• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.6
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• pp.89-96
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• 1985

A pole-placement control of discrete, deterministic, single-input single-output nonmini-mum phase systems is considered using a model reference type approach. The proposed pole-placement controller is designed in the parameter form to make the transfer function of the controller equal to that of the reference model with only single variable polynomial S(q-1). The proposed adaptive pole-placement controllr is designed with the true system para-meters by applying the adaptation method to the proposed pole-placement controller.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.731-733
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• 1996

In this paper, a new time-domain reduction method for unbalanced 3 phase power systems will be represented. The impulse response of the system is used to identify a discrete-time equivalent filter model. The model is formulated directly in the phase domain. Each phase has a self-mode equivalent model and two mutual-mode equivalent models. The equivalent model is determined by the transfer function identification technique based on the Prony analysis. The model is implemented in EMTDC and tested with an unbalanced 3 phase network. The result of test showed that the equivalent model is accurate.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.138-139
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• 2007

This research provides machine designers with some intuition to consider both, magnetic and heat transfer effects. A topological multi-objective function includes magnetic energy and heat inflow rate to the system, which equals to the total heat dissipation by conduction and convection. For the thermal field regarding the heat inflow, introduced as a reaction force, topology design sensitivity is derived by employing discrete equations. The adjoint variable method is used to avoid numerous sensitivity evaluations. As a numerical example, a C-core design excited by winding current demonstrates the strength of the multi-physical approach.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.191-196
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• 1993

Since the welding process is complex and highly nonlinear, it is very difficult to accurately model the process for real-time control. In this paper, a discrete-time transfer function matrix model for gas metal arc welding process is proposed. Although this linearized model is valid only around the operating point of interest, the adaptation mechanism employed in the control system render this model useful over a wide operating range. A multivariable one-step-ahead adaptive control strategy combined with a recursive least-squares method for on-line parameter estimation is implemented in order to achieve the desired weld bead geometries. Command following and disturbance rejection properties of the adaptive control system for both SISO and MIMO cases are investigated by simulation and experiment.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.28-39
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• 1998

This study investigated the natural convection and radiation in a rectangular enclosure with ceiling vent experimentally and numerically. A heat source is located on the center of the bottom surface. The analysis was peformed a pure convection and is combination of natural convection and radiation. The shape of the considered two dimensional model is a square whose center of ceiling($30\%$) is opened. The numerical simulations are carried out for the pure natural convection case and the combined heat transfer case by using the SIMPLE algorithm. For the turbulent flow, Reynolds stresses are closed by the standard $k-{\epsilon}$ model and the wall function is used to determine the wall boundary conditions. The experiment was performed on the same geometrical shape as the computations. The radiative heat transfer is analized by the S-N discrete ordinates method. The results of pure natural convection are compared with those of combined heat transfer by the velocity vectors, stream lines, isothermal lines. The results obtained are as follows 1. Comparing the results of pure convection with those of the combined convection-radiation through the shape of stream lines, isothermal lines are similar to each other. 2. The temperature fields obtained by numerical method are compared to those obtained by experimental one, and it is found that they are showed mean relative error $8.5\%$. 3. Visualization bt smoke is similar to computational results.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.1
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• pp.11-18
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• 2003

As the Internet moves to mobile environment, one of the most serious problems for the security is to required a new security Protocol with safety and efficiency. To solve the problem. we Propose a new Protocol that reduces the communication franc and solves the problem associated with the private security keys supplied by the trusted third party. The protocol is a non-Interactive oblivious transfer protocol, based on the EIGamal public-key algorithm. Due to its Non-Interactive oblivious transfer protocol, it can effectively reduce communication traffic in server-client environment. And it is also possible to increase the efficiency of protocol through the mechanism that authentication probability becomes lower utilizing a challenge selection bit. The protocol complexity becomes higher because it utilizes double exponentiation. This means that the protocol is difficult rather than the existing discrete logarithm or factorization in prime factors. Therefore this can raise the stability of protocol.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.995-1000
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• 2004

A digital adaptive flight control system is presented for a Japanese automatic landing flight experiment vehicle (ALFLEX). In previous adaptive control systems based on a linear-parameter-varying (LPV) form, the output behavior was excellent, while the behavior of the adjusted parameters was unsatisfactory. In the present study, to obtain a more appropriate parameter adjustment law, the relationship between the coefficient matrices in a continuous-time state equation and the coefficients of a pulse transfer function in a discrete system for conventional aircraft is investigated. As a result, it is revealed that the coefficients of the numerator can be treated as a linear function of dynamic pressure (linear-parameter-varying: LPV), while the coefficients of the denominator can be treated as constant (linear-time-invariant: LTI). From the above analysis, an improved parameter adjustment law is derived by reducing the number of the adjustment parameters. Simulation results also revealed both good output tracking and good parameter adjustment compared with the previous results.

• Earthquakes and Structures
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• v.12 no.4
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• pp.425-436
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• 2017

Vibration control using a tuned mass damper (TMD) is an effective technique that has been verified using analytical methods and experiments. It has been applied in mechanical, automotive, and structural applications. However, the damping of a TMD cannot be adjusted in real time. An excessive mass damper stroke may be introduced when the mass damper is subjected to a seismic excitation whose frequency content is within its operation range. The semi-active tuned mass damper (SATMD) has been proposed to solve this problem. The parameters of an SATMD can be adjusted in real time based on the measured structural responses and an appropriate control law. In this study, a stiffness-controllable TMD, called a leverage-type stiffness-controllable mass damper (LSCMD), is proposed and fabricated to verify its feasibility. The LSCMD contains a simple leverage mechanism and its stiffness can be altered by adjusting the pivot position. To determine the pivot position of the LSCMD in real time, a discrete-time direct output-feedback active control law that considers delay time is implemented. Moreover, an identification test for the transfer function of the pivot driving and control systems is proposed. The identification results demonstrate the target displacement can be achieved by the pivot displacement in 0-2 Hz range and the control delay time is about 0.1 s. A shaking-table test has been conducted to verify the theory and feasibility of the LSCMD. The comparisons of experimental and theoretical results of the LSCMD system show good consistency. It is shown that dynamic behavior of the LSCMD can be simulated correctly by the theoretical model and that the stiffness can be properly adjusted by the pivot position. Comparisons of experimental results of the LSCMD and passive TMD show the LSCMD with less demand on the mass damper stroke than that for the passive TMD.

• Journal of radiological science and technology
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• v.32 no.1
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• pp.17-24
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• 2009

Noise evaluation for an image has been performed by root mean square (RMS) granularity, autocorrelation function (ACF), and Wiener spectrum. RMS granularity stands for standard deviation of photon data and ACF is acquired by integration of 1 D function of distance variation. Fourier transform of ACF results in noise power spectrum which is called Wiener spectrum in image quality evaluation. Wiener spectrum represents noise itself. In addition, along with MTF, it is an important factor to produce detective quantum efficiency (DQE). The proposed evaluation method using Wiener spectrum is expected to contribute to educate the concept of Wiener spectrum in educational organizations, choose the appropriate imaging detectors for clinical applications, and maintain image quality in digital imaging systems.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.36-41
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• 2011

In the present paper, a direct forcing/fictitious domain (DF/FD) level set method is proposed to simulate the FSI (fluid-solid interaction) in two-phase flow. The main idea is to combine the direct-forcing/fictitious domain (DF/FD) method with the level set method in the Cartesian coordinates. The DF/FD method is a non-Lagrange-multiplier version of a distributed Lagrange multiplier/fictitious domain (DLM/FD) method. This method does not sacrifice the accuracy and robustness by employing a discrete ${\delta}$ (Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, easy implementation, and utilization of the original governing equation without modification. Simulations of various water-entry problems have been conducted to validate the capability and accuracy of the present method in solving the FSI in two-phase flow. Consequently, the present results are found to be in good agreement with those of previous studies.