• Carbon letters
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• 제16권2호
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• pp.127-131
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• 2015

In this work, highly porous carbons were prepared by chemical activation of carbonized biomass-derived aerogels. These aerogels were synthesized from watermelon flesh using a hydrothermal reaction. After carbonization, chemical activation was conducted using potassium hydroxide to enhance the specific surface area and microporosity. The micro-structural properties and morphologies were measured by X-ray diffraction and scanning electron microscopy, respectively. The specific surface area and microporosity were investigated by $N_2$/77 K adsorption-desorption isotherms using the Brunauer-Emmett-Teller method and Barrett-Joyner-Halenda equation, respectively. Hydrogen storage capacity was dependent on the activation temperature. The highest capacity of 2.7 wt% at 77 K and 1 bar was obtained with an activation temperature of $900^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.573-576
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• 2001

In the research fields of energy storage, and more specifically of supplying high powers, electrochemical supercapacitor have been among the most studied systems for many years. One of the possible applications is in electric vehicles. We have been working on electronically conducting polymers for use as active materials for electrodes in supercapacitors. These polymers have the ability of doping and undoping with rather fast kinetics and have an excellent capacity for energy storage. polythiophene (Pth) and polyparafluorophenylthiophene (PFPT) have been chemically synthesized for use as active materials in supercapacitor electrodes. Electrochemical characterization has been performed by cyclic voltammetry and an electrode study has been achieved to get the maximun capacity out of the polymers and give good cyclability. specific capacity values of 7mAh/g and 40mAh/g were obtained for PFPT and polythiophene, respectively. Supercapacitors have been built to characterize this type of system. Energy storage levels of 260F/g were obtained with Pth and 110F/g with PFPT

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1125-1130
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• 2006

An air source heat pump system producing the ice and water storage energy for cooling and heating of building has been proposed. Cycle design and simulation considering energy balance between heating and cooling capacity has been carried out. The roles of the capacity controlled compressor, refrigerant heating device and air preheating are investigated in detail. System control logic for meeting the predetermined heating capacity when the system is operated at cold climate condition is suggested. Some anticipated problems of the proposed system are also described.

• 한국초전도ㆍ저온공학회논문지
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• 제1권1호
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• pp.22-27
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• 1999

Recently, small-sized superconducting magnetic storage($\mu$SMES) coils become commercially as an energy storage device for a power conditioner. In design and fabrication of the $\mu$SMES coils, to determine optimum current capacity of the superconducting(SC) conductors is one of the important things. We thus investigated the effect of conductor's current capacity, current density, and stability on the coil's maximum stored energy density in consideration of AC losses and switching device's capacities in a power converter. The results show that the smaller current capacity of the SC conductors is preferred for the $\mu$SMES coils but can increase their induced voltage excessively.

• 공업화학
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• 제18권2호
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• pp.99-110
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• 2007

21세기의 새로운 청정 에너지원으로 각광받고 있는 수소의 성공적인 활용을 위해 높은 저장 용량을 갖는 수소 저장체와 효과적인 수소 저장기술의 개발이 필요하다. 본 총설에서는 다양한 수소 저장 방법에 대해 간략히 요약하고 그 가운데 나노세공체를 이용한 저온 물리흡착에 의한 수소 저장기술의 현황에 대해 살펴보았다. 기존에 알려져 있는 고압의 압축 저장기술과 상온 고압의 수소저장 물질의 개발 이외에도 최근에는 높은 표면적과 큰 세공 부피를 갖는 나노세공체를 이용한 저온 물리흡착 방식이 개발 가능한 수소의 저장 기술의 하나로 활발히 연구되고 있다. 본 총설에서는 높은 수소 저장 용량을 위해 필요한 나노세공체의 특성을 요약하였으며 높은 표면적 및 미세 세공부피, 작은 세공 크기, 큰 정전기장 및 불포화 배위자리가 필요함을 알 수 있었다. 최근까지 보고된 나노세공체 흡착제에 의한 수소 저장 능력을 정리하였는데 현재까지 보고된 최고의 결과로는 액체 질소 온도($-196^{\circ}C$)의 약 80 기압에서 약 7.5wt%의 수소를 저장할 수 있다고 알려져 있다. 향후 지속적이고 새로운 나노세공체의 설계, 합성, 제조 및 수식에 대한 노력을 통해 수소에너지 저장에 활용될 수 있는 효과적인 수소 저장체 개발을 기대한다.

• Nutrition Research and Practice
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• 제1권4호
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• pp.260-265
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• 2007

Preservation methods on the physiological and brewing technical characters in bottom and top brewing yeast strains were investigated. The preserved yeasts were reactivated after 24 months storage and grown up to stationary phase. The samples of filter paper storage indicated a higher cell growth and viability during propagation than those of nitrogen and lyophilization storage independent on propagation temperature. In addition, the filter paper storage demonstrated a faster absorption of free amino nitrogen and a highest level of higher aliphatic alcohols production during propagation than other preservation methods, which can be attributed to intensive cell growth during propagation. Moreover, the filter paper storage showed a faster accumulation for glycogen and trehalose during propagation, whereas, in particular, lyophilization storage noted a longer adaptation time regarding synthesis of glycogen and trehalose with delayed cell growth. In beer analysis, the filter paper storage formed an increased higher aliphatic alcohols than control. In conclusion, the preservation of filter paper affected positively on yeast growth, viability and beer quality independent on propagation temperature. In addition, in this study, it was obtained that the HICF and Helm-test can be involved as rapid methods for determination of flocculation capacity.

• 한국식품영양과학회지
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• 제27권3호
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• pp.482-488
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• 1998

This study was carried out to determine the effect of treating with salt-fermented shrimp on quality of pig meat. The treated pig meats were stored at 4$^{\circ}C$, 1$0^{\circ}C$, 2$0^{\circ}C$ or 4$^{\circ}C$ after placing 2$0^{\circ}C$ for 35 hours, respectively. Meat tenderness was improved more at 2$0^{\circ}C$ storage than at 1$0^{\circ}C$ and 4$^{\circ}C$ storage. However, in water holding capacity, the meat stored at 4$^{\circ}C$ was increased more than them of 1$0^{\circ}C$ and 2$0^{\circ}C$. Cooking loss was decreased more at 4$^{\circ}C$ than the other storage temperatures. When meat color observed, it was good at the early stage of storage but went down to the worse gradually. According to the result of SDS-PAGE, myofibrillar proteins were degraded more after treated with salt-fermented shrimp than the control. Among them, titin-I was especially degraded after 2 days at 4$^{\circ}C$ storage even though it was degraded after 1 day at 1$0^{\circ}C$ and 2$0^{\circ}C$ storage. These results suggest that salt-fermented shrimps cause to improve the quality of pork meats by increasing the meat color, meat tenderness and water holding capacity at the early stage of storage.

• 설비공학논문집
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• 제12권11호
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• pp.982-993
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• 2000

This paper describes an optimal control scheduling of an encapsulated ice storage system with a chiller of nominal chiller 34RT(103,200kcal/hr) and an ice storage tank of 170RT-hrs(514,080 kcal). The optimization technique used in the study is dynamic programing. The objective function is summed cost during a day including charge and discharge periods. Control strategies being used commercially are chiller priority and storage priority control. In chiller priority control, the chiller is allowed to run at full capacity during the day, subject to limitations of the building load, and the ice is only melted when and if the load exceeds the chillers full capacity. In contrast to chiller priority control, the aim in storage priority control is to melt as much as ice as possible during the day time period. The system simulation calculates the operation costs for the three control strategies in the condition of the same cooling load and the same ice storage system. The simulation period is a day, assuming that initially the tank is stored fully and the cooling load is perfectly predicted for the scheduling. Also Final state of the tank is to be charged fully.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• 한국군사과학기술학회지
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• 제15권4호
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• pp.519-526
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• 2012

Recently fuel cell is considered to be a new technology that can substitute the ICE(Internal Combustion Engine) as well as overcome environmental issues. In military applications, fuel cell has an unique advantages, which are quietness, namely, stealth. The environmental requirement such as shock and vibration in military application, however, is very severe comparing to civilian demand. Especially, the safety concerning hydrogen storage is the most important problem. Among the candidate methods to store hydrogen, the metal hydride storage is promising method owing to the storage mechanism of chemical absorption of hydrogen to metal hydrides. In this study, the new composition of Ti-Zr type metal hydride(A composition) was suggested and investigated to increase the hydrogen storage capacity. For comparison, the hydrogen charge-discharge properties were investigated with the commercialized Ti-Zr type metal hydride(B composition) using PCT(Pressure-Composition-Temperature) measurement. Also two hydrogen storage cylinders were loaded with each metal hydride and their hydrogen charging and discharging characteristics were investigated. As a result, it was found that the new Ti-Zr type metal hydride has a slightly higher hydrogen storage capacity compared to commercial Ti-Zr type metal hydride.