Three feeding structures are proposed to feed a TE-polarized Bessel antenna for a rotationally symmetric magnetic field distribution. We first propose a spiral coil and a dual half-loop coil to achieve rotationally symmetric magnetic field, resulting in homogeneous current distribution on the coils. Unfortunately, the magnetic field distribution is very sensitive to the coil size for both structures. An alternative solution using a half-loop coil with mushroom structure is then designed to achieve robustness. Both the simulation and the measurement demonstrate that the proposed feeding structures can generate a rotationally symmetric magnetic field distribution; the proposed spiral coil is simple and efficient, while the half-loop coil with mushroom structure is robust.

In this paper we investigate the possibility of using needles, which the interventional radiologist inserts near a deep-seated tumor during an electroporation-based therapy, to characterize the electrical conductivity of patient's tissues. Specifically, we propose to exploit voltage/current measurements and imaging that are performed prior to the application of electroporation pulses. The approach is partly based on the concepts of electrical impedance tomography; however, imaging is used to build a specific geometric model and compensate for the lack of information resulting from the small number of electrodes available. 3D canonical and clinical examples, where a few electrodes surround a tumor, demonstrate the feasibility of this method: solving the inverse problem to estimate tissues conductivity converges in a few iterations. For a given error on the measurement, it is also possible to calculate the error on the estimated conductivities. The uncertainty error with clinical data is at best 5% for one of the tissues identified, due to the limitations of the clinical device used. Various improvements to clinical devices are discussed to make the conductivity estimation more accurate but also to extract more information.

Floating potentials appear in electrokinetic problems when isolated high conductive materials are included in a dielectric or weakly conductive ambient medium. The large contrast of conductivities generates numerical issues that make hard the computation of the electric potential. The paper proposes a rigorous numerical method to tackle such kind of problems. Interestingly, a correction to the case of perfect conductor is given in order to improve the accuracy of the computation. The method involves a cascade of two elementary problems set respectively in the ambient medium and in the high conductive inclusions. An example is proposed with a 4-electrode system designed to both induce electroporation in a biological tissue sample and measure the resulting impedance. The approach is extended to a nonlinear problem by taking advantage of the iterative scheme that is necessarily applied in this case.

In this paper, we propose a comparative study of linear and nonlinear algorithms designed for grid-side control of the power flow in a wind energy conversion system. We performed several simulations and experiments with step and variable power scenarios for different values of the DC-link capacity with the DC storage element being the key element of the grid-side converter. The linear control was designed on the basis of the internal model control theory where an active damping was added to avoid steady state errors. Nonlinear controls were built using first and second order sliding mode controls with theoretical considerations to ensure accuracy and stability. We observed that the first order sliding mode control was the most efficient algorithm for controlling the DC-link voltage but that the chattering degraded the quality of the energy injected into the grid as well as the efficiency of the grid-side converter. The linear control caused overshoots on the DC-link voltage; however, this algorithm had better performance on the grid side due to its smoother control. Finally, the second order sliding mode control did not prove to be more robust than the other two algorithms. This can be explained by the fact that this control is theoretically more sensitive to converter losses.

In this paper, the effect of electroporation on tissue is studied using the concept of distribution of relaxation times (DRT). DRT is an alternative to traditional electrical impedance spectroscopy, where measurement data are analyzed on a time scale rather than in the frequency domain. Applied to biological tissue, this approach is shown to remove the contribution of the electrode polarization in a 2-electrode system in a simple way. DRT also makes it easy to differentiate between dispersions associated with the different compartments of the tissue (counterion cloud, cell membrane, cell content and cell nucleus) and quantify their contribution to the total DC resistance. The study of plant tissue samples reveals the wide spread of the $$\beta$$ dispersion related to cell membrane polarization, which can be explained not only by the variable size of cells but also by the variable content of cells. The effects of electroporation can also be analyzed precisely. In particular, the irreversible electroporation threshold varies according to the cell content, as confirmed by electroporation simulations. In the electric field range of reversible electroporation, the shape of the DRT related to the $$\beta$$ dispersion is significantly modified, while the DC resistance remains constant. One explanation is put forward, involving the counterions cloud whose spatial distribution is altered after the application of the electric field.