• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.652-654
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• 1993

In this paper, time variation properties of acoustic emission pulse were studied from low density polyethylene by using the self developed measuring system of aucoustic emission. When AC 15[kVrms] were applied to specimen of needle shape voids(0.5, 1.0, 1.5, 2.0[mm]), the breakdown time of void specimen was quite shorter than that of non-void specimen, thus the quick accurance of inception discharge were confirmed. It is observed that the skewness of the phase angle for applied voltage distribution phase, the average pulse of amplitude and the number of pulse are characteristic quantity of discharge.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.5
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• pp.271-277
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• 2020

Recoverability and vulnerability of navy ships under underwater explosion are critical verification factors in the acquisition phase of navy ships. This paper aims to establish numerical analysis techniques for the underwater explosion of navy ships. Doubly Asymptotic Approach (DAA) Equation of Motion (EOM) of primary shock wave and secondary bubble pulse proposed by Geers-Hunter was introduced. Assuming a non-compressive fluid, reference solution of the DAA EOM of Geers-Hunter using Runge-Kutta method was derived for the secondary bubble pulse phase with an assumed charge conditions. Convergence analyses to determine fluid element size were performed, suggesting that the minimum fluid element size for underwater explosion analysis was 0.1 m. The spherical and cylindrical fluid domains were found to be appropriate for the underwater explosion analyses from the fluid domain shape study. Because the element size of 0.1 m was too small to be applied to the actual navy ships, a very slender beam with the square solid section was selected for the study of fluid domain existence effect. The two underwater explosion models with/without fluid domain provided very similar results in terms of the displacement and stress processes.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3359-3366
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• 2023

In this study, a spiking cortical model (SCM) based n-g discrimination method is proposed. The SCM-based algorithm is compared with three other methods, namely: (i) the pulse-coupled neural network (PCNN), (ii) the charge comparison, and (iii) the zero-crossing. The objective evaluation criteria used for the comparison are the FoM-value and the time consumption of discrimination. Experimental results demonstrated that our proposed method outperforms the other methods significantly with the highest FoM-value. Specifically, the proposed method exhibits a 34.81% improvement compared with the PCNN, a 50.29% improvement compared with the charge comparison, and a 110.02% improvement compared with the zero-crossing. Additionally, the proposed method features the second-fastest discrimination time, where it is 75.67% faster than the PCNN, 70.65% faster than the charge comparison and 38.4% slower than the zero-crossing. Our study also discusses the role and change pattern of each parameter of the SCM to guide the selection process. It concludes that the SCM's outstanding ability to recognize the dynamic information in the pulse signal, improved accuracy when compared to the PCNN, and better computational complexity enables the SCM to exhibit excellent n-γ discrimination performance while consuming less time.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.309-318
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• 2003

This paper presents an in-depth study of a UWB indoor radio channel between 1 and 9 GHz, which was used for the subsequent development of a new statistical UWB multipath channel model, focusing on short range indoor scenarios. The channel sounding process was carried out covering different indoor environments, such as laboratories, halls or corridors. A combination of new and traditional parameters has been used to accurately model the channel impulse response in order to perform a precise temporal estimation of the received pulse shape. This model is designed specifically for UWB digital systems, where the received pulse is correlated with an estimated replica of itself. The precision of the model has been verified through the comparison with measured data from equivalent scenarios and cases, and highly satisfactory results were obtained.

• Journal of the Korean Institute of Telematics and Electronics
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• v.5 no.3
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• pp.25-30
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• 1968

The characteristics of single mesh discharge circiut for Xenon flashlamp has been analysised in detail. Since flashlamp voltage characteristics is linear in time, though nonlinear in current, the nonliear differential equation , for this system has beens solved by the analog computer. Also for given lamp type, energy input, pulse duration, and pulse shape factor, the inductance, capacatince and operating voltage were discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.549-553
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• 2018

The applications of the pulse power technology are expanding and the necessity of a large current switch as a core component of pulsed power is increasing. A trigger gap switch composed of three electrodes was fabricated and the discharge characteristics were studied according to the change of the pressure, the shape of the main electrode, and the gap distance when the trigger pulse was applied. As a main result, the stable operation range was confirmed through the discharge inception voltage according to the gap distance and electric field analysis was performed in the same structure to confirm the electric field value of the discharge inception voltage.

• Journal of the Optical Society of Korea
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• v.14 no.2
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• pp.137-141
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• 2010

We report, for the first time to our knowledge, observation of polarization bistability from 1.55-${\mu}m$ wavelength single-mode VCSELs of a conventional cylinder-shape under control of their driving current, and demonstration of all-optical flip-flop (AOFF) operations based on the bistability with optical set and reset pulse injection at a 50 MHz switching frequency. The injection pulse energy was less than 14 fJ. The average on-off contrast ratio of the flip-flopped signals was about 7 dB. These properties of the VCSELs will be potentially useful for future high-speed all-optical signal processing applications.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.2
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• pp.49-56
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• 1997

Switched Reluctance Motors(SRMs) have a considerable inherent torque ripple due to the driving characteristics of pulse current waveform and the nonlinear variation inductance profile. This paper describes a current shape characteristics to effect a torque ripple reduction, and one pulse mode switching control method is proposed to minimize torque ripple of a switched reluctance motor regardless of speed and load condition by regulating tow parameters, such as, advance angle and exciting voltage. The experiments are performed to verify the capability of proposed switching method on 6/4 salient type SRM.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2002.05a
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• pp.35-35
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• 2002

Atomic force microscopy was applied to study the formation and growth mechanism of thin chrome layers prepared under various pulse plating conditions. The chrome was electro-deposited from an electrolyte bath containing 250 gl-l of chromic acid, 25 gl-l of sulfuric acid using direct current density of $1.6{\;}mA.$\textrm{mm}^{-2} and pulse currents with on-off time from 5 to 900 ms. The higher current density enhanced nucleation rate which resulted in refining grain size. The chrome growth kinetics determining nodule size and shape significantly depends on the duration of on-time rather than duration of off-time and on/off time ratio.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.5
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• pp.93-99
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• 1998

The chirping characteristics of InGaAsP electroabsorption modulatiors have been analyzed. The effective .alpha. parameters for large signal modulation were estimated by comparing the pulse shape after fiber transmission with constant chirping assumption.We investigated the structure and the operating condition of the modulator to improve the chirping characteristics. The .alpha. parameters were calculated as the function of wavelength detuning and the bias voltage. To minimize the chirping performance, high bias voltage and a small wavelength detuning and the bias voltage. To minimize the chirping performance, high bias voltage and a small wavelength detuning were preferred. An negative .alpha. value is achieved at the wavelength detuning below 30meV with a proper bias voltage so that pulse compression effect was expected.