| 1. |
|
|
| 2. |
|
|
| 3. |
- Rylander, Thomas, 1972, et al.
(författare)
-
Advances in FEM-FDTD hybrid methods
- 2005
-
Ingår i: Computational Electrodynamics: The Finite-Difference Time-DomaMethod (3rd edition) -- Allen Taflove and Susan C. Hagness.
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 4. |
- Rylander, Thomas, 1972, et al.
(författare)
-
FEM algorithms for Maxwell's equations
- 1998
-
Ingår i: EMB 98 - Electromagnetic Computations for Analysis and Design of Complex Systems.
-
Konferensbidrag (refereegranskat)
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Atalaya, Juan, 1981, et al.
(författare)
-
Design and optimization of coreless components using admittance matrix and efficiently calculated sensitivities
- 2007
-
Ingår i: IEEE Transactions on Magnetics. ; 43, s. 1621-1624
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel technique for designing coreless components (inductors and transformers) based on the admittance matrix at quasi-static approximation. In addition, an optimization method based on continuum sensitivity is applied. Efficiency of the design method is shown for inductors that have axisymmetry and carry azimuthal currents. In order to avoid coupling between closely located inductors, a shielding structure is proposed and shape-optimized to confine the magnetic energy.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Botha, Matthys M, et al.
(författare)
-
An improved quadrature error estimate for nearly-singular MoM integrals
- 2018
-
Ingår i: 2018 IEEE Antennas and Propagation Society International Symposium and USNC/URSI National Radio Science Meeting, APSURSI 2018 - Proceedings. ; , s. 2431-2432
-
Konferensbidrag (refereegranskat)abstract
- A well-known numerical integration scheme for weakly near-singular integrands on triangle domains, is the Radial-Angular-RI-Sqrt near-singularity cancellation transformation quadrature scheme. Such integrals feature routinely in the method of moments (MoM), for integral equation based numerical electromagnetic field calculations. Recently, a closed-form quadrature error estimate has been proposed for this scheme. In this paper, the estimate is further improved, such that its range of applicability is extended.
|
|
| 11. |
- Botha, Matthys M, et al.
(författare)
-
Analysis and estimation of quadrature errors in weakly singular source integrals of the method of moments
- 2018
-
Ingår i: International Journal of Numerical Modelling: Electronic Networks, Devices and Fields. - : Wiley. - 0894-3370 .- 1099-1204. ; 31:1
-
Tidskriftsartikel (refereegranskat)abstract
- The method of moments (MoM) is used for the numerical solution of electromagnetic field integral equations. Weakly singular integrals over surfaces in 3 dimensions (3D) are routinely evaluated for the impedance matrix setup and for post-processing. Available numerical integration schemes range from direct application of Gauss-Legendre product-rule quadrature, to singularity and near-singularity cancellation, coordinate transformation schemes. This paper presents a general, explicit, pole-based, a priori procedure to estimate quadrature errors in the numerical evaluation of weakly singular and near-singular, 3D surface integrals in the MoM. It is based on an error theorem for linear Gaussian quadrature, which involves the analytic extension of the integrand into the complex plane. Errors are linked to poles in the complex plane. New closed-form estimates are presented for direct Gaussian product-rule integration, polar-coordinate integration, and the Radial-Angular-R 1 -Sqrt singularity cancellation scheme, for triangle integration domains. This work can serve as a foundation/template for further, 3D MoM-related work to identify appropriate quadrature schemes according to their error characteristics; for automatic selection of optimal schemes and quadrature orders in a computer implementation of the MoM; and for local and global estimation of MoM quadrature errors. This work can be specialized to the MoM for surfaces in 2D.
|
|
| 12. |
|
|
| 13. |
- Botha, Matthys M, et al.
(författare)
-
Quadrature error estimation for MoM matrix entries
- 2017
-
Ingår i: 19th International Conference on Electromagnetics in Advanced Applications, ICEAA 2017; Verona; Italy; 11 September 2017 through 15 September 2017. - 9781509044511 ; , s. 973-975
-
Konferensbidrag (refereegranskat)abstract
- This paper is concerned with the method of moments (MoM) for electric field integral equation (EFIE) based numerical electromagnetic analysis of conducting surface structures. Inner (source) and outer (testing) integrals are encountered, when evaluating matrix entries. The well-known Radial-Angular-R1-Sqrt (RA-R1-Sqrt) weak near singularity cancellation transformation quadrature scheme for the inner integrals and standard Gaussian numerical integration for the outer integrals, are considered. It is shown that the quadrature error in the matrix entries, due to inner integral evaluation, can be accurately estimated under certain circumstances. A closed-form quadrature error estimate for the RA-R1-Sqrt scheme is employed.
|
|
| 14. |
- Botha, Matthys, 1976, et al.
(författare)
-
Results in quadrature error estimation for weak near-singular MoM integrals
- 2017
-
Ingår i: 2017 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538632840 ; 2017-January, s. 1555-1556
-
Konferensbidrag (refereegranskat)abstract
- In the method of moments (MoM) for integral equation based numerical electromagnetic field calculation, weakly singular and near-singular surface integrals must be routinely evaluated. Applicable numerical integration schemes are standard Gaussian quadrature or specialized singularity cancellation transformation quadrature. When applying numerical integration, an error is incurred. Qualitative knowledge of the error behaviour and quantitative error estimates are valuable to MoM developers in identifying appropriate quadrature schemes and orders, which lead to increased efficiency and reliability of MoM implementations. An accurate, closed-form error estimate is presented for direct Gaussian product-rule quadrature, as well as for the Radial-Angular-R1-Sqrt transformation scheme.
|
|
| 15. |
- Candefjord, Stefan, 1981, et al.
(författare)
-
Microwave technology for detecting traumatic intracranial bleedings: tests on phantom of subdural hematoma and numerical simulations
- 2017
-
Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 1741-0444 .- 0140-0118. ; 55:8, s. 1177-1188
-
Tidskriftsartikel (refereegranskat)abstract
- Traumatic brain injury is the leading cause of death and severe disability for young people and a major public health problem for elderly. Many patients with intracranial bleeding are treated too late, because they initially show no symptoms of severe injury and are not transported to a trauma center. There is a need for a method to detect intracranial bleedings in the prehospital setting. In this study, we investigate whether broadband microwave technology (MWT) in conjunction with a diagnostic algorithm can detect subdural hematoma (SDH). A human cranium phantom and numerical simulations of SDH are used. Four phantoms with SDH 0, 40, 70 and 110 mL are measured with a MWT instrument. The simulated dataset consists of 1500 observations. Classification accuracy is assessed using fivefold cross-validation, and a validation dataset never used for training. The total accuracy is 100 and 82–96 % for phantom measurements and simulated data, respectively. Sensitivity and specificity for bleeding detection were 100 and 96 %, respectively, for the simulated data. SDH of different sizes is differentiated. The classifier requires training dataset size in order of 150 observations per class to achieve high accuracy. We conclude that the results indicate that MWT can detect and estimate the size of SDH. This is promising for developing MWT to be used for prehospital diagnosis of intracranial bleedings.
|
|
| 16. |
- Candefjord, Stefan, 1981, et al.
(författare)
-
Microwave technology for localization of traumatic intracranial bleedings—a numerical simulation study
- 2013
-
Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. - 9781457702167 ; , s. 1948-1951
-
Konferensbidrag (refereegranskat)abstract
- Traumatic brain injury (TBI) is a major public health problem worldwide. Intracranial bleedings represents the most serious complication of TBI and need to be surgically evacuated promptly to save lives and mitigate injury. Microwave technology (MWT) is promising as a complement to computed tomography (CT) to be used in road and air ambulances for early detection of intracranial bleedings. In this study, we perform numerical simulations to investigate if a classification algorithm based on singular value decomposition can distinguish between bleedings at different positions adjacent to the skull bone for a similar but simplified problem. The classification accuracy is 94-100% for all classes, a result that encourages us to pursue our efforts with MWT for more realistic scenarios. This indicates that MWT has potential for localizing a detected bleeding, which would increase the diagnostic value of this technique.
|
|
| 17. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Concurrent estimation of space and frequency variation for dielectrics: a microwave tomography system for process sensing applications
- 2011
-
Ingår i: Proceedings of the 9th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances, Kansas City, MO USA, May 31 - June 3, 2011. - 9781629934556 ; , s. 177-184
-
Konferensbidrag (refereegranskat)abstract
- In many powder processing operations, the effective complex permittivity of the material under processing yields important information concerning the state of the process. This complex permittivity varies in general with respect to both space and frequency. For an accurate estimation of the process material parameters, it is important to be able to incorporate these dependencies in the estimation algorithm. Here, we present a rather general type of parameterization that is tailored for this type of situation. The parameterization is described in terms of a parameterization mesh, which makes it feasible to refine the computational mesh without influencing the number of degrees of freedom in the estimation problem. A test case demonstrates that our approach can yield accurate reconstructions.
|
|
| 18. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Determination of model order for inverse scattering applications
- 2010
-
Ingår i: Proceedings of the V European Conference on Computational Fluid Dynamics ECCOMAS CFD 2010 J. C. F. Pereira, A. Sequeira and J. M. C. Pereira (Eds) Lisbon, Portugal,14-17 June 2010. - 9789899677814
-
Konferensbidrag (refereegranskat)
|
|
| 19. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Inverse scattering for a closed cavity equipped with microwave antenna sensors
- 2012
-
Ingår i: AntennEMB, 5-8 March, Stockholm.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Pharmaceutical processes are often hosted by completely closed vessels that are difficult of access by means of measurement equipment. In particular, it is challenging to assess the interior or global process state with sensors placed on the vessel enclosing the process. This information about the process would allow for a better process monitoring and control. Here, a novel application of microwave sensing for process tomography is presented.
|
|
| 20. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Microwave measurement system for dispersive dielectric properties of densely packed pellets
- 2017
-
Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 106, s. 179-189
-
Tidskriftsartikel (refereegranskat)abstract
- We present a microwave measurement system that is intended for the estimation of the dispersive dielectric properties for densely packed pellets. In particular, we estimate the Debye parameters for the effective permittivity of a mixture of air and densely packed moist microcrystalline cellulose pellets for the frequency band 2.7–5.1 GHz. The Debye parameters are estimated by means of minimizing the misfit between the measured scattering parameters and the corresponding computed response given a model of the measurement system. This minimization is performed by means of a nonlinear iterative optimization procedure, which is supported by continuum sensitivities, and the optimum is found in 10–60 iterations for the cases presented in this article. We find that increasing moisture content yields an increase in the static permittivity and a decrease in the relaxation time.
|
|
| 21. |
- Cerullo, Livia, 1982, et al.
(författare)
-
Microwave Measurements for Metal Vessels
- 2013
-
Ingår i: 7th European Conference on Antennas and Propagation, EuCAP 2013, Gothenburg, Sweden, 8-12 April 2013. - 2164-3342. - 9781467321877 ; , s. 3869 - 3873
-
Konferensbidrag (refereegranskat)abstract
- We present two different measurement techniques intended for closed metal vessels, where the objective is to measure the permittivity inside the metal vessel. This problem is relevant for many applications found in e.g. process industry. The first approach exploits the measurement of resonance frequencies, where the metal vessel is used as a microwave resonator. In the second approach, we let the boundary of the metal vessel be equipped with aperture antennas, where the aperture antennas are implemented in terms of rectangular waveguides. The waveguide apertures loads the cavity significantly and we exploit the scattering matrix parameters for the solution of the inverse problem.
|
|
| 22. |
- Christie, Michael, 1946, et al.
(författare)
-
Some issues in online assessment
- 2005
-
Ingår i: IPSI Conference, Pescara, Italy 27-31 July 2005.
-
Konferensbidrag (refereegranskat)
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
- DEGERFELDT, DAVID, 1979, et al.
(författare)
-
A higher-order finite element method with an explicit higher-order time integration scheme
- 2007
-
Ingår i: EMB07 Computational Electromagnetics Methods and Applications, Lund, Sweden, Oct 18-19, 2007. ; , s. 91-98
-
Konferensbidrag (refereegranskat)abstract
- We formulate and analyze a FEM that exploits higher-order approximations of the fields for both space and time. An explicit leap-frog type scheme is used to update Faraday's and Ampére's law, and we present a stability and error analysis for this time-stepping scheme. Our formulation exploits a matrix free representation of Maxwell's equations, which reduces the memory requirementssignificantly. The scheme is tested by solving eigenvalueproblems in a cubic cavity with metal walls. The tests demonstrate that the method yields exponential convergence with respect to spatial order p and polynomial convergence, h2p, with respect to the cell size h. Analogous convergence is achieved for the time-stepping scheme. The method reduces to the standard FDTD method for lowest order of approximation with respect to space and time. The technique presented is useful for computational studies of reverberation chambers and similar applications.
|
|
