• Journal of Internet Computing and Services
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• v.10 no.2
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• pp.179-186
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• 2009

This paper presents an approach to classify normal and Ventricular Tachycardia/Ventricular Fibrillation(VT/VF) from the Creighton University Ventricular Tachyarrhythmia DataBase(CUDB) using the neural network with weighted fuzzy membership functions(NEWFM). In the first step, wavelet transform is used for producing input values which are used in the next step. In the second step, two numbers of input features are extracted by phase space reconstruction method and peak extraction method using coefficients produced by wavelet transform in the previous step. NEWFM classifies normal and VT/VF beats using two numbers of input features, and then the accuracy rate is 90.13%.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.350-350
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• 2017

저수지의 설계홍수량 산정 시 인근의 기상관측 자료를 활용하고 있으나 인근에 기상관측 자료가 없거나 저수지 배후 유역이 큰 경우에는 단일 기상관측 자료를 이용하기에는 한계가 있다. 따라서 실무적으로 지점별 기상관측소의 자료를 이용하여 설계홍수량을 산정할 때에는 각 관측소 자료를 이용하여 확률강우량을 산정하고 Thiessen 가중평균을 한 후 면적우량환산계수 (ARF)를 곱하여 사용하고 있는데, Thiessen 방법의 경우 방법이 간단하지만 지형 고도 효과는 무시되고 우량계의 지배면적에 의한 우량계의 분포 상태만을 고려하게 된다. 그러므로 설계홍수량 산정시 사용되는 Thiessen 방법은 공간적 불확실성을 내포하고 있고, 특히 소규모 저수지의 설계홍수량을 산정하는 경우에는 저수지 유역의 국소적인 특징을 나타내기 어렵다. 본 연구에서는 설계홍수량 산정 시 저수지 위치에 해당하는 확률강우량의 공간적 불확실성을 평가하기 위하여 SIS(Sequential Indicator Simulation) 방법을 이용하였다. SIS 방법은 Kriging 기법과 마찬가지로 베리오그램으로부터 얻어지는 공간적 상관관계를 기반으로 하고 있는 방법으로 Kriging 기법과 달리 공간분포의 국소적인 특성을 평가할 수 있다는 장점을 가지고 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.510-510
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• 2015

우리나라는 1960년대 경제개발에 의한 산업화 이후, 토지이용이 꾸준히 확대되어 왔으며, 이로 인해 불투수면적 증가하였고, 배수시설의 확장은 표면조도계수 및 침투율을 급격히 감소시키는 요인으로 작용하여 우수 및 오수의 유출속도가 증가하여 홍수방어능력이 감소하였다. 또한 기후변화로 인한 국지성 집중호우의 발생빈도가 증가함에 따라 이로 인한 피해가 더욱 가중되고 있다. 현재 이에 대한 대응능력을 갖추기 위한 치수대책을 꾸준히 실시하고 있으나 주로 홍수량을 줄이기 보다는 증가하는 홍수량을 처리하기 위한 하천정비, 하수관, 유수지 및 펌프장 증설을 중심으로 이루어지고 있다. 이는 하천 하류의 홍수량을 증가시켜 하천주변에 침수피해를 일으키고 있어 보다 항구적인 대책이 요구되고 있다. 본 연구에서는 특정유역에 침수가 발생할 시 횡월류위어 가동방식(고정보-가동보)에 따라 미치는 침수영향에 대해 저류조 유입특성(총 유입량, 유입유량 첨두치), 침수지역 침수특성(첨두유량, 첨두수위, 첨두유속, 침수면적, 월류시간)을 정량적으로 분석하여 향후 저류지 설치에 따른 횡월류위어 가동방식 선정에 기여하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.158-158
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• 2016

본 연구에서는 극치 분포의 오른쪽 꼬리 부분 예측 시 안정적인 확률수문량 산정하는 확률분포형과 매개변수 추정 방법을 평가하기 위해 Monte Carlo 모의를 수행하였다. 수문자료의 빈도해석에 적합한 것으로 알려진 generalized extreme value (GEV), Gumbel (GUM), generalized logistic (GLO), gamma3 (GAM3), normal (NOR), log-normal3 (LN3) 총 6개의 확률분포형을 바탕으로 오른쪽 꼬리 부분의 확률수문량 추정 성능을 모의 실험을 통해 평가하고자 한다. 30년 이상 자료를 보유한 기상청 지점의 지속기간별 연최대값 자료를 분석한 결과를 바탕으로 모분포를 GEV분포로 선정하였으며 평균이 1.0, 표준편차 0.5, 왜곡도 계수는 0.5, 1.0, 2.0, 3.0, 4.0이 되도록 가정하였다. 또한 자료 길이에 따른 성능 평가를 위해 표본 크기 20, 50, 100, 150, 200개에 대해 분석을 수행하였다. 위와 같은 가정으로 총 25종류(왜곡도계수 5개 ${\times}$ 표본 크기 5개)의 발생된 모분포에 6가지의 확률분포형과 3가지의 매개변수 추정방법(모멘트법, 최우도법, 확률가중모멘트법)을 조합한 18가지의 모델을 비교 분석해보았다. 평가방법으로는 평균 제곱근 오차(Root Mean Square Error, RMSE), 편의(bias), 평균 상대오차(Mean Relative Difference, MRD), 평균 절대 상대오차(Mean Absolute Relative Difference, MARD)를 사용하여 적용 모델의 성능을 비교 분석하였다.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.65-77
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• 1994

This paper presents a derailed application procedure of the linear quadratic(LQ) theory for a SWATH heave and pitch control. A time domain model of coupled, linear time-invariant second order differential equations is derived from the frequency response model with the frequency dependent added mass and damping approximated as constant values at the heave natural frequency. Wave exciting forces are modeled as a sum of sinusoids. A systematic selection procedure of state and control weighting matrices is presented to obtain good transient behavior and acceptable fin movement. The validity of this controller design process is throughly investigated by simulations both in time domain and frequency domain and singular value plots of transfer function matrices. The finally designed control system shows good overall performances revealing that the applicability of the present study is proved successful.

• Journal of the Korean Society for Railway
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• v.20 no.3
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• pp.413-422
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• 2017

In this study we investigate the importance of the subway station using network centrality measures. For centrality measures, we have used betweenness centrality, closeness centrality, and degree centrality. A new measure called weighted betweenness centrality is proposed, that combines both traditional betweenness centrality and passenger flow between stations. Through correlation analysis and power-law analysis of passenger flow on the Seoul metropolitan subway network, we have shown that weighted betweenness centrality is a meaningful and practical measure. We have also shown that passenger flow between any two stations follows a highly skewed power-law distribution.

• The Korean Journal of Pesticide Science
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• v.20 no.1
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• pp.14-22
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• 2016

A trial of combining and quantifying the effects of food processing on various pesticides was carried out using a meta-analysis. In this study, weighted mean response ratios and confidence intervals about the reduction of pesticide residue levels in fruits and vegetables treated with various food processing techniques were calculated using a statistical tool of meta-analysis. The weighted mean response ratios for tap water washing, peeling, blanching (boiling) and oven drying were 0.52, 0.14, 0.34 and 0.46, respectively. Among the food processing methods, peeling showed the greatest effect on the reduction of pesticide residues. Pearsons's correlation coefficient (r=0.624) between weighted mean response ratios and octanolwater partition coefficients ($logP_{ow}$) for twelve pesticides processed with tap water washing was confirmed as having a positive correlation in the range of significance level of 0.05 (p=0.03). This means that a pesticide having the higher value of $logP_{ow}$ was observed as showing a higher weighted mean response ratio. These results could be used effectively as a reference data for processing factor in risk assessment and as an information for consumers on how to reduce pesticide residues in agricultural products.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.365-371
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• 2009

This paper address the characteristics of loading pollutants caused by the unit agricultural area to establish an efficient management method in NPS (non-point source). The relationship between rainfall and runoff shows good coefficient with 0.92, when the event which shows relatively long antecedent dry days is excepted. The impact of runoff volume on the runoff coefficient can be described by the rainfall intensity strongly. The pollutant EMCs (event mean concentrations) in runoff increased by the increase of antecedent dry days due to dry soil conditions. As the similar pattern of pollutant's loads such as TSS, BOD, COD, TN and TP, it is cleared that other pollutants can be removed when TSS is removed. Therefore the system using only runoff coefficients is not sufficient for the prediction of pollutant loads. It is necessary to consider soil conditions such as rainfall, antecedent dry day, antecedent rainfall etc. for the prediction system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.221-232
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• 2011

Applicability of three soil erosion models for burnt hillslopes was evaluated. The models were estimated with the data from plots established after tremendous wildfire occurred in the east coastal region. Soil erosion and surface runoff were simulated by the Water Erosion Prediction Project (WEPP) and the Revised Universal Soil Loss Equation (RUSLE) of application mode for disturbed forest areas and the Soil Erosion Model for Mountain Areas (SEMMA) developed for burnt hillslopes. Simulated sediment yield and surface runoff were compared with the measured those. In maximum value of sediment yield, three models was under-predicted and RUSLE and WEPP had difference of over two times. SEMMA showed the best model response coefficient, determination coefficient and the model efficiency. In application of models to the soil erosion according to the elapsed year after wildfire, all models were underestimated in initial stage disturbed by wildfire. Evaluation of models in this burnt hillslopes was shown the tends to under-predict soil erosion for larger measured values. Although a lot of sediment can be generated in small rainfall event as fine-grained soil of the high water repellency was exposed excessively right after wildfire, this under-prediction was shown that those models have a limit to estimate the weighted factors by wildfire.

• Journal of Korea Water Resources Association
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• v.43 no.4
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• pp.383-391
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• 2010

The groundwater recharge was assessed by using both SWAT and HELP models in Bocheong-cheon watershed. The SWAT model is a comprehensive surface and subsurface model, but it lacks the physical basis for simulating a soil water percolation process. The HELP model which has a drawback in simulating subsurface lateral flow and groundwater flow component can simulate soil water percolation process by considering the unsaturated flow effect of soil layers. The SWAT model has been successfully applied for estimating groundwater recharge in a number of watersheds in Korea, while the application of HELP model has been very limited. The subsurface lateral flow parameter was proposed in order to consider the subsurface lateral flow effect in HELP model and the groundwater recharge was simulated by the modified exponential decay weighting function in HELP model. The simulation results indicate that the recharge of HELP model significantly depends on the values of lateral flow parameter. The recharge errors between SWAT and HELP are the smallest when the lateral flow parameter is about 0.6 and the recharge rates between two models are shown to be reasonably comparable for daily, monthly, and yearly time scales. The HELP model is useful for estimating groundwater recharge at watershed scale because the model structure and input parameters of HELP model are simpler than that of SWAT model. The accuracy of assessing the groundwater recharge might be improved by the concurrent application of SWAT model and HELP model.