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Implicit Heaviside filter with high continuity based on suitably graded THB splines

《机械工程前沿（英文）》 2022年第17卷第1期页码 14-14 doi: 10.1007/s11465-021-0670-2

摘要： The variable density topology optimization (TO) method has been applied to various engineering fields because it can effectively and efficiently generate the conceptual design for engineering structures. However, it suffers from the problem of low continuity resulting from the discreteness of both design variables and explicit Heaviside filter. In this paper, an implicit Heaviside filter with high continuity is introduced to generate black and white designs for TO where the design space is parameterized by suitably graded truncated hierarchical B-splines (THB). In this approach, the fixed analysis mesh of isogeometric analysis is decoupled from the design mesh, whose adaptivity is implemented by truncated hierarchical B-spline subjected to an admissible requirement. Through the intrinsic local support and high continuity of THB basis, an implicit adaptively adjusted Heaviside filter is obtained to remove the checkboard patterns and generate black and white designs. Threefold advantages are attained in the proposed filter: a) The connection between analysis mesh and adaptive design mesh is easily established compared with the traditional adaptive TO method using nodal density; b) the efficiency in updating design variables is remarkably improved than the traditional implicit sensitivity filter based on B-splines under successive global refinement; and c) the generated black and white designs are preliminarily compatible with current commercial computer aided design system. Several numerical examples are used to verify the effectiveness of the proposed implicit Heaviside filter in compliance and compliant mechanism as well as heat conduction TO problems.

关键词： topology optimization truncated hierarchical B-spline isogeometric analysis black and white designs Heaviside filter

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Multiresolution and multimaterial topology optimization of fail-safe structures under B-spline spaces

《机械工程前沿（英文）》 2023年第18卷第4期 doi: 10.1007/s11465-023-0768-9

摘要： This study proposes a B-spline-based multiresolution and multimaterial topology optimization (TO) design method for fail-safe structures (FSSs), aiming to achieve efficient and lightweight structural design while ensuring safety and facilitating the postprocessing of topological structures. The approach involves constructing a multimaterial interpolation model based on an ordered solid isotropic material with penalization (ordered-SIMP) that incorporates fail-safe considerations. To reduce the computational burden of finite element analysis, we adopt a much coarser analysis mesh and finer density mesh to discretize the design domain, in which the density field is described by the B-spline function. The B-spline can efficiently and accurately convert optimized FSSs into computer-aided design models. The 2D and 3D numerical examples demonstrate the significantly enhanced computational efficiency of the proposed method compared with the traditional SIMP approach, and the multimaterial TO provides a superior structural design scheme for FSSs. Furthermore, the postprocessing procedures are significantly streamlined.

关键词： multiresolution multimaterial topology optimization fail-safe structure B-spline

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Crack fault quantitative diagnosis based on finite element of B-spline wavelet on the interval

XIANG Jia-wei, CHEN Xue-feng, HE Zheng-jia, HE Yu-min

《机械工程前沿（英文）》 2006年第1卷第2期页码 177-182 doi: 10.1007/s11465-006-0001-7

摘要： The model-based forward and inverse problems in the diagnosis of structural crack faults were studied. The forward problem is to solve the natural frequencies through a cracked structural model and the inverse problem is to quantitatively determine the crack parameters using the experimental testing frequencies. Then, the one-dimensional crack element of B-spline wavelet on the interval (BSWI) was built to solve the forward problem. Contour plots of normalized crack location versus normalized crack size were plotted by using the first three natural frequencies as the inputs. The intersection of the three curves predicted the normalized crack location and size. The experimental study verified the validity of the wavelet-based crack element in solving crack singular problems to overcome the disadvantages of the traditional finite element method (FEM), such as low efficiency, insufficient accuracy, slow convergence to correct solutions, etc. At the same time, it had adequate identification precision. The new method can be applied to prognosis and quantitative diagnosis of incipient crack.

关键词： one-dimensional B-spline incipient prognosis identification precision

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基于形参均匀B样条盈亏修正的图像边缘检测

赵颜利,王湛,郭成昊,刘凤玉

《中国工程科学》 2007年第9卷第7期页码 65-70

摘要：

利用形参均匀B样条平滑公式，建立了一种盈亏修正的图像边缘检测新方法。首先对图像的原型值点进行盈亏修正，进一步减少原始图像和平滑图像之间的残余误差；然后利用形参均匀B样条修匀公式对修正后的图像拟合光滑曲面；最后求拟合后的光滑曲面的一阶导数极值点或二阶导数的零交叉点作为边缘特征点

关键词：形状参数均匀B样条边缘检测计算机视觉盈亏修正

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基于双目立体匹配和B样条的三维人脸点云孔洞修补算法 Research Articles

黄源1,2,达飞鹏1,2

《信息与电子工程前沿（英文）》 2022年第23卷第3期页码 398-408 doi: 10.1631/FITEE.2000508

摘要：本文提出一种采用立体匹配技术结合B样条的孔洞修补方法。算法首先利用光栅投影过程中获取的相位信息定位点云中的孔洞区域，同时提取边界点集。再利用B样条曲线形状可由少数关键点大致描述这一特性，将控制点作为关键点放入孔洞区域进行曲面重建迭代计算。仿真使用光滑陶瓷杯和人脸模型进行，结果表明，该算法能够准确再现被测物体表面的细节和复杂形状。

关键词：三维点云；孔洞修补；立体匹配；B样条

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Feature extraction from slice data for reverse engineering

ZHANG Yingjie, LU Shangning

《机械工程前沿（英文）》 2007年第2卷第1期页码 25-31 doi: 10.1007/s11465-007-0004-z

摘要： A new approach to feature extraction for slice data points is presented. The reconstruction of objects is performed as follows. First, all contours in each slice are extracted by contour tracing algorithms. Then the data points on the contours are analyzed, and the curve segments of the contours are divided into three categories: straight lines, conic curves and B-spline curves. The curve fitting methods are applied for each curve segment to remove the unwanted points with pre-determined tolerance. Finally, the features, which consist of the object and connection relations among them, are founded by matching the corresponding contours in adjacent slices, and 3D models are reconstructed based on the features. The proposed approach has been implemented in OpenGL, and the feasibility of the proposed method has been verified by several cases.

关键词： feasibility corresponding B-spline pre-determined tolerance extraction

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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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A novel energy loss model and optimization design of the coin chute flection curve

Qinghua LIANG, Jinqiu MO, Weizhong GUO

《机械工程前沿（英文）》 2012年第7卷第1期页码 38-46 doi: 10.1007/s11465-012-0311-x

摘要：

In this paper, we propose a novel design model based on the energy loss of the coin (ELM model) to optimize the flection curve, which is widely used in coin operated machines. Two different kinds of energy loss models are analyzed according to dynamic characteristics of the coin falling movement. The flection curve is constructed based on cubic quasi-uniform B-spline with the data points and end points derivatives as inputs, and the curve model is governed and affected by energy loss equations, allowing to minimize the total energy loss before the coin arrives at the detecting position, thus to reduce the energy loss and collisions between the coin and the flection, thus to improve the testing accuracy. A case study with a typical Chinese currency coin shows the effectiveness of the model using GA optimization toolbox.

关键词： flection curve B-spline energy loss model (ELM model) optimization design

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Multi-objective optimization of a 3D vaneless diffuser based on fuzzy theory

GAO Chuang, GU Chuangang, WANG Tong, SHU Xinwei

《能源前沿（英文）》 2008年第2卷第1期页码 66-70 doi: 10.1007/s11708-008-0006-5

摘要： An optimization model based on fuzzy theory was set up and the corresponding Interactive modified simplex (IMS) method was developed to solve it. Both static pressure recovery and total pressure loss were considered in the model. Computational fluid dynamics (CFD) method was applied to solve the Reynolds-Averaged Navier-Stokes equation (RANS) and to find flow field distribution to get the value of the object function. After receiving the new shroud curve, grid movement and redrawing technology were adopted to avoid grid-line crossing and negative cells. The shroud curve was fitted with B-spline. The optimized results concur with the results reported in references.

关键词： Computational pressure recovery B-spline technology corresponding Interactive

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High-order phase-field model with the local and second-order max-entropy approximants

Fatemeh AMIRI

《结构与土木工程前沿（英文）》 2019年第13卷第2期页码 406-416 doi: 10.1007/s11709-018-0475-5

摘要： We approximate the fracture surface energy functional based on phase-field method with smooth local maximum entropy (LME) and second-order maximum entropy (SME) approximants. The higher-order continuity of the meshfree methods such as LME and SME approximants allows to directly solve the fourth-order phase-field equations without splitting the fourth-order differential equation into two second-order differential equations. We will first show that the crack surface functional can be captured more accurately in the fourth-order model with smooth approximants such as LME, SME and B-spline. Furthermore, smaller length scale parameter is needed for the fourth-order model to approximate the energy functional. We also study SME approximants and drive the formulations. The proposed meshfree fourth-order phase-field formulation show more stable results for SME compared to LME meshfree methods.

关键词： second-order maximum entropy local maximum entropy second- and fourth-order phase-field models B-spline

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指数多项式均匀样条模型

赵颜利,平萍,刘凤玉

《中国工程科学》 2008年第10卷第7期页码 147-152

摘要：该类模型具有很多与B 样条模型相同的性质，并且增加了一个可调节的形状参数。由该模型构造的曲线，通过改变形状参数的取值，可以调整曲线接近其控制多边形的程度。

关键词：指数多项式样条函数 B样条函数形状参数

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重复镜头视频基于分级B帧结构的长期预测编码方案 None

Xu-guang ZUO, Lu YU

《信息与电子工程前沿（英文）》 2018年第19卷第3期页码 459-470 doi: 10.1631/FITEE.1601552

摘要：特别是，在使用分级B帧预测结构时，HEVC可显著去除临近图像间的时间冗余。实际中，消费者使用的视频——例如电视剧、电影和脱口秀等——通常包含了很多重复镜头。据我们观察，这些视频在分级B帧结构下使用HEVC编码时，每个镜头的时域相关性可以得到很好利用。然而，重复镜头之间的长期相关性并未被使用。然后，使用长期参考帧对分级B帧的编码结构进行调整，以实现长期时域预测。最后，为长期参考帧设计一种自适应量化方法，以提高整体的视频编码效率。

关键词：高效视频编码（HEVC）；长期时域相关性；长期预测；分级B帧结构

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Thermal annealing synthesis of double-shell truncated octahedral Pt-Ni alloys for oxygen reduction reaction

Xiashuang LUO, Yangge GUO, Hongru ZHOU, Huan REN, Shuiyun SHEN, Guanghua WEI, Junliang ZHANG

《能源前沿（英文）》 2020年第14卷第4期页码 767-777 doi: 10.1007/s11708-020-0667-2

摘要： Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), whose tricks lie in well-designed structures and surface morphologies. In this paper, a novel synthesis of truncated octahedral PtNi alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi alloys is reported. By tracking the evolution of both compositions and morphologies, the outward segregation of both PtO and NiO are first observed in Pt-Ni alloys. It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells. It is very attractive that after gently removing the NiO outer shell, the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity. The as-obtained truncated octahedral Pt Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample, and its activity preserves 45.4% after 30000 potential cycles of accelerated degradation test (ADT). The peak power density of the dealloyed truncated octahedral Pt Ni core-shell alloy catalyst based membrane electrolyte assembly (MEA) reaches 679.8 mW/cm , increased by 138.4 mW/cm relative to that based on commercial Pt/C.

关键词： dealloyed Pt-Ni alloys truncated octahedron double-shell thermal annealing oxygen reduction reaction (ORR)

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Interpolation of a spline developable surface between a curve and two rulings

Alicia CANTÓN,Leonardo FERNÁNDEZ-JAMBRINA

《信息与电子工程前沿（英文）》 2015年第16卷第3期页码 173-190 doi: 10.1631/FITEE.14a0210

摘要： In this paper we address the problem of interpolating a spline developable patch bounded by a given spline curve and the first and the last rulings of the developable surface. To complete the boundary of the patch, a second spline curve is to be given. Up to now this interpolation problem could be solved, but without the possibility of choosing both endpoints for the rulings. We circumvent such difficulty by resorting to degree elevation of the developable surface. This is useful for solving not only this problem, but also other problems dealing with triangular developable patches.

关键词： Developable surfaces Spline surfaces Blossoms

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Deep convolutional tree-inspired network: a decision-tree-structured neural network for hierarchical

《机械工程前沿（英文）》 2021年第16卷第4期页码 814-828 doi: 10.1007/s11465-021-0650-6

摘要： The fault diagnosis of bearings is crucial in ensuring the reliability of rotating machinery. Deep neural networks have provided unprecedented opportunities to condition monitoring from a new perspective due to the powerful ability in learning fault-related knowledge. However, the inexplicability and low generalization ability of fault diagnosis models still bar them from the application. To address this issue, this paper explores a decision-tree-structured neural network, that is, the deep convolutional tree-inspired network (DCTN), for the hierarchical fault diagnosis of bearings. The proposed model effectively integrates the advantages of convolutional neural network (CNN) and decision tree methods by rebuilding the output decision layer of CNN according to the hierarchical structural characteristics of the decision tree, which is by no means a simple combination of the two models. The proposed DCTN model has unique advantages in 1) the hierarchical structure that can support more accuracy and comprehensive fault diagnosis, 2) the better interpretability of the model output with hierarchical decision making, and 3) more powerful generalization capabilities for the samples across fault severities. The multiclass fault diagnosis case and cross-severity fault diagnosis case are executed on a multicondition aeronautical bearing test rig. Experimental results can fully demonstrate the feasibility and superiority of the proposed method.

关键词： bearing cross-severity fault diagnosis hierarchical fault diagnosis convolutional neural network decision tree