• Journal of radiological science and technology
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• v.29 no.3
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• pp.167-175
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• 2006

With the recent prevalence of helical CT and multi-slice CT, which deliver higher radiation dose than conventional CT due to overbeaming effect in X-ray exposure and interpolation technique in image reconstruction. Although multi-detector and helical CT scanner provide a variety of opportunities for patient dose reduction, the potential risk for high radiation levels in CT examination can't be overemphasized in spite of acquiring more diagnostic information. So much more concerns is necessary about dose characteristics of CT scanner, especially dose efficient design as well as dose modulation software, because dose efficiency built into the scanner's design is probably the most important aspect of successful low dose clinical performance. This study was conducted to evaluate z-axis geometric dose efficiency in single detector CT and each level multi-detector CT, as well as to compare z-axis dose efficiency with change of technical scan parameters such as focal spot size of tube, beam collimation, detector combination, scan mode, pitch size, slice width and interval. The results obtained were as follows ; 1. SDCT was most highest and 4 MDCT was most lowest in z-axis geometric dose efficiency among SDCT, 4, 8, 16, 64 slice MDCT made by GE manufacture. 2. Small focal spot was 0.67-13.62% higher than large focal spot in z-axis geometric dose efficiency at MDCT. 3. Large beam collimation was 3.13-51.52% higher than small beam collimation in z-axis geometric dose efficiency at MDCT. 4. Z-axis geometric dose efficiency was same at 4 slice MDCT in all condition and 8 slice MDCT of large beam collimation with change of detector combination, but was changed irregularly at 8 slice MDCT of small beam collimation and 16 slice MDCT in all condition with change of detector combination. 5. There was no significant difference for z-axis geometric dose efficiency between conventional scan and helical scan, and with change of pitch factor, as well as change of slice width or interval for image reconstruction. As a conclusion, for reduction of patient radiation dose delivered from CT examination we are particularly concerned with dose efficiency of equipment and have to select proper scanning parameters which increase z-axis geometric dose efficiency within the range of preserving optimum clinical information in MDCT examination.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12C
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• pp.1652-1659
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• 2004

In this paper, we propose the algorithm that automatically measures the height of the object to move on the base plane by using the geometric information. To extract a moving object from real-time images creates the background image and each pixel is modeled by the three values. The extracted region is represented by cardboard model and calculates the coordinate center in the each part. The top and bottom point of an object are extracted by the calculated coordinate center and an iterative computation. The two points, top and bottom, are used for measuring the height. Given the vanishing line of the ground plane, the vertical vanishing point, and at least one reference height in the scene; then the height of any point from the ground may be computed by specifying the image of the point and the image of the vertical intersection with the ground plane at that point. Through a confidence valuation of the height to be measured, we confirmed similar actual height and result in the simulation experiment.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.61-69
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• 2009

By the advent of the high resolution satellite imagery, a ground-coverage included by a single satellite image is decreased. By the reason, there are increasing needs in image mosaicking technology to use images to various GIS fields. This paper describes an edge-based seamline extraction algorithm using edge information such as rivers, roads, buildings for image mosaicking. For this, we developed a method to track and link discontinuous edges extracted by edge detection operator. To estimate the effectiveness of the proposed algorithm, we applied the algorithm to IKONOS, KOMPSAT-1 and SPOT-5 satellite images. The experimental results showed that the algorithm successfully dealts with discontinuities caused by geometric differences in two images.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.45-53
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• 1995

목적 : 뇌정위 방사선수술은 AVM(ateriovenous malformation)이나 작은 크기의 종양에 1회에 고선량의 방사선을 조사하는 기술이다. 선형가속기를 이용한 방사선 수술을 하기 위하여 최근 본원에 설치한 Philips SL 75-5 선형가속기와 isocentric sub system(ISS)에 의한 뇌정위 방사선 수술에 있어서 표적의 위치선정과, gantry와 couch의 회전시 기하학적 오차가 중요시 되는데 isocentric sub system의 오차를 분석 하였다. 대상 및 방법 : 방사선원으로는 Philips SL 75-5 선형가속기의 5MV 광자선을 사용하였고, 원형의 작은 광자선속을 위하여 isocenter에서의 직경이 26mm인 secondary cone을 gimbal baaring에 삽입하여 사용하였다. 표적의 크기와 좌표를 정하기 위하여 CT나 angio localizer를 이용하고, 표적좌표 선정을 위하여 BRW phantom base와 target pointer를 이용하여 임의의 BRW-coordinator를 바꾸어 가면서 gantry angle와 ISS head 각도를 임의로 바꾸어 가면서 film에 방사선을 조사하였다. 흑화된 film을 view box 위에 놓고 광학판독기구로 film 가장자리의 오차를 scale 확대경으로 측정하여 오차를 분석하였다. 결과 : 표적좌표 선정의 정확도를 확인하기 위하여 임의의 표적좌표에 gantry의 10개각도 ISShead의 10개각도에서 각각 광자선을 조사시켜 film을 이용하여 오차를 측정한 결과 collimator cone의 직경이 26mm일때 전체 평균오차가 0.219+-0.03mm이었다. 결론 : Isocentric sub system은 gantry head와 ISS arm 사이에 gimbal bearing이 있어서 이 부위를 flexible하게 연결함으로 gantry의 회전에 무관하게 정확한 isocenter를 유지시켜 주고 ISS head는 couch와 독립되어 움직이므로 isocentric sub system isocenter의 오차를 최대한 줄일수 있음을 알았다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.499-506
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• 2022

For autonomous ships to be commercialized and be able to navigate in coastal water, they must be able to detect maritime obstacles. One of the most common obstacles seen in coastal area are the farm buoys. In this study, a maritime object detection system was developed that detects buoys using the YOLO algorithm and visualizes the distance and bearing between buoys and the ship through geometric interpretation of camera images. After training the maritime object detection model with 1,224 pictures of buoys, the precision of the model was 89.0%, the recall was 95.0%, and the F1-score was 92.0%. Camera calibration had been conducted to calculate the distance and bearing of an object away from the camera using the obtained image coordinates and Experiment A and B were designed to verify the performance of the maritime object detection system. As a result of verifying the performance of the maritime object detection system, it can be seen that the maritime object detection system is superior to radar in its short-distance detection capability, so that it can be used as a navigational aid along with the radar.

• Education of Primary School Mathematics
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• v.21 no.2
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• pp.209-221
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• 2018

Angle concepts have a multifaceted nature such as quantitative aspects as the amount of rotation, qualitative aspects as geometric shapes, and relationship aspects made with planes or lines. This study analysed angle concepts and introduction methods of angles in elementary mathematics textbooks which have been used from the Syllabus Period to the 2015 Revised Mathematics Curriculum. First, the concepts of angles in mathematics textbooks focus through the definitions, representations, and components of angles presented in mathematics textbooks are analyzed. Secondly, how various aspects of each angle are sequenced through the tasks or activties in the introduction of lesson is looked. As a result of analysis, the methods of introducing angles in the changes of mathematics textbooks have mainly focused on learning about geometric shapes and relations of components. In the mathematics classroom, students should experience various aspects of geometric shapes, rotations, relational aspects of points, lines and surfaces, and support and link them to form a wide range of concepts.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1377-1383
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• 2008

Parameterization of a 3D triangular mesh is a fundamental problem in various applications of geometric modeling and computer graphics. There are two major paradigms in mesh parameterization: energy functional minimization and the convex combination approach. In general, the convex combination approach is wifely used because of simple concept and one-to-one mapping. However, the approach has some problems such as high distortion near the boundary and time complexity. Moreover, the stability of the linear system may not be preserved according to the geometric information of the mesh. In this paper, we present an extension of the convex combination approach based on the mean value coordinates, which resolves the drawbacks of the convex combination approach. This may be a more practical solution because it is able to generate a stable linear system in a short time.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.4
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• pp.81-88
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• 2007

The geometry of satellite image captured by linear CCD sensor is different from that of frame camera image. The fact that the exterior orientation parameters for satellite image with linear CCD sensor varies from scan line by scan line, causes the difference of image geometry between frame and linear CCD sensor. Therefore, we need the epipolar geometry for linear CCD image which differs from that of frame camera image. In this paper, we proposed a method of resampling linear CCD satellite image in epipolar geometry under the assumption that image is not formed in perspective projection but in parallel projection, and the sensor model is a 2D affine sensor model based on parallel projection. For the experiment, IKONOS stereo images, which are high resolution linear CCD images, were used and tested. As results, the spatial accuracy of 2D affine sensor model is investigated and the accuracy of epipolar resampled image with RFM was presented.

• Journal of Korean Society for Geospatial Information Science
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• v.7 no.1 s.13
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• pp.41-52
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• 1999

In order to correct mismatches between neighboring digital maps, the middle line method has been widely used. However, it may result in not only a corruption of the topological consistency between the objects near to boundaries but also degeneration of accuracy. In this paper, we propose two edge-matching methods to overcome the problem of the middle line method. The first method is based on the rubber sheeting, which performs an elastic transformation for the objects located around the boundaries. The second method transforms the geometry of objects by the function of the distance from the boundary. These methods have important advantages that they preserve the topology of the original maps and improve tile accuracy, compared with the previous methods.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.6 no.1
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• pp.25-34
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• 1988

Digital Terrain Model is composed of two basic elements, namely, sampling and interpolation. They represent the procurement of data and the geometric reconstruction of terrain relief respectively. For evaluation DTM data, following two paremeters appear to be the most important factor, that is, the accuracy and efficiency and, in particular, the break point information significantly affect to the accuracy of DTM data. The main objective of this study is to improve the accuracy and efficiency of DTM by applying Progressive Sampling with distinct morphologic information. In this study, the total of 240 individual numerical tests has been implemented and the appropriate computer program is also developed for the test. The result of investigation shows that the Progressive Sampling with break point information improves the accuracy of DTM by 30 percent approximately.