• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.664-677
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• 2014

Wind energy has proven its viability by the emergence of countless wind turbines around the world which greatly contribute to the increased electrical generating capacity of wind farm operators. These infrastructures are usually deployed in not easily accessible areas; therefore, maintenance routines should be based on a well-guided decision so as to minimize cost. To aid operators prior to the maintenance process, a condition monitoring system should be able to accurately reflect the actual state of the wind turbine and its major components in order to execute specific preventive measures using as little resources as possible. In this paper, we propose a fault detection approach which combines cluster analysis and frequent pattern mining to accurately reflect the deteriorating condition of a wind turbine and to indicate the components that need attention. Using SCADA data, we extracted operational status patterns and developed a rule repository for monitoring wind turbine systems. Results show that the proposed scheme is able to detect the deteriorating condition of a wind turbine as well as to explicitly identify faulty components.

• International Journal of Internet, Broadcasting and Communication
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• 제7권2호
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• pp.109-112
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• 2015

The Korean electric railway is growing rapidly such as speed of 300km/h in high speed section and 230km/h in the conventional railway section. But, power supply failure occurs because of loss of contact, defective catenary system and high speed vehicle. Therefore preventive maintenance way based reliability has been applied. Typical example is the facility inspection method using trolley inspection system. But it is required differentiated inspection method to prevent problem such as inspection errors. In this paper, a study on the trolley sliding condition inspection system using monitoring techniques is performed for performance enhancement of inspection system. It proposed the efficient maintenance method through monitoring the deviation and height of contact wire after installing inspection system on the top of train which operates in the metropolitan area. Inspection errors were decreased by virtually monitoring the video of faulty facilities. Also those facilities were identified through the impact sound analysis and tests at the main catenary section.

• 한국인터넷방송통신학회논문지
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• 제10권4호
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• pp.115-120
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• 2010

모듈화된 부품을 이용하여 완성된 제품을 만드는 제품완성업체는 효율적인 부품공급시스템을 통해 부품공급업체로부터 적시에 조립라인에 부품을 공급받기를 원하며 이종부품에 대한 결품이 발생하지 않기를 기대한다. 스마트 파렛트 기반 부품공급시스템은 이러한 요구를 만족시키기 위하여 수작업에 의한 과다한 이종부품확인 시간을 소비하는 기존의 바코드 기반 방식의 단점과 RFID 기반 방식이 가진 전송거리 제한 문제를 해결하고자 제안되었다. 본 논문에서는 스마트 파렛트 기반 부품공급시스템이 가진 제한된 전력 문제를 보완하고 운영의 효율성을 극대화하기 위한 PDA 시스템을 제안하고 실제 구현하였다.

• 한국정보전자통신기술학회논문지
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• 제2권2호
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• pp.51-56
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• 2009

본 논문에서는 카메라-투영 시스템에서 비전에 기반을 둔 손동작 인식을 위한 새로운 알고리즘을 제안하고 있다. 제안된 인식방법은 정적인 손동작 분류를 위하여 푸리에 변환을 사용하였다. 손 분할은 개선된 배경 제거 방법을 사용하였다. 대부분의 인식방법들이 같은 피검자에 의해 학습과 실험이 이루어지고 상호작용에 이전에 학습단계가 필요하다. 그러나 학습되지 않은 다양한 상황에 대해서도 상호작용을 위해 동작 인식이 요구된다. 그러므로 본 논문에서는 인식 작업 중에 검출된 불완전한 동작들을 정정하여 적용하였다. 그 결과 사용자와 독립되게 동작을 인식함으로써 새로운 사용자에게 신속하게 온라인 적용이 가능하였다.

• 한국정보통신학회논문지
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• 제13권9호
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• pp.1913-1920
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• 2009

본 논문에서는 오류센서 보정 기능을 갖춘 태양광 조명용 정밀 태양 추적제어기 개발에 대하여 기술하였다. 태양 위치에 대한 광역범위 추적과 미소범위에서의 정밀추적 제어를 위하여 대범위 센서군과 소범위 센서군으로 나뉜 센서모듈을 개발하였다. 태양위치의 정밀 추적을 위하여 소범위 센서군의 응답특성을 분석하여 퍼지 제어엔진을 개발하였으며, 주축성분 분석법(Principal Component Analysis)을 적용하여 오류센서의 감별 및 복원을 하였다. 개발된 시스템의 실외 태양추적 실험을 통하여 본 연구의 유용성을 입증하였다.

• Journal of Communications and Networks
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• 제17권1호
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• pp.40-46
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• 2015

In a mobile ad hoc network (MANET), communication between mobile nodes occurs without centralized control. In this environment the mobility of a node is unpredictable; this is considered as a characteristic of wireless networks. Because of faulty or malicious nodes, the network is vulnerable to routing misbehavior. The resource constrained characteristics of MANETs leads to increased query delay at the time of data access. In this paper, AntHocNet+ Security (ANTSEC) framework is proposed that includes an enhanced cooperative caching scheme embedded with artificial immune system. This framework improves security by injecting immunity into the data packets, improves the packet delivery ratio and reduces end-to-end delay using cross layer design. The issues of node failure and node malfunction are addressed in the cache management.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제8권2호
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• pp.126-131
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• 2008

Wireless Sensor Network(WSNs) consists of small sensor nodes with sensing, computation, and wireless communication capabilities. It has new information collection scheme and monitoring solution for a variety of applications. Faults occurring to sensor nodes are common due to the limited resources and the harsh environment where the sensor nodes are deployed. In order to ensure the network quality of service it is necessary for the WSN to be able to detect the faulty sensors and take necessary actions for the reconstruction of the lost sensor data caused by fault as earlier as possible. In this paper, we propose an recursive PCA-based fault detection and lost data reconstruction algorithm for sensor networks. Also, the performance of proposed scheme was verified with simulation studies.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.882-885
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• 2011

This paper presents testing and self-calibration of RF circuits using MEMS switches to identify process-related defects and out of specification circuits. We have developed a novel multi-tone dither test technique where the test stimulus is generated by modulating the RF carrier signal with a multi-tone signal generated using an Arbitrary Waveform Generator (AWG) with additive white Gaussian noise. This test stimulus is provided as input to the RF circuit and peak-to-average ratio (PAR) is measured at the output. For a faulty circuit, a significant difference is observed in the value of PAR as compared to a fault-free circuit. Simulation is performed for various circuit conditions such as fault-free as well as fault-induced and their corresponding PARs are stored in the look-up table. This testing and self-calibration technique is exhaustive and efficient for present-day communication systems.

• 한국정보통신학회논문지
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• 제13권10호
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• pp.2129-2139
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• 2009

본 논문에서는 셀룰라 오토마타를 이용하여 테스트되는 회로에 상관없이 마지막 테스트 압축치가 일정하게 되도록 조직함으로써 오류를 진단한다. 이 방법은 셀룰라 오토마타를 이용한 테스트 절차를 간결하고 명확하게 한다. 그리고 셀룰라 오토마타의 상태전이 행렬의 역행렬을 사용하여 오류가 있는 입력수열의 오류를 탐지한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2375-2393
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• 2016

Key agreement is paramount in secure wireless communications. A promising approach to address key agreement schemes is to extract secure keys from channel characteristics. However, because channels lack randomness, it is difficult for wireless networks with stationary communicating terminals to generate robust keys. In this paper, we propose a Robust Secure Key Agreement (RSKA) scheme from Received Signal Strength (RSS) in stationary wireless networks. In order to mitigate the asymmetry in RSS measurements for communicating parties, the sender and receiver normalize RSS measurements and quantize them into q-bit sequences. They then reshape bit sequences into new l-bit sequences. These bit sequences work as key sources. Rather than extracting the key from the key sources directly, the sender randomly generates a bit sequence as a key and hides it in a promise. This is created from a polynomial constructed on the sender's key source and key. The receiver recovers the key by reconstructing a polynomial from its key source and the promise. Our analysis shows that the shared key generated by our proposed RSKA scheme has features of high randomness and a high bit rate compared to traditional RSS-based key agreement schemes.