• 한국초전도학회:학술대회논문집
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• v.9
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• pp.222-222
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• 1999

From extensive measurements of the resistance and the dynamic resistance as functions of magnetic field and temperature, we find that the transport in the insulating state beyond the superconductor-insulator (S-I) transition is dominated by bosons(Cooper pairs and/or vortices) and cannot be described by the theory of the fermionic insulating phase. The maximum of the magnetoresistance at B = B$_m$ and the following negative slope in R(B) with increasing field can be explained by the crossover from the "Bose-glass" to the "Fermi-glass" phase as suggested by Paalanen, Hebard, and Ruel. The zero bias peak in dv/dl for biases below the characteristic voltage V$_c$ (or current $I_c$), gives a clue for the assumption of the "dirty boson" model which states that the insulating state above the critical magnetic field is the phase where Cooper pairs are localized due to the Coulomb blockade with a nonvanishing order parameter. The shift to a lower value of the critical magnetic field by overlaying thin Au layer, which is known as a strong spin-orbit scatterer, also supports the bosonic nature of the S-I transition.

• Structural Engineering and Mechanics
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• v.89 no.2
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• pp.199-211
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• 2024

The loading capacity of engineering structures/components reduces after the initiation and propagation of crack eventually leads to the final failure. Hence, it becomes essential to deal with the crack and its effects at the design and simulation stages itself, by detecting the prone area of the fracture. The phase-field (PF) method has been accepted widely in simulating fracture problems in complex geometries. However, most of the PF methods are formulated with second order continuity theoryinvolving C⁰ continuity. In the present study, PF method based on fourth-order (i.e., higher order) theory, maintaining C¹ continuity has been proposed for ductile fracture simulation. The formulation includes fourth-order derivative terms of phase field variable, varying between 0 and 1. Applications of fourth-order PF theory to ductile fracture simulation resulted in novelty in this area. The proposed formulation is numerically solved using a two-dimensional finite element (FE) framework in 3-layered manner system. The solutions thus obtained from the proposed fourth order theory for different benchmark problems portray the improvement in the accuracy of the numerical results and are well matched with experimental results available in the literature. These results are also compared with second-order PF theory and a comparison study demonstrated the robustness of the proposed model in capturing ductile behaviour close to experimental observations.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.826_827
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• 2009

This paper introduces major potential faults of Poly-Phase Permanent Magnet Synchronous Motor and their simulation realization methods. The faults of Poly-Phase PM Synchronous Motor, generally, stator turn faults, demagnetizing field. Based on the derived expressions, Poly-Phase PM synchronous Motor simulation model, which is capable of representing stator turn faults, is implemented in Maxwell.

• Journal of computational fluids engineering
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• v.15 no.2
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• pp.86-94
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• 2010

A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation or condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure distribution that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new reconstruction method to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function, a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the CUPID code.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.380-388
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• 2010

A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation of condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new numerical scheme to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the cupid code.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.18-21
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• 2002

Phytoremediation which uses plants to enhance the bioremediation through stimulation of microbial activity and root uptake, has been a topic of increasing interest. Mathematical model were developed that can be applied to various bioremediation methods in the unsaturated zone, especially phytoremediation, for simulating the fate and transport of contaminants under field conditions. A 2-year field study was conducted using 72 (1.5m long and 0.1 m diameter) column lysimeters with four treatments: Johnsongrass; wild rye grass; a rotation of Johnsongrass and wild rye grass; and unplanted fallow conditions. The developed model represented the fate and transport of contaminant both in vegetated and unplanted soils satisfactorily for field applications. Parameters related to the contaminant concentration in the water phase were the main parameters determining the contaminant fate in the vadose zone and indicated that the bioavailability can be the most important factor in the success of phytoremediation as well as bioremediation applications.

• Journal of Fisheries and Marine Sciences Education
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• v.24 no.1
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• pp.56-78
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• 2012

This study which is an alternative exploration for improving the quality level of instruction considering the perception of the teachers in early childhood education field on instructional design is to develop Differentiated Instructional Design Model coincides with the purpose of differentiated instruction curricula and with instructional design principles, and to find out whether the model has significant effect on development of teacher's professionalism. With these purposes, the perception of 343 teachers from early childhood education institutions are investigated, and after component variables are set by drawing the instructional design model available in early childhood education field and reviewing the literature of differentiated instruction model, the Differentiated Instructional design Model for Early Childhood are developed based on FGI(Focus Group Interview) expert evaluation. The experimental study of 88 teachers working in childcare facilities was implemented for effectiveness verification. As a result, first, most teachers consider the priority on making the lesson plans as the development of early childhood and Kindergarten Educational Subjects, and they realize the development of instructional design model which contributes on lesson planning and implementation is much needed. Second, the Differentiated Instructional design Model for Early Childhood are developed, which consists of the cyclic process - pre-lesson phase, lesson implementation phase, and assessment phase -based on development characteristics of early childhood. Third, the experiment of the developed model showed that the scores of experimental group is significantly higher than those of comparative group in knowledge and technique development aspect, and self-understanding development aspect among the aspects of development of teacher's professionalism.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.124-128
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• 2001

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum ahoy has been studied Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The unposed mathematical model is applied to the die shape of the two type. To calculate the velocities and temperature fields during rheology forming process, the each governing equation correspondent to the liquid and solid region are adapted. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity.

• Journal of computational fluids engineering
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• v.13 no.4
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• pp.86-95
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.71-78
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• 2008

For analyses of multi-phase flows in a water-cooled nuclear power plant, a three-dimensional SIMPLE-algorithm based hydrodynamic solver CUPID-S has been developed. As governing equations, it adopts a two-fluid three-field model for the two-phase flows. The three fields represent a continuous liquid, a dispersed droplets, and a vapour field. The governing equations are discretized by a finite volume method on an unstructured grid to handle the geometrical complexity of the nuclear reactors. The phasic momentum equations are coupled and solved with a sparse block Gauss-Seidel matrix solver to increase a numerical stability. The pressure correction equation derived by summing the phasic volume fraction equations is applied on the unstructured mesh in the context of a cell-centered co-located scheme. This paper presents the numerical method and the preliminary results of the calculations.