• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.283-289
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• 2010

Owing to the increasing worldwide interest in green technology and renewable energy sources, flywheel energy storage systems (FESSs) are gaining importance as a viable alternative to traditional battery systems. Since the energy storage capacity of an FESS is proportional to the principal mass-moment of inertia and the square of the running speed, a design that maximizes the principal inertia while operatingrunning at the highest possible speed is important. However, the requirements for the stability of the system may impose a constraint on the optimal design. In this paper, an optimal design of an FESS that not only maximizes the energy capacity but also satisfies the requirements for system stability and reduces the sensitivity to external disturbances is proposed. Cross feedback control in combination with a conventional proportional-derivative (PD) controller is essential to reduce the effect of gyroscopic coupling and to increase the stored energy and the specific energy density.

• Journal of the East Asian Society of Dietary Life
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• v.27 no.3
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• pp.304-312
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• 2017

This study was carried out to evaluate the effects of yam powder addition (0~40%) on the quality characteristics and oxidative stability of yackwa made with rice flour. While most rice flour (34.35%) had a particle size more than $250{\mu}m$, 75% of yam powder had a particle size less than $65{\mu}m$. Width, height, and volume of rice yackwa added with yam powder increased with increasing yam powder content. While L and b values of rice yackwa added with yam powder decreased with increasing yam powder content, a value increased. Hardness and chewiness of rice yackwa added with yam powder increased as storage period increased at $25^{\circ}C$ for 9 days, whereas they decreased with increasing yam powder content. In a discrimination test, brown color, flavor, sweetness, and bitterness increased with increasing yam powder content, whereas hardness decreased. In a preference test, taste, texture, and overall acceptance increased with increasing yam powder content. The acid and thiobarbituric acid (TBA) values of rice yackwa added with yam powder increased as storage period increased. However, acid and TBA values of the treated groups decreased with increasing yam powder content compared to the control group. Although 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activities decreased with increasing storage period, values increased with increasing yam powder content. It was found that yackwa quality, preference, and oxidative stability increased during storage with increasing yam powder content. From these results, addition of 40% yam powder would be the optimal conditions for making rice yackwa.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.92-96
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• 2009

In this paper, economic analysis of Energy Storage System for power system is performed. Economic analysis is performed to show the benefits of Energy Storage System. Results illustrate the advantages of Energy Storage System not only acting as an alternative generation resource but also giving a better reliability and stability in power system.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.45-49
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• 2022

In the present study, a physical model was built for the Jintan underground gas storage cavern group according to the similarity theory. In this regard, four ellipsoid caverns were built with scaled in-situ stresses and internal pressure. Then the stability of underground caverns was analyzed. The obtained results demonstrate that loss of internal pressure adversely affects the safety of caverns and attention should be paid during the operation of gas storage.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.150-159
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• 2013

It is generally well known that the stratification of thermal energy in heat stores can be improved by increasing the aspect ratio (the height-to-width ratio) of the stores. Accordingly, it will be desirable to apply a high aspect ratio so as to demonstrate the good thermal performance of heat stores. However, as the aspect ratio of a store increases, the height of the store become larger compared to its width, which may be unfavorable for the structural stability of the store. Therefore, to determine an optimum aspect ratio of heat stores, a quantitative mechanical stability assessment should be performed in addition to thermal performance evaluations. In the present study, we numerically investigated the mechanical stability of silo-shaped rock caverns for underground thermal energy storage at different aspect ratios. The applied aspect ratios ranged from 1 to 6 and the mechanical stability was examined based on factor of safety using a shear strength reduction method. The results from the present study showed that the factor of safety of rock caverns tended to decrease with the increase in aspect ratio and the stress ratio of the surrounding rock mass was influential to the stability of the caverns. In addition, the numerical results demonstrated that under the same conditions of rock mass properties and aspect ratio, mechanical stability could be improved by the reduction in cavern size (storage volume), which indicates that one can design high-aspect-ratio rock caverns by dividing a single large cavern into multiple small caverns.

• Journal of Pharmacopuncture
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• v.6 no.2
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• pp.105-111
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• 2003

Objective : The purpose of this study was to investigate the stability of bee venom according to the keeping method and period. Method : The author observed microbial contamination of bee venom in nutrient agar, broth, YPD agar and YPD media and antibacterial activity for S. aureus, E. coli manufactured 12, 6 and 3 months ago as the two type of room temperature and $4^{\circ}C$ cold storage. Results : 1. 1:3,000 and 1:4,000 diluted bee venom solution did not show microbial contamination both room temperature and cold storage within twelve months. 2. There was antibacterial activity of diluted bee venom for S. aureus in cold storage within twelve months and there was no antibacterial activity of diluted bee venom for S. aureus in twelve months, room temperature storage. 3. We could not observe the zone of inhibition around paper disc of all for E.coli. in 1:3,000, 1:30,000 and 1:3,000,000 diluted bee venom solution, respectively. According to results, we expect that diluted bee venom solution is stable both cold and room temperature storage within twelve months.

• The Korean Journal of Community Living Science
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• v.15 no.2
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• pp.179-187
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• 2004

The purpose of this study is to investigate the preservation of traditional sesame dasik when stored in different packaging material by comparing its physical and sensorial characteristics. The quality and sensory characteristics of sesame dasik that were evaluated were moisture content, water activity, number of microflora, texture profile, Hunter color different value, and sensory properties (color, chewiness, overall acceptability, etc) during the storage at 35\pm1^\circ{C}$ temperature and $73\pm{2%}$ relative humidity. And the packaging materials were paper boxes (coated 0.02mm thickness polyethylene film), plastic boxes, and oriented polypropylene laminated film. Traditional sesame dasik is made from sesame powder 100g, honey 25g, rice syrup 25g, and table salt 0.5g. During the storage period, the changes in water content and water activity of sesame dasik with different packaging material showed a slight decline. On the other hand, it increased in hardness, and "a" and "b" value of Hunter color difference during the storage. Texture profile analysis data change in hardness was the greatest after the third day in a paper box, and it was affected by the moisture content of dasik and the temperature and relative humidity of the air. Therefore plastic boxes or oriented polypropylene laminated film was found to be better suited than paper boxes for storing sesame dasik.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.19-26
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• 2006

The test blasts were carried out by detonating some single blastholes at two upper sites of the underground storage cavern for the crude oil. One was performed at the entrance site of the construction tunnel and the other at the middle area of the underground storage cavern. Based on the blast-induced nitration measured by the test blasts, we suggested the propagation equations of blasting vibration that were capable of estimating the peak particle velocity. In addition, in order to assess the stability of the adjacent ground storage tank, we did the frequency analysis and the response spectrum analysis with the particle velocity-time history and the particle acceleration-time history that were measured by the test blast carried out on the entrance site of the construction tunnel. In result, it was predicted that the displacement on the highest part of the tank shell was less than the allowable displacement.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.257-261
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• 2009

In this study, the correlation between color of redness and L-carnitine content in meats was investigated using microplate enzymatic assays. The L-carnitine levels and its storage stabilities of domestic and imported livestock products in Korean markets were also studied. The results showed a high correlation (r=0.9764) between L-carnitine content and redness values of homogenized meat solution. Korean native cattle ('Hanwoo') meat showed the highest L-carnitine content ($3.64{\pm}0.14{\mu}mol/g$) in meat samples analyzed in this study. The L-carnitine level of the meats decreases during periods of storage in cold and freezing conditions, and the level of decrease was more significant at $4^{\circ}C$ than at $-20^{\circ}C$, which suggests that the storage stability of L-camitine is related to its storage temperature. This study gives reliable data about correlation between meat color of redness and L-carnitine content, and gives useful information to determine the characteristics of 'Hanwoo'.

• Transactions of the Society of Information Storage Systems
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• v.9 no.2
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• pp.42-47
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• 2013

In this study, we have experimentally analyzed how the surface properties of transparent electrode layer influence the photovoltaic performance of bulk heterojunction organic solar cell by the contact angle measurement and X-ray photoelectron spectroscopy(XPS) observation. As a result, the power conversion efficiency of test devices improved from 0.64% to 1.83% and 2.15% by UV-ozone exposure and $O_2$ plasma treatment, respectively. Thus, we conclude that the surface activation process is very important for better performance and stability in addition to the cleaning process of carbonate residue on the surface.