• Korean Journal of Cognitive Science
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• v.15 no.3
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• pp.1-14
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• 2004

This research examined the effects of individual differences on visual discrimination skill teaming and its transfer to novel stimuli. Individual participants were categorized as having an analytic or holistic cognitive style, high or low working memory capacity, and high or low levels of rationality, experientiality, and adaptive decision-making styles. Participants received easy or difficult training for the serially presented discrimination task, and then transferred to novel discriminations. Training content interacted with cognitive style and working memory capacity to affect transfer accuracy performance, but individual differences in decision-making styles did not affect transfer performance. Results suggest individual differences should be taken into account when designing an interface for visual discrimination.

• Phonetics and Speech Sciences
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• v.11 no.4
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• pp.63-70
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• 2019

This study investigated individual variability of L2 learners' categorical judgments of L2 stops by exploring English learners' perceptual processing of two acoustic cues (voice onset time [VOT] and f0) and working memory capacity as sources of variation. As prior research has reported that English speakers' greater use of the redundant cue f0 was responsible for gradient processing of native stops, we examined whether the same processing characteristics would be observed in L2 learners' perception of Korean stops (/t/-/t^h/). 22 English learners of L2 Korean with a range of L2 proficiency participated in a visual analogue scaling task and demonstrated variable manners of judging the L2 Korean stops: Some were more gradient than others in performing the task. Correlation analysis revealed that L2 learners' categorical responses were modestly related to individuals' utilizations of a primary cue for the stop contrast (VOT for L1 English stops and f0 for L2 Korean stops), and were also related to better working memory capacity. Together, the current experimental evidence demonstrates adult L2 learners' top-down processing of stop consonants where linguistic and cognitive resources are devoted to a process of determining abstract phonemic identity.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.288-290
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• 2006

An efficiency improving method for Uninterruptible Power Supply System(UPS) was developed by using OP-AMP based application circuits such as voltage detection device, current detection device and static switch control device. The efficiency improving algorithm was made by mixing the operating concepts of On-Line type UPS with the operating concepts of Off-Line type UPS. The UPS' inverter does not work if the UPS' output load current is not higher than the low load operating current which is about 0-30(%) of the UPS' output load capacity. The low load operating current is adjustable within the half of the UPS' output load capacity. If the UPS' output load current is rising over than the low load operating current, the UPS' inverter starts working and the inverter output power feeds to the loads of UPS. If UPS' input power breaks out while UPS' inverter does not operate because the load current is low, the inverter starts working within 4(ms) with excessive output voltage which is ${\pm}$8(%) of normal UPS' output voltage. Like these. UPS can continuously feeds power to it's load device and reduce power consumptions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.218-224
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• 2006

The performance of an air to water vapor compression heat pump has been investigated experimentally. The main purpose of this study was to study the possibilities of using hydrocarbon refrigerants as a working fluid to replace R-22 for vapor compression heat pumps. Pure R-22 and R-290, R-600a, R-1270 were considered as working fluids. The performance of the system was characterized by compression shaft work, refrigeration capacity, pressure ratio, discharge temperature and COP. The experimental apparatus has basic parts of cycle that uses the air as a heat source. The experimental results show that refrigeration capacity of HC refrigerants is same or higher than that of R-22. On the other hand, compression shaft work of HC refrigerants is lower than that of R-22. Compression shaft work is lower than that of R-22. Come to the conclusion that, it is possible that hydrocarbon refrigerants could be drop-in alternatives for R-22.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.485-497
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• 2024

Ring beam is the main anchorage zone of the tendons in the nuclear power prestressed concrete containment vessel (PCCV). Its safety is crucial and has a great influence on the overall performance of PCCV. In this paper, two half-scale ring beams were tested to investigate the mechanical performance of the anchorage zone in the PCCV under multidirectional pressure. The effect of working condition with different tension sequences was investigated. Additionally, a half axisymmetric plane model of the containment was established by the finite element simulation to further predict the experimental responses and propose the local reinforcement design in the anchorage zone of the ring beam. The results showed that the ultimate load of the specimens under both working conditions was greater than the nominal ultimate tensile force. The original reinforcement design could meet the bearing capacity requirements, but there was still room for optimization. The ring beam was generally under pressure in the anchorage area, while the splitting force appeared in the under-anchor area, and the spalling force appeared in the corner area of the tooth block, which could be targeted for local strengthening design.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.14-17
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• 1999

Tin oxide films as an anode layer for microbatteries were deposited by using rf magnetron sputtering. Characterization of the films was carried out in terms of working pressure in the range of 5~30 mtorr. Rf power and substrate temperature during deposition were fixed at 2.5W/$\textrm{cm}^2$ and A.T., respectively. The crystal orientation of $SnO_2$films was changed from (110) to (101) or (211) with the increasing working pressure. Refractive index and film density of the films also decreased with the increasing working pressure. The $SnO_2$ thin film formed under optimum conditions was found to have a reversible capacity of 446.9$\mu$Ah/$\textrm{cm}^2$-$\mu\textrm{m}$ and good reversibility when the working pressure was fixed at 10mtorr. As the working pressure decreased, film density increased. It was thought that the capacity of $SnO_2$films increased due to the increase in the amount of active materials which can react with Li electrochemically. Furthermore, cycle characteristics of the anode material was also influenced by film stress.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.371-378
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• 2001

The working load at pile is sometimes subjected to not only compression load but also lateral load and uplift forces. Pile foundation is essential and uplift load can be applied because of buoyancy, a typhoon, wind or seismic forces. This study was carried out to determine the uplift capacity of concrete pile foundation driven in clay. Pile was driven in clay, between pile and clay adhesion factor was estimated, and it is the mean value between the cast-in-situ-pile and steel pipe pile. When pile foundation is loaded for long time, creep behavior occurs. The behavior of creep is originated from the clay creep contacted with pile. The creep behavior of pile foundation embedded in clay is heavily depended on the thickness of clay around the pile shaft, pore water pressure in clay, and creep behavior of clay.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.505-513
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• 2001

A revised VX cycle using ammonia/water as the working fluid is a cycle which is suitable to produce cooling utilizing low temperature hat sources. The cycle was analyzed numerically to investigate the effects of the design and operating conditions on the performance. It was shown that both COP and cooling capacity were significantly influenced by the performance of he rectifier. Insufficient UA of the rectifier reduced both ammonia mass fraction and mass flow rate of the vapor entering the condenser, which produced cooling effect in the evaporator. As the temperature and the mass flow rate of the heat source increased, both COP and exergetic efficiency decreased due to the irreversibilities produced in heat exchangers, but cooling capacity did not vary much. Cooling capacity increased significantly as the coolant temperature decreased, although COP and exergetic efficiency remained nearly constant.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2284-2293
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• 2016

With the rapid development of clean energy, photovoltaic (PV) generation has been utilized in the harmonic compensation of power systems. This paper presents a novel multi-function PV micro-inverter with three stages (pseudo-two-stage). It can inject active power and compensate harmonic currents in the power grid at the same time. In order to keep the micro-inverter working under the maximum allowable output power, an optimized capacity limitation strategy is presented. Moreover, the harmonic compensation can be adjusted according to the customized requirements of power quality. Additionally, a phase shedding strategy in the DC/DC stage is introduced to improve the efficiency of parallel Boost converters in a wide range. Compared with existing capacity limitation methods, the proposed strategy shows better performance and energy efficiency. Simulations and experiments verify the feasibility of the micro-inverter and the effectiveness of the strategy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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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