• ETRI Journal
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• v.36 no.1
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• pp.183-186
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• 2014

In this letter, we consider a cooperation system with multiple untrusted relays (URs). To keep the transmitted information confidential, we obtain joint channel characteristics (JCCs) through combining the channels from the source to the destination. Then, in the null space of the JCCs, jammers construct artificial noise to confuse URs when the source node broadcasts its data. Through a distributed implementation algorithm, the weight of each node can be obtained from its own channel state information. Simulation results show that high-level security of the system can be achieved when internal and external eavesdroppers coexist.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1011-1014
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• 2002

This paper proposes a multicast packet-switching method which can less affect QoS degradation. The method includes a switch fabric with extra switching paths dedicated for multicast packets. Presented also are both a buffering structure and a scheduling algorithm for the proposed method. Simulation analysis for the method shows that the switching delay of unicast packets is decreased even though arrival rate of multicast packets is increased.

• 전기의세계
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• v.29 no.10
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• pp.678-688
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• 1980

This paper is concerned with the computer design of the multiple-output switching functions by using the improved MASK method in order to obtain the paramount prime implicants (prime implicants of the multiple-output switching function) and new algorithm to design the optimal logic network. All the given minterms for each function are considered as minterms of one switching function to simplify the desigh procedures. And then the improved MASK method whose memory requirement and time consuming are much less than any existing known method is applied to identify the paramount prime implicants. In selecting the irredundant paramount prime implicants, new cost criteria are generated. This design technuque is suitable both for solving a problem by hand or programming it on a digital computer.

• Journal of Power Electronics
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• v.18 no.1
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• pp.137-146
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• 2018

This paper describes a single pulse-width modulation control strategy using the Single Pulse-Width Modulation (SPWM) method with a soft-switching technique for a wide range of output voltages from a bidirectional Dual-Active Bridge (DAB) converter. This method selects two typical inductor current waveforms for soft-switching, and proposes a rule that makes it possible to achieve soft-switching without any compensation algorithm from the waveforms. In addition, both the step-up and step-down conditions are analyzed. This paper verifies that the leakage inductance is independent from the rule, which makes it easier to apply in DAB converters. An integrated algorithm, which includes step-up and step-down techniques, is proposed. The results of experiments conducted on a 50-kW prototype are presented. The system efficiency is experimentally verified to be from 85.6% to 97.5% over the entire range.

• Journal of Korea Society of Digital Industry and Information Management
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• v.18 no.1
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• pp.25-35
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• 2022

The SAP(salt-and-pepper) noise changes the pixel value to the maximum and minimum values of the dynamic region of the pixel. For this reason, unlike white Gaussian noise, SAP noise can predict the ratio of noise relatively easily. Because the condition of the neighboring pixels that can be referenced changes according to the noise ratio, it is necessary to apply different noise reduction methods according to the noise ratio. This paper proposes an adaptive switching filtering algorithm which can eliminates the SAP noise. It consists of two phases. It first detects the location of the SAP noise and calculates the noise ratio. After that, the image is reconstructed using different methods depending on which of the three sections the calculated noise ratio belongs to. As a result of the experiment, the proposed method showed superior objective and subjective image quality compared to the previous methods such as MF, AFSWMF, NAMF and RWMF.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.246-252
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• 2011

In this paper proposes the soft-switching boost converter and MPPT control for improving the efficiency of PV system. The proposed converter designed H-bridge auxiliary resonant circuit. By this circuit, all of the switching devices perform the soft switching under the zero voltage and zero current condition. Therefore the periodic switching losses can be decreased at turn on, off. The soft switching boost converter designs for 1.5[kW] solar module of the power conversion. Thus, this soft switching boost converter is simulated by MATLAB simulation using Newton-Method algorithm. As a result, Proposed Soft Switching Converter compared to a typical boost converter switching loss was reduced about 61%. And the overall system efficiency was verified to increase about 3.3%.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1182-1192
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• 2019

In order to improve the conversion efficiency and mitigate the EMI problem of conventional hard-switching inverters, a new soft-switching DC-AC inverter with a compact structure and a low modulation complexity is proposed in this paper. In the proposed structure, resonant inductors are connected in series for the arm branches, and resonant capacitors are connected in parallel for the neutral point branches. With the help of resonant components, the proposed structure achieves zero-current switching on the arm branches and zero-voltage switching on the neutral point branches. When compared with state-of-art soft-switching topologies, the proposed topology does not need auxiliary switches. Moreover, the commutation algorithm to realize soft-switching can be easily implemented. In this paper, the principle of the resonant operation of the proposed soft-switching converter is presented and its performance is verified through simulation studies. The feasibility of the proposed inverter is evaluated experimentally with a 2.4-kW prototype.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1037-1043
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• 2006

There has been proposed an algorithm to reduce data burst processing delay in group scheduling in core nodes of optical burst switching networks. Since, in this algorithm, look-up tables containing all the void time information in scheduling windows are generated as soon as the primary group scheduling session terminates, it becomes faster to reassign dropped data bursts to proper voids in different data channels by referring to the tables. The group scheduling with this algorithm showed almost the same channel utilization as the one without using the algorithm but performed a little better in both burst loss probability and wavelength conversion rate. On the other hand, per-burst processing time has been reduced dramatically in the load region of higher than 0.8, showing a factor of 2.1 reduction at 0.9.

• Journal of Power Electronics
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• v.10 no.2
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• pp.155-164
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• 2010

This paper presents a voltage control algorithm for a hybrid multilevel inverter based on a staged-perception of the inverter voltage vector diagram. The algorithm is applied to control a three-stage eighteen-level hybrid inverter, which has been designed with a maximum number of symmetrical levels. The inverter has a two-level main stage built using a conventional six-switch inverter and medium- and low- voltage three-level stages constructed using cascaded H-bridge cells. The distinctive feature of the proposed algorithm is its ability to avoid the undesirable high switching frequency for high- and medium- voltage stages despite the fact that the inverter's dc sources voltages are selected to maximize the number of levels by state redundancy elimination. The high- and medium- voltage stages switching algorithms have been developed to assure fundamental switching frequency operation of the high voltage stage and not more than few times this frequency for the medium voltage stage. The low voltage stage is controlled using a SVPWM to achieve the reference voltage vector exactly and to set the order of the dominant harmonics. The inverter has been constructed and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the desired features and all of the major hypotheses have been verified.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.609-615
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• 2020

In the modern society, the use of digital equipment is increasing along with the 4th industrial revolution, and the importance of image and signal processing is increasing. At the same time, research on noise reduction is being actively conducted. In this paper, we propose a switching filter algorithm for random-valued impulse noise cancellation. The proposed algorithm obtains the threshold value by determining the noise level present in the image, and threshold value is compared with the difference between the input pixel value and the reference value, and is used in the weight switching process of the filter. The final output of the filter is estimated by applying a pixel weight and a modified weight median filter according to the switching, and obtains a final output by comparing the estimated value with the input pixel value. To evaluate the performance of the proposed algorithm, we compared it with the existing methods using simulation and PSNR.