Dr Paul Ledger

Dr Paul Ledger

Paul Ledger

 

Associate Professor, College of Engineering

Curriculum Vitae

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Overview

Specialist Subjects: Hp Finite Elements, Computational Electromagnetics, Error estimation, Reduced Order Modelling, Efficient Preconditioning, Inverse problems.

  • PhD Civil and Computational Engineering, Swansea University, 2001
    Thesis: An hp adaptive finite element procedure for electromagnetic scattering problems
  • MSc Computer modelling with finite elements, Swansea University, 1999
    Thesis: Edge elements for waveguide and scattering problems
  • BEng Civil Engineering with Computational Mechanics, Birmingham University 1998
    Thesis: The boundary element solution of water wave problems

Find out more

Research

Programming and development of H(curl) conforming finite element software capable of hp refinement in two and three dimensions.

Further interests in to the development of preconditioners for indefinite linear systems, inverse problems, uncertainty quantification, a-posteriori error estimation schemes, goal orientated adaptivity, reduced order modelling and novel schemes for reducing dispersion in wave propagation problems.

Applications to problems in computational electromagnetics, including scattering computation, eddy current computation, eigenvalue computation and more recently the modelling of biomedical imaging devices.

For further details see:

Computational Electromagnetics

Inverse Problems and Imaging

Selected publications

  • PD Ledger, hp-Finite element discretisation of the electrical impedance tomography problem, Computer Methods in Applied Mechanics and Engineering, 2012, 225-228, [ISSN:00457825], [DOI: 10.1016/j.cma.2012.02.015]
  • PD Ledger, A coupled hp-finite element scheme for the solution of two-dimensional electrostrictive materials, International Journal for Numerical Methods in Engineering, 2012, 91, 11, pp.1158, [ISSN:00295981], [DOI: 10.1002/nme.4308]
  • PD Ledger, hp-Finite element simulation of three-dimensional eddy current problems on multiply connected domains, Computer Methods in Applied Mechanics and Engineering, 2010, 199, 49-52, [ISSN:00457825], [DOI: 10.1016/j.cma.2010.07.010]
  • PD Ledger, An Investigation of a Preconditioner for High-Frequency Maxwell Problems, Electromagnetics, 2010, 30, 1-2, [ISSN:1532-527X], [DOI: 10.1080/02726340903485364]
  • PD Ledger, Frequency-difference MIT imaging of cerebral haemorrhage with a hemispherical coil array: numerical modelling, Physiological Measurement, 2010, 31, 8, [ISSN:1361-6579], [DOI: 10.1088/0967-3334/31/8/S09]
  • PD Ledger, Preconditioners for the indefinite linear system arising from thehpdiscretization of Maxwell's equations, Communications in Numerical Methods in Engineering, 2009, [DOI: 10.1002/cnm.1131]
  • PD Ledger, Imaging cerebral haemorrhage with magnetic induction tomography: numerical modelling, Physiological Measurement, 2009, [DOI: 10.1088/0967-3334/30/6/S13]
  • PD Ledger, Forward modelling of magnetic induction tomography: a sensitivity study for detecting haemorrhagic cerebral stroke, Medical & Biological Engineering & Computing, 2009, 47, 12, pp.1301, [ISSN:0140-01181741-0444], [DOI: 10.1007/s11517-009-0541-1]
  • PD Ledger, An Adjoint Enhanced Reduced-Order Model for Monostatic RCS Computation, Electromagnetics, 2008, [DOI: 10.1080/02726340701818063]
  • PD Ledger, Computation of resonant modes for axisymmetric Maxwell cavities using hp-version edge finite elements, 2005, pp.1652-1676, [ISBN:0029-5981], [DOI: 10.1002/nme.1241]
  • PD Ledger, Parameterised electromagnetic scattering solutions for a range of incident wave angles, 2004, pp.3587-3605, [ISBN:0045-7825], [DOI: 10.1016/j.cma.2004.01.032]

Teaching

  • EG-396 - Computational Aerodynamics (13/14)
  • EG-M67 - Computational Electromagnetics (13/14)
  • EG-189 - Engineering Analysis 1 (13/14)

Research theses supervised

PhD

  • 2011 - Simulation of coupled electro-mechanical-fluid problems using hp-finite elements (2nd Supervisor: Dr Antonio Gil)
  • 2009 - 'Characterisation of Defects in Steel Plates from MFL Signals using Inverse Finite Element Modelling' (2nd Supervisor: Dr John Mason)
  • 2008 - Magnetic induction tomography for imaging cerebral stroke (2nd Supervisor: Professor Huw Griffiths)

MPhil

  • 2011 - Computational simulation of magneto-mechanical effects (2nd Supervisor: Dr Antonio Gil)
  • 2008 - Magnetic induction tomography for imaging cerebral stroke (2nd Supervisor: Professor Huw Griffiths)

MSc

  • 2010 - 'Error Estimation and Adaptivity in Engineering Simulation'
  • 2009 - Coupled Finite Element Simulation of Electrostrictive Fluids (2nd Supervisor: Dr Antonio Gil)
  • 2008 - Simulaton of coupled Electrostatic mechanical behavior with the finite element method (2nd Supervisor: Dr Antonio Gil)

Additional information

Invited presentations

  • Characterising the shape and material properties of hidden targets from magnetic induction data, Applied Mathematics Colloquim, Cardiff University, February 2014.
  • Characterising the shape and material properties of hidden targets from magnetic induction data, Inverse Problems Seminar Series, The University of Manchester, December 2013.
  • Application of hp finite elements to the accurate computation of polarisation tensors for the eddy current problem, Applied Inverse Problems Conference, Daejeon South Korea, July 2013.
  • Application of hp finite elements to the accurate computation of polarisation tensors for the eddy current problem, MAFELAP Conference, Brunel University, June 2013.
  • An application of hp adaptivity to electrical impedance tomography and some application of hp-FEM to coupled problems, ECCOMAS Congress, Vienna, Austria 2012.
  • Application of high order finite elements to the electrical impedance tomography (EIT) inverse problem, AT-CEM, Glasgow 2011.
  • An hp finite element approach to electro-mechanical problems: electrostriction, ECCM Conference, Paris, France, 2010.
  • Eddy current simulations: Medical applications and efficient computation, Graz University of Technology, Austria, September 2009.
  • Efficient preconditioning for high order edge elements applied to wave propagation and eddy current problems, MAFELAP Conference, Brunel University, June 2009.
  • Eddy current simulations: Medical applications and efficient computation, Fallstuduim ETH Zurich, Switzerland, April 2009.
  • Higher order finite elements for electromagnetics, Department of Mathematics Colloquium, University of Reading, UK, March 2009.
  • Finite elements in electromagnetics: subtleties in discretisation. Computer Science Colloquium, Cardiff University, UK, February 2009.
  • Higher order finite elements in electromagnetics, Applied/Computational Mathematics Colloquium, Graz University of Technology, Graz, Austria, August 2008.
  • A preconditioner for indefinite linear systems arising from H(curl) discretisations, The 9th International Workshop on Finite Elements for Microwave Engineering, Bonn, Germany, May 2008.
  • Adjoint enhanced reduced order model for rapid computation of outputs of interest, The 9th International Workshop on Finite Elements for Microwave Engineering, Bonn, Germany, May 2008.
  • Finite elements in electromagnetics: subtlties in discretisation, Applied Mathematics Colloquium, Johannes Kepler University, Linz, Austria, December 2007.
  • A comparison of solution techniques for linear systems for H(curl) problems, US National Congress on Computational Mechanics, July 2007.
  • Recent developments in hp finite elements for problems in electromagnetics. School of Mathematics Colloquium, University of Nottingham, February 2007.
  • Recipes for overcoming the numerical dispersion associated with finite element discretisation of electromagnetic scattering problems. Dept. Mathematics Colloquium, University of Basel, December 2004.
  • Calculation of Maxwell eigenvalues using H(curl) conforming hp version finite element method. ICOSAHOM, Brown University, June 2004
    Computation of Maxwell eigenvalues with exponential rates of convergence. Olberwolfach meeting on Computational Electromagnetics. February 2004.
  • An hp adaptive procedure for electromagnetic scattering problems. ECCOMAS PhD award presentation. ADMOS Conference Götenburg Sweden, October 2003
  • Three dimensional Maxwell eigenvalue computations employing higher order edge elements. MAFELAP, Brunel University June 2003.

 

Academic prizes

  • Winner of the 2002 ECCOMAS PhD award for the best PhD thesis in 2002 on Computational Methods in Applied Science and Engineering awarded in Sweden, October 2003.
  • Winner of the 2002 ACME Phd award for the best UK PhD thesis in 2002 on Computational Mechanics.
  • Finalist for the 2002 Melosh Medal.
  • Awarded fellowship to attend the first M.I.T. Conference on Fluid and Solid Mechanics, June 2001.
  • Winner of the Tom Essay Prize in water engineering from the University of Birmingham, July 1998.
  • Winner of the Whittaker Ellis Bullock Prize from the University of Birmingham, July 1996.

All publications

  • D. Jin, P.D. Ledger and A.J. Gil, An hp framework for the simulation of electro/magnetostrictive materials, Computers & Structures, 2014; 133: 131-148.
  • R. Priewald, C. Magele, P.D. Ledger, N.R. Pearson and J.S.D. Mason, Fast magnetic flux leakage inversion for the reconstruction of arbitary defect profiles in steel using finite elements. IEEE Transactions on Magnetics, 2013; 49: 506-516.
  • A.J. Gil and P.D. Ledger. A coupled hp finite element scheme for the solution of two dimensional electrostriction materials. International Journal for Numerical Methods in Engineering, 2012; 91: 1158-1183.
  • P.D. Ledger.  hp-Finite element discretisation of the electrical impedance tomography problem, Computer Methods in Applied Mechanics and Engineering, 2012; 225-228: 154-176.
  • P.D. Ledger and S. Zaglmayr.  hp-Finite element simulation of three-dimensional eddy current problems on multiply connected domains. Computer Methods in Applied Mechanics and Engineering, 2010; 199: 3386-3401.
  • P.D. Ledger. An investigation of a preconditioner for high frequency Maxwell problems. Electromagnetics, 2010; 30: 94-126.
  • M. Zolgharni, P.D. Ledger and H. Griffiths. Frequency difference MIT imaging of cerebral haemorrhage with a hemispherical coil array: numerical modelling, Physiological Measurement, 2010; 31: 111-125.
  • M. Zolgharni, P.D. Ledger and H. Griffiths. Forward modelling for magnetic induction tomography for cerebral stroke. Medical & Biological Engineering & Computing, 2009; 47: 1301-1313.
  • M. Zolgharni, P.D. Ledger, D.W. Armitage, H. Griffiths and D.S. Holder. Imaging cerebral haemorrhage with magnetic impedance tomography: numerical modelling, Physiological Measurement, 2009; 30: 187-200.
  • P.D. Ledger. Preconditioners for the indefinite linear system arising from hp discretisation of Maxwell's equations.  Communications in Numerical Methods in Engineering, 2009; 25: 275-289.
  • P.D. Ledger and K. Morgan. An adjoint enhanced reduced order model for monostatic RCS computation. Electromagnetics 2008; 28: 54-76.
  • P.D. Ledger, K. Morgan and O. Hassan. Electromagnetic scattering simulation using an H(curl) conforming hp finite element method in three dimensions. International Journal for Numerical Methods in Fluids 2007; 53: 1267-1296.
  • P.D. Ledger and K. Morgan. The application of the hp finite element method to electromagnetic problems. Archives of Computational Methods in Engineering 2005; 12: 235-302.
  • R. Hiptmair and P.D. Ledger. Computation of resonant modes for axisymmetric cavities using hp version finite elements. International Journal for Numerical Methods in Engineering 2005; 62: 1652-1676.
  • P.D. Ledger, K. Morgan and O. Hassan. Frequency and time domain electromagnetic scattering simulations employing higher order edge elements. Computer Methods in Applied Mechanics and Engineering 2005; 194: 105-125.
  • P.D. Ledger and J. Coyle. Evidence of exponential convergence in computing Maxwell eigenvalues. Computer Methods in Applied Mechanics and Engineering 2005; 194: 587-604.
  • P.D. Ledger J. Peraire, K. Morgan, O. Hassan and N.P. Weatherill. Parametrised electromagnetic scattering solutions for a range of incident wave angles. Computer Methods in Applied Mechanics and Engineering, 2004; 193: 3587-3605.
  • M. Ainsworth, J Coyle, P.D. Ledger and K. Morgan. Computation of Maxwell eigenvalues using higher order edge elements in three dimensions. IEEE Transactions on Magnetics, 2003; 39: 2149-2153.
  • P.D. Ledger, K. Morgan, J. Peraire, O. Hassan and N.P. Weatherill. The development of an hp-adaptive finite element procedure for electromagnetic scattering problems. Finite Element Analysis and Design, 2003; 39: 751-764.
  • P.D. Ledger, K. Morgan, O. Hassan and N.P. Weatherill. Plane wave H(curl) conforming finite elements for Maxwell's equations. Computational Mechanics, 2003; 31: 272-283.
  • P.D. Ledger, J. Peraire, K. Morgan, O. Hassan and N.P. Weatherill. Adaptive hp-finite element computations of the  scattering width output of Maxwell's equations. International Journal of Numerical Methods in Fluids, 2003;  43: 953-978.
  • P.D. Ledger, K. Morgan, O. Hassan and N.P. Weatherill.  Arbitrary order edge elements for electromagnetic scattering problems using hybrid meshes and a PML. International Journal of Numerical Methods in Engineering, 2002; 55: 339--358.

Funding awards

  • EPSRC Small Mathematics Grant on Maxwell Generalised Polarisation Tensors. March 2013, Joint with Professor Lionheart, University of Manchester (£27K).
  • EPSRC Project on Inverse Maxwell Problems for Magnetic Induction Tomography. February 2013, Joint with Professors Brown, Marletta and Walker, Cardiff University (£240K (Swansea), £500K (Cardiff)).
  • EPSRC Bridging the Gaps Project on coupled electro-mechanical simulations using hp-FEM for Geophysical Applications. March 2012. (£3K).
  • HESTEM project funding Swansea University's College of Engineering Mathematics Support Service in 2011-2012. July 2011. (£7K).
  • Swansea University small teaching grant for the use of Tablet PC's in engineering mathematics lectures. August 2011.  (£500).
  • Royal Society travel grant (France). November 2009.  (£1.5K).
  • Royal Society travel grant (Austria).  February 2008.  (£1K).
  • Royal Academy of Engineering conference grant (Germany). March 2008.  (£300).
  • Royal Society conference grant (US).  December 2006.  (£1.1K).