• Structural Engineering and Mechanics
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• 제31권2호
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• pp.153-162
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• 2009

The reduction of the dynamic response of an offshore structure subjected to wind-generated random ocean waves is of extreme significance in the aspects of serviceability, fatigue life and safety of the structure. In this study, a new neuro-control scheme is applied to the vibration control of a fixed offshore platform under random wave loads to examine the applicability of the proposed method. It is called the Lattice Probabilistic Neural Network (LPNN), as it utilizes lattice pattern of state vectors as the training data of PNN. When control results of the LPNN are compared with those of the NN and PNN, LPNN showed better performance in effectively suppressing the structural responses in a shorter computational time.

• 대한조선학회지
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• 제21권3호
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• pp.35-42
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• 1984

In this paper, the lateral motions of a ship in the time domain are treated by applying the Impulse Response Function Technique. The acceleration, and displacement of a ship in the time domain are needed for the purpose of such automatic controls as the fire control system and the auto-pilot of ocean-going vessels, etc. The response Amplitude Operators of a ship are calculated by the Strip Method of Salvesen-Tuck-Faltinsen, and the Pierson-Moskowitz Spectrum multiplied by spreading function is used to represent the short crested ocean waves. The ocean wave elevations in the time domain are simulated according to the Method of Borgman. Finally the rudder effect is considered by simply adding the force and moment due to the rudder to the wave exciting force. And the results of lateral motions with and without rudder are shown.

• Earthquakes and Structures
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• 제13권1호
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• pp.17-27
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• 2017

In this study, the characteristics of site amplification at seismic observation stations in Japan were estimated using the attenuation relationship of each station's response spectrum. Ground motion records observed after 32 earthquakes were employed to construct the attenuation relationship. The station correction factor at each KiK-net station was compared to the transfer functions between the base rock and the surface. For each station, the plot of the station correction factor versus the period was similar in shape to the graphs of the transfer function (amplitude ratio versus period). Therefore, the station correction factors are effective for evaluating site amplifications considering the period of ground shaking. In addition, the station correction factors were evaluated with respect to the average shear wave velocities using a geographic information system (GIS) dataset. Lastly, the site amplifications for specific periods were estimated throughout Japan.

• Structural Engineering and Mechanics
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• 제18권2호
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• pp.231-246
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• 2004

In this paper, a comparison of various random vibration and deterministic dynamic analyses of cable-stayed bridges subjected to asynchronous ground motion is presented. Different random vibration methods are included to determine the dynamic behaviour of a cable-stayed bridge for various ground motion wave velocities. As a numerical example the Jindo Bridge located in South Korea is chosen and a 413 DOF mathematical model is employed for this bridge. The results obtained from a spectral analysis approach are compared with those of two random vibration based response spectrum methods and a deterministic method. The analyses suggest that the structural responses usually show important amplifications depending on the decreasing ground motion wave velocities.

• Earthquakes and Structures
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• 제4권6호
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• pp.649-670
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• 2013

It is known that a base-isolated building exhibits a large response to a long-duration, long-period wave and an inter-connected system without base-isolation shows a large response to a pulse-type wave. To compensate for each deficiency, a new hybrid passive control system is investigated in which a base-isolated building is connected to another building (free wall) with oil dampers. It is demonstrated that the present hybrid passive control system is effective both for pulse-type ground motions and long-duration and long-period ground motions and has high redundancy and robustness for a broad range of disturbances.

• Geomechanics and Engineering
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• 제16권6호
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• pp.609-618
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• 2018

A new mechanical model for predicting the vibration of a pipe pile embedded in longitudinally layered visco-elastic media with radial inhomogeneity is proposed by extending Novak's plain-strain model and complex stiffness method to consider viscous-type damping. The analytical solutions for the dynamic impedance, the velocity admittance and the reflected signal of wave velocity at the pile head are also derived and subsequently verified by comparison with existing solutions. An extensive parametric analysis is further performed to examine the effects of shear modulus, viscous damping coefficient, coefficient of disturbance degree, weakening or strengthening range of surrounding soil and longitudinal soft or hard interbedded layer on the velocity admittance and the reflected signal of wave velocity at the pile head. It is demonstrated that the proposed model and the obtained solutions provide extensive possibilities for practical application compared with previous related studies.

• Advances in nano research
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• 제13권4호
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• pp.341-350
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• 2022

The continuous elements method, also known as the dynamic stiffness method, is effective for solving structural dynamics problems, especially over a large frequency range. Before applying this method to fluid-structure interactions, it is advisable to check its validity for pure acoustics, without considering the different coupling parameters. This paper describes a procedure for taking wave propagation into account in the formulation of a Dynamic Stiffness Matrix. The procedure is presented in the context of the harmonic response of acoustic pressure. This development was validated by comparing the harmonic response calculations performed using the continuous element model with the analytical solution. In addition, this paper illustrates the application of this method to a simple compressible flow problem, since it has been applied solely to structural problems to date.

• 지역사회간호학회지
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• 제32권3호
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• pp.254-267
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• 2021

Purpose: The purpose of this study was to identify the effects of brain-wave biofeedback training nursing intervention (NFT) upon enhancing self-regulation response in adolescence with emotional behavior problems in school. Methods: A quasi-experimental design was conducted. The participants were assigned to the experimental group (n=24) or the control group (n=24). The experimental group additionally received NFT. The NFT was conducted 10 sessions for 30 minutes per session with the band reward and inhibit training which matched their Quantitative Electroencephalography (QEEG), participant's demand and chief complaint. Data were collected with QEEG and heart rate variability (HRV) in physiological response, self-efficacy in cognitive response, depression in emotional response, impulsivity and delay gratification in behavioral response of self-regulation. Results: The general characteristics and the pre-test scores of two groups were all homogeneous. The experimental group was reported to be significantly higher in QEEG homeostasis, HRV homeostasis, self-efficacy, and delay gratification than the control group. The experimental group was reported to be significantly lower in depression and impulsivity. Conclusion: The results indicate that NFT using brain cognitive neuroscience approach is effective in enhancing self-regulation response. Therefore, this nursing intervention using brain cognitive neuroscience approach can be applied as an effective self-regulation nursing intervention for adolescents with emotional behavior problems in communities for adaptive life.

• 대한조선학회논문집
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• 제46권5호
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• pp.488-497
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• 2009

The freak wave, also known as New-Year-Wave in the north Atlantic, is relatively large and spontaneous ocean surface wave that can sink even large ships and destroy maritime structures. To understand oceanic conditions that develop freak waves, we simulated and generated two versions of scale-downed waves (1:64 and 1:42) in a numerical wave tank and compared the results with the experiment in wave flume. Both of the breaking and non-breaking waves were generated in the simulation. The numerical simulation was implemented based on the finite volume method and a genetic optimization algorithm. Random values were assigned as the initial values for the parameter in the control function, which produced signals representing the motion of wave-maker. The same signal obtained from the optimization process was used for both of the simulation and the experiment. By varying the object function and restrictions of the simulation, a best profile of design wave was selected based on the characteristics, height and period of simulated waves. Results showed that the simulation and experiment with the scale of 1:42 agreed better with freak waves in the natural condition. The presented simulation method will contribute to saving the time and cost for conducting subsequent response analyses of motion under freak waves in the course of the model test for ship and maritime structure.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.333-347
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• 2013

The present study numerically models the interaction between a regular wave and the roll motion of a rectangular floating structure. In order to simulate two-dimensional incompressible viscous two-phase flow in a numerical wave tank with the rectangular floating structure, the present study used the volume of fluid method based on the finite volume method. The sliding mesh technique is adopted to handle the motion of the rectangular floating structure induced by fluid-structure interaction. The effect of the wave period on the flow, roll motion and forces acting on the structure is examined by considering three different wave periods. The time variations of the wave height and the roll motion of the rectangular structure are in good agreement with experimental results for all wave periods. The present response amplitude operator is in good agreement with experimental results with the linear potential theory. The present numerical results effectively represent the entire process of vortex generation and evolution described by the experimental results. The longer wave period showed a different mechanism of the vortex evolution near each bottom corner of the structure compared to cases of shorter wave periods. In addition, the x-directional and z-directional forces acting on the structure are analyzed.