• Title/Summary/Keyword: free motion

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Numerical Simulation of Two-dimensional Floating Body Motion in Waves Using Particle Method (입자법에 의한 파랑중 2차원 부유체 운동 시뮬레이션)

  • Jung, Sung-Jun;Park, Jong-Chun;Lee, Byung-Hyuk;Ryu, Min-Cheol;Kim, Yong-Soo
    • Journal of Ocean Engineering and Technology
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    • v.22 no.2
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    • pp.20-27
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    • 2008
  • A moon-pool is a vertical well in a floating barge, drilling ship, or offshore support vessel. In this study, numerical simulation of two-dimensional moon-pool flaw coupled with a ship's motion in waves is carried out using a particle method, the so-called MPS method. The particle method, which is recognized as one of the gridless methods, was developed to investigate nonlinear free-surface motions interacting with structures. The method is more feasible and effective than convectional grid methods in order to solve a flaw field with complicated boundary shapes.

FINITE SPEED OF PROPAGATION IN DEGENERATE EINSTEIN BROWNIAN MOTION MODEL

  • HEVAGE, ISANKA GARLI;IBRAGIMOV, AKIF
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.26 no.2
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    • pp.108-120
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    • 2022
  • We considered qualitative behaviour of the generalization of Einstein's model of Brownian motion when the key parameter of the time interval of free jump degenerates. Fluids will be characterised by number of particles per unit volume (density of fluid) at point of observation. Degeneration of the phenomenon manifests in two scenarios: a) flow of the fluid, which is highly dispersing like a non-dense gas and b) flow of fluid far away from the source of flow, when the velocity of the flow is incomparably smaller than the gradient of the density. First, we will show that both types of flows can be modeled using the Einstein paradigm. We will investigate the question: What features will particle flow exhibit if the time interval of the free jump is inverse proportional to the density and its gradient ? We will show that in this scenario, the flow exhibits localization property, namely: if at some moment of time t0 in the region, the gradient of the density or density itself is equal to zero, then for some T during time interval [t0, t0 + T] there is no flow in the region. This directly links to Barenblatt's finite speed of propagation property for the degenerate equation. The method of the proof is very different from Barenblatt's method and based on the application of Ladyzhenskaya - De Giorgi iterative scheme and Vespri - Tedeev technique. From PDE point of view it assumed that solution exists in appropriate Sobolev type of space.

Analysis of Dynamic Behavior of Flexible Rectangular Liquid Containers by the Coupled Boundary Element-Finite Element Method (경계요소-유한요소 연계법에 의한 구형 수조구조물의 동적거동 특성해석)

  • Koh, Hyun Moo;Park, Jang Ho;Kim, Jaekwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.5
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    • pp.1033-1042
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    • 1994
  • Dynamic behavior of flexible rectangular liquid containers is analyzed by a two-dimensional coupled boundary element-finite element method. The irrotational motion of inviscid and incompressible ideal fluid is modeled by boundary elements and the motion of structure by finite elements. A singularity free integral formulation is employed for the implementation of boundary element method. Coupling is performed by using compatibility and equilibrium conditions along the interface between the fluid and structure. The fluid-structure interaction effects are reflected into the coupled equation of motion as added fluid mass matrix and sloshing stiffness matrix. By solving the eigen-problem for the coupled equation of motion, natural frequencies and mode shapes of coupled system are obtained. The free surface sloshing motion and hydrodynamic pressure developed in a flexible rectangular container due to horizontal and vertical ground motions are computed in time domain.

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The effects of scaling factors and quantization in sensors on free motion of teleoperation system

  • Hwang, Dal-Yeon;Cho, SangKyu;Park, Sanguk
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.1512-1515
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    • 1997
  • One of the advantages of master-slave teleoperation is scaling concept such as position scaling, force scaling Meanuhile, lots of quantization effects are generated from position and force sensors in the master and slave manipulator. In this paper, to show the output error caused by the quantizaion effects from the position sensor and position scaling factor, simulation is done for free motion without contact in slave side. Transfer functiion model in which the quantization effect is assumed to be a disturbance input to the system is derived. Model shows that Jacobian, scaling factors, and controller affect the output by quantization effects form esnsors. One dof master and slave are used for simulation. In our study, the higher sensor resolution decreases the output error form quantization. Scaling factors can amplify the quantizatiion effects form the sensors in master and slave manipulators.

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An analytical solution for free vibration of functionally graded beam using a simple first-order shear deformation theory

  • Larbi, Latifa Ould;Hadji, Lazreg;Meziane, Mohamed Ait Amar;Adda Bedia, E.A.
    • Wind and Structures
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    • v.27 no.4
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    • pp.247-254
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    • 2018
  • In this paper, a simple first-order shear deformation theory is presented for dynamic behavior of functionally graded beams. Unlike the existing first-order shear deformation theory, the present one contains only three unknowns and has strong similarities with the classical beam theory in many aspects such as equations of motion, boundary conditions, and stress resultant expressions. Equations of motion and boundary conditions are derived from Hamilton's principle. Analytical solutions of simply supported FG beam are obtained and the results are compared with Euler-Bernoulli beam and the other shear deformation beam theory results. Comparison studies show that this new first-order shear deformation theory can achieve the same accuracy of the existing first-order shear deformation theory.

A Numerical Study on the Toxic Gaseous and Solid Pollutant Dispersion in an Open Atmosphere (고-기상 유해물질 대기확산에 관한 수치해석)

  • 이선경;송은영;장동순
    • Journal of the Korean Society of Safety
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    • v.9 no.1
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    • pp.146-154
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    • 1994
  • A series of numerical calculations are performed in order to investigate the dispersion mechanism of toxic gaseous and solid pollutants in extremely short-term and short range. The calculations are carried out in an open space characterized by turbulent boundary layer. The simulation is made by the use of numerical model, in which a control-volume based finite difference method is used together with the SIMPLEC algorithm for the resolution of the pressure-velocity coupling problem. The Reynolds stresses are solved by two-equation, k-$\varepsilon$ model modified for buoyancy. The major parameters consider-ed in this study are temperature, velocity and Injection height of toxic gases, environmental conditions such as temperature and velocity of free stream air, and topographic factor. The results are presented and discussed in detail. The flow field is commonly characterized by the formation of a strong recirculation zone due to the upward motion of the hot toxic gas and ground shear stress. The driving force of the upward motion is explained by the effect of thermal buoyancy of hot gas and the difference of inlet velocity between toxic gas and free stream.

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A Multi-Axis Contour Error Controller for High-Speed/High-Precision Machining of Free form Curves (고속 고정밀의 자유곡선 가공을 위한 다축 윤곽오차 제어)

  • 이명훈;최정희;이영문;양승한
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.4
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    • pp.64-71
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    • 2004
  • The growing need for higher precision and productivity in manufacturing industry has lead to an increased interest in computer numerical control (CNC) systems. It is well known fact that the cross-coupling controller (CCC) is an effective method for contouring applications. In this paper, a multi-axis contour error controller (CEC) based on a contour error vector using parametric curve interpolator is introduced. The contour error vector is a vector from the actual tool position to the nearest point on the desired path. The contour error vector is the closest error model to the contour error. The simulation results show that the CEC is more accurate than the conventional CCC for a biaxial motion system. In addition, the experimental results on 3-axis motion system show that the CEC is simply applied to 3-axis motions and contouring accuracy is significantly improved.

Vibration of Elevator Rope with a Spring-mass System at the Tip (끝 단에 스프링-질량계가 연결된 엘리베이터 로프의 진동)

  • Kwak, Moon K.;Han, Sangbo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.4
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    • pp.317-323
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    • 2014
  • This study is concerned with the free vibration analysis of an inextensible uniform rope with a spring-mass system at the tip. The rope is hanged vertically in a gravitational field. This problem is related to the free vibration of an elevator rope connected to an elevator cage. The equation of motion and the corresponding boundary conditions are derived by using the Hamilton's principle. The general solution of the governing equation of motion is expressed in terms of Bessel functions. The characteristic equation was derived by applying the boundary conditions. The characteristic values which are in fact non-dimensionalized natural frequencies were obtained numerically. The effects of mass and spring constant were investigated. The numerical results show how the tip mass and spring affect the natural frequencies of the rope.

A Study on Application of PIV to Sloshing Phenomenon inside Rectangular Tank (장방형탱크 내부 슬로싱 현상에 관한 PIV적용에 관한 연구)

  • Kim, K.S.;Choi, J.Y.;Cho, D.H.
    • Proceedings of KOSOMES biannual meeting
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    • 2009.06a
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    • pp.85-86
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    • 2009
  • The sloshing phenomenon can be defined as the nonlinear movement of the free-surface of liquids inside tanks. It generates dynamic loads on the tank structure and thus becomes a problem of relative importance in the design of marine structures. The present study describes a experiment of the sloshing of flows with free-surface which contained in a rectangular tank moving in pitching motion.

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Lift-Off Voltage and Partial Discharge Characteristics of Free Metallic Particles in GIS (GIS 내 금속입자의 부상전압과 부분방전특성 연구)

  • Yun, Jin-Yeol;Han, Sang-Ok
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.2
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    • pp.127-132
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    • 1999
  • Both motion of free metallic particles from which most GIS internal failures are caused and partial discharges from the particles were examined using EHV GIS test chamber. Effects from particle length and gas pressure which are main factors to lead to breakdown failure were investigated theoretically and experimentally. Magnitude of both lift-off voltage and partial discharge inception voltage were measured respectively and, through these measurements, this paper showed the possibility of predicting breakdown fault and of taking action to prevent the fault in advance. The measurement of partial discharge when the particles began to move could be adopted to decide minimum sensitivity in developing predictive diagnostic equipments. Both the amount of apparent discharge and real discharge in GIS were examined theoretically and experimentally, then experimental results were analyzed on the basis of the theory.

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