Y S Lee

Kyungpook National University Hospital, Sŏul, Seoul, South Korea

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Publications (714)1518.11 Total impact

  • K.S. Lee, Y.S. Lee, Y.N. Kwon
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    ABSTRACT: We investigated the influence of annealing and secondary warm rolling on the microstructural evolution and mechanical properties of a roll-bonded three-ply Al/Mg/Al sheet. After annealing at 300 °C, the formation of an intermetallic compound (IMC) layer consisting of Mg17Al12 and Mg2Al3 was identified at the interface. Although the thickness of the IMC layer increased with increasing annealing or preheating time, secondary warm rolling after preheating at 300 °C for 10 min significantly reduced the thickness of the IMC layer below 1.5 μm. Also an equiaxed and homogeneous grain morphology of the constituent magnesium alloy was successfully introduced. This resulted in strongly enhanced elongation up to magnesium fracture by 14.5%.
    Materials Science and Engineering A 06/2014; 606:205–213. · 2.41 Impact Factor
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    ABSTRACT: This study prepared a dense Sm-doped ceria (SDC) and an SDC carbonate composite (abbreviated as SDC-C). The latter was prepared by immersing porous SDC with a formula of (Ce0.8Sm0.2)O1.9 and a relative density of approximately 65-70% into a molten mixture of carbonates containing 1:1 molar ratio of Li2CO3 and Na2CO3 at 500 °C. The relative density of the SDC-C was close to 100%. In addition, SDC oxide without carbonates, which also has a relative density of close to 100%, was heat treated at 1600 °C. At 500 °C, the electrical conductivity and ionic transference number (ti) of the SDC oxide were 1.79(5) × 10−3 S·cm−1 and 0.99(2), respectively, such that electronic conduction could be disregarded. Increasing the temperature caused a gradual decrease in the ti of SDC. Following the addition of carbonates to SDC, the electrical conductivity reached 1.23(9) × 10−1 S·cm−1 at 500 °C. After 14 days (340 h), the electrical conductivity of the SDC-C at 490 °C, leveled off at about 6 × 10−2 S·cm−1. SDC-C could be used as a potential electrolyte in solid oxide fuel cells (SOFCs) at temperatures below 500 °C.
    Journal of the Chinese Chemical Society. 11/2013; 60(11).
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    ABSTRACT: We report on the strong pore-size-dependent optical properties of porous alumina membranes (PAMs) by using the photoluminescence and the optical spectroscopic techniques. The pore diameters of our PAMs varied from 60 to 420 nm. All samples showed a sizable violet/blue emission with a strong temperature dependence. We found that the peak position of the emission shifted to higher energies with increasing pore diameter, which was in accord with the smaller binding energy extracted from the temperature dependence of the emission intensity. From the transmission spectra, we found that the effective bandgap of the PAMs shifted significantly to lower energies with increasing pore diameter, which indicated that the impurity states within the bandgap was affected strongly by the geometry of the PAM.
    Journal- Korean Physical Society 11/2013; 63(9):1789-1793. · 0.51 Impact Factor
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    ABSTRACT: We report a direct measurement of the low-frequency optical conductivity of large-area single-crystal herbertsmithite, a promising spin-liquid candidate material, by means of terahertz time-domain spectroscopy. In the spectral range below 1.4 THz, we observe a contribution to the real part of the in-plane conductivity σ_{ab}(ω) from the spin degree of freedom. This spin-induced conductivity exhibits a power-law dependence on frequency σ_{ab}(ω)∼ω^{β} with β≈1.4. Our observation is consistent with the theoretically predicted low-frequency conductivity arising from an emergent gauge field of a gapless U(1) Dirac spin liquid.
    Physical Review Letters 09/2013; 111(12):127401. · 7.73 Impact Factor
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    ABSTRACT: We investigated the visible emission property of ultrathin-walled Pb(Zr,Ti)O3 (PZT) nanotubes (NTs) with various diameters. The PZTNTs were synthesized using the sol-gel templatedirected method with a spin-coating process. The photoluminescence (PL) spectra were measured by using the 325nm photo-excitation as a function of temperature. We observed a sizable green/yellow emission around 550 nm for the PZTNTs at room temperature. With the decreasing temperature, the PL intensity dramatically enhanced, and the peak position shifted to lower energy. We also observed a clear dependence of the PL spectra on the diameter of the NTs. We applied the self-trap exciton model to explain the origin of the emission, and discuss the correlation between the NT geometry and the optical property in the PZT NTs.
    Journal- Korean Physical Society 09/2013; 63(5):1040-1044. · 0.51 Impact Factor
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    ABSTRACT: We investigated the structural and optical properties of Cu-poor CuGaSe2 (CGSe) films depending on the use of different substrates: indium-doped tin oxide (ITO) coated soda-lime glass (SLG) and fluorine-doped tin oxide (FTO) coated SLG as back contacts, widely used Mo-coated SLG, and pure SLG. The Cu-poor phase is chosen as a counterpart of Cu-poor Cu(In,Ga)Se2 to show the highest efficiency in this class of materials, and also give a test board for parasitic phases which might influence on device properties. Although the Cu-poor CGSe thin-films were deposited on the four substrates at the same time in an identical condition, they showed differences in the morphology and grain size due to different CGSe/substrate interfaces and growth mechanisms depending on the substrates. These surface properties of the CGSe films were identified clearly by atomic force microscopy (AFM) measurements. X-ray diffraction (XRD) measurement also supported the result of the AFM analysis and showed that the preferred orientation of CGSe is (112), independent of the substrates. The existence of parasitic phases was examined by Raman and photoluminescence spectroscopic techniques. While defect compounds such as CuGa3Se5 and CuGa5Se8 were identified for all films, the signals related to these parasitic phases are strongest for the films on the pure SLG substrate. Furthermore, the absorption property was investigated by spectroscopic ellipsometry in a photon energy range of 0.7–5 eV. We found that the absorption coefficient values for the CGSe films are about 104–105 cm−1 in the visible region. The absorption coefficient is also changed according to the use of different substrates. This difference comes from the parasitic phase formation, which leads to an increase of the bandgap and suppression of the optical absorption strength. Our systematic study suggests clearly that the difference in distribution of parasitic phases in the CGSe films could originate primarily from the different substrates used for the film deposition.
    Current Applied Physics 07/2013; 13(5):907–912. · 2.03 Impact Factor
  • Value in Health 05/2013; 16(3):A297. · 2.19 Impact Factor
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    ABSTRACT: We use low temperature spectroscopic scanning tunneling microscopy to study topological materials in which the surface states are protected by time reversal symmetry. We image the local density of states around a variety of single-atom impurities in the presence of a magnetic field. On a subset of these impurities, we observe broad peaks in the local density of states at energies around the Dirac point. Furthermore, we use Landau level spectroscopy and quasiparticle scattering to discuss the interplay between impurities and the surface states.
    03/2013;
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    Dataset: Matan 2011
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    ABSTRACT: Tenebrio molitor has been seriously investigated as a model insect in elucidating Toll signaling pathway and related regulators of innate immunity. However, little is known with regards to the genomic information in T. molitor. In an attempt towards exploiting the rich transcriptomics data that would offer further insights into the study on insect immunity through potential screening of immune-related genes in the model insect, we constructed a cDNA library (library titer = 5.0 × 105pfu/ml) of T. molitor larvae and analyzed expressed sequence tag (EST) sequences from 1056 clones. The base calling and quality check of obtained chromatogram files were performed by using the Phred program (trim_alt 0.05 (P-score > 20). After removal of vector and 100 bp and less sequences, 1023 sequences were generated having an average insert size of 792 bp, including 160 clusters, 164 contigs and 387 singletons through clustering and assembling process using the TGI Clustering Tools (TGICL) package. The unique EST sequences were searched against the NCBI nr database by local BLAST (blastx, E < e−5) with 940 sequences showing significant hits. Subsequently, KOG (clusters of orthologous groups for eukaryotic complete genomes) analysis was conducted (blastx, E < e−10) towards prediction of transcriptomal functions, leading to the categorization of 638 genes. The majority of genes belonged to Z category (cytoskeleton-related genes), R category (general function prediction), and C category (energy production and conversion related genes). These basic EST datasets and their bioinformatics analysis will be helpful in investigating the biological mechanism and molecular pathway related genes involved in innate immunity mechanisms of T. molitor.
    Entomological Research 01/2013; 43(3):162-170.
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    ABSTRACT: To evaluate the correlation between immunohistochemical expression of synuclein-gamma, glucose transporter-1, and survival outcomes in endometrioid endometrial carcinoma. A tissue microarray was constructed using formalinfixed, paraffin-embedded tissue that included 23 early and 18 advanced cases. The intensity and area of the immunohistochemical reactions were evaluated using the semi-quantitative scoring system. Synuclein-y expression was higher in the advanced stage, although it was not statistically significant (p = 0.51). Glucose transporter-1 was overexpressed in the advanced stage (p = 0.01). Synuclein-gamma (score = 0 vs > 0) and glucose transporter-1 (score < or = 7 vs > 7) did not show any differences in overall survival (p = 0.54, p = 0.48) and disease-free survival (p = 0.61, p = 0.14). In this study the expression of synuclein-y and glucose transporter-1 were not considered to be a prognostic factor and were not related with survival outcomes in endometrioid endometrial carcinoma.
    European journal of gynaecological oncology 01/2013; 34(2):128-31. · 0.58 Impact Factor
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    ABSTRACT: A series of (Y2 − xLix)Ti2O7 − x samples abbreviated as YLT-2L were prepared by the addition of 2x moles of LiO0.5 self-flux into the parent compound, where x = 0.040 to 0.110. Preparation temperatures were either 1300 or 1350 °C, depending on the amount of flux addition. However, the Y2Ti2O7 had no LiO0.5 co-existence; it was prepared at the highest temperature, 1600 °C. Relative densities of all the YLT-2L samples were larger than 97%, but for the Y2Ti2O7, it was 94.3(2)% only. By the addition of flux, preparation temperature reduced for more than 250 °C. Among all the YLT-2L samples, the one with x = 0.070 had the highest total electrical conductivity (2.90(2) × 10− 4 S·cm− 1 at 700 °C) and the lowest total activation energy (0.99(1) eV). By doping Li ion into the Y-site, oxygen vacancies were created, although YLT-2L samples had flux co-existence, electrical conductivity was still comparable to the parent compound reported by Yamaguchi et al. (1998) and Kobayashi et al. (2002). At 500, 600 and 700 °C, the ionic transference numbers (ti) found for the YLT-2L samples were 1.00(2), 0.96(2) and 0.90(3), respectively, and did not vary with the amount of substitution and the flux addition. Contribution of the electronic conductivity was due to the presence of a small amount of the Ti3 + ions in the samples investigated by the Ti K-edge XANES spectra.
    Solid State Ionics 01/2013; 253:227–233. · 2.05 Impact Factor
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    ABSTRACT: The Korean mussel Mytilus coruscus, an endemic marine bivalve mollusk, is economically important. Its population is currently decreasing due to overexploitation and invasion of a more competitive species, Mytilus galloprovincialis. In this study, microsatellite markers for M. coruscus were developed using a cost-effective pyrosequencing technique. Among the 33,859 dinucleotide microsatellite sequences identified, 176 loci that contained more than 8 CA, CT, or AT repeats were selected for primer synthesis. Sixty-four (36.4%) primer sets were produced from the 100- to 200-bp polymerase chain reaction products obtained from 2 M. coruscus individuals. Twenty of these were chosen to amplify DNA from 82 M. coruscus individuals, and 18 polymorphic loci and 2 monomorphic loci were selected as microsatellite markers. The number of alleles and the allele richness of the polymorphic loci ranged from 2 to 22 and from 2.0 to 19.7 with means of 10.8 and 10.1, respectively. Null alleles were detected for all but three loci, which resulted in an observed heterozygosity lower than the expected heterozygosity and therefore an excess of homozygotes. In a cross-species transfer analysis of these markers using 7 Mytilidae species, the locus Mc65 was amplified from all species tested and was found to be polymorphic in all of them. Among the species, M. galloprovincialis, Lithophaga curta, and Hormomya mutabilis showed the same transferability of 25%, but the five amplified loci were polymorphic only in M. galloprovincialis and H. mutabilis. These microsatellite markers may be useful for future resource management and artificial production of juveniles for aquaculture.
    Genetics and molecular research: GMR 01/2013; 12(3):4009-4017. · 0.99 Impact Factor
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    D K Singh, Y S Lee
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    ABSTRACT: We report on the study of unusual spin glass properties in the geometrically frustrated pyrochlore Tb_{2}Mo_{2}O_{7}, T_{g}≃24 K. The analysis of the nonlinear part of dc and complex susceptibilities, near the glass transition regime, suggests the existence of a statistical distribution of relaxation times in short-range ordered ferromagnetic clusters. In addition, the magnetic spins are not sufficiently frozen below the glass transition temperature, which is apparently responsible for the nonequilibrium scaling behavior of the static critical exponents of nonlinear susceptibilities. Our report is expected to shed new light in understanding the freezing properties of frustrated pyrochlores with short-range ferromagnetic interactions.
    Physical Review Letters 12/2012; 109(24):247201. · 7.73 Impact Factor
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    ABSTRACT: Sinomenine is an alkaloid compound and a prominent anti-inflammatory agent found in the root of the climbing plant Sinomenium acutum. However, its effects on the mechanism of human mast cell line (HMC)-1-mediated inflammation remained unknown. To provide insight into the biological effects of sinomenine, we examined its influence on the pro-inflammatory cytokine production in HMC-1 cells stimulated by phorbol 12-myristate-13-acetate (PMA) plus A23187 by evaluating the stimulated cells in the presence or absence of sinomenine. In the present study, the pro-inflammatory cytokine production was measured using ELISA, Reverse Transcription-polymerase chain reaction (RT-PCR) and nuclear factor (NF)-kappaB, mitogen-activated protein kinases (MAPKs) pathway activation, as determined by Western blot analysis. Also, cyclooxygenase (COX)-2 expression was measured through Western blot and RT-PCR analysis. Sinomenine inhibited the pro-inflammatory cytokine production induced by PMA plus A23187 in a dose-dependent manner. Furthermore, sinomenine inhibited the phosphorylations of extracellular signal-regulated kinase (ERK) and p38 MAPKs as well as the translocation of NF-kappaB p65 through reduced IkappaBalpha degradation. In addition, sinomenine suppressed COX-2 protein and mRNA expression dose-dependently. Taken together, the results of this study indicate that the anti-inflammatory effects of sinomenine may occur via the inhibition of pro-inflammatory cytokine and COX-2 production through the inhibition of MAPKs and NF-kappaB pathway activation by PMA plus A23187 stimulation in HMC-1 cells.
    European review for medical and pharmacological sciences 09/2012; 16(9):1184-91. · 1.09 Impact Factor
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    ABSTRACT: We perform time- and angle-resolved photoemission spectroscopy of a prototypical topological insulator Bi$_2$Se$_3$ to study the ultrafast dynamics of surface and bulk electrons after photo-excitation. By analyzing the evolution of surface states and bulk band spectra, we obtain their electronic temperature and chemical potential relaxation dynamics separately. These dynamics reveal strong phonon-assisted surface-bulk coupling at high lattice temperature and total suppression of inelastic scattering between the surface and the bulk at low lattice temperature. In this low temperature regime, the unique cooling of Dirac fermions in TI by acoustic phonons is manifested through a power law dependence of the surface temperature decay rate on carrier density.
    Physical Review Letters 08/2012; 109(12). · 7.73 Impact Factor
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    ABSTRACT: We develop a theoretical model that describes the second harmonic generation of light from the surface of the topological insulator Bi2Se3 and experimentally demonstrate that the technique is sensitive to the surface electrons. By performing a crystal symmetry analysis of Bi2Se3(111) we determine the nonlinear electric susceptibility tensor elements that give rise to second harmonic generation. Using these results, we present a phenomenological model that shows that the relative magnitudes of these tensor elements can be determined by measuring the polarization and intensity of the radiated second harmonic light as a function of the in-plane crystal orientation and incident laser polarization. We describe optical techniques capable of isolating second harmonic light and, using these techniques, we measure the first-order linear optical and second-order nonlinear optical responses as a function of crystal orientation and laser polarization on bulk single crystals of Bi2Se3(111). The experimental results are consistent with our theoretical description. By comparing the data to our theoretical model we determine that a portion of the measured second harmonic light originates from the accumulation region of Bi2Se3(111), which we confirm by performing surface doping-dependent studies. Our results show that second harmonic generation is a promising tool for spectroscopic studies of topological surfaces and buried interfaces.
    Physical review. B, Condensed matter 07/2012; 86(3). · 3.77 Impact Factor
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    ABSTRACT: Methicillin-resistant Staphylococcus aureus (MRSA) infections are a rapidly growing health problem around the globe. Recently, there has been considerable interest in the use of plant materials as an alternative method to control pathogenic microorganisms. In this study we evaluated the antibacterial activity of bark of Alnus pendula against MRSA. The MIC determination was done using the microdilution broth method and bacterial growth was determined by measuring optical density using spectrophotometer. Alnus pendula bark EtOH extract and fractions (F-1, -2, -3 and -4) were investigated against MRSA. The most active fractions (F-3 and F-4) led to the isolation of oregonin (ORE) and hirsutanone (HIR). These compounds were active against MRSA strains with minimum inhibitory concentrations (MICs) ranging from 31.25 to 250 microg/ml MIC and 2 MIC of HIR completely inhibited the growth of MRSA. The bark EtOH extract of Alnus Pendula has potent antibacterial activity against MRSA.
    European review for medical and pharmacological sciences 07/2012; 16(7):853-9. · 1.09 Impact Factor

Publication Stats

7k Citations
1,518.11 Total Impact Points

Institutions

  • 2009–2013
    • Kyungpook National University Hospital
      • Department of Obstetrics and Gynecology
      Sŏul, Seoul, South Korea
    • Korea University
      Sŏul, Seoul, South Korea
    • Korea Research Institute of Bioscience and Biotechnology KRIBB
      Anzan, Gyeonggi Province, South Korea
    • Pontificia Universidad Católica de Valparaíso
      Ciudad de Valparaíso, Valparaíso, Chile
  • 2006–2013
    • Soongsil University
      • Department of Physics
      Sŏul, Seoul, South Korea
    • Dong-A University
      • Department of Biotechnology
      Pusan, Busan, South Korea
    • Korea Centers for Disease Control and Prevention
      Daiden, Daejeon, South Korea
    • Genomictree
      Yangju-gun, Gyeonggi Province, South Korea
  • 1996–2013
    • Massachusetts Institute of Technology
      • • Department of Physics
      • • Department of Materials Science and Engineering
      Cambridge, Massachusetts, United States
  • 2012
    • Harvard University
      Cambridge, Massachusetts, United States
  • 2010–2012
    • Wonkwang University
      • College of Pharmacy
      Iksan, North Jeolla, South Korea
    • Chosun University
      • Department of Information and Communication Engineering
      Gwangju, Gwangju, South Korea
    • Kyungnam University
      Changnyeong, South Gyeongsang, South Korea
    • Kwangwoon University
      • Department of Chemistry
      Sŏul, Seoul, South Korea
  • 2011
    • Brookhaven National Laboratory
      • Condensed Matter Physics & Materials Science Department
      New York City, NY, United States
  • 1997–2011
    • Catholic University of Korea
      • • Department of Obstetrics and Gynecology
      • • Department of Internal Medicine
      • • College of Medicine
      • • Department of Radiology
      Seoul, Seoul, South Korea
    • RURAL DEVELOPMENT ADMINISTRATION
      Seikan-ri, South Chungcheong, South Korea
  • 1994–2011
    • Hanyang University
      • • College of Medicine
      • • Department of Physics
      Ansan, Gyeonggi, South Korea
  • 2007–2010
    • Chonbuk National University
      • Semiconductor Physics Research Center
      Seoul, Seoul, South Korea
    • Korea Institute of Machinery and Materials
      Sŏul, Seoul, South Korea
  • 2006–2010
    • Chungnam National University
      • Department of Mechanical Design Engineering
      Daiden, Daejeon, South Korea
  • 2000–2010
    • Sungkyunkwan University
      • • Samsung Medical Center
      • • Department of Molecular and Cell Biology
      Sŏul, Seoul, South Korea
    • National Veterinary Research Quarantine Service
      Sŏul, Seoul, South Korea
    • National Institutes of Health
      • Laboratory of Membrane Biochemistry and Biophysics
      Bethesda, MD, United States
  • 1996–2010
    • Seoul National University
      • • Department of Physics and Astronomy
      • • Research Institute of Pharmaceutical Sciences
      • • Department of Chemistry
      • • College of Veterinary Medicine
      • • Institute of Molecular Biology and Genetics
      • • College of Pharmacy
      • • Department of Microbiology and Immunology
      Seoul, Seoul, South Korea
  • 1994–2010
    • Gyeongsang National University
      • Division of Applied Life Science
      Chinju, South Gyeongsang, South Korea
  • 1993–2010
    • Korea Institute of Science and Technology
      Sŏul, Seoul, South Korea
    • Chung-Ang University Hospital
      Sŏul, Seoul, South Korea
  • 1990–2009
    • Asan Medical Center
      Sŏul, Seoul, South Korea
  • 2008
    • Chonnam National University
      • School of Applied Chemical Engineering
      Gwangju, Gwangju, South Korea
    • National Fusion Research Institute
      Daiden, Daejeon, South Korea
    • Korea Institute of Materials Science
      Sŏngnam, Gyeonggi Province, South Korea
  • 2007–2008
    • Seoul Metropolitan Children's Hospital
      Sŏul, Seoul, South Korea
  • 2006–2008
    • Korea Institute of Radiological & Medical Sciences
      Sŏul, Seoul, South Korea
  • 2003–2008
    • Hanbat National University
      • Department of Information and Communication Engineering
      Taiden, Daejeon, South Korea
    • Pohang Accelerator Laboratory
      Urusan, Ulsan, South Korea
    • University of Toronto
      • Department of Physics
      Toronto, Ontario, Canada
    • Kanagawa University
      Yokohama, Kanagawa, Japan
  • 1995–2007
    • Kyungpook National University
      • • Department of Physics
      • • Center for High Energy Physics
      • • College of Natural Sciences
      Sangju, North Gyeongsang, South Korea
    • Sungshin Women's University
      Sŏul, Seoul, South Korea
    • Seoul National University of Science and Technology
      Sŏul, Seoul, South Korea
  • 1996–2006
    • Ulsan University Hospital
      Urusan, Ulsan, South Korea
  • 2004
    • Korea Advanced Institute of Science and Technology
      • Department of Physics
      Seoul, Seoul, South Korea
  • 2001–2003
    • National Institute of Standards and Technology
      • NIST Center for Neutron Research
      Gaithersburg, MD, United States
    • National Institute of Health Sciences, Japan
      • Division of Cellular and Molecular Toxicology
      Edo, Tōkyō, Japan
    • Keimyung University
      • Department of Microbiology
      Seoul, Seoul, South Korea
    • Saga University
      • Department of Chemistry and Applied Chemistry
      Сага Япония, Saga, Japan
  • 1998–2002
    • Yeungnam University
      • College of Pharmacy
      Asan, South Chungcheong, South Korea
  • 1997–2002
    • Kwandong University
      • College of Medicine
      Gangneung, Gangwon, South Korea
  • 1992–2001
    • National Cancer Center Korea
      Kōyō, Gyeonggi Province, South Korea
  • 1990–2001
    • Seoul National University Hospital
      • • Department of Radiology
      • • Department of Dermatology
      Seoul, Seoul, South Korea
  • 1999–2000
    • Chungbuk National University
      • • Division of Life Sciences
      • • Department of Biochemistry
      Tyundyu, North Chungcheong, South Korea
    • Seoul Women's University
      Sŏul, Seoul, South Korea
  • 1994–1999
    • Seoul Medical Center
      Sŏul, Seoul, South Korea
  • 1993–1999
    • Yonsei University
      • Department of Physics
      Seoul, Seoul, South Korea
  • 1994–1998
    • University of Ulsan
      • • College of Medicine
      • • Department of Pharmacology
      • • Department of Internal Medicine
      Urusan, Ulsan, South Korea