• Interaction and multiscale mechanics
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• 제5권4호
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• pp.399-405
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• 2012

A dissipative particle dynamics (DPD) simulation was presented to analyze surface wettability and contact angles of a droplet on a solid platform. The many-body DPD, capable of modeling vapor-liquid coexistence, was used to resolve the vapor-liquid interface of a droplet. We found a constant density inside a droplet with a transition along the droplet boundary where the density decreased rapidly. The contact angle of a droplet was extracted from the isosurfaces of the density generated by the marching cube and a spline interpolation of 2D cutting planes of the isosurfaces. A wide range of contact angles from $55^{\circ}$ to $165^{\circ}$ predicted by the normalized parameter ($|A_{SL}|/B_{SL}$) were reported. Droplet with the parameters $|A_{SL}|>5.84B{_{SL}}^{0.297}$ was found to be hydrophilic. If $|A_{SL}|$ was much smaller than $5.84B{_{SL}}^{0.297}$, the droplet was found to be superhydrophobic.

• 한국컴퓨터그래픽스학회논문지
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• 제24권1호
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• pp.1-8
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• 2018

본 논문에서는 삼각형 집합(triangle soup)형식의 등가면(isosurface)을 추출하는 기존의 마칭큐브 기법을 개선하여, 연결된 메시(connected mesh)형식으로 추출하는 실시간 기법을 제안한다. 이를 통해 기존에는 불가능했던 다양한 렌더링 기법을 사용하여 동적으로 변하는 등가면을 렌더링할 수 있고, 등가면의 위상(topology)과 기하(geometry) 정보 등을 추출할 수 있다. 또한 지오메트리 셰이더 (geometry shader) 에서 사용하는 인접 삼각형 형태의 구조 (GL_TRIANGLES_ADJACENCY)를 생성하여 보다 다양한 셰이딩 기법을 지원한다. 본 기법은 기존 마칭큐브에 삼각형들을 연결하는 후처리 과정을 추가한 기법에 비해 300% 정도의 향상된 등가면 추출 속도를 보인다.

• 천문학논총
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• 제16권1호
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• pp.11-14
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• 2001

In this paper, we simplify the equations of the Macdonald-Thome black hole magnetosphere. Our major assumption is that the 3-D electric and magnetic flux isosurfaces respectively form families of confocal oblate spheroids and hyperboloids. As a result, the magnetospheric equations are greatly simplified, and may provide a useful framework for instances when rigorous, theoretical approaches are not necessary.

• Journal of the Korean Statistical Society
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• 제36권1호
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• pp.31-55
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• 2007

R is an open source language for statistical computing and graphics based on the ACM software award-winning S language. R is widely used for data analysis and has become a major vehicle for making available new statistical methodology. This paper presents an overview of the design philosophy and the development model for R, reviews the basic capabilities of the system, and outlines some current projects that will influence future developments of R.

• 한국컴퓨터그래픽스학회논문지
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• 제26권4호
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• pp.17-26
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• 2020

본 논문에서는 GPU(Graphic Processing Unit) 연산을 활용하여 BCC(Body Centered Cubic) 볼륨 데이터로부터 실시간으로 메시 형태의 등가면을 추출하는 개선된 마칭 사면체(Marching tetrahedra) 기법을 제안한다. 본 기법은 고전적인 방법과 비교하여 메모리 사용량은 다소 높지만 더 좋은 성능을 보인다. 본 기법은 다섯 단계로 구성되어 있다. 첫 번째 단계는 단 한번만 수행되는 단계로, 빈 공간을 생략하여 성능을 향상 시키기 위해 최소/최댓값 블록(Min/max block)을 생성한다. 두 번째 단계에서는 등갓값(Isovalue)을 포함하고 있는 유효한 블록을 추려낸다. 이후 두 단계에서는 등가면(Isosurface)을 포함하는 셀(Cell)과 엣지(Edge)를 추출하고, 마지막 단계에서 삼각형 메시(Triangle mesh)를 생성한다. 본 기법은 512³ 이상의 고해상도 볼륨 데이터(Volume dataset)에 대한 등가면 추출 시, 삼각형 집합 형태의 등가면을 추출하는 고전적인 마칭 사면체 기법에 비해 최대 5배 정도의 속도 향상을 보인다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2009년도 추계학술발표대회
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• pp.345-346
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• 2009

The segmentation of vessel including portal vein, hepatic vein and artery, from Computed Tomography (CT) images plays an important role in the therapeutic strategies for hepatic diseases. Representing segmented vessels in three dimensional spaces is extremely useful for doctors to plan liver surgery. In this paper, proposed method is focused on smoothing technique of segmented 3D liver vessels, which derived from 3D region growing approach. A pixel expand algorithm has been developed first to avoid vessel lose and disconnection cased by the next smoothing technique. And then a binary volume filtering technique has been implemented and applied to make the segmented binary vessel volume qualitatively smoother. This strategy uses an iterative relaxation process to extract isosurfaces from binary volumes while retaining anatomical structure and important features in the volume. Hard and irregular place in volume image has been eliminated as shown in the result part, which also demonstrated that proposed method is a suitable smoothing solution for post processing of fine vessel segmentation.

• 한국컴퓨터그래픽스학회논문지
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• 제18권4호
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• pp.25-34
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• 2012

본 논문에서는 BCC (body-centered cubic) 볼륨 데이터의 등 가면을 GPU(graphics processing unit)에서 실시간으로 레이 캐스팅 렌더링하는 방법을 제시한다. 우선 준-보합 전치필터를 적용한 후 7-방향 박스-스플라인 필터를 기반으로 하여 4차 스플라인 함수로 볼륨데이터를 복구한다. 그래픽스 하드웨어에서 실시간 렌더링을 하기 위해, 참조테이블 및 조건 분기를 사용하지 않고 데이터 인출시의 비용을 줄이도록 쉐이더 코드를 최적화하였다. 본 방법을 기존의 BCC 레이 캐스팅과 비교해 본 결과, 비슷한 성능의 기존 방법에 비해 렌더링 속도는 20% 이상 빨라졌고 렌더링 이미지의 품질은 가장 좋았다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1806-1813
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• 2003

The stirred tank reactor is one of the most commonly used devices in industry for achieving mixing and reaction. Here we report on results obtained from the large eddy simulations of flow inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius. Stereoscopic PIV measurements (Hill et $al.^{(1)}$) along with the theoretical model of the impeller-induced flow (Yoon et $al.^{(2)}$) were used in defining the impeller-induced flow as superposition of circumferential, jet and tip vortex pair components. Large eddy simulation of flow in a stirred tank was carried out for the three different Reynolds numbers of 4000, 16000 and 64000. The effect of different Reynolds numbers is well observed in both instantaneous and time averaged flow fields. The instantaneous and mean vortex structures are identified by plotting an isosurfaces of swirling strength for all Reynolds numbers. The Reynolds number dependency of the nondimeansional eddy viscosity, resolve scale and subgrid scale dissipations is clearly shown in this study.

• International Journal of CAD/CAM
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• 제3권1_2호
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• pp.61-66
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• 2003

This paper describes a novel experiment that measures skin movement with respect to the flexional motion of a hand. The study was based on MR images in conjunction with CAD techniques. The MR images of the hand were captured in 3 different postures with surface markers. The surface markers attached to the skin where employed to trace skin movement during the flexional motion of the hand. After reconstructing 3D isosurfaces from the segmented MR images, the global registration was applied to the 3D models based on the particular bone shape of different postures. Skin movement was interpreted by measuring the centers of the surface markers in the registered models.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1290-1298
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• 2003

The stirred tank reactor is one of the most commonly used devices in industry for achieving mixing and reaction. Here we report on results obtained from the large eddy simulations of flow inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius. Stereoscopic PlY measurements (Hill et al. $^{(1)}$) along with the theoretical model of the impeller-induced flow (Yoon et al. $^{(2)}$) were used in defining the impeller-induced flow as superposition of circumferential, jet and tip vortex pair components. Large eddy simulation of flow in a stirred tank was carried out for the three different Reynolds numbers of 4000, 16000 and 64000. The effect of different Reynolds numbers is well observed in both instantaneous and time averaged flow fields. The instantaneous and mean vortex structures are identified by plotting an isosurfaces of swirling strength for all Reynolds numbers. The Reynolds number dependency of the non-dimensional eddy viscosity, resolved scale and subgrid scale dissipations is clearly shown in this study.