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Numerical investigation on characteristics of interfacial wave of liquid film in gas-liquid two-phase flow using OpenFOAM

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Chinese Journal of Aeronautics 2024年第2期37卷 233-248页

作者： Xiaoqi MA Yueshe WANG jiaming TIAN State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Liquid film cooling as an advanced cooling technology is widely used in space *** operation of liquid film along the rocket combustion inner wall is crucial for thermal protection of rocket *** stability of liquid film is mainly determined by the characteristics of interfacial wave,which is rarely investigated right *** to improve the stability of thin film has become a hot *** view of this,an advanced model based on the conventional Volume of Fluid(VOF)model is adopted to investigate the characteristics of interfacial wave in gas-liquid flow by using OpenFOAM,and the mechanism of formation and development of wave is revealed intuitively through numerical *** effects from gas velocity,surface tension and dynamic viscosity of liquid(three factors)on the wave are studied *** can be found that the gas velocity is critical to the formation and development of wave,and four modes of droplets generation are illustrated in this ***,a gas vortex near the gas-liquid interface can induce formation of wave easily,so changing the gas vortex state can regulate formation and development of ***’s more,the change rules of three factors influencing on the interfacial wave are obtained,and the surface tension has a negative effect on the formation and development of wave only when the surface tension coefficient is above the critical value,whereas the dynamic viscosity has a positive effect in this ***,the maximum height and maximum slope angle of wave will level off as the gas velocity ***,the maximum slope angle of wave is usually no more than 38°,no matter what happens to the three factors.

关键词： Interfacial wave Gas-liquid Two-phase flow VOF model OpenFOAM

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Harmonic Damping Characteristics of Single-phase Full-bridge Rectifier Based Loads

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CSEE Journal of Power and Energy Systems 2022年第5期8卷 1448-1456页

作者： Yihang Zhang jiaming Lu Jing Yong State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina

With the rapid development of power electronic technology,many linear single-phase loads in low voltage systems are replaced by those equipped with a single-phase diode ***,most of single-phase loads become harmonic producers due to their nonlinear *** nonlinear loads may have different damping characteristics at harmonic frequencies,which could cause potential power quality *** paper studies the harmonic damping characteristics of such nonlinear *** harmonic damping index is defined to quantify the damping effect of nonlinear loads of harmonic frequencies by analyzing the harmonic ***,the harmonic damping index of different harmonic frequencies is compared through simulations and *** results show that the nonlinear load has a constant damping effect for the fundamental frequency,but a stronger damping for the harmonic *** harmonic damping of such nonlinear loads varies with the harmonic phase angle of supply voltage,and becomes stronger with the increase of the harmonic *** implies that this type of nonlinear load may be beneficial to the suppression of harmonic resonance.

关键词： Damping effect harmonic domain model harmonic impedance nonlinear load

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Optimisation method for carbon black distribution of polypropylene-based semi-conductive screen materials and its effect on charge emission behaviour at screen/insulation interface

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High Voltage 2023年第2期8卷 239-250页

作者： jiaming Yang Rui Zhang Xu Yang Zhi Sun Xindong Zhao hong Zhao Xuan Wang Lin Li Heqian Liu Key Laboratory of Engineering Dielectrics and Its Application Harbin University of Science and TechnologyHarbinChina State Grid Heilongjiang Electric Power Company Limited Electric Power Research Institute State Grid Corporation of ChinaHarbinChina

The semi-conductive(SC)screen materials used in polypropylene(PP)-based cables are usually multi-component *** shows poor compatibility with carbon black(CB),and CB particles tend to disperse in the elastomer phase,which results in CB non-uniform dispersion in screen *** non-uniform distribution of CB will cause abnormal electric fields at the screen/insulation interface and affect insulation *** paper prepared modified PP grafted by molecule maleic anhydride,and four PP-based SC shielding materials were blended in combination with PP,PP-g-MAH,and thermoplastic elastomer(POE)as matrix *** CB distribution,electrical conductivity,and basic physical properties of the shielding material were *** screen materials were served as electrodes to test their effects on the space charge and conductivity characteristics of *** relationship between the macroscopic properties and the distribution characteristics of CB was *** show that the selective dispersion of CB in screen material was improved by PPg-MAH and the surface electric potential distribution was *** emission at the screen/insulation interface and conductivity can be reduced by homogenising the CB ***/PP-g-MAH/POE prepared in this paper exhibits relatively uniform CB distribution,which can reduce the charge emission from the screen/insulation interface.

关键词： insulation distribution interface

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An Energy Trading Method Based on Alliance Blockchain and Multi-Signature

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Computers, Materials & Continua 2024年第2期78卷 1611-1629页

作者： hongliang Tian jiaming Wang College of Electrical Engineering Northeast Electric Power UniversityJilin132012China

Blockchain,known for its secure encrypted ledger,has garnered attention in financial and data transfer realms,including the field of energy ***,the decentralized nature and identity anonymity of user nodes raise uncertainties in energy *** broadcast consensus authentication slows transaction speeds,and frequent single-point transactions in multi-node settings pose key exposure risks without protective measures during user *** address these,an alliance blockchain scheme is proposed,reducing the resource-intensive identity verification among *** integrates multi-signature functionality to fortify user resources and transac-tion security.A novel multi-signature process within this framework involves neutral nodes established through central *** neutral nodes participate in multi-signature’s signing and verification,ensuring user identity and transaction content *** interactions among user nodes enhances transaction efficiency by minimizing communication overhead during verification and consensus *** assessments on reliability and operational speed highlight superior security performance,resilient against conventional attack *** shows that compared to traditional solutions,this scheme has advantages in terms of running *** conclusion,the alliance blockchain framework introduces a novel approach to tackle blockchain’s limitations in energy *** integrated multi-signature process,involving neutral nodes,significantly enhances security and *** scheme’s efficiency,validated through analytical assessments and simulations,indicates robustness against security threats and improved transactional *** research underscores the potential for improved security and efficiency in blockchain-enabled energy trading systems.

关键词： Alliance blockchain multi-signature energy trading security performance transaction efficiency

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Distributed Fixed-Time Optimal Energy Management for Microgrids Based on a Dynamic Event-Triggered Mechanism

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IEEE/CAA Journal of Automatica Sinica 2024年第12期11卷 2396-2407页

作者： Feisheng Yang jiaming Liu Xiaohong Guan IEEE the School of Automation Northwestern Polytechnical University (NPU) the Innovation Center NPU Chongqing the Engineering Research Center of Cyber-Physical Systems Ministry of Education Xi'an Jiaotong University the Center for Intelligent and Networked Systems Department of Automation Tsinghua University

The article investigates the optimal energy management(OEM) problem for microgrids. To figure out the problem in fixed time and alleviate communication load with limited resources, this article devises a novel fixed-time stability lemma and an event-triggered(ET) fixed-time distributed OEM approach. Using Lyapunov stability theory, the distributed approach has been proven to converge in fixed time and the upper bound on convergence time can be derived without dependence on the initial states. The dynamic ET method is raised to dynamically adjust the triggering threshold and reduce communication redundancy. In addition, Zeno behavior is avoided. Simulations are given to show the effectiveness and advantage of the designed distributed OEM method.

关键词： Distributed optimization dynamic event-triggered (ET) mechanism fixed-time consensus microgrid optimal energy management (OEM)

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Investigation of the SA evolution by using the CHAOS-4 model over 1997–2013

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Science China Earth Sciences 2016年第5期59卷 1041-1050页

作者： OU jiaming DU AiMin XU WenYao Key Laboratory of Earth and Planetary Physics Chinese Academy of Sciences Institute of Geology and Geophysics Chinese Academy of Sciences

The temporal and spatial evolution characteristics of the geomagnetic secular acceleration(SA) are investigated, based on CHAOS-4 core field model during the period of 1997–2013. The SA evolution on a short time scale is associated with the phenomenon of the geomagnetic jerk. More details of the global extent and the occurrence time of the successive jerks(the 1999, 2003, 2007, and 2011 jerks) are obtained. The location, size and reversed polarity pattern for the 1999 jerk are similar to those for the 2003 jerk in the Asian-Indian sector. While the 2007 and 2011 jerks mainly take place in the Atlantic sector. The direction and speed of the shift for the four jerks are different, identified by the occurrence time of the jerks. The zonal motions of the SA patches exhibit an oscillation pattern in the Asian-Indian sector, whereas a purely westward drifting pattern is along the equator in the Atlantic sector. It is believed that the shift of the jerks is related to the motion of SA-B_r patches observed at the core-mantle boundary(CMB).

关键词： Geomagnetic secular acceleration Geomagnetic jerk Core-mantle boundary Zonal oscillation

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基于Web2.0技术的病案质控信息化探讨

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中国卫生质量管理 2009年第1期16卷 45-48页

作者：赖伏虎陈少英洪嘉铭裘以冰赵淑媛深圳市第八人民医院信息统计科广东深圳518101 肇庆市第一人民医院广东肇庆526021 广东省人民医院广东广州510030

目的探索Web2.0技术在构建医院病案质量控制与评价体系中的应用。方法论证和引入Web7.0技术的Wiki、SNS、RSS等多个元素,在"大质控观"下将病案质控的各个要素、角色、流程纳入"医院病案质量控制与评价平台"。结果基本实现"全员"参与质控... 详细信息

目的探索Web2.0技术在构建医院病案质量控制与评价体系中的应用。方法论证和引入Web7.0技术的Wiki、SNS、RSS等多个元素,在"大质控观"下将病案质控的各个要素、角色、流程纳入"医院病案质量控制与评价平台"。结果基本实现"全员"参与质控、"全过程"的质量教育和"全天候"的病案信息综合服务。结论基于Web2.0技术的"医院病案质量控制与评价平台"建设方案投资小,建设周期短,使用门槛低,保障前期软件投资,达到质量管理功能的整体升级,值得推广。

关键词：病案质控信息化 Web2.0

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Bicycle dynamics and its circular solution on a revolution surface

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Acta Mechanica Sinica 2020年第1期36卷 220-233页

作者： jiaming Xiong Nannan Wang Caishan Liu State Key Laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing100871China

In this paper,we study the dynamics of an idealized benchmark bicycle moving on a surface of *** employ symbolic manipulations to derive the contact constraint equations from an ordered process,and apply the Lagrangian equations of the first type to establish the nonlinear differential algebraic equations(DAEs),leaving nine coupled differential equations,six contact equations,two holonomic constraint equations and four nonholonomic constraint *** then present a complete description of hands-free circular motions,in which the time-dependent variables are eliminated through a rotation *** find that the circular motions,similar to those of the bicycle moving on a horizontal surface,nominally fall into four solution families,characterized by four curves varying with the angular speed of the front ***,we numerically investigate how the topological profiles of these curves change with the parameter of the revolution ***,we directly linearize the nonlinear DAEs,from which a reduced linearized system is obtained by removing the dependent coordinates and counting the symmetries arising from cyclic *** stability of the circular motion is then analyzed according to the eigenvalues of the Jacobian matrix of the reduced linearized system around the equilibrium *** find that a stable circular motion exists only if the curvature of the revolution surface is very small and it is limited in small sections of solution ***,based on the numerical simulation of the original nonlinear DAEs system,we show that the stable circular motion is not asymptotically stable.

关键词： Bicycle dynamics Nonholonomic constraints Stability Nonlinear DAEs Circular motion

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Anisotropic inflation with general potentials

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Science China(Physics,Mechanics & Astronomy) 2016年第4期59卷 48-57页

作者： jiaming Shi XiaoTian Huang TaoTao Qiu Department of Physics Science and Technology Central China Normal University Institute of Astrophysics Central China Normal University

Anomalies in recent observational data indicate that there might be some "anisotropic hair" generated in an inflation period. To obtain general information about the effects of this anisotropic hair to inflation models, we studied anisotropic inflation models that involve one vector and one scalar using several types of potentials. We determined the general relationship between the degree of anisotropy and the fraction of the vector and scalar fields, and concluded that the anisotropies behave independently of the potentials. We also generalized our study to the case of multi-directional anisotropies.

关键词： inflation vector field CMB anisotropies

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Study on the local time asymmetry of the Earth's ring currents based on multiple low-Earth-orbit satellite magnetic observations

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Science China(Technological Sciences) 2024年第11期67卷 3354-3364页

作者： OU jiaming JIANG Yi YAN Qing State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyMacao 999078China Macao Institute of Space Technology and Application Macao 999078China Zhuhai MUST Science and Technology Research Institute Macao University of Science and TechnologyZhuhai 519085China

The azimuthal morphology of Earth's ring currents has consistently shown asymmetry during extreme space weather events at low latitudes,particularly during geomagnetic storms.A dawn-dusk pattern has been detected during the storm main phase through near-Earth and in-situ magnetic *** asymmetry is believed to arise from asymmetric solar windmagnetosphere coupling and is linked to the closure of the ring *** evidence has confirmed the existence of asymmetric ring currents during quiet times and the storm recovery *** phenomenon may be closely related to the evolution of ring currents,including plasma injection and decay *** this study,the local time asymmetry of the ring current is estimated using data from low-Earth-orbit Swarm and Macao Science Satellite-1(MSS-1)*** harmonics models are developed to quantify the magnetic field of ring currents through external Gauss coefficients during both quiet periods and the storm recovery *** features of dawn-dusk asymmetry are observed in various cases in different months.(1)The maximum difference in magnetic value across local time ranges from 3 to 10 nT,showing relative invariance compared with various Sym-H levels.(2)Stronger magnetic signals are detected at the premidnight sector during quiet times and at the afternoon sector during the storm recovery phase.(3)Magnetic perturbations remain at a lower level during the postmidnight and morning *** the pattern of local time asymmetry differs between quiet times and the recovery phase,dawn-dusk asymmetry remains the most pronounced feature,affecting the trapping and loss of charged particles in the inner *** Swarm and MSS-1 magnetic observations can enable convenient monitoring of the detailed azimuthal local time effects of the ring current at various disturbance levels in the future.

关键词： Earth's ring currents local time asymmetry SHA model Macao Science Satellite-1

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