• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.183-188
• /
• 2003

This study is to make the fundamentals of sound quality evaluation in regard of acoustical characteristics of passenger compartment. The deviation of frequency response function level within audible frequency is evaluated at receiving point in the research of room acoustics. In this study, frequency response function is the one between speaker and driver's ear positions. The positions of driver and audio speakers are optimized by analysis of acoustic mode of acoustic cavity. The main reflection planes are determined by analysis sound ray path diffused at optimized speaker positions. Finally, designer selects acoustical material by analysis of absorption effect of acoustical materials on the main reflection planes in order to avoid to distortion and fluctuation of frequency response function..

• Journal of Biomedical Engineering Research
• /
• v.25 no.5
• /
• pp.369-376
• /
• 2004

The tinnitus retraining therapy(TRT) is an effective method for treating tinnitus patients. This therapy use the white noise to stimulate auditory cells for a wide frequency range. In this paper, the small white noise generator using the thermal noise is proposed. And frequency response controller which can compensate the frequency response changed by the human outer and middle ear system is proposed. We can know that proposed system is more proper type on a purpose of the tinnitus retraining therapy comparing with conventional white noise generator.

• Proceedings of the KSME Conference
• /
• 2001.06b
• /
• pp.398-403
• /
• 2001

A simplified modeling approach of forced vibration for occupied car seats was demonstrated by using a mathematical model presented in previous paper. Nonlinear and linear equations of motions were rederived for forced vibration, and the transfer function was used to calculate the frequency response function. The experimental apparatus were set up and hydraulic shaker was used to obtain the system responses. Through the tests, mannequin's head had a lot of problems, and the responses with a head and without a head were measured. To explore the effects of linear dampings and friction moments at the joints, linear analyses were performed. New sets of linear spring and damping coefficients, and torsional dampings at the joints were calculated through parameter study to match up with experimental results. Good agreement between experimental and simulation frequency response estimates were obtained both in terms of locations of resonances and system deflection shapes at resonance, indicating that this is a feasible method of modeling seated occupants.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.5
• /
• pp.1051-1057
• /
• 2001

In this paper, we deal with three types of modelling method for the analysis of galloping in power transmission line (PTL). The single mass model is obtained under linearization method and it is applied into f-order model. On these models, the nature frequencies of PTL are obtained and it makes an effects on the galloping directly. In simulation, we verify that the maximum magnitude of nature frequency depends on the galloping distance of PTL. Also from the analysis of frequency response, a few of reduction method for galloping are introduced which is effected by distance of PTL, wind velocity and icing types.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.436-441
• /
• 2008

One of important factors in designing array-type MEMS resonators is obtaining a desired frequency response function (FRF) within a specific range. In this paper Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented to calculate the FRF of array-type resonators. By matching moments at a frequency around a specific range of the array-type resonators, required FRFs can be efficiently calculated with significantly reduced systems regardless of their operating frequencies. In addition, because of the characteristics of moment-matching method, a minimal order of reduced system with a specified accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1999.10a
• /
• pp.107-112
• /
• 1999

This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far-field soil. The dynamic stiffness matrices of the far-field region formulated in frequency domain using the present method can be easily transformed into the corresponding matrices in time domain. Hence the response can be analytical computed in time domain. Example analysis has been carried out to verify the present method for an embedded block in a multi-layered half-space. The present methods can be easily extended to the nonlinear analysis since the response analysis is carried out in time domain.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.117-124
• /
• 2002

The major purpose of this study is to determine the dynamic behavior of soil-pile-structure interaction system considering the underground cavity. For the analysis, a numerical method fur ground response analysis using FE-BE coupling method is developed. The total system is divided into two parts so called far field and near field. The far field is modeled by boundary element formulation using the multi-layered dynamic fundamental solution that satisfied radiational condition of wave. And this is coupled with near field modeled by finite elements. For the verification of dynamic analysis in the frequency domain, both forced vibration analysis and free-field response analysis are performed. The behavior of soil non-linearity is considered using the equivalent linear approximation method. As a result, it is shown that the developed method can be an efficient numerical method to solve the seismic response analysis considering the underground cavity in 2D problem.

• Structural Engineering and Mechanics
• /
• v.22 no.6
• /
• pp.647-664
• /
• 2006

The main purpose of this paper is to investigate the effect of transient stochastic analysis on nonlinear response of earth and rock-fill dams to spatially varying ground motion. The dam models are analyzed by a stochastic finite element method based on the equivalent linear method which considers the nonlinear variation of soil shear moduli and damping ratio as a function of shear strain. The spatial variability of ground motion is taken into account with the incoherence, wave-passage and site response effects. Stationary as well as transient stochastic response analyses are performed for the considered dam types. A time dependent frequency response function is used throughout the study for transient stochastic responses. It is observed that stationarity is a reasonable assumption for earth and rock-fill dams to typical durations of strong shaking.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.4
• /
• pp.463-468
• /
• 2015

High vibration of a low pressure (LP) turbine casing caused safety problems and life at the facility it was housed in. The main focus of this study was the cause of the high vibration in a low pressure turbine casing with manufacturing defects by frequency response analysis, compared with the results of experiments. Therefore, excited accelerations were obtained from the LP casing fundamental, and frequency responses were analyzed. The measurement and the modal analysis showed that the natural frequency of the LP turbine casing was 61.26 Hz and the excited frequency of the turbine rotor was 60.25 Hz. The manufacturing defect caused a decrease in the casing natural frequency and resulted in the high vibration of the casing because it moved close to the resonant frequency.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.17 no.1
• /
• pp.9-16
• /
• 2009

The analysis of an aircraft flight dynamics is recently very convenient because of the introduction of state-space method and a well-developed package software. The representation of a dynamic system is described as a simple form of matrix calculation and the unique form of model is available for the linear or nonlinear, time variant or time invariant, mono variable or multi variable system with state-space method. And this analysis can be simplified with the specific functions of a package software and it is very simplified to execute the simulation of the dynamic characteristics for an aircraft model with an interactive graphical treatment. The purpose of this study is to develope an educational flight simulator for the students who need to analyze the dynamic characteristics of an aircraft that is primarily to execute the simulation for the analysis of the transient response and frequency response of an aircraft stability. Furthermore the dynamic characteristics of an aircraft motion is set up as dynamical animation tool for the control response on 3-axis motions of an aircraft.