• 한방안이비인후피부과학회지
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• 제27권2호
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• pp.33-50
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• 2014

Objective : The purpose of this study is to analyze research trends on laser output used for treatment of hair loss. Methods : We searched papers using Pubmed, NDSL, KISS, and RISS. First search used the keyword "Laser, Alopecia" in Pubmed. Inclusion criteria were last 15 years, English, related to output. Finally we searched papers using the keyword "Laser and Alopecia" in NDSL, KISS, and RISS. Inclusion criteria were the same as first research except for English. Results : A total of 43 studies were found, 28 studies were excluded and 15 studies were selected and analyzed. And of the 15 studies, 7 studies were foreign papers and 8 studies were domestic papers on clinical application of laser status. Mainly Used type of laser was a diode laser. As a result, we found that treatment group had more improvement than control group. The range of the laser-output was 1mW-150W in Alopecia laser therapy. Conclusions : Low-level (LLLT) as well as High-level laser therapy (HLLT) can be effectively used as an alternative to the treatment of alopecia. Thus, further attention and studies are needed on this topic in order to reduce the side effects and demonstrate the effectiveness clearly.

• 한국정밀공학회지
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• 제21권3호
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• pp.171-179
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• 2004

Micro-stereolithography technology has made it possible to fabricate a freeform 3D microslructure. This technology is based on conventional stereolithography, in which a UV laser beam irradiates the open surface of a UV-curable liquid photopolymer, causing it to solidify. In micro-stereolithography, a laser beam of a few $\mu m$ diameter is used to solidify a very small area of the photopolymer. This is one of the key technological elements, and can be achieved by using a focusing lens. Thus, the solidification phenomena of the liquid photopolymer must be carefully investigated. In this study, the photopolymer solidification phenomena in response to variations in the scanning pitch of a focused laser beam was investigated experimentally. The effect of layer thickness on the solidification width and depth was also examined. These studies were conducted under the conditions of relatively lower laser power and relatively higher scanning speed. Moreover, the photopolymer solidification phenomena for the relatively higher laser power and lower scanning speed was investigated, too. In this case, comparing to the case of lower laser power and higher scanning speed, the photopolymer absorbed large amount of irradiation energy of the laser beam. These results were compared with those obtained from a photopolymer solidification model. From these results, a new laser-scanning scheme was proposed according to the shape of the 3D model. Samples by each method were fabricated successfully.

• 한국표면공학회지
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• 제45권4호
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• pp.143-150
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• 2012

Laser cleaning have been found to be a useful cleaning tool to remove contaminants without inducing damage to the substrate and making secondary pollutant. In this study, the effect of Nd:YAG laser cleaning system, emitting at 1064 nm and 532 nm, on acrylic resin applied onto copper coupons and pieces of bronze was investigated. The samples after laser cleaning tests were examined using microscopy, FT-IR, SEM-EDS. As a result, the acrylic resin could be removed from most of the samples at low laser energy density. Laser wavelength 532 nm was more effective than 1064 nm because of using lower laser energy density, which could reduce heat damage to substrates. Although the acrylic resin was easily removed, it revealed melted surfaces and removed bronze patina which must remain. The problems should be solved by future studies using different laser system or laser wavelengths.

• 방사성폐기물학회지
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• 제19권3호
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• pp.289-295
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• 2021

A laser scabbling experiment was performed using a high-power fiber laser to investigate the removal rate of the concrete block and the scabbled depth. Concrete specimens with a 28-day compressive strength of 30 MPa were used in this study. Initially, we conducted the scabbling experiment under a stationary laser beam condition to determine the optimum scan speed. The laser interaction time with the concrete surface varied between 3 s and 40 s. The degree of spalling and vitrification on the surface was primarily dependent on the laser interaction time and beam power. Furthermore, thermal images were captured to investigate the spatial and temporal distribution of temperature during the scabbling process. Based on the experimental results, the scan speed at which the optical head moved over the concrete was set to be 300 mm·min^-1 or 600 mm·min^-1 for the 4.8-kW or 6.8-kW laser beam, respectively. The spalling rates and average depth on the concrete blocks were measured to be 87 cm³·min^-1 or 227 cm³·min^-1 and 6.9 mm or 9.8 mm with the 4.8-kW or 6.8-kW laser beams, respectively.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.1988-1993
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• 2023

This experimental study investigated the effect of silica fume mixed in concrete blocks on laser-induced explosion behavior. We used a 5.3 kW fiber laser as a thermal source to induce explosive spalling on a concrete surface blended with and without silica fume. An analytical approach based on the difference in the removal rate and thermal behavior was used to determine the effect of silica fume on laser-induced explosive spalling. A scanner was employed to calculate the laser-scabbled volume of the concrete surface to derive the removal rate. The removal rate of the concrete mixed with silica fume was higher than that of without silica fume. Thermal images acquired during scabbling were used to qualitatively analyze the thermal response of laser-induced explosive spalling on the concrete surface. At the early stage of laser heating, an uneven spatial distribution of surface temperature appeared on the concrete blended with silica fume because of frequent explosive spalling within a small area. By contrast, the spalling frequency was relatively lower in laser-heated concrete without silica fume. Furthermore, we observed that a larger area was removed via a single explosive spalling event owing to its high porosity.

• 한국염색가공학회지
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• 제35권2호
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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.

• Current Optics and Photonics
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• 제7권6호
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• pp.714-720
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• 2023

Laser cleaning has the advantages of environmental protection, precision, and high efficiency, and has good prospects for application in removing oxide films on the surface of aluminum alloy. This paper discusses the cleaning threshold and cleaning mechanism of aluminum alloy surface oxide film. A nanosecond pulsed laser was used to remove a 5-㎛-thick oxide film from the surface of 7A04 aluminum alloy, and the target surface temperature and cleaning depth were simulated. The effects of different laser energy densities on the surface morphology of the aluminum alloy were analyzed, and the plasma motion process was recorded using a high-speed camera. The temperature measurement results of the experiment are close to the simulation results. The results show that the laser cleaning of aluminum alloy oxide film is mainly based on the vaporization mechanism and the shock wave generated by the explosion.

• 대한한의학회지
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• 제45권1호
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• pp.45-64
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• 2024

Objectives: This study is purposed to investigate the effect and safety of laser therapy for stroke patients by systematic review and meta-analysis of the randomized controlled trials (RCTs). Methods: RCTs on the treatment of laser therapy for stroke patients were selected among the literature published from January 2000 to June 2022 in twelve domestic and foreign databases. The quality of the literature was evaluated using the Cochrane's Risk of Bias tool and RevMan 5.4 was used for the synthesis of results. Results: Total 2,598 patients with stroke were finally selected from 18 RCTs. Meta-analysis showed that laser therapy was effective in significantly improving activities of daily living (MBI), motor function (effective rate), upper motor function (FMA-UE), shoulder pain related factors (CGRP, ET-1, BK). Overall, the risk of bias was uncertain or low in the quality assessment of the literature. Conclusions: Although it is unclear that laser therapy is more effective than sham laser, laser therapy might be more effective in improving symptoms than conventional rehabilitation alone. Furthermore, no serious adverse events were founded in laser therapy studies. However, the quality of the selected literature was generally low. Therefore, further studies with high methodological quality on laser therapy for stroke patients would be required in the future.

• Korean Journal of Acupuncture
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• 제28권3호
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• pp.1-12
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• 2011

Objectives : The purpose of this study is to review laser acupuncture studies to find possibility for applying high intensity laser to acupuncture and moxibustion treatment. Methods : Searching papers was performed using search engines of five electronic databases, including Pubmed, Thomson ISI, EMBASE, Sciencedirect, and EBSCO, from inception to May 2011 without language limitation. Inclusion criteria were clinical studies with human, randomized controlled trials (RCTs), case-control studies, and case reports. Selecting papers was performed with titles and abstracts in first step, scrutinize full text in second step, and then the extrated data was analyzed by two authors independently. The methodological quality for RCTs was evaluated using Jadad's scale. Results : Total 8 papers, (3 RCTs, 5 controlld studies, and 1 case reports), were finally selected. The study dealt with surgical laser, argon and $CO_2$ laser was one for each, with GaAs laser was two, and with new semiconductor laser, GaN, were four. The output range was from 110 mW to 15 W. The study diseases were alcohol addiction, knee osteoarthritis, bronchopneumonia and asthma for children, and circulation. All studies reported positive effect. The methodological quality in all RCTs was low because of below 3 points and all studies had few subject numbers. Conclusions : We suggest that high intensity laser can be applied to acupuncture and moxibustion. Further rigorous and well-designed study will be needed for various disease. The oriental medical society needs to take active measures to study and clinical application of acupuncture and moxibustion treatment with high intensity laser.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.176-180
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• 2002

During the last two decades the laser beam has progressed from a sophisticated laboratory apparatus to an adaptable and viable industrial tool. Especially, in its welding mode, the laser offers high travel speed, low distortion, and narrow fusion and heat-affected zones (HAZ). The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. Although high-power laser beams have been combined with the plasma from a gas tungsten arc (GTA) torch for use in welding as early as 1980, recent work at the Ohio State University has employed a low power laser beam to initiate, direct, and concentrate a gas tungsten arcs. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process known as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma (LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well focused melted spots.