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International Journal of Minerals,Metallurgy and Materials 2014年第1期21卷 95-103页

作者： seung ho Kim Department of Electronics Engineering Dankook University

Self-lubricating A1203-15wt% ZrO2 composites with sulfides, such as molybdenum disulfide （MoS2） and tungsten disulfide （WSz） serving as solid lubricants, were fabricated by using the pulse electric current sintering （PECS） technique. The coefficient of friction （COF） of the A1203-15wt% ZrO2 composite without/with sulfides was in the range of 0.37-0.48 and 0.27-0.49, respectively. As the amoant of sul- fides increased, the COF and the wear rate decreased. The reduction in COF and wear rate of the sulfide-containing composite is caused by a reduction in shear stresses between the specimen and the tribological medium due to the formation of a lubricating film resulting from the lamellar structure of sulfides located on the worn surface.

关键词： ceramic composites coefficient of friction solid lubricants sulfides wear of materials

Photocatalytic decomposition of mobile-source related pollutants using a continuous-flow reactor

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Journal of Environmental Sciences 2010年第3期22卷 460-466页

作者： Wan-Kuen Jo seung-ho Shin Department of Environmental Engineering Kyungpook National University

This study evaluated the application of a continuous-flow photocatalytic reactor for the control of two mobile-derived pollutants, methyl-tertiary butyl ether （MTBE） and naphthalene, present at in-vehicle levels. Variables tested for this study included the hydraulic diameter （HD）, stream flow rate （SFR）, relative humidity （RH）, and feeding type （FT）. The fixed parameters included contaminant concentration, ultraviolet light source, and the weight of TiO2. In all experimental conditions the adsorption process reached equilibrium within 30 to 180 min for the target compounds, and the outlet concentrations of the photocatalytic oxidation （PCO） reactor while operating reached a steady state within 60 to 180 min. The degradation of the target compounds was dependent on RH, HD, FT, or SFR. The PCO system exhibited high degradation （up to nearly 100% for certain conditions） and mineralization efficiencies of target compounds, suggesting that this system can effiectively be employed to improve indoor air quality. Moreover, it was confirmed that trichloroethylene at urban-ambient level also could enhance the degradation efficiency of naphthalene when applying the PCO technology inside vehicles.

关键词： in-vehicle level methyl-tertiary butyl ether naphthalene trichloroethylene

Evaluation of defects in aluminum piston castings by using ultrasonics and computer tomography

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China Foundry 2012年第3期9卷 275-278页

作者： In-Sung Cho Jeong-ho Hwang Jin-Seok yang seung-Mok Yoo Chae-ho Lim Korea Institute of Industrial Technology

Pistons used in automobile engines are made of aluminum alloy; and endurance of high pressure and high temperature is required. Recently, high strength pistons are needed to cope with the increase of pressure and temperature in the engine cylinder. A high strength piston is possible when the piston casting has little or no casting defects, such as micro-pores and cracks. Generally the defects can be evaluated by non-destructive testing (NDT), and the most efficient ways for evaluation are using ultrasonics and computer tomography. In the present study, two NDT methods were compared and evaluated to investigate the defects in the aluminum piston castings. Artificial defects were machined by using very small drill bits with diameters 1, 0.5, 0.3, 0.2 and 0.1 mm. The defects were investigated by using an ultrasonic tester and a computer tomography system. Defects smaller than 0.3 mm may not be found by using the ultrasonic test, but the defects may be found by using the computer tomography system. The investigation conditions for detecting small defects and the scanning time for in-line defect analysis are discussed in the present study.

关键词： piston ultrasonic test computer tomography aluminum defect

Aerosol-assisted rapid synthesis of SnS-C composite microspheres as anode material for Na-ion batteries

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Nano Research 2015年第5期8卷 1595-1603页

作者： seung ho Choi Yun Chan Kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seou1136-713 Republic of Korea

SnS-C composite powders were prepared through one-pot spray pyrolysis for use as anode materials for Na-ion batteries. C microspheres with uniformly attached cubic-like SnS nanocrystals, which have an amorphous C coating layer, were formed at a preparation temperature of 900 ℃. The initial discharge capacities of the bare SnS and SnS-C composite powders at a current density of 500 mA·g^-1 were 695 and 740 mA·h·g^-1, respectively. The discharge capacities after 50 cycles and the capacity retentions measured from the second cycle of the bare SnS and SnS-C composite powders were 25 and 433 mA.h.g-1 and 5 and 89%, respectively. The prepared SnS-C composite powders with high reversible capacities and good cycle performance can be used as Na-ion battery anode materials.

关键词： tin sulfide anode material carbon composite sodium battery energy storage

Fossil-Winged Fruits of Fraxinus(Oleaceae) and Liriodendron(Magnoliaceae) from the Duho Formation,Pohang Basin,Korea

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Acta Geologica Sinica(English Edition) 2009年第5期83卷 845-852页

作者： seung-ho JUNG Seong-Joo LEE Department of Geology Kyungpook National UniversityDaegu 702-701Korea

A total of 16 specimens of fossil-winged fruits were found from the Middle Miocene marine deposits, Duho Formation, Pohang Basin, Korea. They were identified into two structurally different groups： 15 specimens into a winged fruit of Fraxinus, and one specimen of Liriodendron. The most samaras （13 specimens） were identified as Fraxinus oishii, which is characterized by narrowly ovate or ovate-elliptic shapes that are 2.7-3.6 cm in length and 0.7-1 cm in width （i/w ratio=3.4-4）. The apexes of the Fraxinus oishii samara are round or slightly emarginated, and a seed of the samara is always located at the base, of which the general shape is narrow rhombic-ellipsoidal. The seed is 1.2-2 cm long and 0.5-0.7 cm wide. Two specimens are different from the samara of Fraxinus oishii. They have a 6.6 length/width ratio （3.3 cm long and 0.5 cm wide）, and thus, are temporarily classified into the Fraxinus sp. One specimen was recognized as a winged seed of Liriodendron meisenense. The wing is broadly lanceolate to elliptic in shape, has a smooth, acute apex, and is approximately 3 cm long and 0.7 cm wide. Samaras of Fraxinus oishii and Liriodendron meisenense were early reported from the Middle Miocene deposits from North Korea, but these specimens are the first discovery in South Korea. Further study of the Duho Formation may connect flora relationships between North and South Korea.

关键词： winged fruits Fraxinus Liriodendron Middle Miocene Pohang Basin Korea

ON THE ASYMPTOTIC DYNAMICS OF THE VLASOV-YUKAWA-BOLTZMANN SYSTEM NEAR VACUUM

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Acta Mathematica Scientia 2015年第4期35卷 887-905页

作者： Sun-ho ChoI seung-Yeal HA Department of Mathematical Sciences KAIST Department of Mathematical Sciences and Research Institute of Mathematics Seoul National University

In this pape,~ we study uniform L1-stability and asymptotic completeness of the Vlasov-Yukawa-Boltzmann （V-Y-B） system. For a sufficiently small rand smooth initial data, we show that classical solutions exist globally and satisfy dispersion estimates, uniform L1-stability with respect to initial data and scattering type estimate. We show that the short range nature of interactions due to the Yukawa potential enables us to construct robust Lyapunov type functional to derive scattering states. In the zero mass limit of force carrier particles, we also show that the classical solutions to the V-Y-B system converge to that of the Vlasov-Poisson-Boltzmann （V-P-B） system in any finite time interval

关键词： asymptotic completeness collision operator the Vlasov-Yukawa-Boltzmannsystem uniform L1-stability

Random lasing detection of structural transformation and compositions in silk fibroin scaffolds

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Nano Research 2019年第2期12卷 289-297页

作者： SungYeun yang Soocheol Kim Hyeln Shin seung ho Choi Young L. Kim Chulmin Joo WonHyoung Ryu Department of Mechanical Engineering Yonsei University Yonsei-ro 50 Seodaemun-gu Seoul 03722 Republic of Korea Weldon School of Biomedical Engineering Purdue University West Lafayette Indiana 47907 USA Present address: Center of Bio Microsystems Korea Institute of Science and Technology (KIST) Hwarang-ro Seongbuk-gu Seoul 02792 Republic of Korea School of Electrical Engineering University of Ulsan Daehak-ro Nam-gu Ulsan 44610 Republic of Korea

In tissue engineering, microstructure and material composition of tissue scaffolds have major influences on the proliferation and differentiation of cells in the scaffolds. however, once tissue scaffolds implanted, it is extremely difficult to monitor the change of their microstructure and compositions during tissue regeneration. Here, we report how random lasing can be utilized to non-invasively monitor the structure and composition of scaffolds. We hypothesize that morphological and compositional change of silk fibroin (SF) scaffolds can be conveniently detected based on random lasing responses. Engineered SF scaffolds with hydroxyapatite (HAP) nanoparticles and controlled pore alignment were fabricated, and their random lasing responses were analyzed depending on the concentration of HAP nanoparticles and the degree of,:internal pore alignment. We also examined the real-time random lasing responses of porous SF scaffolds by applying a compressive force to' the scaffolds. Introduction of HAP nanoparticles lowered the lasing thresholds and narrowed the random lasing (RL) width dramatically, which :is likely due to the increase in heterogeneity in both refractive index and physical arrangement within the SF and HAP composites. The strong dependency of RL response on pore alignment was also measured and validated by numerical calculation with the finite element method (FEM).Finally, real-time monitoring of RL on compressed scaffolds demonstrated the possibility of using RL as a monitoring tool for structural change of SF scaffolds in vivo.

关键词： random lasing silk fibroin porous scaffolds aligned pore structure electrospinning hydroxyapatite

Adhesion and Suction Functions of the Tip Region of a Nectar-drinking Butterfly Proboscis

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Journal of Bionic Engineering 2017年第4期14卷 600-606页

作者： seung Chul Lee Jun ho Kim Sang Joon Lee Department of Mechanical Engineering Pohang University of Science and Technology Pohang 37673 Gyeongbuk Republic of Korea Center for Biofluid and Biomimic Research Pohang University of Science and Technology Pohang 37673 Gyeongbuk Republic of Korea

In this study, we investigated the dynamic functions of the tip region of the butterfly proboscis through which liquid is sucked during liquid feeding. The microstructures and flow patterns in the tip region of the proboscis were in vivo analyzed. The tip region can be divided into two functional sections： namely adhesion and suction sections. The liquid adheres to the adhesion section during liquid suction. Although the tip region has numerous slits connected to food canal of the proboscis, liquid is mainly sucked through the suction section, which section is submerged in the fluid pulled by the adhesion section and then successfully imbibes liquid. To check the dynamic functions of the tip region, we fabricated a suction tip model having adhesion and suction parts. The in vitro model experiments show that the hydrophilicity of the adhesion part and the existence of the suction inlet improve the liquid uptake driven by a suction pump. This study may provide insights for the biomimetic design of nectar-feeding butterflies.

关键词： butterfly proboscis nectar-feeding strategy suction

Spindle-like FeySs/N-doped carbon nanohybrids for high-performance sodium ion battery anodes

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Nano Research 2019年第3期12卷 695-700页

作者： Aihua Jin Mi-Ju Kim Kug-seung Lee seung-ho Yu Yung-Eun Sung Center for Nanoparticle Research Institute for Basic Science (IBS) Seoul 08826 Republic of Korea School cf Chemical and Biological Engineering Seoul National University Seoul 08826 Republic cf Korea Beamline Department Pohang Accelerator Laboratory (PAL) Pohang 790-784 Republic of Korea Department of Chemistry and Chemical Biology Cornell University Ithaca New York 14853 USA

Iron sulfides have bee n con sidered as one of the most promising can didates for sodium ion battery anode materials due to their high theoretical capacity and low cost. I n this work, spin dle-like Fe7S8 with n itroge rvdoped carb on (FeiS/N-C) nano hybrids are successfully syn thesized via a solvothermal method by sulfidation iron-based metal organic framework (FeMOF). As sodium ion battery an odes, FeySs/N-C nano hybrids exhibit high reversible capacity of 450.8 mAh g-1 at 200 mA·g^-1, and 406.7 mAh·g^-1 at 500 mA·g^-1 even after 500 cycles. They also show excellent rate properties and delivering the capacity of 327.8 mAh·g^-1 at a very high current density of 3.2 A·g^-1. These outstanding electrochemical performa nces can be attributed to the unique structure of Fe7S8/ N-C nan ohybrids. The nano scale dime nsion in their size can be ben eficial for facile ion and electro n tran sports. Furthermore, the stable n itroge n doped carb on frameworks can also improve electrical conductivity and relieve the problems related to volume expansion. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyses have been performed to study reactions occurred in spindle-like FeySs/N-C nanohybrid electrode at both bulk and surface.

关键词： sodium ion batteries iron sulfides metal organic frameworks X-ray absorption spectroscopy X-ray photoelectron spectroscopy