• 대한전기학회논문지:시스템및제어부문D
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• 제49권1호
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• pp.18-25
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• 2000

In the two-mass servo system driving a load through a flexible shaft, a shaft torsional vibration is often generated. PI controller has been generally used is speed control of such system because of the simplicity of structure and related theory. This paper presents the inertia ratio of the PI servo control system which can be designed by using optimal pole assignment method is fixed. Therefore, it's difficult to obtain the desired control characteristics for different systems only by PI control algorithm. To solve this problems the two-mass speed control system with PID controller is designed by using pole assignment method and an optimum PID parameters are derived by evaluating ITAE(Integral of time multiplied by the absolute error) performance index. But this design method has some problems due to a trade-off between the fast command following property and the attenuation of disturbances and vibrations. In this paper, 2-DOF PID control method which satisfies the command following property, the reduction of overshoot and the property of disturbance rejection at the same time is proposed. This is a practical speed controller using the desired value filter and the feedforward gain. From several simulations, it's clarified that the proposed 2-DOF PID controller is useful for the two-mass system, in comparison with the conventional PID controller.

• Journal of Power Electronics
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• 제18권3호
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• pp.723-735
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• 2018

Linear proportional-integral (PI) controllers are an attractive choice for controlling the speed of induction machines because of their simplicity and ease of implementation. Fractional-order PI (FO-PI) controllers, however, perform better than PI controllers because of their nonlinear nature and the underlying iso-damping property of fractional-order operators. In this work, an FO-PI controller based on the proposed first-order plus dead-time induction motor model and integer-order (IO) controllers, such as Ziegler-Nichols PI, Cohen-Coon PI, and a PI controller tuned via trial-and-error method, is designed. Simulation and experimental investigation on an indirect field-oriented induction motor drive system proves that the proposed FO-PI controller has better speed tracking, lesser settling time, better disturbance rejection, and lower speed tracking error compared with linear IO-PI controllers. Our experimental study also validates that the FO-PI controller maximizes the torque per ampere output of the induction machine and can effectively control the motor at low speed, in field-weakening regions, and under detuned conditions.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1996년도 춘계학술발표회 초록집
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• pp.73-87
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• 1996

The outer-most electrons of metal atoms and the remining valence electrons of any molecular atoms make three dimensional crystallizing $\pi$-bondings. The electrons on the $\pi$-bonding orbital rotate clockwise or counter-clockwise and they then make electro-magnetic waves between atoms on the orbital because electron move between plus charged ions. The three dimensional crystallizing $\pi$-bonding orbitals are quantum-mechanically modeled by a cyclic Kronig-Penny Model and energy band structures are analyzed with their potential barrier thickness. The waves generated between plus charged ions are the particular $\pi$-far infrared rays, which have dual properties between material and electro-magnetic waves and can be measured not by modern electro-magnetic tester but biosensor such as finger's force tester. Because the $\pi$-rays can be modulated with electro-magnetic waves it can be applied for harmful electro-magnetic wave killers. Because the $\pi$-rays make new three dimensional crystallizing $\pi$-bonding orbitals in the material the food and drink can be transformed into a helpful physical constitutional property for human health. Distinction between crystalline and amorphous metals is possible because very strong crystalline $\pi$-bonding orbitals can not easily be transformed into another. The $\pi$-rays can also be applied for biofunctional diagnostics and therapy. Gravitational field is one of the electro-magnetic fields. And also magnetic field and gravitational force field make charge's movement. ($\times$ = q, : magnetic field, : force field, q: plus charge, : velocity field)

• 대한수학회보
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• 제50권6호
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• pp.1887-1903
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• 2013

We continue the study of McCoy condition to analyze zero-dividing polynomials for the constant annihilators in the ideals generated by the coefficients. In the process we introduce the concept of ideal-${\pi}$-McCoy rings, extending known results related to McCoy condition. It is shown that the class of ideal-${\pi}$-McCoy rings contains both strongly McCoy rings whose non-regular polynomials are nilpotent and 2-primal rings. We also investigate relations between the ideal-${\pi}$-McCoy property and other standard ring theoretic properties. Moreover we extend the class of ideal-${\pi}$-McCoy rings by examining various sorts of ordinary ring extensions.

• 대한수학회논문집
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• 제22권4호
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• pp.527-534
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• 2007

This paper deals with the BK-AK property of the integrated rate space ${\int}{\ell}_{\pi}$. Importance of ${\delta}^{(k)}$ in this content is pointed out. We investigate a determining set for the integrated rate space ${\int}{\ell}_{\pi}$. The set of all infinite matrices transforming ${\int}{\ell}_{\pi}$, into BK-AK space Y is denoted $({\int}{\ell}_{\pi}:\;Y)$. We characterize the classes $({\int}{\ell}_{\pi}:\;Y)$. When $Y={\ell}_{\infty},\;c_0,\;c,\;{\ell}^p,\;bv,\;bv_0,\;bs,\;cs,\;{\ell}_p,\;{\ell}_{\pi}$. In summary we have the following table:

• 폴리머
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• 제25권2호
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• pp.160-167
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• 2001

특성이 서로 다른 polyimide (PI) 전구체와 polyamideimide (PAI) 블렌드물을 solvent casting법으로 제조한 후 열처리하여 다양한 조성의 PI/PAI 복합체를 제조하였다. Poly(amic acid) (PAA)를 전구체로 사용한 PAA/PAI 복합체의 경우 산-염기에 의한 ionic force 또는 수소 결합에 의한 분자간력으로 인하여 좋은 혼화성을 나타냈지만, poly(amic dimethyl ester) (PAME)를 전구체로 사용한 PAME/PAI 복합체는 약화된 분자간력으로 인하여 상분리가 뚜렷하게 발생함을 편광 현미경을 통해 관찰하였다. 전구체의 종류에 관계없이 이미드화된 복합체의 인장 탄성 계수는 선형치보나 증가하였으나 PAI 매트릭스 영역에서의 인장강도 및 전 혼합 조성에서의 파단 변형률은 감소하였다 상대적으로 낮은 유리 전이 온도를 가진 PAI에 의한 가소화 때문에 열적 이미드화 과정 중에 PI 분자쇄의 재정렬이 촉진됨을 편광현미경 및 X-선 회절 결과로부터 확인하였다.

• 공업화학
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• 제26권6호
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• pp.674-680
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• 2015

리튬이차전지 실리콘 전극에 활용하기 위해, 유기용매에 용해성이 있는 폴리이미드(Polyimide, PI) 고분자 바인더를 두 단계 반응을 이용해 합성하였다. 두 가지 단량체(Bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic Dianhydride (BCDA)와 4,4-oxydianiline (ODA))의 개환 반응 및 축합 반응을 통해 PI 고분자 바인더를 합성하였다. 합성된 PI 고분자 바인더를 이용해 실리콘(silicon, Si) 음극 전극을 제조하였다. 또한 비교군으로써, Polyvinylidene Fluoride (PVDF)을 고분자 바인더로 사용하는 동일 조성을 가진 실리콘 전극을 제조하였다. PI 바인더를 사용한 Si 전극($2167mAh\;g^{-1}$)의 초기 쿨롱 효율은 기존 PVDF 바인더 조성의 Si 전극($1,740mAh\;g^{-1}$)과 유사했지만, 방전용량은 크게 개선되었다. 특히 수명 특성에서는 PI 바인더를 사용한 Si 전극이 우수한 특성을 나타내었는데, 이는 PI 바인더를 사용한 Si 전극접착력($0.217kN\;m^{-1}$)의 전극 접착력이 PVDF를 사용한 Si 전극($0.185kN\;m^{-1}$)보다 높아, 실리콘 부피팽창에 의한 전극 구조 열화가 적절히 제어되었기 때문이라고 판단된다. Si 전극 내의 접착력은 surface and interfacial cutting analysis system (SAICAS) 장비를 통해 검증하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제12권2호
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• pp.37-41
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• 2008

Melatonin has been reported to protect neurons from a variety of neurotoxicity. However, the underlying mechanism by which melatonin exerts its neuroprotective property has not yet been clearly understood. We previously demonstrated that melatonin protected kainic acid-induced neuronal cell death in mouse hippocampus, accompanied by sustained activation of Akt, a critical mediator of neuronal survival. To further elucidate the neuroprotective action of melatonin, we examined in the present study the causal mechanism how Akt signaling pathway is regulated by melatonin in a rat primary astrocyte culture model. Melatonin resulted in increased astrocytic Akt phosphorylation, which was significantly decreased with wortmannin, a specific inhibitor of PI3K, suggesting that activation of Akt by melatonin is mediated through the PI3K-Akt signaling pathway. Furthermore, increased Akt activation was also significantly decreased with luzindole, a non-selective melatonin receptor antagonist. As downstream signaling pathway of Akt activation, increased levels of CREB phoshorylation and GDNF expression were observed, which were also attenuated with wortmannin and luzindole. These results strongly suggest that melatonin exerts its neuroprotective property in astrocytes through the activation of plasma membrane receptors and then PI3K-Akt signaling pathway.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제36권4호
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• pp.589-610
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• 2022

본 연구는 2023년부터 적용 예정인 6학년 2학기 검정 교과서를 대상으로 초등 수학에서 원주율 개념을 어떻게 지도하고 있는지를 비교·분석하여 교수학적 시사점을 도출하고자 하였다. 이를 위해 원주율 개념과 원주율 지도에 관한 선행연구를 분석하여 분석 기준을 마련하였으며, 개념 추론하기, 속성 이해하기, 관계 적용하기의 교수·학습요소로 나누어 살펴보았다. 분석 결과를 통해, 어림 활동이 원주율 개념의 추론 활동으로 연결되기 위한 다양한 어림 맥락의 개발이 필요하다는 것과 지름과 원주를 실제로 측정을 해야 하는 동기를 제공하는 문제 상황의 제시, 지름을 단위로 하여 원주 위를 반복하여 세는 측도의 속성을 탐구할 수 있는 기회의 제공, 원주율의 상수 속성의 명시화, 상황에 따라 원주율의 근삿값 선택의 유연함을 경험하게 할 것을 시사점으로 제시하였다. 이상의 결론과 교수학적 시사점을 바탕으로 원주율의 도입 맥락과 공학 도구 활용에 초점을 맞추어 초등 수학에서 원주율 개념의 지도 방안과 향후 2022 개정 교육과정에 따른 교과서 개발에 개선점을 제안하였다.

• Korean Journal of Mathematics
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• 제22권1호
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• pp.29-36
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• 2014

The limiting diffusion of special diploid model can be defined as a discrete generator for the rescaled Markov chain. Choi([2]) defined the operator of projection $S_t$ on limiting diffusion and new measure $dQ=S_tdP$. and showed the martingale property on this operator and measure. Let $P_{\rho}$ be the unique solution of the martingale problem for $\mathcal{L}_0$ starting at ${\rho}$ and ${\pi}_1,{\pi}_2,{\cdots},{\pi}_n$ the projection of $E^n$ on $x_1,x_2,{\cdots},x_n$. In this note we define $$dQ_{\rho}=S_tdP_{\rho}$$ and show that $Q_{\rho}$ solves the martingale problem for $\mathcal{L}_{\pi}$ starting at ${\rho}$.