• Structural Engineering and Mechanics
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• v.13 no.4
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• pp.429-436
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• 2002

The current work presents an analysis algorithm for the modal analysis for the dynamic behaviors of offshore structures with concepts of mass perturbation influence term. The mass perturbation concept by using the term, presented in this paper offers an efficient solution procedure for dynamical response problems of offshore structures. The basis of the proposed method is the mass perturbation influence concepts associated with natural frequencies and mode shapes and mass properties of the given structure. The mathematical formulation of the mass perturbation influence method is described. New solution procedures for dynamics analysis are developed, followed by illustrative example problems, which deal with the effectiveness of the new solution procedures for the dynamic analysis of offshore structures. The solution procedures presented herein is compact and computationally simple.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.9 s.102
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• pp.1030-1036
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• 2005

This paper is concerned with the application of perturbation method to the dynamic analysis of space structure floating in space. In dealing with the dynamics of space structure, the use of Lagrange's equations of motion in terms of quasi-coordinates were suggested to derive hybrid equations of motion for rigid-body translations and elastic vibrations. The perturbation method is then applied to the hybrid equations of motion along with discretization by means of admissible functions. This process is very tiresome. Recently, a new approach that applies the perturbation method to the Lagrange's equations directly was proposed and applied to the two-dimensional floating structure. In this paper. we propose the application of the perturbation method to the Lagrange's equations of motion in terms of quasi-coordinates. Theoretical derivations show the efficacy of the proposed method.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.6 no.1
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• pp.22-26
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• 1995

Change of voice, espicially hoarseness show irregular vibration of vocal cord. So, computerized acoustic analysis has presented many acoustic parameters for objective evaluation of voice. We objectively investigated the vocal vibration of normal persons and hoarseness patients in Korea. The RAP(relative average perturbation), PPQ(pitch period perturbation quotient) and APQ(amplitude perturbation quotient) of normal persons were compared with that of hoarseness patients with multidimensional voice program for the possibility of distinguishing the pathologic vocal vibration from normal. Authors agree that RAP, PPQ and APQ showed interesting differences between the normal and the hoarseness patients by the multivariate statistical analysis. In conculusion, relative average perturbation, pitch period perturbation and amplitude perturbation quotient might be meangingful screening parameters distinguishing hoarseness patients from normal.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.2
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• pp.167-175
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• 2001

In this study, a general perturbation method is presented to reanalysis dynamic response of base-isolated systems. The perturbation is expanded to general order and which provide the formulation of perturbed solutions. in which eigensolutions of non-modified system are treated as unperturbed solutions. The accuracy of present method is tested using a 2-DOF system with isolator, where the stiffness and damping coefficients of isolator are changed, respectively, The reanalyzed eigensolutions and response using perturbed solutions are successfully approached to exact ones after just first perturbation. Supposing the practical criterion as ${\pm}5%$ error, the modification range of -50%~30% from original system can be allowed for the first order perturbation. Using higher order solutions, the applicable range will be wide.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.529-535
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• 1989

A general perturbation series solution of the Smoluchowski equation is applied to investigate the rate of recombination and the remaining probability of a pair of particles in liquids. The radiative boundary condition is employed and the convergence of the perturbation series is analyzed in terms of a convergene factor in time domain. The upper bound to the error introduced by the n-th order perturbation scheme is also evaluated. The long time behaviors of the rate of recombination and the remaining probability are found to be expressed in closed forms if the perturbation series is convergent. A new and efficient method of purely numerical integration of the Smoluchowski equation is proposed and its results are compared with those obtained by the perturbation method. For the two cases where the interaction between the particles is given by (i) the Coulomb potential and (ii) the shielded Coulomb potential, the agreement between the two results is found to be excellent.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1800-1807
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• 2018

In this paper, we study the gravitational perturbation of traversable wormhole spacetime, especially the Morris-Thorne wormhole spacetime, by using the linearized theory of gravity. We restrict our interest to the first order term and ignore the higher order terms. We assume that the perturbation is axisymmetric. We also assume that the time dependence follows the Fourier decomposition and the angular dependence is expressed in terms of the Legendre functions. As a result, we derive the gravitational perturbation equation of traversable wormhole in terms of a single linear second-order differential equation. As a consequence, we could analyze the unstability of the spacetime with the effective potentials. Furthermore, we consider the interaction between the external gravitational perturbation and the exotic matter, constituting traversable wormholes and its effect on the stability of traversable wormholes.

• Phonetics and Speech Sciences
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• v.2 no.3
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• pp.165-170
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• 2010

In this study, the most stable portion was identified using 5% moving window during /a/ sustained phonation in normal and pathologic voice signals and the perturbation values were compared between normal and pathologic voices at the mid-point and at the most stable portion using moving window, respectively. The results revealed that some severe pathologic voice signals can be eligible for perturbation analysis by identifying the most stable portion with Err less than 10. In addition, the perturbation acoustic parameters did not differentiate the pathologic voice signals from the normal voice signals when the mid-point was selected to measure the perturbation analysis(p>0.05). However, significantly higher %shimmer and lower SNR values were observed in pathologic voices (p<0.05) when the most stable portion was selected by moving window. In conclusion, moving window could identify the most stable portion objectively which can allow toget the minimum perturbation values (%jitter, %shimmer) and maximum SNR values. Thus, moving window technique can be applicable for more reliable and accurate perturbation acoustic analysis.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.26.2-26.2
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• 2011

Flyby anomaly (unexpected energy increase during Earth Gravity Assists) indicates existence of an unknown non-conservative perturbation which affects hyperbolic trajectories. This presentation focuses on first order position and velocity perturbation formulas derived in terms of classical orbital element variations for hyperbolic orbit. By using both the perturbation formulas and numerical approach, we analyze effects of hypothetical acceleration models proposed by Hasse (2009), Lewis (2009), Gerrad and Sumner (2008), and Busack (2007). Based on analysis of perturbation effect on low earth orbit, we find that typical position perturbation is about 10m which is much larger than current orbit determination accuracy. From this, we deduce that anomalous acceleration only affects hyperbolic orbit or behaves differently in bound orbit. On the other hand, based on analysis of perturbation effects on hyperbolic trajectories, we find that position and velocity perturbations are highly different from acceleration models, and all of proposed models fail to explain observed range and Doppler data. Thus, it can be concluded that not only energy variations but also kinematics gives us crucial clues on the flyby anomaly, and kinematical characteristic should be considered in modeling flyby anomaly.

• Steel and Composite Structures
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• v.8 no.2
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• pp.129-144
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• 2008

This paper demonstrates an application of the perturbation based stochastic finite element method (SFEM) for predicting the performance of structural systems made of composite sections with random material properties. The composite member consists of materials in contact each of which can surround a finite number of inclusions. The perturbation based stochastic finite element analysis can provide probabilistic behavior of a structure, only the first two moments of random variables need to be known, and should therefore be suitable as an alternative to Monte Carlo simulation (MCS) for realizing structural analysis. A summary of stiffness matrix formulation of composite systems and perturbation based stochastic finite element dynamic analysis formulation of structural systems made of composite sections is given. Two numerical examples are presented to illustrate the method. During stochastic analysis, displacements and sectional forces of composite systems are obtained from perturbation and Monte Carlo methods by changing elastic modulus as random variable. The results imply that perturbation based SFEM method gives close results to MCS method and it can be used instead of MCS method, especially, if computational cost is taken into consideration.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.79-81
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• 1994

Petubation in the fundamental frequency and in the peak amplitude of the EGG signal derived with a four-electrode EGG system were investigated for the purpose of developing useful measures for the detection of layngeal pathology. The data were compared to the degree of amplitude perturbation and frequency perturbation. There was a close relation between amplitude perturbation and frequency perturbation analysis of EGG signal and degree of laryngeal pathology.