• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2410-2414
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• 2008

Human heart valves diseased by congenital heart defects, rheumatic fever, bacterial infection, cancer may cause stenosis or insufficiency in the valves. Treatment may be with medication but often involves valve repair or replacement (insertion of an artificial heart valve). Bileaflet mechanical heart valves (BMHVs) are widely implanted to replace the diseased heart valves, but still suffer from complications such as hemolysis, platelet activation, tissue overgrowth and device failure. These complications are closely related to both flow characteristics through the valves and leaflet dynamics. In this study, the physiological flow interacting with the moving leaflets in a bileaflet mechanical heart valve (BMHV) is simulated with a strongly coupled implicit fluid-structure interaction (FSI) method which is newly organized based on the Arbitrary-Lagrangian-Eulerian (ALE) approach and the dynamic mesh method (remeshing) in FLUENT. The simulated results are in good agreement with previous experimental studies. This study shows the applicability of the present FSI model to the complicated physics interacting between fluid flow and moving boundary.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.3-4
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• 2011

The purpose of this study is to suggest basic data for development optimal disassembly manufacturing system during analysis pore structure and heating properties of cementitious joint using conductive resister by induction heating. From the results, we knew cementitious joint is weak easily by heating of conductive resister, such as wire mesh, punching metal, and steel fiber, from induction heating.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.830-833
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• 2005

SDM(Structural Dynamics Modification) is to improve dynamic characteristics of a structure, more specifically of a base structure, by adding or deleting auxiliary(modifying) structures. In this paper, I will focus on the optimal layout of the stiffeners which are attached to the plate to maximize 1st natural frequency. Recently, a new topology method was proposed by yamazaki. He uses growing and branching tree model. I modified the growing and branching tree model. The method is designated modified tree model. To expand the layout of stiffeners, I will consider non-matching problem. The problem is solved by using local lagrange multiplier without the mesh regeneration. Moreover The CMS(Component mode synthesis) method is employed to reduce the computing time of eigen reanalysis using reduced componet models.

• Journal of Aerospace System Engineering
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• v.15 no.6
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• pp.10-18
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• 2021

A flame deflector prevents a launch system from thermal damage by deflecting the exhaust flame of the launch vehicle. During the deflection of the flame, the flame deflector is subjected to a high-temperature and high-pressure flow, which results in thermal ablation damage at the surface. Predicting this ablation damage is an essential requirement to ensure a reliable design. This paper introduces a numerical method for predicting the ablation damage phenomena based on a one-way fluid-structure interaction (FSI) analysis. In the proposed procedure, the temperature and convective heat transfer coefficient of the exhaust flame are calculated using a fluid dynamics analysis, and then the ablation is calculated using a finite element analysis (FEA) based on the user-subroutine UMESHMOTION and Arbitrary Lagrangian-Eulerian (ALE) adaptive mesh technique in ABAQUS. The result of such an analysis was verified by comparison to the ablation test result for a flame deflector.

• Coupled systems mechanics
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• v.8 no.2
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• pp.111-127
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• 2019

In this paper, we present a 2D multi-scale coupling computation procedure for localized failure. When modeling the behavior of a structure by a multi-scale method, the macro-scale is used to describe the homogenized response of the structure, and the micro-scale to describe the details of the behavior on the smaller scale of the material where some inelastic mechanisms, like damage or plasticity, can be defined. The micro-scale mesh is defined for each multi-scale element in a way to fit entirely inside it. The two scales are coupled by imposing the constraint on the displacement field over their interface. An embedded discontinuity is implemented in the macro-scale element to capture the softening behavior happening on the micro-scale. The computation is performed using the operator split solution procedure on both scales.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.435-444
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• 2017

The vehicle-track structure dynamic interaction analysis problem can be treated as sliding contact problem, and it is assumed that vehicle run at a constant speed over a rail modeled as beam elements. Unfortunately, Salome-Meca can not satisfy the compatibility condition for the beam master elements, which are consist of the elements with higher order polynomial shape function, in sliding contact problem. In this study, it is suggested to use more finer beam master element mesh as the remedy for incompatibility in sliding contact problem, and the accuracy of the solution is secured. For this, the effect of beam element mesh refinement consisting runway is analysed through simple examples, and the applicability to the dynamic interaction analysis is evaluated. Finally, the dynamic interaction analysis of railway skewed culvert transition problem is carried out to evaluate the effect of supporting stiffness due to backfill pattern changes and track irregularity due to uneven subgrade settlement.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.255-260
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• 2020

In this study, we developed a method of improving the surface-enhanced Raman spectroscopy (SERS) response characteristics by depositing a nanoporous Ag metal thin film through cluster source sputtering after forming a pyramidal texture structure on the Si substrate surface. A reactive ion etching (RIE) system with a metal mesh inside the system was used to form a pyramidal texture structure on the Si surface without following a complicated photolithography process, unlike in case of the conventional RIE system. The size of the texture structure increased with the RIE process time. However, after a process time of 60 min, the size of the structure did not increase but tended to saturate. When the RF power increased from 200 to 250 W, the size of the pyramidal texture structure increased from 0.45 to 0.8 ㎛. The SERS response characteristics were measured by depositing approximately 1.5 ㎛ of nanoporous Ag metal thin film through cluster sputtering on the formed texture structure by varying the RIE process conditions. The Raman signal strength of the nanoporous Ag metal thin film deposited on the Si substrate with the texture structure was higher than that deposited on the general silicon substrate by up to 19%. The Raman response characteristics were influenced by the pyramid size and the number of pyramids per unit area but appeared to be influenced more by the number of pyramids per unit area. Therefore, further studies are required in this regard.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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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.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.329-342
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• 2003

Most of the existing multicast routing protocols for ad-hoc networks do not take into account the efficiency of the protocol for the cases when there are large number of sources in the multicast group, resulting in either large overhead or poor data delivery ratio when the number of sources is large. In this paper, we propose a multicast routing protocol for ad-hoc networks, which particularly considers the scalability of the protocol in terms of the number of sources in the multicast groups. The proposed protocol designates a set of sources as the core sources. Each core source is a root of each tree that reaches all the destinations of the multicast group. The union of these trees constitutes the data delivery mesh, and each of the non-core sources finds the nearest core source in order to delegate its data delivery. For the efficient operation of the proposed protocol, it is important to have an appropriate number of core sources. Having too many of the core sources incurs excessive control and data packet overhead, whereas having too little of them results in a vulnerable and overloaded data delivery mesh. The data delivery mesh is optimally reconfigured through the periodic control message flooding from the core sources, whereas the connectivity of the mesh is maintained by a persistent local mesh recovery mechanism. The simulation results show that the proposed protocol achieves an efficient multicast communication with high data delivery ratio and low communication overhead compared with the other existing multicast routing protocols when there are multiple sources in the multicast group.

• International Journal of High-Rise Buildings
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• v.4 no.1
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• pp.65-73
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• 2015

Detailed finite element (FE) analyses of a full-scale four-story steel frame structure, subjected to consecutive 60% and 100% excitations from the JR Takatori records during the 1995 Hyogoken-Nanbu earthquake, are conducted using E-Simulator. The four-story frame was tested at the largest shake-table facility in the world, E-Defense, in 2007. E-Simulator is a parallel FE analysis software package developed to accurately simulate structural behavior up to collapse by using a fine mesh of solid elements. To reduce computational time in consecutive dynamic time history analyses, static analysis with gravity force is introduced to terminate the vibration of the structure during the analysis of 60% excitation. An overall sway mechanism when subjected to 60% excitation and a story mechanism resulting from local buckling of the first-story columns when subjected to 100% excitation are simulated by using E-Simulator. The story drift response to the consecutive 60% and 100% excitations is slightly smaller than that for the single 100% excitation.