Stamatis A. Amanatiadis

• PhD in Electrical and Computer Engineering
• Graphene's application to electromagnetic compatibility at Aristotle University of Thessaloniki

Graphene-oriented nano-structures have, recently, drawn a serious research interest, due to graphene's very attractive properties at THz frequencies. Specifically, with respect to wireless communications at the nano-scale, a particularly promising and emerging field, graphene nano-antennas are an excellent counterpart to the classic metallic antenn...

The systematic design of a graphene-based nanoantenna, whose radiation characteristics can be controlled by its gate voltage, is presented in this paper. For its consistent operation in the terahertz regime, the dimensions of the new patchtype radiator are comparable to the surface-wave wavelength. To this aim, a theoretical study of the propagatio...

A systematic method to enhance the performance and radiation characteristics of circularly-polarized antennas, by using a chiral metamaterial superstrate, is presented in this paper. The novel structure consists of a log-spiral radiator, backed by a properly placed reflector and a superstrate involving a periodically-repeated pattern of chiral reso...

Long-term condition monitoring of works of art can provide new insights into object-specific deterioration mechanisms. Detecting change over time allows us to determine whether deterioration is active, to investigate its cause and to establish the efficacy of conservation interventions. However, long-term condition monitoring poses both logistical...

This paper explores graphene’s quasi-normal modes (QNMs) by developing a finite element method solver, which addresses an augmented eigenvalue problem where graphene is represented as an equivalent surface current. This representation correlates with the surface conductivity of the material through a Debye frequency dispersion model. Initially, the...

The purpose of this paper is to conduct a thorough investigation of a stochastic eddy-current testing problem, when the geometric parameters of the system under study are characterized by uncertainty. Focusing on the case of subsurface defect detection, we devise reliable surrogates for the quantities of interest (QoI) based on the principles of th...

This work aims at enhancing the accuracy of finite-difference time-domain (FDTD) models when dispersive media are involved. Focusing on the case of Lorentz dispersion, we propose the proper modification of the model’s constitutive parameters, so that the numerical-dispersion flaws are mitigated. The discretization scheme’s dispersion relation is us...

In this paper, we study the dynamic formation of transients when plane waves impinge on a dispersive slab that abruptly changes its electrical properties in time. The time-varying slab alternates between air and metal-like states, whose frequency dispersion is described by the Drude model. It is shown how the physics of this complex system can be w...

Modifying the constitutive parameters of the background media is a technique that enables the mitigation of numerical dispersion errors in finite-difference time-domain (FDTD) simulations, when wave propagation in non-dispersive materials is modeled. For cases where material dispersion is present, we propose a methodology that alters the parameters...

The credible solution of discretized Maxwell's equations in spaces occupied by Lorentz dispersive media is the main subject of this work. Specifically, we introduce a finite‐difference time‐domain (FDTD) algorithm with a typical (2,4) structure that features dispersion‐relation‐preserving characteristics and produces reduced numerical errors in two...

The functionality of a fully planar metamaterial-inspired substrate-integrated cavity is thoroughly investigated in the present work. The electromagnetic field confinement of the proposed device is realized with the utilization of broadside-coupled complementary split ring resonators that operate as a virtual electric wall. The numerical results fr...

The resonance characteristics of magnetically-biased graphene micro-scatterers are thoroughly investigated in the present work using both eigenvalue and full-wave solvers. Initially, the graphene surface conductivity is presented in a tensor form due to the application of a magnetostatic bias field, which is perpendicular to the material’s surface....

The performance of the metamaterial-inspired substrate-integrated waveguide is discussed in this work, concerning a resonator misalignment potentially caused by the fabrication process. Initially, the design parameters of the aforementioned waveguide at the X-band are presented, while its optimal operation is validated to prove the effectiveness of...

This work develops an optimized (2,4) finite-difference time-domain (FDTD) method that is suitable for modelling electromagnetic problems with dispersive media.

Intelligent metasurfaces are a rapidly emerging field of engineered materials that offer unprecedented control over the propagation of electromagnetic waves (Tsilipakos, et al., in Advanced optical materials, vol. 8, art. no. 2000783, 2020). These metasurfaces are composed of sub-wavelength resonant elements that are arranged in a periodic fashion...

The detection of subsurface cracks via non-destructive eddy-current testing is examine in this work within a stochastic framework. By treating the problem’s geometric parameters as random variables, we develop efficient sparse models for statistically describing the coil impedance change, based on the polynomial-chaos theory and compressive sensing...

The energy leakage due to bad resonator alignment is investigated in this work for the 5G compatible metamaterial-inspired substrate-integrated waveguide. An uncertainty analysis is conducted via an efficient polynomial chaos expansion scheme considering a normal distribution of the resonator location. The extracted results highlight the significan...

This work develops a finite-difference time-domain (FDTD) methodology with controllable accuracy within prescribed frequency bands, which is suitable for problems incorporating material dispersion described by the Lorentz model. An optimization technique is introduced, which is based on the one-dimensional (1D) numerical dispersion relation and mod...

The accurate modeling of frequency-dispersive materials is a challenging task, especially when a scheme with a transient nature is utilized, as it is the case of the finite-difference time-domain method. In this work, a novel implementation for the modeling of graphene-oriented dispersive materials via the piecewise linear recursive convolution sch...

The determination of the natural frequencies for graphene scatterers is attained in the present work using a finite-difference scheme. The frequency-dispersive, two-dimensional material is treated as an equivalent surface current density, while an appropriately derived auxiliary differential equation is introduced to acquire a linear eigenvalue pro...

Stone has been a basic building material of different monuments and structural components such as foundations and masonry. At the same time, dif-ferent types of stones have been used for decorative architectural elements, such as cornices, reliefs, colonnettes, and corbels. The maintenance of stone ele-ments is essential for the continuity of these...

In the current work the endoscopy and retrieval of mortar covered mosaic patterns, such as the Hagia Sophia ones, is presented. In particular, an appropriate instrumentation is developed combining ultra-sonic tomography and an accurate motion planning. The acquisition of high-response tomographic images is performed utilizing transducers in a linea...

A full-vectorial finite-difference (FD) scheme is proposed in this work to accurately extract the propagating modes on a magnetically biased graphene microstrip. Initially, the anisotropic surface conductivity of graphene is introduced, and the appropriate eigenvalue problem is formulated starting from Maxwell’s equations. In particular, an FD appr...

Substrate Integrated Waveguide (SIW) is a well-established technology in the mm-wave frequency range with several related applications of mm-wave components and antennas. Recently, the Broadside-Coupled Complementary Split-Ring Resonator SIW (BC-CSRR SIW) has been proposed as an alternative to the classical SIW design, utilizing printed resonant me...

In this paper, we develop a (2,4) finite-difference time-domain technique for the efficient simulation of wave propagation within lossless Lorentz materials. Specifically, a least-squares approach is proposed, which facilitates the optimization of the spatial finite-difference formulae and ensures considerable improvement of accuracy within the cho...

The accurate modeling of curved graphene layers for time-domain electromagnetic simulations is discussed in the present work. Initially, the advanced properties of graphene are presented, focusing on the propagation of strongly confined surface plasmon polariton waves at the far-infrared regime. Then, the implementation of an unstructured triangula...

The accurate time-domain numerical modeling of graphene surface conductivity due to the interband contribution is presented in this paper. Initially, the lower frequency limit for the interband conductivity inclusion is studied, highlighting that even in the far-infrared regime it should not be ignored. Then, a precise vector-fitting technique is u...

Stone has been a basic building material of different monuments and structural components such as foundations and masonry. At the same time, different types of stones have been used for decorative architectural elements, such as cornices, reliefs, colonnettes, and corbels. The maintenance of stone elements is essential for the continuity of these s...

The degradation effects of artificial aging on the “true” pigment color of Byzantine iconography are thoroughly investigated in this work. For this purpose, a multi-material palette is fabricated, consisting of various popular egg-tempera pigments, while the original recipes from the literature are utilized in order to mimic the genuine art of Byza...

The industry practice of machining hard metal parts using CNC lathe turning machines is through grinding and milling procedures. The typical practice for quality control is through manual inspection, as automated solutions are difficult to integrate in production and do not reach the same level of accuracy. In this scope, the proposed system aims t...

The conductivity of graphene, due to interband electron transitions, is evaluated, in this paper, as rational functions through an efficient iterative optimization of Padé polynomials. Then, the latter are straightforwardly imported in the finite-difference time-domain algorithm, as an equivalent surface current, by means of precise recursive convo...

The core idea of the spectracoustic technique is the development and fabrication of a common probe for two modalities, the infrared spectroscopy and ultrasonic μTomography, for its application as a non-invasive analysis technique for tissue classification. The acquired and fused data from both modalities, provide a spectroscopic mapping tomographic...

The dynamic breast skin temperature evaluation is investigated in the present work for the diagnosis of breast cancer at an initial stage. In particular, a realistic breast model, including a relatively small-sized tumor, is designed and thoroughly analyzed numerically in terms of the biological heat transfer equation. Initially, the skin surface t...

In this paper, the scattering properties of graphene patches are investigated to design arrays that are able to control effectively plane wave propagation. Initially, single patches are examined in terms of their radar cross-section and surface wave generation. Moreover, an array of four identical elements is designed and thoroughly investigated in...

In the present work, the radiation properties of a graphene plasmonic patch antenna are investigated and enhanced in terms of efficiency, utilizing circuit-matching techniques. Initially, the reflection coefficient of graphene surface waves due to discontinuities is studied, while the power flow towards free-space is numerically extracted. This ana...

Purpose The reliable transcranial imaging of brain inner structures for diagnostic purposes is deemed crucial owing to the decisive importance and contribution of the brain in human life. The purpose of this paper is to investigate the potential application of medical ultrasounds to transcranial imaging using advanced techniques, such as the total...

Purpose The coupling characteristics between adjacent circuits are crucial for their efficient design in terms of electromagnetic compatibility features. Specifically, either the wireless power transfer can be enhanced or the interference can be limited. This paper aims to the extraction of the coupling characteristics of surface plasmon polariton...

The self‐healing mechanism of cementitious materials has been investigated by many researchers in the last two decades. In the journey of this quest, more and more advanced methods of analyzing the efficiency of healing have been employed. These methods are intended to clarify and quantify the healing mechanism. This paper presents five techniques,...

In this work, infrared spectroscopy, supported by acoustic microscopy, is utilized for the analysis of artworks regarding the sub-surface details. It is well-known that electromagnetic energy is able to penetrate into deeper than the surface layers as the wavelength is increased. For this reason, the infrared spectral band is capable of revealing s...

Purpose The majority of first-principle, homogenisation techniques makes use of the dipole terms of a small particle radiation, and, consequently, the respective dipole polarisabilities. This paper aims to take the next step and propose a new systematic technique for extracting the quadrupolarisability of planar metamaterial scatterers. Design/met...

Purpose The extraordinary properties of graphene render it ideal for diverse contemporary and future applications. Aiming at the investigation of certain aspects commonly overlooked in pertinent works, the authors study wave-propagation phenomena supported by graphene layers within a stochastic framework, i.e. when uncertainty in various factors af...

The third-order electrodynamic response of graphene and the subsequent non-linear effects are comprehensively investigated and numerically modeled in this article. Initially, the third-order conductivity of the medium is analyzed in order to transform it into a convenient expression for its efficient incorporation to explicit computational algorith...

In the present work, the scattering of an incident plane wave due to magnetically-biased graphene patches is thoroughly investigated at millimeter-wave and THz bands. Initially, the surface conductivity of graphene is evaluated at these spectral regions and a finite layer is placed perpendicular to the propagation of an incident plane wave. Then, t...

In this paper, we propose a hybrid computational model for the reliable simulation of electromagnetic-wave phenomena emerging in graphene structures, which incorporates two variations of an unconditionally-stable finite-difference time-domain algorithm. The new approach features: (a) a dispersive model that relies on the auxiliary differential equa...

The purpose of this work is the development of a method for the acquisition of multispectral images at the infrared region on cultural heritage artworks. The infrared light is able to penetrate into deeper, to the surface, layers, especially at the mid and far infrared spectrum. To this end, Fourier-transform Infrared spectrophotometer, is utilized...

In this paper, the techniques of high-frequency ultrasound and infrared imaging are combined to enhance the sub-surface characterization of cultural heritage artworks. Initially, these two different modalities are studied independently focusing on the extraction of an art object’s stratigraphy through acoustic microscopy and the distinction of mate...

An efficient transmission line model in the micrometric order is presented in this paper, to determine the thickness of thin dielectric films deposited on highly-doped substrates. In particular, the estimation of the thickness is based on multiple reflections of an incident infrared electromagnetic wave generating interference on the sensor. To thi...

An efficient transmission line model, in the micrometric order, is presented in this paper, to determine the thickness of thin dielectric films deposited on highly-doped substrates. In particular, the estimation of the thickness is based on the multiple reflections of an incident infrared electromagnetic wave that generate interference on the senso...

The distribution of the magnetic field in electromagnetic coils, such as those employed in magnetic resonance imaging (MRI), is evaluated in this paper, through graphene gyrotropic properties. Initially, the rotation of an incident linearly polarized plane wave, due to an infinite graphene layer, is studied theoretically via the extraction of the p...

An efficient and consistent technique to implement numerically a magnetically biased graphene layer is introduced in this paper. Through the novel scheme and after applying a magnetic bias perpendicular to graphene, its surface conductivity presents anisotropic behavior and this effect is systematically modeled and incorporated in terms of the recu...

Purpose Important statistical variations are likely to appear in the propagation of surface plasmon polariton waves atop the surface of graphene sheets, degrading the expected performance of real-life THz applications. It is the objective of this paper to introduce an efficient numerical algorithm that is able to accurately and rapidly predict the...

The development of an accurate convolutional perfectly matched layer for the efficient termination of infinite graphene structures is introduced in this paper. Initially, the popular two-dimensional material receives the appropriate theoretical analysis, which reveals the necessity of a flexible terminating condition that can enhance the performanc...

The combination of two versions of a split-step finite-difference time-domain (FDTD) algorithm is proposed for the efficient simulation of waves supported by graphene sheets. A dispersive scheme based on the auxiliary differential equation (ADE) approach is used for the graphene's surface conductivity, while an optimized technique featuring special...

The radiation efficiency improvement of graphene plasmonic antennas via synthesized substrates with metamaterial resonators, is introduced in this paper. Graphene, represented as an ultra-thin layer, can support highly-confined surface waves of significantly decreased wavelength compared to the vacuum one. Although, this concept yields more compact...

In the present paper, a simplified lumped element human body, stroked by a lightning touch volage, is designed and analyzed using the finitedifference time-domain (FDTD) method. The extracted results are compared with an electronic circuit simultor validating our numerical method. Moreover, other touch voltage scenarios are investigated, measuring...

The transmission and reflection coefficients of graphene surface waves, owing to the discontinuities of its substrate, are systematically studied and numerically computed in this paper. In essence, the propagation properties of these graphene-supported waves are theoretically extracted, revealing their strong dependence on the substrate material. T...

The propagating modes on a magnetically biased curved graphene microstrip are thoroughly examined in the present work by means of an efficient finite element modal solver. The influence of the anisotropic surface conductivity due to the magnetic bias is carefully addressed and investigated through a multitude of numerical results, including the eff...

The propagation properties of surface plasmon polariton waves on graphene microtubes were investigated in this paper. A precise vectorial finite element modal solver that models graphene as a surface boundary condition is devised for the graphene microribbon case. The solver extracts the dispersion curves through the effective index of various supp...

The variation of graphene chemical potential owing to surface plasmon polariton excitation and its influence on the propagation properties of the latter is systematically examined in this paper. Although the chemical potential is controlled via a constant electric field bias, the excitation of the highly confined surface wave can considerably affec...

A versatile and straightforward human body model, comprising simple geometric structures, is consistently developed in this study for the precise electromagnetic field exposure assessment owing to mediated lightning strikes. The proposed model incorporates a realistic set of frequency-dependent media, approximated by a 4-Cole-Cole scheme, while eve...

The development of a robust terminating boundary scheme for the transverse magnetic surface plasmon polaritons, supported on graphene, is introduced in this paper and incorporated in the finite-difference time-domain (FDTD) method. First, the 2-D FDTD algorithm is adjusted to efficiently model the graphene sheet as a surface conductivity, and the e...

In this letter, the finite difference time-domain (FDTD) method and the ray-tracing (RT) technique are systematically revisited and compared as potential tools that can reliably characterize new protocols for emerging nanonetwork applications. To this aim, a set of efficient simulation schemes for the precise prediction of the reception quality in...

The present work introduces the explicit modelling of graphene in the time domain, defined by its surface conductivity, as a surface boundary condition via an efficient 2D transverse electric FDTD formulation, derived directly from Maxwell's equations. The analysis is conducted at the far-infrared regime and the proposed method is validated by comp...

The present work investigates the propagation properties of the surface plasmon polariton wave supported on graphene surface over an anisotropic substrate at far-infrared frequencies. Initially, the surface wave’s propagation on isotropic media substrate is studied and verified with the theoretical estimation, including the noteworthy epsilon-near-...

In the present paper, a simplified human body, stroked by a lightning touch voltage, is implemented via lumped elements and analysed through the finite-difference time-domain (FDTD) method. The results, so extracted, are compared with those of an electronic circuit simulator. Furthermore, the current induced to the human body in the vicinity of a l...

The propagation properties of transverse magnetic surface waves onto an infinite graphene layer and the influence of the surrounding media are thoroughly examined in the present paper. After developing a realistic model of graphene, located in a homogeneous medium, its conductivity and the main characteristics of the resulting surface waves are ext...

The accurate analysis of dual-mode resonator filters and carbon nanotube interconnects both in the millimeter and THz regime, is presented in this paper via a higher-order nonstandard LOD-FDTD method. The novel 3-D schemes use a self-adjusting process to identify regions of rapid/smooth field variation and seriously subdue grid re-flection errors....

A class of volume-optimized pyramidal log-periodic antennas (PLPAs) with an adjustable ultra wideband performance is introduced in this paper. To this aim, a parametric analysis is initially conducted to decrease the total size of the prototype Euclidean-toothed PLPA. The new structures are based on the concept of meander curves, which leads to eff...

An efficient technique for the design of millimeter-wave, graphene-loaded waveguides that prevent the propagation of selected higher-order modes and do not allow a significant energy portion to be reflected back to the source plane, is developed in this paper. The optimal location of graphene films is obtained via the theoretical calculation of the...

A dual planar log-periodic antenna with a significantly improved directivity over its conventional counterpart is present-ed in this paper for high-speed WiMAX applications, which re-quire unidirectional attributes. The novel structure consists of four log-periodic arms at a wedge pattern, located in pairs on each side of a planar substrate, thus p...

A dual planar log-periodic antenna with a significantly improved directivity over its conventional counterpart is presented in this paper for high-speed WiMAX applications, which require unidirectional attributes. The novel structure consists of four log-periodic arms at a wedge pattern, located in pairs on each side of a planar substrate, thus pre...

A class of efficient pyramidal log-periodic antennas (PLPAs) with an adjustable ultra wideband performance is presented in this paper. The proposed structures are thoroughly investigated in terms of their radiation characteristics by means of a 3-D finite-difference time-domain (FDTD) formulation, while a parametric analysis is conducted in an atte...