• 한국주조공학회지
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• 제19권5호
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• pp.403-409
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• 1999

Mg-Zn-Zr ternary alloys containing 6wt% Zn and (0, 0.4, 0.6)wt% Zr, which is added for grain refinement, can be cast into complex shape by squeeze casting. The influence of Zn and Zr as additional elements on microstructure and mechanical characteristics is investigated by OM, SEM, WDX, XRD and microvickers hardness measurement. The microstructure of Mg-Zn-Zr alloys consists of primary ${\alpha}-Mg$ and MgZn eutectic compound between dendrites. The grain size is decreased from $136{\mu}m$ to $97\;{\mu}m$ by Zr addition, resulting in that the hardness is increased from 42Hv to 59Hv. Furthermore, the grain size is changed to $83{\beta}$ and the hardness is increased to 65Hv by additional infiltration pressure. These results indicate that the Zr addition and additional infiltration pressure are effective for grain refinement acting as an important factor to increase the hardness. The increment in hardness by the Zr addition is slightly larger than that by the additional infiltration pressure.

• 한국주조공학회지
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• 제28권3호
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• pp.136-140
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• 2008

A new concept of salt core, a melting temperature of which is lower than the solidus temperature of cast alloy, was introduced to produced an integrated casting part having a complicated inner shape or requiring under-cut in high pressure die casting or squeeze casting process. The main goal of this study is to develop a new integrated net-shape forming technology using fusible core of lower melting temperature than that of a casting alloy. This integrated net-shape forming technology would be very successful and cost-effective for producing the integrated products having a complicated inner shape or requiring under-cut. The technology for measuring and evaluating a various property of fusible core such as a thermal conductivity and thermal expansion coefficient, melting temperature was established. Also, the work space can be cleaned without a pollution inducing products.

• Journal of Welding and Joining
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• 제7권2호
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• pp.60-69
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• 1989

The present study was aimed at investigating the effect of welding parameters such as welding current, electrode force(or squeeze force) and parts cleaning on the sound weld, and establishing the most reliable weld conditions for HWP(Heavy Water Reactor) fuel end capping with the resistance upset butt welding. Major results obtained are as follows. 1. The amount of sound weld was increased with increasing weld current(5.0-11KA) because the activated diffusion with increasing heat generation played an important role in eliminating the porosity and weld line in the weld interface. 2. It was found that weld current was not significantly influenced by the electrode force although the increase of it caused a slight increase of weld current and upset deformation. 3. Acetone rinsing before drying for the Zircaloy-4 end cap cleaning produced the reliable sound weld because it would remove the remaining solvent and surface films, and provided the uniform contact between the end cap and the tube. 4. The optimum welding conditions for fuel end capping by a resistance upset hytt welding are obtained as follows. weld current: 10-11KA, electrode force: 62-90KPa parts cleaning: vapor degreasing.rarw.water, acetone rinsing.rarw.drying.

• 한국재료학회지
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• 제8권11호
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• pp.993-998
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• 1998

본 연구는 형상기억합금을 이용하여 제조한 신소재 중의 하나인 형상기억복합재료를 소개하고자 한다. 이 복합재료는 TiNi 섬유의 형상기억효과로 금속복합재료의 취약점이라 할 수 있는 기지와 섬유간의 열팽창차이로 인한 인장잔류응력을 제거하고 기지내에 압축잔류응력을 발생시켜 높은 인장강도를 갖는다. 따라서 본 연구에서는 용탕단조법으로 복합재료를 제조한 후 미세조직을 관찰하고 TiNi 섬유의 역변태온도 이상에서 피로실험을 수행하여 복합재료의 피로특성을 검토하였다. 이 결과 363K에서의 피로균열전파제어효과는 섬유체적률과 예변형에 의하여 증가된다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.222-225
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• 2001

Optical disk drives read information by replacing a laser beam on the disk track. As information has become larger, the more accurate position control of a laser beam is necessary. In this paper, we report the analysis and fabrication of the micro mirror for optical disk drivers. The mirror was fabricated by using MEMS technology and it's characteristics investigated. Also, electrode structure for reducing squeeze effect was discussed.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권4호
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• pp.436-440
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• 2013

An haptic tactile interface (HTI) is presented with its modeling. Its design is dedicated to perform friction coefficient measurement to characterize reachable feelings with that kind of interface. Friction measurements are presented and discussed.

• 연구논문집
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• 통권23호
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• pp.5-13
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• 1993

The present work deals with the theoretical prediction of static & dynamic characteristic of annular type externally pressurized thrust air bearings with metal-sintered porous media. For the evaluation of surface loading effect by machining, it is assumed that the flow at the porous surface is dominant and which is equivalent to the flow through orifice. Finite different method with over-relaxation method is used to solve the numerical problems. The influences of radius ratio, supply pressure and squeeze number on performances are investigated, as the results. The results of this study can be used to predict the optimal running condition and stable realm of porous bearings.

• 한국주조공학회지
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• 제28권1호
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• pp.41-44
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• 2008

레오다이캐스팅 공정은 용탕상태의 원소재로부터 최종형상에 가장 가까운 정형제품(near-net shape)을 원하는 기계적 성질과 동시에 경제적으로 생산할 수 있는 제조방법으로 개발되어 왔다. 본 논문에서는 전자교반 시스템을 이용하여 결정립이 제어된 반용융 상태의 소재를 수직형 다이캐스팅기를 사용하여 리어파트(rear parts) 자동차 부품을 성형실험 하였다. 성형된 시제품들은 성형조건에 따른 조직 및 인장강도를 관찰하였으며, 시효경화 시간에 따른 T6 최적 열처리 조건을 조사하였다.

• Journal of Animal Science and Technology
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• 제48권2호
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• pp.331-336
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• 2006

소의 개체 관리의 효율성을 높이기 위한 수단으로써 축사의 유도로에 시각제어를 처리하였을 때와 시각제어를 하지 않은 경우에 있어서 한우 집단의 이동시간을 비교하였다. 일반적인 파이프로 시설된 유도로에 비해 불투명한 청색 커튼을 처리 하였을 때 유도로를 통과하는 소의 이동시간이 짧아졌으며 짧은 유도로보다 긴 유도로에서 처리간 유의적인 차이가 나타났다. 아울러 본 실험을 통하여 유도로와 함께 유도로 입구 설계 역시 부드러운 곡선의 형태를 함으로써 소의 머뭇거림을 방지할 수 있음을 보여줬다.유도로가 긴 실험에서 crowd pen에서 선두 소가 유도로에 진입하기까지의 시간에서는 시각 제어 처리한 경우와 처리하지 않은 경우 간에 유의적인 차이가 없었다. 그러나 선두 소가 crowd pen 으로부터 우형기까지 진입하는 시간은 시각 제어 처리를 한 경우가 22.78±1.15초로 처리하지 않았을 때의 40.56±4.46초 보다 유의적으로 단축되었다. 또한 선두소가 유도로에 진입한 시간을 뺀 작업시간과 총 작업시간에 있어서도 시각제어 처리한 경우가 96.33±3.98, 104.56±3.89초로 시각제어를 하지 않은 경우의 121.89±5.54, 131.22±6.42초 보다 모두 유의적으로 단축되었다.유도로가 짧은 실험에서는 유도로가 긴 실험에 비하여 crowd pen의 모서리 모양이 직각으로 되어 시험축 집단의 유도로 진입이 부드럽지 않았다. holding pen에서 crowd pen으로 선두 소가 유도로를 진입한 시간에는 처리간 유의적인 차이가 없었다. 총시간에서 선두 소가 crowd pen을 진입한 시간을 뺀 작업시간에 있어서는 처리 간에 유의적인 차는 없었는데 이는 유도로로 연결된 crowd pen의 모서리 형태의 영향이 크게 작용한 것으로 추측된다. 총작업 시간은 시각제어처리가 209.89±6.06초로 처리하지 않았을 때의 243.56±10.53초 보다 유의적으로 단축됨을 보였다.

• Tribology and Lubricants
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• 제24권5호
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• pp.241-249
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• 2008

This paper describes the tribological effects on the nonlinear behavior of a spur gear pair with one-way clutch according to the direct contact elastic deformation model over a wide range of speeds, considering the hydrodynamic effects. The effects of various lubrication parameters, such as viscosity, film width, and friction, on the nonlinear dynamic behavior were analyzed. Forces due to the entraining velocity and the hydrodynamic friction were about two orders smaller than normal forces over the whole speed range. While the viscosity has a strong effect on the behavior of gear pair systems, friction has very little effect on torsional behavior. The inclusion of the hydrodynamic effect facilitates nonlinearity by increasing the overlap and damping, as well as decreasing elastic deformation and tooth reaction forces.