• Structural Engineering and Mechanics
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• v.21 no.2
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• pp.137-150
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• 2005

Dynamic analysis of dam-reservoir-foundation system is usually carried out by employing a simplified and approximate one-dimensional model to account for fluid-foundation interaction. The approximation introduced on this basis is examined thoroughly in this paper by comparing the method with the rigorous approach. It is concluded that the errors due to approximate method could be very significant both for horizontal and vertical ground motions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.405-412
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• 2005

In this study, a numerical method for soil-pile-structure interaction problems in multi-layered half-plane is developed. The total soil-pile-structure interaction system is divided into two parts namely, nonlinear structure part and linear soil-pile interaction parts. In the structure field, the general finite element method is introduced to solve the dynamic equation of motion for the structure. In the soil-pile structure interaction part, physical model consisting of lumped parameter, which is frequency dependent coefficient and determined by rigorous analysis method is introduced. Using proposed analysis procedure, the nonlinear behavior of structure considering soil-structure interaction can be efficiently determined in time domain and the analysis cost is dramatically reduced.

• Journal of Ocean Engineering and Technology
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• v.30 no.3
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• pp.151-160
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• 2016

The diffraction and radiation of linear waves by an array of truncated floating multiple buoys are solved using the interaction theory based on a matched eigenfunction expansion method (MEEM). The interaction processes between multiple buoys are very complex and numerous, because the scattered and radiated waves from each buoy affect the others in the array. Our primary aim is therefore to construct the rigorous wave exciting forces and hydrodynamic forces to deal with the problem of multiple interactions. This present method is applied to a square array of four buoys with two incidence angles, and the results are given for the wave excitation forces on each buoy, heave RAO for each buoy heaving independently, and wave elevations around the buoys and wave run-up. The analytical solutions are in good agreement with the numerical solutions obtained from commercial code (WAMIT).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.33-42
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• 1997

The reciprocating compressors are widely used in industrial fields for its simplicity in principle and high efficiency. But the design of it requires rigorous experiments due to its high dependence on many design parameters. In this work, a mathematical model is developed so that we can analyze the gas-solid interaction during the whole working processes of a reciprocating compressor. The governing equations, which represent the fluid-solid interaction, was derived from the unsteady Bernoulli's equation with the assumption of quasi-steady working process. The valve itself was assumed to be a one degree of freedom spring-mass-damper system. A simple thermodynamic relation, the ideal gas state equation, was used to give it an external force term assuming that the refrigerant behaves like an ideal gas. It was suggested to use a motor of higher driving frequency to enhance the performance of the reciprocating compressor without causing a faster failure of the valve.

• Journal of Korean Elementary Science Education
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• v.38 no.2
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• pp.216-233
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• 2019

The purpose of this study was to identify the aspects of elementary school students' interactions shown conceptual changes in collaborative scientific argumentation. Fifty sixth graders of an elementary school in Jeonju were selected for this study. Ten small groups consisting of five students each were organized evenly with considerations of their gender, science achievement, scientific discussion experience and degree of communication apprehension. 'Food web and Ecosystem' and 'Change of Moon shape' were selected as the proper topics of collaborative scientific argumentation in terms of difficulty to be understanded by the $6^{th}$ graders. The small group's dialogue was recorded. The students' activity sheets, field note and interviews of the participants were collected. Based on the collected data, we analyzed the aspect of small groups' interaction shown conceptual change of each student. The result of this study was as follows: The interaction aspects of the small group of students who showed conceptual changes in the collaborative scientific discussion have a tendency of showing their discussion responses, explanation-opposition discourse, the use of rigorous criteria, their collaborative attitude and participation.

• Structural Engineering and Mechanics
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• v.26 no.4
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• pp.363-376
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• 2007

A FE-BE procedure is presented for dynamic analysis of concrete arch dams. In this technique, dam body is discretized by finite elements, while foundation rock is handled by three dimensional boundary element formulation. This would allow a rigorous inclusion of dam-foundation rock interaction, with no limitations imposed on geometry of canyon shape. Based on this method, a previously developed program is modified, and the response of Morrow Point arch dam is studied for various ratios of foundation rock to dam concrete elastic moduli under an empty reservoir condition. Furthermore, the effects of canyon shape on response of dam, is also discussed.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.533-548
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• 2012

Dynamic analysis of concrete gravity dam-reservoir systems is an important topic in the study of fluid-structure interaction problems. It is well-known that the rigorous approach for solving this problem relies heavily on employing a two-dimensional semi-infinite fluid element. The hyper-element is formulated in frequency domain and its application in this field has led to many especial purpose programs which were demanding from programming point of view. In this study, a technique is proposed for dynamic analysis of dam-reservoir systems in the context of pure finite element programming which is referred to as the wavenumber approach. In this technique, the wavenumber condition is imposed on the truncation boundary or the upstream face of the near-field water domain. The method is initially described. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by this approach, and the results are compared against the exact response. Based on this investigation, it is concluded that this approach can be envisaged as a great substitute for the rigorous type of analysis.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.125-133
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination as a whole. This often imposes a serious computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is to adopt a momentum source method in which the action of rotor is approximated as momentum source over a rotor disc plane in a stationary computational domain. This makes the simulation much simpler. For unsteady simulation, the instantaneous momentum sources are assigned only to a portion of disk plane corresponding to blade passage. The momentum source is obtained by using blade element theory with dynamic inflow model. Computations are carried out for the simple rotor-airframe model (the Georgia Tech model) and the results of the simulation are compared with those of the full Navier-Stokes simulation with moving mesh system for rotor and with experimental data. It is shown that the present simulation yields results as good as those of the full Navier-Stokes simulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.113-120
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination in a single computational domain. This imposes a computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is a momentum source method in which the action of rotor is approximated as momentum source in a stationary mesh system built around the airframe. This makes the simulation much easier. The magnitude of the momentum source is usually evaluated by the blade element theory, which often results in a poor accuracy. In the present work, we evaluate the momentum source from the simulation data by using the Navier-Stokes equations only for a rotor system. Using this data, we simulated the time-averaged steady rotor-airfame interaction and developed the unsteady rotor-airframe interaction. Computations were carried out for the simplified rotor-airframe model (the Georgia Tech configuration) and the results were compared with experimental data. The results were in good agreement with experimental data, suggesting that the present approach is a usefull method for rotor-airframe interaction analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.176-177
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• 2013

Surface plasmon polaritons (SPPs) have attracted the attention of scientists and engineers involved in a wide area of research, microscopy, diagnostics and sensing. SPPs are waves that propagate along the surface of a conductor, usually metals. These are essentially light waves that are trapped on the surface because of their interaction with the free electrons of conductor. In this interaction, the free electrons respond collectively by oscillating in resonance with the light wave. The resonant interaction between the surface charge oscillation and the electromagnetic field of the light constitutes the SPPs and gives rise to its unique properties. In this papers, we studied theoretical and experimental extraordinary transmittance (T) and reflectance (R) of 2 dimensional metal hole array (2D-MHA) on GaAs in consideration of the diffraction orders. The 2d-MHAs was fabricated using ultra-violet photolithography, electron-beam evaporation and standard lift-off process with pitches ranging from 1.8 to $3.2{\mu}m$ and diameter of half of pitch, and was deposited 5-nm thick layer of titanium (Ti) as an adhesion layer and 50-nm thick layer of gold (Au) on the semiinsulating GaAs substrate. We employed both the commercial software (CST Microwave Studio: Computer Simulation Technology GmbH, Darmstadt, Germany) based on a finite integration technique (FIT) and a rigorous coupled wave analysis (RCWA) to calculate transmittance and reflectance. The transmittance was measured at a normal incident, and the reflectance was measured at variable incident angle of range between $30^{\circ}{\sim}80^{\circ}$ with a Nicolet Fourier transmission infrared (FTIR) spectrometer with a KBr beam splitter and a MCT detector. For MHAs of pitch (P), the peaks ${\lambda}$ max in the normal incidence transmittance spectra can be indentified approximately from SP dispersion relation, that is frequency-dependent SP wave vector (ksp). Shown in Fig. 1 is the transmission of P=2.2 um sample at normal incidence. We attribute the observation to be a result of FTIR system may be able to collect the transmitted light with higher diffraction order than 0th order. This is confirmed by calculations: for the MHAs, diffraction efficiency in (0, 0) diffracted orders is lower than in the (${\pm}x$, ${\pm}y$) diffracted orders. To further investigate the result, we calculated the angular dependent transmission of P=2.2 um sample (Fig. 2). The incident angle varies from 30o to 70o with a 10o increment. We also found the splitting character on reflectance measurement. The splitting effect is considered a results of SPPs assisted diffraction process by oblique incidence.