• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.202-206
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• 2001

The paper presents the dynamic stability of a vertical cantilevered pipe conveying fluid and having an intermediate translational linear spring. The translational linear spring can be located at an arbitrary position. Governing equations are derived by energy expressions, and numerical technique using Galerkin's method is applied to discretize the equations of small motion of the pipe. Effects of linear spring supports on the dynamic stability of a vertical cantilevered pipe conveying fluid are fully investigated for various locations and magnitudes of the translational linear spring.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1202-1206
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• 2001

The paper presents the dynamic stability of a vertical cantilevered pipe conveying fluid and having translational linear spring supports. Real pipe systems may have some elastic hanger supports or other mechanical attached parts., which can be regarded as attached spring supports. Governing equations are derived by energy expressions, and numerical technique using Galerkin's method is applied to discretize the equations of small motion of the pipe. Effects of spring supports on the dynamic stability of a vertical cantilevered pipe conveying fluid are fully investigated for various locations and spring constants of elastic supports.

• 지질공학
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• 제30권2호
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• pp.175-184
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• 2020

국내에서는 비탈면을 대상으로 유사정적해석 시 수평 지진계수에 대한 적용 규정과 적용 사례들이 많이 있지만 연직 지진계수에 대한 규정이나 사례는 미비한 실정이다. 본 연구에서는 연직 지진계수의 영향도를 검토하고자 단양군 단양읍 ◯◯리를 대상으로 현장조사 및 실내시험을 수행하고, 이를 반영하여 무한사면 안정해석 기반의 유사정적 사면안정해석을 수행하였다. 분석 결과 지진규모가 5 이하인 경우에는 연직 지진계수의 영향이 거의 없는 것으로 분석되며, 지진규모가 6 이상인 경우에는 연직 지진계수가 안전율 1.1 이하의 불안정 영역을 크게 증가시키는 것으로 나타난다. 이러한 경향은 강우가 없는 조건보다 강우가 있는 조건에서 더욱 뚜렷하게 나타난다.

• 한국대기환경학회지
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• 제12권4호
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• pp.369-376
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• 1996

Major atmospheric stability classification methods were evaluated with meteorological data obtained by scoustic sounding profiler (SODAR/RASS) in Seoul. The Psequill classificatio method, the method most widely used because of its good agreement in respect of synoptic scope under the steady state, fails to describe the time lag, the response time on stability by heating or cooling caused by daily insolation or noctrunal surface radiation. Horizontal and vertical standard deviation of wind fluctuation $(\sigma_A and \sigma_E)$ method tend to classify night-time stable condition (E, F class) into unstable condition (A, B class). The classification matrix tables for Vogt's vertical temperature difference and wind speed using method ($\Delta$T $\cdot$ U) and bulk Richardson number (Rb) were amended for practical use over Seoul. The modified tables for $\Delta$T $\cdot$ U and Rb method were made by using comprehensive frequency distribution from Pasquill's method and other existing results, and the correlation coefficient(r) was equal to 0.829. It was confirmed that atmospheric stability could be changed with monitoring site characteristics, height and vertical difference between sensors of monitoring station, and classification method itself.

• 한국대기환경학회지
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• 제2권1호
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• pp.23-31
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• 1986

Meteorological Measurement was performed for evaluation of the horizontal vertical standard deviation $(\sigma_y, \sigma_z)$, surface roughness length and stmospheric stability during the period of March to October 1985 The major results are as follows; 1) The average value of surface roughness length was 144cm at NEPI. 2) In frequency distribution of atmospheric stability, neutral state (D class) was dominent in Seoul (29%) and Pusan (30%). Unstable states (A. B. C. class) were 26% in Seoul and 24% in Pusan. Also, stable states (D. E. F class) were 74% in Seoul and 76% in Pusan. 3) Standard deviations of horizontal ad vertical direction were evaluated as a function of downwind distance and atmospheric stability at NEPI, Jamsil and Pujeondong (Pusan). Standard deviation of horizontal direction was largest at NEPI among 3 areas because of mechanical turbulence resulting from difference of surface roughness length.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.647-651
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• 2000

This paper deals with the dynamic stability of a vertical cantilevered pipe conveying fluid and having two attached masses. Some valves or other mechanical components in pipe systems can be regarded as attached lumped masses. Governing equations are derived by energy expressions, and numerical technique using Galerkin's method is applied to discretize the equations of small motion of the pipe. Effects of attached masses on the dynamic stability of a vertical cantilevered pipe conveying fluid are investigated for various locations and magnitudes of the attached lumped masses.

• Geomechanics and Engineering
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• 제2권2호
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• pp.71-88
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• 2010

Soil nailing technique is being widely used for stabilization of vertical cuts because of its economic, environment friendly and speedy construction. Global stability and lateral displacement are the two important stability criteria for the soil nail walls. The primary objective of the present study is to evaluate soil nail wall stability criteria under the influence of in-situ soil variability. Finite element based numerical experiments are performed in accordance with the methodology of $2^3$ factorial design of experiments. Based on the analysis of the observations from numerical experiments, two regression models are developed, and used for reliability analyses of global stability and lateral displacement of the soil nail wall. A 10 m high prototype soil nail wall is considered for better understanding and to highlight the practical implications of the present study. Based on the study, lateral displacements beyond 0.10% of vertical wall height and variability of in-situ soil parameters are found to be critical from the stability criteria considerations of the soil nail wall.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.490-496
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• 1995

A four-legged mobile robot can move on the plain terrain with mobility and stability, but if there exist any obstacles on the terrain of the motion direction, it takes extra times for a mobile robot to cross those obstacles and the stability should be considered during motion. The main objevtive is the study of a quadruped which can cross obstacles with better mobility, stability and fuel economy than any other wheeled or tracked vehicles. Vertical step, isolated wall and ditch are the basic obstacles and by understanding those three cases perfectly, a quadruped can move on any mixed rough terrain as 4-legged animal moves. Each leg of a determine the crossing capability in a static analysis. A quadruped can be simplified with links and joints. By applying the research method, a quadruped can determine the control procedures as soon as it receives the terrain informations from scanner and finally can be moved as animals move with mobility and stability.

• 대한기계학회논문집
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• 제15권2호
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• pp.630-643
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• 1991

The hydrodynamic stability equations are formulated for buoyancy-induced flows adjacent to a vertical, planar, isothermal surface in cold pure water. The resulting stability equations, when reduced to ordinary differential equation by a similarity transformation, constitute a two-point boundary-value(eigenvalue) problem, which was numerically solved for various values of the density extremum parameter R=( $T_{m}$ - $T_.inf./) / ( $T_{o}$ - $T_.inf./). These stability equations have been solved using a computer code designed to accurately solve two-point boundary-value problems. The present numerical study includes neutral stability results for the region of the flows corresponding to 0.0.leq. R. leq.0.15, where the outside buoyancy force reversals arise. The results show that a small amount of outside buoyancy force reversal causes the critical Grashof number $G^*/ to increase significantly. A further increase of the outside buoyancy force reversal causes the critical Grashof number to decrease. But the dimensionless frequency parameter $B^*/ at $G^*/ is systematically decreased. When the stability results of the present work are compared to the experimental data, the numerical results agree in a qualitative way with the experimental data.erimental data.

• 제어로봇시스템학회논문지
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• 제18권2호
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• pp.76-80
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• 2012

This paper demonstrates how to implement inherent pitching stability in an insect-mimicking flapping-wing system for vertical takeoff. Design and fabrication of the insect-mimicking flapping-wing system is briefly described focusing on the recent modification. Force produced by the flapping-wing systems is estimated using the UBET (Unsteady Blade Element Theory) developed in the previous work. The estimation shows that the wing twist placed in the modified system can improve thrust production for about 10 %. The estimated thrust is compared with the measured thrust, which proves that the UBET provides fairly good estimations for the thrust produced by the flapping-wing systems. The vertical takeoff test shows that inherent pitching stability can be implemented in an insect-mimicking flapping-wing system by aligning the aerodynamic force center and center of gravity.