• Korean Journal of Plant Resources
• /
• v.23 no.5
• /
• pp.393-398
• /
• 2010

Naturally occurring substances which strongly scavenge peroxynitrite(ONOO-) are evaluated to be beneficial for cardiovascular, diabetic, hypercholesterolemic and obese disease. To search for bioactive substances with peroxynitritescavenging activity from the young leaves of Heracleum moellendorffii(Umbelliferae) used for a mountainous vegetable, the experiment on peroxynitrite-scavenging assay, phytochemical isolation and HPLC analysis were undertaken. Activity-guided fractionation led to the separation of astragalin and hyperoside which were identified by physicochemical and spectroscopic data. The $IC_{50}$ values of astragalin and hyperoside were shown as $5.80{\pm}0.62$ and $0.560{\pm}0.26\;{\mu}M$, respectively, in the assay. The HPLC analysis led to the quantitative determination of astragalin and hyperoside by $30.0{\pm}0.01$ and $17.0{\pm}0.02\;mg/g$ dried weight, respectively.

• Journal of Korea Port Economic Association
• /
• v.33 no.1
• /
• pp.75-87
• /
• 2017

The purpose of this study is to utilize the system dynamics to carry out a medium and long-term forecasting analysis of the bunker price. In order to secure accurate bunker price forecast, a quantitative analysis was established based on the casual loop diagram between various variables that affects bunker price. Based on various configuration variables such as crude oil price which affects crude oil consumption & production, GDP and exchange rate which influences economic changes and freight rate which is decided by supply and demand in shipping and logistic market were used in accordance with System Dynamics to forecast bunker price and then objectivity was verified through MAPEs. Based on the result of this study, bunker price is expected to rise until 2029 compared to 2016 but it will not be near the surge sighted in 2012. This study holds value in two ways. First, it supports shipping companies to efficiently manage its fleet, offering comprehensive bunker price risk management by presenting structural relationship between various variables affecting bunker price. Second, rational result derived from bunker price forecast by utilizing dynamic casual loop between various variables.

• Applied Chemistry for Engineering
• /
• v.29 no.4
• /
• pp.468-473
• /
• 2018

In this study, the reforming reaction of vacuum residues (VR), high viscosity oil residues produced from vacuum distillation process of petroleum oil, was carried out using catalytic aquathermolysis reaction. VR showed a prone to decrease the amount of resins and asphaltenes in the constituents, and to increase saturates and aromatics when reacting with steam at 30 bar and above $300^{\circ}C$ for 24 h. When the amount of steam is not enough at this reaction, the asphaltene content in the products was rather increased after the reaction. As a result of the catalytic aquathermolysis using the metal oxide-zeolite catalyst with the decaline as a hydrogen donor, a 10% decrease in resin and asphaltene as well as a 10% increase in the aromatic hydrocarbon were observed. Consequently, the viscosity of VR decreased by 70% after the reaction. GC-Mass spectroscopy showed that the aquathermolysis of VR resulted in the decomposition of the resins and asphaltens into a low molecular weight material.

• Journal of the Korean Data and Information Science Society
• /
• v.28 no.6
• /
• pp.1471-1479
• /
• 2017

The variability of trade price index of apartment influences on the various aspect, especially economics, social phenomenon, industry, and culture of the country. In this article, the autoregressive error (ARE) model has been considered for analyzing the monthly trading price index of apartment data. About 16 years of the monthly data have been used from September 2001 to May 2017. In the ARE model, six macroeconomic variables are used as the explanatory variables for the rade price index of apartment. The six explanatory variables are mortgage rate, oil import price index, consumer price index, KOSPI stock index, GDP, and GNI. The result has shown that trading price index of apartment explained about 76% by the mortgage rate, and KOSPI stock index.

• Applied Chemistry for Engineering
• /
• v.7 no.3
• /
• pp.443-452
• /
• 1996

Fouling is caused by sedimentation and corrosion of polymer, heavy paraffine, chemicals, heavy organics, asphaltene, etc. in the entire chemical process of heat exchanger, boiler, desalter, etc. Fouling phenomena remains a serious operating problem which results in increased energy consumption, increased pressure drops, reduction or complete loss of products yield, and increased maintenance costs. In order to calculate the separated amounts of foulants and to control the fouling process, the predictive model is developed which is based on Scott & Magat polymer solution theory, Peng-Robinson EOS, BWR EOS, and continuous and multicomponent thermodynamics.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.4
• /
• pp.50-56
• /
• 2008

Aqueous thermal liquefaction of rice, barley, wheat, and rapeseed straws was investigated to compare the amount of heavy oil with catalysts such as $K_2CO_3$, NaOH and KOH in the reaction temperature at $320^{\circ}C$ for 10 minutes. The reaction was carried out in a 5,000ml liquefaction system with dispenser and external electrical furnace. Raw materials (160g), 2,000ml of distilled water and 10% (wt/wt) of catalyst to plant residue were fed into the reactor. It was observed that the maximum heavy oil yield was about 29% from the feeding stock, barley straw, with addition of KOH. The caloric values of crude oil from different crop residues were ranged from 55% to 66% relative to the raw materials depend on crop residue. It was appeared that its maximum calorific value from wheat straw was approximately 6190 kcal/kg.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.1
• /
• pp.40-53
• /
• 1996

In this paper, the wave drift damping is studied. An approximate method is adopted to calculate the wave drift damping for the sake of practical applications. By assuming the ship's forward speed to be low, the Green function and the velocity potential are expanded asymptotically with respect to the Brard number(${\tau}$) and terms up to the first order of ${\tau}$ are retained. Mean wave drift forces are computed straightforwardly. The wave drift damping is estimated as the change rate of the mean wave drift force with respect to the ship's speed. In order to validate the present method, Series 60(Cb=0.7) ship is exemplified for forward speed of Fn=0, 0.02 and 0.04. To predict the wave drift damping experimentally, three geosym models of the Esso-Osaka tanker are used. Also the effect of drift angle on the wave drift damping is also considered. Comparisons between numerical and experimental results show reasonable agreements.

• Journal of Life Science
• /
• v.21 no.1
• /
• pp.134-140
• /
• 2011

One hundred forty five bacterial colonies which were able to degrade crude oil were isolated from soil samples that were contaminated with oil in the Daejon area. Among these colonies, one bacterial strain was selected for this study based on its low surface tension ability, and this selected bacterial strain was identified as Pseudomonas sp. Z1 through physiological-biochemical tests and analysis of its 16S rRNA sequence. Pseudomonas sp. Z1 showed a high resistance to antibiotics such as chloramphenicol and ampicillin, as well as heavy metals such as lithium, manganese, and barium. It was found that the optimal pH and temperature for biosurfactant production of Pseudomonas sp Z1 were pH 6.0-7.0 and $30^{\circ}C$, respectively. After ten hours of inoculation, the biosurfactant activity of the culture broth decreased rapidly, and had maximum surface tension (28 dyne/cm) after twenty-one hours incubation. The biosurfactant activity of the culture broth was also decreased up to 2% NaCl concentration.

• Transactions of the Korean hydrogen and new energy society
• /
• v.32 no.5
• /
• pp.374-387
• /
• 2021

Basic design of 3 MWth chemical looping combustion system for LNG combustion and steam generation was conducted based on the mass and energy balance and the previous reactivity test results of oxygen carrier particles. Process configuration including fast fluidized bed (air reactor), loop seal and bubbling fluidized bed (fuel reactor) was confirmed and their dimensions were determined by mass balance. Then, the external fluidized bed heat exchanger (FBHE) was adopted based on the energy balance to extract heat from the system. The optimum reactor design and operating condition was confirmed with sensitivity analysis by modifying system configuration based on the mass and energy balance.

• Journal of Korea Port Economic Association
• /
• v.36 no.4
• /
• pp.1-16
• /
• 2020

Since Korea has excellent port infrastructure and competitive petrochemical complexes, there is plenty of potential for creating an oil hub in Northeast Asia. In particular, Ship-to-Ship (STS), which creates high added values, contributes greatly to the national economy. In this study, the liquid cargo volumes of chemical industrial products, refined petroleum products, and crude oil were analyzed at the national and regional (Busan, Ulsan, and Yeosu/Gwangyang) levels. Additionally, a Granger causality analysis was performed between imports, exports, and transshipments, in pairs. ADF, PP, and KPSS were analyzed for the unit root test. In addition, the VAR model and expanded VAR model suggested by Toda and Yamamoto were used for further analyses. Findings revealed a difference in Granger causality depending on the region or cargo type. These findings suggest that policies and incentive schemes for ports need to be differentiated according to the region and cargo types. In addition, the different patterns in the relationship between transshipments and import-export petrochemical cargoes should be considered.