• Magazine of the Korean Society of Agricultural Engineers
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• v.20 no.2
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• pp.4645-4687
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• 1978

This study was attempted to investigate the mechanical properties of concrete and crack control effects of reinforced concrete with steel and glass fiber. The experimental program includes tests on the properties of fresh concrete containing fibers, compressive strength, tensile strength, flexural strength, Young's modulus, Shrinkage and deformation of steel or glass fiber reinforced concrete. Also this study was carried out to investigate the effect of steel or glass fiber to retard the development in reinforced concrete subject to uniaxial tension and thus facilitate the use of steels of higher strength. The major conclusions that can be drawn from the studies are as follows: 1. The effect of the fibers in various mixes on fresh concrete confirmed that fibers do have a significant effect on the properties of fresh concrete, bringing much more stable and exhibiting a signiflcant reduction in surface bleeding, and that the cohesion is greatly improved and the internal resistance increases with fiber concentration. But the addition of an excess contents and length of fibers brings about the reduction of workability. 2. With the addition of steel fibers(1.5% Vol.) to concrete, the compressive strength as compared with plain concrete showed a very slight increase, but excess addition, over 1.5% Vol. of steel and glass fiber reduced its strength. 3. Splitting tensile strength of fiber reinforced concrete showed a significant increase tendency, as compared with plain concrete. In case of containing steel fiber (2.5%, 30mm), it showed that the maximum increase rate of 1.48 times as much rate, and in case of containing glass fiber (2.5%, 30mm), the increase rate of strength was 1.25 times as much rate. 4. Flexural strength of fiber reinforced concrete showed a significant tendency, as compared with plain concrete. Containing steel fiber (2.5%, 30mm) showed the maximum increase rate of 1.64 times as much rate and containing glass fiber (2.5%, 30mm) showed the increase rate of strength of 1.32 times as much rate, and in general, the 30mm length brougth the best results. 5. The strength ratio ($\sigma$b/$\sigma$c and $\sigma$t/$\sigma$c) increased, when steel fiber's average spacing was up to 3.05mm, but decreased when beyond 3.05mm, and it was confirmed that tensile or flexural strengths of steel fiber reinforced concrete are apparently governed by fiber's average spacing. 6. The compressive strain of fiber reinforced concrete showed a significant increasing tendency as the fiber was added, but Young's modulus. with the addition of steel and glass fibers, showed a slight decrease tendency. And according to the increase of flexural strength, a considerable increase was seen in toughness. 7. With the addition of fiber's the shrinkage of concrete was significantly decreased, in both case of adding steel fibers 12.5%, 30mm, and showed a significant decrease ratio, in average 30.4% and 36.7%, as compared with plain concrete. 8. With the increase of fiber volume fraction and length, the gained stress in reinforcing bar in concrete specimens increased in all crack widths, but at different rates, with the decrease of fiber diameter, the stress showed a considerable increasing tendency. And the duoform steel fibers showed the greatest improvement, as compared with the other types tested. 9. The influence of fiber dimensions in order of significanse on the machanical properties of concrete and the crack control of reinforced concrete was explained as follows: content, length, aspect ratio and dimeter.

• KIEAE Journal
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• v.12 no.2
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• pp.125-129
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• 2012

With the development of the industry, such as homes and industries of electric energy usage and thereby increase the supply of electrical energy for power generation facilities were also increased. Among them an increase in thermal power plants, such as Bottom Ash was accompanied by an increase in industrial waste. If fly ash is recycled, some ten thousand Fly Ash and Bottom Ash Landfill, the recycling rate is low in most. In this study, in order to resolve the problem of fly ash recycling Bottom Ash to take advantage of low physical and chemical characteristics were analyzed. Evaluation of Physical Properties of Bottom Ash In addition, through the evaluation of functional properties of additives chogyeol condensation of 1 hour or more, within 3 hours of closing, Flow has more than 190mm of wheel load resistance value is less than 3mm flooring developed to study the subsequent emphasis on the Properties is based. Through these studies by developing a functional flooring help with the problem of resource depletion, and losses due to reclamation and pollution is to prevent.

• Geomechanics and Engineering
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• v.15 no.6
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• pp.1193-1205
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• 2018

A footing located on slopes possess relatively lower bearing capacity as compared to the footing located on the level ground. The bearing capacity further reduces under seismic loading. The adverse effect of slope inclination and seismic loading on bearing capacity can be minimized by proving sufficient setback distance. Though few earlier studies considered setback distance in their analysis, the range of considered setback distance was very narrow. No study has explored the critical setback distance. An attempt has been made in the present study to comprehensively investigate the effect of setback distance on footing under seismic loading conditions. The pseudo-static method has been incorporated to study the influence of seismic loading. The rate of decrease in seismic bearing capacity with slope inclination become more evident with the increase in embedment depth of footing and angle of shearing resistance of soil. The increase in bearing capacity with setback distance relative to level ground reduces with slope inclination, soil density, embedment depth of footing and seismic acceleration. The critical value of setback distance is found to increase with slope inclination, embedment depth of footing and density of soil. The critical setback distance in seismic case is found to be more than those observed in the static case. The failure mechanisms of footing under seismic loading is presented in detail. The statistical analysis was also performed to develop three equations to predict the critical setback distance, seismic bearing capacity factor ($N_{{\gamma}qs}$) and change in seismic bearing capacity (BCR) with slope geometry, footing depth and seismic loading.

• Steel and Composite Structures
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• v.19 no.2
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• pp.309-325
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• 2015

A convenient procedure for seismic retrofit of existing buildings is to use passive control methods, like using friction dampers in steel frames with bracing systems. In this method, reduction of seismic demand and increase of ductility generally improve seismic performance of the structures. Some of its advantages are development of a stable rectangular hysteresis loop and independence on environmental conditions such as temperature and loading rate. In addition to friction dampers, masonry-infill panels improve the seismic resistance of steel structures by increasing lateral strength and stiffness and reducing story drifts. In this study, the effect of masonry-infill panels on seismic performance of a three-span four-story steel frame with Pall friction dampers is investigated. The results show that friction dampers in the steel frame increase the ductility and decrease the drift (to less than 1%). The infill panels fulfill their function during the imposed drift and increase structural strength. It can be concluded that infill panels together with friction dampers, reduced structural dynamic response. These infill panels dissipated input earthquake energy from 4% to 10%, depending on their thickness.

• Design & Manufacturing
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• v.17 no.2
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• pp.27-32
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• 2023

Liquid silicon rubber (LSR) has fine thermal compatibility and is widely used in various fields such as medical care and automobiles because it is easy to implement products with good fluidity. With the recent development of flexible sensors, the focus has been on manufacturing conductive elastomers, such as silicone as elastic materials, and carbon black, CNT, and graphene are mainly used as nanomaterials that impart conductive phases. In this study, mechanical behavior and curing behavior were measured and analyzed to manufacture a CB-LSR complex by adding Carbon Black to LSR and to identify properties. As a result of the compression test, the elastic modulus tended to increase as carbon black was added. When the swelling test and the compression set test were conducted, the swelling rate tended to decrease as the content of carbon black increased, and the compression set tended to increase. In addition, DSC measurements showed that the total amount of reaction heat increased slightly as the carbon black content increased. It is considered that carbon black was involved in the crosslinking of LSR to increase the crosslinking density and have a positive effect on oil resistance reinforcement.

• Journal of the Korean institute of surface engineering
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• v.37 no.6
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• pp.350-359
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• 2004

Stress corrosion cracking(SCC) characteristics of shot-peened stainless steel containing Ti (0.09 wt%-0.92 wt%) fabricated by the vacuum furnace were investigated using SCC tester and potentiostat. The homogenization and the sensitization treatment were carried out at $1050^{\circ}C$ for 1hr and $650^{\circ}C$ for 5 hr. The samples for SCC were shot-peened using $\Phi$0.6 mm steel ball for 4 min and 10 min. Intergranular and pitting corrosion characteristics were investigated by using EPR and CPPT. SCC test was carried out at the condition of$ 288^{\circ}C$, 90 kgf pressure, water with 8 ppm dissolved oxygen, and $8.3xl0^{-7}$/s strain rate. After the corrosion and see test, the surface of the tested specimen was observed by the optical microscope, TEM and SEM. Specimen with Ti/C ratio of 6.14 showed high tensile strength at the sensitization treatment. The tensile strength decreased with the increase of the Ti/C ratio. Pitting and intergranular corrosion resistance increased with the increase of Ti/C ratio. Stress corrosion cracking strength of shot-peened specimen was higher than that of non shot- peened specimen. Stress corrosion cracking strength decreased with the increase of the Ti/C ratio.

• Journal of Nutrition and Health
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• v.32 no.6
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• pp.644-653
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• 1999

Background : Excessive intakes of $\omega$6 polyunsaturated fatty acid (PUFA) can increase oxidative stress, which may increase insulin resistance and could be the cause of metabolic syndrome X such as diabetes mellitus. One of the ways to reduce oxidative stress is the consumption of antioxidants such as vitamin E. It is controversial that vitamin E intakes may alleviate insulin resistance. The purpose of the study was whether high vitamin E intake may influence whole body glucose disposal rate(GDR), glycogen deposites, triglyceride content, lipid peroxide levels and antioxidant enzyme activities in Sprague Dawley rats fed high $\omega$6 PUFA diest. Methods : Sprague Dawley rats were divided into three groups. The control group consumed chow diet. High and low vitamin E groups consumed 40% PUFA of total energy intakes. One kilogram of diet mixture contained 300IU of $\alpha$-tocopherol in high vitamin E group, while it had 30 IU in low vitamin E group. Diets were given for 8 weeks. After 7 were of diet consumption, indwelling catheters were inserted in carotid artery and jugular vein of all rats so that GDR could be measured in awake and unstressed state. Results : Daily PUFA intakes were lower in the control group than others. Daily vitamin E intake of high vitamin E group was about ten times higher than those of low vitamin E group and the control group(p<0.0001). $\alpha$-tocopherol content in lier was highest in the high vitamin E group. GDR of the control group was 24% higher than others, and vitamin E intakes did not affect GDR. Glycogen deposit of liver in the control group was significantly higher than others, and it was not altered by vitamin E supplementation. Muscle glycogne content showed a similar tendency as liver glycogen in different diet groups. Triglyceride deposit in muscle was not different among groups. Lipid peroxide content of liver in the high vitamin E group was lower than the low of glutathione peroxidase were lowered in low vitamin E group than others, however, those of superoxide dismutase and catalase were not different. Conclusions : High vitamin E intakes can decrease oxidative stress in rats fed high (())-6 PUFA diet, but they cannot alleviate insulin resistance. Thus, increased oxidative stress through high (())-6 PUFA diet may be minimal for influencing insulin resistance.

• The Plant Pathology Journal
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• v.34 no.5
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• pp.403-411
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• 2018

This study takes strawberry-fruits as the test material and discusses the effect of Burkholderia contaminans B-1 on preventing postharvest diseases and inducing resistance-related substances in strawberry-fruits. Soaking and wound inoculating is performed to analyze the inhibitory effects of different treatment solutions on the gray mold of postharvest strawberry-fruits. The count of antagonistic bacteria colonies in the wound is found, and the dynamic growth of antagonistic bacteria and the pathogenic fungus is observed by electron microscopy. The results indicated that, either by soaking/wound-inoculating, the fermentation and suspension of antagonistic bacteria significantly reduced the incidence of postharvest diseases of strawberry-fruits. With wound inoculation, the inhibition rate of antagonist fermentation and suspension ($1{\times}10^{10}cfu/ml$) respectively reached 77.4% and 66.7%. It also led to a significant increase in the activity of resistance-related enzymes, i.e., phenylalanine ammonia lyase (PAL), 4-coumarate coenzyme A ligase (4CL), cinnamate-4-hydroxylase (C4H) and chalcone isomerase (CHI). On 1 d and 2 d post-treatment, the activity of 4CL was respectively 3.78 and 6.1 times of the control, and on 5 d, the activity of PAL was increased by 4.47 times the control. The treatment of antagonistic bacteria delayed the peaking of cinnamyl-alcohol dehydrogenase (CAD) activity and promoted the accumulation of lignin and total phenols. The antagonistic bacteria could be well colonized in the wounds. On 4-5 d post-inoculation, the count of colonies was $10^8$ times of that upon inoculation. Electronmicroscopy indicated that the antagonistic bacteria delayed the germination of pathogenic spores in the wounds, and inhibited further elongations of the mycelia.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.113-116
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• 2009

This study analyzed fire-resistant characteristics according to changes in repair methods of PFH mixed high-strength concrete roof structures having undergone fire damage. The results of the study are as follows. First, as a repulsive characteristics of structures, the remaining repulsion was shown to increase following fire-resistance tests according to increases in depth of coverings. The results of the relationship between depth of coverings and remaining repulsion rates following fire-proofing tests showed a high correlation. At a covering depth of 67.3mm, remaining repulsion rate was estimated to be 100%. For fire-resistant characteristics following repairs of structure, as for spalling, severe separation was shown in the case of general plaster while general plaster + Metal Lath showed overall superior spalling prevention. For internal structure temperatures, general plaster showed max temperatures of 705℃, average temperatures of 636℃ while general plaster + metal lath showed max temperature of 660℃ and average temperature of 520℃, demonstrating lower temperature distributions than use of only general plaster. In conclusion, after removing the covering of structures damaged due to high temperatures of fires within high-strength concrete installations, the use of fire-resistant mortars and applying metal laths on surfaces of general plaster will provide superior fire-resistance performance in the occurrence of a 2nd fire.

• Elastomers and Composites
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• v.33 no.3
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• pp.193-200
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• 1998

It is well known that EPDM(ethylene propylene diene monomer) rubber has inherently excellent resistance to the weathering, ozone, heat, cold and moisture, whereas crosslinked IIR (isobutylene isoprene divlnyl benzene terpolymer) shows proper resistance to the water and gas permeation. Various characteristics of EPDM blend with crosslinked IIR such as curing characteristics, mechanical properties, dispersion of minor component and gas impermeability were explored. The optimum curing time $(t_{90})$ examined with peroxide was decreased by adding small amount of crosslinked IIR to the EPDM rubber. Mechanical properties of blends such as tensile strength, hardness and elongation at break were enhanced by increasing EPDM content. These results might be explained with the affinity of carbon black to the EPDM rubber. On the other hand, the physical properties were not changed significantly after aging, and the increase of crosslinked IIR fraction caused the decrease of compression set to small rate. EPDM rubber shows different behavior with crosslinked IIR in oxygen permeability. By adding 30wt.% crosslinked IIR to the EPDM rubber, the resistance to the oxygen permeation was improved up to three times than that of pure EPDM rubber. Conclusively, EPDM blend containing 30wt.% crosslinked IIR might be commercially applied to the o-ring and electric parts because of its proper resistance to the weathering, ozone and oxygen permeability.