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Generally, most of the electronic equipments need a metallic enclosure in order to mechanically protect and electrically shield the interior printed circuit boards (PCBs) and subsystems. But in practical situations, the apertures or slots of various forms are essential parts of the shielding enclosure for thermal dissipation, CD-ROMs, connectors, I/O cabling and so on. The performance of shielding enclosures for high-speed digital systems is compromised by these inevitable discontinuities on enclosure. To minimize the electromagnetic interferences and susceptibility risks by these discontinuities, the shielding enclosures with apertures should be designed based on thorough analysis about the electromagnetic coupling mechanism through apertures. In this paper, the effect of apertures and oblique incident plane wave on shielding effectiveness of the enclosure is studied with the Circuital Approach, and the Finite-Difference Time-Domain (FDTD) method, the simulated SE data are verified by experimental technique. Good agreements are found between these approaches.

Plant Microbial Fuel Cell (PMFC) creates electricity from oxidation of root exudates by microbia anaerobic digestion, and reduction of dioxygen to water. In this study, Lobelia Queen Cardinalis was used as a plant model to investigate the impact of ionic connection between stacked Plant microbial fuel cell (shared soil). 10mm thickness carbon felt woven with stainless steel wire was used for both anode and cathode, and soil was a mix of potting soil and ground from pond banks (30\%-70\% weight, respectively). Independent performances did not show any difference between individual and shared soil PMFCs. Stacking independent PMFC in series sums both open circuit potential (OCP) and internal resistance, while stacking in parallel sums current, keeping open circuit potential to the mean of the OCPs. Although series stacking seems to output best performances, this configuration may cause voltage reversal in one PMFC when current is strong, leading to biofilm damage, so stacking in parallel is recommended.

High-voltage direct current (HVDC) links are starting to become widely implemented thanks to their interesting advantages such as reduced operation losses, the absence of reactive power, which allows energy transport via underground cables over long distances, and improved power control. The latter advantage is very essential for renewable energy resource integration into power grids. However, a thorough understanding of the behavior of insulation systems for HVDC components is critical so as to ensure a more reliable service. Indeed, the existence of the direct current (DC) voltage in HVDC components may induce surface and space charge accumulation that can stress insulation further or even promote discharge inception and propagation. As such, this work focuses on showcasing the effect of surface charge on streamers that develop on the interface of liquid–solid insulation due to the advent of lightning impulse (LI) voltage in the HVDC link. This study was performed using finite-element-based numerical simulations that include a quasi-electrostatic model for surface charge accumulation and an electrohydrodynamic fluid model for streamer initiation and propagation. The geometry used was point–plane configuration where the high voltage is applied to the needle electrode located above the liquid–solid interface. The obtained results suggest that streamer initiation is affected by both the accumulated surface charge density and polarity. For a positive streamer, an accumulation of positive surface charge increases the discharge inception voltage as a result of a weakening in the electric field, while an accumulation of negative surface charge decreases the discharge inception voltage due to an intensification in the electric field. Moreover, streamer travel distance and velocity are also both shown to be affected by surface charge accumulation. [ABSTRACT FROM AUTHOR]

Reversible electroporation is a method to introduce molecules into cells by increasing the permeability of their membranes, thanks to the application of pulsed electric fields. One of its main biomedical applications is electro-chemotherapy, where electroporation is used to deliver anticancer drugs into tumor tissues. To improve our understanding of the electroporation effect on tissues and select efficient treatments, in vitro tumor models are needed. Cell spheroids are relevant models as they can reproduce tumor microenvironment and cell–cell interactions better than 2D cell cultures. Various methods offering a relatively simple workflow are now available for their production. However, electroporation protocols usually require handling steps that may damage spheroids and result in random spacing, inducing variations in electric field distribution around spheroids and non-reproducible electroporation conditions. In addition, only a few microsystems allow the production and electroporation of spheroids, and the spheroids produced lack reproducibility in size and location. To overcome these issues, we developed a unique device enabling culture, monitoring, and electroporation of hundreds of regular spheroids in parallel, with a design ensuring that all spheroids are submitted to the same electric field conditions. It is comprised of a microfluidic chamber encompassing a micro-structured agarose gel, allowing easy medium exchange while avoiding spheroid handling. It also enables optical imaging of spheroids in situ, thanks to transparent electrodes. In this paper, we describe the fabrication and characterization of the developed microsystem and demonstrate its applicability to electroporation of a network of spheroids. We present a first successful application as an anticancer drug testing platform, by evaluating the bleomycin effect on HT29 colorectal cancer cell spheroids. This work opens new perspectives in the development of in vitro assays for the preclinical evaluation of electroporation-based treatment. [ABSTRACT FROM AUTHOR]

This paper aims at detecting and characterizing inclusions in concrete structures by inverting ground-penetrating radar (GPR) data. First, the signal is preprocessed using the principal component analysis (PCA) and then used to train an artificial neural network (ANN). The GPR data consists of 1200 time steps. Using PCA, the data can be compressed to 286 dimensions without losing any information. Moreover, with 99.99% of the original variance the data needs only 139 dimensions. This dimensional reduction makes the ANN training easier and faster. The ANN were trained to find the buried inclusions characteristics--depth and radii--considering a nonhomogenous host medium by inverting the preprocessed data. The results show that the expected maximum error was kept under 1%, which is a remarkable result, since the host medium is nonhomogenous. Index Terms--Artificial neural network (ANN), buried objects, ground-penetrating radar (GPR), inverse problem.

This paper investigates the characterization of inclusions in concrete structures, including the number of inclusions, their geometries, and electromagnetic properties. To solve this problem, a two phase algorithm that combines matched-filter-based reverse-time (MFBRT) migration algorithm with the particle swarm optimization (PSO) is employed. The first phase runs the MFBRT that can, robustly, define the number of inclusions and their centers; however, it cannot define the inclusion geometry and electromagnetic properties. Given the results obtained in the first phase, the PSO is launched in the second phase, in a parametric approach, to define the radii of the inclusions and their properties. Three types of inclusions were considered, water, air, and conductor. Results considering a nonhomogenous host medium having from one to three inclusions are presented showing the effectiveness of the proposed approach. Index Terms--Finite-difference time domain (FDTD), inverse scattering, migration algorithms, particle swarm optimization.

An accurate method to compute dual field in high frequency time harmonic problem is presented. From a primal field obtained by a vector finite element discretization, the dual field is obtained without numerical derivation by using a least square argument. The accuracy of the method is compared with the natural method using shape function derivatives. Index Terms--Edge elements, finite element method, post-processing.

In this paper, common mode (CM) conducted perturbations are predicted and compared with experiments in a variable-speed drive system, thanks to a mixed approach based on experimental measurements and on the modeling of the complete CM circuit. Its different parts are considered and represented by a chain of quadripolar matrices: the inverter, the cables, and the induction motor. At last, it is shown that the parasitic currents in the system can be calculated in the different stages of the matrix chain. Experiments have successfully confirmed this approach. Index Terms--Conducted perturbations, quadripolar matrices modeling, variable-speed drive.

This paper deals with some aspects of performance of the symmetric successive over-relaxation preconditioner in a distributed environment. The details of distributed formulation of the preconditioner are presented. Some performance metrics are compared and discussed for the message passing interface implementation of the algorithm. The properties of the solver are estimated for concurrent three-dimensional formulation of the finite-element time-domain method. The analyzed benchmark models are approximated by tetrahedral first order Whitney elements. Index Terms--Edge elements, finite-element (FE) method, iterative solver, parallel numerical algorithms, time-domain algorithm.

This paper presents a three-dimensional computational model for nonlinear microwave heating problems. In order to reduce the computational costs, a new finite element method adaptive time-stepping scheme is proposed. Numerical results are compared with experimental measurements on a problem of dielectric heating of water. Index Terms--Adaptive time-stepping, finite element method (FEM), microwave heating, nonlinear dielectric properties.

Properties of the three-dimensional formulation of the finite element time domain algorithm for the wave equation are analyzed. First-order edge elements are implemented in the formulation. Several issues associated with deformation of the structured mesh and efficiency of the time integration scheme are presented. The convergence and stability of the time domain algorithm depending on the spatial discretization are discussed. The numerical accuracy of the simulation is studied. Index Terms--Edge elements, finite element method, stability, time domain analysis.

A procedure to optimize the specific absorption rate deposed in the patient during oncology hyperthermia treatment is presented. It is based on a genetic algorithm coupled to a finite-element formulation. The optimization procedure is applied to a real human body obtained from computerized tomography scans. Index Terms--Electromagnetic fields, finite-element methods, genetic algorithms, hyperthermia.

This paper deals with a distributed time-domain modeling of electromagnetic phenomena with the finite-element method. The model is approximated by edge elements. The constitutive equations and method of parallelization of the algorithm are presented. The properties Of the distributed finite-element time-domain algorithm are discussed. Some typical performance metrics are studied for the parallel versions of the software. The presented algorithm is executed on a heterogeneous and a homogeneous clusters of workstations. Two different distributed memory environments (MPI and PVM) are used to evaluate the efficiency of the algorithm. Index Terms--Distributed computing, edge elements, finite-element time-domain (FETD) algorithm, high-frequency electromagnetic field.

The boundary integral method is used to solve scattering by perfect electric conducting or perfect dielectric bodies. This paper deals with different aspects of the modeling: frequency domain and time domain formulations, computing, solver. Methods allowing the treatment of geometrical discontinuity for all kinds of mesh are specially discussed. Validation of the formulations is carried by comparison with other codes. Index Terms--Boundary element methods, discontinuities, numerical analysis.

The system capable of harvesting RF energy from the environment through an antenna and converting it into direct current energy to deliver to a load is known as rectenna. The rectifier circuit is an important part of the rectenna and its modeling is arduous since it employs a non-linear device working at extremely low power levels. In addition, there are some losses in the system. Thus, the design of a high-efficient rectifier is a great challenge. In this work, several rectifier topologies are optimized, using the Genetic Algorithm, in order to achieve the highest efficiency and output voltage. An analysis of the influence of the variables on the output of these rectifiers was also performed. The topologies under investigation were optimized for -15 dBm input power and 2.45 GHz operating frequency, in accordance with the most suitable band for energy harvesting. Under these conditions, the Monodiode Series topology presents the best performance. When the input power is -15 dBm, it presents an output voltage of 402 mV and an efficiency of 51.3%. At that power level, the achieved efficiency is higher than that found in the literature. [ABSTRACT FROM AUTHOR]

Generally, most of the electronic equipment need a metallic enclosure in order to mechanically protect and electrically shield the interior printed circuit boards (PCBs) and subsystems. But in practical situations, the apertures or slots of various forms are essential parts of the shielding enclosure for thermal dissipation, CD-ROMs, connectors, I/O cabling and so on. The performance of shielding enclosures for high-speed digital systems is compromised by these inevitable discontinuities on enclosure. To minimize the electromagnetic interferences and susceptibility risks by these discontinuities, the shielding enclosures with apertures should be designed based on thorough analysis about the electromagnetic coupling mechanism through apertures. In this paper, the effect of apertures and oblique incident plane wave on shielding effectiveness of the enclosure is studied with the Circuital Approach, and the Finite-Difference Time-Domain method, the simulated SE data are verified by experimental technique. Good agreements are found between these approaches. [ABSTRACT FROM AUTHOR]

This paper presents a discrete conducted electromagnetic (EM) interference filter optimization procedure, based on a genetic algorithms. A macromodeling technique taking into account the load impedance, the source emissions and the filter parasitic components, including the filter layout, is used to obtain an accurate solution for the optimization process. The latter searches among supplier passive component databases and provides, for a given filter topology, an optimal set of components available on the market. This approach has been applied to a differential Class-D audio amplifier for validation. By considering the electromagnetic interference (EMI), the additional power losses introduced by the filter and the audio gain, two different optimization formulations have been tested. The first corresponds to maximizing the power efficiency of the system while respecting a determined level of EM emissions. The second corresponds to minimizing the EMI without exceeding a determined level of power loss. The optimized filters are built and measurements are carried out. The results show a remarkable power efficiency improvement and a significant EM emission reduction when compared to a reference filter. [ABSTRACT FROM AUTHOR]

Electromagnetic interference (EMI) filters design is a rather difficult task where engineers have to choose adequate magnetic materials, design the magnetic circuit and choose the size and number of turns. The final design must achieve the attenuation requirements (constraints) and has to be as compact as possible (goal). Alternating current (AC) analysis is a powerful tool to predict global impedance or attenuation of any filter. However, AC analysis are generally performed without taking into account the frequency-dependent complex permeability behaviour of soft magnetic materials. That’s why, we developed two frequency-dependent complex permeability models able to be included into SPICE models. After an identification process, the performances of each model are compared to measurements made on a realistic EMI filter prototype in common mode (CM) and differential mode (DM) to see the benefit of the approach. Simulation results are in good agreement with the measured ones especially in the middle frequency range. [ABSTRACT FROM AUTHOR]

A novel rectifying circuit topology is proposed for converting electromagnetic pulse waves (PWs), that are collected by a wideband antenna, into dc voltage. The typical incident signal considered in this paper consists of 10-ns pulses modulated around 2.4 GHz with a repetition period of 100 ns. The proposed rectifying circuit topology comprises a double-current architecture with inductances that collect the energy during the pulse delivery as well as an output capacitance that maintains the dc output voltage between the pulses. Experimental results show that the efficiency of the rectifier reaches 64% for a mean available incident power of 4 dBm. Similar performances are achieved when a wideband antenna is combined with the rectifier in order to realize a rectenna. By increasing the repetition period of the incident PWs to 400 ns, the rectifier still operates with an efficiency of 52% for a mean available incident pulse power of −8 dBm. Finally, the proposed PW rectenna is tested for a wireless energy transmission application in a low- $Q$ cavity. The time reversal technique is applied to focus PWs around the desired rectenna. Results show that the rectenna is still efficient when noisy PW is handled. [ABSTRACT FROM PUBLISHER]

This paper presents the study of conducted and radiated emissions due to common-mode (CM) currents flowing through the power cables of a DC–DC converter system. In order to predict the conducted electromagnetic interferences (EMI) emissions, a model of power converter system is presented. The finite-difference time-domain method (FDTD) is used for predicting the magnetic near field radiated by the power supply cable of a buck converter and that due to CM current flowing through the cable. The CM current resulting from the model is compared with the experimental ones and implemented in the FDTD algorithm as current source of disturbance. The comparison with experimental results shows the validity of the FDTD model over a wide frequency range. The goal of this study is to predict the level of conducted and radiated EMI emissions. Therefore, proposing and investigating a simple and effective filtering solution that allows to reduce the emissions located in the switching noise zone, the results show that the conducted and radiated emission levels can be reduced by as much as 30 dB when using this technique. [ABSTRACT FROM AUTHOR]

The use of a fixed forward power as obtained during the calibration phase in a bulk current injection test, without monitoring the current, may cause damage on the equipment under test (EUT) with low impedances. In this paper, an accurate EUT model has been designed based on impedance investigation. This model can be used to predict the conducted susceptibility of a generic EUT. The model is first based on black-box approach; then, an interaction model is added to provide flexibility of several geometric parameters, which can be changed from one setup to another. This methodology leads to the combined approach, which shows a satisfactory agreement between simulations and measurements. According to the developed equations, the impedance matrix of the described model can be readily switched to modal one. Afterward, asymmetric dummy EUTs were investigated and the analytical equations used to predict differential mode due to common-mode voltage injection were validated. [ABSTRACT FROM PUBLISHER]

In the electromagnetic compatibility behavior of power electronic converters, parasitic magnetic couplings between components are one of the main causes of dysfunctions or poor filtering. These couplings may be either conducted or near-field interferences. To handle interaction problems, full knowledge of these magnetic couplings is essential. This paper is an overview of the work on near magnetic field interference undertaken in the last 15 years by the International Maxwell Laboratory. This paper details a predictive method that accurately and efficiently calculates near magnetic field coupling between two sources. The method uses near-field multipolar expansion in spherical harmonics of electromagnetic sources to determine close magnetic coupling between two sources from their equivalent models. This paper also shows how theoretical developments of large loop antennas have evolved from the van Veen antenna, a model with only two degrees of freedom, to a more complex model in terms of degrees, order, and types of harmonics. In parallel, it describes developments in the measurement method that provides input to the theoretical model. To illustrate how the research has evolved, we discuss coupling between two complex sources to assess the accuracy of this predictive method. [ABSTRACT FROM PUBLISHER]

This paper presents the study of conducted electromagnetic interference (EMI) currents flowing through the power cables of a DC-DC converter system and its correlation with the near field radiated from these cables. The radiated emission measurement contains a common mode (CM) and a differential mode (DM), and accurate separation of the radiated emissions of these two modes is necessary. The finite-difference time-domain (FDTD) method is used to predict the electromagnetic radiation caused by CM currents and DM currents. An experimental bench has been designed to allow access to the measurement of EMI disturbances at various sensitive places. The CM and DM voltages resulting from the experimental measurement are implemented in the FDTD algorithm as voltage sources of disturbances, these disturbance voltages causing the generation of CM and DM currents flowing through the cable. Finally, single and bifilar wire models for modeling the near field using the FDTD method are presented and the simulation results of the near field caused by both of the modes are evaluated and compared with the experimental ones. The main objective is to investigate the significance of the contribution of each of the current modes on the radiated emissions from the cable using the FDTD method, thus characterizing the level of cable radiation versus a specific standard. This allows showing that the radiation is often caused by the CM current along the cable and the largest level is located in the switching noise zone located within the frequency range from 1 MHz to 10 MHz. [ABSTRACT FROM AUTHOR]

In this article, we use a conversion chain to minimize standby-mode power consumption, detailing the different parts of the emitter and the receiver. The proposed technology is based on an efficient radio-frequency (RF) energy transfer and an RF-dc conversion circuit with a self-maintained switch that wakes up an electronic device [e.g., television (TV), home automation systems, etc.], using an integrated emitter and a receiver with performances suitable for home or industrial applications. The developed system works in the industrial, scientific, and medical (ISM) band (2.4-2.48 GHz). [ABSTRACT FROM AUTHOR]

A time reversal (TR) method is investigated for wireless power transmission in an indoor environment. Experiments performed with nanosecond pulses modulated at the frequency of 2.45 GHz reveal that the temporal and spatial focusing makes this technique valuable for applications of wireless power transmission. It is shown that the TR scheme avoids the fading phenomena that usually appear in an indoor environment when the power transmission is realized with a continuous wave: the voltage gain (respectively, the energy gain) can reach 30 dB (respectively, 20 dB) for the proposed scenarios. Moreover, it is theoretically proved that the TR technique is the optimal solution for an energy transmission, whatever the density of the multipath environment. In addition, simulations show that the voltage gain (respectively, the energy gain) of the TR technique is 3 dB (respectively, 9 dB) compared with the inverse filtering technique for a representative scenario. Other potential benefits of the method are discussed, notably concerning the power management of rectennas. [ABSTRACT FROM PUBLISHER]

This paper deals with a new method of metamodel construction for electromagnetic compatibility (EMC) simulation of power electronic converters. The proposed method uses a compressed wavelet coefficients vector of a time-domain signal and a learning method [support vector regression (SVR)]. This can be applied for a black box approach of modeling of complex systems such as power converters. This allows the study of EMC behavior, the impact of the uncertainties and their propagations inside the model or the design of EMC filters. [ABSTRACT FROM PUBLISHER]

In line with the trend toward continuous miniaturization and price reduction, it is crucial to analyze the impact of uncertainties on the performance of electrical circuits. Performance is evaluated for the worst-case scenario and in the frequency domain by computing upper and lower bounds. The purpose is not only to propose a method for the worst-case tolerance analysis but also to provide an efficient and a suitable tool for electrical engineers that can be easily applied to realistic electrical engineering problems. The proposed method is based on the robust analysis method (so-called $\mu$-analysis) for which well known and efficient algorithms exist. However in order to apply it, the problem under consideration has to be transformed in a standard minimal so-called LFT representation. Its derivation is a difficult task even for control systems engineers. This paper proposes a transparent and systematic LFT derivation procedure for users based only on their knowledge of electrical engineering. At the end of this paper, an industrial example is provided, which reveals the benefits and the efficiency of the proposed approach, and how it can be applied to any linear electrical circuit. [ABSTRACT FROM AUTHOR]

Class-D audio amplifiers are switching circuits that produce serious Electromagnetic (EM) emissions and disturb the surrounding electronics. In order to reduce these emissions, electromagnetic compatibility (EMC) filters with ferrite beads are used. However, ferrite beads contain magnetic materials that have a nonlinear behavior. Thus, they have an unfavorable impact on the system audio quality. The common ferrite bead models do not take into account nonlinear phenomena. Thus, to predict the impact on the signal quality, this paper models the ferrite bead using the Jiles-Atherton magnetic material theory. The presented model provides the designers with a tool to quantify the effect of EMC filters on the total harmonic distortion (THD) of audio amplifiers. The simulated and measured results show that the tested ferrite bead have a negative effect on the audio signal for a wide range of amplitudes and can increase the THD up to 37 dB. Finally, this paper highlights the impact of the magnetic material type on the audio distortion by simulating the same component with different types of materials. [ABSTRACT FROM AUTHOR]

In the electromagnetic compatibility (EMC) behavior of power electronic converters, magnetic parasitic couplings between components are one of the main causes of dysfunctions or bad filtering (e.g., in EMC filter). These couplings could be as conducted or near-field interferences. In order to handle interaction problems, a complete knowledge of these magnetic couplings is then necessary. Our study is focused on near magnetic field's interferences. Indeed, the characterization of electromagnetic field in power electronics is still in active research. This paper details a predictive method that calculates accurately and efficiently the near magnetic field coupling between two sources. By using the near-field multipolar expansion in spherical harmonics of electromagnetic sources, the close magnetic coupling between two sources is determined from their equivalent model. It is shown that the increase in degree up to the fourth provides a more precise representation of the elements and thus a better accuracy of the near-field coupling prediction. Also, theoretical and experimental developments will be presented. The coupling between two complex sources will be considered to validate the predictive method. [ABSTRACT FROM AUTHOR]