• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.95-98
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• 2001

Co-cured joining method is an efficient joining technique because both curing and bonding processes for the composite structures can be achieved simultaneously. It requires neither an adhesive nor a surface treatment of the composite adherend because the excess resin, which is extracted from composite materials during consolidation, accomplishes the co-cured joining process. In this paper, we considered three bond parameters, affecting tensile load bearing capacity of the co-cured single and double lap joints. Filially, we nave presented optimal bonding conditions for co-cured single and double lap joints with steel and composite adherends under tensile loads.

• Journal of the Korean Applied Science and Technology
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• v.14 no.1
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• pp.61-76
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• 1997

Triacylglycerols of the seeds of Ginkgo biloba have been resolved by high-performace liquid chromatography(HPLC} in the silver-ion and reverse-phase modes. The fatty acids were identified by a combination of capillary gas chromatography and gas-chromatography /mass spectrometry as the methyl and /or picolinyl ester. The main components are $C_{18:2{\omega}6}$(39.0mol%), $C_{18:1{\omega}7}$(asclepic acid 21.5mol%), and $C_{18:1{\omega}9}$(oleic acid, 13.8mol%). Considerable amounts of unusual acid such as $C_{20:3{\Delta}^{5,11,14}$ (5.7mol%), $C_{18:2{\Delta}^{5,9}$(2.8mol%), and $C_{18:3}{\Delta}^{5,9,12}$(1.6mol%), were checked. In addition, an anteiso-branched fatty acid, 14-methylhexadecanoic acid, was also present as a minor component(0.9 mol%). The triacylglycerols were separated into 17 fractions by reverse-phase HPLC, and the fractionation was achieved according to the partition numnber(PN) in which a ${\Delta}^5$-non methylene interrupted double bond($^5$-NMDB) showed different behaviour from a methylene interrupted double bond in a molecule with a given cahinlength. Silver-ion HPLC exhibited excellent resolution in which fractions(23 fractions) were resolved on the basis of the number and configuration of double bonds. In this instance, the strength of interaction of a ${\Delta}^5$-NMDB system with silver ions seemed to be weaker than a methylene interrupted double bond system. The principal triacylglycerol species are as follows ; $(C_{18:2{\omega}6)2}/C_{18:1{\omega}7}$, $C_{18:1{\omega}9}/C_{18:1{\omega}7}/C_{18:2{\omega}6}$, $(C_{18:1{\omega}7)2}/C_{18:2{\omega}6}$, $C_{16:1{\omega}7}/C_{18:1{\omega}9}/C_{20:3}{\Delta}^{5,11,14}$, $C_{16:1{\omega}7}/C_{18:1{\omega}7}/C_{20:3}{\Delta}^{5,11,14}$, $C_{18:1{\omega}9}/C_{18:1{\omega}7}/C_{18:2{\omega}6}$, $C_{18:1{\omega}9}/C_{18:2}{\Delta}^{5,5}/C_{20:3}{\Delta}^{5,11,14}$, $(C_{18:1{\omega}7)2}/C_{18:2{\omega}6}$ and $(C_{18:1{\omega}9)2}/C_{18:2{\omega}6}$, while simple triacylglycerols without $C_{18:2{\omega}6})_3$ were not present. Stereospecific analysis showed that fatty acids with ${\Delta}^5$-NMDB system and saturated chains were predominantly located at the site of sn-3 carbon of glycerol backbones. It is evident that there is asymmetry in the distribution of fatty acids in the TG molecules of Ginkgo nut oils.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.3
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• pp.153-158
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• 2020

In this study, a numerical approach for evaluating the resisting capacity of a partial concrete-filled steel tube (CFST) column is introduced. By strengthening the plastic hinge part of a traditional reinforced concrete column with a steel tube, a partial CFST shows a similar bending moment capacity as that of a full CFST column but with reduced material cost. To conduct an elaborate numerical analysis of a partial CFST column, an improved bond-slip model is applied to a finite element (FE) model at the interface between the steel tube and in-filled concrete. This numerical model is verified through the results of a double curvature bending-compression test. A parametric study with the proposed numerical model is used to obtain the load moment interaction diagrams for evaluating the resisting capacity based on various dimensions. Finally, the required strengthening length is estimated for each degree of thickness of the steel tube, and the failure mechanism of the partial CFST column based on the dimensions of the steel tube are identified.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.9
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• pp.1120-1127
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• 2007

This study was designed to examine the effects of n-6 PUFA rich corn oil, n-3 PUFA rich perilla oil and their conjugated double bond derivatives on serum lipids status in rats. Experimental diets containing lard (control), corn oil (CO), perilla oil (PO), conjugated double bond derivatives of n-6 PUFA rich corn oil (TCO) and n-3 PUFA rich perilla oil (TPO) at the level of 10% (w/w) were fed to male Sprague Dawley rats for 4 weeks. TCO was found to have three derivatives of linoleic acid and TPO had five derivatives of linolenic acid by GC. Serum total cholesterol levels were significantly lower in the all experimental groups than in the control group, and particularly, the lowest in TCO and TPO groups. HDL-cholesterol concentrations were a little higher in the all experimental groups than in the control group, and TCO and TPO groups were not significantly different from CO and PO groups. Serum LDL, LDL-cholesterol, chylomicron and triglyceride concentrations were significantly lower in the all experimental groups than in the control group, remarkably lower in TCO group and particularly, the lowest in the TPO group. Serum free cholesterol and cholesteryl ester concentrations were lower in TCO and TPO groups than in CO and PO groups. From the above research, TCO and TPO groups were effective on the improvement of the lipid compositions in serum and particularly, TPO group was the most effective on the improvement of serum lipids.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.37-43
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• 2008

The research attempted to develop an eco-friendly wood adhesive based on vegetable oil (soybean oil), the renewable and sustainable natural resources, using ozonification technology for the chemical structure modification. The soybean oils (SBO) were reacted with $O_3$ at the rate of 7.13 g/h for different times, 15 minutes, 30 minutes, 60 minutes, and 120 minutes. Modified chemical structure of the ozonized SBOs were examined by Fourier transform Infrared (FT-IR) spectrum. The FT-IR spectrum of SBO had an absorbance peak at $3010cm^{-1}$ that is the characteristic peak of the unsaturated double bonds. As ozone treatment time increased, the peak of the double bond was disappeared and aldehyde or carboxyl peak appeared at $1700cm^{-1}$. The dry, wet, and cyclic boiling bond strengths of the ozonized SBO mixed with polymeric diphenylmethane-4, 4-diisocyanate (pMDI) were also investigated. In the dry shear test, all strengths met constantly the standard requirement of $7.0kgf/cm^2$ (KS F3101 2006). The bond strengths gradually increased with increasing ozone treatment time. The highest strength showed at 60 minutes ozone treatment and decreased values at 120 minutes. In the cyclic boiling shear test, 30, 60 and 120 minutes exceeded the standard requirement.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.3-15
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• 1992

Electronic structures and reactivities of the chromium, molybdenum, and tungsten carbene complexes, $(CO)_5Cr=CCHCH_2(XCH_3)\;,\;(CO)_5Mo=CCHCH_2(XCH_3)\;, and\;(CO)_5W=CCHCH_2(XCH_3)$, are studied by means of Extended Huckel calculations. The origin of the M=Ccarbene double bond is clarified from the diagram of the orbital correlation with the fragment orbitals. The ${\sigma}$ bond of the M=Ccarbene double bond is formed by the electron transfer interaction from the HOMO of the carbene to the LUMO of the $(CO)_5M$. The ${\pi}$ bond is formed through the back-transfer of electrons from one of the degenerated d${\pi}$ orbitals to the LUMO of the carbene. The polarization of charge of the M=Ccarbene bond is calculated to be M=Ccarbene for Mo, and W carbenes. The chemical and physical properties of these complexes are resulted from an appreciable positive charge on the carbene carbon. The electrophilic reactivity of the carbene carbon is not charge controlled, but is controlled by the frontier orbital, LUMO.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.179-186
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• 2010

The bond between steel and concrete in reinforced concrete members is essential to resist external load, but the bond mechanism in reinforced concrete beams deteriorated by steel corrosion has not been clearly known yet. Most existing researches have dealt with the bond behavior of corroded steel under monotonic loading, but scarce are researches dealing with bond behavior of corroded steel under repeated loading. This study includes the experimental investigation on the bond behavior with respect to the various degrees of steel corrosion under repeated loading. According to the test results, the bond strength of corroded steel under monotonic loading increases as the rate of steel corrosion increases unless the splitting crack occurs. The slip versus number of load cycles relation was found to be approximately linear in double logarithmic scale, not only in specimens without steel corrosion but also in specimens with steel corrosion. The test results also show that the steel corrosion does not negatively affect the bond strength of corroded steel after repeated loading unless the splitting crack occurs. But the fatigue life decreases sharply after splitting crack occurs. This research will be helpful for the realistic durability design and condition assessment of reinforced concrete structures.

• Structural Engineering and Mechanics
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• v.81 no.3
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• pp.305-316
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• 2022

Externally bonded ultrahigh performance fiber-reinforced concrete (UHPFRC) is commonly used as a strengthening material for reinforced concrete (RC) structures. This study reports the results of an experimental program investigating the bonding behavior between concrete and prefabricated UHPFRC plates. The overall experimental program is consisting of five RC specimens, which are strengthened using the different lengths and widths of prefabricated UHPFRC plates. These specimens were analyzed using the pull-pull double-shear test. The performance of each strengthened specimen is presented, discussed and compared in terms of failure mode, maximum load, load-slip relationship, fracture energy and strain distribution. Specimen C-25-160-300 which bonded along the whole width of 160 mm recorded the highest maximum load (109.2 kN) among all the analysed specimens. Moreover, a 3D numerical finite element model (FEM) is proposed to simulate the bond behavior between concrete and UHPFRC plates. Moreover, this study reviews the analytical models that can predict the relationship between the maximum bond stress and slip for strengthened concrete elements. The proposed FEM is verified against the experimental program and then used to test 36 RC specimens strengthened with prefabricated UHPFRC plates with different concrete grades and UHPFRC plate widths. The obtained results together with the review of analytical models helped in the formation of a design equation for estimating the bond stress between concrete and prefabricated UHPFRC plates.

• Magazine of the Korea Concrete Institute
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• v.3 no.4
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• pp.97-106
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• 1991

The object of this study is to propose the Flexural moment-curvature relationship based on the bond property between concrete and steel for noncracking zone, to evaluate the flexural displacement of reinforced concrete member. The bond-slip relationship and the strain hardening effect of steel were taken into consideration in order to evaluate the spacing of the cracks and the curvature distribution. Calculated curvature distribution along the longitudinal axis was transformed into equivalent curvature distribution. The flexural displacement was calculated by means of double integrals of the equivalent curvature. Furthermore, 34 beams were tested in order to verify the proposed procedure Calculated values agreed well with the experimental data, and so it is pointed out that proposed method is widely acceptable for the practical evaluation of flexural displacement of reinforced concrete member.

• Progress in Superconductivity
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• v.4 no.2
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• pp.148-152
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• 2003

We have observed the temperature dependences of Bi $L_{III}$ edge spectra by extended X-ray absorption spectroscopy for a high quality single crystal and a powder of the $Ba_{0.6}K_{0.4}BiO_3$ superconductor. $Ba_{0.6}K_{0.4}BiO_3$ has the cubic structure and metallic states. The deformation of the $BiO_{6}$ octahedra, which is due to the anomalies of the Bi-O and Bi-Ba bond length, was showed by the double-shell fit. It was clearly found that these anomalies are owing to the difference in the strength of Bi-O bonds. The temperature dependences of both bond lengths and the Debye-Walter factor ${\sigma}^2$ of the Bi-O and Bi-(Ba,K) bond are discussed to illustrate local structural features of the $Ba_{0.6}K_{0.4}BiO_3$