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Influence of undissolved second-phase particles on dynamic recrystallization behavior of Mg–7Sn–1Al–1Zn alloy during low-and high-temperature extrusions

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Journal of Materials Science & Technology 2021年第12期71卷 87-97页

作者： hyun Ji Kim Sang-Cheol Jin jae-Gil Jung Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChangwon51508Republic of Korea

This study investigates the effects of fine and coarse undissolved particles in a billet of the Mg–7 Sn–1 Al–1 Zn(TAZ711)alloy on the dynamic recrystallization(DRX)behavior during hot extrusion at low and high temperatures and the resultant microstructure and mechanical properties of the *** this end,partially homogenized(PH)and fully homogenized(FH)billets are extruded at temperatures of250 and 450°*** PH billet contains fine and coarse undissolved Mg_(2) Sn particles in the interdendritic region and along the grain boundaries,*** fine particles(<1μm in size)retard DRX during extrusion at 250°C via the Zener pinning effect,and this retardation causes a decrease in the area fraction of dynamically recrystallized(DRXed)grains of the extruded *** addition,the inhomogeneous distribution of fine particles in the PH billet leads to the formation of a bimodal DRXed grain structure with excessively grown grains in particle-scarce *** contrast,in the FH billet,numerous nanosized Mg_(2) Sn precipitates are formed throughout the material during extrusion at 250°C,which,in turn,leads to the formation of small,uniform DRXed grains by the grain-boundary pinning effect of the *** the PH billet is extruded at the high temperature of 450°C,the retardation effect of the fine particles on DRX is weakened by their dissolution in theα-Mg matrix and the increased extent of thermally activated grain-boundary *** contrast,the coarse Mg_(2) Sn particles in the billet promote DRX during extrusion through the particle-stimulated nucleation phenomenon,which results in an increase in the area fraction of DRXed *** both low and high extrusion temperatures,the extruded material fabricated using the PH billet,which contains both fine and coarse undissolved particles,has a lower tensile strength than that fabricated using the FH billet,which is virtually devoid of second-phase *** lower strength of the former is attributed mai

关键词： Mg–Sn alloy Second-phase particle Extrusion Homogenization Dynamic recrystallization

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Interface properties and phase formation between surface coated SKD61 and aluminum alloys

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中国有色金属学会会刊：英文版 2009年第4期19卷 875-878页

作者： Se-Weon CHOI Young-Chan KIM Se-Hun CHANG Ik-hyun OH Joon-Sik PARK Chang-seog KANG Automotive Components Center Korea Institute of Industrial Technology Division of Advanced Materials Engineering Hanbat National University

The intermediate phase formation and surface protection effects between SKD61 die mold alloys and aluminum alloys were investigated during a simulated die-casting *** surface coatings of SKD61 alloy were carried out via Si pack cementation coatings at 900 ℃ for 10 h and the ε-FeSi phase *** the coated SKD61 alloy was dipped in the liquid aluminum alloy(ALDC12),the surface coated SKD61 alloys showed better surface properties compared with uncoated SKD61 alloys,i.e.,the intermediate phases(FeSiAl compound) were not produced for the coated SKD61 *** coating layer of ε-FeSi served as a diffusion barrier for the formation of FeSiAl compounds.

关键词：表面涂层铝合金接口特性表面合金涂层表面保护合金生产化合物中间相

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Superelastic metastable Ti-Mo-Sn alloys with high elastic admissible strain for potential bio-implant applications

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Journal of Materials Science & Technology 2023年第32期163卷 45-58页

作者： Shuanglei Li jae H.Kim Seung Won Kang jae Ho Kim Tae-hyun Nam Jong-Taek Yeom Titanium Alloys Department Metal Materials DivisionKorea Institute of Materials Science(KIMS)Changwon 51508Republic of Korea Department of Materials Engineering and Convergence Technology&Research Institute for Green Energy Convergence Technology(RIGET) Gyeongsang National University900 GazwadongJinjuGyeongnam 52828Republic of Korea

The demand for titanium alloys simultaneously having high elastic admissible strain and large recovery strain for bio-implant applications is ***-free Ti-based shape memory alloys are promising candidates for obtaining the required multifunctional *** this study,a wide content range of(0-15)wt%of low-cost,toxicity-free,and high-biocompatible Sn element was added to the Ti-8Mo(wt%)alloy to study its effect on the superelastic recovery and mechanical properties of biomedical Ti-Mo-Sn *** tailoring Sn content,desired multifunctional properties of high elastic admissible strain and room temperature superelasticity were achieved in the studied Ti-Mo-Sn *** was found that the increase in Sn content stabilized theβphase and a singleβphase was obtained at room temperature in Ti-8Mo-(13,15)Sn *** addition of Sn modified the lattice parameters of theα″martensite andβphase and affected the lattice deformation stain ofβ→α″.The lattice deformation strain along the[011]βdirection was found to be decreased by-0.26%/wt%*** room temperature superelasticity with a recovery strain of 3.1%and an elastic admissible strain of 1%was obtained in the Ti-8Mo-13Sn *** Sn content increased to 15 wt%,a high elastic admissible strain of 1.56%and a recovery strain of 2.0%were *** Ti-Mo-Sn alloys with excellent multifunctional properties are promising candidates for bio-implant applications.

关键词： Ti-Mo-Sn alloy Shape memory alloy Elastic admissible strain Elastic modulus Superelasticity

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Effects of structure and electronic properties of D-π-A organic dyes on photovoltaic performance of dye-sensitized solar cells

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Journal of Energy Chemistry 2021年第3期30卷 208-216页

作者： Min-Woo Lee jae-Yup Kim hyung-Geun Lee hyun Gil Cha Duck-hyung Lee Min jae Ko Bio-Based Chemistry Research Center Advanced Convergent Chemistry DivisionKorea Research Institute of Chemical Technology(KRICT)Ulsan 44429Republic of Korea Department of Chemical Engineering Dankook UniversityYongin 16890Republic of Korea Department of Chemistry Sogang UniversitySeoul 04107Republic of Korea Department of Chemical Engineering Hanyang UniversitySeoul 04763Republic of Korea Institute of Nano Science and Technology Hanyang UniversitySeoul 04763Republic of Korea

Herein,we examine the performance of dye-sensitized solar cells containing five D-π-A organic dyes designed by systematic modification of π-bridge size and geometric *** dye has a simple push-pull structure with a triarylamino group as an electron donor,bithiophene-4,4-dimethyl-4 H-cyclopenta 1,2-b:5,4-b’]dithiophene(M11),4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophenethiophene(M12),thiophene-4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene(M13),4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene-benzene(M14),and 4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene(M15)units asπ-bridges,and cyanoacrylic acid as an electron acceptor/*** extension of theπ-bridge linkage favors wide-range absorption but,because of the concomitant molecular volume increase,hinders the efficient adsorption of dyes on the TiO_(2) film ***,higher loadings are achieved for smaller dye molecules,resulting in(i)a shift of the TiO_(2) conduction band edge to more negative values,(ii)a greater photocurrent,and(iii)suppressed charge recombination between the photoanode and the redox couple in the ***,under one-sun equivalent illumination(AM 1.5 G,100 mW/cm^(2)),the highest photovoltage,photocurrent,and conversion efficiency(η=7.19%)are observed for M15,which has the smallest molecular volume among M series dyes.

关键词： Dye-sensitized solar cells Donor-acceptor dyes Electron-rich unit Wide-range absorption Impedance spectroscopy

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Complications and management of forgotten long-term biliary stents

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World Journal of Gastroenterology 2017年第4期23卷 622-628页

作者： Se Hoon Sohn jae hyun Park Kook hyun Kim Tae Nyeun Kim Division of Gastroenterology and Hepatology Department of Internal MedicineYeungnam University College of MedicineDaegu 42415South Korea

AIMTo evaluate complications and management outcomes of retained long-term plastic biliary *** plastic biliary stent placement was performed in 802 patients at Yeungnam University Hospital between January 2000 and December 2014. Follow-up loss with a subsequently forgotten stent for more than 12 mo occurred in 38 patients. We retrospectively examined the cause of biliary stent insertion, status of stents, complications associated with biliary stents and management outcomes of long-term plastic biliary stents. Continuous variables were analyzed using the t test. Observed frequencies in subsets of the study population were compared using Fisher’s exact test and χ2 tests. Statistical significance was defined as P < 0.05 (two-tailed).RESULTSMean age of patients was 73.7 ± 12 years and male-to-female ratio was 2.2:1. Indications of plastic biliary stent insertion were bile duct stones (63.2%, 24/38) and benign bile duct stricture (52.6%, 20/38). Mean duration of retained plastic stent was 22.6 ± 12.2 mo, and in 10 cases (26.3%), stents were retained for more than 24 mo. Common bile duct (CBD) stones or sludge were found in most cases (92.1%, 35/38). The most common complication was acute cholangitis (94.7%, 36/38). Stent removal by endoscopic approach was successfully performed in 92.1% (35/38) of the cases. In 3 cases, an additional plastic stent was inserted alongside the previous stent due to failure of the stent removal. Endoscopic removal of bile duct stones was successful in 73.7% (28/38) of the cases. When patients were divided into two groups by duration of stent placement (12 to 24 mo vs over 24 mo), there were no differences in the development of cholangitis, presence of biliary stones, and success rate of endoscopic removal of stones and biliary *** most common complication of retained long-term plastic biliary stents was acute cholangitis associated with CBD stones. Endos

关键词： Biliary stent Long-term complications Forgotten stents Acute cholangitis Biliary stone

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Innovative strategies toward challenges in PV-powered electrochemical CO_(2)reduction

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Journal of Energy Chemistry 2021年第9期30卷 410-416页

作者： Siraj Sultan Jin hyun Kim Seung Hyeon Kim Youngkook Kwon jae Sung Lee Department of Energy Engineering School of Energy and Chemical EngineeringUlsan National Institute of Science and Technology(UNIST)Ulsan 44919South Korea

The solar energy-driven electrochemical CO_(2)reduction to value-added fuels or chemicals is considered as an attractive path to store renewable energy in the form of chemical energy to close the carbon ***,CO_(2)reduction suffers from a number of challenges including slow reaction rates,low selectivity,and low energy conversion ***,innovative strategies have been developed to mitigate this *** the development of flow cell reactors with a gas diffusion electrode,ionic liquid electrolytes,and new electrocatalysts have dramatically improved the reaction rates and selectivity to desired *** this perspective,we highlight the key recent developments and challenges in PVpowered electrochemical CO_(2)reduction and propose effective strategies to improve the reaction kinetics,to minimize the electrical energy losses,and to tune the selectivity of the catalysts for desired products,and then suggest future direction of research and development.

关键词： Electrochemical CO_(2)reduction Photovoltaic cell Ionic liquid electrolytes Flow cell electrolyzers Gas diffusion electrode

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Efficient Gauss-Seidel Precoding with Parallel Calculation in Massive MIMO Systems

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Computers, Materials & Continua 2022年第1期70卷 491-504页

作者： hyun-Sun Hwang jae-hyun Ro Chan-Yeob Park Young-Hwan You Hyoung-Kyu Song Department of Information and Communication Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea Department of Convergence Engineering for Intelligent Drone Sejong UniversitySeoul05006Korea Department of Computer Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea

A number of requirements for 5G mobile communication are satisfied by adopting multiple input multiple output(MIMO)*** inter user interference(IUI)which is an inevitable problem in MIMO systems becomes controllable when the precoding scheme is *** this paper,the horizontal Gauss-Seidel(HGS)method is proposed as precoding scheme in massive MIMO *** massive MIMO systems,the exact inversion of channel matrix is impractical due to the severe computational ***,the conventionalGauss-Seidel(GS)method is used to approximate the inversion of channel *** GS has good performance by using previous calculation results as ***,the required time for obtaining the precoding symbols is too long due to the sequential process of ***,the HGS with parallel calculation is proposed in this paper to reduce the required *** rows of channel matrix are eliminated for parallel calculation *** addition,HGSuses the ordered channelmatrix to prevent performance degradation which is occurred by parallel *** HGS with proper number of parallelly computed symbols has better performance and reduced required time compared to the traditional GS.

关键词： Massive MIMO GS matrix inversion linear precoding

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Emission of particulate and gaseous pollutants from household laser processing machine

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Journal of Environmental Sciences 2021年第5期33卷 148-156页

作者： hyun Sik Ko Sang Bin Jeong Sooyeol Phyo Jiwon Lee jae Hee Jung Department of Mechanical Engineering Sejong UniversitySeoul 05006Republic of Korea Center for Environment Healthand Welfare ResearchKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Graduate School of Energy and Environment Korea UniversitySeoul 02841Republic of Korea Department o f Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea

Indoor air quality(IAQ) directly affects the health of occupants. Household manufacturing equipment(HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment(HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration(PNC) and particle emission rate(PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 m W, the mode diameters of particles were 2.0 × 10^(4) particles/cm^(3). Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C 8 aromatics(ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles(UFPs) was > 5 × 10^(4) particles/cm^(3) during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.

关键词： Indoor air quality(IAQ) Emission Laser processing Ultrafine particles(UFPs) Volatile organic compounds(VOCs)

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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

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Gost effectiveness of crack treatment methods:A field study

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第6期6卷 598-607页

作者： Mithil Mazumder hyun Hwan Kim Soon-jae Lee Moon-Sup Lee Materials Science Engineeringand Commercialization ProgramTexas State UniversitySan MarcosTX 78666USA Department of Engineering Technology Texas State UniversitySan MarcosTX 78666USA Korea Institute of Civil Engineering and Building Technology Gyeonggi-do 10223South Korea

In the United States,more than 94%highways are paved with asphalt materials and placing crack sealant materials has been a common pavement maintenance for *** sealing treatment includes the use of a router to create a reservoir on the intended cracks whereas crack filling is given without doing any modification to the crack *** the initial cost of crack sealing is higher,it is expected to have a longer service period compared to crack *** is little research on comparison of short and long term cost effectiveness between these two treatments using the real field cost data *** this study four test sites in Texas were treated with crack filling and sealing using the same sealant material and finishing *** effectiveness of both treatments was measured in terms of initial,annual average and life cycle cost based on the cost inputs during *** general,the results of this study indicated that(1)on an average approximately 45%initial cost increase was estimated with the two routing configurations of crack sealing;(2)material and labor cost is found to have the most significant effect on the higher initial cost of crack sealing compared to other associated costs;(3)annual average and life cycle costs have shown that crack sealing is more cost effective pavement maintenance compared to crack filling over a long period of time;(4)agency cost is observed to be reduced by approximately 24%with crack sealing treatment based on the35 year analysis period.

关键词： Crack sealing Crack filling Initial cost Annual average cost Life cycle cost

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