• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.41-49
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• 2003

Tube oscillation behaviour is experimentally investigated for the study on the fuel rod fretting that is caused by the flow-induced vibration in nuclear reactor. The experiment was conducted in all at room temperature. The specimen of tube assembly was supported by plate springs which simulated the spacer grids and fuel rods of a fuel assembly. To investigate the influence of contact condition between the grids and rods, normal load of 10 and 5 N, gaps of 0.1 and 0.3 mm were applied. The range of the oscillation at the center of the fuel rod specimen was varied as 0.2, 0.3 and 0.4 mm to simulate the fuel rod vibration due to flow. Displacements near the contact were measured with four displacement sensors during the tube oscillation. As results, the shape of oscillation (phase) varied depending on the contact condition. The oscillation displacement increased considerably from the contact to gap condition. The displacement increased further as the gap size increased. It is regarded that the spring shape influences the tube oscillation behaviour. Simple calculation showed that the slip displacement was very small. Therefore, cumulative damage concept is necessary for the fuel rod wear. The mechanism of plowing is thought required to explain the severe wear in the case of gap existence.

• Journal of applied mathematics & informatics
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• v.9 no.2
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• pp.635-643
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• 2002

The asymptotic behaviour of the solutions of initial - boundary value problem for a class of nonlinear parabolic differential - functional equations is studied via the method of differential inequalities in order to obtain oscillation criterion for the solutions.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.251-255
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• 2015

Unsteady Shock-Induced Combustion has been studied for the past few decades since it is considered as one of the potential ways to reach supersonic flights. Experimental observations of Unsteady SIC were observed as early as 1960's. But Lehr was the first to report in detail the mechanisms of Shock-Induced Combustion experimentally. Numerical Studies on SIC were helpful in explaining the insight into the oscillatory behaviour in the mid 90's to early 2000's. Detailed reaction mechanisms is required to prediction the SIC flowfield more in detail. However at that time, very few reaction mechanisms on hydrogen-oxidation were reported. In the last decade, various number of hydrogen reaction mechanisms were reported. In this study, an attempt has been made to analyze the effect of various reaction mechanisms in an unsteady mode of Shock-Induced Combustion.

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.877-882
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• 1996

The effects of periodic and chaotic behaviour in the Bonhoeffer-Van der Pol (BVP) oscillation of the nerve membrane driven by a periodic stimulating current A1 coswtare investigated through hardware implementation.For hardware implementation of the BVP model. real element values were escaled with computer simulation results to determine the parameter real value.As the parameter A1 varied in the range 0 to 1.3, the BVP model showed an ordinary and reversed period-doubling cascade and a chaotic state. At the low driving amplitude ofa1 the period-doubling showed and at the high driving amplitude of A1 the chaotic state occured. To analyse the BVP model for chaotic behaviour Phase Plane, Time series are used to verify that properties.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.154-156
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• 1995

The effect of a periodic and a chaotic' behaviour in the Bonhoeffer-Van der Pol(BVP) oscillation of the nerve membrane driven by a periodic stimulating current $A_1=cos\;{\omega}\;t$ are investigated by numeric analysis and hardware Implementation. To control the chaotic motion, we are suggested by temperature parameter c, $c=c(1+\eta\;cos\;{\Omega}\;t)$ which the values of $\eta,\;Omega$ varied respectively. The feasibilities of chaotic and periodic phenomena were analysed by phase plane and time series.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.434-436
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• 2000

In this study, we investigate the optical characteristics of merocyanine dye Langmuir-Blodgett(LB) film using the oscillation characteristics of quartz crystal. As results, the resistance and frequency shift at the parallel resonance under the UV irradiation is to be going down. This behaviour of resistance and frequency is different from the case of general mass adsorption into the organic film on the quartz crystal. Generally the frequency decrease of quartz crystal oscillator, which has been considered as mass loading, goes along with the resistance increase. Thus it has been suggested that the J-aggregate dissociation in merocyanine dye LB film by UV irradiation give rise to transformation of oscillation characteristics of quartz crystal.

• Journal of Astronomy and Space Sciences
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• v.10 no.1
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• pp.17-27
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• 1993

The orbit characteristics and perturbation effects of an artificial satellite with critical inclination have been studied. The critical inclination problem in artificial satellite theory is treated as Ideal Resonance Problem(IRP). The KITSAT-1 satellite launched by Arian 42P at Guiana in August 11, 1992 has orbital inclination close to the critical value cos-1(1/√5). In that case, there is a singularity in some perturbation terms and perigee of the orbit is fixed because d$\omega$/dt is theoretically equal to zero. But actually the long periodic behaviour in argument of perigee, $\omega$ shows a small oscillation. The causes of the oscillation and the relativistic effect in IRP have been studied and applied to the KITSAT-1. The geo-potential perturbation terms which are seperated inclination terms have been obtained using Algebraic manipulation. Also luni-solar disturbing funtion based on the relative position of the sun, moon, and satellite has been obtained. Phase portraits are used to depict the change of eccentricity and grgument of perigee. The variations of each orbital elements have been obtained in case of the KITSAT-1.

• Journal of applied mathematics & informatics
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• v.12 no.1_2
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• pp.31-37
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• 2003

In this Paper, we investigate local stability, oscillation and bounde-ness character of positive solutions of the difference equation $X_{N+l}$ = $\alpha$ + ( $X_{N-1}$$^{P/)}$( $X_{N}$$^{P}$), n = 0, 1, … under specified conditions.s.tions.s.

• Journal of applied mathematics & informatics
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• v.30 no.1_2
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• pp.289-304
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• 2012

In this paper, we study asymptotic behaviour of solutions of the following higher order nonlinear dynamic equations $$S_n^{\Delta}(t,x)+{\delta}p(t)f(x(g(t)))=0$$ and $$S_n^{\Delta}(t,x)+{\delta}p(t)f(x(h(t)))=0$$ on an arbitrary time scale $\mathbb{T}$ with sup $\mathbb{T}={\infty}$, where n is a positive integer, ${\delta}=1$ or -1 and $$S_k(t,x)=\{\array x(t),\;if\;k=0,\\a_k(t)S_{{\kappa}-1}^{\Delta}(t),\;if\;1{\leq}k{\leq}n-1,\\a_n(t)[S_{{\kappa}-1}^{\Delta}(t)]^{\alpha},\;if\;k=n,$$ with ${\alpha}$ being a quotient of two odd positive integers and every $a_k$ ($1{\leq}k{\leq}n$) being positive rd-continuous function. We obtain some sufficient conditions for the equivalence of the oscillation of the above equations.

• Journal of the Korean Society of Combustion
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• v.20 no.1
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• pp.32-42
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• 2015

The combustion instability was experimentally investigated in model gas turbine combustor with dual swirl burner. When such instability occurs, a strong coupling between pressure oscillation and unsteady heat release excites a self-sustained acoustic wave which results in a loud sound, and can even cause fatal damage to the combustor and entire system. In present study, to understand the combustion instability with a premixed mixture, the detailed periods of pressure and heat release data in unstable flame mode were investigated by various measurement methods at relatively rich condition and lean condition near flammable limits. Also, to prepare the utilization of synthetic natural gas (SNG) fuel in gas turbine system, an investigation was conducted using a simulated SNG including methane as a reference fuel to examine the effects of $H_2$ content on flame stability. These results provide that the instability due to flash-back behaviour like CIVB phenomenon occurred at rich condition, while the repetition of relighting and extinction caused the oscillation of lean condition near flammable limit. From the analysis of $H_2$ content effects, it is also confirmed that the instability frequency is proportional to the laminar burning velocity at both rich and lean condition.