• Title, Summary, Keyword: Defect

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Determination of Alpha Defect Center in the Nature Using EPR Spectroscopy

  • Cho, Young-Hwan;Hyun, Sung-Pil;Pilsoo Hahn
    • Journal of the Korean Magnetic Resonance Society
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    • v.5 no.1
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    • pp.13-18
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    • 2001
  • Natural alpha radiation produced a stable defect center to certain minerals. Electron Paramagnetic Resonance(EPR) spectroscopy is a powerful tool f3r quantifying this defect center. EPR method has been applied to trace alpha-radiation effect around the uranium ore deposit. The results show that EPR technique can be used to measure rapidly and nondestructively the defect center produced by natural alpha radiation. In general, a good correlation was achieved between defect center concentration and actinide elements(U, Th). These results imply that the concentration of defect center is dependent on the alpha radiation dose over long time scale.

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Defect Structure, Nonstoichiometry and Nonstoichiometry Relaxation of Complex Oxides

  • Yoo, Han-Ill
    • Journal of the Korean Ceramic Society
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    • v.44 no.12
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    • pp.660-682
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    • 2007
  • An SOFC consists of all ceramic complex oxides each with different electrochemical-property requirements. These requirements, in principle, can be made met to a great extent by controlling or tailoring the defect structure of the oxide. This paper reviews the defect structure, nonstoichiometry as a measure of the total defect concentration, and the defect relaxation kinetics of complex oxides that are currently involved in a variety of growing applications today.

A Study on the Implementation of LCD Defect Inspection Algorithm (LCD 결함검사 알고리즘에 관한 연구)

  • 전유혁;김규태;김은수
    • Proceedings of the IEEK Conference
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    • pp.637-640
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    • 1999
  • In this Paper we show the LCD simulator for defect inspection using image processing algorithm and neural network. The defect inspection algorithm of the LCD consists of preprocessing, feature extraction and defect classification. Preprocess removes noise from LCD image, using morphology operator and neural network is used for the defect classification. Sample images with scratch, pinhole, and spot from real LCD color filter image are used. The proposed algorithms show that defect detected and classified in the ratio of 92.3% and 94.6 respectively.

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Identification of Defect Frequencies in Rolling Element Bearing Using Directional Spectra of Vibration Signals (구름 베어링의 결함 주파수 규명을 위한 방향 스펙트럼의 이용)

  • 박종포;이종원
    • Journal of KSNVE
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    • v.9 no.2
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    • pp.393-400
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    • 1999
  • Defect frequencies of rolling element bearings are experimentally investigated utilizing the two-sided directional spectra of the complex-valued vibration signals measured from the outer ring of defective bearings. The directional spectra make it possible to discern backward and forward defect frequencies. The experimental results show that the directional zoom spectrum is superior to the conventional spectrum in identification of bearing defect frequencies, in particular the inner race defect frequencies.

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Proposing provisions of Standard Repair Method of Painting Work Defect by Lawsuit Case Study

  • Seo, Deokseok
    • 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.

Fast Defect Detection of PCB using Ultrasound Thermography (초음파 서모그라피를 이용한 빠른 PCB 결함 검출)

  • Cho, Jai-Wan;Jung, Hyun-Kyu;Seo, Yong-Chil;Jung, Seung-Ho;Kim, Seung-Ho
    • Proceedings of the KIEE Conference
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    • pp.273-275
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    • 2005
  • Active thermography is being used since several years for remote non-destructive testing. It provides thermal images for remote detection and imaging of damages. Also, it is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation. For energy deposition, it use external heat sources (e.g., halogen lamp or convective heating) or internal heat generation (e.g., microwaves, eddy current, or elastic wave). Among the external heat sources, the ultrasound is generally used for energy deposition because of defect selective heating up. The heat source generating a thermal wave is provided by the defect itself due to the attenuation of amplitude modulated ultrasound. A defect causes locally enhanced losses and consequently selective heating up. Therefore amplitude modulation of the injected ultrasonic wave turns a defect into a thermal wave transmitter whose signal is detected at the surface by thermal infrared camera. This way ultrasound thermography(UT) allows for selective defect detection which enhances the probability of defect detection in the presence of complicated intact structures. In this paper the applicability of UT for fast defect detection is described. Examples are presented showing the detection of defects in PCB material. Measurements were performed on various kinds of typical defects in PCB materials (both Cu metal and non-metal epoxy). The obtained thermal image reveals area of defect in row of thick epoxy material and PCB.

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Automatic Metallic Surface Defect Detection using ShuffleDefectNet

  • Anvar, Avlokulov;Cho, Young Im
    • Journal of the Korea Society of Computer and Information
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    • v.25 no.3
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    • pp.19-26
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    • 2020
  • Steel production requires high-quality surfaces with minimal defects. Therefore, the detection algorithms for the surface defects of steel strip should have good generalization performance. To meet the growing demand for high-quality products, the use of intelligent visual inspection systems is becoming essential in production lines. In this paper, we proposed a ShuffleDefectNet defect detection system based on deep learning. The proposed defect detection system exceeds state-of-the-art performance for defect detection on the Northeastern University (NEU) dataset obtaining a mean average accuracy of 99.75%. We train the best performing detection with different amounts of training data and observe the performance of detection. We notice that accuracy and speed improve significantly when use the overall architecture of ShuffleDefectNet.

Influence of Artificial Defect on Fatigue Limit in Austempered Ductile Iron (오스템퍼링처리한 구상흑연주철의 피로한도에 미치는 인공결함의 영향)

  • Kim, Min-Geon;Kim, Jin-Hak
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.11
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    • pp.1922-1928
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    • 1999
  • Rotary bending fatigue tests were carried out to investigate the influence of artificial defects on fatigue limit in annealed and austempered ductile iron. Obtained main results are as follows : (1) Artificial defect(micro hole type, dia.<0.4 mm) on specimen surface did not bring about a obvious reduction of fatigue limit in austempered ductile iron(ADI) as compared with annealed ductile iron. (2) According to the investigation of $\sqrt{area}_c$ which is the critical defect size to crack initiation at artificial defect, $\sqrt{area}_c$ of ADI is larger than that of annealed ductile iron. This shows that the situation of crack initiation at artificial defect in ADI is more difficult in comparison with annealed ductile iron. (3) One of the reasons for the low rate of crack initiation from artificial defect in ADI is that the resistance of matrix to crack initiation is higher than that of annealed ductile iron. (4) In case that the $\sqrt{area}$ of artificial defect and graphite nodule is the same, the rate of crack initiation from graphite nodule is higher than that from artificial defect. This reason is that the serious ruggedness around graphite nodule is formed by austempering treatment.

Prediction of defect shape change using multiple scale modeling during wire rod rolling process (멀티 스케일 모델을 적용한 선재 공정의 미세결함 형상 변화 예측)

  • Kwak, Eun-Jeong;Kang, Gyeong-Pil;Lee, Kyung-Hoon;Son, Il-Heon
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.169-172
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    • 2009
  • Multiple scale modeling has been applied to predict defect shape change during the wire rod rolling process. The size difference between bloom and defect prevent using usual FEM approaches due to the enormous number of elements required to depict the defect. The newly developed multiple scale model can visualize defect shape changes during the multi stands rolling process. The defect positioned at the top and side of bloom are smoothed out but the one at the middle evolved as folding or remained as crack. This approach can be used for defect control with roll shape design and initial bloom shape.

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Performance evaluation of wavelet and curvelet transforms based-damage detection of defect types in plate structures

  • Hajizadeh, Ali R.;Salajegheh, Javad;Salajegheh, Eysa
    • Structural Engineering and Mechanics
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    • v.60 no.4
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    • pp.667-691
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    • 2016
  • This study focuses on the damage detection of defect types in plate structures based on wavelet transform (WT) and curvelet transform (CT). In particular, for damage detection of structures these transforms have been developed since the last few years. In recent years, the CT approach has been also introduced in an attempt to overcome inherent limitations of traditional multi-scale representations such as wavelets. In this study, the performance of CT is compared with WT in order to demonstrate the capability of WT and CT in detection of defect types in plate structures. To achieve this purpose, the damage detection of defect types through defect shape in rectangular plate is investigated. By using the first mode shape of plate structure and the distribution of the coefficients of the transforms, the damage existence, the defect location and the approximate shape of defect are detected. Moreover, the accuracy and performance generality of the transforms are verified through using experimental modal data of a plate.