• 동력기계공학회지
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• 제17권2호
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• pp.78-86
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• 2013

In this research, dilute colloidal suspension alumina nanofluids were prepared by dispersing alumina nanoparticles in DI water and ethylene glycol as base fluids. Particle size analyzer and TEM test results revealed that the size of the alumina nanofluids(3wt% and 5wt%) with dispersion time 3hrs were 46nm and 60nm respectively. Thermal conductivity of these alumina nanofluids was measured by means of hot wire technique using a LAMBDA system. For water based alumina nanofluids, thermal conductivity enhancement was from 2.29% to 3.06% with 5wt% alumina at temperatures ranging from 15 to $40^{\circ}C$. Whereas in case of ethylene glycol based alumina nanofluids under the same temperature range, thermal conductivity enhancement was from 9.6% to 10% with 5wt% alumina. An enhancement of 37% average convective heat transfer was achieved with 5wt% alumina nanofluids at Re of 1,100.

• 한국항행학회논문지
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• 제18권1호
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• pp.56-66
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• 2014

태양광 발전에 있어서 태양전지는 일사량, 온도와 부하에 의해 크게 변동하기 때문에 태양전지에 대한 특성 해석이 필요하다. 또한 태양광 발전에 있어서 가능한 많은 에너지를 얻기 위해서는 환경변화에 따른 태양의 위치추적이 필요하며 태양전지의 출력을 항상 최대로 제어할 필요가 있다. 센서와 마이크로프로세서 칩으로 구현된 본 시스템의 실험 결과는 Boost 컨버터의 승압율은 167[%], 소용량에서 에너지 Harvesting 개념과 위치추적 방식의 태양광 발전 구현 가능성을 제시하였다.

• 한국기계가공학회지
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• 제12권1호
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• pp.52-62
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• 2013

In order to obtain the relation between the cutting force and the process parameters in the chamfering process for the gear of a gear shaft, analysis of the process was performed with a simplified model instead of considering the whole actual 3-dimensional cutting situation produced between cutting tool and gear. The model divided the actual situation into the accumulation of hundreds of 2-dimensional layers with a small thickness in the direction of the height of gear and derived cutting force at a cutting position by accumulating each cutting force calculated in a layer. With proposed method to analyze the cutting forces in the chamfering process, it was revealed that the cutting position and size were exactly searched to calculate the cutting force in each layer. The total cutting force was the highest in the corner where the cutter encountered the gear first during the relative motion between them. The cutting forces were changed in proportion to the cutting parameters such as feed rate and trajectory.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.258-264
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• 2016

This paper presents the experimental result and theoretical analysis result to investigate the correlation between the operating force and locking torque for vehicle hood frame. Also, we derived the experimental equations that using the results of experiment and theory. The hood frame is switching-devices used for opening and closing the vehicle hood. It needs the correlation data between locking torques of each joint and operating force of hood frame because the parameters affects the emotional quality of the vehicle. The correlation data for torque and force of hood frame obtained through experiment and theory analysis. Finally, two experimental equations of correlation are derived. Thus, the developed equations show that has high usefulness for the basic design of hood frame of vehicle.

• 한국레이저가공학회지
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• 제15권2호
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• pp.15-20
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• 2012

A novel joining technology was developed to compensate the camber in polymers. The preheating laser beam circulates on the joining location and the accumulated heat serves to increase the flexibility of neighboring polymers. The temperature rises up to the glass transient temperature of the polymers and continually loading spring force closes the gap of camber. The irradiated laser was 808nm central wavelength and the power varied between 2Watt and 5Watt. The laps were adjusted between 3 and 10 and the optimum process parameters were 3Watt and 5 laps for the specific application. An FEM analysis was introduced to understand the mechanism of joining by the transient temperature distribution on the polymers. Thermocouples experiments were also tried to correlate the numerical analysis results and it showed the trend of heat accumulation in experiments.

• 동력기계공학회지
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• 제20권5호
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• pp.20-28
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• 2016

This study has developed an organic/inorganic hybrid solution by addition of $SiO_2$ polysilicate and Melamine to the urethane. The three types of cold rolled steel were evaluated a corrosion resistance properties by using these solutions. The urethane solution(U) and the urethane solution with $SiO_2$ polysilicate($US_7$) were generate a lot of corrosion. The urethane solution with $SiO_2$ polysilicate and melamine($US_7M_3$) was excellent in corrosion resistance, regardless of the steel type. In addition, corrosion resistance has been shown to depend on the tensile strength. The appearance of coating by U and $US_7$ solution is bumpy surface, and were a lot of fine defects. $US_7M_3$ solution is made a sophisticated molecular cross-linking structure inside the coating, it was a slick surface. Other characteristics are exhibited the excellent property for all solutions.

• 반도체디스플레이기술학회지
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• 제18권3호
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• pp.82-87
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• 2019

One of the most critical aspects of the semiconductor industry is the quality of the wafer surface. And the vibrations of wafer grinder are supposed to be the most dominant factors to damage the wafer surface quality. In this study, structure of a wafer grinder has been analyzed through experiments and computer simulations to figure out the main reasons of the vibrations. And the design alterations based on the analysis were applied to identify the effects of those alterations on the vibration suppression. The result shows that the design alterations can effectively suppress about 90% of the vibrations.

• 산업진흥연구
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• 제1권2호
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• pp.1-6
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• 2016

본 연구에서는 고장력강판(SPFH590)을 이용하여 1차 일반전단가공의 클리어런스가 2차 셰이빙 공정에 미치는 영향에 대하여 실험을 통하여 고찰하였다. 실험 결과 일반전단가공의 클리어런스 15%의 경우에서는 셰이빙에 의해 파단면이 완전하게 제거되지 못하여 일부 잔존하였으며, 일반전단가공 10%로 전단한 제품의 셰이빙 가공에 의한 전단면의 크기가 넓게 되는 것을 알 수 있었다. 일반전단가공 10%로 하고, 셰이빙 클리어런스 2%의 경우에는 93%의 전단면이 발생하였으며, 클리어런스 3%에서는 87%의 전단면이 발생하는 것으로 나타났다.

• Journal of electromagnetic engineering and science
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• 제15권1호
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• pp.6-13
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• 2015

In this paper, a novel monopole antenna for WLAN/WiMAX application is presented. The proposed antenna consists of two arc-shaped strips, a vertical strip, and a slot in the ground plane. In this study, a prototype of the proposed triple-band antenna was designed, fabricated, and tested. The quantitative and experimental results demonstrate that the proposed antenna satisfy the -10 dB impedance bandwidth requirement of 440 MHz for 2.4/2.5 GHz bands (from 2.26 to 2.70 GHz), 970 MHz for 3.5 GHz bands (from 3.27 to 4.24 GHz), and 870 MHz for the GHz bands (from 5.08 to 5.95 GHz), while simultaneously covering the WLAN and WiMAX bands. In addition, the presented triple-band antenna has an omnidirectional radiation pattern at all three frequency bands with an antenna gain of 4.45 dBi for the lowest band, 2.04 dBi for the middle band, and 3.98 dBi for the highest band.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.669-674
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• 2020

Liquid-phase-sintered (LPS) SiC materials were briefly examined with their microstructure and mechanical property. Especially, effect of high-temperature exposure on the tendency of fracture toughness of LPS-SiC were introduced. The LPS-SiC was fabricated in hot-press by sintering powder mixture of sub-micron SiC and sintering additives of Al₂O₃-Y₂O₃. LPS-SiC represented dense morphology and SiC grain-growth with some amount of micro-pores and clustered additives as pore-filling. The strength of LPS-SiC might affected by distribution of micro-pores. LPS-SiC tended to decrease fracture toughness depending on increasing exposure temperature and time.