• 한국정밀공학회지
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• 제17권11호
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• pp.191-198
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• 2000

Laser direct patterning of the coated photoresist (PMER-NSG31B) layer was studied to make halftone dots on gravure printing roll. The selective laser hardening of photoresist by Ar-ion laser(wavelength: 333.6~363.8nm) was controlled by the A/O modulator. The coating thickness in the range of 5~11$\mu m$ could be obtained by using the up-down directional moving device along the vertically located roll. The width, thickness and hardness of the hardened lines formed under the laser power of 200~260㎽ and irradiation time of 4.4~6.6 $\mu$sec/point were investigated after developing. The hardened width increased as the coating thickness increased. Though the hardened thickness was changed due to the effect of the developing solution, the hardened layer showed good resistance to the scratching of 2H pencil. Also, the hardened minimum line widths of 10$\mu m$ could be obtained. The change of line width was also found after etching, and the minimum line widths of 6$\mu m$ could be obtained. The hardened lines showed the good resistance to the etching solution. Finally, the experimental data could be applied to make gravure halftone dots using the developed imaging process, successfully.

• 대한기계학회논문집B
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• 제27권3호
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• pp.275-285
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• 2003

A visualization study on the effect of forcing amplitude in tone-excited jet diffusion flames has been conducted. Visualization techniques are employed using optical schemes. which are a light scattering photography. Flame stability curve is attained according to Reynolds number and forcing amplitude at a fuel tube resonant frequency. Flame behavior is globally grouped into two from attached flame to blown-out flame according to forcing amplitude: one sticks the tradition flame behavior which has been observed in general jet diffusion flames and the other shows a variety of flame modes such as the flame of a feeble forcing amplitude where traditionally well-organized vortex motion evolves, a fat flame. an elongated flame. and an in-burning flame. Particular attention is focused on an elongation flame. which is associated with a turnabout phenomenon of vortex motion and on a reversal of the direction of vortex roll-up. It is found that the flame length with forcing amplitude is the direct outcome of the evolution process of the formed inner flow structure. Especially the negative part of the acoustic cycle under the influence of a strong negative pressure gradient causes the shapes of the fuel stem and fuel branch part and even the direction of vortex roll-up to dramatically change.

• 한국자동차공학회논문집
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• 제20권4호
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• pp.52-59
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• 2012

The subframe has been generally manufactured by using stamped steel material. Recently, automotive designers are considering aluminum as lightweight material. This paper describes the development process of an aluminum subframe which is made by high level vacuum die casting process, which is beneficial for minimizing gas contents and material properties. The weight of manufactured subframe is reduced by 4kg with the comparison of steel subframe. The aluminum subframe is packaged for the current vehicle layout and the imposed requirement is to attain a better structural performance that is evaluated in terms of mounting stiffness, noise and vibration, and endurance performance. The NVH evaluation results show that sound level is decreased by 8dB with the help of high roll-rod mounting stiffness as well as high structural modes.

• 한국재료학회지
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• 제24권11호
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• pp.585-590
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• 2014

Microstructural evolution in the thickness direction of an oxygen free copper processed by accumulative rollbonding (ARB) is investigated by electron back scatter diffraction (EBSD) measurement. For the ARB, two copper alloy sheets 1 mm thick, 30 mm wide and 300 mm long are first degreased and wire-brushed for sound bonding. The sheets are then stacked and roll-bonded by about 50% reduction rolling without lubrication at an ambient temperature. The bonded sheet is then cut to the two pieces of the same dimensions and the same procedure was repeated on the sheets up to eight cycles. The specimen after 1 cycle showed inhomogeneous microstructure in the thickness direction so that the grains near the surface were finer than those near the center. This inhomogeneity decreased with an increasing number of ARB cycles, and the grain sizes of the specimens after 3 cycles were almost identical. In addition, the aspect ratio of the grains decreased with an increasing number of ARB cycles due to the subdivision of the grains by shear deformation. The fraction of grains with high angle grain boundaries also increased with continuing process of the ARB so that it was higher than that of the low angle grain boundaries in specimens after 3 cycles. A discontinuous dynamic recrystallization occurred partially in specimens after 5 cycles.

• 청정기술
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• 제23권4호
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• pp.421-428
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• 2017

본 연구는 상용활성탄을 사용하여 산업공정에서 많이 사용되는 휘발성 유기화합물 중 톨루엔, 메틸에틸케톤(MEK), 이성분계(톨루엔-MEK)를 대상으로 흡착 및 탈착특성을 고찰하였다. 최적탈착온도를 설정하기 위해 온도별 탈착특성을 고찰하였고, 활성탄의 특성을 파악하기 위해 BET분석을 하였다. 상온에서 흡착실험을 진행하였고, $120^{\circ}C$까지 승온하여 탈착실험을 진행하였다. 이 실험을 10회 반복해서 진행하였다. 이를 통해 단일성분에서는 반복횟수가 많아질수록 흡착 및 탈착능이 줄어들며 활성탄과 상대적으로 친화력이 적은 MEK의 경우 톨루엔보다 낮은 흡착 및 탈착능을 보였다. 이성분계의 흡착 및 탈착 반복시험에서 친화력이 낮은 MEK가 먼저 파과되고 결과적으로 주입 농도보다 높은 농도로 탈착되었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.826-831
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• 2004

In this study. problems caused during production process of stainless steel carbody are investigated and solutions are found out. Roll forming process to make complex shape is introduced and surface crack on high strength stainless steel plate is investigated. Also, surface indentation is discussed and the effect of welding condition is clarified. Insulated tip to reduce the indentation is recommended for improvement of surface smoothness. Lastly. corrosion of welded joint is discussed and the effects of material, stress and environment are investigated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.163.3-163
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• 2001

This paper presents the two-step strategy method of performing optimal scheduling of paper mill processes using MINLP (Mixed-Integer Non-Linear Programming) considering the trim loss problem in sheet cutting processes. The mathematical model for a sheet cutting process in the form of MINLP is developed in this study, and minimizing total cost is performed considering the cost of raw paper roll, :hanging cutting patterns, storage of over-product and recycling/burning trim. The paper has been used to deliver and conserve information for a long time, and it is needed to have various sizes and weights ...

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.525-530
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• 1992

This paper deals with an exit strip gauge controller design for a cold rolling mill process with one input and two outputs. In order to attenuate the exit strip gauge variation caused by the Back-up roll eccentricity and the entry guage variation, an H$_{\infty}$ controller design methodology is used to keep the frequency weighted mixed sensitivity function small. Effectiveness of the proposed controller is demonstrated by a computer simulation..

• Composites Research
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• 제23권3호
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• pp.58-63
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• 2010

MWCNT의 형상비 차이에 따른 MWCNT/에폭시 복합재료의 인장 및 굽힘 특성과 전기전도도를 비교하였다. 호모믹서(homomixer)와 3단롤밀(three-roll mill)을 사용하여 분산된 MWCNT와 에폭시 혼합물을 금형에 부어 압축 성형법으로 시편을 제조하였다. 에폭시 내 MWCNT의 분산 정도를 평가하기 위해 SEM을 사용하여 시편의 파단면을 관찰하였다. MWCNT의 첨가로 인해 인장강도는 최대 7%증가 하였으나 굽힘강도는 증가가 미미하였으며 형상비가 가장 큰 MWCNT의 경우에는 감소하였다. MWCNT 포함량을 변화시켰을 때 CM-95의 경우 인장강도는 1wt%에서, 굽힘강도는 0.5wt%에서 최대값을 보였으나 더 많은 포함량에서는 감소하였다. MWCNT/에폭시 복합재료의 두께 방향 및 면내방향 전기전도도는 2단자법에 의한 저항값으로부터 계산되었으며 MWCNT의 형상비가 클수록, 또 포함량이 증가할수록 전기전도도 값은 증가하였다.

• 한국지능시스템학회논문지
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• 제21권3호
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• pp.353-358
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• 2011

본 논문에서는 이족 로봇을 위한 가상의 다리에 기반한 보행 모델을 제시한 후, 시뮬레이션을 통하여 제시한 보행 모델의 근본적인 롤/피치/요(roll/pitch/yaw) 운동 특성을 분석한다. 이를 위하여 로봇의 무게 중심과 압력 중심에서의 운동 경로를 사람의 발걸음 운동 패턴과 유사한 임의의 패턴으로 설정하고, 이러한 경로를 따라 보행할 경우에 나타나는 주요 관성 성분 특성을 확인한다. 결과적으로, 이족 보행에서 롤, 피치 및 요 방향으로의 운동은 보행과정에서 생성될 수 있는 자연스러운 현상이며, 이것은 발걸음의 간격, 무게 중심의 위치 및 로봇 몸체의 이동가속도와 밀접한 관계가 있음을 보인다. 또한, 이족보행의 밸런스 관점에서 발의 위치 설정을 위한 경로계획의 중요성을 고찰한다.