Graham W Griffiths | City, University of London (original) (raw)

Uploads

Books by Graham W Griffiths

Conference: Proceedings of the ISA Conference and Exhibit At: St. Louis, Missouri, Mar 1981

A procedure is given for designing multivariab1e control systems in the direct Nyquist plane usin... more A procedure is given for designing multivariab1e control systems in the direct Nyquist plane using the principle of diagonal dominance. It is shown that Bode techniques can be extended to the mu1tivariab1e case and that dominance can be verified by using straight line approximations to the frequency response. In addition, Rosenbrock's idea of using the union of Gershgorin discs for stability assessment is extended to the Bode diagram where Gershgorin gain and phase bands are used. The methods proposed enable mu1tivariab1e control systems of moderate size to be designed using pencil and paper techniques without the assistance of expensive, computer-driven, interactive graphic displays. Finally, a design example is given.

Cambridge University Press, 2016

This book presents some of the latest numerical solutions to initial value problems and boundary ... more This book presents some of the latest numerical solutions to initial value problems and boundary value problems described by ODEs and PDEs. The author offers practical methods that can be adapted to solve a wide range of problems which are illustrated in the increasingly popular open source computer language R, which allows integration with more statistically based methods.

The book begins with standard techniques, followed by an overview of high resolution 'flux limiter' and 'weighted essentially non-oscillatory' (WENO) methods to solve problems with solutions exhibiting high gradient phenomena. Meshless methods using radial basis functions (RBFs) are then discussed in the context of scattered data interpolation and the solution of PDEs on irregular grids.

Three detailed case studies demonstrate how numerical methods can be used to tackle very different complex problems. With its focus on practical solutions to real-world problems, this book will be useful to students and practitioners in all areas of science and engineering, especially those using R.

Practical solutions to ODEs and PDEs using computer code
Overviews of 'high resolution' schemes and meshless methods
Case studies illustrating the use of real-world numerical analysis
Table of Contents

. ODE integration methods
. Stability analysis of ODE integrators
. Numerical solution of PDEs
. PDE stability analysis
. Dissipation and dispersion
. High resolution schemes
. Meshless methods
. Conservation laws
. Case study: analysis of golf ball flight
. Case study: Taylor–Sedov blast wave
. Case study: the carbon cycle.

All computer code is available for download from:

www.pdecomp.net

World Scientific Pub Co Inc , 2015

The increasing concentration of atmospheric CO2 is now a problem of global concern. Although the ... more The increasing concentration of atmospheric CO2 is now a problem of global concern. Although the consequences of atmospheric CO2 are still evolving, there is compelling evidence that the global environmental system is undergoing profound changes as seen in the recent spike of phenomena: extreme heat waves, droughts, wildfires, melting glaciers, and rising sea levels. These global problems directly resulting from elevated atmospheric CO2, will last for the foreseeable future, and will ultimately affect everyone.

The CO2 problem is generally not well understood quantitatively by a general audience; for example, in respect of the increasing rate of CO2 emissions, and the movement of carbon to other parts of Earth's environmental system, particularly the oceans with accompanying acidification. This book therefore presents an introductory global CO2 mathematical model that gives some key numbers — for example, atmospheric CO2 concentration in ppm and ocean pH as a function of time for the calendar years 1850 (preindustrial) to 2100 (a modest projection into the future). The model is based on seven ordinary differential equations (ODEs), and is intended as an introduction to some basic concepts and a starting point for more detailed study.

Quantitative insights into the CO2 problem are provided by the model and can be executed, with postulated changes to parameters, by a modest computer. As basic calculus is the only required mathematical background, this model is accessible to high school students as well as beginning college and university students. The programming of the model is in Matlab and R, two basic, widely used scientific programming systems that are generally accessible and usable worldwide. This book can therefore also be useful to readers interested in Matlab and/or R programming, or a translation of one to the change.

Academic Press, 2011

Partial differential equations (PDEs) have been developed and used in science and engineer- ing f... more Partial differential equations (PDEs) have been developed and used in science and engineer- ing for more than 200 years, yet they remain a very active area of research because of both their role in mathematics and their application to virtually all areas of science and engineer- ing. This research has been spurred by the relatively recent development of computer solution methods for PDEs. These have extended PDE applications such that we can now quantify broad areas of physical, chemical, and biological phenomena. The current development ofPDE solution methods is an active area of research that has benefited greatly fromadvances in com- puter hardware and software, and the growing interest in addressing PDE models of increasing complexity. ...

Cambridge University Press, 2009

A Compendium of Partial Differential Equation Models presents numerical methods and associated co... more A Compendium of Partial Differential Equation Models presents numerical methods and associated computer codes in Matlab for the solu- tion of a spectrum of models expressed as partial differential equations (PDEs), one of the most widely used forms of mathematics in science and engineering. The authors focus on the method of lines (MOL), a well- established numerical procedure for all major classes of PDEs in which the boundary-value partial derivatives are approximated algebraically by finite differences. This reduces the PDEs to ordinary differential equa- tions (ODEs) and thus makes the computer code easy to understand, im- plement, and modify. Also, the ODEs (via MOL) can be combined with any other ODEs that are part of the model (so that MOL naturally ac- commodates ODE/PDE models). ...

Dynamic process simulation differs from purely steady-state simulation in that the former require... more Dynamic process simulation differs from purely steady-state simulation in that the former requires the mechanical construction of process items be taken into account; the amount of mechanical detail being dependant upon the particular application. The reason for this is that dynamic mass, energy and momentum balances have to be continuously updated. These calculations are fundamental to dynamic process simulation and they require knowledge of volumes, metal mass, etc., to predict the proper dynamic behaviour of a particular plant. ...

Papers by Graham W Griffiths

Prior to the rliddle East war, 'state of the art' low pressure methanol plants operated w... more Prior to the rliddle East war, 'state of the art' low pressure methanol plants operated with an energy consumption of about 34 million BTU plus 55 kWh per ton of methanol product. Today's plants consume less than 27 million BTU per ton whilst at the same time providing all their own electrical power requirements. This paper describes the sequence of process design improvements that led to these significant savings. Davy r'1cKee maintains an ongoing research program, and recent process improvements which are still under develo~ent are outlined. In part icular, the paper presents Davy r1cKee' s version of the next generation of synthesis reactor. The paper also examines the economic justification of the energy saving steps. To complement advances in process design, new control strategies are being developed which enable the latest microprocessor-based systems to play their part in energy conservation. Advanced control is discussed in this context using multi vari...

Cambridge University Press eBooks, Dec 24, 2009