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Electrostabilized homogeneous dispersion of boron nitride nanotubes in wide-range of solvents achieved by surface polarity modulation through pyridine attachment

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Nano Research 2020年第2期13卷 344-352页

作者： Mi Se Chang Min-Sun Jang Sangsun Yang Jihun Yu Taehoon Kim Sedong Kim Hyomin jeong Chong Rae park Jae Won jeong Powder/Ceramic Research Division Korea Institute of Materials Science797 Changwondae-roSeongsan.guChangwon 51508Republic of Korea Research Institute of Advanced Materials and Department of Materials Science and Engineering Seoul National University Seoul 08826Republic of Korea Composites Research Division Korea Institute of Materials Science797 Changwondae-roSeongsan-guChangwon 51508Republic of Korea Dept.of Energy and Mech.Eng Gyeongsang National UniversityCheondaegukchi-Gil 38Tongyeong 53064Republic of Korea

Boron nitride nanotubes(BNNTs)show exceptional physical properties including high mechanical strength and thermal conductivity;however,their applications have been restricted due to limited dispersibility in processing ***,a novel BNNT dispersion method with exceptional dispersibility in a wide range of solvents has been demonstrated by surtace polarity modulation through short-molecule pyridine *** atoms in pyridine are selectively bonded to electron-deficient boron atoms of the BNNT surface through Lewis acid-base reaction,which changes the surface polarity of BNNTs from neutral to ***-dispersing pyridine-attached BNNTs(Py-BNNTs)create a thick and stable electronic double layer(EDL),resulting in uniform dispersion of BNNTs in solvents with an exceptional solubility parameter range of 18.5-48 MPa^1/*** uniform dispersion of BNNTs is maintained even after the mixing with diverse ***,composites incorporating uniformly-distributed BNNTs have been realized,and extraordinary property enhancements have been *** thermal conductivity of 20 wt.%Py-BNNT/epoxy composite has been significantly improved by 69.6%and the tensile strength of 2 wt.%Py-BNNT/PVA has been dramatically improved by 75.3%.Our work demonstrates a simple and facile route to dispersing BNNTs in diverse solvents,consequently leading to selective utlization of BNNT dispersed solvents in various application fields.

关键词： boron nitride nanotube one-dimensional nanomaterials surface polarity modulation electrostabilization boron nitride nanotube composite

New para-magnetic(CoFeNi)(50)(CrMo)(50-x)(CB)x(x=20,25,30)non-equiatomic high entropy metallic glasses with wide supercooled liquid region and excellent mechanical properties

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Journal of Materials Science & Technology 2020年第8期36卷 135-143页

作者： jeong Tae Kim Sung Hwan Hong Jin Man park Jürgen Eckert Ki Buem Kim Erich Schmid Institute of Materials Science Austrian Academy of Sciences(ÖAW)Jahnstrae 128700LeobenAustria Hybrid Materials Center(HMC) Department of Nanotechnology and Advanced Materials EngineeringSejong University209Neungdong-roGwangjin-guSeoul143-747Republic of Korea Global Technology Center(GTC) Samsung Electronics Co.Ltd129 Samsung-roYeongtong-guSuwonsiGyeonggi-do443-742Republic of Korea Department of Materials Science Chair of Materials PhysicsMontanuniversität LeobenJahnstraße 128700LeobenAustria

In this study,high entropy metallic glasses(HEMGs)were developed through a combination of concepts for designing metallic glasses(main element+transition metal+metalloid element)and high-entropy alloys(more than five elements,each element having an atomic concentration between 5 at.%and 35 at.%).The developed metallic glass alloys are composed of Co-Fe-Ni main elements,transition metals(Cr,Mo)and metalloid elements(C,B).Moreover,the present work reports the thermal,mechanical and magnetic properties of(CoFeNi)(50)(CrMo)(50-x)(CB)x alloys with x=20,25,*** developed as-spun HEMGs exhibit typical paramagnetic properties even for a high amount of ferromagnetic elements(Co,Fe,and Ni)and have high elastic modulus(103–160 GPa)and hardness(14–27 GPa),thus possessing mechanical properties similar to well-known Co-based metallic glasses(Co-Cr-Mo-C-B system).In addition,some of the bulk samples prepared with a diameter of 2 mm form bulk metallic glasses with a high compressive strength around 3.5 *** mechanisms determining the stability of the supercooled liquid,as well as the paramagnetic and mechanical properties for the developed non-equiatomic HEMGs,are discussed.

关键词： Metallic glasses Paramagnetism High entropy alloys Phase stability

Long Short-Term Memory Recurrent Neural Network-Based Acoustic Model Using Connectionist Temporal Classification on a Large-Scale Training Corpus

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China Communications 2017年第9期14卷 23-31页

作者： Donghyun Lee Minkyu Lim Hosung park Yoseb Kang jeong-Sik park Gil-Jin Jang Ji-Hwan Kim Department of Computer Science and Engineering Sogang University Department of Information and Communication Engineering Yeungnam University School of Electronics Engineering Kyungpook National University

A Long Short-Term Memory(LSTM) Recurrent Neural Network(RNN) has driven tremendous improvements on an acoustic model based on Gaussian Mixture Model(GMM). However, these models based on a hybrid method require a forced aligned Hidden Markov Model(HMM) state sequence obtained from the GMM-based acoustic model. Therefore, it requires a long computation time for training both the GMM-based acoustic model and a deep learning-based acoustic model. In order to solve this problem, an acoustic model using CTC algorithm is proposed. CTC algorithm does not require the GMM-based acoustic model because it does not use the forced aligned HMM state sequence. However, previous works on a LSTM RNN-based acoustic model using CTC used a small-scale training corpus. In this paper, the LSTM RNN-based acoustic model using CTC is trained on a large-scale training corpus and its performance is evaluated. The implemented acoustic model has a performance of 6.18% and 15.01% in terms of Word Error Rate(WER) for clean speech and noisy speech, respectively. This is similar to a performance of the acoustic model based on the hybrid method.

关键词： acoustic model connectionisttemporal classification large-scale trainingcorpus long short-term memory recurrentneural network

Super-resolving material microstructure image via deep learning for microstructure characterization and mechanical behavior analysis

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npj Computational Materials 2021年第1期7卷 867-877页

作者： Jaimyun Jung Juwon Na Hyung Keun park jeong Min park Gyuwon Kim Seungchul Lee Hyoung Seop Kim Department of Materials AI&Big-Data Korea Institute of Materials Science(KIMS)Changwon-siRepublic of Korea Department of Mechanical Engineering Pohang University of Science and Technology(POSTECH)PohangRepublic of Korea Department of Materials Science and Engineering Pohrepresent the average grainang University of Science and Technology(POSTECH)PohangRepublic of Korea Graduate School of Artificial Intelligence Pohang University of Science and Technology(POSTECH)PohangRepublic of Korea Graduate Institute of Ferrous Technology Pohang University of Science and Technology(POSTECH)PohangRepublic of Korea

The digitized format of microstructures,or digital microstructures,plays a crucial role in modern-day materials ***,the acquisition of digital microstructures through experimental means can be unsuccessful in delivering sufficient resolution that is necessary to capture all relevant geometric features of the *** resolution-sensitive microstructural features overlooked due to insufficient resolution may limit one’s ability to conduct a thorough microstructure characterization and material behavior analysis such as mechanical analysis based on numerical ***,a highly efficient super-resolution imaging based on deep learning is developed using a deep super-resolution residual network to super-resolved low-resolution(LR)microstructure data for microstructure characterization and finite element(FE)mechanical *** characterization and FE model based mechanical analysis using the super-resolved microstructure data not only proved to be as accurate as those based on high-resolution(HR)data but also provided insights on local microstructural features such as grain boundary normal and local stress distribution,which can be only partially considered or entirely disregarded in LR data-based analysis.

关键词： microstructure Microstructure analysis

Dynamic deformation behavior and microstructural evolution during high-speed rolling of Mg alloy having non-basal texture

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Journal of Materials Science & Technology 2019年第4期35卷 473-482页

作者： Sang-Hoon Kim jeong Hun Lee Chong soo Lee Jonghun Yoon Sung Hyuk park School of Materials Science and Engineering Kyungpook National University Ulsan Regional Division Korea Institute of Industrial Technology Graduate Institute of Ferrous Technology Pohang University of Science and Technology Department of Mechanical Engineering Hanyang University

The dynamic deformation behaviors and resultant microstructural variations during high-speed rolling(HSR) of a Mg alloy with a non-basal texture are investigated. To this end, AZ31 alloy samples in which the basal poles of most grains are predominantly aligned parallel to the transverse direction(TD) are subjected to hot rolling with different reductions at a rolling speed of 470 m/min. The initial grains with a TD texture are favorable for {10–12} twinning under compression along the normal direction(ND); as a result, {10–12} twins are extensively formed in the material during HSR, and this consequently results in a drastic evolution of texture from the TD texture to the ND texture and a reduction in the grain size. After the initial grains are completely twinned by the {10–12} twinning mechanism, {10–11} contraction twins and {10–11}-{10–12} double twins are formed in the {10–12} twinned grains by further *** the contraction twins and double twins have crystallographic orientations that are favorable for basal slip during HSR, dislocations easily accumulate in these twins and fine recrystallized grains nucleate in the twins to reduce the increased internal strain energy. Until a rolling reduction of 20%, {10–12}twinning is the main mechanism governing the microstructural change during HSR, and subsequently,the microstructural evolution is dominated by the formation of contraction twins and double twins and the dynamic recrystallization in these twins. With an increase in the rolling reduction, the average grain size and internal strain energy of the high-speed-rolled(HSRed) samples decrease and the basal texture evolves from the TD texture to the ND texture more effectively. As a result, the 80% HSRed sample, which is subjected to a large strain at a high strain rate in a single rolling pass, exhibits a fully recrystallized microstructure consisting of equiaxed fine grains and has an ND basal texture without a TD texture component.

关键词： Magnesium alloy High-speed rolling Texture Dynamic recrystallization Twinning

Characteristics of Atmospheric Circulation Associated with Cold Surge Occurrences in East Asia:A Case Study During 2005/06 Winter

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Advances in Atmospheric Sciences 2008年第5期25卷 791-804页

作者： Tae-Won park Jee-Hoon jeong Chang-Hoi HO Seong-Joong KIM School of Earth and Environmental Sciences Seoul National University Seoul Korea Department of Earth Sciences University of Gothenburg Gothenburg Sweden Korea Polar Research Institute Incheon Korea

The characteristics of the upper-level circulation and thermodynamical properties for the period when two distinct cold surges broke out over East Asia during the 2005/06 winter are investigated. From early December 2005 to early January 2006, exceptionally cold weather lasted for approximately one month due to two successive cold surges that took place on 2 December 2005 and 2 January 2006, respectively. This study reveals that both involve the upper-tropospheric circulation, which induces the amplification and expansion of the surface Siberian high toward East Asia, but arose from different causes： the former is caused by the upper-level blocking originated from the North Pacific and the latter is caused by the upper-level wave train across the Eurasian Continent. In particular, it is suggested that the lower-tropospheric anomalous wind caused by upper-level circulation anomalies and a steep meridional temperature gradient amplified by phase-locked annual cycle combined to induce very strong cold advection in East Asia, which resulted in exceptionally cold weather that lasted for several weeks. The present results emphasize that the characteristics of the upper-tropospheric circulation can be considered as important precursors to cold surge occurrences in East Asia.

关键词： cold surge Siberian high East Asia East Asian winter monsoon upper-tropospheric circulation

Hot electron generation on metal catalysts under surface reaction:Principles, devices, and application

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Chinese Chemical Letters 2018年第6期29卷 727-733页

作者： Ievgen I.Nedrygailov Hyosun Lee Si Woo Lee jeong Young park Center for Nanomaterials and Chemical Reactions Institute for Basic Science Graduate School of EEWS Korea Advanced Institute of Science and Technology(KAIST)

Understanding the fundamental mechanisms for charge transfer in supported catalysts is of great importance for heterogeneous catalysis. Several experimental and theoretical results suggest that charge flow through metal-support interfaces leads to the catalytic enhancement that is often observed in mixed catalysts. Therefore, it is crucial to directly probe this charge flow in metal-support catalysts during catalytic reactions. In this review, we consider the main aspects of research studying the processes that create and allow interfacial transfer of highly excited（hot） charge carriers in supported catalysts, and discuss the effect of this charge transfer on catalytic activity. We show a close connection between the phenomena of hot electron creation and chemical energy dissipation that accompanies catalytic reactions at both the gas/solid and liquid/solid interfaces. The intensity of hot electron flow is well correlated with the turnover rates of corresponding reactions, which opens up the possibility for developing new operando methodologies for studying chemical processes on catalytic surfaces.

关键词： Hot electron Energy dissipation Heterogeneous catalysis Metal-support interactions Nanodiode

Physiological and Biochemical Modulations upon Root Induction in Rose Cuttings as Affected by Growing Medium

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Horticultural Plant Journal 2018年第6期4卷 257-264页

作者： KIM soohoon ABINAYA Manivannan park Yoo Gyeong jeong Byoung Ryong Division of Applied Life Science (BK21 Plus Program) Graduate School Gyeongsang National University Institute of Agriculture and Life Science Gyeongsang National University Research Institute of Life Science Gyeongsang National University

Two cut rose(Rosa hybrida) cultivars ‘Sherbet'(easy-to-root) and ‘Alibaba'(difficult-to-root) were propagated by single nodal cuttings on preformed media. Four commercial media such as Tosilee, Ellepot, rockwool and phenolic foam RC, and four newly-developed foam media namely Oasis PU 14-S1, Oasis TP-S1, Oasis PU-7 B and Oasis PU 15-S1 were employed in this study. All media were manufactured to fit into50-cell plug trays. The experiment was laid out in a complete randomized block design with three replications on a propagation bench with a plastic tunnel installed in a glasshouse, with(98 ± 2)% relative humidity and over 50% shading of the natural sunlight. After four weeks of experiment, growth parameters, localization of superoxide radicals, and activities of rooting biochemical markers were measured. The results suggested that the newly-developed foam media Oasis TP-S1 and Oasis PU-7 B enhanced the growth, density of leaf stomata, and consisted of lesser harmful superoxide radicals in similar manner with the existing commercial media. Moreover, the Oasis TP-S1 and Oasis PU-7 B media significantly enhanced the total phenol content and the activities of important enzymes involved in the phenol metabolism which plays a vital role in the formation of roots. Thus, the understanding of both physiological and biochemical changes implicated by the growing medium during the rooting of cuttings would aid in the selection of optimal growing medium for the propagation of rose cuttings.

关键词： foam medium peroxidase phenol phenylalanine ammonia lyase(PAL) superoxide localization

Improved tensile properties of AZ31 Mg alloy subjected to various caliber-rolling strains

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Journal of Magnesium and Alloys 2019年第3期7卷 381-387页

作者： jeong Hun Lee Byung Je Kwak Taein Kong Sung Hyuk park Taekyung Lee Advanced Forming Process R&D Group Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation *** present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application of caliber *** improving trends in tensile properties were interpreted with various caliber-rolling *** oval/circular-shaped calibers imposed a high plastic strain at the center of crosssection,leading to effective grain refinement to submicron *** work also confirmed the texture randomizing effect of caliber *** microstructural evolutions gave rise to the fabrication of high-strength ***,the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled *** was discussed in terms of activation of non-basal slip systems and suppression of mechanical *** study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties.

关键词： Magnesium AZ31 alloy Caliber rolling Grain refinement Texture randomization Mechanical improvement