• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.436-438
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• 2003

Wind-induced oscillations are known to cause damage to the conductors and related hardware through fatigue, clashing of the bundled conductors and bolt loosening. Wake-induced oscillations have been known since the advent of bundled conductors, they are caused by aerodynamically unstable forces acting on the leeward conductors in the wake of the windward conductors, They take the form of horizontal galloping, snaking or rolling, in which case all subconductors move together in unison. They can also take the form of the subspan oscillation, which appear as elliptical motions of the subconductors moving out of phase, mainly in the horizontal plane within a subspan. In order to decrease amplitudes of the oscillation, this paper examines the application status of the spacer dampers and suggests proper installation methods.

• 천문학회보
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• 제43권2호
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• pp.45.3-46
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• 2018

Oscillations in a sunspot are easily detected through the Doppler velocity observation. Although the sunspot oscillations look erratic, the wavelet analysis show that they consist of successive wave packets which have strong power near three or five minutes. Previous studies found that 3-min oscillation at the chromosphere is a visual pattern of upward propagating acoustic waves along the magnetic field lines. Resent multi-height observations help this like vertical study, however, we also focus on horizontal facet to extend three dimensional understand of sunspot waves. So, we investigate a fragmented sunspot expected to have complex wave profiles according to the positions in the sunspot observed by the Fast Imaging Solar Spectrograph. We choose 4 points at different umbral cores as sampling positions to determine coherence of oscillations. The sets of cross-correlation with three and five minutes bandpass filters during a single wave packet reveal interesting results. Na I line show weak correlations with some lags, but Fe I and Ni I have strong correlations with no phase difference over the sunspots. It is more remarkable at Ni I line with 3-min bandpass that all sets of cross-correlation look like the autocorrelation. We can interpret this as sunspot oscillations occur spontaneously over a sunspot at photosphere but not at chromosphere. It implies a larger or deeper origin of 3-min sunspot oscillation.

• 전기학회논문지P
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• 제58권4호
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• pp.447-450
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• 2009

In order to protect conductors from oscillations or vibrations due to winds, spacer dampers are installed on overhead transmission lines. Generally the spacer damper clamp can move slightly according to oscillation directions, namely in longitudinal, vertical & horizontal directions. This is for reducing fatigue phenomena of the conductor. But the high longitudinal- displacement of the clamp raises a doubt for its necessity. Then this paper carried out oscillation tests by using 4 bundle test lines, to know the relation between longitudinal displacement and oscillation. and suggests design necessity of the longitudinal articulation part for spacer damper clamps.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2094-2095
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• 2008

In order to protect conductors from oscillations or vibrations due to winds, spacer dampers or spacers are installed on bundled conductors in overhead transmission lines. Generally the spacer damper clamp can move slightly according to oscillation directions, namely conductor direction, vertical & horizontal direction This is for reducing fatigue phenomena of the clamps. Sometimes movement of the clamp to conductor direction raises a doubt for its necessity. Then this paper carried out oscillation tests to know clamp displacement due to the subspan oscillation.

• 한국환경과학회지
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• 제8권6호
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• pp.645-652
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• 1999

In order to simulate and investigate the major characteristics of El Nino/Southern Oscillation(ENSO) and Madden Jullian Oscillation(MJO), an intermediate type atmosphere-ocean coupled model is developed and their results are examined. The atmosphere model is a time-dependent non-linear perturbation moist model which can determine the internal heating for itself. The counterpart of the atmosphere model is GCM-type tropical ocean model which has fine horizontal and vertical grid resolutions. In the coupled experiment, warm SST anomaly and increased precipitation and eastward wind and current anomalies associated with ENSO and MJO are properly simulated in Pacific and Indian Oceans. In spite of some discrepancies in simulation MJO, the observed atmospheric and oceanic low-frequency characteristics in the tropics are successfully identified. Among them, positive SST anomalies centered at the 100m-depth of tropical eastern-central Pacific due to the eastward advection of warm water and reduced equatorial upwelling, and negative anomalies in the Indian and western Pacific seem to be the fundamental features of tropical low-frequency oscillations.

• Smart Structures and Systems
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• 제2권4호
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• pp.329-337
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• 2006

This paper illustrates an analytical investigation of the vibration parameters of buildings on sliding seismic isolation bearings with elastic limiters of the relative displacement. The installation scheme of sliding bearings and elastic limiters for the separate unit of a 4 storey hospital building with brick walls is designed. The analysis of the vibrations of the hospital building is conducted for harmonic base excitation.

• 대한조선학회지
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• 제13권2호
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• pp.1-12
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• 1976

Linearized motions of as axisymmetrical dock freely floating in a regular plane wave are discussed. An extension of the Bessho variational principle(Bessho[3]) is derived to obtain a numerical procedure for a solution of the boundary value problem associated with the fluid motion. The added mass and the damping coefficients for a circular dock in vertical(heave) and horizontal(surge) oscillations are evaluated numerically, and the resulte seems to be satisfactory.

• 천문학회보
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• 제39권1호
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• pp.71.2-71.2
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• 2014

For better understanding of the physics of pores, we have investigated horizontal and vertical motions of plasma in a pore obtained on 2013 August 24 by using high time and spatial resolution data from the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer the LOS velocity by applying the bisector method to the wings of Ca II 8542 ${\AA}$ profile, and inspect oscillations of the intensity and the LOS velocity in the pore. In this presentation, we discuss the physical implications of our results in view of a connection between LOS and horizontal plasma flows in a concentrated magnetic flux.

• 한국물환경학회지
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• 제31권4호
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• pp.367-376
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• 2015

The momentum and kinetic turbulent energy carried by the wind to a stratified lake lead to basin-scale motions, which provide a major driving force for vertical and horizontal mixing. A three-dimensional (3D) hydrodynamic model was applied to Lake Tahoe, located between California and Nevada, USA, to simulate the dominant basin-scale internal waves in the deep lake. The results demonstrated that the model well represents the temporal and vertical variations of water temperature that allows the internal waves to be energized correctly at the basin scale. Both the model and thermistor chain (TC) data identified the presence of Kelvin modes and Poincare mode internal waves. The lake was weakly stratified during the study period, and produced large amplitude (up to 60 m) of internal oscillations after several wind events and partial upwelling near the southwestern lake. The partial upwelling and followed coastal jets could be an important feature of basin-scale internal waves because they can cause re-suspension and horizontal transport of fine particles from nearshore to offshore. The internal wave dynamics can be also associated with the distributions of water quality variables such as dissolved oxygen and nutrients in the lake. Thus, the basin-scale internal waves and horizontal circulation processes need to be accurately modeled for the correct simulation of the dissolved and particulate contaminants, and biogeochemical processes in the lake.

• International Journal of Ocean System Engineering
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• 제4권1호
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• pp.19-28
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• 2014

The tension leg platform (TLP) is a vertically moored structure with excess buoyancy. The TLP is regarded as moored structure in horizontal plan, while inherit stiffness of fixed platform in vertical plane. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of tethers length and wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e. 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether length, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about that is significantly dependent on tether length.