathode or anode surfaces. This study demonstrated the advantages of the hot-start ignition method in reducing ignition voltage, alleviating cathode erosion, and enhancing discharge stability.

关键词： Arcjet thruster LaB6/W composite cathode Hot-start ignition Electric propulsion

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Study on Composite Rock-Breaking Mechanism of Ultrahigh-Pressure Water Jet-PDC Cutter

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SPE JOURNAL 2024年第8期29卷 3892-3904页

作者： Cai, Can Cao, Wenyang Yang, Xianpeng Zhang, Pei Zeng, Lang Zhou, Shengwen Southwest Petr Univ Sch Mech Engn High Pressure Jet Theory & Applicat Technol Lab Chengdu Peoples R China Minist Educ Key Lab Oil & Gas Equipment Chengdu Peoples R China Southwest Petr Univ State Key Lab Oil & Gas Reservoir Geol & Exploitat Chengdu Peoples R China Sichuan Jiuzhou Elect Grp Co Ltd Mianyang Peoples R China

The drilling industry is paying increasing attention to deep and ultradeep wells because of the gradual decline and depletion of recoverable resources on the shallow surface. However, the difficulty of conventional mechanical rock-breaking grows significantly with increasing drilling depth. It has been found that the effect of a high-pressure water jet combined with a polycrystalline diamond compact (PDC) cutter is significant and can greatly increase the efficacy of rock breaking. A composite rock-breaking experimental device with a high-pressure jet was designed to carry out composite rock-breaking experiments. Meanwhile, a composite rock-breaking numerical model of high-pressure water jet-PDC cutter was created by smoothed particle hydrodynamics/finite element method (SPH/FEM). After verifying the reliability of the numerical model through experiments, the key factors, including rock stress field, cutting force, and jet field, were extracted to analyze the composite rock-breaking mechanism. The results show that the enhancing effect of jet impact on rock breaking is mainly reflected in three aspects: (1) The high-pressure water jet can create a groove and crater on the rock surface, effectively unloading the rock stress at the bottom of the well and increasing the area of rock damage;(2) PDC cutter vibration can be efficiently reduced with high-pressure jet;and (3) the rock debris in front of the cutter is cleaned in time, avoiding the waste of energy caused by the secondary cutting and reducing the temperature rise of the PDC cutter. Besides, it has been investigated how parameters like jet pressure, nozzle diameter, impact distance, and cutting depth influence the effect of jet rock breaking. The findings indicate that the best rock-breaking efficiency and economy occur at jet pressures of 30-40 MPa. Correspondingly, in terms of nozzle angle, nozzle diameter, and impact distance, the ideal ranges are 60 degrees, 1.0-1.5 mm, and 10 mm, respectively, wherein the

关键词： geologist pdc cutter cutter particle bit design reservoir geomechanics breaking experiment modeling & simulation geological subdiscipline

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Sulfate optimization in ettringite rich cements by SO3/Al2O3 molar ratio: A comparative study of calcium sulfoaluminate and aluminate cements

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CASE STUDIES IN CONSTRUCTION MATERIALS 2024年 21卷

作者： Sun, Huaqiang Lin, Tianzhu Zhuo, Kanghong Qian, Jueshi Chen, Xiangsheng Zhang, Jian Sun, Yubo Fuzhou Univ Sch Adv Mfg Quanzhou 362200 Peoples R China Chongqing Univ Coll Mat Sci & Engn Chongqing 400045 Peoples R China Shenzhen Univ Minist Educ Key Lab Coastal Urban Resilient Infrastruct Shenzhen 518060 Peoples R China Shenzhen Univ Coll Civil & Transportat Engn Shenzhen 518060 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong 999077 Peoples R China

The hydration process of calcium sulfoaluminate (CSA) and aluminate cement (CAC) is influenced by their composition and calcium sulfate sources. Increasing the calcium sulfate content promotes ettringite generation;however, exceeding the optimal threshold may cause volume instability. This study aims to optimize sulfate levels in CSA and CAC by adjusting the SO3/Al2O3 3 /Al 2 O 3 molar ratios. Contour maps were used to analyze how different sulfate sources and calcium sulfate levels affect strength development, ettringite formation, and volume stability. Both gypsum and anhydrite similarly improved compressive strength in CAC and CSA at equivalent SO3/Al2O3 3 /Al 2 O 3 ratios. However, gypsum caused more significant expansion than anhydrite at equivalent SO3/ 3 / Al2O3 2 O 3 ratios, as indicated by the higher expansion values in gypsum-rich regions. The SO3/Al2O3 3 /Al 2 O 3 molar ratio is crucial for regulating ettringite formation, enhancing compressive strength, and ensuring volume stability in CSA and CAC systems. Maintaining this ratio below 1.0 enabled the addition of sufficient calcium sulfate to achieve optimal performance.

关键词： Calcium Sulfoaluminat cement Ettringite formation SO 3 /Al 2 O 3 molar ratio Calcium sulfate

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