• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1457-1458
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• 2006

좁은 공간에 고출력 고에너지 레이저를 집속할 때 발생하는 고밀도, 고에너지 플라즈마 연구는 상태방정식, 실험실 천체물리, 전자가속 둥 기초 분야 뿐 아니라 X-선 및 극자외선 광원 개발, 원전 유지보수 등 다양한 산업 활용 분야를 갖고 있어 최근 미국, 프랑스, 일본, 중국 등 선진강대국에서 크게 주목 받고 있는 연구 분야이다. 한국원자력연구소는 물리나 광학의 원천기술 뿐 아니라 미래 산업에 파급효과 큰 플라즈마 기반 연구를 위하여 1 kJ급 고에너지 Nd:Glass 레이저 시설을 구축하고 있다.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.650-655
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• 2015

A high energy ignition system is essential for lean burn or high EGR gasoline engine, which is getting more and more interest to improve fuel economy. The high energy ignition systems comprise plasma jet, laser beam, corona discharge and so on. In this study, a high energy ignition system using corona discharge is developed and tested in a constant volume combustion chamber. The developed system shows extension of lean limit of propane-air mixture and enhencement of combustion speed. Various shape of corona discharge plugs are also tested and compared in this study.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.290-291
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• 2002

스틸 판재 4KW CO2 레이저 용접시 발생되는 플라즈마 특성 연구를 위하여 용접 품질에 중요한 요인이 되는 용접속도, 주입가스 양, 판재사이의 갭을 변화시키면서 실험을 하였다 발생된 분광학적 스펙트럼을 측정하였고 플라즈마광의 세기를 광파이버를 이용하여 측정하였다 플라즈마 패턴 특성을 알기 위하여 1000 frame/sec의 고속 디지털 카메라를 이용하여 플라즈마 영상을 측정하였다 그 결과, 용접속도가 빠를수록 상단에서 발생되는 플라즈마 광의 세기는 커졌으며, 주입가스의 양이 적을수록 플라즈마광의 세기가 강하게 측정되었다. 또한 판재 사이가 넓을수록 발생된 플라즈마가 판재 사이로 분출이 되면서 그 세기가 감소되는 현상을 보여주었다. 이러한 결과는 2차원 플라즈마 영상실험의 결과와 일치함을 보여주었다. 따라서 표면에서 발생되는 플라즈마 광의 세기는 레이저 용접시 중요한 요인이 되는 침투깊이를 추정하는데 중요한 정보가 되며 레이저 용접 품질에 대한 실시간 모니퍼링이 가능함을 확인하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.421-430
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• 2004

The purpose of this study was to measure and compare the amount of unreacted TEGDMA from pit and fissure sealants cured with three different light sources; conventional halogen light curing unit, plasma arc light curing unit and argon laser. The specimens were eluted in distilled water for different time intervals. The time-related release of TEGDMA were analyzed by reverse-phase high performance liquid chromatography(HPLC). The result of present study can be summarized as follows: 1. The time-related release of TEGDMA decreased with increasing curing time in conventional halogen light, however, that not statistically significant difference(p>0.05). 2. The elution from the specimens cured for 6 and 9 seconds with plasma arc light was similar results corresponding with the time-related TEGBMA release, and was significantly lower than that cured for 3 seconds(p<0.05). 3. The elution of TEGDMA from the specimens cured with argon laser was significantly higher than that cured with halogen and plasma arc light(p<0.05). 4. The elution of TEGDMA from under recommended time of three different light sources were showed to be no statistically significant difference(p>0.05). 5. In time-related release of TEGDMA from recommended time of each light sources, the results correspond to 40 seconds of halogen light and 6 seconds of plasma arc light were similar(p>0.05). 6. The elution of TEGDMA, from over recommended time of three different light sources were showed to be no statistically significant difference(p>0.05). In this study, I suggest that curing time of plasma arc light is 6 and/or 9 seconds in the field of clinical pediatric dentistry claiming its effectiveness in optimal polymerization and reduced chair time.

• The Korean Journal of Pain
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• v.29 no.4
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• pp.249-254
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• 2016

Background: This study aimed to investigate the effect of strenuous exercise on ${\beta}$-endorphine (${\beta}$-END) level in fibromyalgia (FM) patients compared to healthy subjects. Methods: We enrolled 30 FM patients and 15 healthy individuals. All study participants underwent a treadmill exercise test using modified Bruce protocol (M.Bruce). The goal of the test was achieving at least 70% of the predicted maximal heart rate (HRMax). The serum levels of ${\beta}$-END were measured before and after the exercise program. Measurements were done while heart rate was at least 70% of its predicted maximum. Results: The mean ${\pm}$ the standard deviation (SD) of exercise duration in the FM and control groups were $24.26{\pm}5.29$ and $29.06{\pm}3.26$ minutes, respectively, indicating a shorter time to achieve the goal heart rate in FM patients (P < 0.003). Most FM patients attained 70% HRMax at lower stages (stage 2 and 3) of M.Bruce compared to the control group (70% versus 6.6%, respectively; P < 0.0001). Compared to healthy subjects, FM patients had lower serum ${\beta}$-END levels both in baseline and post-exercise status ($Mean{\pm}SD$: $122.07{\pm}28.56{\mu}g/ml$ and $246.55{\pm}29.57{\mu}g/ml$ in the control group versus $90.12{\pm}20.91{\mu}g/ml$ and $179.80{\pm}28.57{\mu}g/ml$ in FM patients, respectively; P < 0.001). Conclusions: We found that FM patients had lower levels of ${\beta}$-END in both basal and post-exercise status. Exercise increased serum the ${\beta}$-END level in both groups but the average increase in ${\beta}$-END in FM patients was significantly lower than in the control group.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.563-574
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• 2007

Laser induced breakdown spectroscopy (LIBS) is a recently developed analytical technique that is based upon the measurement of emission lines generated by atomic species close to the surface of the sample, thus allowing their chemical detection, identification and quantification. With powerful advantages of LIBS compared to the conventional analytical methodology, this technique can be applied in the detection of heavy metals in the field. LIBS allows the rapid analysis by avoiding laborious chemical steps. LES have already been applied for the determination of element concentration in a wide range of materials in the solid, liquid and gaseous phase with simplicity of the instrument and diversity of the analytical application. These feasibility of rapid multi elemental analysis are appealing proprieties for the in-situ analytical technique in geochemical investigation, exploration and environmental analysis. There remain still some limitations to be solved for LIBS to be applied in soil environment as an in-situ analytical technology. We would like to provide the basic principle related to the plasma formation and laser-induced breakdown of sample materials. In addition, the matrix effect, laser properties and the various factors affecting on the analytical signal of LIBS was dealt with to enhance understanding of LIBS through literature review. Ultimately, it was investigated the feasibility of LIBS application in soil environment monitoring by considering the basic idea to enhance the data quality of LIBS including the calibration method for the various effects on the analytical signal of LIBS.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.232-232
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• 1999

교류형 플라즈마 방전 표시기(AC Plasma Display Panel, AC PDP)에 사용되는 플라즈마는 그 부피가 너무 작아서 플라즈마에 변화를 일으키지 않고 그 물성을 관측하기란 쉬운일이 아니다. 그래서 주로 PDP 내의 물성을 관측하는 데 시뮬레이션에 의존하게 된다. 그 물성중에 PDP내의 전계 분포에 대한 정보는 방전의 형성 및 소멸에 대한 많은 단서를 제공하고 있다. 특히 AC PDP의 경우, 유전체에 형성되는 벽적하(wall charge)가 방전의 형성 및 PDP 구동에 중요한 역할을 하는데, 이는 PDP 내의 전계 분포를 살펴봄으로써 대략 예측할 수 있다. 본 연구에서는 시뮬레이션에 의존하지 않고, 직접 레이저 유도 형광법을 이용하여 AC PDP 내의 전계를 측정하였다. 방전 가스인 헬륨(He)의 에너지 준위는 전계의 크기에 따라 에너지 준위가 변화하여, Rydberg(n$\geq$8) 준위가 여러 개의 준위로 나누어지는 현상이 일어나는데, 이를 Stack 효과라고 한다. 따라서 전계의 세기가 커짐에 따라서 각 준위와 준위 사이 값(splitting)이 커지는데, 이를 이용하면 전계를 측정할 수 있다. 즉, 헬륨 원자를 여기시키는 레이저 파장을 변화시키면서 관측되는 레이저 유도 형광 신호를 관측하면, 준위의 splitting을 관측할 수 있다. 본 연구에서는 PDP 내의 전계의 시간적 변화를 관측하였다. 50%, 40kHz의 구형파를 PDP의 두 전극에 가하였을 때, 플라즈마가 켜진 상태뿐만 아니라 플라즈마가 꺼진 후에도 전계에 의한 Splitting 신호가 관측이 되었는데, 전계로 환산하였을 때, 그 값은 대략 수 kV/cm의 값을 갖았는데, 이는 wall charge에 의한 값으로 사료된다.결과로 생각되어진다.플라즈마의 강도값을 입력하여 플라즈마의 radiation을 검출하고, 스퍼터링 공정중 실질적인 in-situ 정보로 이용하였다. PEM을 통하여 In/Sn의 플라즈마 강도변화를 조사하였다. 초기 In/Sn의 플라즈마 강도(intensity)는 강도를 100하여, 산소를 주입한 결과, plasma intensity가 35 줄어들었고, 이때 우수한 ITO 박막을 얻을 수 있었다. Pulsed DC power를 사용하여 아크 현상을 방지하였다. PET 상에 coating 된 ITO 박막의 표면저항과 광투과도는 4-point prove와 spectrophotometer를 이용하여 분석하였고, AES로 박막의 두께에 따른 성분비를 확인하였다. ITO 박막의 광투과도는 산소의 유량과 sputter 된 In/Sn ion의 plasma emission peak에 따라 72%-92%까지 변화하였으며, 저항은 37$\Omega$/$\square$ 이상을 나타내었다. 박막의 Sn/In atomic ratio는 0.12, O/In의 비율은 In2O3의 화학양론적 비율인 1.5보다 작은 1.3을 나타내었다.로 보인다.하면 수평축과 수직축의 분산 장벽의 비에 따라 cluster의 두께비가 달라지는 성장을 볼 수 있었고, 한 축 방향으로의 팔 넓이는 fcc(100) 표면의 경우 동일한 Ed+Ep값에 대응하는 팔 넓이와 거의 동일한 결과가 나타나는 것을 볼 수 있다. 따라서 이러한 비대칭적인 모양을 가지는 성장의 경우도 cluster 밀도, cluster 모양, cluster의 양 축 방향 길이 비, 양 축 방향의 평균 팔 넓이로부터 각 축 방향의 분산 장벽을 얻어낼 수 있을 것으로 보인다. 기대할 수 있는 여러

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.86-91
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• 1999

We have fabricated high-$\textrm{T}_c$ superconducting $\textrm{YBa}_{2}\textrm{Cu}_{3}\textrm{O}_{7-x}$(YBCO) grain boundary junctions at a step-edge on (001) $\textrm{SrTiO}_3$(STO) substrates. A diamond-like carbon (DLC) film grown by plasma enhanced chemical vapor deposition were used as an ion milling mask to make steps on the STO (100) single crystal and was removed by an oxygen reactive ion etch process. The c-axis oriented YBCO and TO thin films were deposited epitaxially on the STO substrate with a step-edge by pulsed laser deposition. The grain boundary junctions were formed at the top and the bottom of the step. The junctions worked at temperatures above 77 K, and had I\ulcornerR\ulcorner products of 7.5mV at 16K and 0.3 mV at 77K, respectively. The I-V characteristics of these junctions showed the shape of the two noisy resistively shunted junction model.

• Journal of the Korean Ceramic Society
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• v.51 no.1
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• pp.43-50
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• 2014

We fabricated undoped and Sb-doped $SnO_2$ thin films on glass substrates by a pulsed laser deposition (PLD) process. Undoped and 2 - 8 wt% $Sb_2O_3$-doped $SnO_2$ targets with a high density level of ~90% were prepared by the spark plasma sintering (SPS) process. Initially, the effects of the deposition temperature on undoped $SnO_2$ thin films were investigated in the region of $100-600^{\circ}C$. While the undoped $SnO_2$ film exhibited the lowest resistivity of $1.20{\times}10^{-2}{\Omega}{\cdot}cm$ at $200^{\circ}C$ due to the highest carrier concentration generated by the oxygen vacancies, 2 wt% Sb-doped $SnO_2$ film exhibited the lowest resistivity value of $5.43{\times}10^{-3}{\Omega}{\cdot}cm$, the highest average transmittance of 85.8%, and the highest figure of merit of 1202 ${\Omega}^{-1}{\cdot}cm^{-1}$ at $400^{\circ}C$ among all of the doped films. These results imply that 2 wt% $Sb_2O_3$ is an optimum doping content close to the solubility limit of $Sb^{5+}$ substitution for the $Sb^{4+}$ sites of $SnO_2$.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.94-99
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• 2009

We have studied the effects of oxygen partial pressure change on the physical properties of the $La_{0.7}Ca_{0.3}MnO_3$ thin films grown by Pulsed laser Deposition. Contrary to the previous reports, thin films of high curie temperature were successfully synthesized at very low oxygen partial pressure ($1.0{\times}10^{-5}$, $1.0{\times}10^{-6}Torr$). These observations indicate that the shape of plasma plume and the kinetic energy of the ablated species in it play an important role in determining the quality of samples. We also fabricated p-n heterojunction of $La_{0.7}Ca_{0.3}MnO_3$ and Nb-doped $SrTiO_3$. The current-voltage curves show rectifying behavior and, furthermore, the current responses to the applied magnetic field, indicating a potential possibility of device applications.