Article
Engineering, Electrical & Electronic
Lihao Song, Eng Leong Tan, Ding Yu Heh, Bowen Bai, Xiaoping Li, Yanming Liu
Summary: This article proposes a novel finite-difference time-domain (FDTD) method for studying electromagnetic wave propagation in time-varying plasma. The method, called the Newton-ADE FDTD method, is based on Newton's equation of motion and provides more accurate results compared to traditional methods in time-varying plasma conditions.
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
(2023)
Article
Optics
Xinye Tian, Xuejun Qiu, Zhenzhou Cao, Jin Hou, Chunyong Yang
Summary: In this paper, a broadband metamaterial absorber (BMA) based on a thin metamaterial nanostructure composed of 2D Au square grating on graphene-SiO2 film and Au substrate is proposed and designed. The optimized structure achieves nearly perfect absorption in a broad range from deep UV light to visible light (100 nm-700 nm), exceeding 90% absorption. The mechanism responsible for the broadband absorption, including the excitation of Rayleigh anomaly (RA), cavity resonance (CR), surface plasmon polaritons (SPPs) and magnetic polaritons (MPs), has been analyzed using finite-difference time-domain (FDTD) method and the LC circuit model. The proposed BMA is also polarization and angle insensitive for incident light, even at large angles. It shows great potential in solar cell and photo-detector applications due to its simple geometry, ordinary metal-based material composition, and high performance in both bandwidth and absorptivity.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Engineering, Electrical & Electronic
Yong-Jin Kim, Kyung-Young Jung
Summary: The paper introduces an accurate and efficient FDTD formulation based on the bilinear transform for dusty plasma analysis, outperforming previous formulations in accuracy and computational efficiency. Numerical examples demonstrate its superiority in comparison to other FDTD formulations, and it further investigates the effect of dust particles on EM wave propagation in the GHz and THz bands.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2021)
Article
Geosciences, Multidisciplinary
Bangyu Wu, Wenzhuo Tan, Wenhao Xu, Bo Li
Summary: In this study, a 3D trapezoid-grid finite-difference time-domain (FDTD) method is proposed to reduce memory usage in 3D large-scale wave modeling. By using a trapezoid-grid mesh that fits the increasing trend of seismic wave velocity with depth, oversampling in high-velocity regions is significantly reduced. The method incorporates trapezoid coordinate transformation and trapezoid-grid convolutional perfectly matched layer (CPML) absorbing boundary condition to handle non-uniform grids and eliminate artificial boundary reflections. Numerical tests demonstrate the effectiveness of the method and show a 50% reduction in memory usage compared to the uniform-grid FDTD method for comparable computational time and accuracy.
FRONTIERS IN EARTH SCIENCE
(2022)
Article
Engineering, Electrical & Electronic
Jeahoon Cho, Min-Seok Park, Kyung-Young Jung
Summary: This work presents a comprehensive study on the numerical accuracy of four FDTD formulations for magnetized plasma. The results show that the E-J collocated ADE method provides the best accuracy.
JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE
(2022)
Article
Acoustics
Yue Li, Julie Meyer, Tapio Lokki, Jacques Cuenca, Onur Atak, Wim Desmet
Summary: Compared to geometrical acoustics, wave-based methods are known for their high accuracy in solving the wave equation. However, their systematic use as professional room acoustic simulation tools is less popular due to the modeling effort and computational time requirements, especially in complex scenarios. This paper provides guidelines for using two wave-based methods, namely the finite-difference time-domain (FDTD) method and the fast multipole boundary element method (FMBEM), in complex room acoustics simulations. Numerical experiments are conducted to address convergence issues and evaluate the capability and efficiency of the solvers.
Article
Engineering, Electrical & Electronic
Yong-Jin Kim, Jeahoon Cho, Kyung-Young Jung
Summary: The finite-difference time-domain (FDTD) method is widely used for analyzing the electromagnetic behavior of dusty plasma sheath in re-entering hypersonic vehicles. This study proposes an efficient FDTD modeling approach for time-varying dusty plasma by combining the bilinear transform and the state-space approach. The proposed FDTD formulation improves computational efficiency while maintaining numerical accuracy compared to the conventional shift operator FDTD counterpart. Numerical examples are provided to validate the proposed FDTD modeling approach for time-varying dusty plasma.
JOURNAL OF ELECTROMAGNETIC ENGINEERING AND SCIENCE
(2022)
Article
Optics
Hung-Chih Hsieh, Jui-Ming Cheng, Yun-Chi Yeh
Summary: A robust and wafer-less wavelength selection methodology is proposed, which selects the optimized wavelength by analyzing the wavelength with the minimum variation of the asymmetry factor. The maximum overlay error of the optimized wavelength selected by this method is 0.21 nm.
Article
Engineering, Electrical & Electronic
Rodrigo M. S. de Oliveira, Rodrigo R. Paiva
Summary: A central least-squares spatial derivative procedure and LS-FDTD method have been developed to approximate spatial derivatives and attenuate nonphysical modes. The proposed method has been successfully validated for 1-D and 2-D problems with time steps beyond the FDTD CFL limit, demonstrating accuracy and stability conditions for LS-FDTD.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2021)
Article
Chemistry, Physical
Qinxiu Zhang, Yue Zhang, Tao Xiong, Wei Wang, Cheng Sun
Summary: In this study, a central symmetrical tetramer structure consisting of gold-broken nanorings is proposed and the plasmonic properties of the system in the visible range are investigated using the finite difference time-domain method. The study focuses on quantitatively analyzing the plasmonic scattering efficiency of the system and examining the electric field distributions at resonance wavelengths. By varying the structural parameters, including the relative orientation of the broken angles, the thickness of the broken nanorings, light polarization, and the refractive index of the surrounding environment, it is shown that different plasmonic resonances can be achieved in the gold broken nanorings, allowing for tunability of resonance wavelengths and peak intensities. The findings of this study have potential applications in the design of plasmonic devices operating in the visible wavelength range.
Article
Engineering, Electrical & Electronic
Xiao-Yao Feng, Zhizhang Chen, Zhi-Meng Xu
Summary: This article introduces a method that incorporates the concept of kurtosis into time-reversal processing, allowing for reconstruction of both spatial locations and source excitation time instants. The method clears the way for the application of time-reversal methods to real-world problems.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2021)
Article
Acoustics
Stefan Bilbao
Summary: The paper explores the modeling of finite spatial extent source distributions in ultrasound and medical imaging applications, focusing on representation over a grid as an optimization problem in the Fourier domain. This method allows control over computational cost and optimization to the wavenumber range of interest for a particular numerical method, with numerical results presented for the special case of spherical cap or bowl sources.
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
(2021)
Article
Physics, Multidisciplinary
Weipeng Yao, Julien Capitaine, Benjamin Khiar, Tommaso Vinci, Konstantin Burdonov, Jerome Beard, Julien Fuchs, Andrea Ciardi
Summary: The dynamics and structuring of plasma in a strong magnetic field are crucial for laboratory astrophysics, inertial confinement fusion, and industrial applications.
MATTER AND RADIATION AT EXTREMES
(2022)
Article
Engineering, Electrical & Electronic
Hui Liu, Li-Xia Yang, Wei Chen, Yong Bo
Summary: This paper introduces a new method that combines the Newtonian equation of motion with the traditional ADE-FDTD method to describe the behavior of electrons when electromagnetic waves propagate in a magnetized plasma. The correctness of the algorithm is verified by calculating the reflection coefficients, and the impact of different incident angles on the reflection coefficients is studied.
APPLIED COMPUTATIONAL ELECTROMAGNETICS SOCIETY JOURNAL
(2022)
Article
Chemistry, Analytical
Hung-Chih Hsieh, Meng-Rong Wu, Xiang-Ting Huang
Summary: The present study introduces an optimized overlay target design to minimize the overlay error caused by asymmetric sidewall structures in semiconductor manufacturing. The overlay error formula was derived by separating the asymmetric bottom grating structure into symmetric and asymmetric parts. The proposed design can effectively control the measurement error of different wavelengths within +/- 0.3 nm, even under varying sidewall angles and film thicknesses.
Article
Chemistry, Multidisciplinary
Jaeho Kim, Hajime Sakakita, Hiromoto Itagaki
Article
Nanoscience & Nanotechnology
H. Itagaki, Y. Fujiwara, Y. Minowa, Y. Ikehara, T. Kaneko, T. Okazaki, Y. Iizumi, J. Kim, H. Sakakita
Article
Multidisciplinary Sciences
Dong-Eog Kim, Jinseong Jang, Dawid Schellingerhout, Wi-Sun Ryu, Jong-Ho Park, Su-Kyoung Lee, Dongmin Kim, Hee-Joon Bae
SCIENTIFIC REPORTS
(2019)
Article
Physics, Fluids & Plasmas
Hiromasa Yamada, Susumu Kato, Tetsuji Shimizu, Masanori Fujiwara, Yutaka Fujiwara, Jaeho Kim, Sanae Ikehara, Nobuyuki Shimizu, Yuzuru Ikehara, Hajime Sakakita
PHYSICS OF PLASMAS
(2020)
Article
Multidisciplinary Sciences
Dongmin Kim, Tomoyuki Yokota, Toshiki Suzuki, Sunghoon Lee, Taeseong Woo, Wakako Yukita, Mari Koizumi, Yutaro Tachibana, Hiromu Yawo, Hiroshi Onodera, Masaki Sekino, Takao Someya
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2020)
Article
Engineering, Electrical & Electronic
Tobias Tymosch, Manuel Fischer, Vasken Ketchedjian, Yutaka Terao, Hiroyuki Ohsaki
Summary: This article evaluates a novel design approach for a 3 MW partially superconducting synchronous machine for electric aircraft propulsion, which uses an electromagnetic Halbach array to reduce back yoke weight and increase overall power density. The Halbach array achieves better magnetic field intensity characteristics compared to traditional superconducting field winding designs, with potential reductions in yoke thickness and weight.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2021)
Article
Physics, Applied
Hajime Sakakita, Hiromasa Yamada, Tetsuji Shimizu, Masanori Fujiwara, Susumu Kato, Jaeho Kim, Sanae Ikehara, Nobuyuki Shimizu, Yuzuru Ikehara
Summary: The experiment found that a monotonic supply of total absolute charge in one period is important for protein aggregation. When the coefficient of variation is small, the amount of protein aggregation becomes larger. Excess or scarcity of averaged total absolute charges does not appear to relate to protein aggregation phenomena, however, the coefficient of variation strongly relates to the mechanism of protein aggregation.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Multidisciplinary Sciences
TaeWoo Kwon, Sang Pyo Lee, Dongmin Kim, Jinseong Jang, Myungjae Lee, Shin Uk Kang, Heejin Kim, Keunyoung Oh, Jinhee On, Young Jae Kim, So Jeong Yun, Kwang Nam Jin, Eun Young Kim, Kwang Gi Kim
Summary: This study aims to develop an AI model for pneumonia diagnosis from chest X-ray images, with the performance evaluated using an external dataset. The AI model achieved a high accuracy in distinguishing pneumonia cases and showed potential for improving efficiency in pneumonia diagnosis and follow-up evaluation.
Article
Engineering, Electrical & Electronic
Kezhen Qian, Yutaka Terao, Hiroyuki Ohsaki
Summary: A versatile 3D electromagnetic and thermal field coupled FEM analysis tool was developed for REBCO coils in this research, and its capability in studying the transient electromagnetic and thermal behaviors was verified through two case studies. The first case study focused on the transient behaviors of SFCL REBCO coils under overcurrent, while the second case study explored the influence of external energy input on the quench of magnet REBCO coils. Additionally, the limitations and improvements of the quench detection scheme based on voltage detection were discussed.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2021)
Article
Chemistry, Multidisciplinary
Takashi Tsuji, Jaeho Kim, Hajime Sakakita, Yoshiki Shimizu, Guohai Chen, Kenji Hata, Don N. Futaba, Shunsuke Sakurai
Summary: Hydrogen is crucial in carbon nanotube synthesis as it supports key growth processes. Without hydrogen, amorphous carbon particles are produced. By converting the electron energy of the plasma into thermal energy, hydrogen provides suitable conditions for catalyst nanoparticle formation and CNT nucleation.
Article
Engineering, Electrical & Electronic
Y. Terao, Y. Iwata, Y. Takagi, S. Fuchino, H. Ohsaki
Summary: This paper presents a new AC loss measurement system for MgB2 superconducting coils under a rotating magnetic field. The system measures the AC loss by measuring the difference in mechanical input. Experimental results show that this method is effective and accurate.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2022)
Article
Engineering, Electrical & Electronic
Yutaka Terao, Haruka Nakamura, Satsuki Okumura, Shuichiro Fuchino, Hiroyuki Ohsaki
Summary: In this paper, the authors measured AC losses of an MgB2 superconducting coil at 20 K by applying a rotating magnetic field and induced alternating current. The AC loss of the coil and the ohmic loss at the load were measured and estimated using torque meter and current probe, respectively. The results showed good agreement between the measured and calculated AC losses at 80 Hz, with values of 7.23 W/cm(3) and 7.17 W/cm(3), respectively. Measurement and analysis results were consistent in the 40-80 Hz range.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
Article
Engineering, Electrical & Electronic
Brian Marchionini, Steve Eckroad, Laura Serri, Giuliano Angeli, Hiroyuki Ohsaki, Donald Mosteller, Luciano Martini
Summary: The International Energy Agency's High Temperature Superconductivity Technology Collaboration Program (IEA HTS TCP) analyzed the readiness levels of HTS applications in the energy delivery sector. A Readiness Map was created to illustrate the technology readiness over time. Assessing these levels is important for the transition to safer, more efficient and cleaner power supply. The experts categorized the applications into low, medium and high readiness levels instead of specific TRL numbers.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
Article
Medicine, General & Internal
Kyu-Chong Lee, Yongwon Cho, Kyung-Sik Ahn, Hyun-Joon Park, Young-Shin Kang, Sungshin Lee, Dongmin Kim, Chang Ho Kang
Summary: This study developed a deep neural network model for the detection of rotator cuff tears in routine shoulder MRI scans. The model showed the highest performance when using all three imaging planes. Among single imaging planes, the axial plane had the best performance. Deep-learning-based automatic rotator cuff tear detection can be useful for detecting torn areas in various regions of the rotator cuff in all three imaging planes.
Article
Medicine, General & Internal
Sangyup Oh, Dongjun Oh, Dongmin Kim, Woohyuk Song, Youngbae Hwang, Namik Cho, Yun Jeong Lim
Summary: This study presents a novel neural encoder based on the Transformer architecture, which takes the entire video frames as input and improves the accuracy of lesion detection. By utilizing the power of Transformer architecture in extracting long-term global correlation within and between frames, as well as capturing the temporal context and attentional features, automated lesion detection for images is significantly enhanced.
