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Effect of anisotropic characteristics on the mechanical behavior of asphalt concrete overlay

Lingyun YOU, Zhanping YOU, Kezhen YAN

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 110-122 doi: 10.1007/s11709-018-0476-4

摘要： Asphalt concrete (AC) overlays placed over old asphalt pavement have become an alternative to repairing and reinforcing pavements. The strength contributed by the AC overlay is strongly influenced by the anisotropic properties of the pavement material. This study was conducted to analyze the influence of anisotropy, modulus gradient properties, and the condition of the AC overlay and old pavement contact plane on the mechanical behaviors of AC overlays, as well as to quantify the influence of the degree of anisotropy on the mechanical behaviors of AC overlay by a sensitivity analysis (SA). The mechanical behaviors of the AC overlay were numerically obtained using the three-dimensional finite element method with the aid of ABAQUS a commercial program. Variations in the AC overlay’s modulus as a function of temperature as well as the contact state between the AC overlay and AC layer were considered. The SA is based on standardized regression coefficients method. Comparing the mechanical behavior in terms of surface deflection, stress, and strain of the anisotropy model against those corresponding to the isotropic model under static loads show that the anisotropic properties had greater effects on the mechanical behavior of the AC overlay. In addition, the maximum shear stress in the AC overlay was the most significant output parameter affected by the degree of anisotropy. Therefore, future research concerning the reinforcement and repair of pavements should consider the anisotropic properties of the pavement materials.

关键词： asphalt concrete overlay     anisotropy     temperature gradients     modulus gradients     finite element simulation     sensitivity analysis    

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Effect of seismic wave propagation in massed medium on rate-dependent anisotropic damage growth in concrete

Alireza DANESHYAR, Hamid MOHAMMADNEZHAD, Mohsen GHAEMIAN

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 346-363 doi: 10.1007/s11709-021-0694-z

摘要： Seismic modeling of massive structures requires special caution, as wave propagation effects significantly affect the responses. This becomes more crucial when the path-dependent behavior of the material is considered. The coexistence of these conditions renders numerical earthquake analysis of concrete dams challenging. Herein, a finite element model for a comprehensive nonlinear seismic simulation of concrete gravity dams, including realistic soil–structure interactions, is introduced. A semi-infinite medium is formulated based on the domain reduction method in conjunction with standard viscous boundaries. Accurate representation of radiation damping in a half-space medium and wave propagation effects in a massed foundation are verified using an analytical solution of vertically propagating shear waves in a viscoelastic half-space domain. A rigorous nonlinear finite element model requires a precise description of the material response. Hence, a microplane-based anisotropic damage–plastic model of concrete is formulated to reproduce irreversible deformations and tensorial degeneration of concrete in a coupled and rate-dependent manner. Finally, the Koyna concrete gravity dam is analyzed based on different assumptions of foundation, concrete response, and reservoir conditions. Comparison between responses obtained based on conventional assumptions with the results of the presented comprehensive model indicates the significance of considering radiation damping and employing a rigorous constitutive material model, which is pursued for the presented model.

关键词： soil–structure interaction     massed foundation     radiation damping     anisotropic damage    

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Finite element analysis of stress concentrations and failure criteria in composite plates with circular holes

null

《机械工程前沿（英文）》 2014年 第9卷 第3期   页码 281-294 doi: 10.1007/s11465-014-0307-9

摘要：

In this study, the stress concentration factors (SCF) in cross-and-angle-ply laminated composite plates as well as in isotropic plates with single circular holes subjected to uniaxial loading is studied. A quadrilateral finite element of four-node with 32 degrees of freedom at each node, previously developed for the bending and mechanical buckling of laminated composite plates, is used to evaluate the stress distribution in laminated composite plates with central circular holes. Based up on the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical results obtained by the present element compare favorably with those obtained by the analytic approaches published in literature. It is observed that the obtained results are very close to the reference results, which demonstrates the accuracy of the present element. Additionally, to determine the first ply failure (FPF) of laminated plate, several failure criterions are employed. Finally, to show the effect of ratio on the failure of plates, a number of figures are given for different fiber orientation angles.

关键词： laminated composite plates     stress concentration     geometric singularity     anisotropic effect    

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Uncoupled state space solution to layered poroelastic medium with anisotropic permeability and compressible

Zhiyong AI, Wenze ZENG, Yichong CHENG, Chao WU

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 171-179 doi: 10.1007/s11709-011-0103-0

摘要： This paper presents an uncoupled state space solution to three-dimensional consolidation of layered poroelastic medium with anisotropic permeability and compressible pore fluid. Starting from the basic equations of poroelastic medium, and introducing intermediate variables, the state space equation usually comprising eight coupled state vectors is uncoupled into two sets of equations of six and two state vectors in the Laplace-Fourier transform domain. Combined with the continuity conditions between adjacent layers and boundary conditions, the uncoupled state space solution of a layered poroelastic medium is obtained by using the transfer matrix method. Numerical results show that the anisotropy of permeability and the compressibility of pore fluid have remarkable influence on the consolidation behavior of poroelastic medium.

关键词： uncoupled state space solution     layered poroelastic medium     three-dimensional consolidation     anisotropic permeability     compressible pore fluid    

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Experimental study on compaction-induced anisotropic mechanical property of rockfill material

Xiangtao ZHANG, Yizhao GAO, Yuan WANG, Yu-zhen YU, Xun SUN

《结构与土木工程前沿（英文）》 2021年 第15卷 第1期   页码 109-123 doi: 10.1007/s11709-021-0693-0

摘要： The anisotropy of rockfill materials has a significant influence on the performance of engineering structures. However, relevant research data are very limited, because of the difficulty with preparing specimens with different inclination angles using traditional methods. Furthermore, the anisotropy test of rockfill materials is complex and complicated, especially for triaxial tests, in which the major principal stress plane intersects with the compaction plane at different angles. In this study, the geometric characteristics of a typical particle fraction consisting of a specific rockfill material were statistically investigated, and the distribution characteristics of particle orientation in specimens prepared via different compaction methods were examined. For high-density rockfill materials, a set of specimen preparation devices for inclined compaction planes was developed, and a series of conventional triaxial compression tests with different principal stress direction angles were conducted. The results reveal that the principal stress direction angle has a significant effect on the modulus, shear strength, and dilatancy of the compacted rockfill materials. Analysis of the relationship between the principal stress direction angles, change in the stress state, and change in the corresponding dominant shear plane shows that the angle between the compacted surface and dominant shear plane is closely related to interlocking resistance associated with the particle orientation. In addition, different principal stress direction angles can change the extent of the particle interlocking effect, causing the specimen to exhibit different degrees of anisotropy.

关键词： rockfill     inclination of specimen preparation     anisotropy     mechanical property     mechanism    

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Anisotropy of multi-layered structure with sliding and bonded interlayer conditions

Lingyun YOU, Kezhen YAN, Jianhong MAN, Nengyuan LIU

《结构与土木工程前沿（英文）》 2020年 第14卷 第3期   页码 632-645 doi: 10.1007/s11709-020-0617-4

摘要： A better understanding of the mechanical behavior of the multi-layered structure under external loading is the most important item for the structural design and the risk assessment. The objective of this study are to propose and develop an analytical solution for the mechanical behaviors of multi-layered structure generated by axisymmetric loading, and to investigate the impact of anisotropic layers and interlayer conditions on the multi-layered structure. To reach these objectives, first, according to the governing equations, the analytical solution for a single layer was formulated by adopting the spatial Hankel transform. Then the global matrix technique is applied to achieve the analytical solution of multi-layered structure in Hankel domain. The sliding and bonded interlayer conditions were considered in this process. Finally, the numerical inversion of integral transform was used to solve the components of displacement and stress in real domain. Gauss-Legendre quadrature is a key scheme in the numerical inversion process. Moreover, following by the verification of the proposed analytical solution, one typical three-layered flexible pavement was applied as the computing carrier of numerical analysis for the multi-layered structure. The results have shown that the anisotropic layers and the interlayer conditions significantly affect the mechanical behaviors of the proposed structure.

关键词： multi-layered structure     Hankel transformation     anisotropic     transversely isotropic     interlayer condition     Gauss-Legendre quadrature    

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Altered white matter microarchitecture in Parkinson’s disease: a voxel-based meta-analysis of diffusion tensor imaging studies

Xueling Suo, Du Lei, Wenbin Li, Lei Li, Jing Dai, Song Wang, Nannan Li, Lan Cheng, Rong Peng, Graham J Kemp, Qiyong Gong

《医学前沿（英文）》 2021年 第15卷 第1期   页码 125-138 doi: 10.1007/s11684-019-0725-5

摘要： This study aimed to define the most consistent white matter microarchitecture pattern in Parkinson’s disease (PD) reflected by fractional anisotropy (FA), addressing clinical profiles and methodology-related heterogeneity. Web-based publication databases were searched to conduct a meta-analysis of whole-brain diffusion tensor imaging studies comparing PD with healthy controls (HC) using the anisotropic effect size–signed differential mapping. A total of 808 patients with PD and 760 HC coming from 27 databases were finally included. Subgroup analyses were conducted considering heterogeneity with respect to medication status, disease stage, analysis methods, and the number of diffusion directions in acquisition. Compared with HC, patients with PD had decreased FA in the left middle cerebellar peduncle, corpus callosum (CC), left inferior fronto-occipital fasciculus, and right inferior longitudinal fasciculus. Most of the main results remained unchanged in subgroup meta-analyses of medicated patients, early stage patients, voxel-based analysis, and acquisition with ＜30 diffusion directions. The subgroup meta-analysis of medication-free patients showed FA decrease in the right olfactory cortex. The cerebellum and CC, associated with typical motor impairment, showed the most consistent FA decreases in PD. Medication status, analysis approaches, and the number of diffusion directions have an important impact on the findings, needing careful evaluation in future meta-analyses.

关键词： Parkinson’s disease     diffusion tensor imaging     fractional anisotropy     meta-analysis     anisotropic effect size–signed differential mapping    

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Analysis of effect of different construction methods of piles on the end effect on skin friction of piles

ZHOU Hongbo, CHEN Zhuchang

《结构与土木工程前沿（英文）》 2007年 第1卷 第4期   页码 458-463 doi: 10.1007/s11709-007-0062-7

摘要： Based on the comparative analysis of end effect on skin friction of displacement-pile (driven pile), the end effect on skin friction of bored pile is studied. The end effect on skin friction between driven pile and bored pile is different and the end effect on skin friction of bored pile is reduce of skin friction in the soil layer adjacent to the pile end. The degradation degree of skin friction is deduced with the increase of the distance from pile end. The concept of additional mud cake formed by the effect of cushion at the bottom of borehole during pouring concrete is introduced to explain the mechanism of end effect on skin friction of the bored pile. The test results of post-grouting piles indicate that the post-grouting technique is an effective way to improve the end effect on skin friction of bored pile.

关键词： distance     different     concept     additional     bottom    

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A review on different theoretical models of electrocaloric effect for refrigeration

《能源前沿（英文）》 2023年 第17卷 第4期   页码 478-503 doi: 10.1007/s11708-023-0884-6

摘要： The performance parameters for characterizing the electrocaloric effect are isothermal entropy change and the adiabatic temperature change, respectively. This paper reviews the electrocaloric effect of ferroelectric materials based on different theoretical models. First, it provides four different calculation scales (the first-principle-based effective Hamiltonian, the Landau-Devonshire thermodynamic theory, phase-field simulation, and finite element analysis) to explain the basic theory of calculating the electrocaloric effect. Then, it comprehensively reviews the recent progress of these methods in regulating the electrocaloric effect and the generation mechanism of the electrocaloric effect. Finally, it summarizes and anticipates the exploration of more novel electrocaloric materials based on the framework constructed by the different computational methods.

关键词： electrocaloric effect     effective Hamiltonian     phase-field modeling     different theoretical models    

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A new miniaturized engine based on thermomagnetic effect of magnetic fluids

Lujun ZHOU, Yimin XUAN, Qiang LI, Wenlei LIAN

《能源前沿（英文）》 2009年 第3卷 第2期   页码 160-166 doi: 10.1007/s11708-009-0018-9

摘要： A new engine system, essentially consisting of a permanent NdFeB magnet, a kerosene-based magnetic fluid and a rotor, is proposed based on the thermomagnetic effect of a temperature-sensitive magnetic fluid. The rotor was driven by the thermal convection of the magnetic fluid in the presence of a homogeneous external magnetic field. A digital camera was used to record the rotation speed of the rotor to investigate the performance of the engine system under varying conditions such as heat load, heat sink temperature, and magnetic field distribution. The peak angle velocity obtained for the rotor was about 2.1 rad/min. The results illustrate that the rotation speed of the rotor increases as the input heat load increases, or as the heat sink temperature decreases. The performance of the motor is considerably influenced by the magnetic field imposed. Therefore, the performance of such an engine can be controlled conveniently by changing the external magnetic field and/or the temperature distribution in the fluid.

关键词： magnetic fluid     thermomagnetic effect     engine    

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各向异性热压稀土永磁体的热变形机制及微磁结构研究

李卫,朱明刚

《中国工程科学》 2011年 第13卷 第10期   页码 4-12

摘要：

重点研究制备工艺对各向异性热压稀土永磁体性能的影响，探讨了热压永磁体的热变形机理和数学描述模型，并尝试从微磁结构的角度研究各向异性纳米晶Nd-Fe-B磁体，揭示纳米晶粒之间的静磁和交换耦合相互作用、磁化和反磁化、热退磁等微观机制。获得了最佳磁性能为：Hcj=1 157 kA/m，Br=1.465 T，(BH)max=426 kJ/m3纳米晶Nd-Fe-B磁体。

关键词： 纳米晶Nd-Fe-B辐向环     热压－热变形     各向异性     微磁结构    

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The cooperation effect of Ni and Pt in the hydrogenation of acetic acid

《化学科学与工程前沿（英文）》 2022年 第16卷 第3期   页码 397-407 doi: 10.1007/s11705-021-2076-4

摘要： The catalytic hydrogenation of carboxylic acid to alcohols is one of the important strategies for the conversion of biomass. Herein, a series of Ni-doped PtSn catalysts were prepared, characterized and studied in the hydrogenation of acetic acid. The Ni dopant has a strong interaction with Pt, which promotes the hydrogen adsorption, providing an activated hydrogen-rich environment for the hydrogenation. Meanwhile, the presence of Ni also improves the Pt dispersion, giving more accessible active sites for hydrogen activation. The cooperation of Pt and Ni significantly promotes the catalytic activity of the hydrogenation of acetic acid to ethanol. As a result, the catalyst with 0.1% Ni exhibits the best reaction activity, and its space time yield is twice as that of the PtSn/SiO2 catalyst. It provides a meaningful instruction on the catalyst design for the carboxylic acid hydrogenation.

关键词： acetic acid     ethanol     hydrogenation     Pt     Ni     cooperation effect    

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Direct energy rebound effect for road transportation in China

《工程管理前沿（英文）》   页码 597-611 doi: 10.1007/s42524-023-0276-y

摘要： The enhancement of energy efficiency stands as the principal avenue for attaining energy conservation and emissions reduction objectives within the realm of road transportation. Nevertheless, it is imperative to acknowledge that these objectives may, in part or in entirety, be offset by the phenomenon known as the energy rebound effect (ERE). To quantify the long-term EREs and short-term EREs specific to China’s road transportation, this study employed panel cointegration and panel error correction models, accounting for asymmetric price effects. The findings reveal the following: The long-term EREs observed in road passenger transportation and road freight transportation range from 13% to 25% and 14% to 48%, respectively; in contrast, the short-term EREs in road passenger transportation and road freight transportation span from 36% to 41% and 3.9% to 32%, respectively. It is noteworthy that the EREs associated with road passenger transportation and road freight transportation represent a partial rebound effect, falling short of reaching the magnitude of a counterproductive backfire effect. This leads to the inference that the upsurge in energy consumption within the road transportation sector cannot be solely attributed to advancements in energy efficiency. Instead, various factors, including income levels, the scale of commodity trade, and industrial structure, exert more substantial facilitating influences. Furthermore, the escalation of fuel prices fails to dampen the demand for energy services, whether in the domain of road passenger transportation or road freight transportation. In light of these conclusions, recommendations are proffered for the formulation of energy efficiency policies pertinent to road transportation.

关键词： road transportation     direct energy rebound effect     asymmetric price effects     panel data model    

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Photoaging mechanism of microplastics: a perspective on the effect of dissolved organic matter in natural

《环境科学与工程前沿（英文）》 2023年 第17卷 第11期 doi: 10.1007/s11783-023-1743-8

摘要：

● Microplastics (MPs) undergo photoaging in natural water under light irradiation.

关键词： Microplastics     Photoaging     Dissolved organic matter     ROS generation    

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Modeling analysis on solar steam generator employed in multi-effect distillation (MED) system

Zhaorui ZHAO, Bao YANG, Ziwen XING

《能源前沿（英文）》 2019年 第13卷 第1期   页码 193-203 doi: 10.1007/s11708-019-0608-0

摘要： Recently the porous bilayer wood solar collectors have drawn increasing attention because of their potential application in solar desalination. In this paper, a thermodynamic model has been developed to analyze the performance of the wood solar collector. A modeling analysis has also been conducted to assess the performance and operating conditions of the multiple effect desalination (MED) system integrated with the porous wood solar collector. Specifically, the effects of operating parameters, such as the motive steam temperature, seawater flow rate, input solar energy and number of effects on the energy consumption for each ton of distilled water produced have been investigated in the MED desalination system combined with the bilayer wood solar steam generator. It is found that, under a given operating condition, there exists an optimum steam generation temperature of around 145°C in the wood solar collector, so that the specific power consumption in the MED system reaches a minimum value of 24.88 kWh/t. The average temperature difference is significantly affected by the solar heating capacity. With the solar capacity increasing from 50 kW to 230 kW, the average temperature difference increases from 1.88°C to 6.27°C. This parametric simulation study will help the design of efficient bilayer wood solar steam generator as well as the MED desalination system.

关键词： solar energy     steam generating     multi-effect desalination    

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标题 作者 时间 类型 操作

Effect of anisotropic characteristics on the mechanical behavior of asphalt concrete overlay

Lingyun YOU, Zhanping YOU, Kezhen YAN

期刊论文

Effect of seismic wave propagation in massed medium on rate-dependent anisotropic damage growth in concrete

Alireza DANESHYAR, Hamid MOHAMMADNEZHAD, Mohsen GHAEMIAN

期刊论文

Finite element analysis of stress concentrations and failure criteria in composite plates with circular holes

null

期刊论文

Uncoupled state space solution to layered poroelastic medium with anisotropic permeability and compressible

Zhiyong AI, Wenze ZENG, Yichong CHENG, Chao WU

期刊论文

Experimental study on compaction-induced anisotropic mechanical property of rockfill material

Xiangtao ZHANG, Yizhao GAO, Yuan WANG, Yu-zhen YU, Xun SUN

期刊论文

Anisotropy of multi-layered structure with sliding and bonded interlayer conditions

Lingyun YOU, Kezhen YAN, Jianhong MAN, Nengyuan LIU

期刊论文

Altered white matter microarchitecture in Parkinson’s disease: a voxel-based meta-analysis of diffusion tensor imaging studies

Xueling Suo, Du Lei, Wenbin Li, Lei Li, Jing Dai, Song Wang, Nannan Li, Lan Cheng, Rong Peng, Graham J Kemp, Qiyong Gong

期刊论文

Analysis of effect of different construction methods of piles on the end effect on skin friction of piles

ZHOU Hongbo, CHEN Zhuchang

期刊论文

A review on different theoretical models of electrocaloric effect for refrigeration

期刊论文

A new miniaturized engine based on thermomagnetic effect of magnetic fluids

Lujun ZHOU, Yimin XUAN, Qiang LI, Wenlei LIAN

期刊论文

各向异性热压稀土永磁体的热变形机制及微磁结构研究

李卫,朱明刚

期刊论文

The cooperation effect of Ni and Pt in the hydrogenation of acetic acid

期刊论文

Direct energy rebound effect for road transportation in China

期刊论文

Photoaging mechanism of microplastics: a perspective on the effect of dissolved organic matter in natural

期刊论文

Modeling analysis on solar steam generator employed in multi-effect distillation (MED) system

Zhaorui ZHAO, Bao YANG, Ziwen XING

期刊论文