• International Journal of Aeronautical and Space Sciences
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• v.12 no.1
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• pp.69-77
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• 2011

A peristaltic micropump with lightweight piezo-composite actuator (LIPCA) membrane valves is presented. The micropump contained three cylinder chambers that were connected by microchannels and two active membrane valves. A circular miniature LIPCA was developed and manufactured to be used as actuating diaphragms. The LIPCA diaphragm acted as an active membrane valve that alternate between open and closed positions at the inlet and outlet in order to produce high pumping pressure. In this LIPCA, a lead zirconium titanate ceramic with a thickness of 0.1 mm was used as an active layer. The results confirmed that the actuator produced a large out-of-plane deflection. During the design process, a coupled field analysis was conducted in order to predict the actuating behavior of the LIPCA diaphragm; the behavior of the actuator was investigated from both a theoretical and experimental perspective. The active membrane valve concept was introduced as a means for increasing pumping pressure, and microelectromechanical system techniques were used to fabricate the peristaltic micropump. The pumping performance was analyzed experimentally in terms of the flow rate, pumping pressure and power consumption.

• The KSFM Journal of Fluid Machinery
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• v.8 no.4 s.31
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• pp.20-26
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• 2005

When the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. The field tests on the waterhammer were carried out for Pangyo booster pumping station in which had six booster pumps and two in-line pumps with the motor of output 1,700 kW, respectively. The booster pumping station was equipped with the pump control valve as the main surge suppression device, and the surge relief valve as auxiliary one. But the pump control valve had not early controlled in the planned closing mode, the slamming occurred to the valve of which abruptly closed during the large reverse flow. Because the positive pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the pump control valve was damaged. After the air chambers were additionally installed in the booster pumping station, it was preyed that the water supply system acquire the safety and reliability on the pressure surge.

• Journal of Soil and Groundwater Environment
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• v.21 no.4
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• pp.42-49
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• 2016

Step-drawdown pumping tests for identifying the improvement of groundwater well performance after rehabilitation treatments were conducted in three longstanding wells. Three selective mechanical treatment methods including power bubble, high-voltage electric pulse, and air surging were applied to these wells and the applicability of these methods to secure additional groundwater resources were evaluated quantitatively. Commonly, drawdown at final stage of stepdrawdown pumping tests after rehabilitation decreased by as much as 0.61~0.70 meters compared to those before rehabilitation. In addition, final specific drawdown values of three wells increased from 9% to 14% after rehabilitation. Formation loss coefficient and well loss coefficient decreased to 6.1% and 60.6%, respectively, indicating some clogging materials by precipitation/corrosion/microbe within pores of aquifer materials, gravel packs, and screens were effectively removed by applied methods. Decrease of formation loss coefficient was higher in the well applied by the power bubble method meanwhile high-voltage electric pulse method demonstrated the higher decrease of well loss coefficient. Additionally secured groundwater amounts after rehabilitation ranged from 23.3 to 32.1 m³/day, which account for 8~16% of initially developed pumping rates of the wells. From the results of this study, the effective selection of rehabilitation treatments considering aquifer characteristics are expected to contribute to secure groundwater resources for irrigation as well as to plan systematic management program for groundwater resources in rural area.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.295-299
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• 2007

This paper presents the photovoltaic(PV) water pumping system with a maximum power point tracking(MPPT). The wale- pumping system uses a variable speed single phase induction motor(SPIM) driven a centrifugal pimp by field oriented control(FOC) inverter. The MPPT using a DC-DC converter controlled the duty cycle to track maximum power from PV under different insolation conditions. The duty cycle directly relate with a flux producing current control($i_{ds}$). The FOC inverter uses a current control voltage source inverter(CC-VSI). The simulation results are shown that the characteristics and performance of drive system, which varies as each conditions of light by expresses in voltage ($V_{dq}$), current($I_{dq}$), speed of motor and torque.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.193-196
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• 2001

This paper deals with the fabrication and characteristic experiment of a high-Tc superconducting(HTSC) power supply using by Bl-2223 tape. The purpose of this research is to apply real HTSC load. This system consists of two heaters, an electromagnet, a Bi-2223 solenoid and a Bi-2223 pancake load. In the experiment. 17sec and 8.5sec were used for pumping period. Mechanism of the superconducting switch is used for heater-trigger. In experiment, the pumping-current has reached about 1.2A.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.16-20
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• 2007

In this paper, convective heat transfer and flow characteristics of $Al_2O_3$ nanoparticles suspended in water flowing through uniformly heated tubes are experimentally investigated under laminar flow regime. The heat transfer coefficient and the pressure drop of nanoparticles suspended in water are experimentally presented according to the pumping power. In addition, the heat transfer coefficient and the pressure drop of $Al_2O_3$ nanoparticles suspended in water are compared with those of pure water under the fixed pumping power. It is shown that the heat transfer coefficient of $Al_2O_3$ nanofluids with 0.1% volume fraction is enhanced by about 12% although the increment of the pressure drop of those is 4% compared with those of pure water.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.220-221
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• 2000

본 연구에서 목표로 하는 집속광학계는 레이저 다이오드의 emitting area가 50$mu extrm{m}$$\times$1.0$\mu\textrm{m}$ 이고 pumping 매질인 crystal의 TE $M_{00}$ mode 발생을 위한 최소 입사빔의 단면도가 단축과 장축의 직경이 각각 206$\mu\textrm{m}$, 204$\mu\textrm{m}$인 타원이어야 하기 때문에 수직 방향으로는 200배 수평 방향으로는 4배의 확대를 할 수 있는 광학계 이어야 한다. 일반적으로 레이저 다이오드용 집속광학계는 레이저다이오드의 수직 수평 emitting area가 다르기 때문에 실린더형, 원통형 또는 toroidal형의 렌즈를 조합하여 구성한다. 그러나 우리의 경우는 emitting area의 수직 수평비 즉 집속광학계의 수직 수평의 굴절능( power )의 비가 50:1 이어야 하기 때문에 그림1과 같은 일반적인 실린더형, 원통형 또는 toroidal형의 렌즈의 조합으로 집속광학계를 구성하기에는, 렌즈 power비를 50:1로 하기 위해 필요로 하는 공간이( 첫번 렌즈와 마지막 렌즈까지의 거리 ) 커지는 점, 필요로 하는 렌즈의 매수가 많아지는 점, 집속 beam의 형상 즉 단면의 이심률이 커져서 pumping에 비효율적이라는 점 등에서, 부적절하다. (중략)략)

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.12-14
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• 2001

This paper deals with the fabrication and characteristic experiment of a high-Tc superconducting (HTSC) power supply using by Hi-2223 tape. The purpose of this research is to apply real HTSC load. This system consists of two heaters, an electromagnet, a Bi-2223 solenoid and a Bi-2223 pancake load. In the experiment, 17sec and 8.5sec were used for pumping period. Mechanism of the superconducting switch is used for heater-trigger. In experiment, the pumping-current has reached about 1.2A.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.47-51
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• 1997

A Cr:LiSAF laser pumped by semiconductor lasers was constructed. The pumping laser was a high-power semiconductor laser (SDL 7432-H1) of wavelength 674 nm and maximum power of 500 mW. The laser crystal was a Cr:LiSAF of plano-Brewster shape with 3% Cr3+ion concentration and 3 mm in length. The plane facet of the crystal was coated to get the maximum transmittance of pupmping laser and maximu reflection over the 800 - 880 nm bandwidth. V-shaped resonator was used to compensate the astigmatism induced by the crystal. The output power of the Cr:LiSAF laser was 19.4 mW at the pumping power of 290 mW. The wavelength was tuned by a steep dive-angled birefringent filter from 840 nm to 880 nm and the characteristics of the filter were agreed well with a theory.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.244-246
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• 1999

This paper deals with the design and fabrication of a novel superconducting power supply system, and characteristics have been analyzed through experiments. Superconducting power supply consists of rotating and static parts, and superconducting magnet. In this experiment, the current pumping characteristics have been analyzed with superconducting sheets placed in parallel within the static part of the machine. In addition, in order to observe the rotating flux distribution in the superconducting sheet, several hall-sensors were placed in it. With the flux distribution acquired, the effect of the flux on the superconducting sheet during the process of current pumping have been analyzed. Also, 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.