Study on Reliability Improvement of Voltage Transformers by Increasing Voltage Factor

Tae‑Sik Kong,Hee‑Dong Kim,Hung‑Sok Park,Soo‑Hoh Lee,Soon‑Yong Kim,Pil‑Bum Joung,Jin‑Yeub Park 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3

Voltage transformers (VTs) must be highly reliable as they are essential components of the electric power industry. VT failures can cause a signifcant impact for important facilities such as nuclear power plants. In fact, VTs which passed the international standard, were damaged and sometimes resulted in the shutdown of the nuclear power plants. In order to improve the reliability, VTs with various iron core was studied. The electromagnetic feld simulation, a saturation characteristics test, and an overvoltage breakdown test were conducted. The result shows that the magnetic fux density signifcantly afects the reliability of VTs. To increase the reliability of VTs, it is required to reduce the magnetic fux density by increasing the knee-point and voltage factor. Owing to limited installation space, increasing the size of the iron core is difcult. Instead, VT by decreasing the thickness of the conductor and increasing the number of turns, it was possible to reduce the magnetic fux density without the size change. Therefore, improved VTs were obtained by decreasing the thickness of the conductor and increasing the number of turns, and the improved reliability was verifed through a comparison test with existing VTs. The fabricated VTs shows a signifcantly higher saturation voltage and breakdown time than existing VTs. Thus, by proposed VTs can contribute the stable operation of the nuclear power plant and improve the manufacturer’s quality.

편측안면경련에 대한 미세혈관압술시 수술시야 확보를 위한 방법으로서 소뇌피질동맥 박리술 - 수 술 수 기 -

김범태,임수빈,장재칠,신윈한,최순관,변박장 대한신경외과학회 1998 Journal of Korean neurosurgical society Vol.27 No.11

Micrococcineae에 속하는 식물 연관 방선균

김태수,한지혜,김승범 충남대학교 생물공학연구소 2012 생물공학연구지 Vol.18 No.-

공동주택 유지관리 FCI 모니터링에 관한 연구

범성우,정영한,박태근 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1

After the 1980' s governmental housing business policy was vigorously attained, demand of apartment housing is still on the increase, but systematic maintenance is not following this current incerase trend. A promotion about the realization on the importance of maintenance due to life-time degradation of apartment housing and a plan of life-long practice of maintenance established together with longterm stratergy for maintance upkeep must be imperative. Purpose of this study presents application plan about FCI from rifle cycle viewpoint of building. Expect that is used laying plan that is middle part of a song miracle in actuality and expense arbor in the mountains of longtimer line plan of apartment house. As administration subject establishes well-timed repair time and more strategic budget, may behave better maintenance.

춘천지역 도시열섬의 특성과 대기질에 미치는 영향

이종범,김용국,김태우 江原大學校 附設 環境硏究所 1994 環境硏究 Vol.11 No.-

An observational study of urban heat is1and was carried out using field data obtained during 6 day in May and August 1992 in Chunchon(Population size 180,000). Air temperature was measured at 04 points along two sampling routes by thermisters attached to cars, Both routes cover urban and rural area and across the center of urban area, Continuous observation of air sonde was performed to clarify heights of nocturnal boundary layer(NBL) at the center of urban area. Surface meteorological observations were performed at both urban and rural site. This study showed that heat island Phenomena was obvious1y observed at the urbanized area during the night time With low wind Speed. The average NBL heights extended to about 100 meters, but varied with meteorological conditions. After sunset the air temperature decreased with time at both sites and cooling rate at the urban site was Heater than the rural site. The maximum heat island intensity was 7.5°C at 21 LST May 4. Using the two meteorological data gets obtained from urban and rural sites, the air Pollutant concentration was calculated by Gaussian plume model which can obtain not only horizontal distribution of concentration but also vertical distribution. The result indicated that the concentration resulted from urban meteorological data set was lower than that from rural meteorological data set. It was also calculated that the air pollutant extended to higher level in urban meteorological data set than that in rural meteorological data set.

膨脹率이 一定한 超音速 노즐흐름에 있어서 非平衡 凝縮과 傾斜衝擊波

권순범,최태민,김병지 慶北大學校 1990 論文集 Vol.49 No.-

In the present study the case of expansion of moist air through a supersonic nozzle of constant expansion rate, which behaves similar to that of wet steam, was adopted. The effect of noneqilibrium condensation on the oblique shock wave generated by placing the wedge into the supersonic part of the nozzle was investigated. Furthermore, the variation of the condensation onset Mach number with the initial stagnation supersaturation, the relationship between noneqilibrium condensation zone and incident point of the oblique shock wave, the varation of angles of incident and reflected shock waves due to the variation of initial stagnation supersaturation, and the relationship between the height of Mach stem and initial stagnation supersaturation are discussed.

하악골에 발생한 골막 골육종

김태우,김승범,권혁찬,문선재,윤정훈,김형준,차인호,육종인,김진 대한악안면성형재건외과학회 2002 Maxillofacial Plastic Reconstructive Surgery Vol.24 No.1

Periosteal osteosarcoma is a distinct entity of malignant bone tumor with characteristic clinical, morphological, and histological features within the group of juxtacortical osteosarcoma. Periosteal osteosarcoma is predominantly located in the tubular long bones, and extremely rarely involving the jaws. A case of periosteal osteosarcoma of the right mandible is presented. A 27-year-old woman complained of the gingival swelling and bleeding tendency of the right posterior mandible. Clinical examination revealed a reddish brown strawberry-like swelling on the affected mucosa, which measured 1.5㎝×1.5㎝. The tumor was located on the lingual cortex of the mandible and extended into the surrounding soft tissues. Microscopically, the tumor consisted exclusively of atypical chondroblastic cells with a small osteoblastic area. A minimal bone marrow involvement was noted and the adjacent cortex was free of tumor. These findings suggested that the tumor originated from the periosteal cambium layer, which lies between the periosteal fibrous layer and the cortex of mandible.

양이온 개환 공중합을 이용한 HTPE (Hydroxy terminated polyether) 합성

김태중,유호준,이범재 충남대학교 바이오응용화학연구소 2007 응용화학공학 Vol.1 No.1

HTPE(hyroxy terminated polyether)의 합성을 위해 Ethylene Oxide(EO)와 Tetrahydrofuran (THF)을 1,4-Butane-diol의 존재 하에서 촉매로서 BF3OEt2를 사용하여 0~15℃의 온도에서 양이온 개환공중합을 통해 합성하였다. 또한 모노머와 개시제의 비율조절과 모노머의 농도조절을 통하여 HTPE의 분자량의 변화를 확인하였다.

광조사 방법에 따른 치과용 심미수복재의 중합수축

윤태호,이용근,임범순,김철위 대한치과기재학회 2000 대한치과재료학회지 Vol.27 No.4

Dental resin composites were introduced commercially in the mid-1960s for the restoration of anterior teeth. Since their advent, resin composites have undergone significant development, which continues to improve the longevity and application of resin composite restorations. Despite the development of new dentin-bonding agents, no system is currently available that completely withstands the formation of contraction gaps at the cementum/dentin-restoration junction, due to the unavoidable polymerization shrinkage of the resin composite during setting, therefore, a major aim of this study was to minimize or control the polymerization shrinkage of composites allowing flow of resin during setting reaction. A thermal dilatometer (DIL 402C, TASC 414/3A Controller, Netzche, Germany) was used to measure and compare conventional continuous cure and pulse cure polymerization shrinkage of seven light curing dental composites and three compomers. For conventional cure, restorative material were polymerized for 2 minutes using VIP (Bisco, U.S.A.) with 400 ㎽/㎠ intensity. After then, further polymerization was allowed for next 12 minutes that total 14 minutes of shrinkage was measured. For pulse cure, material was pre-polymerized irradiating light for 5 seconds with 200 ㎽/㎠ and post-ploymerized 3 minutes later with 400 ㎽/㎠ for 2 minutes. 9 minutes were allowed for further polymerization that total 14 minutes of shrinkage was measured. Polymerization shrinkage ranged from 3.758 ㎛/㎜ (SYC) to 6.897 ㎛/㎜ (P60) for conventional cure and 4.026 ㎛/㎜ (FLT) to 6.996 ㎛/㎜ (SRF) for pulse cure. The highest difference between the two methods was found at EAN (2.713 ㎛/㎜), followed by F20 and CRA which showed significant differences of 2.133, 1.274 ㎛/㎜ respectively (p<0.05). The least difference was found at SYC (0.489 ㎛/㎜). Universal resin composite group showed the highest polymerization shrinkage (6.514±0873 ㎛/㎜), and flowable composite showed the least shrinkage (4.139 ㎛/㎜). Packable composite showed 5.090±1.906 ㎛/㎜, and compomers showed 6.129±2.652 ㎛/㎜.

강우시 침투영향을 고려한 사면안정해석

심태섭,기완서,김선학,최순범 朝鮮大學校 建設技術硏究所 2007 建設技術硏究 Vol.27 No.2

Most of current slope safety analyses consider only the effect of the rise of underground water level. However, because the infiltration of surface water into the ground is believed to have significant effects on slope stability, the present study performed slope safety analysis in case of the rise of underground water level, the infiltration of surface water, and both resulting from rainfall, and examined their effects. For this study, we selected Slope A and B, at which slope failure had happened due to rainfall, and made slope safety analysis in consideration of the fall of wetting front and the rise of underground water level resulting from rainfall. Based on the results of the analysis, we made comparative analysis on the relation between the effect of infiltration on rainfall and the stability of the slopes and proposed a desirable slope safety analysis method. The conclusions of this study are as follows. 1. In slope safety analysis in consideration of the effect of infiltration resulting from rainfall, the variation of safety factor was different depending on whether to consider the fall of wetting front, the rise of underground water level. or both. 2. The decrease of the slope safety factor caused by the fall of wetting front on rainfall was somewhat faster than that caused by the rise of underground water level. This suggests that slope failure caused by rainfall is affected more by the fall of wetting front than by the rise of underground water level. 3. When both the fall of wetting front and the rise of underground water level were considered at the same time, the slope safety factor decreased faster than when either the fall of wetting front or the rise of underground water level was considered. Accordingly, it is considered desirable to consider both the fall of wetting front and the rise of underground water level in slope safety analysis that takes into account the effect of infiltration resulting from rainfall.