• Journal of applied mathematics & informatics
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• 제31권1_2호
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• pp.55-63
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• 2013

In this paper, a general technique is proposed for solving a system of fourth-order boundary value problems. The solution is given in the form of series and its approximate solution is obtained by truncating the series. Advantages of the method are that the representation of exact solution is obtained in a new reproducing kernel Hilbert space and accuracy of numerical computation is higher. Numerical results show that the method employed in the paper is valid. Numerical evidence is presented to show the applicability and superiority of the new method.

• 한국전산구조공학회논문집
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• 제24권5호
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• pp.543-551
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• 2011

본 논문에서는 해양작업 상태의 하중조건을 고려한 부유식 원유생산 저장 하역장치에 설치된 라이져 보강구조의 강도설계에 관련하여 다양한 근사화 기법 기반 설계최적화 및 그 성능을 비교하고자 한다. 설계최적화 문제는 하중조건별 구조강도의 제한조건 하에서 중량을 최소화하여 설계변수인 구조 부재치수가 결정되도록 정식화된다. 비교 연구를 위해 사용된 근사화 기법은 반응표면법 기반 순차적 근사최적화(RBSAO), 크리깅 기반 순차적 근사최적화(KBSAO), 그리고 개선된 이동최소자승법(MLSM) 기반 근사최적화 기법인 CF-MLSM와 Post-MLSM이다. RBSAO와 KBSAO의 적용을 위하여 상용프로세스 통합 설계최적화(PIDO) 코드를 사용하였다. 본 연구에 적용한 MLSM 기반 근사최적화 기법들은 제한조건의 가용성을 보장할 수 있도록 새롭게 개발되었다. 다양한 근사화 모델 기반 설계최적화 기법에 의한 결과는 설계 해의 개선 및 수렴속도 등의 수치적 성능을 기준으로 실제 비근사 설계최적화 결과와 비교 검토하였다.

• Nuclear Engineering and Technology
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• 제16권4호
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• pp.202-216
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• 1984

Nodal method가 소격격자 해석방법의 하나로 정립됨으로써, 계산격자가 비교적 크더라도 각 격자의 평균출력분포를 정확히 계산할 수 있게 하는 균질화변수틀 찾는 방법이 중요하게 되었다. 본 연구에서는 simplified equivalence theory와 approximate node equivalence theory의 두가지 근사방법을 가압경수형 원자로 문제에 적응하여 시험하여 보았다. 균질화계산과 노심분석계산 방법으로서 analytic nodal method에 기초를 둔 ANM 코드를 개발하였다. 여러 균질화 방법외 정확성을 KTDD 코드에 의한 reference solution과 비교하여 본 결과, 균질화 계산은 핵연료영역에서는 영역별 핵연료집합체 계산으로, baffle과 reflector의 공존 격자영역은 이들을 포함하는 color set 계산으로 수행할 수 있음을 알았다. Approximate node equivalence theory에 입각해서 approximate homogenized cross-section들과 approximate discontinuity factor들의 균질화 변수를 사용하면 출력분포와 임계도가 각각 0.8%, 0,1% 오차 범위내에서 예측되었다.

• 한국경영과학회지
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• 제30권1호
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• pp.161-176
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• 2005

In a situation that ordinal preferences on multiattribute weights are captured, we present two solution approaches: an exact approach and an approximate method. The former, an exact solution approach via interaction with a decision-maker, pursues the progressive reduction of a set of non-dominated alternatives by narrowing down the feasible attribute weights region. Subsequent interactive questions and responses, however, sometimes may not guarantee the best alternative or a complete rank order of a set of alternatives that the decision-maker desires to have. Approximate solution approaches, on the other hand, can be divided into three categories including surrogate weights methods, dominance value-based decision rules, and three classical decision rules. Their efficacies are evaluated in terms of choice accuracy via a simulation analysis. The simulation results indicate that a proposed hybrid approach, intended to combine an exact solution approach through interaction and a dominance value-based approach, is recommendable for aiding a decision making in a case that a final choice is seldom made at single step under attribute weights that are imprecisely specified beyond ordinal descriptions.

• Journal of applied mathematics & informatics
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• 제7권2호
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• pp.453-465
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• 2000

In this paper, a new method for finding the approximate solution of a second order nonlinear partial differential equation is introduced. In this method the problem is transformed to an equivalent optimization problem. them , by considering it as a distributed parameter control system the theory of measure is used for obtaining the approximate solution of the original problem.

• Journal of electromagnetic engineering and science
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• 제2권2호
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• pp.65-67
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• 2002

An approximate, numerically-efficient solution for a microstrip T-junction is discussed. The microstrip T-junction is modeled as a rectangular waveguide with top/bottom electric walls and side magnetic walls. Comparisons of our solution with others show favorable agreements.

• Communications for Statistical Applications and Methods
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• 제6권3호
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• pp.871-880
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• 1999

The main purpose of queueing theory is to find the optimal solution for maintaining systems such as service facilities. Analyzing the overfolw process provides an important information for the solution in queueing systems with finite capacity. In this thesis we approximate the expected time until the first overflow in M/G/1/K/N queueing systems. Results will be applied to approximate the expected time until the first reduction of source population system. Simulation results show that our approximation is applicable to real situations.

• International Journal of Air-Conditioning and Refrigeration
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• 제6권
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• pp.14-26
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• 1998

This paper deals with approximate analytical solutions for the two-region one-dimensional model describing the charging process of stratified thermal storage tanks at variable inlet temperature with momentum-induced mixing. An arbitrarily increasing inlet temperature is decomposed into inherent step changes and intervals of continuous change. Each continuous interval is approximated as a finite number of piecewise linear functions, which admits an analytical solution for perfectly mixed region. Using the Laplace transform, the temperature profiles in plug flow region with both the semi-infinite and adiabatic ends are successfully derived in terms of well-defined functions. The effect of end condition on the solution proves to be negligible under the practical operating conditions. For a Quadratic variation of inlet temperature, the approximate solution employing a moderate number of pieces agrees excellently with the exact solution.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.141-144
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• 2007

Given a number of training data, a traditional BPN is normally trained by minimizing the absolute difference between target outputs and approximate outputs. When BPN is used as a meta-model for inequality constraint function, approximate optimal solutions are sometimes actually infeasible in a case where they are active at the constraint boundary. The paper describes the development of the efficient BPN based meta-model that enhances the constraint feasibility of approximate optimal solution. The modified BPN based meta-model is obtained by including the decision condition between lower/upper bounds of a constraint and an approximate value. The proposed approach is verified through a simple mathematical function and a ten-bar planar truss problem.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권4호
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• pp.291-306
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• 2011

We consider the second order Strang splitting method to approximate the solution to the KdV equation. The model equation is split into three sets of initial value problems containing convection and dispersal terms separately. TVD MUSCL or MUSCL scheme is applied to approximate the convection term and the second order centered difference method to approximate the dispersal term. In time stepping, explicit third order Runge-Kutta method is used to the equation containing convection term and implicit Crank-Nicolson method to the equation containing dispersal term to reduce the CFL restriction. Several numerical examples of weakly and strongly dispersive problems, which produce solitons or dispersive shock waves, or may show instabilities of the solution, are presented.