• International Journal of Control, Automation, and Systems
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• 제6권5호
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• pp.639-650
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• 2008

Electricity price forecasting has become an integral part of power system operation and control. In this paper, a wavelet transform (WT) based neural network (NN) model to forecast price profile in a deregulated electricity market has been presented. The historical price data has been decomposed into wavelet domain constitutive sub series using WT and then combined with the other time domain variables to form the set of input variables for the proposed forecasting model. The behavior of the wavelet domain constitutive series has been studied based on statistical analysis. It has been observed that forecasting accuracy can be improved by the use of WT in a forecasting model. Multi-scale analysis from one to seven levels of decomposition has been performed and the empirical evidence suggests that accuracy improvement is highest at third level of decomposition. Forecasting performance of the proposed model has been compared with (i) a heuristic technique, (ii) a simulation model used by Ontario's Independent Electricity System Operator (IESO), (iii) a Multiple Linear Regression (MLR) model, (iv) NN model, (v) Auto Regressive Integrated Moving Average (ARIMA) model, (vi) Dynamic Regression (DR) model, and (vii) Transfer Function (TF) model. Forecasting results show that the performance of the proposed WT based NN model is satisfactory and it can be used by the participants to respond properly as it predicts price before closing of window for submission of initial bids.

• 대한기계학회논문집A
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• 제30권4호
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• pp.420-427
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• 2006

The structural and leakage integrity of steam generator tubes should be sustained against all postulated loads even if a crack is present. During the past three decades, most of the efforts with respect to integrity evaluation of steam generator tubes have been focused on limit load solutions but, recently, the applicability of elastic-plastic fracture mechanics was examined cautiously due to its effectiveness. The purpose of this paper is to introduce a testing method to estimate fracture resistance characteristics of steam generator tubes with a through-wall crack. Due to limited thickness and diameter, inevitably, the steam generator tubes themselves were tested instead of standard specimen or alternative ones. Also, a series of three dimensional elastic-plastic finite element analyses were carried out to derive closed-form estimation equations with respect to J-integral and crack extension for direct current potential drop method. Since the effectiveness of $J_{IC}$ as well as J-R curves was proven through comparison with those of standard specimens taken from pipes, it is believed that the proposed scheme can be utilized as an efficient tool for integrity evaluation of cracked steam generator tubes.

• 한국전자파학회논문지
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• 제16권6호
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• pp.571-579
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• 2005

본 논문은 80 MHz 이하의 주파수 대역에서 사용하기 위해 제안된 강제 공진형 EMI 다이폴 안테나에 대한 시험장 감쇠량 이론 곡선을 계산하고 있다. 이론 해석으로서는 안테나에 흐르는 전류 분포에 관한 연립 적분 방정식을 유도하고 구분 정현 함수를 사용한 Galerkin의 모멘트 법으로 그 해를 구하여 시험장 감쇠 량을 검토하고 있다. 그 결과, 강제 공진형 EMI 다이폴 안테나는 50 MHz 이하 주파수 대역의 수평 편파 시험장 감쇠량 측정에 유용하게 사용할 수 있음을 확인할 수 있었다. 제시된 시험장 감쇠량 이론치는 강제 공진형 EMI 다이폴 안테나를 사용하여 야외 시험장의 적합성을 평가할 때 기준 이론 곡선으로 활용할 수 있다.

• 한국가스학회지
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• 제1권1호
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• pp.120-126
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• 1997

저밀도 폴리에틸렌 (LDPE)과 $25\%{\~}48\%$의 함염소 폴리에틸렌(CPE)에 대한 열분해상태를 20ml/min의 질소기류와 $4^{\circ}C{\~}20^{\circ}C$/min의 여러 가지 가열율에서 열중량분석으로 검토하였다. 반응의 열분해 활성화에너지값을 얻기 위하여 수학적인 방법으로는 미분법(Friedman)과 적분법(Ozawa)법이 사용되었다. 위의 방법으로 평가된 활성화에너지는 각각이 잘 일치하였고, 최고평균 활성화에너지는 71.72kcal/mol로 계산되었다. LDPE와 CPE의 열분해는 주쇄분해반응이고 실제 열분해곡선은 이론식과 잘 일치하는 것으로 사료된다.

• 한국산학기술학회논문지
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• 제13권12호
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• pp.6027-6033
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• 2012

본 논문은 릴레이 피드백을 이용한 주파수 영역에서 내부 및 외부 모델을 동정하고 이 모델을 바탕으로 IMC-Cascade 제어기 파라미터 자동 동조 알고리즘을 제안하였다. 모델 동종 방법은 정상상태와 과도상태를 고려하여 1차의 지연모델로 동정 하였으며, 내부 제어기 및 외부 제어기의 제어 파라미터는 동정된 모델을 활용하여 성능지수 ITAE값이 최소로 되도록 자동동조 하였다. 시뮬레이션 결과 제안된 방법이 기존의 방법보다 우수함을 확인할 수 있었다.

• Ocean Systems Engineering
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• 제1권4호
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• pp.355-372
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• 2011

Based on the fully nonlinear velocity potential theory, the liquid sloshing in a three dimensional tank under random excitation is studied. The governing Laplace equation with fully nonlinear boundary conditions on the moving free surface is solved using the indirect desingularized boundary integral equation method (DBIEM). The fourth-order predictor-corrector Adams-Bashforth-Moulton scheme (ABM4) and mixed Eulerian-Lagrangian (MEL) method are used for the time-stepping integration of the free surface boundary conditions. A smoothing scheme, B-spline curve, is applied to both the longitudinal and transverse directions of the tank to eliminate the possible saw-tooth instabilities. When the tank is undergoing one dimensional regular motion of small amplitude, the calculated results are found to be in very good agreement with linear analytical solution. In the simulation, the normal standing waves, travelling waves and bores are observed. The extensive calculation has been made for the tank undergoing specified random oscillation. The nonlinear effect of random sloshing wave is studied and the effect of peak frequency used for the generation of random oscillation is investigated. It is found that, even as the peak value of spectrum for oscillation becomes smaller, the maximum wave elevation on the side wall becomes bigger when the peak frequency is closer to the natural frequency.

• 대한수학회지
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• 제35권4호
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• pp.903-931
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• 1998

Since the modular curves X(N) = $\Gamma$(N)\(equation omitted)＊ (N =1,2,3) have genus 0, we have field isomorphisms K(X(l))(equation omitted)C(J), K(X(2))(equation omitted)(λ) and K(X(3))(equation omitted)( $j_3$) where J, λ are the classical modular functions of level 1 and 2, and $j_3$ can be represented as the quotient of reduced Eisenstein series. When N = 4, we see from the genus formula that the curve X(4) is of genus 0 too. Thus the field K(X(4)) is a rational function field over C. We find such a field generator $j_4$(z) = x(z)/y(z) (x(z) = $\theta$$_3$((equation omitted)), y(z) = $\theta$$_4$((equation omitted)) Jacobi theta functions). We also investigate the structures of the spaces $M_{k}$($\Gamma$(4)), $S_{k}$($\Gamma$(4)), M(equation omitted)((equation omitted)(4)) and S(equation omitted)((equation omitted)(4)) in terms of x(z) and y(z). As its application, we apply the above results to quadratic forms.rms.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.112-115
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• 2001

This paper illustrates a new nodal effective load model for nodal probabilistic production cost simulation of the load point in a composite power system. The new effective load model includes capacities and uncertainties of generators as well as transmission lines. The CMELDC based on the new effective load model at HLII has been developed also. The CMELDC can be obtain from convolution integral processing of the outage capacity probabilistic distribution function of the fictitious generator and the original load duration curve given at the load point. It is expected that the new model for the CMELDC proposed. In this study will provide some solutions to many problems based on nodal and decentralized operation and control of an electric power systems under competition environment in future. The CMELDC based on the new model at HLII will extend the application areas of nodal probabilistic production cost simulation, outage cost assessment and reliability evaluation etc. at load points. The characteristics and effectiveness of this new model are illustrated by a case study of a test system.

• 한국전자파학회논문지
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• 제15권5호
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• pp.467-472
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• 2004

본 논문은 80 ㎒ 이하의 주파수 대역에서 사용하는 강제 공진형 EMI 다이폴 안테나에 대한 정규화 시험장 감쇠량 이론곡선을 계산하고 있다. 이론 해석으로서는 안테나에 흐르는 전류분포에 관한 연립적분방정식을 유도하고 구분 정현함수를 사용한 Galerkin의 모멘트 법으로 그 해를 구하여 정규화 시험장 감쇠량을 검토하고 있다. 그 결과, 강제 공진형 EMI 다이폴 안테나는 80 ㎒ 이하 주파수 대역의 정규화 시험장 감쇠량 측정에 유용하게 사용할 수 있음을 확인할 수 있었다. 제시된 정규화 시험장 감쇠량 이론치는 강제 공진형 EMI 다이폴 안테나를 사용하여 야외시험장의 적합성을 평가할 때 기준이론 곡선으로 활용할 수 있다.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.83-93
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• 2002

This paper presents a motion control method and its simulation results of a mobile robot for a lattice type welding. Its dynamic equation and motion control methods for welding speed and seam tracking are described. The motion control is realized in the view of keeping constant welding speed and precise target line even though the robot is driven for following straight line or curve. The mobile robot is modeled based on Lagrange equation under nonholonomic constraints and the model is represented in state space form. The motion control of the mobile robot is separated into three driving motions of straight locomotion, turning locomotion and torch slider control. For the torch slider control, the proportional-integral-derivative (PID) control method is used. For the straight locomotion, a concept of decoupling method between input and output is adopted and for the turning locomotion, the turning speed is controlled according to the angular velocity value at each point of the corner with range of 90$^{\circ}$ constrained to the welding speed. The proposed control methods are proved through simulation results and these results have proved that the mobile robot has enough ability to apply the lattice type welding line.