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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 173-174页

作者： yongmin liu Department of Mechanical and Industrial Engineering Northeastern UniversityBoston 02115USA Department of Electrical and Computer Engineering Northeastern UniversityBoston 02115USA

Effective medium theory(EMT)has been widely applied in material science,electromagnetics and photonics to determine the effective material properties for inhomogeneous composites comprising subwavelength *** versatility of this foundational approach has been established through its application in classical Maxwell-Garnet models,which encompass relatively simple structures。

关键词： composites theory dielectric

A data-efficient self-supervised deep learning model for design and characterization of nanophotonic structures

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Science China(Physics,Mechanics & Astronomy) 2020年第8期63卷 23-30页

作者： Wei Ma yongmin liu College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027China Department of Mechanical and Industrial Engineering Northeastern UniversityMassachusetts 02115USA Department of Electrical and Computer Engineering Northeastern UniversityMassachusetts 02115USA

With its tremendous success in many machine learning and pattern recognition tasks,deep learning,as one type of data-driven models,has also led to many breakthroughs in other disciplines including physics,chemistry and material ***,the supremacy of deep learning over conventional optimization approaches heavily depends on the huge amount of data collected in advance to train the model,which is a common bottleneck of such a data-driven *** this work,we present a comprehensive deep learning model for the design and characterization of nanophotonic structures,where a self-supervised learning mechanism is introduced to alleviate the burden of data *** reflective metasurfaces as an example,we demonstrate that the self-supervised deep learning model can effectively utilize randomly generated unlabeled data during training,with the total test loss and prediction accuracy improved by about 15%compared with the fully supervised *** proposed self-supervised learning scheme provides an efficient solution for deep learning models in some physics-related tasks where labeled data are limited or expensive to collect.

关键词： nanophotonics metasurfaces self-supervised deep learning

Broadband angular spectrum analog processors based on all-dielectric metasurfaces

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 188-190页

作者： Lin Deng yongmin liu Department of Electrical and Computer Engineering Northeastern UniversityBoston 02115USA Department of Mechanical and Industrial Engineering Northeastern UniversityBoston 02115USA

Digital signal processors are extensively used to execute mathematical operations and advanced computational tasks on digital ***,they suffer from several inherent limitations,including low speed,high energy consumption,and large memory requirements,because of the hardware bottleneck and the imperative conversion between digital and analogue signals.

关键词： dielectric spectrum hardware

Editorial of special issue on optical metasurfaces:fundamentals and applications

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Chinese Optics Letters 2023年第2期21卷 1-2页

作者： Li, Tao Zhang, Cheng liu, yongmin Nanjing University China Huazhong University of Science and Technology China Northeastern University United States

An optical metasurface is an ultrathin optical design composed of subwavelength meta-atoms that have demonstrated unprecedented capabilities in manipulating light *** now,numerous functionalities have been realized,such as beam engineering,wave plates,polarizers,holograms,and *** are expecting a new version of metasurface 2.0 that will not only enrich the frontiers of optical sciences but also revolutionize traditional optical devices and technology in practical *** to present the impressive progress in this field,Chinese Optics Letters publishes this special issue focusing on multifunctional metasurfaces,coupled plasmonic metasurfaces,reconfigurable metadevices,quantum metasurfaces for entangled photons,and neural network metadesigns that indicate the development directions of metasurfaces to a great extent.

关键词： surfaces frontier directions

Global ionospheric TEC response to a strong magnetic storm

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Science China(Technological Sciences) 2008年第10期51卷 1786-1802页

作者： XU Liang CHENG GuangHui XU JiSheng liu yongmin School of Electronic Information Wuhan UniversityWuhan 430079China

The global characteristics of the ionospheric storm and irregularities as well as propagation of TEC (total electron content) disturbances during the strong mag-netic storm occurring in November 2004 were investigated by using the data of the IGS network. For the response of the global ionospheric TEC to this strong mag-netic storm, the following features are noticeable: 1) the maximum of the iono-spheric storm phase occurred around the main phase maximum of the magnetic storm; 2) the TEC response in equatorial and low latitudes was more remarkable than that in mid-high latitudes; 3) as a whole, the storm phase in the northern hemisphere was mainly positive, and it was negative in the southern hemisphere; 4) during the whole magnetic storm from November 7 to 11, the locations where the maxima of the positive and negative ionospheric storm phases occurred were nearly invariant to the Sun at low and equatorial latitudes, i.e. the 24-h recurrence. Analyzing results of TEC rate and its standard deviation showed that the iono-spheric irregularities and disturbances in the global mainly occurred around the main phase maximum of the storm, and they distributed in a large longitudinal re-gion for both day and night in mid-high latitudes and they generated and developed only after the sunset, and lasted out to the midnight in equatorial and low latitudes. The disturbance propagation parameters were also estimated by using the wavelet reconstruction and cross-correlation technologies for a set of spaced stations in the Northern America.

关键词： ionosphere magnetic storm ionospheric storm irregularity IGS network TEC

Reconfigurable optical neural networks with Plug-and-Play metasurfaces

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Opto-Electronic Advances 2024年第7期7卷 1-3页

作者： yongmin liu Yuxiao Li Department of Mechanical and Industrial Engineering Northeastern UniversityBostonMassachusetts 02115USA Department of Electrical and Computer Engineering Northeastern UniversityBostonMassachusetts 02115USA

In a very recent study,*** Huang and co-workers proposed and demonstrated reconfigurable optical neural networks based on cascaded *** fixing one metasurface and switching the other pluggable metasurfaces,the neural networks,which operate at near-infrared wavelengths,can perform distinct recognition tasks for handwritten digits and fashion *** innovative device opens up an avenue for all-optical,high-speed,low-power,and multifunctional artificial intelligence systems.

关键词： surfaces networks neural

3D direct printing of mechanical and biocompatible hydrogel meta-structures

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Bioactive Materials 2022年第4期7卷 48-55页

作者： Lei Zhang Wenhan Lee Xinhao Li Yanhui Jiang Nicholas Xuanlai Fang Guohao Dai yongmin liu Department of Mechanical&Industrial Engineering Northeastern UniversityBostonMA02115United States State Key Laboratory of Primate Biomedical Research Institute of Primate Translational MedicineKunming University of Science and TechnologyKunming650500China Department of Bioengineering Northeastern UniversityBostonMA02115United States Department of Mechanical Engineering Massachusetts Institute of TechnologyCambridgeMA02139United States Department of Electrical and Computer Engineering Northeastern UniversityBostonMA02115United States

Direct Ink Writing(DIW)has demonstrated great potential as a versatile method to 3D print multifunctional *** this work,we report the implementation of hydrogel meta-structures using DIW at room temperature,which seamlessly integrate large specific surface areas,interconnected porous characteristics,mechanical toughness,biocompatibility,and water absorption and retention *** but hydrophobic polymers and weakly crosslinked nature-origin hydrogels form a balance in the self-supporting ink,allowing us to directly print complex meta-structures without sacrificial materials and heating ***,the mixed bending or stretching of symmetrical re-entrant cellular lattices and the unique curvature patterns are combined to provide little lateral expansion and large compressive energy absorbance when external forces are applied on the printed *** addition,we have successfully demonstrated ear,aortic valve conduits and hierarchical *** anticipate that the reported 3D meta-structured hydrogel would offer a new strategy to develop functional biomaterials for tissue engineering applications in the future.

关键词： Direct ink writing Gyroid meta-structure Mechanical-functional integration Naturally derived hydrogel

Interfacing photonics with artificial intelligence:an innovative design strategy for photonic structures and devices based on artificial neural networks

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Photonics Research 2021年第4期9卷 I0055-I0072页

作者： Yihao Xu Xianzhe Zhang Yun Fu yongmin liu Department of Mechanical and Industrial Engineering Northeastern UniversityBostonMassachusetts 02115USA Department of Electrical and Computer Engineering Northeastern UniversityBostonMassachusetts 02115USA Khoury College of Computer Science Northeastern UniversityBostonMassachusetts 02115USA

Over the past decades,photonics has transformed many areas in both fundamental research and practical *** particular,we can manipulate light in a desired and prescribed manner by rationally designed subwavelength ***,constructing complex photonic structures and devices is still a time-consuming process,even for experienced *** a subset of artificial intelligence,artificial neural networks serve as one potential solution to bypass the complicated design process,enabling us to directly predict the optical responses of photonic structures or perform the inverse design with high efficiency and *** this review,we will introduce several commonly used neural networks and highlight their applications in the design process of various optical structures and devices,particularly those in recent experimental *** will also comment on the future directions to inspire researchers from different disciplines to collectively advance this emerging research field.

关键词： artificial networks neural

Simulation of Morphologies and Mechanical Properties of A/B Polymer Blend Film

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Chinese Journal of Chemical Engineering 2011年第4期19卷 549-557页

作者： ZHAO Xuezhe DENG Shengwei HUANG yongmin liu Honglai HU Ying Key Laboratory for Advanced Materials and Department of Chemistry East China University of Science and Technology Shanghai 200237 China

The effects of blend composition and micro-phase structure on the mechanical behavior of A/B polymer blend film are studied by coupling the Monte Carlo(MC) simulation of morphology with the lattice spring model(LSM) of micro mechanics of *** MC method with bond length fluctuation and cavity diffusion algorithm on cubic lattice is adopted to simulate the micro-phase structure of A/B polymer *** information of morphology and structure is then inputted to the LSM composed of a three-dimensional network of springs to obtain the mechanical properties of polymer blend *** results show that the mechanical response is mainly affected by the density and the composition of polymer blend film through the morphology *** a force is applied on the outer boundary of polymer blend film,the vicinity of the inner cavities experiences higher stresses and strains responsible for the onset of crack propagation and the premature failure of the entire system.

关键词： polymer blend film mechanical behavior Monte Carlo lattice spring model

Some Recommendations for Improving Renewable Energy Policies in China

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Management Studies 2015年第2期3卷 110-128页

作者： yongmin Zhang Wenwen liu University of Nottingham Ningbo China Ningbo China

Renewable energy is the one of the most promising solutions for environmental protection and energy deficiency. Since 2005, the Chinese government has put forward a number of measures in promoting renewable energy. This paper presents those renewable energy policies in China and illustrates their achievements and limits. Comparing the renewable energy policies in Europe and US, feed-in-tariffs and quotas are two main measures that are adopted by western countries. A detailed performance review of feed-in-tariffs and quotas is examined by using effectiveness and efficiency as criteria. The enlightenments to improve renewable policies in China include strengthening compliance with quotas, developing priority dispatch and technical standards for interconnection, putting forward a more advanced feed-in-tariff system, and ultimately guaranteeing the electricity consumer＇s right of choice.

关键词： feed-in-tariffs renewable power quotas priority dispatch distributed generation