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Journal of Traditional Chinese Medicine 2013年第5期33卷 658-663页

作者： Eunjeong choi Gunhee Kim Plant Resources Research Institute Duksung Women's University

OBJECTIVE:To investigate the mechanism underlying the anticancer effect of Artemisia species through the inhibition of cell growth and induction of apoptosis in breast carcinoma ***:To evaluate the anticancer activity of methanol extracts of eight Artemisia species(Artemisia stolonifera,Artemisia selengensis,Artemisia japonica,Artemisia Montana,Artemisia capillaris,Artemisia sylvatica,Artemisia keiskeana,and Artemisia scoparia),we first investigated the proliferation of estrogen receptor(ER)-positive MCF-7breast carcinoma cells exposed to 5 or 200 g/mL for72 *** induction was assessed by an Annexin V binding assay in cells exposed to extracts at a high concentration(200 g/mL).To verify the mechanism of apoptosis,ER expression and its related signaling was investigated using an immunoblot assay under the same ***:MCF-7 cells showed the strongest antiproliferative response to the tested ***-er,a biphasic effect was observed:the extracts inhibited proliferation at high concentrations whereas they stimulated it at low *** expression was similarly modulated by the ***,all of the extracts induced apoptosis at a high concentration(200 g/mL).Compared to the control level,exposure to the extracts resulted in a remarkable increase in the shift of cell ***:The present study suggests that the tested Artemisia species exerted their anticancer effects through the induction of apoptosis via an ER-related pathway.

关键词： Artemisia Breast neoplasms Bcl-2gene Cyclin D1 Estrogen receptor

Study of Partial Coefficients for Design of Semicircular Breakwaters

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China Ocean Engineering 2010年第1期24卷 29-40页

作者：郄禄文 Byung Ho choi College of Civil Engineering Hebei University Department of Civil and Environmental Engineering Sungkyunkwan University300 Chunchun-dongJangan-GuSuwon

In the present study, the reliability design of semicircular breakwater is based on the verification of the rules defined by standard specifications, where partial coefficients are introduced to ensure safety. The reliability of the semicircular breakwaters has been analyzed by using the Hasofer-Lind method to determine the reliability index of structure that has correlated loads, utilizing the long-term observed wave data at a given place. The relation curve between reliability index and safety factor in the traditional design method, as well as the relationships between reliability index and partial coefficients, have been obtained. This paper proposes values of partial coefficients for the design expression of semicircular breakwaters in the cases of anti-sliding and anti-overturning.

关键词： partial coefftcient reliability index correlated variables semicircular breakwater

Laser-assisted deposition of Cu bumps for microelectronic packaging

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中国有色金属学会会刊：英文版 2012年第S3期22卷 683-687页

作者： Won-Seok choi Joohan KIM Department of Nano IT Fusion Program Seoul National University of Science and Technology Department of Mechanical and Automotive Engineering Seoul National University of Science and Technology

Cu bump was transferred using a focused laser pulse for microelectronic *** Nd:YAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absorption layer with copper *** focused laser beam induced plasma between the semi-transparent donor slide and the sacrificial layer,causing a shock *** shock wave pressure pushed the Cu layer and transferred material to deposit a bump on substrate.A beam-shaper was used to produce uniform pressure at the interface to reduce fragmentation of the transferred material on the *** calculated shock wave pressure with respect to laser fluence was 1-3 GPa.A Cu bump of diameter of 200 μm was successfully deposited at laser fluence of 0.6 kJ/cm *** pressure control at the sacrificial layer using a laser pulse was critical to produce a bump with less *** technique can be applied to forming Cu bump for an interconnecting process in electronics.

关键词： laser induced forward transfer bump deposition Nd:YAG pulsed laser micro system packaging beam shaping

High-Performance Perovskite Quantum Dot Solar Cells Enabled by Incorporation with Dimensionally Engineered Organic Semiconductor

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Nano-Micro Letters 2022年第12期14卷 272-285页

作者： Seyeong Lim Dae Hwan Lee Hyuntae choi Yelim choi Dong Geon Lee Sung Beom Cho Seonkyung Ko Jongmin choi Younghoon Kim Taiho Park Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Materials Science and Engineering Hanyang UniversitySeoul 04763Republic of Korea Center of Materials Digitalization Korea Institute of Ceramic Engineering and Technology(KICET)Jinju 52851Republic of Korea Department of Materials Science and Engineering Ajou UniversitySuwon 16499Republic of Korea Department of Energy Science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu 42988Republic of Korea Department of Chemistry Kookmin UniversitySeoul 02707Republic of Korea

Perovskite quantum dots(PQDs)have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and ***,they exhibit low moisture stability at room humidity(20-30%)owing to many surface defect sites generated by inefficient ligand exchange *** surface traps must be re-passivated to improve both charge transport ability and moisture *** address this issue,PQD-organic semiconductor hybrid solar cells with suitable electrical properties and functional groups might dramatically improve the charge extraction and defect *** organic semiconductors are typically low-dimensional(1D and 2D)and prone to excessive self-aggregation,which limits chemical interaction with *** this work,we designed a new 3D star-shaped semiconducting material(Star-TrCN)to enhance the compatibility with *** robust bonding with Star-TrCN and PQDs is demonstrated by theoretical modeling and experimental *** Star-TrCN-PQD hybrid films show improved cubic-phase stability of CsPbI_(3)-PQDs via reduced surface trap states and suppressed moisture *** a result,the resultant devices not only achieve remarkable device stability over 1000 h at 20-30%relative humidity,but also boost power conversion efficiency up to 16.0%via forming a cascade energy band structure.

关键词： CsPbI3 quantum dots Star-shaped organic semiconductors Hybrid perovskite quantum dots Solar cell stability High-efficiency photovoltaics

Investigation of ZrO2 nanoparticles concentration and processing time effect on the localized PEO coatings formed on AZ91 alloy

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Journal of Magnesium and Alloys 2019年第4期7卷 555-565页

作者： Zeeshan Ur Rehman Dongjin choi School of Materials Science and Engineering Hongik UniversitySejongRepublic of Korea

AZ91 Mg alloy was treated through a new localized PEO(Plasma Electrolytic Oxidation)coating approach,using electrolyte solutions with varying ZrO2 nanoparticles concentration(2-8 g/L)and processing *** increase in the ZrO2 concentration,several microstructural changes were observed including;formation of cluster-type structure,damage to the inner layers(∼30 min)and sealing of *** analysis of the final coatings was carried out using potentiodynamic polarization,electrochemical impedance spectroscopy and post-corrosion *** was explored that highest corrosion resistance(Rp∼81.17 kΩcm^2)of the coatings was obtained for ZrO2∼2 g/***,higher concentration of the ZrO2 nanoparticles caused weak crystalline coating structure,due to unstable and lower intensity discharges,thus failed to offer high corrosion resistance performance.

关键词： Magnesium alloy PEO coating ZrO2 Corrosion Nanoparticles addition

Groundwater contamination and natural attenuation capacity at a petroleum spilled facility in Korea

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Journal of Environmental Sciences 2011年第10期23卷 1650-1659页

作者： Hyun-Mi choi Jin-Yong Lee Department of Geology Kangwon National University

As a remedial option, the natural attenuation capacity of a petroleum contaminated groundwater at a military facility was examined. Hydrogeological conditions, such as high water level, permeable uppermost layer and frequent heavy rainfall, were favorable to natural attenuation at this site. The changes in the concentrations of electron acceptors and donors, as well as the relevant hydrochemical conditions, indicated the occurrence of aerobic respiration, denitrification, iron reduction, manganese reduction and sulfate reduction. The calculated BTEX expressed biodegradation capacity ranged between 20.52 and 33.67 mg/L, which appeared effective for the reduction of the contaminants levels. The contribution of each electron accepting process to the total biodegradation was in the order： denitrification 〉 iron reduction 〉 sulfate reduction 〉 aerobic respiration 〉 manganese reduction. The BTEX and benzene point attenuation rates were 0.0058-0.0064 and 0.0005-0.0032 day-1, respectively, and the remediation time was 0.7-1.2 and 2.5-30 years, respectively. The BTEX and benzene bulk attenuation rates were 8.69 × 10^-4 and 1.05 × 10^-3 day-l, respectively, and the remediation times for BTEX and benzene were 7.2 and 17.5 years, respectively. However, most of the natural attenuation occurring in this site can be attributed to dilution and dispersion. Consequently, the biodegradation and natural attenuation capacities were good enough to lower the contaminants levels, but their rates appeared to be insufficient to reach the remediation goal within a reasonable time frame. Therefore, some active remedial measures would be required.

关键词： petroleum contaminated site BTEX electron acceptor expressed biodegradation capacity natural attenuation

Shear deformable finite beam elements for composite box beams

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Acta Mechanica Sinica 2014年第2期30卷 223-240页

作者： Nam-Il Kim Dong-Ho choi Department of Architectural Engineering Sejong University Department of Civil and Environmental Engineering Hanyang University

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated.

关键词： Thin-walled Composite box beam Deflection Twisting angle Buckling load Shear deformation

Development of a Biomimetic Quadruped Robot

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Journal of Bionic Engineering 2007年第4期4卷 193-199页

作者： Thanhtam Ho Sunghac choi Sangyoon Lee Department of Mechanical Design and Production Engineering Konkuk University Seoul 143-701 Korea

This paper presents the design and prototype of a small quadruped robot whose walking motion is realized by two piezocomposite actuators. In the design, biomimetic ideas are employed to obtain the agility of motions and sustainability of a heavy load. The design of the robot legs is inspired by the leg configuration of insects, two joints （hip and knee） of the leg enable two basic motions, lifting and stepping. The robot frame is designed to have a slope relative to the horizontal plane, which makes the robot move forward. In addition, the bounding locomotion of quadruped animals is implemented in the robot. Experiments show that the robot can carry an additional load of about 100 g and run with a fairly high velocity. The quadruped prototype can be an important step towards the goal of building an autonomous mobile robot actuated by piezocomposite actuators.

关键词： quadruped robot piezocomposite actuator bounding locomotion

Temperature Distribution and Thermal Stresses in Various Conditions of Moving Heating Source during Line Heating Process

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Journal of Thermal Science 2012年第1期21卷 82-87页

作者： Yoon Hwan choi Yeon Won Lee Kwang choi Deog Hee Doh Kyoung Joon Kim Department of Mechanical and Automotive Engineering Pukyong National University Steel Structure Research Division Research Institute of Industrial Science & Technology Division of Mechanical and information Engineering Korea Maritime University

Line heating method is widely used to manufacture curved surfaces in ship building. The main factors governing the quality of the manufactured products are the moving velocity of the heating source, heating strength, and heating ways. In this study, the temperature distributions of the heated plate were investigated with the condition that the line heating process was automatic. The temperature variations were also investigated with the changes of those three variables. The numerical results showed that the peak temperature decreased as the moving velocity of the heating source increased. It also revealed that the peak temperatures changed linearly with the changes of the heating source.

关键词： Moving heat source Line heating Thermal stress Residual deformation Conductive heat transfer

Theory of phonon-modulated electron spin relaxation time based on the projection reduction method

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Chinese Physics B 2014年第8期23卷 436-443页

作者： Nam Lyong Kang Sang Don choi Department of Applied Nanoscience Pusan National University Department of Physics Kyungpook National University

This paper introduces a new method for a formula for electron spin relaxation time of a system of electrons interacting with phonons through phonon-modulated spin-orbit coupling using the projection-reduction method. The phonon absorption and emission processes as well as the photon absorption and emission processes in all electron transition processes can be explained in an organized manner, and the result can be represented in a diagram that can provide intuition for the quantum dynamics of electrons in a solid. The temperature （T） dependence of electron spin relaxation times （T1） in silicon is T1 ∝ T-1.07 at low temperatures and T1 ∝ T-3.3 at high temperatures for acoustic deformation constant Pad = 1.4 × 10^7 eV and optical deformation constant Pod = 4.0 × 10^17 eV/m. This means that electrons are scattered by the acoustic deformation phonons at low temperatures and optical deformation phonons at high temperatures, respectively. The magnetic field （B） dependence of the relaxation times is T1 ∝ B-2.7 at 100 K and T1 ∝ B-2.3 at 150 K, which nearly agree with the result of Yafet, T1 ∝ B-3.0- B -2.5.

关键词： electron spin resonance spin-orbit coupling projection-reduction method phonon scattering