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Bagci, Hakan (23)

Ulku, Huseyin Arda (23)

Sayed, Sadeed B (12)Uysal, Ismail Enes (9)Haji Ali, Abdul Lateef (2)View MoreDepartmentComputer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division (23)
Electrical Engineering Program (23)

Physical Sciences and Engineering (PSE) Division (11)Applied Mathematics and Computational Science Program (3)Center for Uncertainty Quantification in Computational Science and Engineering (SRI-UQ) (1)View MoreJournal2016 IEEE/ACES International Conference on Wireless Information Technology and Systems (ICWITS) and Applied Computational Electromagnetics (ACES) (2)2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) (1)2015 1st URSI Atlantic Radio Science Conference (URSI AT-RASC) (1)2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting (1)IEEE Antennas and Wireless Propagation Letters (1)View MorePublisherInstitute of Electrical and Electronics Engineers (IEEE) (8)SubjectCEM (6)transient analysis (3)band-limited interpolation (1)Buffa-Christiansen functions (1)electric field volume integral equation (1)View MoreTypePoster (15)Conference Paper (5)Article (2)Abstract (1)Year (Issue Date)2017 (1)2016 (5)2015 (8)2014 (8)Item Availability
Open Access (23)

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Mixed Discretization of the Time Domain MFIE at Low Frequencies

Ulku, Huseyin Arda; Bogaert, Ignace; Cools, Kristof; Andriulli, Francesco Paolo; Bagci, Hakan (IEEE Antennas and Wireless Propagation Letters, Institute of Electrical and Electronics Engineers (IEEE), 2017-01-10) [Article]

Solution of the magnetic field integral equation (MFIE), which is obtained by the classical marching on-in-time (MOT) scheme, becomes inaccurate when the time step is large, i.e., under low-frequency excitation. It is shown here that the inaccuracy stems from the classical MOT scheme’s failure to predict the correct scaling of the current’s Helmholtz components for large time steps. A recently proposed mixed discretization strategy is used to alleviate the inaccuracy problem by restoring the correct scaling of the current’s Helmholtz components under low-frequency excitation.

Analysis of electromagnetic wave interactions on nonlinear scatterers using time domain volume integral equations

Ulku, Huseyin Arda; Sayed, Sadeed B; Bagci, Hakan (2014 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), Institute of Electrical and Electronics Engineers (IEEE), 2014-07-06) [Abstract]

Effects of material nonlinearities on electromagnetic field interactions become dominant as field amplitudes increase. A typical example is observed in plasmonics, where highly localized fields “activate” Kerr nonlinearities. Naturally, time domain solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation easier and the material nonlinearity can be easily accounted for using an auxiliary differential equation (J.H. Green and A. Taflove, Opt. Express, 14(18), 8305-8310, 2006). On the other hand, explicit marching on-in-time (MOT)-based time domain integral equation (TDIE) solvers have never been used for the same purpose even though they offer several advantages over FDTD (E. Michielssen, et al., ECCOMAS CFD, The Netherlands, Sep. 5-8, 2006). This is because explicit MOT solvers have never been stabilized until not so long ago. Recently an explicit but stable MOT scheme has been proposed for solving the time domain surface magnetic field integral equation (H.A. Ulku, et al., IEEE Trans. Antennas Propag., 61(8), 4120-4131, 2013) and later it has been extended for the time domain volume electric field integral equation (TDVEFIE) (S. B. Sayed, et al., Pr. Electromagn. Res. S., 378, Stockholm, 2013). This explicit MOT scheme uses predictor-corrector updates together with successive over relaxation during time marching to stabilize the solution even when time step is as large as in the implicit counterpart. In this work, an explicit MOT-TDVEFIE solver is proposed for analyzing electromagnetic wave interactions on scatterers exhibiting Kerr nonlinearity. Nonlinearity is accounted for using the constitutive relation between the electric field intensity and flux density. Then, this relation and the TDVEFIE are discretized together by expanding the intensity and flux - sing half and full Schubert-Wilton-Glisson (SWG) functions, respectively. Equations are Galerkin tested in space and the resulting semi-discrete system is integrated in time for the unknown expansion coefficients using the aforementioned predictor-corrector scheme. The explicitness of the MOT scheme allows for incorporation of the nonlinearities as simple discretized function evaluations on the right hand side of the system. Numerical results that demonstrate the accuracy, efficiency, and applicability of the proposed nonlinear MOT-TDVIE solver will be presented.

A Stable Marching on-in-time Scheme for Solving the Time Domain Electric Field Volume Integral Equation on High-contrast Scatterers

Sayed, Sadeed B; Ulku, Huseyin Arda; Bagci, Hakan (IEEE Transactions on Antennas and Propagation, Institute of Electrical and Electronics Engineers (IEEE), 2015-05-05) [Article]

A time domain electric field volume integral equation (TD-EFVIE) solver is proposed for characterizing transient electromagnetic wave interactions on high-contrast dielectric scatterers. The TD-EFVIE is discretized using the Schaubert- Wilton-Glisson (SWG) and approximate prolate spherical wave (APSW) functions in space and time, respectively. The resulting system of equations can not be solved by a straightforward application of the marching on-in-time (MOT) scheme since the two-sided APSW interpolation functions require the knowledge of unknown “future” field samples during time marching. Causality of the MOT scheme is restored using an extrapolation technique that predicts the future samples from known “past” ones. Unlike the extrapolation techniques developed for MOT schemes that are used in solving time domain surface integral equations, this scheme trains the extrapolation coefficients using samples of exponentials with exponents on the complex frequency plane. This increases the stability of the MOT-TD-EFVIE solver significantly, since the temporal behavior of decaying and oscillating electromagnetic modes induced inside the scatterers is very accurately taken into account by this new extrapolation scheme. Numerical results demonstrate that the proposed MOT solver maintains its stability even when applied to analyzing wave interactions on high-contrast scatterers.

Quantum-corrected plasmonic field analysis using a time domain PMCHWT integral equation

Uysal, Ismail Enes; Ulku, Huseyin Arda; Bagci, Hakan (2016 IEEE/ACES International Conference on Wireless Information Technology and Systems (ICWITS) and Applied Computational Electromagnetics (ACES), Institute of Electrical and Electronics Engineers (IEEE), 2016-03-13) [Conference Paper]

When two structures are within sub-nanometer distance of each other, quantum tunneling, i.e., electrons "jumping" from one structure to another, becomes relevant. Classical electromagnetic solvers do not directly account for this additional path of current. In this work, an auxiliary tunnel made of Drude material is used to "connect" the structures as a support for this current path (R. Esteban et al., Nat. Commun., 2012). The plasmonic fields on the resulting connected structure are analyzed using a time domain surface integral equation solver. Time domain samples of the dispersive medium Green function and the dielectric permittivities are computed from the analytical inverse Fourier transform applied to the rational function representation of their frequency domain samples.

An Explicit MOT-TD-VIE Solver for Time Varying Media

Sayed, Sadeed B; Ulku, Huseyin Arda; Bagci, Hakan (2016 IEEE/ACES International Conference on Wireless Information Technology and Systems (ICWITS) and Applied Computational Electromagnetics (ACES), Institute of Electrical and Electronics Engineers (IEEE), 2016-03-15) [Conference Paper]

An explicit marching on-in-time (MOT) scheme for solving the time domain electric field integral equation enforced on volumes with time varying dielectric permittivity is proposed. Unknowns of the integral equation and the constitutive relation, i.e., flux density and field intensity, are discretized using full and half Schaubert-Wilton-Glisson functions in space. Temporal interpolation is carried out using band limited approximate prolate spherical wave functions. The discretized coupled system of integral equation and constitutive relation is integrated in time using a PE(CE)m type linear multistep scheme. Unlike the existing MOT methods, the resulting explicit MOT scheme allows for straightforward incorporation of the time variation in the dielectric permittivity.

Analysis of electromagnetic wave interactions on graphene sheets using time domain integral equations

Shi, Yifei; Uysal, Ismail Enes; Li, Ping; Ulku, Huseyin Arda; Bagci, Hakan [Conference Paper]

A marching on-in-time (MOT) scheme for analyzing transient electromagnetic wave interactions on graphene sheets is described. The proposed scheme discretizes a time domain-resistive boundary condition (TDRBC) enforced on the infinitesimally thin graphene sheet. Time domain samples of the graphene's surface resistivity required by the MOT-TDRBC solver are computed from its frequency domain samples using a fast relaxed vector fitting (FRVF) algorithm. Numerical results, which demonstrate the applicability and accuracy of the proposed scheme, are presented.

Computation of Electromagnetic Fields Scattered From Dielectric Objects of Uncertain Shapes Using MLMC

Litvinenko, Alexander; Haji Ali, Abdul Lateef; Uysal, Ismail Enes; Ulku, Huseyin Arda; Oppelstrup, Jesper; Tempone, Raul; Bagci, Hakan (2016-01-06) [Poster]

Simulators capable of computing scattered fields from objects of uncertain shapes are highly useful in electromagnetics and photonics, where device designs are typically subject to fabrication tolerances. Knowledge of statistical variations in scattered fields is useful in ensuring error-free functioning of devices. Oftentimes such simulators use a Monte Carlo (MC) scheme to sample the random domain, where the variables parameterize the uncertainties in the geometry. At each sample, which corresponds to a realization of the geometry, a deterministic electromagnetic solver is executed to compute the scattered fields. However, to obtain accurate statistics of the scattered fields, the number of MC samples has to be large. This significantly increases the total execution time.
In this work, to address this challenge, the Multilevel MC (MLMC [1]) scheme is used together with a (deterministic) surface integral equation solver. The MLMC achieves a higher efficiency by balancing the statistical errors due to sampling of the random domain and the numerical errors due to discretization of the geometry at each of these samples. Error balancing results in a smaller number of samples requiring coarser discretizations. Consequently, total execution time is significantly shortened.

Stabilizing MOT Solution of TD-VIE for High-Contrast Scatterers using Accurate Extrapolation

Sayed, Sadeed B; Ulku, Huseyin Arda; Bagci, Hakan (2014-05-04) [Poster]

A Novel Time Domain Method for Simulating Dissipative Electromagnetic Field Interactions

Uysal, Ismail Enes; Ulku, Huseyin Arda; Bagci, Hakan (2014-05-04) [Poster]

MOT Solution of Time Domain PMCHWT Integral Equation for Conductive Dielectric Scatterers

Uysal, Ismail Enes; Ulku, Huseyin Arda; Bagci, Hakan (2014-01-06) [Poster]

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