• Journal of the Korean Society for Precision Engineering
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• v.1 no.1
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• pp.34-49
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• 1984

The stability of machine tool systems is analyzed by considering the machining process as a stochastic process without decomposing into machine tool structural dynamics and cutting processes. In doing so the time series analysis technique developed by Wu and Pandit is applied systematically to the relative vibration between cutting tool and work- piece measured under actual working conditions. Various characteristic properties derived from the fitted ARMA(Autoregressive Moving Average) Models and those from raw data directly are investigated in relation with the system stability. Both damping ratio and absolute value of the characteristic roots of the AR part of the most significant dynamic mode are preferred as stability indicating factors to the other pro-perties such as theoretical variance .gamma. (o) or absolute power of the most dominant dynamic mode. Maximum aplitude during a certain interval and variance estimated from raw data are shown to be very sensi- tive to the type of the signal and the location of measurement point although they can be obtained rather easily. The relative vibration signal is also analyzed by FFT(Fast Fourier Transform) Analyzer for the purpose of comparison with the spectrums derived from the fitted ARMA models.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1394-1399
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• 2001

The purpose of this paper is that investigates the dynamic behavior characteristic of W.T.S(Wind Turbine System) and carries out the evaluation analysis during operating W.T.S. To investigate the dynamic behavior characteristic of W.T.S. the experiments to measure vibration of the blade from the attached accelerometer on the flap and edge section of the blade that is one of the most important elements of dynamic characteristic of W.T.S are performed. Natural frequency and mode shape are calculated with commercial program (STAR MODAL) using the measured vibration acceleration that receives the signal with F.F.T Analyzer from the accelerometer. For validation of these experiments. the finite element analysis is performed with commercial F.E.M Program (ANSYS) on the basis of the natural frequency and mode shape. The results indicate that experimental values have good agreements with the finite element analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.469-470
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• 2008

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.62-69
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• 2010

Internal lathe machining with a boring bar is weak with respect to vibration because the bar is long and slender. Therefore, it is important to study the dynamic characteristics of a boring bar. The purpose of this study was to identify the effects of overhang and cutting conditions on the dynamic response characteristics of a boring bar. For an efficient experiment, an $L_g(3^3)$ orthogonal array was applied and the results were quantitatively analyzed by ANOVA. Overhang, feed per revolution, and depth of cut were selected as independent variables. Meanwhile, dynamic stiffness, damping ratio, damping coefficient, and acceleration were chosen as dependent variables. The vibration signal was obtained from an accelerometer attached to the boring bar, followed by visualization by a signal analyzer. The effect of overhang was found to have a significant effect on the dynamic stiffness, damping ratio, and damping coefficient, but the other variables did not. As the length of the overhang increased, the dynamic stiffness decreased and the damping ratio increased. In addition, the damping coefficient increased until the length of the overhang was 4D (where D is the shank diameter), after which it remained constant. The acceleration decreased until the overhang length was 4D, and then increased sharply when the overhang was increased further. From these results, the behavioral trend of the damping characteristics changed when its overhang length was 4D. Consequently, there is a critical point that the dynamic characteristics of boring bar change.

• ETRI Journal
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• v.36 no.3
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• pp.514-517
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• 2014

In this paper, alternative dynamic features for speech recognition are proposed. The goal of this work is to improve speech recognition accuracy by deriving the representation of distinctive dynamic characteristics from a speech spectrum. This work was inspired by two temporal dynamics of a speech signal. One is the highly non-stationary nature of speech, and the other is the inter-frame change of a speech spectrum. We adopt the use of a sub-frame spectrum analyzer to capture very rapid spectral changes within a speech analysis frame. In addition, we attempt to measure spectral fluctuations of a more complex manner as opposed to traditional dynamic features such as delta or double-delta. To evaluate the proposed features, speech recognition tests over smartphone environments were conducted. The experimental results show that the feature streams simply combined with the proposed features are effective for an improvement in the recognition accuracy of a hidden Markov model-based speech recognizer.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.799-804
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• 2004

Dynamic characteristic of CD/DVD deck for vehicle is analyzed in this paper. Generally CD/DVD deck for vehicle is used from inferior environment with the vibration of the vehicle and shock of outside and so on. Therefore it must have the structure which is stabilized from the vibration to prevent read error. For this purpose, vibration characteristic of the deck for vehicle should be identified. To analyze characteristic of the deck system, we perform the signal analysis and modal testing using the FFT analyzer. Also we change the design factor degrading the performance of the deck system and verify the efficiency improvement using the acceleration measurement occurring to the sound discontinuation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1035-1041
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• 2005

Dynamic characteristics of CD/DVD deck fur vehicle are analyzed in this paper. Generally CD/DVD deck for vehicle is used from inferior environment with the vibration of the vehicle, shock of outside and so on. Therefore it must have the structure which is stabilized from the vibration to prevent read error. For this purpose, vibration characteristic of the deck for vehicle should be identified. To analyze characteristic of the deck system, we perform the signal analysis and modal testing using the EFT analyzer. Also we change the design factor degrading the performance of the deck system and verify the efficiency improvement using the acceleration measurement occurring to the sound discontinuation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.29-34
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• 2006

In general, the vertical vibration problems for .strength of members and serviceability of building structures are not considered in structural design process, but the prediction of the vertical vibration is very important and essential to structural design process. This study aims to investigate the characteristics of vertical vibration in terms of the transfer of horizontal directions on the rahmen building structures. In order to examine the characteristics of vertical vibration, the modal test and the impact (heel-drop and hammer) excitation experiments were conducted several times on three building structures. The results from the experiments are analyzed and compared. with the results. The results of this study suggest that the characteristics of vertical vibration transfer in horizontal way are effected from the fundamental frequency of the slabs and excitation forces.

• Journal of the Korean Institute of Navigation
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• v.19 no.2
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• pp.107-113
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• 1995

Since the most of the mal-functions in the industrial equipments controlled by processors have been occured by the Electrical Fast Transient(EFT), the International Electrotechnical Commision(IEC) prepare the dummy signal to test the immunity level of the equipments controlled by processors and recommend it for the measuring. In this paper, the defined dummy EFT signal by IEC are analyzed by the spectrum analyzer in the frequency domain and studied the developed countermeasuring parts. The new developed parts are consist of the feedthrough capacitors ( $C_y$ type ) in the input and materials with high permeaility which was wound or inserted in the second layer of the Power Cable in order to increase Common Mode inductance. And it is compared inserted Permalloy to material with high permeability increasing Common Mode inductance. We could gotten a excellent insertion loss on the wide band against EFT signal. Especially, we confirm that countermeasuring Power Cable have been an excellent dynamic characteristics in computer system above the 3.6Kv. This new parts could be effectively used for industrial, MIL, and medical equipments to reduce a mal-functions on the site. Furthermore, these parts also have a good characteristics for EMI countermeasuring over the 60MHz up to several GHz band, they are also expected to be used for all kind of EMS test with IEC801-2, 3, 5 and 6 on the power distributed line.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.10b
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• pp.18-28
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• 1996

The outer-most electrons of metal atoms and the remaining valence electrons of any molecular atoms make three-dimensional crystallizing $\pi$-bondings. The rotating electrons on the three-dimensional crystallizing $\pi$-bonding orbitals of atoms make $\pi$-far infrared rays. Longitudinal wave is a propagation of a bundle of $\pi$-far infrared rays, which are produced by a dynamic impact on a solid bar. The $\pi$-far infrared rays make three-dimensional crystallizing $\pi$-bondings in the material, which reproduce the same $\pi$-far infrared rays. If a current signal is input into water molecules under a given electric potential field with $\pi$-far infrared rays (input information), the signal can be amplified because the $\pi$-far infrared rays make the $\pi$-bondings, which reduce electric resistance. The three-dimensional crystallizing $\pi$-bondings can induce normal electrons to move from one orbital to next one with a aid of potential electric field. Quantum Resonance Spectrometer is composed of tesla coil absorbing $\pi$-far infrared rays, tesla coil emitting varying electromagnetic waves signal generator, signal storage, human body amplifier, signal analyzer and data indicator. The absorbing tesla coil making varying magnetic field and downward and upward electric field, which resonates the $\pi$-far infrared rays coming out from specimen and absorbs them. The modulated current signal from the input square signal can generate and emit varying electromagnetic waves from the tesla coil. The varying electro-magnetic waves make the three-dimensional crystallizing $\pi$-bondings and the $\pi$-far infrared rays in the water molecules.