• 한국정밀공학회지
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• 제25권11호
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• pp.100-106
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• 2008

We have studied the characteristic changes of optical device using imprint lithography. An imprinted structure is inherently involved in residual stress due to the temperature and the pressure cycle during fabrication process. A structure with residual stress undergoes stress relaxation, which leads io dimensional change. Therefore, annealing processes was performed to reduce the residual stress of imprinted polymer channel. Reduction of residual stress was confirmed through dimensional change, birefringence, and the mechanical properties. We have fabricated an optical device, and it saw the optical intensity changes within 0.1% for 1 month.

• 한국가구학회지
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• 제20권3호
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• pp.247-252
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• 2009

The objective of this study was the dimensional stabilization of Korean red pine (Pinus densiflora) wood by the water-based thermosetting resin. A commercial melamine-formaldehyde resin was impregnated into wood samples and cured. The weight and dimensional change of woods treated by the resin, and the absorption and dimensional behavior of treated woods were investigated. The melamine-formaldehyde resin treatment improved significantly the dimensional stability of pine wood and showed about 40% of antiswelling efficiency. The mechanism of dimensional stabilization was interpreted as the complicated reason, such as bulking effect by the resin in cell wall, mechanical restraint and/or blocking of hygroscopic site by the resin in lumen.

• 산업기술연구
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• 제25권B호
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• pp.107-114
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• 2005

Digital media was realized by two-dimensional design backup. But, digital medium decides form of architecture, and act as a design tool that can expand area of thinking. With such social change, investigate for digital architecture. And, wish to analyze design process of digital architecture and search the characteristics. Through comparison of digital and analogue, clear up that the digital world had complex and ambivalent attribute. Define digital design process as "Digital continuum" with characteristic of digital architecture and divided in 3-steps of concept - development - representation. Analyzed digital design process of Frank O, Ghery, Peter Eisenman and Greg Lynn on th assumption division. As a result, design concept is starting from three-dimensional thinking instead of existent two-dimensional thinking. And because general work of process was gone by digital media, "mass costomization" was possible. Also, it gave architect new role. Differ with former days, select various variables, should tuning and cording, and emphasize role as coordinator who must select the result. Digital is summoning very radical and epoch-making change in architecture. At center of these change, digital design process asks architect complex thinking and creative concept.

• 한국정밀공학회지
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• 제22권9호
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• pp.188-193
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• 2005

To provide the various machining materials with excellent quality and dimensional accuracy, high -speed machining is very useful tool as one of the most effective rapid manufacturing processes. However, high-speed machining is not suitable for microscale thin-walled structures because of the lack of the structure stiffness to resist the cutting force. A new method which is able to make a very thin-walled structure rapidly will be proposed in this paper. This method is composed two processes, high-speed machining and filling process. Strong workholding force comes out of the solidification of filling materials. Low-melting point metal alloys are used in order to minimize the thermal effect during phase change and to hold arbitrary shape thin-walled structures quickly during high-speed machining. To verify the usefulness of this method, we will show some applications, for examples thin -wall cylinders and hemispherical shells, and compare the experimental results to analyze the dimensional accuracy of typical parts of the structures.

• 대한치과교정학회지
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• 제21권3호
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• pp.657-670
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• 1991

It was said that early rapid palatal expansion was the treatment of choice in case of maxillary constriction with posterior crossbite. The author tried to assess dimensional changes of nasal and oral cavity before rapid palatal expansion and over 4 months of retention by use of three coronal tomograms through the incisal, molar, and maxillary tuberosity areas. The subjects of this study were consisted of 9 boys and 11 girls ranging from 11 to 13 years old. The results were as follows: 1. A mean change in maxillary first molar width was 3.68mm and a mean change in nasal cavity width was 2.26mm after 6.70mm expansion by Hyrax-type screw and over 4 months of retention tomographically in molar cut. 2. A change in nasal cavity width tomographically showed in order of molar cut, incisal cut, maxillary tuberosity cut respectively. 3. There was no correlation between changes in oral cavity width and nasal cavity width.

• 한국분무공학회지
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• 제27권1호
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• pp.36-41
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• 2022

In this study, the combustion instability characteristics according to the change in the hydrogen ratio in the fuel in the single nozzle system of the hydrogen-natural gas mixed gas turbine for power generation was analyzed using a three-dimensional finite element analysis-based Helmholtz solver. This combustor shows the instability characteristics in which mode transition occurs from a mode having a low amplitude near 70 Hz to a mode having a high amplitude of 250 Hz or higher as the hydrogen fraction in the fuel increases. The current modeling results are found to reasonably predict the main characteristics of the change in measured instability frequency and growth rate with the change in fuel composition.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1436-1444
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• 2002

A three dimensional numerical model was developed to analyze the mold filling and solidification processes straightforwardly in a casting processes. On the basis of the SIMPLER algorithm, the VOF method and the Equivalent Specific Heat method were adopted to deal with the free surface behavior and the latent heat evolution. The complete model has been validated using exact solutions and experimental results. The importance of three-dimensional effects has been highlighted by comparing the results from the three-dimensional analysis with those given by a two-dimensional analysis.

• Journal of Forest and Environmental Science
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• 제30권2호
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• pp.226-232
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• 2014

To understand transition characteristics from wood to charcoal the dimensional changes of carbonized woods at low temperature from $300^{\circ}C$ to $350^{\circ}C$ at the intervals of $10^{\circ}C$ were investigated. Three species of hardwoods and two species of softwoods were used in this study. Measurements of dimensional changes of cells were observed by stereoscopic microscope and an image analyzer. The apparent volume of each specimen decreased greatly with increasing temperature. Severe cracks and collapse were observed frequently in hardwoods and hardly in softwoods. Vessel diameter and tracheid cell wall thickness of the wood samples were decreased with increasing carbonization temperature. Contraction of vessel diameter in tangential direction was greater than that in radial direction. Cell wall thickness of tracheids decreased with increasing carbonization temperature. Consequently, even though it was small range of carbonization temperature, dimensions of wood components were changed considerably.

• 한국항만학회지
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• 제15권1호
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• pp.47-56
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• 2001

A numerical model for practical use based on the 1-line theory is presented to simulate shoreline changes due to construction of offshore structures. The shoreline change model calculates the longshore sediment transport rate using breaking waves. Before the shoreline change model execution, a wave model, adopting the modified Boussinesq equation including the breaking parameters and bottom friction term, was used to provide the longshore distribution of the breaking waves. The contents of present model are outlined first. Then to examine the characteristics of this model, the effects of the parameters contained in this model are clarified through the calculations of shoreline changes for simple cases. Finally, as the guides for practical application of this model, several comments are made on the parameters used in the model, such as transport parameter, average beach slope, breaking height variation alongshore, depth of closure, etc. with the presentation of typical examples of 3-dimensional movable bed experimental results for application of this model. Here, beach change behind the offshore structures is represented by the movement of the shoreline position. Analysis gives that the transport parameters should be taken as site specific parameters in terms of time scale for the shoreline change and adjusted to achieve the best agreement between the calculated and the observed near the structures.

• 한국해안·해양공학회논문집
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• 제32권3호
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• pp.180-201
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• 2020

유한길이의 혼성방파제 선단에서 발생되는 회절파의 영향으로 방파제 길이를 따라 중복파고가 변동하고, 이로 인하여 케이슨에 작용하는 파압이 공간적으로 변동하며, 또한 케이슨의 활동거리가 상이한 사행피해가 발생한다는 것은 잘 알려져 있다. 제체에 작용파력의 공간적인 변동은 2차원적인 실험이나 수치해석으로서는 접근될 수 없는 문제이다. 본 연구는 olaFlow 모델을 적용하여 고천단의 사석마운드 상에 놓인 케이슨의 선단 주변에서 회절파의 발생과 배후역으로의 영향 및 제체에 작용하는 충격쇄파압을 포함한 파압의 공간적인 변동 등을 2차원 및 3차원수치기법으로 접근한다. 또한, 수치해석에서는 혼성방파제 주변에서 평균파고, 평균수평유속 및 평균난류운동에너지의 변동특성을 면밀히 분석·검토한다. 이로부터 동일한 입사파랑에 대해 케이슨에 작용하는 파압분포가 방파제의 길이에 따라 크게 변동하며, 2차원수치해석에서는 발생되지 않았든 충격쇄파압이 3차원수치해석에서는 발생되는 경우가 나타나고, 충격쇄파압의 발생 시 경우에 따라 기존의 설계조건보다 매우 큰 파압이 정수면 근방의 케이슨 전면 벽체에 작용되는 등의 중요한 결과를 확인할 수 있었다.