• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.153-168
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• 1993

The ship sailing among waves suffers from the various wave loads that comes from its motion throughout its life. In the rationally-based design, the dynamic structural analysis is carried out using dynamic wave loads provided from the results of the ship motion calculation as the rigid body. This method is based on the linear theory assumed low wave height and small amplitude of motion. But at the rough sea condition, relatively high wave compared to the height ship's depth is induced the large ship motion, so configuration of the ship section below waterline changes rapidly at each time. This re-sults in a non-linear problem. Considering above situation we have already introduced the non-linear dynamic strength analysis method for the hull girder(refer vol. 29. No.4 November, 1992, Journal of SNAK). In this paper, estimation of the hull girder strength for various ship types such as tankers, containers and log carriers is carried out based on the introduced non-linear method. We expect that the results will be used as useful basic data for the es-timation of dynamic strength of ships in the rough sea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.305-308
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• 2011

In this study, generation methods of 3-D multi-directional random wave are examined using the fully non-linear numerical model with non-reflected wave generation system (LES-WASS-3D). Directional distribution functions obtained by EMLM method are compared for multidirectional random waves generated by various generation methods. As a results, it is revealed that multi-directional wave field can be simulated using LES-WASS-3D.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.6
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• pp.401-406
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• 2011

In this study, generation methods of oblique incident wave are newly proposed and examined using the fully non-linear numerical model with non-reflected wave generation system(LES-WASS-3D). In order to verify, free surface elevation and horizontal velocities are compared with $3^{rd}$ -order Stokes wave theory in 3-D oblique incident wave field. As a results, it is revealed that the numerical results by newly proposed technique are in good agreement with the theory.

• Structural Engineering and Mechanics
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• v.50 no.3
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• pp.287-304
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• 2014

A computer based iterative numerical procedure has been developed to analyse reinforced high strength concrete columns subjected to horizontal wave loads and eccentric vertical load by taking the material, geometrical and wave load non-linearity into account. The behaviour of the column has been assumed, to be represented by Moment-Thrust-Curvature relationship of the column cross-section. The formulated computer program predicts horizontal load versus deflection behaviour of a column up to failure. The developed numerical model has been applied to analyse several column specimens of various slenderness, structural properties and axial load ratios, tested by other researchers. The predicted values are having a better agreement with experimental results. A simplified user friendly hydrodynamic load model has been developed based on Morison equation supplemented with a wave slap term to predict the high frequency non-linear impulsive hydrodynamic loads arising from steep waves, known as ringing loads. A computer program has been formulated based on the model to obtain the wave loads and non-dimensional wave load coefficients for all discretised nodes, along the length of column from instantaneous free water surface to bottom of the column at mud level. The columns of same size and material properties but having different slenderness ratio are analysed by the developed numerical procedure for the simulated wave loads under various vertical thrust. This paper discusses the results obtained in detail and effect of slenderness in resisting wave loads under various vertical thrust.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.111-115
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• 2011

When formulating a general, non-linear mathematical model of ship dynamics in waves the hydrostatic forces and moments along with the Froude-Krylov part of wave load are usually concerned. Normally radiation and the diffraction forces are regarded as linear ones. The paper discusses briefly few approaches, which can be used in this respect. The concerned models attempt to model the non-linearities of the surface waves; both regular and the irregular ones, and the nonlinearities of the restoring forces and moments. The approach selected in the Laidyn method, which is meant for the evaluation of large amplitude motions in the 6 degrees-of-freedom, is presented in a bigger detail. The workability of the method is illustrated with the simulation of ship motions in irregular stern quartering waves.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.1-5
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• 2000

A numerical analysis for wave motion in the shallow water is presented. The method is based on potential theory. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed common boundary to a linear solution in outer domain. In two-dimensional problem Cauchy's integral theorem is applied to calculate the complex potential and its time derivative along boundary.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.447-454
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• 2011

Power-line interference(PLI) can distort certain regions in analysing the ECG signal. In particular, the regions such as P and R wave that are important element in diagnosing with arrhythmia is expressed as different type of noise according to the case whether power-line frequency is multiples of sampling frequency and or not. Noise characteristics is also divided into linearity and non-linearity. In this paper, adaptive subtraction method for removing variable PLI of ECG signal is proposed. We classify the multiple relationship between power line and sampling frequency as Multiple and Non-multiple. PLI of Linear segment is extracted through moving average filter, PLI of non-linear segment is extracted through the interference component that is extracted in the linear segment and stored in the temporary buffer. The performance of P wave and R wave detection is evaluated by using 119 data record of MIT-BIH arrhythmia database. The achieved scores indicate P wave detection rate of 97.91%, R wave detection rate of 96.66% and P wave detection rate of 99.01%, R wave detection rate of 97.93% accuracy respectively for Notch filter and proposed subtraction method.

• Journal of applied mathematics & informatics
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• v.13 no.1_2
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• pp.53-65
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• 2003

Here we present a study of small-amplitude, shallow water waves on sloping beds. The beds considered in this analysis are linear and quadratic in nature. First we start with stating the relevant governing equations and boundary conditions for the theory of water waves. Once the complete prescription of the water-wave problem is available based on some assumptions (like inviscid, irrotational flow), we normalize it by introducing a suitable set of non-dimensional variables and then we scale the variables with respect to the amplitude parameter. This helps us to characterize the various types of approximation. In the process, a summary of equations that represent different approximations of the water-wave problem is stated. All the relevant equations are presented in rectangular Cartesian coordinates. Then we derive the equations and boundary conditions for small-amplitude and shallow water waves. Two specific types of bed are considered for our calculations. One is a bed with constant slope and the other bed has a quadratic form of surface. These are solved by using separation of variables method.

• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.841-852
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• 2016

The present paper is concerned with the investigation of propagation of thermoelastic media, the finite difference technique is used to obtain the solution for the uncoupled dynamic thermoelastic stress problem in a non-homogeneous orthrotropc thick cylindrical shell. In implementing the method, the linear dynamic thermoelasticity equations are used with the appropriate boundary and initial conditions. Thermal shock stress becomes of significant magnitude due to stress wave propagation which is initiated at the boundaries by sudden thermal loading. Numerical results have been given and illustrated graphically in each case considered. The presented results indicate that the effect of inhomogeneity is very pronounced.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.277-286
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• 2013

Cross-shore sediment transport is very important factor in the design of coastal structures, and the beach profile is mainly affected by a number of parameters, such as wave height and period, beach slope, and the material properties of the bed. In this study cross-shore sediment movement was investigated using a physical model and various offshore bar geometric parameters were determined by the resultant erosion profile. The experiments on cross- shore sediment transport carried out in a laboratory wave channel for initial base slopes of 1/8, 1/10 and 1/15. Using the regular waves with different deep-water wave steepness generated by a pedal-type wave generator, the geometrical of sediment transport rate and considerable characteristics of beach profiles under storm conditions and bar parameters affecting on-off shore sediment transport are investigated for the beach materials with the medium diameter of $d_{50}$=0.25, 0.32, 0.45, 0.62 and 0.80 mm. Non-dimensional equations were obtained by using linear and non-linear regression methods through the experimental data and were compared with previously developed equations in the literature. The results have shown that the experimental data fitted well to the proposed equations with respect to the previously developed equations.