• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.5
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• pp.552-559
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• 2005

Recurrent neural networks(RNNs) trained with gradient based such as real time recurrent learning(RTRL) has a drawback of slor convergence rate. This algorithm also needs the derivative calculation which is not trivialized in error back propagation process. In this paper a derivative free Kalman filter, so called the unscented Kalman filter(UKF), for training a fully connected RNN is presented in a state space formulation of the system. A derivative free Kalman filler learning algorithm makes the RNN have fast convergence speed and good tracking performance without the derivative computation. Through experiments of nonlinear channel equalization, performance of the RNNs with a derivative free Kalman filter teaming algorithm is evaluated.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06c
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• pp.138-141
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• 1994

기존의 HMM을 이용한 음성인식기는 대부분 ML 추정에 기초한 Baum-Welch 알고리듬으로 학습되었다. ML학습은 기본적으로 무한한 양의 학습 데이터가 주어지고, 각 모델들이 서로 독립이라는 가정에 기초한다. 하지만 실제적인 학습의 경우에 각 모델들이 서로 독립이라고 보기 어렵고, 학습 데이터의 양도 상당히 제한되어 있어서 인식기의 변별력을 저하시키는 주된 원인이 되고 있다. 본 논문에서는 전통적인 패턴분류기법인 Bayes 결정이론에 따라 최소오차율분류를 위한 MAP 수식화를 유도하고, 그에 기초한 HMM의 변별력 있는 학습 알고리듬을 제안한다. 최소오차율분류를 근사화한 사후확률로 표현된 비용함수를 정의하고, 그 비용함수에 조건부 경사강하법을 적용한다. 제안된 알고리듬을 분류하기 어려운 한국어 단음절 인식에 적용한 결과, 기존의 ML 알고리듬으로 학습한 경우 발생한 오인식 개수의 약 10% 가량이 개선되었다.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.2
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• pp.92-100
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• 1992

플렉시블한 관절을 가지고 있는 로보트에 대하여 계단(step) 혹은 경사(ramp) 함수로 기준입력이 주어졌을 때, 모델의 불확실성이나 외란 아래에서 추적오차가 없는 디지찰 제어기법을 제시하고 실제로 실험을 통하여 제어기를 MC 68000으로 구현함으로써 제안한 제어 알고리즘의 유용성을 보였다. 제어기 설계에 있 어서 고려한 사항들은 비선형 마찰력, 중력에 의한 외란, 구동기와 부하사이의 뒤틀림 스프링 효과, 구리고 측 정할 수 없는 상태변수들이다. 또한 미분불가능한 쿨롱마찰로 인하여 전체 시스템이 이산/연속 혼성 시스템이 되어 출력에서 나타나는 리미트 싸이클을 해석/추정하기 위하여 혼성 시스템에서의 기술함수(Describing Function) 법을 제시하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.134-142
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• 1990

A wide-angle approximation in the parabolic equation method is presented to calculate wave transformation in the shallow water. The parabolic approximation to the mild-slope equation is obtain-ed by the use of a splitting matrix, which leads to a generalized equation in form. A numerical model based on a finite difference scheme is presented and computational results are provided to test the model against the laboratory measurements of circular and elliptical shoals. The numerical results are in good agreement with most of experimental data. Therefore it can be concluded that the model shows greater capability to reproduce the characteristics of waves in the refractive focus.

• Journal of Auto-vehicle Safety Association
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• v.12 no.2
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• pp.14-20
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• 2020

This paper presents a vehicle mass and road grade estimator for developing an automated bus. To consider the dynamic characteristics of a bus varying with the number of passengers, the longitudinal controller needs the estimation of the vehicle's mass and road grade in real-time and utilizes the information to adjust the control gains. Discrete Kalman filter is applied to estimate the time-varying road grade, and the recursive least squares algorithm is adopted to account for the constant mass estimation. After being implemented in MATLAB/Simulink, the estimators are evaluated with the dynamic model and experimental data of the target bus. The proposed estimators will be applied to complement the algorithm of the longitudinal controller and proceed with algorithm verification.

• Journal of Korean Society of Transportation
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• v.25 no.2 s.95
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• pp.63-72
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• 2007

The purpose of this study is to develop a traffic characteristic analysis, a correlation analysis with the variables of traffic characteristics, and accident estimation models while recognizing the seriousness of the traffic accidents. The analyses deal with the 181 4-legged signalized intersections that accounted for 1,183 out of 3,115 accidents in Cheongju in 2004. After measuring ADT, intersection area, average lane width, elevation, and other items as independent variables and the number of traffic accidents, the traffic accident rate (accidents per million entering vehicles) and equivalent property damage only (EPDO) figures as dependent variables which are estimated as influencing signalized intersection accidents, the estimation models are developed using correlation analysis and multiple regression analysis. In the analysis of the number of traffic accidents, the model indicates an $R^2$ of 0.612, and five independent variables are taken as significant factors. In the analysis of traffic accident rates, the model indicates an $R^2$ of 0.304 and five significant factors, including intersection area and ADT. Also, for the analysis or the EPDO numbers, which coincides with understanding the seriousness of the traffic accidents and the traffic characteristic analysis, the model indicates an $R^2$ of 0.559, and four independent variables (ADT, main street average lane width, elevation, and speed limit) as significant factors.

• Journal of the Korean GEO-environmental Society
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• v.9 no.7
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• pp.73-85
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• 2008

320 national groundwater monitoring stations have been constructed since 1995 and groundwater levels are measured automatically 4 times a day at each well. It has a difficulty to estimate an average recharge rate of watershed using the recharge rate of the monitoring site because of the lack of its representative on converting a point recharge rate into a spatial one. In this study, the relations between site characteristics (topography, hydraulics, geology, facilities, etc.) and recharge rates of 223 monitoring sites, which were selected using cluster analysis, were analyzed using statistical methods, and finally, regression models were constructed for a recharge rate estimation of non-measured areas. The independent variables for these simple regression models, 1) width of adjacent stream, 2) distance to the nearest stream, 3) topographic slope, and 4) rock type, are proposed using analysis of variance. These models have lots of advantages such as an easy data collection from topographic and geologic maps, a few input variables, and also simplicity in use. Suitability analysis from the comparison between estimation values and original ones at monitoring sites shows that these models are useful for a groundwater recharge estimation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.2
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• pp.95-107
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• 2002

A reliability analysis on sliding of monolithic vertical caisson of composite breakwaters is extensively carried out in order to make the basis for the applicability of reliability-based design method. The required width of caisson of composite breakwaters is determined by the deterministic design method including the effect of impulsive breaking waves as a function of water depth, also studied interactively with the results of reliability analyses. It is found that the safety factor applied in current design may be a little over-weighted magnitude for the sliding of caisson. The reliability index/failure probability is also seen to slowly decrease as the water depth increases for a given wave condition and a safety factor. In addition, optimal safety factor can roughly be evaluated by using the concept of target reliability index for several incident waves. The variations of optimal safety factor may be resulted from the different wave conditions. Finally, it may be concluded from the sensitivity studies that the reliability index may be more depended on the incident wave angles and the wave periodsrather than on the bottom slopes and the thickness of rubble mound.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.125-130
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• 2009

Storage function method which considers the non-linearity of the relationship between rainfall and runoff has been frequently used to predict runoff in a basin and a flood pattern. However, it is time-consuming to estimate appropriate parameters of every basin and rainfall event, which requires the empirical parameter equation applicable in Korea. In this study, multiple regression analysis is used to develop empirical equations to estimate parameters of Storage Function method using basin characteristics. The basin area, maximum stream length, and stream slope are considered as the basin characteristics as the result of the regression analysis. Collinearity is removed and trial-and-error method is used to choose the most descriptive parameters to the dependent variables in Han River basin which is divided into 30 subbasins. The developed equations are validated using the rainfall events in MunMak gauging station and named as 'Han River equation'. The equation could provide the useful information about Storage Function method parameter to calculate runoff from a basin and predict river stage.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.30-36
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• 2017

SS(Suspended Solid) concentration by soil erosion into river at normal and flood season should be measured. However, to present the variation of SS due to various development project such as EIA(Environmental Impact Assessment), River Master Plan, and so on, it is necessary to estimate not measure SS, but there are not exist how to estimate SS. In the present study, therefore, we propose the hydrologic method of estimating SS concentration using the results of particular frequency flood discharge and sediment discharge by RUSLE method. SS consists of silty and clay soil and colloid particle etc. However, in the present study, silty and clay soils of sediment discharge except send set up SS standards. The flow discharge to estimate SS concentration are 1~2 years for normal season, 30~100 years for flood season. Meanwhile, analysis software for probable rainfall uses Fard2006, probable rainfalls under 2-year frequency are estimated using rainfall data and frequency factor of Gumbel distribution. The results of estimating SS concentration using runoff volume by sediment and flow discharges of silty and cray soils as above method show that reliable level of SS concentration is considered in predevelopment of natural condition and under development of barren condition. Especially, SS concentration takes notice that the value of sediment discharge makes a huge difference according to channel slope, it was confirmed that the value obtained by dividing the SS concentration by the channel slope is relatively constant even though the topographical factors are different. Therefore, if the present study will be proceeded for various watersheds, it will be developed as estimation method of SS concentration.