• Current Optics and Photonics
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• v.7 no.6
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• pp.708-713
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• 2023

A robust all-fiber nonlinear amplifying loop-mirror-based mode-locked femtosecond laser is demonstrated. Power-dependent nonlinear phase shift in a Sagnac loop enables stable and power-efficient mode-locking working as an artificial saturable absorber. The pump power is adjusted to achieve the lowest intensity noise for stable long-term operation. The minimum pump power for mode-locking is 180 mW, and the optimal pump power is 300 mW. The lowest integrated root-mean-square relative intensity noise of a free-running mode-locked laser is 0.009% [integration bandwidth: 1 Hz-10 MHz]. The long-term repetition-rate instability of a free-running mode-locked laser is 10^-7 over 1,000 s averaging time. The repetition-rate phase noise scaled at 10-GHz carrier is -122 dBc/Hz at 10 kHz Fourier frequency. The demonstrated method can be applied as a seed source in high-precision real-time mid-infrared molecular spectroscopy.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.323-332
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• 1999

The bus should supply an equal service to the whole community as feeder trip. However the existing bus route can not supply an effective feeder service in spite of the changes in the latent demand by the variety of regional structural change. This study aimed to establish the concept which frames the bus operation and management to cope with the latent demand to the bus. This study tackled this evidence by analyzing the transportation problems in terms of the urban growth emphasizing the following issues ; First, the strategy to improve the bus operation Second the land use control appropriate for the public transportation network Third economical range to justify the bus operation Second, the land use control appropriate for the public transportation network Third, economical range to justify the bus operation Fourth, the allowance for the private transportation mode On the latter part, the difference on the bus operation was compared to determine the range within which the bus operation could be justified. This study would provide some implications to improve the management for bus operation and fundamental information to develop the bus operation system.

• Journal of Korean Institute of Industrial Engineers
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• v.8 no.1
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• pp.61-67
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• 1982

This paper is concerned with the optimal control of dynamic expansion and operation of a single capacity under deterministic demand. Three cases of financing mode are considered : unlimited borrowing, debt aversion, and self financing. Using the net revenue as the objective function, the optimal paths of production and investment are analytically derived.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.2
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• pp.292-300
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• 2015

This paper proposes a high-efficiency, dual-mode PWM / linear buck converter with a wide-input range. The proposed converter was designed with a mode selector that can change the operation between PWM / linear mode by sensing a load current. The proposed converter operates in a linear mode during a light load and in PWM mode during a heavy load condition in order to ensure high efficiency. In addition, the mode selector uses a bit counter and a transmission gate designed to protect from a malfunction due to noise or a time-delay. Also, in conditions between $-40^{\circ}C$ and $140^{\circ}C$, the converter has variations in temperature of $0.5mV/^{\circ}C$ in the PWM mode and of $0.24mV/^{\circ}C$ in the linear mode. Also, to prevent malfunction and breakdown of the IC due to static electricity, the reliability of IC was improved by embedding a self-produced 8 kV-class(Chip level) ESD protection circuit of a P-substrate Triggered SCR type with high robustness characteristics.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.37-42
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• 2008

This study is focused on the numerical predictions for different smoke-control ventilation modes for the subway fire. Smoke-control ventilation mode in the domestic platform is that exhausting for the smoke detected zones while supplying air or stopping any ventilation for other zones in the platform. Three cases of smoke control ventilation modes are considered. First and second case are present running smoke control mode in Korea. The third is that smoke-control ventilation fans equipped in the platform are operated in first 4 minute(platform evacuation time, NFPA130) since then the fans equipped in the platform are stopped and the fans equipped in the tunnels are operated. Distributions of heat, carbon monoxide and visible range are compared at a height of 1.7m(passenger breath/sight height) above the platform. The numerical results show that air supply fan operation in the platform causes the smoke disturbance and a rapid spread of the smoke. The switch-operation with fans in both the platform and tunnel are better than operation with only platform fans in smoke rejection efficiency.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1048-1057
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• 2017

An indirect matrix converter (IMC) is a modern power generation system that enables a direct ac/ac conversion without the need for any bulky and limited lifetime electrolytic capacitor. This system also allows four-quadrant operation, generation of sinusoidal output voltage waveforms with variable frequency and amplitude, and control of input power factor. This study proposes a pulse-width modulation-based sliding-mode controller to achieve unity input-power factor operation of the IMC independently of the active power exchanged with the grid, as well as a fast dynamic response. The designed equivalent control law determines, at each sampling period, the appropriate q-axis component of the modulated input current to be injected into the grid through the LC input filter. An integral term of the error is included in the expression of the sliding surface to increase the accuracy of the control method. A double space vector modulation method is used to synthesize the direction of the space vector of the input currents as required by the sliding-mode controller and the space vectors of the target output voltages. Simulation and experimental results are provided to show the effectiveness and evaluate the performance of the proposed control method.

• Journal of the Korean Institute of Gas
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• v.23 no.4
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• pp.19-27
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• 2019

The consumption of liquefied natural gas (LNG) has increased annually due to the strengthening of international environmental regulations. In order to produce stable and efficient LNG, it is essential to divide the global (overall) operating condition and construct a quick and accurate monitoring system for each operation condition. In this study, multi-mode monitoring system is proposed to the LNG plant fractionation process. First, global normal operation data is divided to local (subdivide) normal operation data using global principal component analysis (PCA) and k-means clustering method. And then, the data to be analyzed were matched with the local normal mode. Finally, it is determined the state of process abnormality through the local PCA. The proposed method is applied to 45 fault case and it proved to be more than 5~10% efficient compared to the global PCA and univariate monitoring.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.4
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• pp.588-594
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• 2021

SIMON, a lightweight block cipher developed by the US National Security Agency, is a family of block ciphers optimized for hardware implementation. It supports many kinds of standards to operate in various environments. The counter mode of operation is one of the operational modes. It provides to encrypt plaintext which is longer than the original size. The counter mode uses a constant(Nonce) and Counter value as an input value. Since Nonce is the identical for all blocks, so it always has same result when operates with other constant values. With this feature, it is possible to skip some instructions of round function by pre-computation. In general, the input value of SIMON is affected by the counter. However in an 8-bit environment, it is calculated in 8-bit units, so there is a part that can be pre-computed. In this paper, we focus the part that can be pre-calculated, and compare with previous works.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1033-1037
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• 2005

We have studied on the effect of the operation voltage according to the reverse twist for the different fringe field switching (FFS) structure. The FFS structure with a vertically patterned edge of the pixel electrode (VPP) has lower operation voltage comparing to the one with a horizontally patterned edge of the pixel electrode (HPP). The reason is like that the number of the pattern of the pixel edge for the VPP structure is one third comparing with the HPP structure and thus, there is small reverse twist area for the VPP structure. Actually, the reverse twist disturbs the twist of LC near adjacent active area, result that LCs near there have the unstable dynamics. That is, the operation voltage increases as the reverse twist area increases. Therefore, it is very important to design pixel electrode with a small reverse twist region for the FFS mode.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.162-167
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• 2004

The ascent and descent market screen door (PSD-Platform Screen Door) between the electromotive car which is in the process of operating from the subway ascent and descent market and the passenger it is an immediacy and crisis as the system which it intercepts currently the inside and outside of the country of course signal system automatic operation signal system (ATO) establishment is operated from the segment. Manual operation signal system (the ATS and the ATC) almost it is a condition which is wholly lacking from the segment. This year from second half of the year 2 line manual operation signal system (ATS). It established the shutting tightly elder brother and the railing elder brother in PSD system in segment 12 reverses and the death accident due to the passenger hurt accident which occurs from the subway. It prevented an energy curtailment in the same time when it raises air cooling efficiency, It gathered it restricted the underground space which is comfortable in the use citizen and and and service it did interface the electromotive car and PSD entrance and exit literature course from the manual operation segment to sleep technically optimizationt. It researched a minute dust diffusion.