基于区间运算的字典序多目标模型预测控制

考虑优化级多目标优化控制问题,提出一种基于区间运算的字典序多目标模型预测控制算法。对约束线性系统,结合字典序列法和滚动优化原理,建立按优先级定义的分层多目标模型预测控制策略。在此基础上,引入区间运算法则,在线求解预测控制量。通过一双容水箱单输入双输出液位控制,仿真验证了该方法的有效性。     

一种求解数据校正问题的基于经验增强的方法

基于机理模型的数据校正问题中,过程系统比较复杂时就要面临求解大规模非线性规划问题.如果直接求解,由于方程维数大且为非线性,问题自由度大,因此求解难度较高,容易导致求解收敛失败.数据校正问题的特点是当测量变量的测量值发生变化时对同一过程对象模型重复地进行求解计算.基于此特点,今提出了一种基于经验增强的求解方法.此方法通过...     

基于实体流模型注射成型的高效模拟及实验验证

基于笔者在欧拉描述下模拟注射填充过程的显式算法，应用实体流模型实现了用于注塑填充过程的全矢量化运算显式算法。此算法通过反馈修正的方式来满足不可压缩条件，从而避免了压力场的全局求解。矩阵操作仅在单元一级进行，使计算代价与节点的自由度近似成正比，实现了填充模拟的高效运算。应用新算法和MINI单元的算法对同一模型进行注塑过程的模拟，通过比较两种算法的计算时间，证实了新算法的高效性；通过比较另一典型模型的计算模拟结果和相应的实验结果，验证了新算法的有效性。     

换热网络综合的广义析取规划模型及求解方法

提出了针对通用换热网络综合(HENS)的广义析取规划(GDP)模型。广义析取规划模型通过引入逻辑变量代替0-1整形变量,使用析取式实现约束的分支选择。相比于传统MINLP模型,换热网络综合的广义析取模型具有以下优点:(1)条件建模的直观性;(2)通过对约束的动态选择,在减少冗余约束的同时更消去了不存在单元所带来的非线性费用计算模块,从而大大降低NLP子问题的求解复杂度,使求解更简单。另外,提出了一种混杂算法用来求解换热网络算例的广义析取规划模型。在外层使用启发式算法搜索最优结构,在内层调用确定型算法求解非线性规划子问题。结果表明,GDP模型无论在简洁性还是易求解性上都优于传统MINLP模型,可以有效地求解通用换热网络的综合问题。     

基于行波法的段塞流瞬态捕捉模型建立与验证

气液两相流中,准确预测段塞流的特征参数具有重要的现实意义。Renault模型是基于非黏性Kelvin-Helmholtz（IKH）稳定性准则与黏性Kelvin-Helmholtz（VKH）稳定性准则建立的能够捕捉段塞前后界面运动的双流体模型,但该模型在液相单元格之间采用Riemann精确解,求解速度较慢。为简化计算,本文将行波法引入到Renault模型的液相方程求解过程,并对可能出现的干区用薄液膜代替,使行波法适用于所有计算单元,在保证模型精度的条件下,极大地提高了计算速度,运算时间相比Renault模型平均减少28%。对比本模型计算结果与室内小型环道实验数据,持液率与实测结果相一致,压降、段塞长度计算相对误差分别在25%、30%以内,且主要分布在20%以内。说明本文改进的瞬态段塞流模型具备运算快速、计算精度较高的特点,具有一定的工程应用价值。     

使用EXCEL进行PET装置热媒蒸发器的设计计算

通过对热媒蒸发器的特点进行分析,选取了合适的计算模型和公式,使用EXCEL电子表格的单变量求解和宏工具,方便地实现了热媒蒸发器的设计型计算。为实现程序自动迭代运算,文中还列出了通过EXCEL电子表格的数据处理功能对气相热媒和液相热媒参数在所使用的温度区间内进行连续化归纳的计算公式。     

关于水泥生料三组分配料求解的公式表示法

利用率值公式法进行生料的配料计算,是近几年总结推导出来的一种易于掌握、计算结果准确的方法。只要原料适宜,可一次计算成功。只是在计算过程中涉及到解方程组的问题。由于算术运算较多,稍有疏忽就会出现差错。笔者通过对三组分配料进行求解,得出用字母(率值系数)表示的配料结果,从而简化了一些运算过程和减少了计算差错出现的机会。     

多重网格法在求解泊松方程中的应用进展

多重网格(Multigrid,简称MG)法是求解复杂科学运算中由偏微分方程离散以后所得的大型代数线性方程组的最高效、最快速的迭代求解方法。本文详述了多重网格法在求解二维、三维泊松方程求解问题研究中的应用,与传统迭代方法相比在收敛速度、精度和稳定性上多重网格方法都有其固有的高效性。并初步的讨论了多重网格并行算法求解泊松方程正演问题,针对多重网格法应用于地球物理的各种数值模拟研究,提出了四点具体的研究发展方向,希望对今后研究有所帮助。     

生态工业园区的MINLP模型

生态工业园区的设计和管理需要建立在定量分析的基础上，目前仍然是一个薄弱环节. 本文提出了一个引入逻辑表达式的生态工业园区模型，可以通过对一个混合整数非线性规划(MINLP)问题进行求解来获得有价值的参考信息. 模型可以分为成员模型和连接模型两部分，成员模型作为积木，通过连接模型搭建成不同拓扑结构的生态工业园区方案. 开发的生态工业园区模型具有良好的扩展性、可修改性、可重用性，可以作为生态工业园区决策系统的核心模型. 以山东枣庄市南工业区为对象进行了案例分析. 模型用非线性优化软件LINGO求解.     

改进的无分流换热器网络最优综合法

提出了不分流换热网络改进的同步最优综合混合整数非线性规则模型，通过引入处理带０－１整型变量的规则，提出了采用非线性规划求解换网络综合ＭＩＮＬＰ问题的方法，只需求解ＮＬＰ问题就可得到连续变量和０－１变量同步优化的网络结果。算例表明，该模型和方法是有效的。     

Solution of nonlinear boundary value problems—X: The false transient method

The solution of a nonlinear boundary value problem may be found by solving a pertinent transient equation until the solution ceases to change significantly (the false transient method). The method is used to get a solution of a strongly nonlinear diffusion problem as well as towards solution of equations arising in the boundary layer theory. If multiple solutions occur the false transient method is not capable of calculating all profiles. For the boundary layer problems it is difficult to construct a reliable false transient equation if it is not based on a physically “sound” transient model.     

EXACT ANALYTICAL SOLUTION OF A LUMPED MODEL OF THE TRANSIENT CONVECTIVE-RADIATIVE COOLING OF A HOT SPHERICAL BODY IN AN ENVIRONMENT

In this study the exact analytical solution of the lumped parameter model of a nonlinear heat transfer process representing the transient convective-radiative cooling of a spherical body has been obtained. The process is governed by a nonlinear ordinary differential equation, and the exact analytical solution has been found in the implicit form of an elementary transcendental function. The obtained exact analytical solution not only yields accurate results but also successfully simulates a recent experimental study of cooling of metallic ball bearings by the combined mechanism of convection and radiation. In addition, the exact explicit solution for a simplified case of the above problem, recently tackled by several researchers in various approximate ways, has also been found. These exact solutions are quite appealing since they are accurate and superior to the available approximate solutions, provide better insight of the physical process, and can also serve as yardsticks for future testing of the approximate solutions.     

A reformulated nonlinear model to solve the facility layout problem

The facility layout problem is fundamental during the plant design. The solution of this problem has required strategies that become in numerical challenges. One of them is the exact method, which finds optimal distributions for facility layout, as demonstrated in the linear and disjunctive models. Both models are distinguished by a high quantity of nonoverlapping constraints. In contrast, a nonlinear model was formulated with low number of constraints, but it has been solved by genetic algorithms. Herein, that model is reformulated to a MINLP (mixed integer nonlinear programing) problem. The solution was possible using a visual interface linked to GAMS (General Algebraic Modeling System). Three case studies were solved to compare them. The reformulated model reached feasible solutions, and its computational time and binary variables were lower than those of the others. This suggests that the reformulated model can be extended to solve topics about process safety.     

AN INTEGRAL-SPECTRAL FORMULATION FOR CONVECTIVE-DIFFUSIVE TRANSPORT IN A PACKED-BED WITH ADSORPTION AT THE WALL AND BULK REACTION

A solution for a convective-diffusive transport problem coupled with bulk reaction and adsorption at the wall in packed-bed reactor has been obtained. Such solution has been derived in terms of a particular solution that satisfies the non-homogeneous boundary conditions, at the wall, and the solution to the differential model with homogeneous boundary conditions. The latter is given in terms of integral equations whose kernel is the Green function of the parabolic differential operator of the transport problem. The Green function is expanded in terms of the eigenvalues and the eigenfunctions of the radial diffusion operator of the differential problems. This methodology allows a decoupling of the linear aspects of the problem (i.e., transport part) of the nonlinear source (i.e., kinetic of the reaction) and facilitates the convergence of the Fourier series involved in the spectral expansion in the case of a need for numerical solutions. Details about the solution methodology and the identification and solution of the eigenvalue problem, are given.     

Optimization-based cosmetic formulation: Integration of mechanistic model,surrogate model,and heuristics

Multiple functional and hard-to-quantify sensorial product attributes that can be satisfied by a large number of cosmetic ingredients are required in the design of cosmetics. To overcome this problem, a new optimization-based approach for expediting cosmetic formulation is presented. It exploits the use of a hierarchy of models in an iterative manner to refine the search for creating the highest-quality cosmetic product. First, a systematic procedure is proposed for optimization problem formulation, where the cosmetic formulation problem is defined, design variables are specified, and a set of models for sensorial perception and desired product properties are identified. Then, a solution strategy that involves iterative model adoption and two numerical techniques (i.e., generalized disjunctive programming reformulation and model substitution) is applied to improve the efficiency of solving the optimization problem and to find better solutions. The applicability of the proposed procedure and solution strategy is illustrated with a perfume formulation example.     

Creeping flow relative to permeable spheres

The several possible solutions to the problem of creeping flow relative to an isolated permeable sphere are discussed and compared quantitatively. The most satisfactory solutions is that based upon Brinkman's extension of Darcy's Law. This solution is generalized, using Happel's free-surface model, to cover the practically important problem of flow relative to a swarm of permeable spheres. A physically realistic and mathematically consistent expression for the hydrodynamic resistance experienced by a typical sphere within such a system is derived. This expression is then used to predict the settling rate and the overall permeability of the swarm.     

TRIZ理论在组合式移动喷漆室故障诊断中的应用

TRIZ理论是一种高效解决问题的办法。利用TRIZ理论,通过对系统的39个通用工程参数的分析,查询阿奇舒勒矛盾矩阵,得到相应的解决方案模型。通过对设备运行具体情况的分析,得到故障预测的具体解决方法,并对采用的方法如何在工程实际中进行应用进行了详细地解释。整个方案安全可靠、经济实用,投入使用后,在实际应用中得到良好的反映。     

反应器网络综合三分布参数通用模型

提出了一种应用于反应器网络综合的三分布参数通用模型 .3个分布参数分别是侧线进料、侧线循环和侧线采出参数 ,这些参数能影响反应器网络内部的浓度和停留时间分布 ,所以由它们构成的通用模型具有简捷有效的特点 .基于此模型可将反应器网络集成转化成一个优化问题 ,通过有限元正交配置将原来含有微分方程的优化模型转化为非线性优化问题 ,优化计算后得到最优分布参数 .从案例研究可以看出 ,侧线进料、循环和采出策略能较全面地反映在不同动力学和优化目标函数下的最优反应器网络特征 ,并进而简化为工业可行的反应器网络     

Effective Viscosity of Suspensions of Spheres

Modeling the effective viscosity of suspensions of spheres beyond the dilute limit is a difficult problem that has challenged researchers for nearly a century since Einstein derived an equation for dilute suspensions. Hydrodynamics modeling requires complex mathematical treatments of integral equations describing interactions between spheres, and its solutions have been limited to semidilute dispersion of monosized hard spheres. Mechanics modeling treats suspensions in a statistical sense and generally provides upper and lower bounds solutions for polydispersed suspensions. A closed-form solution for the effective viscosity of concentrated suspensions of monosized spheres using both the elastic-viscous analogy and the analogy between the effective dielectric constant of a polarizable medium and the effective viscosity of two-phase flow is derived in the present study. Existing measurements and numerical simulations support present analytical results. A closed-form solution for polydispersed suspensions using a differential model is also derived, and the results are within existing bounds solutions.