• 열처리공학회지
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• 제33권3호
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• pp.107-116
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• 2020

Four air hardening steels with carbon, silicon, manganese, chromium, and molybdenum variations have been used in this study to find out the optimal chemical compositions of steels with over 1200 MPa tensile strength for automotive subframe. The dimensional changes after heat treatment were determined for two automotive parts with open and closed cross sections using 3D scanner. When four steels were austenitized at 900℃ for 30 seconds, cooled at 3℃/s, reheated to 450℃ for 10 seconds followed by air cooling to simulate hot-dip galvanizing treatment showed ultra high tensile strength over 1200 MPa. Rear floor cross member with open cross section revealed much bigger dimensional changes than subframe with closed cross section after heat treatment at 900℃ for 20 minutes followed by air cooling.

• Geosystem Engineering
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• 제21권6호
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• pp.309-317
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• 2018

We employ a three-dimensional indirect boundary element method (BEM) to simulate temperature change around an underground liquefied natural gas storage cavern. The indirect BEM (IBEM) uses fictitious heat source strength on boundary elements as basic variables which are solved from equations of boundary conditions and then used to compute the temperature change at other points in the considered problem domain. The IBEM requires evaluation of singular integration for temperature change due to heat conduction from a constant heat source on a planar (triangular) region. The singularity can be eliminated by a semi-analytical integration scheme. However, it is found that the semi-analytical integration scheme yields sharp temperature gradient for points close to vertices of triangle. This affects the accuracy of heat flux, if they are evaluated by finite difference method at these points. This difficulty can be overcome by a combination of using a direct numerical integration for these points and the semi-analytical scheme for other points distance away from the vertices. The IBEM and the hybrid integration scheme have been verified with an analytic solution and then used to the application of the underground storage.

• 대한치과보철학회:학술대회논문집
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• 대한치과보철학회 1999년도 Asian Academy of Prosthodntics. Korean Academy of Prosthodontics
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• pp.77.2-78
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• 1999

• 구강회복응용과학지
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• 제31권4호
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• pp.316-328
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• 2015

목적: 보관 조건과 석고 주입 시간에 따라 알지네이트 인상체로부터 제작된 모형의 정확성을 알아보고자 하였다. 연구 재료 및 방법: 채득된 알지네이트 인상체는 습도가 유지되는 항습조에 보관하는 것과 진료실 내의 공기 중에 노출되는 상태로 보관 조건을 달리하였다. 보관 조건에 따라 각각 즉시, 채득된 후 10분, 30분, 180분, 360분으로 나누어 보관한 후에 석고 모형을 제작하였다. 제작된 석고 모형을 3D 레이저 스캐너로 삼차원 디지털 모형을 구성하였고 구성된 디지털 모형의 참고점에서 거리를 측정하여 변형률을 비교하였다. 또한 각 실험군의 삼차원 디지털 평균 모형을 제작한 후 중첩을 시행함으로써 표면 변위가 발생한 부위와 크기를 확인하였다. 결과: 인상 채득 즉시 제작한 모형의 변형률이 가장 작게 나타났고, 공기 중에 보관한 인상체보다 항습조에 보관한 인상체의 변형률이 작게 나타났다. 석고 주입 시간이 증가함에 따라서 변형률도 증가하였으며, 석고 주입 시간이 180분을 지나면 보관 조건에 관계없이 대구치 부위에서 변형률과 표면 변위가 증가한다. 결론: 알지네이트 인상체로부터 제작된 모형의 정확성을 위해서는 인상 채득 후, 즉시 모형을 제작해야 한다. 보관이 필요한 경우에는 100% 상대습도가 유지되는 항습조를 이용하고, 보관 시간은 180분을 넘지 않도록 해야 정확한 모형을 얻을 수 있다.

• 보존과학회지
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• 제32권2호
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• pp.155-165
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• 2016

수침고목재인 목재유물의 보존처리에 가장 많이 사용되는 PEG 함침 후 진공동결건조 방법의 단점인 표면 결함에 대한 안정화처리를 위해 HPC를 도포하였다. HPC의 효과를 확인하기 위해서 외관 및 실체현미경 관찰, 색차, 중량변화율, 치수변화율을 측정하고, 통계분석을 실시하였다. 목재시료의 표면에 HPC가 얇은 층을 형성하였고, 가도관의 관공과 균열의 틈 사이를 메우고 있었다. HPC 1,000,000을 처리한 시료의 부후되지 않은 표면에서 나타난 백화현상을 제외하고 다른 변화는 나타나지 않았다. 열화시킨 시료는 수분 흡착에 의한 색변화가 나타났다. 시료 표면의 얇은 HPC 층은 열화 후에도 유지되고 있었으며, 수분 흡착에 의한 중량변화와 치수변화는 HPC에 의해 억제되는 것으로 나타났다.

• 대한기계학회논문집B
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• 제23권10호
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• pp.1213-1222
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• 1999

A finite element method is developed for calculating the temperature and enthalpy distribution and accordingly the solid, liquid and mushy zone in a three-dimensional body subjected to any heat boundary conditions. The method concurrently consider both temperature and enthalpy for consideration of the latent heat effect, differently from other methods of using a special energy balance equation for solving a mushy zone. The developed brick element has eight nodes with one degree of freedom at each node. The numerical method and procedure are verified using the results of one and two dimensional analytic solutions and by other researchers. It is shown that the present method presents a consistent and stable results in either abrupt or ranged phase change problems. Moreover, the numerical results by the present method are hardly effected by the calculation time steps which otherwise are difficult to determine in most phase change problems. Finally, as a three-dimensional application, a T-shaped body of a phase change is presented and the temperature and enthalpy variation along the time are solved.

• 한국실내디자인학회논문집
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• 제19권5호
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• pp.56-66
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• 2010

This study proposes a thesis of architectural concepts and visual dimension systems, and the comparison between steps of spatial formation and dimensional alteration. The second chapter, to form the basis of this study, explains the dimensional alterations and changes of fundamental notion of space. In the third chapter, history of space, architectural formations, and changes of the viewpoint are analyzed as objects of study. The forth chapter presents the interrelation between dimensional alteration and the transition in fundamental notion of space, demonstrating that modern architecture has been born from these cultural movements. Lastly, the fifth chapter suggests possibilities on further studies and the following conclusions: First, architectural spaces have been changed, in accordance with the changes of culture, art and the tools that regulate architectural design. Proportional regulations by two-dimensional tools and depth through three-dimensional drawings are created. Second, architectural spaces gained depth by recognizing movement and time that have induced formations to change, creating various aesthetic backgrounds and attempts. Third, the aesthetic background and cosmologic spatial concept have led the visualization and changes of architectural experience. It created the design tools and shapes originated in dynamism and vitality. Forth, diversification of fundamental spatial concepts has become palimpsest and complex, and been divided into four dimensions; expressional two-dimensional space, perspective three-dimensional space, forth-dimensional space of time and experience, and imagery space formed by body movement. Fifth, architecture has been influenced by the elevated viewpoint that understands the whole world as a space. It has evolved from the two-dimensional proportion principle, change of depth and vanishing point to multidimensional space of movement and time. Sixth, changes of fundamental notion of space have arisen from changes of visual dimensions in times. In other words, space has been developed from two-dimensional space to multidimensional space by accepting visual dimension, grasping distance, direction, depth, height, velocity, movement, gravity, power and structure.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.789-794
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• 1998

원전수명관리 측면에서 경수로와 중수로를 비교해 보면, 경수로의 경우 원자로 압력용기가 주요기기중 가장 중요한 위치에 있는 반면에 중수로는 압력관이 가장 중요한 기기이다. 압력관 손상종류는 DHC와 dimensional change로 크게 분류되는데 dimensional change는 creep, 부식마모, 처짐현상으로 구분된다. 본 논문에서는 creep과 부식마모 현상 발생시 예상되는 압력관 두께 변화를 계산하였으며, 중수로 수명관리 측면에서 가동 시작년도부터 50년까지 변화되는 두께를 ASME 허용기준과 비교하였다. creep과 부식마모에 의하여 감소 예상되는 압력관 두께는 50년까지 모두 ASME 허용 Margin안에 있음을 볼 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.854-859
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• 2000

When the round bar with step is twisted and bent, stress concentration is occurred in the irregular geometric parts. Two dimensional axisymmetric stress analysis is carried out according to the geometric change of the stress-concentrated part of round bar with step. Three dimensional cases are also investigated.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.237-240
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• 2008

Numerical Analysis for exchanging seawater experiment is carried out in Do-Jang fish port. The change of tidal velocity and water level is derived by the two-dimensional nonlinear shallow-water numerical model. To calculate exchange rate of seawater with the change of tidal velocity and water level, a two-dimensional numerical model is employed which governing equations are Fokker-Plank equations. The calculated exchange rates of each time are described in tables and figures.