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A multiscale-contour-based interpolation framework for generating a time-varying quasi-dense point cloud

Chu-hua HUANG,Dong-ming LU,Chang-yu DIAO

《信息与电子工程前沿（英文）》 2016年 第17卷 第5期   页码 422-434 doi: 10.1631/FITEE.1500316

摘要： To speed up the reconstruction of 3D dynamic scenes in an ordinary hardware platform, we propose an efficient framework to reconstruct 3D dynamic objects using a multiscale-contour-based interpolation from multi-view videos. Our framework takes full advantage of spatio-temporal-contour consistency. It exploits the property to interpolate single contours, two neighboring contours which belong to the same model, and two contours which belong to the same view at different times, corresponding to point-, contour-, and model-level interpolations, respectively. The framework formulates the interpolation of two models as point cloud transport rather than non-rigid surface deformation. Our framework speeds up the reconstruction of a dynamic scene while improving the accuracy of point-pairing which is used to perform the interpolation. We obtain a higher frame rate, spatio-temporal-coherence, and a quasi-dense point cloud sequence with color information. Experiments with real data were conducted to test the efficiency of the framework.

关键词： Multi-view video     Free-viewpoint video     Point-pair     Multiscale-contour-based interpolation     Spatio-temporal-contour     Consistency     Time-varying point cloud sequence    

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Image automatic mosaics based on contour phase correlation

ZHANG Jing, HU Zhiping, OU Zongying, LIU Zhitai

《机械工程前沿（英文）》 2007年 第2卷 第2期   页码 228-234 doi: 10.1007/s11465-007-0040-8

摘要： The image planar mosaics is studied, and an image automatic mosaics algorithm on the basis of contour phase correlation is proposed in this paper. To begin with, by taking into account mere translations and rotations between images, a contour phase correlation algorithm is used to realize the preliminary alignments of images, and the initial projective transformation matrices are obtained. Then, an optimization algorithm is used to optimize the initial projective transformation matrices, and complete the precise image mosaics. The contour phase correlation is an improvement on the conventional phase correlation in two aspects: First, the contours of images are extracted, and the phase correlation is applied to the contours of images instead of the whole original images; Second, when there are multiple peak values approximate to the maximum peak value in the ? function array, their corresponding translations can be regarded as candidate translations and calculated separately, and the best translation can be determined by the optimization of conformability of two images in the overlapping area. The running results show that the proposed algorithm can consistently yield high-quality mosaics, even in the cases of poor or differential lighting conditions, existences of minor rotations, and other complicated displacements between images.

关键词： function     conventional     multiple     algorithm     correlation algorithm    

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Chord error constraint based integrated control strategy for contour error compensation

Tie ZHANG, Caicheng WU, Yanbiao ZOU

《机械工程前沿（英文）》 2020年 第15卷 第4期   页码 645-658 doi: 10.1007/s11465-020-0601-7

摘要： As the traditional cross-coupling control method cannot meet the requirements for tracking accuracy and contour control accuracy in large curvature positions, an integrated control strategy of cross-coupling contour error compensation based on chord error constraint, which consists of a cross-coupling controller and an improved position error compensator, is proposed. To reduce the contour error, a PI-type cross-coupling controller is designed, with its stability being analyzed by using the contour error transfer function. Moreover, a feed rate regulator based on the chord error constraint is proposed, which performs speed planning with the maximum feed rate allowed by the large curvature position as the constraint condition, so as to meet the requirements of large curvature positions for the chord error. Besides, an improved position error compensation method is further presented by combining the feed rate regulator with the position error compensator, which improves the tracking accuracy via the advance compensation of tracking error. The biaxial experimental results of non-uniform rational B-splines curves indicate that the proposed integrated control strategy can significantly improve the tracking and contour control accuracy in biaxial contour following tasks.

关键词： cross-coupling controller     contour error     tracking error     position error compensator     feed rate regulator    

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Topology optimization based on reduction methods with applications to multiscale design and additive

Emmanuel TROMME, Atsushi KAWAMOTO, James K. GUEST

《机械工程前沿（英文）》 2020年 第15卷 第1期   页码 151-165 doi: 10.1007/s11465-019-0564-8

摘要： Advanced manufacturing processes such as additive manufacturing offer now the capability to control material placement at unprecedented length scales and thereby dramatically open up the design space. This includes the considerations of new component topologies as well as the architecture of material within a topology offering new paths to creating lighter and more efficient structures. Topology optimization is an ideal tool for navigating this multiscale design problem and leveraging the capabilities of advanced manufacturing technologies. However, the resulting design problem is computationally challenging as very fine discretizations are needed to capture all micro-structural details. In this paper, a method based on reduction techniques is proposed to perform efficiently topology optimization at multiple scales. This method solves the design problem without length scale separation, i.e., without iterating between the two scales. Ergo, connectivity between space-varying micro-structures is naturally ensured. Several design problems for various types of micro-structural periodicity are performed to illustrate the method, including applications to infill patterns in additive manufacturing.

关键词： multiscale topology optimization     micro-structure     additive manufacturing     reduction techniques     substructuring     static condensation     super-element    

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Connected morphable components-based multiscale topology optimization

Jiadong DENG, Claus B. W. PEDERSEN, Wei CHEN

《机械工程前沿（英文）》 2019年 第14卷 第2期   页码 129-140 doi: 10.1007/s11465-019-0532-3

摘要： The advances of manufacturing techniques, such as additive manufacturing, have provided unprecedented opportunities for producing multiscale structures with intricate latticed/cellular material microstructures to meet the increasing demands for parts with customized functionalities. However, there are still difficulties for the state-of-the-art multiscale topology optimization (TO) methods to achieve manufacturable multiscale designs with cellular materials, partially due to the disconnectivity issue when tiling material microstructures. This paper attempts to address the disconnectivity issue by extending component-based TO methodology to multiscale structural design. An effective linkage scheme to guarantee smooth transitions between neighboring material microstructures (unit cells) is devised and investigated. Associated with the advantages of components-based TO, the number of design variables is greatly reduced in multiscale TO design. Homogenization is employed to calculate the effective material properties of the porous materials and to correlate the macro/structural scale with the micro/material scale. Sensitivities of the objective function with respect to the geometrical parameters of each component in each material microstructure have been derived using the adjoint method. Numerical examples demonstrate that multiscale structures with well-connected material microstructures or graded/layered material microstructures are realized.

关键词： multiscale topology optimization     morphable component     material microstructure     homogenization    

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基于相邻关系的等高线树建立算法研究

郭沛沛,李成名,殷勇

《中国工程科学》 2013年 第15卷 第5期   页码 42-46

摘要：

等高线树在提取地形线、地貌综合等方面具有重要的应用意义。常用的等高线树表达的是等高线的层次关系，直接表达等高线的包含和邻接关系，建树过程复杂，对数据要求较高，需要对数据进行预处理。本文将图幅内等高线按照是否闭合分为两类，分别对两类等高线群进行建树，最后将两个独立的等高线树合并，形成完整的等高线树。最后生成的等高线树表示了等高线之间的相邻关系，再借助其高程值就可以判断出等高线之间的包含邻接关系，算法容易理解，程序实现简单。

关键词： 等高线树     相邻关系     高程值     闭合等高线     不闭合等高线    

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Fractal characteristic evaluation and interpolation reconstruction for surface topography of drilled

《机械工程前沿（英文）》 2021年 第16卷 第4期   页码 840-854 doi: 10.1007/s11465-021-0643-5

摘要： In this paper, an improved fractal interpolation model is proposed to reconstruct the surface topography of composite hole wall. This model adopts the maximum positive deviations and maximum negative deviations between the measured values and trend values to determine the contraction factors. Hole profiles in 24 directions are measured. Fractal parameters are calculated to evaluate the measured surface profiles. The maximum and minimum fractal dimension of the hole wall are 1.36 and 1.07, whereas the maximum and minimum fractal roughness are 4.05 × 10 −5 and 4.36 × 10 −10 m, respectively. Based on the two-dimensional evaluation results, three-dimensional surface topographies in five typical angles (0°, 45°, 90°, 135°, and 165°) are reconstructed using the improved model. Fractal parameter D s and statistical parameters Sa, Sq, and Sz are used to evaluate the reconstructed surfaces. Average error of D s, Sa, Sq, and Sz between the measured surfaces and the reconstructed surfaces are 1.53%, 3.60%, 5.60%, and 9.47%, respectively. Compared with the model in published literature, the proposed model has equal reconstruction effect in relatively smooth surface and is more advanced in relatively rough surface. Comparative results prove that the proposed model for calculating contraction factors is more reasonable.

关键词： surface topography     fractal evaluation     fractal interpolation     reconstruction     composite    

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Special Column on Multiscale Stochastic Finite Element Method

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 105-106 doi: 10.1007/s11709-015-0297-7

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A multiscale material model for heterogeneous liquid droplets in solid soft composites

《结构与土木工程前沿（英文）》 2021年 第15卷 第5期   页码 1292-1299 doi: 10.1007/s11709-021-0771-3

摘要： Liquid droplets in solid soft composites have been attracting increasing attention in biological applications. In contrary with conventional composites, which are made of solid elastic inclusions, available material models for composites including liquid droplets are for highly idealized configurations and do not include all material real parameters. They are also all deterministic and do not address the uncertainties arising from droplet radius, volume fraction, dispersion and agglomeration. This research revisits the available models for liquid droplets in solid soft composites and presents a multiscale computational material model to determine their elastic moduli, considering nearly all relevant uncertainties and heterogeneities at different length scales. The effects of surface tension at droplets interface, their volume fraction, size, size polydispersity and agglomeration on elastic modulus, are considered. Different micromechanical material models are incorporated into the presented computational framework. The results clearly indicate both softening and stiffening effects of liquid droplets and show that the model can precisely predict the effective properties of liquid droplets in solid soft composites.

关键词： liquid in solid     soft composite     computational modeling     multiscale model     heterogeneity    

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Implementation of an adaptive feed speed 3D NURBS interpolation algorithm

LIANG Hong-bin, WANG Yong-zhang, LI Xia

《机械工程前沿（英文）》 2006年 第1卷 第4期   页码 403-408 doi: 10.1007/s11465-006-0047-6

摘要： NURBS (non-uniform rational B-spline) interpolation algorithms have been provided in modern CNC (computer numerical control) systems. However, most of them focus on a constant feed speed without considering the contour accuracy. In order to deal with this problem, an adaptive feed speed interpolation algorithm for 3D NURBS parametric curves with confined chord errors is proposed. When the instantaneous radius of the curvature is small enough, the proposed interpolation algorithm automatically reduces the feed speed to meet the specified chord error. In the other situation it uses the second-order Taylor s expansions approximation interpolation algorithm to obtain a constant feed speed so that the contour accuracy in the CNC system is guaranteed. Experimental results were provided to verify the feasibility and precision of the proposed interpolation algorithm.

关键词： NURBS parametric     rational B-spline     second-order     non-uniform rational     precision    

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Three-scale stochastic homogenization of elastic recycled aggregate concrete based on nano-indentation

Chen WANG, Yuching WU, Jianzhuang XIAO

《结构与土木工程前沿（英文）》 2018年 第12卷 第4期   页码 461-473 doi: 10.1007/s11709-017-0441-7

摘要： In this paper, three-scale stochastic elastic finite element analyses are made for recycled aggregate concrete (RAC) based on nano-indentation digital images. The elastic property of RAC contains uncertainties across scales. It has both theoretical and practical values to model and predict its mechanical performance. Based on homogenization theory, effective stochastic elastic moduli of RAC at three different scales are obtained using moving window technique, nano-indentation digital images, and Monte-Carlo method. It involves the generation of a large number of random realizations of microstructure geometry based on different volume fraction of the inclusions and other parameters. The mean value, coefficient of variation and probability distribution of the effective elastic moduli are computed considering the material multiscale structure. The microscopic randomness is taken into account, and correlations of RAC among five phases are investigated. The effective elastic properties are used to obtain the global behavior of a composite structure. It is indicated that the response variability can be considerably affected by replacement percentage of recycled aggregates.

关键词： RAC     nano-indentation digital image     multiscale     microscopic randomness     homogenization    

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Multiscale RBF-based central high resolution schemes for simulation of generalized thermoelasticity problems

Hassan YOUSEFI, Alireza TAGHAVI KANI, Iradj MAHMOUDZADEH KANI

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 429-455 doi: 10.1007/s11709-018-0483-5

摘要： In this study, average-interpolating radial basis functions (RBFs) are successfully integrated with central high-resolution schemes to achieve a higher-order central method. This proposed method is used for simulation of generalized coupled thermoelasticity problems including shock (singular) waves in their solutions. The thermoelasticity problems include the LS (systems with one relaxation parameter) and GN (systems without energy dissipation) theories with constant and variable coefficients. In the central high resolution formulation, RBFs lead to a reconstruction with the optimum recovery with minimized roughness on each cell: this is essential for oscillation-free reconstructions. To guarantee monotonic reconstructions at cell-edges, the nonlinear scaling limiters are used. Such reconstructions, finally, lead to the total variation bounded (TVB) feature. As RBFs work satisfactory on non-uniform cells/grids, the proposed central scheme can handle adapted cells/grids. To have cost effective and accurate simulations, the multiresolution–based grid adaptation approach is then integrated with the RBF-based central scheme. Effects of condition numbers of RBFs, computational complexity and cost of the proposed scheme are studied. Finally, different 1-D coupled thermoelasticity benchmarks are presented. There, performance of the adaptive RBF-based formulation is compared with that of the adaptive Kurganov-Tadmor (KT) second-order central high-resolution scheme with the total variation diminishing (TVD) property.

关键词： central high resolution schemes     RBFs     higher order accuracy     generalized thermoelasticity     multiresolution-based adaptation    

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Multiscale computation on feedforward neural network and recurrent neural network

Bin LI, Xiaoying ZHUANG

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1285-1298 doi: 10.1007/s11709-020-0691-7

摘要： Homogenization methods can be used to predict the effective macroscopic properties of materials that are heterogenous at micro- or fine-scale. Among existing methods for homogenization, computational homogenization is widely used in multiscale analyses of structures and materials. Conventional computational homogenization suffers from long computing times, which substantially limits its application in analyzing engineering problems. The neural networks can be used to construct fully decoupled approaches in nonlinear multiscale methods by mapping macroscopic loading and microscopic response. Computational homogenization methods for nonlinear material and implementation of offline multiscale computation are studied to generate data set. This article intends to model the multiscale constitution using feedforward neural network (FNN) and recurrent neural network (RNN), and appropriate set of loading paths are selected to effectively predict the materials behavior along unknown paths. Applications to two-dimensional multiscale analysis are tested and discussed in detail.

关键词： multiscale method     constitutive model     feedforward neural network     recurrent neural network    

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复杂地质曲面三维插值—逼近拟合构造方法

李明超,缪正建,刘菲,王刚

《中国工程科学》 2011年 第13卷 第12期   页码 103-107

摘要：

针对水利水电工程多源地质数据的特点，充分考虑了地质精度要求、曲面连续性和数据存储量等多方面的均衡，提出并实现了基于NURBS(non-uniform rational B-splines，非均匀有理样条曲线）技术的复杂地质曲面插值—逼近拟合构造方法。该方法对于工程关键区域集中且均匀分布的原始数据，采用NURBS蒙皮插值方法，使曲面严格通过这些数据点；对于周边区域分布离散的数据，采用NURBS逼近拟合方法，使曲面在给定精度下充分逼近原始数据；最后对整体曲面的地质结构合理性、几何性和精度进行检查分析和调整。实例表明，该方法所构造的地质曲面能满足地质工程师的实际需要，并能为进一步的三维地质建模提供基础。

关键词： 地质曲面     插值—逼近拟合     三维构造     多源地质数据    

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Multiscale mechanical modeling of hydrated cement paste under tensile load using the combined DEM-MD

Yue HOU, Linbing WANG

《结构与土木工程前沿（英文）》 2017年 第11卷 第3期   页码 270-278 doi: 10.1007/s11709-017-0408-8

摘要： In this paper, a combined DEM-MD method is proposed to simulate the crack failure process of Hydrated Cement Paste (HCP) under a tensile force. A three-dimensional (3D) multiscale mechanical model is established using the combined Discrete Element Method (DEM)-Molecular Dynamics (MD) method in LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). In the 3D model, HCP consists of discrete particles and atoms. Simulation results show that the combined DEM-MD model is computationally efficient with good accuracy in predicting tensile failures of HCP.

关键词： hydrated cement paste     multiscale     MD simulation     DEM    

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标题 作者 时间 类型 操作

A multiscale-contour-based interpolation framework for generating a time-varying quasi-dense point cloud

Chu-hua HUANG,Dong-ming LU,Chang-yu DIAO

期刊论文

Image automatic mosaics based on contour phase correlation

ZHANG Jing, HU Zhiping, OU Zongying, LIU Zhitai

期刊论文

Chord error constraint based integrated control strategy for contour error compensation

Tie ZHANG, Caicheng WU, Yanbiao ZOU

期刊论文

Topology optimization based on reduction methods with applications to multiscale design and additive

Emmanuel TROMME, Atsushi KAWAMOTO, James K. GUEST

期刊论文

Connected morphable components-based multiscale topology optimization

Jiadong DENG, Claus B. W. PEDERSEN, Wei CHEN

期刊论文

基于相邻关系的等高线树建立算法研究

郭沛沛,李成名,殷勇

期刊论文

Fractal characteristic evaluation and interpolation reconstruction for surface topography of drilled

期刊论文

Special Column on Multiscale Stochastic Finite Element Method

期刊论文

A multiscale material model for heterogeneous liquid droplets in solid soft composites

期刊论文

Implementation of an adaptive feed speed 3D NURBS interpolation algorithm

LIANG Hong-bin, WANG Yong-zhang, LI Xia

期刊论文

Three-scale stochastic homogenization of elastic recycled aggregate concrete based on nano-indentation

Chen WANG, Yuching WU, Jianzhuang XIAO

期刊论文

Multiscale RBF-based central high resolution schemes for simulation of generalized thermoelasticity problems

Hassan YOUSEFI, Alireza TAGHAVI KANI, Iradj MAHMOUDZADEH KANI

期刊论文

Multiscale computation on feedforward neural network and recurrent neural network

Bin LI, Xiaoying ZHUANG

期刊论文

复杂地质曲面三维插值—逼近拟合构造方法

李明超,缪正建,刘菲,王刚

期刊论文

Multiscale mechanical modeling of hydrated cement paste under tensile load using the combined DEM-MD

Yue HOU, Linbing WANG

期刊论文