• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.2
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• pp.72-78
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• 2001

A compact size high voltage pulse generator with nanosecond rise time has been designed and investigated experimentally. The inductance of a pulse generator can be reduced by fixing the Marx generator and pulse forming network components into a single cylindrical unit. As a result, nanosecond rise time about $8{\sim}10[ns]$ and pulse width of several hundred [ns] can be obtained from a modified Marx pulse generator. And parametric studies showed that the rise time of the output pulse was depended little on the change of the load resistance and the charging capacitance while, the pulse width of the output pulse was depended greatly upon the change of the load resistance and the charging capacitance. The theoretical showed the possibility to design the laboratory-size pulse generator very fast rising time and a proper pulse width by minimizing stray inductance and varying resistance and capacitance.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1819-1821
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• 1996

A compact size high voltage pulse generator with nanosecond rise time has been fabricated and investigated experimentally. It can be reduced the inductance of the generator by fixing the Marx generator components and pulse forming network components into a single cylindrical unit. As a result, it can be obtained nanosecond rise time about $8{\sim}10[ns]$ and pulse width of several hundred nanoseconds from the modified Marx pulse generator. And parametric studies showed that the rise time of the output pulse was depended little on the change of the load resister and the charging capacitor while the pulse width of the output pulse was depended greatly upon the change of the load resistor and the charging capacitor.

• Fire Science and Engineering
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• v.25 no.1
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• pp.1-6
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• 2011

An evacuation simulation was carried out to confirm evacuation efficiency for stair width and problems in calculation of occupant load for high-rise buildings. The evacuation time and number of evacuated persons from a 39 story condominium-mercantile building were calculated by using Simulex for stair widths of 1.2 m, 1.5 m, and 1.8 m. The total occupant load based on the Korean code was higher than the number of actual residents by 2.3 times, and that based on the NFPA 101 Life Safety Code by 2.6 times, respectively. For the occupant load based on the Korean code, smaller stair width resulted in lower evacuation efficiencies due to bottlenecks in egress. For the actual residents and NFPA code-based occupant load, a high evacuation efficiency and negligible effects of the stair width on evacuation efficiency were confirmed. It was shown that there was a bottleneck even at the stair width of 1.8 m for the Korean code-based occupants, while the stair width of 1.2 m provided safe egress to the actual residents or NFPA code-based occupants. This recommended further studies on possibility of lowering the level of the Korean code in calculation of the occupant load.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.215-225
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• 2011

During the past decade, the performance-based design method of caisson breakwaters has been developed, which allows a certain damage while maintaining the function of the structure. However, the existing method does not consider the changing coastal environment due to climate change impacts so that the stability of the structure is not guaranteed over the lifetime of the structure. In this paper, a time-dependent performance-based design method is developed, which is able to estimate the expected sliding distance and the probability of failure of a caisson breakwater considering the influence of sea level rise and wave height increase due to climate change. Especially, time-dependent probability of failure is calculated by considering the sea level rise and wave height increase as a function of time. The developed method was applied to the East Breakwater of the Hitachinaka Port which is located on the east coast of Japan. It was shown that the influence of wave height increase is much greater than that of sea level rise, because the magnitude of sea level rise is negligibly small compared with the water depth at the breakwater site. Moreover, investigation was made for the change of caisson width due to climate change impacts, which is the main concern of harbor engineers. The longer the structure lifetime, the greater was the increase of caisson width. The required increase of caisson width of the Hitachinaka breakwater whose width is 22 m at present was about 0.5 m and 1.5 m respectively for parabolic and linear wave height increase due to climate change.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.5
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• pp.7-15
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• 1973

The gain stability of the nuclear pulse ampifiers with negative feedback for such a fast pulse input as the step voltge or the nuclear radiation detector pulse is analyzed in detail and the experimental results are given. It is shown that a few risetime should elapse to get the full effect of the negative feedback upon the liearity and the stability of the amplifiers for the fast pulse input, and to reduce this limitation the risetime of the negative feedback amplifier must be designed to be short compared with the width of the input pulse.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1870-1872
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• 2003

High voltage pulse generator with fast rise time has been studied theoretically and experimentally. The complexity and stray inductance of a pulse generator components can be very difficult to reduce. As a result, a compact size and stable Pulse can be obtained by using a rotary air-hole. Parametric studies showed that the rise time of the output pulse was depended little on the change of the revolutions per minute(RPM) while the pulse width of the output pulse was depended greatly upon the change of the revolutions per minute (RPM).

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1205-1208
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• 1995

The optically-gated p-i-n diode switches have been fabricated with gold-compensated silicon. The turn-on and turn-off delay times and the rise and fall times were measured as a function of optical power level, bias, and pulse width. The turn-on characteristics shows a strong dependence an optical pulse power and a delay time(${\delta}{\iota}$) between two pulses, but a weak dependence on the width of optical pulse. Actually there is no turn-off delay in gold-doped p-i-n switches and the fall time is negligible.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.86-91
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• 2009

The electrons injected into a laser wakefield undergo betatron oscillation and give rise to the emission of intense X-ray radiation. To investigate the generation conditions of the X-rays, the relativistic motion of an electron injected in an off-axis position has been simulated with wakefield profiles which are pre-calculated with a two-dimensional particle-in-cell code. The wakefield with a plasma density of $1.78{\times}10^{18}\;cm^{-3}$ is generated by the laser with an intensity of $1.37{\times}10^{18}\;W/cm^2$ and a pulse width of 30 fs. From the calculation of the single particle motion, the characteristics of the betatron radiation are investigated in the time domain. As the transverse injection position increases, the power and the duration time of the radiation increase, but the width of each pulse decreases.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.3
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• pp.1-14
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• 1974

The gain stability of the nuclear pulse linear amplifiers with feedback for such a fast pulse input as the step voltage or the nuclear radiation detector pulse is analysed in detail. The expression is derived which describes the waveform at the anode circuit of the photomultiplier tube which is a part of the nuclear radiation detector. It is analysed and compared when the feedback amplifier has one and two time-constants. When these fast input pulse voltages are applied to the feedback amplifier, the effects of feedback in linearity and stability of the output voltage appear only after two or three rise-times of the amplifier, And it is proved that in order to reduce this limitation, the rise time of the feedback amplifier shou1d be less than the input pulse width. It is also shown that the above theory can be applied directly to the voltage-shunt feedback amplifier stages designed as the basic amplifier of the linear amplifier, and that the gain stability is more improved for the smaller input impedance of this amplifier stage.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.14-19
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• 2018

In this study, the method considering the influence of the high-rise building in urban rainfall-runoff analysis using SWMM was proposed. The method proposed in this study was to calculate the time of reaching the surface of the rainwater considering the size and height of the building, and to modify the basin width to reflect this. In the method proposed in this study, the concentration time considering the size and height of the building is calculated and based on this time the basin width is modified. The proposed method was verified with the experimental result of Isidoro et al. (2012). As a result, the proposed method was found to be valid since the simulated hydrograph was fairly identical to experimental result. In both hydrographs, it was confirmed that the change of the discharge characteristic, such as decrease of peak discharge and lag of peak time, over increasing density of the building was similar each other.