• KEPCO Journal on Electric Power and Energy
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• v.7 no.2
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• pp.249-254
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• 2021

As the spreading speed of electric vehicles increases rapidly, those are expected to be able to use them as flexible resources in the power system beyond the concern for the supply of its charging power. Especially when the Renewable Energy sources (RES) which have no intrinsic control capability have replaced the synchronous generators more and more, the power system needs to secure the additional frequency control resources to ensure its stability. However, the feasibility of using electric vehicles as the frequency control resources should be analyzed from the perspective of the power system operation and it requires the existing simulation frameworks for the power system. Therefore, this paper proposes the grid connected modeling of the primary frequency control provided by electric vehicles which can be integrated into the existing power system model. In addition, the proposed model is implemented considering technical performances constrained by the characteristics of the Vehicle-Grid Integration (VGI) system so that the simulation results can be accepted by the power utilities operating the power system conservatively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.2
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• pp.202-208
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• 2016

The physicochemical properties and antioxidant activities of fermented mulberry by lactic acid bacteria were investigated. The viable cell counts of lactic acid bacteria slowly increased up to 8.31 log CFU/mL. The pH and titratable acidity were 3.90 and 0.15%, respectively, after 24 h of fermentation. Color in terms of L and a values decreased, whereas b and ${\Delta}E$ values increased. The total anthocyanin contents of fermented mulberry (171.40 mg/100 g) was higher than that of mulberry (144.70 mg/100 g). The cyanidin-3-glucoside and cyanidin-3-rutinoside contents of fermented mulberry were 61.39 mg/100 g and 85.45 mg/100 g, respectively. Total phenolic and flavonoid contents of fermented mulberry (10.75 g/100 g and 5.02 g/100 g, respectively) was higher than those of mulberry (4.53 g/100 g and 1.77 g/100 g, respectively). The oxygen radical absorbance capacity of fermented mulberry was $292.94{\mu}M/g$. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and superoxide radical scavenging activity of fermented mulberry at $250{\sim}2,500{\mu}g/mL$ were 17.40~58.21% and 32.63~87.34%, respectively. The ferric reducing antioxidant power and reducing power of fermented mulberry at $250{\sim}2,500{\mu}g/mL$ were $37.03{\sim}762.13{\mu}M$ and 0.12~0.74, respectively. The results suggest that mulberry fermented by lactic acid bacteria has potential as functional materials in food industry.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.1
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• pp.221-227
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• 2014

When implementing cryptographic algorithms in mobile devices like smart cards, the security against side-channel attacks should be considered. Side-channel attacks try to find critical information from the side-channel infromation obtained from the underlying cryptographic devices' execution. Especially, the power analysis attack uses the power consumption profile of the devices as the side-channel information. This paper proposes a new gate-level countermeasure against the power analysis attack and the glitch attack and suggests how to apply the measure to securely implement AES.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.157-160
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• 2008

Solar receiver in the solar power tower system has a similarity to a boiler of the thermal power plant in many aspects. However Boiler is operated long time without stopping while solar receiver repeats start and stop every day. The objective of this study is to investigate start-up characteristics of solar receiver. The experimental device was constructed in a bench scale. Basic experimental condition of water/steam was set by 25 bar and $223^{\circ}C$. Initially, the heat was added into risers only, then another experiment with input into drum additionally was done. When the heat flux was valid only risers, it took about 300 minutes until the water temperature in drum reached $223^{\circ}C$. Water temperature of drum was increased by $44^{\circ}C$/hr with 91.14 g/s of water circulation. With additional heat input into drum, 200 minutes was required to reach $223^{\circ}C$. In this case temperature was increased $66^{\circ}C$/hr with 96.5 g/s of water circulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1272-1278
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• 2009

The cancellation method of P/G(power/ground) plane resonances which are generated between the power plane and the ground plane in a 4-layer PCB(Printed Circuit Boards) with a via-hole for the improvement of the RE(Radiated Emission) characteristic is presented. The validity of the proposed method was confirmed from simulation and measurement of performances of signal transmission characteristic, intensities of edge-radiation and radiated emission of PCB with a via-hole.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.300-308
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• 2016

Application of demand-side resources to automatic generation control (AGC) has a great significance for improving the dynamic control performance of power system frequency regulation. This paper investigates the possibility of providing regulation services by demand-side energy storage in electric vehicle battery swapping stations (BSS). An interaction framework, namely station-to-grid (S2G), is presented to integrate BSS energy storage into power grid for giving benefits to frequency regulation. The BSS can be regarded as a lumped battery energy storage station through S2G framework. A supplementary AGC method using demand-side BSS energy storage is developed considering the vehicle user demand of battery swapping. The effects to the AGC performance are evaluated through simulations by using a two-area interconnected power grid model with step and random load disturbance. The results show that the demand-side BSS can significantly suppress the frequency deviation and tie-line power fluctuations.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.227-238
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• 1993

IRRI Engineering Division has developed a well drilling rig attachment that matched power tiller or hand tractor. It was designed in response to the growing demand for ground water utilization for small-scale irrigation, especially in drought-sticken and rained farms in Asian countries. The power tiller-driven rig can drill 30 meters of 100mm well in an unconsolidated formation in one day and can be rapidly converted from rotary to jetting or to the percussion method of drilling to suit different soil and rock formation. In addition, the power tiller can be quickly installed or removed from the rig frame and can be used for transporting the rig to other sites. The rig can be dismantled into smaller sub-assemblies for carrying by hand into less accessible areas. One manufacturer in Central luzon Philippines has started to produce the rig for well drillers in Central Luzon. The Department of Agriculture in the Philippines have procured thirty three(33) units of these machines f r their Shallow Tubewell program.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.133-136
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• 2004

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• Tribology and Lubricants
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• v.12 no.3
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• pp.12-25
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• 1996

The friction and wear behaviors of ceramics against steels with lubricants were investigated and compared with those observed in air. Lubrications wbre done by a water and a commercial engine oil as received. The investigated ceramics were $Al_{2}O_{3}$, SiC, and $Si_{3}N_{4}$. Steels with 0.2 wt.% C were heat treated to obtain tempered structure. A cylinder-on-plate tribometer with rotated sliding motion was used to carry out the experiments. In the experiments reported here, the ranges of different testing speeds and loads were used. It was found that the friction and wear characteristics of tested pairs were significantly influenced by environments. In water and oil environments the wear of ceramics was reduced from 10$^{-6}$ g/s down to 10$^{-8}$ g/s in dry sliding at the same values of the frictional power which are the products of the friction coefficient, the load and the sliding speed. SiC showed excellent wear resistant behavior in water sliding, which was the lowest among tested ceramics, but it was, very poor in oils. In case of $Si_{3}N_{4}$, the wear rates were very low under oil environment, but the highest in water. The wear rates of $Al_{2}O_{3}$ were very low in both lubricating conditions at low values of the frictional power, but high at high values of the frictional power.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.25-27
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• 2002

This paper describes a new economical voltage sag and swell generator suitable to the evaluations of high power custom power devices such as DVR (Dynamic Voltage Restorer) and DSTATCOM (Distribution Static Compensator). This system was designed to generate the several power quality disturbances in MVA power ratings - voltage sag and swell, under voltage, over voltage and harmonic distortions. The basic idea for voltage sag and swell is to use the voltage drop across a reactor, while the voltage swell is to use the step-up transformer and the TCR(Thyristor Controlled Reactor). In this paper, two identical 3 phase TCRs and a step-up transformer with tap changer are used. Additional harmonic filters are added to reduce the voltage distortion when TCRs are operated. Simulation results are given for several cases of voltage sag and swell generations.