• Composites Research
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• v.19 no.4
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• pp.15-22
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• 2006

One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.

• Polymer(Korea)
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• v.28 no.5
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• pp.391-396
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• 2004

In order to overcome drawbacks in the conventional preparation of epoxy/silica nanocomposites, such as formation of micro voids and dimensional instability caused by evolution of volatile by-products during curing reaction, a novel preparation method using Si-N precursor has been proposed. When prepared through in-situ reaction of epoxy curing reaction with sol-gel reaction of Si-N precursor, methyltripiperidinylsilane (MTPS) which does not produce by-products during reaction, epoxy/silica nanocomposites of extremely even dispersion of inorganic phase could be successfully prepared, resulting in high enhancement of mechanical and thermal properties as well as outstanding transparency.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.606-613
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• 1993

This was studied about aging characteristic of AC4A/$SiC_{w}$ 10-30v/o reinforced composite. Aging hardenability was decreased $SiC_{w}$ 30% > 10% > 20%. Aging hardening of T6 treatmented composite was higher absolute value than AC4A I/M material. And this results indicated initial hardening phenomenon according to increase $SiC_{w}$ volume fraction. Reinforced effect by pressure was the same effect as before aging treatment and the best condition pressure at 75MPa. Similar to reinforced effect according to $SiC_{w}$ volume fraction was 30 % > 10 % > 20 %. In case of pressure is low, whisker is not break the same time press with base metal after wetting. After it is wetting with base metal, a part transformed or wetting part break and whisker maintain original shape or a part transformed on the otherhand, in case of pressure is high, whisker is break in same time it was not against pressure and whisker's shape is near a polygon or spherical shape.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.33-41
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• 2011

This study presents modeling technologies applicable to an unbonded post-tension system using a finite element software package. In this study, both direct modeling method and multiple spring method were used. The direct modeling method adopts tube-to-tube contact elements to represent the physical feature of a post-tension system. The multiple spring method uses virtual tendons attached to the real tendons using a number of rigid axial springs that freely rotate at the ends. Both modeling technologies provide accurate predictions. However, only the multiple spring method provides numerically stable and reliable responses with a consideration of concrete tension stiffening effects. Therefore, the multiple spring method turned out to be a generally applicable modeling technology for the unbonded post-tension system. Comparisons were made for the analytical and experimental results for the verification of the selected method, and parameter studies were carried out to confirm the appropriateness of the modeling assumptions and parameters adopted in the analysis.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.3
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• pp.510-515
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• 2001

This study was performed to evaluate the effect of mushrooms powder (Lentinus edodes, Ganoderma lucidum, Pleurotus ostreatus; 5:3:2, w/w/w) of on the lipid concentration in female Sprague-Dawley rats for 4 weeks. Experimental groups were divided into two dietary groups, the cholesterol diet (Cholesterol group) and the cholesterol diet supplemented mixed mushrooms powder (Mushroom group). The concentration of total cholesterol in serum was significantly decreased by 57.4% in mushroom group compared to cholesterol group. The concentration of HDL-cholesterol was significantly increased by 230% in mushroom group compared to cholesterol group. At the same time, atherogenic index was also significantly decreased by 68.4% in mushroom group compared to cholesterol group. The concentration of triglyceride in liver was significantly increased by 50% in mushroom group compared to cholesterol group. However, the concentrations of triglyceride and phospholipid in serum and cholesterol and phospholipid in liver had no significant difference both groups. This study suggested that mixed mushroom powders exert a cholesterole-lowering effect in hyperlipidemic female rats.

• Biomedical Science Letters
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• v.6 no.4
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• pp.253-260
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• 2000

Obesity is the risk factor of atherosclerosis and not only increases triglyceride concentration in blood but also decreases relatively the ratio of TG to HDL-Cholesterol in blood. In case of obesity, systolic blood pressure is also increased in responding the increase of TG in blood. Index of obesity in red ginseng-taking group (ginseng group) was lower as compared with non-red ginseng-taking group (control group). The TG concentration, the ratio of triglyceride to HDL-cholesterol in blood and systolic blood pressure were decreased in the subjects of ginseng group compared with that in control group. It is inferred that long-term intake of ginseng products may help to prevent the risk of atherosclerosis and obesity.

• Polymer(Korea)
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• v.28 no.2
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• pp.194-200
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• 2004

Porcine small intestine submucosa (SIS) has been widely used as a biomaterial without immunorejection responses. Crosslinked SIS sponges were characterized for the possibility of the bio-interactive wound dressings and tissue engineered scaffolds. SIS powders were dissolved in 3% acetic acid aqueous solution at 48hrs followed by pouring into mold and then fabricated by freeze-drying method. SIS sponge was prepared by crosslinked with 1-ethyl-(3-3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC) solution (deionized water: ethanol=5:95) with 1-100mM concentration for 24 hrs and Iyophilized. SIS sponges were characterized by scanning electron microscopy, differential scanning calorimeter, and Fourier transform infrared spectrometer and were tested their porosity and water absorption ability. It was observed that the concentration of EDC might be exceeded 50 mM to get good physical characteristics. In conclusion, it seems that SIS sponge could be very useful for the applications of wound healing and tissue construction.

• Journal of Adhesion and Interface
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• v.20 no.4
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• pp.146-154
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• 2019

In this study, alkoxysilane-functionalized amphiphilic polymer (AFAP), which have hydrophilic segment and hydrophobic segment functionalized by alkoxysilane group at the same backbone, was synthesized and used as a dispersant and control agent for reaction rate in the preparation of colloidally stable organic-inorganic (O-I) hybrid sols. After reaction with fluorosilane compounds, fluorinated O-I hybrid sols were prepared and coated onto glass substrate to form hydrophobic O-I hybrid coating films through low-temperature curing process. Surface hardness and hydrophobicity of cured coating films were varied with type of solvent and composition of AFAP and fluorinated alkoxysilane compounds. At appropriate solvent and composition of fluorinated alkoxysilane compounds, O-I hybrid coating film having high transparency and surface hardness could be prepared, which could be applicable to cover window of solar cell and displays.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.209-216
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• 2009

Flexible frames on their own offer little resistance to lateral forces, resulting often in large deflections and rotations at the joints. On the other hand, walls subjected to lateral loads fail mainly in shear at relatively small displacements. Therefore, when the nonductile frames and wall act together, the combined action of the composite system differs significantly from that of the frame or wall alone. The objective of the study is to evaluate seismic response of infill walls with notched midsection. Reinforcement detail of wall was main variable in the experiment. Also SHCC was used in order to prevent damage concentration into notched midsection of walls. Test results, SHCC infill walls show the multiple crack patterns as expected. However, PIW-ND specimen exhibits less story drift, stiffness and energy dissipation capacity than those of PIW-NC specimen.

• Polymer(Korea)
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• v.24 no.2
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• pp.220-227
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• 2000

Silica and carbon black filled natural rubber (NR) vulcanizates were prepared with different mixing modes and amounts of fillers. Curing characteristics, morphology. and tear properties of the NR vulcanizates were investigated. The NR vulcanizates filled with silica and carbon black sequentially showed longer induction time ($t_2$), cure index ($t_{90}$ ), and lower maximum torque ($T_{max}$ ) than the NR vulcanizates filled with them simultaneously, during curing process. The former showed superior dispersion of fillers and tear properties to the latter. The NR vulcanizates containing 30 phr of silica showed excellent properties in the experimental range.