• Journal of radiological science and technology
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• v.39 no.3
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• pp.337-344
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• 2016

The purpose of this study was to evaluate the radiolucency for the phantom output to the 3D printing technology. The 3D printing technology was applied for FDM (fused deposition modeling) method and was used the material of ABS (acrylonitrile butadiene styrene) resin. The phantom was designed in cylindrical uniformity. An image uniformity was measured by a cross-sectional images of the 3D printed phantom obtained from the CT equipment. The evaluation of radiolucency was measured exposure dose by the inserted ion-chamber from the 3D printed phantom. As a results, the average of uniformity in the cross-sectional CT image was 2.70 HU and the correlation of radiolucency between PMMA CT phantom and 3D printed ABS phantom is found to have a high correlation to 0.976. In the future, this results will be expected to be used as the basis for the phantom production of the radiation quality control by used 3D printing technology.

• Composites Research
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• v.29 no.6
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• pp.347-352
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• 2016

This work presents the free vibration characteristics of laminated composite corrugated rectangular plates using the analytical method. Because it is very difficult to determine its mechanical behavior of 3-dimensional corrugated structures analytically, the equivalent homogenization model is adapted to investigate the overall mechanical behavior of corrugated structures. The corrugated element can be homogenized as an orthotropic material. Both the effective extensional and flexural stiffness of this homogenized equivalent orthotropic material are considered in the analysis. The present analytical results are validated by those obtained from 3D finite element analysis based on shell elements. The natural frequencies and global vibration mode shapes obtained from present analytical and finite element analysis are presented. Some numerical results are presented to check the effect of the geometric properties.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.223.1-223.1
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• 2015

본 연구에서는 지름이 다른 두 개의 디스크가 적층된 구조를 갖는 금 나노 구조체를 제작하고 그 광학적 특성에 대해 연구하였다. 나노임프린팅을 통하여 패턴된 폴리머 포어 어레이에 금 박막을 증착하고, 포어 내부에 증착된 금 나노구조체를 선택적으로 수거하는 방법을 이용하였다 [1]. 특히 금 증착 시, 빗각으로 증착 (oblique-angle deposition)을 하여 지름이 다른 두 개의 디스크가 적층되어 있는 구조를 형성하는 것이 가능하였다. 증착 각도의 조절을 통해 적층된 두 디스크의 지름 비율을 변화시킬 뿐만 아니라, 2차원 디스크 형태의 나노구조체부터 3차원 디쉬 형태의 구조체도 제작이 가능함을 확인하였다. 제안된 하향식 나노공정을 통하여 합성된 금 나노구조체를 이용하여 광열 전환(photothermal heat conversion)과 광 간섭성 단층 (optical coherence tomography) 측정을 진행하였고, 서로 다른 두 개의 디스크가 적층된 형태의 금 나노구조체는 상용 금 나노로드 (Au nanorod) 보다 높은 광 열 전환 효율을 갖을 뿐 아니라 우수한 OCT 이미징 특성을 보였다. 광열 전환 및 OCT 이미징 실험 결과는 각각 플라즈모닉 나노구조의 광흡수, 광산란 특성에 기반하므로, 본 연구를 통하여 제안된 금 나노구조체는 광흡수 및 광산란을 기반한 바이오이미징 나노프로브로 유용하게 사용될 수 있을 것으로 전망된다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.136-136
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• 2004

허근 차세대 반도체, 정보통신, 및 디스플레이 산업 등에 응용하기 위하여 초정밀화와 저비용 대량생산을 하기 위해서 기존의 공정을 대체할 수 있는 새로운 나노 공정기술의 요구가 급증하고 있다. 최근 연구에서는 펨토초 레이저 (femto second laser)의 이광자흡수 고화현상을 이용한 나노공정 개발에 대하여 다양한 연구가 진행되고 있다. 특히, 기존의 패터닝과 에칭공정 중심의 소형화 기술(miniature technology)로 제작이 어려운 3차원 자유곡면을 가지는 구조물 제작에 관한 공정개발에 대하여 다양한 연구가 진행되고 있다.(중략)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.65-71
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• 2016

In recent years, 3D printing has received increasing attention due to releases of low-cost 3D printers based on open-source platform. 3D printing is expected to reduce the barrier to entry in the traditional manufacturing processes by increasing flexibility and creating an advantage to manufacture customized products at low costs. In this study, a unique eyeglass frame was designed to have a snake shape, which has an asymmetric geometry unlike traditional frames. The eyeglass frame was designed in a customized manner by reflecting dimensional characteristics of a customer's face. Finite element analysis was performed to investigate the structural safety of the 3D printed frames during the assembly process. The analysis also considered the effect of anisotropic material properties as determined by tensile tests. The eyeglass frame was then printed using the customized sizes and the best building process. The eyeglass frame was successfully assembled with lenses and without structural failure during its assembly procedure.

• Polymer(Korea)
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• v.29 no.4
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• pp.418-421
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• 2005

Three-dimensional (3D) microfabrication process using two-photon polymerization (TPP) is developed to fabricate the curved microstructures in a layer, which can be applied potentially to optical MEMS, nano/micro-devices, etc. A 3D curved structure can be expressed using the same height-contours that are defined by symbolic colors which consist of 14 colors. Then, the designed bitmap figure is transformed into a multi-exposure voxel matrix (MVM). In this work a multi-exposure voxel matrix scanning method is used to generate various heights of voxels according to each laser exposure time that is assigned to the symbolic colors. An objective lens with a numerical aperture of 1.25 is employed to enlarge the variation of a voxel height in the range of 1.2 to 6.4 um which can be controlled easily using the various exposure time. Though this work some 3D curved micro-shapes are fabricated directly to demonstrate the usefulness of the process without a laminating process that is generally required in a micro-stereolithography process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1601-1610
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• 1991

본 연구에서는 3차원 스트레칭 문제의 2차원화가 가능한 주요 단면에 대해서 박막요소와 적층 셸(degenerated shell) 요소를 혼합하여 사용하는 선택적 M/S 방법을 이용하여 2차원 문제로 해석하였다. M/S변환 조건으로는 변형형상의 기하학적 조건 을 고려하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.2
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• pp.257-261
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• 2022

Additive manufacturing (AM, also known as 3D printing) applied to the construction industry is implemented and verified for various effects since advantages such as high design freedom, improving worker safety, and predictable construction period. However, due to the low maturity compared to the existing technology, studies are underway to solve new problems that occur in the overall of AM technology. In this paper, we confirm the effect of low construction surface flatness on the stacked features in the process of on-site AM construction. In particular, unstable AM features are determined through quantitative analysis by laser scanning, and a construction strategy is proposed for the surface flattening.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.1
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• pp.1-7
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• 2012

This study investigates free vibration characteristics of laminated composite structures with different embedded delamination sizes and locations using the solid element. The three-dimensional finite element (FE) delamination model described in this paper, in comparison with the conventional approaches, is more attractive not only because it shows better accuracy but also it shows the entire mode shape. The FE model using ABAQUS is used for studying free vibrations of laminates containing an various embedded delamination. The numerical results obtained are in good agreement with those reported by other investigators. In particular, new results reported in this paper are focused on the significant effects of the local vibration mode for various parameters, such as size of delamination, aspect ratio, and location of delamination.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.239-241
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• 2009

DRIE(Deep Ion Reactive Etching) 공정은 실리콘 웨이퍼를 식각하는 기술로서 Si wafer 비아 홀 제조에 주로 사용되고 있다. 즉, DRIE 공정은 식각 및 보호층 증착을 반복함으로써 직진성 식각을 가능하게 하는 공정이다. 또한, 3차원 적층 실장에서 Si wafer 비아 홀에 결함없이 효과적으로 구리 충진을 하기 위해서는 직각형 via보다 경사벽을 가진 via가 형상적으로 유리하다. 본 연구에서는 3차원 적층을 위한 Si wafer 비아 홀의 결함 없는 효과적인 구리 충진을 위해, DRIE 공정을 이용하여 기존의 경사벽을 가지는 via 흘 형성 공정보다 더욱 효과적인 공정을 개발하였다.