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Effective Length of Counterpoises Connected to Wind Turbine Foundation

IEEE TRANSACTIONS ON POWER DELIVERY 2021年第6期36卷 3956-3963页

作者： Kose, Morioki Tanaka, Saki Yamamoto, Kazuo Sekioka, Shozo Baba, Yoshihiro Nagaoka, Naoto CTI Engn Co Ltd Osaka 5410045 Japan Chubu Univ Dept Elect & Elect Engn Kasugai Aichi 4878501 Japan Shonan Inst Technol Dept Elect & Elect Engn Fujisawa Kanagawa 2518511 Japan Doshisha Univ Dept Elect Engn Kyoto 6100394 Japan

Many failures of wind turbine blades and electrical equipment due to powerful lightning strikes have occurred. The lightning-induced wind turbine failures that have occurred in recent years can be classified into two main categories. The first is a mechanical component failure. The second is a failure or malfunction of electric or electronic equipment inside or around the wind turbine due to an increase in the potential of the wind turbine grounding system or the electromagnetic induction caused by the lightning strike. In the latter case, the equipment often fails owing to the increase in the potential of the grounding system, the method of suppressing the potential rise by laying a grounding wire vertically or horizontally to the wind turbine foundation is adopted. We propose an empirical expression for the effective length of counterpoises connected to a large grounding electrode such as a wind turbine foundation, and verify the expression using finite-difference time-domain (FDTD) method.

关键词： Grounding Wind turbines Wires Electric potential Lightning Electrodes Mathematical model Effective length finite-difference time-domain method grounding wind turbine

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Ultra-fast tunable optoelectronic half adder/subtractor based on photonic crystal ring resonators covered by graphene nanoshells

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OPTICAL AND QUANTUM ELECTRONICS 2021年第7期53卷 1-16页

作者： Naghizade, Saleh Saghaei, Hamed Islamic Azad Univ Tabriz Branch Young Researchers & Elite Club Tabriz Iran Islamic Azad Univ Shahrekord Branch Dept Elect Engn Shahrekord Iran

This paper reports a new design of a tunable optoelectronic half adder/subtractor. Two photonic crystal (PhC) ring resonators are used to realize the proposed structure. Several silicon rods surrounded by silica rods covered with graphene nanoshells (GNSs) form every PhC ring resonator. Setting the chemical potential of GNS with an appropriate gate voltage, we can tune the PhC resonant mode as desired. The plane wave expansion technique is used to study the photonic band structure of the fundamental PC microstructure, and the finite-difference time-domain method is employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We systematically study the effects of physical parameters on the transmission reflection and absorption spectra. By optimizing the geometric dimensions, resonant absorption peaks can be excited at the same time for GNSs. Our numerical results also reveal the maximum time response is about 0.8 ps. The 200 mu m(2) area of the proposed half adder/subtractor makes it the building block of every photonic integrated circuit. Also, the design of various fast signal processing systems in optical communication networks is possible due to using tunable GNSs in PhC ring resonators. This study can introduce the use of two-dimensional materials in the design and implementation of logic circuits.

关键词： Photonic crystal microstructure Nonlinear material Optoelectronic half adder subtractor Ring resonator Plane wave expansion method Optical Kerr effect finite-difference time-domain method

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Speed-up of scattered field formulation of FDTD method combining with time-domain EFIE by using spherical harmonic expansion of Green's function

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INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS 2021年第1期65卷 17-25页

作者： Kawaguchi, Hideki Muroran Inst Technol Dept Informat & Elect Engn Mizumoto Cho Muroran Hokkaido Japan

This paper proposes a scattered field formulation of the finite-difference time domain method (S-FDTD) combining with a time-domain electric field integral equation (TD-EFIE) based on surface equivalence theorem. The scattered field formulation enables us to reduce computation cost effectively for the case that scatterers are located at a far distance from field sources of electromagnetic wave since we need to calculate the scattered field component only on the region in the vicinity of the scatterers. Then it is required for the use of the scattered field formulation that the field source for the incident field component has to be expressed by any analytical solutions such as a point dipole source, plane wave, and so on. In this work, the scattered field formulation of the FDTD method is applied to cases that there are no analytical expressions of the field sources, in which the field source contains conductors such as antennas, combining with the TD-EFIE on a virtual surface which encloses the field sources. Then, it is known that calculation of the TD-EFIE itself is time consuming. This paper considers speed-up of the S-FDTD simulation based on the TD-EFIE using a spherical harmonic expansion of Green's function of Helmholtz equation, additionally.

关键词： finite-difference time-domain method microwave propagation scattered field formulation surface equivalence theorem time-domain electric field integral equation spherical harmonic expansion Green's function of Helmholtz equation

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NDE of Discontinuities in Thermal Barrier Coatings with Terahertz time-domain Spectroscopy and Machine Learning Classifiers

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MATERIALS EVALUATION 2021年第2期79卷 125-135页

作者： Cao, Binghua Cai, Enze Fan, Mengbao China Univ Min & Technol Sch Informat & Control Engn Xuzhou 221116 Jiangsu Peoples R China China Univ Min & Technol Sch Mechatron Engn Xuzhou 221116 Jiangsu Peoples R China

Internal discontinuities are critical factors that can lead to premature failure of thermal barrier coatings (TBCs). This paper proposes a technique that combines terahertz (THz) time-domain spectroscopy and machine learning classifiers to identify discontinuities in TBCs. First, the finite-difference time-domain method was used to build a theoretical model of THz signals due to discontinuities in TBCs. Then, simulations were carried out to compute THz waveforms of different discontinuities in TBCs. Further, six machine learning classifiers were employed to classify these different discontinuities. Principal component analysis (PCA) was used for dimensionality reduction, and the Grid Search method was utilized to optimize the hyperparameters of the designed machine learning classifiers. Accuracy and running time were used to characterize their performances. The results show that the support vector machine (SVM) has a better performance than the others in TBC discontinuity classification. Using PCA, the average accuracy of the SVM classifier is 94.3%, and the running time is 65.6 ms.

关键词： thermal barrier coatings terahertz machine learning classifiers finite-difference time-domain method

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Virtual lattice resonance of a single nanoresonator in a metal nanoslit

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Physical Review A 2023年第3期107卷 033520-033520页

作者： Ofer Doron Tal Ellenbogen Faculty of Engineering Department of Physical Electronics Tel Aviv University Tel Aviv 69978 Israel Raymond and Beverly Sackler School of Physics & Astronomy Tel Aviv University Tel Aviv 69978 Israel Tel Aviv Center for Light-Matter Interaction Tel Aviv University Tel Aviv 69978 Israel

We study the transmission through a subwavelength metallic slit loaded with a single nanoresonator. To gain physical insight into the problem a theoretical model combining the dipole approximation and image theory is developed. The model shows that the coupling between the single nanoresonator and the slit's cavity modes serves as a localized analog to an infinite nanoresonator array. This virtual array supports a surface image-lattice resonance due to the coherent self-scattering of the single nanoresonator. Thereby, it may lead to the ability to mimic many recently reported intriguing physical phenomena of real surface-lattice resonances in nanoresonator arrays, by a single-subwavelength system. We specifically show that it leads to enhanced light-matter interaction, and to the appearance of an extraordinary transmission window. The theoretical results are in good agreement with full-wave numerical simulations.

关键词： Extraordinary optical transmission Nanoantennas Nanophotonics Plasmonics Metasurfaces Dipole approximation finite-difference time-domain method

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Frequency-selective spin-wave propagation in magnonic waveguide with a local laser-heated region

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Physical Review B 2023年第2期107卷 024427-024427页

作者： V. A. Gubanov V. V. Kruglyak S. E. Sheshukova V. D. Bessonov S. A. Nikitov A. V. Sadovnikov Magnetic Metamaterials Saratov State University 410012 Saratov Russia Department of Physics and Astronomy University of Exeter Exeter EX4 4QL United Kingdom Institute of Physics of Metals 620108 Ekaterinburg Russia Kotel'nikov Institute of Radioengineering and Electronics 125009 Moscow Russia

We report on the spin-wave propagation along a magnonic waveguide with a local area of decreased magnetization, which is induced by heating produced with a focused laser spot. A phase-sensitive Brillouin light scattering technique is used to image how the spin wave propagates along the waveguide with a local heat landscape. Frequency-selective signal propagation along the waveguide is demonstrated. Micromagnetic simulations reveal intermodal interference variation in the region after the heated area. The proposed way to reconfigure the magnetization landscape can be used in magnonic devices with frequency-selective spin-wave transport.

关键词： Brillouin scattering & spectroscopy Magnons Micromagnetism Spin waves Ferrimagnets finite-difference time-domain method Landau-Lifschitz-Gilbert equation

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Analysis of all-optical priority encoder using plasmonics waveguide

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JOURNAL OF COMPUTATIONAL ELECTRONICS 2021年第5期20卷 1884-1890页

作者： Karki, Bhishma Pal, Amrindra Sharma, Sandeep Tribhuvan Univ Dept Phys Trichandra Multiple Campus Kathmandu 44600 Nepal DIT Univ EECE Dept Photon Lab Dehra Dun 248009 Uttarakhand India OMKARR Tech New Delhi India iNurture Educ Solut Bengaluru Karnataka India Ajeenkya DY Patil Univ Dept IT Pune Maharashtra India

The proposed all-optical circuit utilizes the deep sub-wavelength confinement properties of plasmonic metal-insulator-metal waveguides. All-optical priority encoder accepts 2(n) outputs. The priority encoder is designed using the plasmonics waveguide-based Mach-Zehnder interferometer (P-MZI). The P-MZI works as an all-optical switch. The switching of the signal depends on the power of the applied optical input signal. This waveguide has a nonlinear material inside. The proposed work is analyzed using the finite-difference time-domain method, and a mathematical description is also given. Parameters such as insertion loss and extinction ratio are reported as 15.82 dB and 0.57 dB, respectively.

关键词： Priority encoder finite-difference time-domain method Plasmonic Nonlinear material

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Single-sized phase-change metasurfaces for dynamic information multiplexing and encryption

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Physical Review Research 2024年第2期6卷 023258-023258页

作者： Tingting Liu Jie Li Shuyuan Xiao School of Information Engineering Institute for Advanced Study Optoelectronic Sensor Devices and Systems Key Laboratory of Sichuan Provincial University College of Optoelectronic Engineering

Optical metasurfaces empower us to manipulate the electromagnetic space and control light propagation at the nanoscale, offering a powerful tool to achieve modulation of light for information processing and storage. In this paper, we propose a phase-change metasurface to realize dynamic multiplexing and encryption of near-field information. Based on the orientation degeneracy and polarization control governed by Malus's law, we elaborately design the orientation distribution of Sb2S3 meta-atoms with the same dimension to simultaneously satisfy the amplitude modulation requirements of three independent channels. Using the corresponding polarization control as decoding keys, three different nanoprinting images can be displayed, and these multiplexed images can be switched on and off by leveraging the reversible tunability of the Sb2S3 meta-atoms between the amorphous and crystalline states. With the unparalleled advantages of ultracompactness, simple design strategy, high information density and security, the proposed metasurfaces afford promising prospects for high-end applications in ultracompact and intelligent dynamic display, high-dense optical data storage, and optical information encryption.

关键词： Imaging & optical processing Nanophotonics Phase-change materials Polarization of light Chalcogenides Metasurfaces finite-difference time-domain method

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Modeling spatiotemporal dynamics of chiral coupling of quantum emitters to light fields in nanophotonic structures

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Physical Review A 2023年第2期107卷 023502-023502页

作者： Jan Olthaus Maximilian Sohr Stephan Wong Sang Soon Oh Doris E. Reiter Institut für Festkörpertheorie Universität Münster 48149 Münster Germany School of Physics and Astronomy Cardiff University Cardiff CF24 3AA United Kingdom Condensed Matter Theory Department of Physics TU Dortmund 44221 Dortmund Germany

A quantum emitter placed in a nanophotonic structure can result in nonreciprocal phenomena like chiral light excitation. Here, we present a theoretical model to couple circularly polarized emitters described by the density-matrix formalism to the electromagnetic fields within a finite-difference time-domain simulation. In particular, we discuss how to implement complex electric fields in the simulation to make use of the rotating-wave approximation. By applying our model to a quantum emitter in a dielectric waveguide and an optical circulator, we show how the excitation of the quantum system depends on its position and polarization. In turn, the back-coupling can result in strongly asymmetric light excitation. Our framework and results will help better explain spatiotemporal dynamics of light fields in nanophotonic structures containing quantum emitters.

关键词： Chirality Light-matter interaction Photonics finite-difference time-domain method Two-level models

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Strong coupling in an Au plasmonic antenna–SiO2 layer system: A hybrid-mode analysis

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Physical Review B 2023年第12期107卷 125144-125144页

作者： Pavel Gallina Michal Kvapil Jiří Liška Andrea Konečná Vlastimil Křápek Radek Kalousek Jakub Zlámal Tomáš Šikola Central European Institute of Technology Brno University of Technology Purkyňova 123 612 00 Brno Czech Republic Institute of Physical Engineering Brno University of Technology Technická 2 616 69 Brno Czech Republic

A detailed analysis of the optical response of a system accommodating several coupled modes is needed for the complete understanding of the strong coupling effect. In this paper, we report on the analysis of scattering cross-section spectra of Au antennas on a SiO2 layer on a Si substrate in the IR region. A classical model of coupled oscillators is used for determining the resonant energies, damping rates, and coupling strengths of four phonon polariton modes in the SiO2 layer coupled to a localized surface plasmon mode in a Au antenna. The calculated Hopfield mixing coefficients then show the contribution of the individual uncoupled modes to the hybrid modes of the coupled system.

关键词： Nanoantennas Optical phonons Phonon polariton Plasmonics Surface plasmon polariton finite-difference time-domain method Fourier transform infrared spectroscopy

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