• Journal of Radiation Industry
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• v.5 no.1
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• pp.21-24
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• 2011

This study was conducted to evaluated the sensory properties of Miyukgook, Korean seaweed soup, with gamma-irradiated Undaria pinnadifida for enhancing the storage of the harvested seaweed. The harvested seaweed was irradiated at the doses of 1, 3, 5, and 10 kGy. The Miyukgook was made by following the general recipe. The values of pH and acidity of the Miyukgook were not changed by the irradiation of harvested Undaria. The sensory evaluation result showed that the preference scores in all the sensory properties was a little decreased when it was irradiated, but sensory score of less than 5 kGy samples was similar in all terms. Therefore, it was considered that gamma irradiation with less than 5 kGy was effective for improvement of the storage stability of U. pinnatifida without the changes in the sensory of its major cooked food, Miyukgook.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.301-308
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• 2007

Silicate mineral serpentine with magnesium and calcium was selected as a mineral carbonation mediators for carbon dioxide storage. Serpentine has various metallic elements as an oxides form of magnesium, iron, calcium, aluminium etc. Magnesium and calcium could be carbonation salt preferentially than other metal component within serpentine. Systemic thermochemical treatment for serpentine could change physicochemical properties like a surface area and pore dimensions. Due to the rapid chemical reaction rate depended on dimensional values, carbonation formation could determined by surface property change of thermochemical treated serpentine.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.2
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• pp.85-92
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• 1998

The hydrogenation behavior of $Mg_2Ni$ powder prepared by ball milling has been studied. Ball milled $Mg_2Ni$ was transformed to an amorphous-like state after 200hr ballmilling, and crystallized to $Mg_2NiH_x$ by hydrogenation at got. The hydrogen storage capacity gradually increased as a function of ball milling time. $Mg_2Ni$ by 400hr ballmilling shows higher hydrogen storage capacity (3H/M) than $Mg_2Ni$ by VIM(Vacuum Induction Melting).

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.180-184
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• 2000

The dymanic properties of the high-Tc superconductor journal bearings used in the KEPRI flywheel energy storage system was experimentally estimated by using the imbalance excitation method. The test reveals that the superconductor bearings have very low stiffness compared to that of typical oil film bearings with similar geometry and almost the same amount of damping as in roller bearings, which may not be helpful for the system to pass through the critical speeds. However, it was found out that the cross-coupled stiffness and damping terms were almost negligible so that the system could be more stable than the one using lil film bearings. Also with proper design of the rotor-bearing system and accurate balancing of the rotor, the high-Tc superconductor bearing is one of the most viable alternatives to the conventional ones due to its oil-free, non-contact running capability in a vacuum environment, which is literally essential for highly efficient flywheel energy storage systems.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.4
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• pp.41-46
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• 1983

The current-fed DC-DC converter has only one energy storage reactor in series with the input for any number of outputs and is insensitive to transformer volt-second unbalance. It is considered that these properties of the converter are considerable advantages over other maltiple-output circuits. The steady-state and dynamic characteristic and stability for the current-fed DC-DC con-verter are analyzed in detail. The analysis is carried out by the state-space averaging method for the operation with the duty ratio less than 50% and is confirmed by the experiment. From the evaluation of stability it is identified that the stability of this converter is excellent as compared with that of the conventional buck type converter.

• Korean Journal of Food Science and Technology
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• v.16 no.1
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• pp.66-70
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• 1984

An attempt was made on the development of a commercial scale storage method of garlic by irradiation. Irradiated garlics with 50, 100 and 150 Gy were stored at natural low temperature storage room $(12{\pm}6^{\circ}C,{\;}75-85%{\;}RH)$ and the physicochemical properties during the 10 months storage were investigated. The unirradiated garlic was mostly sprouted after 8 months storage, whereas the sprouting of all irradiated groups was completely inhibited until 10 months storage, The rotting rate and weigh loss of garlic after 10 months storage were reduced by 25 to 54% at 100 Gy irradiation compared with those of an unirradiated group. The moisture content remained relatively constant during the whole storage period. The total sugar content was increased with storage period. Ascorbic acid content was also decreased until 8 months storage but its content was rapidly increased along with sprouting. Garlic was marketable after 10 months storage by 100 Gy irradiation combined with natural low temperature.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.429-433
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• 2015

The binding ability and hydrogen storage capacity of nitrogen doped carbon nanotube with divacancy (4NDCN_xNT) that is decorated with transition metals was investigated based on density functional theory calculations. Results indicate that scandium shows an ideal reversible hydrogen binding capability with promising system-weight efficiency compared with other transition metals when functionalized with 4ND-CN_xNT. The (Sc/4ND)₁₀-CN_xNT can store up to 50H₂ molecules, corresponding to a maximum gravimetric density of 5.8 wt%. Detailed structural stability and electronic properties were reported as hydrogen molecules were absorbed. It takes about 0.16 eV/H₂ to add one H₂ molecule, which assures reversible storage of H₂ molecules under ambient conditions.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.280-288
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• 2017

Nanocarbon base materials such as, graphene and graphene hybrid with high electrochemical performances have great deal of attention to investigate flexible, stretchable display and wearable electronics in order to develop portable and high efficient energy storage devices. Battery, fuel cell and supercapacitor are able to achieve those properties for flexible, stretchable and wearable electronics, especially the supercapacitor is a promise energy storage device due to their remarkable properties including high power and energy density, environment friendly, fast charge-discharge and high stability. In this study, we have fabricated flexible supercapacitor composed of graphene/conductive polymer composite which could improve its electrochemical performance. As a result, specific capacitance value of the flexible supercapacitor (unbent) was $198.5F\;g^{-1}$ which decreased to $128.3F\;g^{-1}$ (65% retention) after $500^{th}$ bending cycle.

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.43-49
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• 2018

The demand for energy storage devices capable of operating at high temperatures is increasing. In order to operate at high temperatures, a device must have excellent thermal stability and no risk of explosion. Ionic liquids are electrolytes that satisfy the above conditions, and studies on improving their performance have attracted great interest. Here, we report the results of a study on the fabrication of a supercapacitor that has a composite electrolyte prepared by dispersing fumed silica in an ionic liquid. The fumed silica filler exhibits improved ionic conductivity and lower interfacial resistance. In particular, the silica nanoparticles with diameters of 10 nm exhibit better electrochemical properties than fillers of other diameters and have excellent device performance of 33 times higher than the pristine ionic liquid at high temperatures. This study can be used to improve the electrolytes of electrochemical devices, such as the next generation battery or lithium ion battery.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.6
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• pp.578-586
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• 2018

In this study, we prepared the modified PBI random copolymer to reduce the problems of the pristine PBI about low solubility and proton conductivity. The random copolymer was synthesized from suberic acid, 5-aminoisophthalic acid, and 3,3'-diaminobenzidine to obtain $X_1Y_9$, $X_1Y_1$, $X_9Y_1$. Then, the membrane was fabricated by using solvent casting method with methanesulfonic acid at $140^{\circ}C$. Subsequently, the membrane was doped with phosphoric acid at $40^{\circ}C$. The chemical structure of the polymers was characterized by FT-IR. In addition, the physiochemical properties of the PBI were investigated by TGA, oxidative stability, acid uptake. Finally, the proton conductivity was measured at $100-180^{\circ}C$ without humidification. As the result, $X_1Y_9$ PBI random copolymer membrane showed higher conductivity.