检索结果-内蒙古大学图书馆

Estimation of magnetic particle size distribution for ferrofluids based on nonlinear programming optimization and an improved Bayesian method

引用

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 2019年 482卷 99-107页

作者： Li, Yanbin Xiao, Junming Zhu, Yongsheng Zhongyuan Univ Technol Sch Elect & Informat Engn Zhengzhou Henan Peoples R China

For the fundamental research and industrial application of ferrofluids, the particle size distribution (PSD) of magnetic nanoparticles is crucial to characterize their material properties. This work aims to develop efficient and robust PSD estimation methods for ferrofluids without interacting particles under two cases, known and unknown distribution types. The main task of the first case is to estimate the distribution parameters for a given PSD. For this purpose, L-p norm method is employed to convert the PSD estimation matrix equation into a constrained nonlinear programming problem. Then the nonlinear programming method (NPM) is presented to estimate the PSD parameters based on the magnetization data. The main tasks of the second case are to reconstruct the PSD curve and estimate the distribution type and parameters. To achieve these goals, an improved Bayesian method is proposed by using the estimation obtained from NPM as its prior information. Then a non-parameter hypothesis test method, Shapiro-Wilk test is introduced to determine the distribution type of the PSD. To illustrate the effectiveness of the proposed methods, theoretical analysis and Monte Carlo simulation are conducted based on the material parameters and experimental results of two ferrofluid samples. Through the comparison, it is found that the NPM is less sensitive to the noise like measurement errors and it can provide more accurate estimations than conventional inversion methods. Moreover, the proposed improved Bayesian method is efficient and robust to the noise, which can be used to reconstruct the PSD curves of ferrofluids without using the conventional time-consuming experimental methods like transmission electron microscopy.

关键词： Bayesian method Ferrofluid Monte Carlo method nonlinear programming method Particle size distribution

来源：评论

学校读者我要写书评

暂无评论

Construction of improved rigid blocks failure mechanism for ultimate bearing capacity calculation based on slip-line field theory

引用

Journal of Central South University 2013年第4期20卷 1047-1057页

作者：赵炼恒杨峰 School of Civil Engineering Central South University

Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framework of the upper bound limit analysis theorem. In the velocity discontinuities in transition area, the velocity changes in radial and tangent directions are allowed. The objective functions of the stability problems of geotechnical structures are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities, and then the objective functions are transformed as an upper-bound mathematic optimization model. The upper bound solutions for the objective functions are obtained by use of the nonlinear sequential quadratic programming and interior point method. From the numerical results and comparative analysis, it can be seen that the method presented in this work gives better calculation results than existing upper bound methods and can be used to establish the more accurate plastic collapse load for the ultimate bearing capacity of rough foundation.

关键词： ultimate bearing capacity rough foundation slip-line field theory upper bound limit analysis theorem slip failure mechanism nonlinear programming method

来源：评论

学校读者我要写书评

暂无评论

nonlinear finite-part singular integral equations arising in two-dimensional fluid mechanics

引用

nonlinear ANALYSIS-THEORY methodS & APPLICATIONS 2000年第2期42卷 277-290页

作者： Ladopoulos, EG Zisis, VA Interpaper Res Org GR-10672 Athens Greece

The extension of the method obtained for linear finite-part singular integral equations to nonlinear ones is demonstrated. Following the new method, the δ,σ-measure of the conditioning of the problem for the determi... 详细信息

关键词： nonlinear finite-part singular integral equations nonlinear programming method steep descent algorithm two-dimensional fluid mechanics Banach spaces

来源：评论

学校读者我要写书评

暂无评论

Damage tolerance based design optimisation of a fuel flow vent hole in an aircraft structure

引用

STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION 2009年第3期38卷 245-265页

作者： Das, R. Jones, R. CSIRO Math & Informat Sci Clayton Vic 3168 Australia Monash Univ Dept Mech Engn Clayton Vic 3168 Australia

This paper investigates the design optimisation of a fuel flow vent hole (FFVH) located in the wing pivot fitting (WPF) of an F-111 aircraft assuming a damage tolerance design philosophy. The design of the vent hole shape is undertaken considering the basic durability based design objectives of stress, residual (fracture) strength, and fatigue life. Initially, a stress based optimised shape is determined. Damage tolerance based design optimisation is then undertaken to determine the shape of the cutout so as to maximise its residual strength and fatigue life. For stress optimisation, the problem is analysed using the gradient-less biological algorithm and the gradient-based nonlinear programming methods. The optimum designs predicted by the two fundamentally different optimisation algorithms agree well. The optimum shapes of the vent hole are subsequently determined considering residual strength and fatigue life as the distinct design objectives in the presence of numerous 3D cracks located along the vent hole boundary. A number of crack cases are considered to investigate how the crack size affects the optimal shapes. A semi-analytical method is employed for computation of the stress intensity factors (SIF), and an analytical crack closure model is subsequently used to evaluate the fatigue life. The 3D biological algorithm is used for designing the cutout profiles that optimise residual strength and fatigue life of the component. An improved residual strength/fatigue life (depending on the optimisation objective) is achieved for the optimal designs. The variability in SIF/fatigue life around the cutout boundary is reduced, thereby making the shape more evenly fracture/fatigue critical. The vent hole shapes optimised for stress, residual strength, and fatigue life are different from each other for a given nature and size of the flaws. This emphasises the need to consider residual strength and/or fatigue life as the explicit design objective. The durability based opt

关键词： Shape optimisation Damage tolerance Fatigue life Residual strength Stress intensity factor Biological algorithm nonlinear programming method Finite element analysis Industrial application

来源：评论

学校读者我要写书评

暂无评论

Designing cutouts for optimum residual strength in plane structural elements

引用

INTERNATIONAL JOURNAL OF FRACTURE 2009年第2期156卷 129-153页

作者： Das, R. Jones, R. CSIRO Math & Informat Sci Clayton Vic 3168 Australia Monash Univ Dept Mech Engn Clayton Vic 3168 Australia

The paper presents a new approach for shape optimisation of structures with residual strength as the design objective. It must be emphasized that flaws are inevitably present in most structures, and hence the influence of cracks on optimised shapes needs to be investigated. Numerical simulation of cracks using the finite element method requires a very fine mesh to model the singularity at crack tip. This makes fracture calculations computationally intensive. Furthermore, for a damage tolerance based optimisation numerous cracks are to be considered along the structural boundary, and fracture analysis needs to be repeated for each crack at every iteration, thus making the whole process extremely computationally expensive for practical purpose. Moreover, the lack of information concerning crack size, orientation, and location makes the formulation of the optimisation problem difficult. As a result, little attention has been paid to date to consider fracture parameters in the optimisation objective. To address this, the paper presents a methodology for the shape optimisation of structures with strength and durability as the design objectives. In particular, the damage tolerance optimisation is illustrated via the problem of optimal design of a 'cutout in a rectangular block under biaxial loading'. A parametric shape representation has been used to describe the problem geometry. Damage tolerance based optimisation was performed using nonlinear programming algorithms, and NE-NASTRAN was used for finite element analysis. The first order mathematical programming algorithms, viz: the Broydon-Fletcher-Goldfarb-Shanno (BFGS) and the Fletcher-Reeves (Conjugate Direction) methods were evaluated as the potential algorithms for optimising the residual strength in the presence of flaws. Another recently developed Sequential Unconstrained Minimisation Technique (SUMT), based on an exterior penalty function method and especially suited for large problems, was also investigated for f

关键词： Shape optimisation nonlinear programming method Damage tolerance Residual strength Stress intensity factor Finite element analysis

来源：评论

学校读者我要写书评

暂无评论

Fatigue life enhancement of structures using shape optimisation

引用

THEORETICAL AND APPLIED FRACTURE MECHANICS 2009年第3期52卷 165-179页

作者： Das, R. Jones, R. CSIRO Math & Informat Sci Clayton Vic 3168 Australia Monash Univ Dept Mech Engn Clayton Vic 3168 Australia

The paper proposes a new approach for shape optimisation with fatigue life as the design objective. Conventional designs often incorporate stress optimisation that aims at reducing stress concentrations around a structural boundary by minimising the peak stress. However, this is only an effective and sufficient measure for an 'ideal' or 'flaw-less' structure. It is a well-known fact that flaws (cracks) are inevitably present in most structures. This emphasises the need to investigate the influence of cracks on optimised shapes. Numerical modelling of cracks using the Finite Element method requires a fine mesh to model the singularity at crack tips, which makes fracture calculations computationally expensive. Furthermore, for a damage tolerance based optimisation, numerous cracks are to be considered at various arbitrary locations in a structure, and fatigue life evaluation needs to be repeated for each crack at every iteration. This makes the optimisation process extremely computationally inefficient for practical purpose. Moreover, the lack of information concerning crack size, orientation, and location makes the formulation of the optimisation problem difficult. As a result, there has been inadequate research to consider fracture parameters, such as fatigue life, in the optimisation objective. To address this, the paper presents an approach for the shape optimisation of damage tolerant structures with fatigue life as the design constraint. The damage tolerance based optimisation was performed using a number of nonlinear programming algorithms, namely the Broydon-Fietcher-Goldfarb-Shanno (BFGS) method, the Fletcher Reeves (Conjugate Direction) method, and the Sequential Unconstrained Minimisation Technique (SUMT). These methods were extended for optimising the fatigue life in the presence of numerous surface cracks. A significant enhancement in fatigue life was achieved for various crack cases consisting of different initial and final crack sizes. It is shown that

关键词： Damage tolerance Fatigue life Residual strength Cracks Shape optimisation nonlinear programming method

来源：评论

学校读者我要写书评

暂无评论

Hydrodynamic Optimization of Foreship Hull-Form Using Contrastive Optimization Algorithms

引用

JOURNAL OF COASTAL RESEARCH 2021年第5期37卷 1063-1078页

作者： Yin, Xunbin Lu, Qingliang Lu, Yu Zou, Jin Wan, Lei Harbin Engn Univ Coll Shipbldg Engn Harbin 150001 Peoples R China Naval Res Acad Beijing 100161 Peoples R China Dalian Maritime Univ Naval Architecture & Ocean Engn Coll Dalian 116026 Peoples R China

In this study, a hydrodynamic optimization design of the foreship hull-form for the Series 60 ship is presented in terms of minimum wave-making resistance by using contrastive optimization algorithms. The partially parametric approach was developed to modify the original foreship hull-form. The wave-making resistance as an objective function was obtained by the Rankine source panel method with nonlinear free-surface boundary conditions in which the numerical computation results were validated against available experimental data and found to be in good agreement with the test. Different optimal design methods were proposed based on the minimum wave-making resistance: the nonlinear programming method (NLP), the nondominated sorting genetic algorithm (NSGA-II), and particle swarm optimization (PSO). Through the implementation and integration of the hull-form deformation module, the hydrodynamic module, and the optimization module the hydrodynamic optimization framework can be established subsequently. This module realizes the full automation of ship-shape optimization design and searches for the most efficient target through intelligent optimization algorithm. The hydrodynamic optimization applications for the Series 60 ship indicate that the wavemaking resistance is reduced distinctly at various Froude numbers by the contrastive optimization algorithms and each optimized foreship hull-form is smoothing. The present study demonstrates an effective and robust integrated approach for the hydrodynamic optimization of ship design.

关键词： Nondominated sorting genetic algorithm nonlinear programming method particle swarm optimization Rankine source method wave making resistance

来源：评论

学校读者我要写书评

暂无评论

Cluster flight orbit design method for fractionated spacecraft

引用

AIRCRAFT ENGINEERING AND AEROSPACE TECHNOLOGY 2012年第5期84卷 330-343页

作者： Wang, Jihe Nakasuka, Shinichi Univ Tokyo Dept Aeronaut & Astronaut Tokyo Japan

Purpose - The purpose of this paper is to propose an intuitive and effective cluster flight orbit design method for fractionated spacecraft. Design/methodology/approach - Based on the concept of fractionated spacecraft, orbit design requirements for cluster flight in the case of fractionated spacecraft are proposed, and categorized into three requirements: stabilization requirement, passive safety requirement, and the maximum inter-satellite distance requirement. These design requirements are then reformulated in terms of relative eccentricity and inclination vectors (E/I vectors) using a relative motion model based on relative orbital elements (ROEs). By using ROEs theory, the cluster flight orbit design issue is modelled as the distribution of relative E/I vectors for each member satellite in the cluster, and solved by combining three different heuristic search methods and one nonlinear programming (NLP) method. Findings - The simulation results show that the NLP method is valid and efficient in solving the cluster flight orbit design problem and that for some cluster flight scenarios, the heuristic search methods can be adopted to give feasible solutions without the NLP method. Research limitations/implications - The cluster flight scenario in this paper is limited because the cluster should be in the near-circular low earth orbit (LEO), and the relative distance between the member satellites should be small enough to satisfy the relative motion linearization assumption. Practical implications - The cluster flight orbit design method proposed in this paper can be applied by fractionated spacecraft mission designers to propose potential cluster flight orbit solutions. Originality/value - In this paper, the relative E/I vectors method is adopted to propose an intuitive and effective cluster flight orbit design method for fractionated spacecraft.

关键词： Spacecraft Flight Design Cluster flight orbit design Relative eccentricity and inclination vectors Heuristic search methods nonlinear programming method

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：