Huygens Principle

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Grzegorz Wyleżek - One of the best experts on this subject based on the ideXlab platform.

  • The Huygens Principle and cosmological gravitational waves in the Regge–Wheeler gauge
    Classical and Quantum Gravity, 2005
    Co-Authors: Edward Malec, Grzegorz Wyleżek
    Abstract:

    We study the propagation of axial gravitational waves in Friedmann universes. The evolution equation is obtained in the Regge–Wheeler gauge. The gravitational waves obey the Huygens Principle in the radiation-dominated era, but in the matter-dominated universe their propagation depends on their wavelengths, with the scale fixed essentially by the Hubble radius. Short waves practically satisfy the Huygens Principle while long waves can backscatter off the curvature of a spacetime.

Thomas W Noonan - One of the best experts on this subject based on the ideXlab platform.

Edward Malec - One of the best experts on this subject based on the ideXlab platform.

  • The Huygens Principle and cosmological gravitational waves in the Regge–Wheeler gauge
    Classical and Quantum Gravity, 2005
    Co-Authors: Edward Malec, Grzegorz Wyleżek
    Abstract:

    We study the propagation of axial gravitational waves in Friedmann universes. The evolution equation is obtained in the Regge–Wheeler gauge. The gravitational waves obey the Huygens Principle in the radiation-dominated era, but in the matter-dominated universe their propagation depends on their wavelengths, with the scale fixed essentially by the Hubble radius. Short waves practically satisfy the Huygens Principle while long waves can backscatter off the curvature of a spacetime.

  • the Huygens Principle and cosmological gravitational waves in the regge wheeler gauge
    arXiv: General Relativity and Quantum Cosmology, 2005
    Co-Authors: Edward Malec, Grzegorz Wylezek
    Abstract:

    We study the propagation of axial gravitational waves in Friedman universes. The evolution equation is obtained in the Regge-Wheeler gauge. The gravitational waves obey the Huygens Principle in the radiation dominated era, but in the matter dominated universe their propagation depends on their wavelengths, with the scale fixed essentially by the Hubble radius. Short waves practically satisfy the Huygens Principle while long waves can backscatter off the curvature of a spacetime.

Gianluigi Tiberi - One of the best experts on this subject based on the ideXlab platform.

  • A Phantom Investigation to Quantify Huygens Principle Based Microwave Imaging for Bone Lesion Detection
    Electronics, 2019
    Co-Authors: Banafsheh Khalesi, Behnaz Sohani, Sandra Dudley, Mohammad Ghavami, Navid Ghavami, Gianluigi Tiberi
    Abstract:

    This paper demonstrates the outcomes of a feasibility study of a microwave imaging procedure based on the Huygens Principle for bone lesion detection. This study has been performed using a dedicated phantom and validated through measurements in the frequency range of 1–3 GHz using one receiving and one transmitting antenna in free space. Specifically, a multilayered bone phantom, which is comprised of cortical bone and bone marrow layers, was fabricated. The identification of the lesion’s presence in different bone layers was performed on images that were derived after processing through HuygensPrinciple, the S21 signals measured inside an anechoic chamber in multi-bistatic fashion. The quantification of the obtained images was carried out by introducing parameters such as the resolution and signal-to-clutter ratio (SCR). The impact of different frequencies and bandwidths (in the 1–3 GHz range) in lesion detection was investigated. The findings showed that the frequency range of 1.5–2.5 GHz offered the best resolution (1.1 cm) and SCR (2.22 on a linear scale). Subtraction between S21 obtained using two slightly displaced transmitting positions was employed to remove the artefacts; the best artefact removal was obtained when the spatial displacement was approximately of the same magnitude as the dimension of the lesion.

  • Phase-weighted UWB Imaging through Huygens Principle
    2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring), 2019
    Co-Authors: Gianluigi Tiberi, Banafsheh Khalesi, Behnaz Sohani, Sandra Dudley, Mohammad Ghavami, Navid Ghavami
    Abstract:

    Phase information is used in many imaging modalities to enhance resolution, such as in magnetic resonance imaging. However, its impact in Ultra-wideband (UWB) microwave imaging is still unexplored. Here, examples using analytical simulations are shown to address the impact of phase information in Huygens Principle (HP) based UWB imaging. Conventional amplitude-weighted HP imaging has a resolution, which achieves the optical resolution limit of λ/4, where $A$ represents the wavelength in the investigation domain calculated at the highest frequency. Simulation results show that HP phase-weighted modality leads to an improvement in the resolution of approximately 30% with respect to the HP amplitude-weighted modality, and to an increase in signal-to-average ratio of approximately 40% with respect to the HP amplitude-weighted modality.

  • Huygens Principle based UWB microwave imaging method for skin cancer detection
    2016 10th International Symposium on Communication Systems Networks and Digital Signal Processing (CSNDSP), 2016
    Co-Authors: Navid Ghavami, Gianluigi Tiberi, Sandra Dudley, Mohammad Ghavami, Majella Lane
    Abstract:

    In recent years, Ultra Wideband (UWB) technology has emerged as a promising alternative for use in a wide range of applications. One of the potential applications of UWB is in healthcare and imaging, motivated by its non-ionizing signals, low cost, low complexity, and its ability to penetrate through mediums. Moreover, the large bandwidth covered by UWB signals permits the very high resolution required in imaging experiments. In this paper, a recently introduced UWB microwave imaging technique based on the Huygens Principle (HP), has been applied to multilayered skin model with an inclusion representing a tumor. The methodology of HP permits the capture of contrast such that different material properties within the region of interest can be discriminated in the final image, and its simplicity removes the need to solve inverse problems when forward propagating the waves. Therefore the procedure can identify and localize significant scatterers inside a multilayered volume. Validation of the technique through simulations on multilayered cylindrical model of the skin with inclusion representing the tumor has been performed.

  • Huygens Principle based imaging of multilayered objects with inclusions
    Progress In Electromagnetics Research B, 2014
    Co-Authors: Navid Ghavami, Gianluigi Tiberi, David J. Edwards, Ahmad Safaai-jazi, Agostino Monorchio
    Abstract:

    The application of a recently introduced microwave imaging technique based on the Huygens Principle (HP), has been extended to multilayered objects with inclusions in this paper. The methodology of HP permits the capture of contrast such that difierent material properties within the region of interest can be discriminated in the flnal image, and its simplicity removes the need to solve inverse problems when forward propagating the waves. Therefore the procedure can identify and localize signiflcant scatterers inside a multilayered volume, without having apriori knowledge on the dielectric properties of the target object. Additionally, an analytically-based approach for analyzing UltraWide Bandwidth (UWB) body propagation is presented, where the body is modeled as a 3-layer stratifled cylinder with an eccentric inclusion. Validation of the technique through both simulations and measurements on multilayered cylindrical objects with inclusions has been performed.

  • Huygens Principle-based approach for UWB medical imaging
    2011
    Co-Authors: Navid Ghavami, Gianluigi Tiberi, David J. Edwards
    Abstract:

    In this paper, the algorithm of a novel imaging method based on Ultra WideBand (UWB) microwave signals has been developed and presented. The method is based on the Huygens Principle (HP), which removes the need to solve inverse problems and consequently, the need for matrix generation and inversion. Aside from the simplicity of the HP, it enables the detection of the extent to which different tissues, or different types of tissues, can be discriminated and render contrast in the final image. It should be pointed out that prior knowledge of electrical properties of the inclusions is not required when performing the imaging. The validation of HP technique through simulations on cylinders with multiple inclusions, representing realistic examples are presented. Simulation results show that the method successfully identifies the presence and location of significant scatterers within a target volume.

Igor Loutsenko - One of the best experts on this subject based on the ideXlab platform.