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Performance Improvement of Satellite Navigation System Using Inter-satellite Distance Information
Choi, Moonseok,Ahn, Jongsun,Sung, Sangkyung,Jang, Jaegyu,Lee, Young Jae The Korean Society for Aeronautical Space Sciences 2018 International Journal of Aeronautical and Space Sc Vol.19 No.2
A satellite navigation system calculates the position of a user using measurement values from a satellite, receiver, and broadcast ephemeris, which provides position information about the navigation satellite. However, in scenarios where it is difficult to secure sufficient satellite visibility, such as in a downtown area, the position accuracy of a global navigation satellite system is reduced. This study proposes a navigation algorithm for improving the accuracy of navigation using a measurement value in addition to the existing pseudorange measurement. A user who cannot secure a sufficient navigation visibility uses a standalone scheme that depends exclusively on the pseudorange measurement to estimate the position. The proposed method uses a position estimation algorithm that uses the measured value of the distance between satellites and geometric relation between users to construct a measurement equation, and combines this with the existing pseudorange measurement equation. The results obtained from static and dynamic experiments verify the superior performance of the proposed navigation algorithm.
Performance Improvement of Satellite Navigation System Using Inter-satellite Distance Information
Moonseok Choi,Jongsun Ahn,Sangkyung Sung,Jaegyu Jang,Young Jae Lee 한국항공우주학회 2018 International Journal of Aeronautical and Space Sc Vol.19 No.2
A satellite navigation system calculates the position of a user using measurement values from a satellite, receiver, and broadcast ephemeris, which provides position information about the navigation satellite. However, in scenarios where it is difficult to secure sufficient satellite visibility, such as in a downtown area, the position accuracy of a global navigation satellite system is reduced. This study proposes a navigation algorithm for improving the accuracy of navigation using a measurement value in addition to the existing pseudorange measurement. A user who cannot secure a sufficient navigation visibility uses a standalone scheme that depends exclusively on the pseudorange measurement to estimate the position. The proposed method uses a position estimation algorithm that uses the measured value of the distance between satellites and geometric relation between users to construct a measurement equation, and combines this with the existing pseudorange measurement equation. The results obtained from static and dynamic experiments verify the superior performance of the proposed navigation algorithm.
Kitae Kim,Sangkyung Choen,Jaewoo Hwang,Moonjung Jang,Junghee Yoon,Mincheol Choi 한국임상수의학회 2018 한국임상수의학회지 Vol.35 No.6
A 7-year-old intact female Shih-Tzu with chylothorax was presented. Percutaneous popliteal computedtomographic lymphangiography was performed to evaluate the thoracic duct and seek any potential cause of chylothorax. Despite two attempts, visualization of the thoracic duct failed and perianal subcutaneous computed tomographiclymphangiography with injection of iodinated, nonionic water-soluble contrast medium (0.6 ml/kg) was performed. Asingle branch of intact thoracic duct and dilated and tortuous lymphatics were detected. It was diagnosed as idiopathicchylothorax. Perianal subcutaneous lymphangiography is considered a less-invasive, easy and reliable method tovisualize lymphatics in patients with chylothorax.
복합소재 Woven CFRT를 이용한 프론트 범퍼빔 개발 연구
최희동(Heedong Choi),이태민(Taemin LeeGiltong),이은호(Eunho Lee),한상경(Sangkyung Han),강창모(Changmo Kang) 한국자동차공학회 2016 한국자동차공학회 학술대회 및 전시회 Vol.2016 No.11
This paper discusses that development of front bumper beam using woven CFRT(Continuous fiber reinforced thermo plastic), also introduce the procedure to design optimized structure with light weight material. The optimum design has been reached by DFSS and CAE, and the performance proved low speed and high speed crash test. Through comparing with the performance of conventional high strength steel bumper beam, woven CFRT bumper beam has been verified to be one of the prospective alternative as a light weight solutions
Clinical Efficacy and Complications of Intraocular Lens Exchange for Opacified Intraocular Lenses
Seung Mo Kim,Sangkyung Choi 대한안과학회 2009 Korean Journal of Ophthalmology Vol.23 No.1
Purpose: To evaluate the clinical efficacy and complications of intraocular lens (IOL) exchange. Methods: A review of medical records was performed for 52 eyes that had undergone an IOL exchange due to IOL opacification. Surgical complications and their incidences were analyzed. The mean best corrected visual acuity (BCVA) after the IOL exchange was compared with the mean pre-exchange BCVA and with the mean BCVA after the initial IOL implantation. Prediction error of refraction and biometric data obtained for the IOL exchange were, if available, compared with those obtained for the initial IOL implantation. The prediction error for the IOL exchange, calculated from the biometric data obtained before the IOL exchange, was compared with that calculated from the measurements obtained before the initial IOL implantation. Results: The overall complication rates were low and no serious complications were found. The mean BCVA improved significantly after the IOL exchange and was not significantly different from that obtained after the initial IOL implantation. However, the refractive prediction for the IOL exchange was not as good as it was for the initial IOL implantation, which was thought to be related with difficulties in axial length (AL) measurements. Biometric data taken before the initial IOL implantation was associated with a significantly better refractive prediction than those taken before the IOL exchange. Conclusions: IOL exchange was both efficacious and safe for visual recovery. However, IOL exchange was related with increased difficulty of predicting postoperative refraction; difficulties in AL measurements are the suggested cause.