• 공업화학
• /
• 제28권2호
• /
• pp.257-262
• /
• 2017

본 연구에서는 electrospinning method의 공정변수를 다르게 하여 CNF (carbon nanofiber)를 제조하였다. 제조된 CNF의 섬유의 형태, 직경 등의 변화를 SEM 분석을 통해 관찰하였으며 인가전압, TCD (tip to collecor distance), 고분자 용액의 농도, 열처리 단계가 CNF 물성을 형성함에 있어 주요한 영향인자임을 확인하였다. 또한 서로 다른 물성으로 제조된 CNF를 전기분해 공정의 전극으로 적용하여 toluene의 제거 효율을 비교하였고, 이를 통해 anode 뿐만 아니라 cathode 역시 전기분해 효율에 직접적인 영향을 미침을 확인하였다.

• 한국식품과학회지
• /
• 제37권6호
• /
• pp.951-956
• /
• 2005

Bifidobacteria의 효과적인 이용을 위해서는 산소에 내성을 갖는 균주를 선발하는 연구 외에도 산소 스트레스에 대한 방어 기작에 대한 기초적인 연구가 필요하다. 인체로부터 분리된 산소 내성 bifidobacteria는 산소제거활성을 가지고 있었으며 이는 열처리 및 극단적인 pH(pH 2.0)하에서 산소제거활성이 소실되는 것으로 보아 효소가 관여 할 가능성을 확인하였다. 또한 산소제거활성을 보이는 주된 효소를 탐색해본 결과 NADH를 공급하였을 때만 산소제거활성을 보여 NADH oxidase가 주된 역할을 하는 효소임을 알 수 있었다. 또한 산소 내성 균주는 높은 NADH peroxidase 활성을 보유한 것으로 보아 NADH oxidase의 작용에 의해 생성되는 $H_2O_2$는 NADH peroxidase에 의해 무독화 되는 것으로 판단되었다. 배양 중 산소를 공급하여 산소스트레스를 주었을 경우 NADH oxidase와 NADH peroxidase 활성이 1시간 이내에 급격히 증가하였고 산소 공급 후 2시간 동안 배양액 중 용존 산소가 크게 증가하지 않았다. 산소공급 후 2시간 이상이 경과하면 NADH oxidase와 NADH peroxidase활성이 감소하고 용존 산소가 급격히 증가하였고 산소스트레스에 대한 방어 체계가 붕괴되는 현상이 관찰되었다. 즉, 산소 내성 bifidobacteria는 일정 한계까지는 환경중의 산소를 NADH oxidase로 제거하고 생성되는 $H_2O_2$는 NADH peroxidase에 의해 제거시키는 방어 체계를 갖고 있음을 알 수 있었다.

• 한국식품과학회지
• /
• 제27권4호
• /
• pp.439-444
• /
• 1995

Preparative conditions and characteristics of six-vegetable and fruit juice were studied for the effects of mixing ratio, heat treatment and addition of sugar, salt and organic acid. The vegetables and fruit used were carrot(Ct), cabbage(Cg), pear(Pr), cucumber(Cr), celery(Cy) and dongchimi(Di). From the sensory results of mixing ratio of three of binary mixtures of Cg-Pr(1:3):Ct-Di(1:4):Cr-Cy(3:1), two ratios of 5.0:2.5:2.5(V-6A) and 6.0:2.0:2.0(V-6B) were suggested optimal for six-vegetable and fruit juice. Addition of 2% sucrose and 0.3% NaCl improved the preference significantly. The pH 4.0 for V-6A and pH 3.5 for V-6B were more prefered when pH was adjusted by citric acid. Heating the juice at $100^{\circ}C$ for 100 minutes slightly decreased pH and increased the acidity. Total solids and viscosity were also decreased by heating. All of those changes were more significant in V-6B than V-6A, probably due to lower pH. Heating the juice resulted in a slight decrease in L value and an increase in a and b values. Heating at $100^{\circ}C$ caused an increase in moldy flavor and a decrease in fresh vegetable flavor while heating at $80^{\circ}C$ for 20 minutes changed them little.

• 대한금속재료학회지
• /
• 제46권4호
• /
• pp.189-198
• /
• 2008

The changes in microstructure and mechanical properties of AZ31 alloy subjected hot-rolling process were investigated. The AZ31 plates fabricated by horizontal continuous casting process were prepared and have hot-rolled from 30 mm to 1 mm in thickness under different processing conditions. At the rolling temperature of $400^{\circ}C$, little surface and side crack was observed up to 20% reduction rate. As total reduction and reduction rate increase to more than 75% and 20% pass, respectively, Grains were more uniformly refined through overall thickness, and particularly lots of shear bands were appeared to be inclined at less than $20^{\circ}C$ along the rolling direction. Average grain size of less than $5{\mu}m$ and tensile properties of YS ${\geq}$ 250 MPa, UTS ${\geq}$ 300 MPa and El. ${\geq}$ 13% were acquired for hot-rolled AZ31 sheets without post-heat treatment. Maximum intensity of (0002) pole figure was decreased with an increase in reduction rate, indicating the improvement of texture by means of high reduction rate.

• 한국염색가공학회지
• /
• 제34권2호
• /
• pp.109-116
• /
• 2022

Tire codes are made of materials such as hemp, cotton, rayon, nylon, steel, polyester, glass, and aramid are fiber reinforcement materials that go inside rubber to increase durability, driveability, and stability of vehicle tires. The reinforcement of the tire cord may construct a composite material using tires such as automobiles, trucks, aircraft, bicycles, and fibrous materials such as electric belts and hoses as reinforcement materials. Therefore, it is essential to ensure that the adhesive force between the rubber and the reinforced fiber exhibits the desired physical properties in the rubber composite material made of a rubber matrix with reinforced fibers. This study is a study on the heat treatment conditions for improving the adhesion strength of the tire cord and the reinforced fiber for tires. The core technology of the drying process is a uniform drying technology, which has a great influence on the quality of the reinforcement. Therefore, the uniform airflow distribution is determined by the geometry and operating conditions of the dryer. Therefore, this study carried out a numerical analysis of the shape of a drying nozzle for improving the performance of hot air drying in a dryer used for drying the coated reinforced fibers. In addition, the flow characteristics were examined through numerical analysis of the study on the change in the shape of the chamber affecting drying.

• 한국세라믹학회지
• /
• 제42권9호
• /
• pp.624-630
• /
• 2005

To investigate the possibility of the $ZrO_2$ buffer layer as the insulator for the Metal-Ferroelectric-Insulator-semiconductor (MFIS) structure, $ZrO_2$ and $SrBi_2Ta_2O_9$ (SBT) thin films were deposited on the P-type Si(111) wafer by the R.F. magnetron-sputtering method. According to the process with and without the post-annealing of the $ZrO_2$ buffer layer and SBT thin film, the diffusion amount of Sr, Bi, Ta elements show slight difference through the Glow Discharge Spectrometer (GDS) analysis. From X-ray Photoelectron Spectroscopy (XPS) results, we could confirm that the post-annealing process affects the chemical binding condition of the interface between the $ZrO_2$ thin film and the Si substrate. Compared to the MFIS structure without the post-annealing of the $ZrO_2$ buffer layer, memory window value of MFlS structure with post-annealing of the $ZrO_2$ buffer layer were considerably improved. The window memory of the Pt/SBT (260 nm, $800^{\circ}C)/ZrO_2$ (20 nm) structure increases from 0.75 to 2.2 V under the applied voltage of 9 V after post-annealing.

• 한국가구학회지
• /
• 제19권6호
• /
• pp.475-486
• /
• 2008

In this study, fire-retardant chemicals were melt with mixed composition ratios of dibasic ammonium phosphate and each half of boric acid and borax in hot water, in which hammer-milled chips were immersed to increase swelling of waste particleboards. Also, fire-retardant treated particles from sawn lumber chip and recycled particleboard chip were composed in ratio of 70:30 in core layer to improve boards' properties. Retention ratio of fire-retardant chemicals for the particles for face layer was high due to high specific surface area, and that of sawn lumber chips was somewhat higher than that of recycled particleboard chips. The mixture of particles from sawn lumber chips and recycled PB of 70:30 in weight ratio exceeded bending strength of 100 $kgf/cm^2$. It seemed that the relatively greater portions of dibasic ammonium phosphate affected adversely to dimensional stability, however fire-retardants treatment resulted in distinct effect lowering formaldehyde emission such as $E_0$ type(0.5mg/$\ell$ or less) in KS F 3104. In fire-retardancy, the recycled boards with a mixed ratio of dibasic ammonium phosphate to boric acid borax(50:50 mixture) of 70% to 30% in weight satisfied fire-retardancy 3rd grade in KS F 2271, and also this composition from cone calorimeter test met same standard grade figuring total heat release of 4.6MJ/$m^2$.

• Journal of Microbiology and Biotechnology
• /
• 제28권2호
• /
• pp.218-226
• /
• 2018

Nanometric Lactobacillus plantarum nF1 (nLp-nF1) is a biogenics consisting of dead L. plantarum cells pretreated with heat and a nanodispersion process. In this study, we investigated the immune-enhancing effects of nLp-nF1 in vivo and in vitro. To evaluate the immunostimulatory effects of nLp-nF1, mice immunosuppressed by cyclophosphamide (CPP) treatment were administered with nLp-nF1. As expected, CPP restricted the immune response of mice, whereas oral administration of nLp-nF1 significantly increased the total IgG in the serum, and cytokine production (interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-${\alpha}$)) in bone marrow cells. Furthermore, nLp-nF1 enhanced the production of splenic cytokines such as IL-12, TNF-${\alpha}$, and interferon gamma (IFN-${\gamma}$). In vitro, nLp-nF1 stimulated the immune response by enhancing the production of cytokines such as IL-12, TNF-${\alpha}$, and IFN-${\gamma}$. Moreover, nLp-nF1 given a food additive enhanced the immune responses when combined with various food materials in vitro. These results suggest that nLp-nF1 could be used to strengthen the immune system and recover normal immunity in people with a weak immune system, such as children, the elderly, and patients.

• 한국수산과학회지
• /
• 제27권2호
• /
• pp.133-139
• /
• 1994

식품의 가공 저장 및 조리 중에 일어나는 식품성분간의 반응 중 대표적인 반응으로 알려져 있는 Maillard 반응생성물의 돌연변이원성에 대한 그 억제 기구를 밝히기 위하여 glucose-arginine계 및 glucose-lysine${\cdot}$HCl계 Maillard 반응 생성물에 일상 생활에서 많이 섭취하고 있는 해조류 및 야채류의 수용성 추출물을 첨가하여 그 억제효과를 조사하였고, 아울러 이들 수용성추출물의 가열($100^{\circ}C$, 10분)에 따른 억제효과의 영향에 대해 조사 검토하였다. 그 결과, 실험에 사용한 해조류 및 야채류 수용성 추출물 전부가 돌연변이원성 억제효과를 나타내었고, 특히 양배추, 파, 산초, 및 청각에 있어서 억제효과가 높게 나타났다. 가열한 경우, 야채류의 돌연변이원성 억제효과는 감소하였으나 해조류는 크게 영향을 받지 않았다. 이 결과로 미루어 보아 당-아미노산계 Maillard 반응생성물의 돌연변이원성 억제에 해조류 및 야채류 추출물에 존재하는 환원성 물질, 고분자 물질 catalase 및 peroxidase와 같은 효소 등이 일조를 하는 것으로 나타났다.

• 공업화학
• /
• 제29권1호
• /
• pp.43-48
• /
• 2018

본 연구에서는 PCC (precipitated calcium carbonate) 제조에 있어 칼슘이온 추출 최적화를 위하여 추출 용제, 용제의 농도, 추출원의 투입량, 전처리 공정 등 다양한 추출 조건에 따른 실험을 수행하였다. 칼슘추출원으로 CaO를 사용하였으며, 칼슘이온의 추출량과 CaO의 입자크기를 확인하기 위하여 ICP와 SEM 분석을 수행하였다. 그 결과 2 M의 hydrochloric acid를 용제로 사용한 경우 100%의 칼슘이온이 추출되었으며, 추출원의 최적 투입량은 6 g으로 확인하였다. 반면 반응시간, 반응온도, 입자 분쇄 및 열처리 공정은 칼슘이온 추출량에 큰 영향이 없음을 확인하였다.