• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.65-70
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• 2009

Reduction of groundwater surface tension prior to air sparging (SEAS, surfactant-enhanced air sparging) was known to increase air saturation in the aquifer under influence, possibly enhancing the removal rates of volatile contaminants. Although SEAS was known to be efficient for increasing air saturation, little information is available for different hydrogeological settings including soil particle sizes and the depth of aquifer. We investigated water saturations in the sparging influence zone during SEAS using one-dimensional column packed with sands of different particle sizes and different aquifer depths. An anionic surfactant was used to suppress the surface tension of water. Two different sands were used; the air entry pressures of the sands were measured to be $15.0\;cmH_2O$, and $36.3\;cmH_2O$, respectively. No significant difference was observed in the water saturation-surface tension relationship for sands with different particle sizes. As the surface tension decreased, the water saturation decreased to a lowest point and then it increased with further decrease in the surface tension. Both sands reached their lowest water saturations when the surface tension was set approximately at 42 dyne/cm. SEAS was conducted at three different aquifer depths; 41 cm, 81 cm, and 160 cm. Water saturation-surface tension relationship was consistent regardless of the aquifer depth. The size of sparging influence zone during SEAS, measured using two-dimensional model, was found to be similar to the changes in air saturation, measured using one-dimensional model. Considering diverse hydrogeological settings where SEAS to be applied, the results here may provide useful information for designing SEAS process.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.449-453
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• 2007

Has been being operated since 1974, recently, the flood forecasting and warning system is applied in almost all the rivers in Korea, and the Storage Function Method(SFM) is used for flood routing. The SFM which was presented by Toshimitsu Kimura(1961) routes floods in channels and basins with the storage function as the basic equation. A watershed is devided into two zone, runoff and percolation area and Runoff is occured when cumulated rainfall is not exceed saturation rainfall, but exceed, runoff is occured from percolation area, too. Runoff area is given and not changed, runoff ratio is constant. In routing process, runoff from runoff and percolation area is routed seperately with nonlinear cenceptual reservior having same characteristics and it is unreasonable assumption. Modified SFM is proposed with storage function and continuity Equation which has no assumption for routing process and effective rainfall is calculated by SCS Method. For Wi Stream, comparision of Kimura and Modified SFM is conducted and It could be seen that Modified SFM is more improvemental and easily applicable method.

• Journal of Korea Water Resources Association
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• v.40 no.7
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• pp.523-532
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• 2007

It has been operated since 1974, recently, the flood forecasting and warning system is applied in almost all the rivers in Korea, and the Storage Function Method (SFM) is used for flood routing. The SFM which was presented by Toshimitsu Kimura (1961) routes floods in channels and basins with the storage function as the basic equation. A watershed is divided into two zone, runoff and percolation area and runoff from runoff area is occurred when cumulated rainfall is not exceed saturation point, but exceed runoff is occurred from percolation area, too. Runoff area is given and not changed, runoff ratio is constant. In routing Process, runoff from runoff and percolation area is routed seperately with nonlinear conceptual reservoir having the same characteristics and it is unreasonable assumption. A modified SFM is proposed with storage function and continuity equation which has no assumption for routing process and effective rainfall is calculated by SCS Method. For Wi-stream, comparison of Kimura and the modified SFM is conducted, and it could be seen that the modified SFM is more improvable and applicable method easily by reducing the parameters.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.23-30
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• 2000

To compensate the nonlinearity of electroabsorption modulator(EAM) resulting from its near exponential transfer function, a semiconductor optical amplifier(SOA) that has a log transfer function is used. Since the transfer function of SOA is inverse to that of EAM, the intermodulation distortion(IMD) of EAM can be reduced by cascading SOA to EAM. Also, the RF gain can be increased by the optical gain of SOA. For these reasons, spurious free dynamic range(SFDR) of EAM is enhanced by connecting SOA to EAM in series and operating in gain salutation region. To improve the nonlinearity compensation of EAM, the increased gain of SOA is required and the slope of gain saturation, the ratio of gain to input SOA power, needs to be steep. However, signal spontaneous beat noise that is the dominant system noise increases in proportion to the gain such that the SFDR of EAM is reduced. The higher the gain of SOA is, the more ASE is increased. Thus the noise level of system is increased and the following SFDR of EAM is decreased. The slope of gain saturation region and ASE of have trade-off relation and the optimization is achieved at 8㏈ optical gain. 9㏈ enhancement of SFDR of EAM is obtained. This scheme is easy to embody the linear EAM and the integration with three components (DFB-LD, EAM and SOA) offers many merits, such as low insertion loss, low chirping and low polarization sensitivity.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.165-173
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• 2015

People with color vision deficiency (CVD) experience difficulties in discriminating some color combinations and color differences due to the abnormal retinal cone systems. While there exist smartphones with a re-coloring function for CVD, monitors do not provide the re-coloring function. In this paper, we propose a new re-coloring algorithm that adjusts the displayed colors for CVD using a color controller embedded in the monitor. The proposed algorithm converts the hue and saturation in HSV color space, according to the type and strength of the color deficiency. The results of the performance evaluation with a certain number of people with CVD show that the proposed system can convert colors imperceptible into perceptible.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1425-1435
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• 2013

The useful method for determining parameters of weighting functions used to design the $H_{\infty}$ current controller for attenuating the current ripple due to saliencies which SPMSM(Surface Permanent Magnet Synchronous Motor) also incorporates is described. To analyze the effect, the current ripple due to the structural and the saturation saliencies, the SPMSM model with nonlinear inductance function depending on the two independent variables, rotor position and stator current is simulated. After analysis, parameters of the weighting functions for $H_{\infty}$ current controller is selected to satisfy the robust stability, robust performance and specific performance in time and frequency domain by using the PSO(Particle Swarm Optimization) algorithm in the linear SPMSM model. Especially, the robust performance is proved that the selected weighting functions play a role in reducing the current ripple caused by the saliencies of SPMSM at the desired frequency range by the simple experiment.

• Journal of Electrical Engineering and Technology
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• v.2 no.4
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• pp.478-484
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• 2007

This paper deals with the high efficient vector control for the reduction of copper losses of the doubly fed motor. Firstly, the feedback linearization control based on Lyapunov approach is employed to design the underlying controller achieving the double fluxes orientation. The fluxes# controllers are designed independently of the speed. The speed controller is designed using the Lyapunov method especially employed to the unknown load torques. The global asymptotic stability of the overall system is theoretically proven. Secondly, a new Torque Copper Losses Factor is proposed to deal with the problem of the machine copper losses. Its main function is to optimize the torque in keeping the machine saturation at an acceptable level. This leads to a reduction in machine currents and therefore their accompanied copper losses guaranteeing improved machine efficiency. The simulation and experimental results in comparative presentation confirm largely the effectiveness of the proposed DFIM control with a very interesting energy saving contribution.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.383-394
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• 2007

Due to the clutch's non-linear dynamics, time-delays, external disturbance and parameter uncertainty, the automated clutch is difficult to control precisely during the launch process or automatic mechanical transmission (AMT) vehicles. In this paper, an enhanced fuzzy sliding mode controller (EFSMC) is proposed to control the automated clutch. The sliding and global stability conditions are formulated and analyzed in terms of the Lyapunov full quadratic form. The chattering phenomenon is handled by using a saturation function to replace the pure sign function and fuzzy logic adaptation system in the control law. To meet the real-time requirement of the automated clutch, the region-wise linear technology s adopted to reduce the fuzzy rules of the EFSMC. The simulation results have shown hat the proposed controller can achieve a higher performance with minimum reaching time and smooth control actions. In addition, our data also show that the controller is effective and robust to the parametric variation and external disturbance.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.130-134
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• 2007

DCF(Distributed Coordination Function) of IEEE 802.11 WLAN(Wireless Local Area Network) MAC Layer apply to CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) for solution of collision when the station try to access at the same time. But DCF happens falling performance as increasing a number of stations. In this paper, we suggest algorithm that improved performance in congestion. And we compare DCF, DCF+ and proposed algorithm respect to saturation throughput, delay, collision rate and drop rate using NS2(Network Simulator 2) simulation tool.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.2
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• pp.305-313
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• 2002

The genetic algorithm(GA), an optimization technique based on the theory of natural selection, has proven to be relatively robust means to search for global optimum. It is converged near to the global optimum point without auxiliary information such as differentiation of function. When studying some optimization problems with continuous variables, it was found that premature saturation was reached that is no further improvement in the object function could be found over a set of iterations. Also, the general GA oscillates in the region of the new global optimum point so that the speed of convergence is decreased. This paper is to propose the concept of restarting and elitist preserving strategy as a measure to overcome this difficulty. Some benchmark examples are studied involving 3-bar truss and cantilever beam with plane stress elements. The modifications to GA improve the speed of convergence.