基于复变量求导法反演边坡岩土体强度参数初探

提出了弹塑性参数反演的一种新方法,即复变量求导法、优化计算方法以及弹塑性有限元法三者的结合.利用弹塑性有限元方法正演计算测点处位移(复数形式),采用复变量求导法求解灵敏度矩阵,通过迭代优化方法完成变量更新,直至最终得到符合要求的解.数值算例表明,该方法对岩土体抗剪强度参数反演有效可靠,解决了参数反演时位移对反演参数不敏...     

碳九芳烃精馏分离模拟计算

用peng-Robinson模型和三对角矩阵法建立C_9芳烃分离计算的模拟计算程序,通过多种设计方案的计算和比较,对分离过程选出一组最佳设计参数,提出改进意见,计算结果满足工厂分离要求。     

填充床电化学反应器普遍化模型方程数值求解方法

以有限差分法与正交配置法联用对填充床电化学反应器的模型方程进行了求解，结果表明该法是一种快速、有效地求解具有较为复杂的边界条件的偏微分方程的计算方法。     

特征线法计算管道的水力瞬变

特征线法是把不稳定流问题的两个偏微分方程,用两个特征值,转换成四个长微分方程,然后使用显示差分法把常微分方程表示成差分方程,在计算机上求解的一种方法,文章结合具体算例,采用特征线法用MATLAB进行编程计算。结果表明,这种方法计算速度快,收敛性好是一种很有效的计算方法。     

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     

试差矩阵熬及其在复杂反应动力学研究中的应用

本文提出了一种研究高维拟一级复杂反应动力学的新方法——试差矩阵法.该方法充分运用有效的数学方法和计算技术,以减少实验工作量,并能大大减少待定参数个数,提高估值精度.研究表明,该方法具有良好的方法统计特性,能耐受较大的实验误差。本文还提出了新的八碳芳烃临氢异构化和六碳组份重整体系的反应网络,应用试差矩阵法成功地研究了这两个体系的双曲型动力学模型,求取了各模型参数,模型拟合值与实验值能很好地吻合.     

虚拟仪器动态测量系统参数辨识

在对虚拟仪器动态测量系统做离散域分析的基础上,应用最小二乘法实现虚拟仪器动态测量系统参数辨识.鉴于应用最小二乘法系统参数辨识计算时存在矩阵求逆困难,不适宜于在线实时参数评估,探讨一种递推改进方法去弥补最小二乘法的不足,通过具体的虚拟仪器动态测量实例,验证所提议的改进方法的正确性和优越性.     

三对角与二对角矩阵法应用于非理想溶液精馏计算的收敛性

讨论了多组分精馏塔定态模拟计算中三对角矩阵法的敛散性,并提出了一种修正法——二对角矩阵.对两种方法的收敛性进行了分析和比较,将这两种方法用于多种非理想体系的计算,结果表明,二对角矩阵法的收敛性和稳定性均比三对角矩阵法好.     

三对角与二对角矩阵法应用于非理想溶液精馏计算的收敛性

讨论了多组分精馏塔定态模拟计算中三对角矩阵法的敛散性,并提出了一种修正法——二对角矩阵.对两种方法的收敛性进行了分析和比较,将这两种方法用于多种非理想体系的计算,结果表明,二对角矩阵法的收敛性和稳定性均比三对角矩阵法好.     

脱水明矾石还原过程动力学研究之二—用氢还原脱水明矾石动力学的研究

本文系用氫作还原剂对本研究之一提出的串並联反应动力字模型,进行了不同温度下模型参数的求取,並修正了模型。由不同温度下速率常数,求得各反应活化能。结果证实了串並联反应动力学模型的合理性。对非线性化拟合求模型参数的计算方法和程序进行了一些探讨,计算时应用了积分变换法解非线性偏微分方程组以提高计算速率获得了一些初步经验。     

THE DEVELOPMENT AND VALIDATION OF A SYSTEM MODEL FOR A COUNTERCURRENT CASCADING ROTARY DRYER

An overall system model for a countercurrent rotary dryer has been developed with the ullimale aim of assessing controller pairings in these dryers. This model is based on heat and mass balances within dryer regions combined with two subsidiary models, one describing the equipment (which determines particle transport and heat transfer)and the other describing the behaviour of the material (the drying kinetics). Six partial differential equations have been set up to evaluate six state variables: solids moisture content, solids temperature, gas humidity, gas temperature, solids holdup and gas holdup as functions of time and rotary dryer length. A control-volume method has been used to reduce the six partial differential equations with respect to time and the length of the rotary dryer to six ordinary differential equations in time.

The drying model has been implemented in the SPEEDUP flowsheeting package (with FORTRAN subroutines) The model has been validated by fifteen experiments-in a pilot scale countercurrent-flow rotary dryer (0.2m in diameter and 2m in length)     

THE DEVELOPMENT AND VALIDATION OF A SYSTEM MODEL FOR A COUNTERCURRENT CASCADING ROTARY DRYER

ABSTRACT

An overall system model for a countercurrent rotary dryer has been developed with the ullimale aim of assessing controller pairings in these dryers. This model is based on heat and mass balances within dryer regions combined with two subsidiary models, one describing the equipment (which determines particle transport and heat transfer)and the other describing the behaviour of the material (the drying kinetics). Six partial differential equations have been set up to evaluate six state variables: solids moisture content, solids temperature, gas humidity, gas temperature, solids holdup and gas holdup as functions of time and rotary dryer length. A control-volume method has been used to reduce the six partial differential equations with respect to time and the length of the rotary dryer to six ordinary differential equations in time.

The drying model has been implemented in the SPEEDUP flowsheeting package (with FORTRAN subroutines) The model has been validated by fifteen experiments-in a pilot scale countercurrent-flow rotary dryer (0.2m in diameter and 2m in length)     

Addressing the control problem of algae growth in water reservoirs with advanced dynamic optimization approaches

In this work, we develop a lake eutrophication model to determine restoration policies for water quality improvement. This hybrid biogeochemical model has been formulated within a simultaneous dynamic optimization framework as an optimal control problem, whose solution provides limiting nutrient inflow profiles to the lake, as well as in-lake biomanipulation profiles. The water quality model comprises a set of partial differential algebraic equations in time and space, which result from dynamic mass balances on main phytoplankton groups, nutrients, dissolved oxygen and biochemical demand of oxygen. Spatial discretization has been performed in two layers. The simultaneous approach proceeds by discretizing control and state variables by collocation over finite elements and solving the large scale nonlinear program with an interior point method with successive quadratic programming techniques.     

DYNAMIC MATHEMATICAL MODEL OF A ROTARY DRYER: METHOD OF CHARACTERISTICS

A mathematical model for the dynamic behavior of a countercurrent rotary dryer has been developed and solved. The model consists of four hyperbolic partial differential equations with split boundary conditions. The equations are solved numerically using an algorithm based on the method of characteristics. The solution is stable and rapid. Sample results of a dryer simulation are presented.     

An Improved LES on Dense Particle‐Liquid Turbulent Flows Using Integrated Boltzmann Equations

An improved large eddy simulation (LES) using a dynamic second‐order subgrid stress (SGS) model has been developed for simulating dense particle‐liquid two‐phase turbulent flows. The governing equations of each phase are obtained from a microscopic point of view, using the kinetic theory of molecular gas. They are derived by multiplying the Boltzmann equation of each phase by property parameters and integrating over the velocity space. An inter‐particle collision term is included in the governing equation of the particle phase. Assuming a Maxwellian distribution of the velocity for particle‐phase, an inter‐particle collision term is derived.     

Detailed Dynamic Modeling of a Molten Carbonate Fuel Cell Stack with Indirect Internal Reformers

A detailed dynamic model of a molten carbonate fuel cell (MCFC) stack that can predict the distribution of process variables over the cell surface and along the stacking direction is presented. The model describes a repeating unit of the stack, which is composed of eight cells and one indirect internal reformer (IIR). The set of partial differential equations for the MCFC model is reduced to a set of ordinary differential equations through discretization using the cubic spline collocation method and the finite difference method. The steady‐state and dynamic behaviors of the eight‐cell stack model are compared with those of the one‐cell model, which has been commonly used in previous studies on MCFC dynamics, and three‐cell aggregate model. The distribution of the process variables along the stacking direction cannot be disregarded, and thus more detailed model should be used for the accurate reproduction of MCFC dynamics.     

Sensitivity analysis of systems of differential and algebraic equations

Formulae are derived for parametric sensitivity analysis of mathematical mo dels consisting of sets of differential and algebraic equations. Such equations often arise in dynamic modeling of equilibrium stage processes, and in solution of partial differential equations via the numerical method of lines. These formulae can be used to efficiently produce the model sensitivity coefficients, simultaneously with the solution of the model.     

Development of Two‐point Dynamic Method for Evaluating Extraction Columns

The steady‐state method by measuring the concentration profile along the column height is an effective way, but it is a time and material consumption method for large extraction columns. In order to investigate the axial‐mixing and mass transfer performances in a large pulsed‐sieve‐plate extraction column with the diameter of 150mm, a two‐point dynamic method with mass transfer based on the diffusion model has been developed. The results proved that the two‐point dynamic method has the advantages of good accuracy, simple boundary equations and flexible sampling position over the traditional single‐point dynamic method. It is a reliable tool for studying the axial‐mixing and the mass transfer performances.     

Solving partial differential equations of gas–solid reactions by orthogonal collocation

In this work the solution of the coupled partial differential equations for noncatalytic gas–solid reactions has been considered by orthogonal collocation. First of all, by an integral transformation and then by applying the orthogonal collocation method, these partial differential equations are converted to the ordinary differential equations. Then the equations are solved and the conversion–time profiles are obtained. The solution of the equations for volume reaction model, grain model and grain model with product layer resistance, modified grain model, random pore model, nucleation model and reaction of two gas with one solid has been presented in this work. The orthogonal collocation is a rapid method for solving of these equations and shows a good accuracy with respect to other solution techniques in the literature.     

A model for the oxidation of carbon silicon carbide composite structures

A mathematical theory and an accompanying numerical scheme have been developed for predicting the oxidation behavior of carbon silicon carbide (C/SiC) composite structures. The theory is derived from the mechanics of the flow of ideal gases through a porous solid. The result of the theoretical formulation is a set of two coupled non-linear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The non-linear differential equations are cast into matrix equations by applying the Bubnov-Galerkin weighted residual method, allowing for the solution of the differential equations numerically. The numerical method is demonstrated by utilizing the method to model the carbon oxidation and weight loss behavior of C/SiC specimens during thermogravimetric experiments. The numerical method is used to study the physics of carbon oxidation in carbon silicon carbide composites.