• 대한전기학회논문지:전력기술부문A
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• 제49권5호
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• pp.233-241
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• 2000

This paper presents a systematic design procedure of $H_{\infty}$ controller of TCSC for damping low frequency inter-area oscillations in large power systems. Sensitivities of the inter-area mode for changes in line susceptance are computed using the eigen-sensitivity theory of augmented system matrix and TCSC locations are selected using the line sensitivities. The reduced model required for designing a manageable-size $H_{\infty}$ controller is obtained using the reduced frequency domain system identification method and the various weighting functions are tuned systematically to provide a robust performance. The proposed $H_{\infty}$ controller proved to be very effective for damping the inter-area mode of the large KEPCO power system.

• 한국치위생학회지
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• 제16권1호
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• pp.85-92
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• 2016

Objectives: The purpose of this study was to investigate comparison of the effectiveness on knowledge improvement before and after the oral health education focusing on foreign students. Methods: A self-reported questionnaire was filled out by 40 foreign students in Sun Moon University from June 2 to September 30, 2014. The experimental group had an online oral health education and the control group had an off line education. The questionnaire consisted of oral health(10 items), toothbrushing(10 items), dental caries(10 items), periodontal disease(5 items), tooth sensitivity(5 items), oral cancer(6 items), and smoking(5 items). The data were analyzed by SPSS Win 18.0 program. Results: Knowledge scores of online education increased to average 1.257 points, and that of offline education was average of 2.56 points. There were statistically significant results for toothbrushing, dental caries, periodontal disease, tooth sensitivity, oral cancer and TMD except for smoking in offline education group. Conclusions: This study suggests that the offline oral health education is more effective than online oral health education.

• 대한전기학회논문지:전력기술부문A
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• 제50권8호
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• pp.388-394
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• 2001

This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.559-579
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• 2015

An experimental study of the effect of mooring systems on the dynamics of a SPAR buoy-type floating offshore wind turbine is presented. The effects of the Center of Gravity (COG), mooring line spring constant, and fairlead location on the turbine's motion in response to regular waves are investigated. Experimental results show that for a typical mooring system of a SPAR buoy-type Floating Offshore Wind Turbine (FOWT), the effect of mooring systems on the dynamics of the turbine can be considered negligible. However, the pitch decreases notably as the COG increases. The COG and spring constant of the mooring line have a negligible effect on the fairlead displacement. Numerical simulation and sensitivity analysis show that the wind turbine motion and its sensitivity to changes in the mooring system and COG are very large near resonant frequencies. The test results can be used to validate numerical simulation tools for FOWTs.

• 농촌계획
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• 제7권1호
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• pp.37-48
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• 2001

The purpose of this study is to suggest the landscape potential index for visualizing landscape information in the conservation of hilly landscape in urban fringe. For the visual and quantitative approach to topological landscape assessment, numerical entity data of DEM(digital elevation model) were processed with CAD-based utilities that we developed and were mainly focused on analysis of visibility and visual sensitivity. Some results, with reference in assessing greenbelt area of Eodeung Mt. in Gwangju, proved to be considerable in the landscape assessment of suburban hilly landscapes. 1) Since the viewpoints and viewpoint fields were critical to landscape structure, randomized 194 points(spatially 500m interval) were applied to assessing the generalized visual sensitivity, we called. Because there were similar patterns of distribution comparing to those by 56 points and 18 Points given appropriately, it could be more efficient by a few viewpoints which located widely. 2) Regressional function was derived to represent the relationships between probabilities of visibility frequency and the topological factors(topological dominance, landform complexity and relational aspect) of target field. 3) Visibility scores of each viewpoint were be calculated by summing the visual sensitivity indices within a scene. The scores to the upper part including ridge line have been more representative to overall distributions of visual sensitivities. Also, with sum of deviations of sensitivity indices from each single point's specific index to the weighting values of view points could be estimated rotationally. 4) The deviational distributions of visual sensitivity classes in the topological unit of target field were proved to represent the visual vulnerability of the landform. 5) Landscape potential indices combined with the visual sensitivity and the DGN(degree of green naturality) were proposed as visualized landscape information distributed by topological unit.

• 디지털융복합연구
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• 제12권11호
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• pp.49-55
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• 2014

온라인 쇼핑몰의 증가로 인해 소비자들의 생활방식에도 많은 변화가 일어났다. 소비자들은 브랜드 상품을 더욱 저렴한 가격에 구매하려는 경향을 보임으로써 백화점은 브랜드 상품의 온라인 쇼핑몰 판매를 늘리고 있다. 이에 본 논문에서는 쇼핑몰의 실용적 쇼핑가치와 쾌락적 쇼핑가치가 쇼핑몰 만족에 미치는 영향과 가격민감도의 조절효과에 대해 검증하였다. 연구한 결과 쇼핑가치는 쇼핑몰 만족에 긍정적인 영향을 미치는 것으로 나타났고, 가격민감도가 높은 집단은 실용적 쇼핑가치에 긍정적인 영향을 미치고 가격민감도가 낮은 집단은 쾌락적 쇼핑가치에 더 긍정적인 것으로 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.186-189
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• 2001

The main method in micro-etching process, used in manufacturing semiconductors, electronic components, circuits, is Photo Masking method that exposes and develops on the photo-sensitivity solutions or films. This method enables one to process highly precisely, $\pm$0.03 mm in end line location area. But this has limits in a high speed / wide width process, difficulties in endless masking, and the problem of high price. We have developed the direct masking method to make use of Gravure printing, widely used in grocery packing sheet printing. We made cylinder tools to influence the masking quality by laser stream process. We have confirmed that the end line location accuracy in the line width of the product is improved from 0.12 mm to $\pm$0.07 mm level, after etching process.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권8호
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• pp.394-400
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• 2001

This paper describes an application of the on line partial discharge measurement method in operating transformer. In the operating transformer, the partial discharge signal may be superimposed by radio intereference voltage(RIV) and pulse shaped noise signals generated by external corona. The partial discharge quantity showed about 3,800pC due to very high sinusoidal interferences at the measuring impedance terminal of the transformer bushing tap. In order to reject these noises, this paper applied RIV filter, band-pass filters and noise gating method. The resulting measuring sensitivity was improved from 3,800pC to 160pC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.590-593
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• 2004

This paper presents recent trends on the on-line monitoring and diagnostic systems for oil-immersed transformers. Specially, our system on YeoSu thermal power plant is introduced for high sensitivity and accuracy of ours. It is combined with communication networks to provide an on-line remote monitoring system. Several alarm criteria are formulated to enable a superimposed monitoring system to perform decisive action. The reasons for monitoring the condition and maintaining the health of electrical apparatus were discussed. The experience at the fields and the criteria for the judgment are also discussed in detail.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.10-12
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• 2000

As power systems tend to be operated more closely to their ultimate ratings. the role of SCOPF is changed and the importance for real-time security inhancement will be more increased in the new and competitive electricity market. This paper deals with the application of the SCOPF which make possible the On-Line application. The security margin of power system truly is changed according to the conditions or configuration of power system, therefore, the sensitivity factor related to the security is recalculated and the application should be updated in accordance with the state of power system. The proposed mechnism has been tested on modified Woolenberg 18-bus system and the results show more secure conditions against critical contingencies.