• 제목/요약/키워드: Defect

검색결과 8,062건 처리시간 0.031초

Pipeline defect detection with depth identification using PZT array and time-reversal method

  • Yang Xu;Mingzhang Luo;Guofeng Du
    • Smart Structures and Systems
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    • 제32권4호
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    • pp.253-266
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    • 2023
  • The time-reversal method is employed to improve the ability of pipeline defect detection, and a new approach of identifying the pipeline defect depth is proposed in this research. When the L(0,2) mode ultrasonic guided wave excited through a lead zirconate titinate (PZT) transduce array propagates along the pipeline with a defect, it will interact with the defect and be partially converted to flexural F(n, m) modes and longitudinal L(0,1) mode. Using a receiving PZT array attached axisymmetrically around the pipeline, the L(0,2) reflection signal as well as the mode conversion signals at the defect are obtained. An appropriate rectangle window is used to intercept the L(0,2) reflection signal and the mode conversion signals from the obtained direct detection signals. The intercepted signals are time reversed and re-excited in the pipeline again, result in the guided wave energy focusing on the pipeline defect, the L(0,2) reflection and the L(0,1) mode conversion signals being enhanced to a higher level, especially for the small defect in the early crack stage. Besides the L(0,2) reflection signal, the L(0,1) mode conversion signal also contains useful pipeline defect information. It is possible to identify the pipeline defect depth by monitoring the variation trend of L(0,2) and L(0,1) reflection coefficients. The finite element method (FEM) simulation and experiment results are given in the paper, the enhancement of pipeline defect reflection signals by time-reversal method is obvious, and the way to identify pipeline defect depth is demonstrated to be effective.

Automatic Metallic Surface Defect Detection using ShuffleDefectNet

  • Anvar, Avlokulov;Cho, Young Im
    • 한국컴퓨터정보학회논문지
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    • 제25권3호
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    • pp.19-26
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    • 2020
  • 일반적으로 품질 관리는 많은 제조 공정, 특히 주조 또는 용접과 관련된 공정의 기본 구성 요소가 된다. 그러나 사람이 일일이 수동으로 품질 관리 절차를 하는 것은 종종 시간이 걸리고 오류가 발생하기 쉽다. 최근 고품질 제품에 대한 요구를 만족시키기 위해 지능형 육안 검사 시스템의 사용이 생산 라인에서 필수적이 되고 있다. 본 논문에서는 이를 위해 딥 러닝 기반의 ShuffleDefectNet 결함 감지 시스템을 제안하고자 한다. 제안된 결함 검출 시스템은 NEU 데이터 세트의 결함 검출에 대한 여러 최신 성능들보다 높은 평균 정확도 99.75% 정도를 얻는다. 이 논문에서 여러 다른 트레이닝 데이터로부터 최상의 성능을 탐지하고 탐지 성능을 관찰하였다. 그 결과 ShuffleDefectNet의 전체 아키텍처를 사용할 때 정확성과 속도가 크게 향상됨을 알 수 있었다.

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

  • Seo, Deokseok
    • 교육녹색환경연구
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    • 제16권2호
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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.

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

  • 조재완;정현규;서용칠;정승호;김승호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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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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오스템퍼링처리한 구상흑연주철의 피로한도에 미치는 인공결함의 영향 (Influence of Artificial Defect on Fatigue Limit in Austempered Ductile Iron)

  • 김민건;김진학
    • 대한기계학회논문집A
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    • 제23권11호
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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.

딥러닝 알고리즘을 이용한 3D프린팅 골절합용 판의 표면 결함 탐지 모델에 관한 연구 (A Study on Surface Defect Detection Model of 3D Printing Bone Plate Using Deep Learning Algorithm)

  • 이송연;허용정
    • 반도체디스플레이기술학회지
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    • 제21권2호
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    • pp.68-73
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    • 2022
  • In this study, we produced the surface defect detection model to automatically detect defect bone plates using a deep learning algorithm. Bone plates with a width and a length of 50 mm are most used for fracture treatment. Normal bone plates and defective bone plates were printed on the 3d printer. Normal bone plates and defective bone plates were photographed with 1,080 pixels using the webcam. The total quantity of collected images was 500. 300 images were used to learn the defect detection model. 200 images were used to test the defect detection model. The mAP(Mean Average Precision) method was used to evaluate the performance of the surface defect detection model. As the result of confirming the performance of the surface defect detection model, the detection accuracy was 96.3 %.

Effects of electronic energy deposition on pre-existing defects in 6H-SiC

  • Liao, Wenlong;He, Huan;Li, Yang;Liu, Wenbo;Zang, Hang;Wei, Jianan;He, Chaohui
    • Nuclear Engineering and Technology
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    • 제53권7호
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    • pp.2357-2363
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    • 2021
  • Silicon carbide is widely used in radiation environments due to its excellent properties. However, when exposed to the strong radiation environment constantly, plenty of defects are generated, thus causing the material performance downgrades or failures. In this paper, the two-temperature model (2T-MD) is used to explore the defect recovery process by applying the electronic energy loss (Se) on the pre-damaged system. The effects of defect concentration and the applied electronic energy loss on the defect recovery process are investigated, respectively. The results demonstrate that almost no defect recovery takes place until the defect density in the damage region or the local defect density is large enough, and the probability of defect recovery increases with the defect concentration. Additionally, the results indicate that the defect recovery induced by swift heavy ions is mainly connected with the homogeneous recombination of the carbon defects, while the probability of heterogeneous recombination is mainly dependent on the silicon defects.

개방성 동맥관과 우폐동맥 이상기시를 동반한 대동맥 폐동맥 중격결손증 1례 보 (Aortopulmonary septal defect with anomalous origin of the RPA from aorta and PDA)

  • 남구현
    • Journal of Chest Surgery
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    • 제17권3호
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    • pp.398-401
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    • 1984
  • Aortopulmonary septal defect is rare congenital heart disease. An 8-year-old girl was diagnosed as a ventricular septal defect with patent ductus arteriosus at Department of Thoracic and Cardiovascular Surgery of Chungnam National University Hospital. On operation, the defect was confirmed as an aortopulmonary septal defect [Type I], anomalous origin of right pulmonary artery from aorta [Type Ill] and patent ductus arteriosus. The defect was repaired anatomically with cardiopulmonary bypass. But she was not survived because of uncontrollable bleeding from aorta.

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Defect Structure, Nonstoichiometry and Nonstoichiometry Relaxation of Complex Oxides

  • Yoo, Han-Ill
    • 한국세라믹학회지
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    • 제44권12호
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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.

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

  • 전유혁;김규태;김은수
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 1999년도 추계종합학술대회 논문집
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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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