• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.113-118
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• 2007

In this paper, a new method is proposed for robust proportional- integral - derivative (PID) control that is to ensure specified phase margin and iso - damping property using reduction model. This method is based on the second order plus dead time(SOPDT) reduction model of the high order model. Reduction model used to ensure iso-damping property in the feature frequency. Simulation results gives proof of effectiveness of proposed method.

• 충청수학회지
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• 제21권4호
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• pp.483-492
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• 2008

The k-fold pseudo-Newton's method is proposed and its convergence behavior is investigated near a simple zero. The order of convergence is proven to be at least k + 2. The asymptotic error constant is explicitly given in terms of k and the corresponding simple zero. High-precison numerical results are successfully implemented via Mathematica and illustrated for various examples.

• International Journal of Control, Automation, and Systems
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• 제6권2호
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• pp.180-185
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• 2008

A new method for relative error continuous and discrete time model order reduction is proposed. The reduction technique is based on two recently developed methods, namely frequency domain balanced truncation within a frequency bound and inner-outer factorization techniques. The proposed method is of interest for practical model order reduction because in this context it shows to keep the accuracy of the approximation as high as possible without sacrificing the computational efficiency. Numerical results show the accuracy and efficiency enhancement of the method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.287-288
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• 2007

In this paper, we propose a fake-iris detection method. In order to detect the fake-iris, we measure physiological features which are the reflectance ratio of the iris to the sclera at 750 nm and that at 850nm. In order to classify live and fake iris features, we use support vector data description (SVDD). From our experimental results, it is clear that our fake-iris detection method achieves high performance when distinguishing between a live-iris and a fake-iris.

• 한국통신학회논문지
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• 제31권6C호
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• pp.629-636
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• 2006

Array 신호처리에서 복소 지수함수의 합으로 구성된 신호의 파라미터를 추정하는데 고차 통계를 이용할 수 있다. 본 논문에서는 기존의 MPM(matrix pencil method)보다 효과적으로 DOA를 판별하기 위해 MPM에 4차 cumulant와 moment 통계량을 적용하였다. 4차 cumulant 통계량은 선형 배열안테나에 입사하는 신호에 포함된 Gaussian 잡음을 효과적으로 감소시킬 수 있다. Gaussian 잡음이 존재하는 환경에서 기존의 방법과 4차 통계량을 이용한 방법을 시뮬레이션 함으로써 SNR과 DOA 분해능에 대하여 성능을 분석하였다. 결과로써 4차 통계량을 이용한 MPM이 기존의 MPM보다 우수함을 보였으며, 또한 4차 moment보다는 4차 cumulant 적용이 더 우수함을 증명하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.56-59
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• 2007

The screech tone of an underexpanded jet is numerically calculated without any specific modeling for the screech tone itself. A fourth-order optimized compact scheme and fourth-order Runge-Kutta method are used to solve the 2D axisymmetric Euler equation. The Fourier transform of pressure signal at upstream shows the directivity pattern of the screech tone very clearly. Pressure signal is shown to observe the generation of the screech tone. Most importantly, we can simulate the axisymmetric mode change of the screech tone very precisely with the proposed method. It can be concluded that the basic phenomenon of the screech tone including its frequency can be calculated and its mode change can be simulated with inviscid Euler equations.

• 대한수학회논문집
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• 제14권4호
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• pp.815-832
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• 1999

High-order weighted difference schemes with uniform meshes are considered for the convection-diffusion problem depending on Reynolds numbers. For small Reynolds numbers, a weighed cen-tral difference scheme is suggested since there is no boundary layer. For large Reynolds numbers, we propose a modified up wind method with an artificial diffusion in order to overcome nonphysical oscilla-tion of central schemes and obtain good accuracy in the boundary later. Existence and corresponding error estimates of the solution for the difference scheme have been shown. Numerical experiments are provided to back up the analysis.

• 수산해양교육연구
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• 제12권2호
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• pp.142-151
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• 2000

The studies on the electronic control fuel injection system for a DI diesel engine have done for reducing the exhaust emission and improving fuel consumption. The electronic control fuel injection system is classified into a common rail system, a unit injector system and a high pressure injection system. The characteristics of these systems are largely depends on the operating characteristics of its solenoid that have high speed on-off operation. In order to improve these characteristics of fuel injection system, it is necessary to design the optimal shape of solenoid and select the input method of its power source. It was proposed HELENOID, COLENOID, DISOLE, and Multipole Solenoid in the studies of design for the optimal shape of solenoid. The studies on the energizing method, input method for power of solenoid were dealt with the conventional energizing method, the chopping method and the pre-energizing method. In order to find out the high response characteristics of solenoid, it is necessary to test the performance of optimally designed solenoid with a new energizing method. In this paper, the solenoid of multi-pole type with plat armature and its power control unit to control input current by the chopping method designed, and its response tests were performed according to its energizing conditions. As a result, the maximum input current for solenoid was controlled by the period of first stage exciting current and chopping duty ratio of control stage exciting current, and the fastest "on" time was able to get 0.46ms. The conditions of fastest "on" time was 0.3ms for first stage exciting current, 0.16ms for control exciting current and 75% for chopping duty ratio.

• 한국정밀공학회지
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• 제22권9호
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• pp.188-193
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• 2005

To provide the various machining materials with excellent quality and dimensional accuracy, high -speed machining is very useful tool as one of the most effective rapid manufacturing processes. However, high-speed machining is not suitable for microscale thin-walled structures because of the lack of the structure stiffness to resist the cutting force. A new method which is able to make a very thin-walled structure rapidly will be proposed in this paper. This method is composed two processes, high-speed machining and filling process. Strong workholding force comes out of the solidification of filling materials. Low-melting point metal alloys are used in order to minimize the thermal effect during phase change and to hold arbitrary shape thin-walled structures quickly during high-speed machining. To verify the usefulness of this method, we will show some applications, for examples thin -wall cylinders and hemispherical shells, and compare the experimental results to analyze the dimensional accuracy of typical parts of the structures.

• 소성∙가공
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• 제13권1호
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• pp.78-83
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• 2004

High-temperature superconduction materials(Bi2223) possess electrical/electronic and magnetic properties. Because high-temperature superconduction materials is a ceramic powder, that cannot be produced singlehandedly. So Ag sheathed Bi-2223 wire was produced by drawing process using powder-in-tube(PIT) method. This superconductor has many difficulties to produce. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. And by these properties, Bi2223 high-temperature superconductor, which has a single filament drawing process and multi-filament drawing process, has a defect like sausaging and bursting at a center. This study analyzed multi-filament drawing process by FEM, and a defect generated during multi-filament drawing was studied by FEH. Specially, in order to prevent a bursting at a center, this study presented a method that inserts a pure Ag at a center of multi-filament wire