• (The)Korea Educational Review
• /
• v.22 no.3
• /
• pp.67-87
• /
• 2016

The paper has tried to analyze the sense of 'meta-praxis' in the educational discourse. Against the dichotomy of theory vs practice, the senses of practice and 'meta-praxis' can be hold under the Greek conception of human activities such as theoria, poiesis and praxis. We can establish the meaning of meta-praxis contrasted with one of metaphysics, not with one of meta-theory. Some significant points included in the concept then have been minutely examined so as to lead us to get the recursive structure and practicability. The Buddhist notion such as 'Well-Rounded Discretion' and the linguistic one such as 'Grand Father' throw light on the educational practice and discourse. These are ones that we never fail to recognize in terms of 'meta-praxis'.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.12
• /
• pp.1289-1295
• /
• 2012

An adaptive digital predistortion (PD) technique is proposed for linearization of power amplifiers (PAs) in multiple-input multiple-output (MIMO) transmitters. We consider a PD structure equipped with only one combined feedback path while conventional systems have multiple feedback paths. Hence, the proposed structure is much simpler than that of multiple feedback paths. Based on the structure, a new PD algorithm is derived. The simulation results show that linearization performance of the proposed method is almost the same as the conventional multiple feedback technique while the former is much simpler to implement than the latter.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.3
• /
• pp.155-159
• /
• 2013

In this paper, a nonlinear matrix inequality problem and a nonlinear optimization problem are proposed for obtaining a structured static output feedback controller. The proposed nonlinear optimization problem has LMI (Linear Matrix Inequality) constraints and a nonlinear objective function. Using the conditional gradient method, the nonlinear optimization problem can be solved. A numerical example shows the effectiveness of the proposed approach.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.4
• /
• pp.343-350
• /
• 2004

This study is on control gain estimation of energy dissipation control algorithms. Velocity feedback saturated, bang bang, and energy gain control algorithms are proposed based on the Lyapunov stability theory and their performances are evaluated and compared. Saturation problem is considered in the design of the velocity feedback saturated and energy-gain control algorithms, and chattering problem in bang bang control is solved by using boundary layer. Numerical results show that the proposed control algorithms can dissipate the structural energy induced by wind loads efficiently.

• Aerospace Engineering and Technology
• /
• v.7 no.1
• /
• pp.151-160
• /
• 2008

In this paper, the analysis results of synthetic resonance characteristics are described for the electrohydraulic thrust vector control actuation system. The synthetic resonance is induced by integration of position servo actuation system on the flexible launch vehicle mounting structure. The new resonance mode is synthesized due to composition of hydraulic resonance for electrohydraulic position servo system with inertia load condition and structural resonance for flexible mounting structure. This synthetic resonance can make stability of control system worse by feedback and amplification of control system. The exact nonlinear analysis model of this phenomenon is developed to predict and design a control algorithm for improvement characteristics. The DPF (Dynamic Pressure Feedback) control algorithm has been designed and has excellent resonance suppression capability.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.140-143
• /
• 2011

본 연구에서는 준능동형 제진장치로 복합형 제진장치(HMD, Hybrid Mass Damper)의 운용에 요구되는 제어알고리즘 개발에 대한 연구를 진행하였다. 제어력을 산정하기 위한 알고리즘 내장화 과정에서 구조물의 상태를 피드백하기 위해서는 구조물의 가속도를 계측하고 이로부터 변위, 속도를 추정하게 되는데 여기서 발생하는 오차의 문제점을 개선하기 위하여 GPS의 실시간 변위측정기술을 활용하여 변위를 직접 입력하면서 구조물의 응답을 제어할 수 있는 알고리즘을 구성하려 한다. 이 때 측정된 데이터의 값에는 잡음이 발생하고 미분기의 동적특성을 가지고 있는 HMD에 입력신호로 사용하는 경우 상당한 오차가 생기는 변위 되먹임(Feedback)의 문제점을 확인하였다. 이러한 문제점을 개선하기 위해 제진장치 입력신호의 시간간격(Time-interval)을 조정하여 오차를 줄일 수 있는 방안을 제안하였다. 수치해석결과, 입력신호에는 최적의 시간간격(Time-Interval)이 존재하였으며 이를 적용할 경우 건물의 변위와 가속도 응답을 크게 줄일 수 있음을 확인하였다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.37 no.3
• /
• pp.138-146
• /
• 2010

It is well known that many biological networks are very robust against various types of perturbations, but we still do not know the mechanism of robustness. In this paper, we find that there exist a number of feedback loops in a real biological network compared to randomly generated networks. Moreover, we investigate how the topological property affects network robustness. To this end, we properly define the notion of robustness based on a Boolean network model. Through extensive simulations, we show that the Boolean networks create a nearly constant number of fixed-point attractors, while they create a smaller number of limit-cycle attractors as they contain a larger number of feedback loops. In addition, we elucidate that a considerably large basin of a fixed-point attractor is generated in the networks with a large number of feedback loops. All these results imply that the existence of a large number of feedback loops in biological networks can be a critical factor for their robust behaviors.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.102-103
• /
• 2000

최근 광통신 시스템에서는 파장분할다중화(WDM) 방식의 도입으로 인해, 한 개의 레이저 신호를 입사시켜 여러 개의 레이저 신호를 발생시켜 광원으로 사용하는 연구가 활발히 진행되어 왔다. Park et al.[1]은 Erbium Doped Fiber Laser(EDFL)에서 1.1nm 파장간격으로 24라인을 얻었고, Yamashita et al.[2]은 내부 에탈론 구조를 가진 EDFL에서 0.8nm 간격으로 17라인, D.Yu et al.[3]은 반사형 거울과 Circulator를 사용한 Brillouin/Erbium Fiber Laser(BEFL)에서 0.08nm 간격으로 30라인, G.J.Cowle et al.[4]은 Injection-Seed Locking을 이용한 BEFL.에서 0.09nm 간격으로 12라인 그리고 N.S.Kim et al.[5]은 내부 되먹임을 이용한 BEFL에서 0.09nm 간격으로 4라인을 각각 발생시켰다. 여기서 중요한 요소로는 발생된 레이저 신호의 안정성, 각 신호들 간의 파장간격, 레이저 신호의 수 그리고 Peak Intensity 간의 차이 등이 있는데 각 연구방식에 따라 다양한 결과를 보여준다. 본 실험에서는 향상된 되먹임 구조를 가진 BEFL에서 다파장 발생에 관한 연구를 하였다. (중략)

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.7
• /
• pp.501-513
• /
• 1987

Conditions for achieving noninteraction in nonlinear multivariable systems via the decomposition of state space are well established. The main contribution of this paper is to fully characterize the class of decomposing control laws. The characterization corresponds to a family of simple control laws which are applied to a standard decomposed system(SDS). The SDS is similar to the decomposed systems of Isidori, Krener, Gori-Giorgi, and Monaco but has a finer structure. The finer structure parallels the one used by Gilbert for linear systems. A weaker form of noninteraction, based on input-output behaviour, is decoupling. Some connections between decomposition and decoupling are also established. An example illustrating the importance of the results is given.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.2
• /
• pp.129-137
• /
• 2010

This paper presents a position tracking control of a flexible beam using the piezoelectric actuator. This is achieved by implementing both feedforward hysteretic compensator of the actuator and PID feedback controller. The Preisach model is adopted to develop the feedforward hysteretic compensator. In the design of the compensator, estimated displacement of the piezoceramic actuator is used based on the limiting triangle database that results from collecting data of the main reversal curve and the first order ascending curves. Experimental implementation is conducted for position tracking control and performance comparison is made between a PID feedback controller without considering the effect of hysteresis, and a PID feedback controller integrated with the feedforward hysteretic compensator.