• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.1
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• pp.17-35
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• 2016

In this study, the dynamic behaviour of a rotating Timoshenko beam when under the actions of a variable magnitude load moving at non-uniform speed is carried out. The effect of cross-sectional dimension and damping on the flexural motions of the elastic beam was neglected. The coupled second order partial differential equations incorporating the effects of rotary and gyroscopic moment describing the motions of the beam was scrutinized in order to obtain the expression for the dynamic deflection and rotation of the vibrating system using an elegant technique called Galerkin's Method. Analyses of the solutions obtained were carried out and various results were displayed in plotted curve. It was found that the response amplitude of the simply supported beam increases with an increase in the value of the foundation reaction modulus. Effects of other vital structural parameters were also established.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.106-113
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• 1996

This paper presents a modeling of undersea robot manipulators and a control scheme appropriate for manipulating the manipulators working under the unstrcuctured sea water environment. Under the sea, the added mass and added moment of inertia, buoyancy, and drag forces should be considered in modeling the dynamics of the robot manipulators. Due to the complexity of them, the desired dynamics of manipulators can not be accomplished by the conventional control schemes. Hence, a sliding mode control is applied to control the modeling error.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.35-42
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• 2003

This paper provides the first known flexural vibration data for thick (Mindlin) rectangular plates having V-notches. The V-notch has bending moment and shear force singularities at its sharp corner due to the transverse vibratory bending motion. Based upon Mindlin plate theory, in which transverse shear deformation and rotary inertia effects are considered, the Ritz procedure is employed with a hybrid set of admissible functions assumed for the rotational and transverse vibratory displacements. This set includes: (1) a mathematically complete set of admissible algebraic-trigonometric polynomials which guarantee convergence to exact frequencies as sufficient terms are retained; and (2) an admissible set of Mindlin corner functions which account for the bending moment and shear force singularities at the sharp corner of the V-notch. Extensive convergence studies demonstrate the necessity of adding the Mindlin corner functions to achieve accurate frequencies for rectangular plates having sharp V-notches.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.266-273
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• 2002

Pushover analysis is frequently used for evaluation of seismic performance and determination of seismic demand of a building structure in the current structural engineering practice field. However, pushover analysis has a advantage for estimation of seismic demands, which cannot account for the contributions of higher modes to response or for a redistribution of inertia forces because of structural yielding and the associated changes in the vibration properties of the structures. Recently, Chopra and Coel(2001) derived uncoupled inelastic dynamic equation of motion with several assumptions in the pushover analysis. By using this approach, pushover analysis for each mode is carried out and modal pushover analysis method, which can consider higher mode effects of the building, was suggested. The principle objective of this study is to introduced the modal pushover analysis by Chopra et al.(2001) and investigated the applicability and validity of this method for the steel moment frames subjected to various earthquake ground motions.

• Steel and Composite Structures
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• v.22 no.1
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• pp.183-201
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• 2016

Perforated steel beams can be optimised by increased beam depth and the moment of inertia combined with a reduced web thickness, favouring the use of original I-section beams. The designers are often confronted with situations where optimisation cannot be carried out effectively, taking account of the buckling risk at web posts, moment-shear transfers and local plastic deformations on the transverse holes of the openings. The purpose of this study is to suggest solutions for reducing these failure risks of tested optimal designed beams under applying loads in a self-reacting frame. The design method for the beams is the hunting search optimisation technique, and the design constraints are implemented from BS 5950 provisions. Therefore, I have aimed to explore the strengthening effects of reinforced openings with ring stiffeners, welded vertical simple plates on the web posts and horizontal plates around the openings on the ultimate load carrying capacities of optimally designed perforated steel beams. Test results have shown that compared to lateral stiffeners, ring and vertical stiffeners significantly increase the loadcarrying capacity of perforated steel beams.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4E
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• pp.20-25
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• 1999

To get accurate natural frequencies of an engine crankshafts, finite element equations of motion are developed, taking real geometries of the shaft into account. For the crankshaft with wide crank webs, a specialized rotating web element is developed. This includes the effects of rotary inertia, gyroscopic moment, and shear. After the finite element equations are constructed, eigenvalues are extracted from the system equations to get natural frequencies, based on the Sturm sequence method which exploits the banded forms of the system matrices to reduce computations. The scheme developed can be used for the free vibration analysis of any type of spinning structures which include skew symmetric gyroscopic moment matrix in the system matrices. The results are compared with experimental data in order to confirm the study.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.291-298
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• 2001

When the compression members have the variable cross sections along their member axes, the determination of the elastic critical loads by classical methods becomes impossible and if possible involves complicated calculation only to obtain the approximate values of critical load. In this paper the elastic critical load coefficients of the tapered members with simply supported ends were determined by finite element method. And then the results were represented by simple algebraic equations of two parameters, a( =taper parameter) and m ( = sectional property parameter). One the basis of algebraic equations, the equivalent moment of inertia concept originally proposed by Bleich for a spesific case, are extended to the general cases.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.47.2-47.2
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• 2011

Gravitational waves from the pulsar glitch can be detected by next generation gravitational wave observatories. We investigate characteristics of the modes that can emit the gravitational waves excited by three different types of perturbations satisfying conservation of total rest mass and angular momentum. These perturbations mimic the pulsar glitch theories i.e., change of moment of inertia due to the star quakes or angular momentum transfer by vortex unpinning at crust-core interface. We carry out numerical hydrodynamic simulations using the pseudo-Newtonian method which makes weak field approximation for the dynamics, but taking all forms of energies into account to compute the Newtonian potential. Unlike other works, we found that the first and second strongest modes that give gravitational waves are $^2p_1$ and $H_1$ rather than$^2f$. We also found that vortex unpinning model excites the inertial mode in quadrupole moment quite effectively. The inertial mode may evolve into the non-axisymmetric r-mode.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.1
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• pp.41-51
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• 2007

Differential equations and their solutions were formulated to describe the deflection of the tapered, nonuniform thickness and width's temple, clamped at one end while the perpendicular force is acting on the other end which is freely suspended. The model was derived based on laws of continuity at every point inside the elastic medium that the deflection, tangent slope, bending moment, shearing force must be continuous within the medium. The model is found to be in good agreement with measurements on the beta titanium temple with the correlation 0.992 and p=0.999(Chi test). Therefore it is possible to predict the effect of various temple parameters such as elastic modulus, thickness, width on the deflection of the temples being considered.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2331-2336
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• 2005

This paper proposes a new haptic device using a parallel mechanism with gimbal type actuators. This device has three legs actuated by 2-DOF gimbal mechanisms, which make the device simple and light by fixing all the actuators to the base. Three extra sensors are placed at passive joints to obtain a unique solution of the forward kinematics problem. The proposed haptic device is developed for an operator to use it on a desktop in due consideration of the size of an average Korean. The proposed haptic device has a small workspace for on operator to use it on a desktop and more sensitivity than a serial type haptic device. Therefore, the motors of the proposed haptic device are fixed at the base plate so that the proposed haptic device has a better dynamic bandwidth due to a low moving inertia. With this conceptual design, optimization of the design parameters is carried out. The objective function is defined by the fuzzy minimum of the global design indices, global force/moment isotropy index, global force/moment payload index, and workspace. Each global index is calculated by a SVD (singular value decomposition) of the force and moment parts of the jacobian matrix. Division of the jacobian matrix assures a consistency of the units in the matrix. Due to the nonlinearity of this objective function, Genetic algorithms are adopted for a global optimization.