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Author

Bagci, Hakan (8)

Salama, Khaled N. (4)Agambayev, Agamyrat (3)Farhat, Mohamed (2)Patole, Shashikant P. (2)View MoreDepartmentComputer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division (8)
Electrical Engineering Program (8)

Physical Sciences and Engineering (PSE) Division (3)Journal2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting (2)2017 International Applied Computational Electromagnetics Society Symposium - Italy (ACES) (1)AIP Advances (1)ChemElectroChem (1)IEEE Antennas and Wireless Propagation Letters (1)View MorePublisherInstitute of Electrical and Electronics Engineers (IEEE) (5)AIP Publishing (1)American Physical Society (APS) (1)Wiley (1)SubjectAccelerated steepest descent (1)Antennas (1)Buffa-Christiansen functions (1)Composite materials (1)constant phase angle (1)View MoreTypeArticle (5)Conference Paper (3)Year (Issue Date)
2017 (8)

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Open Access (8)

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Metallic nanoparticles in dielectrics: A comparative study

Agambayev, Agamyrat; Farhat, Mohamed; Bagci, Hakan; Salama, Khaled N. (2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, Institute of Electrical and Electronics Engineers (IEEE), 2017-10-25) [Conference Paper]

The Maxwell-Garnett method is used to predict the effective dielectric constant and the tangent loss of various composites consisting of a PVDF-TrFE-CFE-matrix and metallic microsphere fillers made of Cu, Ni, W, Zn, or Fe. Simulation results demonstrate that for small filler fraction values and at low frequencies, the electrical properties of the resulting composite do not depend on the conductivity of the filler. These findings show that composites fabricated using cheaper metal nanoparticle fillers are as effective as those fabricated using expensive ones.

Ferroelectric Fractional-Order Capacitors

Agambayev, Agamyrat; Patole, Shashikant P.; Farhat, Mohamed; Elwakil, Ahmed S.; Bagci, Hakan; Salama, Khaled N. (ChemElectroChem, Wiley, 2017-07-25) [Article]

Poly(vinylidene fluoride)-based polymers and their blends are used to fabricate electrostatic fractional-order capacitors. This simple but effective method allows us to precisely tune the constant phase angle of the resulting fractional-order capacitor by changing the blend composition. Additionally, we have derived an empirical relation between the ratio of the blend constituents and the constant phase angle to facilitate the design of a fractional order capacitor with a desired constant phase angle. The structural composition of the fabricated blends is investigated using Fourier transform infrared spectroscopy and X-ray diffraction techniques.

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.

An explicit MOT scheme for solving the TD-EFVIE on nonlinear and dispersive scatterers

Sayed, Sadeed B; Ulku, H. Arda; Bagci, Hakan (2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, Institute of Electrical and Electronics Engineers (IEEE), 2017-10-25) [Conference Paper]

An explicit marching-on-in-time (MOT) scheme for solving the time domain electric field volume integral equation (TD-EFVIE) on nonlinear and dispersive scatterers is described. The unknown electric field intensity, electric flux density, and polarization densities representing Kerr nonlinearity along with Lorentz dispersion relation, all of which are induced inside the scatterer upon excitation, are expanded using half and full Schaubert-Wilton-Glisson functions in space. The TD-EFVIE and the constitutive relations between polarization, field, and flux terms are cast in the form of a first-order ordinary differential equation. The resulting matrix system is integrated in time using a predictor-corrector scheme to obtain the time dependent unknown expansion coefficients. The resulting MOT scheme is explicit and accounts for nonlinearity by simple function evaluations.

On the initial condition problem of the time domain PMCHWT surface integral equation

Uysal, Ismail Enes; Bagci, Hakan; Ergin, A. Arif; Ulku, H. Arda (2017 International Applied Computational Electromagnetics Society Symposium - Italy (ACES), Institute of Electrical and Electronics Engineers (IEEE), 2017-05-13) [Conference Paper]

Non-physical, linearly increasing and constant current components are induced in marching on-in-time solution of time domain surface integral equations when initial conditions on time derivatives of (unknown) equivalent currents are not enforced properly. This problem can be remedied by solving the time integral of the surface integral for auxiliary currents that are defined to be the time derivatives of the equivalent currents. Then the equivalent currents are obtained by numerically differentiating the auxiliary ones. In this work, this approach is applied to the marching on-in-time solution of the time domain Poggio-Miller-Chan-Harrington-Wu-Tsai surface integral equation enforced on dispersive/plasmonic scatterers. Accuracy of the proposed method is demonstrated by a numerical example.

Sparse Nonlinear Electromagnetic Imaging Accelerated With Projected Steepest Descent Algorithm

Desmal, Abdulla; Bagci, Hakan (IEEE Transactions on Geoscience and Remote Sensing, Institute of Electrical and Electronics Engineers (IEEE), 2017-04-03) [Article]

An efficient electromagnetic inversion scheme for imaging sparse 3-D domains is proposed. The scheme achieves its efficiency and accuracy by integrating two concepts. First, the nonlinear optimization problem is constrained using L₀ or L₁-norm of the solution as the penalty term to alleviate the ill-posedness of the inverse problem. The resulting Tikhonov minimization problem is solved using nonlinear Landweber iterations (NLW). Second, the efficiency of the NLW is significantly increased using a steepest descent algorithm. The algorithm uses a projection operator to enforce the sparsity constraint by thresholding the solution at every iteration. Thresholding level and iteration step are selected carefully to increase the efficiency without sacrificing the convergence of the algorithm. Numerical results demonstrate the efficiency and accuracy of the proposed imaging scheme in reconstructing sparse 3-D dielectric profiles.

Tunable fractional-order capacitor using layered ferroelectric polymers

Agambayev, Agamyrat; Patole, Shashikant P.; Bagci, Hakan; Salama, Khaled N. (AIP Advances, AIP Publishing, 2017-09-05) [Article]

Pairs of various Polyvinylidene fluoride P(VDF)-based polymers are used for fabricating bilayer fractional order capacitors (FOCs). The polymer layers are constructed using a simple drop casting approach. The resulting FOC has two advantages: It can be easily integrated with printed circuit boards, and its constant phase angle (CPA) can be tuned by changing the thickness ratio of the layers. Indeed, our experiments show that the CPA of the fabricated FOCs can be tuned within the range from -83° to -65° in the frequency band changing from 150 kHz to 10 MHz. Additionally, we provide an empirical formula describing the relationship between the thickness ratio and the CPA, which is highly useful for designing FOCs with the desired CPA.

Localized surface plate modes via flexural Mie resonances

Farhat, M.; Chen, P. -Y.; Guenneau, S.; Salama, Khaled N.; Bagci, Hakan (Physical Review B, American Physical Society (APS), 2017-05-11) [Article]

Surface-plasmon polaritons are naturally generated upon excitation of metals with high-frequency electromagnetic waves. However, the concept of spoof plasmons has made it possible to generate plasmoniclike effects in microwave electrodynamics, magnetics, and even acoustics. Similarly, in this paper, the concept of localized surface plate modes (SPMs) is introduced. It is demonstrated that SPMs can be generated on a two-dimensional (clamped or stress-free) cylindrical surface with subwavelength corrugations, which resides on a thin elastic plate, under excitation by an incident flexural plane wave. Numerical characterization of this corrugated rigid structure shows that it is elastically equivalent to a cylindrical scatterer with dispersive but uniformly negative flexural rigidity. This, indeed, suggests that plasmoniclike elastic materials can be engineered with potential applications in various areas including earthquake sensing and elastic imaging and cloaking.

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