• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.212-213
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• 2017

In this paper is presented a pre-charging sequence for single-phase cascaded neutal-point-clamped(NPC) converters for capacitors voltage balancing. capacitor imbalance problem in pre-charge sequence is caused in cascaded NPC converter by its topology. the DC link voltage at each NPC converter module can be balanced by the proposed switching method. the design and performance of the proposed sequence are verified by simulation and experimental results using prototype.

• Journal of Power Electronics
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• v.14 no.5
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• pp.946-956
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• 2014

Cascaded H-Bridge (CHB) converters can be directly connected to medium-voltage grids without using transformers and they possess the advantages of large capacity and low harmonics. They are significant tools for providing grid connections in large-capacity renewable energy systems. However, the reliability of a grid-connected CHB converter can be seriously influenced by the number of power switching devices that exist in the structure. This paper proposes a fault-tolerant control strategy based on double zero-sequence voltage injection and DC voltage optimization to improve the reliability of star-connected CHB converters after one or more power units have been bypassed. By injecting double zero-sequence voltages into each phase cluster, the DC voltages of the healthy units can be rapidly balanced after the faulty units are bypassed. In addition, optimizing the DC voltage increases the number of faulty units that can be tolerated and improves the reliability of the converter. Simulations and experimental results are shown for a seven-level three-phase CHB converter to validate the efficiency and feasibility of this strategy.

• Journal of Distribution Science
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• v.10 no.11
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• pp.79-88
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• 2012

Purpose - The objective of this paper is to suggest that a company's CRM activities have an effect on customer loyalty in the Korean retail industry. Typically, Korean customers use large local marts with convenience in the absence of any other choice. Therefore, this study aims to shed light on the fact that customers do not break away from their preferred retail stores, either owing to their stringent loyalty (the lie loyalty) or difficulty in turning to alternative choices. Research design, data, methodology - By surveying a sample of 200 hyper-markets through a questionnaire, and excluding dubious and missing responses, I obtained 181 samples to be included in the empirical analysis. The survey was conducted for two weeks during October 2011. AMOS and SPSS18 statistical packages were used for conducting statistical analysis for this study. This paper was developed using the concept of customer equity on CRM, which is known to have a positive impact on customer loyalty through the satisfaction and switching-barrier parameters. The hypothesis of this paper is that customer equity is composed of relationship equity, value equity and brand equity, and that the relationship equity variable has positive effects on the value equity and brand equity amongst other types of customer equity. Moreover, customer equity influences customer loyalty through parameters including customer satisfaction and switching costs in the Korean retail industry. Results - According to the results of the analysis, it was confirmed that relationship value had a positive effect (+) on all variables, including the perceived QoS (Quality of Service), store brand images, economic value, and store convenience. It was also confirmed that the assumption that the perceived QoS (Quality of Service), economic value, and store convenience had a positive effect on customer satisfaction was shown to be statistically significant, with a p-value below 0.05. Only the store brand value variable had an effect on the switching-cost variable with respect to the causal sequence of the variables, including the perceived QoS, store brand value, economic value, and store convenience. The remaining variables did not seem to influence the switching-cost variable. On the other hand, another effect showed that customer satisfaction had a statistically significant influence on the switching-costs variable. Moreover, the customer satisfaction and switching-cost variables also had a statistical influence on customer loyalty. Conclusions - The CRM activities had an influence on various variables (including perceived QoS, perceived economic value, store brand value, and store convenience) pertaining to customer values. Customer satisfaction and switching-cost had some effects on customer loyalty as a parameter. This confirms that stringent loyalty exists with respect to customer loyalty in the retail industry. The fact that the variable had such a statistically significant influence on the switching-cost and store brand equity variables means that consumers react to the reputation of a brand, confidence about the store, and quality confidence. The implications of this study in the retail industry should be further extended to devise strategies for customer retention.

• Journal of IKEEE
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• v.10 no.2 s.19
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• pp.103-108
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• 2006

This paper proposed a low power resource allocation algorithm for the minimum switching activity of operators in high level synthesis. In this paper, the proposed method finds switching activity in circuit each functional unit exchange for binary sequence length and value bit are logic one value. To use the switching activity was found the allocation with minimal power consumption, the proposed method visits all control steps one by one and determines the allocation with minimal power consumption at each control step. As the existing method, the execution time can be fast according to use the number of operator and maximal control step. And it is the reduction effect from 8.5% to 9.3%.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1631-1633
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• 2001

In manufacturing processes, various and suitable pulse shapes are required for the purpose of material processing and the pulseshape is regarded as a dominant factor due to the specific property of processing materials. Therefore, in this study, a variable pulse width, high duty cycle Pulse Forming Network(PFN) is constructed by time sequently. The power supply for this experiment consists of three switching circuits. The PFN elements operate at low voltage and drive the primary of HV leakage transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence of properly phased and nested increments. We investigated laser pulse width as various delay time among three switching circuit. As a result, we tan obtain various laser pulse width from about 4ms to 10ms. The maximum laser pulse width obtained at this experiment was about 10ms at delay time of 4ms among each switching circuit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.5
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• pp.379-389
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• 1988

In this paper, an algorithm for obtaining 2-state switching failure function and a terminal pair reliability evaluation method in a communication network are proposed. The communication network is modeled by a graph. By using the sequence of matrix transformations for the graph, minimal cut-set matrix representing all minimal cut-sets which completely interrupt the communication path is determined and 2-state switching failure function is then obtained from the minimal cut-set matrix. The terminal pari reliability of the communication network is evaluated by corresponding the random variables to 2-state switching failure function. Illustrative examples are provided to demonstrate the algorithm. A computer program evaluating the terminal pair reliability in a complex and large network has also been developed.

• Journal of Power Electronics
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• v.12 no.6
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• pp.895-903
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• 2012

This paper presents a fast switching direct torque control (FS-DTC) using only a single DC-link current sensor. In FS-DTC, six new active voltage complex space vectors (CSVs) are synthesized by the conventional active voltage space vectors (SVs). The corresponding sectors are rotated in the anticlockwise direction by 30 degrees. A selection table is defined to select the CSVs. Based on the "Different Phase Mode", the output sequence of the selected CSV is optimized. Accordingly, a reconstruction method is proposed to acquire the phase currents. The core of the FS-DTC is that all of the three phase currents can be reliably reconstructed during every two sampling periods, which is the result of the fast switching between different phases. The errors between the reconstructed and actual currents are strictly limited in one sampling period. The FS-DTC has the advantages of the standard DTC scheme such as simple structure, quick torque response and robustness. As can be seen in the analysis, the FS-DTC can be thought of as an equivalent standard DTC scheme with 86.6% of the maximum speed, 173.2% of the torque ripple, and 115% of the response time of the torque. Based on a dSPACE DS1103 controller, the FS-DTC is implemented in an induction machine drive system. The results verify the effectiveness of the FS-DTC.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3433-3446
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• 2019

Aiming at the high complexity of traditional single-channel demodulation algorithm for PCMA signals, a new demodulation algorithm based on neural network is proposed to reduce the complexity of demodulation in the system of non-cooperative PCMA communication. The demodulation network is trained in this paper, which combines the preprocessing module and decision module. Firstly, the preprocessing module is used to estimate the initial parameters, and the auxiliary signals are obtained by using the information of frequency offset estimation. Then, the time-frequency characteristic data of auxiliary signals are obtained, which is taken as the input data of the neural network to be trained. Finally, the decision module is used to output the demodulated bit sequence. Compared with traditional single-channel demodulation algorithms, the proposed algorithm does not need to go through all the possible values of transmit symbol pairs, which greatly reduces the complexity of demodulation. The simulation results show that the trained neural network can greatly extract the time-frequency characteristics of PCMA signals. The performance of the proposed algorithm is similar to that of PSP algorithm, but the complexity of demodulation can be greatly reduced through the proposed algorithm.

• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.44-48
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• 2009

A simulation study of a 10-bit two-stage DAC was done by using a conventional current switch cell. The DAC adopts the segmented architecture in order to reduce the circuit complexity and the die area. The 10-bit CMOS DAC was designed in 2 blocks, a unary cell matrix for 6 MSBs and a binary weighted array for 4 LSBs, for fabrication in a 0.35-${\mu}m$ CMOS process. To cancel the accumulation of errors in each current cell, a symmetrical switching sequence is applied in the unary cell matrix for 6 MSBs. To ensure high-speed operation, a decoding circuit with one stage latch and a cascode current source were developed. Simulations show that the maximum power consumption of the 10-bit DAC is 74 mW with a sampling frequency of 100 MHz.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.394-398
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• 1988

In this paper, the time-averaged behavior of the three-phase Inductor-Converter Bridge (ICB) circuit has been analyzed by using the state-space averaging method. The results are in closed form far from the results obtained by using the Fourier series. Therefore, the computational difficulties of the infinite Fourier series can be avoided and the results derived in this paper are available especially in real time control. Unlike the SFC, $S^{4}LCL$, DFC and other circuits which have time varying switching intervals for a constant time-averaged value of coil voltage, the ICB circuits operate with a clock-driven sequence of gate pulses which have constant switching intervals.