• Journal of Power System Engineering
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• v.15 no.4
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• pp.37-41
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• 2011

This paper introduces the special eddy current sensor and its characteristic for bolt hole defect evaluation in gas turbine rotor. In the past, Fluorescent penetration inspection method was used for qualitative defect evaluation in gas turbine rotor bolt hole. This method can defect the bolt hole defect but can not evaluate the defect size. Nowadays, eddy current method is used quantitative defect evaluation due to advanced sensor design technology. And eddy current method is more time and cost saving than the old method. We developed bolt shape eddy current sensor for the rotor bolt hole defect detection and evaluation. The eddy current sensor moves to the bolt hole guided by screw nut and detects the defect on the bolt hole. The bolt hole mock-up and artificial defects were made and used for the signal detection & resolution analysis of eddy current sensor. The results show that signal detection capability is enough to detect 0.2 mm depth defect. And the resolution capability is enough to differentiate 02, 0.5, 1.0 and 2.0 mm depth defect.

• Proceedings of the Safety Management and Science Conference
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• 2010.11a
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• pp.551-557
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• 2010

The research proposes the hypergeometric, binomial and Poisson yield models for defective and defect. The paper also presents the hypothesis test, confidence interval and control charts for DPU(Defect Per Unit) and DPO(Defect Per Opportunity). Especially the study considers the analysis of compound Poisson yield models using various DOU density distributions.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.05a
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• pp.151-155
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• 2002

Memory의 공정기간은 2∼3개월 정도, 공정은 수백가지에 이를 정도로 많기에 defect은 존재할 수밖에 없다. 많은 defect이 있다면 어쩔 수 없겠지만 적은 defect이 발생한 경우에는 해당 die를 reject시키는 것보다는 repair해서 사용하는 것이 memory생산 업체 입장에서는 보다 효율적이고 원가 절감 차원에서 필수적이다. 이와 같은 이유로 laser repair라는 공정이 필요하고 laser repair공정의 정확한 target을 설정하기 위해 redundancy analysis가 필요하게 되었다. 지금까지 redundancy analysis는 장비 개발 업체에서 제공하는 경우가 대부분 이었고 각 장비 제조 업체별로 redundancy analysis algorithm을 개발하여 제공하여왔기에 동일한 defect 유형에 분석하는 redundancy analysis time이 각 장비 업체 별로 다른 경우가 대부분이었다. 이에 본 연구에서는 기존의 redundancy analysis algorithm의 개념에서 벗어나 defect 유형별로 simulation한 후 redundancy analysis를 진행함으로써 redundancy analysis에 소요되는 시간을 절약함으로써 원가 경쟁력 강화를 하고 correlation 개념을 업무에 적용하는데 목적이 있다

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.702-704
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• 2003

In this paper, analysis of bobbin probe signal in steam generator tube with bulge defect on CE system 80 nuclear power plant is represented. The CE system 80 steam generator is adopted in ULJIN-4 nuclear power plant. From Maxwell's equation, the electromagnetic governing equation for eddy current problem is derived and by performing the finite element formulation the 3-dimensional finite element code with brick element is developed. For the ease of the comparison the numerical results with experimental ones, the calculated signals are adjusted by using the ASME standard 100[%] through hole signal. For analysis of the effect of variation of the bulge depth on the impedance signal 0.2[mm] and 0.4[mm] depth of bulge defect signals are calculated and analyzed. As the depth of the bulge defect is increased, the magnitude of the signal is increased, too. But the rate of the increment of the signal is less than that of the depth of defect. From the result of this paper, we can obtained the information of the effect of bulge defect on the impedance signal.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.48-49
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• 2019

The number of disputes over defects after completion of construction work in apartment buildings is increasing every year. In this situation, the prediction of reasonable defect repair costs is very important. In this paper, we are going to collect basic data for predicting defect repair costs through the correlation analysis of the construction period and defect repair cost of apartment houses. For this purpose, first of all, the construction period and defect repair cost of apartment houses were analyzed to analyze the construction period for each type of work, the construction period for each project type, and the construction period for each standard calculation. Next, the correlation between defect repair cost and the independent variables of the candidate was conducted. According to the analysis, the ratio of framing air, the ratio of finishing air, and the number of delay days showed strong correlation.

• Transactions of Materials Processing
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• v.23 no.3
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• pp.159-163
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• 2014

In the current study, the effect of small surface defects in the starting material including roughness, indentations, or scratches, which are perpendicular to the direction of drawing, on the product quality is investigated using the finite element method. An axisymmetric defect is assumed. Such defects are defined by a cylindrical defect area and two tapered regions connecting the defect area to the non-defective area of the material. Various conditions for these initial surface defects are considered, including defect depth, defect slope and defect length. To describe the plastic deformation of the defect in detail during the simulation, local remeshing is applied. Based on the finite element results, defect disappearance maps were generated. It was found that defect disappearance is significantly dependent on the defect depth and the defect length coupled with the defect slope.

• The Journal of Sustainable Design and Educational Environment Research
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• v.16 no.2
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• pp.1-9
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• 2017

Defect dispute in apartment building has become a debating social issue. The system of defect lawsuit and the conciliation process are applicable to solve defect problems in South Korea. Among various defects, painting work defect is a critical issue because it requires large area works and entails a lot of cost. Accordingly, disputes on work procedure and cost calculation are argued oftenly between residents and housing providers. This study reviewed detailed main issues of painting work and propose relevant systems and standards. In this analysis, the main issues are categorized into pre-works, main work, and others. The most recent cases are compared and analyzed for each issue. After the analysis, following conclusions are obtained, (1) In defect lawsuit system, even though surface treatment work in pre-work step is part of main work, it has been separated and regarded as a separate work. (2) Although the main painting work are not significantly different from two systems, it is still necessary to achieve a consensus to close the gap in the methodology of painting area calculation and determining whole painting or partial painting. (3) In addition, unlike the profit rate of general construction works, that of painting work remained the maximum rate and additional charge rate for works carried out in higher place are different among cases. Therefore, it is determined that establishing consistent standards is urgent.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.2
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• pp.10-16
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• 2004

Data mining technique is the exploration and analysis, by automatic or semiautomatic means, of large quantities of data in order to discover meaningful patterns and rules. This paper uses a data mining technique for the prediction of defect types in manufacturing Process. The Purpose of this Paper is to model the recognition of defect type Patterns and Prediction of each defect type before it occurs in manufacturing process. The proposed model consists of data handling, defect type analysis, and defect type prediction stages. The performance measurement shows that it is higher in prediction accuracy than logistic regression model.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.607-612
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• 2008

The groove rolling is a process that transforms the bloom or billet into a shape with circular section through a series of rolling. Inhibition of surface defect generation in groove rolling is a matter of great importance and therefore many research groups proposed a lot of models to find the location of surface defect initiation. In this study, we propose a model for maximum shear stress ratio over equivalent strain to catch the location of surface defect onset. This model is coupled with element removing method and applied to box groove rolling of POSCO No.3 Rod Mill. Results show that proposed model in this study can find the location of surface defect initiation during groove rolling when finite element analysis results is compared with experiments. The proposed criterion has been applied successfully to design roll grooves which inhibit the generation of surface defect.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.177-178
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• 2011

Recently a great deal of people are taking legal action against the housing provider due to the defects of their Apartment house. And most of the housing companies are spending a huge amount of expenses and efforts to keep their brand value. This essay will carry out time series analysis the 20 housing district which are constructed by huge construction companies. This analysis itemised by metropolitan area(Seoul) and others to keep the degree of reliability, and converted future defect maintenance cost into current cost applied by discount rate to figure out suitability of defect maintenance cost. Even though, this essay is not able to represent standard of defect maintenance cost due to the insufficiency of record, while it will be assisted as a referance when long-term record of time series is estabilished.