Y J Lee

National Fusion Research Institute, Daiden, Daejeon, South Korea

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Publications (198)324.73 Total impact

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    ABSTRACT: After a contract with Hyundai Heavy Industries Co. Ltd. (HHI) on January 2010 for the manufacture of the ITER equatorial and lower ports, manufacturing preparation activities have been performed. As part of the preparation activities, a full scale mock-up of the lower port stub extension (LPSE) #16 was fabricated by HHI in order to verify fabrication feasibility and set up the fabrication sequence for the LPSE. In this paper, major technical results from fabrication of a full scale mock-up will be presented with emphasis on the main manufacturing procedure, welding, nondestructive examination (NDE) and 3D dimensional inspection. Afterwards, progress of real product manufacturing is introduced.
    Fusion Engineering and Design 10/2014; · 1.15 Impact Factor
  • Otolaryngology Head and Neck Surgery 09/2014; 151(1 Suppl):P154-P154. · 1.72 Impact Factor
  • S.J. Cho, Y.J. Lee, Y.H. Kim, J.Y. Koo
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    ABSTRACT: HVDC transformers are one of the main components for long distance transmission, for which many investigations have been done all over the world in order to increase their efficiency and reliability. Regarding their insulation, oil immersed pressboards are widely used, representing one of the most important elements playing a role in transformer behaviors. Under DC operation, space charges accumulating between the oil and pressboard have been reported as the influential cause possibly giving rise to unexpected service failures under the transient voltage from the grid. However, it might be possible to presume that the accumulation of space charge could be facilitated inside the multilayered pressboard causing insulation breakdown in a different way. In addition, other parameters could be potential issues to investigate: non homogeneous temperature distribution along the oil circulation path and the DC field intensity. The former could explain the conductivity variation causing the non-uniform DC field distribution, while the latter plays a role in the variation of conductivity. With these in mind, three parameters have mainly been put under experimental investigation. For this purpose, a DC voltage is applied to the oil immersed pressboard, and then the polarization and leakage current are measured and analyzed. The mobility of the space charge is calculated from the former as a function of the number of layers, while the conductivity is obtained from the latter.
    IEEE Transactions on Dielectrics and Electrical Insulation 04/2014; 21(2):866-872. · 1.23 Impact Factor
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    ABSTRACT: This study was conducted to compare the expression patterns of serum alpha-fetoprotein (AFP) and proteins induced by vitamin K absence or antagonist-II (PIVKA-II) in hepatocellular carcinoma (HCC) patients undergoing liver transplantation (LT) and resection at a high-volume single institution. First, 663 liver transplant recipients with HCC were selected. They were divided into hepatitis B virus (HBV) (n = 628) and hepatitis C virus (HCV) groups (n = 35). Their medical records were retrospectively reviewed. Second, another cohort of 2709 patients who underwent HCC resection included 2258 HBV, 143 HCV, and 308 non-HBV non-HCV (NBNC) patients. In the transplantation group, pretransplantation AFP level >20 ng/mL was observed in 42.5% of HBV patients and 60% of HCV patients (P = .042). PIVKA-II level >40 mAU/mL was observed in 30.6% of HBV patients and 42.9% of HCV patients (P = .127). In the resection group, a preoperative AFP level >20 ng/mL was observed in 51.7% of HBV patients and 43.3% of HCV patients (P = .052). PIVKA-II level >40 mAU/mL was observed in 59.7% of HBV patients and 56.6% of HCV patients (P = .47). Preoperative AFP level >20 ng/mL and PIVKA-II level >40 mAU/mL were observed in 35.7% and 61% of NBNC patients, respectively. Receiver-operator characteristic curve analyses revealed that the expression pattern of PIVKA-II in patients with elevated AFP level was not predictable and vice versa, regardless of background liver diseases. This study indicates that serum AFP and PIVKA-II may be expressed variably regardless of the types of background liver disease. Further large-volume multicenter studies are needed to evaluate the possibility of the etiology-dependent expression of tumor markers.
    Transplantation Proceedings 04/2014; 46(3):888-93. · 0.95 Impact Factor
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    ABSTRACT: In this paper, we develop pixels with concentric-photogates for applications in time-of-flight 3-D image sensors with single-tap architecture. The pixel uses a buried-channel device and features a reduced effective electron transit length, for the rapid transfer of a signal electron. A reduction in the interpixel irregularity of signal levels and a consequent increase in the demodulation signal amplitude are observed in the single-tap operation mode as opposed to the multitap operation mode. Specifically, we are able to achieve a demodulation contrast higher than 50% from 20 MHz modulation of an 850 nm light-emitting diode illumination. Finally, we construct a sensor composed of 198 x 108 concentric photogate pixels, each with a pitch of 28 μm, and use it to generate a 3-D image conveying gross distance information and detailed object features with a distance error of less than 1% over a range of 1 to 7 m.
    IEEE Transactions on Electron Devices 02/2014; PP(99):1-1. · 2.36 Impact Factor
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    ABSTRACT: High-availability Seamless Redundancy (HSR) is an emerging standard that is suitable for mission-critical communication of IEC 61850 based Substation Automation System in smart grid, where the dependability is very important. This redundancy protocol provides zero recovery time by offering duplicated frames for separate physical paths, but it generates and circulates unnecessary traffic inside the network that will degrade the performance of the network and may cause the congestion, delay, or frame loss. To improve the HSR network performance, the main drawback of generating extra traffic should be considered and eliminated. This paper demonstrates comprehensive performance analysis of IEC 61850 based substation automation networks and applies the quick removing (QR) algorithm to improve the performance of the HSR network to overcome the major drawback. The performance analysis includes the HSR modules, i.e., Doubly Attached Node for HSR (DANH), Redundancy Box (RedBox), and Quadruple Box (QuadBox), and IEC 61850 services, i.e., Generic Object Oriented Substation Events (GOOSE), Sampled Measurement Values (SMV), and report service. Performance analysis was conducted to verify the timing constraints described in IEC 61850 as a reference for designing proper HSR network topology. The numerical results show that the frame loss, restricted in mission-critical network, occurs due to large amount of traffic volume, which is the main drawback of HSR. The QR algorithm improves the traffic performance of HSR by reducing the unnecessary traffic along with the decrease of packet loss significantly.
    ICACT 2014; 02/2014
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    ABSTRACT: Aluminothermic reduction of K2TiF6 in the presence of C, B, or N2 was investigated as a low exothermic combustion process for synthesizing nanoparticles of titanium ceramics such as TiC, TiB2, and TiN. Sample pellets were prepared by mixing powders of K2TiF6, Al, and non-metal (C, B) powders in stoichiometric ratios. Experiments were conducted at room temperature under either an Ar or N2 atmosphere. The combustion parameters were estimated from the temperature-time profiles, measured in the combustion wave using thermocouples. The reaction drastically proceeds within seconds, raising the temperature to 890–1170°C. The size of TiC, TiB2, and TiN nanoparticles prepared by the developed approach were, respectively, 5–30 nm, 10–60 nm, and 70–100 nm.
    Combustion Science and Technology 01/2014; 186(1). · 0.98 Impact Factor
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    ABSTRACT: A study has been conducted on the electrodeposition of tantalum in a 61 mol% LiF–39 mol% NaF melt containing 1 mol% K2TaF7 at 800 °C. Tantalum was coated onto a stainless-steel base (SUS316L) by molten salt electrodeposition (MSE) at different current densities (0.5, 1.5, 2, 5, 10, 20 mA/cm2). Electrodeposition of metallic tantalum occurred primarily by electroreduction of Ta(V), i.e. TaF72 −, at a potential of <− 0.27 V (vs. Pt used as a pseudo reference electrode). At potentials less than − 0.324 V, TaF2(s) also underwent reduction to metallic tantalum. Pure metallic tantalum, without any entrapped salt, was successfully deposited on SUS316L by electrodeposition at 5 mA/cm2. This showed that the deposition efficiency and microstructure of the tantalum coating layer were strongly dependent on the current density. The densest microstructure was obtained at a current density of 5 mA/cm2. Current densities above 5 mA/cm2 caused non-uniform microstructures because of rapid deposition. A dense microstructure and an intact coating layer contributed to a significant enhancement in corrosion resistance.
    Surface and Coatings Technology 11/2013; 235:819–826. · 2.20 Impact Factor
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    ABSTRACT: Background: Pneumonia is the primary source of sepsis and is associated significantly with mortality. However, little is focused on about its clinical characteristics and outcomes. Methods : We evaluated 500 intensive care unit patients who met severe sepsis or septic shock criteria, dividing them into two distinct groups (43%, sepsis with pneumonia; 41%, sepsis with an infection other than pneumonia). Results: Moderate differences between the groups were observed. The group of sepsis with pneumonia had a higher 28-day in-hospital mortality (41% vs. 30%; P = 0.02). Multivariate analysis revealed that the presence of pneumonia associated significantly with mortality (OR 1.76, 95% CI 1.11-2.78) along with cardiopulmonary resuscitation (OR 4.20, 95% CI 1.50-11.74), serum lactate ≥3.5 mmol/L (OR 1.92, 95% CI 1.20-3.08), and SOFA score ≥12 (OR 2.41, 95% CI 1.52-3.82). Survival analysis revealed for both groups that the patients with PaO2/FiO2 (PF) ratio <170 and lactate ≥3.5 mmol/L had a worse prognosis than the patients with PF ratio ≥170 and lactate ≥3.5 mmol/L or PF ratio <170 and lactate <3.5 mmol/L. Conclusion: In patients admitted with sepsis, the pneumonia infection independently predicts 28-day inhospital mortality. Combining the levels of serum lactate and PF ratio could be a useful approach in predicting mortality of these patients.
    Minerva anestesiologica 09/2013; · 2.27 Impact Factor
  • Institute of Electrical 44th Summer Conference; 07/2013
  • Ultrasound in Medicine & Biology 05/2013; 39(5):S17–S18. · 2.10 Impact Factor
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    ABSTRACT: The effects of genomic changes in hepatitis B virus (HBV) on the occurrence of hepatocellular carcinoma (HCC) are still unclear, especially in relation to the genotype of HBV. In this study, we examined the effects of genomic changes in HBV of genotype C2 on the development of HCC. A total of 318 patients with HBV-associated HCC and 234 patients with chronic hepatitis B (CHB) were studied. All of HCC cases were diagnosed histologically and treated with surgical resection. The whole of the X, S, basal core promoter (BCP) and precore regions of the viral genome from sera or liver tissues were sequenced. All subjects had HBV of genotype C2. The prevalence of the T1653 mutation in the X region and the A1896 mutation in the precore region of HBV was significantly higher in the HCC group than in the control CHB group (22% vs 11%, P = 0.003; 50% vs 23%, P < 0.001, respectively). Moreover, the T1762/A1764 mutations in the BCP region in combination with either T1653 or A1896 were more common in the HCC compared with the CHB group (BCP+X1653: 18% vs 11%, P = 0.05; BCP+PC, 40% vs 15%, P < 0.001, respectively). In multivariate analysis, T1653 and A1896 were revealed to be independent risk factors for HCC development. G1896A in the precore region and C1653T mutation in the X region of genotype C2 HBV are important risk factors for HCC development. Also, the A1762T/G1764A double mutation may act in synergy with C1653T to increase the risk of HCC in patients chronically infected with HBV genotype C2.
    Journal of Viral Hepatitis 03/2013; 20(3):219-24. · 3.08 Impact Factor
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    ABSTRACT: In this study, intermetallic compound formation at the interface between aluminum and copper during hydrostatic extrusion was simulated by performing a solid state diffusion bonding experiment with various processing parameters, including bonding temperature and pressure and holding time, and by inserting an Ag colloid layer between the aluminum and copper. Regression equations were developed to predict thickness of diffusion layer and interface hardness.An intermetallic compound formed at the interface between the Al and Cu during diffusion bonding at 420 °C and 240 MPa for 60 min, and it was effectively controlled by inserting an Ag colloid. These experimental data will be useful for setting up processing parameters to prepare Al/Cu matrix composite materials by using hydrostatic extrusion.
    Journal of Materials Processing Technology 03/2013; 213(3):487–494. · 2.04 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the cytotoxic activities of ovotransferrin (OTF) from egg white and its enzyme hydrolysates (OTH). The OTF was hydrolyzed at 45°C for 3 h using neutrase, alcalase, acid (0.03 N HCl, pH 2.5), protamex, protex 6L, flavorzyme, α-chymotrypsin, trypsin, and collupulin MG. The enzyme to substrate ratio was 1:25 (wt/wt) in all experiments. Using the 3-(4,5-dimethylthizol-2-yl)-2,5-diphenylatetetrazolium bromide (MTT) assay, the cytotoxicity of OTF and OTH was evaluated in human cancer cell lines of various tissue origins, including the lung (A549 and SK-MES-1), stomach (AGS), breast (MCF-7), larynx (Hep-2), cervix (HeLa), and liver (HepG2). The growth of all cancer cell lines was inhibited by both OTF and OTH in a dose-dependent manner. In particular, OTF displayed relatively high cytotoxicity (≤60% inhibition effects) at 40 mg/mL. At lower concentrations (≤5 mg/mL), however, OTF- and OTH-mediated cytotoxic effects were not significant in all cancer cell lines tested. The MCF-7 cells were the least sensitive to all treatments among all cancer cell lines tested. The OTH-trypsin and OTH-neutrase showed a potent cytotoxicity (over 90% cytotoxicity) to HeLa cells at the 10 mg/mL level. The OTH-trypsin, OTH-protamex, OTH-protex 6L, and OTH-collupulin MG caused 95, 96, 86, and 87% growth inhibition, respectively, in AGS cells. These results indicated there are possibilities that OTF and OTH can be used as natural growth inhibitors of human cancer cell lines.
    Poultry Science 02/2013; 92(2):424-34. · 1.54 Impact Factor
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    ABSTRACT: Recently, the superconductivity projects to develop commercial superconducting devices for extra high voltage transmission lines have been undergoing in many countries. One of the critical components to be developed for high voltage superconducting devices, including superconducting transformers, cables, and fault current limiters, is a high voltage bushing, to supply high current to devices without insulating difficulties, that is designed for cryogenic environments. Unfortunately, suitable bushings for HTS equipment were not fully developed for some cryogenic insulation issues. Such high voltage bushings would need to provide electrical insulation capabilities from room temperature to cryogenic temperatures.In this paper, design factors of cryogenic bushings were discussed and test results of specimen were introduced in detail. First, the dielectric strength of three kinds of metals has been measured with uniform and non-uniform electrodes by withstand voltage of impulse and AC breakdown test in LN2. Second, puncture breakdown voltage of glass fiber reinforced plastics (GFRPs) plates has been analyzed with non-uniform electrodes. Finally, creepage discharge voltages were measured according to the configuration of non-uniform and uniform electrode on the FRP plate. From the test results, we obtained the basic design factors of extra high voltage condenser bushing, which could be used in cryogenic environment.
    Physica C Superconductivity 01/2013; 484:338–342. · 1.11 Impact Factor
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    ABSTRACT: HGMS (High Gradient Magnetic Separator) uses matrix to make high magnetic field gradient so that ferro- or para-magnetic particles can be attracted to them by high magnetic force. The magnetic force generated by the field gradient is several thousand times larger than that by background magnetic field alone. So the HGMS shows excellent performance compared with other magnetic separators. These matrixes are usually composed of stainless steel wires having high magnetization characteristics. This paper deals with superconducting HGMS which is aimed for purifying waste water by using stainless steel matrix. Background magnetic field up to 6 T is generated by a superconducting solenoid and the stainless steel matrixes are arranged inside of the solenoid. Based on magnetic field calculated by FEM (Finite Element Method), we could calculate magnetic force acting on a magnetic particle such as hematite and maghemite consisting of major impurities in the condenser water of a thermal power station.
    Physica C Superconductivity 01/2013; 484:333–337. · 1.11 Impact Factor
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    ABSTRACT: We report enhanced switching margin in perpendicular MTJ cells at 20nm node. By introducing a novel structure with superior pinned layer stability, stable magnetization switching without magnetostatic interference has been achieved. Wide switching field margins over 40s have been secured for reproducible STT switching as well as a tightly controlled Hoffset below 100Oe. Switching voltage margin of the novel structure are also wide enough to show definite STT switching.
    VLSI Technology (VLSIT), 2013 Symposium on; 01/2013
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    ABSTRACT: thin films were prepared on the Si substrate by radio frequency (RF) magnetron sputtering and then surface of the films were irradiated with intense Ar ion beam to investigate the effect of Ar ion irradiation on the properties and hydrogen gas sensitivity of the films. From atomic force microscope observation, it is supposed that intense Ar bombardments promote rough surface and increase gas sensitivity of films for hydrogen gas. The films that Ar ion beam irradiated at 6 keV show the higher sensitivity than the films were irradiated at 3 keV and 9 keV. These results suggest that the thin films irradiated with optimized Ar ion beam are promising for practical high-performance hydrogen gas sensors.
    Journal of the Korean Society for Heat Treatment. 11/2012; 25(6).
  • Smart Grid Research Conference; 11/2012
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    ABSTRACT: thin films were prepared on the Si substrate by radio frequency (RF) magnetron sputtering and then post deposition vacuum annealed to investigate the effect of annealing temperature on the structural properties and hydrogen gas sensitivity of the films. The films that annealed at show the higher sensitivity than the other films annealed at . From atomic force microscope observation, it is supposed that post deposition annealing promotes the rough surface and also, increase gas sensitivity of films for hydrogen gas. These results suggest that the vacuum annealed thin films at optimized temperatures are promising for practical high-performance hydrogen gas sensors.
    Journal of the Korean Society for Heat Treatment. 09/2012; 25(5).

Publication Stats

2k Citations
324.73 Total Impact Points


  • 2009–2014
    • National Fusion Research Institute
      Daiden, Daejeon, South Korea
  • 2005–2014
    • Chungnam National University
      • • Graduate School of Green Energy Technology
      • • College of Agriculture and Life Sciences
      Daiden, Daejeon, South Korea
  • 2000–2013
    • Ulsan University Hospital
      Urusan, Ulsan, South Korea
    • University of Minnesota Twin Cities
      • Department of Electrical and Computer Engineering
      Minneapolis, MN, United States
    • Seoul National University Hospital
      Sŏul, Seoul, South Korea
  • 2012
    • Korean Institute of Ceramic Engineering and Technology
      Sŏul, Seoul, South Korea
    • Hoseo University
      Onyang, South Chungcheong, South Korea
  • 2011–2012
    • Hanyang University
      • College of Medicine
      Sŏul, Seoul, South Korea
  • 2003–2012
    • Asan Medical Center
      • • Department of Gastroenterology
      • • Division of Liver Transplantation and Hepato-Biliary Surgery
      • • Division of Hepato-Biliary and Pancreas Surgery
      • • Department of Orthopedic Surgery
      Seoul, Seoul, South Korea
    • Pohang University of Science and Technology
      • Department of Electronic and Electrical Engineering
      Andong, North Gyeongsang, South Korea
  • 1996–2012
    • University of Ulsan
      • • Department of Materials Engineering
      • • Asan Medical Center
      • • Department of Surgery
      Ulsan, Ulsan, South Korea
  • 2001–2011
    • Ajou University
      Sŏul, Seoul, South Korea
  • 2010
    • Yonsei University
      • Department of Pharmacology
      Seoul, Seoul, South Korea
  • 2007–2010
    • National Veterinary Research Quarantine Service
      Sŏul, Seoul, South Korea
  • 2008
    • Seoul Metropolitan Children's Hospital
      Sŏul, Seoul, South Korea
  • 2000–2008
    • Korea University
      Sŏul, Seoul, South Korea
  • 2005–2006
    • Catholic University of Korea
      • • Department of Radiology
      • • College of Medicine
      Sŏul, Seoul, South Korea
  • 2000–2005
    • Sungkyunkwan University
      • School of Advanced Materials Science and Engineering (AMSE)
      Seoul, Seoul, South Korea
  • 2004
    • Korea Basic Science Institute KBSI
      Sŏul, Seoul, South Korea
    • Electronics and Telecommunications Research Institute
      Sŏul, Seoul, South Korea
  • 2001–2003
    • Cheju Halla University
      Tse-tsiu, Jeju, South Korea
  • 1997–2003
    • Seoul National University
      • • Department of Nuclear Medicine
      • • College of Pharmacy
      Sŏul, Seoul, South Korea
  • 1999–2001
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 1991–1992
    • Korea Institute of Science and Technology
      • Center for Opto-Electronic Convergence Systems
      Sŏul, Seoul, South Korea