• Journal of the East Asian Society of Dietary Life
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• v.17 no.4
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• pp.571-579
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• 2007

The aim of this study was to predict the development process of the Korean food service industry by forecasting the per capita GDP. Forecasting the GDP, involved two primary approaches. One was related to looking at the Korean food service industry's situation by per capita GDP and comparing it to that of the US and Japan. The other was to predict food service industry projections in Korea by quantitative forecasting models. Holt's simple exponential smoothing method and new types of the series models(Damped trend exponential smoothing method), were employed to predict the per capita GDP. The accuracy of the models was measured by MAPE. The empirical results of the forecasting models indicate that the three time series models performed fairly well. Of these Damped trend Damped trend exponential smoothing performed best with the lowest MAPE(9.9%). The results show that the time for reaching a per capita GDP level of $20,000 was 2008 with the Damped trend model and 2009 with the Holt model. Moreover, we found that a per capita GDP level of $30,000 will be achieved in 2012 from the Damped trend model and in 2013 from the Holt model. Within this study, the implications for the Korean food service industry are further discussed. It was predicted there will be a stabilization period in 2008 or 2009 in Korea with achievement of a per capita GDP of $20,000. At this time, major food service industry companies will need to invest in equipment toy external growth and there will be industry trends toward ethnic food and theme restaurants. Also, if a per capita GDP of $30,000 is achieved by 2012 or 2013, the Korean food industry will need to be highly responsive. Therefore, food industry companies should forecast and study customer values and prepare for changes.

• Journal of the Korean Mathematical Society
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• v.19 no.2
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• pp.105-109
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• 1983

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.277-285
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• 2000

This paper presents a very simple procedure for determining the sensitivities of the eigenpairs of damped vibratory system with distinct eigenvalues. The eigenpairs derivatives can be obtained by solving algebraic equation with a symmetric coefficient matrix whose order is (n＋1)×(n＋1), where n is the number of degree of freedom the method is an improvement of recent work by I. W. Lee, D. O. Kim and G. H. Junng; the key idea is that the eigenvalue derivatives and the eigenvector derivatives are obtained at once via only one algebraic equation, instead of using two equations separately as like in Lee and Jung's method Of course, the method preserves the advantages of Lee and Jung's method.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.441-444
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• 2007

Surge tank generally are used near the downstream end of tunnels of penstocks to reduce change in pressure caused by waterhammer resulting from load changes on the turbines. In this paper, the surge tank with chamber is selected to analyze water surface oscillation. the governing equation are derived using the law of conservation of mass and momentum. the water surface oscillation in the surge tank are computed using governing equation. In the case of upsurging, water surface oscillation is damped gradually and in the case of downsurging, it is damped rapidly.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.380-383
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• 1990

When the MOSPET is applied as a switching device for the resonant inverter, a damped oscillating noise is appeared at specific frequency band. This damped Oscillation is caused by the series and parallel resonance due to distributed circuit parameter of snubber and main circuit. This paper describes the frequency-impedance characteristic of the resonant inverter and optimal snubber design strategy to reduce the RF noise.

• Journal of Mechanical Science and Technology
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• v.14 no.9
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• pp.968-977
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• 2000

The motion of an aircraft landing gear over a rough runway can be modeled by a nonclassically damped system subject to nonstationary random excitations. In this paper, the approximate analysis methods based on either the real or complex normal modes for the computation of nonstationary response covariances are proposed. It has been found by simulation involving a realistic example that, for the nonclassically damped random vibrational systems, the approximate solution method based on the complex normal mode is superior to other approaches with respect to the accuracy and computation time.

• Journal of KSNVE
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• v.7 no.6
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• pp.1039-1048
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• 1997

This paper describes the effects of dual dynamic vibration absorbers attached to a primary vibration system with damping. The efficiency of dual dynamic vibration absorbers was investigated with the height of amplitude ratio at the resonance frequency ratio of the damped vibration system according to mass ratio, natural frequency ratio and damping ratio. The variation of amplitude ratio related to frequency ratio of primary vibration system is verified experimentally and theoretically according to dual dynamic vibration systems using computer program designed to find mutual relationship between two absorbers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.865-868
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• 2005

A Helmholtz resonator is one of noise control elements widely used in many practical applications. The resonator has very high absorption at resonance frequency but the frequency bandwidth is very small. Therefore many kinds of additional resistive screens have been applied to the resonator's neck in order to increase the bandwidth. This paper discusses the absorptive characteristics of a Helmholtz resonator damped by a flexible porous screen in form of wire mesh. First, various experimental results are introduced and studied. Secondly, the effect of the resistive screen is theoretically predicted. It is shown that the distance between the screen and aperture affects on the resonance frequency as well as the absorption of the system.

• Journal of KSNVE
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• v.10 no.2
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• pp.325-330
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• 2000

A dynamic absorber is used to protect the primary vibration system under the steady-state harmonic disturbance. In a number of cases it appears expedient to install several absorbers of smaller masses instead of one. This may be due to the need of distribute the absorber's response along the construction, restrictions on the absorber's installation. So, we studied characteristics of the primary vibration system for the optimal natural frequency ratio and the optimal damping ratio of serial multi-dynamic absorber. Also we obtained the optimum values of the serial multi-dynamic absorber parameters using computer simulation for the damped primary vibration system. In designing multi-dynamic absorber, we presented for the optimal natural frequency and the optimal damping ratio of multi-dynamic absorbers.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.129-135
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• 1996

This paper presents the effectiveness of the dynamic vibration absorber consisting of a single mass, coil springs and oil damper on the resonance freauency ratio and amplitude ratio for damped linear systems, that is, primary vibration system with damping. The effects of the dynamic vibration absorber are investigated numerically and experimentally for values of mass ratio, natural frequency ratio, and damping ratio. The experimental results show good agreement with calculated ones. As a result, the characteristics shown by the present work are useful in optimal tuning the dynamic vibration absorber in practice.