• Proceedings of the KIEE Conference
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• 2006.07e
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• pp.17-18
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• 2006

최근 전기설비의 용량이 커짐에 따라 전기설비와 송전설비 및 배전설비 등에서 발생되는 사고는 '2003년 코로나 방전에 의한 미국 동북부 정전사고와 같은 대형사고로 직결될 수 있기 때문에 전기설비에서 발생되는 코로나방전 검출을 통한 기간시설 및 송배전 설비에 대한 사고 원인을 사전 도출하여 전기설비의 장기간에 걸친 원활한 운용과 신뢰성 확보가 매우 중요하다. 이를 위해서 최적의 무정전 첨단계측장비의 필요성이 대두되고 있다. 현재 전력공급의 중단없이 설비의 이상유무를 진단, 감시하기 위한 기술이 활발히 진행되고 있으며 전기설비의 예고 없는 고장발생시 파생되는 악영향은 매우 심각하며, 국내의 경우 전기설비의 노후화로 대형 사고의 위험성이 매우 높아 이러한 사고의 예방을 위한 예지보전(예측보전)을 위한 기술에 대한 도입이 필요하다. 최근 미국전기연구원(EPRI)의 주도로 코로나가 전기설비에 미치는 부정적 영향에 대한 연구가 활발하게 진행되었으며 그 결과 코로나 방전으로부터 전기설비의 안정성과 신뢰성을 확보하고 사고를 방지하기 위한 진단기술로서 OFIL사(社)의 DayCorII가 개발되었다. 이 논문에서는 전력설비와 송전 및 배전분야에 있어 발생하는 코로나 방전의 영향과 이를 탐지하는 진단기술에 대하여 초점을 맞추고자 한다.

• Journal of the Korean Geographical Society
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• v.49 no.1
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• pp.45-56
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• 2014

Data composite methods have been typically applied to satellite-based vegetation index(VI) data to continuously acquire vegetation greenness over the land surface. Data composites are useful for construction of long-term archives of vegetation indices by minimizing missing data or contamination from noise. In addition, if multi-sensor vegetation indices that are acquired during the same composite periods are used interchangeably, data stability and continuity may be significantly enhanced. This study evaluated the influences of sensor geometry on MODIS vegetation indices and investigated data compatibility of two difference vegetation indices, the Normalized Difference Vegetation Index(NDVI) and the Enhanced Vegetation Index(EVI), for potential improvement of long-term data construction. Relationships between NDVI and EVI turned out statistically significant with variations among vegetation covers. Due to their curvilinear relationships, NDVI became saturated and leveled off as EVI reached high ranges. Correlation coefficients between Terra- and Aqua-based vegetation indices ranged from 0.747 to 0.963 for EVI, and from 0.641 to 0.880 for NDVI, showing better compatibility for EVI compared to NDVI. In-depth analyses of VI outliers that deviated from regression equations constructed from the two different sensors remain as a future study to improve their compatibility.

• Journal of Agricultural Extension & Community Development
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• v.9 no.1
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• pp.131-145
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• 2002

국제연합에서는 $15{\sim}24$세의 젊은이를 청소년이라고 정의하고 있는데 그 중에서도 특히 농촌청소년은 미래 농촌발전의 핵심주체라 할 것이다. 일반적으로 농촌청소년은 그들 부모세대보다 더 높은 교육수준과 도전의식 그리고 더 높은 창의성을 지니고 있기 때문이다. 더욱이 그들은 미래가 자신의 장래와 직접적으로 연결되어 있기 때문에 장기적인 전망, 미래의 비전에 관심이 크다. 청소년에 대한 교육은 민주사회의 미래에서 한 사회가 할 수 있는 가장 중요한 투자 중의 하나라고 인식되며 현재 진행되고 있는 고도의 경쟁적인 시장경제로의 진입에서 청소년의 사회경제적 비전을 향상시키기 위해서는 교육과 훈련의 질적 양적 향상이 최우선시 되어야 할 것이다. 세계무역기구 출범 이후 농산물 수출국가와 선진국에서의 소득균형은 일반적으로 향상되었으나 순식량 수입국가나 개발도상국가에서는 소득균형이 더 악화되고 농업영역의 쇠퇴를 초래하고 있는 부작용이 국제연합 식량농업기구 등의 분석이다. 더욱이 식량안전상황은 농산물의 급격한 수입으로 여전히 불안하고 농가 판매의 지속적인 악화, 농촌과 도시간의 소득격차가 큰 것으로 나타났다. 특히 인간의 건강과 환경에 유해한 유전자조작 농산물 (GMO)의 교역은 소비자의 식품안전과 잠재적 위해 때문에 합당한 조치가 요구되고 있는 실정이다. 이러한 상황에서 농업교육, 연구 그리고 지도, 특히 아시아의 주요작물 영역에 대한 더 많은 투자가 필요하며 많은 아시아국가들에서 우선적으로 요구되는 농촌 청소년교육은 빈곤퇴치, 식량의 안정적 공급 및 식품의 안전 그리고 지속적이고 균형있는 농촌개발 등이다. 이를 위한 정부와 국민, 특히 농촌 청소년들의 연결망을 통해 함께 협력해야 빈곤퇴치와 식량의 안정적 공급 및 식품의 안전 등 농촌의 사회경제적 발전이 가능할 것이다. 이 연구에서는 아시아지역 농촌사회 및 식량농업의 발전을 위한 청소년 연결망을 예시적으로 검토하고 미래사회에서의 협력을 위한 접근을 탐색하였다.국제연합에서는 $15{\sim}24$세의 젊은이를 청소년이라고 정의하고 있는데 그 중에서도 특히 농촌청소년은 미래 농촌발전의 핵심주체라 할 것이다. 일반적으로 농촌청소년은 그들 부모세대보다 더 높은 교육수준과 도전의식 그리고 더 높은 창의성을 지니고 있기 때문이다. 더욱이 그들은 미래가 자신의 장래와 직접적으로 연결되어 있기 때문에 장기적인 전망, 미래의 비전에 관심이 크다. 청소년에 대한 교육은 민주사회의 미래에서 한 사회가 할 수 있는 가장 중요한 투자 중의 하나라고 인식되며 현재 진행되고 있는 고도의 경쟁적인 시장경제로의 진입에서 청소년의 사회경제적 비전을 향상시키기 위해서는 교육과 훈련의 질적 양적 향상이 최우선시 되어야 할 것이다. 세계무역기구 출범 이후 농산물 수출국가와 선진국에서의 소득균형은 일반적으로 향상되었으나 순식량 수입국가나 개발도상국가에서는 소득균형이 더 악화되고 농업영역의 쇠퇴를 초래하고 있는 부작용이 국제연합 식량농업기구 등의 분석이다. 더욱이 식량안전상황은 농산물의 급격한 수입으로 여전히 불안하고 농가 판매의 지속적인 악화, 농촌과 도시간의 소득격차가 큰 것으로 나타났다. 특히 인간의 건강과 환경에 유해한 유전자조작 농산물 (GMO)의 교역은 소비자의 식품안전과 잠재적 위해 때문에 합당한 조치가 요구되고 있는 실정이다. 이러한 상황에서 농업교육, 연구 그리고 지도, 특히 아시아의 주요작물 영역에 대한 더 많은 투자가 필요하며 많은 아시아국가들에서 우선적으로 요구되는 농촌 청소년교육은 빈곤퇴치, 식량의 안정적 공급 및 식품의 안전 그리고 지속적이고 균형있는 농촌개발 등이다. 이를 위한 정부와 국민, 특히 농촌 청소년들의 연결망을 통해 함께 협력해야 빈곤퇴치와 식량의 안정적 공급 및 식품의 안전 등 농촌의 사회경제적 발전이 가능할 것이다. 이 연구에서는 아시아지역 농촌사회 및 식량농업의 발전을 위한 청소년 연결망을 예시적으로 검토하고 미래사회에서의 협력을 위한 접근을 탐색하였다.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.71-79
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• 2015

This paper describes vegetation based soil-media hydroseeding measures that have been previously applied as slope revegetation methods show problems such as insufficient binding force, drying, and insufficient organic matter. In particular, in the case of slope faces in regions where scattering is severe, a vicious circle exists in which remarkably low vegetation cover rates and increases in withering rates over time lead to further decreases in vegetation cover rates, which lead to further increases in erosion and scattering. Therefore, in the present study, environment friendly soil stabilizers were applied for resistance against erosion or scattering and engineering evaluations such as long-term immersion tests and flow resistance tests were conducted to determine appropriate mixing ratios. According to the results of long-term immersion tests utilizing environment friendly soil stabilizers and existing greening soil based materials, 100% collapse occurred at 30 hours and 40 days in the case of soil stabilizer mixing ratios of 0% and 2%, respectively. While the original form of the samples remained intact until the experiment was completed in the case of mixing ratios exceeding 4% indicating that 2% or higher soil stabilizer mixing ratios could affect the maintenance of forms even under extreme conditions. In addition, artificial rainfall tests were conducted on 40, 45, and 55 degree slope faces to evaluate the structural stability of vegetation based materials. Flow resistance tests were conducted on soil stabilizer mixing ratios of 0, 4, 8% to evaluate erosion resistance capability. Based on the results of the tests, environment friendly soil stabilizers applied for prevention of scattering or resistance against erosion by rainwater are considered to provide large effects to reduce losses and loss rates showed a tendency of decreasing rapidly when soil stabilizers were mixed.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.361-370
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• 2016

This study was performed in order to evaluate the efficiency of groundwater well installed in alluvial aquifer that has filter layers, using laboratory experiment. We manufactured test equipment that can simulate dual filter layer and single filter layer and evaluated the initial volume of water intake, pumping efficiency, and long term stability using the experiment and analysis. In an early stage within 60 minutes, the case that took the dual filter showed an increase of 19.4 % in the initial volume of water intake compared to the case without it. It was found that after 24 hours of the test, the well installed with the dual filter showed higher than 68.9% compared to the well with single filter. It was calculated that it took 1.35 days to reach the point corresponding to the half of the water intake in case of single filter while it took 38.66 days to do so in case of dual filter. Therefore, it is highly recommended that the well with dual filter is much more favorable in the long term stability.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.251-259
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• 2014

The transition zone between an earthwork and a bridge effect to the vehicle's running stability because support stiffness of the roadbed is suddenly changed. The design criteria for the transition structure on ballast track were not particular in the past. However with the introduction of concrete track is introduced, it requires there is a higher performance level required because of maintenance and running stability. In this present paper, a transition structure reinforced with geosynthetics is suggested to improve the performance of existing bridge-earthwork transition structures. The suggested transition structure, in which there is reinforcing of the approach block using high-tension geosynthetics, has a structure similar to that of earth reinforced abutments. The utilized backfill materials are cement treated soil and gravel. These materials are used to reduce water intrusion into the approach block and to increase the recycling of surplus earth materials. An experiment was performed under the same conditions in order to allow a comparison of this new structure with the existing transition structure. Evaluation items are elastic displacement, cumulative settlement, and earth pressure. As for the results of the real-scale accelerated testing, the suggested transition structure has excellent performance for the reduction of earth pressure and settlement. Above all, it has high resistance the variation of the water content.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.453-459
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• 2021

The system marginal price of electricity is the amount paid to all the generating units, which is an important decision-making factor for the construction and maintenance of an electrical power unit. In this paper, we suggest a long-term forecasting model for calculating the system marginal price based on prices of natural gas and oil. As most variables used in the analysis are nonstationary time series, the long run relationship among the variables should be examined by cointegration tests. The forecasting model is similar to an error correction model which consists of a long run cointegrating equation and another equation for short run dynamics. To mitigate the robustness issue arising from the relatively small data sample, this study employs various testing and estimating methods. Compared to previous studies, this paper considers multiple fuel prices in the forecasting model of system marginal price, and provides greater emphasis on the robustness of analysis. As none of the cointegrating relations associated with system marginal price, natural gas price and oil price are excluded, three error correction models are estimated. Considering the root mean squared error and mean absolute error, the model based on the cointegrating relation between system marginal price and natural gas price performs best in the out-of-sample forecast.

• The Journal of the Korea Contents Association
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• v.22 no.7
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• pp.73-80
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• 2022

In this study, prior studies of 280 small business owners in Korea over the past two decades were comprehensively analyzed through keyword network and LDA topic modeling analysis, and overall views and trends in academia were examined. As core keywords, "sales" and "protection," which conflict with each other but are essential for stable and sustainable growth were selected, and 7 topics (Topic 1: start-up, topic 2: digital, topic 3: tax system, topic 4: capability, topic 5: coexistence, topic 6: regulation, and topic 7: funding) were drawn up. Based on the results of the analysis, the need to improve digital maturity for the continued growth and development of small business owners was raised, and the response at the pan-ministerial level and the stability of the performance of functions that can survive even after the new administration to solve the economic damage problems facing small business owners were suggested. In addition, attention to the long-term, speed, detail, and direction of government support in a new way, and a flexible approach to the negative way in which pre-allowance and post-regulation is given were suggested.

• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.506-525
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• 2006

For the design of large scale rock slope which has complex formations and geological structures, generally, insufficiency of geotechnical investigations and laboratory tests are the main factors of slope failures doling construction. In such case, remedial measures to stabilize slope should be selected and applied through reliable investigations and analysis considering the geotechnical characteristics. The rock slope of this study, one of the largest cut slopes in Korea with a length of 520.0 m and maximum height of 122.0 m consists of metasedimentary rocks. And a case study on the causes of large-scale rock slope failure was carried out by analysis of landslides history and site investigations during construction. When the slope with the original design slope of 0.7: 1.0 (H:V) was partially constructed, the slope failure was occurred due to the factors such as poor conditions of rocks (weathered zone, coaly shale and fault shear zone), various discontinuities (joints, foliations and faults), severe rain storm and so on. The types of failures were rockfall, circular failure, wedge failure and the combination of these types. So, the design of slope was changed three times to ensure long-term slope stability. This paper is intended to be a useful reference for analyzing and estimating the stability of rock slopes whose site conditions are similar to those of this study site such as geological structures and geotechnical properties.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.40 no.3
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• pp.227-236
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• 2014

In this study, O/W and W/S emulsions were prepared by combining oils having different required hydrophilic lipophilic balance (HLB) values under the diverse conditions of HLB values composed of a hydrophilic surfactant and a lipophilic surfactant and their stability was investigated. Results showed that the higher the viscosity of O/W emulsions was as the lower the HLB value of emulsifier and emulsion particle showed a tendency to be a smaller and compact and stabler in centrifugal filtration. W/S emulsions also showed a similar tendency to be a smaller and compact as HLB values of emulsifier was higher and stabler in centrifugal filtration. However, the viscosity of W/S emulsion tended to get lower in HLB conditions of all emulsifiers as the time passed. This indicated that the emulsions had an unstable feature in long-term stability. In conclusion, the results showed opposite to the known theory that O/W emulsion is proper to be applied by nonionic surfactant with a high HLB value and W/S emulsion to be applied by nonionic surfactant with a low HLB value and provide useful information for the cosmetics research and related areas.