Effects of Pilger Rolling and Heat Treatment on Microstructure and Corrosion Resistance of Ag-electroplated 304 Stainless Steel Tubes

Hyun Park,Woo‑Jin Lee,Jae‑Han Son,Han‑Kyun Shin,Sung‑Kyu Hong,Hyo‑Jong Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

We introduce a cost-effective method that combines electroplating with metal cold working processes to manufacture compositetubes with robust corrosion resistance. First, a 3-step electroplating process was developed to form an adhesive anduniform Ag coating on the outer wall of a 304 stainless steel tube. The process consisted of a Ni-strike step for removing thepassivation layer of the initial 304 tube, Cu deposition for smoothing the surface by adding a buffer layer, and Ag deposition. To reinforce the interfacial adhesion between the electroplated layers and the 304 tube and increase the area of the Ag coating,a pilger rolling or pilger rolling + heat-treatment process was performed after the Ag electroplating process. Scanningelectron microscopy of the composite tubes after each process indicated that the as-deposited Ag coating changed fromhaving a rough to smooth surface after only pilger rolling and with additional heat treatment. Electron backscatter diffractionanalysis of the microstructures and textures of the tubes revealed that dynamic recrystallization occurred extensively duringpilger rolling, resulting in the formation of a relatively defect-free grain structure without heat treatment. Furthermore,electrochemical polarization curves determined that the Ag-coated composite tubes are superior to the uncoated 304 tubein terms of corrosion resistance under Cl−atmosphere, owing to the formation of a AgCl passivation layer during testing. Surface analysis of the composite tubes suggests that the properties of the AgCl passivation layer are related to the grainsize of the Ag coating and the density of plastic-deformation-induced defects.

Antigastritis effects of <i>Armillariella tabescens</i> (Scop.) Sing. and the identification of its anti-inflammatory metabolites

Lee, Seulah,Lee, Dahae,Park, Jun Yeon,Seok, Soonja,Jang, Tae Su,Park, Hyun Bong,Shim, Sang Hee,Kang, Ki Sung,Kim, Ki Hyun Pharmaceutical Society of Great Britain 2018 Journal of pharmacy and pharmacology Vol.70 No.3

Performance of electrochemical double layer capacitors using highly porous activated carbons prepared from beer lees

Sang Guk Lee,Hee Moon,Kwang Hyun Park,심왕근,M.S. balathanigaimani 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.3

Beer lees precursor is chosen to prepare activated carbons having different physical and chemical properties. The beer lees-based activated carbons (BL-ACs) are characterized by N2 adsorption/desorption isotherms, adsorption energy distributions (AEDs), and X-ray photoelectric spectroscopy (XPS). Furthermore the electrochemical properties of the BL-ACs are assessed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and constant current charge/discharge method. The maximum specific capacitance (about 188 F/g at discharge current of l mA/cm2) is obtained in 0.1 M H2SO4 electrolyte solution, which is a relatively low electrolyte concentration. The overall results suggest that the BL-ACs are good candidates for EDLC electrode materials.

Evaluation of Hot Deformation and Dynamic Recrystallization Behaviors of Advanced Reduced-Activated Alloy (ARAA)

Sang‑Wook Kim,Hyeon‑Woo Son,Taek‑Kyun Jung,Young‑Bum Chun,Yi‑Hyun Park,Ji‑Woon Lee,Soong‑Keun Hyun 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4

The hot deformation behavior of advanced reduced-activation alloy (ARAA) was investigated using hot torsion tests. Thefl ow stress decreased as deformation temperature increased and as strain rate decreased. The fl ow behavior demonstratedthe typical dynamic recrystallization (DRX). Based on the constitutive analysis of peak stress, the activation energy for hotdeformation was found to be 330.3 kJ mol −1 . Peak stress was analyzed as a function of the Zener–Hollomon parameter, andcalculated and experimental values were in good agreement. A DRX kinetic model for ARAA was derived with deformationconditions based on the Avrami-type model. It was confi rmed that the volume fraction of dynamically recrystallized grainsincreased as deformation temperature increased and as strain rate decreased. The necklace structure and grain boundarybulging were observed in the deformed microstructure of ARAA. The suggested DRX mechanism for ARAA during hotworking is discontinuous DRX.

Estimating Leaf Area Index of Paddy Rice from RapidEye Imagery to Assess Evapotranspiration in Korean Paddy Fields

Sang?Il Na,Suk Young Hong,Yi?Hyun Kim,Kyoung?Do Lee,So?Young Jang 한국토양비료학회 2013 한국토양비료학회지 Vol.46 No.4

Leaf area index (LAI) is important in explaining the ability of crops to intercept solar energy for biomass production, amount of plant transpiration, and in understanding the impact of crop management practices on crop growth. This paper describes a procedure for estimating LAI as a function of image?derived vegetation indices from temporal series of RapidEye imagery obtained from 2010 to 2012 using empirical models in a rice plain in Seosan, Chungcheongnam?do. Rice plants were sampled every two weeks to investigate LAI, fresh and dry biomass from late May to early October. RapidEye images were taken from June to September every year and corrected geometrically and atmospherically to calculate normalized difference vegetation index (NDVI). Linear, exponential, and expolinear models were developed to relate temporal satellite NDVIs to measured LAI. The expolinear model provided more accurate results to predict LAI than linear or exponential models based on root mean square error. The LAI distribution was in strong agreement with the field measurements in terms of geographical variation and relative numerical values when RapidEye imagery was applied to expolinear model. The spatial trend of LAI corresponded with the variation in the vegetation growth condition.

THE VARIATIONS OF JAPANESE APRICOT (PRUNUS MUME) CULTIVATED AROUND IN MTS. JIRI.

Lee,Jun-Ki,Hyun,Sang-Ki,Lee,Sang-Sun,Chai,Jung-Ki 한국자원식물학회 2002 Plant Resources Vol.5 No.1

Twenty-three plants of Japanese apricot (Prunus mume) were collected from several sites around Mountains JIRI in Korea. Japanese apricots having the different morphological features were evenly distributed in the groups made from the cluster analysis, indicating no geographic distributions but artificial vegetations in Korea. Japanese apricots were, as based on the PCR-RAPD techniques, clustered into the three groups; a group (prototype) having the five white petals with the five red sepals, a group (green type) having the five white petals with the five green sepals, and a group (hybrid type) having the more than five red petals with various colored sepals. The prototype apricots showed higher toxicities than other type apricot against bacteria and production of less compounds in TLC plates. The polypetal types of Japanes apricot were related to those of p. armebiaca in the characteristics of seed (the ruggedness), but also to be closed to those of p. armebiaca in PCR-RAPD analysis. The cluster analysis of the twenty three apricots and its related species calculated from the two primers were shown to distinguish relationships of cultivars within species, or of individual plants within cultivars, but also to display the two overlapping bands resulted from PCR-RAPD technique.

입력전류 파형 개선형 단상 정류기의 토폴로지

이상현(Sang-Hyun Lee),박진민(Jin-Min Park),문상필(Sang-Pil Mun),서기영(Ki-Young Suh) 한국조명·전기설비학회 2003 한국조명·전기설비학회 학술대회논문집 Vol.2003 No.-

For small capacity rectifier circuits such as these for consumer electronics and appliances, capacitor input type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been presented previously. However, most of these employ switching devices, such as FETs and the like. The absence of switching devices makes systems more tolerant to over-load, and brings low radio noise benefits. We propose a power factor correction scheme using a LC resonant in commercial frequency without switching devices. In this method, it makes a sinusoidal wave by widening conduction period using the current resonance in commercial frequency, Hence the harmonic characteristics can be significantly improved, where the lower order harmonics, such as the fifth and seventh order are much reduced. The result are confirmed by the theoretical and experiment implementations.

판상형 충전제의 함량과 배향에 따른 PP복합체의 영률 변화 연구

서상범(Sang Bum Seo),이용현(Yong Hyun Lee),정선경(Sun Kyoung Jeong),이승구(Seung Goo Lee),이기윤(Kee Yoon Lee) 한국고분자학회 2012 폴리머 Vol.36 No.2

이 논문은 판상형 충전제의 함량과 배향에 따라 폴리프로필렌 복합체의 영률 변화에 미치는 영향을 연구 하였다. 이론적인 예측은 Lee와 그의 연구자들에 의해 제안된 두 개의 종횡비, ρα=a1/a3과 ρβ=a1/a2 를 이용하여 3차원 타원체의 형상을 계산하였고 실험값과 비교 분석하였다. 판상형 충전제로 운모와 탈크를 사용하였다. 충전제의 형태는 SEM을 이용해 관찰하였고, 종횡비는 고분자의 흐름을 기준으로 좌표축을 설정하여 통계적 방법으로 계 산하였다. 충전제가 운모인 경우에 ρα=13.5와 ρβ=1.8이었고, 탈크의 경우는 ρα=3.8과 ρβ=1.4이었다. 또한 충전제 의 2개의 종횡비와 함량이 기계적 물성에 미치는 영향을 실험적으로 연구하였다. 운모의 경우 30 wt% 함량일 때 E11이 약 2.7배 향상되었다. 탈크의 경우는 E11이 약 2.3배 향상하였다. This paper studied the effects of the content and the orientation of the disk shape fillers on the modulus of PP composites. The experimental results were compared with the theoretical calculations which included the three dimensional ellipsoids and analyzed by two aspect ratios, ρα=a1/a3 and ρβ=a1/a2 proposed by Lee and his researchers. Mica and talc were used as disk shape fillers in the composites. The shapes of mica and talc were observed by SEM and aspect ratios were statistically calculated. For the case of mica, the average aspect ratios were ρα=13.5 and ρβ=1.8, and for the case of talc, they were ρα=3.8 and ρβ=1.4. Also, the effects of two aspect ratios and the content of filler on the mechanical properties were studied: For 30 wt% of mica, E11 increased up to about 2.7 times, and for the other case of talc, E11 increased up to about 2.3 times, respectively.

양주 노고산(老姑山) 독재동(篤才洞)의 장소성과 역사문화경관 해석

노재현 ( Jae Hyun Rho ),김화옥 ( Hwa Ok Kim ),이정한 ( Jung Han Lee ),박주성 ( Joo Sung Park ) 한국전통조경학회 2015 한국전통조경학회지 Vol.33 No.1

본 연구는 경기도 양주시 장흥면 삼하리 독재동 바위글씨와 노고산의 장소성에 주목하여, 이곳의 경관 및 장소특질을 고찰하고 바위글씨에 담긴 경관의미를 추론함으로써 노고산과 독재동 계곡의 역사문화경관적 함의를 밝히고자 한 것으로 연구 결과는 다음과 같다. 삼각산은 조선왕조 6백년 도읍지의 주산(主山)이며 오악(五嶽)을 이루는 중앙의 성산(聖山)으로, 노고산은 삼봉산(三峰山)즉 삼각산의 우람한 세봉우리를 향배하는 의미공간으로서 그 장소성이 획득된다. 더불어 노고산은 조선의 정기를 상징하는 삼각산을 가장 완벽하게 조망할 수 있는 ‘망삼각산(望三角山)’의 절대 시점장이다. 독재동 계곡에 산포(散布)된 다수의 바위글씨는 미수 허목의『고양산수기』의 내용을 현현(顯現)하기 위한 행위이자 경물로 재생산된 산물이다. 그리고 추사 필적의 몽재(夢齋)는 중의적(衆意的) 표현이 읽혀지는 바위글씨로, 먼저 글자 그대로의 뜻인 ‘꿈꾸는 집’ 이지만 내면적 의미는 “한낮 몽상(夢想)도 바탕을 깊이 헤아려 보면 정당성이 확보된다.”는 의미로 ‘몽재거사’로 알려진 성재(性齋) 허전(許傳)의 『몽재집(夢齋集)』서(序)의 내용으로 보아 성재의 독재동 거주와 관련된 징표로 추정된다. 또한 몽재라 쓴 바위 하단의 갑자(甲子)·경오(庚午)·무술(戊戌)·갑인(甲寅) 등의 간지(干支)는 추사와의 교유관계가 있는 1804년 5월생 유생(儒生)의 사주팔자로 판단된다. 노고산과 독재동 계곡은 삼각산을 조망하는 장소일 뿐 아니라 송월재·성재 등 미수의 학통을 계승한 기호지역의 남인학자의 공통된 장구지소로써의 응집력을 보여준다. 또한 이곳에 각자(刻字)된 추사체와 미수체(전서체) 바위글씨는 우리나라 서예사의 큰 흐름을 함축적으로 보여준다는 측면에서도 매우 의미 깊은 역사문화경관이다. This study was focused on the placeness of Nogosan Dokjae-dong and rock inscription located in Jangheung-myeon, Yangju-si, Gyeonggi-do. The purpose was to reveal the implication of Nogosan and Dokjae-dong Valley in terms of Historic cultural landscape by considering the characteristics of the place and its landscape, and inferring the significance of the letters engraved on the rock. The result is as follows.10)Samgaksan is one of the five famous mountains in Korea. It is the sacred mountain that stands behind the capital city of the Joseon Dynasty that lasted for 600 years. On the other hand, the placeness of Nogosan is significant since it was the place where people used to bow low to the three great summits of Samgaksan. Furthermore, Nogosan was the perfect place to view Samgaksan that represented the Joseon spirit.Many letters were engraved on the rocks around Dokjae-dong Valley by Misu(眉수) Heo Mok(許穆) as part of his memories to describe his experience in the mountain and became a scenery. Chusa(秋史) Kim Jung-Hee(金正喜) also engraved letters of ``Mongjae`` on the rock that contains a double meaning. Literally, it means ‘a dreaming house’ However, it also implies that even just a daydream is significant in a way. These letters are presumed to be the signs that are related to Sung-Jae(性齋) Heo Jeon(許傳)’s experience in Dokjae-dong since the letters were part of his famous book title. Below these two letters, Chusa also engraved letters that describe the sexagenary cycle including the year of the rat, horse, dog, and tiger. They are regarded as the letters that describe the fate of Chusa’s friend, a scholar born in May 1804. Nogosan and Dongjae-dong Valley are very significant in terms of historic cultural landscape as a viewpoint to see Samgaksan; and a place that cherishes the traces of Misu and shows common values and cohesiveness of well-known scholars of the Joseon Dynasty including Song Wol-Jae(松月齋) and Sung-Jae as a of Gihonamin(畿湖南人). The engraved letters of Chusa and Misu also implicitly demonstrates the major trends of Korea’s calligraphy history.

SNL-EFDC를 이용한 군산항 유사퇴적고 계산의 비교 연구

이동주 ( Dong-joo Lee ),송상현 ( Sang-hyun Song ) 한국환경기술학회 2015 한국환경기술학회지 Vol.16 No.4

본 논문은 Ziegler, Lick, and Jones에 의해 개발된 SEDZLJ라 부르는 유사역학 알고리즘이 계산되는 SNL-EFDC 모델을 이용하여 군산항의 퇴적고 계산에 관하여 연구하였다. SEDZLJ모듈은 SEDflume 이나 Annular flumes로부터 얻은 현장 침식률 및 침식 한계전단응력 자료를 직접 결합할 필요가 있다. 군산항에서는 SEDflume 자료를 구할 수 없기 때문에 Ryu와 Yim에 의한 Annular flumes 실험으로부터 얻은 현장 침식률 및 침식 한계전단응력 자료를 이용하였다. SNL-EFDC 모델이 군산항의 유사퇴적고를 계산하기 위해 적용되었고 관측된 부유사 농도와 퇴적고를 사용하여 검증되었다. 유사 퇴적고 계산에 대한 모델의 적용성은 NSEC가 0.72로 침식과 퇴적의 물리적 변화가 적절하게 재현됨이 입증되었다. 부가적으로 검증된 모델은 저면 활성층두께에 대한 매개변수 α값의 영향을 조사하기 위해 사용되었고, Lee와 Park에 의해 수행된 SEDTM을 이용한 유사이동 계산의 결과와 비교하기 위해 사용되었다. 그 결과, 매개변수 α값의 변화는 유사퇴적고 계산에 미미한 영향이 미치는 것으로 나타났다. SEDZLJ에 의한 결과를 SEDTM의 것과 비교할 때 SEDZLJ모듈이 군산항에서 SEDTM 보다 NSEC가 0.03향상 되어 토사이송 과정을 재현함이 확인되었다. This paper was studied on the sediment deposition height computation at Gunsan port using recently advanced SNL-EFDC model which the sediment dynamics algorithm was called as SEDZLJ developed by Ziegler, Lick and Jones. SEDZLJ module needs to directly incorporate site-specific erosion rate and critical shear stress data from SEDflume or Annularflumes. Here this model attempted to use site-specific erosion rate and critical shear stress data from Annular flumes experiment by Ryu and Yim instead of unavailable SEDflume data at Gunsan port. SNL-EFDC was applicated to calculate deposition height at Gunsan port and verified using observed values for suspended sediment concentration and sediment deposition height. The model applicability for sediment deposition height computation was evaluated as NSEC 0.72 and verified that it reproduced the physical variations of erosion and deposition. In addition, the verified model was used to investigate the effect of parameter “α” on the active bed layer thickness and used to compare with the result of sediment transport computation using SEDTM done by Lee and Park. As a result, it was found that the change of parameter “α” value has a negligible effect on sediment deposition height computation. As results of SEDZLJ are compared with those of SEDTM, it was identified that SEDZLJ module reproduces the sediment transport process more appropriately than SEDTM at Gunsan port with advanced NSEC 0.03.