IEEE Journal on Multiscale and Multiphysics Computational Techniques

Modeling of terahertz plasmonic device is a multiscale and multiphysics problem that requires fine mesh in the electron transport regions, inevitably leading to long simulation times. In this paper, we tackle this problem by employing unconditionally stable FDTD methods for these simulations. Specifically, we present alternating direction implicit (ADI) FDTD and iterative-ADI-FDTD based efficient ... View full abstract»

Metasurfaces represent one of the most vibrant fields of modern science and technology. A metasurface is a complex electromagnetic structure, which is typically deeply subwavelength in thickness, electrically large in transverse size, and composed of subwavelength scattering particles with extremely small features; it may generally be bianisotropic, space-varying and time-varying, nonlinear, curve... View full abstract»

The properties that quantify photonic topological insulators (PTIs), Berry phase, Berry connection, and Chern number, are typically obtained by making analogies between classical Maxwell's equations and the quantum mechanical Schrödinger equation, writing both in Hamiltonian form. However, the aforementioned quantities are not necessarily quantum in nature, and for photonic systems they ca... View full abstract»

We apply the transformation-optics approach to the design of a metamaterial radome that can extend the scanning angle of a phased-array antenna. For moderate enhancement of the scanning angle, via suitable parameterization and optimization of the coordinate transformation, we obtain a design that admits a technologically viable, robust, and potentially broadband implementation in terms of thin-met... View full abstract»

This paper presents the stability analyses of nonuniform time-step (NUTS) locally one-dimensional finite-difference time-domain (LOD-FDTD) methods for electromagnetic (EM) and thermal simulations. The overall (spatial domain) transition matrix for the whole 3-D computational domain is considered for NUTS, which takes into consideration general inhomogeneous and lossy media. Rigorous stability anal... View full abstract»

A fast and memory efficient three-dimensional full-wave simulator for analyzing electromagnetic (EM) wave propagation in electrically large and realistic mine tunnels/galleries loaded with conductors is proposed. The simulator relies on Muller and combined field surface integral equations (SIEs) to account for scattering from mine walls and conductors, respectively. During the iterative solution o... View full abstract»

The interaction between electromagnetic field and plasmonic nanostructures leads to both strong linear and nonlinear behaviors. In this paper, a time-domain hydrodynamic model for describing the motion of electrons in plasmonic nanostructures is presented, in which both surface and bulk nonlinearity are considered. A coupled Maxwell-hydrodynamic system capturing full-wave physics and free-electron... View full abstract»

A new method for making an explicit time-domain finite-element method unconditionally stable is developed for general electromagnetic analysis, where the dielectrics and conductors can be inhomogeneous, lossless, or lossy. In this method, for a given time step, we find the unstable modes that are the root cause of instability, and deduct them directly from the system matrix resulting from a time-d... View full abstract»

Quantization of the electromagnetic field has been a fascinating and important subject since its inception. This subject topic will be discussed in its simplest terms so that it can be easily understood by a larger community of researchers. A new way of motivating Hamiltonian mechanics is presented together with a novel way of deriving the quantum equations of motion for electromagnetics. All equa... View full abstract»

A formal inverse design procedure which combines the advantageous aspects of both multiobjective optimization and system-by-design is proposed. The solution technique provides a systematic method to discover the various tradeoffs inherent in engineering design. To showcase the robustness and flexibility of the proposed approach, two unique highly directive nanodevices are explored. First, the prob... View full abstract»

A task-oriented multiscale material synthesis problem is addressed through an instance of the system-by-design (SbD) paradigm. More specifically, wide-angle impedance matching (WAIM) layers based on printed metasurfaces are designed to enhance the radiation efficiency of planar phased arrays. Toward this end, a task-oriented formulation is adopted where the layer geometrical features are the micro... View full abstract»

A thorough studyon the finite-difference time-domain (FDTD) simulation of the Maxwell-Schrödinger system in the semiclassical regime is given. For the Maxwell part which is treated classically, this novel approach directly using the vector and scalar potentials (A and Φ) is taken. This approach is stable in the long-wavelength regime and removes the need to extract the potentials at... View full abstract»

Rapid plasma formation and evolution during high-power microwave (HPM) air breakdown in an HPM device produce a macroscopic plasma shield to the microwave transmission, which can severely limit the performance of the device. In this paper, the electromagnetic (EM)–plasma interaction and the HPM breakdown in air are modeled by a nonlinearly coupled full-wave Maxwell and plasma fluid system u... View full abstract»

An adaptive h-refinement algorithm is investigated for the electric field integral equation applied to a conducting missile target. The process incorporates the advancing front Delaunay algorithm to refine the triangular-cell surface mesh in conjunction with Laplacian smoothing to maintain the mesh quality. The performance of several error estimators used to guide the refinement p... View full abstract»

The protection of power transmission systems against voltage surges is based on station class arresters. An important design criterion is to achieve thermal stability after operating duties. In order to study the transient behavior of arresters, a fully coupled electroquasi-static-thermal finite-element-method simulation approach is introduced. The procedure includes an efficient multirate time in... View full abstract»

A series feeding network with dispersion engineered compensation lines to reduce beam-squint radiation in linear antenna applications is investigated. The compensation lines are loaded in sections with left-handed and right-handed unit cells and branch off the main feed line. The signals from the branch points to the antenna elements are slowed down appropriately. Measurements of the radiation pat... View full abstract»

Agriculture is facing the challenge of increasing the quality of food production with environmentally friendly and health compatible processes featuring limited use of chemicals. The elimination of pathogens and harmful biological agents still remains a fundamental requirement. Therefore, soil physical disinfestation and disinfection represent a promising approach to a sustainable and profitable a... View full abstract»

In this paper, we show how mantle cloaking can be effectively used in satellite scenarios to reduce the deteriorating effects of the deployable equipment on the link budget between a miniaturized satellite and its ground station. The proposed idea is applied to a nanosatellite scenario and is validated through a simple analytical analysis of its communication link with the ground. The effectivenes... View full abstract»

Quasi-periodic arrays have appeared in many electromagnetic devices, such as reflectarray antennas, metasurfaces, and nanoparticle arrays. In these devices, elements with similar configuration are positioned on a periodic lattice. The entire array is usually a large multiscale structure. Therefore, efficient modeling of quasi-periodic arrays can be very challenging due to the loss of periodicity a... View full abstract»

To simulate the behavior of a passive antenna strain sensor, current multiphysics coupled simulation (between mechanics and electromagnetics) has mainly adopted the frequency domain solution. For every frequency point in the sweeping range, the frequency domain solver computes the value of scattering parameter S11. The S11 curve is used to identify the new resonance frequency... View full abstract»

This paper presents an adaptive mesh methodology to construct simulation source which has unlimited spectrum coverage for the discontinuous Galerkin time-domain (DGTD) method. The limitation of grid size (i.e., λ/20) for the construction of time-domain signal is relaxed by using a nonuniform sampling technique. The excitation source is modeled by using a standard gauss pulse with... View full abstract»

The fully quantized problem of a dipole atom coupled to transverse electric fields is solved for both simple harmonic and two-level atoms in a general lossless electromagnetic environment. The method employed is a direct factorization of the Hamiltonian in terms of coupled excitations of atom and fields. Time evolution of the system is considered with emphasis on the effect of an atom-photon bound... View full abstract»

A cylindrically symmetric problem can be simulated by a two-dimensional (2-D) axisymmetric finite-element model by exploiting the symmetry and thus reducing the original 3-D geometry to a 2-D cross section. This is, however, no longer possible when boundary conditions or excitations that violate the geometrical symmetry are applied. To avoid a computationally expensive 3-D simulation, a quasi-3-D ... View full abstract»

In this paper, we propose an optimized field/circuit coupling approach for the simulation of magnetothermal transients in superconducting magnets. The approach improves the convergence of the iterative coupling scheme between a magnetothermal partial differential model and an electrical lumped-element circuit. Such a multiphysics, multirate, and multiscale problem requires a consistent formulation... View full abstract»

Microelectromechanical systems (MEMS) resonators serve as frequency-selective components in applications ranging from biology to communications. In this paper, the dynamic behavior of an RF MEMS disk resonator is formulated using an analytical method. The resonator is simultaneously subjected to a DC-bias voltage superimposed with an ac harmonic voltage applied across the electrode-to-resonator ga... View full abstract»

An efficient method for simulating electromagnetic scattering from a dielectric rough surface over a frequency band is proposed. The method is based on the Chebyshev series and the Maehly approximation. The tapered plane wave is chosen as the incident wave to avoid the artificial edge diffraction caused by the finite length of the simulated rough surface. The Gaussian rough surface is considered. ... View full abstract»

This paper presents a numerical analysis on metallic micro/nanoparticles as LC-circuit resonators at microwave frequencies and with strong absorption for cancer therapy. We pushed the LC -structure design to the limit to provide an optimized structure within desired size limits, which can achieve resonance at the frequencies commonly used in interstitial microwave thermal therapies. Moreover, we d... View full abstract»

Low-complexity iterative and direct solvers are developed for the volume integral equation (VIE) based general largescale electrodynamic analysis. The dense VIE system matrix is first represented by a new cluster-based multilevel low-rank representation. In this representation, all the admissible blocks associated with a single cluster are grouped together and represented by a single low-rank bloc... View full abstract»

The concept of creating a composite tissue-type-image (cTTI) along with an associated probability image is introduced for ultrasound and microwave tomography. The cTTI integrates information available within different quantitative property images, and the associated probability image provides an indication of the level of confidence regarding the reconstructed tissue types. It is shown that the cT... View full abstract»

In this work, quantization of electromagnetic fields in a general anisotropic inhomogeneous media is considered. First, the classical Hamiltonian is derived. Once the Hamiltonian is derived, with it the classical equations of motion follow. Next, the fields are elevated to become quantum operators, for which conjugate pairs are endowed with commutators. Since as previously shown, such commutators ... View full abstract»

We present a scheme to compress the method of moments (MoM) matrix, which is linear in complexity for low to intermediate frequency problems in electromagnetics. The method is fully kernel independent and easy to implement using existing codes. The O(N) complexity for both memory and time (setup and matrix-vector product) is achieved thanks to the application of a recursive skeletonization to the ... View full abstract»

A new semi-implicit conformal finite-difference time-domain (FDTD) method is proposed for accurately modeling a short spark gap between metallic objects with curved surfaces. This new scheme is formulated on the basis of hybridizing the Newmark-Beta method and the simplified conformal scheme without cell enlargement. No dependency of mesh step in the direction of a spark channel is included in the... View full abstract»

This paper presents a multiphysics modeling of pin–socket under uniaxial vibration stress. The pin–socket behaves as a typically cylindrical dynamic contact structure as a function of the stress events. The pin–socket contact resistance fluctuation is expressed under the configuration of ideal, arbitrary roughness, and degraded surface contacts. To treat the problem, the pin s... View full abstract»

Scalar and vector basis functions have been developed that permit accurate modeling of singularities in electromagnetic fields at geometric edges and corners. This review attempts to organize the different types of functions, to summarize what philosophies have been used in their development, and help identify future work needed in this area. View full abstract»

Nanoparticles designed with high electric conductivity and magnetic permeability are injected into oil reservoirs to enhance fluid flow monitoring. The movement of nanoparticles with the flow in a porous medium can be modeled by solving the flow transport equation. In this research, the three-dimensional spectral-element time-domain method based on Gauss-Lobatto-Legendre polynomials is employed to... View full abstract»

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 everywhere is computationally very exhaustive. The use of irreg... View full abstract»

Higher-order polynomials as basis functions can be adapted to deal with extremely nonuniform meshes, which range from approximately 10-6 λ to 2 λ in electrical size. Thus, they are quite suitable and very flexible for modeling multiscale structures. The development of higher-order basis functions (HOBs) is not new, but its application to complex composite structures is the... View full abstract»

I present an accurate and efficient technique for numerical evaluation of singular 6-dimensional integrals over tetrahedon-product domains, with applications to calculation of Galerkin matrix elements for discretized volume-integral-equation (VIE) solvers using Schaubert-Wilton-Glisson (SWG) and other tetrahedral basis functions. My method extends the generalized Taylor-Duffy strategy—used ... View full abstract»

This paper presents multiscale modeling of electromagnetic interaction between a short relativistic electron bunch and long resistive structures at cryogenic temperatures. The considered physical problems include multiple spatial scales such as structure, bunch size, and skin depth. In order to simulate such multiscale problems, a directionally implicit finite-difference time-domain (FDTD) scheme ... View full abstract»

The objective of this review paper is to illustrate the principle of analytic continuation and provide its relationship to reduced rank modeling using the total least-squares-based singular value decomposition methodology. The principles are illustrated in the different domains using the matrix pencil method and the Cauchy method for various reduced computational applications. In a companion paper... View full abstract»

Microwave ablation is based on localized heating of biological tissues, enabled by an electromagnetic field. Ablation antennas are commonly designed in a forward approach, where the shape and type of antenna are manipulated to generate elevated temperatures in the target region. However, little attention has been dedicated to designing antennas in an inverse approach to allow controlled synthesis ... View full abstract»

Piezoelectric resonators have been generally modeled with the electrostatic approximation, which does not predict any electromagnetic (EM) wave behavior. In this research, we develop and validate a fully coupled finite-element (FE) model to study the interaction between elastodynamics and electrodynamics. We simulate the EM radiation from a vibrating piezoelectric resonator excited by harmonic she... View full abstract»

This review paper is a sequel to our earlier paper entitled “Application of the principle of analytic continuation to interpolate/extrapolate system responses resulting in reduced computations-Part A: Parametric methods” dealing with parametric methods in the context of the principle of analytic continu-ation and providing its relationship to reduced rank modeling using the total lea... View full abstract»

Time-domain electromagnetic simulations employing unstructured tetrahedral meshes offer smooth boundary approximations and graded meshes for multiscale problems. However, multiscale effects may arise not only as a consequence of fine geometry but also from CAD and mesh generation artifacts, and it is critical that the simulation algorithms can be employed in their presence without unduly compromis... View full abstract»

This paper presents a compact electro-mechanical-fluidic system-modeling method for multidomain system simulation based on multidomain physics that considers the total energy conservation condition, in terms of respective potential and flow quantities. Models for electrical, mechanical, and fluidic domains are developed to design the example of a blood pumping system, where the blood flow is drive... View full abstract»

Joule heat losses of electronics components may change behaviors of electrical and electronic devices, especially for semiconductor components whose electrical parameters are temperature-dependent. In this paper, a meshless approach based on radial point interpolation method (RPIM) is developed to numerically simulate the coupled electrical-thermal process that consists of electric potential equat... View full abstract»

This paper presents a fully coupled two-dimensional (2-D) multiphysics model for predicting the location of the arc discharge and lightning channel, and modeling its thermal and electrical behavior as a highly conductive plasma channel. The model makes no assumptions on the physical location of the lightning channel but predicts its appearance purely from the electromagnetic (EM) field conditions.... View full abstract»