• Proceedings of the KSME Conference
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• 2000.04b
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• pp.721-727
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• 2000

Impedance method was carried out to design the electrode that can measure the void fraction of the bubbly flow in pool reservoir. To find out the optimum electrode shape, Styrofoam-tests were performed in a specially designed acrylic reservoir. Three kinds of electrodes were designed to compare the characteristics of water-air flow. The resistance was increased as the void fraction increased and the capacitance was decreased as the void fraction increased. The resistance is a main parameter to express the nature of the water-air flow in impedance method. Almost all the values of impedance were involved in resistance. The degree of deviation from the mean-resistance values showed reasonable results. Electrode type-I expressed excellent results among the three electrode shapes. The impedance values in void fraction 0-10% were similar to those of Maxwell's equation. But the impedance values in void fraction 10-20% were not similar to those of Maxwell' equation because of the edge effect near electrode.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.754-757
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• 1995

This system can detect a ground fault point or a bad insulated line by measuring a power plant DC feeder insulation resistance at the uninterruptible power status. And when the power plant DC feeder with low frequency AC signal has a ground fault, this measuring system can keep recording of its ground fault current and phase checked by Z.C.T. Therefore the power plant could protect a unexpected service interruption.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.589-592
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• 2002

The $Sr_{0.7}Bi_{2.3}Ta_2O_9$(SBT) thin films are deposited on Pt-coated electrode(Pt/TiO2/SiO2/Si) using RF magnetron sputtering method. The structural and electric properties of SBT capacitors were influenced with annealing atmosphere. In the XRD pattern, the SBT thin films in all annealing atmosphere had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized in all annealing atmosphere and grains largely grew in oxygen annealing atmosphere. The maximum remanent polarization and the coercive electric field in oxygen annealing atmosphere are $12.40{\mu}C/cm^2$ and 48kV/cm respectively. The dielectric constant and leakage current density annealing in oxygen atmosphere are 340 and $6.81{\times}10^{-10}A/cm^2$ respectively. The fatigue characteristics of SBT capacitors did not change up to $10^{10}$ switching cycles.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.387-390
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• 1998

In this paper, HBT's with lower phase noise and passive elements, such as resistors, capacitors and inductors, for resonance and impedance matching networks are designed, fabricated, tested, and carefully analysed, respectively, and then, they are integrated for the design and fabrication of functional X-band oscillators with lower phase noise. Epi-wafers for HBT's with the structure of graded $Al_{x}$G $a_{1-x}$ As emitter and C-doped base layer of 700.angs. thick were used to specially emphasize the improvement of $f_{T}$ and $f_{max}$, and the lowering of phase noise, in design aspects. At the test frequencies of 12GHz, capacitances of MIM capacitors, spiral inductor, and resistances are 0.5~10pF, 0.4~11.06nH, and 20~1,380.ohm., respectively. The emitter size of HBY's for the X-band MMIC oscillators is 3*10u $m^{2}$, and find chip size is 0.9*0.9m $m^{2}$..EX>.

• Korean Journal of Microbiology
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• v.31 no.2
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• pp.166-174
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• 1993

Streptomyces coeUc%r (Muller) cells were treated with $100 \mu$M hydrogen peroxide for I hour and proteins synthesized during hydrogen peroxide stress were labeled with L-[$^{35}S$]-methionine. Total cellular proteins were extracted and analyzed by two-dimensional polyacrylamide gel electrophoresis. In exponential growth phase, synthesis of about 100 proteins was increased by hydrogen peroxide treatment. These proteins were named as Pin (£eroxide-inducib]e) proteins and classified into 4 subgroups according to their induction time after hydrogen peroxide treatment. About 60 of them were found to be induced within 20 minutes and maintained throughout I hour of treatment. In stationary growth phase. synthesis of 62 proteins was increased by hydrogen peroxide and 21 of them were the same Pins found in exponential growth phase. Proteins from the mutants which are resistant to hydrogen peroxide were obtained in exponential growth phase and compared with those from the wild type on two-dimensional gel. The three mutants, N7, N9. and N24, were found to have higher constitutive leve]s of ]5, 17, and 15 Pin proteins respectively, than the wild type. 9 of these Pin proteins (D74.7a, E76.0c, E23.3. F50.7, F47.2a. F25.5, G39.6b, G24.0, H39.6a) increased in two of the three mutants and 3 proteins (F39.7, H6I.7. 120.8) increased in all of the three mutants. These proteins might play important roles in the response of S. coelic%r to hydrogen peroxide.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.587-592
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• 2003

The thin films of 316L stainless steel were made on glass and S45C substrate by Ion beam assisted deposition with reactive atmosphere of argon and nitrogen. The films were deposited at the various conditions of ion beam power and the ratios of Ar/$N_2$gas. Properties of these films were analyzed by glancing x-ray diffraction method(GXRD), AES, potentiodynamic test, and salt spray test. The results of GXRD showed that austenite phase could be appeared by $N_2$ion beam treatment and the amount of austenite phase increased with the amount of nitrogen gas. The films without plasma ion source treatment had the weak diffraction peak of ferrite phase. But under the Ar plasma ion beam treatment, the strong diffraction peaks of ferrite phase were appeared and the grain size was increased from 12 to 16 nm. Potentiodynamic polarization test and salt spray test indicated that the corrosion properties of the STS 316L films with nitrogen ion source treatment were better than bulk STS 316L steel and STS 316L films with Ar ion source treatment.

• Bulletin of the Korean Chemical Society
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• v.25 no.4
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• pp.545-548
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• 2004

A sensitive, selective and rapid method for the determination of nickel based on the rapid reaction of nickel(II) with QADMAA and the solid phase extraction of the Ni(II)-QADMAA chelate with $C_{18}$ membrane disks has been developed. In the presence of pH 6.0 buffer solution and sodium dodecyl sulfonate (SDS) medium, QADMAA reacts with nickel to form a violet complex of a molar ratio of 1 : 2 (nickel to QADMAA). This chelate was enriched by solid phase extraction with $C_{18}$ membrane disks. An enrichment factor of 50 was obtained by elution of the chelates form the disks with the minimal amount of isopentyl alcohol. The molar absorptivity of the chelate was $1.32{\times}10^5L\;mol^{-1}cm^{- 1}$ at 590 nm in the measured solution. Beer's law was obeyed in the range of 0.01-0.6 ${\mu}$g/mL. This method was applied to the determination of nickel in water and biological samples with good results.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.9-17
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• 2001

The effect of air entrainment in twin-fluid spray structure is investigated experimentally by varing the amount of itemizing air. The air entrainment is expected to affect on droplet size and velocity, droplet number density, turbulent kinetic energy and vorticity. PDA(Phase Doppler Anemometer) and PIV(Particle Image Velocimetry) system are used to measure those important factors in analyzing spray structure. The results show that spray structure consists of three distinctive regions ; the atomizing region near nozzle, characterizing strong convective effect, the central core region where droplets are accelerated, and the spray sheath region where droplets are decelerated due to air entrainment. The local air entrainment rate is largest near nozzle, characterizing strong turbulent kinetic energy and vorticity but deceases along axial distance.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1654-1656
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• 1997

Tracking currents related to field exposure for ADSS in T/L is of importance. At phase-ta-phase voltage in excess of 100 kV self-supporting aerial cables with solid insulation tend to suffer damage in regions close to the tower. The damage can be put down to surface tracking currents resulting from different degrees of surface contamination and moisture. Main characteristic of this exposure is the induced voltage analysis and position of ADSS. For complicated calculation of induced voltage on ADSS, this paper described an effective numerical calculation method based on CSM. The proposed methods are applied to 275 kV T/L of Malaysia.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1458-1463
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• 2004

By using unique experimental techniques and careful construction of the experimental apparatus, the characteristics of the local heat transfer were investigated using the condensing R134a two-phase flow, in horizontal single mini-channels. The circular channels ($D_h=0.493$, 0.691, and 1.067 mm) and rectangular channels ($D_h=0.494$, 0.658, and 0.972 mm) were tested and compared. Tests were performed for a mass flux of 100, 200, 400, and 600 $kg/m^2s$, a heat flux of 5 to 20 $kW/m^2$, and a saturation temperature of $40^{\circ}C$. In this study, effect of heat flux, mass flux, vapor qualities, hydraulic diameter, and channel geometry on flow condensation were investigated and the experimental local condensation heat transfer coefficients are shown. The experimental data of condensation Nusselt number are compared with existing correlations.