重大事故救灾路线双目标优化模型及算法

运用运筹学的理论和方法,建立一种重大事故救灾路线双目标优化数学模型.基于启发式算法思想,提出适合该模型且收敛速度较快的优化算法.该算法通过构造辅助函数调用Dijkstra算法,在最优解的近似区间内多次迭代逐渐逼近最优解,实现了双权重网络图最短路的求解,是一种近似的、快速的算法.基于所构造辅助函数的性质,给出实现该算法的具体步骤.对误差进行线性估计,分析了该算法收敛速度的影响因素,并讨论了算法的时间复杂度及优势.最后在案例分析中编译并运行该算法,证实其模拟结果与理论分析结论相吻合.      

单端行波测距新算法的研究

传统的单端测距算法需要考虑时间和行波波速两个因素,本文在原有的单端测距算法的基础上消去了行波波速参数,提出了一种不受行波波速影响的的单端测距新算法,与之前的单端行波测距算法相比该算法不受行波波速的影响的优点,而且计算方便、精确.经过ATP对该算法进行仿真验证,仿真结果证明了该算法的实用性.用该算法在超高压长距离输电线路测距误差可以保持在400m以内,更好的满足了电网的可靠运行要求.     

基于遗传算法的电液位置伺服系统模糊控制

将遗传算法应用于模糊控制系统中,该算法利用遗传算法强大的空间搜索能力,对模糊隶属函数进行优化.并将该算法应用到电液位置伺服系统中,仿真结果表明了该算法的有效性.     

基于Tikhonov和变差正则化的磁感应断层成像重建算法

为了解决磁感应断层成像(MIT)逆问题的病态性和改善重建图像的质量,提出一种新的组合算法.该组合算法首先利用Tikhonov正则化算法对解的适定性产生初步的成像区域,之后再利用变差正则化算法对解的保边缘性和锐化作用进行图像重建.该组合算法与Tikhonov正则化算法及变差正则化算法相比,不仅有效地克服了磁感应断层成像(MIT)重建图像数值解的不稳定性,还加快了重建图像的收敛速度,提高了目标导体的分辨能力,有效改善了重构图像的质量.仿真结果表明了该组合算法的有效性.     

基于改进差分进化算法的无人机在线低空突防航迹规划

为了解决无人机在部分未知敌对环境中的低空突防航迹规划问题,提出了一种改进的差分进化算法.该算法的进化模型采用冯.诺伊曼拓扑结构,并对其进行拓展,使种群在进化初期保持多样性,避免进化早期陷入局部最优,而进化后期加快收敛速度.该算法改进了差分进化算子中的变异操作,从而加快算法的收敛速度,快速找到多目标优化问题的最优解;同时,采用将绝对笛卡儿坐标和相对极坐标相结合的编码方式以提高搜索效率.将该算法用于无人机在线航迹规划仿真实验,并和未改进的算法结果作比较,验证了该算法的有效性.      

基于遗传与SQP算法的轧机负荷分配优化研究

针对热连轧精轧机组负荷分配优化问题的特点,将遗传算法与序列二次规划法相结合,构成用于优化该问题的混合遗传算法.该算法通过改进遗传算子与序列二次规划算法结合,提高了局部搜索的速度和求解质量.根据模型仿真验证,该算法提高了收敛速度和求解精度,保证了全局收敛性,在热连轧精轧机组负荷分配优化中作用是有效的.     

一种基于神经网络的快速预测控制算法

由于普通广义预测控制在快速性方面存在局限性,本文提出一种基于BP神经网络的(GPC)算法,该算法用训练好的BP去解决GPC算法中的丢潘图方程求解、大矩阵的求解、求逆等复杂运算.本文将该法用于冷连轧机快速系统中进行仿真,结果表明,该算法比普通的GPC算法速度提高了很多,具有很好的控制性能.     

WPANT:应用于移动对等网络的轻量级层次蚁群路由算法

针对移动对等网络中存在的节点移动、拓扑多变、资源受限和可扩展性差等问题,提出了一种基于轻量级层次结构的蚁群路由算法.该算法通过选取活动路由上的节点将网络划分成轻量级的层次结构,在此结构上运行蚁群路由算法.轻量级的层次结构提高了蚁群算法中信息素更新机制的效率,同时,蚁群路由算法的自组织和流量均衡等特性增强了轻量级层次结构的健壮性.模拟仿真表明了该算法的有效性.     

一种基于人工鱼群算法的Choquet积分回归推广模型

设计了一种基于区间值带符号模糊测度的Choquet积分的非线性回归模型.该模型采用线性规划的方法计算关于区间值带符号模糊测度的Choquet积分值,并通过一种进化算法--人工鱼群算法(AFSA)确定了模型的参数.该算法具有鲁棒性、分组计算、易于结合特定问题等诸多优点.数值试验结果证实了该算法确定模型参数的可行性与有效性.     

简化二次型规划算法在新钢中板厂的应用

针对中宽厚板轧制道次的负荷分配问题,开发了简化二次型规划算法,解决了负荷分配算法稳定性问题,该算法运算快捷,能适应钢种、规格变化频繁的复杂工况。该算法已在新余钢铁集团有限公司中板厂稳定应用,尺寸命中率提高了近3个百分点,效果显著。     

Evolutionary Design of Steel Structures in Tall Buildings

This paper presents results of a study on evolutionary computation in the design of the steel structural systems of tall buildings. It describes results of extensive research on both short-term (up to a few hundred generations) and long-term evolutionary design processes (at least a few thousand generations). The experiments were conducted with Inventor 2001, an evolutionary design support tool developed at George Mason University, for generating conceptual and detailed designs of steel structural systems in tall buildings. First, the paper discusses conceptual design of steel structural systems in tall buildings and briefly introduces Inventor 2001 as well as its design representation and evolutionary computation characteristics. Next, it provides the results obtained from systematic parametric design experiments conducted with Inventor 2001. The objective of these experiments was to qualitatively and quantitatively investigate evolution of steel structural systems of tall buildings during a multistage evolutionary design process as well as the influence of various evolutionary computation parameters. Mutation and crossover rates, population size, the length of the evolutionary processes, and the importance of a symmetry requirement have been analyzed and results produced. Emergence of structural shaping patterns has been also studied and several interesting patterns found in the evolutionary design process. Finally, research conclusions are presented as well as recommendations for further research and development of evolutionary design support tools.     

GCr15棒线材粗轧过程的隐式静力和隐式动力算法有限元模拟

借助大型商用有限元软件MSC.Marc,采用隐式静力和隐式动力有限元算法,对GCr15棒线材的粗轧过程进行了热力耦合有限元模拟,模拟采用生产实际中的轧制参数.2种算法的出辊速度、温度场和平均轧制力模拟结果基本一致,温度场模拟值与实测值的比较证明了这2种算法的可靠性.实际模拟时,隐式动力学算法计算时间少于隐式静力学算法,效率较高.     

辐射离散坐标法在柱形炉膛中的辐射传热计算

利用离散坐标法对圆柱形炉膛辐射传热进行了计算,结果与计算精确的区域法的计算结果符合较好;同时又利用离散坐标法和热流法对旋流燃烧室温度场进行比较计算,结果表明:离散坐标法计算结果与文献中实验结果符合较好;离散坐标法具有较好计算精度,可应用旋流燃烧辐射计算中.     

Simulation of Stochastic Wind Velocity Field on Long-Span Bridges

An improved algorithm is introduced in this paper for digital simulation of the stochastic wind velocity field on long-span bridges, when the cross-spectral density matrix of the field is given. The target wind velocity field is assumed to be a one-dimensional, multivariate, homogeneous stochastic process. The basic method of simulation used is the spectral representation method. It is improved by explicitly expressing Cholesky's decomposition of the cross-spectral density matrix in the form of algebraic formulas, then cutting off as many as possible of the cosine terms, so long as the accuracy of results is not affected. The fast Fourier transform technique is used to enhance the efficiency of computation. A numerical example of simulation for buffeting analysis is included in this paper to illustrate the improved method introduced. It is demonstrated that deviations between the simulated correlation functions and the target are sufficiently small and that the simulated power spectra are close to the target.     

半无头轧制超长铸坯均热过程中温度场的数值模拟

利用ABAQUS有限元软件对半无头轧制超长铸坯均热过程中的温度场变化进行了数值模拟。在建模过程中,利用ABAQUS的用户子程序USDFLD和FILM,采用改变材料导热系数和与环境的综合换热系数的方法,模拟了铸坯进入均热炉的过程,使模型的计算量大幅减小,计算结果与现场实测数据吻合较好。计算了拉坯速度分别为4、5和6 m/...     

Inferring pattern and process: maximum-likelihood implementation of a nonhomogeneous model of DNA sequence evolution for phylogenetic analysis

A nonhomogeneous, nonstationary stochastic model of DNA sequence evolution allowing varying equilibrium G + C contents among lineages is devised in order to deal with sequences of unequal base compositions. A maximum-likelihood implementation of this model for phylogenetic analyses allows handling of a reasonable number of sequences. The relevance of the model and the accuracy of parameter estimates are theoretically and empirically assessed, using real or simulated data sets. Overall, a significant amount of information about past evolutionary modes can be extracted from DNA sequences, suggesting that process (rates of distinct kinds of nucleotide substitutions) and pattern (the evolutionary tree) can be simultaneously inferred. G + C contents at ancestral nodes are quite accurately estimated. The new method appears to be useful for phylogenetic reconstruction when base composition varies among compared sequences. It may also be suitable for molecular evolution studies.     

Evolutionary Programming for Inverse Problems in Civil Engineering

Two main contributions to evolutionary computation and their applications are reported in this paper: (1) a new evolutionary programming (EP) algorithm is proposed with several improved techniques added to the conventional EP algorithm; and (2) the improved EP algorithm is incorporated with the finite-element method (FEM) to form an integrated algorithm, called FEMEP, for solving the inverse problems in civil and structural engineering. In the improved EP algorithm, two types of mutation—namely, random and uniform—are proposed to increase the efficiency and to retain the versatility of the conventional EP algorithm. Simulated annealing is adopted to prevent the chromosomes in the early generations from stagnating in a local optima. The algorithm is examined with two typical numerical examples. Results show that the improved EP algorithm is efficient and versatile. It is able to find better solutions than genetic algorithms and other evolution programs. The FEMEP algorithm is then applied to the inverse problems, with two parameter identification problems as illustrations. Although simple, they demonstrated the potency of the proposed integrated algorithm to solve inverse problems in civil and structural engineering.     

Detection of Stiffness Reductions in Concrete Decks with Arbitrary Damage Shapes Using Incomplete Dynamic Measurements

A new refined nondestructive evaluation technique for concrete decks with arbitrary damage shapes is presented, and its utility in detecting the location and extent of the damage using only a single dynamic measurement signal is demonstrated. Six unknown parameters are considered to determine the damage distribution, which is a modified form of the bivariate Gaussian distribution function. Using a combination of the combined finite-element method (FEM) and the advanced uniform microgenetic algorithm, the various influences of different measurement locations on the damage detection are studied. In addition, the effect of noise is simulated in order to study the influence of the measurement errors and the uncertainty of the method. The sample studies demonstrate the excellence of the proposed method from the standpoints of its computation efficiency as well as its ability to investigate the complex distribution of an arbitrary stiffness reduction.     

Time Domain Analysis on the Dynamic Response of a Flexible Floating Structure to Waves

A time-domain numerical method is developed to analyze the hydroelastic responses of flexible floating structures to waves; in which, the boundary element method is applied to evaluate the fluid motion and the finite-element method to analyze the elastic deformation of structure. The dynamic wave-structure interaction is simulated by prescribing the conditions on a wave generation boundary for each time step and by satisfying the continuity of the pressure and displacement on the fluid-structure interface. A time-domain solution is obtained in a predictor-corrector scheme and through a time-stepping computation. The effect of space and time discretizations on the convergence and stability of solution for regular, random and solitary waves is discussed by comparing among numerical solutions. The validity of the present method is verified by comparing it with the experimental results for the three kinds of waves mentioned. Further, the fission of a solitary wave under a flexible floating structure is observed both in numerical analysis and experiments.     

Study of transient flow and particle transport in continuous steel caster molds: Part II. Particle transport

Particle motion and capture in continuous steel casters were simulated using a Lagrangian trajectory-tracking approach, based on time-dependent flow fields obtained from large-eddy simulations (Part I of this article). A computation was first conducted on a water model of a full-scale standard slab caster, where measurements were available. It simulated the transport of 15,000 plastic particles and their removal by a screen positioned near the mold top surface. The computation shows the screenremoval fractions to be 27±5 pct for 0 to 10 seconds and 26±2 pct for 10 to 100 seconds, which agrees with previous measurements. The flow exiting the nozzle was relatively uniform, and turbulent motion in the domain was very chaotic, so particle removal did not depend on the initial location of particles introduced in the nozzle port. A computation of motion and capture of 40,000 small inclusions (10 and 40 μm) was then performed in an actual thin-slab steel caster. The particles moved through the mold region with an asymmetrical distribution, which was caused by transients in fluid turbulence in the lower recirculation region, rather than by inlet variations at the nozzle port. Only about 8 pct of these small particles were removed to the top surface. This removal fraction was independent of both particle size and density, likely because all the simulated particles were too small to deviate significantly from the surrounding fluid flow. Finally, the computational results were further processed to predict the ultimate distribution of impurity particles in the solid thin slab after a short burst of inclusions entered the mold. They were reprocessed to reveal the distribution of total oxygen content for a steady inclusion supply from the nozzle. The results of this work confirm the important role of flow transients in the transport and capture of particles during continuous casting and can serve as a benchmark for future simplified models.