• 대한기계학회논문집
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• 제10권2호
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• pp.247-256
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• 1986

본 연구에서는 종횡비가 0.2인 직각 밀폐용기내에서 소금물을 시험유체로 하여 양단의 온도 및 농도차가 수평방향으로 가해지는 경우(CASE 1,2) 밀폐용기내 에서의 유동현상과 열전달 특성을 온도 및 농도분포, 흐름의 가시화를 통해 실험적 으로 관찰, 조사하였다

• 한국공간구조학회논문집
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• 제18권3호
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• pp.105-116
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• 2018

The objective of this study is to investigate the response reducing effect of a seismic isolation system installed between 300m dome and supports under both horizontal and vertical seismic ground motion. The time history analysis is performed to investigate the dynamic behavior of single layer lattice domes with and without a lead rubber bearing seismic isolation system. In order to ensure the seismic performance of lattice domes against strong earthquakes, it is important to investigate the mechanical characteristics of dynamic response. Horizontal and vertical seismic ground motions cause a large asymmetric vertical response of large span domes. One of the most effective methods to reduce the dynamic response is to install a seismic isolation system for observing seismic ground motion at the base of the dome. This paper discusses the dynamic response characteristics of 300m single layer lattice domes supported on a lead rubber seismic isolation device under horizontal and vertical seismic ground motions.

• 한국과학교육학회지
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• 제33권1호
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• pp.193-207
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• 2013

이 연구는 지구와 달 표면에서 물체의 운동에 대한일반 중학생들과 과학영재학생들의 개념을 조사하였다. 연구 대상은 일반 중학교 중학생 1학년 61명, 2학년 51명, 3학년 51명 총 163명과 대학부속 과학영재교육원 중등 과학영재학생 32명으로 하였다. 연구 내용은 지구와 달 표면에서 연직, 경사면, 수평면에 따른 물체의 운동에 대한 개념으로 하였다. 각각 지구와 달 표면에서 크기는 같고 질량이 다른 두 물체를 동시에 놓거나, 같은 속력으로 위쪽으로 던지거나, 수평면에서 굴렸을 때 '어느 것이 먼저 도착하는가?'를 조사하였다. 지구와 달 동시 상황에서는 같은 물체를 지구와 달 표면에서 동시에 놓거나, 던지거나, 굴렸을 때 '어느 장소에 먼저 도착하는가?'를 조사하였다. 연구결과 과학영재학생들이 일반 중학생들 보다 지구 표면에서 연직, 경사면, 수평면의 모든 조건에서 물체의 운동에 대한 개념에 유의미한 차이가 있었고, 달 표면에서 연직 위 방향에서 물체의 운동에 대한 개념에 유의미한 차이가 있었다. 지구와 달 표면 동시 상황에서는 연직 아래 방향에서 물체의 운동에 대한 개념에 유의미한 차이는 없었고, 연직 위 방향, 경사면, 수평면에서 물체의 운동에 대한 개념에 유의미한 차이가 있었다. 연구 결과를 통해서 얻은 결론은 첫째, 지구와 달 표면에서 물체의 운동에 대한 설명을 할 때 진공에 대한 의미와 중력의 크기에 대한 학습이 먼저 이루어져야 한다. 둘째, 중학생들에게 다양한 상황과 조건에서 물체의 운동을 통합적으로 이해하도록 지도해야한다. 셋째, 중학생들은 상황을'동일시'하려는 사고 경향이 있다. 마지막으로 힘과 물체의 운동은 물리 영역에서 매우 중요한 단원이며, 교사가 물체의 운동을 설명할 때 위 결과들을 유념해서 가르쳐야 한다.

• 한국해양공학회지
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• 제28권2호
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• pp.119-125
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• 2014

A vertical planar motion mechanism(VPMM) test was used to increase the prediction accuracy for the maneuverability of an underwater glider model. To improve the accuracy of the linear hydrodynamic coefficients, the analysis techniques of a pure heave test and pure pitch test were developed and confirmed. In this study, the added mass and damping coefficient were measured using a VPMM test. The VPMM equipment provided pure heaving and pitching motions to the underwater glider model and acquired the forces and moments using load cells. As a result, the hydrodynamic coefficients of the underwater glider could be acquired after a Fourier analysis of the forces and moments. Finally, a motion control simulation was performed for the glider control system, and the results are presented.

• 대한조선학회논문집
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• 제47권4호
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• pp.496-507
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• 2010

It is well known that when a high-speed planing craft travels in following seas it experiences long-periodic motions due to low encounter frequency, and it often loses its course keeping stability. Therefore, it is necessary to study the sea-keeping performance and stability of it in the following seas. In this paper, the vertical motions of a planing craft were measured in following regular waves, and the test results were compared with the theoretical results. In the case of the same encounter frequency, non-dimensionalized motion amplitudes become larger as Froude number is higher, and non-dimensionalized motion amplitudes in head waves are larger than those in following waves. The mean values of the motions in following waves are similar to the running attitudes of a craft in calm water at the same Froude number.

• Earthquakes and Structures
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• 제10권1호
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• pp.179-190
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• 2016

A single rigid footing constructed on sandy-clay soil was modeled and analyzed using FLAC software under static conditions and vertical ground motion using three accelerograms. Dynamic analysis was repeated by changing the elastic and plastic parameters of the soil by changing the percentage of cement grouting (2, 4 and 6 %). The load-settlement curves were plotted and their bearing capacities compared under different conditions. Vertical settlement contours and time histories of settlement were plotted and analyzed for treated and untreated soil for the different percentages of cement. The results demonstrate that adding 2, 4 and 6 % of cement under specific conditions increased the dynamic bearing capacity 2.7, 4.2 and 7.0 times, respectively.

• Journal of Biosystems Engineering
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• 제14권4호
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• pp.242-250
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• 1989

The performance of a vertical type centrifugal distributor of granular materials was studied by means of mathematical models and experimental investigations. To develop the mathematical description of particle motion, some assumptions were made. The distribution process consisted of three stages: the entrance of a particle to the blade, the motion of the particle on the blade, and the motion of the particle in the air. The physical properties of fertilizer, which affected the particle motion, were investigated: bluk density, coefficient of friction, coefficient of restitution, and particle size distribution. The particle motion were simulated by using a computer. A prototype distributor was designed and constructed for experimental tests. The following conclusions were drawn from the computer simulation and experiment results. 1. The fertilizer may slide or roll at the point of contact when they impact on the blade and move along the blade. 2. The interaction among fertilizers may prevent them from bouncing. 3. When fertilizers roll on the blade, rolling resistance is one of the factors affecting the particle's motion. 4. The trajectory angle and position of fertilizers from a disc depend on the blade position and particle shape, but the rotating speed of the disc affected them only slightly.

• 대한전기학회논문지
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• 제41권4호
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• pp.339-345
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• 1992

Estimates of maximum amplitudes of conductor galloping are needed in order to determine appropriate phase-to-phase clearances on the overhead lines. One approach to obtaining these estimates is through the use of mathematical models of conductor galloping. Unfortunately, the models that consider both vertical conductor motion (Den Hartog type) and torsional conductor motion are often too complex for practical use. However, the estimates of maximum amplitude obtained from galloping models that assume only vertical (Den Hartog type) conductor motion tend to be too conservative. This paper presents the DF method to obtain the estimates of the amplitude and the frequency of galloping limit cycle, along with the wind pressure at which they occur, from a nonlinear dynamic model that considers both Den Hartog type and torsional conductor motion. From these results, the useful data for the line design guide and further insight into the mechanism of the conductor galloping are obtained.

• 한국해양공학회지
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• 제33권1호
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• pp.10-16
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• 2019

The aim of this study was to improve the vertical motion performance of floating marina structures and to optimize the shapes of the structures for the Korea coastal environment. The floating body is connected to a plate-shaped submerged body through a connecting line under the water that has a stiff spring that serves to reduce the heave response. This system, which has two degrees of freedom, was modelled to analyze the interaction between the floating body and the submerged body. The vertical motion of the two-body system was compared with the motion of a single body to verify that the system could perform as an optimized model.

• 대한기계학회논문집
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• 제18권9호
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• pp.2454-2462
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• 1994

The effects of thermal stratification on the flow of a stratified fluid past a heated circular cylinder were examined in a wind tunnel. Turbulent intensities, rms values of temperature and turbulent convective heat flux distributions in the heated cylinder wake with and without thermal stratification were measured by using a hot-wire and cold-wire combination probe. A phase averaging method was also used to estimated coherent motion in the near wake. It is found that the vertical turbulent motion in the stably stratified flow case dissipates faster than that of the neutral case, i.e., vertical growth of vortical structure is suppressed under the strongly stratified condition. The coherent motion of temperature makes a large contribution like velocity coherent motion. However, the coherent motions of temperature fluctuation become very different with the change of experimental conditions, though the velocity coherent motions are quite similar in all experimental conditions.