• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.1-6
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• 2023

In CO₂ laser surface machining of plastic films in modern display manufacturing, scattering of fume particles could be a major source of well-recognized film surface contamination. This computational fluid dynamics research investigates the suction air flow patterns over a film surface as well as the dispersion of micron-sized fume particles with low-Reynolds number particle drag model. The numerical results show the recirculatory flow patterns near laser machining point on film surface and also over the surface of vertical suction slot, which may hinder the efficient removal of fume particles from film surface. The dispersion characteristics of fume particles with various particle size have been tested systematically under different levels of suction flow intensity. It is found that suction removal efficiency of fume particles heavily depends on the particle size in highly nonlinear manners and a higher degree of suction does not always results in more efficient particle removal.

• Journal of the Korean Society of Safety
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• v.7 no.4
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• pp.73-83
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• 1992

A new technique for the measurement of surface roughness based on the Intensity fluctuations of laser light backscattered form a moving surface has been introduced. The developed method will be quite useful for evaluating the surface quality under machining with more detailed Information by detecting the surface roughness along both directions simultaneously.

• Journal of ILASS-Korea
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• v.7 no.3
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• pp.24-30
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• 2002

In the analysis of the mass distribution and SMD(Sauter Mean Diameter), planar laser imaging technique is a convenient and useful one when compared to the mechanical pattemator or PDPA (Phase Doppler Particle Analyzer). But recorded signals at cameras and intensity of laser are distorted by attenuation. Using experimental datum and assumptions, we study measurement errors due to attenuation in plannar image technique.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.76-77
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• 2002

• Journal of Biomedical Engineering Research
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• v.36 no.5
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• pp.191-197
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• 2015

Laser acupuncture is defined as the stimulation of traditional acupuncture points with low-intensity, nonthermal laser irradiation. Possible advantages in using laser acupuncture are the noninvasive, painless and low risks of infection treatment. The purpose of this study is to assess the effect of laser acupuncture on the quality and waveform of arterial pulses. Ten acupuncture points were stimulated repeatedly three times in 30 individuals by laser with emission in the near infrared spectral region (808 nm) using an out power and power density of 45 mW and $143W/cm^2$. The analysis of pulse quality and waveform was performed based on the measurement of arterial pressure of the left and right wrist, using a 3-dimensional blood pressure pulse analyzer. Excess-like pulse quality of subjects before laser acupuncture changed significantly to balanced pulse quality after 10, 20, and 30 minutes of laser acupuncture; coefficient of deficient or excess, $C_{DE}$, decreased significantly from 0.68 before acupuncture to 0.61, 0.55, and 0.55 after 10, 20, 30 minutes of laser acupuncture ($$p{\leq_-}0.006$$), respectively. Other pulse qualities, floating or sinking, slow or rapid, choppy or slippery did not change significantly by laser acupuncture (p > 0.05). Pulse waveform analysis showed that amplitude of main peak (systolic function or aortic compliance, $h_1$) of left and right artery pulse waves decreased significantly after 10, 20, and 30 minutes of laser acupuncture (p < 0.05). Other parameters, duration of one cardiac cycle (T), duration of rapid systolic ejection ($T_1$), duration of the systolic phase ($T_4$), and duration of the diastolic phase ($T_5$) of left and right artery pulses did not change significantly after laser acupuncture (p > 0.05).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.407-408
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• 2011

Natural boron consists of two stable isotopes 10B and 11B with natural abundance of 18.8 atom percent of 10B and 81.2 atom percent of 11B. The thermal neutron absorption cross-section for 10B and 11B are 3837 barn and 0.005 barn respectively. 10B enriched specific compounds are used for control rods and as a reactor coolant additives. In this work 2 methods for boron enrichment were analysed: 1) Gas irradiation in static conditions. Dissociation occurs due to multiphoton absorption by specific isotopes in appropriately tuned laser field. IR shifted laser pulses are usually used in combination with increasing the laser intensity also improves selectivity up to some degree. In order to prevent recombination of dissociated molecules BCl3 is mixed with H2S 2) SILARC method. Advantages of this method: a) Gas cooling is helpful to split and shrink boron isotopes absorption bands. In order to achieve better selectivity BCl3 gas has to be substantially rarefied (~0.01%-5%) in mixture with carrier gas. b) Laser intensity is lower than in the first method. Some preliminary calculations of dissociation and recombination with carrier gas molecules energetics for both methods will be demonstrated Boron separation in SILARC method can be represented as multistage process: 1) Mixture of BCl3 with carrier gas is putted in reservoir 2) Gas overcooling due to expansion through Laval nozzle 3) IR multiphoton absorption by gas irradiated by specifically tuned laser field with subsequent gradual gas condensation in outlet chamber It is planned to develop software which includes these stages. This software will rely on the following available software based on quantum molecular dynamics in external quantized field: 1) WavePacket: Each particle is treated semiclassicaly based on Wigner transform method 2) Turbomole: It is based on local density methods like density of functional methods (DFT) and its improvement- coupled clusters approach (CC) to take into account quantum correlation. These models will be used to extract information concerning kinetic coefficients, and their dependence on applied external field. Information on radiative corrections to equation of state induced by laser field which take into account possible phase transition (or crossover?) can be also revealed. This mixed phase equation of state with quantum corrections will be further used in hydrodynamical simulations. Moreover results of these hydrodynamical simulations can be compared with results of CFD calculations. The first reasonable question to ask before starting the CFD simulations is whether turbulent effects are significant or not, and how to model turbulence? The questions of laser beam parameters and outlet chamber geometry which are most optimal to make all gas volume irradiated is also discussed. Relationship between enrichment factor and stagnation pressure and temperature based on experimental data is also reported.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.155-159
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• 1997

We investigated the effect of mechanical backside damage in Czochralski silicon wafer. The intensity of mechanical damage were evaluated by minority carrier recombination lifetime by a laser excitation/microwave reflection photoconductance decay method, photo-acoustic displacement method, X-ray section topography, and wet oxidation/preferential etch methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the photoacoustic displacement values are also increased proportionally.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.435-436
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• 2009

In this paper, the absorption line of $NH_3$ is investigated by photoacoustic effect. And then an experiment with CO2 laser is conducted to demonstrate a method of measuring the intensity of NH3 using absorption line.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.289-295
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• 2013

Although low-level laser therapy (LLLT) has been a valuable therapeutic technology in the clinic, its efficacy may be reduced in deep tissue layers due to strong light scattering which limits the photon density. In order to enhance the photon density in deep tissue layers, this study developed an optical tissue clearing (OTC) laser probe (OTCLP) system which can utilize four different OTC methods: 1) tissue temperature control from 40 to $10^{\circ}C$; 2) laser pulse frequency from 5 to 30 Hz; 3) glycerol injection at a local region; and 4) a combination of the aforementioned three methods. The efficacy of the OTC methods was evaluated and compared by investigating laser beam profiles in ex-vivo porcine skin samples. Results demonstrated that total (peak) intensity at full width at half maximum of laser beam profile when compared to control data was increased: 1) 1.21(1.39)-fold at $10^{\circ}C$; 2) 1.22 (1.49)-fold at a laser pulse frequency of 5 Hz; 3) 1.64 (2.41)-fold with 95% glycerol injection; 4) 1.86 (3.4)-fold with the combination method. In conclusion, the OTCLP system successfully improved the laser photon density in deep tissue layers and may be utilized as a useful tool in LLLT by increasing laser photon density.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1322-1327
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• 2007

Many automotive companies have tried to apply the aluminum alloy sheet to car body because reducing the car weight can improve the fuel efficiency of vehicle. In order to do that, sheet materials require of weldablity, formability, productivity and so on. Aluminum alloy was not easy to join these metals due to its material properties. Thus, the laser is good heat source for aluminum alloy welding because of its high heat intensity. However, the welding quality was not good by porosity, underfill, and magnesium loss in welded metal for AA5182 aluminum alloy. In this study, Nd:YAG laser welding of AA 5182 with filler wire AA 5356 was carried out to overcome this problem. The weldability of AA5182 laser welding with AA5356 filler wire was investigated in terms of tensile strength and Erichsen ratio. For full penetration, mechanical properties were improved by filler wire. In order to optimize the process parameters, model to estimate tensile strength by artificial neural network was developed and fitness function was defined in consideration of weldability and productivity. Genetic algorithm was used to search the optimal point of laser power, welding speed, and wire feed rate.