• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.336.2-336.2
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• 2014

Indium Tin Oxide (ITO) thin films are used as the Transparent Conducting Oxide (TCO), such as flat panel display, transparent electrodes, solar cell, touch screen, and various optical devices. ZnO has attracted attention as alternative materials to ITO film due to its resource availability, low cost, and good transmittance at the visible region. Recently, very thin film deposition is important. In order to minimize the damage caused by bending. However, ZnO thin film such as Ga-doped ZnO(GZO) has poor sheet resistance characteristics. To solve this problem, By adding the conductive metal on films can decrease the sheet resistance and increase the mobility of the films. In this study, We analyzed the electrical and optical characteristics of GZO/Ag/GZO (GAG) films by change in Ag and GZO thickness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.48-53
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• 2002

Sheet or plate bending is one of the most important industrial metal forming processes. And considerable attention has been focused on gaining a better understanding of many of bending characteristics. One of defaults in bending process is the springback. In this study, the springback characteristics of tailor-welded strips in U-bending process was investigated. Furthermore, not only the relationships between the springback and the process variables such as the geometry of the tools and thickness combination of workpiece but also the heat effect which affects the springback due to welding process was experimentally considered. First, tailor-welded strips are joined by the laser welding process and consisted of two types of thickness combinations of the SCPI sheet, 0.8t${\times}$1.2t and 0.8${\times}$1.6t to investigate the effect of different thickness combination on the springback. Secondly, two different directionally welded strips, one was welded along the centerline of the strip-width and the other was along the centerline of strip-length, were adopted to compare the effects of the location of weld line on the springback. And three punch profile radii of 3, 9, and 15 m were used. Some cases of the experimental results were simulated by using a commercial FEM code, PAM-STAMP to compare the experimental results to the analytical ones.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.203-206
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• 2009

$Sn_XSe_{100-X}$ (15|X|30) alloys have been studied to explore their suitability as phase change materials for nonvolatile memory applications. The phase change characteristics of thin films prepared by a Radio Frequency (RF) magnetron co-sputtering system were analyzed by an X-ray diffractometer and 4-point probe measurement. A phase change static tester was also used to determine their crystallization under the pulsed laser irradiation. X-ray diffraction measurements show that the transition in sheet resistance is accompanied by crystallization. The amorphous state showed sheet resistances five orders of magnitude higher than that of the crystalline state in $Sn_XSe_{100-X}$ (x = 15, 20, 25, 30) films. In the optimum composition, the minimum time of $Sn_XSe_{100-X}$ alloys for crystallization was 160, 140, 150, and 30ns at 15mW, respectively. The crystallization temperature and the minimum time for crystallization of thin films were increased by increasing the amount of Sn, which is correlated with the activation energy for crystallization.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.300-300
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• 2010

후면 패시베이션, back contact의 가변, 후면 접촉면적의 가변 등으로 Laser Fired Contact 태양전지의 효율을 증가 시킬 수 있다. 이 중 spacing의 가변으로 후면 접촉 면적을 가변 할 수 있으며, 이로 인하여 LFC 태양 전지의 효율을 높일 수 있을 것으로 전망된다. 본 연구에서는 후면 접촉 면적을 가변하였으며 이에 따른 효과를 확인하였다. series resistance가 작고, open circuit voltage 가 높은 최적의 조건을 찾는 것에 그 목적을 두었다. 실험 순서는 texturing 후, 후면에 SiNx를 10nm 증착하였으며, drive-in 방법으로 $POCl_3$을 도핑하였다. ARC후, spacing 조건 가변으로 접촉 면적을 가변시키면서 소자의 특성 변화를 비교하였다. 접촉 면적 및 spacing 조건은 5개의 set에 대하여 reference, 50%의 접촉 면적을 가지는 $150{\mu}m$ line, 10%의 접촉 면적을 가지는 $700{\mu}m$ line, 1%의 접촉 면적을 가지는 $700{\mu}m$ dot, 그리고 0.2%의 접촉 면적을 가지는 $1500{\mu}m$ dot으로 하였다. 각각의 경우에 대한 short circuit current density, fill factor, seris resistance, sheet resistance, open circuit voltage를 측정하였으며, 특히 series resistance는 각각의 경우에 대하여 $6.1m{\Omega}$, $5.1m{\Omega}$, $7.8m{\Omega}$, $10.1m{\Omega}$, 그리고 $15.7m{\Omega}$으로 측정되었다. wafer의 외각 테두리를 접촉 면적이 증가함에 따라서 sheet resistance가 증가하는 것을 확인 할 수 있었다.

• Transactions of Materials Processing
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• v.12 no.5
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• pp.440-448
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• 2003

Sheet or plate bending is one of the most important industrial metal forming processes. Considerable attention has been focused on gaining a better understanding of bending characteristics. One of defaults in bending process is the springback. In this study, the springback characteristics of tailor-welded strips in U-bending process was investigated. Furthermore, effect of the process variables such as the geometry of the tools, thickness combination of workpiece, and welding prcoessing on springback were experimentally clarified. First, tailor-welded strips are joined by the laser welding process and consisted of two types of thickness combinations of the SCPl sheet, $0.8t{\times}1.2t$ and $0.8t{\times}1.6t$ to investigate the effect of different thickness combination on the springback. Secondly, two different directionly welded strips, one was welded along the centerline of the strip-width and the other was along the centerline of strip-length, were adopted to compare the effects of the location of weld line on the springback. Some cases of the experimental results were compared to the results simulated by using a commercial FEM code, PAM-STAMP and the theoretical results using the springback formula as well.

• Journal of the Korean institute of surface engineering
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• v.56 no.1
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• pp.69-76
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• 2023

The effects of hairline treatment on surface blackening and thermal diffusion behaviors of Zn-Al-Mg alloy coated steel sheet were evaluated by the three-dimensional surface profiler and laser-flash technique. The metallographic observation of coating damages by hairline treatments showed that several cracks were initiated and propagated along the interface between primary Zn/eutectic phases. As the hairline processing became more severe, the crack occurrence frequency in eutectic phase of coating layer and the surface roughness increased, which had a proportional relationship with the level of blackening on the coating surface. In addition, the higher interfacial areas of the blackened coating surface, caused by the hairline process, led to an increase in thermal diffusivity and conductivity of the coated steel sheet. On the other hand, when the coating damage by hairline treatment was excessive and the steel substrate was exposed, there was little difference between the thermal diffusivity/conductivity of the untreated sample though the blackening degree was higher than that of untreated sample. This work suggests that the increase in the surface areas of the coating layer without exposure to steel substrate through hairline treatment can be one of the effective technical strategies for the development of Zn-Al-Mg alloy coated steel sheets with higher blackening level and thermal diffusivity.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.922-930
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• 2004

An experimental investigation was performed to study on the generation of air bubble and air core with swirling flow in a horizontal cicular tube. To determine some characteristics of the flow, 2D PIV technique is employed for velocity measurement in water. The experimental rig is manufactured from an acryl tube. The test tube diameter of 80mm, and a length of 3000mm. The used algorithm is the gray leve cross-correlation method(Kimura et al. 1986). An Ar-ion laser is used and the light from the laser(500mW) passes through a probe to make two-dimensional light sheet. In order to make coded images of the tracer particles on one frame, an AOM(Acoustic-Optical Modulator) is used. The maximum axial velocities showed near the test tube wall at y/D =0.1 and y/D =0.9 along the test tube. The higher Reynolds number increase, the lower axial velocities are showed in the center of the test tube. The air bubbles are generated from Re =10,000 and developed into air core from the recirculating water pump rpm equal 30Hz. The pressure and temperature are measured across the test tube at X/D=3.33.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.160-166
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• 2011

Weight reduction while maintaining functional requirements is one of the major goals in the automotive industry. The use of lightweight magnesium alloys offers great potential for reducing weight because of the low density of these alloys. However, the formability and the surface quality of the final magnesium alloy product for auto-body structures are not acceptable without a careful optimization of the design parameters. In order to overcome some of the main formability limitations in the stamping of magnesium alloys, a new approach, the so-called "hybrid technology", has been recently proposed for body-in-white structural components. Within this approach, necessary level of mechanical joining can be obtained through the use of lightweight material-steel adhesion promoters. This paper presents the development process of an automotive hybrid hood assembly using magnesium alloy sheets. In the first set of material pairs, the selected materials are magnesium alloy AZ31B alloy and steel(SGCEN) as inner and outer panels, respectively. In order to optimize the design of the inner panel, the stamping process was analyzed with the finite element method (FEM). Laser welding by CW Nd:YAG were used to join the magnesium alloy sheets. Based on the simulation results and mechanical test results of the joints, the determination of die design variables and their influence on formability were discussed. Furthermore, a prototype based on the proposed design was manufactured and the static stiffness test was carried out. The results demonstrate the feasibility of the proposed hybrid hood with a weight reduction of 25.7%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.285-288
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• 2009

In order to understand spray characteristics with inflowing air from the compressor in the APU gas turbine combustor, we performed spray visualization test by using ND-Yag Laser sheet beam. The sector combustor which size is 1/6 of the real combustor was manufactured. Turbo blower is used as an air supplying device to simulate gas turbine air flow condition. In the case of 75 m/s combustor inlet air flow condition, spray angle way increased and dispersed widely than without airflow condition.

• Journal of ILASS-Korea
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• v.6 no.4
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• pp.14-21
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• 2001

Rotary atomizer is widely used in practical application ranging from combustion, cooling, spray drying, agriculture, chemical system. Rotary cup atomizer has some advantages such as extreme versatility and liquid atomization successfully varying widely in viscosity. In rotary atomization, the feed liquid is centrifugally accelerated to high velocity and the liquid extends over the rotating surface as a thin film before being discharged into an atmosphere. The degree of rotary atomization depends upon peripheral speed, feed rate, liquid properties and atomizer design. An important asset is that thickness and uniformity of the liquid sheet can readily be controlled by regulating the liquid flow rate and the rotational speed. LDPA(Laser Diffraction Particle Analyser) and image aquisition system are used to measure drop size distribution and spray pattern. The atomization characteristics of the rotary cup atomizer is investigated experimentally by varing the liquid feed rate, rotary cup speed and air velocity for atomization. As a results, the effect of air velocity on the atomization characteristics such as drop size and spray uniformity is considerably greater than variation of those with liquid feed rate.