• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1513-1523
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• 2017

Improvement of numerical analysis methods has been required to solve complicated phenomena that occur in nuclear facilities. Particularly, fluid-structure interaction (FSI) behavior should be resolved for accurate design and evaluation of complex reactor vessel internals (RVIs) submerged in coolant. In this study, the FSI effect on dynamic characteristics of RVIs in a typical 1,000 MWe nuclear power plant was investigated. Modal analyses of an integrated assembly were conducted by employing the fluid-structure (F-S) model as well as the traditional added-mass model. Subsequently, structural analyses were carried out using design response spectra combined with modal analysis data. Analysis results from the F-S model led to reductions of both frequency and Tresca stress compared to those values obtained using the added-mass model. Validation of the analysis method with the FSI model was also performed, from which the interface between the upper guide structure plate and the core shroud assembly lug was defined as the critical location of the typical RVIs, while all the relevant stress intensities satisfied the acceptance criteria.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2004.11a
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• pp.250-261
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• 2004

A novel method for ab initio prediction of protein tertiary structures, PROFESY (PROFile Enumerating SYstem), is introduced. This method utilizes secondary structure prediction information and fragment assembly. The secondary structure prediction of proteins is performed with the PREDICT method which uses PSI-BLAST to generate profiles and a distance measure in the pattern space. In order to predict the tertiary structure of a protein sequence, we assemble fragments in the fragment library constructed as a byproduct of PREDICT. The tertiary structure is obtained by minimizing the potential energy using the conformational space annealing method which enables one to sample diverse low lying minima of the energy function. We apply PROFESY for prediction of some proteins with known structures, which shows good performances. We also participated in CASP5 and applied PROFESY to new fold targets for blind predictions. The results were quite promising, despite the fact that PROFESY was in its early stage of development. In particular, the PROFESY result is the best for the hardest target T0161.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1262-1267
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• 2003

TF magnet structures are the main structural components in the KSTAR magnet systems to protect the superconducting coils from mechanical, electrical, and thermal loads. TF coil structure supports CS and PF coil system. The inter-coil structure contains adjustable shear keys and conical bolts to provide pre-loading in toroidal direction and to resist against in-plane and out-of-plane forces that are the most critical loads on the TF magnet system. The conical bolts and shear keys are specially designed to assemble easily and to provide a convenient accommodation for a good alignment. The connection plate that is one of the prototype fabrications had been manufactured to study adjustability of conical bolts and shear keys for assembly of TF coil structure. We could measure the misalignments at the keyways and conical holes with the misalignment measuring instrument.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.95-99
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• 2008

The block assembly of ship consists of a certain type of heat processes such as cutting, bending welding residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. The validity of the prediction method must be also clarified through experiments. This paper proposes a simplified analysis method to predict the welding deformation of panel block structure. For this purpose, a simple prediction model for fillet welding deformations has been derived based on numerical and experimental results through the regression analysis. On the basis of these results, the simplified analysis method has been applied to some examples to show its validity.

• Structural Engineering and Mechanics
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• v.55 no.2
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• pp.315-334
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• 2015

This study's primary aim is to check the existence of a representative volume element for granular materials and determine the link between the properties (responses) of macro structures and the size of the discrete particle assembly used to represent a constitutive relation in a two-scale model. In our two-scale method the boundary value problem on the macro level was solved using finite element method, based on the Cosserat continuum; the macro stresses and modulus were obtained using a solution of discrete particle assemblies at certain element integration points. Meanwhile, discrete particle assemblies were solved using discrete element method under boundary conditions provided by the macro deformation. Our investigations focused largely on the size effects of the discrete particle assembly and the radius of the particle on macro properties, such as deformation stiffness, bearing capacity and the residual strength of the granular structure. According to the numerical results, we suggest fitting formulas linking the values of different macro properties (responses) and size of discrete particle assemblies. In addition, this study also concerns the configuration and displacement fluctuation of discrete particle assemblies on the micro level, accompanied with the evolution of bearing capacity and deformation on the macro level.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.57-62
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• 2003

The block assembly of ship consists of a certain type of heat processes such as cutting, bending, welding, residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. The validity of the prediction method must be also clarified through experiments. This paper proposes a simplified analysis method to predict the welding deformation of panel block structure. For this purpose, a simple prediction model for fillet welding deformations has been derived based on numerical and experimental results through the regression analysis. On the basis of these results, the simplified analysis method has been applied to some examples to show its validity.

• Fibers and Polymers
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• v.5 no.4
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• pp.280-288
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• 2004

Split-type nylon/polyester microfiber and polyester microfiber fabrics possess drapeability, softness, bulkiness, and smoothness, so that they can be applied in various industrial fields. In particular, these fabrics are able to absorb various organic solvents, and can be used as clean room materials. To investigate the chemical affinity between solvents and the compositional materials of these fabrics, the contact angle of thermally pressed film fabrics was measured with different solvents. The thermally pressed nylon/polyester fabric films showed a chemical attraction to formamide. The sorption properties of the microfiber fabrics were investigated using a real time testing device, and these tests showed that the sorption behavior was more influenced by the structure of the fibrous assembly than by any chemical attraction. The effect of the fabric density, specific weight, and sample structure on the sorption capacity and rate was examined for various organic solvents. The sorption capacity was influenced by the density and the specific weight of the fibrous assembly, and knitted fabric showed a higher sorption capacity than woven fabric. However, the sorption rate was less affected in lower viscosity solvents. On applying Poiseuille's Law, the lower viscosity solvents showed higher initial sorption rates, and more easily penetrated into the fibrous assembly.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.117-129
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• 2022

The downward discharge of the molten fuel to the lower structure of the fuel assembly could increase of the pressure drop and degrade of coolability of the assembly. To analyze the phenomena, experiments for the generation of the debris bed were conducted as LOF-DT series. Based on the debris bed in the LOF-DT, pressure drop experiment was conducted with intact and blocked component. Parametric study on the pressure drop was conducted by CFD. The LOF-DT experiments were conducted for the position and porosity of the debris bed. 85% of the debris were sedimented in the lower reflector, and 15% were in the nose piece, approximately. Porosity of the debris bed were about 0.7 and 0.85 in the lower reflector and nose piece, respectively. Pressure drop increased significantly with debris bed, especially in the lower reflector. More than 120 time of the pressure drop increased in the lower reflector, while only 10% increased in the nose piece. According to the parametric study, mass of the debris was the most important for pressure drop. The lower discharge phenomena could have a significant effect to the total pressure drop of the fuel assembly, approximately 10.8 times for the base case.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.293-293
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• 2006

Self-assembled nanostructures of block copolymer thin films have gathered significant attention due to their potential applications as templates for nanofabrication. However the lack of a robust strategy to control the structure formation in thin film geometries has been considered a major obstacle for the practical application. In this presentation 'epitaxial self-assembly' will be introduced as a successful strategy to control the self-assembled nanostructure of block copolymer. Chemically patterned surfaces prepared by advanced lithographic techniques successfully registered nanodomains in block copolymer thin film without any single defect over an arbitrarily large area.

• Land and Housing Review
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• v.10 no.3
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• pp.77-87
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• 2019

In Korea, the modular construction method was applied to the construction of facilities such as military barracks and school dormitories, beginning with the pilot project of Seoul New Elementary School in 2003. In 2017, public modular houses were supplied to Busan(Yongho-dong) and Seoul(Gayang-dong), and modular housing is expected to continue to be supplied in the future. However, there is no clear construction standard for the modular housing construction yet, and there are few cases where the infill modular system is applied. Therefore, this study established the work breakdown structure and proposed a standard process focusing on the infill modular system applied to the construction of Dujeong-dong modular house in Cheonan. Level 1 of the work breakdown structure by construction stage of Infill modular was defined as modular manufacturing, assembly, and finishing process. Level 2 was defined as preparation, modular production, modular infill, modular fixing, floor plastering, building finishing, and other site finishing. Level 3 is defined as 57 detailed unit work of infill modular construction. The standard process of infill modular is proposed for the assembly stage that is commonly applicable to infill modular housing construction. The results of this study can be used for the process plan, transportation plan, lifting plan of modular housing construction.