Key Features in the Operation of KSTAR

Jong-Gu Kwak,Oh, Y. K.,Kim, K. P.,Kim, S. W.,Hong, S. H.,Chu, Y.,Lee, H. J.,Kim, Y. O.,Kim, J.,Park, S. L.,Hahn, S. H.,Park, M. K.,Kim, H. K.,Bak, J. G.,Bae, Y. S.,Ko, W. H.,Lee, S. G.,Lee, J. H.,Jung IEEE 2012 IEEE transactions on plasma science Vol.40 No.3

<P>The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb<SUB>3</SUB>Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb<SUB>3</SUB>Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350°C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ~1.8, δ>;0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at B<SUB>T</SUB> = 2 T with I<SUB>p</SUB> = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.</P>

Progress in the development of heating systems towards long pulse operation for KSTAR

Kwak, J.G.,Bae, Y.D.,Chang, D.H.,Chang, D.S.,Hong, B.G.,Hwang, C.K.,In, S.R.,Jeong, S.H.,Jin, J.T.,Jung, K.S.,Kim, B.R.,Kim, J.,Kim, S.K.,Kim, T.S.,Lee, D.W.,Lee, K.W.,Oh, B.H.,Seo, C.S.,Seo, M.S.,Yoo International Atomic Energy Agency 2007 Nuclear fusion Vol.47 No.5

<P>Construction of the Korea superconducting tokamak advanced research (KSTAR) tokamak is in its final phase. For the long-pulse KSTAR discharges, the ion cyclotron range of frequencies (ICRF) and neutral beam injection (NBI) heating systems are expected to play important roles through a selective heating of ions and electrons, control of the plasma pressure and current profiles, a core fuelling and beam diagnostics for the KSTAR. In addition, the ICRF system is expected to be used for possible discharge cleaning and assisting in the tokamak startup. In this paper, the recent progress in the development of the ICRF and the NBI heating systems is described. The four-strap ICRF antenna has been successfully tested for a voltage up to 41 kV for a pulse length of 300 s (to 46 kV for 20 s) in a test chamber. A prototype KSTAR NBI system has been developed. At present, the system has successfully produced a 1 MW beam power for 200 s and a 3.5 MW output beam power for 4 s.</P>

S-57 전자해도의 GML 변환 및 데이터베이스 관리

전성환(S.H.Jeon),이성대(S.D.Lee),곽용원(Y.W.Kwak),박철현(C.H.Park),박휴찬(H.C.Park) 한국정보과학회 2006 한국정보과학회 학술발표논문집 Vol.33 No.2C

S-57 포맷으로 기술된 전자해도는 바다에 대한 디지털 지도로서 해안선, 수심, 항로표시 등과 같은 다양한 정보를 표현하고 있다. 이러한 전자해도는 주로 선박의 항해라는 특수한 목적으로만 사용되어 왔고, 전용의 시스템을 통해서만 이용할 수 있는 단점이 있다. 또한, S-57이라는 특수한 포맷으로 기술되어 있기 때문에 다양한 활용이 어렵다는 문제점을 가지고 있다. 이러한 전자해도를 손쉽게 이용하고 해양정보시스템의 기반 데이터로 활용하기 위해서는 범용의 표준 포맷으로 변환할 필요가 있다. 이러한 범용 표준으로 OGC(Open Geospatial Consortium)에서는 지리정보를 효과적으로 표현할 수 있는 XML(eXtensible Markup Language) 기반의 GML(Geography Markup Language) 표준을 발표하였다. 이에 본 논문에서는 선박의 항해에만 제한적으로 사용되던 전자해도를 손쉽고 다양한 활용이 가능하도록 GML로 변환하고 관리하는 방법을 제한한다. 즉, S-57 포맷의 전자해도를 GML 포맷으로 변환하고, 변환된 GML을 데이터베이스로 관리하는 시스템을 설계하고 구현하였다.

Production of (S)-3-hydroxybutyrate by metabolically engineered Saccharomyces cerevisiae

Yun, E.J.,Kwak, S.,Kim, S.R.,Park, Y.C.,Jin, Y.S.,Kim, K.H. Elsevier Science Publishers 2015 Journal of biotechnology Vol.209 No.-

(S)-3-Hydroxybutyrate (S-3HB) can be used as a precursor for the synthesis of biodegradable polymers such as polyhydroxyalkanoate and stereo-specific fine chemicals such as antibiotics, pheromones, and drugs. For the production of S-3HB in yeast, the biosynthetic pathway of S-3HB from acetyl-CoA, consisting of the three enzymes, acetyl-CoA C-acetyltransferase (ACCT), acetoacetyl-CoA reductase (ACR), and 3-hydroxybutyryl-CoA thioesterase (HBT), was introduced into Saccharomyces cerevisiae. An engineered yeast strain overexpressing ERG10, hbd, and tesB genes not only exhibited enzyme activities of AACT, ACR, and HBT, but also produced S-3HB from ethanol. In order to increase the titer of S-3HB, a fed-batch fermentation based on pulse feeding of ethanol as a carbon source was performed, and a final S-3HB titer of 12.0g/L was achieved. This is the first report on the production of 3HB by engineered yeast, utilizing ethanol as the carbon source, suggesting that the industrially preferred S. cerevisiae can be a promising host for producing S-3HB.

Preparation and characterization of NbF₅-added Mg hydrogen storage alloy

Lee, S.H.,Kwak, Y.J.,Park, H.R.,Song, M.Y. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.29

A sample with a composition of 95 wt% Mg-5 wt% NbF<SUB>5</SUB> (named Mg-5NbF<SUB>5</SUB>) was prepared by reactive mechanical grinding using Mg instead of MgH<SUB>2</SUB> as a starting material. Its hydriding and dehydriding rates were then measured under nearly constant hydrogen pressures. The activation of Mg-5NbF<SUB>5</SUB> was not required, and Mg-5NbF<SUB>5</SUB> had an effective hydrogen storage capacity, which was defined as the quantity of hydrogen absorbed for 60 min, of 5.50 wt%. At the first cycle (n = 1) at 593 K, the sample absorbed 4.37 wt% H for 5 min and 5.50 wt% H for 30 min under 12 bar H<SUB>2</SUB>, and desorbed 1.03 wt% H for 5 min, 4.66 wt% H for 30 min, and 5.43 wt% H for 60 min under 1.0 bar H<SUB>2</SUB>. Reactive mechanical grinding of Mg with NbF<SUB>5</SUB>, which formed MgH<SUB>2</SUB>, MgF<SUB>2</SUB>, NbH<SUB>2</SUB>, and NbF<SUB>3</SUB> by the reaction of 11 Mg + 7NbF<SUB>5</SUB> + 3H<SUB>2</SUB> → MgH<SUB>2</SUB> + 10MgF<SUB>2</SUB> + 2NbH<SUB>2</SUB> + 5NbF<SUB>3</SUB>, is considered to create defects, to produce reactive clean surfaces, and to reduce the particle size of Mg. The XRD pattern of Mg-5NbF<SUB>5</SUB> dehydrided at n = 3 revealed Mg, small amounts of β-MgH<SUB>2</SUB> and MgO, and very small amounts of MgF<SUB>2</SUB> and NbH<SUB>2</SUB>. An increase in the dehydriding rate of Mg-5NbF<SUB>5</SUB> was attempted by adding Ni to Mg-5NbF<SUB>5</SUB>. Mg-5NbF<SUB>5</SUB> had higher initial hydriding and dehydriding (after the incubation period) rates and a larger effective hydrogen storage capacity than Mg-10NbF<SUB>5</SUB>, Mg-10MnO, and Mg-10Fe<SUB>2</SUB>O<SUB>3</SUB>, which were reported to have quite high hydriding rate and/or dehydriding rate.

Overestimation of on-road air quality surveying data measured with a mobile laboratory caused by exhaust plumes of a vehicle ahead in dense traffic areas

Woo, S.H.,Kwak, K.H.,Bae, G.N.,Kim, K.H.,Kim, C.H.,Yook, S.J.,Jeon, S.,Kwon, S.,Kim, J.,Lee, S.B. Elsevier Applied Science Publishers 2016 Environmental pollution Vol.218 No.-

The unintended influence of exhaust plumes emitted from a vehicle ahead to on-road air quality surveying data measured with a mobile laboratory (ML) at 20-40 km h<SUP>-1</SUP> in dense traffic areas was investigated by experiment and life-sized computational fluidic dynamics (CFD) simulation. The ML equipped with variable sampling inlets of five columns by four rows was used to measure the spatial distribution of CO<SUB>2</SUB> and NO<SUB>x</SUB> concentrations when following 5-20 m behind a sport utility vehicle (SUV) as an emitter vehicle equipped with a portable emission monitoring system (PEMS). The PEMS measured exhaust gases at the tailpipe for input data of the CFD simulations. After the CFD method was verified with experimental results of the SUV, dispersion of exhaust plumes emitted from a bus and a sedan was numerically analyzed. More dilution of the exhaust plume was observed at higher vehicle speeds, probably because of eddy diffusion that was proportional to turbulent kinetic energy and vehicle speed. The CO<SUB>2</SUB> and NO<SUB>x</SUB> concentrations behind the emitter vehicle showed less overestimation as both the distance between the two vehicles and their background concentrations increased. If the height of the ML inlet is lower than 2 m and the ML travels within 20 m behind a SUV and a sedan ahead at 20 km h<SUP>-1</SUP>, the overestimation should be considered by as much as 200 ppb in NO<SUB>x</SUB> and 80 ppm in CO<SUB>2</SUB>. Following a bus should be avoided if possible, because effect of exhaust plumes from a bus ahead could not be negligible even when the distance between the bus and the ML with the inlet height of 2 m, was more than 40 m. Recommendations are provided to avoid the unintended influence of exhaust plumes from vehicles ahead of the ML during on-road measurement in urban dense traffic conditions.

수중 플라즈마 방전 방식 농업용 보일러 유닛 성능평가

강상구 ( S. G. Kang ),박인철 ( I. C. Park ),김길호 ( G. H. Kim ),차두환 ( D. H. Cha ),이다희 ( D. H. Lee ),김영천 ( Y. C. Kim ),신준환 ( J. H. Shin ),곽다현 ( D. H. Kwak ),김지훈 ( J. H. Kim ),강태환 ( T. H. Kang ) 한국농업기계학회 2022 한국농업기계학회 학술발표논문집 Vol.27 No.2

본 연구는 ㈜GA에서 개발한 플라즈마 보일러의 발열체인 단위 유닛(S-10, ㈜GA, KOREA)을 사용하여 유닛 조합에 따른 내부 순환수 경로 형태에 따라 보일러 성능 특성을 분석하여 플라즈마 보일러의 적정 운전 조건을 구명하고자 하였다. 본 연구에서 사용된 플라즈마 보일러 유닛은 정격용량이 10 kW/h 로 설계 제작한 2개의 유닛을 사용하였으며, 전극 코어와 하우징으로 구성되었다. 재질은 타이타늄(Ti) Grade2 소재를 기본으로 백금족의 이리듐(Ir)을 도금하였다. 플라즈마 보일러 유닛의 성능평가는 탱크 용량 200 L 의 순환수를 유량 25 ~ 30 L/min 으로 유지한 상태에서 설정온도 60℃까지 상승시키는 동안 5분 단위로 측정된 입출수 온도, 유량, 소비전력량, 투입열량 및 방출열량을 측정하여 성능계수(COP)를 산출하였고, 보일러 내부 순환수 경로는 병렬과 직렬형 2가지로 나누어 5 반복으로 성능평가를 수행하였다. 실험 결과 AC 3상 4선식 380V 전원 인가 시 순환수 경로가 병렬 형태의 경우에는 운전 전류는 평균 35.88 A 로 측정되었고, 이 때 총 투입열량과 방출열량은 각각 21,981 Kcal/h, 15,855 Kcal/h 로 계산되어 성능계수가 0.8로 나타났다. 순환수 경로가 직렬인 경우에는 운전 전류는 평균 33.31A로 측정되었고, 총 투입 열량과 방출열량은 각각 19,814Kcal/h, 20,088Kcal/h 로 계산되었으며, 성능계수는 1.01 로 나타나 병렬 형태보다 COP가 약 0.21 높게 나타났다. 이로써 직렬형 경로가 병렬형 경로에 비해 평균 운전전류가 2.57A 적게 소비됨에 따라 소비전력이 감소하여 성능계수는 0.21 높게 측정된 것으로 판단된다. 따라서 순환수가 2개의 보일러 유닛에 병렬로 나뉘어 공급되는 병렬형 연결 구조보다 2개의 유닛을 직결하여 순환수를 1차와 2차로 나누어 연속으로 가열하는 직렬형 연결 구조가 플라즈마 보일러에 적합한 것으로 판단된다.

Synthesis, crystal structures, and deprotonation of cis- and trans-octahedral nickel(II) complexes with a 14-membered tetraaza macrocycle bearing two N-phenacyl pendant arms

Kim, H.,Kang, S.G.,Kwak, C.H. Elsevier Sequoia [etc.] 2012 Inorganica chimica acta Vol.387 No.-

The di-N-functionalized macrocycle 2,13-bis(2-phenacyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.<SUP>1.18</SUP>0<SUP>7.12</SUP>]docosane (H<SUB>2</SUB>L<SUP>2</SUP>) bearing two N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> groups has been prepared by the reaction of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0<SUP>7.12</SUP>]docosane (L<SUP>1</SUP>) with phenacyl bromide. Interestingly, H<SUB>2</SUB>L<SUP>2</SUP> reacts with Ni<SUP>2+</SUP> ion to form two geometric isomers, trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> and cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP>. The axial Ni-O (N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> group) bond distance (2.080(2)A) of trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)](ClO<SUB>4</SUB>)<SUB>2</SUB>.2DMSO is shorter than the in-plane Ni-N distances (2.096(2) and 2.100(2)A). However, the Ni-O distances (2.105(2) and 2.124(2)A) of cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)](ClO<SUB>4</SUB>)<SUB>2</SUB>.H<SUB>2</SUB>O are considerably longer than the Ni-N distances (2.053(2)-2.086(2)A). Each N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> group of trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> and cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> exists as its keto form in the solid state and in various solvents. Two N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> groups of trans-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> are readily deprotonated in basic aqueous solutions, producing the enolate form trans-[Ni(L<SUP>2</SUP>)]. On the other hand, cis-[Ni(H<SUB>2</SUB>L<SUP>2</SUP>)]<SUP>2+</SUP> undergoes deprotonation to yield cis-[Ni(HL<SUP>2</SUP>)]<SUP>+</SUP>, in which one N-CH<SUB>2</SUB>COC<SUB>6</SUB>H<SUB>5</SUB> group is not deprotonated, under similar conditions.

수중 플라즈마 방전 방식 농업용 보일러 실증 평가

강상구 ( S. G. Kang ),박인철 ( I. C. Park ),김길호 ( G. H. Kim ),홍지웅 ( J. W. Hong ),차두환 ( D. H. Cha ),이다희 ( D. H. Lee ),김영천 ( Y. C. Kim ),신준환 ( J. H. Shin ),곽다현 ( D. H. Kwak ),강태환 ( T. H. Kang* ) 한국농업기계학회 2021 한국농업기계학회 학술발표논문집 Vol.26 No.2

보일러 실증 테스트에 사용된 보일러는 실험구의 경우 주식회사 ㈜ GA에서 개발한 수중 플라즈마 방전 방식 보일러(S-70, (주) GA, KOREA)를 사용하였고, 대조구는 일반 시설하우스 농가에서 사용되는 상업용 전기보일러(DBE-100, 대성, KOREA)를 사용하여 실증 테스트를 수행하였다. 보일러 실증 테스트에 사용한 하우스는 36,000×6,000×18,000 ㎜(L×H×W)크기로서, 하우스 중앙에 3중 단열층을 설치하여 실험구와 대조구로 분리한 후 난방 특성 및 금전수 생육 실험을 수행하였다. 그 결과를 요약하면 다음과 같다. 일주일간 대조구에 공급된 누적 전열량은 10,138.3 MJ/h 이 공급되었고, 실험구의 경우에는 8,334.0MJ/h 의 전열량이 공급되어 실험구가 대조구보다 1,804.3 MJ/h 적게 공급된 것으로 나타났다. 출수온도 편차는 플라즈마 보일러가 전기보일러보다 23~47.7℃ 낮은 것으로 나타났다. 설정 출수온도 도달시간은 플라즈마 보일러가 10분이 소요되는 것으로 나타났고, 일반 상용 전기보일러의 경우에는 약 30분이 소요되는 것으로 나타나 플라즈마 보일러 가열 메커니즘이 일반 전기보일러의 전도에 의한 가열 메커니즘 우수한 것으로 판단된다. 실험구의 정규화 식생지수값(NDVI)은 평균 0.678 정도를 나타내었고, 대조구의 정규식생지수는 평균 0.632 정도로서 실험구가 대조구와 비교하여 약 0.046 정도 높은 것으로 나타났다. 금전수의 클로로필 함량을 나타내는 SPAD 값은 플라즈마 보일러를 설치한 실험구가 일반 전기보일러를 설치한 대조구보다 높은 경향을 나타내었다. 10주간 실험구 금전수의 누적 수고 생장량은 73.5 ㎜ 이었고, 대조구의 경우에는 53 ㎜로 나타나 실험구가 대조구보다 약 20 ㎜ 정도 높이 성장량이 양호한 것으로 나타났다. 10주간 실험구 금전수의 누적 엽장 생장량은 8.2 ㎜ 이었고, 대조구의 경우에는 6.9 ㎜ 로 나타나 실험구가 대조구 보다 약 1.3 ㎜정도 엽장 성장량이 높은 것으로 나타났다. 소비전력량은 플라즈마 보일러가 상용 전기보일러보다 약 0.500~0.522 MWh 적게 소비되어 약 16.1~17.8% 정도 에너지 절감효과가 있는 것으로 나타났다. 플라즈마 보일러의 내구연구 20년은 기준으로 총 이득비용은 26,732,400원으로 나타났고. 연간 이득비용으로 환산하면 연간 약 1,336,620원의 경제적 효과가 있는 것으로 판단된다.

Molecular characterization of biotic and abiotic stress-responsive MAP kinase genes, IbMPK3 and IbMPK6, in sweetpotato

Kim, H.S.,Park, S.C.,Ji, C.Y.,Park, S.,Jeong, J.C.,Lee, H.S.,Kwak, S.S. Gauthier-Villars ; Elsevier Science Ltd 2016 Plant physiology and biochemistry Vol.108 No.-

<P>Plants are continually exposed to numerous environmental stresses. To decrease damage caused by these potentially detrimental factors, various stress-related signaling cascades are activated in plants. One such stress-responsive signaling pathway, the mitogen-activated protein kinase (MAPK) module, plays a critical role in diverse plant stress responses. Here, we functionally characterized biotic and abiotic stress-responsive MAPK genes, IbMPK3 and IbMPK6, from sweetpotato. IbMPK3/6 contain totally 11 MAPK conserved subdomains and the phosphorylating motif TEY. Bacterially expressed IbMPK3/6 could be autophosphorylated in vitro, and these proteins phosphorylated universal kinase substrate, such as myelin basic protein. IbMPK3/6 transcripts were expressed in leaf, stem, and root of sweetpotato cultivars with storage roots of various colors. IbMPK3 and IbMPK6 were induced by various biotic/abiotic stress treatments. Furthermore, the kinase activity of IbMPK3/6 was induced during early NaCl, SA, H2O2, and ABA treatment. IbMPK3/6 were predominantly localized to the nucleus. To determine the biological functions of IbMPK3/6, we transiently expressed the IbMPK genes in tobacco (Nicotiana benthamiana) leaves, which resulted in enhanced tolerance to bacterial pathogen and increased expression of pathogenesis-related (PR) genes. These data demonstrate that IbMPK3 and IbMPK6 play significant roles in plant responses to environmental stress. (C) 2016 Elsevier Masson SAS. All rights reserved.</P>