• 대한수학회보
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• 제47권1호
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• pp.73-79
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• 2010

A pair of point vortices of the same strength but opposite sign is called a vortex dipole. We consider the limiting case where two vortices approach infinitely close while the ratio of the strength to the distance kept constant. The motion of such point vortex dipole on the ellipsoid of revolution is investigated geometrically to conclude that the trajectory draws a geodesic up to the leading order of perturbation, whose direction is determined by the initial orientation of the dipole. Related issues are also remarked.

• 대한조선학회지
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• 제9권1호
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• pp.1-6
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• 1972

To contribute towards more accurate estimation of the virtual coefficient for the vertical vibration of the chine-type ship, experimentally obtained three-dimensional correction factors, J, of added mass of prismatic beams having cross section shape of hypotrocoid characters, slightly concaved Lewis form and elliptic form are investigated in connection with the applicability of an approximate analytical calculation method compared to that proposed by T. Kumai[6] for the Lewis form cylinders, and synthetically in compared with the experimental works on various cross section shapes of the other type by L.C. Burril et al[8] and the analytical works on the ellipsoid of revolution by F.M. Lewis[1] and J.L. Taylor[2]. The experimental results show that the aforementioned analytical method gives, unlike that for the Lewis form cylinders, considerably larger J-values for the chine-type cylinders, and that the influence of the character of the cross section shape on J-values is not remarkable in practical sense. Finally, considering in synthesis the experimental results on prismatic beams, the Burril's works on palabolic plan form and elliptic plan form, and that the chine-type ship usually has a hull form of transom stern, it is fairly safe to say, at the present stage, that adoptation of the Taylor's J-values will not results in any large error in estimation of the virtual inertia coefficients of the chine-type ships.

• 한국측량학회지
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• 제15권2호
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• pp.269-275
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• 1997

GPS(Global Positioning System)측량을 이용한 차량항법시스템은 인공위성으로부터 전파신호를 받아 차량내부의 수치지도가 내장된 모니터에 차량의 현재 위치 및 진행방향을 표시, 목적지까지의 최단거리 주행로 등을 알려주게 된다 이 수치지도상에 차량의 위치를 표시하기 위해서는 차량에 탑재된 GPS수신기가 위성으로부터 WGS84좌표 계에 의한 경위도 데이터를 수신하여 이를 Bessel좌표계로 변환한 후 다시 TM투영과정을 거쳐 화면상에 나타나게된다. 본 연구에서는 지형도를 디지타이징하여 제작한 수치지도와 GPS장비를 자동차에 탑재하여 획득한 자료를 분석하여 제작한 수치지도를 비교하므로서 WGS84좌표계에 의한 수치지도 제작기법에 대해 고찰하고자 한다.