• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.465-472
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• 2003

Creep Poisson's ratio reported by previous experimental studies on multiaxial creep of concrete was controversial. The Poisson's ratio is very sensitive to small experimental error that is inevitably induced, and the sensitivity may cause the controversy. It is difficulty to find out the properties on multiaxial creep of concrete. Therefore, a new approach method to analyze the test results is needed to precisely understand the properties on multiaxial creep of concrete. In this study, microplane model is used as a new approach method in analyzing the multiaxial creep test data. The six data sets extracted from the literature are fitted from regression analysis. Double-power law as a model representing volumetric and deviatoric creep evolutions on microplane is used, and six parameters in volumetric and deviatoric compliances are determined on the assumption that the volumetric and deviatoric creep strains are linearly proportional to corresponding stresses. The optimum fits give very accurate description of the test data. The Poisson's ratio calculated from the optimum fits varies with time and does not depends on the stress states, namely, uniaxial, biaxial, and triaxial stress states. Regression analysis is also performed on the assumption that the Poisson's ratio remains constant with titre. The constant Poisson's ratio can be use in practice without serious error.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.43-46
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• 1989

Epoxy, noticed as a new insulation material for electrical equipments, may become an excellent cured material from the crosslink reaction with some curing agents and accelerators. The characteristics of cured epoxy is determined by the method of lattice formation according to curing method. The purpose of this paper, varing the process of lattice formation by various surrounding temperatures and heating time during the curing process, is to obtain the optimum cured condition for electrical insulation from the results of investigation on the physical and dielectric properties of cured epoxy. In this investigation, it is found that the excessive temperature and heating time brings on the growth of metamorphic methyl and the insulating properties of cured epoxy is decreased by this phenomenon. As a result, it is concluded that the optimum dielectric characteristics can be obtained when cured at a curing temperature at 14$0^{\circ}C$ for one hour.

• Advances in concrete construction
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• 제5권2호
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• pp.145-154
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• 2017

In the present day scenario, concrete construction is rapidly becoming uneconomical and non sustainable practice, due to the scarcity of raw materials and environmental pollution caused by the manufacturing of cement. In this study an attempt has been made to propose recycled aggregates from demolition wastes as coarse aggregate in geopolymer concrete (GPC). Experimental investigations have been conducted to find optimum percentage of recycled aggregates (RA) in GPC by replacing 20%, 30%, 40%, 50% and 60% of coarse aggregates by RA to produce recycled aggregate geopolymer concrete (RGPC). From the study it has been found that the optimum replacement percentage of recycled aggregates was 40% based on mechanical properties and workability. In order to study and compare the flexural behaviour of RGPC and GPC four beams of size $175mm{\times}150mm{\times}1200mm$ were prepared and tested under two point loading. Test results were evaluated with respect to first crack load, ultimate load, load-deflection characteristics, ductility and energy absorption characteristics. Form the experimental study it can be concluded that the addition of recycled aggregate in GPC causes slight reduction in its strength and ductility. Since the percentage reduction in strength and behaviour of RGPC is meager compared to GPC it can be recommended as a sustainable and environment friendly construction material.

• 한국CDE학회논문집
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• 제21권2호
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• pp.177-185
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• 2016

In this paper, an optimal planning system for operating transporters in shipyard is developed. The system is designed to utilize the geometries of shipyard, and manage the data of blocks and transporters directly. There are four major menus such as shipyard map management based on GIS, block transportation request, transporter management, and optimal transportation planning in the system. The geometries and properties of the shops, roads, and addresses are manipulated in the shipyard map management menu. The block transportation requests and the properties of transporters are managed in the block transportation request and transporter management menus, respectively. The optimum transportation is planned automatically for minimizing the unload times of the transporters, and the optimum transportation plans are confirmed and printed to the transporter drivers. The effectiveness of the system was verified through the application to a large-sized shipyard.

• 한국도로학회논문집
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• 제16권6호
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• pp.19-25
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• 2014

PURPOSES : This study was performed to evaluate the possibility of Indirect Tensile Strength (ITS) as a testing method that can predict cracking on pavement. METHODS : Three asphalt binders and one kind of aggregate were used in this study, and all asphalt mixtures were produced using Gyratory Compactor followed asphalt mix design. The ITS test was performed for the mixture which are artificially short-term aged using the oven. The ITS properties were analyzed by air void, compaction temperature, asphalt content, and asphalt binder. RESULTS : The results of this study indicated that (1) the compaction temperature did not show relationship with the ITS test; (2) there was no specific trend between the asphalt content and the ITS test; (3) the ITS could reveal the property of kinds of asphalt binders; (4) the asphalt mixture that were produced at optimum temperature suggested by manufacturer did not exhibit optimum result for all asphalt binder. CONCLUSIONS : The possibility of ITS was confirmed from this study for replacement of the Marshall Stability method. However, it needs to perform in further studies of aggregate and compaction property to suggest a new ITS standard value.

• Journal of Welding and Joining
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• 제13권3호
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• pp.147-156
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• 1995

The change of microstructure in the bonded interlayer and tensile properties of joints were studied for liquid phase diffusion bonding using STS-310 and Incoloy-825 as base metal and base metal+B alloy as insert inetal. Main experimental results obtained in this study are as follows. 1) The optimum amount of B addition into the insert metal was found to be about 4mass%. 2) When isothermal solidification was completed, the microstructure in the bonded interlayer was the same with that of the base metal because of the grain boundary migration in the bonded interlayer. 3) All of the tensile specimen fractured at base metal and joints bonded at optimum condition exhibited tensile properties in excess of base metal requirements. 4) It was determined that fine car-borides and bordes such as M$_{23}$(C,B)$_{6}$, Cr$_{2}$B, and CrB in STS-310S and TiB in Incoloy-825 exist at the grain boundary around bonded interlayer. These precipitates almost disappeared after homogenizing treatment at 1373K for 86.4ks.s.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.541-548
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• 2001

The interest in the dynamic properties of soils has increased strongly because of earthquake, heavy traffic, and foundations undergo high amplitude of vibrations. Most of soils in Korean peninsula are composed of granite soils, especially the decomposed mudstone soils are widely spread in Pohang areas, Kyong-buk province. Therefore, it Is very important to investigate the dynamic properties of these types of soils. The most important soil parameters under dynamic loadings are shear modulus and material dampings. Furthermore, few definitive data exist that can evaluate the behavior of unsaturated decomposed mudstone soils under dynamic loading conditions. The investigations described in this paper is designed to identify the shear modulus and damping ratio due to a surface tension for the unsaturated decomposed mudstone soils ulder low and high strain amplitude, For this purpose, the resonant column test and the cyclic triaxial test were performed. Test results and data have shown that the optimum degree of saturation under low and strain amplitude is 32 ∼ 37% which is higher than that of decomposed granite due to the amount of fine particles as well as the type and proportion of chief rock-forming minerals.

• 한국의류산업학회지
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• 제8권6호
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• pp.702-708
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• 2006

The purpose of this study was to investigate the dyeing-property and antibacterial activity on nylon fabric dyed with cochineal at variable dyeing conditions. Al, Cr, Fe, Cu and Sn were used as mordants and adsorption was compared with different mordanting methods. The maximum UV-visible absorption band of cochineal extract was 495 nm. The dyeability on nylon fabric was good because of having a amine group. The optimum dyeing conditions of nylon fabrics are dyeing concentration 1.5%(o.w.s), dyeing temperature $60^{\circ}C$, pH 3 and dyeing time 30 minutes. The pre-mordanting method is preferred for Al and Cr, and the post-mordanting one is preferred for Cu, Sn and Fe to achieve better dyeing. The optimum mordanting conditions of wool fabrics dyed with cochineal are mordanting concentration of 0.5%(o.w.s), mordanting temperature $60^{\circ}C$, and dyeing time 30 minutes. Nylon fabrics dyed with cochineal show a little antibacterial activity, but it was increased by Sn mordanting. MIC test results in antibacterial activities revealed that the antibacterial activity of Cu was the highest among mordants, but Sn mordant was the most effective in antibacterial activities after mordanting treatment of nylon fabric. The fastness properties of dyed nylon fabric showd a little worse or a similar level and there was no significant difference between a mordanted and non-mordanted fabric.

• 한국재료학회지
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• 제9권2호
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• pp.163-167
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• 1999

LiNbO$_3$films were prepared by an rf-magnetron sputtering technique using sintered target containing potassium. The potassium was included to help to fabricate stoichiometric LiNbO$_3$film. Structural and electrical properties of thin films was investigated as a function of deposition condition. Optimum sputtering conditions were rf power of 100W, working pressure of 1m Torr and substrate temperature of 58$0^{\circ}C$. The thin film was grown to (012) preferred orientation. The dielectric constant of the thin film LiNbo$_3$ fabricated under optimum condition was 55 at 1MHz. Average grain size is about 200$\AA$ and roughness of the film is small enough to apply to optic devices.

• Preventive Nutrition and Food Science
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• 제2권1호
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• pp.71-76
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• 1997

Pullulanase was produced from the Klebisella pneumonias NFB_320 with the conmposition of 0.1% pullualn 1.5% yeast extract, 0.2% $K_2$HPO$_4$ and 0.02% MgSO$_4$.7$H_2O$(pH5.5). The optimum temperature for activity of the pulluanase was 3$0^{\circ}C$ and the highest yield of the enzyme was obtained after cell growth at 3$0^{\circ}C$ for 18hr, and maintained until 24hr cultivation. The pullulanase was successively purified 52.6 folds with 7.8% yield by acetone precipitation. DEAE-cellulose column chromatography and gel fitrations. The purified enzyme hydrolyzed pullulan into maltotriose exclusively. Chemical and physical properties of purified pullulanase from Klebisella pneumonias NFB-320 were examined. The optimum pH and temperature for enzyme activity were 5.0 and 6$0^{\circ}C$, respectively. The enzyme was stable between pH4 and 7, and up 5$0^{\circ}C$. The effect of mo-dification on the rate of enzyme reaction was studies with various chemicals and metal ions. The enzyme has been found to be inactivated by I$_2$ and N-bromosussinimide(NBS), which probably indicated the involve- ment of tryptophan residues in the active center of the enzyme.