• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.57-60
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• 2009

Alcohol oxidase catalyzes the oxidation of short lines alcohol to aldehyde. In this study, alcohol oxidase from Hansenula polymorpha (HpAOD) was induced by addition of 0.5% methanol as the carbon source and purified to electrophoretic homogeneity by column chromatographies. The purified HpAOD was immobilized with DEAE-cellulose particles and its biochemical properties were compared with those of free enzyme. The substrate specificity and the optimum pH of immobilized enzyme were similar to those of free enzyme. On the other hand, the Km values of free and immobilized enzymes for ethanol were 6.66 and 14.65 mM, respectively. The optimum temperature for free enzyme was ${50^{\circ}C}$, whereas that for immobilized enzyme was ${65^{\circ}C}$. Immobilized enzyme showed high stability against long storage. Immobilized enzyme was also tested for the enzymatic determination of ethanol by the colorimetric method. We detected 1 mg/liter ethanol ($1{\times}10^{-4}$% ethanol) by 2,6- dichloroindophenol system. Therefore, the present study demonstrated that immobilized HpAOD has high substrate specificity toward ethanol and storage stability, which may be of considerable interest for alcohol biosensor and industrial application.

• 한국농공학회논문집
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• 제52권1호
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• pp.51-59
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which that can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the unconfined compressive strength properties and freezing and thawing resistance of CSG materials with unit cement content. The three types of CSG-80, CSG-100 and CSG-120 with cement content were designed to evaluate the optimum water content, dry density, strength, stress-strain, micro structure and durability factor. As the results, the optimum water content ratio with cement content showed almost similar tendency, and the unconfined compressive strength and dry density increased as cement content increases. The strength ratio of 7 days for 28 days were in the range of 55~61 % and the strain ratio in stress-strain curve were in the range of 0.8~1.6 % nearby maximum strength in 28 days. It is expected that this study will contribute to increasing application of CSG method as well as to increasing the utilizing of CSG materials as a environmentally friendly CSG method.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.33-36
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• 2010

$MgF_2$ is a current material used for optical applications in the ultraviolet and deep ultraviolet range. Process variables for manufacturing $MgF_2$ thin film were established in order to clarify the optimum conditions for the growth of the thin film, dependant upon the process conditions, and then by changing a number of the vapor deposition conditions, substrate temperatures, and heat treatment conditions, the structural and optical characteristics were measured. Then, optimum process variables were thus derived. Nevertheless, modern applications still require improvement in the optical and structural quality of the deposited layers. In the present work, in order to understand the composition and microstructure of $MgF_2$, single layers grown on a slide glass substrate using an Electron beam Evaporator (KV-660), were analyzed and compared. The surface substrate temperature, having an effect on the quality of the thin film, was changed from $200^{\circ}C$ to $350^{\circ}C$ at intervals of $50^{\circ}C$. The heat treatment temperature, which also has an effect on the thin film, was changed from $200^{\circ}C$ to $400^{\circ}C$ at intervals of $50^{\circ}C$. The physical properties of the thin film were investigated at various fabrication conditions, such as the substrate temperature, the heat treatment temperature, and the heat treatment time, by X-ray diffraction, and field emission-scanning electron microscopy.

• 폴리머
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• 제31권2호
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• pp.105-110
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• 2007

ABS(acrylonitrile butadiene styrene)수지의 성능저하에 미치는 영향을 알아보기 위해 ABS, 도장, 도료, 사출 등 전 부문에 대한 영향도를 파악함으로써 ABS수지의 성능저하를 최소화하기 위한 최적화 방안을 수립하였다. ABS수지의 성능저하에 영향을 미치는 인자를 실험실 규모에서 검토한 결과 변형에 의한 기계적 요인보다는 사용된 화학물질의 화학적, 물리적 특성에 의한 요인이 지배적인 것으로 나타났다. ABS수지를 이용한 제조 현장에서 여러 인자(ABS수지, 사출, 화학물질, 도장 등)에 대해 검토한 결과 ABS수지 표면에 직접적으로 접촉하는 화학물질인 희석제 (시너)에 의한 영향도가 가장 큼을 확인할 수 있었다. 이번 연구 결과를 통해 수지의 성능저하에 미치는 각 인자별 영향도 수준 평가가 가능하게 되었으며, 이를 토대로 양산 시 나타나는 도장불량 등의 문제해결을 위한 관리 과정의 체계화 및 품질 변동요인의 제거 방안을 구체화할 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제32권6호
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• pp.783-791
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• 2022

Gamma-aminobutyric acid (GABA) improves various physiological illnesses, including diabetes, hypertension, depression, memory lapse, and insomnia in humans. Therefore, interest in the commercial production of GABA is steadily increasing. Lactic acid bacteria (LAB) have widely been reported as a GABA producer and are safe for human consumption. In this study, GABA-producing LAB were preliminarily identified and quantified via GABase assay. The acid and bile tolerance of the L. plantarum FBT215 strain were evaluated. The one-factor-at-a-time (OFAT) strategy was applied to determine the optimal conditions for GABA production using HPLC. Response surface methodology (RSM) with Box-Behnken design was used to predict the optimum GABA production. The strain FBT215 was shown to be acid and bile tolerant. The optimization of GABA production via the OFAT strategy resulted in an average GABA concentration of 1688.65 ± 14.29 ㎍/ml, while it was 1812.16 ± 23.16 ㎍/ml when RSM was applied. In conclusion, this study provides the optimum culture conditions for GABA production by the strain FBT215 and indicates that L. plantarum FBT215 is potentially promising for commercial functional probiotics with health claims.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.37-38
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• 2022

During the past decades, the corrosion of the steel rebar embedded in concrete structure surrounding marine environment is actually problematic and required the suitable preventive method. An eco-friendly corrosion inhibitor mix is investigated to stifle the active corrosion in comparison with other commercial corrosion inhibitors. The hybrid inhibitor enhances the corrosion resistance and the workability of concrete. However, it reduces the compressive strength slightly after 28-day-age. The electrochemical studies and mechanical studies are pointed out the corrosion resistance property, corrosion kinetics, and the mechanical properties of all concrete samples. H-3 is the optimum dose of hybrid inhbitor that meets the demand of both electrochemical property and mechanical property. It performs the noble features due to the formation of optimum amount of P-Zwitterions-(Cl)-Fe complex onto the steel rebar surface.

• Computers and Concrete
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• 제31권6호
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• pp.501-511
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• 2023

The strengthening efficiency of biopolymer treated soil depends on biopolymer type, concentration ratio, soil type, initial water content, curing time and mixing method. In this study, the physical and mechanical properties of xanthan gum (XG) treated kaolinite were investigated through compaction test, Atterberg limit test, triaxial test and unconfined compression test. The results indicated that the optimum water content (OWC) increased from 30.3% of untreated clay to 33.5% of 5% XG treated clay, while the maximum dry density has a slight increase from 13.96 kg/m³ to 14 kg/m³ of 0.2% XG treated clay and decrease to 2.7 kg/m³ of 5% XG treated clay. Meanwhile, the plastic limit of XG treated clay increased with the increase of XG concentration, while 0.5% XG treated clay can be observed the maximum liquid limit with 79.5%. Moreover, there are the ideal water content about 1.3-1.5 times of the optimum water content achieving the maximum dry density and curing time to obtain the maximum compressive strength for different XG contents, which the UCS is 1.52 and 2.07 times of the maximum UCS of untreated soil for 0.5% and 1% XG treated clay, respectively. In addition, hot-dry mixing can achieve highest UCS than other mixing methods (e.g., dry mixing, wet mixing and hot-wet mixing).

• Geomechanics and Engineering
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• 제32권4호
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• pp.361-373
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• 2023

This study aimed to investigate the engineering properties and mechanical behaviors of polymer-fibers treated sand. Para rubber (PR), natural fiber (NF), and geosynthetic fiber (GF) were used to reinforce poorly graded sand. A series of unconfined compressive and splitting tensile strength tests were performed to analyze the engineering behaviors and strength enhancement mechanism. The experiment results indicated that the PR-fibers mixture could firmly enhance the strength properties of sand. The stress-strain characteristics and failure patterns have been changed due to the increase of PR and fibers content. The presence of PR and fibers strengthened the sand and enhanced the stiffness and ductility behavior of the mixture. The stiffness of reinforced sand reaches an optimum state when both NF and GF are 0.5%, while the optimum PR contents are 20% and 22.5% for the mixture with NF and GF, respectively. An addition of PR and fiber into sand contributed to increasing interlocking zone and bonding of PR-sand interfacial.

• Applied Biological Chemistry
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• 제10권
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• pp.23-31
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• 1968

Chaetomium globosum의 Cellulase 생산(生産)과 조효소(粗酵素)의 성질(性質)은 시험(試驗)한바 다음의 결과(結果)를 얻었다. 1. 효소생성배양(酵素生成培養)은 맥피고체배양(麥皮古體培養)이 다른 어떤 액체(液體) 혹(或)은 진탕배양보다 좋은 결과(結果)를 나타낸다. 2. 효소생산(酵素生産)은 $8{\sim}10$일(日)이 최고(最高)이며 그 후(後)는 감소(減少)된다. 3. 환원당(還元糖) 측정(測定)에 의(依)한 Cellulase 활성(活性) 측정법(測定法)으로 최적(最適) pH, 최적(最適) 온도(溫度), pH 안전(安全) 및 열안전(熱安全)은 다음 같다. (1) 조효소(粗酵素)의 최적(最適) pH는 $4.0{\sim}4.5$이다. (2) 조효소(粗酵素)의 최적(最適) 온도(溫度)는 $40^{\circ}C$이다. (3) 조효소(粗酵素)의 안전(安全) pH는 $.3.5{\sim}6.5$이다. (4) 조효소(粗酵素)의 열안전(熱安全)은 $50^{\circ}C$ 이하(以下)이다. 4. 투석조효소(透析粗酵素)는 $Mn^{2+},\;Mg^{2+},\;Fe^{2+},o^{2+}$에 상당(相當)히 부활(賦活)되며 $Hg^{2+}$은 현저히 저해(沮害)된다.

• 한국식품과학회지
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• 제38권6호
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• pp.762-766
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• 2006

골판지 상자의 수분저항성을 증진시키기 위해 골판지 상자 제조에 사용되는 라이너지의 표면을 알긴산으로 표면코팅을 하기 위한 최적 조건을 결정하기 위하여 농도, 가소제의 종류와 사용량, 알긴산의 불용화를 위한 다가 금속이온의 종류와 최적농도 및 침지시간 등을 결정하였다. 라이너지의 표면코팅을 위한 알긴산의 농도는 2.5%(w/w)가 적합하였으며, 가소제인 글리세롤은 알긴산 대비 35%의 농도로 사용하는 것이 적합하였고, 알긴산 필름의 불용화를 위해서는 2% $CaCl_2$ 용약을 사용하여 3분간 처리하는 것이 라이너지의 수분에 대한 저항성 증진에 최적조건을 결정되었다. 다가 금속이온으로 $CA^{2+}＄ 이외에 $Cu^{2+}＄를 사용했을 때 낮은 투습계수와 수분용해도를 나타냈다. 가소재의 종류에 따라서는 수분 흡습에 대한 저항성이 큰 솔비톨을 첨가 했을 때 라이너지의 수분저항성이 유의적인 차이를 보이며 증가하였다.