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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, Illjoo,Park, Hyungkwon,Kim, Jaeick,Lee, Changhee Elsevier Sequoia 2016 Surface & coatings technology Vol.307 No.1
<P><B>Abstract</B></P> <P>Heavy steel automotive parts have been replaced with aluminum-based lightweight materials worldwide. In particular, grey cast iron engine blocks, which are very heavy components in vehicles, have been replaced by aluminum-silicon hypoeutectic alloys in order to reduce emissions and fuel consumption. However, aluminum alloys are not able to withstand severe engine cylinder conditions due to their poor mechanical properties. In this study, a Mo blended ferrous coating was fabricated using atmospheric plasma spraying to replace the grey cast iron liner in the automotive cylinder bore. Five fractions of Mo, 0, 5, 10, 15, and 20wt%, with ferrous powder were prepared to investigate the effect of Mo on the microstructure and mechanical properties of coatings. All of the Mo-added coating layers showed significantly improved mechanical properties, such as hardness and wear resistance compared to that of grey cast iron. However, as Mo content exceeded 10wt% of the blend, the tribological properties gradually degraded due to brittle fracture of Mo. As a result, 10wt% Mo blended with ferrous powder provided optimized mechanical properties and can be substitute for grey cast iron liners in the automotive industry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mo-added ferrous coating to protect the automotive engine was investigated and it showed excellent mechanical properties. </LI> <LI> The Mo fraction was optimized to maximize the tribological property and minimize the amount of Mo. </LI> <LI> The effect of Mo fraction in the coating later was proven by various mechanical property measurements. </LI> <LI> The effect of Mo on fracture mechanism was investigated based on the microstructure analysis. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( 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.
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 Changhee,Jung Yong Gi,Kim Hyo Yeol,Hong Sang Duk 대한비과학회 2022 Journal of rhinology Vol.29 No.2
Various invasive fungal infections can occur in immunocompromised hosts, and an acute invasive fungal infection (AIFI) can be fatal. Because of its high mortality rate, AIFI must be quickly diagnosed and treated, such as anti-fungal agents or surgical debridement. In an immunocompromised host, nasal herpes simplex infection, usually caused by herpes simplex virus (HSV) type-1, can have various clinical manifestations, some of which can mimic AIFI. However, the management of acute viral infection differs significantly from invasive fungal infections of the nose. A fast and accurate differential diagnosis is mandatory because a delay in the disease-specific treatment of acute invasive infections can lead to mortality. This report describes two immunocompromised patients with mucosal and skin lesions around the nose. We provide clinical clues when mucosal lesions of the nasal cavity and skin lesions around the nose develop in immunocompromised hosts.
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>
Lee, Youngho,Moon, Ohak,Lee, Honam,Lee, Bonggeun,Kang, Bongsoon,Hong, Changhee 동아대학교 정보기술연구소 2000 情報通信硏究所論文誌 Vol.8 No.1
In this paper, we propose an algorithm, an optimized architecture, and an implementation for an improved performance of image downscaler. The proposed downscaler uses two-dimensional digital filters for horizontal and vertical scalings, respectively. It also improves scaling precisions and decreases the loss of data, compared with the 1/32 scaler. In order to achieve the optimization, the digital filters are implemented by the multiplexer-adder type scheme. The scaler is designed by using the Verilog-HDL. It is synthesized into gates by using the SAMSUNG 0.35um STD90 TLM.
Changhee Lee,Eiji Tomota,Nobuyuki Kawahara,Kyungbin Lim,MoonChul Kim 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
Non-intrusive measurement of transient unburned gas temperatures was developed with a fiber-optic heterodyne interferometry system. Using the value of the Gladstone-Dale constant for DME gas and combustion pressure we can calculate the in-cylinder temperature inside unburned and burned region. In this experimental study, it was performed to set up a fiber-optic heterodyne interferometry technique to measure the temperature before and behind the combustion region in a DME-HCCI engine. At first, measured temperature was almost the same as the temperature history assuming that the process that changes of the unburned and the burned are polytropic. In addition, we measured the temperature after combustion which of condition was burned gas with DME-HCCI combustion.