• Journal of the Korean Society of Safety
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• v.7 no.2
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• pp.71-79
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• 1992

This paper presents a least-square algorithms of lattice structures and their use for adaptive prediction of time series generated from the dynamic system. As the view point of adaptive prediction, a new method of Identification of dynamic characteristics by means of estimating the parameters of linear auto regressive model is proposed. The fast convergence of adaptive lattice algorithms is seen to be due to the orthogonalization and decoupling properties of the lattice. The superiority of the least-square lattice is verified by computer simulation, then predictor coefficients are computed from the linear sequential time data. For the application to the dynamic characteristic analysis of unknown system, the transfer function of ideal system represented in frquency domain and the estimated one obtained by predicted coefficients are compared. Using the proposed method, the damping ratio and the natural frequency of a dynamic structure subjected to random excitations can be estimated. It is expected that this method will be widely applicable to other technical dynamic problem in which estimation of damping ratio and fundamental vibration modes are required.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.541-546
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• 1999

The head-related transfer function (HRTF), which expresses the acoustic process from the sound source to the human ears in the free field, contains critical informations which the location of the source can be traced. It also makes it possible to realize multi-dimensional acoustic system that can approximately generate non-existing sound source. The use of non-individual, common HRTF brings performance degradation in localization ability such as front-back judgment error, elevation judgment error. In this paper, we have reduced the error on vertical plane by increasing the spectral notch level. The performance of the proposed method was Proved through subjective test that it is Possible to improve the ability to locate stationary/moving source.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.831-835
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• 2016

In this paper, a dual-channel feed-forward transimpedance(TIA) array is realized in a standard $0.18-{\mu}m$ CMOS technology which exploits automatic gain control function to provide 40-dB input dynamic range for either detecting targets nearby or sensing imminent danger situations. Compared to the previously reported conventional feed-forward TIA, the proposed automatic-gain-control feed-forward TIA(AFF-TIA) extends the input dynamic range 25 dB wider by employing a 4-level automatic gain control circuit. Measured results demonstrate the linearly varying transimpedance gain of 47 to $72dB{\Omega}$, input dynamic range of 1:100, the bandwidth of $${\geq_-}670MHz$$, the equivalent input referred noise current spectral density of 6.9 pA/${\surd}$HZ, the maximum sensitivity of -26.8 dBm for $10^{-12}BER$, and the power consumption of 27.6 mW from a single 1.8-V supply. The dual-channel chip occupies the area of $1.0{\times}0.73mm^2$ including I/O pads.

• Smart Structures and Systems
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• v.17 no.6
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• pp.1067-1085
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• 2016

Nonstationary features existing in tropical storms have been frequently captured in recent field measurements, and the applicability of the stationary theory to the analysis of wind characteristics needs to be discussed. In this study, a tropical storm called Nakri measured at Taizhou Bridge site based on structural health monitoring (SHM) system in 2014 is analyzed to give a comparison of the stationary and nonstationary characteristics. The stationarity of the wind records in the view of mean and variance is first evaluated with the run test method. Then the wind data are respectively analyzed with the traditional stationary model and the wavelet-based nonstationary model. The obtained wind characteristics such as the mean wind velocity, turbulence intensity, turbulence integral scale and power spectral density (PSD) are compared accordingly. Also, the stationary and nonstationary PSDs are fitted to present the turbulence energy distribution in frequency domain, among which a modulating function is included in the nonstationary PSD to revise the non-monotonicity. The modulated nonstationary PSD can be utilized to unconditionally simulate the turbulence presented by the nonstationary wind model. The results of this study recommend a transition from stationarity to nonstationarity in the analysis of wind characteristics, and further in the accurate prediction of wind-induced vibrations for engineering structures.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.57-65
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• 2000

In this paper, a model reference adaptive control for the atomic force microscope (AFM) of tapping mode is investigated. The dynamics between the AFM system and al sample is mathematically modeled as a second order spring-mass-damper system with oscillatory inputs. The attractive and repulsive forces between the tip of the AFM system and the sample are derived using the Lennard-Jones potential energy. By non-dimensionalizing the displacement of the tip and the input frequency, the chaotic behavior near a resonance frequency is better depicted through the non-dimensionalized equations. Four nonlinear analysis techniques, a phase portrait, sensitive dependence on initial conditions, a power spectral density function, and a Pomcare map are investigated. Because the equations of motion derived in this paper involve unknown parameter values such as the damping effect of the air and the interaction constants between materials, the standard model reference adaptive control is adopted. Two control objectives, the prevention of chaos and the tracking of reference signal, are pursued. Simulation results are included.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.541-546
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• 2016

In this paper, by using the Rayleigh-Sommer field theory and the cross-spectral density function, the analytical expression for the intensity distribution of a double half-Gaussian hollow beam in a turbulent atmosphere is obtained. The influence of the initial spot size of this beam on its propagation properties in a turbulent atmosphere is simulated, and the intensity distributions for such beams with different spot sizes are obtained. The results show that the initial spot size has an important influence on the propagation properties in the near field, while this influence in the far field is very weak.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.91-91
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• 2012

We present high-resolution near-infrared host galaxy spectra of low-z quasars, PG0844+349 (z=0.064), PG1226+023 (z=0.158), and PG1426+015 (z=0.086). The observation was done by using the near-IR high resolution echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by using an Adaptive Optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. The signal-to-noise ratios are increased by the total exposure time up to several hours per targets and the development of data reduction method. We compare our results to the stellar spectra library and sample spectra from Dasyra et al. (2007) and Watson et al. (2008). The identified spectral lines will be used to study the physical mechanism of quasars, and the velocity dispersions of the stars in the bulge of the host galaxy.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.136-139
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• 2018

The inhibitory compound (Compound S) against Ralstonia solanacearum and its conversion product (Compound S') were isolated from the culture filtrate of Bacillus subtilis JW-1 using a series of chromatography procedures. The structures were elucidated as alanyl-L-${\beta}$-(2,3-epoxycyclohexyl-4-one)alanine and alanyl-L-${\beta}$-(2,3-dihydroxycyclohexyl-4-one)alanine, respectively on the basis of nuclear magnetic resonance spectral data, including $^1H$, $^{13}C$, $^1H-^1H$ correlation spectroscopy and heteronuclear multiple bond correlation spectroscopy. The compound S exhibited a broad antimicrobial activity against $G^+$, $G^-$ bacteria, Saccharomyces cerevisiae and Candida albicans. The activity loss of the conversion product revealed that the epoxy function was essential for activity of Compound S.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.418-426
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• 2005

Based upon three level approximation and the steepest descent path(SDP) method, we consider an optimum choice of approximation path for derivation of new class of closed-flrm Green's functions which can lead to the analytic evaluation of MoM(Method of Moment) matrix elements. It is observed that the present method can give more accurate evaluation of the spatial Green's functions than the previous method, even without the advance investigation of the spectral functions, over a wide frequency range. In order to check the validity of the present method, some numerical results are presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1057-1060
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• 2005

Noises from circuits components and interference with other circuits components generate the phase noise in voltage controlled oscillators (VCO). The effects of the random noise on the phase noise is depending on the instant when the noise enters the VCO. When the noise enters at the transition time of the output of VCO, the effect is most prominent. Using this time variable system, it is revealed that the power spectral density of phase noise of VCO is made of the integrated noise powers of frequency components slightly offset from the fundamental and harmonic frequencies.