• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.343-350
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• 2006

This paper introduces a new high efficient bi-directional, non-isolated DC/DC converter. Through variations of the topology of the conventional Cuk converter, an optimum bi-directional DC/DC converter is proposed. Voltage and current in the proposed DC/DC converter are continuous. Furthermore, the efficiency in both step-up and step-down mode is improved over that of the conventional bi-directional converter. To prove the validation for the proposed converter, simulations and experiments are executed with a 300W bi-directional converter.

• 인터넷정보학회논문지
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• 제12권3호
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• pp.69-76
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• 2011

온라인 중개 서비스 시스템에서 원하는 고객을 상호 매칭시키는 기능은 핵심 역할 중의 하나이다. 매칭은 정보검색과 같이 한쪽의 의사만으로 결정되는 단방향과, 양쪽 사용자의 의사를 모두 고려하는 양방향 방식이 있다. 기존의 양방향 방식은 사용자가 상대에 대한 관심을 직접 입력하여야 하므로 입력의 번거로움 뿐만 아니라 상대가 나에 대해 관심을 입력하지 않은 경우는 서비스 활용이 어렵다는 문제점이 있었다. 따라서 본 연구는 퍼지 알고리즘을 이용하여 시스템이 상대의 흥미를 자동으로 계산하도록 하여 양방향 방식을 자동화 하고자한다. 개발된 퍼지 알고리즘의 구인/구직 정보매칭 결과가 모두 95%이상의 취업알선가능률을 보였다. 또한 실 서비스에 구축하여 도입효과를 분석한 결과 취업활동 동기 부여에 통계적으로 유의미한 긍정적인 효과가 나타났다.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1692-1699
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• 2015

This paper presents an analysis of the mechanism of failure modes in bi-directional phase-shift full-bridge converters, composed of MOSFET, based on the circuit operation and parasitic parameters of MOSFET. In addition, the relation between circuit operation and parameters is suggested through an experimental comparison. From this relation, the suitable ranges of parameters for stable performance are analyzed. The design criteria of the bi-directional phase-shift full-bridge converter are presented and evaluated from the experimental verification.

• IEIE Transactions on Smart Processing and Computing
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• 제3권5호
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• pp.285-297
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• 2014

This paper presents the results of an investigation into bi-directional communication in spectrum sharing-based cognitive radio (Bi-CR) systems. A Bi-CR system can increase the spectral efficiency significantly by sharing the spectrum and through the bi-directional use of spatial resources for two-way communication. On the other hand, the primary user experiences more interference from the secondary users in a Bi-CR system. Satisfying the interference constraint by simply reducing the transmission power results in performance degradation for secondary users. In addition, secondary users also experience self-interference from echo channels due to full duplexing. These imperfections may weaken the potential benefits of the Bi-CR system. Therefore, a new way to overcome these defects in the Bi-CR system is needed. To address this need, this paper proposes some novel power allocation schemes for the Bi-CR system. This contribution is based on two major analytic environments, i.e., noise-limited and interference-limited environments, for providing useful analysis. This paper first proposes an optimal power allocation (OPA) scheme in a noise-limited environment and then analyzes the achievable sum rates. This OPA scheme has an effect in the noise-limited environment. In addition, a power allocation scheme for the Bi-CR system in an interference-limited environment was also investigated. The numerical results showed that the proposed schemes can achieve the full duplexing gain available from the bi-directional use of spatial resources.

• 전기학회논문지
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• 제63권5호
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• pp.615-621
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• 2014

With development of electrical power system, the DC distribution system has been considered as a promising technology to be used in the future smart distribution system. Among the various components comprising the DC distribution system, the bi-directional DC/DC converter is one of the most important equipment to interconnect between main power system and various renewable resources such as photovoltaic power generation, wind power generation, and electrical vehicles. In this paper, a bi-directional DC/DC converter based on three-phases interleaved method which is effective to reduce ripple of input current and output voltage is modeled using ElectroMagnetic Transient Program(EMTP), and the verification of modeled bi-directional DC/DC converter is conducted.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.319-324
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• 2012

This paper presents the study of 3-Phase bi-directional DC to AC inverter with unity power factor. 3-Phase bi-directional DC to AC inverter is important for the bi-modal PV PCS with an energy storage system. Both Inverting and converting are needed to connect between the grid side and boost converting side to charge and discharge the energy storage system. The paper proposes the appropriate circuit topology and proper control system for the bi-directional inverter. It also proposes the method of selecting the optimum control method considering system stability. PSIM simulation is used to validate the proposed algorithm.

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.101-122
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• 2016

Elasticity solutions for bi-directional functionally graded beams subjected to arbitrary lateral loads are conducted, with emphasis on the end effects. The material is considered macroscopically isotropic, with Young's modulus varying exponentially in both axial and thickness directions, while Poisson's ratio remaining constant. In order to obtain an exact analysis of stress and displacement fields, the symplectic analysis based on Hamiltonian state space approach is employed. The capability of the symplectic framework for exact analysis of bi-directional functionally graded beams has been validated by comparing numerical results with corresponding ones in open literature. Numerical results are provided to demonstrate the influences of the material gradations on localized stress distributions. Thus, the material properties of the bi-directional functionally graded beam can be tailored for the potential practical purpose by choosing suitable graded indices.

• 전력전자학회논문지
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• 제17권1호
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• pp.14-20
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• 2012

This paper presents a design and topology selection of bi-direcional buck converter based on PV PCS for managing the electric power. Futhermore, Current Ringing on DCM bi-directional buck converter for soft switching is analyzed in detail. PSIM Simulation and Experiments at the various operating points show the propriety of this paper. Building on the result of simulation and experiment, a comparative analysis is performed with the approximate estimate. By use of a study, the selecion of switch and diode which improve efficiency of the overall system is appiled to DCM bi-directional buck converter based on PV PCS.

• 조명전기설비학회논문지
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• 제28권8호
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• pp.90-97
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• 2014

This paper presents a compensation method of unbalanced phase currents in interleaved bi-directional converters. Phase currents in interleaved bi-directional converter are apt to be unbalanced due to circuit parameter error and switch operation difference. This problem causes the switch element failure and the reduced efficiency of the converter. Therefore, it is necessary that a certain balance control algorithm is provided in interleaved bi-directional converter system. In this paper, a balance control algorithm based on the circular chain control method is proposed. Further, in order to reduce the number of phase current sensors, this paper shows a simple method in which phase currents can be extracted indirectly through a DC-link current sensor in both charging and discharging modes. The validity and the effectiveness of the proposed phase currents balance control algorithm are illustrated through the simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.632-634
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• 1996

In modern train systems, the high-speed and the high-density of train operation have been required. Effective train control systems need various information interchanged between the ground-site and on-board devices. So the systems are essential to the digital systems to admit lots of information and to raise the accuracy of transmission. In this paper, it is dealt with n bi-directional transmission of digital information between on-board devices and ground-site. Especially, this paper shows the experiment of bi-directional transmission of mass information by using transponder.