• Structural Engineering and Mechanics
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• 제48권5호
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• pp.711-736
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• 2013

In this paper new implicit time integration called N-IHOA is presented for dynamic analysis of high damping systems. Here, current displacement and velocity are assumed to be functions of the velocities and accelerations of several previous time steps, respectively. This definition causes that only one set of weighted factors is calculated from the Taylor series expansion which leads to a simple approach and reduce the computational efforts. Moreover a comprehensive study on stability of the proposed method i.e., N-IHOA compared with IHOA integration which is performed based on amplification matrices proves the ability of the N-IHOA in high damping vibrations such as control systems. Also, wide range of numerical examples which contains single/multi degrees of freedom, damped/un-damped, free/forced vibrations from finite element/finite difference demonstrate that the accuracy and efficiency of the proposed time integration is more than the common approaches such as the IHOA, the Wilson-${\theta}$ and the Newmark-${\beta}$.

• 대한기계학회논문집
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• 제14권6호
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• pp.1365-1381
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• 1990

본 연구에서는 Kant 등이 제안한 고차판이론의 C연속변위 유한요소 모델을 사 용하여 충격자와 적층판의 저속 충격 응답에 대하여 연구하여 그 결과를 Mindlin의 판 이론에 의한 계산 결과와 비교하고, 경계 조건의 영향 및 충격자의 충격속도, 질량변 화에 대한 접촉력의 변화를 고찰하고자 한다.

• 한국측량학회지
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• 제28권6호
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• pp.573-578
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• 2010

위성항법시스템에서 정확한 위성궤도결정 기술은 측위 정확도 향상의 필수적인 조건이다. 이 연구에서는 GLONASS의 방송궤도력과 4차 Runge-Kutta 수치적분법을 이용하여 위성좌표를 결정하였으며, 적분간격과 적분시간에 따른 위성궤도의 정확도를 비교하였다. 적분간격에 따른 위성궤도 정확도분석결과, 적분간격이 l초일 때와 300초일 때의 3차원 RMS 오자의 차이가 3cm에 불과한 반면 처리시간은 100배 이상 향상되었다. 적분시간에 따른 위성좌표의 3차원 RMS 오차는 적분시간이 30분, 150분, 300분일 때 각각 8.3m, 187.3m, 661.5m로 나타났으며, 이를 통해 적분시간을 짧게 할수록 정확도가 향상되는 것을 확인하였다. 따라서 이 연구에서는 GLONASS 측위를 위한 위성좌표 결정의 정확도 향상을 위해 적분시간을 최소화할 수 있는 Forward와 Backward 적분을 적용하는 방안을 제안하였으며, 이와 같은 방법을 사용할 경우 5m이하의 위성좌표 산출 정확도를 확보할 수 있다.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.495-504
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• 2017

This paper proposes a new direct numerical integration algorithm for solving equation of motion in structural dynamics problems with nonlinear stiffness. The new implicit method's degree of accuracy is higher than that of existing methods due to the higher order of the acceleration. Two parameters are defined, leading to a new family of unconditionally stable methods, which helps to take greater time steps in integration and eliminate concerns about the duration of solving. The method developed can be utilized for a number of solid plane finite elements, examples of which are given to compare the proposed method with existing ones. The results indicate the superiority of the proposed method.

• 한국광학회:학술대회논문집
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• 한국광학회 1998년도 제15회 광학 및 양자전자 학술발표회 논문집
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• pp.220-221
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• 1998

An optical implementation of higher order neural networks based on based principal component analysis and time integration has been described. The principal component analysis combined with time integration allows larger input size than fully spatial neural networks at the cost certain amount of time consumption. This time-integration usage actually breaks down the barrier of the maximum space-bandwidth product that optical systems can offer.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.61-62
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• 2003

In this paper, the new higher order wall boundary conditions are proposed for solving the incompressible flows. The square driven cavity flows are simulated by using the variable order method of lines with the present wall boundary conditions. The variable order method of lines is constructed by the spatial discretization, i.e., the variable order proper convective scheme for convective terms and the modified differential quadrature method for diffusive terms, and time integration. The 2nd, 4th, and 6th order solutions are presented and these results show this higher order boundary conditions are very promising for the incompressible flow simulations.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.30-40
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• 2007

The implicit discontinuous Galerkin method for the two-dimensional Euler equations was developed on unstructured triangular meshes, which can achieve higher-order accuracy by wing hierachical basis functions based on Legendre polynomials. Numerical tests were conducted to estimate the convergence order of numerical solutions to the Ringleb flow and the supersonic vortex flow for which analytic solutions are available. And, the flows around a circle and a NACA0012 airfoil was also numerically simulated. Numerical results show that the implicit discontinuous Galerkin methods with higher-order representation of curved solid boundaries can be an efficient higher-order method to obtain very accurate numerical solutions on unstructured meshes.

• 대한기계학회논문집
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• 제17권12호
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• pp.2982-2994
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• 1993

Low-velocity impact responses of composite laminates are investigated using the finite element method based on various theories. In two-dimensional nonlinear analysis, a displacement field considering higher order shear deformation and large deflection of the laminate is assumed and a finite element formulation is developed using a C$^{o}$-continuous 9-node plate element. Also, three-dimensional linear analysis based on the infinitesimal strain-displacement assumptions is performed using 8-node brick elements with incompatible modes. A modified Hertzian contact law is incorporated into the finite element program to evaluate the impact force. In the time integration, the Newmark constant acceleration algorithm is used in conjuction with successive iterations within each time step. Numerical results from static analysis as well as the impact response analysis are presented including impact force histories, deflections, strains in the laminate. Impact responses according to two typical low-velocity impact conditions are compared each other.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 춘계학술대회 논문집
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• pp.52-57
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• 2001

Laminar two-dimensional time-dependent flow past a circular cylinder is numerically investigated using direct numerical simulation for the low Reynolds number (Re=164∼280). The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. The convection term is applied by the 7th order up wind scheme and the pressure and viscosity terms are applied by the 4th order central difference. The grid system makes use of the regular grid system and it is generated by an equation. The calculated results of drag coefficients, lift coefficients, pressure distributions, and vorticity contours and other information are compared with experimental and numerical ones. These results obtained by the present DNS show good agreement with the previous studies.

• 전기학회논문지
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• 제60권8호
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• pp.1473-1478
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• 2011

Since IT technology was combined with the power system, many systems and applications have been developed and also Integration between systems has been followed in order to meet much higher level. Futher more to reduce the cost of system integration there were needs standardized data model and interfaces among systems or applications. so IEC has reached to establish standard interfaces and data model. Most of the current distribution automation system in South Korea, each operating independently in an enclosed environment, are managed. As time goes by, however, because of resons that the system is increasingly complex by implenting new kind of power source and demand for electricity is rapidly increasing, it became difficult to predict with a independent data from one system. In this paper, In order to apply common infomation model and standard interfaces which are defined in IEC 61970/61968 to the exisiting distribution automation system in KEPCO, several software tools and applications which have been created will be introduced.