• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.71-74
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• 2003

The signal processing algorithm for a PSD(Position Sensitive Detector) using amplitude modulation/demodulation is addressed in this paper. Dark currents and external noises such as daylight and fluorescent lights are eliminated by using amplitude modulation/demodulation and a low pass filter. The proposed amplitude modulation/demodulation method for a PSD sensor is compared with pulse amplitude modulation method. The proposed amplitude modulation is proved to be more accurate and robust than PAM method by analysis and experiments. Multiple measurements using one PSD sensor by amplitude modulation/demodulation is also addressed. The Power variation of light source is compensated by normalization process using a divider.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.89-95
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• 2004

The measured damping ratio was analysed to obtain amplitude dependence. Wind-induced vibration of 20 story steel-framed building was measured to investigate amplitude dependence by RD method. Micro-tremo vibrations of 20 RC bearing wall typed buildings were performed to analysis the amplitude dependence by formula proposed by Tamua and ESDU. Amplitude dependent damping in 17 story steel-framed building was showed clearly in the increasing rate of 9%. But Amplitude dependent damping of 17 RC bearing wall typed buildings was very low in the increasing rate of 2.5%. The tendency of dynamic properties of building obtained here are useful for the validation of dynamic properties of buildings in the evaluation of serviceability.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.27-40
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• 2024

The prediction of VIV amplitude is essential for the design and fatigue life estimation of steel tubes in tubular transmission towers. Limited to costly and time-consuming traditional experimental and computational fluid dynamics (CFD) methods, a machine learning (ML)-based method is proposed to efficiently predict the VIV amplitude of steel tubes in transmission towers. Firstly, by introducing the first-order mode shape to the two-dimensional CFD method, a simplified response analysis method (SRAM) is presented to calculate the VIV amplitude of steel tubes in transmission towers, which enables to build a dataset for training ML models. Then, by taking mass ratio M^*, damping ratio ξ, and reduced velocity U^* as the input variables, a Kriging-based prediction method (KPM) is further proposed to estimate the VIV amplitude of steel tubes in transmission towers by combining the SRAM with the Kriging-based ML model. Finally, the feasibility and effectiveness of the proposed methods are demonstrated by using three full-scale steel tubes with C-shaped, Cross-shaped, and Flange-plate joints, respectively. The results show that the SRAM can reasonably calculate the VIV amplitude, in which the relative errors of VIV maximum amplitude in three examples are less than 6%. Meanwhile, the KPM can well predict the VIV amplitude of steel tubes in transmission towers within the studied range of M^*, ξ and U^*. Particularly, the KPM presents an excellent capability in estimating the VIV maximum amplitude by using the reduced damping parameter S_G.

• Steel and Composite Structures
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• v.27 no.1
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• pp.89-94
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• 2018

Uniaxial ratcheting behavior of Z2CND18.12N austenitic stainless steel used nuclear power plant piping material was studied. The results indicated that ratcheting strain increased with increasing of stress amplitude under the same mean stress and different stress amplitude, ratcheting strain increased with increasing of mean stress under the same stress amplitude and different mean stress. Based on least square method, a suitable method to arrest ratcheting by loading the materials was proposed, namely determined method of zero ratcheting strain rate. Zero ratcheting strain rate occur under specified mean stress and stress amplitudes. Moreover, three dimensional ratcheting boundary surface graph was established with stress amplitude, mean stress and ratcheting strain rate. This represents a graphical surface zone to study the ratcheting strain rates for various mean stress and stress amplitude combinations. The graph showed the ratcheting behavior under various combinations of mean and amplitude stresses. The graph was also expressed with the help of experimental results of certain sets of mean and stress amplitude conditions. Further, experimentation cost and time can be saved.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.434-438
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• 2004

This paper has proposed presumable method of ergonomics estimate index from evoked potential of visual stimulation for establishment a fixed ergonomics estimate index. The proposed method presumes continuance time and amplitude of ergonomics using prony method. Band characteristic of alpha and beta band, and that of background and evoked potential was analyzed using FFT method. And, that were presumed continuance time and amplitude of ergonomics using porny method. As a result of that proposed method presumed band characteristic, continuance time and amplitude of ergonomics, classification of ergonomics of impatient, rage and fear were practicable.

• Journal of Korean Association for Spatial Structures
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• v.19 no.1
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• pp.117-126
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• 2019

Micro-Electro-Mechanical Systems (MEMS) sensors have been widely used in Structural Health Monitoring due to their convenience and lower costs in comparison to conventional sensors. Triggered measurements are relevant in events such as earthquakes because unlike continuous measurements, they only record the structural response once an event happens. This is more cost effective and it makes the data more manageable because only the required measurements from the event are recorded. The most common method of triggering is amplitude triggering. However, lower input amplitudes (less than 0.1g) cannot be triggered by using this method. In this paper, sound triggering was introduced to allow triggered measurements for lower input amplitude values. The performance of the sound triggering and amplitude triggering were compared by a series of shaking-table tests. It was seen that sound-triggering method has a wider frequency (0.5~10Hz) and amplitude (0.01~1.0g) range of measurements. In addition, the sound triggering method performs better than the amplitude triggering method at lower amplitudes. The performance of the amplitude triggering, in terms of the triggering being simultaneous improves at higher input amplitudes.

• Journal of Digital Convergence
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• v.14 no.1
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• pp.195-201
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• 2016

In this paper, we present the direction finding accuracy of correlative interferometer method and amplitude-phase comparison method. Spiral antennas are used for amplitude-phase comparison method and blade antennas are used for correlative interferometer method. Those are made for uniform circular array (UCA) direction finding antenna systems. We simulate the accuracy of azimuth angle with 3 antennas UCA when SNR is 20 dB and baseline is 0.5 wave length. Correlative interferometer method has better accuracy than amplitude-phase comparison method.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.261-265
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• 2011

We investigate the sunspot area data spanning from solar cycles 1 (March 1755) to 23 (December 2010) in time domain. For this purpose, we employ the Hilbert transform analysis method, which is used in the field of information theory. One of the most important advantages of this method is that it enables the simultaneous study of associations between the amplitude and the phase in various timescales. In this pilot study, we adopt the alternating sunspot area as a function of time, known as Bracewell transformation. We first calculate the instantaneous amplitude and the instantaneous phase. As a result, we confirm a ~22-year periodic behavior in the instantaneous amplitude. We also find that a behavior of the instantaneous amplitude with longer periodicities than the ~22-year periodicity can also be seen, though it is not as straightforward as the obvious ~22-year periodic behavior revealed by the method currently proposed. In addition to these, we note that the phase difference apparently correlates with the instantaneous amplitude. On the other hand, however, we cannot see any obvious association of the instantaneous frequency and the instantaneous amplitude. We conclude by briefly discussing the current status of development of an algorithm for the solar activity forecast based on the method presented, as this work is a part of that larger project.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.3-7
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• 2007

There are many techniques to calculate the exact position of deep seated tunnel. Especially, tomography method has been used generally in present days. This method has been performed mainly by wave traveltime. Because of short interval of two measuring boreholes, it was very hard to interpret the exact tunnel position. To solve this problem, seismic amplitude method was tried to detect exact pososition of tunnel in this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1439-1444
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• 2005

A two-dimensional boundary element method was used for the scattering analysis of side-drilled hole(SDH). The far-field scattering amplitude was calculated for shear vertical(SV) wave, and their frequency and time-domain results were presented. The time-domain scattering amplitude showed the directly reflected wave from the SDH leading edge as well as the creeping wave. In an immersion, pulse-echo testing, two measurement models were introduced to predict the response from SDHs. The 2-D boundary element scattering amplitude was converted to the 3-D amplitude to be used in the measurement model. The receiver voltage was calculated fer SV wave incidence at 45$^{\circ}C$ on the 1 m diameter SDH, and the result was compared with experiment.