• Advances in concrete construction
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• v.11 no.4
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• pp.285-298
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• 2021

This study focused on experimental evaluation of mechanical properties of pervious concrete mixtures with the aim of achieving higher values of strength while considering the associated costs. The effectiveness of key parameters, including cement content, water to cement ratio (W/C), aggregate to cement ratio (A/C), and sand replacement was statistically analyzed using paired-samples t-test, Taguchi method and one-way ANOVA. Taguchi analysis determined that in general, the role of W/C was more significant in increasing strength, both compressive and flexural, than cement content and A/C. It was found that increase in replacing percent of coarse aggregate with sand could undermine specimens to percolate water, though one-way ANOVA analysis determined statistically significant increases in values of strength of mixtures. Cost analysis revealed that higher strengths did not necessarily correspond to higher costs; in addition, increasing the cement content was not an appropriate scenario to optimize both strength and cost. In order to obtain the optimal values, response surface method (RSM) was carried out. RSM optimization helped to find out that W/C of 0.40, A/C of 4.0, cement content of about 330 kg/m3 and replacing about 12% of coarse aggregate with sand could result in the best values for strength and cost while maintaining adequate permeability.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.185-186
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• 2020

This study In order to reduce the amount of cement that generates a large amount of carbon dioxide and attempts to find a recycling method to solve environmental problems by using biomass fly ash. Experiments were conducted according to replacement ratio of biomass fly ash based on GGBFS, The test items are flowability, air content, unit volume weight, water absorption, flexural strength and compressive strength. As a result of the experiment, as increased replacement ratio of biomass fly ash, the flowability and air content was increased. As increased replacement ratio, the density was decreased and water absorption was increased. The compressive strength tended to decrease as increased replacement ratio. The flexural strength tended to increased as increased replacement ratio.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.1
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• pp.205-212
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• 1998

In this study, the effects of water vapor in inlet air on combustion efficiency, general performance, knock characteristics and emission gas concentration were investig- ated through the experiments of combustion and vibration analyses, emission gas analysis by changing water vapor quantity in inlet air with temperature and humidity auto control unit. With partial vapor pressure increase, the brake torque at wide open throttle status decreased and the average ignition delay angle increased, IMEP (indicated mean effective pressured using the integral and 3rd derivatives of filtered cylinder pressure as knock intensity, which matched well with the method of frequency power spectrum of block vibration signal. Water vapor in intake air had influence on the spark knock sensitivity. With the increase of water vapor content in intake air NOx emission was decreased and HC emission was increased.

• Journal of the Mineralogical Society of Korea
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• v.18 no.2
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• pp.93-107
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• 2005

The estuary of Nakdong River area including Noksan industrial complex and Busan New Port is composed of thick unconsolidified sediments containing abundant clay, and thus is a potential hazardous area of ground subsidence. We analyzed mineral compositions and geotechnical properties of the clay sediments that sampled from 4 boreholes of the area, and examined vertical variations and their correlations. The results showed correlations between some mineral constituents and geotechnical properties of clay sediments. A positive correlation showed between quartz content and wet unit weight, whereas a negative correlation showed between quartz content and liquid limit. Feldspar content and water content showed a negative correlation, whereas content of clay minerals and liquid limit showed a positive correlation. And also, there is a negative correlation between content of clay minerals and wet unit weight. Correlation equations are obtained from the multiple regression analyses among plastic index, content of clay mineral, smectite and clay fraction.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.14-20
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• 2002

In order to improve the quality and sensory evaluation of Fermented Soybean(Chungkugjang meju) were investigated. The samples were prepared and fermented by the inoculation of Bacillus strains (B. subtilis, number 1, B. natto, number 2) that the product made With sanitary canned food. 1. The water content of samples was 46.75~50.60%, pH 5.35~6.95 and total acidity 3.26~3.62. 2. The reducing sugar of content for sample was 9.49~10.05%, Amino-N, 67~396mg% and the activity of protease was 0.36~1.49unit/g. 3. The heavy metals analyzed from sample cans, iron, tin and lead content of sample were 5.32~5.84ppm, 27.31~29.04ppm and 0.019~0.021ppm. 4. Therefore, results that Chungkugjang-meju manufactured from B. natto starter induced better product Quality and sensory test than that of the B. subtilis strain.

• The Journal of Engineering Geology
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• v.20 no.4
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• pp.415-424
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• 2010

A prototype of a Concrete-Faced Rock-fill Dam (CFRD) was constructed to evaluate the behavior of the materials in each zone within the dam. The tested materials, selected based on their grain size distribution, were used in constructing the prototype dam with layers of variable thickness, settlement ratio, and water content. We investigated the suitability of various values of hydraulic conductivity, water content, dry unit weight, and settlement ratio for zones within the dam. The test results revealed the relationships between the number of passes and the dry unit weight, between the dry unit weight and the settlement ratio, and between the settlement ratio and the number of passes. This paper focuses on the relationship between hydraulic conductivity and the number of passes. The results of the present analysis could be used to establish reasonable compaction standards for materials used in dam construction.

• Food Science and Preservation
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• v.31 no.3
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• pp.394-407
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• 2024

The poultry industry faces disposal difficulty in waste, but recent advancements in material science and sustainability have enabled the innovative transformation of waste into valuable resources. In this study, eggshell (EC) was added as a bio-filler to gum Arabic (GA) to fabricate a GA-EC bio-composite film. Bio-composites containing 0.5 g (GA-EC_0.5) and 1.0 g (GA-EC_1.0) EC dispersed in 30 mL of 15% GA solution were fabricated and characterized using standard analytical techniques. The GA-EC_0.5 composites showed significantly higher moisture content, transparency, water solubility, and water vapor permeability but lower tensile strength and thermal stability than GA-EC_1.0. Following a post-harvest wrapping of tomato fruits with the GA-EC composite films and storage at 25±2℃ for 20 days, significant (p>0.05) reductions in weight loss, pH, lycopene content, and activities of polyphenol oxidase and pectin methylesterase compared to unwrapped fruits were recorded. Adding EC to GA has enabled the fabrication of composite films with improved mechanical, barrier, and thermal properties with potential application in the post-harvest storage of tomato fruits.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.373-373
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• 2009

Relative humidity, membrane conductivity and water activity are critical parameters of polymer electrolyte membrane fuel cells (PEMFC) for high performance and reliability. These parameters are closely related with temperature. Moreover, the ideal values of these parameters are not always identical along the channels. Therefore, the cooling channel design and its operating condition should be well optimized along the all location of the channels. In the present study, we have performed a numerical investigation on the effects of cooling channels on performance of a PEMFC. Three-dimensional Navier-Stokes equations are solved with the energy equation including heat generated by the electrochemical reactions in the fuel cell. The present numerical model includes the gas diffusion layers (GDL) and serpentine channels for both anode and cathode gas flows, as well as cooling channels. To accurately predict the water transport across the membrane, the distribution of water content in the membrane is calculated by solving a nonlinear differential equation with a nonlinear coefficient, i.e., the water diffusivity which is a function of water content as well as temperature. Main emphasis is placed on the heat transfer between the solid bipolar plate and coolant flow. The present results show that local current density is affected by cooling channels due to the change of the oxygen concentration and the membrane conductivity as well as the water content. It is also found that the relative humidity is influenced by the generated water and the gas temperature and thus it affects the distribution of fuel concentration and the conductivity of the membrane, ultimately fuel cell performance. Unit-cell experiments are also carried out to validate the numerical models. The performance curves between the models and experiments show reasonable results.

• Journal of the Korea Institute of Building Construction
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• v.11 no.4
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• pp.371-378
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• 2011

Concrete is affected by various deterioration factors, such as $CO_2$ and chloride ions from the sea, which cause carbonation and salt attack on concrete. These deterioration phenomena cause steel corrosion in RC structures. Although a great deal of research has been carried out in this area thus far, it is difficult to know the point at which corrosion will occur to a reinforced bar. As the diffusion of deterioration factors depends on the water content in concrete, it is imperative to assess the condition of absorbed water content. A mass measuring method was applied to calculate the absorbed water diffusion coefficient, as well as non-linear finite element method(FEM) analysis. As a result, it was found that W/C and unit water content in concrete mixture affect the diffusion coefficient decision.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.585-593
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• 2021

This study investigates the compressive strength of high-strength cement composites with 64 mixture designs and 2 curing conditions. The cement composites were designed with varying water-to-binder ratios, silica fume content to cement, and binder content per unit volume of cement composite to explore compressive strength development depending on its mix design. An increase in the water-to-binder ratio decreased the compressive strength of the composites, having consistency with the trend in normal concrete. The compressive strength increased with ages at an ambient curing temperature, but it was not identified at high-temperature curing. The compressive strength development was negligible in case that silica fume content to OPC is 15%~25%, but a decrease in the con ten t below 15% reduced compressive stren gth. It was more obvious in the specimen of low water-to-binder ratio. The specimen with 840kg/m³ of binder content per unit volume had the highest compressive strength in this study, and the decrease in binder content reduced the compressive strength of high strength cement composites in low silica fume content.