• Journal of Advanced Marine Engineering and Technology
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• 제26권4호
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• pp.464-471
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• 2002

Porosity formation in partial penetration welds by high power lasers is a serious problem in industry. There are two main causes that induce porosity formation. One form of porosity is due to gases (e.g. hydrogen, oxygen) dissolving into the weld pool because of the high temperature and then the rapid solidification traps gases as a bubble in the weld metal. The second problem is voids formed by the keyhole collapsing due to unstable keyhole fluid dynamics. The voids that form at the bottom of the keyhole are relatively large and irregular in shape compared to the gas bubbles; this void formation is the primary concern in this paper. The reduction of voids formed by keyhole collapse is achieved by improving the stability of keyhole. Two methods to improve keyhole stability are discussed in this paper: pulse modulation and beam incident angle. Pulse modulation of the laser beam was performed between 100 Hz and 500 Hz to find out the optimum frequency for the keyhole dynamics. The incident beam angle changed the impact angle of the laser beam to the work surface in a range of 0 to 25 degrees. Glycerin in a semi-solidified state is used as a medium for performing the welding because its transparency allows of visualization of the keyhole.

• 천문학회보
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• 제43권1호
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• pp.45.3-46
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• 2018

Although mass accretion from the disk to the central protostar is a key process of low mass star formation, the accretion mechanism is still poorly understood. To investigate "episodic accretion", which has been suggested as an accretion mechanism in low mass star formation, we have carried out near-infrared spectroscopic observations of three very low-luminosity objects (VeLLOs) and one background source, using InfraRed Camera onboard the AKARI space telescope. The ice absorption features of $H_2O$, $CO_2$, and CO were detected around the wavelengths of 3.0, 4.26, and $4.67{\mu}m$, respectively. In addition, we revealed the XCN ice feature, which is attributed to high energy UV photons produced by the episodic burst accretion. The comparisons of the ice abundances of our targets with those of other YSOs observed previously with AKARI IRC imply that the three VeLLOs had experienced burst accretions although they are now in a very quiescent phase.

• Journal of Yeungnam Medical Science
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• 제40권4호
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• pp.423-425
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• 2023

Porokeratosis ptychotropica is an uncommon form of porokeratosis, which was initially described in 1995. It is clinically characterized by symmetrical reddish to brown-colored hyperkeratotic, verrucous, or psoriasiform plaques on the perianal and gluteal regions. The lesions tend to integrate and expand centrally, with small peripheral satellite lesions. Early skin biopsy and appropriate diagnosis are essential because malignant change occurs in 7.5% of porokeratotic lesions. Conventional treatment options include topical steroid, retinoid, imiquimod, 5-fluorouracil, isotretinoin, excimer laser, photodynamic therapy, intralesional steroid or bleomycin injection, cryotherapy, carbon dioxide (CO₂) laser, and dermatome and excision, but none seem to achieve complete clearance. A 68-year-old woman presented with diffuse hyperkeratotic scaly lichenoid plaques on the buttocks that had persisted for several years. A skin biopsy of the buttocks revealed multiple cornoid lamellae and intense hyperkeratosis. There were some dyskeratotic cells beneath the cornoid lamellae and the granular layer was absent. Porokeratosis ptychotropica was diagnosed based on the characteristic clinical appearance and typical histopathological manifestations. She was treated with a CO₂ laser in one session and topical application of urea and imiquimod cream for 1 month. The lesions slightly improved at the 1-month follow-up. We herein present a rare case of porokeratosis ptychotropica.

• Journal of Oral Medicine and Pain
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• 제35권2호
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• pp.119-122
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• 2010

이산화탄소 레이저(Carbondioxide laser, $CO_2$ laser)는 구강 연조직 수술에 가장 널리 사용되고 있는 레이저의 한 종류로 수분이 많은 연조직에 특히 좋은 친화력을 가지고 있다. 또한 수술도, 열소작술, 냉동수술, 전기수술 같은 기존의 외과적 술식들과 비교했을 때, 우수한 지혈 효과, 술 후 부종 감소, 세균집락 감소, 봉합 필요성 감소, 반흔 형성 감소, 술 후 통증 감소 같은 많은 장점들을 가지고 있다. 30세 남자가 상악 우측 구치부 협측 치은 부위에 발생한 경계가 뚜렷한 유경형 섬유성 병소를 주소로 내원하였다. 방사선 사진 검사 상 특기할 이상 소견은 관찰되지 않았다. 레이저를 이용한 절제 생검 계획하에 $CO_2$ 레이저(Panalas $CO5{\Sigma}$, Panasonic, 4.0W, 연속파 조사 방식)를 이용하여 보존적 절제술을 시행하였다. 병소의 절제 시 최소한의 출혈 양상으로 인해 우수한 시야 확보와 좋은 접근성을 유지할 수 있었고, 술 후 양호한 치유 경과를 보였으며, 환자는 아무런 불편감을 호소하지 않았다. 조직학적 진단은 "자극성 섬유종(Irritation fibroma)"이었다. $CO_2$ 레이저는 구강 내 병소의 외과적 치료에 적합한 많은 장점들을 가지고 있으므로, 치과의사들이 레이저의 특성을 잘 이해하고 레이저를 이용한 술기에 대한 지식을 적절히 습득하여 사용한다면, 구강 연조직 질환의 효율적인 치료를 위한 좋은 수단이 될 수 있을 것이다.

• Journal of Periodontal and Implant Science
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• 제27권3호
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• pp.469-478
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• 1997

The purpose of this study was to evaluate the structural change of root surface and the occlusion of dentinal tubule following $CO_2$ laser treatment. Seven extracted healthy human premolar werw curetted, sectioned, and four specimens were randomly assigned to each of 6 different treatment groups : 1) untreated EDTA etched control: 2) root plande only: 3) $CO_2$ laser treated with 2W mode 6(10msec/pulse, 20pps) for 1 minute: 4) $CO_2$ laser treated with 2W mode 6(lOmsec/pulse, 20pps) for 2 minutes: 5) $CO_2$ laser treated with 2W mode 7(20msec/pulse, 20pps) for 1 minute: 6) $CO_2$ laser treated with 2W mode 7(20msec/pulse, 20pps) for 2 minutes. Following the prescribed treatment, the specimens were prepared for SEM evaluation. Results showed that $CO_2$ laser may be effective to occlude dentinal tubules tor dentin sensitivity treatment. The effect of dentinal tubule occlusion was enhanced with increasing the total energy level lased to specimen regardless of lasing mode. The structural changes of root surfaces were restricted to superficies, and these changes included fissuring, charring, crater formation over the smooth lava like texture. The charring and crater formation implying root damage was observed in the case of the longer duration of a pulse. The results of the present study suggests that the pulsed $CO_2$ laser with shorter pulse duration and longer exposure time can be used effectively in order to obtain the optimal dentinal tubule occlusion with minimal root damage.

• 대한의생명과학회지
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• 제14권3호
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• pp.173-178
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• 2008

With the widespread use of laser in medical and industrial settings, the incidence of laser injury to the ocular continues to grow among workers involved in handling lasers. The aim of this study is to compare ocular damages after irradiation with various laser wavelengths and power density. Ocular of pigmented rats was irradiated with $CO_2$ laser, 1064 nm Nd:YAG laser, and 532 nm diode laser. We observed damage of cornea, lens, and retina using slit lamp microscope and funduscopy. H&E staining of histopathology were applied to study the specimens. The higher exposure ($200mW/cm^2$, 10 sec) with $CO_2$ laser resulted in severe damage at the cornea. For the 1064 nm Nd:YAG laser, the higher exposure than $10mW/cm^2$ (10 sec) resulted in damage at the cornea and lens. Further, with the 532 nm diode laser, retinal lesions were induced when $10mW/cm^2$ (0.25 sec) was delivered to the eye. Theses results suggest that the ocular damages are different from various laser wavelength and power density.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.540-545
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• 2008

Since mid 20th century, dental treatments with laser have been introduced and improved a lot. Because early $CO_2$, Nd:YAG, diode, argon, and holmium lasers are used for dealing soft tissue, so it applied just limited field. But, in 1997 the lasers of erbium family that able to dealing soft and hard tissue also were introduced, laser application fields are enlarged. In today, the application fields reach on implantation treatment, so clinicians can use the laser to make holes for implantation, and flap elevation, even though treating peri-implantitis. So our class want to discover the optimal setting of Er:YAG laser when treating peri-implantitis. We observed the surface that initially treated by RBM and TPS passion and laser with varied options of exposure time and power with SEM image. For this we conclude the optimal setting range that does not alter the implant surface structure and report it.

• 대한후두음성언어의학회지
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• 제27권1호
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• pp.51-53
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• 2016

Surgical fires require an ignition source, oxidizer, and fuel. The pulsed dye laser (PDL) has been shown to be effective in the treatment of hypertrophic scars and keloids in dermatology. With the increasing number of applications of $CO_2$, laser as ignition source has been associated with operating room fires in the otorhinolaryngologic field. There have been many case reports on PDL-induced fires in dermatology, but until now, there were no reports in the larynx. We describe a 57-year-old patient diagnosed with laryngeal hyperkeratosis treated by PDL-assisted laryngomicrosurgery. In this case, we experienced incidental PDL tip flaring during pulsed dye laser vaporization.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.3-5
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• 1998

The interest in the use of borate crystals in ultraviolet(UV) nonlinear optics(NLO) has increased because all solid-stste UV lasers obtained with NLO are in highly demand. Much effort has been spent on developing borates series, such as{{{{ { beta -BaB }_{2 } {O }_{4 }(BBO), {LiB }_{ 3}{O }_{5 }(LBO)}}}} and{{{{{ CsKiB}_{6 }{O }_{10 }(CLBO)}}}} in this decade. Recently another new borate crystals, {{{{{ YCa}_{4 }O({BO }_{3 })_{3}}}}} and{{{{{Gd }_{x }{Y }_{1-x }{Ca }_{4 }O({BO }_{ 3})({Gd }_{x }{Y }_{1-x }COB)}}}} have been developed by the present authors. Here, the growth and NLO properties of YCOB and {{{{ {Gd }_{ x} {Y }_{ 1-x} }}}}CO B crystal are reported and their properties discussed in relation to those of other nonlinear optical crystals, such as LBO.

• Journal of Photoscience
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• 제5권2호
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• pp.63-67
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• 1998

New photoinitiator systems of dimethylphenacylsulfonium butyltnphenylborate (DMPSB) as a donor-acceptor initiator and styryl dyes have been investigated for free radical polymerization of an acrylate with visible lasers (488, 514 and 647 nm). DMPSB was able to be sensitized by many styryl dyes. When polymerized with pentaerythrithol triacrylate, the sensitivity value of the photosensitive layer containing DMPSB was higher than that of an tetrabutylammonium butyltnphenylborate (TBAB) as an electron donating initiator or a dimethylphenacylsulfonium tetrafiuoroborate (DMPS) as an electron accepting initiator. The sensitivity values of the photosensitive layer containing the photoinitiator systems had a close relation to the free energy changes between the excited singlet styryl dyes and DMPSB.