• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.444-451
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• 2017

In this paper, we have evaluated and analyzed OTFS(Orthogonal Time Frequency Space) modulation and OTFS-MIMO(Multiple Input Multiple Output) system. OTFS modulation can concisely compensate delay-Doppler spreading effect by using 2D(2-Dimension) iDFT (inverse Discrete Fourier Transform) and DFT(Discrete Fourier Transform) operation. It enables OTFS system to transmit high-speed data. Especially, OTFS-MIMO system can transmit all data streams without performance degradation on high Doppler frequency channel. As simulation results, we have confirmed that $1{\times}1$ OTFS system's achievable rate is a similar to each stream of $2{\times}2$ OTFS-MIMO system. That is, we have also confirmed that $2{\times}2$ MIMO system can completely achieve double achievable rate in comparison with OTFS system on high Doppler frequency channel.

• Fire Science and Engineering
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• v.23 no.2
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• pp.111-116
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• 2009

17 kinds of fire resistant paint which are currently used were painted on the MDF(middle density fiber board), which suitable to the regulation of Fire Service Act. And we investigate a ignition delay effect under a exposure condition of radiative heat of fire. Radiative heat flux was controlled from $10kW/m^2$ to $30kW/m^2$ using the cone heater. Ignition time, ignition type and surface temperature of the sample were measured. Based on the experimental result, critical heat flux of the fire resistant paint treated sample was $10kW/m^2$ and there were no ignition delay effect above the $30kW/m^2$. And it was found that it will be difficult to expect the fire resistant effect above $400^{\circ}C$ of sample surface temperature.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2803-2806
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• 2003

In this paper considers the design of the effective controllers for the plant with an integrator and a long dead time. The structure of the new DTC(Dead Time Compensator) that has an additive filter is proposed. Our DTC shows the improved performance in set-point response and disturbance rejection. Especially the bad effect of the long dead time in the disturbance rejection is fairly reduced by using the additive filter. illustrative examples are provided to show the availability of the proposed controller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.349-359
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• 2009

In this paper, we propose a stereo-video transmission method for reduction of delay and maximization of 3D effect. Conventional multimedia synchronization algorithms were designed to achieve minimum delay and synchronize multiple video and audio streams, however, they could not be effective for 3D video transmission. In this paper, we proposed a synchronization algorithm by considering the minimum error of time difference between streams for 3D effect. The minimum error of time difference for 3D effect was derived based on a 3D subjective quality test. We compute display time of the delivered videos within the allowed time-difference and the video are displayed according to the display time. To evaluate the performance of the proposed algorithm, we implemented a real-time video communication system and subjective quality test has been conducted with the proposed system. We found that video quality displayed by the proposed system. We found that video quality displayed by the proposed algorithm ranks 'good' and 'excellent' in the DMOS (Differential Mean Opinion Score) scale, based on the MOS (Mean Opinion Score) test.

• Clean Technology
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• v.25 no.3
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• pp.238-244
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• 2019

In this study, the ignition characteristics of petroleum-based aviation fuel (Jet A-1), bio aviation fuel (Bio-6308), and blended aviation fuel (50:50, v:v) were analyzed in accordance with change of temperature and pressure. The ignition delay time of each aviation fuel was measured by combustion research unit (CRU) and the compositions of the fuels were analyzed by GC/MS and GC/FID for qualitative and quantitative results. From the results, it was confirmed that the ignition delay times of all aviation fuels were shortened with increasing temperature and pressure. In particular, the effect of temperature was larger than the effect of pressure. Also, the ignition delay time of Jet A-1 was the longest at all measurement conditions, and it was judged that this result is because of the structurally stable characteristics of the benzyl radical generated during the oxidation reaction of the aromatic compound (about 22.48%) in Jet A-1. Also, it was confirmed that Jet A-1 had no section where the degree of shortening of ignition delay time was decreased by increasing temperature, which was because the benzyl radical inhibits the response that can affect the negative temperature coefficient (NTC). The ignition characteristics of blended aviation fuel (50:50, v:v) showed a similar tendency to those of Jet A-1, rather than to those of Bio-6308, so that the blended aviation fuel (50:50, v:v) can be applied to the existing system without any change.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.40-44
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• 2015

Sensitivity on the reactor safety was evaluated for the safety margin and time delay applied to the opening pressure of liquid relief valve(LRV) of the primary heat transport system(PHTS) in the pressurized heavy water reactor(PHWR) type nuclear power plant. Since the LRV is the pressure boundary for the PHTS in the safety analysis, the operating of LRV has a significant effect on the safety analysis results. Therefore it is required during the regulatory review of Wolsong Unit 1 safety analysis to find the safety effect of the application of safety margin and time delay to the LRV opening pressure for the safety analysis of PHTS pressurizing events.

• Fire Science and Engineering
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• v.32 no.1
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• pp.66-75
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• 2018

A barrier installed within a rack plays a significant role in delaying the initial spread of fire but it can be an obstacle to a ceiling-type sprinkler installed for extinguishing fires and for supplying fire extinguishing water. An in-rack sprinkler and a barrier can be applied at the same time, but a study on a barrier's ability to delay fire spread or its effect on the in-rack sprinkler is needed. Accordingly, this study examined the effect of a barrier on the delay of fire spread and the in-rack sprinkler according to installation conditions through the reduced scale fire test. As a result, the delay in fire spread increased more than four times when a horizontal barrier and a vertical barrier were installed at the same time. The temperature was also increased two to three times with the compartment, resulting in the early operation of the in-rack sprinkler.

• Journal of Korean Society of Transportation
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• v.32 no.3
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• pp.218-226
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• 2014

This study examines a way to install a crosswalk that can improve pedestrians' convenience and safety and that goes beyond the crosswalk design standard of existing roundabouts. When a scrambled crosswalk, one of the crosswalk installation methods, is introduced to the roundabout system, it shortens the cross-walking distance of pedestrians and thus enhances convenience. Although the installation of a scrambled crosswalk may enhance pedestrians' convenience, it may obstruct vehicular traffic. Thus, this study presents standards for reasonable diagonal crosswalk installation based on the investigation on its effects on a vehicle's delay time. This study includes an analysis of the various geometric structures of roundabouts. The study results show that as v/c and the number of pedestrians increased, the delay time after the installation of a scrambled crosswalk increased although the extent was different. In general, the effect of the installation of a scrambled crosswalk was insignificant regardless of the number of pedestrians when v/c was under 0.6. When the number of pedestrians was 300/hour or lower, the difference in the delay time was quite insignificant regardless of v/c. In addition, as the inscribed circle of the roundabout was larger, the difference in the delay time decreased depending on v/c and the number of pedestrians.

• Journal of the Korean Mathematical Society
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• v.55 no.1
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• pp.43-58
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• 2018

In this paper, we study a delayed predator-prey system with Holling type IV functional response incorporating the effect of habitat complexity. The results show that there exist stability switches and Hopf bifurcation occurs while the delay crosses a set of critical values. The explicit formulas which determine the direction and stability of Hopf bifurcation are obtained by the normal form theory and the center manifold theorem.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.9
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• pp.517-522
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• 1999

This paper addresses the issue of current sampling in a high performance AC drive system fed by a discontinuous PWM inverter. The effect of the sampling error due to the measurement delay produced by an input stage low pass filter and an A/D converter is described in the case of discontinuous PWM. To compensate for the sampling error, a method to estimate the delay time of the whole measurement system based on the measured current is proposed and its effectiveness is verified by experimental results. The proposed algorithm can automatically estimate the system delay introduced by the low pass filter and the A/D converter at the commissioning stage. By delaying the current sampling by the estimated value, experimental results indicate that more than 50% reduction of current ripple can be achieved.