• Applied Microscopy
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• 제34권1호
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• pp.61-69
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• 2004

The microwave dielectric properties and microstructures of the Complex Perovskite (1-x)$(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$(LNST) system were investigated using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). LNST had not only the antiphase tilting of oxygen octahedron but also the inphase tilting of oxygen octahedron and the antiparallel shift of cations. Also, when $0.0{\leq}x{\leq}0.4$, LNST had the vacancy ordering of A-sites because of the evaporation of Li ions. From the observation of the microstructure, abnormal grain growth phenomena were observed over the whole range of x. The temperature coefficient of resonant frequency ($T_{cf}$) of the $({Li_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(LST) system has a large negative value ($-220ppm/^{\circ}C$) but the $({Na_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(NST) system which substituted $Na^{+1}$ has a large positive value ($+173ppm/^{\circ}C$). The dielectric properties of ${\varepsilon}_r=103,\;Q*f_{0}=3,700GHz$ and $T_{cf}=+50ppm/^{\circ}C$ at 4GHz were obtained when x =0.4.

• Proceedings of the KIEE Conference
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1804-1805
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• 2011

In recent year there has been an increasing interest in the dynamic simulation of complex systems. This study uses a large-scale forty-seventh order fossil fuel power plant. Twenty-three state variables are associated with the physical processes and twenty-four state variables associated with the control system. The plant model is expected to predict all dominant effects in a steady and transient state. In this study, the power plant model is reorganized into four subsystems, each with its controller, and the four connected to each other through a manager, which is a fifth part to the system. The four parts of the unit are the boiler system, steam turbine system, condenser system, and feedwater system.

• Journal of the Korean Society of Systems Engineering
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• 제5권1호
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• pp.21-32
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• 2009

The systems engineering (SE) process shall be applied to the project for successful development of ultra-high-speed (UHS) Maglev train system which is one of very large and complex systems. It is important to abolish technology differentials from the advanced developers such as Germany, Japan, etc. and to ensure discriminatory competitiveness of the application of systems engineering process for the development of the system based on appropriate concepts and requirements. General operation concept and stakeholder's requirements of UHS Maglev train system must be elicited with system concept for initiating the project. The management plan should be devised for all sorts of systems engineering activities of risk management, performance management, lifecycle cost management, etc. This paper would support to establish the systems engineering management plan (SEMP) for the program of UHS Maglev train system development with associated documents.

• Journal of Applied Reliability
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• 제12권3호
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• pp.187-199
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• 2012

In general, accelerated life testing is performed to reduce testing time. But it is difficult to apply accelerated life testing to a system besides components. This paper developed a software which estimates reliability measures of the system from results of accelerated life testing of components building the system. This software can handle the system with a large number of components and complex topology. Multiple failure modes of a component were also considered in this software. Based on the software, reliability measures of a gearbox example at several conditions were estimated from the accelerated life testing results of three components of the gearbox.

• Proceedings of the KIEE Conference
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• 대한전기학회 2006년도 추계학술대회 논문집 전력기술부문
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• pp.342-344
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• 2006

The modem enormous electric power system has made power system analysis much more complex and difficult. For effective analysis of the power system, model reduction and aggregation is required. In this paper, a new aggregation method is presented to aggregate the coherent generators in the large scale power system while matching the power flow. In order to demonstrate the effects of this aggregation method, it is applied to a small scale power system. A multi-variable control technique of $H_{\infty}$ control is also applied to enhance the dynamic stability of the aggregated power system.

• Proceedings of the KIEE Conference
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.34-37
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• 2001

This paper evaluate reliability indices of a part of transmission network of KEPCO system. Quantitative evaluation of transmission system reliability is very important because successful operation of an electric power system in the deregulated electricity market depends on transmission system reliability management. Monte Carlo methods are often preferable, when complex operating conditions are involved and/or the number of sever events is relatively large. Monte Carlo simulation methods and CMELDC(CoMposite power system Effective Load Duration Curve) were used in this paper.

• Proceedings of the KIEE Conference
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.180-182
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• 2009

As a train control system becomes a large scale and complex, it is necessary to control rigorously the system requirements specification of the train control system at the early phase. This paper describes Use Cases and activity diagrams of ATS functions requirements in the train control system. Basic functions of the train control system refers to IEC 62290-land are suggested. And the basic functions includes train operation without a driver. It is anticipated that this paper will be helpful for the analysis of ATS functions, ATO functions and EI function in the train control system.

• Ecology and Resilient Infrastructure
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• 제7권3호
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• pp.199-207
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• 2020

Against the backdrop of frequent weather disasters such as floods, droughts, and heat waves worldwide, urban parks should provide functions for the safety of urban residents as well as rest, culture, and ecological functions. In this study, a classification system for urban disaster prevention parks is proposed for the safety of the urbanites with the aim of securing a complex function in a green space in response to climate changes in the city. Analytical indicators were extracted through literature research, and the classification system was verified through on-site surveys of the target sites and interviews with those involved. The large class for evaluation was divided into three types: location, spatial composition, and disaster prevention complex facilities of urban parks; the direction of improvement was proposed for problems identified through empirical analysis.

• International conference on construction engineering and project management
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.361-368
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• 2009

In the Urban Regeneration Project, the scale becomes huge and the composition of participating organizations is complex. It is necessary to establish the master plan fast and effectively harmonize conflict options and interests in the early stage of the project. However, the master planner, who is tasked to establish the master plan, and the master planning team, are difficult to establish the master plan fast while effectively considering various and complex information related to regeneration. The Urban Regeneration Project is composed of various types of computer files like HWP, EXL, PDF, DWG and others. When the master plan is established, it is necessary to link the information items and physical files of urban generation in order to effectively save the files in storage for easy search and utilization. This study developed a prototype system to support participating subjects of the Urban Regeneration Projects. It will effectively utilize the information items in the physical computer files using information blocks and Metadata. The developed system provides the base to effectively manage large amount of documents in the early stage of the Urban Regeneration Project and make effective decision-making using the concept of data warehouse.

• KIEAE Journal
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• 제16권1호
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• pp.73-79
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• 2016

This study aimed to investigate the flood prevention effect expected from the afforestation of a large area metal roof of an industrial complex located in an area prone to floods in the rainwater outflow reduction aspect through computer simulation based on soil, which is a key element of the system. In order to conduct a more realistic simulation, the properties of the surveyed soil were generated through substantive analysis, soil texture analysis, and saxton method. A comparative performance evaluation was conducted by using soil depth and ponding depth, which are key elements of the system, as variables. The study result showed that during the heavy rainfall period, the bottom ash artificial soil had 61% rainwater outflow reduction effect, which was 11% higher than the SWMM standard sand.