• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.65-74
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• 2009

Glass fiber reinforced polymer (GFRP) bars are sometimes used when corrosion of conventional reinforcing steel bar is of concern. In this study, a total of 36 beams and one-way slabs reinforced using GFRP bars were tested in flexure. Four different GFRP bars of 13 mm diameter were used in the test program. In most test specimens, the GFRP bars were lap spliced at center. All beams and slabs were tested under 4-point loads so that the spliced region be subject to constant moment. Test variables were splice lengths, cover thicknesses, and bar spacings. No stirrups were used in the spliced region so that the tests result in conservative bond strengths. Average bond stresses that develop between GFRP bars and concrete were determined through nonlinear analysis of the cross-sections. An average bond stress prediction equation was derived utilizing two-variable linear regression. A splice length equation based on 5% fractile concept was then developed. As a result of this study, a rational equation with which design splice lengths of the GFRP bars can be determined, was proposed.

• Composites Research
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• v.24 no.5
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• pp.9-16
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• 2011

This paper describes the crashworthiness evaluation and performance improvement of tilting train made of sandwich composites. The applied sandwich composite of carbody structure was composed of aluminum honeycomb core and glass/epoxy & carbon/epoxy laminate composite facesheet. Crashworthiness analysis of tilting train was carried out using explicit finite element analysis code LS-DYNA 3D. The 3D finite element model and 1D equivalent model were applied to save the finite element modeling and calculation time for crash analysis. The crash conditions of tilting train were conducted according to four crash scenarios of the Korean railway safety law. It found that the crashworthiness analysis results were satisfied with the performance requirements except the crash scenario-2. In order to meet the crashworthiness requirements for crash scenario-2, the stiffness reinforcement for the laminate composite cover and metal frames of cabmask structure was proposed. Consequentially, it has satisfied the requirement for crash scenario-2.

• Plant Biotechnology Reports
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• v.2 no.2
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• pp.123-131
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• 2008

Vitrification methods are convenient for cryopreserving plant specimens, as the specimens are plunged directly into liquid nitrogen (LN) from ambient temperatures. However, tissues and species with poor survival are still not uncommon. The development of vitrification solutions with high survival that cover a range of materials is important. We attempted to develop new vitrification solutions using bromegrass cells and found that VSL, comprising 20% (w/v) glycerol, 30% (w/v) ethylene glycol, 5% (w/v) sucrose, 10% (w/v) DMSO and 10 mM $CaCl_2$, gave the highest survival following cryopreservation, as determined by fluorescein diacetate staining. However, the cryopreserved cells showed little regrowth, for unknown reasons. To check its applicability, VSL was used to cryopreserve gentian axillary buds and the performance was compared with those of conventional vitrification solutions. Excised gentian stem segments with axillary buds (shoot apices) were two-step precultured with sucrose to induce osmotic tolerance prior to cryopreservation. Gentian axillary buds cryopreserved using VSL following the appropriate preculturing approach exhibited 78% survival (determined by the regrowth capacity), which was comparable to PVS2 and PVS1 and far better than PVS3. VSL had a wider optimal incubation time (20-45 min) than PVS2 and was more suitable for cryopreserving gentian buds. The optimal duration of the first step of the preculture was 7-11 days, and preculturing with sucrose and glucose gave a much higher survival than fructose and maltose. VSL was able to vitrify during cooling to LN temperatures, as glass transition and devitrification points were detected in the warming profiles from differential scanning calorimetry. VSL and its derivative, VSL+, seem to have the potential to be good alternatives to PVS2 for the cryopreservation of some materials, as exemplified by gentian buds.

• Korean Journal of Veterinary Research
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• v.30 no.4
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• pp.479-485
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• 1990

This study was carried out to observe in vitro effect of praziquantel on the viability and internal organ changes of Heterophyopsis continua with light microscopy. Metacercariae were collected from the perch, Lateolabrax japonicus, by artificial digestion technique and fed to 2-week old chickens. Adult worms were recovered from the small intestines of chickens 8 days after infection. For working solutions, praziquantel was diluted with TC199 medium at the concentration of 0.01, 0.1, 1 and $10{\mu}g/ml$. To each petri dish containing 10ml of solution, 5~10 worms were introduced and incubated at $37^{\circ}C$. Motlity of worms was observed at 5, 15, 30, 60 minutes, 1, 2, 4 and 6 hours after incubation. For light microscopy, worms were fixed in 10% formalin under cover glass pressure and stained with Semichon's acetocarmine. The results were as follows: 1. In $0.01{\mu}g/ml$ praziquantel, the worms had their mobility until 6 hours post treatment. However, worms in over $0.1{\mu}g/ml$ of praziquantel contracted within 5 minutes and immobilized. 2. Intestine of the worm incubated in $0.001{\mu}g/ml$ praziquantel for 5 minutes was dilated and intestinal wall was thickened. 3. In incubated over $0.1{\mu}g/ml$ praziquantel, pharynx of the worm protruded out from oral sucker. 4. The lowest effective lethal concentration of praziquantel on H. continua was $0.1{\mu}g/ml$. The worms exposed to the drug were observed to be immobilized immediately after incubation in solutions of over $0.1{\mu}g/ml$ concentration. All of the worms in early period showed severe contraction and those in late period showed severe dilation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.92-98
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• 2014

Spacer is a construction material for maintaining cover depth and steel installation, however several problems like staining, leakage, and cracking are currently issued due to performance degradation and unsatisfactory dimensional stability of spacer. Plastic composite is widely used for prevention of brittle failure in cement based material, which yields improvement of crack resistance and ductile failure. This study is for development and applicability evaluation of high strength spacer with slag cement for environmental load reduction and plastic composite like polypropylene fiber, nylon fiber, and glass fiber. For this work, unit weight of 4 different plastic fibers are evaluated through preliminary tests. Physical tests including compressive, flexural, and tensile strength and durability tests including absorption, permeability, length change, crack resistance, carbonation, and freezing and thawing are performed. Through various tests, optimum plastic fiber is selected and manufacturing system for high strength spacer with the selected fiber is developed. Dimensional stability of the developed spacer is evaluated through field applicability evaluation.

• Smart Structures and Systems
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• v.17 no.4
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• pp.593-610
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• 2016

In this study, an innovative and smart glass fiber-reinforced polymer (GFRP) hybrid bar was developed for stronger durability of concrete structures. As comparing with the conventional GFRP bar, the smart GFRP Hybrid bar can promise to enhance the modulus of elasticity so that it makes the cracking reduced than the case when the conventional GFRP bar is used. Besides, the GFRP Hybrid bar can effectively resist the corrosion of conventional steel bar by the GFRP outer surface on the steel bar. In order to verify the bond performance of the GFRP hybrid bar for structural reinforcement, uniaxial pull-out test was conducted. The variables were the bar diameter and the number of strands and pitch of the fiber ribs. Tensile tests showed a excellent increase in the modulus of elasticity, 152.1 GPa, as compared to that of the pure GFRP bar (50 GPa). The stress-strain curve was bi-linear, so that the ductile performance could be obtained. For the bond test, the entire GFRP hybrid bar test specimens failed in concrete splitting due to higher shear strength resulting in concrete crushing as a function of bar deformation. Investigation revealed that an increase in the number of strands of fiber ribs enhanced the bond strength, and the pitch guaranteed the bond strength of 19.1 mm diameter hybrid bar with 15.9 mm diameter of core section of deformed steel the ACI 440 1R-15 equation is regarded as more suitable for predicting the bond strength of GFRP hybrid bars, whereas the CSA S806-12 prediction is considered too conservative and is largely influenced by the bar diameter. For further study, various geometrical and material properties such as concrete cover, cross-sectional ratio, and surface treatment should be considered.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.467-472
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• 2002

In this paper, we propose a polarization-insensitive temperature sensor using a thermo-optic effect of the upper and (or) lower cladding of a planar waveguide in contact with a side-polished fiber. A microscope cover glass with thickness of a 170 ${\mu}{\textrm}{m}$ is adopted as an overlay waveguide because this waveguide opposes sudden temperature change and ensures polarization-insensitive responses. The measured polarization-dependence loss is less than 0.3 dB. The temperature can be detected as a result of the shift in coupling wavelength of the sensor. We investigate the shift in coupling wavelength as a function of the temperature variation with respect to the different thermo-optic coefficients of lower and upper claddings. We also show that the temperature sensitivity of the device can be easily controlled by the thermo-optic coefficients of lower and upper claddings of the overlay waveguide.

• 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 Concrete Institute
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• v.22 no.2
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• pp.229-235
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• 2010

In this study, fire resistance performance of high strength concrete specimen with fireproof gypsum board was investigated for possible use in upgrading fire-resistant performance of the existing building and repair of fire damaged structures. Fire test of eight identical high strength concrete columns were carried out for 180 minutes in accordance with ISO-834. The temperature distributions in longitudinal reinforcement and concrete temperature at various depths were recorded. The fireproof performance of gypsum board and explosive spalling of concrete were observed. The specimens with 15 mm thick twoply fireproof gypsum board spalled after gypsum board crumbled regardless of fastening methods. However, when the thickness of fireproof gypsum board was more than 30 mm, it was possible to prevent the explosive spalling and control the rebar temperature. Although the effect of cover thickness could not be compared because the explosive spalling occurred, there seemed to be no difference in insulation efficiency.

• Korean Journal of Veterinary Research
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• v.10 no.1
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• pp.25-31
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• 1970

The techniques which have been used for the fecal examination of ruminant infected with the pancreatic flukes, Eurytrema Pancreaticum, were reviewer in their efficiency to detect the ova. One of modified fecal examination: H.F.E. (hydrochloric acid-formalin-ether) sedimentation method was devised in this study. Efficiency in the detecting ability of the fluke eggs with H.F.E. sedimentation method was determined by a series of repeat tests. Among 20 head of cattle known to harbor 1-5 adult worms of the pancreatic fluke, 75% of the infected cattle were detected, and among 60 head of cattle known to harbor more than 6 adult worms, 95% of the infected cattle were detected with H.F.E. sedimentation method. The procedures of the H.F.E. sedimentation method are as follows; 1) Take the sample 5-10 gm., emulsify throughly with 20 ml. of 50% hydrochloric acid in a cup. 2) Strain this mixture through one or two layers of wet surgical gauze into 15ml. centrifuge tube. 3) Washing the cup with 5ml. of 50% hydrochloric acid and strain again. 4) Centrifuge at 2,300 rpm. for 2 minutes. 5) Pour off the supernatant fluid. 6) After the sediment mixed with 10% formalin, stand for 5 minutes. 7) Add 2-3ml. of ether, shake vigorously up and down, after the top of the tube covered with thumb. 8) Centrifuge at 2,300 rpm. for 2 minutes. 9) Loosen the fecal plug in the tube by ringing with an applicator stick. 10) Quickly, but carefully, pour of all, but the bottom layer of sediment. 11) Thoroughly mix the sediment, pour on a slide (or pick up it with a pipett), mount with a cover glass. 12) Examine carefully.