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Numerical study on the heat dissipation characteristics of high-power LED module

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Science China(Technological Sciences) 2013年第9期56卷 2150-2155页

作者： lee DaeWoo CHO sung-wook KIM Youn-Jea Graduate School of Mechanical Engineering Sungkyunkwan University School of Mechanical Engineering Sungkyunkwan University

LED lighting has problems such as short life span, power reduction due to the LED chip's heat, and decreased luminance efficiency etc. Many studies on the optimization of the thermal performance of LEDs have been conducted actively to solve these problems. The present study changes the fin shape and intervals of various heat sink designs so that LED can effectively produce a thermal effect. The water-cooling heat release system and the heat pipe methods show higher thermal performance results than the existing systems; however, the system is of high cost and requires a large-scale apparatus. This study carried out a numerical analysis of the thermal control system by applying heat flux and heat sink properties as an active heat release system using the commercial code ANSYS ver. 13.0 and verified the validity of the new heat sink design for temperature distribution analysis.

关键词： LED lighting water-cooling heat release system heat loss

Curcumin-induced cell death depends on the level of autophagic flux in A172 and U87MG human glioblastoma cells

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Chinese Journal of Natural Medicines 2020年第2期18卷 114-122页

作者： lee Jong-Eun Yoon sung Sik lee Jae-wook Moon Eun-Yi Department of Bioscience and Biotechnology Sejong UniversitySeoul 05006Republic of Korea

Glioblastoma is the deadliest neoplasm with the worst 5-year survival rate among all human *** promotes autophagic cell death or blocks the induction of apoptosis in eukaryotic ***,we investigated whether varying levels of autophagic flux in glioblastoma lead to different efficacies of curcumin treatment using U87 MG and A172 human glioblastoma *** number of LC3 puncta,the number of cells with LC3 puncta and the level of LC3 Ⅱ,Atg5 and Atg7 protein were higher in U87 MG cells compared with A172 *** the cells were incubated with curcumin for 24 or 48 h,the percentage of cell death was higher in A172 cells compared with U87 MG *** the level of LC3 was lower,that of curcumin-induced LC3 was higher,in A172 cells than in U87 MG *** relative increases in cell death and LC3-mediated autophagy were greater under serum starvation in A172 cells compared with U87 MG ***-induced A172 cell death was reduced by serum *** both types of cells were transfected with LC3-GFP,the percentage of cell death was higher in A172 cells than that in U87 MG *** together,the data demonstrate that curcumin-mediated tumor cell death is regulated by the basal level of autophagic flux in different glioblastoma *** suggests that prior to the use of various curcumin therapeutics,the level of basal or induced autophagic flux should be carefully examined in tumor cells for the best efficacy.

关键词： Glioblastoma A172 U87MG Autophagic flux Curcumin

Versatile control of concentration gradients in non-fullerene acceptor-based bulk heterojunction films using solvent rinse treatments

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Green Energy & Environment 2022年第5期7卷 1102-1110页

作者： Chang-Mok Oh Soyeong Jang Jihoon lee sung Heum Park In-wook Hwang Advanced Photonics Research Institute Gwangju Institute of Science and TechnologyGwangju61005Republic of Korea Department of Physics Pukyong National UniversityBusan48513Republic of Korea

Solvent rinse treatments using polar methanol(Me OH)and nonpolar n-hexane have been developed for controlling material concentration gradients along the longitudinal direction of non-fullerene acceptor-based bulk heterojunction(BHJ)films comprised of electron donor polymer,PBDB-T and acceptor,*** the used solvents(chlorobenzene with 1 vol%DIO)were completely evaporated,ITIC-m rich domains were formed at the top surface of the BHJ films after they were rinsed with Me OH,as evidenced by water contact angle,atomic force microscopy,time-of-flight secondary ion mass spectroscopy,which led to enhanced electron transport in the conventional structure of organic solar cells(OSCs).In contrast,after rinsing with n-hexane,ITIC-m rich domains were formed at the bottom surface of the films,which improved electron transport in the inverted structure *** enhanced carrier transports increased the PCEs(11.80%and 11.15%)in both conventional and inverted OSCs by 10.29%and 10.35%compared with control *** versatile control of material concentration gradients is determined to be feasible owing to the chemical interaction of the used substrates(glass,PEDOT:PSS,and Zn O)and rinsing solvents.

关键词： films treatment heterojunction

Direct dynamic-simulation approach to trajectory optimization

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Chinese Journal of Aeronautics 2021年第10期34卷 6-19页

作者： sung wook HUR Seong Han lee Yong Hyeon NAM Chang-Joo KIM Department of Aerospace Information Engineering Konkuk UniversitySeoul 05029Republic of Korea

This paper proposes a new direct method for an efficient trajectory optimization using the point that the dynamics of a deterministic system are uniquely determined by initial states and controls imposed over the time horizon of *** effectively implement this concept,the Hermite spline is adopted to interpolate the continuous controls and the system dynamics are integrated with corresponding control parameters in *** a result,the optimal control problem can be transcribed into a nonlinear programming problem which has no dynamic equality constraints and no intermediate states in its design *** addition,the paper proposes an efficient recursive Jacobian estimation technique and introduces a Jacobian transformation matrix to straightforwardly handle the general state *** properties of the present method are thoroughly investigated through its applications to the trajectory optimization for a soft lunar landing from a parking orbit,including the detailed analyses for the de-orbiting *** computed results are compared with those using the pseudo-spectral method to demonstrate an extreme outperformance of the proposed method in the aerospace applications over the traditional direct method.

关键词： Trajectory optimization Direct method Hermite spline interpolation Pseudo-spectral integrator Soft lunar landing

Enhanced charge separation by interchain hole delocalization in nonfullerene acceptor-based bulk heterojunction materials

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Carbon Energy 2023年第7期5卷 27-37页

作者： Chang-Mok Oh Sujung Park Jihoon lee sung Heum Park Shinuk Cho In-wook Hwang Advanced Photonics Research Institute Gwangju Institute of Science and TechnologyGwangjuRepublic of Korea Department of Physics and Energy Harvest Storage Research Center University of UlsanUlsanRepublic of Korea Department of Physics Pukyong National UniversityBusanRepublic of Korea

Bulk heterojunction(BHJ)composites show improved power conversion efficiencies when optimized in terms of morphology using various film processing methods.A reduced carrier recombination loss in an optimized BHJ was characterized ***,the driving force that leads to this reduction was not clearly *** this study,we focus on the decreased carrier recombination loss and its driving force in optimized nonfullerene acceptor-based PTB7-Th:IEICO-4F BHJ *** demonstrate that the optimized BHJ shows deactivation in the sub-nanosecond nongeminate carrier recombination *** driving force for this deactivation was determined to be the improved interchain hole delocalization between the *** enhanced interchain hole delocalization was observed using steady-state photoinduced absorption(PIA)*** particular,increased splitting between the polaron PIA bands was ***,improved interchain hole delocalization was observed for other state-of-the-art BHJ materials,including D18:Y6 with optimized morphologies.

关键词： bulk heterojunction interchain hole delocalization nonfullerene acceptor photoinduced absorption spectroscopy solar cell

Photosynthesis,Metabolite Composition and Anatomical Structure of Oryza sativa and Two Wild Relatives,*** and ***

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Rice science 2017年第4期24卷 218-227页

作者： Jwakyung sung Suyeon lee Jong-wook CHUNG Gerald EDWARDS Hojin RYU Taewan KIM National Institute of Agricultural Science Rural Development Administration(RDA)WanjuJeollabu-do 55365Korea Department of Industrial Plant Science and Technology Chungbuk National UniversityCheongju 28644Korea School of Biological Science Washington State UniversityPullmanWA 99164-4236USA Department of Biology Chungbuk National UniversityCheongju 28644Korea Department of Plant Resources and Science and Institute of Ecological Phytochemistry Hankyung National UniversityAnseong 17579Korea

Photosynthesis, enzyme activities and metabolite pools associated with primary carbon metabolism in leaves were studied in O. grandiglumis and O. alta （wild relatives of rice which produce high biomass） versus O. sativa （a japonica cultivar and a indica-japonica hybrid） to assess their potential for identifying traits which might be utilized to enhance rice productivity. The wild relatives had higher rates of photosynthesis on a fresh weight basis, and higher water use efficiency than the O. sativa lines. There were no striking differences in activities of a number of key enzymes in carbon and nitrogen metabolism between the wild relatives and cultivated rice lines. Along with higher rates of photosynthesis on a fresh weight basis, the leaves of the two wild species had higher nitrate content, higher levels of starch, glucose and fructose, and higher levels of organic acids （malate, succinate and acetate）, compared to the O. sativa lines. The results suggested that O. grandiglumis and O. alta have differences in physiology and primary metabolism which might be exploited to improve growth and productivity of cultivated rice.

关键词： carbohydrate photosynthesis rate nitrogen assimilation metabolite composition leaf rice wild relative

Electrochemical Performance and ex situ Analysis of ZnMn2O4 Nanowires as Anode Materials for Lithium Rechargeable Batteries

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Nano Research 2011年第5期4卷 505-510页

作者： sung-wook Kim Hyun-wook lee Pandurangan Muralidharan Dong-Hwa Seo Won-Sub Yoon Do Kyung Kim Kisuk Kang Research Institute of Advanced Materials Seoul National University 599 Kwanak-ro Kwanak-gu Seoul 151-742 Republic of Korea Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology 335 Gwahangno Yuseong-gu Daejeon 305-701 Republic of Korea Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology 335 Gwahangno Yuseong-gu Daejeon 305-701 Republic of Korea Department of Materials Science and Engineering Seoul National University 599 Kwanak-ro Kwanak-gu Seoul 151-742 Republic of Korea

One-dimensional ZnMn2O4 nanowires have been prepared and investigated as anode materials in Li rechargeable batteries. The highly crystalline ZnMn2O4 nanowires about 15 nm in width and 500 nm in length showed a high specific capacity of about 650 mAh.g-1 at a current rate of 100 mA.g-1 after 40 cycles. They also exhibited high power capability at elevated current rates, i.e., 450 and 350 mAh.g 1 at current rates of 500 and 1000 mA.g 1, respectively. Formation of Mn3O4 and ZnO phases was identified by ex situ X-ray diffraction （XRD） and transmission electron microscopy （TEM） studies after the initial discharge-charge cycle, which indicates that the ZnMn2O4 phase was converted to a nanocomposite of Mn3O4 and ZnO phases immediately after the electrochemical conversion reaction.

关键词： Energy storage lithium rechargeable battery anode ZnMn204 nanowire

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

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Light(Science & Applications) 2024年第6期13卷 1075-1087页

作者： Hyeongmun Kim Chul Kang Dogeun Jang Yulan Roh Sang Hwa lee Joong wook lee Jae Hee sung Seong Ku lee Ki-Yong Kim Advanced Photonics Research Institute GISTGwangju61005Korea Department of Physics and Optoelectronics Convergence Research Center Chonnam National UniversityGwangju61186Korea Pohang Accelerator Laboratory POSTECHPohang37673Korea Center for Relativistic Laser Science Institute for Basic ScienceGwangju61005Korea Institute for Research in Electronics and Applied Physics Department of PhysicsUniversity of MarylandCollege ParkMaryland20742USA

Terahertz(THz)waves,known as non-ionizing radiation owing to their low photon energies,can actually ionize atoms and molecules when a sufficiently large number of THz photons are concentrated in time and ***,we demonstrate the generation of ionizing,multicycle,15-THz waves emitted from large-area lithium niobate crystals via phase-matched optical rectification of 150-terawatt laser pulses.A complete characterization of the generated THz waves in energy,pulse duration,and focal spot size shows that the field strength can reach up to 260 megavolts per *** particular,a single-shot THz interferometer is employed to measure the THz pulse duration and spectrum with complementary numerical *** intense THz pulses are irradiated onto various solid targets to demonstrate THz-induced tunneling ionization and plasma *** study also discusses the potential of nonperturbative THz-driven ionization in gases,which will open up new opportunities,including nonlinear and relativistic THz physics in plasma.

关键词： optical interferometer matched

Microstructure and corrosion resistance of a Mg2Sn-dispersed Mg alloy subjected to pulsed electron beam treatment

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Journal of Magnesium and Alloys 2020年第2期8卷 345-351页

作者： Daseul lee Beomcheol Kim Soo-Min Baek Jisoo Kim Hyung wook Park Jung Gu lee sung Soo Park School of Materials Science and Engineering Ulsan National Institute of Science and TechnologyUlsan 44919Republic of Korea School of Mechanical Aerospace and Nuclear EngineeringUlsan National Institute of Science and TechnologyUlsan 44919Republic of Korea School of Materials Science and Engineering University of UlsanUlsan 44610Republic of Korea

We report that the corrosion resistance of a Mg-Sn-based alloy with MgzSn precipitates can be considerably improved by surface modification using pulsed electron beam *** alloy subjected to a pulse electron beam treatment showed a modified surface layer with a thickness of〜12 μm,appearing more resistant to corrosion attack than the bare surface of the *** 0.6 M NaCl solution,the alloys with and without the surface modification exhibited average corrosion rates of 4.3 and 8.1 mm y^-1,*** improved corrosion resistance was attributed to reduced cathodic activation,resulting from the surficial reduction of relatively noble Mg2Sn precipitates.

关键词： Magnesium alloy Mg2Sn Intermetallic compound Pulsed electron beam treatment Corrosion