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Improved MIMO Signal Detection Based on DNN in MIMO-OFDM System

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Computers, Materials & Continua 2022年第2期70卷 3625-3636页

作者： jae-hyun ro Jong-Gyu Ha Woon-Sang Lee Young-Hwan You Hyoung-Kyu Song Department of Convergence Engineering for Intelligent Drone Sejong UniversitySeoul05006Korea Department of Information and Communication Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea Department of Computer Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea

This paper proposes the multiple-input multiple-output(MIMO)detection scheme by using the deep neural network(DNN)based ensemble machine learning for higher error performance in wireless communication systems.For the MIMO detection based on the ensemble machine learning,all learning models for the DNN are generated in offline and the detection is performed in online by using already learned models.In the offline learning,the received signals and channel coefficients are set to input data,and the labels which correspond to transmit symbols are set to output data.In the online learning,the perfectly learned models are used for signal detection where the models have fixed bias and weights.For performance improvement,the proposed scheme uses the majority vote and the maximum probability as the methods of the model combinations for obtaining diversity gains at the MIMO receiver.The simulation results show that the proposed scheme has improved symbol error rate(SER)performance without additional receive antennas.

关键词： MIMO DNN ensemble machine learning ML

A Strategy of Signal Detection for Performance Improvement in Clipping Based OFDM System

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Computers, Materials & Continua 2020年第7期64卷 181-191页

作者： jae-hyun ro Won-Seok Lee Min-Goo Kang Dae-Ki Hong Hyoung-Kyu Song Department of Information and Communication Engineering Sejong UniversitySeoulKorea Department of IT Contents Hanshin UniversityOsan-siKorea Department of System Semiconductor Engineering SangMyung UniversityCheonan-si31066Korea

In this paper,the supervised Deep Neural Network(DNN)based signal detection is analyzed for combating with nonlinear distortions efficiently and improving error performances in clipping based Orthogonal Frequency Division Multiplexing(OFDM)ssystem.One of the main disadvantages for the OFDM is the high Peak to Average Power Ratio(PAPR).The clipping is a simple method for the PAPR reduction.However,an effect of the clipping is nonlinear distortion,and estimations for transmitting symbols are difficult despite a Maximum Likelihood(ML)detection at the receiver.The DNN based online signal detection uses the offline learning model where all weights and biases at fully-connected layers are set to overcome nonlinear distortions by using training data sets.Thus,this paper introduces the required processes for the online signal detection and offline learning,and compares error performances with the ML detection in the clipping-based OFDM systems.In simulation results,the DNN based signal detection has better error performance than the conventional ML detection in multi-path fading wireless channel.The performance improvement is large as the complexity of system is increased such as huge Multiple Input Multiple Output(MIMO)system and high clipping rate.

关键词： Clipping DNN ML nonlinear distortion OFDM

Weighted Gauss-Seidel Precoder for Downlink Massive MIMO Systems

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Computers, Materials & Continua 2021年第5期67卷 1729-1745页

作者： Jun-Yong Jang Won-Seok Lee jae-hyun ro Young-Hawn You Hyoung-Kyu Song Department of Information and Communication Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea Department of Computer Engineering Sejong UniversitySeoul05006Korea

In this paper,a novel precoding scheme based on the Gauss-Seidel(GS)method is proposed for downlink massive multiple-input multiple-output(MIMO)systems.The GS method iteratively approximates the matrix inversion and reduces the overall complexity of the precoding process.In addition,the GS method shows a fast convergence rate to the Zero-forcing(ZF)method that requires an exact invertible matrix.However,to satisfy demanded error performance and converge to the error performance of the ZF method in the practical condition such as spatially correlated channels,more iterations are necessary for the GS method and increase the overall complexity.For efficient approximation with fewer iterations,this paper proposes a weighted GS(WGS)method to improve the approximation accuracy of the GS method.The optimal weights that accelerate the convergence rate by improved accuracy are computed by the least square(LS)method.After the computation of weights,the different weights are applied for each iteration of the GS method.In addition,an efficient method of weight computation is proposed to reduce the complexity of the LS method.The simulation results show that bit error rate(BER)performance for the proposed scheme with fewer iterations is better than the GS method in spatially correlated channels.

关键词： Massive MIMO GS matrix inversion complexity weight

Participatory Risk Governance for Seoul, South Korea's Flood Risk Management

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International Journal of Disaster Risk Science 2024年第3期15卷 317-331页

作者： Bokjin ro Gregg Garfin School of Geography Development and Environment The University of Arizona Interdisciplinary Program for Disaster Crisis and Risk Management Sungkyunkwan University School of Natural Resources and the Environment The University of Arizona

Risk governance is a widely used framework in natural and societal risk management research. Risks from natural hazards in urban areas call for the establishment of rigorous and participatory urban risk governance. In this study, we examined participatory risk governance(PRG) of flood risk management(FRM) in Seoul, South Korea. We conducted key informant interviews and implemented a survey with citizens, to explore perceptions of flood risks and risk management, and to examine prospects for improving PRG in Seoul. We found a gap between the perceptions of key informants and citizens.Key informants believed that citizens' low awareness of flood risks hinders PRG. Yet our research found that citizens' risk awareness was not low, and risk awareness may not be the main barrier to participation in PRG. Instead, we found that citizens lacked knowledge of FRM actions, and they assigned government bodies a high level of responsibility for FRM,compared to the level of responsibility that citizens assigned to themselves. Moreover, the actors involved in FRM tended not to trust each other, which implies a lack of mutual understanding. To increase the eff ectiveness of PRG, we suggest a polycentric governance structure anchored by a leading actor group, and active promotion of the participation of actors at multiple levels of governance. Communication between government and citizen participants, designed to foster improved understanding and recognition of one another's roles and contributions to FRM, will enhance trust and improve the implementation of PRG in Seoul.

关键词： Citizen participation Flood risk management Participatory risk governance Risk awareness South Korea Urban flood risk

Synergistically coupling of Ni–Fe LDH arrays with hollow Co–Mo sulfide nanotriangles for highly efficient overall water splitting

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Rare Metals 2024年第2期43卷 522-532页

作者： Yun jae Lee Seung-Keun Park Department of Advanced Materials Engineering Chung-Ang UniversityAnseongGyeonggi-do17546Republic of Korea Department of Intelligent Energy and Industry Chung-Ang University84 Heukseok-ro Dongjak-guSeoul06974Republic of Korea Western Seoul Center Korea Basic Science Institute150 Bugahyeon-roSeodaemun-guSeoul03759Republic of Korea

Developing bifunctional catalysts that can catalyze both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)is pivotal to commercializing large-scale water splitting.Herein,a novel hollow nanotriangle composed of NiFe LDH-CoMoS_(x) heterojunction(H-CMSx@NiFe LDH)is proposed as a highly efficient bifunctional electrocatalyst for both OER and HER.To fabricate a heterojunction system,ultra-thin nickel–iron layered double hydroxide(NiFe LDH)nanosheets are uniformly electrodeposited onto a metal–organic framework-derived hollow CoMoS_(x) nanotriangle.The strong coupling of CoMoS_(x) and NiFe LDH catalysts forms the intimate heterojunction interfaces to facilitate interfacial charge transfer,which is favorable to enhance the bifunctional catalytic activity.Moreover,the large void of CoMoS_(x) nanotriangles and interconnected ultra-thin NiFe LDH nanosheets result in good electrolyte penetration and gas release.Therefore,the as-prepared H-CMSx@NiFe LDH on nickel foam(NF)exhibits an impressive catalytic activity and durability for OER and HER activities,delivering a current density of 100 mA·cm^(−2) at the small overpotentials of 214 and 299 mV in OER and HER,respectively.Meanwhile,H-CMSx@NiFe LDH/NF proves to be an effective electrode for an alkaline electrolyzer,as a voltage of only 1.99 V is enough to achieve a current density voltage of only 1.99 V is enough to achieve a current density of 400 mA·cm^(−2) with no degradation in performance over 50 h.

关键词： Overall water splitting Metal-organic framework Molybdenum sulfide Layered double hydroxide Heterojunction

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Varifocal occlusion in an optical see-through near-eye display with a single phase-only liquid crystal on silicon

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Photonics Research 2024年第4期12卷 833-853页

作者： WOONGSEOB HAN jae-WON LEE JUNG-YEOP SHIN MYEONG-HO CHOI HAK-RIN KIM jae-HYEUNG PARK Department of Electrical and Computer Engineering Inha University100 Inha-roMichuhol-guIncheon 22212Republic of Korea School of Electronic and Electrical Engineering Kyungpook National University80 Daehak-roBuk-guDaegu 41566Republic of Korea School of Electronics Engineering Kyungpook National University80 Daehak-roBuk-guDaegu 41566Republic of Korea Department of Information and Communication Engineering Inha University100 Inha-roMichuhol-guIncheon 22212Republic of Korea

We propose a near-eye display optics system that supports three-dimensional mutual occlusion.By exploiting the polarization-control properties of a phase-only liquid crystal on silicon (LCoS),we achieve real see-through scene masking as well as virtual digital scene imaging using a single LCoS.Dynamic depth control of the real scene mask and virtual digital image is also achieved by using a focus tunable lens (FTL) pair of opposite curvatures.The proposed configuration using a single LCoS and opposite curvature FTL pair enables the self-alignment of the mask and image at an arbitrary depth without distorting the see-through view of the real scene.We verified the feasibility of the proposed optics using two optical benchtop setups:one with two off-the-shelf FTLs for continuous depth control,and the other with a single Pancharatnam–Berry phase-type FTL for the improved form factor.

关键词： optics crystal phase

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Integration of earth-abundant cocatalysts for high-performance photoelectrochemical energy conversion

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Journal of Energy Chemistry 2024年第1期88卷 336-355,I0008页

作者： Joonhee Ma Sang hyun Ahn Soo Young Kim Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea School of Chemical Engineering and Materials Science Chung-Ang University84 Heukseok-roDongjak-guSeoul 06974Republic of Korea

Photoelectrochemical(PEC)energy conversion has emerged as a promising and efficient approach to sustainable energy harvesting and storage.By utilizing semiconductor photoelectrodes,PEC devices can harness solar energy and drive electrochemical reactions such as water splitting or carbon dioxide(CO_(2))reduction to generate clean fuels and value-added chemicals.However,PEC energy conversion faces several challenges such as high overpotential,sluggish reaction kinetics,charge carrier recombination,and stability issues,which limit its practical implementation.Recently,significant research has been conducted to improve the overall conversion efficiency of PEC devices.One particularly promising approach is the use of cocatalysts,which involves introducing specific cocatalysts onto the photoelectrode surface to promote charge separation,improve reaction kinetics,and reduce the overpotential,thereby enhancing the overall performance of PEC energy conversion.This review provides a comprehensive overview of the recent developments in the earth-abundant cocatalysts for PEC water splitting and CO_(2) reduction.The main earth-abundant catalysts for the PEC water splitting include transition-metal dichalcogenide(TMD)-based materials,metal phosphides/carbides,and metal oxides/hydroxides.Meanwhile,PEC-CO_(2)RR was divided into C_(1) and C_(2+)based on the final product since various products could be produced,focusing on diverse earth-abundant materials-based cocatalysts.In addition,we provide and highlight key advancements achieved in the very recent reports on novel PEC system design engineering with cocatalysts.Finally,the current problems associated with PEC systems are discussed along with a suggested direction to overcome these obstacles.

关键词： Solar energy Photo-electrochemical Water splitting CO_(2)reduction Cocatalysts

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Comparative efficacy and optimal duration of first-line antibiotic regimens for acute otitis media in children and adolescents:a systematic review and network meta-analysis of 89 randomized clinicaltrials

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World Journal of Pediatrics 2024年第3期20卷 219-229页

作者： Min Seo Kim jae Han Kim Seohyun Ryu Seung Won Lee Dong Keon Yon Eunyoung Kim Ai Koyanagi Elena Dragioti jae Il Shin Lee Smith Samsung Advanced Institute forHealth Sciences&Technology(SAIHST) Samsung Medical CenterSungkyunkwan UniversitySeoulRepublic of Korea Yonsei University Collegeof Medicine SeoulRepublicof Korea Department of Precision Medicine Sungkyunkwan University School of MedicineSuwonRepublic of Korea Center for Digital Health Medical Science Research InstituteKyung Hee University College of MedicineSeoulRepublic of Korea Evidence-Based Research Laboratory Department of Clinical Pharmacy and Pharmaceutical CareCollege of PharmacyChung-Ang UniversitySeoulRepublic of Korea Parc Sanitari Sant Joan de Deu/CIBERSAM/ISCIII Universitat de BarcelonaFundacio Sant Joan de Déu.Sant Boi de LlobregatBarcelonaSpain ICREA Pg.Lluis Companys 23BarcelonaSpain Pain and Rehabilitation Centre and Department of Medical and Health SciencesLinkoping University58185 LinkopingSweden Department of Pediatrics Yonsei University College of MedicineYonsei-ro 50Seodaemun-gu8044Seoul 03722Republic of Korea Centre for Health Performanceand WellbeingAnglia Ruskin UniversityCambridge CB11PTUK Research Laboratory Psychology of Patients Families&Health ProfessionalsDepartment of NursingSchool of Health SciencesUniversity of IoanninaIoannina 45500Greece

Introduction Antibiotic use for acute otitis media(AOM)is one of the major sources of antimicrobial resistance.However,the effective minimal antibiotic duration for AOM remains unclear.Moreover,guidelines often recommend broad ranges(5-10 days)of antibiotic use,yet the clinical impact of such a wide window has not been assessed.Methods We systematically searched PubMed/MEDLINE,Embase,Scopus,Web of Science,and Cochrane Library from database inception to 6 October 2021.Network meta-analysis was conducted on randomized controlled trials that assessed antibiotic treatment for AOM in children(ProSPEro CRD42020196107).Results For amoxicillin and amoxicillin-clavulanate,7-day regimens were noninferior to 10-day regimens in clinical responses[amoxicillin:risk ratio(RR)0.919(95%CI 0.820-1.031),amoxicillin-clavulanate:RR 1.108(0.957-1.282)],except for≤2 years.For the third-generation cephalosporins,7-day and 10-day regimens had similar clinical responses compared to placebo[7-day:RR 1.420(1.190-1.694),10-day:RR 1.238(1.125-1.362)compared to placebo].However,5-day regimens of amoxicillin-clavulanate and third-generation cephalosporins were inferior to 10-day regimens.Compared to amoxicillin,a shorter treatment duration was tolerable with amoxicillin-clavulanate.Conclusions Our findings indicated that 1O days of antibiotic use may be unnecessarily long,while the treatment duration should be longer than 5 days.Otherwise,5-day regimens would be sufficient for a modest treatment goal.Our findings revealed that the current wide range of recommended antibiotic durations may have influenced the clinical outcome of AOM,and a narrower antibiotic duration window should be re-established.

关键词： Amoxicillin-potassium Amoxicillin Antibacterial agents Cephalosporins Duration of therapy

Acoustofluidic separation of prolate and spherical micro-objects

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Microsystems & Nanoengineering 2024年第1期10卷 217-230页

作者： Muhammad Soban Khan Mushtaq Ali Song Ha Lee Keun Young Jang Seong jae Lee Jinsoo Park Department of Mechanical Engineering Chonnam National University77 Yongbong-roBuk-guGwangju 61186Republic of Korea Department of Polymer Engineering The University of Suwon17 Wauan-gilBongdam-eupHwaseongGyeonggi 18323Republic of Korea

Most microfluidic separation techniques rely largely on object size as a separation marker.The ability to separate micro-objects based on their shape is crucial in various biomedical and chemical assays.Here,we develop an ondemand,label-free acoustofluidic method to separate prolate ellipsoids from spherical microparticles based on traveling surface acoustic wave-induced acoustic radiation force and torque.The freely rotating non-spherical microobjects were aligned under the progressive acoustic field by the counterrotating radiation torque,and the major axis of the prolate ellipsoids was parallel to the progressive wave propagation.The specific alignment of the ellipsoidal particles resulted in a reduction in the cross-sectional area perpendicular to the wave propagation.As a consequence,the acoustic backscattering decreased,resulting in a decreased magnitude of the radiation force.Through the variation in radiation force,which depended on the micro-object morphology enabled the acoustofluidic shape-based separation.We conducted numerical simulations for the wave scattering of spherical and prolate objects to elucidate the working mechanism underlying the proposed method.A series of experiments with polystyrene microspheres,prolate ellipsoids,and peanut-shaped microparticles were performed for validation.Through quantitative analysis of the separation efficiency,we confirmed the high purity and high recovery rate of the proposed acoustofluidic shapebased separation of micro-objects.As a bioparticle,we utilize Thalassiosira eccentrica to perform shape-based separation,as the species has a variety of potential applications in drug delivery,biosensing,nanofabrication,bioencapsulation and immunoisolation.

关键词： separation spherical rotating