• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.309-312
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• 2018

지금까지 영상 콘텐츠 제작 기술의 발전은 SD(Standard Definition)에서 시작하여 HD(High Definition)와 FHD(Full High Definition)를 거쳐, UHD(Ultra High Definition)에 이르기까지 화질을 중심으로 이루어져 왔다. UHD 에 이르며 육안으로는 그 이상의 해상도로 제작된 콘텐츠와 구분하는 것이 힘들어졌으며, 이에 영상 콘텐츠 제작은 화질이 아닌 제한된 촬영 장비들로부터 촬영 방법, 영상 화각의 개선 작업 등으로 그 방향을 전환하고 있다. 이의 연장선 상에서 360 도 영상에 대한 기술개발이 활발히 이루어 지고 있다. 방송 분야에서는 360 도 영상의 실시간 스트리밍 적용 가능성이 모색되고 있는데, 이것이 가능 하려면 대량의 동영상 데이터를 실시간으로 스티칭하여 전달하는 기술이 필요하다. 따라서 고속 이미지 스티칭이 가능해질 경우 실시간 동영상 스티칭을 통해 방송 통신 분야에서의 서비스 향상에 기여할 것으로 보인다. 본 논문은 이미지의 edge 정보를 방향성을 가진 데이터로 분할하여 특징점을 추출하고, 이후 가중치를 통한 특징점 매칭으로 기존의 이미지 스티칭 방법 보다 빠른 속도의 알고리즘을 제안한다.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.1
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• pp.46-55
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• 2021

Seam puckering and the seam strength of conductive threads used to produce smart clothing were analyzed according to stitching methods and fabrics. Samples were prepared in a lock stitch and zigzag stitch on plain woven and jersey knit fabric, using one type of polyester sewing thread and three types of commercial conductive threads that consisted of two types of stainless-steel conductive threads (TST and MST) and one type of silver conductive thread (SSV). Seam pucker percentages, shapes, and seam strength were measured. On plain woven fabric as well as jersey knit fabric, three-ply TST and MST showed a higher SP percentage compared to a polyester sewing thread. Meanwhile, single-ply SSV showed the lowest SP percentage. In addition, the SP percentage of the zigzag stitch decreased along the weft and course directions of the fabric, and decreased significantly as the number of fabric layers increased. Moreover, there was a marked tendency for a higher SP percentage in jersey knit fabric compared to plain woven fabric, and the two-dimensional cross-section waveforms of stitches obtained using three-dimensional data that showed increased irregular waveforms and peaks in the zigzag stitch. There were no correlations between seam strength and tensile strength.

• Current Optics and Photonics
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• v.5 no.6
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• pp.699-710
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• 2021

In this study, we propose a biomimetic optical structure design methodology for investigating micro-optical mechanisms associated with the compound eyes of insects. With these compound eyes, insects can respond fast while maintaining a wide field of view. Also, considerable research attention has been focused on the insect compound eyes to utilize these benefits. However, their nano micro-structures are complex and challenging to demonstrate in real applications. An effectively integrated design methodology is required considering the manufacturing difficulty. We show that photorealistic ray-traced visualization is an effective method for designing the biomimetic of a micro-compound eye of an insect. We analyze the image formation mechanism and create a three-dimensional computer-aided design model. Then, a ray-trace visualization is applied to observe the optical image formation. Finally, the segmented images are stitched together to generate an image with a wide-angle; the image is assessed for quality. The high structural similarity index (SSIM) value (approximately 0.84 to 0.89) of the stitched image proves that the proposed MATLAB-based image stitching algorithm performs effectively and comparably to the commercial software. The results may be employed for the understanding, researching, and design of advanced optical systems based on biological eyes and for other industrial applications.

• Current Optics and Photonics
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• v.5 no.4
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• pp.362-369
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• 2021

Absolute position sensors are widely used in machine tools and precision measuring instruments because measurement errors are not accumulated, and position measurements can be performed without initialization. The laser speckle-based absolute position sensor, in particular, has advantages in terms of simple system configuration and high measurement accuracy. Unlike traditional absolute position sensors, it does not require an expensive physical length scale; instead, it uses a laser speckle image database to measure a moving surface position. However, there is a problem that a huge database is required to store information in all positions on the surface. Conversely, reducing the size of the database also decreases the accuracy of position measurements. Therefore, in this paper, we propose a new method to measure the surface position with high precision while reducing the size of the database. We use image stitching and approximation methods to reduce database size and speed up measurements. The absolute position error of the proposed method was about 0.27 ± 0.18 ㎛, and the average measurement time was 25 ms.

• Journal of Chest Surgery
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• v.56 no.1
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• pp.56-58
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• 2023

Untreated severe tricuspid regurgitation (TR) is associated with poor outcomes. Functional TR occurs secondary to dilatation of the annulus and tethering of the leaflets. Ring annuloplasty alone can correct most cases, but is insufficient in cases of severe annular dilatation due to severe leaflet tethering. In such cases, a tricuspid edge-to-edge technique may be an option. However, stitching of the leaflet tips alone is likely to result in tearing of the leaflets. Approximation of the durable chordae tendineae is considered helpful for this problem. Herein, we present the case of a 39-year-old man who had undergone open-heart surgery for acute type A aortic dissection 13 months earlier. A right mini-thoracotomy approach with a beating-heart strategy was used, which did not require unnecessary pericardial adhesiolysis and dissection. This technique had the advantage of reducing the operation time and the risk of bleeding. To summarize, we present a case of tricuspid valve repair in a high-risk patient with severe leaflet tethering that was successfully managed using these methods.

• Journal of Biomedical Engineering Research
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• v.44 no.3
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• pp.176-181
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• 2023

During cancer treatment, the patient's response to drugs appears differently at the cellular level. In this paper, an image-based cell phenotypic feature quantification and key feature selection method are presented to predict the response of patient-derived cancer cells to a specific drug. In order to analyze the viability characteristics of cancer cells, high-definition microscope images in which cell nuclei are fluorescently stained are used, and individual-level cell analysis is performed. To this end, first, image stitching is performed for analysis of the same environment in units of the well plates, and uneven brightness due to the effects of illumination is adjusted based on the histogram. In order to automatically segment only the cell nucleus region, which is the region of interest, from the improved image, a superpixel-based segmentation technique is applied using the fluorescence expression level and morphological information. After extracting 242 types of features from the image through the segmented cell region information, only the features related to cell viability are selected through the ReliefF algorithm. The proposed method can be applied to cell image-based phenotypic screening to determine a patient's response to a drug.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.10-13
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• 2020

최근 초고화질 영상, 가상현실 등 프리미엄 콘텐츠에 대한 요구가 커지면서 360° VR과 8K TV 등의 시장이 확대되고 있다. 360° VR 영상을 만드는 데에 스티칭 기술이 사용되고 있고, 8K 영상을 촬영할 수 있는 장비는 매우 제한적이기 때문에 스티칭 기술을 통해 콘텐츠를 확보하려는 노력이 이어지고 있다. 스티칭 기술은 여러 영상을 합성하여 기존 카메라의 좁은 시야각 문제를 해결하고 보다 넓은 시야각의 영상을 만드는 기술이다. 최근에는 해당 분야에 관한 연구가 진행됨에 따라 이미지를 넘어 동영상 스티칭에 대한 연구가 주로 진행되고 있다, 기존 동영상 스티칭 방식은 이미지 스티칭 방식을 프레임마다 반복하기 때문에 시간이 오래 걸린다는 단점이 있다. 컴퓨터 비전 분야에서는 딥러닝을 활용하여 객체가 존재할 것으로 예측되는 부분에 사각형 모양의 경계 상자(Bounding box)를 생성하는 객체 탐지(Object detection) 분야에 관한 많은 연구가 이루어져 왔고 이를 기반으로 객체의 경계선을 검출하여 해당 영역만을 구분하는 객체 분할(Instance segmentation)에 대한 연구 또한 진행 중이다. 본 논문에서는 앞서 말한 스티칭 속도 문제를 해결하기 위하여 빠른 속도로 객체 분할이 가능한 YOLACT를 이용하여 스티칭 속도를 개선하는 방안을 제안한다.

• Journal of KIISE:Software and Applications
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• v.36 no.8
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• pp.653-663
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• 2009

In this paper, we propose a blind spots elimination system using three cameras. A wide-angle camera is attached on trunk for eliminating blind spots of a rear-view mirror and two cameras are attached on each side-view mirror for eliminating blind spots of vehicle's sides. In order to eliminate blind spots efficiently, we suggest a method to build a panoramic mosaic view with two side images and one wide-angle rear image. First, we obtain an undistorted image from a wide-angle camera of rear-view and calculate the focus-of-contraction (FOC) in undistorted images of rear-view while the car is moving straight forward. Second, we compute a homography among side-view images and an undistorted image of rear-view in flat road scenes. Next, we perform an image registration process after road and background region segmentation. Finally, we generate various views such as a cylinder panorama view, a top view and an information panoramic mosaic view.

• Journal of Broadcast Engineering
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• v.22 no.4
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• pp.473-483
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• 2017

Since the advent of 3D and UHD contents, demand for high-quality panoramic images has been increasing. The UWV(Ultra-Wide Viewing) service uses a wider viewing angle than conventional panoramas to provide a lively experience for users and enhance their understanding of the event. In this paper, we propose a spatial adjacency map generation method and an UWV file storage format technology to provide UWV service. The spatial adjacency map measures the similarity between images and generate the position information of the images based on similarity. And the stitching time of the image can be shortened through the generated position information. Through the spatial adjacency map, we generate the large screen content quickly. The UWV file format which is based on ISOBMFF process spatial adjacency map and videos and support random access. In this paper, we design the UWV player to verify the spatial adjacency map and UWV file format and show the result of experiments.

• Geomechanics and Engineering
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• v.15 no.5
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• pp.1091-1100
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• 2018

In this study, the relationships between hydraulic conductivity of GCLs and physico-chemical properties of bentonites were assessed. In addition to four factory manufactured GCLs, six artificially prepared GCLs (AP-GCLs) were tested. AP-GCLs were prepared in the laboratory without bonding or stitching. A total of 20 hydraulic conductivity tests were conducted using flexible wall permeameters ten of which were permeated with distilled deionized water (DIW) and the rest were permeated with tap water (TW). The hydraulic conductivity of GCLs and AP-GCLs were between $5.2{\times}10^{-10}cm/s$ and $3.0{\times}10^{-9}cm/s$. The hydraulic conductivities of all GCLs to DIW were very similar to that of GCLs to TW. Then, simple regression analyses were conducted between hydraulic conductivity and physicochemical properties of bentonite. The best correlation coefficient was achieved when hydraulic conductivity was related with clay content (R=0.85). Liquid limit and plasticity index were other independent variables that have good correlation coefficients with hydraulic conductivity (R~0.80). The correlation coefficient with swell index is less than other parameters, but still fairly good (R~0.70). In contrast, hydraulic conductivity had poor correlation coefficients with specific surface area (SSA), smectite content and cation exchange capacity (CEC) (i.e., R < 0.5). Furthermore, some post-test properties of bentonite such as final height and final water content were correlated with the hydraulic conductivity as well. The hydraulic conductivity of GCLs had fairly good correlation coefficients with either final height or final water content. However, those of AP-GCLs had poor correlations with these variables on account of fiber free characteristics.