多层雷达吸波材料涂层反射系数的研究

不同极化下反射系数的计算是雷达散射截面(RCS)预估中的主要问题之一,对于涂敷雷达吸波材料(RAM)涂层的目标,进行预估首先要建立反射系数与众多相关参数之间的关系式.从麦克斯韦方程和边界条件出发,导出了电磁波频率、入射角度及多层RAM涂层各层电磁参数与反射系数之间的关系式;实现了对任意层数RAM涂层反射系数的计算.最后,以两层和三层RAM涂层为例,通过仿真实验分析了电磁波的入射角、极化状态等对反射系数的影响.     

NSGA-Ⅱ应用于圆筒型永磁直线电机的多目标优化

针对圆筒型永磁直线电机提出了使用二代非支配排序遗传算法(NSGA-Ⅱ)优化其功率和效率。首先根据电机的二维有限元模型，计算电流、电压等参数；其次利用敏感参数法建立以气隙长度等为变量的优化模型，并计算电机的电磁参数；再对电磁参数数据训练，以NSGA-Ⅱ为优化算法的多目标优化模型，优化电机的功率和效率；最后根据优化结果加工出了MTS100kN万能试验机。样机实验结果验证了所提出的多目标优化设计方法和性能分析的正确性。     

基于Ordered-RAMP模型的热固耦合结构多材料拓扑优化方法

针对传统单材料热固耦合拓扑优化设计难以实现结构材料与性能综合最优的问题,提出一种基于变密度理论有序材料属性有理近似模型的多材料拓扑优化方法.该方法通过搭建比例系数与平移系数,将多种材料属性采用[0,1]连续分布的单设计变量进行描述,并研究和比较与有序固体各向同行惩罚微结构模型的优缺点;其次借助归一化加权方法定义以结构柔度最小化和散热弱度最小化为目标函数的数学模型.结合设计变量敏度分析,详细推导多材料、多目标条件下热固耦合结构拓扑优化的迭代公式.通过数值算例分析对比了不同权系数以及不同材料属性组合对优化结果的影响;结果表明,所提出的优化方法在热固耦合结构多材料多目标拓扑优化设计中具有可行性和有效性.     

最小偏差法在机械多目标优化设计中的应用

提出了处理多目标问题的最小偏差法,并将其应用于机械多目标优化设计.以流体动压滑动轴承多目标优化设计为例,建立了以摩擦系数最小、发热量最小和承载能力最大为目标函数的多目标优化设计数学模型,根据最小偏差法原理构造统一目标函数,利用改进遗传算法对该问题进行了优化设计.算例整个求解过程和结果表明,该方法既可以避免人为因素的影响...     

多工况条件下滚针轴承的改进粒子群优化方法

为了获得在复杂工况下滚针轴承的最优尺寸参数,提出了一种利用改进粒子群算法优化滚针轴承尺寸参数的方法.在考虑了污染、载荷、润滑、转速、游隙、倾斜、滚针修形等工况的前提下,建立了以滚针轴承额定修正寿命为目标函数的有约束优化模型;采用随机权重策略改进惯性权重值,以反余弦策略来调整学习因子大小,用保证粒子合法性的方法求解约束的问题,从而实现了多工况下滚针轴承非线性优化设计;最后通过对优化结果进行对比分析,验证了该方法是一种有效的轴承设计方法.     

PSO随机数参数设置的多目标定位方法研究

为了解决林业部门对森林防火安全监测系统中对多个声音目标的跟踪及定位问题,根据声音能量随距离衰减模型,提出了采用粒子群算法(PSO)的多目标定位与优化方法.通过利用极大似然法对声音强度模型的定位算法,采用惯性权重的粒子群算法,着重讨论了随机参数不同的设置方法对定位追踪精度性能的影响.通过仿真实验证明,粒子群算法中设置随机数参数为常数,可以有效提高目标定位精度,并减小搜索复杂度.     

遗传/粒子群混合算法在飞剪机结构优化中的应用

飞剪机结构参数设计需满足若干技术性能要求才能保证剪切质量。飞剪机结构参数优化设计问题要满足多个非线性约束要求,同时需优化多个目标函数,提出遗传算法/粒子群混合算法用于曲柄连杆式飞剪机结构参数优化设计,结合各自算法的优势,在算法运行初期利用遗传算法的全局搜索能力进行优化搜索,在算法运行后期利用粒子群较强的局部搜索能力进行搜索,综合考虑多个目标函数和约束条件,通过实例计算表明,该混合方法可以稳定、有效的获取到满意的优化设计结果。     

监督学习模型指导的函数级编译优化参数选择方法研究

基于机器学习的迭代编译方法可以在对新程序进行迭代编译时,有效预测新程序的最佳优化参数组合。现有方法在模型训练过程中存在优化参数组合搜索效率较低、程序特征表示不恰当、预测精度不高的问题。因此,基于机器学习的迭代编译方法是当前迭代编译领域内的一个研究热点,其研究挑战在于学习算法选择、优化参数搜索以及程序特征表示等问题。基于监督学习技术,提出了一种程序优化参数预测方法。该方法首先通过约束多目标粒子群算法对优化参数空间进行搜索,找到样本函数的最佳优化参数;然后,通过动静结合的程序特征表示技术,对函数特征进行抽取;最后,通过由函数特征和优化参数形成的样本构建监督学习模型,对新程序的优化参数进行预测。分别采用k近邻法和softmax回归建立统计模型,实验结果表明,新方法在NPB测试集和大型科学计算程序上实现了较好的预测性能。     

基于遗传粒子群的永磁低速直线电机优化研究

本文以改善电机效率和降低永磁低速直线电机制造成本为优化设计目标,把单台电机造价和电机电磁推力的比值作为目标函数,由于目标函数的优化变量多,参数间相互约束,目标函数复杂等特点,因此本文采用遗传粒子群算法对永磁低速直线电机进行优化设计,通过对两种设计仿真结果对比证明了该算法在提高电机电磁性能,降低制造成本方面有明显的优越性。     

飞剪机结构参数优化设计

飞剪机是连续式轧钢机组中重要而复杂的辅助设备，其结构参数设计的好坏直接影响剪切质量。飞剪机结构参数优化设计问题属非线性的多目标优化问题，以模拟退火算法为代表的计算智能方法在求解此类优化问题中体现了一定了优势，本文利用改进的模拟退火算法（Improved Simulated Annealing，ISA）对曲柄连杆式飞剪机结构参数进行优化设计，将整个优化过程分成若干个阶段，根据各个子目标函数优化的状态，采用不同的退火系数和归一化系数，综合考虑多个目标函数和约束条件，通过实例计算表明，该方法可以稳定、有效的获取到满意的优化设计结果。     

A fortran program for the design of laminates with required mechanical properties

A FORTRAN 77 program for designing laminates with required mechanical properties is presented. This user-friendly program is developed for interactive use by users with either micro or mainframe computers to provide maximum flexibility and reduce the amount of inputting. The inputs required to the program are layer orthotropic unidirectional (UD) material properties and thickness and the desired laminate mechanical properties. The output is the optimum lamination that will provide these properties. This optimum is obtained by minimizing the difference between the calculated properties of trial laminates and the desired properties. The program allows such designed laminates to be unsymmetric in either geometry or material about the middle surface of a plate and consist of a specified number of different fibre-reinforced orthotropic layers. This program can either be used on its own for the purpose of designing laminated plates or be considered as a package-subroutine within a complex structural design package. As a demonstration of the use of the program, the design of a symmetric laminate is conducted to show how an optimal lay-up sequence can provide the required laminate mechanical properties determined by the design. A full listing of the program is given as an Appendix.     

带矢量ABC底面的共形完全匹配层

共形完全匹配层是一种有耗各向异性媒质组成的凸且光滑的壳体,其底面一般是PEC面或PMC面,但是PEC面或PMC面会对原散射场产生反射;为了减少底面反射,将CPML原有的PEC（或PMC）底面改为矢量ABC吸收边界,并给出了带矢量ABC底面的CPML泛函公式。通过数值算例证明,这种带矢量ABC底面的CPML边界不仅减少了底面反射,而且吸收效果好,计算精度高。     

Optimal packing of transformer coil via dynamic programming

One of the transformer major design elements is its core design. The good performance of the transformer requires its coil core to be laminated and composed of different - widths stepped layers of specific steel packed together. For optimum design, the cross sectional shape of the core must be as circular as possible. So, an optimal packing can be attained by maximizing the steel core coverage. The number of different widths of steel plates n is selected to compose the packed core for a coil of diameter d. Then, an optimum sequence of decisions, for the n widths as well as the number of thin plates of each, is required. Dynamic programming (dp) is concerned with this optimum sequential decisions. An adequate forward recursive equation is formulated , because there isn't a standard dp model for all sequential decision making problems. To implement the recursive computations, a FORTRAN program is developed. Assuming that d is given the values 150, 200, 250, 300, 400 and 500 mm. while giving n the values from 2 to 15, the program is run at different combinations of n and d. It is found that maximum core coverage is sensitive to changing of n but it is slightly affected by changing of d.     

轨道车辆新型组合结构吸能装置耐碰撞性分析

为保证列车碰撞时车体次要部位或附加装置尽可能多地吸收撞击能量,减少财产损失和人员伤亡,提出组合结构吸能装置的设计思想.根据耐撞性车体吸能装置设计原理,设计出不同截面形状管的组合结构吸能装置.利用ANSYS/LS-DYNA对其分别进行动态仿真,研究其吸能特性,并取其最优方案与试验结果进行对比,从而验证仿真模型的正确性.通过对原始设计方案外箱板的截面形状和吸能管的端部结构加以改进,设计出两种新型的组合结构吸能装置.仿真分析结果表明,结构的截面形状对整个装置的吸能特性有较大影响,改变结构的截面形状可以有效调节碰撞界面力峰值和均值载荷,改进后的吸能装置耐撞性综合指标更优。     

Optimum design of electromagnetic shielding rooms with minimum usage of absorbing materials

In this article, a novel method has been proposed to optimize the electromagnetic shielding rooms. This method is based on using minimum electromagnetic absorbing materials on the inner surface of the rooms. The positions of the absorbing materials are found optimally to produce a “best” performance for the shielding rooms. The ray‐tracing method is used to predict the shielding effectiveness (SE) of the electromagnetic shielding rooms with apertures. The performance of the proposed method is verified by a comprehensive example. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

Interactive microcomputer-aided design of circular suspension cable roofs

This paper presents interactive computer-aided design of circular suspension cable roofs. A microcomputer program developed in Advanced BASIC and according to the principles of structured programming is presented. The program can display/plot the plan of cable roof, the elevation of the structure including the loading on the cables and the cross-section of the reinforced concrete compression ring. The interactive program helps the user to explore many design alternatives rapidly and arrive at a practically optimum design.     

Topology optimization for minimum mass design considering local failure constraints and contact boundary conditions

This paper studies the optimum design of a 1×2 mechanical optical switch. First, a novel switch configuration is designed with an included antithermal mechanism. Then, parametric programs are developed to automatically generate the solid model and to analyze thermal behavior of the switch. From the analysis of the initial design, it revealed that the amount of transverse offset between fiber tips failed in satisfying the Bellcore specifications. Finally, an integrated program combining CAD software, genetic algorithms, and finite element software was developed for optimum design of optical switches. With the capability of continuously changing critical design parameters of the switch in the integrated design program, the final optimum design satisfying the design constraints and specifications can be found.     

TEFOOL/2: a program for theoretical drug design on microcomputers

TEFOOL/2, a program written in BASIC, is presented in this paper. The purpose of TEFOOL/2 is to provide people interested in drug design with an easy-to-handle program where some of the most important techniques in QSAR are included. The program permits the selection of the training series, performs regression calculations and searches for optimum substituents. The latter is achieved by using either a Hansch's strategy or geometrical procedures. The program is interactive and can be implemented on an IBM-PC or compatible microcomputer. Although TEFOOL/2 has been developed for its application in drug design studies, its great flexibility makes it suitable for application to any experimental design or optimization process.     

FDTD方法吸收边界条件的研究及应用

用时域有限差分法(FDTD)求解电磁散射问题中,吸收边界条件的设置起着关键性作用.通过时间和空间上的递推算法对时域有限差分法中的两种吸收边界条件:Mur吸收边界条件和完全匹配层(PML)的吸收效果进行了比较和分析.同时,引入参数对PML的差分方程进行了优化,避免了将电磁场分裂为两个分量进行计算,进而降低了计算内存开销.实验结果证明PML具有更优越的吸收性能.最后,在FDTD算法中应用PML吸收层对一圆柱形导体的雷达散射截面积(RCS)进行数值仿真,验证了FDTD算法在计算雷达散射截面积(RCS)上的有效性.     

Reinforced concrete interaction diagrams

A time sharing program for reinforced concrete beam-column interaction diagrams is presented. The program is limited to doubly symmetric rectangular sections, but can handle multiple layers of reinforcing. The program is founded on the fact that for each assumed neutral axis location, one interaction diagram point is defined. The basic algorithm is easy to understand, and output is organized so that a novice could verify a few diagram points by simple hand calculations. Thus, the program aids in describing theory as well as serving as a tool for use in student design projects.