• 전기학회논문지P
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• 제65권1호
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• pp.1-6
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• 2016

Recently, proportion of the induction motor load is gradually increased. When a contingency in the power systems, it has been discovered phenomenon that the voltage is delayed recover caused mechanical characteristics of the induction motor load. It can be a serious impact on the voltage stability of the power system considering induction motor load. The scheme to mitigate this phenomenon tripping off the motors to prevent voltage drop and delayed voltage recovery on the load demand side. Fault induced delayed voltage recovery phenomenon is caused by stalling of small induction motor load in transmission level contingencies. In this paper, fault induced delayed voltage recovery phenomenon mitigation method implementation under voltage load shedding on the korean power system considering induction motor load.

• 전자공학회논문지A
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• 제32A권5호
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• pp.14-23
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• 1995

A new dual-mode algorithm for blind equalization of quadrature amplitude modulation (QAM) signals is proposed. To solve the problem that the constant modulus algorithm (CMA) converges to the constellation with the arbitrary phase rotation, with the modification of the CMA, the proposed algorithm accomplishes blind equalization and carrier phase recovery simultaneously. In addition, the dual-mode algorithm combining the modified constant modulus algorithm (MCMA) with decision-directed (DD) algorithm achieves the performance enhancement of blind convergence speed and steady-state residual ISI. So we can refer the proposed algorithm to as a scheme for joint blind equalization and carrier phase recovery. Simulation results for i.i.d. input signals confirm that the dual-mode algorithm results in faster convergence speed, samller residual ISI, and better carrier phase recovery than those of the CMA and DD algorithm without any significant increase in computational complexity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.980-985
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• 2003

The present study addresses a computational work to investigate the influence of a turbulent wake flow on the pressure recovery of a subsonic diffuser. The turbulent wake is generated by a cylinder with a small diameter, which is installed at the inlet of a 2-dimensional diffuser. Computation are applied to three-dimensional steady Navier-Stokes equations. The fully implicit finite volume scheme is used to discretize the governing equations. The computational results are qualitatively well compared to the experimental results. The results show that the pressure recovery of the subsonic diffuser is dependent on the diameter and location of cylinder. It is found that a certain diameter and location of the cylinder to generate the turbulent wake give a better pressure recovery, compared with no cylinder flow.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.329-330
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• 2006

This paper presents a recovery technique for images with block-based corruption by transmission losses. Conventional methods that do not consider edge directions can cause blocked blurring artifacts. In this paper, we present a block recovery scheme using Haar wavelet features. The adaptive selection of neighboring blocks is performed based on the energy ratio f wavelet subbands. The lost blocks are recovered by linear interpolation in the spatial domain using selected block pairs. The proposed directional recovery method is effective for the strong edge because it exploits the varying neighboring blocks adaptively according to the edges and the directional information in the image. The proposed method outperforms the previous methods that used only a predefined set of neighboring blocks.

• 전기학회논문지
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• 제62권1호
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• pp.120-126
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• 2013

This paper proposes a novel scheme of fault detection and self-recovery for space-borne dual ring counters subject to transient faults. The considered ring counter is equipped with hardware redundancy, but it has a limited output domain where direct access to the current state is unavailable. We employ the theory of corrective control to detect any transient fault occurring to the counter bits and to realize immediate self-recovery of the ring counter back to the normal state. The structure of the fault-tolerant controller is designed to be minimal regardless of the counter size. To validate the applicability, we implement the proposed system on a commercial FGPA board.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2013년도 추계학술발표대회
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• pp.400-401
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• 2013

Mobility in a network causes link disconnections and link recovery is vital for reliability of a network. A link failure affects all the preceding nodes on a damaged routing path; creates communication delay, throughput degradation, and congestion. This paper proposes link recovery mechanisms in CCN based networks. Packet overhearing is used to update neighboring nodes information. The recovery is done by forwarding node resulting in low control overhead, and better efficiency. The proposed mechanisms increase overall performance of a typical CCN and simulation results show that our proposed scheme works very well in densely populated networks with high mobility.

• 전력전자학회논문지
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• 제3권3호
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• pp.222-230
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• 1998

본 논문에서는 스너버 회로를 사용하지 않고 턴-온시 역회복 전류의 영향과 턴-오프 시 구동되는 IGBT에 발생하는 과전압을 제한할 수 있는 새로운 IGBT 게이트 구동회로를 제안한다. 제안하는 턴-온 게이트 구동기법은 턴-온 지연 시간을 증가시키지 않고 게이트-에이터 전압이 문턱전압 이상이 되면 IGBT의 입력 커패시턴스를 증가시킴으로써 게이트-에이터 전압의 증가율을 감소시키는 특징을 갖는다. 제안하는 턴-오프 게이트 구동기법은 전류의 크기에 따라 과전압을 제한하여 단락사고와 같은 대전류가 흐르는 경우 더욱 효과적으로 과전압을 제한하는 특징을 가진다. 또한, 여러 가지 조건에서 실험을 수행하여 제안한 IGBT 게이트 구동회로의 타당성을 검증한다.

• 대한기계학회논문집B
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• 제24권3호
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• pp.443-449
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• 2000

The performance of 2-frame PTV(particle tracking velocimetry) system was improved using an adaptive hybrid scheme. The original 2-frame PTV method based on the match probability concept employs global match parameters for the entire flow field. Since this does not reflect fully the detailed local velocity change, it sometimes reduces the recovery rate of velocity vectors and increases the number of erroneous vectors in the region where an extraordinary flow structure exists. In this study, the preliminary FFT-based PIV results are used as an input parameter to determine the local match parameters needed for the 2-frame particle tracking algorithm. A computer simulation using synthetic particle images was carried out to study the performance of the adaptive 2-frame PTV technique. The adaptive hybrid method shows the better performance with increasing the velocity vector recovery rate and decreasing the computation time, compared to the original 2-frame PTV method.

• 한국인터넷방송통신학회논문지
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• 제11권4호
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• pp.17-22
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• 2011

수중 환경은 육상 환경과 많은 차이를 보이며 무선 통신에 사용되는 자원과 제약 조건들도 다르다. 일반적으로 수중 통신 환경은 육상 통신 환경보다 열악하고, 파도, 조류와 같은 해수의 흐름으로 인한 노드의 이동성 때문에 오류 발생 가능성이 기존의 지상 무선 센서 네트워크 보다 높다. 따라서 수중 무선 센서 네트워크의 통신 환경을 고려하여 노드 간 데이터 전송률을 향상시키기 위한 기법들에 대한 요구가 높아지고 있다. 본 논문에서는 수중 무선 센서 네트워크의 통신 환경을 고려하여 클러스터 헤드 노드의 오류 발생 시 이를 빠른 시간 내에 복구하기 위한 체크포인팅 기법을 제안한다. 또한 실험을 통해 제안 기법이 네트워크 운영의 신뢰도를 향상 시킬 수 있을 뿐만 아니라, 에너지 소모량과 오류 복구 지연 시간 측면에서 제안 기법을 적용하지 않았을 때보다 좋은 성능을 보인다는 것을 검증한다.

• 한국항해항만학회지
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• 제36권8호
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• pp.631-635
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• 2012

수중에서의 통신은 해수면과 해저면 등에 의한 신호의 반사가 생겨 다중경로 전달현상이 발생한다. 이러한 다중경로 전달의 영향으로 신호는 왜곡되고 원활한 수신을 방해하게 된다. 본 논문에서는 이러한 다중경로 환경에서 효율적인 패킷 설계를 위하여 채널 부호화 기법으로는 부호화 후의 크기 N = 1944 비트, 전송하고자 하는 데이터의 크기 K = 972 비트를 가지는 부호화율 1/2 인 LDPC(Low Density Parity Check codes) 부호를 이용하였으며, 다중경로로 인한 위상 오차 추정은 decision directed 방식을 이용하여 위상 추정을 하였다. 실제 동해 바다에서 송수신 거리가 200m, 500m 그리고 데이터 속도를 1Kbps, 4Kbps로 설정하여 각 거리 및 데이터 속도에 따른 QEF(Quasi Error Free)가 되는 지점에서의 최적의 패킷 구성을 위한 데이터 길이를 제시하였다.