• 한국생산제조학회지
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• 제26권1호
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• pp.44-49
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• 2017

Titanium has been used in various fields due to its good corrosion and erosion resistance, and superior mechanical properties. The process for selective electro-deposition on a titanium surface using laser beam is proposed in this paper. The process consists of laser irradiation, electro-deposition, and ultrasonic cleaning. Laser irradiation can change the surface morphology of titanium. Through laser irradiation, the surface cleaning effect and a rough surface can be achieved. The surface roughness of titanium was measured according to the laser beam conditions. The characteristics of selective electro-deposition on titanium surface according to surface roughness are investigated by various analytical methods such as SEM, and EDS.

• 소성∙가공
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• 제18권7호
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• pp.519-530
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• 2009

The study is concerned with shape correction of stamped product using the laser irradiation. As a fundamental study, laser irradiation process has been analyzed through the thermo-mechanical FE analysis. For the purpose of validation, laser scanning experiment has been carried out also. Since the deformation mechanism involved in the laser scanning is extremely complicated due to the highly temperature dependent material properties, the determination of laser scanning pattern is not easy for the application of real stamped parts. A simplified method for the application of springback correction has been suggested with the thermo-mechanical FE analysis.

• Journal of Welding and Joining
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• 제21권6호
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• pp.20-25
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• 2003

Various welding methods such as Gas Tungsten Arc Welding(GTAW), magnetic force electrical resistance welding and Laser Beam Welding(LBW) are now available for end cap closure of nuclear fuel rods. Even though the resistance and GTA welding processes are widely used in manufacturing commercial fuel rods, they can not be recommended for the remote seal welding of fuel rods in the hot cell Facility due to the complexity of the electrode alignment, the difficulty in replacing parts in a remote manner and the large heat input for the thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for the end cap welding of irradiation fuel rods in the hot cell. The remote laser welding apparatus in the hot cell Facility was developed using a pulsed Nd:YAG laser of 500 watt average power with an optical fiber transmission. The weldment quality such as microstructure and mechanical strength was satisfactory. The optimum conditions of laser welding for encapsulating irradiation fuel rods in the hot cell were obtained.

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.45-48
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• 1990

CO2 laser beam was focused by a ZnSe lens onto the center of the occlusal surface f extracted lower molars. K-type thermocouple was contacted with the pulp chamber and the changes of temperature in the during and after the laser irradiation were measured as function of the power of laser beam, the time of laser irradiation and thickness of the sample. An empirical formula for temperature effect was derived from the measured data.

• Journal of Periodontal and Implant Science
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• 제41권5호
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• pp.234-241
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• 2011

Purpose: One of the most frequent complications related to dental implants is peri-implantitis, and the characteristics of implant surfaces are closely related to the progression and resolution of inflammation. Therefore, a technical modality that can effectively detoxify the implant surface without modification to the surface is needed. The purpose of this study was to evaluate the effect of erbium-doped: yttrium, aluminium and garnet (Er:YAG) laser irradiation on the microstructural changes in double acid-etched implant surfaces according to the laser energy and the application duration. Methods: The implant surface was irradiated using an Er:YAG laser with different application energy levels (100 mJ/pulse, 140 mJ/pulse, and 180 mJ/pulse) and time periods (1 minute, 1.5 minutes, and 2 minutes). We then examined the change in surface roughness value and microstructure. Results: In a scanning electron microscopy evaluation, the double acid-etched implant surface was not altered by Er:YAG laser irradiation under the condition of 100 mJ/pulse at 10 Hz for any of the irradiation times. However, we investigated the reduced sharpness of the specific ridge microstructure that resulted under the 140 mJ/pulse and 180 mJ/pulse conditions. The reduction in sharpness became more severe as laser energy and application duration increased. In the roughness measurement, the double acid-etched implants showed a low roughness value on the valley area before the laser irradiation. Under all experimental conditions, Er:YAG laser irradiation led to a minor decrease in surface roughness, which was not statistically significant. Conclusions: The recommended application settings for Er:YAG laser irradiation on double acid-etched implant surface is less than a 100 mJ/pulse at 10 Hz, and for less than two minutes in order to detoxify the implant surface without causing surface modification.

• The Journal of Korean Physical Therapy
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• 제14권2호
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• pp.234-249
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• 2002

This study was performed, using c-fos and Substance P, to investigate the effect of GaAlAs laser on acute pain model induced by wound in lumbar region's spinal level. The test group was divided into control and experimental group. Control group is shamed group(c-fos and substance P expression after non-irradiation by a GaAlAs laser), The experimental group was divided into two subgroups: one is experimental group I (c-fos expression after irradiation by a GaAlAs laser), and the other is experimental group II (substance P expression after irradiation by a GaAlAs laser). The results of this study were as following: 1. The numbers of c-fos immunoreactive neuron in spinal cord was increased markedly 1 day after wound, and decreased gradually from 1 day to 2 days in wound with GaAlAs laser irradiation. 2. The changes of the average percentages of substance P immunoreactive neurons in spinal cord was increased markedly 1 day after wound, and decreased gradually from 1 day to 2 days in wound with GaAlAs laser irradiation. Therefore, decreasing the changes of c-fos and substance P expression after irradiation by a GaAlAs laser indicates and GaAlAs laser have effect on pain control.

• 한국분말재료학회지
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• 제8권4호
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• pp.239-244
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• 2001

To investigate the effect of process parameters on selective laser sintering of Cu/polyamide mixed powder, Cu/polyamide mixed powder was sintered by selective laser with changing laser power and scanning speed. The properties of sintered body were evaluated by measuring the density and tensile strength, and analysis of XRD, FT-Raman and microstructure. With an increase in the laser power, the density and ultimate tensile strength of sintered Cu/polyamide body increase and then decrease. The maximum values of the density and ultimate tensile strength were decreased with increasing laser scanning speed. These changes were concerned with the difference of irradiation energy of laser into the powder layer. It was considered that the change of the mechanical property of the sintered body with irradiation energy of laser is due to the changes of amount of copper particle and property of polyamide.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.228-234
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• 2002

The CO$_2$ laser beam irradiation strengthening of 35kgf/mm$_2$ grade steel sheet is investigated to reduce the weight of bumper beam. The increase of tensile strength is dominated by the number of fully penetrated melting lines. The optimal laser irradiation pattern is obtained by 3-point bending test of hat-type specimens. Laser should be irradiated not only on the center specimen densely in the width direction, but also on the edge densely in the longitudinal direction. Local laser strengthening may be effective for the weight reduction of automobile bumper beam.

• 대한소아치과학회지
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• 제33권2호
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• pp.201-206
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• 2006

건전한 치질에 탄산가스 레이저의 조사로 내산성을 증가시키거나 탄산가스 레이저의 조사 전 후에 국소적 불소도포를 함께 시행함으로써 치아우식증 예방효과를 얻을 수 있다. 따라서 이 논문에서는 치아의 법랑질 평활면에 레이저를 조사한 후 법랑질 표면의 변화를 주사 전자 현미경과 원자 현미경을 통하여 관찰하고 불소도포와 레이저 조사를 병용하였을 경우의 차이 및 원자 현미경의 효율성을 알아보고자 한다. 그 결과 대조군과 비교 시 레이저를 조사한 군들에서 미세한 균열과 소와 및 입자형 성상이 관찰되었으며, 불소도포 시에는 좀더 평활한 표면을 보였다. 이러한 레이저와 불소의 병용은 치아 표면에 칼슘, 인 불소가 재흡착되어 표면에 입자형태를 보이며 이것이 치아우식증에 대한 저항성을 나타내는 원인 중 하나라고 생각된다.

• 한국군사과학기술학회지
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• 제14권5호
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• pp.897-903
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• 2011

The objective of this study is to investigate the thermal behavior on material surface and the variation in the surface morphology of aluminum 6061 alloy by the Nd:YAG pulsed-laser irradiation. First, we predicted the surface temperature variation during pulsed-laser irradiation by using the two dimensional finite element analysis. When the pulsed-laser of 133 mJ energy and 5 ns pulse duration is irradiated on the surface of aluminum alloy, the material surface is thought to be melting because the surface temperature rises steadily up to about $660^{\circ}C$ exceeding the melting point. Also, the experimental results show that the solidification microstructure has been developed clearly after surface melting. Second, the diameter of melted zone was analysed by finite element analysis and measured by OM(Optical Microscopy). It increased logarithmically with increase in the number of laser irradiation. In addition, AFM(Atomic Force Microscopy) measurement showed an increase in the average surface roughness during pulsed-laser irradiation.