• Journal of the Korean Wood Science and Technology
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• 제45권4호
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• pp.463-470
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• 2017

The objectives of this study are to obtain the basic knowledge of anatomical characteristics and wood properties of thinning trees of young teak (Tectona grandis L.F.) for fulfill the timber demand in Indonesia. Nine thinning trees of 5-year-old teak clone trees were used for analyzing the cell morphology and air-dry density. Vessel diameters in pore and outer pore zones were 165 and $90{\mu}m$, respectively. Mean value of fiber diameter, cell wall thickness, and fiber length in outer pore zone were $14.6{\mu}m$, $2.07{\mu}m$, and 1.04 mm, respectively. In addition, mean value of air-dry density was $0.55g/cm^3$. The measurement and values of vessel diameter, fiber diameter, cell wall thickness, fiber length and air-dry density in the experimental had lower than those in the older teak. Therefore, it could be suggested that the wood from thinning young teaks was not appropriate as construction material, but it could be used for furniture which do not need high of strength properties. Furthermore, since the measurements values of anatomical characteristics were still increasing from pith to bark, it could be suggested that 5-year-old teak clones are still in a juvenile phase. Positively significant correlations were found between air-dry density and cell wall thickness, indicating that cell wall thickness is strongly correlated with wood density of teak.

• 대한기계학회논문집 C: 기술과 교육
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• 제2권1호
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• pp.57-63
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• 2014

태양광 모듈의 과열을 방지하여 효율을 향상시키기 위해 스털링기관을 이용한 새로운 공랭식 냉각 시스템을 개발하였다. 베타 타입 스털링기관에 냉각팬을 연결하고 태양광 모듈의 뒷면에 반원형의 에어가이드를 부착함으로써 스털링기관 작동에 의해 발생된 강제대류가 에어가이드를 따라 이동하면서 태양광 모듈의 후면을 냉각하는 방식이다. 할로겐 조명을 활용한 하절기 모사 성능 평가 실험 결과 본 연구를 통해 개발된 새로운 냉각시스템을 적용할 경우 태양광 모듈의 온도가 냉각을 적용하지 않은 경우에 비해 약 $12^{\circ}C$ 낮아지고 출력 전압은 약 25% 향상되었다.

• 설비공학논문집
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• 제6권2호
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• pp.120-129
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• 1994

A numerical investigation has been carried out for the electrochemical reaction, mass and heat transfer characteristics of the Molten Carbonate Fuel Cell(MCFC) stack. The effects of cooling air channel and water gas shift reaction were taken into account. The current density distribution of electrodes, the molecular fractions of reactant gasses and three dimensional temperature distribution can be calculated and shown by several lines of equivalent values. The results have been compared with the existing ones, and reasonable agreement has been obtained. To examine the influence of changing parameters, such as the composition of reactant gases, the target average current density, the utilization of reactant gases, the cooling air inlet temperature and flow rates, the computer simulation has been done. The analysis method and computer program developed in this study will be greatly helpful to design and verify the optimum operating condition of MCFC stack.

• 한국통신학회논문지
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• 제34권11A호
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• pp.844-851
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• 2009

핸드오버는 multi-hop relay 시스템에서 이동성을 제공하기 위해 필요하다. 핸드오버의 주요 목적은 MS가 한 BS의 air-interface에서 다른 BS의 air-interface로 이동할 때 연속 연결을 제공하는 것이다. 특히 이종기계간의 핸드오버는 차세대 네트워크에 필수적이다. Mobile WiMAX MMR system에서의 수직 핸드오버 기술은 기술자들이 Mobile WiMAX system을 overlaid cell환경으로 가져오는데 매우 유용하다. 이 기술은 Micro cell(Frequency 1,FA1) and Macro cell(Frequency 2,FA2)사이에 놓인 Ubiquitous 환경에서 시스템 성능향상을 위해 MRS를 다른 시스템으로 핸드오버 하는 기술에 적용될 것이다. 이 논문에서 FA1과 FA2 주파수를 사용하여 제안된 조건들에 따라 MRS들이 수직 핸드오버를 수행했다. 그리고 중심에 있는 Macro cell과 그것을 싸고 있는 6개의 Macro cell들의 BS나 섹터로부터 받은 간섭 및 성능을 분석한다.

• 한국군사과학기술학회지
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• 제18권6호
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• pp.755-761
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• 2015

Satellite Air-defence Warning System receives the aircraft/ballistic track information and air defense control command obtained from Master Control & Reporting Center (MCRC) and Air Missile Defence Cell (AMD Cell) Systems. It consists of terminal and control system to propagate track information and air defense control command control via the military satellite communications. In this paper, there were described track information, air defense control command, the frame structure of modem to transmit a voice information and modulation/demodulator design, network synchronization methods via the satellite network.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.236-237
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• 2017

This study discusses the development of waterproofing layer jet-spray nozzle that forms a three-dimensional air cell. This nozzle has an air flow generation mechanism in the air groove of the attachment cell part located at the end of the injection nozzle. Since the air grooves also function as an air curtain, the airborne particles generated when the waterproof material is sprayed is effectively blocked. In the past, spraying of the waterproof material through the high pressure was possible, but this technology allows stable injection due to the static agitation method, and various problems caused by particle generation has been (damages to neighboring areas, economic loss, etc.) minimized.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.881-890
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• 2011

Analyses of performance and behavior of the individual PEM fuel cells (PEMFC) under different operating conditions are of importance optimally to design and efficiently to operate the stack. The paper focuses on experimental analyses of a two-cell stack under different operating conditions, which performance and behavior are measured by the voltage of a cell as well as the stack. Experimental parameters include stoichiometric ratio, temperature of the air supplied under different working stack temperatures and loads. Results showed that the cell voltages are dominantly influenced by the temperature of the air supplied among others. In addition, an inherent difference between the first and the second cell voltage exists because of the tolerances of the cell components and the resulting different over-potentials at different equilibrium states. Furthermore, it is shown that the proton conductivity in the membranes conditioned by the humidity in the cathode channel highly affects the voltage differences of the two cells.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1664-1669
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• 2004

Design analysis of the solid oxide fuel cell and gas turbine combined power system is performed considering different methods for preheating cell inlet air. The purpose of air preheating is to keep the temperature difference between cell inlet and outlet within a practical design range. Three different methods are considered such as a burner in front of the cell, a preheater in front of the cell and recirculation of the cathode exit gas. Analyses are carried out for two maximum cell temperature differences. The greater temperature difference ensures higher efficiency. The cathode exit gas recirculation exhibits better performance than other methods.

• 한국수소및신에너지학회논문집
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• 제20권4호
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• pp.283-290
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• 2009

This study focuses on the performance characteristics of polymer electrolyte membrane fuel cell (PEMFC) using the AC impedance technique. The experiment was carried out to investigate the optimal operating conditions of PEMFC such as cell temperature, flow rate, humidified temperature and back-pressure. The fuel cell performance was analyzed by DC electronic-loader with constant voltage mode and expressed by voltage-current density. Additionally, AC impedance was measured to analysis of ohmic and activation loss and expressed by Nyquist plot. The results showed that the cell performance increased with increase of cell temperature, air flow rate, humidified temperature and backpressure. Also, the activation loss decreased as the increase of cell temperature, air flow rate, humidified temperature and backpressure.

• 전기학회논문지P
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• 제63권3호
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• pp.212-217
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• 2014

The electric power output characteristics of magnesium fuel cell were investigated with regard to internal resistance. A equivalent circuit with the series-connected three internal resistance was introduced to analyze of the response to change of power. The power output analysis was employed in order to investigate the effect of internal resistances for the electrolyte concentration, air electrode area, Mg electrode area and distance between the electrodes. It was confirmed that internal resistance is generated by the electrolyte, air electrode and metal electrode, then those Internal resistances had a significant effect on the power output decrease. The power output was a maximum when the load resistance maches the internal resistance of the magnesium fuel cell. The fuel efficiency was only 50% at maximum power output. Higher fuel efficiency was achieved when the load resistance is greater than the internal resistance.