• Journal of Korean Society of Environmental Engineers
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• v.37 no.11
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• pp.642-648
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• 2015

Oak wood based activated carbon was modified with surface impregnation of $Fe^{3+}$ and $Al^{3+}$ metal ions mixture for enhancements of phosphate adsorption capacity in aqueous solution. The phosphate adsorption capacity of the prepared metal impregnated carbon (MC) was about 8 times higher than that of the original activated carbon (OC). Adsorption equilibrium capacities of the phosphate increased with increasing system temperature. The adsorption equilibrium isotherm of phosphate on the prepared MC could be represented by the Langmuir equation. Thermodynamic parameters also indicated that adsorption system was spontaneous and endothermic reaction. The internal diffusion coefficient was measured to analyze the adsorption behavior and kinetic rate. To determine the internal diffusion coefficient, pore diffusion model (PDM) was employed and the result was in good agreement with experimental data.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.311-317
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• 2015

Cement zero concrete produced by alkali-activators and industrial by-products such as slag instead of cement, enables to solve the environmental pollution problems provoked by the exhaustion of natural resources and energy as well as the discharge of carbon dioxide. However, researches on the cement zero concrete are still limited to material studies and thus, study on the structural behavior of relevant members is essential to use the cement zero concrete as structural materials. This paper aims to evaluate experimentally and analytically the flexural behavior of RC beams using 50 MPa alkali activated slag concrete. To achieve such a goal, flexural tests on three types of RC beam specimens were conducted. A nonlinear analysis model is proposed using the modulus of elasticity and stress-strain relationship of alkali activated slag concrete. The analysis results obtained by the proposed model agree well with the experimental results, which could verify the validity of the proposed model.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.58-63
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• 2015

Several researches on cement zero concrete using alkali-activators have been conducted to investigate its fundamental material properties such as slump, strength and durability, however, research on the structural behavior of relevant members involving the elastic modulus, stress-strain relationship is essential for the application of this cement zero concrete to structural members. In this paper the shear behavior of reinforced concrete beams using 50 MPa-alkali activated slag concrete was experimentally evaluated. To achieve such a goal, six reinforced concrete beam specimens were fabricated and their shear behaviors were observed. The maximum difference between test results and analysis results in crack shear stress for beam specimens without stirrups is 31%, while that for beam specimens with stirrup is 15%. Furthermore, it is also found that the shear strength of alkali activated slag concrete is by 22~57% greater than the nominal shear strength calculated by design code, implying that shear design equations would provide conservative results on the safety side.

• Journal of the Korea Organic Resources Recycling Association
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• v.7 no.2
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• pp.73-82
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• 1999

To verify the usefulness of enzyme activity as a index for the stability or maturity of apple pomace composting. the succession of microbial populations using viable count procedure. and Vmax of ${\beta}$-glucosidase and cellobiohydrolase were measured. based on an increase in fluorescence as the nonfluorescent methylumbelliferyl substrates were enzymatically hydrolyzed, leading to the highly fluorescent methylumbelliferyl molecule 4-methylumbelliferone(MUF). The activities of these enzymes in the decomposition of carbohydrates were gradually decreased in the course of the time. Correlation between microbial population and enzyme activity was not significant with exception of fungi. and the fungi were represented in high density. This indicates that the fungi probably play a major role in composting of apple pomace.

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.170-176
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• 2014

This study examined the effect of chemical attack on the stress-strain relationship of alkali-activated Hwangtoh concrete. Water-to-binder ratio and air content were selected as mixture parameters. The stress-strain relationship of concrete was measured at chemical immersion times of 0, 7, 28, 56, and 91 days from an age of 28 days. Based on the test results, the reduction in compressive strength of alkali-activated hwangtoh concrete owing to chemical attack was formulated. In sddition the present study demonstrated that the stress-strain behavior of concrete under chemical attack is significantly dependent on the air content and chemical immersion time, indicating the rate of decrease of modulus of elasticity was greater than that of compressive strength at the same immersion time. As a result, the stress-strain behavior of concrete under chemical attack was significantly inconsistent with the conventional models specified in the CEB-FIP provision.

• Analytical Science and Technology
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• v.22 no.4
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• pp.307-312
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• 2009

A spectrofluorimetric methods has been developed for the determination of carbaryl in an aqueous solution. The effects of excitation wavelength, concentration of surfactant, concentration of ethanol as cosurfactant and emission wavelength on the fluorescence intensity were investigated to find the optimum experimental conditions to determine carbaryl. The emission intensity of the carbayl was increased with addition of sodium dodecyl sulfate (SDS) as a surfactant. The emission intensity of the carbaryl was further increased with addition of ethanol as a co-surfactant. The optimum conditions were 281 nm for excitation wavelength, $1.0{\times}10^{-2}mol/L$ SDS, 20% (v/v) ethanol and 349 nm for emission wavelength. Under the optimum conditions, the emission intensity increased with the carbaryl concentration in the range of $5{\times}10^{-7}$ to $1.0{\times}10^{-4}mol/L$ with a detection limit ($3{\sigma}$) of $1.1{\times}10^{-8}mol/L$. The resulting correlation coefficient of the working curve was 0.9996.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1270-1276
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• 2005

When gas/particle partitioning of PAHs in the atmosphere approached an equilibrium state, the slope of linear regression between gas/particle partitioning coefficient($logK_p$) and subcooled liquid vapour pressure($logP_L^O$) was -1. But it was alleged that the slope of equilibrium state might not be -1 in real atmospheric environment due to heterogeneous characteristics of particulate matter. In This study, it would be found if gas/particle partitioning of PAHs segregated with particle size in equilibrium state was based on the hypothesis mentioned above. We have calculated the slopes of $logK_p$ v.s. $logP_L^O$ after collecting 10 set samples which consisted of particulate and vaporous phases. The slope was close to -1 in equilibrium states. But despite of equilibrium state, all slopes segregated with particle size were not close to -1 and those were gentler with larger particle size. The difference of slopes in equilibrium states was almost against the assumption of gas/particle partitioning theory. When the gas/particle partitioning was due to adsorption, the desorption enthalpy was different in each particle size. When it was absorption, the activity coefficient was different. The difference of desorption enthalpy and activity coefficient in each particle size indicate the heterogeneous characteristics of the bulk particle. This may be the reason for slope variation with particle size even though in an equilibrium state.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.193-201
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• 2000

Partitioning of hydrophobic organic compounds (HOCs) to a biosurfactant, hydroxypropyl-${\beta}$-cyclodextrin (HPCD), was conducted to evaluate the feasibility of using HPCD to remove HOCs from soil/groundwater. HOC partitioning to HPCD was very fast, with over 95% of the complexation occurring within 10 min. Some influence of solution chemistry and HOC concentration on HOC-HPCD complex formation coefficients was observed. HPCD sorption on soil as quantified by both a fluorescence technique and total organic carbon measurements was negligible, indicating no significant affinity of HPCD for the solid phase. Although the HOC solubilization capability of HPCD was lower than that of synthetic surfactants such as SDS and Tween 80, HPCD can be effective in removing sorbed HOCs from a model subsurface environment, primarily because of its negligible sorption to the solid phase (i.e., all the HPCD added facilitates HOC elution). However, in contrast with conventional surfactants, HPCD becomes relatively less effective for HOC partitioning with increasing HOC size and hydrophobicity. Therefore, comparisons between HPCD and synthetic surfactants for enhanced remediation applications must consider the specific HOC(s) present and the potential for surfactant material losses to the solid phase, as well as other more generally recognized considerations such as material costs and potential toxicological effects.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.88-96
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• 2006

Among the various methods for minimization of waste activated sludge, maintaining a low F/M ratio in the bioreactor is known to be the most effective reliable one. In this research, various experiments were performed to check the capability of the nonwoven fabric filter bioreactor, which has been proved able to maintain a low F/M ratio by maintaining a high MLSS concentration, for excess sludge minimization. The reactor was intermittently fed with a synthetic wastewater having a COD concentration of approximately 300 mg/L and no SS. Results of the experiments showed that the F/M ratio in the reactor decreased to a minimum value of 0.02 g COD/g MLSS-day as the MLSS concentration increased to a maximum value of 31,010 mg/L. However, the measured endogenous decay coefficients and oxygen uptake rates of the MLSS confirmed that the activity of the MLSS decreased as the MLSS concentration increased. Based on the increase of MLSS in the reactor and the mass balance during the whole experimental period, the average microorganism yield coefficients were computed to be low values of 0.148 and 0.139 g MLSS/g COD, respectively. These results indicate that the nonwoven fabric filter bioreactor employed in this research is effective for minimization of excess sludge production.

• The Journal of the Korea Contents Association
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• v.21 no.3
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• pp.616-625
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• 2021

Deep neural networks are an approximation method that approximates an arbitrary function to a linear model and then repeats additional approximation using a nonlinear active function. In this process, the method of evaluating the performance of approximation uses the loss function. Existing in-depth learning methods implement approximation that takes into account loss functions in the linear approximation process, but non-linear approximation phases that use active functions use non-linear transformation that is not related to reduction of loss functions of loss. This study proposes parametric activation functions that introduce scale parameters that can change the scale of activation functions and location parameters that can change the location of activation functions. By introducing parametric activation functions based on scale and location parameters, the performance of nonlinear approximation using activation functions can be improved. The scale and location parameters in each hidden layer can improve the performance of the deep neural network by determining parameters that minimize the loss function value through the learning process using the primary differential coefficient of the loss function for the parameters in the backpropagation. Through MNIST classification problems and XOR problems, parametric activation functions have been found to have superior performance over existing activation functions.