• Nuclear Engineering and Technology
• /
• v.26 no.3
• /
• pp.425-432
• /
• 1994

Voltammogram analysis of U(VI) reduction at electrochemically non-pretreated/pretreated Ti electrodes in nitric acid and hydrazine($N_2$H$_4$)/protonated hydrazine($N_2$H$_{5}$$^{＋}$) media was done in order to determine the effect of hydrazine form and Ti electrode condition on the reduction of U(VI) in nitric acid. In the case of non-pretreated Ti electrode, the reduction in nitric acid and hydrazine mono-hydrate solution needed a high activation overpotential and was affected by the ratio of hydrazine to nitric acid rather than by only absolute amount of hydrazine because of the decrease of solution conductivity and increase of iR drop, which were caused by proton consumption in the solution by the hydrazine. In the case of pretreated Ti electrode in nitric acid and protonated hydrazine solution, the reduction current peaks of U(VI) were clearer and higher enough to perform a kinetic analysis, compared with the case with the non-pretreated Ti electrode at the same potential, and the behavior was strongly affected by nitric acid. The presence of hydrazine was important in the reduction of U(VI) at the pretreated Ti electrode for preventing the reoxidation of U(IV), but the concentration of protonated hydrazine was not.t.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.39 no.4
• /
• pp.631-636
• /
• 2010

To develop a natural antioxidant from three Chrysanthemum species, flower and shoot extracts of Chrysanthemum frutescens, Chrysanthemum morifolium and Chrysanthemum zawadskii ssp. naktongense were obtained and their phenolic compound contents, scavenging effects on DPPH and ABTS radicals, ferrous ion chelating effects and inhibition activity on lipid peroxidation of linoleic acid were studied. Shoots of C. morifolium showed the highest levels in all above mentioned analyses. Especially, shoot extract of C. morifolium had high scavenging activities on ABTS radicals, similar to ascorbic acid or BHT. Ferrous ion chelating effect was the lowest in a C. morifolium shoot extract, but the highest in a C. morifolium flower extract. Inhibition activity on lipid peroxidation of linoleic acid was the highest with C. frutescens and C. morifolium shoots, but activity was lower than BHT. From present study, a shoot extract of C. morifolium is demonstrated as a valuable source for the development of a natural antioxidant. However, due to its low levels of ferrous ion chelating effects and inhibition activity on lipid peroxidation, a combination of other antioxidants with C. morifolium extract is recommended for the development of a new antioxidant.

• Journal of the Korean Electrochemical Society
• /
• v.19 no.1
• /
• pp.21-27
• /
• 2016

Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

• Korean journal of food and cookery science
• /
• v.24 no.6
• /
• pp.876-881
• /
• 2008

The aim of this study was to evaluate the quality characteristics and antioxidant activities of green tea garlic paste added calcium. Garlic was heated with green tea and charcoal at high temperature ($120^{\circ}C$) and high pressure ($1.5\;kgf/cm^2$) for 20 min, and then added several calcium sources (calcium carbonate, calcium citrate, calcium lactate, mixed calcium, calcium powder). Calcium carbonate, mixed calcium or calcium powder significantly increased pH of green tea garlic paste (p<0.05). All kinds of calcium sources significantly increased the viscosity of green tea garlic paste (p<0.05). Solid soluble content of green tea garlic paste was increased only in calcium citrate and calcium powder groups. Lightness, redness and yellowness of green tea garlic paste with calcium were increased, compared with control group (green tea garlic paste without calcium). The antioxidant activities by DPPH and hydroxyl radical scavenging activity of green tea garlic paste added calcium citrate, calcium lactate or calcium carbonate group were much higher than those of the other control groups. The garlic odor and garlic taste by sensory test were significantly weaker in calcium carbonate or calcium citrate group (p<0.05). Based on these results, it was suggested that calcium carbonate or calcium citrate is appropriate material for deodorizing and fortifying agent for green tea garlic paste.

• Journal of the Korean Magnetics Society
• /
• v.3 no.2
• /
• pp.108-114
• /
• 1993

This paper presents a study on the effects of silica coating in the production of ${\gamma}-Fe_{2}O_{3}$ powders suitable for magnetic recording media. Emphasis has been put on investigating the relationship between the powder characteristics and the effects of silica coating in the heat-treatment stage of ${\gamma}-Fe_{2}O_{3}$ production. After we prepared non-coated ${\gamma}-Fe_{2}O_{3}$ and silica coated ${\gamma}-Fe_{2}O_{3}$ with coating water glass on the surface of goethite and heattreatment process, we compared and investigated powder characteristics. As silica coated layer played a role of preventing the powders from overreduction to metal iron and rapid oxidation, silica coated ${\gamma}-Fe_{2}O_{3}$ showed superior magnetization value due to inhibiting t!1e adulteration of ${\alpha}-Fe_{2}O_{3}$ into the final product. When silica coated layer acted as a sintering restrainer, silica coated ${\gamma}-Fe_{2}O_{3}$ showed high coercivity and specific sur-face area due to good acicularity.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.35 no.6
• /
• pp.543-547
• /
• 1990

Diurnal courses of $CO_2$ concentration and air temperature in the rice seedbed tunnel covered with polyethylene film, subjected to three different ventilation methods, were traced. Regaredless of ventilation methods, $CO_2$ concentrations in the tunnel on a clear day were lower than that in ambient air, and vice versa before dawn. $CO_2$ concentration during the day was lowest in the tunnel with non-ventilation (NV), followed by horizontal slit ventilation (HSV) and traditional one(TN), reaching down to the lowest level of 58ppm, 155ppm and 272ppm, respectively. Air temperature in the tunnel reached 46$^{\circ}C$ in NV, 37$^{\circ}C$ in HSV and 32$^{\circ}C$ in TV at the daytime when ambient air temperature was 22$^{\circ}C$. Even at night time of ambient air temperature below 15$^{\circ}C$, HSV was more effective than TV in raising the air temperature in the tunnel. The dry weight of 40-day old seedling weighed heaviest in HSV, followed by TV and NV.

• Journal of Dairy Science and Biotechnology
• /
• v.31 no.2
• /
• pp.99-108
• /
• 2013

Kefir is a unique fermented dairy product resulting from combined lactic acid and alcoholic fermentation of lactose in milk. Kefir is produced by the microbial activity of kefir grains. Kefir has numerous health benefits such as the reduction of cholesterol levels, stimulation of the immune system, antimutagenic and anticarcinogenic properties, and improvements of lactose intolerance. Furthermore, kefir is excellent as both a dietetic beverage and for protection against various diseases in small babies. Therefore, kefir has recently been regarded as an important functional dairy food. To date, the majority of research on kefir has focused on the applications of functional kefir using advanced biotechnology methods. The purpose of this review article is to facilitate the recognition of kefir as a novel functional food.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.4
• /
• pp.393-400
• /
• 2012

In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.2
• /
• pp.141-149
• /
• 2015

In the fabrication of electronic circuits used in electronic products, molybdenum thin films are deposited on semiconductors to prevent oxidation. During the deposition, the presence of a particle or dust at the interface between the thin film and substrate causes the decrease of adhesion, performance, and life cycle. In this study, a damage measurement targeting two kinds of glass substrate, with and without particles, was performed in order to measure the change in the molybdenum thin film deposition area in the presence of a particle. Clean and dirty molybdenum thin film specimens were fabricated and directly deposited on a substrate using the sputtering method, and a reflection-type digital holographic interferometer was configured for measuring the damage. Reflection-type digital holography has several advantages; e.g., the configuration of the interferometer is simple, the measurement range can be varied depending on the magnification of a microscopic lens, and the measuring time is short. The results confirm that reflection-type digital holography is useful for the measurement of the damage and defects of thin films.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.6
• /
• pp.876-881
• /
• 2003

Physicochemical characteristics of the red peppers dried in hot-air by various processing to shorten drying time were investigated during storage at -2$0^{\circ}C$ for 120 days. The pH of red pepper powders gradually decreased in proportion to storage day, but there were no significant differences between samples during storage. The pH of red pepper powder treated with 0.1% vitamin C was the lowest as 4.64 at 120 storage days. Capsaicin and dihydrocapsaicin contents gradually decreased during storage, but the red pepper powder treated with 0.1% vitamin C was higher than others after 120 storage days. As a result of color evaluation, L values of red pepper powder dried after only mashing and dried after aging next to mashing were higher than the control, whereas a and b values of red pepper powder dried after mashing were higher at 120 storage days, compared with the control. Results of color and taste acceptability showed color value of red pepper powder dried after mashing was 93.0% higher than 43.0% of the control, and in taste acceptability the control was 48.0%, whereas its dried after treatment of 0.1% vitamin C was the highest value as 92.0%.