• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1248-1257
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• 2014

Overhead transmission lines are crucial components in power transmission systems. Well-designed maintenance strategy for overhead lines is required for power utilities to minimize operating costs, while improving the reliability of the power system. This paper presents a maintenance priority index (MPI) of overhead lines for a reliability centered approach. Proposed maintenance strategy is composed of a state index and importance indices, taking into account a transmission condition and importance in system reliability, respectively. The state index is used to determine the condition of overhead lines. On the other hand, the proposed importance indices indicate their criticality analysis in transmission system, by using a load effect index (LEI) and failure effect index (FEI). The proposed maintenance method using the MPI has been tested on an IEEE 9-bus system, and a numerical result demonstrates that our strategy is more cost effective than traditional maintenance strategies.

• 한국컴퓨터정보학회논문지
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• 제24권12호
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• pp.85-92
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• 2019

기업들은 소셜 미디어로부터 특정 주제 및 자사 제품에 대한 다수의 사용자들의 의견을 수집하고 분석하여 사용자 집단이나 소비 트렌드를 식별할 수 있고, 이를 기반으로 미래 예측 및 마케팅 등의 다양한 목적으로 활용하고 있다. 따라서 현재 소셜 미디어 분석 도구들이 네트워크 통계 분석을 통해 기업의 소셜 미디어 마케팅의 성과를 측정하기 위한 수단으로 사용되고 있다. 그러나 이러한 도구들은 방대한 양의 소셜 미디어 데이터를 수집하고 이를 분석하기 위해 고가의 컴퓨팅 자원 및 네트워크 자원을 소모하고, 복잡한 소프트웨어 플랫폼 구축 및 운용에 따른 비용 부담과 많은 운영 노하우를 필요로 한다. 그 결과 중소기업이나 개인 사업자의 경우는 이러한 소셜 미디어 데이터를 효율적으로 활용하지 못하는 어려움이 있다. 따라서 본 논문에서는 중소기업이나 개인 컴퓨터에서도 운영이 가능한 소셜 미디어 데이터 수집 및 분석 시스템 개발에 필요한 프레임워크 설계와 제시된 프레임워크 설계에 대한 완전성이나 일관성을 검증하기 위한 정형 명세 기법을 제시한다. 또한 정형명세 기법으로 Z 언어를 통해 명세한 결과를 Z-EVES Tool을 통해 Z 모델 체킹을 수행하여 프레임워크 설계의 명확성을 검증한다.

• 대한토목학회논문집
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• 제42권3호
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• pp.391-398
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• 2022

외국인 관광객의 편의를 제공하기 위하여 개발 판매되었던 M-pass(왹국인 전용카드)의 이용률은 최근5년간 서울방문객의 0.051 %에 불과 하였다. 이렇게 저조한 판매마저도 코로나 19로 인하여 2020년 경우 0.024 % 수준으로 하락하였다. 성과부진의 원인은 국토부와 카드발행사가 교통운영기관을 배제하고 추진하였고 홍보부진과 가격결정의 불합리성, 소수의 판매장소 한정 등이 문제점으로 나타났다. 이러한 문제를 해결하기 위하여 Digital Matketing 체계의 구축과 함께 모든 관련기관의 참여와 의견이 반영된 새로운 상품 개발 등의 경영전략이 필요한 것으로 연구결과 나타났다. 본 연구로 포스트코로나 시대 외국인 서울관광객의 편의 제공 뿐만아니라 지하철 운영기관의 경영개선에 도움이 될 수 있기를 기대 한다.

• Strategy21
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• 통권43호
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• pp.125-174
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• 2018

The purpose of this paper is to analyze the status of naval arms race in Northeast Asia. To this end, the scope of the research was limited to national security strategies, maritime strategies and naval strengthening of the United States, China, Russia and Japan. The major powers' active maritime strategies and naval arms race give some strategic implications to the Republic of Korea Navy as follows. First, China and Japan, unlike the past, are actively using submarines in offshore waters including the Korean Peninsula. Therefore, the ROK Navy must successfully promote the Jangbogo-III-class submarine, which is currently constructed, and get a nuclear-powered submarine and P-8 MPA capable of long-range and long-time operations to enhance ASW capability. Second, North Korea's current building submarines capable of loading SLBMs and SLBMs are a new threat to the ROK Navy. The current building KAMD, which focuses on terminal phase defense, cannot effectively respond to North Korea's SLBMs and should be converted to a multi-layered defense system including SM-3 at a mid-course phase. Third, as China militarizes the South China Sea, the instability of the South China Sea is growing. Therefore, the ROK Navy should strengthen its maritime cooperation with the regional countries such as Japan and ASEAN navies to protect SLOC. In conclusion, the ROK Navy needs to build a strong naval power to keep in mind that the 21st century naval rivalry in Northeast Asia is accelerating. The navy must do one's best to protect national strategic and vital interests by strengthening cooperation with regional countries. South Korea is also accelerating its defense reforms in accordance with the pattern of future warfare and the ROK Navy do one's best to have a balanced naval capability capable of actively operating in the offshore waters.

• 복식문화연구
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• 제11권1호
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• pp.165-176
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• 2003

The purpose of this study is to understand the characteristics and concepts behind Design for Environment(DfE) and Environmental Management System(EMS). This study highlights the success of domestics and foreign corporations that have utilized DfE and EMS as well as explored how DfT based EMS is being used in domestic corporations. Although corporations acknowledge that using environmentally conscious designs provide them with a competitive edge, only 53.6% of fashion corporations have established the environmental policies and use such tools. Furthermore, only 41% use DfE strategies for operating their corporations.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.626-630
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• 2001

MPPT (maximum power point tracking) control is very important for the practical PV (photovoltaic) systems to maintain efficient power generating conditions irrespective of the deviation in the PV array insolation or/and temperature conditions. Although a plenty of researches have been done so far, most of them are too costly because of being too dependant on expensive sensors for measuring photovoltaic power and micro-processors for achieving elaborate and complicated control strategies. From this point of view, authors have been researching on sensor-less approaches for MPPT control, and have proposed two types of new control schemes 'Power Equilibrium Scheme' and 'Limit Cycle Scheme'. This paper summarises these two schemes with focussing on their :- operating principles and some results of simulation and experiments.

• 전기학회논문지
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• 제59권5호
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• pp.882-889
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• 2010

This paper presents a method of finding the optimal operating point minimizing a given objective function with 3 phase power flow equations and operational constraints, called 3 phase optimal power flow (3POPF). 3 phase optimal power flow can provide operation and control strategies for the distribution systems with distributed generation assets, which might be frequently in unbalanced conditions assuming that high penetration rate of renewable energy sources in the systems. As the solution technique for 3POPF, this paper adopts a simulation-based method of particle swarm optimization (PSO). In the PSO based 3POPF, a utility function needs to be defined for evaluation of the degree in operational improvement of each particle's current position. To evaluate the utility function, in this paper, NR-based 3 phase power flow algorithm was developed which can deal with looped distributed generation systems. In this paper, illustrative examples with a 5-bus and a modified IEEE 37-bus test systems are given.

• 한국분무공학회지
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• 제19권4호
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• pp.221-226
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• 2014

This paper described the effect of split injections on the stability of combustion and emission characteristics in a direct injection gasoline engine at various operating conditions. In order to investigate the influence of direct injection gasoline engine, the fuel injection timing was varied direct fuel injection at various fuel pressure. The experimental apparatus consisted of GDI engine with 4 cylinder, EC dynamometer, injection control system, and exhaust emissions analyzer. The emission and combustion characteristics were analyzed for the fuel injection timing and fuel injection pressure strategies. It is revealed that CO and HC emissions are dramatically decreased at advanced injection timing. Also, engine performance is increased at increase fuel injection pressure.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.597-604
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• 2013

Containment Filtered Vent Systems (CFVSs) have been mainly equipped in nuclear power plants in Europe and Canada for the controlled depressurization of the containment atmosphere under severe accident conditions. This is to keep the containment integrity against overpressure during the course of a severe accident, in which the radioactive gas-steam mixture from the containment is discharged into a system designed to remove the radionuclides. In Korea, a CFVS was first introduced in the Wolsong unit-1 nuclear power plant as a mitigation measure to deal with the threat of over pressurization, following post-Fukushima action items. In this paper, the overall features of a CFVS installation such as risk assessments, an evaluation of the performance requirements, and a determination of the optimal operating strategies are analyzed for the Wolsong unit 1 nuclear power plant using a severe accident analysis computer code, ISAAC.

• Nuclear Engineering and Technology
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• 제46권6호
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• pp.753-772
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• 2014

The paper presents functional modelling and its application for diagnosis in nuclear power plants. Functional modelling is defined and its relevance for coping with the complexity of diagnosis in large scale systems like nuclear plants is explained. The diagnosis task is analyzed and it is demonstrated that the levels of abstraction in models for diagnosis must reflect plant knowledge about goals and functions which is represented in functional modelling. Multilevel flow modelling (MFM), which is a method for functional modelling, is introduced briefly and illustrated with a cooling system example. The use of MFM for reasoning about causes and consequences is explained in detail and demonstrated using the reasoning tool, the MFMSuite. MFM applications in nuclear power systems are described by two examples: a PWR; and an FBR reactor. The PWR example show how MFM can be used to model and reason about operating modes. The FBR example illustrates how the modelling development effort can be managed by proper strategies including decomposition and reuse.