Corrosion Behavior of Inconel X-750 for Carbon Anode Oxide Reduction Application

Jeon, Min Ku,Kim, Sung-Wook,Lee, Sang-Kwon,Choi, Eun-Young Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.3

The corrosion behavior of the Inconel X-750 alloy was investigated for its potential application under a Cl₂-O₂ mixed gas flow in an Ar atmosphere. The corrosion rate was found to be negligible at temperatures up to 400℃ under a flow rate of 30 mL·min^-1 Cl₂ + 170 mL·min^-1 Ar, whereas an exponential increase was observed in the corrosion rate at temperatures greater than 500℃. The suppression of the corrosion reaction due to the presence of O₂ was verified experimentally at flow rates of 30 mL·min^-1 Cl₂ (4.96 g·m^-2·h^-1), 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂ (2.02 g·m^-2 ·h^-1), and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂ (1.34 g·m^-2·h^-1) under a constant Ar flow rate of 170 mL·min^-1 at 600℃ for 8 h. The surface morphology analysis results revealed that porous surfaces with tunnel-type holes were produced under the Cl₂-O₂ mixed-gas condition. Furthermore, the effects of the Cl₂ flow rate on the corrosion rate were investigated, indicating that its impact was negligible within the range of 5-30 mL·min^-1 Cl₂ at 600℃.

Corrosion Behavior of Hastelloy C-276 for Carbon-anode-based Oxide Reduction Applications

Jeon, Min Ku,Kim, Sung-Wook,Choi, Eun-Young Korean Radioactive Waste Society 2020 방사성폐기물학회지 Vol.18 No.3

The corrosion behavior of Hastelloy C-276 was investigated to identify its applicability for carbon-anode-based oxide reduction (OR), in which Cl₂ and O₂ are simultaneously evolved at the anode. Under a 30 mL·min^-1 Cl₂ + 170 mL·min^-1 Ar flow, the corrosion rate was less than 1 g·m^-2·h^-1 up to 500℃, whereas the rate increased exponentially from 500 to 700℃. The effects of the Cl₂-O₂ composition on the corrosion rate at flow rates of 30 mL·min^-1 Cl₂, 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂, and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂ with a constant 170 mL·min^-1 Ar flow rate at 600℃ was analyzed. Based on the data from an 8 h reaction, the fastest corrosion rate was observed for the 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂ case, followed by 30 mL·min^-1 Cl₂ and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂. The effects of the chlorine flow rate on the corrosion rate were negligible within the 5-30 mL·min^-1 range. A surface morphology analysis revealed the formation of vertical scratches in specimens that reacted under the Cl₂-O₂ mixed gas condition.

Ultrasonic Degradation of Endocrine Disrupting Compounds in Seawater and Brackish Water

So Young Park,Jong Sung Park,Ha Yoon Lee,Ji Yong Heo,Yeo Min Yoon,Kyung Ho Choi,Nam Guk Her 대한환경공학회 2011 Environmental Engineering Research Vol.16 No.3

In this study, a series of experiments was conducted on the relative degradation of commonly known endocrine-disrupting compounds such as bisphenol A (BPA) and 17α-ethinyl estradiol (Ee₂) in a single-component aqueous solution using 28 and 580 kHz ultrasonic reactors. The experiments were conducted with three different types of model water: deionized water (DI), synthetic brackish water (SBW), and synthetic seawater (SSW) at pH 4, 7.5, and 11 in the presence of inert glass beads and humic acids. Significantly higher sonochemical degradation (93-97% for BPA) occurred at 580 kHz than at 28 kHz (43-61% for BPA), regardless of water type. A slightly higher degradation was observed for Ee₂ compared to that of BPA. The degradation rate of BPA and Ee₂ in DI water, SBW, and SSW after 30 min of ultrasound irradiation at 580 kHz increased slightly with the increase in pH from 4 (0.073-0.091 min-1 for BPA and 0.081-0.094 min-1 for Ee₂) to 7.5 (0.087-0.114 min-1 for BPA and 0.092?0.124 min-1 for Ee₂). In contrast, significant degradation was observed at pH 11 (0.149-0.221 min-1 for BPA and 0.147-0.228 min-1 for Ee₂). For the given frequencies of 28 and 580 kHz, the degradation rate increased in the presence of glass beads (0.1 mm and 25 g) for both BPA and Ee₂: 0.018-0.107 min-1 without beads and 0.052-0.142 min-1 with beads for BPA; 0.021-0.111 min-1 without beads and 0.054-0.136 min-1 with beads for Ee₂. A slight increase in degradation of both BPA and Ee₂ was found as the concentration of dissolved organic carbon (DOC, humic acids) increased in both SBW and SSW: 0.107-0.115 min-1 in SBW and 0.087-0.101 min-1 in SSW for BPA; 0.111-0.111 min-1 in SWB and 0.092-0.105 min-1 in SSW for Ee₂. After 30 min of sonicating the humic acid solution, DOC removal varied depending on the water type: 27% (3 mg L-1) and 7% (10 mg L-1) in SBW and 7% (3 mg L-1) and 4% (10 mg L-1) in SSW.

Prognostic Value of Multidetector Coronary Computed Tomography Angiography in Relation to Exercise Electrocardiogram in Patients With Suspected Coronary Artery Disease

Cho, I.,Shim, J.,Chang, H.J.,Sung, J.M.,Hong, Y.,Shim, H.,Kim, Y.J.,Choi, B.W.,Min, J.K.,Kim, J.Y.,Shim, C.Y.,Hong, G.R.,Chung, N. Elsevier Biomedical 2012 JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY - Vol.60 No.21

Objectives: This study was designed to determine the prognostic value of multidetector coronary computed tomography angiography (CTA) in relation to exercise electrocardiography (XECG) findings. Background: The prognostic usefulness of coronary CTA findings of coronary artery disease in relation to XECG findings has not been explored systematically. Methods: Patients with suspected coronary artery disease who had undergone both coronary CTA and XECG (<90 days between tests) from 2003 through 2009 were enrolled retrospectively. Coronary CTA results were classified according to the severity of maximal stenosis (normal, mild: <40% of luminal stenosis, moderate: 40% to 69%, severe: ≥70%), XECG results were categorized as positive and negative, and Duke XECG score was calculated. Clinical follow-up data were collected for major adverse cardiac events (MACE): cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, and revascularization after 90 days from index coronary CTA. C-statistics were calculated to compare discriminatory values of each test. Results: Among the 2,977 (58 +/- 10 years) study patients, 12% demonstrated positive XECG results. By coronary CTA, patients were categorized as normal (56%) or having mild (26%), moderate (13%), or severe (5%) disease. During a median follow-up of 3.3 years (interquartile range: 2.3 to 4.6), 97 MACE were observed and the 5-year cumulative event rate was 3.6% (95% confidence interval: 3.0 to 4.3). Although both XECG (C-statistic: 0.790) and coronary CTA (C-statistic: 0.908) improved risk stratification beyond clinical risk factors (C-statistic: 0.746, p < 0.05 for all), XECG in addition to coronary CTA (C-statistic: 0.907) did not provide better discrimination than coronary CTA alone (p = 0.389). In subgroup analyses, coronary CTA stratified risk of MACE in groups with both positive and negative XECG results (all p < 0.001 for trend). However, positive XECG results predicted risk of MACE on coronary CTA only in the moderate stenosis group (hazard ratio: 2.58, 95% confidence interval: 1.29 to 5.19, p = 0.008) and severe stenosis group (hazard ratio: 2.28, 95% confidence interval: 1.19 to 4.38, p = 0.013). Conclusions: In patients with suspected coronary artery disease, coronary CTA discriminates future risk of MACE in patients independent of XECG results. Compared with coronary CTA, XECG has an additive prognostic value only in patients with moderate to severe stenosis on coronary CTA.

Endoscopic submucosal tunnel dissection salvage technique for ulcerative early gastric cancer.

Choi, Hyuk Soon,Chun, Hoon Jai,Seo, Min Ho,Kim, Eun Sun,Keum, Bora,Seo, Yeon Seok,Jeen, Yoon Tae,Lee, Hong Sik,Um, Soon Ho,Kim, Chang Duck,Ryu, Ho Sang WJG Press 2014 WORLD JOURNAL OF GASTROENTEROLOGY Vol.20 No.27

<P>Endoscopic submucosal dissection is an effective treatment modality for early gastric cancer (EGC), though the submucosal fibrosis found in ulcerative EGC is an obstacle for successful treatment. This report presents two cases of ulcerative EGC in two males, 73- and 80-year-old, with severe fibrosis. As endoscopic ultrasonography suggested that the EGCs had invaded the submucosal layer, the endoscopic submucosal tunnel dissection salvage technique was utilized for complete resection of the lesions. Although surgical gastrectomy was originally scheduled, the two patients had severe coronary heart disease, and surgeries were refused because of the risks associated with their heart conditions. The endoscopic submucosal tunnel dissection salvage technique procedures described in these cases were performed under conscious sedation, and were completed within 30 min. The complete en bloc resection of EGC using endoscopic submucosal tunnel dissection salvage technique was possible with a free resection margin, and no other complications were noted during the procedure. This is the first known report concerning the use of the endoscopic submucosal tunnel dissection salvage technique salvage technique for treatment of ulcerative EGC. We demonstrate that endoscopic submucosal tunnel dissection salvage technique it is a feasible method showing several advantages over endoscopic submucosal dissection for cases of EGC with fibrosis. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.</P>

A Colorimetric Microplate Assay Method for High Throughput Analysis of Lipase Activity

Choi, Suk-Jung,Hwang, Jung-Min,Kim, Sung-Il Korean Society for Biochemistry and Molecular Biol 2003 Journal of biochemistry and molecular biology Vol.36 No.4

The present work describes a colorimetric microplate assay for lipase activity based on the reaction between 5,5'-dithiobis(2-nitro benzoic acid) (DTNB) and the hydrolysis product of 2,3-dimercapto-1-propanol tributyrate (DMPTB). Reaction mixtures containing DTNB, DMPTB, and lipase were prepared in microplate wells, and the absorbance at 405nm was recorded after incubation at $37^{\circ}C$ for 30 min. A linear relationship was obtained in the range of 0.1-1 U of lipase activity by this method. The reaction conditions were also optimized for the range of 0.01-0.1 U or 1-10 U. When assaying crude tissue extracts, the reaction of DTNB with non-specific reducing agents created a major source of error. However, this error was corrected by the use of blank samples that did not contain DMPTB.

Nanogenerators: Fully Rollable Transparent Nanogenerators Based on Graphene Electrodes (Adv. Mater. 19/2010)

Choi, Dukhyun,Choi, Min-Yeol,Choi, Won Mook,Shin, Hyeon-Jin,Park, Hyun-Kyu,Seo, Ju-Seok,Park, Jongbong,Yoon, Seon-Mi,Chae, Seung Jin,Lee, Young Hee,Kim, Sang-Woo,Choi, Jae-Young,Lee, Sang Yoon,Kim, Jo WILEY-VCH Verlag 2010 ADVANCED MATERIALS Vol.22 No.19

<B>Graphic Abstract</B> <P>The cover shows an image of fully rollable transparent nanogenerators synthesized using chemical vapor deposition grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO nanorod arrays. Sang-Woo Kim, Jae-Young Choi, and co-workers report on p. 2187 the electrical and structural stability of the nanogenerators, with excellent charge scavenging performance under external mechanical loads such as bending and rolling. This study shows that graphene-based nanogenerators are very promising for self-powered rollable transparent device applications. <img src='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content.gif' alt='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content'> </P>

A Colorimetric Microplate Assay Method for High Throughput Analysis of Lipase Activity

Choi, Suk-Jung,Hwang, Jung Min,Kim, Sung Il 한국생화학분자생물학회 2003 BMB Reports Vol.36 No.4

The present work describes a colorimetric microplate assay for lipase activity based on the reaction between 5,5'-dithiobis(2-mitro benzoic acid)(DTNB) and the hydrolysis product of 2,3-dimercapto-1-propanol tributyrate (DMPTB). Reaction mixtures containing DTNB, DMPTB, and lipase were prepared in microplate wells, and the absorbance at 405nm was recorded after incubation at 37℃ for 30 min. A linear relationship was obtained in the range of 0.1-1 U of lipase activity by this method. The reaction conditions were also optimized for the range of 0.01-0.1 U or 1-10 U. When assaying crude tissue extracts, the reaction of DTNB with non-specific reducing agents created a major source of error. However, this error was corrected by the use of blank samples that did not contain DMPTB.

Effects of Mechanical Stimulation on the Proliferation of Bone Marrow-derived Human Mesenchymal Stem Cells

Choi, Kyung-Min,Seo, Young-Kwon,Yoon, Hee-Hoon,Song, Kye-Yong,Kwon, Soon-Yong,Lee, Hwa-Sung,Park, Jung-Keug Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.6

To support and enhance the in vitro growth and activity of mesenchymal stem cells (MSCs), the cell culture medium may be supplemented with various proteins and factors to mimic the physiological environment in which the cells optimally proliferate and differentiate. In this study, the effects of mechanical factors on cellular metabolic responses were investigated experimentally using a bioreactor. The effects of various chemical factors, such as growth factors, cytokines, and hormones, were also investigated. Based on previous reports demonstrating the important roles of mechanical factors in the growth and activity of MSCs, we sought to evaluate the effects of mechanical stimuli on the proliferation of bone marrow-derived MSCs using a cell training bioreactor that imposed cyclic mechanical stretch, with parameters of 240 min/day, 0.03 Hz, and $5{\sim}15%$ strain. The application of cyclic stretch $(5{\sim}15%\;strain)$ to the MSCs enhanced their proliferation during the early stage(3 days), but not the late stage (14 days), of batch culture. Mechanical stretch did not increase the release of lactate dehydrogenase (LDH) from the MSCs during culture. Appropriate levels of mechanical stretch $(5{\sim}10%\;strain)$ increased collagen synthesis, but did not alter MSC stretch was able to serve as a potent positive modulator of MSC proliferation during the initial stages of culture.

Effects of Supercritical Carbon Dioxide Treatment on Meat Quality and Sensory Evaluation in Soy Sauce and Hot-pepper Paste Marinated Pork

Choi, Young Min,Lee, Sang Hoon,Choe, Jee Hwan,Kim, Kyoung Heon,Rhee, Min Suk,Kim, Byoung Chul Korean Society for Food Science of Animal Resource 2013 한국축산식품학회지 Vol.33 No.5

The objective of this study was to investigate the effects of supercritical carbon dioxide (SC-$CO_2$) treatment on meat quality and sensory evaluation of marinated pork. Meat marinated in two traditional Korean marinades, soy sauce and hot-pepper paste, and raw marinated meat were then treated with 7.4, 12.2, or 15.2 MPa $CO_2$ at $31.1^{\circ}C$for 10 min. The SC-$CO_2$ treatments had no effect on the meat pH (p>0.05) or Warner-Bratzler shear force (p>0.05). There was no significant difference (p>0.05) in the total loss (sum of treatment loss and cooking loss) between the control and SC-$CO_2$ treated samples at 15.2 MPa (soy sauce marinated pork: 21.78 vs. 18.97%; hot-pepper marinated pork: 21.61 vs. 18.01%). After the SC-$CO_2$ treatment, lighter surface colors were observed in the treatment samples compared to those of the control samples (p< 0.001). However, tasting panelists were unable to distinguish a difference in color or in overall acceptability of the control and treatment (p>0.05). In the case of soy sauce marinated pork, when SC-$CO_2$ applied at 15.2 MPa and $31.1^{\circ}C$for 10 min, treatment samples showed a tenderer meat than the control samples. Therefore, the SC-$CO_2$ treatment conditions had no adverse effects on the sensory quality characteristics of the marinated meat products.