• Current Optics and Photonics
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• 제7권1호
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• pp.47-53
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• 2023

We propose a centralized passive-optical-network monitoring scheme using the resonance-spectrum properties of a Fabry-Perot cavity based on fiber Bragg gratings. Each cavity consists of two identical uniform fiber Bragg gratings and a varying cavity length or grating length, which can produce a unique single-mode resonance spectrum for the drop-fiber link. The output spectral properties of each cavity can be easily adjusted by the cavity length or the grating length. The resonance spectrum for each cavity is calculated by the transfer-matrix method. To obtain the peak wavelength of the resonance spectrum more accurately, the effective cavity length is introduced. Each drop fiber with a specific resonance spectrum distinguishes between the peak wavelength or linewidth. We also investigate parameters such as reflectivity and bandwidth, which determine the basic performance of the fiber Bragg grating used, and thus the output-spectrum properties of the Fabry-Perot cavity. The feasibility of the proposed scheme is verified using the Optisystem software for a simplified 1 × 8 passive optical network. The proposed scheme provides a simple, effective solution for passive-optical-network monitoring, especially for a high-density network with small end-user distance difference.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.211-215
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• 1997

Localized communication networks for office automation, security monitoring, environmental management of buildings, computer communications, and other applications enjoy every increasing demand. This paper proposes a direct sequence spread spectrum communication system for use in power line data transmission. Advantages of power distribution circuits include reasonably universal coverage and easy access vis a standard wall plug. Disadvantages include limited communication bandwidth, relatively high noise levels, and varying levels of impedance, noise, and attenuation. Spread spectrum signalling provides immunity to narrow-band signal impairments and multiplexing capability. Our prototype power line communication module supports completely physical and data link layers based on the international standard ISO 10368 for reliable high-speed power line communication system. Moreover it provides useful functions to compose a plant monitoring and control system. All the circuits of the communication module are included in one compact circuit. Thus a functional communication system for the power line plant monitoring and control is implemented.

• International Journal of Internet, Broadcasting and Communication
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• 제11권2호
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• pp.27-30
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• 2019

Factory monitoring systems are gaining importance in wide areas of industry. Especially, there have been many efforts in implementation of vibration measurement and analysis for monitoring the status of rotating machines. In this paper, a digital signal processor (DSP) based monitoring system dedicated to the vibration monitoring and analysis on rotating machines is discussed. Vibration signals are acquired and processed for the continuous monitoring of the machine status. Time domain signals and fast Fourier transform (FFT) are used for vibration analysis. All of the signal processing procedures are done in the DSP to reduce the production and maintenance cost. The developed system could also provide remote and mobile monitoring capabilities to operator via internet connection. This paper describes the overview of the functional blocks of the implemented system. Test results based on signals from small-size single phase motors are discussed for monitoring and defect diagnosis of the machine status.

• 한국통신학회논문지
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• 제33권8A호
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• pp.846-851
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• 2008

통신 산업의 급격한 발달로 통신서비스의 종류가 다양해지고 전파사용이 증가함에 따라 이전의 전파감시 시스템을 대체할 효율적이고, 지능화된 전파감시 시스템의 개발이 필요하게 되었다. 차세대 지능형 전파감시 시스템은 ITU-R, 무선설비규칙 및 전파법을 근간으로 하여 V/UHF대역의 On-Air 상의 아날로그 및 디지털신호에 대해 스펙트럼분석을 통한 채널전력과 주파수편차 및 편이, 점유대역폭(99% 또는 x-dB)을 정확하고 효율적으로 전파측정 할 수 있도록 개발되었다, 시스템의 주요 기능은 전파품질측정, 불요파(스퓨리어스, 고조파)측정, 고속스펙트럼측정, 주파수이용효율조사, 불법전파탐사, 운용감시이고, 본 논문에서는 차세대 지능형 전파감시 시스템의 주요기능 중 전파품질측정, 고속스펙트럼측정에 대해 기술한다.

• 정보화정책
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• 제17권3호
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• pp.57-73
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• 2010

우리나라 정부는 전파이용질서를 유지 보호하고 주파수를 제때 알맞은 곳에 공급할 수 있는 전파감시 사업으로 전파의 효율적 이용을 촉진하고자 한다. 이에 본 연구에서는 우리나라 유비쿼터스 전파감시 사업의 경제적 편익 분석을 통해 유비쿼터스 전파감시 사업의 발전을 위한 전략 및 정책 방향을 도출하고자 한다. 이에 본 연구는 CVM을 활용하여 엄밀한 경제이론에 근거하여 유비쿼터스 전파감시 사업의 편익을 정량적으로 규명하고자 하였다. 분석 결과 유비쿼터스 전파감시 사업을 위한 연간 가구당 평균 WTP가 1,268원으로 나타났다. 이를 7대 대도시 전체 가구로 환산한 유비쿼터스 전파감시 사업의 경제적 편익은 연간 79억원에 이르는 것으로 나타났다. 본 연구의 결과는 향후 유비쿼터스 전파감시 사업 정책 수립 및 투자정책 등에 정량적인 자료로 활용될 수 있다.

• Wind and Structures
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• 제22권2호
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• pp.235-252
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• 2016

A wind velocity power spectrum (WVPS) with high fidelity is extremely important for accurate prediction of structural buffeting response. WVPS heavily depends on the geographical locations, local terrains and topographies. Hence, field measurement of wind characteristics may be the unique way to obtain the accurate WVPS for a specific region. In this paper, a systematic analysis and discussions of existing WVPSs were performed. Six recorded strong wind data from the structural health monitoring systems (SHMS) of Runyang Suspension Bridge (RSB) and Sutong Cable-stayed Bridge (SCB) in Jiangsu Province of China were selected for analysis. The measured and pre-processed wind velocity data was first transformed from time domain to frequency domain to obtain the measured spectrum. The spectrum for each strong wind was then fitted using the nonlinear least square method and compared with both the fitted spectrum from statistical analysis and the recommended spectrum in specifications. The modified Kaimal spectrum was proved to be the "best" choice for the coastal area of East Jiangsu Province. Finally, a suitable WVPS formula fit for the coastal area of East Jiangsu Province was presented based on the modified Kaimal spectrum. Results in this study provide a more accurate and reliable WVPS for wind-resistant design of engineering structures in the coastal area of East Jiangsu Province.

• Structural Monitoring and Maintenance
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• 제7권1호
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• pp.13-25
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• 2020

One of the most important aspects in structural health monitoring is the detection of fatigue damage. Structural components such as heavy-duty bolts work under high dynamic loads, and thus are prone to accumulate fatigue damage and cracks may originate. Those heavy-duty bolts are used, for example, in wind power generation and mining equipment. Therefore, the investigation of new and more effective monitoring technologies attracts a great interest. In this study the acoustic emission (AE) technology was employed to detect incipient damage during fatigue testing of a M36 bolt. Initial results showed that the AE signals have a high level of background noise due to how the load is applied by the fatigue testing machine. Thus, an advanced signal processing method in the time-frequency domain, the Hilbert-Huang Spectrum (HHS), was applied to reveal AE components buried in background noise in form of high-frequency peaks that can be associated with damage progression. Accordingly, the main contribution of the present study is providing insights regarding the detection of incipient damage during fatigue testing using AE signals and providing recommendations for further research.

• 한국정보통신학회논문지
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• 제6권6호
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• pp.873-878
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• 2002

고정자 전류 스펙트럼(stator current spectrum)은 유도전동기의 고장 검출에 널리 사용되어왔다. 본 논문에서는 고정자 전류 스펙트럼 중에서 회전자 고장에 의해서 큰 영향을 받는 주파수 성분들로 특징벡터(feature vector)를 구성하고, 특징벡터와 기준벡터(reference vector)와의 평균 절대치 차이(mean absolute difference)를 구함으로써, 회전자 고장을 검출하는 방법을 제안한다. 제안한 방법에서는 전류 스펙트럼 중에서 추출된 매우 작은 크기(dimension)의 특징 벡터에 대한 평균 절대치 차이를 이용하기 때문에 신경회로망에 의한 고장 검출 알고리즘 둥에 비해서 훨씬 적은 계산량만으로 모터의 고장을 효율적으로 검출할 수 있다

• 제어로봇시스템학회논문지
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• 제8권10호
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• pp.827-832
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• 2002

We propose a prediction method of the pollutant and a synchronous classification of the current state of SOx emission in the power plant. We use the auto-regressive with exogeneous (ARX) model as a predictor of SOx emission and use a radial basis function network (RBFN) as a pattem classifier. The ARX modeling scheme is implemented using recursive least squares (RLS) method to update the model parameters adaptively. The capability of SOx emission monitoring is utilized with the application of the RBFN classifier. Experimental results show that the ARX model can predict the SOx emission concentration well and ARX modeling parameters can be a good feature for the state monitoring. in addition, its validity has been verified through the power spectrum analysis. Consequently, the RBFN classifier in combination with ARX model is shown to be quite adequate for monitoring the state of SOx emission.

• 한국콘텐츠학회논문지
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• 제13권1호
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• pp.48-54
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• 2013

IT융합기술의 발전에 따라 누수탐지를 위한 인프라스트럭처가 구축되면서, 파손된 관로의 위치 및 규모의 파악 기술이 부각되고 있다. 또한 상수도 시설의 누수로 인한 수자원의 고갈 때문에 효율적으로 누수를 탐지할 수 있는 방법이 시급하다. 본 논문에서는 파워스펙트럼 분석을 이용한 누수탐지 모니터링 시뮬레이션을 제안하였다. 제안한 누수탐지 모니터링 시뮬레이션에서 반사파 파형을 측정한다. 수집된 반사파 파형으로부터 변화율을 계산한다. 그리고 고속 퓨리에 변환을 이용한 파워 스펙트럼 분석은 누수의 크기와 반사파 파형의 상관관계를 평가한다. 이를 시뮬레이션의 논리적 타당성과 유효성을 검증하기 위해 실험적인 적용을 시도하고자 한다. 따라서 실시간 누수탐지를 제공하여 효율적인 관리에 대한 만족도와 서비스의 질을 향상시켰다.