• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.11
• /
• pp.2954-2965
• /
• 1996

In this paper, the electromagnetic field characteristics of leaky caxial cable are anlyzed by using the finite difference-time domain(FDTD) technique. Finite difference equations of Maxwell's equations are definedin cylindrical coordinate systems. To simulate the open boundary problem like a free space, the Mur's Absorbing Boundary condition(Mur-ABC) is also used. After modeling the leaky coaxial cable with the three dimensional grid structure, the transient response of the field distribution and the current distribution, the field pattern, the coupling effect are depicted in the time domain.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.5
• /
• pp.94-101
• /
• 1996

The purpose of this paper is to analyze the field distribution and the current distribution of leaky coaxial cable with the finite difference-tiem domain(FDTD) algorithm. finite difference equations of maxwell's equations are defined in cylindrical coordinate systems. To simulate the unbounded problem like a free space, the Mur's absorbing boundary conditon is also used. After modeling the leaky coaxial cable with the three dimensional grid structure, the transient resoponse of th efield distribution and the current distribution are depicted in the time domain.

• Journal of Mechanical Science and Technology
• /
• v.15 no.2
• /
• pp.232-238
• /
• 2001

Fast Fourier Transformation is employed to convert the head variation of a pipeline in the time domain to the amplitude of the frequency domain. Applying method of characteristics to a pipeline provides a significant frequency range for a surge introduced from the valve modulation. Inverse Fast Fourier Transformation and a Finite Impulse Response Filter can be used to remove any possible noise existing from the significant frequency range of an unsteady condition. A filtered signal shows higher potential for the inverse calculation of leakage detection than the noise-added signal does. The respective performances of Inverse Fast Fourier Transformation and a Finite Impulse Response Filter are compared in terms of leakage detection capability. Characteristics of the frequency range for multiple leakages were investigated to validate the effectiveness of the noise control method in the frequency domain.

• Journal of the Optical Society of Korea
• /
• v.13 no.2
• /
• pp.272-278
• /
• 2009

Recently, there has been a growing interest in optical imaging of neural activity because the optical neuroimaging has considerable advantages over conventional imaging. Birefringence of the axon has been reported to change during neural activation, but the neurophysiological origin of the change is still unresolved. This study hypothesizes that the birefringence signal is at least partially attributed to the transient cellular volume change associated with nerve excitation. To examine this hypothesis, we investigated how the intensity of cross-polarized light transmitting through the axon would change as the size of the axon changes. For this purpose, a two-dimensional finite-difference time-domain program was developed with the improvement of the total-field/scattered-field method which reduces numerical noise. The results support our hypothesis in that the computed cross-polarized signals exhibit some agreement with previously-reported birefringence signals.

• Coupled systems mechanics
• /
• v.1 no.1
• /
• pp.19-37
• /
• 2012

In this work, the iterative coupling of finite element and boundary element methods for the investigation of coupled fluid-fluid, solid-solid and fluid-solid wave propagation models is reviewed. In order to perform the coupling of the two numerical methods, a successive renewal of the variables on the common interface between the two sub-domains is performed through an iterative procedure until convergence is achieved. In the case of local nonlinearities within the finite element sub-domain, it is straightforward to perform the iterative coupling together with the iterations needed to solve the nonlinear system. In particular, a more efficient and stable performance of the coupling procedure is achieved by a special formulation that allows to use different time steps in each sub-domain. Optimized relaxation parameters are also considered in the analyses, in order to speed up and/or to ensure the convergence of the iterative process.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.2 no.2
• /
• pp.197-205
• /
• 1998

The purpose of this paper is to analyze the electromagnetic field characteristics of array antenna with the finite difference-time domain algorithm. Finite difference equations of Maxwell's equations are defined in cylindrical coordinate systems. To simulate the unbounded problem like a free space, the Mur's absorbing boundary condition is also used. After modeling the array antenna with the grid structure, the transient response of the field distribution is depicted in the time domain.

• Korean Journal of Mathematics
• /
• v.31 no.4
• /
• pp.419-431
• /
• 2023

In this paper, we propose an iterative method for a symmetric interior penalty Galerkin method for heterogeneous elliptic problems. The iterative method consists mainly of two parts based on a non-overlapping domain decomposition approach. One is an intermediate preconditioner constructed by understanding the properties of the discontinuous finite element functions and the other is a preconditioning related to the dual-primal finite element tearing and interconnecting (FETI-DP) methodology. Numerical results for the proposed method are presented, which demonstrate the performance of the iterative method in terms of various parameters associated with the elliptic model problem, the finite element discretization, and non-overlapping subdomain decomposition.

• International Journal of Ocean System Engineering
• /
• v.2 no.3
• /
• pp.176-184
• /
• 2012

Installing floating structures in a coastal area requires careful observation of the finite-depth effect. In this paper, a Rankine panel method that includes the finite-depth effect is developed in the time domain. The bottom boundary condition is satisfied by directly distributing Rankine panels on the bottom surface. A stepwise analysis is performed for the radiation diffraction problems and consequently freely-floating motion responses over different water depths. The hydrodynamic properties of two test hulls, a Series 60 and a floating barge, are compared to the results from another computation program for validation purposes. The results for both hulls change remarkably as the water depth becomes shallower. The important features of the results are addressed and the effects of a finite depth are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.7 s.178
• /
• pp.1763-1770
• /
• 2000

A finite element interface system for the design of optimal spot welding locations has been developed. In order to find out the optimal locations of spot welding points, iterative finite element an alyses are necessary, and thus automatic generation of finite element model for the structures with spot welded pointsis required. In this interface system, quadrilateral shell elements are automatically generated for finite element analysis of spot welded structured, which employs a domain decomposition methodand adaptive mesh(h-method).

• East Asian mathematical journal
• /
• v.37 no.3
• /
• pp.295-305
• /
• 2021

In this paper, we analyze the efficiency of a domain decomposition method for the two-dimensional telegraph equations. We formulate the theoretical spectral radius of the iteration matrix generated by the domain decomposition method, because the rate of convergence of an iterative algorithm depends on the spectral radius of the iteration matrix. The theoretical spectral radius is confirmed by the experimental one using MATLAB. Speedup and operation ratio of the domain decomposition method are also compared as the two measurements of the efficiency of the method. Numerical results support the high efficiency of the domain decomposition method.