• Journal of applied mathematics & informatics
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• v.32 no.1_2
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• pp.39-53
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• 2014

In this paper, a non-asymptotic method is presented for solving singularly perturbed delay differential equations whose solution exhibits a boundary layer behavior. The second order singularly perturbed delay differential equation is replaced by an asymptotically equivalent first order neutral type delay differential equation. Then, Simpson's integration formula and linear interpolation are employed to get three term recurrence relation which is solved easily by Discrete Invariant Imbedding Algorithm. Some numerical examples are given to validate the computational efficiency of the proposed numerical scheme for various values of the delay and perturbation parameters.

• Structural Engineering and Mechanics
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• v.66 no.5
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• pp.649-663
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• 2018

The scaled boundary finite element method is extended to evaluate the dynamic stress intensity factors and T-stress with a numerical procedure based on the improved continued-fraction. The improved continued-fraction approach for the dynamic stiffness matrix is introduced to represent the inertial effect at high frequencies, which leads to numerically better conditioned matrices. After separating the singular stress term from other high order terms, the internal displacements can be obtained by numerical integration and no mesh refinement is needed around the crack tip. The condition numbers of coefficient matrix of the improved method are much smaller than that of the original method, which shows that the improved algorithm can obtain well-conditioned coefficient matrices, and the efficiency of the solution process and its stability can be significantly improved. Several numerical examples are presented to demonstrate the increased robustness and efficiency of the proposed method in both homogeneous and bimaterial crack problems.

• Journal of applied mathematics & informatics
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• v.27 no.1_2
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• pp.441-452
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• 2009

In this paper, a fifth order numerical method is presented for solving singularly perturbed differential-difference equations with negative shift. In recent papers the term negative shift has been using for delay. Similar boundary value problems are associated with expected first exit time problem of the membrane, potential in models for neuron and in variational problems in control theory. In the numerical treatment for such type of boundary value problems, first we use Taylor approximation to tackle terms containing small shifts which converts it to a boundary value problem for singularly perturbed differential equation. The two point boundary value problem is transformed into general first order ordinary differential equation system. A discrete approximation of a fifth order compact difference scheme is presented for the first order system and is solved using the boundary conditions. Several numerical examples are solved and compared with exact solution. It is observed that present method approximates the exact solution very well.

• Bulletin of the Korean Mathematical Society
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• v.53 no.3
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• pp.765-777
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• 2016

In this paper, we prove the existence of nontopological solutions to the self-dual equations arising from the Chern-Simons gauged O(3) sigma models. The property of solutions depends on a parameter ${\tau}{\in}[-1,1]$ appearing in the nonlinear term. The case ${\tau}=1$ lies on the borderline for the existence of solutions in the previous results [4, 5, 7]. We prove the existence of solutions in this case when there are only vortex points. Moreover, if $-1{\leq}{\tau}$<1, we establish solutions which are perturbed from the solutions of singular Liouville equations.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2002.05a
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• pp.28-32
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• 2002

웹 상의 많은 정보들 속에서 사용자가 원하는 정보를 찾아내는 일은 쉽지 않다. 사용자가 의도하는 양질의 정보 제공을 위해 특정 영역과 관련한 정보 제공 시스템이 .개발되고 있다. 이전 시스템은 특정 영역 관련 지식베이스를 토대로 하여 웹 문서를 수집해 놓고, 사용자에게 정보를 제공한다. 본 논문에서는 전문 사이트 내에 문서간의 유사성을 토대로 하여 동물 영역에 대한 효과적인 문서 클러스타링(clustering)에 관해 실험하였다. 기존의 방법에서는 문서의 분류나 질의어와 관련한 문서 선택이나 순위 결정이 주로 텀(term)을 바탕으로 하고 있다. 본 논문에서는 각 문서 내의 텀 뿐만 아니라 HTML 태그(tag), 지식베이스에 WordNet의 계층구조를 적용한 data를 활용하고, SVD(Singular Value Decomposition)를 사용하여 문서간의 관계를 밝혀내어 문서 분류 및 수집에 이용하였다. 특정 영역의 전문 문서를 많이 제공하는 사이트에 적용하여 좋은 결과를 볼 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1590-1595
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• 2006

This paper proposes a technique of user oriented document ranking using user refile to provide more satisfied results which reflect preference of specific users. User profile is constructed to represent his or her preference. User pfofile consists of 'term array' and 'preference vector' according to the interest field of one. And the User profile for a particular person is updated by 'user access', 'latent relaeon', 'User Profile' proposed in this paper. The latent structures of documents in same domain are analysed by singular value decomposition(SVD). Then, the rank of documents is determined by comparison of user profile with analyzed document on the basis of relevance.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.391-393
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• 1992

This paper proposes an adaptive control system using a 80286 microprocessor-based system and DC servo motors for the control of flexible joint manipulator. In this paper, we construct the controller based on a singular perturbation strategy damping out the elastic oscillations at the joints. we added to the controller the compensator for damping the joint and the term for decreasing the position error between the actuator and the link in order to improve the asymptotical convergence of the position of the link. It is shown that the implementation of this control algorithm can be practical.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.255-259
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• 1989

A suboptimal output feedback controller is designed and applied to a flexible rotor bearing system in order to control the unstable or lilghtly damped vibrations. The reduced order model is the truncated modal equation of the distributed parameter system obtained through the singular perturbation. The instability problem arising from the spillover effects caused by the uncontrolled high frequency modes is prevented through the constrained optimization by incorporating the spillover term into the performance index. The efficiency of the proposed method is demonstrated experimentally with a flexible rotor by using a magnetic bearing.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.21 no.3
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• pp.109-124
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• 2017

The numerical solution of the Stokes equation with discontinuous viscosity and singular force term is challenging, due to the discontinuity of pressure, non-smoothness of velocity, and coupled discontinuities along interface.In this paper, we give an efficient algorithm to solve this problem by employing spectral Legendre and Chebyshev approximations.First, we present the algorithm for a problem defined in rectangular domain with straight line interface. Then it is generalized to a domain with smooth curve boundary and interface by employing spectral element method. Numerical experiments demonstrate the accuracy and efficiency of our algorithm and its spectral convergence.

• ETRI Journal
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• v.46 no.4
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• pp.633-647
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• 2024

In e-commerce platforms, sentiment analysis on an enormous number of user reviews efficiently enhances user satisfaction. In this article, an automated product recommendation system is developed based on machine and deep-learning models. In the initial step, the text data are acquired from the Amazon Product Reviews dataset, which includes 60 000 customer reviews with 14 806 neutral reviews, 19 567 negative reviews, and 25 627 positive reviews. Further, the text data denoising is carried out using techniques such as stop word removal, stemming, segregation, lemmatization, and tokenization. Removing stop-words (duplicate and inconsistent text) and other denoising techniques improves the classification performance and decreases the training time of the model. Next, vectorization is accomplished utilizing the term frequency-inverse document frequency technique, which converts denoised text to numerical vectors for faster code execution. The obtained feature vectors are given to the modified convolutional neural network model for sentiment analysis on e-commerce platforms. The empirical result shows that the proposed model obtained a mean accuracy of 97.40% on the APR dataset.