• 대한치과보철학회지
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• 제45권5호
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• pp.633-643
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• 2007

Statement of problem: Recently there are on an increasing trend of using implants-especially in edentulous mandible of severly alveolar bone recessed. Purpose: The aim of this study was to analyze the displacement and stress distribution of various mandibular implant-retained overdenture models supported by two implants in interforaminal region under the occlusion scheme load. Material and method: FEA models were made by the 3D scanning of the edentulous mandibular dentiform. The three models were named as Model M1, M2, and M3 accord ing to the position of implants: M1, Lt. incisor area, M2, Canine area, and M3, 1st Premolar area. Inter-implant angulation model was named as M4. Conventional complete denture was named M5 and used as a control group. Ball implant and Gold matrice were used as a retentive anchors. The occlusion type loads were applied horizontally over each tooth. Results: 1. In mandibular implant retained overdenture Canine Protected Occlusion type load resulted in higher levels of stress to the implants and female matrices than other types of loads. 2. The overdenture model M1, with implants in lateral incisor areas resulted in lower stress concentration to the implants and female matrices than other models. 3. In mandibular implant retained overdenture the stresses of the implant and female matrice were lower in mesially inclined implant than these of parallel installed implant. Conclusion: Lateral incisor areas could be the best site for the implants in mandibular implant-retained overdenture. The mandibular implant retained overdenture models mentioned above showed to the lowest stress to the implants and female matrices.

• 대한원격탐사학회지
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• 제26권3호
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• pp.347-359
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• 2010

Ortho-photos provide valuable spatial and spectral information for various Geographic Information System (GIS) and mapping applications. The absence of relief displacement and the uniform scale in ortho-photos enable interested users to measure distances, compute areas, derive geographic locations, and quantify changes. Differential rectification has traditionally been used for ortho-photo generation. However, differential rectification produces serious problems (in the form of ghost images) when dealing with large scale imagery over urban areas. To avoid these artifacts, true ortho-photo generation techniques have been devised to remove ghost images through visibility analysis and occlusion detection. So far, the Z-buffer method has been one of the most popular methods for true ortho-photo generation. However, it is quite sensitive to the relationship between the cell size of the Digital Surface Model (DSM) and the Ground Sampling Distance (GSD) of the imaging sensor. Another critical issue of true ortho-photo generation using high resolution satellite imagery is the scan line search. In other words, the perspective center corresponding to each ground point should be identified since we are dealing with a line camera. This paper introduces alternative methodology for true ortho-photo generation that circumvents the drawbacks of the Z-buffer technique and the existing scan line search methods. The experiments using real data are carried out while comparing the performance of the proposed and the existing methods through qualitative and quantitative evaluations and computational efficiency. The experimental analysis proved that the proposed method provided the best success ratio of the occlusion detection and had reasonable processing time compared to all other true ortho-photo generation methods tested in this paper.

• 한국산학기술학회논문지
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• 제20권11호
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• pp.305-313
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• 2019

최근 드론을 이용한 공간정보 구축이 활성화되면서 공간정보 산업발전에 많은 기여를 하고 있다. 하지만 드론 공간정보는 카메라의 중심투영에 의한 발생하는 폐색영역 뿐 아니라 가로수, 보행자, 현수막과 같은 적치물에 의한 폐색 영역이 필연적으로 발생한다. 이러한 폐색영역을 효율적으로 해결하기 위한 다양한 방안이 연구되고 있다. 본 연구에서는 폐색영역 해결을 위해 원초적인 재촬영이 아닌 딥러닝 알고리즘을 적용하기 위한 다양한 알고리즘별 조사 및 비교 연구를 수행하였다. 그 결과, 객체 검출 알고리즘인 HOG부터 기계학습 방법인 SVM, 딥러닝 방식인 DNN, CNN, RNN까지 다양한 모델들이 개발 및 적용되고 있으며, 이 중 영상의 분류, 검출에 가장 보편적이고 효율적인 알고리즘은 CNN 기법임을 확인하였다. 향후 AI 기반의 자동 객체 탐지와 분류는 공간정보 분야에서 각광받는 최신 과학기술이다. 이를 위해 다양한 알고리즘에 대한 검토와 적용은 중요하다. 따라서, 본 연구에서 제시하는 알고리즘별 적용 가능성은 자동으로 드론 영상의 폐색영역을 탐지하고 해결할 수 있어 공간정보 구축의 시간, 비용, 인력에 대한 효율성 향상에 기여할 것으로 판단된다.

• 구강회복응용과학지
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• 제38권4호
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• pp.204-212
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• 2022

목적: 수면이갈이 환자에서 한달 간 수면 시 교합안정장치를 장착하였을 때 교합력과 교합 접촉 면적 및 동기능적교합분석의 변화량을 비교하고자 하였다. 연구 재료 및 방법: 2021년 10월부터 2022년 7월까지 연세대학교 치과대학병원 구강내과 외래에 방문한 수면이갈이 환자 30명 중 교합안정장치를 수면 중 착용하는 실험군(treatment; n = 15)과 교합안정장치를 착용하지 않는 대조군(control; n = 15)으로 구성하였다. 교합안정장치 장착 전, 장착 1개월 후에 교합력 검사와 동기능적교합분석(측방, 전후방 하악 운동 시 좌/우 힘의 균형, 평균 교합력, 최대 교합력, 최대 접촉 개수)을 진행하였다. 결과: 한달 간 수면 중 교합안정장치를 착용하는 실험군과 교합안정장치를 착용하지 않는 대조군에서 교합력과 교합 접촉 면적은 차이가 없었으나 측방 및 전후방 운동에서 평균 교합력과 최대 교합력, 전후방 운동에서 최대 접촉 개수가 유의한 차이가 있었음을 관찰하였다. 결론: 교합안정장치가 측방, 전후방 운동을 하는 이갈이 환자에게 도움이 될 것으로 사료되며, 향후 추가적으로 대단위 집단을 대상으로 하는 이중 맹검연구가 필요할 것으로 사료된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.2796-2798
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• 2005

This Paper presents a method that a mobile robot can track persons in complex environment using particle filters. The topic of person following using mobile robot is researched in many different areas. The main problems of following a person are real time constraint, motion change of person during the tracking and occlusion with other objects. We present appearance adaptive models in a particle filter to realize robust visual tracking algorithm. Adaptive appearance model can handle occlusion with other people while target is moving.

• 대한의생명과학회지
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• 제11권3호
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• pp.307-310
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• 2005

Cerebral ischemia results in neuronal changes in remote areas that have fiber connections with the ischemic area. The aim of this study was to investigate the nigral changes by examining the correlation between the apparent diffusion coefficient (ADC) and the tissue structure. Sprague-Dawley rats were subjected to middle cerebral artery occlusion. Four days after the occlusion, when T2-weighted images revealed the presence of an area of high signal intensity in the ipsilateral substantia nigra, and the ADCs were calculated and imaged. Histopathologic examination by both light and electron microscopy was performed on day 4 after surgery. This finding was consistent with the high signal intensity seen on T2-weighted and diffusion-weighted images, as well as with the ADC reduction, but we did not expect to observe uniform ADC reduction attributable mainly to astrocytic swelling in the perivascular end-feet.

• 한국CDE학회논문집
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• 제19권1호
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• pp.68-79
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• 2014

Human model simulation has been widely used in various industrial areas such as ergonomic design, product evaluation and characteristic analysis of work-related musculoskeletal disorders. However, the process of building digital human models and capturing their behaviors requires many costly and time-consuming fabrication iterations. To overcome the limitations of this expensive and time-consuming process, many studies have recently presented a markerless motion capture approach that reconstructs the time-varying skeletal motions from optical devices. However, the drawback of the markerless motion capture approach is that the phenomenon of occlusion of motion data occurs in real-time human simulation. In this study, we propose a systematic method of discriminating missing or inaccurate motion data due to motion occlusion and interpolating a sequence of motion frames captured by a markerless depth camera.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.305.1-305.1
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• 2002

The temporal profiles of the changes of dopaminergic cell and microglial activation induced by transient cerebral ischemia was investigated in the substantia nigral region which lay outside ischemic areas of rat brain after middle cerebral artery occlusion (MCAO). Transient cerebral ischemia was induced by intraluminal occlusion of the right middle cerebral artery for 2 hand reperfusion was continued for 1, 2. 3. 7. 10. 14. 30, 60. and 120 days. Activated microglial cells were visualized with immunohistochmistry using OX-43 antibody. (omitted)

• 대한한의학회지
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• 제23권3호
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• pp.134-144
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• 2002

Objective : The purpose of this study was to investigate the effect of Jukryuk and Saengkang-juices on cerebral vascular ischemia (CVI) of the middle cerebral artery (MCA). Method : By admiuistration Jukryuk and Saengkang-juices, we compared treated groups with untreated groups, in view of five points as follows: 1) cerebral damage; 2) damaged area of ischemia; 3) cerebral edema; 4) the number of neuronal cells adjacent to the areas damaged by ischemia; and 5) the number of neuronal cells adjacent to the areas damaged by ischemia Results : In this experiment, the effect of Jukryuk and Saengkang-juices was determined by inducing cerebral vascular ischemia after occluding the middle cerebral artery (MCA) in mice, and making observations and comparisons such as alterations in damaged areas and neuronal cellular changes in the brain. Conclusions : According to the above results, Jukryuk and Saengkang-juices can protect the cerebral vascular ischemia.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.371-374
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• 2008

In very high-spatial resolution remote sensing imagery, it is difficult to extract the feature information of various objects because of occlusion and shadows. Moreover, various and feeble information within shadows can be of use in GIS-based applications and remote sensing analysis. In this paper, we developed a radiometric restoration method for shadow areas using KOMPSAT-2 satellite image. After detecting the shadow, non-shadow pixels nearby are extracted using a morphological filter. An iterative linear regression method is applied to calculate the relationship between shadow and non-shadow pixels. The shadows are restored by the parameters of the linear regression algorithm. Tests show that recovery of shadowed areas by our method leads to improved image quality.