• 대한전자공학회논문지SD
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• 제40권11호
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• pp.45-53
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• 2003

DRAM에서 사용되는 내부 승압 전원 전압과 기판인가 전원 전압 발생기를 공유함으로써 단일 Charge Pump에서 승압 전원과 기판 전원을 동시에 발생시키는 회로를 설계하였다. 이 회로는 0.14um의 DRAM 공정을 사용하여 기존 보다 전력 소모를 30%, 전체 면적을 40% 그리고 Pumping capacitor 면적을 29.6% 각각 감소하였으며 또한 전류 공급 효율을 13.2% 향상 시켰다. Charge Recycling 기법을 적용하여 Pumping capacitor의 Precharge 구간 동안 소모되는 전류를 75% 감소하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.39-44
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• 2009

We proposed a linear type magnetic flux pump (LTMFP) as a power supply for superconducting magnet system. In order to explain the operating mechanism of pumping action, the pumping sequence based on penetrated position and moving speed of magnetic flux on the superconducting Nb foil should be understood. In this paper, we induced a theoretical equation for pumping current of LTMFP according to the position of normal spot and corresponding equivalent circuit. In addition, current charging tendencies under the intensity of magnetic flux and frequency were described based on the theoretical pumping equation.

• 한국초전도ㆍ저온공학회논문지
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• 제6권1호
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• pp.43-48
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• 2004

This paper deals with design and fabrication of heater-triggered switching system for the high-Tc superconducting (HTS) power supply with series-connected double-pancake load. Amongst all components, heater triggering is the most important element for the performance of HTS power supply. To fabricate the optimal heater-triggered system, its characteristics have been analysed through the simulation and expriment. The thermal analysis of switching parts of the Bi-2223 solenoid according to the heater input was carried out. Based upon the analysis, 8A electromagnet current and 1.5A DC Heater current were optimally derived, and 8s and 20s for the pumping period were selected in this experiment. In the experiment. the maximum pumping current reached about 24A with Bi-2223 pancake load of 6mH.

• 한국진공학회지
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• 제8권3B호
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• pp.353-360
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• 1999

The global balance model is applied to investigate the transient behavior of the electron density and temperature in helicon plasmas. The power absorption calculated from the solutions of the Maxwell equations is used in solving the power balance equation. A balance model for the neutral gas is also considered to fins its density self-consistently. It is turned out that the numerical results reasonably explain consequences of the ion pumping effect including the occurrence of two distinct modes of pulsed helicon discharge which have been observed experimentally. The behavior of the discharge parameters are fond to be primarily dependent on the power absorption and the gas flow rate, but the pressure controls the electron density and temperature of the final steady state as well as the transient state even with the same flow rate. Finally, it is shown that the electron density virtually the linear relationship between the density and the magnetic field is retained for a higher pressure when the effect of the ion pumping is negligible.

• 설비공학논문집
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• 제12권3호
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• pp.251-257
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• 2000

District heating and cooling systems offer highly efficient energy utilization and maintenance by centralizing heat management. More pumping power, however, is required because the water has to travel long distance from heat source to the users. In the present study, a trace of drag reduction additives is added to the District Cooling system to achieve a significant drag reduction and save pumping power. Water-soluble polymers, surfactants, and environment-friendly degradable polymers are used as effective drag reducing additives. Time dependent percent drag reductions are compared for various additive solutions at 100 wppm concentration for different water velocity. Without as an anionic surfactant, copolymer was most effective in percent drag reduction. It is found that there exists an optimal condition when copolymer is mixed with SDS. An environment-friendly degradable polymer, xanthan gum, is found to be a significant drag reduction additive. Ice slurry systems, can give less pressure drops compared with chilled water system for certain condtions. Drag reduction additives were also effective for the ice slurry system.

• 한국유체기계학회 논문집
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• 제3권4호
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• pp.52-58
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• 2000

The numerical study on the waterhammer was carried out for the intake pumping station of the metropolitan water supply 6th stage project. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully investigated. The surge tank and the stand pipes effectively protected the tunnels md the downstream region of pipeline from the pressure surge. In case the moment of inertia of the pump and motor was above $5080\;kg{\cdot}m^2$, the column separation did not occur in the pipeline between the pumping station and the inlet of 1st tunnel. As the moment of inertia increased, the pressure surges decreased in the pipeline conveying raw water. The pump control valve was chosen as the main surge suppression device for the intake pumping station. After power failure, the valve disc should be rapidly closed in 2.5 seconds and controlled the final closure to 15 seconds by the oil dashpot. If the slamming happened to the pump control valve, there was some danger of this system damaging. As the reverse flow through the valve increased, the upsurge extremely increased.

• 한국광학회지
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• 제3권4호
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• pp.222-226
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• 1992

$Ar^{+}$레이저로 펌핑되는 Nd:glass레이저를 제작하여 그 특성을 조사하였다. 레이저 공진기는 오목거울 두 개와 98% 고반사 평면경, 그리고 Brewster 각도로 놓인 Nd:glass 의 이득 매질로 구성되었으며, 효율적인 펌핑을 위해서 $Ar^{+}$레이저 광선을 공진기 길이 방향으로 입사하여 공진모우드의 beam waist에서 초점이 맺히도록 하였다. Nd:glass의 열존도도가 작아서 흡수된 펌핑빔에 의해 생성된 잔열로 인한 매질의 손상이 우려되기 때문에 mechanical chopper 로 펌핑빔을 100Hz로 끊어서 입사하여 잔열의 생성을 줄였다. 1.5W로 펌핑될 때 Nd:glass 레이저의 출력은 70mW이었고 발진이 되는 문턱에서의 펌핑파워는 520mW이었으며 slope efficiency는 7.4%이었다.

• 상하수도학회지
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• 제26권3호
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• pp.383-397
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• 2012

In this study, a System Dynamics (SD) simulation model for the efficient operations of an industrial water supply system was developed by investigating the feedback loop mechanisms involved in the operations of the system. The system was modeled so that as demand is determined the water supply quantity of intake pumping stations and dams are allocated. The main feedback loop showed that many variables such as the combinations of pump operation, unit electric power(kWh/$m^3$), unit electric power costs(won/$m^3$), water level of water way tunnel, suction pressure and discharge of pumping station, and tank and service reservoir water level had causal effects and produced results depending on their causal relationship. The configurations of the model included an intake pumping station model, water way tunnel model, pumping station model (including the tank and service reservoir water level control model), and unit electric power model. The model was verified using the data from the case study industrial water supply system that consisted of a water treatment plant, two pumping stations and four dams with an annual energy costs of 5 billion won. It was shown that the electric power costs could have been saved 7~26% during the past six years if the operations had been based on the findings of this study.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권12호
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• pp.771-777
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• 2000

This paper deals with the design and fabrication of a novel superconducting power supply system, and characteristics have been investigated through experiments. Superconducting power supply consists of rotating and static parts, and superconducting magnet. In this experiment, superconducting foils were placed in parallel within the static part of the machine, pumping currents were measured with respect to rotor speeds and excitation currents. In addition, in order to observe the rotating flux distribution in the superconducting foils, several hall-sensors were placed in it. With the flux distribution acquired, effect of the flux on the superconducting foil during the process of current pumping has been discussed. Also, the general operational characteristics of the superconducting power supply system have been investigated on the basis of the current and voltage data, and magnetic field values acquired through the experiments.

• 한국초전도ㆍ저온공학회논문지
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• 제11권3호
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• pp.40-45
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• 2009

Many superconductor applications such as MRI and SMES must be operated in persistent current mode to eliminate the electrical ohmic loss. This paper presents the characteristic analysis of the high temperature superconducting (HTS) power supply made of YBCO coated conductor (CC). In this research, we have manufactured the HTS power supply to charge the 0.73 mH HTS double-pancake magnet made of YBCO CC. Among the all design parameters, the heater triggerring time and magnet applying time were the most important factors for the best performance of the HTS power supply. In this paper, three-dimensional simulation through finite element method (FEM) was used to study the heat transfer in YBCO CC and the magnetic field of the magnetic circuit. Based upon these results, the final operational sequence could be determined to generate the pumping current. In the experiment, the maximum pumping current reached about 16 A.