• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.39-48
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• 2006

In this research, in order to study the spray, combustion, and emission characteristics of the common rail DME engine, the target engine was disassembled, and 3D CAD file was constructed using a 3D measurement machine and a rapid prototyping machine. Using the obtained 3D geometry, fine moving meshes are generated, and three dimensional non-steady turbulence flow field and combustion phenomenon including spray were numerically analyzed. As a result, IMEP of DME and diesel in medium and high speed revolution showed similar performance. As the DME fuel start to burn in spray area, the vaporized fuel rapidly spreads squish area in low speed revolution. In the case of DME engine, CO and NOx are relatively consistent with experiment results. It was found that the break-up, evaporation, collision model of DME fuel need to be properly adjusted through matching the characteristics of fuel and injector for further improvement.

• Journal of Powder Materials
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• v.10 no.6
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• pp.395-405
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• 2003

In the conventional metallothermic reduction (MR) process for obtaining tantalum powder in batch-type operation. it is difficult to control morphology and location of deposits. On the other hand, a electronically mediated reaction (EMR) process is capable to overcome these difficulties and has a merit of continuous process, but it has the defect that the reduction yield is poor. MR-EMR combination process is a method that is able to overcome demerits of MR and EMR process. In this study, a MR-EMR combination process has been applied to the production of tantalum powder by sodium reduction of $K_2$TaF$_{7}$. The total charge passed through external circuit and average particle size (FSSS) were increased with increasing reduction temperature. The proportion of fine particle (-325 mesh) was decreased with increasing reduction temperature. The yield was improved from 65% to 74% with increasing reduction temperature. Considering the charge, impurities, morphology, particle size and yield, an reduction temperature of 1,123 K was found to be optimum temperature for MR-EMR combination process.

• Journal of Powder Materials
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• v.11 no.4
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• pp.333-340
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• 2004

In this study, tantalum powder has been producted by MR-EMR combination process. MR-EMR combination process is a method that is able to improve demerits of MR(metallothermic reduction) and EMR(electronically mediated reaction) process. This study examined the characteristics of powder with the amount of reductant excess using $K_2$TaF$_{7}$ as feed materials, Na as a reductant and KCl/KF as a diluent. In addition, this study examined acid treatment that affect the high purification of powder. The impurities contained in powder was removed in various conditions of acid treatment. The total charge passed through external circuit and average particle size(FSSS) were increased with increasing amount of sodium excess. The proportion of fine particle(-325mesh) was decreased with increasing amount of sodium excess. The yield was improved from 70％ to 76% with increasing amount of sodium excess. Considering the impurities, charge, morphology, particle size and yield, an amount of sodium excess of 10wt% were found to be optimum conditions for MR-EMR combination process.s.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.3
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• pp.158-170
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• 2009

In this paper, we propose the new torus network which has the hypercube Q3 as the basic module. The proposed Hyper-torus has the degree 4, and is the network which has the scalability, and the fine diameter. If we compare the class of the torus in the viewpoint of network cost, the hyper-torus with $1.4{\sqrt{N}}$+ 16 is proved to be approximately 65% than the torus with $4{\sqrt{N}}$ and 50% than the honeycomb with $2.45{\sqrt{N}}$. This result means that hyper-torus is better for the class of the existing mesh in the viewpoint of network cost.

• Journal of Welding and Joining
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• v.22 no.6
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• pp.25-29
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• 2004

Some industrial steel structures are composed by components linked by several welding joints to constitute an assembly. The main interest of assembly simulation is to evaluate the global distortion of welded structure. The general method, thermo-elasto-plastic analysis, leads to excessive model size and computation time. In this study, a simplified method called "Local and Global approach" was developed to break down this limit and to provide a accurate solution for distortion. Local and global approach is composed of 3 steps; 1) Local simulation of each welding joint on a dedicated mesh (usually very fine due to high thermal gradients), taking into account for the non linearity of the material properties and the moving heat source. 2) Transfer to the global model of the effects of the welding joints by projection of the plastic strain tensors. 3) Elastic simulation to determine final distortions in global model. The welding deformation test for mock-up structure was performed to verify this approach. The predicted welding distortion by this approach had a good agreement with experiment results.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.2
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• pp.8-15
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• 2008

Wastewoods (logging residues) generated in Korea were used to make lignocellulosic fillers for papermaking. Lignocellulosic fillers could play great roles to increase retention efficiency and thus decrease turbidity of white water in papermaking process. In addition, lignocellulosic fillers could be used to improve physical properties of paper through their high affinity to cellulosic fibers, leading to the less use of chemical additives like retention aids. Wastewoods including Pinus densiflora and Quercus variabilis were chemically and mechanically treated for making fine particles passing through 100 mesh wire. The newly generated fillers showed larger particle size distribution than ground calcium carbonates but similar distribution to talc. In particular, pretreatment by hot water was more effective to generate smaller particle size than by alkali treatment. Lignocellulosic particles mixed with ground calcium carbonates under intense hybridizing condition greatly contributed to surface coverage of organic fillers in addition to filling to lumen and pits.

• Korea-Australia Rheology Journal
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• v.17 no.3
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• pp.99-110
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• 2005

This work presents results of finite element analysis of isothermal incompressible creeping viscoelastic flows with the tensor-logarithmic formulation of the Leonov model especially for the planar geometry with singular comers in the domain. In the case of 4:1 contraction flow, for all 5 meshes we have obtained solutions over the Deborah number of 100, even though there exists slight decrease of convergence limit as the mesh becomes finer. From this analysis, singular behavior of the comer vortex has been clearly seen and proper interpolation of variables in terms of the logarithmic transformation is demonstrated. Solutions of 4:1:4 contraction/expansion flow are also presented, where there exists 2 singular comers. 5 different types spatial resolutions are also employed, in which convergent solutions are obtained over the Deborah number of 10. Although the convergence limit is rather low in comparison with the result of the contraction flow, the results presented herein seem to be the only numerical outcome available for this flow type. As the flow rate increases, the upstream vortex increases, but the downstream vortex decreases in their size. In addition, peculiar deflection of the streamlines near the exit comer has been found. When the spatial resolution is fine enough and the Deborah number is high, small lip vortex just before the exit comer has been observed. It seems to occur due to abrupt expansion of the elastic liquid through the constriction exit that accompanies sudden relaxation of elastic deformation.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.11b
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• pp.172-177
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• 1999

Effect of fiber treatment with cellulase (Liftase A40), and with two refining methods (Valley beating and impact refining) on wood fiber and handsheet properties were investigated at three refining levels (300, 400, and 500ml) for two furnishes (NBKP and LBKP). Part of the treated furnishes were classified by 150 mesh screen into fine-free fiber, and fines. Fiber length analysis, WRV, zero-span strength, and other handsheet mechanical properties were compared. The study showed that Liftase A40 lowered the zero-span and the folding endurance of both furnishes (NBKP much more and LBKP much less). Pretreatment with Liftase A 40 followed by refining significantly lowered the fiber length and refining energy to reach to the target freeness. Impact refining, which is done by hitting the fibers vertically with rod at 20% solid content, kept the fiber length increased WRV, and improved handsheet mechanical properties much more than valley beating. Properties of fines from different sources were compared in detail in the study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.599-607
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• 2002

During the shape optimization, relocations of nodes happen successively. However, excessive movement of nodes often results in the mesh distortion and eventually deteriorates the accuracy of the optimum solution. To overcome this problem, an efficient method lot the shape optimization has been developed. The method starts from the design domain which is large enough to hold the possible shape of the structure. The design domain has pre-defined uniform fine meshes. In each cycle, the method allots real properties to the elements inside the structure and nearly zero to ones outside. The performance of the method is evaluated through two examples with displacement and frequency constraints.