• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.852-862
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• 1996

This study was carried out to develop tools to detect defects of apple using machine vision. For the purpose, 6 kinds of frame for color images, R, G, B, h, S, and I frame, and a frame for near infra-red images (NIR frame) were tested first to select one which is useful to segment defect areas from apple images. After then, several methods to classify kind of defect for the segmented defect areas were developed and tested. Five kinds of apple defect -bruise , decay ,fleck worm hole and scar were investigated . The results are as follows: NIR frame was selected as the best one among the 7 kinds of image frame, and R, G and I frames showed favourable result to segment areas of apple defect. Various features of the segmented defect areas were measured to classify the defect areas. Eight kids of feature of the areas-size, roundness, axes length ratio, mean and variance of pixel values, variance of real part of spectrum, mean and variance of power spectrum resulted from spacial ourier transform were observed for the segmented defect areas in the selected 4 frames. then procedures to classify defects using the features were developed for the 4 frames and tested with 75-113 defects on apples. The test resulted that NIR and I frames showed high accuracies to classify the kind of defect as 77% and 76% , respectively.

• 한국임상수의학회지
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• 제19권1호
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• pp.110-113
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• 2002

An atrial septal defect (ASD) is a congenital hole in the atrial septum that allows flow between the two atria. Small ASDs are usually well-tolerated defects and do not result in significant clinical abnormalities. In large ASDs or in the presence of other cardiac defects, clinically significancy is increased. Atrial septal defects in 2 Dogs with cardiac and respiratory signs were diagnosed at seoul animal medical center. In ascultation, systolic murmur and the splitting of second heart sound were heard at pulmonary or tricuspid valve region. In radiograph, right-sided cardiomegaly, pulmonary artery dilation, increased pulmonary vasculature makings, and pleural effusion or pulmonary edema signs were observed. In echocardiography, the region, location and size of septal defect was identified. Also, the direction and degree of shunt was measured. These dogs were treated with medicine for cardiac failure. One dog is well-tolerated, the other dog died.

• 비파괴검사학회지
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• 제6권1호
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• pp.23-30
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• 1986

The optimumultrasonic test conditions for the thin carbon fiber reinforced plastic (CFRP) sheet were determined for the immersed reflector plate method. The effects of the water distance, the surface conditions of the specimen and transducer characteristics were studied. For a reliable test the water distance between the transducer and the front surface of the specimen should be determined when the beam profile of the transducer appears in the bell-shape. The detectability of the defect was improved as the effective beam width of the ultrasonic transducer became narrow. The transducer should be properly chosen considering to the surface condition of the test material as well as the size and type of the defect to be detected. It was possible to detect the flat bottom hole whose diameter is as small as about 500 micrometer.

• Journal of Biosystems Engineering
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• 제22권2호
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• pp.217-226
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• 1997

This study was to develop a machine vision system to detect and to discriminate 5 kinds of apple surface defectbruise, decay. fleck, worm hole and scar. To detect the defects from an image of apple, thresholding technique was applied to images on various frames (R, G, B, H, S and I) of the color machine vision and an image of near infrared (NIR). To discriminate the detected region of defect, various features of the 5 kind defect regions were extracted from the 4 kinds of images selected above. The features were size of area, roundness, axes length ratio, mean and valiance of pixel values, standard deviation of real part of amplitude spectrum in frequency domain obtained by Fourier transform of pixel data and mean and standard deviation of power spectrum obtained by the same transform of pixel data. Routines to discriminate the defects from the features of image were developed and tested to prove their validity. The test resulted that I-frame and NIR images were the most desirable. Accuracies of the two images to discriminate the defects were noted as 76% and 77%, respectively.

• 한국정밀공학회지
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• 제21권9호
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• pp.63-68
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• 2004

The high pressure vessels that are constructed by welding process have many welding lines and most of the leakage defects are occurred on these welding lines. The acoustic emission(AE) technique has adopted to detect the defect location and leakage on welding parts, but the AE signal in leakage are incomplete due to the attenuation, reiteration, instability and limit of defect size. To overcome these troubles, the experiments in this study are conducted to measure the indirect media-propagated AE signal perpendicular to the leakage hole. The AE signals that are acquired from the direct and indirect media are analyzed, and the reliability of the indirect media-propagated AE signal are examined experimentally. By AE signal investigation, this method can be adopted to detect efficiently the leakage in welding parts.

• 비파괴검사학회지
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• 제29권3호
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• pp.242-247
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• 2009

The ability of time reversal techniques to focus ultrasonic beams on the source location is important in many aspects of ultrasonic nondestructive evaluation. In this paper, we investigate the time reversal beam focusing of ultrasonic array sensors on a defect in layered media. Numerical modeling is performed using the commercially available software which employs a time domain finite difference method. Two different time reversal approaches are considered - the through transmission and the pulse-echo. Linear array sensors composed of N elements of line sources are used for signal reception/excitation, time reversal, and reemission in time reversal processes associated with the scattering source of a side-drilled hole located in the second layer of two layer structure. The simulation results demonstrate the time reversal focusing even with multiple reflections from the interface of layered structure. We examine the focusing resolution that is related to the propagation distance, the size of array sensor and the wavelength.

• 전기학회논문지
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• 제66권10호
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• pp.1508-1515
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• 2017

This paper proposes the defect detection method for automatic inspection machines in printed circuit boards (PCBs) manufacturing system. The defects of PCB such as open, short, pin hole and scratch can be detected by comparing the standard image and the target image. The standard image is obtained from CAD file such as ODB++ format, and the target image is obtained by arranging, filtering and binarization of captured PCB image. Since the PCB size is too large and image resolution is too high, the image processing requires a lot of memory and computational time. The wavelet transform is applied to compress the standard and target images, which results in reducing the memory and computational time. To increase the inspection accuracy, we utilize the he HH-domain as well as LL-domain of the transformed images. Experimental results are finally presented to show the performance improvement of the proposed method.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제37권
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• pp.37.1-37.4
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• 2015

Keratocystic odontogenic tumors can occur in any area of the maxilla or mandible. According to their size, location, and relations with surrounding structures, they are treated by cyst enucleation or enucleation after either marsupialization or decompression. Enucleation is performed when cysts are not large and when only minor damage to adjacent anatomical structures is expected. Although marsupialization and decompression follow the same basic bone-regeneration principle, which is to say, by reducing the pressure within the cyst, the former leaves a large defect after healing due to the large fistula necessary to induce the conversion of the cyst-lining epithelia to oral epithelia; the latter leaves only a relatively small defect, because of the continuous washing carried out by means of a tube inserted into a small hole in the cyst. In the latter case too, a decompressor appropriate for the focal position is required, owing to the importance of maintaining the device and controlling for oral hygiene. We report herein decompression treatment with a patient-customized device for an extensive cyst in the anterior region of the mandible.

• 한국수정란이식학회지
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• 제32권1호
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• pp.33-38
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• 2017

A 10-day-old, Holstein calf with facial mass of 10 cm in diameter at the forehead region referred to Veterinary Medical Teaching Hospital in Chungnam National University. The mass was soft and fluctuating swelling. It had normal skin and hair hanging forward from frontal region and was thought to contain cerebrospinal fluid. On the skull radiography, cauliflower like-irregular marginated, soft tissue opacity mass was identified craniodorsal to the frontal bone. The mass appeared as a cyst filled with anechoic fluid on ultrasonography. Soft tissue structures considered brain tissues were observed in the deep area of the mass. On the computed tomography, a large skull defect of left side frontal bone was found, and heterogeneous materials were exposed through the defect but exposure of cerebral meninges and brain tissue were not confirmative. On magnetic resonance imaging, herniated left brain parenchyma showed heterogenous T2 and T1 hyperinsensity. In the intracranium, T2 hyperinstense and T1 hypointense fluid was identified on the left side, instead of left cerebral parenchyma. Also leftward shift of right hemisphere and midline structure, including thalamus and midbrain, were observed. The definitive diagnosis was confirmed as a meningoencephalocele based on computed tomography and magnetic resonance imaging. The calf was euthanized and necropsy was performed. On necropsy, both hemisphere were developed unequally with different size. One side hemisphere was grown in the outside through 10 cm hole on the median plane.

• 비파괴검사학회지
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• 제31권2호
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• pp.157-164
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• 2011

위상잠금 적외선 열화상(lock-in infrared thermography) 기법의 조선해양공학 분야에 적용 가능성을 검토하였다. 이를 위해 실험계획법에 의해 향상된 결함부와 건전부의 위상차 대비영상을 얻기 위한 탐색 연구를 수행하였다. 위상차 대비영상의 평가를 정량회하기 위하여 대비 기준표와 홀 크기에 가중치를 주는 방법을 적용하여 유용한 판별기준임을 입증하였다. 그리고 표면에 광 조사 세기는 중간이나 낮은 조사량이 좋은 결과를 보여주고, 높은 조사는 유용한 결과를 주지 못했다. 위상잠금 주파수는 가진 광원의 세기에 비례하여 좋은 결과를 획득할 수 있었고, 열화상 카메라의 노출시간(integration time)은 조사 광원의 세기와 반비례하여 실험을 수행하는 것이 좋은 결과를 얻을 수 있었다. 그러나 시험편(specimen)의 차이는 약간의 편향된 결과를 얻었지만 유의하지는 못했다.