• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.23-29
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• 2007

We present an improved immersed boundary method for computing incompressible viscous flow around an arbitrarily moving body on a fixed computational grid The main idea is to incorporate feedback forcing scheme of virtual boundary method with Peskin's regularized delta function approach in order to use large CFL number and transfer quantities between Eulerian and Lagrangian domain effectively. From the analysis of stability limits and effects of feedback forcing gains, optimum regions of the feedback forcing are suggested.

• 한국전통조경학회지
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• 제38권2호
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• pp.108-117
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• 2020

본 연구는 경주시 역사유적지구 대릉원지구를 대상으로 Virtual Walkthrough 기법을 이용하여 가상체험한 후 평가를 통해 경관 시각적 특성을 분석하고 이미지 요인과 시각적 선호도 간의 관계를 파악하기 위해 분산분석 및 다중회귀분석을 실시하였다. 연구의 결과, 대릉원지구에 대한 선호도 분석으로 노서리 고분군 서쪽 경계에 위치하는 경관3이 선호도가 가장 높게 나타났으며, 대릉원 서쪽 경계에 위치하는 경관5는 3점 미만의 낮은 점수로 분석되었다. 시각적 특성에 관한 요인분석 결과로 특이성, 공간성, 역사성 3가지의 요인을 도출하였으며, 요인점수와 시각적 선호도에 대한 분산분석 및 다중회귀분석을 실시한 결과는 특이성이 역사문화경관 대릉원지구의 시각적 선호도에 영향을 미치는 가장 큰 요인으로 분석되었다. 또한 Virtual Walkthrough 기법은 입체성이 강하고 실재 경관에 대한 재현 정도가 높으며, 경관분석에 효율적인 기법으로 분석되었다. 연구를 통하여 도출된 결과로 역사문화경관 시각적 질의 향상에 자료 및 정보를 제공하고 앞으로 경관계획에 활용될 것으로 기대된다.

• 정보처리학회논문지B
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• 제9B권2호
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• pp.173-180
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• 2002

기존의 VOB(Virtual Output Buffer) 모델에서 신경회로망의 학습 패턴 처리를 위해 가상 셀 손실율이 도입되었다. VOB모델은 신경망이 실제 셀 손실율 없이도 연결 수락 경계을 잘 찾을 수 있음을 보여주었다. 그러나 VOB 모델은 셀 손실율을 과다 평가하는 경향이 있어 결과적으로 망 자원의 이용률이 낮은 단점이 있다. 본 논문에서는 이러한 단점을 보완하는 방법으로 연결 수락 경계에서 셀 손실율의 평균에 대한 정보를 충분히 포함하는 셀 손실율 참조 곡선의 개념을 제안하였다. 그리고 제안된 셀 손실율 참조 곡선을 이용하여 가상 셀 손실율을 처리하는 방법을 제안하였다. 제안된 한습 패턴 처리 방법은 ATM 트래픽 중에 가장 대표적인 두 가지 호원에 대하여 실험하였다. 실험에 사용된 호원은 LAN 데이터의 그래픽 특성을 가시는 On-Off 트래픽과 비디오 화상 통신의 특성을 가지는 Auto-Regressive 트래픽이다.

• 한국통신학회논문지
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• 제34권10B호
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• pp.1070-1075
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• 2009

본 논문에서는 3차원 영상 생성을 위한 깊이맵 추정 및 중간시점 영상합성 방법을 제안한다. 제안하는 방법은 깊이맵의 시간적 상관도를 향상시키기 위해 깊이값을 추정하는 과정에서 기존의 정합 함수에 이전 프레임에서 추정한 깊이값을 고려하는 가중치 함수를 추가한다. 또한, 중간시점 영상을 합성하는 과정에서 발생하는 경계 잡음을 제거하는 방법을 제안한다. 중간시점 영상을 합성할 때, 비폐색 영역을 합성한 후 경계 잡음이 발생할 수 있는 영역을 비폐색 (disocclusion) 영역을 따라 구별한 다음, 잡음이 없는 참조 영상을 이용하여 경계 잡음을 처리한다. 컴퓨터 모의실험 결과를 통해 깊이맵의 시간적 상관도를 향상시켜서 사용자의 시각적 피로감을 줄일 수 있었고, 배경 잡음이 사라진 자연스러운 중간시점 영상을 생성할 수 있었다.

• Advances in aircraft and spacecraft science
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• 제8권4호
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• pp.345-372
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• 2021

The analysis of nonlinear vibrations, buckling, post-buckling, flutter boundary determination and post-flutter behavior of a homogeneous curved plate assuming cylindrical bending is conducted in this article. Other assumptions include simply-supported boundary conditions, supersonic aerodynamic flow at the top of the plate, constant pressure conditions below the plate, non-viscous flow model (using first- and third-order piston theory), nonlinear structural model with large deformations, and application of mechanical and thermal loads on the curved plate. The analysis is performed with constant environmental indicators (flow density, heat, Reynolds number and Mach number). The material properties (i.e., coefficient of thermal expansion and modulus of elasticity) are temperature-dependent. The equations are derived using the principle of virtual displacement. Furthermore, based on the definitions of virtual work, the potential and kinetic energy of the final relations in the integral form, and the governing nonlinear differential equations are obtained after fractional integration. This problem is solved using two approaches. The frequency analysis and flutter are studied in the first approach by transferring the handle of ordinary differential equations to the state space, calculating the system Jacobin matrix and analyzing the eigenvalue to determine the instability conditions. The second approach discusses the nonlinear frequency analysis and nonlinear flutter using the semi-analytical solution of governing differential equations based on the weighted residual method. The partial differential equations are converted to ordinary differential equations, after which they are solved based on the Runge-Kutta fourth- and fifth-order methods. The comparison between the results of frequency and flutter analysis of curved plate is linearly and nonlinearly performed for the first time. The results show that the plate curvature has a profound impact on the instability boundary of the plate under supersonic aerodynamic loading. The flutter boundary decreases with growing thermal load and increases with growing curvature.

• 제어로봇시스템학회논문지
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• 제19권5호
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• pp.423-428
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• 2013

This paper investigates a boundary tracking problem using multiple quadrotor UAVs to detect and track the boundary of physical events. We set the boundary estimation problem as a classification problem of the region in which the physical events occur, and employ SVL (Support Vector Learning). We also demonstrate a velocity vector field which is globally attractive to a desired closed path with circulation at the desired speed and a virtual phase for stabilizing the collective configuration of the multiple quadrotors. Experimental results with multiple quadrotors show that this study provides good performance of the collective boundary tracking.

• 한국실내디자인학회논문집
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• 제27권2호
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• pp.45-54
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• 2018

Immersive space is a new type of space, which is converged with other domains and expressed in various ways and here, a mutual exchange between space and participants is realized with active intervention of participants. The purpose of this study is to examine boundary changes and characteristics in virtual space and reality or inside and outside, focusing on immersive space. For this study, a case analysis was conducted, based on the key words regarding flow experience and boundary characteristics in immersive space. The boundary characteristics extracted are as follow. First, while immersive space is overlapped in many different ways, the boundary in space gradually changes and one unique and convergent space is formed. Also, a combination of overlap is made with internal and external physical force and a convergent boundary is created. Second, forms are mixed in diverse ways and an unrealistic boundary space is revealed. For new experience, it has familiar, but new experiential characteristics and also shows an expanded boundary by the medium of different domains. Third, a simultaneous space, based on variability of time and space, has an ambiguous boundary due to a meaningless physical boundary of space and changing into a space region constantly, it becomes an unlimited variable space. Fourth, a linear expansion-based emergent space has nonlinearity, which creates a meaningless boundary, recognized as an irregular, dynamic and transformative space and expands to a creative space. In conclusion, it is anticipated that based on diverse characteristics found in immersive space, this study would give unlimited inspiration to many design fields and art creation activities and contribute to a further development through continued research on immersive space.

• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.1996-2008
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• 2004

A seamless analysis of material behavior incorporating complex geometry and crack- tip modeling is one of greatly interesting topics in engineering and computational fracture mechanics fields. However, there are still large gaps between the industrial applications and fundamental academic studies due to a time consuming detailed modeling. In order to resolve this problem, a numerical method to calculate an energy release rate by virtual crack closure technique was proposed in this paper. Both free mesh method and finite element method have been utilized and, thereafter, robust local and global elements for various geometries and boundary conditions were generated. A validity of the proposed method has been demonstrated through a series of fracture mechanics analyses without tedious crack-tip meshing.

• Asia Marketing Journal
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• 제25권2호
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• pp.61-70
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• 2023

Although research on Virtual Reality (VR) has uncovered numerous technical advantages of VR over traditional media, little is known about how individual VR users with varying prior experience respond to VR differently. This paper examines the effect of users' prior VR experience on their subsequent real-life behavior in the domain of charitable consumption. Specifically, we find that compared to experienced VR users, novice VR users are more likely to support a charitable cause in real life (e.g., ocean conservation) after experiencing this cause in VR. The increased support among novice VR users occurs because they perceive the use of VR to be more novel. We find a boundary of this effect such that when VR is used to promote a noncharitable cause, novice VR users no longer increase their real-life support after VR. This research offers new possibilities for future studies on the use of VR in societal marketing.

• Steel and Composite Structures
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• 제38권1호
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• pp.1-15
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• 2021

In this paper, a higher order shear deformation theory for bending analysis of functionally graded plates resting on Pasternak foundation and under various boundary conditions is exposed. The proposed theory is based on the assumption that porosities can be produced within functionally graded plate which may lead to decline in strength of materials. In this research a novel distribution of porosity according to the thickness of FG plate are supposing. Governing equations of the present theory are derived by employing the virtual work principle, and the closed-form solutions of functionally graded plates have been obtained using Navier solution. Numerical results for deflections and stresses of several types of boundary conditions are presented. The exactitude of the present study is confirmed by comparing the obtained results with those available in the literature. The effects of porosity parameter, slenderness ratio, foundation parameters, power law index and boundary condition types on the deflections and stresses are presented.