Yong Hoon Lee

Chonbuk National University, Tsiuentcheou, Jeollabuk-do, South Korea

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Publications (98)97.56 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the infection mechanisms of pathogens will lead to better management of the associated diseases. The flagella of these pathogens play significant roles not only in bacterial motility, but also in virulence. In the present study, two genes involved in flagella construction, fliJ and fliI of Pseudomonas cichorii, were analyzed. The results revealed that these genes are vital for flagella formation and play significant roles not only in motility, but also in virulence. When we inoculated host plants with fliI- and fliJ-defective mutants (ΔfliJ and ΔfliI) through the dipping method, the degree of disease severity caused by both mutants was significantly reduced compared to those of the wild-type. However, the virulence of ΔfliI was stronger than that of ΔfliJ. Electron microscope observation and swarming and leaf attachment assays indicated a reduced number of flagella in ΔfliI, but not complete absence, because of the presence of another copy of fliI. Furthermore, a vacuum infiltration assay revealed that flagella are indispensable in the pre- and post-penetration stages for complete virulence. Overall, we created semi-defective (ΔfliI) and completely defective (ΔfliJ) mutants and elucidated the fact that flagella play significant roles in virulence of the pathogen at different stages of the infection process.
    No preview · Article · Jan 2016 · Research in Microbiology
  • Sang‐Mi Yu · Yong Hoon Lee
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    ABSTRACT: Understanding the mechanisms underlying biocontrol activity in biocontrol agents is indispensable to implement biological control. However, the understanding of specific mechanisms for nutrient competition in nutrient limited environments is still limited. This study was performed to control green mold of postharvest satsuma mandarin (mandarin) using Pseudomonas putida JBC17 (JBC17), and identify the genes involved in nutrient competition. Treatment with JBC17 on wounded mandarin fruits at a concentration of 10(6) and 10(7) cfu ml(-1) suppressed the incidence of green mold with efficacy of 74.1 and 91.4%, respectively, compared to the untreated control. In spite of there being no antifungal activity in a dual culture test, JBC17 significantly inhibited the conidial germination of Penicillium digitatum. The results from the nutrient competition assay revealed that the inhibition of conidial germination was exerted by nutrient starvation. From the constructed transposon (Tn) library of JBC17, exopolyphosphatase (ppx) and Xaa-Pro aminopeptidase (pepP) were recognized as potential factors responsible for the inhibition of conidial germination. In conclusion, the understanding of nutrient depletion specific to the inhibition of conidial germination by JBC17 may ultimately lead to a deeper understanding of the bacterial metabolism and conidial metabolism for germination as well as biocontrol activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · Feb 2015 · Journal of Basic Microbiology
  • Rajalingam Nagendran · Yong Hoon Lee
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    ABSTRACT: Light influences many physiological processes in most organisms. To investigate the influence of light on plant and pathogen interaction, we challenged tomato seedlings with Pseudomonas cichorii JBC1 by flood inoculation and incubated the seedlings under different light conditions. Tomato seedlings exposed to green or red light showed a significant reduction in disease incidence compared to those grown under white light or dark conditions. To understand the underlying mechanisms, we investigated the effects of each light wavelength on P. cichorii JBC1 and tomato plants. Treatment with various light wavelengths at 120 µmol m-2s-1 revealed no significant difference in growth, swarming motility, or biofilm formation of the pathogen. In addition, when we vacuum infiltrated P. cichorii JBC1 into tomato plants, green and red light also suppressed disease incidence which indicated that the reduced disease severity was not from direct influence of light on the pathogen. Significant upregulation of the defense-related genes, phenylalanine ammonia-lyase (PAL) and pathogenesis-related protein 1a (PR-1a) was observed in P. cichorii JBC1 infected tomato seedlings grown under green or red light compared to seedlings grown under white light or dark conditions. The results of this study indicate that light conditions can influence plant defense mechanisms. In particular, green and red light increase the resistance of tomato plants to infection by P. cichorii.
    No preview · Article · Dec 2014 · Phytopathology

  • No preview · Article · Sep 2014
  • Nguyen Bao Hung · Gandhimani Ramkumar · Yong Hoon Lee
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    ABSTRACT: Pseudomonas cichorii is a devastating pathogen which infects a wide range of ornamental as well as agricultural crops worldwide. Characterization of virulence genes helps to understand pathogens' infection processes, which may lead to development of resistant crops. For functional validation of novel genes, we re-constructed pUCP18 vector with λ phage red operon and sacB gene (pUCP18_RedS), which simplified conventional marker exchange system. The effector gene hopA1 of P. cichorii JBC1 was marker exchanged with PCR product of kanamycin gene flanked by hopA1 flanking region using pUCP18_RedS. The virulence and internal growth of hopA1 defective mutant (ΔhopA1) in tomato seedlings was significantly reduced compared to wild type (WT) and hopA1 complemented strain (ΔhopA1::phopA1). The analysis on role of hopA1 in host range revealed that P. cichorii was hopA1-dependent to infect cabbage, tomato, soybean, hot pepper, and cucumber, but not melon and eggplant. Despite the similarity in growth pattern, the biofilm formation and swarming motility of ΔhopA1 was significantly reduced compared to WT and ΔhopA1::phopA1. The results of this study indicate that hopA1 plays a significant role not only in virulence and host specificity, but also motility and biofilm formation of P. cichorii which may influence the infection processes.
    No preview · Article · Aug 2014 · Research in Microbiology
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    ABSTRACT: Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a very serious disease in rice growing regions of the world. In spite of economic importance, there are no effective ways of protecting rice plant from this disease. Bacteriophages infecting Xoo affect the population dynamics of the pathogen and consequently the occurrence of the disease. In this study, we investigated the diversity, host range, and infectivity of Xoo phages, and their use as a bicontrol agent on BLB was tested. Among the 34 phages that were isolated from floodwater in paddy fields, 29 belonged to Myoviridae family, which suggests that the dominant phage in the ecosystem was Myoviridae. The isolated phages were classified into two groups based on plaque size produced on the lawn of Xoo. In general, there was a negative relationship between plaque size and host range, and interestingly the phages having a narrow host range had low efficiency of infectivity. The deduced protein sequence analysis of htf genes indicated that the gene was not a determinant of host specificity. Although the difference in host range and infectivity depending on morphotype needs to be addressed, the results revealed deeper understanding of the interaction between the phages and Xoo strains in floodwater and damp soil environment. The phage mixtures reduced the occurrence of BLB when they were treated with skim milk. The results indicate that the Xoo phages could be used as an alternative control method to increase the control efficacy and reduce the use of agrochemicals.
    No preview · Article · Mar 2014 · Journal of Microbiology and Biotechnology
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    ABSTRACT: Volatile compounds produced by bacteria play an important role in plant and bacteria interactions. Volatiles from the rhizobacterium Proteus vulgaris JBLS202 or synthetic indole increased the fresh weight of Arabidopsis thaliana Col-0 by 74.9–80.3 %, and 48.0–56.3 %, respectively. However, exposure to volatiles from JBLS202 or indole was unable to promote growth in the mutant lines of A. thaliana defective in auxin transport (eir1), cytokinin (cre1), and brassinosteroid metabolism (cbb1), whereas growth was significantly stimulated in the ethylene- (etr1) and gibberellin-insensitive (gai 1) mutants. In addition, Arabidopsis Col-0 treated with auxin, and brassinosteroid biosynthesis inhibitors was considerably arrested in growth-promoting performance by the volatiles. Moreover, exposure of Col-0 seedlings to JBLS202 or indole for 14 days resulted in overexpression of small auxin up RNA, histidine kinase1, and brassinosteroid biosynthetic cytochrome P450 genes. Overall, the results indicate that the indole emitted by JBLS202 stimulates the growth of A. thaliana through an interplay between the auxin, cytokinin, and brassinosteroid pathways. This is the first report on how bacterial indole influences the plant hormone signaling pathways.
    No preview · Article · Mar 2014 · Journal of Plant Growth Regulation
  • Dipto Bhattacharyya · Sang-Mi Yu · Yong Hoon Lee
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    ABSTRACT: Volatile compounds from rhizobacteria are known to elicit and regulate plant growth and defense against various biotic and abiotic stresses. In the present study, we elucidated the biological role of volatiles from Alcaligenes faecalis strain JBCS1294 on the growth performance of Arabidopsis thaliana under salt stress. JBCS1294 volatiles promoted gains in fresh weight and shoot length of Arabidopsis Col-0 under salt stress by 61.5 and 45.8 %, respectively. Hexanedioic acid and butanoic acid were identified as major volatiles emitted from JBCS1294. However, volatiles from JBCS1294 were unable to induce salt tolerance in eir1 and gai-1 mutant lines of A. thaliana, or in auxin and gibberellin inhibitor-treated Col-0 plants. On the other hand, a significant increase of growth in cytokinin-, brassinosteroid-, and ethylene-defective mutant lines, or in respective inhibitor-treated Col-0, led us to conclude that the auxin and gibberellin pathways are mediators which confer salt tolerance in Arabidopsis upon introduction of JBCS1294 volatiles. Exposure to JBCS1294 volatiles did not alter proline content in gai-1 and gibberellin inhibitor-treated lines. Additionally, AtNHX1, AtHKT1, AtSOS1, AtAVP1, auxin and brassinosteroid pathway genes were upregulated in the roots after exposure of salt-stressed seedlings to JBCS1294 volatiles, suggesting tissue-specific remodeling of gene expression.
    No preview · Article · Jan 2014 · Plant Growth Regulation
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    ABSTRACT: MicroRNAs (miRs) play important roles in the development and progression of human cancers. MiR-146a down-regulates epidermal growth factor receptor and the nuclear factor-κB regulatory kinase interleukin-1 receptor-associated kinase 1 genes that play important roles in lung carcinogenesis. This study was conducted to evaluate the association between rs2910164C>G, a functional polymorphism in the pre-miR-146a, and lung cancer risk. The rs2910164C>G genotypes were determined in 1,094 patients with lung cancer and 1,100 healthy controls who were frequency matched for age and gender. The rs2910164 CG or GG genotype was associated with a significantly decreased risk for lung cancer compared to that of the CC genotype (adjusted odds ratio=0.80, 95% confidence interval=0.66-0.96, P=0.02). When subjects were stratified according to smoking exposure (never, light and heavy smokers), the effect of the rs2910164C>G genotype on lung cancer risk was significant only in never smokers (adjusted odds ratio=0.66, 95% confidence interval=0.45-0.96, P=0.03, under a dominant model for the C allele) and decreased as smoking exposure level increased (Ptrend<0.001). In line with this result, the level of miR-146a expression in the tumor tissues was significantly higher in the GG genotype than in CC or CG genotypes only in never-smokers (P=0.02). These findings suggest that the rs2910164C>G in pre-miR-146a may contribute to genetic susceptibility to lung cancer, and that miR-146a might be involved in lung cancer development. HIGHLIGHT:
    No preview · Article · Oct 2013 · Gene
  • Gandhimani Ramkumar · Sang-Mi Yu · Yong Hoon Lee
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    ABSTRACT: Bacillus amyloliquefaciens JBC36 (JBC36) is a potent biocontrol agent and was proved to control green and blue molds of Satsuma mandarin (Citrus unshiu). Moreover, light qualities affected its biocontrol efficacy; green and red light significantly increased the antifungal activity of the antagonist in our previous study. The disparity in antagonism on Penicillium digitatum under different light qualities prompted us to investigate further to identify the factors responsible for the noted variation. Purification and quantification of antifungal lipopeptides by HPLC revealed that a three-fold higher quantity of fengycin and a two-fold higher quantity of iturin were produced in cultures incubated with red and green light sources in comparison with white light illumination. Gene expression analysis by real-time PCR also revealed nearly fourfold higher fenA transcripts in cultures subjected to green and red light in comparison with white light illumination. The lowest gene expression was observed with blue light illumination. This study clearly proved that light affects the synthesis of antifungal lipopeptides in JBC36. A light-based lipopeptide production strategy may lead to better exploitation of the microbes for overproduction of the antifungal secondary metabolites and crop disease management.
    No preview · Article · Oct 2013 · European Journal of Plant Pathology

  • No preview · Article · Sep 2013
  • Sang-Mi Yu · Yong Hoon Lee
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    ABSTRACT: Backgrounds and aims The functional role of volatile indole in interaction between rhizobacteria and plant remains unknown. In this study, we investigated the functional role of the volatile indole emitted by rhizobacterial strain Proteus vulgaris JBLS202 in plant growth promoting activity. Methods P. vulgaris strain JBLS202 was used to study the role of volatile organic compounds (VOCs) on growth stimulation of Chinese cabbage (cabbage) at seedling stage. SPME-GC/MS analysis employed to identify headspace VOCs emitted from the rhizobacterium. Synthetic indole was assayed at various concentrations for the growth stimulation of cabbage and the emission of indole from the bacterized cabbage seeds was identified. Results P. vulgaris JBLS202 promoted the growth of cabbage via volatiles in a dose-dependent manner. VOC emission assay by SPME-GC/MS revealed that indole was a major headspace volatile compound emitted from the rhizobacterium. Moreover, the growth of cabbage was promoted significantly in the presence of 0.63 μg of synthetic indole. The vigor index and fresh weight of the seedlings were increased by 39.9 % and 32.6 %, respectively when the seeds of cabbage were bacterized with P. vulgaris JBLS202 cells (1 × 107 CFU/ml). The emission of indole from the bacterized seeds was demonstrated by SPME-GC/MS. Conclusions Results indicated that either synthetic or biological/bacterial indole could increase the growth of cabbage significantly. Though the molecular biological role of indole in plant growth promotion remains to be investigated, this is the first report on detailed interaction between bacterial indole and plants.
    No preview · Article · Sep 2013 · Plant and Soil
  • Sang-Mi Yu · Gandhimani Ramkumar · Yong Hoon Lee
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    ABSTRACT: To explore the effects of light quality on the physiology and pathogenicity of Colletotrichum acutatum, we analysed the morphological traits, melanin production and virulence of the pathogen under different light wavelengths. The influence of light wavelength on the mycelial growth and conidial germination of C. acutatum was investigated using red, green, blue and white light sources. Red and green light reduced the mycelial growth in comparison with blue and white light, and dark conditions. The least percentage of conidial germination was observed under blue light, while the germination rate among white, red and green light, as well as in the dark, was insignificant. In comparison with its influence on mycelial growth and conidial germination, light wavelength significantly affected the pathogen's virulence towards hot pepper fruits. The highest disease severity was observed under blue light, which was at least a twofold increase compared with the disease severity under other light conditions. To elucidate the effect of light on the disparity in virulence, scytalone was assayed by HPLC, and scd1 gene expression was examined with real-time PCR. The highest and lowest scytalone production was observed in the cultures incubated under blue (10·9 mAU) and green light (1·5 mAU), respectively. Higher scd1 gene expression (~ 40-fold increase) was observed in cultures incubated under blue and white light in comparison with those incubated in the dark. This study revealed that light affects the growth, colonial morphology and virulence of C. acutatum. The pathogen needs light for its active melanin production and also to attain higher virulence. This is the first report on the effect of light quality on the virulence of C. acutatum. The findings of this study will broaden our knowledge of the influence of light on physiological responses of fungal pathogens.
    No preview · Article · May 2013 · Journal of Applied Microbiology
  • Sang-Mi Yu · Yong Hoon Lee
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    ABSTRACT: Light is one of the most important environmental signals regulating physiological processes of many microorganisms. However, very few studies have been reported on the qualitative or quantitative effects of light on control of postharvest spoilage using antagonistic bacteria. In this study, we investigated the effects of white, red, green, and blue light at photon flux densities of 40, 240, and 360 μmol m−2 s−1 on Bacillus amyloliquefaciens JBC36 (JBC36), which has been reported as a promising candidate for biocontrol of green and blue mold on mandarin fruit. With the exception of blue light at 240 and 360 μmol m−2 s−1, light generally stimulated growth of JBC36 compared to the controls grown in the dark. Red light increased swarming motility irrespective of intensity and significantly enhanced biofilm formation at 240 μmol m−2 s−1. Production of antifungal metabolites and antifungal activity on Penicillium digitatum was also affected by light quality. Interestingly, antifungal activity was significantly increased when JBC36 and P. digitatum was co-incubated under red and green light at an intensity of 240 μmol m−2 s−1. We also demonstrated that the quality of light resulted in changes in colonization of JBC36 on mandarin fruit and control of green mold. In particular, red light increased the population level on mandarin fruit and biocontrol efficacy against green mold. These results represent the first report on the effect of light quality on an antagonistic bacterium for the control of postharvest spoilage. We believe that an improved understanding of the JBC36 response to light quality may help in the development of strategies to increase biocontrol efficacy of postharvest spoilage.
    No preview · Article · Mar 2013 · Biological Control
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    ABSTRACT: Multicentric Castleman's disease (CD) is a rare atypical lymphoproliferative disorder, which is characterized by various systemic manifestations. Some patients with multicentric CD may have concomitant lung parenchymal lesions, for which lymphoid interstitial pneumonia (LIP) is known to be the most common pathologic finding. Follicular bronchiolitis and LIP are considered to be on the same spectrum of the disease. We describe a case of multicentric CD with pulmonary involvement, which was pathologically proven as follicular bronchiolitis.
    Full-text · Article · Jan 2013 · Tuberculosis and Respiratory Diseases
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    ABSTRACT: Reported herein is an adult case of Fisher syndrome (FS) that occurred as a complication during the course of community-acquired pneumonia caused by Mycoplasma pneumoniae. A 38-yr-old man who had been treated with antibiotics for serologically proven M. pneumoniae pneumonia presented with a sudden onset of diplopia, ataxic gait, and areflexia. A thorough evaluation including brain imaging, cerebrospinal fluid examination, a nerve conduction study, and detection of serum anti-ganglioside GQ1b antibody titers led to the diagnosis of FS. Antibiotic treatment of the underlying M. pneumoniae pneumonia was maintained without additional immunomodulatory agents. A complete and spontaneous resolution of neurologic abnormalities was observed within 1 month, accompanied by resolution of lung lesions.
    Full-text · Article · Jan 2013 · Journal of Korean medical science
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    ABSTRACT: Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has received considerable attention in recent years as the cause of infections in individuals in the community who do not have traditional risk factors for MRSA infection, such as hospitalization or contact with healthcare services. CA-MRSA strains have different molecular and antimicrobial susceptibilities, as compared to hospital-associated MRSA. Although CA-MRSA strains are primarily associated with skin and soft tissue infections, they can cause more invasive infections, such as severe community-acquired pneumonia. Reports on CA-MRSA pneumonia in Korea are sparse. Therefore, we report a case of CA-MRSA pneumonia with molecular typing of the MRSA isolate.
    No preview · Article · Jan 2013
  • Sang-Mi Yu · Byung-Taek Oh · Yong Hoon Lee
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    ABSTRACT: In order to control postharvest rots of satsuma mandarin (mandarin) fruits, a new strain of Bacillus amyloliquefaciens JBC36 (JBC36) was isolated from rhizosphere of a mandarin orchard and tested for its suppression on decay due to green and blue molds caused by Penicillium digitatum and Penicillium italicum, respectively, and its mode of action was investigated. Additionally, carnauba wax-based and paraffin oil-based coating formulations were developed to increase the control efficacy of the antagonist. The strain JBC36 at 10 CFU mL inhibited incidence of green and blue molds on wounded mandarin fruits with control efficacies of 88 and 80.2%, respectively. Mycelial growth and spore germination of P. digitatum and P. italicum were strongly inhibited in the presence of JBC36 or antagonistic metabolites. In order to determine antifungal activity, three kinds of antibiotics were isolated by RP-HPLC and identified as lipopeptide families, iturin A, fengycin, and surfactin by RP-HPLC and TLC analysis. Fengycin was further identified as C16 fengycin A by LC/ESI-MS and MS/MS analysis. Volatile organic compounds from the antagonist also reduced the mycelial growth of P. digitatum and P. italicum. Carnauba wax-based and paraffin oil-based coating formulations containing 10 CFU mL of JBC36 efficiently decreased the incidence of green mold with control efficacy of 91 and 80.9%, respectively. Overall, the antagonistic rhizobacterium JBC36 is a promising biocontrol agent for use in preventing postharvest spoilage of mandarin fruits by green and blue molds.
    No preview · Article · Oct 2012 · Biocontrol Science and Technology
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    Wooseok Nam · Sae-Young Chung · Yong Hoon Lee
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    ABSTRACT: In this paper, we consider a class of single-source multicast relay networks. We assume that all outgoing channels of a node in the network to its neighbors are orthogonal while the incoming signals from its neighbors can interfere with each other. We first focus on Gaussian relay networks with interference and find an achievable rate using a lattice coding scheme. We show that the achievable rate of our scheme is within a constant bit gap from the information theoretic cut-set bound, where the constant depends only on the network topology, but not on the transmit power, noise variance, and channel gains. This is similar to a recent result by Avestimehr, Diggavi, and Tse, who showed an approximate capacity characterization for general Gaussian relay networks. However, our achievability uses a structured code instead of a random one. Using the idea used in the Gaussian case, we also consider a linear finite-field symmetric network with interference and characterize its capacity using a linear coding scheme.
    Preview · Article · Dec 2011 · IEEE Transactions on Information Theory
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    Sungho Choi · Eui-Rim Jeong · Yong Hoon Lee
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    ABSTRACT: A new predistortion technique for dynamic spec- trum allocation systems such as cognitive radio (CR) is proposed. The system model considered in this paper occupies a small band at a time, but the center frequency can be changed in the wide range of frequency. In this scenario, the front-end filter may not eliminate the harmonics of the power amplifier (PA) output. The proposed PD reduces the spectral regrowth of the fundamental signal at the carrier frequency (ωo) and removes the harmonics (2ωo, 3ωo, ··· ) at the same time. The proposed PD structure is composed of multiple predistorters (PDs) centered at integer multiples of ωo. The PD at ωo is for removing spectral regrowth of the fundamental signal, and the others are for harmonic reduction. In the proposed PD structure, parameters of PDs are found jointly. Simulation results show that the spectral regrowth can be reduced by 20dB, and the 2nd and 3rd harmonics can be reduced down to -70dB from the power of the fundamental signal. Index Terms—Cognitive radio (CR), dynamic spectrum allo- cation, harmonics, power amplifier (PA), predistortion
    Full-text · Conference Paper · May 2011

Publication Stats

1k Citations
97.56 Total Impact Points


  • 2010-2015
    • Chonbuk National University
      • Department of Biotechnology
      Tsiuentcheou, Jeollabuk-do, South Korea
  • 2013
    • Kyungpook National University Hospital
      Sŏul, Seoul, South Korea
  • 2011-2013
    • Kyungpook National University
      • Department of Internal Medicine
      Daikyū, Daegu, South Korea
    • Hanbat National University
      • Department of Information and Communication Engineering
      Daiden, Daejeon, South Korea
  • 1990-2011
    • Korea Advanced Institute of Science and Technology
      • • Department of Electrical Engineering
      • • School of EECS
      Sŏul, Seoul, South Korea
  • 2009
    • Kookmin University
      Sŏul, Seoul, South Korea
      Seikan-ri, Chungcheongnam-do, South Korea
  • 1999
    • LG Electronics
      Sŏul, Seoul, South Korea
  • 1997
    • Electronics and Telecommunications Research Institute
      Sŏul, Seoul, South Korea
    • Agency for Defense Development
      Sŏul, Seoul, South Korea
  • 1994
    • Seoul Semiconductor Co.
      Sŏul, Seoul, South Korea
  • 1991
    • University of Michigan-Dearborn
      • Department of Electrical and Computer Engineering
      Dearborn, Michigan, United States
  • 1985-1989
    • University at Buffalo, The State University of New York
      • Department of Electrical Engineering
      Buffalo, New York, United States