• 한국식품영양과학회지
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• 제27권1호
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• pp.38-45
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• 1998

To extract insoluble proteins and to improve funtional properties of abolished proteins, an phytase producing Aspergillus sp. SM-15 was isolated from soil. The enzyme was purified and its enzymological characteristics were investigated. Phytase production reached to maximum when the wheat bran medium containing 1% mannose, 1% yeast extract, 1% (NH4)2HPO4 and 0.2% calcium chloride was cultured for 4 days. Phytase was purified 17.1 fold and specific activity was 244.32unit/mg by a sequencial process of ammonium sulfate fraction, ion exchange chromatography and gel filtrations Pruified enzyme was confirmed as a single band by the polyacrylamide gel electro-phoresis. The molecular weight of phytase was estimated to be 46,000. The optimum pH and temperature for the phytase activity were 5.5 and 5$0^{\circ}C$. The enzyme is stable in pH 4.5~5.5, 6$0^{\circ}C$. The activity of purified enzyme was inhibited by Hg2+ whereas activited by Pb2+ and Fe2+. The activity of phytase was inhibited by the treatment with iodine. The result indicate the possible involvement of histidine at active site. Km and Vmax of the puridied phytase were 37.037mM/L and 159.87umol/min, respectively.

• Bulletin of the Korean Chemical Society
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• 제24권1호
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• pp.37-44
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• 2003

We examined the effect of polyether-type nonionic surfactants (Brij 35, Triton X-100, Tween 20 and Tween 80) on the potentiometric properties of sodium-, potassium- and calcium-selective membranes which are prepared with widely used ionophores and four kinds of polymer matrices [poly(vinyl chloride) (PVC), polyurethane (PU), PVC/PU blend, and silicone rubber (SR)]. It was found that the PVC-based membranes, which provide the best performance among all other matrix-based membranes in the absence of nonionic surfactants, exhibited larger change in their potentiometric properties when nonionic surfactants are added to the sample solution. On the other hand, the sodium-selective SR-based membrane with calix[4]arene, potassium-selective PVC/PU- or SR-based membrane with valinomycin, and the calcium-selective SR-based membrane with ETH 1001 provide almost identical analytical performance in the presence and absence of Tween 20 or Tween 80 surfactants. The origin of nonionic surfactants effect was also investigated by interpreting the experimental results obtained with various matrices and ionophores. The results suggest that the nonionic surfactant extracted into the membrane phase unselectively form complexes with the primary and interfering ions, resulting in increased background potential and lower binding ability for the ionophore. Such effects should result in deteriorated detection limits, reduced response slopes and lower selectivity for the primary ions.

• 콘크리트학회논문집
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• 제14권3호
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• pp.349-356
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• 2002

본 연구는 고반응성 메타카올린(HRM)을 혼입한 고성능 콘크리트(HPC)의 굳지 않은 콘크리트와 경화된 콘크리트의 특성을 평가하기 위해 수행되었다. 굳지 않은 콘크리트에 대해서는 공기량과 슬럼프 플로우, 응결시간 및 수화열 측정 시험을 실시하였다. 경화된 콘크리트에 대해서는 압축강도 및 염화물 투수시험, 마모저항성, 동결ㆍ응해 저항성 시험을 하였다. HRM 콘크리트의 특성은 또한 보통 포틀랜드 시멘트 콘크리트와 실리카 흄 콘크리트와 비교하여 나타내었다. 실험 결과 HRM 재료가 고성능 콘크리트를 생산하기 위한 시멘트 대체 재료로서 사용할 수 있음을 보여주었다.

• Journal of Electrochemical Science and Technology
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• 제8권1호
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• pp.35-42
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• 2017

In this study, the effect of electrolyte addition on the removal of organics and nutrients in electrochemical wastewater using a copper electrode, and the characteristics of the by-product of electrolysis were investigated. The removal of organics increased significantly as shorter reaction times upon the addition of chloride ion, and most of the electrolysis reaction was completed within 20 min. The reaction rate gradually increased in proportion to the $Cl^-$/COD ratio, whereas the highest removed mass of organic matter per mass of added electrolyte was observed at a $Cl^-$/COD ratio of 1. After the addition of electrolyte, significant removal of ammoniacal nitrogen was observed as a result of the enhanced generation of oxidizers such as hypochlorite. Excellent phosphorus removal was also achieved in a very short reaction time (within 2 min) by electro-coagulation. As the electrolysis progressed, the amount of by-product increased gradually, whereas a decrease of sludge volume index was observed after the addition of electrolyte. This indicated that the settling performance of the by-products was better, and their removal would be easily achieved.

• KSBB Journal
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• 제5권2호
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• pp.183-189
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• 1990

1,000l 규모의 인뇨로부터 순수한 urokinase를 정제하는 새로운 공정이 고안되었다. 2가 금속이온인 아연을 첨가하여 선택적으로 urokinase를 침전시켰으며, 이 방법은 뇨 중에 포함된 다른 단백질을 100~1,000배 농축할때도 사용할 수 있으며 10~20배의 경제효과를 얻었다. 침전물 속에 포함된 urokinate를 경제적으로 용출할기 위하여 0.1M EDTA/0.5M glycine, pH 9.0용액이 조성되었고, 용출액속에 포함된 높은 농도의 salt와 ion,뇨색소 등이 CM-Toyopeal column에 의해 신속하고 효과적으로 제거되었다. 최종적으로 사용된 benzamidine-Sepharose chromatog-raphy는 urokinase 정졔에 매우 효과적이었다. 이상의 공정을 통해, 1,000liter의 인뇨로부터 3$\times$$O^6IO$의 urokinase가 순수 정제 되었으며, 수욜은 약 50%, 정제도는 1,300배이었다. 또한 urokinase중에 12~14%의 pro-urokinase가 함유되어 있음이 확인되었다.

• 대한토목학회논문집
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• 제33권2호
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• pp.609-617
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• 2013

본 연구에서는 역삼투 공정 농축수에 존재할 수 있는 내분비계 장애물질의 처리에 있어, 고급산화 공정의 적용가능성을 다양한 조건하에서 평가하였다. 오염물 제거에는 Fe(II)를 촉매로 한 과황산나트륨 산화를 이용하였으며, 초기 pH와 이온강도 등, 영향인자에 따른 산화능을 검토하였다. Fe(II) 촉매 과황산나트륨에 의한 $17{\alpha}$-ethynylestradiol(EE2) 제거효율은 초기 pH와 이온강도가 증가할수록 감소하였다. 반면, 이온강도 물질로 염소이온과 같은 할로겐족 이온을 적용 시 산화반응에 긍정적인 영향을 나타냈는데, 이는 라디칼 전이에 따른 영향으로 판단된다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.860-866
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• 2009

It is very important to choose optimal material having good corrosion resistance and capabilities for the part materials such as the automotive exhaust system under a hot salt corrosion atmosphere. Generally, two types of corrosion come into the automotive exhaust system. One is 'Condensate Corrosion', which is occurred by exhaust gas condensate formed at the inner surface of exhaust system heated up during driving, which results in the acid condensate pitting. The other is 'High Temperature Salt Corrosion' occurring from the interaction between the chloride ion coming from salt at the seaside district or snow salt and the outer surface of exhaust system. By the corrosion attack, the main muffler is firstly damaged and the life cycle of an automobile is significantly decreased. It has been investigated that the hot salt corrosion properties of a STS 409L and 436L ferritic stainless steels which are well-known for the materials of the automotive exhaust system. In addition, the corrosion properties of hot dip aluminum coated STS 409L have been compared with uncoated steels. Aluminum coated STS 409L showed a superior corrosion resistance than uncoated STS 409L, and futhermore showed a better corrosion resistance than a STS 436L, which is an expensive ferritic stainless steel having a excellent corrosion resistance caused from more chromium content of an alloying element.

• Corrosion Science and Technology
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• 제16권2호
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• pp.69-75
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• 2017

Zinc coating on carbon steels give the higher corrosion resistance in chloride containing environments and in carbonated concrete. However, hydrogen evolution accompanies the corrosion of zinc in the initial activity in fresh concrete, which can lead to the formation of a porous structure at the reinforcement -concrete interface, which can potentially reduce the bond-strength of the reinforcement with concrete. The present study examines the mechanism of the corrosion of hot-dip galvanized steel in detail, as in the model pore solutions and real concrete. Calcium ion plays an important role in the corrosion mechanism, as it prevents the formation of passive layers on zinc at an elevated alkalinity. The corrosion rate of galvanized steel decreases in accordance with the exposure time; however, the reason for this is not the zinc transition into passivity, but the consumption of the less corrosion-resistant phases of hot-dip galvanizing in the concrete environment. The results on the electrochemical tests have been confirmed by the bond-strength test for the reinforcement of concrete and by evaluating the porosity of the cement adjacent to the reinforcement.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 춘계 학술논문 발표대회 학계
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• pp.239-242
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• 2009

As the high-rise building increase due to the gravitation of population to big cities recently, it requires high quality and high performance of Concrete. As a result, people are keenly interested in Meta-kaolin as new admixture favorable from an economic perspective, which has strength and endurance with admixture at the same level like Silica-fume. Accordingly, as to Meta-kaolin, this study was to set by three levels like domestic one, foreign one, and Silica-fume, the water-binding material ratio 25%, and four level substitute like 0, 10, 20, and 30(%) in order to compare and analyze the quality durability of high-concrete according to the substitute of Meta-kaolin applicable with replacement of Silica-fume. As a result of performing experiment it was found that when water-binding material ratio increases, resistance of neutralization, carbonation, salt damage and sulfate decrease, and when replacement ratio of mineral admixture increases, depth of accelerating carbonation gets greater. Also, the combination of SF and MK-B favored resistance to chloride ion penetration better than MK-A, and it was found that when replacement ratio of binding material increases, the resistance to sulphuric acid increases. Therefore, based on this study, it was understood that meta-kaolin is useable in replacement of silicafume.

• 한국분말재료학회지
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• 제15권2호
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• pp.148-155
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• 2008

Nano magnetite particles have been prepared by two step reaction consisting of urea hydrolysis and ammonia addition at certain ranges of pH. Three different concentrations of aqueous solution of ferric ($Fe^{3+}$) and ferrous ($Fe^{2+}$) chloride (0.3 M-0.6 M, and 0.9 M) were mixed with 4 M urea solution and heated to induce the urea hydrolysis. Upon reaching at a certain pre-determined pH (around 4.7), 1 M ammonia solution were poured into the heated reaction vessels. In order to understand the relationship between the concentration of the starting solution and the final size of magnetite, in-situ pH measurements and quenching experiments were simultaneous conducted. The changes in the concentration of starting solution resulted in the difference of the threshold time for pH uprise, from I hour to 3 hours, during which the akaganeite (${\beta}$-FeOOH) particles nucleated and grew. Through the quenching experiment, it was confirmed that controlling the size of ${\beta}$-FeOOH and the attaining a proper driving force for the reaction of ${\beta}$-FeOOH and $Fe^{2+}$ ion to give $Fe_3O_4$ are important process variables for the synthesis of uniform magnetite nanoparticles.