• 한국정밀공학회지
• /
• 제23권4호
• /
• pp.162-167
• /
• 2006

Hot embossing lithography(HEL) has the production advantage of comparatively few process step, simple operation, a relatively low cost for embossing tools(Si), and high replication accuracy for small features. In this paper, we considered the nano-molding characteristic according to molding parameters(temperature, pressure, times, etc) and induced a optimal molding condition using HEL. High precision nano-patter master with various shapes were designed and manufactured using the DRIE(Deep Reactive ion Etching), LPCVD(Low Pressure Chemical Vapor Deposition) and thermal oxidation process, and we investigated the molding characteristic of DVD and Blu-ray nickel stamp. We induced flow behaviors of polymer, rheology by shapes and sizes of the pattern through various molding experiments. Finally, with achieving nano-structure molding with high aspect ratio, we will secure a basic technology about the molding of large-area nano-pattern media.

• Structural Engineering and Mechanics
• /
• 제60권5호
• /
• pp.829-849
• /
• 2016

In this paper, experimental as well as numerical analysis of Glass Fiber Reinforced Polymer (GFRP) laminated composite has been presented under ballistic impact with varying projectile nose shapes (conical, ogival and spherical) and incidence velocities. The experimental impact tests on GFRP composite plate reinforced with woven glass fiber ($0^{\circ}/90^{\circ}$)s are performed by using pneumatic gun. A three dimensional finite element model is developed in AUTODYN hydro code to validate the experimental results and to study the ballistic perforation characteristic of the target with different parametric variations. The influence of projectile nose shapes, plate thickness and incidence velocity on the variation of residual velocity, ballistic limit, contact force-time histories, energy absorption, damage pattern and damage area in the composite target have been studied. The material characterization of GFRP composite is carried out as required for the progressive damage analysis of composite. The numerical results from the present FE model in terms of residual velocity, absorbed energy, damage pattern and damage area are having close agreement with the results from the experimental impact tests.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
• /
• pp.275-278
• /
• 2010

핀틀형 추력기는 운용 도중에 노즐목 면적을 변경시켜 고체추진기관과 같은 추력기를 액체 추진기관과 같이 추력을 자유자재로 조절할 수 있다. 본 논문에서는 SNECMA사(社)에서 개발한 Divert용 핀틀추력기의 핀틀의 형상 변화에 대해 수치해석 기법으로 분석하였다. Bore에 의하여 핀틀 구동시 받게되는 핀틀의 하중은 줄어들었고, 핀틀 형상에 따라 유동장이 크게 변하는걸 확인하였다.

• 정보교육학회논문지
• /
• 제16권4호
• /
• pp.451-462
• /
• 2012

본 연구는 초등수학 도형영역의 문제점을 해결하기 위한 방안의 하나로 초등학교 6학년 수학과 도형영역을 중심으로 현실세계에 가상 객체를 부가하여 학생 스스로 탐구하는 학습, 원리나 개념을 스스로 발견하게 하는 학습 객체를 만들었다. 본 연구에서 제안한 방법으로 서울 소재 M 초등학교 6학년 2급 학급을 선정하여 증강현실을 활용한 도형영역의 수업이 학생들의 학업성취도에 어느 정도의 영향을 미치는지 확인하기로 하였다. 그 결과 실험집단의 학습자들은 통제집단의 학습자보다 수업 흥미도 및 수업 만족도, 학업성취도에서 통계적으로 높게 나타났다. 이는 증강현실 도형 학습이 학습자에게 수업참여에 적극성을 가지게 하고, 도형 관련 개념 형성 및 학업성취도 관련이 있음을 알 수 있다.

• 복식
• /
• 제64권4호
• /
• pp.106-117
• /
• 2014

The purpose of this study is to provide basic information for the development of well-fitting and comfortable brassieres for women in their 30s, based on the classification of breast shapes by utilizing 3D body measurement data of women in the age group. The result of processing the measurements from the 3D body scan data through RapidForm 2006 shows that while the vertical body measurements decrease, the horizontal measurements, which indicates the degree of obesity, increase proportionally with age. Also, the relevant measurements for upper breasts increase proportionally with age, while the measurements for lower part of the breasts decrease as the degree of sagging increases. Four composition factors of the breasts were identified through the factor analysis: Factor 1 is the level of volume in the breasts and the surrounding area; Factor 2 is the position of nipples and the shape of upper part of breasts; Factor 3 is the position and vertical length of the breasts; Factor 4 is the shape of lower part of breasts; and Factor 5 is the shape of inner part of breasts and degree of width between both breasts. The breasts have been categorized into three distinctive shapes: Breast Shape 1, Breast Shape 2 and Breast Shape 3. According to the results of the cluster analysis, the largest percentage (36.68%) of women in their 30s falls into the category of Breast Shape 2 with small volume and flat upper breasts, followed by Breast Shape 1 (32.66%) with large volume in the upper and lower parts of breasts, and large side to side area, and Breast Shape 3 (30.65%) with average volume and width between breasts.

• 한국항공우주학회지
• /
• 제38권11호
• /
• pp.1094-1104
• /
• 2010

익형주위 착빙 현상과 관련한 기존 연구는 수치적으로 예측된 결빙형상과 실험 결과를 정성적으로 비교하는데 그쳐, 해석 결과의 정확도에 대한 판단과 외기 조건 변화에 따른 결빙형상의 체계적 분석에 한계가 있었다. 이에 본 논문에서는 실린더와 익형의 결빙 형상을 가용한 실험 및 타 수치해석 결과와 비교, 검증하고 정량적으로 분석하는 연구를 수행하였다. 먼저, 개발된 코드로부터 획득한 결빙형상을 얼음의 최대두께와 얼음의 진행방향, 얼음의 분포, 얼음의 면적을 기준으로 나타낸 후 이를 정량적으로 분석하였다. 정량적 분석을 통해 유사한 결빙 형상을 직관적으로 비교할 수 있었다. 개발한 수치해석 코드는 아랫면에서의 결빙 면적, 얼음의 두께를 작게 예측하였다. 이를 개선하기 위하여 보다 정밀한 유동장 계산을 통해 획득한 입자의 궤적이 요구된다.

• 청정기술
• /
• 제14권4호
• /
• pp.265-270
• /
• 2008

본 연구는 전자기기 모듈의 공기 냉각용 정렬 배열된 핀-휜 열교환기에서 휜 형상의 변화가 유동 및 열전달에 미치는 영향을 수치적으로 해석하였다. 휜 단면의 기하학적 형상은 세 가지로서 원형, 타원형, 그리고 날개형이었다. 취급된 모든 휜의 단면적과 높이는 서로 동일하지만, 그 표면적만은 서로 달랐다. 그 결과, 휜의 표면적, 열전달계수, 그리고 열전달 성능은 휜의 형상에 크게 의존하였다. 적절한 형상을 갖는 휜의 열전달 성능은 세 가지 형태의 핀-휜 중에서 날개형 핀-휜이 가장 우수하였다. 이러한 결과로부터 공기의 유량증가측은 휜의 밀도증가 없이 적절한 핀-휜의 형상변화만으로도 핀-휜 열교환기의 냉각성능을 크게 향상 시킬 수 있음을 알 수 있었다.

• Structural Engineering and Mechanics
• /
• 제30권6호
• /
• pp.699-712
• /
• 2008

The effectiveness of wavelet transform in detecting delamination damages in multilayered composite beams and plates is studied here. The damaged composite beams and plates are modeled in finite element software ABAQUS and the first few mode shapes are obtained. The mode shapes of the damaged structures are then wavelet transformed. It is observed that the distribution of wavelet coefficients can identify the damage location of beams and plates by showing higher values of wavelet coefficients at the position of damage. The effectiveness of the method is studied for different boundary conditions, damage location and size for single as well as multiple delaminations in composite beams and plates. It is observed that both discrete wavelet transform (DWT) and continuous wavelet transform (CWT) can detect the presence and location of the damaged region from the mode shapes of the structures. DWT may be used to approximately evaluate the size of the delamination area, whereas, CWT is efficient to detect smaller delamination areas in composites.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.213-218
• /
• 2006

Hot spot phenomenon is caused by non-uniform contact area between brake pad and disk frequent braking. Brake disk deformed by locally concentrated heat increases magnitude of frictional vibration. And this deformation can highly influence the judder vibration. In this experimental study, vibration and hot spot was measured in accordance with rotation of disk and pressure of master cylinder for finding the factors that causes hot spot phenomena. For comparing hot spot aspects with mode shapes of disk, mode shapes were measured by conducting modal test, and analyzed by using finite element analysis. Relation between hot spot phenomenon, and mode shape, pressure of master cylinder and rotation speed of disk respectively, was achieved by hot spot measurement and frequency analysis.

• 한국소음진동공학회논문집
• /
• 제16권8호
• /
• pp.886-892
• /
• 2006

Hot spot phenomenon is caused by non-uniform contact area between brake pad and disk frequent braking. Brake disk deformed by locally concentrated heat increases magnitude of frictional vibration. And this deformation can highly influence the judder vibration. In this experimental study, vibration and hot spot was measured in accordance with rotation of disk and pressure of master cylinder for finding the factors that causes hot spot phenomena. For comparing hot spot aspects with mode shapes of disk, mode shapes were measured by conducting modal test, and analyzed by using finite element analysis. Relation between hot spot phenomenon, and mode shape, pressure of master cylinder and rotation speed of disk respectively, was achieved by hot spot measurement and frequency analysis.