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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 ) 국어교육학회 2020 國語敎育學硏究 Vol.55 No.5
This study reviewed 41 domestic studies using a systematic literature analysis method to investigate the kind of research conducted in relation to digital reading in the research field of Korean language education. First, overall trends such as publication year, school level, and research method were examined. Studies on digital reading began in 2004 in the field of Korean language education, and a total of forty-one studies were selected. Among the 41studies, eleven studies (27%) were conducted on digital reading at the secondary school level. In addition, based on Coiro’s (2020) heuristics on digital reading, this study examines, how Korean digital reading studies were conducted in terms of text, readers, activities, and contexts. Regarding text, most (78%) focused on reading Internet text in an open Internet environment. Regarding readers, eight studies (44%) related to readers’ cognitive capabilities , followed by studies related to reading dispositions (39%). Regarding activity, with 7 items, online inquiry to solve problems ranked the highest. In case of context, most studies on digital reading in Korean language education are on reading on Internet web pages using computers. Based on this systematic literature review, this study proposes the following two discussions.
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, Hyunkoo,Kang, Chan-Mo,Park, Myeongjin,Kwak, Jeonghun,Lee, Changhee American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.6
<P>We demonstrated highly efficient inverted bottom-emission organic light-emitting diodes (IBOLEDs) using tin dioxide (SnO<SUB>2</SUB>) nanoparticles (NPs) as an electron injection layer at the interface between the indium tin oxide (ITO) cathode and the organic electron transport layer. The SnO<SUB>2</SUB> NP layer can facilitate the electron injection since the conduction band energy level of SnO<SUB>2</SUB> NPs (−3.6 eV) is located between the work function of ITO (4.8 eV) and the lowest unoccupied molecular orbital (LUMO) energy level of typical electron transporting molecules (−2.5 to −3.5 eV). As a result, the IBOLEDs with the SnO<SUB>2</SUB> NPs exhibited a decrease of the driving voltage by 7 V at 1000 cd/m<SUP>2</SUP> compared to the device without SnO<SUB>2</SUB> NPs. They also showed a significantly enhanced luminous current efficiency of 51.1 cd/A (corresponds to the external quantum efficiency of 15.6%) at the same brightness, which is about two times higher values than that of the device without SnO<SUB>2</SUB> NPs. We also measured the angular dependence of irradiance and electroluminescence (EL) spectra in the devices with SnO<SUB>2</SUB> NPs and found that they had a nearly Lambertian emission profile and few shift in EL spectrum through the entire viewing angles, which are considered as remarkable and essential results for the application of OLEDs to display devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-6/am302787y/production/images/medium/am-2012-02787y_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am302787y'>ACS Electronic Supporting Info</A></P>
Zero-line modes at stacking faulted domain walls in multilayer graphene
Lee, Changhee,Kim, Gunn,Jung, Jeil,Min, Hongki American Physical Society 2016 Physical Review B Vol.94 No.12
<P>Rhombohedral multilayer graphene is a physical realization of the chiral two-dimensional electron gas that can host zero-line modes (ZLMs), also known as kink states, when the local gap opened by inversion symmetry breaking potential changes sign in real space. Here we study how the variations in the local stacking coordination of multilayer graphene affects the formation of the ZLMs. Our analysis indicates that the valley Hall effect develops whenever an interlayer potential difference is able to open up a band gap in stacking faulted multilayer graphene, and that ZLMs can appear at the domain walls separating two distinct regions with imperfect rhombohedral stacking configurations. Based on a tight-binding formulation with distant hopping terms between carbon atoms, we first show that topologically distinct domains characterized by the valley Chern number are separated by a metallic region connecting AA and AA' stacking line in the layer translation vector space. We find that gapless states appear at the interface between the two stacking faulted domains with different layer translation or with opposite perpendicular electric field if their valley Chern numbers are different.</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>