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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, 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, Hyunho,Tyagi, Priyanka,Rhee, Seunghyun,Park, Myeongjin,Song, Jiyun,Kim, Jaehoon,Lee, Changhee IEEE 2017 IEEE journal of photovoltaics Vol.7 No.6
<P>We present the analysis of photovoltaic properties in perovskite solar cells to explore the impact of excitonic features, disorder, recombination, and space charge effects using temperature and photo-intensity dependence. Photo-intensity dependence reveals an enhancement of classical Einstein relation due to the presence of traps and formation of space charge effects resulting in reduced conductivity. Exciton versus free charge density upon photo-excitation is analyzed from temperature dependence of photocurrent. Temperature dependence of V-OC is excellently explained by considering a combined energetic disorder in a solar cell, and a moderately high value of variance similar to 125 meV is obtained.</P>
Camp2Vec: Embedding cyber campaign with ATT&CK framework for attack group analysis
Lee Insup,Choi Changhee 한국통신학회 2023 ICT Express Vol.9 No.6
As the cyberattack subject has expanded from individual to group, attack patterns have become a complicated form of cyber campaigns. Although detecting the attack groups that operated the cyber campaigns is an important issue, complex methods such as deep learning are difficult to use due to the lack of campaign data. This paper proposes Camp2Vec, a lightweight statistics-based embedding for cyber campaigns, enabling attack group detection. The proposed method models a relationship between a campaign and techniques in the ATT&CK® framework as a document and words. Experimental results with expert-labeled datasets prove that Camp2Vec identifies representative attack groups successfully.
Lee, Sunkyu,Kim, Changhee,Kwon, Dowan,Kim, Mi-Bo,Hwang, Jae-Kwan Hindawi 2018 Evidence-based Complementary and Alternative Medic Vol.2018 No.-
<P>Obesity, a metabolic disorder caused by an imbalance between energy intake and energy expenditure, is accompanied with fat accumulation and skeletal muscle atrophy.<I> Kaempferia parviflora</I> Wall. ex Baker, also called black ginger, is known to increase physical fitness performance and improve energy metabolism. In this study, we investigated whether<I> Kaempferia parviflora</I> extract (KPE) alleviates both obesity and muscle atrophy using<I> ob/ob</I> mice. Wild-type C57BL/6J and<I> ob/ob</I> mice were provided with a normal diet ad libitum, and<I> ob/ob</I> mice were orally given KPE at a dose of 100 mg/kg/day or 200 mg/kg/day for eight weeks. KPE significantly decreased body weight, fat volume, and fat weight without affecting appetite. It inhibited the expression of adipogenic transcription factors and lipogenic enzymes by upregulating AMP-activated protein kinase (AMPK) in epididymal fat. In contrast, it markedly increased the muscle fiber size, muscle volume, and muscle mass, resulting in the enhancement of muscle function, such as exercise endurance and grip strength. On the molecular level, it activated the phosphatidylinositol 3 kinase (PI3K)/Akt pathway, a key regulator in protein synthesis in skeletal muscle. KPE could be a promising material to alleviate obesity by inhibiting adipogenesis, lipogenesis, and muscle atrophy.</P>