• Computers and Concrete
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• v.19 no.3
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• pp.263-273
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• 2017

In this paper, a finite element model (FEM) in ATENA-3D software was constructed to investigate the behavior of circular ultra high performance concrete (UHPC) filled steel tube stub columns (UHPC-FSTCs) under concentric loading on concrete core. The "CC3DNonLinCementitious2User" material type for concrete in ATENA-3D software with some modifications of material laws, was adopted to model for UHPC core with consideration the confinement effect. The experimental results obtained from Schneider (2006) were then employed to verify the accuracy of FEM. Extensive parametric analysis was also conducted to examine the influence of concrete compressive strength, steel tube thickness and steel yield strength on the compressive behavior of short circular UHPC-FSTCs. It can be observed that the columns with thicker steel tube show better strength and ductility, the sudden drop of load after initial peak load can be prevented. Based on the regression analysis of the results from parametric study, simplified formulae for predicting ultimate loads and strains were proposed and verified by comparing with previous analytical models, design codes and experimental results.

• Journal of Ocean Engineering and Technology
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• v.26 no.2
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• pp.68-78
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• 2012

This study proposes an improved 3-D model that includes a new non-reflected wave generation system for oblique incident and multi-directional random waves, which enables us to estimate the effect of the various wave-types on 3-D wave fields in a coastal area with permeable submerged breakwaters. Then, using the numerical results,the three-dimensional wave field characteristics around permeable submerged breakwaters are examined in cases of oblique incident and multi-directional random waves. Especially, the wave height, mean surface elevation and mean flow around the submerged breakwaters are discussed in relation to the variation of incident wave condition.

• Journal of Korea Water Resources Association
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• v.47 no.1
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• pp.11-24
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• 2014

In this study, the characteristics of the propagation of dam-break wave through a porous structure in a water tank is numerically analyzed by using the three-dimensional numerical model (ANSYS CFX model). As results of comparison between the existing measured and simulated water depth distributions in and around a porous structure, the agreement is relatively well satisfied. Moreover, for the case of the presence in part of a porous structure in a water tank, the three-dimensional flow structure is numerically analyzed In general, compared with in the area with a porous structure, the abrupt variation of water depth occurs in the area without a porous structure. It is shown that the porous structure can play a role to decrease the abrupt variation of water depth.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.518-522
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• 2008

Recently, many patients related to heart disease have surgical operation by expanding a blood vessel to treat the angiostenosis. So far most angioplasties have been performed using balloon-dilative stent made of stainless steel. Some researchers are studying the stent made of shape memory alloy (SMA) to operate the angioplasty more easily. and there are several papers which introduce the angioplasty using SMA. However, most of the analysis models for stents are constructed using solid elements. So much computing time is required to solve the analysis model. In this study, we suggest the SMA stent model using 1D truss element which is much faster than stent model using 3D solid element. To represent non-linear behavior of SMA, we apply 1D SMA constitutive equation of Lagoudas'. Pseudo-elastic behavior of stent structures is presented as a numerical example.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4B
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• pp.429-439
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• 2008

The purpose of this study is to examine the characteristics of run-up height over sandy beach due to the shape of submerged breakwater. For the discussion on it in detail, 3-Dimensional numerical model with Large Eddy Simulation, which is able to simulate directly interaction of Wave Structure Sandy beach (hereafter, LES-WASS-3D; Hur and Lee, 2007) has been used to simulate run-up height over sandy beach as well as wave field around submerged breakwaters. Using the results obtained from numerical simulation, the effects of the shape of submerged breakwaters (crown height, crown width, crown length and submerged breakwater's slope gradient) on run-up height over sandy beach have been discussed related to the wave height distribution and characteristics of up-layer flow around ones.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.571-575
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• 2012

하구역에서의 대표적인 수리특성인 염수쐐기현상에 대한 정확한 이해는 하구역 수질 및 환경관리 측면에서 필수적인 사항이다. 본 연구에서는 정상염수쐐기 경계층 거동에 대한 실험적 연구결과와 3차원 전산유체역학 프로그램인 FLOW-3D를 이용한 수치모의 결과를 비교해봄으로써 염수쐐기현상에 대한 3차원 수치모형의 적용성을 살펴보았다. FLOW-3D를 이용하여 실험장치의 수로구간을 구성하고 경계조건으로 염수의 수위와 담수의 유량을 입력하였으며 밀도차를 두어 이층류가 발생하도록 모의하였다. 모의결과를 통해 시간평균농도와 표준편차를 무차원화하여 단면별 연직분포를 알아보고 각 단면을 중첩하여 경계층의 거동을 살펴보았으며 염수쐐기길이와 염수심을 무차원화하여 밀도프루드수의 변화에 따른 염수쐐기형상을 살펴보았다. 그리고 각 결과를 기 수행된 실험결과와 비교해 보았다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.563-567
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• 2017

This paper deals with the depth and speed controls of a class of nonlinear large diameter unmanned underwater vehicles (LDUUVs), while maintaining its attitude. The concerned control problem can be viewed as an asymptotic stabilization of the error model in terms of its desired depth, surge speed and attitude. To tackle its nonlinearities, the linear parameter varying (LPV) model is employed. Sufficient linear matrix inequality (LMI) conditions are provided for its asymptotic stabilization. A numerical simulation is provided to demonstrate the effectiveness of the proposed design methodology.

• Transactions on Electrical and Electronic Materials
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• v.17 no.6
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• pp.369-374
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• 2016

This paper presents a design procedure of an integrated inductor with a magnetic core for power converters. This procedure considerably reduces design time and effort. The proposed design procedure is verified by the development of an inductor model dedicated to the monolithic integration of DC-DC converters for portable applications. The numerical simulation based on the FEM (finite elements method) shows that 3D modeling of the integrated inductor allows better estimation of the electrical parameters of the desired inductor. The optimization of the electrical parameter values is based on the numerical analysis of the influence of the geometric parameters on the electrical characteristics of the inductor. Using the VHDL-AMS language, implementation of the integrated inductor in a micro Buck converter demonstrate that simulation results present a very promising approach for the monolithic integration of DC-DC converters.

• Geomechanics and Engineering
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• v.8 no.6
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• pp.845-857
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• 2015

The 3D numerical analysis is carried out to investigate the settlement behavior of flexible mat foundations subjected to vertical loads. Special attention is given to the improved analytical method (YS-MAT) that reflects the mat flexibility and soil spring coupling effect. The soil model captures the stiffness of the soil springs as well as the shear interaction between the soil springs. The proposed method has been validated by comparing the results with other numerical approaches and field measurements on mat foundation. Through comparative studies, the proposed analytical method was in relatively good agreement with them and capable of predicting the behavior of the mat foundations.

• Journal of Magnetics
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• v.16 no.4
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• pp.423-426
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• 2011

This paper presents numerical analysis and design of high power contactless transformer with a large air-gap for moving on a guided linear track which is appropriate for high-speed train or MAGLEV. The system has the typical characteristics of large leakage inductance, small magnetizing inductance, and low coupling coefficients giving rise to lower power transfer efficiency, which have been compensated by the purposely-designed contactless transformer coupled with the resonant converter modulating with high switching frequency. In particular, the best model selected from the generated six design candidates has been applied for 3D Finite Element Analysis (FEA) investigating on iron loss to evaluate the overall system efficiency.