• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.291-300
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• 1999

An idealized analytical model is proposed to estimate the effects of restrainer upon global response behaviors of a bridge system under seismic excitations. Pounding actions between adjacent vibration units and friction at movable supports are introduced in addition to other phenomena such as nonlinear behaviors of pier, motions of the foundation and abutment to achieve the better prediction of the bridge motion. The applied restrainer is assumed to be a dead-band system, which has the force clearance and the linear-elastic force. Using the proposed model, the dynamic characteristics of a bridge system retrofitted by restrainers is examined, and the effects of stiffness and clearance length of restrainer is also investigated. The main effect of the application of restrainers is found to reduce the relative displacements and the trend becomes greater with the shorter clearance length except between pier units. It is found that the relative displacements between abutment and adjacent pier units are decreased as the stiffness of restrainer increases, but almost independent upon the stiffness increments of restrainer. However, the relative displacements between pier units tend to be increased due to the applications of the restrainers.

• Wind and Structures
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• v.32 no.1
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• pp.31-46
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• 2021

The current research deals with, stability/instability and cylindrical composite nano-scaled shell's resonance frequency filled by graphene nanoplatelets (GPLs) under various thermal conditions (linear and nonlinear thermal loadings). The piece-wise GPL-reinforced composites' material properties change through the orientation of cylindrical nano-sized shell's thickness as the temperature changes. Moreover, in order to model all layers' efficient material properties, nanomechanical model of Halpin-Tsai has been applied. A functionally modified couple stress model (FMCS) has been employed to simulate GPLRC nano-sized shell's size dependency. It is firstly investigated that reaching the relative frequency's percentage to 30% would lead to thermal buckling. The current study's originality is in considering the multifarious influences of GPLRC and thermal loading along with FMCS on GPLRC nano-scaled shell's resonance frequencies, relative frequency, dynamic deflection, and thermal buckling. Furthermore, Hamilton's principle is applied to achieve boundary conditions (BCs) and governing motion equations, while the mentioned equations are solved using an analytical approach. The outcomes reveal that a range of distributions in temperature and other mechanical and configurational characteristics have an essential contribution in GPLRC cylindrical nano-scaled shell's relative frequency change, resonance frequency, stability/instability, and dynamic deflection. The current study's outcomes are practical assumptions for materials science designing, nano-mechanical, and micromechanical systems such as micro-sized sensors and actuators.

• Steel and Composite Structures
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• v.46 no.1
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• pp.15-31
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• 2023

Organic solar cells utilized natural polymers to convert solar energy to electricity. The demands for green energy production and less disposal of toxic materials make them one of the interesting candidates for replacing conventional solar cells. However, the different aspects of their properties including mechanical strength and stability are not well recognized. Therefore, in the present study, we aim to explore the chaotic responses of these organic solar cells. In doing so, a specific type of organic solar cell constructed from layers of material with different thicknesses is considered to obtain vibrational and chaotic responses under different boundaries and initial conditions. A square plate structure is examined with first-order shear deformation theory to acquire the displacement field in the laminated structure. The bounding between different layers is considered to be perfect with no sliding and separation. On the other hand, nonlocal elasticity theory is engaged in incorporating the structural effects of the organic material into calculations. Hamilton's principle is adopted to obtain governing equations with regard to boundary conditions and mechanical loadings. The extracted equations of motion were solved using the perturbation method and differential quadrature approach. The results demonstrated the significant effect of relative glass layer thickness on the chaotic behavior of the structure with higher relative thickness leading to less chaotic responses. Moreover, a comprehensive parameter study is presented to examine the effects of nonlocality and relative thicknesses on the natural frequency of square organic solar cell structure.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1779-1784
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• 1991

The problem of fine manipulation is considered in this paper. By fine manipulation, we mean the positioning of the object relative to the palm as opposed to gross manipulation by the arm. The compliance in the fingers and the object is modeled by linear springs. It is shown that the motion of the fingers and object can be predicted by minimizing a quadratic objective function. A method for simulating position control algorithms is developed.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.21-26
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• 1996

Recently several PWR Nuclear Plant experienced fuel rod fretting wear failures due to Flow Induced Vibration. When such multi-span supported fuel assembly has vibration excitation, it is important to know how fretting wears are progress and when the fuel rods are start to failure. In this study, we estimate the amount of wear depth using Archard theory when the fuel rod starts to relative motion against spacer grid dimples.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.289-292
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• 1994

In this paper, the equations of motion are constructed systematically for multibody systems containing closed kinematic loops. For the displacement analysis of the closed loops, we introduce a new mixed coordinates by adding to the reference coordinates, relative coordinates corresponding to the degrees of freedom of the system. The mixed coordinates makes easy derive the explicit closed form solution. The explicit functional relationship expressed in closed form is of great advantages in system dimension reduction and no need of an iterative scheme for the displacement analysis. This forms of equation are built up in the general purpose computer program for the kinematic and dynamic analysis of multiboty systems.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1683-1690
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• 2001

A Lagrangian stochastic model is adopted for the calculations of turbulent dispersion in turbulent channel flows. Dispersion of a fluid particle and relative dispersion between two particles released at the sane location are investigated and compared with the classical seating relations for homogeneous turbulence. The viscous effect is realized by adding a Browinian random walk to the calculation of the position of a particle. The near-wall accumulation of particles is examined.

• Tribology and Lubricants
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• v.4 no.1
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• pp.74-80
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• 1988

For an analytic investigation on the dynamic behaviour of the eccentric piston and roller in the cylinder of small rotary vane compressors the hydrodynamic lubrication theory is opplied, analogous to the dynamic analysis of a engine bearing. An adequate modification of the equation of journal motion permits stable convergencies of the numeric calculation of the journal orbits. The increase of the outer diameter of the roller and the eccentricity of the piston gives a relative large decrease of the minimum gap between the roller and cylinder.

• Journal of the Korean Society of Marine Environment & Safety
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• v.4 no.2
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• pp.25-33
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• 1998

This paper deals with PC-based ship handling simulator, which is now widely utilized not only for total assessment of safety in harbour area but also for training purpose. The suitable mathematical model for low advance speed manoeuvre is treated with the effects of current, wind, wave, tug force and water depth. We adopt 3 dimensional graphic technique for perspective representation of relative ship motion. Some graphical panels on the screen are devised for data input/output or ship manoeuvring information. We show the real time simulation of berthing menoeuvre applied to Pusan harbour as an example.

• Nuclear Engineering and Technology
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• v.29 no.6
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• pp.451-458
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• 1997

Signal shapes from a closed-ended coaxial HPGe detector are investigated by numerical methods. The detector used in this study has a volume of 72 ㎤ with relative efficiency of 15%. The electric field and potential distributions in the detector are determined by solving the Poisson equation at the depletion and operating bias. Hence the time dependent signal shapes induced on the electrode are obtained from the energy balance consideration and tv solving the equation of motion for the charge carriers. For various initial positions of a charge carrier pair, the collection times of induced charge vary in the range of 70 - 404 nsec.