Modelling,Synthesis, and Simulation of Supervisory Process Control Systems

Modelling, synthesis, and simulation issues of the supervisory systems in process control are investigated in the paper. Petri nets are used as a basic modelling framework for the supervisory part of the system. It is shown how the final verification effort can be minimised by applying formal synthesis methods. A straightforward approach to the industrial implementation of the developed solutions is suggested by means of sequential function chart representation. A batch process cell case study is used to illustrate the described concepts. Corresponding continuous and discrete event models of the process cell units are developed and a co-ordinating supervisor is designed by the method of place invariants. The system is simulated by the continuous simulation tool Matlab-Simulink, which is enhanced for simulation of the sequential control logic represented by sequential function chart.     

Process Modelling under Uncertainty: Simulation Analysis of Indian Steel

The process model of the Indian iron and steel industry is presented, with particular focus on energy use and conservation possibilities. Uncertainty problems in the industry are analysed by using probabilistic Monte-Carlo simulations, where model parameters are assumed to be stochastic and distributed normally. Instead of the usual random sampling methods for generating inputs into the simulations, a stratified (Latin hypercube) sampling method is used. Statistical analysis of the output results shows that, for the steel industry in India, energy-conservation technologies would have insignificant impact on performance. A further contribution of the paper is the use of a microcomputer for large-scale Monte-Carlo simulations.     

Theory of Modelling and Simulation

Journal of the Operational Research Society -     

Modelling and Simulation of Food Foams

The rheological behaviour of protein solutions containing bubbles at rest, but particularly during fluid mechanical transport is not sufficiently investigated yet. Protein foams have a great importance in food production because of their special sensory properties. A suspension that contains bubbles in a Newtonian liquid exhibits inherently a complex rheological behaviour, such as elastic effects, a shear- and time-dependent viscosity and normal stress differences. The deformation state of the bubbles in a suspension subjected to a steady shear is a function of the gas volume fraction ϕ and the capillary number N_Ca. In the present article, material equations for protein solutions with gas volume fractions ϕ ≤ 0.75 and small bubble deformations, i. e. N_Ca ≪ 1, are analysed and further developed. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling the Pulsating Process

We continue research on machine-oracle modelling of second-order arithmetic. The pulsating process described in [1, 2] is simulated using oracles of so-called autonomous hierarchies. The outcome is constructing a generalized constructive model for a fragment of second-order arithmetic described in [2].     

Recent Developments in Simulation Modelling

Current trends in simulation software development are towards the automation of the modelling process. Some systems provide a method of specifying the problem so that a computer program can be automatically generated. Other systems provide a generic framework for a particular class of modelling problem that can be input as data to the system. Examples of the latter are flexible manufacturing systems simulations. Most current developments are colour-graphics-aided in one form or another. Computer advances in hardware and software are emerging through better user interfaces, more power and lower costs. The major benefit is an increasing customer involvement in the modelling process. An overview of these developments and future directions are given in this paper.     

Simulation Modelling Using an Interactive Simulation Program Generator

The development of an interactive simulation program generator which is available on micro and mainframe computers is outlined. The generator forms part of a simulation environment being researched into and constructed by a group of researchers at the London School of Economics. The generated programs are written in Pascal, using a suite of routines which assume a three-phase structure for simulation programs. Experiences of modelling using such a simulation modelling environment are outlined, as well as details of related research and future research plans.     

Modelling the Process of Multiattribute Choice

In most of the multiattribute utility models it is assumed that the analytical forms of partial and overall utility functions are known, and hence the problem becomes one of estimating the values of model parameters. This assumption is rather restrictive since one may not possess prior knowledge as to the analytical forms of such functions. The present paper is an attempt to eliminate some of the shortcomings of the existing models by proposing two new formulations of the multiattribute choice problem without a priori limitation to any strict form of partial utility function.     

Modelling and Simulation of the Transport of Protein Foams

The behaviour of foams at rest, but particularly during fluid mechanical transport is not sufficiently investigated yet. The present article deals with protein foams as they have a great importance in food production. In the first part, the foaming process of a highly viscous liquid due to gaseous materials dispersed under pressure in the liquid and mass transport of volatile components dissolved in the liquid is considered. The aim is to calculate the foam volume and the concentration of the dissolved, volatile components as a function of the material and process parameters. In the second part, material equations for bubble suspensions with gas volume fractions ϕ ≤ 0.6 and small bubble deformations (i.e. N_Ca ≪ 1) are presented. The basics form two constitutive laws which are used for describing a steady shear flow. If the rates of work of the two models are compared, material equations for the shear viscosity and the normal stress differences can be derived. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling and Simulation of Curing Processes of Epoxy Resin

During the curing reaction, the adhesive changes its thermomechanical material behaviour from a viscous fluid to a viscoelastic solid. This phase transition is an exothermal chemical reaction which is accompanied by thermal expansion, chemical shrinkage and changes in temperature. In this work the numerical simulation of the curing process will be presented. The material model for the implementation is presented in [1]. For the implementation of the material model the consistent tangent operator has been derived. In the presentation, experimental data and simulation are shown. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modelling Techniques for Simulation of Submarine Engagements

The process of designing complex, costly military systems benefits substantially from analyses of performance as predicted by some form of model of the system and its operating environment. In this paper, techniques are described that have been implemented in a suite of computer programs to represent the tactical situations that can develop between two opposing submarines. The kernel of the program suite is the Submarine Interactive Attack Model (SIAM). This is sufficiently versatile that a wide range of scenarios can be simulated, and meaningful statistics for expected submarine performance obtained. Emphasis is placed on the modelling of both the dynamic tactical situations that can evolve in underwater warfare and the tactical decision-making that influences the outcome of submarine operations. Although the techniques have been applied to a specific domain it is believed that they are applicable to a wide range of complex problems.     

Space-Time Transfer Function-Noise Modelling of Rainfall-Runoff Process

An explanatory model class belonging to the family of Space-Time Transfer Function-Noise (STTFN) process is presented. The paper develops a three-stage iterative procedure for building STTFN models of the rainfall-runoff process. Four precipitation and runoff stations located in a watershed in southern Ontario, Canada, sampled at 15-day intervals are used for the numerical analysis. Three STTF models are identified. The model parameters are estimated by the polytope technique, a nonlinear optimization algorithm. Two of the developed space-time models proved adequate in describing the spatio-temporal characteristics of precipitation and runoff time series.