• 한국정보처리학회논문지
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• 제4권2호
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• pp.628-638
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• 1997

VSLI회로에서 스위치 레벨 결함 모델은 stuck-at결함만 사용하는데 한계가 있다. 따라서 본 연구는 스위치 레벨 결함 모델인 트랜지스터 stuck-open과 stuck-close결함을 다룰 수 있는결함 시뮬레이터를 구현한다. 스위치 레벨 회로는 이론적으로 신호 흐름이 양방향으로 전달되지만 실제로 대부분의 신호 흐름은 약 95%정도가 단 방향을로 설정되어 평가되는 것으로 나타내고 있다. 본 연구에서는 스위치 레벨 회로를 단반향 그래프 모델 로 변환시켜 해석한다. 스위치 레벨 회로는 EDIF컴파일러에 의해 입력되고 두개의 단방향으로 재구성된 자료구조를 만든다. 스위치 레벨 회로는 신호 흐름 경로가 도입되는 지배적 경로 기법이 제시된다. 지배적 경로는 경로를 판단하여 최종 출력 상태값을 결정하는 논리 시뮬레이션을 수행한다. 스위치 레벨 결함 시뮬레이션은 노들들로 연결되는 경로 상에 임의 트랜지스터의 stuck-open,stuck-close 결함을 주입시키고, 트랜지스터 저항값을 적용한 노드세기의 계산에 의한 지배적 경로를 평가한다. 이때 최초 입력은 two pattern vector를 인가하여 정상회로의 최종 출력 상태값과 결함회로의 출력 상태값을 비교하여 결함 검색하며, 그결함 검색의 정확성 을 보인다.

• 한국통신학회논문지
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• 제31권9A호
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• pp.868-877
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• 2006

센서 네트워크에서 시각 동기 기술은 위치 추적, 암호화 기술에서의 타임 스탬프, 타 노드들로부터의 같은 이벤트 중복 감지 인식, 기록된 이벤트들의 발생 순서 구분 등 다양한 응용을 위해 필수적이다. 그리고 최근 센서 네트워크에서 신뢰성 및 고장 허용성에 대한 문제가 최근 연구의 주요한 영역으로 대두되고 있다. 본 논문에서는 네트워크 고장과 클럭 고장이라는 두가지 고장 모델을 가정하여 센서 네트워크에서 고장 허용 시각 관리 기법에 대해 제시한다. 제안한 기법은 노드 클럭의 불안정한 동요나 표류율에 심각한 변화가 발생하는 등의 고장이 발생했을 때 이러한 클럭 오류의 네트워크 전파를 제한하며 토폴로지 변화에 대응한다. 시뮬레이션 결과는 제안한 동기 기법이 기존의 TPSN과 비교하여 클럭 고장이 있을 때 동기화 비율이 $1.5{\sim}2.0$배 나은 성능을 보인다.

• Journal of Electrical Engineering and Technology
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• 제2권4호
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• pp.485-493
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• 2007

This paper deals with the problem of detection of induction motor incipient faults. Artificial Neural Network (ANN) approach is applied to detect two types of incipient faults (1). Interturn insulation and (2) Bearing wear faults in single-phase induction motor. The experimental data for five measurable parameters (motor intake current, rotor speed, winding temperature, bearing temperature and the noise) is generated in the laboratory on specially designed single-phase induction motor. Initially, the performance is tested with two inputs i.e. motor intake current and rotor speed, later the remaining three input parameters (winding temperature, bearing temperature and the noise) were added sequentially. Depending upon input parameters, the four ANN based fault detectors are developed. The training and testing results of these detectors are illustrated. It is found that the fault detection accuracy is improved with the addition of input parameters.

• 한국정보처리학회논문지
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• 제5권11호
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• pp.2989-2996
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• 1998

집적회로의 집적도가 높아지고 성능이 향상됨에 따라 회로의 지연고장에 대한 관심이 날로 높아지고 있다. 회로의 지연고장은 게이트 지연고장과 경로지연고장으로 분류할 수 있는데, 이 논문에서는 경로지연고장 시뮬레이션에 대한 두 가지 동적 메모리 사용 방법을 제안하였다. 첫 번째 방법은 고착고장에 대한 동시 고장 시뮬레이션과 유사한 방식이며, 두 번째 방법은 고장기술자의 값이 X일 때 이를 고장리스트에 삽입하지 않는 묵시적-X 방식이다. 제안된 두 방식 중 묵시적-X 방식이 동적 메모리 사용과 시뮬레이션 시간 측면에서 효율적이었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.341-344
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• 2003

This paper proposes a tree-winding transformer protective relaying algorithm based on the ratio of increment of flux linkages (RIFL). The RIFL of the two windings is equal to the turns ratio for all operating conditions except an internal faults. For a single-phase transformer and three-phase transformer containing the wye-connected windings, the increments of flux linkages are calculated. for a three-phase transformer containing the delta-connected windings, the difference of the increments of flux linkages between the two phases are calculated using the line currents, because the winding currents are practically unavailable. Their ratios are compared with the turns ratio. The results of various tests show that the algorithm successfully discriminates internal faults from normal operation conditions such as magnetic inrush, overexcitation and external faults. The algorithm can not only detect internal winding faults, but reduce the operating time of a relay.

• Journal of Power Electronics
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• 제16권4호
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• pp.1415-1425
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• 2016

This paper presents a new approach for fault diagnosis in three-level neutral point clamped inverters. The proposed method is based on the average values of the positive and negative parts of normalized output currents. This method is capable of detecting and locating multiple open-circuit faults in the controlled power switches of converters in half of a fundamental period of those currents. The implementation of this diagnostic approach only requires two output currents of the inverter. Therefore, no additional sensors are needed other than the ones already used by the control system of a drive based on this type of converter. Moreover, through the normalization of currents, the diagnosis is independent of the load level of the converter. The performance and effectiveness of the proposed diagnostic technique are validated by experimental results obtained under steady-state and transient conditions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.321-322
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• 2006

Faults on power systems are inevitable phenomena. These faults can be classified by two categories, temporary and permanent faults. Without distinction of fault types, the faults would induce several changes on power system such as transmission line trip. Especially, the most common phenomena which loads experience by the power system fault is voltage sag. Voltage sags mean that the bus voltage maintains under 0.9 p.u. of rating for several cycles, and they give serious effects to operation of load devices. To ensure proper operation of the load, the flywheel systems, one of the energy storage system, are suggested in this paper. This paper demonstrates the efficiency of flywheel energy storage system against voltage sag by PSCAD/EMTDC simulation.

• Nuclear Engineering and Technology
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• 제29권6호
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• pp.433-443
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• 1997

In this work, an analytic approach to the dependability of software in the operational phase is suggested with special attention to the hardware fault effects on the software behavior : The hardware faults considered are memory faults and the dependability measure in question is the reliability. The model is based on the simple reliability theory and the graph theory which represents the software with graph composed of nodes and arcs. Through proper transformation, the graph can be reduced to a simple two-node graph and the software reliability is derived from this graph. Using this model, we predict the reliability of an application software in the digital system (ILS) in the nuclear power plant and show the sensitivity of the software reliability to the major physical parameters which affect the software failure in the normal operation phase. We also found that the effects of the hardware faults on the software failure should be considered for predicting the software dependability accurately in operation phase, especially for the software which is executed frequently. This modeling method is particularly attractive for the medium size programs such as the microprocessor-based nuclear safety logic program.

• 한국세라믹학회지
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• 제35권6호
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• pp.535-542
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• 1998

SOI(silicon oninsulator) was fabricated through the direct bonding of a hydrophilized single crystal Si wafer and a thermally oxidized SiO2 thin film to investigate the stacking faults in silicon at the Si/SiO2 in-terface. At first the oxidation kinetics of SiO2 thin film and the stacking fault distribution at the oxidation interface were investigated. The stacking faults could be divided into two groups by their size and the small-er ones were incorporated into the larger ones as the oxidation time and temperature increased. The den-sity of the smaller ones based critically lower eventually. The SOI wafers directly bonded at the room temperature were annealed at 120$0^{\circ}C$ for 1 hour. The stacking faults at the bonding and oxidation interface were examined and there were anomalies in the distributions of the stacking faults of the bonded region to arrange in ordered ring-like fashion.

• 한국자동차공학회논문집
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• 제1권2호
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• pp.49-59
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• 1993

A new signal processing technique is applied to four-cylinder spark and compression ignition engines for the diagnosis of power faults inside the cylinders. This technique utilizes two-sided directional power spectra(예S) of complex vibration signals measured from engine blocks as the patterns for engine cylinder power faults. The dPSs feature that they give not only the frequency contents but also the directivity of the engine block motion. For the automatic detection/diagnosis of cylinder power faults, pattern recognition method using multi-layer neural networks is employed. Experimental results show that the sucess rate for diagnosis of cylinder power faults using dPSs is higher than that using the conventional one-sided power spectra. The proposed technique is also tested to check the robustness to the sensor position and the engine rotational speed.