• Journal of Welding and Joining
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• v.13 no.1
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• pp.138-144
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• 1995

Recently, as the industrial structure tends to become large, the thickness of structural plate becomes thicker. Therefore, the thicker the plate of welded structure is, the larger the shape of welded joint. The effect of large heat input makes large heat affected zone(HAZ). These bring to complict welding residual stress and to weaken material, which may cause extremely harm to the safety of structures. Nevertheless, welding is design is regulated by the KS, JIS or standard in the resister of shipping such as KR, ABS or LR. However, these rules are based on rather experimental than theoretical. In this study, the computer program of heat conduction, considering un-steady state and quasi-steady state, is developed for optimizing(minimizing) a shape of welded joint. The characteristics of heat on the welded joints with various shapes are clarified by the results of the analyses.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.172-175
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• 2003

Run-Out-Table is the region between EDT and CT. Hot killed strip is cooled by air and water in ROT. In this procedure, phase transformation and shape deformation occur due to temperature drop. Because of un-ideal cooling condition, deformation of strip and non-uniform phase distribution come into existence. This phenomenon affects the strip property and lead th the existence of residual stress. And it exerts effects on the Coiling process, Coil Cooling process, and Un-coiling process. Through these process, the residual stresses of strip are more larger and unbalance of these stresses become more severe. Finite element (FE) based models for the analysises of non-steady state heat transfer and elastoplastic deformation are described in this investigation. The analysises of thermodynamics and phase transformation kinetics are suggested also. Using the ROT simulation result coiling process and coil cooling process simulations are carried out.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.2
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• pp.43-49
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• 2000

It is a complex process to analyze power system voltage stability problems with all of the dynamics of a system, because a large power network system sophisticatedly consists of generators, lines, loads and so forth. So we considered the dynamics of loads so as to analyze voltage stability method- by carrying out an analysis of steady state voltage stability and dynamic voltage stability simultaneously. To perform a steady state voltage stability program in advance makes it possible to cut down on laborious calculations so that an analysis of dynamic voltage stability becomes concise. The validity and efficiency of the method presented in this paper were verified by applying the IEEE 14 bus system.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.875-881
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• 2000

We study the rheological properties of concentrated polymer solution and the melt under simple shear and elon-gational flow using Brownian dynamicssimulation. In order to describe the anisotropic molecular motion, we modifiedthe Giesekus' mobility tensor by incorporating the finitely extensible non-linear elastic (FENE) spring force into dumbbell model. To elucidate the nature of this model, our simulation results are compared with the data of FENE-P ("P"standsfor the Perterin) dumbbell model and experiments. While in steady state both original FENE and FENE-P models exhibit a similar viscosity response,the growthof viscosity becomes dissimilar as the anisotropy decreases and the flowrate increases. The steady state viscosity obtained from the simulation well describes the experiments including the shear-thinning behavior in shear flow and viscosity-thinning behavior in elongational flow. But the growth of viscosity oforiginal FENE dumbbell model cannot describe the experimental results in both flow fields.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.113-121
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• 2011

Rollover accident is one of the serious traffic accident and rollover accident takes high portion of all accident. The most common type of rollover is a tripped rollover which occupy 95% of all type of single-vehicle rollover. Tripped rollover occurs when a vehicle leaves normal road way and tripped by loose gravel, soil of fixed object such as guard rail, curbs and ditches. And the rest of the type of rollover is un-tripped rollover. An un-tripped rollovers that occurs during high-speed collision avoidance maneuvers. In this paper, presents the explanation of the un-tripped rollover test method and procedure, additionally this paper deals with various occurrence in the un-tripped test such as occurring excessive tire camber in the un-tripped test, tire side-wall contact with road surface and roll oscillation. And this paper analyzes the analysis of the roll rate amplitude in specific frequency through the FFT (Fast Fourier Transform) and the roll angle at the steering reverse timing which is the Fishhook test roll rate feedback time. Finally, this paper analyzes the relations between the estimated steady state roll gain and rollover stability.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.523-528
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• 2001

This paper deals with two non-conventional HVDC system, that are, the Capacitor Commutated Converter (CCC) in which series capacitors are included between the converter transformer and the valves, and the Controller Series Capacitor Converter (CSCC), based on more conventional topology, in which series capacitors are inserted between the AC filter bus and the AC network. The simulation waveforms show that if these compare to conventional HVDC, these HVDC systems have many advantages in steady-state and transient performance.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.629-630
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.466-467
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• 2005

• Transactions of Materials Processing
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• v.12 no.4
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• pp.302-307
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• 2003

Hot rolled strip is cooled by air and water in Run-Out-Table. In this process, phase transformation and shape deformation occurs due to temperature drop. Because of un-ideal cooling condition of ROT, irregular shape deformation and phase transformation arise in the strip. which affect the strip property and lead to the residual stress of strip. And these exert effects on the following processes, coiling process, coil cooling process, and re-coiling process. Through these processes, the residual stress becomes higher and severe. For the prediction of residual stress distribution and shape deformation of final product, Finite element(FE) based model was used. It consists of non-steady state heat transfer analysis, elasto-plastic analysis. thermodynamic analysis and phase transformation kinetics. Successive FEM simulation were applied from ROT process to coil cooling process. In each process simulation, previous process simulation results were used for the next process simulation. The simulation results were matched well with the experimental results.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1804-1805
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• 2011

In recent year there has been an increasing interest in the dynamic simulation of complex systems. This study uses a large-scale forty-seventh order fossil fuel power plant. Twenty-three state variables are associated with the physical processes and twenty-four state variables associated with the control system. The plant model is expected to predict all dominant effects in a steady and transient state. In this study, the power plant model is reorganized into four subsystems, each with its controller, and the four connected to each other through a manager, which is a fifth part to the system. The four parts of the unit are the boiler system, steam turbine system, condenser system, and feedwater system.