• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.556-558
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• 2005

본 연구에서 제안하는 3차원 인터렉티브 스케칭 시스템은 쉽고 간략한 인터페이스 환경으로 유연하고 정교한 물체 생성 및 변형이 가능한 3차원 개념설계 시스템이다. 제품의 설계 과정에서 무선 완드를 이용하여 3차원 공간에 일련의 프리핸드 스트로크로 곡면을 정의하고 생성된 곡면은 캘리그래픽 스트로크를 이용하여 실시간으로 변형할 수 있는 공간 곡면의 정의와 실시간 자유 변형 알고리즘을 포함한다. 공간 곡면 정의 알고리즘은 무선완드의 입력 방위에 따라 상이한 물체를 생성하고 변형하는 기술로서 물체 생성시 필요한 인터페이스의 양을 최소화 할 수 있다. 또한 절러 차례 캘리그라픽 스트로크 입력으로 수정과 변형이 실시간 통합적으로 이루어지는 자유변형 알고리즘은 기존의 공학적. 수치적 접근방식에서 탈피한 직관적이며 유연한 모델링 방식을 제안하여 전문가가 아니더라도 쉽게 공학적 모델을 생성. 변형 할 수 있다. 누구나 쉽게 본 시스템의 도움으로 직관적이며 공학적으로 건전한 제품을 설계할 수 있는 디자인 설계의 획기적인 변화를 마련할 것이다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.178-179
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• 2018

증강현실 환경에서 현실 세계의 물체를 포착하여 디지털화 시키는 것은 몰입감 향상에 있어 매우 중요한 기술이다. Faster R - CNN 은 영상에서 여러 물체를 인식하는 기술 중 하나이며, 지금껏 많은 응용 기술의 개발과 함께 많은 연구가 진행되고 있다. 본 논문은 증강현실 환경에서 평면물체의 2D 변환관계를 설명하는 Homography 와 Faster R - CNN 을 활용하여 여러 개의 비콘에 대한 6 자유도(6DOF) 를 추정하는 방법을 제안한다. 또한 증강현실에서 주로 사용되는 마커 기술에 존재하는 단점들을 극복할 수 있는 비콘 구조를 소개하고 여러 개의 비콘을 용이하게 관리하는 시스템을 제안한다.

• Journal of Navigation and Port Research
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• v.32 no.1
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• pp.9-14
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• 2008

VOF method is known as one of the most effective numerical techniques handling two-fluid domains of different density simultaneously. Present study deals with the numerical analysis of flow field around bodies steadily moving near free-surface using FLUENT-VOF method. Validations were made by applying to three typical examples ; 2-D submerged hydrofoil, 3-D surface piercing body and container ship. It was found that the commercial software, FLUENT, is useful in practical use, and VOF method is capable of handling free-surface around moving bodies although discussions are limited to the analysis in qualitative sense.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.104-114
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• 1993

In this paper, effects of free surface on viscous flow is investigated. Continuity equation coupled with Navier-Stokes equations are solved numerically by using an artificial compressibility method[1, 2]. The body-fitted generalized curvilinear coordinate system is employed to deal with arbitrary body shape. The IAF scheme with finite difference method is used to solve the equations, and a diagonal algorithm is applied to time-varying Jacobian matrices for the computational economics. Free surface shape is obtained by applying zero pressure condition to still water surface at each time step. A numerical test is made for larminar flow around a circular cylinder vertically piercing the free surface. Computed flow patterns are largely affected by the existance of free surface in low Reynolds number flows treated in this paper. Free surface causes viscous pressure drag to vary much in depth direction in accordance with the variations of flow pattern.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.1
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• pp.8-15
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• 2002

A two-dimensional higher order panel method using B-splines has been developed to overcome the disadvantages of the low order panel method and to obtain more accurate solution. The sources and the normal dipoles are distributed on both the body and the free surface. Instead of applying the upwind finite difference schemes to satisfy the linearized free surface and the radiation condition, the derivatives of the basis functions of the B-splines are directly applied to the linearized free surface condition. Numerical damping in the Dawson's method are avoided in the Present computations. In order to validate the present method, numerical computations are carried out for a submerged cylinder and a two-dimensional hydrofoil steadily moving beneath a free surface. The numerical results show that fast convergence and better accuracies have been achieved by the present method.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.35-47
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• 1996

A surface panel method treating a boundary-value problem of the Dirichlet type is presented to design a three dimensional body with free surface corresponding to a prescribed pressure distribution. An integral equation is derived from Green's theorem, giving a relation between total potential of known strength and the unknown local flux. Upon discretization, a system of linear simultaneous equations is formed including free surface boundary condition and is solved for an assumed geometry. The pseudo local flux, present due to the incorrect positioning of the assumed geometry, plays a role f the geometry corrector, with which the new geometry is computed for the next iteration. Sample designs for submerged spheroids and Wigley hull and carried out to demonstrate the stable convergence, the effectiveness and the robustness of the method. For the calculation of the wave resistance, normal dipoles and Rankine sources are distributed on the body surface and Rankine sources on the free surface. The free surface boundary condition is linearized with respect to the oncoming flow. Four-points upwind finite difference scheme is used to compute the free surface boundary condition. A hyperboloidal panel is adopted to represent the hull surface, which can compensate the defects of the low-order panel method. The design of a 5500TEU container carrier is performed with respect to reduction of the wave resistance. To reduce the wave resistance, calculated pressure on the hull surface is modified to have the lower fluctuation, and is applied as a Dirichlet type dynamic boundary condition on the hull surface. The designed hull form is verified to have the lower wave resistance than the initial one not only by computation but by experiment.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.85-98
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• 1998

본 논문의 수치해법은 경계치문제를 풀기 위하여 코시이론(Cauchy's theorem)을 사용하였다. 경계치문제는 완전한 물체표면조건과 자유표면조건을 만족시키는 초기치문제로 귀결된다. 현 수치해법에서 무한영역은 수치계산 영역인 비선형 영역과 선형 자유표면조건을 만족하는 선형영역으로 나누어진다. 선형영역의 해는 과도 그린(Green)함수를 사용하여 정합조건을 부과함으로써, 수치계산은 비선형 영역에서만 수행된다. 본 논문에서 저자는 수치계산 영역에서 코시이론을 사용하여 적분방정식을 도출하였고, 무한영역의 해는 정합면에서 과도 그린함수를 사용하여 표현하였다. 본 수치계산에서 자유표면에 요소 재분배법을 적용함으로써 쇄파현상에 대해서도 안정적인 수치해석을 할 수 있었다. 본 논문에서 개발된 수치방법을 적용한 문제는 다음과 같다. 첫째는 자유표면에서 실린더가 강제동요하는 경우에 자유표면형상과 힘을 계산하여 이전의 실험치 및 계산치와 비교하였다. 두번째로는 실린더가 자유수면하에서 일정한 속도로 항주하는 경우에는 조파저항과 양력을 계산하여 고차 스펙트럴법과 비교하였다.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.80-86
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• 1994

A numerical method for simulations of inviscid incompressible flow fields around a ship advancing on the free surface is developed. A body fitted coordinate system, generated by numerically solving elliptic type partial differential equations is used to conform the ship and free surface configurations. Three dimensional Euler equations transformed to the non-staggered body fitted coordinate system are discretised by finite difference method. Time and spatial derivatives are discretised by forward and centered differencings, respectively, and artificial dissipations are added to discretised convection terms for improvements of numerical stability. At each time steps, free surface elevations are recomputed to satisfy nonlinear free surface conditions. Poisson equations for pressure field are solved iteratively and the velocity field for next time step is extrapolated. To verify the developed numerical method, flow fields around a Wigley model are simulated(Fn=0.250-0.408) and compared with experimental data to show good agreements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.19-29
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• 2006

In this study, numerical simulation of airframes separating from a missile system has been preformed. For the time-accurate trajectory simulation, six D.O.F equations of motion of multiply connected bodies were derived and these equations have been coupled with the unstructured overset mesh technique for the treatment of independent mesh blocks moving with each body component. Applications were made for the simulation of the airframe separation at missile angles of attack of 0 and 5 degrees. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.577-578
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• 2010