• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.207-207
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• 2023

데이터 기반 강수 예측 모델은 극한 강수 이벤트의 크기를 과소 추정하는 경향이 있다. 이는 훈련 데이터에 극한 강수 이벤트보다 일반적인 강수 이벤트가 많이 포함되어 있기 때문이다. 본 연구는 이러한 딥러닝의 데이터 불균형 문제를 해소하고자 모델을 학습시킬 때 격자별 극한 강수에 더 큰 가중치를 주어 극한 강수 예측의 정확성을 높이는 방법을 제안한다. 딥러닝 모델 중 공간-시간 필드를 정확하게 예측할 수 있는 ConvLSTM 기반 강수 예측 모델을 활용하여 레이더 강수량을 예측하였다. 먼저, 훈련 기간 동안의 강수 이벤트의 누적 분포 함수 CDF(Cummulative distribution funcion)을 그린 후 극한 강수 이벤트와 일반적인 강수 이벤트의 분포를 확인하였다. 그다음, 적은 분포를 가진 극한 강수 이벤트의 더 큰 가중치를 두어 모델을 학습시켰다. 이 모델은 대한민국 중부 지역 (200km x 200km)의 5km-10분 해상도 레이더-계량기 복합 강수 필드에 대해 2009-2014년 기간 동안 훈련 되었고 2015-2016년 동안 모델의 훈련을 검증 하였고, 2017-2018년 동안 테스트 되었다. 다양한 가중치 함수를 기반으로 훈련 시킨 결과 최적화 가중치 함수 모델의 평균 NSE는 0.6 평균 RMSE는 0.00015 그리고 극한 강수 이벤트만 따로 추출한 평균 MAE는 6이다. 결과적으로 제안된 모델은 기존 방법에 비해 예측 성능을 향상 시켰으며, 격자별 가중치를 두었을 경우 일반적인 강수 이벤트 뿐만 아니라 극한 강수 이벤트의 예측의 정확도를 향상시켰다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.2
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• pp.63-72
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• 2016

An expected-discounted cost model based on RRP(Renewal Reward Process), referred to as a stochastic decision model, has been developed to estimate the optimal period of in-depth inspection which is one of critical issues in the life-cycle maintenance management of harbor structures such as rubble-mound breakwaters. A mathematical model, which is a function of the probability distribution of the service-life, has been formulated by simultaneously adopting PIM(Periodic Inspection and Maintenance) and CBIM(Condition-Based Inspection and Maintenance) policies so as to resolve limitations of other models, also all the costs in the model associated with monitoring and repair have been discounted with time. From both an analytical solution derived in this paper under the condition in which a failure rate function is a constant and the sensitivity analyses for the variety of different distribution functions and conditions, it has been confirmed that the present solution is more versatile than the existing solution suggested in a very simplified setting. Additionally, even in that case which the probability distribution of the service-life is estimated through the stochastic process, the present model is of course also well suited to interpret the nonlinearity of deterioration process. In particular, a MCS(Monte-Carlo Simulation)-based sample path method has been used to evaluate the parameters of a damage intensity function in stochastic process. Finally, the present stochastic decision model can satisfactorily be applied to armor units of rubble mound breakwaters. The optimal periods of in-depth inspection of rubble-mound breakwaters can be determined by minimizing the expected total cost rate with respect to the behavioral feature of damage process, the level of serviceability limit, and the consequence of that structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1140-1144
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• 2012

In this paper, we propose a timing offset estimation scheme for initial ranging of IEEE 802.16e systems. The conventional scheme estimates the timing offset by using the cross-correlation between the local and received signals only. On the other hand, this paper proposes a timing offset estimation scheme with additional cross-correlations accumulated on the conventional cross-correlation. The additional cross-correlations are obtained by using the ranging signal with a repetitive structure. Numerical results show that the proposed scheme provides the better timing offset estimation performance compared with that of the conventional scheme.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.123-128
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• 2010

The space radiation/total ionizing Dose(TID) and its effects, and the GEO satellite system design considerations in space radiation environment are studied in this paper using Spenvis(Space Environment Information System). The GEO satellite system in space environment is simulated by NASA AP8/AE8, JPL91 and NRL CREME models, repectively for trapped particle, solar proton and cosmic-ray. The total ionizing Dose which is accumulated continuously to spacecraft electronics has been expressed as the function of aluminum thickness. These values can be used as the criteria for the selection of electronic parts and shielding thickness of the Digital Channel Amplifier(DCAMP) structure.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.2
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• pp.43-51
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• 2018

The objective of this research was to assess the effect of moisture content and water injection method into the landfill on waste decomposition in an aerobic landfill. Firstly, respirometric experiments were performed in order to assess the effect of initial moisture content (20%, 30%, 40% and 50% respectively) on landfilled waste decomposition. The cumulative oxygen uptake and oxygen uptake rate were highly increased with the increase of initial moisture content. Secondly, lysimeter experiments showed that in comparison with the vertical injection method, dry fog system enhanced decomposition of organic wastes. Also, dry fog system provided uniform moisture distribution more than the vertical injection method within landfill.

• Journal of the Korean Data and Information Science Society
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• v.27 no.5
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• pp.1119-1131
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• 2016

The Neyman-Scott Rectangular Pulses Model (NSRPM) is mainly used to construct hourly rainfall series. This model uses a modest number of parameters to represent the rainfall processes and underlying physical phenomena, such as the arrival of storms or rain cells. In NSRPM, the method of moments has often been used because it is difficult to know the distribution of rainfall intensity. Recently, approximated likelihood function for NSRPM has been introduced. In this paper, we propose a hierarchical model for applying a spatial structure to the NSRPM parameters using the approximated likelihood function. The proposed method is applied to summer hourly precipitation data observed at 59 weather stations (Korea Meteorological Administration) from 1973 to 2011.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.1
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• pp.1-13
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• 2022

A weighted linear combination of seismic fragility models previously developed for cut-and-cover railway tunnels was presented and the appropriateness of the combined model was evaluated. The seismic fragility function is expressed in the form of a cumulative probability function of the lognormal distribution based on the peak ground acceleration. The model uncertainty can be reduced by combining models independently developed. Equal weight is applied to four models. The new seismic fragility function was developed for each damage level by determining the median and standard deviation, which are model metrics. Comparing fragility curves developed for other bored tunnels, cut-and-cover tunnels for high-speed railway system have a similar level of fragility. We postulated that this is due to the high seismic design standard for high-speed railway tunnel.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.213-223
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• 2000

It is necessary that radiation dose would be detect exactly generated from facility related to nuclear, space, radiotherapy center, etc. This paper is to use of the radiation-induced threshold voltage change as an accumulated radiation dose monitoring sensor. Commercial P Channel Power MOSFET(metal oxide field effect transistor) were tested in a Co-60 gamma irradiation facility to see their capabilities as a radiation dosimeter. We found that the transistors showed good linearity in their threshold voltage shift characteristics with radiation dose. The results demonstrate the potential use of commercial P Channel Power MOSFET as inexpensive radiation sensors.

• Journal of Broadcast Engineering
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• v.25 no.1
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• pp.48-57
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• 2020

Recently, with the rapid development of image recognition technology, the demand for object analysis in road CCTV videos is increasing. In this paper, we propose a method that can adaptively find the counting line for traffic analysis in road CCTV videos. First, vehicles on the road are detected, and the corresponding positions of the detected vehicles are modeled as the two-dimensional pointwise Gaussian map. The paths of vehicles are estimated by accumulating pointwise Gaussian maps on successive video frames. Then, we apply clustering and linear regression to the accumulated Gaussian map to find the principal direction of the road, which is highly relevant to the counting line. Experimental results show that the proposed method for detecting the counting line is effective in various situations.

• Journal of Animal Science and Technology
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• v.51 no.2
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• pp.111-122
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• 2009

This study was performed to make it possible to adjust milk production records which are changing with days in milk more accurately as developing new 305-day adjustment factors considering current circumstance and to offer easier application by converting adjustment factors to formulas. Total 4,264,347 records were used in this analysis after eliminating unusual value and data was classified by first parity and over second parity. Herd-year effects were classified with 2,878 and 19,783 classes in first parity and over second parity, respectively and number of subclass of age-calving season-lactation stage effects were 136 (age 2, calving season 4, lactation stage 17). For calculation of least square mean, SAS GLM was used and multiplicative adjustment factors were developed. The result of error analysis, deviations between means of adjusted yields and cumulated yields were the lowest in new adjustment factor which was developed in this study comparing with other adjustment factors which were developed in the past (94', 02') in first parity and in over second parity, results of adjustment factors which were developed in 2002 and this study were similar. For easier application, formulas of 305-day adjustment factors were developed using SAS NLIN.