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On the added value of multi-scale modeling of concrete

《结构与土木工程前沿（英文）》 2022年第16卷第1期页码 1-23 doi: 10.1007/s11709-021-0790-0

摘要： This review of the added value of multi-scale modeling of concrete is based on three representative examples. The first one is concerned with the analysis of experimental data, taken from four high-dynamic tests. The structural nature of the high-dynamic strength increase can be explained by using a multi-scale model. It accounts for the microstructure of the specimens. The second example refers to multi-scale thermoelastic analysis of concrete pavements, subjected to solar heating. A sensitivity analysis with respect to the internal relative humidity (RH) of concrete has underlined the great importance of the RH for an assessment of the risk of microcracking of concrete. The third example deals with multi-scale structural analysis of a real-scale test of a segmental tunnel ring. It has turned out that multi-scale modeling of concrete enables more reliable predictions of crack opening displacements in tunnel segments than macroscopic models taken from codes of practice. Overall, it is concluded that multi-scale models have indeed a significant added value. However, its degree varies with these examples. In any case, it can be assessed by means of a comparison of the results from three sources, namely, multi-scale structural analysis, conventional structural analysis, and experiments.

关键词： experiments multi-scale analysis conventional structural analysis concrete reinforced concrete

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Environmental dispersivity in free-water-surface-effect dominated wetland: multi-scale analysis

Zi WU, Zhi LI, Li ZENG, Ling SHAO, Hansong TANG, Qing YANG, Guoqian CHEN

《环境科学与工程前沿（英文）》 2011年第5卷第4期页码 597-603 doi: 10.1007/s11783-011-0311-9

摘要： Distinct from the case with width-dominated shallow wetland flows, the longitudinal evolution of contaminant concentration in the most-typical pattern of wetland as dominated by free-water-surface-effect is characterized by a multi-scale analysis in the present study. An environmental dispersion model for the evolution of the mean concentration is deduced as an extension of Taylor's classical formulation by Mei’s multi-scale analysis. Corresponding environmental dispersivity is found identical to that determined by the method of concentration moments.

关键词： free-surface wetland environmental dispersion multi-scale analysis

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Macro-architectured cellular materials: Properties, characteristic modes, and prediction methods

Zheng-Dong MA

《机械工程前沿（英文）》 2018年第13卷第3期页码 442-459 doi: 10.1007/s11465-018-0488-8

摘要：

Macro-architectured cellular (MAC) material is defined as a class of engineered materials having configurable cells of relatively large (i.e., visible) size that can be architecturally designed to achieve various desired material properties. Two types of novel MAC materials, negative Poisson’s ratio material and biomimetic tendon reinforced material, were introduced in this study. To estimate the effective material properties for structural analyses and to optimally design such materials, a set of suitable homogenization methods was developed that provided an effective means for the multiscale modeling of MAC materials. First, a strain-based homogenization method was developed using an approach that separated the strain field into a homogenized strain field and a strain variation field in the local cellular domain superposed on the homogenized strain field. The principle of virtual displacements for the relationship between the strain variation field and the homogenized strain field was then used to condense the strain variation field onto the homogenized strain field. The new method was then extended to a stress-based homogenization process based on the principle of virtual forces and further applied to address the discrete systems represented by the beam or frame structures of the aforementioned MAC materials. The characteristic modes and the stress recovery process used to predict the stress distribution inside the cellular domain and thus determine the material strengths and failures at the local level are also discussed.

关键词： architectured material cellular materials multi-scale modeling homogenization method effective material properties computational method

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Hydromechanical model for hydraulic fractures using XFEM

Bo HE

《结构与土木工程前沿（英文）》 2019年第13卷第1期页码 240-249 doi: 10.1007/s11709-018-0490-6

摘要： In this study, a hydromechanical model for fluid flow in fractured porous media is presented. We assume viscous fluids and the coupling equations are derived from the mass and momentum balance equations for saturated porous media. The fluid flow through discrete cracks will be modelled by the extended finite element method and an implicit time integration scheme. We also present a consistent linearization of the underlying non-linear discrete equations. They are solved by the Newton-Raphson iteration procedure in combination with a line search. Furthermore, the model is extended to includes crack propagation. Finally, examples are presented to demonstrate the versatility and efficiency of this two-scale hydromechanical model. The results suggest that the presence of the fracture in a deforming, porous media has great impact on the fluid flow and deformation patterns.

关键词： multi-phase medium porous fracture multi-scale method

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A multi-scale model for CO

G. X. WANG, X. R. WEI, V. RUDOLPH, C. T. WEI, Y. QIN

《化学科学与工程前沿（英文）》 2009年第3卷第1期页码 20-25 doi: 10.1007/s11705-009-0138-0

摘要： This paper presents a multi-scale model to simulate the multicomponent gas diffusion and flow in bulk coals for CO sequestration enhanced coalbed methane recovery. The model is developed based on a bi-dispersed structure model by assuming that coal consists of microporous micro-particles, meso/macro-pores and open microfractures. The bi-disperse diffusion theory and the Maxwell-Stefan approach were incorporated in the model, providing an improved simulation of the CH —CO /CH —N counter diffusion dynamics. In the model, the counter diffusion process is numerically coupled with the flow of the mixture gases occurring within macro-pores or fractures in coal so as to account for the interaction between diffusion and flow in gas transport through coals. The model was validated by both experimental data from literature and our CO flush tests, and shows an excellent agreement with the experiments. The results reveal that the gas diffusivities, in particular the micro-pore diffusivities are strongly concentration-dependent.

关键词： multi-scale model gas transport coal coalbed methane CO₂ sequestration

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Characterization of random stress fields obtained from polycrystalline aggregate calculations using multi-scale

Bruno SUDRET,Hung Xuan DANG,Marc BERVEILLER,Asmahana ZEGHADI,Thierry YALAMAS

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 121-140 doi: 10.1007/s11709-015-0290-1

摘要： The spatial variability of stress fields resulting from polycrystalline aggregate calculations involving random grain geometry and crystal orientations is investigated. A periodogram-based method is proposed to identify the properties of homogeneous Gaussian random fields (power spectral density and related covariance structure). Based on a set of finite element polycrystalline aggregate calculations the properties of the maximal principal stress field are identified. Two cases are considered, using either a fixed or random grain geometry. The stability of the method w.r.t the number of samples and the load level (up to 3.5% macroscopic deformation) is investigated.

关键词： polycrystalline aggregates crystal plasticity random fields spatial variability correlation structure

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Multi-scale investigation of active failure for various modes of wall movement

《结构与土木工程前沿（英文）》 2021年第15卷第4期页码 961-979 doi: 10.1007/s11709-021-0738-4

摘要： Retained backfill response to wall movement depends on factors that range from boundary conditions to the geometrical characteristic of individual particles. Hence, mechanical understanding of the problem warrants multi-scale analyses that investigate reciprocal relationships between macro and micro effects. Accordingly, this study attempts a multi-scale examination of failure evolution in cohesionless backfills. Therefore, the transition of retained backfills from at-rest condition to the active state is modeled using the discrete element method (DEM). DEM allows conducting virtual experiments, with which the variation of particle and boundary properties is straightforward. Hence, various modes of wall movement (translation and rotation) toward the active state are modeled using two different backfills with distinct particle shapes (spherical and nonspherical) under varying surcharge. For each model, cumulative rotations of single particles are tracked, and the results are used to analyze the evolution of shear bands and their geometric characteristics. Moreover, dependencies of lateral pressure coefficients and coordination numbers, as respective macro and micro behavior indicators, on particle shape, boundary conditions, and surcharge levels are investigated. Additionally, contact force networks are visually determined, and their influences on pressure distribution and deformation mechanisms are discussed with reference to the associated modes of wall movement and particle shapes.

关键词： discrete-element modelling granular materials retaining walls particle shape arching

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Multi-scale evaluation of river health in Liao River Basin, China

Fei XU, Yanwei ZHAO, Zhifeng YANG, Yuan ZHANG

《环境科学与工程前沿（英文）》 2011年第5卷第2期页码 227-235 doi: 10.1007/s11783-010-0219-9

摘要： Previous studies on river health evaluation mainly focused on characterizations at a river-corridor scale and ignored the complex interactions between the river ecosystem and other components of the river basin. Based on the consideration of the interactions among rivers, associated river basin and habitats, an assessment framework with multi-scale indicators was developed. An index system divided among these three scales to characterize the health of river ecosystems in China’s Liao River Basin was established. Set pair analysis was applied to integrate the multi-scale indicators and determine the health classes. The evaluation results indicated that the rivers in the western and eastern zones of the Liao River were classified as sick, and rivers in the main stream of the Liao and Huntai rivers were classified as unhealthy. An excessive level of disturbances, such as large pollution loads and dense construction of water conservation projects within the river basin, were the main causes of the river health deterioration.

关键词： multi-scale characterization river health evaluation Liao River Basin set pair analysis

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碳基固体氧化物燃料电池理论模拟概述

李家玉,王宝轩,陈美娜,李昂,方秀荣,宋策,林子敬

《中国工程科学》 2013年第15卷第2期页码 39-49

摘要：

主要对碳基固体氧化物燃料电池（SOFC）中三传二反的控制方程、不同尺度的不同物理场理论模型以及碳基燃料的重整、催化和硫化等方面进行概括总结。SOFC有可使用氢气、一氧化碳、甲烷和其他的碳氢化合物作为燃料进行电化学反应的燃料灵活性，但使用碳氢燃料需要解决诸如碳基燃料的重整、电极的催化、积碳和硫化等问题。电池内部反应气体的物质输运、电荷输运、能量输运、动量输运和化学及电化学反应状态均可以用偏微分方程来描述。运用这些电化学反应和输运的偏微分方程，结合材料的微观性质，可以建立SOFC的多尺度多物理场模型。通过理论模型研究材料微结构与性质、工作条件、几何构型等参数对电池性能的影响，对SOFC材料组成与电池堆结构进行定量分析和优化设计，可以加速SOFC技术的更快发展。

关键词：多尺度模拟结构性能优化重整反应催化硫化

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Multi-scale UDCT dictionary learning based highly undersampled MR image reconstruction using patch-based

Min YUAN,Bing-xin YANG,Yi-de MA,Jiu-wen ZHANG,Fu-xiang LU,Tong-feng ZHANG

《信息与电子工程前沿（英文）》 2015年第16卷第12期页码 1069-1087 doi: 10.1631/FITEE.1400423

摘要： Recently, dictionary learning (DL) based methods have been introduced to compressed sensing magnetic resonance imaging (CS-MRI), which outperforms pre-defined analytic sparse priors. However, single-scale trained dictionary directly from image patches is incapable of representing image features from multi-scale, multi-directional perspective, which influences the reconstruction performance. In this paper, incorporating the superior multi-scale properties of uniform discrete curvelet transform (UDCT) with the data matching adaptability of trained dictionaries, we propose a flexible sparsity framework to allow sparser representation and prominent hierarchical essential features capture for magnetic resonance (MR) images. Multi-scale decomposition is implemented by using UDCT due to its prominent properties of lower redundancy ratio, hierarchical data structure, and ease of implementation. Each sub-dictionary of different sub-bands is trained independently to form the multi-scale dictionaries. Corresponding to this brand-new sparsity model, we modify the constraint splitting augmented Lagrangian shrinkage algorithm (C-SALSA) as patch-based C-SALSA (PB C-SALSA) to solve the constraint optimization problem of regularized image reconstruction. Experimental results demonstrate that the trained sub-dictionaries at different scales, enforcing sparsity at multiple scales, can then be efficiently used for MRI reconstruction to obtain satisfactory results with further reduced undersampling rate. Multi-scale UDCT dictionaries potentially outperform both single-scale trained dictionaries and multi-scale analytic transforms. Our proposed sparsity model achieves sparser representation for reconstructed data, which results in fast convergence of reconstruction exploiting PB C-SALSA. Simulation results demonstrate that the proposed method outperforms conventional CS-MRI methods in maintaining intrinsic properties, eliminating aliasing, reducing unexpected artifacts, and removing noise. It can achieve comparable performance of reconstruction with the state-of-the-art methods even under substantially high undersampling factors.

关键词： Compressed sensing (CS) Magnetic resonance imaging (MRI) Uniform discrete curvelet transform (UDCT) Multi-scale dictionary learning (MSDL) Patch-based constraint splitting augmented Lagrangian shrinkage algorithm (PB C-SALSA)

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图像边缘检测二维小波算法研究与实现

张红岩,张登攀

《中国工程科学》 2003年第5卷第4期页码 61-64

摘要：

边沿作为图像视觉的最主要特征，成为图像信息获取的重要内容。小波变换具有检测局域突变的能力，而且可以结合多尺度信息进行检测，因此成为图像信息边缘检测的优良工具。根据二维小波变换的特点,分析了利用二维小波进行图像边缘检测的基本原理，并设计了利用二维小波变换进行多尺度边缘匹配的检测算法。基于研究结果，编写了计算机应用程序，进行实例分析。

关键词：小波变换多尺度边缘检测

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Decreasing complexity of glucose time series derived from continuous glucose monitoring is correlated with deteriorating glucose regulation

《医学前沿（英文）》 2023年第17卷第1期页码 68-74 doi: 10.1007/s11684-022-0955-9

摘要： Most information used to evaluate diabetic statuses is collected at a special time-point, such as taking fasting plasma glucose test and providing a limited view of individual’s health and disease risk. As a new parameter for continuously evaluating personal clinical statuses, the newly developed technique “continuous glucose monitoring” (CGM) can characterize glucose dynamics. By calculating the complexity of glucose time series index (CGI) with refined composite multi-scale entropy analysis of the CGM data, the study showed for the first time that the complexity of glucose time series in subjects decreased gradually from normal glucose tolerance to impaired glucose regulation and then to type 2 diabetes (P for trend < 0.01). Furthermore, CGI was significantly associated with various parameters such as insulin sensitivity/secretion (all P < 0.01), and multiple linear stepwise regression showed that the disposition index, which reflects β-cell function after adjusting for insulin sensitivity, was the only independent factor correlated with CGI (P < 0.01). Our findings indicate that the CGI derived from the CGM data may serve as a novel marker to evaluate glucose homeostasis.

关键词： complexity of glucose time series continuous glucose monitoring impaired glucose regulation insulin secretion and sensitivity refined composite multi-scale entropy

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计算成像领域新理论和新方法 Review

Xue-mei HU, Jia-min WU, Jin-li SUO, Qiong-hai DAI

《信息与电子工程前沿（英文）》 2017年第18卷第9期页码 1207-1221 doi: 10.1631/FITEE.1700211

摘要：计算成像学从光传播和信息传递角度为光的整个成像过程建模，将计算能力引入传统光学成像，旨在突破视觉信息记录的局限。计算成像领域的进展，促进了不同基础学科和应用学科的发展。我们概述了计算成像领域的基本原则和方法、发展过程及其在科学发展中起到的重要作用，从视觉信号的不同维度——包括空间、时间、角度、光谱、相位——分别综述了计算成像领域最新和最先进的研究进展，并讨论了该领域有发展前景的研究方向。

关键词：计算成像；多维多尺度；超分辨；飞秒成像；3D重建；超光谱成像

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复合材料构件设计理论及仿真研究进展

陶然,贺春旺,罗俊荣,毛贻齐,马连华

《中国工程科学》 2023年第25卷第1期页码 121-130 doi: 10.15302/J-SSCAE-2023.07.008

摘要：

复合材料构件设计及仿真是复合材料性能与应用研究的重要组成部分，在复合材料产业国际竞争中发挥着关键作用；我国在此领域的系统性研究起步较晚，理论水平滞后、自主标准受制、仿真软件基础薄弱、设计与制造分离等诸多风险共存，相比支撑复合材料构件在重要装备上大规模、高水平应用的长远目标差距明显。本文针对复合材料构件在重要装备应用方面的难题与挑战，剖析了复合材料构件设计理论及仿真的共性需求，梳理了国内外发展现状与主要趋势，提出了我国复合材料构件设计理论及仿真的重点方向：极端和多场环境下复合材料构件的设计理论、复合材料构件动力学分析与设计理论、数据驱动的复合材料构件仿真方法、复合材料构件强度与寿命仿真评价方法。为此建议，开展面向装备工程应用的复合材料构件多场多尺度设计技术、动载荷下的复合材料构件性能设计技术、数据驱动的复合材料构件设计与仿真技术、复合材料构件强度与寿命仿真软件平台等研究，全面提升我国复合材料构件的设计及工程应用水平。

关键词：复合材料构件；多场多尺度设计；动力学设计；数据驱动；强度与寿命评价

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Two-scale modeling of granular materials: A FEM-FEM approach

Yun-Zhu CAI, Yu-Ching WU

《结构与土木工程前沿（英文）》 2013年第7卷第3期页码 304-315 doi: 10.1007/s11709-013-0213-y

摘要： In the present paper, a homogenization-based two-scale FEM-FEM model is developed to simulate compactions of visco-plastic granular assemblies. The granular structure consisting of two-dimensional grains is modeled by the microscopic finite element method at the small-scale level, and the homogenized viscous assembly is analyzed by the macroscopic finite element method at large-scale level. The link between scales is made using a computational homogenization method. The two-scale FEM-FEM model is developed in which each particle is treated individually with the appropriate constitutive relations obtained from a representative volume element, kinematic conditions, contact constraints, and elimination of overlap satisfied for every particle. The method could be used in a variety of problems that can be represented using granular media.

关键词： homogenization two-scale representative volume element compaction granular assembly finite element method