• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.462-466
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• 1997

Proportional directional control valves (PDCVl adjust the amount of flow as well as flow direction in response to an electrical signal. This valves includes direct operated valves with or without spool position feedback. This paper investigates if it is possible to control pressure of fluids by means of the PDCV. A pressure signal is feed back to the Proportional-Integral (PI) controller, which is based upon a personal computer (PC). The PI control algorithm is implemented in a graphical programming language of LabVIEW. The results of experiments show the PDCV can be used a multi function valve of pressure control as well as direction control.

• Journal of KSNVE
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• v.8 no.3
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• pp.408-419
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• 1998

Dynamic characteristics are investigated when a nonlinear system showing periodic and chaotic responses under harmonic excitation is exposed to random perturbation. Approach for both qulitative and quantitative analysis of the noise effect in a nonlinear system under harmonic excitation is presented. For the qualitative analysis, Lyapunov exponents are calculated and Poincar map is illustrated. For the quatitative analysis. Fokker-Planck equatin is solved numerical by means of a Path-integral solution procedure. Eigenvalue problem obtained from the numerical caculation is solved and the relation of eigenvalue, eigenvector and chaotic motion is investigated.

• Communications of the Korean Mathematical Society
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• v.9 no.3
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• pp.711-730
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• 1994

We consider Gibbs measures on $(R \times W_{0,0})^{Z^\nu}, W_{0,0} = {\omega \in C[0,1] : \omega(0) = \omega(1)}$, which are associated to an interaction between particles in lattice boson systems (quantum unbounded spin systems). In [4], the Gibbs measures were introduced in the study of equilibrium states of interacting lattice boson systems and were characterized by means of the equilibrium conditions. In this paper we utilize the techniques of the stochastic calculus of variations and the infinite dimensional Ito integral to derive stochastic equations which we call the equilibrium equations. We show that under appropriate conditions the equilibrium conditions and the equilibrium equations are equivalent. The lattice boson systems with superstable and regular interactions, which we studied in [4], are typical examples.

• Journal of the Korean Society for Library and Information Science
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• v.28
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• pp.3-21
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• 1995

The library as nonprofit organization is required to have micro-planning for the organization itself and macro-planning for the relationship of the organization and its environment. Both the micro and macro planning are rational and effective means to library objectives. The library planning must be based on clearly formulated objectives that will encourage all parts of the organization to work toward the same goal and mission. The planning to library objectives should make programming. which should make processing. The mission here should precede goal. which should precede objectives and objectives should precede activities in planning. There is an integral relationship among them. Just as the objectives of the library may be thought of in a hierarchy such as the above. so the library planning must be based on such a hierarchy from strategic or long range planning to administrative planning, from administrative planning to operational planning or short range ones.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.05a
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• pp.228-231
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• 2000

A hybrid fuzzy controller by means of the genetic algorithms is presented. The control input for the system in the HFC is a convex combination of the FLC's output in transient state and PlD's output in steady state by a fuzzy variable. The HFC combined a PID controller with a fuzzy controller concurrently produces the better output performance than any other controller. A auto-tuning algorithms is presented to automatically improve the performance of hybrid fuzzy controller using genetic algorithms. The algorithms estimates automatical Iy the optimal values of scaling factors, PID parameters and membership function parameters of fuzzy control rules. Especially, in order to auto-tune scaling factors and PID parameters of HFC using GA three kinds of estimation modes are effectively utilized. The HFCs are applied to the second process with time-delay. Computer simulations are conducted at step input and the performances of systems are evaluated and also discussed in ITAE(Integral of the Time multiplied by the Absolute value of Error ) and other ways.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.8
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• pp.33-38
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• 1982

This paper deals with the simplification of the transfer function in a frequency domain, viz. the integral of the squared errors between the original and the simplified model is minimized and the latter is estimated by the Walsh function. It tries to minimize the errors between the frequency responses of the two functions. This method is compared with the existing method by means of a numercal example. The frequency response of this simplified model approximates closely to that of the original model. The proposed method is simpler in analysis and easier in implementation than the existing methods. Though the Walsh function can be easily generated with the discrete values, it has errors because its zero crossings are not continuous. This method aims at the reduction of the errors in the real parts and the imaginary parts of the two functions by dividing into the more sub-intervals, and selecting the reduced-order model according to the response of the model. As a result, it can be applied for the simplification of higher order functions into lower order functions and for the design of control systems.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.8
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• pp.2501-2507
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• 1996

In this paper actively controlled air bearing is investigated to overcome the defects of air bearing such as low stiffness and damping coefficients. The actively controlled air beairng is composed of an air bearing, a gap sensor, a controller, and a piezo actuator. By controlling the position of air bearing with piezo actuator, the position of floating object is controlled. In this study the proportional-Integral-Derivative controller is employed. Active air bearing is investigated numerically and experimentally. There is good agreement between the simulation and the experimental results. It is shown that the stiffness and damping characteristics and positioning experimental results. It is shown that the stiffness and damping characteristics and positioning accuracy of air bearing can be improved by means of adopting actively controlled air bearing.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.485-490
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• 2004

Flywheel Energy Storage System(FESS) consists of a high speed flywheel with an integral motor/generator suspended on non contact bearings and in an evacuated housing. Permanent magnet machines as the FESS motor/generator are a popular choice, since there are no excitation losses which means substantial increase in the efficiency. In this paper, the structural design method of rotor retainer for a high speed motor/generator are presented.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.205-209
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• 1998

A synthesis of fuzzy variable structure control is proposed to design a high-angle-of-attack flight system for a modification version of the F-18 aircraft. The knowledge of the proportional, integral, and derivative control is combined into the fuzzy control that addresses both the highly nonlinear aerodynamic characteristics of elevators and the control limit of thrust vectoring nozzles. A simple gain scheduling method with multi-layered fuzzy rules is adopted to obtain an appropriate blend of elevator and thrust vectoring commands in the wide operating range. Improving the computational efficiency, an accelerated kernel for on-line fuzzy reasoning is also proposed. The resulting control system achieves the good flying quantities during a high-angle-of- attack excursion. Thus the fuzzy logic can afford the control engineer a flexible means of deriving effective control laws in the nonlinear flight regime.

• East Asian mathematical journal
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• v.18 no.1
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• pp.111-125
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• 2002

Many different families of infinite series were recently observed to be summable in closed forms by means of certain operators of fractional calculus(that is, calculus of integrals and derivatives of any arbitrary real or complex order). In this sequel to some of these recent investigations, the authors present yet another instance of applications of certain fractional calculus operators. Alternative derivations without using these fractional calculus operators are shown to lead naturally a family of analogous infinite sums involving hypergeometric functions.