• Progress in Superconductivity
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• v.3 no.2
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• pp.247-251
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• 2002

In general, the bubbling, generated during the fabrication of the tapes, breaks the superconducting filament, and critical current of the tapes will be decreased. Heat-treatment schemes of Bi-2223/Ag HTS tapes were modified, such as pre-annealing of multi-stacked billet, 2-step main sintering and ramp rate etc. The generation of bubbling was drastically decreased from 20 bubbles/m to 0 ~ 1 bubble/m by the modified heat-treatment. Therefore, the value of critical current of the tapes without bubbling was increased almost twice higher than that of already existing tapes. Critical current up to 42 A in 40 m length Bi-22231Ag tapes have been measured at 77K, self-field, 1$mutextrm{V}$/cm criterion. It could be confirmed that elimination of bubbling is effective to maintain the superconducting property along the tape length.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2005.11a
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• pp.97-100
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• 2005

The handicapped as a member of a society should possess the same opportunity of a perfect participation in public affairs and an equal opportunity in parity of treatment. All sorts of physical and social barriers surrounding the handicapped who can not having a impairment and disability give a less chance to have a share in their society. Therefore, this discrimination barriers must be phased off not only by handicapped but also by normal social members so as to perfect and free access to movement, all of social institution and social activities. Therefor, this paper provides a basic data which conducts investigation and analysis on the outdoor access environment for the handicapped's easy access to public building or facilities. It would be most import rules to make a decision between improvement rate and object for public building or public facilities.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.6
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• pp.368-371
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• 2004

The quench current characteristics of the superconducting solenoids with large diameter were experimentally investigated. Three solenoids with inside diameter of 450mm were fabricated with different tensions and different types of epoxy applications. The quench current of each solenoid was measured according to the various ramping rates of current. The highest quench current was obtained in the solenoid impregnated with epoxy after winding with tension of 20 percents of the yield strength of the superconducting wire. It was found that the quench currents were almost independent of the ramp rate of current. From the results, although the training effect in the solenoid appeared with epoxy impregnation, the quench current of solenoid impregnated with epoxy was higher than that without epoxy impregnated The test results are presented and discussed.

• Journal of Information Processing Systems
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• v.13 no.6
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• pp.1487-1495
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• 2017

With increasing interests in renewables, more consumers are installing an energy storage system (ESS) in their backyards, and thus, the ESS will play a critical role in the emerging smart grid. Due to mechanical properties, however its operational dynamics must be well understood before connecting the ESS to the smart grid (and eventually to an IT system). To this end, we investigate charging and discharging processes in detail. This paper, then, proposes methods for four type tests (state of charge test, conversion efficiency test, response time test, and ramp rate test) that can assess the dynamics of the ESS. The proposed methods can capture accurate delay values of mechanical processes in the ESS, and it is expected for those values to help design real-time communication systems in the smart grid involving the ESS.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.2
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• pp.107-114
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• 2018

In recent years, ESS (Energy Storage System) has been widely used in various parts of a power system. Especially, due to its fast response time and high ramp rate, ESS is known to play an important role in regulating grid frequency and providing rotational inertia. As the number of installed and commercially operating ESSs increases, the reliability becomes an important issue. This paper introduces control schemes and presents its test method for grid-connected ESS for primary frequency regulation. The test method allows to verify the control operation in the individual operation mode and state. A validation of the method through actual ESS test in a electrical substation is presented in the case study section.

• Journal of Korean Physical Therapy Science
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• v.8 no.2
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• pp.1039-1045
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• 2001

The aim of this study is to show the results which we analyse the interrelation among the physiological variable elements. We survey thirty fat women who don't do exercise regularly and are thirties. in order to offer basic data for setting the optimal exercise intensity through the efficient fat oxidation. We use RAMP II protocol of the Ever Green Hospital. The results are followings: 1. When the optimal exercise intensity for fat oxidation is done, there's a meaningful relation among the fat oxidation, $O_2$ max, and respiratory change. 2. When the optimal exercise intensity for fat oxidation is done, there's no meaningful relation statistically in $O_2$ max, heart rate, respiratory change, and caloric rate. 3. When the optimal exercise intensity for fat oxidation is done, there's a meaningful difference among three groups in %$VO_2$ max. However, there's a meaningful difference between group C and group A. B, and there's no meaningful difference between group B and group A.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1772-1781
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• 2004

The mechanical as well as tribological characteristics of coating films as thin as a few nm become more crucial as applications in micro-systems grow. Especially, the amorphous carbon film has a potential to be used as a protective layer for micro-systems. In this work, quantitative evaluation of nano-indentation, scratching, and wear tests were performed on the 7nm thick amorphous carbon film using an Atomic Force Microscope (AFM). It was shown that AFM-based nano-indentation using a diamond coated tip can be feasibly utilized for mechanical characterization of ultra-thin films. Also, it was found that the critical load where the failure of the carbon film occurred was about 18${\mu}$N by the ramp load scratch test. Finally, the wear experimental results showed that the quantitative wear rate of the carbon film ranged 10$\^$-9/～10$\^$-8/ ㎣ /N cycle. These experimental methods can be effectively utilized for a better understanding the mechanical and tribological characteristics at the nano-scale.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1265-1267
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• 1993

The switching and the retention characteristics with the injection conditions(pulse height and pulse width) were investigated in the nonvolatile MNOS memories with thin oxide layer of $23{\AA}$ thick. The shift of flatband voltage was measured using the fast ramp C-V method and experimental results were analized using the previously developed models. It was shown that the experimental results were described quit well by the trap-assisted and modified Fowler-Nordheim tunneling models for the voltage pulse of $15V{\sim}19V,\;24V{\sim}25V$, respectively. However, the direct tunneling model was agreement with experimental values in all range of pulse height. As increasing the initial shift of the flatband voltage, the decay rate was increased. But for the same initial shift of the flatband voltage, the decay rate was smaller for low and long pulse than for high and short one.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.98-107
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• 2000

This paper compares the performance of feedback consolidation algorithms with or without a fast overload indication function which has been recently proposed in the ATM Forum for multicast ABR (Available Bit Rate) services in ATM networks. We use the performance criteria such as the ACR (Allowed Cell Rate) of a source, queue length at a switch, link utilization, fairness, and BRM (Backward Resource Management) cell overhead. Simulation results show that performance of the feedback consolidation algorithms with a fast overload indication function can be improved sign.ificantly than that of algorithms without this function in terms of ramp-down delay, particularly in initial start-up period or under a severe overload situation. The fast overload indication function can be combined with any feedback consolidation algorithm, whereas its performance is highly dependent on an underlying basic feedback consolidation algorithm.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.4
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• pp.205-211
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• 2021

Recently, it is necessary for study on renewable energy due to environmental pollution and fossil fuel depletion. Therefore, in this study, the filling temperature according to the nozzle geometry was evaluated based on the limit temperature specified in SAEJ2601 for charging hydrogen, a new energy. There are three types of nozzles, normal, angle and round, fixed the average pressure ramp rate at 52.5 MPa/min, and the injection temperature was set at 293.4 K. As a result, the lowest temperature distribution was found in the round type, although the final temperature did not differ significantly in the three types of nozzles. In addition, Pearson's coefficient was calculated to correlate the mass flow rate with the heat transfer rate at the inner liner wall, which resulted in a strong linear relationship of 0.98 or higher.