• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.10
• /
• pp.1451-1457
• /
• 2002

When an aqueous liquid such as water having high electric conductivity and high surface tension is discharged from a nozzle under a strong DC electric field, fine drops ranging from 30 to 450 microns can be obtained only through the spindle mode. In the present study, effects of the electric conductivity and the surface wettability of nozzle materials on formation of drops with this mode were investigated. For that, three nozzles with the same size but with different materials were prepared and tested; a stainless steel needle, and a plain and a metal (gold)-coated (except for the tip portion) silica needles. Uniform drops were obtained with the gold-coated silica nozzle over the wider range of the DC voltage input. That is, formation of the liquid cone and detachment of the liquid spindle (ligament) can be more stabilized and frequent with the needles having high electric conductivity but with low surface wettability at their tips.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.726-728
• /
• 1998

Optical and electrical properties of GaSe:$Er^{3+}$ single crystals grown by the Bridgeman technique was been investigated by using optical absorption and Hall-effect measurements. The Hall coefficients were measured by using a high impedance electrometer in the temperature range from 360K to 150K. The temperature dependence of hole concentration shows the characteristic of a partially compensated p-type semiconductor. carrier density($N_H$) of GaSe doped with Erbium was measured about $3.25{\times}10^{16}\;[cm^{-3}}$ at temperature 300K, which was high than undoped specimen. Photon energy gap ($E_{gd}$) was measured about 1.7geV.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.4-6
• /
• 2003

We have developed the active matrix OLED displays with a high efficiency red emission material which uses an emitting assist (EA) dopant system. The EA dopant (rubrene) did not itself emit but assisted the energy transfer from the host ($Alq_s$) to the red emitting dopant(DCM2). A stable red emission (chromaticity coordinates: x=0.64, y=0.36) was obtained in this cell within the luminance range of 100 - 4000 $cd/m^2$ By using EA dopant system, we can realize the reduction of the power consumption of the OLED display..

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.1
• /
• pp.7-11
• /
• 2008

A new continuously variable transmission (CVT) for electric bicycles was developed using a traction drive mechanism with inner and outer spherical rotors. This electric bicycle CVT permits three propulsion modes: human-power only, motor-power only, or a combination of motor power and human power. In addition, the electric bicycle CVT has high power efficiency, large torque capacity, improved drivability, and good packageability. A prototype was manufactured based on a conceptual design, a performance analysis, and a detailed design. This prototype has a rated power of 250 W and input motor speed of 20 rad/s for an overall speed ratio in the range 0.3-1.2. A bench test was conducted to measure the power transmission performance of the prototype.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.5
• /
• pp.573-580
• /
• 2014

The electrical reliability of the power generation and distribution system of Floating Liquefied Natural Gas vessels has been analyzed according to the operating modes using Electrical Transient Analysis Program in this paper. Electricity is used for the topside processes, cargo pumps for off-loading, thrusters for heading control and marine equipment. It is very important to improve the safety, efficiency, and stability of the electrical power system for successful operation. The voltage variation of the high and the low voltage bus shall be within the primitive limitation range at normal operation loads both in steady state and in the transient state. The power system was simulated and compared with class rule for design verification.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1463-1466
• /
• 2002

In this paper, the thermal analysis and dielectric/insulation properties were investigated with considering the temperature depenence Using the sheet of semi-conductor/XLPE came from 22 kV power cables, the dielectric/insulation properties and temperature dependence were measured under 1kHz. According to the results we can verify that only semi-conductor sheet changed linearly, and with the unstable results. the dielectric/insulation properties of the semi-conductor/XLPE sheet show the highest value in the range of 40 $^{\circ}C$ and 50 $^{\circ}C$ and are rely on XLPE rather than semi-conductor in terms of the temperature.

• Progress in Superconductivity
• /
• v.5 no.2
• /
• pp.132-135
• /
• 2004

We fabricated YBCO thick films by using a screen printing method with $Y_2$BaCuO$_{5}$(Y211) and BaCO$_3$ powders on Cu-substrate in $N_2$ atmosphere. Cu-sheathed YBCO thick film process is more simple and economic than YBCO coated conductor methods. The heat treatment is performed in the range of 860 - 875 $^{\circ}C$ for 5 min in the tube furnace of $N_2$ atmosphere. The flow rate of $N_2$ gas is fixed 60 $m\ell$/min. Microstructure and phases of thick films were investigated by optical microscope, X-ray diffraction(XRD) and SEM. At heat-treatment temperature, the thick films were partially melted by liquid reaction between CuO of oxidized copper substrate and the powders screen-printed on Cu-sheath. During the heat-treatment procedure, YBCO superconducting grains nucleate.e.

• KEPCO Journal on Electric Power and Energy
• /
• v.1 no.1
• /
• pp.121-125
• /
• 2015

Distribution of rare earth metals (REMs) and rare valuable metals (RVMs) contents in coal ashes (fly ash, bottom ash, and pond ash) and leachate from 11 coal-fired power plants in Korea were investigated. Coal ashes and leachates were found to contain important REMs and RVMs such as Yttrium (Y) and Neodymium (Nd), which was in the range of 23~75 mg/kg. However, it still requires developing effective recovery and separation methods in order to utilize REMs and RVMs in ash and leachate. Recovery of valuable elements (Y and Nd) from various and extensive ash sources (8.21 million tons/year in 2013) can provide the existing power plants with additional profit; therefore, it can significantly improve economics of the power plants.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.10a
• /
• pp.847-849
• /
• 2009

Usually, after the decisions of the performance and range in the commercial vehicle, it is designed the ratings of the electric and mechanical elements for the vehicles. In this paper, the given performance and driving conditions, which are the maximum velocity, mileage, total weight of the normal gasoline scooter, battery type and size, and so on, are analysed for the design of the electric scooter. The maximum rotational speed and needed torque values of the electric motor which is substituted for the gasoline engine are calculated. These values can help to calculate the rating of the electric motor. In the calculation to obtain the torque and speed values, battery discharge and the running resistances are considered. We can decide the electric motor current value from the torque and speed values. The electric motor current values, which are significant parameter to decide the motor type and dimensions and characteristics of the electric motor, are decided by numerical simulation by the above conditions.

• Proceedings of the IEEK Conference
• /
• 2001.06e
• /
• pp.33-36
• /
• 2001

An automatic TCXO frequency-temperature test apparatus was firstly developed by using thermoelectric device may. The developed system swing stably the test temperature range from -40$^{\circ}C$ to +80$^{\circ}C$ for about 1 hour The rising temperature ratio was fairly linear with time in this test temperature range. The temperature could be controlled error in error range of ${\pm}$0.05$^{\circ}C$ in this system. The frequency-Temperature properties of TCXO or the thermoelectric properties of other electric device.