• Journal of information and communication convergence engineering
• /
• v.5 no.3
• /
• pp.259-264
• /
• 2007

According to the development and wide use of broad band internet etc., diverse application technologies using large capacity data such as images have been progressed and in these systems, for accurate acquisition and precise applications of an original signal, the degradation phenomenon generated in the transmission process etc. should be removed. Noises have become known as the main cause of the degradation phenomenon and especially Gaussian noise represents characteristics occurring dependently in image signals and degrades detail information such as edge. In this paper, we removed Gaussian noise using a subdivided nonlinear function according to a threshold value and analyzed the histogram acquired from an edge image to establish a threshold value adaptively, and strengthened detail information of image by using the postprocessing. In simulation results, the proposed method represented excellent performance from comparison of MSE with existing methods.

• ETRI Journal
• /
• v.5 no.2
• /
• pp.17-28
• /
• 1983

This paper deals with the problem of optimally controlling traffic flows in urban transportation traffic networks. For this, a nonlinear discrete-time model of urban traffic network is first suggested in order to handle the phenomenon of traffic flows such as oversaturatedness and/or undersaturatedness. Then an optimal control problem is formulated and a hierarchical optimization technique is applied, which is based upon a prediction-type two-level method of Hirvonen and Hakkala.

• Honam Mathematical Journal
• /
• v.43 no.3
• /
• pp.561-570
• /
• 2021

In this paper, applying the bifurcation method and topological analysis, we investigate the global structures of solutions for one-dimensional Minkowski-curvature problems under certain behavior of nonlinear term near zero.

• Steel and Composite Structures
• /
• v.27 no.1
• /
• pp.13-25
• /
• 2018

The main objective of this study is to develop a dual approach for geometrically nonlinear finite element analysis of plane truss structures. The geometric nonlinearity is considered using the Total Lagrangian formulation. The nonlinear solution is obtained by introducing and minimizing an objective function subjected to displacement-type constraints. The proposed method can fully trace the whole equilibrium path of geometrically nonlinear plane truss structures not only before the limit point but also after it. No stiffness matrix is used in the main approach and the solution is acquired only based on the direct classical stress-strain formulations. As a result, produced errors caused by linearization and approximation of the main equilibrium equation will be eliminated. The suggested algorithm can predict both pre- and post-buckling behavior of the steel plane truss structures as well as any arbitrary point of equilibrium path. In addition, an equilibrium path with multiple limit points and snap-back phenomenon can be followed in this approach. To demonstrate the accuracy, efficiency and robustness of the proposed procedure, numerical results of the suggested approach are compared with theoretical solution, modified arc-length method, and those of reported in the literature.

• Journal of Korean Association for Spatial Structures
• /
• v.10 no.2
• /
• pp.45-60
• /
• 2010

Nonlinear problems for membrane structures are very sensitive in convergence procedure in nonlinear iterations. Therefore many researchers have suggested a lot of ideas in published papers. In this study, authors are trying to get easier solution for taking membrane shape by initial stresses from substitution of the membrane to line elements. To obtain nonlinear stiffness, the nonlinear finite element method is used for both membrane and cable elements, and only geometric nonlinear terms are taken for shape analysis. By some examined models, we can find that the substituted models show better results to get, initial shape in which the concentrating phenomenon is removed at edge parts.

• Journal of Advanced Marine Engineering and Technology
• /
• v.26 no.1
• /
• pp.116-124
• /
• 2002

The bubble model by Keller and Prosperetti is adapted to solve the nonlinear oscillation of a gas bubble. This formulation leads to accurate results since it introduces the energy equation instead of the polytropic assumption for the bubble interior. The numerical method used in this study is stable enough to handle large amplitude of bubble oscillation. The numerical results show some interesting nonlinear phenomena fur the bubble oscillator. The excitation changes the natural frequency of the bubble and makes some harmonic resonances at $f/f_0=1/2, 1/3$ and so on. The natural frequency of a bubble oscillator decreases compared with the linear case result, which means that the nonlinear bubble oscillation system is a "softening"system. In addition, the frequency response curve jumps up or down at a certain frequency. It is also found that there exist multi-valued regions in the frequency response curve depending on the initial conditions of bubble. The dependency of the bubble motion on the initial condition can generate extremely large pressure and temperature which might be the cause of the acoustic cavitation and the sonoluminescence.inescence.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.746-757
• /
• 2021

To investigate the mechanism of friction-induced vibration and noise of ship water lubricated stern bearings, a two-degree-of-freedom (2-DOF) nonlinear self-excited vibration model is established. The novelty of this work lies in the detailed analysis of influence of different parameters on the stability and nonlinear vibration characteristics of the system, which provides a theoretical basis for the various friction vibration and noise phenomenon and has a very important directive meaning for low noise design of water lubricated stern bearings. The results reveal that the change of any parameter, such as rotating speed of shaft, contact pressure, friction coefficient, system damping and stiffness, has an important influence on the stability and nonlinear response of the system. The vibration amplitudes of the system increase as (a) rotating speed of shaft, contact pressure, and the ratio of static friction coefficient to dynamic friction coefficient increase and (b) the transmission damping between motor and shaft decreases. The frequency spectrum of the system is modulated by the first mode natural frequency, which is continuous multi-harmonics of the first mode natural frequency. The response of the system presents a quasi-periodic motion.

• Journal of Ocean Engineering and Technology
• /
• v.6 no.1
• /
• pp.62-68
• /
• 1992

In this study, a system coupled with the nonlinear dynamic vibration absorber was modelled, and its equation of motion was analized by the harmonic balance method to obtain the amplitude ratio. And also, the stability analysis was done by the Routh Hurwitz method. In the vibration systems coupled with the nonlinear dynamic vibration absorber, the unstable region and the jump phenomenon can be ramarkably affected by the damping ratio. The stable and unstable region that obtained to differential method excellently agreed to the result of the stability analysis of Routh Hurwitz.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.50.1-50.1
• /
• 2015

The origin of globular cluster (GC) color bimodality, which is one of the salient phenomena observed in most large galaxies, has not yet been fully resolved. The phenomenon has conventionally been interpreted as a bimodal metallicity distribution based on an assumption of linear GC color-metallicity relations (CMRs). Recent studies however suggest that nonlinear GC CMRs can cause a bimodal color distribution even from a single-peaked metallicity spread. Using photometric and spectroscopic data on GCs in NGC 5128 (Cen A) and NGC 4594 (Sombrero), we investigate the nonlinearity of GC CMRs and compare the observed GC CMRs with the predictions of stellar population simulation models. Our careful selection of old GCs effectively reduces the scatter and reveals the nonlinear nature of the GC CMRs for various colors. The overall shape of the observed CMRs agrees well with that of the modeled CMRs, while offsets are present for some colors. We discuss the implications of our results in terms of the GC color bimodality and GC formation in NGC 5128 and NGC 4594.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.12
• /
• pp.1314-1321
• /
• 2004

The non-linear responses of a slender rectangular cantilever beam subjected to lateral harmonic base-excitation are investigated by the 2-channel FFT analyzer. Both linear and nonlinear behaviors of the cantilever beam are compared with each other. Bending mode, torsional mode, and transverse mode are coupled in such a way that the energy transfer between them are observed. Especially, superharmonic, subharmonic, and chaotic motions which result from the unstable inertia terms in the transverse mode are analyzed by the FFT analyzer The aim is to give the explanations of the route to chaos, i.e., harmonic motion \longrightarrow superharmonic motion \longrightarrow subharmonic motion \longrightarrow chaos.