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Creep and recovery behaviors of magnetorheological elastomers

Weihua LI, Yang ZHOU, Tongfei TIAN, Gursel ALICI,

《机械工程前沿（英文）》 2010年 第5卷 第3期   页码 341-346 doi: 10.1007/s11465-010-0096-8

摘要： This paper presents experimental and modeling study of creep and recovery behaviors of magneto-rheological elastomers (MREs) under constant stresses. Experimental study was accomplished using a rheometer with parallel-plate geometry. Under constant stresses ranging from a small value to a large one, the resultant strains were recorded. The experimental results demonstrated that MREs behave as linear visocleastic properties. The effects of the magnetic field and stress on MRE creep behaviors were discussed. Moreover, a four-parameter viscoelastic model was developed to describe MRE creep behaviors. The comparison between the experimental results and the modeling predictions indicates that the model can predict MRE creep behaviors very well.

关键词： magneto-rheological elastomers (MREs)     creep     recovery     linear viscoelastic model    

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Linear viscoelastic behavior of asphalt binders and mixtures containing very high percentages of reclaimed

《结构与土木工程前沿（英文）》   页码 1211-1227 doi: 10.1007/s11709-023-0983-9

摘要： The primary aim of this study is to correlate the impact of aggregates, if any, on the viscoelastic behavior of rejuvenated asphalt mixtures containing very high amounts of reclaimed asphalt pavement (RAP) (> 50%). First, gradation of 100% RAP was rectified, using a modified Bailey method by adding virgin aggregates to achieve two coarse dense-graded and one fine dense-graded blends. Complex modulus test was then performed from −35 to +35 °C and 0.01–10 Hz. In addition to performance grade (PG) testing, extracted and recovered binders from different asphalt mixtures underwent shear complex modulus test within −8 °C to high temperature PG and frequencies from 0.001 to 30 Hz. Cole−Cole, Black space, complex modulus and phase angle master curves were constructed and Shift-Homothety-Shift in time-Shift (SHStS) transformation was used to compare the linear viscoelastic behavior of asphalt binders and mixtures. The influence of aggregates on the viscoelastic behavior of asphalt mixtures depends on temperature and/or frequency. The role of asphalt binders in the behavior of asphalt mixtures is more pronounced at high temperatures and the effect of the aggregate structure increases as the temperature falls. The maximum difference (60% to 70%) in the viscoelastic behavior of the binder and mixture based on SHStS transformed Cole−Cole curves is within the phase angle of 15°–20°.

关键词： RAP     complex modulus     SHStS transformation     rejuvenation     behavior of asphalt binder and mixture    

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An autonomous system for thermal convection of viscoelastic fluids in a porous layer using a thermalnonequilibrium model

Qi WEI, Xiaohui ZHANG

《能源前沿（英文）》 2010年 第4卷 第4期   页码 507-516 doi: 10.1007/s11708-010-0017-x

摘要： Thermal convection of viscoelastic fluids saturating a horizontal porous layer heated from below is analyzed using a thermal nonequilibrium model to take account of the interphase heat transfer between the fluid and the solid. The viscoelastic character of the flow is considered by a modified Darcy’s law. An autonomous system with five differential equations is deduced by applying the truncated Galerkin expansion to the momentum and heat transfer equations. The effects of interphase heat transfer on the thermal convection of viscoelastic fluids in a porous medium are analyzed and discussed. The results show that the weak interphase heat transfer tends to stabilize the steady convection.

关键词： thermal convection     porous media     viscoelastic fluid     thermal nonequilibrium model    

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General expression for linear and nonlinear time series models

Ren HUANG, Feiyun XU, Ruwen CHEN

《机械工程前沿（英文）》 2009年 第4卷 第1期   页码 15-24 doi: 10.1007/s11465-009-0015-z

摘要： The typical time series models such as ARMA, AR, and MA are founded on the normality and stationarity of a system and expressed by a linear difference equation; therefore, they are strictly limited to the linear system. However, some nonlinear factors are within the practical system; thus, it is difficult to fit the model for real systems with the above models. This paper proposes a general expression for linear and nonlinear auto-regressive time series models (GNAR). With the gradient optimization method and modified AIC information criteria integrated with the prediction error, the parameter estimation and order determination are achieved. The model simulation and experiments show that the GNAR model can accurately approximate to the dynamic characteristics of the most nonlinear models applied in academics and engineering. The modeling and prediction accuracy of the GNAR model is superior to the classical time series models. The proposed GNAR model is flexible and effective.

关键词： linear and nonlinear     autoregressive model     system identification     time series analysis    

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Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 199-207 doi: 10.1007/s11709-011-0102-1

摘要： Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities. Firstly, validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars. The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied. It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation. Wave attenuation as well as time delay is affected by the length, quantity, specific stiffness of the distributed microcracks as well as the incident stress wave frequency. The storage and loss moduli of the defected rock are also affected by the microcrack properties; however, they are independent of incident stress wave frequency.

关键词： stress wave propagation     defected rock     numerical manifold method     viscoelastic behavior     storage modulus     loss modulus    

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Comparison between linear and non-linear forms of pseudo-first-order and pseudo-second-order adsorption

Junxiong LIN , Lan WANG ,

《环境科学与工程前沿（英文）》 2009年 第3卷 第3期   页码 320-324 doi: 10.1007/s11783-009-0030-7

摘要： The best-fit equations of linear and non-linear forms of the two widely used kinetic models, namely pseudo-first-order and pseudo-second-order equations, were compared in this study. The experimental kinetics of methylene blue adsorption on activated carbon was used for this research. Both the correlation coefficient () and the normalized standard deviation Δ(%) were employed as error analysis methods to determine the best-fitting equations. The results show that the non-linear forms of pseudo-first-order and pseudo-second-order models were more suitable than the linear forms for fitting the experimental data. The experimental kinetics may have been distorted by linearization of the linear kinetic equations, and thus, the non-linear forms of kinetic equations should be primarily used to obtain the adsorption parameters. In addition, the Δ(%) method for error analysis may be better to determine the best-fitting model in this case.

关键词： adsorption     pseudo-first order     pseudo-second order     kinetic model     linear method     non-linear method    

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Cutting CO emissions through demand side regulation: Implications from multi-regional input–output linearprogramming model

《工程管理前沿（英文）》   页码 452-461 doi: 10.1007/s42524-022-0209-1

摘要： This study combines multi-regional input–output (MRIO) model with linear programming (LP) model to explore economic structure adjustment strategies for the reduction of carbon dioxide (CO2) emissions. A particular feature of this study is the identification of the optimal regulation sequence of final products in various regions to reduce CO2 emissions with the minimum loss in gross domestic product (GDP). By using China’s MRIO tables 2017 with 28 regions and 42 economic sectors, results show that reduction in final demand leads to simultaneous reductions in GDP and CO2 emissions. Nevertheless, certain demand side regulation strategy can be adopted to lower CO2 emissions at the smallest loss of economic growth. Several key final products, such as metallurgy, nonmetal, metal, and chemical products, should first be regulated to reduce CO2 emissions at the minimum loss in GDP. Most of these key products concentrate in the coastal developed regions in China. The proposed MRIO–LP model considers the inter-relationship among various sectors and regions, and can aid policy makers in designing effective policy for industrial structure adjustment at the regional level to achieve the national environmental and economic targets.

关键词： CO2 emissions     demand side regulation     multi-regional input–output model     linear programming model    

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Model reduction techniques for dynamics analysis of ultra-precision linear stage

Xuedong CHEN, Zhixin LI

《机械工程前沿（英文）》 2009年 第4卷 第1期   页码 64-70 doi: 10.1007/s11465-009-0009-x

摘要： Spring-damping elements are used to simplify the internal interaction in the proposed finite element (FE) model of an ultra-precision linear stage. The dynamics behavior is studied. The comparison between mode shapes from the eigenvalue analysis shows that the components, except the translator, can represent system dynamics characteristics. A reduction approach is used to simplify the system in a dynamic studied. There is little difference between the vibration mode and the response analysis. The experimental modal analysis proves the validity of the reduction approach, which can be generalized to the development and dynamics characteristic study of a complex system model to obviously save computational resource.

关键词： dynamics analysis     air-bearing     linear stage     reduction    

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深厚表土层冻结壁厚度计算方法研究

沈慰安,王建州

《中国工程科学》 2011年 第13卷 第11期   页码 89-93

摘要：

针对冻结法凿井工程面临的表土层厚度不断增加，而现有冻结壁的设计理论滞后于工程实践的问题，目前冻结壁的设计和计算多数是将冻结壁视为均质和各向同性的厚壁圆筒，基于弹性和弹塑性理论进行计算的结果已经不能适用于未来深厚表土层的冻结法凿井工程，文章综述了冻结壁厚度设计理论的研究现状和存在的问题，并提出了考虑冻结壁径向非均匀的粘弹性分层计算模型，考虑径向非均质条件，井帮的径向变形较均质冻结壁小25 %~30 %，可以充分发挥冻结壁的承载和变形性能，有效减小冻结壁的厚度，具有一定的的工程应用价值。

关键词： 冻结壁     深厚表土层     分层计算模型     粘弹性    

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Linear and nonlinear elastic analysis of closely spaced strip foundations using Pasternak model

Priyanka GHOSH, S. RAJESH, J. SAI CHAND

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 228-243 doi: 10.1007/s11709-016-0370-x

摘要： In this study, an attempt is made to determine the interaction effect of two closely spaced strip footings using Pasternak model. The study considers small strain problem and has been performed using linear as well as nonlinear elastic analysis to determine the interaction effect of two nearby strip footings. The hyperbolic stress-strain relationship has been considered for the nonlinear elastic analysis. The linear elastic analysis has been carried out by deriving the equations for the interference effect of the footings in the framework of Pasternak model equation; whereas, the nonlinear elastic analysis has been performed using the finite difference method to solve the second order nonlinear differential equation evolved from Pasternak model with proper boundary conditions. Results obtained from the linear and the nonlinear elastic analysis are presented in terms of non-dimensional interaction factors by varying different parameters like width of the foundation, load on the foundation and the depth of the rigid base. Results are suitably compared with the existing values in the literature.

关键词： bearing capacity     linear and non-linear elasticity     foundation     interaction effect     numerical modeling     Pasternak model    

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Design and modeling of a free-piston engine generator

《能源前沿（英文）》   页码 811-821 doi: 10.1007/s11708-022-0848-2

摘要： Free-piston engine generators (FPEGs) can be applied as decarbonized range extenders for electric vehicles because of their high thermal efficiency, low friction loss, and ultimate fuel flexibility. In this paper, a parameter-decoupling approach is proposed to model the design of an FPEG. The parameter-decoupling approach first divides the FPEG into three parts: a two-stroke engine, an integrated scavenging pump, and a linear permanent magnet synchronous machine (LPMSM). Then, each of these is designed according to predefined specifications and performance targets. Using this decoupling approach, a numerical model of the FPEG, including the three aforementioned parts, was developed. Empirical equations were adopted to design the engine and scavenging pump, while special considerations were applied for the LPMSM. A finite element model with a multi-objective genetic algorithm was adopted for its design. The finite element model results were fed back to the numerical model to update the LPMSM with increased fidelity. The designed FPEG produced 10.2 kW of electric power with an overall system efficiency of 38.5% in a stable manner. The model provides a solid foundation for the manufacturing of related FPEG prototypes.

关键词： free-piston engine generator     linear permanent magnet synchronous machine     system design     numerical model     finite element method    

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Design and analysis of linear oscillating motor for linear pump application-magnetic field, dynamics

Zongxia JIAO,Tianyi WANG,Liang YAN

《机械工程前沿（英文）》 2016年 第11卷 第4期   页码 351-362 doi: 10.1007/s11465-016-0407-9

摘要：

A linear oscillating motor is an electromagnetic actuator that can achieve short-stroke reciprocating movement directly without auxiliary transmission mechanisms. It has been widely used in linear pump applications as the source of power and motion. However, because of the demand of high power density in a linear actuation system, the performance of linear oscillating motors has been the focus of studies and deserves further research for high power density. In this paper, a general framework of linear oscillating motor design and optimization is addressed in detail, including the electromagnetic, dynamics, and thermal aspects. First, the electromagnetic and dynamics characteristics are modeled to reveal the principle for optimization. Then, optimization and analysis on magnetic structure, resonant system, and thermal features are conducted, which provide the foundation for prototype development. Finally, experimental results are provided for validation. As a whole, this process offers complete guidance for high power density linear oscillating motors in linear pump applications.

关键词： linear oscillating motor     linear pump     magnetic field     motor optimization    

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有限资源下最大可靠性网络流中断模型

赵 佳,于 华

《中国工程科学》 2015年 第17卷 第1期   页码 137-142

摘要：

提出了最大可靠性网络流中断模型。此模型是在给定的网络图中，通过在边上设置监测点来阻止给定两个顶点之间的网络流量，同时考虑所设置监测点失效的可能，在给定的资源限制下，最大化中断网络流的可能性，即给定起点和终点的网络图，在资源有限的情况下，选择一些边设置监测点使得从起点到终点的所有路都包含尽可能多的已被设置中断点的边。在给定图中，两点之间的路的条数是图的规模的指数次幂，为此将此模型转化为双层整数规划模型，鉴于双层整数规划模型在一般情况下是不可解的，通过探讨下层整数规划问题与其线性规划松弛之间的关系以及线性规划对偶理论来解此双层整数规划模型。本文不仅将该模型约束的个数从图的规模的指数次幂降到一次幂，同时也提供了一种解双层整数规划问题的方法。

关键词： 中断模型；k-可靠性；对偶；线性规划松弛；互补松弛型    

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Microdamage study of granite under thermomechanical coupling based on the particle flow code

《结构与土木工程前沿（英文）》   页码 1413-1427 doi: 10.1007/s11709-023-0953-2

摘要： The thermomechanical coupling of rocks refers to the interaction between the mechanical and thermodynamic behaviors of rocks induced by temperature changes. The study of this coupling interaction is essential for understanding the mechanical and thermodynamic properties of the surrounding rocks in underground engineering. In this study, an improved temperature-dependent linear parallel bond model is introduced under the framework of a particle flow simulation. A series of numerical thermomechanical coupling tests are then conducted to calibrate the micro-parameters of the proposed model by considering the mechanical behavior of the rock under different thermomechanical loadings. Good agreement between the numerical results and experimental data are obtained, particularly in terms of the compression, tension, and elastic responses of granite. With this improved model, the thermodynamic response and underlying cracking behavior of a deep-buried tunnel under different thermal loading conditions are investigated and discussed in detail.

关键词： thermomechanical coupling effect     granite     improved linear parallel bond model     thermal property     particle flow code    

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超越巴斯德象限的基础研究动态演化模型及其实践内涵

张慧琴,王鑫,王旭,孙昌璞

《中国工程科学》 2021年 第23卷 第4期   页码 145-152 doi: 10.15302/J-SSCAE-2021.04.017

摘要：

国家需求牵引的基础研究关系着我国源头创新能力和国际科技竞争力的提升，是颠覆性科技产生的重要驱动力，对我国创新型国家建设的重要性十分突出。为此，需要深入理解其内涵及基本发展规律，以更好引导基础研究的发展。本文回顾了布什科学研究线性模型的内涵、应用及其如何推广至巴斯德象限模型，在此基础上，考虑时间维度，引入基础度和应用度概念，提出由3个维度刻画的基础研究动态演化模型。为展示基础研究动态演化模型的适用性和优越性，以激光和强激光的发展为案例进行说明，阐述了国家需求牵引下基础研究、应用研究和技术开发之间的相互促进、螺旋上升的互动关系。基于本文模型描述的基础研究发展规律，针对需求牵引的基础研究，今后应更加强调学术诚信及可证伪性；要发挥基础研究对关键技术发展的方向性判定作用，并避免需求牵引引起的主观性诱导和误导。

关键词： 基础研究，需求牵引，布什科学研究线性模型，巴斯德象限模型，基础研究动态演化模型，可证伪性    

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标题 作者 时间 类型 操作

Creep and recovery behaviors of magnetorheological elastomers

Weihua LI, Yang ZHOU, Tongfei TIAN, Gursel ALICI,

期刊论文

Linear viscoelastic behavior of asphalt binders and mixtures containing very high percentages of reclaimed

期刊论文

An autonomous system for thermal convection of viscoelastic fluids in a porous layer using a thermalnonequilibrium model

Qi WEI, Xiaohui ZHANG

期刊论文

General expression for linear and nonlinear time series models

Ren HUANG, Feiyun XU, Ruwen CHEN

期刊论文

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Feng REN, Lifeng FAN, Guowei MA

期刊论文

Comparison between linear and non-linear forms of pseudo-first-order and pseudo-second-order adsorption

Junxiong LIN , Lan WANG ,

期刊论文

Cutting CO emissions through demand side regulation: Implications from multi-regional input–output linearprogramming model

期刊论文

Model reduction techniques for dynamics analysis of ultra-precision linear stage

Xuedong CHEN, Zhixin LI

期刊论文

深厚表土层冻结壁厚度计算方法研究

沈慰安,王建州

期刊论文

Linear and nonlinear elastic analysis of closely spaced strip foundations using Pasternak model

Priyanka GHOSH, S. RAJESH, J. SAI CHAND

期刊论文

Design and modeling of a free-piston engine generator

期刊论文

Design and analysis of linear oscillating motor for linear pump application-magnetic field, dynamics

Zongxia JIAO,Tianyi WANG,Liang YAN

期刊论文

有限资源下最大可靠性网络流中断模型

赵 佳,于 华

期刊论文

Microdamage study of granite under thermomechanical coupling based on the particle flow code

期刊论文

超越巴斯德象限的基础研究动态演化模型及其实践内涵

张慧琴,王鑫,王旭,孙昌璞

期刊论文