• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.655-661
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• 2017

Sparse view CT has been widely used to reduce radiation dose to patient in radiation therapy. In this work, we performed sinogram restoration from sparse sampling data by using inpainting method for simulation and experiment. Sinogram restoration was performed in accordance with sampling angle and restoration method, and their results were validated with root mean square error (RMSE) and image profiles. Simulation and experiment are designed to fan beam scan for various projection angles. Sparse data in sinogram were restored by using linear interpolation and inpainting method. Then, the restored sinogram was reconstructed with filtered backprojection (FBP) algorithm. The results showed that RMSE and image profiles were depended on the projection angles and restoration method. Based on the simulation and experiment, we found that inpainting method could be improved for sinogram restoration in comparison to linear interpolation method for estimating RMSE and image profiles.

• Conservation Science in Museum
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• v.14
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• pp.29-35
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• 2013

In cases, such as white porcelain with openwork lotus scroll design, where the ceramics has intricate form and decorations, we normally use casts to restore the work, in that current restoration materials have short molding time which causes difficulties in delicate work. However, since using a cast for restoration requires longer work-time and uses more materials, we decided to restore in direct. Since the molding time in the restoration material is closely related to the workability, restoration material which secures longer work hours is necessary when directly restoring a complex form of body. Therefore we experimented on the work-time, color variation and workability as time passes by making mixtures of Epoxy putty and Baked clay in different ratios. As a result of the experiment, the mixture ratio of OS8:RQ2 turned out to be the most effective ratio.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.654-659
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• 2016

Recently, the passenger ship 'Sewol' capsized with an abrupt inclination while she was making a small angle alteration. It is very important to fully understand the concepts, causes and relevant corrections for a ship's transverse inclination, which is classified into heel, list and loll. In this study, the concept, development and calculation of loll were well considered and the actual magnitude of the angle of loll was simulated in a box-shaped model-ship experiment. The experimental values and its development according to different values of negative stability were compared with calculated values. In the results, experimental values for the angle of loll coincided closely with calculated values and the model inclined symmetrically on both port and starboard sides indicating an outstanding feature of loll. This study is expected to expand the concept of loll and help in the analysis of capsize incidents with unknown causes. Further experimental research or case studies concerning the risk of inappropriate correction for loll arising from misunderstandings will be needed.

• Korean Journal of Heritage: History & Science
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• v.57 no.2
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• pp.6-25
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• 2024

This study concentrated on a report on the results of smelting experiments conducted eight times by the Jungwon National Research Institute of Cultural Heritage, put together the goals and results of the operation, and examined changes in the content of experiments and in the experimental results. First, changes related to operation, such as the ratio of raw materials to fuel and the presence or absence of additives, were reviewed depending on the operation goal. In addition, the results of metallurgical analysis of raw materials, formations, and byproducts were summarized and reviewed by comparing them with materials excavated from the ruins. The operation method varied up to the eighth smelting experiment in terms of iron ore roasting, additives, and raw material/fuel ratio. After reviewing the results again, pure iron with a low carbon content began to be confirmed through metallurgical analysis. As a result, it was confirmed that the charging ratio of raw materials and fuel plays an important role depending on the purpose of production. In addition, most of the products are gray cast iron, and it was deemed that this is due to changes in the internal structure of the pig iron while it was left in the furnace for a long time. The iron was an ingot that was in a molten state even though the carbon content did not reach 4.3%, where the process reaction takes place, and it was deemed to have been caused by excessive operating temperature. Based on the previously reviewed results and the structure and shape of the experimental furnace used in other ironmaking technology restoration experiments, this study finally attempted to restore the structure of an ancient iron smelting furnace, including the furnace's upper structure. By comprehensively referring to the remaining conditions of the excavated iron smelting furnace and the characteristics of the blow pipe, the form of the ancient iron smelting furnace was subdivided into six categories: furnace wall thickness, furnace height, blower height, blow pipe size, furnace inner wall shape, and top shape, and a restoration plan was proposed. To improve the problems of the restoration plan and the Jungwon National Research Institute of Cultural Heritage's experiments that have been conducted through continuous trial and error, an experiment that reflects changes in operating methods by lowering the furnace height and controlling the blowing volume is necessary.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1996.06a
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• pp.237-240
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• 1996

본 논문에서는 방향성을 갖는 새로운 공간적응 조절연산자와 비선형필터를 이용한 제한 반복적 영상복원 알고리듬을 제안하고 제안한 알고리듬의 수렴성에 대하여 분석을 하고 있다. 일반적인 제한반복적 영상복원 기법에서는 열화된 영상을 복원하는 과정에서 에지 및 경계부분의 재번짐이 지나친 잡음성분의 증폭에 의한 고리현상 등이 발생한다. 이러한 문제들을 해결하기 위하여 본 논문에서는 다음과 같은 기법을 도입하고 있다. 첫째는, 방향성을 갖는 새로운 공간적응 조절연산자를 적용하여 에지 등의 재번짐을 막고 고주파수 영역의 복원성능을 개선하고 있다. 둘째로, 적응적인 비선형필터를 사용하여 잡음성분과 같은 고주파수 영역의 지나친 증폭에 따른 문제를 해결하고 있다. 그리고, 제안한 논문의 안정성과 수렴성을 보장하기 위한 조건을 분석하고 있다. 열화된 영상에 대하여 실험한 결과, 기존의 다른 결과보다 우수한 성능이 있었고, 특히, 에지의 복원성능 및 고리현상의 제거에 두드러진 특징을 나타내었다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.407-410
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• 2000

본 논문에서는 3차원 웨이블릿 부호화 방식으로 압축된 영상 시퀸스를 정칙화 기반 영상복원 방법으로 후처리하는 알고리듬을 제안한다. 우선, 웨이블릿 압축 시스템을 적절한 영상 열화 시스템으로 모델화한다. 그리고, 시간축에 관하여 프레임 간의 같은 위치에 있는 각 픽셀에 대하여 복원을 수행한다. 그 다음으로 2차원 영상 신호에 대하여 복원을 수행하는데. 즉 웨이블릿 변환 계수 정보를 이용하여 영상 및 시간 정보를 여러 스케일의 에지로 분류한 다음, 에지의 방향에 따른 적응적인 제약조건을 사용한다. 이는 각각의 에지 방향에 적합한 고주파 성분을 유지하고, 신호의 각 특성에 적합한 적응적인 정칙화 매개변수를 적용한다. 마지막으로 시간 축에서의 복원과 그것에 이어지는 적응적인 공간 복원에 대한 실험 결과를 보여준다.

• The Korean Journal of Applied Statistics
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• v.10 no.2
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• pp.309-323
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• 1997

Although there are many photochemical images of which are censored while they are recorded, normal approaches are often applied to the restorations for them. In this case, it yields a restored image which might have serious bias. However, solutions for this problem are hardly found in the research of image restorations. This article provides a method of image restoration via EM algorithm for the censored images of which are contaminated with Gaussian noise and blur, also presents some results of simulation for artificial images censorized.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.75-77
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• 2016

IMO는 해상에서의 선박 안전 향상을 위해 선박의 복원성능과 조종성능에 관한 국제적 기준을 제시하고 있다. 이러한 기준은 선박 연구자가 수행하는 연구의 방향에도 영향을 미치고 있다. 기존의 수행된 연구는 복원성능과 조종성능의 각각의 분야에서 독립적으로 수행되어 왔으며, 아직 두 분야의 상호 관계에 관한 연구는 미비한 실정이다. 이에 본 논문에서는 선박의 복원성능과 조종성능의 상호 관계를 정량적으로 규명하고자 기초적인 실험 연구를 수행하였다. 이를 위해 복원성능을 나타내는 지표인 GM과 선박의 조종성능을 나타내는 지표인 선회성능을 통해 두 항복 간 상호 관계의 정량적 분석을 시도하였다. 자유항주 모형선을 이용한 선회 시험을 실시하였고, 그 결과 GM 감소에 따른 선회반경 감소 및 초기 횡경사 각도 증가를 확인했으며, 그 변화의 경향은 서로 다르게 나타나는 것을 확인하였다.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.281-286
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• 2007

비디오 복원(video completion)은 비디오 영상에서 색상값에 대한 정보가 없는 픽셀에 적절한 색을 채워 영상을 복원하는 기술이다. 본 논문에서는 움직이는 두 물체가 교차하는 입력영상으로부터 하나의 물체를 제거함으로 발생하는 홀(hole)을 채우는 비디오 복원 기술을 제안한다. 입력 영상에서의 두 물체 중 카메라와 가까운 물체를 제거함으로써 영상의 홀이 발생하게 되고, 이 홀을 다른 프레임들의 정보를 이용하여 채움으로써 가려진 물체를 복원한다. 모든 프레임에 대해 각 물체의 중심을 추정하여 물체의 중심을 기준으로 시-공간 볼륨(spatio-temporal volume)을 생성하고, 복셀 매칭(voxel matching)을 통한 시간적 탐색을 수행한 후 두 물체를 분리한다. 가리는 물체 영역으로 판단 된 부분을 삭제하고 공간적 탐색 방법을 이용하여 홀을 채워 가려짐이 있는 물체를 복원하는 과정을 소개한다. 실험 결과를 통해 제안한 기술이 비교적 자연스러운 결과를 얻을 수 있다는 것을 보여준다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.232-238
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• 2003

In this paper, we propose a spatially adaptive image restoration algorithm using local statistics. The local mean, variance, and maximum values are utilized to constrain the solution space, and these parameters are computed at each iteration step using partially restored image. A parameter defined by the user determines the degree of local smoothness imposed on the solution. The resulting iterative algorithm exhibits increased convergence speed when compared to the non-adaptive algorithm. In addition, a smooth solution with a controlled degree of smoothness is obtained. Experimental results demonstrate the capability of the proposed algorithm.