• 한국환경과학회지
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• 제29권8호
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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).

• 상하수도학회지
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• 제21권5호
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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.

• 한국도로학회논문집
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• 제20권1호
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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.

• 대한기계학회논문집
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• 제19권9호
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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.

• 한국도로학회논문집
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• 제20권1호
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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).

• 한국전산구조공학회논문집
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• 제35권2호
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• pp.101-107
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• 2022

본 논문에서는 지오폴리머의 상변화를 관찰하기 위하여 나노인덴테이션 데이터를 가우시안 믹스쳐 모델로 분석하는 방법을 제시하였다. 지오폴리머는 일반 시멘트 대비 CO₂ 발생량을 줄일 수 있어 시멘트 대체 재료로써 많은 연구가 이루어지고 있다. 기존 연구들로부터 최적의 실리콘/알루미늄 비율을 찾았으나 1.8 초과에서 압축강도 저하의 원인은 아직 불분명하다. 본 연구에서는 실리콘/알루미늄 비율이 재료에 미치는 영향을 조사하고자 나노인덴테이션 실험을 수행하였다. 실험 결과를 가우시안 믹스쳐 모델로 상분석하였고, 실리콘/알루미늄 비율이 증가할수록 재료가 균질거동을 하는 것을 관찰할 수 있었다. 본 연구결과는 강도저하를 규명하는데 직접적인 근거로 활용될 수 있을 것으로 기대된다.

• 대한기계학회논문집
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• 제19권8호
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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....

• 한국수소및신에너지학회논문집
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• 제1권1호
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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 : $$-\frac{dP_{H{_2}}}{dt}=1.6909{\times}10^2\exp(-17560/RT)(P{_{H_2}}_{-P_{eq}})$$.

• 한국의류학회지
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• 제32권9호
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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.

• 콘크리트학회논문집
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• 제19권3호
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• pp.377-383
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• 2007

최근 콘크리트의 품질과 구조물의 신뢰성을 향상시키기 위해서 고성능콘크리트의 현장 적용이 늘고 있다. 이러한 고성능콘크리트의 배합 설계 방법으로는 모르타르-굵은골재 2상계 배합 이론과 페이스트-골재 2상계 배합 이론이 있다. 이 중 모르타르-굵은골재 2상계 배합이론은 모르타르의 레올로지 특성을 부여함에 있어 반복적인 실험을 통해서 그 값을 결정해야 하는 문제점을 가지고 있다. 페이스트-골재 2상계 배합 이론은 최적 잔골재율과 단위결합재량과의 관계 및 콘크리트의 충전성을 확보할 수 있는 한계 골재 용적비 등이 고려되어 있지 않아 고성능콘크리트에의 적용 예가 없는 실정이다. 또한 이들 고성능콘크리트의 배합 설계 이론은 일반콘크리트와는 달리 유동성 및 충전성에 중점을 두고 있어 배합 설계에서 강도 특성을 고려하지 않고 있으며, 사용 재료의 단위량은 일반콘크리트와 같이 시행착오법으로 결정하고 있다. 이에 본 연구에서는 고성능콘크리트의 배합 설계에 최대 밀도 이론을 도입하여 사용 골재의 공극이 최소가 되는 최적 잔골재율 산정으로 배합 설계 시 시행착오를 줄이고, 강도를 고려한 최소 단위 결합재량의 결정으로 강도와 유동성을 동시에 만족할 수 있는 합리적이며 간편한 고성능콘크리트의 배합 설계법을 제안하고자 하였다. 연구 결과 본 연구에서 제안된 배합 설계법은 최소 공극을 갖는 최적 잔골재율 사용과 최소 단위 결합재량 이상의 결합재를 사용함으로써 시행착오를 줄일 수 있어 자기충전성을 갖는 고성능콘크리트를 간편하게 제조할 수 있다.