• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2089-2098
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• 2017

Microgrid is a convenient, reliable, and eco-friendly approach for the integration of Distributed Generation (DG) sources into the utility power systems. To date, AC microgrids have been the most common architecture, but DC microgrids are gaining an increasing interest owing to the provision of numerous benefits in comparison with AC ones. These benefits encompass higher reliability, power quality and transmission capacity, non-complex control as well as direct connection to some DG sources, loads and Energy Storage Systems (ESSs). In this paper, main challenges and available approaches for the protection of AC and DC microgrids are discussed. After description, analysis and classification of the existing schemes, some research directions including coordination between AC and DC protective devices as well as development of combined control and protection schemes for the realization of future hybrid AC/DC microgrids are pointed out.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06c
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• pp.139-143
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• 2007

양방향 데이터 방송 기술이 급속도로 발전하고 전세계적으로 표준화가 진행되고 있는 가운데 데이터 방송 콘텐츠에 대한 수요는 제자리를 맴돌고 있다. 이는 특화된 데이터 방송 콘텐츠에 대한 필요성을 의미하는 것으로 본 논문에서는 시나리오를 기반으로 기존 방송 콘텐츠를 활용하여 데이터 방송 부가 콘텐츠를 제작하는 모델안을 제안한다. 연구 모델은 1)시나리오 기반으로 기존 데이터 방송 콘텐츠 분석, 2)분석된 객체 아이템 메타데이터 스키마 설계 3)부가 콘텐츠 화면 구현의 단계로 구성한다. DMB 단말환경에서 가볍게 움직이는 콘텐츠 제작을 위해 메타데이터를 25개로 제한하고 이 안에서 Content Description, Shot Detection, Object Tracking로 메타데이터를 구분하여 스키마 다이어그램을 설계한다. 본 논문은 기존의 익숙한 콘텐츠를 재가공하여 제공함으로 DMB 수요 활성화 측면과 CP의 제작 비용감소 측면에서 긍정적인 영향을 끼칠 것으로 예상된다.

• Composites Research
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• v.15 no.4
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• pp.43-48
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• 2002

This paper presents the brief description of Composite Materials Research carried out at Massachusetts Institute of Technology (MIT). The researches regarding Composites are performed at four Departments, they are Laboratory for Manufacturing ＆ Productivity (LMP) within Mechanical Engineering Department, Technology Laboratory for Advanced Composites (TELAC) within Aerospace Engineering Department, Structures & Materials Program within Civil & Environmental Engineering Department and Building Technology Program within Department of Architecture.

• KIEAE Journal
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• v.3 no.2
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• pp.17-24
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• 2003

The purpose of this study is to present rational methods of multi-criteria optimization of the envelope of buildings. The object is to determine the optimum R-value of the envelope of a building, based on the following criteria: minimum building costs (including the cost of materials and construction) and yearly heating costs. Mathematical model described heat losses and gains in a building during the heating season. It takes into consideration heat losses through wall, roof, floor and windows. Particular attention was paid to have a more detailed description of heat gains due to solar radiation. On the assumption that shape of building is rectangle in order to solve the problem, optimum R-value of the envelope of a building is determined by using non-linear programing methods(Kuhn-Tucker Conditions). The results constitute information for designers on the optimum R-value of a building envelope for energy saving buildings.

• KIEAE Journal
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• v.3 no.2
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• pp.51-58
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• 2003

The purpose of this study is to present rational methods of multi-criteria optimization of the shape of energy saving buildings. The object is to determine the optimum dimension of the shape of a building, based on the following criteria: minimum building costs (including the cost of materials and construction) and yearly heating costs. Mathematical model described heat losses and gains in a building during the heating season. It takes into consideration heat losses through wall, roof, floor and windows. Particular attention was paid to have a more detailed description of heat gains due to solar radiation. On the assumption that shape of building is rectangle in order to solve the problem, the proportions of wall length and building height are determined by using non-linear programing methods(Kuhn-Tucker Conditions). The results constitute information for designers on the optimum proportions of wall lengths, height, and the ratios of window to wall areas for energy saving buildings.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.62-64
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• 2006

With the advent of the international standard IEC 61850 for communication networks and systems in substations, utilities are beginning to implement substation automation systems (SAS) that can give support to interoperability, interchangeability and self-description features. This paper describes with the SAS design accordance with this new standard. After a brief introduction of IEC 61850 SCL, this paper addresses some issues related to the specification of an IEC 61850 based SAS, and describes the Substation Configuration Language (SCL) based on Extensible Markup Language (XML). The SAS design process is explored with examples including the Intelligent Electronic Device (IED) selection, Logical Nodes (LN) allocation and the related services and the SAS communication architecture.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.403-413
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• 1996

We study the propagation of two pulses with orthogonal linear polarizations in a nonlinear periodic dielectric structure with $X^{(3)}$ nonlinearity. Using an envelope- function approach, we derive the coupled nonlinear Schrodinger equations governing the spatio-temporal evolutions of the two orthogonally polarized modes in a nonlinear periodic structure. We then find their solitary-wave solutions referred to as coupled gap solitons. We show that two orthogonally polarized pulses can co-propagate as a coupled gap soliton through a nonlinear periodic structure while each pulse alone will be strongly reflected due to the Bragg reflection. Based on the results, we present an all-optical switching scheme which has a novel architecture and principle. We also study the stability of coupled gap solitons to find the dragging phenomena in a nonlinear birefringent periodic medium.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.293-295
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• 1992

This Paper presents the design of an automated EEG analyzing system. The design considerations including processing speed, A/D conversion, filtering, and waveforms detection, are overviewed with the description of the associated EEG charateristics. The architecture of the currently implemented system consists of a -controller based front-end signal processing unit and a host computer system. The data acquisition procedures are described along with a couple of illustrations of the acquired EEG/EOG signal.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.29-38
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• 2006

As the complexity of engineering design environment has been increased, it becomes difficult to exchange design data among design support systems. The purpose of this paper is to develop the XML-based Generalized Mechanical Data Exchange Formats(GMDEF) independent of specific mechanical element and to improve the interoperability of them using ontology, in order to integrate diverse design data and facilitate communication between design support systems. GMDEF consists of PartDoc and AssemblyDoc. PartDoc represents the information of a single part. AssemblyDoc represents the relation of parts composing an assembly. GMDEF is validated by GMDEF Schema. GMDEF Schema consists of separated XML Schemas and has flexible architecture to facilitate extension. The ontology is applied to GMDEF Schema to share and reuse vocabularies of specific mechanical elements.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.8
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• pp.3243-3256
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• 2020

Recent years have shown a great interest of public in buying and selling of crypto/digital currency. With hundreds of digital currencies in financial market, bitcoin remains the most widely used, adapted, and accepted currency around the world. However, the critics of bitcoin still consider it a threat to modern day power usage. This paper discusses the important pitfalls, pros, and cons related to bitcoin's energy consumption. The paper begins by highlighting the flexibilities cryptocurrency can bring to online money transfers compared to traditional 'fiat' architecture. Then, the focus of the paper entirely remains on listing various facts related to bitcoin's energy utilization including a brief description of several emerging approaches for energy optimization. This paper is concluded by revealing key current challenges associated to bitcoin's energy usage.