• 한국방사선학회논문지
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• 제7권1호
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• pp.57-62
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• 2013

자기공명영상은 많은 장점에도 불구하고 체내에 정형보철이 있는 경우 자화율 차이로 영상왜곡이 발생한다. 스테인리스와 티타늄 시험편을 $65{\times}15{\times}2mm$로 동일하게 제작하여 phantom과 돼지고기에 부착 한 후 자기공명영상과의 관계를 알아보았다. phantom 영상을 통해 영상왜곡의 길이와 돼지 뼈를 통한 신호강도의 변화, 피하조직의 지방억제 정도를 정량적으로 평가 하였다. 스테인리스는 티타늄에 비해 길이 방향으로 4.4배, 높이 방향으로 2.8배 영상왜곡이 크며, 신호강도는 58.5%로 상대적으로 낮았다. 피하조직 지방억제는 Normal의 56.2%에 비해 스테인리스는 16.04%, 티타늄은 54.53%로 나타났다. 실험 결과 자기공명영상의 영상학적 진단가치는 스테인리스 보다 티타늄 금속이 부착 된 경우 더 우수한 것을 알 수 있었다.

• 한국터널지하공간학회 논문집
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• 제23권2호
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• pp.119-131
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• 2021

초근접 병렬터널의 필라부에는 응력이 집중되고, 기존에는 터널의 안정성을 확보하기 위하여 강연선을 이용하여 필라부를 보강한다. 하지만 토사 지반에서는 필라부의 강도가 감소하기 때문에 필라부를 강연선으로 보강하는 것으로는 터널 안전성을 충분히 확보하지 못한다. 본 연구에서는 초근접 병렬터널의 필라부를 강관으로 보강하는 새로운 공법의 보강효과를 검토하기 위하여 실내터널모형실험을 수행하였다. 그 결과 상부응력에 대한 필라부의 지지능력은 강관 보강하는 경우가 강연선 보강하는 경우보다 22% 큰 것으로 나타났다. Particle Image Velocimetry 기법을 이용한 분석결과 필라부 강관 보강은 강연선 보강보다 병렬터널과 필라부에 상재하중이 균일하게 작용할 수 있는 더 유리한 조건을 형성하였다. 실험결과에 기반하여 필라부 강관보강공법은 강연선 보강공법보다 터널 안정성에 긍정적인 효과를 가져올 것으로 기대된다.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.20-23
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• 2014

Dual phase steels have a microstructure comprising of a polygonal ferrite matrix together with dispersed islands of martensite. There are clear differences between the image quality (IQ) map of the dual phase and the corresponding ferritic/pearlitic structures, both in the as-heat treated and cold rolled conditions. Electron backscatter diffraction (EBSD) techniques were used to study the evolution substructure of steel due to plastic deformation. The martensite-ferrite and ferrite-pearlite interfaces were observed. The interface can be a source of mobile dislocations which the bands seem to originate from the martensite islands. In particular, the use of image quality is highlighted.

• 반도체디스플레이기술학회지
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• 제17권2호
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• pp.26-31
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• 2018

In this paper, surface defects and typical illumination mechanisms for steel plates are analyzed, and then optimum illumination mechanism is selected using discrete wavelet transform (DWT) synthetic images and discriminant measure (DM). The DWT synthetic images are generated using component images decomposed by Haar wavelet transform filter. The best synthetic image according to surface defects is determined using signal to noise ratio (SNR). The optimum illumination mechanism is selected by applying discriminant measure (DM) to the best synthetic images. The DM is applied using the tenengrad-euclidian function. The DM is evaluated as the degree of contrast using the defect boundary information. The performance of the optimum illumination mechanism is verified by quantitative data and intuitive image looks.

• Smart Structures and Systems
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• 제32권2호
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• pp.111-121
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• 2023

This study proposes an automated assembly performance evaluation method for prefabricated steel structures (PSSs) using machine learning methods. Assembly component images were segmented using a modified version of the receptive field pyramid. By factorizing channel modulation and the receptive field exploration layers of the convolution pyramid, highly accurate segmentation results were obtained. After completing segmentation, the positions of the bolt holes were calculated using various image processing techniques, such as fuzzy-based edge detection, Hough's line detection, and image perspective transformation. By calculating the distance ratio between bolt holes, the assembly performance of the PSS was estimated using the k-nearest neighbors (kNN) algorithm. The effectiveness of the proposed framework was validated using a 3D PSS printing model and a field test. The results indicated that this approach could recognize assembly components with an intersection over union (IoU) of 95% and evaluate assembly performance with an error of less than 5%.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.190-202
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• 2018

Maintaining the integrity of the major equipment in nuclear power plants is critical to the safety of the structures. In particular, the soundness of the piping is a critical matter that is directly linked to the safety of nuclear power plants. Currently, the limit state of the piping design standard is plastic collapse, and the actual pipe failure is leakage due to a penetration crack. Actual pipe failure, however, cannot be applied to the analysis of seismic fragility because it is difficult to quantify. This paper proposes methods of measuring the failure strain and deformation angle, which are necessary for evaluating the quantitative failure criteria of the steel pipe elbow using an image measurement system. Furthermore, the failure strain and deformation angle, which cannot be measured using the conventional sensors, were efficiently measured using the proposed methods.

• 제어로봇시스템학회논문지
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• 제21권8호
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• pp.742-747
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• 2015

The quality of steel plate products is determined by the number of defects and the process problems are estimated by shapes of defects. Therefore pinholes defects of cold rolled steel have to be controlled. In order to improve productivity and quality of products, within each production process, the product is inspected by an adequate inspection system individually in the lines of steelworks. Among a number of inspection systems, we focus on the pinholes detection system. In this paper, we propose an embedded system using FPGA which can detect pinholes defects. The proposed system is smaller and more flexible than a traditional system based on expensive frame grabbers and PC. In order to detect consecutive defects, FPGAs acquire two dimensional image and process the image in real time by using correlation of lines. The proposed pinholes detection algorithm decreases arithmetic operations of image processing and also we designed the hardware to shorten the data path between logics due to decreasing propagation delay. The experimental results show that the proposed embedded system detects the reliable number of pinholes in real time.

• 전기화학회지
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• 제6권3호
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• pp.217-223
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• 2003

The present work is concerned with characterization of surface roughness and inhomogeneity of four kinds of hot-rolled carbon steels in terms of the fractal dimension and the depression parameter by using image analysis method and electrochemical impedance spectroscopy, respectively. From the analysis of the 3D AFM image, it is realized that all the hot-rolled steel surfaces show the self-affine fractal property. The values of the fractal dimension of the hot-rolled steels were determined by the analyses of the AFM images on the basis of both the perimeter-area method and the triangulation method. In addition, the Nyquist plots were found to be depressed from a perfect semicircle form. From the experimental findings, the changes in the values of the fractal dimension and the depression parameter with chemical composition have been discussed in terms of the change in the value of hardness of base steel.

• 센서학회지
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• 제17권5호
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• pp.338-345
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• 2008

Steel bearing balls are important component in machines having moving parts. In this paper we describe a vision-based automatic inspection system designed for sensing defects on the surface of steel bearing balls. The system has a camera looking down over a rail on which balls roll. Two mirrors are installed at both sides of the rail so that the side parts of a ball can be well inspected. The entire ball surface can be sufficiently seen by taking three images at $120^{\circ}$ rotation interval. Defects are detected by thresholding the difference image between an image captured and the reference image of a good ball.

• 전기학회논문지
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• 제58권5호
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• pp.1025-1034
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• 2009

In steel making production line, steel slabs are given a unique identification number. This identification number, Slab management number(SMN), gives information about the use of the slab. Identification of SMN has been done by humans for several years, but this is expensive and not accurate and it has been a heavy burden on the workers. Consequently, to improve efficiency, automatic recognition system is desirable. Generally, a recognition system consists of text localization, text extraction, character segmentation, and character recognition. For exact SMN identification, all the stage of the recognition system must be successful. In particular, the text localization is great important stage and difficult to process. However, because of many text-like patterns in a complex background and high fuzziness between the slab and background, directly extracting text region is difficult to process. If the slab region including SMN can be detected precisely, text localization algorithm will be able to be developed on the more simple method and the processing time of the overall recognition system will be reduced. This paper describes about the slab region localization using SIFT(Scale Invariant Feature Transform) features in the image. First, SIFT algorithm is applied the captured background and slab image, then features of two images are matched by Nearest Neighbor(NN) algorithm. However, correct matching rate can be low when two images are matched. Thus, to remove incorrect match between the features of two images, geometric locations of the matched two feature points are used. Finally, search rectangle method is performed in correct matching features, and then the top boundary and side boundaries of the slab region are determined. For this processes, we can reduce search region for extraction of SMN from the slab image. Most cases, to extract text region, search region is heuristically fixed [1][2]. However, the proposed algorithm is more analytic than other algorithms, because the search region is not fixed and the slab region is searched in the whole image. Experimental results show that the proposed algorithm has a good performance.