• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.147-149
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• 1987

On the colling mill plant, the qulity of products depends on the ability to follow up the command of roll speed and the magnitude of impact drop. In this paper, the frequency response method is applied to the main motor system of No.1 Plate Mill Plant in POSCO. This paper show the influences when the pseudo random noise as test signal is applied to the system to be measured and presents the proper magnitude of test signal.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.4
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• pp.598-603
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• 1990

This study evaluates the performance of an optical receiver for binary phase shift keying (BPSK) signals in the presence of short noise originating from the photo diode and phase noise of the optical source. The case of using I.O. hybrid compare with the fiber optic hybrid to mix received optical signal and laser local oscillator signal. The impact of these noise is minimized if loop natural frequency and power split ratio between data and carrier recovery branch are choosen optimally. Then it is obtained that required laser linewidt to achieve a BER of 10**-9. The results are the same except theat in case of using the fiber optic hybrid the required optical power is twice as much as the I.O. hybrid.

• Journal of Drive and Control
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• v.15 no.3
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• pp.36-42
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• 2018

Agricultural tractors require frequent shifting to improve operation efficiency, and PST (Powershift Transmission) is considered as a suitable transmission. However, due to the inherent characteristics of the PST, shocks arise during shifting, which imparts a negative effect on the operator. Therefore, in order to improve the transmission performance of the tractor PST, researches on various methods including the hydraulic system circuit, the engine input speed control, and the mechanical system of the transmission are steadily being conducted. In this study, in order to reduce the impact of PST on a shift based on SimulationX software, we analyzed the characteristics of the input signal of PCV (Pressure Control Valve) through sensitivity analysis and verified the simulation model through actual vehicle test. Optimization was performed for minimizing the shift shock for some of the parameters of the input signal at constant temperature and RPM conditions.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.32.2-32.2
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• 2014

We present a prediction for 21cm differential brightness temperature (dTb) from a set of strongly clustered sources of Population III and II objects at high redshift, from a suite of numerical simulations of their formation and radiative processes. These objects are located inside a highly biased density environment ("Rarepeak"), which is a rare, high-density peak which extends to ~7 comoving Mpcs. We study the impact on the resulting 21 cm signal from their ultraviolet and X-ray properties. The boost of emission (dTb>0) by high-density environment, moderate leakage of X-ray photons, and strong absorption due to Lyman-alpha pumping contrive to make Rarepeak a discernible, spatially-extended (sky angle~10') object around z~15, which is found to be detectable as a single object by Square Kilometre Array (SKA) with integration time of ~[600-2000] hours. We also examine detectability of many such peaks through SKA precursors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.11
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• pp.123-129
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• 2011

In terrestrial wireless optical communication links, atmospheric effects including turbulence, absorption and scattering have significant impact on the system performance. Based on the analysis of transmission in atmospheric channel concerning 830[nm] wavelength diode laser beam, performance of free space optical (FSO) link utilizing Galilean optics as a laser beam transmitting and receving optics, PIN photodiode as a detecting device. In this paper we designed optical link equation for received optical power and we analyze the atmospheric effects on the signal to noise ratio (SNR) and bit error rate (BER) of an terrestrial FSO system. We show that the possible communication distance for BER=$10^{-9}$ in proposed adverse atmospheric conditions.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.72-79
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• 2005

Gearing system emits inconsistent noise from gear teeth impact in case of gear defects. But, it is not easy for inspection operator in production line to distinguish objectively the defective product. Therefore, customer complains continuously bad noise of the geared motor. Because impulsive signal at low frequency has a tendency not to appear in frequency domain, it is difficult to separate the gear inconsistent noise of defective gear from overall geared motor's noise using general signal processing method such as FFT. In this paper, the method to estimate more objectively the inconsistent noise of gearing system and to measure the quantities is suggested. Suggested method uses Cepstrum, Autocorrelation, Comb Lifter and Inverse Cepstrum by turns to make objective quantities about noise level.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.9
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• pp.1596-1612
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• 2011

Coordinated Multi-Point (CoMP) transmission / reception is being studied in Long Term Evolution-Advanced (LTE-A) for future evolution of the $3^{rd}$ Generation Partnership Project (3GPP) LTE. Support of soft handover is essential for improving the performance of cell edge users. CoMP provides a natural framework for enabling soft handover in the LTE system. This paper evaluates the soft handover gain in LTE-A downlink. Mathematical analysis of signal to interference plus noise ratio (SINR) gain and the handover margins for soft handover and hard handover are derived. CoMP system model is developed and an inter-cell and intra-cell interference model is derived, taking into account the pathloss, shadowing, cell loading, and traffic activity. Reference signal received power (RSRP) is used to define the triggers and the measurements for soft handover. Our results indicate that parameter choices such as handover margin and the CoMP set size impact CoMP performance gain.

• Communications for Statistical Applications and Methods
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• v.30 no.3
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• pp.311-330
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• 2023

The present work describes simulation studies to compare the performances in terms of averaged mean squared error of bayesian wavelet shrinkage methods in estimating component curves from aggregated functional data. Five bayesian methods available in the literature were considered to be compared in the studies: The shrinkage rule under logistic prior, shrinkage rule under beta prior, large posterior mode (LPM) method, amplitude-scale invariant Bayes estimator (ABE) and Bayesian adaptive multiresolution smoother (BAMS). The so called Donoho-Johnstone test functions, logit and SpaHet functions were considered as component functions and the scenarios were defined according to different values of sample size and signal to noise ratio in the datasets. It was observed that the signal to noise ratio of the data had impact on the performances of the methods. An application of the methodology and the results to the tecator dataset is also done.

• ETRI Journal
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• v.45 no.4
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• pp.678-689
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• 2023

This paper describes a novel end-to-end deep generative model-based speaker recognition system using prosodic features. The usefulness of variational autoencoders (VAE) in learning the speaker-specific prosody representations for the speaker recognition task is examined herein for the first time. The speech signal is first automatically segmented into syllable-like units using vowel onset points (VOP) and energy valleys. Prosodic features, such as the dynamics of duration, energy, and fundamental frequency (F₀), are then extracted at the syllable level and used to train/adapt a speaker-dependent VAE from a universal VAE. The initial comparative studies on VAEs and traditional autoencoders (AE) suggest that the former can efficiently learn speaker representations. Investigations on the impact of gender information in speaker recognition also point out that gender-dependent impostor banks lead to higher accuracies. Finally, the evaluation on the NIST SRE 2010 dataset demonstrates the usefulness of the proposed approach for speaker recognition.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.30.3-30.3
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• 2021

In order to generate the 3D structure of the 21-cm signal during the reionization, semi-numerical simulations based on Excursion set formalism are broadly used. However, semi-numerical simulations in the realization of the 3D structure are known to be the ionizing photon non-conserving by the structure of the Excursion set approach. Recently, explicit photon conserving algorithms for semi-numerical simulations introduced, but they are still too slow when forward modelling the 21-cm signal with high-dimensional parameter spaces. Here, we introduce a new method for approximately correcting photon non-conservation, which can be applied on-the-fly. This method is tailored towards the efficient simulation and Bayesian inference with high-dimensional parameter space. Then, we investigate how large an impact that photon non-conservation has on astrophysical parameter inference by performing an MCMC analysis. We find that the ionizing escape parameter is deviated from the fiducial value by 2 sigma when we infer astrophysical parameters without this correction.