• ETRI Journal
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• v.21 no.2
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• pp.31-39
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• 1999

Given two sorted lists A=(a0, a1, ${\cdots}$,a${\ell}$-1}) and B=(b0, b1, ${\cdots}$, bm-1), we are to merge these two lists into a sorted list C=(c0,c1, ${\cdots}$, cn-1), where n=${\ell}$+m. Since this is a fundamental problem useful to solve many problems such as sorting and graph problems, there have been many efficient parallel algorithms for this problem. But these algorithms cannot be performed efficiently in the postal model since the communication latency ${\lambda}$, which is of prime importance in this model, is not needed to be considered for those algorithms. Hence, in this paper we propose an efficient merge algorithm in this model that runs in $$2{\lambda}{\frac{{\log}n}{{\log}({\lambda}+1)}}+{\lambda}-1$$ time by using a new property of the bitonic sequence which is crucial to our algorithm. We also show that our algorithm is near-optimal by proving that the lower bound of this problem in the postal model is $f_{\lambda}({\frac{n}{2}})$, where $${\lambda}{\frac{{\log}n-{\log}2}{{\log}([{\lambda}]+1)}{\le}f_{\lambda}({\frac{n}{2}}){\le}2{\lambda}+2{\lambda}{\frac{{\log}n-{\log}2}{{\log}([{\lambda}]+1)}}$$.

• Journal of the Korean Society of Safety
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• v.35 no.3
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• pp.1-5
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• 2020

The leakage accident from a storage tank in an oil refinery plant occurred in April 2014 and the total loss is KRW 18 billion. This accident has prompted many companies to develop their own mitigation system to minimize the loss of the leakage accident. The aim of this study is to design the temporary storage facility system for dealing with leakage accidents. The basic concept of this system is that the leakage fluid of a hazardous material flows into a temporary storage tank and this is transferred to a spare tank by a pump as avoiding the overflow of a temporary storage tank. In order to design this system, the leakage velocity and quantity according to time series should be evaluated. In addition, a proper pump capacity should be determined to avoid repeating the pump switching on and off frequently. In this study, the benzene tank is selected to verify the efficacy of this system. This study can play a critical role to provide a guideline for designing a new system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.89-101
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• 2006

Frequency-variant transmission line parameters are determined. Then the signal transient characterizations of frequency-dependent multi-coupled lines are investigated. With the proposed method, an accurate signal integrity degradation such as signal ringing (overshoot, undershoot) and crosstalk noises relevant to the switching patterns of signals, rising / falling time(tr, tf) and line lengths is investigated. It is shown that there may be approximately 26% discrepancy of signal transients and 260% difference of crosstalk noises between the constant RLC model and frequency-variant RLC model in on-chip global interconnects while those of package lines are 11% and 70%, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.53-59
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• 2012

Smart phones are very convenient for communication, but you need to not to forget to change to silent mode when you go to church or cinema. Many people used to forget changing their cell phones to silent mode. In this paper, we have developed an android smart phone app. for automatic changing silent mode, which exploited smart phones' GPS and computing capability. According to the GPS location data and time, this app. will automatically change a cell phone to silent mode. We believe that this app. would provide us a lot of convenience.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.151-160
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• 2017

This paper presents a new technique of reference current generator based on Kalman filter (KF) estimator for three-phase shunt active power filter (APF). The stationary reference frame (d-q algorithm) is used to transform the load currents into DC component. The harmonics of load currents are extracted and the three-phase reference currents are generated using KF estimator. The work is simulated using Matlab/Simulink platform. To validate the simulation results, an experimental test-rig have been perform using real-time control dSPACE DS1104. In addition, hysteresis current control was used to generate the switching signal for the correction of the harmonics in the system. The non-linear load were constructed with three-phase rectifier which connected in series with inductor and parallel with resistor and capacitor. The results shows that the new technique of shunt APF embedded with KF is proven to eliminate the harmonics created by the non-linear load with some improvement on the total harmonics distortion (THD).

• Journal of Power Electronics
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• v.15 no.5
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• pp.1207-1216
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• 2015

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.7
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• pp.489-494
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• 2009

Since multimedia content is often independently encoded into multiple variations having diverse bandwidths, resolutions and compression formats, the same segment might be stored at different temporal positions within the variations. In this paper, we present a durable multimedia bookmark mechanism which provides a convenient way of switching to any variation before or during playback of the multimedia content, without experiencing temporal discontinuity or overlapping a portion of the content. We also present a new multimedia bookmark player with which users can manage a personal collection of bookmarks with an intuitive visual interface.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.3 s.147
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• pp.322-330
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• 2006

Numerical calculations are carried out for flow past a circular cylinder forced oscillating normal to the free-stream flow at a fixed Reynolds number equal to 185. The cylinder oscillation frequency ranged from 0.8 to 1.2 of the natural vortex-shedding frequency, and the oscillation amplitude extended up to 20% of the cylinder diameter. IBM (Immersed Boundary Method) with direct momentum forcing was adopted to handle both of a stationary and an oscillating cylinder Present results such as time histories of drag and lift coefficients for both stationary and oscillating cases are in good agreement with previous numerical and experimental results. The instantaneous wake patterns of oscillating cylinder with different oscillating frequency ratios showed the synchronized wakes pattern in the lock-in region and vortex switching phenomenon at higher frequency ratio than the critical frequency ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1071-1079
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• 2007

In this paper, a novel space vector control method for isolated multi-level inverter using 3-phase low frequency transformers is proposed. This method is based on the simplification of the space-vector diagram of a five-level inverter using calculated table into fully programming method. The execution time of the proposed method is about same as that of the method using calculated table. Also, the proposed method is easily applied to other case level inverter. We applied this method into the 3-phase IHCML inverter using common arm. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformers could be reduced compare with an exiting 3-phase multi-level inverter using single phase transformer. In addition, this method generates very low harmonic distortion operation with nearly fundamental switching frequency. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.51-56
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• 2010

There are two main software in COMS ground station at the normal mode operation - stationkeeping and wheel off-loading. In this paper, ground software validation test for wheel off-loading is summarized and described. The wheel off-loading was performed the design change from E3000 heritage and analyzed. The wheel off-loading of ground software has two part; one is wheel off-loading management for parameters change at the thruster set switching time and the other is wheel off-loading set-point being sent to satellite for the reference momentum.