• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.335-337
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• 1993

Offset voltage and drift characteristics of operational amplifier are critical factor to precision AID conversion System. In this study, a method is suggested to design the programmable A/D conversion system which has high resolution and low drift characteristics. First, hardware was designed to reduce the offset voltage of integrator and comparator, and analog switches are connected to reduce the drift characteristics of operational amplifier. And then, a calibration software technique was performed to obtain the stable data from A/D converter. The main advantage of our method is high precision A/D converter can be constructed with low cost and high confidence. Therefore proposed method is expected to be used in the industrial field where a high precision measurement is required.

• Journal of computational fluids engineering
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• v.1 no.1
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• pp.142-149
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• 1996

이차원 노즐을 통하여 저밀도 환경으로 팽창하는 희박류의 분석에 있어서 불연속좌표법과 결합된 유한차분법(finite-difference method coupled with the discrete-ordinate method, FDDO)과 직접모사법(direct-simulation Monte-Carlo method, DSMC)이 비교되었다. FDDO를 이용한 분석에서는 충돌적분모델을 도입하여 간단해진 볼츠만식(Boltzmann equation)이 불연속좌표법을 이용하여 물리적 공간에서는 연속이나 분자속도 공간에서는 불연속좌표로 표시되는 편미분방정식군으로 변환되어 유한차분법에의하여 수치해석 되었다. 직접모사법에서는 분자모델로 가변강구모델(variable hard sphere model, VHS)이, 충돌샘플링모델로는 비시계수법(no time counter method, NTC)이 채택되었다. 전혀 다른 두 가지 방법에 의한 노즐 내부에서의 유체흐름 해석결과는 매우 잘 일치하였으며, 노즐 외부의 plume 영역에서는 FDDO에 의한 해석결과가 직접모사법에 의한 해석결과에 비하여 약간 느린 팽창을 보였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.57-64
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• 2001

For the dynamic nonlinear analysis of stiffened plate and shell structures, total Lagrangian formulation is presented based upon the degenerated shell element considering finite rotation effects. Assumed strain concept is adopted in order to overcome shear locking phenomena and to eliminate spurious zero energy mode. In the elasto-plastic analysis, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to collapse analysis of shell structures. Newmark integration method is used for dynamic nonlinear analysis of shell structures under dynamic forces.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.710-715
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• 2001

Rubber is used extensively in many industries because of its large reversible elastic deformation, excellent damping and energy absorption characteristics, and wide availability. It becomes very important to predict the fatigue life of rubber components. But a great deal of time and cost are necessary for the fatigue test of rubber components. In this study the fatigue life of rubber components is evaluated by performing the fatigue test of a specimen and FE analysis. The fatigue life of Jang-gu type specimen which is considered as a simple rubber component is predicted and compared with experimental results. Its material is natural rubber of which hardness is 60 and used for the engine mount of commercial vehicles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.47-48
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• 2006

A roughness measuring system which comprises an integrating sphere and a stabilized laser has been fabricated with the aim of measuring the roughness correction value which is necessary in gauge block measurement by optical interferometry. To calibrate the system, a Newton's ring interferometer has been introduced. The method how to calibrate the roughness measurement system has been described.

• Communications of Mathematical Education
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• v.18 no.1 s.18
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• pp.239-248
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• 2004

본 논문에서는 맨델브로트(Mandelbrot) 집합의 개념을 3차의 복소 다항식 z^3$+c 에 확장시켜 3차 분기집합을 정의하고, 이 집합의 2-주기 성분의 경계선 방정식과 관련 기하학적 성질을 고등학교 및 대학에서 다루는 미적분학 관점에서 분석하고자 한다. 복소수, 삼각함수, 매개함수, 함수의 극값, 미분 및 적분 등의 기초 이론을 활용하여 2-주기 성분의 경계선 방정식을 매개함수로 표시하고, 경계선의 내부 면적, 둘레 길이, 무게중심 등을 이론적으로 기술한다. 수학 소프트웨어인 매스매티카(Mathematica)를 활용하여 2-주기성분의 작도 및 기하학적 성질에 관한 수치 해석적 결과를 제시하고자 한다.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.84-91
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• 2000

This paper describes a state feedback controller design method of the integral type magnetic levitation servo system which satisfies the design objectives. The design objective is a $H_{\infty}$ performance, asymptotic disturbance rejection and a robust pole assignment in linear matrix inequality(LMI) region. To the end, we investigated the validity of the designed controller which considering a robust pole assignment region, through results of simulation.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.180-182
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• 1993

A distance protection algorithm for detecting faults at power transmission lines is presented in this paper. The algorithm is based on the differential equation related to the voltage and the current at an equivalent circuit of a transmission line which is composed of the lumped resistance and inductance. The presented integration method has high performance at though the fault voltage and the current are heavily distorted with the DC offset and harmonics which occurred at transient states after faults.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.187-188
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• 2018

본 논문에서는 영구자석 동기 전동기의 온도 변화를 인공신경망을 통해 예측 및 추정하는 방법을 제시한다. 고정자와 회전자의 온도와 속도, 토크를 입력으로 하여 다음 샘플링 주기까지의 온도 변화를 출력하는 인공 신경망이 제시되었다. 여러 운전점에서 수집된 온도 데이터를 사용하여 훈련된 신경망은 임의의 온도를 시작 온도로 설정하고 출력인 온도 변화를 적분하여 현재의 온도를 추정한다. 제시된 방식은 시뮬레이션을 통해 검증되었고 훈련에 사용되지 않았던 운전경로에 대해 항상 $2^{\circ}C$ 이하의 추정 오차 성능을 보였다.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.22-29
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• 1993

A remote control system was developed in order to operate by push-buttons the conventional drum and chute components, which have been operated manually, in a concrete mixer-truck. As actuators, a hydraulic power unit was used for chute operations: two DC motors for drum operations. The devised drum controller consisted of three electric circuits : an analog proportional-integral control circuit, a drum acceleration circuit, and an emergency stop circuit. The remote control system was installed to be tested experimentally and then was evaluated to work successfully with a desirable accuracy.