• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.972-976
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• 2008

본 연구는 유량과 하천유사를 현장에서 직접 관측하여 분석한 연구로서 그 동안 하천에서 유사량을 산정할 때 부유사만을 측정하던 방법과 달리 미호천 석화수위표는 유역특성상 소류사량의 이송이 상당할 것으로 판단되어 미호천유역의 소류사를 부유사와 동시에 관측하는 연구를 수행하였다. 유량의 측정 방법은 간략법인 삼선법을 이용하였고 부유사 관측에는 수심적분 채취법을 적용, 채취기의 이동속도를 모든 채취선에서 일정하게 유지하는 등이동속도법을 이용하고 소류사 관측은 부유사 관측과 동일한 채취선에서 이루어졌다. 각각 부유사량과 소류사량을 15회 측정하여 더한 값을 유사량으로 산출하였고 이를 그 동안 많은 연구에 이용되었던 수정아인슈타인 방법으로 추정한 값과 실측된 유사량의 값을 비교하였다. 본 연구는 소류사량과 부유사량의 관계를 비교할 수 있는 연구로서 연구결과는 다음과 같다.

• The Korean Journal of Applied Statistics
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• v.11 no.2
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• pp.287-302
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• 1998

Saddlepoint approximation to the distribution function of sample mean(Daniels, 1987) is extended to the case of general statistic in this paper. The suggested approximation methods are applied to derive the approximations to the distributions of some statistics, including sample valiance and studentized mean. Some comparisons with other methods show that the suggested approximations are very accurate for moderate or small sample sizes. Even in extreme tail the accuracies are also maintained.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1084-1094
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• 1993

An efficient method for determining forced responses of a general linear structural system in time domain using subtructure modes and Lagrange multipliers is presented. Compared with the conventional mode synthesis methods, the suggested method does not construct the equations of motion of the combined whole structure and thus the modal parameters of the whole structure are not required. Only modal parameters of each substructure and geometric compatibility conditions are needed. Both the loaded interface free-free modes and free interface modes can be employed as the modal bases of each substructure. Recurrence discrete-time state equations based upon state transition matrix are formulated for the transient analysis of a parameter-changing system. It is shown form numerical examples that the suggested method is very accurate and efficient to calculate transient responses compares with the direct numerical integration method.

• Geophysics and Geophysical Exploration
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• v.11 no.1
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• pp.60-67
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• 2008

In this paper we consider an application of the method of electromagnetic (EM) migration to the interpretation of a typical marine controlled-source (MCSEM) survey consisting of a set of sea-bottom receivers and a moving electrical bipole transmitter. Three-dimensional interpretation of MCSEM data is a very challenging problem because of the enormous number of computations required in the case of the multi-transmitter and multi-receiver data acquisition systems used in these surveys. At the same time, we demonstrate that the MCSEM surveys with their dense system of transmitters and receivers are extremely well suited for application of the migration method. In order to speed up the computation of the migration field, we apply a fast form of integral equation (IE) solution based on the multigrid quasi-linear (MGQL) approximation which we have developed. The principles of migration imaging formulated in this paper are tested on a typical model of a sea-bottom petroleum reservoir.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.33-42
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• 2003

This paper deals with the FEM analysis of nonlinear sloshing of incompressible, invicid and irrotational flow in two dimensional rectangular tank. We use laplace equation based on potential theory as governing equation. For large amplitude sloshing motion, kinematic and dynamic free surface conditions derived from Bernoulli equation are applied. This problem is solved by FEM using 9-node elements. For the time integration and accurate velocity calculation, we introduce predictor-corrector time marching scheme and least square method. Also, numerical stability in tracking of free surface is obtained by direct calculation of free surface location to time variation. Numerical results of sloshing induced by harmonic excitations, while comparing with those of linear theory and references, prove the accuracy and stability. After verification of our program, we analyze sloshing response characteristics to the fluid height and the excitation amplitude.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.2
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• pp.105-116
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• 1996

The design and analysis of the transversely fed EMC(electromagnetically coupled) microstrip dipole have been accomplished by using the integral equation and MOM(method of moment)in frequency domain in order to find the current distribution of the dipole. In this study, we proposed the possibilities for design and analysis of EMC micro-strip dipole array antenna by means of calculating the current distribution of each dipole directly using the FDTD(finite difference time domain) method. In this case, we applied the formulation which is the finite difference expression of the Maxwell's integral equation. From the current distribution of each dipole, we calculated the far field electric component and showed that the calculation process and running time was reduced with respect to the method which calculates the radiation field with surface electric and magnetic current density.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.376-385
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• 2017

In this paper, a method for the estimation of structural displacements using structure's mode shapes and accelerations is suggested to reduce the disadvantages of acceleration time integration method. Acceleration time integration method requires accurate information on initial conditions, and errors caused by noise can be accumulated during time integration. To avoid these problems, the method for the estimation of structural displacements based on mode superposition method is developed and two vibration experiments for cantilever beam are conducted to verify this method. Static displacements and dynamic displacements of beam structure are estimated using measured accelerations from experiments and mode shapes of cantilever beam, and they are compared with measured displacements using laser displacement sensor. From these results, the validity and usefulness of this method are verified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.93-103
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• 1994

Two beam/column elements are developed in order to analyze the geometric nonlinear plane irames including the effects of internal hinge and transverse shear deformation. In the case of the first element (finite segment method), tangent stiffness matrix is derived by directly integrating the equilibrium equations whereas in the case of the second element (finite element method) elastic and goemetric stiffness matrices are calculated by using the hermitian polynomials including the effects of internal hinge and shear deformation as the shape function. Numerical results are presented for the selected test problems which demonstrate that both elements represent reliable and highly accurate tools.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.27-36
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• 1990

Two beam/column elements in order to analyze the geometric nonlinear plane framed structures including the effects of transverse shear deformation and bending stretching coupling are developed. In the case of the first element (finite segment method), tangent stiffness matrix are derived by directly integrating the equilibrium equations whereas in the case of the second element (finite element method) elastic and geometric stiffness matrices are calculated by using the hermitian polynomials including shear deformation effect as the shape function. Both elements possess the usual six degree of freedoms. Numerical results are presented for the selected test problems which demonstrate that both elements represent reliable and highly accurate tools.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.93-101
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• 1989

A geometrically nonlinear cable finite element is presented to use in the static or dynamic modeling of offshore and onshore structures such as guyed tower, tension leg platform or mooring buoy, submarine cable, cable-stayed bridge, suspension bridge, cable roof and so on. The cable finite element is derived directly from the compatibility equations and flexibility matrix of elastic catenary cable theory for the arbitary plane loading and geome try. A general and virsatile computer program has been developed to perform the analyses of cable member itself or cable guyed or suspened structures, in which Newmark-$\beta$ method is used to obtain a time domain solution and Newton-Raphson iteration method is used to solve the nonlinear system of compatibility equations of cable and algebraic static or dynamic equations at each time step. The results from the static and dynamic analysis of a cable member by the computer program are summarized and presented.