• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2005년도 추계학술대회 및 정기총회
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• pp.45-50
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• 2005

Research and development of grid computing ware mainly focused on high performance computing field such as large-scale computing operation. Many companies and organizations concentrated on existing computational grid. However, service grid focusing on enterprise environments has been noticed gradually. Grid service providers of service grid construct diverse and specialized services and provide service resources that have economic feasibility to grid users. But, service resources are geographically dispersed and divided into many classes and have individual owners and management policies. In order to utilize and allocate resources effectively, service grid needs a resource management model that handles and manages heterogeneous resources of service grid. Therefore, this paper presents the third party grid service marketplace model using virtualization to solve problems of grid service resource management. Also, this paper proposes resource dealing mechanism and pricing algorithms applicable for service grid. Empirical results show usefulness and efficiency of the third party grid service marketplace model in comparison with typical economic models for grid resource management such as single auction model and double auction model.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제22권1호
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• pp.13-27
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• 2019

초등 수학 교과서에서 모눈종이의 활용은 수와 연산, 도형, 측정 영역에서 사용하고, 이 중에서 도형 영역에서 가장 많이 사용하고 있다. 이러한 사용에도 불구하고 실제 초등 수학 교과서의 모눈종이를 활용한 수업 과정을 보면 모눈종이 사용에 따른 시행착오의 수정이나 보완이 어려워서 보다 효과적인 방안이 필요해보였다. 이에 본 연구에서는 한국과학창의재단(2017)의 '수학 수업용 교구 표준안'에서 제시한 교구 중에서 모눈종이보다 더 효과적인 모눈종이판 교구의 활용성을 설문 조사 하였다. 조사는 초등 수학 교과서에서 모눈종이를 활용하고 있는 차시별 학습주제 중에서 모눈종이와 모눈종이판에서 어느 것이 더 효과적인지를 교사들에게 조사한 후, 모눈종이판의 활용이 더 효과적인 학습주제의 성취기준을 찾아 분석하고, 영역별로 가장 효과적인 학습 주제의 구체적인 활동 과정을 제시하였다.

• 한국전자거래학회지
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• 제25권1호
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• pp.35-43
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• 2020

효율적인 에너지 운영을 목표로 하는 스마트 그리드는 인간의 삶의 질의 향상을 목표로 하는 스마트 시티의 일부로 자리 잡을 것이다. 이 논문에서는 성숙된 스마트 그리드의 모습이 스마트 시티에 자연스럽게 통합되는 모습임을 논증한다. 또한, 스마트 시티의 핵심 구성요소로서 스마트 그리드의 모습을 그리고, 이에 필요한 제도, 인프라, 기술 요소에 대한 문헌을 조사한다.

• 한국시뮬레이션학회논문지
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• 제14권3호
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• pp.91-100
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• 2005

Grid computing is widely applicable to various fields of industry including process control and manufacturing, military command and control, transportation management, and so on. In a viewpoint of application area, grid computing can be classified to three aspects that are computational grid, data grid and access grid. This paper focuses on computational grid which handles complex and large-scale computing problems. Computational grid is characterized by system dynamics which handles a variety of processors and jobs on continuous time. To solve problems of system complexity and reliability due to complex system dynamics, computational grid needs scheduling policies that allocate various jobs to proper processors and decide processing orders of allocated jobs. This paper proposes a service prediction-based job scheduling model and present its scheduling algorithm that is applicable for computational grid. The service prediction-based job scheduling model can minimize overall system execution time since the model predicts the next processing time of each processing component and distributes a job to a processing component with minimum processing time. This paper implements the job scheduling model on the DEVS modeling and simulation environment and evaluates its efficiency and reliability. Empirical results, which are compared to conventional scheduling policies, show the usefulness of service prediction-based job scheduling.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2005년도 춘계학술대회 논문집
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• pp.29-33
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• 2005

Grid computing is widely applicable to various fields of industry including process control and manufacturing, military command and control, transportation management, and so on. In a viewpoint of application area, grid computing can be classified to three aspects that are computational grid, data grid and access grid. This paper focuses on computational grid which handles complex and large-scale computing problems. Computational grid is characterized by system dynamics which handles a variety of processors and jobs on continuous time. To solve problems of system complexity and reliability due to complex system dynamics, computational grid needs scheduling policies that allocate various jobs to proper processors and decide processing orders of allocated jobs. This paper proposes the service prediction-based job scheduling model and present its algorithm that is applicable for computational grid. The service prediction-based job scheduling model can minimize overall system execution time since the model predicts a processing time of each processing component and distributes a job to processing component with minimum processing time. This paper implements the job scheduling model on the DEVSJAVA modeling and simulation environment and simulates with a case study to evaluate its efficiency and reliability Empirical results, which are compared to the conventional scheduling policies such as the random scheduling and the round-robin scheduling, show the usefulness of service prediction-based job scheduling.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권1호
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• pp.83-104
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• 2011

Mobile grid is a combination of grid computing and mobile computing to build grid systems in a wireless mobile environment. The development of network technology is assisting in realizing mobile grid. Mobile grid based on established grid infrastructures needs effective resource management and reliable job scheduling because mobile grid utilizes not only static grid resources but also dynamic grid resources with mobility. However, mobile devices are considered as unavailable resources in traditional grids. Mobile resources should be integrated into existing grid sites. Therefore, this paper presents a mobile grid middleware interconnecting existing grid infrastructures with mobile resources and a mobile service agent installed on the mobile resources. This paper also proposes a mobile resource reliability-based job scheduling model in order to overcome the unreliability of wireless mobile devices and guarantee stable and reliable job processing. In the proposed job scheduling model, the mobile service agent calculates the mobile resource reliability of each resource by using diverse reliability metrics and predicts it. The mobile grid middleware allocated jobs to mobile resources by predicted mobile resource reliability. We implemented a simulation model that simplifies various functions of the proposed job scheduling model by using the DEVS (Discrete Event System Specification) which is the formalism for modeling and analyzing a general system. We also conducted diverse experiments for performance evaluation. Experimental results demonstrate that the proposed model can assist in improving the performance of mobile grid in comparison with existing job scheduling models.

• 한국시뮬레이션학회논문지
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• 제15권3호
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• pp.1-9
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• 2006

현재 그리드 컴퓨팅은 네트워크 컴퓨팅 환경에서 대용량의 데이터와 엄청난 컴퓨팅의 문제를 해결하는데 매우 효과적인 해결책으로 각광받고 있다. 그리드는 애플리케이션을 여러 부분으로 나누어, 각 부분을 수많은 컴퓨터에서 동시에 수행함으로써 대규모 시뮬레이션 및 대용량 컴퓨팅을 실현할 수 있다. 그러나, 이를 위해서는 효과적인 자원 관리와 스케줄링 기법이 필요하다. 이 논문에서 우리는 분산된 그리드 컴퓨팅 환경에서의 자원관리와 스케줄링에 적용 가능한 그리드 거래망 모델을 제안하고 자율적인 자원 거래를 위한 가격 입찰 알고리즘을 소개한다. 우리는 모델의 효율성과 능력을 입증하기 위해 DEVSJAVA 모델링 & 시뮬레이션 환경 하에서 프로토타입 모델을 설계하고 실험하였다.

• Journal of Power Electronics
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• 제13권5호
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• pp.896-908
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• 2013

Under high grid impedance conditions, it is difficult to guarantee the stability of grid-connected inverters with an LCL filter designed based on ideal grid conditions. In this paper, the theoretical basis for output impedance calculation is introduced. Based on the small-signal model, the d-d channel closed-loop output impedance models adopting the converter-side current control method and the grid-side current control method are derived, respectively. Specifically, this paper shows how to simplify the stability analysis which is usually complemented based on the generalized Nyquist stability criterion (GNC). The stability of each current-controlled grid-connected system is analyzed via the proposed simplified method. Moreover, the influence of the LCL parameters on the stability margin of grid-connected inverter controlled with converter-side current is studied. It is shown that the stability of grid-connected systems is fully determined by the d-d channel output admittance of the grid-connected inverter and the inductive component of the grid impedance. Experimental results validate the proposed theoretical stability analysis.

• 전기학회논문지
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• 제62권2호
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• pp.201-207
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• 2013

This paper propose seamless transfer operation between grid-connected and stand-alone mode in the three-phase inverter for microgrid. The inverter operates grid-connected mode and stand-alone mode. Grid-connected mode is the inverter connected to grid and stand-alone mode is to deliver energy to the load from inverter at grid fault. When conversion from gird-connected to stand-alone mode, the inverter changes current control to voltage control. When grid restored, the inverter system is conversion from stand-alone to grid-connected mode. In this case, load phase and grid phase are different. Therefore, synchronization is essential. Thus Seamless transfer operation stand-alone to grid-connected mode. In this paper, propose sealmless transfer operation between grid-connceted and stand-alome mode, and this method is verified through simulation and experiment.

• 전기학회논문지
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• 제56권5호
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• pp.841-847
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• 2007

This paper deals with the micro-grid consisting of micro-sources which adopt voltage sourced inverters with independent real and reactive power control capability for providing premium power quality. This paper presents dynamic modeling and the stable operating range of the micro-grid system varying the parameters of the micro-sources. The fundamental frequency model of the micro-source inverters are considered to form a dynamic model of the micro-grid system. Stability analysis is performed based on the linearized dynamic model of the micro-grid system. Case study results show the parameters affecting the stability of the micro-grid and the stable operating range of the micro-sources.