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Effects of surface roughness on bending properties of rolled AZ31 alloy

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Journal of Magnesium and Alloys 2023年第4期11卷 1224-1235页

作者： Gyo Myeong lee jong Un lee Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

This study investigated the effects of mechanical-polishing-induced surface roughness and the direction of polishing lines on the bending properties of a rolled AZ31 *** this end,three-point bending tests were performed on one sample without polishing lines(SS sample)and two samples with polishing lines—one in which the polishing lines were parallel to the rolling direction(RS-RD sample)and the other in which they were parallel to the transverse direction(RS-TD sample).In all three samples,macrocracks were formed in the width direction on the outer surface,where tensile stress was predominantly generated in the longitudinal ***,the macrocracks formed in the SS sample were curved because of the merging of uniformly formed fine microcracks,whereas those formed in the RS-TD sample were linear owing to the formation of relatively coarse microcracks along the polishing *** bendability of the samples was in the order of SS>RS-RD>RS-TD,and their limiting bending depths were 4.8,4.6,and 4.4 mm,*** the presence of mechanical-polishing-induced surface roughness,polishing lines perpendicular to the direction of the major stress(i.e.,tensile stress along the longitudinal direction)resulted in a greater degree of stress concentration on the outer surface of the bending *** higher stress concentration promoted the formation of undesirable{10–11}contraction and{10–11}–{10–12}double twins—which typically act as crack initiation sites—and thereby facilitated crack generation and ***,the surface roughness caused premature fracture during bending deformation,which,in turn,caused deterioration of the bendability of the rolled Mg alloy.

关键词： AZ31 alloy Bending Surface roughness Stress concentration Crack

Bending properties of extruded AZ91–0.9Ca–0.6Y alloy and their improvement through precompression and annealing

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Journal of Magnesium and Alloys 2022年第8期10卷 2238-2251页

作者： jong Un lee Gyo Myeong lee Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

In this study,an extruded Mg–9Al–1Zn–0.3Mn–0.9Ca–0.6Y(AZXW9110)alloy is subjected to precompression and subsequent annealing(PCA)treatment for improving its bending formability,and the three-point bending properties of the as-extruded material and the precompressed and subsequently annealed(PCAed)material at room temperature are *** bending,microcracks formed in undissolved Al2Ca,Al2Y,and Al8Mn4Y particles propagate along the grain boundaries or twin boundaries and consequently form a macrocrack in the tension zones of the bending samples of both the ***,the bending formability of the PCAed material is 75%higher than that of the as-extruded material owing to the promoted twinning and slip behaviors in the *** as-extruded material has a strong normal direction(ND)texture and a weak transverse direction(TD)texture,and the ND-and TD-oriented grains are unfavorable for both{10–12}twinning and basal slip in the tension zone of the bending sample of this material,which eventually results in its low bending *** PCAed material has a strong extrusion direction(ED)texture,weak TD texture,and spread ND *** bending,{10–12}twins are fully formed in the ED-oriented grains,and this{10–12}twinning effectively accommodates the plastic strain in the tension *** addition,the activation of basal slip in the ND-oriented grains of the PCAed material is promoted owing to the spread ND texture of this ***,this material exhibits substantially superior bending formability because of the vigorous{10–12}twinning in its ED-oriented grains and promoted basal slip in its ND-oriented grains.

关键词： Magnesium Bending Formability Twinning Texture

Recent research progress on magnesium alloys in Korea:A review

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Journal of Magnesium and Alloys 2023年第10期11卷 3545-3584页

作者： Sung Hyuk Park Ye Jin Kim Hyun Ji Kim sang-Cheol Jin jong Un lee Alexander Komissarov Kwang Seon Shin School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Laboratory of Hybrid Nanostructured Materials National University of Science and TechnologyMoscow 119049Russia Laboratory of Medical Bioresorption and Bioresistance Moscow State University of Medicine and DentistryMoscow 127473Russia Magnesium Technology Innovation Center School of Materials Science and EngineeringSeoul National UniversitySeoul 08826Republic of Korea

This review highlights the recent advancements in Mg research in South Korea with a prime focus on high-speed-extrudable Mg–Bi-based alloys for high productivity and strength,innovative techniques utilizing{10–12}twinning for improved mechanical properties,and alloying and processing methods for enhanced corrosion ***-alloyed Mg–Bi-based alloys possess thermally stableα-Mg matrix and secondary phase,which ensures high-speed extrusion of these alloys at elevated temperatures without hot ***,they exhibit outstanding extrudability with a maximum extrusion speed of up to 70 m/***,their high alloying contents offer excellent strength even after high-speed extrusion through strong solid solution hardening and particle hardening effects,making them suitable for high-performance extruded Mg *** pre-twinning process utilizing{10–12}twinning and the combined process of pre-twinning and subsequent annealing have shown promise in controlling microstructure and texture of wrought Mg alloys and thus enhancing their mechanical *** pre-twinning process enhances tensile strength,fatigue properties,and age-hardening rate of Mg ***,the combined processes of pre-twinning and subsequent annealing considerably improve their ductility,stretch formability,bending formability,and damping *** have been made to improve the corrosion resistance of Mg alloys through alloying additions,process treatments,and surface *** elements like Ca,Sc,and Sm alter the microstructural features(such as secondary phases and grain size)that affect the corrosion *** treatments such as multidirectional forging,screw rolling,and pulse electron beam can also improve the corrosion resistance by refining the ***,advanced surface coating technologies can create durable and corrosion-resistant layers for effectively protecting the Mg *** these research activities conducted

关键词： South Korea Mg–Bi alloys {10–12}twinning Corrosion Mechanical properties

Enhanced KOCED Routing Protocol with K-means Algorithm

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Computers, Materials & Continua 2021年第6期67卷 4019-4037页

作者： SeaYoung Park jong-Yong lee Daesung lee Department of Plasma Bioscience and Display KwangWoon University Graduate SchoolSeoul01897Korea Ingenium College of Liberal Arts KwangWoon UniversitySeoulKorea Department of Computer Engineering Catholic University of PusanBusanKorea

Replacing or recharging batteries in the sensor nodes of a wireless sensor network(WSN)is a significant ***,efficient power utilization by sensors is a critical requirement,and it is closely related to the life span of the *** a sensor node consumes all its energy,it will no longer function ***,various protocols have been proposed to minimize the energy consumption of sensors and thus prolong the network ***,clustering algorithms combined with artificial intelligence have been proposed for this *** particular,various protocols employ the K-means clustering algorithm,which is a machine learning *** number of clustering configurations required by the K-means clustering algorithm is greater than that required by the hierarchical ***,the selection of the cluster heads considers only the residual energy of the nodes without accounting for the transmission distance to the base *** terms of energy consumption,the residual energy of each node,the transmission distance,the cluster head location,and the central relative position within the cluster should be considered *** this paper,we propose the KOCED(K-means with Optimal clustering for WSN considering Centrality,Energy,and Distance)protocol,which considers the residual energy of nodes as well as the distances to the central point of the cluster and the base station.A performance comparison shows that the KOCED protocol outperforms the LEACH protocol by 259%(223 rounds)for first node dead(FND)and 164%(280 rounds)with 80%alive nodes.

关键词： WSN routing protocol K-means K-optimal LEACH KCE KOCED

Permeability evaluation for artificial single rock fracture according to geometric aperture variation using electrical resistivity

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 787-797页

作者： Hangbok lee jong-Won lee Tae-Min Oh Deep Subsurface Research Center Korea Institute of Geoscience and Mineral ResourcesDaejeon34132Republic of Korea Department of Civil and Environmental Engineering Pusan National UniversityBusan46241Republic of Korea

A convenient approach was proposed by which to evaluate and monitor the permeability of a rock fracture by verifying the quantitative correlation between the electrical resistivity and permeability at laboratory *** this purpose,an electrical resistivity measurement system was applied to the laboratory experiments using artificial cells with the shape of a single rock *** experiments were conducted using rock fractures according to the geometry,aperture sizes,wavelengths,and roughness *** overall negative relationship between the normalized electrical resistivity values and the aperture sizes directly linked with the permeability,was well fitted by the power-law function with a large determination coefficient(≈0.86).The effects of wavelength and roughness amplitude of the rock fracture on the electrical resistivity were also *** showed that the electrical resistivity was slightly increased with decreasing wavelength and increasing roughness *** empirical model for evaluating the permeability of a rock fracture was proposed based on the experimental *** the field,if the electrical resistivity of pore groundwater could be measured in advance,this empirical model could be applied effectively for simple,quick monitoring of the fracture *** uncertainty may be associated with the permeability estimation due to the limited control parameters considered in this research,this electrical resistivity approach could be helpful to monitor the rock permeability in deep underground facilities such as those used for radioactive waste repositories or forms of energy storage.

关键词： Permeability Rock fracture Electrical resistivity Fracture geometry Long-term monitoring

Design and compensation of second-order sub-sampling digital frontend

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Journal of Central South University 2012年第2期19卷 408-416页

作者：王洪梅 KIM Jae-hyung lee sang-hyuk KIM Hyung-jung KIM Jin-up KOH jong-seog School of Mechatronics Changwon National University Electrical and Electronic Engineering Xi'an Jiaotong-Liverpool University Smart Radio Team Electonics and Telecommunication Research Institute Korea Telecommunication Company

The problem of designing a digital frontend (DFE) was considered which can dynamically access or sense dual bands in any radio frequency (RF) regions without requiring hardware changes. In particular, second-order bandpass sampling (BPS) as a technique that enables to realize the multiband reception function was discussed. In a second-order BPS system, digital reconstruction filters were utilized to eliminate the interferences generated while down converting arbitrarily positioned RF-band signals by using the direct digitization method. However, the inaccuracy in the phase shift or the amplitude mismatch between the two sample streams may cause insufficient rejection of interference. Practical problems were studied, such as performance degradation in signal-to-interference ratio (SIR) and compensation methods to overcome them. In order to demonstrate the second- order BPS as a flexible DFE suitable for software-defined radio (SDR) or cognitive radio (CR), a DFE testbed with a reconfigurable structure was implemented. Moreover, with a view to further demonstrate the proposed compensation algorithms, experimental results show that dual bands are received simultaneously.

关键词： bandpass sampling second order band-pass sampling reconfiguration software-defined radio

Gene editing of authentic Brassica rapa flavonol synthase 1 generates dihydroflavonol-accumulating Chinese cabbage

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Horticulture Research 2023年第12期10卷 58-69页

作者： sangkyu Park Hyo lee Jaeeun Song Chan Ju Lim Jinpyo Oh sang Hoon lee Saet Buyl lee jong-Yeol lee Sunhyung Lim Jin A.Kim Beom-Gi Kim Metabolic Engineering Division National Institute of Agricultural SciencesRural Development AdministrationJeonju54874South Korea Institute of Biotechnology and Breeding Asiaseed Inc.Icheon17414South Korea Food and Nutrition Division National Institute of Agricultural SciencesRural Development AdministrationWanju55365South Korea Department of Horticultural Biotechnology School of BiotechnologyHankyong National UniversityAnseong17579South Korea

Flavonols are the major class of flavonoids of green Chinese cabbage(Brassica rapa ***).The *** genome harbors seven flavonol synthase genes(BrFLSs),but they have not been functionally ***,transcriptome analysis showed four BrFLSs mainly expressed in Chinese *** them,only BrFLS1 showed major FLS activity and additional flavanone 3β-hydroxylase(F3H)activity,while BrFLS2 and BrFLS3.1 exhibited only marginal F3H *** generated BrFLS1-knockout(BrFLS1-KO)Chinese cabbages using CRISPR/Cas9-mediated genome editing and obtained transgene-free homozygous plants without off-target mutation in the T1 generation,which were further advanced to the T2 generation showing normal ***-ESI-QTOF-MS analysis revealed that flavonol glycosides were dramatically decreased in the T2 plants,while dihydroflavonol glycosides accumulated concomitantly to levels corresponding to the reduced levels of *** PCR analysis revealed that the early steps of phenylpropanoid and flavonoid biosynthetic pathway were upregulated in the BrFLS1-KO *** accordance,total phenolic contents were slightly enhanced in the BrFLS1-KO plants,which suggests a negative role of flavonols in phenylpropanoid and flavonoid biosynthesis in Chinese *** surveys revealed that the BrFLS1-KO Chinese cabbages showed normal head formation and reproductive phenotypes,but subtle morphological changes in their heads were *** addition,their seedlings were susceptible to osmotic stress compared to the controls,suggesting that flavonols play a positive role for osmotic stress tolerance in *** *** this study,we showed that CRISPR/Cas9-mediated BrFLS1-KO successfully generated a valuable breeding resource of Chinese cabbage with distinctive metabolic traits and that CRISPR/Cas9 can be efficiently applied in functional Chinese cabbage breeding.

关键词： steps slightly phenolic

Nielsen coincidence theory on infra-solvmanifolds of Sol

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Science China Mathematics 2021年第8期64卷 1861-1884页

作者： jong Bum lee Karen Regina Panzarin Department of Mathematics Sogang UniversitySeoul 121-742Korea Departamento de Matematica Universidade Federal de Sao CarlosSao CarlosSP 13565-905Brazil

We derive averaging formulas for the Lefschetz coincidence numbers,the Nielsen coincidence numbers and the Reidemeister coincidence numbers of maps on infra-solvmanifolds modeled on a connected and simply connected solvable Lie group of type(R).As an application,we compare our formula for the Nielsen coincidence numbers with a result of Jezierski(1992)for pairs of maps on some infra-solvmanifolds of *** all the pairs of self-maps of a nonorientable infra-solvmanifold of Sol,we determine the sets of all the possible values of the Nielsen coincidence numbers and the Reidemeister coincidence numbers.

关键词： averaging formula infra-solvmanifold Lefschetz coincidence number Nielsen coincidence number Reidemeister coincidence number Sol-geometry

Assessment criteria for nonverbal interaction contents in r-learning

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Journal of Central South University 2013年第9期20卷 2388-2398页

作者： CHOI jong-hong lee jong-yun YOON Heung-seob Department of Computer Education Chungbuk National University Department of English Education Chungbuk National University

r-learning,which is based on e-learning and u-learning,is defined as a learning support system that intelligent robots serve verbal and nonverbal interactions on ubiquitous computing *** order to guarantee the advantages of r-learning contents with no limits of timc and place and with nonverbal interaction which are not in e-learning contents,in recent years,assessment criteria for r-learning contents are urgently ***,the reliable and valid assessment criteria were developed for nonverbal interaction contents in r-learning,and its detailed research content is as ***,assessment criteria for nonverbal interaction in r-learning contents will be specified into gesture,facial expression,semi-verbal message,distance,physical contact and ***,the validity of the developed assessment criteria will be proved by ***,the assessment criteria for nonverbal interaction contents will be helpful when choosing the better r-learning content and producing the better r-learning content,and the reliability of school education is improved ultimately.

关键词： r-learning, r-learning contents assessment criteria nonverbal interaction contents confirmatory factor analysis construct validity