• 전기학회논문지
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• 제65권1호
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• pp.179-193
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• 2016

In power quality monitoring, voltage fluctuation is one of the power quality problems, which cause light flickers. To determine the flicker severity, the flicker meter concept was developed in an IEC 61000-4-15 standard. Generally, voltage fluctuations are described as an amplitude modulation(AM). The flicker meter of IEC 61000-4-15 as an international standard for flicker measurement recommends square demodulation method to detect flicker signals from voltage fluctuation signals. This paper suggests a new effective method using filter bank to detect and estimate flicker signals, which do not need square demodulation. For the accurate detection of flicker signals, the filter bank is designed with a full consideration of the spectrum characteristics of voltage fluctuation signals described as AM. The frequency and magnitude of the detected flicker signals are estimated using recursive method. Computer simulations were performed on synthesized signals to prove validity of the proposed method.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.151-154
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• 2002

The objective of this study is to find the change of signal characteristics of matrix cracks due to the different specimen shapes. As the concept of the smart structure, monitoring of acoustic emission (AE) can be applied to inspect the fracture of the structures in operating condition using built-in sensors. To understand the characteristics of matrix crack signals, we performed tensile tests by changing the thickness and width of the specimens. This paper describes the implementation of time-frequency analysis such as wavelet transform (WT) fur the quantitative evaluation of fracture signals. The experimental result shows the distinctive signal features in frequency domain due to the different specimen shapes.

• 대한기계학회논문집
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• 제19권8호
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• pp.1787-1798
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• 1995

Monitoring and diagnosis of the operating machine mean evaluating the condition of a machine such as the detection of the defects and the prediction of the time to failure in the machine elements, while it is running. In this study, a technique of automatic diagnosis using probability concept is studied and the analyses of the pattern comparison are introduced. An expert system, which is able to analyze the automatic identification of the multiple defects in the ball bearings, is also developed. Finally, to confirm the effectiveness of the programmed algorithms, some tests were made with specimens of the ball bearings involving the multiple defects. The proposed system reasonably predicts the defects.

• 한국전자거래학회:학술대회논문집
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• 한국전자거래학회 2005년도 e-Biz World Conference 2005
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• pp.62-67
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• 2005

In traditional approach, enterprise-wide consistent security policy enforcement for applications is very difficult task. Therefore, industry is now moving towards new unified enterprise application security concept that consist of centralized authentication and authorization mechanism. The eXtensible Access Control Markup Language (XACML); an XML-based standard defined by OASIS, is most suitable choice which can support centralized, role based, context aware access control mechanism. It is designed to provide universal standard for writing authorization policies and access control request/response language for managing access to the resources. This paper includes a brief overview on XACML and discusses its benefits, limitations and a data flow process. We propose a new generic access control architecture that supports enterprise wide centralized application level access control mechanism using XACML. The other benefits which can be achieved through this architecture are, reduce adnministration cost and complexity, support of heterogeneous computing platforms, centralized monitoring system, automatic fail over, scalability and availability, open standard based solution and secure communication.

• 대한임베디드공학회논문지
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• 제11권5호
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• pp.287-298
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• 2016

This paper proposes an effective smart plug system capable of monitoring power, cutting off standby power and overload current. The key design concept is focused on measurement accuracy, self power consumption and controlling via smart phone application. The system is composed of several plugs and a hub, and adopts a star-topology-styled TDMA wireless protocol for communication between plug and hub. The test result shows that the implemented smart plug system meets K10026 regulation and is worth in electrical safety, energy saving, easy living.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1398-1402
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• 2007

In a high speed train, OBCS(On-Board Computer System) is a up-to-date computer control system that provide controlling, monitoring, maintaining and reparing of the important device, supporting a driver, status of a train, service maintenance, managing the remote control mode, driving order & control, control of a electrical or pneumatic circuit and a passenger service. In general, OBCS is located in each car but in a power car, both main and auxiliary computers are used. These avoid a network collision and maintain the independence of condition and failure records with the information of line number, train number and car number. This paper is intended to provide the information about the identification coding method of domestic and foreign OBCS, for the new high speed train (KTX-II).

• 한국정밀공학회지
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• 제6권4호
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• pp.61-70
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• 1989

A new analytical method is proposed to monitor the chip form of cutting forces applying the techinque of signal process. Cutting experiments are carried out under various cutting conditons and cutting forces are measured in-processing through Tool Dynamometer. In this report, auto-correlation functions, frequency characteristics of dynamic force, high frequency distribution and Peak/RMS values are calculated from the measured cutting forces, and the concept of method is also discussed. The experimental results show that six types of the form of chips are possible to classify from the signal of cutting forces not related to cutting conditions.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.181-184
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• 2008

The quality of orthoimages mainly depends on the elevation information and exterior orientation (EO) parameters. Since LiDAR data directly provides the elevation information over the earth's surface including buildings and trees, the concept of true orthorectification has been rapidly developed and implemented. If a LiDAR-driven digital surface model (DSM) is used for orthorectification, the displacements caused by trees and buildings are effectively removed when compared with the conventional orthoimages processed with a digital elevation model (DEM). This study sequentially utilized LiDAR data to generate orthorectified digital aerial images. Experimental orthoimages were produced using DTM and DSM. For the preparation of orthorectification, EO components, one of the inputs for orthorectification, were adjusted with the ground control points (GCPs) collected from the LiDAR point data, and the ground points were extracted by a filtering method. The orthoimage generated by DSM corresponded more closely to non-ground LiDAR points than the orthoimage produced by DTM.

• 전기학회논문지P
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• 제60권1호
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• pp.32-36
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• 2011

In this study, authors have proposed the autonomous state estimation which has been composed with IEC61850, GPS time synchronization and objective model design concept. The proposed method is able to supervise/correct measurement and communication error from SCADA. The major advantages of the proposed autonomous state estimation are that it is possible to evaluate integrity of data measured and transferred from SCADA, to reduce human intervention and to expense national-size applications such as EMS (Energy Management System), WAMS (Wide Area Monitoring System) or WAPS (Wide Area Protection System). This study addresses the issues related to the operation of the smart grid and proposes a new automated approach to achieve this goal. Through applying the proposed system to IEEE 14-bus test electric system, we prove the possibility of the proposed idea.

• Structural Monitoring and Maintenance
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• 제4권3호
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• pp.269-299
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• 2017

This paper presents a Level III damage evaluation methodology, which simultaneously, identifies the location, the extent, and the severity of stiffness damage in deep beams. Deep beams are structural elements with relatively high aspect (depth-to-length) ratios whose response are no longer based on the simplified Euler-Bernoulli theory. The proposed methodology is developed on the bases of the force-displacement relations of the Timoshenko beam theory and the concept of invariant stress resultants, which states that the net internal force existing at any cross-section of the beam is not affected by the inflicted damage, provided that the external loadings in the undamaged and damaged beams are identical. Irrespective of the aspect ratios, local changes in both the flexural and the shear stiffnesses of beam-type structures may be detected using the approach presented in this paper.