Artificial neural network based hole image interpretation techniques for integrated topology and shape optimization

Homogenization based and density based topology optimization seeks the best conceptual structural configuration on a predefined design domain with specific boundary and loading conditions. Such structural configuration is most often the minimum-compliance design under a fixed material usage constraint. Shape optimization must be subsequently executed so as to ensure the satisfaction of other practical design constraints such as stress and displacement, and attain the detailed definition of the structure configuration with a smooth circumference and interior hole contours. Complicated procedures involved in connection between topology and shape optimization are major obstacle for most design engineers to overcome. A fully automated configuration optimization system was developed [C.Y. Lin, L.S. Chao, Automated image interpretation for integrated topology and shape optimization, Structural and Multidisciplinary Optimization 20(2) (2000) 125–137] to execute the entire configuration design process automatically with room of improvements in the hole representation templates and hole interpretation reliabilities. In response, this paper proposes two-stage artificial neural networks based hole image interpretation techniques with improved template variety and recognition reliability.     

Structural application of a shape optimization method based on a genetic algorithm

This paper presents a structural application of a shape optimization method based on a Genetic Algorithm (GA). The method produces a sequence of fixed-distance step-wise movements of the boundary nodes of a finite element model to derive optimal shapes from an arbitrary initial design space. The GA is used to find the optimal or near-optimal combination of boundary nodes to be moved for a given step movement. The GA uses both basic and advanced operators. For illustrative purposes, the method has been applied to structural shape-optimization. The shape-optimization methodology presented allows local optimization, where only crucial parts of a structure are optimized as well as global shape-optimization which involves finding the optimal shape of the structure as a whole for a given environment as described by its loading and freedom conditions. Material can be removed or added to reach the optimal shape. Two examples of structural shape optimization are included showing local and global optimization through material removal and addition. Received October 14, 1999     

基于组件技术特定应用的嵌入式操作系统构造

面向Internet网络的、特定应用的嵌入式操作系统正发展成为当今国际上实时嵌入式系统极为重要的研究内容。该文论述了特定应用嵌入式操作系统ASOS（Application Specific Embedded Operating Systems)的概念和构成特点，阐述了基于组件技术构造ASOS的基本方法。     

Interactive optimal design of truss structures

A CAD system based on combining structural optimization methods and graphical interaction is presented. The optimization methods implement the automated decisions and algorithms while the interaction provides the means to implement the designer's decisions. A new interactive optimization procedure for optimal truss design is proposed. The structural topology, geometry and member sizes are treated as design variables. Results show that the system provides a powerful tool to obtain a practical optimum design.     

机械结构多机分布式优化的集成策略研究

为了解决复杂机械结构的优化集成问题,提出了跨广义优化平台与有限元分析平台的多计算机分布式优化的集成策略及系统总体框架,详细探讨了实现集成的一些关键技术,包括在有限元前处理中的边界载荷条件的自动施加、网格自动修改、数据通讯问题、远程控制技术等,提出了相应的解决方案,并已有效地用于求解液压挖掘机的广义优化模型。     

特定应用的嵌入式操作系统构造方法研究

随着通用型嵌入式实时操作系统的发展，一个以面向Internet网络的、特定应用的嵌入式操作系统成为实时嵌入式系统极为重要的发展方向。本文详细阐述了特定应用嵌入式操作系统ASOS(Application Specific embedded Operating Systems)的概念和特点，提出了ASOS的三种构造方法：面向对象技术，组件技术，模式生成。     

An efficient procedure for structural reliability-based robust design optimization

This paper focuses on the development of an optimization tool with the aim to obtain robust and reliable designs in short computational time. The robustness measures considered here are the expected value and standard deviation of the performance function involved in the optimization problem. When using these robustness measures combined, the search of optimal design appears as a robust multiobjective optimization (RMO) problem. Reliable design addresses uncertainties to restrict the structural probability of failure. The mathematical formulation for the reliability based robust design optimization (RBRDO) problem is obtained by adding a reliability based constraint into the RMO problem. As both, statistics calculations and the reliability analysis could be very costly, approximation technique based on reduced-order modeling (ROM) is also incorporated in our procedure. The selected ROM is the proper orthogonal decomposition (POD) method, with the aim to produce fast outputs considering structural non-linear behavior. Moreover, to obtain RBRDO designs with reduced CPU time we propose others developments to be added in the integrated tool. They are: Probabilistic Collocation Method (PCM) to evaluate the statistics of the structural responses and, also, an approximated reliability constraints procedure based on the Performance Measure Approach (PMA) for reliability constraint assessment. Finally, Normal-Boundary Intersection (NBI) or Normalized Normal-Constraint (NNC) multiobjective optimization techniques are employed to obtain fast and even spread Pareto robust designs. To illustrate the application of the proposed tool, optimization studies are conducted for a linear (benchmark) and nonlinear trusses problems. The nonlinear example consider different loads level, exploring the material plasticity. The integrated tool prove to be very effective reducing the computational time by up to five orders of magnitude, when compared to the solutions obtained via classical standard approaches.     

Optimization of hole reinforcements by doublers

For various technical reasons, cutouts such as holes in thin-walled structures are inevitable and are of significant technical relevance. Unfortunately holes lead to an undesired stress concentration at the hole vicinity and a reduced strength of the structure. Therefore in practice a local reinforcement is usually applied around the hole. The increasing requirements for modern structures in terms of low weight and high strength lead to the question of an optimal reinforcement design. The present paper addresses the well-approved techniques of mathematical structural optimization to determine the aforementioned optimal design of the reinforcement. Thus it is necessary to set up an optimization model, as well as an appropriate structural model, to obtain the structural response (displacements, stresses ...). In this work, the finite element method has been applied for the structural analysis. The optimization procedure described has been utilized for a number of different reinforcement alternatives under various load cases. The numerical procedure implemented works with good reliability and efficiency and gives optimal reinforcement designs that are very useful for the direct engineering application. The results obtained illustrate the necessity and usefulness of the applied optimization procedure. Received April 28, 1999     

永磁型MRI系统中磁体的仿真分析与优化

针对永磁型核磁共振成像系统（MRI）中的磁体，该文阐述了一种利用计算机软件对其进行仿真建模、数据分析的优化方法，使磁体优化设计技术更具有科学性。MRI磁体的AutoCAD三维实体建模与仿真数据分析是实现该方法的主要部分，仿真数据分析中采用了有限元的分析方法，分析结果主要以图像形式给出，直观形象地表示了磁路中的磁场分布情况。使用该方法能够简单快捷地对MRI磁体进行仿真分析，得到磁体的优化方案。     

A two phase optimization method for Petri net models of manufacturing systems

Optimization is a key issue in the design of large manufacturing systems. An adequate modeling formalism to express the intricate interleaving of competition and cooperation relationships is needed first. Moreover, robust and efficient optimization techniques are necessary. This paper presents an integrated tool for the automated optimization of DEDS, with application to manufacturing systems. After a very quick overview of optimization problems in manufacturing systems, it presents the integration of two existing tools for the modeling and evaluation with Petri nets and a general-purpose optimization package based on simulated annealing. The consideration of a cache and a two phase technique for optimization allows to speed-up the optimization by a factor of about 35. During the first preoptimization phase, a rough approximation of the optimal parameter set is computed based on performance bounds. Two application examples show the benefits of the proposed technique.     

Bio-surfaces and geometric references for mass customization in bio-interface design

Mass customization of products that interface with the human body poses unique problems due to the complexities of bio-interface design, the lack of biomechanical techniques in traditional mechanical design, and the absence of specific parametric strategies. Current biomechanical design often follows craftsman-like design processes using less than state-of-the-art tools and techniques. Thus, products that interface with the human body are not readily parameterized or automated. This paper presents a strategy for implementing mass customization in the design of mechanical devices that interface with the human body. This strategy is based on three methods that include: a method for capturing and representing the human body so that the model can be used with state-of-the-art tools and solid modeling techniques, a design methodology based on feature structure planning allowing the design process to be reused and automated, and a strategy for identifying parametric variables tied to the human body. A case study is presented to illustrate the proposed process.     

A simple and effective inverse projection scheme for void distribution control in topology optimization

The ability to control both the minimum size of holes and the minimum size of structural members are essential requirements in the topology optimization design process for manufacturing. This paper addresses both requirements by means of a unified approach involving mesh-independent projection techniques. An inverse projection is developed to control the minimum hole size while a standard direct projection scheme is used to control the minimum length of structural members. In addition, a heuristic scheme combining both contrasting requirements simultaneously is discussed. Two topology optimization implementations are contributed: one in which the projection (either inverse or direct) is used at each iteration; and the other in which a two-phase scheme is explored. In the first phase, the compliance minimization is carried out without any projection until convergence. In the second phase, the chosen projection scheme is applied iteratively until a solution is obtained while satisfying either the minimum member size or minimum hole size. Examples demonstrate the various features of the projection-based techniques presented.     

ASOS操作系统的QoS资源管理结构与实现

讨论了面向应用特制的嵌入式操作系统的一般功能和特征,给出了ASOS资源管理模型结构,并提出了以推理规则为基础的软件实现框架。最后以嵌入式视频服务器为应用背景,试验结果验证了该模型和算法的有效性。     

Evolutionary optimization of model specification searches between project management knowledge and construction engineering performance

Many studies have attempted to specify alternative model configurations as fitting empirical data with the aid of structural equation modeling (SEM) method. However, significant path searching between constructs has increased in difficulty and complexity. One way to enhance modeling efficiency is evolutionary optimization by genetic algorithm (GA). This study applies the project management (PM) knowledge possessed by construction personnel and uses techniques, tools, and skills (TTS) to explore the causal relationship between TTS usage and construction engineering project performance (PP). A questionnaire survey is used to empirically measure the effectiveness of PM TTS on PP. The research framework is first defined by hypotheses supported by the literature. The GA is then applied to the model fitting process to optimize the structural paths. Analytical results show that evolutionary optimization for singular and multiple goodness of fit effectively searches the SEM specifications. By using GA in SEM procedure, researchers can perform automated specification searches to find the best empirical model fit to the data.     

Structural shape optimization—A survey

This paper is a survey of structural shape optimization with an emphasis on techniques dealing with shape optimization of the boundaries of two- and three-dimensional bodies. Attention is focused on the special problems of structural shape optimization which are due to a finite element model which must change during the optimization process. These problems include the requirement for sophisticated automated mesh generation techniques and careful choice of design variables. They also include special problems in obtaining sufficiently accurate sensitivity derivatives.     

GCC代码优化技术的研究

GCC是基于Linux下的开放源码的优化编译系统，可以接收多种高级源语言，广泛支持多平台操作系统。其代码优化机制，不仅能兼顾时间、空间效率，生成高质量的目标代码，而且具有很强的可移植性与可扩充性，是编译器优化研究的目标。通过对GCC的整体结构、优化策略、优化方法与关键技术、中间语言等进行详细的剖析，抽取出完整的GCC优化体系结构。文中集中探讨了GCC的优化策略和实现技术，首先从GCC优化体系的总体规划入手，着重分析了GCC的优化组织策略，设计、引入中间代码RTL的技巧和内涵，进一步研究了GCC所涉及的控制流分析技术、数据流分析技术的实现机制。     

NURBS modeling and structural shape optimization of cardiovascular stents

Cardiovascular stents have been used since the 1990s to treat atherosclerosis, one of leading causes of death in the western world, and structural optimization has led to significant improvements in stent performance. Much of the potential variation in stent geometry, however, has remained unconsidered. This paper presents a non-uniform rational basis spline (NURBS) parameterization of a stent, the inclusion of structural fatigue resistance as a design consideration, and the results of a design optimization based on response surface techniques. Results show the feasibility and merits of the NURBS approach, which models a much broader range of shapes than was previously possible. Multi-objective optimization produces a range of geometrically diverse Pareto-optimal designs; these can be used to develop future clinical design guides, accounting for the variation observed across patients. We conclude by motivating future work with increasingly complex physical modeling and optimization capabilities.     

基层医院信息系统的数据库设计及优化

依据数据库建模及设计规范化的原则,结合医院信息数据库的设计要求,对医院信息系统数据库的总体结构进行了设计说明。给出了数据存储模型的整体规划、系统数据库的总体设计和实现。选择了最佳的数据库建模技术,对数据模型及实体进行描述。提出了医院信息系统数据库的性能优化策略。为构造基于多层体系结构、高运行效率的医院信息系统奠定基础。