IJJEH , Abdelrahman

Many practical problems are of multiscale nature. This issue appears when relatively small regions inside the computational domain have a large impact on the overall behavior of the structure. This requires using small mesh size in these regions of interest for adequately representing their geometrical details. Using uniform fine grid...

Volumic time-domain computational methods such as FDTD or Transmission-Line Matrix method (TLM) are widely used for full-wave simulation of structures with arbitrary geometry. While FDTD is a direct discretization of curl Maxwell's equation using finite-difference operators, TLM is seen as a discretized version of Huygens' principle of wave...

Many problems in nature and engineering are multiscale. Thus, for adequately representing structure geometrical details, one has to use small cell sizes which impose small time-step values. In addition, if the mesh is irregular but structured it might lead to exhaustive computer expenditure and higher dispersion. The alternate approach is to...

To find a stable Time-Domain (TD) numerical scheme, that adopts a local time-step in unstructured meshing, is a real challenge in numerical methods. This article presents a theoretical investigation on the origins of such instabilities. New finding shows that using multiple time-steps in one computational domain with TD methods produces a...

With the advancement of technology, modern equipment involves new functionalities that require complex media (e.g., anisotropic dispersive media such as ferrite, lossy dielectrics, or graphene) for a variety of applications. This imposes the necessity to extend simulation techniques capable of solving Maxwell's equations in such media. However,...

Ultra wideband (UWB) antennas are used extensively in the area of biomedical communication devices. The main reasons behind that are their robust performance for indoor environments, high data rates, inherently encrypted data…etc. UWB antennas propagate EM-signals of up to few GHz in bandwidth. However, the dispersive nature of human tissues...

This article presents a time-domain numerical scheme for simulating EM-computational problems that include complex media and fine geometrical details in critical regions. These problems are common in engineering and applied physics. To name a few, microwave and optical devices that contain complex media, antennas characterization in presence of...

This article presents an optimal connection topology to model the voltage-exchange at the interface between different sub-grids in nonstructured TLM meshes. As a first step, the derivation—using Kirchhoff's circuit laws—of these voltage-exchange equations between two subdomains with an arbitrary meshing ratio and a specific connection topology...

This article presents a study of the impact of finite-radius wire antennas in the High Frequency (HF) and the Very HighFrequency (VHF) bands on human operators located in the near-field zone. Modeling a finite-radius wire antenna can be a verytricky task, since the antenna parameters, such as the input impedance and the...

La modélisation et la caractérisation d'antennes basses fréquences dans des environnements réels sont considérées comme l'un des problèmes de calcul les plus difficiles. Cette complexité provient principalement de la nature multi-échelle des scénarios basse fréquence. Dans cet article, nous présentons une technique de maillage par blocs...

Modeling and characterizing low frequency antennas in realistic environments is considered as one of the most difficult computational problems. This complexity arises mainly from the multiscale nature of low-frequency scenarios. In this article, we present a block meshing technique with TLM to accurately represent the geometry of thin-wire...

The insatiable demand to optimize and engineer new functionalities in electromagnetic devices has risen their geometrical complexity to unprecedented levels. This usually results in computationally multiscale problems with some tiny components of great importance to the overall behavior of these devices. Block meshing is a powerful...

This article revisits the ideal transformer model used at the interface between different sub-grids in non-structured TLM meshes. The derivation of the voltage-exchanges equations between two subdomains with an arbitrary meshing ratio and connection topology is presented. The voltage-exchanges process is then generalized as a scattering-matrix...

Numerical dosimetry is a mandatory step in the designing process of any new EM device that operates in presence of living beings. One of its objectives is to ensure that a maximum Specific Absorption Rate (SAR) never exceeds the recommended values. In addition, including human models in simulations is necessary to evaluate the impact of human...

To design any new EM-device, it is of great importance to have a good estimation of the specific absorption rate (SAR) distribution or the Power Density (PD) it induces in users or people in its proximity. Respecting the recommended SAR limits is mandatory for any new technology to go public. Moreover, the good knowledge of SAR/PD is critical...

La conception de nouveaux dispositifs micro-ondes et optiques nécessite de traiter des problèmes de calcul avec des complexités géométriques croissantes et de développer des schémas numériques plus rapides et plus efficaces. Le maillage par blocs est une technique puissante de réduction de ressources informatiques en termes de temps processeur...

This article revisits the ideal transformer model used at the interface between different sub-grids in non-structured TLM meshes. The derivation of the voltage-exchanges equations between two subdomains with an arbitrary meshing ratio and connection topology is presented. The voltage-exchanges process is then generalized as a scattering-matrix...

This article presents an optimal connection topology to model the voltage-exchange at the interface between different sub-grids in nonstructured TLM meshes. As a first step, the derivation—using Kirchhoff's circuit laws—of these voltage-exchange equations between two subdomains with an arbitrary meshing ratio and a specific connection topology...

The constant and rapid increase in connected devices popularity raises questions about their possible impact on living beings. Dosimetry is used to assess the levels of EM-exposure induced by these devices. Numerical methods become handy when measurements are impossible to conduct. These numerical techniques require 3D human models; however,...

L'équation de bio-chaleur (Pennes) est une équation aux dérivées partielles du deuxième ordre (EDP) permettant de calculer la distribution de température dans les milieux biologiques. En calculant simultanément le flux de chaleur via l'équation de Fourier, celle-ci peut être résolue de façon analogue aux équations de l'électromagnétisme. Ainsi,...

In lossy dielectrics (e.g., human tissues) the skin effect plays a major role in Electromagnetic (EM) waves propagation as frequencies increase. This skin effect indicates that EM-waves decay exponentially as they penetrate good conductors, and they practically vanish as they traverse a distance of few skin depths. Moreover, in such media, the...

The interaction between electromagnetic waves and complex media and its consequences on other physical phenomena such as hyperthermia is a crucial issue for various types of applications. To name a few, electromagnetic compatibility, microwave ovens design, medical applications, and the design of electromagnetic devices and circuits that...

Cet article consiste à effectuer des études dosimétriques dans des milieux hétérogènes dans les bandes de fréquence de la 5G et au-delà pour fournir des estimations de niveaux de DAS. A ces fréquences, la distribution de DAS devient surfacique, aussi afin d'étudier l'influence de la répartition des tissus sur les premiers millimètres du corps...

Numerical dosimetry is an essential procedure in designing and optimizing propagating EM-devices that confirm to the recommended limits of Specific Absorption Rate (SAR). However, as frequencies go higher, the complexity of the computational problem increases substantially. Moreover, the high heterogeneity of the human body and the uncertainty...

Two distinct aspects of linear media, namely, material dispersion and non-stationarity are usually misinterpreted. The dispersive nature of media is taken into account by applying time-domain filtering processes (such as the convolution process between electric field and electric susceptibility in Maxwell's equations). This implies that the...