• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.825-834
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• 2008

Nose chine shape optimization study has been performed to maximize the directional stability at high angle of attack supersonic flow. Various chine shapes are generated using super ellipse equation. By numerically investigating the directional stability characteristics of those shapes, the baseline configuration for the shape optimization has been selected using the three-dimensional Navier-Stokes equations. The configuration is represented by the NURBS curves which can adjust the surface geometry by the control points. The response surfaces are constructed to obtain optimum shape which has high directional stability characteristics and lift-to-drag ratio. From this study, an efficient configuration design and optimization process which utilizes the parameter-based configuration generation techniques and approximation method has been established, then 29% improvement of the directional stability by strong vortexes from chine nose is accomplished.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.5
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• pp.360-368
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• 2008

A lumped parameter model of Li-ion battery in hybrid electric vehicle(HEV) is constructed and system parameters are identified by using recursive least square estimation for different C-rates, SOCs and temperatures. The system characteristics of pole and zero in the frequency domain are analyzed with the parameters obtained from different conditions. The parameterized model of a Li-ion battery indicates highly dependent of temperatures. To estimate SOC and polarization voltage, a Luenberger state observer is utilized. The P- or PI-gains of observer based on a suitable natural frequency and damping ratio is adopted for the state estimation. Satisfactory estimation accuracy of output voltage and SOC is especially obtained by a PI-gain. The feasibility of the proposed estimation method is verified through experiment under the conditions of different C-rates, SOCs and temperatures.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.90-96
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• 2014

This paper presents a practical linearization technique for a wide-band bang-bang digital phase locked-loop(BBDPLL) by selecting optimal loop gains. In this paper, limitation of the theoretical design method for BBDPLL is explained, and introduced how to implement practical BBDPLLs with CMOS process. In the proposed BBDPLL, the limited cycle noise is removed by reducing the proportional gain while increasing the integer array and dither gain. Comparing to the conventional BBDPLL, the proposed one shows a small area, low power, linear characteristic. Moreover, the proposed design technique can control a loop bandwidth of the BBDPLL. Performance of the proposed BBDPLL is verified using CppSim simulator.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.2
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• pp.102-110
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• 1999

The aim of this paper is to suggest a design method of the optimal model following control system using gerelic algoritlun (GA). This control system is designed by applying GA with reference model to the optimal determinination of weighting matrices Q, R that are given by LQ regulator prooblem. The method to do this is that all the diagooal elements of weighting matrices are optimized simultaneously by GA, in the search domain selected adequately. And, we design the mxiel following control system to boiler-turbine equipment by the proposed mothod. The model following control system designed by this mothod has the better command tracking perfannaoce than that of the control system designed by the trial-and-error method. The effectiveness of this cootrol System is verified by computer simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.738-742
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• 2005

Rapid Prototype has been used to design and Production of part in a variety of fields ; Car, Electronic products, Aviation, Heavy industry etc. Moreover development of hardware gave rise to use the method of Rapid Prototype more and more at high precision and complicated shapes. Expecially, to be using process of products that shapes of Micro-hole ; Cellular phones, Antennas, Jewels, Semi conductor cases. In case of Micro-shape, precision of the shape turns on various condition ; Laser size, Laminate height, scanning speed, overcure, viscosity of resin, etc. Sometimes breaks out the case that interner hole of shape is blocked by viscosity of resin. The phenomenon has solved easily to reduce viscosity of resin. But, in case of the method brings about the problem that strength goes down in actuality products hardening. This study on verify to change of shape of Micro-hole and makes the semiconductor case which has shape of Micro-hole by using resin of higher viscosity, scanning speed and overcure

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.1
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• pp.52-59
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• 2011

가계가공은 절삭 부위의 냉각작용과 윤활작용을 위해 절삭유를 많이 소모한다. 절삭유는 염소계의 극압첨가제 등이 함유되어 있어 작업자들에게 유독할 뿐만 아니라 대기의 오염을 초래하여 청정생산을 저해하게 되므로 이런 전통적인 방법은 작업자의 직업병으로부터 보호와 환경보호를 위하여 새로운 가공방법으로 변경되어야만 한다. MQL 기계가공 방법은 절삭유를 아주 소량 소모하므로 청정생산을 위한 대안으로 떠오르고 있지만 많은 작업자들이 이에 대한 기술적인 확신이 부족하여 이 방식의 사용을 주저하고 있다. 본 연구는 MQL 가공 방식에서 가공의 특성을 파악하여 표면거칠기에 영향을 미치는 인자와 범위를 찾고자 다양한 실험을 계획하고 그 결과를 분석하였다. 실험의 계획에서는 각 가공의 특성을 잘 나타낼 수 있는 인자와 수준을 선정하고, 다양한 상황의 결과를 분석하여 MQL 가공의 특성과 최적의 가공조건을 도출하였다. 본 연구의 실험 및 분석의 결과로서, 절삭 파라미터와 그의 수준이 가공특성을 잘 반영할 수 있도록 적절히 선택된다면 MQL 기계가공은 표면거칠기 향상 및 원가절감이나 환경보호 측면에서 절삭유 윤활방식을 대체하는 green manufacturing을 위한 대안이 될 수 있음을 보였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.73-81
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• 2007

To improve the capability of instantaneous torque control, a design method of an MRAC-based adaptive current controller for a PMSM servo motor is proposed. In the synchronous frame current controller, a new control inputs can be obtained through the decoupling compensation. Using this, a desired controller bandwidth can be assigned However, the control performance may be degraded due to disturbances caused by the parameter variations or dead time of the switch. To improve these drawbacks, an adaptive current controller is proposed and the design method is obtained using the hyperstability theory. The asymptotic stability is proved and the effectiveness is verified through simulations and experiments using DSP TMS320C31.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.285-286
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• 2016

We aim to propose the prediction modeling method of ship's position with extracting ship's trajectory model through pattern recognition based on the data that are being collected in VTS centers at real time. Support Vector Machine algorithm was used for data modeling. The optimal parameters are calculated with k-fold cross validation and grid search. We expect that the proposed modeling method could support VTS operators' decision making in case of complex encountering traffic situations.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.65-72
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• 2001

Power system stabilizer act efficiently to damp the electromechanical oscillations in interconnected power systems. This paper presents an algorithm for the optimal parameter selection of a power system stabilizer in two-area power systems with a series HVDC link. This method is one of the classical techniques by allocating properly pole-zero positions to fit as closely as desired the ideal phase lead between the voltage reference and the generator electrical power and by changing the gain to produce a necessary damping torque over the matched frequency range. Control of HVDC converter and inverter are used a constant current loop. Proper parameters of PI controllers are obtain based on the Root-locus technique in other to have sufficient speed and stability margin to cope with charging reference values and disturbance. The small signal stability arid transient stability studies using the PSS parameters obtained from this method show that a natural oscillation frequency of the studycase system is adequately damped. Also the simulation results using the HVDC converter and inverter parameters obtained from this proposed method show proper current control characteristics. The simulation used in the paper was performed by the Power System Toolbox software program based on MATLAB.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.289-295
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• 2003

In this paper, the option valuation of venture business was calculated by utilizing growth option model, chosen from real option valuation method. The evaluation of venture business was estimated by adding option value to the terminal value discounted from cashflow method. As the result of the empirical analysis, ROV model applied in the Study is more reliable Han the DCF model concerning the pricing of venture business. Unlike the previous study of Schartz & Moon which only analyzed one venture business, this study estimated and analyzed the rational pricing of venture business with comparative methods using various parameters of sampling 99 domestic venture businesses.