• Analytical Science and Technology
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• v.15 no.2
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• pp.108-114
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• 2002

The new system using a glow discharge atomic emission spectrometer for the direct analysis of solid samples has been developed and characterized. The system was consisted of new glow discharge cell improved previous gas-jet boosted nozzle and radio-frequency power supply. In the case of previous type glow discharge chamber, it had been fitted trace analysis of low alloy steel with low discharge power, because it was to decrease redeposition and increase sample weight loss. But it had a problem that plasma becomes unstale due to increased sample weight loss and redeposition resulting from the high discharge power. Because of being problem of previous glow discharge, it is impossible to analyze using high power. The modified gas-jet boosted glow discharge to solve this problem would improve to be less sample loss rate of modified nozzle than sample loss rate of previous nozzle on the equal discharge condition, and improve to increase stability of plasma. The effect of discharge parameters such as discharge pressure, gas flow rate and power on the sample loss rate, emission intensity has been studied to find optimum discharge conditions. The calibration curves of Fe were obtained with 3 low-alloy samples.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.12
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• pp.1077-1082
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• 2005

In this paper, it is proposed that the method for constituting pressure control system controlled by Direct Drive Valve (DDV). The DDV has a pressure-feedback-loop itself. It can eliminate non-linearity and uncertainty oi hydraulic system such as uncertain discharge coefficient and change of bulk-modulus. However, the internal feedback-loop can not compensate them perfectly. And fixed gain of the DDV's internal feedback-loop is not proper to apply it through wide pressure range. The steady state error and nonlinear characteristic of transient behaviour is observed in the experiment. So another controller is needed for the desirable performance of the system. To compose the controller, the pressure control system controlled by DDV is modeled mathematically and the parameters of the model are identified using signal-compression method. Then sliding mode controller is designed based on mathematical model. Desirable performance of the pressure control system controlled by DDV is obtained.

• Journal of ILASS-Korea
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• v.19 no.1
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• pp.9-14
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• 2014

Performance of DI diesel engine with high-pressure fuel injection equipment is directly related to its emission characteristics and fuel consumption. So, the electro-hydraulic injector for the common-rail injection system should be designed to meet the precise high fuel delivery control capability. Currently, most high pressure injector in use has a needle driven by the solenoid coil energy or the piezo actuator controlled by charge-discharge of output pulse current. In this study, macroscopic spray approaching method was applied under constant volume chamber to research the performance of three different injectors : solenoid, indirect-acting piezo and direct-acting piezo type for CR direct-injection. LED back illumination for Mie scattering was applied on the liquid spray visible of direct-acting piezo injector, including hydraulic-servo type solenoid and piezo-driven injectors. As main results, we found that a direct-acting piezo injector had better a spray tip penetration than hydraulic-servo injectors in spray visualization.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.238-243
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• 2014

This paper dealt with the measurement and analysis of partial discharge (PD) under high voltage direct current (HVDC) in SF6 gas. Electrode systems such as a protrusion on conductor (POC), a protrusion on enclosure (POE), a crack on epoxy plate and a free particle (FP) were fabricated to simulate the insulation defects. The analysis system was designed with a Time-Frequency (T-F) map algorithm programed based on LabVIEW. This can arrange the acquired PD pulses into frequency and time domain. A HVDC power source is composed of a transformer (220 V/50 kV), a diode (100 kV) and a capacitor (50 kV, 0.5 ${\mu}F$). The gap between the electrodes is 3 mm, and the $SF_6$ gas was set at 5 bar. PD pulses were detected by a 50 ${\Omega}$ non-inductive resistor. In the analysis, PD pulses were distributed below 0.5 MHz and 20 ns ~ 35 ns for the POC, 0.7 MHz ~ 1.7 MHz, below 0.6 MHz and 10 ns ~ 40 ns and 60 ns ~125 ns for the POE, below 0.1 MHz and 135 ns ~ 215 ns for the crack, and below 1.6 MHz and 250 ns for the FP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.726-728
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• 2013

Optoelectronic arc discharge sensor was used to detect arc discharge inside power distribution panel. Arc discharge is fatal to power system once it begins, thus preventive detection is necessary before power failure occurs. Optoelectronic detection method was used to avoid direct electrical contact to power apparatus inside power distribution panel. 180 degree detection angle and detection range far exceeding 6m, which was sufficient for monitoring purpose, was achieved using the photodiode having $7.5mm^2$ of active surface area and flash source with $0.4cal/cm^2$ energy density, which is equivalent to 1.9J with $2.16cm^2$ emitting area. The response speed of arc discharge sensor was measured to be below 1 msec. The above optoelectronic arc discharge sensor was measured to be sensitive enough to detect 0.94 pC charge.

• Analytical Science and Technology
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• v.15 no.6
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• pp.496-501
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• 2002

The electrolyte cathode glow discharge (ELCAD) is a new optical system for direct determination of trace heavy metals in flowing water. ELCAD has been successfully developed for on-line monitoring of heavy metals in flowing water. The application of an atmospheric glow discharge between an electrolyte solution cathode and a platinum rod anode led to the development of stable discharge. The fundamental aspects of new plasma source have been investigated. The fundamental study of ELCAD system has been measured plasma temperature using Einstein-Boltzmann equation after searching Fe atomic emission lines. The spectrum of each elements such as Cu, Pb, Fe, Ni and Cr show only major elemental line and no ionic line possibly due to low temperature plasma source. The detection limits of each elements are also investigated. These informations show that this type of plasma may apply for monitoring of heavy metals in waste water which consists of complex matrix.

• Korean Journal of Metals and Materials
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• v.47 no.8
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• pp.488-493
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• 2009

Direct syntheses of bulk $Ti_3Al$ via electro-discharge-sintering (EDS) of a stoichiometric elemental powder mixture were investigated. A capacitor bank of $450{\mu}F$ was charged with three input energies, 0.5, 1.0, and 1.5 kJ. The charged capacitor bank was then instantaneously discharged through 0.3 g of a Ti-25.0 at.%Al powder mixture for consolidation. Complete phase transformation occurred in less than $200{\mu}sec$ by the discharge and a bulk $Ti_3Al$ compact was obtained. Compared with consolidated samples fabricated by conventional methods such as high vacuum sintering and casting, the electro-discharge-sintered $Ti_3Al$ compact shows a very fine microstructure with a hardness value of 425 Hv. Electro-discharge-sintering under a $N_2$ atmosphere successfully modified the surface Ti oxide of the $Ti_3Al$ compact into Ti nitride, which concurred with the synthesis and consolidation of $Ti_3Al$. Complete conversion yielding a single phase $Ti_3Al$ is primarily dominated by the fast solid state diffusion reaction.

• Fire Science and Engineering
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• v.26 no.6
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• pp.15-23
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• 2012

Indirect Test Method is often used instead of direct test method in test method for extinguishing performance of $CO_2$ extinguishing facility because of high cost, environment problems and difficulties of procedure. But in the danger facilities for a unit of nation, such as a petrochemical plant, a nuclear power plant, or etc. is better to verify the performance of the extinguishment through direct discharge test. In $CO_2$ extinguishing system for total flooding system installed in dangerous facilities in Korea, each protected area in surface fire and deep-seated fire had selected and verified of extinguishing performance of $CO_2$ extinguishing facilities. To get recognized as extinguishing performance, discharged $CO_2$ concentration to protected area should be equivalence with design concentration standards (NFSC and NFPA). The Design Concentration means that $CO_2$ extinguishing agent is considerate of concentration for percentage of allowance (20 %) from extinguishing concentration which available to control of flame. As test result, surface fire and deep seated fire in protected area is obtained $CO_2$ design concentration and maintained design concentration more than 20 minutes as deep-seated fire. Through this study, we introduced direct discharging test method and decision method. And furthermore, especially in the dangerous facilities as a unit of Nation, we suggested necessity about reliability of extinguishing facilities to use direct test method.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.984-993
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• 2009

There have been growing concerns of algal growth at Daecheong reservoir due to eutrophication with excess nutrient inflow. Rainfall-driven runoff and pollutant from watershed are responsible for eutrophication of the Daecheong reservoir. In this study, two subwatersheds of the Daecheong reservoir were selected and water quality characteristics were analyzed. The L-THIA ArcView GIS model was used for evaluation of direct runoff and water quality. The $R^2$ and the EI value for direct runoff were 0.95 and 0.93 at Wol-oe watershed and were 0.81, 0.71 at An-nae watershed, respectively. The $R^2$ for SS, T-P were 0.53, 0.95 at Wol-oe watershed and 0.89, 0.89 at An-nae watershed, respectively. It has been proven that the L-THIA ArcView GIS model could be used for evaluating direct runoff and pollutant load from the watershed with reasonable accuracies.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.3
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• pp.242-253
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• 2020

This study examined the ef ects of freshwater discharge by artificial dikes from the Kanwol and Bunam lakes on the dynamics in the Chunsu Bay, Yellow Sea, Korea, during the summer season based on three-dimensional numerical modeling experiments. Model performances were evaluated in terms of skill scores for tidal elevation, velocity, temperature, and salinity and these scores mostly exceeded 90 %. The variability in residual currents before and after the freshwater discharge was examined. The large amount of lake water discharge through artificial dikes may result in a dramatically changed density field in the Chunsu Bay, leading to an estuarine circulation system. The density-driven current formed as a result of the freshwater inflow through the artificial dikes (Kanwol/Bunam) caused a partial change in the tidal circulation and a change in the scale and location of paired residual eddies. The stratification formed by strengthened static stability following the freshwater discharge led to a dramatic increase in the Richardson number and lasted for a few weeks. The strong stratification suppressed the vertical flux and inhibited surface aerated water mixing with bottom water. This phenomenon would have direct and indirect impacts on the marine environment such as hypoxia/anoxia formation at the bottom.