• Journal of the Korea Concrete Institute
• /
• v.15 no.4
• /
• pp.574-584
• /
• 2003

The most common deterioration cause of concrete structures in urban environment is carbonation. Recently, the $CO_2$ concentration and temperature at atmosphere is sharply increased with time due to global warming phenomena. In this study, the climate scenario IS92a, which was suggested by the IPCC, is used to consider temperature and atmospheric $CO_2$ concentration change in the model of service life prediction. The modified mathematical solution, which was based on the Fick's 1st law of diffusion, was used to reflect concrete materials properties such as the degree of hydration of concrete with elapsed time, and important parameters, which associated with deterioration rate. The techniques of service life prediction are developed introducing the method of reliability and stochastic concept to consider microclimatic condition in Seoul, South Korea. From the result of service life prediction, concrete containing high W/C ratio is shown fast carbonation rate due to $CO_2$ concentration increase. It is concluded that the deterioration of concrete structures due to carbonation is insignificant problem on the conditions that below W/C 55%, well curing concrete.

• The Korea Journal of Herbology
• /
• v.30 no.3
• /
• pp.13-17
• /
• 2015

Objectives : Taraxacum platycarpum H. Dahlstedt has been reported to have several biological properties such as skin hydration and antiinflammation. The purpose of this study was to examine the antidepressive effects of water extract of T. platycarpum (WTP) on an animal model of depression. Methods : In the present study, normal ICR mice (4 weeks) were used, and orally administered with WTP (25, 50 and 100 mg/kg). Depression-like behavior was monitored the forced swimming test (FST) and tail suspension test (TST) in mice. The locomotor activity was evaluated to eliminate the false-positive activity in the open field test (OFT). Fluoxetine, the selective serotonin reuptake inhibitor, as a positive control was intraperitoneally administered at a dose of 15 mg/kg at 30 min before starting the behavioral test. Moreover, we evaluated the effects of WTP on the expression of brain-derived neurotrophic factor (BDNF) and the extracellular signal-regulated kinase (ERK)/ cyclic AMP response-element binding protein (CREB) signaling pathway in the hippocampus using Western blot. Results : The administration of WTP (50 and 100 mg/kg) significantly (P < 0.05, respectively) reduced the immobility time during FST and TST without accompanying changes in locomotor activity by OFT. Furthermore, WTP at dose of 100 mg/kg increased the BDNF expression and the phosphorylation of ERK and CREB in the hippocampus region. Conclusions : These results suggest that WTP has a useful anti-depressant effect through the regulation of BDNF/ERK/CREB signaling pathway.

• Journal of the Korean Chemical Society
• /
• v.48 no.6
• /
• pp.616-622
• /
• 2004

Liposome powders were prepared by a freeze-drying method for the application to the field of drug carrier. The effect of maltose as a liposome stabilizer was studied on the stability and the drug-loading efficiency of the freeze-dried liposome powders. The particle size of liposomes before and after freeze-drying was determined to evaluate the liposome stability. The drug-loading efficiency was measured by Fluorescence spectrophotometer using calcein as a model drug. When maltose was added after the preparation of the liposomes, the liposomes was stable, compared to the case of maltose addition at the hydration procedure. By the addition of maltose, the liposome was stable for 30 days at $4{\sim}37^{\circ}C$, while the particle size of the liposome without maltose increased with time. The liposome showed relatively high stability when the maltose/lipids molar ratio was 3 and 6.

• Journal of the Korea Concrete Institute
• /
• v.26 no.6
• /
• pp.707-714
• /
• 2014

CFT (Concrete-Filled Tube) is a type of steel column comprised of steel tube and concrete. Steel tube holds concrete and the concrete inside tube takes charge of compressive load. This study presents structural performance of the CFT column which has 73~100 MPa high strength concrete inside. Fluidity, mechanical compression, pump pressure test in flexible pipe were conducted for understanding properties of the high strength concrete. Material properties were achieved by various experimental tests, such as slump, slump flow, air content, U-box, O-Lot, L-flow. In addition, mock-up tests were conducted to monitor concrete filling, hydration heat, compressive strength. From construction sites in Sang-am dong and University of Seo-kang, long-term behaviors could be effectively predicted in terms of ACI 209 material model considering elastic deformation, shrinkage and creep.

• Journal of the Korean GEO-environmental Society
• /
• v.2 no.1
• /
• pp.91-101
• /
• 2001

This paper investigates the effectiveness of quick lime piles for soft ground improvement. The field tests based on the results of the laboratory test were performed, and the results of field tests were compared with those of numerical analyses(FEM). The results of the field test showed that the domestic quick lime was very effective in reducing the water contents of the surrounding ground quickly due to its characteristics such as digestion, absorption, and exothermic reactions. Accordingly, consolidation occurred without any additional load increment and the shear strength of surrounding ground was increased more than twice. Therefore the quick lime pile method could be considered as an excellent improvement technique reducing the improvement period for soft ground. For the practical applications of the quick lime pile method, issues such as hydration heat, particulation and equipment enhancement should be solved through continuous research and development.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.4
• /
• pp.650-657
• /
• 2021

Alkali activators that stimulate mineral compounds are expensive materials, but in order to replace industrial products of high alkali in gredien ts, both product an d econ omic feasibility must be satisfied. In this study, alkali in dustrial waste(LW) from the LCD man ufacturin g process were used for the purpose of alkali active reaction of GGBFS for high stren gth concrete over 50MPa. Concrete mixed with LW had reduced workability, but it had the characteristic of increasing compressive strength. Analysis using ACI 209 Compressive Strength Model Equation was made to compare the changes in strength coefficients according to LW mixing. The durability test of concrete, such as Chloride Penetration Resistance and carbonation resistance, also showed excellent performance. In the Adiabatic temperature rise test results, the concrete mixed with LW had the effect of accelerating the initial hydration heat. However, the final Adiabatic temperature rise was not significantly affected by the mixing of LW.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.48 no.1
• /
• pp.25-32
• /
• 2022

In this study, basic skin characteristics data were collected by measuring skin hydration, skin melanin, skin redness, and skin torsion elasticity from Korean women in from 20's to 40's ages, and then, age and correlation analysis were conducted. This was used to create a skin index, and cluster analysis was performed to classify the groups into 4 clusters, and the skin characteristics of each cluster were confirmed. Then, two prototypes were used for two weeks to confirm the improvement effect on skin moisture, skin redness, and skin dead mass reduction, and then analyzed which product was more effective in which cluster of subjects participated in the skin characteristics test. As a result of the study, the possibility of preparing for the customized cosmetics market was confirmed by applying the skin index and cluster analysis results to product efficacy evaluation.

• Journal of the Korea Concrete Institute
• /
• v.19 no.3
• /
• pp.359-366
• /
• 2007

Recently, analysis researches on durability are focused on chloride attack and carbonation due to increased social and engineering significance. Generally, chloride penetration and carbonation occur simultaneously except for in submerged condition and chloride behavior in carbonated concrete is evaluated to be different from that in normal concrete. Furthermore, if unavoidable crack occurs in concrete, it influences not only single attack but also coupled deterioration more severely. This is a study on analysis technique with system dynamics for chloride penetration in concrete structures exposed to coupled chloride attack and carbonation through chloride diffusion, permeation, and carbonation reaction. For the purpose, a modeling for chloride behavior considering diffusion and permeation is performed through previous models for early-aged concrete such as MCHHM (multi component hydration heat model) and MPSFM (micro pore structure formation). Then model for combined deterioration is developed considering changed characteristics such as pore distribution, saturation and dissociation of bound chloride content under carbonation. The developed model is verified through comparison with previous experimental data. Additionally, simulation for combined deterioration in cracked concrete is carried out through utilizing previously developed models for chloride penetration and carbonation in cracked concrete. From the simulated results, CCTZ (chloride-carbonation transition zone) for evaluating combined deterioration is proposed. It is numerically verified that concrete with slag has better resistance to combined deterioration than concrete with OPC in sound and cracked concrete.

• Journal of the Korea Concrete Institute
• /
• v.15 no.2
• /
• pp.305-313
• /
• 2003

The setting and hardening of concrete is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. Especially at early ages, this nonlinear distribution has a large influence on the crack evolution. As a result, in order to predict the exact temperature history in concrete structures it is required to examine thermal properties of concrete. In this study, the coefficient of air convection, which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind and types of form. From experimental results, the coefficient of air convection was calculated using equations of thermal equilibrium. Finally, the prediction model for equivalent coefficient of air convection including effects of velocity of wind and types of form was theoretically proposed. The coefficient of air convection in the proposed model increases with velocity of wind, and its dependance on wind velocity is varied with types of form. This tendency is due to a combined heat transfer system of conduction through form and convection to air. From comparison with experimental results, the coefficient of air convection by this model was well agreed with those by experimental results.

• Journal of the Korea Concrete Institute
• /
• v.15 no.2
• /
• pp.314-322
• /
• 2003

Pipe cooling method is widely used for reduction of hydration heat and control of cracking in mass concrete structures. However, in order to effectively apply pipe cooling systems to concrete structures, the coefficient of flow convection relating the thermal transfer between inner stream of pipe and concrete must be estimated. In this study, a device measuring the coefficient of flow convection was developed. Since a variation of thermal distribution caused by pipe cooling has a direct effect on internal forced flows, the developed testing device is based on the internal forced flow concept. Influencing factors on the coefficient of flow convection are mainly flow velocity, pipe diameter and thickness, and pipe material. Using experimental results from the developed device, the coefficient of flow convection was calculated. Finally, a general prediction model was proposed by theoretical procedures. The proposed prediction model is able to estimate the coefficient of flow convection with flow velocity and material properties of pipe. From comparison with experimental results, the coefficient of flow convection by this model was well agreed with those by experimental results.