• 시멘트 심포지엄
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• 통권49호
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• pp.29-30
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• 2022

기후 문제의 심각성이 대두되면서 탄소중립에 세계적인 관심이 커지고 있다. 석회석 미분말은 충전재로써 시멘트 혼합재로 사용할 경우 긍정적인 효과를 얻을 수 있을 것으로 기대된다. 본 연구에서는 석회석 미분말 혼합재의 화학특성이 모르타르 플로우와 압축강도에 미치는 영향을 평가하려고 한다. 결과적으로 모든 석회석 종류와 치환량 수준에서 OPC 수준의 강도보다 저하하는 경향을 나타내었지만 석회석 혼합재를 사용할 경우 유동성이 향상되는 것을 확인하였다. 추후 석회석 시멘트의 단위수량 저감 효과를 이용해 강도 저하를 개선하는 연구를 진행할 계획이다.

• 대한화학회지
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• 제55권3호
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• pp.490-494
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• 2011

이산화탄소 방출을 줄이기 위해 포트랜드 시멘트 성분 일부를 시멘트 보충재를 혼합해준 시멘트의 제조에 대해 연구하였다. 이산화탄소를 0.18 kg $CO_2$/kg 정도 줄이기 위해 포트랜드 시멘트에 보충재를 20 wt% 정도 혼합하였다. 이 혼합시멘트의 압축 강도는 포트랜드 시멘트 ASTM C-150의 표준치를 초과하며, 28일간의 굳는 과정중에 37 MPa의 압축 강도를 가졌다. 혼합시멘트의 미세구조는 포트랜드 시멘트와 유사하였다.

• 수산해양기술연구
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• 제36권3호
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• pp.244-248
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• 2000

199년경 한국 남해안 어선의 특징은 독창적이고 견고하여 한반도 주변의 해양조건에 적합하고 우리 선조들의 훌륭한 조선기술을 확인할 수 있었으며, 그 결과를 요약하면 다음과 같다. (1) 본 연구에 사용한 시험대상 어선은 고대 어선에 비하여 비교적 세형으로서 1900년경의 선형이 개량되었음을 알 수 있었다. (2) 용골은 각형단면인 방형용골(bar keel)로 되어 있으며, 선수부는 방형선수재의 구조로서 예리한 pointed stem을 이루고 있다. (3) 외판은 턱붙이 클링커 이음방법으로 접합되어 있었다. (4) 권형망어선의 L/B, L/D, B/D의 값이 자망어선의 값에 비하여 크게 나타났다. (5) 복원성은 두 선박이 양호한 편이며 권형망어선이 자망어선에 비해서 더 우수한 것으로 나타났다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.102-108
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• 2009

Fossil power plants firing lower grade coals or equipped with modified system for NOx controls are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. In order to develop a on-line combustion tuning system, field test was conducted at operating power boiler. During the field test the exhaust gases' $O_2$, NOx and CO was monitored by using a spatially distributed monitoring grid located in the boiler's high temperature vestibule and upper convective back-pass region. At these locations, the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. using these monitored information we can improving combustion at every point within the furnace, therefore the boiler can operate at reduced excess $O_2$ and gas temperature deviation, reduced furnace exit gas temperature levels while also reducing localized hot spots, corrosive gas conditions, slag or clinker formation and UBC. Benefits include improving efficiency, reducing NOx emissions, increasing output and maximizing availability. Discussion concerning the reduction of greenhouse gases is prevalent in the world. When taking a practical approach to addressing this problem, the best way and short-term solution to reduce greenhouse gases on coal-fired power plants is to improve efficiency. From this point of view the real time optimized combustion tuning approach is the most effective and implemented with minimal cost.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.296-302
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• 1999

The state of the art of the 2-stage swirl calciner is to make 2-stage counter gas flow in a calciner with cooler hot air. Gas flow in the calciner increases retention time of raw mix particles. Simple structure of the 2-stage swirl calciner operated optimally the rotary cement kiln. In this study, in order to decide the entrance type of the cooler air of the optimal calciner model, an entrance cooler air velocity, the input points of raw mix were analyzed in many aspects with cold model experiment and computational fluidized dynamic simulation. It was found that the entrance type of cooler air fully splite 2-stage for the optimal condition of the cold model calciner. The operation conditions were that the input feeding, the cooler air velocity and the air velocity of throat were 0.33kg/$\textrm m$3$, 15m/s and 20m/s respectively. The performance of 150 t/d the pilot plant connected with the kiln rising duct was that volume capacity of the calciner is over 430 kg/$\textrm m$3$-h, decarbonation rate of raw mix apparently 90%, heat consumption 950 kcal/kg-cli and retention time of raw mix 2.4 sec. Its the best operating condition is cooler air velocity 18m/s, the gas velocity of throat 25m/s, feeding rate of raw mix 10t/h. The operating experience of the pilot plant confirmed the success of scale up for over 3000 t-cli/d.

• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.45-52
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• 2009

Fossil power plants firing lower grade coals or equipped with modified system for $NO_x$ controls are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. In order to develop a on-line combustion tuning system, field test was conducted at operating power boiler. During the field test the exhaust gases' $O_2,\;NO_x$ and CO was monitored by using a spatially distributed monitoring grid located in the boiler's high temperature vestibule and upper convective rear pass region. At these locations, the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. using these monitored information we can improving combustion at every point within the furnace, therefore the boiler can operate at reduced excess $O_2$ and gas temperature deviation, reduced furnace exit gas temperature levels while also reducing localized hot spots, corrosive gas conditions, slag or clinker formation and UBC. Benefits include improving efficiency, reducing $NO_x$ emissions, increasing output and maximizing availability. Discussion concerning the reduction of greenhouse gases is prevalent in the world. When taking a practical approach to addressing this problem, the best way and short-term solution to reduce greenhouse gases on coal-fired power plants is to improve efficiency. From this point of view the real time optimized combustion tuning approach is the most effective and implemented with minimal cost.

• 한국세라믹학회지
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• 제23권1호
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• pp.51-59
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• 1986

It was the first time the MgO-C brick was developed for the lining materials in the hot spots in electric are furnace in 1972. MgO-C brick is high registant to thermal and structural spalling. Futhermore for the reason that carbon is hard to react with slag and MgO is high fireproof MgO-C brick shows a high corrosion registance to slag attack compared with conventional basic refractories. Owing to their excellent properties the use of MgO-C refractories are being developed widely in the field of shaped refractories and even in that of monolithic refractories. In this paper the oxidation of carbon the infiltration of slag into the brick texture and effects of additions were investigated. The results obtained were as follows : 1) The use of fused MgO-clinker and high purity carbon as raw materials increased the corosion registance and hot modulus of rupture of MgO-C brick. 2) As the oxidation reaction of the carbon proceeded the slag infiltrated into the brick texture. And then the slag components reacted with the MgO grains and formed low melting point compounds particulary CaO.MgO.$SiO_2$ and 3CaO.MgO.$2SiO_2$ that resulted in the wear of the brick. 3) It is recongnized the Al, Si, $B_3C$ effects on the oxidation registant properties of MgO-C brick by contribu-ting to the decrease of permeability according to the formation of $Al_4C_3$, SiC, $B_2O_3$ and the decrease of open pores relating to the formation of MgO.Al2O3, $SiO_2$, 3MgO.$B_2O_3$ at the decarbonized layer.

• 한국세라믹학회지
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• 제56권4호
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• pp.403-411
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• 2019

In this work, the hydration process and cytotoxicity of lab-synthesized experimental Portland cements (EPCs) were investigated for dental applications. For this purpose, EPCs were prepared using laboratory-synthesized clinker constituents, tricalcium silicate (C₃S), dicalcium silicate (C₂S), and tricalcium aluminate (C₃A). C-A was prepared by the Pechini method, whereas C₃S and C₂S were synthesized by solid-state reactions. The phase compositions were characterized by X-ray diffraction (XRD) analysis, and the hydration process of the individual constituents and their combinations, with and without the addition of gypsum, was investigated by electrochemical impedance spectroscopy (EIS). Furthermore, four EPC compositions were prepared using the lab-synthesized C-A, C₃S, and C₂S, and their hydration processes were examined by EIS, and their cytotoxicity to HPC and HIPC cells were tested by performing an XTT assay. None of the EPCs exhibited any significant cytotoxicity for 7 days, and no significant difference was observed in the cell viabilities of ProRoot MTA and EPCs. The results indicated that all the EPCs are sufficiently biocompatible with human dental pulp cells and can be potential substitutes for commercial dental cements.

• Asian Journal of Atmospheric Environment
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• 제12권1호
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• pp.37-46
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• 2018

The Minamata Convention on Mercury entered into force on August 16, 2017. It requires Parties to the Convention to control and, where feasible, reduce mercury emissions from the listed sources. To implement the Convention, Japan amended the Air Pollution Control Law and added clauses that force operators to control their mercury emissions below emission limit values (ELVs). The ELVs have been established separately for new and existing sources, targeting the source categories listed in the Convention: coal-fired boilers, smelting and roasting processes used in the production of non-ferrous metals (lead, zinc, copper and industrial gold), waste incineration facilities and cement clinker production facilities. The factors used to establish the ELVs include the present state of mercury emissions from the targeted categories as well as the mercury content in fuels and materials, best available techniques (BATs) and best environmental practices (BEPs) to control and reduce mercury emissions and ELVs or equivalent standards to control mercury emissions in other countries. In this regard, extensive data on mercury emissions from flue gas and the mercury content of fuels and materials were collected and analyzed. The established ELVs range from $8{\mu}g/Nm^3$ for new coal-fired boilers to $400{\mu}g/Nm^3$ for existing secondary smelting processes used in the production of copper, lead and zinc. This paper illustrates the ELVs for the targeted source categories, explaining the rationales and approaches used to set the values. The amended Law is to be enforced on April 1, 2018. From future perspectives, checks of the material flow of mercury, following up on the state of compliance, review of the ELVs and of the measurement and monitoring methods have been noted as important issues.

• 보존과학회지
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• 제4권1호
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• pp.3-10
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• 1995

This study focused on the reconstructional point of Shinan ship-wreck that was excavated between $1976\~1984$. The wreck, which might be sunk in the beginning of the 14th century, is regarded as a vessel of Yuan dynasty, China. This paper tried to find out some structural characteristics and principal dimensions for restoration. The Shinan shipwreck's structural characteristics are summarized as follow, 1) The Shinan shipwreck is formed V-shaped cross section with bar keel, 2) The vessel is divided 8 holds by 7 bulkheads. 3) The ship has flat type stem and transome stern. 4) A rabbeted clinker -built is basically adopted on planking joint. 5) A wooden sheathing, which means a sort of protecting board against marine insects, is covered outside of the main hull, 6) For making an watertight structure, oakum and lime mixtured t'ung-oil are used along the seam of planking and bulkhead. 7) A V-shaped deep water-way exists at both deck side. 8) The shipwreck is believed to have 2 masts at least. 9) The shiptimbers are classified as Chinese Red Pine(Pinus Massonina) which is mainly grown in the southern part of China. Considering as mentioned above the structural characteristics, Shinan ship-wreck could be classified as Chinese Fu-chuan type(복선형) of sea-going ship. The Shinan ship's principal dimensions which are calculated on the basis of Chinese traditional shipbuilding custom, are as follow, Length overall(L.O.A). : 34.80m Length water line(L.W.L) : 24.90m Breadth(B.max.) : 11m Breadth(B) : 10m Depth at keel line(H) : 3.75m Draft(D). : 3.15m Freeboard(F) : 0.65m Ratio, length/breadth(L/B). : 2.26 Ration, breadth/depth(B/D) : 3.5 Height of stem : 7m Height of stern : 10m Displacement : ab.340ton.