• 대한전기학회논문지:전력기술부문A
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• 제53권9호
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• pp.500-506
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• 2004

This paper proposes a modified current differential relay for transformer protection unaffected by the remanent flux. The relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. To cope with the remanent flux, before saturation, the relay calculates the core-loss current and uses it to modify the measured differential current. When the core then enters saturation, the initial value of the flux is obtained by inserting the modified differential current at the start of saturation into the magnetization cure. Thereafter, the actual core flux is then derived and used in conjunction with the magnetization curve to calculate the magnetizing current. A modified differential current is then derived that compensates for the core-loss and magnetizing currents. The performance of the proposed differential relay was compared against a conventional differential relay. Results indicate that the modified relay remained stable during severe magnetic inrush and over-excitation because the exciting current was successfully compensated. This paper concludes by implementing the relay on a hardware platform based on a digital signal processor. The relay discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

• 게임&엔터테인먼트 논문지
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• 제2권1호
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• pp.8-16
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• 2006

인터넷에서 게임 트래픽과 같은 대용량 데이터의 부하를 분산하고 안정적인 전송을 위해 멀티캐스트 라우팅 프로토콜을 사용한다. 다양한 멀티캐스트 알고리즘 중 최근 CBT(Core Based Tree) 방식이 널리 사용되고 있으나 코어 라우터로 트래픽 집중되는 병목현상과 코어라우터의 위치에 따라 푸어 코어(Poor core)현상이 발생한다. 본 논문에서는 코어 라우터의 병목현상을 초래하는 링크 레이트(Link Rate)에 따라 코어 라우터의 상태를 SS(Steady State), NS(Normal State), BS(Bottleneck State)로 구분하였으며, 코어 라우터의 과부하에 따라 멀티캐스트 라우팅 전략을 CBT에서 Anycast로 전환하는 방식을 제안하였다. 온라인 게임에서 교환되는 주요 패킷의 크기에 준하여 두 가지 라우팅 방식을 비교하고 트래픽의 증가에 따라 Anycast 라우팅 방식의 성능개선을 보였다.

• 한국분말재료학회지
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• 제17권4호
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• pp.295-301
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• 2010

Multi shell graphite coated Ag nano particles with core/shell structure were successfully synthesized by pulsed wire evaporation (PWE) method. Ar and $CH_4$ (10 vol.%) gases were mixed in chamber, which played a role of carrier gas and reaction gas, respectively. Graphite layers on the surface of silver nano particles were coated indiscretely. However, the graphite layers are detached, when the particles are heated up to $250^{\circ}C$ in the air atmosphere. In contrast, the graphite coated layer was stable under Ar and $N_2$ atmosphere, though the core/shell structured particles were heated up to $800^{\circ}C$. The presence of graphite coated layer prevent agglomeration of nanoparticles during heat treatment. The dispersion stability of the carbon coated Ag nanoparticles was higher than those of pure Ag nanoparticles.

• Current Photovoltaic Research
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• 제4권4호
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• pp.140-144
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• 2016

In this paper, core-shell structure of nickel/gold (Ni/Au) conductive layer on poly-methyl-methacrylate (PMMA) micro-ball was fabricated and its conduction property was investigated. Firstly, PMMA micro-ball was synthesized by using dispersion polymerization method. Size of the ball was $2.8{\mu}m$ within ${\pm}7%$ deviation, and appropriate elastic deformation of the PMMA micro-ball ranging from 31 to 39% was achieved under 3 kg pressure. Also, 200 nm thick Ni/Au conductive layer was fabricated on the PMMA micro-ball by uniformly depositing with electroless-plating. Adhesion of the conductive layer was optimized with help of surface pre-treatment, and the layer adhered without peeling-off despite of thermal expansion by collision with accelerated electrons. Composite paste containing core-shell structured particles well cured at low temperature of $130^{\circ}C$ while pressing the test chip onto the substrate to make electrical contact, and electrical resistance of the conductive layer showed stable behavior of about $6.0{\Omega}$. Thus, it was known that core-shell structured particle of the Ni/Au conductive layer on PMMA micro-ball was feasible to flexible electronics.

• 한국농공학회논문집
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• 제54권3호
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• pp.11-17
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• 2012

In this study, an experiment with large-scale model was performed according to raising embankment in order to investigate the cause of collapse by a change in water level of reservoir. Also, the settlement and pore water pressure by high water level and a rapid drawdown were compared and analyzed. After raising embankment for inclined core, there was no infiltration by leakage. For the vertical core, the pore water pressure showed a largely change by faster infiltration of pore water than in the inclined core. In a rapid drawdown, inclined core was remained stable but vertical core showed a largely change in pore water pressure. A settlement after a raising embankment showed a larger measure of settlement than before the raising embankment. The leakage quantity before a raising embankment and an inclined extension showed no leakage. Leakage in vertical extension was measured 160 $l$. From the result, a instrument system that can accurately estimate a change of pore water pressure shall be established for a rational maintenance and stabilization of raising embankment for agricultural reservoir.

• 한국게임학회 논문지
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• 제2권1호
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• pp.30-35
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• 2002

The deployment of multicast communication services in the Internet is expected to lead a stable packet transfer even in heavy traffic as in On-Line Game environment. The Core Based Tree scheme among many multicast protocols is the most popular and suggested recently. However, CBT exhibit two major deficiencies such as traffic concentration or poor core placement problem. So, measuring the bottleneck link bandwidth along a path is important for understanding the performance of multicast. We propose not only a definition of CBT's core link state that Steady-State(SS), Normal-State(NS) and Bottleneck State(BS) according to the estimation link speed rate, but also the changeover of multicast routing scheme for traffic overload. In addition, we introduce anycast routing tree, a efficient architecture for construct shard multicast trees.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.2936-2938
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• 2005

The deployment of multicast communication services in the internet is expected to lead a stable packet transfer even in heavy traffic as in network system environment. The core based tree scheme among many multicast protocols is the most popular and suggested recently. However, CBT exhibit two major deficiencies such as traffic concentration or poor core placement problem. so, measuring the bottleneck link bandwidth along a path is important for understanding th performance of multicast. We propose not only a definition of CBT's core link state that Steady-State, Normal-State and Bottleneck State according to the estimation link speed rate, but also the changeover of multicast routing scheme for traffic overload. In addition, we introduce anycast routing tree, a efficient architecture for construst shard multicast trees.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1077-1081
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• 2007

Thermal expanded core (TEC) fiber can reduce, being advantaged from thermal diffusion technology, connection loss by expanding the tolerance in relation to axial offset and gap when making optical connection having mode field diameter (MFD) of optical fiber expanded locally. In this paper, TEC fiber fabrication system based on the frame brushing techniques using twin-torch tip was designed and developed in order to maintain a stable thermal diffusion and single-mode when manufacturing TEC fiber. We were able to obtain that varied kinds of TEC fibers of which MFD could have been extended between $20\;{\mu}m$ and $40\;{\mu}m$ by TEC fiber fabrication system. In addition, the characteristic of connection loss was measured by alignment two TEC fibers of which MFD was $30\;{\mu}m$.

• 정보보호학회논문지
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• 제22권1호
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• pp.93-98
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• 2012

이동 노드로만 구성된 MANET은 유비쿼터스 컴퓨팅 환경을 구축하기 위한 핵심 기술로 많은 관심을 받고 있다. 또한 중앙 기반 시설이 없기 때문에 보안에 더욱 취약하다. 따라서 악의적인 공격을 탐지해 낼 수 있는 침입탐지 시스템이 반드시 필요하다. 본 논문에서는 안정된 침입탐지를 위해 클러스터를 이용하였으며, 네트워크 문제인 것처럼 보이는 공격도 정확히 탐지할 수 있도록 다양한 공격에 대해 규칙을 정의하였다. 실험을 통해 본 논문에서 제안한 기법이 노드의 수가 증가하더라도 안정된 탐지율을 보이는 것을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제14권4호
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• pp.673-679
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• 2004

A microbial cryoprotectant formulation using a W/O/W multiple emulsion system was developed. The psychrotolerant microorganism, B4, isolated from soil in South Korea, was observed by the drop freezing method, in which the microorganism sample inhibited ice nucleation activity. The antifreeze activity was eliminated when the microorganism sample was treated with protease, indicating that the antifreeze activity was due to the presence of antifreeze protein. The result of the l6S rDNA sequencing indicated the B4 strain was most closely related to a species of the genus Bacillus. Culture broth of B4 strain (Bacillus sp.) and rapeseed oil containing 1 % polyglycerine polyricinolate (PGPR) were used as core and wall material, respectively. The most stable W/O emulsion was prepared at a core/oil ratio of 1:2. The highest W/O/W emulsion stability was achieved when the primary emulsion to external aqueous phase containing 0.5% caster oil polyoxyethylene ether $(COG25^{TM})$ ratio was 1:1. Microcrystalline cellulose showed better W/O/W emulsion stability than other polymer types. The viability of cells in a W/O/W emulsion was higher than free cells during storage at $37^\circ{C}$. An acidic pH and UV exposure decreased the viability of free cells, but cells in W/O/W emulsion were more stable under these conditions.