• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.907-913
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• 2017

The performance of a spark jet driven by pulsed-arc plasma was investigated experimentally for various energy input. A high-speed jet (about 330 m/s) was obtained by rapid gas heating produced by 37 mJ of deposited energy per pulse. The peak velocity and penetration distance of the jet were proportional to the deposited power and the deposited energy per pulse, respectively. A smaller orifice diameter produces a higher velocity jet at lower energy levels. For the same deposited energy, higher-current pulses produce a higher jet velocity than higher-pulse-width pulses. A total deposited energy of about 10 mJ per pulse with a pulse duration of about $10{\mu}s$ was found to be the optimum for energy- efficient operation.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.46-52
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• 2009

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for an internal combustion engine. This study is about fuel reforming to produce hydrogen enriched gas as a fuel for engine. Especially gasoline, which consists of numerous hydrocarbon fuels, considered as source of reformed gas. Various hydrocarbons, including commercial fuel were reformed and potentialities of reformed gas on vehicles were accessed. The reforming efficiency and hydrogen yield were observed. Maximum hydrogen yield were found with different gas hourly space velocity(GHSV) and O2/C ratio of reforming conditions.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.374-380
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• 2011

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils according to the injection stage of $SF_6$ gas incorporation were investigated. A continuous injecting of $SF_6$ gas flow could give rise to many types of carbon coils-related geometries, namely linear tub, micro-sized coil, nano-sized coil, and wave-like nano-sized coil. However, the limitation of the geometry as the nano-sized geometries of carbon coils could be achieved by the incorporation of $SF_6$ in a short time (1 min) during the initial deposition stage. A delayed injection of a short time $SF_6$ gas flow can deteriorate the limitation of the geometries. It confirms that the injection time and its starting point of $SF_6$ gas flow would be very important to determine the geometries of carbon coils.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.62-66
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• 2017

In this paper, we present the development of communication and data processing strategy for the electromagnetic wave precipitation gauge system. The electromagnetic wave precipitation gauge system is a small system for deriving area rainfall rates within 1 km radius through dual polarization radar observation at 24GHz band. It is necessary to take consider for measurement of accurate precipitation under limited computing resources originating from small systems and to minimize the use of network for the unattended operation and remote management. To overcome computational resource limitations, we adopted the fuzzy logic for quality control to eliminate non-precipitation echoes and developed the method by weighted synthesis of various rain rate fields using multiple radar QPE formulas. Also we have designed variable data packets rules to minimize the network traffic.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.80-86
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• 2010

This paper describes the development result of S-band Transmitter of STSAT-3 by satellite research center(SaTReC), KAIST. STSAT-3 has two kinds of communication channels, S- band for Telemetry & Command and X-band for mission payload. S-band Transmiiter(STX) consist of modulator, frequency synthesizer, power amp and DC/DC converter. The modulation scheme of STX is FSK(Frequency Shift Keying). The interface between spacecraft OBC and STX is RS-422. The STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under 1E-5. The Test of STX is completed successfully such as functional Test and environmental(vibration, thermal vacuum) Test.

• Journal of Pharmaceutical Investigation
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• v.25 no.2
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• pp.109-116
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• 1995

For the administration of narcotic antagonist with short half-life and low patient compliance, the sustained release system using biodegradable matrix is effective. Polyphosphazenes are of considerable interest as biodegradable matrix systems for controlled release of drugs. In this study, biodegradable polyphosphazenes available for the sustained release implantable device were synthesized, and their application was examined. Poly[dichlorophosphazene] was synthesized by solution polymerization method and confirmed with IR spectrum. Poly[bis(ethyl glycinate) phosphazene] and poly[ (diethyl glutamate)-co-(ethyl glycinate)phosphazene] were then produced by substitution of amino acid alkyl esters for chloride side groups. Using these polymers, the implantable devices of 1 mm thickness and $10{\times}10\;mm$ size containing naloxone hydrochloride were prepared and their release and degradation profiles were measured. In the case of poly[bis(ethyl glycinate)phosphazene] with swelling characteristics, degradation rate was slower than the release rate, showing that the release rate is partly dependent on the swelling rate. In contrast, the degradation rate of polyl[(diethyl glutamate)-co-(ethyl glycinate)phosphazene] matrix was identical with release rate of naloxone hydrochloride. On the basis of these results, it is expected that these polymers can be applied to sustained release implantable systems delivering narcotic antagonist.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.7
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• pp.378-388
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• 2000

In this paper, we propose Fuzzy Polynomial Neural Networks(FPNN) based on Polynomial Neural Networks(PNN) and Fuzzy Neural Networks(FNN) for model identification of complex and nonlinear systems. The proposed FPNN is generated from the mutually combined structure of both FNN and PNN. The one and the other are considered as the premise part and consequence part of FPNN structure respectively. As the consequence part of FPNN, PNN is based on Group Method of Data Handling(GMDH) method and its structure is similar to Neural Networks. But the structure of PNN is not fixed like in conventional Neural Networks and self-organizing networks that can be generated. FPNN is available effectively for multi-input variables and high-order polynomial according to the combination of FNN with PNN. Accordingly it is possible to consider the nonlinearity characteristics of process and to get better output performance with superb predictive ability. As the premise part of FPNN, FNN uses both the simplified fuzzy inference as fuzzy inference method and error back-propagation algorithm as learning rule. The parameters such as parameters of membership functions, learning rates and momentum coefficients are adjusted using genetic algorithms. And we use two kinds of FNN structure according to the division method of fuzzy space of input variables. One is basic FNN structure and uses fuzzy input space divided by each separated input variable, the other is modified FNN structure and uses fuzzy input space divided by mutually combined input variables. In order to evaluate the performance of proposed models, we use the nonlinear function and traffic route choice process. The results show that the proposed FPNN can produce the model with higher accuracy and more robustness than any other method presented previously. And also performance index related to the approximation and prediction capabilities of model is evaluated and discussed.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.636-640
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• 2001

In order to improve the optical Performance of green emitting phosphor for plasma display panel (PDP) application, the wet chemical method for preparing $Zn_{2-x}$ $SiO_4$:xMn (xi=0.02. 0.08) phosphor was designed. The spherical phosphor particles were obtained and the size can be between 0.5$\mu\textrm{m}$ and 2$\mu\textrm{m}$. The formation of phosphor, which had the willemite structure, was completed at relatively low temperature of 108$0^{\circ}C$. Also, photoluminescence Properties of the phosphors prepared were investigated under vacuum ultraviolet excitation. In particular, the emission intensity of Zn$_2$SiO$_4$:0.08Mn phosphor having the 1$\mu\textrm{m}$ of particle size was higher than that of commercial phosphor by 40%. The decay time of zinc silicate powder prepared as containing 8 mole% of manganese has been measured as 7.8ms.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.32.2-32.2
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• 2011

반도체 생산공정에서 CMP (Chemical-mechanical planarization) 공정은 우수한 전기전도성 재료인 Cu의 사용과 다층구조의 소자를 형성하기 위해서 도입되었으며, 최근 소자의 집적도가 증가함에 따라 CMP 공정 비중은 점점 높아지고 있다. Cu CMP 공정에서 연마제인 슬러리는 금속 표면과의 물리적 화학적 반응을 동시에 사용하여 표면을 연마하게 되며, 연마특성을 향상시키기 위해 산화제, 부식방지제, 분산제 및 다양한 계면활성제가 첨가된다. 하지만 슬러리는 Cu 표면을 평탄화하는 동시에 오염입자, 유기오염물, 스크레치, 표면부식 등을 발생시키며 결과적으로 소자의 결함을 야기시킨다. 특히 부식방지제로 사용되는 BTA (Benzotriazole)은 Cu CMP 공정 중 Cu-BTA 형태로 표면에 흡착되어 오염원으로 작용하며 입자오염을 증가시시고 건조공정에서 물반점 등의 표면 결함을 발생시킨다. 이러한 문제점을 해결하기 위해 Cu 표면에서 식각과 부식반응을 최소화하며, 오염입자 제거 및 유기오염물을 효과적으로 제거하기 위한 Post-CMP 세정 공정과 세정액 개발이 요구된다. 본 연구에서는 오염입자 및 유기물 제거와 동시에 표면 거칠기와 부식현상을 제어할 수 있는 post Cu CMP 세정액을 개발 평가하였다. 오염입자 및 유기오염물을 제거하기 위해서 염기성 용액인 TMAH 사용하였으며, Cu 이온을 용해할 수 있는 Chelating agent와 표면 부식을 억제하는 부식 방지제를 사용하여 세정액을 합성하였다. 접촉각 측정과 FESEM(field Emission Scanning Electron Microscope) 분석을 통하여 CMP 공정에서 발생하는 유기오염물과 오염입자의 흡착과 제거를 확인하였으며 Cu 웨이퍼 세정 전후의 표면 거칠기의 변화와 식각량을 AFM(Atomic Force Microscope)과 4-point probe를 사용하여 각각 평가하였다. 또한 세정액 내에서의 연마입자의 zeta-potential을 측정 및 조절하여 세정력을 향상시켰다. 개발된 세정액과 Cu 표면에서의 화학반응 및 부식방지력은 potentiostat를 이용한 전기화학 분석법을 통해서 chelating agent와 부식방지제의 농도를 최적화 시켰다. 개발된 세정액을 적용함으로써 Cu-BTA 형태의 유기오염물과 오염입자들이 효과적으로 제거됨을 확인하였다.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.363-363
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• 2001

In order to improve the optical Performance of green emitting phosphor for plasma display panel (PDP) application, the wet chemical method for preparing $Zn_{2-x}$ $SiO_4$:xMn (xi=0.02. 0.08) phosphor was designed. The spherical phosphor particles were obtained and the size can be between 0.5$\mu\textrm{m}$ and 2$\mu\textrm{m}$. The formation of phosphor, which had the willemite structure, was completed at relatively low temperature of 108$0^{\circ}C$. Also, photoluminescence Properties of the phosphors prepared were investigated under vacuum ultraviolet excitation. In particular, the emission intensity of Zn$_2$SiO$_4$:0.08Mn phosphor having the 1$\mu\textrm{m}$ of particle size was higher than that of commercial phosphor by 40%. The decay time of zinc silicate powder prepared as containing 8 mole% of manganese has been measured as 7.8ms.