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시효 열처리 된 Al-Si-Mg-Cu-(Ti) 합금의 고온 열팽창 계수 변화
최세원,Choi, Se-Weon 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.5
The relationship between precipitation and coefficient of thermal expansion of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments were studied by the thermodynamic analyzer (TMA) and differential scanning calorimetry (DSC). Solution heat treatment of the alloy was carried out at 535℃ for 6 h followed by water quenching, and the samples were artificially aged in the air at 180℃ and 220℃ for 5 h. The coefficient of thermal expansion (CTE) curve showed some residual strain and decreased with increasing aging temperature. The CTE curves changed sharply in the temperature range of 200℃ to 400℃, and the corresponding peak shifted for the aged samples due to the change in the precipitation behavior of the secondary phase. These transformation peaks in the aged sample are related to the volume of the precipitation of the Si phase as determined by DSC analysis. The change in CTE is mainly caused by the precipitation of the Si phase in the Al-Si alloy, and the size of the change occurs simultaneously with the size of the precipitate.
최세원,고태훈,홍기정,김경환 대한의료정보학회 2019 Healthcare Informatics Research Vol.25 No.4
Objectives: Triage is a process to accurately assess and classify symptoms to identify and provide rapid treatment to patients. The Korean Triage and Acuity Scale (KTAS) is used as a triage instrument in all emergency centers. The aim of this study was to train and compare machine learning models to predict KTAS levels. Methods: This was a cross-sectional study using data from a single emergency department of a tertiary university hospital. Information collected during triage was used in the analysis. Logistic regression, random forest, and XGBoost were used to predict the KTAS level. Results: The models with the highest area under the receiver operating characteristic curve (AUROC) were the random forest and XGBoost models trained on the entire dataset (AUROC = 0.922, 95% confidence interval 0.917–0.925 and AUROC = 0.922, 95% confidence interval 0.918–0.925, respectively). The AUROC of the models trained on the clinical data was higher than that of models trained on text data only, but the models trained on all variables had the highest AUROC among similar machine learning models. Conclusions: Machine learning can robustly predict the KTAS level at triage, which may have many possibilities for use, and the addition of text data improves the predictive performance compared to that achieved by using structured data alone.
Si 나노 입자와 Er<sup>3+</sup>를 공첨가한 SiO<sub>2</sub>계 도파로의 제작과 평가
최세원,고영호,장세훈,오익현,강창석,Choi, Se-Weon,Ko, Young-Ho,Chang, Se-Hun,Oh, Ik-Hyun,Kang, Chang-Seog 한국재료학회 2007 한국재료학회지 Vol.17 No.4
[ $SiO_2$ ]thin films containing Si-nanocrystals and $Er^{3+}$ were fabricated by the RF-sputtering method. Intense emission of $Er^{3+}$ was observed at 1530 nm region after the annealing of the film at $1050^{circ}C$ for 5 min. Channel waveguides were fabricated using such films for the core. The films containing Si higher than 2.4 at% exhibited the change in stress from compression to tension after annealing, which induced the fatal loss-increase in waveguide. The optical gain might be attained by the Er-doped waveguide with Si lower than 2.4 at% by a visible-light-excitation.
Al-Si-Mg-Cu 합금의 자동차 엔진 사용 온도에서 열처리 조건에 따른 열확산도 변화
최세원,Choi, Se-Weon 한국재료학회 2021 한국재료학회지 Vol.31 No.11
The precipitation effect of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments was studied using a laser flash device (LFA) and differential scanning calorimetry (DSC). Solid solution treatment was performed at 535 ℃ for 6 h, followed by water cooling, and samples were artificially aged in air at 180 ℃ and 220 ℃ for 5 h. The titanium-free alloy Al-6%Si-0.4%Mg-0.9%Cu showed higher thermal diffusivity than did the Al-6%Si-0.4%Mg-0.9%Cu-0.2%Ti alloy over the entire temperature range. In the temperature ranges below 200 ℃ and above 300 ℃, the value of thermal diffusivity decreased with increasing temperature. As the sample temperature increased between 200 ℃ and 400 ℃, phase precipitation occurred. From the results of DSC analysis, the temperature dependence of the change in thermal diffusivity in the temperature range between 200 ℃ and 400 ℃ was strongly influenced by the precipitation of θ'-Al<sub>2</sub>Cu, β'-Mg<sub>2</sub>Si, and Si phases. The most important factor in the temperature dependence of thermal diffusivity was Si precipitation.
Whole-genome DNA 프로브를 이용한 구강 Bacteroides 균종의 식별
최세원,이정숙,최선진,김각균 대한구강생물학회 1992 International Journal of Oral Biology Vol.16 No.1
The need for a rapid and sensitive microbiological assay has become necessary for both research and clinical diagnostic. This need has become clear as a result of extensive documentation linking specific bacterial species and periodontal destruction. DNA probe technology seems to be able to provide both a sensitive and specific assay and may be able to alleviate the concern for transport of fastidious microorganisms. We have been trying to establish the method of identifying the periodontopathic microorganisms by DNA probe. As the first step we tried to know if whole-genomic DNA probe could differentiate between bacterial species, using three different serotype-strains of both bacteroides gingivalis and bacteroides intermedius. Also we tested if there is any cross-hybridization between bacteroides spp· and Streptococcus spp. The experimental procedures were as follows: anaerobic culture of bacterial cells, preparation of whole-genomic DNA from bacteria and measurement of DNA concentration, immobilization of DNA onto a nitrocellulose filter using dot-blot apparatus after 2-fold serial dilution of DNA, radio-labelling of DNA with ^32P by random oligonucleotide-primed synthesis, which would serve as a DNA probe, blocking unbound nitrocellulose with 0.05×BLOTTO, hybridization of the filter with ^32P-labelled probe, and washing and detection of bound probe by autoradiography. The results were as follows. The whole-genomic DNA probe of B. gingivalis strain 381 (serotype a) was able to hybridize with all three serotypes a, b, and c) of the species. Also, the whole-genomic DNA probe of B. intermedius strain 9336 (serotype b) was able to hybridize with all three serotypes of the species. There was no detectable cross-hybridization between B. gingivalis and B. intermedius or bacteroides DNA probe with streptococcal DNA, within the range of DNA amount used in the experiment. The DNA probe was able to detect 3ng of homologous DNA in a dot. It seems likely that whole-genomic probe could be used for identification of Bacteroides spp, in the clinical samples using DNA probe, if a suitable method to lyse the cell on the filter is provided.
Al-Mg계 합금과 Al-Si계 합금의 다이캐스팅 응고과정의 차이
최세원,김영찬,조재익,강창석,홍성길,Choi, Se-Weon,Kim, Young-Chan,Cho, Jae-Ik,Kang, Chang-Seog,Hong, Sung-Kil 한국재료학회 2012 한국재료학회지 Vol.22 No.2
The effect of the alloy systems Al-Mg alloy and Al-Si alloy in this study on the characteristics of die-casting were investigated using solidification simulation software (MAGMAsoft). Generally, it is well known that the casting characteristics of Al-Mg based alloys, such as the fluidity, feedability and die soldering behaviors, are inferior to those of Al-Si based alloys. However, the simulation results of this study showed that the filling pattern behaviors of both the Al-Mg and Al-Si alloys were found to be very similar, whereas the Al-Mg alloy had higher residual stress and greater distortion as generated due to solidification with a larger amount of volumetric shrinkage compared to the Al-Si alloy. The Al-Mg alloy exhibited very high relative numbers of stress-concentrated regions, especially near the rib areas. Owing to the residual stress and distortion, defects were evident in the Al-Mg alloy in the areas predicted by the simulation. However, there were no visible defects observed in the Al-Si alloy. This suggests that an adequate die temperature and casting process optimization are necessary to control and minimize defects when die casting the Al-Mg alloy. A Tatur test was conducted to observe the shrinkage characteristics of the aluminum alloys. The result showed that hot tearing or hot cracking occurred during the solidification of the Al-Mg alloy due to the large amount of shrinkage.