• 상하수도학회지
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• 제35권4호
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• pp.277-284
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• 2021

The ballasted flocculation effects of the mill scale and magnetite on activated sludge were investigated. Both ballasted flocculants (BF) could remarkably improve the sludge settleability in terms of zone settling velocity (ZSV) and sludge volume index (SVI). With the BF dosage of 0.2 to 2.0 g-BF/g-SS, the magnetite particles showed better efficiency on improving settling behavior of activated sludge than the mill scale due to higher surface area and hydrophobic property. The efficiency of SVI₃₀ with magnetite injection was 2.5 to 11.3% higher than mill scale injection and that of the ZSV appreciated from 23.7% to 44.4% for magnetite injection. Averaged floc size of the BF sludge with magnetite dosage (0.5 g-BF/g-SS) was 2.3 times higher than that of the control sludge. Dewaterability of the sludge was also greatly improved by addition of the BF. The specific resistance to filtration (SRF) was reduced exponentially with increasing the dosage of BF. However, the BF's particle size effect on the SRF looks to be marginal. Consequently, for improving the dewaterability, the BF played a physical role to remove the pore water of the biological flocs by intrusive attachment and a chemical role to induce aggregation of the flocs by charge neutralization.

• Tribology and Lubricants
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• 제13권2호
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• pp.74-81
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• 1997

The purpose of this study is to develop a cold rolling oil with lubricity and mill cleanness property under the rolling conditions of high reduction ratio and high rolling speed. Six kinds of oil samples were blended. Evaluation of lubricity and anti-seizuro property of the samples were carried out with a laboratory scale rolling mill, where the contact conditions between work roll and strip are very close to actual cold rolling mill. Laboratory evaluation for dispersion, contamination, anti-oil stain property and residual carbon, etc. were carried out with several testers such as longterm circulation tester, Coulter counter and Conradson tester. A new high speed cold rolling oil with good lubricity and mill cleanness property was developed compared with the previously developed rolling oil.

• 한국세라믹학회지
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• 제24권1호
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• pp.1-8
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• 1987

The validity of Alyavdin-Chujyo's Equation was re-examined over the broader milling conditions that those previously examined. Ordinary ball mill grinding with a laboratory scale batch mill (133mmø×144mm length) were selected as the grinding methods. The results show that in ball milling the Alyavdin-Chunjyo's Equation can be applicable over wide grinding time and size range with few exceptions. The validity of which are examined and discussed. The theoretical consideration of the relation between Alyavdin-Chujyo's Equation and size distributiion equation, such as Rosin-Rammler's law, was tried, and it is found that, under the condition of alyardin-Chujyo's relation, the Rosin-Rammler size distribution law can hold.

• 자원리싸이클링
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• 제16권5호
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• pp.25-30
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• 2007

건설폐기물 발생량이 매년 급격히 증가함에 따라 건설폐기물 처리의 중요성이 점차 심화되고 있으며, 그 중에서도 가장 많은 비중을 차지하고 있는 폐콘크리트의 처리에 가장 많은 노력을 기울이고 있다. 현재 폐콘크리트는 단순 파쇄를 통해 매움재나 채움재 등의 저급한 용도의 순환골재로 재활용되고 있다. 그러나 부족한 구조용 골재 수급문제를 해결하고 자원의 효율적인 활용을 위해서, 천연골재를 대체하여 구조용 골재로 사용될 수 있는 고품질의 순환골재 생산이 절실히 요구되고 있다. 따라서 본 연구에서는 autogenous mill과 가열처리 방법을 이용하여 고품질 순환골재 생산 공정을 개발하였다. 개발된 공정을 이용하여 약 30분간 파분쇄과정을 통해 생산된 순환골재의 품질은 밀도 $2.5\;g/cm^3$이상, 흡수율 3% 이하로 KS F 2573의 1종 굵은 순환골재 품질 기준을 만족하였으며, 이를 바탕으로 고품질의 순환골재 생산을 위한 연속공정을 개발하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.115-118
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• 1997

Recently, hot rolling oil lubrication technology is required to face with the new environments such as the rapid introduction of high wear resistent high speed steel roll the development of continuous hot rolling technology. In the hot strip mill, according to rolling and quality required conditions are constrict, Roll material of hot rolling finishing stand is changing Hi-Cr Roll to High Speed Steel [HSS] Roll. The problem of HSS Roll of roll force and strip scale defects are increasing in hot strip mill, So we have tested HSS Roll in hot rolling simulator as rolling condition, rolling speed, draft, hot oil concentration. To reduce roll force and prevent scale defects. We get some merit rolling force, rolling torque, roll wear reduction, roll and strip surface roughness and hot rolling critical oil concentration 0.4%. Finally we are going to investigate the effect of hot rolling oil of on rolling with HSS Roll.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1101-1106
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• 2006

The water fluidized bed heat exchanger was installed to recover heat from paper mill hood exhaust air containing lot of moisture and also fouling contaminants. The hood exhaust air flow rate was about $110,000m^3/hr$ at $70^{\circ}C$. The commercial scale field test apparatus has been operated for 3 months. As a result of operation, total heat recovered was 2,380,000 kcal/hr and proportion of the latent heat to total heat was 74%. The annual energy saving was estimated as 450 million won.

• 펄프종이기술
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• 제36권2호
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• pp.54-59
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• 2004

The methods for the minimization of fresh water consumption, waste water generation and water contamination have been greatly investigated and developed for last ten years. Recently, the rising cost of waste water treatment and the more strict environmental regulation lead to the higher demand of more efficient and systematic methods for process water management. The water reuse technology, which not only reduce the process water needs but also minimize waste water generation within the process, could be one of most efficient way for current demand. In this study, the practical way for reduction of water pollution and optimal reuse or recycle of process water in a newsprint mill was investigated by using a simulation model. The result of computer simulation showed that the COD level of approach system could be reduced by 50% after the stock concentration at the 2nd disc filter was increased upto 30%. The application of WRDF(Wrinkled Rotary Drum Filter) to the newsprint mill was carried out with pilot scale. The process water treated by WRDF had enough cleanliness to substitute the forming fabric shower water with the PDF water, which could result in the 30% reduction in fresh water consumption.

• 한국강구조학회 논문집
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• 제12권2호통권45호
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• pp.167-175
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• 2000

본 논문에서는 내후성강재의 고장력볼트 마찰이음부 미끄럼계수 평가를 위한 실험연구를 수행하였다. 표면 상태는 흑피 부착표면을 수동 및 전동솔질로 청소한 경우, 숏브라스트 표면, 무기징크 하도 및 웨더코트를 적용한 경우들을 고려하였다. 또한, 각 표면 상태에 대하여 500 시간 동안 볼트축력 감소율을 측정하였다. 실험결과로부터 흑피표면을 전동솔질한 경우를 제외하면 미끄럼계수는 모두 0.4보다 컸다. 볼트축력 감소율은 표면상태에 따라 달랐으며 $3{\sim}8%$ 정도로서 10% 이내의 값을 보였다.

• 한국강구조학회 논문집
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• 제12권2호통권45호
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• pp.177-185
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• 2000

본 논문에서는 대기 중에 폭로한 내후성강재의 고장력볼트 마찰이음부 미끄럼계수 평가를 위한 실험연구를 수행하였다. 표면 상태는 흑피 부착된 시험체와 숏브라스트로 흑피를 제거한 시험체를 각각 3개월 및 6개월 폭로한 후 수동솔질, 전동솔질 및 청소하지 않은 표면 등을 고려하였다. 또한, 6개월 폭로 시험편의 각 표면 상태에 대하여 600 시간 동안 볼트축력 감소율을 측정하였다. 실험으로부터 모든 시험체에서 폭로 기간에 따라 미끄럼 계수는 증가하였으며 흑피부착 표면을 전동솔질로 청소한 경우를 제외하곤 모두 0.6 이상의 값을 보였다. 볼트 축력 감소율 역시 초기 비폭로 시험체에 비해 폭로한 시험 체에서 증가하였으며 최대 감소율은 약 10%에 이르렀다.

• 한국IT서비스학회지
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• 제10권3호
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• pp.49-59
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• 2011

A ship scheduling model is presented for the raw material transportation problem with yard storage constraints in a steel mill. The problem is formulated as 0, 1 mixed integer programming considering such constraints as loading port conditions, ship size and hold capacity, unloading conditions, and yard storage space. In addition, inventory related constraints including safety stock are taken into consideration to support the continuous operations of steel making process. The proposed model has been implemented and applied successfully to a real world problem, and its results show the improvement of performance compared to the traditional method. For example, the arrival dates of ships are determined satisfying the constraints. The total inventory level is minimized at the stock yard as a result. Also, the safety inventory level is always kept at the planning stage, and the standard deviation of total inventory level is reduced significantly. Further research is expected to develop efficient heuristics to have a better response time for even larger scale problems.