• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.365-370
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• 2000

A sliding mode fuzzy control (SMFC) algorithm is applied to design a controller for a benchmark problem on a wind- excited building. The structure is a 76-story concrete office tower with a height of 306 meters, hence the wind resistance characteristics are very important for the serviceability as well as the safety. A control system with an active tuned mass damper is assumed to be installed on the top floor. Since the structural acceleration is measured only at ,limited number of locations without measurement of the wind force, the structure of the conventional continuous sliding mode control may have the feed-back loop only. So, an adaptive least mean squares (LMS) filter is employed in the SMFC algorithm to generate a fictitious feed-forward loop. The adaptive LMS filter is designed based on the information of the stochastic characteristics of the wind velocity along the structure. A numerical study is carried out. and the performance of the present SMFC with the ,adaptive LMS filter is investigated in comparison with those of' other control, of algorithms such as linear quadratic Gaussian control, frequency domain optimal control, quadratic stability control, continuous sliding mode control, and H/sub ∞///sub μ/, control, which were reported by other researchers. The effectiveness of the adaptive LMS filter is also examined. The results indicate that the present algorithm is very efficient .

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.42-50
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• 2002

The duration and H/V ratio(the amplitude ratio of the horizontal to vertical components) of ground motions caused by earthquakes in southern Korea are analyzed. Total 329 seismograms of horizontal component recorded at hypocentral distances of 10 to 350 km from 27 earthquakes with local magnitude 2 to 4 are used for the analysis. Simplified relation between the duration of ground motion( $T_{d}$) and the ratio($\chi$) of Arias intensity( $I_{A}$) and squared maximum acceleration($\alpha$$_{max}$$^{2}$) is determined to be $T_{d}$ = 3.423$\chi$$^2$+ 8.200$\chi$ + 0.029, which is useful for the estimation of the duration in southern Korea. There are three distinct distance ranges with different linear variations of the duration in hypocentral distance. They are distance intervals of 10~80km, 80~140km, and the distance greater than 140km. The duration in southern Korea shows clear proportionality to the local magnitude at magnitudes greater than 3.1. The value 1.37 of the H/V ratio obtained in southern Korea is similar to the value 1.4 of ENA(Eastern North America). The H/V ratio in southern Korea increases in the frequency range from 0.3 to 10Hz. The duration and H/V ratio of ground motions derived in this study could be used in the stochastic simulation of strong ground motion.ion.n.n.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.505-511
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• 2018

Recently, a new foundation model called "Dynamic foundation model" was proposed for the dynamic analysis of structures on the foundation. This model includes a linear elastic spring, shear layer, viscous damping and the special effects of mass density parameter of foundation during vibration. However, the relationship of foundation property parameters with the experimental parameter of the influence of foundation mass also has not been established in previous research. Hence, the purpose of the paper presents a simple experimental model in order to establish relationships between foundation properties such as stiffness, depth of foundation and experimental parameter of the influence of foundation mass. The simple experimental model is described by a steel plate connected with solid rubber layer as a single degree of freedom system including an elastic spring connected with lumped mass. Based on natural circular frequencies of the experimental models determined from FFT analysis plots of the time history of acceleration data, the experimental parameter of the influence of foundation mass is obtained and the above relationships are also discussed.

• Smart Structures and Systems
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• v.18 no.6
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• pp.1125-1143
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• 2016

Forced vibration analysis of a simple supported viscoelastic nanobeam is studied based on modified couple stress theory (MCST). The nanobeam is excited by a transverse triangular force impulse modulated by a harmonic motion. The elastic medium is considered as Winkler-Pasternak elastic foundation.The damping effect is considered by using the Kelvin-Voigt viscoelastic model. The inclusion of an additional material parameter enables the new beam model to capture the size effect. The new non-classical beam model reduces to the classical beam model when the length scale parameter is set to zero. The considered problem is investigated within the Timoshenko beam theory by using finite element method. The effects of the transverse shear deformation and rotary inertia are included according to the Timoshenko beam theory. The obtained system of differential equations is reduced to a linear algebraic equation system and solved in the time domain by using Newmark average acceleration method. Numerical results are presented to investigate the influences the material length scale parameter, the parameter of the elastic medium and aspect ratio on the dynamic response of the nanobeam. Also, the difference between the classical beam theory (CBT) and modified couple stress theory is investigated for forced vibration responses of nanobeams.

• Structural Monitoring and Maintenance
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• v.5 no.3
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• pp.325-343
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• 2018

This study aims to propose a performance-based design method of a novel passive base isolation system, BIO isolation system, which is inspired by an energy dissipation mechanism called 'sacrificial bonds and hidden length'. Fragility functions utilized in this study are derived, indicating the probability that a component, element, or system will be damaged as a function of a single predictive demand parameter. Based on PEER framework methodology for Performance-Based Earthquake Engineering (PBEE), a systematic design procedure using performance and fragility objectives is presented. Base displacement, superstructure absolute acceleration and story drift ratio are selected as engineering demand parameters. The new design method is then performed on a general two degree-of-freedom (2DOF) structure model and the optimal design under different seismic intensities is obtained through numerical analysis. Seismic performances of the biologically inspired (BIO) isolation system are compared with that of the linear isolation system. To further demonstrate the feasibility and effectiveness of this method, the BIO isolation system of a 4-storey reinforced concrete building is designed and investigated. The newly designed BIO isolators effectively decrease the superstructure responses and base displacement under selected earthquake excitations, showing good seismic performance.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.58-64
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• 2006

This work focuses on reducing the noise and vibration levels of an LPi fuel pump, which are generated from the dynamic motions of pump elements and non-uniform flow of fuel. The noise and vibration levels increase as the revolution speed of the cam goes up. The fuel pump consists of five cavity cells, plungers and diaphragms, which are driven by the cam. The optimal design of the cam profile is performed to decrease the accelerations of moving Parts and to obtain a smooth hydraulic force through a dynamic analysis of a cam-plunger mechanism. The cam-Plunger with a cavity is modeled as a 2 degrees of freedom system having non-linear contacts, the cam profile being represented in terms of Fourier series in order to determine the optimal shape of the cam. From the optimized cam Profile, the acceleration of the diaphragm is reduced in $78\%$, the hydraulic force becoming smoother in case that the hydraulic force is rapidly dropped.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.3 no.2
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• pp.1-4
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• 1999

The Helmholtz equation is very important in physics and engineering. However, solution of the Helmholtz equation is in general known as a very difficult phenomenon. For if the ${\omega}$ is negative, the FDM discretized linear system becomes indefinite, whose solution by iterative method requires a very clever preconditioner. In this paper we assume that ${\omega}$ is nonnegative, and determine the optimal ${\rho}$ parameter for the three dimensional ADI iteration for the Helmholtz equation. The ADI(Alternating Direction Implicit) method is also getting new attentions due to the fact that it is very suitable to the vector/parallel computers, for example, as a preconditioner to the Krylov subspace methods. However, classical ADI was developed for two dimensions, and for three dimensions it is known that its convergence behaviour is quite different from that in two dimensions. So far, in three dimensions the so-called Douglas-Rachford form of ADI was developed. It is known to converge for a relatively wide range of ${\rho}$ values but its convergence is very slow. In this paper we determine the necessary conditions of the ${\rho}$ parameter for the convergence and optimal ${\rho}$ for the three dimensional ADI iteration of the Peaceman-Rachford form for the real Helmholtz equation with nonnegative ${\omega}$. Also, we conducted some experiments which is in close agreement with our theory. This straightforward extension of Peaceman-rachford ADI into three dimensions will be useful as an iterative solver itself or as a preconditioner to the the Krylov subspace methods, such as CG(Conjugate Gradient) method or GMRES(m).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.945-953
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• 2005

The purpose of this paper is to develop a linear regression model for the sound quality index of vehicle Interior noise. For this, objective measurement data of the vehicles driving in acceleration was measured. On the basis of analysis, psychoacoustic parameters were extracted and subjective evaluation was performed by noise and vibration expert evaluators. For the subjective evaluation, the paired comparisons and the semantic differential methods were used to evaluate sound quality of vehicle interior noise. By the paired comparison which evaluate two pairs of vehicle interior noise, the preference was estimated. With the semantic differential and the factor analysis, it was evaluated words of two pairs which expressed appropriately the sense of evaluator about noise source. Therefore the characteristics of the sound qualify for the vehicle were differentiated. From the results of both the correlation analysis and the multiple factor regression analysis, the sound quality evaluation model for the sense of human hearing was derived and indexed.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.64-71
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• 2012

In this paper, a parallel manipulator is comprised of two sliders and four links. Sliders execute a linear reciprocating motion depending on parallel guides and make the connected links rotate. A couple of links connected by sliders do coupling motion. The end-effector called a link tip has orientation angle. Through the kinematics analysis of this manipulator, we found displacement, velocity and acceleration using direct and inverse kinematics. We used equations that derived from this analysis and determined five constraint conditions. These conditions had much to do with rotation states of links, the relative relation of link length and coupling motion state. To verify those, we suggest a new algorithm regarding constraint conditions of a manipulator. With the result which performed the algorithm, we found out that operation range of coupled links was limited by relative relation of link length and that manipulator was not able to carry out a series of link motion, in case of being the link vertical between two parallel guides.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.113-120
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• 2006

This paper proposed the control algorithm fur aspheric surface grinding and was verified by the experiment. The functions of the algorithm were simultaneous control of the position and interpolation of the aspheric curve. The non-linear formula of the tool position was derived from the aspheric equations and the shape of the tool. The function was partitioned by an certain interval and the control parameters were calculated at each control section. The movement in a session was interpolated with acceleration and velocity. The position error was feed-backed by rotary encorder. The concept of feedback algorithm was correcting position error by increasing or decreasing the speed. In the experiment, two-axis machine was controlled to track the aspheric surface by the proposed algorithm. The effect of the control and process parameters was monitored. The result showed that the maximum tracking error was under sub-micro level for the concave and convex surfaces.