• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.32-38
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• 2004

Laser-induced thermochemical wet etching of titanium in phosphoric acid has been investigated to examine the feasibility of this method fur fabrication of microstructures. Cutting, drilling, and milling of titanium foil were carried out while examining the influence of process parameters on etch width, etch depth, and edge straightness. Laser power, scanning speed of workpiece, and etchant concentration were chosen as major process parameters influencing on temperature distribution and reaction rate. Etch width increased almost linearly with laser power showing little dependence on scanning speed while etch depth showed wide variation with both laser power and scanning speed. A well-defined etch profile with good surface quality was obtained at high concentration condition. Fabrication of a hole, micro cantilever beam, and rectangular slot with dimension of tess than 100${\mu}{\textrm}{m}$ has been demonstrated.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1344-1348
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• 2003

It is generally known to be difficult to etch a surface of a transparent material such as fused silica by conventional laser ablation in which the surface is simply irradiated with a laser beam. A lot of studies have been done to provide a method capable of efficiently etching transparent materials without defects such as cracks. One of the promising methods or the micro-machining of optically transparent materials is laser induced etching. In this study, micro-drilling of fused silica by laser induced wet etching was conducted. KrF excimer and YAG laser were used as light sources. Acetone solution pyrene and ethanol solution of rhodamine were used as etchant.

• Textile Coloration and Finishing
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• v.35 no.2
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• pp.121-127
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• 2023

In this study, a comprehensive investigation was conducted on the morphological and property changes of laser-induced nanocarbon (LINC) as a function of laser process parameters. LINC was formed on the surfaces of polyimide films with different backbone structures under various process conditions, including laser power, scan speed, and resolution. Three different forms of LINC electrodes (i.e., continuous 3D porous graphene, wooly nanocarbon fibers, line cut) were formed depending on the laser power and scan speed. Furthermore, heteroatom doping induced from the chemical structure of the polyimide during laser patterning was found to be effective in modifying the electrical properties of LINC electrodes. The LINC surfaces exhibited different microstructures depending on the laser beam resolution under constant laser power and scan speed, allowing for controllable surface wettability. The correlation between the chemical structure of the polymer substrate, laser process parameters, and carbonized surface properties in this study is expected to be utilized as fundamental understanding for the manufacturing of next-generation carbon-based electronic devices.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.83-89
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• 2017

The corrosion of metal specimens was analyzed in this study using laser-induced breakdown spectroscopy. The samples used in the study were magnesium alloys and corrosion, and standard specimens were prepared and analyzed using surface and depth analysis. The spectral wavelengths used in the oxide layer analysis were 777.196 nm, 777.421 nm, and 777.543 nm. The spectral line of the surface corrosion was confirmed by experimentation, and surface micro morphology analysis was performed using an optical microscope. Approximately $100{\mu}m$ corrosion depth was confirmed via laser irradiation in the depth direction. The results of laser-induced breakdown spectroscopy and the SEM-EDS analysis were compared and analyzed.

• Journal of Korean Physical Therapy Science
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• v.10 no.1
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• pp.180-189
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• 2003

The experiments were designated to evaluate the anti-nociceptive effect of low power laser stimulation on acupoint or non-acupoint using arthrogenic solution induced poly arthritis animal model. Evaluation of potential antinociceptive effect of low power laser on arthritis has employed measurements of the foot bending test, the development of either thermal or mechanical hyperalgesia following the arthritis induction. The analysis of thermal hyperalgesia includes Hargreaves's method. Randall-Sellitto test was utilized for evaluating mechanical hyperalgesia. In addition, the antinociceptive effect of low power laser stimulation on arthritis induced spinal Fos expression was analyzed using a computerized image analysis system. The results were summerized as follows: 1. In laser stimulation on acupoint treated animal, laser stimulation dramatically inhibited the development of pain in foot bending test as compared to those of non acupoint treated animal group and non treated animal group. 2. The threshold of thermal stimulation was significantly increased by low power laser stimulation on acupoint as compared to that of non treated control group. 3. Laser stimulation on acupoint dramatically attenuated the development of mechanical hyperalgesia as compared to that of non treated group. 4. Low power laser stimulation on acupoint significantly suppressed arthritis induced Fos expression in the lumbar spinal cord at 3 week post arthritis induction. In conclusion, the results of the present study demonstrated that low power laser stimulation on acupoint has potent anti-nociceptive effect on arthritis. Additional supporting data for an antinociceptive effect of laser stimulation was obtained using Fos immunohistochemical analysis on spinal cord section. Those data indicated that laser stimulation induced antinociception was mediated by suppression of spinal neuron activity in pain sensation.

• Korean Journal of Acupuncture
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• v.27 no.1
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• pp.49-62
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• 2010

Objective: This study was performed to investigate the effect of manual acupuncture, invasive laser acupuncture and laser skin irradiation at LU8, LR4, HT8 and LR2(Liver Seunggyeok) on D-galN-induced liver injury in rats. Method: Liver injury was induced with D-galN. The experimental rats were divided four groups(Control group, EXP-1, EXP-2, EXP-3). In the Control group, liver injury-induced and not treated. EXP-1 group was liver injury-induced and carried out manual acupuncture with Young-Su(against the meridian course and following the course of the meridian) & Won-Bang(by twisting and rotating the needle) acupuncture method at Liver Seunggyeok. EXP-2 group was liver injury-induced and carried out invasive laser acupuncture at Liver Seunggyeok. EXP-3 group was liver injury-induced and carried out laser skin irradiation at Liver Seunggyeok. Result: In the change of body weight(in 1 week), EXP-1, EXP-2 and EXP-3 groups were significantly increased as compared with control group. In the change AST & ALT, EXP-1 and EXP-2 groups were significantly decreased as compared with control group. In the change of SOD, EXP-1, EXP-2 and EXP-3 groups were significantly increased as compared with control group. In the change of WBC, EXP-2 group was significantly increased as compared with control group. Conclusion: Manual acupuncture, invasive laser acupuncture and laser skin irradiation at Liver Seunggyeok had hepatotherapeutic effect on the treatment of hepatocytotoxity. Invasive laser acupuncture was as effective as manual acupuncture on the treatment of hepatocytotocity.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.8-16
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• 1999

In this study, a new type of laser-induced ignition using a conical cavity has been developed to utilize all the available incident laser energy. In the method, it is possibile to ignite combustible methane/air mixtures by directing a laser beam of a constant small diameter into a small conical cavity, without focusing the laser beam. Shadow graphs for the early stage of combustion process show that a hot gas jet is ejected from the cavity, especially with lean mixture. After a very show time, the hot gas jet finishes issuing and the flame behavior is quite similar to flame propagation initiated by a conventional spark ignition. The combustion process using the new method exhibits more rapid pressure increase and a higher maximum pressure rise than that of the center ignition using laser-induced spark, with significant decrease in the combustion time. Also, the new ignition method is numerically modeled to simulate the flame kernel development and subsequent combustion process using the KIVA-IIcode. The calculated results show satisfactory agreement with experimental results.

• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.387-394
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• 1997

The influences of laser-induced damage threshold by the after-processing of $Al_2O_3$ thin films was investigated. The samples were fabricated at the substrate temperature of $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$ respectively, and the LIDT were measured by using Nd:YAG laser. After the processing with baking and laser conditioning of the samples, the variation of LIDT was measured. It was found that LIDT was enhanced twice by laser-conditioning process and 1.5 times by baking process. In addition, we measured the chemical properties of the thin film structure before and after the processing by using XPS.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.164-173
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• 2006

The cooling capacity of a micro-heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro-heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. Micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro-heat pipe based on the high-aspect-ratio microchannels is demonstrated.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.64-71
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• 2000

In order to clarify the characteristics of soot formation and oxidation in-cylinder of a diesel engine, it is necessary to diagnose accurately for combustion of in-cylinder. The past techniques for soot measurement have limitations in providing the characteristics of soot in a diesel engine, whereas, laser-based 2D imaging diagnostics have the potential to provide better temporally and spatially resolved measurements of the soot distribution. We rebuilt an optically accessible diesel engine which is similar to the conditions of a conventional engine and tried to measure soot distribution in a cylinder of the diesel engine using laser induced scattering(LIS) and laser induced incandescence(LII). Some results were acquired in this study. LIS and LII signal that show soot distribution of a in-cylinder were taken by ICCD properly. The signal of LIS was intenser than that of LII. Although they have some differences of signal intensity in early combusion period, both of signals show that they are generally similar in late combustion period, after ATDC 50 degree.