• Journal of Welding and Joining
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• v.22 no.5
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• pp.26-31
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• 2004

In order to propose the optimum welding condition for field application, the effects of welding heat input and cooling rate at PWHT on the mechanical properties were investigated. Submerged arc welding of 1.25Cr-0.5Mo steel for pressure vessel was conducted at welding heat inputs of 15.2kJ/cm, 30.9kJ/cm, and 44.8kJ/cm, and cooling rates of 184$^{\circ}C$/hr, 55$^{\circ}C$/hr, and 2$0^{\circ}C$/hr at PWHT. From the test results, as the welding heat input increase up to 30.9kJ/cm, the changes of microstructure and impact toughness were small. At the heat input of 44.8kJ/cm, however, toughness decreased obviously due to the coarsening of coarse-grained HAZ and formation of ferrite at bainite grainboundary of weld metal. On the other hand, cooling rates at PWHT did not effect on the changes in microstructure and mechanical properties. Even though tensile strength and impact toughness at all welding conditions of this study were above the minimum specification requirement, it was confirmed that heat input of 30.9kJ/cm was the optimum welding condition to improve welding performance by higher heat input.

• Journal of the Korean Vacuum Society
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• v.10 no.4
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• pp.440-448
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• 2001

The operation properties of DBD plasma reactors were observed by using 20 kV square pulse at the cylindrical and planar type of reactors in the condition of air pressure. The optimum operation frequency $f_0$ which optimizes the efficiency of operation was found as such $f_0\proptoexp(-C)$ when the current-voltage curve and charge-voltage curve were observed. Using these properties the dissipated power was evaluated. The dissipated power at the optimum frequency of operation was varied as the value of capacitance which is dependent on the structure and the dielectric material of the reactor, and had the maximum value at the specific value of capacitance. With these value of capacitance, DBD reactors which has a high level of efficiency can be formed.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.847-854
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• 2004

The resistivity of soils depends on grains size, porosity, water saturation, pore fluid resistivity, caly contents and son on. It is very important to understand the relationship between resistivity and such physical properties of soils, in order to interpret and evaluate ground conditions by using resistivity data obtained from electrical resistivity prospecting. In this paper, to study the relationship between resistivity and physical properties of soils, the resistivity of glass beads and compacted soil samples both in saturated and unsaturated conditions is measured. As the results, the resistivity of saturated soils depends mainly on porosity and clay contents, while that of unsaturated soils is sensitive to compaction conditions, and decreases with increasing water content until the optimum water condition, that is the maximum dry density. But, the relationship between resistivity and water saturation for soils is unique, being independent of compaction energy. Also, the resistivity ratio decrease with increasing water saturation, followed by no significant change of resistivity ratio over 80 percent of water saturation (the optimum water content).

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.603-608
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• 2006

The main purpose of the present study has been placed on investigating the mechanical properties and microstructures of C-Si-Mn-V steels for cold forming manufactured by controlled rolling and cooling technology. The steels were manufactured in electric arc furnace (EAF) and casted to $160{\times}160mm$ billet. The billets were reheated in walking beam furnace and rolled to coil, the stocks were rolled by Controlled Rolling and Cooling Technology (CRCT), so rolled at low temperature by water spraying applied in rolling stage and acceleratly cooled before coiling. Rolled coils were cold drawed to the degree of 16%, 27% of area reduction respectively without heat treatment. Microstructual observation, tensile test, compression test and charpy impact tests were conducted. The mechanical properties of the steels were changed by area reduction of cold drawing and it is founded that there are optimum level of cold drawing to minimize compression stress for these steels. From the result of this study, it is conformed that $80kg_{f}/mm^{2},\;90kg_{f}/mm^{2}$ grade high strength microalloyed steel for cold forming are developed by accelerated cooling and optimum cold drawing.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.3_4
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• pp.444-451
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• 2004

This study was carried out to investigate the chemical and dyeing properties of Petasites japonicus leaf extract under the various extracting and dyeing conditions such as temperature, time, the ratio of water and pH, repetition of dyeing in silk and cotton fabrics with Petasites japonicus leaf. The results were as follows: 1. It was found that λ$_{\max}$ of color solution extracted by Petasites japonicus leaf has two peaks at 290nm and 323nm. 2. The optimum extracting conditions were studied at 10$0^{\circ}C$, 40min., pH 7 and 1 : 20(the ratio of water and Petasites japonicus leaf), the optimum dyeing temperature, dyeing time, dyeing pH and repetition of dyeing were 10$0^{\circ}C$, 60min., pH 7, repetitions of three times, respectively. 3. Silk and cotton fabrics dyed with Petasites japonicus leaf extract were colored yellowish orange. The colory Petasites japonicus leaf extract in silk and cotton fabrics were deeped by same-mordanting with aluminum potassium sufate and cupric sulfate. 4. Washing fastness of silk fabrics was 4∼5 grade, but cotton fabrics was 3∼4 grade, so washing fastness of silk fabrics washed with neutral detergent was excellent.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.1
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• pp.131-142
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• 2004

When the cotton/polyester fiber mixed fabrics were treated with ferrous sulfate and oxalic acid for burn out finishing, it was examined how the effects of process conditions as concentration of burn out agents, temperature, time and pressure act onto the properties of polyester ground fabrics. The results are as follows. The effect of burn out finishing by pressure was greated in 3 kgf/$\textrm{cm}^2$. The properties as white index and tensile strength of polyester ground fabrics were decreased according as processing concentration, temperature time increases. The shrinkage was increased according as processing concentration, temperature time increases. The optimum condition of burn out agents to ferrous sulfate was 30% concentration, 150$^{\circ}C$, 1 min, 3 kgf/$\textrm{cm}^2$ and to oxalic acid was 10% concentration, 110$^{\circ}C$, 1min, 3 kgf/$\textrm{cm}^2$. And the optimum of ferrous sulfate and oxalic acid used in combination was 10% ferrous sulfate and 7% oxalic acid, 110$^{\circ}C$, 1 min., 3 kgf/$\textrm{cm}^2$.

• Journal of the Korean Society of Clothing and Textiles
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• v.36 no.7
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• pp.703-713
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• 2012

This study analyzed the physical properties and flame retardancy of Tencel FR/Cotton complex knit fabrics in order to satisfy two aspects of eco-friendliness and functionality. The flame retardant (FR) treatment of complex knit fabrics was applied by a pad-dry-cure method for additional functionality. Tensile strength, extension, bursting strength, LOI, and flame retardancy were measured by the KS (Korean Standard) K manual. The hand value knit fabrics were measured by KES-FB system. Subsequently, tensile strength and extension of wale and tensile strength of course increased in tandem with the Tencel FR yarn content. Tencel FR/Cotton complex knit fabrics were suitable for summer-weight and for baby clothes through the KES-FB system measurements. The bursting strength of Tencel FR/Cotton complex knit fabrics decreased as the contents of the Tencel FR increased; in addition, LOI increased as the contents of Tencel FR increased. This was due to the Tencel FR flame resistance function; however, the tensile strength decreased. The optimum fiber content of Tencel FR/cotton content was 1:1. The optimum conditions of flame retardant treatment were a treatment temperature $130^{\circ}C$ and the concentration of finishing agent and assistance binder (AR4260) was 35% and 1%, respectively.

• Journal of the Korea Institute of Building Construction
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• v.2 no.3
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• pp.131-138
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• 2002

The objective of the study is to examine the characteristic correlations between reinforcing carbon fiber and interfacial adhesion agent since the interfacial adhesion strength between reinforcing carbon fiber and matrices is believed to be an essential element influencing the physical properties in carbon fiber reinforced cement composite using slurry method. The integrity of interfacial adhesion between reinforcing fiber and cement not only affects the quality of fiber reinforced cement composite but also influences to a large degree the physical properties of the cement composite when producing carbon fiber reinforced cement composite using slurry method. Having analyzed the physical properties 1.e., water content, tensile strength, flexural strength and flexural toughness of carbon fiber reinforced cement composite specimens, C-PAM(cation polyacrylamide) was determined to be an optimum interfacial adhesion agent. The study has also demonstrated that interfacial adhesion strength varies largely on the content and type of the reinforcing fiber. Judging from magnified view of the tensile shear cross-section using VMS(video microscope system), interfacial adhesion strength between reinforcing fiber and matrices is affected by the type of interfacial adhesion agent. According to the result of the experiments, C-PAM was determined to be an ideal interfacial adhesion agent when using carbon fiber in producing carbon fiber reinforced cement composite with the optimum content of carbon fiber being established.

• Fibers and Polymers
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• v.6 no.1
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• pp.13-18
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• 2005

PLA/LPCL/HPCL blend fibers composed of poly (lactic acid) (PLA), low molecular weight poly ($\varepsilon$-caprolactone) (LPCL), and high molecular weight poly ($\varepsilon$-caprolactone) (HPCL) were prepared by melt blending and spinning for bioab­sorbable filament sutures. The effects of blending time and blend composition on the X-ray diffraction patterns and tensile properties of PLA/LPCL/HPCL blend fibers were characterized by WAXD and UTM. In addition, the effect of in vitro degra­dation on the weight loss and tensile properties of the blend fibers hydrolyzed during immersion in a phosphate buffer solu­tion at pH 7.4 and 37$^{\circ}C$ for 1-8 weeks was investigated. The peak intensities of PLA/LPCL/HPCL blend fibers in X-ray diffraction patterns decreased with an increase of blending time and LPCL contents in the blend fibers. The weight loss of PLA/LPCL/HPCL blend fibers increased with an increase of blending time, LPCL contents, and hydrolysis time while the tensile strength and modulus of the blend fibers decreased. The tensile strength and modulus of the blend fibers were also found to be increased with an increase of HPCL contents in the blend fibers. The optimum conditions to prepare PLA/LPCL/HPCL blend fibers for bioabsorbable sutures are LPCL contents of $5 wt\%, HPCL contents of $35 wt\%, and blending time of 30 min. The strength retention of the PLA/LPCL/HPCL blend fiber prepared under optimum conditions was about $93.5\% even at hydrolysis time of 2 weeks.

• Polymer(Korea)
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• v.25 no.2
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• pp.233-239
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• 2001

The ethylene propylene diene terpolymer (EPDM) blends with acrylonitrile butadiene rubber (NBR) were prepared by mechanical mixing method. Mooney viscosity, cure behaviors, compression set and dynamic mechanical properties were subsequently examined. Dynamic characteristics of the entire blends determined from a Rheovibron generally showed two glass transitions (T'$_{g}$s), -43$^{\circ}C$ and -4$^{\circ}C$ for NBR and EPDM, respectively. The tan $\delta$ peak monotonically shifted toward the higher temperature with increasing NBR content. It was also found that the optimum cure time was significantly decreased with loading of NBR.