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℃.

Low Cost and Portable Parahydrogen Generator for the PHIP

Kwon, Soonmo,Min, Sein,Chae, Heelim,Namgoong, Sung Keon,Jeong, Keunhong 한국자기공명학회 2017 Journal of the Korean Magnetic Resonance Society Vol.21 No.4

In the developed NMR hyperpolarization techniques, Parahydrogen-Induced Polarization (PHIP) technique is widely utilized to overcome the low sensitivity of the NMR/MRI. Parahydrogen generator is essential to produce high spin order of parahydrogen molecule. Commercial parahydrogen generator is well developed with user-friendly systems. However, it has drawbacks of long preparation time (~ 2h including cooling down time of 1h) and high cost (~ 200 million won) for the commercial setup. We designed a simple and portable parahydrogen generating system with low cost (~ 2 million won), which produce polarization in less than 1 min. With the designed parahydrogen generator, we successfully performed the PHIP with Wilkinson's catalyst on styrene. This study will broaden the parahydrogen based polarization transfer study on many researchers by providing the simple portable and low cost parahydrogen generator.

Label-free, microfluidic separation and enrichment of human breast cancer cells by adhesion difference

Kwon, Keon Woo,Choi, Sung Sik,Lee, Sang Ho,Kim, Byungkyu,Lee, Se Na,Park, Min Cheol,Kim, Pilnam,Hwang, Se Yon,Suh, Kahp Y. GENERAL AND APPLIED CHEMISTRY JOURNALS 2007 LAB ON A CHIP Vol.7 No.11

<P>A label-free microfluidic method for separation and enrichment of human breast cancer cells is presented using cell adhesion as a physical marker. To maximize the adhesion difference between normal epithelial and cancer cells, flat or nanostructured polymer surfaces (400 nm pillars, 400 nm perpendicular, or 400 nm parallel lines) were constructed on the bottom of polydimethylsiloxane (PDMS) microfluidic channels in a parallel fashion using a UV-assisted capillary moulding technique. The adhesion of human breast epithelial cells (MCF10A) and cancer cells (MCF7) on each channel was independently measured based on detachment assays where the adherent cells were counted with increasing flow rate after a pre-culture for a period of time (<I>e.g.</I>, one, two, and four hours). It was found that MCF10A cells showed higher adhesion than MCF7 cells regardless of culture time and surface nanotopography at all flow rates, resulting in label-free separation and enrichment of cancer cells. For the cell types used in our study, an optimum separation was found for 2 hours pre-culture on the 400 nm perpendicular line pattern followed by flow-induced detachment at a flow rate of 200 µl min<SUP>−1</SUP>. The fraction of MCF7 cells was increased from 0.36 ± 0.04 to 0.83 ± 0.04 under these optimized conditions.</P> <P>Graphic Abstract</P><P>A label-free microfluidic cell separation and enrichment device is presented here by using cell adhesion as a physical marker. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b710054j'> </P>

Effect of Forging Type on the Deformation Heterogeneities in Multi‑Axial Diagonal Forged AA1100

Min‑Seong Kim,Sang‑Chul Kwon,Sun‑Tae Kim,Seong Lee,Hyo‑Tae Jeong,Shi‑Hoon Choi 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3

The present study investigated the effects that different types of forging exert on the deformation heterogeneities developedin AA1100 during multi-axial diagonal forging. To measure the deformation heterogeneities of deformed workpieces, thevalues for hardness and Kernel average misorientation were measured at the center section following each forging process. Type-D forging that consists of diagonal forging and return-diagonal forging was relatively advantageous compared withType-P forging that includes plane forging and return-plane forging for minimizing the non-uniformity of deformationdeveloped in workpieces. The effective strain developed in a workpiece during the 2 types of forging was simulated using3-D FEA. FEA revealed that the positions and degrees of occurrence for soft and hard-zones in workpieces vary greatlydepending on the forging type. Type-D forging was relatively advantageous compared with Type-P forging for minimizingthe non-uniformity of effective strain developed in workpieces.

공급사슬에서의 리스크 대응이 공급사슬통합과 리스크 관리 성숙도, 기업경영성과에 미치는 영향

박찬권(Park, Chan-Kwon),박성민(Park, Sung-Min),김채복(Kim, Chae-Bogk) 한국경영교육학회 2021 경영교육연구 Vol.36 No.2

[연구목적] 본 연구는 공급사슬에서 발생할 수 있는 리스크를 규명하고, 리스크에 대응하기 위한 과정에서 공급사슬통합의 필요성과 함께 리스크 관리 성숙도 제고가 기업경영성과 역시 제고할 수 있다는 것을 규명하는 것이다. 이를 위해 리스크 대응과 공급사슬통합, 리스크 관리 성숙도, 기업경영성과 간의 관계구조를 분석하고 시사점을 제공하는 것이다. [연구방법] 본 연구는 공급사슬에서 발생할 수 있는 리스크 유형, 공급사슬통합, 리스크 관리 성숙도, 기업경영성과에 대한 기존 선행연구들과 논의를 충분히 검토하였고 최종적으로 6개의 가설을 도출하였다. 연구목표 달성을 위해 국내 제조업체들을 대상으로 124개의 설문 자료를 수집하였다. 수집된 자료에 대해 신뢰성과 타당성을 검토하였고, Smart PLS 2.0을 활용하여 경로분석 방식으로 연구가설을 검증하였다. [연구결과] 내부리스크대응, 외부리스크대응, 공급사슬리스크대응은 공급사슬통합에 유의한 정(+)의 영향을 미치며, 내부리스크대응과 공급사슬리스크대응은 리스크관리성숙도에 정(+)의 영향을 미친다. 공급사슬통합과 리스크 관리 성숙도는 기업경영성과에 정(+)의 영향을 미친다. 또한 공급사슬통합은 외부리스크대응 및 공급사슬리스크대응과 기업경영성과 사이에서 매개변수의 역할을 하는 것으로 검정되었다. [연구의 시사점] 공급사슬에서의 리스크 대응, 공급사슬통합, 리스크 관리 성숙도, 기업경영성과 간의 전체적인 관계구조에 대하여 연구를 진행하였으며, 우리나라의 기업들에게 리스크 대응과 관련한 이론적, 실무적 시사점을 제공하였다. [Purpose] This study is to identify risks that may occur in the supply chain, and to identify that supply chain integration is necessary in the process of responding to the risks, and that corporate management performance can also be improved by enhancing risk management maturity. The purpose of this study was to analyze the relationship structure between risk response, supply chain integration, risk management maturity, and corporate management performance and to provide implications. [Methodology] This study has sufficiently reviewed the previous studies and discussions on the types of risks that can occur in the supply chain, supply chain integration, risk management maturity, and business management performance, and finally derived six hypotheses. For the study, 124 data were collected from domestic manufacturers. The reliability and validity of the collected data were reviewed, and the research hypothesis was verified through a path analysis method using Smart PLS 2.0. [Findings] Internal risk response, external risk response, and supplier chain integration have a significant positive (+) effect on supply chain integration, while internal risk response and supplier chain risk response have a positive (+) effect on risk management maturity. Supply chain integration and risk management maturity have a positive (+) effect on corporate management performance. In addition, it was verified that supply chain integration plays a role as a parameter between external risk response and supplier chain risk response and corporate management performance. [Implications] A study was conducted on the overall relationship structure between risk response in the supply chain, supply chain integration, risk management maturity, and corporate management performance, and provided theoretical and practical implications for risk response to Korean companies.

Effect of spark plasma sintering conditions on the thermoelectric properties of (Bi_0.25Sb_0.75)₂Te₃ alloys

Lim, Sang-Soon,Kim, Ju-Heon,Kwon, Beomjin,Kim, Seong Keun,Park, Hyung-Ho,Lee, Ki-Suk,Baik, Jeong Min,Choi, Won Jun,Kim, Dong-Ik,Hyun, Dow-Bin,Kim, Jin-Sang,Baek, Seung-Hyub Elsevier 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.678 No.-

<P><B>Abstract</B></P> <P>As a field-assisted technique, spark plasma sintering (SPS) enables densification of specimens in a very short period of time compared to other sintering techniques. For high performance thermoelectric material synthesis, SPS is widely used to fabricate nanograin-structured thermoelectric materials by rapidly densifying the nanopowders suppressing grain growth. However, the microstructural evolution behavior of thermoelectric materials by SPS, another important process during sintering, has been rarely studied. Here, we explore SPS as a tool to control the microstructure by long-time SPS. Using p-type (Bi<SUB>0.25</SUB>Sb<SUB>0.75</SUB>)<SUB>2</SUB>Te<SUB>3</SUB> thermoelectric materials as a model system, we systematically vary SPS temperature and time to understand the correlations between SPS conditions, microstructural evolution, and the thermoelectric properties. Our results show that the relatively low eutectic temperature (∼420 °C) and the existence of volatile tellurium (Te) are critical factors to determine both microstructure and thermoelectric property. In the liquid-phase sintering regime, rapid evaporation of Te leads to a strong dependence of thermoelectric property on SPS time. On the other hand, in the solid-phase sintering regime, there is a weak dependence on SPS time. The optimum thermoelectric figure-of-merit (Z) of 2.93 × 10<SUP>−3</SUP>/K is achieved by SPS at 500 °C for 30 min. Our results will provide an insight on the optimization of SPS conditions for materials containing volatile elements with low eutectic temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spark plasma sintering (SPS) is used to synthesize the thermoelectric (Bi<SUB>0.25</SUB>Sb<SUB>0.75</SUB>)<SUB>2</SUB>Te<SUB>3</SUB>. </LI> <LI> Liquid phase and volatile element are a key for the microstructure and thermoelectric property. </LI> <LI> Thermoelectric figure-of-merit of 2.9 × 10<SUP>−3</SUP>/K is achieved at 500 °C for 30 min. </LI> </UL> </P>

난치성 백반증에 대한 흡입물집을 이용한 비배양 표피세포이식술 20례

배정민 ( Jung Min Bae ),정한미 ( Han Mi Jung ),이한나 ( Han Na Lee ),이로우 ( Ro Woo Lee ),은성혜 ( Sung Hye Eun ),권혁선 ( Hyuck Sun Kwon ),이지혜 ( Ji Hae Lee ),김경문 ( Gyong Moon Kim ) 대한피부과학회 2018 대한피부과학회지 Vol.56 No.7

Background: As nonsurgical interventions for vitiligo are not always successful, various surgical modalities have been used in patients with refractory vitiligo. Of these, non-cultured epidermal suspension transplantation (NCES) was recently introduced to treat large recipient sites using cells from small donor tissue. Objective: We assessed the effectiveness and safety of NCES as a surgical treatment for patients with refractory vitiligo. Methods: We retrospectively reviewed 20 cases in 17 patients (11 females; median age 25 years) who underwent NCES from July 2015 through March 2018. Suction blisters (20 mm in diameter) were collected from the patient’s inner thigh at a donor-to-recipient area ratio of 1:5. After the addition of 5 mL recombinant trypsin solution to the suction blisters, followed by incubation at 37°C for 60 min, epidermal cells were manually scraped off the blister surface, and epidermal cell suspension was obtained by centrifugation at 1,500 RPM for 5 min. The suspension was applied to the vitiligo regions after epidermal ablation of those regions. Phototherapy resumed 1 month later. Treatment success was defined as ≥75% repigmentation of the surgical site, and all adverse events were noted. Results: Overall, 85.0% of cases (17/20) exhibited treatment success. Adverse events included hyperpigmentation (20%) and surgical site infection (5%), but the treatment was tolerable in all cases. Conclusion: NCES is a reliable surgical option for patients with vitiligo refractory to nonsurgical treatment. Large areas of vitiligo can be treated by NCES, and use of this technique should be encouraged in Korea. (Korean J Dermatol 2018;56(7):426∼432)

기계적 자극을 이용한 인체 중간엽줄기세포로부터 유사-섬유모세포로의 분화 유도

최경민 ( Kyung Min Choi ),서영권 ( Young Kwon Seo ),윤희훈 ( Hee Hoon Yoon ),권순용 ( Soon Yong Kwon ),이화성 ( Hwa Sung Lee ),박용순 ( Yong Soon Park ),손영숙 ( Young Sook Son ),송계용 ( Kye Yong Song ),김영진 ( Young Jin Kim 한국조직공학과 재생의학회 2006 조직공학과 재생의학 Vol.3 No.4

Recently, in vitro reconstruction of anterior cruciate ligament(ACL) has been tried using tissue engineering technique, especially mesenchymal stem cell(MSC) is considered as a good cell source. In this study, we tried to find the effect of mechanical stimulus on the differentiation of bone marrow-derived MSC into ACL fibroblastlike cell using a cell training bioreactor imposing cyclic mechanical tension whose parameters were 120 min/day, 1 Hz, and 5% strain. After 2 weeks of culture, MSCs under cyclic tension showed more regularly oriented alignment and lower expression of CD73 and CD105 than control by microscopy and FACS analysis. In transcriptional level, type I collagen, type II collagen, fibronectin, elastin, α-smooth muscle actin mRNA expressions of MSCs under cyclic tension were higher than control and similar to native ACL. In conclusion, it is thought that mechanical cyclic tension induced the loss of stemness of MSC, therefore improved the differentiation into ACL fibroblast-like cell.

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.

대학생들의 인터넷 사용정도에 따른 신체활동량과 신체구성의 관련성

김권민(Kim, Gwon-Min),박상갑(Park, Sang-Kab),권유찬(Kwon, Yoo-Chan) 한국체육과학회 2015 한국체육과학회지 Vol.24 No.3

The purpose of this study was to examine the association perceived physical activity patten and body composition according to habitual internet usage among university students. Data were analyzed for 500 students who responded to an self-reported based cross-sectional survey relating to socio-demographic variables, internet usage status, and a long version of the international physical activity questionnaire. Prevalence rate of physical activity status showed that 40.2% at 150 min/week over, 59.8% at 150 min/week under. Prevalence rate of internet usage showed that 94.6% at normal group, 3.0% at potential, 2.4% at addiction. Prevalence rate of physical activity levels of 150 min/week under according to internet usage status showed that 92.0% at normal, 4.3% at potential, 3.7% at addiction. In comparison with the physical activity levels was significantly more likely potential internet usage (OR, 4.82; 95% confidence Interval [95%CI], 1.07, 21.86; p〈.05) and addiction usage (OR, 8.00; 95% confidence interval [95%CI], 1.02, 62.56; p〈.05) The results revealed that physical activity levels correlates of internet usage status. This findings suggests the necessity of developing specific strategies for physical activity intervention by internet addiction among university students.