• 한국재료학회지
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• 제29권1호
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• pp.52-58
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• 2019

The microstructure, hardness, and wear behaviors of a High Velocity Oxygen Fuel(HVOF) sprayed WC-CoFe coating are comparatively investigated before and after laser heat treatments of the coating surface. During the spraying, the binder metal is melted and a small portion of WC is decomposed to $W_2C$. A porous coating is formed by evolution of carbon oxide gases formed by the reaction of the free carbon and the sprayed oxygen gas. The laser heat treatment eliminates the porosity and provides a more densified microstructure. After laser heat treatment, the porosity in the coating layer decreases from 1.7 % to 1.2 and the coating thickness decreases from $150{\mu}m$ to $100{\mu}m$. The surface hardness increases from 1440 Hv to 1117 Hv. In the wear test, the friction coefficient of coating decreases from 0.45 to 0.32 and the wear resistance is improved by the laser heat treatment. The improvement is likely due to the formation of oxide tribofilms.

• Medical Lasers
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• 제10권3호
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• pp.176-180
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• 2021

Several methods have been used to treat androgenetic hair loss, ranging from hair transplants to finasteride and minoxidil. Sometimes platelet-rich plasma injection therapy may be used to increase the satisfaction of patients who come to the hospital. However, some patients are sensitive to pain and are subjected to the inconvenience of requiring treatment after each blood sampling. The author had reported the effects of using a hair growth-promoting solution and Jetpeel^TM in parallel with a painless hair loss treatment method. However, the author was interested in more effective methods for patients with M-shaped or vertex hair loss who do not want to take medications or undergo hair transplant. In addition to the existing light-emitting diode therapy and electromagnetic field treatment, the author has made considered attempts to use various laser wavelength bands. However, the equipment for these methods can be expensive and are not suitable for patients who emphasize on cost-effectiveness. Therefore, the author used an existing reported method and a device based on the fractional erbium:YAG laser to provide the hair growth-promoting solution in parallel. The author chose a fractional 2940 nm-based laser device as a medium that could efficiently increase the growth phase, reduce the catagen phase, and facilitate intradermal product and drug delivery. As a result, there was a therapeutic benefit without any significant side effects such as redness and itching. Among the patients, the author reported the effects of the treatment on one patient with frontal M-shaped, mid, and vertex hair loss.

• 대한치과의사협회지
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• 제47권8호
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• pp.479-486
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• 2009

Purpose: The aim of this study was to show the clinical results of combination of Nd-YAP (1340nm) laser therapy with conventional endodontic and periodontal treatment. Materials and Methods: Four patients with chronic advanced periodontitis and endodontic infection were treated with conventional treatment and Nd-YAP laser therapy. Occlusal adjustment and splinting were done for stabilization of the teeth with severe horizontal and vertical mobility. The protocol for periodontal treatment was followed as scaling and root planing, pocket irrigation with 3% $H_2O_2$ and exposure of Nd-YAP laser using 320${\mu}m$ optical fiber with 160mJ/pluse, 30Hz. The other protocol for endodontic treatment was followed as access opening, canal preparation by hand and rotary instrument, canal filling, and exposure of Nd-YAP laser using 200${\mu}m$ optical fiber with 200mJ/pluse, 10Hz and 180mJ/pluse, 5Hz which were used respectively for disinfection and canal filling. The assessments of probing depth, mobility, and radiography were made prior to and after treatment. Result: All of these four clinical cases showed good healing of periodontium, which presented decrease of mobility and pocket depth, and increase of bone regeneration and bone density on the radiography. Conclusion: The bactericidal effect of Nd-YAP laser would provide benefits for improving clinical results that are obtained from conventional therapy.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.322-322
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• 2010

For boron doping on n-type silicon wafer, around $1,000^{\circ}C$ doping temperature is required, because of the relatively low solubility of boron in a crystalline silicon comparing to the phosphorus case. Boron doping by fiber laser annealing and lamp furnace heat treatment were carried out for the uniformly deposited p-a-Si:H layer. Since the uniformly deposited p-a-Si:H layer by cluster is highly needed to be doped with high temperature heat treatment. Amorphous silicon layer absorption range for fiber laser did not match well to be directly annealed. To improve the annealing effect, we introduce additional lamp furnace heat treatment. For p-a-Si:H layer with the ratio of $SiH_4:B_2H_6:H_2$=30:30:120, at $200^{\circ}C$, 50 W power, 0.2 Torr for 30 min. $20\;mm\;{\times}\;20\;mm$ size fiber laser cut wafers were activated by Q-switched fiber laser (1,064 nm) with different sets of power levels and periods, and for the lamp furnace annealing, $980^{\circ}C$ for 30 min heat treatment were implemented. To make the sheet resistance expectable and uniform as important processes for the $p^+$ layer on a polished n-type silicon wafer of (100) plane, the Q-switched fiber laser used. In consequence of comparing the results of lifetime measurement and sheet resistance relation, the fiber laser treatment showed the trade-offs between the lifetime and the sheet resistance as $100\;{\omega}/sq.$ and $11.8\;{\mu}s$ vs. $17\;{\omega}/sq.$ and $8.2\;{\mu}s$. Diode level device was made to confirm the electrical properties of these experimental results by measuring C-V(-F), I-V(-T) characteristics. Uniform and expectable boron heavy doped layers by fiber laser and lamp furnace are not only basic and essential conditions for the n-type crystalline silicon solar cell fabrication processes, but also the controllable doping concentration and depth can be established according to the deposition conditions of layers.

• 전기학회논문지
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• 제56권2호
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• pp.334-337
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• 2007

After the advent of micro-Total Analysis Systems(${\mu}-TAS$) based on silicon various polymer for microfluidic chip has been studied. Polymer materials for microfluidic compared with silicon and glass which were traditional materials of a microfluidic chip, have the advantages of economical efficiency simple manufacturing process and wide materials selectivity corresponding to fluids. Surface energy of polymers we, however lower than silicon or glass. To overcome this problem, various surface modification methods have been investigated. The surface modification using laser has the advantage of the simple experiment that only directly irradiated laser beam on the material surface in the air. This work discuss the surface modification of polymethly methacrylate(PMMA) by 4th harmonic Nd:YAG laser (${\lambda}266nm$, pulse) treatment. After the laser treatment, the PMMA surface was investigated using a contact angle measuring instrument. The contact angle was decreased with a increase of the surface oxygen content. This result means the surface energy of PMMA was increased by the laser treatment without changing of its bulk characteristics.

• 대한물리치료과학회지
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• 제8권2호
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• pp.1033-1038
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• 2001

본 실험은 당뇨로 인한 말초신경병증에 저에너지 레이저의 효과를 알아보기 위해 것으로 흰쥐에 streptozotocin으로 당뇨를 일으켜 당뇨로 인한 말초신경병증을 유발시킨 후 He-Ne IR 레이저를 3주 동안 매일 5분간 조사하여 혈액화학 성분의 변화를 조사한 바 다음과 같은 결론을 얻었다. ALT의 활성치는 당뇨군에 비해 레이저군에서 증가하였으나 유의성은 없었다. AST의 활성치는 대조군과 당뇨군에 비해 레이저군에서 유의하게 증가되었다. LDH는 대조군에 비해 당뇨군과 레이저군에서 유의하게 감소되었다. ALP는 대조군에 비해 당뇨군과 레이저군에서 유의하게 증가되었다. CHOL은 당뇨군에 비해 레이저군에서 유의하게 감소되었다. TRlG는 당뇨군에 비해 레이저군에서 유의하게 증가되었다. CPK는 대조군과 당뇨군에 비해 레이저군에서 유의하게 증가되었다.

• Medical Lasers
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• 제10권1호
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• pp.31-36
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• 2021

Background and Objectives Several predicted optimal parameters for laser treatment have been suggested, making the settings subject to variation. Thus, picosecond lasers may require more data and studies to optimize the laser parameters, increase the efficacy of each session, and minimize the total number of sessions. This study evaluated the results of picosecond laser tattoo removal in variable locations, focusing on the aesthetic outcome, number of procedures, and adverse effects. Materials and Methods Nine patients who underwent picosecond laser treatment from February 2014 to July 2020 were enrolled. Before the procedures, the required number of sessions was estimated using the Kirby-Desai scale. At the end of the treatment, the patients assessed their satisfaction. The patient and two plastic surgeons assessed the clearance of the tattoo. Results The mean of the clearance was 86.6% in both the patient and investigators assessment. The patients reported satisfaction for an average score of 5.1 ± 0.78 for the aesthetic outcome, 4.5 ± 0.78 for pain, 4.1 ± 0.92 for the number of procedures, and 4.7 ± 0.97 for adverse effects. The average number of actual procedures was 6.7 ± 1.20. The average Kirby-Desai score was 7.1 ± 1.45. Their correlation coefficient was 0.803, which is considered a strong positive correlation. Conclusion Picosecond lasers have a remarkable ability to degrade smaller tattoo pigments through a photoacoustic effect. Moreover, a picosecond laser treatment for tattoo removal can be a safe and effective method. Picosecond lasers are a promising technology with the potential to optimize the treatment of tattoos.

• 한국정밀공학회지
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• 제22권11호
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• pp.51-58
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• 2005

Laser surface hardening technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for automotive parts. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser heat treatment for the case of SM45C medium carbon steel. CW Nd:YAG laser is selected as the heat source. The optical lens with the elliptical profile is designed to obtain a wide heat treatment area with a uniform hardness. From the results of the experiments, it has been shown that the maximum hardness is approximatly 780 Hv when the power and the travel speed of laser are 1,095 W and 0.6 m/min, respectively. In addition, the hardening width using the elliptical lens was three time larger than that using the defocusing of laser beam.

• 대한후두음성언어의학회지
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• 제19권1호
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• pp.7-10
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• 2008

The early glottic cancers are traditionally treated by radiotherapy or endoscopic surgery. The excellent effectiveness of both treatment modalities for local control, larynx preservation, and disease specific death is similar. Therefore, functional voice outcome after treatment is one of the most important factors in the choice of treatment for early glottic cancer. To assess the functional outcomes and compare the voice quality in patients with early glottic cancer treated with curative intent with radiotherapy or laser cordectomy, we performed literature review. Most studies showed that the voice quality after radiation therapy is slightly better than that after laser cordectomy. Subanalysis according to types of laser cordectomy, however, indicates that voice quality depends on type of laser cordectomy. Especially, type I or type II laser cordectomy might be superior to other types of laser cordectomy and radiation therapy. We conclude that the laser cordectomy is a good surgical alternative for properly selected early glottic cancer including professional voice users.

• 대한물리치료과학회지
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• 제9권2호
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• pp.99-109
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• 2002

We designed the experiments to elucidate the anti-inflammatory effect of low power laser stimulation on acupoint or non-acupoint using arthrogenic solution induced poly arthritis animal model. In order to achieve the experimental purpose, change in body weight paw edema, pathological changes in inflammed pint and the serum interlukin-6 level were measured after arthritis induction in acupoint later stimulated group, non acupoint laser stimulated group and non treated control animal. The results were summerized as follows: 1. The consistent increase in body weight was observed in the normal animal during whole experimental period, while the induction of arthritis significantly suppressed increase in body weight from the 15 day after arthritis induction. Especially, non treated animal group showed more suppressive effect on increase in body weight as compared to that of low power laser stimulated groups (P<0.05). 2. Low power laser stimulation on acupoint (Zusanli) significantly inhibited edema in the left side paw from the 12th day after arthritis induction as compared to that of non treated animals. This suppressive effect on paw edema was maintained until the end of experiment. 3. Laser treatment on acupoint dramatically suppressed the radiological change (i.e. new bone proliferation and soft tissue swelling) caused by arthritis as compared to that of non treated group animals. 4. Low power laser treatment reduced the increase in serum interlukin-6 caused by arthritis induction to levels observed in the normal animals. In conclusion, the results of the present study demonstrated that low power laser stimulation on acupoint has potent anti-inflammatory effect on arthritis. Thus it is recommended that low power laser be used for long term treatment of arthritis induced inflammation. However, further study is necessary to clarify the possible side effect of laser treatment depending upon intensity and duration of stimulation.