Recovery process of wall condition in KSTAR vacuum vessel after temporal machine-vent for repair

Kim, Kwang Pyo,Hong, Suk-Ho,Lee, Hyunmyung,Song, Jae-in,Jung, Nam-Yong,Lee, Kunsu,Chu, Yong,Kim, Hakkun,Park, Kaprai,Oh, Yeong-Kook Elsevier 2015 Fusion engineering and design Vol.98 No.-

<P><B>Abstract</B></P> <P>Efforts have been made to obtain vacuum condition that is essential for the plasma experiments. Under certain situations, for example, the vacuum vessel should be vented to repair in-vessel components such as diagnostic shutter, exchange of window for diagnostic equipment, and PFC damaged by high energy plasma. For the quick restart of the campaign, a recovery process was established to make the vacuum condition acceptable for the plasma experiment. In this paper, we present the recovery process of wall condition in KSTAR after temporal machine-vent for repair. It is found that an acceptable vacuum condition has been achieved only by plasma based wall conditioning techniques such as baking, GDC, and boronization. This study was that the proper recovering method of the vacuum condition should be developed according to the severity of the accident.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Efforts have been made to obtain vacuum condition that is essential for the plasma experiments. </LI> <LI> For example, the vacuum vessel should be vented to repair in-vessel components such as diagnostic shutter, and PFC damaged by high energy plasma. </LI> <LI> Here, we present the recovery process of wall condition in KSTAR after temporal machine-vent for repair. </LI> <LI> It is found that an acceptable vacuum condition has been achieved only by plasma based wall conditioning techniques such as baking, GDC, and boronization. </LI> <LI> This study was that the proper recovering method of the vacuum condition should be developed according to the severity of the accident. </LI> </UL> </P>

사례 기반 추론을 이용한 서비스 컴포지션 연구

김건수(Kunsu Kim),이동훈(Dong-hoon Lee),박두경(Doo-Kyung Park),이지형(Jee-Hyong Lee) 한국지능시스템학회 2008 한국지능시스템학회논문지 Vol.18 No.2

웹서비스와 상황인식서비스는 사용자의 요구에 따라 많은 종류의 서비스를 제공할 수 있어야 한다. 사용자의 요구는 날로 다양해지고 있고 그에 발맞추어 다양한 종류의 서비스들이 서비스 제공 업체에 의해 새롭게 시장에 등장하고 있다. 하지만 사용자의 새로운 요청에 맞추어 새로운 서비스를 생산하거나 일부 사용자의 요구때문에 새로운 서비스를 만드는 것은 비효율적이다. 그래서 최근에는 유저의 다양한 요청에 보다 유연하게 대응할 수 있는 기술들에 대한 연구가 이루어지고 있다. 그 중 단일 서비스의 조합을 통해 복합서비스를 제공할 수 있는 서비스 컴포지션이라는 기술이 주목을 받고 있다. 하지만, 기존 연구들은 다소 늦은 처리속도로 인해 빠른 응답이 필요한 실시간 상황인식서비스에는 부적합하다. 그래서 본 논문은 사례기반추론을 이용하여 기존 방법보다 빠른 서비스 컴포지션을 구현하는 방법을 제안한다. 그리고 제안하는 알고리즘을 검증하기 위해 사용자에게 이동서비스와 구매정보서비스를 이용하여 사용자의 이동 및 구매 요구를 만족하는 조합을 찾아주는 물건 구매 서비스 서비스를 구현하고 이 구현된 물건 구매 도우미 서비스에 제안하는 알고리즘과 기존 서비스 컴포지션 기법을 적용하여 각 알고리즘의 성능을 비교분석 한다. Context-aware service environment should provide many kinds of services according to users' requests. Users want a great variety of services. In response to their demands the service provider should make a new service every time. But making a new service every time may be inefficient even for a small number of users' requests. So, there are studies on how to efficiently support various and complex requests from users. In many researches, service compositions have lately attracted considerable attention. However, existing researches have mainly focused on Web services. So they are not proper to rapidly providing services in response to users' requests, especially in context-aware service environment. This paper proposes a rapid service composition using case-based reasoning. For evaluating the proposed algorithm we implement 'purchasing service agent'. With this system, we compare our algorithm and the existing service composition algorithms.

Characteristic research of pellet injection system in KSTAR

Park, SooHwan,Kim, HongTack,Song, JaeIn,Woo, InSik,Lee, KunSu,Lee, HyunMyung,Kim, YoungOk,Yonekawa, Hirofumi,Kim, KwangPyo,Chu, Yong,Oh, YeongKook Elsevier 2018 Fusion engineering and design Vol.136 No.2

<P><B>Abstract</B></P> <P>20 Hz pellet injection system was installed for improving a fueling system of KSTAR (Korea Superconducting Tokamak Advanced Research) in 2016. Several things of hardware such as a liquid helium transfer line, an extruder nozzle and an extension part of pellet guide tube are changed for 2017 campaign. For plasma experiments, the pellet injection system uses the smallest pellet (1.5 mm of length, 2 mm of diameter). The pellet velocity can be variable from 150 m/s to over 200 m/s by controlling of propellant gas pressure. The clear increase of plasma density observed during KSTAR experiments is also presented in this paper.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The smallest pellet (1.5 mm of length, 2 mm of diameter) injection is successful. </LI> <LI> Slower pellet injection less than 150 m/s is achieved. </LI> <LI> Pellet trajectory is closer to plasma by straight extension part. </LI> </UL> </P>

Large‐Scale Synthesis and Characterization of the Size‐Dependent Thermoelectric Properties of Uniformly Sized Bismuth Nanocrystals

Son, Jae Sung,Park, Kunsu,Han, Mi‐,Kyung,Kang, Chanyoung,Park, Sung‐,Geun,Kim, Jae‐,Hee,Kim, Woochul,Kim, Sung‐,Jin,Hyeon, Taeghwan WILEY‐VCH Verlag 2011 Angewandte Chemie Vol.123 No.6

<P><B>Gepresste Bi‐Nanokristalle</B>, die durch eine einfache Kolloidmethode erhalten wurden, zeigten sehr hohe elektrische Leitfähigkeiten von 10<SUP>4</SUP>–10<SUP>5</SUP> S m<SUP>−1</SUP> bei einer extrem niedrigen thermischen Leitfähigkeit von 0.35 W m<SUP>−1</SUP> K<SUP>−1</SUP>. Die Synthesemethode kann für die kostengünstige Herstellung von hoch effizienten thermoelektrischen Materialien durch gezielten Größenzuschnitt der Nanokristalle genutzt werden (siehe Bild; Skalierung 50 nm; <I>ZT</I>=Gütezahl).</P>

전자기적 발열에서의 KSTAR In-Vessel Control Coil의 열 및 기계적 거동

강진구(Jin Gu Kang),박성현(Sunghyun Park),장민용(Minyoung Jang),이현정(Hyunjung Lee),김현욱(Hyun Wook Kim),이근수(KunSu Lee),김광표(Kwang Pyo Kim),박갑래(Kaprai Park),김범석(Beom Seok Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

To settle fusion technology, technical- and engineering challenges should be solved to control unstable fusion plasma. In-vessel control coil (IVCC) in Korea Superconducting Tokamak Advanced Research (KSTAR) has been implemented for plasma control. We characterize the mechanical behaviors of IVCC under high heat-generation environments due to electrically induced eddy currents. Numerical evaluations reveal electromagnetic-, thermal- and mechanical responses under operating conditions. Thermal stability is assessed in terms of transient temperature variations and consequent thermal stress distributions. Experimental approaches using IVCC mock-up models are employed to validate the numerical results. We suggest candidates reduce eddy current and guarantee heat-dissipating performance via tailored methods with an upgrade of the IVCC case. The preliminary results will be the fundamental data for feasible upgrade of IVCC in KSTAR.

전자기적 발열에서의 KSTAR In-Vessel Control Coil의 열 및 기계적 거동

강진구(Jin Gu Kang),박성현(Sunghyun Park),장민용(Minyoung Jang),이현정(Hyunjung Lee),김현욱(Hyun Wook Kim),이근수(KunSu Lee),김광표(Kwang Pyo Kim),박갑래(Kaprai Park),김범석(Beom Seok Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

To settle fusion technology, technical- and engineering challenges should be solved to control unstable fusion plasma. In-vessel control coil (IVCC) in Korea Superconducting Tokamak Advanced Research (KSTAR) has been implemented for plasma control. We characterize the mechanical behaviors of IVCC under high heat-generation environments due to electrically induced eddy currents. Numerical evaluations reveal electromagnetic-, thermal- and mechanical responses under operating conditions. Thermal stability is assessed in terms of transient temperature variations and consequent thermal stress distributions. Experimental approaches using IVCC mock-up models are employed to validate the numerical results. We suggest candidates reduce eddy current and guarantee heat-dissipating performance via tailored methods with an upgrade of the IVCC case. The preliminary results will be the fundamental data for feasible upgrade of IVCC in KSTAR.

Proposal of Evaluation Matrix for Clearance Waste Disposal Plan

Kunsu Lim,Chang-Lak Kim,Sanghwa Shin 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

The Korean administration assumed that the amount of low and medium level waste generated during the decommissioning of nuclear facilities in Korea was 14,500 drums (based on 200 L) and designed the LILW repository accordingly. Accordingly, it is necessary to separate the nuclear power plant decommissioning waste into clearance waste by mobilizing means such as decontamination and cutting as much as possible, and to deregulate it together with non-radioactive waste. As a result, clearance waste and non-radioactive waste are dominated by concrete and metal, and it is necessary to evaluate how to recycle them. Many existing studies have conducted research on each recycling method, and accordingly, it can be judged that the technological maturity is sufficient. Accordingly, we would like to propose a method for comprehensive management and evaluation of concrete. By applying the decision matrix proposed in IAEA TRS No. 401, it will be possible to compare the 5 factors (cost, technical feasibility, risk, availability of disposal, and full cycle impact). However, in the case of concrete, if the existing construction waste recycling methodologies are fully used, the technical feasibility can be considered equal. Therefore, it was judged that it would be good to introduce the aspect of public acceptance as an evaluation item instead of technical feasibility. The amount of waste that can be generated when decommission a nuclear power plant is only insignificant compared to the total amount of waste concrete that is generated during the year. Accordingly, one option is to fully integrate the waste concrete recycling system and utilize it for road construction. Next, it is possible to suggest the option of recycling in the construction of shields in the nuclear industry, as suggested in previous studies, and the method of using it as a backfill material such as for a decommissioned NPP site or other sites. As an example, and a draft stage, this study was evaluated based on existing studies after all options were equally weighted. When the profit and loss was evaluated in a way that a maximum of 5 points were given to each option, the case of using it as a backfill in various applications was evaluated as the best option. Unlimited recycling, such as road construction, was evaluated to be highly damaging in terms of public acceptance.

사례기저 수치화와 트리구조 관리를 이용한 서비스 컴포지션의 속도 향상 연구

이승훈(Seunghoon Lee),김건수(Kunsu Kim),윤태복(Taebok Yoon),박두경(Dookyung Park),이지형(Jee-Hyung Lee) 한국정보과학회 2008 한국정보과학회 학술발표논문집 Vol.35 No.1

유비쿼터스 컴퓨팅의 목표 중 하나는 사용자의 직접적이거나 은연중에 내포된 요청에 따라 적절한 서비스를 제공하는 것이다. 최근에는 사용자의 다양한 요청에 보다 유연하게 대응할 수 있는 연구가 이루어지고 있으며 그 중 단일서비스의 조합을 통해 복합서비스를 제공할 수 있는 서비스 컴포지션(Service Composition)이 주목을 받고 있다. 하지만 기존 연구들은 늦은 처리속돌 인해 실시간 상황인식 서비스에서 빠른 응답을 바라는 사용자의 요구사항을 만족시키기 어렵다. 또한 사례기반추론은 사례기저에 쌓인 사례의 수가 늘어감에 따라 속도가 저하되는 단점이 있다. 이러한 단점을 최소화 하기 위하여 클러스터링 기법이 사용되고 있다. 그러나 클러스터링 기법은 사례기저의 수를 줄여가면서 속도를 유지하기 때문에 기존의 사례가 다시 발생하였을 경우에도 새로운 문제로 인식하게 되는 문제를 가지고 있다. 이러한 문제점을 해결하기 위해서 본 논문에서는 사례기저의 수를 유지하면서 사례기저의 수치화 및 트리구조 관리를 이용하여 기존방법보다 빠른 서비스 컴포지션을 구현하는 방법을 제안한다. 그리고 기존의 서비스 컴포지션 기법과 비교 분석을 통하여 제안하는 기법의 유효함을 확인하였다.

IEEE 802.11e MAC의 성능향상을 위한 적응형 EDCF

김건수,김범준,박중신,이재용,Kim Kunsu,Kim Beomjoon,Park Jungshin,Lee Jaiyong 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.1a

최근 IEEE802.11 Working Group(WG)에서는 QoS(Quality of Service)를 제공하기 위하여 기존의 IEEE802.11 MAC(Medium Access Control)프로토콜을 개선한 IEEE802.11e MAC프로토콜에 대한 표준화 작업 중에 있다. IEEE802.11e MAC프로토콜 중에서 EDCF는 기존의 DCF에서 QoS를 제공하기 위하여 서로 다른 우선수위에 대하여 서로 다른 서비스를 제공할 수 있도록 개선한 것이다. 하지만 EDCF는 DCF가 가지고 있던 문제점이었던 throughput에 대한 최적화 문제와 우선순위 보장에 대한 문제점을 가지고 있다. 본 논문에서 제안하는 알고리듬은 먼저 보다 효과적인 우선순위를 위한 보장방안을 제안하고 이와 함께 처리율을 최적화하기 위하여 수학적인 분석을 통해서 보다 효과적인 처리율을 얻을 수 있는 방안을 제시한다. 제안된 알고리듬을 컴퓨터 모의실험을 통해서 기존의 알고리듬보다 노드 수에 상관없이 항상 나은 처리율을 가짐을 확인하였고 노드수의 증가로 인한 처리율의 저하도 감소되는 것을 확인하였다. 또한 기존의 EDCF보다 효과적으로 우선순위를 보장함을 확인하였다. Efforts for standardization of medium access control (MAC) protocol in IEEE802.11e have been made to support quality of service (QoS) in IEEE802.11e MAC protocol. Enhanced disoibuted coordination function (EDCF) of 802.11e MAC protocol is modified to support QoS for packets that have differentiated priority. However, EDCF still has the problem of throughput optimization and priority support. Therefore, we have proposed a scheme called adaptive EDCF for both supporting priority of packets and throughput optimization. We have derived the relation between the number of nodes and contention window size for throughput optimization. Based on the analytic results, we have evaluated the performance of the proposed scheme using OPNET simulations. The simulation results show that using the proposed scheme can improve the overall throughput regardless of the number of nodes and the decrement of the throughput with increasing the number of nodes can be alleviated. Additionally, we have shown that the adaptive EDCF can support priority of packets more effectively than existing EDCF.

Microstructural investigation of phases and pinning properties in MBa₂Cu₃O_7−<i>x</i> (M?=?Y and/or Gd) coated conductors produced by scale-up facilitie

Jin, Hye-Jin,Moon, Han-Kyoul,Yoon, Seokhyun,Jo, William,Kim, Kunsu,Kim, Miyoung,Ko, Rock-Kil,Jo, Young-Sik,Ha, Dong-Woo IOP 2016 Superconductor science & technology Vol.29 No.3

<P>To expedite the commercialization of coated conductors, a robust stacking architecture of the wires must be developed and the performance of the critical currents improved. More importantly, the manufacturability, or large-scale delivery, and the capability of sustaining production at a high rate must be considered. The products of three companies, American Superconductor, Superpower Inc., and SuNAM Co., Ltd, were selected because these companies have announced commercial-grade production lines and delivered a significant amounts of wires to the open market that meet the standards demanded by power devices. X-ray diffraction patterns were used to verify the structural properties and the phase formation in the wires, and transmission electron microscopy with energy dispersive spectroscopy was used to investigate the microstructure and composition of the conductors. In addition, Raman scattering spectroscopy was used for the analysis of the phase formation and for the elucidation of secondary phases in the superconducting layers. The field dependence of the critical current was also studied to compare the transport characteristics under relatively low and medium magnetic field at 77 K and 60 K. Pinning forces were obtained from the field dependence of transport properties and pinning characteristics were investigated. The theoretical and experimental analyses were combined together using the Dew-Hughes formula to extract the scaling exponents and estimate the irreversibility lines of the fields. The results showed that the three conductors possess pinning mechanisms that originate from core pinning with a surface pinning geometry. It is remarkable that the wires discussed in this paper exhibit very similar pinning characteristics even though they have different characteristics in terms of chemical composition, microstructure, stacking architectures, and distribution of parasitic phases.</P>