• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.57-58
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• 2015

In this study, we present geometrical and kinematical analysis of Moreton wave observed in 2012 June 3rd and July 6th, recorded in H-${\alpha}$ images of Global Oscillation Network Group (GONG) archive. These large-scale waves exhibit different features compared to each other. The observed wave of June 3rd has angular span of about $70^{\circ}$ with a diffuse wave front associated to NOAA active region 11496. It was found that the propagating speed of the wave at 17:53 UT is about $931{\pm}80km/s$. The broadness nature of this Moreton wave can be interpreted as the vertical extension of the wave over the chromosphere. On the other hand, the wave of July 6th associated with X1.1 class are that occurred at 23:01 UT in AR NOAA11515. From the kinematical analysis, the wave propagated with the initial velocity of about $994{\pm}70km/s$ which is in agreement with the speed of coronal shock derived from type II radio burst, v ~ 1100 km/s. These two identified waves add the inventory of the large-scale waves observed in 24th Solar Cycle.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.107.1-107.1
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• 2014

We apply a machine learning algorithm, artificial neural network, to the search for gravitational-wave signals associated with short gamma-ray bursts. The multi-dimensional samples consisting of data corresponding to the statistical and physical quantities from the coherent search pipeline are fed into the artificial neural network to distinguish simulated gravitational-wave signals from background noise artifacts. Our result shows that the data classification efficiency at a fixed false alarm probability is improved by the artificial neural network in comparison to the conventional detection statistic. Therefore, this algorithm increases the distance at which a gravitational-wave signal could be observed in coincidence with a gamma-ray burst. We also evaluate the gravitational-wave data within a few seconds of the selected short gamma-ray bursts' event times using the trained networks and obtain the false alarm probability. We suggest that artificial neural network can be a complementary method to the conventional detection statistic for identifying gravitational-wave signals related to the short gamma-ray bursts.

• Korean Journal of Optics and Photonics
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• v.19 no.5
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• pp.343-348
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• 2008

This study was carried out to commercialize FTTH by developing a burst mode optical receiver for E-PON. The optical receiver was manufactured by minimizing the capacitance of a photodiode to improve sensitivity for meeting 10, 20 km OLT Rx standard of E-PON at the transmission speed of 1.25 Gb/s. When bit-error ratio is $10^{-12}$ and PRBS is $2^5-1$, sensitivity is -26 dBm, loud/soft ratio is 23 dB. Both preamble time and guard time were set to 102.4 ns (128 bit). After comparing a photodiode whose capacitance is 0.53 pF with another photodiode whose capacitance has been minimized to 0.26 pF, we could see that sensitivity improved to 0.7 dBm and so did bandwidth to 190 MHz of burst mode for the optical receiver manufactured by the photodiode whose capacitance is 0.26 pF.

• Geomechanics and Engineering
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• v.16 no.1
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• pp.85-95
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• 2018

Water affects the mechanical properties of coal and stress wave propagation. To comprehensively investigate the effect of water content on the properties of coal, laboratory tests including X-Ray Diffraction (XRD) analysis, P-wave test, S-wave test, static and dynamic compression test with different water contents were conducted. The compressive strength, elastic modulus and failure strain and their mechanism of coal specimen under coupled static-dynamic load with the increased water content were observed. Meanwhile, energy transmission and dissipation characteristics of a stress wave in coal specimens with different water contents under dynamic load and its relation with the failure features, such as fragmentation and fractal dimension, of coal was analyzed. Furthermore, the dynamic interpretation of water infusion to prevent coal burst based on water infusion model of coal seam roadway was provided.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.151-160
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• 2012

In medical ultrasound imaging, elasticity imaging helps to diagnose tumors such as cancer. This paper is concerned with the application of acoustic radiation force to soft tissue of interest to implement elasticity imaging. In order to reduce the data acquisition time, instead of relying on transmit focusing, a plane wave of burst type is transmitted to apply the acoustic radiation force simultaneously to an entire imaging region to be observed. A homogeneous phantom experiment confirms that increasing the transmit excitation duration instead of employing transmit focusing generates a high enough acoustic radiation force to obtain elasticity images. It is found, however, that a different displacement versus time characteristic is observed unlike the case of using a conventional focused acoustic radiation force. Experimental results obtained through the use of an ultrasound phantom and a bovine liver show that lesions can be correctly differentiated.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.2
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• pp.61-68
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• 2004

Electric stimulation of teeth has been used for assessing pulp vitality. The principle is based upon the assumption that a subject feels the pain produced by electrical current stimulation of intradental nerve. Because of very high and wide range of impedance of the enamel, it is very difficult to determine stimulation levels regardless of teeth status. Most pulp testers adopt voltage stimulation method and thus, their stimulating threshold levels significantly depend on each individual. Therefore, a constant current stimulator is necessary to minimize the effect of wide variation due to different enamel thickness. And it is also necessary to test teeth vitality with a wide current range regardless of tooth impedance. In this study, we constructed a burst-wave type pulp tester to reduce the pain using a current stabilizing circuit with the maximum current of 150 uA.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.689-694
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• 2016

The objective of this study is to identify the requirements for a energy metering device and develop a real-time energy metering device for measuring energy (electricity) consumption of the electric railway vehicle during its operation. The study also evaluated the performance of the AC voltage sensor, current sensor, and data meter for the device and performed EMC tests such as surge and EFT (Burst). The performance tests showed that the percent errors of the AC voltage sensor and current sensor were ${\leq}0.1%$, and ${\leq}0.5%$ under 10~127V, and 10~250A, respectively. The result of surge and EFT (Burst) tests also indicated that the device had no malfunction in any wave (combination and ring waves) under the treat level with 2kV. The result of the field test also confirmed that the device had no malfunction in data metering.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.59.1-59.1
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• 2018

On 2018 February 5 a gamma ray burst with trigger time 04:25:29.3 UT was detected by Swift BAT and this event was named GRB 180205A. We observed the optical afterglow of GRB 180205A starting from about 1 hour after the burst until February 22 in the optical bands with the 1m telescope of Deokheung Optical Astronomy Observatory (DOAO), the 1m telescope at Mt. Lemmon Optical Astronomy Observatory(LOAO) and the 0.8m and 0.25m telescopes at McDonald Observatory. According to the fireball model, which is a well-accepted and conventional model for the afterglow of the GRB, the mechanism of the afterglow is that the expanding external blast wave of the GRB successively collides with the ambient medium and loses its energy, and as a result emits radiation at wavelengths longer than gamma rays. Here we present optical photometry and light curve of the afterglow in the R band and analyze it to characterize GRB 180205A.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.1
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• pp.59-64
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• 2016

In this study, the application was developed for the simulation of functional electrical stimulation. It functions to calculate the electrical energy which is transmitted to the patient, to visualize the electrical stimulation waveform, Therapy, Burst and Pulse section as setup of time period requested. The application was verified by comparing the oscilloscope and the graph of the application. XML schema was developed to utilize the contents of simulation which consist of the standard codes that are identified by OID. Using the application, medical experts will be able to research and share the contents of simulation.

• Publications of The Korean Astronomical Society
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• v.22 no.2
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• pp.43-54
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• 2007

Many gravitational wave detectors are now being built or under operation throughout the world. In particular, LIGO has taken scientific data several times, although current sensitivity is not sufficient to detect the weak signals routinely. However, the sensitivities have been improving steadily over past years so that the real detection will take place in the near future. Data analysis is another important area in detecting the gravitational wave signal. We have carried out the basic research in order to implement data analysis software in Korea@home environment. We first studied the LIGO Science Collaboration Algorithm Library(LAL) software package, and extracted the module that can generate the virtual data of gravitational wave detector. Since burst sources such as merging binaries of neutron stars and black holes are likely to be detected first, we have concentrated on the simulation of such signals. This module can generate pure gravitational wave forms, noise suitable for LIGO, and combination of the signal and noise. In order to detect the gravitational signal embedded in the noisy data, we have written a simple program that employs 'matched filtering' method which is very effective in detecting the signal with known waveform. We found that this method works extremely well.