• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.51-58
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• 2023

Hypergolic propellants, which can ignite themselves without an ignition source, are difficult to handle due to their corrosiveness and toxicity. Therefore, it is necessary to develop green hypergolic propellants with little or no toxicity. In this study, basic research on green hypergolic ignition propellants was conducted. With 95% hydrogen peroxide as an oxidizer and CNU_HGFv1 as a fuel, ignition and combustion characteristics of propellants were evaluated through a drop test, an ignition test, and a combustion test. As a result of the drop test, the ignition delay time was 9.7 ms. It was 27 ms in the ignition test, which was fast enough to be used as a propellant. As a result of the combustion test, a combustion efficiency of 95.4~98.1% was achieved at about 11.7 bar. It was confirmed that fast and stable combustion was possible without hard start or combustion instability.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.715-726
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• 2023

This study suggested that protective panels should be installed as sacrificial members as a safety design method for structures with potential explosions such as hydrogen charging stations to minimize direct damage to the structure and have resilience. To this end, the focus of the experiment is on quantitatively evaluating the impact of the structure when the protection panel is installed closely or spaced apart from the structure in a high-speed collision situation of the projectile. The experimental design used steel plates instead of concrete structural members mainly used in the past for excellent reproducibility, and the impact of structural members was compared and analyzed through deformation differences on the back of the steel plate. In addition, the impact of changes in the physical properties of the elastic body used as a separation material for the protective member and the difference in shock wave transmission time according to the protective member and the elastic body on the structural member was investigated.

• Journal of the Korean Applied Science and Technology
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• v.40 no.6
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• pp.1373-1380
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• 2023

This study investigated the effects of coumarin, a flavonoid known for various physiological activities like antiviral, anticancer, and antibacterial properties, on anti-oxidants and anti-inflammatory processes, aiming to explore its application in functional cosmetics. The results are as follows: Cell toxicity experiments using RAW 264.7 cells showed no significant cytotoxicity for coumarin at any concentration, indicating its safety for skin application. Observing coumarin's antioxidant activity through DPPH radical scavenging showed concentration-dependent effectiveness, though not significantly varied with concentration. The inhibition of silica-induced ROS production in cells was concentration-dependent. Both NO production inhibition and histamine release measurements showed concentration-dependent suppression. These findings suggest that Coumarin can be effectively used as a natural ingredient in cosmetic development for its antioxidant and anti-inflammatory properties.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.529-540
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• 2011

The purpose of this study was to analyze experiments for the rules of material change unit in 9th grade science textbooks and develop experiments applying small-scale chemistry (SSC). For this study, experimental methods for the precipitation experiment, water electrolysis experiment, decomposition of hydrogen peroxide experiment presented in the 9 science textbooks were analyzed. Problems and improvements that were needed were extracted by 13 science teachers performing the experiments. Experiments applying SSC were developed based on the improvements needed. Afterwards, 19 pre-service science teachers performed both the developed SSC experiments and the science textbooks' experiments. A questionnaire about merits and demerits of the experiments applying SSC was performed. According to the results of this study, most of the 9th grade science textbooks included the lead iodide precipitation experiment, water electrolysis experiment by Hoffman voltameter, and decomposition of hydrogen peroxide experiment using catalytic manganese dioxide. Improvements were needed on the quantity of reagents, time for performing experiments, and scale of experimental apparatus. Merits of the developed experiments applying SSC which used small amount of reagents were safety, easy waste material disposal, short reaction time, and reproducible experimental results. Demerits of the experiments applying SSC were difficulty in observing, decreased achievement, and lack of skill in handling small-scale apparatus. Therefore, if the experiments developed applying SSC were to be utilized in 9th grade science experiments, it will be possible to use less reagent and be able to teach and carry out reproducible experiments at the same time. Also, the reproducible experiments based on SSC will help students under stand the scientific concepts for the rules of material change unit.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.105-120
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• 2016

Most of riverside in Korea, in case of application of water curtain cultivation (WCC) technique, has been inveterately suffering from the gradual drawdown of groundwater level and related shortage of water resources during the WCC peak time. We believe that the water resources issue in these riverside areas can be effectively solved when the interaction between groundwater and nearby surface water is well understood. To investigate the connection between stream and ground water, and the influence of stream water on the nearby aquifer, this study examined the water temperature and oxygen and hydrogen stable isotopic compositions. The study area is well-known strawberry field applying the WCC technique in Sangdae-ri, Gadeok-myon, Cheongju City, and the sampling was done from February 2012 through June 2014 for stream and ground water. Some groundwater wells near stream showed big temporal variations in water temperature, and their oxygen and hydrogen stable isotopes showed similar compositions to those of adjacent stream water. This indicates that the influence of stream water is highly reflected in the stable isotopic composition of groundwater. Four cross-sectional lines from stream to hillside were established in the study area to determine the spatial differences in water quality of wells. At the late stage of WCC in February to March, groundwater of wells in line with short cross-sectional length showed the narrow range of isotopic compositions; however, those in the long cross-sectional line showed a wide compositional range. It was shown that the influence of the stream water at the late WCC stage have reached to the distance of 160 to 165 m from stream line, which is equivalent to the whole length and one-third point in each short and long cross-sectional line, respectively. Therefore, the wide compositional range in the long cross-sectional lines was not only due to the influence of stream water, but apparently resulted from the change of relative impact of each groundwater supplying from two or more aquifers. In view of stable isotopic compositions, there seems to be three different aquifers in this study area, which is competing for dominance of water quality in wells at each period of WCC.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.169-175
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• 2018

This study deals with a process for the recovery of hydrogen isotopes from methane ($CQ_4$) and water ($Q_2O$) containing tritium in the nuclear fusion exhaust gas (Q is Hydrogen, Deuterium, Tritium). Steam Methane Reforming and Water Gas Shift reactions are used to convert $CQ_4$ and $Q_2O$ to $Q_2$ and the produced $Q_2$ is recovered by the subsequent Pd membrane. In this study, one circulation loop consisting of catalytic reactor, Pd membrane, and circulation pump was applied to recover H components from $CH_4$ and $H_2O$, one of $CQ_4$ and $Q_2O$. The conversion of $CH_4$ and $H_2O$ was measured by varying the catalytic reaction temperature and the circulating flow rate. $CH_4$ conversion was 99% or more at the catalytic reaction temperature of $650^{\circ}C$ and the circulating flow rate of 2.0 L/min. $H_2O$ conversion was 96% or more at the catalytic reaction temperature of $375^{\circ}C$ and the circulating flow rate of 1.8 L/min. In addition, the amount of $CQ_4$ generated by Korean Demonstration Fusion Power Plant (K-DEMO) in the future was predicted. Then, the treatment process for the $CQ_4$ was proposed and HAZOP (hazard and operability) analysis was conducted to identify the risk factors and operation problems of the process.

• Journal of Food Hygiene and Safety
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• v.33 no.4
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• pp.316-323
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• 2018

The purpose of the present study was to investigate the effect of Salvia Plebia R. Br. (SP) powder on the antioxidative defense system and oxidative stress in rats which were fed a high fat high cholesterol diet. Accordingly, the rats were divided into four experimental groups which were composed of a high fat high cholesterol diet group (HF), HF diet with 5% SP powder supplemented group (PA), a HF diet with 10% SP powder supplemented group (PB), and a normal group (N). Consequently, the hepatic catalase activity of the HF group was decreased compared to the normal group (N), but it is recorded that of the PA and PB groups were significantly increased. With this in mind, the PA and PB groups resulted in the case of significantly increased activities of hepatic GSH-px and SOD. The hepatic superoxide radical and hydrogen peroxide contents of the PA and PB groups were significantly decreased, as compared to the HF group. The GOT and GPT activities of the PB group were also significantly decreased when thus compared to the HF group. Notably, the carbonyl values contents of the PA and PB groups were significantly reduced compared to the HF group. The hepatic TBARS values in the liver were significantly reduced as measured in the PA and PB groups. These results suggest that the SP powder may reduce the incidence of oxidative damage, by the activation of an antioxidative enzyme in rats fed with high fat high cholesterol diets.

• Journal of Food Hygiene and Safety
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• v.21 no.2
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• pp.65-69
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• 2006

In this study, we evaluated bacteriocidal effect of CaO (scallop shell powder) for the reduction of microorganism in Scomber japonicus and Pseudosciaena ciean manchurica, and compared with main chemical sanitizers such as chlorine, ethanol, hydrogen peroxide. As a result, the effectiveness of CaO showed dramatic reduction rate for total aerobic bacteria, Escherichia coli and Vibrio parahaemolyticus. The reduction rates of total aerobic bacteria for Scomber japonicus and Pseudosciaena ciean manchurica showed $2.6{\times}10^3\;and\;3.2{\times}10^4$ respectively; Those of Escherichia Coli were $6.3{\times}10^3\;and\;1.2{\times}10^4$, those of Vibrio parahaemolyticus were $5.4{\times}10^4\;and\;5.6{\times}\2.6{\times}10^310^4$, respectively. According to this result, bacteriocidal effect of CaO was about $10^4$ and was similar to bacteriocidal effects of other three chemical sanitizers. According to these results, CaO can alternate the currently used chemical sanitizers due to its natural origin as well as the effectiveness for sterilization.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.4
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• pp.339-344
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• 2010

Oxygen depleted water mass can damage aquatic animals not only in direct way but also in indirect way by generating toxic substances including occurrence of hydrogen sulfide and ammonia which are also highly detrimental to animal life in the water mass. An oxygen dissolution device was developed, which makes turnover of the oxygen rich (over 20 mg/L) surface water down to the bottom where hypoxia is evident and tested the device in terms of oxygen recovery in the oxygen depleted bottom water. the device with turnover rates of $3.6\;m^2$/min at the liquid oxygen injection rate of 48~26.3 L/min could recover dissolved oxygen level to 7~25 mg/L at depth 7 m to lead to the dissolution level of over 90% by the supply of liquid oxygen. The running advantage of the device is that it does not require any auxiliary tank and higher energy for operation. Therefore, it can be highly useful device to relieve damages to the farmed animals in the oxygen depleted waters.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.346-351
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• 1999

To develop a lactic starter to produce antimicrobial substance for inhibiting the growth of a variety of foodborne spoilage bacteria in fermented foods, we investigated the anti-bacterial effect of the antibacterial substance, produced by Lactobacillus amylovorus IMC-1, against foodborne spoilage strains, and its sensitivity on the treatment of proteolytic enzymes. L. amylovorus IMC-1, which was isolated from a traditional cheese in Inner Mongolia, produced a maximum amount of antibacterial substance in the skim milk medium after 72 h incubation at 37$^{\circ}C$, and further incubation resulted in the same activity. The substance obtained from gel filtration inhibited all strains used such as Bacillus subtilis IFO 3025, Staphylococcus aureus IAM 1011, Listeria monocytogenes VTU 206, Escherichia coli RB, and Pseudomonas fragi IFO 3458 at the concentration of 20 units/ml. This substance was found to show bactericidal action against B. subtilis, E. coli, and Ps. fragi, and bacteriostatic activity against both Staph. aureus and L. monocytogenes. The bactericidal action was due to cellular Iysis. The substance is not organic acid, hydrogen peroxide and proteinaceous compound.