冷轧带钢压下规程优化设计

通过实际算例，优化压下规程可使各道次的板型系数相等，表明板型达到最佳状态。该方法通过离散压下量，迭代计算得出板型良好的轧制压力所对应的变形量，对实际生产有指导作用。     

复用等储备负荷法在热连轧粗轧负荷分配中的应用

 基于带钢热连轧粗轧区的特点,提出了复用等储备负荷法。该方法运用多层迭代算法进行粗轧机组负荷分配,外层对总轧制道次进行递增迭代,内层通过交替迭代确定带钢厚度和宽度轧制方向的综合负荷函数值,逐步优化平 立辊轧制规程。基于该方法设计了带钢热连轧粗轧过程设定系统软件,并结合实例进行了分析。分析结果表明该方法的适应性和灵活性很强,可适用于实时粗轧轧制过程中的设定计算。     

中厚板矫直规程的计算模型及其优化设定

为了有效控制中厚板矫直板形和发挥矫直机生产能力,提出了中厚板矫直规程计算模型及优化方法.依据钢板的钢种和温度得到材料的屈服应力,在不同厚度和屈服应力条件下基于实际生产经验进行矫直规程预设定,一并给出了预设定方案中各道次模型计算的初始值,在矫直规程模拟器中,运用迭代计算方法,得出优化的矫直规程,此矫直规程满足最终残余曲率和力能要求.     

采用序列二次规划法进行空间网架结构优化设计中的关键问题

采用序列二次规划法对空间网架结构优化设计时，起控制作用的约束条件是应力约束，在对应力约束函数进行序列二次归格化时必须进行应力灵敏度分析，同时设计变量运动极限的选取将直接影响到迭代过程的平稳度、迭代次数以及迭代计算结果的精确度，既此提出了应力灵敏度和设计变量运动极限的计算方法及理论依据。     

综合等负荷函数法在中厚板规程分配中的应用

基于综合等负荷函数法及中厚板轧制的特点，用两层迭代算法来分配中厚板轧制规程。外层对总轧制道次数进行迭代求解，内层采用二分法对综合负荷函数值差别最大的两个道次进行调整。该算法克服了综合等负荷函数法在中厚板轧制中应用的主要障碍，适用于实时中厚板轧制过程控制系统。     

中厚板轧制过程中道次修正计算方法的研究与应用

针对传统的中厚板道次修正计算方法的弊端,结合中厚板生产线的实际生产特点,提出道次锁定与重新计算相结合的道次修正计算方法.普通道次采用道次锁定计算方式,首道次控温结束后采用重新计算方式.如果各道次按照道次锁定计算方式最终使得阶段出口目标厚度无法达到时,该次修正计算改用重新计算方式.道次修正计算利用已轧道次实测数据修正道次...     

工字钢腿腰延伸系数均匀分配的计算方法

对轧制工字钢采用一种新的腿腰划分方法，用计算机迭代计算，使腿腰延伸系数趋于均匀更趋于实际，使孔型设计更为合理。     

热带钢连轧机精轧机组板凸度仿真与实验研究

根据热带钢连轧机的特点,将以变分法为基础的金属模型和用分段离散法建立的辊系弹性模型进行迭代求解,最终求出各道次轧件出口厚度横向分布。在攀钢１４５０ｍｍ六机架热带钢连轧机现场轧制过程中突然抬辊,获得含有完整的六个道次变形区的阶梯板,其实测数据与计算值吻合很好。     

迭代函数法计算机稀土串级萃取最优化k值

建立了计算机串级萃取优化k值的迭代函数：R=c/k d/(k-1)。实例应用和分析对比结果表明，用该迭代函数来计算串级萃取最优化k值，计算简便，结果可靠。     

迭代算法A与Q/Hampel方法在能力验证结果分析中的比较

能力验证计划实施中,要按照科学的统计方法分析能力验证参加者的测定结果,并给出公平合理的评价。通常优先采用对离群值相对不敏感的稳健统计方法进行能力验证结果分析。通过实际检测数据计算实例,对比了迭代算法A与Q/Hampel两种稳健统计方法的计算结果。研究表明:两种稳健统计方法计算的稳健平均值基本相同,计算的稳健标准差存在区别,但对各实验室检测能力评价一致。能力验证结果中存在局部众数时,迭代算法A和Q/Hampel方法计算所得稳健平均值比值为1.03,而两者稳健标准差比值达到了2.32,Q/Hampel方法比迭代算法A表现出更好的稳健可靠性。     

Selection of task-dependent diffusion filters for the post-processing of SPECT images

Iterative reconstruction from single photon emission computed tomography (SPECT) data requires regularization to avoid noise amplification and edge artefacts in the reconstructed image. This is often accomplished by stopping the iteration process at a relatively low number of iterations or by post-filtering the reconstructed image. The aim of this paper is to develop a method to automatically select an optimal combination of stopping iteration number and filters for a particular imaging situation. To this end different error measures between the distribution of a phantom and a corresponding filtered SPECT image are minimized for different iteration numbers. As a study example, simulated data representing a brain study are used. For post-reconstruction filtering, the performance of 3D linear diffusion (Gaussian filtering) and edge preserving 3D nonlinear diffusion (Catté scheme) is investigated. For reconstruction methods which model the image formation process accurately, error measures between the phantom and the filtered reconstruction are significantly reduced by performing a high number of iterations followed by optimal filtering compared with stopping the iterative process early. Furthermore, this error reduction can be obtained over a wide range of iteration numbers. Only a negligibly small additional reduction of the errors is obtained by including spatial variance in the filter kernel. Compared with Gaussian filtering, Catté diffusion can further reduce the error in some cases. For the examples considered, using accurate image formation models during iterative reconstruction is far more important than the choice of the filter.     

目标厚度函数法在板带轧制规程计算中的应用

板带轧制过程控制要求快速计算出满足指定目标负荷分配比的轧制规程,针对常用的Newton迭代法对厚度迭代初始值限制较多,不能确保迭代收敛的特点,提出目标厚度函数法.该方法建立轧制出口厚度对于轧制负荷的函数方程,通过求解一系列非线性方程得到满足目标负荷分配比的轧制规程,摆脱了厚度初始值的提供和Jacobi矩阵的计算.分别基于2种方法编制程序并采用实际数据计算,结果表明:目标厚度函数法在计算时间和收敛性方面均满足在线应用的要求,可成功取代Newton迭代法.     

Improvement of Eigensolution Method for Nonproportionally Damped Systems by Step Length

This study presents an efficient eigensolution method for nonproportionally damped systems. The proposed method is obtained by applying the accelerated Newton–Raphson technique and the orthonormal condition of the eigenvectors to the linearized form of the quadratic eigenproblem. In the Newton–Raphson scheme, a step length and a selective scheme are introduced to increase the convergence of the solution. The step length can be evaluated by minimizing the norm of the residual vector using the least-squares method. While the singularity may occur during the factorizing process in other iteration methods such as the inverse iteration method and the subspace iteration method if the shift value is close to an exact eigenvalue, the proposed method guarantees the nonsingularity by the orthonormal condition of eigenvectors, which can be proved analytically. A numerical example is presented to demonstrate the effectiveness of the proposed method.     

Domain-by-Domain Algorithm for Nonlinear Finite-Element Analysis of Structures

Parallel and distributed computers have been shown to provide the necessary computational power to solve large-scale engineering problems. However, in order for this computation style to be effectively used, efficient computational algorithms must be devised. In this work, a domain-by-domain algorithm is developed for the parallel solution of nonlinear structural dynamics problems. In the proposed algorithm, the original structure is partitioned into a number of subdomains. Each subdomain is solved independently and, therefore, concurrently using a traditional direct-solution method. Finally, the solution for the interface degrees of freedom between neighboring subdomains is obtained by enforcing compatibility and equilibrium using an iterative procedure. The nonlinear version of the algorithm involves two iterations: The nonlinear dynamic equilibrium iteration and the interface equilibrium and compatibility iteration. The integration of these two iterations is investigated and two strategies are developed. It is found that the strategy in which the two iterations are isolated is the most efficient. As a demonstration, the fully nonlinear transient analysis of a 20-story model building is carried out. Excellent accuracy in the solution and significant speed up values are obtained.     

六辊CVC冷轧机凸度控制能力分析及应用

 基于三维有限元建立了六辊CVC辊系模型,该模型耦合了CVC辊形曲线、辊间轧制力分布以及带钢的弹塑性变形和辊系弹性变形,通过迭代计算辊间轧制力及轧辊与轧件的弹塑性变形。通过实际轧制规程数据对比验证了模型的有效性,其模拟计算结果与实际数据的绝对误差在10 μm内,相对误差小于1%。采用该模型研究了板形控制机构如中间辊弯辊、中间辊窜辊和工作辊弯辊对带钢2次凸度和4次凸度的控制规律,并成功消除了生产现场宽薄带钢的边中复合浪缺陷。     

Simulation of Highly Skewed Non-Gaussian Stochastic Processes

In this paper, a simulation methodology is proposed to generate sample functions of a stationary, non-Gaussian stochastic process with prescribed spectral density function and prescribed marginal probability distribution. The proposed methodology is a modified version of the Yamazaki and Shinozuka iterative algorithm that has certain difficulties matching the prescribed marginal probability distribution. Although these difficulties are usually sufficiently small when simulating non-Gaussian stochastic processes with slightly skewed marginal probability distributions, they become more pronounced for highly skewed probability distributions (especially at the tails of such distributions). Two major modifications are introduced in the original Yamazaki and Shinozuka iterative algorithm to ensure a practically perfect match of the prescribed marginal probability distribution regardless of the skewness of the distribution considered. First, since the underlying “Gaussian” stochastic process from which the desired non-Gaussian process is obtained as a translation process becomes non-Gaussian after the first iteration, the empirical (non-Gaussian) marginal probability distribution of the underlying stochastic process is calculated at each iteration. This empirical non-Gaussian distribution is then used instead of the Gaussian to perform the nonlinear mapping of the underlying stochastic process to the desired non-Gaussian process. This modification ensures that at the end of the iterative scheme every generated non-Gaussian sample function will have the exact prescribed non-Gaussian marginal probability distribution. Second, before the start of the iterative scheme, a procedure named “spectral preconditioning” is carried out to check the compatibility between the prescribed spectral density function and prescribed marginal probability distribution. If these two quantities are found to be incompatible, then the spectral density function can be slightly modified to make it compatible with the prescribed marginal probability distribution. Finally, numerical examples (including a stochastic process with a highly skewed marginal probability distribution) are provided to demonstrate the capabilities of the proposed algorithm.     

等值面上的凸组合法

利用等值面上的凸组合法求解了线性规划问题 .首先借助于一般的起作用集法找到一非最优极点 ,再由此极点的等值面与容许集的交集得一锥 ,然后沿着由该锥的下降棱方向与 -c方向所作的凸组合方向作直线搜索得到一新迭代点 .重复以上步骤直至得到最优点为止     

能力验证检测数据的两种稳健统计分析方法比较及结果合理性判断

四分位法和迭代法均是计算检测能力验证数据目标标准偏差的稳健统计分析方法, 其计算结果将直接用于判断实验室上报数据是否合格。利用195套(100多个检测项目)检测能力验证数据, 比较了两种稳健统计分析方法计算结果。模拟和实际数据计算结果均表明, 当数据分布趋势是正态分布时, 两种方法结果基本吻合, 但对于数据分布明显偏离正态分布检测项目, 四分位法计算得到的标准偏差过严, 导致实验室上报数据满意率明显下降, 出现统计学“弃真”错误。以删掉离群值后的经典统计法结果作为依据, 对两种方法合理性进行了判断。对于固体样品, 四分法与迭代法结果(标准偏差)比较接近, 两者相对偏差平均值为5.7%;液体样品为13.8%, 两者差别较大。迭代法既减小了离群值对统计分析结果的影响, 又避免了判断离群值时采用不同规则可能带来的人为因素影响。建议尽快将迭代法纳入国内检测能力验证数据评价标准体系。     

MMSE准则下基于玻尔兹曼机的快速重构算法

全连接的玻尔兹曼机模型可全面描述稀疏系数间统计依赖关系,但时间复杂度较高.为了提高基于玻尔兹曼机的贝叶斯匹配追踪算法(BM-BMP)的重构速度和质量,本文提出一种改进算法.第一,将BM-BMP算法的最大后验概率(MAP)估计评估值分解为上一次迭代的评估值与增量,使得每次迭代仅需计算增量,极大缩短了计算耗时.第二,利用显著最大后验概率估计值平均的方式,有效近似最小均方误差(MMSE)估计,获得了更小的重构误差.实验结果表明,本文算法比BM-BMP算法的运行时间平均缩短了73.66%,峰值信噪比(PSNR)值平均提高了0.57 dB.