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정연택,서영수,김연풍 明知大學校 産業技術硏究所 1986 産業技術硏究所論文集 Vol.5 No.-
In this paper, we combine the lead condensor connected on the side of load with the dual 3-pulse converter which has the intermediate-point interphase reactor in the symmetrical phase displacemental transformer, to improve power factor. For the variation of reactive power variable inductor acts as VAR compensator to reduce harmonics, and to improve power factor and waveform.
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최형일,채희정,김연풍,조도호,설동화,정숙경,김정애 조선대학교 생산기술연구소 2007 生産技術硏究 Vol.29 No.1
This study has been conducted to achieve the following objectives: First, in order to understand the horizontal propagation and attenuation characteristics for the road traffic noise, we selected actively developed areas within 100 meters away from the road to measure the level of traffic noise near a road. To measure the noise near a railroad, we selected areas within 100 meters away from the road. In this way, we analyzed the horizontal propagation and attenuation characteristics for the traffic noise occurring in diversified areas. Second, in order to understand the vertical propagation and attenuation characteristics for the road traffic noise, we measured and analyzed the distributional characteristics of vertical sound pressure levels on each floor of multi-storied apartment buildings according to changes of traffic load and types, and the existence or nonexistence of soundproof walls. For the case of the road traffic noise, we also selected we measured and analyzed the different noise levels on each floor of multi-storied apartment buildings from the soundproof wall. The results of Horizontal propagation and attenuation characteristics for the road traffic noise are as follows: In cases of the soundproof wall + raising ground, raising ground, cutting land, and flat land as distance increases, the sound pressure level steadily decreases. The soundproof wall + raising ground has an especially high distance decrease compared to the other areas, and the sound pressure level for the raising ground is higher than that of the cutting land with a measurement of 10.7~12.1dB(A). Vertical propagation and attenuation characteristics for the road traffic noise are as follows: The amount of sound pressure level decrease is 12.6- 14.5dB(A) for first floor when measuring the vertical sound pressure levels at soundproof wall, which indicates a fairly large decrease. At fifth and sixth floor, the amount of decrease is 2.3dB(A), which indicates a small decrease.
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최형일,김난희,강영주,채희정,김연풍,조도호,설동화 조선대학교 환경공해연구소 2007 環境公害硏究 Vol.20 No.1
Because mountain streams have narrow widths and steep slopes compared to streams and lakes, hours of immobility are considerably short, and the quality of mountain streams has been greatly influenced by rainfall, land-use, components of the streambed and types of forests. During the summer when heavy rainfall occurs, eroded earth and sand flow into mountain streams and cause temporarily high turbidity. It is also the cause of eutrophication, which is frequently found in downstream. As evaluation standards for the quality of mountain streams were not established in Korea, this quality was evaluated by examining some items based on quality standards for drinkable water and research on the influences of pollution in mountain streams, which showed that these were seldom in downstream water systems. Mountain streams within Wolchulsan National Park flow into a reservoir and when characteristics of mountain streams from forests and rainfall that flow into mountain streams through forest ecosystems were studied, results of measuring its changes are as follows. Monthly changes of pH were low between April and August and higher starting October, and the EC was measured higher in the winter and the spring and tended to be low starting April. The EC on the 19th of May and the 23rd of October and the concentration of floating materials and COD_(Mn) were observed to be higher due to the influence of rainfall on the 19th of May and the 22nd of October, and it was judged that the washing out of dried deposits attached to the water pipe and the leaching of woods were influenced by rainfall. It is considered that real-time monitoring of water quality for a long time and water quality conditions during and after rainfall should be examined for ensuring basic data of water quality and evaluating characteristics and seasonableness of mountain streams, which may be greatly changed by artificial influence in the future.
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최형일,강영주,채희정,김연풍,조도호,설동화,정숙경 조선대학교 환경공해연구소 2007 環境公害硏究 Vol.20 No.1
After the vehicle has become a large formation with high-speed, loud noise from an express highway is increasing, and the number of large-scale apartment complexes, which are recently being constructed in the metropolitan area nearby the express highway and IC, is increasing gradually. Compared with a main road, the traffic volume and the speed of a vehicle between IC and the ramp way [turn-off] are smaller. If the ramp way is rightly connected with the downtown area, however, the traffic-noise that comes about in surrounding areas will be in conjunction with the traffic-noise from the main road of express highway and that of the ramp way. This research has selected a place that hasn't had a road or a commercial quarter nearby the main-road of IC and ramp way. Then we have studied the traffic-noise status under minimizing influence of its outer-noise, which occurs in IC. 1. The traffic volume change of a small and full-sized car with time has been kept on regularity in 2004 and 2005. As the traffic volume of a full-sized car has diminished remarkably, it has been maintaining through 6:00a.m.-10:00 a.m. As it has decreased since lO:OO a.m.. we have also observed the traffic proportion going up. 2. Monthly traffic volume of small cars was higher in May, August and October than other months. We have observed that the high traffic volume during these months is due to the following: May-The Damyang festival, August-a high-demand season, October-viewing scarlet maple leaves. Monthly traffic volume of full-sized cars was generally higher in August, but it has decreased during 2006. This was due to the many construction trucks that were working on the extension of the 88 Olympic expressway. Therefore, there was more traffic volume in 2006 compared to 2004 and 2005. 3. In this study, the noise figures have been less than 55 dB(A) in 18 spots. There were 14 spots from 55dB(A) to 58dB(A). 58-61dB(A) : 20, 61-64dB(A) : 17, 64-67dB(A) : 18. There were 8 spots we observed at the highest level from 67dB(A) to 70dB(A). Those were the nearby spots separating the main road and Damyang IC. 4. Traffic-noise at the boundary between IC and the main road of an expressway was higher than that of the same distance in other places. 5. We have observed that traffic-noise is low in places with mountains that serve the role of soundproofing walls. Thus, the fundamental sound hadn't affected it.
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김동욱(D.U.Kim),김연풍(Y.P.Kim),신현주(H.J.Shin),백병산(B.S.Baek),류승표(S.P.Ryu),민병권(B.G.Min) 전력전자학회 1999 전력전자학술대회 논문집 Vol.- No.-
When several UPSs are connected in parallel, individual UPS should take charge of exactly same load current Because the output impedance of each UPSs is very low, small voltage difference among them will give rise to circulating current will bring about the decrease of UPS own capacity.<br/> In order to solve this problem in this paper an inverter controller for the UPS which has a good response characteristic and robustness for directly applying in industrial world is proposed. This paper also describes that difference between load current divided by number of operating inverters and its own current is detected as unbalanced current Then frequency and voltage are controlled to minimize the active component and the reactive component respectively. A good controller load-sharing technique is verified by experiments in the parallel poerating system with 40kVA UPSs.
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