• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.351-354
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• 2003

We present a 12.5-GHz interleaved bidirectional ultra-dense wavelength-division-multiplexing transmission over a conventional single mode fiber of 80 km achieving spectral efficiency as high as 0.8-bit/s/Hz. The beat-frequency-locking method is used to stabilize the channel frequency within $\pm$200 MHz error. To facilitate the identification of multiple beat frequency signals, we use a radio-frequency spectrum analyzer. The bidirectional transmission penalty is about 0.3 dB compared with the unidirectional transmission over the same fiber.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.125-128
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• 2006

This paper presents a novel type soft switching PWM power frequency AC-AC converter using bidirectional active switches or single phase utility frequency AC-high frequency AC matrix converter. This converter can directly convert utility frequency AC (UFAC, 50Hz/60Hz) power to high frequency AC (HFAC) power ranging more than 20kHz up to 100kHz. A novel soft switching PWM prototype of high frequency multi-resonant PWM controlled UFAC-HFAC matrix converter using antiparallel one-chip reverse blocking IGBTs manufactured by IXYS corp. is based on the soft switching resonance with asymmetrical duty cycle PWM strategy. This single phase UFAC-HFAC matrix converter has some remarkable features as electrolytic capacitor DC busline linkless topology, unity power factor correction and sine-wave line current shaping, simple configuration with minimum circuit components, high efficiency and downsizing. This series load resonant UFAC-HFAC matrix converter, incorporating bidirectional active power switches is developed and implemented for high efficiency consumer induction heated food cooking appliances in home uses and business-uses. Its operating performances as soft switching operating ranges and high frequency effective power regulation characteristics are illustrated and discussed on the basis of simulation and experimental results.

• 한국어정보학회:학술대회논문집
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• 2016.10a
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• pp.14-19
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• 2016

본 논문은 문장에서의 어절 간 의존관계가 성립될 때 의존소와 지배소가 어떠한 관계를 가지는지 의존 관계명을 부착하는 모델을 제안한다. 국내에서 한국어 의존구문분석에 관한 연구가 활발히 진행되고 있지만 의존 관계만을 결과로 제시하고 의존 관계명을 제공하지 않는 경우가 많았다. 따라서 본 논문에서는 의존경로(Dependency Path)와 음절의 의존 관계명 분포를 반영하는 음절 임베딩를 이용한 의존 관계명 부착모델을 제안한다. 문장에서 나올 수 있는 최적의 입력 열인 의존 경로(Dependency Path)를 순차 레이블링에서 좋은 성능을 나타내고 있는 bidirectional LSTM-CRFs의 입력 값으로 사용하여 의존 관계명을 결정한다. 제안된 기법은 자질에 대한 많은 노력 없이 의존 경로에 따라 어절 및 음절 단어표상(word embedding)만을 사용하여 순차적으로 의존 관계명을 부착한다. 의존 경로를 사용하지 않고 전체 문장의 어절 순서를 바탕으로 자질을 추출하여 CRFs로 분석한 기존 모델보다 의존 경로를 사용했을 때 4.1%p의 성능향상을 얻었으며, 의존 관계명 분포를 반영하는 음절 임베딩을 사용한 bidirectional LSTM-CRFs는 의존 관계명 부착에 최고의 성능인 96.01%(5.21%p 개선)를 내었다.

• Proceedings of the KSRS Conference
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• v.1
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• pp.79-81
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• 2006

Geostationary ocean satellite, unlike other sun-synchronous polar-orbit satellites, will be able to take a picture of a large region several times a day (almost with every one hour interval). For geostationary satellite, the target region is fixed though the location of sun is changed always. Thus, the ocean signal of a given target point is largely dependent on time. In other words, the ocean signal detected by geostationary satellite sensor must translate to the signal of target when both sun and satellite are located in nadir, using another correction model. This correction is performed with a standardization of signal throughout relative geometric relationship among satellite - sun - target points. One signal value of a selected pixel point of the target region of Geostationary Ocean Colour Imager (GOCI) would be set up as a standard, and the ratio of all remained pixel point can be calculated. This relative ratio called bidirectional factor, the result of modelling of spatiotemporal variation of bidirectional factor is shown.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1279-1300
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• 2017

In the interweave cognitive networks, the interference from the primary user degrades the performance of the cognitive user transmissions. In this paper, we propose an adaptive cooperation scheme in the interweave cognitive networks to improve the performance of the cognitive user transmissions. In the proposed scheme for the bidirectional communication of two end-source cognitive users, the bidirectional communication is completed through the non-relay direct transmission, the one-way relaying cooperation transmission, and the two-way relaying cooperation transmission depending on the limited feedback from the end-sources. For the performance analysis of the proposed scheme, we derive the outage probability and the finite-SNR diversity multiplexing tradeoff (f-DMT) in a closed form, considering the imperfect spectrum sensing, the interference from the primary user, and the power allocation between the relay and the end-sources. The results show that compared with the direct transmissions (DT), the pure one-way relaying transmissions (POWRT), and the pure two-way relaying transmissions (PTWRT), the proposed scheme has better outage performance. In terms of the f-DMT, the proposed scheme outperforms the full cooperation transmissions of the POWRT and PTWRT.

• Journal of Power Electronics
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• v.10 no.1
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• pp.27-33
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• 2010

This paper presents a bidirectional DC-DC converter suitable for low-voltage super capacitor-based electric energy storage systems. The DC-DC converter presented here consists of a full-bridge circuit and a current-fed push-pull circuit with a high frequency (HF) transformer-link. In order to reduce the device-conduction losses due to the large current of the super capacitor as well as unnecessary ringing, synchronous rectification is employed in the super capacitor-charging mode. A wide range of voltage regulation between the battery and the super capacitor can be realized by employing a Phase-Shifting (PS) Pulse Width Modulation (PWM) scheme in the full-bridge circuit for the super capacitor charging mode as well as the overlapping PWM scheme of the gate signals to the active power devices in the push-pull circuit for the super capacitor discharging mode. Essential performance of the bidirectional DC-DC converter is demonstrated with simulation and experiment results, and the practical effectiveness of the DC-DC converter is discussed.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.169-177
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• 2013

This paper proposes a new configuration of bidirectional intelligent semiconductor transformer with rating of 1.9kV/127V, 2kVA. The proposed transformer consists of high-voltage high-frequency AC-DC rectifier, and low-voltage DC-DC and DC-AC converters. The operational feasibility of proposed transformer was verified by computer simulation with PSCAD/EMTDC software. Based on the simulation results, a hardware prototype with rating of 1.9kV/127V, 2kVA was built and tested in the lab to confirm the feasibility of hardware implementation. Using three units of this transformer, a 3-phase transformer with rating of 3.3kV/220V, 6kVA can be built.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.42-49
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• 2013

A simultaneous bidirectional inductively-coupled link is presented. In the conventional inductively-coupled link, data can be bidirectionally transmitted through channel, however not simultaneously. We propose simultaneous bidirectional link for higher data rate with effective echo cancellation technique. Each chip performs TX-mode and RX-mode simultaneously. Instead chip stacking for test, similar test enviroment is realized in a single chip that is fabricated in a $0.13-{\mu}m$ standard CMOS technology.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.97-105
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• 2013

The control method of the bidirectional DC/DC converter for instantaneous regenerative current control is described in this paper. The general method to control the DC/DC converter is the output voltage control. However, the regenerative current cannot be controlled to be constant with this control method. To improve the performance of the conventional control method, the DC-link voltage of the inverter is controlled within the tolerance range by the instantaneous boost and buck operations of the bidirectional DC/DC converter. By the proposed control method, the battery current can be controlled to be constant regardless of the motor speed variation. The improved performance of the DC/DC converter controlled by the proposed control method is verified by the experiment and simulation of the system with the inverter and IPMSM(Interior Permanent Magnet Synchronous Motor) which is operated by the reduced practical speed profile.

• Journal of Power Electronics
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• v.11 no.1
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• pp.1-9
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• 2011

This paper describes a two quadrant bidirectional soft switching converter for ultra capacitor interface circuits. The total efficiency of the energy storage system in terms of size and cost can be increased by a combination of batteries and ultra capacitors. The required system energy is provided by a battery, while an ultra capacitor is used at high load power pulses. The ultra capacitor voltage changes during charge and discharge modes, therefore an interface circuit is required between the ultra capacitor and the battery. This interface circuit must have good efficiency while providing bidirectional power conversion to capture energy from regenerative braking, downhill driving and the protecting ultra capacitor from immediate discharge. In this paper a fully soft switched two quadrant bidirectional soft switching converter for ultra capacitor interface circuits is introduced and the elements of the converter are reduced considerably. In this paper, zero voltage transient (ZVT) and zero current transient (ZCT) techniques are applied to increase efficiency. The proposed converter acts as a ZCT Buck to charge the ultra capacitor. On the other hand, it acts as a ZVT Boost to discharge the ultra capacitor. A laboratory prototype converter is designed and realized for hybrid vehicle applications. The experimental results presented confirm the theoretical and simulation results.