• 반도체디스플레이기술학회지
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• 제10권2호
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• pp.7-12
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• 2011

In this paper, a laser scattering mechanism are designed to detect micro defects such as dent, scratch, pinhole, etc. Its influential parameters are experimentally selected and scattering patterns of micro defects have been analyzed for silicon wafer in solar cell. As a result of experiments, scattered lights are rather increased in wafer surface with micro defects, in comparison to no micro ones. Scattering parameters are optimally selected for obtaining robust and high quality laser scattering images of micro defects. It is shown that scattered light components are linearly increased according to the increase of micro defect sizes, and the depth of micro-defects give a large influence on optical deflection.

• 한국주거학회논문집
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• 제14권4호
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• pp.11-19
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• 2003

This study intends to predict prospective defects and establish the plan of Preventive Maintenance through research and analysis of defect occurrences and their repair costs in the public equipment of ‘H’ apartment house from 1998 to 2001. According to results of the analysis, more than 90% of defects and their repair costs for 4 years of the building have occurred in heating, hot water and water supply equipments. In case of specific classification in each equipment, more than 60% of defects were found at hot water pipes and heating pipes, and their repair costs covered more than 60% of the total defect costs. After two repairs by ‘Preventive Maintenance’ had been performed in the year 1998, total defects and defects of each equipment each yew have increased in number from 1999 to 2001. But total repair costs and repair costs of each equipment have not increased as time has gone by, because repair costs have relationship with the price of materials and labor, the part of defect and the scale of repair.

• 전기학회논문지
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• 제66권7호
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• pp.1100-1104
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• 2017

A detector-based approach shows the limited performances for the defect inspections such as shallow fine cracks and indistinguishable defects from background. Deep learning technique is widely used for object recognition and it's applications to detect defects have been gradually attempted. Deep learning requires huge scale of learning data, but acquisition of data can be limited in some industrial application. The possibility of applying CNN which is one of the deep learning approaches for surface defect inspection is investigated for industrial parts whose detection difficulty is challenging and learning data is not sufficient. VOV is adopted for pre-processing and to obtain a resonable number of ROIs for a data augmentation. Then CNN method is applied for the classification. Three CNN networks, AlexNet, VGGNet, and mofified VGGNet are compared for experiments of defects detection.

• Journal of Welding and Joining
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• 제18권2호
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• pp.204-204
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• 2000

There are many weld defects such as surface crack, lack of fusion, and incomplete penetration(IP) in the butt joint weld of the existing steel bridges. The crack-like defects may significantly reduce the life of the structure. This paper presents the procedure and the results of the fatigue life assessment of the butt joints with weld defects in the existing steel girder bridge. The butt joint welds with incomplete penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analysis were performed for the fatigue life assessment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joint welds with serious weld defects in the existing steel bridge. (Received October 1, 1999)

• Journal of Welding and Joining
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• 제18권2호
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• pp.77-85
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• 2000

There are many weld defects such as surface crack, lack of fusion, and incomplete penetration (IP) in the butt joint weld of existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue life assessment of the butt joints with weld defects in the existing steel girder bridge. The butt joint welds with incomplete penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analysis were performed for the fatigue life assessment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joint welds with serious weld defects in the existing steel bridge.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1398-1405
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• 2019

We use a molecular dynamics simulation to explore thermal transport in oxide nuclear fuels with point defects. The effect of vacancy and substitutional defects on the thermal conductivity of plutonium dioxide and uranium dioxide is investigated. It is found that the thermal conductivities of these fuels are reduced significantly by the presence of small amount of vacancy defects; 0.1% oxygen vacancy reduces the thermal conductivity of plutonium dioxide by more than 10%. The missing of larger atoms has a more detrimental impact on the thermal conductivity of actinide oxides. In uranium dioxide, for example, 0.1% uranium vacancies decrease the thermal conductivity by 24.6% while the same concentration of oxygen vacancies decreases the thermal conductivity by 19.4%. However, uranium substitution has a minimal effect on the thermal conductivity; 1.0% uranium substitution decreases the thermal conductivity of plutonium dioxide only by 1.5%.

• Journal of information and communication convergence engineering
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• 제21권3호
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• pp.233-238
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• 2023

This study presents a method for identifying partial discharge defects in an eco-friendly gas insulated system using a backpropagation algorithm. Four partial discharge (PD) electrode systems, namely, a free-moving particle, protrusion on the conductor, protrusion on the enclosure, and voids, were designed to simulate PD defects that can occur during the operation of eco-friendly gas-insulated switchgear. The PD signals were measured using an ultrahigh-frequency sensor as a nonconventional method based on IEC 62478. To identify the types of PD defects, the PD parameters of single PD pulses in the time and frequency domains and the phase-resolved partial discharge patterns were extracted, and a back-propagation algorithm in the artificial neural network was designed using a virtual instrument based on LabVIEW. The backpropagation algorithm proposed in this paper has an accuracy rate of over 90% for identifying the types of PD defects, and the result is expected to be used as a reference database for asset management and maintenance work for eco-friendly gas-insulated power equipment.

• Applied Microscopy
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• 제50권
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• pp.27.1-27.6
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• 2020

Transition metal dichalcogenides (TMD), which is composed of a transition metal atom and chalcogen ion atoms, usually form vacancies based on the knock-on threshold of each atom. In particular, when electron beam is irradiated on a monolayer TMD such as MoS₂ and WS₂, S vacancies are formed preferentially, and they are aligned linearly to constitute line defects. And then, a hole is formed at the point where the successively formed line defects collide, and metal clusters are also formed at the edge of the hole. This study reports a process in which the line defects formed in a monolayer WS₂ sheet expends into holes. Here, the process in which the W cluster, which always occurs at the edge of the formed hole, goes through a uniform intermediate phase is explained based on the line defects and the formation behavior of the hole. Further investigation confirms the atomic structure of the intermediate phase using annular dark field scanning transition electron microscopy (ADF-STEM) and image simulation.

• 한국정밀공학회지
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• 제13권3호
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• pp.63-69
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• 1996

Recently, vibrational signal processing as a tool of machinery diagnosis has been actively studying. In this study, a new scheme for detection and diagnosis of localized defects in ball bearings, using unwrapped phase spectrum of FFT is described. The characteristic phase spectra for such defects shows linearly varying patterns due to the repetitive impact signals generated by localized defects, i.e., one linear line for single defect and various linearly changing shape according to angle between the two defect located points. The effectiveness of this method is confirmed by computer simulation and experiments on bearing with single or double defects at different locations.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.56-57
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• 2021

Apartments, an intensive residential type, exist and are supplied in large quantities regardless of the size of the city. The value of an apartment is affected not only by the surrounding infrastructure, but also in terms of maintenance. Defects that occur in apartments come in various forms, and mainly poor finishing accounts for 60% of the defects. Among them, tile defects accounted for a large proportion and were found to be caused by several factors. This paper analyzed the influence of each factor considering the coefficient of thermal expansion affecting tile defects according to the domestic seasonal climate.