• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.24-24
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• 2018

One of the challenges in tissue engineering is the design of optimal biomedical scaffolds, which can be governed by topographical surface characteristics, such as size, shape, and direction. Of these properties, we focus on the effects of nano - to micro - sized hierarchical surface. To fabricate the hierarchical surface structure on poly(${\varepsilon}$-caprolactone) (PCL) film, we employed a nano/micro-casting technique (NCT) and modified plasma process. The micro size topography of PCL film was controlled by sizes of the micro structures on lotus leaf. Also, the nano-size topography and hydrophilicity of PCL film were controlled by modified plasma process. After the plasma treatment, the hydrophobic property of the PCL film was significantly changed into hydrophilic property, and the nano-sized structure was well developed, as increasing the plasma exposure time and applied power. The surface properties of the modified PCL film were investigated in terms of initial cell morphology, attachment, and proliferation using osteoblast-like-cells (MG63). In particular, initial cell attachment, proliferation and osteogenic differentiation in the hierarchical structure were enhanced dramatically compared to those of the smooth surface.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.208.2-208.2
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• 2016

Many researchers have paid attention to the studies on the interaction between non-thermal plasma and aqueous solutions for biomedical applications. The gas composition in the plasma is very important. Oxygen and nitrogen are the main gases of interest in biological applications. Especially, we focus on the oxygen concentration. In this experiment, we studied the role of oxygen concentration in plasma induced chemical reactions in solution. At first, the amount of ions are measured according to changing the oxygen concentration. And we checked the relationship between these ions and pH value. Secondly, when the oxygen concentration is changed, it identified the type and amount of radical generated by the plasma. In order to confirm the effect of these chemical property change to biological material, hemoglobin and RBCs are chosen. RBCs are one of the common basic biological cells. Thirdly, when plasma treated according to oxygen concentration in nitrogen feeding gas, oxidation of hemoglobin and RBC is checked. Finally, membrane oxidation of RBC is measured to examine the relation between hemoglobin oxidation and membrane damage through relative hemolysis and Young's modulus. Our results suggest that reactive species generated by the plasma differsdepending on the oxygen concentration changes. The pH values are decreased when oxygen concentration increased. OH decrease and NO increase are also observed. These reactive species makes change of chemical properties of solution. We also able to confirm that the difference in these reactive species to affect the oxidation of the Hb and RBCs. The Hb and RBCs are more oxidized with the high oxygen concentration conditions. But membrane is damaged more by plasma treatment with only nitrogen gas. It is shown that red blood cells membrane damage and oxidation of hemoglobin are not directly related.

• 대한의용생체공학회:의공학회지
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• 제44권4호
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• pp.275-283
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• 2023

The demand for skincare has increased due to the end of the COVID-19 pandemic, leading to a focus on skincare devices and technologies designed to improve the delivery of cosmetics. Among these technologies, skincare medical devices that utilize plasma therapy (Plasma) and sonophoresis (Sono) are commonly used in dermatology clinics. However, there is still a lack of quantitative analysis for transdermal absorption effects of Plasma and Sono skincare medical devices. In this study, we quantified enhanced transdermal absorption effects of Plasma and Sono devices through in-silico and ex-vivo studies. The Sono treatment demonstrated an increased transdermal absorption effect, showing a 10~13% difference in penetration compared to the control group in the in-silico experiment, and 159% and 184% increase in the ex-vivo experiment. The Plasma treatment revealed increased transdermal absorption effects, with a 1.0~2.5% penetration difference in the in-silico experiment, and a 124% increase in the ex-vivo experiment compared to the control group. We also observed a synergistic effect from the combined treatment of Plasma and Sono, as indicated by the highest increases of 197% and 242% in penetration. Furthermore, we have determined the optimal device settings and treatment conditions for Plasma-Sono skincare medical devices. Notably, higher on/off durations (Intensity levels) and longer Sono treatments resulted in greater transdermal absorption effects.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.523-524
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• 2006

The $TiB_2$ dispersion strengthened copper alloy was attracted as thermal and electrical functional material for the high mechanical strength, high thermal stability and good conductivity of $TiB_2$. In the present study, the focus is on the synthesis of $TiB_2$ dispersed copper alloy by spark plasma sintering process using copper oxide and titanium diboride as raw materials. The mechanical, thermal and electrical properties of sintered bodies were discussed with the sintering parameters, and developed microstructure and phase of sintered bodies.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 추계학술발표대회 요약집
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• pp.391.2-391.2
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• 2003

• 천문학회보
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• 제40권1호
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• pp.66.3-67
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• 2015

Without scrutinizing reflection, the plasma comprising a coronal loop is usually regarded to reside within a flux rope. This picture seems to have been adopted from laboratory plasma pinches, in which a plasma of high density and pressure is confined in the vicinity of the flux rope axis by magnetic tension and magnetic pressure of the concave inward magnetic field. Such a configuration, in which the plasma pressure gradient and the field line curvature vector are almost parallel, however, is known to be vulnerable to ballooning instabilities (to which belong interchange instabilities as a subset). In coronal loops, however, ideal MHD (magnetohydrodynamic) ballooning instabilities are impeded by a very small field line curvature and the line-tying condition. We, therefore, focus on non-ideal (resistive) effects in this study. The footpoints of coronal loops are constantly under random motions of convective scales, which twist individual loop strands quite randomly. The loop strands with the axial current of the same direction tend to coalesce by magnetic reconnection. In this reconnection process, the plasma in the loop system is redistributed in such a way that a smaller potential energy of the system is attained. We have performed numerical MHD simulations to investigate the plasma redistribution in coalescence of many small flux ropes. Our results clearly show that the redistributed plasma is more accumulated between flux ropes rather than near the magnetic axes of flux ropes. The Joule heating, however, creates a different temperature distribution than the density distribution. Our study may give a hint of which part of magnetic field we are looking to in an observation.

• 대한기계학회논문집B
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• 제23권5호
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• pp.593-602
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• 1999

This paper presents combustion characteristics of LPG-air mixture ignited by the plasma jet in a cylindrical vessel with constant volume, in which our focus is placed on the multi-hole plug configuration. Four types of the plug configuration depending on the number of orifice and the arranged angle are considered, along with two cases of conventional spark ignition for comparison. Not only the flame propagation is photographed at intervals, but the pressure in the combustion chamber is also recorded through the entire combustion process. The results show that the plasma jet ignition enhances the overall combustion rate remarkably in comparison to the spark ignition by generating irregular flame front and penetrating through the unburned mixture. The combustion enhancement rate agrees favorably with the available data, which supports the validity of our experiment. Synthetically estimating, the two-hole sixty-degree plug appears to be the most desirable, in that the maximum pressure as well as the combustion duration is less affected by the sub-energy level than the others. It is also deduced that there may exist an optimal plug configuration capable of rapid combustion for a specific combustion chamber.

• 센서학회지
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• 제33권4호
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• pp.216-223
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• 2024

Electric propulsion systems, including electrothermal, electrostatic, and electromagnetic thrusters, are promising systems for producing thrust from satellites. These systems generally operate under vacuum plasma conditions and exhibit high specific impulses and thrust-to-weight ratios. Despite their high efficiencies, electric propulsion systems are susceptible to performance variations due to physical factors such as plasma instabilities, which require an accurate diagnosis of their status during operation. In this study, we review various measurement systems adopted to diagnose electric propulsion systems operating under vacuum conditions. Specifically, we review electrical, optical, and other methods that can directly or indirectly measure the status of a thruster, with a particular focus on Hall effect thrusters. The system configurations and fundamental mechanisms of the different measurement systems are described based on case studies of the diagnosis of propulsion systems. We anticipate that this study will contribute to the efficient development and safe operation of electric propulsion systems for use in artificial satellites.

• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1619-1626
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• 2024

In order to optimize the operational safety and reliability of the upper launcher for the CFETR ECRH system, a design of the launcher for NTM control based on the remote steering concept is currently being carried out for comparison with the front steering equivalent. This paper presents the layout design and analysis of the quasi-optical system in the remote steering launcher. A 3D visual quasi-optical design tool has been developed for the quasi-optical system, which can parameterize modeling, perform general astigmatic beam calculation and show the accurate beam propagation path in the upper port. Three identical sets of quasi-optical modules are arranged in the launcher, and each one consists of two fixed double-curvature focusing mirrors, which focus and reflect the steering beams (- 12°-12°) from two square corrugated waveguides. The beam characteristics at the resonance layer are described, and the average beam radius is < 100 mm. The peak head loads on the surfaces of the two fixed mirrors are 1.63 MW/m² and 1.52 MW/m². The position and size of the beam channel in the blanket are obtained, and the opening apertures on the launcher-facing and plasma-facing sides of the blanket module are 0.54 m² and 0.4 m², respectively.

• 한국진공학회지
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• 제15권6호
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• pp.581-586
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• 2006

차세대 리소그래피 기술인 극자외선(EUV : Extreme Ultraviolet) 빛샘 연구의 기초단계로써, 동축타입의 전극구조가 설치된 다이오드 챔버를 통해 Ar 플라스마를 생성하였으며, 방출 분광기술(emission spectroscopy)를 이용하여 방출된 가시광선 영역의 빛을 조사하였다. 장치의 입력 전압을 0.5kV씩 변화를 주어 $2\sim3.5kV$까지 인가를 했으며 이극챔버의 최적 압력인 330mTorr 일 때 각 전압에 따른 방출 분광선 데이터를 얻었다. 이때 Ar I과 Ar II 방출선을 관측하였으며 국소적인 열적평형 (LTE ; Local Thermodynamic Equilibrium) 상태의 가정 하에 볼츠만 도표(Boltzmann plot)와 사하(Saha) 방정식을 이용해 Ar I 및 Ar II의 전자온도와 이온 밀도를 각각 계산하였다. 각 입력전압에 대해 이온밀도는 Ar I과 Ar II에서 각각 $\sim10^{15}/cc$ 및 $\sim10^{13}/cc$의 값으로 계산되었다.