• The KIPS Transactions:PartB
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• v.13B no.1 s.104
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• pp.35-46
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• 2006

The dynamic change of background and moving objects is an important factor which causes the problem of occlusion in tracking moving objects. The tracking accuracy is also remarkably decreased in the presence of occlusion. We therefore propose an active fusion model which is robust against partial occlusions that are occurred by background and other objects. The active fusion model is consisted of contour-based md region-based snake. The former is a conventional snake model using contour features of a moving object and the latter is a regional snake model which considers region features inside its boundary. First, this model classifies total occlusion into contour and region occlusion. And then it adjusts the confidence of each model based on calculating the location and amount of occlusion, so it can overcome the problem of occlusion. Experimental results show that the proposed method can successfully track a moving object but the previous methods fail to track it under partial occlusion.

• Journal of Biomedical Engineering Research
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• v.23 no.5
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• pp.375-383
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• 2002

Aneurysm embolisation method using coils have been widely used. Micro coils are introduced via a small catheter, and are packed inside of aneurysm sac, which induces intraaneurysmal flow stagnation and thrombus formation. When partial blocking of an aneurysm is inevitable, the location of coils is important since it changes the flow patterns inside the aneurysm, which affect the embolisation process. We measured the flow field inside the partially blocked lateral aneurysm models in vitro, and tried to suggest the effective locations of coils for aneurysm embolisation. Velocity fields are measured using a particle image velocitimeter for different coil locations- proximal neck, distal neck, proximal dome and distal dome. Flow into the aneurysm sac was significantly reduced in the distally blocked models, and coils at distal neck blocked inflow more effectively comparing to those at distal dome. This study suggests that distal neck should be the most effective location for aneurysm embolisation.

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.143-148
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• 2000

레이저 프로파일링 시스템의 등장으로, 기존에는 얻을 수 없었던 도시 지역에 대한 DTM 취득이 가능해졌고, 더욱 정확한 정사투영영상 또한 제작할 수 있게 되었다. 하지만, 높이 변화를 보이는 자연지물과 인공구조물이 있는 지역에 대해 기존의 정사투영사진 제작기법이 적용될 때, 폐색이나 이중매핑과 같은 문제가 발생하게 된다. 특히 고층건물이 밀집되어 있는 도심지에서 이러한 현상은 두드러져 정사투영영상의 품질을 저해하는 주요한 원인이 된다. 따라서, 본 연구에서는 카메라의 외부표정요소와 DTM을 이용하여 폐색영역을 탐지하고, 폐색이 안된 다른 영상의 정보를 통해 폐색영역을 복원하여 더욱 완전한 정사투영을 제작할 수 있는 알고리즘을 제안하였다. 제안된 알고리즘에 의해 자연지물이나 인공고조물에 의한 폐색영역을 탐지할 수 있었고 폐색영역의 많은 부분을 부가영상을 이용하여 복원하였다. 건물에 대한 사전지식을 이용하여 폐색영역을 탐지하는 국내 연구가 있지만, 본 연구는 건물에 대한 부가정보나 모델링을 사용하지 않고 DTM과 카메라 외부표정요소만을 이용하여 폐색영역을 탐지한다는 점에서 이러한 연구들과 차별성을 가진다.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.319-324
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• 2017

Patients with maxillectomy defects predisposed to not only difficulty in deglutition, mastication, speech but also psychological depression from impaired facial esthetics that affect life quality. Obturator prostheses play a important role in restoring the lost form, function and the quality of life for patients with maxillectomy defects. This clinical report presents the simplified approach to predict the degree of adequate facial support by Artificial palate which reflected from a maxillary interim obturator during the stabilization period after maxillectomy.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.295-300
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• 2004

Coil embolization technique has been used recently to treat cerebral aneurysms. When a giant or a multilobular aneurysm are treated by roils, filling an aneurysm sac completely with coils is difficult and partial blocking of an aneurysm sac is inevitable. Blood flow characteristics, which nay affect the embolization process of an aneurysm sac, are changed by the locations of coils for the Partially blocked aneurysms. Blood flow fields are also influenced by the geometry of a parent vessel. In order to suggest the coil locations effective for aneurysm embolization, the blood flow fields of lateral aneurysm models were analyzed for the different coil locations and parent vessel geometries. Three dimensional pulsatile flow fields are analyzed by numerical methods considering non-Newtonian viscosity characteristics of blood. Flow rate into the aneurysm sac (inflow rate) and wall shear stress, which are suspected as flow dynamic factors influencing aneurysm embolization, are also calculated. Inflow rates were smaller and the low wall shear stress zones were larger in the neck blocked models compared to the dome blocked models. Smaller inflow and larger low wall shear stress zones in the distal neck blocked model imply that the distal neck should be the effective coil locations for aneurysm embolization.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.4
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• pp.229-236
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• 2023

Maxillary bone defects may follow surgical treatment of benign and malignant tumors, trauma, and infection. Palatal defects often lead to problems with swallowing and pronunciation from the leakage of air into the nasal cavity and sinus. Obturators have been commonly used to solve these problems, but long-term use of the device may cause irritation of the oral mucosa or damage to the abutment teeth. Utilizing implants in the edentulous area for the fabrication of the obturators has gained attention. This case report describes a patient, who had undergone partial resection of the maxilla due to adenocarcinoma, in need of a new obturator after losing abutment teeth after long-term use of the previous obturator. Implants were placed in strategic locations, and an implant-retained maxillary obturator was fabricated, showing satisfactory results in the rehabilitation of multiple aspects, including palatal defect, masticatory function, swallowing, pronunciation, and aesthetics.

• The KIPS Transactions:PartB
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• v.13B no.7 s.110
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• pp.663-670
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• 2006

For virtual target to be displaying on real image realistically, it is essential to determine the location of the virtual object together with producing the occlusions area after registering two world. In this paper, we propose the new method to solve occlusions which happens during virtual target moves according to the simulated route on real image. For this purpose, we first construct three dimensional virtual world by DEM of experimental area and register CCD camera image on it by visual clues. Next, we also propose a method to solve the occlusion using snake and picking algorithm which can extract the three dimensional information of the position happening occlusion in the image and can use it when target moves that area. In the experiment, we proved the effectiveness of the proposed method in the environment which a partial occlusions happens.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.18 no.1
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• pp.51-57
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• 2000

With the emergence of laser mapping systems, higher resolution DTM of urban area can be acquired and can be used to generate precise orthoimage. But, when the conventional orthoimage generation methods are applied to the area containing features with height difference such as cliffs, bridges, banks. elevated highways and buildings, they cause problems such as occlusion and double mapping. Therefore, this study proposes a new algorithm by modifying and refining conventional orthoimage generation methods. With this algorithm, areas which have occlusion are detected from the base image using camera orientation parameters and DTM. Also, detected areas are restored using alternative images which does not have occlusion in that area. This study can be distinguished from the other studies in the aspects that the proposed algorithm in this paper doesn't need information on building and that uses DTM data and orientation parameters.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.250-250
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• 2015

ASR(Aquifer Storage Recharge) 또는 ASTR(Aquifer Storage Transfer Recharge)과 같은 직접적인 지하수 인공함양기법은 대수층을 활용하여 수자원을 공급하고 관리하기 위한 적극적인 방안으로 고려될 수 있다. 그러나 하천 수와 같은 지표수를 주입할 경우 부유물질 그리고 생물학적 및 화학적 물질 등에 의해 주입정 내 스크린 부분에서 폐색이 발생할 수 있으며, 이로 인해 인공함양 시설의 운영에 있어 부정적인 영향을 미칠 수 있다. 주입정 내 폐색을 저감시키기 위해서는 주기적인 주입정 역세척과 같은 방법이 적용될 수 있다. 본 연구에서는 물리적인 폐색을 발생시키는 부유물질이 포함되어 있는 지표수를 주입할 경우 주입정 내에서의 부유물질의 거동을 수치적 기법을 통해 모의 및 분석을 수행하였다. 본 모의에서는 부유물질을 구성하는 입자들은 세 가지 서로 다른 비중(0.8, 1.3, 1.5)을 가지며, 각각의 경우에 대해 입자분포는 정규분포를 통해 발생시켰다. 비중이 서로 다른 부유입자들은 동시에 주입정 내로 주입된다고 가정하였다. 모의는 비정상상태 조건으로 수행되었으며, 시간에 따라 변화되는 주입정 내 부유물질의 거동에 대해 분석하였다.

• Journal of Broadcast Engineering
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• v.20 no.2
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• pp.265-272
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• 2015

A new technology on video frame rate up-conversion (FRUC) is presented by combining the median filter and motion estimation (ME) with an occlusion detection (OD) method. First, ME is performed to have a motion vector. Then, the OD method is used to refine motion vector in the occlusion region. Since the wrong motion vector can be obtained with high possibility in the occluded area, a median filtering that less depends on the motion vector is applied to that area, and since the motion vector is continuous and robust in the non-occluded area, BDMC(Bi-Directional Motion Compensated interpolation) is applied to obtain interpolated image in that area. BDMC using the bi-directional motion vectors achieves good results when continuity and robustness of the motion vector is higher. Experimental results show that the proposed algorithm provides better performance than the conventional approach. The average gain of PSNR (Peak Signal to Noise Ratio) is approximately 0.16 dB in the test sequences compared with BDMC.