A generalized multi-field coupling approach and its application to stability and deformation control of a high slope

Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engineering disturbances are important factors that would alter the natural evolutionary processes or change the multi-field interactions in the rock masses from their initial equilibrium states. The concept of generalized multi-field couplings was proposed by placing particular emphasis on the role of engineering disturbances in traditional multi-field couplings in rock masses. A mathematical model was then developed, in which the effects of engineering disturbances on the coupling-processes were described with changes in boundary conditions and evolutions in thermo-hydro-mechanical （THM） properties of the rocks. A parameter, d, which is similar to damage variables but has a broader physical meaning, was conceptually introduced to represent the degree of engineering disturbances and the couplings among the material properties. The effects of blasting excavation, bolting and grouting in rock engineering were illustrated with various field observations or theoretical results, on which the degree of disturbances and the variations in elastic moduli and permeabilities were particularly focused. The influences of excavation and groundwater drainage on the seepage flow and stability of the slopes were demonstrated with numerical simulations. The proposed approach was further employed to investigate the coupled hydro-mechanical responses of a high rock slope to excavation, bolting and impounding of the reservoir in the dam left abutment of Jinping I hydropower station. The impacts of engineering disturbances on the deformation and stability of the slope during construction and operation were demonstrated.

COMSOL Multiphysics在锂离子电池中的应用

作为一种具有前景的能量存储系统,锂离子电池需要进一步提高能量密度、功率密度、可靠性和循环稳定性,以满足不断增长的大型能源存储、电动汽车和便携式电子设备需求。当前对锂离子电池的实验研究仍然面临多个挑战,这些挑战包括电解液的导电性和安全性、高能量负极的沉积-剥离机制的优化、高能量正极的循环电压和容量维持、高电流条件下的界面极化和容量释放,以及在极端电流-温度-针刺条件下的热失控管理等问题。这些问题涉及到电-化-力-热等多个场的耦合作用,需要进行协同优化处理。COMSOL Multiphysics提供了一种可行的工具,通过求解多物理场耦合的连续方程,能够同时考虑载流子浓度、电流密度、电-化学势、温度、应力/应变和几何形态等综合信息的演化。本文概述了该工具在锂离子电池的电解液、负极和正极设计等方面的研究,并聚焦于多场耦合对电池性能的综合影响、多场耦合模拟方法以及理论模拟与实验表征的结合。最后,本文对理论与实验联合研究中的多场和多尺度问题进行了展望。

MULTI-FIELD COUPLING BEHAVIOR OF SIMPLY-SUPPORTED CONDUCTIVE PLATE UNDER THE CONDITION OF A TRANSVERSE STRONG IMPULSIVE MAGNETIC FIELD

In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynamic buckling phenomenon of the thin plates in the effect of the magnetic volume forces produced by the interaction between the eddy current and the magnetic fields, a FEM analysis program is developed to characterize the phenomena of magnetoelastic buckling and instability of the plates. The critical values of magnetic field for the three different initial vibrating modes are obtained, with a detailed discussion made on the effects of the lengththickness ratio a/h of the plate and the length-width ratio a/b as well as the impulse parameter on the critical value BOcr of the applied magnetic field.

Analysis of high-frequency local coupling instability induced by multi- transmitting formula - P-SV wave simulation in a 2D waveguide

Local coupling instability will occur when the numerical scheme of absorbing boundary condition and that of the field wave equation allow energies to spontaneously enter into the computational domain. That is, the two schemes support common wave solutions with group velocity pointed into the computation domain. The key to eliminate local coupling instability is to avoid such wave solutions. For lumped-mass finite element simulation of P-SV wave motion in a 2D waveguide, an approach for stable implementation of high order multi-transmitting formula is provided. With a uniform rectangular mesh, it is proven and validated that high-freqaency local coupling instability can be eliminated by setting the ratio of the element size equal to or greater than x/2 times the ratio of the P wave velocity to the S wave velocity. These results can be valuable for dealing instability problems induced by other absorbing boundary conditions.

Multi-Field Analysis and Experimental Verification on Piezoelectric Valve-Less Pumps Actuated by Centrifugal Force

A piezoelectric centrifugal pump was developed previously to overcome the low frequency responses of piezoelectric pumps with check valves and liquid reflux of conventional valveless piezoelectric pumps. However, the electro-mechanical-fluidic analysis on this pump has not been done. Therefore, multi-field analysis and experimen- tal verification on piezoelectrically actuated centrifugal valveless pumps are conducted for liquid transport appli- cations. The valveless pump consists of two piezoelectric sheets and a metal tube with piezoelectric elements pushing the metal tube to swing at the first bending resonant fre- quency. The centrifugal force generated by the swinging motion will force the liquid out of the metal tube. The governing equations for the solid and fluid domains are established, and the coupling relations of the mechanical, electrical and fluid fields are described. The bending res- onant frequency and bending mode in solid domain are discussed, and the liquid flow rate, velocity profile, and gauge pressure are investigated in fluid domain. The working frequency and flow rate concerning different components sizes are analyzed and verified through experiments to guide the pump design. A fabricated pro- totype with an outer diameter of 2.2 mm and a length of 80 mm produced the largest flow rate of 13.8 mL/min at backpressure of 0.8 kPa with driving voltage of 80 Vpp. Bysolving the electro-mechanical-fluidic coupling problem, the model developed can provide theoretical guidance on the optimization of centrifugal valveless pump characters.

Citation and bibliographic coupling between authors in the field of social network analysis

Purpose:We analyzed the structure of a community of authors working in the field of social network analysis(SNA)based on citation indicators:direct citation and bibliographic coupling metrics.We observed patterns at the micro,meso,and macro levels of analysis.Design/methodology/approach:We used bibliometric network analysis,including the“temporal quantities”approach proposed to study temporal networks.Using a two-mode network linking publications with authors and a one-mode network of citations between the works,we constructed and analyzed the networks of citation and bibliographic coupling among authors.We used an iterated saturation data collection approach.Findings:At the macro-level,we observed the global structural features of citations between authors,showing that 80%of authors have not more than 15 citations from other works.At the meso-level,we extracted the groups of authors citing each other and similar to each other according to their citation patterns.We have seen a division of authors in SNA into groups of social scientists and physicists,as well as into other groups of authors from different disciplines.We found some examples of brokerage between different groups that maintained the common identity of the field.At the micro-level,we extracted authors with extremely high values of received citations,who can be considered as the most prominent authors in the field.We examined the temporal properties of the most popular authors.Research limitations:The main challenge in this approach is the resolution of the author’s name(synonyms and homonyms).We faced the author disambiguation,or“multiple personalities”(Harzing,2015)problem.To remain consistent and comparable with our previously published articles,we used the same SNA data collected up to 2018.The analysis and conclusions on the activity,productivity,and visibility of the authors are relative only to the field of SNA.Practical implications:The proposed approach can be utilized for similar objectives and identifying key structures and characteristics in other disciplines.This may potentially inspire the application of network approaches in other research areas,creating more authors collaborating in the field of SNA.Originality/value:We identified and applied an innovative approach and methods to study the structure of scientific communities,which allowed us to get the findings going beyond those obtained with other methods.We used a new approach to temporal network analysis,which is an important addition to the analysis as it provides detailed information on different measures for the authors and pairs of authors over time.

Mechanism of hybrid-magnetic-circuit multi-couple motor

Discusses the interval between laminations in a permanent magnet inductor motor which makes the air gap magnetic field produced by the permanent magnet very uneven in the axial direction, and limits the performance of a motor. Proposes a hybrid magnetic circuit multi couple motor to compensate for the uneven air gap magnetic field, thereby improving the performance of a motor.

Mathematical modeling for coupled solid elastic-deformation and gas leak flow in multi-coal-seams

Based on the new viewpoint of solid and gas interaction mechanics, gas leakage in a double deformable coal seam can be understood. That is, under the action of geophysical fields, the methane flow in a double deformable coal seam can be essentially considered to be compressible with time dependent and mixed permeation and diffusion through a pore cleat deformable heterogeneous and anisotropy medium. Based on this new viewpoint, a coupled mathematical model for coal seam deformation and gas leakage in a double coal seam was formulated and numerical simulations for gas emission from the coal seam are presented. It is found that coupled models might be closer to reality.

Coupling Analysis of Tourism Development and Rural Revitalization in Yannanfei Tea Field Resort of Guangdong Province

By deconstructing the dimensions of rural tourism and rural revitalization and constructing a coupled conceptual model,a coupled evaluation model is constructed.Yannanfei Tea Field Resort in Guangdong is taken as a research case for empirical analysis,to explore the coupled development trend of the two.The results show that①the tourism development of Guangdong Yannanfei Tea Field Resort has a good synergistic relationship with rural revitalization.The two complement and promote each other,and rural tourism has significantly promoted the development of rural revitalization.②The coupling development of tourism development and rural revitalization in Guangdong Yannanfei Tea Field Resort is divided into coupling imbalance period and coupling coordination period.The results indicate that the coordination between the two has not yet reached a level of good coordination and high-quality coordination.It is recommended that the resort should fully utilize the opportunity of rural revitalization strategy,increase investment in rural tourism,promote the transformation and upgrading of the resort,impel the integration of tea and tourism,and develop new business model of tea-tourism rural vacation.

Thermal–structure coupling analysis and multi-objective optimization of motor rotor in MSPMSM

With the high speed, the rotor of magnetically suspended permanent magnet synchronous motor(MSPMSM) suffers great thermal stress and mechanical stress resulting from the temperature rise problem caused by rotor losses, which leads to instability and inefficiency.In this paper, the mechanical–temperature field coupling analysis is conducted to analyze the relationship between the temperature field and structure, and multi-objective optimization of a rotor is performed to improve the design reliability and efficiency. Firstly, the temperature field is calculated by the 2 D finite element model of MSPMSM and the method of applying the 2 D temperature result to the 3 D finite element model of the motor rotor equivalently is proposed. Then the thermal–structure coupling analysis is processed through mathematic method and finite element method(FEM),in which the 3 D finite element model is established precisely in a way and approaches the practical operation state further. Moreover, the impact produced by the temperature and structure on the mechanical strength is analyzed in detail. Finally, the optimization mathematical model of the motor rotor is established with Sequential Quadratic Programming-NLPQL selected in the optimization scheme. Through optimization, the strength of the components in the motor rotor increases obviously and satisfies the design requirement, which to a great extend enhances the service life of the MSPMSM rotor.

Multi-physical field coupling simulation of TCVI process for preparing carbon/carbon composites

To prepare Carbon/Carbon (C/C) composites with advanced performance, the thermal gradient chemical vapor infiltration (TCVI) process has been optimized by simulation. A 2D axisymmetric unstable model was built, which included convection, conduction, diffusion, densification reactions in the pores and the evolution of the porous medium. The multi-physical field coupling model was solved by finite element method (FEM) and iterative calculation. The time evolution of the fluid, temperature and preform density field were obtained by the calculation. It is indicated that convection strongly affects the temperature field. For the preform of carbon/carbon composites infiltrated for 100 h by TCVI, the radial average densities from simulation agrees well with those from experiment. The model is validated to be reliable and the simulation has capability of forecasting the process.

A 3D multi-field element for simulating the electromechanical coupling behavior of dielectric elastomers

We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible constraint of the hyperelastic material. Linearization of the variational form and finite element discretization are adopted for the numerical implementation. A general FEM program framework is devel- oped using C＋＋ based on the open-source finite element library deal.II to implement this proposed algorithm. Numerical examples demonstrate the accuracy, convergence properties, mesh-independence properties, and scalability of this method. We also use the method for eigenvalue analysis of a dielectric elastomer actuator subject to electromechanical loadings. Our finite element implementation is available as an online supplementary material.

Design of a conduction-cooled 4 T superconducting racetrack for a multi-field coupling measurement system

A conduction-cooled superconducting magnet producing a transverse field of 4 T has been designed for a new generation multi-field coupling measurement system, which will be used to study the mechanical behavior of superconducting samples at cryogenic temperatures and intense magnetic fields. A compact cryostat with a two-stage GM cryocooler is designed and manufactured for the superconducting magnet. The magnet is composed of a pair of flat racetrack coils wound by NbTi/Cu superconducting composite wires, a copper and stainless steel combinational former and two Bi2Sr2CaCu20~ superconducting current leads. The two coils are connected in series and can be powered with a single power supply. In order to support the high stress and attain uniform thermal distribution in the superconducting magnet, a detailed finite element （FE） analysis has been performed. The results indicate that in the operating status the designed magnet system can sufficiently bear the electromagnetic forces and has a uniform temperature distribution.

Temperature field analysis and its application in hot continuous rolling of Inconel 718 superalloy

A coupled thermo-mechanical model containing metal flow and temperature field for calculating temperature variation has been developed on fourteen-pass hot continuous rolling of round rod for Inconel 718 alloy using 3D elastic-plastic finite element method （FEM）. The temperature of characteristic analysis points in the intermediate cross-section of the workpiece has been simulated at initial temperature ranging from 960 to 1000 ℃ and initial velocity in range of 0.15-0.55 m·s^-1. Based on finite element analysis and microstructural observation in cylindrical hot compression experiments, the appropriate hot continuous rolling technologies have been designed for rod products with different diameters. For a real rolling practice, the simulated surface temperature was examined and is in good agreement with the measured one.

STUDY OF TOPOLOGY OPTIMIZATION FOR THERMO-STRUCTURAL COUPLING FIELD

A number of critical problems of topology optimization concerning the thermostructural coupling field axe studied at length. The governing equations and topology optimization model for the thermal-structural coupling field axe derived, with an adjoint method for sensitivity analysis of the thermo-structural coupling field proposed. The optimization algorithm for coupling field topology optimization is investigated and a flowchart of coupling field topology optimization presented. The theory and algorithms axe implemented and verified by two numerical examples.

STUDY ON COUPLING MODEL OF (SEEPAGE-FIELD) AND STRESS-FIELD FOR ROLLED CONTROL CONCRETE DAM

Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters. The principle on establishing the coupling model of seepage_field and stress_field for RCCD was presented. A 3_D Finite Element Method(FEM) program was developed. Study shows that such parameters as the thickness of construction interfaces,the elastic ratio and the (Poisson's) ratio obtained by tests and theoretical analysis are more reasonable, the coupling model of seepage_field and stress_field for RCCD may indicate the coupling effect between the two fields scientifically, and the developed 3_D FEM program can reflect the effect of the construction interfaces more adequately. According to the study, many scientific opinions are given both to analyze the influence of the construction interfaces to the (dam's) characteristic, and to reveal the interaction between the stress_field and the seepage_field.

Analysis of 1989/1990 main physical fields for air-sea coupled system in the tropical western Pacific

In this paper, the marine ship observation data sets in the seventh (October 16-December 4. 1989) and eighth (June 1-July 16, 1990) cruises of PRC -US tropical ocean and global atmosphere (TOGA) joint scientific investigation in the tropical western Pacific are used to analyze the elements such as sea surface temperature (SST), surface wind field, fluxes and net heat budget, which are important physical parameters of underlying earth's surface influencing the global mean circulation evolution on seasonal and interannual time scales. These diagnostic analyses are very beneficial to the understanding of the regional climate characteristics and the air-sea interaction mechanism, and the improving of surface flux parameterizations and regional or global climate model.

煤矿矿井水水质形成及演化的水动力场-水化学场-微生物场耦合作用与数值模拟

煤矿矿井水的水质形成与演化过程机理复杂,受水动力场、水化学场和微生物场等多场作用影响显著。深入研究并揭示煤矿矿井水水质形成机理与演化趋势、阐明采空区封闭后矿井水的多场耦合作用机制是矿井水污染防控与修复的理论基础。以鄂尔多斯盆地某煤矿采空区为水文地质原型,在前期研究的基础上,进一步建立了煤矿采空区积水水位回升、蓄满后水动力-水化学-微生物场(HCB)多场耦合室内相似模拟和数值模型。采空区水动力场研究结果表明基质-裂隙双孔隙模型能有效模拟采空区水位回升过程,模拟误差为9.9%,其模拟精度远高于理论预测和单孔隙模型。水化学场模拟结果与试验较为吻合,SO_(4)^(2-)、HCO_(3)-和p H模拟相对误差分别为3.0%、21.0%和6.2%,模拟结果较为可靠。模拟结果显示采空区蓄水过程中水岩反应和微生物作用不明显;而蓄满后水动力几乎停滞,但水化学场和微生物场较为活跃,2号煤和3号煤层中黄铁矿的氧化反应使得SO_(4)^(2-)质量浓度提升约24.6%;后期采空区水环境演化为弱酸性、厌氧还原条件,微生物降解作用凸显,将SO_(4)^(2-)有一定的“自净”能力。通过调整微生物代谢速率常数,可将SO_(4)^(2-)降解比例提高到61.6%。实际工程场景中可通过补充碳源、人工建立密闭厌氧环境等强化手段实现这一目标。将多场耦合室内试验和数值模拟技术拓展到煤矿采空区积水水质形成与演化规律研究,研究结论可为煤矿区矿井水污染防治提供指导。

跟网型变换器的小扰动同步稳定机理分析与致稳控制

弱电网下,跟网型变换器易出现因阻尼不足导致的小扰动同步失稳问题。为此,该文借鉴复转矩分析理论,计及复杂控制耦合,建立跟网型变换器的复转矩模型。量化多环控制耦合、线路阻抗、控制参数等因素对系统阻尼转矩的影响,从阻尼的角度揭示跟网型变换器的小扰动同步失稳机理。根据理论分析,提出一种基于相位补偿的锁相环阻尼重塑控制策略,通过补偿多环控制耦合引入的负阻尼,增强变换器的小扰动同步稳定性。最后,开展相应的仿真与实验,验证理论分析的正确性与改进控制策略的有效性。

水资源-能源-粮食-生态系统耦合协调及驱动力分析

为加深对我国水资源、能源、粮食、生态系统协同演变趋势的认识,构建水资源-能源-粮食-生态多维系统指标体系,运用耦合协调度模型对我国2005—2020年水资源-能源-粮食-生态系统耦合协调度进行评价,并采用多因素归因分析法进行驱动力分析。结果表明:我国水资源-能源-粮食-生态系统耦合协调度从2005年的0.55增长到2020年的0.84,各地区耦合协调度从勉强协调发展水平过渡到中级协调发展水平,各子系统对耦合协调度上升的驱动分别经历了由粮食子系统到生态子系统再到水资源子系统主导的过程;能源子系统的贡献率虽然比较小,但是未来可能是各地区提升水资源-能源-粮食-生态系统多维系统协调发展水平的突破口。