• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.221-223
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• 1993

The Hopfield model is defined as an adaptive dynamic system. In this paper we propose a modified neural network which is capable of solving linear programming problems and a set of linear equations. The model is directly implemented from the given system, and solves the problem without calculating the inverse of the matrices. We get the better stability results by the addition of scaling property and by using the nonlinearities in the linear programming neural networks.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.195-196
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• 2006

In recent years, demands for sintered ferrous material with higher strength are increasing. To satisfy these demands, studies and commercial use of the die wall lubrication method, the warm compaction method and the combination of both methods are widely carried out to achieve high density. The die wall lubrication warm compaction method makes it possible to achieve high density by reducing internal lubricant through die wall lubrication, although the method involves several issues such as prolonged cycle time due to lubricant spraying and difficulty in spraying lubricant in the case of compacting with complicated geometry. Meanwhile, the conventional warm compaction method requiring no die wall lubricant application cannot achieve such a high density as in the case of die wall lubrication warm compaction due to higher volume of internal lubricant. However, this report discloses our study result in which the possibility of improving density is exhibited by using a lubricant type with superior dynamic ejection property that can reduce volume of lubricant additive.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.199-202
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• 1996

In this paper, we suggested the combination of HMM(Hidden Markov Model) and MLP (Multi-Layer Perceptron) with GA(genetic algorithm) for a recognition of EMG signals. To describe EMG signal's dynamic properties, HMM algorithm was adapted and due to its outstanding abilities in static signal classification MLP was connected as a real processor. We also used GA( Genetic Algorithm) for improving MLP's learning rate. Experimental results showed that the suggested classifier gave higher EMG signal recognition rates with faster learning time than other one.

• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.253-256
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• 2010

Since the amplitude of voiced fall off at about -20dB/decade, dynamic range is often compressed prior to spectral analysis so that details at weak, high frequencies may be visible. Preemphasizing the speech, either by differentiating the analog speech $s_a$(t) prior to A/D conversion or by differencing the discrete-time s(n)=$s_a$(nT), compensating for falloff at high frequencies. The most common form of preemphasis is y(n)=s(n)-As(n-1), where A typically lies between 0.9 and 1.0 and reflects the degree of pre-emphasis. In this paper, we proposed that A is adjusted at each time by measuring the slope of envelope in frequency domain.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.322-325
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• 1994

Mareel and Bitmead proved the presence of chaotic signal in random noise by applying dead beat control theory to adaptive mechanism. In this paper robust adaptive theory is proposed. With the property of chaotic signal that has order and law, the proposed theory can enhance the control Performance by applying the recursive algorithm that uses dynamic relation which have small correlation. The performance of proposed algorithm is demonstrated with the computer simulation of position control of electric motor. In this simulation, the adaptive low is adopted to control electric motor and the Presence of chaotic signal in feedback signal is proved by using several method such as time series, fourier spectrum phase portrait method.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.366-369
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• 1994

In this paper, reduced-order $H_{\infty}$ robust controller is designed for the drum-type boiler system. From the known nonlinear dynamic model, a linearized multivariable model is obtained. To reduce order of robust controller, observer-based proper $H_{\infty}$ compensator is designed. The designed controller has robust property against the influence of sensor noise, system parameter variation and model uncertainty. A good Performance of the designed controller is shown by simulation.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2320-2322
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• 2001

This paper describes the design of a robust adaptive neural-net(NN) observer for uncertain nonlinear dynamical system. The Lyapunov synthesis approach is used to guarantee a uniform ultimate boundedness property of the state estimation error, as well as of all other signals in the closed-loop system. Especially, for reducing the dynamic oder of the observer, we propose a new method in which no strictly positive real(SPR) condition is needed with on-line estimation of weights of the NNs. No a priori knowledge of an upper bounds on the uncertain terms is required. The theoretical results are illustrated through a simulation example.

• Journal of KSNVE
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• v.9 no.2
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• pp.348-354
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• 1999

An AC traction motor was developed, of which the rotor core has an unique structure, made of multi-layered silicon steel plates which were shrink-fitted to a shart. the equivalenet material properties were estimated with a newly proposed efficient method, based on the correlation between finite element analysis results and modal testing. A general rotordynamic analysis for the rotor with the equivalent material properties was carried out to evaluate the structural integrity of the virtually built-up motor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.490-495
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• 2003

This paper presents investigation of damping characteristics of squeeze mode type MR (magneto-rheological) mount experimentally. Since damping property of the MR fluid is changed by variation of the applied magnetic field strength, squeeze mode type MR mount proposed in the study has variable damping characteristics according to the applied magnetic field strength. In the present work, the performance of the mount was experimentally Investigated according to the magnetic field strength and exciting frequencies. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic field strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents in this study and MR effect is reduced by increasing exciting frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.994-1000
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• 2002

In periodically repeated cyclic structures, small property irregularity of their substructures often causes significant difference in their dynamic responses. which results in unpredicted premature failures. The small irregularity and the resulting phenomenon are called the mistuning and the vibration localization. respectively. In this paper, the vibration localization phenomena due to mistuned coupling effects are investigated. To effectively achieve the objective, a simple coupled multi-pendulum system Is employed. The results show that if there exists some coupling stiffness irregularity, vibration localization may occur and becomes more predominant as the number of substructures increases.