Ki Young Kim

Samsung Advanced Institute of Technology, Usan-ri, Gyeonggi-do, South Korea

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Publications (161)

  • Iseul Park · Ki Young Kim · Joongmoo Byu
    Article · May 2016
  • Abid Ali · Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: To determine the near-surface shear wave velocities (Vs) and characterize seismic site conditions in Gangneung, on the east coast of South Korea, passive and active surface waves were recorded at 136 sites. Dispersion images of the Rayleigh waves were obtained by the spatial autocorrelation method and inverted to Vs models. From these one-dimensional Vs models, the depth to the soft bedrock, average Vs at the top of the bedrock, average Vs of the overburden layer, average Vs in the top 30-m interval (Vs 30 ), and average resonance frequency were estimated to be 16 ± 1 m, 481 ± 14 m/s, 254 ± 5 m/s, 374 ± 16 m/s, and 5.5 ± 0.3 Hz, respectively. A lower estimate for Vs 30 and a relatively thick overburden layer make the downtown and agricultural areas in the region more prone to significant ground amplifications. Multiple regression analysis of Vs 30 yielded a correlation coefficient of 0.79 with respect to the variables of elevation and topographic slope. Using this proxy-based empirical relationship, Vs 30 values were computed at 13,583 sites covering the entire city. A microzonation map, constructed based on the Vs 30 data, indicates that the ground in Gangneung is categorized mainly into B (44%), C (39%), and D (15%) National Earthquake Hazards Reduction Program site classes, with minor constituents assigned to the A and E classes.
    Article · Apr 2016 · Geosciences Journal
  • Geun-Hee Kwak · Ki Young Kim · Hwa-Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: Methionine sulfoxide reductase B3 (MsrB3), which is primarily found in the endoplasmic reticulum (ER), is an important protein repair enzyme that stereospecifically reduces methionine-R-sulfoxide residues. We previously found that MsrB3 deficiency arrests the cell cycle at the G1/S stage through up-regulation of p21 and p27. In this study, we report a critical role of MsrB3 in gene expression of heme oxygenase-1 (HO-1), which has an anti-proliferative effect associated with p21 up-regulation. Depletion of MsrB3 elevated HO-1 expression in mammalian cells, whereas MsrB3 overexpression had no effect. MsrB3 deficiency increased cellular reactive oxygen species (ROS), particularly in the mitochondria. ER stress, which is associated with up-regulation of HO-1, was also induced by depletion of MsrB3. Treatment with N-acetylcysteine as an ROS scavenger reduced augmented HO-1 levels in MsrB3-depleted cells. MsrB3 deficiency activated Nrf2 transcription factor by enhancing its expression and nuclear import. The activation of Nrf2 induced by MsrB3 depletion was confirmed by increased expression levels of its other target genes, such as γ-glutamylcysteine ligase. Taken together, these data suggest that MsrB3 attenuates HO-1 induction by inhibiting ROS production, ER stress, and Nrf2 activation.
    Article · Apr 2016 · Biochemical and Biophysical Research Communications
  • Abid Ali · Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: In Chuncheon, Wonju, and Gangneung in Gangwon province, Korea, seismic site conditions and microzonation were studied using the dispersion curves of Rayleigh waves at 313 sites by the extended spatial autocorrelation method. Using the shear-wave velocities (Vs) inferred from the fundamental mode of the dispersion curves, average depths to the bedrock (Db), Vs at the top of the bedrock (Vsb), of the overburden layer (Vso), and of the uppermost 30-m depth(Vs30) were determined. The resonance frequencies (fr) were also computed using both Db and Vso. The estimated averages of the three major cities are 13±0.4 m for Db, 479±7 m/s for Vsb, 255±3 m/s for Vso, 416±9 m/s for Vs30, and 5.9±0.2 Hz for fr. Among the cities, Gangneung has the least Vso, Vs30, and fr and the greater Db, which indicates the greater susceptibility to ground shaking in case of large earthquakes. Microzonation maps for the cities were yielded based on proxy-based Vs30 computed using the empirical relationships. The assembled maps indicate that the three cities are mainly classified into NEHRP classes B, C, and D with small proportions of A. Although no area of class E is estimated from the proxy-based Vs30, 13 of the recording sites in Gangneung actually belong to class E. This indicates greater susceptibility of seismic amplification in the city than the other two during large earthquakes. The microzonation maps with information of fr can be used effectively in seismic risk assessment, urban planning, and disaster management.
    Conference Paper · Apr 2016
  • [Show abstract] [Hide abstract] ABSTRACT: Persistent energy demands of portable electronic devices necessitate the development of efficient charging protocols for the lithium ion cells powering these applications. In addition to a minimization in charging time and cell degradation, an optimal profile needs to ensure the maximization of lithium intercalation in the electrodes. Thus an electrochemical understanding of the system is highly beneficial in the design of efficient charging profiles. In this work, in order to identify and assess charging profiles, the essential features of an electrochemical model is combined with a phenomenological nonlinear resistor description to develop a simplified hybrid electrochemical model for lithium ion cells. This structure of themodel allows for the simultaneous fast evaluation of charging profiles at the same time capturing the essential physical processes. Common charging protocols rely on a constant voltage charging segment, which is implemented here by the use of a new implicit analytical expression obtained for the charging current. The model outputs in various conditions are compared with experiments conducted on a commercial battery. Subsequently, alternate charging candidates are assessed using the model. To highlight the capability of the model, cyclic charge-discharge studies are conducted to quickly assess the degradation effects of the various charging profiles.
    Article · Jan 2016 · Journal of The Electrochemical Society
  • Ji Won Youn · Je-Beom Jeon · Kum Hee Seo · [...] · Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: The optimum rotational speed (RS) of a novel centrifugation method for obtaining high-purity Si separated from Al-Si melts was evaluated numerically and experimentally. Numerical calculations showed that the separation efficiency (Si to Al ratio in the separated solid) increases and finally reaches a plateau at a high RS. The calculated relationship between RS and the separation efficiency was consistent with experimentally measured data except for the removal of primary Si crystallites, which happened at centrifugation at 800 revolutions per minute (RPM). Based on the acquired data, it was established that 700 RPM is the optimal RS for our centrifugation apparatus (developed in a previous study) to maximize the separation efficiency.
    Article · Nov 2015 · Journal of Crystal Growth
  • Source
    Jee In Kim · Mi Ra Noh · Ki Young Kim · [...] · Kwon Moo Park
    [Show abstract] [Hide abstract] ABSTRACT: Methionine sulfoxide reductase A (MsrA), which stereospecifically catalyzes the reduction of methionine-S-sulfoxide, is an important reactive oxygen species (ROS) scavenger. Tissue fibrosis is a maladaptive repair process following injury, associated with oxidative stress. In this study, we investigated the role of MsrA in unilateral ureteral obstruction (UUO)-induced kidney fibrosis and its underlying mechanisms by using MsrA gene-deleted mice (MsrA(-/-)). MsrA deletion increased collagen deposition in the interstitium and the expression of collagen III and α-smooth muscle actin in the UUO kidneys, indicating that MsrA deficiency exacerbated the progression of UUO-induced kidney fibrosis. UUO reduced the kidney expression of MsrA, MsrB1, and MsrB2, thereby decreasing MsrA and MsrB activity. UUO increased hydrogen peroxide and lipid peroxidation levels and the ratio of oxidized glutathione (GSSG) to total glutathione (GSH) in the kidneys. The UUO-induced elevations in the levels of these oxidative stress markers and leukocyte markers were much higher in the MsrA(-/-) than in the MsrA(+/+) kidneys, the latter suggesting that the exacerbated kidney fibrosis in MsrA(-/-) mice was associated with enhanced inflammatory responses. Collectively, our data suggest that MsrA plays a protective role in the progression of UUO-induced kidney fibrosis via suppression of fibrotic responses caused by oxidative stress and inflammation. Copyright © 2015. Published by Elsevier Inc.
    Full-text Article · Jul 2015 · Free Radical Biology and Medicine
  • Abid Ali · Ki Young Kim
    Conference Paper · Jul 2015
  • Abid Ali · Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: To reveal seismic site characteristics among Chuncheon, Wonju and Gangneung in Gangwon-do, both active and passive seismic data were recorded to extract Rayleigh waves. Active data were acquired using an 8-kg wooden hammer. The seismic surface waves were recorded for 8, 30, and 64 s using twelve or twenty four 4.5-Hz geophones and digitized at 125, 250, and 500 Hz sample rates by a 24-channel engineering seismograph. Phase-velocity spectra of Rayleigh waves were derived by the extended spatial autocorrelation method. Shear-wave velocity models were retrieved from the dispersion curves of phase velocity using the damped least-squares inversion scheme. From these 1-D velocity models, computed values of mean Vs30 in Chuncheon, Wonju and Gangneung are 436±13, 423±12, and 365±15, respectively. Seismic zonation maps were yielded by multiple regression analysis on the inverted Vs data. The entire areas of Chuncheon, Wonju and Gangneung belong to B, C, D and E of NEHRP classes. In downtown and agricultural areas, both lower Vs30 and thick overburden layer make such areas susceptible to substantial ground shaking effects in case of seismic moment. Based on lower estimates of Vs30 in Gangneung comparing with Chuncheon and Wonju, it is inferred that Gangneung is more prone to ground amplification than others.
    Conference Paper · May 2015
  • Eun Seok Jang · Ki Young Kim · Suk Jun Kim
    Article · Apr 2015
  • Iseul Park · Ki Young Kim
    Article · Feb 2015
  • Ki Young Kim · Young-Gyu Park
    [Show abstract] [Hide abstract] ABSTRACT: Microtremors were analysed using the reference-dependent horizontal spectral (H/H) method and the horizontal-to-vertical spectral ratio (H/V) method to estimate site effects of the Cheongcheon earthen dam in Korea. Seismic vibrations were recorded on the dam's crest, at the toe of the dam, and in a downstream borehole using three-component accelerometers. The H/H peaks for crest versus toe-of-dam accelerations occurred at 3.1, 6.7 and 13.1Hz with ratios of 6.9, 11.4 and 8.9, respectively. The H/V peaks for the crest of the dam occurred at 3.0, 7.0 and 13.4Hz with ratios of 6.7, 7.8 and 5.6, respectively. The peak near 3Hz may correspond to depth to bedrock, whereas the other peaks at higher frequencies may reflect the geometrical effect of the dam or overtone responses to the thickness of dam fill overlying the clay core. For the toe data, from the H/V spectral ratio method, the basement boundary appeared as double peaks near 8 and 10Hz with corresponding amplification factors of 5.2 and 6.2. These may indicate a gradual change in velocity across the basement boundary at ∼10m depth. The third resonance, which occurred at 15Hz, may correlate with the refraction boundary at 5-6m depth in the overburden layer. Both the frequencies and magnitudes of resonance derived from the H/H and H/V methods are reasonably well matched to the theoretical response curves computed by the reflection and transmission matrix and the two-dimensional finite difference methods.
    Article · Jan 2015 · Exploration Geophysics
  • Source
    Abid Ali · Ki Young KIm
    [Show abstract] [Hide abstract] ABSTRACT: To determine the near-surface shear wave velocities (Vs) and seismic site characteristics in densely populated areas in Gangneung on the eastern coast of Korea, passive and active surface waves were recorded at 117 sites of low altitude using twelve or twenty four 4.5-Hz geophones and a 24-channel engineering seismograph during this year. An 8-kg wooden hammer was used as an active source. The seismic waves were recorded for 8 to 30 s and digitized at 125 to 500 Hz sample rates. Dispersion images of the Rayleigh waves were obtained by the extended spatial autocorrelation (ESPAC) method. At 46 recording sites, the overburden layer was too thick to investigate bedrock with this shallow geophysical method. Shear-wave velocity models were derived from the estimated dispersion curves using the damped least-squares inversion scheme. From these 1-D velocity models, estimated mean values of Vs at the top of bedrock, depth to the bedrock, average Vs of the overburden layer, and average Vs of the top 30-m depth (Vs30) are 672±37 m/s, 17±0.5 m, 253±9 m/s, and 343±15 m/s, respectively, in the 95% confidence range. The estimated values from the inverted profiles were interpolated to yield maps for the entire low altitude area. Most of the investigated areas in Gangneung belong to NEHRP site class D (58%), C (34%), E (4%), and B (4%). In downtown area, both the lower estimates of Vs30 and thick overburden layer make it more prone to significant ground amplifications. The computed correlation coefficients (r) of Vs30 with elevation and topographic gradient, on linear scales, are 0.7 and 0.6, respectively.
    Full-text Conference Paper · Dec 2014
  • Bok Hyun Kang · Yu Ran Gwak · Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: In this study, gas bubbling was used to deoxidise a copper melt. Prior to the deoxidation of copper, a water model was developed and evaluated to investigate the characteristics of bubbles produced by air injection with nozzles of different shapes and sizes. Bubble frequency, floating velocity and diameter were measured by a high speed video camera and were compared to theoretical results. Approximately 500 g of 99.9 % pure copper was melted in a graphite crucible by induction melting under an argon atmosphere. After samples were completely melted, CO gas was introduced from the nozzle into the copper melt to achieve deoxidisation. Oxygen concentrations in the melt were reduced to less than 6 ppm by CO gas bubbling. Electrical conductivities of the samples produced by CO bubbling were between 101.6 and 102.3 % IACS.
    Article · Oct 2014 · Transactions of the Indian Institute of Metals
  • Ki Young Kim · Je Beom Jeon · Jong Sik Shin
    [Show abstract] [Hide abstract] ABSTRACT: This study describes the formation of a primary silicon network during separation of an Al-30% Si melt and the process conditions to make bigger primary silicon crystals. As the crucible rotates in the centrifugal separation, the unfrozen aluminum-rich phase and small silicon particles are pushed outside through the openings in the silicon network. As a result, primary silicon crystals are separated in the form of a foam after centrifugation. The recovery of the silicon ranged from 13 to 18% depending on the location in the crucible. The size of the primary silicon achieved by changing the cooling rate and quenching temperature during solidification is also measured using a quenching furnace. Primary silicon particles exhibit a coarse, plate-like morphology, although small star-like silicon particles are also found in the aluminum-rich matrix. The fraction of plate silicon decreases, while the fraction of small globular silicon increases with an increasing cooling rate. The thickness of the primary silicon plate also decreases with an increasing cooling rate in the samples quenched at various temperatures during solidification.
    Article · Oct 2014 · Crystal Research and Technology
  • Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical, physical and chemical properties of the alloys should be removed. On the other hand, Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process. One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts. This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation, draining, filtration, electromagnetic separation and centrifugal separation, focused on the iron removal and on the separation of silicon in the solvent refining process.
    Article · Jul 2014 · China foundry
  • Arim Han · Keehoon Kim · Ki Young Kim
    Article · May 2014
  • Iseul Park · Ki Young Kim
    Article · May 2014
  • Ki Young Kim · Jong Sik Shin · Dong Wha Park
    [Show abstract] [Hide abstract] ABSTRACT: Pure silicon can be obtained from Al-Si alloys by a combination of solvent refining and centrifugation. Primary silicon crystals are separated in the form of a foam after centrifugation. A vertical centrifugal separator is used which needs no more effort for further separation since each part of the high and low silicon content is divided automatically into two pieces after centrifugation. This centrifugal method does not use the density difference between two phases as in other methods, but uses the order of solidification in Al-Si alloys. How to make the Si foam, its characteristics including its density and strength, and purity of the extracted Si particles after acid leaching are reviewed.
    Article · May 2014 · Materials Science Forum
  • Source
    Pavel Turalchuk · Orest Vendik · Irina Vendik · [...] · Ki Young Kim
    [Show abstract] [Hide abstract] ABSTRACT: A novel high-Q resonant structure comprising the bulk acoustic resonator (BAR) and inductive loop is proposed to be used for wireless power transmission system. The proposed resonant structure operating at MHz frequency range has significantly miniature size in relation to the electrical wavelength (<λ/100) that could be attractive in the field of biology and medicine applications. The efficiency of the wireless power transfer system consisting of ordinary transmitting loop and proposed resonant structure with diameter of 6 mm based on high-Q BAR has been estimated as higher than 60% at the distance 10 mm.
    Full-text Article · Mar 2014 · Microwave and Optical Technology Letters

Publication Stats

1k Citations

Institutions

  • 2012-2014
    • Samsung Advanced Institute of Technology
      Usan-ri, Gyeonggi-do, South Korea
  • 2012-2013
    • Korea University of Technology and Education
      • Department of Energy, Materials and Chemical Engineering
      창녕읍, Gyeongsangnam-do, South Korea
  • 2009-2012
    • National Cheng Kung University
      • Department of Physics
      臺南市, Taiwan, Taiwan
    • Hanyang University
      • Department of Industrial Engineering
      Sŏul, Seoul, South Korea
    • Korea Institute of Energy Research
      Sŏul, Seoul, South Korea
    • National Institute of Crop Science
      Sŏngnam, Gyeonggi Province, South Korea
  • 2000-2012
    • Kyungpook National University
      • • Department of Electronic Engineering
      • • School of Computer Science and Engineering
      • • Department of Electrical Engineering
      Daikyū, Daegu, South Korea
  • 2011
    • Sejong University
      Sŏul, Seoul, South Korea
  • 2008-2011
    • Korea Institute of Science and Technology
      Sŏul, Seoul, South Korea
    • Kangwon National University
      • Department of Geophysics
      Shunsen, Gangwon-do, South Korea
  • 2001-2009
    • Chung-Ang University
      • School of Mechanical Engineering
      Seoul, Seoul, South Korea
    • Chonnam National University Hospital
      Sŏul, Seoul, South Korea
  • 2003-2008
    • Information and Communications University
      Daiden, Daejeon, South Korea
    • Sungkyunkwan University
      • Department of Chemical Engineering
      Sŏul, Seoul, South Korea
  • 2007
    • Konyang University Hospital
      Gaigeturi, Jeju-do, South Korea
  • 2003-2007
    • Dongseo University
      • Department of International Logistics
      Tsau-liang-hai, Busan, South Korea
  • 2006
    • Electronics and Telecommunications Research Institute
      Sŏul, Seoul, South Korea
  • 2004-2006
    • Korea Institute of Industrial Technology
      Anzan, Gyeonggi Province, South Korea
    • Keimyung University
      Sŏul, Seoul, South Korea
  • 2002-2005
    • Konyang University
      • College of Medicine
      Ronsan, Chungcheongnam-do, South Korea
    • Hongik University
      • Department Electronic and Electrical Engineering
      Sŏul, Seoul, South Korea
  • 1997-2005
    • Pusan National University
      • • Department of Atmospheric Sciences
      • • Department of Industrial Engineering
      Tsau-liang-hai, Busan, South Korea
  • 1994-1999
    • Korea Advanced Institute of Science and Technology
      • Department of Chemical and Biomolecular Engineering
      Sŏul, Seoul, South Korea