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  • 101.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM. Lund University.
    Gustafsson, Mats
    Lund University.
    Sjödén, Therese
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Soldovieri, Francesco
    National Research Council, Italy.
    Data fusion for electromagnetic and electrical resistive tomography based on maximum likelihood2011Ingår i: International Journal of Geophysics, ISSN 1687-885X, E-ISSN 1687-8868, Vol. 2011, artikel-id 617089Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a maximum likelihood based approach to data fusion for electromagnetic (EM) and electrical resistive (ER) tomography. The statistical maximum likelihood criterion is closely linked to the additive Fisher information measure, and it facilitates an appropriate weighting of the measurement data which can be useful with multiphysics inverse problems. The Fisher information is particularly useful for inverse problems which can be linearized similar to the Born approximation. In this paper, a proper scalar product is defined for the measurements and a truncated Singular Value Decomposition (SVD) based algorithm is devised which combines the measurement data of the two imaging modalities in a way that is optimal in the sense of maximum likelihood. As a multiphysics problem formulation with applications in geophysics, the problem of tunnel detection based on EM and ER tomography is studied in this paper. To illustrate the connection between the Green's functions, the gradients and the Fisher information, two simple and generic forward models are described in detail regarding two-dimensional EM and ER tomography, respectively.

  • 102.
    Nordebo, Sven
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Gustafsson, Mats
    Sohl, Christian
    Kristensson, Gerhard
    On the optimal limitations for scattering of spherical modes2008Ingår i: URSI 19 General Assembly, 2008Konferensbidrag (Refereegranskat)
  • 103.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Gustafsson, Mats
    Soldovieri, Francesco
    Data fusion for reconstruction algorithms via different sensors in geophysical sensing2010Ingår i: European Geosciences Union General Assembly, 2010Konferensbidrag (Refereegranskat)
  • 104.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Gustafsson, Mats
    Soldovieri, Francesco
    Data fusion for reconstruction algorithms via different sensors in geophysical sensing2011Ingår i: Journal of Geophysics and Engineering, ISSN 1742-2132, E-ISSN 1742-2140, Vol. 8, nr 3, s. S54-S60Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Information fusion via multimodal inverse problems and different sensors is addressed using a Fisher information analysis approach. The Fisher information measure is inherently additive, and it facilitates an appropriate weighting of the measurement data that is statistically optimal and can hence be useful with reconstruction algorithms in geophysical sensing. Given that there exists proper knowledge about the sensor noise statistics, correlations and spectral contents, as well as a correct forward model, the Fisher information is a natural measure of information because it is closely linked to the statistical maximum likelihood principle. To illustrate the concept of data correlation based on statistical Fisher information analysis, two simple and generic examples are employed in electrical resistivity and electromagnetic tomography, which are motivated by geophysical applications, such as tunnel detection. The examples demonstrate that a properly weighted data fusion can be of crucial importance for an ill-posed multimodal inverse problem.

  • 105.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Gustafsson, Mats
    Soldovieri, Francesco
    Tunnel detection based on data fusion with radio frequency and electrical resistive tomography2011Ingår i: Geophysical Research Abstracts, 2011, s. 4927-Konferensbidrag (Refereegranskat)
  • 106.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Gustafsson, Stefan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Ioannidis, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Nilsson, Börje
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Toft, Joachim
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    On the generalized Jordan's lemma with applications in waveguide theory2013Ingår i: Proceeding of 2013 URSI International Symposium on Electromagnetic Theory (EMTS): International Conference Center Hiroshima, Hiroshima, Japan, May 20-24, 2013, 2013, s. 1039-1042Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents two variants of a generalized Jordan's lemma with applications in waveguide theory. As a main application is considered an asymptotic analysis for open waveguide structures with circular geometry. In particular, the generalized Jordan's lemma can be used to justify that field components can be calculated as the sum of discrete and non-discrete modes, i.e., as the sum of residues and an integral along the branch-cut defined by the transversal wavenumber of the exterior domain. An explicit example regarding the axial symmetric TM0 modes of a single core transmission line, wire, or optical fibre is included to demonstrate the associated asymptotic behavior for a typical open waveguide structure.

  • 107.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Gustafsson, Stefan
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nilsson, Börje
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Fault localization for HVDC Power Cables2012Konferensbidrag (Refereegranskat)
  • 108.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Gustfsson, Mats
    Lund University.
    Nilsson, Börje
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Sjöberg, Daniel
    Lund University.
    Cylindrical multipole expansion for helical structures2015Ingår i: M3ST (2015) Kalamat, Greece, 30 August-1 September: Book of Abstracts, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 109.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Ioannidis, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Nilsson, Börje
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Reduced volume integral formulations for an open waveguide based on the cylindrical vector wave expansion2013Ingår i: PIERS 2013 Stockholm: Progress in Electromagnetics Research Symposium : Proceedings, Electromagnetics Academy , 2013, s. 633-637Konferensbidrag (Refereegranskat)
    Abstract [en]

    A Fourier representation of the electric field volume integral equation for an open and cylindrically symmetrical waveguide is given in this paper. The waveguide material is assumed to be isotropic, non-magnetic and with an arbitrary radial variation in the relative permittivity. The Fourier representation yields a system of one-dimensional integral equations, one system for each azimuthal index and where the Fourier variable for the longitudinal direction plays the role of a spectral parameter. The integral equation is of the second kind and has a kernel that is generally discontinuous on the diagonal and singular at the origin. In the axial symmetric case, it can readily be shown that the elements of the matrix kernel belong to an L2-space, and hence that the integral operator is compact and the analytic Fredholm theorem is applicable.

  • 110.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Ivanenko, Yevhen
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Periodic Green's dyadics for helical current distributions2015Ingår i: Progress in Electromagnetics Research Symposium (PIERS), Electromagnetics Academy , 2015, s. 1069-Konferensbidrag (Övrigt vetenskapligt)
  • 111.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Kristensson, Gerhard
    Lund University.
    Mirmoosa, Mohammad
    Aalto Univ, Finland.
    Tretyakov, Sergei
    Aalto Univ, Finland.
    Optimal plasmonic multipole resonances of a sphere in lossy media2019Ingår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, nr 5, artikel-id 054301Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fundamental upper bounds are given for the plasmonic multipole absorption and scattering of a rotationally invariant dielectric sphere embedded in a lossy surrounding medium. A specialized Mie theory is developed for this purpose and when combined with the corresponding generalized optical theorem, an optimization problem is obtained which is explicitly solved by straightforward analysis. In particular, the absorption cross section is a concave quadratic form in the related Mie (scattering) parameters and the convex scattering cross section can be maximized by using a Lagrange multiplier constraining the absorption to be non-negative. For the homogeneous sphere, the Weierstrass preparation theorem is used to establish the existence and the uniqueness of the plasmonic singularities and explicit asymptotic expressions are given for the dipole and the quadrupole. It is shown that the optimal passive material for multipole absorption and scattering of a small homogeneous dielectric sphere embedded in a dispersive medium is given approximately as the complex conjugate and the real part of the corresponding pole positions, respectively. Numerical examples are given to illustrate the theory, including a comparison with the plasmonic dipole and quadrupole resonances obtained in gold, silver, and aluminum nanospheres based on some specific Brendel-Bormann (BB) dielectric models for these metals. Based on these BB models, it is interesting to note that the metal spheres can be tuned to optimal absorption at a particular size at a particular frequency.

  • 112.
    Nordebo, Sven
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen. elektro.
    Lundbäck, Jonas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen. elektro.
    Biro, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen. matematik.
    Method and device for monitoring a system2008Patent (Övrig (populärvetenskap, debatt, mm))
  • 113.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Mirmoosa, Mohammad
    Aalto Univ, Finland.
    Tretyakov, Sergei
    Aalto Univ, Finland.
    On the quasistatic optimal plasmonic resonances in lossy media2019Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, nr 10, s. 1-11, artikel-id 103105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper discusses and analyzes the quasistatic optimal plasmonic dipole resonance of a small dielectric particle embedded in a lossy surrounding medium. The optimal resonance at any given frequency is defined by the complex valued dielectric constant that maximizes the absorption of the particle under the quasistatic approximation and a passivity constraint. In particular, for an ellipsoid aligned along the exciting field, the optimal material property is given by the complex conjugate of the pole position associated with the polarizability of the particle. In this paper, we employ the classical Mie theory to analyze this approximation for spherical particles in a lossy surrounding medium. It turns out that the quasistatic optimal plasmonic resonance is valid, provided that the electrical size of the particle is sufficiently small at the same time as the external losses are sufficiently large. Hence, it is important to note that this approximation cannot be used for a lossless medium, and which is also obvious, since the quasistatic optimal dipole absorption becomes unbounded for this case. Moreover, it turns out that the optimal normalized absorption cross sectional area of the small dielectric sphere has a very subtle limiting behavior and is, in fact, unbounded even in full dynamics when both the electrical size and the exterior losses tend to zero at the same time. A detailed analysis is carried out to assess the validity of the quasistatic estimation of the optimal resonance, and numerical examples are included to illustrate the asymptotic results.

  • 114.
    Nordebo, Sven
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Mohammed, Abbas
    A Semidefinite Programming Approach to Spatial Decorrelation of Independently Polarized Signals2007Ingår i: Wireless Communications & Mobile Computing Journal, Vol. 7, nr 1, s. 91-101Artikel i tidskrift (Refereegranskat)
  • 115.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nilsson, Börje
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Biro, Thomas
    Cinar, Gökhan
    Gustafsson, Mats
    Gustafsson, Stefan
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Karlsson, Anders
    Sjöberg, Mats
    Wave modeling and fault localization for underwater power cables2011Ingår i: 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC), IEEE Press, 2011, s. 698-701Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes some preliminary results regarding Time-Domain pulse Reflection (TDR) measurements and modeling performed on the Baltic Cable submarine HVDC link between southern Sweden and northern Germany. The measurements were conducted in collaboration between the Linnaeus University, Lund University, Baltic Cable AB and ABB High Voltage Cables AB, and is part of the research project: “Fundamental wave modeling for signal estimation on lossy transmission lines”. Preliminary results on measurements and modeling are included here, as well as a first numerical study regarding the low-frequency dispersion characteristics of power cables. The numerical study shows that the finite conductivity of the cable lead shield has a great impact on the losses at low frequencies (0-1 kHz), and that the low-frequency asymptotics of the propagation constant is consistent with common propagation models based on the skin-effect.

  • 116.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Nilsson, Börje
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Gustafsson, Stefan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Biro, Thomas
    Cinar, Gökhan
    Gustafsson, Mats
    Karlsson, Anders
    Sjöberg, Mats
    Low-frequency dispersion characteristics of a multilayered coaxial cable2013Ingår i: Journal of Engineering Mathematics, ISSN 0022-0833, E-ISSN 1573-2703, Vol. 83, nr 1, s. 169-184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper provides an exact asymptotic analysis regarding the low-frequency dispersion characteristics of a multilayered coaxial cable. A layer-recursive description of the dispersion function is derived that is well suited for asymptotic analysis. The recursion is based on two well-behaved (meromorphic) subdeterminants defined by a perfectly electrically conducting (PEC) and a perfectly magnetically conducting termination, respectively. For an open waveguide structure, the dispersion function is a combination of two such functions, and there is only one branch point that is related to the exterior domain. It is shown that if there is one isolating layer and a PEC outer shield, then the classical Weierstrass preparation theorem can be used to prove that the low-frequency behavior of the propagation constant is governed by the square root of the complex frequency, and an exact analytical expression for the dominating term of the asymptotic expansion is derived. It is furthermore shown that the same asymptotic expansion is valid to its lowest order even if the outer shield has finite conductivity and there is an infinite exterior region with finite nonzero conductivity. As a practical application of the theory, a high-voltage direct current (HVDC) power cable is analyzed and a numerical solution to the dispersion relation is validated by comparisons with the asymptotic analysis. The comparison reveals that the low-frequency dispersion characteristics of the power cable is very complicated and a first-order asymptotic approximation is valid only at extremely low frequencies (below 1 Hz). It is noted that the only way to come to this conclusion is to actually perform the asymptotic analysis. Hence, for practical modeling purposes, such as with fault localization, an accurate numerical solution to the dispersion relation is necessary and the asymptotic analysis is useful as a validation tool.

  • 117.
    Nordebo, Sven
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nilsson, Börje
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Lindhe, Oscar
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Estimation of Parameters of an Inhomogeneous Dielectric Layer2009Ingår i: Mathematical Modeling of Wave phenomena.: 3rd Conference on Mathematical Modelling of Wave Phenomena, Växjö, Sweden, 9 – 13 June 2008, Melville, New York: American Institute of Physics , 2009, s. 94-103Konferensbidrag (Refereegranskat)
    Abstract [en]

     

    This paper presents a general framework for sensitivity analysis for fewparameter inverse problems using the Fisher information and the Cram´er-Rao bound. In particular, the one-dimensional inverse problem of estimating the dispersive parameters of an inhomogeneous dielectric layer with linear spatial variation is studied. The analysis technique is particularly well-suited for inverse problems using few parameters, and it is anticipated that the framework may be used as a basis for extensive numerical investigations and physical interpretations. The ill-posedness of the inverse problem can be explicitely quantified by using the Fisher information analysis. As an example, the sensitivity analysis is used together with asymptotic theory to show that the inverse problem becomes extremely ill-posed when the linear spatial variation vanishes.

     

  • 118.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Sjödén, Therese
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Gustafsson, Mats
    Lund University.
    Soldovieri, Francesco
    National Research Council.
    Fisher information analysis in electrical impedance tomography2012Ingår i: Geophysical Research Abstract: EGU General Assembly 2012, 2012, s. 2012-3553-1-Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this contribution it is demonstrated how the Cramér-Rao lower bound provides a quantitative analysis of theoptimal accuracy and resolution in inverse imaging, see also Nordebo et al., 2010, 2010b, 2010c. The imagingproblem is characterized by the forward operator and its Jacobian. The Fisher information operator is defined fora deterministic parameter in a real Hilbert space and a stochastic measurement in a finite-dimensional complexHilbert space with Gaussian measure. The connection between the Fisher information and the Singular ValueDecomposition (SVD) based on the Maximum Likelihood (ML) criterion (the ML-based SVD) is established. Itis shown that the eigenspaces of the Fisher information provide a suitable basis to quantify the trade-off betweenthe accuracy and the resolution of the (non-linear) inverse problem. It is also shown that the truncated ML-basedpseudo-inverse is a suitable regularization strategy for a linearized problem, which exploits a sufficient statisticsfor estimation within these subspaces.The statistical-based Cramér-Rao lower bound provides a complement to the deterministic upper bounds and theL-curve techniques that are employed with linearized inversion (Kirsch, 1996; Hansen, 1992, 1998, 2010). To thisend, the Electrical Impedance Tomography (EIT) provides an interesting example where the eigenvalues of theSVD usually do not exhibit a very sharp cut-off, and a trade-off between the accuracy and the resolution may be ofpractical importance. A numerical study of EIT is described, including a statistical analysis of the model errors dueto the linearization. The Fisher information and sensitivity analysis is also used to compare, evaluate, and optimizemeasurement configurations in EIT.

  • 119.
    Nordebo, Sven
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Stumpf, Martin
    Brno Univ Technol, Czech Republic.
    Ivanenko, Yevhen
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    A multi-resolution 4-D FFT approach to parametric boundary integral equations for helical structures2016Ingår i: 2016 URSI International Symposium on Electromagnetic Theory (EMTS), IEEE Press, 2016, s. 218-221Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper gives a report of an ongoing research to develop parametric boundary integral equations for helical structures and their application in the computation of induced currents and losses in three-phase power cables. The proposed technique is formulated in terms of the Electric Field Integral Equation (EFIE) or the Magnetic Field Integral Equation (MFIE) for a penetrable object together with the appropriate periodic Green's functions and a suitable parameterization of the helical structure. A simple and efficient numerical scheme is proposed for the computation of the impedance matrix in the Method of Moments (MoM) which is based on a multi-resolution 4-D FFT computation followed by polynomial extrapolation. Numerical examples are included demonstrating that the singular integrals have almost linear convergence and hence that linear or quadratic extrapolation can be used to yield accurate results.

  • 120. Persson, Per
    et al.
    Nordebo, Sven
    Claesson, Ingvar
    Design of Discrete Coefficient FIR Filters by a Fast Entropy-Directed Deterministic Annealing Algorithm2005Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 53, nr 3, s. 1006-1014Artikel i tidskrift (Refereegranskat)
  • 121.
    Proto, Monica
    et al.
    National Research Council, Italy.
    Bavusi, Massimo
    National Research Council, Italy.
    Bernini, Romeo
    National Research Council, Italy.
    Bigagli, Lorenzo
    National Research Council, Italy.
    Bost, Marie
    Laboratoire central des ponts et chaussées, France.
    Bourquin, Fredreric
    Laboratoire central des ponts et chaussées.
    Cottineau, Louis-Marie
    Laboratoire central des ponts et chaussées.
    Cuomo, Vincenzo
    National Research Council, Italy.
    Della Vecchia, Pietro
    T.D.E. Territorial Data Elaboration S.R.L., Romania.
    Dolce, Mauro
    Dipartimento Protezione Civile, Italy.
    Dumoulin, Jean
    Eppelbaum, Lev
    Fornaro, Gianfranco
    Gustafsson, Mats
    Hugenschmidt, Johannes
    Kaspersen, Peter
    Kim, Hyunwook
    Lapenna, Vincenzo
    Leggio, Mario
    Loperte, Antonio
    Mazzetti, Paolo
    Moroni, Claudio
    Nativi, Stefano
    Nordebo, Sven
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Pacini, Fabrizio
    Palombo, Angelo
    Pascucci, Simone
    Perrone, Angela
    Pignatti, Stefano
    Ponzo, Felice Carlo
    Rizzo, Enzo
    Soldovieri, Francesco
    Taillade, Fedreric
    Transport Infrastructure Surveillance and Monitoring by Electromagnetic Sensing: The ISTIMES Project2010Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 10, nr 12, s. 10620-10639Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ISTIMES project, funded by the European Commission in the frame of a joint Call "ICT and Security" of the Seventh Framework Programme, is presented and preliminary research results are discussed. The main objective of the ISTIMES project is to design, assess and promote an Information and Communication Technologies (ICT)-based system, exploiting distributed and local sensors, for non-destructive electromagnetic monitoring of critical transport infrastructures. The integration of electromagnetic technologies with new ICT information and telecommunications systems enables remotely controlled monitoring and surveillance and real time data imaging of the critical transport infrastructures. The project exploits different non-invasive imaging technologies based on electromagnetic sensing (optic fiber sensors, Synthetic Aperture Radar satellite platform based, hyperspectral spectroscopy, Infrared thermography, Ground Penetrating Radar-, low-frequency geophysical techniques, Ground based systems for displacement monitoring). In this paper, we show the preliminary results arising from the GPR and infrared thermographic measurements carried out on the Musmeci bridge in Potenza, located in a highly seismic area of the Apennine chain (Southern Italy) and representing one of the test beds of the project.

  • 122.
    Seifnaraghi, Nima
    et al.
    Middlesex University, UK.
    Tizzard, Andrew
    Middlesex University, UK.
    de Gelidi, Serena
    Middlesex University, UK.
    Khodadad, Davood
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Van Kaam, Anton
    University of Amsterdam, The Netherlands.
    Frerichs, Inez
    University Medical Centre Schleswig-Holstein, Germany.
    Waldmann, Andreas
    Swisstom AG company, Switzerland.
    Sorantin, Erich
    Medical University of Graz, Austria.
    Tschauner, Sebastian
    Medical University of Graz, Austria.
    Demosthenous, Andreas
    UCL, UK.
    Christofides, Stelios
    Nicosia General Hospital, Cyprus.
    Bayford, Richard
    Middlesex University, UK.
    Estimation of thorax shape for forward modelling in lungs EIT2017Ingår i: Proceedings of the 18th International Conference on Biomedical Applications of Electrical Impedance Tomography / [ed] Alistair Boyle, Ryan Halter, Ethan Murphy & Andy Adler, Hanover, New Hampshire, USA: Thayer School of Engineering at Dartmouth , 2017, s. 58-58Konferensbidrag (Refereegranskat)
    Abstract [en]

    The thorax models for pre-term babies are developed based on the CT scans from new-borns and their effect on image reconstruction is evaluated in comparison with other available models.

  • 123.
    Shiraz, A.
    et al.
    University College London, UK.
    Khodadad, D.
    Örebro University, Sweden.
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Yerworth, R.
    University College London, UK.
    Frerichs, I
    Univ Med Ctr Schleswig Holstein, Germany.
    van Kaam, A.
    Emma Childrens Hosp, Netherlands;Vrije Univ Amsterdam Med Ctr, Netherlands.
    Kallio, M.
    Univ Oulu, Finland.
    Papadouri, T.
    Minist Hlth, Cyprus.
    Bayford, R.
    University College London, UK;Middlesex Univ, UK.
    Demosthenous, A.
    University College London, UK.
    Compressive sensing in electrical impedance tomography for breathing monitoring2019Ingår i: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 40, nr 3, s. 1-9, artikel-id 034010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective: Electrical impedance tomography (EIT) is a functional imaging technique in which cross-sectional images of structures are reconstructed based on boundary trans-impedance measurements. Continuous functional thorax monitoring using EIT has been extensively researched. Increasing the number of electrodes, number of planes and frame rate may improve clinical decision making. Thus, a limiting factor in high temporal resolution, 3D and fast EIT is the handling of the volume of raw impedance data produced for transmission and its subsequent storage. Owing to the periodicity (i.e. sparsity in frequency domain) of breathing and other physiological variations that may be reflected in EIT boundary measurements, data dimensionality may be reduced efficiently at the time of sampling using compressed sensing techniques. This way, a fewer number of samples may be taken. Approach: Measurements using a 32-electrode, 48-frames-per-second EIT system from 30 neonates were post-processed to simulate random demodulation acquisition method on 2000 frames (each consisting of 544 measurements) for compression ratios (CRs) ranging from 2 to 100. Sparse reconstruction was performed by solving the basis pursuit problem using SPGL1 package. The global impedance data (i.e. sum of all 544 measurements in each frame) was used in the subsequent studies. The signal to noise ratio (SNR) for the entire frequency band (0 Hz-24 Hz) and three local frequency bands were analysed. A breath detection algorithm was applied to traces and the subsequent errorrates were calculated while considering the outcome of the algorithm applied to a down-sampled and linearly interpolated version of the traces as the baseline. Main results: SNR degradation was generally proportional with CR. The mean degradation for 0 Hz-8 Hz (of interest for the target physiological variations) was below similar to 15 dB for all CRs. The error-rates in the outcome of the breath detection algorithm in the case of decompressed traces were lower than those associated with the corresponding down-sampled traces for CR >= 25, corresponding to sub-Nyquist rate for breathing frequency. For instance, the mean error-rate associated with CR = 50 was similar to 60% lower than that of the corresponding down-sampled traces. Significance: To the best of our knowledge, no other study has evaluated the applicability of compressive sensing techniques on raw boundary impedance data in EIT. While further research should be directed at optimising the acquisition and decompression techniques for this application, this contribution serves as the baseline for future efforts.

  • 124.
    Sjöberg, Daniel
    et al.
    Lund University.
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Convex optimization for approximations of positive real functions2015Ingår i: Progress in Electromagnetics Research Symposium (PIERS), 2015, s. 85-Konferensbidrag (Övrigt vetenskapligt)
  • 125.
    Sjöberg, Daniel
    et al.
    Lund University, Sweden.
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Gustafsson, Mats
    Lund University, Sweden.
    Convex optimization for optimal realization of material properties2014Ingår i: 2014 International Conference on Electromagnetics in Advanced Applications (ICEAA), 3-8 Aug. 2014, Palm Beach, IEEE Press, 2014, s. 782-785Konferensbidrag (Refereegranskat)
    Abstract [en]

    We show how the best passive approximation to a given target material or structure can be found byconvex optimization. The approach is based on a representation of positive real functions, where some of the parameters can be given physical relevance by comparison to low- and high-frequency asymptotics of the material or structure under study. A number of different optimization problems can be formulated, which generalizes previous approaches using sum rules.

  • 126.
    Sjödén, Therese
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nilsson, Börje
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nordebo, Sven
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Determination of wood parameters using electromagnetic measurements2010Ingår i: 5th International Conference on Inverse Problems, Modeling and Simulation, Antalya, Turkey, 24-29 May, 2010., 2010, s. 70-71Konferensbidrag (Refereegranskat)
  • 127.
    Sjödén, Therese
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nilsson, Börje
    Nordebo, Sven
    Microwave modelling and measurements for early detection of spiral grain in wood2005Ingår i: 14th International  Symposium on Nondestructive Testing of Wood, Eberswalde, Germany, May 2005., 2005Konferensbidrag (Refereegranskat)
  • 128.
    Sjödén, Therese
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nilsson, Börje
    Nordebo, Sven
    Microwave modelling and signal estimation for detection of wood properties2005Ingår i: Radiovetenskaplig konferens RVK, Linköping, Sweden, June 2005., 2005Konferensbidrag (Refereegranskat)
  • 129.
    Sjödén, Therese
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nilsson, Börje
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nordebo, Sven
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Numerical verification of a microwave impedance model for a twisted wooden cylinder2009Ingår i: Mathematical modelling of wave phenomena: 3rd Conference on Mathematical Modelling of Wave Phenomena, Växjö, Sweden, 9 – 13 June 2008, Melville, New York: American Institute of Physics (AIP), 2009, s. 243-252Konferensbidrag (Refereegranskat)
    Abstract [en]

    To determine the grain angle under bark for wooden logs, microwaves are suitable in contrast to a laser system that requires that a part of the bark layer is removed. Such measurements can be used to sort out logs in a sawmill in order to avoid problems in the processing, low quality in finished products and unnecessary costs with sawing, drying and transporting. Since the logs are moving with a high speed, the measurements must be done quickly in real time. To get quick algorithms it has been proposed to model the log with a normal surface impedance rather than as a penetrable cylinder. This paper determines the accuracy in such a modelling by comparing results from the two models in two-dimensions. The comparison is based on measured values of dielectric data for wood. The conclusion is that there exists a region of moisture content, frequency and azimuthal angle for which the relative error is less than 1% for the longitudinal and less than 10% for the tangential component of the electric field, and still lower for a technically interesting narrow angular region. The induced model error in the determination of the grain angle is about 5% which is of the same order or less than the error introduced by measurement noise.

     

  • 130.
    Sjödén, Therese
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nilsson, Börje
    Nordebo, Sven
    Sensitivity analysis for the estimation of twist in logs based on microwave scattering2008Ingår i: Proceedings of Radio Science and Communications & Mathematical Modelling of Wave Phenomena RVK08/MMWP08, Växjö, Sweden, 2008, s. 188-191Konferensbidrag (Övrigt vetenskapligt)
  • 131.
    Sjödén, Therese
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Sensitivity Analysis for Measurement Configuration Evaluation in Electrical Impedance Tomography2015Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Fisher information and sensitivity analysis can be used to compare, evaluate, and optimize measurement configurations. In this paper, an electrical impedance tomography measurement is considered. Four-electrode measurement pairs are applied on a circular, two-dimensional disk. Adjacent and polar current configurations are compared. Adjoint field techniques are used for gradient calculation. Gradient methods, connected to Fisher information and singular value decomposition, are used for the reconstructions. The impact of different noise models is studied. According to the Fisher information analysis, the adjacent current configurations consistently outperforms the polar in the present formulations. The conclusion is verified by numerical reconstructions based on synthetic data.

  • 132.
    Sjödén, Therese
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Nilsson, Börje
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    On the accuracy and resolution in inverse imaging2015Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    This paper provides a quantitative analysis of the optimal accuracy and resolution in inverse imaging based on the Cram ́er-Rao lower bound. The imaging problem is characterized by the forward operator and its Jacobian. The Fisher information operator is defined for a deterministic parameter in a real Hilbert space and a stochastic measurement in a finite-dimensional complex Hilbert space with Gaussian measure. The connection between the Fisher information and the Singular Value Decomposition (SVD) based on the Maximum Likelihood (ML) criterion (the ML-based SVD) is established. It is shown that the eigenspaces of the Fisher information provide a suitable basis to quantify the trade-off between the accuracy and the resolution of the (non-linear) inverse problem. It is also shown that the truncated ML-based pseudo-inverse is a suitable regularization strategy for a linearized problem, which exploits a sufficient statistics for estimation within these subspaces.

    The statistical-based Cram ́er-Rao lower bound provides a complement to the deterministic upper bounds and the L-curve techniques that are employed with linearized inversion. To this end, the Electrical Impedance Tomography (EIT) provides an interesting example where the eigenvalues of the SVD usually do not exhibit a very sharp cut-off, and a trade-off between the accuracy and the resolution may be of practical importance. A numerical study of EIT is described, including a statistical analysis of the model errors due to the linearization.

  • 133.
    Sjödén, Therese
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nordebo, Sven
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nilsson, Börje
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Sensitivity analysis for inverse problems in Electrical Impedance Tomography2012Konferensbidrag (Refereegranskat)
  • 134.
    Sjödén, Therese
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Nordebo, Sven
    Nilsson, Börje
    Wood grain angle estimation in logs with microwave modeling2006Övrigt (Övrigt vetenskapligt)
  • 135.
    Sjödén, Therese
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen. elektro.
    Nordebo, Sven
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen. elektro.
    Nilsson, Börje
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen. matematik.
    Wood Grain Angle Estimation in Logs with Microwave Modeling2006Ingår i: Mathematical Modeling of Wave phenomena: 2nd Conference on Mathematical Modelling of Wave Phenomena, Växjö, Sweden, American Institute of Physics , 2006, s. 278-285Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the detection of the wood grain angle using microwaves in order to avoid twist in finished boards. For such a determination of spiral grain, we exploit the anisotropic dielectric properties of wood affecting the polarization of an electromagnetic field. A cylindrical model is used for calculating the electromagnetic scattering from a wooden log. In the model, the material has anisotropic dielectric properties, and is considered homogeneous. Furthermore, the grain angle is small and modelled without radial dependence.

    Based on the model, we present a measurement strategy using a linearly polarized incident plane wave without z‐dependence, together with sensors placed close to the log. The grain angle can be estimated, also when the effect of the cylindrical geometry is substantial, through a comparison between the measured and the calculated field. No information on the log except its radius is required; the moisture content can, e.g., be unknown. We apply the Cramér Rao Lower Bound, to present error estimates for the determined grain angle as well as for the dielectric parameters.

  • 136. Sohl, Christian
    et al.
    Gustafsson, Mats
    Kristensson, Gerhard
    Nordebo, Sven
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    A general approach for deriving bounds in electromagnetic theory2008Ingår i: URSI 19 General Assembly, 2008Konferensbidrag (Refereegranskat)
  • 137.
    Stumpf, Martin
    et al.
    Brno University of Technology, The Czech Republic.
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Pulsed EM field propagation in cylindrically layered structures2015Ingår i: Progress in Electromagnetics Research Symposium (PIERS), Electromagnetics Academy , 2015, s. 1061-Konferensbidrag (Övrigt vetenskapligt)
  • 138.
    Toft, Joachim
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nilsson, Börje
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nordebo, Sven
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Decompositions of Gelfand-Shilov kernels into kernels of similar class2012Ingår i: Journal of Mathematical Analysis and Applications, ISSN 0022-247X, E-ISSN 1096-0813, Vol. 396, nr 1, s. 315-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We prove that any linear operator with kernel in a Gelfand-Shilov space is a composition of two operators with kernels in the same Gelfand-Shilov space. We also give links on numerical approximations for such compositions. We apply these composition rules to establish Schatten-von Neumann properties for such operators.

  • 139.
    Vakili, Iman
    et al.
    Lund Univ.
    Gustafsson, Mats
    Lund Univ.
    Sjöberg, Daniel
    Lund Univ.
    Seviour, Rebecca
    Lund Univ.
    Nilsson, Martin
    Lund Univ.
    Nordebo, Sven
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Sum Rules for Parallel-Plate Waveguides: Experimental Results and Theory2014Ingår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 62, nr 11, s. 2574-2582Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An experimental approach to investigate the forward scattering sum rule for periodic structures is presented. This approach allows an upper bound on the total cross section integrated over a bandwidth from a simple static problem to be found. Based on energy conservation, the optical theorem is used to construct a relation between the total cross section and the forward scattering of periodic structures as well as single scatterers inside a parallel-plate waveguide. Dynamic measurements are performed using a parallel-plate waveguide and a parallel-plate capacitor is utilized to find the static polarizability. Convex optimization is introduced to identify the total cross section in the dynamic measurements and estimate an optimal lower bound on the polarizability for objects. The results show that the interactions between the electromagnetic field and an object over all wavelengths are given by the static polarizability of the object.

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