• 대한수학회논문집
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• 제16권1호
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• pp.137-152
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• 2001

Steady two-dimensional flows due to an applied pressure distribution in water of finite depth are considered. Gravity is included in the dynamic boundary condition. Gravity is included in the dynamic boundary condition. The problem is solved numerically by using the boundary integral equation technique. It is shown that, for both supercritical and subcritical flows, solutions depend on three parameters: (i) the Froude number, (ii) the magnitude of applied pressure distribution, and (iii) the span length of pressure distribution. For supercritical flows, there exist up to two solutions corresponding to the same value of Froude number for positive pressures and a unique solution for negative pressures. For subcritical flows, there are solutions with waves behind the applied pressure distribution. As the Froude number decreases, these waves when the Froude numbers approach the critical values.

• 산업식품공학
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• 제22권4호
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• pp.304-308
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• 2018

건강 지향적인 사회 추세의 영향으로 건강 기능 식품의 관심과 개발이 증가되고 있다. 계피는 기능적 특성으로 인해 한약뿐만 아니라 식품 성분으로도 사용되고 있어서 본 연구에서는 추출용매와 추출방법을 달리하여 육계피 추출액의 향기 성분과 항산화활성도를 조사하였다. 육계피 추출물의 향기 성분인 coumarin, cinnamic acid, cinnamaldehyde, cinnamyl alcohol의 함량을 조사하였다. 에탄올 70%의 추출물에서 courmarin, cinnamic acid 그리고 cinnamylaldehyde의 함량은 증류수를 이용한 열수추출물과 아임계추출물에 비하여 높게 나타났다. 증류수를 이용한 아임계추출물의 courmarin, cinnamic acid, 그리고 cinnamaldehyde 함량은 열수추출물보다 높게 나타났지만, cinnamyl alcohol은 반대로 낮게 나타났다. DPPH 분석을 통한 항산화활성도 측정에서 DPPH scavenging activity는 추출물의 농도가 증가할수록 증가하였고, 70% 에탄올 추출물의 항산화활성도가 가장 크게 나타났다. FRAP 분석을 통한 항산화활성도 측정에서 70% 에탄올 추출물의 ascorbic acid 함량이 가장 크게 나타났고, 열수추출물과 아임계추출물은 유의적인 차이가 없었다(p<0.05).

• 신재생에너지
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• 제3권1호
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• pp.38-45
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• 2007

To characterize thermo-chemical feature of sugar conversion of woody biomass, poplar wood ($Populus\;alba{\times}glandulosa$) powder was treated with supercritical water system. Supercritical water treatment (SCWT) was performed for 60 seconds at different temperatures (subcritical zone 350; supercritical zone $300,\;400,\;425^{\circ}C$) under two pressures $230{\pm}10atm$ as well as $330{\pm}10atm$, respectively, using flow type system. After separation of solid residues from SCWT products, the monomeric sugars in aqueous part converted from poplar wood powder were quantitatively determined by high performance anionic exchange chromatography [HPAEC] equipped with PAD detector and Carbo Pac PA10 column. As the temperature treated increased, the degradation of poplar wood powder was enhanced and ca 83% of woody biomass was dissolved into the water at $425^{\circ}C$. However, the pressure didn't help the degradation of biomass components. At subcritical temperature range, xylose was first formed by degradation of xylan, which is main hemicellulose component in hardwood species, while cellulose degradation started at the transition zone between sub and supercritical conditions and was remarkably accelerated at the supercritical temperature. In the supercritical water system the maximum yield of monomeric sugars amounts to ca. 7.3% based on oven dried wood weight at $425^{\circ}C$.

• Journal of Hydrospace Technology
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• 제2권1호
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• pp.10-17
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• 1996

If a point impulse travels over free surface of water of finite depth, surface waves consist of divergent waves. The crestlines of those divergent waves are short and end on the cusp line if the impulse travels at a subcritical speed. But the crestlines become infinitely long and there are no cusps if the impulse travels at a supercritical speed.

• 방사성폐기물학회지
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• 제16권3호
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• pp.315-330
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• 2018

미임계 시설은 정상 또는 사고상태에서 핵임계안전성이 확보되어야 한다. 이를 위해선 계산된 임계도가 바이어스와 불확실도로 결정된 미임계상한치(USL)를 초과하지 않는다는 것을 검증하는 절차가 반드시 필요하다. 하지만 핵임계안전성 검증방법론은 여러 가지가 존재하며, 방법론이 달라지면 USL도 달라지므로 가장 적절한 한가지의 방법론으로 평가하는 것이 중요하다. 본 연구에서는 핵임계안전성 검증 방법론이 기술된 두 개의 문서를 비교 분석하여 한 가지 방법론으로 정립하였고, SCALE6.1 코드를 이용한 용기 설계에서의 미임계상한치 결정에 적용하였다.

• 한국수자원학회논문집
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• 제34권1호
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• pp.45-55
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• 2001

천이류는 하나의 계산 영역내에서 사류와 상류가 동시에 발생하는 흐름을 의미하는 용어이다. 천이류 해석 모형 개발에서 중요한 사항은 상류와 사류 영역에서 발생하는 신호의 전파특성을 정확하게 반영할 수 있어야 한다는 것과 보존성을 유지해야 한다는 것이다. 본 연구에서는 지금까지 하천 천이류 해석을 위해 적용된 적이 없는 음해적 ENO 기법을 이용하여 새로운 모형을 개발하였다. 음해적 ENO 기법은 전 구간에 걸쳐 수치진동없이 고정확도가 유지될 수 있는 장점을 지닌 수치기법인 ENO 기법과 수치적으로 무조건적 안정성이 보장되는 장점을 지닌 음해법을 결합한 기법이다. 본 연구에서 개발한 모형을 가상적인 댐붕괴파의 해석에 적용한 결과 매우 강한 천이류가 발생하는 경우에도 안정적으로 정확한 해를 구할 수 있는 것으로 나타났다.

• Environmental Engineering Research
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• 제11권6호
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• pp.311-317
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• 2006

Feasibility of destroying synthetic and actual leachate containing humic acids and ammonia compounds by supercritical water oxidation (SCWO) was evaluated. In this study, destruction efficiencies of humic acids and ammonia respectively were investigated at various reaction temperatures and residence times under pressure a supercritical pressure (280 atm). To lower reaction temperature, chemical oxidants were used. The experiment was carried out in a cylindrical batch reactor made of Hastelloy C-276 that can withstand high temperature and pressure. Concentrations of humic acids and ammonia were measured using a $COD_{Cr}$ method and an ammonia selective electrode, respectively. The optimal destructive condition of humic acids in the presence of stoichiometric oxygen(air) was 3 min at $380^{\circ}C$, but the temperature could be lowered to subcritical region ($360^{\circ}C$) along with $H_2O_2$ as an oxidant. For ammonia, the optimal destructive condition with air was 5 min at $660^{\circ}C$, but it was possible to operate the process for 3 minutes at $550^{\circ}C$ or 2 min at $600^{\circ}C$ along with $H_2O_2$ as an oxidant. At 2 min and $550^{\circ}C$ along with $H_2O_2$ as an oxidant, humic and ammonia compounds in the actual leachate were easily destructed and the effluent quality met the Korea Standard Leachate Quality.

• 한국식품과학회지
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• 제46권4호
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• pp.465-469
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• 2014

버려지는 자몽 껍질에 다량 함유되어있는 플라바논을 추출하여 기능성 성분을 재이용하였다. 친환경용매인 아임계수 추출기술을 이용하여 $170^{\circ}C$, 10 min의 최적 조건에서 추출함으로써 무독성 용매로 빠르고 경제적으로 추출할 수 있었다. 자몽껍질 추출물을 ${\beta}$-cyclodextrin을 이용하여 처리함으로써 플라바논과 같은 비극성 물질을 캡슐화하여 소재의 가용화를 용이하게 하였다. 이것은 항산화 기능이 향상된 대체 소재의 개발 및 건강지향식품에 이용할 수 있으며, 이를 통하여 세계 기능성 식품 시장으로의 진출을 위한 발판으로도 삼을 수 있을 것으로 기대된다.

• Fisheries and Aquatic Sciences
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• 제26권1호
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• pp.24-34
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• 2023

Reactive oxygen species (ROS) at high concentrations induce oxidative stress, an imbalanced redox state that is a prevalent cause of neurodegenerative disorders. This study aimed to investigate the protective effect of Capsosiphon fulvescens (CF) extract on oxidative stress-induced impairment of cognitive function in models of neurodegenerative diseases. CF was extracted with subcritical water and several solvents and H₂O₂ (0.25 mM) or aluminum chloride (AlCl₃; 25 µM) as an inducer of ROS was treated in PC12 neuronal cells and zebrafish larvae. All statistical analyses were performed using one-way analysis of variance and Dunnett's test using GraphPad Prism. H₂O₂ and AlCl₃ were found to significantly induce ROS production in PC12 neuronal cells and zebrafish larvae. In addition, they strongly affected intracellular Ca²⁺ levels, antioxidant enzyme activity, brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) signaling, acetylcholinesterase (AChE) activity, and hallmarks of Alzheimer's disease. However, treatment of H₂O₂-induced PC12 cells or AlCl₃-induced zebrafish larvae with CF subcritical water extract at 90℃ and CF water extract effectively regulated excessive ROS production, intracellular Ca²⁺ levels, and mRNA expression of superoxide dismutase, glutathione peroxide, glycogen synthase kinase-3 beta, β-amyloid, tau, AChE, BDNF, and TrkB. Our study suggested that CF extracts can be a potential source of nutraceuticals that can improve the impairment of cognitive function and synaptic plasticity by regulating ROS generation in neurodegenerative diseases.

• Advances in materials Research
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• 제13권3호
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• pp.233-241
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• 2024

Quantitative analysis of the Zingiber Officinale sample using subcritical water extraction (SWE) was developed employing High-Performance Liquid Chromatography (HPLC) to bolster the advancement of this innovative green extraction process. This research focuses on three principal ginger bioactive compounds: 6-gingerol, 6-shagoal, and 10-gingerol. Various stages were undertaken to establish the quantitative analysis method, encompassing the optimisation of HPLC operating conditions and the formulation of standard calibration curves, yielding individual compound equations. A robust correlation within the calibration curve was achieved, exhibiting an r² value of 0.9814 and an RSD of 5.00%. A simultaneous, swift, and dependable method was established with an injection time of 20 minutes and an 8-minute delay between injections, in contrast to the previous HPLC analysis requiring a 45-minute injection time for detecting and quantifying all components. Notably, no post-treatment was applied after the SWE process. This advancement allows for potential future online measurement of Zingiber Officinale bioactive compounds extracted using subcritical water extraction through this technology.