• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.219-224
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• 2012

In this paper, vibration and flow-induced flutter instability analysis of cantilever multiwall carbon nanotubes conveying fluid and modelled as a thin-walled beam is investigated. Non-classical effects of transverse shear and rotary inertia are incorporated in this study. The governing equations and the associated boundary conditions are derived through Hamilton's principle. Numerical analysis is performed by using extend Galerkin method which enables us to obtain more exact solutions compared with conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for flow velocity below a certain critical value, however, beyond this critical flow velocity, flutter instability may occur. Variations of critical flow velocity with both radius ratio and length of carbon nanotubes are investigated and pertinent conclusion is outlined.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.55-64
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• 1990

The fatigue crack growth behavior of physically-short cracks(0.2${\Delta}K$ with $da/dN<1{\times}10^{-7}m/cycle$. The transition crack lengths where similtude with ${\Delta}K$ existed was between 1 and 2mm. The effective stress intensity factor range based on COD measurements gave better correlation between the physically-short and long cracks. Thus it can be considered that the crack closure effect is one of the main factors which causes the differences between these two cracks.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.2 no.3
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• pp.65-73
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• 2004

In experimental method, this study was that galvanic vestibular stimulation in vestibular system influenced the excitability of spinal neuron through. H-reflex was measured by galvanic vestibular stimulation of binaural(right-negative pole and left-positive pole) at left head turning and prone position in sixteen normal subjects in their twenties age were selected. The summary of the comparison results were obtained below. 1. In the change of H reflex according to galvanic vestibular stimulation(GVS), Hmax amplitude(p<.05) increased significantly after stimulation. 2. In the change of H reflex according to galvanic vestibular stimulation(GVS), Hmax/Mmax ratio(p<.05) increased significantly after stimulation. In the conclusion, galvanic vestibular stimulation influenced the excitability of vestibulospinal tract and spinal neuron.

• Journal of electromagnetic engineering and science
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• v.7 no.4
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• pp.201-206
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• 2007

When the M-ary signal experiences the Rayleigh fading, the diversity schemes can reduce the effects of fading since the probability that all the signals components will fade simultaneously are reduced considerably. The symbol error probabilities for various M-ary signals, such as MDPSK, MPSK and MQAM, are mathematically derived for the SC-2(Selection Combining 2) demodulation system, whereby the two signals with the two largest amplitudes are coherently combined among the L branches. On the other hand, maximum ratio combining(MRC) requires the individual signals from each path to be time-aligned, cophased, optimally weighted by their own fading amplitude, and then summed. The propagation model used in this paper is the frequency-nonselective slow Rayleigh fading channel corrupted by the Additive White Gaussian Noise(AWGN). The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1778-1780
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• 1996

In this paper, we describe the partial discharge measurement with measuring impedance to have two wide frequency band transformers(filters) in the oil-paper and air insulation. The measuring impedance consists of high and low limiting frequency transformers. This measuring impedance could be measured the partial discharge current wave. We have the results that the amplitude partial discharge pulse ratio of low limiting frequency tranformer to high limiting frequency one is varied in the condition(in oil-paper insulation and air) to generate partial discharge.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1391-1392
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• 2008

The modulation quality of the I/Q modulator in a wireless transmitter usually affects system performance and it mostly depends on both a nonlinearity and a distortion, from the third order intermodulation(IM3) signal and the imperfection features such as an input amplitude error and a local phase error, respectively. This paper focused on how much the Single Sideband Ratio(SSR), which indicates the signal distortion, changes according to the variation of the imperfection features. Since a desired signal, side band and IM3 signals at the I/Q modulator output are also represented with those power series coefficients and the imperfection features, the effects of the imperfection features on SSR can be clearly analyzed.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.9
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• pp.1360-1363
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• 2003

A feeding trial was conducted on pigs to study the effect of La on their growth performance. Sixty barrows were randomly assigned to two groups (each of which included three replicates) and they were fed same basal diet supplemented with 0 or 100 mg/kg lanthanum (La) respectively for 30 d. Blood samples were collected and analyzed to study the growth hormone secretion pattern. La residues in selected organs were analyzed to test the safety level. The results showed that average daily gain and feed conversion ratio of pigs were increased by 12.95% (p<0.05) and 6.78% (p<0.05) respectively with the supplementation of La. Blood samples analysis showed that peak amplitude, base-line level and mean level of growth hormone in serum were elevated by 80.42% (p<0.05), 70.99% (p<0.05) and 64.91% (p<0.05) respectively. No significant difference of La residues was found in selected organs between the control and La-treated group.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2523-2532
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• 1994

In this paper, active noise control is performed in a duct system using the periodic pulse train which corresponds to the periodic component of noise source as a reference signal. Control algorithm applied in this study is possible to eliminate the acoustic feedback which occurs in the conventional filtered-x and filtered-u LMS algorithm by using electrical reference signal and has the fast adaptation speed with low filter orders by using synchronous sampling method is discussed via computer simulations and experiments of case studies such as frequency modulation, amplitude modulation and frequency differency between source signal and reference signal.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.862-870
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• 1998

In this paper an experimental investigation of characteristics of developing transitional unsteady flows in a square-sectional 180。 curved duct are presented. The experimental study using air is carried out to measure axial velocity profiles secondary flow velocity profiles and entrance length by using Laser Do ppler Velocimeter(LDV) system. The flow development is found to depend upon Dean number dimensionless angular frequency velocity amplitude ration and cur-vature ratio. Of special interest is the secondary flow generated by centrifugal effects in the plane of the cross-section of the duct. The secondary flows are strong and complicate at entrance region. The entrance length of transitional pulsating flow is obtained to 120。 of bended angle of duct in this experimental conditions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.613-617
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• 2000

This paper descries the effect of the stylus tip size on the measuring error in surface topography measurement. To analyze the distortional effect of an actual surface geometry originating from the finite stylus size, the surface is modeled as a sinusoid and the stylus tip as a circle. the measuring error is defined as the ratio of the standard deviation of a tracing profile and an original profile. It is shown that this measuring error depends on the amplitude and wavelength of an original profile. In this paper, the spectrum analysis is applied to investigate the distortional effect due to the mechanical filtering of the stylus in the frequency domain. and, the cumulative power spectrum is applied to determinate the minimum wavelength limits to be measured with the various stylus tip radius from these results, a new method to select proper stylus tip radius is proposed.