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Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.3
The aim of this study is to investigate the structural evolution and mechanical properties of TiAlSiN coatings when processedby the arc ion plating method. To form a hard coating, Ti, Al, and Si powders were mechanically alloyed by planetary ballmilling; the powders were then densely compacted during a rapid sintering process into a ternary system coating, i.e. TiAlSi. The evolution of the structural phase from a powder to a compact material is dominated considerably by phase states suchas a supersaturated solid solution or intermetallic compounds. In the case of coating layers, the factors that determine thestructural evolution are associated with the phase stability of the nano-crystalline structure that in turn is associated withthe Ti/Al composition ratio. Motivated by this, we performed experiments to investigate the distribution of microstructures;the material’s binding energy, quantitative properties, transformation of crystal structure, and distribution of amorphous/crystalline were all recorded. In particular, the relationship between the physical and chemical properties during the coatingprocess is considered to be the dominant factor controlling the orientation and morphology of that zone (1, T, and 2). TheTiAlSiN coating layer was found to have hardness above 45 GPa and an adhesion above 100 N. In other words, understandingthe evolution and structure of TiAlSin helped us to produce a material with excellent properties that can be used as a hardcoating. Specifically, these properties were induced by a grain refinement of the nano-crystalline structure that correspondsto an increase in the silicon nitride contents.
Jeong‑Han Lee,Ik‑Hyun Oh,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9
Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4was fabricated by spark plasma sintering at 1400 ℃ ata constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried outfor 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. Itwas observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents,and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact wasfound to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical propertiesof the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to thepresence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zirconfrom a transgranular to a ductile component (fcc) where the crack tips could be absorbed.
Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
In this study, Al, Cr and Si fine powders were alloyed by planetary ball milling to investigate their microstructural evolution,following their mechanical alloying behavior. The formation of Al(Cr) supersaturated solid solution by the Cr grainsembedded in Al-matrix, which contributed substitutional structure is discussed in relation to their structural evolution inaccordance with the distortion of a crystal lattice. The compacts of Al–Cr–Si alloys were prepared by rapid sintering withina short time by dense consolidation above the density of 99.9% as the formation of intermetallics, except in the case of thedistribution of single-phases induced by the Al-melting. The formation behavior of intermetallics was dominated by dependenceon the structures of the milled-powder and subsequent sintering temperature. To estimate the consolidated behaviorsof compacts, various approaches derived from TEM and XRD analysis were taken to obtain microstructural evidences ofthe inter-diffusion, following the presence of thermally stable intermetallics.
A case of polysplenia syndrome with multiple intraabdominal anomalies
( Jeong Min Lee ),( Yang Hyun Baek ),( Sung Wook Lee ),( Sang Young Han ),( Seok Reyol Choi ),( Jong Hun Lee ),( Jin Seok Jang ),( Myung Hwan Roh ) 대한내과학회 2011 대한내과학회 추계학술대회 Vol.2011 No.1
Polysplenia syndrome is a rare disease with presence of multiple spleens in many different sizes and numbers, involving multiple congenital anomalies, such as cardiovascular anomalies, abdominal heterotaxia, major venous system and bronchial malformation. The spectrum ofabnormalities in patients with this syndrome is broad. It often occurs in childhood, only 25% of patients diagnosed with polysplenia survive past 5 years of age and only 10% survive into mid-adolescence because of associated anomalies. Severe cardiac malformations, biliary atresia, and duodenal atresia are the common causeds of death during infancy. Some patients with polysplenia syndrome have a normal heart or only minor cardiac defects, are often diagnosed incidentally in patients being treated for other disease. A 20 year old man presented with intermittent febrile sensation and cough. He was diagnosed with duodenal atresia shortly after birth, and had surgery. During the management of pneumonia, he complained of abdominal discomfort. An abdominal computed tomography(CT) showed multiple spleens, intestinal malrotation, hypoplasia of pancreas tail portion, and absence of the suprarenal inferior vena cava(IVC) with continuation of azygos vein. These findings are consistent with criteria of polysplenia syndrome. In Korea, few cases have been reported in adults and our case showed the incidental finding of polysplenia syndrome while examining the patient who comoplaining of abdominal discomfort and cough.
Sang Hun Lee,Myung Ho Jeong,Joon Ho Ahn,Dae Young Hyun,Kyung Hoon Cho,Min Chul Kim,Doo Sun Sim,Young Joon Hong,Ju Han Kim,Youngkeun Ahn,Jin Yong Hwang,Weon Kim,Jong Seon Park,Chang-Hwan Yoon,Seung Ho 대한내과학회 2022 The Korean Journal of Internal Medicine Vol.37 No.4
Background/Aims: Recurrent acute myocardial infarction (AMI) is an adverse cardiac event in patients with a first AMI. The predictors of recurrent AMI after the first AMI in patients who underwent successful percutaneous coronary intervention (PCI) have not been elucidated. Methods: We analyzed the data collected from 9,869 patients (63.2 ± 12.4 years, men:women = 7,446:2,423) who were enrolled in the Korea Acute Myocardial Infarction Registry-National Institute of Health between November 2011 and October 2015, had suffered their first AMI and had received successful PCI during the index hospitalization. Multivariable logistic regression analysis was performed to identify the independent predictors of recurrent AMI following the first AMI. Results: The cumulative incidence of recurrent AMI after successful PCI was 3.6% (359/9,869). According to the multivariable logistic regression analysis, the significant predictive factors for recurrent AMI were diabetes mellitus, renal dysfunction, atypical chest pain, and multivessel disease. Conclusions: In this Korean prospective cohort study, the independent predictors of recurrent AMI after successful PCI for the first AMI were diabetes mellitus, renal dysfunction, atypical chest pain, and multivessel disease.