一种新的求解非线性方程组的混合量子遗传算法

针对传统非线性方程组的解法对初始值敏感、收敛性差、精度低等问题,提出一种求解非线性方程组的混合量子遗传算法。该算法综合考虑了量子遗传算法和拟牛顿法的优点,充分发挥了前者的群体搜索和全局收敛性,并有效克服了后者的初始点敏感问题。数值模拟试验表明,该算法具有很高的精确性和收敛性,是求解非线性方程组的一种有效算法。     

基于进化策略的非线性方程组求解

基于在求解非线性方程组过程中传统算法存在着对于初始点敏感和串行运行速度过慢的问题,提出一种求解非线性方程组的进化策略算法.该算法充分发挥了进化策略的群体搜索和全局收敛的特性,能够快速求得非线性方程组的根,有效地克服了经典算法的初始点敏感和速度过慢的问题.仿真计算表明,该算法比传统的经典算法、改进的遗传算法和神经网络算法具有更高的求解质量和求解效率,为求解非线性方程组提供了一条比较有效的途径.     

基于极大熵差分进化混合算法求解非线性方程组*

针对非线性方程组,给出了一种新的算法——极大熵差分进化混合算法。首先把非线性方程组转换为一个不可微优化问题;然后用一个称之为凝聚函数的光滑函数直接代替不可微的极大值函数,从而可把非线性方程组的求解转换为无约束优化问题,利用差分进化算法对其进行求解。计算结果表明,该算法在求解的准确性和有效性均优于其他算法。     

一种求解非线性方程组的量子粒子群算法

针对传统非线性方程组的解法对初始值敏感、收敛性差等问题,提出一种求解非线性方程组的量子粒子群算法.用量子位的概率幅对粒子位置编码,通过量子旋转门和量子非门完成粒子的更新与变异.该算法可发挥量子粒子群的群体搜索能力和全局收敛性,在算法中融入拟牛顿法,加强局部搜索能力,提高求解精度.数值模拟实验表明,算法有着可靠的收敛性和较高的收敛速度与精度.     

求解非线性方程组的BFGS差分进化算法

针对差分进化算法进化后期收敛缓慢和稳定性不强的缺陷,将BFGS算法插入差分进化算法当中,提出了一种BFGS差分进化算法,用来求解非线性方程组。通过5个非线性方程组和一个工程实例的实验,说明：算法收敛精度较高、收敛速度较快、鲁棒性强、收敛成功率高,是一种较好的解决非线性方程组的方法。     

基于改进人工鱼群算法的逆变器SHEPWM方法的研究

对于特定谐波消除调制策略(SHEPWM)的开关角求解问题,传统数值方法需要提供方程的特定初值,现有的智能算法如遗传算法容易陷入局部最优解中。针对以上不足,将人工鱼群算法引入到非线性超越消谐方程组的求解,因其具有较好的全局收敛性,通过群体寻优较易达到全局最优解,同时为了避免鱼群搜索的盲目性,利用差分进化算法的快速局部收敛性,将二者相结合,有效地提高了进化效率。为了验证新算法的可行性,用MATLAB/Simulink仿真软件,将求解出的开关角用于两电平逆变器进行仿真研究,并利用以TMS320F28335为核心的实验平台进行了实验,实验证明了所求解能够消除选定的低频次谐波。     

一种求解多项式根最大模的区间进化AFSA

针对多项式根的最大模求解问题,给出一种求解多项式根最大模的区间进化人工鱼群算法(AFSA)。该算法利用公告板上前后两代的信息,将搜索区间映射到更为有效的区域中,其搜索区间是动态的和进化的,从理论上证明该算法的收敛性。仿真实验结果表明,该算法在求多项式根最大模中是可行有效的,收敛速度快,求解精度高。     

求解非线性方程组的自适应细菌觅食算法

针对传统的数值算法求解非线性方程组时对方程组要求高和初始值敏感等缺点,提出了一种自适应细菌觅食算法。该算法改变了传统算法的固定趋化步长,进行自适应调整,加快算法的收敛速度,具有更好的全局搜索能力,改变了固定迁移概率,避免了在进化后期精英解丢失的问题。将自适应细菌觅食算法应用到求解非线性方程组中,结果表明,与其他算法相比,该算法能够有效避免陷入局部最优,能更好地寻求最优解。     

差分进化算法在双指数拟合中的应用

利用差分进化算法较好地解决了一元四参数双指数和两元三参数双指数拟合问题。与传统优化算法相比,不受初值的影响,并具有全局收敛性,与PSO算法相比,收敛速度快,是一种求解非线性约束优化问题的有效方法。     

竞选优化算法求解非线性方程组的应用研究

针对非线性方程组的求解在工程上具有广泛的实际意义,经典的数值求解方法存在其收敛性依赖于初值而实际计算中初值难确定的问题,将复杂非线性方程组的求解问题转化为函数优化问题,引入竞选优化算法进行求解。同时竞选优化算法求解时无需关心方程组的具体形式,可方便求解几何约束问题。通过对典型非线性测试方程组和几何约束问题实例的求解,结果表明了竞选优化算法具有较高的精确性和收敛性,是应用于非线性方程组求解的一种可行和有效的算法。     

基于混合遗传算法求解非线性方程组

将非线性方程组的求解问题转化为函数优化问题,且综合考虑了拟牛顿法和遗传算法各自的优点,提出了一种用于求解非线性方程组的混合遗传算法。该混合算法充分发挥了拟牛顿法的局部搜索、收敛速度快和遗传算法的群体搜索、全局收敛的优点。为了证明该混合遗传算法的有效性,选择了几个典型的非线性方程组,从实验计算结果、收敛可靠性指标对比不同算法进行分析。数值模拟实验表明,该混合遗传算法具有很高的精确性和收敛性,是求解非线性方程组的一种有效算法。     

Hybrid approach for solving systems of nonlinear equations using chaos optimization and quasi-Newton method

Solving systems of nonlinear equations is one of the most difficult numerical computation problems. The convergences of the classical solvers such as Newton-type methods are highly sensitive to the initial guess of the solution. However, it is very difficult to select good initial solutions for most systems of nonlinear equations. By including the global search capabilities of chaos optimization and the high local convergence rate of quasi-Newton method, a hybrid approach for solving systems of nonlinear equations is proposed. Three systems of nonlinear equations including the “Combustion of Propane” problem are used to test our proposed approach. The results show that the hybrid approach has a high success rate and a quick convergence rate. Besides, the hybrid approach guarantees the location of solution with physical meaning, whereas the quasi-Newton method alone cannot achieve this.     

多模态多目标差分进化算法求解非线性方程组

针对当前算法在求解非线性方程组时面临解的个数不完整、精确度不高、收敛速度慢等问题进行了研究,提出一种多模态多目标差分进化算法。首先将非线性方程组转换为多模态多目标优化问题,初始化一个随机种群并对种群中全部个体进行评价;然后通过非支配解排序和决策空间拥挤距离选择机制,挑选种群中的一半优质个体进行变异;接着在变异过程中采用一种新的变异策略和边界处理方法以增加解的多样性;最后通过交叉和选择机制使优质个体进行进化,直到搜索到全部最优解。在所选测试函数集和工程实例上的实验结果表明,该算法能有效地搜索到非线性方程组的解,并通过与当前四个算法进行比较,该算法在解的数量和成功率上具有优越性。     

Nonlinear Least Square Regression by Adaptive Domain Method With Multiple Genetic Algorithms

In conventional least square (LS) regressions for nonlinear problems, it is not easy to obtain analytical derivatives with respect to target parameters that comprise a set of normal equations. Even if the derivatives can be obtained analytically or numerically, one must take care to choose the correct initial values for the iterative procedure of solving an equation, because some undesired, locally optimized solutions may also satisfy the normal equation. In the application of genetic algorithms (GAs) for nonlinear LS, it is not necessary to use normal equations, and a GA is also capable of avoiding localized optima. However, convergence of population and reliability of solutions depends on the initial domain of parameters, similarly to the choice of initial values in the above mentioned method using the normal equation. To overcome this disadvantage of applying GAs for nonlinear LS, we propose to use an adaptive domain method (ADM) in which the parameter domain can change dynamically by using several real-coded GAs with short lifetimes. Through an example problem, we demonstrate improvements in terms of both the convergence and the reliability by ADM. A further merit in the proposed method is that it does not require any specialized knowledge about GAs or their tuning. Therefore, the nonlinear LS by ADM with GAs are accessible to general scientists for various applications in many fields     

粒子群算法在求解方程组中的应用

提出了采用粒子群算法求解线性方程组和非线性方程组的智能算法。采用粒子群算法求解方程组具有形式简单、收敛迅速和容易理解等特点,且能在一次计算中多次发现方程组的解,可以解决非线性方程组多解的求解问题,为线性方程组和非线性方程组的求解提供了一种新的方法。     

A Chebyshev spectral method based on operational matrix for initial and boundary value problems of fractional order

We are concerned with linear and nonlinear multi-term fractional differential equations (FDEs). The shifted Chebyshev operational matrix (COM) of fractional derivatives is derived and used together with spectral methods for solving FDEs. Our approach was based on the shifted Chebyshev tau and collocation methods. The proposed algorithms are applied to solve two types of FDEs, linear and nonlinear, subject to initial or boundary conditions, and the exact solutions are obtained for some tested problems. Numerical results with comparisons are given to confirm the reliability of the proposed method for some FDEs.     

一种基于同伦函数的迭代法—同伦迭代法

§１．引言 工程中的许多问题常常最后可归结为求解一组非线性多项式代数方程．对非线性多项式方程组的求解,可采用符号求解和数值求解两种方式．符号求解可求出问题的封闭形式的解析解,当然是最理想的,但其难度往往也是很大的,随着问题数学模型的增大,消元过程变得愈加复杂,使得即使采用计算机也无法进行下去．因此,对于复杂的大规模问题,仍只能采用数值迭代法进行数值求解． 传统的数值迭代法存在的最大问题是方法的有效性依赖于初值的选取．初值选取不当常导致迭代过程不收敛,而且一次只能求出问题的一个数值解．山提出的区间分…     

高维复杂函数的混合模拟退火全局优化策略

对于高维复杂函数优化问题,经典的优化算法存在着初始点敏感、局部收敛等问题;而模拟退火算法等智能算法则有着计算成本高昂、算法早熟等缺陷。NFL定理犤1犦预示了混合优化策略是解决实际优化问题的最好途径。该文融合了模拟退火算法和经典算法的优点,设计了高维复杂函数混合模拟退火优化策略。混合优化策略具有模拟退火算法的全局收敛性,同时引入强局部收敛经典算法作为模拟退火算法的精英个体提高算子,提高了模拟退火算法局部开采能力,加快了收敛速度。数值仿真计算结果表明,混合模拟退火策略求解高维复杂函数的性能大大优于单一算法,具有强鲁棒性、高收敛速度和高精度等优点。该文的算法设计思想对于解决实际问题有较好的借鉴意义。     

Multilevel augmentation methods for nonlinear ill-posed problems

We propose multilevel augmentation methods for solving nonlinear ill-posed problems, involving monotone operators in the Hilbert space by using the Lavrentiev regularization method. This leads to a fast solutions of the discrete regularization methods for the nonlinear ill-posed equations. The regularization parameter choice strategies considered by Pereverzev and Schock (2005) are introduced and the optimal convergence rates of the regularized solutions are obtained. Numerical results are presented to illustrate the accuracy and efficiency of the proposed methods.     

Multigrid method for nonlinear poroelasticity equations

In this study, a nonlinear multigrid method is applied for solving the system of incompressible poroelasticity equations considering nonlinear hydraulic conductivity. For the unsteady problem, an additional artificial term is utilized to stabilize the solutions when the equations are discretized on collocated grids. We employ two nonlinear multigrid methods, i.e. the “full approximation scheme” and “Newton multigrid” for solving the corresponding system of equations arising after discretization. For the steady case, both homogeneous and heterogeneous cases are solved and two different smoothers are examined to search for an efficient multigrid method. Numerical results show a good convergence performance for all the strategies.