• Journal of ILASS-Korea
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• v.12 no.4
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• pp.185-190
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• 2007

There is a growing interest to develop a new cleaning technology to overcome the disadvantages of wet cleaning technologies such as environmental pollution and the cleaning difficulty of contaminants on integrated circuits. Laser cleaning is a potential technology to remove various pollutants on a wafer surface. However, there is no fundamental data about cleaning efficiencies and cleaning mechanisms of contaminants on a wafer surface using a laser cleaning technology. Therefore, the cleaning characteristics of a wafer surface using an excimer laser were investigated in this study. Fingerprint consisting of inorganic and organic materials was chosen as a representative of pollutants and the effectiveness of a laser irradiation on a wafer cleaning has been investigated qualitatively and quantitatively. The results have shown that cleaning degree is proportional to the laser irradiation time and repetition rate, and quantitative analysis conducted by an image processing method also have shown the same trend. Furthermore, the cleaning efficiency of a wafer contaminated by fingerprint strongly depended on a photothermal cleaning mechanism and the species were removed in order of hydrophilic and hydrophobic contaminants by laser irradiation.

• Journal of Powder Materials
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• v.30 no.5
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• pp.431-435
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• 2023

An irradiation hardening of Inconel 718 produced by selective laser melting (SLM) was studied based on the microstructural observation and mechanical behavior. Ion irradiation for emulating neutron irradiation has been proposed owing to advantages such as low radiation emission and short experimental periods. To prevent softening caused by the dissolution of γ' and γ" precipitates due to irradiation, only solution annealing (SA) was performed. SLM SA Inconel 718 specimen was ion irradiated to demonstrate the difference in microstructure and mechanical properties between the irradiated and non-irradiated specimens. After exposing specimens to Fe³⁺ ions irradiation up to 100 dpa (displacement per atom) at an ambient temperature, the hardness of irradiated specimens was measured by nano-indentation as a function of depth. The depth distribution profile of Fe³⁺ and dpa were calculated by the Monte Carlo SRIM (Stopping and Range of Ions in Matter)-2013 code under the assumption of the displacement threshold energy of 40 eV. A transmission electron microscope was utilized to observe the formation of irradiation defects such as dislocation loops. This study reveals that the Frank partial dislocation loops induce irradiation hardening of SLM SA Inconel 718 specimens.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.335-340
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• 2009

Ultrashort pulse laser drilling of polycarbonate track-etched membrane (pTEM) material was used to fabricate a mouse embryo cell trapping device. Holes with a diameter of $2{\mu}m$ to $5{\mu}m$ were fabricated on a $10{\mu}m$ thick membrane using a femtosecond laser with a 150 fs pulse width and 775 nm wavelength and multiple-pulse irradiation. In cell trapping tests, the overall cell occupancy of the machined holes in the fabricated pTEM was found to be more than 80%. The results of a single pulse and multiple pulse irradiation were compared in terms of the surface quality. It was generally found that a single pulse with high energy was less desirable than irradiation with multiple pulses of lower energy.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.154-154
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• 2000

FED(Field emission display)의 FEAs(Field emitter arrays)에 형성되어 있는 micro-tip 은 tip 표면의 오염이나 진공내부의 잔류가스에 대단히 민감하다. 특히, emitter 물질의 일함수 및 겉모양 같은 기하학적 요소에 민감한 전계방출 소자의 특성상 tip 선단이 oxidation 될 경우 일함수가 증가하여 전자방출에 필요한 구동전압이 증가하고 전자 방출의 불균일성이 커지는 문제점이 발생한다. 이에 고진공의 동작 환경 및 FEAs 제작과정이나 공기의 노출에 발생하는 tip 표면의 오염물질 제거가 요구된다. 따라서 본 연구에서는 40$\times$40mm2 FEAs에 laser power, scan speed을 달리하며 laser(cw Nd-YAG, 1064nm)을 조사하였다. laser cleaning 효과를 보기 위해 laser irradiation 전, 후에 진공도 5$\times$10-7torr irradiation 후에 emitter tip의 뚜렷한 기하학적 모양의 변화를 볼 수는 없었지만, I-V 특성이 향상 되는 것을 볼 수 있었다.

• Journal of Oral Medicine and Pain
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• v.18 no.2
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• pp.97-106
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• 1993

This study was performed to investigate the effects of infrared and visible light laser irradiation on cell viability of human gingival fibroblast. For the present study, the author used cultured fibroblast originated from sound gingiva which were fifth of sixth passage. Laser machine utilized here were stomalaser which irradiate infrared (GaAs diode) and red (HeNe) laser in turn with pulse wave pattern or continuous wave pattern, and the machine had several frequency mode presented by regeneration, relaxation and analgesic modalities. Cultured fibroblast samples were divided by this modalities of cell counts and laser exposure time which were 7-seconds of 150 seconds, respectively. 1 day after laser irradiation, each cell-well was treated with MTT and measured optical density with ELISA. The obtained results were as follows : 1. There was a tendency of increasing optical density in proportion to irradiation time in groups of $1\times10^4$ cell per well but in groups of $5\times10^3$ cell per well, reverse phenomena were observed. 2. The difference of optical density according to frequency modalities were not showed significantly except several cases in groups of $5\times10^3$ cell per well. 3. In general, cell viability of cultured human gingival fibroblast wer not showed consistent feature by low level laser irradiation.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.51-64
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• 1986

The purpose of this study is to obtain the data of prestep in cavity preparation by observing changed conditions of laser irradiated dental hard tissues. The forty five extracted caries free human molars were divided into three groups and each group into five subgroups. A $CO_2$ laser irradiation was performed each subgroup of group I for one second with output power of 5 W, 10 Wand 20 W. On group II, laser irradiation was done ten times for 0.1 second duration using same power ratings as group I. On group III, laser irradiation was done 0.1 second, 0.2 second and 0.4 second with output power of 50 W. We investigated mineral contents and crater wall of obtained specimens, i.e., laser irradiated teeth, using computer controlled electron probe microanalyzer and scanning electron microscope. The following results were obtained: 1. Both calcium and phosphorus contents in laser irradiated enamel crater wall were increased, and magnesium content was decreased, but these trends were not statistically significant. 2. In laser irradiated dentin, change of mineral content was more significant. 3. In laser irradiated enamel and dentin, there were no significant differences on mineral content change due to irradiation condition and energy density. 4. In scanning electron microscopic study, enamel rods of the crater wall were fused and clefts were observed in parallel with the direction of enamel rod for all groups. 5. In laser irradiated dentin, irregular fusion and clefts were observed. In irradiated teeth with high power and short duration, the locally formed narrow crater wall was observed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.51-57
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• 2021

The quality of the ceramic sintered coating on a metal surface through laser surface treatment is affected by the laser irradiation pattern. Depending on the laser irradiation pattern, the amount of residual stress and heat applied or accumulated on the surface increases or decreases, affecting the thickness attained in the ceramic sintering area. When the heat energy accumulated in the sintering area is high, the ceramic and the metal alloy melt and sufficiently mix to form a homogeneous and thick bonding interface. In this study, the thermal energy accumulation in the region sintered with zirconia was controlled using four types of laser processing patterns. The thickness of the diffusion region is analyzed by laser-induced breakdown spectroscopy of Mg-ZrO2 generated by laser sintering zirconia powder on the magnesium alloy surface. On the basis of the analysis of the Mg and Zr present in the sintered region through LIBS, the effect of the irradiation pattern on the sintering quality is confirmed by comparing and analyzing the heat and mass transfer tendency of the diffusion layer and the degree of diffusion according to the irradiation pattern. The derived diffusion coefficients differed by up to 9.8 times for each laser scanning pattern.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.432-442
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• 2023

Characterizing the behavior of nuclear reactor plate fuels is vital to the progression of advanced fuel systems. The states of pre- and post-irradiation plates need to be determined effectively and efficiently prior to and following irradiation. Due to the hostile post-irradiation environment, characterization must be completed remotely. Laser-based characterization techniques enable the ability to make robust measurements inside a hot-cell environment. The Laser Shock (LS) technique generates high energy shockwaves that propagate through the plate and mechanically characterizes cladding-cladding interfaces. During an irradiation campaign, two Idaho National Laboratory (INL) fabricated MP-1 plates had a fuel breach in the cladding-cladding interface and trace amounts of fission products were released. The objective of this report is to characterize the cladding-cladding interface strengths in three plates fabricated using different fabrication processes. The goal is to assess the risk in irradiating future developmental and production fuel plates. Prior LS testing has shown weaker and more variability in bond strengths within INL MP-1 reference plates than in commercially produced vendor plates. Three fuel plates fabricated with different fabrication processes will be used to bound the bond strength threshold for plate irradiation insertion and assess the confidence of this threshold value.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.293-299
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• 2015

We analyzed the damage effect on Glass Fibre Reinforced Plastics(GFRP) under air flow by irradiation of continuous wave near-IR laser. Damage process and temporal temperature distribution were demonstrated and material characteristics were observed with laser intensity, surface flow speed and angle. Surface temperature on GFRP rapidly increased with laser intensity, and the damaged pattern was different with flow characteristics. In case of no flow, penetration on GFRP by burning and flame generation after laser irradiation was appeared at once. GFRP was penetrated by the heat generated from resin ignition. In case of laser irradiation under flow, a flame generated after burning extinguished at once by flow and penetration pattern on GFRP were differently shown with flow angle. From the results, we presented the damage process and its mechanism.

• The Journal of Korean Physical Therapy
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• v.13 no.3
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• pp.603-611
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• 2001

This study was performed. using EGF, to observated the effect of GaAIAs laser on wound model induced designedly in lumbar region. The results of this study were as following: 1. In expression of EGF which used marker of wound healing, laser irradiating group made EGF to more induce significantly than laser non-irradiating group at 3 days. 2. EGF immunoreactivity in epidermis were increased markedly 3 days after wound, and increased gradually from 1 day to 2 days in wound which is laser irradiation. Therefore, EGF immunoreactivity which increased after wound with GaAIAs laser irradiation indicate that GaAIAs laser have wound healing effect. This study also can become a part of scientific evidence on electrotherapy through measuring quantitively effects of GaAIAs laser in wound