• Steel and Composite Structures
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• v.41 no.5
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• pp.761-773
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• 2021

This study presents a 3D non-linear finite element (FE) assessment of dynamic soil-structure interaction (SSI). The numerical investigation has been performed on the time domain through a Finite Element (FE) system, while considering the nonlinear behavior of soil and the multi-directional nature of genuine seismic events. Later, the FE outcomes are analyzed to the recorded in-situ free-field and structural movements, emphasizing the numerical model's great result in duplicating the observed response. In this work, the soil response is simulated using an isotropic hardening elastic-plastic hysteretic model utilizing HSsmall. It is feasible to define the non-linear cycle response from small to large strain amplitudes through this model as well as for the shift in beginning stiffness with depth that happens during cyclic loading. One of the most difficult and unexpected tasks in resolving soil-structure interaction concerns is picking an appropriate ground motion predicted across an earthquake or assessing the geometrical abnormalities in the soil waves. Furthermore, an artificial neural network (ANN) has been utilized to properly forecast the non-linear behavior of soil and its multi-directional character, which demonstrated the accuracy of the ANN based on the RMSE and R² values. The total result of this research demonstrates that complicated dynamic soil-structure interaction processes may be addressed directly by passing the significant simplifications of well-established substructure techniques.

• Journal of IKEEE
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• v.24 no.2
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• pp.409-418
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• 2020

In this paper, an integrated optical, evanescent-wave biosensor utilizing a multimode interferometer based on a Si₃N₄ rib-optical waveguide consisting of the Si/SiO₂/Si₃N₄/SiO₂ stacked structure was described. The theoretical background of the multimode interferometer was reviewed, and the structure and design process were presented through numerical computational analysis. We analyzed how the dimension (length, width) of the multimode interferometer affected the sensor performance. It has been confirmed through computational analysis that the changes in the refractive index of an analyte greatly affect the mode pattern formation position and output optical power of a multimode interferometer, and proved that this principle could be applied to integrated-optic biosensor.

• Atmosphere
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• v.22 no.4
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• pp.387-400
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• 2012

This study aims at examining the sensitivity of numerical simulations to the resolution of initial and boundary data, and to an application of WRF (Weather Research and Forecasting) 3DVAR (Three Dimension Variational data Assimilation). To do this, we ran the WRF model by using GDAS (Global Data Assimilation System) FNL (Final analyses) and the KLAPS (Korea Local Analysis and Prediction System) analyses as the WRF's initial and boundary data, and by using an initial field made by assimilating the radar data to the KLAPS analyses. For the sensitivity experiment, we selected a heavy rainfall case of 21 September 2010, where there was localized torrential rain, which was recorded as 259.5 mm precipitation in a day at Seoul. The result of the simulation using the FNL as initial and boundary data (FNL exp) showed that the localized heavy rainfall area was not accurately simulated and that the simulated amount of precipitation was about 4% of the observed accumulated precipitation. That of the simulation using KLAPS analyses as initial and boundary data (KLAPC exp) showed that the localized heavy rainfall area was simulated on the northern area of Seoul-Gyeonggi area, which renders rather difference in location, and that the simulated amount was underestimated as about 6.4% of the precipitation. Finally, that of the simulation using an initial field made by assimilating the radar data to the KLAPS using 3DVAR system (KLAP3D exp) showed that the localized heavy rainfall area was located properly on Seoul-Gyeonggi area, but still the amount itself was underestimated as about 29% of the precipitation. Even though KLAP3D exp still showed an underestimation in the precipitation, it showed the best result among them. Even if it is difficult to generalize the effect of data assimilation by one case, this study showed that the radar data assimilation can somewhat improve the accuracy of the simulated precipitation.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.72-78
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• 1996

This thesis deals with a method to solve a two-and-one-half-dimensional ($2\frac12$ D) problem, which means that the ocean environment is two-dimensional whereas the source is fully three-dimensionally propagating, including three-dimensional refraction phenomena and three-dimensional back-scattering, using two-dimensional two-way parabolic equation method combined with Fourier synthesis. Two dimensional two-way parabolic equation method uses Galerkin's method for depth and Crank-Nicolson method and alternating direction for range and provides a solution available to range-dependent problem with wave-field back-scattered from discontinuous interface. Since wavenumber, k, is the function of depth and vertical or horizontal range, we can reduce a dimension of three-dimensional Helmholtz equation by Fourier transforming in the range direction. Thus transformed two-dimensional Helmholtz equation is solved through two-way parabolic equation method. Finally, we can have the $2\frac12$ D solution by inverse Fourier transformation of the spectral solution gained from in the last step. Numerical simulation has been carried out for a canonical ocean environment with stair-step bottom in order to test its accuracy using the present analysis. With this spectral parabolic equation method, we have examined three-dimensional acoustic propagation properties in a specified site in the Korean Straits.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.1001-1010
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• 2001

In TLM method, Discrete Green's function ABC have been used when improved the exactness of analyzing in wide frequency band. But this technology has a complicated process to apply absorbing boundary, which means it needs additional numerical analyzing process to obtain discrete Green's function data. so, In this paper, we propose new Green's absorbing layer for simple process to apply absorbing boundary. newly proposed Green's absorbing layer is produced by applying of loss operation, loading discrete Green's function with attenuation. A state of optimum absorbing would be obtained by relation between increasing rate of loss, attenuation constant and length of green's absorbing layer. and then Analysts of waveguide BPF is carried out using Green's absorbing layer within state of optimum absorbing, then this result is in corrective agreement with the result applying traditional discrete Green's function ABC.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.1-4
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• 2002

The numerical alaysis of optical device, silicabased device, are presented. The purpose of this paper is to simulate and to design a 8-channel optical wavelength division multiplexer(OWDM) based on Mach-Zehnder Interferometer(MZI) with wavelength spacing between channels Δλ=0.8 nm at central wavelength λ=1.55 ${\mu}{\textrm}{m}$. In initial condition fur simulating, we assumed as follows. A channel waveguide is made from silica based P-doped SiO2 core layers in order to coupling with a fiber easily and its core dimension was 6 ${\mu}{\textrm}{m}$$\times$6 ${\mu}{\textrm}{m}$. The core and clad index of channel waveguide were 1.455 and 1.444, separately, at λ=1.55 ${\mu}{\textrm}{m}$. Where, the separation between channel waveguides in coupling region was 3 ${\mu}{\textrm}{m}$. As a result of analysis, a group mode index of channel waveguide was 1.4498370, was gained by Hermite-Gaussian Method(HGM). Also, the channel spacing was determined by the waveguide arm length difference and was Δλ=0.8 nm as like a proposed condition. The central wavelength of a designed-multiplexer was activated about wavelength λ=1.55 ${\mu}{\textrm}{m}$, and we certificated that it can be used to 8-channel optical wavelength division multiplexer/demultiplexer.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.309-332
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• 2021

Natural barrier systems surrounding the geological repository for the high-level radioactive waste should guarantee the hydraulic performance for preventing or delaying the leakage of radionuclide. In the case of the behavior of a crystalline rock, the hydraulic performance tends to be decided by the existence of discontinuities, so the coupled hydro-mechanical(HM) processes on the discontinuities should be characterized. The discontinuum modelling can describe the complicated behavior of discontinuities including creation, propagation, deformation and slip, so it is appropriate to model the behavior of a crystalline rock. This paper investigated the coupled HM processes in discontinuum modelling such as UDEC, 3DEC, PFC, DDA, FRACOD and TOUGH-UDEC. Block-based discontinuum methods tend to describe the HM processes based on the fluid flow through the discontinuities, and some methods are combined with another numerical tool specialized in hydraulic analysis. Particle-based discontinuum modelling describes the overall HM processes based on the fluid flow among the particles. The discontinuum methods that are currently available have limitations: exclusive simulations for two-dimension, low hydraulic simulation efficiency, fracture-dominated fluid flow and simplified hydraulic analysis, so it could be improper to the modelling the geological repository. Based on the concepts of various discontinuum modelling compiled in this paper, the advanced numerical tools for describing the accurate coupled HM processes of the deep geological repository should be developed.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.90-96
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• 2012

In order to determine optimal design length of adhesive joint of a composite rocket motor case, stress analysis of joint part according to changes of adhesive length was done. Adhesive length has a range of 50 mm to 300 mm as design variables. The ratio of adhesive length without any stress gradient to initial non-stressed adhesive length was determined as evaluation criteria for selection of adhesive length, which called "stress gradient length ratio". The numerical result showed that stress gradient length ratio of joint part with adhesive length of more than 200 mm was increased very slowly with increase of adhesive length. It means that adhesive length of about 200 mm could be the optimal dimension to ensure the structural safety of joint part against internal pressure of 2,500 psi.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.281-290
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• 2022

The direct shear test is commonly used to evaluate the shear behavior of frozen soil-structure interfaces under normal stress. However, failure criteria, such as the Mohr-Coulomb failure criterion, are needed to obtain the unconfined shear strength. Hence, the punch shear test, which is usually used to estimate the shear strength of rocks without confinement, was examined in this study to directly determine the adfreezing strength. It is measured as the shear strength of the frozen soil-structure interface under unconfined conditions. Different soils of silica sand, field sand, and field clay were prepared inside the steel and concrete ring structures. Soil and ring structures were frozen at the target temperature for more than 24 h. A punch shear test was then conducted. The test results show that the adfreezing strength increased with a decrease in the target temperature and increase in the initial water content, owing to the increase in ice content. The adfreezing strength of field clay was the smallest when compared with the other soil specimens because of the large amount of unfrozen water content. The field sand with the larger normalized roughness showed greater adfreezing strength than the silica sand with a lower normalized roughness. From the experiment and analysis, the applicability of the punch shear test was examined to measure the adfreezing strength of the frozen soil-structure interface. To find a proper sample dimension, supplementary experiments or numerical analysis will be needed in further research.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2373-2377
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• 2009

In this paper, the threshold voltage characteristics have been analyzed using three dimensional Poisson's equation for FinFET. The FinFET is extensively been studing since it can reduce the short channel effects as the nano device. We have presented the short channel effects such as subthreshold swing and threshold voltage for PinFET, using the analytical three dimensional Poisson's equation. We have analyzed for channel length, thickness and width to consider the structural characteristics for FinFET. Using this model, the subthreshold swing and threshold voltage have been analyzed for FinFET since the potential and transport model of this analytical three dimensional Poisson's equation is verified as comparing with those of the numerical three dimensional Poisson's equation.