• 비파괴검사학회지
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• 제30권2호
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• pp.121-125
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• 2010

회전기기의 결함진단에 있어서 기존의 방법과 달리 적외선열화상기술은 회전기기의 결함진단에 대해 비접촉, 비파괴 및 상태감시 모니터링을 할 수 있다. 본 논문에서는 적외선열화상 상태진단을 기반으로 하는 회전기기의 결함진단에 대한 새로운 접근법을 제안한다. 따라서 회전기에서 가장 많이 사용되어지는 볼베어링을 이용하여 실험을 수행하였고, 진동 스펙트럼 분석과 적외선열화상을 이용하여 실시간 모니터링을 수행하였다. 적외선열화상기법을 이용하여 볼베어링의 윤활 불균형에 따른 온도 특성을 확인할 수 있었다. 이러한 실험을 통한 결과를 분석 검토하여 향후 산업전반의 회전기기의 상태감시연구에 있어서 다양한 분야에 사용되어 질 것으로 예상된다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.307-312
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• 2003

The average frictional coefficient was used generally to analyze the moving state of lubricated machine. But It is difficult of getting the correct friction coefficient because the average frictional coefficient of it is progressed always unstably with a large amplitute on driving condition. If correct analysis of frictional coefficient on working condition for lubricated machine can be possible, it can be effect on diagnosis of lubricated machine. The purpose of this study is carried out to get the working condition with a minimum frictional coefficient of transmission gear materials using statistical techniques.

• 전기학회논문지P
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• 제58권2호
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• pp.231-234
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• 2009

Recently, to the development of a highly information-oriented society to a large increase in dependence on power, Accordingly, it is need that active development and spread of preservation technology on accident prevention in operation electrical equipment. However, to lack of the use on maintenance technology of power equipment and to increase of power usage is growing deterioration of power equipment, this is a cause on casualties, property damage and the occurrence of disasters is a growing. GIS equipments which are operated from domestic except the equipment which manages from the big business are depend on a most visual inspection, and do inspection method or measuring instrument etc. a condition which is not supplied widely. Currently, many to measure instrument used in domestic is very expensive or foreign, it will be able to substitute this, the development necessity of the diagnosis technique and the measuring instrument is demanded.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.856-860
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• 2000

Liquid ejector is widely used for power plant water pump, marine pump and transportation of solid materials. It has high working confidence and simple configuration. However, It is not easy to know performance degradation of ejectors in field. When the geometry of ejector is complicate, the diagnosis of faults is required more skillful method without disassemble. This paper gives numerical method to predict cause of $45^{\circ}$ slurry suction ejector performance degradation.

• 한국전기전자재료학회논문지
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• 제24권3호
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• pp.208-214
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• 2011

In this thesis, the partial discharge according to applied voltage and variations of cross-sectional area and length of the conductor related to general condition for using cable was measured in order to study degradation diagnosis for 2-Core cable of the PVC insulator used in industrial fields for other safety installations. Also the thermal degradation conditions under various installation circumstances of cables were studied by assuming degradation conditions with each different degradation rate (50%, 67%, 100%) such as variation in degradated temperature, thermal exposure time, normal state, partially degradated state and overall degradated state for thermal degradation diagnosis. The quantity of electric discharge (V-Q) according to applied voltage was measured for measurement of inception voltage and extinction voltage. The quantity of electric discharge and the number of electric discharge (Q-N) were measured with applied voltage kept constantly. In addition, pictures were taken using SEM (scanning electron microscope) to compare the surface of external insulator to degradated state of internal insulator according to thermal degradation temperature and also compare the surface of external insulator to degradated surface state of internal insulator according exposure time of cables to thermal stress.

• 소음진동
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• 제11권1호
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• pp.125-131
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• 2001

There is a clearance between the parts of a machine due to design tolerance, manufacturing error, wear, looseness, or misalignment. If the clearance is large, the vibration and noise of the machine is generally large. Therefore, the analysis on the nitration and noise of a machine can tell the clearance of the machine, which reveals the condition of the machine, i.e., the existence of faults and the safety of the machine. The investigation of this kind of research should be on the basis of experimental results. A link mechanism with a clearance at a joint between the coupler and locker is made for the investigation of the condition monitoring of a machine due to clearance. The vibration and sound are measured from the link driving system during the operation. The signals are clarified using line enhancement technique. The noise removed signals are used to develop the dynamic model of the system for a model based fault diagnosis. Also this study showed that the clarified signals can be used for the calculation of the joint forces between the coupler and rocker and for the correlation between the vibration and sound levels and the clearance sizes.

• Imaging Science in Dentistry
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• 제41권2호
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• pp.43-51
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• 2011

Purpose : The purpose of this article is to review the current status of dental caries diagnosis using cone beam computed tomography (CBCT). Materials and Methods : An online PubMed search was performed to identify studies on caries research using CBCT. Results : Despite its usefulness, there were inherent limitations in the detection of caries lesions through conventional radiograph mainly due to the two-dimensional (2D) representation of caries lesions. Several efforts were made to investigate the three-dimensional (3D) image of lesion, only to gain little popularity. Recently, CBCT was introduced and has been used for diagnosis of caries in several reports. Some of them maintained the superiority of CBCT systems, however it is still under controversies. Conclusion : The CBCT systems are promising, however they should not be considered as a primary choice of caries diagnosis in everyday practice yet. Further studies under more standardized condition should be performed in the near future.

• 전기학회논문지P
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• 제58권4호
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• pp.476-482
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• 2009

This paper describes the development of capacitive sensor for the diagnosis of liquid dielectrics, which is widely used as the electrical insulating oil of transformer, circuit breaker, cable and etc. To survey the dielectric properties of the virgin and aged electrical insulating oils, we utilized the highly precise measuring system, using the principle of cross capacitance. The measured properties were used to determine the design factors of the sensor. Then the factors were optimized with the help of computational analysis. To evaluate diagnosis by the sensor, we performed accelerated thermal aging test about electrical insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor. And to evaluate the hysteresis characteristics with the change of temperature, we constructed a testing system, which was composed with vacuum drying oven, oil chamber and measuring instruments, such as LCR meter, MUX and so forth. Through the results of this investigation, we confirmed the superior characteristics of the newly developed sensor.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제7권2호
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• pp.102-108
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• 2007

The issues of preventive and condition-based maintenance, online monitoring, system fault detection, diagnosis, and prognosis are of increasing importance. This study introduces a technique to detect and identify faults in induction motors. Stator currents were measured and stored by time domain. The time domain is not suitable for representing current signals, so wavelet transform is used to convert the signal; onto frequency domain. The raw signals can not show the significant feature, therefore difference values are applied. The difference values were transformed by wavelet transform and the features are extracted from the transformed signals. The dynamic time warping method was used to identify the four fault types. This study describes the results of detecting fault using wavelet analysis.

• Journal of Advanced Marine Engineering and Technology
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• 제31권1호
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• pp.95-102
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• 2007

The issues of preventive and condition-based maintenance, online monitoring, system fault detection, diagnosis and prognosis are of increasing importance. This study introduces a technique to detect and identify faults in induction motors. Stator currents were measured and stored by time domain. The time domain is not suitable for representing current signals, so wavelet transform is used to convert the signals onto frequency domain. The raw signals can not show the significant feature, therefore difference values between the signal of the health conditions and that of the fault conditions are applied. The difference values were transformed by wavelet transform and the features are extracted from the transformed signals. The dynamic time warping method was used to identify the fault type. This study describes the results of detecting fault using wavelet analysis.