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Correlation Between Constituent Phase and Weld Metal Properties in Ni-Reduced Duplex Stainless Steel
Youngchai Lee,Jae Hee Lee,Joonoh Moon,Tae‑Ho Lee,Changhee Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8
The intrinsic properties of austenite and ferrite on the mechanical properties and corrosion resistance of the duplex stainlesssteel weld metals was studied by substituting Ni with Mn, N, and Mn + N. The properties of the weldments fabricated throughgas tungsten arc welding (GTAW) were evaluated using tensile test, Vickers hardness, and potentiodynamic polarizationtests. The mechanical properties and corrosion resistance of the constituent phases were measured using nanoindentationand electron probe microanalysis, respectively. The austenite and ferrite phase fractions of the weld metal were maintainedat approximately 50:50, and no harmful phases degraded the properties. Excessive Mn decreased the corrosion resistance; alarge difference in corrosion resistance between austenite and ferrite also decreased the overall corrosion resistance. In thefiller metal in which Ni was replaced with only Mn or N, the austenite became harder than ferrite, as a result cracks initiatedinside the austenite. The tensile test showed that austenite, which became a relatively hard phase compared to ferrite accordingto the chemical composition, increased the yield strength and decreased the elongation of the weld metal.
Lee, Seung-Chul,Noh, Yun-Hee,Lee, Sunhee,Choi, Hwan-Won,Yoon, In-Joong,Kang, Shien-Young,Lee, Changhee The Korean Society of Veterinary Science 2018 大韓獸醫學會誌 Vol.58 No.3
The efficacy of the CA-2-MP120 vaccine, a cell culture-attenuated strain of virulent porcine reproductive and respiratory syndrome virus (PRRSV), was assessed in pigs. Despite the persistence of viremia in all vaccinated animals during the immunization period, the virus was not detected in vaccinated pigs following challenge. Furthermore, no pigs in the vaccinated group shed PRRSV nasally, orally or rectally throughout the experiment. Moreover, histopathological lung and lymph node lesions in the immunized group were much milder than those in the unimmunized and challenged group. These results indicated that CA-2-MP120 can provide effective protection against virulent wild-type PRRSV-2.
Lee, Sunhee,Son, Kyu-Yeol,Noh, Yun-Hee,Lee, Seung-Chul,Choi, Hwan-Won,Yoon, In-Joong,Lee, Changhee Elsevier 2017 Veterinary microbiology Vol.207 No.-
<P><B>Abstract</B></P> <P>Porcine epidemic diarrhea virus (PEDV) has emerged or re-emerged worldwide, posing a significant financial threat to major pig-producing countries. In the present study, a virulent Korean pandemic PEDV strain, KNU-141112, was serially propagated in Vero cells for up to 100 passages. Through cell culture adaptation, we obtained four distinct deletion (DEL) mutants by plaque purification followed by nucleotide sequencing of the spike (S)/ORF3 gene-coding region, which were designated KNU-141112-S DEL2, −S DEL5, −S DEL2/ORF3, and −S DEL5/ORF3. Further whole genome sequencing identified 12 or 14 amino acid changes in the cell-adapted DEL strains. Animal inoculation studies revealed that the virulence of both S DEL2/ORF3 and S DEL5/ORF3 viruses with a large 46-nt deletion in the intergenic portion of S and ORF3 was remarkably diminished, indicating viral attenuation in the natural host. Furthermore, these cell-adapted strains elicited potent neutralizing antibody responses in immunized pigs. Taken together, our data indicate that the cell-attenuated S DEL2/ORF3 and S DEL5/ORF3 strains are promising candidates for the development of a safe and effective live PEDV vaccine.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A virulent G2b PEDV strain KNU-141112 was subjected to Vero cell culture passage. </LI> <LI> Deletions (DEL) in S and ORF3 of KNU-141112 at high passage levels were identified. </LI> <LI> Cell-adapted KNU-141112 DEL strains were highly attenuated and immunogenic in pigs. </LI> <LI> Large deletions in ORF3 appear to be associated with PEDV attenuation in pigs. </LI> <LI> High-cell-passage KNU-141112 DEL strains can be live, attenuated vaccine candidates. </LI> </UL> </P>
Lee, Changhee,Rathi, Servin,Khan, Muhammad Atif,Lim, Dongsuk,Kim, Yunseob,Yun, Sun Jin,Youn, Doo-Hyeb,Watanabe, Kenji,Taniguchi, Takashi,Kim, Gil-Ho IOP 2018 Nanotechnology Vol.29 No.33
<P>Molybdenum disulfide (MoS<SUB>2</SUB>) based field effect transistors (FETs) are of considerable interest in electronic and opto-electronic applications but often have large hysteresis and threshold voltage instabilities. In this study, by using advanced transfer techniques, hexagonal boron nitride (hBN) encapsulated FETs based on a single, homogeneous and atomic-thin MoS<SUB>2</SUB> flake are fabricated on hBN and SiO<SUB>2</SUB> substrates. This allows for a better and a precise comparison between the charge traps at the semiconductor-dielectric interfaces at MoS<SUB>2</SUB>−SiO<SUB>2</SUB> and hBN interfaces. The impact of ambient environment and entities on hysteresis is minimized by encapsulating the active MoS<SUB>2</SUB> layer with a single hBN on both the devices. The device to device variations induced by different MoS<SUB>2</SUB> layer is also eliminated by employing a single MoS<SUB>2</SUB> layer for fabricating both devices. After eliminating these additional factors which induce variation in the device characteristics, it is found from the measurements that the trapped charge density is reduced to 1.9?×?10<SUP>11</SUP> cm<SUP>−2</SUP> on hBN substrate as compared to 1.1?×?10<SUP>12</SUP> cm<SUP>−2</SUP> on SiO<SUB>2</SUB> substrate. Further, reduced hysteresis and stable threshold voltage are observed on hBN substrate and their dependence on gate sweep rate, sweep range, and gate stress is also studied. This precise comparison between encapsulated devices on SiO<SUB>2</SUB> and hBN substrates further demonstrate the requirement of hBN substrate and encapsulation for improved and stable performance of MoS<SUB>2</SUB> FETs.</P>
Lee, Changhee,Kim, Youngnam,Jeon, Ji Hyun Elsevier 2016 VIRUS RESEARCH Vol.222 No.-
<P><B>Abstract</B></P> <P>The mitogen-activated protein kinase (MAPK) pathways, which are central building blocks in the intracellular signaling network, are often manipulated by viruses of diverse families to favor their replication. Among the MAPK family, the extracellular signal-regulated kinase (ERK) pathway is known to be modulated during the infection with porcine epidemic diarrhea virus (PEDV); however, involvement of stress-activated protein kinases (SAPKs) comprising p38 MAPK and c-Jun NH<SUB>2</SUB>-terminal kinase (JNK) remains to be determined. Therefore, in the present study, we investigated whether activation of p38 MAPK and JNK cascades is required for PEDV replication. Our results showed that PEDV activates p38 MAPK and JNK1/2 up to 24h post-infection, whereas, thereafter their phosphorylation levels recede to baseline levels or even fall below them. Notably, UV-irradiated inactivated PEDV, which can enter cells but cannot replicate inside them, failed to induce phosphorylation of p38 MAPK and JNK1/2 suggesting that viral biosynthesis is essential for activation of these kinases. Treatment of cells with selective p38 or JNK inhibitors markedly impaired PEDV replication in a dose-dependent manner and these antiviral effects were found to be maximal during the early times of the infection. Furthermore, direct pharmacological inhibition of p38 MAPK or JNK1/2 activation resulted in a significant reduction of viral RNA synthesis, viral protein expression, and progeny release. However, independent treatments with either SAPK inhibitor did not inhibit PEDV-induced apoptotic cell death mediated by activation of mitochondrial apoptosis-inducing factor (AIF) suggesting that SAPKs are irrelevant to the apoptosis pathway during PEDV infection. In summary, our data demonstrated critical roles of the p38 and JNK1/2 signaling pathways in facilitating successful viral infection during the post-entry steps of the PEDV life cycle.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PEDV infection activated p38 MAPK and JNK1/2 <I>in vitro</I>. </LI> <LI> UV-inactivated virus failed to induce p38 MAPK and JNK1/2 activation. </LI> <LI> Pharmacological inhibition of p38 MAPK or JNK activation impaired PEDV replication. </LI> <LI> SAPK cascades do not affect the apoptosis pathway during PEDV infection. </LI> <LI> PEDV exploits the p38 MAPK and JNK signaling pathways for optimal replication. </LI> </UL> </P>
Lee, Changhee,Jeong, Soon-Ki Elsevier 2018 ELECTROCHIMICA ACTA Vol.265 No.-
<P><B>Abstract</B></P> <P>We report on the effects of the changed hydration number of calcium ions due to the variation in the electrolyte concentration in a Prussian blue analogue electrode, CuHCF, and aqueous electrolyte system on its performance, for calcium-ion batteries (CIBs). As determined by Raman spectroscopy, the coordination number of the calcium ions, that is, the number of nitrate anions surrounding it in the aqueous electrolyte gradually increased upon increasing the electrolyte concentration from 1.0 to 8.4 mol dm<SUP>−3</SUP>. In other words, the hydration number of calcium ions gradually decreased. Additionally, the activation energy, <I>E</I> <SUB> <I>a</I> </SUB>, for the interfacial charge transfer during the process of calcium ion insertion into the CuHCF electrode was estimated from the temperature dependence of the charge transfer resistance in these aqueous electrolytes <I>via</I> electrochemical impedance spectroscopy. The <I>E</I> <SUB> <I>a</I> </SUB> value gradually decreased with increasing electrolyte concentration. These results are directly related to the electrochemical performance such as the discharge/charge capacities, rate capability, and cyclability in this system for CIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Prussian blue electrode/aqueous electrolyte system for calcium-ion battery is studied. </LI> <LI> Ca(NO<SUB>3</SUB>)<SUB>2</SUB> dissolved in water at various concentrations is used as the electrolyte. </LI> <LI> The radius of the hydrated Ca ion decreased with increasing Ca(NO<SUB>3</SUB>)<SUB>2</SUB> concentration. </LI> <LI> Superior electrochemical performance is achieved at high electrolyte concentration. </LI> </UL> </P>
Outbreak-Related Porcine Epidemic Diarrhea Virus Strains Similar to US Strains, South Korea, 2013
Lee, Sunhee,Lee, Changhee Centers for Disease Control and Prevention 2014 Emerging infectious diseases Vol.20 No.7
<P>In late 2013, outbreaks of porcine epidemic diarrhea virus (PEDV) infection recurred in South Korea. Genetic and phylogenetic analyses showed that isolates from the outbreaks were most closely related to emergent US strains of PEDV. These US strain–like PEDV variants are prevalent in South Korea and responsible for recent outbreaks in the country.</P>
Changhee Lee,Minjun Kim,Dongeon Kim,Joohyeok Choi,Eunsu Song,Minsu Park,Gi-dong Lee 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
Molecular orientation at an emission layer(EML) in OLEDs has a effects on the external quantum efficiency (EQE)[1,2]. Based on the angular dependence of the p-polarized fluorescent spectra, we have extracted the anisotropic factor using the Finite-Difference Time-Domain (FDTD) method so that the vertical and horizontal orientation coefficients(θv and θh) can be calculated. The effect of the Brewster angle on the thickness and refractive indices of the EML was investigated. The angular dependent fluorescence of PGH-02 (30 nm) EML was measured and each coefficient of the material was obtained.