• Journal of Power Electronics
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• v.7 no.3
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• pp.213-221
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• 2007

A digital state feedback control method for the current mode control of DC-DC converters is proposed in this paper. This approach can precisely achieve interleaved current sharing among the converter modules. As the controller design and system analysis are performed in the time domain, the proposed method can easily satisfy the required converter specification by using the pole placement technique. The digital state feedback controller in the continuous and discrete time domain is derived for the robust tracking control. For the verification of the proposed control scheme, a parallel module bi-directional converter in a prototype 42V/14V hybrid automotive power system, which is a design example in the continuous time domain, and a parallel module buck converter, which is a design example in the discrete time domain, are implemented using a TMS320F2812 digital signal processor (DSP).

• Journal of Power Electronics
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• v.7 no.3
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• pp.265-270
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• 2007

Equal rating DC-DC converter modules can be connected in series at the input for circuits requiring higher input voltages and in parallel at the output for circuits requiring higher output currents. Since the converter modules may not be practically identical, closed loop control has to ensure that each module equally shares the total input voltage and the load current. A control scheme consisting of a common output voltage loop, individual inner current loops and individual input voltage loops have been designed in this work to achieve input voltage and load current sharing as well as load voltage regulation under supply and load disturbances. The output voltage loop provides the basic reference for the inner current loops, which are also modified by the respective input voltage loops. The average of the converter input voltages, which is dynamically varying, is chosen as the reference for input voltage loops. This choice of reference eliminates interaction among different control loops. Type II compensators and Fuzzy Logic Controllers (FLCs) are designed and compared through MATLAB based simulation and FLC is found to be satisfactory. Hence TMS320F2407A DSP based FLC is implemented and the results are presented which prove the superiority of the FLC developed for this research.

• Progress in Superconductivity and Cryogenics
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• v.21 no.1
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• pp.1-5
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• 2019

The pulsed field magnetization of the short-circuited soldered double pancake coil made of stabilized commercial high-Tc superconductor (HTS) tape is experimentally studied. The evolution of the shielding current induced by the pulsed field and the trapped field after the pulsed magnetization was measured at 77 K. It is shown that the trapped field in the coil is close to the value reached in the field cooling process and reduces weakly at 5-fold increasing of pulsed field amplitude. The current relaxation at t~2 ms after the pulse is defined by the current sharing between the tape's copper coating and the $YBa_2Cu_3O_{7-d}$ layer. In the intermediate time scale (1 s < t < 100 s) the flux creep in HTS layer dominates. At t > 100 s the current's relaxation is defined by the resistance of soldered joint between tapes.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_1
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• pp.387-395
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• 2021

Distributed resources such as renewable energy sources and ESS are connected to the low voltage direct current(LVDC) distribution network through the power conversion system(PCS). Control power is required for the operation of the PCS. In general, controller power is supplied from AC power or DC power through switch mode power supply(SMPS). However, the conventional SMPS has a low input voltage, so development and research on high input voltage self-power suitable for LVDC is insufficient. In this paper, to develop Self-Power that can be used for LVDC, the characteristics of the conventional topology are analyzed, and a series-input single-output flyback converter using a flux-sharing transformer for high voltage is designed. The high input voltage Self-Power was designed in the DCM(discontinuous current mode) to reduce the switching loss and solve the problem of current dissipation. In addition, since it operates even at low input voltage, it can be applied to many applications as well as LVDC. The validity of the proposed high input voltage self-power is verified through experiments.

• Management & Information Systems Review
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• v.39 no.2
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• pp.77-94
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• 2020

While the importance of the service industry has increased at the national economy level, the service rate and job satisfaction of the flight attendants in the aviation service industry are not high. In this regard, this study aims to recognize what factors can reduce their job stress in the emotional work environment, and how job stress affects their attitude and job performance. More specifically, the current study tries to investigate how flight attendants' positive psychological status affect their job stress, organizational commitment, and knowledge sharing in the aspect of job performance. The main five constructs in these interrelationships include the flight attendants' positive psychological capital, leader-member exchange(LMX), job stress, organizational commitment, and knowledge sharing. This study conducted a quantitative research with 390 questionnaire for flight attendants, and analyzed the data using SPSS/PC version 20.0 and structural equation modeling program of AMOS 20.0. The findings show that the favorable leader-member exchange relationship between flight attendants plays a significant role in lowering job stress, while high job stress has a negative effect on organizational commitment and knowledge sharing. The result also shows that personal positive psychological capital acts as a trigger to influence other factors. Therefore, this study suggests that it is essential for airlines not only to promote an organizational system to support the flight attendants' emotional work but also to maintain a positive psychological state for securing competitive human resources.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.32 no.1
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• pp.391-413
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• 2021

Policy study information is the essential source of information in every step of decision making process to plan, execute and assess the national operation policy. The policy study subject of a national policy research center from study design the performance assessment on its practical effect is managed via thorough process to secure its effectiveness and efficiency. However, the directly exposed information to the practical user or the public who are in need of actual policy study information is the resource published in a form of policy study report, the final result. NKIS operated by the National Research Council for Economics, Humanities and Social Sciences under the Office for Government Policy Coordination, Prime Minister's Secretariat is a public information offering service that conduct integrated management on study reports from cooperative study among institutes along with policy outcome from 27 national policy research centers. This study aims to introduce the current status of operation and information management of NKIS, apprehend the management characteristics of policy study information resources of national policy research center, and deduce remarks that need to be considered for API with external service for the derivation of standardized sharing data element.

• Journal of Korean Library and Information Science Society
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• v.54 no.1
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• pp.25-44
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• 2023

This study was to prepare a development plan for nationwide authority control system based on national authority sharing system of NLK through the survey targeting on libraries which do not participate in the system. Six plans were suggested to establish a nationwide authority control system based on this survey. First, an authority data construction module and a module linked to the national authority sharing system should be developed. Second, describing external identifiers such as ISNI to the national authority sharing system is to provides reliability of data and to utilizes to build linked data. Third, it is necessary to prepare strategies for promoting the national authority sharing system and diversifying services. Fourth, both authority establishment and non-establishment show difficulties and diversity in the selection and description of authorized access point, so it is necessary to prepare rules related to authorized access points. Fifth, since the data described in authority records is not enough, it is necessary to improve and upgrade authority records by using bibliographic records. Sixth, it is necessary to educate librarians about the necessity and function of authority control. As such, this study is meaningful in that it investigated the current status and requirements of libraries that do not participate in the nationwide authority system and sought ways to establish a nationwide cooperative authority control system.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.413-422
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• 1999

Auto-connected multipulse(12/24pulse) rectifier schemes are cost effective methods for reducing line current hamonics in PWM drive systems. Employing these schemes to enhance utility power quality requires careful attention to several design considerations In particular, excursion of dc-link voltage at no load, effect of pre-existing voltage distortion, impedance mismatches, unequal diode drops on rectifier current sharing and performance, are fully analyzed, Several corrective measures to improve the performance of 12/24­pulse rectifier systems are also discussed. Finally, experimental results on a 460V, 60Hz 400kVA commercial ASD, retrofitted with 12/24pulse rectifier systems are discussed in detail.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.971-976
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• 2011

This paper proposes a test system for a valve and poles building blocks used for large scale inverters such as STATCOM, SSSC, UPFC and VSC HVDC. Power semiconductors in the valve are normally connected in series to withstand switching voltage much larger than the voltage rating of a single power semiconductor. Therefore, there is a need to verify if the dynamic voltage sharing during switching in a valve is satisfactory. In this paper, we propose a test system that provides the necessary test condition: voltage and current in the valve using resonant circuits. A test scheme for a single phase inverter consisting two poles is also proposed. The performance of the inverter pole has to be verified at the factory test, before the system is installed at the site to secure the reliability of the system. The proposed scheme makes it possible to confirm if the pole can withstand voltage and current switching condition and handle loss.

• Transactions on Electrical and Electronic Materials
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• v.16 no.5
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• pp.241-249
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• 2015

Phase-locked-loops (PLL) have been employed in high-speed data transmission systems like wireless transceivers, disk read/write channels and high-speed interfaces. The majority of the researchers use a charge pump (CP) to obtain high performance from PLLs. This paper presents a review of various CMOS CP schemes that have been implemented for PLLs and the relationship between the CP parameters with PLL performance. The CP architecture is evaluated by its current matching, charge sharing, voltage output range, linearity and power consumption characteristics. This review shows that the CP has significant impact on the quality performance of CP PLLs.