• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.587-596
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• 2011

Ultra rapid-hardening cement is widely used for latex-modified mortar and concrete as repair and finishing material during urgent work. The purpose of this study is to evaluate the improvements in strength made to SBR cement mortars by the adding of various admixtures and by the use of different curing methods. SBR cement mortar was prepared with various polymer-cement ratios, curing conditions and admixture contents, and tested for flow, flexural and compressive strengths. From the test results, it was determined that the flow of SBR cement mortar increased with an increase in the polymer-cement ratio, and the water reducing ratio also increased. The strength of cement mortar is improved by using SBR emulsion, and is strengthened by adding metakaoline. The strength of SBR cement mortar cured in standard conditions was increased with an increase in the polymer-cement ratio, and attained the maximum strengths at polymer-cement ratios of 15 % and 10 %, respectively. The maximum strengths of SBR cement mortar are about 1.8 and 1.3 times the strengths of plain mortar, respectively. In this study, it is confirmed that the polymer-cement ratio and curing method are important factors for improving the strengths of rapid-hardening SBR cement mortar.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.236-245
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• 2021

It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

• Journal of Environmental Science International
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• v.31 no.8
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• pp.715-725
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• 2022

Lactic Acid Bacteria (LAB) are among the representative probiotics that have been used for a long time in fermented food. Although there are many studies on detecting the radical scavenging activity of LAB, few studies have been conducted on the environmental factors that improve scavenging activity. This study investigated the environmental factors affecting the DPPH radical scavenging and various antioxidant activities of Kimchi-derived Lactobacillus plantarum K-21 with antihypertensive and radical scavenging activities. The optimal conditions for scavenging DPPH radicals were glucose 2%, bactopeptone 0.5%, Tween 80 0.05%, L-cysteine 0.05%, and an initial pH 6.5 at 35℃. Under optimal conditions, the DPPH radical scavenging activity was 94.8±2.2%, which was 1.5 times higher than that of the basic medium. In addition, L. plantarum K-21 had other antioxidant activities; ABTS radical scavenging (93.6±1.5%), hydroxyl radical scavenging (8.5±0.9%), metal chelating (65.9±0.5%), NO scavenging (53.1±19%), SOD-like (25.1±1.5%), and reducing power (11.7±1.4%) activities were detected. Therefore, L. plantarum K-21 may act not only as a starter for lactic acid-fermented foods with improved functionality but also as a drug for various diseases caused by oxidative stress.

• Clean Technology
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• v.17 no.3
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• pp.225-230
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• 2011

Characteristics of hydrocarbon selective catalytic reduction of NOx using various noble metal catalysts were investigated. The best active metal is Pt, supports are $CeO_2$ and $TiO_2$ by strong interactions between active metals, and 55% of conversion rate of NOx is shown. Pd, Rh and Ag catalysts presented a conversion of less than 20% as active metals, and supports also showed the poor activity compared to $SiO_2$ and $ZrO_2$. Experiments were performed with different types of reducing agents, amount, concentration of oxygen and space velocity in order to investigate the performance of catalysts according to operating conditions. The results confirm that the methane is better than propane as a reducing agent, and as the ratio of methane/nitrogen oxide increases, the catalytic activity increased, as the concentration of oxygen increases and space velocity decreases, the performance of catalysts increased.

• Journal of Korean Society on Water Environment
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• v.39 no.4
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• pp.343-355
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• 2023

After the implementation of the total pollution load control system, the effect of improving river water quality by expanding investments in basic environmental facilities, inducing operational efficiency, and reducing the load of various pollutants was clear. However, since the implementation of the system, the management of non-point pollutants has been neglected; management focused on specific substances (biochemical oxygen demand (BOD) and total phosphorus (T-P)) and lacked specific cause analysis and action plans, failed to establish a relationship between water quality and pollution load, failed to reflect stakeholder demands for river water quality management, and failed to apply technical conditions. Therefore, to overcome the limitations raised and achieve a practical and efficient advanced total pollution system, the current system was partially improved and will continue to be improved. This study analyzed the performance and limitations of the total pollution system and introduced recent improvements and the contents that are being improved. The main contents included reducing emissions and reduction monitoring, using water quality tele-monitoring system (TMS) data and self-measurement data, adding population-inducing facilities, and adjusting regional development projects from 20 to 30 multi-family housing units, currentizing each pollutant source according to the roadmap. If the system is improved in a developmental direction and responds to various changes, it will be a more practical and effective policy.

• Journal of Korean Society of Water and Wastewater
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• v.38 no.4
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• pp.233-242
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• 2024

This study evaluates the potential of various coagulants to enhance the efficiency of total phosphorus removal facilities in a sewage treatment plant. After analyzing the existing water quality conditions of the sewage treatment plant, the coagulant of poly aluminium chloride was experimentally applied to measure its effectiveness. In this process, the use of poly aluminium chloride and polymers in various ratios was explored to identify the optimal combination of coagulants. The experimental results showed that the a coagulants combination demonstrated higher treatment efficiency compared to exclusive use of large amounts of poly aluminium chloride methods. Particularly, the appropriate combination of poly aluminium chloride and polymers played a significant role. The optimal coagulant combination derived from the experiments was applied in a micro flotation method of real sewage treatment plant to evaluate its effectiveness. This study presents a new methodology that can contribute to enhancing the efficiency of sewage treatment processes and reducing environmental pollution. This research is expected to make an important contribution to improving to phosphorus remove efficiency of similar wastewater treatment plant and reducing the ecological impact from using coagulants in the future.

• International Journal of Highway Engineering
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• v.18 no.6
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• pp.87-96
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• 2016

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between different sizes of variable speed limit signs and the legibility distance under various fog density conditions. By using this study, appropriate sizes of signs can be selected depending on the density of fog. METHODS : An actual tunnel was selected as the area for this test, as other places cannot maintain the fog condition because of rapid air current. A total 121 subjects were recruited for this test, which took place over the course of four days. The test on the first day was conducted under normal weather conditions for comparison. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS : The test results show the relationship between the different sizes of signs and the legibility distance corresponding to the visibility distance due to both non-fog and fog generated conditions. According to the technical test results, appreciable amount of reduction in legibility distance due to fog was resulted in all sizes of signs. Moreover, the legibility distance is reduced proportionately with the decrease in the visibility distance due to fog. CONCLUSIONS : The results of this study can be used to select appropriate sizes of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.

• Journal of the Korea Institute of Building Construction
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• v.8 no.6
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• pp.131-137
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• 2008

In recent years, the light-weight aggregate has widely been used to reduce the weight of construction structures, and to achieve the thermal insulation of building structures. The purpose of this study is to evaluate the heat resistance of polymer concrete composites with light-weight aggregate made by binders as resin and cement with polymer dispersion. The light-weight polymer concrete composites are prepared with various conditions such as binder content, filler content, void-filling ratio, light-weight aggregate content and polymer-cement ratio, and tested for heat resistant test, and measured the weight reducing ratio, strengths and exhaustion content of gas such as CO, NO and $SO_2$. From the test results, the weight reducing ratio of light weight polymer concrete using UP binder after heat resistance test increase with an increase in the UP content irrespective of the filler content. The weight reducing ratio of polymer cement concrete is considerably smaller than that of UP concrete. In general, the strengths after heat resistance of polymer concrete composites are reduced about 40 to 65% compared with those before test. The exhausted quantity of CO, NO and $SO_2$ gases in polymer concrete composites is less than EPS(Expanded poly styrene). From the this study, it is confirmed that the many types gases discharge according to binder type of polymer concrete composites, its amount is controlled by selection of the binder type and mix proportions.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.9
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• pp.273-302
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• 1998

INTERNATIONAL MONITORY FUNDS wave swept the Economic structural insolvency lies one upon another with low growth, low trust, low prices, low interest and low employment as[2 down 3 up] phenomenons have been distinguished and low enterprise a control of structures due to forecasting 200 million unemployment, including 600 million unemployed the head of a family population have a difficulty in their life. Only way to give them hope is through the commencement of an enterprises to have 2nd career development. But end of 1995, 467,00 dining out companies have been established and recently business are in depression. There are many business conditions of change of business or reduce operations, if unemployment populations of 5%, 100,000 peoples doing the commencement of an enterprises, enormous number of dining out companies will be increased and the competition will be fierce, especially those who have short knowledge and experience doing the commencement of an enterprises have high failure than success which will give a problems to society. Our study is to make the commencement of an enterprise to reducing the faiure and to be successful for main point to successful commencement of an enterprise, the established can self capability and mental condition, the main important factor is types of industry selection, successful and those established who takes this conditions will very carefully inspect various matters by scientifically and rationally mind industrys propulsion graphs and open official fixture graphs will framing detail factors. One by inspect the reduction of failure, and successful commencement of an enterproses mind industry have been studied.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.4
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• pp.680-683
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• 2002

Bovine aortic endothelial cells(BAEC) produce two variant forms of laminin with a subunit composition of AB1B2 and A'B1B2. Analyses of the intracellular assembly of these subunits revealed that the B1B2 dimer formed first, and that A or A' joined to form the AB1B2 or A'B1B2 trimer. Angiostatic steroids shifted the relative size of the A and A' monomer pool in BAEC, and competition between the A and A' subunits in joining the B1B2 dimer produced AB1B2 and A'B1B2 in different ratios. This result suggests that subunit replacement is the general mechanism for producing laminin variants by various cells for tissue morphogenesis. When laminin subunits in BAEC were cross-linked with dithio-bis-succinimidylpropionate(DSP) and immunoprecipitated with anti-Iaminin antiserum, monomeric A,A',B1 and B2 monomers and the B1B2 dimer migrated as extremely large molecules in sodium dodecyl sulfate gel electrophoresis under nonreducing conditions. When the crosslinking disulfide bonds were cleaved under reducing conditions, they migrated as the usual subunits. This result suggests that molecular chaperones were involved in the process of the assembly and replacement of laminin subunits.