• 한국정밀공학회지
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• 제7권3호
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• pp.75-82
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• 1990

Automatic monitoring of the cutting conditions is one of the most improtant technologies in machining. In this study, the feasibility in applying acoustic emission(AE) signals for the in-process detection of endmill wear and fracture has been investigated by performing experimental test on the NC vertical milling machine with SM45C for specimen. As the results of detecting and analyzing AE signals on various cutting conditions, the followings have confirmed. (1) The RMS value of acoustic emission is related sensitively to the cutting velocity, but is not affected largely by feed rate. (2) The burst type AE signals of high level have been observed when removing chips distorderly and discontinuously. (3) When the RMS value grows up rapidly due to the increase of wear the endmill are generally broken or fractured, but when the endmills fracture at the conditions of smooth chip-flow or built-up-edge(BUE) occurred frequently, the rapid change of the RMS arenot found. And it is expected that this technigue will be quite useful for in-process sensing of tool wear and fracture.

• Advances in aircraft and spacecraft science
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• 제7권1호
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• pp.1-17
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• 2020

In this paper, a new model-based Fault Detection and Diagnosis (FDD) method for an agile supersonic flight vehicle is presented. A nonlinear model, controlled by a classical closed loop controller and proportional navigation guidance in interception scenario, describes the behavior of the vehicle. The proposed FDD method employs the Inertial Navigation System (INS) data and nonlinear dynamic model of the vehicle to inform fins damage to the controller before leading to an undesired performance or mission failure. Broken, burnt, unactuated or not opened control surfaces cause a drastic change in aerodynamic coefficients and consequently in the dynamic model. Therefore, in addition to the changes in the control forces and moments, system dynamics will change too, leading to the failure detection process being encountered with difficulty. To this purpose, an equivalent aerodynamic model is proposed to express the dynamics of the vehicle, and the health of each fin is monitored by the value of a parameter which is estimated using an adaptive robust filter. The proposed method detects and isolates fins damages in a few seconds with good accuracy.

• 한국안전학회지
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• 제15권2호
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• pp.1-7
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• 2000

This paper presents the approach involving fault detection and diagnosis of gears using pattern recognition and Wavelet transform. It describes result of the comparison between KDI (Kullback Discrimination Information) with the nearest neighbor classification rule as one of pattern recognition methods and Wavelet transform to know a way to detect and diagnosis of gear damages experimentally. To model the damages 1) Normal (no defect), 2) one tooth is worn out, 3) All teeth faces are worn out 4) One tooth is broken. The vibration sensor was attached on the bearing housing. This produced the total time history data that is 20 pieces of each condition. We chose the standard data and measure distance between standard and tested data. In Wavelet transform analysis method, the time series data of magnitude in specified frequency (rotary and mesh frequency) were earned. As a result, the monitoring system using Wavelet transform method and KDI with nearest neighbor classification rule successfully detected and classified the damages from the experimental data.

• 한국소음진동공학회논문집
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• 제16권4호
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• pp.404-413
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• 2006

Induction motors are the workhorse of our industry because of their versatility and robustness. The diagnosis of mechanical load and power transmission system failures is usually carried out through mechanical signals such as vibration signatures, acoustic emissions, motor speed envelope. The motor faults including mechanical rotor imbalances, broken rotor bar, bearing failure and eccentricities problems are reflected in electric, electromagnetic and mechanical quantities. The recent research has been directed toward electrical monitoring of the motor with emphasis on inspecting the stator current of the motor, The stator current spectrum has been widely used for fault detection in induction motor systems. The motor current signature analysis is the useful technique to assess machine electrical condition. This paper describes the motor condition detected by the current signatures Paralleled with vibration signatures analysis of induction motors with the roller bearing and the journal bearing type for large vertical pumps in power plant as examples to discuss for motor fault detection and diagnosis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권8호
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• pp.2209-2221
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• 2023

As the supply of electric vehicles increases, research on wireless charging methods for convenience has been increasing. Because the electric vehicle wireless transmission device is installed on the ground and the electric vehicle battery is installed on the floor of the vehicle, the transmission and reception antennas are approximately 15-30 cm away, and thus strong magnetic fields are exposed during wireless charging. When a metallic foreign object is placed in the magnetic field area, an eddy current is induced to the metallic foreign object, and heat is generated, creating danger of fire and burns. Therefore, this study proposes a method to detect metallic foreign objects in the magnetic field area of a wireless electric vehicle charging system. An active detection-only coil array was used, and an LC resonance circuit was constructed for the frequency of the supply power signal. When a metallic foreign object is inserted into the charging zone, the characteristics of the resonance circuit are broken, and the magnitude and phase of the voltage signal at both ends of the capacitor are changed. It was confirmed that the proposed method has about 1.5 times more change than the method of comparing the voltage magnitude at one node.

• 전기학회논문지
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• 제62권4호
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• pp.584-590
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• 2013

Depending on the operating characteristics, track circuit is installed for the purpose of control directly or indirectly of the signal device, point switch machine and other security device. These are mainly used for train detection, transmission of information, broken train detection and transmission of return current. Especially, the return current is related to signal system, power system and catenary line, and track circuit systems. It is one of the most important component shall be dealt for the safety of track side staff and for the protection of railway-related electrical system according to electrification. Therefore, an accurate analysis of the return current is needed to prevent the return current unbalance and the system induced disorder and failure due to an over current condition. Also, if the malfunction occurred by the return current harmonics, it can cause problems including train operation interruption. In this paper, we presented measurement and analysis method at return current and it's harmonics by train operation. By the test criteria, we evaluated for safety. Hereafter, it is expected to contribute to the field associated with it.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.617-622
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• 2002

This paper presents that the Wavelet Transform can be used to detect the various local defects in a gearbos. Two types of defects which are broken tooth and localized wear, are experimented and the signals are collected by accerometer and analyzed. Because of the complecity of the signals acquired from sensor, it is needed to identify the interesting signal. The natural frequencies of shafts and the gear mesh frequency(GMF) is calculated theretically. DWT, CWT and the aplication are used to extract a gear-localized defect feature from the vibration signal of the gearbox with the defective gear. The results shows the transform is more effective to detect the failures than the Fourier Transform.

• 한국통신학회논문지
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• 제33권8B호
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• pp.689-698
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• 2008

The performance of a TCP protocol on MANETs has been studied in a numerous researches. One of the significant reasons of TCP performance degradation on MANETs is inability to distinguish between packet losses due to congestion from those caused by nodes mobility and as consequence broken routes. This paper presents the Cluster-Label-based Routing (CLR) protocol that is an attempt to compensate source of TCP problems on MANETs - multi-hop mobile environment. By utilizing Cluster-Label-based mechanism for Backbone, the CLR is able to concentrate on detection and compensation of movement of a destination node. The proposed protocol provides better goodput and delay performance than standardized protocols especially in cases of large network size and/or high mobility rate.

• Journal of Electrical Engineering and information Science
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• 제3권1호
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• pp.45-50
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• 1998

This paper deals with some characteristics of a nondestructive eddy current detector to measure OPGW(Composite overhead ground wire with optical fiber) corrosion. This detector is designed to automatically run on OPGW and to continuously inspect the corrosion of the line. The impedance of the eddy current coil changing by any corrosion phenomenon of OPGW is analyzed. Several performances of the detector are described and experimental procedures and test results are also given. As a result, it is shown that the implemented detector can be measured some quantitative data for crack, broken wires or severe deteriorations in OPGW. This nondestructive test method would be applied to improve the reliability and efficiency of transmission line in service.

• 한국표면공학회지
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• 제29권6호
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• pp.691-694
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• 1996

Two models of scratch testers developed recently are applied to the adhesion measurement of thin coatings. In both models the critical load is determined from the frictional irregularity when coated surface is broken in the scratching process. One model is effective for coatings thicker than 1m and the other for thin coatings down to $0.1\mu\textrm{m}$. The mechanism and the measurement principle of these testers are described. High sensitivity and good reproducibility of the measurement are attained primarily by the employment of new detection devices. These testers are even more useful for the quality control and the inspection of commercial products of coatings because only a small area of specimen is required for the test.