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The design approximation problem is a well known problem in stock cutting, where, in order to facilitate the optimization techniques used in the cutting process, it is required to approximate complex designs by simpler ones. Although there are algorithms available to solve this problem, they all suffer from an undesirable feature that they only produce one optimal solution to the problem, and do not identify the complete set of all optimal solutions. The focus of this paper is to study this hitherto unexplored aspect of the problem: specifically, the case is considered in which both the design and the parent material are convex shapes, and some essential properties of all optimal solutions to the design approximation problem are ascertained. These properties are then used to devise two efficient schemes to identify the set of all optimal solutions to the problem. Finally, the recovery of a desired optimal approximation from the identified sets of optimal solutions, is discussed. 相似文献
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H. CHICKERMANE H. C. GEA 《International journal for numerical methods in engineering》1996,39(5):829-846
A new method for solving structural optimization problems using a local function approximation algorithm is proposed. This new algorithm, called the Generalized Convex Approximation (GCA), uses the design sensitivity information from the current and previous design points to generate a sequence of convex, separable subproblems. The paper contains the derivation of the parameters associated with the approximation and the formulation of the approximated problem. Numerical results from standard test problems solved using this method are presented. It is observed that this algorithm generates local approximations which lead to faster convergence for structural optimization problems. 相似文献
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L. WANG R. V. GRANDHI R. A. CANFIELD 《International journal for numerical methods in engineering》1996,39(5):787-803
An approximation based on multiple function and gradient information is developed using Hermite interpolation concepts. The goal is to build a high-quality approximation for complex and multidisciplinary design optimization problems employing analysis such as aeroservoelasticity, structural control, probability, etc. The proposed multidimensional approximation utilizes exact analyses data generated during the course of iterative optimization. The approximation possesses the property of reproducing the function and gradient information of known data points. The accuracy of the new approach is compared with linear, reciprocal and other standard approximations. Because the proposed algorithm uses more data points, its efficiency has to be compared in the context of iterative optimization. 相似文献
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A HEURISTIC FOR THE DYNAMIC FACILITY LAYOUT PROBLEM 总被引:5,自引:0,他引:5
Timothy L. Urban 《IIE Transactions》1993,25(4):57-63
This paper presents a heuristic for the dynamic facility layout problem. All existing methods for solving this problem require the use of a dynamic programming model, the optimal solution of the quadratic assignment problem, or both. The proposed heuristic is based on the steepest-descent pairwise-interchange procedure to develop layouts utilizing material handling cost data from varying lengths of forecast windows as well as the explicit consideration of the corresponding rearrangement costs. Numeric results indicate that it typically performs as well as any existing methodology and only slightly worse than optimal. 相似文献
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基于球面三角网格逼近的等距曲面逼近算法 总被引:2,自引:0,他引:2
给出了一种基于球面三角网格逼近的等距曲面逼近新算法。利用三角网格逼近基球面,然后计算此三角网格按中心沿在曲面扫凉而成空间区域的边界作为等距曲面的逼近。该算法计算简单,方便地解决了整体误差问题,而且所得到的逼近曲面是与原曲面同次数的NURBS曲面。 相似文献
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通过复变函数论的方法,对Ⅰ型裂纹面中心区受均布载荷作用下的非对称动态扩展问题进行研究。采用自相似函数的方法可以获得应力、位移和应力强度因子的解析解。应用该法可以很容易地将所讨论的问题转化为Riemann—Hilbert问题,然后应用Muskhelishvili方法就可以相当简单地得到问题的闭合解。利用这些解并采用叠加原理,就可以很容易地求得任意复杂问题的解。 相似文献
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通过复变函数论的方法,对Ⅰ型裂纹面中心区受均布载荷作用下的非对称动态扩展问题进行研究.采用自相似函数的方法可以获得应力、位移和应力强度因子的解析解.应用该法可以很容易地将所讨论的问题转化为Riemann-Hilbert问题, 然后应用Muskhelishvili方法就可以相当简单地得到问题的闭合解.利用这些解并采用叠加原理,就可以很容易地求得任意复杂问题的解. 相似文献
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MARKOV APPROXIMATION TO FATIGUE CRACK SIZE DISTRIBUTION 总被引:1,自引:0,他引:1
G. P. Solomos A. C. Lucia 《Fatigue & Fracture of Engineering Materials & Structures》1990,13(5):457-471
The distribution of the crack size during the fatigue crack propagation phenomenon is investigated. A Markovian modeling of the crack is introduced through the fatigue crack growth law, and the associated Fokker-Planck equation is written while special care is devoted to specifying its boundary conditions. This equation is solved by the method of separation of variables and the sought distribution function is obtained in the form of a convergent infinite series. An illustrative example, demonstrating the applicability of the approach, shows satisfactory agreement between theoretical results and experimental data. 相似文献
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基于广义遗传算法的结构动力响应优化 总被引:5,自引:1,他引:4
为提高广义遗传算法的收敛效率,提出了防止遗传算法发生早熟收敛的异种机制,给出了一个判断种群近亲繁殖程度的判别式和两种选择异种的方法,并结合种群隔离机制、算术杂交、自适应随机变异等数值方法设计了新的广义遗传算法。将该算法应用于结构动力响应的支撑位置优化问题。数值算例表明:异种机制能够明显提高遗传算法的收敛效率,并有效防止早熟收敛;带有异种机制的新广义遗传算法能够解决具有抗弯刚度的结构动力响应支撑位置优化问题,对于求解复杂的结构动力响应支撑位置优化具有较强的适用性。 相似文献
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为了避免积分变换方法在求解Lord-Shulman(L-S)型广义热弹性耦合问题时由于数值反变换所引起的计算精度降低的问题,该文应用直接有限元方法,求解了基于L-S型广义热弹性理论的窄条薄板受热冲击作用的动态响应问题,结果表明,该方法对求解L-S型广义热弹性耦合的一维问题具有很高的精度。该文给出了L-S型广义热弹性理论下的热弹耦合的控制方程,建立了L-S型的广义热弹性问题的虚位移原理,推导得到了相应的有限元方程。计算得到了窄条薄板中无量纲温度、无量纲位移及无量纲应力的分布规律,从温度分布图上可以清晰地观察到热波波前的特有属性,即热波波前处存在明显的温度梯度的突变。 相似文献
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Branched trajectory optimization problems can exhibit peculiar properties In the normal formulation of such problems, it is generally assumed that one should always include all trajectory segments after the branch point in the solution. In this paper, it is shown that for a certain important class of branched optimization problems, the inclusion of all trajectory segments after the branch can sometimes lead to non-optimal results 相似文献
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用Kissinger方法测定非晶材料晶化激活能时应注意的问题 总被引:1,自引:0,他引:1
应用Kissinger方法测定非晶材料晶化激活能时应确保所选温度对应的晶化分数相差不大,否则将会引入较大误差。以NiTi非晶薄膜为例对此作了讨论。 相似文献
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George Tagaras 《IIE Transactions》1994,26(3):48-56
Recent technological advances have rendered dynamic process control a viable alternative. A dynamic programming approach is proposed for the modeling and cost minimization of statistical process control activities. The decision parameters of the control chart are allowed to change dynamically as new information about the process becomes available. This general approach has been known as a theoretical possibility for many years, but its practical performance is explicitly investigated in this paper. It is shown with numerical examples that the dynamic programming solution can be much more economical than the conventional static solution with fixed control chart parameters. The substantial potential cost savings and the feasibility of a dynamic control procedure suggest that dynamic process control should replace standard statistical or economic design of control charts as the preferred method in automated production processes. 相似文献
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基于Biot理论和u-p列式,推导了两相介质动力问题的控制方程。固相的位移和液相孔隙压力是两个基本的未知量。采用更新的Lagrangian方法和Jaumann应力对这一耦合问题进行了大变形分析。用建议的方法,对一饱和土柱在静力和动力荷载作用下的反应进行了数值模拟,并对大、小变形理论下的计算结果进行了对比。 相似文献