The Experts below are selected from a list of 5187 Experts worldwide ranked by ideXlab platform

Tie Jun Cui - One of the best experts on this subject based on the ideXlab platform.

  • dc illusion and its experimental verification
    Applied Physics Letters, 2012
    Co-Authors: Min Liu, Zhong Lei Mei, Tie Jun Cui
    Abstract:

    Based on the transformation optics method, we propose a dc illusion device, which can transform a metallic Object into a magnified Dielectric Object using anisotropic conducting materials. Utilizing the analogy between electric conductivities and resistor networks, we design and fabricate the device using metal film resistors. The practical measurement data agree very well with simulation results. The proposed dc illusion device is easy to process and measure, and thus has potential applications in various sectors.

  • Virtual conversion from metal Object to Dielectric Object using metamaterials.
    Optics express, 2010
    Co-Authors: Wei Xiang Jiang, Hui Feng, Qiang Cheng, Tie Jun Cui
    Abstract:

    We propose an illusion device which transforms a perfectly-electric-conducting (PEC) Object into a virtual Dielectric Object with arbitrary material parameters. Such an illusion device has unconventional electromagnetic properties as verified by accurate numerical simulations. The presented illusion device is composed of inhomogeneous and anisotropic media with finite and positive permittivity and permeability components. Hence the designed device is possible to be realized using artificial metamaterials.

  • Enhancement of specific absorption rate in lossy Dielectric Objects using a slab of left-handed material.
    Physical Review E, 2005
    Co-Authors: Lei Zhao, Tie Jun Cui
    Abstract:

    An enhancement of the specific absorption rate (SAR) inside a lossy Dielectric Object has been investigated theoretically based on a slab of left-handed medium (LHM). In order to make an accurate analysis of SAR distribution, a proper Green's function involved in the LHM slab is proposed, from which an integral equation for the electric field inside the Dielectric Object is derived. Such an integral equation has been solved accurately and efficiently using the conjugate gradient method and the fast Fourier transform. We have made a lot of numerical experiments on the SAR distributions inside the Dielectric Object excited by a line source with and without the LHM slab. Numerical experiments show that SAR can be enhanced tremendously when the LHM slab is involved due to the proper usage of strong surface waves, which will be helpful in the potential biomedical applications for hyperthermia. The physical insight for such a phenomenon has also been discussed.

Shoji Tominaga - One of the best experts on this subject based on the ideXlab platform.

  • metal Dielectric Object classification by combining polarization property and surface spectral reflectance
    Proceedings of SPIE, 2013
    Co-Authors: Shoji Tominaga, Hideki Kadoi, Keita Hirai, Takahiko Horiuchi
    Abstract:

    We propose a method for automatically classifying multiple Objects in a natural scene into metal or Dielectric. We utilize polarization property in order to classify the Objects into metal and Dielectric, and surface-spectral reflectance in order to segment the scene image into different Object surface regions. An imaging system is developed using a liquid crystal tunable filter for capturing both polarization and spectral images simultaneously. Our classification algorithm consists of three stages; (1) highlight detection based on luminance threshold, (2) material classification based on the spatial distribution of the degree of polarization at the highlight area, and (3) image segmentation based on illuminant-invariant representation of the spectral reflectance. The feasibility of the proposed method is examined in detail in experiments using real-world Objects.

  • estimation of multiple illuminants based on specular highlight detection
    Computational Color Imaging Workshop, 2011
    Co-Authors: Yoshie Imai, Hideki Kadoi, Takahiko Horiuchi, Yu Kato, Shoji Tominaga
    Abstract:

    This paper proposes a method for estimating the scene illuminant spectral power distributions of multiple light sources under a complex illumination environment. The spectral power distributions including natural and artificial illuminants are estimated based on the image data from a high-dimensional spectral imaging system. We note that specular highlights on inhomogeneous Dielectric Object surfaces includes much information about scene illumination according to the dichromatic reflection model. First, we describe several methods for detecting specular highlight areas. We assume a curved Object surface illuminated by multiple light sources from different directions. Then we estimate the illuminant spectrum of each light source from the image data of that highlight area. Based on this principle, we present an algorithm to estimate multiple illuminants. The feasibility of the proposed method is shown in experiments.

  • CCIW - Estimation of multiple illuminants based on specular highlight detection
    Lecture Notes in Computer Science, 2011
    Co-Authors: Yoshie Imai, Hideki Kadoi, Takahiko Horiuchi, Yu Kato, Shoji Tominaga
    Abstract:

    This paper proposes a method for estimating the scene illuminant spectral power distributions of multiple light sources under a complex illumination environment. The spectral power distributions including natural and artificial illuminants are estimated based on the image data from a high-dimensional spectral imaging system. We note that specular highlights on inhomogeneous Dielectric Object surfaces includes much information about scene illumination according to the dichromatic reflection model. First, we describe several methods for detecting specular highlight areas. We assume a curved Object surface illuminated by multiple light sources from different directions. Then we estimate the illuminant spectrum of each light source from the image data of that highlight area. Based on this principle, we present an algorithm to estimate multiple illuminants. The feasibility of the proposed method is shown in experiments.

  • metal Dielectric Object classification by polarization degree map
    International Conference on Pattern Recognition, 2008
    Co-Authors: Shoji Tominaga, T Yamamoto
    Abstract:

    Material classification of Object surfaces from captured image data is an essential problem in computer vision. The present paper proposes a method for stably classifying the material of an Object surface based on the distribution of the degree of polarization (DOP) around specular highlight on the surface. We show that the characteristic of spatial distribution for DOP is remarkably different in metal and Dielectric substance. Based on the characteristic, an algorithm is presented for effectively classifying any Object surface into two material categories from images captured by a digital camera with rotating a polarization filter. The feasibility of the proposed method is verified on experiments using a variety of Object surfaces made of different materials.

Michael S. Yeung - One of the best experts on this subject based on the ideXlab platform.

  • Solution of Electromagnetic Scattering Problems Involving Three-Dimensional Homogeneous Dielectric Objects by the Single Integral Equation Method
    Journal of Scientific Computing, 2000
    Co-Authors: Michael S. Yeung
    Abstract:

    The problem of electromagnetic scattering by a homogeneous Dielectric Object is usually formulated as a pair of coupled integral equations involving two unknown currents on the surface S of the Object. In this paper, however, the problem is formulated as a single integral equation involving one unknown current on S . Unique solution at resonance is obtained by using a combined field integral equation. The single integral equation is solved by the method of moments using a Galerkin test procedure. Numerical results for a Dielectric sphere are in good agreement with the exact results. Furthermore, the single integral equation method is shown to have superior convergence speed of iterative solution compared with the coupled integral equations method.

  • single integral equation for electromagnetic scattering by three dimensional homogeneous Dielectric Objects
    IEEE Transactions on Antennas and Propagation, 1999
    Co-Authors: Michael S. Yeung
    Abstract:

    A single integral equation formulation for electromagnetic scattering by three-dimensional (3-D) homogeneous Dielectric Objects is developed. In this formulation, a single effective electric current on the surface S of a Dielectric Object is used to generate the scattered fields in the interior region. The equivalent electric and magnetic currents for the exterior region are obtained by enforcing the continuity of the tangential fields across S. A single integral equation for the effective electric current is obtained by enforcing the vanishing of the total field due to the exterior equivalent currents inside S. The single integral equation is solved by the method of moments. Numerical results for a Dielectric sphere obtained with this method are in good agreement with the exact results. Furthermore, the convergence speed of the iterative solution of the matrix equation in this formulation is significantly greater than that of the coupled integral equations formulation.

Yeqin Huang - One of the best experts on this subject based on the ideXlab platform.

  • Green's dyadics for a bounded lossy medium
    2013 IEEE Antennas and Propagation Society International Symposium (APSURSI), 2013
    Co-Authors: Yeqin Huang, James Zhang, Robert Adams, Weiguo Yang
    Abstract:

    Dyadic Green's function for an arbitrarily shaped lossy Dielectric Object is presented. It is derived based on surface integral equations. Application of the presented dyadic Green's function allows a detailed study of radiation pattern and power loss of an antenna in the presence of a lossy medium. Numerical computations are implemented for a dipole in the vicinity of a lossy Dielectric sphere, the radiation pattern and power loss as a function of loss tangent are presented in graphs.

  • Electromagnetic radiation of antennas in the presence of an arbitrarily shaped Dielectric Object: Green dyadics and their applications
    IEEE Transactions on Antennas and Propagation, 2001
    Co-Authors: Mook-seng Leong, Yeqin Huang
    Abstract:

    Although numerical solutions to the electromagnetic scattering by an arbitrarily shaped Object have been obtained using Waterman's (1971) T-matrix method (TMM), the general electromagnetic radiation due to an antenna of a three-dimensional (3-D) current distribution in the presence of an arbitrarily shaped Object has not been well considered. In this paper, the technique of surface integral equations has been employed; and as a result, a terse and analytical representation of the dyadic Green's functions (DGFs) in the presence of an arbitrarily shaped Dielectric Object is obtained for the antenna radiation. In a form similar to that associated with the electromagnetic radiation in the presence of a Dielectric sphere, the DGFs inside and outside of the Object of arbitrary shape are expanded in terms of spherical vector wave functions. However, their coefficients are no longer decoupled due to the arbitrary surface of a 3-D Object. The coupled coefficients are then determined using the surface integral equation approach, in a fashion similar to that in the T-matrix method. To confirm the applicability and correctness of the approach in this paper a Dielectric sphere, as a special case, is utilized as an illustration. It is found that exactly the same expressions as in the rigorous analysis for the inner and outer spherical regions of the Object are obtained using the different approaches. As applications of the approach in this paper, radiation problems of an electric dipole in the presence of superspheroids and rotational parabolic bodies are solved.

  • Electromagnetic radiation of antennas in the presence of an arbitrarily shaped Dielectric Object: Green dyadics and their applications
    IEEE Antennas and Propagation Society International Symposium. 1999 Digest. Held in conjunction with: USNC URSI National Radio Science Meeting (Cat. N, 1999
    Co-Authors: Yeqin Huang, Le-wei Li, Mook-seng Leong
    Abstract:

    Although electromagnetic scattering problems have been investigated extensively by using Waterman's (1971) T-matrix method (TMM), the radiation problem of an antenna in the presence of an arbitrarily shaped Object were not considered thereof. In this paper, the technique of surface integral equations has been employed; and as a result, a terse and analytical representation of the dyadic Green's functions (DGFs) in the presence of an arbitrarily shaped Dielectric Object is obtained in a similar fashion to that in the TMM. In the case of a Dielectric sphere, this representation reduces to the same expression as obtained elsewhere in a different approach. As applications of the approach proposed in the paper, radiation problems of an electric dipole in the presence of superspheroids and rotational parabolic bodies are solved although the theoretical formulas derived can be applied to arbitrary current distributions located anywhere in the presence of an Object of arbitrary shape.

Hélène Roussel - One of the best experts on this subject based on the ideXlab platform.

  • Full-Wave Indoor Measurements' Cross-Validation With the Model Demos for Foliage Penetrating Applications
    IEEE Geoscience and Remote Sensing Letters, 2020
    Co-Authors: Lydia Hettak, Hassan Saleh, Cyril Dahon, Massimiliano Casaletti, Olivier Meyer, Jean Michel Geffrin, Hélène Roussel
    Abstract:

    For foliage penetrating (FoPen) radar development, we previously developed a hybrid volume-surface model, named Domain dEcomposition Model (DEMOS), to evaluate the electromagnetic scattering from large scenes composed by targets (metallic Objects) placed in a natural environment (Dielectric Object). In this letter, we compare the scattered field obtained by DEMOS with the quasi-monostatic measurements done in an anechoic chamber on scaled models composed of Dielectric and metallic structures. For all measurements, we consider both polarizations, HH and VV. Our final Objective is to determine the optimal configurations for the detection of a target placed in a forest environment in the very high-frequency (VHF)-UHF frequency bands.

  • DEMOS : a Domain dEcomposition MOdel for Scattering in forest environments compared with mono and bistatic measurements on scaled models
    2017
    Co-Authors: Lydia Hettak, Hassan Saleh, Cyril Dahon, Massimiliano Casaletti, Olivier Meyer, Jean Michel Geffrin, Hélène Roussel
    Abstract:

    We developed an efficient model to evaluate the electromagnetic scattering from large scenes composed by targets (metallic Objects) placed in natural environment (Dielectric Object). Our model, named DEMOS, is a hybrid volume/surface model that integrate both metallic and Dielectric scatterers. In this paper we compare the scattered field obtained with DEMOS with measurements done in an anechoïc chamber on scaled models composed of Dielectric and metallic structures.