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이기형,이대욱,이광순,정상태 ( Ki Hyoung Lee,Dae Wook Lee,Kwang Soon Lee,Sang Tae Jeoung ) 한국화학공학회 1993 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.31 No.5
A loop control method, where all potential manipulated variables are actively utilized, is proposed for a process which has redundant manipulated inputs. Through analyses in the frequency domain, it was shown that the performance and stability of the proposed method are improved in comparison with those of the conventional method where extra manipulated variables are fixed at constant values. For experimental evaluation, the proposed method was applied to temperature control of a batch reaction calorimeter. As a result, tracking as well as regulation performances were found to be greatly improved compared to the conventional approach.
이기형,박정순,고한옥,정명조,Lee, Ki Hyoung,Park, Jeong Soon,Ko, Han Ok,Jhung, Myung Jo 한국압력기기공학회 2013 한국압력기기공학회 논문집 Vol.9 No.1
Reactor Vessel Internals(RVIs), which are installed within the reactor pressure vessel and support the fuel assembly, take responsibility for safety of reactor core. In operating Nuclear Power Plants(NPPs), the RVIs have been exposed to severe conditions such as neutron irradiation, high temperature, high pressure, and high velocity of coolant flow and have degraded by materials aging with long-term operation. Therefore, the effective aging management plan and the appropriate regulatory requirements are necessary to maintain the integrity of RVIs. The purpose of this paper is to provide a review guide for Periodic Safety Review(PSR) of RVIs in presurized water reactor. The review guide is developed based on the revised review guides and reports established from IAEA and USNRC, and the analysis results of design characteristics, aging mechanisms, and operating experiences of RVIs in domestic and international NPPs. Consequently, the developed review guide for PSR of RVIs is expected to contribute an overall strategy and standard for the PSR of RVIs.
Ni-Mo-Cr계 저합금강의 천이온도영역에서의 파괴인성에 미치는 Ni 및 Cr 함량의 영향
이기형 ( Ki Hyoung Lee ),박상규 ( Sang Gyu Park ),김민철 ( Min Chul Kim ),이봉상 ( Bong Sang Lee ),위당문 ( Dang Moon Wee ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.9
Materials used for a reactor pressure vessel(RPV) are required high strength and toughness, which determine the safety margin and life of a reactor. Ni-Mo-Cr low alloy steel shows better mechanical properties than existing RPV steels due to higher Ni and Cr contents compared to the existing RPV steels. The present study focuses on effects of Ni, Cr contents on the cleavage fracture toughness of Ni-Mo-Cr low alloy steels in the transition temperature region. The fracture toughness was characterized by a 3-point bend test of precracked Charpy V-notch(PCVN) specimens based on ASTM E1921-08. The test results indicated that the fracture toughness was considerably improved with an increase of Ni and Cr contents. Especially, control of Cr content was more effective in improving fracture toughness than manipulating Ni content, though Charpy impact toughness was changed more extensively by adjusting Ni content. These differences between changes in the fracture toughness and that in the impact toughness were derived from microstructural features, such as martensite lath size and carbide precipitation behavior.
이득기,박상도,김성현,이주엽,이기형,이광순 ( Deuk Ki Lee,Sang Do Park,Sung Hyun Kim,Joo Youp Lee,Ki Hyoung Lee,Kwang Soo Lee ) 한국화학공학회 1992 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.30 No.6
A mathematical model is proposed for a thin film evaporator that is used for fuel oil recovery from waste lubricating oil. The model is contructed to predict pressure, temperature, and yield distributions along the axial direction. Comparison of the calculated values of the process variables with the experimental data has shown that the proposed model can represent the thin film evaporator with good accuracy.
차세대 원전 대형 압력용기용 고강도 SA508 Gr.4N Ni-Cr-Mo계 저합금강 개발
김민철,박상규,이기형,이봉상,Kim, Min-Chul,Park, Sang-Gyu,Lee, Ki-Hyoung,Lee, Bong-Sang 한국압력기기공학회 2014 한국압력기기공학회 논문집 Vol.10 No.1
There is a growing need to introduce advanced pressure vessel steels with higher strength and toughness for the optimizatiooCn of the design and construction of longer life and larger capacity nuclear power plants. SA508 Gr.4N Ni-Cr-Mo low alloy steels have superior strength and fracture toughness, compared to SA508 Gr.3 Mn-Mo-Ni low alloy steel. Therefore, the application of SA508 Gr.4N low alloy steel could be considered to satisfy the strength and toughness required in advanced nuclear power plants. The purpose of this study is to characterize the microstructure and mechanical properties of SA508 Gr.4N low alloy steels. 1 ton ingot of SA508 Gr.4N model alloy was fabricated by vacuum induction melting followed by forging, quenching, and tempering. The predominant microstructure of the SA508 Gr.4N model alloy is tempered martensite having small packet and fine Cr-rich carbides. The yield strength at room temperature was 540MPa, and it was decreased with an increase of test temperature while DSA phenomenon occurred at around $288^{\circ}C$. Overall transition property of SA508 Gr.4N model alloy was much better than SA508 Gr.3 low alloy steel. The index temperature, $T_{41J}$, of SA508 Gr.4N model alloy was $-132^{\circ}C$ in Charpy impact tests, and reference nil-ductility transition temperature, $RT_{NDT}$ of $-105^{\circ}C$ was obtained from drop weight tests. From the fracture toughness tests performed in accordance with the ASTM standard E1921 Master curve method, the reference temperature, $T_0$ was $-147^{\circ}C$, which was improved more than $60^{\circ}C$ compared to SA508 Gr.3 low alloy steels.
피대훈,나요원,장기영,서우근,이기형,은백린,Pee, Dae Hun,Na, Yo Won,Chang, Ki Young,Seo, Woo Keun,Lee, Kee Hyoung,Eun, Baik-Lin 대한소아청소년과학회 2002 Clinical and Experimental Pediatrics (CEP) Vol.45 No.10
저자들은 반복적인 안면 신경 마비의 과거력을 가진 환아에서 좌측 안면부의 부종과 함께 나타난 Melkersson-Rosenthal 증후군 증례를 경험하였기에 문헌 고찰과 함께 보고하는 바이다. Melkersson-Rosenthal syndrome(MRS) is a rare disorder, having a symptom triad of recurrent facial palsy, orofacial swelling and fissured tongue(lingua plicata). This disorder is usually recurrent or progressive, and monosymptomatic or oligosymptomatic forms have been reported to be more common than classic forms. Generally, MRS occurs in young adults at the end of the second decade of life and incidence of the disease in childhood is known to be very low. Although the clinical manifestation of MRS in children is similar to that in adults, early diagnosis and management is essential to avoid long-lasting functional disorders and psychological problems. We experienced MRS in a 13 year old boy with a history of recurrent facial palsy. We report this case with review of related literature.
Ni-Cr-Mo계 고강도 저합금강 용접클래드 계면의 미세조직 특성 평가
김홍은 ( Hong Eun Kim ),이기형 ( Ki Hyoung Lee ),김민철 ( Min Chul Kim ),이호진 ( Ho Jin Lee ),김경호 ( Keong Ho Kim ),이창희 ( Chang Hee Lee ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.8
SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are higher than in commercial SA508 Gr.3 Mn-Mo-Ni low alloy steels, may be a candidate reactor pressure vessel (RPV) material with higher strength and toughness from its tempered martensitic microstructure. The inner surface of the RPV is weld-cladded with stainless steels to prevent corrosion. The goal of this study is to evaluate the microstructural properties of the clad interface between Ni-Cr-Mo low alloy steel and stainless weldment, and the effects of post weld heat treatment (PWHT) on the properties. The properties of the clad interface were compared with those of commercial Mn-Mo-Ni low alloy steel. Multi-layer welding of model alloys with ER308L and ER309L stainless steel by the SAW method was performed, and then PWHT was conducted at 610℃ for 30 h. The microstructural changes of the clad interface were analyzed using OM, SEM and TEM, and micro-Vickers hardness tests were performed. Before PWHT, the heat affected zone (HAZ) showed higher hardness than base and weld metals due to formation of martensite after welding in both steels. In addition, the hardness of the HAZ in Ni-Cr-Mo low alloy steel was higher than that in Mn-Mo-Ni low alloy steel due to a comparatively high martensite fraction. The hardness of the HAZ decreased after PWHT in both steels, but the dark region was formed near the fusion line in which the hardness was locally high. In the case of Mn-Mo-Ni low alloy steel, formation of fine Cr-carbides in the weld region near the fusion line by diffusion of C from the base metal resulted in locally high hardness in the dark region. However, the precipitates of the region in the Ni-Cr-Mo low alloy steel were similar to that in the base metal, and the hardness in the region was not greatly different from that in the base metal.