• Journal of Communications and Networks
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• v.11 no.5
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• pp.433-444
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• 2009

The bi-directional relay channel is the natural extension of a three-terminal relay channel where node a transmits to node b with the help of a relay r to allow for two-way communication between nodes a and b. That is, in a bi-directional relay channel, a and b wish to exchange independent messages over a shared channel with the help of a relay r. The rates at which this communication may reliably take place depend on the assumptions made on the relay processing abilities. We overview information theoretic limits of the bi-directional relay channel under a variety of conditions, before focusing on half-duplex nodes in which communication takes place in a number of temporal phases (resulting in protocols), and nodes may forward messages in four manners. The relay-forwarding considered are: Amplify and forward (AF), decode and forward (DF), compress and forward (CF), and mixed forward. The last scheme is a combination of CF in one direction and DF in the other. We derive inner and outer bounds to the capacity region of the bi-directional relay channel for three temporal protocols under these four relaying schemes. The first protocol is a two phase protocol where a and b simultaneously transmit during the first phase and the relay r alone transmits during the second. The second protocol considers sequential transmissions from a and b followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. We provide a comprehensive treatment of protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries.

• 한국어정보학회:학술대회논문집
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• 2017.10a
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• pp.41-44
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• 2017

기계이해 시스템은 주어진 문서를 이해하고 질의에 해당하는 정답을 출력하는 방법으로 심층 신경망을 활용한 주의집중 방법이 발달하면서 활발히 연구되기 시작했다. 본 논문에서는 어휘 정보를 통해 문서와 질의를 이해하는 어휘 이해 모델과 품사 등장 정보, 의존 구문 정보를 통해 문법적 이해를 하는 구문 이해 모델을 함께 사용하여 기계이해 질의응답을 하는 Dual Bi-Directional Attention Flow모델을 제안한다. 한국어로 구성된 18,863개 데이터에서 제안 모델은 어휘 이해 모델만 사용하는 Bi-Directional Attention Flow모델보다 높은 성능(Exact Match: 0.3529, F1-score: 0.6718)을 보였다.

• Journal of International Society for Simulation Surgery
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• v.3 no.1
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• pp.9-11
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• 2016

Purpose In this paper we proposed bi-directional hierarchical regression for accurate human finger landmark detection with only using depth information.Materials and Methods Our algorithm consisted of two different step, initialization and landmark estimation. To detect initial landmark, we used difference of random pixel pair as the feature descriptor. After initialization, 16 landmarks were estimated using cascaded regression methods. To improve accuracy and stability, we proposed bi-directional hierarchical structure.Results In our experiments, the ICVL database were used for evaluation. According to our experimental results, accuracy and stability increased when applying bi-directional hierarchical regression more than typical method on the test set. Especially, errors of each finger tips of hierarchical case significantly decreased more than other methods.Conclusion Our results proved that our proposed method improved accuracy and stability and also could be applied to a large range of applications such as augmented reality and simulation surgery.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.31-37
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• 2015

This paper proposes a 3.3-kW bi-directional EV charger with V2G and V2H functions. The bi-directional EV charger consists of a DC-DC converter and a DC-AC inverter. The proposed EV charger is suitable for wide battery voltage control due to the two-stage configuration of the DC-DC converter. By employing a fixed-frequency series loaded resonant converter as the isolated DC-DC converter, zero-current-switching can be achieved regardless of battery voltage variation, load variation, and power flow. A 3.3-kW prototype of the proposed EV charger has been built and verified with experiments, and indicates a maximum efficiency of 94.39% and rated efficiency of 94.23%.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.184-188
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• 2009

To interactively share High Definition (HD)-quality visualization over emerging ultra-high-speed network infrastructure, several lossless and low-delay real-time media (i.e., uncompressed HD video and audio) transport systems are being designed and prototyped. However, most of them still rely on expensive hardware components. As an effort to reduce the building cost of system, in this paper, we propose the integration of both transmitter and receiver machines into a single bi-directional transport system. After detailed bottleneck analysis and subsequent refinements of embedded software components, the proposed integration can provide Real-time Transport Protocol (RTP)-based bi-directional transport of uncompressed HD video and audio from a single machine. We also explain how to interface the Gbps-bandwidth display output of uncompressed HD media system to the networked tiled display of 10240 $\times$ 3200 super-high-resolution. Finally, to verify the feasibility of proposed integration, several prototype systems are built and evaluated by operating them in several different experiment scenarios.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.149-152
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• 2001

A Single-phase bi-directional inverter Using a diode bridge-type resonant circuit to implement ZVT(Zero Voltage Transition) switching is Presented. It is shown that the ZACE(Zero Average Current Error) algorithm based polarized ramptime current control can provide a suitable interface between diode bridge-type resonant circuit DC link and the inverter. The current control algorithm is analyzed about how to design the circuit with analyzed switch which m ZVT operation for the main power switch The simulation and experimental results would be shown to verify the proposed current algorithm, because the main power switch is turn on with ZVT and the bi-directional inverter is operated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.3
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• pp.172-179
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• 2013

In this paper, we consider network-coded bi-directional relaying (NCBR) schemes over an asymmetric channel, in which bi-directional links have the different channel quality, as well as the asymmetric traffic load. In order to deal with asymmetric nature, two different types of NCBR schemes are considered: network coding after padding (NaP) and network coding after fragmentation (NaF). Even if NaP has been known as only a useful means of dealing with the asymmetry in traffic load up to now, our analysis shows that its gain can be significantly lost by the asymmetry in channel quality, under the given bit error performance constraint. Furthermore, it is shown that NaF always outperforms NaP, as well as traditional bi-directional relaying scheme.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.190-206
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• 2011

We propose an adaptive combination scheme of intra and inter prediction modes, where uni-directional intra prediction, bi-directional intra prediction, and inter prediction method are adaptively selected in an EMB (extended macro block). For each EMB, after all inter blocks have been encoded and decoded, the reconstructed blocks are used as reference data for bi-directional intra prediction of other blocks. Whereas conventional intra coding scheme does not use the right and below side pixels of the current block as reference data, the proposed method uses those for bi-directional intra prediction mode. In this paper, we propose three advanced techniques; (a) filter design for bi-directional prediction, (b) adaptive coding order scheme which increases the chance to use the bi-directional intra prediction mode, (c) modification of syntax to represent coding order. The information for the coding order is informed to the decoder by using the modified syntax structure without adding any additional flag. The simulation results show that the proposed scheme reduces the BD-Rate by 0.5%, on average, compared to KTA.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.45-53
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• 2013

Fuel cell power system is one of the most promising energy source for the alternative energy because it has unique advantages such as high energy density, no power drop during operation, and feasible to make compact size. However, due to very low response time, fuel cell is difficult to correspond to drastic load changes and start-up operation. For solving these problem, fuel cell power system must include energy storage device such as Li-Poly battery or super capacitor. Therefore, bi-directional DC-DC converter must be required for this storage device and fuel cell-PCS control. This paper presents a design and modeling of the bi-directional DC/DC converter. Firstly, we present modeling the boost and buck mode of the bi-directional converter through both PWM switch model and state space averaging technique. Secondly, in order to minimize output ripple and transient response overshoot, we have two identical DC-DC converters interleaved and adopt two-loop voltage-current controller. The proposed bi-directional DC-DC converter's modeling method and control design have been verified with computer simulation and experimentation.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.3
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• pp.197-205
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• 2014

In applications of adaptive noise control or active noise control, the presence of a transfer function in the secondary path following the adaptive controller and the error path, been shown to generally degrade the performance of the Least Mean Square (LMS) algorithm. Thus, the convergence rate is lowered, the residual power is increased, and the algorithm can become unstable. In general, in order to solve these problems, the filtered-x LMS (FX-LMS) type algorithms can be used. But these algorithms have slow convergence speed and weakness in the environment that the secondary path and error path are varied. Therefore, I present the new algorithm called the "Bi-directional Filtered-x (BFX) LMS" algorithm with nearly equal computation complexity. Through experimental study, the proposed BFX-LMS algorithm has better convergence speed and better performance than the conventional FX-LMS algorithm, especially when the secondary path or error path is varied and the impulsive disturbance is flow in.