• 복합신소재구조학회 논문집
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• 제6권3호
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• pp.20-25
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• 2015

This paper introduces a digital image processing(DIP) method as a method for measuring the displacement of pylon. The comparison of DIP results and ANSYS analysis results verified the validity of the image processing technique. Normalized cross-correlation(NCC) coefficient was used and experiments were performed three times. It shows that the displacement difference was 22% and 5% compared to ANSYS results. Therefore, the image processing method is expected to be able to measure the displacement of pylon sufficiently.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.692-697
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• 2000

In Particle Tracking Velocimetry, the analysis of double-exposed photographic plate can be carried out either by means of Young's fringe analysis or by a digital image processing technique. In this study, we used digital image processing to two images in one frame far analyzing in-cylinder flow fields, and compared PTV with PSV(Particle Streak Velocimetry). Additionally, this technique was verified by two different calibration method. One is interpolation by invert distance, the other is interpolation by area ratio. Finally, the results between two interpolation methods were similar in whole flow fields.

• 대한기계학회논문집B
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• 제34권3호
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• pp.309-316
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• 2010

본 연구에서는 입자의 크기 및 3차원 속도를 측정할 수 있는 디지털 업자 홀로그래피 시스템을 개발하고, 개발된 시스템의 효용성을 검증하기 위하여 층류 채널 유동장에 적용하여 보았다. 디지털 홀로그램을 기록할 수 있는 이중 펄스 홀로그래피 시스템을 구축하였고, 상관계수법을 이용한 초점면 결정, Wiener 필터를 사용한 잡음 제거, 두 개의 이진화값 및 분할 이진화방법 등을 사용하여 기록된 홀로그램 및 재생이미지를 처리하였으며, 동일 입자의 추적은 입자가 액적처럼 큰 경우는 일치확률법을, 유동장의 추적 입자처럼 작은 경우는 상호상관법을 사용하였다. 개발된 시스템을 사용하여 층류 채널 유동의 축방향 속도를 측정하였으며, 이론적 예측식과 비교하여, 디지털 입자 홀로그래피 시스템의 유용성을 확인하였다.

• Structural Engineering and Mechanics
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• 제81권5호
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• pp.575-589
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• 2022

In order to enhance the greenness in the strain-hardening composites and to reduce the high cost of typical polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC), an affordable strain-hardening composite with green binder content has been proposed. For optimizing the strain-hardening behavior of cementitious composites, this paper investigates the effects of polypropylene fibers on the first cracking strength, fracture properties, and micromechanical parameters of cementitious composites. For this purpose, digital image correlation (DIC) technique was utilized to monitor crack propagation. In addition, to have an in-depth understanding of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. To understand the effect of fibers on the strain hardening behavior of cementitious composites, ten mixes were designed with the variables of fiber length and volume. To investigate the micromechanical parameters from fracture tests on notched beam specimens, a novel technique has been suggested. In this regard, mechanical and fracture tests were carried out, and the results have been discussed utilizing both fracture and micromechanical concepts. This study shows that the fiber length and volume have optimal values; therefore, using fibers without considering the optimal values has negative effects on the strain-hardening behavior of cementitious composites.

• 한국측량학회지
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• 제9권2호
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• pp.49-56
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• 1991

본 연구에서는 SPOT 위성자료를 이용함에 있어 경제적 시간적 효용성을 증대시키기 위해, CCT 형태의 수치영상자료를 일반 PC 영상처리체계로 처리하여 3차원 위치를 결정하고자 하였으며, 위성영상의 상좌표취득에는 통계적 이론에 근거한 영상정합기법을 도입, 좌표취득의 신뢰도를 분석하여 수치표고모형생성, 정사사진의 작성 등에 요구되는 3차원 위치결정에 관한 새로운 알고리즘을 제시하였다. CCT 형태의 수치위성영상을 이용한 상좌표취득에 있어서 영상정합기법을 적용한 결과, 육안관측에 의하여 상좌표를 취득하는 방법에 비하여 수평위치 및 높이결정의 정확도를 향상시킬 수 있었다. 상좌표취득을 위해 영상상관기법을 적용할 경우, 기준영역의 크기를 변화시켜 상관계수를 구한 결과, 19$\times$19 영상소의 기준영역이 상좌표취득에 있어 가장 적합한 크기임을 알 수 있었으며, 이러한 결과를 바탕으로 SPOT 위성자료를 해석함에 있어 수치영상의 활용에 관한 알고리즘을 제시할 수 있었다.

• Geomechanics and Engineering
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• 제17권6호
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• pp.565-572
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• 2019

Spatial variability is an inherent characteristic of soil, and auto-correlation length (ACL) is a very important parameter in the reliability or probabilistic analyses of geotechnical engineering that consider the spatial variability of soils. Current methods for estimating the ACL need a large amount of laboratory or in-situ experiments, which is a great obstacle to the application of random field theory to geotechnical reliability analysis and design. To estimate the ACL reasonably and efficiently, we propose a micro-structure based numerical simulation method. The quartet structure generation set algorithm is used to generate stochastic numerical micro-structure of soils, and scanning electron microscope test of soil samples combined with digital image processing technique is adopted to obtain parameters needed in the QSGS algorithm. Then, 2-point correlation function is adopted to calculate the ACL based on the generated numerical micro-structure of soils. Results of a case study shows that the ACL can be estimated efficiently using the proposed method. Sensitivity analysis demonstrates that the ACL will become stable with the increase of mesh density and model size. A model size of $300{\times}300$ with a grid size of $1{\times}1$ is suitable for the calculation of the ACL of clayey soils.

• 대한디지털의료영상학회논문지
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• 제15권2호
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• pp.55-61
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• 2013

The purpose of this study is to evaluate image blurring according to variation of the ETL and propose the clinically appropriate ETL range. SIEMENS MAGNETOM Skyra 3.0T and 20 channel head coil were used for the study. MRI phantom was kept the lines horizontally to three direction(X,Y,Z) of the coil and T1, T2 weighted images that used the fast spin echo technique acquired. The ETL with increase of 10 was applied from 10 to 80. In addition, the ETL with increase of 1 was applied in the interval statistically significant differences occurred. And T1, T2 weighted images that used the conventional spin echo technique acquired to compare image blurring of the images that used the fast spin echo technique. The slope of lattice in the images was measured using Image J 1.47v program to evaluate image blurring. And image blurring was determined by the degree of the slope. The statistical significance of both techniques was evaluated by the Kruskal-Wallis test of the SPSS 17.0v. And the correlation of the ETL and image blurring was evaluated quantitatively by regression analysis. The slope of the T1, T2 weighted images that used fast spin echo technique decreased as contrasted with conventional spin echo technique. In the result of the Kruskal-Wallis test, the T1, T2 weighted images that used fast spin echo technique made a significant difference with conventional spin echo technique. Particularly, in the Tomhane' T2 test, the T1, T2 weighted images made a significant difference from ETL 22 and 31 respectively. In the result of the regression analysis, the R-squared of the T1, T2 weighted images are 0.762 and 0.793. It is difficult to apply the long ETL in the T1 weighted image caused by the short TR and multi-slices study. Therefore, clinical impact according to variation of the ETL is very slight in the T1 weighted images. But the application of the proper ETL is demanded in T2 weighted images using the fast spin echo technique in order to prevent image blurring.

• 한국안전학회지
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• 제28권4호
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• pp.26-32
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• 2013

A digital image correlation(DIC) method is a whole-field measurement technique that acquires surface displacements and strains from images information which characterized a random speckle as intensity grey levels. Recently years, this DIC method is being developed and used increasingly in various research. In this study, we tried to apply to aluminum alloy(Al 6061-T6) using DIC method and strain gauge. DIC results demonstrated the usefulness and ability to determine a strain. The test specimen used in this study was an aluminum alloy(Al 6061-T6, thickness 1 mm). For a strain measurement, a strain gauge was attached at the center of a specimen. A specimen was lightly sprayed with a white paint and a black dot pattern was sprayed on its fully dried white surface to obtain a random speckle. The experimental apparatus used to perform the tensile test consisted of universal dynamic tester(5 kN; T.O. Co.) under displacement speed of 0.5, 1.0 and 3.0 mm/min. A Model 5100 B Scanner(V. Co.) used to obtain a strain. A CCD camera connected to a PC uses to record the images of the specimen surface. After acquisition, the images were transferred to PC where the DIC software was implemented. An acquired image was evaluated by the DIC program. DIC method for displacement and strain was suggests and it results show a good consistent remarkably. DIC results demonstrated the usefulness and ability to determine surface strain was better than by using classical measurements. The strain field measurement using a DIC is so useful that it can be applied to map strain distributions at a full area. DIC method can evaluate a strain change so it can predict a location of fracture. The findings of the investigation suggest that the DIC method is an efficient and reliable tool for full-field monitoring and detailed damage characterization of materials.

• 화약ㆍ발파
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• 제37권4호
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• pp.1-9
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• 2019

본 연구에서는 지하채광 발파에 따른 암반광주에서의 변위 및 진동을 측정하는 방법을 통해 디지털 이미지 영상상관 기법(DIC)이라는 기술의 적용성을 시험하였다. 디지털 이미지 영상상관 기법은 고속 사진촬영 기술과 접목하면 구조물 또는 대상물의 전면변화 속성을 2차원 또는 3차원 좌표로 변환할 수 있는 우수한 광학영상 처리능력을 제공한다. 이렇게 측정된 좌표들은 구조물이나 대상물의 변위, 변형률, 속도 등을 계산하는 데 사용된다. 이 기술은 과학 및 공학 분야에서 널리 사용되고 있으며, 그 밖의 많은 분야로도 적용성을 확장해 나가고 있다. 본 연구에서는 이와 같은 DIC 시스템과 기존의 진동계측기를 사용하여 발파로 발생된 변위와 진동을 측정함으로써 그 성능을 서로 비교하였다. 현장시험 결과, 두 방법은 비슷한 결과를 보였다. 이로부터 DIC 시스템을 이용한 발파 진동 및 변위 측정에 대한 적용성을 확인할 수 있었다.

• 인터넷정보학회논문지
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• 제4권3호
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• pp.39-46
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• 2003

일반적으로 디지털 영상의 저작권 보호를 위한 기존의 워터마킹 기법들은 기하학적 왜곡에 약할 뿐 아니라 왜곡의 정도에 관계없이 모든 워터마크 추출에 동일한 시간을 요구한다. 본 논문에서는 이러한 문제를 해결하기 위하여 콤플렉스 웨이블릿 변환을 이용한 점진적 워터마킹 기법을 제안한다. 제안한 점진적 워터마킹 기법은 원 영상을 콤플렉스 웨이블릿 변환하여 위상 성분에 워터마크를 삽입하며 워터마크가 삽입된 영상으로부터 단계적으로 워터마크를 추출한다. 추출된 워터마크와 원 워터마크의 상관관계를 비교하여 임계값이상이면 영상에 대한 저작권을 주장할 수 있다. 또한 단계적 워터마크의 추출은 왜곡의 정도와 왜곡정도에 따른 워터마크의 추출시간을 결정할 수 있게 한다. 성능평가를 통하여 본 논문에서 제안한 기법이 기존 웨이블릿 변환 기법보다 기하학적 왜곡에 강함을 증명하였다.