• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.27-28
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• 2006

This study performs to investigate deformation of wall thinning pipe and to find out the position of the internal thinning defect by shearography. Shearography is one of optical methods those have applied to nondestructive testing (NDT) and the strain/stress analysis. This technique has the merit of the directly measuring the first derivative of displacement, sensitivity of which can be adjusted by the handling of optical component in interferometer. In this paper, we tested carbon steel pipe locally wall thinned and loaded internal pressure and developed the nondestructive out-of-plane deformation analysis technique fur internal thinning defect of elbow by shearography. From the results, it was confirmed that this technique is proper to the practical application on the pipe line system with internal defect.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.3
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• pp.256-261
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• 2013

In the steel manufacturing area, researches for defect inspection receive a big attention for quality control. This paper proposes an algorithm to detect a scratch defect on steel billets. This algorithm takes ROIs (Regions of Interest), and extracts 11 features which represent properties of defect on a ROI. SVM (Support Vector Machine) is used to classify defect and normal ROIs. The algorithm classifies a frame image of a Billet as a defect image if there is one or more defect ROIs. In the experiments, the proposed algorithm had reliable classifying accuracy.

• Journal of Biosystems Engineering
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• v.26 no.2
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• pp.169-176
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• 2001

Defect of apple was depreciated the product value and causes storage disease seriously. To detect the defect of ‘Fuji’apple with machine vision system, the optical characteristics of defect should be investigated. In this research, absorbance spectra of defect were acquired by spectrophotometer in the range of visible and NIR region(400∼1,100nm) and L*a*b* color values were also acquired by colorimeter. NIR machine vision system was constructed with B&W camera, frame grabber, 16 tungsten-halogen lamps, variable focal length lens and NIR bandpass filter which was mounted to lens outward. Average gray values of defect at 15 NIR wavelength were acquired and the significant NIR wavelength was selected by comparing Mahalanobis distance between sound and defective apple. As the result of Mahalanobis distance analysis, the significant wavelength to discriminate the defectives in ‘Fuji’apple were found to be 720nm for scab and 970nm for bruise and cuts and 920nm was also effective regardless of defective types.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.180-187
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• 1999

This document illustrates the relationship between the wire rod wrinkle defect and the roll caliber design. The wrinkle defect is caused by the incongruent rolling conditions of the roll caliber design, the roll adjustment, and the extracting temperature. In this document, we restrict the study scope to the roll caliber design's effect on wrinkle defect at the base of real condition of the No.2 Wire Rod mill, POSCO. There has been wrinkle defect problem in the No.2 Wire Rod Mill, POSCO for many years. The engineers of the wire rod mill have been making efforts to solve the problem. As one of the efforts, we take the samples of the wire rod in the each stands of the 2'nd wire rod mill and then analyze the samples. Through the analysis, we find out the problem of the roll caliber design. So, we suggest the roll caliber design method to be more effective to weaken the wrinkle defect.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.185-186
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• 2011

The latest domestic construction sector is receiving economic damage because of defect litigation. The Concrete Crack among them has the largest component in expense of apartment house defect. Also, contradictory suggestion of appraiser is problem. To improve these problem, need objective plan that people concerned can recognize about decision sequence. Therefore, in this study, compared general defect investigation and defect decision of appraiser taking advantage of Data Dictionary analysis method. Also, deduced current problem and amelioration plan.

• Journal of IKEEE
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• v.5 no.2 s.9
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• pp.190-200
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• 2001

This paper is addressed to welding defect feature vector selection and implementation method of welding defect classifier using fuzzy techniques. We compare IAV, zero-crossing number as time domain analysis, power spectrum coefficient as frequency domain, histogram as both domain for welding defect feature selection. We choose histogram as feature vector by graph analysis and find out that maximum frequent occurrence number and section of corresponding signal scale in relative histogram show obvious difference between normal welding and voiding with penetration depth defect. We implement a fuzzy welding defect classifier using these feature vector, test it to verify its effectiveness for 695 welding data frame which consist of 4000 sampled data. As result of test, correct classification rate is 92.96%. Lab experimental results show a effectiveness of fuzzy welding defect classifier using relative histogram for practical Laser welding monitoring system in industry.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.307-316
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• 2004

This study examined the cause of the wrinkle defect which is frequently encountered in wire rod rolling of low carbon steel$(C0.08\~0.13wt.\%)$. Even a small defect on the surface of rolled bars can easily develop into fatal cracks during cold heading process of low carbon steel, and it is therefore necessary to minimize inherent defects on the surface of hot rolled bars. Hot rolling process of low carbon steel was analyzed to identify the cause of the wrinkle defect in conjunction with FE analysis. The integrated analysis revealed that the wrinkle defect initiated in the first stage of rolling, and it was at the billet edge where severe deformation and drastic temperature drop were present. To elucidate the micro-mechanical mechanism of the wrinkle defect, hot compression tests were carried out at various temperatures and strain rates using Gleeble-3800. The surface profile of the each other compressed specimens was compared, and rough surface lines were observed at relatively low temperatures. Those surface defects can develop into wrinkles during multi-pass rolling. To control the wrinkle defect in rolling, it is necessary to design an adequate caliber which can minimize the loss of ductility, and thereby prevent flow localization. To use the result of this study fur other steels, the quantitative measure of the wrinkle defect and flow localization parameter should be proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.807-812
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• 2009

Most structure engineers give the casting components over-estimated factor of safety without any reasonable foundation due to the worries about the unavoidable defects such as shrinkages and porosity in castings; the engineers have little knowledge on the relation between the defect and structural behavior. And the workers in casting field also do not know how to control the defects by manufacturing; they do not know to where the defects move or until how size they reduce the defects. In this study, shrinkage defect was scanned by industrial computerized tomography instrument (CT), and subsequently was modeled to a spheroid primitive for structural analysis. Using these simplified models of shrinkage, we observed the effects of the defect on the results of the structural analysis. A commercial structural analysis code was used to do the analysis works. Considering the conclusions, it is possible to manage the shrinkages effectively in casting process and to design the products with more reliable

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.20-29
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• 2014

This research aims to study the new paradigm of NDE measurement which allows the identification of defect locations and sizes of a certain structure by measuring its surface temperature after applying heat. STS which has a certain defect is applied by the heat of 70000W by a heater. Its difference of STS surface temperature is measured by using Infrared thermography. The estimated result of STS experiment and that of theoretical analysis of Flex-PDE are compared and analyzed to diagnose STS defect. Moreover, this study can save time and money and improve accuracy in contrast to the existing ultrasonic NDE experiment. In addition, the new paradigm of NDT/NDE by reverse-engineering will be valid if the data of thermal analysis and temperature distribution from the specifications of many materials is accumulated and verified.

• Journal of the Korea Institute of Building Construction
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• v.9 no.2
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• pp.93-101
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• 2009

Recently, public interest in housing defects, such as construction errors, occupiers' complaints, faults in production, and so on, is increasing. In addition, the construction requirements of high-rise residential buildings have increased, due to the higher prices of urban areas, especially in metropolitan areas. While previous research has focused on the defects occurring in apartment housing complexes, research has not been carried out on the defects occurring in high-rise residential buildings. In this paper, the defects patterns and characteristics of high-rise residential buildings are examined and analyzed and a defect management plan is then suggested. In order to do this, we collected the defects data of high-rise residential buildings recorded by 2,299 of 2,327 occupants. The defect occurrence rate (DOR) in the residential area is 98.8%. The frequency rate of defect occurrence over the total defect occurrence since building completion is 63.28% during the first year, 24.63% (second year), 6.88% (third year), 2.27% (fourth year), and 2.53% (fifth year). The result of correlation analysis between work types showed that there is a relationship between the built-in furniture and electronics (F&E) and painting works, and the F&E and masonry works, such as marble finishing. We expect that this research will assist in the efforts to decrease the number of defects in high-rise buildings.