• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3479-3489
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• 2000

Most of the study on fairness control method for Distributed-Queue Dual-Bus(DQDB) have been performed under specific load types such as equal probability load types or symmetric load types. On Web-based internet enviroments client-server load types are more practical traffic patlerns than specrfic load types. In this paper, an effiective fairness control method to distribute DQDR network bandwidth fairly to all stations under a client-server load is proposed. In order to implement a dynamic bandwidth timing capabihty needed to distribute the bandwidth fairty at heavy loads, the proposed method uses two pararnetexs, one is an access hrnit to legulate each station's packet transmission and the other is the number of extra emply slots that are yielded to downstream stations. In point of implementation this mechanism is simpler and easier than Bandwidth Tuning Mechanism(BTM) that uses an intermediate pattern and an adptation function. Simulation results show that it outperforms othen mecharusms.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1733-1740
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• 2004

In the transverse flux linear induction motor(TFLIM) with the general secondary composed of conductor and back-yoke, there exists a magnetized force into the normal direction or the air-gap direction of the thrust motion as well as the thrust force. Therefore, the various methodologies have been tried to use the normal force by the two independent control variables of the multi-phase input. But, as the force depends inevitably and strongly on the thrust force, it is essential to decouple both forces for two control index. In this paper, we suggest a novel approach capable of compensating the couple between both forces and the control index by using the DC-biased multi-phase input, and then realizing the independent control of TFLIM.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.22-33
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• 2005

In this paper, an efficient signal interference control technique to improve the high convergence speed of LMS algorithms is introduced in the adaptive transversal filter of DS/SS. The convergence characteristics of the proposed algorithm, whose coefficients are multiply adapted in a symbol time period by recycling the received data, is analyzed to prove theoretically the improvement of high convergence speed. According as the step-size parameter ${\mu}$ is increased, the rate of convergence of the algorithm is controlled. Also, an increase in the stop-size parameter ${\mu}$ has the effect of reducing the variation in the experimentally computed learning curve. Increasing the eigenvalue spread has the effect of controlling which is downed the rate of convergence of the adaptive equalizer. Increasing the steady-state value of the average squared error, proposed algorithm also demonstrate the superiority of signal interference control to the filter algorithm increasing convergence speed by (B+1) times due to the data-recycling LMS technique.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.295-295
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• 2012

본 연구에서는 아크방전을 이용한 질화 티타늄의 합성 과정 중에서, 시편 청정 공정변수를 변화시킴에 따라 계면에서의 미세조직 변화와 코팅층의 물성을 평가하였다. 아크 소스에 장착된 타겟은 $120mm{\Phi}$, 99.5 %의 티타늄 타겟을 사용 하였고, 시편과 타겟 간의 거리는 약 30 cm이며, 시편은 SUS를 사용하였다. 시편을 진공용기에 장착하고 진공배기를 실시한 후 Ar 가스 분위기에서 시편에 전압을 인가한 후 아크를 발생시켜 약 5분간 시편 청정을 실시하였다. 이 시편 청정 과정에서 시편 인가전압을 0~1,000 V로 변화시켰고 시편 정청이 끝나면 시편에 인가된 전압을 차단하고 코팅하였다. 질화 티타늄의 두께는 약 $3{\mu}m$로 동일하게 코팅하였다. 시편 인가전압 변화에 따라 시편청정 공정 시 계면에서 티타늄층이 코팅되거나 모재 내부까지 침투하는 현상을 관찰하였다. 시편청정 공정변수 변화에 따른 질화 티타늄의 코팅을 통해 계면의 미세조직과 성분의 변화를 주사전자현미경, 투과전자현미경 이미지와 에너지 분산분광기 (Energy Dispersive Spectroscopy ; EDS)를 통해 확인하였으며 나노인덴터를 이용해 경도, 탄성계수 등의 물성변화를 측정하였다. 본 연구에서 얻어진 결과를 이용하여 시편 청정 공정 제어를 통한 다양한 물성변화가 가능 할 것으로 예상된다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.6
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• pp.64-72
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• 2010

In general, due to the interactions among subsystems, it is difficult to design an decentralized controller for nonlinear interconnected systems. In this study, the model of nonlinear interconnected systems is studied via decentralized fuzzy control method with time delay and polytopic uncertainty. First, the nonlinear interconnected system is represented by an equivalent Takagi-Sugeno type fuzzy model. And the represented model can be rewritten as Parameterized Linear Matrix Inequalities(PLMIs), that is, LMIs whose coefficients are functions of a parameter confined to a compact set. We show that the resulting fuzzy controller guarantees the asymptotic stability and disturbance attenuation of the closed-loop system in spite of controller gain variations within a resulted polytopic region by example and simulations.

• The Transactions of the Korea Information Processing Society
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• v.6 no.2
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• pp.534-542
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• 1999

A sell-designed rate control strategy can improve overall picture quality for video transmission over a constant bit rate channel and the rate control method is not a normative part of MPEG-video standard, the performance of MPEG video codec can be quite different depends on how to implement the rate control scheme. The rate control scheme proposed in MPEG show good results when scene changes is not occurred. But it has weakness that it does not properly handle scene-changed pictures. Therefore picture quality after scene change is deteriorated, and possibility of overflow occurrence becomes high. In this paper, a new method for detection of scene change occurrence using local variance and a new determination scheme for adaptive quantization parameter, mqunt, which can consider local characteristic of an image by using previously computed the local variance from the scene change detection part are proposed. IN addition, and adaptive rate control scheme which can handles scene changed picture very efficiently by scene-changed picture is proposed. Computer simulations are performed to verify the performance of the proposed algorithm. The suggested detection algorithm precisely detected scene change. And the proposed rate control scheme shows better rate control performance as compared with that of the conventional MPEG scheme.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.284-297
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• 2021

A simple kinematic model for the prediction of ship manoeuvres based on trial data is proposed in this study. The model consists of first order differential equations in surge, sway, and yaw directions which simulate the time series of each velocity component. Actually instead of sea trial data, dynamic model simulations are conducted with randomly varied control inputs such as propeller revolution rates and rudder angles. Based on learning of control inputs and velocity outputs of dynamic model simulations in sufficient time, kinematic model coefficients are optimized so that the kinematic model can be approximately reproduce the velocity outputs of dynamic model simulations with arbitrary control inputs. The resultant kinematic model is verified with new dynamic simulation sets.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.380-382
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• 1998

ABR 은 ATM의 서비스 중에서 가장 최근에 추가된 것으로서 트래픽 소스의 전송률을 제어하기 위해서 피드백 메커니즘을 사용한다. ABR 서비스의 성능은 스위치를 통해서 피드백되는 RM 셀에 의해서 결정적인 영향을 받는다. ATM 표준에는 EPRCA, CAPC, ERICA 등의 알고리즘을 다루고 있다. 하지만 이러한 스위치 알고리즘에 대한 성능평가 및 분석 은 자세히 이루어지지 않고 있다. 본 논문에서는 현재 사용중인 ABR 스위치 알고리즘 중 단순히 큐의 길이에 위해 폭주를 판단하는 EPRCA 방법에 대해서 자세히 분석하고 EPRCA 의 단점을 극복하기 위해서 큐의 길이뿐만 아니라 새로운 변수 즉 평균 분산 및 표준편차을 이용해서 각 송신원의 공정성을 높이고 시스템의 효율성을 증대시키는 방안을 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.9A
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• pp.1525-1534
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• 2001

국내 통신사업자들이 xDSL 등 초고속 인터넷 액세스 서비스를 왜곡된 요금구조로 경쟁적으로 보급함에 따라 급속히 확산되고 있으나, 엄밀히 원가를 감안한다면 여전히 AO/DI는 인터넷 트래픽 폭증으로 인한 전기통신망의 과부하를 통신사업자가 경제적이며 효과적으로 대처할 수 있는 현실적인 대안이라 할 수 있다. 본 논문은 AO/DI의 동적 채널 할당 및 해지에 있어서 VIA가 권고한 정책보다 효율적으로 대역폭을 할당, 해지할 수 있는 알고리즘을 제안한다. 관찰 시점까지의 누적된 트래픽의 양과 변화를 감안하여 평균 트래픽과 분산을 추정함으로써 트래픽의 변화에 적응하여 채널 할당, 해지 시점을 결정할 수 있으며 트래픽 특성에 따라 매개 변수의 조정을 통하여 D 채널, B 채널의 이용률을 제어할 수 있고 평균 대기시간 등의 성능을 최적화할 수 있음을 보인다. 또한, 이를 기초로 응용 프로토콜을 감지하여 응용이 갖는 고유의 트래픽 특성과 요구사항에 적합한 채널 할당/해지 방안도 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.232-238
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• 2003

In this paper, we propose a spatially adaptive image restoration algorithm using local statistics. The local mean, variance, and maximum values are utilized to constrain the solution space, and these parameters are computed at each iteration step using partially restored image. A parameter defined by the user determines the degree of local smoothness imposed on the solution. The resulting iterative algorithm exhibits increased convergence speed when compared to the non-adaptive algorithm. In addition, a smooth solution with a controlled degree of smoothness is obtained. Experimental results demonstrate the capability of the proposed algorithm.