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Nano-Micro Letters 2023年第6期15卷 1-23页

作者： Horim Lee Seung Han Ryu suk jin kwon Jae Ryung Choi Sang‑bok Lee Byeongjin Park Composites Research Division Korea Institute of Materials Science797 ChangwondaeroSeongsan‑GuChangwonGyeongsangnam‑Do 51508Republic of Korea

Although there is a high demand for absorption-dominant electromagnetic interference(EMI) shielding materials for 5G millimeter-wave(mmWave) frequencies, most current shielding materials are based on reflection-dominant conductive materials. While there are few absorption-dominant shielding materials proposed with magnetic materials, their working frequencies are usually limited to under 30 GHz. In this study, a novel multi-band absorption-dominant EMI shielding film with M-type strontium ferrites and a conductive grid is proposed. This film shows ultralow EMI reflection of less than 5% in multiple mmWave frequency bands with sub-millimeter thicknesses, while shielding more than 99.9% of EMI. The ultralow reflection frequency bands are controllable by tuning the ferromagnetic resonance frequency of M-type strontium ferrites and composite layer geometries. Two examples of shielding films with ultralow reflection frequencies, one for 39 and 52 GHz 5G telecommunication bands and the other for 60 and 77 GHz autonomous radar bands, are presented. The remarkably low reflectance and thinness of the proposed films provide an important advancement toward the commercialization of EMI shielding materials for 5G mmWave applications.

关键词： 5G communication MmWave EMI shielding M-type ferrites

Liquid Metal Grid Patterned Thin Film Devices Toward Absorption‑Dominant and Strain‑Tunable Electromagnetic Interference Shielding

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Nano-Micro Letters 2024年第11期16卷 541-553页

作者： Yuwen Wei Priyanuj Bhuyan suk jin kwon Sihyun Kim Yejin Bae Mukesh Singh Duy Thanh Tran Minjeong Ha Kwang‑Un Jeong Xing Ma Byeongjin Park Sungjune Park Department of Polymer‑Nano Science and Technology Department of Nano Convergence EngineeringJeonbuk National UniversityJeonju 54896Republic of Korea School of Chemical Engineering Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Composites Research Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea School of Materials Science and Engineering Gwangju Institute of Science and TechnologyGwangju 61005Republic of Korea School of Materials Science and Engineering and Sauvage Laboratory for Smart MaterialsHarbin Institute of Technology(Shenzhen)ShenzhenGuangdong 518055People’s Republic of China

The demand of high-performance thin-film-shaped deformable electromagnetic interference(EMI)shielding devices is increasing for the next generation of wearable and miniaturized soft *** highly reflective conductive materials can effectively shield EMI,they prevent deformation of the devices owing to rigidity and generate secondary electromagnetic pollution ***,soft and stretchable EMI shielding thin film devices with absorption-dominant EMI shielding behavior is *** devices consist of liquid metal(LM)layer and LM grid-patterned layer separated by a thin elastomeric film,fabricated by leveraging superior adhesion of aerosol-deposited LM on *** devices demonstrate high electromagnetic shielding effectiveness(SE)(SE_(T) of up to 75 dB)with low reflectance(SER of 1.5 dB at the resonant frequency)owing to EMI absorption induced by multiple internal reflection generated in the LM grid ***,the excellent stretchability of the LM-based devices facilitates tunable EMI shielding abilities through grid space adjustment upon strain(resonant frequency shift from 81.3 to 71.3 GHz@33%strain)and is also capable of retaining shielding effectiveness even after multiple strain *** newly explored device presents an advanced paradigm for powerful EMI shielding performance for next-generation smart electronics.

关键词： Absorption-dominant electromagnetic interference shielding Liquid metals Soft and stretchable electronics Thin film devices Tunable electromagnetic interference shielding

Enhanced electrical and optical properties of single- layered MoS2 by incorporation of aluminum

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Nano Research 2018年第2期11卷 731-740页

作者： Hyung-Jun Kim suk Yang Hojoong Kim jin Young Moon Kyung Park Yun-jin Park Jang-Yeon kwon School of Integrated Technology Yonsei University Incheon Republic of Korea Yonsei Institute of Convergence Technology Incheon Republic of Korea

Electrical and optical enhancements of single-layer semiconducting materials such as transition metal dichalcogenides have recently been studied to achieve sensitive properties via external treatments, such as the formation of organic/ inorganic protecting layers on field-effect transistors （FETs）, thermal annealing, and nano-dot doping of sensors and detectors. Here, we propose a new analytical approach to electrical and optical enhancement through a passivation process using atomic layer deposition （ALD）, and demonstrate a synthesized MoS2 monolayer incorporated with A1 atoms in an A1203 passivation layer. The incorporated A1 atoms in the MoS2 monolayer are dearly observed by spherical aberration-corrected scanning transmission electron microscopy （Cs-STEM） and TEM-energy-dispersive X-ray spectroscopy results. We demonstrate that the chemically incorporated FETs exhibit highly enhanced mobilities of approximately 3.7 crn2-V-los-1, forty times greater than that of as-synthesized MoS2, with a three- fold improvement in the Dhotoluminescence properties.

关键词： MoS2 aluminum incorporation chemical vapor deposition atomic layer deposition

SUBic:A Scalable Unsupervised Framework for Discovering High Quality Biclusters

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Journal of Computer Science & Technology 2013年第4期28卷 636-646页

作者： Jooil Lee Yanhua jin Won suk Lee Department of Computer Science Yonsei University

A biclustering algorithm extends conventional clustering techniques to extract all of the meaningful subgroups of genes and conditions in the expression matrix of a microarray dataset. However, such algorithms are very sensitive to input parameters and show poor scalability. This paper proposes a scalable unsupervised biclustering framework, SUBic, to find high quality constant-row biclusters in an expression matrix effectively. A one-dimensional clustering algorithm is proposed to partition the attributes, that is, columns of an expression matrix into disjoint groups based on the similarity of expression values. These groups form a set of short transactions and are used to discover a set of frequent itemsets each of which corresponds to a bicluster. However, a bicluster may include any attribute whose expression value is not similar enough to others, so a bicluster refinement is used to enhance the quality of a bicluster by removing those attributes based on its distribution of expression values. The performance of the proposed method is comparatively analyzed through a series of experiments on synthetic and real datasets.

关键词： biclustering clustering expression matrix frequent itemset sub-matrix

Impact of Spectral Nudging on the Downscaling of Tropical Cyclones in Regional Climate Simulations

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Advances in Atmospheric Sciences 2016年第6期33卷 730-742页

作者： suk-jin CHOI Dong-Kyou LEE Atmospheric Sciences Program School of Earth and Environmental SciencesKorea-USA Weather and Climate Research Center Seoul National University

This study investigated the simulations of three months of seasonal tropical cyclone （TC） activity over the western North Pacific using the Advanced Research WRF Model. In the control experiment （CTL）, the TC frequency was considerably overestimated. Additionally, the tracks of some TCs tended to have larger radii of curvature and were shifted eastward. The large-scale environments of westerly monsoon flows and subtropical Pacific highs were unreasonably simulated. The overestimated frequency of TC formation was attributed to a strengthened westerly wind field in the southern quadrants of the TC center. In comparison with the experiment with the spectral nudging method, the strengthened wind speed was mainly modulated by large-scale flow that was greater than approximately 1000 km in the model domain. The spurious formation and undesirable tracks of TCs in the CTL were considerably improved by reproducing realistic large-scale atmospheric monsoon circulation with substantial adjustment between large-scale flow in the model domain and large-scale boundary forcing modified by the spectral nudging method. The realistic monsoon circulation took a vital role in simulating realistic TCs. It revealed that, in the downscaling from large-scale fields for regional climate simulations, scale interaction between model-generated regional features and forced large-scale fields should be considered, and spectral nudging is a desirable method in the downscaling method.

关键词： tropical cyclone spectral nudging technique dynamic downscaling regional climate simulation

Addition of cerium and yttrium to ferritic steel weld metal to improve hydrogen trapping efficiency

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International Journal of Minerals,Metallurgy and Materials 2017年第4期24卷 415-422页

作者： Sung jin Kim Kang Mook Ryu Min-suk Oh Department of Advanced Materials Engineering Sunchon National University Jungang-ro Suncheon 540-742 Republic of Korea POSCO Steel Solution Marketing Division Geidong-Dong Pohang 790-704 Republic of Korea Automotive Components & Materials R&D Group Korea Institute of Industrial Technology 6 Cheomdan-gwagiro 208 beon-gil Gwangju 61012 Republic of Korea

The applicability of Ce and Y as promising candidate elements to form irreversible traps in weld metal was investigated by thermal desorption spectroscopy(TDS) with gas chromatography(GC). The precise nature of the precipitate particles newly formed in the weld metal by the addition of Ce and Y to a certain alloy system was characterized. Moreover,the hydrogen trapping efficiency expressed as the reduction of the diffusible hydrogen in the weld metal was analyzed. The results showed that the addition of Ce and/or Y to this alloy system led to the formation of a mixed type of(Ce,Ti)-based oxide,(Y,Ni)-based carbide,or(Ce,Y,Ti)-based oxide particles. Because of the high activation energy of the mixed type of particles(≥ 150 k J/mol),the trapping efficiency for hydrogen was considered to be sufficiently high to effectively reduce the diffusible hydrogen content.

关键词： hydrogen trapping weld rare earth metals cerium yttrium activation energy

Graphene quantum dots/Ni(OH)_(2) nanocomposites on carbon cloth as a binder-free electrode for supercapacitors

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Journal of Materials Science & Technology 2020年第23期58卷 73-79页

作者： Yiwen Hong jingli Xu jin suk Chung Won Mook Choi School of Chemical Engineering University of Ulsan93 Daehak-ro Nam-guUlsan44610Republic of Korea College of Chemistry and Chemical Engineering Shanghai University of Engineering ScienceLongTeng Road 333201620ShanghaiPR China

Graphene quantum dots(GQDs)/Ni(OH)_(2) composites on carbon cloth(G-NH//CC) are prepared through simple hydrothermal reactions. The resulting G-NH//CC is employed as a binder-free electrode of supercapacitors. Due to the enhanced electrical conductivity and efficient ion transport by the addition of GQDs, the G-NH//CC electrode exhibits enhanced electrochemical performances. Specifically, the GNH//CC delivers a maximum specific capacitance of 1825 F g^(-1) at a current density of 1 A g^(-1) as well as a good cycle stability of 83.5 % capacity retention after 8000 cycles. Additionally, all-solid-state symmetric supercapacitor(SSC) is assembled with G-NH//CC composites as both positive and negative *** fabricated SSC exhibits a high energy density of 80.8 Wh kg^(-1)at a power density of 2021 W kg^(-1). The present study provides a facile and efficient strategy to prepare high-performance electrode materials for advanced electrochemical energy storage devices.

关键词： Graphene quantum dots Ni(OH)_(2) Carbon clothes Symmetric supercapacitors

Distribution of Chancelloriids in a Middle Cambrian Carbonate Platform Deposit, Taebaek Group, Korea

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Acta Geologica Sinica(English Edition) 2016年第3期90卷 783-795页

作者： HONG Jongsun CHOH suk-Joo LEE Dong-jin Department of Earth and Environmental Sciences Korea University Department of Earth and Environmental Sciences Andong National University

The onset of the Cambrian witnessed the diversification of ＂small shelly fossils （SSF）＂, which affected carbonate depositional system. One of the problematic SSF, chancelloriids, are common components of the early to middle Cambrian carbonate and shale, and their contributions toward Cambrian carbonates are not yet fully understood. This study assesses distribution patterns of chancelloriid sclerites in the Cambrian Series 3 Daegi Formation based on microfacies analysis and discusses their sedimentologic implications. In the lower part of the formation, partially articulated chancelloriid sclerites occur mainly in bioclastic packstone and grainstone facies, with isolated sclerite rays in nodular packstone to grainstone facies. In the middle part of the formation, chancelloriid fragments occur only sporadically in bioclastic wackestone to packstone, bioclastic grainstone and oolitic packstone to grainstone facies, whereas boundstone facies are nearly devoid of their fragments. There are no chancelloriid fragments in the upper part of the formation, which consists of oolitic packstone to grainstone facies. Chancelloriids are interpreted to have primarily occupied platform margin shoal environments, shedding their sclerites to surrounding areas, and thus contributed as sediment producers. The distribution of Daegi chancelloriid sclerites is similar to other Cambrian examples, with the exception of common chancelloriids in Cambrian Series 2 reefs and their apparent near absence in the Daegi and other Cambrian Series 3 reefs. This disparity resulted from changes in the ecologic niche of chancelloriids after the end-Cambrian Series 2 reef crisis, coupled with an overall decline of chancelloriids in the middle Cambrian.

关键词： Cambrian Series 3 chancelloriid shoal carbonate platform reef

Dendrite Spacing Selection during Directional Solidification of Pivalic Acid-Ethanol System

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Journal of Materials Science & Technology 2008年第3期24卷 340-342页

作者： Myung-jin suk Young-Min Park Youn-Che Kim Department of Materials and-Metallurgical Engineering Kangwon National University

Unidirectional solidification of pivalic acid （PVA）-ethanol （Eth） mixture was performed to examine whether an allowable range of primary dendrite spacing definitely exists at a given growth velocity and how the range is history-dependent. PVA-0.59 wt pct Eth was unidirectionally solidified in the range of growth velocity 0.5-64 μm/s at the temperature gradient of 2.3 K/ram. Sequential change in growth velocity was imposed to determine the upper and lower limits for the allowable range of stable spacing. An allowable range of the steady state primary spacing was observed at a given growth velocity, and the extent of the range seems to be dependent on the degree to which step-increase or step-decrease in growth velocity is accomplished. As the degree of sequential change in growth velocity increases, the history-dependence of the selection for the primary dendrite spacing tends to disappear.

关键词： Dendrite spacing History-dependent Spacing selection Pivalic acid-ethanol

Microstructure of porous Cu fabricated by freeze-drying process of CuO/camphene slurry

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中国有色金属学会会刊：英文版 2012年第S3期22卷 688-691页

作者： Sung-tag OH Si-young CHANG Myung-jin suk Department of Materials Science and Engineering Seoul National University of Science and Technology Department of Materials Engineering Korea Aerospace University Department of Materials and Metallurgical Engineering Kangwon National University

Porous Cu with macroscopically aligned channels was synthesized using a freeze-drying ***-based CuO slurry was prepared by milling at 60 °C with a small amount of *** of a slurry was done at 25 °C while unidirectionally controlling the growth direction of the *** were generated subsequently by sublimation of the camphene during *** green body was hydrogen-reduced at 300 °C for 30 min,and sintered in the furnace at 700 °C for 1 h under a hydrogen *** observation reveals that all of the sintered samples are composed of only Cu phase and show macroscopic open pores with an average size of 100 μm which are aligned along its macroscopic growth *** internal wall of the macroscopic aligned pore shows relatively small pores due to the traces of the camphene left between the concentrated Cu particles on the internal *** in the porosity and pore size with increasing camphene content was explained by the change of the growth behavior of the camphene crystals.

关键词： porous Cu CuO-camphene slurry freeze-drying hydrogen reduction sintering