• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1102-1106
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• 2015

A hybrid supercapacitor (HS) is an energy storage device used to enhance the low weight energy density (Wh/kg) of a supercapacitor. On the other hand, a sudden decrease in capacity has been pointed out as a reliability problem after many charge/discharge cycles. The reliability problem of a HS affects the early aging process. In this study, the capacity performance of a HS was observed after charge/discharge. For detailed analysis of the initial charge/discharge cycles, the charge and discharge curve was measured at a low current density. In addition, a solid electrolyte interphase (SEI) layer was confirmed after the charge/discharge. A HC composed of a lithium titanate (LTO) anode and active carbon cathode was used. The charge/discharge efficiency of the first cycle was lower than the late cycles and the charge/discharge rate was also lower. This behavior was induced by SEI layer formation, which consumed Li ions in the LTO lattice. The formation of a SEI layer after the charge/discharge cycles was confirmed using a range of analysis techniques.

• Journal of the Korean Society of Safety
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• v.9 no.2
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• pp.18-25
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• 1994

In this thesis, the fatigue tests were performed on a series of reinforced concrete to Investigate the variation of strength and the safety of reinforced concrete structures under fatigue load. The specimens were of the same rectangular cross-section, of effective height 24cm and width 30cm and their span was 330cm. The three point loading system is used in the fatigue tests. In these tests, the fracture mode of reinforced concrete structures under fatigue load, relationship between the repeated loading cycles and the mid-span displacement of the specimens were observed. According to the test results, the following fatigue behavior of reinforced concrete specimens were observed. By increasing of the number of repeated loading cycles, the mid-span displacement became greater, however the Incremental amounts of the displacement were reduced. It could be also known that the inelastic strain energy of the doubly reinforced rectangular beams was larger than that of the singly reinforced rectangular beams as increasing the number of repeated loading cycles. Compliance of reinforced concrete structures tended to be reduced as increasing the repeated loading cycles, and the compliance of the doubly reinforced rectangular beams was generally smaller than that of the singly reinforced rectangular beams. Based on the above investigation, it could be concluded that the doubly reinforced rectangular beams under fatigue load were more efficient to resist the brittle fracture than the singly reinforced rectangular beams.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.252-257
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• 2000

An efficient method is developed for mold thermal cycle analysis in repeated forming process, which is well suited to the analysis in TV glass production. plunger, which is a mold to press-form the glass, undergoes temperature fluctuation during a cycle due to the repeated contact and separation from the glass, which attains a cyclic steady state in the end. If analyzed straightforwardly of this problem, it leads to more than 80 cycles to get reasonable solution, and it is yet hard to setup stopping creteria due to extremely slow convergence. An exponential fitting method is proposed to solve the problem, where an exponential function is found to best approximate temperature values of 3 consecutive cycles, and new cycle is restarted with the function value at infinite time. From numerical implementation, it is found that the method reduces the number of cycles dramatically to only $6{\sim}15$ cycles to reach accurate solution within $1^{\circ}$ error. A system for the analysis is contructed, in which the thermal analysis is performed by commercial software ANSYS, and the fitting of the result is done by IMSL library.

• Atmosphere
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• v.18 no.4
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• pp.475-483
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• 2008

The hourly precipitation data from 1973 to 2007 observed at 60 weather stations over Korea are used to characterize the diurnal and semidiurnal cycles of total precipitation amount, intensity and frequency and examine their spatial patterns and interannual variations. The results show that the diurnal cycle peaks in the morning (03-09LST) and the semidiurnal cycle peaks in the late afternoon (16-20LST). It is found that the spatial variations of the peak phase of diurnal or semidiurnal cycle relative to their corresponding seasonal mean cycle are considerably small (large) for total precipitation amount and intensity (frequency, respectively) in both winter and summer seasons. Also, the diurnal phase variations for individual years relative to the seasonal mean precipitation show the significant interannual variability with dominant periods of 2-5 years for all three elements of precipitation and the slightly decreasing trend in total precipitation amount and intensity. To compare the relative contributions of frequency and intensity to the diurnal and semidiurnal cycles (and their sum) of total precipitation amount, the percentage variance of each cycle of precipitation amount explained by frequency is estimated. The fractional variance accounted for by precipitation intensity is greater than that of frequency for these three cycles. All above analyses suggest that intensity plays a more important role than frequency in the diurnal variations of total precipitation amount.

• Korean System Dynamics Review
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• v.12 no.1
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• pp.5-37
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• 2011

This article aims to clarify what is the best investment behavior in Capital Intensive Industries(hereinafter CIIs) which show repeated business cycles. In CIIs, investments is centered in the period of upturns and goes beyond the adequate level because of the time that takes to completion of facilities. This over-investment causes oversupply and downturn, and in period of downturn, investments shrinks under the adequate level. The repeated change of over-investment and under-investment is the reason for the business cycles. In this article, a simulation model replicating the business cycles in CIIs was constructed and the effects of various investment strategies was tested. The results are as follows. First, the investment behavior following market condition causes the ongoing fluctuation of profits. Second, strategic increase in flexibility such as adjustment of facility utilization and shortening of facility construction time contributes to the increase in profit and stabilization of income. Third, in relation to market condition, the constant investment is more profitable in stagnated market and the counter-market investment is more profitable in growing market. In sum, it is desirable not to synchronize their investment with those of competitors.

• Journal of Plant Biotechnology
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• v.43 no.1
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• pp.119-124
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• 2016

Anthocyanin accumulation and plant growth were examined in petunia (NT and $T_2$ transgenic plants) by determining the effects of different sources of light and varying light/dark cycles. Red light significantly enhanced anthocyanin content of B-peru+mPAP1; however, it had a negative effect on anthocyanin production in RsMYB1 plants. In general, white light was found to be reasonable for anthocyanin accumulation in all plants. In case of light/dark cycles, application of seven days of light:14 days of dark significantly enhanced anthocyanin content. We found that anthocyanin content detected in transgenic plants expressing anthocyanin regulatory transcription factor genes (B-peru+mPAP1 or RsMYB1) was higher than that in NT plants in all treatments. Plant growth was also influenced by the different light sources and dark/light cycles. Taken together, our results suggest that light source and light/dark cycle play an important role in anthocyanin production and plant growth. The choice of the optimal conditions is also important for anthocyanin production and plant growth depending on NT or transgenic plants carrying anthocyanin regulatory transcription factors.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.2
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• pp.85-90
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• 2000

The influence of transformation cycles (${\alpha}^{\prime}{\leftrightarrow}{\gamma}^{\prime}$) on the microstructure and mechanical properties of lath and lenticular martensites has been studied in Fe-Ni alloys. The width of lath in Fe-15%Ni alloy decreased with increasing the number of transformation cycles, while no appreciable change in dislocation density inside the lath was observed. In case of Fe-31%Ni alloy, a number of dislocations were additionally introduced into the martensite plate after the transformation cycling. Tensile strength and Vickers hardness of lath martensite decreased with the increase in number of transformation cycles, whereas those of lenticular martensite increased up to 1 cycle and then remained constant. Elongation of two alloys was deteriorated after 1 transformation cycling, corresponding to the tensile strength. But the decrement of elongation in Fe-31%Ni alloy was smaller than that in Fe-15%Ni alloy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5307-5327
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• 2016

Restricted by finite battery energy, traditional wireless sensor networks (WSNs) can only maintain for a limited period of time, resulting in serious performance bottleneck in long-term deployment of WSN. Fortunately, the advancement in the wireless energy transfer technology provides a potential to free WSNs from limited energy supply and remain perpetual operational. A mobile charger called wireless charging vehicle (WCV) is employed to periodically charge each sensor node and keep its energy level above the minimum threshold. Aiming at maximizing the ratio of the WCV's vocation time over the cycle time as well as guaranteeing the perpetual operation of networks, we propose a feasible and optimal solution to this issue within the context of a real-time large-scale deployed WSN. First, we develop two different types of charging cycles: initialization cycles and renewable cycles and give relevant algorithms to construct these two cycles for each sensor node. We then formulate the optimization problem into an optimal construction algorithm and prove its correctness through theoretical analysis. Finally, we conduct extensive simulations to demonstrate the effectiveness of our proposed algorithms.

• Food Science of Animal Resources
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• v.40 no.6
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• pp.969-979
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• 2020

Fresh grass carp was used to produce surimi and 50 g/kg, 100 g/kg, or 150 g/kg pork back fat was added. The water distribution, thiobarbituric acid reactive substances (TBARS), myoglobin oxidation, color parameter (L*, a*, and b*), heme and non-heme iron content of samples were determined to analyze the effects of different fat content on the oxidation of myoglobin and lipids during multiple freeze-thaw cycles of grass carp surimi. Both multiple freeze-thaw cycles and increased fat content lead to an increase in TBARS, a blue shift in the absorption peak of myoglobin porphyrin, a decrease in heme iron content, and an increase of non-heme iron content. Repeated freeze-thaw caused a decrease in immobilised water content and L*, and caused an increase in a* and b*. Increased fat content caused an increase in immobilised water content, L* and a*, and caused a decrease in b*.

• Journal of Hydrogen and New Energy
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• v.22 no.1
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• pp.109-117
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• 2011

Since the thermal performance of cycles for use of low-temperature source is low if a pure working fluid is used, the cycles using ammonia-water binary mixture as a working fluid has attracted much attention over past two decades. Recently, several commercial power plants using Kalina cycles have been built and being operated successfully. In this work thermodynamic performance of Kalina cycles using ammonia-water mixture as a working fluid is investigated for the purpose of extracting maximum power from low-temperature energy source. Special attention is paid to the effect of system parameters such as concentration of ammonia and turbine inlet pressure on the characteristics of the system. Results show that the system performance is influenced sensitively by the ammonia concentration, and the role of the performance of heat exchangers is crucial.