• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.275-280
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• 2011

In the present study, a unified viscoplastic-damage model has been applied in order to describe the mechanical characteristics of fresh water ice such as nonlinear material behavior and volume fraction. The strain softening phenomenon of fresh water ice under quasi-static compressive loading has been evaluated based on unified viscoplastic model. The material degradation such as growth of slip/fraction has quite close relation with material inside damage. The volume fraction phenomenon of fresh water ice has been identified based on volume fraction (nucleation and growth of damage) model. The viscoplastic-damage model has been transformed to the fully implicit formulation and the discretized formulation has been implemented to ABAQUS user defined subroutine (User MATerial: UMAT) for the benefit of application of commercial finite element program. The proposed computational analysis method has been compared to uni-axial compression test of fresh water ice in order to validate the compatibilities, clarities and usefulness.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.633-642
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• 2008

It's important to measure quantitative properties about thermal-nano behavior of polymer for producing high quality components using Nanoimprint lithography process. Nanoscale indents can be used to make the cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, formability of polymethylmetacrylate(PMMA) and polycarbonate(PC) were characterized Polymer has extreme variation in thermo mechanical variation during forming high temperature. Because of heating the polymer, it becomes softer than at room temperature. In this case it is particularly important to study high temperature-induced mechanical properties of polymer. Nanoindenter XP(MTS) was used to measure thermo mechanical properties of PMMA and PC. Polymer was heated by using the heating stage on NanoXP. At CSM(Continuous Stiffness Method) mode test, heating temperature was $110^{\circ}C,120^{\circ}C,130^{\circ}C,140^{\circ}C$ and $150^{\circ}C$ for PMMA, $140^{\circ}C,150^{\circ}C,160^{\circ}C,170^{\circ}C$ and $180^{\circ}C$ for PC, respectively. Maximum indentation depth was 2000nm. At basic mode test, heating temperature was $90^{\circ}C$ and $110^{\circ}C$ for PMMA, $140^{\circ}C,160^{\circ}C$ for PC. Maximum load was 10mN, 20mN and 40mN. Also indented pattern was observed by using SEM and AFM. Mechanical properties of PMMA and PC decreased when temperature increased. Decrease of mechanical properties from PMMA went down rapidly than that of PC.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1109-1113
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• 1999

sothemal reduction at $50^{\circ}C$ using $Pt/MoO_3$ or $Pt/MoO_3/SiO_2$ made by dry impregnation or physical mixture of $Pt^{\circ}$ and $MoO_3$ demonstrated that the $H_2$ uptake vis $H_2$ spillover from Pt into $MoO_3$ was enhanced as calcination temperature was increased. Surface area of exposed Pt crystallites measured by CO chemisorption was decreased with higher calcination temperature. In addition, TEM showed that $MoO_x$ overlayers were formed on Pt crystallites after calcination at $400^{\circ}C$. Consequentially, it was found that this increased active contact sites between Pt and $MoO_3$ due to surface morphological change was one of the dominant factors for this increased $H_2$uptake via $H_2$ spillover from Pt crystallites into $MoO_3$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.567-578
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• 2002

The main purpose of this study is to investigate the dynamic behaviour of containment building in nuclear power plant excited by aircraft impact loading using a lower order 8-node solid element. The yield and failure surfaces for concrete material model is formulated on the basis of Drucker-Prager yield criteria and are assumed to be varied by taking account of the visco-plastic energy dissipation. The standard 8-node solid element has prone to exhibit the element deficiencies and the so-called B bar method proposed by Hughes is therefore adopted in this study. The implicit Newmark method is adopted to ensure the numerical stability during the analysis. Finally, the effect of different levels of cracking strain and several types of aircraft loading are examined on the dynamic behaviour of containment building and the results are quantitatively summarized as a future benchmark.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.269-277
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• 2017

In this work, as a preliminary experimental works, which focuses on utilizing separated pastes from activated (or radioactive) concrete as solidifying agents for radioactive waste immobilization, were performed. It was found that density of hydrated cement paste, which was lower than that of ordinary portland cement, increased as temperature for heat treatment increased. Highest compressive strength was observed with the specimens that was heat treated at $600^{\circ}C$. However, heat treatment over $700^{\circ}C$ showed higher CaO content that caused higher heat of hydration after in contact with water, lows of workability, and lower strength. Based on experimental results, it is suggested that $600^{\circ}C$ heat treatment is more appropriate for waste cement paste to be used as a solidifying agent.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.21-26
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• 2003

Develop and need design application of carbon sex design concept that consider plasticity in elastic design concept until now. To Place that is representative construction of hull in this research rain deflection pattern analysis technique and grandeur increment method such as general load type increment law and displacement type increment law and Newton-Raphson method increment body law to use jointly compare. Specialty. through analysis by initial deflection pattern. examined closely carbon set conduct of place by initial deflection pattern. Applied thin plate structure which receive compressive load used ANSYS that analysis method is mediocrity finite element analysis program to save complicated conduct that effect that conduct after initial buckling and conduct after secondary buckling get in the whole construction is very big and such and grandeur increment law presumes complicated rain fan shape conduct in bifurcation point specially.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.111-120
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• 2010

This study evaluated strength properties of recycled asphalt concretes using warm-mix technology. Granite with maximum size of 13mm and penetration grade of 80-100 virgin binder were used for mixing in recycled mixtures. Mix design was performed using 20% and 30% RAP(coarse : fine= 6 : 4) contents. GPC, penetration, absolute viscosity and kinematic viscosity were measured for determining ratio of two warm-mix additives (Evotherm and Sasobit). Low-density polyethylene(LD) used as asphalt modifier for improving stiffness of recycled WMA mixtures in this study. Therefore, a total of 11 mixtures were prepared in this study; 8 warm-mix recycled mixtures(2 RAP contents${\times}$2 warm-mix additives${\times}$2 modifiers), 2 hot-mix recycled mixtures and 1 HMA virgin mixture(control). Deformation strength, indirect tensile strength, moisture sensitivity, permanent deformation by wheel tracking tests were measured out for evaluating fundamental properties of recycled asphalt concretes using warm-mix technology.

• Journal of the Korean Geotechnical Society
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• v.36 no.9
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• pp.33-44
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• 2020

In order to analyze the shear strength characteristics of the grout with sudden gelation in the pre-hardening state, the viscosity of the mixture and the indoor vane shear test were performed. The grout was prepared according to the water-cement (w/c) ratio and the shear strength test was conducted. The plastic-state shear strength of grout was affected by the w/c ratio, so the lower the w/c ratio, the higher the initial shear strength was, and the longer the curing time was, the higher the shear strength was. The maximum shear strength occurred at the faster rotation angle as the higher shear strength was developed, and the lower shear strength occurred at the larger rotation angle. In addition, it was confirmed that the pre-hardening grout rapidly decreased in strength after the maximum shear strength was gained, and converged at a certain level after the rotation angle of the vane blade was about 70° to 90°.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.304-310
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• 2018

The aim of the research is to provide possibility of quality controlling by rheological properties for lightweight foamed concrete. The lightweight foamed concrete achieves its low density by containing air bubbles (foam) produced during the mixing process. Therefore, containing foamed volume during setting period is critical for the securing the performance as an insulating material. In this research, regarding foam collapse during the setting period, rheolgocial properties of fresh state lightweight foamed concrete were assessed to get its relationship with volume stability, or foam stability. For the experiment regarding foaming factors including mixing time, mix design of contents for materials, rheological properties of fresh state lightweight foamed concrete were tested with its density and settling depth. Based on the settling depth with various factors, relationship with rheological properties was analyzed, and especially, close relationship of plastic viscosity and settling depth was found. Therefore, from the results of this research, it is considered to contribute on suggesting a new approach of quality controlling for lightweight foamed concrete using rheological test method.

• Journal of the Korea Institute of Building Construction
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• v.19 no.3
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• pp.219-228
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• 2019

The aim of the research is to provide a fundamental data of low viscosity typed superplasticizer (SP) on cement-based materials incorporating various supplementary cementitious materials (SCMs). As a relatively new product, low-viscosity typed SP has introduced for high performance concrete with high viscosity due to its high solid volume fraction with various SCMs. However, there are not enough research or reports on the performance of the low viscosity typed SP with cement-based materials incorporting SCMs. hence, in this research, for cement paste and mortar, fluidity and rheological properties were evaluated when the mixtures contained various SCMs such as fly ash, blast furnace slag, and silica fume. From the experiment conducted, it was checked that the low viscosity typed superplasticizer decreased the plastic viscosity of the mixture as well as the yield stress. From the results of this research, it is expected to contribute on introduction of new type SP for high performance concrete or high-viscous cementitious materials.