Search results for "Continuous"

Automatic regrouping of strata in the goodness-of-fit chi-square test

2019

Pearson’s chi-square test is widely employed in social and health sciences to analyze categorical data and contingency tables. For the test to be valid, the sample size must be large enough to provide a minimum number of expected elements per category. This paper develops functions for regrouping strata automatically no matter where they are located, thus enabling the goodness-of-fit test to be performed within an iterative procedure. The functions are written in Excel VBA (Visual Basic for Applications) and in Mathematica. The usefulness and performance of these functions is illustrated by means of a simulation study and the application to different datasets. Finally, the iterative use of …

Continuous auditing in public sector and central banks: a framework to tackle implementation challenges

2022

Purpose This paper aims to analyse the implementation challenges faced by internal audit departments of public sector organisations and central banks when implementing continuous auditing (CA) systems. CA aims to monitor internal control systems and risk levels on a continuous basis to support the audit process. This study identifies the implementation challenges of CA systems and proposes adequate countermeasures. Design/methodology/approach This study employs the design science information system research and the design science research process methodologies to ensure the rigor of this analysis. These research methodologies are adopted to tackle identified organisational problems and pro…

On the Real-Time Simulation and Control of the Continuous Casting Process

1990

Ll this paper we present a method for controlling in real-time the secondary cooling of the continuous casting machine. The method is based on the heat transfer model, which simulates the temperature distribution of the cast, and on the use of direct digital control (DDC). Off-line simulation results considering the control method is presented.

On the optimal cooling of the steel during continuous casting

2006

On the Control of the Secondary Cooling in the Continuous Casting Process

1987

Continuous casting is today replacing ingot casting as the major process for the production of steel in the form of slabs, blooms, billets etc. The complexity of this process is such that until recently innovations to machine design could only be tested by full scale runs on the production machine. This is extremely costly and in many cases production cannot be delayed for such tests to occur. For offering alternative means of testing new designs, numerical simulation models of the continuous casting process have been developed, especially during the last decade. We refer to conference proceedings [3], [5], [6] [16]. Furthermore we mention articles [4], [9], [13], [23], [24] concerning heat…

Real-time simulation and control system for the continuous casting process

2005

In this paper we present a real-time system which is used to simulate the unsteady-state continuous casting process and to control the secondary cooling water sprays. The aim of the control system is to keep the surface temperature of the slab constant with respect to time in spite of casting speed variations, and in this way minimize the formation of cracks in the final product. The simulator calculates the temperature distribution using a mathematical model based on a heat conduction formula with phase changes. The optimal spray water flow rates for each spray cooling zone will be calculated by minimizing the deviation between the target surface temperature and the calculated actual surfa…

Automatic Secondary Cooling Control for the Continuous Casting Process of Steel

1991

Two simulation models for finding the optimal secondary cooling strategy in continuous casting process are presented. The first one is a two-dimensional off-line model for optimizing steady state casting operation. The second one is a one-dimensional model which can be used for simulating casting operation in real-time during varying casting conditions.

FE-Modelling of Continuous Casting Problem

1986

A mathematical model for simulating the heat transfer during solidification in continuous casting of steel is presented. The heat transfer coefficients along and across the strand are optimized. The evolution and location of thermal stresses are computed. Numerical examples are included.

Nonsmooth Penalty Techniques in Control of the Continuous Casting Process

1991

We introduce a mathematical model which is used to simulate the continuous casting process and to control the secondary cooling water sprays. The main object is to minimize the defects in the final products. The problem is formulated as an optimal control problem where the cost function is constructed according to certain metallurgical criteria and constraints. The temperature distribution of the strand is calculated by solving a nonlinear heat equation with free boundaries between solid and liquid phases.

On Fixed Point (Trial) Methods for Free Boundary Problems

1992

In this note we consider the trial methods for solving steady state free boundary problems. For two test examples (electrochemical machining and continuous casting) we discuss the convergence of a fixed point method. Moreover, using the techniques of shape optimization we introduce a modification of the method, which gives us superlinear convergence rate. This is also confirmed numerically.