• Coupled systems mechanics
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• v.1 no.4
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• pp.361-379
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• 2012

This paper presents a fully coupled three-dimensional solver for the analysis of interaction between pulsatile flow and large deformation structure. A partitioned time marching algorithm is employed for the solution of the time dependent coupled discretised problem, enabling the use of highly developed, robust and well-tested solvers for each field. Conservative transfer of information at the fluid-structure interface is combined with an effective multi-predict-correct iterative scheme to enable implicit coupling of the interacting fields at each time increment. The three-dimensional unsteady incompressible fluid is solved using a powerful implicit time stepping technique and an ALE formulation for moving boundaries with second-order time accurate is used. A full spectrum of total variational diminishing (TVD) schemes in unstructured grids is allowed implementation for the advection terms and finite element shape functions are used to evaluate the solution and its variation within mesh elements. A finite element dynamic analysis of the highly deformable structure is carried out with a numerical strategy combining the implicit Newmark time integration algorithm with a Newton-Raphson second-order optimisation method. The proposed model is used to predict the wave flow fields of a particular flow-induced vibrational phenomenon, and comparison of the numerical results with available experimental data validates the methodology and assesses its accuracy. Another test case about three-dimensional biomedical model with pulsatile inflow is presented to benchmark the algorithm and to demonstrate the potential applications of this method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2442-2449
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• 2002

This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.932-940
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• 2011

This study describes computational simulation results in 2-dimensional and 3-dimensional space concerning large scale gap test(LSGT) by using commercial hydrocode such as AUTODYN and LS-DYNA to analyze the detonation phenomenons of high explosives. To consider the possibilities of LSGT simulation, we used Lee - Tarver reaction rate model of PBX-9404 and Comp-B which were implemented AUTODYN's material library. Also we have tried the diverse numerical schemes such as Lagrangian, Eulerian and ALE(Arbitary Lagrangian Eulerian), SPH(Smoothed Particle Hydrodynamics) in LSGT simulations. After LSGT simulations, we compared the simulation results with published results to verify the LSGT simulations. According to the LSGT simulations, we have concluded as follows. In 2-dimensional and 3-dimensional space, Lagrangian solver provided the most reliable results based on analysis time and accuracy. When using two hydrocodes in 2-dimensional space, the simulation results are almost same except one explosive model. We have verified the modeling method and simulation results of the LSGT by using the commenrcial hydrocode in this study.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.489-494
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• 2015

This research focused on minimizing the response of fixed cylindrical offshore structures to a ship impact considering the seawater fluid part. A collision between a ship and offshore structure is generally a complex problem and it is often impractical to perform rigorous finite element analyses to include all the effects and sequences during the collision. The structural behavior of a fixed cylindrical type offshore substructure with a seawater fluid part has a simpler response and small deformation due to the dissipation of impact energy. Upon applying the impact force of a ship to the cylindrical structure, the maximum acceleration, internal energy, and plastic strain are calculated for each load cases using Ls-dyna finite element software. In the maximum cases 2.0 m/s velocity, the response result for the structure was carried out to compare between having a fluid region and no fluid region. Fluid-structure interaction analysis was performed using the ALE method, which make it possible to apply a fluid region on the impact problem. The case of a fixed cylindrical type offshore structure without a seawater fluid part can be a more conservative design.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.111-118
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• 2004

The work presented in this paper concerns the aerodynamic characteristics and compression wave generated in a tunnel when a high speed train enters it. A large number of solutions have been proposed to reduce the amplitude of the pressure gradient in tunnels and some of the most efficient solutions consist of (a) addition ofa blind hood, (b) addition of inclined part at the entrance, and (c) holes in the ceiling of the tunnel. These are numerically studied by using the three-dimensional unsteady compressible Euler equation solver with ALE, CFD code, based on FEM method. Computational results showed that the smaller inclined angle leads to the lower pressure gradient of compression wave front. This study indicated that the most efficient slant angle is in the range from $30^{\circ}$ to $50^{\circ}$. The maximum pressure gradient is reduced by $26.81\%$ for the inclined angle of $30^{\circ}$ as compared to vertical entry. Results also showed that maximum pressure gradient can be reduced by $15.94\%$ in blind hood entry as compared to $30^{\circ}$ inclined tunnel entry. Furthermore, the present analysis showed that inclined slant angle has little effect on aerodynamic drag. Comparison of the pressure gradient between the inclined tunnel hood and the vertical entry with air vent holes indicated that the optimum inclined tunnel hood is much more effective way in reducing pressure gradient and increasing the pressure rise time.

• Korean Journal of Construction Engineering and Management
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• v.6 no.1 s.23
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• pp.99-108
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• 2005

Interactive electronic technical manual(IETM) for construction projects means an electronic tool that regulations and specifications related to construction method or maintenance process ale described by electronic book type. It has a meaning of integrated information system that includes virtual reality(VR), 3D animation and image contents for representing real construction information so that user can easily understand the construction situation and maintenance process. The basic information and technical manuals of construction facilities are being written as paper documents in our construction industry. As the result, the information management in the maintenance phase of construction projects is inefficient, and maintenance cost is being increased. This study attempts to improve the lack of understanding about construction IETM through the analysis of necessity and unique function of construction IETM comparing with the IETMS in other industry, Finally, this study shows a scenario of construction IErM for mitigating natural disaster of construction facilities to verify applicability of IETM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.206-214
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• 2018

This study was conducted from August 2017 to May 2018. Beer was prepared by different ratio of rice and malt and different types of beer, and quality analysis were conducted. The ratio of rice and malt was divided into 0:100 (S0), 20:80 (S1), 40:60 (S2), 60:40 (S3) and 80:20 respectively. We compared the characteristics of the mashing methods(infusion and decoction method) and investigated the characteristics of different types of beer (lager, ale, wheat beer) using yeast (bottom and top yeast). Even with different ratios of rice and malt, normal infusion time was observed and the iodine test was confirmed to be normal. Also, the mashing proceeded normally and the sugar content of the primary wort was between $21.0{\sim}21^{\circ}brix$. In mashing method, the mash concentration, color and flavor of wort were the highest in the three mash method(decoction method). During the fermentation period of beer, the sugar content, pH and yeast number did not differ significantly depending on the ratio of rice and malt, and the type of yeast. Higher alcohol and esters also had no correlation with the ratio of rice to malt, and wheat beer was somewhat higher. The higher the ratio of rice, the more the color intensity(EBC) decreased, the bitter unit(BU) and the preference decreased. When the rice ratio was higher than the malt rate, the degree of preference decreased significantly. Based on the results of this study, it is expected that the rice ratio will be less than the malt ratio and the flavor of the wort will be improved by using the deccoction method. If the malt is supplemented with the use of the special malt and the various hops according to the beer type, it may be helpful to manufacture rice beer.