• 한국통신학회논문지
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• 제33권6A호
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• pp.635-642
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• 2008

본 논문에서는 time-varying Rayleigh fading channel에서 분산 안테나 시스템의 최적 전력 분배 기법을 제안한다. 기존 관련 연구에서는 각 기지국으로부터 수신되는 전력의 차이를 기지국간 전력 분배에 고려하지 않았으나, 최근 들어 빠르게 변하는 small scale fading까지 Channel State Information (CSI)로하여 전력 분배를 하는 경우에 대한 연구가 진행되었다. 하지만, 실제 무선통신 환경에서 송수신단간의 거리 차이 때문에 피드백이 반영된 신호가 수신될 때의 페이딩 채널은 피드백을 하는 시점과는 차이가 있고, 이로 인한 성능저하가 나타난다. 본 논문에서는 이러한 성능저하를 극복하고 CSI 피드백의 부담을 경감시키기 위하여 small scale fading을 제외하고, 느리게 변하는 경로손실과, 섀도잉에 의한 large scale fading값만을 피드백하는 분산 안테나 시스템을 제안하고 Bit Error Rate (BER)을 최소화하기 위한 최적 전력 분배 공식을 유도했다. 빠른 페이딩 환경에서, 제안된 최적 전력 분배 기법이 small scale fading까지 고려한 전력 분배 기법보다 월등히 좋은 성능을 보이며, 피드백 지연이 없는 환경에서도 1dB 이내의 성능을 보이는 것을 확인했다. 또한, 본 논문에서 Rayleigh fading channel을 가정하여 유도한 전력 분배 기법이 Line-of-Sight (LOS) 성분의 크기가 작은 Ricean fading channel에서도 최소의 BER과 거의 비슷한 값을 달성함을 보였다.

• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.267-273
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• 2007

A depletion-mode MOSFET has been analyzed to evaluate its electrical behavior using a novel 3-D numerical simulation package. The characterizing analysis of the BC MOSFET was performed through short-channel narrow-channel and small-geometry effects that are investigated, in detail, in terms of the threshold voltage. The DIBL effect becomes significant for a short-channel device with a channel length of $<\;3({\mu}m)$. For narrow-channel devices the variation of the threshold voltage was sharp for $<4({\mu}m)$ due to the strong narrow-channel effect. In the case of small-geometry devices, the shift of the threshold voltage was less sensitive due to the combination of the DIBL and substrate bias effects, as compared with that observed from the short-channel and narrow-channel devices. The characterizing analysis of the narrow-channel and small-geometry devices, especially with channel width of $<\;4({\mu}m)$ and channel area of $<\;4{\times}4({\mu}m^2)$ respectively, can be accurately performed only from a 3-D numerical simulation due to their sharp variations in threshold voltages.

• International journal of advanced smart convergence
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• 제13권1호
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• pp.1-11
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• 2024

Cognitive small cell networks, consisting of macro-cells and small cells, are foreseen as a promising candidate solution to address 5G spectrum scarcity. Recently, many technological issues (such as spectrum sensing, spectrum sharing) related to cognitive small cell networks have been studied, but the common control channel (CCC) establishment problem has been ignored. CCC is an indispensable medium for control message exchange that could have a huge significant on transmitter-receiver handshake, channel access negotiation, topology change, and routing information updates, etc. Therefore, establishing CCC in cognitive small cell networks is a challenging problem. In this paper, we propose a potential game theory-based approach for CCC establishment in cognitive radio networks. We design a utility function and demonstrate that it is an exact potential game with a pure Nash equilibrium. To maintain the common control channel list (CCL), we develop a CCC update algorithm. The simulation results demonstrate that the proposed approach has good convergence. On the other hand, it exhibits good delay and overhead of all networks.

• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.281-288
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• 2010

This paper investigates the performance of IEEE 802.11p wireless access in vehicular environments (WAVE) system in small-scale fading models reported by Georgia Institute of Technology (Georgia Tech). We redesign the small-scale fading models to be applied to the computer simulation and develop the IEEE 802.11p WAVE physical layer simulator to provide the bit error rate and packet error rate performances. Moreover, a new channel estimator using decision directed channel estimation and linear minimum mean square error smoothing is proposed in order to improve the performance of the conventional least square channel estimator using two identical long training symbols. The simulation results are satisfactorily coincident with the scenarios of Georgia Tech report, and the proposed channel estimator significantly outperforms the conventional channel estimator.

• 혜화의학회지
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• 제14권1호
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• pp.149-154
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• 2005

I have come to next conclusions in consequence of documentary study about medical books of many generations regarding Medical treatment with Acupuncture Point of Flank pain. The urinary bladder channel of foot-taiyang is most used. Next there are the ren channel, the gall baldder channel of foot-shaoyang, the liver channel of foot-jueyin, the triple-warmer channel of hand-shaoyang, the kidney channel of foot-shaoyin, the stomach channel of foot-yangming, the spleen channel of foot-taiyin, the pericardium channel of hand-jueyin, the lung channel of hand-taiyin, the small intestine channel of hand-taiyang, the large intestine channel of hand-yangming, the heart channel of hand-shaoyin in the order of frequency in used channel among the twelve channels. The liver channel of foot-jueyin is most used. The gall baldder channel of foot-shaoyang, the urinary bladder channel of foot-taiyang, the triple-warmer channel of hand-shaoyang, the spleen channel of foot-taiyin, the stomach channel of foot-yangming, the ren channel, the small intestine channel of hand-taiyang, the kidney channel of foot-shaoyin, the pericardium channel of hand-jueyin, the large intestine channel of hand-yangming, the lung channel of hand-taiyin, the heart channel of hand-shaoyin in the order of frequency in used point among the twelve channels.

• 대한전자공학회논문지
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• 제24권5호
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• pp.818-822
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• 1987

Gate capacitances have been measured directly on small-geometry MOSFET's with the drain voltage as a parameter for various channel lengths and for p and n channel types and the characteristics have been compared with each other. The influence of 'hot carrier effect' of short channel devices on capaciatance has been compared with long channel devices. The results show that gate capacitance characteristics of short channel device deviate from those of long channel device. The accuracy of the measurement system is less than a few femto Farad, and the minimum geometry (W/L) of device for which reliable measurement can be obtained is 6/3.

• 인터넷정보학회논문지
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• 제23권5호
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• pp.9-15
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• 2022

본 논문은 매크로 기지국(Macro base station, MBS) 커버리지에 위치한 건물 내부의 밀집된 스몰셀 네트워크 환경에서 매크로 사용자 단말(Macro user equipment, MUE)의 성능향상을 위한 채널 선택 기반 다중점 협력통신(Coordinated multi-point, CoMP) 방법을 제안한다. 제안하는 CoMP 방법에서 건물 내에 위치한 MUE의 성능향상을 위해 스몰셀 기지국(Small-cell base station, SBS)들이 이웃한 MUE에게 간섭을 적게 미치는 방법으로 채널을 선택하고 CoMP가 필요한 MUE에게 적절한 신호를 송신한다. 시뮬레이션 결과에서 제안하는 CoMP 방법이 기존의 랜덤채널할당 기반의 스몰셀 네트워크 방법과 CoMP방법보다 MUE의 성능을 각각 최대 164%와 51%까지 향상시킨다.

• 물과 미래
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• 제28권3호
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• pp.197-204
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• 1995

인구의 도시집중으로 인하여 유역의 유출용적이 증대하며 이로 인한 합류부의 수위상승으로 내수배제가 불가능하게 되어 침수피해가 발생하고 있다. 본 실험연구에서는 소유역 하천에서 우수거의 합류로 인한 본류하천의 흐름변화를 실험하였으며, 하천의 수위상승을 소하천(본류)의 유량과 경사, 우수거(지류)의 유량과 경사 및 합류각에 따른 본류의 수위상승을 분석하였다. 실험결과 본류하천의 경사에 대해서는 경사가 급할수록 수심비가 증대하는 것으로 나타났으며, 본류의 유량은 적을수록, 지류의 유량은 많을 수록 수심비는 크게 나타났다. 합류각에 대해서는 합류각이 작을수록 수심비가 작은값을 나타내고 있다. 이와 같이 도시 소하천의 합류시 수심비의 상승영향을 보면 합류각, 지류유량 및 본류유량 등의 순으로 상승영향이 밀접하게 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1604-1610
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• 2004

A steady dilute premixed combustion at transonic speeds in a diverging channel is investigated. The model explores the nonlinear interactions between the near-sonic speed of the flow, the small changes in geometry from a straight channel, and the small heat release due to the one-step first-order Arrhenius chemical reaction. The reactive flow can be described by a nonhomogeneous transonic small-disturbance (TSD) equation coupled with an ordinary differencial equation for the calculation of the reactant mass fraction in the combustible gas. The asymptotic analysis results in the similarity parameters that govern the reacting flow problem. The model is used to study transonic combustion at various amounts of incoming, reactant mass, reaction rates, and channel geometries.

• 한국통신학회논문지
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• 제21권6호
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• pp.1567-1575
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• 1996

This paper presents a new power control method for compensating the short term fading of the reverse link channel in the CDMA mobile telephone system. The fixed step closed loop power control which is now adopted in IS-95, is very simple in structure. However, the step size in the closed loop power control is too big for the channel with a small variation or too big for the channel with a small variation or too small for the channel with a large variation. The method presented in this paper has a simple structure and shows a new model employing the combination of the fixed step size method and variable step size method which results in compensatingthe disadvantages mentioned above. This paper also evaluates the performance inthe fundamental channel model.