• Journal of Ocean Engineering and Technology
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• v.10 no.1
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• pp.75-80
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• 1996

The importance of the impact force on the vertical offshore circular structure member in the surf zone due to the breaking wave has been recognized recently. In this paper characteristics of breaking wave forces and the corresponding estimation procedures for them are investigated. For the characterization of the wave forces, three parts, drag force, inertia force, impact force are categorized and identified, respectively. Among them the impact force is maimly studied and the concise form of the force is proposed with the application scheme for the design of offshore circular structure member. The resulting form porposed here for impact force is well coincided with former research results by other people. Except the impact force, so called Morison equation can be employed for the common offshore structure design. The drag force and inertia force are represented as convertionally for the profile except the breaking part. In the numerical example, for thpical sea condition and the member size, the proposed procedures for the breaking wave forces calculation are demonstrated. It is found that the impact force is the most deminant one comparing with inertia and drag forces in the surf zone.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.3
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• pp.136-149
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• 2016

Green water impact occurs frequently on offshore platform due to waves with a height greater relative to the freeboard of the structure. This phenomenon exerts a large impact load on the deck. In this paper, offshore platform models with green water protectors of various shapes were fixed to the center of a 3D wave tank to measure the impact pressure acting on the various points on deck and protectors. The impact pressure distribution differed depending on the protector shape, and various patterns of wave creeping up the protector were observed. The protector shape that exerted the lowest pressure impact on the deck will be useful in the deck design of offshore platform, and the model test results will be expected to be used for designers to select the best protector form.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.311-314
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• 2007

The experimental method of measuring dynamic properties of structures was presented. The method is based on the flexural wave propagation characteristics. Using the method, change in structural dynamic properties due to damage is measured. The crack has much more significant impact on the strain energy than the inertial effects. From this, the sensitivity of the dynamic stiffness on the crack location is estimated by calculating the strain energy. When the wave propagates, the strain and kinetic energies shows cyclic changed over space. The crack that occurred at locations where the wave energy is in the form of the potential energy affected most significantly the wave propagation characteristics. The effects of crack location on the wave propagation were used to determine the crack location.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1638-1642
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• 2007

This paper investigated the destruction effect of the semiconductors by impact of high power electromagnetic wave. The experiments is employed as an open-ended waveguide to study the destruction effects on semiconductor using a 2.45 GHz 600 W Magnetron as a high power electromagnetic wave. The semiconductors are located at a distance of $31cm\sim40cm$ from the open-ended waveguide and are composed of a LED drive circuit for visual discernment. Also the chip condition of semiconductor is observed by SEM(Scanning Electron Microscope) analysis. The semiconductor are damaged by high power electromagnetic wave at about 860 V/m. The SEM analysis of the destructed devices showed onchipwire and bondwire destructions. Based on the result, semiconductor devices should have plan to protect the semiconductor devices form high power electromagnetic wave. And the database from this experiment provides the basis for future investigation.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.93-101
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• 2013

The incident bore impact loads acting on a tall structure is simulated using the refined Moving Particle Simulation (MPS) method. The particle method is more feasible and effective than conventional grid-based methods for the violent free-surface problems. In the present study, the simulation results for the temporal change of the hydrodynamic force on the structure and longitudinal velocity component around the structure are compared with the experiments (Radd and Bidoae, 2005). And the mitigation effects by installation of various obstacles in front of the main structure are investigated and discussed form the simulation results.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.439-445
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• 2017

Plunging breaker slamming pressures on vertical or sloping sea dikes are one of the most severe and dangerous loads that sea dike structures can suffer. Many studies have investigated the impact forces caused by breaking waves for maritime structures including sea dikes and most predictions of the breaker forces are based on empirical or semi-empirical formulae calibrated from laboratory experiments. However, the wave breaking mechanism is complex and more research efforts are still needed to improve the accuracy in predicting breaker forces. This study proposes a semi-empirical formula, which is based on impulse-momentum relation, to calculate the slamming pressure due to plunging wave breaking on a sloping sea dike. Compared with some measured slamming pressure data in two literature, the calculation results by the new formula show reasonable agreements. Also, by analysing probability distribution function of wave heights, the proposed formula can be converted into a probabilistic expression form for convenience only.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.2
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• pp.139-146
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• 2011

The breaking wave pressure occurs when a plunging breaker instantaneously impinges on structural surface, and appears differently depending on whether or not to form air pockets at the instant of contact. The Wagner type normally forms a single pressure peak at the contact spot due to the direct collision of water volume to the structure whereas in the Bagnold type the time lagged oscillation of the air pocket causes pressure peaks even at areas away from the spot. In the present study, the Bagnold's impact pressure is numerically and experimentally investigated for the bulkhead of an underwater tunnel under construction which is subjected to nearby breaking waves. A numerical solver of Navier-Stokes equations was applied to reproduce the breaking waves near a bulkhead, and the results showed the Bagnold's impact pressure occurring on the back (land side) face of the bulkhead. The existence of the impact pressure was also verified by a hydraulic model testing, and it was found that the experimental results well conformed to their numerical counterparts.

• Coupled systems mechanics
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• v.11 no.5
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• pp.459-483
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• 2022

In the present work, a new photothermoelastic model based on Moore-Gibson-Thompson theory has been constructed. The governing equationsfor orthotropic photothermoelastic plate are simplified for two-dimension model. Laplace and Fourier transforms are employed after converting the system of equations into dimensionless form. The problem is examined due to various specified sources. Moving normal force, ramp type thermal source and carrier density periodic loading are taken to explore the application of the assumed model. Various field quantities like displacements, stresses, temperature distribution and carrier density distribution are obtained in the transformed domain. The problem is validated by numerical computation for a given material and numerical obtained results are depicted in form of graphs to show the impact of varioustheories of thermoelasticity along with impact of moving velocity, ramp type and periodic loading parameters. Some special cases are also explored. The results obtained in this paper can be used to design various semiconductor elements during the coupled thermal, plasma and elastic wave and otherfieldsin thematerialscience, physical engineering.

• Ocean Systems Engineering
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• v.14 no.3
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• pp.301-314
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• 2024

In this study, the lift coefficient and wave deformations for a two-dimensional flat-plate in non-cavitating condition were computed using a closed-form (analytic) solution. This plate moves at a constant speed beneath a free surface in water of finite depth. The model represents the flat-plate using a lumped vortex element within the constraints of potential flow theory. The kinematic and dynamic free surface conditions were combined and linearized. This linearized free surface condition was then applied to get the total velocity potential. The method of images was utilized to account for the effects of finite depth in the calculations. The lift coefficient of the flat-plate and wave elevations on the free surface were calculated using the closed-form solution. The lift coefficients derived from the present analytic solution were validated by comparing them with Plotkin's method in the case of deep water. Wave elevations were also compared with those obtained from a numerical method. A comprehensive discussion on the impact of Froude number, submergence depth of flat-plate from the calm free surface, the angle of attack and the depths of finite bottom on the results - namely, lift coefficients and free surface deformations - is provided.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.521-532
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• 2007

Elastic wave propagations in the semi-infinite transversely isotropic cylinder under various kinds of longitudinal impact loads are analyzed using the axisymmetric finite element method and Houbolt time-integration scheme. For which the finite element program is newly constructed and verified through the comparison of present numerical results with those by other researchers. E-type glass-epoxy composite cylinders with different fiber volume fractions are adopted and studied in detail with dynamic responses of the isotropic cylinder. Three dimensional wave motions are given in graphic form to show the realistic view of the wave propagation. Nondimensionalized dynamic characteristic variables which relate the size of finite element mesh, the time step, and the wave speed are presented for obtaining accurate and stable numerical results.