• 대한전기학회논문지:시스템및제어부문D
• /
• 제54권10호
• /
• pp.615-619
• /
• 2005

Token coherence protocol has many good reasons against snooping/directory-based protocol in terms of latency, bandwidth, and complexity. Token counting easily maintains correctness of the protocol without global ordering of request which is basis of other dominant cache coherence protocols. But this lack of global ordering causes starvation which is not happening in snooping/directory-based protocols. Token coherence protocol solves this problem by providing an emergency mechanism called persistent request. It enforces other processors in the competition (or accessing same shared memory block, to give up their tokens to feed a starving processor. However, as the number of processors grows in a system, the frequency of starvation occurrence increases. In other words, the situation where persistent request occurs becomes too frequent to be emergent. As the frequency of persistent requests increases, not only the cost of each persistent matters since it is based on broadcasting to all processors, but also the increased traffic of persistent requests will saturate the bandwidth of multiprocessor interconnection network. This paper proposes a new request mechanism that defines order of requests to reduce occurrence of persistent requests. This ordering mechanism has been designed to be decentralized since centralized mechanism in both snooping-based protocol and directory-based protocol is one of primary reasons why token coherence protocol has advantage in terms of latency and bandwidth against these two dominant Protocols.

• 한국멀티미디어학회논문지
• /
• 제12권9호
• /
• pp.1323-1332
• /
• 2009

본 논문은 IEEE 802.11i의 4-Way 핸드쉐이크의 취약점을 분석하고, 고속의 안전한 2-Way 핸드쉐이크 방식을 제안한다. PTK 생성에서 난수 대신에 순번(Sequence Number)을 사용하여, 재생공격, DoS 공격을 방지한다. 또한 Re-association Request 프레임과 Re-association Response 프레임을 변형하여 MS(Mobile Station)과 AP(Access Point) 사이의 상호 인증과, PTK(Pairwise Transient Key)의 도출을 가능하게 하여, 전송되는 메시지의 개수를 감소시켜, 4-Way 핸드쉐이크보다 고속의 핸드오프 방식을 제안한다. 그리고 고속의 안전한 핸드오프를 제안하는 기존의 기법들과 비교 분석한다.

• 한국멀티미디어학회:학술대회논문집
• /
• 한국멀티미디어학회 1998년도 추계학술발표논문집
• /
• pp.214-218
• /
• 1998

분산 객체 컴퓨팅 환경이 대두되고 있는 오늘날, 네트워크 상에 분산되어 있는 객체들을 효율적으로 관리할 수 있는 기능이 필요하게 되었다. OMG(Objective Request Broker Architecture)에서는 개체를 바인딩하기 위한 두 가지 형태의 객체 참조, 즉 일시적 객체참조(Transient Object Reference)와 영구적 객체참조(Persistent Object Reference)가 있으며 영구적 객체 참조를 바인딩하기 위해서 ORB는 구현저장소를 제공해야 한다. 이를 위해 CORBA 스펙에서는 구현저장소의 개념만을 정의되어 있을 뿐 인터페이스는 아직 정의되어 있지 않은 상태이다. 본 논문에서는 구현저장소의 도움만을 받아 구현객체를 바인딩 할 수 있도록 하기 위한 구현저장소의 인터페이스를 설계하였다.

• 대한전자공학회논문지
• /
• 제14권5호
• /
• pp.1-6
• /
• 1977

synchronizer의 입력단에 비동기된 두 신호가 인가되었을 때 일어나는 Metastable 현상에 대한 회로의 해석과 Metastable point에서 stable state로 천이되는 과정에서 일어나는 현상을 해석하였으며, 이러한 mishappen 상태에 의해 기인하는 logic failure를 개선하기 위한 방법으로써, Inverter Method, open collector Method를 사용하여 올바른 논리를 이론과 실험을 통하여 구현하였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.336-340
• /
• 1998

In this paper, an effective control scheme of a single phase UPS inverter is proposed to have no steady state error of the output voltage and the fast response for the load request. The cosine wave tranfer function is proposed to control the output voltage. This controller clearly removes errors of magnitude and phase both in the steady state. On the other hand, a current controller is proposed to reduce the transient time of the voltage control and to improve the bad distorted factor of the output voltage waveform by the load fluctuation and the presences of nonlinear parameters in the plant. The current controller is designed parallel to the voltage controller and performs separately from it.

• 한국멀티미디어학회논문지
• /
• 제13권3호
• /
• pp.349-358
• /
• 2010

모바일 환경의 비디오 스트리밍에서 클라이언트들은 작업 부하의 차이가 큰 비디오를 요청할 수 있기 때문에 적응성은 중요한 문제이다. 본 논문에서는 모바일 또는 무선 통신망에서 MPEG-4 비디오 스트림을 효율적으로 전송하기 위해 제한된 대역폭을 스케쥴링하는 기법이 제시된다. 수락 제어 단계에서는 요청된 각 비디오 대역폭이 평균 대역폭 요건에 따라 할당된다. 실제 스케쥴링 단계에서는 클라이언트들의 재생 상황에 더욱 적합한 스케쥴링이 수행될 수 있도록 하기 위해 클라이언트의 버퍼 수준에 따라 대역폭이 동적으로 할당된다. 제시된 RTA(Real-Time Adaptive) 스케쥴링 프로토콜에서는 버퍼 수준이 낮은 클라이언트에게 일시적으로 더 많은 대역폭이 할당될 수 있다. 버퍼 수준에 기반한 스케쥴링 정책을 사용하는 RTA 프로토콜은 일시적인 과부하 영향을 최소화하는 한편 재생시 실시간적 성능을 최대화할 수 있다. RTA 프로토콜의 성능은 다양한 실험을 통하여 측정되었으며 BSBA(Buffer Sensitive Bandwidth Allocation) 프로토콜과 비교한 결과 RTA 프로토콜이 더 많은 수의 프레임들을 전송함으로써 우수한 성능을 가지는 것으로 분석되었다.

• KEPCO Journal on Electric Power and Energy
• /
• 제6권2호
• /
• pp.123-127
• /
• 2020

KEPCO has installed Frequency Regulation ESS (FR ESS) of 376 MW since 2015. Frequency Regulation is ancillary service to support stabilizing system frequency, which is divided into governor free and automatic generation control. KEPCO operates FR ESS as governor free application and leads FR ESS market with capability of diverse demonstration and operation experiences. To expand FR ESS role during transient states of power system, KEPCO has extended operating time of charging and discharging. KEPCO has also changed speed droop lower than before to improve contribution on frequency compensation, and acquired much experiences of differentiating bad cells from others. Based on these technologies and know-hows, KEPCO Research Institutes received request of feasibility study and technical cooperation for overseas FR ESS business. This paper suggests the simple and practical method for making technological feasibility study of FR ESS.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2015년도 특별논문집
• /
• pp.50-55
• /
• 2015

Application of newly conceptualized Anti-Splash Devices designed for COT vent pipes were studied on a P/V valve located on the upper deck of an oil carrier vessel. Anti-Splash devices are used in the shipbuilding industry in order to avoid oil overflow and spray accidents caused by excess pressure and vacuum condition in the cargo oil tanks. These conditions are caused by the transverse and longitudinal sloshing forces that arise from ship motion during sea voyages. The main issue with existing Anti-Splash device model is flux at the outlet of the Anti-Splash Device, and so, new conceptual models for the Anti-Splash device were developed and compared to existing Anti-Splash device model using CFD analysis. Transient analysis was used to capture the flow and velocity of each model and a comparative analysis was performed between old and new-concept models. This data was used to determine the optimal design parameters in order to develop an optimized Anti-Splash Device. A Factory acceptance test was performed on the new-concept models in order to verify the performance and efficiency against their design requirements and other criterion. The final step performed was to apply the optimized Anti-Splash Device models for COT vent pipes to an actual vessel and verify performance through a seawater cargo operation during a sea voyage as per the ship owner's request. The patent for the aforementioned device was obtained by the Korean Intellectual property Office dated Dec. 18th,2014.