• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.437-446
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• 2006

Open-steel-plate-girder(OSPG) bridges are one of the most prevalent bridge types among Korean railway bridges. They account for about 40% of all Korean railway bridges. However, the line-type bearings used for OSPG bridges generate several problems with respect to the bridges' dynamic behavior and maintenance. The replacement of the existing bearings with polyurethane disk bearings could be a possible solution to this problem. This type of disk bearing is an elastic bearing using a polyurethane disk. This study estimated the variations in the natural frequency of a bridge when disk bearings were installed and the bridge's dynamic behavior with a running locomotive and running trains. The first natural frequency of the bridge was 3% lower than that of the as-built bridge after the installation of the disk lower, respectively. Also, the second and third frequencies were 7 and 15% lower, respectively. The disk bearings increased the vertical displacement of the bridge, but the pure displacement, excluding the disk deformation, did not vary. The vertical acceleration did not increase when the disk bearing was installed, with trains running. The shear pin in the disk bearing reduced the lateral displacement and the acceleration of the bridge.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.594-605
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• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By investigating existing experiments and numerical results, it was found that flexural pinching which has no relation with shear action appears in RC members subject to axial compression force. However, members with specific arrangement and amount of re-bars, have the same energy dissipation capacity regardless of the magnitude of the axial force applied even though the shape of the cyclic curve varies due to the effect of the axial force. This indicates that concrete as a brittle material does not significantly contribute to the energy dissipation capacity though its effect on the behavior increases as the axial force increases, and that energy dissipation occurs primarily by re-bars. Therefore, the energy dissipation capacity of flexure-dominated member can be calculated by the analysis on the cross-section subject to pure bending, regardless of the actual compressive force applied. Based on the findings, a practical method and the related design equations for estimating energy dissipation capacity and damping modification factor was developed, and their validity was verified by the comparisons with existing experiments. The proposed method can be conveniently used in design practice because it accurately estimates energy dissipation capacity with general design parameters.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.49-57
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• 2007

Au-Sn solder alloy were deposited in multilayer and co-sputtered film by rf-magnetron sputter and the composition control and analysis were studied. For the alloy deposition condition, each components of Au or Sn were deposited separately. On the basis of pure Sn and Au deposition, the deposition condition for Au-Sn solder alloy were set up. As variables, the substrate temperature, the rf-power, and the thickness ratio were used for the optimum composition. For multilayer solder alloy, the roughness and the composition of solder alloy were controlled more accurately at the higher substrate temperature. In contrast, for co-sputtered solder, the substrate temperature influenced little to the composition, but the composition could be controlled easily by rf-power. In addition, the co-sputtered solder film mostly consisted of intermetallic compound, which formed during deposition. The compound were confirmed by XRD. Without flux during bonding of solder alloy film on leadframe, the adhesion strength were measured. The maximum shear stress was $330(N/mm^2)$ for multilayer solder with Au 10wt% and $460(N/mm^2)$ for co-sputtered solder with Au 5wt%.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.46-49
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• 2003

Cu have been widely used as signal transmission materials for electrical electronic components owing to its high electrical conductivity. However, it's size have been limited to small ones due to its poor mechanical properties, Until now, strengthening of the copper at toy was obtained either by the solid solution and precipitation hardening by adding alloy elements or the work hardening by deformation process. Adding the at toy elements lead to reduction of electrical conductivity. In this aspect, if carbon nanofiber is used as reinforcement which have outstanding mechanical strength and electric conductivity, it is possible to develope Cu matrix nanocomposite having almost no loss of electric conductivity. It is expected to be innovative in electric conduct ing material market. The unidirectional alignment of carbon nanofiber is the most challenging task developing the copper matrix composites of high strength and electric conductivity In this study, the unidirectional alignment of carbon nanofibers which is used reinforced material are controlled by drawing process in order to manufacture the intermediary materials for the carbon nanofiber reinforced Cu matrix nanocomposite and align mechanism as well as optimized drawing process parameters are verified via experiments and numerical analysis. The materials used in this study were pure copper and the nanofibers of 150nm in diameter and of $10~20\mu\textrm{m}$ In length. The materials have been tested and the tensile strength was 75MPa with the elongation of 44% for the copper it is assumed that carbon nanofiber behave like porous elasto-plastic materials. Compaction test was conducted to obtain constitutive properties of carbon nanofiber. Optimal parameter for drawing process was obtained by experiments and numerical analysis considering the various drawing angles, reduction areas, friction coefficient, etc Lower reduction areas provides the less rupture of cu tube is not iced during the drawing process. Optimal die angle was between 5 degree and 12 degree. Relative density of carbon nanofiber embedded in the copper tube is higher as drawing diameter decrease and compressive residual stress is occurred in the copper tube. Carbon nanofibers are moved to the reverse drawing direct ion via shear force caused by deformation of the copper tube and alined to the drawing direction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.347-354
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• 2012

In this study, the equations of torsional and warping constants of a I-shaped plate girder with sine corrugated web are suggested. Because of geometric characteristics of the section, a I-shaped plate girder with corrugated web shows high out-of-plane stiffness, shear strength, and torsional stiffness. Torsional constant and warping constant definitely affect lateral-torsional buckling loads. Therefore, exact estimation of the sectional properties is quite important. But, it is difficult to estimate these properties by former methods. So, this study was focused on suggestion of the rational equations to calculate torsional and warping constants. In order to investigate the effects of geometric characteristics of sine-corrugated webs on torsional stiffness and warping torsional constant, finite element analyses for pure torsional behavior and warping torsional behavior of I-shaped plate girders were performed. By regression analyses of the analytical results, rational equations of the torsional constant and warping constant were suggested. Suggested equations for the properties were validated based on the analytical results of lateral-torsional buckling of simply supported I-shaped plate girder. By suggested equations, torsional and warping constants of I-shaped plate girders with a sine-corrugated web can be rationally estimated and more exact lateral-torsional buckling load can be simply calculated.

• Food Science of Animal Resources
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• v.31 no.6
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• pp.807-816
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• 2011

The present study evaluated the difference in objective and subjective meat quality properties among the pure-breed boars of Duroc, Berkshire and Yorkshire. Ten longissimus lumborum (LD) muscles were collected from each breed after 24 h slaughtering. The breed type showed a significant effect on intramuscular fat content, moisture (p<0.01), pH, sarcoplasmic protein solubility and color (p<0.05), whereas cooking loss and Warner Blazer shear force (WBsf) did not differ among the breeds. The Yorkshire breed showed significant (p<0.05) lower sarcoplasmic protein solubility, pH and CIE $a^*$ value when compared with other breeds. The sensory panels identified Duroc as having greater overall acceptability and higher rating values than other breeds. The oleic acid content was significantly lower in the Berkshire (29.85 %) than in the Duroc (40.19 %) and Yorkshire breeds (38.18 %, p<0.05). The Yorkshire breed showed the most desirable ratio of polyunsaturated and saturated fatty acids (0.31) than the Berkshire (0.16) and Duroc breeds (0.15, p<0.05). 40 volatile compounds have been identified and quantified, while aldehydes were the most abundant among flavor substances. Aldehydes were negatively correlated with oleic acid content (p<0.05). Current data indicated that each breed had their own merits and deficiencies in terms of meat qualityThe Yorkshire breed showed a greater number of weak points. Furthermore, this study indicated that individual fat-driven flavor components were greatly influenced by fatty acid composition. The polyunsaturated fatty acids did not show any negative effects on meat flavor if cooked meats were consumed soon after cooking.

• KSBB Journal
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• v.22 no.2
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• pp.91-96
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• 2007

The saccharogenic liquid (SFW) obtained by the enzymatic saccharification of food wastes was used as a medium for production of bacterial cellulose (BC). The enzymatic saccharification of food wastes was carried out by the cultivation supernatant of Tricoderma inhamatum KSJ1 culture. Acetobacter xylinum KJ1 was employed for the BC production culture. Under the scaled-up aeration condition of 1.0 vvm, 5.64 g/L of BC was produced in 3 days cultivation in 50 L air circulation bioreactor using SFW medium with addition of 0.4% agar. The productivity was similar to that of 10 L air circulation bioreactor (5.84 g/L). This cultivation method with 50 L air circulation bioreactor decreasing shear stress and increasing oxygen transfer coefficient ($k_La$) was very useful in BC mass production. The physical properties, such as morphology, molecular weight, crystallinity, and tensile strength of BC produced by the static culture (A), the air circulation culture using 10 L bioreactor (B) and 50 L bioreactor (C) were investigated. The number average molecular weight of BCs produced under the different culture conditions (A-C) showed 2,578,000, 1,975,000, and 1,809,000, respectively. Tensile strength was 1.72 $kg/mm^2$, 1.19 $kg/mm^2$, and 1.18 $kg/mm^2$, respectively. All of the BCs had a form of cellulose I representing pure cellulose. The relative degree of crystallinity showed the range of 86.2$\sim$87.8%. BC production by the air circulation culture mode brought more favorable results in terms of the physical properties and its ease of scale-up. Therefore, it is expected that the new BC production method, the air circulation culture using SFW, would contribute greatly to BC-related manufacturing.

• Journal of the Korea Institute of Building Construction
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• v.19 no.2
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• pp.113-121
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• 2019

Single walled carbon nanotube (SWCNT) has been used as a material for reinforcing various advanced materials because it has superior mechanical properties. However, pure SWCNT that does not have any functional group has a hydrophobic character, and exists as bundles due to the strong Van der Waals attraction between each SWCNT. Due to these reasons, it is very difficult to disperse SWCNTs in the water. In this work, in order to use SWCNT for production of cementitious composites, SWCNT was first dispersed in water to make an aqueous solution. Sodium deoxycholate (DOC) and Sodium dodecyl sulfate (SDS) were chosen as surfactants, and the dosage of DOC and SDS were 2wt% and 1wt%, respectively. Sonication and ultracentrifugation were applied to separate each SWCNT and impurities. Using such processed SWCNT solutions, cement paste was prepared and its shear stress vs. strain rate relationship was studied. The yield stress and plastic viscosity of cement paste were obtained using Bingham model. According to the results in this work, cement pastes made with DOC and SDS showed similar rheological behavior to that of air entrained cement paste. While cement paste made with DOC 2 wt.% SWCNT solution showed similar rheological behavior to that of plain cement paste, cement paste made with SDS 1 wt.% SWCNT solution showed different rheological behavior showing much less yield stress than plain cement paste.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.133-146
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• 2001

We report the results of structural field observation and measurement of anisotropy of magnetic susceptibility (AMS) of the diamictitic Hwanggangri Formation distributed in Chungju-Suanbo area of the Okchon Belt, Korea. The outcrops of the Hwanggangri Formation show two types of cleavage in general: slaty cleavage (SI) and crenulation cleavage (5z). 5] cleavage is, however, well observable only in the notheastem (NE) part of study area, while overwhelmed by 52 cleavage in the southwestern (5W) part, indicating stronger later deformation in 5W part of the study area. This partitioning of the study area is corroborated by both IRM and AMS parameters: NE part of the study area is characterized by higher IRM intensity, higher bulk magnetic susceptibility, higher AM5 degree, and by oblate shape of magnetic susceptibility ellipsoid. Their values become drastically lowered toward southwest, and reach to a stable minimum in the whole 5W part of the study area. In addition, degree of both metamorphism and deformation tends to increase gradually from northeast toward southwest and also from northwest toward southeast in the study area. Based on the distribution pattern of the principal axes ( $k_1, k_2, k_3$ axes) of magnetic anisotropy ellipsoids revealed in the NE part of the study area, three episodes of deformation ( $D_1, D_2, D_3$ ) are recognized: D_1$ deformation produced $S_2$ cleavage with NE-5W trend, which is caused by a strong NW-SE tlattening of a coaxial pure shear. $D_2$ deformation produced 5z cleavage characterized by a non-coaxial deformation. It was caused by a ductile or semi-ductile thrusting toward NW and concurrent sinistral shearing along $S_2$ cleavage plane. Lastly, $D_3$ deformation produced tlexural folding of all previous structures with a nearly horizontal NE fold axis. Distribution pattern of the principal axes of magnetic anisotropy ellipsoid from the SW part of the study area, on the other hand, does not show any coherency among sites or samples. We interpret that this dispersed pattern of $k_1, k_2, k_3$ axes together with lower anisotropy strength indicates that magnetic fabrics in the SW part have been disturbed either by a superposition of strong deformation/metamorphism or by a kind of reciprocal strain due to an overlapping of $D_1$ and $D_2$ or by both processes.

• The Journal of the Petrological Society of Korea
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• v.19 no.1
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• pp.31-49
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• 2010

Nearly NS-trending Fe-Ti ore bodies intermittently occur in the Hadong anorthosites, south Korea, irrespective of the rock types of the anorthosites. In order to determine their occurrence mode and deformation history, we collected the features of occurrence and geological structures in the field, petrographic features using thin sections of the principal constituent rocks, and geochemical data of ilmenites in the ore body using electron probe microanalysis. Fe-Ti ore bodies examined in this study are divided into two types: dike- and lamina-types. It is steadily supported that the dike-type has intruded into the anorthositic rocks after their emplacement and solidification. And the laminar-type is probably a result of the mylonitization and transposition of the dike-type ore bodies parallel to the shear planes, due to later strong dextral ductile shearing. In the meantime, the Fe-Ti ore bodies have experienced the stronger dextral shearing in the more northern part of the study area, i.e. Cheongryong-ri, Wolhoeng-ri, Jonghwa-ri, and Jayangri and Baekun-ri in ascending order of its strength, together with the less content of $TiO_2$. All ilmenites of the ore bodies have very similar chemical composition, as pure ilmenite of 52~55 wt.% in $TiO_2$ content, irrespective of the occurrence mode and degree of later ductile shearing of the ore bodies. And they didn't experience to exsolve into magnetite. The structural data indicate that the Hadong anorthosites have deformed by NNE-trending folding, intrusion of the Fe-Ti ore bodies, NNW~NNE-trending dextral ductile shearing, NW~NNW-trending sinistral semi-brittle shearing, and intrusion of NNE~NE-trending mafic dykes in descending order of chronology after the formation of foliation of the anorthositic rocks. The foliation is interpreted as a result of the accumulation of crystals that settle out from the magma by the action of gravity.