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Sim, J.K.,Ashok, K.,Ra, Y.H.,Im, H.C.,Baek, B.J.,Lee, C.R. Elsevier 2012 CURRENT APPLIED PHYSICS Vol.12 No.2
In this paper, we propose low temperature co-fired ceramic-chip on board (LTCC-COB) package with improved thermal characteristics; no insulation layer exists between the LED chip and metal base. In actual measurement as well as in thermal simulation, the proposed LED lamp structure showed excellent thermal properties, compared with surface mound device-printed circuit board (SMD-PCB) package LED lamp. The optical output power, thermal distribution, current-voltage (I-V) and electroluminescence (EL) were measured and compared to analyze the characteristics of LTCC-COB package LED lamp with SMD-PCB package LED lamp. EL peak intensity of LTCC-COB package LED lamp is 1.75 times better than that of SDM-PCB package LED lamp. The thermal resistance between packing area and air was found to be 7.3 K/W and 7.9 K/W for LTCC-COB package and SMD-PCB package respectively. The proposed LTCC-COB packaged LED lamp is not only suitable for high power LED package due to its low thermal resistance but also a promising solution for illumination modules.
Lithium-silica nanosalt as a low-temperature electrolyte additive for lithium-ion batteries
Hamenu, L.,Lee, H.S.,Latifatu, M.,Kim, K.M.,Park, J.,Baek, Y.G.,Ko, J.M.,Kaner, R.B. Elsevier 2016 Current Applied Physics Vol.16 No.6
<P>A lithium-modified silica nanosalt (Li-SiO2, coded Li202) of hydrophobic fumed silica (R202) is synthesized to use as an electrolyte additive for lithium-ion batteries (LIBs) under low temperature conditions. The synthesis method consists of reacting the silica nanoparticles with LiH and consequently quickly reacting the conjugate silicate ions with 1,3-propanesultone as a surface stabilizer. The obtained Li202 nanosalt (2.5 wt%) is added into an electrolyte solution of 1.0 M LiPF6 dissolved in ethylene carbonate/propylene carbonate/ethylmethyl carbonate/diethyl carbonate (20:5:55:20 vol%) + 2 wt% vinylene carbonate. The electrolyte solution including the Li202 nanosalt shows higher ionic conductivity and superior electrochemical stability over 5 V, which is due to the stabilized surface group. The high-rate capability at -20 degrees C of the LiCoO2/graphite cell is particularly enhanced by adding Li202 nanosalt. In addition, excellent cycle performance at -20 degrees C endorses the use of Li202 nanosalt as a low-temperature electrolyte additive for LIBs. (C) 2016 Elsevier B.V. All rights reserved.</P>
Upregulation and secretion of macrophage inhibitory cytokine-1 (MIC-1) in gastric cancers
Baek, K.E.,Yoon, S.R.,Kim, J.T.,Kim, K.S.,Kang, S.H.,Yang, Y.,Lim, J.S.,Choi, I.,Nam, M.S.,Yoon, M.,Lee, H.G. Elsevier Scientific Pub. Co 2009 Clinica chimica acta Vol.401 No.1
Background: Macrophage inhibitory cytokine-1 (MIC-1), a distant member of the transforming growth factor (TGF)-β superfamily, has been reported to be upregulated and secreted from several cancers. We examined MIC-1 expression and secretion in gastric cancers. Methods: MIC-1 mRNA and protein levels in cancer tissues and cell lines were analyzed by RT-PCR and Western blot. MIC-1 expression in cancer tissues and its secretion in serum were analyzed using immunohistochemistry and ELISA. Results: MIC-1 was significantly upregulated in gastric cancer tissues and cell lines. MIC-1 was secreted from gastric SNU620 cells and its levels in the serum of cancer patients were 10-fold higher than those of healthy controls. In addition, the staining of MIC-1 expression was strongly increased in metastatic gastric cancers. Conclusions: MIC-1 was obviously overexpressed in gastric cancers and MIC-1 secretion into blood may be useful for the prediction of gastric cancer progression.
Baek, J.Y.,Kim, S.H.,Kang, C.I.,Chung, D.R.,Peck, K.R.,Ko, K.S.,Song, J.H. Elsevier Science 2016 INFECTION GENETICS AND EVOLUTION Vol.38 No.-
Since the introduction of the pneumococcal conjugate vaccine (PCV7) in Korea in 2003, the proportion of non-vaccine serotypes has increased. Among non-vaccine serotypes, serotype 11A is highly prevalent in Korea. We investigated the prevalence and characteristics of Streptococcus pneumoniae serotype 11A isolates in a Korean tertiary-care hospital, during 2004-2013. A total of 1579 non-duplicate clinical S. pneumoniae isolates, collected from 2004 to 2013, were included in this study. Serotype was determined by the capsular Quellung method, and in vitro susceptibility testing was performed by broth microdilution method. Multilocus sequence typing was performed to determine the genotypes of the S. pneumoniae isolates. We identified 90 serotype 11A isolates (5.7%). During this period, the proportion of serotype 11A has increased from 3.2% up to 13.2% (in 2012). Among the serotype 11A isolates, two main clonal complexes (CCs), CC166 and CC99, were identified. The increase of serotype 11A was mainly due to the increase of CC166 isolates, which have high antimicrobial resistance rates. In addition, we identified that 14 isolates, belonging to ST8279, ST9875, and ST3598 of CC166, were non-susceptible to all antimicrobial agents tested in this study. We identified the increase of S. pneumoniae serotype 11A in Korea, which mainly due to the expansion of a resistant clonal group, CC166.
Baek, K.,Shim, W. H.,Jeong, J.,Radhakrishnan, H.,Rosen, B. R.,Boas, D.,Franceschini, M.,Biswal, B. B.,Kim, Y. R. Springer Science + Business Media 2016 BRAIN STRUCTURE AND FUNCTION Vol.221 No.5
<P>The spontaneous cerebral hemodynamic fluctuations observed during the resting state have been frequently visualized using functional magnetic resonance imaging (rsfMRI). However, the neuronal populations and neuroelectric characteristics underlying the functional connectivity of cerebrohemodynamic activities are poorly understood. We investigated the characteristics of bi-hemispheric functional connectivity via electrophysiology and rsfMRI in the primary sensory cortex of rats anesthetized by alpha-chloralose. Unlike the evoked responses, the spontaneous electrophysiological activity was concentrated in the infragranular layers and could be classified into subtypes with distinctive current sources and sinks. Both neuroelectric and rsfMRI signals were interhemispherically correlated in a layer-specific manner, suggesting that there are independent neural inputs to infragranular and granular/supragranular layers. The majority of spontaneous electrophysiological activities were bilaterally paired with delays of up to similar to 50 ms between each pair. The variable interhemispheric delay implies the involvement of indirect, multi-neural pathways. Our findings demonstrated the diverse activity patterns of layer-specific electrophysiological substrates and suggest the recruitment of multiple, non-specific brain regions in construction of interhemispheric functional connectivity.</P>
Status of the KSTAR superconducting magnet system development
Kim, K.,Park, H.K.,Park, K.R.,Lim, B.S.,Lee, S.I.,Chu, Y.,Chung, W.H.,Oh, Y.K.,Baek, S.H.,Lee, S.J.,Yonekawa, H.,Kim, J.S.,Kim, C.S.,Choi, J.Y.,Chang, Y.B.,Park, S.H.,Kim, D.J.,Song, N.H.,Kim, K.P.,So International Atomic Energy Agency 2005 Nuclear fusion Vol.45 No.8
<P>The aim of the Korea superconducting tokamak advanced research (KSTAR) project is to develop a steady-state-capable advanced superconducting tokamak for establishing a scientific and technological basis for an attractive fusion reactor. Since the KSTAR mission includes the achievement of a steady-state-capable operation, the use of superconducting coils is an obvious choice for the magnet system. The KSTAR superconducting magnet system consists of 16 toroidal field (TF) and 14 poloidal field (PF) coils which include 8 central solenoid coils. Both the TF and PF coil systems use internally-cooled cable-in-conduit conductors (CICC). The TF coil system provides a magnetic field of 3.5 T at the plasma centre and the PF coil system provide a flux swing of 17 V s. The major achievement in the KSTAR magnet system development includes the development of CICC, a full size TF model coil, a background magnetic field generation coil system and the construction of a large scale superconducting magnet and the CICC test facility. TF and PF coils are at the stage of fabrication for the KSTAR completion in the year 2007.</P>
Barik, R.K.,Bera, A.,Tanwar, A.K.,Baek, I.K.,Min, S.H.,Kwon, O.J.,Lee, W.S.,Park, G.S. MPR Pub. Services 2013 INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HAR Vol.38 No.-
A novel synthesis approach for scandia-doped tungsten nano-powder using a sol-gel method is developed. It involves dissolving tungsten oxide at 300<SUP>o</SUP>C in the presence of a mixture of nitric acid, citric acid and ammonia. The dissolved tungsten oxide reacts with an aqueous solution of scandium nitrate in the liquid-liquid phase, which results in the homogeneous mixing of tungsten and scandium particles. A spherical shape particle was obtained due to the dissolving of tungsten oxide in the solution. Citric acid enhances the mixing of ions at the atomic scale, which affects the hydrolysis reactions and leads to the formation of the phase pure nano-particle. The synthesized nano-powder was characterized by SEM (Scanning Electron Microscopy), EDS (Energy-dispersive X-ray spectroscopy), TEM (Transmission Electron Microscopy), and XRD (X-ray Diffraction) analyses. The spherical morphology was observed via a SEM analysis and a narrow particle size distribution was noted by means of a TEM analysis. The XRD analysis of the powder showed the complete formation of the phase pure nano-particle with an average diameter of 50nm without any contamination by other materials.