• 한국초전도ㆍ저온공학회논문지
• /
• 제17권2호
• /
• pp.36-40
• /
• 2015

Electron cyclotron resonance (ECR) ion source is an essential component of heavy-ion accelerator. For a given design, the intensities of the highly charged ion beams extracted from the source can be increased by enlarging the physical volume of ECR zone [1]. Several models for ECR ion source were and will be constructed depending on their operating conditions [2-4]. In this paper three simulation models with 3, 4 and 6 solenoid system were built, but it's not considered anything else except the number of coils. Two groups of optimization analysis are presented, and the evolution strategy (ES) is adopted as an optimization tool which is a technique based on the ideas of mutation, adaptation and annealing [5]. In this research, the volume of ECR zone was calculated approximately, and optimized designs for ECR solenoid magnet system were presented. Firstly it is better to make the volume of ECR zone large to increase the intensity of ion beam under the specific confinement field conditions. At the same time the total volume of superconducting solenoids must be decreased to save material. By considering the volume of ECR zone and the total length of solenoids in each model with different number of coils, the 6 solenoid system represented the highest coil performance. By the way, a certain case, ECR zone volume itself can be essential than the cost. So the maximum ECR zone volume for each solenoid magnet system was calculated respectively with the same size of the plasma chamber and the total magnet space. By comparing the volume of ECR zone, the 6 solenoid system can be also made with the maximum ECR zone volume.

• 조명전기설비학회논문지
• /
• 제24권3호
• /
• pp.20-26
• /
• 2010

In ultrashort-pulse reflectometry (USPR), a chirped waveform transformed from the USPR source impulse signal via waveguide makes it possible to employ millimeter-wave mixers for the frequency up-conversion process. Consequently, the frequency bandwidth of the USPR system is sufficiently wide to cover a large portion of the electron density profile of the plasma. Some physical aspects of the chirped waveform, such as maximum amplitude and length, are critical factors to determine the performance of the system. In this paper, the propagation of the USPR impulse signal through a rectangular waveguide is numerically studied to derive the chirped waveform using the impulse response of the waveguide. The results of numerical computation show that the chirped waveform significantly depends on the waveguide cutoff frequency as well as the waveguide length.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
• /
• pp.97-99
• /
• 2005

Laser arc hybrid process is actively researched as a new welding method since it has several advantages by the combination of laser beam and electric arc. By the coupling of two different heat sources, laser and arc mutually assist and influence. High power laser can make the deep keyhole and arc plasma can form the large bead shape. In this paper the effect of two different heat sources to weld bead are investigated and as a result of analysis, it is shown that the lower part of keyhole is heated by laser and the upper part of weld pool is dominantly heated by arc.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2007년도 춘계학술발표회 초록집
• /
• pp.80-81
• /
• 2007

평판 디스플레이의 대면적 플라즈마 공정을 위하여 내장형 선형 안테나를 설치하였고 실질적인 식각 균일도를 알아보기 위하여 floating antenna의 전압 분포 조건에서 glass 위에 $2{\mu}m$의 photoresist가 도포된 시편을 사용하여 식각을 하였다. 식각 균일도 실험은 5 kW의 입력전력과 15mTorr의 $O_2$ gas 조건에서 40분 동안 진행하였다. 그 결과 $2,300\;mm{\times}2,000\;mm$의 기판 상에서 약 11 %의 식각 균일도를 얻을 수 있었다.

• Journal of Nutrition and Health
• /
• 제26권5호
• /
• pp.566-577
• /
• 1993

The study was to compare the effect of dietary fatty acids on fatty acid profile in tissue and the status of tocopherol and lipid peroxidation, and superoxide dismutase and glutathione peroxidase activities at two fat levels. Male Sprague Dawley rats weighing average 350g(17 weeks) were fed either low fat(LF, 4.3% w/w, 10% kcal) or high fat(HF, 20.8%, w/w, 40% kcal)diet for 6 weeks. The fats used were beef tallow as a source of saturated fatty acid, corn oil for n-6 linoleic acid, perilla oil for n-3 $\alpha$-linolenic acid and fish oil for n-3 eiocosapentatenoic acid(EPA) and n-3 docosahexaenoic acid(DHA). Palsma tocopherol was significantly reduced by fish oil compared to beef tallow at body fat level. However, there was no significant effect on the levels of plasma MDA, RBC MDA and tocopherol, and RBC hempolysis by the type and amount of dietary fat. The peroxidizibility index of fatty acid profile in plasma and liver was increased and liver MDA level was significantly increased by fish oil when dietary fat level was increased. The activities of SOD and GSHPx tended to be increased by perilla oil and fish oil at both fat oil significantly reduced the incorpration of c20:4 and increased the incorporation of c20:5 into liver compared to corn oil. The incorporation of n-3 fatty acids into tissue by perilla oil rich in $\alpha$-linolenic acid was significantly higher tan corn oil and its effect was improved with higher amount of perilla oil in diet by high fat diet. Overall, the lipid peroxidation of tissue could be prevented by tocopherol supplementation when dietary fat level was low in diet. However, at high fat diet, tocopherol supplementation might not be enough to prevent the lipid peroxidation in tissue since the potential for lipid peroxidation was tended to be increased with higher incorporation of higher unsaturated n-3 fatty acids into tissue. Therefore, it could not be recommended to consume large amount of fish oil even with excess amount of tocopherol supplemented to the high fat diet.

• 대한치과교정학회지
• /
• 제36권3호
• /
• pp.198-206
• /
• 2006

제논 플라즈마 아크 광중합기나 LED 광중합기가 치과영역에 소개된 이후로 기존의 텅스텐 할로겐 광중합기를 사용할 때에 비해 교정장치의 부착시간이 현저하게 줄어들 수 있게 되었다. 제논 플라즈마 아크 광중합기에 대한 중합시간과 전단강도에 대해서는 여러 연구가 있어왔던 반면, LED 광중합기를 이용하여 교정용장치의 부착을 위한 중합시간에 대한 연구는 미진하다. 본 연구의 목적은 LED 광중합기의 중합시간에 따른 결합강도를 플라즈마 아크 광중합기와 비교하여 적절한 브라켓의 부착강도를 얻기 위해 요구되는 중합시간을 알아보는데 있다. 120개의 발치된 사람의 소구치에 컴포짓 레진으로 브라켓을 부착시킨 후 4초, 6초, 8초 동안 플라즈마 아크 광원과 LED 광원으로 각각 중합시켰다. 그 후 결합강도를 만능시험기(Universal Testing Machine)로 계측한 결과, 플라즈마 아크 광중합기에서는 4초 이상에서, LED 광중합기에서는 8초 이상의 중합시간에서 기존의 할로겐 광원을 40초간 노출시켰을 때와 비슷한 전단결합강도를 나타내었다. 플라즈마 아크 광중합기와 LED 광중합기의 중합시간이 접착제 잔류지수 (adhesive remnant index) 수치에 대해 영향을 미치지 않았다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.391-392
• /
• 2012

In these days, the desire for the precise and tiny displays in mobile application has been increased strongly. Currently, laser displays ranging from large-size laser TV to mobile projectors, are commercially available or due to appear on the market [1]. In order to achieve a mobile projectors, the semiconductor laser diodes should be used as a laser source due to their size and weight. In this presentation, the continuous etch characteristics of Pd and AlGaN/GaN superlattice for the fabrication of blue laser diodes were investigated by using inductively coupled $CHF_3$ and $Cl_2$ -based plasma. The GaN laser diode samples were grown on the sapphire (0001) substrate using a metal organic chemical vapor deposition system. A Si-doped GaN layer was grown on the substrate, followed by growth of LD structures, including the active layers of InGaN/GaN quantum well and barriers layer, as shown in other literature [2], and the palladium was used as a p-type ohmic contact metal. The etch rate of AlGaN/GaN superlattice (2.5/2.5 nm for 100 periods) and n-GaN by using $Cl_2$ (90%)/Ar (10%) and $Cl_2$ (50%)/$CHF_3$ (50%) plasma chemistry, respectively. While when the $Cl_2$/Ar plasma were used, the etch rate of AlGaN/GaN superlattice shows a similar etch rate as that of n-GaN, the $Cl_2/CHF_3$ plasma shows decreased etch rate, compared with that of $Cl_2$/Ar plasma, especially for AlGaN/GaN superlattice. Furthermore, it was also found that the Pd which is deposited on top of the superlattice couldn't be etched with $Cl_2$/Ar plasma. It was indicating that the etching step should be separated into 2 steps for the Pd etching and the superlattice etching, respectively. The etched surface of stacked Pd/superlattice as a result of 2-step etching process including Pd etching ($Cl_2/CHF_3$) and SLs ($Cl_2$/Ar) etching, respectively. EDX results shows that the etched surface is a GaN waveguide free from the Al, indicating the SLs were fully removed by etching. Furthermore, the optical and electrical properties will be also investigated in this presentation. In summary, Pd/AlGaN/GaN SLs were successfully etched exploiting noble 2-step etching processes.

• Journal of Electrical Engineering and Technology
• /
• 제1권2호
• /
• pp.216-225
• /
• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2016년도 추계학술대회 논문집
• /
• pp.181-181
• /
• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1678-1683
• /
• 2003

DBD(Dielectric Barrier Discharge) plasma in air is well established for the production of large quantities of ozone and is more recently being applied to aftertreatment processes for HAPs(Hazardous Air Pollutants). Although DBD high electron density and energy, its potential use as nano and sub-micron sized particle charging are not well known. Aim of this work is to determine design and operating parameters of a two-stage ESP with DBD. DBD and ESP are used as particle charger and precipitator, respectively. We measured particle precipitation efficiency of two-stage ESP and estimated ozone decomposition of both pelletized $MnO_2$ catalyst and pelletized activated carbon. To examine the particle precipitation efficiency, nano and sub-micron sized particles were generated by a tube furnace and an atomizer. AC voltage of $7{\sim}10$ kV(rms) and 60 Hz is used as DBD plasma source. DC -8 kV is applied to the ESP for particle precipitation. The overall particle collection efficiency for the two-stage ESP with DBD is over 85 % under 0.64 m/s face velocity. Ozone decomposition efficiency with pelletized $MnO_2$ catalyst or pelletized activated carbon packed bed is over 90 % when the face velocity is under 0.4 m/s in dry air.