• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.91-95
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• 2003

There is a problem to be solved for improvement of durability and safety supervision. When you do the waterproofing and anticorrosive work of main concrete from the design stage, the material and method of construction need to be correctly applied to appropriate circumstance conditions. Epoxy have mostly been used for concrete water tank structure. Lately, lots of subjects on adaption of polyurea resin waterproofing and anticorrosive are under discussion. Then, we attempt to approach by evaluating and comparing every capabilities with another waterproofs in this study. Performance evaluation items include the adherence performance, the imprint of seal performance, temperature dependence performance, promotion weatherizing ability, inner chemical performance, drinking water eruptive performance. Through the experiment analysis, we found that the polyurea resin waterproofing membrane is dominantly superior to other waterproofs. According to this study, we suggest the polyurea resin waterproofing membrane as a new waterproofing material for concrete structure.

• Journal of Korean Society of Forest Science
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• v.96 no.1
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• pp.54-57
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• 2007

Urea-formaldehyde (UF) resin was formulated similarly to plywood resin in the laboratory. The synthesized UF resin adhesive was mixed with extender, filler and acid catalyst. The mixture contained 56.1% total solids and 43.9% water. The mixes was used to bond five Com-Ply types using Korean wood species. The Com-Ply made were tested for shear strength and wood failure according to KS F 3101 ordinary plywood as well as for bending strength per KS F 3104 particleboard. The performance test results showed good strength properties for all Com-Ply types made in this study. This result represented that the UF resin adhesive mix was adequate for bonding Com-Ply with domestic wood species.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.91-95
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• 2003

There is a problem to be solved for improvement of durability and safety supervision. When you do the waterproofing and anticorrosive work of main concrete from the design stage, the material and method of construction need to be correctly applied to appropriate circumstance conditions. Epoxy have mostly been used for concrete water tank structure. Lately, lots of subjects on adaption of polyurea resin waterproofing and anticorrosive are under discussion. Then, we attempt to approach by evaluating and comparing every capabilities with another waterproofs in this study. Performance evaluation items include the adherence performance. the imprint of seal performance, temperature dependence performance. promotion westernizing ability, inner chemical performance. drinking water eruptive performance. Through the experiment analysis, we found that the polyurea resin waterproofing membrane is dominantly superior to other waterproofs. According to this study, we suggest the polyurea resin waterproofing membrane as a new waterproofing material for concrete structure.

• Polymer(Korea)
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• v.30 no.2
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• pp.135-139
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• 2006

To evaluate the dental restorative application of polymer composites filled with hydroxyapatite (HAP) which is an inorganic component of human bone material, dental properties of the polymer composites were investigated. A visible light system was utilized to activate the acrylate resin matrix of the composites. Maximum loading percentage of HAP in composite was 65 wt% and the depth of cure was 6.0 mm which can be applicable for dental restoration. With increasing the HAP content, degree of conversion of polymer composites was slightly decreased, however, polymerization shrinkage value was not varied. Diametral tensile strength value was enhanced with an increase of HAP content, however, there was no strict trend between flexural strength and HAP concentration. Anyhow, polymer composites prepared herein have superior mechanical properties sufficient specifications applicable to dental materials.

• Nuclear Engineering and Technology
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• v.6 no.2
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• pp.73-79
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• 1974

The preparation method of the mortar-plastic composites(M P C) were studied with styrene, methyl methacrylate and vinyl acetate as monomers. Radiation, thermal-catalytic and radiation-catalytic methods were used as curing methods. Almost all of the above monomers and methods were possible to use for preparing M P C Although thermal-catalytic method was excellent to get M P C in a short time, the tensile strength of the product was less than those obtained by radiation method. It was possible to prepare the M P C which included up to about 10% plastics and was strengthened about ten times on the properties of acid resistandes and tensile strength comparing with the control. The improvement of the properties is much superior to concrete-plastic composite(C P C).

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.456-461
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• 2004

The dynamic behavior of sheet metals must be examined to ensure the impact characteristics of auto-body by a finite element method. An appropriate experimental method has to be developed to acquire the material properties at the intermediate strain rate which is under 500/s in the crash analysis of auto-body. In this paper, tensile tests of various different steel sheets for an auto-body were performed to obtain the dynamic material properties with respect to the strain rate which is ranged from 0.003/sec to 200/sec. A high speed material testing machine was made for tension tests at the intermediate strain rate and the dimensions of specimens that can provide the reasonable results were determined by the finite element analysis. Stress-strain curves were obtained for each steel sheet from the dynamic tensile test and used to deduce the relationship of the yield stress and the elongation to the strain rate. These results are significant not only in the crashworthiness evaluation under car crash but also in the high speed metal forming.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.442-446
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• 2004

Computer simulation of a swaging manufacturing process is presented in this paper. Commercially available software has been used to develop the simulation algorithm. Based on the experience gained from trial runs, simulation of a tube swaging process has been carried out. The material parameters "n" (strain hardening exponent) and "K" (plastic modulus) are obtained from actual tensile test measurements of the tube material. Two different geometries for the die and the tube have been used in this work and a comparison made. Numerical simulation of the swaging process has been performed using the commercially available HyperMesh(r) for pre-processing, LS-DYNA(r) for analysis and LS-TAURUS(r) for post-processing. Some of the results obtained from this study are compared with those available in the literature.

• Korean Journal of Agricultural Science
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• v.7 no.2
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• pp.119-130
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• 1980

This study was conducted to determine the effect of curing temperature on the strength of briquette ash mortar hardened by cement. The six different kinds of briquette ash mortars were made by mixing the cement : briquette ash, ((cement (90%)+lime (10%)) : briquette ash and cement : standard sand at the ratio of 1:2, 1:3, 1:4, 1:5, 1:7, and 1:9, respectively and the cu ring temperatures were $20^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$. The strength of compression, bending and tensile were measured at ${\sigma}_7$ and ${\sigma}_{28}$. The summarized results were as follows. 1. At the ${\sigma}_7$ of 1:2 the compressive strength of the cement : briquette ash and (cement+lime) : briquette ash were 69.3% and 75.1%, respectively of the mortar made of the standard sand. At the ${\sigma}_{28}$ the strength of those materials were 56.4% and 49.0%, respectively. 2. At the ${\sigma}_7$ of 1:2 the tensile strength of the cement : briquette and (cement+lime) : briquette ash were 64.4% and 47.1%, respectively of the mortar made of standard sand. At the ${\sigma}_{28}$ the tensile strength of those materials were 69.6% and 64.8%, respectively. 3. At the ${\sigma}_7$ of 1:2 the bending strength of the cement : briquette ash and (cement+lime) : briquette ash were 46.3% and 65.9%, respectively of the mortar made of the standard sand. At the ${\sigma}_{28}$ the strength of those materials were 89.9% and 96.7%, respectively. 4. The increment of strength per $1^{\circ}C$ increase of curing temperature were on the average $0.92{\sim}1.75kg/cm^2$ of compressive strength, $0.12{\sim}0.16kg/cm^2$ of the tensile strength and $0.21{\sim}0.38kg/cm^2$ of the bending strength.

• Polymer(Korea)
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• v.28 no.1
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• pp.77-85
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• 2004

It has been widely used ultra high molecular weight polyethylene (UHMWPE) for the biomaterials due to its excellent mechanical properties and biocompatibility. In the case of blend of UHMPE with another polymeric biomaterials, however, UHMWPE might have low blend compatibility due to surface inertness. In this study, in order to improve the mechanical properties of poly(methyl methacrylate) (PMMA) bone cement by means of the impregnation of UHMWPE powder, we developed the novel surface modification method by the mixture of methyl methacrylate (MMA) and xylene. We investigated the variation of composition of MMA/xylene. It was confirmed by the analysis of Fourier transform infrared-attenuated total reflectance, scanning electron microscope, universal transverse mercator, and digital thermometer. The maximum mechanical strength of surface modified UHMWPE powder impregnated PMMA bone cement compound was observed the ratio of 1 : 1 (v/v％) MMA/xylene. Also its curing temperature decreased from 103 $^{\circ}C$ to 58 ∼ 73 $^{\circ}C$ The mechanism of surface modification of UHMWPE powder by the mixture of MMA/xylene has been proposed.

• Journal of the Korean Wood Science and Technology
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• v.42 no.1
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• pp.49-57
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• 2014

The pre-air-drying of Korean pine before the high-temperature and low-humidity drying was shown to be effective in uniform moisture content distribution and prevention of surface check. Our results suggest that initial moisture content of the timber also plays important role in high-temperature and low-humidity drying method. The pre-air-drying also helps in the reduction of surface checks in Korean pine when compared to the Korean pine dried by only high-temperature and low-humidity. End-coating was not effective in the prevention of twist, shrinkage, case hardening and internal checks. The pre-air-drying reduces the internal tension stresses which occur during high-temperature and low-humidity drying thus decreasing case hardening and also preventing internal checks. The pre-air-drying decreases the moisture content and causes shrinkage which leads to increased twist in the Korean pine.