• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.6
• /
• pp.1455-1464
• /
• 1994

A new and efficient algorithm for the integration of the thermal-elasto-plastic constitutive equation is proposed. While it falls into the category of the return mapping method, the algorithm adopts the three point approximation of plastic corrector within one time increment step. The results of its application to a von Mises-type thermal-elasto-plastic model with combined hardening and temperature-dependent material properties show that the accurate iso-error maps are obtained for both angular and radial errors. The accuracy achieved is because the predicted stress increment in a single step calculation follows the exact value closely not only at the end of the step but also through the whole path. Also, the comparison of the computational time for the new and other algorithms shows that the new one is very efficient.

• Proceedings of the IEEK Conference
• /
• 1999.11a
• /
• pp.441-447
• /
• 1999

본 논문은 복잡 적응 시스템의 분석 및 모델링을 위해, 인공생명의 기본 패러다임인 셀룰라 오토마타를 선택하여, 무정형의 구조를 가지며 투명한 자료 전파 특성을 갖는 셀룰라 신경 회로망의 설계하고 개발하는데 중점을 두었다. 우선, 신경 회로망의 불규칙한 구조를 발생학적으로 다루어 무정형의 은닉층을 생성하고, 다윈의 진화론을 적용하여 구조적 진화 및 선택을 통해 최적화된 신경 회로망을 설계하였다. 주변 셀의 상태를 감지하여 자신의 상태를 수정해나가는 방식의 셀룰라 오토마타의 투명한 신호 전파 모델로 자료 및 오차의 역전파에 적용하도록 고안하였고, 라마르크의 용불용설을 활용한 오차의역전파 학습 알고리즘을 유도하였다. 이러한 복잡 적응계의 학습 과정을 유도하여 시뮬레이션에서 그 타당성을 입증하였다. 시뮬레이션에서는 신경 회로망의 XOR 문제와 다중 입력 다중 출력 함수에 대한 근사화 문제를 풀었다.

• Journal of KIISE:Software and Applications
• /
• v.32 no.9
• /
• pp.868-877
• /
• 2005

Arcs are usually treated as significant features in the field of pattern recognition. This paper presents a method to detect arcs from digital planar curves and estimate their arc centers and radii by using geometric analysis. The deviation of distance between the original curve and the detected arc by the proposed method does not exceed a tolerant error. The experimental results show that the proposed method is available for the detection of arcs iron not only smooth but also heavily noisy curves.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05a
• /
• pp.309-314
• /
• 1996

가압 경수로형 원전 안전정지/ 안전 주입 변수와 관련된 계기는 관련 기술 기준에 따라 정기 보수시 교정이 이루어지면, 정지 신호를 모의 주입하여 물리량 검출기로 부터 원자로 정지집계 권선의 풀림시간까지의 총 응답 시간이 사고해석시 가정된 계통의 응답 지연시간이내에 들어 있는 지를 확인한다. 이 정지 신호에 응답하는 동적 보상기의 특성과 관련하여 설계과정에서 삽입된 근사화 오차에 대한 정략적인 평가가 이미 알려진 바 있고, 시간 응답 측정시 삽입되는 지연 요소로 인한 오차도 이에 포함시켜 분석한 바 있어 실제 교정시 정밀도 향상을 위하여 활용하고 있다. 이 논문을 통하여 원자로 정지계통의 응답시간 측정시 노 냉각수 평균 온도 변화율 동적 보상 미분-지연 카드에 모의입력으로 스텝신호를 주입할 경우, 이를 과도하게 큰 신호로 인식하여 매우 짧은 시간(1초 이내)에 응답되고, 스텝신호대신 1%P.U./초로 평균온도 변화율만을 주입할 경우, 보다 늦게 응답됨을 밝혔다. 따라서 모의 시험 방범에 있어서 입력 선택을 적합하게 하여야만 계통의 건전성을 응답시간으로 확인한 수 있는 데, 이에 적합한 모의 입력 방법을 제안하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.9
• /
• pp.2887-2893
• /
• 1996

Governing equations infrictional contact problems are introduced using variational inequality formulations which are regularized to overcome the diffculties of non-differentiability of the friction functional. Also finite element approximations and a priori error estimations are derived based on those formulations. Numerical simulations are performed illustrating the theoretical results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.4
• /
• pp.387-397
• /
• 1992

The spatial domain design of 2-dimensional separable denominator digital filters(SDDF) based on the reduced dimensional decomposition can be realized when the given 2-D impulse response specifications are decomposed into a pair of 1-D specifications via singular value decompositions(SVD). Because of use of the balaned approximation and equivalent transform as 1-D design algorithm, 2-D design algorithm retains the advantage that is numerically stable and can minimize quantization errors. In this paper in order to analyze and reduce these errors, minimum comfficient quantization realization is directly derived from impulse response specification. And using the equivalent trans form relation between mininum coefficient quantization error and minimum roundoff error realizations, we optimally realize a SDDF. This algorithm is analyzed by the simulation, which shows that it is superior to direct or balanced realization in quantization errors.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.5
• /
• pp.976-983
• /
• 1988

An efficient unbalance response analysis method for rotor-bearing systems with spin speed dependent parameters is developed by utilizing a generalized modal analysis scheme. The spin speed dependent eigenvalue problem of the original system is transformed into the spin speed independent eigenvalue problem by introducing a lambda matrix, assuming the bearing dynamic coefficients are well approximated by polynomial functions of spin speed. This method features that it requires far less computational effort in unbalance response calculations and that the influence coefficients are readily available. In addition, the critical speeds and the corresponding logarithmic decrements can be readily identified from the resulting eigenvalues.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.39 no.1
• /
• pp.16-23
• /
• 2002

In this paper, we propose the growing and pruning algorithm to design the optimal structure of modular wavelet neural network(MWNN) with F-projection and geometric growing criterion. Geometric growing criterion consists of estimated error criterion considering local error and angle criterion which attempts to assign wavelet function that is nearly orthogonal to all other existing wavelet functions. These criteria provide a methodology which a network designer can construct MWNN according to one's intention. The proposed growing algorithm increases in number of module or the size of modules of MWNN. Also, the pruning algorithm eliminates unnecessary node of module or module from constructed MWNN to overcome the problem due to localized characteristic of wavelet neural network which is used to modules of MWNN. We apply the proposed constructing algorithm of the optimal structure of MWNN to approximation problems of 1-D function and 2-D function, and evaluate the effectiveness of the proposed algorithm.

• Korean Journal of Computational Design and Engineering
• /
• v.17 no.4
• /
• pp.282-293
• /
• 2012

This paper presents an error-bounded B-spline fitting technique to approximate unorganized data within a prescribed error tolerance. The proposed approach includes two main steps: leastsquares minimization and error-bounded approximation. A B-spline hypervolume is first described as a data representation model, which includes its mathematical definition and the data structure for implementation. Then we present the least-squares minimization technique for the generation of an approximate B-spline model from the given data set, which provides a unique solution to the problem: overdetermined, underdetermined, or ill-conditioned problem. We also explain an algorithm for the error-bounded approximation which recursively refines the initial base model obtained from the least-squares minimization until the Euclidean distance between the model and the given data is within the given error tolerance. The proposed approach is demonstrated with some examples to show its usefulness and a good possibility for various applications.

• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.35T no.1
• /
• pp.33-39
• /
• 1998

This paper discusses approximation modelling of discrete-time linear time-varying system(LTVS). The wavelet transform is considered as a tool for representing and approximating a LTVS. The joint time-frequency properties of wave analysis are appropriate for describing the LTVS. Simulation results is included to illustrate the potential application of the technique.