• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.77-82
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• 2017

This paper related with the VSS_SE-MMA (Varying Step Size_Signed Error-MMA) which possible to improving the equalization performance that employing the varying adaptive step size based on the nonlinearities of error signal of SE-MMA (Signed Error-MMA), compensates the intersymbol interference by distortion occurs at the communication channel, in the transmitting the spectral efficient nonconstant modulus signal such as 16-QAM. The SE-MMA appeared to the reducing the computational arithematic operation using the polarity of error signal in the updating the tap coefficient of present MMA adaptive equalizer, but have a problem of equalization performance degradation. The VSS_SE-MMA improves the problem of such SE-MMA, using the varying step size consider the error signal in the update the adaptive equalizer tap coefficient, and its improved performance were confirmed by simulation. For this, the output signal constellation of equalizer, the residual isi and maximum distortion, MSE and SER were applied. As a result of computer simulation, it was confirmed that the VSS_SE-MMA algorithm has nearly same in convergence speed and has more good performance in every performance index at the steady state.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.10 no.4
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• pp.15-24
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• 2014

This study conducted a computational fluid dynamics(CFD) analysis to find an appropriate diameter or sectional area of air ducts and fluid pipes which have an electromagnetic pulse(EMP) shied to protect indoor electronic devices in special buildings like military fortifications. The result shows that the optimized outdoor air intake size can be defined with either the ratio of the maximum air velocity in the supply duct to the air intake size, or the shape ratio of indoor supply diffuser to the outdoor air intake. In the case of water channel, the fluid velocity at EMP shield with the identical size of the pipe, decreases by 25% in average due to the resistance of the shield. The enlargement of diameter at the shield, 2 step, improves the fluid flow. It illustrated that the diameter of downstream pipe size is 1step larger than the upstream for providing the design flow rate. The shield increases friction and resistance, in the case of oil pipe, so the average flow velocity at the middle of the shield increase by 50% in average. In consideration of the fluid viscosity, the oil pipe should be enlarged 4 or 5 step from the typical design configuration. Therefore, the fluid channel size for air, water, and oil, should be reconsidered by the engineering approach when EMP shield is placed in the middle of channel.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.229-232
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• 2008

The Central East Sea Tsunami caused huge damage to the eastern coast of the Korean Peninsula, eapecially Imwon port was damaged relatively strongly beacause of water depth variation which makes the wave concentration on this port. there are many virtual tsunami in east sea which has a possibility of happening. So, it is very important to expect the region which may be damaged by vritual tsunmis. In this study, modified dispersion-correction terms are used. The modified scheme has the advantage of using the constant spatial grid size and time step size even in real topography. Dynamic linking technique and staggered grid system are used. Using this model some cases of virtual tsunami was simulated and check the region which is occured maximum wave heights on the eastern sea of the Korean peninsula.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.869-878
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• 2001

Alumina $(Al_2O_3)$ green bodies were fabricated by gel-casting using three kinds of alumina with different particle size (mean particle size: 4.6 $\mu\textrm{m}$, 0.32 $\mu\textrm{m}$, 10nm). The effects of particle size on gel-casting process and green microstructure were investigated. The optimum dispersion conditions using ammonium salt (D-3019) as dispersant were 0.2 wt% (4.63 $\mu\textrm{m}$), 0.5 wt% (0.32 $\mu\textrm{m}$), and 5.0 wt% (10 nm), in high solid loading. The optimum solid loading of each starting material for gel-casting was obtained as 59 vol% (4.63 $\mu\textrm{m}$), 57 vol% (0.32 $\mu\textrm{m}$), 15 vol% (10 nm), depending on particle size, indicating that nano-size particle (10 nm) represent lower solid loading as high specific surface area than those of other two starting materials. The drying at ambient conditions (humidity; $\thickapprox$90%) was performed more than 48hrs to enable ejection of the part from the mold and then at $120^{\circ}C$ for 2hrs in an air oven, showing no crack and flaw in the dried green bodies. The pore size and distribution of the gelcast green bodies showed the significant decrease with decreasing particle size. Green microstructure was dependent on the pore size and distribution due to the particle size, and on the deairing step. The green density maximum obtained was 58.9% (4.63 $\mu\textrm{m}$), 60% (0.32 $\mu\textrm{m}$), 47% (10 nm) theoretical density (TD), and the deairing step applied before gel-casting did not affect green density.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.97-102
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• 2020

This paper relates with the Hybrid-SE-MMA (Signed-Error MMA) that is possible to improving the equalization performance by using the adaptive modulus and adaptive step size in SE-MMA adaptive equalizer for the minimizing the intersymbol interference. The equalizer tap coefficient is updatted use the error signal in MMA algorithm for adaptive equalizer. But the sign of error signal is used for the simplification of arithmetic operation in SE-MMA algorithm in order to updating the coefficient. By this simplification, we get the fast convergence speed and the reduce the algorithm processing speed, but not in the equalization performance. In this paper, it is possible to improve the equalization performance by computer simulation applying the adaptive modulus to the SE-MMA which is proposional to the power of equalizer output signal. In order to compare the improved equalization performance compared to the present SE-MMA, the recovered signal constellation that is the output of the equalizer, residual isi, MD(maximum distortion), MSE and the SER perfomance that means the robustness to the external noise were used. As a result of computer simulation, the Hybrid-SE-MMA improve equalization performance in the residual isi and MD, MSE, SER than the SE-MMA.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.75-78
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• 1989

In this paper, A last time delay damper is presented for HB ( HyBrid ) step motor, which has large oscillation characteristics.The design objective is to develop a cost-effective and good-performance damper that would be applyed to HB step motor / driver system without the addition of transducer that would add a weight, size and cost to the system. The Back EMF signal which is recovered from current and voltage signal is used for the measuring the rotor position. It would be possible to get more accurate delay time for the motor driver system. It is proved that the maximum overshoot can be reduced to 13% at stopping through experiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.1
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• pp.8-13
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• 2003

In this paper, suitablility of 1 GHz CISPR limits establishment fur broadcast communication quality protection is examined and the optimum turn step resolution of EUT for spurious measurement of frequency above 1 GHz to increase the accuracy of maximum values extraction is examined. As a result of 500 MHz and 1.7 GHz clock speed personal computer of micro-processor measurement, optimum turn step resolution extracted by National Institution of National Instrument of Standard & Technology(NIST) Koepke method is estimated 40 table positions per polarization in 500 MHz. And in case of 1.7 GHz, step size is 36 table positions. Prediction of turn step size required for fully scan method in gjgahertz measurement will increase measurement accuracy and reduce considerable measurement time as well.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.20 no.1
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• pp.64-81
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• 1994

O/W emulsions with mixed nonionic surfactants(polyoxyethylene(20)sorbitan monostearate/sorbitan sesquioleate), liquid paraffin, water prepared by direct inversion emulisification method and continuous inversion emulsification Method. The one-step, two-step and three-step phase inversion emulsification method were used in experiments. Effect of added water on droplet size of final O/W emulsions which is prepared by phase inversion emulsification method were investigated. In direct inversion emulsification method(two-step emulsification method), fine and homogeneous droplets of OIW emulsions were formed after phase inversion steps i.e. ,W/O - (W/O) If double emulsion - O/W emulsion. In continuous inversion emulsification method(three-step emulsification method), fine and homogeneous O/W emulsion were formed after phase inversion steps i.e., W/O - pseudomicroemulsion - O/W. By latter method, more Fine and homogenuous droplets were formed than former method. 10-10, 8 HLB region of mixed non-ionic surfactants could produce most fine droplets. This HLB region had maximum values of solubilization water and This HLB value of mixed nonionic surfactants produced fine and homogenuous droplets.

• Journal of Microbiology and Biotechnology
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• v.19 no.11
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• pp.1385-1392
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• 2009

This work evaluates the effect of different amino acids on production of Cyclosporin (CyA) production in solid-state fermentation that was previously optimized for different fermentation parameters by one factor at-a-time for the maximum production of CyA by Tolypocladium inflatum MTCC557. Based on the Plackett-Burman design, glycerol, ammonium sulfate, $FeCl_3$, and inoculum size were selected for further optimization by response surface methodology (RSM). After identifying effective nutrients, RSM was used to develop mathematical model equations, study responses, and establish the optimum concentrations of the key nutrients for higher CyA production. It was observed that supplementation of medium containing (% w/w) glycerol, 1.53; ammonium sulfate, 0.95; $FeCl_3$, 0.18; and inoculum size 6.4 ml/5g yielded a maximum of 7,106 mg/kg as compared with 6,480 mg CyA/kg substrate using one factor at-a-time. In the second step, the effect of amino acids on the production of CyA was studied. Addition of $_L$-valine and $_L$-leucine in combination after 20 h of fermentation resulted in maximum production of 8,166 mg/kg.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1214-1220
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• 2010

This paper proposes an efficient under frequency relay load shedding scheme for the korea power system which is more than two times than the system size and its capacity of the power system 10 years ago. The proposed method is keeping the power system stability and supports for the operating system during critical situations such as big disturbances and unstable in supply and demand. In order to determine the number of load shedding steps, the load to be shed per step, and frequency level, it is necessary to investigate and analyze maximum losses of generation due to the biggest contingency, maximum system overload, maximum keeping frequency, maximum load to be shed, and recovery frequency. The proposed method is applied to Off-peak load(25,400MW) and Peak load(62,290MW) of Korea Electric Power Corporation to demonstrate its effectiveness.