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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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Numerical simulation of sudden-expansion two-phase flows with two-scale second-order moment particle

ZENG Zhuoxiong, HAN Shoulei, ZHOU Lixing

《能源前沿（英文）》 2007年第1卷第2期页码 202-206 doi: 10.1007/s11708-007-0026-6

摘要： A two-scale second-order moment particle turbulence model is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. The model is employed to simulate gas-particle flows in a sudden-expansion chamber. Simulation results are compared with the experimental results and with those obtained by the single-scale second-order moment two-phase turbulence model. It is shown that the two-scale model is with higher calculating accuracy than the single-scale model.

关键词： gas-particle single-scale second-order large-scale fluctuation second-order sudden-expansion

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Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

《机械工程前沿（英文）》 2021年第16卷第3期页码 593-606 doi: 10.1007/s11465-021-0636-4

摘要： This paper proposes a novel method for the continuum topology optimization of transient vibration problem with maximum dynamic response constraint. An aggregated index in the form of an integral function is presented to cope with the maximum response constraint in the time domain. The density filter solid isotropic material with penalization method combined with threshold projection is developed. The sensitivities of the proposed index with respect to design variables are conducted. To reduce computational cost, the second-order Arnoldi reduction (SOAR) scheme is employed in transient analysis. Influences of aggregate parameter, duration of loading period, interval time, and number of basis vectors in the SOAR scheme on the final designs are discussed through typical examples while unambiguous configuration can be achieved. Through comparison with the corresponding static response from the final designs, the optimized results clearly demonstrate that the transient effects cannot be ignored in structural topology optimization.

关键词： topology optimization solid isotropic material with penalization transient response aggregation function second-order Arnoldi reduction

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Time-varying formation tracking for uncertain second-order nonlinearmulti-agent systems

Mao-peng RAN, Li-hua XIE, Jun-cheng LI

《信息与电子工程前沿（英文）》 2019年第20卷第1期页码 76-87 doi: 10.1631/FITEE.1800557

摘要：

Our study is concerned with the time-varying formation tracking problem for second-order multi-agent systems that are subject to unknown nonlinear dynamics and external disturbance, and the states of the followers form a predefined time-varying formation while tracking the state of the leader. The total uncertainty lumps the unknown nonlinear dynamics and the external disturbance, and is regarded as an extended state of the agent. To estimate the total uncertainty, we design an extended state observer (ESO). Then we propose a novel ESO based time-varying formation tracking protocol. It is proved that, under the proposed protocol, the ESO estimation error and the time-varying formation tracking error can be made arbitrarily small. An application to the target enclosing problem for multiple unmanned aerial vehicles (UAVs) verifies the effectiveness and superiority of the proposed approach.

关键词： Multi-agent system Time-varying formation Formation tracking Nonlinear dynamics Extended state observer (ESO)

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Analysis of nonlinear channel friction inverse problem

CHENG Weiping, LIU Guohua

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 205-210 doi: 10.1007/s11709-007-0024-0

摘要： Based on the Backus-Gilbert inverse theory, the singular value decomposition (SVD) for general inverse matrices and the optimization algorithm are used to solve the channel friction inverse problem. The resolution and covariance friction inverse model in matrix form is developed to examine the reliability of solutions. Theoretical analyses demonstrate that the convergence rate of the general Newton optimization algorithm is in the second-order. The Wiggins method is also incorporated into the algorithm. Using the method, noise can be suppressed effectively, and the results are close to accurate solutions with proper control parameters. Also, the numerical stability can be improved.

关键词： singular SVD second-order covariance Theoretical

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Principle of maximum entropy for reliability analysis in the design of machine components

Yimin ZHANG

《机械工程前沿（英文）》 2019年第14卷第1期页码 21-32 doi: 10.1007/s11465-018-0512-z

摘要： We studied the reliability of machine components with parameters that follow an arbitrary statistical distribution using the principle of maximum entropy (PME). We used PME to select the statistical distribution that best fits the available information. We also established a probability density function (PDF) and a failure probability model for the parameters of mechanical components using the concept of entropy and the PME. We obtained the first four moments of the state function for reliability analysis and design. Furthermore, we attained an estimate of the PDF with the fewest human bias factors using the PME. This function was used to calculate the reliability of the machine components, including a connecting rod, a vehicle half-shaft, a front axle, a rear axle housing, and a leaf spring, which have parameters that typically follow a non-normal distribution. Simulations were conducted for comparison. This study provides a design methodology for the reliability of mechanical components for practical engineering projects.

关键词： machine components reliability arbitrary distribution parameter principle of maximum entropy

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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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Maximum entropy based finite element analysis of porous media

Emad NOROUZI, Hesam MOSLEMZADEH, Soheil MOHAMMADI

《结构与土木工程前沿（英文）》 2019年第13卷第2期页码 364-379 doi: 10.1007/s11709-018-0470-x

摘要： The maximum entropy theory has been used in a wide variety of physical, mathematical and engineering applications in the past few years. However, its application in numerical methods, especially in developing new shape functions, has attracted much interest in recent years. These shape functions possess the potential for performing better than the conventional basis functions in problems with randomly generated coarse meshes. In this paper, the maximum entropy theory is adopted to spatially discretize the deformation variable of the governing coupled equations of porous media. This is in line with the well-known fact that higher-order shape functions can provide more stable solutions in porous problems. Some of the benchmark problems in deformable porous media are solved with the developed approach and the results are compared with available references.

关键词： maximum entropy FEM fully coupled multi-phase system porous media

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Nonlinear analysis of pre-tensioned glass wall facade by stability function with initial imperfection

Siu-Lai CHAN, Yaopeng LIU, Andy LEE,

《结构与土木工程前沿（英文）》 2010年第4卷第3期页码 376-382 doi: 10.1007/s11709-010-0086-2

摘要： Pre-tensioned high strength trusses using alloy steel bar are widely used as glass wall supporting systems because of the high degree of transparency. The breakage of glass panes in this type of system occurs occasionally, likely to be due to error in design and analysis in addition to other factors like glass impurity and stress concentration around opening in a spider system. Most design does not consider the flexibility of supports from finite stiffness of supporting steel or reinforced concrete beams. The resistance of lateral wind pressure of the system makes use of high tension force coupled with the large deflection effect, both of which are affected by many parameters not generally considered in conventional structures. In the design, one must therefore give a careful consideration on various effects, such as support settlement due to live loads and material creep, temperature change, pre-tension force, and wind pressure. It is not uncommon to see many similar glass wall systems fail in the wind load test chambers under a design wind speed. This paper presents a rigorous analysis and design of this type of structural systems used in a project in Hong Kong, China. The stability function with initial curvature is used in place of the cubic function, which is only accurate for linear analysis. The considerations and analysis techniques are believed to be of value to engineers involved in the design of the structural systems behaving nonlinearly.

关键词： tension system glass wall nonlinear analysis pre-tensioning second-order analysis

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Adaptive selective ES-FEM limit analysis of cracked plane-strain structures

H. NGUYEN-XUAN,T. RABCZUK

《结构与土木工程前沿（英文）》 2015年第9卷第4期页码 478-490 doi: 10.1007/s11709-015-0317-7

摘要： This paper presents a simple and efficient approach for predicting the plastic limit loads in cracked plane-strain structures. We use two levels of mesh repartitioning for the finite element limit analysis. The master level handles an adaptive primal-mesh process through a dissipation-based indicator. The slave level performs the subdivision of each triangle into three sub-triangles and constitutes a dual mesh from a pair of two adjacent sub-triangles shared by common edges of the primal mesh. Applying a strain smoothing projection to the strain rates on the dual mesh, the incompressibility constraint and the flow rule constraint are imposed over the edge-based smoothing domains and everywhere in the problem domain. The limit analysis problem is recast into the compact form of a second-order cone programming (SOCP) for the purpose of exploiting interior-point solvers. The present method retains a low number of optimization variables. It offers a convenient way for designing and solving the large-scale optimization problems effectively. Several benchmark examples are given to show the simplicity and effectiveness of the present method.

关键词： cracked structure limit analysis von Mises criterion edge-based strain smoothing second-order cone programming adaptive

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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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Fractional order extremum seeking approach for maximum power point tracking of photovoltaic panels

Ammar NEÇAIBIA,Samir LADACI,Abdelfatah CHAREF,Jean Jacques LOISEAU

《能源前沿（英文）》 2015年第9卷第1期页码 43-53 doi: 10.1007/s11708-014-0343-5

摘要： Due to the high interest in renewable energy and diversity of research regarding photovoltaic (PV) array, a great research effort is focusing nowadays on solar power generation and its performance improvement under various weather conditions. In this paper, an integrated framework was proposed, which achieved both maximum power point tracking (MPPT) and minimum ripple signals. The proposed control scheme was based on extremum-seeking (ES) combined with fractional order systems (FOS). This auto-tuning strategy was developed to maximize the PV panel output power through the regulation of the voltage input to the DC/DC converter in order to lead the PV system steady-state to a stable oscillation behavior around the maximum power point (MPP). It is shown that fractional order operators can improve the plant dynamics with respect to time response and disturbance rejection. The effectiveness of the proposed controller scheme is illustrated with simulations using measured solar radiation data.

关键词： extremum seeking (ES) fractional order control (FOC) fractional calculus photovoltaic (PV) panel maximum power point tracking (MPPT)

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知识创新随机过程最大熵模型

陈欣,和金生,董丽平

《中国工程科学》 2004年第6卷第12期页码 43-46

摘要：

根据创新知识的形成受已有相关知识影响的假设，综合运用概率统计、最优化、最大熵原理构建了知识创新随机过程最大熵模型，给出了以已有知识x∈X为约束的新知识y∈Y的条件概率p(y|x)。模型具有随机性与因果性对立统一的特点。

关键词：最大熵知识创新条件熵随机过程

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具有领航者的二阶非线性多智能体系统在外部扰动下的同步控制 None

Mao-bin LU, Lu LIU

《信息与电子工程前沿（英文）》 2019年第20卷第1期页码 88-94 doi: 10.1631/FITEE.1800611

摘要：研究了一类异质二阶非线性多智能体系统在外部扰动影响下的同步控制问题。其中，非线性系统允许包含可线性参数化的未知参数。提出一种新颖的分布式控制器，此控制器依赖于系统的相对状态，因此可以在多智能体系统之间没有通讯的情况下应用。通过Barbalat引理，证明此分布式控制器可求解二阶非线性多智能体系统的同步控制问题。对一组Van der Pol振荡器进行同步控制的应用示例验证了主要结果的有效性。

关键词：多智能体系统；同步控制；分布式控制

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间歇通信下基于采样数据的二阶多智能体系统包含控制 Research Articles

王付永1,2,刘忠信1,2,陈增强1,2

《信息与电子工程前沿（英文）》 2021年第22卷第8期页码 1059-1067 doi: 10.1631/FITEE.2000204

摘要：在间歇通信且智能体间相对速度不可测的情况下，基于采样位置数据研究了二阶多智能体系统的包含控制问题，提出一种基于间歇采样位置测量的二阶分布式包含控制器。通过分析系统控制增益、拉普拉斯矩阵特征值、采样周期和通信宽度之间的关系，得到二阶多智能体系统在间歇通信下实现包含控制的充要条件。最后，通过仿真实例验证了理论结果的正确性和有效性。

关键词：包含控制；二阶多智能体系统；采样位置数据；间歇通信；通信宽度

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标题作者时间类型操作

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

Fatemeh AMIRI

期刊论文

Numerical simulation of sudden-expansion two-phase flows with two-scale second-order moment particle

ZENG Zhuoxiong, HAN Shoulei, ZHOU Lixing

期刊论文

Topology optimization of transient problem with maximum dynamic response constraint using SOAR scheme

期刊论文

Time-varying formation tracking for uncertain second-order nonlinearmulti-agent systems