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Efficient computation of magnetic polarizability tensor spectral signatures for object characterisation in metal detection (2024)
Journal Article
Elgy, J., & Ledger, P. D. (in press). Efficient computation of magnetic polarizability tensor spectral signatures for object characterisation in metal detection. Engineering Computations, https://doi.org/10.1108/ec-04-2024-0343

Purpose
Magnetic polarizability tensors (MPTs) provide an economical characterisation of conducting magnetic metallic objects and their spectral signature can aid in the solution of metal detection inverse problems, such as scrap metal sorting, sear... Read More about Efficient computation of magnetic polarizability tensor spectral signatures for object characterisation in metal detection.

Computations and Measurements of the Magnetic Polarizability Tensor Characterisation of Highly Conducting and Magnetic Objects (2023)
Journal Article
Elgy, J., Ledger, P. D., Davidson, J. L., Özdeger, T., & Peyton, A. J. (2023). Computations and Measurements of the Magnetic Polarizability Tensor Characterisation of Highly Conducting and Magnetic Objects. Engineering Computations, 40(7/8), 1778-1806. https://doi.org/10.1108/EC-11-2022-0688

Purpose
The ability to characterise highly conducting objects, that may also be highly magnetic, by the complex symmetric rank–2 magnetic polarizability tensor (MPT) is important for metal detection applications including discriminating between thre... Read More about Computations and Measurements of the Magnetic Polarizability Tensor Characterisation of Highly Conducting and Magnetic Objects.

Reduced order modelling using neural networks for predictive modelling of 3d-magneto-mechanical problems with application to magnetic resonance imaging scanners (2023)
Journal Article
Miah, S., Sooriyakanthan, Y., Ledger, P. D., Gil, A. J., & Mallett, M. (2023). Reduced order modelling using neural networks for predictive modelling of 3d-magneto-mechanical problems with application to magnetic resonance imaging scanners. Engineering with Computers, 39(6), 4103-4127. https://doi.org/10.1007/s00366-023-01870-3

The design of magnets for magnetic resonance imaging (MRI) scanners requires the numerical simulation of a coupled magneto-mechanical system where the effects that different material parameters and in-service loading conditions have on both imaging a... Read More about Reduced order modelling using neural networks for predictive modelling of 3d-magneto-mechanical problems with application to magnetic resonance imaging scanners.

Characterising small objects in the regime between the eddy current model and wave propagation (2023)
Journal Article
Ledger, P. D., & Lionheart, W. R. B. (2023). Characterising small objects in the regime between the eddy current model and wave propagation. European Journal of Applied Mathematics, 1-24. https://doi.org/10.1017/S0956792523000207

Being able to characterise objects at low frequencies, but in situations where the modelling error in the eddy current approximation of the Maxwell system becomes large, is important for improving current metal detection technologies. Importantly, th... Read More about Characterising small objects in the regime between the eddy current model and wave propagation.

Measuring the Magnetic Polarizability Tensor of Non-Symmetrical Metallic Objects (2023)
Journal Article
Özdeğer, T., Ozdeger, T., Davidson, J. L., Davidson, J., Ledger, P. D., Conniffe, D., …Peyton, A. (2023). Measuring the Magnetic Polarizability Tensor of Non-Symmetrical Metallic Objects. IEEE Sensors Journal, 23(17), 20027-20036. https://doi.org/10.1109/jsen.2023.3296439

The Magnetic Polarizability Tensor (MPT) is a representative electromagnetic property of a metallic object, which depends on the size, material, shape, and excitation frequency of the object. The MPT can be used to describe the response of metal dete... Read More about Measuring the Magnetic Polarizability Tensor of Non-Symmetrical Metallic Objects.

Reduced order model approaches for predicting the magnetic polarizability tensor for multiple parameters of interest (2023)
Journal Article
Elgy, J., & Ledger, P. D. (2023). Reduced order model approaches for predicting the magnetic polarizability tensor for multiple parameters of interest. Engineering with Computers, 39(6), 4061-4076. https://doi.org/10.1007/s00366-023-01868-x

The design of magnets for magnetic resonance imaging (MRI) scanners requires the numerical simulation of a coupled magneto-mechanical system where the effects that different material parameters and in-service loading conditions have on both imaging a... Read More about Reduced order model approaches for predicting the magnetic polarizability tensor for multiple parameters of interest.

Effect of Scanning Acceleration on the Leakage Signal in Magnetic Flux Leakage Type of Non-destructive Testing (2023)
Journal Article
Zhang, L., Cameron, I., Ledger, P., Belblidia, F., Pearson, N., Charlton, P., & Sienz, J. (2023). Effect of Scanning Acceleration on the Leakage Signal in Magnetic Flux Leakage Type of Non-destructive Testing. Journal of Nondestructive Evaluation, https://doi.org/10.1007/s10921-023-00925-1

This work investigates the influence of acceleration on the leakage signal in magnetic flux leakage type of non-destructive testing. The research is addressed through both designed experiments and simulations. The results showed that the leakage sign... Read More about Effect of Scanning Acceleration on the Leakage Signal in Magnetic Flux Leakage Type of Non-destructive Testing.

Minimal Object Characterisations using Harmonic Generalised Polarizability Tensors and Symmetry Groups (2022)
Journal Article
Ledger, P., & Lionheart, B. (2022). Minimal Object Characterisations using Harmonic Generalised Polarizability Tensors and Symmetry Groups. SIAM Journal on Applied Mathematics, 2057-2079. https://doi.org/10.1137/22M1471547

We introduce a new type of object characterisation, which is capable of accurately describing small iso?lated inclusions for potential field inverse problems such as in electrostatics, magnetostatics and related
low frequency Maxwell problems. Relev... Read More about Minimal Object Characterisations using Harmonic Generalised Polarizability Tensors and Symmetry Groups.

Properties of generalized magnetic polarizability tensors (2022)
Journal Article
Ledger, P., & Lionheart, W. R. B. (2023). Properties of generalized magnetic polarizability tensors. Mathematical Methods in the Applied Sciences, 46(5), 5604-5631. https://doi.org/10.1002/mma.8856

We present new alternative complete asymptotic expansions for the time harmonic low‐frequency magnetic field perturbation caused by the presence of a conducting permeable object as its size tends to zero for the eddy current approximation of the Maxw... Read More about Properties of generalized magnetic polarizability tensors.

Properties of Generalised Magnetic Polarizability Tensors (2022)
Journal Article
Ledger, P., & Lionheart, B. (2022). Properties of Generalised Magnetic Polarizability Tensors. Mathematical Methods in the Applied Sciences, 46(5), 5604-5631. https://doi.org/10.1002/mma.8856

We present new alternative complete asymptotic expansions for the time harmonic low–frequency magnetic field perturbation caused by the presence of a conducting permeable object as its size tends to zero for the eddy current approximation of the Maxw... Read More about Properties of Generalised Magnetic Polarizability Tensors.

Transient changes during microwave ablation simulation : a comparative shape analysis. (2022)
Journal Article
Kernot, D., Yang, J., Williams, N., Thomas, T., Ledger, P., Arora, H., & van Loon, R. (2022). Transient changes during microwave ablation simulation : a comparative shape analysis. Biomechanics and Modeling in Mechanobiology, https://doi.org/10.1007/s10237-022-01646-6

Microwave ablation therapy is a hyperthermic treatment for killing cancerous tumours whereby microwave energy is dispersed into a target tissue region. Modelling can provide a prediction for the outcome of ablation, this paper explores changes in siz... Read More about Transient changes during microwave ablation simulation : a comparative shape analysis..

Benchmark computations for the polarization tensor characterization of small conducting objects (2022)
Journal Article
Amad, A., Ledger, P. D., Betcke, T., & Praetorius, D. (2022). Benchmark computations for the polarization tensor characterization of small conducting objects. Applied Mathematical Modelling, 111, 94-107. https://doi.org/10.1016/j.apm.2022.06.024

The characterisation of small low conducting inclusions in an otherwise uniform background from low-frequency electrical field measurements has important applications in medical imaging using electrical impedance tomography as well as in geological i... Read More about Benchmark computations for the polarization tensor characterization of small conducting objects.

Identification of metallic objects using spectral magnetic polarizability tensor signatures: Object classification (2022)
Journal Article
Wilson, B. A., Ledger, P. D., & Lionheart, W. R. B. (2022). Identification of metallic objects using spectral magnetic polarizability tensor signatures: Object classification. International Journal for Numerical Methods in Engineering, 123(9), 2076-2111. https://doi.org/10.1002/nme.6927

The early detection of terrorist threat objects, such as guns and knives, through improved metal detection, has the potential to reduce the number of attacks and improve public safety and security. To achieve this, there is considerable potential to... Read More about Identification of metallic objects using spectral magnetic polarizability tensor signatures: Object classification.

Measurement of GMPT Coefficients for Improved Object Characterisation in Metal Detection (2021)
Journal Article
Ledger. (2021). Measurement of GMPT Coefficients for Improved Object Characterisation in Metal Detection. IEEE Sensors Journal, 2430-2446. https://doi.org/10.1109/JSEN.2021.3133950

Magnetic polarizability tensors (MPTs) have become popular for characterising conducting permeable objects and assisting with the identification of hidden objects in metal detection for applications in security screening, humanitarian demining and sc... Read More about Measurement of GMPT Coefficients for Improved Object Characterisation in Metal Detection.

Identification of metallic objects using spectral MPT signatures: object characterisation and invariants (2021)
Journal Article
Ledger, P. D., Wilson, B. A., Amad, A. A. S., Amas, A., & Lionheart, W. R. B. (2021). Identification of metallic objects using spectral MPT signatures: object characterisation and invariants. International Journal for Numerical Methods in Engineering, 122(15), 3941-3984. https://doi.org/10.1002/nme.6688

The early detection of terrorist threat objects, such as guns and knives, through improved metal detection, has the potential to reduce the number of attacks and improve public safety and security. To achieve this, there is considerable potential to... Read More about Identification of metallic objects using spectral MPT signatures: object characterisation and invariants.

Efficient Computation of the Magnetic Polarizabiltiy Tensor Spectral Signature using POD (2020)
Journal Article
Wilson, B. A., & Ledger, P. D. (2021). Efficient Computation of the Magnetic Polarizabiltiy Tensor Spectral Signature using POD. International Journal for Numerical Methods in Engineering, 122(8), 1940-1963. https://doi.org/10.1002/nme.6606

The identification of hidden conducting permeable objects from measurements of the perturbed magnetic field taken over a range of low frequencies is important in metal detection. Applications include identifying threat items in security screening at... Read More about Efficient Computation of the Magnetic Polarizabiltiy Tensor Spectral Signature using POD.

A staggered high-dimensional Proper Generalised Decomposition for coupled magneto-mechanical problems with application to MRI scanners (2020)
Journal Article
Barroso, G., Seoane, M., Gil, A., Ledger, P., Mallett, M., & Huerta, A. (2020). A staggered high-dimensional Proper Generalised Decomposition for coupled magneto-mechanical problems with application to MRI scanners. Computer Methods in Applied Mechanics and Engineering, 370, 113271. https://doi.org/10.1016/j.cma.2020.113271

Manufacturing new Magnetic Resonance Imaging (MRI) scanners represents a computational challenge to industry, due to the large variability in material parameters and geometrical configurations that need to be tested during the early design phase. Thi... Read More about A staggered high-dimensional Proper Generalised Decomposition for coupled magneto-mechanical problems with application to MRI scanners.

A combined reduced order‐full order methodology for the solution of 3D magneto‐mechanical problems with application to magnetic resonance imaging scanners (2020)
Journal Article
Seoane, M., Ledger, P. D., Gil, A. J., Zlotnik, S., & Mallett, M. (2020). A combined reduced order‐full order methodology for the solution of 3D magneto‐mechanical problems with application to magnetic resonance imaging scanners. International Journal for Numerical Methods in Engineering, 121(16), 3529-3559. https://doi.org/10.1002/nme.6369

The design of a new magnetic resonance imaging (MRI) scanner requires multiple numerical simulations of the same magneto-mechanical problem for varying model parameters, such as frequency and electric conductivity, in order to ensure that the vibrati... Read More about A combined reduced order‐full order methodology for the solution of 3D magneto‐mechanical problems with application to magnetic resonance imaging scanners.

A regularised-adaptive Proper Generalised Decomposition implementation for coupled magneto-mechanical problems with application to MRI scanners (2019)
Journal Article
Barroso, G., Gil, A. J., Ledger, P. D., Mallett, M., & Huerta, A. (2020). A regularised-adaptive Proper Generalised Decomposition implementation for coupled magneto-mechanical problems with application to MRI scanners. Computer Methods in Applied Mechanics and Engineering, 358, 112640. https://doi.org/10.1016/j.cma.2019.112640

Latest developments in high-strength Magnetic Resonance Imaging (MRI) scanners with in-built high resolution, have dramatically enhanced the ability of clinicians to diagnose tumours and rare illnesses. However, their high-strength transient magnetic... Read More about A regularised-adaptive Proper Generalised Decomposition implementation for coupled magneto-mechanical problems with application to MRI scanners.