• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.223-228
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• 2008

In order to acquire the images requested by users, it is very important to calculate mission schedule parameters such as imaging execution time and attitude tilt angle accurately. These parameters are based on orbit prediction. This paper describes the accuracy of orbit propagation for image planning. The orbit prediction data from PSS and MAPS has a certain discrepancy due to different orbit propagator. It is necessary for mission planner to confirm this value during mission planning phase. The pointing error which means the difference between target center and real image received is calculated and analyzed using KOMPSAT-2 image data.

• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.373-379
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• 2018

The purpose of this study was to investigate quantitative data on the difference in breast entrance surface dose with changes in focus-film distance, patient posture (anteroposterior-posteroanterior), thoracic wall thickness, rib bone thickness, lung tissue thickness, tube voltage, and high-voltage rectification method in Whole Spine Scanography, which is necessary for the treatment of scoliosis patients. Given a tube voltage of 90 kVp, kerma of 0.1 mGy, focus-film distance of 260 cm, tube voltage ripple rate of 0, filter thickness of 3.5 mm, and thickness of patient's thoracic wall of 120 mm as an X-ray exposure condition, from the simulation results using the Simulation of X-ray Spectra program to confirm the reduction effect of breast entrance surface dose according to the patient's posture (AP and PA), there was a dose reduction effect in aluminum filter thickness of 2.6 times at 3.5 mm, 25.7 times the thoracic wall thickness at 120 mm, 1.43 times higher tube voltage, and 0 to 1.14 times the tube voltage ripple rate. The total dose reduction effect was about 109 times. In order to confirm the dose reduction effect of RANDO phantom posture (AP and PA), from the results of the measurements taken under the conditions that the focus-film distance was 260 cm, the tube voltage was 90 kVp, the tube current was 270 mA, the exposure time was 0.31 sec, and the tube voltage ripple rate of X-ray generators was 0, the entrance surface dose reduction effect of the breast in the PA position was found to be 20.56 times lower than that of the AP position.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.899-900
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• 2017

본 논문에서는 도로주행 영상 내에서 차선을 검출하는 알고리즘을 제안한다. 제안하는 알고리즘은 차량 내부 카메라로 촬영된 영상에 대하여 바타차야 거리를 이용해 차선 후보 영역을 검출한다. 검출된 영역에 대해 도로와 차선의 레퍼런스 RGB 값과의 바타차야 거리를 이용해 분류한 뒤, 차선이 갖는 특징을 모델링하여, 분류된 영역에서 차선으로 추정되는 영역만을 남긴다. 차선 영역 세그먼트의 흰 차선과 노란 차선의 클래스와의 유사도를 계산하여 검출된 차선정보를 제공한다.

• Journal of Convergence for Information Technology
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• v.9 no.6
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• pp.7-12
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• 2019

In order to shoot underwater, the photographer must be equipped with shooting equipment and enter into the water. Since the photographer directly enters the water, safety accidents occur frequently due to various obstacles or deep water in the water. The proposed underwater stereo photography technique can solve the safety accident problem caused by the entry of the photographer into the water by using the drone for underwater photographing. In addition, this technique has the advantage of obtaining underwater images at low cost. In this study, the angle of the proposed cam for stereoscopic photography was analyzed and the condition that the proper stereoscopic image can be viewed was defined as the distance from the floor of 18cm to the floor distance of 41.4cm. This provision is proposed to be used to adjust the height of the shooting area descended by the elevation chain of the water surface hovering drones.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.3
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• pp.317-326
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• 2011

The mental foramen and anterior loop of the mandibular canal are important landmarks for mandibular surgical procedures. The purpose of this study was to analyze the shape and position of the mental foramen and anterior loop of the mandibular canal on the computed tomography (CT) images, and apply the results clinically. CT images of 96 patients (33 male, 36 female, age range 17~43 years, mean $24.6{\pm}4.99$ years) were enrolled. The horizontal and vertical position of the mental foramen, as well as the distance from the root apices were measured. The distance of the anterior loop of the mandibular canal to the root apices, and the buccal angle were measured. The mental foramen was found mostly below the second premolar observed in 81 cases (46.0%), between the first and second premolars in 67 cases (38.0%), and between the second premolar and first molar in 19 cases (10.2%). The mean distance between the mental foramen and the lower border of the mandible was $12.20{\pm}1.77$ mm, the mean distance between the mental foramen and root apex was $5.16{\pm}0.98$ mm. The mean distance of the anterior loop of the mandibular canal was $5.80{\pm}2.00$ mm. The buccal angle measured at $47.7{\pm}9.07^{\circ}$. The distance between the root apex and mental foramen measured as $5.16{\pm}0.98$ mm on panoramic radiography, and $6.2{\pm}3.07$ mm on CT. The mean distance between the mental foramen and mandibular canal was $5.39{\pm}1.62$ mm. When performing surgical procedures such as installing dental implants, it is important to minimize surgical trauma, especially the risk of damage to the mental nerve. To optimize the surgical outcome, a careful assessment of the shape and position of the mental foramen and the anterior loop of the mandibular canal must be made. CT images are useful for finding such anatomic structures.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.8 no.2
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• pp.23-29
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• 1990

Non-metric camera is more profitable than metric camera for geometric analysis of small and elaborate structures, because focal length control of non-metric camera is flexible while generally metric camera has limited focal length. And if the problem of conventional method requiring much time and endeavor to measure three dimensional positions of control points will be solved effectively, it is possible to analyze very close-range photogrammetry more easily and quickly. The purposes of this study are to propose the efficiency of non-metric camera and to reduce difficulty of control survey sharply by introducing self-control survey method. For these, very close-range photographs of the small object were obtained by using non-metric camera calibrated for systematic errors and then bundle adjustment is used for analysis procedure. As a result, the superiority of non-metric camera in analyzing very close-range photographs and the application proptriety of self-control survey were proved, therefore it is expected to be able to apply to precise analysis of small structures or spearhead parts.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.71-71
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• 2015

표면영상유속계(Surface Image Velocimety, SIV)는 하천 표면의 영상을 분석하여 유속을 산정하는 매우 실용적이며 간편한 유속측정 방법이다. 그러나 표면영상유속계는 수표면의 움직임을 계산하여 표면유속을 산정하기 때문에 빛이 없는 야간의 경우 수표면의 움직임을 촬영하기 어려워 밤에 발생하는 홍수 유량 측정이 어려운 단점이 있다. 이를 해결하기 위해 수표면에 야광 입자를 흘려 촬영하는 방법이 있었으나 대하천의 경우 야광물질의 크기가 작아 영상 내에서 식별이 어려운 문제가 있었고, 높은 밝기의 조명을 사용하여 영상을 획득하는 방법 또한 수행되었으나 빛이 수표면에 반사되어 하천 전체를 촬영하기 어려운 문제점이 있었다. 이 후 근적외선 카메라를 이용하여 야간 측정의 어려움을 극복하고자 하였으나 촬영범위가 최대 50 m 정도로 조사 거리의 한계를 나타내었다. 최근 Fujita(2013)는 원적외선카메라를 이용한 하천 유량 측정을 실시하였는데 이는 기존 야간촬영 시 시도되었던 방법의 문제점을 해결할 수 있음을 보여주었다. 이에 본 연구에서는 원적외선 카메라를 이용한 표면영상유속계의 적용성을 검토하고자 실험수로에서 실험을 수행하였다. 실험 시 주간 및 야간의 상황을 설정하여 원적외선 카메라, 근적외선 카메라 그리고 일반 캠코더를 이용하여 흐름을 촬영하였다. 또한 프로펠러유속계를 이용하여 흐름의 표면유속을 측정하였다. 원적외선 카메라를 이용하여 촬영된 영상을 상호상관법을 이용하여 표면유속을 측정하였고, 이를 프로펠러유속계 측정결과와 비교하여 정확도를 검토하였다. 또한 일반 캠코더와 근적외선카메라의 영상 분석 결과와도 비교하여 개선점을 확인하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.541-547
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• 2017

Climate change has become the main cause of the exacerbation in natural disasters. Social Overhead Capital(SOC) structure needs to be checked for displacement and crack periodically to prevent damage and the collapse caused by natural disaster and ensure the safety. For efficient structure maintenance, the optical image technology is applied to the Structure Health Monitoring(SHM). However, optical image is sensitive to environmental factors. So it is necessary to verify its validity. In this paper, the accuracy of estimating the vertical displacement was verified with respect to environmental condition such as natural light, measurement distance, and the number of image sheets. The result of experiments showed that the effect of natural light on accuracy of estimating vertical displacement was the greatest of all. The measurement angle which was affected by the change in measurement distance was also important to check the vertical displacement. These findings will be taken into account by applying appropriate environmental condition to minimize errors when the bridge was measured by camera. It will also enable the application of optical images to the SHM.

• Korean Journal of Cleft Lip And Palate
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• v.5 no.2
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• pp.109-112
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• 2002

구순 구개열 환자의 악교정 성형수술로 구강내 Le Fort II 골절단술이나 비중격 성형술이 많이 이용되는데, 이때 비골의 외측골절단술을 요하며, 이에 대한 술 후 합병증으로 비루관의 폐쇄나 비골의 분쇄골절 등이 발생할 수 있어, 악안면기형 환자를 다루는 구강악안면외과의사에게 비루관의 웅용해부학적 연구는 중요하다. 본 연구의 목적은 교합면을 기준으로 촬영된 컴퓨터 단충 촬영에서 비루관의 위치와 크기를 조사하는데 있다. 2000년 7월부터 2003년 2월까지 서울대학교병원 구강악안면방사선과에서 컴퓨터 단층촬영을 시행한 환자 62명을 대상으로 비상악봉합선에서 비루관까지의 최단거리와 비루관의 최대반경과 최소반경을 측정하였다. 우측비상악 봉합선에서 비루관까지의 거리는 5.68mm이고, 좌측은 5.67mm였다. 좌우 및 성별간의 차이는 없었다. 이의 해부학적 지견은 악기형 수술시의 비루관 폐쇄라는 합병증의 예방책으로 기여하리라 생각된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.400-406
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• 2006

Knowledge of camera parameters, such as position, orientation and focal length, is essential to 3D information recovery or virtual object insertion. This paper analyzes the error sensitivity of focal length due to position error of feature points which are employed for self-calibration. We verify the dependency of the focal length on the distance from the principal point to feature points with simulations, and propose a criterion for feature selection to reduce the error sensitivity.