• 대한인간공학회지
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• 제30권6호
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• pp.757-764
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• 2011

Objective: The aim of this study was to provide a method to improve the compliance and reduce the time by reducing the workload during the model change work. Background: The enterprises are constructing the small quantity batch production system by increasing the number of model change and reducing model-changing. However, the compliance is low because the work is strenuous and high skills are needed, so the system management is facing with many difficulties. Method: After classifying the model change work according to the purposes(preparation, change and adjustment) with the target of mascara filling machine, element tasks time were measured and the motion analysis(therblig symbol) and REBA analysis were performed. The study incorporated 3 independent variables as the number of motion, REBA score and the element time. The dependent variable is the type of element work as preparation, change and adjustment. The statistical test was performed by one-way ANOVA(${\alpha}$ < 0.05). Results: For the preparation, the number of motions appeared in the order of Use(U), Transport Loaded(TL), and Position(P). The order appeared in change is Use(U), Release Load(RL), and Grasp (G). The adjustment appeared in the order of Position(P) and Use(U). The results of average motion time as the element work times divided by the number of motion appeared in the order of adjustment(1.85sec/motion), preparation(1.11sec/motion), and change(0.62sec/motion). The results of REBA showed that the average risk level of change and adjustment were medium, but 53.1% of change and 42.9% of adjustment were evaluated as high. Conclusion: Reducing the avoidance and improving the compliance of work could be expected if the job autonomy were improved by improving the working postures with high risk level. Application: It is expected to solve the problem of reducing the time of model change work in the small quantity batch production system. The future work is to carry out the improvement directions found in the results and compare the results after improvement.

• Membrane and Water Treatment
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• 제9권4호
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• pp.255-262
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• 2018

This study attempted to evaluate the process of self-forming dynamic membrane formation on mesh filter in membrane bioreactor with a two-stage method of batch (agitation) and continues (aeration) stage at different sludge concentrations. Four concentrations of activated sludge including $6{\pm}0.4$, $8{\pm}0.5$, $10{\pm}0.3$, $14{\pm}0.3g/L$ were used to demonstrate the optimal concentration of sludge for treating municipal wastewater and reducing fouling in dynamic membrane bioreactor. The formation time and effluent turbidity were decreased in the batch stage when increasing the activated sludge concentration. The minimum values of formation time and effluent turbidity were 14 min and 43 NTU for the optimum mixed liqueur suspended solids of $8{\pm}0.5g/L$, respectively. To improve operational condition and fouling reduction in the aeration stage, critical fluxes were measured for all concentrations by flux-step method. With increasing the sludge concentration, the relevant critical fluxes reduced. The optimum subcritical flux of $30L/m^2/h$ was applied as operating flux in the second stage. The maximum COD removal efficiency of 98% was achieved by the concentration of $8{\pm}0.5g/L$. Compressibility index of self-forming dynamic membrane and transmembrane pressure trend remained somewhat constant until the optimal concentration of $8{\pm}0.5g/L$ and thereafter they increased steeply.

• 한국광물학회지
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• 제22권4호
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• pp.289-295
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• 2009

카올리나이트 KGa-1b (표준 점토)의 인산염 탈착 특성을 규명하기 위하여 벳치(batch) 흡착-탈착 실험을 실시하였으며, 탈착 과정은 연속추출법에 따라 pH 4에서 시행하였다. 인의 함량은 UV 분광분석기를 시용하여 측정하였으며, 이 때 파장은 820 nm를 이용하였다. 카올리나이트의 인산염 흡착-탈착 반응은 비가역적으로 일어나며, 흡착된 대부분의 인산염은 고착되는 경향을 나타낸다. 인산염 탈착 등온선은 반응 시간이 짧은 경우 프로인드리히 등온선에, 반응 시간이 긴 경우 탬킨 등온선에 더 일치하는 경향을 보인다. 인산염 탈착 반응은 초기의 빠른 반응과, 후기의 느린 반응으로 구분된다. 흡착된 인산염의 농도가 높아질수록 탈착률은 감소하는 경향을 보이며, 탈착 시간이 길어지면 탈착률은 감소하는 경향을 보여준다.

• 한국초전도ㆍ저온공학회논문지
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• 제21권2호
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• pp.40-44
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• 2019

In this study, the effects of the compaction method for (Mg+2B) powders on the apparent density and superconducting properties of $MgB_2$ bulk superconductor were investigated. The raw powders used in this study were nano-sized boron (B) and spherical magnesium (Mg). A batch of a powder mixture of (Mg+2B) was put in a steel mold and uniaxially pressed at 1 ton or 3 tons into pellets. Another batch of the powder mixture was uniaxially pressed at 1 ton and then pressed isostatically at $1800kg/cm^2$ in the water chamber. All pellets were heat-treated at $650^{\circ}C$ for 1 h in flowing argon gas for the formation of $MgB_2$. The apparent density of powder compacts pressed at 3 ton was higher than that at 1 ton. The cold isostatic pressing (CIP) in a water chamber allowed further increase of the apparent density of powder compacts, which influenced the pellet density of the final products ($MgB_2$). The compaction methods (uniaxial pressing and CIP) did not affect the formation of $MgB_2$ and superconducting critical temperature ($T_c$) of $MgB_2$, but affected the critical current density ($J_c$) of $MgB_2$ significantly. The sample with the high apparent density showed high $J_c$ at 5 K and 20 K at applied magnetic fields (0-5 T).

• 디지털융복합연구
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• 제17권9호
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• pp.127-133
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• 2019

임의상환가능 상품은 옵션을 이용하여 수요창출과 리스크를 줄이는 서비스 파생상품의 일종이다. 본 논문은 임의상환가능 상품이 도입된 후, 예약 요청의 온라인승인 방법과 일괄승인 방법 둘의 성능을 비교한다. 최적의 예약관리법을 계산하기 위하여, 역행 동적계획법(Backward Dynamic Programming)과 확률적 최적화(Stochastic Optimization) 방법을 이용한다. 직관적으로는 공급자는 수요정보를 이용하여 일괄승인 방법으로 더 높은 수익을 올릴 것으로 예상되지만, 본 논문은 두 예약 요청 승인 방법의 예약관리전략과 수익은 동일하다는 것을 증명함으로써, 현행 예약 요청 승인 방법의 변화 없이 임의상환가능 상품을 빠르게 도입할 수 있다는 실무적인 기여도가 있다. 본 논문은 세 종류의 서비스 요금 클래스가 있을 경우 최적의 해를 정확히 구하였다. 향후 연구는 다양한 요금 모델에서 최적의 해를 구하는 것이다.

• 한국물환경학회지
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• 제36권6호
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• pp.500-507
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• 2020

This study examined the wastewater at a livestock farm, and found that the dairy wastewater from the milking parlor had a lower concentration than the piggery wastewater, and that it was produced at a rate under 1.3 ㎥/day in a single farmhouse. The amount of dairy wastewater was determined based on the performance of the milking machine, the maintenance method of the milking parlor, and the amount of milk production allocated for each farmhouse, not by the area. The results confirmed that both dairy wastewater treatment processes, specifically those using Hanged Bio-Compactor (HBC) and Sequencing Batch Reactor (SBR), can fully satisfy the water quality standards of discharge. The dairy wastewater has a lower amount and concentration than piggery wastewater, meaning it is less valuable as liquid fertilizer, but it can be easily degraded using the conventional activated sludge process in a public sewage treatment plant. Therefore, discharging the dairy wastewater after individual treatment was expected to be a more reasonable method than consigning it to the centralized wastewater treatment plant. The effluent after the SBR process showed a lower degree of color than the HBC effluent, which was attributed to biological adsorption. In the case of the milking parlor in the livestock farm, the concentrations of the effluents obtained after HBC and SBR treatments both satisfied water quality standards for the discharge of public livestock wastewater treatment plants at 99% confidence intervals, and the concentrations of total nitrogen and phosphorous in untreated wastewater were even lower than the water quality standards of discharge. Therefore, we need to discuss strengthening the water quality standards to reduce environmental pollution.

• 한국가스학회지
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• 제24권3호
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• pp.33-39
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• 2020

일반적으로 인화성 액체를 사용하여 제품을 만들어 내는 회분식 반응 공정에서는 작업 후 반응기 세척(Cleaning) 시 제품 생산을 위해 사용되는 원료인 인화성 액체를 일정압력으로 분사하여 반응기 벽면 등을 세척하는 스플래쉬 필링(Splash Filling) 형태의 작업 방법을 적용한다. 이러한 작업과정에서 인화성 액체의 미스트 등이 발생하여 폭발하한계가 낮아지며 유동대전, 충돌대전, 분출대전과 같이 여러 형태의 복합 대전에 따른 방전현상으로 화재·폭발이 발생할 수 있다. 따라서 최근의 사고사례를 바탕으로 회분식 공정에서 톨루엔을 통한 스플래쉬 필링(Splash Filling) 형태의 작업 시 위험성을 파악하고 당량법을 이용한 폭발영향분석을 수행하여 사고결과를 분석하여 이러한 사고를 예방하기 위한 상시적 불활성화, 세척 방법 개선, 탄탈럼 사용 등의 예방대책을 제시하고자 한다.

• 한국지반환경공학회 논문집
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• 제9권3호
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• pp.35-43
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• 2008

본 연구는 소규모 하수고도처리시설에 대해 변형 연속회분식공정을 적용하여 그 효용성을 평가하였다. 변형 연속회분식공정은 단일 반응조 내에서 유기물질 및 질소, 인 등이 제거되며 유입수의 유량 및 수질특성에 의해 적합한 운전방식을 선택할 수 있다. 각 공정의 기능 향상을 위해 원수 유입조건의 제어, 간헐 폭기방식에 의한 무산소 및 호기조건의 적절한 분배 그리고 처리수와 잉여슬러지의 고액분리를 위한 처리수 배출장치의 적용으로 설계된 유량 및 수질에 비해 낮은 부하 조건임에도 1일 3Cycle 운전모드로써 안정적인 처리효율을 나타냈다. 평가결과 유기물질 제거효율은 BOD의 경우 평균 120.4mg/L에서 6.8mg/L로 94.4%, CODMn은 95.7mg/L에서 11.0mg/L로 88.5%의 처리효율을 나타냈다. T-N의 제거효율은 평균 32.2mg/L의 유입수 농도에 대해서 약 69.6%, T-P의 경우는 유입수 농도 4.65mg/L에 대해 73.6%의 처리효율을 나타냈다. 동절기 평균 T-N과 T- P의 처리효율은 58.8%, 68.5%로 약간 감소하였지만 안정적인 처리효율을 나타냈다. 1차 무산소 호기조건에서 BOD는 90%, T-N은 67% T-P는 46%정도로 제거되었으며 T-P는 2차 무산소 호기조건에서 약 70%정도 제거되었다. 따라서 유입수의 간헐유입과 무산소 호기조건의 적정한 분배에 의해 질산화, 탈질 및 인의 과잉섭취에 유기물이 적절히 이용된 것으로 평가되어 소규모 고도하수처리시설에 적합한 공정으로 판단된다.

• 열처리공학회지
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• 제15권1호
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• pp.16-20
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• 2002

In conventional metallothermic reduction(MR) for obtaining tantalum powder in batch-type operation, it is difficult to control morphology and location of deposits because the reaction occurs by direct physical contact between reductants and feed materials. On the other hand, a electronically mediated reaction(EMR) is capable to overcome these difficulties through the reaction by electron transfer and have a merit of continuous process. In this study an MR and EMR method has been applied to the production of a tantalum powder by sodium reduction of $K_2TaF_7$. As the reduction temperature increases, the particle size and yield of tantalum powder obtained by MR and EMR method is increased.

• 한국염색가공학회지
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• 제17권1호
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• pp.14-19
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• 2005

Study on the use of enzymes for textile wet processing has been very active. The exploratory research conducted herein is related to the bioscouring process for cotton fabric. The optimum concentration of alkaline pectinase(BioPrep) was in the range of 0.05～0.2 g/l, the proper treatment time was 30～60 minutes, the appropriate treatment temperature was $60^{\circ}C$ for both the batch method and the padding method. The simultaneous desizing/bioscouring by padding method did not give water absorbency as good as the bioscouring after desizing. Color of fabrics which were bioscoured and dyed with direct dyes and a reactive dye was just a little darker than that of NaOH scoured one. K/S and Lab values of the bioscoured fabrics, regardless of the degree of water absorbency, were quite similar to each other.