• Journal of the Korean Society of Combustion
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• v.18 no.4
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• pp.37-43
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• 2013

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

• Economic and Environmental Geology
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• v.38 no.1
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• pp.91-99
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• 2005

Acid Rock Drainage(ARD) is the product formed by the atmospheric(i.e. by water, oxygen and carbon dioxide) oxidation of the relatively common iron-sulphur mineral pyrite($FeS_2$). ARD causes the acidification and heavy metal contamination of water and soil and the reduction of slope stability. In this paper the generation characteristics and the prediction of ARD of various cut slopes were studied. An attempt to classify the rocks into several groups according to their acid generation potentials was made. Acid Base Accounting(ABA) tests, commonly used as a screening tool in ARD predictions, were performed. Fourteen rock samples were classified into PAF(potentially acid forming) group and four rock samples into NAF(non-acid forming) group. The chemical analysis of water samples strongly suggested that ARD with high content of heavy metals and low pH could pollute the ground water and/or stream water.

• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.1
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• pp.39-48
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• 2009

Biodiesel is estimated to be the best recycling energy source as an alternative fuel for transportation vehicles which represents the biggest share of greenhouse effect gas exhausts. Thus, in order to widely expand use of biodiesel and to enhancement its reliability, studies on quality improvement of biodiesel is needed. In this study, we have produced biodiesel(BD100, BD20) through esterification reaction using raw material of waste frying oil and analyzed compatibility with 24 items of quality criteria. As waste frying oil has high contents of unsaturated fatty acid such as Oleic acid, Linoleic acid and Linolenic acid, it is confirmed that there is no problem in using the same as a raw material of biodiesel. The result of analyzing the quality criteria items of biodiesel showed that it satisfied all the quality criteria except the oxidation stability of BD100, which was 2 hours, fatty acid methyl ester of BD20, which was 18.6w% and the filter plugging point, which was $-5^{\circ}C$. We believe that it will contribute to improved utilization of waste resources as alternative energy if studies on technology to improve quality of some items are provided.

• Korean Journal of Food Science and Technology
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• v.50 no.3
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• pp.308-315
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• 2018

To select suitable cultivars to produce sweet potato (SP) chips instead of potato chips, ten Korean cultivars, Sinjami, Yeunjami, Sinhwangmi, Juhwangmi, Sincheonmi, Sinyulmi, Gunhwangmi, Dahomi, Daeyumi, and Pungwonmi were used. The acrylamide content, quality characteristics, and oxidation stability of SP chips were investigated. Acrylamide content was shown to be under 0.48 mg/kg in case of all cultivars except Yeunjami (1.07 mg/kg). The color values significantly differed among the cultivars and were maintained like those of raw roots. The hardness, brittleness, and fracturability of Juhwangmi and Sinhwangmi chips showed the lowest values, while those of Daeyumi were the highest. According to the sensory evaluation data, the quality characteristics of chips were influenced by not only hardness, fracturability, and crunchiness, but also the flavor taste. Pungwonmi chips showed the highest score, followed by Gunhwangmi and Dahomi chips. Therefore, Pungwonmi, Dahomi, and Gunhwangmi are suggested as suitable cultivars to make SP chips, because of their high overall quality and very low acrylamide content.

• Food Science of Animal Resources
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• v.25 no.4
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• pp.507-512
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• 2005

This study was designed to investigate the effect of $\beta-carotene$ on the heat oxidation stability of deep fried laid with different healing temperature. Commercially purchased $\beta-carotene$ was used to this experiment $\beta-carotene$ was added to the deep fried lard at final concentration of $0\%\;0.001\%\;and\;0.004\%$ (wt/wt fat basis). Total plate count peroxide value, acid value, and TBA(thiobarbituric acid) values of the samples were determined regulary at $50^{\circ}C$ during 15 days. The result of the study are as follows: The number of microorganism was decreased by $\beta-carotene$ added to the deep fried lard Deep fried lard with $0.004\%$ $\beta-carotene$ have higher antioxidative effect than those of control and $0.001\%$ treated group. Peroxide and TBA values were significantly (P<0.05) decreased in all samples by added $\beta-carotene$ at $0.004\%$ Antioxidative effect increased with increasing concentration of $\beta-carotene$. These results suggest that $\beta-carotene$ might inhibit the growth of microganisms and retard lipid oxidation in the deep fried lard.

• Journal of Food Hygiene and Safety
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• v.20 no.2
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• pp.89-97
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• 2005

The influence of different storage temperature and packaging methods on the flying cultured eel bone were investigated. The acid values, peroxide values and fatty acid composition were measured during storage 20$^{\circ}C\;and\;40^{\circ}C$ for 60 days. The lipid oxidation was rapidly progressed with the increased temperature. The addition of oxygen absorber remarkably repressed lipid oxidation during storage of the living cultured eel bone at $20^{\circ}C\;and\;40^{\circ}C$, followed by $N_{2},\;BHA,\;\alpha$-tocopherol and control. The monounsaturated fatty acid content was the highest in the frying cultured eel bone, followed by saturated fatty acid and polyunsaturated fatty acid. The major fatty acids were oleic acid, palmitic acid and linoleic acid. The saturated fatty acids increased with the rise of storage temperature and prolonging the storage period, while monounsaturated fatty acid and polyunsaturated fatty acid were decreased. The changes of fatty acid composition were the lowest in sample by packing with oxygen absorber, followed by packing $N_{2},\;BHA,\;\alpha$-tocopherol and control. from the result of sensory evaluation, sample by packing with oxygen absorber were rated as higher quality than the others.

• Journal of Animal Science and Technology
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• v.46 no.4
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• pp.635-644
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• 2004

This experiment was earned out to investigate the effects of dietary vitamin C and E on lipid oxidation and stability of color in Hanwoo steer beef. Thirty seven Hanwoo steers were randomly assigned to one of four treatments. The four treatments were control(vitamin E 20IU/kg feed), vitamin C(vitamin C 0.l%/kg feed and vitamin E 20IU/kg feed), vitamin E(vitamin E 220IU/kg feed) and vitamin C plus E(vitamin C 0.l%/kg feed and vitamin E 20IU/kg feed). Hanwoo steers were fed the experimental diets for 3 months at the last finishing period and pH, color, TBARS, concentration of myoglobin, water holding capacity, reduction by heat, drip loss and purge loss of longissimus dorsi were analyzed at 1, 3, 5, 7 and 10th day of storage, respectively. pH value, Hue angle, metmyoglobin concentration, TBARS, drip loss and purge loss in longissimus dorsi were increased as the storage period elapsed. However, water holding capacity in longissimus dorsi was decreased as the storage period elapsed. The animals fed the vitamin C plus E diet were higher in pH value and oxymyoglobin concentration, and lower in metmyoglobin concentration than in those fed the other diets during the whole storage period and lowest in TBARS. TBARS and Hue angle in longissimus dorsi were 10wer(P<0.05) in the animals fed the vitamin-supplemented diets than in those fed the control diet. Reduction by heat in longissimus dorsi was higher(P<0.05) in the animals fed the diets supplemented with vitamin E or vitamin C plus E than in those fed the control diet or vitamin C-supplemented diet. According to these results, it may be concluded that feeding the diets containing 0.1% vitamin C or 220IU vitamin E per kg feed or the diet mixed 0.1% vitamin C with 220IU vitamin E to Hanwoo steers can retard lipid oxidation of longissimus dorsi and stabilize beef color.

• Journal of Nutrition and Health
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• v.12 no.1
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• pp.51-58
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• 1979

It is a general trend everywhere that the uses of vegetable oils are increasing due to the fact that they are effective in curing and preventing symptoms of high blood pressure and various heart failure conditions. At the same time the concept that oxidative rancidity is caused by the oxidation of unsaturated fatty acid moieties whose subsequent decomposition gives rise to various undesirable, sometimes toxic compounds is now well accepted. Linolenic acid (C, 18:3) is one of highly unsaturated and readily oxidizable fatty acid. The content of this essential polyunsaturated fatty acid in perilla seed oil (PSO) was found to be as high as 48% while only 1.5% in sesame seed oil (SSO). In this experiment the oxidative stability of PSO was compared with that of SSO. The experimental test group were as follows: A) Stored at different temperatures, namely $4^{\circ}C,\;30^{\circ}C,$ and $60^{\circ}C,$ B) Stored at room temperature $(20{\pm}5^{\circ}C)$ ; a. protected from sunlight and air, b. exposed to air without sunlight c. exposed to sunlight but protected front air, d. completely exposed to both air and sunlight. The following results were obtained; 1) It was found to be most stable against oxidation to store both PSO and SSO under the low temperature $(4^{\circ}C)$ condition. According to P.V. measurements it was found to be safe to keep both oils up to $30^{\circ}C$ for at least 8 weeks. When exposed to air, sunlight and high temperature $(60^{\circ}C)$, P.V. of PSO reached there peak values, which were much higher than those of SSO. This explains much of its instability as compared to SSO against oxidation. 2) The effect of high temperature $(60^{\circ}C)$ on A.V. was found to be more striking than those of all the other storage conditions. The condition of refrigeration was most effective in keeping A.V. low for both oils as was the case in P.V. 3) For both oils, I.V. decreased throughout the experimental period (8 weeks). The range of decrement was larger for PSO than SSO. 4) There was no significant change in the compositions of fatty acids of SSO caused by various experimental storage conditions. But for PSO the compositions of stearic, oleic and linoleic acid were decreased, whereas linolenic acid was increased proportionally.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.729-734
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• 2008

The higher valence state of iron i.e., Fe(VI) was employed for the treatment of Cu(II)-EDTA in the aqueous/waste waters. The ferrate(VI) was prepared through wet oxidation of Fe(III) by sodium hypochlorite. The purity of prepared Fe(VI) was above 93%. The stability of Fe(VI) solution decreased as solution pH decreased through self decomposition. The reduction of Fe(VI) was obtained by using the UV-Visible measurements. The dissociation of Cu(II)-EDTA complex through oxidation of EDTA using Fe(VI) and subsequent treatment of organic matter and metal ions by Fe(III) reduced from Fe(VI) in bench-scale of continuous flow reactor were studied. The removal efficiencies of copper were 69% and 79% in pH control basin and reactor, respectively, at 120 minutes as retention time. In addition, Cu(II)-EDTA in the reactor was decomplexated more than 80% after 120 minutes as retention time. From this work, a continuous treatment process for the wastewater containing metal and EDTA by employing Fe(VI) as muluti-functional agent was developed.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.167-172
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• 2004

In the human skin, vitamin C (L -ascorbic acid) that is well known as the activated materials has effects that is skin anti-aging and wrinkle repair by giving impetus to collagen biosynthesis and anti-oxidation, and that is the sun screen, a wound recovering, inhibition melanogenesis and so on. In spite of its effects, vitamin C has the defects of the skin stimulation and easily oxidized instability by water, air, heat and light. For solving their matters, many investigation is advanced and its results are synthesized the various vitamin C derivatives. And yet they have not solved the unstable property of vitamin C and were still insufficient for the comparing with the effect of the pure vitamin C itself. In this study, in order to prepare vitamin C derivative of being improved the stability and to apply vitamin C effect in the skin, we prepared new vitamin C derivative, phytosphingosine ascorbate, by using phytosphingosine, one of sphingolipids, which have a distinguished skin affinity. Phytosphingosine ascorbate can be prepared as the ionic bond between amine group (-NH$_2$) of phytosphingosine and hydroxy group (-OH) of vitamin C by way of the relatively simple reaction. So the structure and properties of the synthesized phytosphingosine ascorbate was confirmed the use of elemental analysis (C 58.3 : H 9.3 : N 2.8 : O 29.5), MALDI TOF-MS (Mw=492.58), Ultraviolet spectra (268.5nm), lH NMR, FT-IR spectra, thermal analysis (m.p=l54$^{\circ}C$), HPLC and so on. And we could confirm the anti-bacterial and anti-oxidation effects. Based on these results, we could confirm to prepare a new material that was expected of both effects of vitamin C and phytosphingosine and that is improved properties of vitamin C.