• 대한음성학회:학술대회논문집
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• 대한음성학회 2007년도 한국음성과학회 공동학술대회 발표논문집
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• pp.227-229
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• 2007

We investigate whether the word frequency effects occur in native speakers' homophone speech in such a way that less frequent words are produced with greater magnitudes in duration and F0 than more frequent words. Acoustic analyses of homophone data produced by four speakers reveal that there is a tendency that vowels in less frequent words get longer than those in more frequent words, and statistical tests verify the significance of their differences. On the other hand, no considerable correlation has been discovered between F0 and word frequency.

• Computers and Concrete
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• 제19권3호
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• pp.325-331
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• 2017

In this study, vibration and stability of concrete pipes reinforced with carbon nanotubes (CNTs) conveying fluid are presented. Due to the existence of CNTs, the structure is subjected to magnetic field. The radial fore induced with fluid is calculated using Navier-Stokes equations. Characteristics of the equivalent composite are determined using Mori-Tanaka model. The concrete pipe is simulated with classical cylindrical shell model. Employing energy method and Hamilton's principal, the motion equations are derived. Frequency and critical fluid velocity of structure are obtained analytically based on Navier method for simply supported boundary conditions at both ends of the pipe. The effects of fluid, volume percent of CNTs, magnetic field and geometrical parameters are shown on the frequency and critical fluid velocity of system. Results show that with increasing volume percent of CNTs, the frequency and critical fluid velocity of concrete pipe are increased.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.106-113
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• 2002

In this study, a numerical analysis method for soil-pile interaction in frequency domain problem is presented. The total soil-pile interaction system is divided into two parts so called near field and far field. In the near field, beam elements are used for a pile and plain strain finite elements for soil. In the far field, dynamic fundamental solution for multi-layered half planes based on boundary element formulation is adopted for soil. These two fields are coupled using FE-BE coupling technique In order to verify the proposed soil-pile interaction analysis, the dynamic responses of pile on multi-layered half planes are simulated and the results are compared with the experimental results. Also, the dynamic response analyses of interface spring elements are performed. As a result, less spring stiffness makes the natural frequency decrease and the resonant amplitude increase.

• Journal of Power Electronics
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• 제11권1호
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• pp.74-81
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• 2011

The cutoff frequency of the output LC filters of PWM inverters limits the control bandwidth of the converter system while it attenuates voltage ripples that are caused by inverter switching activities. For a selected cutoff frequency of an output LC filter, an infinite number of L-C combinations is possible. This paper analyses the characteristics of output LC filters for PWM inverters terms of the L-C combinations. Practical circuit conditions such as no-loads, full resistive-loads, and inductive-load conditions are considered in the analysis. This paper proposes a LC filter design method for PWM inverters considering both the voltage ynamics and he inverter stack size. An experimental PWM inverter system based on the proposed output LC lter design uideline is built and tested.

• 대한기계학회논문집A
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• 제31권5호
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• pp.541-549
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• 2007

In the case of control for mechanical systems, it is highly useful to be able to provide a compact model of the mechanical system to control engineers using the smallest number of state variables, while still providing an accurate model. The reduced mechanical model can then be inserted into the complete system models and used for extended system-level dynamic simulation. In this paper, moment-matching based model order reductions (MOR) using Krylov subspaces, which reduce the number of degrees of freedom of an original finite element model via the Arnoldi process, are presented to study the eigenvalue and frequency response problems of a HDD actuator and suspension system.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.343-346
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• 2008

To improve the reliability and extend the life for a wind-turbine gearbox, the gearbox needs to be monitored and analysed exactly. This study was conducted to analyze and detect the gearbox conditions when lubricating oil contaminated by wear particles was used. Characteristics of the gearbox failure by wear particles were monitored simultaneously by the on-line measurement sensor of vibration, oil condition and temperature. For the detail vibration analyses, frequency analysis(FFT) was performed. The results of the study were summarized as follows: Vibrational signal was found sensitive to abnormal changes of the gearbox conditions when lubricant was contaminated by wear particles. Also, using frequency analysis for the harmonics of gear mesh frequency(GMF), it is found that the failure of gearbox was caused by the damages of meshing gears. However, temperature and oil condition measuring signals were found not so effective to detect any gearbox failure by oil contamination.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.72-83
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• 2009

The purpose of this study is to examine the effects of a degree of discretization in the direction of longitudinal dam axis on the results of three dimensional fill dam dynamic analysis. In this study, the three dimensional dynamic analyses of the existing 'H' dam which is modeled with a different degree of discretization were carried out. From these results, the fundamental frequency of the dam and the responses at the dam crest such as acceleration and settlement were compared and analyzed. It was concluded that the size of finite element discretized in the direction of the longitudinal axis mush be smaller than 1/8 of dam length in order to obtain the reasonable fundamental frequency and response of acceleration and mush be smaller than 1/10 in order to obtain the reasonable settlement behaviors from the three dimensional dynamic analysis of the fill dam.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.225-232
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• 1997

A study of effects of design parameters on the seismic responses of base isolated structure is performed to reduce the seismic responses using a linear tw0-degree of freedom system and a lumped-mass model of a nuclear power p;ant(NPP). From the simplified 2 DOF system the optimal isolation frequency being less than 1/10th of the fundamental frequency of superstructure is obtained, and the isolator damping minimizing the peak acceleration depends on superstructure frequency. From the time history analyses for lumped mass model of NPP the optimal damping is calculated as 40% in containment building and 65% in reactor internal structure. Similar results are obtained in 2 DOF system

• Earthquakes and Structures
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• 제6권3호
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• pp.251-266
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• 2014

Dynamic analyses for a suite of ground of motions were conducted on concrete gravity dam sections to examine the earthquake induced stresses and effective damping. For this purpose, frequency domain methods that rigorously incorporate dam-reservoir-foundation interaction and time domain methods with approximate hydrodynamic foundation interaction effects were employed. The maximum principal tensile stresses and their distribution at the dam base, which are important parameters for concrete dam design, were obtained using the frequency domain approach. Prediction equations were proposed for these stresses and their distribution at the dam base. Comparisons of the stress results obtained using frequency and time domain methods revealed that the dam height and ratio of modulus of elasticity of foundation rock to concrete are significant parameters that may influence earthquake induced stresses. A new effective damping prediction equation was proposed in order to estimate earthquake stresses accurately with the approximate time domain approach.

• 대한가정학회지
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• 제36권1호
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• pp.35-49
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• 1998

The purpose of this study was to investigate the relationship between mothers' marital adjustment and children's social adjustment in commuter couples. The subjects of this study were 96 mother-child dyads. The children were first to sixth grade in the elementary schools. For data analyses, one-way ANOVAs, Scheffe Test for pairwise comparison, Pearson's Correlation were used. Results indicated that there were significant differences in mothers' marital adjustment in terms of the duration of commuting, the number of children, the frequency of fathers' visit and frequency of making a call. And, there was significant difference in children's adaptation in terms of the frequency of fathers' visit. Also, there were significant positive correlations between mothers' marital adjustment subscales and children's social adjustment subscales in commuter couples.