• 전기의세계
• /
• v.21 no.4
• /
• pp.7-14
• /
• 1972

The author has established a general equation for the travelling magnetic field in air gap with the end effect taken into consideration, which constitutes the basics for the analysis of characteristics of linear induction motor. This equation is verified by comparison of the experimental values with the theoretically calculated values. The properties of the travelling wave with attenuation, which is contained in the travelling magnetic field of linear induction motor, have been verified, and consequently the practicable equation is established with these effects taken into consideration. This provides the solid foundation for the theoretical analysis of the characteristics of the linear induction motor.

• 전기의세계
• /
• v.16 no.1
• /
• pp.14-18
• /
• 1967

To analyze th frequency modulation system the characteristic equation of the F-M system, i.e., Mathieu's equation, is derived from the equivalent circuits of direct modulation system. The analysis of F-M equation is undertaken by the Yonsei 101 Analog Computer. And the computer solution is compared with the theoretical solution. It is concluded that not only the frequency but also the amplitude of the carrier wave are changed by varying the modulation index and the system becomes unstable if the modulation index is increased near to unity.

• 한국연소학회:학술대회논문집
• /
• 2005.10a
• /
• pp.28-31
• /
• 2005

The numerical simulation is conducted for analysis flame structure of superdetonative ram accelerator experiment by ISL(French-German Research Institute in Saint Louis). Fully coupled chemically non-equilibrium Navier-Stokes equation is used. Shockwave structure of superdetonative ram accelerator and behavior of detonation wave is studied. Maintaining of detonation wave is very important to accelerate projectile, Because detonation wave make high pressure gases and this high pressure accelerate projectile.

• Geophysics and Geophysical Exploration
• /
• v.3 no.2
• /
• pp.39-47
• /
• 2000

A great deal of computing time and a large computer memory are needed to solve wave equation in a large complex subsurface layers using the finite difference method. The computing time and memory can be reduced by decreasing the number of grid points per minimum wave length. However, the decrease of grids may cause numerical dispersion and poor accuracy. In this study we performed the grid dispersion analysis for several rotated finite difference operators, which was commonly used to reduce grids per wavelength with accuracy in order to determine the solution for the acoustic wave equation in frequency domain. The rotated finite difference operators were to be extended to 81, 121 and 169 difference stars and studied whether the minimum grids could be reduced to 2 or not. To obtain accuracy (numerical errors less than $1\%$) the following was required: more than 13 grids for conventional 5 point difference stars, 9 grids for 9 difference stars, 3 grids for 25 difference stars, and 2.7 grids for 49 difference stars. After grid dispersion analysis for the new rotated finite difference operators, more than 2.5 grids for 81 difference stars, 2.3 grids for 121 difference stars and 2.1 grids for 169 difference stars were needed. However, in the 169 difference stars, there was no solution because of oscillation of the dispersion curves in the group velocity curves. This indicated that the grids couldn't be reduced to 2 in the frequency acoustic wave equation. According to grid dispersion analysis for the determination of grid points, the more rotated finite difference operators, the fewer grid points. However, the more rotated finite difference operators that are used, the more complex the difference equation terms.

• Journal of Industrial Technology
• /
• v.17
• /
• pp.261-275
• /
• 1997

The objective of this paper is to develop two numerical model for predicting the wave height with set-up/down near the surfzone on a arbitrary beach profile. Two wave models, regular wave model and random wave model, are based on the energy flux equation with the energy dissipation effects. The developed numerical models are verified by comparison of numerical results with analytical solutions that are derived under the simple conditions. The characteristics of parameters included in each model are then investigated and decided to the range of behaviour by the sensitivity analysis. For sensitivity analysis, we carried out total 46 laboratory tests. Finally, the developed numerical models are applied to the field where the wave height near the surfzone has been measured. From the applications of numerical models, it is concluded that the developed numerical models may accurately predict the wave height with the set-up/down near the surfzone on a arbitrary beach profile.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.276.1-277
• /
• 2000

Absorptive bistable laser diode was analyzed by using traveling wave model in conjunction with the finite-difference method. Carrier and photon density distributions were calculated and the output characteristics were obtained. The results for both the steady-state and transient (switching) cases were compared with those of the rate equation approach.

• Journal of Navigation and Port Research
• /
• v.30 no.3 s.109
• /
• pp.181-187
• /
• 2006

In the wave spectrum distribution based on linear wave theory, the appearance of a giant wave whose wave height reaches to 30m has been considered next to almost impossible in a real sea However since more than 10 giant waves were observed in a recent investigation of global wave distribution which was carried out by the analysis of SAR imagines for three weeks, the existence of the giant waves is being recognized and it is considered the cause of many unknown marine disasters. The change of wave height distribution concerning a formation of wave train, nonlinear wave to wave interaction and so on were raised as the causes of the appearance of the giant waves, but the occurrence mechanism of the giant waves hasn't been cleared yet. In present study, we investigated appearance circumstances of the giant waves in real sea and its occurrence mechanism was analyzed based on linear and nonlinear wave focusing theories. Also, through a development of numerical model of the nonlinear $schr\"{o}dinger$ equation, the formations of the giant wave from progressive wave train were reproduced.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1998.10a
• /
• pp.137-144
• /
• 1998

• Journal of computational fluids engineering
• /
• v.17 no.3
• /
• pp.99-107
• /
• 2012

In this paper, the shock waves in compressible solids and liquids are simulated using a six-equation diffuse interface multiphase flow model that is extended to the Cochran and Chan equation of state. A pressure relaxation method based on a volume fraction function and a pressure-correction equation are newly implemented to the six-equation model. The developed code has been validated by a shock tube problem with liquid nitromethane and an impact problem of a copper plate on a solid explosive. In addition, a new problem, an impact of a copper plate on liquid nitromethane, has been solved. The present code well shows the wave structures in compressible solids and liquids without any numerical oscillations and overshoots. After the impact of a solid copper plate on liquid, two shock waves (one propagates into liquid and the other into solid) are generated and a material interface moves to the impacting direction. The computational results show that the shock velocity inside the liquid linearly increases with the impact velocity.

• Water for future
• /
• v.21 no.2
• /
• pp.173-182
• /
• 1988

Characteristics of finite difference schemes for St. Venant equation were compared with two input cases. One is the monoclinal wave which has large friction slope without discontinuity and the other is the shock wave with discontinuity. For monoclinal wave, Keller Box scheme is the best in terms of accuracy, efficiency and stability when two parameters were selected with a rele : $0.5{\leq}{\theta}{\leq}1.0$, ${\theta}+{\psi}$=1, But for shock wave only the Preissmann type of parameter ${\psi}$(=0.5) showed stable results. Numerical experiments of monoclinal wave showed that Lax-Wendroff and Richtmyer schemes were more stable than leap Frog and more accurate than Lax-Fredrich scheme. For shock wave Lax-Fredrich showed larger numerical dissipation than other explicit schemes and Leap Frog produced slower mass transport.