• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권9호
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• pp.541-545
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• 2000

We propose a pulsed $CO_2$laser below 30W by the AC(60Hz) switching control of leakage transformer primary which has some advantages of cost and size compared to a typical pulsed power supply. Pulse repetition rate is adjusted from 5 Hz to 60 to Hz control laser output. In this laser a low voltage open loop control for high voltage pulse discharge circuit is employed to aviod the Hv sampling or switching and high voltage leakage transformer is used to convert low voltage pulse rectified from AC to high voltage one. A ZCS(Zero Crossing Switch) circuit and a PIC(programble one-chip microprocessor are used to control gate signal of SCR precisely. The pulse repetition rate is limited by 60Hz due to the frequency of AC line and a high leadkage inductance. The maximum laser output was about 23 W at pulse repetition rate of 60Hz total gas mixture of $CO_2$ : $N_2$ : He=1: 9: 15 and total pressure of 18 Torr

• 한국레이저가공학회지
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• 제6권1호
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• pp.17-24
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• 2003

The purpose of this study is to evaluate thermal shock resistance and thermal shock fracture toughness for ATJ graphite. Thermal shock resistance and thermal shock fracture toughness of ATJ graphite are evaluated by using CO$_2$ laser irradiation technique. The laser heat source is irradiated at the center of specimens. Temperature distribution on the specimen surface is measured using the thermocouples of type K and C. SEM and radiographic images are used to observe the cracks which are formed at the thermal shock specimens.

• 한국컴퓨터산업학회논문지
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• 제2권8호
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• pp.1055-1062
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• 2001

본 연구에서는 1KHz 부근의 펄스 반복율을 가지는 경제적이고 컴팩트한 펄스형 $CO_2$ 레이저의 개발에 관해서 기술하였다. 고압 고주파 펄스 변압기와 수 십 KHz의 스위칭에 적합한 IGBT를 사용한 고압 펄스전원 장치를 레이저 공진기에 접목시켜 새로운 방식의 고반복 $CO_2$ 레이저 장치를 개발하였다. 전원장치에 사용된 2개의 IGBT를 정밀하게 제어하기 위해서 제어부에는 PIC 마이크로프로세서가 사용되었고 공진기는 수냉방식의 저속축류형으로 제작되었다. 완성된 장치의 펄스 반복율과 동작압력 그리고 레이저 매질 가스의 혼합비의 변화에 따른 레이저빔의 출력 특성실험을 통하여 가스 배압비 $CO_2$： $N_2$：He ＝ 1：9：15펄스 반복율 700 Hz, 동작압력 15 Torr에서 최대 레이저 출력 약 20.5 W, 최대 효율 약 8%를 달성하였다.

• 한국산업융합학회 논문집
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• 제26권4_1호
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• pp.517-527
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• 2023

Many techniques have been proposed and investigated for microlens array manufacturing in three-dimensional (3D) structures. We present fabricating a microlens array using selective laser etching and a CO₂ laser. The femtosecond laser was employed to produce multiple micro-cracks that comprise the predesigned 3D structure. Subsequently, the wet etching process with a KOH solution was used to produce the primary microlens array structures. To polish the nonoptical surface to the optical surface, we performed reflow postprocessing using a CO₂ laser. We confirmed that the micro lens array can be manufactured in three primary shapes (cone, pyramid and hemisphere). Compared to our previous study, the processing time required for laser processing was reduced from approximately 1 hour to less than 30 seconds using the proposed processing method. Therefore, micro lens arrays can be manufactured using our processing method and can be applied to mass productionon large surface areas.

• Journal of Welding and Joining
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• 제24권1호
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• pp.56-63
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• 2006

The characteristics of $CO_2$ or Nd:YAG laser welded 600MPa ade TRIP steel was investigated. He or Ar gas was used as a shield gas in case of $CO_2$ laser welding, but the shield gas was not used in case of Nd:YAG laser welding. Bead on plate welding was performed with various welding conditions. Defects in the joints of both welding type occurred at 1.8m/min but were not observed over the welding speed of 2.1m/min in case of Nd:YAG laser welding. However, porosity occurred in $CO_2$ laser welding and the tendency of decreasing with the increase of welding speed. The hardness was the highest at heat affected zone near fusion zone as well as at the fusion zone and decreased on approaching the base metal. In a perpendicular tensile test to the weld line, all specimens that have been welded at optimum conditions were fractured at the base metal, and the tensile properties showed the rather higher than those of raw material. In a parallel tensile test, the strength of the joints was higher than that of the base metal. Elongation was found to be lower than that of the raw material. Forming height by Erichsen test and elongation were deeply related with the ratio of base metal/weld metal and the maximum hardness of the weld metal. Also porosity induced to decrease the strength and the elongation. The maximum formability was recorded at approximately 80% as compared with that of the raw material with the optimum condition.

• 열처리공학회지
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• 제9권3호
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• pp.177-186
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• 1996

Surface alloying of Ti alloy by $CO_2$ laser is able to produce few hundred micrometers thick TiN or TiC surface-alloyed layer with high hardness on the substrate by injecting reaction gas($N_2$ or $CH_4$). Laser surface alloying by means of process control is in many applications essential in order to obtain predictable hardening layer. This research has been investigated the effect of such parameters on TiN and TiC gas alloying of Ti-6Al-4V alloy by $CO_2$ laser. The maximum surface hardness of TiN layer was obtained 1750Hv on the conditions of 0.8kW laser power, 0.8m/min scanning speed and 100% $N_2$ atmosphere. However, the maximum hardness of TiC formation layer after laser treatment was about 630Hv. As scanning speed was increased, the hardness and depth of these layers were decreased at constant laser power.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1983년도 제17차 학술대회연제순서 및 초록
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• pp.7.2-8
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• 1983

만성 후두및 기관협착증의 빈도는 점차 증가하고 있는 추세에 있으며 이에 대한 치료로서 후두 및 기관확장술이나 성형술을 비롯하여 단단문합술등, 여러종류의 방법들이 각각의 적응증에 따라 시행되어 왔지만 아직도 만족스러운 결과를 얻기 어려운 경우가 적지 않다. 1972년 Strong과 Jako가 후두질환에 $CO_2$ Laser 사용을 시도한 것을 비롯하여 이비인후과영역에서 $CO_2$ Laser는 새로운 수술방법으로 각광을 받게 되었고 그 뒤를 이어 Mihashi(1976), Lyons(1980)등에 의하여 성공적으로 후두협착증의 치료에 이용된 바가 있다. 저자들은 1982년 4월부터 1983년 3월까지 1년간 후두기관성형술 및 확장술로는 성공적으로 기도를 유지하기 어려웠던 4례와 후두암으로 반측후두절제술 및 성문성형술 (neoglottis)을 받은 후 기도협착을 초래하였던 1례에서 수술현미경하에 $CO_2$ Laser를 사용함으로써 만족할 만한 결과를 얻었기에 문헌고찰과 함께 보고하는 바이다. 1) 후두 및 기관협착의 치료에 Laser를 이용한 술식은 기도유지에 있어 매우 효과적인 새로운 방법이다. 2) Laser수술 후 육아조직형성은 다른 방법에 비하여 비교적 적었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1903-1904
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• 1997

This paper was dealt with the experiments of the traverse flow and excited CW $CO_2$ Laser. The discharge and laser output characteristics of CW $CO_2$ laser has been investigated. A stable resonator was adopted for the power extraction from the length of 0.9m discharge region with the gap length of 15mm. The maximum output power of about 100W was obtained at the first experiment with the total filling pressure of 30torr, $CO_2$ : $N_2$ : He = 1:3:16.

• 대한두경부종양학회지
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• 제25권1호
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• pp.18-23
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• 2009

Objectives : In $CO_2$ laser surgery for supraglottic cancer, neck dissection is generally done in second stage. We investigated simultaneous neck dissection with primary resection could be available in laser supraglottic surgery. Material and Methods : We analyzed 13 patients with supraglottic cancer who were treated with transoral supraglottic laryngectomy and simultaneous neck dissection from 2001 to 2007. Tumor stage, extent of laser surgery, histological results, survival rate, local control rate, complications, and functional results were reviewed. Results : 5-year local control rate, survival rate and disease specific survival rate from the neck was 100%, 69.9%, 100% respectively. Tracheotomy was done in all 13 cases. One patient had a long tracheotomy indwelling (191 days). In the rest of 12 patients average decanulation time was 7.4 days(1-22 days). Nasogastric tube was inserted in 5 cases, and average oral intake was possible in 3.5 days(1-16 days). Average hospital days was 29.7 days. There was no serious complication associated with neck dissection. Conclusion : Simultaneous neck dissection with primary laser resection for supraglottic cancer is oncologic sound and can be performed without significant surgical morbidity.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1256-1261
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• 2009

Today, implementation of the defect detection in laser welding has been researched for a long time, but most studies have been made around thin plate within $1{\sim}3mm^t$. Therefore, this study was measured and analyzed light emission signals of the induced plasma in $CO_2$ laser lap welding of $6mm^t$ Zn primer-coated steel, and based on this analysis, research made an investigation into possibility of monitoring in thick plate welding. It was been analyzing the measured signals by RMS and FFT processing, as a results, we were able to confirm definite difference of two signals between humping bead and sound bead. Thus, possibility of real time monitoring in $CO_2$ laser lap welding verified experimentally.