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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.
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.
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.
隔板을 가진 水平環狀空間에서 自然對流에 관한 實驗的 硏究
鄭泰鉉,金善政,李範澈,權純錫 동아대학교 공과대학 부설 한국자원개발연구소 1988 硏究報告 Vol.12 No.2
Natural convection from a horizontal annulus with spacers has been studied on the effects of Rayleigh numbers and position of spacers by experimental method. In case of vertical spacers, the maximum local Nusselt number appears at θ=150° in a conducting tube and θ=30° in a cylinder. The local spacer Nusselt numbers show positive values on the lower spacer, but negative values on the upper spacer. In case of horizontal spacers, the flow over the spacer is more active than that of under the spacer as the Rayleigh number increase. The maximum local Nusselt number appears at θ=180° In a tube and at θ=0° in a cylinder. The local spacer Nusselt number show positive values on the upward surface of spacer, but negative values on the downward surface of spacer. The mean tube Nusselt numbers and mean cylinder Nusselt numbers with vertical spacer are increased 11% And 2.7%, respectively by those of horizontal spacer.
튜브형 이산화질소 passive sampler의 태양광 영향에 관한 분석
이범진,김학민,인치경,김선태 대전대학교 산업기술연구소 2000 산업기술연구소 論文集 Vol.11 No.2
The purpose of this study is to estimate the effect of sunlight on the measurement results of the tube type of NO2 passive sampler. Total 252 samples; seven duplicates, two sites with different concentration level, and nine days concerning to both exposure to sunlight and screened passive samplers with aluminium foil, were measured and analyzed. Relative standard deviation(%) of measurement data in this study was calculated as less than 10%, and it meant that even the simplest passive sampler showed comparatively high precision. The average concentration values of the screened passive samplers were turned out to be 22.4%∼25.5% higher than that of the passive samplers which were exposed to sunlight. Consequently, the sunlight was found to be the most important meteorological factor to affect the measurement for the tube type of passive samplers.
감광성 Maleimide 공중합체의 합성과 Epoxyacrylate의 영향
김태호,김용범,이재우,김상민 成均館大學校 科學技術硏究所 1997 論文集 Vol.48 No.1
Poly[[N-(4-hydroxyphenyl)maleimide]-co-styrene] and epoxyacrylate were synthesized. In order to give photosensitive properties cinnamoyl group was added to the copolymer and epoxyacrylate was mixed with copolymer for high crosslinking density and conversion rate. And the chemical structures of synthesized materials were confirmed using instrumental analysis such as FT-IR and ^1H-NMR. Mn ̄ of the copolymer was measured via GPC 17300 and Tg of the copolymer was measured via DSC 130-180℃. Photosensitive characteristics of the prepared resins were tested using UV and FT-IR. From this test the following phenomena were found; 1)the conversion rate of crosslinkable double bonds in early stage of photoreaction was increased as increase the ratio of epoxyacrylate to copolymer, 2)the final conversion was also increased, 3)the resolution power of the mixture was up to 2㎛.
Horizontal Variation of Primary Productivity and Enviromental Factors in the Lake Soyang
김범철,조규송,안태석 江原大學校 附設 環境硏究所 1989 環境硏究 Vol.6 No.-
소양호 일차생산력의 계절적 변화와 수평적 변이를 존사하기 위하여 Chlorophylla의 농도를 측정하고 Bannister의 model에 의해 일차생산력을 추산하였다. Bannister는 Smith의 P vs, I 관계식인 P=P_(max)I/(I_(k)^(2) + I^(2)^(1/2)을 변형하여 P=12Q_(max)K_(c)CI/ I^(2)^(1/2)과 같은 P vs. Chl. a의 관계식을 만들었다. 이 Model에 의해 추산된 소양호의 일차생산력을 보면 하류의 댐앞에서 연중 200∼2000mgC/㎡/day로서 봄에 가장 높고 여름과 겨울에 낮게 나타나는 계절적 변이를 보인다. 연간 생산량은 하류에서 약 250gC/㎡/yr로서 mestotrophic lake 수준인 것으로 판정된다. 상류에서 하류에 이르기까지 10여개의 정점에서 조사된 결과를 보면 수역에 따라 큰 차이를 보이고 있다. 대체로 봄과 가을에 하천의 유입부 근처에서 높은 값을 보이며 10,000mgC/㎡/day이상에 이르기도 한다. 이는 이곳에 우점 식물플랑크톤인 Peridinium이 밀집하는 현상때문이다.