• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.813-816
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• 2006

Complex pressure pulsation phenomenon in fuel rails is generated by rapid opening and closing of injectors and it commonly causes undesirable noise. In this study, fluid-structure interaction analyses based on CFD and FEM have been conducted to examine the pulsation damping characteristics for different shapes of fuel rails. It is shown from the present results that the fuel rail with a high aspect ratio rectangular cross section seems to be best in order to reduce the pressure pulsations. It also agrees well with the previous experimental test by Mizuno, K. et al.

• 산업기술연구
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• 제26권B호
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• pp.111-118
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• 2006

The reinforced concrete structure is one of the most popular structures in real construction. Concrete has been strengtened rapidly due to the development of new material and construction technology. But as the concrete has been getting stronger, the brittleness of material has increased and the better ductility has been required. So, the study for strengthening stiffener has been urgently needed. As we said above, it is expected that the use of high strength steel and concrete will be increased. However, The experimental data is not enough for solving problems of the use of high strengthened steel and concrete. In this research, we analyzed 45 combinations of the strength levels of concrete, the thickness of material and the steel strength with regard to simple Reinforced Concrete SLAB Beam bridge. The program MIDAS CIVIL was used to find the optimal combination. As a result, it was found that strength ratio per unit section is in inverse proportion to the strength of material and that the strengths of steel are respectively 400 MPa for low strengthened concrete and 300 MPa for high strengthened concrete. For economic aspect and usability, the effect of high strength steel is not as high as we expected it would be.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.31.1-31.1
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• 2010

Various ZnO nanostructures were synthesized and ZnO nanostructure-based self-assembled transistors were fabricated. Compared to spindle and flower like nanostructure, the ZnO nanorod (NR) structure showed much stronger gate controllability, and greatly enhanced device performance, demonstrating that this structural variation leads to significant differences of the nanostructure network-based device performance. Also, patterned dry transfer-printing technique that can generate monolayer-like percolating networks of ZnO NRs has been developed. The method exploits the contact area difference between NR-NR and NR-substrate, rather than elaborate tailoring of surface chemistry or energetic. The devices prepared by the transferring method exhibited on/off current ratio, and mobility of ${\sim}2.7{\times}10^4$ and ${\sim}1.03\;cm^2/V{\cdot}s$, respectively. Also, they exhibited showing lower off-current and stronger gate controllability due to defined-channel between electrodes and monolayer-like network channel configuration. With multilayer stacks of nanostructures on stamp, the monolayer-like printing can be repeated many times, possibly on large area substrate, due to self-regulating printing characteristics. The method may enable high-performance macroelectronics with materials that have high aspect ratio.

• 대한기계학회논문집B
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• 제39권4호
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• pp.301-307
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• 2015

MC-50 사이클로트론에서 방출되는 양성자 빔은 직경이 2-3 mm 의 가우시안 분포를 가진다. 이렇게 넓게 조사되는 양성자 빔은 작은 스팟과 정밀한 위치정밀도를 요구하는 반도체 식각, 마이크로 머시닝 등에는 사용될 수 없다. 본 연구에서는 좀 더 경제적인 대안으로 양성자 빔을 마이크로 홀에 통과시켜 수십 ${\mu}m$ 의 직경을 가지도록 조형하는 방법을 제시하였다. 양성자 빔의 조형을 위하여 평균 직경 $21{\mu}m$, 두께 9mm 의 세장비 428 의 마이크로 홀을 제작하였다. 마이크로 홀과 양성자 빔을 정밀하게 정렬하여 양성자 빔을 조형하였다. 이렇게 조형된 양성자 빔을 이용하여 수십 ${\mu}m$ 크기의 마이크로 구조물의 가공성 확인 실험을 실시하였다. 또한 GEANT4 를 이용한 전산모사를 이용하여 해석한 후, 실험결과와 비교하고 분석하였다. 본 연구를 통하여 MC-50 사이클로트론이 조형 장치와 함께 20 마이크론 대의 3 차원 구조물 제작을 위한 마이크로 공정기술에의 사용 가능성을 확인하였다.

• 항공우주기술
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• 제12권2호
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• pp.209-220
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• 2013

본 논문에서는 항공우주연구원에서 주최하는 2012년 인간 동력 항공기 시범 경진대회에 참가하기 위하여 제작한 충남대학교 Light Bros. 팀의 Human Powered Aircraft인 Volante 날개에 대한 설계/제작과정과 프로펠러의 설계/제작과정을 기술하였다. 동력장치는 두 개의 프로펠러로 구성되어 있고 베벨기어와 지상에서 작동하게 만들어졌다. 프로펠러의 상태변화와 시간에 따른 동력변화를 측정하여 가장 효율적인 프로펠러는 찾는 것이다. 복합재의 사용과 글라이더 형태의 큰 Aspect Ratio(AR)을 갖는 날개의 하중 해석 및 구조 해석을 수행하였다. 주익 Spar의 모델링 및 구조 해석을 수행한 후 구조 시험을 통해 변위 및 Strain 비교를 수행하였으며 결과적으로 주익의 성능 및 안전성을 확인하였다.

• Steel and Composite Structures
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• 제28권1호
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• pp.73-82
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• 2018

This paper experimentally and analytically elucidates the shear behavior and shear bearing capacity of partially prefabricated steel reinforced concrete (PPSRC) columns and hollow partially prefabricated steel reinforced concrete (HPSRC) columns. Seven specimens including five PPSRC column specimens and two HPSRC column specimens were tested under static monotonic loading. In the test, the influences of shear span aspect ratio and difference of cast-in-place concrete strength on the shear behavior of PPSRC and HPSRC columns were investigated. Based on the test results, the failure pattern, the load-displacement behavior and the shear capacity were focused and analyzed. The test results demonstrated that all the column specimens failed in shear failure mode with high bearing capacity and good deformability. Smaller shear span aspect ratio and higher strength of inner concrete resulted in higher shear bearing capacity, with more ductile and better deformability. Furthermore, calculation formula for predicting the ultimate shear capacity of the PPSRC and HPSRC columns were proposed on the basis of the experimental results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.285-287
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• 2008

AAO(Anodic Aluminum Oxidation) method has been known that it is practically useful for the fabrication of nano-structures and makes it possible to fabricate the highly ordered nano masters on large surface and even on the 2.5 or 3D surface at low cost comparing to the expensive e-beam lithography or the conventional silicon processing. In this study, by using the multi-step anodizing and etching processes, highly ordered nano patterned master with concave shapes was fabricated. By varying the processing parameters, such as initial matter and chemical conditions; electrical and thermal conditions; time scheduling; and so on, the size and the pitch of the nano pattern can be controlled. Consequently, various alumina/aluminum nano structures can be easily available in any size and shape by optimized anodic oxidation in various aqueous acids. In order to replicate nano patterned master, the resulting good filled uniform nano molded structure through electro-forming process shows the validity of the fabricated nano pattern masters.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.350-353
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• 2009

In the present study, the effect of initial microstructure, cold reduction ratio, and annealing temperature on the spherodization rate of SK85 high carbon steel sheet was investigated. High carbon steel sheet fabricated by POSCO was soaked at $800^{\circ}C$ for 2 hr in a box furnace and then treated at $570^{\circ}C$ for 5 min in a salt bath furnace followed by water quenching to obtain a fine pearlite structure. Cold rolling was conducted on the sheets of fine pearlite by reduction ratios of 20, 30, and 40% and heat treatment for spheroidization was carried out at 600 and $720^{\circ}C$ for the various time intervals from 0.1 to 32 hrs. Area fraction of spheroidized cementite was measured with an image analyzer as a function of cold reduction ratios and duration times.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.129-130
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• 2008

In this paper, optimal DRIE process conditions for fused quartz are experimentally determined by Taguchi method to develop high-performance inertial sensors based on the fused quartz material, which is known to have high Q-factors. Using Si layer as an etch mask, which was formed by previously developed bonding process of the fused quartz and Si wafer, fused quartz DRIE process was performed. Different 9 flow rate conditions of $C_4F_8$, $O_2$, He gas have been tested and the optimum combination of these factors was estimated. By this work, the ability to fabricate high aspect ratio fused quartz structure was confirmed.

• 한국정밀공학회지
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• 제23권4호
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• pp.162-167
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• 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.