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The support vector machine (SVM) is proposed as a response surface model to accelerate the solution speed of metaheuristic algorithms in solving inverse problems. The detail formulations of the SVM regression model using [epsilon]-insensitive loss function are derived. Primary numerical results are reported to demonstrate the feasibility, performance, and robustness of the proposed SVM based response surface model for solving both mathematical functions and engineering design problems. Index Terms--Inverse problem, metaheuristic algorithm, response surface model, support vector machine (SVM).

A double-sided broadband antenna for applications including ground-penetrating radar for detecting buried target is described. When compared with traditional coplanar-strip antennas, a better performance is achieved with a more practical design for construction. The steps in the design procedure are demonstrated herein. In addition, using incremental segments of current elements, a distributed dipole array model is derived and presented for determining [S.sub.11] in the time domain and for determining the radiation pattern of this antenna. By comparing measured results and HFSS simulations, our straightforward dipole array model of the more complicated antenna structure is justified by the accuracy of the results obtained. Finally, an experimental example is presented to show that this antenna in a GPR system application is effective in detecting even small plastic targets. Index Terms--Double-sided antenna, double-sided microstrip, GPR, target detection, transmission line.

A three-dimensional spectral-element method (SEM) based on Gauss-Lobatto-Legendre polynomials is proposed to solve vector electromagnetic-wave equations. To suppress spurious solutions, mixed-order curl conforming vector basis functions are used in the SEM. The advantages of this method include its high-order accuracy and its diagonal mass matrix due to the use of orthogonal Legendre polynomials. Thus, the proposed method leads to a regular eigenvalue problem rather than a generalized eigenvalue problem, greatly reducing the computer memory requirement and CPU time in comparison with the conventional high-order finite-element method (FEM). Numerical examples of eigenvalue problems verify the spectral accuracy with the interpolation orders and show that the SEM is superior to the FEM for the class of problems considered. A waveguide model is analyzed with mixed boundary conditions and its results are in excellent agreement with reference values. All numerical results show that the SEM is an efficient alternative to the FEM for electromagnetic fields. Index Terms--Eigenvalue problems, finite-element method (FEM), Gauss-Lobatto-Legendre (GLL) polynomials, mixed boundary conditions, mixed-order curl conforming vector basis functions, resonators, spectral-element method (SEM), waveguides.

We systematically investigated the surface plasmon resonance in one-dimensional (1D) subwavelength nanostructured metal films under the Kretschmann configuration. We calculated the reflectance, transmittance, and absorption for varying the dielectric fill factor, the period of the 1D nanostructure, and the metal film thickness. We have found that the small dielectric slits in the metal films reduce the surface plasmon resonance angle and move it toward the critical angle for total internal reflection. The reduction in surface plasmon resonance angle in nanostructured metal films is due to the increased intrinsic free electron oscillation frequency in metal nanostructures. Also we have found that the increasing the spatial frequency of the 1D nanograting reduces the surface plasmon resonance angle, which indicates that less momentum is needed to match the momentum of the surface plasmon-polariton. The variation in the nanostructured metal film thickness changes the resonance angle slightly, but mainly remains as a mean to adjust the coupling between the incident optical wave and the surface plasmon-polariton wave. [ABSTRACT FROM AUTHOR]

The spectral element method (SEM) is implemented for the numerical simulation of high electron mobility transistors (HEMTs) through a selfconsistent solution of the Schrödinger-Poisson equations. The electron conduction band structure and electron density distribution are calculated and plotted, and results compared to those based on methods utilizing a finite-difference approach. Simulation accuracy and efficiency are analyzed and compared with traditional finite difference method (FDM). DC current-voltage (I-V) characteristics for the HEMT structure are simulated, based on a quasi-2D current model. The SEM approach offers advantages in speed and efficiency over FDM, while yielding results which conform well to reported experimental results. These advantages are particularly important for compound heterojunction devices with complex material profiles, for which FDM methods may be inefficient and computationally slow. [ABSTRACT FROM AUTHOR]

The crosstalk effects in single- and double-walled carbon-nanotube (SWCNT and DWCNT) bundle-interconnect architectures are investigated in this paper. Some modified equivalent-circuit models are proposed for both SWCNT and DWCNT bundles, where capacitive couplings between adjacent bundles are incorporated. These circuit models are further used to predict the performance of SWCNT and DWCNT bundle interconnects in comparison with the Cu wire counterpart at all interconnect levels for advanced future technology generations. It is found that, compared with the SWCNT bundle, the DWCNT bundle interconnect can lead to a reduction of crosstalk-induced time delay, which will be more significant with increasing bundle length, while the peak voltage of the crosstalk-induced glitch in SWCNT and DWCNT bundle interconnects is in the same order as that of Cu wires. Due to the improvement in time delay, it is numerically confirmed that the DWCNT bundle interconnect will be more suitable for the next generation of interconnect technology as compared with the SWCNT bundle counterpart. [ABSTRACT FROM AUTHOR]

Recent advances in murine cardiac studies with three-dimensional (3D) cone beam micro-CT used a retrospective gating technique. However, this sampling technique results in a limited number of projections with an irregular angular distribution due to the temporal resolution requirements and radiation dose restrictions. Both angular irregularity and undersampling complicate the reconstruction process, since they cause significant streaking artifacts. This work provides an iterative reconstruction solution to address this particular challenge. A sparseness prior regularized weighted l2 norm optimization is proposed to mitigate streaking artifacts based on the fact that most medical images are compressible. Total variation is implemented in this work as the regularizer for its simplicity. Comparison studies are conducted on a 3D cardiac mouse phantom generated with experimental data. After optimization, the method is applied to in vivo cardiac micro-CT data. [ABSTRACT FROM AUTHOR]

A double-sided broadband antenna for applications including ground-penetrating radar for detecting buried target is described. When compared with traditional coplanar-strip antennas, a better performance is achieved with a more practical design for construction. The steps in the design procedure are demonstrated herein. In addition, using incremental segments of current elements, a distributed dipole array model is derived and presented for determining S11 in the time domain and for determining the radiation pattern of this antenna. By comparing measured results and HFSS simulations, our straightforward dipole array model of the more complicated antenna structure is justified by the accuracy of the results obtained. Finally, an experimental example is presented to show that this antenna in a GPR system application is effective in detecting even small plastic targets. [ABSTRACT FROM AUTHOR]

A spectral-element time-domain (SETD) method based on Gauss–Lobatto–Legendre (GLL) polynomials is presented to solve Maxwell's equations. The proposed SETD method combines the advantages of spectral accuracy with the geometric flexibility of unstructured grids. In addition, a 4th-order Runge–Kutta method for time integration provides high-order accuracy and thus reduces the temporal discretization errors. The numerical results demonstrate its spectral accuracy with the order of basis function and show the high efficiency of the proposed method due to its exponential convergence. © 2006 Wiley Periodicals, Inc. Microwave Opt Technical Lett 48: 673–680, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21440 [ABSTRACT FROM AUTHOR]

A three-dimensional spectral-element method (SEM) based on Gauss-Lobatto-Legendre polynomials is proposed to solve vector electromagnetic-wave equations. To suppress spurious solutions, mixed-order curl conforming vector basis functions are used in the SEM. The advantages of this method include its high-order accuracy and its diagonal mass matrix due to the use of orthogonal Legendre polynomials. Thus, the proposed method leads to a regular eigenvalue problem rather than a generalized eigenvalue problem, greatly reducing the computer memory requirement and CPU time in comparison with the conventional high-order finite-element method (FEM). Numerical examples of eigenvalue problems verify the spectral accuracy with the interpolation orders and show that the SEM is superior to the FEM for the class of problems considered. A waveguide model is analyzed with mixed boundary conditions and its results are in excellent agreement with reference values. All numerical results show that the SEM is an efficient alternative to the FEM for electromagnetic fields. [ABSTRACT FROM AUTHOR]

The stabilized biconjugate gradient fast Fourier transform (BCGS-FFT) method is applied to simulate electromagnetic and acoustic scattering from inhomogeneous objects embedded in a layered medium in two dimensions. Two-dimensional layered-media Green's functions are computed adaptively by using Gaussian quadratures after singularity subtraction. The Green's function is split into convolutional and correlational components in order to apply the FFT so as to solve the scattering problem efficiently. The CPU time and memory cost of this BCGS-FFT method is O(N log N) and O(N), respectively, where N is the number of unknowns, which is significantly more efficient than using the method of moments (MoM). As a result, this method is capable of solving large-scale electromagnetic and acoustic scattering problems for inhomogeneous objects embedded in a layered medium with an arbitrary number of layers. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 128–134, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21101 [ABSTRACT FROM AUTHOR]

For microwave signals within the 0.5 to 10.5 GHz range, we present an integrated broadband balun that carries signals from coaxial cable to microstrip to parallel-plate line. We use this arrangement as the feed line for a broadband double-sided antenna, and this antenna feed is presented as an application of the integrated balun. In addition, we devise a testing method for the balun, which is demonstrated. Through this testing method, the transmission, reflection, and radiation losses associated with the balun are readily determined. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 501–504, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20679 [ABSTRACT FROM AUTHOR]