• Journal of Environmental Science International
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• v.29 no.8
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• pp.793-800
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• 2020

The conventional development of multi-component electrodes is based on the researcher's experience and is based on trial and error. Therefore, there is a need for a scientific method to reduce the time and economic losses thereof and systematize the mixing of electrode components. In this study, we use design of mixture experiments (DOME)- in particular a simplex lattice design with Design Expert^Ⓡ program- to attempt to find an optimum mixing ratio for a three-component electrode for the high RNO degradation; RNO is an indictor of OH radical formation. The experiment included 12 experimental points with 2 center replicates for 3 different independent variables (with the molar ratio of Ru, Ti, Ir). As the Prob > F value of the 'Quadratic' model is 0.0026, the secondary model was found to be suitable. Applying the molar ratio of the electrode components to the corrected response model results is an RNO removal efficiency (%) = 59.89 × [Ru] + 9.78 × [Ti] + 67.03 × [Ir] + 66.38 × [Ru] × [Ir] + 132.86 × [Ti] × [Ir]. The R² value of the equation is 0.9374 after the error term is excluded. The optimized formulation of the ternary electrode for an high RNO degradation was acquired when the molar ratio of Ru 0.100, Ti 0.200, Ir 0.700 (desirability d value, 1).

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.641-647
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• 2007

This study aims to find out optimum condition for hydrogen production and organic removal when treating food and swine wastewater together. For this purpose, various batch tests were conducted by changing mixture ratio from 6:4 (food wastewater:swine wastewater) to 1:9 without pretreatment process. For hydrogen production through anaerobic fermentation, the mixture ratios of R-1 (6:4), R-2 (5:5) and R-6 (1:9) were out of pH range appropriate for hydrogen production and mixture ratios of R-3 (4:6), R-4 (3:7), and R-5(2:8) showed appropriate hydrogen production where their pH ranges were 5.1~5.5. Especially in case of R-3, it consistently maintained appropriate pH range for hydrogen production for 72hr and produced maximum hydrogen. The characteristics of hydrogen production and cumulative hydrogen production according to each mixture ratio showed that R-1, R-2 and R-6 did not produce any hydrogen, and maximum hydrogen productions of R-3, R-4 and R-5 were 593ml, 419ml and 90ml, respectively. Total cumulative hydrogen productions of R-3, R-4 and R-5 were 1690ml, 425ml and 96ml, respectively. Based on previous results, it was concluded that, the most appropriate mixture ratio of food wastewater and swine wastewate rwas 4:6 (R-3). The experiment for COD removal rate to evaluate organic removal efficiency revealed that R-3, R-4 and R-5 showed high removal efficiencies during the highest hydrogen production amount and the highest efficiency was 41% with R-3.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.27-33
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• 2018

PURPOSES : The purpose of this study is to estimate the optimum content of an inorganic additive for cold-recycled asphalt mixtures and evaluate its performance. METHODS : An indirect tensile test, a tensile-strength ratio test, and an indirect tensile-fatigue test were conducted on cold-recycling asphalt mixtures with various additives. RESULTS : The laboratory performance tests indicated that granulated blast-furnace slag mixed with inorganic and cement activators provided optimum performance. The performance results of the cold-recycled asphalt pavement were similar to the inorganic and cement activators' performance in terms of the indirect tensile strength, tensile strength ratio, and indirect tensile-fatigue test. CONCLUSIONS : Overall, the performance of a cold-recycled asphalt mixture using inorganic additives and emulsion asphalt was comparable to a warm-recycled asphalt mixture. However, more experiments aimed at improving its performance and studying the effect of the inorganic additives must be conducted.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2308-2315
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• 1995

We studied the effects on the ignitability of mixture, the combustion duration, and the maximum combustion pressure, of various initial combustion factors such as temperature, pressure, and each equivalence ratio in order to identify the combustion characteristics of lean mixture and improve ignitability through the proper control of the ignition energy. It is concluded that there is an optimum turbulent intensity that enables the combustion to have the best ignitability and the shortest duration under each equivalent ratio, and the combustion duration is only dependent upon the distribution and magnitude of discharge energy within the limit of inflammability.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.69-76
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• 2018

PURPOSES : This study determined the optimal usage rate of RAP (reclaimed asphalt pavement) using cold central-plant recycling (CCPR) on a road-surface layer. In addition, a mixture-aggregate gradation design and a curing method based on the proposed rate for the surface-layer mix design were proposed. METHODS : First, current research trends were investigated by analyzing the optimum moisture content, mix design, and quality standards for surface layers in Korea and abroad. To analyze the aggregate characteristics of the RAP, its aggregate-size characteristics were analyzed through the combustion asphalt content test and the aggregate sieve analysis test. Moreover, aggregate-segregation experiments were performed to examine the possibility of RAP aggregate segregation from field compaction and vehicle traffic. After confirming the RAP quality standards, coarse aggregate and fine aggregate, aggregate-gradation design and quality tests were conducted for mixtures with 40% and 50% RAP usage. The optimum moisture content of the surface-layer mixture containing RAP was tested, as was the evapotranspiration effect on the surface-layer mixture of the optimum moisture content. RESULTS : After analyzing the RAP recycled aggregate size and extraction aggregate size, 13-8mm aggregate was found to be mostly 8mm aggregate after combustion. After using surface-chipping and mixing methods to examine the possibility of RAP aggregate segregation, it was found that the mixing method contributed very little for 3.32%, and because the surface-chipping method applied compaction energy directly as the maximum assumption the separation ratio was 15.46%. However, the composite aggregate gradation did not change. Using a 40% RAP aggregate rate on the surface-layer mixture for cold central-plant recycling satisfied the Abroad quality standard. The optimum moisture content of the surface-layer mixture was found to be 7.9% using the modified Marshall compaction test. It was found that the mixture was over 90% cured after curing at $60^{\circ}C$ for two days. CONCLUSIONS : To use the cold central-plant recycling mixture on a road-surface layer, a mixture-aggregate gradation design was proposed as the RAP recycled aggregate size without considering aggregate segregation, and the RAP optimal usage rate was 40%. In addition, the modified Marshall compaction test was used to determine the optimum moisture content as a mix-design parameter, and the curing method was adapted using the method recommended by Asphalt Recycling & Reclaiming Association (ARRA).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.101-107
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• 2022

This study proposes the deconvolution method for the nanoindentation test results of geopolymer employing the Gaussian mixture model. Geopolymer has been studied extensively as an alternative construction material because it emits relatively lower CO₂ compared to ordinary Portland cement. Geopolymer is made of aluminosilicate and alkaline solution, and the Si/Al molar ratio affects its mechanical properties. Previous studies revealed that the Si/Al molar ratio of 1.8~2.0 results in the highest compressive strength, and the Si/Al molar ratio over 1.8 degrades the compressive strength of geopolymer severely; however the reason for the compressive strength degradation is still unclear. To understand the effect of the Si/Al molar ratio on the geopolymer structure, this study exploits the nanoindentation. The phase deconvolution of the indent modulus data is successful using the Gaussian mixture model, and it is observed that the Si/Al molar ratio alters the homogeneity of the geopolymer. Geopolymer becomes more homogeneous up to an Si/Al molar ratio of 1.8 at which geopolymer exhibits the highest compressive strength. The examination of this study is assumed to be adopted as evidence of strength degradation by the Si/Al ratio higher than the optimum value.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.2022-2029
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• 1995

The experiment was performed by using the condenser discharge ignition device in a constant volume combustion chamber for high pressure, equivalent to the TDC of spark ignition engine, which makes the forced turbulent field possible. The conclusions obtained under various initial pressures, initial temperatures, and turbulent conditions of the methanol-air mixture are as follows : As initial pressure, initial temperature of the mixture, and the ignition energy increase, the inflammability limit expands, but the lean inflammability limit decreases as turbulence intensity increases. Combustion duration is shorter in the case of the lower initial pressure, the higher initial temperature, an equivalence ratio of 1.1-1.2, and even though turbulence intensity increases up to optimum value. Maximum combustion pressure increases in turbulent ambience under the same mixture condition, only in the case each optimum turbulence intensity exists under every condition. As the turbulence intensity increases .tau.$_{10}$ proportion increases while the .tau.$_{pr}$ proportion decreases....

• Transactions of the Korean hydrogen and new energy society
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• v.1 no.1
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• pp.15-23
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• 1989

The selective separation of hydrogen from gas mixture containing hydrogen was experimentally studied using $LaNi_5$. The capacity and the rate of hydrogen separation, the purity of recovered hydrogen and the optimum condition of the regeneration of deactivated $LaNi_5$ were investigated. The separation rate and the recovery ratio of hydrogen were slowly decreased with the increase of the number of hydrogen absorption cycle. It was found that this result comes from the deactivation of $LaNi_5$ partly because of the blocking of hydrocarbon compounds in the $LaNi_5$ lattice and partly because of the poisoning of $LaNi_5$ surface by carbon monoxide contained in the gas mixture. The optimum condition for the regeneration of deactivated $LaNi_5$ was obtained by heating in a vacuum to about 637 K. The recovery ratio of hydrogen at the optimum condition was observed to be about 80%. The rates of hydrogen separation were measured in the ${\alpha}$-phase and two phase regions. The rate equations could be expressed as follows ; ${\alpha}$ - phase : $$-\frac{dP{_{H_2}}}{dt}=9.836{\times}10^{-3}(P{_{H_2}}_{-P_{eq}})$$ two phase region : $$-\frac{dP_{H{_2}}}{dt}=1.6909{\times}10^2\exp(-17560/RT)(P{_{H_2}}_{-P_{eq}})$$.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.9
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• pp.1461-1466
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• 2008

This study provides effects of mixed activators on enzymatic activation and determines optimum mixture ratio for enzymatic treatment. Wool 80% and polyester 20% blend fabric and papain from carica papaya are used in this experiment. L-cysteine and sodium sulfite are used as activators for papain treatment process. The treatment condition is pH 7.5, $70^{\circ}$, papain concentration 10%(o.w.f), 60 minutes. L-cysteine and sodium sulfite are added in enzyme solution with various concentrations($0{\sim}50mM$). The optimum treatment condition is determined by measuring weight loss, tensile strength, whiteness, water contact angle(WCA), dyeability and surface micrographs. The results are as follow; The optimum mixture ratio of activators is L-cysteine 2mM and sodium sulfite 10mM. Mixed activators assists in improving the activation of papain. WCA of papain treated fabrics is decreased since papain treatment with activator mixture makes wool polyester blend fabrics more hydrophilic. Dyeing property of papain-treated fabrics more improves by the treatment with mixed activators than with single activator. It means that this method can save time and lower cost. After papain treatment in the presence of mixed activator, the surface of fabrics is modified. The surface of wool fiber shows to be descaled and hydrolyzed, and that of polyester fiber shows to be cracked.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.377-383
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• 2007

In recent years the field application of high performance concrete has been increased to improve the quality and reliability of concrete structures. The mix design of the high performance concrete includes the 2 set-off mixture theory of mortar and coarse aggregate and that of paste and aggregate. The 2 set-off mixture theory of mortar and coarse aggregate has a problem of having to determine its value through repeated experiments in applying the rheological characteristics of mortar. The 2 set-off mixture theory of paste and aggregate has never been applied to high performance concrete since it doesn't take into account the relationship between optimum fine aggregate ratio and unit volume of powder nor does it consider the critical aggregate volume ratio. As the mixture theory of these high performance concretes, unlike that of general concrete, focuses on flowability and charge-ability, it does not consider intensity features in mix design also, the unit quantity of the materials used is determined by trial and error method in the same way as general concrete. This study is designed to reduce the frequency of trial and error by accurately calculating the optimum fine aggregate ratio, which makes it possible to minimize the aperture of aggregate in use by introducing the maximum density theory to the mix design of high performance concrete. Also, it is intended to propose a simple and reasonable mix design for high performance concrete meeting the requirements for both intensity and flowability. The mix design proposed in this study may reduce trial and error and conveniently produce high performance concrete which has self-chargeability by using more than the minimum unit volume of powder and optimum fine aggregate with minimum porosity.