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Nonreciprocal coupling in space-time modulated systems at exceptional points

Physical Review B 2022年第10期105卷 L100304-L100304页

作者： Junfei Li Yun Jing Steven A. Cummer Department of Electrical and Computer Engineering Duke University Durham North Carolina 27708 USA Graduate Program in Acoustics The Pennsylvania State University University Park Pennsylvania 16802 USA

Exceptional points (EPs) are critical points in the parameter space of non-Hermitian systems, where two or more eigenvalues and eigenvectors simultaneously coalesce. The remarkable physics and behavior of waves at these EPs have raised considerable attention. Previous research has accessed EPs in parity-time (PT) symmetric systems through spatially modulated parameters. Using acoustics, this Letter demonstrates a different family of EPs in classical wave systems that emerge from coordinated modulation of mass density and loss/gain in time. This condition can create nonreciprocal coupling between arbitrary modes at the EPs, leading to exotic behaviors such as unilateral frequency conversion and linear amplification of waves that are unattainable at conventional time-invariant systems. Moreover, these phenomena can be attained with only loss, and acoustic gain via modal energy transfer is demonstrated in a loss-only system at such EPs. Our work marries time-varying systems with EPs, which could open new avenues for wave manipulation.

关键词： Classical mechanics Continuum mechanics Dynamical systems Hamiltonian systems Traveling waves

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Channel Estimation for Optical Intelligent Reflecting Surface-Assisted VLC System: A Joint Space-Time Sampling Approach

arXiv

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arXiv 2024年

作者： Sun, Shiyuan Yang, Fang Mei, Weidong Song, Jian Han, Zhu Zhang, Rui The Department of Electronic Engineering Tsinghua University Beijing100084 China The National Key Laboratory of Wireless Communications University of Electronic Science and Technology of China Chengdu611731 China The Shenzhen International Graduate School Tsinghua University Shenzhen518055 China The Department of Electrical and Computer Engineering The University of Houston HoustonTX77004 United States The Department of Computer Science and Engineering Kyung Hee University Seoul446-701 Korea Republic of School of Science and Engineering Shenzhen Research Institute of Big Data The Chinese University of Hong Kong Guangdong Shenzhen518172 China The Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

Optical intelligent reflecting surface (OIRS) has attracted increasing attention due to its capability of overcoming signal blockages in visible light communication (VLC), an emerging technology for the next-generation advanced transceivers. However, current works on OIRS predominantly assume known channel state information (CSI), which are essential to practical OIRS configuration. To bridge such a gap, this paper proposes a new and customized channel estimation protocol for OIRSs under the alignment-based channel model. Specifically, we first unveil OIRS spatial and temporal coherence characteristics and derive the coherence distance and the coherence time in closed-form. Next, to achieve fast beam alignment over different coherence time, we propose to dynamically tune the rotational angles of the OIRS reflecting elements following a geometric optics-based non-uniform codebook. Given the above beam alignment, we propose an efficient joint space-time sampling-based algorithm to estimate the OIRS channel. In particular, we divide the OIRS into multiple subarrays based on the coherence distance and sequentially estimate their associated CSI, followed by a spacetime interpolation to retrieve full CSI for other non-aligned transceiver antennas. Numerical results validate our theoretical analyses and demonstrate the efficacy of our proposed OIRS channel estimation scheme as compared to other benchmark schemes. Copyright © 2024, The Authors. All rights reserved.

关键词： Channel estimation

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An overview on the principle of inkjet printing technique and its application in micro-display for augmented/virtual realities

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Opto-electronic Advances 2022年第6期5卷 20-43页

作者： Xiao Yang Yue Lin Tingzhu Wu Zijun Yan Zhong Chen Hao-Chung Kuo Rong Zhang Department of Electronic Science Fujian Engineering Research Center for Solid-State LightingXiamen UniversityXiamen 361005China Institute of Future Display Technology Xiamen UniversityXiamen 361005China Department of Photonics&Graduate Institute of Electro-Optical Engineering College of Electrical and Computer EngineeringChiao Tung UniversityHsinchu 30010TaiwanChina.

Augmented reality(AR)and virtual reality(VR)are two novel display technologies that are under *** essential feature of AR/VR is the full-color display that requires high pixel *** generate three-color pixels,the fluorescent color conversion layer inevitably includes green and red *** fabricate such sort of display kits,inkjet printing is a promising way to position the color conversion *** this review article,the progress of AR/VR technologies is first reviewed,and in succession,the state of the art of inkjet printing,as well as two key issues-the optimization of ink and the reduction of coffee-ring effects,are ***,some potential problems associated with the color converting layer are highlighted.

关键词： micro-LED quantum dots augmented reality virtual reality inkjet printing

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Intelligent Omni-Surfaces (IOSs) For Full-dimensional Wireless Coverage Extension: IOS Orientation and Location Optimization

Intelligent Omni-Surfaces (IOSs) For Full-dimensional Wirele...

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IEEE International Conference on Communications in China (ICCC)

作者： Menghan Li Shuhao Zeng Hongliang Zhang Boya Di Xi Weng Lingyang Song School of Electronics Engineering and Computer Science Peking University Beijing China School of Electronic and Computer Engineering Peking University Shenzhen Graduate School Shenzhen China Department of Electrical and Computer Engineering Princeton University NJ USA School of Electronics Peking University Beijing China Guanghua School of Management Peking University Beijing China

ISBN: (数字)9798350378412

ISBN: (纸本)9798350378429

The intelligent omni-surface (IOS), a type of metasurface which can simultaneously reflect and refract incident signals, is a promising technology for full-dimensional cell coverage extension. Existing works only explore the IOS configuration optimization for coverage extension given the IOS location, while how to deploy the IOS to maximize the cell coverage has not been investigated. In this paper, we aim to maximize the coverage of an IOS-assisted network by optimizing the deployment of the IOS. The placement optimization for metasurfaces in existing works mainly focuses on the reflective metasurface, which can not be applied here directly since the reflection and refraction of the IOS are coupled. To cope with this problem, we consider a downlink IOS-assisted multiple-input-single-output (MISO) system. The cell coverage of the IOS-assisted system is first analyzed, based on which we formulate a coverage maximization problem and solve it by jointly optimizing the IOS orientation and relative position between the IOS and the BS based on the projected gradient descent method. Numerical results verify the effectiveness of the proposed algorithm.

关键词： Wireless communication Simulation MISO communication Directive antennas Metasurfaces Downlink Reflector antennas

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NOMAD: nonlinear manifold decoders for operator learning 22

NOMAD: nonlinear manifold decoders for operator learning

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Proceedings of the 36th International Conference on Neural Information Processing Systems

作者： Jacob H. Seidman Georgios Kissas Paris Perdikaris George J. Pappas Graduate Program in Applied Mathematics and Computational Science University of Pennsylvania Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania Department of Electrical and Systems Engineering University of Pennsylvania

ISBN: (纸本)9781713871088

Supervised learning in function spaces is an emerging area of machine learning research with applications to the prediction of complex physical systems such as fluid flows, solid mechanics, and climate modeling. By directly learning maps (operators) between infinite dimensional function spaces, these models are able to learn discretization invariant representations of target functions. A common approach is to represent such target functions as linear combinations of basis elements learned from data. However, there are simple scenarios where, even though the target functions form a low dimensional submanifold, a very large number of basis elements is needed for an accurate linear representation. Here we present NOMAD, a novel operator learning framework with a nonlinear decoder map capable of learning finite dimensional representations of nonlinear submanifolds in function spaces. We show this method is able to accurately learn low dimensional representations of solution manifolds to partial differential equations while outperforming linear models of larger size. Additionally, we compare to state-of-the-art operator learning methods on a complex fluid dynamics benchmark and achieve competitive performance with a significantly smaller model size and training cost.

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On Reliability Assessment of a Battery Energy Storage Systems Supporting PV Plants

On Reliability Assessment of a Battery Energy Storage System...

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IEEE Annual Southern Power electronics Conference (SPEC)

作者： William Caires Silva Amorim Allan Fagner Cupertino Victor Flores Mendes Renata Oliveira De Sousa Rodrigo Cássio De Barros Heverton Augusto Pereira Graduate Program in Electrical Engineering Federal University of Minas Gerais Belo Horizonte Brazil Department of Electrical Energy Federal University of Juz de Fora Juiz de Fora Brazil Department of Electrical Engineering Federal University of Minas Gerais Belo Horizonte Brazil Department of Electronics Federal University of Tech. - Paraná Curitiba Brazil Department of Electrical Engineering Federal University of Recôncavo da Bahia Cruz das Almas Brazil Department of Electrical Engineering Federal University of Viçosa Viçosa Brazil

Battery energy storage system (BESS) has been highlighted for its possibilities of performing ancillary services to the power system, such as voltage and frequency regulation, power quality, power smoothing, and peak shaving, among others. The BESS is very promising especially associated with renewable energies, such as photovoltaic (PV) and wind. Among some of these ancillary services, this work evaluates the battery lifetime and reliability. The proposed methodology includes the combined analysis of rainflow counting algorithm, Monte Carlo simulation, and nonlinear damage accumulation rule for battery reliability assessment. Monte Carlo simulation is used to approximate the battery reliability estimation of practical applications, by considering stochastic variations in the battery lifetime model. The case study is based on a 100 $\textbf{kW}$ PV system, assessed using a one-year mission profile of solar irradiance and ambient temperature from Goiânla-Brazll associated with a mission profile of 100 $\textbf{kW}$ industrial load. The PV plant is connected to a 440 V grid associated with a BESS that mitigates oscillations of 10% of PV nominal power per minute. The peak shaving service presented a decrease in the battery lifetime by approximately 11 % in relation to the deterministic battery lifetime analysis. On the other hand, the peak shaving presented a decrease in the battery lifetime by approximately 17.4 %. In addition, the pack-level analysis revealed a maximum reduction in the battery lifetime by approximately 30%, when compared to the conventional deterministic battery reliability estimation procedure.

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Ambient conditions to reproduce gamma-ray glow energy spectra assuming cosmic ray as source 38

Ambient conditions to reproduce gamma-ray glow energy spectr...

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38th International Cosmic Ray Conference, ICRC 2023

作者： Diniz, Gabriel Sousa Wada, Yuuki Ohira, Yutaka Nakazawa, Kazuhiro Tsurumi, Miwa Enoto, Teruaki Department of Physics Graduate School of Science Kyoto University Kitashirakawa Oiwake-cho Sakyo-ku Kyoto-shi Kyoto606-8502 Japan Division of Electrical Electronic and Infocommunications Engineering Graduate School of Engineering Osaka University 2-1 Yamadaoka Suita Osaka565-0871 Japan Department of Earth and Planetary Environmental Science The University of Tokyo 7 Chome-3-1 Hongo Bunkyo City Tokyo113-8654 Japan Kobayashi-Maskawa Institute for the Origin of Particles and the Universe Nagoya University Furo-cho Chikusa-ku Aichi Nagoya464-8601 Japan Graduate School of Science and Engineering Aoyama Gakuin University 5-10-1 Fuchinobe Kanagawa Sagamihara252-5258 Japan Extreme Natural Phenomena RIKEN Hakubi Research Team RIKEN Cluster for Pioneering Research 2-1 Hirosawa Saitama Wako351-0198 Japan

The electric field of thunderclouds modifies components and energy spectra of the cosmic-ray air shower resulting in an enhancement of gamma-ray fluxes on the ground, known as a gamma-ray glow. The Gamma-Ray Observation of Winter THunderclouds (GROWTH) collaboration has measured this phenomenon for several years in the Hokuriku area of Japan. The present work examines the ambient conditions required to produce spectral features of the previously detected gamma-ray glows. We use Monte Carlo simulations of particle interactions in the atmosphere with the cosmic-ray electron spectrum as input from the EXcel-based program for calculating Atmospheric Cosmic-ray Spectrum (EXPACS). We focus on three parameters, the strength and length of the electric field and the size of a null-field attenuation region below the electrified region. The average spectrum of observed gamma-ray glows in winter thunderstorms of Japan requires an electric field intensity close to the Relativistic Runaway Electron Avalanche (RREA) threshold of 0.284 MV/m. The vertical size of the electric field region should be in the range of 0.5—1 km. The estimated attenuation region size is 300–500 m, necessary to reduce the low-energy photon flux of the average gamma-ray glows. The whole space of phase capable of generating the gamma-ray glow spectra uses only cosmic-ray electron shower as input. Thus, the interaction between cosmic-ray and the thundercloud is capable of producing the signal detected at the ground. © Copyright owned by the author(s) under the terms of the Creative Commons.

关键词： Particle interactions

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A Study on Giant Magnetostrictive Actuator for Interior Sound Control System of the Ultra-Compact Mobility: Fundamental Consideration on Formation of the Giant Magnetostrictive Phases Depending on Heat Treatment Condition

A Study on Giant Magnetostrictive Actuator for Interior Soun...

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International Conference on electrical Machines and Systems (ICEMS)

作者： Taro Kato Ryusei Naganuma Koki Bando Kentaro Sawada Wu Wenbao Ikkei Kobayashi Jumpei Kuroda Daigo Uchino Kazuki Ogawa Keigo Ikeda Ayato Endo Hideaki Kato Takayoshi Narita Mitusaki Furui Department of Mechanical Engineering Tokyo University of Technology Hachioji-shi Tokyo Japan Sustainable Engineering Program Graduate School of Engineering Tokyo University of Technology Hachioji-shi Tokyo Japan Course of Mechanical Engineering Tokai University Hiratsuka-shi Kanagawa Japan Course of Science and Technology Tokai University Hiratsuka-shi Kanagawa Japan Department of Mechanical Engineering National Institute of Technology (KOSEN) Numazu College Numazu-shi Shizuoka Japan Department of Electronic Robotics Aichi University of Technology Gamagori-shi Aichi Japan Department of Mechanical Engineering Hokkaido University of Science Sapporo Hokkaido Japan Department of Electrical Engineering Fukuoka Institute of Technology Fukuoka-shi Fukuoka Japan Department of Mechanical System Engineering Tokai University Hiratsuka-shi Kanagawa Japan

ISBN: (数字)9784886864406

ISBN: (纸本)9798350379105

An active noise control system using giant magnetostrictive actuator has been proposed as a countermeasure for interior noise of the ultra-compact mobilities, which is a new transportation tools. In this paper, as basic research toward the development of the proposed giant magnetostrictive actuator for active noise control, we conduct experiments on the material properties when terbium, dysprosium, and iron powder, which make up the giant magnetostrictive material, are mixed and the heat treatment conditions are changed. In this study, the heat treatment temperature was varied from $800^{\circ}\mathrm{C}$ to $1100^{\circ}\mathrm{C}$ in $100^{\circ}\mathrm{C}$ incrementsbased on the equilibrium state temperature of each material, and the heat treatment time was set in 30-minute increments from 1 hour to 3 hours. As a result, TbFe2 was confirmed after heat treatment at an electric furnace temperature of $1000^{\circ}\mathrm{C}$ for 3 hours, although its strength was insufficient.

关键词： Actuators Heat treatment Powders Temperature Magnetostriction Noise Terbium Iron Resistance heating Material properties

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Foldable three dimensional neural electrode arrays for simultaneous brain interfacing of cortical surface and intracortical multilayers

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npj Flexible electronics 2022年第1期6卷 840-853页

作者： Ju Young Lee Sang Hoon Park Yujin Kim Young Uk Cho Jaejin Park Jung-Hoon Hong Kyubeen Kim Jongwoon Shin Jeong Eun Ju In Sik Min Mingyu Sang Hyogeun Shin Ui-Jin Jeong Yuyan Gao Bowen Li Aizhan Zhumbayeva Kyung Yeun Kim Eun-Bin Hong Min-Ho Nam Hojeong Jeon Youngmee Jung Huanyu Cheng Il-Joo Cho Ki Jun Yu School of Electrical and Electronic Engineering Yonsei University50 Yonsei-roSeodaemunguSeoul 03722Republic of Korea Department of Biomedical Sciences College of MedicineKorea UniversitySeoul 02841Republic of Korea Brain Science Institute Korea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea School of Electrical Engineering Korea UniversitySeoul 02841Republic of Korea Department of Engineering Science and Mechanics The Pennsylvania State UniversityUniversity ParkPA 16802USA Center for Biomaterials Biomedical Research InstituteKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Biomaterials Research Center Biomedical Research DivisionKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Department of Mechanical Engineering Seoul National UniversitySeoul 08826Republic of Korea Department of Biotechnology College of Life Science and BiotechnologyYonsei UniversitySeoul 03722Republic of Korea Department of KHU-KIST Convergence Science and Technology Kyung Hee UniversitySeoul 02447Republic of Korea KU-KIST Graduate School of Converging Science and Technology Korea UniversitySeoul 02841Republic of Korea School of Electrical and Electronic Engineering YU-KIST InstituteYonsei UniversitySeoul 03722Republic of Korea Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA 16802USA Materials Research Institute The Pennsylvania State UniversityUniversity ParkPA 16802USA Department of Anatomy College of MedicineKorea UniversitySeoul 02841Republic of Korea Department of Electrical and Electronic Engineering YU-Korea Institute of Science and Technology(KIST)InstituteYonsei University50Yonsei-roSeodaemun-guSeoul 03722Korea

Challenges in the understanding of three-dimensional(3D)brain networks by simultaneously recording both surface and intracortical areas of brain signals remain due to the difficulties of constructing mechanical design and spatial limitations of the implanted ***,we present a foldable and flexible 3D neural prosthetic that facilitates the 3D mapping of complex neural circuits with high spatiotemporal dynamics from the intracortical to cortical *** device is the tool to map the 3D neural transmission through sophisticatedly designed four flexible penetrating shanks and surface electrode arrays in one integrated *** demonstrate the potential possibilities of identifying correlations of neural activities from the intracortical area to cortical regions through continuous monitoring of electrophysiological *** also exploited the structural properties of the device to record synchronized signals of single spikes evoked by unidirectional total whisker *** platform offers opportunities to clarify unpredictable 3D neural pathways and provides a next-generation neural interface.

关键词： neural electrode simultaneous

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Pencil-beam scanning catheter for intracoronary optical coherence tomography

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Opto-electronic Advances 2022年第3期5卷 69-75页

作者： Jiqiang Kang Rui Zhu Yunxu Sun Jianan Li Kenneth K.Y.Wong School of Electronic and Information Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China International Graduate School at Shenzhen Tsinghua UniversityShenzhen 518055China Shenzhen Vivolight Medical Device&Technology Co. Ltd.Shenzhen 518055China State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi’an 710119China Department of Electrical and Electronic Engineering The University of Hong KongPokfulam RoadHong KongChina Advanced Biomedical Instrumentation Centre Hong Kong Science ParkShatinNew TerritoriesHong KongChina

Current gradient-index(GRIN)lens based proximal-driven intracoronary optical coherence tomography(ICOCT)probes consist of a spacer and a GRIN lens with large gradient *** design provides great flexibility to control beam profiles,but the spacer length should be well controlled to obtain desired beam profiles and thus it sets an obstacle in mass catheter ***,although GRIN lens with large gradient constant can provide tight focus spot,it has short depth of focus and fast-expanded beam which leads to poor lateral resolution for deep *** this paper,a type of spacer-removed probe is demonstrated with a small gradient constant GRIN *** design simplifies the fabrica-tion process and is suitable for mass *** output beam of the catheter is a narrow nearly collimated light beam,referred to as pencil beam *** full width at half maximum beam size varies from 35.1μm to 75.3μm in air over 3-mm *** design principles are elaborated with probe/catheter fabrication and performance *** in vivo imaging of the catheter was verified by a clinical ICOCT *** results prove that this novel pencil-beam scanning catheter is potentially a good choice for ICOCT systems.

关键词： optical coherence tomography endoscopic imaging intravascular imaging fiber optics imaging

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