페라이트-펄라이트 조직 아공석강의 상온 및 저온 충격 인성에 미치는 미세조직적 인자의 영향

이승용,정상우,황병철,Lee, Seung-Yong,Jeong, Sang-Woo,Hwang, Byoungchul 한국재료학회 2015 한국재료학회지 Vol.25 No.11

This paper presents a study on the room- and low-temperature impact toughness of hypoeutectoid steels with ferrite-pearlite structures. Six kinds of hypoeutectoid steel specimens were fabricated by varying the carbon content and austenitizing temperature to investigate the effect of microstructural factors such as pearlite volume fraction, interlamellar spacing, and cementite thickness on the impact toughness. The pearlite volume fraction usually increased with increasing carbon content and austenitizing temperature, while the pearlite interlamellar spacing and cementite thickness mostly decreased with increasing carbon content and austenitizing temperature. The 30C steel with medium pearlite volume fraction and higher manganese content, on the other hand, even though it had a higher volume fraction of pearlite than did the 20C steel, showed a better low-temperature toughness due to its having the lowest ductile-brittle transition temperature. This is because various microstructural factors in addition to the pearlite volume fraction largely affect the ductile-brittle transition temperature and low-temperature toughness of hypoeutectoid steels with ferrite-pearlite structure. In order to improve the room- and low-temperature impact toughness of hypoeutectoid steels with different ferrite-pearlite structures, therefore, more systematic studies are required to understand the effects of various microstructural factors on impact toughness, with a viewpoint of ductile-brittle transition temperature.

2개의 H형강이 합성된 가설교량 상부구조의 구조거동 평가

이승용,박영훈,박상현,Lee, Seung Yong,Park, Young Hoon,Park, Sang Hyun 대한토목학회 2013 대한토목학회논문집 Vol.33 No.1

본 논문에서는 가설교량의 지간장 증대를 위하여 중앙부 주거더 H형강 상단에 작은 H형강을 보강하고, 지점부 주거더 H형강 하단에 강판을 합성시킨 가설교량을 설계 및 시공하여 현장재하시험으로 실 거동을 분석하고, 해석적 전단좌굴강도와 비선형 거동을 일반 가설교량과 비교 평가하였다. 그 결과, 현장재하시험에 의하여 제안된 가설교량의 실제 거동이 설계 과정에서 고려된 거동과 일치하는 것으로 나타났으며, 본 연구의 설계조건에 있어서 제안한 가설교량의 해석적 전단좌굴강도가 일반 가설교량의 전단좌굴강도보다 약 40% 정도 높은 것으로 분석되었다. 또한 제안된 가설교량의 해석적 극한강도는 일반 가설교량 보다 높은 것으로 평가되어 현장여건의 필요에 의해 제안한 가설교량을 적용할 수 있을 것으로 판단된다. In this study, in order to increase the span length, the temporary bridge which the center part of span is strengthened by small H-beam and the end part of span is strengthened by steel plate is designed and constructed. Real behavior of proposed temporary bridge is analyzed by field loading test. Analyzed shear buckling strengths and nonlinear behavior of suggested temporary bridge are compared with the those of general temporary bridge. From the field loading test results, it is analyzed that real static behavior of suggested temporary bridge is agree with the analyzed behavior which is considered in design process. Under the proposed design condition, it is investigated that the shear buckling strength of suggested temporary bridge is about 40% higher than that of general temporary bridge, and the ultimate strength of suggested temporary bridge is about higher than that of general temporary bridge. From the study results, it is concluded that the proposed temporary bridge can be applied by the needs of field condition.

RF 열플라즈마를 이용한 Y₂O₃:Eu³⁺ 적색 나노 형광체 분말 합성

이승용,구상만,황광택,김진호,한규성,Lee, Seung-Yong,Koo, Sang-Man,Hwang, Kwang-Taek,Kim, Jin-Ho,Han, Kyu-Sung 한국결정성장학회 2015 한국결정성장학회지 Vol.25 No.6

$Y_2O_3:Eu^{3+}$ is an excellent red-emitting phosphor, which has been widely used for display devices due to highly luminescent property and chemical stability. In this study, $Y_2O_3:Eu^{3+}$ red phosphors were prepared using the solid state reaction and RF thermal plasma synthesis. The particle size of $Y_2O_3:Eu^{3+}$ phosphors obtained by the solid state reaction varied from 10 to $20{\mu}m$, and 30~100 nanometer sized $Y_2O_3:Eu^{3+}$ particles were obtained from a liquid form of raw material through RF thermal plasma synthesis without an additional heat treatment. Photoluminescence measurements of the obtained $Y_2O_3:Eu^{3+}$ particles showed a red emission peak at 611 nm ($^5D_0{\rightarrow}^7F_2$). PL intensity of red nano phosphors prepared by RF thermal plasma synthesis was comparable to that of red phosphors prepared by the solid state reaction, indicating that nano-sized $Y_2O_3:Eu^{3+}$ red phosphors could be successfully synthesized using one-step process of RF thermal plasma. $Y_2O_3:Eu^{3+}$는 우수한 적색 발광 특성을 가지고 있는 형광체로 최근 고화질 디스플레이에 대한 수요가 증가함에 따라 관련 연구가 활발히 진행되고 있다. 본 연구에서는 RF 열플라즈마 합성법과 고상법을 이용하여 $Y_2O_3:Eu^{3+}$ 적색 형광체를 합성하였으며, 합성 방법에 따른 $Y_2O_3:Eu^{3+}$ 적색 형광체의 결정 구조, 미세 구조, 발광 특성의 차이를 XRD, TEM, PL 분석을 통해 비교하였다. 고상법으로 합성된 $Y_2O_3:Eu^{3+}$ 적색 형광체의 입자는 약 $10{\sim}20{\mu}m$ 크기를 가지는 반면, RF 열플라즈마 합성법을 통해 합성된 적색 형광체는 반응부는 약 100 nm, 필터부는 약 30 nm의 크기를 갖는 나노 형광체로 확인되었다. 합성된 모든 분말들은 PL 측정결과 611 nm($^5D_0{\rightarrow}^7F_2$)에서 발광하는 것을 확인하였으며, 결정 크기와 입도가 증가할수록 PL intensity가 증가하였다. 또한, 추가 열처리 공정이 필요 없는 one-step 공정의 RF 열플라즈마 공정을 통해 합성된 $Y_2O_3:Eu^{3+}$ 적색 나노 형광체는 고상법으로 합성된 적색 형광체와 비슷한 발광 특성을 보이는 것을 확인할 수 있었다.

유도 열플라즈마를 이용한 카본나노시트 합성

이승용,고상민,구상만,황광택,한규성,김진호,Lee, Seung-Yong,Ko, Sang-Min,Koo, Sang-Man,Hwang, Kwang-Taek,Han, Kyu-Sung,Kim, Jin-Ho 한국결정성장학회 2014 韓國結晶成長學會誌 Vol.24 No.5

2차원 흑연구조를 갖는 카본나노시트는 큰 비표면적과 우수한 전기적, 화학적 및 기계적 물성으로 인하여 미래소재로 각광받고 있다. 경제적이고 쉬운 카본나노시트의 양산공정개발을 위해 본 연구에서는 메테인($CH_4$)과 프로페인($C_3H_8$) 가스를 이용한 유도 열플라즈마 공정을 통해 기상 합성하여 카본나노시트 분말을 합성하였다. 유도 열플라즈마를 이용한 카본나노시트 합성은 촉매나 증착공정 없이 진행되었으며, 합성된 카본나노시트의 물성을 TEM, Raman, XRD, BET로 분석하였다. 메테인과 프로페인으로부터 합성된 카본 나노시트는 각각 5~6개의 그래핀 층과 15~16개의 그래핀 층으로 이루어진 분말로 합성되었으며 분말의 크기는 약 100 nm임을 확인할 수 있었다. An ultrathin sheet-like carbon nanostructure provides an important model of a two-dimensional graphite structure with strong anisotropy in physical properties. As an easy and cheap route for mass production, RF thermal plasma synthesis of freestanding carbon nanosheet from $CH_4$ (Methane) and $C_3H_8$ (Propane) is presented. Using vapor synthesis process with RF inductively thermal plasma, carbon nanosheets were obtained without catalysts and substrates. The synthesized carbon nanosheets were characterized using transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. The carbon nanosheets synthesized using methane and propane generally showed 5~6 and 15~16 layers with a wrinkled morphology and size of approximately 100 nm.

Comparative Smoke Analysis of CORESTA Monitoring Cigarettes

이승용,지상운,신해근,Lee, Seung-Yong,Ji, Sang-Un,Shin, Hea-Geun The Korean Society of Tobacco Science 2011 한국연초학회지 Vol.33 No.1

This experiment was conducted as a part of Asia collaborative study on purpose of verifying the difference between CM6 and CM7 including 3R4F for reference. It carried out using various analytical categories for example, main stream, sidestream and Av. smoke. Additional analysis such as physical properties, blending ratio, combustibility and general leaf component analysis also implemented in order to investigate the difference. We complied with ISO standard and CORESTA recommended method during analytical operating procedures. In this study, we described that comparative analytical result for CM6 and CM7 known as reference or monitoring cigarettes including 3R4F for reference. All sample cigarettes were conditioned at $22^{\circ}C$, 60% relative humidity for 48 hours. Av. Smoke, MS and SS smoke analysis were performed over five times with two smoking condition, ISO and Health Canada with the exception of Av. smoke analysis. We complied with ISO standard method during analytical operating procedures. And, we conducted additional analysis, such as physical properties, blending ratio, combustibility and leaf component analysis also in order to investigate the difference. In conclusion, we found out some differences between CORESTA monitoring cigarette No. 6 and No 7. The smoke components such as total particulate matters, NFDPM, nicotine and carbon monoxide contents of CM7 were a little lower than CM6. And, these phenomena were the same as not only main stream smoke but also side stream smoke and Av. smoke. This tendency was consistent with ISO and Health Canada smoking condition. Besides, leaf constituents' color of CM7 was darker than CM6. In case of combustibility, it showed short combustion time approximately 30 seconds.

고온-고압 수소 주입된 Fe-30Mn-0.2C-(1.5Al) 고망간강의 인장 거동에 미치는 표면 조건의 영향

이승용,이상혁,황병철,Lee, Seung-Yong,Lee, Sang-Hyeok,Hwang, Byoungchul 한국재료학회 2017 한국재료학회지 Vol.27 No.6

In this study, two Fe-30Mn-0.2C-(1.5Al) high-manganese steels with different surface conditions were hydrogen-charged under high temperature and pressure; then, tensile testing was performed at room temperature in air. The yield strength of the 30Mn-0.2C specimen increased with decreasing surface roughness(achieved via polishing), but that of the 30Mn-0.2C-1.5Al specimen was hardly affected by the surface conditions. On the other hand, the tendency of hydrogen embrittlement of the two high-manganese steels was not sensitive to hydrogen charging or surface conditions from the standpoints of elongation and fracture behavior. Based on the EBSD analysis results, the small decrease in elongation of the charged specimens for the Fe-30Mn-0.2C-(1.5Al) high-manganese steels was attributed to the enhanced dislocation pile-up around grain boundaries, caused by hydrogen.

Convalescence from Saturday Night Palsy

이승용,한수홍,이순철,이인성,김진우,Rhee, Seung-Yong,Han, Soo-Hong,Lee, Soon-Chul,Lee, In-Sung,Kim, Jin-Woo The Korean Society for Microsurgery 2012 Archives of reconstructive microsurgery Vol.21 No.2

Purpose: Saturday night palsy is a transient form of nerve palsy that occurs after a prolonged period of direct pressure on the course of radial nerve by one's own or spouse's head. Although commonly encountered, there have been only few studies concerning its convalescence. The purpose of this study is to predict the prognosis of Saturday night palsy based on the causes, time to recovery and degree of recovery. Materials and Methods: Retrospective study of 20 patients who were diagnosed compression radial nerve palsy was performed. The average age was 36.7 years old and the mean follow-up period was 19.6 months. We investigated sleeping hours as an indirect measure of nerve compression time, recovery of wrist and finger extension, DASH score on the monthly based follow up. Results: The mean sleeping hours was 5.8 hours and all patients showed full recovery of wrist and fingers extension with the mean duration of symptom for 3.2 months. DASH score was an average 1.53 at the last follow up and we found no statistical significance between the time to recovery and the sleeping hours. Conclusion: Complete natural recovery can be expected in compression radial nerve palsy in this study without correlation with sleeping time. Accurate diagnosis is important in order to avoid unnecessary therapeutic intervention and further study should be accomplished for clarifying the related prognostic factors in larger scale of the cases.

Evaluation of Stability Following Two-Jaw Surgery

이승용,김수관,김서윤,오지수,문경남,윤대웅,김훈,김정선,Lee, Sung-Yong,Kim, Su-Gwan,Kim, Seo-Yoon,Oh, Ji-Su,Moon, Kyung-Nam,Yoon, Dae-Woong,Kim, Hoon,Kim, Jeong-Sun Korean Association of Maxillofacial Plastic and Re 2011 Maxillofacial Plastic Reconstructive Surgery Vol.33 No.2

Purpose: Orthognathic surgery is required in patients with severe skeletal disharmony and facial asymmetry, which results in functional and esthetic improvement. Recently, bimaxillary surgery has become generalized. Establishment of the occlusal plane among several other factors included in the surgery plan is a major consideration for the diagnosis and treatment plan and it is also an important factor for postoperative stability. Methods: In this study, we assessed postoperative stability of occlusal plane, B-point, and pogonion point on 20 patients who underwent two-jaw surgery in the Chosun Dental Hospital from 2000 to 2007. Preoperative and postoperative states and at least a one year postoperative follow-up were compared. Results: The postsurgical relapse volume of the occlusal plane to the SN plane and the FH plane was $-0.26{\pm}2.8^{\circ}$ and $-0.44{\pm}3.29^{\circ}$, respectively and after two-jaw surgery, the stability of occlusal plane was maintained. The horizontal relapse degree was $0.85{\pm}0.46$ mm and $0.76{\pm}0.48$ mm, respectively, and the vertical relapse degree was $1.16{\pm}0.36$ mm and $1.13{\pm}0.71$ mm of the B point and the Pogonion point at the time after minimal 1 year. Conclusion: The vertical relapse amount was shown to be slightly larger than the horizontal relapse amount.

인라인 마그네트론 스퍼티링에 의한 ITO/Ag/ITO 다층 구조 투명전극의 최적화에 관한 연구

이승용,윤여탁,조의식,권상직,Lee, Seung Yong,Yoon, Yeo Tak,Cho, Eou Sik,Kwon, Sang Jik 한국전기전자재료학회 2017 전기전자재료학회논문지 Vol.30 No.3

Indium tin oxide (ITO) thin films show a low sheet resistance and high transmittance in the visible range of the spectrum. Therefore, they play an important role as transparent electrodes for flat panel displays. However, their resistivity is rather high for use as a transparent electrode in large displays. One way to improve electrical and optical properties in large displays is to use ITO/Ag/ITO multilayer films. ITO/Ag/ITO multilayer films have lower sheet resistance than single layer ITO films with the same thickness. Prior to the ITO/Ag/ITO multilayer experiments, optimal condition for thickness change are necessary. Their thicknesses were deposited differently in order to analyze electrical and optical properties. However, when optimal single film characteristics are applied to ITO/Ag/ITO multilayer films, other phenomena appeared. After analyzing the electrical and optical properties by changing ITO and Ag film thickness, ITO/Ag/ITO multilayer films were optimized. By combining ITO film at $586\;{\AA}$ and Ag film at 10 nm, the ITO/Ag/ITO multilayer films showed optimized high optical transmittance of 87.65%, and the low sheet resistance of $5.5{\Omega}/sq$.

홍화씨 추출물이 MC3T3-E1 조골세포의 증식과 분화에 미치는 영향

이승용 ( Sung Yong Lee ),김수관 ( Su Gwan Kim ),이슬아 ( Seul Ah Lee ),박민경 ( Min Gyeong Park ),박선영 ( Sun Young Park ),오지수 ( Ji Su Oh ),김진수 ( Jin Soo Kim ),이동설 ( Dong Seol Lee ),문소라 ( So Ra Moon ),모신엽 ( Shin Ye 조선대학교 치의학연구원 2013 Oral Biology Research (Oral Biol Res) Vol.37 No.2

Purpose: The main aim of this study was to determine the effect of Carthamus tinctorius seed extract in the proliferation and differentiation of MC3T3-E1 osteoblastic cell line. Materials and Methods: To determine the characteristic alteration of MC3T3-E1 cells by C. tinctorius, it was examined by cell culture, MTT assay, Von Kossa staining, reverse transcriptase-polymerase chain reaction and quantitative real-time polymerase chain reaction analysis in MC3T3-E1 cells. Results: The treatment of C. tinctorius did not significantly affect the cell proliferation in MC3T3-E1 cells. C. tinctorius significantly accelerated the mineralization as compared with the control culture in the differentiation of MC3T3-E1 cells. C. tinctorius significantly increased the expression of alkaline phosphatase mRNA as compared with the control in the differentiation of MC3T3-E1 cells. C. tinctorius significantly accelerated the decrease of osteonectin mRNA expression as compared with the control in a time-dependent manner in the differentiation of MC3T3-E1 cells. Carthamus tinctorius significantly increased the expression of osteocalcin mRNA as compared with the control in the differentiation of MC3T3-E1 cells. Conclusion: These results suggest that the C. tinctorius facilitate the osteoblast differentiation and mineralization in the differentiation of MC3T3-E1 osteoblastic cells, and therefore, that it may have potential properties for development and its clinical application of bone regeneration materials.