• Journal of Electrical Engineering and Technology
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• v.9 no.4
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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.

• Journal of the Korea Society of Computer and Information
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• v.24 no.12
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• pp.85-92
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• 2019

Companies can identify user groups or consumption trends by collecting and analyzing opinions of many users on special subjects or their products as well as utilize them as various purposes such as predicting some specific trends or marketing strategies. Therefore current analyzing tools of social media have come into use as a means to measure the performances of social media marketing through network's statistical analysis. However these tools require expensive computing and network resources including burden of costs for building up and operating complex software platforms and much operating know-how. Hence, small companies or private business operators have difficulty in utilizing those social media data effectively. This paper proposes a framework applied into developing analysis system of social media. The framework could be set up and operate the system to extract necessary social media's data. Also to design the system, this study suggests a meta-model of proposed framework and to guarantee completeness and consistency, a formal specification of meta-model by using Z language is suggested. Finally, we could verify the clearness of framework's design by performing Z model checking of formal specification's output through Z-EVES tool.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.391-398
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• 2022

The use rate of M-pass(transportation card for foreigners),developed and sold to provide convenience to foreign tourists, was only 0.0051 % of visitors to Seoul over the past five years. Even this poor sales fell to the 0.024 % level in 2020 due to COVID-19. The cause of the sluggish performance was that the Ministry of land, Transport and Maritime Affairs and the card issuer excluded transportation operating organizations, and problems such as poor public relation, irrationality in pricing, and limitied number of sales locations appeared. In order to solve this problem, the research result showed that business strategies such as the establishment of a digital marketing system, realistic pricing, and the establishment of a mobile sales system that fit the trend, as well as the development of new product that reflect the participation and opinions of all related organizations are necessary. It is expected that this study will not only provide convenience to foreign Seoul tourist in the age of Post Corona, but also help improve the management of subway operating organizations.

• Strategy21
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• s.43
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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.

• The Research Journal of the Costume Culture
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• v.11 no.1
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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.

• Proceedings of the KIPE Conference
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• 2001.10a
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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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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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.

• Journal of ILASS-Korea
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• v.19 no.4
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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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• v.45 no.5
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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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• v.46 no.6
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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.