• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.45-51
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• 1998

In the realization of a high speed digital transmission over several tens kbps in mobile communications, it follow delay distortion on a count of transmission path variation by multipath interference waves. Therefore it is inevitably necessary to establish the techniques overcoming the frequency selective fading. In this paper, a feedback running RLS algorithm which is improved the RLS algorithm using exponential weighting factor, is proposed for the control algorithm of DFE and by the computer simulation method, and the performance characteristics of DFE is analyzed for the one-ray and two-ray waves model under the random Gaussian noise. The computer simulation results of proposed RLS algorithm for the $\pi$/4QPSK signal with one symbol time delayed interference signal of S/I = 20［dB］, under the S/N = 10［dB］ with $\lambda$= 0.9 showed excellent following characteristics and equalization characteristics.

• The KIPS Transactions:PartA
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• v.9A no.1
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• pp.9-18
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• 2002

In this paper, we propose scalable scheduling techniques based on EDF to efficiently integrate hard real-time and multimedia soft real-time tasks in the distributed real-time multimedia database system. Hard tasks are guarangteed based on worst case execution times, whereas multimedia soft tasks are served based on mean execution times. This paper describes a served-based scheme for partitioning the CPU bandwidth among different task classes that coexist in the same system. To handle the problem of class overloads characterized by varying number of tasks and varying task arrival rates, thus scheme shows how to adjust the fraction of the CPU bandwidth assigned to each class. This scheme fixes the maximum time that each hard task can execute in the period of the server, whereas it can dynamically change the bandwidth reserved to each multimedia task. The proposed method is capable of minimizing the mean tardiness of multimedia tasks, without jeopardizing the schedulability of the hard tasks. The performance of this scheduling method is compared with that of similar mechanisms through simulation experiments.

• Journal of Wetlands Research
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• v.15 no.1
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• pp.79-90
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• 2013

Stormwater wetland targeted to treat the rainfall runoff from cow feeding-lot basin has been monitored from May 2010 to November 2011. Reduction efficiency estimated based on 20 rainfall event monitoring was 88%, 54%, 70%, 31%, and 64% for TSS, BOD, $COD_{Cr}$, TN, and TP, respectively. Theoretically, as rainfall depth increases, hydraulic exchange ratio has to be increased. When the exchange ratio approaches to 1 (usually design goal), TSS reduction efficiency was estimated about 55%. Uncertainty in reduction efficiency of the stormwater wetland is normally very high due to the continuous rainfall activity, its magnitude and intensity, antecedent dry days, and other natural variables which can not be controlled by experiment conductors. In this study, predominant affecting variables was found to be hydraulics caused by consecutive rainfall events having different intensity and algal growth during dry days.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.101-101
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• 2015

1986년 한강종합개발사업으로 대규모 준설이 실시되고, 수위가 낮아지면서 발생한 문제점을 해결하고자, 1988년 김포대교 직하류 지점에 신곡수중보를 건설하였다. 당시 수중보의 설치목적은 취수시설 유지를 위한 수위유지가 주요기능이었으나, 30년이 지난 지금 생활용수 취수시설은 잠실 수중보 상류로 모두 이전하였고, 농업용수와 일부 공업용수 등의 일부 시설만이 남아 있어 신곡수중보 시설의 필요성 및 현재 기능에 대한 재평가가 필요한 시점이다. 신곡수중보 철거시 변화하는 한강 본류의 수위를 모의하기 위해 수리학적 모형인 HEC-RAS를 이용한 부정류 모의를 실시하였다. 모형의 보정을 위해 저수기를 대표하는 2014년 4월부터 5월까지 45일간과 풍수기를 대표하는 2014년 8월부터 9월까지 45일간을 모의하였다. 조위영향을 받고 있는 강화대교 관측수위를 기점수위로 선정하고, 팔당댐 유량을 유량조건으로 모의하였으며, 본류구간의 전류, 행주대교, 한강대교 지점의 실측수위와 모의결과는 잘 일치하는 것으로 나타났다. 신곡수중보 철거시 평가를 위해 팔당댐 방류량이 최소가 되는 조건과 한강의 갈수량, 저수량, 계획홍수량 등 유량조건 변화에 따른 한강 본류수위를 비교하였다. 보 철거시 서해안의 조위영향이 잠실수중보 직하류지점까지 영향을 미치고, 일시적인 수위하강 현상이 발생하는 것으로 모의되었다. 보 철거에 의해 감조하천으로 변화되는 구간에서는 전반적인 유속이 증가하여, 현재 문제가 되고 있는 신곡수중보 직상류 및 지천 합류부 주변의 퇴적문제와 수질 문제개선에 도움을 줄 것으로 예상된다. 또한 신곡수중보 상류지역에서 잠실수중보 하류까지 발생하는 수위변화와 수면폭변화는 간조대 형성에 유리한 조건을 제공하여 한강변의 퇴적지 면적 증가 및 생태계 서식처 제공에 도움을 줄 것으로 기대된다. 다만 신곡수중보 하류지역의 수위는 현재보다 전반적인 상승이 예상되어 장항습지 면적이 일부 감소할 것으로 예상되지만, 홍수시 침식 및 퇴적이 가장 활발히 발생하므로 하상변동 등에 대한 면밀한 평가가 필요하다. 또한 홍수기 신곡수중보 구조물에 대한 평가 결과에서는 철거 시 한강 본류의 하천 수위가 일부 하강하는 것으로 모의되어 하천을 횡단하는 구조물이 홍수위 상승에 기여한다고 판단되므로 대안마련을 위한 종합적인 평가가 필요하다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.265-265
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• 2019

기후변화로 의한 기온의 상승은 가뭄, 홍수와 같은 재해를 일으킬 뿐만 아니라 깊은 호수나 저수지와 같은 수자원에도 용존 산소, 물질, 영양소 및 식물플랑크톤의 수직적 분포 등과 같은 다양한 부분에 영향을 미친다. 본 연구의 목적은 SWAT, HEC-ResSim 및 CE-QUAL-W2(이하 W2)모델을 사용하여 미래의 기후 변화에 따른 소양호의 수온, 성층강도 및 열적 안정성의 변화를 장기 예측하고 그 영향을 평가하는데 있다. W2 모델의 보정은 2005 년부터 2015 년까지의 실측 과거 데이터를 이용하여 보정하였고 기후변화 시나리오는 IPCC의 AR5 RCP 4.5 시나리오를 사용하였다. 기후자료는 GCM 모델인 HadGEM2-AO 결과를 상세화하여 모의기간의 자료를 생성하였다. SWAT모델을 이용하여 모의기간인 2016 년부터 2070 년까지 일단위로 저수지 유입을 예측했으며 HEC-ResSim모델을 이용하여 소양강댐 저수지 운영 조건에 따라 저수지 방류량 및 수위 변화를 모의하였다. 수온 해석을 위해 W2를 적용하여 저수지의 장기간의 수온 변화를 예측하였다. 결과적으로 대기 온도는 $0.0279^{\circ}C/year$(p < 0.05) 상승할 것으로 예측되었으며, 동일기간 상층(수면으로부터 5m 깊이)과 하층 (바닥으로부터 5m 높이) 수온은 각각 $0.0191^{\circ}C$/년(p < 0.05) 및 $0.008^{\circ}C$/년(p < 0.05) 상승할 것으로 예측되었다. 모의된 수온을 계절별로 분석했을 때 상층수온은 여름철 가장 큰 폭으로 상승하였으며 하층의 경우 겨울철에 가장 큰 폭으로 상승하였다. 계절별 상-하층 수온의 차는 여름이 가장 컸으며, 겨울에 온도차가 가장 작았다. 또한 미래 온도의 상승에 따라, 소양호의 성층 강도가 강해지는 경향을 보였으며 상층 및 하층의 온도차 $5^{\circ}C$를 기준으로 성층이 형성되는 기간은 큰 변동이 없었으나 소멸되는 시점이 점점 늦어지는 추세를 보여 성층 형성 기간이 길어지는 것으로 나타났다. 저수지 표면의 수온 상승은 식물플랑크톤의 계절 성장률에 영향을 미쳤는데, 특정 조건에서 규조류는 최적 성장 범위를 벗어나는 고온 조건에서 성장속도가 감소하였으나 녹조류와 남조류의 출현 시기가 빨라지며 장기화될 것으로 예측되었다.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.27-34
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• 2018

In this study, the generating of torque regarding the Control Moment Gyro (CMG) is proportional to the angular velocity of gimbal. This is the case because gimbal affects the attitude control of the satellite directly, and it is necessary to reduce the incidence of torque ripple of gimbal. In this paper, the cause of the torque ripple of gimbal is reviewed and mathematically modeled by assuming the friction imbalance of bearing, the magnetic field and the phase current imbalance of the motor. We are able to confidently estimate the modeling parameters of gimbal disturbance using a constant speed test, and then analyze the influence of applying feedforward control to our modeling. Additionally, the simulation results show that the torque ripple and angular velocity fluctuations are reduced when apply this modeling to the identified study parameters. Finally, we present the disturbance reduction technique using our disturbance modeling.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.623-628
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• 2019

The aim of this study was to design fast non local means (FNLM) noise reduction algorithm and to confirm its application feasibility in light microscopic image. For that aim, we acquired mouse first molar image and compared between previous widely used noise reduction algorithm and our proposed FNLM algorithm in acquired light microscopic image. Contrast to noise ratio, coefficient of variation, and no reference-based evaluation parameter such as natural image quality evaluator (NIQE) and blind/referenceless image spatial quality evaluator (BRISQUE) were used in this study. According to the result, our proposed FNLM noise reduction algorithm can achieve excellent result in all evaluation parameters. In particular, it was confirmed that the NIQE and BRISQUE evaluation parameters for analyzing the overall morphologcal image of the tooth were 1.14 and 1.12 times better than the original image, respectively. In conclusion, we demonstrated the usefulness and feasibility of FNLM noise reduction algorithm in light microscopic image of small animal tooth.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.3
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• pp.264-272
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• 2019

The aim of this study is to analyze the relationship between international oil price as a fuel cost in overseas fisheries and skipjack tuna price as a part of main products in overseas fisheries using monthly time series data from 2008 to 2017. The study also tried to analyze the change of fishing profits by fuel cost. For a time series analysis, this study conducted both the unit-root test for stability of data and the Johansen cointegration test for long-term equilibrium relations among variables. In addition, it used not only the Granger causality test to examine interactions among variables, but also the Vector Auto Regressive (VAR) model to estimate statistical impacts among variables used in the model. Results of this study are as follows. First, each data on variables was not found to be stationary from the ADF unit-root test and long-term equilibrium relations among variables were not found from a Johansen cointegration test. Second, the Granger causality test showed that the international oil prices would directly cause changes in skipjack tuna prices. Third, the VAR model indicated that the posterior t-2 period change of international oil price would have an statistically significant effect on changes of skipjack tuna prices. Finally, fishing profits from skipjack would be decreased by 0.06% if the fuel cost increases by 1%.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.4
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• pp.625-632
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• 2022

Gas turbine generators in load-following operation in the domestic power system play a major role in maintaining the rated frequency, but often have poor frequency control. Therefore, after examining the control characteristics of the governor, which is a gas turbine speed control device, and analyzing the failure types, countermeasures were suggested for each case. In addition, it was confirmed through the governor response test that the gas turbine helps in frequency recovery depending on the speed of fuel control, but also acts as a factor impeding stable operation, such as rapid fluctuations in combustion chamber temperature and combustion vibration. Therefore, in order to maintain stable power quality, there was a need for thorough facility management as well as research on the governor control method in which the traditional PID control method and the machine learning algorithm, a core field of the 4th industry, were fused.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.290-302
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• 2022

In this study, it was examined for the reduction of wave overtopping and water level fluctuation in front of the revetment when applying a reinforcement method to revetment where wave overtopping occurs. As a result of the study, in the case of the cross-sectional experiment. more than 70% of the wave overtopping reduction effect depending on the reinforcement conditions was occurred, and it was analyzed that the result increases by about four times or more in the comparison with the 3d test. The average water level in front of the revetment was lowered when a low crest structure was not installed. and there was a tendency to rise under the condition of low crest structures installed. In the comparison with the wave basin test, there was a difference of about 0.5 to 0.6 times when a low crest structure was not installed, and it was increased by 5.5 times after low crest structures were installed.