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电力系统自动化 2012年第8期36卷 115-121页

作者： xiong, Xiaofu Ouyang, Jinxin State Key Laboratory of Power Transmission Equipment and System Security Chongqing University Chongqing 400030 China

Large-scale doubly-fed induction generator(DFIG)wind turbines are connected to the grid and required to remain grid-connection during faults,the short-circuit current contributed by the generation has become a significant ***,the traditional calculation methods aiming at synchronous generators cannot be directly applied to the DFIG wind turbines.A new method is needed to calculate the short-circuit current required by the planning,protection and control of the power *** short-circuit transition of DFIG under symmetrical and asymmetric short-circuit conditions are mathematically deduced,and the short-circuit characteristics of DFIG are analyzed.A new method is proposed to calculate the steady-state short-circuit current of DFIG based on the derived *** time-domain simulations are conducted to verify the accuracy of the proposed method.

关键词：双馈风力发电机短路电流短路特性计算变速恒频稳态双馈感应发电机非对称短路

Recyclable polythioesters and polydisulfides with near-equilibrium thermodynamics and dynamic covalent bonds

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Science China Chemistry 2023年第3期66卷 725-738页

作者： Wei xiong Hua Lu Beijing National Laboratory for Molecular Sciences Center for Soft Matter Science and EngineeringKey Laboratory of Polymer Chemistry and Physics of Ministry of EducationCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

The accumulation of discarded petroleum-based plastics causes serious environmental ***,recyclable polymers with neutrality in thermodynamics,such as polyesters,polycarbonates,and polyolefins,have been developed as promising alternatives to traditional petroleum-based ***,the chemical recycle of these polymers usually requires high energy input and expensive *** covalent bonds,such as thioester and disulfide bonds,have emerged as building blocks for constructing recyclable polymers that can be rapidly degraded/recycled under mild *** this review,we introduce representative studies on recyclable polythioesters and polydisulfides with respect to their synthetic strategies,thermodynamic manipulation,physicochemical properties,and preliminary *** also highlight the important role of kinetic factors played in the design of recyclable ***,major challenges,perspectives,and future opportunities in the synthesis and applications of polythioesters/polydisulfides are discussed.

关键词： polythioesters polydisulfides recyclable near-equilibrium thermodynamics dynamic covalent bond

Adsorptive removal of As(Ⅲ) ions from water using spent grain modified by polyacrylamide

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Journal of Environmental Sciences 2016年第7期28卷 124-130页

作者： Yunnen Chen Changshi xiong School of Resource and Environmental Engineering Jiangxi University of Science and Technology

In order to enhance the removal efficiency of As（III）, a pre-oxidation process is generally applied first to convert As（III） to As（V）, which may cause unwanted new contaminants. To overcome this problem, efforts were made to develop an effective way to remove As（III）directly without an oxidation step. The effect of polyacrylamide polymers（PAMs） such as anionic PAM, cationic PAM and nonionic PAM, on As（III） ion adsorption by spent grain（SG）was investigated. The physico-chemical properties of the three PAM-polymerized SGs（APSG（anionic PAM-polymerized modified spent grain）, CPSG（cationic PAM-polymerized spent grain） and NPSG（nonionic PAM-polymerized spent grain）） were analyzed using Fourier transform infrared（FT-IR）, scanning electron microscope（SEM） and zeta *** experimental data showed that the sequence of preferential adsorption for As（III） was APSG 〉 CPSG 〉 NPSG. Active functional groups such as amino group（NH2）, carbonyl group（C_O）, C–N bond of the amide group（CONH2）, and hydroxyl group（O–H） were responsible for As（III） adsorption. Many tubular structures occurring on the surface of APSG possibly increase the specific surface areas and favor the adsorption of As（III） ions. A fixed-bed study was carried out by using APSG as an adsorbent for As（III） from water. Three factors such as bed height, initial concentration and flow rate were studied, and breakthrough curves of As（III） were obtained. The Adams–Bohart model was used to analyze the experimental data and the model parameters were evaluated.

关键词： Arsenite(As(Ⅲ)) Adsorption Polyacrylamide(PAM) Spent grain(SG) Functional groups

Effect of stress ratio on HCF and VHCF properties at temperatures of 20 °C and 700 °C for nickel-based wrought superalloy GH3617M

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Chinese Journal of Aeronautics 2019年第9期32卷 2199-2210页

作者： Aoshuang WAN Junjiang xiong School of Transportation Science and Engineering Beihang University

This paper attempts to investigate the effects of stress ratio and high temperature on the HCF(high-cycle-fatigue) and VHCF(very-high-cycle-fatigue) behaviors of nickel-based wrought superalloy GH3617 M. Fatigue tests over the full HCF and VHCF regimes were conducted on superalloy GH3617 M subjected to constant-amplitude loading at five stress ratios of -1, -0.5, 0,0.4, and 0.8 in environments of 20 °C and 700 °C temperatures. From experimental observation and fractographic analysis, fatigue mechanisms were deduced to reveal the synergistic interaction between high temperature and stress ratio on the HCF and VHCF behaviors of superalloy GH3617 M. A phenomenological model was crafted from available fatigue design knowledge to evaluate the synergistic interaction, and a good correlation between predictions and experiments has been achieved.

关键词： High cycle fatigue High-temperature Nickel-based superalloy Stress ratio Very high cycle fatigue

Temperature effect on buckling properties of ultra-thin-walled lenticular collapsible composite tube subjected to axial compression

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Chinese Journal of Aeronautics 2014年第5期27卷 1312-1317页

作者： Bai Jiangbo xiong Junjiang School of Transportation Science and Engineering Beihang University

This paper seeks to outline the temperature effect on the buckling properties of ultra-thin-walled lenticular collapsible composite tube（LCCT） subjected to axial *** buckling tests of the LCCT specimens subjected to axial compression were carried out on INSTRON-500 N servo-hydraulic machine in dry state and at the temperatures of 25 C, 100 C and 80 C. The load–displacement curves and buckling initiation loads were measured and the buckling initiation mechanism was discussed from experimental observations. Experiments show that the buckling initiation load, on average, is only about 2.2% greater at the low temperature of 80 C than at the room temperature of 25 C due to the material hardening, demonstrating an insignificant increase in the buckling initiation load, whereas it is about 19.5% lower at the high temperature of 100 C than at the room temperature owing to the material softening, implying a significant decrease in the buckling initiation load. The failure mode of the LCCT in axial compression tests at three different temperatures can be reckoned to be characteristic of the buckling initiation and propagation around the central region until rupture. The finite element（FE） model is presented to simulate the buckling initiation mechanism based on the eigenvalue-based methodology. Good correlation between experimental and numerical results is achieved.

关键词： Axial compression Buckling Composite Finite element analysis Lenticular collapsible tube

A three-dimensional cellular automaton model for simulation of dendritic growth of magnesium alloy

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Acta Metallurgica Sinica(English Letters) 2012年第3期25卷 169-178页

作者： Mengwu WU Shoumei xiong Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Automobile Safety and Energy Tsinghua UniversityBeijing 100084China

A numerical model based on the cellular automaton method for the three-dimensional simulation of dendritic growth of magnesium alloy was developed. The growth ki- netics was calculated from the complete solution of the transport equations. By con- structing a three-dimensional anisotropy model with the cubic CA cells, simulation of dendritic growth of magnesium alloy with six-fold symmetry in the basal plane was achieved. The model was applied to simulate the equiaxed dendritic growth and columnar dendritic growth under directional solidification, and its capability was addressed by comparing the simulated results to experimental results and those in the previously published works. Meanwhile, the three-dimensional simulated results were also compared with that of in two dimensions, offering a deep insight into the microstructure formation of magnesium alloy during solidification.

关键词： Magnesium alloy Dendritic growth Cellular automaton method: Three-dimensional

A robust and efficient structural reliability method combining radial-based importance sampling and Kriging

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Science China(Technological Sciences) 2018年第5期61卷 724-734页

作者： xiong Bo TAN HuiFeng Center for Composite Materialsa nd Structures Harbin Institute of Technology

Simulation based structural reliability analysis suffers from a heavy computational burden, as each sample needs to be evaluated on the performance function, where structural analysis is performed. To alleviate the computational burden, related research focuses mainly on reduction of samples and application of surrogate model, which substitutes the performance function. However,the reduction of samples is achieved commonly at the expense of loss of robustness, and the construction of surrogate model is computationally expensive. In view of this, this paper presents a robust and efficient method in the same direction. The present method uses radial-based importance sampling (RBIS) to reduce samples without loss of robustness. Importantly, Kriging is fully used to efficiently implement RBIS. It not only serves as a surrogate to classify samples as we all know, but also guides the procedure to determine the optimal radius, with which RBIS would reduce samples to the highest degree. When used as a surrogate, Kriging is established through active learning, where the previously evaluated points to determine the optimal radius are reused. The robustness and efficiency of the present method are validated by five representative examples, where the present method is compared mainly with two fundamental reliability methods based on active learning Kriging.

关键词： structural reliability simulation radial-based importance sampling Kriging active learning

Lower bound for transient growth of inclined buoyancy layer

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Applied Mathematics and Mechanics(English Edition) 2017年第6期38卷 779-796页

作者： Xiangming xiong Jianjun TAO Center for Applied Physics and Technology (CAPT)-MOE Key Laboratory of High Energy Density Physics Simulation (HEDPS) State Key Laboratory for Turbulence and Complex System (SKLTCS)Department of Mechanics and Engineering ScienceCollege ofEngineeringPeking University

The relationship between stabilities of the buoyancy boundary layers along an inclined plate and a vertical plate immersed in a stratified medium is studied theoretically and numerically. The eigenvalue problem of energy stability is solved with the method of descending exponentials. The disturbance energy is found to be able to grow to 11.62 times as large as the initial disturbance energy for Pr = 0.72 when the Grashof number is between the critical Grashof numbers of the energy stability and the linear stability. We prove that, with a weighted energy method, the basic flow of the vertical buoyancy boundary layer is stable to finite-amplitude streamwise-independent disturbances.

关键词： natural convection boundary layer energy method transient growth

Characterization of the Protective Surface Films Formed on Molten AZ91D Magnesium Alloy in SO_2/Air Atmospheres in a Sealed Furnace

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Journal of Materials Science & Technology 2014年第4期30卷 353-358页

作者： Xianfei Wang Shoumei xiong Department of Mechanical Engineering Tsinghua University State Key Laboratory of Automotive Safety and Energy Tsinghua University

Surface films that formed on molten AZ91D magnesium alloy in S02/air cover gases at 680 ℃ in a sealed furnace were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and Auger electron spectroscopy. It is revealed that the film formed on molten AZ91D alloy surface in cover gas with high air content can prevent the molten AZ91D alloy from oxidation and ignition. The surface film contained three elements, namely magnesium, oxygen and sulfur, and was mainly composed of MgO and MgS. The properties of the film depended on air content in the cover gas and holding time. Thermodynamic calculation showed that MgSO4 was the stable phase, and it was concluded that the formation of MgS04 was important for the formation of the protective surface film in S02/air atmospheres.

关键词： Magnesium alloy S02 Sealed furnace Gas protection Surface film

Fractional-order generalized thermoelastic diffusion theory

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Applied Mathematics and Mechanics(English Edition) 2017年第8期38卷 1091-1108页

作者： Chunbao xiong Yanbo NIU School of Civil Engineering Tianjin UniversityTianjin 300072China

The present work aims to establish a fractional-order generalized themoelastic diffusion theory for anisotropic and linearly thermoelastic diffusive media. To numerically handle the multi-physics problems expressed by a sequence of incomplete differential equations, particularly by a fractional equation, a generalized variational principle is obtained for the unified theory using a semi-inverse method. In numerical implementation, the dynamic response of a semi-infinite medium with one end subjected to a thermal shock and a chemical potential shock is investigated using the Laplace transform. Numerical results, i.e., non-dimensional temperature, chemical potential, and displacement, are presented graphically. The influence of the fractional order parameter on them is evaluated and discussed.

关键词： fractional Laplace anisotropic infinite variational handle unified inverse Liouville calculus