SwePub - sökning: WFRF:(WINGES JOHAN 1987)

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1.	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.
2.	Nohlert, Johan, 1987, et al. (författare) Global monitoring of fluidized-bed processes by means of microwave cavity resonances 2014 Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 55, s. 520-535 Tidskriftsartikel (refereegranskat)abstract We present an electromagnetic measurement system for monitoring of the effective permittivity in closed metal vessels, which are commonly used in the process industry. The measurement system exploits the process vessel as a microwave cavity resonator and the relative change in its complex resonance frequencies is related to the complex effective permittivity inside the vessel. Also, thermal expansion of the process vessel is taken into account and we compensate for its influence on the resonance frequencies by means of a priori information derived from a set of temperature measurements. The sensitivities, that relate the process state to the measured resonance frequencies, are computed by means of a detailed finite element model. The usefulness of the proposed measurement system is successfully demonstrated for a pharmaceutical fluidized-bed process, where the water and solid contents inside the process vessel is of interest.
3.	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.
4.	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.
5.	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.
6.	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.
7.	Hamnerius, Yngve, 1950, et al. (författare) Design of Safe Wireless Power Transfer Systems for Electric Vehicles 2018 Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018. - 9789082598735 Konferensbidrag (refereegranskat)abstract Wireless charging of electric vehicles is convenient but in order to make it safe the exposure of humans to electromagnetic fields must be below acceptable limits. We have designed a prototype system that transmits 3 kW with an efficiency of 85% where the magnetic fields around and inside the vehicle are below the EU council recommendation of 6.25μT at 85 kHz.
8.	WINGES, JOHAN, 1987, et al. (författare) A Microwave Measurement System for Measurement of Dielectric Properties 2014 Ingår i: AntennEMB, 11-12 March, Göteborg. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract We present a prototype of a microwave measurement system for the estimation of dispersive dielectric properties. The measurement system consists of a metal cavity that features a measurement region in the center formed by the intersection of six rectangular waveguides. The waveguides are terminated by adapters connected to coaxial cables. We exploit the frequency band 2.7-5.1 GHz and a connected network analyzer and switch allows for automatic measurements of the 6-by-6 scattering matrix S.We estimate the complex effective permittivity of densely packed MCC (micro-crystalline-cellulose) pellets over frequency for different moisture contents. This material is used in pharmacutical processes.
9.	Winges, Johan, 1987, et al. (författare) Compressed Sensing Applied to Non-Ideal Microwave Measurements in Metal Enclosures 2019 Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. - 9788890701887 Konferensbidrag (refereegranskat)abstract Compressed sensing can make use of a priori information in the sense that its dictionary may be constructed for an expected object of particular size and shape, should the application deal with the detection and positioning of exactly such expected objects. Here, we test such a compressed-sensing approach on measurements that include objects that are foreign to the dictionary. It is found that the compressed-sensing approach shows reasonable performance that degrades gracefully as the measurement region is contaminated by dielectric objects that are foreign to the dictionary, where the degradation also becomes more severe as more dielectric material is present in the measurement region due to mutual interactions not accounted for by the dictionary.
10.	WINGES, JOHAN, 1987, et al. (författare) Compressed Sensing for the Detection and Positioning of Dielectric Objects Inside Metal Enclosures by Means of Microwave Measurements 2018 Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 66:1, s. 462-476 Tidskriftsartikel (refereegranskat)abstract Based on compressed sensing and microwave measurements, we present a procedure for the detection and positioning of dielectric objects inside a metal enclosure, where the number of objects is unknown but assumed to be limited. The formulation features a convex quadratic optimization problem with 1-norm regularization, which allows for rapid detection and positioning given a precomputed dictionary. The dictionary consists of the scattering parameters computed from a single scattering object placed at the grid points of a structured grid that covers the entire measurement region. We test our method experimentally in a microwave measurement system that features a measurement region with a diameter of 11.6 cm. The measurement region is encircled by six aperture antennas, where each aperture is the end-opening of a rectangular waveguide operated from 2.7 to 4.2 GHz. We use acrylic-glass cylinders of radius 5.2 mm as scatterers and find that the compressed sensing method can correctly detect at least up to five scatterers with an average positioning accuracy of 3 mm. In addition, we investigate the performance of the method with respect to scarcity of data, where we omit scattering parameters or frequency points.
11.	WINGES, JOHAN, 1987, et al. (författare) Estimating Scatterer Positions using Sparse Approximation 2016 Ingår i: Swedish Microwave Days, March 15-16, Linköping. ; 2016, s. 120- Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract We present a convex optimization method for a class of inverse scattering problems. The method is based on three steps: (i) compute a database of scattering data for the measurement situations of interest; (ii) find a sparse approximation of a measured response in terms of the database; and (iii) estimate a representative description from the sparse approximation as a weighted average.We use the method to estimate the position of multiple scatters inside a microwave measurement system.
12.	WINGES, JOHAN, 1987, et al. (författare) Higher-order brick-tetrahedron hybrid method for Maxwell's equations in time domain 2016 Ingår i: Journal of Computational Physics. - : Elsevier BV. - 1090-2716 .- 0021-9991. ; 321, s. 698-707 Tidskriftsartikel (refereegranskat)abstract We present a higher-order brick-tetrahedron hybrid method for Maxwell's equations in time domain. Brick-shaped elements are used for large homogeneous parts of the computational domain, where we exploit mass-lumping and explicit time-stepping. In regions with complex geometry, we use an unstructured mesh of tetrahedrons that share an interface with the brick-shaped elements and, at the interface, tangential continuity of the electric field is imposed in the weak sense by means of Nitsche's method. Implicit time-stepping is used for the tetrahedrons together with the interface. For cavity resonators, the hybrid method reproduces the lowest non-zero eigenvalues with correct multiplicity and, for geometries without field singularities from sharp corners or edges, the numerical eigenvalues converge towards the analytical result with an error that is approximately proportional to h^2p, where h is the cell size and p is the polynomial order of the elements. For a rectangular waveguide, a layer of tetrahedrons embedded in a grid of brick-shaped elements yields a low reflection coefficient that scales approximately as h^2p. Finally, we demonstrate hybrid time-stepping for a lossless closed cavity resonator, where the time-domain response is computed for 300,000 time steps without any signs of instabilities.
13.	WINGES, JOHAN, 1987, et al. (författare) Higher-Order Finite Element Solver for Maxwell’s Equations 2014 Ingår i: AntennEMB, 11-12 March, Göteborg. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract We present a finite element formulation equipped with higher-order basis functions for the electric and magnetic field, which are used together to approximate the electromagnetic field in Maxwell’s equations. The first type of basis functions are formulated on hexahedral elements, where mass lumping is feasible for the special case of brick-shaped elements. Our implementation allows for automatic generation of arbitrary order p for the field approximation, where the lowest-order approximation is the linear representation with p = 1. The second type of basis functions are formulated on tetrahedral elements, which allows for meshing of arbitrary geometries. These basis functions are of hierarchical type and are implemented for orders p=1 to 4 for complete order spaces as well as incomplete (gradient reduced) order spaces.We test our basis functions on eigenvalue problems and find that the eigenvalues arei. reproduced with the correct multiplicityii. converge towards the analytical result with an error that is proportional to ℎ^2p where ℎ is the element size
14.	WINGES, JOHAN, 1987, et al. (författare) Higher-order hybrid method for curl-conforming elements on tetrahedrons and bricks 2015 Ingår i: Electromagnetics in Advanced Applications (ICEAA), 2015 International Conference on. - 9781479978069 ; :7-11 Sept. 2015, s. 1016 - 1019 Konferensbidrag (refereegranskat)abstract We present a brick-tetrahedron hybrid finite-element method with higher-order basis functions for solving electromagnetic field problems. For the brick-shaped elements, we use mass lumping for interpolatory basis-functions of incomplete order, which yields a diagonal mass-matrix. Hierarchical basis functions of incomplete and/or complete order are used for the tetrahedral elements. We enforce tangential continuity at the brick-tetrahedron interface in the weak sense. Our hybrid method correctly reproduces the lowest eigenvalues with correct multiplicity for a closed cavity-resonator. For tests in a rectangular waveguide, we demonstrate that the hybrid interface yields a low reflection coefficient.
15.	Winges, Johan, 1987, et al. (författare) Huygens' surface excitation for the finite element method applied to Maxwell's equations – A construction based on Nitsche's method 2023 Ingår i: Journal of Computational Physics. - 1090-2716 .- 0021-9991. ; 488 Tidskriftsartikel (refereegranskat)abstract We present a Huygens' surface for the finite element method applied to Maxwell's equations, where the equivalent electric and magnetic surface currents are incorporated in the weak form by means of Nitsche's method. The proposed method preserves the reciprocity of Maxwell's equations and it allows for the computation of the total field inside the Huygens' surface, whereas on its outside only the scattered field is computed. The equivalent magnetic surface current at the Huygens' surface requires a double representation of the discontinuous tangential component of the electric field and we demonstrate that it can be efficiently combined with a previously presented higher-order brick-tetrahedron hybridization. Also, it is demonstrated that the near-to-far-field transformation can be evaluated in an accurate manner if collocated with the Huygens' surface, which allows for a compact computational domain and a reduction in the required computational resources. The proposed Huygens' surface is tested on two scattering problems with perfect electric conductor scatterers: (i) a sphere that demonstrates second-order convergence towards the analytical result for a piecewise linear approximation of the electric field; and (ii) a double ogive with two sharp tips which gives a computed monostatic radar cross section that compares well with measurements and computations in the open literature for both polarizations.
16.	WINGES, JOHAN, 1987 (författare) Inverse and optimization problems in electromagnetics -- a finite-element method perspective 2016 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract In this thesis, a selection of inverse and optimization problems are studied where the finite element method (FEM) serves as a comprehensive tool to solve electromagnetic field problems that lack an analytic solution. The inverse problems are typically formulated in terms of an optimization problem where the misfit between a measurement and the corresponding result of a computational model is minimized. The optimization problems are solved by a combination of techniques that involve gradient-based methods, stochastic methods and parameter studies.The first contribution of the thesis is a new higher-order hybrid FEM for Maxwell's equations that combines (i) brick-shaped elements for large homogeneous regions with (ii) tetrahedrons for regions where local refinement is necessary. The tangential continuity of the electric field at the interface between the different element types is enforced in the weak sense using Nitsche's method. This yields a flexible and efficient computational method that is free of spurious solutions and features a low dispersion error. We employ a stable implicit-explicit time-stepping scheme using an implicitness parameter associated with the tetrahedrons and the hybrid interface. No late-time instabilities are observed in the solution for computations with up to 300 000 time steps.The second contribution of this thesis deals with four inverse scattering problems: (i) gradient-based estimation of the dielectric properties of moist micro-crystalline cellulose in terms of a Debye model; (ii) detection and positioning of multiple scatterers inside a metal vessel using compressed sensing; (iii) monitoring of the material perturbations in a pharmaceutical process vessel using a linearized model around an operation point that varies with the process state; and (iv) a subspace-based classification method for the detection of intracranial bleedings in a simulated data set. The third contribution of the thesis explores stochastic optimization for an inductive power transfer (IPT) system consisting of four magnetically coupled resonance circuits, which is intended for power transfer distances on the order of the coils' radius. A genetic algorithm is employed to compute the Pareto front that contrast the maximum efficiency and power transfer. Results are presented for both linear and non-linear circuits: (i) a time-harmonic model for magnetically coupled resonance circuits with a resistive load; and (ii) a transient model for an IPT system with square-wave excitation, rectifier, smoothing filter and battery.
17.	WINGES, JOHAN, 1987 (författare) Microwave Measurement Systems for Parameter Estimation and Classification 2014 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Microwave measurement systems are attractive for diagnostics and monitoring purposes in a number of important applications. For example, the strong interaction between microwaves and water make microwaves well-suited for moisture measurements. Moreover, the power used in microwave measurements is often sufficiently low such that the measurement can be classified as non-destructive. As such, microwave measurements systems are appropriate for applications in, for example, biomedical imaging and monitoring of pharmaceutical processes.In this thesis, parameter estimation methods are employed for two microwave measurement systems with application in the pharmaceutical industry. Additionally, we present a numerical study of a simplified microwave measurement system for the localization of intracranial bleedings via classification. In order to achieve good agreement between measured and simulated data, we utilize accurate electromagnetic models by means of the finite element method and calibration methods using a reference case measurement. In addition, we utilize a priori information to mitigate problems associated with parameter ambiguity, where the a priori information may be incorporated by means of regularization. First, we consider a transmission/reflection tomography measurement system. Here, the parameter estimation method involves a goal function that corresponds to the misfit between the measured and simulated scattering data, where a non-linear gradient-based optimization method is used to determine the parameters. The gradients are computed by means of continuum sensitivity expressions based on an adjoint field problem. The tomography system is used to estimate the effective permittivity of densely packed microcrystalline cellulose (MCC) pellets and we find that the estimated permittivity depends on the moisture content of the MCC pellets. Second, we solve a minimization problem for resonance measurements in a pharmaceutical process vessel, which acts as a metal cavity. Here, we estimate parameters using a quadratic minimization problem with a regularization term, which incorporates a priori information provided from other sensors. The physical model is linearized and small perturbations of the resonant frequencies are related to small variations in the permittivity. During operation, the vessel is loaded with MCC pellets that are fluidized and circulated by injection of air, which yields a dilute MCC/air mixture. The measured resonant frequencies are used to estimate the effective complex permittivity of three different sub-regions inside the process vessel as a function of process time.
18.	Winges, Johan, 1987, et al. (författare) Multi-objective optimization of wireless power transfer systems with magnetically coupled resonators and nonlinear loads 2019 Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 83:2019, s. 25-42 Tidskriftsartikel (refereegranskat)abstract © 2019 Progress In Electromagnetics Research B. We present an optimization procedure for wireless power transfer (WPT) applications and test it numerically for a WPT system design with four resonant circuits that are magnetically coupled by coaxial coils in air, where the magnetic field problem is represented by a fully populated inductance matrix that includes all magnetic interactions that occur between the coils. The magnetically coupled resonators are fed by a square-wave voltage generator and loaded by a rectifier followed by a smoothing filter and a battery. We compute Pareto fronts associated with a multi-objective optimization problem that contrasts: 1) the system efficiency; and 2) the power delivered to the battery. The optimization problem is constrained in terms of: 1) the physical construction of the system and its components; 2) the root-mean-square values of the currents and voltages in the circuit; and 3) bounds on the overtones of the currents in the coils in order assure that the WPT system mainly generates magnetic fields at the operating frequency. We present optimized results for transfer distances from 0.8 to 1.6 times the largest coil radius with a maximum power transfer from 4 kW to 9 kW at 85 kHz, which is achieved at an efficiency larger than 90%.
19.	WINGES, JOHAN, 1987, et al. (författare) System Identification and Tuning of Wireless Power Transfer Systems with Multiple Magnetically Coupled Resonators 2018 Ingår i: Transactions on Environment and Electrical Engineering. - : EEEIC International Publishing. - 2450-5730. ; 2:2, s. 86-92 Tidskriftsartikel (refereegranskat)abstract We present a procedure for system identification and tuning of a wireless power transfer (WPT) system with four magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductance and losses of the coils. This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3 kW power transfer with 91 % system efficiency over an air-gap distance of approximately 20 cm.
20.	WINGES, JOHAN, 1987, et al. (författare) System Identification and Tuning of WPT Systems 2017 Ingår i: 2017 IEEE 17th International Conference on Environment and Electrical Engineering (EEEIC). Konferensbidrag (refereegranskat)abstract We present a procedure for system identificationand tuning of a wireless power transfer (WPT) system withfour magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductances and losses of the coils.This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3 kW power transfer with 91% system efficiency over an air-gap distance of approximately 20 cm.
21.	Yu, Yinan, 1985, et al. (författare) Model reduction for inverse scattering problems 2012 Ingår i: AntennEMB, 5-8 March, Stockholm. Konferensbidrag (övrigt vetenskapligt/konstnärligt)

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