• Journal of Power Electronics
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• v.17 no.4
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• pp.1071-1087
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• 2017

This paper introduces a DC/AC converter, which can be connected in parallel with a diode rectifier for regenerative applications. The DC/AC converter is supposed to transmit regenerative energy to the power grid when a motor is braking. Isolation transformers are not needed in the topology, which can reduce the size and cost. An analysis of the zero-order current existing in the system is carried out. In addition, algorithms to minimize the zero-order current, control the power factor and keep the DC bus voltage stable are discussed. A 55kW industrial prototype is built to verify the proposed analysis and control strategies.

• Journal of Power Electronics
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• v.6 no.4
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• pp.330-339
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• 2006

This paper deals with novel electronic ballast based on single-stage power processing topology using a symmetrical half-bridge inverter and current injection circuit. The half-bridge inverter drives the output parallel resonant circuit and injects current through the power factor correction (PFC) circuit. Because of high frequency current injection and high frequency modulated voltage, the proposed circuit maintains the unity power factor (UPF) with low THD even under wide variation in ac input voltage. This circuit needs minimum and lower sized components to achieve the UPF and high efficiency. This leads to an increase in reliability of ballast at low cost. Furthermore, to reduce cost, the electronic ballast is designed for two series-connected fluorescent lamps (FL). The analysis and experimental results are presented for ($2{\times}36$ Watt) fluorescent lamps operating at 50 kHz switching frequency and input line voltage (230 V, 50 Hz).

• Journal of Power Electronics
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• v.9 no.2
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• pp.133-145
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• 2009

In this paper a modular high performance MV-to-LV rectifier based on a cascaded H-bridge rectifier is presented. The proposed rectifier can directly connect to the medium voltage levels and provide a low-voltage and highly-stable DC interface with the consumer applications. The input stage eliminates the necessity for heavy and bulky step-down transformers. It corrects the input power factor and maintains the voltage balance among the individual DC buses. The second stage includes the high frequency parallel-output DC/DC converters which prepares the galvanic isolation, regulates the output voltage, and attenuates the low frequency voltage ripple ($2f_{line}$) generated by the first stage. The parallel-output converters can work in interleaving mode and the active load-current sharing technique is utilized to balance the load power among them. The detailed analysis for modeling and control of the proposed structure is presented. The validity and performance of the proposed topology is verified by simulation and experimental results.

• Journal of Korean Society of Rural Planning
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• v.23 no.1
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• pp.41-52
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• 2017

This study began to learn wether or not satisfaction factor of rural tourism is effective to visit for the ordinary foreign people. Research method was parallel-site investigation literature, questionnaire. The analytical data of the study, literature 40 reviews, questionnaire 179 survey in 200 of the subject was using. Measurement and scale was set factors of satisfaction with 'Transportation Infrastructure', 'Festival Experience Program', 'Place', 'Room and Food', 'Local People', and 'Buying the Local Product' through the previous studies and preliminary survey. In the statistical analysis method, frequency analysis, crosstabs, multiple regression analysis and a structural equation model analysis was performed, using SPSS and AMOS program. The Structural analysis results showed 'Place' and 'Local People' have an positive effect on the 'Overall Satisfaction'. Satisfaction of the 'Festival ExperienceProgram', had a major impact also 'Intention of Revisit'. Finally for rural tourism fascination, the contents such as the distinctive local attraction, human resources, information transmission and convenient use is more important than the format and scale.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.314-320
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• 2001

A novel mode of parallel operation of a modular 3-phase AC-DC flyback converter for power factor correction along with tight regulation was recently analyzed and presented. The advantage of the proposed converter does not require expensive high voltage and high current devices that are normally needed in popular boost type 3-phase converter. In this paper the detailed small signal analysis of the modular 3-phase AC-DC flyback converter is provided for control purposes and also experimental results are included to confirm the validity of the analysis.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.4
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• pp.75-87
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• 2015

A redundant structure typically consists of primary component and standby component taking over the function of the primary component when the primary component fails. In this research, we consider a redundant structure in which a standby component can take over the function of more than one primary component when primary components fail. And we assume that the system has multi-state according to the states of components while all components have two states. This system is called as the multi-state redundant system with a multi-functional standby component. This type of redundant structure is frequently adapted by the system such as an aircraft in which the weight is an important design factor. In this paper, we propose new reliability model for this multi-state redundant system with a multi-functional standby component in order for evaluating the reliability of the system. Under the assumption that all components have constant failure rate, we evaluate the reliability of the system by applying Markov analysis method. And we investigate the effect of the multi-functional standby component by comparing reliabilities of the parallel system with multi-functional standby component and a simple parallel system and a parallel system with redundant structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.345-356
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• 2016

The purpose of this study was to develop a scale to evaluate the safety competency of perioperative nurses and to examine its validity and reliability. The research process included the development of preliminary items through literature reviews and the construct validity examination of the conceptual framework for the preliminary scale. The content validity of the identified items was evaluated by experts, resulting in 30 preliminary items. The participants involved in testing the validity and reliability of the preliminary scale were 377 perioperative nurses. The data were analyzed using exploratory factor analysis, parallel analysis, confirmatory factor analysis, and internal consistency. To verify the construction factor of the preliminary scale, exploratory factor analysis and parallel analysis were performed, resulting in 3 factors and 27 items. The internal structure of the scale was schematized using confirmatory factor analysis and the goodness of fit of the final research model was very appropriate, as shown by the values of TLI=.90, CFI=.91, RMSEA=.07, and SRMR=.07. The final scale consisted of 27 items and 3 factors including knowledge (6 items), skill (13 items), and attitude (8 items). Cronbach' ${\alpha}$ for the final scale was .94, showing good internal consistency. This safety competency scale can be used for assessing the competency of perioperative nurses regarding patient safety, for developing patient safety studies and for the career development of perioperative nurses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.481-489
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• 1993

The charge distribution is calculated to analyze the quasi-static impedance of periodic interdigital transducer taking into account the effect of infinite neighboring electrodes. The charge distribution can be represented by the element factor and array factor. The radiation conductance, susceptance and static capacitance of the input and output IDT's with arbitrary voltages are obtained by the charge distribution. The impedance of apodized IDT, is analyzed by multi-track model in which IDT is represented by the parallel connection of the uniform tracks. The calculated input and output impedances are in good agreement with the experimental results.

• KSTLE International Journal
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• v.2 no.1
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• pp.12-16
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• 2001

A finite element analysis of crack propagation in a half-space due to sliding contact was performed. The sliding contact was simulated by a rigid asperity moving across the surface of an elastic half-surface containing single and multiple cracks. Single, coplanar, and parallel cracks were modeled to investigate the interaction effects on the crack growth in contact fatigue. The analysis was based on linear elastic fracture mechanics and the stress intensity factor concept. The crack propagation direction was predicted based on the maximum range of the shear and tensile stress intensity factors.

• Education of Primary School Mathematics
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• v.25 no.1
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• pp.43-55
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• 2022

It is critical to examine changes in teachers' beliefs on how to teach and learn mathematics through teacher education programs. This study aims to develop an instrument measuring elementary pre-service teachers' beliefs on student- and teacher-centered instruction. After developing questionnaires with mathematics education experts, the structural validity of the instrument was evaluated by collecting and analyzing data from 166 pre-service teachers. Parallel analysis and exploratory factor analysis were applied sequentially to collect validity and reliability evidence. The results showed that this instrument can be used to examine changes in pre-service teachers' two different types of belief: student- and teacher-centered instruction. We also suggested how to interpret scores appropriately.