• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6284-6289
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• 2013

With the application of k-space trajectory in a different manner and analyzing the influence of noise and its direction, this study was conducted to obtain high-quality images with minimal influence of noise during an MRI examination for cerebrovascular disease, which has a low signal for imaging. To evaluate influence of the noise of different k-space trajectories, a linear Cartesian coordination trajectory and non-Cartesian coordination trajectory were applied to 38 people who had received a high-resolution MRI examination for the early detection of cerebrovascular disease. As a result, the non-Cartesian coordination trajectory showed a 43.32% lower signal of lumens in the internal carotid artery than a linear Cartesian coordination trajectory, and the noise level was also 50.19% lower in a non-Cartesian coordination trajectory. This result shows that noise occurs less in a non-Cartesian coordination trajectory than a linear Cartesian coordination trajectory, and a non-Cartesian coordination trajectory is more effective in low-signal and low-resolution MRI examination. Therefore, when performing high-resolution MRI examination with a low-signal cerebrovascular system, the use of non-Cartesian coordination k-space trajectory will minimize the influence of noise and provide good images.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.183-196
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• 1998

The Synthetic Aperture Radar(SAR) image and the Digital Elevation Model(DEM) of an target area are put into use to generate three dimensional image map. An method of image map generation is explained. The orbit and attitude determination of satellite makes it possible to model signal acquisition configuration precisely, which is a key to mapping image coordinates to geographic coordinates of concerned area. An application is made to RADARSAT in the purpose of testing its validity. To determine the orbit, zero Doppler range is used. And to determine the attitude, Doppler centroid frequency, which is the frequency observed when target is put in the center of antenna's view, is used. Conventional geocoding has been performed on the basis of direct method(mapping image coordinates to geographic coordinates), but in this reserch the inverse method(mapping from geographic coordinates to image coordinates) is taken. This paper shows that precise signal acquisition modeling based on the orbit and attitude determination of satellite as a platform leads to a satellite-centered accurate geocoding process. It also shows how to model relative motion between space-borne radar and target. And the relative motion is described in ECIC(earth-centered-initial coordinates) using Doppler equation and signal acquisition geometry.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.303-310
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• 2009

We processed seven years data of 142 IGS(International GNSS Service) stations were processed, which have been selected with an optimal network algorithm, to realize terrestrial reference system. To verify the result, a comparison with the ITRF2005 was given both in positions and velocities with transformation parameters estimation. The transformation parameters are within 4.3 mm in length, while the RMS(root mean square) difference of positions and velocities are 6.7 mm and 1.3 mm/yr in horizontal and 13.3 mm and 2.4 mm/yr in vertical, respectively, which represent good coincidences with ITRF2005. This research would help developing our own geodetic reference frame and may be applied for the global earth observations such as the global tectonics. A further improved TRF would be expected by applying various data processing strategies and with extension of data in number and observation period.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.57-67
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• 2005

Fast scalar multiplication of points on elliptic curve is important for elliptic curve cryptography applications. In order to vary field sizes depending on security situations, the cryptography coprocessors should support variable length finite field arithmetic units. To determine the effective variable length finite field arithmetic architecture, two well-known curve scalar multiplication algorithms were implemented on FPGA. The affine coordinates algorithm must use a hardware division unit, but the projective coordinates algorithm only uses a fast multiplication unit. The former algorithm needs the division hardware. The latter only requires a multiplication hardware, but it need more space to store intermediate results. To make the division unit versatile, we need to add a feedback signal line at every bit position. We proposed a method to mitigate this problem. For multiplication in projective coordinates implementation, we use a widely used digit serial multiplication hardware, which is simpler to be made versatile. We experimented with our implemented ECC coprocessors using variable length finite field arithmetic unit which has the maximum field size 256. On the clock speed 40 MHz, the scalar multiplication time is 6.0 msec for affine implementation while it is 1.15 msec for projective implementation. As a result of the study, we found that the projective coordinates algorithm which does not use the division hardware was faster than the affine coordinate algorithm. In addition, the memory implementation effectiveness relative to logic implementation will have a large influence on the implementation space requirements of the two algorithms.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.10a
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• pp.350-351
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• 2008

현재 우리나라의 측량체계는 크게 측지분야와 지적분야로 이원화되어 있으며 측지분야에서는 2001년도에 측량법을 개정하여 ITRF2000좌표계와 GRS80 타원체를 측량기준으로 사용하는 세계측지계를 도입하였다. 하지만 지적 분야에서는 국민의 재산권과 직접적으로 관련이 있는 필지의 경계와 면적의 변화 연구는 미미한 상태이다. 따라서 본 연구는 2010년 세계측지계 도입 후 지적분야에서 발생할 수 있는 필지별 면적 변동에 따른 사회적 혼란 여부를 판단하기 위하여 서울특별시 종로구 숭인등 숭인4구역주택재개발지구를 연구 대상지로 선정하여 세계측지계 전환에 지적 필지별 면적 변화를 분석하였다. 분석결과 연구대상지는 세계측지계와 지역측지계가 종선(X)축으로 305.87m. 종선(Y)축으로 70.87m 편차로 두 좌표계 간 북동방향으로 313.97m의 차이가 있고, 현행성과와 비교한 결과 종선(X) 방향으로는 평균 +4.0cm, 횡선(Y) 방향으로는 평균 -3.0cm의 차이가 나타났으며, 필지별 면적의 변동량은 $1.0m^2{\sim}3.0m^2$ 차이가 있지만 허용오차 범위 내에 있으므로 세계측지계 전환에는 문제점이 없는 것으로 판단된다. 하지만 본 연구의 결과는 그 대상범위가 한정되어 있고 기 검증된 지적기준점 성과를 사용한 결과이므로, 향후 보다 효율적인 세계측지계 전환과 도입을 위해서는 현 지적기준점체계의 정확한 세계좌표계 변환 성과를 기준으로 한 대단위의 필지별 면적 변동량 및 허용범위 분석과 같은 추가적인 연구가 조속히 이루어져야 할 것으로 판단된다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.1
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• pp.29-39
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• 1997

The need of transformation parameters from local geodetic datums to a geocentric coordinate system is becoming more common, with the increasing application of satellite positioning techniques to LIS/GIS survey with cadastral management. In this paper, the national transformation parameters between the Korean geodetic coordinates which is based on the Bessel 1841 ellipsoid and the WGS84 ellipsoid are determined by the least square methods with weighted parameter constraints. Three-dimensional geocentric coordinates are based on GPS observation at 31 stations in the geodetic network, the datum parameters are computed within a standard deviation of less than 1 meter. In South Korea, the national transformation parameters with Bessel geoid-heights are useful for GPS baseline processing and for middle-scale map/database transformation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.13 no.2
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• pp.117-124
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• 1995

The main purpose of the present study was to investigate coordinate transformation based on two different systems: one was the World Geodetic System 1984(WGS84) adopted as a reference system for GPS satellite surveying;and another was the current Korean geodetic system based on Bessel ellipsoid. For this purpose, three methods were used to determine 7 parameters as follows: Bursa-Wolf model, Molodensky-Badekas model, and Veis model. The coordinate transformation was carried out using simillity transformation applied the obtained 7 parameters and the precision of transformed coordinate was evaluated. From this results, we found that Bursa-wolf model is more suitable than others for the determination of transformation parameters in Korea.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.2
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• pp.269-275
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• 1997

Car Navigation System with Global Positioning System (GPS) can display position direction and the shortest cut of one's destination. The position datum for GPS in World Geodetic System 1984 (WGS-84) coordinates system need to transform Bessel coordinates system and process Map projection. Since 1987, GPS has used the WGS-84. WGS-84 is a geocentric equipotential ellipsoid of revolution which is defined four parameters. In this study, by comparing the digitized topographical map with the digital map of GPS datum we can consider the technique of WGS84 digital map.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.4
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• pp.3-11
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• 2009

Open source is recently much more made and distributed by on-line such as internet in various fields. Therefore, end users could rapidly develop applications needed for some purposes using minimal efforts if use open sources. But, open source must be customized for their purposes. In this paper, we developed software for coordinates conversion and compared the software with NGI Pro which is developed by National Geographic Information Institute. Consequently, it is possible for us to easily develop the coordinates conversion module and we know that the use of open source is effective to develop various applications.

• Journal of Radiation Protection and Research
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• v.31 no.2
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• pp.105-113
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• 2006

The oxidizing species are generated from the radiolysis of groundwater in the pore of buffer material around the canister used for the disposal of spent fuels. A mathematical model was introduced to calculate the cathodic current density induced by the oxidant around the canister, which determined the corrosion of carbon steel. An analytical solution was derived to get the cathodic current density in the cylindrical coordinate. The cathodic current densities from both the rectangular coordinate and cylindrical coordinate were compared with each other. The source terms and absorbed dose rate for the calculation of the radiolysis were calculated using the ORIGEN2 and MCNP computer code, respectively. The radius of the canister was determined with the new model in order to prevent the local corrosion. The results showed that the new solution made the cathodic current density around 25 % lower than the Marsh model.