• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.06a
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• pp.16-24
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• 2006

Silicon Nitride ($Si_3N_4$), which is widely used in a variety of applications, is hard-to-machine due to its high hardness. At high temperature (e.g. above $1000^{\circ}C$), however, the machinability can be greatly improved. In this work, we used a $CO_2$ laser with a high absorptivity to $Si_3N_4$ of 0.9 to locally heat the surface of a rotating $Si_3N_4$ rod on a lathe. In order to examine the effects of the laser-assisted heating on hardness, an $Si_3N_4$ md is heated to temperatures from 900 to $1800^{\circ}C$ and is rotated at speeds from 440-900 rpm in experiments. When the rod is naturally cooled to room temperature, we measured the Victors hardness (Hv): and observed the surface of HAZ using a scanning electron microscopy (SEM). Energy dispersive spectroscopy(EDS) was used for ingredient analysis. Results showed that when heated at $1600^{\circ}C$, the hardness of $Si_3N_4$ decreased from 1500 Hv to 1000 Hv. Also, in order to predict the depth of HAZ, we numerically analyzed the laser-assisted heating of $Si_3N_4$.

• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.26-35
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• 2006

This work forcus on the development of gas sensor that measure the concentrations of exhaust gas using diode laser, Each diode laser for exhaust gas measurement is set to work at near-IR using both DA and WMS methods. Also use of fiber-coupled optical elements makes such a sensor rugged and easy to align. The results showed that gas concentrations of $O_2$, CO, $CO_2$, NO are accurately measured within ${\pm}2%$ error. The application of WMS method increased the beam intensity 2-3 times higher than DA method. It were experimentally compared WMS (Wavelength Modulation Spectroscopy) with DA (Direct Absorption) for the accuracy.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.4
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• pp.230-236
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• 1993

The laser beam hardening has been experimentally tried to find the hardened characteristics of STD11. Experiment was performed on the optimum hardening condition with 2kW $CO_2$ laser. The microstructure of the hardened layers was observed using the microscope. The hardened zones exhibits very high Vickers microhardness of 720 Hv, however, the deoxidation was observed under the surface of hardened area. The case depth of hardened zones is about 0.6mrn and case width is 4mm. FEM-simulation on laser surface hardening of STD11 steel are described. With the proper assumption of the absorbed energy density, the calculated case depth and width in 2 kW $CO_2$ laser hardening were in good agreement with the experimental result. It was found that there is optimum absorbed energy density of STD11.

• Medical Lasers
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• v.10 no.2
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• pp.111-114
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• 2021

A 38-year-old man visited the hospital for a voice change that began two months previously. There were no other accompanying symptoms; the patient had a history of 20 years of smoking. Carbon dioxide (CO₂) laser cordectomy was performed on the left side of the vocal cord, and the biopsy results showed squamous cell carcinoma. Radiation therapy was not performed, and CO₂ laser cordectomy was performed again because of a recurrence of left vocal cord mass three years after a progress observation.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1995.04a
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• pp.91.2-91
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• 1995

레이저를 이용한 구강 및 인후두 수술시 endotracheal tubes의 손상은 치명적이라 아니 할 수 없다. 이에 저자들은 여러 가지 endotracheal tube를 실험 재료로 사용하여 보다 안전한 레이저 수술을 위해서 적절한 endotracheal tube를 찾기 위해 본 실험을 시행하였다. 실험에 사용된 tube는 총 5가지 - $Bivona^{TM}$, Xomed Laser Shield $II^{TM}$, Mallinckrodt Laser-$Flex^{TM}$, Rusch tube wrapped with aluminium foil tape(Rusch tube), Polyvinylchloride tube wrapped with aluminium foil tape(PVC tube) - 가 사용되었다. 사용된 레이저는 KTP/532 와 $CO_2$ laser 이며 모든 실험에서 tube를 $FiO_2$ 95%-98% 상태에서 조사하여 각각 5회씩 실시하였다. tube에 이상이 없거나 발화가 되지 않는 한 90초 동안 시행하였다. 실험 결과, KTP/532 조사시 $Bivona^{TM}$, Mallinckrodt 와 PVC tube는 심한 손상을 받거나 발화하였으며 Xomed 와 Rusch tube는 안정된 상태를 유지하였고 $CO_2$ Laser 조사시는 KTP/532 조사시와 유사한 결과를 얻었다. 한편 혈액을 endotracheal tube에 도포한 상황에서는 모든 tube가 더 심한 손상을 보이는 바 KTP/532 조사시 Xomed는 상당히 안정된 상태를 유지하였고 나머지 tube는 심한 손상 또는 발화를 보이고 $CO_2$ Laser 조사시 $Bivona^{TM}$ 와 Mallinckrodt는 발화하였고 Rusch tube는 표면이 녹았으며 Xomed와 PVC tube도 1례에서 발화하였다. 향후 이비인후과 영역에서의 레이저 수술이 증가함을 예상할 때 좀 더 레이저에 대하여 안정적이고 경제적인 endotracheal tube의 개발이 필요할 것으로 사료된다.

• Proceedings of the KWS Conference
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• 2000.04a
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• pp.80-83
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• 2000

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.134-135
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• 2004

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.245-247
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• 2006

• Proceedings of the Korean Society of Veterinary Clinics Conference
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• 2008.05a
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• pp.97-97
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• 2008

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.234-237
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• 2003