• 대한임베디드공학회논문지
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• 제16권1호
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• pp.9-15
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• 2021

Recently, it is increasingly necessary to run high-end neural network applications with huge computation overhead on top of resource-constrained embedded systems, such as wearable devices. While the huge computational overhead can be alleviated by distributed neural networks running on multiple separate devices, existing distributed neural network techniques suffer from a large traffic between the devices; thus are very vulnerable to communication failures. These drawbacks make the distributed neural network techniques inapplicable to wearable devices, which are connected with each other through unstable and low data rate communication medium like human body communication. Therefore, in this paper, we propose a distributed neural network partitioning technique that is resilient to communication failures. Furthermore, we show that the proposed technique also improves the inference accuracy even in case of no communication failure, thanks to the improved network partitioning. We verify through comparative experiments with a real-life neural network application that the proposed technique outperforms the existing state-of-the-art distributed neural network technique in terms of accuracy and resiliency to communication failures.

• Structural Engineering and Mechanics
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• 제69권4호
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• pp.407-416
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• 2019

This paper develops a wireless sensor for online fatigue crack detection and failure warning based on crack-induced nonlinear ultrasonic modulation. The wireless sensor consists of packaged piezoelectric (PZT) module, an excitation/sensing module, a data acquisition/processing module, a wireless communication module, and a power supply module. The packaged PZT and the excitation/sensing module generate ultrasonic waves on a structure and capture the response. Based on nonlinear ultrasonic modulation created by a crack, the data acquisition/processing module periodically performs fatigue crack diagnosis and provides failure warning if a component failure is imminent. The outcomes are transmitted to a base through the wireless communication module where two-levels duty cycling media access control (MAC) is implemented. The uniqueness of the paper lies in that 1) the proposed wireless sensor is developed specifically for online fatigue crack detection and failure warning, 2) failure warning as well as crack diagnosis are provided based on crack-induced nonlinear ultrasonic modulation, 3) event-driven operation of the sensor, considering rare extreme events such as earthquakes, is made possible with a power minimization strategy, and 4) the applicability of the wireless sensor to steel welded members is examined through field and laboratory tests. A fatigue crack on a steel welded specimen was successfully detected when the overall width of the crack was around $30{\mu}m$, and a failure warnings were provided when about 97.6% of the remaining useful fatigue lives were reached. Four wireless sensors were deployed on Yeongjong Grand Bridge in Souht Korea. The wireless sensor consumed 282.95 J for 3 weeks, and the processed results on the sensor were transmitted up to 20 m with over 90% success rate.

• 대한전자공학회논문지SD
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• 제47권2호
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• pp.40-50
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• 2010

본 논문은 미세 CMOS 공정의 PMOS 트랜지스터에 높은 전류가 인가될 때 발생하는 기생 PNP 바이폴라 트랜지스터의 스냅백과 breakdown 동작에 초점을 맞춘다. $0.13\;{\mu}m$ CMOS 공정을 이용해 제작한 다양한 I/O 구조를 분석함으로써 PMOSFET의 ESD 손상 현상의 원인을 규명하였다. 즉, 인접한 다이오드로부터 PMOSFET의 바디로 전하가 주입됨으로써 PMOSFET의 기생 PNP 트랜지스터가 부분적으로 turn-on되는 현상이 발생하여 ESD에 대한 저항성을 저하시킨다. 2차원 소자 시뮬레이션을 통해 레이아웃의 기하학적 변수의 영향을 분석하였다. 이를 기반으로 새로운 PMOSFET ESD 손상을 방지하는 설계 방법을 제안한다.

• 한국언론정보학보
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• 제20권
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• pp.7-32
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• 2003

디지털방송은 나라마다 전략 산업으로 확정되어 급속히 발전하는 중이다. 디지털 방송은 지상파방송, 위성방송, CATV에 이르기까지 방송의 구조를 근본적으로 바꾸는 힘을 갖고 있다. 경제적으로 보면 디지털 방송은 천문학적인 비용이 들어가는 사업이다. 그래서 디지털방송정책은 신중히 수립되어야 한다. 디지털방송 사업자 역시 다른 어떤 사업보다 신중한 자세로 사업을 진척시켜야 할 것이다. 하지만 디지털방송의 전도는 지극히 불투명하다 특히 디지털 지상파방송의 불투명성은 더 심각하다. 한국에서도 디지털 지상파방송은 충 70조 원까지 들어간다는 예측도 있지만 막대한 자본이 소요되는 사업이어서 정부, 방송사, 수용자, 학계 누구하나 디지털 방송사업에 소극적인 자세를 보이고 있다. 이런 상황에서 우리보다 먼저 디지털 지상파방송을 실시한 나라를 참고하면 많은 교훈을 얻을 수 있을 것이다. 이에 필자는 영국 ITV Digital 방송의 실패 원인을 분석함으로써 한국 디지털 지상파방송의 발전에 유용한 교훈을 얻으려 할 것이다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2009년도 정보통신설비 학술대회
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• pp.285-288
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• 2009

The emergency recovery scheme in time of a disaster or accident up to now has been focused on how to build a backup for the public service or communication network in national scale, also, all the mobile operators have done as recovery scheme for the equipment failure in their network was to make a backup copy of billing data or package data, and they have usually studied only on the backup and failure recovery scheme in the circuit-switched network. However, since it has become more probable recently that a disaster or accident could occur in the switching office buildings, a recovery scheme in time of the failure of these entire switching offices became necessary. The purpose of this paper is to propose various recovery schemes, and by having checkups on many issues that could arise while carrying out these schemes, it presents the best solution for each issue. Moreover, it presents the future tasks that need to be studied as well as initial study directions.

• 전자공학회논문지B
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• 제31B권8호
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• pp.1-10
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• 1994

In this paper load redistribution algorithm to allow fault-tolerance by redistributing the workload of n failure nodes to the remaining good nodes in distributed systems are investigated. To evaluate the efficiency of the algorithms a simulation model of algorithms is developed using SLAM II simulation language. The job arrival rate service rate failure and repair rate of nodes and communication delay time due to load migraion are used as parameters. The result of the simulation shows that the job arrival rate failure and repair rate of nodes do not affected on the relative efficiency of algorithms. If the communication delay time is greater than average job processing time algorithm B is better. Otherwise algorithm C is superior to the others.

• Asia Marketing Journal
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• 제9권3호
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• pp.75-115
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• 2007

본 연구는 고객이 서비스 실패와 복구를 경험하는 과정에서 서비스 제공자의 서비스 복구노력과 서비스 실패 이전의 고객-종업원의 친밀감이 만족, 재구매의도, 긍정 구전에 미치는 영향을 고찰하였다. 첫째, 본 연구는 서비스 실패와 복구 후 소비자의 반응에 대한 서비스 제공자의 복구노력과 친밀감의 상호작용효과를 검증하였다. 실험결과 서비스 실패 이전 고객과 종업원의 친밀도가 높은 집단에서는 친밀도가 낮은 집단에 비하여 서비스 실패후의 복구노력이 낮아도 만족, 재구매의도, 긍정적 구전정도가 크게 감소하였다. 둘째, 본 연구는 서비스실패 후 적절한 복구노력을 경험한 고객의 만족이 서비스 실패를 겪기 전보다 높아질 수 있다는 서비스 리커버리 패러독스를 검증하였다. 실험결과 서비스 리커버리 패러독스는 서비스 복구노력수준과 고객-종업원의 친밀도에 관계없이 모든 집단에서 지지되지 않았다. 두 가설의 결과를 종합하여 보면 고객과 종업원의 긍정적인 친밀감은 서비스 실패로 인한 부정적인 영향을 서비스 실패가 없었던 상황으로 되돌릴 수는 없지만, 실패로 인한 부정적인 영향을 감소시켜주는 완충작용을 하는 것으로 나타났다.

• Journal of Communications and Networks
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• 제16권5호
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• pp.534-547
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• 2014

Large-scale failures resulting from natural disasters or intentional attacks are now causing serious concerns for communication network infrastructure, as the impact of large-scale network connection disruptions may cause significant costs for service providers and subscribers. In this paper, we propose a new framework for the analysis and prevention of network service disruptions in large-scale failure scenarios. We build dynamic deterministic and probabilistic models to capture the impact of regional failures as they evolve with time. A probabilistic failure model is proposed based on wave energy behaviour. Then, we develop a novel approach for preventive protection of the network in such probabilistic large-scale failure scenarios. We show that our method significantly improves uninterrupted delivery of data in the network and reduces service disruption times in large-scale regional failure scenarios.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.121-130
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• 2021

Cascading failure is the main cause of large blackouts in electrical power systems; this paper analyzes a cascading failure in Hanbit nuclear power plant unit two (2) caused by a circuit breaker (CB) operation failure. This malfunction has been expanded to the loss of offsite power (LOOP). In this study, current practices are reviewed and then the methodologies of how to prevent cascading failures in protection power systems are introduced. An overview on the implementation of IEC61850 GOOSE messaging-based zone selective interlocking (ZSI) scheme as key solution is proposed. In consideration of ZSI blocking time, all influencing factors such as circuit breaker opening time, relay I/O response time and messages travelling time in the communication network should be taken into account. The purpose of this paper is to elaborate on the effect of cascading failure in NPP electrical power protection system and propose preventive actions for this failures. Finally, the expected advantages and challenges are elaborated.

• 한국정보시스템학회지:정보시스템연구
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• 제4권
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• pp.85-104
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• 1995

In a loosely-coupled distributed database server system, a server failure and/or a communication failure can be masked by a resiliency mechanism. Recognizing that a distributed transaction executes at several servers during its lifetime, we propose a resiliency mechanism which allows continuous transaction processing in distributed database server systems in the presence of a server failure. The resiliency mechanism for transaction processing is achieved by keeping redundant information using a primary/backup approach. The purpose of this paper is to analyze the performance improvement opportunities with the resiliency mechanism and to present the design of the proposed system.