• ETRI Journal
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• 제36권1호
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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.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -2
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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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• 제29권10호
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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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• 제18권1호
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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.

• 디지털산업정보학회논문지
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• 제18권1호
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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.

• 전기학회논문지P
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• 제60권4호
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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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• 제19권5호
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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.

• 한국통신학회논문지
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• 제31권12B호
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• pp.1037-1043
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• 2006

본 논문에서는 광 버스트 스위칭 네트워크의 코어 노드에 그룹 스케줄링을 적용한 경우 발생하는 데이터 버스트 처리 지연시간의 감소를 위한 알고리즘을 제안하였다. 이 알고리즘에서는 일차 스케줄링 세션 종료 직후에, 스케줄링 창 내의 모든 빈 공간(void) 정보를 나타내는 표를 생성하기 때문에, 직전 스케줄링에서 예약에 실패한 데이터 버스트들을 다른 채널의 빈 공간에 재할당할 때, 이 표를 활용하여 효과적으로 버스트 처리 시간 지연을 감소시킬 수가 있다. 이 알고리즘이 적용된 그룹 스케줄링 방식과 기존의 그룹 스케줄링 방식을 비교한 결과, 채널 이용률에 있어서는 서로 거의 동일한 성능을 보이나, 버스트 손실 확률과 파장 변환률은 알고리즘을 적용한 그룹 스케줄링 방식이 기존의 그룹 스케줄링 방식보다 약간 우수하였다. 버스트 처리 시간에 있어서는 부하가 약 0.6이하인 영역에서는 기존 그룹 스케줄링 방식이 약간 빠른 반면에, 부하가 0.8이상인 영역에서는 알고리즘을 적용한 방식의 처리 시간이 현저히 짧게 나타났다, 부하 0.9에서 약 1/2.1로 감소하였다.

• Journal of Power Electronics
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• 제10권2호
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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.

• 한국정보통신학회논문지
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• 제24권5호
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• pp.609-615
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• 2020

현대 사회는 4차 산업 혁명과 더불어 디지털 장비의 사용이 증가하여 영상 및 신호처리의 중요성이 높아지고 있으며, 이와 함께 잡음 제거에 관한 연구가 활발하게 이루어지고 있다. 본 논문은 랜덤 임펄스 잡음 제거를 위한 스위칭 필터 알고리즘을 제안한다. 제안한 알고리즘은 영상에 존재하는 잡음 수준을 판단하여 임계값을 구하며, 임계값은 입력 화소값과 기준치의 차이와 비교되어 필터의 가중치 스위칭 과정에 사용한다. 필터의 최종 출력은 스위칭에 따라 화소 가중치 및 변형된 가중치 메디안 필터를 적용하여 추정치를 구하며, 추정치와 입력 화소값을 비교하여 최종 출력을 구한다. 제안한 알고리즘의 성능을 평가하기 위해 시뮬레이션 및 PSNR 등을 이용하여 기존 방법들과 비교하였다.