• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.400-409
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• 1997

Design of single stage AC/DC converter with high power factor and high efficiency based on half-bridge topology for low power application is proposed. To obtain design equations, modelling and detailed analysis are performed. The proposed converter gives and power factor and high efficiency by employing aynchronous rectifiers. To verify the performances of the proposed converter 90W-converter has been designed. This prototype converter meets IEC555-2 requirements with near unity power factor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.741-743
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• 2003

A reliability-based topology optimization (RBTO) for electromagnetic systems using the finite element method is presented. Permeability and applied current density are considered as uncertain variable. In order to compute reliability constraints, performance measure approach is used. To find the reliability index, the limit state function is linearly approximated at each iteration. Numerical examples show the effectiveness of the proposed method.

• 전기학회논문지
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• 제58권8호
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• pp.1605-1614
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• 2009

The technique of simultaneous localization and mapping is the most important research topic in mobile robotics. In the process of building a map in its available memory, the robot memorizes environmental information on the plane of grid or topology. Several approaches about this technique have been presented so far, but most of them use mapping technique as either grid-based map or topology-based map. In this paper we propose a frame of solving the SLAM problem of linking map covering, map building, localizing, path finding and obstacle avoiding in an automatic way. Some algorithms integrating grid and topology map are considered and this make the SLAM performance faster and more stable. The proposed scheme uses an occupancy grid map in representing the environment and then formulate topological information in path finding by A${\ast}$ algorithm. The mapping process is shown and the shortest path is decided on grid based map. Then topological information such as direction, distance is calculated on simulator program then transmitted to robot hardware devices. The localization process and the dynamic obstacle avoidance can be accomplished by topological information on grid map. While mapping and moving, pose of the robot is adjusted for correct localization by implementing additional pixel based image layer and tracking some features. A laser range finer and electronic compass systems are implemented on the mobile robot and DC geared motor wheels are individually controlled by the adaptive PD control method. Simulations and experimental results show its performance and efficiency of the proposed scheme are increased.

• 대한지리학회지
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• 제39권5호
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• pp.804-818
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• 2004

공간데이터자원이 많아 질수록 그들끼리 불일치가 일어날 확률은 높아지고 있다. 이러한 불일치는 같은 지역을 커버하는 같은 종류의 공간데이터사이에서도 일어날 수 있다. 그러므로, 이런 공간데이터를 효율적으로 연결시켜 Geometry 및 Topology측면에서 일관성을 지닌 새로운 공간데이터를 생성시키는 일의 중요성은 증가 할 것이다. 이러한 공간데이터중의 하나로서 미국 인구통계국의 TIGER파일을 예로 들 수 있다. 현재 인구통계국 지도들은 지방정부의 지도 레이어들과 공간적으로 일치 하지 않기 때문에 인구적, 경제적인 많은 유용한 정보가 지방정부의 레이어들과 연계되어 공간적으로 충분히 활용되어지고 있지 않고 있다. 그러므로, 인구통계국 지도의 위치정보는 좀 더 정확한 위치정보를 가지고 있는 지방정부의 레이어들과 융합되어 Geometry 및 Topology측면에서 새로운 정보로 대체되어져야 한다. 이 논문은 참고맵을 이용하여 Geometry 및 Topology측면에서 일관성을 지닌지도를 만들기 위한 개념적인 프레임과 두가지 맵모델을 제시한다. 첫번째 모델은 셀 모델인데 맵은 0셀, 1셀, 그리고 2셀로 구성되어진다. 두번째 모델은 수학적으로 다른 원형을 가진 물체는 지도 일반화후에도 유사성을 가지고 있다는 것이다. 새롭게 제시된 계층적인 맵 융합은 물리적, 수학적, 논리적 경계에 바탕을 두고 있고 복잡성과 계산적인 부담을 감소시킬 수 있다. 반복성을 가진 맵 융합 원리는 인구통계지도를 예로하여 형성되었다. 이것들은 속성 매치, 의미있는 노드발견, 지도학적인 0-cell 매치. 지도학적인 1-cell 매치, 그리고 맵 변형으로 구성된다.

• 한국인터넷방송통신학회논문지
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• 제13권3호
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• pp.177-181
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• 2013

최근 NFC(Near Field Communication) 기반의 통신 기능을 채용한 스마트기기 및 OS 등이 확산되면서, 기존의 RFID를 이용한 다양한 응용분야가 NFC로 대체되고 있다. Smart NFC 기술은 기존 서비스 및 기기와 쉽게 융 복합이 가능하며, 스마트폰을 활용한 결제 의료 인증 등 새로운 Network Communication 패러다임의 창출이 예상되고 있다. Smart NFC 보안 인증기기(Smart NFC Security Authenticator: SNSA)의 H/W와 S/W를 개발하고, 무선통신 시험 결과 허용기준값 이내를 만족하고, 토폴로지 영향의 실험 및 분석 결과, Daisy Chain 토폴로지가 Star 토폴로지에 비해 신호성능이 우수함을 보였다.

• 전력전자학회논문지
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• 제24권6호
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• pp.419-427
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• 2019

Several multilevel converter topologies have been proposed and compared. The three-level (3L) neutral-point-clamped (NPC) topology is promising and widely accepted. However, this topology suffers from uneven loss distribution among switches due to its fixed switching strategy. The 3L active NPC (ANPC) topology, which exhibits improved loss distribution profile, was proposed to address this disadvantage. The 3L T-NPC topology, a hybrid configuration of 2L and 3L NPC topologies, was introduced to address not only the loss distribution problem but also the reduction in the number of switches. In the present research, the application of these three topologies in PMSG-based medium-voltage wind turbines was investigated. The power devices considered were 10 kV IGCTs. Performance was evaluated in terms of a power loss of 10 kV IGCT for each NPC topology, which is a crucial indicator of thermal behavior, reliability, cost, and lifetime of any converter. The comparison was performed using ABB make 10 kV IGCT 5SHY17L9000 and the simulation tool PLECS.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.934-937
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• 2006

This investigation presents a topology formulation to design optimal poroelastic acoustic foams to maximize absorbing ability. For successful formulation, a single set of equations based on Biot's theory is adopted and an appropriate material interpolation strategy is newly developed. Because there was no earlier attempt to solve poroelastic acoustic foam design problems in topology optimization setting, many challenging issues including modeling and interpolation must be addressed. First, the simulation accuracy by a proposed unified model encompassing acoustic air and poroelastic material was checked against analytical and numerical results. Then a material interpolation scheme yielding a distinct acoustic air-poroelastic material distribution was developed. Using the proposed model and interpolation scheme, the topology optimization of a two-dimensional poroelastic acoustic foam for maximizing its absorption coefficient was carried out. Numerical results show that the absorption capacity of an optimized foam layout considerably increases in comparison with a nominal foam layout.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.938-941
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• 2006

We present a new design method of one-dimensional multi-layered acoustic foams for transmission loss maximization by topology optimization. Multi-layered acoustic foam sequences consisting of acoustic air layers and poroelastic material layers are designed for target frequency values. For successful topology optimization design of multi-layered acoustic foams, the material interpolation concept of topology optimization is adopted. In doing so, an acoustic air layer is modeled as a limiting poroelastic material layer; acoustic air and poroelastic material are handled by a single set of governing equations based on Biot's theory. For efficient analysis of a specific multi-layered foam appearing during optimization, we do not solve the differential equations directly, but we use an efficient transfer matrix approach which can be derived from Biot's theory. Through some numerical case studies, the proposed design method for finding optimal multi-layer sequencing is validated.

• 한국콘텐츠학회논문지
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• 제8권7호
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• pp.35-42
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• 2008

본 논문에서 제안된 스패닝 트리 토폴로지 요약기법은 모든 경로를 찾는 대신 홉 카운트 기반의 깊이 우선 방식을 사용하여 효율적으로 다중 경로를 탐색할 수 있도록 하였다. 이를 위해 토폴로지 요약 정보를 줄이고 다중링크 요약에 유연성을 부여하기 위하여 대역폭과 지연의 한 쌍으로 구성된 두 개의 라인 세그먼트를 이용하는 수정된 라인 세그먼트 기법을 제안하였다. 그리고, 이를 기존의 스패닝 트리 토폴로지 요약에 적용한 효율적인 토폴로지 요약기법을 제안하였다. 제안된 기법의 성능을 평가하기 위해 기존의 스패닝 트리 기법과 호 성공율, 접근시간 및 크랭크 백 율에 대하여 컴퓨터 시뮬레이션을 통해 비교 분석하였다. 시뮬레이션 분석결과 제안된 스패닝 트리 토폴로지 요약 기법이 기존의 기법보다 성능이 향상됨을 알 수 있었다.

• Journal of Communications and Networks
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• 제14권3호
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• pp.319-335
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• 2012

In this study, we design an applicable model enabling internet protocol television (IPTV) service providers to use a virtual network (VN) for IPTV service delivery. The model addresses the guaranteed service delivery, cost effectiveness, flexible control, and scalable network infrastructure limitations of backbone or IP overlay-based content networks. There are two major challenges involved in this research: i) The design of an efficient, cost effective, and reliable virtual network topology (VNT) for IPTV service delivery and the handling of a VN allocation failure by infrastructure providers (InPs) and ii) the proper approach to reduce the cost of VNT recontruction and reallocation caused by VNT allocation failure. Therefore, in this study, we design a more reliable virtual network topology for solving a single virtual node, virtual link, or video server failure. We develop a novel optimization objective and an efficient VN construction algorithm for building the proposed topology. In addition, we address the VN allocation failure problem by proposing VNT decomposition and reconstruction algorithms. Various simulations are conducted to verify the effectiveness of the proposed VNT, as well as that of the associated construction, decomposition, and reconstruction algorithms in terms of reliability and efficiency. The simulation results are compared with the findings of existing works, and an improvement in performance is observed.