• 한국전자파학회논문지
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• 제28권1호
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• pp.69-75
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• 2017

본 논문에서는 자기공진형 무선전력전송의 실용화에 있어, 공진기 간 자기결합을 방해하는 그라운드 문제를 해결하기 위해 슬릿 구조를 설계하고, 커패시터를 연결하여 공진기로써의 성능을 기본적인 루프형의 수신 공진기와 비교하였다. 제안된 슬릿 그라운드 공진기(slit ground resonator)는 가로 31 cm, 세로 20.5 cm, 두께 $35{\mu}m$의 구리박판에 넓이 1 cm의 슬릿을 한 방향이 열린 십자 형태로 설계하였으며, 열린 방향 양단에 6.78 MHz에서 공진하도록 최적의 커패시터가 연결되어 공진기 역할이 가능하다. 수신 공진기는 스위치를 연결하여 열림형(open mode)과 닫힘형(short mode)일 때를 측정하고, 최고 전송효율을 표시하였다. 측정 결과, 수신 공진기가 루프 공진기일 때 가장 높은 전송효율을 보였다. 그러나 노트북 모델의 수신부에 그라운드를 삽입했을 때, 전송효율이 0 %에 가깝게 감소하였다. 반면, 슬릿 그라운드 공진기를 수신 공진기로 사용했을 때, 전송효율은 가장 높았던 루프 공진기의 67 % 회복하였다. 제안된 슬릿 그라운드 공진기는 슬릿을 통해 자기장을 통과시키며, 커패시터를 연결이 공진기로 동작하게 하여 주변 공진기 간 자기결합을 통해 전력을 전송해주는 역할을 수행한다.

• 한국진공학회지
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• 제5권1호
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• pp.85-92
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• 1996

The external electricla characteristics of helicon wave plasmas were measured over a wide range of RF power and magnetic filed. External parameters. such as antenna voltage , current, phase shift, and interanl parameter, electron density were measured at 7MHz, 1mTorr Ar discharge . The equivalent discharge resistance and reactance, and the power transfer efficiency were calculated through these measurements. There are a helicon mode which produces high density plasma by helicon wave and a lowmode which produces low density plasma by capaictive electric field. In case of the helicon mode, the anternna voltage and current were lower than those of the low-mode. The phase difference between voltage and current decreased suddenly at the transition point from the low-mode to the helicon mode. Equivalent resistance and power efficiency increased and reactance decreased suddenly at the transition point. These results mean that the power transperred to plasma and the nutual coupling between the antenna and plasma increase as the mode changes from the low-mode to the helicon mode.

• 전자공학회지
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• 제18권12호
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• pp.29-38
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• 1991

CCITT에 의해서 표준화 되고 있는 SDH(synchronous digital hierarchy)기본의 광대역 전송방식과 이의 향후 응용 방향에 대해 개관한다. 또한 광대역 전송방식으로서 고려될 수 있는 STM(synchronous transfer mode)망과 ATM(asynchronous transfer mod)망의 구조를 살펴보고 1991년도를 중심으로 일어나고 있는 이들 각각의 국내ㆍ외적인 표준화 동향, 기술개발 현황, 그리고 망구축 동향 등에 대해서 간단히 기술한다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.159-166
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• 2005

The vibration on building structures due to exciting vibration forces has been studied only for the vibration level on existing buildings. Recently, several researches have been performed on the prediction of vertical vibration on structures by using an analytical method. However, these studies have been focused on mainly the vibration analysis through analytical modeling of structures. This study aims to investigate the characteristics of vertical vibration transfer in terms of the directions of transfer(upward transfer and downward transfer) on the shear wall building structures due to 2 type vibration forces. In order to examine the characteristics of vertical vibration transfer, the mode analysis and the impact experiment were conducted several times on one building structure. The results of this study suggest that the characteristics of vertical vibration transfer are different in terms of the directions of transfer.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.70-73
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• 2006

Recently, several researches have been performed on the prediction of vertical vibration on structures by using an analytical method. However, these studies have been focused on mainly the vibration analysis through analytical modeling of structures. This study aims to investigate the characteristics of vertical vibration transfer in terms of the directions of transfer(upward transfer and downward transfer) on the shear wall building structures due to heel-drop impact forces. In order to examine the characteristics of vertical vibration transfer, the mode analysis and the impact experiment were conducted several times on two shear wall building structures. The results of this study suggest that the characteristics of vertical vibration transfer are similar in terms of the directions of transfer.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.279-282
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• 2002

Recently, gas turbines for power generation adopt multistage DLN(Dry Low NOx) type combustion, where diffusion combustion is applied at low load and, with increase in load, the combustion mode is changed to lean premixed combustion to reduce NOx emissive concentration. However, during the mode changeover from diffusion to premixed flame, unfavorable phenomena, such as flashback, high amplitude combustion oscillations, or thermal damage of combustor parts could frequently occur. In the present study, to apply for the analysis of such unfavorable phenomena, three-dimensional CFD investigations are carried out to compare the detailed flow characteristics and temperature distribution inside the gas turbine combustor before and after combustion mode changeover. The fuel considered here is pure methane gas. A standard $k-{\varepsilon}$ turbulence model with wall function and a P-N type radiation heat transfer model, have been utilized. To analyze the complex geometric effects of combustor parts on combustion characteristics, fuel nozzles, a swirl vane f3r fuel-air mixing, and cooling air holes on the combustor liner wall, are included in this simulation.

• 한국수소및신에너지학회논문집
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• 제23권2호
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• pp.162-172
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• 2012

This paper presents a research about free piston linear engine (FPLE) fueled with hydrogen, in which, the numerical models are built to simulate the operation during the full stroke of the engine. Dynamic model, linear alternator model and thermodynamic model are used as the numerical models to predict piston velocity, in-cylinder pressure and electric power of FPLE. The spark timing and air gap length are changed to provide information for the prediction. Beside, the heat transfer problem is also investigated in the paper. The results of research are divided by two parts, including motoring mode and firing mode. The result of motoring mode showed that there is validation between simulation and experiment for volume and pressure in cylinder. For firing mode, by increasing spark timing, the velocity of piston, peak pressure and electric power also increase respectively. Beside, when increasing air gap length, the electric power increases accordingly while the motion of piston is not symmetric. The effect of heat transfer also observed clearly by reducing of the peak pressure, velocity of piston and electric power.

• Journal of the Korean Wood Science and Technology
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• 제37권5호
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• pp.440-450
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• 2009

In case of wood flooring, the high emissivity would be one of the most important properties especially as the cover material of underfloor heating system. The FIR (Far Infrared) materials such as wood emit FIR energy by heating, which has been used as the medical therapy such as dry sauna. This research investigated the emissivity and the emission power of wood composites by comparing the amount of the three heat transfer modes transferred by infrared radiation which came from the increased temperature of the bottom board of the plywood box by the heater. The results showed the value of radiation mode was the highest mode for the plywood box, and the convection mode was the main mode for the aluminum box. The rate of convection was 81.8% in the aluminum box and 48.2% in the plywood box, respectively. In case of the rate of radiation, the aluminum box showed only 15.4% and the plywood box showed 51%. The emissivity and the emission power of birch plywood showed the same values as those of wood. The amount of energy required for the temperature rising of water within vial in the aluminum box and in the plywood box were 3.32 kJ and 6.70 kJ respectively, which showed that the vial temperature of the plywood box was two times higher than that of the aluminum box.

• 전기학회논문지
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• 제64권12호
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• pp.1709-1717
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• 2015

In remote islands PV (Photo Voltaic) panel with BESS (Battery Energy Storage System) supplies electric power to the customers in parallel operation with EG (Engine Generator) to save fuel consumption and to mitigate environmental load. BESS operates in voltage control mode when it supplies power to the load alone, while it operates in current control mode when it supplies power to the load in parallel with EG. This paper proposes a smooth mode change scheme from current control to voltage control of BESS by adding proper initial value to the integral part of voltage control, and a smooth mode change scheme from voltage control to current control by tracking the EG output voltage to the BESS output voltage using PLL (Phase-Locked Loop). The feasibility of proposed schemes was verified through computer simulations with PSCAD/EMTDC, and the feasibility of actual hardware system was verified by experiments with scaled prototype. It was confirmed that the proposed schemes offer a seamless operation in the stand-alone power system in remote islands.

• 한국연소학회지
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• 제22권1호
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• pp.39-45
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• 2017

Combustion instability analysis of partially premixed model gas turbine combustor was conducted with 1D lumped method. Flame Transfer Function(FTF) was obtained with variation of fuel composition by Photo Multiplier Tube(PMT) and Hot Wire Anemometry(HWA). Decreasing instability frequency was observed when combustor length increased and multi-mode instability was confirmed. Instability frequency mode was changed while $H_2$ composition rate was increased and had agreement with experimental value. This work confirms that prediction of longitudinal combustion instability mode of partially premixed combustor is possible using 1D lumped method.