• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1324-1326
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• 1998

To drive motor or heating machine, it needs the electric power system like the apparatus of inverter. This electric power system obviously comprises power switching devices and drivers to run them. And this system has the topology comprised one/many arm(s), - each arm has high side switching device and low side switching device. Transformer, photocoupler, and HVIC having functions of isolation and level shift which are important thing to drive high side switching device are used as component of drivers in conventional apparatus. Piezoelectric transformers are proposed in this paper, and applied to drive high side swiching device. Through experiments, the possiblities of driving high side switching device are presented and the problems are mooted concurrently. But, we also consider a counterplan for solving the mooted trouble issues.

• 대한기계학회논문집A
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• 제27권12호
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• pp.2047-2054
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• 2003

In this paper, an approach of automatically finding and modifying the most appropriate orthogonal array (GO) is suggested and applied to a new structural optimization procedure with two steps. GO is motivated by the situation where finding a proper orthogonal array from the tables in the literature is difficult or impossible. Now the Taguchi method is made available for various numbers of variables and levels. In the two-step structural optimization, the Taguchi method equipped with GO and a shape optimization using the finite differencing method is consecutively applied. The existence or non-existence of an element can be taken as a factor level and this feature is utilized finding the best topology from a set of potential topologies suggested from the user's expertise. This greatly enhances applicability and one can expect a better result than the case in which each step is applied independently because these steps are complementary each other.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 봄 학술발표논문집 Vol.31 No.1 (A)
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• pp.430-432
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• 2004

Multicasting is an efficient means of one to many (or many to many) communications. Due to the frequent and unpredictable topology changes, multicast still remains as challenge and no one-size-fits-all protocol could serve all kinds of needs in ad hoc network. Protocols and approaches currently proposed on this issue could be classified mainly into four categories, tree-based, meshed-based, statelessness and hybrid. In this article, we borrow the concept of Eulerian ring in graph theory and propose a novel ring-based multicast framework--Hierarchical Eulerian Ring-Oriented Multicast Architecture (HEROMA) over wireless mobile Ad hoc network. It is familiar with hybrid protocol based on mesh and tree who concentrates on efficiency and robustness simultaneously. Architecture and recovery algorithm of HEROMA are investigated in details. Simulation result is also presented, which show different level of improvements on end-to-end delay in scenario of small scale.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2458-2460
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• 1998

To drive motor or heating machine, it needs the electric power system like the apparatus of inverter. This electric power system obviously comprises power switching devices and drivers to run them. And this system has the topology comprised one/many arm(s), - each arm has high side switching device and low side switching device. Transformer, photocoupler, and HVIC having functions of isolation and level shift which are important thing to drive high side switching device are used as component of drivers in conventional apparatus. Piezoelectric transformers are proposed in this paper, and applied to drive high side swiching device. Through experiments, the possiblities of driving high side switching device are presented and the problems are mooted concurrently. But, we also consider a counterplan for solving the mooted trouble issues.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.577-595
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• 2017

${\bullet}$ Silicon Carbide (SiC) had excellent material properties as the base material for next generation of power semiconductor. In developing SiC MOSFET, gate oxide reliability issues had to be first overcome before commercial application. Besides, a high and stable gate-source voltage threshold $V_{GS(th)}$ is also an important parameter for operation robustness. SiC MOSFET with such characteristics can directly use existing high-speed IGBT gate driver IC's. ${\bullet}$ The linear voltage drop characteristics of SiC MOSFET will bring lower conduction loss averaged over full AC cycle compared to similarly rate IGBT. Lower switching loss enable higher switching frequency. Using package with auxiliary source terminal for gate driving will further reduce switching losses. Dynamic characteristics can fully controlled by simple gate resistors. ${\bullet}$ The low switching losses characteristics of SiC MOSFET can substantially reduce power losses in high switching frequency operation. Significant power loss reduction is also possible even at low switching frequency and low switching speed. in T-type 3-level topology, SiC MOSFET solution enable three times higher switching freqeuncy at same efficiency.

• 전기학회논문지
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• 제67권12호
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• pp.1678-1684
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• 2018

Dental caries is one of the most popular oral disease. The aim of automatic dental cavity detection system is helping dentist to make accurate diagnosis. It is very important to separate cavity from the teeth in the detection system. In this paper, We compared two active contour algorithms, Snake and DRLSE(Distance Regularized Level Set Evolution). To improve performance, image is selected ROI(region of interest), then applied bilateral filter, Canny edge. In order to evaluate the algorithms, we applied to 7 tooth phantoms from incisor to molar. Each teeth contains two cavities of different shape. As a result, Snake is faster than DRLSE, but Snake has limitation to compute topology of objects. DRLSE is slower but those of performance is better.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1630-1642
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• 2016

Inter-domain routing is the most critical function of the Internet. The routing system is a logical network relying on the physical infrastructure with geographical characteristics. Nature disasters or disruptive accidents such as earthquakes, cable cuts and power outages could cause regional failures which fail down geographically co-located network nodes and links, therefore, affect the resilience of inter-domain routing system. This paper presents a model for regional failures in inter-domain routing system called REFER for the first time. Based on REFER, the resilience of the inter-domain routing system could be evaluated on a finer level of the Internet, considering different routing policies of intra-domain and inter-domain routing systems. Under this model, we perform simulations on an empirical topology of the Internet with geographical characteristics to simulate a regional failure locating at a city with important IXP (Internet eXchange Point). Results indicate that the Internet is robust under a city-level regional failure. The reachability is almost the same after the failure, and the reroutings occur at the edge of the Internet, hardly affecting the core of inter-domain routing system.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.750-753
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• 2013

배터리 기반 센서 시스템과 달리 태양 에너지 기반 센서 시스템에서는 정확한 양은 알 수 없지만 적어도 주기적으로 에너지가 수집될 수 있으므로 에너지 사용의 최소화가 목표가 아니라 에너지 사용의 최적화가 목표가 된다. 본 연구에서는 네트워크 토폴로지 최적화를 목적으로 태양 에너지 수집형 센서 시스템에서 잔존 에너지양에 따른 3단계 전송 파워 조절 알고리즘을 제안한다. 아울러 이 기법이 전체 센서 네트워크의 성능에 어떤 영향을 미치는지 실험을 통하여 살펴보았는데, 대부분의 지표에서 전송 파워를 고정한 기법들 보다 우수한 성능을 보이는 것을 확인할 수 있다.

• 전력전자학회논문지
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• 제25권1호
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• pp.61-67
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• 2020

This study deals with the modulation index (MI) of a voltage source converter (VSC) HVDC system based on a modular multilevel converter (MMC). In the two-level converter, the purpose of the MI is to maximize the achievable AC voltage of the converter from a fixed DC voltage. Unlike that in a two-level converter, the MI in the MMC topology plays a role in making the converter a voltage source using a capacitor. The circulating current in the MMC distorts the AC voltage reference, and the distortion affects the MI. In addition, the AC network conditions, such as AC voltage variation and reactive power, affect the MI. Therefore, the MI should be optimized with consideration of internal and external factors. This study proposes a method to optimize the MI of an MMC HVDC system.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권4호
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• pp.441-445
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• 2008

우리 군은 장차전 양상인 네트워크 중심전(NCW: Network Centric Warfare)과 같은 새로운 전쟁 수행 개념 구현에 대한 연구 및 발전을 추진하고 있는데, IPv6는 이러한 미래 전장을 지원하는 차세대 국방정보통신망에 필수적인 기반 요소이다. 국방정보통신망의 IPv6 주소 할당과 관련된 연구들이 있었지만, 군 조직 구조 기반으로 계층적 할당을 하거나, 서비스망부터 할당하여 경로 요약(route aggregation)이 비효율적이고 라우팅 테이블 크기가 커지는 단점이 있었다. 본 논문에서는 차세대 국방정보통신망의 토폴로지를 검토하고, 네트워크 토폴로지 기반으로 서비스망을 구분하는 필드의 위치를 조정하여 경로 요약 및 라우팅 테이블 크기를 기존 연구보다 효율적으로 개선했으며, OPNET 시뮬레이터를 이용하여 이를 검증했다.