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Development of temperature-robust damage factor based on sensor fusion for a wind turbine structure

Frontiers of Structural and Civil Engineering 2015年第1期9卷 42-47页

作者： Jong-Woong park sung-han SIM Jin-Hak YI Hyung-Jo JUNG Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign Urbana IL 61801 USA School of Urban and Environmental Engineering Ulsan National Institute of Science and Technology (UNIST) Ulsan 689- 798Republic of Korea Coastal Development & Ocean Engineering Research Division Korea Institute of Ocean Science and Technology Ansan 426-744Republic of Korea Department of Civil and Environmental Engineering KAIST Daejeon 305-701 Republic of Korea

Wind power systems have gained much attention due to the relatively high reliability, maturity in technology and cost competitiveness compared to other renewable alternatives. Advances have been made to increase the power efficiency of the wind turbines while less attention has been focused on structural integrity assessment of the structural systems. Vibration-based damage detection has widely been researched to identify damages on a structure based on change in d^mmic characteristics. Widely spread methods are natural frequency-based, mode shape-based, and curvature mode shape-based methods. The natural frequency-based methods are convenient but vulnerable to environmental temperature variation which degrades damage detection capability; mode shapes are less influenced by temperature variation and able to locate damage but requires extensive sensor instrumentation which is costly and vulnerable to signal noises. This study proposes novelty of damage factor based on sensor fusion to exclude effect of temperature variation. The combined use of an accelerometer and an inclinometer was considered and damage factor was defined as a change in relationship between those two measurements. The advantages of the proposed method are： 1） requirement of small number of sensor, 2） robusmess to change in temperature and signal noise and 3） ability to roughly locate damage. Validation of the proposed method is carried out through numerical simulation on a simplified 5 MW wind turbine model.

关键词： sensor fusion damage detection structural health monitoring

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A hierarchical salt-rejection strategy for sustainable and high-efficiency solar-driven desalination

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Nano Materials Science 2024年第1期6卷 38-43页

作者： Zhengyi Mao Xuliang Chen Yingxian Chen Junda Shen Jianpan Huang Yuhan Chen Xiaoguang Duan Yicheng han Kannie Wai Yan Chan Jian LU CityU-Shenzhen Futian Research Institute Shenzhen518045China Department of Mechanical Engineering City University of Hong Kong83 Tat Chee AvenueKowloonHong KongChina Department of Material Science and Engineering City University of Hong Kong83 Tat Chee AvenueKowloonHong KongChina Department of Biomedical Engineering City University of Hong Kong83 Tat Chee AvenueKowloonHong KongChina School of Chemical Engineering and Advanced Materials The University of AdelaideAdelaideAustralia Hong Kong Branch of National Precious Metals Material Engineering Research Centre City University of Hong Kong83 Tat Chee AvenueKowloonHong KongChina Centre for Advanced Structural Materials City University of Hong Kong Shenzhen Research InstituteGreater Bay Joint DivisionShenyang National Laboratory for Materials ScienceShenzhen518057China

Solar steam generation(SSG)is widely regarded as one of the most sustainable technologies for seawater ***,salt fouling severely compromises the evaporation performance and lifetime of evaporators,limiting their practical ***,we propose a hierarchical salt-rejection(HSR)strategy to prevent salt precipitation during long-term evaporation while maintaining a rapid evaporation rate,even in high-salinity *** salt diffusion process is segmented into three steps—insulation,branching diffusion,and arterial transport—that significantly enhance the salt-resistance properties of the ***,the HSR strategy overcomes the tradeoff between salt resistance and evaporation ***,a high evaporation rate of 2.84 kg m^(-2) h^(-1),stable evaporation for 7 days cyclic tests in 20 wt%NaCl solution,and continuous operation for 170 h in natural seawater under 1 sun illumination were *** with control evaporators,the HSR evaporator exhibited a>54%enhancement in total water evaporation mass during 24 h continuous evaporation in 20 wt%salt ***,a water collection device equipped with the HSR evaporator realized a high water purification rate(1.1 kg m^(-2) h^(-1)),highlighting its potential for agricultural applications.

关键词： Solar water evaporation 3D printing Salt-rejection Hierarchical structures High efficiency

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Experiments and computer simulation analysis of impact behaviors of micro-sized abrasive in waterjet cutting of thin multiple layered materials

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中国有色金属学会会刊：英文版 2012年第S3期22卷 864-869页

作者： Jung-han LEE Kang-Su park Myung Chang KANG Bo Sik KANG Bo sung SHIN Engineering Research Center Pusan National University National Core Research Center Pusan National University Mechanical System Safety Research Division Korea Institute of Machinery and Materials

The abrasive waterjet (AWJ) is now widely used in the advanced cutting processes of polymers,metals,glass,ceramics and composite materials like thin multiple-layered material (TMM).Various research and development efforts have recently been made to understand the science of ***,the interaction mechanism between a workpiece and high-velocity abrasive particles still remains a complicated *** this work,the material removal mechanisms of AWJ such as micro penetration and micro dent were experimentally *** addition,a new computer simulation model considering high strain rate effect was proposed to understand the micro impact behavior of high-velocity micro-sized abrasives in AWJ cutting.

关键词： abrasive waterjet thin multiple layered materials micro-sized abrasive micro penetration micro dent

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Incidence, prevalence and risk of stroke in patients with Takayasu arteritis: a nationwide population-based study in South Korea

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Stroke & Vascular Neurology 2022年第2期7卷 149-157页

作者： sung Soo Ahn Minkyung han Yong-Beom park Inkyung Jung Sang-Won Lee Department of Internal Medicine Yongin Severance HospitalYonsei University College of MedicineYonginSouth Korea Biostatistics Collaboration Unit Department of Biomedical Systems InformaticsYonsei University College of MedicineSeoulSouth Korea Division of Rheumatology Department of Internal MedicineYonsei University College of MedicineSeoulSouth Korea Institute for Immunology and Immunological Diseases Yonsei University College of MedicineSeoulSouth Korea Division of Biostatistics Department of Biomedical Systems InformaticsYonsei University College of MedicineSeoulSouth Korea

Background Takayasu arteritis(TAK)is a disease associated with increased risk of cardiovascular *** aimed to evaluate the incidence,prevalence and risk of stroke in patients with *** Data from 1065 patients were obtained from a national database(2010–2018).The annual incidence and prevalence per 100000 persons were estimated using the registration population in the midst of every year,and the standardised incidence ratio(SIR)of stroke was compared with the general population based on the data from the 2006 national report for cardiovascular and cerebrovascular ***-adjusted incidence rate ratio(IRR)of stroke based on the time interval after diagnosis was also calculated.A time-dependent Cox regression was conducted to investigate predictive factors of *** The overall incidence rate of TAK ranged between 0.2 and 0.3/100000 person-years annually;the prevalence of TAK gradually increased,reaching 3.25/100000 person-years in ***-three(6.9%)patients experienced stroke during follow-up,and the risk of developing stroke was higher than the general population(overall SIR 7.39,95%CI 5.79 to 9.29;men:SIR 5.70,95%CI 2.84 to 10.20;women:SIR 7.06,95%CI 5.41 to 9.05).Most stroke events(90.9%)were cerebral infarction for men,whereas the proportion of cerebral infarction was lower(62.9%)in *** half of stroke events occurred within 6 months after diagnosis,and stroke was more common within 6 months of diagnosis compared with after 3 years in women(IRR 13.46,95%CI 6.86 to 26.40).In Cox regression analysis,age was the sole predictor of stroke(adjusted HR 1.02,95%CI 1.00 to 1.04,p=0.043).Conclusions The annual incidence of TAK was similar to the previous studies from Asia,and the risk of stroke increased in *** patterns of subtype and incidence of stroke were found according to sex,although age was the only predictor.

关键词： prevalence patients diagnosis

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Improvement in tensile strength of extruded Mg-5Bi alloy through addition of Sn and its underlying strengthening mechanisms

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Journal of Magnesium and Alloys 2022年第11期10卷 3100-3112页

作者： Sang-Cheol Jin Jae Won Cha Jeong Hun Lee Taekyung Lee Sang-Ho han sung Hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Ulsan Regional Division Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea Department of Materials Analysis Korea Institute of Materials ScienceChangwon 51508Republic of Korea

Through an investigation of the microstructure and mechanical properties of extruded Mg–5Bi–x Sn(BT5x, x = 0, 2, 4, and 6 wt%) alloys,this study demonstrates that the addition of Sn to an Mg–5Bi binary alloy significantly improves the tensile strength of the extruded *** the extruded alloys exhibit a typical basal fiber texture and a partially dynamically recrystallized(DRXed) microstructure consisting of fine DRXed grains and coarse un DRXed grains. As the Sn content increases from 0 wt% to 6 wt%, the average size of the DRXed grains decreases from 4.2 to 2.8 μm owing to the increase in the amount of precipitates via their grain-boundary pinning effect. The extruded B5 and BT52 alloys contain numerous Mg_(3)Bi_(2) precipitates, but their size and number density are smaller and higher, respectively, in the latter *** Mg_(2)Sn precipitates as well as Mg_(3)Bi_(2)precipitates are present in the extruded BT54 and BT56 alloys, and the number density of the Mg_(2)Sn precipitates is higher in the latter alloy because of its higher Sn content. The addition of 2 wt% Sn to the B5 alloy significantly improves the yield strength(YS) and ultimate tensile strength(UTS) of the extruded alloy—by 76 and 57 MPa, respectively. This drastic improvement is the combined outcome of enhanced grain-boundary hardening, precipitation hardening, and solid-solution hardening effects induced by the refined DRXed grains, numerous precipitates, and Sn solute atoms, respectively. The further addition of 2 wt% or 4 wt% Sn to the BT52 alloy leads to moderate increments in the YS and UTS of the extruded alloy. Specifically, each addition of 2 wt% Sn increases the YS and UTS by ~26 and ~20 MPa, respectively, which is attributed mainly to the additional precipitation hardening effect induced by the Mg_(2)Sn precipitates.

关键词： Mg-Bi-Sn alloy Extrusion Precipitation Microstructure Tensile property

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QKD system with fast active optical path length compensation

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Science China(Physics,Mechanics & Astronomy) 2017年第6期60卷 1-7页

作者： Byung Kwon park Min Soo Lee Min Ki Woo Yong-Su Kim Sang-Wook han sung Moon Center for Quantum Information Korea Institute of Science and Technology Department of Nano-materials Science and Engineering Korea University of Science and Technology

We develop a quantum key distribution (QKD) system with fast active optical path length compensation. A rapid and reliable active optical path length compensation scheme is proposed and applied to a plug-and-play QKD system. The system monitors changes in key rates and controls it is own operation automatically. The system achieves its optimal performance within three seconds of operation, which includes a sifted key rate of 5.5 kbps and a quantum bit error rate of less than 2% after an abrupt temperature variation along the 25 km quantum channel. The system also operates well over a 24 h period while completing more than 60 active optical path length compensations.

关键词： quantum key distribution optical path length compensation plug and play field programmable gate array

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Morphology Control of Bi2S3 Nanostructures and the Formation Mechanism

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Chinese Journal of Chemistry 2013年第6期31卷 752-756页

作者： HeeJin Kim Ji-eun park Kyung Kim Mi-Kyung han sung-Jin Kim Wooyoung Lee Department of Materials Science and Engineering Yonsei University Seou1120- 749 Korea Department of Chemistry and Nano Science Ewha Womans University Seoul 120-750 Korea

Bismuthinite （Bi2S3）nanostructures were prepared by a hydrothermal method with sodium ethylenediamine- tetraacetate （EDTA-Na2）. The morphology of Bi2S3 nanostructures was changed from a nanorod to a nanoplate by presence of the EDTA-Na2. The altered morphology was caused by the capping effect of EDTA-Na2 with Bi3＋ ions, which induces the suboptimal growth direction due to partially blocking the preferential orientation direction. When the EDTA-Na2/Bi3＋ molar ratio= 1, the growth of Bi2S3 nanostructures was not allowed due to the chelating effect of EDTA-Na2. The obtained Bi2S3 nanorods, stacked nanorods, nanoplates and nanoparticles were characterized using X-ray diffraction （XRD）, transmission electron microscopy （TEM）, high-resolution transmission electron mi- croscopy （HRTEM） and selected area electron diffraction （SAED） pattern. A possible formation mechanism of these morphologies was proposed. The successful synthesis of various morphologies of nanostructured Bi2S3 may open up new possibilities for thermoelectric, electronic and optoelectronic uses of nanodevices based on Bi2S3 nanostructure.

关键词： bismuth sulfide (Bi2S3) hydrothermal nanorod nanoplate thermoelectric material

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Method of characteristics and first integrals for systems of quasi-linear partial differential equations of first order

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Science China Mathematics 2015年第8期58卷 1665-1676页

作者： han ChongKyu park JongDo Department of Mathematics Seoul National University Department of Mathematics and Research Institute for Basic Sciences Kyung Hee University

Given a set of independent vector fields on a smooth manifold, we discuss how to find a function whose zero-level set is invariant under the flows of the vector fields. As an application, we study the solvability of overdetermined partial differential equations: Given a system of quasi-linear PDEs of first order for one unknown function we find a necessary and sufficient condition for the existence of solutions in terms of the second jet of the coefficients. This generalizes to certain quasi-linear systems of first order for several unknown functions.

关键词： overdetermined PDE system quasi-linear first order PDEs first integrals Pfai:fian systems Frobe-nius theorem

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Fabrication of cast carbon steel with ultrafine TiC particles

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 54-57页

作者： Sang-Hoon LEE Jin-Ju park sung-Mo HONG Byoung-Sun han Min-Ku LEE Chang-Kyu RHEE Nuclear Materials Research Division Korea Atomic Energy Research Institute Daejeon 305-353 Korea

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.

关键词： TiC particles mechanical milling carbon steel casting dispersion wettability

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Optimal Control of a Mackerel-Mimicking Robot for Energy Efficient Trajectory Tracking

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Journal of Bionic Engineering 2007年第4期4卷 209-215页

作者： Seunghee Lee Jounghyun park Cheolheui han Department of Mechanical Engineering hanyang University Seoul 133-791 Korea Department of Aeronautical and Mechanical Design Engineering Chungju National University Chungju 380-702 Korea

A robotic fish, BASEMACK1, is designed and fabricated by mimicking the shape of a live mackerel. Three DC servo-motors are serially linked together and actuated to mimic the mackerel＇s Carangiform motion. Hydrodynamic characteristics of a fish-mimetic test model are experimentally identified and utilized in order to numerically simulate fish swimming. The discrete set of kinematic and dynamic parameters are obtained by considering required horizontal and lateral forces and minimum energy consumption. Using the optimized parameter set, optimal control of the robot is studied.

关键词： mackerel-mimicking robot optimal control trajectory tracking

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