• 한국해안해양공학회지
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• 제4권4호
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• pp.219-224
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• 1992

이차원 비선형 정상파의 파낭포텐셜과 수면 파형곡선을 임의 계수를 갖는 Fourier 급수로 대치하고 그 계수를 지배방정식 및 경계조건으로부터 비롯되는 비선형 연립방정식의 Newton 해법에 의하여 결정하는 방법을 제시하였다. 해석결과의 유효성을 검증하기 위하여 본 교치분석을 재내의 4차 미소치 섭동기법과 비교하였으며, 또한 파형과 파염을 관측하기 위한 수리실험을 실시하여 그 결과를 수치해석결과와 비교ㆍ검토하였다. 검토 결과, 본 해석 기법은 수심조건에 관계없이 비교적 큰 파형 경사에서도 정확한 해를 주는 것으로 나타났으며 또한 비선형성이 강한 정상파에서 파염곡선의 파봉부분에 일반적으로 나타나는 이중 돌출부를 잘 예측함으로써 그 타당성을 입증하였다.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.109-116
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• 2014

An electrical resistance tomography (ERT) technique combining the particle swarm optimization (PSO) algorithm with the Gauss-Newton method is applied to the visualization of two-phase flows. In the ERT, the electrical conductivity distribution, namely the conductivity values of pixels (numerical meshes) comprising the domain in the context of a numerical image reconstruction algorithm, is estimated with the known injected currents through the electrodes attached on the domain boundary and the measured potentials on those electrodes. In spite of many favorable characteristics of ERT such as no radiation, low cost, and high temporal resolution compared to other tomography techniques, one of the major drawbacks of ERT is low spatial resolution due to the inherent ill-posedness of conventional image reconstruction algorithms. In fact, the number of known data is much less than that of the unknowns (meshes). Recalling that binary mixtures like two-phase flows consist of only two substances with distinct electrical conductivities, this work adopts the PSO algorithm for mesh grouping to reduce the number of unknowns. In order to verify the enhanced performance of the proposed method, several numerical tests are performed. The comparison between the proposed algorithm and conventional Gauss-Newton method shows significant improvements in the quality of reconstructed images.

• 대한토목학회논문집
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• 제9권1호
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• pp.11-23
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• 1989

본 논문에서는 guyed tower의 mooring system에 관한 수치해석결과를 제시하였다. 가상일의 원리와 유한요소법을 사용하여 기본식을 유도하였으며 케이블의 기하학적 비선형성을 고려하였다. 유체의 항력과 관성력은 Morrison식을 사용하여 고려하였으며 비선형 운동방정식의 해는 Newton-Raphson방법과 Newmark-${\beta}$ 방법을 사용하여 구하였다. Tower와 mooring line의 부착점에서의 초기경사각, 인장력, clump weight를 집중하중으로 이상화 시키는 종래의 해석방법의 문제점도 아울러 고찰하였다. 수치해석 예를 통하여 본 논문에서의 해석방법의 정당성을 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.918-922
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• 1998

With the development of industry, the qualitical advancement of power is needed. Since it is placed in the end step of power system, the fault at the distribution system causes some users blackout directly. So if the fault occurs, quick restoration is very important subject and, for the reason, induction of the distribution automation system is now being progressed briskly. For the quick restoration of the faulted distribution system, the load shedding of the blackout-area must be followed, and the other problems like the shedded load, faulted voltage and the rest may cause other accident. Accordingly load shedding must be based on the precise calculation technique during the distribution system load flow(dist flow) calculation. In these days because of its superior convergence characteristic the Newton-Raphson method is most widely used. The number of buses in the distribution system amounts to thousands, and if the fault occurs at the distribution system, the speed for the dist flow calculation is to be improved to apply to the On-Line system. However, Newton-Raphson method takes much time relatively because it must calculate the Jacobian matrix and inverse matrix at every iteration, and in the case of huge load, the equation is hard to converge. In this thesis. matrix equation is used to make algebraical expression and then to solve load flow equation and to modify above defects. Then the complex matrix is divided into real part and imaginary part to keep sparcity. As a result time needed for calculation diminished. Application of mentioned algorithm to 302 bus, 700 bus, 1004 bus system led to almost identical result got by Newton-Raphson method and showed constant convergence characteristic. The effect of time reduction showed 88.2%, 86.4%, 85.1% at each case of 302 bus, 700 bus system 86.4%, and 1004 bus system.

• 대한의용생체공학회:의공학회지
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• 제6권1호
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• pp.13-18
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• 1985

A solution scheme for the squeeze film problem using the Newton-Raphson method with a tangential matrix is presented. The integration of elasticity equation is done with the aid of isoparametric elements and the film thickness under a sinusoidal load is obtained. A new squeeze-suction phenomenon which shoㅁvs the possibility oi maintaining fluid film under cyclic positive load conditions is observed for small load and Period and large compliance parameter cases. Thia could be an interesting result in applications like the viscous hydroplaning and the biological joints.

• 대한토목학회논문집
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• 제8권3호
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• pp.1-10
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• 1988

본 연구에서는 고차 판 유한요소의 판의 기하학적 비선형 해석에의 적용성을 고찰한다. 고차판요소는 3 차원 연속체로부터 Total Lagrangian 형태로 나타낸 운동방정식을 이산화하고 고차 판이론을 도입하여 유도한다. 유한변형을 고려한 기하학적 비션형 방정식은 Newton-Raphson반복법으로 내력벡터를 선형화하여 강도매트릭스를 반복계산하여 푼다. 요소매트릭스는 shear locking 현상을 피하기 위하여 Gauss 적분법을 이용한 선택적 감차적분으로 계산한다. 여러가지 예제해석을 통하여 고차 판요소의 효율성과 정확도를 고찰하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.335-342
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• 2002

A continuum-based design sensitivity analysis (DSA) method fur non-shape problems is developed for geometrically nonlinear elastic structures. The non-shape problem is characterized by the design variables that are not associated with the domain of system like sizing, material property, loading, and so on. Total Lagrangian formulation with the Green-Lagrange strain and the second Piola-Kirchhoff stress is employed to describe the geometrically nonlinear structures. The spatial domain is discretized using the 4-node isoparametric plane stress/strain elements. The resulting nonlinear system is solved using the Newton-Raphson iterative method. To take advantage of the derived analytical sensitivity In topology optimization, a fast and efficient design sensitivity analysis method, adjoint variable method, is employed and the material property of each element is selected as non-shape design variable. Combining the design sensitivity analysis method and a gradient-based design optimization algorithm, an automated design optimization method is developed. The comparison of the analytical sensitivity with the finite difference results shows excellent agreement. Also application to the topology design optimization problem suggests a very good insight for the layout design.

• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.312-316
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• 2010

Conformal mapping has been a familiar tool of science and engineering for generations. The methods of numerical mapping are usually classified into those which construct the map from standard domain such as the unit disk onto the 'problem domain', and those which construct the map in the reverse direction. We treat numerical conformal mapping from the unit disk onto the Jordan regions as the problem domain in this paper. The traditional standard methods of this type are based on Theodorsen integral equation. Wegmann's method is well known as a Newton-like efficient one for solving Theodorsen equation. An improved method for convergence by applying low frequency pass filter to the Wegmann's method was proposed. In this paper we propose an effective algorithm for numerical conformal mapping based on the improved method. This algorithm is able to determine the discrete numbers and initial values automatically in accordance with the given region and the required accuracy. This results come from analyzing the shape of given domain as seen in the Fourier Transform.

• 대한수학회지
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• 제52권1호
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• pp.23-41
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• 2015

We present a semilocal convergence analysis of a third order method for approximating a locally unique solution of an equation in a Banach space setting. Recently, this method was studied by Chun, Stanica and Neta. These authors extended earlier results by Kou, Li and others. Our convergence analysis extends the applicability of these methods under less computational cost and weaker convergence criteria. Numerical examples are also presented to show that the earlier results cannot apply to solve these equations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.790-793
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• 1997

The most of conventional power flow(PF) calculations which adopt the well-known numerical methods such as Newton-Raphson method often diverge in certain critical cases like near the voltage collapse point. Some Approaches have been reported for the application of Genetic Algorithm(GA) to PF problem to overcome the disadvantages mentioned above. This paper presents a new application technique of GA for PF problem, in which some improvements and modifications are made ; modification of fitness function, improvements on crossover method, mutation law and convergence criterion, introduction of reactive power check routine. Some case studies with IEEE 5, 6, 14 bus systems are performed to show the performance of proposed algorithm.