• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.109-111
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• 2002

The fundamental principles of the operation of microwave discharges that are used to convert microwave energy to broad spectrum visual light are known. In this paper, emission dependance of microwave discharges in mixture content of sulfur with noble gases was studied. It is shown that the excitation of this gaseous mixture is carried out in two phases; (1) ionization of noble gas atoms by a microwave field and (2) the consequent maintenance of slightly ionized nonequilibrium plasma by the field. These two processes have essentially various thresholds for the microwave pump. The purpose of this work is to investigate spectral properties of the high frequency discharges in a mixture sulfur vapors with noble gases.

• Tribology and Lubricants
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• v.16 no.3
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• pp.188-193
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• 2000

An experimental study was performed to discover the effect of environment on the tribological behavior of Si-incorporated diamond-like carbon(Si-DLC) film slid on a steel ball. The films were deposited on Si(100) wafers by a radio-frequency glow discharge of mixtures of benzene and dilute silane gases. Experiments using a ball-on-disk test-rig was performed in vacuum, dry air and ambient air conditions. It was observed that coefficient of friction decreased as the environment changed from vacuum, to dry air. Chemical analyses of debris suggested that low and stable friction is closely related to the formation of silicon-rich oxide debris and the rolling action.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.223-230
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• 1997

최근들어 그 활용도가 점점 증대되고 있는 DLU(Diamond-like Carbon) /Diamond 박막(thin film)의 합성기술을 개발하여 원자력분야에 응용하고자 시도하였다. 이를 위하여 13.56 MHz의 고주파(RF: radio-frequency)를 사용하는 플라즈마 화학증착(PECVD: Plasma Enhanced Chemical Vapor Deposition) 장치를 직접 제작하여 탄소함유(CH$_4$, $CO_2$...등) 기체로부터 기본적인 DLC 박막증착시험을 수행하였다. 실험은 진공증착기(vacuum chamber)내의 압력(pressure), 탄소함유 기체의 조성비, 그리고 바이어스전압(negative self-bias voltage)둥을 변화시키면서 수행하였다. 증착속도(deposition rate)는 증착층의 두께를 알파스템($\alpha$-step)으로 측정하여 결정하였으며, 이로부터 증착속도가 압력 및 바이어스 전압의 증가에 따라 증가함을 알 수 있었다. 또한 바이어스 전압 300V 이상에서 $CO_2$량 증가가 증착속도를 촉진시킨다는 사실도 확인하였다. 그리고 EPMA(electron probe micro-analyser) 및 Raman 스펙트럼분석을 통하여 증착층의 구조가 DLC 임을 확인하였다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.174-176
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• 2019

최근 미세먼지(PM10 또는 PM2.5)로 인한 인체 유해성 및 실제 피해사례가 인터넷, TV 매체 등에 의해 화두가 됨에 따라 각종 제조, 사업장 및 발전소에서는 미세먼지 배출기준을 충족하기 위한 고효율 집진 기술이 필요로 되고 있는 상황이다. 고압 코로나 방전에 의해 미세먼지를 포집하는 고전압 하전방식 집진장치의 경우 전류를 광범위로 조절 가능하며 역전리 방지에 탁월하여 고효율의 집진이 가능하다. 본 논문에서는 기존의 다전원(펄스전원, 기본전원)을 이용한 마이크로 펄스 하전방식이 아닌 공진형 컨버터와 고압 트랜스포머, 배전압 회로를 적용한 고전압 단전원 제어 하전방식 및 이를 이용한 고전압 전압원의 저속 스위칭 제어기법을 제안하고, 실제 측정을 통해 제안 방식의 실효성을 검증하였다.

• The Journal of Internal Korean Medicine
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• v.32 no.1
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• pp.100-112
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• 2011

Objectives : This study investigated the effects of electroacupuncture on memory, depression, and plasma stress hormone levels in rats that were under immobilization stress. Materials and Methods : The immobilization-only group was given two hours of immobilization stress for 10 consecutive days. The immobilization and high frequency EA group was given two hours of immobilization stress simultaneously with high frequency (100Hz) electroacupuncture stimulation on the right ST-36 (Zusanli) for 10 consecutive days. We conducted the inhibitory avoidance and forced swimming tests to recognize whether immobilization stress and electroacupuncture have effects on memory and depression. We collected blood samples from the tail of each rat at 30, 60, 90, and 120-minute intervals during the immobilization stress and EA stimulation to measure plasma concentrations of ACTH, corticosterone, melatonin, and norepinephrine induced by immobilization stress and electroacupuncture. Results : There was a significant effect of high frequency on the increase in anamnesis based on the result of the inhibitory avoidance test, but there was no significant effect of decreasing depression based on the result of the forced swim test. Also, there was no significant effect on the response indicated by stress hormones. Conclusions : 1. High frequency electroacupuncture (100Hz) improved anamnesis in immobilization stress states under the inhibitory avoidance task. 2. High frequency electroacupuncture (100Hz) did not reduce depression induced by immobilization stress under the forced swimming test. 3. High frequency electroacupuncture (100Hz) did not decrease stress hormones through blood sampling.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.380-381
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• 2012

Bioinspired sea urchin-like structures were fabricated on silicon by inductively coupled plasma (ICP) etching using lens-like shape hexagonally patterned photoresist (PR) patterns and subsequent metal-assisted chemical etching (MaCE) [1]. The lens-like shape PR patterns with a diameter of 2 ${\mu}m$ were formed by conventional lithography method followed by thermal reflow process of PR patterns on a hotplate at $170^{\circ}C$ for 40 s. ICP etching process was carried out in an SF6 plasma ambient using an optimum etching conditions such as radio-frequency power of 50 W, ICP power of 25 W, SF6 flow rate of 30 sccm, process pressure of 10 mTorr, and etching time of 150 s in order to produce micron structure with tapered etch profile. 15 nm thick Ag film was evaporated on the samples using e-beam evaporator with a deposition rate of 0.05 nm/s. To form Ag nanoparticles (NPs), the samples were thermally treated (thermally dewetted) in a rapid thermal annealing system at $500^{\circ}C$ for 1 min in a nitrogen environment. The Ag thickness and thermal dewetting conditions were carefully chosen to obtain isolated Ag NPs. To fabricate needle-like nanostructures on both the micron structure (i.e., sea urchin-like structures) and flat surface of silicon, MaCE process, which is based on the strong catalytic activity of metal, was performed in a chemical etchant (HNO3: HF: H2O = 4: 1: 20) using Ag NPs at room temperature for 1 min. Finally, the residual Ag NPs were removed by immersion in a HNO3 solution. The fabricated structures after each process steps are shown in figure 1. It is well-known that the hierarchical micro- and nanostructures have efficient light harvesting properties [2-3]. Therefore, this fabrication technique for production of sea urchin-like structures is applicable to improve the performance of light harvesting devices.

• Journal of Korean Biological Nursing Science
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• v.15 no.3
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• pp.99-106
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• 2013

Purpose: The purpose of this study was to examine the effect on plasma beta endorphin concentration level and the influences on pain score of transcutaneous electrical nerve stimulation (TENS) mediation to patients During a prostate needle biopsy. Methods: TENS was administered to only the experimental group. The electric current was given in high frequency (40-100 pps) and low intensity ($2-50{\mu}s$) from the waiting room stage until the end of the procedure. The average time spent was 35 minutes. Following 10 minutes of retention in the rectum, there was a biopsy. In two groups, the pain score was assessed twice when vas pain penetrated into the rectum, during the needle biopsy. The Beta endorphin concentration level was assessed through blood gathering 2 times in the Nuclear Medicine Labs before and after the test. Results: There was not much difference in pain levels from both groups when a microscope probe penetrated into the rectum and in the time when tissues were collected. However, the average overall pain level was reduced during those two procedures. The plasma beta endorphin level was increased in the TENS medicated group compared with the unmedicated group after the procedures were completed. Conclusion: The research indicates that TENS was desirable to be considered as a non-invasive method for controlling pain.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.178-178
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• 2016

Every display is equipped with a cover glass to protect the underneath displaying devices from mechanical and environmental impact during its use. The strengthened glass such as Gorilla glass.$^{TM}$ has been exclusively adopted as a cover glass in many displays. Conventionally, the strengthened glass has been manufactured via ion-exchange process in wet salt bath at high temperature of around $500^{\circ}C$ for hours of treatment time. During ion-exchange process, Na ions with smaller diameter are substituted with larger-diameter K ions, resulting in high compressive stress in near-surface region and making the treated glass very resistant to scratch or impact during its use. In this study, PIIID (plasma immersion ion implantation and deposition) technique was used to implant metal ions into the glass surface for strengthening. In addition, due to the plasmonic effect of the implanted metal ions, the metal-ion implanted glass samples got colored. To implant metal ions, plasma immersion ion implantation technique combined with HiPIMS method was adopted. The HiPIMS pulse voltage of up to 1.4 kV was applied to the 3" magnetron sputtering targets (Cu, Ag, Au, Al). At the same time, the sample stage with glass samples was synchronously pulse-biased via -50 kV high voltage pulse modulator. The frequency and pulse width of 100 Hz and 15 usec, respectively, were used during metal ion implantation. In addition, nitrogen ions were implanted to study the strengthening effect of gas ion implantation. The mechanical and optical properties of implanted glass samples were investigated using micro-hardness tester and UV-Vis spectrometer. The implanted ion distribution and the chemical states along depth was studied with XPS (X-ray photo-electron spectroscopy). A cross-sectional TEM study was also conducted to investigate the nature of implanted metal ions. The ion-implanted glass samples showed increased hardness of ~1.5 times at short implantation times. However, with increasing the implantation time, the surface hardness was decreased due to the accumulation of implantation damage.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.108-115
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• 2013

Oxide coatings were prepared on Al-1050 substrates by an environment-friendly plasma electrolytic oxidation (PEO) process using an electrolytic solution of $Na_2SiO_3$ (8 g/L) and NaOH (3 g/L). The effects of three different duty cycles (20%, 40%, and 60%) and frequencies (50 Hz, 200 Hz, and 800 Hz) on the structure and micro-hardness of the oxide coatings were investigated. XRD analysis revealed that the oxides were mainly composed of ${\alpha}-Al_2O_3$, ${\gamma}-Al_2O_3$, and mullite. The proportion of each crystalline phase depended on various electrical parameters, such as duty cycle and frequency. SEM images indicated that the oxide coatings formed at a 60% duty cycle exhibited relatively coarser surfaces with larger pore sizes and sintering particles. However, the oxides prepared at a 20% duty cycle showed relatively smooth surfaces. The PEO treatment also resulted in a strong adhesion between the oxide coating and the substrate. The oxide coatings were found to improve the micro-hardness with the increase of duty cycle. The structural and physical properties of the oxide coatings were affected by the duty cycles.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.182-192
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• 1999

The new GD/ICP-AES quick change over system has been developed and characterized. Within less than 15 minutes, ICP-AES could be switched to GD-AES and vise a versa. As a result, both solid and liquid samples could be analyzed in a very short period of time by the ICP/GD-AES quick change over system developed in our laboratory. The influences of the experimental variables, such as flow rate of coolant gas, flow rate of auxiliary gas, flow rate of sample carrier gas, sampling depth, orifice size of sampling cone, and rf (radio frequency) power on emission intensity have been presented. The detection limits of Cd(I) 228.8 nm, Mn (II) 257.61 nm, and Fe(II) 259.95 nm were found to be 3.86, 1.49, and 5.79 ppb, respectively. And linealities of the calibration curves were measured to be unity.