• Title/Summary/Keyword: Reinforcing Effect

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Corrosion Protection of Rebars Using High Durability Polymer Cementitious Materials for Environmental Load Reduction (환경부하저감형 고내구성 폴리머 시멘트계 재료를 이용한 철근 부식저감기술)

  • Kim, Wan-Ki;Chung, Seung-Jin
    • KIEAE Journal
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    • v.10 no.5
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    • pp.131-137
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    • 2010
  • The building industry must aim at high-durability and sustainability. A holistic life cycle based approach is recommended to reduce the environmental load. In recent years, technical innovations in the construction industry have advanced to a great extent, and caused the active research and development of high-performance and multifunctional construction materials. Nowadays, various polymer powders have been commercialized to manufacture construction materials in the form of prepackaged-type products, which have rapidly been developed for lack of skilled workmen in construction sites. Recently, terpolymer powders of improved quality have been developed and commercialized as cement modifiers. And, hydrocalumite is a material that can adsorb the chloride ions (Cl-) causing the corrosion of reinforcing bars and liberate the nitrite ions (NO2-) inhibiting the corrosion in reinforced concrete, and can provide a self-corrosion inhibition function to the reinforced concrete. The purpose of this study is to ascertain the self-corrosion inhibition function of polymer-modified mortars using redispersible powders with hydrocalumite. Polymer-modified mortars using VA/E/MMA and VAE redispersible powders are prepared with various calumite contents and polymer-binder ratios, and tested for chloride ion penetration depth, corrosion inhibition. As a result, regardless of the polymer-binder ratio, the replacement of ordinary portland cement with hydrocalumite has a marked effect on the corrosion-inhibiting property of the polymer-modified mortars. Anti-corrosion effect of polymer-modified mortars using VA/E/MMA terpolymer powder with hydrocalumite is higher than that of VAE copolymer powder.

Wild Ginseng Attenuates Repeated Morphine-Induced Behavioral Sensitization in Rats

  • Lee, Bom-Bi;Kwon, Sun-Oh;Yeom, Mi-Jung;Shim, In-Sop;Lee, Hye-Jung;Hahm, Dae-Hyun
    • Journal of Microbiology and Biotechnology
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    • v.21 no.7
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    • pp.757-765
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    • 2011
  • Many studies have suggested that the behavioral and reinforcing effects of morphine are induced by hyperactivation of the mesolimbic dopaminergic system, which results in increases in locomotor activity, c-Fos expression in the nucleus accumbens (NAc), and tyrosine hydroxylase (TH) in the ventral tegmental area (VTA). In order to investigate the effect of wild ginseng (WG) on treating morphine addiction, we examined the behavioral sensitization of locomotor activity and c-Fos and TH expression in the rat brain using immunohistochemistry. Intraperitioneal injection of WG (100 and 200 mg/kg), 30 min before administration of a daily injection of morphine (40 mg/kg, s.c.), significantly inhibited morphine-induced increases in c-Fos expression in NAc and TH expression in VTA as well as in locomotor activity, as compared with Panax ginseng. It was demonstrated that the inhibitory effect of WG on the behavioral sensitization after repeated exposure to morphine was closely associated with the reduction of dopamine biosynthesis and postsynaptic neuronal activity. It suggests that WG extract may be effective for inhibiting the behavioral effects of morphine by possibly modulating the central dopaminergic system and that WG might be a useful resource to develop an agent for preventing and treating morphine addiction.

Behaviors of concrete filled square steel tubes confined by carbon fiber sheets (CFS) under compression and cyclic loads

  • Park, Jai Woo;Hong, Young Kyun;Choi, Sung Mo
    • Steel and Composite Structures
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    • v.10 no.2
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    • pp.187-205
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    • 2010
  • The existing CFT columns present the deterioration in confining effect after the yield of steel tube, local buckling and the deterioration in load capacity. If lateral load such as earthquake load is applied to CFT columns, strong shearing force and moment are generated at the lower part of the columns and local buckling appears at the column. In this study, axial compression test and beam-column test were conducted for existing CFT square column specimens and those reinforced with carbon fiber sheets (CFS). The variables for axial compression test were width-thickness ratio and the number of CFS layers and those for beamcolumn test were concrete strength and the number of CFS layers. The results of the compression test showed that local buckling was delayed and maximum load capacity improved slightly as the number of layers increased. The specimens' ductility capacity improved due to the additional confinement by carbon fiber sheets which delayed local buckling. In the beam-column test, maximum load capacity improved slightly as the number of CFS layers increased. However, ductility capacity improved greatly as the increased number of CFS layers delayed the local buckling at the lower part of the columns. It was observed that the CFT structure reinforced with carbon fiber sheets controlled the local buckling at columns and thus improved seismic performance. Consequently, it was deduced that the confinement of CFT columns by carbon fiber sheets suggested in this study would be widely used for reinforcing CFT columns.

The Stress Distribution around a Circular Hole Reinforced by a Ring of Different Material in a Plate under Biaxial Loading (이질원환(異質圓環)으로 보강(補强)된 원형(圓形)구멍 주위(周圍)에서의 응력분포(應力分布))

  • S.J.,Yim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.6 no.1
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    • pp.43-67
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    • 1969
  • The effect of a circular hole reinforced by a ring of different material in a plate under biaxial loadings is considered. In this problem, an infinitely large flat is assumed. The reinforcing ring is of uniform rectangular cross-section of same thickness as the plate. The outer boundary of the ring is cemented to the inner boundary of the hole in the plate. The plate is subjected to hydrostatic tension and pure shear loadings. The stress distribution around the hole is obtained by means of the two dimensional theory of elasticity. To conform the validities of above solutions, a series of photo-elastic stress analysis for a composite model was carried out. Fair agreements were observed between two sets of values. The conclusions arrived at are as follows: 1) The theoretical solutions are exact ones for the case of infinitely large flat plate. 2) The solutions can be used for most case of engineering problem if the bonding between the plate and ring is perfect. 3) If the ratio of Young's moduli of the ring and the plate is increased, the stresses in the plate decrease whereas those in the ring increase. 4) The stress concentration near the hole has localized effect. 5) Under hydrostatic tension, maximum principal stress and maximum shear stress increase as the ratio of inner and outer diameters of the ring increases. 6) Under pure shear, the stresses depend upon angular orientations of the points and maximum principal stress and maximum shear stress appear at 45 degree. They increase as the ratio of inner and outer diameters of the ring increases.

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Music Program Development Using the Ukulele in Community-dwelling Old Adults and Its Effect (지역사회 거주 노인의 우쿨렐레를 활용한 음악 프로그램 개발 및 효과)

  • Kang, Gyeong Hye;Je, Nam Joo
    • Research in Community and Public Health Nursing
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    • v.32 no.2
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    • pp.220-231
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    • 2021
  • Purpose: This study is a pseudo-experimental study of design before and after the non-equivalent control group, which was attempted to verify that the application of the ukulele to the elderly has the effects of reducing depression, improving self-efficacy, strengthening social bonding, and improving cognitive function. Methods: 46 (23 in the experimental group and 23 in the control group) participants were selected. The experimental group was provided with three sessions of a music program using eight Ukuleles for the elderly, while the control group was provided with three sessions for the elderly. IBM SPSS 25.0 was used for data analysis, and the independent t-test, 𝑥2-test, and Fisher's exact probability test were performed to verify the homogeneity of the subject's general characteristics. The effect verification after the experimental treatment was analyzed by Fisher's exact probability test, Friedman test, and Mann-Whitney U test. Results: Depression showed a statistically significant difference between the two groups (F=39.88, p<.001), self-efficacy showed a statistically significant difference between the two groups (z=-4.96, p<.001), social bonding showed a statistically significant difference between the two groups (z=-5.19, p<.001), and cognitive function showed a statistically significant difference between the two groups (z=-3.98, p<.001). Conclusion: It was found that the 'Music Program using the Ukulele' was effective in reducing depression of the elderly, improving self-efficacy, reinforcing social bonding, and improving cognitive function. We hope that the Music Program using the Ukulele can be used in the elderly nursing curriculum in the future, and we suggest it should be applied as a nursing intervention to those who are experiencing cognitive decline.

Effect of Unidirectional Carbon Fiber Sheet Manufacturing Process Using Coated Glass Fiber and Carbon Fiber on Concrete Reinforcement (유리섬유 코팅사와 탄소섬유를 이용한 일방향 탄소섬유시트 제조공정이 콘크리트 보강에 미치는 영향)

  • Kwon, Jieun;Kwon, Sunmin;Chae, Seehyeon;Jeong, Yedam;Kim, Jongwon
    • Textile Coloration and Finishing
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    • v.34 no.3
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    • pp.185-196
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    • 2022
  • In this study, carbon fiber and coated glass fiber are applied to warp and weft fiber in order to reduce the amount of carbon fiber used in carbon fiber fabrics, which are often used for reinforcement of building structures. A low-cost thermoplastic resin was coated on glass fibers to prepare a shape-stabilizing glass fiber. A unidirectional carbon fiber sheet was manufactured using the prepared coated glass fiber and carbon fiber. In order to identify whether it can be used for reinforcing architectural and civil structures, it was attached to a concrete specimen and its mechanical properties were analyzed. The optimum manufacturing conditions for the coated glass fiber were 0.3 mm in diameter of the coating nozzle, the coating temperature was 190 ℃, and the coating speed was 0.3 m/s. 14 mm was optimal for the weft spacing of the coated glass fiber. The flexural strength of the concrete reinforced with the manufactured unidirectional carbon fiber sheet was slightly lower than that of the concrete reinforced with carbon fiber fabric, but it was confirmed that the reinforcement effect was better when the amount of carbon fiber was considered.

Korean Red Ginseng inhibits methamphetamine addictive behaviors by regulating dopaminergic and NMDAergic system in rodents

  • Lee, Bo-Ram;Sung, Su-Jeong;Hur, Kwang-Hyun;Kim, Seong-Eon;Ma, Shi-Xun;Kim, Seon-Kyung;Ko, Yong-Hyun;Kim, Young-Jung;Lee, Youyoung;Lee, Seok-Yong;Jang, Choon-Gon
    • Journal of Ginseng Research
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    • v.46 no.1
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    • pp.147-155
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    • 2022
  • Background: Methamphetamine (METH) is the most widely used psychostimulant and has been known to exhibit reinforcing effects even after long abstinence. We showed the inhibitory effect of Korean Red Ginseng extract (RGE) on METH-induced addictive behaviors in animal models mimicking the human drug-use pattern. Methods: We first investigated the effect of RGE on the acquisition of METH-induced dependence using self-administration and conditioned place preference (CPP) tests. Additionally, further experiments such as METH-induced motivational behavior and seeking behavior were conducted. To study the underlying mechanism, dopamine receptor, dopamine transporter, and N-methyl-D-aspartate receptor were assessed through Western blot analysis. Results: Treatment with RGE significantly reduced METH-induced self-administration on a fixed-ratio 1 schedule of reinforcement. It could be also decreased a progressive ratio schedule, and inhibited METH-primed reinstatement. In CPP, RGE significantly prevented the development of METH-induced CPP. Moreover, RGE not only shortened the withdrawal period clearly, but also prevented the reinstatement of CPP. RGE treatment also reversed METH-induced overexpression of dopamine transporter, dopamine receptor D1, and NMDA receptor in the nucleus accumbens. Conclusion: Our findings reflect that RGE has therapeutic potential to suppress METH-induced addictive behaviors by regulating dopaminergic and NMDAergic system.

Effect of Corrosion Level and Crack Width on the Bond-Slip Behavior at the Interface between Concrete and Corroded Steel Rebar (부식 수준 및 균열폭에 따른 부식된 철근과 콘크리트 계면의 부착-미끄러짐 거동 )

  • Sang-Hyeon Jo;Seong-Hoon Kee;Jung-Jae Yee;Changkye Lee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.1
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    • pp.54-63
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    • 2023
  • In this paper, the effect of corrosion level and crack width on the cohesive strength-slip behavior of corroded steel rebar and concrete interface is conducted. The existing studies mainly focus on the decrease in bond strength with respect to the level of corrosion; there are, however, few studies on the decrease in cohesive strength according to the crack width of the concrete surface due to corrosion. Therefore, in this study, a series of tests for the cohesive strength, slip behavior and mass loss of the reinforcing bar is evaluated at the surface of corroded rebar and concrete. It is found that the tendency to decrease the bond strength is closely related to the crack width rather than the corrosion level. Hence, to determine the degradation performance for the bond strength-slip behavior relation, the occurrence of cracks on the concrete surface can be a suitable index.

The Pull-out Behavior of Rock Bolts According to Grout Strength during Rock Bolt Pull-out (록볼트 인발 시 그라우트 강도에 따른 인발 거동)

  • Seongmin Jang;Hyuksang Jung
    • Journal of the Korean GEO-environmental Society
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    • v.24 no.4
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    • pp.13-22
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    • 2023
  • In this paper, through experimental research, the period when rock bolts exert support effects is presented as grout strength and through numerical analysis, the rock bolt pull-out behavior according to ground conditions and strength reduction factors is analyzed. As a result, it is determined that rock bolts exhibit their reinforcing effect at a grout strength of 5 MPa (cured for 18 hours). The influence of the boundary interface strength reduction factor was found to be significant for rock bolt displacement in weak ground conditions, for shear stress between grout and ground in highly elastic ground conditions, and for grout stress in all ground conditions. These findings are expected to contribute to the establishment of specific standards for rock bolt testing and numerical analysis, and to facilitate improved design and implementation of rock bolt reinforcement.

Investigation on Support Mechanism of Geogrid-Encased Stone Columns in Soft Ground (연약지반에 시공되는 지오그리드 감쌈 스톤컬럼의 하중 지지 메카니즘에 관한 연구)

  • Yoo, Chung-Sik;Kim, Sun-Bin
    • Journal of the Korean Geotechnical Society
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    • v.24 no.12
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    • pp.93-101
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    • 2008
  • This paper presents the results of numerical investigation on support mechanism of geogrid-encased stone columns for use in soft ground improvement. A number of cases were analyzed using a 3D stress-pore pressure coupled model that can effectively model construction sequence and drainage as well as reinforcing effects of geogrid-encased stone columns. The results indicated that the geogrid encasement provides additional confinement effect that reduces vertical stress in the soft ground, thus resulting in less excess pore water pressures and associated settlement. Also revealed was that such a confinement effect depends on encasement length and stiffness of geogrid. It is also shown that there exist critical encasement length and stiffness of geogrid for a given condition.