• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.27-39
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• 1998

The interaction of monochromatic incident waves with a horizontal flexible membrane is investigated in the context of two-dimensional linear hydro-elastic theory. First, analytic diffraction and radiation solutions for a submerged impermeable horizontal membrane are obtained. Second, the theoretical prediction was compared with a series of experiments conducted in a two-dimensional wave tank at Texas A&M University. The measured reflection and transmission coefficients reasonably follow the trend of predicted values. Using the developed computer program, the performance of surface-mounted or submerged horizontal membrane wave barriers is tested with various system parameters and wave characteristics. It is found that the properly designed horizontal flexible membrane can be an effective wave barrier.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.1-10
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• 2002

Hull-propeller-rudder interactions are studied by the iterative computational procedures. Hull effects on the propeller are reflected through the effective velocities computed by the vortex ring method which used the measured nominal wake as input data. A potential based panel method has been developed to solve the propeller-rudder interactions using the obtained effective velocities. Steady flow characteristics around the rudder surface can be obtained by computing the induced velocities on the rudder by the propeller and vice versa are computed by the iterative manner until the converged solutions are obtained. Flow characteristics around the propeller and the rudder are measured by Laser Doppler Velocimetry(L.D.V.) in large cavitation tunnel at Samsung Heavy industries. The gap flow model is adopted to solve the characteristics of the horn rudder. Numerical results are compared with the experimental values and the computed velocity fields and pressure distributions with rudder angle on the horn rudder surface show good agreement with measured ones in large cavitation tunnel.

• Journal of the Korean Electrochemical Society
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• v.5 no.2
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• pp.86-92
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• 2002

The present article is concerned with the application of the kinetic Monte Carlo simulation to electrochemistry of lithium intercalation from the kinetic view point. Basic concepts of the kinetic Monte Carlo method and the transition state theory were first introduced, and then the simulation procedures were explained to evaluate diffusion process. Finally the kinetic Monte Carlo method based upon the transition state theory was employed under the cell-impedance-controlled constraint to analyse the current transient and the linear sweep voltammogram for the $LiMn_2O_4$ electrode, one of the intercalation compounds. From the results, it was found that the kinetic Monte Carlo method is much relevant to investigate kinetics of the lithium intercalation in the field of electrochemistry.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.242-251
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• 2020

In this study, the extraction efficiency and reflection coefficient by a two-dimensional OWC (Oscillating Water Column) WEC (wave energy converter) installed in front of a seawall was investigated for regular/irregular waves. The matched eigenfunction expansion method (MEEM) based on the linear potential theory was applied as an analytical tool. The diffraction problem by the incident wave in the open-chamber and the radiation problem by the oscillating pressure in the closed-chamber were solved to obtain the volume fluxes at the internal free-surface. Applying the volume fluxes into the continuity equation for the airflow in a chamber, we got the oscillating air pressure. The maximum extracted power and corresponding reflection coefficient were determined at the optimal turbine coefficient that maximizes the extracted power. OWC device designed for a high extracted efficiency simultaneously contributes to reduce reflected waves.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.3
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• pp.41-50
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• 1989

A basic formulation of the panel method, which is based on the potential field formulation, is reviewed for the case of two-dimensional hydrofoil problems. Numerical procedures to improve the computational efficiency of the panel method are suggested. By investigating local behavior of the flow around the trailing edge, a wedge type Kutta condition is formulated. By subdividing the trailing edge panels, where dipole strengths of the subdivided panels follow the local behavior of the potential values of the flow outside a wedge, the circulation around a hydrofoil is calculated accurately with a relatively small number of panels. The subdividing technique to improve the accuracy of the numerical Kutta condition is proved to be efficient. A local behavior of the flow around the leading edge is also investigated. By matching the flow around the leading edge with that around a parabola, a very accurate velocity distribution is obtained with relatively small number of panels. An accurate prediction of the stagnation point and the pressure distribution near the leading edge may contribute to improve the accuracy of cavity predictions and boundary layer calculations around hydrofoils.

• 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 Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.3
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• pp.87-95
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• 2009

As information theoretic learning techniques, error entropy minimization criterion (MEE) and maximum cross correntropy criterion (MCC) have been studied in depth for supervised learning. MEE criterion leads to maximization of information potential and MCC criterion leads to maximization of cross correlation between output and input random processes. The weighted combination scheme of these two criteria, namely, minimization of Error Entropy with Fiducial points (MEEF) has been introduced and developed by many researchers. As an approach to unsupervised, blind channel equalization, we investigate the possibility of applying constant modulus error (CME) to MEE criterion and some problems of the method. Also we study on the application of CME to MEEF for blind equalization and find out that MEE-CME loses the information of the constant modulus. This leads MEE-CME and MEEF-CME not to converge or to converge slower than other algorithms dependent on the constant modulus.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.1-13
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• 2003

For spatial free vibration of non-symmetric thin-walled curved beams with shear deformation, an improved formulation is proposed in the present study. The elastic strain and the kinetic energies are first derived by considering constant curvature and shear deformation effects due to shear forces and restrained warping torsion. Next equilibrium equations and force-deformation relations are obtained using a stationary condition of total potential energy. And the finite element procedures are developed by using isoparametric curved beam element with arbitray thin-walled sections. Particularly not only shear deformation and thickness-curvature effects on vibration behaviors of curved beams but also mode transition and crossover phenomena with change in curvatures of beams are parametrically investigated. In order to illustrate the accuracy and the reliability of this study, various numerical solutions for spatial free vibration are compared with results by available references and ABAQUS's shell element.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.4
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• pp.93-99
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• 2022

Analytical solutions for regular waves generated by bottom wave makers in a 3-dimensional wave basin were derived in this study. Bottom wave makers which have triangular, rectangular and combination of two shapes were adopted. The 3-dimensional velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions in a wave basin. Then, analytical solutions of 3-dimensional particle velocities and free surface displacement were derived from the velocity potential. The solutions showed physically valid results for regular waves generated by bottom wave makers in a wave basin. The analytical solution for obliquely propagating wave generation from bottom wave maker which works like a snake was also derived. Numerical results of the solution agree well with theoretically predicted results.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.761-766
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• 2020

Phenylamine derivatives are substances that have a biochemical action and are widely applied as psychotropic drugs. In particular, with regard to the quantitative analysis of substances such as ephedrine, amphetamine, pentermine, and dopamine, many previous studies such as electrochemical, vacuum ultraviolet method, and gas chromatography have been conducted. However, there have not been many studies on the structural characteristics of molecular units. Therefore, In this study, we used (HyperChem8.0's, HC) semi-empirical PM3 method to calculate the total energy, band gap, electrostatic potential, and net charge of ephedrine, amphetamine, pentamine and dopamine to investigate the chemical properties of each derivative according to the molecular structure change. The results showed that for total energy -43,171.8, -32,9538.3, -36,407.3 and -43,061.2 Kcal/mol, respectively, while for band gaps, 10.16379377, 9.9531666, 9.7878002 and 9.0589282 eV. Also, for electrostatic potentials, 1.301~-0.045, 1.694~0.299, 0.694~-0.158 and 1.587~-0.048 respectively. Finally, looking at the distribution of net charges, the oxygen atoms, nitrogen atoms and carbon atoms were -0.312~-0.242, -0.161~-0.051 and +0.13~-0.12 respectively. These results are expected to lead to chemical action centered on phenyl radicals and oxygen and nitrogen atoms common to phenethylamine derivatives.