• Proceedings of the KSR Conference
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• 2003.10b
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• pp.397-402
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• 2003

Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment are defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.56-61
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• 2012

The dynamic instability and natural frequency of axially moving beam with an attached mass are investigated. Thus, the effects of an attached mass on the stability of the moving beam are studied. The governing equation of motion of the moving beam with an attached mass is derived from the extended Hamilton's principle. The natural frequencies are investigated for the moving beams via the Galerkin method under the simple support boundary. Numerical examples show the effects of the attached mass and moving speed on the stability of moving beam. Moreover, the lowest critical moving speeds for the simple supported conditions have been presented. The results can be used in the analysis of axially moving beams with an attached mass for checking the stability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.390.2-390
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• 2002

The stability ratio and vibrational amplitude of each tube inside a steam generator have different values. We estimate the characteristics of flow-induced vibration for CE type steam generator with various column and row number of the tube. To obtain the thermal-hydraulic data and stability ratio we use the ATHOS3 and PIAT-FEI/TE code respectively. It turns out that the steam generator has a bounded central zone which the distributed values of the stability ratio and the vibrational amplitude, and those values across the zone boundary become decreased.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.407-412
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• 2012

The dynamic instability and natural frequency of an axially moving pipe conveying fluid are investigated. Thus, the effects of fluid velocity and moving speed on the stability of the system are studied. The governing equation of motion of the moving pipe conveying fluid is derived from the extended Hamilton's principle. The eigenvalues are investigated for the pipe system via the Galerkin method under the simple support boundary. Numerical examples show the effects of the fluid velocity and moving speed on the stability of system. Moreover, the lowest critical moving speeds for the simply supported ends have been presented.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.389-394
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• 2014

This paper presents the effect of a reflective force computed from a first-order-hold method on the stability of a haptic system. A haptic system is composed of a haptic device with a mass and a damper, a virtual spring, a sampler and a sample-and-hold. The boundary condition of the maximum virtual stiffness is analytically derived by using the Routh-Hurwitz criterion and the condition shows that the maximum virtual stiffness is proportional to the square root of the mass and the damper of a haptic device and also is inversely proportional to the sampling time to the power of three over two. The effectiveness of the derived condition is evaluated by the simulation. When the reflective forces are computed by using the first-order-hold method, the maximum available stiffness to guarantee the stability is increased several hundred times as large as when the zero-order-hold method is applied.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.895-900
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• 1997

A Quench in cable-in-conduit (CIC) conductors is often initiated by a disturbance such as strand motion that generates a highly localized normal zone in a strand or a few strands of the CIC conductors. The localized normal zone causes current and heat transfer between a disturbed strand and neighboring strands. Electrical and thermal contact characteristics between strands thus have an effect on the transient stability of the CIC conductors. In this paper the effect of contact characteristics between strands on the CIC conductor stability is presented based on the measured heat transfer characteristics of supercritical helium (SHe) for the local heating. The quench and recovery processes of the strands for the abrupt and highly localized disturbance are analyzed at the boundary between quench and recovery.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.885-887
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• 1999

The piezoelectric ceramic resonator using length extensional vibration rather than contour extensional vibration in terms of the size is suitable for personal portable communication. In this paper, $Pb(Zr_{x}Ti_{l-x})O_{3}$ + r[wt%]$Cr_{2}O_{3}$ ceramics, x=0.56, 0.53, 0.50 (ie, Zr/Ti ratios = 56 /44, 53/47, 50/50) r=0, 0.3[wt %], were fabricated. Temperature stability of length extensional vibration mode of those specimens was investigated. Both crystal structure with rhombohedral phase in the case of no addition of $Cr_{2}O_{3}$ and crystal structure with morphotrophic phase boundary in case of additions of 0.3[wt %]$Cr_{2}O_{3}$ had the vest temperature stability and improved temperature stability through thermal aging.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.69-82
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• 1991

The dynamic stability of the long vertical beam subjected to the periodic axial load is investigated. As a solution method, the Galerkin's method is used to obtain a set of coupled Mathieu type equations. To obtain the stability chart, both the perturbation method and numerical method are used, and the results of the both methods are compared with each other. The stability regions for the various boundary conditions are obtained, Also the effects of the viscous damping, the mean tension and the multi-frequency parametric excitation are studied in detail.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.670-676
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• 2003

To investigate the group plugging effect the fluid-elastic instability analysis has been performed on various column and row number of the KSNP steam generator lutes. This study compares the stability ratio of the plugged tube with that of the intact one. The information on the thermal-hydraulic data of the steam generator have been obtained by using the ATHOS3-MOD1 code with and without the thermal energy transfer at the plugged region. Both of the boundary conditions of hot-leg temperature and feedwater mass flow rate are fixed for this investigation. From the results of this study the stability ratios inside the group plugging zone are decreased slightly. At the outside of group plugging zone, however, most of the stability ratios tend to be increased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.565-572
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• 2004

Numerical stability analysis of one-dimensional axial flow in solid rocket motors is performed based on the Euler equation coupled with an unsteady combustion equation of solid propellant. In order to check the numerical scheme, behavior of a standing wave in a closed tube is examined. A standing wave in solid rocket motor decays or grows depending on the total effect of propellant combustion, nozzle flow, and so on. The stability boundary of the fundamental mode standing wave is determined by changing one of the combustion parameters. In addition growth rates of the wave are calculated numerically in relatively low Mach number flow region for the motors with different port and nozzle throat diameters. The results obtained here agree well with the approximate solution. The same scheme is applied to a motor with shorter length and L＊-instability is observed.