• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.119-125
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• 2005

A method of predicting the tritium concentration in the air leaving an atmospheric detritiation dryer was modeled for designing a fixed bed dryer and preparing an advanced dryer control. In order to quantify the bed utilization and the dynamic capacity against an inlet humidity and a flow rate, a series of quantitative tests based on the break-through behavior were carried out in an isothermal fixed bed of synthetic zeolites such type as molecular sieve 4A, 5A, 13X and mordenite. The amount of water vapor breaking during the adsorption was estimated to give a breakthrough capacity at the various inlet flow rates and humidity conditions. The molecular sieve 13X exhibited a better adsorption performance at a given bed height.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.661-663
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• 1996

The thyristor controlled series compensator can vary the impedance continuously to levels below and up to the line's natural impedance, thus enabling transmission line capability to be increased and power flow to be controlled. The dynamic performance of TCSC to increase the power system damping is mainly analyzed in this paper. The TCSC controller used here is of the PID type and the input signal to the controller is the active power flow through the TCSC. The TCSC parameters are determined so as to minimize the modal performance measure for duping of power system oscillations.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.127-128
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• 2014

The aim of this research is selecting an economical aggregate type for ultra-high strength concrete with 80 to 120 MPa of compressive strength. As the tests, the effect of water-to-binder ratios and types of aggregate on autogenous shrinkage of ultra-high strength concrete were evaluated. as the results of a series of tests performed, the slump flow was satisfied the target range of 600 ± 100 mm, and the concrete mixture with RLA showed higher elastic modulus than the other cases. For the autogenous shrinkage preventing performance, in the case of water-to-binder ratio of 15, and 20 %, the mixture with BA showed slightly improved autogenous shrinkage reducing effect than the mixture with RLA while the mixture with RLA showed better performance at 25 % of water-to-binder ratio. Therefore, based on the tests results of slump flow, elastic modulus, and autogenous shrinkage, the RLA is considered as a better aggregate type for this purpose.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.179-189
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• 2008

The performance of Lean NOx Trap (LNT) based on the catalysts of Pt/K/Ba/$\gamma-Al_2O_3$ with proprietary washcoat formulation is studied using a bench flow reactor system. To investigate the effect of temperature and gas hourly space velocity (GHSV) on the nitrogen oxides (NOx) trapping capacity as well as NOx breakthrough time and final ratio of $NO_2$ to NO of LNT, series of adsorption isotherms are carried out with simulated exhaust gases of the lean burn engines. Since typical operation of LNT requires periodic regeneration with a short rich excursion, where the stored or trapped NOx is released and subsequently reduced to $N_2$, the effect of the duration of lean and rich phase and type of reductants on the NOx conversion is investigated. NOx storage capacity and breakthrough time obtained from adsorption isotherms shows a volcano-type dependence on the temperature with a maximum NOx storage capacity occurring $350^{\circ}C$ and with a maximum breakthrough time occurring $400^{\circ}C$ at all GHSVs investigated in this study. Also, maximum ratio of $NO_2$ to NO is obtained at $400^{\circ}C$ with a GHSV of $75,000\;hr^{-1}$ Lean/rich cycle of 100 s lean and 5 s rich used with a concentration of 1.33% of $H_2$ and 4% of CO in the rich phase is found to be optimum at operating temperature of $350^{\circ}C$ and a GHSV of $50,000\;hr^{-1}$.

• International Journal of Control, Automation, and Systems
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• v.6 no.4
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• pp.495-505
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• 2008

This paper describes modeling Voltage Sourced Inverter (VSI) type Flexible AC Transmission System (FACTS) controllers and control methods for power system dynamic stability studies. The considered FACTS controllers are the Static Compensator (STATCOM), the Static Synchronous Series Compensator (SSSC), and the Unified Power Flow Controller (UPFC). In this paper, these FACTS controllers are derived in the current injection model, and it is applied to the linear and nonlinear analysis algorithm for power system dynamics studies. The parameters of the FACTS controllers are set to damp the inter-area oscillations, and the supplementary damping controllers and its control schemes are proposed to increase damping abilities of the FACTS controllers. For these works, the linear analysis for each FACTS controller with or without damping controller is executed, and the dynamic characteristics of each FACTS controller are analyzed. The results are verified by the nonlinear analysis using the time-domain simulation.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.36-42
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• 2003

A CFD simulation technique has been developed to handle the unsteady body motion with large amplitude by use of overlapping multi-block grid system. The three-dimensional, viscous and incompressible flow around body is investigated by solving the Navier-Stokes equations, and the motion of body is represented by moving effect of the grid system. Composite grid system is employed in order to deal with both the body motion with large amplitude and the condition of numerical wave maker in convenience at the same time. The governing equations, Navier-Stokes (N-S) and continuity equations, are discretized by a finite volume method, in the framework of an O-H type boundary-fitted grid system (inner grid system including test model) and a rectangular grid system (outer grid system including simulation equipments for generation of wave environments). If this study, several flow configurations, such as an oscillating cylinder with large KC number, are studied in order to predict and evaluate the hydrodynamic forces. Furthermore, the motion simulation of a Series 60 model advancing in a uniform flow under the condition of enforced roll motion of angle 20$^{\circ}$ is performed in the developed numerical wave tank.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.3
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• pp.329-335
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• 2008

Volatile organic compounds emitted to the atmosphere can cause adverse effects on human health and participate in photochemical smog formation reactions. The destruction of a series of VOCs has been carried out by non-thermal plasma in other researches. And the characteristic of non-thermal plasma was operated at atmospheric pressure and low temperature. A new type non-thermal plasma reactor was investigated combined Glidarc plasma with water jet in this research. Also, it was found that the water-jet had an significant effect on the toluene removal efficiency. But too much water content does not favor toluene decomposition by decreasing of reaction temperature. The input toluene concentration, gas flow rate, water flow rate and specific energy input were used as experiment variables. The toluene removal efficiency, energy efficiency and specific energy input were 75.3%, 146.6 g/kWh and $1.12kWh/m^3$ at a water flow rate of 100 mL/min.

• 전기의세계
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• v.24 no.1
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• pp.75-85
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• 1975

In order to develop the commercial frequency (60Hz) plasma torch of small capacity for material cutting, welding and other industrial heating, the A.C plasma jet generator of non-transfered type is made domestically and the electrode configurations of plasma torch are composed of two kinds of electrodes W-C and W-Cu, combined by thermal emission and field emission electrode materials. In this paper, the characteristics of input power, thermal efficiency, electrode consumption, the flame and forms of arc voltage and arc current for A.C plasma torch are investigated in relation to such variables as arc current, argon flow and magnetic field intensity to obtain the basic design data necessary to A.C plasma jet generator. The result are as follows; (1)The input power, thermal efficiency and electrode consumption are influenced greatly by argon flow, magnetic field intensity and nozzle materials. (2)A.C arc voltage and current are non-symmetrial, involving D.C Component. Due to this current of D.C Component, transformer core is saturated and a large abnormal current flows into the primary winding coil. In order to prevent this abnormal current flow, a condenser must be connected in series to the main discharge circuit. (3)The stability and sharpness of jet flame are improved more in the torch of W-C electrode configuration than in the torch of W-Cu electrode configuration.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.634-639
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• 2003

It has been studied the flow near a rotating disk with surface topography. The system Ekman number is assumed very small, i.e., $E[{\equiv}\frac{\nu}{{\Omega}^{\ast}L^{\ast2}}]<<1$ in which $L^{\ast}$ denotes a disk radius, ${\nu}$ kinematic viscosity of the fluid and ${\Omega}^{\ast}$ angular velocity of the basic state. Disk surface has a sinusoidal topographic variation along radial coordinate, i.e., $z={\delta}cos(2{\pi}{\omega}r)$, where ${\delta}$ and ${\omega}$ are, respectively, nondimensional amplitude and wave number of the disk surface. Analytic solutions, being useful over the parametric ranges of ${\delta}{\sim}O$( $E^{1/2}$ ) and ${\omega}{\leq}O$ ( $E^{1/2}$ ), are secured in a series-function form of Fourier-Bessel type. An asymptotic behavior, when $E{\rightarrow}0$, is clarified as : for a disk with surface roughness, in contrast to the case of a flat disk, the azimuthal velocity increases in magnitude, together with the thickening boundary layer. The radial velocity, however, decreases in magnitude as the amplitude of surface waviness increases. Consequently, the overall Ekman pumping at the edge of the boundary layer remains unchanged, maintaining the constant value equal to that of the flat disk.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_1
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• pp.559-567
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• 2020

As the renewable energy market grows, grid-connected inverters have been improving and expanding in several fields in recent years because energy conversion devices are the main components of solar systems. In this paper, a high-precision new grid-connected three-phase inverter system is proposed. The proposed system consists of a main inverter, a sub inverter and a transformer. The main inverter operates at a low switching frequency and high power and transmits power to the grid. A sub-inverter connected in series with the transmission line through a matching transformer operates at lower power than the main inverter to provide input values to the transformer. The transformer acts as a power supply according to the voltage compensation value. This study is based on the principle of operation of the UPFC(Unified Power Flow Controller) structure used to regulate power flow in AC transmission lines. The grid-connected inverter system proposed in this paper is implemented with high precision and high resolution. The proposed system was verified through its ability to enhance and ensure the safety of the proposed system through simulation and experiment.